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  • 122151.
    Yousif, Osama
    KTH, School of Architecture and the Built Environment (ABE), Urban Planning and Environment, Geodesy and Geoinformatics.
    Change Detection Using Multitemporal SAR Images2013Licentiate thesis, comprehensive summary (Other academic)
    Abstract [en]

    Multitemporal SAR images have been used successfully for the detection of different types of environmental changes. The detection of urban change using SAR images is complicated due to the special characteristics of SAR images—for example, the existence of speckle and the complex mixture of the urban environment. This thesis investigates the detection of urban changes using SAR images with the following specific objectives: (1) to investigate unsupervised change detection, (2) to investigate reduction of the speckle effect and (3) to investigate spatio-contextual change detection. Beijing and Shanghai, the largest cities in China, were selected as study areas. Multitemporal SAR images acquired by ERS-2 SAR (1998~1999) and Envisat ASAR (2008~2009) sensors were used to detect changes that have occurred in these cities.

    Unsupervised change detection using SAR images is investigated using the Kittler-Illingworth algorithm. The problem associated with the diversity of urban changes—namely, more than one typology of change—is addressed using the modified ratio operator. This operator clusters both positive and negative changes on one side of the change-image histogram. To model the statistics of the changed and the unchanged classes, four different probability density functions were tested. The analysis indicates that the quality of the resulting change map will strongly depends on the density model chosen. The analysis also suggests that use of a local adaptive filter (e.g., enhanced Lee) removes fine geometric details from the scene.

    Speckle suppression and geometric detail preservation in SAR-based change detection, are addressed using the nonlocal means (NLM) algorithm. In this algorithm, denoising is achieved through a weighted averaging process, in which the weights are a function of the similarity of small image patches defined around each pixel in the image. To decrease the computational complexity, the PCA technique is used to reduce the dimensionality of the neighbourhood feature vectors. Simple methods to estimate the dimensionality of the new space and the required noise variance are proposed. The experimental results show that the NLM algorithm outperformed traditional local adaptive filters (e.g., enhanced Lee) in eliminating the effect of speckle and in maintaining the geometric structures in the scene. The analysis also indicates that filtering the change variable instead of the individual SAR images is effective in terms of both the quality of the results and the time needed to carry out the computation.

    The third research focuses on the application of Markov random field (MRF) in change detection using SAR images. The MRF-based change detection algorithm shows limited capacity to simultaneously maintain fine geometric detail in urban areas and combat the effect of speckle noise. This problem has been addressed through the introduction of a global constraint on the pixels’ class labels. Based on NLM theory, a global probability model is developed. The iterated conditional mode (ICM) scheme for the optimization of the MAP-MRF criterion function is extended to include a step that forces the maximization of the global probability model. The experimental results show that the proposed algorithm is better at preserving the fine structural detail, effective in reducing the effect of speckle, less sensitive to the value of the contextual parameter, and less affected by the quality of the initial change map compared with traditional MRF-based change detection algorithm.

  • 122152.
    Yousif, Osama
    KTH, School of Architecture and the Built Environment (ABE), Urban Planning and Environment, Geoinformatics.
    Urban Change Detection Using Multitemporal SAR Images2015Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    Multitemporal SAR images have been increasingly used for the detection of different types of environmental changes. The detection of urban changes using SAR images is complicated due to the complex mixture of the urban environment and the special characteristics of SAR images, for example, the existence of speckle. This thesis investigates urban change detection using multitemporal SAR images with the following specific objectives: (1) to investigate unsupervised change detection, (2) to investigate effective methods for reduction of the speckle effect in change detection, (3) to investigate spatio-contextual change detection, (4) to investigate object-based unsupervised change detection, and (5) to investigate a new technique for object-based change image generation. Beijing and Shanghai, the largest cities in China, were selected as study areas. Multitemporal SAR images acquired by ERS-2 SAR and ENVISAT ASAR sensors were used for pixel-based change detection. For the object-based approaches, TerraSAR-X images were used.

    In Paper I, the unsupervised detection of urban change was investigated using the Kittler-Illingworth algorithm. A modified ratio operator that combines positive and negative changes was used to construct the change image. Four density function models were tested and compared. Among them, the log-normal and Nakagami ratio models achieved the best results. Despite the good performance of the algorithm, the obtained results suffer from the loss of fine geometric detail in general. This was a consequence of the use of local adaptive filters for speckle suppression. Paper II addresses this problem using the nonlocal means (NLM) denoising algorithm for speckle suppression and detail preservation. In this algorithm, denoising was achieved through a moving weighted average. The weights are a function of the similarity of small image patches defined around each pixel in the image. To decrease the computational complexity, principle component analysis (PCA) was used to reduce the dimensionality of the neighbourhood feature vectors. Simple methods to estimate the number of significant PCA components to be retained for weights computation and the required noise variance were proposed. The experimental results showed that the NLM algorithm successfully suppressed speckle effects, while preserving fine geometric detail in the scene. The analysis also indicates that filtering the change image instead of the individual SAR images was effective in terms of the quality of the results and the time needed to carry out the computation.

    The Markov random field (MRF) change detection algorithm showed limited capacity to simultaneously maintain fine geometric detail in urban areas and combat the effect of speckle. To overcome this problem, Paper III utilizes the NLM theory to define a nonlocal constraint on pixels class-labels. The iterated conditional mode (ICM) scheme for the optimization of the MRF criterion function is extended to include a new step that maximizes the nonlocal probability model. Compared with the traditional MRF algorithm, the experimental results showed that the proposed algorithm was superior in preserving fine structural detail, effective in reducing the effect of speckle, less sensitive to the value of the contextual parameter, and less affected by the quality of the initial change map.

    Paper IV investigates object-based unsupervised change detection using very high resolution TerraSAR-X images over urban areas. Three algorithms, i.e., Kittler-Illingworth, Otsu, and outlier detection, were tested and compared. The multitemporal images were segmented using multidate segmentation strategy. The analysis reveals that the three algorithms achieved similar accuracies. The achieved accuracies were very close to the maximum possible, given the modified ratio image as an input. This maximum, however, was not very high. This was attributed, partially, to the low capacity of the modified ratio image to accentuate the difference between changed and unchanged areas. Consequently, Paper V proposes a new object-based change image generation technique. The strong intensity variations associated with high resolution and speckle effects render object mean intensity unreliable feature. The modified ratio image is, therefore, less efficient in emphasizing the contrast between the classes. An alternative representation of the change data was proposed. To measure the intensity of change at the object in isolation of disturbances caused by strong intensity variations and speckle effects, two techniques based on the Fourier transform and the Wavelet transform of the change signal were developed. Qualitative and quantitative analyses of the result show that improved change detection accuracies can be obtained by classifying the proposed change variables. 

  • 122153.
    Yousif, Osama A.
    et al.
    KTH, School of Architecture and the Built Environment (ABE), Urban Planning and Environment, Geoinformatics (closed 20110301).
    Ban, Yifang
    KTH, School of Architecture and the Built Environment (ABE), Urban Planning and Environment, Geoinformatics (closed 20110301).
    Multitemporal Spaceborn SAR Data For Change Detection In Urban Areas: A Case Study In Shanghai2009In: Proceedings, ISPRS Virtual Changing Globe for Visualization and Analysis / [ed] Jianya Gong,Qiming Zhou, 2009Conference paper (Other academic)
    Abstract [en]

    The objective of this research is to perform automatic change detection within urban areas using multitemporal spaceborne SAR datain Shanghai. Two scenes of ENVISAT ASAR C-VV images were acquired in September, 2008 and one scene of ERS-2 SAR C-VVimage was acquired in September, 1999. A generalized version of Kittler Illingworth minimum-error thresholding algorithm, thattakes into account the non-Gaussianity of SAR images, was tested to automatically classify the SAR ratio image into two classes,change and no change. Two types of comparison operators were performed. First, the conventional ratio image was calculated in away that only increases in backscatter coefficient are detected. Second, a modified ratio operator that takes into accounts bothpositive and negative changes was also examined. Various probability density functions such as, Log normal, Generalized Gaussian,Nakagami ratio, and Weibull ratio were tested to model the distribution of the change and no change classes. An iterative refinementof the Log normal model is also applied to improve the resolution of the change map. The preliminary results showed that thisunsupervised change detection algorithm is very effective in detecting temporal changes in urban areas using SAR images. The bestchange detection result was obtained using Log normal model with modified ratio operator at 81.5%, which is over 10% high thanthat of the other three models tested. The initial findings indicated that change detection accuracy varies depending on how theassumed conditional class density function fits the histograms of change and no change classes.

  • 122154.
    Yousif, Osama A.
    et al.
    KTH, School of Architecture and the Built Environment (ABE), Urban Planning and Environment, Geodesy and Geoinformatics. KTH, School of Architecture and the Built Environment (ABE), Urban Planning and Environment, Geoinformatics (closed 20110301). KTH, School of Architecture and the Built Environment (ABE), Urban Planning and Environment, Geoinformatics.
    Ban, Yifang
    KTH, School of Architecture and the Built Environment (ABE), Urban Planning and Environment, Geoinformatics.
    Object-based change detection in urban areas using multitemporal high resolution SAR images with unsupervised thresholding algorithms2016In: Remote Sensing and Digital Image Processing, Springer, 2016, p. 89-105Chapter in book (Refereed)
    Abstract [en]

    With the recent launches of optical and SAR systems that are capable of producing images in very high resolution, the quantification of temporal changes can be achieved with unprecedented level of details. However, very high resolution data presents new challenges and difficulties such as the strong intensity variations within land cover classes thus the noisy appearance of change map generated by pixelbased change detection. This has led to the development of object-based approaches that utilize image segmentation. For unsupervised change detection, on the other hand, automatic thresholding algorithms provided a simple yet effective technique to produce a binary change map. Thresholding techniques have been used successfully for pixel-based change detection using medium resolution SAR images. They have also been used for object-based change detection using high resolution optical imagery. However, they have not been tested in the context of object-based change detection using high resolution SAR images. Therefore, this chapter investigates the potential of several thresholding techniques for object-based unsupervised detection of urban changes using high resolution SAR images. To avoid the creation of sliver polygons, the multidate image segmentation strategy is adopted to produce image objects that are spectrally, spatially, and temporally homogeneous. A change image is generated by comparing objects multitemporal mean intensities using the modified ratio operator. To threshold the change image and generate a binary change map, three thresholding algorithms, i.e., the Kittler-Illingworth algorithm, the Otsu method, and the outlier detection technique, are tested and compared. Two multitemporal datasets consisting of TerraSAR-X images acquired over Beijing and Shanghai are used for evaluation. Quantitative and qualitative analyses reveal that the three algorithms achieved similar results. The three algorithms achieved Kappa coefficients around 0.6 for the Beijing dataset and 0.75 for the Shanghai datasets. The analysis also reveals the limitation of the mathematical comparison operator in accentuating the difference between the changed and the unchanged class, thus calls for the development of more sophisticated object-based change image generation mechanisms capable of reflecting all types of changes in the complex urban environment.

