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THE INFLUENCE OF MIXING-RATIO ON THE WORKING TIME, STRENGTH AND WEAR OF COMPOSITES

AUSTRALIAN DENTAL JOURNAL 1989年第5期34卷 466-469页

作者： DEGEE, AJ TENHARKEL, HC DAVIDSON, CL Research Associate Department of Dental Materials Science ACTA University of Amsterdam Engineering Technician Department of Dental Materials Science ACTA University of Amsterdam Professor and Chairman Department of Dental Materials Science ACTA University of Amsterdam

The influence of varying the paste-to-paste ratio of chemically initiated composites on the working time, diametral tensile strength and in vitro ‘occlusal’ wear was investigated. If the mixing ratio was varied, the working time was not equally affected for the various brands. This is explained by different relative inhibitor concentrations in the pastes. Within reasonable deviations from the 1:1 ratio, no significant influence on the diametral tensile strength occurred. Wear properties as determined by a simulated occlusal wear test on three posterior composites, was more sensitive to the mixing ratio.

关键词： Composites mixing ratios wearing properties

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The Effect of Processing on Autohesive Strength Development in Thermoplastic Resins and Composites

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1987 Symposium on Advances in Thermoplastic Matrix Composite Materials

作者： Howes, Jeremy C. Loos, Alfred C. Hinkley, Jeffrey A. JGraduate research assistant and associate professor respectively Department of Engineering Science and Mechanics Virginia Polytechnic Institute State University BlacksburgVA24061 United States Chemical engineer Polymeric Materials Branch NASA Langley Research Center HamptonVA23665 United States

ISBN: (纸本)9780803112728

The effects of processing on autohesive bond strength development in polysulfone resin and graphite-polysulfone composites were investigated. Autohesive bond strength development in polysulfone resin was observed by measuring the refracture toughness of precracked compact tension specimens that were healed at a given temperature and contact time. The fractured specimens, when completely healed, achieved the original toughness of the virgin resin. Results of the compact tension (CT) tests, when corrected for nonisothermal effects, compared favorably with diffusion models explaining crack healing and welding of amorphous potymers. Interply strength development in graphite-polysulfone unidirectional composites was measured as a function of healing temperature and contact time using a double cantilever beam (DCB) interlaminar fracture toughness test. The critical strain energy release rate of the refractured composites did not show a strong time or temperature dependence as observed in the neat resin tests. Furthermore, only 80 to 90~ of the undamaged fracture energy can be recovered. The fracture mechanisms were determined to be different in the healed DCB specimen from those in the virgin specimen due to resin flow at the crack plane upon healing. © 1989 ASTM International. All rights reserved.

关键词： Cracks

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A MICROcomputer BASED DIESEL-ENGINE SIMULATOR FOR ADVANCED SHIP PROPULSION MONITORING AND CONTROL-SYSTEMS

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NAVAL ENGINEERS JOURNAL 1989年第1期101卷 66-72页

作者： KYRTATOS, NP NICHOLAS P. KYRTATOS PH.D. is associate professor of marine engineering at the National Technical University of Athens Greece. He obtained a 1st Class Hons. B.Sc. degree in marine engineering from the University of Newcastle upon Tyne (1975) and a Ph.D. degree in mechanical engineering from the Imperial College of Science and Technology London University (1979). He was postdoctoral research associate at Imperial College London (1979–1980). He was visiting professor in the Department of Mechanical Engineering McGill University Montreal Canada (1980–1982). He served at the Greek Airforce Research Centre Athens (1982–1984). He was assistant professor of marine engineering at NTUA (1984–1988).

The increasing use of on-board computers will make the utilization of sophisticated engine simulation models within integrated computerized ship propulsion plant management systems possible. These models can be used to provide reference performance data for advanced control, performance optimisation, fault diagnosis, and predictive maintenance systems. This paper describes briefly the structure of advanced engine performance prediction models, commenting on the areas which require further development in view of the above applications. An engine simulation model originally developed on a mainframe computer was adapted to run on a microcomputer. Selected results are presented, using the model to predict the performance of a large slow-speed marine diesel engine, simulating various typical fault conditions.

