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1997

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Articles 1531 - 1560 of 2472

Full-Text Articles in Physical Sciences and Mathematics

Random Walks On Wheels, Matthew Lee, Mark Stamp Jan 1997

Random Walks On Wheels, Matthew Lee, Mark Stamp

Faculty Publications, Computer Science

Suppose two particles occupy distinct vertices of a wheel graph and at each step the two particles move independently to adjacent vertices. In this paper we find the expected number of moves until the particles land on the same vertex.


Anomalous Flow Profile Due To The Curvature Effect On Slip Length, Alejandro Garcia, K. Tibbs, F. Baras Jan 1997

Anomalous Flow Profile Due To The Curvature Effect On Slip Length, Alejandro Garcia, K. Tibbs, F. Baras

Faculty Publications

No abstract provided.


Three-Dimensional Direct Simulation Monte Carlo Method For Slider Air Bearings, Alejandro Garcia, W. Huang, D. B. Bogy Jan 1997

Three-Dimensional Direct Simulation Monte Carlo Method For Slider Air Bearings, Alejandro Garcia, W. Huang, D. B. Bogy

Faculty Publications

The direct simulation Monte Carlo (DSMC) method is used to solve the three-dimensional nano-scale gas film lubrication problem between a gas bearing slider and a rotating disk, and this solution is compared to the numerical solution of the compressible Reynolds equations with the slip flow correction based on the linearized Boltzmann equation as presented by Fukui and Kaneko [molecular gas film lubrication (MGL) method] [ASME J. Tribol. 110, 253 (1988)]. In the DSMC method, hundreds of thousands of simulated particles are used and their three velocity components and three spatial coordinates are calculated and recorded by using a hard-sphere collision …


Structural And Dynamical Uncertainties In Modelling Axisymmetric Elliptical Galaxies, Aaron J. Romanowsky, C. S. Kochanek Jan 1997

Structural And Dynamical Uncertainties In Modelling Axisymmetric Elliptical Galaxies, Aaron J. Romanowsky, C. S. Kochanek

Faculty Publications

Quantitative dynamical models of galaxies require deprojection of the observed surface brightness to determine the luminosity density of the galaxy. Existing deprojection methods for axisymmetric galaxies assume that a unique deprojection exists for any given inclination, even though the projected density is known to be degenerate to the addition of ‘konus densities’ that are invisible in projection. We develop a deprojection method based on linear regularization that can explore the range of luminosity densities that are statistically consistent with an observed surface brightness distribution. The luminosity density is poorly constrained at modest inclinations (i ≿ 30°), even in the limit …


A One-Pass Algorithm For Accurately Estimating Quantiles For Disk-Resident Data, Khaled Alsabti, Sanjay Ranka, Vineet Singh Jan 1997

A One-Pass Algorithm For Accurately Estimating Quantiles For Disk-Resident Data, Khaled Alsabti, Sanjay Ranka, Vineet Singh

College of Engineering and Computer Science - Former Departments, Centers, Institutes and Projects

The '-quantile of an ordered sequence of data values is the element with rank ' \Theta n, where n is the total number of values. Accurate estimates of quantiles are required for the solution of many practical applications. In this paper, we present a new algorithm for estimating the quantile values for disk-resident data. Our algorithm has the following characteristics: (1) It requires only one pass over the data; (2) It is deterministic; (3) It produces good lower and upper bounds of the true values of the quantiles; (4) It requires no a priori knowledge of the distribution of the …


A Load Balancing Technique For Multiphase Computations, Jerrell Watts, Marc Rieffel, Stephen Taylor Jan 1997

A Load Balancing Technique For Multiphase Computations, Jerrell Watts, Marc Rieffel, Stephen Taylor

College of Engineering and Computer Science - Former Departments, Centers, Institutes and Projects

Parallel computations comprised of multiple, tightly interwoven phases of computation may require a different approach to dynamic load balancing than single-phase computations. This paper presents a load sharing method based on the view of load as a vector, rather than as a scalar. This approach allows multiphase computations to achieve higher efficiency on large-scale multicomputers than possible with traditional techniques. Results are presented for two large-scale particle simulations running on 128 nodes of an Intel Paragon and on 256 processors of a Cray T3D, respectively.


