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INFLUENCE OF ION-BOMBARDMENT ON A-SI-H FILMS FABRICATED BY PLASMA chemical-VAPOR-DEPOSITION

ELECTRONICS AND COMMUNICATIONS IN JAPAN PART II-ELECTRONICS 1995年第2期78卷 70-78页

作者： KATO, I YONEDA, T MATSUSHITA, T Member School of Science and Engineering Waseda University Tokyo Japan 169 Nonmembers Torn Matsushita:received his B.E. degree in 1993 from the Department of Electronic and Communications Waseda University where at present he is in the graduate program engaged in research on microwave plasma chemical vapor deposition. He is a member of the Applied Physics Society.

Plasma parameters of Ar/SiH4 plasma were measured as a function of de bias in a double-tubed coaxial line-type microwave plasma chemical vapor deposition (CVD) apparatus. The results indicate that it is possible to control the ion bombardment energy without affecting either the gas phase reaction or ion flux density incident to the substrate. Hydrogenated amorphous silicon films were deposited as a function of the ion bombardment energy and characteristics of the deposited films were investigated. The results indicate that the ion bombardment improves film density, bonding characteristics of hydrogen, and optical band gap but increases the concentration of dangling bonds due to Ar ion implantation. The ion bombardment not only causes the heating of the films but also induces sputtering and ion implantation.

关键词： PLASMA CVD A-SI, H DC BIAS VOLTAGE SHEATH VOLTAGE ION BOMBARDMENT

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Near-equilibrium multiple-wave plasma states

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Physical Review E 1994年第2期50卷 1465-1465页

作者： Mark Buchanan J. Dorning Engineering Physics Program and Department of Applied Mathematics University of Virginia Charlottesville Virginia 22903-2442

We report results showing that spatially periodic Bernstein-Greene-Kruskal (BGK) waves, which are exact nonlinear traveling wave solutions of the Vlasov-Maxwell equations for collisionless plasmas, satisfy a nonlinear principle of superposition in the small-amplitude limit. For an electric potential consisting of N traveling waves, cphi(x,t)= Ji=1Ncphi(i)(x-νit), where νi is the velocity of the ith wave and each wave amplitude cphi(i) is of order ε which is small, we first derive a set of quantities scrĒ(i)(x,u,t) which are invariants through first order in ε for charged particle motion in this N-wave field. We then use these functions scrĒ(i)(x,u,t) to construct smooth distribution functions for a multispecies plasma which satisfy the Vlasov equation through first order in ε uniformly over the entire x-u phase plane for all time. By integrating these distribution functions to obtain the charge and current densities, we also demonstrate that the Poisson and Ampère equations are satisfied to within errors that are O(ε3/2). Thus the constructed distribution functions and corresponding field describe a self-consistent superimposed N-wave solution that is accurate through first order in ε. The entire analysis explicates the notion of small-amplitude multiple-wave BGK states which, as recent numerical calculations suggest, is crucial in the proper description of the time-asymptotic state of a plasma in which a large-amplitude electrostatic wave undergoes nonlinear Landau damping.

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Statistical quality control of multivariable continuous processes

Statistical quality control of multivariable continuous proc...

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American Control Conference (ACC)

作者： A. Negiz E.S. Lagergren A. Cinar Department of Chemical Engineering Illinois Institute of Technology Chicago IL USA Statistical Engineering Division TechnologyComputing and Applied Mathematics Laboratory National Institute for Standards and Technology Gaithersburg MD USA

Multivariate statistical methods are utilized for developing statistical quality control techniques for multivariable continuous processes. The performance of univariate Shewhart charts, Hotelling's T/sup 2/ combined with univariate Shewhart charts, residuals based SPC techniques, and parameter based SPC techniques are compared. Control of mean droplet size and droplet size distribution in a spray drying process are utilized to illustrate the techniques discussed.

