作者：
camberos, JAWhite, MDUSAF
Res Lab Computat Sci Branch Aeronaut Sci DivAir Vehicles Directorate Wright Patterson AFB OH 45433 USA
Parallel performance of FVTD computational electromagnetics code was analyzed. Average run time for the SGI O2K was calculated by dividing total program execution time by the number of periods specified, then averagin...
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Parallel performance of FVTD computational electromagnetics code was analyzed. Average run time for the SGI O2K was calculated by dividing total program execution time by the number of periods specified, then averaging the numbers obtained. Parallel performance supported the conclusion that the code is portable, scalable and performs well on various massively parallel computer architectures.
Fortran has long been the mother-tongue of the scientificcommunity. This note looks at the cprogramminglanguage from the viewpoint of numerical computing with the emphasis placed on econometric applications. ccan ...
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Fortran has long been the mother-tongue of the scientificcommunity. This note looks at the cprogramminglanguage from the viewpoint of numerical computing with the emphasis placed on econometric applications. ccan be used as a replacement for other lower level programminglanguages, and also a replacement or as a complement to higher level matrix programminglanguages such as GAUSS, MATLAB, Ox, and S-PLUS.
The personal computer hardware marketplace has grown rapidly in recent years. Many software projects, as a cost-cutting measure, are buying "off-the-self" items to meet heir hardware requirements. Almost all...
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ISBN:
(纸本)1581131275
The personal computer hardware marketplace has grown rapidly in recent years. Many software projects, as a cost-cutting measure, are buying "off-the-self" items to meet heir hardware requirements. Almost all of the device drivers for these devices are written in the cprogramminglanguage. However, the selection of the programminglanguage for the project does not need to be confined to c. This paper details the powerful tools in Ada 95, such as pragmas to interface code written in other programminglanguages to Ada 95 applications. An example of a generic realtime Ada 95 application interfacing with a low-level c serial device driver is used to aid the reader in the concepts and idea's discussed in the paper.
A toothbrush/dentifrice abrasion machine was developed to use in dental research laboratory. The mechanism was designed as a hexagonal block driven by two stepping motors which move the mechanism in four directions. I...
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A toothbrush/dentifrice abrasion machine was developed to use in dental research laboratory. The mechanism was designed as a hexagonal block driven by two stepping motors which move the mechanism in four directions. In order to control the stepping motors speed, position and direction commands or signals were generated by a software written in cprogramminglanguage and then these commands were applied the stepping motor drives through parallel port of a personal computer. The toothbrush/dentifrice abrasion machine was finally used to measure different longevity of tooth brush. It was experimentally shown that the mechanism can be used for highly accurate position and speed applications.
The personal computer hardware marketplace has grown rapidly in recent years. Many software projects, as a cost-cutting measure, are buying "off-the-self" items to meet heir hardware requirements. Almost all...
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ISBN:
(纸本)9781581131277
The personal computer hardware marketplace has grown rapidly in recent years. Many software projects, as a cost-cutting measure, are buying "off-the-self" items to meet heir hardware requirements. Almost all of the device drivers for these devices are written in the cprogramminglanguage. However, the selection of the programminglanguage for the project does not need to be confined to c. This paper details the powerful tools in Ada 95, such as pragmas to interface code written in other programminglanguages to Ada 95 applications. An example of a generic real-time Ada 95 application interfacing with a low-level c serial device driver is used to aid the reader in the concepts and idea's discussed in the paper.
SimRoot, a geometric simulation model of plant root systems, is described. This model employs a data structure titled the Extensible Tree, which is well suited to the type of data required to model root systems. As im...
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SimRoot, a geometric simulation model of plant root systems, is described. This model employs a data structure titled the Extensible Tree, which is well suited to the type of data required to model root systems. As implemented on Silicon Graphics workstations, the data structure and visualization code provides for continuous viewing of the simulated root system during growth. SimRoot differs from existing models in the explicit treatment of spatial heterogeneity of physiological processes in the root system, and by inclusion of a kinematic treatment of root axes. Examples are provided of the utility of the model in estimating the fractal geometry of simulated root systems in 1, 2, and 3 dimensional space. We envision continued development of the model to incorporate competition from neighboring root systems, linkage with crop simulation models to simulate root-shoot interactions, explicit treatment of soil heterogeneity, and plasticity of root responses to soil factors such as presence of mycorrhizal associations.