  • 122155.
    Yousif, Osama
    et al.
    KTH, School of Architecture and the Built Environment (ABE), Urban Planning and Environment, Geoinformatics.
    Ban, Yifang
    KTH, School of Architecture and the Built Environment (ABE), Urban Planning and Environment, Geoinformatics.
    A novel approach for object-based change image generation using multitemporal high-resolution SAR images2017In: International Journal of Remote Sensing, ISSN 0143-1161, E-ISSN 1366-5901, Vol. 38, no 7, p. 1765-1787Article in journal (Refereed)
    Abstract [en]

    Object-based change detection offers a unique approach for high-resolution images to capture meaningful detailed change information while suppressing noise in change detection results. In this approach, mean intensities of objects are commonly used as a feature and images comparison is carried out based on simple mathematical operations such as ratioing. The strong intensity variations within an object - a consequence of high spatial resolution - combined with synthetic aperture radar (SAR) image speckle degrade the accuracy of object mean intensity estimate, and consequently, affect the quality of the estimated object-based change image. A change quantification approach that takes into account the characteristics of high-resolution SAR images, that is, SAR speckle and the strong intensity variation, is proposed. By descending to the pixel level, a new representation of change data (i.e. the change signal) is proposed. With this representation, change quantification boils down to measuring the roughness of the change signal. Two techniques to assess the intensity of change at the object-level, based on Fourier and wavelet transforms (WT) of the change signal, are proposed. Their main advantages lie in their ability to capture the dominant change behaviour of the object, while being insusceptible to irrelevant disturbances. The proposed approach is evaluated using two multitemporal data sets of TerraSAR-X images acquired over Beijing and Shanghai. The qualitative and quantitative analyses of the results demonstrate the superior discrimination power of the proposed change variables compared with the object-based modified ratio (MR) and the absolute log ratio (LR) images.

  • 122156.
    Yousif, Osama
    et al.
    KTH, School of Architecture and the Built Environment (ABE), Urban Planning and Environment, Geoinformatics.
    Ban, Yifang
    KTH, School of Architecture and the Built Environment (ABE), Urban Planning and Environment, Geoinformatics.
    Fusion of SAR and optical data for unsupervised change detection: A case study in Beijing2017In: 2017 Joint Urban Remote Sensing Event, JURSE 2017, Institute of Electrical and Electronics Engineers (IEEE), 2017, article id 7924636Conference paper (Refereed)
    Abstract [en]

    Change detection can either be carried out using multitemporal optical or synthetic aperture radar (SAR) images. Due to the different electromagnetic spectrum used, these two types of imagery provide different representations of the same physical reality. Change information extraction can benefit from the fusion of SAR and optical data. In this paper we investigate the fusion of SAR and optical for change detection application. Beijing, the capital of China that has experienced rapid urbanization, is selected as a case study. Two multitemporal datasets that consist of Landsat and SAR (ERS-2 and ENVISAT) images are used. An unsupervised classification framework that combines the virtues of the k-mean and SVM supervised classifier is proposed. Different fusion strategies are tested including fusion at the feature level and at the decision level. The analysis reveals that the best result can be obtained when the fusion of change information is carried out at the decision level.

  • 122157.
    Yousif, Osama
    et al.
    KTH, School of Architecture and the Built Environment (ABE), Urban Planning and Environment, Geodesy and Geoinformatics.
    Ban, Yifang
    KTH, School of Architecture and the Built Environment (ABE), Urban Planning and Environment, Geodesy and Geoinformatics.
    Improving SAR-Based Urban Change Detection by Combining MAP-MRF Classifier and Nonlocal Means Similarity Weights2014In: IEEE Journal of Selected Topics in Applied Earth Observations and Remote Sensing, ISSN 1939-1404, E-ISSN 2151-1535, Vol. 7, no 10, p. 4288-4300Article in journal (Refereed)
    Abstract [en]

    In remote sensing change detection, Markov random field (MRF) has been used successfully to model the prior probability using class-labels dependencies. MRF has played an important role in the detection of complex urban changes using optical images. However, the preservation of details in urban change analysis turns out to be a highly complex task if multi-temporal SAR images with their speckle are to be used. Here, the ability of MRF to preserve geometric details and to combat speckle effect at the same time becomes questionable. Blob-region phenomenon and fine structures removal are common consequences of the application of traditional MRF-based change detection algorithm. To overcome these limitations, the iterated conditional modes (ICM) framework for the optimization of the maximum a posteriori (MAP-MRF) criterion function is extended to include a nonlocal probability maximization step. This probability model, which characterizes the relationship between pixels' class-labels in a nonlocal scale, has the potential to preserve spatial details and to reduce speckle effects. Two multitemporal SAR datasets were used to assess the proposed algorithm. Experimental results using three density functions [i.e., the log normal (LN), generalized Gaussian (GG), and normal distributions (ND)] have demonstrated the efficiency of the proposed approach in terms of detail preservation and noise suppression. Compared with the traditional MRF algorithm, the proposed approach proved to be less-sensitive to the value of the contextual parameter and the chosen density function. The proposed approach has also shown less sensitivity to the quality of the initial change map when compared with the ICM algorithm.

  • 122158.
    Yousif, Osama
    et al.
    KTH, School of Architecture and the Built Environment (ABE), Urban Planning and Environment, Geodesy and Geoinformatics.
    Ban, Yifang
    KTH, School of Architecture and the Built Environment (ABE), Urban Planning and Environment, Geodesy and Geoinformatics.
    Improving Urban Change Detection from Multitemporal SAR Images Using PCA-NLM2013In: IEEE Transactions on Geoscience and Remote Sensing, ISSN 0196-2892, E-ISSN 1558-0644, Vol. 51, no 4, p. 2032-2041Article in journal (Refereed)
    Abstract [en]

    Multitemporal synthetic aperture radar (SAR) images have been increasingly used in change detection studies. However, the presence of speckle is the main disadvantage of this type of data. To reduce speckle, many local adaptive filters have been developed. Although these filters are effective in reducing speckle in homogeneous areas, their use is often accompanied with the degradation of spatial details and fine structures. In this paper, we investigate a nonlocal means (NLM) denoising algorithm that combines local structures with a global averaging scheme in the context of change detection using multitemporal SAR images. First, the ratio image is logarithmically scaled to convert the multiplicative noise model to an additive model. A multidimensional change image is then constructed using image neighborhood feature vectors. Principle component analysis is then used to reduce the dimensionality of the neighborhood feature vectors. Recursive linear regression combined with fitting-accuracy assessment strategy is developed to determine the number of significant PC components to be retained for similarity weight computation. An intuitive method to estimate the unknown noise variance (necessary to run the NLM algorithm) based on the discarded PC components is also proposed. The efficiency of the method has been assessed using two different bitemporal SAR datasets acquired in Beijing and Shanghai, respectively. For comparison purposes, the algorithm is also tested against some of the most commonly used local adaptive filters. Qualitative and quantitative analyses of the algorithm have demonstrated the efficiency of the algorithm in recovering the noise-free change image while preserving the complex structures in urban areas.

  • 122159.
    Yousif, Osama
    et al.
    KTH, School of Architecture and the Built Environment (ABE), Urban Planning and Environment, Geoinformatics.
    Ban, Yifang
    KTH, School of Architecture and the Built Environment (ABE), Urban Planning and Environment, Geoinformatics.
    Object-based urban change detection using high resolution SAR images2015In: 2015 Joint Urban Remote Sensing Event, JURSE 2015, IEEE conference proceedings, 2015Conference paper (Refereed)
    Abstract [en]

    In this study, the unsupervised detection of urban changes, based on high-spatial resolution SAR imagery, is approached using the object-oriented paradigm. Multidate images segmentation strategy was adopted to avoid the creation of sliver polygon. Following segmentation, a change image was generated by comparing objects' mean intensities using a modified version of the traditional ratio operator. Three different unsupervised thresholding algorithms - that is, Kittler-Illingworth algorithm, Otsu method, and outlier detection technique - are used to threshold the change image and generate a binary change map. Two TerraSAR-X SAR images acquired over Shanghai in August, 2008, and September, 2011, were used to test the methods. The results indicate that, compared with pixel-based, the object-based approach helps in improving the quality of the produced change maps. The results also show that the three unsupervised thresholding algorithms performed equally well.

  • 122160.
    Yousif, Robert
    KTH, School of Industrial Engineering and Management (ITM), Machine Design (Dept.), Mechatronics.
    A Practical Approach of an Internet of Robotic Things Platform2018Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    This thesis aims to design and develop a platform based on a novel concept - the Internet of Robotic Things (IoRT) constructed by a robotic platform, an Internet of Things (IoT) platform and cloud computing services. A robotic platform enables hardware abstraction, facilitating the management of input/output between software, mechanical devices  andelectronic systems. The IoT platform is a global network enabling a massive number of devices known as things to communicate with each other and transfer data over the Internet. Cloud computing is a shared pool of scalable hardware usually provisioned as cloud services by third party cloud vendors. The integration of these concepts constitutes the core of the IoRT platform, as a global infrastructure facilitating robots to interconnect over the Internet utilizing common communication technology. Moreover, the pool of cloud resources shared by the connected robots enables scalable storage and processing power.

    The IoRT platform developed in this study constitutes firstly of the Amazon Web Service (AWS) IoT core serving as the IoT platform. Secondly, it incorporates the Robot Operating system (ROS) as the robotic platform and thirdly the cloud services Amazon DynamoDB and AWS Lambda for data storing and data processing respectively.The platform was evaluated in terms of delays & utilization and visualization capabilities. The platform demonstrates promising result in terms of delays exchanging small packages of data, round-trip delays in order of 50-60ms were obtained between a robot placed in Stockholm and the communication platform AWS IoT placed in Dublin, Ireland. Most of the delay is due to the traveling distance, where a round trip ping between Stockholm and Dublin takes around 50ms. The platforms ability to visualize streaming data from the robots, enables an operator to visualize selected data from any service in the platform over the Internet in near real-time, with round-trip delays in order of 250-300ms where the data propagates through multiple cloud service. In conclusion, this report illustrates the feasibility of merging two major platforms together: ROS and AWS IoT, and moreover, the accessibility to exploit the power and potential enabled by the modern data centers.

