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  • Public defence: 2018-01-26 09:00 Kollegiesalen, Stockholm
    Jerpdal, Lars
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering, Lightweight Structures.
    Processing of self-reinforced poly(ethylene terephthalate) composites for automotive applications2017Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    The vehicles of the future must have less negative environmental impact during their use phase than the vehicles of today in order to avoid major climate change on earth. Consequently electric vehicles are currently under development with the purpose of reducing CO2 emissions when the vehicle is

    driven. There are also efforts put in to reducing the weight of vehicles in order to reduce the demand for energy to drive them. One important aspect of weight reduction is that new materials and technologies are developed. Plastic materials have low a density and can therefore be used to reduce the weight of vehicle components and with composite materials there is further potential for weight reduction. Self-reinforced thermoplastic composite materials are materials in which both reinforcement and matrix are thermoplastic materials and thanks to their low density and relatively good mechanical properties, these materials may be used for weight reduction of vehicle components.

     

    The aim of this thesis is to study selected process parameters for component manufacturing with self-reinforced poly(ethylene terephthalate) (SrPET) in order to increase knowledge and thereby advance the field of self-reinforced PET composites. This thesis shows that stretching the material in the manufacturing process increases the mechanical performance of the material due to increased orientation of the amorphous phase in the PET reinforcement. However, stretching introduces stresses in the material that give rise to negative shape distortions in the formed component. The degree of stretching during forming must therefore be controlled in order to achieve a robust serial production. The concept of a SrPET component over-moulded for integration of stiffeners and attachments has been evaluated in a life-cycle-assessment. This evaluation shows that the component weight can be reduced compared to technology currently in use and thereby contribute to increased sustainability of transport.

  • Public defence: 2017-12-19 10:00 Q2, Stockholm
    Talebi Mazraeh Shahi, Mohammad Sadegh
    KTH, School of Electrical Engineering (EES), Automatic Control.
    Minimizing Regret in Combinatorial Bandits and Reinforcement Learning2017Doctoral thesis, monograph (Other academic)
    Abstract [en]

    This thesis investigates sequential decision making tasks that fall in the framework of reinforcement learning (RL). These tasks involve a decision maker repeatedly interacting with an environment modeled by an unknown finite Markov decision process (MDP), who wishes to maximize a notion of reward accumulated during her experience. Her performance can be measured through the notion of regret, which compares her accumulated expected reward against that achieved by an oracle algorithm always following an optimal behavior. In order to maximize her accumulated reward, or equivalently to minimize the regret, she needs to face a trade-off between exploration and exploitation.

    The first part of this thesis investigates combinatorial multi-armed bandit (MAB) problems, which are RL problems whose state-space is a singleton. It also addresses some applications that can be cast as combinatorial MAB problems. The number of arms in such problems generically grows exponentially with the number of basic actions, but the rewards of various arms are correlated. Hence, the challenge in such problems is to exploit the underlying combinatorial structure.For these problems, we derive asymptotic (i.e., when the time horizon grows large) lower bounds on the regret of any admissible algorithm and investigate how these bounds scale with the dimension of the underlying combinatorial structure. We then propose several algorithms and provide finite-time analyses of their regret. The proposed algorithms efficiently exploit the structure of the problem, provide better performance guarantees than existing algorithms, and significantly outperform these algorithms in practice.

    The second part of the thesis concerns RL in an unknown and discrete MDP under the average-reward criterion. We develop some variations of the transportation lemma that could serve as novel tools for the regret analysis of RL algorithms. Revisiting existing regret lower bounds allows us to derive alternative bounds, which motivate that the local variance of the bias function of the MDP, i.e., the variance with respect to next-state transition laws, could serve as a notion of problem complexity for regret minimization in RL. Leveraging these tools also allows us to report a novel regret analysis of the KL-UCRL algorithm for ergodic MDPs. The leading term in our regret bound depends on the local variance of the bias function, thus coinciding with observations obtained from our presented lower bounds. Numerical evaluations in some benchmark MDPs indicate that the leading term of the derived bound can provide an order of magnitude improvement over previously known results for this algorithm.

  • Blom Västberg, Oskar
    KTH, School of Architecture and the Built Environment (ABE), Transport Science, System Analysis and Economics.
    Five papers on large scale dynamic discrete choice models of transportation2018Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    Travel demand models have long been used as tools by decision makers and researchers to analyse the effects of policies and infrastructure investments. The purpose of this thesis is to develop a travel demand model which is: sensitive to policies affecting timing of trips and time-space constraints; is consistent with microeconomics; and consistently treats the joint choice of the number of trips to perform during day as well as departure time, destination and mode for all trips. This is achieved using a dynamic discrete choice model (DDCM) of travel demand. The model further allows for a joint treatment of within-day travelling and between-day activity scheduling assuming that individuals are influenced by the past and considers the future when deciding what to do on a certain day.

    Paper I develops and provides estimation techniques for the daily component of the proposed travel demand model and present simulation results provides within sample validation of the model. Paper II extends the model to allow for correlation in preferences over the course of a day using a mixed-logit specification. Paper III introduces a day-to-day connection by using an infinite horizon DDCM. To allow for estimation of the combined model, Paper III develops conditions under which sequential estimation can be used to estimate very large scale DDCM models in situations where: the discrete state variable is partly latent but transitions are observed; the model repeatedly returns to a small set of states; and between these states there is no discounting, random error terms are i.i.d Gumble and transitions in the discrete state variable is deterministic given a decision.

    Paper IV develops a dynamic discrete continuous choice model for a household deciding on the number of cars to own, their fuel type and the yearly mileage for each car. It thus contributes to bridging the gap between discrete continuous choice models and DDCMs of car ownership.

    Infinite horizon DDCMs are commonly found in the literature and are used in, e.g., Paper III and IV in this thesis. It has been well established that the discount factor must be strictly less than one for such models to be well defined.Paper V show that it is possible to extend the framework to discount factors greater than one, allowing DDCM's to describe agents that: maximize the average utility per stage (when there is no discounting); value the future greater than the present and thus prefers improving sequences of outcomes implying that they take high costs early and reach a potential terminal state sooner than optimal.

  • Stankovic, Stefan
    et al.
    KTH, School of Electrical Engineering (EES), Electric Power and Energy Systems.
    Söder, Lennart
    KTH, School of Electrical Engineering (EES), Electric Power and Energy Systems.
    Cable Impact on Integration of Wind and Solar Power2017Conference paper (Refereed)
  • Public defence: 2018-01-25 13:00 Stockholm
    Ghafoori Roozbahany, Ehsan
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Building Materials.
    Flow behavior of asphalt mixtures under compaction2017Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    Asphalt compaction is one of the most important phases of road construction, being the decisive phase when the structure of the asphalt pavement layer is formed. In spite of its importance, the knowledge about this construction phase is still based on empirical and technological background and therefore surprisingly limited. This lack of knowledge is also due to the fact that the existing laboratory scale compaction devices for mix design are not fully capable of simulating the field compaction. The simulation of asphalt compaction in the laboratory is normally focused on the vertical rearrangements of asphalt particles whereas the flow behavior of these particles in other directions is mostly neglected. However, existing literature suggests that the neglected flow is one of the most important factors for the quality of the road construction, particularly in special cases such as asphalt joints. Therefore, building up a better understanding of the flow behavior of asphalt mixtures subjected to compaction loads is needed for improving the quality of the pavements.

    In this study, a new test setup, the so called Compaction Flow Test (CFT), was developed to simulate the flow behavior of asphalt mixtures at early stages of compaction. In the first step, feasibility tests were performed, substituting asphalt mixtures by model materials with simple geometries and less complex properties. X-ray Computed Tomography (CT) was utilized for capturing 2D radiography images of the flow patterns in the model material during the test. Results of the CFT showed the capability of the new test setup to clearly distinguish between model mixtures with different characteristics. Hence, in the next step, the CFT was applied to real asphalt mixtures and the obtained results were found to support the findings of the feasibility tests with the model materials.

    The results from the feasibility tests encouraged examining the possible use of an ultrasonic sensor as alternative to the complex and costly X-ray imaging for flow measurements during the CFT. Hence, the CFT was used along with a distance measuring ultrasonic sensor for testing asphalt mixtures with different characteristics. The test results confirmed that an ultrasonic sensor could be effective for capturing the differences of the flow behavior of asphalt mixtures tested by the CFT. 

    In addition, a parametric study with the X-ray setup was carried out to examine the capability of the CFT in reflecting the possible changes of the flow behavior in asphalt mixtures due to the change of construction parameters such as lift thickness, bottom roughness and compaction modes. The results obtained also confirmed the capability of the CFT in showing the possible differences in the flow behavior of the mixtures under the chosen conditions.

