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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
551

Improving routing in the global Internet

Klockar, Tomas January 2005 (has links)
Routing is an important part of the Internet and even though routing in the Internet has been investigated since Internet's creation, there are still open issues. Routing protocols have been evolved since the birth of Internet. Currently the Border Gateway Protocol(BGP) is the de-facto standard inter domain routing protocol on the Internet. In 1990 came the first version of BGP which has evolved to todays BGP-4 through several versions and extensions. The capability has increased for every new version and extension, but so has the complexity. This makes it harder to get an overview of how routers behave. In many cases the global view of the routing within the Autonomous System (AS) is missing. When the global view is missing, it is difficult for routers to chose a stable route and in some cases it is impossible. Oscillation is one of the larger problems and for I-BGP several solutions have been suggested. We present a new algorithm that prevents intra AS oscillation. The basic idea is to store routes that are not explicitly removed because those routes can still be used, although they are currently not active. This way the selection algorithm has a larger set of routes to choose from when it selects the best route. Routes that are not currently used can not be selected but can be used to remove others from the allowed set. BGP can also be improved by adjusting it to a new decentralized router architecture and at the same time solving several intra AS problems. We have been investigating this problem and suggested a modularization of BGP. The modularization is designed to fit on top of the Forward Element and Control Element separation of the router. The forwarding table and session manager have been separated from the decision process and Routing Information Bases(RIB). The solution is very flexible and allows that the router is built with redundancy and still keeps the cost down. We also present algorithms for calculating the k shortest paths in a distributed manner. This algorithm has its roots in BGP. It runs in waves to compute the k shortest paths. The algorithm produces paths that can be used for routing to solve load-balancing problems or as backup paths. / <p>Godkänd; 2005; 20060922 (ysko)</p>
552

Detektering och visualisering av sårbarheter samt beroenden i tredjepartsbibliotek

Meleri, Robin, Gustafsson, Max January 2021 (has links)
Att förstå hur olika tredjepartsbibliotek i ett projekt är beroende av varandra kanvara problematiskt. Ännu mer problematiskt kan det bli om dessatredjepartsbibliotek innehåller allvarliga sårbarheter som kan orsaka stor skada. I dethär arbetet har verktyg som idag existerar för att visualisera beroenden mellantredjepartsbibliotek i ett projekt, samt för att upptäckta dess sårbarheter,analyserats. Utifrån analysen har två verktyg identifierats och sedan utvecklats till ettlätthanterligt sammansatt verktyg.Visualiseringen av de tredjepartsbibliotek samt de sårbarheter som upptäckts bestårav en interaktiv graf som visar varje tredjepartsbibliotek som en nod. Varje nod i sintur har tilldelats en färg beroende på om den innehåller sårbarheter eller ej, samtberoende på dess allvarlighetsgrad. Detta arbete har resulterat i ett verktyg som kanvisualisera sårbarheter hos tredjepartsbibliotek beroende på dess allvarlighetsgrad,samt de beroenden som existerar mellan tredjepartsbiblioteken i en interaktiv graf.Vilket underlättar och förbättrar identifieringsprocessen av sårbarheter ijavabaserade system. / To keep track of how different third-party libraries in a project are dependent oneach other can be quite problematic. It can become even more problematic if thesethird-party libraries contain severe vulnerabilities that can lead to serious harm. Inthis work different tools that exist today for visualizing the dependencies betweenthird-party libraries in a project, and for discovering vulnerabilities, have beenanalyzed. Based on the analysis, two tools have been identified and then developedinto one easy-to-use tool.The visualization of the third-party libraries as well as their vulnerabilities that gotdiscovered, consists of an interactive graph that shows every dependency as a node.Each node is then given a color depending on if it contains any vulnerabilities or not,as well as the severity of the vulnerability. This work has resulted in a tool that canvisualize vulnerabilities in third-party libraries depending on its severity, as well asthe dependencies between the libraries in an interactive graph. Which simplifies andimproves the identification process of vulnerabilities in java-based systems.
553

Undersökning om hur machine learning kan användas för att förutspå fel i en databas

Vilhelmsson, Jonatan January 2020 (has links)
I en värld som digitaliseras allt mer blir databaser mer komplexa än någonsin. För att kunna lita att information är korrekt uppdaterad i system behöver man kunna lita på underliggande integrationer. Det sker fel i många databaser och detta kan resultera i problem i framtiden då fel kan orsaka skador både för kunden och ett företags rykte. Det är viktigt att en databas är säker och att det uppstår så lite fel som möjligt. I detta examensarbete undersöks det hur machine learning kan användas för att förutspå fel i en databas för att enkelt kunna förebygga dessa. Olika typer av inlärningsalgoritmer analyseras för att finna den som passar bäst in för arbetet. Fyra olika algoritmer som ML.NETbidrar med analyseras sedan för att presentera vilken algoritm som är mest passande till problemet och som har bäst prestanda med hänsyn till noggrannhet och körtid.
554

