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1997

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Articles 1801 - 1830 of 2472

Full-Text Articles in Physical Sciences and Mathematics

Front Matter Jan 1997

Front Matter

Journal of the Iowa Academy of Science: JIAS

No abstract provided.

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Photo, Dr. Richard W. Pohl, February 1982 & Foreward To V.104 No.3, Lynn G. Clark Jan 1997

Photo, Dr. Richard W. Pohl, February 1982 & Foreward To V.104 No.3, Lynn G. Clark

Journal of the Iowa Academy of Science: JIAS

No abstract provided.

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Cover - Table Of Contents Jan 1997

Cover - Table Of Contents

Journal of the Iowa Academy of Science: JIAS

No abstract provided.

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Awards And Recognition, Iowa Academy Of Science, 1997 Jan 1997

Awards And Recognition, Iowa Academy Of Science, 1997

Journal of the Iowa Academy of Science: JIAS

No abstract provided.

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Editorial Board & Iowa Academy Of Science Officers And Directors Jan 1997

Editorial Board & Iowa Academy Of Science Officers And Directors

Journal of the Iowa Academy of Science: JIAS

No abstract provided.

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Analysis Of Environmental Data With Censored Observations, Shiping Liu, Jye-Chyi Lu, Dana Kolpin, William Meeker Jan 1997

Analysis Of Environmental Data With Censored Observations, Shiping Liu, Jye-Chyi Lu, Dana Kolpin, William Meeker

United States Geological Survey: Staff Publications

The potential threats to humans and to terrestrial and aquatic ecosystems from environmental contamination could depend on the sum of the concentrations of different chemicals. However, direct summation of environmental data is not generally feasible because it is common for some chemical concentrations to be recorded as being below the analytical reporting limit. This creates special problems in the analysis of the data. A new model selection procedure, named forward censored regression, is introduced for selecting an appropriate model for environmental data with censored observations. The procedure is demonstrated using concentrations of atrazine (2-chloro- 4-ethylamino-6-isopropylamino-s-triazine), deethylatrazine (DEA, 2-amino-4-chloro-6-isopropylamino-s-triazine), and deisopropylatrazine …

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A Land-Use And Water-Quality History Of White Rock Lake Reservoir, Dallas, Texas, Based On Paleolimnological Analyses, J. Platt Bradbury, Peter C. Van Metre Jan 1997

A Land-Use And Water-Quality History Of White Rock Lake Reservoir, Dallas, Texas, Based On Paleolimnological Analyses, J. Platt Bradbury, Peter C. Van Metre

United States Geological Survey: Staff Publications

White Rock Lake reservoir in Dallas, Texas contains a 150-cm sediment record of silty clay that documents land-use changes since its construction in 1912. Pollen analysis corroborates historical evidence that between 1912 and 1950 the watershed was primarily agricultural. Land disturbance by plowing coupled with strong and variable spring precipitation caused large amounts of sediment to enter the lake during this period. Diatoms were not preserved at this time probably because of low productivity compared to diatom dissolution by warm, alkaline water prior to burial in the sediments. After 1956, the watershed became progressively urbanized. Erosion decreased, land stabilized, and …

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Fracture Permeability And Its Relationship To In-Situ Stress In The Dixie Valley, Nevada, Geothermal Reservoir, Colleen A. Barton, Stephen Hickman, Roger H. Morin, Mark D. Zoback, Thomas Finkbeiner, John Sass, Dick Benoit Jan 1997

Fracture Permeability And Its Relationship To In-Situ Stress In The Dixie Valley, Nevada, Geothermal Reservoir, Colleen A. Barton, Stephen Hickman, Roger H. Morin, Mark D. Zoback, Thomas Finkbeiner, John Sass, Dick Benoit

United States Geological Survey: Staff Publications

An extensive suite of spinner flowmeter, high-resolution temperature and borehole televiewer logs were acquired in a 2.7-km-deep well drilled into a fault-hosted geothermal reservoir at Dixie Valley, Nevada. Localized perturbations to wellbore temperature and flow were used to identify hydraulically conductive fractures. Comparison of these data with fracture orientations from the borehole televiewer logs indicates that hydraulically conductive fractures in crystalline rocks within and adjacent to the producing fault zone have an orientation distinct from the overall fracture population. In conjunction with in-situ stress measurements from this well, Coulomb analysis indicates that these permeable fractures are critically stressed, potentially active …

