Orion GN and C Overview and Architecture

The Crew Exploration Vehicle, named Orion, is a critical element in the Constellation Program to develop the transportation system needed to send humans back to the moon and then beyond. Lockheed Martin is the prime contractor for the Orion spacecraft, which is managed by the Johnson Space Center. The Orion GN&C sub-system is being jointly developed by NASA and Lockheed Martin through a mode team approach. The GN&C is a critical element of the Orion mission to carry astronauts to low earth orbit to service the International Space Station and then on later flights to transfer and return a crew of four to the moon. The Orion GN&C system must perform monitoring and abort functions during ascent, rendezvous and docking in both low earth and lunar orbits, perform uncrewed lunar loiter operations, perform trans earth injection and atmospheric entry and landing. The Orion also must be integrated with the Ares I Crew Launch Vehicle, the Earth Departure Stage of the Ares V and the Lunar Surface Access Module. This paper provides an overview of the Orion GN&C system. The functional capabilities of the Orion GN&C will be provided in the context of Constellation architecture, the key GN&C requirements will be summarized, the GN&C architecture will be presented, the development schedule and plans will summarized and finally conclusions will be presented

XRound : A reversible template language and its application in model-based security analysis

Successful analysis of the models used in Model-Driven Development requires the ability to synthesise the results of analysis and automatically integrate these results with the models themselves. This paper presents a reversible template language called XRound which supports round-trip transformations between models and the logic used to encode system properties. A template processor that supports the language is described, and the use of the template language is illustrated by its application in an analysis workbench, designed to support analysis of security properties of UML and MOF-based models. As a result of using reversible templates, it is possible to seamlessly and automatically integrate the results of a security analysis with a model. (C) 2008 Elsevier B.V. All rights reserved

Environmental and Occupational Exposures in Immigrant Health

Immigrants comprise vulnerable populations that are frequently exposed to a multitude of environmental and occupational hazards. The historical context behind state and federal legislation has helped to foster an environment that is particularly hostile toward caring for immigrant health. Current hazards include toxic exposures, air and noise pollution, motor vehicle accidents, crowded living and work environments with inadequate ventilation, poor sanitation, mechanical injury, among many others. Immigrants lack the appropriate training, materials, health care access, and other resources to reduce their exposure to preventable environmental and occupational health risks. This dilemma is exacerbated by current anti-immigrant sentiments, miscommunication between native and immigrant populations, and legislation denying immigrants access to publicly funded medical care. Given that current health policy has failed to address immigrant health appropriately and political impetus is lacking, efforts should also focus on alternative solutions, including organized labor. Labor unions that serve to educate workers, survey work environments, and defend worker rights will greatly alleviate and prevent the burden of disease incurred by immigrants. The nation's health will benefit from improved regulation of living and workplace environments to improve the health of immigrants, regardless of legal status

Non-Axisymmetric Instability of Core-Annular Flow

Stability of core-annular flow of water and oil in a vertical circular pipe is studied with respect to non-axisymmetric disturbances. Results show that when the oil core is thin, the flow is most unstable to the asymmetric sinuous mode of disturbance, and the core moves in the form of corkscrew waves as observed in experiments. The asymmetric mode of disturbance is the most dangerous mode for quite a wide range of material and flow parameters. This asymmetric mode persists in vertical pipes with upward and downward flows and in horizontal pipes. The analysis also applies to the instability of freely rising axisymmetric cigarette smoke or a thermal plume. The study predicts a unique wavelength for the asymmetric meandering waves

An Explicit Finite-Difference Scheme for Simulation of Moving Particles

We present an explicit finite-difference scheme for direct simulation of the motion of solid particles in a fluid. The method is based on a second order MacCormack finite-difference solver for the flow, and Newton’s equations for the particles. The fluid is modeled with fully compressible mass and momentum balances; the technique is intended to be used at moderate particle Reynolds number. Several examples are shown, including a single stationary circular particle in a uniform flow between two moving walls, a particle dropped in a stationary fluid at particle Reynolds number of 20, the drafting, kissing, and tumbling of two particles, and 100 particles falling in a closed box