Performance comparison between C and Rust compiled to WebAssembly

medin, magnus January 2021 (has links)
No description available.
555

Designing an algorithm to build communities by combining semi-cliques spanning multiple graphs

McLeod, Tyson January 2021 (has links)
Community detection is an important graph mining task and one of the most researched problems in its field of study. One reason for this is its applicability in a variety of disciplines ranging from biology to computer science. Community detection methods differ, however, and a major reason for this is due to the fact that there does not exist a unique definition for what a community is. This project involved creating a new method for detecting and building communities for a specific type of network represented by multi-layered graphs, where each layer represents an edge type/ type of relation. More specifically, an algorithm for detecting and building communities in multi-layered graphs was built by first implementing a method to detect semi-cliques spanning multiple graphs, and then integrating the method with a second method which builds communities using multi-layered cliques. The new method wasthen tested on synthetic as well as real-world data to demonstrate functionality and test validity.
556

Radar odometry based on Fuzzy-NDT scan registration

Henriksson, Johan January 2021 (has links)
Visual and lidar-based odometry for mobile robots has been thoroughlyinvestigated and performs very well in good weather conditions. However,both are sensitive to bad weather conditions with atmospheric disturbancessuch as rain and snow. Recently Radar sensors specialized for mobilerobot use have become available. Radar sensors are much more robustagainst atmospheric disturbances, which makes them an exciting alternative.This thesis presents a radar odometry pipeline that can handle both lidar andradar data with minor modifications. The results show that it outperformsthe current state of the art radar odometry solutions. While also being able tohandle 3d lidar odometry with good performance.
557

Automatic Handwritten Text Detection and Classification

Dahlstedt, Olle January 2021 (has links)
As more and more organizations digitize their records, the need for automatic document processing software increases. In particular, the rise of ‘digital humanities’ precede a new set of problems on how to digitize historical archival material in an efficient and accurate manner. The transcription of archival material to formats fit for research purposes, such as handwritten spreadsheets, is still expensive and plagued by tedious manual labor. Over the decades, research in handwritten text recognition has focused on text line extraction and recognition. In this thesis, we examine document images that contain complex details, contain more categories of text than handwriting, and handwritten text that is not separated easily to lines. The thesis examines the sub-problem of handwritten text segmentation in detail. We propose a broad definition of text segmentation that requires both text detection and text classification, since this enables us to detect multiple kinds of text within the same image. The aim is to design a system which can detect and identify both handwriting and machine-text within the same image. Working with photographs of spreadsheet documents from the years 1871-1951, a topdown layout-agnostic image processing pipeline is developed. Different kinds of preprocessing are examined, to correct illumination and enhance contrast before binarization, and to detect and clear line contours. To achieve text region detection, we evaluate connected components labeling and MSER as region detectors, extracting textual and non-textual sub-images. On detected sub-images, we perform a Bag-of-Visual-Words quantization of k-means clustered feature descriptor vectors and perform categorical classification by training a Naïve Bayesclassifier on the feature distances to the cluster centroids. Results include a novel two-stage illumination correction and contrast enhancement algorithm that improves document quality as a precursor to binarization, increasing the mean grayscale values of an image while retaining low grayscale variance. Region detectors are evaluated on images with different types of preprocessing and the results show that clearing document outlines influences text region detection. Training on a small sample of sub-images, the categorical classification model proves viable for discrimination between machine-text and handwriting, enabling the use of this model for further recognition purposes.
558

