| The Dislocation Structure and Deformation Mechanism of TiB2/NiAl Composites. |
1991 |
|
| Authors:
L. Wang; R. J. Arsenault; MARYLAND UNIV COLLEGE PARK
|
 | Dislocation structures in 0, 10, and 20 vol% tib2/nial composites have been thoroughly investigated with a 1 mev hvem after compression testing at 760 - 1000 c. samples with 0 and 10 vol% tib2/nial additions have almost identical dislocation structures which can be described as a screw dislocation with extensive jogs and superjogs. prismatically punched dislocations were observed in all of the deformed composites and deformed samples of 20 vol% ... |
|
| Temperature Dependence of the Mechanical Properties of GaAs Wafers. |
1991 |
|
| Authors:
Jun M. Hu; Michael Pecht; MARYLAND UNIV COLLEGE PARK
|
| #L027220 Today increasing numbers of structural components are either being designed with polymeric composites or their metallic counterparts are being replaced by composites. The hygroscopic nature of polymeric systems, however, necessitates a complete understanding of the interaction between structural integrity and a moist environment. Research reports published in the past 20 years have already established the fact that there is a certain amount of degradation of mechanical properties, especially shear, ... |
|
| Experimental Evaluation of Mechanical Behavior of GaAs Wafer Material. |
1991 |
|
| Authors:
Jun M. Hu; Michael Pecht; Donald Barker; MARYLAND UNIV COLLEGE PARK
|
| The mechanical behavior of non-metalized GaAs wafer material at different temperatures were evaluated. The material properties of GaAs, including the modulus of elasticity, the modulus of rupture, the critical value of stress intensity factor, and the coefficient of thermal expansion, were experimentally determined over various temperature ranges. |
|
| Parametric and Non-Parametric Schemes for Discrete Time Signal Discrimination |
13 NOV 90 |
125 pages |
| Authors:
Joseph A. Haimerl; MARYLAND UNIV COLLEGE PARK
|
 | In this thesis parametric and non-parametric schemes for discrete time signal discrimination are considered. Discrete time signal discrimination is the problem of classifying a random discrete time signal into one of two classes. The term discrimination arises from the more specific problem where the two classes are a target of interest and a decoy target. The thesis considers both parametric and non-parametric schemes for discriminating between the two classes. Chapter ... |
|
| Applications of Operator Theory to Maximum Entropy Problems |
12 OCT 90 |
6 pages |
| Authors:
Robert L. Ellis; Israel Gohberg; David C. Lay; MARYLAND UNIV COLLEGE PARK
|
| This project was concerned with problems in operator theory and matrix theory that underlie the maximum entropy principle in signal processing and systems theory. Two papers have been completed that generalize this principle to a wide class of indefinite hermitian matrices. Three new papers give a thorough study of rank-preserving extensions of band matrices. Factorization theorems are obtained for wide classes of Toeplitz and Hankel matrices, and connections are given ... |
|
| Non Parametric Classification Using Learning Vector Quantization |
21 AUG 90 |
98 pages |
| Authors:
Anthony LaVigna; MARYLAND UNIV COLLEGE PARK
|
| We study several properties of Learning Vector Quantization (LVQ). LVQ is a nonparametric detection scheme proposed in the neural network community by Kohonen. We examine it in detail, both theoretical and experimentally, to determine its properties as a nonparametric classifier. In particular, we study the convergence of the parameter adjustment rule in LVQ, we present a modification to LVQ which results in improving he convergence of the algorithm, we show ... |
|
| Signal Processing and Recognition in Adaptive Neural Networks |
09 AUG 90 |
6 pages |
| Authors:
Shihab Shamma; P. S. Krishnaprasad; MARYLAND UNIV COLLEGE PARK
|
| This research can be subdivided into four areas: (1) Models and neurophysiology of the auditory cortex. This includes mappings of physiological responses to sound, psychoacoustical studies, and mathematical models of the data. (2) Implementations of the cochlear and other auditory models both in DSP and VLSI forms. (3) Unsupervised learning algorithms applied to problems in sound segmentation, timbre characterization, and pitch extraction. (4) Applications of wavelet transforms to the analysis ... |