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Correlation Of Late-Pleistocene Lake-Level Oscillations In Mono Lake, California, With North Atlantic Climate Events, Larry Benson, Steve P. Lund, James W. Burdett, Michaele Kashgarian, Timothy P. Rose, Joseph P. Smoot, Martha Schwartz Jan 1997

Correlation Of Late-Pleistocene Lake-Level Oscillations In Mono Lake, California, With North Atlantic Climate Events, Larry Benson, Steve P. Lund, James W. Burdett, Michaele Kashgarian, Timothy P. Rose, Joseph P. Smoot, Martha Schwartz

United States Geological Survey: Staff Publications

Oxygen-18 (18O) values of sediment from the Wilson Creek Formation, Mono Basin, California, indicate three scales of temporal variation (Dansgaard-Oeschger, Heinrich, and Milankovitch) in the hydrologic balance of Mono Lake between 35,400 and 12,900 14C yr B.P. During this interval, Mono Lake experienced four lowstands each lasting from 1000 to 2000 yr. The youngest low stand, which occurred between 15,500 and 14,000 14C yr B.P., was nearly synchronous with a desiccation of Owens Lake, California. Paleomagnetic secular variation (PSV) data indicate that three of four persistent low stands occurred at the same times as Heinrich events …

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Expressing Code Mobility In Mobile Unity, Gian Pietro Picco, Gruia-Catalin Roman, Peter J. Mccann Jan 1997

Expressing Code Mobility In Mobile Unity, Gian Pietro Picco, Gruia-Catalin Roman, Peter J. Mccann

All Computer Science and Engineering Research

Advancements in network technology have led to the emergence of new computing paradigms that challenge established programming practices by employing weak forms of consistency and dynamic forms of binding. Code mobility, for instance, allows for invocation-time binding between a code fragment and the location where it executes. Similarly, mobile computing allows hosts (and the software they execute) to alter their physical location. Despite apparent similarities, the two paradigms are distinct in their treatment of location and movement. This paper seeks to uncover a common foundation for the two paradigms by exploring the manner in which stereotypical forms of code mobility …

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Eliding The Arguments Of Cases, Ronald P. Loui, Jeff Norman Jan 1997

Eliding The Arguments Of Cases, Ronald P. Loui, Jeff Norman

All Computer Science and Engineering Research

No abstract provided.

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Dynamic Flow Switching: A New Communication Service For Atm Networks, Qiyong Bian, Kohei Shimoto, Jonathan Turner Jan 1997

Dynamic Flow Switching: A New Communication Service For Atm Networks, Qiyong Bian, Kohei Shimoto, Jonathan Turner

All Computer Science and Engineering Research

This paper presents a new communication service for ATM networks that provides one-way, adjustable rate, on-demand communication channels. The proposed dynamic flow service is designed to operate within a multi-service cell switched network that supports both conventional switched virtual circuits and IP packet routing and is designed to complement those services. It is particularly well suited to applications that transmit substantial amounts of data (a few tens of kilobytes or more) in fairly short time periods (up to a few seconds). Much of the current world-wide web traffic falls within this domain. Like IP packet networks, the new service permits …

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Balancing Consistency And Lag In Transaction-Based Computational Steering, Eileen Kraemer, Delbert Hart, Gruia-Catalin Roman Jan 1997

Balancing Consistency And Lag In Transaction-Based Computational Steering, Eileen Kraemer, Delbert Hart, Gruia-Catalin Roman

All Computer Science and Engineering Research

Computational steering, the interactive adjustment of application parameters and allocation of resources, is a promising technique for higher-productivity simulation, finer-grained optimization of dynamically varying algorithms, and greater understanding of program behavior and the characteristics of data sets and solution spaces. Tools for computational steering must provide monitoring, visualization, and interaction facilities. In addition, these tools must address issues related to the consistency, latency, and scalability at each of these phases, and must consider the perturbation that results. In this paper we describe transaction-based components for a computational steering system and present an approach that guarantees consistent monitoring and displays, supports …

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The Programmers' Playground Application Management System User Guide, William M. Shapiro, T. Paul Mccartney, E.F. Berkley Shands Jan 1997

The Programmers' Playground Application Management System User Guide, William M. Shapiro, T. Paul Mccartney, E.F. Berkley Shands

All Computer Science and Engineering Research

Application Management permits the advertising, launching, and configuring of distributed applications created using the Programmers' Playground. Applications can be documented and made available to end-users through the use of application pages on the World Wide Web. The launching and configuring of applications is performed by a brokerage system consisting of an applicatoin broker and one or more hierarchies of module launchers. This document describes how to setup and use the components of the Application Management system.

