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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.
41

Password Behaviour : A Study in Cultural and Gender Differences

Gärdekrans, Rasmus January 2017 (has links)
No description available.
42

Jämförelse av algoritmer för polygonisering utav volymetrisk data / Comparison of algorithms used in polygonization of volumetric data

Brodal, Kristian January 2014 (has links)
Digitala spel har länge använt sig av terräng, det vanligaste sättet att lagra dessa terränger är med så kallade höjdkartor. Höjdkartor har en stor begränsning, de inte kan innehålla tunnlar. Denna rapport undersöker två alternativ till höjdkartor som arbetar med voxlar. Dessa två algoritmer är Marching Cubes (Lorensen & Cline, 1987) och Constrained Elastic Surface Nets (Gibson, 1998). Syftet med undersökningen är att evaluera dessa algoritmer med avseende på tidseffektivitet, minneseffektivitet och visuell korrekthet för att ta reda på vilken algoritm som öveträffar den andra med avseende på vilken aspekt. De utförda experimenten visade att Marching Cubes (Lorensen & Cline, 1987) var den mest tidseffektiva av de två, Constrained Elastic Surface Nets (Gibson, 1998) var mest minneseffektiv och Marching Cubes (Lorensen & Cline, 1987) var mest visuellt korrekt. Vidare forskning i ämnet skulle kunna göras på terränger som är för stora för enskilda modeller.
43

Methods and Tools for Efficient Model-Based Development of Cyber-Physical Systems with Emphasis on Model and Tool Integration

Mengist, Alachew January 2019 (has links)
Model-based tools and methods are playing important roles in the design and analysis of cyber-physical systems before building and testing physical prototypes. The development of increasingly complex CPSs requires the use of multiple tools for different phases of the development lifecycle, which in turn depends on the ability of the supporting tools to interoperate. However, currently no vendor provides comprehensive end-to-end systems engineering tool support across the entire product lifecycle, and no mature solution currently exists for integrating different system modeling and simulation languages, tools and algorithms in the CPSs design process. Thus, modeling and simulation tools are still used separately in industry. The unique challenges in integration of CPSs are a result of the increasing heterogeneity of components and their interactions, increasing size of systems, and essential design requirements from various stakeholders. The corresponding system development involves several specialists in different domains, often using different modeling languages and tools. In order to address the challenges of CPSs and facilitate design of system architecture and design integration of different models, significant progress needs to be made towards model-based integration of multiple design tools, languages, and algorithms into a single integrated modeling and simulation environment. In this thesis we present the need for methods and tools with the aim of developing techniques for numerically stable co-simulation, advanced simulation model analysis, simulation-based optimization, and traceability capability, and making them more accessible to the model-based cyber physical product development process, leading to more efficient simulation. In particular, the contributions of this thesis are as follows: 1) development of a model-based dynamic optimization approach by integrating optimization into the model development process; 2) development of a graphical co-modeling editor and co-simulation framework for modeling, connecting, and unified system simulation of several different modeling tools using the TLM technique; 3) development of a tool-supported method for multidisciplinary collaborative modeling and traceability support throughout the development process for CPSs; 4) development of an advanced simulation modeling analysis tool for more efficient simulation.
44

Design & implementation av kösystemet Inline

Fredriksson, Niclas January 2019 (has links)
No description available.
45

Approximations and abstractions for reasoning about machine arithmetic

Zeljic, Aleksandar January 2016 (has links)
Safety-critical systems rely on various forms of machine arithmetic to perform their tasks: integer arithmetic, fixed-point arithmetic or floating-point arithmetic. The problem with machine arithmetic is that it can exhibit subtle differences in behavior compared to the ideal mathematical arithmetic, due to fixed-size representation in memory. Failure of safety-critical systems is unacceptable, because it can cost lives or huge amounts of money, time and effort. To prevent such incidents, we want to formally prove that systems satisfy certain safety properties, or otherwise discover cases when the properties are violated. However, for this we need to be able to formally reason about machine arithmetic. The main problem with existing approaches is their inability to scale well with the increasing complexity of systems and their properties. In this thesis, we explore two alternatives to bit-blasting, the core procedure lying behind many common approaches to reasoning about machine arithmetic. In the first approach, we present a general approximation framework which we apply to solve constraints over floating-point arithmetic. It is built on top of an existing decision procedure, e.g., bit-blasting. Rather than solving the original formula, we solve a sequence of approximations of the formula. Initially very crude, these approximations are frequently solved very quickly. We use results from these approximations to either obtain a solution, obtain a proof of unsatisfiability or generate a new approximation to solve. Eventually, we will either have found a solution or a proof that solution does not exist. The approximation framework improves the solving time and can solve a number of formulas that the bit-blasting cannot. In the second approach, we present a novel method to reason about the theory of fixed-width bit-vectors. This new decision procedure is called mcBV and it is based on the model constructing satisfiability calculus (mcSAT). The procedure uses a lazy representation of bit-vectors and attempts to avoid bit-blasting altogether. It is able to reason about bit-vectors on both bit- and word-level, leveraging both Boolean constraint propagation and native arithmetic reasoning. It also features a greedy explanation generalization mechanism and is capable of more general learning compared to existing approaches. mcBV is able to reason about bit-vectors with sizes that significantly exceed the usual 32, 64 and 128 bits. Evaluation of mcBV shows an improvement in performance (compared to bit-blasting) on several classes of problems. / UPMARC
46

