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  • Chatzis, Vasileios
    KTH, School of Information and Communication Technology (ICT).
    SDN Benefits in a Legacy World2016Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    This dissertation aims to explore how one could leverage Software Dened Network (SDN) and Network Function Virtualization (NFV) principles in order to realize Service Function Chaining (SFC) in a network. SDN is a new networking paradigm, which makes a network programmable through the use of a software entity called SDN controller. NFV is intended to enable deployment of virtualized network functions, therefore replacing existing hardware solutions. SFC provides the ability to route user traffic to one or more network functions in an orderly manner. SFC will potentially enable many use cases such as data providers being able to dynamically steer user traffic through a set of network functions such as rewall and loadbalancer.

    This study is based on a set of goals. These goals evolve around the implementation of a prototype that will enable a SDN controller to steer user traffic through a series of virtualized network functions (VNFs). An important part of the prototype setup is a Network Management Software (NMS) named BECS, which is developed by Packetfront Software AB. BECS is acting as an orchestrator on the network and has complete awareness of all the network devices present on the network it manages. One of the main requirements of the prototype is to enable BECS to communicate with a SDN controller. Once that has been achieved, BECS could provide the necessary information that the controller needs in order to create and install a set of forwarding rules in the SDN enabled switches of the network. All those steps are necessary in order to achieve SFC. In this prototype, SFC is realized by demonstrating the user specific traffic steering through a set of VNFs in a specific order, based on control messages originated from BECS.

    Until now, network architecture has been limited to the capabilities of the actual hardware equipment. SDN and NFV help us to overcome this limitation. Information needs to be available anywhere and at any time, in a reliable and secure way. To ensure that, we propose a new scheme of network architecture through our prototype solution. This solution intends to give the ability to network managers to re-shape their networks based on their needs by the use of SFC.

  • You, Yantian
    KTH, School of Information and Communication Technology (ICT).
    Sparsity Analysis of Deep Learning Models and Corresponding Accelerator Design on FPGA2016Independent thesis Basic level (degree of Bachelor), 10 credits / 15 HE creditsStudent thesis
    Abstract [en]

    Machine learning has achieved great success in recent years, especially the deep learning algorithms based on Artificial Neural Network. However, high performance and large memories are needed for these models , which makes them not suitable for IoT device, as IoT devices have limited performance and should be low cost and less energy-consuming. Therefore, it is necessary to optimize the deep learning models to accommodate the resource-constrained IoT devices.

    This thesis is to seek for a possible solution of optimizing the ANN models to fit into the IoT devices and provide a hardware implementation of the ANN accelerator on FPGA. The contribution of this thesis mainly lies in two aspects: 1). analyze the sparsity in the two mainstream deep learning models – DBN and CNN. The DBN model consists of two hidden layers with Restricted Boltzmann Machines while the CNN model consists of 2 convolutional layers and 2 sub-sampling layer. Experiments have been done on the MNIST data set with the sparsity of 75%. The ratio of the multiplications resulting in near-zero values has been tested. 2). FPGA implementation of an ANN accelerator. This thesis designed a hardware accelerator for the inference process in ANN models on FPGA (Stratix IV: EP4SGX530KH40C2). The main part of hardware design is the processing array consists of 256 Multiply-Accumulators array, which can conduct multiply-accumulate operations of 256 synaptic connections simultaneously. 16-bit fixed point computation is used to reduce the hardware complexity, thus saving power and area.

    Based on the evaluation results, it is found that the ratio of the multiplications under the threshold of 2-5 is 75% for CNN with ReLU activation function, and is 83% for DBN with sigmoid activation function, respectively. Therefore, there still exists large space for complex ANN models to be optimized if the sparsity of data is fully utilized. Meanwhile, the implemented hardware accelerator is verified to provide correct results through 16-bit fixed point computation, which can be used as a hardware testing platform for evaluating the ANN models.

  • Ali Kazmi, Syed
    KTH, School of Industrial Engineering and Management (ITM), Applied Mechanical Engineering (KTH Södertälje).
    Impact of Natural, Man-made Risks and Stakeholders Relationship on effectiveness of Supply Chain Management in Developing Countries2017Independent thesis Advanced level (degree of Master (One Year)), 10 credits / 15 HE creditsStudent thesis
  • Giannokostas, Vasileios
    KTH, School of Information and Communication Technology (ICT).
    Policy-Driven YARN Launcher2016Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    In recent years, there has been a rising demand for IT solutions that are capable to handle vast amount of data. Hadoop became the de facto software framework for distributed storage and distributed processing of huge datasets with a high pace. YARN is the resource management layer for Hadoop ecosystem which decouples the programming model from the resource management mechanism. Although Hadoop and YARN create a powerful ecosystem which provides scalability and flexibility, launching applications with YARN currently requires intimate knowledge of YARN’s inner workings. This thesis focuses on designing and developing support for a human-friendly YARN application launching environmen twhere the system takes responsibility for allocating resources to applications. This novel idea will simplify the launching process of an application and it will give the opportunity to inexperienced users to run applications over Hadoop.

  • Yu, Yiting
    KTH, School of Information and Communication Technology (ICT).
    Energy- and Cost-Efficient 5G Networks in Rural Areas2016Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    Energy- and cost-efficiency is becoming a criteria of ever increasing importance in the design of 5G wireless solutions, especially for suburban and rural areas where the realistic barrier of providing mobile broadband service lies in the economic drawback of low revenue potential. Thus net-work operators are highly sensitive to the energy performance and economic affordability of potential solutions in futuristic 5G wireless network.In this thesis, we investigate the energy performance of 5G wireless networks with two key technical components (massive beamforming and ultra-lean design) in a rural environment for two real-life cases commonly faced by network operators: (1) A hardware upgrade to 5G in existing LTE sites (2) 5G greeneld deployments. The results are compared with a currently deployed LTE network in rural environment.

    Furthermore, we conduct economic viability evaluations in a study of energy-cost trade-off in rural scenario to derive the condition when the proposed energy-efficient 5G solutions are also cost-efficient. The analysis are performed separately in two cases based on different methods.

    The simulation results indicate that 5G systems provides much better energy performance compared with LTE systems, achieving maximum 56% and 64% reduction in daily average area power consumption in hardware upgrade case and greenfield deployment case respectively. The significant saving mainly comes from the incorporated effect of beamforming technology and possibility of longer sleep durations.

    For cost-efficiency, a hardware upgrade to 5G is economically highly motivated in higher energy-pricing regions or in systems with longer sleep durations. In greenfield deployments, the analysis result shows that itis always cost-efficient to deploy 5G solutions other than LTE solutions in rural areas despite of the variation in regional energy prices, network lifetime expectation and the DTX factor in 5G solutions.

  • Public defence: 2017-04-24 10:00 T2, Stockholm
    Zhu, Lin
    KTH, School of Technology and Health (STH), Basic Science and Biomedicine, Structural Biotechnology.
    Structural studies of HDL and applications of EM on membrane proteins2017Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    A large number of proteins interact with biological membranes, either integrated in the membrane (PepTSo2), embedded on a membrane surface (5-lipoxygenase) or encircling a cutout of lipid bilayer (apolipoprotein1 (apoA-I). They function as transporters, receptors or biocatalysts in cellular processes like inflammation or cholesterol transport which are touched upon here. Malfunction of specific membrane proteins are the cause for several diseases or disorders.

    Knowledge of protein structure supports understanding of its mechanism of function. Here, transmission electron microscopy (TEM) was used for structure determination. To obtain structure information to high resolution for membrane proteins, normally surrounded by lipids, demands specific methods and materials for stabilization. Stabilized in detergent the structure of the bacterial transporter PepTSo2 was shown to form a tetramer even bound to substrate. However, with a protein based stabilizer, Salipro, the structure of PepTSo2 could be determined to high resolution.

    High density lipoprotein (HDL) in blood plasma, involved in the removal of cholesterol from peripheral tissues, have a central role in cardiovascular function, metabolic syndrome and diabetes.

    The HDL-particle is composed of two copies of ApoA1 and around hundred lipid molecules. From TEM data, for the first time the clearly discoidal shape could be shown by 3-dimendional reconstructions. These were used for modelling the ApoA1 protein dimer by a "biased fitting" procedure. The results indicate how ApoA1 folds around a lipid bilayer in a disc-shaped structure.

    Modified HDL called nanodiscs were here used to show the Ca2+ dependent binding of 5-lipoxygenase on the nanodisc bilayer and thereby increased production of the inflammatory mediator leukotrieneA4. Dimerization of 5-lipoxygenase inactivates these functions.

  • Public defence: 2017-04-18 14:00 F3, Stockholm
    Ahmad Termida, Nursitihazlin
    KTH, School of Architecture and the Built Environment (ABE), Transport Science, System Analysis and Economics. Universiti Tun Hussein Onn Malaysia, Faculty of Civil and Environmental Engineering, Department of Infrastructure and Geomatic Engineering.
    Understanding Individuals' Learning and Decision Processes in a Changing Environment by Using Panel Data2017Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    When a new transport service is introduced, people have to learn and familiarize themselves with the new service before they decide to adopt it. These processes are developed over time, thus produce dynamics in individuals’ behavioural responses towards the service. This affects the demand of the new service, thus affect revenues. Available studies have examined the factors influencing these responses from microeconomic perspectives. The influence of the theory-based subjective factors has not been examined empirically. Understanding these would assist transport and urban planners to design a better marketing strategy to increase the market share of the new service. A change in seasons affect individuals’ activity-travel decisions, thus produce dynamics in activitytravel patterns in different seasons. Individuals’ constraints, in a form of mandatory activities (working/studying), are influencing individuals’ decisions to participate in day-to-day nonmandatory activities (leisure and routine activities). The interdependency between travel demand, time allocation and mode choice that considers interactions between mandatory and non-mandatory activities, in different seasons is less explored. Understanding these would assist transport planners and operators to manage travel demand strategies across different seasons of the year and provide better transportation systems for all individuals. This thesis includes five papers. Paper I explores individuals’ characteristics of the quick-response and the adopters of the new public transport (PT) service and examines the temporal effects. Paper II investigates the subjective factors influencing a quick-response to the new PT service by proposing a modified attitude-behaviour framework. Paper III and IV analyse the effects of seasonal variations and individuals’ constraints on their day-to-day activity-travel decisions and patterns. Paper V analyses the attrition and fatigue in the two-week travel diary panel survey instrument.