关键词： Diesel Engines

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INSITU MEASUREMENT AND NUMERICAL-SIMULATION OF OXYGEN LIMITED BIOTRANSFORMATION

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GROUND WATER MONITORING AND REMEDIATION 1989年第1期9卷 83-91页

作者： BORDEN, RC LEE, MD THOMAS, JM BEDIENT, PB WARD, CH Dr. Robert C. Borden is an assistant professor of civil engineering at North Carolina State University (Raleigh NC 27604). His primary research interest is in the development of field methods and numerical models for the prediction of adsorption and biotransformation of hazardous organic compounds in the subsurface. Dr. Michael D. Lee is a senior environmental scientist with Biosystems Inc. (2100 Concord Rd. Chester Township PA 19013). His primary emphasis is on the development of efficient technologies for the bioremediation of contaminated soil and ground water. Dr. J. Michele Thomas is a research associate with the National Center for Ground Water Research at Rice University (Houston TX 77251). Her research interests are in the ecology and transport of microorganism in the subsurface at hazardous waste sites. Thomas’interests also include improving current methods of enhanced subsurface biorestoration. Dr. Philip B. Bedient is a professor of environmental science and engineering and member of the National Center for Ground Water Research at Rice University (Houston TX 77251). His research interests are in the development and application of ground water quality models. Dr. C.H. Ward is a professor and chairman of the Department of Environmental Science and Engineering and a director of the National Center for Ground Water Research at Rice University (Houston TX 77251). Dr. Ward's research interests are in the general field of environmental microbiology specifically in the area of microbial degradation and transformation of synthetic and petroleum derived hydrocarbons in the subsurface.

Enhanced subsurface biorestoration is rapidly becoming recognized as a valuable tool for the restoration of hydrocarbon-contaminated aquifers and sediments. Previous field and laboratory studies at a former wood creosoting facility near Conroe, Texas, have indicated that insufficient oxygen is the primary factor limiting the biotransformation of polynuclear aromatics (PNAs) in sediments and ground water at this site. A series of laboratory experiments and field push-pull injection tests were performed as part of this project to: (1) study the effect of low oxygen concentrations on the biotransformation of PNAs; (2) identify the minimum concentration of PNAs that could be achieved through the addition of oxygen alone; (3) confirm that enhanced subsurface biorestoration is feasible at this site; and (4) test an existing numerical model of the biotransformation process (BIOPLUME). The laboratory studies demonstrated that biotransformation of the PNAs was not inhibited at dissolved oxygen concentrations as low as 0.7 mg/L although this work did suggest that there may be a minimum PNA concentration of 30 to 70 μg/L total PNAs below which biotransformation was inhibited. The field push-pull tests confirmed that addition of oxygen was effective in enhancing the subsurface biodegradation of the PNAs. The minimum concentration achieved using oxygen alone was approximately 60 μg/L total PNAs. Minimal biotransformation of these compounds was observed without oxygen addition. The numerical model BIOPLUME was tested against monitoring data from the field experiments and appears to provide a good approximation of the biodegradation process.

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ESTIMATION OF STRUCTURAL SERVICE LIFE OF SHIPS

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NAVAL ENGINEERS JOURNAL 1989年第3期101卷 156-166页

作者： AYYUB, BM WHITE, GJ PURCELL, ES P.E. Bilal M. Ayyub:is currently an associate professor of civil engineering at the University of Maryland. He received his B.S. degree in civil engineering from the University of Kuwait in 1980. He completed both his M.S. (1981) and Ph.D. (1983) in civil engineering at the Georgia Institute of Technology. Dr. Ayyub has an extensive background in risk-based analysis and design simulation and construction engineering. He is engaged in research work involving structural reliability bridges marine structures and mathematical modeling using the theories of probability statistics and fuzzy sets. His research work is sponsored by the National Transportation Safety Board the National Science Foundation the U.S. Coast Guard the State of Maryland and the University of Maryland. Dr. Ayyub is a member of ASNE the American Society of Civil Engineers (ASCE) the American Concrete Institute (ACI) the Committee on Forensic Engineering of ASCE and the Committee on Structural Safety of ACI. He is the author of more than three dozen publications in national and international journals conference proceedings and reports. Dr. Ayyub received the ASNE “Jimmie” Hamilton Award for 1985 and the ASCE “Outstanding Research Oriented Paper” in the Journal of Water Resources Planning and Management for 1987. Gregory J. White:is an associate professor of naval architecture at the U.S. Naval Academy. He received his B.S. degree in engineering mechanics from Vanderbilt University in 1975 an M.E. degree in naval architecture from the University of California Berkeley in 1981 and a Ph.D. in civil engineering (structures) from the University of Maryland in 1986. Dr. White served on active duty with the U.S. Navy from 1975 to 1979 as a junior officer in the engineering and operations departments of Pacific Fleet destroyers. Prior to coming to the Naval Academy he worked at Mare Island Naval Shipyard in the scientific code and in the R&D division of Exxon International Company's Tanker Department. Dr. White is a lieutenant commande