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Design And Implementation Of A New Connection Admission Control Algorithm Using A Multistate Traffic Source Model, Robert Engel Jan 1997

Design And Implementation Of A New Connection Admission Control Algorithm Using A Multistate Traffic Source Model, Robert Engel

All Computer Science and Engineering Research

This report develops a practical method for connection admission control in ATM networks. The method is based on a virtual cell loss probability criterion, is designed to handle heterogeneous traffic types and allows each traffic source to be described by an individual finite-state model with as many states as are needed to describe the source traffic. To make connection admission decisions with respect to individual links, an aggregate finite state model is computed from the individual models and used to estimate the virtual cell loss probabilities. To reduce the computational requirements for maintaining the aggregate traffic model, the aggregate model …

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Principles For Developing And Measuring High-Performance Web Servers Over Atm, James C. Hu, Sumedh Mungee, Douglas C. Schmidt Jan 1997

Principles For Developing And Measuring High-Performance Web Servers Over Atm, James C. Hu, Sumedh Mungee, Douglas C. Schmidt

All Computer Science and Engineering Research

High-performance Web servers are essential to meet the growing demands of the Internet. Satisfying these demands requires a thorough understanding of the key factors that affect Web server performance. This paper provides three contributions to the design, implementation, and evaluation of high-performance Web servers. First, we report the results of a comprehensive empirical study of popular high-performance Web servers (such as Apache, Netscape Enterprise, PHTTPD, and Zeus) over high-speed ATM networks. This study illustrates their relative performance and identifies their performance bottlenecks. To measure performance accurately, we developed a new benchmarking technique that subjects Web servers to varying connection frequencies. …

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Optimizing The Performance Of The Corba Internet Inter-Orb Protocol Over Atm, Aniruddha Gokhale, Douglas C. Schmidt Jan 1997

Optimizing The Performance Of The Corba Internet Inter-Orb Protocol Over Atm, Aniruddha Gokhale, Douglas C. Schmidt

All Computer Science and Engineering Research

The Internet Inter-ORB Protocol (IIOP) enables heterogeneous CORBA-compliant Object Request Brokers (ORBs) to interoperate over TCP/IP networks. The IIOP uses the Common Data Representation (CDR) transfer syntax to map CORBA Interface Definition Langauge (IDL) data types into a bi-canonical wire format. Due to the excessive marshaling/demarshaling overhead, data copying, and high-levels of function call overhead, conventional implementation of IIOP protocols yield poor performance over high-speed networks. To meet the demands of emerging distributed multimedia applications, CORBA-compliant ORBs must support both interoperable and highly efficient IIOP implementations. This paper provides two contributions to the study and design of high performance CORBA …

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Using Snapshot Streams To Support Visual Exploration, Delbert Hart, Eileen Kraemer, Gruia-Catalin Roman Jan 1997

Using Snapshot Streams To Support Visual Exploration, Delbert Hart, Eileen Kraemer, Gruia-Catalin Roman

All Computer Science and Engineering Research

The non-determinism, complexity, and size of distributed software systems present significant difficulties for designers and maintainers. Visualization can help alleviate these difficulties through interactive exploratory tools that allow both novice and experienced users to investigate a distributed computation using a common tool set. Essential to the success of a visual exploration tool is the ability to provide accurate representations of global states. This paper is concerned with the use of snapshots in support of interactive visual exploration of distributed computations. The nature of the visualization process requires snapshots that (1) are consecutive, thus facilitating smooth animation of state changes, (2) …

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The Impact Of Tsunami On The Coastline Of Jervis Bay, Southeastern Australia, Edward A. Bryant, R. W. Young, D. M. Price, D. J. Wheeler, M. I. Pease Jan 1997

