Role of Computational Fluid Dynamics and Wind Tunnels in Aeronautics R and D

The purpose of this report is to investigate the status and future projections for the question of supplantation of wind tunnels by computation in design and to intuit the potential impact of computation approaches on wind-tunnel utilization all with an eye toward reducing the infrastructure cost at aeronautics R&D centers. Wind tunnels have been closing for myriad reasons, and such closings have reduced infrastructure costs. Further cost reductions are desired, and the work herein attempts to project which wind-tunnel capabilities can be replaced in the future and, if possible, the timing of such. If the possibility exists to project when a facility could be closed, then maintenance and other associated costs could be rescheduled accordingly (i.e., before the fact) to obtain an even greater infrastructure cost reduction

Cumulative index to NASA Tech Briefs, 1986-1990, volumes 10-14

Tech Briefs are short announcements of new technology derived from the R&D activities of the National Aeronautics and Space Administration. These briefs emphasize information considered likely to be transferrable across industrial, regional, or disciplinary lines and are issued to encourage commercial application. This cumulative index of Tech Briefs contains abstracts and four indexes (subject, personal author, originating center, and Tech Brief number) and covers the period 1986 to 1990. The abstract section is organized by the following subject categories: electronic components and circuits, electronic systems, physical sciences, materials, computer programs, life sciences, mechanics, machinery, fabrication technology, and mathematics and information sciences

Placement for fast and reliable through-silicon-via (TSV) based 3D-IC layouts

The objective of this research is to explore the feasibility of addressing the major performance and reliability problems or issues, such as wirelength, stress-induced carrier mobility variation, temperature, and quality trade-offs, found in three-dimensional integrated circuits (3D ICs) that use through-silicon vias (TSVs) at placement stage. Four main works that support this goal are included. In the first work, wirelength of TSV-based 3D ICs is the main focus. In the second work, stress-induced carrier mobility variation in TSV-based 3D ICs is examined. In the third work, temperature inside TSV-based 3D ICs is investigated. In the final work, the quality trade-offs of TSV-based 3D-IC designs are explored. In the first work, a force-directed, 3D, and gate-level placement algorithm that efficiently handles TSVs is developed. The experiments based on synthesized benchmarks indicate that the developed algorithm helps generate GDSII layouts of 3D-IC designs that are optimized in terms of wirelength. In addition, the impact of TSVs on other physical aspects of 3D-IC designs is also studied by analyzing the GDSII layouts. In the second work, the model for carrier mobility variation caused by TSV and STI stresses is developed as well as the timing analysis flow considering the stresses. The impact of TSV and STI stresses on carrier mobility variation and performance of 3D ICs is studied. Furthermore, a TSV-stress-driven, force-directed, and 3D placement algorithm is developed. It exploits carrier mobility variation, caused by stress around TSVs after fabrication, to improve the timing and area objectives during placement. In addition, the impact of keep-out zone (KOZ) around TSVs on stress, carrier mobility variation, area, wirelength, and performance of 3D ICs is studied. In the third work, two temperature-aware global placement algorithms are developed. They exploit die-to-die thermal coupling in 3D ICs to improve temperature during placement. In addition, a framework used to evaluate the results from temperature-aware global placements is developed. The main component of the framework is a GDSII-level thermal analysis that considers all structures inside a TSV-based 3D IC while computing temperature. The developed placers are compared with several state-of-the-art placers published in recent literature. The experimental results indicate that the developed algorithms help improve the temperature of 3D ICs effectively. In the final work, three block-level design styles for TSV-based die-to-wafer bonded 3D ICs are discussed. Several 3D-IC layouts in the three styles are manually designed. The main difference among these layouts is the position of TSVs. Finally, the area, wirelength, timing, power, temperature, and mechanical stress of all layouts are compared to explore the trade-offs of layout quality.PhDCommittee Chair: Lim, Sung Kyu; Committee Member: Bakir, Muhannad; Committee Member: Kim, Hyesoon; Committee Member: Mukhopadhyay, Saibal; Committee Member: Swaminathan, Madhava

Modeling the spatio-temporal evolution of fracture networks and fluid-rock interactions in GPU : Applications to lithospheric geodynamics

