<p>With an increasing number of computers connected to the Internet, the number of malicious attacks on computer systems also raises. The key to all successful attacks on information systems is finding a weak spot in the victim system. Some types of bugs in software can constitute such weak spots. This thesis presents and evaluates a technique for statically detecting such security related bugs. It models the analyzed program as well as different types of security bugs with dependence graphs. Errors are detected by searching the program graph model for subgraphs matching security bug models.</p><p>The technique has been implemented in a prototype tool called GraphMatch. Its accuracy and performance have been measured by analyzing open source application code for missing input validation vulnerabilities. The test results show that the accuracy obtained so far is low and the complexity of the algorithms currently used cause analysis times of several hours even for fairly small projects. Further research is needed to determine if the performance and accuracy can be improved.</p>

<p>In this thesis we study multipole moments of axisymmetric spacetimes. Using the recursive definition of the multipole moments of Geroch and Hansen we develop a method for computing all multipole moments of a stationary axisymmetric spacetime without the use of a recursion. This is a generalisation of a method developed by Herberthson for the static case.</p><p>Using Herberthson’s method we also develop a method for finding a static axisymmetric spacetime with arbitrary prescribed multipole moments, subject to a specified convergence criteria. This method has, in general, a step where one has to find an explicit expression for an implicitly defined function. However, if the number of multipole moments are finite we give an explicit expression in terms of power series.</p> / Note: The two articles are also available in the pdf-file. Report code: LiU-TEK-LIC-2006:4.

<p>The concept and advantages of a Parallel Memory Architecture (PMA) in computer systems have been known for long but it’s only in recent time it has become interesting to implement modular parallel memories even in handheld embedded systems. This thesis presents a method to analyse source code to expose possible parallel memory accesses. Memory access Patterns may be found, categorized and the corresponding code marked for optimization. As a result a PMA compatible with found pattern(s) and code optimization may be specified.</p>

<p>Ett företags kapitalstruktur och i förlängningen dess val av finansiering för strategiska</p><p>investeringar omgärdas av motstridiga uppfattningar och teorier. Vi har genomfört en</p><p>fallstudie av Home Properties AB, ett renodlat hotellfastighetsägarbolag noterat på</p><p>Stockholmsbörsens lista för medelstora bolag.</p><p>Uppsatsens syfte är att beskriva hur Home Properties agerar och resonerar vid finansiering av</p><p>strategiska investeringar och jämföra beskrivningen med Åkerbloms hypotes om sär- och</p><p>samfinansiering, pecking order teorin och static trade-off modellen. I syftet ingår också att ge</p><p>förslag på vidare forskning.</p><p>Enligt pecking order teorin prioriterar företag internt kapital framför externt. Vid finansiering</p><p>av strategiska investeringar väljer Home Properties emellertid inteckningslån först. I Home</p><p>Properties fall förklaras företagets val av finansieringskällor bättre av static trade-off</p><p>modellen och Åkerbloms hypotes om sär- och samfinansiering. Anledningen är delvis att</p><p>Home Properties strävar efter ett soliditetsmål för att åstadkomma en optimal kapitalstruktur</p><p>vilket inte överensstämmer med pecking order teorin.</p><p>Home Properties val av finansiering kan inte helt och hållet förklaras av vare sig pecking</p><p>order teorin, static trade-off modellen eller Åkerbloms hypotes om sär- och samfinansiering.</p><p>Efter utförd fallstudie kan vi konstatera att Home Properties vid finansiering av strategiska</p><p>investeringar i regel vänder sig till (1) särfinansiering (2) internt kapital (3) gemensamt</p><p>låneutrymme och (4) nytt eget kapital/ lån/ hybrid. En viktig förutsättning för denna ordnings</p><p>giltighet är att soliditetsmålet inte störs långsiktigt.</p>

