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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.

Self-management for large-scale distributed systems

Al-Shishtawy, Ahmad January 2012 (has links)
Autonomic computing aims at making computing systems self-managing by using autonomic managers in order to reduce obstacles caused by management complexity. This thesis presents results of research on self-management for large-scale distributed systems. This research was motivated by the increasing complexity of computing systems and their management. In the first part, we present our platform, called Niche, for programming self-managing component-based distributed applications. In our work on Niche, we have faced and addressed the following four challenges in achieving self-management in a dynamic environment characterized by volatile resources and high churn: resource discovery, robust and efficient sensing and actuation, management bottleneck, and scale. We present results of our research on addressing the above challenges. Niche implements the autonomic computing architecture, proposed by IBM, in a fully decentralized way. Niche supports a network-transparent view of the system architecture simplifying the design of distributed self-management. Niche provides a concise and expressive API for self-management. The implementation of the platform relies on the scalability and robustness of structured overlay networks. We proceed by presenting a methodology for designing the management part of a distributed self-managing application. We define design steps that include partitioning of management functions and orchestration of multiple autonomic managers. In the second part, we discuss robustness of management and data consistency, which are necessary in a distributed system. Dealing with the effect of churn on management increases the complexity of the management logic and thus makes its development time consuming and error prone. We propose the abstraction of Robust Management Elements, which are able to heal themselves under continuous churn. Our approach is based on replicating a management element using finite state machine replication with a reconfigurable replica set. Our algorithm automates the reconfiguration (migration) of the replica set in order to tolerate continuous churn. For data consistency, we propose a majority-based distributed key-value store supporting multiple consistency levels that is based on a peer-to-peer network. The store enables the tradeoff between high availability and data consistency. Using majority allows avoiding potential drawbacks of a master-based consistency control, namely, a single-point of failure and a potential performance bottleneck. In the third part, we investigate self-management for Cloud-based storage systems with the focus on elasticity control using elements of control theory and machine learning. We have conducted research on a number of different designs of an elasticity controller, including a State-Space feedback controller and a controller that combines feedback and feedforward control. We describe our experience in designing an elasticity controller for a Cloud-based key-value store using state-space model that enables to trade-off performance for cost. We describe the steps in designing an elasticity controller. We continue by presenting the design and evaluation of ElastMan, an elasticity controller for Cloud-based elastic key-value stores that combines feedforward and feedback control.

RSA-systemets sårbarheter idag och i framtiden

Gårdlund, Julia January 2019 (has links)
Denna uppsats undersöker sårbarheter relaterade till ett av de äldsta och mest säkra krypteringssystemen som existerar idag; RSA. Med hjälp av primärt kvalitativa litteraturstudier förklaras RSA-algoritmen, i vilka sammanhang RSA implementeras, några av de mest kända attackerna samt vilka framtida utmaningar systemet står inför. Många av attackerna har förklarats förut men syftet med denna studie är att bidra med mer lättförståeliga exempel på ett och samma ställe. De framtida hot som undersöks är relaterade till utvecklingen av kvantdatorer och dess potentiella förmåga att knäcka RSA. I och med att framtiden inte går att förutse baseras resultatet på uppskattningar. En sammanställning av vad olika publikationer anser om kvantdatorers hot mot RSA samt vid vilken tidpunkt de i sådant fall kan skadliggöra RSA är genomförd och presenteras i denna uppsats.

Utredande undersökning av NoSQL grafdatabaser : En utredande undersökning av OrientDB, ArangoDB och HypergraphDBför ett specifikt användningsfall / Investigative analysis of NoSQL graph databases : An investigative analysis of OrientDB, ArangoDB and HypergraphDB for aspecific use case