  • Public defence: 2017-04-28 14:00 Kollegiesalen, Stockholm
    Fu, Jiali
    KTH, School of Architecture and the Built Environment (ABE), Transport Science, Transport Planning, Economics and Engineering.
    Evaluating and Improving the Transport Efficiency of Logistics Operations2017Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    The thesis focuses on evaluating and improving the transport efficiency of two types of logistics operations in the supply chain.

    One research area is the production of raw material in construction operations, specifically earthmoving operations. Methods and tools are developed to provide decision support in improving the transport efficiency of earthmoving at the vehicle and the systems levels. Using known road topography and a GPS unit, an optimal control problem is formulated and solved (Paper III) to determine the optimal gear shift sequence and timing in order to improve the transport efficiency at the vehicle level. For decision support at the systems level, a Fleet Performance Simulation (FPS) model is designed (Paper IV) to evaluate the transport efficiency for a given mix of construction vehicles in earthmoving. The FPS system is integrated with an optimization algorithm to solve the optimal fleet composition problem for earthmoving operations (Paper V & VI). Construction operations are dynamic and the environment is changing constantly, which bring difficulties in decision-making. Using GPS data from construction vehicles, a map inference framework (Papers I & II) is developed to automatically extract relevant input to decision support at the vehicle and the systems levels, which include the locations of various workstations, driving time distributions and road networks.

    The second research area is the transport efficiency of urban distribution system, which is in the final phase of the supply chain. An off-peak delivery pilot project in Stockholm is used as the background, designed to evaluate the potential for commercial vehicles to make use of off-peak hours for goods delivery. The thesis (Paper VII) evaluates the transport efficiency impacts of the off-peak pilot. An evaluation framework is defined where transport efficiency is studied in a number of dimensions. GPS data, fleet management data, and logistic information are used to assess the impacts.

  • Rasheed-Hilmy Abdalmoaty, Mohamed
    Luleå University of Technology.
    Measures and LMIs for optimal control of piecewise-affine dynamical systems: Systematic feedback synthesis in continuous-time2012Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    The project considers the class of deterministic continuous-time optimal control problems (OCPs) with piecewise-affine (PWA) vector fields and polynomial data. The OCP is relaxed as an infinite-dimensional linear program (LP) over space of occupation measures. The LP is then written as a particular instance of the generalized moment problem which is then approached by an asymptotically converging hierarchy of linear matrix inequality (LMI) relaxations. The relaxed dual of the original LP gives a polynomial approximation of the value function along optimal trajectories. Based on this polynomial approximation, a novel suboptimal policy is developed to construct a state feedback in a sample-and-hold manner. The results show that the suboptimal policy succeeds in providing a stabilizing suboptimal state feedback law that drives the system relatively close to the optimal trajectories and respects the given constraints.

  • Li, Yuxin
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Industrial Economics and Management (Dept.).
    Zhang, Bo
    KTH, School of Industrial Engineering and Management (ITM), Industrial Economics and Management (Dept.).
    The adaptation of Methodology in Swedish Cultures: The innovation approaches to lean Manufacturing2017Independent thesis Advanced level (degree of Master (One Year)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    The Japanese automobile manufacturer invented Lean Production or Toyota Production System (TPS) which has been introduced and implemented in Swedish manufacturers for around 20 years (Dabhilkar, et al., 2005). Many studies discussed how it creates success in optimizing production process and quality. However, many researches show that the gap between culture become the main barrier in the process of realizing ‘true’ lean manufacturing. So, what problems has been brought out because of cultural difference in the process of implementing the lean method in Swedish industry and how to eliminate them?

     

    The adaptation of lean method will have influences on the culture of a company. The purpose of this paper is to find out the problems which brought out by the cultural difference and a set of general approaches and principles which can be used for Swedish cultures to adapt and implement lean methodologies successfully and effectively.

  • Public defence: 2017-04-20 10:00 F3, Stockholm
    Sandhi, Arifin
    KTH, School of Architecture and the Built Environment (ABE), Sustainable development, Environmental science and Engineering, Land and Water Resources Engineering.
    ARSENIC REMOVAL BY PHYTOFILTRATION AND SILICON TREATMENT: A POTENTIAL SOLUTION FOR LOWERING ARSENIC CONCENTRATIONS IN FOOD CROPS2017Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    Use of arsenic-rich groundwater for crop irrigation can increase the arsenic (As) content in food crops and act as a carcinogen, compromising human health. Using aquatic plant based phytofiltration is a potential eco-technique for removing arsenic from water. The aquatic moss species Warnstorfia fluitans grows naturally in mining areas in northern Sweden, where high concentrations of arsenic occur in lakes and rivers. This species was selected as a model for field, climate chamber and greenhouse studies on factors governing arsenic removal and arsenic phytofiltration of irrigation water. The arsenic and silicon (Si) concentrations in soil, water and plant samples were measured by AAS (atomic absorption spectrophotometry), while arsenite and arsenate species were determined using AAS combined with high pressure liquid chromatography (HPLC) with an anion exchange column. The arsenic content in grains of hybrid and local aromatic rice (Oryza sativa) cultivars with differing arsenic accumulation factor (AF) values was investigated in an arsenic hotspot in Bangladesh. The results showed that arsenic AF was important in identifying arsenic-safer rice cultivars for growing in an arsenic hotspot. The study based on silicon effect on arsenic uptake in lettuce showed that arsenic accumulation in lettuce (Lactuca sativa) could be reduced by silicon addition. The aquatic moss had good phytofiltration capacity, with fast arsenic removal of up to 82% from a medium with low arsenic concentration (1 µM). Extraction analysis showed that inorganic arsenic species were firmly bound inside moss tissue. Absorption of arsenic was relatively higher than adsorption in the moss. Regarding effects of different abiotic factors, plants were stressed at low pH (pH 2.5) and arsenic removal rate was lower from the medium, while arsenic efflux occurred in arsenate-treated medium at low (12°C) and high (30°C) temperature regimes. Besides these factors, low oxygenation increased the efficiency of arsenic removal from the medium. Finally, combining W. fluitans as a phytofilter with a lettuce crop on a constructed wetland significantly reduced the arsenic content in edible parts (leaves) of lettuce. Thus W. fluitans has great potential for use as an arsenic phytofilter in temperate regions.

  • MARAKBI, ZAKARIA
    KTH, School of Industrial Engineering and Management (ITM), Industrial Economics and Management (Dept.), Industrial Marketing and Entrepreneurship.
    Mean-Variance Portfolio Optimization: Challenging the role of traditional covariance estimation2016Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    Ever since its introduction in 1952, the Mean-Variance (MV) portfolio selection theory has remained a centerpiece within the realm of e_cient asset allocation. However, in scienti_c circles, the theory has stirred controversy. A strand of criticism has emerged that points to the phenomenon that Mean-Variance Optimization su_ers from the severe drawback of estimation errors contained in the expected return vector and the covariance matrix, resulting in portfolios that may signi_cantly deviate from the true optimal portfolio.

    While a substantial amount of e_ort has been devoted to estimating the expected return vector in this context, much less is written about the covariance matrix input. In recent times, however, research that points to the importance of the covariance matrix in MV optimization has emerged. As a result, there has been a growing interest whether MV optimization can be enhanced by improving the estimate of the covariance matrix.

    Hence, this thesis was set forth by the purpose to investigate whether nancial practitioners and institutions can allocate portfolios consisting of assets in a more e_cient manner by changing the covariance matrix input in mean-variance optimization. In the quest of chieving this purpose, an out-of-sample analysis of MV optimized portfolios was performed, where the performance of ve prominent covariance matrix estimators were compared, holding all other things equal in the MV optimization. The optimization was performed under realistic investment constraints, taking incurred transaction costs into account, and for an investment asset universe ranging from equity to bonds.

    The empirical _ndings in this study suggest one dominant estimator: the covariance matrix estimator implied by the Gerber Statistic (GS). Speci_cally, by using this covariance matrix estimator in lieu of the traditional sample covariance matrix, the MV optimization rendered more e_cient portfolios in terms of higher Sharpe ratios, higher risk-adjusted returns and lower maximum drawdowns. The outperformance was protruding during recessionary times. This suggests that an investor that employs traditional MVO in quantitative asset allocation can improve their asset picking abilities by changing to the, in theory, more robust GS  ovariance matrix estimator in times of volatile nancial markets.

  • SANDMAN, SARA
    KTH, School of Industrial Engineering and Management (ITM), Industrial Economics and Management (Dept.).
    Pharmaceutical Opportunities: A three-step repositioning model for evaluating market options2016Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    Pharmaceutical industry is today struggling with its productivity as products keep failing after long and expensive development programs. The protability is further threatened by erce competition from cheaper product copies. As an attempt to increase the pipeline output, pharmaceutical companies have lately turned to the strategy of drug repositioning. By applying an already developed drug in new disease areas the lifetime of the product is prolonged and return time on already made investments elongated.  Such development is imbued by less risk than a de novo development and has proven to be a faster and cheaper way to meet the medical demand.