|
| Modeling Failure and Reliability in New-Generation Devices |
15 JUL 90 |
25 pages |
| Authors:
Jeffrey Frey; MARYLAND UNIV COLLEGE PARK
|
| A two-dimensional device simulation program (UMDFET) designed to produce information on the reliability of both silicon and compound- semiconductor electron devices was constructed. The program uses either the drift-diffusion description of carrier transport, for relatively large devices, or the newer energy transport method of solving the Boltzmann Transport Equation, for submicron-scale devices. Multi-layered heterostructure MESFETs, as well as silicon MOSFETs, may be simulated. UMDFET has been used to examine performance ... |
|
| Ionospheric Predictions--2, |
03 MAY 1990 |
|
| Authors:
N. C. Gerson; MARYLAND UNIV COLLEGE PARK
|
| The objective of this paper is to stimulate discussion on the topic of ionospheric predictions the better to determine whether additional effort is warranted, and if so, what and where. |
|
| Electron-Phonon Interaction and transport in Artificially Made Semiconductor Microstructures |
MAR 90 |
17 pages |
| Authors:
Sankar Das Sarma; MARYLAND UNIV COLLEGE PARK
|
| Our research accomplishments under this contract cover a wide area of transport and electron phonon interaction processes in artificially made semiconductor microstructures including a complete theory for picosecond relaxation phenomena and hot electron energy loss in semiconductor quantum wells and heterostructures, a theory for inelastic scattering in ballistic hot electron transistors, a theory for elementary excitations in low dimensional semiconductor microstructures, a theory for the quasiparticle properties of semiconductor microstructures ... |
|
| A Study of the Influence of Manufacturing Techniques on the Mechanical Properties of Dacron Fibers Employed in Vascular Grafts. |
1990 |
|
| Authors:
M. Feldstein; B. Pourdeyhimi; MARYLAND UNIV COLLEGE PARK
|
| This paper concerned mmc in some important way and contained information about, utilized, or discussed these subjects: basic topics:, composite materials, data, mmc data, reinforcement data, materials and material types:, dacron fibers, dacron yarns, epoxy matrix material characteristics and data fields:, breaking strains, creep behaviors, elongation data, linear density, load elongation curves, load-elongation curves (see also load elongation curves), shrinkage, tenacity, tensile strength, yarn geometry, young's modulus parameter values relevant ... |
|
| Development of Efficient Computer Program for Dynamic Simulation of Telerobotic Manipulation. |
15 DEC 1989 |
|
| Authors:
S. K. Ider; F. M. L. Amirouche; MARYLAND UNIV COLLEGE PARK
|
| Research in robot control has generated interest in computationally efficient forms of dynamic equations for multi-body systems. For a simply connected open-loop linkage, dynamic equations arranged in recursive form were found to be particularly efficient. A general computer program capable of simulating an open-loop manipulator with arbitrary number of links has been developed based on an efficient recursive form of Kane's dynamic equations. Also included in the program is some ... |
|
| International Conference on Operator Theory: Advances and Applications |
AUG 89 |
13 pages |
| Authors:
Seymour Goldberg; MARYLAND UNIV COLLEGE PARK
|
| The conference attracted 93 participants from 17 different countries and included 13 graduate students. The very latest developments in operator and matrix theory, and their uses in modern control and systems engineering were presented and discussed by many of the world's leading investigators. There were 13 plenary speakers, 36 invited papers, and 16 contributed papers. Keywords: Systems engineering; Operator theory; Matrix theory; Conference. (JES) |
|
| Connectionist Models for Intelligent Computation |
26 JUL 89 |
4 pages |
| Authors:
H. H. Chen; Y. C. Lee; MARYLAND UNIV COLLEGE PARK
|
| 1) Research Objectives: -- To study the underlying principles, architectures and applications of artificial neural networks for intelligent computations. 2) Approach: -- We use both numerical simulation and theoretical analysis to investigate various alternatives in connection schemes, organization principles and architectures of artificial neural networks. 3) Progress for period 9/1/88-8/31/89: -- In the past year, our research on neural network models for intelligent computing under the sponsorship of AFOSR continues ... |
