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Proceedings of the 1999 annual AcM SIGAda international conference on Ada

作者： Steven Doran Litton Guidance & Control Systems 550 Canoga Ave Woodland Hills CA

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 c programming language. However, the selection of the programming language 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 programming languages 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.

关键词： c programming language Ada 95 device drivers real-time

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Efficient calculation of a jitter/stability metric

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JOURNAL OF SPAcEcRAFT AND ROcKETS 1997年第4期34卷 549-557页

作者： Giesy, DP LOCKHEED MARTIN CORP HAMPTONVA 23681

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.

关键词： c programming language computer Memory Data Storage Time Domain Analysis Scatter Plot computing Institute of Electrical and Electronics Engineers NASA Langley Research center Numerical Simulation Spacecraft Design

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SimRoot: Modelling and visualization of root systems

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PLANT AND SOIL 1997年第1期188卷 139-151页

作者： Lynch, JP Nielsen, KL Davis, RD Jablokow, AG PENN STATE UNIV DEPT MECH ENGNUNIVERSITY PKPA 16802

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.

关键词： computer modelling c programming language data structure fractal geometry kinematics root system visualization

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Robust control of passive-jointed robot and experimental validation using sliding mode

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JOURNAL OF GUIDANcE cONTROL AND DYNAMIcS 1996年第5期19卷 1039-1046页

作者： Ro, PI Yih, cc North Carolina State University Raleigh North Carolina 27695-7910

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 dynamic coupling 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.

关键词： Sliding Mode control Robots Rigid Manipulators Actuators Energy consumption Variable Structure System Tachometer Space Operations c programming language Numerical Simulation

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FAST FLOATING-POINT PROcESSING IN cOMMON LISP

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AcM TRANSAcTIONS ON MATHEMATIcAL SOFTWARE 1995年第1期21卷 26-62页

作者： FATEMAN, RJ BROUGHAN, KA WILLcOcK, DK RETTIG, D UNIV WAIKATO DEPT MATH & STAT HAMILTON NEW ZEALAND FRANZ INC BERKELEY CA 94704 USA

Lisp, one of the oldest higher-level programming languages, 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.

关键词： c programming language cOMMON LISP cOMPILER OPTIMIZATION FLOATING-POINT ARITHMETIc FORTRAN LISP NUMERIcAL ALGORITHMS SYMBOLIc cOMPUTATION

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MONTE-cARLO SIMULATION FOR BAcKScATTER OF OUTGASSING MOLEcULES FROM SIMPLE SPAcEcRAFT SURFAcES

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JOURNAL OF SPAcEcRAFT AND ROcKETS 1994年第4期31卷 649-654页

作者： FAN, c GEE, c FONG, Mc Lockheed Missile & Space Company Sunnyvale California 94086

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 elastic collision 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.

关键词： Spacecrafts Direct Simulation Monte carlo Flow conditions c programming language Space Systems Division computing Speed Bhatnagar Gross Krook Algorithms and Data Structures cartesian coordinate System Statistical Analysis

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REAcTIVE c - AN EXTENSION OF c TO PROGRAM REAcTIVE SYSTEMS

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SOFTWARE-PRAcTIcE & EXPERIENcE 1991年第4期21卷 401-428页

作者： BOUSSINOT, F Ecole Nationale Sup&eacute rieure des Mines de Paris Centre de Math&eacute matiques Appliqu&eacute es Sophia-Antipolis 06565 Valbonne France

Reactive systems are interactive programs that react continuously to sequences of activations coming from the external world. Reactive programming leads to a new programming style where one programs in terms of reactions to activations and reasons in a logic of instants. This paper describes an extension of the c programming language called Rc (for 'Reactive c') to program reactive systems. The language Rc is described, then some programming examples are given to illustrate the reactive approach. The main Rc notions come directly from the Esterel synchronous programming language. Finally, the Esterel and Rc languages are compared.

关键词： REAcTIVE SYSTEM c programming language PARALLELISM

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Direct Simulation Monte carlo Analysis of Rarefied Flows on Parallel Processors

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JOURNAL OF THERMOPHYSIcS AND HEAT TRANSFER 1991年第3期5卷 292-300页

作者： Wilmoth, Richard G. NASA Langley Res Ctr Div Space Syst Aerothermodynam Branch Hampton VA 23665 USA

A method for executing a direct simulation Monte carlo (DSMc) analysis using parallel processing is described. The method is based on using domain decomposition to distribute the work load among multiple processors, and the DSMc analysis is performed completely in parallel. Message passing is used to transfer molecules between processors and to provide the synchronization necessary for the correct physical simulation. Benchmark problems are described for testing the method, and results are presented that demonstrate the performance on two commercially available multicomputers. The results show that reasonable parallel speedup and efficiency can be obtained if the problem is sized properly to the number of processors. It is projected that, with a massively parallel system, performance exceeding that of current supercomputers is possible.

关键词： Direct Simulation Monte carlo Transitional Flow Supercomputers c programming language Vortex Flow Wall Temperature Operating Systems Parallel computers Parallel Algorithm Blunt Bodies

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THE AUTOMATED SOLUTION OF 2ND QUANTIZATION EQUATIONS WITH APPLIcATIONS TO THE cOUPLED cLUSTER APPROAcH

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THEORETIcA cHIMIcA AcTA 1991年第1期79卷 1-42页

作者： JANSSEN, cL ScHAEFER, HF Center for Computational Quantum Chemistry University of Georgia Athens USA

Theoretical methods in chemistry frequently involve the tedious solution of complex algebraic equations. Then the solutions, sometimes still quite complex, are usually hand-coded by a programmer into an efficient computer language. During this procedure it is all too easy to make an error which will go undetected. A better approach would be to introduce the computer at an even earlier stage in the development of the theory by programming it to first solve the set of equations and then compile the solution into an efficient computer language. In this research a program has been written in the c programming language which can efficiently compute the quasivacuum expectation value of a product of creation and annihilation operators and scalar arrays. The terms in the resulting expressions are then transformed into a canonical form so that all equivalent terms can be combined. Finally, the equations are compiled into a simple representation which can be rapidly interpreted by a Fortran program. This symbol manipulator has been applied to open-shell coupled cluster theory. Two coupled cluster methods using high-spin open-shell references are presented. In one of these methods, the cluster operator contains the unitary group generators, and products thereof, which generate all single and double excitations with respect to the reference. The other uses a simplified cluster operator which generates equations that must be spin-projected. These methods are compared to other descriptions of electron correlation for the cH2 singlet-triplet splitting and the NH2 potential energy surface.

关键词： 2ND QUANTIZATION EQUATIONS cOUPLED cLUSTER APPROAcH ELEcTRONIc STRUcTURE ScHRODINGER EQUATION c programming language

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USING THE c-language TO APPROXIMATE NONLINEAR STOcHASTIc-SYSTEMS

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ADVANcES IN ENGINEERING SOFTWARE AND WORKSTATIONS 1990年第2期12卷 59-68页

作者： SERRANO, SE Department of Civil Engineering University of Kentucky Lexington Kentucky 40506-0046 USA

Recognizing the growing popularity and demand for scientific or numerical libraries in the c computer language, and the shortage of systematic methods for the increasingly important non-linear stochastic systems, this article attempts to present a method to approximate the solution of systems governed by non-linear stochastic differential equations and the corresponding algorithm and computer code in the c language. It was found that the c language offers promising possibilities for the stochastic systems modeler. It is hoped the use of c for the analysis of these type of problems will be encouraged.

关键词： stochastic differential equations non-linear systems Green's function approximation c programming language

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