With increasing clock-rates in CPUs coming to an end, a need for parallelization has emerged. This thesis proposes a dynamic purity analysis of objects, detecting independent execution paths that may be run in parallel. The analysis relies in speculative guesses and may be rolled back when proven wrong. It piggybags on an efficient replicating garbage collector integrated to JVM. The efficiency of the algorithms are shown in benchmark, and are comparable to the speed of state of the art garbage collectors in hotspot’s JVM. With this dynamic purity analysis now accessible in Java programs, the potential for automatic JIT-parallelization of pure methods is possible.

Kyoto University (京都大学) / 0048 / 新制・課程博士 / 博士(工学) / 甲第15646号 / 工博第3304号 / 新制||工||1499(附属図書館) / 28183 / 京都大学大学院工学研究科社会基盤工学専攻 / (主査)教授 岡 二三生, 教授 勝見 武, 准教授 木元 小百合 / 学位規則第4条第1項該当

Kyoto University (京都大学) / 0048 / 新制・課程博士 / 博士(工学) / 甲第16375号 / 工博第3456号 / 新制||工||1523(附属図書館) / 29006 / 京都大学大学院工学研究科社会基盤工学専攻 / (主査)教授 岡 二三生, 教授 勝見 武, 准教授 木元 小百合 / 学位規則第4条第1項該当

Doctor of Philosophy / Department of Computing and Information Sciences / David A. Schmidt, Anindya Banerjee, Thomas Jensen / With the intensification of communication in information systems, interest in security has increased. The notion of noninterference is typically used as a baseline security policy to formalize confidentiality of secret information manipulated by a program. This notion, based on ideas from classical information theory, has first been introduced by Goguen and Meseguer (1982) as the absence of strong dependency (Cohen, 1977). "information is transmitted from a source to a destination only when variety in the source can be conveyed to the destination" Cohen (1977) Building on the notion proposed by Goguen and Meseguer, a program is typically said to be noninterfering if the values of its public outputs do not depend on the values of its secret inputs. If that is not the case then there exist illegal information flows that allow an attacker, having knowledge about the source code of the program, to deduce information about the secret inputs from the public outputs of the execution. In contrast to the vast majority of previous work on noninterference which are based on static analyses (especially type systems), this PhD thesis report considers dynamic monitoring of noninterference. A monitor enforcing noninterference is more complex than standard execution monitors. "the information carried by a particular message depends on the set it comes from. The information conveyed is not an intrinsic property of the individual message." Ashby (1956). The work presented in this report is based on the combination of dynamic and static information flow analyses. The practicality of such an approach is demonstrated by the development of a monitor for concurrent programs including synchronization commands. This report also elaborates on the soundness with regard to noninterference and precision of such approaches.

Unreinforced masonry (URM) structures have shown tobe susceptible to significant damage during strong earthquakes. Vulnerability assessment of URM buildings is needed so that appropriate mitigation strategies can be implemented. The existing Canadian practice consists of rapid seismic screening of buildings to assign priorities for further and more refined assessments, followed by refined analysis of individual critical buildings. The current seismic screening procedure, from 1992, is based on qualitative observations of seismic vulnerability, enabling the assignment of seismic priority indices, quantified on the basis of expert opinion and experience. More refined tools are needed for seismic vulnerability assessment of URM buildings in Canada, based on the current Canadian seismic hazard values. The objective of the research project is to fulfill these needs by developing fragility curves that provide a probabilistic assessment of different levels of building performance under different intensities ofeastern and western seismicity. Using an inventory of over 50,000 structures, a seismic assessment of typical low-rise and mid-rise URM structures located in eastern and western Canada was carried out. The required analyses were done using applied element method software which effectively modeled the in-plane and out-of-plane behaviour of masonry walls. Using incremental dynamic analysis, fragility curves were developed to reflect the capacity of URM structures with a wide variety of selected structural and ground motion parameters. The results were verified against available fragility information in the literature. They show the significance of selected parameters, while providing effective tools for seismic vulnerability assessment of URM buildings in eastern and western Canada.