|
| Meeting the Needs of Polonia: A Comparison of the Polish-American Press Before and After 1980-1981 |
89 |
144 pages |
| Authors:
Donald T. Zajackowski; MARYLAND UNIV COLLEGE PARK
|
| The paper explores the role of the Polish American press before and after 1981. It surveys the history and demographics of Polish immigration to the United States and analyzes the rise, decline and resurgence of the Polish American press during different periods of immigration and assimilation. The paper compares and contrasts the characteristics of the resurgent press influence of the press which followed a wave of Polish immigration after the ... |
|
| A Comparison of Censorship, Control, and Freedom of the Press in Israel and Egypt: An Update from the Journalists' Perspective |
89 |
106 pages |
| Authors:
Donald T. Zajackowski; MARYLAND UNIV COLLEGE PARK
|
| The paper explores government censorship and control of the press in both Egypt and Israel. It gives an historical overview of how and why government controls evolved in each nation, and provides analysis regarding the state of freedom of the press from the point of view of journalists currently working in each locality. The author analyzes the conditions under which constraints have been imposed and provides observations regarding what conditions ... |
|
| Theoretical Investigations of Chaotic Dynamics |
30 NOV 88 |
6 pages |
| Authors:
James Yorke; MARYLAND UNIV COLLEGE PARK
|
| Ten papers have been published: Pseudo-orbit shadowing in the family of tent maps; Is every approximate trajectory of some process near an exact trajectory of a nearby process? Noise reduction in dynamical systems; Using dynamic embedding methods to analyze experimental data; Period halving for x sub H+1 = MF (sub N) where F has negative Schwarzian derivative; Numerical orbits of chaotic processes represent true orbits; A procedure for finding numerical ... |
|
| Connectionist Models for Intelligent Computation |
31 AUG 88 |
|
| Authors:
H. H. Chen; Y. C. Lee; MARYLAND UNIV COLLEGE PARK
|
| We have continued our study of higher order neural networks. The superior processing power capacity and speed of the higher order neural network has been demonstrated for many tasks including text to speech, character recognitions, noise removal, time series prediction etc. Currently, we are applying it to the speech recognition problem. We have constructed a neural network to learn the task of stereopsis from random dot stereogram. The connection weights ... |
|
| Applications of Operator Theory to Maximum Entropy Problems |
08 JUL 88 |
8 pages |
| Authors:
David C. Lay; Robert L. Ellis; Israel Gohberg; MARYLAND UNIV COLLEGE PARK
|
| This project is focusing on problems in operator theory and matrix theory that underlie the maximum entropy principle in signal processing and system theory. We have found generalizations of this principle for finite- dimensional problems to certain broad classes of hermitian band matrices, including Toeplitz matrices, and we have shown why a similar principle cannot exist for all hermitian band matrices. Zeros of orthogonal polynomials are studied in a setting ... |
|
| Non-Monotonic Reasoning, Belief Systems, and Parallelism |
JUL 88 |
11 pages |
| Authors:
Jack Minker; Donald Perlis; MARYLAND UNIV COLLEGE PARK
|
| This research can be categorized in terms of the following inter- related concepts: 1) Non-monotonic reasoning and circumscription; 2) Belief systems and deductive databases (in which we take account of models of an intelligent agent's belief set, especially with regard to intelligent answers to queries in deductive databases; 3) Resource-limited non-monotonic belief systems (a special case of the above, in which the non-monotonic nature of beliefs is studied); and 4) ... |
|
| Parallel Logic Programming and ZMOB |
26 APR 88 |
12 pages |
| Authors:
Jack Minker; Mark Weiser; MARYLAND UNIV COLLEGE PARK
|
| This final report presents a summary of research accomplished to investigate parallel problem solving. Under the current grant a parallel problem solving system, PRISM (Parallel Inference System), that was implemented on the VAX/11-780, the PYRAMID and SUN machines, was ported successfully to McMOB and then to the BBN Butterfly parallel architecture. The McMOB architecture is essentially the ZMOB architecture with 16 Motorola 68000 processors, upgrading the Z80A microprocessors, interconnected in ... |