  • 122161.
    Yousif, Shather
    et al.
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Building Technology and Design.
    Douglah, Amir
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Building Technology and Design.
    Hur skall en ishallsvägg byggas?: Fuktrisker och mögelanalys2017Independent thesis Basic level (university diploma), 10 credits / 15 HE creditsStudent thesis
    Abstract [en]

    In Sweden there are many ice halls and ice halls climate differ from the usual buildings' climate, because temperatures are lower indoors than outdoors during the summer months. This results in a higher vapor content outdoors compared with indoors during the course of the year. Moisture transport takes place from the outside towards the ice halls, which is contrary to what happens in a common building.

    During the critical period, the vapor transport direction is inward. When the hot air hits the cold surface of the wall structure, it leads to a risk of condensation in the wall that leads to moisture damage. Moisture damage can impair the wall structure and lead to unwanted consequences.

    The purpose of this study was to dimension a number of walls that meet climate conditions, which are done by dynamic humidity calculation in WUFI Pro 5.1 with adapted climate data and real climate data and then mold analysis in WUFI Bio.

    The aim of the bachelor thesis work was that the results from this study can then be used as a guide to the future building of ice skating walls.

    The results from WUFI Pro 5.1 and WUFI Bio have shown that a number of walls designed during this master thesis are judged to work as well as revealed how an ice hallway wall should not be constructed.

    The conclusion shows that climate conditions control the design of the wall structure.

  • 122162.
    Youssef, Peter
    et al.
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering.
    Onursal, Roshat
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering.
    Nytt företagsområde i Haninge Kommun Med visionen hållbar stadutveckling2011Independent thesis Basic level (university diploma), 10 credits / 15 HE creditsStudent thesis
    Abstract [en]

    The people of the country are increasing, cities growing and growing environmental pollution. People are looking to big cities. Not least, firms wishing to locate in attractive environments in these cities. For Local Authorities means such establishments of business development of the economy. The development also complies with responsibility for municipal politicians. And to avoid straining the environment even more one want to create something that is sustainable into the future. Haninge municipality wishing to develop business in the municipality to create a second business park in addition to the already known Jordbro Business Park. The park is located in Albyberg in Alby, near highway 73. The aim for the politicians is set to sustainable urban development. To develop a modern business park that hopefully will serve as a model for future business parks on sustainability. To achieve this, the Haninge municipality set certain requirements for exploitation and for which companies will establish themselves. It can be a design and format that gives rise to a low energy, using materials that have minimal environmental impact, green spaces, good lighting, a joint center for developing in ecology and sustainable urban development, etc.

    A survey study conducted shows that the attitude towards Haninge is positive among firms in different industries. The survey also reveals that the attitude of the participating companies is quite positive for a particular Sustainable urban development and wind energy. The municipality declares the planning program from January 2006 that it will create opportunities to build a center for research and development, and a cars-on-rail system who commute between Haninge C and Albyberg Business Park. The survey shows that the attitude is quite positive for a center for research and development, but weak for a cars-on-rail system as a collective means of transport.

    Albyberg is a major activity of about 81 hectares of land. The exploitation of the area is divided into five stages according to the planning program from 2006. The report highlights how the exploitation spreadsheet looks like and explains the detailed financial terms. A rough estimate for the exploitation phase 1 shows that a price below SEK 800 per square meter did not provide enough income to cover the costs of the common auxiliary devices for the first phase.

    For external developers end up disposable costs for the creation of a developer around SEK 11 000 per square meter in Albyberg Business Park, including construction costs, according to cost estimates.

  • 122163.
    Youssef, Robert
    et al.
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Building Technology and Design.
    Bchar, Paul
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Building Technology and Design.
    Bygga till ett våningsplan på befintligt flerbostadshus: Utredning av konstruktionstekniska och byggnadstekniska åtgärder2018Independent thesis Advanced level (degree of Master (One Year)), 10 credits / 15 HE creditsStudent thesis
    Abstract [sv]

    Flerbostadshuset som studeras i rapporten är uppfört och dimensionerat med ett äldre regelverk och benämns BABS. Idag tillämpas Eurokod vid dimensioner av byggnadsverk. Skillnader i dessa regelverk skapar problem som förekommer vid en våningspåbyggnad. Dessa problem är både konstruktionstekniska och byggnadstekniska. Syftet med rapporten är att studera den mest effektiva varianten av våningspåbyggnad med avseende på bärighet, gällande krav, tilläggsåtgärder och effektivitet.

    Arbetet har utförts i samarbete med Sweco Structures för ett referensobjekt som har blivit modellerat i FEM för att få fram lasten vid den kritiska punkten i tre olika skeden. De tre olika skedena består av grundbyggnad, grundbyggnad med påbyggnad i betong och grundbyggnad med påbyggnad i trä.

    Erhållna resultat jämförs sedan med handberäkningar i enlighet med Eurokod och till viss del medhandberäkningar för BABS. Alla resultat jämförs sedan med maximal kapacitet på mark från den kritiska punkten för att kontrollera behovet av grundförstärkning.

    Referensobjektet undersöks även med avseende på de krav som gäller och jämförs med kraven från det äldre regelverket. Därefter analyseras eventuella tilläggsåtgärder som kan göras i samband med våningspåbyggnaden.

    Resultaten som erhölls var av stor betydelse för bestämmandet av typen av våningspåbyggnad. Detta eftersom resultaten bidrog till förståelse kring lastskillnader vid olika materialval och olika bestämmelser. Vid ett dåligt materialval kan lönsamhet och effektivitet äventyras. Vid oklarheter kring regelverk kan missförståelse förekomma och risk för feldimensionering uppstå.

    Resultaten påvisade att det mest effektiva valet av påbyggnad var påbyggnaden i trä. Detta eftersom att denna klarade av diverse krav. Påbyggnaden i betong bidrog med för stora krafter vilket skulle kunna äventyra markens stabillitet. Att förstärka marken är kostsamt och därmed drogs slutsatsen att trä var det mest effektiva materialvalet.

  • 122164. Youssefmir, Michael
    et al.
    Ottersten, Björn
    KTH, School of Electrical Engineering (EES), Signal Processing.
    Rogard, Roger
    Downlink transmission in a wireless data communication system having a base station with a smart antenna system2000Patent (Other (popular science, discussion, etc.))
  • 122165.
    YOUSUF, USMAN
    KTH, School of Information and Communication Technology (ICT).
    Security of Hard Disk Encryption2013Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    In order to provide confidentiality to digital information and safety to computer hard disk, encryption is considered to be best solutions. Now a day, several hard disks encryption software’s with a range of different features are commercially available. Majority of the software uses that encryption algorithm, whose cryptanalyses are already known. Now the vital question is that how much these encryption software’s provide security to the data. Any implementation and design flaw leave loop hole or backdoors in these softwares. Either by take the advantage of user unawareness or by using any external hardware, software’s security can be defeated by using smart and easy methods.

    This thesis will provide possible weaknesses and vulnerabilities of commercially available hard disk encryption software, who offering complete security to the hard disk data. This thesis will also access the real world performance of hard disk encryption softwares.

  • 122166.
    Yousuff, Razu
    KTH, School of Electrical Engineering (EES).
    Network security2014Independent thesis Basic level (degree of Bachelor), 10 credits / 15 HE creditsStudent thesis
  • 122167.
    Yousuff, Razu
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Applied Mechanical Engineering (KTH Södertälje).
    Omar Salim, Lava
    KTH, School of Industrial Engineering and Management (ITM), Applied Mechanical Engineering (KTH Södertälje).
    Dataöverföring från BIM till BEAst Portal genom att uppnå interoperabilitet2017Independent thesis Advanced level (degree of Master (One Year)), 10 credits / 15 HE creditsStudent thesis
  • 122168.
    Ytterberg, A. Jimmy
    et al.
    Karolinska Inst, Dept Med Biochem & Biophys, Chem Div 1, Stockholm, Sweden.;Karolinska Inst, Dept Med, Rheumatol Unit, Stockholm, Sweden.;Swedish Orphan Biovitrum AB Publ, Stockholm, Sweden..
    Zubarev, Roman A.
    Karolinska Inst, Dept Med Biochem & Biophys, Chem Div 1, Stockholm, Sweden..
    Baumgarten, Thomas
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Chemistry, Glycoscience.
    Posttranslational Targeting of a Recombinant Protein Promotes Its Efficient Secretion into the Escherichia coli Periplasm2019In: Applied and Environmental Microbiology, ISSN 0099-2240, E-ISSN 1098-5336, Vol. 85, no 13, article id UNSP e00671Article in journal (Refereed)
    Abstract [en]

    Many recombinant proteins that are produced in Escherichia coli have to be targeted to the periplasm to be functional. N-terminal signal peptides can be used to direct recombinant proteins to the membrane-embedded Sec translocon, a multiprotein complex that translocates proteins across the membrane into the periplasm. We have recently shown that the cotranslational targeting of the single-chain variable antibody fragment BL1 saturates the capacity of the Sec translocon leading to impaired translocation of secretory proteins and protein misfolding/aggregation in the cytoplasm. In turn, protein production yields and biomass formation were low. Here, we study the consequences of targeting BL1 posttranslationally to the Sec translocon. Notably, the posttranslational targeting of BL1 does not saturate the Sec translocon capacity, and both biomass formation and protein production yields are increased. Analyzing the proteome of cells producing the posttranslationally targeted BL1 indicates that the decreased synthesis of endogenous secretory and membrane proteins prevents a saturation of the Sec translocon capacity. Furthermore, in these cells, highly abundant chaperones and proteases can clear misfolded/aggregated proteins from the cytoplasm, thereby improving the fitness of these cells. Thus, the posttranslational targeting of BL1 enables its efficient production in the periplasm due to a favorable adaptation of the E. coli proteome. We envisage that our observations can be used to engineer E. coli for the improved production of recombinant secretory proteins. IMPORTANCE The bacterium Escherichia coli is widely used to produce recombinant proteins. To fold properly, many recombinant proteins have to be targeted to the E. coli periplasm, but so far the impact of the targeting pathway of a recombinant protein to the periplasm has not been extensively investigated. Here, we show that the targeting pathway of a recombinant antibody fragment has a tremendous impact on cell physiology, ultimately affecting protein production yields in the periplasm and biomass formation. This indicates that studying the targeting and secretion of proteins into the periplasm could be used to design strategies to improve recombinant protein production yields.