Semantics Vs. Syntax Vs. Computations: Machine Models For Type-2 Polynomial-Time Bounded Functionals, James S. Royer Jan 1997

Semantics Vs. Syntax Vs. Computations: Machine Models For Type-2 Polynomial-Time Bounded Functionals, James S. Royer

College of Engineering and Computer Science - Former Departments, Centers, Institutes and Projects

This paper investigates analogs of the Kreisel-Lacombe-Shoenfield Theorem in the context of the type-2 basic feasible functionals. We develop a direct, polynomial-time analog of effective operation in which the time bounding on computations is modeled after Kapron and Cook's scheme for their basic polynomial-time functionals. We show that if P = NP, these polynomial-time effective operations are strictly more powerful on R (the class of recursive functions) than the basic feasible functions. We also consider a weaker notion of polynomial-time effective operation where the machines computing these functionals have access to the computations of their procedural parameter, but not to …


Concurrent Simulation Of Plasma Reactors, Marc Rieffel, Stephen Taylor, Jerrell Watts, Sadasivan Shankar Jan 1997

Concurrent Simulation Of Plasma Reactors, Marc Rieffel, Stephen Taylor, Jerrell Watts, Sadasivan Shankar

College of Engineering and Computer Science - Former Departments, Centers, Institutes and Projects

This paper summarizes the computational techniques behind a novel concurrent simulation method used for studying the neutral flow inside plasma reactors. The technique is intended to cope with low pressure flow (less than 1.5 Torr) in realistic three-dimensional geometries. It is based on the Direct Simulation Monte Carlo method to accurately model rarefied gas flow. The concurrent formulation operates on a broad variety of shared-memory multiprocessors, multicomputers, and networked workstations.


Practical Algorithms For Selection On Coarse-Grained Parallel Computers, Ibraheem Al-Furaih, Srinivas Aluru, Sanjay Goil, Sanjay Ranka Jan 1997

Practical Algorithms For Selection On Coarse-Grained Parallel Computers, Ibraheem Al-Furaih, Srinivas Aluru, Sanjay Goil, Sanjay Ranka

College of Engineering and Computer Science - Former Departments, Centers, Institutes and Projects

In this paper, we consider the problem of selection on coarse-grained distributed memory parallel computers. We discuss several deterministic and randomized algorithms for parallel selection. We also consider several algorithms for load balancing needed to keep a balanced distribution of data across processors during the execution of the selection algorithms. We have carried out detailed implementations of all the algorithms discussed on the CM-5 and report on the experimental results. We demonstrate that the randomized algorithms are superior to their deterministic counterparts.


Integer Sorting Algorithms For Coarse-Grained Parallel Machines, Khaled Alsabti, Sanjay Ranka Jan 1997

Integer Sorting Algorithms For Coarse-Grained Parallel Machines, Khaled Alsabti, Sanjay Ranka

College of Engineering and Computer Science - Former Departments, Centers, Institutes and Projects

Integer sorting is a subclass of the sorting problem where the elements have integer values and the largest element is polynomially bounded in the number of elements to be sorted. It is useful for applications in which the size of the maximum value of element to be sorted is bounded. In this paper, we present a new distributed radix-sort algorithm for integer sorting. The structure of our algorithm is similar to radix sort except that it typically requires less number of communication phases. We present experimental results for our algorithm on two distributed memory multiprocessors, the Intel Paragon and the …


Diagonal Operators, S-Numbers, And Bernstein Pairs, Asuman Güven Aksoy, Grzegorz Lewicki Jan 1997

Diagonal Operators, S-Numbers, And Bernstein Pairs, Asuman Güven Aksoy, Grzegorz Lewicki

CMC Faculty Publications and Research

Replacing the nested sequence of ''finite" dimensional subspaces by the nested sequence of "closed" subspaces in the classical Bernstein lethargy theorem, we obtain a version of this theorem for the space B(X , Y) of all bounded linear maps. Using this result and some properties of diagonal operators, we investigate conditions under which a suitable pair of Banach spaces form an exact Bernstein pair.We also show that many "classical" Banach spaces, including the couple (Lp [O, 1] , Lq[O, 1]) form a Bernstein pair with respect to any sequence of s-numbers (sn) ,for 1 < p < ∞ and 1 ≤ q < ∞ …


Jamaican Cave Vertebrates, Donald A. Mcfarlane Jan 1997

Jamaican Cave Vertebrates, Donald A. Mcfarlane

WM Keck Science Faculty Papers

Limestone caves in the tropics are typically associated with a more diverse assemblage of vertebrates than are caves in temperate regions. Chapman [87] for example, has reported 37 species from the caves of Gunung Mulu National Park, Sarawak, whereas Bailey [43] lists only 13 for the equally cavernicolous Guadeloupe Mountains National Park, New Mexico, USA. Twenty-eight vertebrate species have been recorded from Jamaican caves. The relative importance of the five Classes differ in these three areas as shown in Table 1 (overleaf).


