Evaluation of reliability modeling tools for advanced fault tolerant systems

The Computer Aided Reliability Estimation (CARE III) and Automated Reliability Interactice Estimation System (ARIES 82) reliability tools for application to advanced fault tolerance aerospace systems were evaluated. To determine reliability modeling requirements, the evaluation focused on the Draper Laboratories' Advanced Information Processing System (AIPS) architecture as an example architecture for fault tolerance aerospace systems. Advantages and limitations were identified for each reliability evaluation tool. The CARE III program was designed primarily for analyzing ultrareliable flight control systems. The ARIES 82 program's primary use was to support university research and teaching. Both CARE III and ARIES 82 were not suited for determining the reliability of complex nodal networks of the type used to interconnect processing sites in the AIPS architecture. It was concluded that ARIES was not suitable for modeling advanced fault tolerant systems. It was further concluded that subject to some limitations (the difficulty in modeling systems with unpowered spare modules, systems where equipment maintenance must be considered, systems where failure depends on the sequence in which faults occurred, and systems where multiple faults greater than a double near coincident faults must be considered), CARE III is best suited for evaluating the reliability of advanced tolerant systems for air transport

A fault injection experiment using the AIRLAB Diagnostic Emulation Facility

The preparation for, conduct of, and results of a simulation based fault injection experiment conducted using the AIRLAB Diagnostic Emulation facilities is described. An objective of this experiment was to determine the effectiveness of the diagnostic self-test sequences used to uncover latent faults in a logic network providing the key fault tolerance features for a flight control computer. Another objective was to develop methods, tools, and techniques for conducting the experiment. More than 1600 faults were injected into a logic gate level model of the Data Communicator/Interstage (C/I). For each fault injected, diagnostic self-test sequences consisting of over 300 test vectors were supplied to the C/I model as inputs. For each test vector within a test sequence, the outputs from the C/I model were compared to the outputs of a fault free C/I. If the outputs differed, the fault was considered detectable for the given test vector. These results were then analyzed to determine the effectiveness of some test sequences. The results established coverage of selt-test diagnostics, identified areas in the C/I logic where the tests did not locate faults, and suggest fault latency reduction opportunities

A NASA-wide approach toward cost-effective, high-quality software through reuse

NASA Langley Research Center sponsored the second Workshop on NASA Research in Software Reuse on May 5-6, 1992 at the Research Triangle Park, North Carolina. The workshop was hosted by the Research Triangle Institute. Participants came from the three NASA centers, four NASA contractor companies, two research institutes and the Air Force's Rome Laboratory. The purpose of the workshop was to exchange information on software reuse tool development, particularly with respect to tool needs, requirements, and effectiveness. The participants presented the software reuse activities and tools being developed and used by their individual centers and programs. These programs address a wide range of reuse issues. The group also developed a mission and goals for software reuse within NASA. This publication summarizes the presentations and the issues discussed during the workshop

Integration of tools for the Design and Assessment of High-Performance, Highly Reliable Computing Systems (DAHPHRS), phase 1

Systems for Space Defense Initiative (SDI) space applications typically require both high performance and very high reliability. These requirements present the systems engineer evaluating such systems with the extremely difficult problem of conducting performance and reliability trade-offs over large design spaces. A controlled development process supported by appropriate automated tools must be used to assure that the system will meet design objectives. This report describes an investigation of methods, tools, and techniques necessary to support performance and reliability modeling for SDI systems development. Models of the JPL Hypercubes, the Encore Multimax, and the C.S. Draper Lab Fault-Tolerant Parallel Processor (FTPP) parallel-computing architectures using candidate SDI weapons-to-target assignment algorithms as workloads were built and analyzed as a means of identifying the necessary system models, how the models interact, and what experiments and analyses should be performed. As a result of this effort, weaknesses in the existing methods and tools were revealed and capabilities that will be required for both individual tools and an integrated toolset were identified

Surface flow profiles for dry and wet granular materials by Particle Tracking Velocimetry; the effect of wall roughness

Two-dimensional Particle Tracking Velocimetry (PTV) is a promising technique to study the behaviour of granular flows. The aim is to experimentally determine the free surface width and position of the shear band from the velocity profile to validate simulations in a split-bottom shear cell geometry. The position and velocities of scattered tracer particles are tracked as they move with the bulk flow by analyzing images. We then use a new technique to extract the continuum velocity field, applying coarse-graining with the postprocessing toolbox MercuryCG on the discrete experimental PTV data. For intermediate filling heights, the dependence of the shear (or angular) velocity on the radial coordinate at the free surface is well fitted by an error function. From the error function, we get the width and the centre position of the shear band. We investigate the dependence of these shear band properties on filling height and rotation frequencies of the shear cell for dry glass beads for rough and smooth wall surfaces. For rough surfaces, the data agrees with the existing experimental results and theoretical scaling predictions. For smooth surfaces, particle-wall slippage is significant and the data deviates from the predictions. We further study the effect of cohesion on the shear band properties by using small amount of silicon oil and glycerol as interstitial liquids with the glass beads. While silicon oil does not lead to big changes, glycerol changes the shear band properties considerably. The shear band gets wider and is situated further inward with increasing liquid saturation, due to the correspondingly increasing trend of particles to stick together