    With limited company budgets and the often many repositioning possibilities, an informed repositioning selection must be made. As such theoretical model is not publicly available this thesis takes on the task to determine which parameters to take into consideration and how these should be weighted in relation to each other in order to evaluate di erent drug repositioning possibilities. Six main topics are identied to a ect the repositioning success, these are: medical need, economic return, scientic support, timing, life cycle extenders and external relations. These ndings are derived from empirics collected during interviews with employees from ve di erent competence areas involved in repositioning initiatives, na mely: research & development, clinical studies, regulatory a airs, pricing, and commercial. By further support from literature within the elds of drug repositioning and R&D project selection a three-step repositioning model was developed.

    The first step in the three-step repositioning model consists of primary parameters, these are essential parameters that have to be fullled in order to perform a repositioning strategy. If any of the primary parameters are not fullled, the repositioning opportunity should be killed in a go/no-go decision. In a second step, the secondary parameters are evaluated in a scoring model in order to determine the economical outlook of each repositioning opportunity. The opportunities showing greatest economical outlook should further be evaluated in the third and nal step in the three-step repositioning model. In this nal step the di erent repositioning opportunities are evaluated by their coherence with an overall corporate strategy.

    By applying this repositioning model to a repositioning selection scarce company resources  ay be focused on the repositioning opportunities showing best future prospect. Evaluating the potential of repositioning opportunities in a structured way should also increase chances to succeed. If successful, a repositioning initiative may a ect both company and society as the company improves return on earlier investments, while more patients in need of treatment will receive access to it. However, the three-step repositioning model presented in this thesis should be tested for more cases and perhaps be complemented with additional parameters or di erent gradings in order to optimize the selection.

  • Faried, Aamir
    KTH, School of Industrial Engineering and Management (ITM), Industrial Economics and Management (Dept.).
    Social media marketing strategies forweb startups2016Independent thesis Advanced level (degree of Master (One Year)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    A successful startup requires not only great product but also requires effective marketing strategy. After explosion of internet, online marketing has changed the way brands and businesses approach market using technology and digital marketing. The penetration of social media platforms in large audience gave birth to new marketing channel called social media marketing. Social media marketing can be very effective for startups with right planning and good execution. While talking about social media strategy, different people talked about different things and available social media marketing strategies are scattered in terms of context and content and it is difficult for startups to find out the one that can help them with their newly started venture, especially in their early stage. So the purpose of this thesis to go through all available social media strategies in literature and device a common framework that can help and guide startups to adopt social media marketing.

  • Piadehbasmenj, Amirali
    KTH, School of Industrial Engineering and Management (ITM), Industrial Economics and Management (Dept.), Entrepreneurship and innovation. KTH, School of Industrial Engineering and Management (ITM), Industrial Economics and Management (Dept.), Industrial Marketing and Entrepreneurship.
    Entrepreneurial Venture Failure Experiences: An analysis into causes, costs, and outcomes of venture failure2016Independent thesis Advanced level (degree of Master (One Year)), 10 credits / 15 HE creditsStudent thesis
    Abstract [en]

    Research on entrepreneurship focuses on success which ignores the high failure rate of new ventures. Many new ventures fail so how entrepreneurs deal with it when their venture fails? Successful entrepreneurs praising the advantages of failure as a valuable teacher. The result of failure is regularly filled with economic, social, psychological, and physical health disorder. The aim of this research is to assessment venture failure experiences for entrepreneurs, from the instant result through to recovery for coping with entrepreneurial failure and exit for impact of the closed venture. In this research, aspects of life affected by entrepreneurial failure examine economically, socially and psychologically in highlighting factors that may influence the amount of costs of failure. Next, the research describes how entrepreneurs learn from failure. It presents on the outcomes of venture failure, including coping with failure and recovery together with cognitive and behavioral outcomes.

    The main objective of the research study is to understand the failure from entrepreneurs who have experienced it and also to make a theoretical framework of failure based on entrepreneurial venture failure experiences. Every entrepreneur starts up a venture with high expectations of achieving success. Failure can be emotionally disturbing, devastating, painful, distressing and costly for the entrepreneur who may have to aspect the stigma of failure and the loss of reputation. The entrepreneur can get involved in grief, heartache, anxiety, depression, shame, rejection and discouragement (Politis & Gabrielsson, 2009). The purpose of the research is to investigate how entrepreneurs realize and react to venture failure.

    Moreover, entrepreneurs are looking for positive aspects of failure as enhancing experiences that help their coping with entrepreneurial failure, learning from failure, the willingness to begin a new venture and also trigger changes in upcoming decision-making. The purpose of the research is to take a view of the existed experience of failure, taking into consideration impact from the entrepreneurship.

  • Söderberg, Martin
    KTH, School of Computer Science and Communication (CSC).
    Identifying Website Usability Solely from Gaze Data of Visual Search2017Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    If researchers are able to derive usability simply by analysing gaze data it provides a quick, objective and potentially automatic way of measuring the usability of an interface. In order to do that it is essential to know which traits of the gaze data that have an impact on usability. This paper investigates these traits by analysing different eye tracking metrics in the data. The goal is to see which of these metrics have a general correlation with usability. Previous research provides a clue about which metrics are useful when analysing usability. However, much of the research is based on subjective analysis or lacks in general applicability. This research provides an objective analysis that is independent of characteristics of the interface.

    A user study is done on 20 participants. They complete tasks on nine different ecommerce websites while their eye movements are recorded. Correlation is measured between usability and eye tracking metrics in order to investigate which metrics that are sensitive to changes in usability.

    The results show that fixational backtracks and number of fixations have the strongest correlation with usability. Previous research did suggest that both of these eye tracking metrics have an impact on usability.

  • Sörensen, Ingrid
    KTH, School of Computer Science and Communication (CSC).
    Expectations on Chatbots among Novice Users during the Onboarding Process2017Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    In recent years a type of Conversational User Interface (CUI) called chatbots has been more common, these are integrated and used on various platforms such as Slack, Facebook and Skype. Chatbots are based on Artificial intelligence and are a written conversation between a human and an intelligent system. One example is Microsoft‘s chatbot Zo, a social chatbot aimed to entertain. As chatbots are becoming more commonly occurring, the need to study peoples expectations and demands is important in order to improve the user experience and usages of chatbots.

    In this paper, a study is presented, looking at the requirements and expectations of a chatbot by novice users. The study showed that onboarding is important in order for users to perform tasks successfully. Onboarding is the process for new users to become successful when adopting a product. In the study, eight participants were exposed to two different chatbots, a human-like and a robot-like, and interviewed about their thoughts and experiences from using it. The chatbots is applied to the case of customer support for insurance. The participants received the tasks; sign a new insurance, cancel an old one, get a recommendation for an pregnancy insurance and react on a notification.

    The results from the study also illustrate the importance of giving the user feedback in form of summaries, give system status of what is going on, sentences from the chatbot should be with concise information, and being able to handle input independent of the formulation. Regardless of which of the chatbots the participants tried first, they favored the second chatbot because they perceived it as easier to talk to with less misunderstandings. This might indicate a learning curve among the users and hint towards the need to design for onboarding. 

  • Lindström, Caroline
    KTH, School of Computer Science and Communication (CSC).
    Visualising Web Accessibility Performance to Raise Awareness and Understanding Amongst Product Stakeholders2017Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    With the rapid development and increased use of technology, making technology accessible for every user is becoming even more important. A vital part in the process of achieving this is evaluating products as part of the development process. This design-oriented study explores how a visualisation of a product’s accessibility performance can aid in creating a more inclusive and accessible product by increasing awareness and understanding amongst product stakeholders. To explore the requirements of such a visualisation a prototype was developed for a music streaming service’s desktop application and evaluated through a study with six stakeholders.

    All participants had a positive attitude towards the prototype and expressed that it helped them find accessibility issues. Five out of six participants felt they understood what an issue entailed and whom it could affect. Several different areas of usage were proposed by the participants, who also believed a broad group of different stakeholders could benefit from using a tool like this. The results showed that the proposed design could increase awareness and create a deeper understanding for accessibility issues amongst stakeholders. No specific part of the design could be identified as more valuable than the other, which indicated that the value lied within the prototype as a whole. Together all parts created a versatile tool that could be used to fulfil different users’ need in different situations. 

  • Johansson, Emma
    KTH, School of Engineering Sciences (SCI), Mathematics (Dept.), Optimization and Systems Theory.
    The thermal comfort of the cockpit: A pilot's experience2017Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    Saab takes great measures to ensure that the cockpit is a great working environment for the pilot. This paper aims to expand the knowledge of thermal comfort by assembling Saab’s atmosphere-, cabin and pilot-models. In order to ensure the viability of the assembled model, a qualitative study was performed with test pilots. The interviews were reduced to a few flight cases, which were tested in the assembled model to verify that the thermal discomforts that the pilots experience could be accurately predicted. Furthermore, a prediction of comfort, according to European standards, was implemented. From the interviews situations when the pilot feel discomfort could be identified, two flight cases situations and one ground case. The model simulate how the thermal environment affect the pilot, hence only the two flight cases could be analyzed. The result from the model shows the temperature in those body parts that the pilots have expressed are uncomfortable. Predicted Mean Vote, PMV, predicts comfort on a 6-degree scale, given environment parameters such as pressure and temperature. The Predicted Percentage Dissatisfied, PPD, describes the number of people, in percent, who are uncomfortable at a given PMV. These measures of comfort were used to compute the comfort in the different parts of the body. The model simulation agrees with the pilot’s experiences in some of the body parts, but not all of them. By taking the humidity into account the simulation result may be more accurate. The humidity increases the PPD value in case 2 when the humidity increases. Finally, in order to adopt the comfort analysis presented in this paper, the model had to be revised, and updated with increased detail.