Soils, like several other materials, exhibit strong time-dependent behaviour which can be evidenced in terms of creep or strain-rate effects. The degree of this rheological behaviour varies with the type of soil, its structure, and with the stress history. This effect is exacerbated in pile load testing where the procedure duration tends to be shortened under increasing time pressures. The modelling needed to interpret the results therefore becomes more and more complex, including soil viscosity, wave radiation into the soil and other significant phenomena. The objective of the research reported herein is to refine the rheological parameters characterizing the influence of the loading rate within the framework of a relevant pile/soil interaction model fed with dynamic measurements acquired during pile Dynamic Load Tests (DLTs). The final goal is to predict and simulate the quasi-static pile load settlement curve. The pile/soil interaction system is described by a non-linear mass/spring/dashpot system supposed to represent the pile and the soil, with constitutive relationships existing within and between them. These relationships account for the static and the dynamic or rheologic behaviour. A back-analysis process based on a matching procedure between measured and computed quantities allows one to characterize the pile/soil interaction in terms of constitutive and rheologic parameters based on the dynamic measurements. After optimisation of the matching procedure, the parameters obtained are used to simulate the “static” load-settlement curve. The matching procedure is based on an automatic and stochastic parameter perturbation analysis. Since the parameters influence the system response with a relative weight, they are sorted in order to optimise all the parameters by successively retrieving the most influential ones and working on the remaining ones. The back-analysis performed on real dynamic measurements in this research leads to an improved pile/soil interaction model. The slippage between pile and soil along the pile shaft must be explicitly taken into account. This refinement increases the number of degrees of freedom needed to describe the pile/soil system but brings deeper insight into the behaviour of an interfacing zone of limited thickness surrounding the pile shaft.

Online auctions are arguably one of the most important and distinctly new applications of the internet. The predominant player in online auctions, eBay, has over 18.9 milllion users, and it was the host of over $5 billion worth of goods sold in the year 2000. Using methods from approximate dynamic programming and integer programming, we design algorithms for optimally bidding for a single item online auction, and simultaneous or overlapping multiple online auctions. We report computational evidence using data from eBay's web site from 1772 completed auctions for personal digital assistants and from 4208 completed auctions for stamp collections that show that (a) the optimal dynamic strategy outperforms simple but widely used static heuristic rules for a single auction, and (b) a new approach combining the value functions of single auctions found by dynamic programming using an integer programming framework produces high quality solutions fast and reliably. / Singapore-MIT Alliance (SMA)

Real-time system refers to the computing, communication, and information system with deadline requirements. To meet these deadline requirements, most systems use a mechanism known as the schedulability test which determines whether each of the admitted tasks can meet its deadline. A new task will not be admitted unless it passes the schedulability test. Schedulability tests can be either direct or indirect. The utilization based schedulability test is the most common schedulability test approach, in which a task can be admitted only if the total system utilization is lower than a pre-derived bound. While the utilization bound based schedulability test is simple and effective, it is often difficult to derive the bound. For its analytical complexity, utilization bound results are usually obtained on a case-by-case basis. In this dissertation, we develop a general framework that allows effective derivation of schedulability bounds for different workload patterns and schedulers. We introduce an analytical model that is capable of describing a wide range of tasks' and schedulers'€™ behaviors. We propose a new definition of utilization, called workload rate. While similar to utilization, workload rate enables flexible representation of different scheduling and workload scenarios and leads to uniform proof of schedulability bounds. We introduce two types of workload constraint functions, s-shaped and r-shaped, for flexible and accurate characterization of the task workloads. We derive parameterized schedulability bounds for arbitrary static priority schedulers, weighted round robin schedulers, and timed token ring schedulers. Existing utilization bounds for these schedulers are obtained from the closed-form formula by direct assignment of proper parameters. Some of these results are applied to a cluster computing environment. The results developed in this dissertation will help future schedulability bound analysis by supplying a unified modeling framework and will ease the implementation practical real-time systems by providing a set of ready to use bound results.