|
| Grief Reporting: A Print Media Content Analysis of the Gander, Newfoundland Air Disaster |
11 MAR 88 |
126 pages |
| Authors:
Barbara A. Goodno; MARYLAND UNIV COLLEGE PARK
|
| When reporting grief, the media are often regarded as an insensitive monolith. This study of grief reporting shows that print media reports of a shocked, angry and saddened society in the aftermath of a disaster correspond with predictable human responses and are not necessarily the sensationalized product of an adversarial press. The study examined 117 news stories reporting the December 12, 1985 crash of a DC-8 jetliner in Gander, Newfoundland, ... |
|
| Final Design and Cold Tests of a Harmonic Ubitron Amplifier |
88 |
11 pages |
| Authors:
H. Bluem; R. H. Jackson; D. E. Pershing; J. H. Booske; V. L. Granatstein; MARYLAND UNIV COLLEGE PARK
|
| A harmonic ubitron amplifier has been designed and is nearing final assembly. The experiment is intended to be a proof-of-principle study of the feasibility of harmonic operation of the ubitron. Harmonics are a key in reducing the high voltage requirements of ubitrons. The configuration of the experiment consists of a 250kV/100A electron gun, an input transition from single mode to overmoded waveguide, a linear wiggler, mode selective output couplers, and ... |
|
| Multiple-Access Capability of Frequency-Hopped Spread-Spectrum Revisited: An Exact Analysis of the Effect of Unequal Power Levels |
1988 |
49 pages |
| Authors:
E. Geranlotis; MARYLAND UNIV COLLEGE PARK
|
| In this paper we present a new method for the evaluation of the probability of error of uncoded frequency-hopped spread-spectrum multiple-access (FH/SSMA) communications. For systems with binary FSK modulation the method provides an accurate approximation and a tight upper bound to the bit error probability; for systems with M-ary FSK modulation it provides tight upper bounds to the symbol error probability. This method relies on the integration of the product ... |
|
| Tactile Sensing and Inverse Problems |
OCT 87 |
|
| Authors:
R. Yang; P. S. Krishnaprasad; MARYLAND UNIV COLLEGE PARK
|
| In recognizing a grasped object or grasp an object stably with a multifingered robotic hand, tactile sensors mounted on robot fingers have been identified as essential detecting tool. In general, grasp stability has two requirements: sliding avoidance and excess force avoidance. Hence, it is required that a tactile sensor be able to detect the nature of the force distribution which exists between the surface of the grasped object and the ... |
|
| The Dynamics of Two Coupled Rigid Bodies |
OCT 87 |
|
| Authors:
R. Grossman; P. S. Krishnaprasad; Jerrold E. Marsden; MARYLAND UNIV COLLEGE PARK
|
| In this paper we derive a Poisson bracket on the phase space so(3) x so(3) x SO(3) such that the dynamics of two three dimensional rigid bodies coupled by a ball and socket joint can be written as a Hamiltonian system. This paper we introduce a Poisson bracket on the phase space. SO(3) is the dual of the Lie algebra of SO(3), so that the dynamics of two rigid bodies ... |
|
| Identifiability of Multivariate ARMA Models |
SEP 87 |
|
| Authors:
Shuyuan He; MARYLAND UNIV COLLEGE PARK
|
| This paper proved that multivariate ARMA models are identifiable. Some properties of Multivariate ARMA models were given. Keywords: Matrix coefficient polynomials; Stationary; Holomorphic; White noise. |
|
| On Observer Problems for Systems Governed by Partial Differential Equations |
30 JUL 87 |
|
| Authors:
J. S. Baras; A. Bensoussan; MARYLAND UNIV COLLEGE PARK
|
| The problem of observers has been introduced in the control literature by Luenberger. Let us consider a dynamic system which is deterministic, but whose initial state is unknown. An observer is a model which mimics the behavior of the physical system, and in particular its state becomes closer and closer as time evolves to the state of physical system. There is a great deal of freedom in such a design ... |
|
| On an Overdetermined Neumann Problem |
30 JUL 87 |
|
| Authors:
Carlos A. Bernstein; MARYLAND UNIV COLLEGE PARK
|