  • Pietroniro, Asuka Gabriele
    KTH, School of Engineering Sciences (SCI), Mechanics.
    Modelling coaxial jets relevant to turbofan jet engines2016Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    Simulations of subsonic turbulent coaxial hot jets were conducted on two types ofunstructured grids within the framework of STAR-CCM+. The study case is based on atypical airliner turbofan engine model with a core nozzle and a fan nozzle, having a bypassratio of five. The two meshes used are a polyhedral one, suitable for complex surfaces, and atrimmed one mainly made of hexahedral cells. The sensitivity of the study case to variousinputs is attested using second and third order upwind schemes, modelling turbulence with aSST k-omega model. The project proves to be a valid feasibility study for a steady-statesolution on which an aeroacoustic analysis could be based in future works.

  • Winroth, Marcus
    KTH, School of Engineering Sciences (SCI), Mechanics.
    Pressure measurements in pulsatingflows2014Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    Due to confidentiality several axis in the figures and large parts of the specifics of the resultsand of the experimental setups have been replaced by symbols. Also one section of the report,concerning a prototype sensor, has been removed completely due to the sensitive nature of theresults.Measuring the exhaust gas pressure and the boost pressure at the air intake manifold isconsidered a standard procedure in modern cars and trucks. Although how to measure thepressure accurately for steady flows is well known, the pressure measurements in pulsatingflows is not a trivial task. This theses shows, experimentally, how well the characteristics of apressure measurement systems, using different dimensions of straight pneumatic tubing, canbe predicted using the Helmholtz resonator model. Also how much this resonance influencethe pressure measurements for different pressure transducers used in trucks today. This thesisalso demonstrates the effects that the sampling frequency and the averaging time has on theaccuracy of measuring an average pressure in pulsating gas flows and how clogging of thepneumatic tubes influence the measurements. This was done using two types of experiments;a step response experiment to properly show the characteristics of the measuring system and apulse rig experiment that shows the impact, of the tubing, on the measurements for typicalfrequencies found in medium sized trucks. The experiments shows that the response time andresonance frequency of a measurement system can be predicted with an accuracy of 𝜇! % fortubes longer than 725 mm. It also that the average absolute pressure measurement keeps anaccuracy of 𝜇! % for all tube dimensions, including clogging of the tube with a decrease ofdiameter up to 𝜇! %. It does however show that if the sensor has some internal resonance that4matches the Helmholtz resonance the measurement can be overestimated by over 𝜇! %. Testsof the sampling frequency shows that if the sampling frequency is chosen as a divisor or amultiple of the pulse frequency the error due to averaging is increased by one order ofmagnitude. Using the information given in this thesis it is possible to avoid unnecessary errorswhen performing pressure measurements in a pulsating flow.

  • Tanabe, Yoko
    KTH, School of Engineering Sciences (SCI), Mechanics.
    Assessment of Volume of fluid Method for high-pressure gasinjection into liquid2015Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    Carbonated sparkling water has been widely used from ancient age [1]. The original ideacame from natural sparkling water and people believed that taking baths at carbonatedhot springs was good for health and healed their sicknesses. This fact led people to startthinking that sparkling water could have more effective uses. Joseph Priestley success-fully produced artificial carbonated water in 1767 and sparkling water quickly becamewidely spread because it gives people refreshing feeling. The bottled and canned beverageindustry has grown from the 19th century and has become one of the biggest markets inthe world. According to Bloomberg Intelligence and Euromonitor, the global market ofthe carbonated beverages is around 350 billion dollar. One main drawback was that itwas not possible to re-cork the bottle to save the carbonation so that once it was opened,fizz was kept only for a short time. In 1813, the method to dispense a portion of carbon-ated water was invented by Charles Plinth[2]. This was the origin of the Soda Syphon.As the demand of sparkling water increased, the machine with which people could makesparkling water by themselves was introduced. Recently, it has become a very popularhome appliance, especially in Europe and North America. The most common way tocarbonate water is by injecting high-pressure CO2 into a water bottle. However, currentsystems waste a lot of CO2 during this carbonating process. In this thesis, the flow insidethe bottle during the injection of CO2 into water was studied in order to determine the pa-rameters that had most influence on the carbonation process. CFD (Computational FluidDynamics) simulations were performed in STAR-CCM+ of an axisymmetric 2D modeland a 3D model that was a 30 degree wedge of the real bottle shape. The Volume of Fluidmethod was used to solve the multiphase flow of gas and liquid. The RANS approachwas used with k 􀀀ϵ model and implicit time marching. To validate the simulations, axialpropagation of the volume fraction of CO2 was compared with the experimental visual-ization of the CO2 and H2O distribution. At the beginning of the phenomena, the gaspropagation was reasonably predicted and the results capture the features of the bubbleshape. However the results did not perfectly match with the experimental visualization.To seek the reason for the unrealistic results, the grid sensitivity study was performedand to consider the 3D effect the results with the 2D and the 3D model were compared.In addition, the bubble breakup process was deeply investigated.

  • Stenberg, Erik
    KTH, School of Engineering Sciences (SCI), Mechanics.
    On numerical simulations of turbulent flows subjected to system rotation2016Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    Different aspects of numerical simulations of turbulent flows are assessed by consideringa fully-developed turbulent channel flow that is rotating in the spanwise direction.Differences between differential and explicit algebraic Reynolds-stress models(RSMs) are investigated theoretically and numerically. Simulation results are comparedwith existing DNS-data. Both families of RSMs are demonstrated to achievegood qualitative agreement with the DNS. The results constitutes a demonstration ofthe validity of the so called extended weak-equilibrium assumption for systems witha superimposed solid body rotation. An original derivation, based on sound physicalgrounds, of the extended weak-equilibrium assumption is presented.It is further examined if the roll-cell vortex pattern, that constitutes a secondaryflow field, has an influence on the averaged solutions obtained by application of theReynolds-Averaged Navier-Stokes equations. This is assessed by comparison of resultsobtained by either considering the secondary plane as homogeneous in the spanwisedirection or by accounting for a fully three-dimensional flow field. Simulationsdemonstrate that existence of roll-cells in the latter case yields results that are in closeragreement with DNS-data compared with if they are suppressed as for the former case.Aspects of numerical treatment of explicit source terms are also assessed in theframework of finite volume methods for collocated grids.

  • Pietroniro, Asuka Gabrielle
    KTH, School of Engineering Sciences (SCI), Mechanics.
    Modelling coaxial jets relevat to turbofan jet engines2016Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    Simulations of subsonic turbulent coaxial hot jets were conducted on two types ofunstructured grids within the framework of STAR-CCM+. The study case is based on atypical airliner turbofan engine model with a core nozzle and a fan nozzle, having a bypassratio of five. The two meshes used are a polyhedral one, suitable for complex surfaces, and atrimmed one mainly made of hexahedral cells. The sensitivity of the study case to variousinputs is attested using second and third order upwind schemes, modelling turbulence with aSST k-omega model. The project proves to be a valid feasibility study for a steady-statesolution on which an aeroacoustic analysis could be based in future works.

  • Johansson, Lars
    KTH, School of Engineering Sciences (SCI), Mechanics.
    SURFACE DRAG MODELING FOR MILLED SURFACES2015Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    One of the governing sources of energy loss in a modern day jet engine is attributed to surfacedrag. This energy loss can be divided into friction loss and to surface geometry loss. Thefriction loss is the shear stress the fluid experience due to a no slip condition at the wall, whilethe surface geometry loss is due to pressure drop when the fuel passes an obstacle.The objective of this work is to study the drag coefficient of a plate for different types ofmilled tracks and for different kinds of flow conditions. The theories used to calculate thedrag coefficient are based on the momentum thickness theory including shear stress- andpressure integration. The computations were carried out with ANSYS CFX assuming a ShearStress Transport 𝑘 − 𝜔 turbulence model. The steady state flow conditions tested are varyingboundary layer thicknesses, milled track heights, milled track widths, Reynolds numbers overthe milled track height, Reynolds numbers over the plate length and free-stream angle ofattack. By knowing what affects the drag coefficient for different types of milled tracks, morepractical models can be developed making the prediction of surface drag inside the jet enginemore accurate.This report has resulted in a formula that predicts the drag coefficient for different types ofmilled surfaces. The formula is derived from the assumption that the CFD results on ANSYSCFX are correct. A physical test has not been made to verify those results, however this has tobe done to prove that this formula is valid.

  • William-Olsson, Patrik
    KTH, School of Architecture and the Built Environment (ABE), Sustainable development, Environmental science and Engineering, Industrial Ecology.
    Environmental benefits of reuse: A simplified ESA-tool for measuring avoided environmental impacts from second hand operations.2017Independent thesis Basic level (degree of Bachelor), 10 credits / 15 HE creditsStudent thesis
    Abstract [en]

    Today we live in a world with an increasing consumption and limited resources. To be able to

    continue and thrive is now a matter of sustainability. We need to remake our linear economy

    in to a more circular model and try to decouple the extraction of natural resources from the

    economic growth. One way to work towards decoupling is to increase the number of reused

    articles. Life cycle assessments are often used to assess the magnitude of environmental loads

    related to the life cycle of an article. However, the tool is very demanding of resources which

    some of the times requires information that is classified and unverifiable. A simpler

    environmental analysis tool is therefore created to better streamline the process of comparing

    the environmental benefits of reuse and to then identify possibilities to develop second hand

    operations. The simpler environmental analysis tool analyses the carbon dioxide and energy

    consumption of the material related to an article and couples that with the rate of substitution

    which describes how much it is of a newly produced article that is substituted by a second

    hand sold article. The process is divided in to sub steps which yields individual results that

    when added together creates the result of the simpler tool. The report analyses four different

    second hand products namely a cotton sweater, a polyester sweater, a table and a glass ware.