  • 122169.
    Ytterberg, Kim
    KTH, School of Electrical Engineering and Computer Science (EECS).
    Procedurers inverkan på kodförståelse i Java: En studie med eye-tracking2018Independent thesis Basic level (degree of Bachelor), 10 credits / 15 HE creditsStudent thesis
    Abstract [en]

    In the software life cycle, a great amount of time is spent on the final stage, the maintenance phase. At this stage, the software is fully developed and needs continuous maintenance to ensure constant functionality and efficiency of the software [25]. It is therefore important for the software to be as readable as possible since other programmers might start working on the software. It is also important to keep the code readable to quickly troubleshoot the code. Procedures are taught as a way to keep the code structured and easy to read among other abstractions. In recent years, the study of code readability has gained an increasing popularity and with the help of eye-tracking it has allowed for the study of readability in a more concrete way.

    In this report, the impact of procedures on code readability has been investigated by conducting a controlled experiment, which has been done by examining the eye movements of ten test subjects who had been tasked with interpreting a number of problems in Java, where the problems ranged from the use of procedures or not (being plain monolithic code blocks). The assigned problems involve the interpretation of code while their eye movements are recorded and presented as images and as data in a spreadsheet.

    The results show that beginners generally take longer to read methods compared to sequential code, while experienced programmers did not differ as much- or were even faster to resolve the procedural code segments. It can also be said that experienced programmers have a different way of reading code compared to beginners which may be interesting to study further. The conclusion is that control flow abstractions in the form of procedures make it easier for programmers to read code, but it takes time and experience to take advantage of their beneficial effects.

  • 122170.
    Ytterfors, Sanna
    KTH, School of Architecture and the Built Environment (ABE), Real Estate and Construction Management.
    Hur kan en checklista för miljöegenskaper viden fastighetsvärdering utformas?- Med fokus på samhällsfastigheter2014Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    The real estate market has shown an increased demand among real estate appraisers for a tool

    to facilitate the implementation of green building features into the valuation process, and for

    investors to discern a specific green feature’s impact upon value. The wide range of green

    building rating systems used on the real estate market today causes difficulties in comparison.

    To supplement the valuation report with an extended description of the properties including a

    systematic presentation of relevant features from a sustainability perspective, RICS (2012)

    has formed a draft of a ”sustainability checklist”, which purpose is to highlight differences,

    increase the supply of information and enhance transparency in the property market.

    The study aims to investigate the development, design and function of a sustainability

    checklist, and whether it can be implemented on public properties. A list was created based on

    the draft from RICS ”Sustainability Checklist”, and interviewed players in the real estate

    market, which were implemented on a specific project consisting of a public building. The

    result of the study was analysed and has formed the basis of the conclusions drawn.

    The result of the study conducted within this thesis shows that the list based on

    RICS ”Sustainability Checklist” with sustainability aspects included can be implemented also

    on public buildings, as these buildings possess similar features as the commercial buildings.

    Some main differences can be seen, overall resulting from: budget constraints, local

    conditions and regulations from the municipality and other parties. Also, the choice of a

    certain green building rating system influence the effect on the outcome, whereas a close

    relationship can be find between certain aspects within the sustainability checklist and green

    building rating systems, and the commercial real estate developers increasingly chose to

    certify their buildings with the international systems, which are more complex and contain a

    higher number of aspects.

    However, in order to achieve a successful implementation of the list among appraisers within

    the real estate market, the role of the valuer must change to more informative, which also

    make demands on the level of knowledge and the provision of training and guidance for

    professional appraisers, a task to be undertaken by professional valuators. Furthermore, it is

    also established within this study that the list should be further processed and modified in

    order to facilitate the gathering of information and to simplify for the appraiser to use it as a

    supplement within the valuation process.

  • 122171.
    Yttergren, Rose-Marie
    KTH, Superseded Departments, Materials Science and Engineering.
    Mechanical properties of laminated ceramic composites1999Doctoral thesis, monograph (Other scientific)
  • 122172.
    Ytterström, Anders
    KTH, Superseded Departments, Aeronautical Engineering.
    Parallel Computing for Applications in Aeronautical CFD2001Doctoral thesis, comprehensive summary (Other scientific)
  • 122173. Yu, A. B.
    et al.
    Liu, A. Q.
    Oberhammer, Joachim
    KTH, School of Electrical Engineering (EES), Microsystem Technology.
    Zhang, Q. X.
    Hosseini, H. M.
    Characterization and optimization of dry releasing for the fabrication of RF MEMS capacitive switches2007In: Journal of Micromechanics and Microengineering, ISSN 0960-1317, E-ISSN 1361-6439, Vol. 17, no 10, p. 2024-2030Article in journal (Refereed)
    Abstract [en]

    This paper discusses fabrication aspects of photoresist sacrificial layers for fabricating metal bridges of capacitive radio frequency (RF) microelectromechanical systems (MEMS) switches. First, reflow of the photoresist layer after lithography is investigated for reducing mechanical fracture of the metal layer by smoothing the edges of the sacrificial layer. Second, the dry-etch releasing process of the structures in an O-2 plasma has been investigated by identifying suitable etching parameters. The findings in this paper reveal that the mechanical performance of the released bridges strongly depends on the etch parameters. It is shown that especially the etching power affects the mean stress and the stress gradient in the bridge, which results in buckling and deformed bridge shape for an etching power above 500 W, drastically increasing the actuation voltage and reducing the down-state capacitance. Finally, the paper presents a suitable parameter set for the release etching of capacitive MEMS metal bridges.

  • 122174. Yu, Aiping
    et al.
    Chen, Zhongwei
    Maric, Radenka
    Zhang, Lei
    Zhang, Jiujun
    Yan, Jinyue
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology, Energy Processes.
    Electrochemical supercapacitors for energy storage and delivery: Advanced materials, technologies and applications2015In: Applied Energy, ISSN 0306-2619, E-ISSN 1872-9118, Vol. 153, p. 1-2Article in journal (Refereed)
  • 122175. Yu, Biying
    et al.
    Ma, Ye
    Xue, Meimei
    Tang, Baojun
    Wang, Bin
    Yan, Jinyue
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology.
    Wei, Yi-Ming
    Environmental benefits from ridesharing: A case of Beijing2017In: Applied Energy, ISSN 0306-2619, E-ISSN 1872-9118, Vol. 191, p. 141-152Article in journal (Refereed)
    Abstract [en]

    Emerging ridesharing travel could be an effective way in China to reduce travel demand by cars, which can further seek to shift personal transportation choices from an owned asset to a service used on demand and lessen the traffic jam and emissions. Drawing on the raw observed ridesharing trip data provided by DiDi Chuxing company, this study evaluated the direct environmental benefits of ridesharing resulted from the travel mode shift and the indirect environmental benefits resulted from the attitude change towards car purchase behavior. The megacity Beijing is taken as the empirical context given its more serious situation of traffic congestion and difficulties for car purchase. Estimation results show that direct annual energy savings made by ridesharing are approximately 26.6 thousand tce, and annual emission reductions of CO2 and NOx are approximately 46.2 thousand tons and 253.7 tons, respectively. Besides, using ridesharing service will lead to substantial energy savings and emission reductions from the long-term perspective attributing to the weakening willingness on purchasing new cars. Promoting EVs among ridesharing vehicles and switching to clean electricity generation as well as improving vehicle efficiency can further enhance the environmental benefits of ridesharing, with maximum effects amounting to 67% of energy savings and 57% of CO2 emission reductions compared to 2016 level of the fuel related energy consumption and emissions made by ridesharing.

  • 122176.
    Yu, Caroline
    et al.
    KTH, School of Electrical Engineering and Computer Science (EECS).
    Zhang, Ann-Mia
    KTH, School of Electrical Engineering and Computer Science (EECS).
    The different viewing experiences between special and visual effects2019Independent thesis Basic level (degree of Bachelor), 10 credits / 15 HE creditsStudent thesis
    Abstract [en]

    Computer graphics field is rapidly growing and is widely used in many industries, especially in cinematics. The visual effects, which is a part of the field, have become more affordable in comparison to special effect. By using more visual effects, safety during the shooting increases and the use of resources decreases. However, the field is still young and there are a lot of flaws to consider when creating such an effect. It is important that CGI in movies are created in such a way that it does not disrupt the viewing experience unless it’s done on purpose. Therefore, CGI in a real-life setting should look real. To create CGI that is closer to reality, this study examines the differences between special effects and visual effects in the aspect of the viewing experience.

    To investigate this question, we conducted an experiment following a semi-structured interview. 13 students participated in this study where they had to watch video clips representing the special respective visual effect. During the experiment, they did a self- report by filling in a questionnaire. A Valence-Arousal model was used to examine the subject’s emotional reactions.

    The result suggests that there are no significant differences between the two effects in regard to an emotional reaction. However, it shows that the visual effect had flaws of being too plastic and too perfect which makes it less convincing compared to the special effects. In contrary, the special effects do not have the ability to be exaggerating, which in turn makes it more exciting to watch the visual effects. Although this study does not solve any flaws, it highlights those that need to be fixed for the goals of improving CGI.

  • 122177.
    Yu, Cedric Jacques
    KTH, School of Architecture and the Built Environment (ABE), Architecture, Urban Design.
    Housing and Social Capital: Prototypes for Collective Living2017Independent thesis Advanced level (degree of Master (One Year)), 10 credits / 15 HE creditsStudent thesis
    Abstract [en]

    Challenges to contemporary urban cities can be traced to levels of social health and wellbeing experienced by its citizens.  

    This paper looks at traditional space economics in housing from the lens of social capital theory and examines design alternatives in the form of collective housing.   