El comercio infame: capitalismo milenarista, valores humanos y justicia global en el tráfico de órganos

This article documents the growth of “transplant tourism” and the global traffic in human bodies, desires, and needs. Organ transplantation today takes place in a transnational space with surgeons, patients, donors, sellers and brokers following new paths of capital and technology. In general, organs flow from South to North, from third to first world, and from poorer to richer bodies, and from black and brown to whites and from females to males. The “scarcity” of organs and tissues combined with the scarcity of patients of sufficient means to pay for these expensive operations, has spawned a lucrative business driven by the market calculus of supply and demand. The spread of new medical technologies and the new needs, scarcities, and commodities –for instance, fresh organs and tissues– that they inspire raises urgent public issues concerning: the reordering of relations between bodies and the state in late modernity; the appearance of “fluid” and divisible bodies that disrupt early modern notions of the indivisible and autonomous body-self; the emergence of new forms of barter and social exchange that breach the conventional dichotomy between gifts and commodities and between kin and strangers; the interplay of magic and science; and the power of rumours and urban legends to challenge the official medical and transplant “narratives” on the meanings of life, death, and sacrifice.Este artículo documenta el crecimiento del “turismo de transplante” y el tráfico global de cuerpos, deseos y necesidades humanas. El transplante de órganos tiene lugar hoy en día en un espacio transnacional en el que circulan cirujanos, pacientes, donantes, vendedores e intermediarios que siguen los nuevos caminos del capital y de la tecnología. En general, los órganos fluyen de sur a norte, del tercer al primer mundo, de los cuerpos más pobres a los más ricos, de negros y cobrizos a blancos, y de mujeres a hombres. La “escasez” de cuerpos y tejidos, en combinación con la escasez de pacientes con medios suficientes para pagar estas costosas intervenciones, han hecho surgir un lucrativo negocio impulsado por el cálculo de oferta y demanda de mercado. La extensión de nuevas tecnologías médicas y las nuevas necesidades, escasez y mercancías –por ejemplo, órganos y tejidos frescos– que inspiran, hacen surgir debates públicos de carácter urgente, relacionados con: la reordenación de las relaciones entre los cuerpos y el Estado en la modernidad tardía; la aparición de cuerpos “fluidos” y divisibles que ponen en cuestión nociones de la primera modernidad acerca de lo indivisible del cuerpo –self–; la aparición de nuevas formas de trueque e intercambio social que rompen la dicotomía convencional entre dones y mercancías y entre parientes y extraños; el juego mutuo entre magia y ciencia; y el poder de los rumores y leyendas urbanas de plantear un reto a las “narrativas” oficiales médicas y de transplantes acerca de los significados de la vida, de la muerte y del sacrificio

The association between muscle strength and activity limitations in patients with the hypermobility type of Ehlers–Danlos syndrome : the impact of proprioception

Purpose: The patients diagnosed with Ehlers-Danlos Syndrome Hypermobility Type (EDS-HT) are characterized by pain, proprioceptive inacuity, muscle weakness, potentially leading to activity limitations. In EDS-HT, a direct relationship between muscle strength, proprioception and activity limitations has never been studied. The objective of the study was to establish the association between muscle strength and activity limitations and the impact of proprioception on this association in EDS-HT patients. Methods: Twenty-four EDS-HT patients were compared with 24 controls. Activity limitations were quantified by Health Assessment Questionnaire (HAQ), Six-Minute Walk test (6MWT) and 30-s chair-rise test (30CRT). Muscle strength was quantified by handheld dynamometry. Proprioception was quantified by movement detection paradigm. In analyses, the association between muscle strength and activity limitations was controlled for proprioception and confounders. Results: Muscle strength was associated with 30CRT (r = 0.67, p = <0.001), 6MWT (r = 0.58, p = <0.001) and HAQ (r = 0.63, p = <0.001). Proprioception was associated with 30CRT (r = 0.55, p <0.001), 6MWT (r = 0.40, p = <0.05) and HAQ (r = 0.46, p < 0.05). Muscle strength was found to be associated with activity limitations, however, proprioceptive inacuity confounded this association. Conclusions: Muscle strength is associated with activity limitations in EDS-HT patients. Joint proprioception is of influence on this association and should be considered in the development of new treatment strategies for patients with EDS-HT. Implications for rehabilitation : Reducing activity limitations by enhancing muscle strength is frequently applied in the treatment of EDS-HT patients. Although evidence regarding treatment efficacy is scarce, the current paper confirms the rationality that muscle strength is an important factor in the occurrence of activity limitations in EDS-HT patients. Although muscle strength is the most dominant factor that is associated with activity limitations, this association is confounded by proprioception. In contrast to common belief proprioception was not directly associated with activity limitations but confounded this association. Controlling muscle strength on the bases of proprioceptive input may be more important for reducing activity limitations than just enhancing sheer muscle strength