New techniques for handling quantifiers in Boolean and first-order logic

Backeman, Peter January 2016 (has links)
The automation of reasoning has been an aim of research for a long time. Already in 17th century, the famous mathematician Leibniz invented a mechanical calculator capable of performing all four basic arithmetic operators. Although automatic reasoning can be done in different fields, many of the procedures for automated reasoning handles formulas of first-order logic. Examples of use cases includes hardware verification, program analysis and knowledge representation. One of the fundamental challenges in first-order logic is handling quantifiers and the equality predicate. On the one hand, SMT-solvers (Satisfiability Modulo Theories) are quite efficient at dealing with theory reasoning, on the other hand they have limited support for complete and efficient reasoning with quantifiers. Sequent, tableau and resolution calculi are methods which are used to construct proofs for first-order formulas and can use more efficient techniques to handle quantifiers. Unfortunately, in contrast to SMT, handling theories is more difficult. In this thesis we investigate methods to handle quantifiers by restricting search spaces to finite domains which can be explored in a systematic manner. We present this approach in two different contexts. First we introduce a function synthesis based on template-based quantifier elimination, which is applied to gene interaction computation. The function synthesis is shown to be capable of generating smaller representations of solutions than previous solvers, and by restricting the constructed functions to certain forms we can produce formulas which can more easily be interpreted by a biologist. Secondly we introduce the concept of Bounded Rigid E-Unification (BREU), a finite form of unification that can be used to define a complete and sound sequent calculus for first-order logic with equality. We show how to solve this bounded form of unification in an efficient manner, yielding a first-order theorem prover utilizing BREU that is competitive with other state-of-the-art tableau theorem provers. / UPMARC
47

Skissamarbete på digitala plattformar

Ahmadi, Dara, Panin, Vadim January 2019 (has links)
Datorstött kooperativt arbete (hädanefter förkortat CSCW efter engelskans Computer-Supported Cooperative Work) är när ett system underlättar datorbaserat arbete i grupp på distans och söker lämplig teknik för att uppnå optimal effektivitet i gruppens arbetsprocess. Ett exempel på ett sådant system kan vara skissamarbete på digitala plattformar. Inom interaktionsdesign finns ett intresse för skissamarbete på digitala plattformar. Vi har därför valt att inom ramen för vårt arbete undersöka om skissamarbete på digitala plattformar är ett effektivt arbetssätt för designers och vilka funktioner en sådan plattform bör ha. För att få svar på våra frågor har vi valt att skapa en Android samt en Webbapplikation för skissamarbete. I våra applikationer har vi beaktat designers önskemål gällande funktioner. Applikationerna användes i en undersökning för att kunna grundligt analysera hur designers skissamarbetar på digitala plattformar. Resultatet har visat att skissamarbete på digitala plattformar är ett smidigt och mobilt arbetssätt som medför aktiva diskussioner, skapar nya idéer och bättre lösningar, bidrar till kunskapsöverföring, bättre arbetsmiljö och samspel mellan designers. / Computer-Supported Cooperative Work (CSCW) relates to working in group by distance using computer-based systems and aims to achieve the optimal efficiency in the group's working process. Such systems include computersupported collaborative sketching system. In interaction design, there is an interest in sketch collaboration on digital systems. We have therefore chosen, within the frame of this work, to investigate whether collaborative sketching using digital platform applications lead to an effective way of working for designers and what functionalities such applications should include. To get answers to our questions, we have chosen to create an Android as well as a Web application for sketch collaboration. In our applications we have considered the designers' wishes regarding functionalities. The applications were used in a research to be able to analyze how designers collaborate on digital platforms. Our results have proven that collaborative sketching on digital platforms is a smooth and mobile way of working which involves active discussions, creating new ideas and better solutions, contributes to knowledge transfer and a better working environment and interaction between designers.
48