  • 122178.
    Yu, ChaoQing
    et al.
    Tsinghua Univ, Dept Earth Syst Sci, Minist Educ, Key Lab Earth Syst Modeling, Beijing, Peoples R China.;Cross Strait Tsinghua Res Inst, AI Earth Lab, Xiamen, Peoples R China..
    Huang, Xiao
    Tsinghua Univ, Dept Earth Syst Sci, Minist Educ, Key Lab Earth Syst Modeling, Beijing, Peoples R China.;Norwegian Inst Bioecon Res, Saerheim, Norway..
    Chen, Han
    Tsinghua Univ, Dept Earth Syst Sci, Minist Educ, Key Lab Earth Syst Modeling, Beijing, Peoples R China..
    Godfray, H. Charles J.
    Univ Oxford, Dept Zool, Oxford, England.;Univ Oxford, Oxford Martin Sch, Oxford, England..
    Wright, Jonathon S.
    Tsinghua Univ, Dept Earth Syst Sci, Minist Educ, Key Lab Earth Syst Modeling, Beijing, Peoples R China..
    Hall, Jim W.
    Univ Oxford, Environm Change Inst, Oxford, England..
    Gong, Peng
    Tsinghua Univ, Dept Earth Syst Sci, Minist Educ, Key Lab Earth Syst Modeling, Beijing, Peoples R China.;Cross Strait Tsinghua Res Inst, AI Earth Lab, Xiamen, Peoples R China..
    Ni, ShaoQiang
    Tsinghua Univ, Dept Earth Syst Sci, Minist Educ, Key Lab Earth Syst Modeling, Beijing, Peoples R China..
    Qiao, ShengChao
    Tsinghua Univ, Dept Earth Syst Sci, Minist Educ, Key Lab Earth Syst Modeling, Beijing, Peoples R China..
    Huang, GuoRui
    Tsinghua Univ, Dept Earth Syst Sci, Minist Educ, Key Lab Earth Syst Modeling, Beijing, Peoples R China..
    Xiao, YuChen
    Tsinghua Univ, Dept Earth Syst Sci, Minist Educ, Key Lab Earth Syst Modeling, Beijing, Peoples R China..
    Zhang, Jie
    Tsinghua Univ, Dept Earth Syst Sci, Minist Educ, Key Lab Earth Syst Modeling, Beijing, Peoples R China..
    Feng, Zhao
    Tsinghua Univ, Dept Earth Syst Sci, Minist Educ, Key Lab Earth Syst Modeling, Beijing, Peoples R China..
    Ju, XiaoTang
    China Agr Univ, Coll Resources & Environm Sci, Beijing, Peoples R China..
    Ciais, Philippe
    LSCE, Gif Sur Yvette, France..
    Stenseth, Nils Chr.
    Tsinghua Univ, Dept Earth Syst Sci, Minist Educ, Key Lab Earth Syst Modeling, Beijing, Peoples R China.;Univ Oslo, CEES, Oslo, Norway..
    Hessen, Dag O.
    Univ Oslo, Sect Aquat Biol & Toxicol AQUA, Oslo, Norway..
    Sun, ZhanLi
    Leibniz Inst Agr Dev Transit Econ IAMO, Halle, Saale, Germany..
    Yu, Le
    Tsinghua Univ, Dept Earth Syst Sci, Minist Educ, Key Lab Earth Syst Modeling, Beijing, Peoples R China..
    Cai, WenJia
    Tsinghua Univ, Dept Earth Syst Sci, Minist Educ, Key Lab Earth Syst Modeling, Beijing, Peoples R China..
    Fu, HaoHuan
    Tsinghua Univ, Dept Earth Syst Sci, Minist Educ, Key Lab Earth Syst Modeling, Beijing, Peoples R China..
    Huang, XiaoMeng
    Tsinghua Univ, Dept Earth Syst Sci, Minist Educ, Key Lab Earth Syst Modeling, Beijing, Peoples R China..
    Zhang, Chi
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH).
    Liu, HongBin
    Chinese Acad Agr Sci, Inst Agr Resources & Reg Planning, Beijing, Peoples R China..
    Taylor, James
    Newcastle Univ, Sch Nat & Environm Sci, Newcastle, England..
    Managing nitrogen to restore water quality in China2019In: Nature, ISSN 0028-0836, E-ISSN 1476-4687, Vol. 567, no 7749, p. 516-520Article in journal (Refereed)
    Abstract [en]

    The nitrogen cycle has been radically changed by human activities(1). China consumes nearly one third of the world's nitrogen fertilizers. The excessive application of fertilizers(2,3) and increased nitrogen discharge from livestock, domestic and industrial sources have resulted in pervasive water pollution. Quantifying a nitrogen 'boundary'(4) in heterogeneous environments is important for the effective management of local water quality. Here we use a combination of water-quality observations and simulated nitrogen discharge from agricultural and other sources to estimate spatial patterns of nitrogen discharge into water bodies across China from 1955 to 2014. We find that the critical surface-water quality standard (1.0 milligrams of nitrogen per litre) was being exceeded in most provinces by the mid-1980s, and that current rates of anthropogenic nitrogen discharge (14.5 +/- 3.1 megatonnes of nitrogen per year) to fresh water are about 2.7 times the estimated 'safe' nitrogen discharge threshold (5.2 +/- 0.7 megatonnes of nitrogen per year). Current efforts to reduce pollution through wastewater treatment and by improving cropland nitrogen management can partially remedy this situation. Domestic wastewater treatment has helped to reduce net discharge by 0.7 +/- 0.1 megatonnes in 2014, but at high monetary and energy costs. Improved cropland nitrogen management could remove another 2.3 +/- 0.3 megatonnes of nitrogen per year-about 25 per cent of the excess discharge to fresh water. Successfully restoring a clean water environment in China will further require transformational changes to boost the national nutrient recycling rate from its current average of 36 per cent to about 87 per cent, which is a level typical of traditional Chinese agriculture. Although ambitious, such a high level of nitrogen recycling is technologically achievable at an estimated capital cost of approximately 100 billion US dollars and operating costs of 18-29 billion US dollars per year, and could provide co-benefits such as recycled wastewater for crop irrigation and improved environmental quality and ecosystem services.

  • 122179.
    Yu, Dong
    KTH, School of Industrial Engineering and Management (ITM), Industrial Ecology.
    Landfill Leachate Treatment Case Study, SRV Atervinning, Sweden2007Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    SRV återvinning AB is a joint-stock waste company located in the south of Stockholm. Since the first operation, three landfills have been practiced successively. The landfill generates about 200,000 to 250,000 cubic meters of leachate per year. An on-site leachate treatment plant consists of sequencing batch reactor (SBR) and constructed wetland was build for Landfill III. The research was to find out:

    - the capacity and efficiency of the existing on-site leachate treatment plant;

    - to analyse the costs and environmental benefits of different alternatives; and

    - using the above results, to assess and suggest supplementary methods to treat total landfill leachate concerning the site-specific conditions.

    This thesis contains a literature review of leachate production and composition as well as leachate treatment technologies. The technologies are described, evaluated or compared. The contents of this thesis divided into 11 chapters. Various calculations and assumptions that have been developed for effective controlling and treating leachate from landfills.

    Chapter 1 is devoted to basic facts of the leachate problems at SRV återvinning AB. Chapter 2 presented the methodologies that have been set up for solutions and suggestions. Chapter 3 provides a general background of the generation and compositions of waste leachate. A general overview of leachate treatment methods and systems is presented in Chapter 4. Costs of different leachate treatment methods is also exhibited. Chapter 5 provides a detailed current situation review of SRV återvinning AB on landfilling site, leachate quality and quantity and the existing treatment plant. Chapter 6 showed the previous application experience from other treatment plant. The calculation and comparison procedure for the capacity and efficiency of the plant at the landfill is presented in Chapter 7. Different alternatives to solve the leachate problem concerning the site-specification are proposed in Chapter 8. Their applicability, effectiveness are analyzed. Chapter 9 provides detailed discussion of alternatives and calculation procedure. After the conclusion of the thesis, recommendations for the further work are presented.

    This thesis will provide SRV återvinning AB different alternatives to solve leachate problems. Finally, considering the site-specification, economic perspective and environmental benefits, applying reverse osmosis after SBR as final step; the combination of aerated lagoon, sand filter and soil infiltration are proposed. Furthermore, the control of leachate production is also taken into account. Eventually, recommendations for the further work were presented.

  • 122180. Yu, Eunseon
    et al.
    Ryu, Seung Wook
    Radamson, Henry H.
    KTH, School of Information and Communication Technology (ICT).
    Cho, Seongjae
    Structural and Optical Characteristics of Epitaxially Grown SiGe on Si for Electronic and Photonic Device Applications2017In: Journal of Nanoelectronics and Optoelectronics, ISSN 1555-130X, E-ISSN 1555-1318, Vol. 12, no 10, p. 1129-1133Article in journal (Refereed)
    Abstract [en]

    For higher device performances including low-power consumption and high-speed operation, functional materials in wide variety are actively studied. In particular, Si compatibility is regarded as one of the indispensable prerequisites owing to cost effectiveness and high maturity of Si platform and its process integration. SiGe is gaining much interest owing to Si compatibility, high carrier mobilities, and higher optical confinement capability compared with Si. In this work, SiGe layers have been epitaxially grown on Si substrate under different conditions and their structural and optical characteristics are analyzed in depth. Various analysis tools are used cooperatively, including high-resolution transmission electron microscopy (HR-TEM), dynamic secondary ion mass spectroscopy (SIMS), X-ray diffraction spectroscopy (XRD), and long-wavelength ellipsometer, in order to extract the thickness as the result of epitaxy condition, Ge fraction, interface status, lattice constant, and refractive index with extinction coefficient for setting up parameter database for electronic and photonic device applications.

  • 122181. Yu, F.
    et al.
    Li, F.
    Yao, T.
    Du, J.
    Liang, Y.
    Wang, Y.
    Han, H.
    Sun, Licheng
    KTH, School of Chemical Science and Engineering (CHE), Centres, Centre of Molecular Devices, CMD. KTH, School of Chemical Science and Engineering (CHE), Chemistry, Organic Chemistry. KTH, School of Information and Communication Technology (ICT), Centres, Zhejiang-KTH Joint Research Center of Photonics, JORCEP.
    Fabrication and Kinetic Study of a Ferrihydrite-Modified BiVO4 Photoanode2017In: ACS Catalysis, ISSN 2155-5435, E-ISSN 2155-5435, Vol. 7, no 3, p. 1868-1874Article in journal (Refereed)
    Abstract [en]

    In spite of great progress in the surface modification of semiconductor photoelectrodes, the role of the metal oxide cocatalyst on photoelectrochemical (PEC) performance is still not well understood. In this study, ferrihydrite (Fh) as a novel cocatalyst was decorated on a wormlike nanoporous BiVO4 photoanode. A surface kinetics study of Fh/BiVO4 by intensity-modulated photocurrent spectroscopy (IMPS) evidences the primary role of Fh on PEC performance enhancement, varying with the loading of Fh. It was found that dispersed Fh nanoparticles accelerate hole transfer for water oxidation, but the resulting photoanode suffers from poor stability. The thick layers of Fh address the stability of the electrode by suppressing surface charge recombination but result in reduced hole transfer rates. Modification of a BiVO4 film with optimally thick layers of discrete nanoflakes effectively reduces charge recombination without compromising stability, leading to a high AM 1.5 G photocurrent of 4.78 mA/cm2 at 1.23 V versus the reversible hydrogen electrode and an applied bias photon to current efficiency of 1.81% at 0.61 V. These values are comparable to the best results reported for undoped BiVO4. (Chemical Equation Presented).