关键词： Quality control Control charts Spraying Monitoring Temperature Slurries Statistical analysis Size control Signal processing chemical engineering

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GROUND-WATER MONITORING STATISTICS UPDATE .1. PROGRESS SINCE 1988

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GROUND WATER MONITORING AND REMEDIATION 1994年第4期14卷 148-158页

作者： DAVIS, CB MCNICHOLS, RJ Charles B. Davis is principal statistician with Environmet- rics & Statistics Ltd. (EnviroStat 1853 Wellington Court Henderson NV 89014). After receiving his M.S. in mathematics and statistics and Ph.D. in statistics from the University of New Mexico he joined the Mathematics Department of the University of Toledo to establish its graduate program in statistics with emphasis on consulting and applications. He and McNichols became involved in consulting and research related to statistical issues arising in RCRA ground water monitoring regulation in 1985 and formed EnviroStat in 1990. Davis left academia in 1992 to concentrate on environmental statistics. Roger J. McNichols is professor and chairman of the Industrial Engineering Department at The University of Toledo (Toledo OH 43606). After receiving his Ph.D. in industrial engineering from The Ohio State University he joined the faculty of Texas A and M University where he directed the Maintainability Engineering Graduate Program at Red River Army Depot. At University of Toledo he is also chairman of the Systems Doctoral Program and has served as associate dean of engineering. His research and consulting interests include reliability quality control manufacturing environmental monitoring mathematical modeling and applied statistics.

Current federal ground water monitoring statistical regulation dates from the revised RCRA Subtitle C Final Rule of 1988. That rule was a considerable advance over previous RCRA statistical rules. However, two major problem areas remained: facility-wide false positive rate (FWFPR) control and spatial variability. Progress has been made in the 1991 Subtitle D Final Rule and in guidance;the 1992 Addendum to Interim Final Guidance in particular includes a substantial conceptual advance toward resolving the FWFPR problem. Other areas of improvement include normality testing and distribution assumptions, dropping the four independent samples per monitoring period requirement, allowing a preliminary evaluation short of a 40 CFR Part 258 Appendix II assessment upon finding a statistically significant increase, and suggesting superior alternatives to analyses of variance (ANOVAs) and tests of proportions. The problem of dealing with natural spatial variability remains. Although certain techniques listed in the regulations can control for inherent spatial variability and the performance standards require doing so ''when necessary,'' little attention has been paid to the ubiquity of such spatial variation. Moreover, regulatory traditions favoring upgradient-downgradient comparisons often make control of natural spatial variation difficult and ineffective. With new, lined facilities easily implemented statistical solutions are available;however, dealing with the several existing solid waste facilities which will now be regulated under Subtitle D will present major challenges. In short, the 1988 revision of the Subtitle C rules made it more possible to provide statistically sound monitoring programs, and there has been steady progress since then. Challenges remain, however. These vary from state to state, particularly with regard to controlling false positives and false negatives in the presence of natural spatial variability.

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MODAL TEST OF JONES,JOHN,PAUL (DDG-53) MAST AND MAST-MOUNTED ANTENNAS

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NAVAL ENGINEERS JOURNAL 1994年第2期106卷 110-117页

作者： MCLEAN, M HILL, J COBB, R RANDALL, F Mark McLean:has been with the Naval Sea Systems Command for eight years and is currently with Code 03K. He is responsible for survivability assessment of combat systems equipment. He has participated in all U.S. Navy ship shock tests conducted since 1985 and is responsible for failure assessment and redesign efforts for numerous combat systems equipment. He was selected by the NavSea Program Offices to be a member of the damage assessment teams providing early inspection in the Samuel B. Roberts (FFG-58) and Princeton (CG-59) incidents. Mr. McLean graduated from the University of Virginia in 1983 with an MS degree in chemical engineering. Jerry Hill:has been with NKF Engineering Inc. for twelve years. Currently managing the structural dynamics department Mr. Hill is responsible for numerous survivability related analysis and design efforts. This includes dynamic mathematical simulation and prediction field testing and qualification and full-scale ship shock testing. Mr. Hill graduated from the University of Maryland with a BS degree in mechanical engineering. He is a registered Professional Engineer. Dr. Richard Cobb:has been with NKF Engineering Inc. as a senior engineer since 1990. He is involved with research and development projects including dynamics modal testing vibration design instrumentation and underwater explosion. Prior to joining NKF he was an instructor of mechanical engineering at Virginia Tech. Dr. Cobb holds a Ph.D. in mechanical engineering from Virginia Tech with dissertation research in the areas of experimental modal analysis and frequency response function estimation using Fast Fourier transform methods. Fred Randall:has been manager of the noise shock and vibration department at Bath Iron Works since 1987. As such he is responsible for all dynamic measurements conducted by the shipyard. From 1982 to 1987 he was with TRW in the survivability department conducting investigations of shock propagation structural media interaction and soils modeling and analysis. Mr. Randall gr