    The encouraging results suggested that the CFT may have potential to become a simple but effective tool for assessing compactability of the mixtures on-site, right after production in an asphalt plant or before placing the mixture on the road. Hence, discrete element method (DEM) was utilized to understand both the influence of selected boundaries of the CFT and the effect of its design on the results.

    As one specific example of application, an investigation was carried out using the CFT to find the most suitable tracking method for flow measurements in the field. Based on the literature review and feasibility tests, a tracking method with the highest potential for conducting flow measurements during field compaction was introduced. X-ray radiography confirmed the validity of the results obtained with the suggested method.

    The overall results obtained from this study suggest that the recommended CFT along with the suggested field tracking method may be helpful in building up a comprehensive basis of knowledge on the flow and compaction behavior of asphalt mixtures thus helping to close the gap between the field and laboratory.

  • Lind, Torbjörn
    et al.
    Walldius, Åke
    KTH, School of Computer Science and Communication (CSC).
    Certifieringsprotokoll User Certified 2006 TakeCare Journalsystem: Användarnas certifiering 20062009Other (Other academic)
  • Alfasfos, Rami
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology, Heat and Power Technology.
    Cavern Thermal Energy Storage for District Cooling. Feasibility Study on Mixing Mechanism in Cold Thermal Energy Storage2017Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
  • Laestander, Simon
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology, Heat and Power Technology.
    Battery- and Degradation Modeling of Hybrid Electric Heavy-Duty Long Hauler2017Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
  • Li, Jing
    KTH, School of Information and Communication Technology (ICT).
    Clustering and forecasting for rain attenuation time series data2017Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    Clustering is one of unsupervised learning algorithm to group similar objects into the same cluster and the objects in the same cluster are more similar to each other than those in the other clusters. Forecasting is making prediction based on the past data and efficient artificial intelligence models to predict data developing tendency, which can help to make appropriate decisions ahead.

    The datasets used in this thesis are the signal attenuation time series data from the microwave networks. Microwave networks are communication systems to transmit information between two fixed locations on the earth. They can support increasing capacity demands of mobile networks and play an important role in next generation wireless communication technology. But inherent vulnerability to random fluctuation such as rainfall will cause significant network performance degradation.

    In this thesis, K-means, Fuzzy c-means and 2-state Hidden Markov Model are used to develop one step and two step rain attenuation data clustering models. The forecasting models are designed based on k-nearest neighbor method and implemented with linear regression to predict the real-time rain attenuation in order to help microwave transport networks mitigate rain impact, make proper decisions ahead of time and improve the general performance.

  • Zhang, Xiaodong
    KTH, School of Information and Communication Technology (ICT).
    Multi-Cloud simulation environment for WebRTC streams2017Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    Real-time streaming is becoming popular nowadays on the internet. WebRTC is a promising web technology that enables media stream transmission between two browsers without other third-party plugins. However, traditional WebRTC applications can only establish peer-to-peer (P2P) communications, which cannot be directly used in one-to-more streaming scenarios such as a multi-party video conference.

    This thesis project presents a development of a multi-cloud simulation framework to implement software multicast of WebRTC streams to enable oneto-more real-time streaming. The framework can generate a cloud network topology with a simple script, and provides flexible ways to model the network links with parameters such as bandwidth, packet loss, and link latency. By using selective forwarding units (SFUs), a stream publisher only needs to send a single copy of the data to the cloud, the data packets are duplicated and forwarded to multiple subscribers. In addition, three resource allocation algorithms are included in the framework to determine the data center for a task.

    To evaluate the performance, this framework enables people to monitor the throughputs and running streams on the data centers during the experiments. We develop benchmark applications as substitutes for real WebRTC traffic. These applications can generate UDP stream packets with the same dimension of WebRTC packets and provide the customization of stream parameters. In this report, we present a comparison of the stream performances under different allocation algorithms. Finally, as an outcome of this project, we design an integrated functional test to simulate a real-world scenario. The result shows that the framework is able to work well on complex real cases and simulate most of the multi-cloud networks.

  • Sarah, Annisa
    KTH, School of Information and Communication Technology (ICT).
    Analysis of 5G Mobile Broadband Solutions in Rural and Remote Areas: A Case Study of Banten, Indonesia2017Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    Providing a broadband access anytime and anywhere is one of the visions of the future 5G network. However, deploying a reliable network connection in remote/rural areas has been a challenging task because of its wide area that needed to be covered and a low density of user compared to urban area. Different geography and traffic condition may need different system solution. In this thesis, we analyze several solutions to providing a broadband access network in practical remote and rural area in Banten, Indonesia: Leuwidamar (remote) and Panimbang (rural). Two approaches are discussed, first one is fulfilling futuristic traffic demand by having LTE System, and the second one is by having 5G System. We included three key technology components in a 5G network: occupying wide bandwidth in high frequency, applying UE-Specific Beamforming, and implementing Carrier Aggregation (CA) scheme. We also account a rain attenuation when deploying a network in high operating frequency, since Indonesia has a high rain rate thus it is important to be considered. We compared five cases of solution: Case 1 is Single Carrier (SC) LTE 1.8 GHz system; Case 2 is Carrier Aggregation (CA) LTE 1.8 GHz + 2.6 GHz; Case 3 is SC 5G 15GHz; Case 4 is SC 5G 28 GHz; Case 5 is CA LTE 1.8 GHz + 5G 15 GHz. Basedon the evaluation, in Leuwidamar scenario, Case 5 gives us the least number of BS needed in order to meet the futuristic requirement with only 1.6 x densification from the current network. In Panimbang, the least number of BS neededis offered by two cases, Case 3 and Case 5 without any additional BS needed(1x densification). However, the solution with the lowest energy consumption for both area is Case 3. This is due to the fact that the carrier aggregation scenario needs additional power to generate the second system. Furthermore, if we introduce cell DTX ability in the 5G network, the Case 3 can give us impressive amount of energy saving, with 97% saving for Leuwidamar and 94% saving for Panimbang, compared to Case 1 solution without any DTX Capability.

  • Palma, Michael
    et al.
    KTH, School of Information and Communication Technology (ICT).
    Zhou, Shidi
    KTH, School of Information and Communication Technology (ICT).
    A Web Scraper For Forums: Navigation and text extraction methods2017Independent thesis Basic level (degree of Bachelor), 10 credits / 15 HE creditsStudent thesis
    Abstract [en]

    Web forums are a popular way of exchanging information and discussing various topics. These websites usually have a special structure, divided into boards, threads and posts. Although the structure might be consistent across forums, the layout of each forum is different. The way a web forum presents the user posts is also very different from how a news website presents a single piece of information. All of this makes the navigation and extraction of text a hard task for web scrapers.

    The focus of this thesis is the development of a web scraper specialized in forums. Three different methods for text extraction are implemented and tested before choosing the most appropriate method for the task. The methods are Word Count, Text-Detection Framework and Text-to-Tag Ratio. The handling of link duplicates is also considered and solved by implementing a multi-layer bloom filter. The thesis is conducted applying a qualitative methodology. The results indicate that the

    Text-to-Tag Ratio has the best overall performance and gives the most desirable result in web forums. Thus, this was the selected methods to keep on the final version of the web scraper.

  • Nordström, Rikard
    et al.
    KTH, School of Information and Communication Technology (ICT).
    Gustafsson, Johan
    KTH, School of Information and Communication Technology (ICT).
    Förbättrad användarvänlighet hos kunskapsbeskrivningar för mjukvaruutveckling2017Independent thesis Basic level (professional degree), 10 credits / 15 HE creditsStudent thesis
    Abstract [en]

    Society’s need for software is drastically increasing in tandem with elevated requirements for functionality and security. It is therefore necessary to investigate what sort of competences are needed for high-quality development and maintenance of software. This investigation is of particular interest given the existing gap in competence between students of software engineering and demands of the industry.

    Software engineering skill descriptions that have been developed and revised by experts may be the link between education and industry. However, the skill descriptions that exist today — SWEBOK and ACM/IEEE Curriculum — lack a common structure, which presents an obstacle with respect to the establishment of such a link. An attempt to impose a suitable structure is made in the report Everything is Possible to Structure— Even the Software Engineering Body of Knowledge, which forms a partial basis for this study.