  • 122182.
    Yu, Fangxian
    KTH, School of Information and Communication Technology (ICT).
    Implement Image Processing Algorithm on Vector Processing Platform2016Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    Image processing is processing of images using mathematical operations by using any form of signal processing for which the input is a image, a series of images, or a video. The DSPs usually excute digital signal processing algorithm with better power efficiency thus they are more suitable in portable devices. In this project, one image processing algorithm will be implemented and optimized on a specific vector dsp platform. By comparing the performance of this vector dsp platform with tobii own Eyechip, we will get the advantages and disadvantages of this vector dsp platform, and evaluate the usability of this platform under different data type conditions.

  • 122183.
    Yu, Feifan
    KTH, School of Biotechnology (BIO), Protein Technology.
    Generating Affinity Proteins for Biotechnological, Diagnostic and Therapeutic Applications2015Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    Protein engineering is a powerful tool to modify proteins to generate novel and desired properties that could be applied in biotechnological, diagnostics and therapeutic areas. In this thesis, both rational design and library based engineering principles have been exploited to develop affinity proteins with desired traits.

    One study was focused on the use of site-directed mutagenesis to obtain variants of the staphylococcal protein A-derived 58-residue immunoglobulin binding Z domain with improved affinity for mouse IgG1 Fc. Screening of ca. 170 constructed variants revealed one variant with a single F5I amino acid substitution, denoted ZF5I, with a ten-fold higher affinity. The Fc binding ZF5I variant was further investigated for use in affinity-driven site-specific covalent photoconjugation to mIgG1 monoclonal antibodies. Here, nine candidate positions in the domain were investigated for introduction of a UV-activatable maleimide benzophenone (MBP) group via conjugation to an introduced cysteine residue. The best photo-conjugation results were obtained for a variant in which the MBP was introduced at position 32, denoted ZF5I-Q32C-MBP, which could be conjugated at high yields to all nineteen mouse IgG1s tested. The use of a biotinylated Z-based probe for biotinylation via photoconjugation of a monoclonal anti-interferon gamma antibody resulted in a higher antigen binding activity than if a conventional amine directed biotinylation strategy was used.

    In a second study, the goal was to develop a new homogeneous immunoassay for quick antigen detection, based on split-protein complementation and pairs of antigen recognizing proteins. In one of the formats investigated, separate fragments of a split-beta-lactamase enzyme reporter were genetically linked to ZF5I-Q32C-MBP units which were individually photo-conjugated to two different mAbs recognizing different epitopes on a human interferon gamma model target analyte. Simultaneous binding of the two mAb-enzyme half probes to the analyte resulted in an analyte concentration-dependent enzyme fragment complementation which could be spectrophotometrically detected using a nitrocefin substrate.

    Using ribosome display technology, Z-domain based binders to mouse IgG1 were selected from an affibody library. One binder denoted Zmab25 was shown capable of selective binding to mouse IgG in a background of bovine IgG, and could be used for species-selective recovery of monoclonal antibodies from complex samples, resembling hybridoma culture supernatants. Epitope mapping experiments showed that that the binding site on mouse IgG was located in the Fab fragment and was overlapping with that of streptococcal protein G.

    In a final study, phage display technology was used to select affibodies binding to human interleukin 6 (IL-6), for potential use in rheumatoid arthritis (RA) therapy via blocking of the signaling involving the ternary complex between IL-6, the IL-6 receptor α (IL-6R α) and the gp130 co-receptor. Several affibodies were shown to be capable of blocking the interaction between gp130 and preformed complexes of IL-6 and soluble IL-6R α (IL-6/sIL-6R α) in vitro, corresponding to the so-called trans-signaling interaction. One of these affibody variants denoted ZIL-6_13 showed a KD of approx. 500 pM for IL-6 and was genetically fused to different chain ends of the monoclonal anti-TNF antibody adalimumab to build bi-specific “AffiMab” constructs. One construct, ZIL-6_13-HCAda,in which the affibody was fused to the N-terminus of the adalimumab heavy chain had the most optimal properties in different cell assays and was also evaluated in vivo in an acute serum amyloid A (SAA) mouse RA model, involving a dual challenge of animals with both IL-6 and TNF. Compared to adalimumab that could only reduce SAA levels to 50% at the highest dose, the bi-functional AffiMab reduced SAA levels to below the detection level. 

  • 122184.
    Yu, Feifan
    et al.
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Protein Science.
    Alesand, Veronica
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Protein Science.
    Nygren, Per-Åke
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Protein Science, Protein Engineering.
    Site-Specific Photoconjugation of Beta-Lactamase Fragments to Monoclonal Antibodies Enables Sensitive Analyte Detection via Split-Enzyme Complementation2018In: Biotechnology Journal, ISSN 1860-6768, E-ISSN 1860-7314, Vol. 13, no 7, article id 1700688Article in journal (Refereed)
    Abstract [en]

    Protein fragment complementation assays (PCA) rely on a proximity-driven reconstitution of a split reporter protein activity, typically via interaction between bait and prey units separately fused to the reporter protein halves. The PCA principle can also be formatted for use in immunossays for analyte detection, e.g., via the use of small immunoglobulin binding proteins (IgBp) as fusion partners to split-reporter protein fragments for conversion of pairs of antibodies into split-protein half-probes. However, the non-covalent binding between IgBp and antibodies is not ideal for development of robust assays. Here, the authors describe how split-enzyme reporter halves can be both site-specifically and covalently photoconjugated at antibody Fc-parts for use in homogeneous dual-antibody in vitro immunoassays based on analyte-dependent split-enzyme fragment complementation. The half-probes consist of parts of a beta-lactamase split-protein reporter fused to an immunoglobulin Fc binding domain equipped with a unique cysteine residue at which a photoactivable maleimide benzophenone group (MBP) is attached. Using such antibody conjugates the authors obtain an analyte-driven complementation of the reporter enzyme fragments monitored via conversion of a chromogenic substrate. Results from detection of human interferon-gamma and the extracellular domain of HER2 is shown. The described principles for site-specific conjugation of proteins to antibodies should be broadly applicable.

  • 122185.
    Yu, Feifan
    et al.
    KTH, School of Biotechnology (BIO), Protein Technology.
    Alesand, Veronica
    KTH, School of Biotechnology (BIO), Protein Technology.
    Nygren, Per-Åke
    KTH, School of Biotechnology (BIO), Protein Technology.
    Site-specific photoconjugation of betalactamase split-protein fragments to monoclonal antibodies for homogeneous assay developmentManuscript (preprint) (Other academic)
  • 122186.
    Yu, Feifan
    et al.
    KTH, School of Biotechnology (BIO), Protein Technology.
    Gudmundsdotter, Lindvi
    Akal, Anastassja
    KTH, School of Biotechnology (BIO), Protein Technology.
    Gunneriusson, Elin
    Frejd, Fredrik
    Nygren, Per-Åke
    KTH, School of Biotechnology (BIO), Protein Technology.
    An affibody-adalimumab hybrid blocks combined IL-6 and TNF-triggered serum amyloid A secretion in vivo2014In: mAbs, ISSN 1942-0862, Vol. 6, no 6, p. 1598-1607Article in journal (Refereed)
    Abstract [en]

    In inflammatory disease conditions, the regulation of the cytokine system is impaired, leading to tissue damages. Here, we used protein engineering to develop biologicals suitable for blocking a combination of inflammation driving cytokines by a single construct. From a set of interleukin (IL)-6-binding affibody molecules selected by phage display, five variants with a capability of blocking the interaction between complexes of soluble IL-6 receptor a (sIL-6R alpha) and IL6 and the co-receptor gp130 were identified. In cell assays designed to analyze any blocking capacity of the classical or the alternative (trans) signaling IL-6 pathways, one variant, Z(IL-6_13) with an affinity (K-D) for IL-6 of similar to 500 pM, showed the best performance. To construct fusion proteins ("AffiMabs") with dual cytokine specificities, Z(IL-6_13) was fused to either the N-or C-terminus of both the heavy and light chains of the anti-tumor necrosis factor (TNF) monoclonal antibody adalimumab (Humira (R)). One AffiMab construct with Z(IL-6_13) positioned at the N-terminus of the heavy chain, denoted Z(IL-6_13)-HCAda, was determined to be the most optimal, and it was subsequently evaluated in an acute Serum Amyloid A (SAA) model in mice. Administration of the AffiMab or adalimumab prior to challenge with a mix of IL-6 and TNF reduced the levels of serum SAA in a dose-dependent manner. Interestingly, the highest dose (70 mg/kg body weight) of adalimumab only resulted in a 50% reduction of SAA-levels, whereas the corresponding dose of the Z(IL-6_13)-HCAda AffiMab with combined IL-6/TNF specificity, resulted in SAA levels below the detection limit.

  • 122187.
    Yu, Feifan
    et al.
    KTH, School of Biotechnology (BIO), Molecular Biotechnology.
    Järver, Peter
    KTH, School of Biotechnology (BIO), Molecular Biotechnology.
    Nygren, Per-Åke
    KTH, School of Biotechnology (BIO), Molecular Biotechnology.
    Tailor-Making a Protein A-Derived Domain for Efficient Site-Specific Photocoupling to Fc of Mouse IgG(1)2013In: PLoS ONE, ISSN 1932-6203, E-ISSN 1932-6203, Vol. 8, no 2, p. e56597-Article in journal (Refereed)
    Abstract [en]

    Affinity proteins binding to antibody constant regions have proved to be invaluable tools in biotechnology. Here, protein engineering was used to expand the repertoire of available immunoglobulin binding proteins via improvement of the binding strength between the widely used staphylococcal protein A-derived Z domain and the important immunoglobulin isotype mouse IgG(1) (mIgG(1)). Addressing seven positions in the 58-residue three-helix bundle Z domain by single or double amino acid substitutions, a total of 170 variants were individually constructed, produced in E. coli and tested for binding to a set of mouse IgG(1) monoclonal antibodies (mAbs). The best variant, denoted Z(F5I) corresponding to a Phe to Ile substitution at position 5, showed a typical ten-fold higher affinity than the wild-type as determined by biosensor technology. Eight amino acid positions in the Z(F5I) variant were separately mutated to cysteine for incorporation of a photoactivable maleimide-benzophenone (MBP) group as a probe for site-specific photoconjugation to Fc of mIgG(1), The best photocoupling efficiency to mIgG(1) Fc was seen when the MBP group was coupled to Cys at position 32, resulting in adduct formation to more than 60% of all heavy chains, with no observable non-selective conjugation to the light chains. A similar coupling yield was obtained for a panel of 19 different mIgG(1) mAbs, indicating a general characteristic. To exemplify functionalization of a mIgG(1) antibody via site-specific biotinylation, the Z(F5I-Q32C-MBP) protein was first biotinylated using an amine reactive reagent and subsequently photoconjugated to an anti-human interferon-gamma mIgG(1) mAb. When comparing the specific antigen binding ability of the probe-biotinylated mAb to that of the directly biotinylated mAb, a significantly h`igher bioactivity was observed for the sample biotinylated using the Z(F5I-Q32C-MBP) probe. This result indicates that the use of a site-specific and affinity probe-mediated conjugation strategy can result in antibody reagents with increased assay sensitivity.