A modal test of the John Paul Jones (DDG-53) mainmast structure and mast-mounted antennas was conducted. The test was part of a larger effort to accurately determine dynamic characteristics of the ''as-built'' mast/antenna system and survivability in the vibration and underwater explosion (UNDEX) shock environment. Previous mathematical analysis of the DDG-51 class mast and antennas predicted response acceleration levels during a shock trials scenario to be excessive in some areas. The modal test results now provide, however, confirmed dynamic response characteristics including mode shapes, frequencies, and damping for the structure. The test data accounts for the flexibility of ship's structure including the deckhouse supporting the mast. In addition, the natural frequencies of the antennas were determined for the response range of the mast structure with the flexibility of the supporting foundations taken into account. Using the test results, a finite element model of the mast structure and antennas was built accurately representing the dynamic characteristics of the system. Dynamic transient shock analysis was conducted to provide response predictions of the mast and antennas using the validated model. Any potential response amplification conditions that might result in failure during shock trials were identified.

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NONOSCILLATORY SPECTRAL ELEMENT CHEBYSHEV METHOD FOR SHOCK-WAVE CALCULATIONS

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JOURNAL OF COMPUTATIONAL PHYSICS 1993年第1期107卷 10-22页

作者： SIDILKOVER, D KARNIADAKIS, GE Department of Mechanical and Aerospace Engineering Program in Applied and Computational Mathematics Princeton University Princeton New Jersey 08544

A new algorithm based on spectral element discretization and non-oscillatory ideas is developed for the solution of hyperbolic partial differential equations. A conservative formulation is proposed based on cell averaging and reconstruction procedures, that employs a staggered grid of Gauss-Chebyshev and Gauss-Lobatto Chebyshev discretizations. The non-oscillatory reconstruction procedure is based on ideas similar to those proposed by Cai et al. (Math. Comput. 52, 389 (1989)) but employs a modified technique which is more robust and simpler in terms of determining the location and strength of a discontinuity. It is demonstrated through model problems of linear advection, inviscid Burgers equation, and one-dimensional Euler system that the proposed algorithm leads to stable, non-oscillatory accurate results. Exponential accuracy away from the discontinuity is realized for the inviscid Burgers equation example.

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A molecular dynamical study of granular fluids I: The unforced granular gas in two dimensions

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Journal of Scientific Computing 1993年第1期8卷 1-40页

作者： Goldhirsch, I. Tan, M.-L. Zanetti, G. Department of Fluid Mechanics and Heat Transfer Faculty of Engineering Tel-Aviv University Ramat Aviv 69978 Tel-Aviv Israel Program in Applied and Computational Mathematics Princeton University Princeton 08544 New Jersey United States

Results of a numerical study of the dynamics of a collection of disks colliding inelastically in a periodic two-dimensional enclosure are presented. The properties of this system, which is perhaps the simplest model for rapidly flowing granular materials, are markedly different from those known for atomic or moleclar gases, in which collisions are of elastic nature. The most prominent feature characterizing granular systems, even in the idealized situation in which no external forcing exists and the initial condition is statistically homogeneous, is their inherent instability to inhomogeneous fluctuations. Granular "gases" are thus generically nonuniform, a fact that suggests extreme caution in pursuing direct analogies with molecular gases. We find that once an inhomogeneous state sets in, the velocity distribution functions differ from the classical Maxwell-Boltzmann distribution. Other characteristics of the system are different from their counterparts in molecular systems as well. For a given value of the coefficient of restitution, e, a granular system forms clusters of typical separation L₀≈l/(1-e²)^1/2, where l is the mean free path in the corresponding homogeneous system. Most of the fluctuating kinetic energy then resides in the relatively dilute regions that surround the clusters. Systems whose linear dimensions are less then L⁰ do not give rise to clusters;still they are inhomogeneous, the scale of the corresponding inhomogeneity being the longest wavelength allowed by the system's size. The present article is devoted to a detailed numerical study of the above-mentioned clustering phenomenon in two dimensions and in the absence of external forcing. A theoretical framework explaining this phenomenon is outlined. Some general implications as well as practical ramifications are discussed. © 1993 Plenum Publishing Corporation.