A methodology for the structural life assessment of a ship's structure is suggested. The methodology is based on probabilistic analysis using reliability concepts and the statistics of extremes. In this approach, the estimation of structural life expectancy is based on selected failure modes. All possible failure modes of the ship must be investigated and the most likely paths to structural failure identified. For the purpose of illustration two failure modes are considered in this study. They are plate plastic deformation and fatigue cracking. Structural life based on these two failure modes is determined for an example vessel. The methodology determines the probability of failure of the ship's structural components according to the identified failure modes as a function of time. The results can be interpreted as the cumulative probability distribution function (CDF) of structural life. Due to the unknown level of statistical correlation between failure modes, limits or bounds on the CDF of the structural life are established. The limits correspond to the extreme cases of fully correlated and independent failure modes. The CDFs of structural life are determined for two inspection strategies; namely, inspection every year and inspection every two years with a warranty inspection at the end of the first year. The meaning of the results for the case investigated in this study is that, for example, given an inspection strategy of two years and a desired life of 15 years, there is a 72% chance that the vessel will not experience enough partial damage‘ in the failure modes identified to constitute reaching the “end of structural life” as defined.

关键词： Ships

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THE QUANTIFICATION OF INTEROPERABILITY

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NAVAL ENGINEERS JOURNAL 1989年第3期101卷 251-256页

作者： MENSH, DR KITE, RS DARBY, PH Dennis Roy Mensh:is currently the task leader Interoperability Project with the MITRE Corporation in McLean Va. He received his B.S. and M.S. degrees in applied physics from Loyola College in Baltimore Md. and the American University in Washington D. C. He also has completed his course work towards his Ph.D. degree in computer science specializing in the fields of systems analysis and computer simulation. He has been employed by the Naval Surface Warfare Center White Oak Laboratory Silver Spring Md. for 20 years in the areas of weapon system analysis and the development of weapon systems simulations. Since 1978 he has been involved in the development of tools and methodologies that can be applied to the solution of shipboard combat system/battle force system architecture and engineering problems. Mr. Mensh is a member of ASNE MORS IEEE U.S. Naval Institute MAA and the Sigma Xi Research Society. Robert S. Kite:is a systems engineer with the Naval Warfare Systems Engineering Department of the MITRE Corporation in McLean Va. Mr. Kite received his B.S. degree in electronic engineering from The Johns Hopkins University in Baltimore Md. Mr. Kite retired from the Federal Communications Commission in 1979 and served a project manager of the J-12 Frequency Management Support Project for the Illinois Institute of Technology Research Institute in Annapolis Md. before joining MITRE. Mr. Kite is presently a member of ASNE the Military Operations Research Society and an associate member of Sigma Xi. Paul H. Darby:has worked in the field of interoperability both in the development of interoperability concepts and systems since joining the Department of the Navy in 1967. He was the Navy's program manager for the WestPacNorth TACS/ TADS and IFFN systems. He is currently head of the Interoperability Branch Warfare Systems Engineering Office Space and Naval Warfare Systems Command. He holds a B.S. from the U.S. Naval Academy.