  • 122188. Yu, Fengshou
    et al.
    Li, Fei
    Hu, Jixiang
    Bai, Lichen
    Zhu, Yong
    Sun, Licheng
    Electrocatalytic water oxidation by a macrocyclic Cu(II) complex in neutral phosphate buffer2016In: Chemical Communications, ISSN 1359-7345, E-ISSN 1364-548X, Vol. 52, no 68, p. 10377-10380Article in journal (Refereed)
    Abstract [en]

    A single-site copper complex, [Cu(TMC)(H2O)](NO3)(2) (1, TMC = 1,4,8,11-tetramethyl-1,4,8,11-tetraazacyclotetradecane), was found to be the most active copper-based catalyst towards electrocatalytic water oxidation in neutral aqueous solution. Complex 1 leads to a cathodic shift of approximately 200 mV in potential to reach a current density of 1 mA cm(-2) in comparison with that of the previously reported dinuclear copper complex under the same conditions. Upon immobilization of complex 1 on carbon cloth, it shows greatly improved activity than other copper-based WOCs including CuOx and Cu2+.

  • 122189. Yu, Fengshou
    et al.
    Li, Fei
    Sun, Licheng
    Dalian University of Technology, China.
    Stainless steel as an efficient electrocatalyst for water oxidation in alkaline solution2016In: International journal of hydrogen energy, ISSN 0360-3199, E-ISSN 1879-3487, Vol. 41, no 10, p. 5230-5233Article in journal (Refereed)
    Abstract [en]

    Commercially available 316L stainless steel was found to be a highly efficient material for catalytic water oxidation. By directly using the stainless steel as an anode without any substrate support, a 10 mA/cm(2) current density with 96% Faradaic efficiency was obtained at n = 0.37 V in alkaline solution (1 M KOH). The stainless steel film exhibits excellent longevity and a small Tafel slope of 30 mV/decade in water oxidation, making it an ideal anodic electrocatalyst. Copyright 

  • 122190. Yu, Fengshou
    et al.
    Li, Fei
    Zhang, Biaobiao
    Li, Hua
    Sun, Licheng
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Organic Chemistry. Dalian University of Technology, China .
    Efficient Electrocatalytic Water Oxidation by a Copper Oxide Thin Film in Borate Buffer2015In: ACS Catalysis, ISSN 2155-5435, E-ISSN 2155-5435, Vol. 5, no 2, p. 627-630Article in journal (Refereed)
    Abstract [en]

    A robust water oxidation catalyst based on copper oxide was prepared by facile electrodeposition of Cu2+ from borate buffer solution under near neutral conditions. The Cu-B-i thin film exhibits high activity and long-term stability in Cu2+-free pH 9 borate buffer. A steady current density of 1.2 mA/cm(2) was sustained for at least 10 h at 1.3 V versus NHE without iR compensation, which sets a new benchmark for copper-based OEC.

  • 122191.
    Yu, Fiona
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH).
    Sulfur Addition to Reduce CO Emissions2018Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    In autumn 2017, an experiment was conducted for the reduction of carbon

    monoxide (CO) emissions commissioned by Holmen Paper Braviken, one

    of the world’s most production-efficient paper mills. Digitalization has increased

    in recent years, which has resulted in a decreased demand for graphic

    paper. The goal of finding cost-reducing solutions in the manufacturing process

    has been increased in Holmen Paper Braviken to meet the rising price

    pressure and strengthen competitiveness. Braviken consumes large quantities

    of steam in the paper machines and some of this steam is produced in

    the solid fuel boiler. The solid fuel boiler combusts bark, wood chips, and

    water treatment sludge. When adding sulfur-rich water treatment sludge to

    the fuel mix, it has been observed that CO levels decrease without increasing

    NOx levels. To control the amount of sulfur addition, it has been proposed

    that pure sulfur can be microdosed into the fuel mix. A previous short-term

    experiment was conducted in Braviken during autumn 2016 with a successful

    result.

    The present study was conducted with the aim of mapping the effects of

    sulfur addition to the solid fuel boiler in Braviken concerning CO emissions.

    The possibility to operate the plant and interaction with the water treatment

    sludge have also been investigated. The study was performed through

    the construction of a microdosing system and a long-term attempt of sulfur

    addition.

    The result shows that the optimal sulfur concentration of Braviken’s solid

    fuel boiler for reducing CO emissions is 6 kg/h S (1.03 kg S/ton C). The

    interaction between elemental sulfur with the sulfur-rich water treatment

    sludge is complex, but with sulfur dosage a reduction of 42% CO can be

    achieved. NOx levels have not shown any change on the addition of sulfur.

    The study shows that CO emissions are at a more stable level with sulfur dosing.

    The result becomes difficult to analyze because the parameters varied.

    The effects of parameters should be investigated with the recommendation

    to perform a more prolonged experiment on sulfur addition.

  • 122192. Yu, G.
    et al.
    Yin, S. W.
    Liu, Y. Q.
    Chen, J. S.
    Xu, X. J.
    Sun, X. B.
    Ma, D. G.
    Zhan, X. W.
    Peng, Q.
    Shuai, Z. G.
    Tang, B. Z.
    Zhu, D. B.
    Fang, W. H.
    Luo, Yi
    KTH, School of Biotechnology (BIO), Theoretical Chemistry.
    Structures, electronic states, photoluminescence, and carrier transport properties of 1,1-disubstituted 2,3,4,5-tetraphenylsiloles2005In: Journal of the American Chemical Society, ISSN 0002-7863, E-ISSN 1520-5126, Vol. 127, no 17, p. 6335-6346Article, review/survey (Refereed)
    Abstract [en]

    The excellent electroluminescent (EL) properties of 1,1-disubstituted 2,3,4,5-tetraphenylsiloles, 1-methyl-1,2,3,4,5-pentaphenylsilole (MPPS), and 1,1,2,3,4,5-hexaphenylsilole (HPS) have been found. Despite some studies devoted to these materials, very little is known about the real origin of their unique EL properties. Therefore, we investigated the structures, photoluminescence (PL), and charge carrier transport properties of 1,1-disubstituted 2,3,4,5-tetraphenylsiloles as well as the effect of substituents on these characteristics. The single crystals of the three siloles involving 1,1-dimethyl-2,3,4,5-tetraphenylsilole (DMTPS), MPPS, and HIPS were grown and their crystal structures were determined by X-ray diffraction. Three siloles have nonplanar molecular structures. The substituents at 1,1-positions enhance the steric hindrance and have predominant influence on the twisted degree of phenyl groups at ring carbons. This nonplanar structure reduces the intermolecular interaction and the likelihood of excimer formation, and increases PL efficiency in the solid state. The silole films show high fluorescence quantum yields (75-85%), whereas their dilute solutions exhibit a faint emission. The electronic structures of the three siloles were investigated using quantum chemical calculations. The highest occupied molecular orbitals (HOMOs) and the lowest unoccupied molecular orbitals (LUMOs) are mainly localized on the silole ring and two phenyl groups at 2,5-positions in all cases, while the LUMOs have a significant orbital density at two exocyclic Si-C bonds. The extremely theoretical studies of luminescent properties were carried out. We calculated the nonradiative decay rate of the first excited state as well as the radiative one. It is found that the faint emission of DMTPS in solutions mainly results from the huge nonradiative decay rate. In solid states, molecular packing can remarkably restrict the intramolecular rotation of the peripheral side phenyl ring, which has a large contribution to the nonradiative transition process. This explains why the 1,1-disubstituted 2,3,4,5-tetraphenylsiloles in the thin films exhibit high fluorescence quantum yields. The charge carrier mobilities of the MPPS and HPS films were measured using a transient EL technique. We obtained a mobility of 2.1 x 10(-6) cm(2)/V(.)s in the MPPS film at an electric field of 1.2 x 10(6) V/cm. This mobility is comparable to that of Alq(3), which is one of the most extensively used electron transport materials in organic light-emitting diodes (LEDs), at the same electric field. The electron mobility of the HPS film is about similar to 1.5 times higher than that of the MPPS film. To the best of our knowledge, this kind of material is one of the most excellent emissive materials that possess both high charge carrier mobility and high PL efficiency in the solid states simultaneously. The excellent EL performances of MPPS and HPS are presumably ascribed to these characteristics.

  • 122193. Yu, H.
    et al.
    Jin, Z. P.
    Chen, Q.
    Hillert, Mats
    KTH, Superseded Departments, Materials Science and Engineering.
    Thermodynamic assessment of the lithium-borate system2000In: Journal of The American Ceramic Society, ISSN 0002-7820, E-ISSN 1551-2916, Vol. 83, no 12, p. 3082-3088Article in journal (Refereed)
    Abstract [en]

    The Li2O-B2O3 quasi-binary system is assessed. A two-sublattice ionic solution model, (Li1+)(P)(O2-, BO33-, B4O72-, B3O4.5)(Q), is adopted to describe the liquid phase, All solid phases are treated as stoichiometric compounds. A set of parameters consistent with most of the available experimental data on phase diagram and thermodynamic properties is obtained by using the CALPHAD technique.

  • 122194.
    Yu, Hang
    KTH, School of Information and Communication Technology (ICT).
    A/B testing data-driven user experinece2017Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    A/B testing was an unpopular part in big data area in the past. Because of the unequal investment (finance and techniques) return have always been disappointing to the market. Fortunately, in recent years with lowering barriers to entry, many companies have the ability to initiate A/B testing. The barriers are expressed as specific cost on techniques and financial. A/B testing has become an emerging technique of optimizing web pages or applications. However, the feedback from real market is less productive in some ways than we anticipated. One of the important reasons leading to the rising complaints is that A/B testing is abused. At present, more developers step into A/B testing thinking it can easily help them to increase the conversion rate by using popular A/B testing analysis tools such as Google Analytics and Optimizely, but the important knowledge and research before testing are ignored. A/B testing is based on hypothesis and the outcome of the hypothesis belongs to predictive conclusion. So the test initiating from an arbitrary hypothesis will inevitably lead to errors. What is worse is that with increasing business needs, sometimes only one metric is not enough to decide whether the change is good or not. Also, when more metrics are involved into the evaluation system, the decision making becomes more complicated. Therefore, the decision engine is implemented for solving these kind of problems by selection of representative testing scenarios and related metrics, statistical significance of sample and algorithms applicability. In comparison to popular analysis tools, the decision engine is more comprehensive, it is guidance and algorithms selective. It also has the ability to run multiple metrics simultaneously. The data-driven decision engine evolves A/B testing to the next generation.