    The results show that articles composed of a high amount of polyester give the highest

    environmental benefit per kilogram when substituted while articles composed of a high

    amount of glass give the lowest environmental benefits per kilogram when substituted. It also

    showed that an analysis of waste management sub step did not affect the rankings of the

    articles regarding the magnitude of the environmental benefits of reuse. The indifference of

    the sub step indicates that other sub steps of higher magnitude should be of higher priorities

    when doing these types of analyses. The results also show that articles are unsuitable for

    comparisons since their material compositions of an article changes between different studies.

    This leads to their environmental loads being different. A more suitable approach may

    therefore be to compare materials. Since reuse and second hand activities have the potential to

    substitute a lot of products, their potential for environmental benefits are high. It is therefore

    recommended to invest in increasing the rate of substitution. This can be achieved by

    implementing marketing strategies to increase the perceived value of all the sold second hand

    articles.

  • Zhang, Chi
    KTH, School of Architecture and the Built Environment (ABE), Sustainable development, Environmental science and Engineering, Industrial Ecology.
    Apply on Instance of IBM Watson Cognitive Computing System2017Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    Smart Cities concern a variety of domains such as information, data, energy, transport, health, etc. The ‘Information Age’, which shifts from the Industrial Revolution to information computerisation, accesses to large volumes of data explored by sophisticated computer based analytics. ICT solutions interconnect businesses and customers through the cloud while driving the global economy and development of Smart Cities. This MSc thesis aims to investigate connections between Smart Cities and cloud-based Cognitive Computing, then demonstrate with instances how the combination of Watson cognitive system and Pepper humanoid robot can enhance living experience. The investigation is based on literature review in the area of Smart Cities and ICT focusing on Internet of Things, Cloud Computing, and Cognitive Computing, observation of services on Bluemix, and interview with consultants and engineers of IBM. The services of Watson cognitive computing system enable Pepper to process unstructured information and interact with humans. The results also contain use cases of the functionality of Watson-powered Pepper, which could be further implemented for public services.

  • Public defence: 2017-04-10 14:00 F3, Stockholm
    Marzinotto, Alejandro
    KTH, School of Computer Science and Communication (CSC), Robotics, perception and learning, RPL.
    Flexible Robot to Object Interactions Through Rigid and Deformable Cages2017Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    In this thesis we study the problem of robotic interaction with objects from a flexible perspective that complements the rigid force-closure approach. In a flexible interaction the object is not firmly bound to the robot (immobilized), which leads to many interesting scenarios. We focus on the secure kind of flexible interactions, commonly referred to as caging grasps. In this context, the adjective secure implies that the object is not able to escape arbitrarily far away from the robot which is caging it. A cage is a secure flexible interaction because it does not immobilize the object, but restricts its motion to a finite set of possible configurations. We study cages in two novel scenarios for objects with holes: caging through multi-agent cooperation and through dual-arm knotting with a rope. From these two case studies, we were able to analyze the caging problem in a broader perspective leading to the definition of a hierarchical classification of flexible interactions and cages.

    In parallel to the geometric and physical problem of flexible interactions with objects, we study also the problem of discrete action scheduling through a novel control architecture called Behavior Trees (BTs). In this thesis we propose a formulation that unifies the competing BT philosophies into a single framework. We analyze how the mainstream BT formulations differ from each other, as well as their benefits and limitations. We also compare the plan representation capabilities of BTs with respect to the traditional approach of Controlled Hybrid Dynamical Systems (CHDSs). In this regard, we present bidirectional translation algorithms between such representations as well as the necessary and sufficient conditions for translation convergence. Lastly, we demonstrate our action scheduling BT architecture showcasing the aforementioned caging scenarios, as well as other examples that show how BTs can be interfaced with other high level planners.

  • Persson, Tobias
    KTH, School of Engineering Sciences (SCI), Mechanics.
    Wind Tunnel Effects on Truck Aerodynamica and Soiling2017Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
  • Lyu, Zhipeng
    KTH, School of Engineering Sciences (SCI), Mechanics.
    Aerodynamic Wind Tunnel in Passenger Car Application2016Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    The thesis aims to provide an evaluation on the Volvo 1/5th scaled wind tunnel regarding its potentials and capabilities in aerodynamic study. The flow quality in the test section was evaluated. The experiments were performed included measurements of airspeed stability, tunnel-wall boundary layer profile and horizontal buoyancy. A numerical model was developed to predict the boundary layer thickness on the test floor. Repeatability tests were also conducted to establish the appropriate operating regime.A correlation study between the 1/5th scaled wind tunnel (MWT) and full scale wind tunnel (PVT) was performed using steady force and unsteady pressure measurements. The Volvo Aero 2020 concept car was selected to be the test model.The Reynolds effect and the tunnel-wall boundary layer interference were identified in the steady force measurements. Unsteady near-wake phenomena such as wake pumping and wake flapping were discussed in the unsteady base pressure measurements.

  • Gallarotti, Maura
    KTH, School of Engineering Sciences (SCI), Mechanics.
    CFD ANALYSIS ON THE COOLING OF NON GUIDED OIL NATURAL AIR NATURAL TYPES OF TRANSFORMERS2016Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    ABB is moving towards more powerful and compact transformers and an efficient cooling is of paramount importance in order to avoid overheating.In this master thesis, transformers without guides for the oil flow have been analysed: they allow a faster and cheaper manufacturing process, but at the same time the absence of guides makes the cooling design more difficult.In order to be able to perform several parametric studies, a script with the Pointwise mesher has been developed for the automatic generation of the geometry and mesh of transformer windings. This has allowed to analyse transformer windings with a different shape, assessing the effect of a certain number of geometrical parameters on the cooling efficiency.The software ANSYS Fluent was used to perform 2D axisymmetric unsteady simulations on the company cluster and the simulation set up was validated thanks to comparison with experimental measurements in ABB in Vaasa (Finland), that showed an average relative error below 2%.A remarkable result of this study is the identification of a periodic pattern in the temperature of the windings from the inlet to the outlet of the transformer, with hot spot locations every 10-20 disc windings. This conclusion has also been confirmed by the experimental measurements performed in Vaasa on a test transformer. Furthermore, a periodic behaviour of the temperature of the windings and of the oil in time has also been identified.Finally, transformers with an additional cooling channel in the disc windings have been studied, revealing that an accurate design is needed when adding oil channels through the windings in order to avoid the formation of unexpected hot spots.

  • Bergsjö, Cathrina
    et al.
    KTH, School of Engineering Sciences (SCI), Mechanics.
    Pettersson, Marcus
    KTH, School of Engineering Sciences (SCI), Mechanics.
    A Simulation of the Millau Viaduct2016Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    Cable-stayed bridges have become very popular over the last ve decades due totheir aesthetic appeal, structural eciency, the limited amount of material usageand nancial benets. The rapid increase of new techniques creating longer spans,slender decks and more spectacular design has given rise to a major concern ofthe dynamic behavior of cable-stayed bridges. This has resulted in a more carefulmodelling procedure that will represent the reality in the most particular way. Amodel is simply an approximation of the reality, thus it is important to establishwhat simplications and approximations that are reasonable to make in order forthe model to be as accurate as possible.The Millau Viaduct is a cable-stayed bridge unique of its kind. At the time thatit was built it was breaking many records: span length, height of deck above thefoundations and the short construction time in just three years. Due to the slendernessof the structure, the extreme height and the location in a deep valley, theviaduct is naturally subjected to external loads. This thesis attempts to describea performed dynamic nonlinear analysis of two models of the Millau Viaduct usingthe FEA packages SAP2000 and BRIGADE/Plus. The models have been renedin order to be compared between the programs and to the reality i.e. the measuredmode shapes and frequencies obtained from reports.The viaduct required many specically designed solutions in order to obtain theelegance and the aesthetic appeal. Approximations in geometry has been essentialdue to the many details that the viaduct consists of, but the details are nonethelessimportant to capture to get the structural mechanics correct. The support conditionshas been considered as important as these were designed to allow for movementthat were caused by a combination of the external loads and the slenderness of thestructure. The most critical support conditions were the deck-pier connection inwhich the piers are split into two columns equipped with spherical bearings allowingfor angular rotation. The two shafts were modelled by one single column and thespherical bearings were simulated by creating two alternative models; one assignedwith a pinned constraint to allow for the angular rotation and the second, since thissupport condition is in fact rigid has been assigned as xed.The SAP and BRIGADE models showed to be consistent with each other, thoughthe beam theories, Euler-Bernoulli were applied to the SAP model and Timoshenkoin BRIGADE. The alternative models with the dierent constraints generated fairresults yet diers signicantly from each other. Alternative approaches towards themodelling have been addressed in the conclusions.