Damage observed after previous earthquakes indicates that a large number of existing buildings are vulnerable to seismic hazard. This research intends to assess seismic vulnerability of regular and irregular shear wall buildings in Canada, having different heights and different levels of seismic design and detailing. As seismic hazard is a probabilistic event, a probabilistic methodology has been adopted to assess the seismic vulnerability of the shear wall buildings. The proposed research encompasses a comprehensive fragility analysis for seismic vulnerability of shear wall buildings in Canada. The first phase of the investigation involves shear wall buildings with different heights (hence different structural periods), designed based on the 2010 National Building Code of Canada. The second phase involves shear wall buildings designed prior to 1975, representing pre-modern seismic code era. The third phase involves the evaluation of pre-1975 shear wall buildings with irregularities. 3-Dimensional simulations of the buildings were constructed by defining nonlinear modelling for shear wall and frame elements. These models were subjected to dynamic time history analyses conducted using Perform 3D software. Two sets of twenty earthquake records, compatible with western and eastern Canadian seismicity, were selected for this purpose. Spectral acceleration and peak ground acceleration were chosen as seismic intensity parameters and the first storey drift was selected as the engineering demand parameter which was further refined for irregular cases. The earthquake records were scaled to capture the structural behaviour under different levels of seismic excitations known as Incremental Dynamic Analysis. The resulting IDA curves were used as the input for seismic fragility analysis. Fragility curves were derived as probabilistic tools to assess seismic vulnerability of the buildings. These curves depict probability of exceeding immediate occupancy, life safety and collapse prevention limit states under different levels of seismic intensity.

The earliest design of a wind power system with multiple rotors on a single support structure dates back to the late 1800s. Such a system called a Multi-Rotor Wind Turbine (MRWT) was proposed by several researchers due to its perceived advantages over a single-rotor wind turbine. As turbine size increases, power produced by a rotor tends to scale up as the square of its diameter, as opposed to rotor weight which varies as its cube. So, several smaller rotors will weigh and cost less than one large rotor producing the same power. MRWTs offer several advantages such as better distribution of loads, better logistics of the components and scope for standardization. The MRWT system can also continue operation even if some of the rotors fail. However, MRWTs require a complex support structure to connect the rotors to the tower and an arrangement to yaw them into the wind. A recent study involving a scaling model for a three-rotor MRWT system estimates a cost saving of 13.1% as compared to the NREL 5 MW single-rotor model. A triangular truss type support structure for the MRWT model is designed and its preliminary static analysis is performed in that study. This thesis is a continuation of that study where the scaling model is extended to include MRWT systems having two to seven rotors. A systematic design method is developed for modeling any MRWT support structure for two to seven rotors for the given 5 MW configuration. The structure consists of frames and cables and the design constraints for the static analysis are stress, deflection and buckling. A dynamic analysis of the MRWT solution is also carried out to verify that the structure can withstand loads induced at varying wind conditions and design load cases – especially steady, turbulent and extreme wind conditions. Some special cases for the three-rotor MRWT system, such as use of two-bladed rotors, direct-drive machines, analysis for zero wind loads, load analysis for each of the assembly stages are also discussed. Finally, as the support structure design for the three and seven-rotor models is the main focus of the thesis, the scaling model is validated by comparing these models with similar turbines having rated power corresponding to the rotors used in the models.