The Impact Of Tsunami On The Coastline Of Jervis Bay, Southeastern Australia, Edward A. Bryant, R. W. Young, D. M. Price, D. J. Wheeler, M. I. Pease

Faculty of Science - Papers (Archive)

The Jervis Bay area offers а diversity of landforms that do not fit within con¬temporary views of coastal evolution. Field evidence indicates that catastrophic tsunami have had а significant impact on the coast and its hinterland both within and outside the embayment. Runup has overtopped cliffs 80 m above sea level and deposited chevron-shaped ridges to elevations of 130 m on the southern headland. Boulders, up to 6 m in diameter, have been deposited in an imbricated fashion against cliffs, on clifftops, and along shoreline ramps. Bedform features and the size of transported material indicate flow depths up tо 10 …

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Late Pleistocene Marine Chronology Of The Gippsland Lakes Region, Australia, Edward A. Bryant, D. M. Price Jan 1997

Late Pleistocene Marine Chronology Of The Gippsland Lakes Region, Australia, Edward A. Bryant, D. M. Price

Faculty of Science - Papers (Archive)

Thermoluminescence dating is used to define the chronology of the coastal barriers of the Gippsland Lakes region, Australia. The area evidences а long history of marine deposition extending back со the Middle Pleistocene. However, the majority of Pleistocene barriers have formed since the Last Interglacial during two phases at 59 to 72 ka and 40 to 48 ka corresponding to interstadials. А third phase, with dates around the Last Glacial, appears со represent rapid shoreward movement of Late Pleistocene sediment from the shelf during the Holocene. Barriers have developed in an en echelon fashion seaward as the region has been …

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Comment On “Electronic Structure Of Insulating Salts Of The-(Bedt-Ttf Family Studied By Low-Temperature Specific-Heat Measurements”, Nathanael Fortune, Yu V. Sushko Jan 1997

Comment On “Electronic Structure Of Insulating Salts Of The-(Bedt-Ttf Family Studied By Low-Temperature Specific-Heat Measurements”, Nathanael Fortune, Yu V. Sushko

Physics: Faculty Publications

Recently reported specific-heat measurements by Nakazawa and Kanoda between 20 and 50 K show no evidence for an expected antiferromagnetic ordering transition in the quasi-two-dimensional (2D) molecular conductor (Formula presented)-(BEDT-TTF)(Formula presented)Cu[N(CN)(Formula presented)]Cl [Y. Nakazawa and K. Kanoda, Phys. Rev. B 53, R8875 (1996)]. Although the absence of an observable transition was taken as evidence for 2D short-range ordering at elevated temperatures, even a small increase in pressure from the application of the grease used to mount the sample would shift this magnetic transition below 20 K. In their paper, Nakazawa and Kanoda erroneously assume that pressure-induced effects can be ruled …

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Lithium Bonding Interaction In H2Cy⋯Lif (Y=O,S) Complexes: A Theoretical Probe, Salai Cheettu Ammal, P. Venuvanalingam, S. Pal Jan 1997

Lithium Bonding Interaction In H2Cy⋯Lif (Y=O,S) Complexes: A Theoretical Probe, Salai Cheettu Ammal, P. Venuvanalingam, S. Pal

Faculty Publications

Ab initio calculations at 6-31++G(d,p) level have been done on H2CY⋯LiF (Y=O,S) complexes choosing ten possible orientations in each complex. The effect of correlation on complex binding energies has been studied via single point MP2 (full) calculations done on 6-31++G(d,p) geometry. Binding energies have been corrected for basis set superposition error. Frequency calculations confirm that H2CO⋯LiF and H2CS⋯LiF complexes have three and two stable forms, respectively. The most stable form in each complex has been found to have a strong lithium bonding interaction and a secondary hydrogen bondinginteraction. NBO analysis has revealed that in this form oxygen donates nσ lone …

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Karl Patterson Schmidt, John A. Drobnicki Jan 1997

Karl Patterson Schmidt, John A. Drobnicki

Publications and Research

Karl Patterson Schmidt turned herpetology firom a hobby into a branch of biology, and influenced numerous young biologists as an editor, teacher, author, and curator.