| Several questions in harmonic analysis, partial differential equations and applied mathematics lead to the question of characterizing domains for which overdetermined boundary value problems have solutions. Theorem Let M = R superscript n (resp. H superscript n), the existence of infinitely many eigenvalues for either of the problems (D) or (N) characterizes the balls (resp. geodesic balls) among all the relatively compact domains omega with connected Lipshitz boundary. |
|
| Small Degree Solutions for the Polynomial Bezout Equation |
30 JUL 87 |
|
| Authors:
Carlos A. Berenstein; Daniele C. Struppa; Scuola N. Superiore; MARYLAND UNIV COLLEGE PARK
|
| The purpose of this paper is to briefly report on some new advances due to Brownawell on the problem of explicit (concretely computable) solutions to the Bezout equations, which are based on some recent developments in complex analysis due to Yger and the authors. Keywords: Polynomials; Variables; Integrals. |
|
| A Distributed Reservation-Based CDMA (Code Division Multiple Access) Protocol That Does Not Require Feedback Information |
17 JUN 87 |
|
| Authors:
Jeffrey E. Wieselthier; Anthony Ephremides; Julie A. Tarr; MARYLAND UNIV COLLEGE PARK
|
| In some multi-user radio systems the receiver is not allowed to transmit feedback information to the senders. In other applications the transmitters cannot receive feedback information sent by the receiver. For these cases a multiple access protocol is needed that maintains satisfactory performance in the absence of feedback. In this paper, such a protocol is introduced and an exact analysis and performance evaluation of it are provided. The protocol, which ... |
|
| Alterations in the Pathogenic Properties of Human Pathogens in the Marine Environment |
16 JUN 87 |
|
| Authors:
Rita R. Colwell; D. J. Grimes; C. Somerville; B. A. Ortiz-Conde; Phyllis Brayton; MARYLAND UNIV COLLEGE PARK
|
| Human pathogenic bacteria that enter the marine environment became non-culturable, yet remain viable and capable of initiating disease in animal models. Pathogenic properties are retained by viable but non-culturable bacteria, as are the genetic determinants for those properties. Pathogens of the genus Vibro exhibit strong phylogenetic relationship, based on comparisons of 5s ribosomal RNA sequences. One human pathogen, Vibrio vulnificus, contains chitinolytic enzymes arranged in an operon which has been ... |
|
| Higher Order Crossings |
MAY 87 |
|
| Authors:
B. Kedem; MARYLAND UNIV COLLEGE PARK
|
| A graphical device that is useful as a diagnostic tool for higher order crossings was introduced. The graphical tool is also useful as a descriptive similarity measure for time series models. Higher order crossings analysis has been applied to real data, revealing several known periodicities as well as several previously undiscovered periodicities. The class of strictly oscillatory processes was introduced. |
|
| Nonlinear Filtering and Large Deviations: A PDE-Control Theoretic Approach |
26 FEB 87 |
|
| Authors:
M. R. James; J. S. Baras; MARYLAND UNIV COLLEGE PARK
|
| We consider the asymptotic nonlinear filtering problem dx = f(x) dt + sq. rt. epsilon, dy = h(x) dt + sq. rt. epsilon, and obtain the limit as epsilon approaches 0 of epsilon log (q(xt) to the epsilon power) = - W(x, t) for unnormalised conditional densities (q(x,t)) to the epsilon power, using PDE methods. Here, W(x,t) is the value function for a deterministic optimal control problem arising in Mortensen's ... |
|
| Stability Analysis of a Rigid Body with a Flexible Attachment Using the Energy-Casimir Method |
87 |
|
| Authors:
Thomas A. Posbergh; P. S. Krishnaprasad; Jerrold E. Marsden; MARYLAND UNIV COLLEGE PARK
|
| The authors consider a system consisting of a rigid body to which a linear extensible shear beam is attached. For such a system the Energy-Casimir method can be used to investigate the stability of the equilibria. In this case, it can be shown that a test for (formal) stability reduces to checking the positive definiteness of two matrices which depend on the parameters of the system and the particular equilibrium ... |
|
| Local Bifurcation Control |
87 |
|
| Authors:
Eyad H. Abed; MARYLAND UNIV COLLEGE PARK
|