Christian, Larsson January 2019 (has links)
Behovet av att lagra stora mängder data för applikationer växer mer och mer. I samband med detta ökar även utvecklingen av olika sorters databaser, speciellt så kallade ”NoSQL”-databaser. Det kan vara svårt att navigera i denna uppsjö av databaslösningar för att hitta den databaslösning som passar bäst för ett specifikt projekt. Denna rapport försöker utreda vilken av databaserna OrientDB, ArangoDB samt HypergraphDB som passar bäst för ett specifikt användningsfall där data ska sparas för att representera en byggnadsstruktur. Kriterierna för undersökningen är hur organisationen bakom databasen ser ut, hur deras datamodeller ser ut, vilka prismodeller de erbjuder samt en empirisk undersökning av databasernas prestanda för det specifika användningsfallet. Denna undersökning är inte designad för att vara en generell jämförelse utan görs på uppdrag av ett företag för att se vilken databas som skulle passa deras specifika projekt bäst. Utredningen visar att det är en komplex uppgift att utföra rättvisa prestandajämförelser för olika ”NoSQL”-databaser men baserat på kriterierna i denna rapport skulle OrientDB passa bäst för det specifika användningsfallet. / The need to store large quantities of data is increasing more and more. In correlation to this the development of various kinds of databases, especially so-called ”NoSQL”-databases, is also increasing. It can be difficult to navigate in this plethora of database solutions to find the the database that best suits a specific project. This report attempts to investigate which of the databases OrientDB, ArangoDB and HypergraphDB is best suited for a specific use case where data is to be saved to represent a building structure. The criteria for the investigation are how the organization behind the database looks, how their datamodels looks, which price models they offer as well as an emperical study of the databases’ performance in the specific use case. This survey is not designed to be a general comparison, but is commissioned by a company to see which database would suit their specific project best. The investigation shows that it’s a complex task to do fair comparisons on performance between NoSQL databases but based on the criteria in this report OrientDB would be best suited for the specific use case.

Mapping Swedish Parties by Subject Participation on Twitter

Norberg, Anton January 2019 (has links)
In this thesis a subject mapping data mining method has been developed. The method maps the 8 political parties in the Swedish parliament to 25 subjects based on their participation in the subjects on Twitter. The method is based on tweets written by the commissioners in the Swedish parliament and the ministers in the Swedish government between 2018-04-01 and 2019-04-01. The method shows what subjects each party participate in on Twitter and how the participation changes over time. Further, it shows the similarity and dynamics between the parties according to their subject participation. The purpose of the method is to offer a quantitative analysis tool, useful to social scientist, that provides new information about political parties.It can not be concluded how the resulting findings from the method should be interpreted. However, I present three questions to investigate in future work. The questions regard correlation between the subject map and party cooperation, political spectra and public statements.The result indicate that there is a significance issue, due to low participation in certain subjects by specific parties. This issue can be resolved by decreasing the number of subjects or expand the data set on which the subject mapping is based.

Sentiment classification of Swedish Twitter data

Palm, Niklas January 2019 (has links)
Sentiment analysis is a field within the area of natural language processing that studies the sentiment of human written text. Within sentiment analysis, sentiment classification is a research area that has been of growing interest since the advent of digital social-media platforms, concerned with the classification of the subjective information in text data. Many studies have been conducted on sentiment classification, producing numerous of openly available tools and resources that further advance research, though almost exclusively for the English language. There are very few openly available Swedish resources that aid research, and sentiment classification research in non-English languages most often use English resources one way or another. The lack of non-English resources impedes research in other languages and there is very little research on sentiment classification using Swedish resources. This thesis addresses the lack of knowledge in this area by designing and implementing a sentiment classifier using Swedish resources, in order to evaluate how methods and best practices commonly used in English research transfer to Swedish. The results in this thesis indicate that Swedish resources can be used in the construction of internationally competitive sentiment classifiers and that methods commonly used in English research for pre- processing text data may not be optimal for the Swedish language.

Data Protection Impact Assessment (DPIA) and Risk Assessment in the context of the General Data Protection Regulation (GDPR)

Duricu, Alexandra January 2019 (has links)
No description available.

The rise of Brutalism and Antidesign : And their implications on web design history

Brage, Ellen January 2019 (has links)
The following bachelor thesis is written by a student at New Media Design within Informatics at the School of Engineering, Jönköping University. The background of this study is based on the emergence of web design trends brutalism and antidesign, which have been argued to originate from styles used during early periods of the web’s history. Furthermore, a lack of cultural analysis within web design has been identified. The visual evolution of the world wide web is not sorted into distinct and widely acknowledged periods or categories such as is the case with most other cultural areas like music and art. The emergence and popularity of brutalism and antidesign were identified as potential cases of visual styles returning from the past. They were therefore considered opportunities to examine visual periods in web design and predict where the field is heading in the future. The study was conducted using the qualitative method of semi-structured interviews. The empirical data was analysed using a thematic analysis and was later compared with theories derived from literature studies. The study found three reasons behind the rise of brutalism and antidesign in web design; the world wide web’s coming of age, reactions towards the mainstream web and the interest in retro trends. The study also aimed to find the possible implications of their emergence on the aesthetic evolution of web design.  It was found that brutalism and antidesign are part of a large number of experimental and retro trends that will continue to emerge. Though they are unlikely to directly affect mainstream web design in its current state, they may be seen as design movements. This may be viewed as a step in the direction of visual categories within web design.