    This study explores an enhanced structure of the skill descriptions SWEBOK and ACM/IEEE curriculum. The explorative work is then extended by the development of a software system prototype that can improve the usability and user-friendliness of the skill descriptions’ contents. Additionally, the information in the prototype should be exportable and easily available. Ultimately, the goal of the enhanced structure and the prototype is to facilitate the evaluation of quality in software engineering curricula.

    The development of an information system that embodies the qualities of usability and user-friendliness can be performed using scientific methodology. In this qualitative study, the hypothetico-deductive method has been chosen. Additionally, a suitable choice of technology for the implementation is required. For the purpose of this study, Google Sheets and the Google Apps Script framework have been chosen.

    The result of the study is a concrete implementation of a system prototype as a Google Sheets spreadsheet with an underlying relational database. Moreover, the spreadsheet is extended with filtering functionality for various types of information. The prototype also offers the ability to assess and compare academic curricula based on software engineering skill descriptions. Lastly, the information in the prototype can be exported and used in its entirety.

    The results infer that software engineering skill descriptions found in literature can be structured, in addition to being made more usable and user-friendly. However, the developed prototype is in need of further evaluation and testing before its validity can be fully ascertained.

  • Jansson, Simon
    et al.
    KTH, School of Information and Communication Technology (ICT).
    Sandström, Theodor
    KTH, School of Information and Communication Technology (ICT).
    Mobile Framework for Real-Time Database Management2017Independent thesis Basic level (professional degree), 10 credits / 15 HE creditsStudent thesis
    Abstract [en]

    The primary purpose of this thesis is to explore what issues may arise during development of a framework for handling and display of streamed real-time data. In addition to this, it also investigates how the display of different types of data, along with a change of execution platform, impacts execution time.

    Through the undertaking of two case studies, each split into developmental and an experimental phases, the thesis goes through the development of such a real-time data handling framework. The framework was developed in both stationary and mobile forms, and the developmental issues encountered along each of these paths are highlighted. Afterwards, the results gathered from performance tests run on each framework version were compared, in order to ascertain whether the handling and display of different data types, along with a change in execution platform, had had an impact upon the frameworks execution time.

    The results from the developmental observations revealed that the most commonly encountered issues were those relating to program latency, commonly due to sub-optimal program architecture along with connectivity issues encountered during data streaming. The second most encountered issue regarded the choice of an appropriate display method, in order to communicate changes in the displayed data along with correlation between several tracked data points.

    The results from the experimental comparisons revealed that while the impact on execution time caused by the use of calculated data, as opposed to raw data values, was marginal at most, a change of execution platform impacted said time drastically. By porting the framework to the mobile platform, the different processes whose execution time were measured during the tests experienced an increase in execution time ranging from 2405% all the way to 15860%.

    The authors recommend that the framework be developed towards gaining the ability to connect to any given relational database, and to handle and display the data therein, in order for it to have application areas other than as a test instrument. Further, the authors also recommend that additional tests be run on the framework using a wider variety of stationary and mobile devices, in order to determine whether the conclusions drawn from the results in the thesis hold up in the face of greater hardware variety.

  • Amaya de la Pena, Ignacio
    KTH, School of Information and Communication Technology (ICT).
    Fraud detection in online payments using Spark ML: Master thesis performed in collaboration with Qliro AB2017Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    Frauds in online payments cause billions of dollars in losses every year. To reduce them, traditional fraud detection systems can be enhanced with the latest advances in machine learning, which usually require distributed computing frameworks to handle the big size of the available data.

    Previous academic work has failed to address fraud detection in real-world environments. To fill this gap, this thesis focuses on building a fraud detection classifier on Spark ML using real-world payment data.

    Class imbalance and non-stationarity reduced the performance of our models, so experiments to tackle those problems were performed. Our best results were achieved by applying undersampling and oversampling on the training data to reduce the class imbalance. Updating the model regularly to use the latest data also helped diminishing the negative effects of non-stationarity.

    A final machine learning model that leverages all our findings has been deployed at Qliro, an important online payments provider in the Nordics. This model periodically sends suspicious purchase orders for review to fraud investigators, enabling them to catch frauds that were missed before.

  • Phadke, Dhruv
    KTH, School of Industrial Engineering and Management (ITM), Machine Design (Dept.).
    Electrification of a diesel-hydraaulic off-road machine2017Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
  • Mörk, Therése
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology.
    Jonsson, Åsa
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology.
    Evaluation of alternative energy schemes for maximized electricity generation in a Cuban sugar mill2016Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
  • Öhman, Amanda
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology.
    Lundberg, Linnea
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology.
    Maximization of electricity generation or pelletization of the surplus bagasse in a Cuban sugar mill: A comparative analysis2016Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
  • Aaman, Sophia
    et al.
    KTH, School of Industrial Engineering and Management (ITM).
    Hessel Lundberg, Johan Henrik
    KTH, School of Industrial Engineering and Management (ITM).
    Setting the seeds for a green growth -A Study of biofuel development in Indonesia’s transport sector2017Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
  • Zhang, Huang
    KTH, School of Industrial Engineering and Management (ITM).
    Energy Modelling for Data CenterInfrastructure2017Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
  • Jansson Aldenfalk, Staffan
    KTH, School of Information and Communication Technology (ICT).
    Prediction of alarms in a pump station using neural networks2017Independent thesis Advanced level (professional degree), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    Prediction of pump station alarms based on data is an interesting future service for companies as it allows them to both offer a new service and reduce the downtime of the pumps. In order to predict the alarms a study of the available data was done in order to examine feasibility and identify problems. The chosen solution was to use two neural networks which were connected in a chain to create a complete solution. The first neural network used long short term memory (LSTM) neurons in order to recursively predict time-series data from sensors, such as sump water level and pump electric current, this was then used by the second LSTM neural network in order to determine if these parameter values would trigger an alarm. The second LSTM network was unable to determine if an alarm would happen and thus the whole solution did not work. There were two main reasons for this, the first being that the alarms stop time did not correlate to the time-series sensor data which created an uncertainty of which parameter levels actually belonged to an alarm, making the LSTM network unable to identify what an alarm is. The second reason was that the data was downsampled too much making it even harder for the LSTM network to identify what an alarm was. This thesis has helped Xylem further understand the use and needs of machine learning, which will help Xylem progress further into the area of predictive and smart services.

  • Parvez, Bilal
    KTH, School of Information and Communication Technology (ICT).
    Embedded Vision Machine Learning on Embedded Devices for Image classification in Industrial Internet of things2017Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    Because of Machine Learning, machines have become extremely good at image classification in near real time. With using significant training data, powerful machines can be trained to recognize images as good as any human would. Till now the norm has been to have pictures sent to a server and have the server recognize them. With increasing number of sensors the trend is moving towards edge computing to curb the increasing rate of data transfer and communication bottlenecks. The idea is to do the processing locally or as close to the sensor as possible and then only transmit actionable data to the server. While, this does solve plethora of communication problems, specially in industrial settings, it creates a new problem. The sensors need to do this computationally intensive image classification which is a challenge for embedded/wearable devices, due to their resource constrained nature.

    This thesis analyzes Machine Learning algorithms and libraries from the motivation of porting image classifiers to embedded devices. This includes, comparing different supervised Machine Learning approaches to image classification and figuring out which are most suited for being ported to embedded devices. Taking a step forward in making the process of testing and implementing Machine Learning algorithms as easy as their desktop counterparts. The goal is to ease the process of porting new image recognition and classification algorithms on a host of different embedded devices and to provide motivations behind design decisions.

    The final proposal goes through all design considerations and implements a prototype that is hardware independent. Which can be used as a reference for designing and then later porting of Machine Learning classifiers to embedded devices.

  • Bogati, Rajendra
    KTH, School of Information and Communication Technology (ICT).
    Performance Evaluation of Non-commercial LTE Network For Smart Grid Application: Modification of IEC 61850-90-5 Protocol stack and its Testing over Non-commercial LTE2017Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    The introduction of smart grid technology has changed the way traditional power grid network function. It made the grid structure more dynamic by enhancing electrical usage management capability. Also, it has increased the scope to enhance communication infrastructure in a smart grid structure. The current smart grid solution is based on IEC 61850 architecture where the exchange of information between the electrical utilities is over the fast Ethernet LAN connection. This communication mechanism is fast, efficient but lacks scalability, flexibility and less susceptible to failure. Also, earlier technical paper from IEC 61850 standard was for communication within a substation.

