Physical electronics and surface physics
Physical electronics and surface physics - contact potential measurements of adsorption of oxygen on Ta and steady-state analysis of desorption of molecules from nonuniform surfaces
CONTACT POTENTIAL↗
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Results for “state analysis”
Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.
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Feedback controlled variable conductance heat pipes
Variable conductance heat pipes feedback mechanisms for spacecraft electrical temperature control system design, using steady state analysis based performance model
Bienert, W. B.↗
Reduction of alternator apparent-power requirements and harmonic distortion caused by phase-controlled parasitic loads
Steady state analysis of phase controlled parasitic current, discussing reduction of alternator apparent power requirements and harmonic distortion
Gilbert, L. J.↗
Pressure drop and pumping power for fluid flow through round tubes
Program, written for Hewlett-Packard 9100A electronic desk computer provides convenient and immediate solution to problem of calculating pressure drop and fluid pumping power for flow through round tubes. Program was designed specifically for steady-state analysis and assumes laminar flow.
Jelinek, D.↗
Study of ground proximity effects on powered-lift STOL landing performance
Data from wind-tunnel measurements are presented to show the magnitude of adverse ground effects on the longitudinal aerodynamic coefficients of a powered-lift STOL airplane. A steady-state analysis shows the changes in thrust and angle of attack required during the landing approach and flare as the airplane flies close to the ground. The piloting problems that these ground effects may create were investigated with an in-flight simulator to find the consequences of lift loss during the landing-flare maneuver for a STOL transport. Flight tests were made using the variable stability Navion setup with STOL transport aerodynamics and control responses and were flown at design approach speeds and descent conditions.
Hassell, J. L., Jr.↗
The effect of support flexibility and damping on the dynamic response of a single mass flexible rotor in elastic bearings
The dynamic unabalance response and transient motion of the single mass Jeffcott rotor in elastic bearings mounted on damped, flexible supports are discussed. A steady state analysis of the shaft and the bearing housing motion was made by assuming synchronous precession of the system. The conditions under which the support system would act as a dynamic vibration absorber at the rotor critical speed were studied. Plots of the rotor and support amplitudes, phase angles, and forces transmitted were evaluated by the computer and the performance curves were plotted by an automatic plotter unit. Curves are presented on the optimization of the support housing characteristics of attenuate the rotor synchronous unbalance response.
Kirk, R. G.↗
Steady flow of a non-Newtonian fluid through a contraction
A steady-state analysis is conducted to examine the basic flow structure of a non-Newtonian fluid in a domain including an inflow region, a contraction region, and an outflow region. A Cartesian grid system is used throughout the entire flow domain, including the contraction region, thus creating an irregular grid cell structure adjacent to the curved boundary. At node points adjacent to the curved boundary symmetry conditions are derived for the different flow variables in order to solve the governing difference equations. Attention is given to the motion and non-Newtonian constitutive equations, the boundary conditions, the numerical modeling of the non-Newtonian equations, the stream function contour lines for the non-Newtonian fluid, the vorticity contour lines for the non-Newtonian fluid, the velocity profile across the contraction, and the shear stress contour lines for the non-Newtonian fluid.
Gatski, T. B.↗
On the modulation of the Jovian decametric radiation by Io. I - Acceleration of charged particles
A steady-state analysis of the current circuit between Io and the Jovian ionosphere is performed, assuming that the current is carried by electrons accelerated through potential double layers in the Io flux tube. The circuit analysis indicates that electrons may be accelerated up to energies of several hundred keV. Several problems associated with the formation of double layers are also discussed. The parallel potential drops decouple the flux tube from the satellite's orbital motion.
Smith, R. A.↗
Low-altitude wind measurements from wide-body jet transports
For a 2-week period in the spring of 1977, data were collected onboard wide-body jet transports for the determination of winds and wind shear during landings and take-offs. The data represent about 640 take-offs or landings at 14 airports in Europe and the United States. Analysis of the wind-shear data indicates that shears of a given value are equally likely to occur at any altitude in the lower 1400-ft section of the atmosphere. Analysis of the data indicates that low shears (plus or minus .033 knot/per ft) have a 67-percent chance of occurrence during a landing or take-off, while higher values (plus or minus 0.15 knot/per ft) have a 0.5-percent chance of occurrence. A determination of the duration of a given shear was not made.
