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COMPARATIVE STRUCTURAL LIFE ASSESSMENT OF PATROL BOAT BOTTOM PLATING

NAVAL ENGINEERS JOURNAL 1990年第3期102卷 253-262页

作者： AYYUB, BM WHITE, GJ BELLWRIGHT, TF PURCELL, ES 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. He is engaged in research work involving structural reliability marine structures and mathematical modeling using the theories of probability statistics and fuzzy sets. His research work has been sponsored by the National Transportation Safety Board National Science Foundation U.S. Coast Guard Department of Defense State of Maryland and University of Maryland. He is the author of more than 100 publications in national and international journals conference proceedings and reports. Dr. Ayyub was a recipient of the ASNE “Jimmie” Hamilton Award for 1985 the ASCE “Outstanding Research Oriented Paper” in theJournal of Water Resources Planning and Managementfor 1987 and Edmund Friedman Young Engineer Award for Professional Achievement from ASCE for 1989. Gregory J. White:is an associate professor of naval architecture at the U.S. Naval Academy. He received his B.S. degreein 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 the author of more than two dozen technical articles and reports and is one of the U.S. representatives to the International Ship and Offshore Structures Congress (ISSC). His research interests lie in t

The estimation of an absolute life expectancy of a structure is a complex process and the results are expected to have relatively large levels of uncertainty. In this study, a comparative analysis is undertaken between two different patrol boats. This is an approach which results in a higher confidence level because certain factors common to both boats can be eliminated by assuming them to be at constant normal levels. The study is limited to the critical forward bottom plating and takes into account the differences in material, plate dimensions, operational profile, structure and loading of the two vessels. Two failure modes, plastic plate deformation and fatigue, are considered, and a novel approach to plate wastage is included. Many factors affect the structural life of a vessel. They include structural type, operational profile, structural details, loads, inspection and maintenance, design methods, safety factors, corrosion, and environmental factors. There are three types of uncertainty associated with these factors; namely, physical randomness, statistical uncertainties, and model uncertainties. The method described is designed to address these uncertainties. The objective of the paper is to present the reliability-based structural life assessment method, and then to use it to evaluate and compare the structural performance of the forward bottom plating of the two patrol boats. The results of the evaluation are presented in the form of graphs and tables in order to facilitate the comparative evaluation. The method is performed within a computer-based format which allows parametric sensitivity analysis of several variables including the size of the plating panel, thickness, operational profile and loading. The sensitivity of the structural life expectancy of the forward bottom plating to variations in these parameters is evaluated.

关键词： Naval Vessels

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A QUANTIFICATION OF DEXTERITY

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ROBOTICS AND computer-INTEGRATED MANUFACTURING 1989年第1期6卷 3-14页

作者： STURGES, RH WRIGHT, PK Department of Mechanical Engineering and the Robotics Institute Carnegie-Mellon University Pittsburgh PA 15213 U.S.A. The second author is now in the Department of Computer Science of the Courant Institute of Mathematical Sciences at New York University New York NY 10012 U.S.A.

The need for a quantitative measure of dexterity has been reviewed. The interactions of the task being performed and the candidate robotic manipulator to be used have been considered. Intuitive notions of dexterity have been discussed, based on the scaling laws of biological systems. They can be expressed as effector capabilities, independent of task. Task/manipulator interactions have been quantified in the human perspective through design rules and measures of human motor capacity. Machine dexterity is shown to have parallel measures and limitations. A non-dimensional definition of dexterity has been proposed. The definition is independent of scale, and it can provide a quantitative measure between different robotic systems that have varying degrees of dexterity.

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Construction of polyhedral surfaces from serial sections: Exact and heuristic solutions

Construction of polyhedral surfaces from serial sections: Ex...

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Medical Imaging III: Image Capture and Display 1989

作者： Shaw, Alan Schwartz, Eric L. Computational Neuroscience Laboratories New York University School of Medicine Department of Psychiatry 550 First Avenue New YorkNY10016 United States Dept. of Computer Science Courant Institute of Mathematical Sciences New York University 715 Broadway New YorkNY10003 United States

The problem of reconstructing a polyhedral surface from cross-sectional data admits of an exact and automatic solution when the surface is densely sampled as a voxel surface. We regard such a surface as a discrete sampling of a smooth manifold in general position. Using the full adjacency graph of the surface provided by a voxel model, we are able to classify the small set of possible topological changes in the sections of the surface;we then deal with these cases exhaustively, and thereby guide the triangulation process. In this way we are able to carry out triangulation without human interaction. When the sections are sparsely sampled, heuristic methods must suffice for triangulation. These methods work well on segments of "generalized cylinder," i.e., runs of sections containing single loops, but they often fail when attempting to process highly convoluted surfaces. This is because the topology of the sections changes when a critical point of the surface is encountered. We outline a heuristic algorithm based upon the same theoretical considerations as the full (dense-sampling) algorithm. This second algorithm follows a parsing step similar to that of the full algorithm, but locates critical nodes which are saddle points by a least-squares procedure, and uses this fit to supply the information required to complete the triangulation. This method provides a solution which is comparable in quality to the correct solution derived from the first algorithm. © 1989 SPIE. All rights reserved.