JCS Pub 1 defines interoperability as “The ability of systems, units or forces to provide services to and accept services from other systems, units or forces and to use the services so exchanged to enable them to operate effectively together.” With JCS Pub 1 as a foundation, interoperability of systems, units or forces can be factored into a set of components that can quantify interoperability. These components are: media, languages, standards, requirements, environment, procedures, and human factors. The concept described in this paper uses these components as an analysis tool to enable specific detailed analyses of the interoperability of BFC3 systems, units, or forces for the purpose of uncovering and resolving interoperability issues and problems in the U.S. Navy, Joint, and Allied arenas. Also, as a management tool, the components can help determine potential interoperability characteristics of future U.S. Navy BFC3 systems for compliance with battle force systems architectures. The approach selected for the quantification of interoperability was the development of a set of measures of performance (MOPs) and measures of effectiveness (MOEs). The MOPs/MOEs were integrated with a candidate set of components, which were used to partition the totality of interoperability into measurable entities. The methodology described employs basic truth table theory in conjunction with logic equations to evaluate the interoperability components in terms of MOPs that were aggregated to MOEs. It is believed that this concept, although elementary and based on fundamental principles, represents an operationally significant approach rather than a theoretical approach to the quantification of interoperability. The vehicle used as a means to measure the MOPs and MOEs was the Research Evaluation and Systems Analysis (RESA) computer modeling and simulation capability at the Naval Ocean Systems Center (NOSC), San Diego, Calif. Data for the measurements were collected during a Tactical I

关键词： Military engineering

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CLEER - AN AI-SYSTEM DEVELOPED TO ASSIST EQUIPMENT ARRANGEMENTS ON WARSHIPS

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NAVAL ENGINEERS JOURNAL 1989年第3期101卷 127-137页

作者： ZHOU, HH SILVERMAN, BG SIMKOL, J Dr. H. Harry Zhou:is a research professor at the Institute for Artificial Intelligence of The George Washington University. Dr. Zhou received his master's degree and Ph.D. in computer science from Vanderbilt University in 1984 and 1987 respectively. He did his dissertation in the fields of artificial intelligence analogical reasoning and machine learning. His research interests include: classifier systems genetic algorithms learning by analogy inductive learning adaptive expert systems automated knowledge acquisition and adaption. He is also interested in data base design programming languages mental modeling and software engineering. Dr. Barry G. Silverman:is director of the Institute for Artificial Intelligence and a professor at the Engineering Administration Department of The George Washington University. He is also president of IntelliTek Inc. an AI consulting firm. Dr. Silverman received the B.S.E. M.S.E. and Ph.D. degrees from the University of Pennsylvania. He has been a principal developer of four generic AI products as well as eight AI applications. Since 1979 he has written over 100 papers and reports on these AI efforts. Joel Simkol:is a research scientist currently engaged in designing expert system architectures to support electronic warfare vulnerability analyses threat assessments shipboard topside antenna arrangements and C3countermeasures employment. Mr. Simkol's work in applying expert systems technology to electromagnetic interference and to spectrum management has generated increased interest and participation from all branches of government agencies.

This paper describes a modularized AI system being built to help improve electromagnetic compatibility (EMC) among shipboard topside equipment and their associated systems. CLEER is intended to act as an easy to use integrator of existing expert knowledge and pre-existing data bases and large scale analytical models. Due to these interfaces; to the need for portability of the software; and to artificial intelligence related design requirements (such as the need for spatial reasoning, expert data base management, model base management, track-based reasoning, and analogical (similar ship) reasoning) it was realized that traditional expert system shells would be inappropriate, although relatively off-the-shelf AI technology could be incorporated. In the same vein, the rapid prototyping approach to expert system design and knowledge engineering was not pursued in favor of a rigorous systems engineering methodology. The critical design decisions affecting CLEER's development are summarized in this paper along with lessons learned to date all in terms of “how,” “why,” and “when” specific features are being developed.