    Wide Area Monitoring Protection and Control implementation which utilizes coherent real time synchrophasor information would play a vital role in realizing the utility physical status. IEC 61850-90-5, a new technical report from International Electrotechnical Commission provides the mechanism to transmit and receive the synchrophasor information using the advance IP protocol over a wireless communication infrastructure for WAMPAC application. IEC 61850-90-5 provide a way to exchange routable synchrophasor information over public IP network such as LTE, WiMax, WLAN, etc. Out of all the available wireless solution, LTE provides high flexibility, distance coverage, data rate with low latency and hence can play an important role in replacing the existing communication structure in a smart grid.

    The thesis work evaluates the performance and applicability of LTE for smart grid communication. An IEC 61850-90-5 communication model utilizing UDP/IP protocol to transmit and receive data over the LTE network was developed from the open source project. The modified model was used to benchmark the performance of LTE. Different communication metrics such as reliability, availability, latency, and throughput was evaluated to benchmark the performance of LTE for time critical smart grid application. The metrics were measured for different packet sizes and transmission rates combination.

    The result shares some interesting findings on the readiness of LTE for smart grid solution. It is concluded that cellular network can play an important role in realizing communication infrastructure in a smart grid application.

  • Theorell, Jim
    KTH, School of Information and Communication Technology (ICT).
    Modular embedded system for electronic code locks2017Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    This thesis aims to build a modular embedded system for a set of pre defined constrains, including a code algorithm for temporary access codes. The system are to be physically adapted for electronic code locks and foremost a pre-existing lock. The thesis provides a set of tools that will be used for creating the system. Furthermore the choice of components and the design decisions are accounted for. The software of the system is discussed along with the choosen security solutions. Lastly it discusses the problems with product certifications that this kind of system has to face.

  • Zhu, Jixiang
    KTH, School of Information and Communication Technology (ICT).
    Computation Offloading and Task Scheduling among Multi-Robot Systems2017Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    In a Multi-Robot System (MRS), robots perform some collaborative behaviors so that some goals that are impossible for a single robot to achieve become feasible and attainable. Developing rapidly and exploited widely, cloud further extends the resources a robot can access thereby bringing significant potential benefits to robotic and automation systems. One of the potential benefits is Computation Offloading that moves the computational heavily parts of an application onto a server to reduce the execution time. However, to enable the computation offloading, the question must be answered when, what, where and how to offload? While some offloading mechanisms proposed in the mobile computing area (i.e., smartphones, pads), the question remains not fully answered and many new challenges emerge when it comes to the robotic realm.

    This paper aims to apply computation offloading technology to a Multi-Robot System and investigate the performance impact it has on the processing time of robot applications. For this purpose, a computation offloading framework is proposed for an elastic computing model with the engagement of a two-tier cloud infrastructure, i.e., a public cloud infrastructure and an ad-hoc local network (fog) formed by a cluster of robots. Two scheduling algorithms: Heterogeneous-Earliest-Finish-Time (HEFT) and Critical-Path-on-a-Processor (CPOP) are implemented to schedule the offloaded tasks to available robots and servers such that the total execution time of the application is minimized. The offloading framework is implemented based on Robot Operating System (ROS) and tested through simulated applications. The results prove the feasibility of proposed offloading framework and indicate potential execution speeding up of robot applications by exploiting offloading technology.

  • Purwidi, Gregorius Kristian
    KTH, School of Information and Communication Technology (ICT).
    Quantitative Analysis on the Feasibility and Benefits of Local Licensing2017Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    In-building connectivity in enterprises and vertical industries will emerge as an important use case of future 5G mobile services, given the fact that 80% of the traffic is generated indoor [1]. However, spectrum solution to this use case, which is unlicensed spectrum, may not be able to secure spectrum availability for large traffic demand as well as critical use case due to the nature of Listen-before-Talk (LBT) protocol.

    To cope with that, several novel spectrum sharing schemes have been discussed recently. One approach is to grant exclusive access to a spectrum in limited geographical area, or so called local licensing. It is motivated to reduce external interference from multiple networks that operates in a common area. This thesis evaluated such approach in terms of QoS improvement compared to unlicensed spectrum. To carry out the evaluation, two type of network deployment were simulated in three different scenarios:

    • unlicensed case (LBT-based system in overlapping deployment)

    • intermediate case (LBT-based system in non-overlapping deployment)

    • local licensed case (non-LBT system network in non-overlapping deployment)

      By simulating these three simulation scenarios, we have been able to compare two vari- ables (usage of LBT and deployment type) one by one.

      Comparing the first case (unlicensed) and third case (local licensed), the local li- censed case’s throughput does not decrease as rapidly as unlicensed case’s throughput when the traffic load increases. Local licensed case has 130% higher system capacity than unlicensed case in 10 Mbps QoS requirement. Between LBT and deployment type, LBT has more significant impact on the result. The increase of traffic load in LBT-based system caused a much significant increase in interference compared to non-LBT based system. LBT-based system performed well in low traffic, giving twice as much through- put as the third case, but the throughput also decrease rapidly as the traffic increase. Comparing the first and second case, the throughput gain of separating the deployment was not significant in LBT-based system.

      All in all, we proved that local licensing is worthwhile in term of QoS improvement compared to unlicensed case, given that the traffic load is high enough.

  • Ghosh, Binayak
    KTH, School of Information and Communication Technology (ICT).
    Opto-Acoustic Slopping Prediction System in Basic Oxygen Furnace Converters2017Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    Today, everyday objects are becoming more and more intelligent and some-times even have self-learning capabilities. These self-learning capacities in particular also act as catalysts for new developments in the steel industry.Technical developments that enhance the sustainability and productivity of steel production are very much in demand in the long-term. The methods of Industry 4.0 can support the steel production process in a way that enables steel to be produced in a more cost-effective and environmentally friendly manner.

    This thesis describes the development of an opto-acoustic system for the early detection of slag slopping in the BOF (Basic Oxygen Furnace) converter process. The prototype has been installed in Salzgitter Stahlwerks, a German steel plant for initial testing. It consists of an image monitoring camera at the converter mouth, a sound measurement system and an oscillation measurement device installed at the blowing lance. The camera signals are processed by a special image processing software. These signals are used to rate the amount of spilled slag and for a better interpretation of both the sound data and the oscillation data. A certain aspect of the opto-acoustic system for slopping detection is that all signals, i.e. optic, acoustic and vibratory, are affected by process-related parameters which are not always relevant for the slopping event. These uncertainties affect the prediction of the slopping phenomena and ultimately the reliability of the entire slopping system. Machine Learning algorithms have been been applied to predict the Slopping phenomenon based on the data from the sensors as well as the other process parameters.

  • Darda, Abu
    KTH, School of Information and Communication Technology (ICT).
    Modelling and Analysis of Substrate Noise in Delta Sigma ADCs2017Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    The rapid development in the semiconductors industry has enabled the placement of multiple chips on a single die. This has helped boost the functionality of modernday application specific integrated circuits (ASICs). Thus, digital circuits are being increasingly placed along-side analog and RF circuits in what are known as mixed signal circuits. As a result, the noise couplings through the substrate now have an increased role in mixed-signal ASIC design. Therefore, there is a need to study the effects of substrate noise and include them in the traditional design methodology.

    ∆Σ analog-to-digital converters (ADCs) are a perfect example of digital integration in traditionally analog circuits. ADCs, used to interface digital circuits to an analog world, are indispensable in mixed-signal systems and therefore set an interesting case study. A ∆Σ ADC is used in this thesis to study the effects of substrate noise. A background study is presented in the thesis to better understand ∆Σ modulators and substrate couplings. An intensive theoretical background on generation, propagation and reception of substrate noise is presented in light of existing researches.

    System and behavioural level models are proposed to include the effects of substrate noise in the design stages. A maximum decay of 10dB is seen due to injection of substrate noise system level simulations while a decay of 12dB is seen in behavioural simulations. A solution is proposed using controlled clock tree delays to overcome the effects of substrate noise. The solution is verified on both the system and behavioural levels. The noise models used to drive the studies can further be used in mixed-signal systems to design custom solutions.

  • Chen, Minjia
    et al.
    KTH, School of Information and Communication Technology (ICT).
    Engberg, Johan
    KTH, School of Information and Communication Technology (ICT).
    Satellite communication simulator for Cubsats2017Independent thesis Basic level (degree of Bachelor), 10 credits / 15 HE creditsStudent thesis
    Abstract [en]

    The Miniature Student Satellite (MIST) is a project at the Royal Institute of Technology in Stockholm, Sweden. The goal of the project is to launch a satellite designed and constructed by different student teams. The satellite carries seven scientific experiments that continuously collects experiment data as the satellite orbits the Earth. When the satellite is launched, the communication link between the satellite and the ground station is an essential part. This communication consists of a radio link between the on-board computer through a radio module and the ground station on Earth. Satellite communication is not a new field and there exist predefined communication standards and protocols. These standards and protocols are quite extensive and need to be tailored for the specific mission.