  • 122195.
    Yu, Hanxiao
    et al.
    Beijing Inst Technol, Sch Informat & Elect, Beijing 100081, Peoples R China..
    Fei, Zesong
    Beijing Inst Technol, Sch Informat & Elect, Beijing 100081, Peoples R China..
    Cao, Congzhe
    Univ Alberta, Dept Elect & Comp Engn, Edmonton, AB T6G 1H9, Canada..
    Xiao, Ming
    KTH, School of Electrical Engineering and Computer Science (EECS), Information Science and Engineering.
    Jia, Dai
    Beijing Inst Technol, Sch Informat & Elect, Beijing 100081, Peoples R China..
    Ye, Neng
    Beijing Inst Technol, Sch Informat & Elect, Beijing 100081, Peoples R China..
    Analysis of irregular repetition spatially-coupled slotted ALOHA2019In: Science China Information Sciences, ISSN 1674-733X, E-ISSN 1869-1919, Vol. 62, no 8, article id 080302Article in journal (Refereed)
    Abstract [en]

    Contention-based access is a promising technology for massive and sporadic transmissions. In this paper, we propose a novel contention-based multiple access scheme, named irregular repetition spatiallycoupled slotted ALOHA (IRSC-SA), motivated by the spatial coupling and irregular repetition techniques. There are different classes of users and slots in IRSC-SA, which result in unequal protection for different users. Considering that, we derive a novel density evolution (DE) method, which deals with unequal packet protection and introduces Bayesian reasoning to analyze the throughput threshold of the proposed IRSC-SA. Theoretical analysis and simulation results show that the proposed scheme achieves better asymptotic threshold and system packet throughput performance than the conventional spatially-coupled slotted ALOHA.

  • 122196. Yu, Hoi-Fung
    et al.
    Greiner, Jochen
    van Eerten, Hendrik
    Burgess, J. Michael
    KTH, School of Engineering Sciences (SCI), Physics, Particle and Astroparticle Physics.
    Bhat, P. Narayana
    Briggs, Michael S.
    Connaughton, Valerie
    Diehl, Roland
    Goldstein, Adam
    Gruber, David
    Jenke, Peter A.
    von Kienlin, Andreas
    Kouveliotou, Chryssa
    Paciesas, William S.
    Pelassa, Veronique
    Preece, Robert D.
    Roberts, Oliver J.
    Zhang, Bin-Bin
    Synchrotron cooling in energetic gamma-ray bursts observed by the Fermi Gamma-Ray Burst Monitor2015In: Astronomy and Astrophysics, ISSN 0004-6361, E-ISSN 1432-0746, Vol. 573, article id A81Article in journal (Refereed)
    Abstract [en]

    Context. We study the time-resolved spectral properties of energetic gamma-ray bursts (GRBs) with good high-energy photon statistics observed by the Gamma-Ray Burst Monitor ((IBM) onboard the Fermi Gamma-Ray Space Telescope. Aims. We aim to constrain in detail the spectral properties of GRB prompt emission on a time-resolved basis and to discuss the theoretical implications of the fitting results in the context of various prompt emission models. Methods. Our sample comprises eight GRBs observed by the Fermi (IBM in its first five years of mission, with 1 keV-1 MeV fluence f > 1.0 x 10(-4) erg cm(-2) and a signal-to-noise ratio level of S/N >= 10.0 above 900 keV. We performed a time-resolved spectral analysis using a variable temporal binning technique according to optimal S/N criteria, resulting in a total of 299 time-resolved spectra. We performed Band function fits to all spectra and obtained the distributions for the low-energy power-lay index alpha, the high-energy power-law index beta, the peak energy in the observed nu F-nu, spectrum E-p, and the difference between the low- and high-energy power-law indices Delta s = alpha-beta. We also applied a physically motivated synchrotron model, which is a triple power-law with constrained power-law indices and a blackbody component, to test the prompt emission for consistency with a synchrotron origin and obtain the distributions for the two break energies E-b,E-1 and E-b,E-2 the middle segment power-law index beta, and the Planck function temperature kT. Results. The Band function parameter distributions are alpha = -0.73(-0.21)(+0.16), beta = -2.13(-0.56)(+0.28), E-p = 374.47(-187.7)(+307.3) keV (log(10) E-p = 2.577(-0.30)(+0.26)), and Delta s = 1.38(-0.31)(+0.54), with average errors sigma(alpha) similar to 0.1, sigma(beta) similar to 0.2, and sigma(Ep) similar to 0.1E(p). Using the distributions of Delta s and beta, the electron population index p is found to be consistent with the "moderately fast" scenario, in which fast- and slow-cooling scenarios cannot be distinguished. The physically motivated synchrotron-fitting function parameter distributions are E-b,E-1 = 129.6(-32.4)(+132.2) keV, E-b,E-2 = 631.4(-309.6)(+582) keV, beta = 1.721(-0.25)(+0.48), and kT = 10.4(-3.7)(+4.9) keV, with average errors sigma(beta) similar to 0.2, sigma E-b,E-1 similar to 0.1E(b,1), sigma E-b,E-2 similar to 0.4E(b,2,) and sigma(kT) similar to 0.1kT. This synchrotron function requires the synchrotron injection and cooling break (i.e., E-min and E-cool) to be close to each other within a factor of ten, often in addition to a Planck function. Conclusions. A synchrotron model is found that is consistent with most of the time-resolved spectra for eight energetic Fermi (IBM bursts with good high-energy photon statistics as long as both the cooling and injection break are included and the leftmost spectral slope is lifted either by including a thermal component or when an evolving magnetic field is accounted for.

  • 122197.
    Yu, Hoi-Fung
    et al.
    KTH, School of Engineering Sciences (SCI), Physics.
    Hui, Chung Yue
    Chungnam Natl Univ, Dept Astron & Space Sci, Daejeon 34134, South Korea..
    Kong, Albert K. H.
    Natl Tsing Hua Univ, Inst Astron, Hsinchu, Taiwan..
    Takata, Jumpei
    Huazhong Univ Sci & Technol, Inst Particle Phys & Astron, Wuhan, Hubei, Peoples R China..
    Bayesian Inference on the Radio-quietness of Gamma-ray Pulsars2018In: Astrophysical Journal, ISSN 0004-637X, E-ISSN 1538-4357, Vol. 857, no 2Article in journal (Refereed)
    Abstract [en]

    For the first time we demonstrate using a robust Bayesian approach to analyze the populations of radio-quiet (RQ) and radio-loud (RL) gamma-ray pulsars. We quantify their differences and obtain their distributions of the radiocone opening half-angle d and the magnetic inclination angle a by Bayesian inference. In contrast to the conventional frequentist point estimations that might be non-representative when the distribution is highly skewed or multi-modal, which is often the case when data points are scarce, Bayesian statistics displays the complete posterior distribution that the uncertainties can be readily obtained regardless of the skewness and modality. We found that the spin period, the magnetic field strength at the light cylinder, the spin-down power, the gamma-rayto-X-ray flux ratio, and the spectral curvature significance of the two groups of pulsars exhibit significant differences at the 99% level. Using Bayesian inference, we are able to infer the values and uncertainties of d and a from the distribution of RQ and RL pulsars. We found that d is between 10 degrees and 35 degrees and the distribution of a is skewed toward large values.

  • 122198.
    Yu, Hong
    KTH, School of Information and Communication Technology (ICT).
    Creating Public Trust in Electronic Voting Systems2017Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    There are many positive aspects of electronic voting systems: security, verifiability, convenience, resource conservation, and the like. However, there is still lack of trust for electronic voting systems within the public. One of the reasons could be that the notions involved in electronic voting are challenging to understand for the general public. In this project, we tried to create public trust through an explanation system.

    An explanation system was made to explain how a modern electronic voting system works. User testing was performed after that, to verify whether this explanation system is able to increase people’s trust in electronic voting system. After analysing the data collected through the user testing, we got promising results to believe that this explanation can be used to create public trust in electronic voting systems.

  • 122199. Yu, Huakang
    et al.
    Fang, Wei
    Gu, Fuxing
    Qiu, Min
    KTH, School of Information and Communication Technology (ICT), Microelectronics and Applied Physics, MAP.
    Yang, Zongyin
    Tong, Limin
    Longitudinal Lorentz force on a subwavelength-diameter optical fiber2011In: Physical Review A. Atomic, Molecular, and Optical Physics, ISSN 1050-2947, E-ISSN 1094-1622, Vol. 83, no 5, p. 053830-Article in journal (Refereed)
    Abstract [en]

    We analyze the longitudinal Lorentz forces that a propagating continuous-wave light exerts on a subwavelength-diameter optical fiber. Our theoretical results show that, during the propagating process, the guided light exerts no net time-averaged force on the fiber. Via numerical simulation, we find a significant overall pull force of 0.4 pN/mW acting on a 450-nm-diam fiber tip at a wavelength of 980 nm due to the scattering of the end face and a calculated force distribution reveals the feature of a near-field accumulation. Our results may be helpful to the configuration of optomechanical components or devices based on these fibers.

  • 122200. Yu, Huakang
    et al.
    Wang, Shanshan
    Fu, Jian
    Qiu, Min
    KTH, School of Information and Communication Technology (ICT), Microelectronics and Applied Physics, MAP.
    Li, Yuhang
    Gu, Fuxing
    Tong, Limin
    Modeling bending losses of optical nanofibers or nanowires2009In: Applied Optics, ISSN 1559-128X, E-ISSN 2155-3165, Vol. 48, no 22, p. 4365-4369Article in journal (Refereed)
    Abstract [en]

    Bending losses of nanofibers or nanowires with circular 90 degrees bends are simulated using a three-dimensional finite-difference time-domain (3D-FDTD) method. Dependences of bending losses on wavelength and polarization of guided light are investigated, as well as the diameters, refractive indices, and bending radii of nanowires. The acceptable bending losses (similar to 1 dB/90 degrees) predicted in glass, polymer, and semiconductor nanowires with bending radii down to micrometer level may offer valuable references for assembling highly compact photonic integrated circuits or devices with optical nanowires.

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