Dunham, R. E., Jr.↗
On board processing for future satellite communications systems: Comparison of FDM, TDM and hybrid accessing schemes
Several satellite uplink and downlink accessing schemes for customer premises service are compared. Four conceptual system designs are presented: satellite-routed frequency division multiple access (FDMA), satellite-switched time division multiple access (TDMA), processor-routed TDMA, and frequency-routed TDMA, operating in the 30/20 GHz band. The designs are compared on the basis of estimated satellite weight, system capacity, power consumption, and cost. The systems are analyzed for fixed multibeam coverage of the continental United States. Analysis shows that the system capacity is limited by the available satellite resources and by the terminal size and cost.
Berk, G.↗
The Michigan data needs questionnaire
The data needs questionnaire is an element in the project design study for the Michigan Resource Inventory Act and is aimed at gathering information on what inventory information is required by land use planners throughout the state. Analysis of questionnaire responses is discussed. Some information on current use categories was tabulated. The respondents selected a broad range of categories at all levels of detail. Those most frequently indicated were urban categories.
Hill-Rowley, R.↗
Reanalysis and design in structural dynamics
A unified efficient formulation for the static and dynamic reanalysis of locally modified structures is presented. The reanalysis problem is to find the structural responses when some of the element properties are adjusted as a result of design modifications or when additional structures are appended to the original system. The reanalysis problem is formulated as a problem of much lower order than the original system. This is achieved by utilizing the linearity property of the structure using the pseudoload concept together with the solution of the original system. The modifications to the structure are treated as displacement-dependent pseudoloads of the system. By expressing the modified system response as linear combinations of the response of the original system and a term depending on the pseudoload, a reduced set of response equations can be obtained. In the static and sinusoidal steady state analysis, this leads to a set of linear algebraic equations. For a free vibration analysis, this results in a reduced eigenvalue problem. Using these reduced equations, a design problem can be solved; that is, the magnitude of a specified local modification for given dynamic response characteristics can be calculated. Several examples are presented to illustrate the general formulations.
Wang, B. P.↗
Solar variability and quasi-stationary planetary wave behavior
A steady state analysis of winter winds shows that the speed of the upper atmospheric polar vortex approaches and occasionally exceeds the value required to reflect externally forced planetary wave 1 energy back towards the surface of the earth. Historical observations suggest that solar UV variability and geomagnetic disturbances are two primary forces which modulate the planetary wave trapping mechanism. Through the solar-terrestrial process described, small changes in the sun's behavior can be physically linked to both shortand long-term changes in tropospheric weather patterns.
Springer, B. D.↗
Numerical modeling of multidimensional flow in seals and bearings used in rotating machinery
The rotordynamic behavior of turbomachinery is critically dependent on fluid dynamic rotor forces developed by various types of seals and bearings. The occurrence of self-excited vibrations often depends on the rotor speed and load. Misalignment and rotor wobbling motion associated with differential clearance were often attributed to stability problems. In general, the rotative character of the flowfield is a complex three dimensional system with secondary flow patterns that significantly alter the average fluid circumferential velocity. A multidimensional, nonorthogonal, body-fitted-grid fluid flow model is presented that describes the fluid dynamic forces and the secondary flow pattern development in seals and bearings. Several numerical experiments were carried out to demonstrate the characteristics of this complex flowfield. Analyses were performed by solving a conservation form of the three dimensional Navier-Stokes equations transformed to those for a rotating observer and using the general-purpose computer code PHOENICS with the assumptions that the rotor orbit is circular and that static eccentricity is zero. These assumptions have enabled a precise steady-state analysis to be used. Fluid injection from ports near the seal or bearing center increased fluid-film direct dynamic stiffness and, in some cases, significantly increased quadrature dynamic stiffness. Injection angle and velocity could be used for active rotordynamic control; for example, injection, when compared with no injection, increased direct dynamic stiffness, which is an important factor for hydrostatic bearings.