    Once a satellite is launched, it is out of reach for further development. This makes it crucial that the software running on the on-board computer are well tested and correctly integrated with the mission control system (MCS) that are used the send commands to control the satellite from Earth.

    Since satellite radio equipment is expensive, this bachelor thesis describes how to set up, implement and test an end-to-end communication chain between the satellite on-board computer and the MCS using a hardware simulator. The simulator both mimics the functionality of an on-board radio and replaces the ground station and radio link. Communication standards and protocols are studied and investigated, alongside with on-board pre-implemented subsystem libraries and an MCS named Elveit from Solenix. As the simulator also replaces the radio link, data transfer errors such as data loss, data corruption and, connection time windows can be simulated and tested.

    The simulator development results in a feasible end-to-end communication chain between the on-board computer and the MCS. This includes mimicking and acting as a radio module against the on-board computer, simulation of the radio link with the possibility to add transmission errors and, acting as a ground station against the MCS. To ensure that the simulator performs as the on-board radio module, the simulator performance is tested against the on-board computer. These results can be compared with on-board radio module performance to make sure that the behavior is similar.

  • Fu, Xinye
    KTH, School of Information and Communication Technology (ICT).
    Building Evolutionary Clustering Algorithms on Spark2017Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    Evolutionary clustering (EC) is a kind of clustering algorithm to handle the noise of time-evolved data. It can track the truth drift of clustering across time by considering history. EC tries to make clustering result fit both current data and historical data/model well, so each EC algorithm defines snapshot cost (SC) and temporal cost (TC) to reflect both requests. EC algorithms minimize both SC and TC by different methods, and they have different ability to deal with a different number of cluster, adding/deleting nodes, etc.Until now, there are more than 10 EC algorithms, but no survey about that. Therefore, a survey of EC is written in the thesis. The survey first introduces the application scenario of EC, the definition of EC, and the history of EC algorithms. Then two categories of EC algorithms model-level algorithms and data-level algorithms are introduced oneby-one. What’s more, each algorithm is compared with each other. Finally, performance prediction of algorithms is given. Algorithms which optimize the whole problem (i.e., optimize change parameter or don’t use change parameter to control), accept a change of cluster number perform best in theory.EC algorithm always processes large datasets and includes many iterative data-intensive computations, so they are suitable for implementing on Spark. Until now, there is no implementation of EC algorithm on Spark. Hence, four EC algorithms are implemented on Spark in the project. In the thesis, three aspects of the implementation are introduced. Firstly, algorithms which can parallelize well and have a wide application are selected to be implemented. Secondly, program design details for each algorithm have been described. Finally, implementations are verified by correctness and efficiency experiments.

  • Rashid, Zahin Azher
    KTH, School of Information and Communication Technology (ICT).
    Intelligent Scheduling for Yarn: Using Online Machine Learning2017Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    Many big companies who provide cloud infrastructure, platforms and services have to face a lot of challenges in dealing with big data and execution of thousands of tasks that run on servers. Thousands of servers running in cloud consume a large amount of energy which increases operating cost to a great extent for companies hosting infrastructures and platforms as services. Hundreds of thousands of applications are submitted every day on these servers by users. On submission of applications, somehow the total resources are not properly utilized which cause the overall operating cost to increase.

    A distribution of Apache Hadoop called HOPS is developed at SICS Swedish ICT and efforts are made to make it a better platform for institutions and companies. Yarn is used as the resource management and scheduling framework which is responsible for allocating resources such as memory and CPU cores to submitted applications. Yarn simply allocate resources based on the default set of values or what user has demanded. Yarn has no prior information about the submitted applications so it is very much possible that allocated resources are more or less than required. Energy is being wasted if fewer resources are required or application will probably not succeed if required more. In this research project, different techniques and methods are looked into for the collection of useful metrics related to applications and resources from Yarn, Spark and other sources.

    Machine Learning is becoming a very popular technique nowadays for the optimization of systems dealing with big data in a cloud environment. The goal is to collect these vital metrics and build a machine learning model to commission smart allocation of resources to submitted applications. This can help to increase the efficiency of the servers in the cloud and reduce the operating cost. Finally, a machine learning model was developed and memory and vCores were successfully predicted to be allocated to applications.

  • Sinha, Udayan Prabir
    KTH, School of Information and Communication Technology (ICT).
    Memory Management Error Detection in Parallel Software using a Simulated Hardware Platform2017Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    Memory management errors in concurrent software running on multi-core architectures can be difficult and costly to detect and repair. Examples of errors are usage of uninitialized memory, memory leaks, and data corruptions due to unintended overwrites of data that are not owned by the writing entity. If memory management errors could be detected at an early stage, for example when using a simulator before the software has been delivered and integrated in a product, significant savings could be achieved.

    This thesis investigates and develops methods for detection of usage of uninitialized memory in software that runs on a virtual hardware platform. The virtual hardware platform has models of Ericsson Radio Base Station hardware for baseband processing and digital radio processing. It is a bit-accurate representation of the underlying hardware, with models of processors and peripheral units, and it is used at Ericsson for software development and integration.

    There are tools available, such as Memcheck (Valgrind), and MemorySanitizer and AddressSanitizer (Clang), for memory management error detection. The features of such tools have been investigated, and memory management error detection algorithms were developed for a given processor’s instruction set. The error detection algorithms were implemented in a virtual platform, and issues and design considerations reflecting the application-specific instruction set architecture of the processor, were taken into account.

    A prototype implementation of memory error presentation with error locations mapped to the source code of the running program, and presentation of stack traces, was done, using functionality from a debugger. An experiment, using a purpose-built test program, was used to evaluate the error detection capability of the algorithms in the virtual platform, and for comparison with the error detection capability of Memcheck. The virtual platform implementation detects all known errors, except one, in the program and reports them to the user in an appropriate manner. There are false positives reported, mainly due to the limited awareness about the operating system used on the simulated processor

  • Castro Leiva, Luis Alfonso
    KTH, School of Information and Communication Technology (ICT).
    DDR3 memory integration for a softcore in a new radiation hardened FPGA technology2017Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    New and more capable electronics are required to push forward future space missions, and to pursue this goal the first step is the evaluation of novel technologies. The present thesis tackles the problem of evaluating new FPGA and memory technologies for spaceborne missions, while assessing its benefits and improvements. In this project, a novel soft SoC design based on the existing MDPA device was proposed and implemented. The new design includes a memory controller for the DDR3 technology, while targets a new radiation hardened FPGA technology. Additionally, the rad-hard FPGA is also assessed with the Cortex-R5 CPU to push its capabilities up to the limits. This latter, to find out how feasible is to use this FPGA to implement modern soft microprocessors. The thesis demonstrates that the new FPGA technology is able to match the current timing and resources requirements of the MDPA while improving its reliability. Also, it proves that the DDR3 technology has benefits over internal RAM in terms of bandwidth and capacity. Finally, it shows some problems when trying to use the FPGA technology to implement the Cortex-R5 CPU.

  • Bampi, Roberto
    KTH, School of Information and Communication Technology (ICT).
    LenticularFS: scalable hierarchical filesystem for the cloud2017Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    The Hadoop platform is the most common solution to handle the explosion of big-data that both companies and research institutions are facing. In order to store such data, the Hadoop platform provides HDFS, a scalable distributed filesystem which runs on commodity hardware and enables linear scalability by adding new storage nodes. While storage capacity of the system can be increased by adding new storage nodes, the component that handles metadata for the filesystem, the namenode, is a single point of failure and cannot easily replaced or linearly scaled. The Hops projects provides an alternative implementation of the namenode, which increases performance and scalability by storing metadata on an external distributed NewSQL database called MySQL Cluster. With the new architecture, the system is much more scalable and can transparently manage the failover of namenodes which are now stateless components. HopsFS is, however, still limited to running within a single datacenter which can cause severe outages in case the entire datacenter becomes unavailable. Cloud native storage systems, such as Amazon’s Simple Storage Service (S3), solve this problem by replicating data across different, geographically distant datacenters, so that the failure of any given zone does not cause data unavailability. The objective of this thesis is to enable HopsFS to work across geographical regions while, as far as possible, maintaining the semantics of a POSIX-style hierarchical filesystem. We leverage asynchronous replication functionality provided by MySQL Cluster to obtain replication of metadata across geographical regions and we present a detailed analysis on how to maintain the consistency properties of HDFS in such an environment. Furthermore, we analyze the issue of split brain scenarios and propose a way for namenodes to detect this condition and continue operating correctly. Finally, we discuss the changes to the codebase which are required to implement the proposed plan.