关键词： Triangulation

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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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Book reviews

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Artificial Intelligence Review 1988年第4期2卷 253-309页

作者： Tony Dodd Leonard Bolc Paul Taylor Judith Wusterman Blay Whitby Carlton McDonald J. Garwood Jim Sholicar Wendy J. Milne M. Pengelly Tony Priest Antony Galton Mahesan Niranjan D. Rainton J. R. Thomas Steve Hedges Barbara Gorayska Expert Systems International Ltd. Oxford Institute for Informatics Warsaw University Poland Expert Systems International Oxford U.K. Department of Computer Science Exeter University U.K. Brighton U.K. Department of Computing Oxford Polytechnic U.K. Department of Experimental Psychology Oxford University U.K. Department of Engineering University of Cambridge U.S.A. Department of Computer Science University of Exeter U.K. Engineering Department University of Cambridge U.K. Department of Engineering Cambridge University U.K. Department of Psychology University of Warwick U.S.A. Expert Systems Internatinal Ltd Oxford U.K. Department of Computing and Mathematical Sciences Oxford Polytechnic U.K.

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Wave envelope technique for multimode wave guide problems

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Journal of Scientific Computing 1987年第4期2卷 371-387页

作者： Hariharan, S.I. Sudharsanan, S.I. Department of Mathematical Sciences University of Akron Akron 44325 Ohio United States Institute for Computer Applications in Science and Engineering United States Applied Physics Group University of Tennessee Space Institute Tullahoma 37388 TN United States

In this paper we propose a fast method for solving wave guide problems. In particular, we consider the guide to be inhomogeneous, and allow propagation of waves of higher-order modes. Such techniques have been handled successfully for acoustic wave propagation problems with single mode and finite length. This paper extends this concept to electromagnetic wave guides with several modes and infinite in length. The method is shown and results of computations are presented. © 1987 Plenum Publishing Corporation.

关键词： acoustic waves electromagnetic waves multimode waveguides Wave envelope

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Space debris: Electrodynamic effects

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Advances in Space Research 1986年第7期6卷 127-130页

作者： Horanyi, M. Mendis, D.A. Supercomputer Computational Research Institute Florida State University Tallahassee FL 32306 United States Department of Electrical Engineering and Computer Sciences the Center for Astrophysics and Space Science University of California San Diego La Jolla CA 92093 United States

It is shown that electrodynamic forces play a crucial role in the orbital dynamics of the small Al2O3 particles that are injected into the terrestrial magnetosphere during solid rocket propellent burns. Due to the sim...

It is shown that electrodynamic forces play a crucial role in the orbital dynamics of the small Al₂O₃ particles that are injected into the terrestrial magnetosphere during solid rocket propellent burns. Due to the simplified model that is used to describe the plasma distribution in the magnetosphere, the present results are necessarily preliminary. Even so, it appears that the smallest particles (a = 0.1 μm) will be rapidly eliminated from the magnetosphere. Evaluation of the fate of the somewhat larger (a = 1 μm) particles awaits the construction of a more complete and realistic model of the magnetospheric plasma. © 1987.

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Moving a polygon around the corner in a corridor 86

Moving a polygon around the corner in a corridor

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2nd Annual Symposium on computational Geometry, SCG 1986

作者： Maddila, Sanjeev R. Yap, Chee K. Coordinated Science Laboratory Department of Electrical and Computer Engineering University of Illinois UrbanaIL61801 United States Courant Institute of Mathematical Sciences New York University 251 Mercer Street New YorkNY10012 United States

ISBN: (纸本)0897911946

We consider the problem of moving an n vertex simple polygon around a corner in a right-angular corridor. We give an O (n log n ) algorithm for a convex polygon which constructs a motion of the polygon when one exists;otherwise It reports that none exists. In the case of non-convex polygons, we have anO(n2) time algorithm. © 1986 ACM.

关键词： computational geometry

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Finding minimal convex nested polygons 85

Finding minimal convex nested polygons

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1st Annual Symposium on computational Geometry, SCG 1985

作者： Aggarwal, Alok Booth, Heather O'Rourke, Joseph Suri, Subhash IBM Research Center Mathematical Science Department Yorktown HeightsNY10598 United States Department of Electrical Engineering and Computer Science Johns Hopkins University BaltimoreMD21218 United States Courant Institute of Mathematical Sciences 251 Merce Trrpot New YorkNY10012 United States

ISBN: (纸本)0897911636

We consider the problem of finding a polygon nested between two given convex polygons that has a minimal number of vertices. Our main result is an O(nlogfc) algorithm for solving the problem, where n is the total number of vertices of the given polygons, and k is the number of vertices of a minimal nested polygon. We also present an 0(n) sub-optimal algorithm, and a simple 0(nk) optimal algorithm. © 1985 ACM.

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Simplification of radical expressions 76

Simplification of radical expressions

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3rd ACM Symposium on Symbolic and Algebraic Computation, SYMSAC 1976

作者： Caviness, B.F. Fateman, R.J. Computer Science Department Illinois Institute of Technology ChicagoIL United States Computer Science Division Department of Electrical Engineering and Computer Sciences University of California at Berkeley BerkeleyCA United States Department of Mathematical Sciences Rensselaer Polytechnic Institute TroyNY12181 United States

ISBN: (纸本)9781450377904

In this paper we discuss the problem of simplifying unnested radical expressions. We describe an algorithm implemented in MACSYMA that simplifies radical expressions and then follow this description with a formal treatment of the problem. Theoretical computing times for some of the algorithms are briefly discussed as is related work of other authors.

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