关键词： Granular flow dynamics molecular dynamics numerical simulation

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Modeling of multilayer ion etching processes

Journal of Vacuum Science & Technology B: Microelectronics a...

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Journal of Vacuum Science & Technology B: Microelectronics and Nanometer Structures Processing, Measurement, and Phenomena 1993年第4期11卷 1310-1313页

作者： S. J. Sherwin E. Barouch G. E. Karniadakis S. A. Orszag Department of Mechanical and Aerospace Engineering Princeton University Princeton New Jersey 08540 Program in Applied and Computational Mathematics Princeton University Princeton New Jersey 08540

Numerical simulation is used to model ion etching in trilayer lithography. The simulations are capable of capturing the evolution of the boundary between two materials as well as the physically observed phonemena reactive ion etching lag and undercutting. Numerical results are compared with experimental data and a good agreement is found except close to the material interface where the slope of the surface is large. This error is attributed to a purely energy dependent yield used in the simulations.

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Parallel spectral-element-Fourier simulation of turbulent flow over riblet-mounted surfaces

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Theoretical and Computational Fluid Dynamics 1992年第4期3卷 219-229页

作者： Chu, Douglas Henderson, Ron Karniadakis, George Em Department of Mechanical and Aerospace Engineering and Program in Applied and Computational Mathematics Princeton University Princeton 08544 NJ United States

The flow in a channel with its lower wall mounted with streamwise V-shaped riblets is simulated using a highly efficient spectral-element-Fourier method. The range of Reynolds numbers investigated is 500 to 4000, which corresponds to laminar, transitional, and turbulent flow states. Our results suggest that in the laminar regime there is no drag reduction, while in the transitional and turbulent regimes drag reduction up to 10% exists for the riblet-mounted wall in comparison with the smooth wall of the channel. For the first time, we present detailed turbulent statistics in a complex geometry. These results are in good agreement with available experimental data and provide a quantitative picture of the drag-reduction mechanism of the riblets. © 1992 Springer-Verlag.

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Three-dimensional dynamics and transition to turbulence in the wake of bluff objects

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Journal of Fluid Mechanics 1992年第1期238卷 1-30页

作者： Karniadakis, George Em Triantafyllou, George S. Department of Mechanical and Aerospace Engineering and Program of Applied and Computational Mathematics Princeton University Princeton NJ 08544 United States The Levich Institute and Department of Mechanical Engineering The City College of New York New York NY 10031 United States

The wakes of bluff objects and in particular of circular cylinders are known to undergo a ‘fast ’ transition, from a laminar two-dimensional state a t Reynolds number 200 to a turbulent state a t Reynolds number 400. The process has been documented in several eXperimental mvestigations, but the underlying physical mechanisms have remained largely unknown so far. In this paper, the transition process is investigated numerically, through direct simulation of the NavierStokes equations at representative Reynolds numbers, up to 500. A high-order timeaccurate, miXed spectral/spectral element technique is used. It is shown that the wake first becomes three-dimensional, as a result of a secondary instability of the two-dimensional vorteX street. This secondary instability appears at a Reynolds number close to 200. For slightly supercritical Reynolds numbers, a harmonic state develops, in which the flow oscillates at its fundamental frequency (Strouhal number) around a spanwise modulated time-average flow. In the near wake the modulation wavelength of the time-average flow is half of the spanwise wavelength of the perturbation flow, consistently with linear instability theory. The vorteX filaments have a spanwise wavy shape in the near wake, and form rib-like structures further downstream. At higher Reynolds numbers the three-dimensional flow oscillation undergoes a period-doubling bifurcation, in which the flow alternates between two different states. Phase-space analysis of the flow shows that the basic limit cycle has branched into two connected limit cycles. In physical space the period doubling appears as the shedding of two distinct types of vorteX filaments. Further increases of the Reynolds number result in a cascade of period-doubling bifurcations, which create a chaotic state in the flow at a Reynolds number of about 500. The flow is characterized by broadband power spectra, and the appearance intermittent phenomena. It is concluded that the wake undergoes transit

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