关键词： Artificial Intelligence

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Philatelic Mixtures and Multimodal Densities

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Journal of the American Statistical Association 1988年第404期83卷 941-941页

作者： Izenman, Alan J. Sommer, Charles J. Associate Professor Department of Statistics and Member Center for Advanced Computational Science Temple University Philadelphia PA 19122. Assistant Professor Department of Mathematics and Computer Science State University of New York Brockport NY 14420

A century ago, postage stamps were printed on a deliberate mixture of different paper types, each having its own thickness characteristics due to poor quality control in paper manufacture. It was not unusual for different types of paper to be used for a single stamp issue, because ordinary white wove paper was often not readily available in quantities necessary for production of a new stamp issue. Unfortunately, the different paper types used were not always well documented. Each paper type was purchased by the ream, which was required to consist of a specific number of sheets and had to weigh a certain amount. To cut costs, manufacturers often satisfied both requirements by mixing a few 'thick' sheets of paper into an otherwise underweight ream. Although the importance of paper thickness in the philatelic literature is reflected by a higher market value for stamps printed on the thicker and more scarce paper, stamp catalogs have been notoriously vague about characterizing paper thickness, relying instead on classifying stamps by whether they were printed on 'thin,' 'regular,' or 'thick' paper. In this article, the term philatelic mixture is introduced to describe any situation in which a particular stamp issue is known to have been printed on a mixture of paper types with possible differences in paper thickness. In statistical terms, this is a mixture-of-distributions problem, in which identification of the mixture components (different paper types) is achieved using measurements on stamp thickness, and where information regarding the number of such components is vague, at best. The focus of this article is on parametric and nonparametric perspectives of the mixture problem and its special application to identifying the components of philatelic mixtures. The parametric approach tries to fit a finite mixture of component densities of a given type, usually normal, where... [ABSTRACT FROM AUTHOR]

关键词： Bootstrap Likelihood ratio test Maximum likelihood Mixtures of distributions Modes Nonparametric density estimation Postage stamps Quality control Tests for multimodality.

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A New Family of Multivariate Distributions with Applications to Monte Carlo Studies

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Quarterly Publications of the American Statistical Association 1988年第404期83卷 984-989页

作者： Nachtsheim, Christopher J. Johnson, Mark E. Associate Professor Department of Operations and Management Science University of Minnesota Minneapolis MN 55455. Professor School of Industrial and Systems Engineering Georgia Institute of Technology Atlanta GA 30332

We consider a new class of multivariate probability distributions having representationX=RLY(p), whereRis distributed as√χ2(p),Lis the Choleski factorization of the scaling matrix Σ, andY(p)represents an arbitrary distribution on thep-dimensional unit hypersphere. IfY(p)is uniform, thenXhas a multivariate normal distribution with mean0and covariance matrix Σ. The use of classical spherical distributions or other nonuniform distributions forY(p)leads to interesting, controllable departures from normality that are particularly relevant to robustness studies. Their use is illustrated in a Monte Carlo investigation of the robustness of Hotelling'sT2. Variate generation routines for the cardioid, triangular, offset normal, wrapped normal, wrapped Cauchy, von Mises, power sine, Fisher, and Bingham distributions are developed.

关键词： Circular distributions Pearson system Spherical distributions

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FLUID-FLOW AND TRACER DISPERSION IN SHALLOW TUNDISHES

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STEEL RESEARCH 1988年第9期59卷 399-405页

作者： ILEGBUSI, OJ SZEKELY, J Research Associate Department of Materials Science and Engineering Massachusetts Institute of Technology (MIT) Cambridge USA Professor

A mathematical model is developed to describe fluid flow and tracer dispersion in shallow tundishes. Two tundish designs are considered, namely one with a point inlet and a point outlet, and another with a point inlet and a slot outlet. Each of these designs is investigated, both in the absence and presence of flow control devices, the latter consisting of either conventional use of dams and weirs, or a magnetic field imposed perpendicularly to the main flow direction. Ein mathematisches Modell wurde entwickelt, um das Fließverhalten und die Tracerdispersion in flachen Gießverteilern zu ermitteln. Zwei Ausführungen von Gießverteilern wurden untersucht, d. h. einer mit sowohl punktförmigem Einlaß wie Auslaß, der andere mit punktförmigem Einlaß und schlitzförmigem Auslaß. Beide Ausführungen wurden untersucht sowohl mit als auch ohne Vorrichtungen für die Strömungsbeeinflussung, die entweder aus konventionellen Dämmen und Wehren bestanden oder einem Magnetfeld, das senkrecht zur Hauptfließrichtung erzeugt wurde.

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