<div>System programming languages such as C and C++ are ubiquitously used for systems software such as browsers and servers due to their flexibility and high performance. However, this flexibility comes with a price of lack of memory and type safety.</div><div><br></div><div>Control-Flow Hijacking (CFH), by taking advantage of the inherent lack of memory and type safety, has become one of the most common attack vectors against C/C++ programs. In such attacks, an attacker attempts to divert the normal control flow of the program to an attacker-controlled location. The most prominent defense against these kind of attacks is Control-Flow Integrity (CFI), which restricts the attack surface by limiting the set of possible targets for each indirect control-flow transfer. However, current analyses for the CFI target sets are highly conservative. Due to the ambiguity and imprecision in the analyses, CFI restricts adversaries to an over-approximation of the possible targets of individual indirect call sites. State-of-the-art CFI approaches fail to protect against special attack classes such as over-writing variadic function arguments. Furthermore, mitigation of control-flow attacks is not explored to its full potential in the context of language boundaries in current literature. Hence, we need effective solution to improve the precision of the CFI approaches as well as strong protection mechanisms against commonly abused corner cases.</div><div><br></div><div>We leverage the effectiveness of dynamic analysis in deriving a new approach to efficiently mitigate control-flow hijacking attacks. We present Ancile, a novel mechanism to improve the precision of the CFI mechanism by debloating any extraneous targets from the indirect control-flow transfers. We replaced the traditional static analysis approach for target discovery with seed demonstrated fuzzing. We have evaluated the effectiveness of our proposed mechanism with standard SPEC CPU benchmarks and other popular C and C++ applications.</div><div><br></div><div>To ensure complete security of C and C++ programs, we need to shield commonly exploited corners of C/C++ such as variadic functions. We performed extensive case studies to show the prevalence of such functions and their exploits. We also developed a sanitizer, HexVASAN, to effectively type-check and prevent any attack via variadic functions. CFH attacks, by abusing the difference of managed languages and their underlying system languages, are very frequent in client and server side programs. In order to safe-guard the control-flows in language boundaries, we propose a new mechanism, FitJit, to enforce type integrity. Finally, to understand the effectiveness of the dynamic analysis, we present Artemis, a comprehensive study of binary analysis on real world applications.</div>

In the current thesis, the Banafjäl Bridge located on the Bothnia line (Botniabanan) in northern Sweden was studied. The bridge is a 40m long composite ballasted high-speed railway bridge. A 3D FE model of the bridge was developed using a commercial FE software, Abaqus. The FE model was calibrated against the measured data of the bridge. The dynamic response of the bridge's FE model was investigated under the dynamic load of the passing HSLM-A train using modal dynamic analysis. The vertical acceleration induced by excitation of the passing train exceeded the permissible limit of 3.5 m/s2 for the speed range of 220-240 km/h. Thus, damping solutions using multiple tuned mass dampers (MTMDs) were investigated. According to the results of this study, a 4 tonnes MTMD system consist of 5 parallel TMDs attached to the mid-span of the bridge could effectively control the undesired vibration of the bridge. The suggested solution could account for the changes in the stiffness of the bridge caused by freezing and ice forming in the ballast.

The economic and technologic development experienced by the society in the last decades has caused the demand of a new type of faster and more comfortable transport. This type of demand has been covered by the air transport, the road transport and the railway transport. This situation where the society demands an improvement in her quality of life is the best situation for the birth of the high speed trains. Different studies carried out in the transport field have demonstrated that for distances between four hundred and one thousand of kilometres, the high speed trains provide a lower travelling times than the rest of the transports. These types of high speed trains have increased the axle loads and the average speeds, thus generally a dynamic analysis is required by the ERRI in all the railway bridges when the train speed is higher than 200 Km/h. Besides, when the train speed is going to be higher than 200 Km/h, the vibrations induced in the bridge can reduce the service life of the vehicles and structure, and generally, this fact leads to become the dynamic effect in the principal factor to take into account in order to design the structure. Therefore, an important knowledge in railway bridges dynamic is required to not to oversize the structures with the consequent economic cost. The purpose of this thesis is to study the possibility of accurately predicting the dynamic response of an existing railway bridge, subjected to the high speed train Gröna Tåget, implementing a simplified 2D finite element model with the aid of the program Abaqus. The bridge chosen is the Lögdeälv Bridge, a two spans composite bridge, located along the Bothnia Line (the new Swedish high-speed line), between the localities of Nordmaling and Rundvik. The measured eigenfrequencies due to bending modes of vibration are used for updating the model and then, these frequencies and the accelerations measured are used to compare and validate the different 2D updated models. The parameters used to update the models are; the damping coefficient of the structure, the mass and the stiffness of the bridge, and the supports stiffness. Finally it is concluded that the best model is achieved when the rotational support stiffness is modified in the two extremes supporters of the bridge.