A tool for computing a jitter/stability metric used in NASA requirements statements is developed. An efficient algorithm is given for computing this metric. Two ways of implementing it an a computer are discussed. One...
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A tool for computing a jitter/stability metric used in NASA requirements statements is developed. An efficient algorithm is given for computing this metric. Two ways of implementing it an a computer are discussed. One is optimized for computational speed;the other sacrifices some speed to conserve memory. Timing studies are given to show that the improvement of computation times using the present algorithm over previously existing techniques can run to several orders of magnitude and that previous techniques were so costly that the present algorithm represents enabling technology. Further comparisons show that the memory-conservative implementation runs at about half the speed of the fast implementation but can cut the major data storage requirement of the fast implementation by 95-99%, making the algorithm implementable on much smaller computers, such as personal computers, than it would be otherwise. Software for both implementations is included in version 2.0 of the NASA time- and frequency-domain analysis program PLATSIM.
A robust control strategy for a passive-jointed robot using sliding mode control is investigated. Instead of an actuator, the passive joint has a brake to reduce the weight and energy consumption of the robot. While t...
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A robust control strategy for a passive-jointed robot using sliding mode control is investigated. Instead of an actuator, the passive joint has a brake to reduce the weight and energy consumption of the robot. While the brake is released, the passive joint is indirectly controlled by the motion of the active joint using the dynamiccoupling of the robot manipulators, However, there are uncertainties associated with parameters in the links as well as in the operation of the actuator and the brake, To ensure minimum variation from the desired mode of operation in the presence of these uncertainties, a sliding mode control algorithm is developed and the performance evaluated. From simulation results, the sliding mode scheme is superior to a simple computed torque method in terms of passive-joint tracking performance and robustness. A two-link manipulator was designed and built to evaluate the proposed control scheme experimentally. The robot consists of one active joint and one passive joint and operates in a horizontal plane. The planar manipulator was controlled from a 32-bit 80486 microcomputer via DT2811 input/output board. The experimental results indicate that the sliding mode controller, when compared to the computed torque controller, reduces the tracking error by 50% and improves the robustness to variations in payloads.
Lisp, one of the oldest higher-level programminglanguages, has rarely been used for fast numerical (floating-point) computation We explore the benefits of common Lisp, an emerging new language standard with some exce...
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Lisp, one of the oldest higher-level programminglanguages, has rarely been used for fast numerical (floating-point) computation We explore the benefits of common Lisp, an emerging new language standard with some excellent implementations, for numerical computation. We compare it to Fortran in terms of the speed of efficiency of generated code, as well as the structure and convenience of the language. There are a surprising number of advantages to Lisp, especially in cases where a mixture of symbolic and numeric processing is needed.
A computer program has been developed for the Monte carlo simulation of molecular flux impingement on simple spacecraft surfaces due to self- and ambient scattering of outgassing molecules. The outgassing and ambient ...
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A computer program has been developed for the Monte carlo simulation of molecular flux impingement on simple spacecraft surfaces due to self- and ambient scattering of outgassing molecules. The outgassing and ambient molecules are assumed to be elastic spheres with a Maxwellian velocity distribution. Binary elasticcollision processes have been adopted in a hard-sphere collision model. A test-particle Monte carlo methodology is used to simulate sequentially the motions, collisions, and trajectories of the outgassing molecules inside a control volume by means of uniformly distributed random numbers. A unique Monte carlo computational scheme has been developed that reduces the computer processing time by three to four orders of magnitude for a typical outgassing problem without introducing additional assumptions or compromising the solution accuracy. Monte carlo results are obtained in the form of backscatter flux distribution and return flux ratios, for various sample sizes, control-volume sizes, and outgassing and ambient flow conditions. The cPU time for a typical run is about 2 to 4 min on a VAX-8700 computer, and less than about 2 to 4 s on a cray X-MP system.
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