Environmental and Occupational Exposures in Immigrant Health

Immigrants comprise vulnerable populations that are frequently exposed to a multitude of environmental and occupational hazards. The historical context behind state and federal legislation has helped to foster an environment that is particularly hostile toward caring for immigrant health. Current hazards include toxic exposures, air and noise pollution, motor vehicle accidents, crowded living and work environments with inadequate ventilation, poor sanitation, mechanical injury, among many others. Immigrants lack the appropriate training, materials, health care access, and other resources to reduce their exposure to preventable environmental and occupational health risks. This dilemma is exacerbated by current anti-immigrant sentiments, miscommunication between native and immigrant populations, and legislation denying immigrants access to publicly funded medical care. Given that current health policy has failed to address immigrant health appropriately and political impetus is lacking, efforts should also focus on alternative solutions, including organized labor. Labor unions that serve to educate workers, survey work environments, and defend worker rights will greatly alleviate and prevent the burden of disease incurred by immigrants. The nation’s health will benefit from improved regulation of living and workplace environments to improve the health of immigrants, regardless of legal status

Stability of a Core-Annular Flow in a Rotating Pipe

The linear stability of core-annular flow in rotating pipes is analyzed. Attention is focused on the effects of rotating the pipe and the difference in density of the two fluids. Both axisymmetric and nonaxisymmetric disturbances are considered. Major effects of the viscosity ratio, interfacial tension, radius ratio, and Reynolds number are included. It is found that for two fluids of equal density the rotation of the pipe stabilizes the axisymmetric (n= 0) modes of disturbances and destabilizes the nonaxisymmetric modes. Except for small script R sign, where the axisymmetric capillary instability is dominant, the first azimuthal mode of disturbance |n| = 1 is the most unstable. When the heavier fluid is outside centripetal acceleration of the fluid in the rotating pipe is stabilizing; there exists a critical rotating speed above which the flow is stabilized against capillary instability for certain range of small script R sign. When the lighter fluid is outside the flow is always unstable

A three‑dimensional whole‑body model to predict human walking on level ground

Predictive simulation of human walking has great potential in clinical motion analysis and rehabilitation engineering assessment, but large computational cost and reliance on measurement data to provide initial guess have limited its wide use. We developed a computationally efficient model combining optimization and inverse dynamics to predict three-dimensional whole-body motions and forces during human walking without relying on measurement data. Using the model, we explored two different optimization objectives, mechanical energy expenditure and the time integral of normalized joint torque. Of the two criteria, the sum of the time integrals of the normalized joint torques produced a more realistic walking gait. The reason for this difference is that most of the mechanical energy expenditure is in the sagittal plane (based on measurement data) and this leads to difficulty in prediction in the other two planes. We conclude that mechanical energy may only account for part of the complex performance criteria driving human walking in three dimensions

Lubricated Pipelining: Stability of Core-Annular Flow. Part 2

In this paper, we study the linearized stability of three symmetric arrangements of two liquids in core-annular Poiseuille flow in round pipes. Deferring to one important application, we say oil and water when we mean more viscous and less viscous liquids. The three arrangements are (i) oil is in the core and water on the wall, (ii) water is in the core and oil is outside and (iii) three layers, oil inside and outside with water in between. The arrangement in (iii) is our model for lubricated pipelining when the pipe walls are hydrophobic and i t has not been studied before. The arrangement in (ii) was studied by Hickox (1971) who treated the problem as a perturbation of long waves, effectively suppressing surface tension and other essential effects which are necessary to explain the flows observed, say, in recent experiments of W. L. Olbricht and R. W. Aul. The arrangement in (i) was studied in Part 1 of this paper (Preziosi, Chen & Joseph 1987). We have confirmed and extended their pseudo-spectral calculation by introducing a more efficient finite-element code. We have calculated neutral curves, growth rates, maximum growth rate, wavenumbers for maximum growth and the various terms which enter into the analysis of the equation for the evolution of the energy of a small disturbance. The energy analysis allows us to identify the three competing mechanisms underway : interfacial tension, interfacial friction and Reynolds stress. Many results are presented