This study aims at the description, modelling and numerical prediction of ductile fracture in inelastic solids undergoing thermomechanical static or dynamic loading. Several research areas of contemporary interest in computer analysis of solids and structures are covered. The theoretical methodologies, computer implementations and practical applications will be treated. This thesis summarizes my recent research works since 1989 at the MSM Department of the University of Liège. However, it should also be useful to those who are interested in the most recent developments in finite element methods and in applying these techniques to the analysis of real industrial problems. Numerous references to original sources are included. For the convenience of the reader, each chapter of the thesis is designed to be self-contained, starts with a summary of the topic addressed, and finishes with an outline of the main results presented. Numerical examples are organized at the end of chapter 2 to 8 to assess the performance and applicability of the proposed mechanical and finite element models developed in each of them. Hereafter, a brief overview of the thesis is given. After a brief introduction in chapter 1, the numerical tools that are necessary to perform large strain thermomechanical static or dynamic analysis of solids are presented. In chapter 2, a general strategy for nonlinear dynamic finite element formulation is presented, including explicit and implicit time integration schemes. A special emphasis is placed on the application of high-speed metalforming and frictional contact-impact problems. Chapter 3 describes a strategy for solving problems involving transient thermal and thermomechanical analysis. A class of unified and mixed solid, thermal and coupled thermomechanical finite elements by assumed strain method is developed in chapter 4. Special care is taken to hourglass ans locking control. Once these developments are validated and their efficiency tested, it is then possible to tackle the problem of ductile fracture prediction and propagation. In chapter 5, a bibliographic research on the "local approach of ductile fracture" is presented. The implementation of six fracture criteria into various constitutive laws for predicting fracture initiation sites is also shown. A fully coupled elasto(-visco)-plastic damage model for isotropic material is developed in chapter 6. This model is based on irreversible thermodynamics theory and on the energy equivalence hypothesis. Chapter 7 presents the theoretical and experimental comparison for isotropic ductile material at fracture. Finally in chapter 8, the isotropic damage model of chapter 6 is extended to the case of anisotropic solids in which the damage growth itself is also anisotropic. The above developments have been implemented to an existing finite element code LAGAMINE developed since 1982 at the MSM Department of the University of Liège and are applied to many real engineering problems such as high speed rolling, magnetoforming, impact upsetting, dynamic forging, deep drawing of axisymmetric ans square cups, hot upsetting, warm folding of 3D sheet, non-isothermal hemispherical punch stretching, and other contact-impact examples.

The main concern of this work is the development of methodsfor automatic condition monitoring of control loops withapplication to the process industry. By condition monitoringboth detection and diagnosis of malfunctioning control loops isunderstood, using normal operating data and a minimum amount ofprocess knowledge. The use of indices for quantifying loop performance is dealtwith in the first part of the thesis. The starting point is anindex proposed by Harris (1989). This index has been modifiedin order to cover a larger range of processes. The same conceptis then used to assess the sampling rate in control loops.Other index-based monitoring methods where some amount ofprocess knowledge is available are discussed. The evaluation of the performance indices discussed requiresknowledge of the process dead-time. Therefore a concept calledevent-triggered estimation is introduced in the second part ofthe thesis. Both automatic data selection and dead-timeestimation methods are proposed and conditions for successfulestimation are discussed. The last part of the thesis deals with the diagnosis ofoscillations. A method to automatically diagnose staticfriction (stiction) in the actuator is presented. Furthermore,two methods are proposed which allow automatic distinction ofexternally and internally generated oscillations. All describedmethods have been implemented in a MATLAB-based graphical userinterface which is briefly described.

Ett företags kapitalstruktur och i förlängningen dess val av finansiering för strategiska investeringar omgärdas av motstridiga uppfattningar och teorier. Vi har genomfört en fallstudie av Home Properties AB, ett renodlat hotellfastighetsägarbolag noterat på Stockholmsbörsens lista för medelstora bolag. Uppsatsens syfte är att beskriva hur Home Properties agerar och resonerar vid finansiering av strategiska investeringar och jämföra beskrivningen med Åkerbloms hypotes om sär- och samfinansiering, pecking order teorin och static trade-off modellen. I syftet ingår också att ge förslag på vidare forskning. Enligt pecking order teorin prioriterar företag internt kapital framför externt. Vid finansiering av strategiska investeringar väljer Home Properties emellertid inteckningslån först. I Home Properties fall förklaras företagets val av finansieringskällor bättre av static trade-off modellen och Åkerbloms hypotes om sär- och samfinansiering. Anledningen är delvis att Home Properties strävar efter ett soliditetsmål för att åstadkomma en optimal kapitalstruktur vilket inte överensstämmer med pecking order teorin. Home Properties val av finansiering kan inte helt och hållet förklaras av vare sig pecking order teorin, static trade-off modellen eller Åkerbloms hypotes om sär- och samfinansiering. Efter utförd fallstudie kan vi konstatera att Home Properties vid finansiering av strategiska investeringar i regel vänder sig till (1) särfinansiering (2) internt kapital (3) gemensamt låneutrymme och (4) nytt eget kapital/ lån/ hybrid. En viktig förutsättning för denna ordnings giltighet är att soliditetsmålet inte störs långsiktigt.