In this thesis, I present the theory and modeling of poro-elasto-plastic rheology coupled to a non-linear diffusion equation with a step increase in permeability at the onset of slip. This theoretical model is implemented in the graphic processing unit (GPU) architecture and programmed using the nVidia CUDA programming language. The numerical models are benchmarked by investigating fracture orientation for the solid-mechanical aspects, and by using the Method of Manufactured solutions for the diffusion part. I find that the GPU platform is ideal for these models because very high resolution simulations can be performed on an explicit finite difference algorithm using a single GPU card, outperforming CPU by a factor of at least five. The inherent problem with these coupled systems is the wide range of time and length scales that needs to be considered, and the advantage of GPU is its inherent parallel architecture that allows to do so. In these models, numerical fractures develop and evolve in response to prevailing far-field stresses, to local stress heterogeneity and pore-elastic stresses resulting from fracture growth, dislocation slip and fluid pressure diffusion within the domain. The numerical models, once benchmarked, are used to understand a variety of important and diverse lithospherical geodynamical problems, including enhanced geothermal systems (EGS), volcano-tectonic interactions and aftershocks. Envisaged future applications include hydro-fracture (’Fracking’), CO2 sequestration, earthquake nucleation and nuclear waste isolation. The potential of this model is far-reaching, and future developments in 3 dimensions will open up countless new avenues of insight and understanding of fluid-rock interactions and lithospheric dynamics

Aeronautical engineering: A continuing bibliography with indexes (supplement 306)

This bibliography lists 181 reports, articles, and other documents recently introduced into the NASA STI Database. Subject coverage includes the following: design, construction and testing of aircraft and aircraft engines; aircraft components, equipment, and systems; ground support systems; and theoretical and applied aspects of aerodynamics and general fluid dynamics

The Role of Computers in Research and Development at Langley Research Center

This document is a compilation of presentations given at a workshop on the role cf computers in research and development at the Langley Research Center. The objectives of the workshop were to inform the Langley Research Center community of the current software systems and software practices in use at Langley. The workshop was organized in 10 sessions: Software Engineering; Software Engineering Standards, methods, and CASE tools; Solutions of Equations; Automatic Differentiation; Mosaic and the World Wide Web; Graphics and Image Processing; System Design Integration; CAE Tools; Languages; and Advanced Topics

The Fifth NASA Symposium on VLSI Design

The fifth annual NASA Symposium on VLSI Design had 13 sessions including Radiation Effects, Architectures, Mixed Signal, Design Techniques, Fault Testing, Synthesis, Signal Processing, and other Featured Presentations. The symposium provides insights into developments in VLSI and digital systems which can be used to increase data systems performance. The presentations share insights into next generation advances that will serve as a basis for future VLSI design

Potential and Challenges of Analog Reconfigurable Computation in Modern and Future CMOS

In this work, the feasibility of the floating-gate technology in analog computing platforms in a scaled down general-purpose CMOS technology is considered. When the technology is scaled down the performance of analog circuits tends to get worse because the process parameters are optimized for digital transistors and the scaling involves the reduction of supply voltages. Generally, the challenge in analog circuit design is that all salient design metrics such as power, area, bandwidth and accuracy are interrelated. Furthermore, poor flexibility, i.e. lack of reconfigurability, the reuse of IP etc., can be considered the most severe weakness of analog hardware. On this account, digital calibration schemes are often required for improved performance or yield enhancement, whereas high flexibility/reconfigurability can not be easily achieved. Here, it is discussed whether it is possible to work around these obstacles by using floating-gate transistors (FGTs), and analyze problems associated with the practical implementation. FGT technology is attractive because it is electrically programmable and also features a charge-based built-in non-volatile memory. Apart from being ideal for canceling the circuit non-idealities due to process variations, the FGTs can also be used as computational or adaptive elements in analog circuits. The nominal gate oxide thickness in the deep sub-micron (DSM) processes is too thin to support robust charge retention and consequently the FGT becomes leaky. In principle, non-leaky FGTs can be implemented in a scaled down process without any special masks by using “double”-oxide transistors intended for providing devices that operate with higher supply voltages than general purpose devices. However, in practice the technology scaling poses several challenges which are addressed in this thesis. To provide a sufficiently wide-ranging survey, six prototype chips with varying complexity were implemented in four different DSM process nodes and investigated from this perspective. The focus is on non-leaky FGTs, but the presented autozeroing floating-gate amplifier (AFGA) demonstrates that leaky FGTs may also find a use. The simplest test structures contain only a few transistors, whereas the most complex experimental chip is an implementation of a spiking neural network (SNN) which comprises thousands of active and passive devices. More precisely, it is a fully connected (256 FGT synapses) two-layer spiking neural network (SNN), where the adaptive properties of FGT are taken advantage of. A compact realization of Spike Timing Dependent Plasticity (STDP) within the SNN is one of the key contributions of this thesis. Finally, the considerations in this thesis extend beyond CMOS to emerging nanodevices. To this end, one promising emerging nanoscale circuit element - memristor - is reviewed and its applicability for analog processing is considered. Furthermore, it is discussed how the FGT technology can be used to prototype computation paradigms compatible with these emerging two-terminal nanoscale devices in a mature and widely available CMOS technology.Siirretty Doriast

