Testing for delay defects utilizing test data compression techniques

textAs technology shrinks new types of defects are being discovered and new fault models are being created for those defects. Transition delay and path delay fault models are two such models that have been created, but they still fall short in that they are unable to obtain a high test coverage of smaller delay defects; these defects can cause functional behavior to fail and also indicate potential reliability issues. The first part of this dissertation addresses these problems by presenting an enhanced timing-based delay fault testing technique that incorporates the use of standard delay ATPG, along with timing information gathered from standard static timing analysis. Utilizing delay fault patterns typically increases the test data volume by 3-5X when compared to stuck-at patterns. Combined with the increase in test data volume associated with the increase in gate count that typically accompanies the miniaturization of technology, this adds up to a very large increase in test data volume that directly affect test time and thus the manufacturing cost. The second part of this dissertation presents a technique for improving test compression and reducing test data volume by using multiple expansion ratios while determining the configuration of the scan chains for each of the expansion ratios using a dependency analysis procedure that accounts for structural dependencies as well as free variable dependencies to improve the probability of detecting faults. Finally, this dissertation addresses the problem of unknown values (X’s) in the output response data corrupting the data and degrading the performance of the output response compactor and thus the overall amount of test compression. Four techniques are presented that focus on handling response data with large percentages of X’s. The first uses X-canceling MISR architecture that is based on deterministically observing scan cells, and the second is a hybrid approach that combines a simple X-masking scheme with the X-canceling MISR for further gains in test compression. The third and fourth techniques revolve around reiterative LFSR X-masking, which take advantage of LFSR-encoded masks that can be reused for multiple scan slices in novel ways.Electrical and Computer Engineerin

In-situ acoustic-based analysis system for physical and chemical properties of the lower Martian atmosphere

The Environmental Acoustic Reconnaissance and Sounding experiment (EARS), is composed of two parts: the Environmental Acoustic Reconnaissance (EAR) instrument and the Environmental Acoustic Sounding Experiment (EASE). They are distinct, but have the common objective of characterizing the acoustic environment of Mars. The principal goal of the EAR instrument is "listening" to Mars. This could be a most significant experiment if one thinks of everyday life experience where hearing is possibly the most important sense after sight. Not only will this contribute to opening up this important area of planetary exploration, which has been essentially ignored up until now, but will also bring the general public closer in contact with our most proximate planet. EASE is directed at characterizing acoustic propagation parameters, specifically sound velocity and absorption, and will provide information regarding important physical and chemical parameters of the lower Martian atmosphere; in particular, water vapor content, specific heat capacity, heat conductivity and shear viscosity, which will provide specific constraints in determining its composition. This would enable one to gain a deeper understanding of Mars and its analogues on Earth. Furthermore, the knowledge of the physical and chemical parameters of the Martian atmosphere, which influence its circulation, will improve the comprehension of its climate now and in the past, so as to gain insight on the possibility of the past presence of life on Mars. These aspect are considered strategic in the contest of its exploration, as is clearly indicated in NASA's four main objectives on "Long Term Mars Exploration Program" (http://marsweb.jpl.nasa.gov/mer/science).Comment: 16 pages including figure

High precision hybrid RF and ultrasonic chirp-based ranging for low-power IoT nodes

Hybrid acoustic-RF systems offer excellent ranging accuracy, yet they typically come at a power consumption that is too high to meet the energy constraints of mobile IoT nodes. We combine pulse compression and synchronized wake-ups to achieve a ranging solution that limits the active time of the nodes to 1 ms. Hence, an ultra low-power consumption of 9.015 µW for a single measurement is achieved. The operation time is estimated on 8.5 years on a CR2032 coin cell battery at a 1 Hz update rate, which is over 250 times larger than state-of-the-art RF-based positioning systems. Measurements based on a proof-of-concept hardware platform show median distance error values below 10 cm. Both simulations and measurements demonstrate that the accuracy is reduced at low signal-to-noise ratios and when reflections occur. We introduce three methods that enhance the distance measurements at a low extra processing power cost. Hence, we validate in realistic environments that the centimeter accuracy can be obtained within the energy budget of mobile devices and IoT nodes. The proposed hybrid signal ranging system can be extended to perform accurate, low-power indoor positioning

Star cluster evolution in barred disc galaxies. I. Planar periodic orbits

The dynamical evolution of stellar clusters is driven to a large extent by their environment. Several studies so far have considered the effect of tidal fields and their variations, such as, e.g., from giant molecular clouds, galactic discs, or spiral arms. In this paper we will concentrate on a tidal field whose effects on star clusters have not yet been studied, namely that of bars. We present a set of direct N-body simulations of star clusters moving in an analytic potential representing a barred galaxy. We compare the evolution of the clusters moving both on different planar periodic orbits in the barred potential and on circular orbits in a potential obtained by axisymmetrising its mass distribution. We show that both the shape of the underlying orbit and its stability have strong impact on the cluster evolution as well as the morphology and orientation of the tidal tails and the sub-structures therein. We find that the dissolution time-scale of the cluster in our simulations is mainly determined by the tidal forcing along the orbit and, for a given tidal forcing, only very little by the exact shape of the gravitational potential in which the cluster is moving.Comment: 15 pages, 17 figures, 5 tables; accepted for publication in MNRAS. Complementary movies can be be found at this http URL http://lam.oamp.fr/research/dynamique-des-galaxies/scientific-results/star-cluster-evolution