  • Sarlin, Axel
    KTH, School of Engineering Sciences (SCI), Mathematics (Dept.), Mathematics (Div.).
    The étale fundamental group, étale homotopy and anabelian geometry2017Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    In 1983 Grothendieck wrote a letter to Faltings, [Gro83], outlining what is today known as the anabelian conjectures. These conjectures concern the possibility to reconstruct curves and schemes from their étale fundamental group. Although Faltings never replied to the letter, his student Mochizuki began working on it. A major achievement by Mochizuki and Tamagawa was to prove several important versions of these conjectures.

    In this thesis we will first introduce Grothendieck’s Galois theory with the aim to define the étale fundamental group and formulate Mochizuki’s result. After recalling some necessary homotopy theory, we will introduce the étale homotopy type, which is an extension of the étale fundamental group developed by Artin, Mazur and Friedlander. This is done in order to describe some recentwork by Schmidt and Stix that improves on the results of Mochizuki and Tamagawa by extending them from étale fundamental groups to étale homotopy types of certain (possibly higher-dimensional) schemes.

     

  • Molin, Felix
    KTH, School of Engineering Sciences (SCI), Mathematics (Dept.), Mathematical Statistics.
    Cluster analysis of European banking data2017Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    Credit institutions constitute a central part of life as it is today and has been doing so for a long time. A fault within the banking system can cause a tremendous amount of damage to individuals as well as countries. A recent and memorable fault is the global financial crisis 2007-2009. It has affected millions of people in different ways ever since it struck. What caused it is a complex issue which cannot be answered easily. But what has been done to prevent something similar to occur once again? How has the business models of the credit institutions changed since the crisis? Cluster analysis is used in this thesis to address these questions. Banking-data were processed with Calinski-Harabasz Criterion and Ward's method and this resulted in two clusters being found. A cluster is a collection of observations that have similar characteristics or business model in this case. The business models that the clusters represents are universal banking with a retail focus and universal banking with a wholesale focus. These business models have been analyzed over time (2007-2016), which revealed that the credit institutions have developed in a healthy direction. Thus, credit institutions were more financially reliable in 2016 compared to 2007. According to trends in the data this development is likely to continue.

  • Khodaei, Mohammad
    et al.
    KTH, School of Electrical Engineering (EES), Network and Systems engineering.
    Messing, Andreas
    KTH, School of Computer Science and Communication (CSC).
    Papadimitratos, Panagiotis
    KTH, School of Electrical Engineering (EES), Network and Systems engineering.
    RHyTHM: A Randomized Hybrid Scheme To Hide in the Mobile Crowd2017In: IEEE Vehicular Networking Conference (VNC) 2017, IEEE, 2017Conference paper (Refereed)
    Abstract [en]

    Any on-demand pseudonym acquisition strategy is problematic should the connectivity to the credential management infrastructure be intermittent. If a vehicle runs out of pseudonyms with no connectivity to refill its pseudonym pool, one solution is the on-the-fly generation of pseudonyms, e.g., leveraging anonymous authentication. However, such a vehicle would stand out in the crowd: one can simply distinguish pseudonyms, thus signed messages, based on the pseudonym issuer signature, link them and track the vehicle. To address this challenge, we propose a randomized hybrid scheme, RHyTHM, to enable vehicles to remain operational when disconnected without compromising privacy: vehicles with valid pseudonyms help others to enhance their privacy by randomly joining them in using on-the-fly self-certified pseudonyms along with aligned lifetimes. This way, the privacy of disconnected users is enhanced with a reasonable computational overhead. 

  • Lindén, Carl
    et al.
    KTH, School of Education and Communication in Engineering Science (ECE).
    Silasson, Alexander
    KTH, School of Education and Communication in Engineering Science (ECE).
    Villkor för effektivaschemaläggningsprocesser: En flerfallsstudie i gymnasieskolan2017Independent thesis Advanced level (professional degree), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    In this study, timetabling processes in Swedish upper secondary schools were examined. School timetabling is a complex activity, with a great impact on working conditions for teachers and pupils’ learning conditions. Hence, it is of great importance that the timetabling is of high quality. As a result of the Swedish educational reforms in the 1990’s, timetabling decision-making was decentralized. This places great demands on responsibility of individual schools, which implies that local conditions are of great significance for the outcomes of timetabling. It is therefore of interest to examine the factors that promote school timetabling.

    The purpose of this study is to investigate the conditions that need to be fulfilled to ensure the efficacy of the timetabling process in an upper secondary school. Effective timetabling processes are defined based on previous research on school timetabling. The study has been conducted as a multiple case study, in which two comparatively chosen upper secondary schools were examined and compared. Interviews were used for data collection and data were analyzed using qualitative content analysis. In this way, factors that influence and constrain the timetabling processes could be identified. Based on a comparison of the results from both cases, four conditions were suggested that render timetabling processes effective. Two of the conditions deal with work structure of timetablers: Timetablers should apply strategies to handle timetabling constraints and the timetabling should be focused on its main task. The other two conditions deal with structural features necessary for effective timetabling: The school needs a stable pupil population and the class composition should be organized in a way that supports timetabling.

  • Brorsson, Ellinor
    et al.
    KTH, School of Education and Communication in Engineering Science (ECE).
    Bartoletti, Michaela
    KTH, School of Education and Communication in Engineering Science (ECE).
    Kontinuerligt lärande förhållbara förbättringar: En fallstudie i hur miljöförbättringsarbete kanbelysa det lärande som sker hoselinstallatörsföretag som arbetar efter konceptetständiga förbättringar2017Independent thesis Advanced level (professional degree), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    The expectations for a company to actively work on reducing their environmental impact are higher today than ever before. With an environmental certification, companies can show their responsibilities towards the environment to their stakeholders, and improve the chances to securing a position on the future market. An environmental certification, such as the standard ISO 14001, includes the need for continuous improvements to an organization’s processes and strategic environmental work. The term continuous improvements origins from Toyota Motors successful way of working - kaizen. It implies that everything can be madea little better than it is right now. This interpretation of continuous improvements goeswell together with environmental improvements in business since we are still on a journeytowards the most sustainable way of living.

    Two electrical contracting companies have through the web-based application System C2TM excelled in their work with continuous environmental improvements. Since a success factor to continuous improvements has proven to be education, one can assume that the two studied companies have a learning culture in their workplace that has led to this success. However, this learning culture is not specified. The purpose of this study is to examine what a training session in ecologically sustainable development should involve, not only lead to continuous improvements, but also to continuous learning. To generate knowledge about this, a qualitative study has been made. Two focus group conversations with each of the studied companies were made to gather data about their work with continuous environmental improvements. The data from the focus group conversations were analyzed through a thematic analysis. The results show that a training session that aims to lead to continuous improvements and learning within the organization consists of several sessions. The training sessions should make use of the knowledge within the organization, connect the environmental issue to the organization, involve an engaged leadership, and make use of the personal engagement amongst the coworkers. Apart from this, demands on the company culture are being made in order to create a learning organization. The culture should be open to challenge the existing routines and strive to develop the company to the better. The results from this study show that there are similarities between continuous improvements and learning. Suggested as further research is to examine the similarities between learning and continuous improvements. Another example for further research is to test the factors presented in this study, in a training session about ecologically sustainable development.

  • Ihrén, Erik
    KTH, School of Electrical Engineering (EES), Automatic Control.
    Evaluating the Handling of New Assignments in a Global Truck Platooning System Using Large-Scale Simulations2017Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    Truck transportation is a big part of goods transportation aroundthe world, with over 100,000 trucks per day in Sweden alone. By usingadaptive cruise control, trucks can drive very close together in aplatoon. Driving close together leads to a signicant reduction in airresistance, which in turn results in lower fuel consumption. This thesisinvestigates a global coordination system that trucks can registerwith, which will plan how all the trucks should drive. This systemthen has to regularly change the speed proles of individual trucksthroughout the system to automatically have them form 'platoons' sothat they can save as much fuel as possible.This thesis specically investigates what happens when a new truckassignment is registered with the system. When this happens, the systemshould take this into consideration and change the truck platoons.This might mean breaking up existing platoon or forming new ones.This has to be done regularly in an ecient manner as more and moreassignments are added to the system. To investigate the fuel savingsof this system, a simulation engine was created. Dierent parameters,such as update frequency and the time in advance that the system isinformed of new assignments, are evaluated to see how they impactthe result. In simulations of 5,000 trucks in one day, the coordinationsystem was able to accomplish a reduction in fuel consumptionof around 7%.