  • YIN, XING
    KTH, School of Architecture and the Built Environment (ABE), Urban Planning and Environment, Urban and Regional Studies.
    Design to Promote UrbanEcosystem Services: Examples of solutions with green - blueinfrastructure in public spaces2017Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    The world is increasingly urbanizing with approximately 54% of the world population livingin cities (Langemeyer, 2015). This number is expected to rise to 66% by 2050 (UN, 2014),which means that urbanized areas will expand in size with an additional 2.5 billion new urbaninhabitants (Langemeyer, 2015). Studies show that urban expansion has the effect ofdecreasing, fragmenting, and isolating natural patches by altering the size, shape, andinterconnectivity of the natural landscape (Ricketts, 2001; Alberti, 2005). The consequentloss and degradation of urban and peri-urban green/blue space and elements couldadversely affect ecosystem and its services as well as human health and well-being.Through literature review, the concepts of urban ecosystem services and green-blueinfrastructures are introduced, as well as the main design principles for green-blueinfrastructures. The thesis also briefly introduces urban policies and implementation throughcase study with a focus on Malmö city. Meanwhile, the thesis discusses how the planninginstruments of Green Space Factor and Green Points are used in the Bo01 project and howthey contributed to promote ecosystem services in built environment.Through literature review and case study, the aim of this thesis is to collect design solutionsthat can be used as inspiration and guidance to promote urban ecosystem services throughgreen-blue infrastructures in built environments at different scales.

  • Garcia Pardo, Diego
    KTH, School of Engineering Sciences (SCI), Mechanics.
    Piston bowl combustion simulation - From fuel spray calibration to emissions minimization2016Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    The current pollution policies in all European and American countries are forcing the industry to movetowards a more efficient and environmentally friendly engines. On the other hand, customers requiremaintaining the power and fuel consumption. Lowering mainly nitrous oxides (NOx) and carbon particles(Soot) is therefore a challenging task with a very strong impact on mainly the automotive andaeronautical market.The purpose of the current work is to research the pollution production of automotive diesel enginesand optimize the fuel injection and piston geometry to lower the emissions. The interaction betweenfuel and air as well as the combustion are the two main physical and chemical processes governing thepollutants formation. Converged-CFD will be the CFD tool employed during the analysis of the previousproblems.The fuel-air interaction is related to jet break up, vaporization and turbulence. The strong dependenceon the surrounding flow field of the previous processes require the equations to be solved numericallywithin a CFD code. The fuel is to be placed in a combustion chamber (piston) where the spray will affectthe surrounding flow field and ultimately the combustion process.In order to accurately represent the nature of the processes, the current work is divided into two mainchapters. Spray modelling and Combustion Modelling. The first will help to accurately model the discretephase (fuel spray) and the vapour entrainment. The second chapter, combustion modelling willretrieve the knowledge gain in the first part to accurately represent the fuel injection in the chamber aswell as the combustion process to ultimately model the pollutants emissions.Finally, a piston bowl optimization will be performed using the previous analysed models and give theindustry a measure of the potential improvement by just adjusting the fuel injection or by modifyingthe piston bowl geometry.

  • Catagay, Daniel
    et al.
    KTH, School of Engineering Sciences (SCI), Mechanics.
    Yuan, Haoqian
    KTH, School of Engineering Sciences (SCI), Mechanics.
    Lifting body design and CFD analysis of a novellong range pentacopter, the TILT LR drone2016Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    In the thesis, a lifting body has been designed aiming to generate lift force for the pentacopter,called TILT LR (Long Range), at higher velocities during flights to improve the aerodynamicperformances. The configuration, which is used as the skeleton of the long range drone for upto 75 kilometers flights, is based upon a tilting system allowing the rotors to rotate around theirown axis in both pitch and roll angles. This offers the possibility to the TILT LR flying withoutany vertical excess thrust at a proper angle of attack and velocity. This new drone can be directlyapplied to missions require long flight time or cover long distance, such as Search & Rescue(SAR), power lines and off-shore structures inspection, fire monitoring or surveillance.Several main CAD models have been created during the process of design and presented in thereport together with the final design. For each model in the process, CFD simulations have beenapplied to observe the behaviors of the flows around the surfaces of the body during steadyflights, followed by a brief analysis for further modification. A series of simulations withvarying velocities and angle of attack have been performed for the final design, analyzing itsperformances under different air conditions. Flight envelope of the design has been presentedalso, together with some ideas of possible further studies on the pentacopter.

  • Public defence: 2017-04-13 10:00 Gardaulan, Stockholm
    Ramachandraiah, Harisha
    KTH, School of Biotechnology (BIO), Proteomics and Nanobiotechnology.
    Microfluidic based isolation of circulating tumor cells from whole blood for cancer diagnostics2017Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    Detection of circulating tumor cells (CTC) in peripheral blood is indicative of early recognition of tumor progression and such an important biomarker for early diagnosis, staging, monitoring and prognosis of cancer. However, CTC are found in very low concentrations and reliable isolation of these rare cells is challenging. Microfluidics enables precise manipulation of fluids and cells and is ideal for cell sorting methods for clinical diagnostics. The thesis contributes towards the development of microfluidic based CTC isolation methods from peripheral blood. The methods are based on size and immunoaffinity. The first part of the thesis describes the phenomenon of inertial focusing for size based cell separation at high throughputs. In paper 1, we demonstrate continuous filtration of leukocytes from diluted blood, with an efficiency of 78% at a flow rate of 2.2ml/min. In the paper 2, separation of total and subpopulation of leukocytes with a purity of 86% for granulocytes and 91% for lymphocytes is demonstrated. Furthermore, cancer cells spiked into whole blood could be separated at a yield of 88%. Finally, in paper 3 and 4 we unravel parts of the unexplored elasto-inertial microfluidics and was utilized to precisely focus the cells, as part of an integrated optofluidic micro flow cytometer device, capable to simultaneously measure fluorescence and scattering of cells and particles at a rate of 2500 particles/sec (paper 4). Second part of the thesis focuses on acoustophoresis. In (paper 5), a multifunctional acoustic microdevice was developed for isolation of cancer cells from red blood cells with a separation efficiency of 92.4% and trapping efficiency of 93%. In (paper 6), microbubbles activated acoustic cell sorter was developed for affinity based cell separation. As a proof of principle, cancer cells in a suspension were separated at an efficiency of 75%. In the third part, using cellulose nano fibrils (paper 7), we demonstrate efficiently capture and release of cancer cells at a release efficiency of 95%. Finally, a novel, single step self-assembly of spider silk proteins is introduced inside microfluidic channels for effective capture of cancer cells with 85% capture efficiency and subsequent release of captured cells with 95% release efficiency (paper 8). The novel recombinant silk modified microfluidic device was validated using pancreatic cancer patients. In summary, we have developed different microfluidic based isolation technologies for the capture and characterization of CTC.

  • Norrby, David
    KTH, School of Engineering Sciences (SCI), Mechanics.
    A CFD Study Of The Aerodynamic Eects OfPlatooning Trucks2014Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    In the present work the aerodynamic forces on trucks driving in so-called platoon are

    investigated in a numerical fashion. Driving in platoon, or convoy, refers to in an orderly

    manner driving in a line, one truck after the other, taking advantage of the unrecovered

    _ow behind each truck. The phenomenon is called slipstreaming or drafting. The Compu-

    tational Fluid Dynamics (CFD) software STAR-CCM+ is used to calculate the flow field

    around a platoon consisting of two and three trucks at different distances, ranging from 5

    to 70 m. Two numerical approaches are used, one is the Reynolds Averaged Navier Stokes

    based (RANS) two-equation turbulence model k 􀀀 " realizable model with a two-layer

    treatment. The second one is the Menter's Shear Stress Transport (SST) k 􀀀 ! Detached

    Eddy Simulation (DES) model. The first one is time independent, so-called steady-state,

    where platoons consisting of two and three trucks are used in the simulations. However,

    the nature of the flow field around vehicles is inherently time-dependent, which makes

    it difficult to receive a steady-state solution and thus, the reliability of the result is neg-

    atively affected. The second model is time dependent and much more computationally

    expensive, where only a platoon consisting of two trucks is simulated. Addition to this,

    simulations with an isolated truck will be conducted in order to make a relative study for

    both turbulence models. Since numerous of errors are introduced when approaching the

    problem numerically, it is important to have a reference case to compare with, set under

    the same conditions. Also, comparisons with other studies are done. A mesh independent

    study is conducted with the function of investigating how the mesh density influences the

    result, together with a mesh quality study, both helpful when assessing the credibility of

    the results.

    For the RANS approach, it is shown that for the 2-truck platoon, drag reductions

    are the greatest at the closest distance, 5 m, with 26:9 and 28:1 % reductions in drag

    for the leading and trailing vehicle, respectively, compared to the isolated case. There is

    an increase in drag for both vehicles with increasing distance, however, the trend turns

    around at 10 m for the trailing vehicle, where it also reaches its maximum, 5:5 % larger

    drag than that of the reference case's. Then a reduction is seen for all distances greater

    than 11 m. For the leading truck, the drag coeffcient CD is equal to the reference case's

    around 18 m, with an overshoot of 2 􀀀 3 % afterward, which may be a result of numerical

    errors. The same trend is seen for the 3-truck platoon, with largest reductions at the

    closest distance 5 m, with the reductions 31:5 %, 48:5 % and 33:2 % for truck one, two

    and three, respectively. At 10 m, there is also an abrupt increase in drag for the trailing

    trucks, however, the drag never reaches over the drag of an isolated truck. An overshoot

    is also seen for the first vehicle in the 3-truck platoon and it stops benefiting from platoon

    driving around 22 m. It was found that at 10, thick low-velocity boundary layers were

    formed on the leading trucks, which may be one of the reasons for the increase in drag.