NASA Tech Briefs, February 1987

Topics include: NASA TU Services; New Product Ideas; Electronic Components and Circuits; Electronic Systems; Physical Sciences; Materials; Computer Programs; Mechanics; Fabrication Technology; Machinery; Mathematics and Information Sciences; Life Sciences

Physically-based 6-DoF Nodes Deformable Models: Application to Connective Tissues Simulation and Soft-Robots Control

The medical simulation is an increasingly active research field. Yet, despite the promising advance observed over the past years, the complete virtual patient’s model is yet to come. There are still many avenues for improvements, especially concerning the mechanical modeling of boundary conditions on anatomical structures.So far, most of the work has been dedicated to organs simulation, which are generally simulated alone. This raises a real problem as the role of the surrounding organs in the boundary conditions is neglected. However, these interactions can be complex, involving contacts but also mechanical links provided by layers of soft tissues. The latter are known as connective tissues or fasciae. As a consequence, the mutual influences between the anatomical structures are generally simplified, weakening the realism of the simulations.This thesis aims at studying the importance of the connective tissues, and especially of a proper modeling of the boundary conditions. To this end, the role of the ligaments during laparoscopic liver surgery has been investigated. In order to enhance the simulations’ realism, a mechanical model dedicated to the connective tissues has been worked out. This has led to the development of a physically-based method relying on material points that can, not only translate, but also rotate themselves. The goal of this model is to enable the simulation of multiple organs linked by complex interactions.In addition, the work on the connective tissues model has been derived to be used in soft robotics. Indeed, the principle of relying on orientable material points has been used to developed a reduced model that can reproduce the behavior of more complex structures. The objective of this work is to provide the means to control – in real-time – a soft robot made of a deformable arm.La simulation médicale est un domaine de recherche de plus en plus actif. Cependant, malgré les avancées prometteuses observées ces dernières années, le modèle complet du patient virtuel reste un objectif ambitieux. Il existe encore de nombreuses opportunités de recherche, notamment concernant la modélisation mécanique des conditions aux limites des organes.Jusqu'à présent, la majorité des travaux était consacrée à la simulation d'organes, ces derniers étant généralement simulés seuls. Cette situation pose un réel problème car l'influence qu'ont les organes environnants sur les conditions aux limites est négligée. Ces interactions peuvent être complexes, impliquant des contacts mais aussi des liaisons mécaniques dues à des couches de tissus connus sous le nom de tissus conjonctifs ou fasciae. Pour cette raison, les influences mutuelles entre les structures anatomiques sont généralement simplifiées, diminuant le réalisme des simulations.Cette thèse visé à étudier l'importance des tissus conjonctifs, et plus particulièrement d'une bonne modélisation des conditions aux limites. Dans ce but, le rôle des ligaments lors d'une intervention chirurgicale sur la foie par laparoscopie a été étudié. Afin d'améliorer le réalisme des simulations, un modèle mécanique dédié aux tissus conjonctifs a été mis au point. Ainsi, une méthode basée sur la mécanique des milieux continus et un ensemble de nœuds à 6 degrés de liberté a été développée. L'objectif de ce modèle étant de permettre la simulation simultanée de plusieurs organes liés par des interaction complexes.En outre, les travaux sur les tissus conjonctifs ont donné lieu à la mise au point d'une méthode de modélisation utilisée dans le cadre des robots déformables. Cette méthode permet un contrôle précis, et temps-réel, d'un bras robotisé déformable. En effet, l'utilisation de nœuds orientables a permis de développer un modèle a nombre de degrés de liberté réduit, qui permet de reproduire le comportement de structures plus complexes