Kinetics Of Cleavage Of Intra- And Extracellular Simian Virus 40 Dna With The Enediyne Anticancer Drug C- 1027, Jerry Goodisman, James C. Dabrowiak, Christopher A. Kirk, Terry A. Beerman, Loretta S. Gawron Jan 1997

Kinetics Of Cleavage Of Intra- And Extracellular Simian Virus 40 Dna With The Enediyne Anticancer Drug C- 1027, Jerry Goodisman, James C. Dabrowiak, Christopher A. Kirk, Terry A. Beerman, Loretta S. Gawron

Chemistry - All Scholarship

A kinetic analysis of cleavage of simian virus DNA (SV40 DNA) inside and outside green monkey BSC-I cells by the enediyne-protein antibiotic C-1027 and its free chromophore is described. Information on rate constants was obtained by fitting populations of forms I (closed circular DNA), II (nicked circular DNA) and III (linear DNA) of SV4f.J DNA as a function of drug concentration to a kinetic model which includes: cutting of form I to give form II with rate constant k1. cutting of form I to give form III with rate constant k4, and cutting of form II to give form III …


Resource Access Control For An Internet User Agent, Nataraj Nagaratnam, Steven B. Byrne Jan 1997

Resource Access Control For An Internet User Agent, Nataraj Nagaratnam, Steven B. Byrne

Electrical Engineering and Computer Science - All Scholarship

The rapid increase in the Internet's connectivity has lead to proportional increase in the development of Web-based applications. Usage of downloadable content has proved effective in a number of emerging applications including electronic commerce, software components on-demand, and collaborative systems. In all these cases, Internet user agents (like browsers, tuners) are widely used by the clients to utilize and execute such downloadable content. With this new technology of using downloadable content comes the problem of the downloaded content obtaining unauthorized access to the client's resources. In effect, granting a hostile remote principal the requested access to client's resources may lead …


The Software Architecture Of A Virtual Distributed Computing Environment, Haluk Topcuoglu, Salim Hariri, Wojtek Furmanski, Jon Valente Jan 1997

The Software Architecture Of A Virtual Distributed Computing Environment, Haluk Topcuoglu, Salim Hariri, Wojtek Furmanski, Jon Valente

Electrical Engineering and Computer Science - All Scholarship

The requirements of grand challenge problems and the deployment of gigabit networks makes the network computing framework an attractive and cost effective computing environment with which to interconnect geographically distributed processing and storage resources. Our project, Virtual Distributed Computing Environment (VDCE), provides a problem-solving environment for high-performance distributed computing over wide area networks. VDCE delivers well-defined library functions that relieve end-users of tedious task implementations and also support reusability. In this paper we present the conceptual design of VDCE software architecture, which is defined in three modules: a) the Application Editor, a user-friendly application development environment that generates the Application …


A Compiler Algorithm For Optimizing Locality In Loop Nests, Mahmut Kandemir, J. Ramanujam, Alok Choudhary Jan 1997

A Compiler Algorithm For Optimizing Locality In Loop Nests, Mahmut Kandemir, J. Ramanujam, Alok Choudhary

Electrical Engineering and Computer Science - All Scholarship

This paper describes an algorithm to optimize cache locality in scientific codes on uniprocessor and multiprocessor machines. A distinctive characteristic of our algorithm is that it considers loop and data layout transformations in a unified framework. We illustrate through examples that our approach is very effective at reducing cache misses and tile size sensitivity of blocked loop nests; and can optimize nests for which optimization techniques based on loop transformations alone are not successful. An important special case is the one in which data layouts of some arrays are fixed and cannot be changed. We show how our algorithm can …


Parallel Domain Decomposition And Load Balancing Using Space-Filling Curves, Srinivas Aluru, Faith E. Sevilgen Jan 1997

Parallel Domain Decomposition And Load Balancing Using Space-Filling Curves, Srinivas Aluru, Faith E. Sevilgen

Electrical Engineering and Computer Science - All Scholarship

Partitioning techniques based on space-filling curves have received much recent attention due to their low running time and good load balance characteristics. The basic idea underlying these methods is to order the multidimensional data according to a space-filling curve and partition the resulting one-dimensional order. However, space-filling curves are defined for points that lie on a uniform grid of a particular resolution. It is typically assumed that the coordinates of the points are representable using a fixed number of bits, and the run-times of the algorithms depend upon the number of bits used. In this paper, we present a simple …


An Efficient K-Means Clustering Algorithm, Khaled Alsabti, Sanjay Ranka, Vineet Singh Jan 1997

An Efficient K-Means Clustering Algorithm, Khaled Alsabti, Sanjay Ranka, Vineet Singh