| Local feedback stabilization of bifurcated solution branches is studied. Two cases are considered: that in which the nominal system undergoes a Hopf bifurcation as a parameter is varied, and the case of a stationary bifurcation from a simple zero eigenvalue. For each case, results on the existence of a stabilizing feedback are given, Moreover, simple synthesis techniques for the stabilizing controllers are discussed. A concept of proximity stabilization is introduced ... |
|
| On the Maneuvering of Vehicles |
87 |
|
| Authors:
James C. Alexander; J. H. Maddocks; MARYLAND UNIV COLLEGE PARK
|
| Equations are derived to govern the motion of vehicles which move on rolling wheels. A relation between the centers of curvature of the trajectories of the wheels and the center of rotation of the vehicle is established. From this relation the general kinematic laws of motion are derived. Applications to questions of offtracking (the difference between the trajectories of the front and back wheels of the vehicle) and optimal steering ... |
|
| Dynamic Observers as Asymptotic Limits of Recursive Filters: Special Cases |
01 DEC 86 |
|
| Authors:
J. S. Baras; A. Bensoussan; M. R. James; MARYLAND UNIV COLLEGE PARK
|
| The authors' objective is to describe a method for constructing an observer for a certain dynamical system as the asymptotic limit of nonlinear filters associated with the noisy version of another document entitled Dynamic Observers as Asymptotic Limits of Recursive Filters. Keywords: Linear systems; Large deviations. |
|
| Microcomputer-Based Data Acquisition, Analysis and Control of Information Processing by Neural Networks |
21 NOV 86 |
|
| Authors:
Herbert Levitan; MARYLAND UNIV COLLEGE PARK
|
| This instrumentation award was used to purchase a masscomp 5700 computing system with multiple, tightly-coupled microprocessors. The system will be used for the acquisition, analysis, control and display of data obtained in real time from several neurons in a simple invertebrate nervous system for the purpose of gaining insight into how nervous systems process information. The system as originally ordered was finally installed on October 27, 1986. (Author) |
|
| Analysis of the Performance of Mixed Finite Element Methods |
OCT 86 |
|
| Authors:
Manil Suri; MARYLAND UNIV COLLEGE PARK
|
| The investigator was able to prove an optimal error estimate for approximating functions in sobolev spaces using a space of pieceurse polynomial functions (based on the p-version of the finite element method). Optimal approximation results were also obtained for the h-p version of the finite element method using quasiuniform meshes. Papers accepted for publication during this period of effort included such titles as The optimal convergence rate of the p-version ... |
|
| Applied Surfac Science. Volume 25. Number 4 |
MAY 86 |
|
| Authors:
L. C. Feldman; Murray Hill; W. F. van der Weg; MARYLAND UNIV COLLEGE PARK
|
| Contents: Quantitative analysis of mixtures by Auger electron spectroscopy; Low work function emitter electrodes for advanced thermionic converters; In situ Auger electron spectroscopy applied to the study of chemisorption and diffusion during reactive implantation of titanium into iron; Stoichiometric changes in the surface of (100) cubic SiC caused by ion bombardment and annealing; A SIMS study of ion beam induced migration of nitrogen in thermally oxidized silicon; Material displacing processes ... |
|
| Software Metrics for Ada |
03 FEB 86 |
|
| Authors:
Victor R. Basili; MARYLAND UNIV COLLEGE PARK
|
| The investigators monitored a software development project written in Ada by integrating measurement into the software development process. Their goal is to identify areas of success and difficulty in learning and using Ada as a design and coding language. The underlying process and the evolving product are measured, and the resulting information characterizes this project's successes and failures. It may be used to make recommendations about training, methodology, and metrics ... |
|
| Control Theory and Distributed Parameter Systems |
86 |
|
| Authors:
Thomas I. Seidman; MARYLAND UNIV COLLEGE PARK
|
| This research was concerned with analytical results related to control of distributed parameter systems. Existence of optimal controls was established for a variety of systems governed by partial differential equations, most of which involved boundary control. Much of the work also dealt nonlinearity. The work on switching systems promises to provide a theoretical baais for dealing under this grant, including A class of stabilizing feedback laws for marginally stable systems ... |