Comparison of Supervised LearningModels for predicting prices of UsedCars

Totakura, Sri Sai Ganesh Satyadeva Naidu, Kosuru, Harika January 2021 (has links)
Background: There has been a consistent increase in the used cars industry from the past decade as there is an increase in the usage of cars. Usedcars are attracting more attention as they are affordable than new ones.This situation demands high-performance algorithms that can be used topredict prices for the used cars. Many machine learning algorithms are usedto predict the price of cars. Objectives: This thesis aims in detecting features that impact predicting the price of used cars, and experiments are performed to investigatean optimal algorithm for price prediction of used cars. Algorithms selectedfor experimenting are Linear Regression (LR), Light Gradient Boosted Machine (LGBM), Random Forest Regression (RFR), Decision Tree Regression(DTR). These algorithms are further compared using performance metricsof regression models. Methods: The initial step in this study is to gather a suitable dataset andapplying preprocessing techniques to that data. Feature selection is performed using a correlation matrix with the heat map. Label Encoding isperformed on the data to change the categorical values into numerical values. A new dataset is created based on the feature "region" from the originaldataset. train-test-split technique is used to divide the original dataset intotrain and test data in the ratio of 80:20. The new dataset is manually divided into unique regions of train and test data. Selected Machine Learningalgorithms were trained using both datasets. The accuracy score of selectedalgorithms is derived using performance metrics. An optimal algorithm isachieved by comparing the accuracy scores derived. Results: Light Gradient Boosted Machine is considered as optimal algorithm based on R2score, for the original dataset, it obtained 91.12% on testdata. Light Gradient Boosted Machine achieved 85.30% on test data for thenew dataset. The feature "region" has the highest feature importance overthe remaining features. It has a feature importance of 55220 with respectto number of instances i.e, 568654. Conclusions: Among selected algorithms, Light Gradient Boosted Machine obtained a high R2score over other algorithms on both original andnew datasets. Feature "region" has a significant impact on predicting theprice of the used car, and this is justified by performing feature importanceon Light Gradient Boosted Machine.
559

Facial Emotion Recognition by Hyper-Parameter tuning of Convolutional Neural Network using Genetic Algorithm

Bellamkonda, Satyachandra Saurabh January 2021 (has links)
Context: Importance of facial emotion recognition is increasing significantly as it's applications play a key role in several sectors and fields. Deep learning techniques in machine learning provide good performance in facial recognition tasks, Where as deep neural networks like convolutional neural networks are most widely used for image recognition and classification tasks. However, these neural networks depend on configuration parameters called hyper-parameters. So, tuning these parameters play a vital role in facial emotion recognition. Moreover, it is challenging and time consuming to tune the hyper-parameters of neural networks since it involves many parameters. Tuning these hyper-parameters is considered as optimization task where evolutionary algorithms like genetic algorithms play a major role. Studying and experimenting different genetic algorithm concepts not only provide interesting insights for facial recognition tasks but also provide significant progresses in deep learning, gaming, and virtual reality. Objectives: The thesis aims to develop a model for facial emotion recognition by applying evolutionary mechanisms like genetic algorithms on convolutional neural networks. The developed model recognizes seven basic emotions in images of human beings such as fear,happy, surprise, sad, neutral, disgust and angry using FER-2013(facial emotion recognition) dataset. Methods: Emotion recognition of the facial images is done by hyper-tuning of convolutional neural network using evolutionary mechanisms. Literature review is performed for studying the working mechanism of genetic algorithm, techniques, best methods of genetic algorithms, genetic operators for hyper-parameter tuning of neural network. After studying the methods, experiment is conducted to evaluate and study the impact of applying genetic algorithm methods in hyper-parameter tuning which in turn helps in facial emotion recognition. Results: Genetic algorithm concepts which are identified from literature review improved the performance of convolutional neural network. Elitism and multiparent recombination concepts of genetic algorithm showed satisfying results by significantly boosting the performance of neural networks. Multipoint cross-over established a new theme in genetic algorithm by introducing sharp variations and gave scope for genetic diversity which results in increasing efficiency of neural network. Performed experimental model portrayed these concepts and has improved the performance of convolutional neural network. Conclusions: The genetic algorithm worked constructively for the improvement of performance of convolutional neural networks. Results from experimental model portrayed improvement of neural network and has helped in increasing accuracy of the images of facial emotion recognition. Variable length genetic algorithm helped the model in tracing out important variable parameters thus helping the neural networks to perform better. Different genetic mechanisms have different functions for effective functioning of neural network. Key observations, new insights gained from the experimental results of the current research are helpful and expand the scope of deep learning applications with evolutionary mechanisms.
560

Evaluation of Battery Usage and Scalability when Performing Parallel Applications on Mobile Devices

Lindgren, Malte January 2021 (has links)
The advances made in mobile and low-powered computing within the last decade has made mobility a key term of today, where one cannot imagine a daily life without a mobile phone. This is largely due to the availability of smaller and faster hardware, such as multi-core processors and high-speed mobile networks. However, heavy computations or applications performed on multiple cores can be very power consuming and as a result, leave the user with an unusable device. This thesis explores and measures the battery usage when performing parallel tasks on an Android device. This is done by developing an application and algorithm able to be executed on a chosen number of cores. The result is presented with both a system-wide battery usage as well as an app-specific battery usage of the developed application

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