Electrical Engineering and Computer Science - All Scholarship

In this paper, we present a novel algorithm for performing k-means clustering. It organizes all the patterns in a k-d tree structure such that one can find all the patterns which are closest to a given prototype efficiently. The main intuition behind our approach is as follows. All the prototypes are potential candidates for the closest prototype at the root level. However, for the children of the root node, we may be able to prune the candidate set by using simple geometrical constraints. This approach can be applied recursively until the size of the candidate set is one for each …


Selective Crossover: Towards Fitter Offspring, Chilukuri K. Mohan Jan 1997

Selective Crossover: Towards Fitter Offspring, Chilukuri K. Mohan

Electrical Engineering and Computer Science - All Scholarship

A new general-purpose crossover operator is proposed. The representation of a candidate solution is slightly perturbed, and the ensuing changes in fitness are calculated. Such fitness changes (for parents) are used in constructing the offspring resulting from crossover. Experiments with several sets of problems demonstrate that this approach leads to rapid increases in average and best fitness, and performs much better than traditional general-purpose crossover operators.


A Global Computing Environment For Networked Resources, Haluk Topcuoglu, Salim Hariri Jan 1997

A Global Computing Environment For Networked Resources, Haluk Topcuoglu, Salim Hariri

Electrical Engineering and Computer Science - All Scholarship

Current advances in high-speed networks and WWW technologies have made network computing a cost-effective, high-performance computing alternative. New software tools are being developed to utilize efficiently the network computing environment. Our project, called Virtual Distributed Computing Environment (VDCE), is a high-performance computing environment that allows users to write and evaluate networked applications for different hardware and software configurations using a web interface. In this paper we present the software architecture of VDCE by emphasizing application development and specification, scheduling, and execution/runtime aspects.


Simulated Annealing And Genetic Algorithms For Partial Shape Matching, Ender Ozcan, Chilukuri K. Mohan Jan 1997

Simulated Annealing And Genetic Algorithms For Partial Shape Matching, Ender Ozcan, Chilukuri K. Mohan

Electrical Engineering and Computer Science - All Scholarship

Partial shape matching may be viewed as an optimization problem, to be solved using methods such as simulated annealing (SA) and genetic algorithms (GAs). We apply and compare both these methods for matching input shapes with model shapes described in terms of features such as line segments and angles. The quality of matching is gauged using a measure derived from attributed shape grammars [10, 11]. Current results show that both SA and GA succeed in the shape matching task; the GA is faster and yields the global optimum more often than the versions of SA implemented.


Standardization Of A Communication Middleware For High-Performance Real-Time Systems, Arkady Kanevsky, Anthony Skjellum, Jerrell Watts Jan 1997

Standardization Of A Communication Middleware For High-Performance Real-Time Systems, Arkady Kanevsky, Anthony Skjellum, Jerrell Watts

Electrical Engineering and Computer Science - All Scholarship

The last several years saw an emergence of standardization activities for real-time systems including standardization of operating systems (series of POSIX standards [1]), of communication for distributed (POSIX.21 [10]) and parallel systems (MPI/RT [5]) and real-time object management (realtime CORBA [9]). This article describes the ongoing standardization work and implementation of communication middleware for high performance real-time computing. The real-time message passing interface (MPI/RT) advances the non-real-time high-performance communication standard Message Passing Interface Standard (MPI), emphasizing changes that enable and support real-time communication, and is targeted for embedded, fault-tolerant and other real-time systems. MPI/RT is the only communication middleware layer …


Topology And Logic Programming Semantics, Pascal Hitzler Jan 1997

Topology And Logic Programming Semantics, Pascal Hitzler

Computer Science and Engineering Faculty Publications

Logic programming employs logic as a programming language. Thus a logic program consists of a set of clauses of a certain form most often a subset of the clauses of first order logic viewed as axioms. Computation in this paradigm is deduction from these axioms via some interpreter.

Logic programming semantics is concerned with background theory for logic programming. It tries to provide models for logic programs to give them their intended meaning and to connect them with practically implementable interpreters.


Positive Solutions And Nonlinear Multipoint Conjugate Eigenvalue Problems, Paul W. Eloe, Johnny Henderson Jan 1997

Positive Solutions And Nonlinear Multipoint Conjugate Eigenvalue Problems, Paul W. Eloe, Johnny Henderson

Mathematics Faculty Publications

Values of λ are determined for which there exist solutions in a cone of the nth order nonlinear differential equation (see PDF) satisfying themultipoint boundary conditions (see PDF) where a and f are nonnegative valued, and where both (see PDF) exist.