|
| Delay Analysis of Interacting Queues with an Approximate Model |
1986 |
35 pages |
| Authors:
A. Ephremides; Rong-Zhu Zhu; MARYLAND UNIV COLLEGE PARK
|
| An approximate model of coupled Markov chains is proposed and analyzed for a slotted ALOHA system with a finite number of buffered nodes. This model differs from earlier ones in that it attempts to capture the interdependence between the nodes. The analytical results lead to a set of equations that, when solved numerically, yield the average packet delay. Comparison between computational and simulation results for a small number of nodes ... |
|
| Department of Defense Instrumentation Award |
01 JUL 85 |
|
| Authors:
William W. Destler; MARYLAND UNIV COLLEGE PARK
|
| These funds were used to purchase a complete fast digital data acquisition system now completely installed in the Charged Particle Beam Laboratory at the University of Maryland. This instrumentation, consisting of five channels of fast digitization ( two donated by the University) controlled by a DEC 11/73 computer, is now assembled in a shielded room with trench access to all of the experiments underway in the laboratory. The projects of ... |
|
| Parallel Matrix Computations |
11 APR 85 |
|
| Authors:
G. W. Stewart; D. P. O'Leary; MARYLAND UNIV COLLEGE PARK
|
| The purpose of this effort is to develop realistic algorithms for matrix computations on parallel computers. It has been long observed that the usual algorithms of numerical linear algebra contain a great deal of inherent parallelism. For example, if the arithmetic operations that can be performed in parallel in Gaussian elimination are actually so executed, the time to decompose an nXn matrix is reduced from cu n to n only ... |
|
| Alterations in the Pathogenic Properties of Human Pathogens in the Marine Environment |
24 JAN 85 |
|
| Authors:
R. R. Colwell; D. J. Grimes; MARYLAND UNIV COLLEGE PARK
|
| The ability of marine vibrios to degrade chitin plays a significant role in survival and seasonal distribution. In order to study the genetic control of chitinolytic activity, the chitobiase gene was isolated by cloning chromosomal DNA from V. vulnificus. Chimeric plasmids were constructed from SAU3A1 partial digests of V. vulnificus DNA which were sized by sucrose gradient. The 5-15 Kb pieces were ligated into the BamH1 site (in the Tetr ... |
|
| Restricted Quadratic Forms, Inertia Theorems and the Schur Complement |
85 |
|
| Authors:
J. H. Maddocks; MARYLAND UNIV COLLEGE PARK
|
| The starting point of this investigation is the properties of restricted quadratic forms, x (Transposed) Ax, X an element of S a subset of R superscript m where A is an mxm real symmetric matrix, and S is a subspace. The index theory of Hestenes (1951) and Maddocks (1985) that treats the more general Hilbert space version of this problem is first specialized to the finite dimensional context, and appropriate ... |
|
| Interfacial Bond Strength in an Aluminum Alloy 6061-SiC Composite |
85 |
|
| Authors:
Y. Flom; R. J. Arsenault; MARYLAND UNIV COLLEGE PARK
|
| An investigation was undertaken to evaluate the strength of the interfacial bond between SiC and the aluminum alloy 6061 matrix. Approximate bounding analysis provided the conditions for separation of the inclusion from the ductile matrix under local negative pressure (the triaxial tensile stress). The experimental data were analyzed to determine the local interfacial stresses at the particle-matrix interfaces. The lower bound value of the bond strength was determined to be ... |
|
| An In Situ HVEM Study of Dislocation Generation at Al/SiC Interfaces in Metal Matrix Composites |
85 |
|
| Authors:
M. Uogelsang; R. J. Arsenault; R. M. Fisher; MARYLAND UNIV COLLEGE PARK
|
| Annealed aluminum/silicon carbide (Al/SiC) composites exhibit a relatively high density of dislocations, which are frequently decorated with fine precipitates, in the Al matrix. This high dislocation density is the major reason for the unexpected strength of these composite materials. The large difference (10:1) between the coefficients of thermal expansion (CTE) of Al and SiC results in sufficient stress to generate dislocations at the Al/SiC interface during cooling. In this in ... |
|
Reports by Corporate Author