    For the time-dependent approach, the drag behavior is similar to the RANS cases for

    the leading vehicle, but no overshoot is seen, instead the drag is always smaller than the

    reference case's. The maximum reduction is also found at 5 m, with the value 31:7 %. A

    completely different trend is found for the second vehicle, where the drag decreases with

    increasing distance, where there is a minimum reduction at 5 m (4:0 %) and a maximum

    reduction at the largest investigated distance 50 m (24:3 %). This kind of trend is also

    seen for the RANS-based simulation in the interval 10 􀀀 50 m, but the reductions are not

    as large. After 12 m, the trailing truck benefits the most.

    It was found that the vortices and the time dependence of the flow field are important

    features. The RANS-based model produced poor results in region of strong swirl and

    therefore it is not a suitable model for the flows of this type. Also, based on the good

    agreement with PowerFlow VLES (Very Large Eddy Simulation) simulations with the

    DES ones even further puts great distrust on the RANS simulations. The k 􀀀 " realizable

    model with a two-layer treatment has also shown deficiencies in predicting the downstream

    effects (over predicts) and the size and intensity of recirculation areas (for instance, the

    wake) as shown in the work of P.L. Davis, A.T. Rinehimer and M. Uddin, 20th Annual

    Conference of the CFD Society of Canada.

  • Bordogna, Marco Tito
    KTH, School of Engineering Sciences (SCI), Mechanics.
    Performance Evaluation of the EjectionSystem for the RAIN RocketExperiment2014Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    This master's thesis work was performed at the department of Mechanics of the RoyalInstitute of Technology (KTH) in Stockholm as part of my Master of Science studiesin Aerospace Engineering at KTH. This thesis study has two major purposes: (1) toevaluate the performance of the spring-based ejection system used in the RAIN rocketexperiment and (2) to suggest improvements to reduce de-spin and tip-o of the ejectedprobes.To evaluate the performance of the ejection system two sets of data have been analyzed:on-ground tests data and ight data. Data from on-ground ejection tests have beenanalyzed by means of video analysis and inertial sensor analysis while for ight dataonly inertial sensor data were available. Moreover, simple mechanical analytical modelshave been created to model the behavior of the probes during the ejection.The results from data analysis and mechanical models are able to suggests some improvementsfor the ejection system. However, it is not possible to make any strongconclusion on what might have caused the de-spin and the tip-o of the probes.

  • Acharya, Rutvika
    KTH, School of Engineering Sciences (SCI), Mechanics.
    Investigation of Differences in Ansys Solvers CFX and Fluent2016Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    This thesis aims at presenting Computational Fluid Dynamics studies conducted on an axisymmetric model of the Siemens SGT-800 burner using Ansys Fluent, Ansys CFX and Ansys ICEM. The goal is to perform a mesh study and turbulence model study for isothermal flow. The result will show the differences observed while using the two solvers by Ansys, Fluent and CFX. Two different meshes, A, coarse and B, optimal have been used for the mesh study. This will reveal the mesh dependency of the different parameters and if any differences are observed between the solver’s convergence and mesh independency performance. To further validate the mesh independency, a simplified test case is simulated for turbulent flow for 32 different cases testing the numerical algorithms and spatial discretization available in Ansys Fluent and finding the optimal method to achieve convergence and reliable results. Turbulence model study has been performed where k-ε, k-ω and k-ω Shear Stress Transport (SST) model have been simulated and the results between solvers and models are compared to see if the solvers’ way of handling the different models varies.Studies from this thesis suggest that both solvers implement the turbulence models differently. Out of the three models compared, k-ω SST is the model with least differences between solvers. The solution looks alike and therefore it could be suggested to use this model, whenever possible, for future studies when both solvers are used. For the models k-ε and k-ω significant differences were found between the two solvers when comparing velocity, pressure and turbulence kinetic energy. Different reasons for its occurrence are discussed in the thesis and also attempts have been made to rule out few of the reasons to narrow down the possible causes. One of the goals of the thesis was to also discuss the differences in user-interface and solver capabilities which have been presented in the conclusions and discussions section of the report. Questions that still remain unanswered after the thesis are why these differences are present between solvers and which of the solvers’ results are more reliable when these differences have been found.

  • Ma, Shuhan
    KTH, School of Electrical Engineering (EES), Electromagnetic Engineering.
    Load-current response to severe changes of voltage2017Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    Electric loads, such as computers, lamps, refrigerators and heaters connected to low-voltage distributionsystems in homes and offices differ widely in how their current responds to changes in the applied voltage.These voltage changes could be a total collapse of the voltage, a weak or strong reduction of amplitude,or a sudden phase-shift.This thesis investigates the currents into some modern power-electronic interfaced loads, at sub-cycletimescales, in response to sudden changes of AC voltage magnitude. One reason for this interest was anearlier project about fault-location methods in which the necessary level of modeling of loads wasquestioned [1]. A related issue that is also investigated is the response of such loads when Wye-connectedin a three-phase system with a high-impedance neutral such as a broken conductor.Several related matters have been studied a lot in other work. For example, active and reactive powerconsumptions of loads can change in response to the variation of voltage magnitude and frequency.Studies of power system oscillations, and angle and voltage stability, typically make use of such models.At distribution level, the relation of power consumption of loads to the feeder voltage has been includedin studies of Conservation Voltage Reduction (CVR). In these examples, the variation of voltage is typicallysmall, and the result is a value that summarizes an entire cycle (active or reactive power) without givinginformation about the current’s faster changes. Studies of voltage dip tolerance have instead workedwith larger changes of voltage, and short and variable durations, but without the resulting current beingthe interest.This thesis starts with a literature survey about different types of modern loads with differentcharacteristics, especially electronic loads which have become a far greater proportion of the totaldistribution-system load over the past several decades. It is known that the number of the electronicdevices has increased significantly due to the boom in the consumer electronic market. The most commonexamples of these loads include: computers, monitors, TVs and DVD players. Based on a survey of loadbehaviors and models, the current response of these loads to the voltage dips or recoveries are modeledby circuit simulation. Measurements of the currents into some computer equipment were performedwith voltage dips and recoveries, and compared to the results from models. The voltage amplitude dropsto 25%, 50% or 75% of its original value, and recovers afterwards. The current response is studied, focusingmainly during a short time period up to a few AC cycles. A similar mixture of simulation and measurementis then used to study the situation of the potential that arises at the neutral point of a three-phaseconnected electronic load when the neutral conductor has a high resistance.

  • Reimegård, Johan
    et al.
    Kundu, Snehangshu
    Pendle, Ali
    Irish, Vivian F
    Shaw, Peter
    Nakayama, Naomi
    Sundström, Jens F
    Emanuelsson, Olof
    KTH, School of Biotechnology (BIO), Gene Technology.
    Genome-wide identification of physically clustered genes suggests chromatin-level co-regulation in male reproductive development in Arabidopsis thaliana2017In: Nucleic Acids Research, ISSN 0305-1048, E-ISSN 1362-4962Article in journal (Refereed)
  • Public defence: 2017-04-07 10:00 Q2, Stockholm
    Aytekin, Arda
    KTH, School of Electrical Engineering (EES), Automatic Control.
    Asynchronous Algorithms for Large-Scale Optimization: Analysis and Implementation2017Licentiate thesis, monograph (Other academic)
    Abstract [en]

    This thesis proposes and analyzes several first-order methods for convex optimization, designed for parallel implementation in shared and distributed memory architectures. The theoretical focus is on designing algorithms that can run asynchronously, allowing computing nodes to execute their tasks with stale information without jeopardizing convergence to the optimal solution.

    The first part of the thesis focuses on shared memory architectures. We propose and analyze a family of algorithms to solve an unconstrained, smooth optimization problem consisting of a large number of component functions. Specifically, we investigate the effect of information delay, inherent in asynchronous implementations, on the convergence properties of the incremental prox-gradient descent method. Contrary to related proposals in the literature, we establish delay-insensitive convergence results: the proposed algorithms converge under any bounded information delay, and their constant step-size can be selected independently of the delay bound.

    Then, we shift focus to solving constrained, possibly non-smooth, optimization problems in a distributed memory architecture. This time, we propose and analyze two important families of gradient descent algorithms: asynchronous mini-batching and incremental aggregated gradient descent. In particular, for asynchronous mini-batching, we show that, by suitably choosing the algorithm parameters, one can recover the best-known convergence rates established for delay-free implementations, and expect a near-linear speedup with the number of computing nodes. Similarly, for incremental aggregated gradient descent, we establish global linear convergence rates for any bounded information delay.

    Extensive simulations and actual implementations of the algorithms in different platforms on representative real-world problems validate our theoretical results.

  • Winet, Martin
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering, Flight Dynamics.
    Development of an Automated Testing Tool for Flight Dynamic Models2016Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
  • V Krishna, Visakh
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering, Rail Vehicles.
    The potential of Fluid Dynamic Absorbers for railway vehicle suspensions2016Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    The main running objectives concerning the vertical dynamics of passenger rail vehicles are ride comfort and safety. The goal of this thesis is to employ the use of a Fluid Dynamic Absorber to minimize the vertical acceleration of the car body while minimizing the dy-namic force fluctuations in the wheel rail contact. The Fluid Dynamic Absorber is a device which employs a tube with a varying cross section containing oscillating fluid. The device is characterized by two effects: The inertia effect of the oscillating fluid in the varying cross section and the damping effect due to the pressure losses during the fluid flow. It is in-troduced as a potential damping device for automobiles and also for earthquake resistant buildings. The work encompasses the creation of a linearized approximation of the non-linear model for parameter selection. Then, a non-linear model is built with the help of the Modelica language for use in time simulation of quarter-car models in the Dymola interface. A generalized design methodology for the device is then developed with the help of design procedures used for common tuned mass dampers and liquid column dampers. Finally, the non-linear model built using the Dymola interface is also exported for use in the full-car model in Simpack using Functional Mock-up Interface. A reduction of about 4% to 5% in the magnitude of the root mean square of the carbody acceleration was observed while the wheel-rail dynamic forces remained the same. Further improvement possibilities and the parameters influencing the vertical dynamic behavior of the vehicle are discussed.