A study on load balancing within microservices architecture

Sundberg, Alexander January 2019 (has links)
This study addresses load balancing algorithms for networked systems with microservices architecture. In microservices applications, functionality and logic have been split into small pieces referred to as services. Such divisions allow for higher levels of scalability and distributivity than obtainable for more classical architectures where functionality and logic is packaged into large non-separable applications. As a first step, we investigate existing load balancing algorithms in the literature. A conclusion reached from this literature survey is that there is a lack of proposed load balancing algorithms for microservices, and it is not obvious how to adapt such algorithms to the architecture under consideration. In particular, many existing algorithms incorporate queues, which should be avoided for microservices, where the small services should be provided in fast manner. Hence, we provide modified and new candidates for load balancing, where one such is a probabilistic approach including a distribution that is a function of service providers' load. The algorithms are implemented in microservices simulation environment developed in Erlang by Ericsson AB. We consider a range of scenarios for evaluation, where amongst other things, we vary the number of service consumers and providers. To evaluate the load balancing algorithms, we perform statistical analysis, where first and second order moments are computed for relevant metrics under the different scenarios considered. A conclusion drawn from the results is that the algorithm referred to as "Round Robin" performed best according to the results from various simulation scenarios. This study serves as a stepping stone for further investigations. We outline several possible extensions such as more in-depth statistical analysis accounting for the time-varying aspects of the systems (currently omitted), as well other classes of algorithms.

Light scattering in two-dimensional inhomogeneous paper : Analysis using general radiative transfer theory

Nukala, Madhuri January 2019 (has links)
Modeling light scattering is important in diverse reasearch fields such as paper and print, optical tomography, remote sensing and also in computer rendering of im­ages. Particularly in paper and printing industry light scattering simulations play a significant role in understanding the optical response of paper in relation to its properties. Light scattering models are used in paper and print for improving the paper making process, designing new paper qualities, and evaluating printing tech­niques. The models most widely used for light scattering calculations in the paper and printing industry are based on the Kubelka-Munk theory. The theory proposed by Kubelka and Munk, a special case of radiative transfer theory, has several limi­tations and it can only be applied to homogeneous media with isotropic scattering and diffuse illumination. Real paper and print in particular do not satisfy these as­sumptions. These limitations of the Kubelka-Munk model encouraged scientists to develop models based on angle-resolved geometry to account for anisotropic scat­tering of light in paper and print, but in a single spatial dimension. To correctly represent spatial inhomogeneities like ink dots which spread as a function of depth, length and width of the paper, one-dimensional (lD) models are insufficient. In addi­tion to angle-resolved geometry, multi-dimensional models are necessary to analyze light scattering effects in a printed paper. The method used in this thesis, unlike the Kubelka-Munk method employs gen­eral radiative transfer formulation to obtain the reflectances of paper with inhomo­geneities like ink dots. These ink dots printed on plain sheet of paper are consid­ered to spread not only as a function of depth but also as a function of length or width of the paper. First, a numerical solution method comprising of a combination of discrete ordinates and finite differences is developed to solve the general two­dimensional (2D) radiative transfer equation (RTE) with the two dimensions repre­senting the depth and length of the paper. The solver is validated by comparing the results obtained with Monte Carlo simulations adapted to suit paper optics and DORT2002. For isotropic scattering, and for angles close to the normal direction, good agreement is observed among all the three solvers. As the anisotropy factor increases, the present solver needs higher number of radiation streams for conver­gence. The 2D radiative transfer (RT) solver is then applied to printed paper and re­flectances obtained are analyzed. The ink distribution is considered to be non-uniform such that the density of ink decreases linearly with depth. The dots are separated by a distance to study the interference pattern of the intensity distribution which is use­ful in understanding defects like print mottle, print density and optical dot gain. The reflectances obtained are analyzed based on medium parameters such as thickness of the paper sample, its optical parameters and assymetry factor. The illuminating and viewing angles and the depth of ink penetration also influence the optical response and appearance of print. It is observed that the reflectance of dots largely depends on the illuminating and viewing angles with an apparent increase in the size of the dots seen more prominently when viewed across the line. A 2D RT solver is superior in understanding the interference pattern of radiation as observed in the results presented in this thesis, when compared to a lD RT solver. A lD RT solver uses independent columns to approximate the radiation in the lateral direction. It also assumes that the layers in the lateral direction are homogeneous and the radiation from the columns do not interfere with each other. The independent column approximation pays little attention to the lateral variations in intensity. / <p>Vid tidpunkten för framläggningen av avhandlingen var följande delarbete opublicerat: delarbete 1 (manuskript).</p><p>At the time of the defence the following paper was unpublished: paper 1 (manuscript).</p>

Random numbers for generation in web games : And how the quality of them effects the end user.

Jacobsson, Linus January 2019 (has links)
No description available.

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