  • Singh, Sandeep
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering.
    Varmduktilitet vid stränggjutning av duplexa rostfria stål2017Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    Abstract

    Hot ductility during continuous casting of duplex stainless steels

    In the continuous casting of the duplex stainless steel, longitudinal corner cracks in the first casted bloom of SAF 2507 have been discovered by Sandvik. SAF 2205 contains the same alloying substances as SAF 2507, but with some difference in the concentration of the elements. Despite this similarity, the occurrence of corner cracks in SAF 2205 is minimal and thus is not considered to be a significant problem. The reason for the appearance of hot cracks in SAF 2507 may be due to reduced ductility and due to stress variations in the material that occurs during casting. An earlier research for mapping longitudinal corner cracks in SAF 2507 and SAF 2205 proved to occur due to thermal stresses created by shrinkage of the shell in the mold. A reduced ductility can be obtained by embrittlement of grain boundaries that may arise with a brittle phase. The high amount of alloy elements in duplex stainless steels can result in precipitation of intermetallic phase, which is a brittle phase. Through a mapping of microstructure of continuous casted SAF 2507 and SAF 2205, intermetallic phase was observed in samples from SAF 2507.In order to gain an understanding of the appearance of hot cracks in SAF 2507, in situ hot tensile tests were performed. The hot tensile tests were performed in order to compare and analyze the ductile behavior of SAF 2507 with SAF 2205. The purpose of the tensile tests was to simulate continuous casting process at Sandvik.The results from the tensile tests show that SAF 2507 and SAF 2205 are not sensitive to hot cracking at temperatures near solidus. However, intermetallic phases were found in SAF 2507 during hot tensile testing at 800 ° C. But no intermetallic phase could be found in SAF 2205. Temperature measurements and calculations by CFD during continuously casting of SAF 2507 showed that intermetallic phases could possibly precipitate in the mold. In a previous research done by Sandvik Materials Technology, shows how thermal stresses can occur on the corners of a cast inside the mold, during continuous casting of SAF 2205 and SAF 2507.The conclusion of this work is that longitudinal corner crackers in SAF 2507 can be initiated in the mold, because of a combination of thermal stresses and intermetallic phases.

    Keywords ∙ Duplex rostfritt stålVarmsprickkänslighet SAF 2507 SAF 2205 Stränggjutning Duktilitet Sigma Kromnitrider

  • Public defence: 2018-01-19 14:00 F3, Stockholm
    Bore, Nils
    KTH, School of Computer Science and Communication (CSC), Robotics, perception and learning, RPL.
    Object Instance Detection and Dynamics Modeling in a Long-Term Mobile Robot Context2017Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    In the last years, simple service robots such as autonomous vacuum cleaners and lawn mowers have become commercially available and increasingly common. The next generation of service robots should perform more advanced tasks, such as to clean up objects. Robots then need to learn to robustly navigate, and manipulate, cluttered environments, such as an untidy living room. In this thesis, we focus on representations for tasks such as general cleaning and fetching of objects. We discuss requirements for these specific tasks, and argue that solving them would be generally useful, because of their object-centric nature. We rely on two fundamental insights in our approach to understand environments on a fine-grained level. First, many of today's robot map representations are limited to the spatial domain, and ignore that there is a time axis that constrains how much an environment may change during a given period. We argue that it is of critical importance to also consider the temporal domain. By studying the motion of individual objects, we can enable tasks such as general cleaning and object fetching. The second insight comes from that mobile robots are becoming more robust. They can therefore collect large amounts of data from those environments. With more data, unsupervised learning of models becomes feasible, allowing the robot to adapt to changes in the environment, and to scenarios that the designer could not foresee. We view these capabilities as vital for robots to become truly autonomous. The combination of unsupervised learning and dynamics modelling creates an interesting symbiosis: the dynamics vary between different environments and between the objects in one environment, and learning can capture these variations. A major difficulty when modeling environment dynamics is that the whole environment can not be observed at one time, since the robot is moving between different places. We demonstrate how this can be dealt with in a principled manner, by modeling several modes of object movement. We also demonstrate methods for detection and learning of objects and structures in the static parts of the maps. Using the complete system, we can represent and learn many aspects of the full environment. In real-world experiments, we demonstrate that our system can keep track of varied objects in large and highly dynamic environments.​

  • Serra, Andreas
    KTH, School of Computer Science and Communication (CSC).
    A difference analysis method for detecting differences between similar documents2017Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    Similarity analysis of documents is a well studied field. With a focus instead on the opposite concept, how can we try to define and distinguish the differences within documents? This project tries to determine if differences within documents can be detected as well as quantified based on their semantic qualities. We propose a method for quantifying differences by applying tf-idf based models with analysis methods for lemmatization and synonym extraction, together with utility ranking algorithms. The method is implemented and tested. The results show that the method has potential but that further studies are required in order to fully evaluate to what extent it could be of practical use. Such a method could though reap significant benefits within several different fields in which automatic difference detection could replace error prone manual labor in document management, as well as other beneficial purposes such as to provide automatically generated difference summaries.

  • Public defence: 2018-01-26 10:00 F3, Stockholm
    Saffar Shamshirgar, Davood
    KTH, School of Engineering Sciences (SCI), Mathematics (Dept.), Numerical Analysis, NA.
    Fast methods for electrostatic calculations in molecular dynamics simulations2018Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    This thesis deals with fast and efficient methods for electrostatic calculations with application in molecular dynamics simulations. The electrostatic calculations are often the most expensive part of MD simulations of charged particles. Therefore, fast and efficient algorithms are required to accelerate these calculations. In this thesis, two types of methods have been considered: FFT-based methods and fast multipole methods (FMM).

    The major part of this thesis deals with fast N.log(N) and spectrally accurate methods for accelerating the computation of pairwise interactions with arbitrary periodicity. These methods are based on the Ewald decomposition and have been previously introduced for triply and doubly periodic problems under the name of Spectral Ewald (SE) method. We extend the method for problems with singly periodic boundary conditions, in which one of three dimensions is periodic. By introducing an adaptive fast Fourier transform, we reduce the cost of upsampling in the non periodic directions and show that the total cost of computation is comparable with the triply periodic counterpart. Using an FFT-based technique for solving free-space harmonic problems, we are able to unify the treatment of zero and nonzero Fourier modes for the doubly and singly periodic problems. Applying the same technique, we extend the SE method for cases with free-space boundary conditions, i.e. without any periodicity.

    This thesis is also concerned with the fast multipole method (FMM) for electrostatic calculations. The FMM is very efficient for parallel processing but it introduces irregularities in the electrostatic potential and force, which can cause an energy drift in MD simulations. In this part of the thesis we introduce a regularized version of the FMM, useful for MD simulations, which approximately conserves energy over a long time period and even for low accuracy requirements. The method introduces a smooth transition over the boundary of boxes in the FMM tree and therefore it removes the discontinuity at the error level inherent in the FMM.

  • Public defence: 2018-01-26 13:00 Kollegiesalen, Stockholm
    Tsaknaki, Vasiliki
    KTH, School of Computer Science and Communication (CSC), Media Technology and Interaction Design, MID.
    Making Preciousness: Interaction Design Through Studio Crafts2017Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    This dissertation explores value-creation in interaction design through practical collaborations with studio craftspersons. A focus is on the meaning of “preciousness” from a design perspective – what I refer to as Making Preciousness –  which highlights aspects of material properties, design processes, and the attitude to the design space. Theoretically, the work takes inspiration from the Japanese philosophy of Wabi-Sabi, which is based on the fact that things are impermanent, incomplete, and imperfect. This reflects a view of preciousness beyond notions of practical use, luxury or monetary cost. In addition to theoretical studies, I engaged in practice-based research at the intersection of interaction design and studio crafts, in the domains of leather, silversmith and textile crafting. Through an approach that blends these practices with the making of interactive artefacts, preciousness for interaction design was explored.

    Through this work, I extract three qualities, all of which are closely linked to attributes and values ​​embedded in the craft practices examined. I refer to these as resourceful composition, material sensuality and the aiming for mattering artefacts. Resourceful composition refers to approaching a design space “resourcefully”, meaning that the designer actively values and uses the specific qualities of materials and tools consciously, for what they are suitable for. Material sensuality is about appreciating the sensory experience of interacting with materials, arriving through particular material qualities, such as texture, temperature or smell, but also interactive qualities. Aiming for mattering artefacts involves actively designing for impermanence, incompleteness and imperfection, and through that contributing to notions of preciousness through use, care, ownership and interaction between users and artefacts over time.