  • Pálinkó, Márton
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering, Rail Vehicles.
    Estimation of wheel-rail friction at vehicle certication measurements2016Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    In certification of new rail vehicles with respect to running characteristics, a wide variety of operating conditions needs to be considered. Behaviour on straight and curved tracks, including twisted tracks at various speeds, is of great importance. However, the wheel-rail friction should always be high corresponding to dry conditions. It means that the certification tests have to be carried out during dry weather conditions and unlubricated rails. But measuring the friction at test conditions is a great challenge.Therefore, in a recent work (Petrov et al.), an algorithm was proposed for the continu-ous estimation of wheel-rail friction along both rails. The algorithm is based on wheel-rail forces in all three directions (Y, Q, X ) for both wheels in a wheelset, lateral contact po-sition on its wheels and wheelset angle of attack. The algorithm was evaluated with a fictional vehicle with vehicle-track dynamics simulations on various tracks (straight and curves) and track irregularities.In cooperation with SNC Lavalin (formerly Interfleet Technology), an opportunity arose to get the required data from on-track tests. In this way, all nine quantities above were measured during test runs of a new vehicle, so the algorithm could be evaluated under realistic conditions. The tests in tight curves of radius 150 m are used in the present work for this purpose. The measured data and the algorithm were processed in a Matlab program to get the friction estimate. Apart from the friction, the creepages and spin are also estimated with the aim to serve as quality indicators of the estimated friction.As the vehicle measurements include noise, errors and uncertainties, a statistical tool was introduced. Moreover, a sensitivity analysis was performed. It was observed that in these tight curves, the friction estimation on the outer wheel is poor, but a phenomenon arose that with increasing spin corresponding to even higher contact angle the friction might be estimated again. However, small spin gives a good friction estimation provided the total creep is high enough. Therefore, sharp curves, traction/braking or large track irregularities are necessary to estimate the friction well.In order to continue the work deeper into the area, other tests with the above scenarios would be useful

  • Palmquist, Jonatan
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering, Lightweight Structures.
    Structural Health Monitoring of Composite Fan Outlet Guide Vane: Detecting damages and impacts using piezoelectric wafer active sensors and Lamb waves2016Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    The use of composite materials within the aerospace industry has increased in the last decades and is still on the rise. Most composite applications are in the aircraft body parts but engine components such as fan blades and fan outlet guide vanes (FOGV) are now also to be found. Metals are well studied and both their fatigue and cracking behavior are well known but for composites this is not the case. Composites also have problems such as micro-cracking, delamination and porosity, which all can be difficult to detect but yet result in significant decreas in load carrying capacity. The ability to monitor a structure in real time would increase safety, lead to a reduction of maintenance costs, both in terms of reduced downtime and easier repairs, and allow for reduced requirements in design loads. One of the most promising techniques for a structural health monitoring system is using Lamb waves since they have a great ability to propagate over large area and have good sensitivity and resolution. A number of carbon fiber FOGV, equipped with piezoelectric transducers, has been manufactured at GKN Aerospace Sweden AB. By using the piezoelectric transducers to send a wave pulses through the structures and compare the pulse response for a damaged and an undamaged case, it has been investigated if it is possible to detect damages, what the main limitations of the system are and if there are any possible improvements to be made. The piezoelectric elements ability to detect impacts has also been investigated. Most of the testing has been performed on a carbon fiber sandwich plate, to then apply the same principles for a FOGV. Lamb waves do indeed seem to have a great potential for detecting damages and a difference between the undamaged plate and the damaged plate could be observed both in the root mean square value, the peak-to-peak alue, the time of flight and the frequency content of the pulse response. The piezoelectric sensors are very sensitive and have a great ability to detect impacts. The greatest limitations encountered during the project have been problems with the hardware, both with the amplifiers used and restrictions in data acquisition unit. Other limitations of the system are the sensitivity due to changes of boundary conditions and disturbances form external sources.

  • O’Brien, Joseph
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering, Naval Systems.
    Course Stability of a Towed Submarine Rescue Vehicle A manoeuvre-based approach2016Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    Marine vessels designed to be self-propelled are generally unstable when towed. Submarines are not an exception; holding a course while towing a surfaced submarine is a challenging operation that often requires several tug boats or special methods. The Swedish navy’s submarine rescue vehicle URF, for example, is directionally unstable when being towed at lower speeds, and this report examines methods of improving URF’s course stability under these circumstances. An experimental evaluation was conducted to assess the effect of static trim angle on URF’s course stability; by adjusting URF’s trim angle, the center of pressure can be shifted in a way that is favourable to course stability. A 1:19 scale model was developed and towed in calm water at equivalent full-scale speeds of 2 to 8 knots and at trim angles between 0 and 15 degrees. Course stability was assessed on the basis of the model’s observed behaviour during towing, including the model’s maximum angle during wandering, stable angle, tendency to dive and behaviour upon sudden release of the towline.

  • Möller, Niklas
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering, Naval Systems.
    Development of an automatic autonomous sensor carrier for sound profile measurement in deep sea2016Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    This Master Thesis main purpose was to answer the question "Can you measure or calculate the velocity sound profile while performing a bathrymetric survey in an offshore environment like the North Sea, without any interaction nor modification of the existing equipment?".This, since today underwater surveys are a complex and expensive operation to perform where you either are mapping the sea floor or on a searching mission for a sunken wrecks. To achieve this successfully, one has to ensure that the accuracy of the position for every discovery or created map over the sea floor is entirely correct. This is an identified problem since the bathrymetric device sends its position by sonar, which relies in the sound propagation velocity, which in return varies with the water density. In order to increase the accuracy one need to determine the water density for all depths, i.e measure the salinity and temperature between the towing ship and the device that travels close to the sea bed. This because of layers consisting of fresh water and saltwater that never entirely mixes with each other in the ocean.The outcome of this project is a manufactured conceptual design of an autonomous sensor carrier that has the ability to measure temperature to a theoretical maximum depth down to 150m. It ascends and descends autonomously with an propagation speed of 0.54m/s in a static condition along an existing tether line, connected to a bathrymetric device that follows the sea floor. The sensor carrier ascend and descends its motion with help of two connected drive wheels powered by an electric motor, combined with two hall sensors to to reverse its movement when reaching desired depth. It has the ability to store sampled data onto a removable SD card, with a theoretical maximum endurance of 6,2km and it can be handled by one single person.Unfortunately, the concept as a whole is not entirely successful, and must therefore be supplemented within some areas. The major occurrence is that the drive mechanism tender to slip along the tether when climbing in vertical direction with a risk of damaging the tether coating. Furthermore one needs to increase the operational depth rating. This to be able to utilize the sensor carrier at all depths in the North Sea and also the Baltic Sea. However, the project as whole has achieved a solid framework and platform ready to be developed further in a future second version.

  • Mohlin, Martin
    et al.
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering, Lightweight Structures.
    Hanneberg, Mikael
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering, Lightweight Structures.
    Chassis component made of composite material: An investigation of composites in the automotive industry and the redesign of a chassis component2016Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    The demands on fuel efficiency and environmental friendliness of cars have driven the automotive industry towards composite materials which reduce the weight compared to the traditional aluminum and steel solutions. The purpose of this master thesis is to evaluate the possibility and feasibility of redesigning a high volume metal chassis part in composite materials.  To accomplish this the thesis work was divided into two parts. The first part consists of a composite study which explores the available composite technologies in the industry such as implemented chassis components and available manufacturing methods. The composite study shows that almost no high volume chassis component in the market are made out of composites, with exception to leaf springs. In the industry there are many different composite manufacturing methods but in general the most ready for high volume production are Injection molding, compression molding and RTM. A method was also explored to efficiently evaluate different material and manufacturing methods against each other. By knowing the critical requirement both materials and manufacturing methods can be evaluated separately against each other. The second part consists of a design phase where the knowledge from the composite study was used to choose and redesign a chassis component in composite. A motor mount was chosen and redesigned using injection molding. The new design shows that a weight decrease of at least 38% is possible without significant cost differences. 

  • Menzio, Davide
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering.
    Long term chaotic attitude behaviour on highly eccentric orbits: INTEGRAL Case Study2016Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    The main issues discussed in this paper are related to the refinement of the on-ground casualty risk computation for the specific case of INTErnational Gamma-Ray Astrophysics Laboratory (INTEGRAL). The current approach, unable to predict the spacecraft attitude motion, assumes random tumbling motion as initial condition to simulate the fragmentation process. The wide experience in break-up analysis, acquired after years of practice with simulation, identified attitude to be one of the major drivers of uncertainty. The Space Debris Office (SDO) demanded a specific research in the field of the long-term propagation applied to the attitude motion and INTEGRAL offered the perfect test bench to conduct a preliminary study in this direction. In particular, observing whether environmental torques were able to trigger stable attitude motion, maintainable till re-entry, was considered to be the major challenge. The propagation of coupled orbital􀀀attitude motion for a random attitude configuration represents only one side of the coin. Indeed, chaos theory analysis constituted the other. The use of the Poincaré map in a non-canonical way managed to bring evidence for constrained motion in the angular rate motion of INTEGRAL, under gravity perturbations. Such results allowed to conduct further investigation on the overall attitude motion and estimate that the attitude configuration at the re-entry appears as precession about the maximum axis of inertia, in the majority of the cases.