Scalloped Leading Edge Vaned Diffuser Analysis for a Compact High Pressure Ratio Centrifugal Compressor

Microturbines and small gas turbines are often an attractive option for turbo-hybryd application research in aviation due to their simple design and high power to weight ratio. However, the low operating pressure ratios of microturbines leads to low thermal efficiency, which results in very high fuel consumption. Higher operating pressure ratios in microturbines could vastly improve their current fuel efficiency. This thesis focuses on developing a compact, single stage 8:1 pressure ratio centrifugal compressor stage designed to meet the high-pressure ratio requirements of microturbines and small gas turbine engines in turbo hybrid-electric propulsion applications. The first stage vaned diffuser was modified to include a scalloped leading edge ridge to aid stage total-total compression efficiency improvement. A full 3D Navier-Strokes based CDF solver was used in estimating the delta increase in device total-total efficiency due to scalloped leading edge, from the baseline configuration. The solution obtained using CFD was also used to investigate the ameliorating effects of the scallop ridge

Performance Analysis of a Reciprocating Piston Expander and a Plate Type Exhaust Gas Recirculation Boiler in a Water-Based Rankine Cycle for Heat Recovery from a Heavy Duty Diesel Engine

The exhaust gas in an internal combustion engine provides favorable conditions for a waste-heat recovery (WHR) system. The highest potential is achieved by the Rankine cycle as a heat recovery technology. There are only few experimental studies that investigate full-scale systems using water-based working fluids and their effects on the performance and operation of a Rankine cycle heat recovery system. This paper discusses experimental results and practical challenges with a WHR system when utilizing heat from the exhaust gas recirculation system of a truck engine. The results showed that the boiler’s pinch point necessitated trade-offs between maintaining adequate boiling pressure while achieving acceptable cooling of the EGR and superheating of the water. The expander used in the system had a geometric compression ratio of 21 together with a steam outlet timing that caused high re-compression. Inlet pressures of up to 30 bar were therefore required for a stable expander power output. Such high pressures increased the pump power, and reduced the EGR cooling in the boiler because of pinch-point effects. Simulations indicated that reducing the expander’s compression ratio from 21 to 13 would allow 30% lower steam supply pressures without adversely affecting the expander’s power output

Desenvolvimento de um provete heterogéneo recorrendo à otimização de forma do recorte

Nowadays, virtual predictions are essential in the design and development of new engineering parts. A critical aspect for virtual predictions is the accuracy of the constitutive model to simulate the material behaviour. A state-of-the-art constitutive model generally involves a large number of parameters, and according to classical procedures, it requires many mechanical experiments for its accurate identification. Fortunately, this large number of mechanical experiments can be reduced using heterogeneous mechanical tests, which provide richer mechanical information than classical homogeneous tests. However, the richness is much dependent on the specimen’s geometry and can be improved with the development of new specimens. Therefore, this work aims to design a uniaxial tensile load test that presents heterogeneous strain fields using a shape optimisation methodology, by controlling the specimen’s interior notch shape. The optimisation problem is driven by a cost function composed by several indicators of the heterogeneity present in the specimen. Results show that the specimen’s heterogeneity is increased with a non-circular interior notch, compared to a circular one. The achieved virtual mechanical test originates both uniaxial tension and shear strain states in the plastic region, being the uniaxial tension strain state predominant.Hoje em dia, as previsões virtuais do comportamento dos materiais são essenciais para o projeto e desenvolvimento de novas peças e componentes de engenharia. Um aspeto fulcral para a sua virtualização é a exatidão dos modelos constitutivos. Um modelo constitutivo do comportamento de materiais geralmente implica um elevado número de parâmetros que, para uma correta identificação, são necessários diversos ensaios mecânicos clássicos. Este número de ensaios pode ser reduzido utilizando ensaios mecânicos heterogéneos, que providenciam mais informação mecânica do que os ensaios homogéneos clássicos. Contudo, a riqueza do ensaio mecânico é bastante dependente da geometria do provete usado, que pode ser melhorada através do desenvolvimento de novos provetes. Portanto, o objetivo deste trabalho é desenvolver um ensaio de carregamento uniaxial que apresenta estados de deformação heterogéneos, utilizando uma metodologia de optimização de forma, com o intuito de controlar a geometria do recorte interior do provete. O problema de otimização é guiado através de uma função objetivo composta por diversos indicadores de heterogeneidade presente no provete. Os resultados mostram que a heterogeneidade de um provete com um recorte interior não circular é superior ao de um circular. O ensaio mecânico obtido origina estados de tensão uniaxial e corte puro, na região de deformação plástica, sendo o estado de tensão uniaxial predominante.Mestrado em Engenharia Mecânic