    The attitude of making preciousness can be seen as tying together materials and making with user experiences of computational artefacts. For interaction design, this points towards making processes in which computation and material knowledge, craftsmanship and aesthetic intentions are placed at the core. These values ​​relate to cultural, but also sensual experiences, which can be seen as under-explored in the design of interactive products.

  • Schönbeck, Pia
    et al.
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Concrete Structures.
    Löfsjögård, Malin
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Concrete Structures.
    Ansell, Anders
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Concrete Structures.
    Requirements on concrete floor structures - a comparison of medical imaging facilities2017In: Nordic Concrete Research Publications , 2017 / [ed] Marianne Tange Holst, 2017Conference paper (Refereed)
    Abstract [en]

    Requirements management in construction projects have a tendency towards production-driven processes and definition of technical solutions. The stakeholders are involved by being asked to comment on defined products which can have consequences on the performance of the end-product. This comparison describes three projects within the Stockholm County where the scope to build new medical imaging facilities with the same requirements on the concrete floor structure. The result shows that the same requirements have resulted in different solutions which could have an impact on the performance of the buildings. Further research regarding tools for systematic requirements management is needed to ensure performance and sustainability of new buildings.

  • Orre, Inger
    KTH, Superseded Departments (pre-2005), Industrial Economics and Management.
    Reporterskap: äventyr, irrbloss, dygder2001Doctoral thesis, monograph (Other academic)
  • Pettersson, David
    KTH, School of Education and Communication in Engineering Science (ECE).
    Towards stimuli-reformable paperboard and flipped classroom in chemistry education: A study of how to create a paper with controllable mechanical properties and a study in how the flipped classroom is used in chemistry education2017Independent thesis Advanced level (professional degree), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    Today, paper and paperboard is an important part of the packaging industry, as well as natural part of our daily lives. The alternatives to paper and paperboard is often produced from nonrenewable sources such as petroleum and as demands on sustainability increase in the packaging sector, it gives paper a desirable advantage over plastics. To increase the use of paper, some of the limiting factors for paper needs to be overcome, such as its limited formability. One way to create a paper that can be formed in new ways is to imbibe the paper with an additive that makes its modulus changeable. This would make it possible to control the stiffness of the paper which would make it more formable. This have been the aim of this thesis. To create this formable paper four different approaches were used. Of these four, three included how paper can be treated with polyelectrolytes to be able to increase its modulus when stimuli are applied. The two first approaches were based on the layer-by-layer technique adsorbing alginate and cationic fibrils to form a layer that could be cross-linked, either on the surface of a film (the first approach) or in the network of fibres in a porous paper (the second approach). The last approach was to impregnate the papers with alginate. The results show that the first approach gave a too low adsorption of polyelectrolytes, why no difference could be detected. The second approach resulted in a higher adsorbed amount, but the effects were still too small. The third approach gave a paper which could, depending on the concentration of alginate, either increase or decrease its modulus when cross-linked. The last approach was to create a laminate, using unmodified fibers together with dialcohol cellulose fibres. This resulted in a paper that could be formed using heat and allowing the paper to cool down in the desirable form.

    In the curriculum for chemistry in Swedish high schools there is a paragraph that says that research in chemistry should be a part of the content the students learn. This is a challenge both to teachers and researchers. For teachers, to find research at an appropriate level and teach it in an understandable way. For researchers, to communicate the research so it is understandable for society. With this as a motivation, a second part of this thesis discuss the method flipped classroom in chemistry education at Swedish high schools. It was seen that from the teacher’s perspective, flipped classroom meant advantages that could be categorized into five categories. The categories that was found were Time to interact, Student responsibility, dialogue, laboratory work and understanding and using the language.

  • Forsvik, Louise
    KTH, School of Architecture and the Built Environment (ABE), Urban Planning and Environment.
    Odling på bostadsgårdar: grönare gårdsrum för granngemenskap och biologisk mångfald2017Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [sv]

    Stadsodling har allt oftare börjat påtalas i städers styrdokument, till exempel Stockholms stad, som en strategi för att främja social och ekologisk stadsutveckling. Familjebostäder, ett av Stockholms allmännyttiga bostadsföretag har vidare fått som verksamhetsdirektiv att arbeta med stadsodling i sin verksamhet. Genom en kvalitativ studie av tre av Familjebostäders bostadsgårdar, där en stadsodling har startats på en av gårdarna, undersöks boendes möjligheter att odla. Detta konkretiseras i hur stadsodling på innergårdar kan skapa sociala mervärden för brukarna och bidra till ekologiska värden på/i gården, som en del av stadens övergripande grönstruktur. Studien undersöker även åtgärdsbehov och utvecklingsmöjligheter för Familjebostäders arbete med planering och förvaltning av sina innegårdar framöver. Underlaget till studien utgörs av en litteraturstudie, fallstudie och intervjuer som en del av fallstudien. Totalt har 33 semistrukturerade intervjuer genomförts med två särskilt sakkunniga inom stadsodling, fyra tjänstepersoner från Familjebostäder och 27 boende, varav fem stycken är brukare av stadsodlingen. Studien visar att hyresgäster kan involveras i odling på sin gård genom att initiativet till odling kommer antingen centralt, organiserat av förvaltaren, eller att initiativet kommer från de boende själva, vilket förutsätter att förvaltaren kan bemöta sådana initiativ. De ekosystemtjänster som odling kan skapa på gårdar, är främst kulturella - men även till viss del stödjande och reglerande ekosystemtjänster. Organisatoriskt sett kan Familjebostäder i sin verksamhet systematisk arbeta med att inkludera boende i frågor som handlar om deras utemiljö i allmänhet och stadsodling i synnerhet, både i ett kortsiktigt och långsiktigt perspektiv. Slutligen bidrar studien till en slutsats och diskussion om hur brukarmedverkan i boendes närmiljö och odling kan bidra till social aktivitet och som en målpunkt på gården. Gårdar som är interaktiva upplevs som trivsamma av sina hyresgäster, leder till möten mellan grannar och främjar ekosystemtjänster och biologisk mångfald i allmänhet. Av de tre studerade gårdarna har gårdens struktur visat på vissa skillnader i de boendes intresse för att odla.     

  • ZHAO, WEIJIE
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering.
    Corrosion initiation induced by sodium sulfate and sodium chloride particles on Cu and the golden alloy Cu5Al5Zn at simulated atmospheric conditions2017Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    Effects of sodium sulfate (Na2SO4) particle deposition on the atmospheric corrosion of copper (Cu) metal and a Cu-based alloy (Cu5Al5Zn) used in architectural applications were investigated at laboratory conditions compared with effects induced by sodium chloride (NaCl) and to some extent ammonium sulfate (NH4)2SO4 induced corrosion. Pre-deposited surfaces were exposed to repeated wet/dry conditions in a climatic chamber and the formation of corrosion products were assessed using light optical microscopy (LOM), scanning electron microscopy with elemental analysis (SEM/EDS), Fourier transform infrared techniques (FTIR microscopy) and cathodic reduction (CR). Na2SO4 induced corrosion resulted in corrosion cells locally over the surface on both Cu and Cu5Al5Zn, of increased oxygen content in the anodic area of the cells (center of pre-deposited area). The main corrosion products formed on Cu metal are basic copper sulfates and cuprite (Cu2O), while basic sulfates (copper and/or zinc) and Cu2O were the main corrosion products formed on Cu5Al5Zn. A combined deposition of Na2SO4 + NaCl was carried out on the Cu5Al5Zn alloy using two different deposition methods to investigate the possible interplay from a corrosion initiation perspective between the two salt particles. For short time exposed Cu5Al5Zn (1 cycle), two different corrosion cells formed, mainly induced by Na2SO4 and NaCl. Corrosion products formed in anodic areas of a Na2SO4 induced corrosion cell were similar to findings observed for Cu5Al5Zn pre-deposited with Na2SO4 only, whereas peripheral cathodic areas primarily were affected by NaCl dissolution and predominantly composed of Cu2O that was the main corrosion product with small amount of hydroxides and carbonates of the NaCl induced corrosion cells. After relatively longer exposure periods (2 and 6 wet/dry cycles), NaCl dominated the corrosion of the entire surface with the formation of more Cu2O, hydroxides and carbonates. Cathodic reduction findings revealed a negative interplay on corrosion for the mixed salt after short time exposures (1 and 2 cycles), whereas a slight synergistic effect was evident after a longer exposure period (6 cycles), compared with corrosion induced by single salts.