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The quality and reliability of software systems, in terms of their functional correctness, critically relies on the effectiveness of the testing tools and techniques to detect errors in the system before deployment. A lack of testing tools for concurrent programs that systematically control thread scheduling choices has not allowed concurrent software development to keep abreast with hardware trends of multi-core and multi-processor technologies. This motivates a need for the development of systematic testing techniques that detect errors in concurrent programs. The work in this dissertation presents a potentially scalable technique that can be used to detect concurrency errors in production code. The technique is a viable solution for software engineers and testers to detect errors in multi-threaded programs before deployment. We present a guided testing technique that combines static analysis techniques, systematic verification techniques, and heuristics to efficiently detect errors in concurrent programs. An abstraction-refinement technique lies at the heart of the guided test technique. The abstraction-refinement technique uses as input potential errors in the program generated by imprecise, but scalable, static analysis tools. The abstraction further leverages static analyses to generate a set of program locations relevant in verifying the reachability of the potential error. Program execution is guided along these points by ranking both thread and data non-determinism. The set of relevant locations is refined when program execution is unable to make progress. The dissertation also discusses various heuristics for effectively guiding program execution. We implemented the guided test technique to detect errors in Java programs. Guided test successfully detects errors caused by thread schedules and data input values in Java benchmarks and the JDK concurrent libraries for which other state of the art analysis and testing tools for concurrent programs are unable to find an error.

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Ever since chip manufacturers hit the power wall preventing them from increasing processor clock speed, there has been an increased push towards parallelism for performance improvements. This parallelism comes in the form of both data parallel single instruction multiple data (SIMD) instructions, as well as parallel compute cores in both central processing units (CPUs) and graphics processing units (GPUs). While these hardware enhancements offer potential performance enhancements, programs must be re-written to take advantage of them in order to see any performance improvement Some lower level languages that compile directly to machine code already take advantage of the data parallel SIMD instructions, but often higher level interpreted languages do not. Java, one of the most popular programming languages in the world, still does not include support for these SIMD instructions. In this thesis, we present a vector library that implements all of the major SIMD instructions in functions that are accessible to Java through JNI function calls. This brings the benefits of general purpose SIMD functionality to Java. This thesis also works with the data parallel Aparapi Java extension to bring these SIMD performance improvements to programmers who use the extension without any additional effort on their part. Aparapi already provides programmers with an API that allows programmers to declare certain sections of their code parallel. These parallel sections are then run on OpenCL capable hardware with a fallback path in the Java thread pool to ensure code reliability. This work takes advantage of the knowledge of independence of the parallel sections of code to automatically modify the Java thread pool fallback path to include the vectorization library through the use of an auto-vectorization tool created for this work. When the code is not vectorizable the auto-vectorizer tool is still able to offer performance improvements over the default fallback path through an improved looped implementation that executes the same code but with less overhead. Experiments conducted by this work illustrate that for all 10 benchmarks tested the auto-vectorization tool was able to produce an implementation that was able to beat the default Aparapi fallback path. In addition it was found that this improved fallback path even outperformed the GPU implementation for several of the benchmarks tested. / Master of Science

This dissertation discusses the thermomechanical analyses performed on threaded fasteners and curvilinearly stiffened composite panels with internal cutouts. The former problem was analyzed using a global/local approach using the commercial finite element software ANSYS while a fully functional code using isogeometric analysis was developed from scratch for the latter. For the threaded fasteners, a global simplified 3D model is built to evaluate the deformation of the structure. A second local model reproducing accurately the threads of the fasteners is used for the accurate assessment of the stresses in the vicinity of the fasteners. The isogeometric analysis code, capable of performing static, buckling and vibration analysis on stiffened composite plates with cutouts using single patch, multiple patches and level set methods is then discussed. A novel way to achieve displacement compatibility between the panel and stiffeners interfaces is introduced. An easy way of modeling plates with complicated cutouts by using edge curves and generating a ruled NURBS surface between them is described. Influence on the critical thermal buckling load and the fundamental mode of vibration due to the presence of circular, elliptical and complicated cutouts is also investigated. Results of parametric studies are presented which show the influence of ply orientation, size and orientation of the cutout, and the position and profile of the curvilinear stiffener. The numerical examples show high reliability and efficiency when compared with other published solutions and those obtained using ABAQUS, a commercial software. / PHD / Aircraft in flight are subjected to different loads due to maneuvers and gust; there external forces cause internal loads and depend on the location of the panel in the aircraft. The internal loads, may result in the buckling of the panel. Hence, there is a need for studying structural efficiency and develop strong and stiff lightweight structures. Stiffened composite panels is a technology capable of addressing these needs. However, when used in space vehicles moving at hypersonic speeds, such structures experience significant temperature rise in a very short time resulting from the aerodynamic heating due to friction between the vehicle surface and the atmosphere. Such phenomena is more prominent during reentry and launch processes. Hence, it is really important to consider thermal effects while designing and analyzing such structures. Composite stiffened panels have many advantages like small manufacturing cost, high stability, great energy absorption, superior damage tolerance etc. One of the main failure modes for stiffened composite panels is thermal buckling. An extensive literature review on thermal buckling of stiffened composite panels was conducted in this dissertation. Thermal buckling and vibration analysis as well as a parametric study of a stiffened composite panel with internal cutouts was conducted, and verified using ABAQUS, a Finite Element Software.

The Recursive Multi-Threaded (RMT) software process management tool gives software developers the following capabilities: break a large project into a sequence of prototypes (or threads) track these threads individually, and estimate the progress and completion date of the project from these individual threads. The goal of this project is to provide the RMT Tool with an ability to support multi-database for collaborative software development. As a demonstration, actual data is used from several previous algorithma projects.

ITC/USA 2011 Conference Proceedings / The Forty-Seventh Annual International Telemetering Conference and Technical Exhibition / October 24-27, 2011 / Bally's Las Vegas, Las Vegas, Nevada / The Spectrum Efficient Technology Science and Technology (SET S&T) Program is sponsoring the development of the Dynamic Commutation and Decommutation System (DCDS), which optimizes telemetry data transmission in real time. The goal of DCDS is to improve spectrum efficiency - not through improving RF techniques but rather through changing and optimizing contents of the telemetry stream during system test. By allowing the addition of new parameters to the telemetered stream at any point during system test, DCDS removes the need to transmit measured data unless it is actually needed on the ground. When compared to serial streaming telemetry, real time re-formatting of the telemetry stream does require additional processing onboard the test article. DCDS leverages advances in microprocessor technology to perform this processing while meeting size, weight, and power constraints of the test environment. Performance gains of the system have been achieved by significant multi-threading of the application, allowing it to run on modern multi-core processors. Two other enhancing technologies incorporated into DCDS are the Java programming language and lossless compression.

Threaded fastener is one of the most common ways to join components. Having a method to test threaded fasteners is key when designing a joint and even more a nutrunner. A joint is often tightened by a torque applied on the head. The applied torque is equal to three quantities in the joint, the thread torque, the underhead torque and the clamp force. To measure these quantities are the propose of a friction test rig. A test rig was built last year to be able to do that in a flexible and effective way. But the test rig built last year does not have the possibility to measure the underhead torque. A new transducer is constructed to add that possibility. The transducer is constructed by using methods such as concept generation, strength calculations, FEM simulations and a comparison of sensors are made. An easy way to change the stiffness is also investigated but no possible solution could be found. Some modifications and trims are also done on the test rig and also a comparison with the older BLM rig. A validation is made of how good the rig perform is also done. The results shows in favour for the FTR but precise results is not possible to determine.