Evaluating and Reducing Multipath Transport Latency

Yedugundla, Kiran January 2019 (has links)
Access to the Internet is a very significant part of everyday life with increasing online services such as news delivery, banking, gaming, audio and high quality movies. Applications require different transport guarantees with some requiring higher bandwidth and others low latency. Upgrading access link capacity does not guarantee faster access to the Internet as it offers higher bandwidth but may not offer low latency. With increasing number of mobile devices supporting more than one access technologies (e.g., WLAN, 3G, 4G,..), there is a need to analyse the impact of using multiple such technologies at the same time. Legacy transport protocols such as TCP or SCTP are only able to connect to one access network at a time to create an end-to-end connection. When more than one access technology is used, there may be a large difference in the data rate offered by each technology. This asymmetry might impact latency sensitive applications by creating out of order delivery. In this thesis, we focus on the latency aspect of multipath transport protocol performance. We consider CMT-SCTP and Multipath TCP as available multipath protocols that were designed for exploiting multiple paths for better throughput and reliability. We consider various real world traffic scenarios such as Video, Gaming and Web traffic to measure end-to-end latency. We perform simulations, emulations and experiments using heterogeneous network settings involving access networks with different bandwidth, delay and loss characteristics. MPTCP performs better in terms of latency than CMT-SCTP and TCP in certain scenarios where available paths are symmetric. However, MPTCP does not perform well in asymmetric scenarios with latency sensitive traffic. This analysis provides insights in to various areas of improvement in MPTCP such as scheduling and loss recovery to achieve low latency. We further focus on packet loss recovery in MPTCP for specific cases of tail losses to reduce latency. Tail losses are the losses that occur at the end of a packet stream. Recovering such losses is of higher significance to latency sensitive applications. We propose a modification to the use of TLP, a mechanism in TCP for tail loss recovery. We evaluate the performance of proposed TLP modification, first using emulations and with real world network experiments. Our results show significant improvements in latency for specific loss scenarios in emulations and up to 50% improvement in experiments. / With an increasing number of mobile devices supporting more than one access technologies (e.g., WLAN, 3G, 4G), there is a need to analyse the impact of using multiple such technologies at the same time. The inherent asymmetry among these technologies might affect latency sensitive applications by creating out of order delivery. In this thesis, we consider CMT-SCTP and Multipath TCP as available multipath protocols designed to exploit multiple paths for better throughput and reliability.  We perform simulations, emulations and experiments using various real-world traffic scenarios such as Video, Gaming and Web traffic to measure end-to-end latency. MPTCP performs better in terms of latency than CMT-SCTP and TCP in certain scenarios where available paths are symmetric. This analysis provides insights into various areas of improvement in MPTCP such as scheduling and loss recovery to achieve low latency. We further focus on packet loss recovery in MPTCP for specific cases of tail losses (losses that occur at the end of a packet stream) to reduce latency. This thesis presents a modification to the use of Tail Loss Probe (TLP) in MPTCP that provides improvements in latency for specific loss scenarios in emulations and upto 50% improvement in experiments.
49

Program för schemadesign / Program for Designing Schedules

Yassin, Amin January 2018 (has links)
Databaser är en teknologi som aktivt används inom olika områden och branscher, och det är mer nu än någonsin som nya varianter av databashanterare kommer ut för att tillfredsställa de olika behoven för att hantera data. Den här rapporten handlar om utvecklingen av ett schemaprogram för Institutionen för naturvetenskap och teknik vid Örebro universitet. I utvecklingen av detta program används WPF-ramverket från Microsoft för att kunna skapa Windows-applikationer. Det används en SQLite-databas också för att spara och hämta data i form av resurser för scheman. I rapporten undersöks också SQL- och NoSQL-databaser utifrån hur de skiljer sig ifrån varandra och hur kan de användas för Windows-applikationer. Slutsatsen på det senare är att SQL-databaser är lämpliga för applikationer, där utvecklaren är medveten om exakt vilka data som kan behövas och vill säkra datakonsistens över allt annat. Å andra sidan, NoSQLdatabaser är lämpliga för applikationer som är anslutna till distribuerade databassystem, där det viktiga prioriteras enligt CAP-satsen av datatillgänglighet, datakonsistens, och partitionstolerans. / Database technology is becoming more actively used in different sectors and branches and the variations of database management systems (DBMS) are on the increase now more than ever. This increase is due to the strive to satisfy the variating needs to manage data. This report presents the development of a scheduling application on Windows for the School of Science and Technology at Örebro University. For this development process the WPF framework by Microsoft is used. Also, SQLite database is used to save and retrieve data in the form of resources for schedules. This report also investigates SQL- and NoSQL-databases. This investigation focuses on the differences between these two when incorporating them into Windows applications and the conclusion is that SQL-databases are to be used when the programmer is aware exactly of what types of data are needed for the application and to ensure that integrity constraints on data is a top priority. On the other hand, NoSQL-databases are suitable for applications that are a part of a distributed database system and that two of the three letters in the CAP-theorem are to be considered.
50

DICOM Second Generation RT : An Analysis of New Radiation Concepts by way of First-Second Generation Conversion

Holst, David January 2019 (has links)
The current DICOM communication standard for radiotherapy is outdated and has serious design issues. A new version of the standard, known as DICOM 2nd generation for Radiotherapy, has been introduced and this thesis examines new concepts relating to radiation delivery. Firstly, some background into the practice of radiotherapy is given, as well as a description of the DICOM standard. Secondly, the thesis describes the design issues of the current standard and how the 2nd generation aims to solve these. Thirdly, the thesis explores the conversion of a first generation C-Arm Photon/Electron treatment plan to the second generation RT Radiation and RT Radiation Set IODs. A converter is implemented based on a model proposed in a previous work. With some simplifications, the conversion of Basic Static and Arc treatment plans is shown to be successful. Conversion of further dynamic plan types is judged to be fairly simple to implement following the same methodology. The conversion model’s efficacy and testability are discussed and while the model is flexible and facilitates extension to further modalities some areas of improvement are suggested. Lastly, a GUI for the converter is demonstrated and the possibilities of user interaction during conversion are discussed.

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