Hendricks, R. C.↗
Quantification of the memory imprint effect for a charged particle environment
The effects of total accumulated dose on the single-event vulnerability of NMOS resistive-load SRAMs are investigated. The bias-dependent shifts in device parameters can imprint the memory state present during exposure or erase the imprinted state. Analysis of these effects is presented along with an analytic model developed for the quantification of these effects. The results indicate that the imprint effect is dominated by the difference in the threshold voltage of the n-channel devices.
Bhuva, B. L.↗
Small Engine Technology. Task 4: Advanced Small Turboshaft Compressor (ASTC) Performance and Range Investigation
This contact had two main objectives involving both numerical and experimental investigations of a small highly loaded two-stage axial compressor designated Advanced Small Turboshaft Compressor (ASTC) winch had a design pressure ratio goal of 5:1 at a flowrate of 10.53 lbm/s. The first objective was to conduct 3-D Navier Stokes multistage analyses of the ASTC using several different flow modelling schemes. The second main objective was to complete a numerical/experimental investigation into stall range enhancement of the ASTC. This compressor was designed wider a cooperative Space Act Agreement and all testing was completed at NASA Lewis Research Center. For the multistage analyses, four different flow model schemes were used, namely: (1) steady-state ADPAC analysis, (2) unsteady ADPAC analysis, (3) steady-state APNASA analysis, and (4) steady state OCOM3D analysis. The results of all the predictions were compared to the experimental data. The steady-state ADPAC and APNASA codes predicted similar overall performance and produced good agreement with data, however the blade row performance and flowfield details were quite different. In general, it can be concluded that the APNASA average-passage code does a better job of predicting the performance and flowfield details of the highly loaded ASTC compressor.
Hansen, Jeff L.↗
Stochastic Effects in Computational Biology of Space Radiation Cancer Risk
Estimating risk from space radiation poses important questions on the radiobiology of protons and heavy ions. We are considering systems biology models to study radiation induced repair foci (RIRF) at low doses, in which less than one-track on average transverses the cell, and the subsequent DNA damage processing and signal transduction events. Computational approaches for describing protein regulatory networks coupled to DNA and oxidative damage sites include systems of differential equations, stochastic equations, and Monte-Carlo simulations. We review recent developments in the mathematical description of protein regulatory networks and possible approaches to radiation effects simulation. These include robustness, which states that regulatory networks maintain their functions against external and internal perturbations due to compensating properties of redundancy and molecular feedback controls, and modularity, which leads to general theorems for considering molecules that interact through a regulatory mechanism without exchange of matter leading to a block diagonal reduction of the connecting pathways. Identifying rate-limiting steps, robustness, and modularity in pathways perturbed by radiation damage are shown to be valid techniques for reducing large molecular systems to realistic computer simulations. Other techniques studied are the use of steady-state analysis, and the introduction of composite molecules or rate-constants to represent small collections of reactants. Applications of these techniques to describe spatial and temporal distributions of RIRF and cell populations following low dose irradiation are described.
Cucinotta, Francis A.↗
FAILSAFE Health Management for Embedded Systems
The FAILSAFE project is developing concepts and prototype implementations for software health management in mission- critical, real-time embedded systems. The project unites features of the industry-standard ARINC 653 Avionics Application Software Standard Interface and JPL s Mission Data System (MDS) technology (see figure). The ARINC 653 standard establishes requirements for the services provided by partitioned, real-time operating systems. The MDS technology provides a state analysis method, canonical architecture, and software framework that facilitates the design and implementation of software-intensive complex systems. The MDS technology has been used to provide the health management function for an ARINC 653 application implementation. In particular, the focus is on showing how this combination enables reasoning about, and recovering from, application software problems.
Horvath, Gregory A.↗