Grand Tour-Part 2: Petrogenesis And Thermal Evolution Of Deep Continental-Crust: The Record From The East Humboldt Range, Nevada, Allen J. Mcgrew, Mark T. Peters Jan 1997

Grand Tour-Part 2: Petrogenesis And Thermal Evolution Of Deep Continental-Crust: The Record From The East Humboldt Range, Nevada, Allen J. Mcgrew, Mark T. Peters

Geology Faculty Publications

The northern part of the East Humboldt Range, Nevada, provides a rare opportunity to explore the petrogenetic environment of deep levels in the middle crust during both large-scale Mesozoic contraction and Cenozoic regional extension. On this segment of the field trip, we will explore evidence bearing on the character of the metamorphic and magmatic history of this terrane, and attempt to link these constraints to the rheology and tectonic evolution of the middle crust during the Mesozoic and Cenozoic.


Hydrogeology And Ground-Water Monitoring Of Coal-Ash Disposal Sites In A Karst Terrane Near Burnside, South-Central Kentucky, Shelley Minns Hutcheson, Lyle V. A. Sendlein, James S. Dinger, James C. Currens, Arsin M. Sahba Jan 1997

Hydrogeology And Ground-Water Monitoring Of Coal-Ash Disposal Sites In A Karst Terrane Near Burnside, South-Central Kentucky, Shelley Minns Hutcheson, Lyle V. A. Sendlein, James S. Dinger, James C. Currens, Arsin M. Sahba

Report of Investigations--KGS

The effects of two coal-ash disposal facilities on ground-water quality at the John Sherman Cooper Power Plant, located in a karst region of south-central Kentucky, were evaluated using dye traces in springs. Springs were used for monitoring rather than wells, because in a karst terrane wells are unlikely to intercept individual conduits.

A closed-out ash pond located over a conduit-flow system discharges to three springs in the upper Salem and Warsaw Formations along Lake Cumberland. Water discharging from these downgradient springs is similar to springs unaffected by ash-disposal facilities and is a calcium-bicarbonate type. No constituent concentrations found in this …


Fresh-Water Aquifer In The Knox Group (Cambrian–Ordovician) Of Central Kentucky, James A. Kipp Jan 1997

Fresh-Water Aquifer In The Knox Group (Cambrian–Ordovician) Of Central Kentucky, James A. Kipp

Report of Investigations--KGS

Fresh water can be found in Cambrian and Ordovician carbonate rocks of the Knox Group in central Kentucky. The top of the aquifer is as much as 300 ft above mean sea level (m.s.l.) on the crest of the Cincinnati Arch, but descends off the flanks of the arch. Water is normally found in the upper 100 to 250 ft of the Knox, primarily in secondary porosity apparently associated with the unconformity at the top of the unit. Knox wells commonly exceed 750 ft in total depth, but because the aquifer is artesian, water rises to an elevation of about …


Multiprocessor Out-Of-Core Ffts With Distributed Memory And Parallel Disks, Thomas H. Cormen, Jake Wegmann, David M. Nicol Jan 1997

Multiprocessor Out-Of-Core Ffts With Distributed Memory And Parallel Disks, Thomas H. Cormen, Jake Wegmann, David M. Nicol

Computer Science Technical Reports

This paper extends an earlier out-of-core Fast Fourier Transform (FFT) method for a uniprocessor with the Parallel Disk Model (PDM) to use multiple processors. Four out-of-core multiprocessor methods are examined. Operationally, these methods differ in the size of "mini-butterfly" computed in memory and how the data are organized on the disks and in the distributed memory of the multiprocessor. The methods also perform differing amounts of I/O and communication. Two of them have the remarkable property that even though they are computing the FFT on a multiprocessor, all interprocessor communication occurs outside the mini-butterfly computations. Performance results on a small …


Cover - Table Of Contents Jan 1997

Cover - Table Of Contents

Journal of the Iowa Academy of Science: JIAS

No abstract provided.


Richard W. Pohl: Distinguished Botanist, Marjorie Conley Pohl Jan 1997

Richard W. Pohl: Distinguished Botanist, Marjorie Conley Pohl

Journal of the Iowa Academy of Science: JIAS

In her biographical portrait of Dr. Richard W. Pohl, Mrs. Pohl provides an engaging personal perspective of her late husband, his development as a botanist, his career, and his family life. We gain a sense of Dr. Pohl as a dedicated scientist as well as a humanist. Although Dr. Pohl possessed an abiding curiosity regarding all things natural, he is best known and remembered for his focus on grasses. As Mrs. Pohl documents, this interest in grasses began in the late 1930's and continued throughout his life-ultimately he was regarded as an authority on grass taxonomy both nationally and internationally. …