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A Fast Algorithm For Complete Subcube Recognition, Fikret Erçal, H. J. Burch Jan 1997

A Fast Algorithm For Complete Subcube Recognition, Fikret Erçal, H. J. Burch

Computer Science Faculty Research & Creative Works

The complete subcube recognition problem is defined as, given a collection of available processors on an n-dimensional hypercube, locate a subcube of dimension k that consists entirely of available processors, if one exists. Despite many algorithms proposed so far on this subject, improving the time complexity of this problem remains a challenge. Efficiency limits that can be reached have not been exhausted yet. This paper proposes a novel algorithm to recognize all the overlapping subcubes available on an n-dimensional hypercube whose processors are partially allocated. Given P=2n, as the total number of processors in the hypercube, the new algorithm runs …

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Semiclassical Picture Of Collision-Induced Λ-Doublet Transitions In Diatomic Molecules, Laurie J. Kovalenko, J. B. Delos Jan 1997

Semiclassical Picture Of Collision-Induced Λ-Doublet Transitions In Diatomic Molecules, Laurie J. Kovalenko, J. B. Delos

Arts & Sciences Articles

We investigate collision-induced Λ-doublet transitions in a system similar to NO+Ar, based on a semiclassical model in which nuclear motion is treated classically and electronic motion quantum mechanically. We present a picture of this process by monitoring〈Λ〉, the expectation value of the projection of electronic orbital-angular momentum onto the molecular NO axis, over the duration of the collision. In a typical collision, the interaction with Ar would cause the electronic orbital-angular momentum to precess about the rotating NO–Ar vector. However, since this angular momentum is locked tightly to the diatomic axis, it is restricted to oscillation along this axis. This …

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Radiation And Gas Exchange Of Understory Species At Boreas: Research Annual Performance Report For Period June 15, 1997- June 14, 1998, E. A. Walter-Shea, T. J. Arkebauer Jan 1997

Radiation And Gas Exchange Of Understory Species At Boreas: Research Annual Performance Report For Period June 15, 1997- June 14, 1998, E. A. Walter-Shea, T. J. Arkebauer

School of Natural Resources: Documents and Reviews

No abstract provided.

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Improving Minority Class Prediction Using Case-Specific Feature Weights, Claire Cardie, Nicholas Howe Jan 1997

Improving Minority Class Prediction Using Case-Specific Feature Weights, Claire Cardie, Nicholas Howe

Computer Science: Faculty Publications

This paper addresses the problem of handling skewed class distributions within the case-based learning (CBL) framework. We first present as a baseline an information gain-weighted CBL algorithm and apply it to three data sets from natural language processing (NLP) with skewed class distributions. Although overall performance of the baseline CBL algorithm is good, we show that the algorithm exhibits poor performance on minority class instances. We then present two CBL algorithms designed to improve the performance of minority class predictions. Each variation creates test-case-specific feature weights by first observing the path taken by the test case in a decision tree …

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General Remarks On Spectral Entropy Vs. Statistical Entropy, John D. Ramshaw Jan 1997

General Remarks On Spectral Entropy Vs. Statistical Entropy, John D. Ramshaw

Physics Faculty Publications and Presentations

Crepeau and Herzel [1] (CH) have recently compared the spectral entropy of Powell and Percival [2] with the standard statistical (Boltzmann-Gibbs-Shannon) entropy in three simple physical systems. Here we compare and contrast these two entropies in a more general way by considering their values for an arbitrary stationary process X(t).

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Optical Imaging Of Carrier Dynamics In Silicon With Subwavelength Resolution, Andres H. La Rosa, B. I. Yakobson, H. D. Hallen Jan 1997

Optical Imaging Of Carrier Dynamics In Silicon With Subwavelength Resolution, Andres H. La Rosa, B. I. Yakobson, H. D. Hallen

Physics Faculty Publications and Presentations

Characteristic rate variations of carrier processes are imaged using near-field scanning optical microscopy. We couple both a visible pump and an infrared probe light through a subwavelength aperture to investigate the interband recombination and intraband diffusion of excess carriers in oxidized silicon. Typical values of the locally measured life time constants agree well with those obtained by conventional space-averaged techniques. Moreover, the images locate defects, reveal variations, and can map the regions in which a recombination process is active.

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Cryptology Through Time, Susan Danelle Vaucher Jan 1997

Cryptology Through Time, Susan Danelle Vaucher

Capstone Research Projects

No abstract provided.

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