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1998

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Articles 1801 - 1830 of 2574

Full-Text Articles in Physical Sciences and Mathematics

Pressure Induced Reversal Of The Volume Expansion Caused By Interstitial Nitrogen In Nd2fe17n3, G. K. Marasinghe, William Joseph James, P. C. Ezekwenna, H. Luo, W. B. Yelon, Y. Zhao, R. B. Von Dreele, M. Ellouze, Ph L'Héritier Jan 1998

Pressure Induced Reversal Of The Volume Expansion Caused By Interstitial Nitrogen In Nd2fe17n3, G. K. Marasinghe, William Joseph James, P. C. Ezekwenna, H. Luo, W. B. Yelon, Y. Zhao, R. B. Von Dreele, M. Ellouze, Ph L'Héritier

Chemistry Faculty Research & Creative Works

Crystallographic properties of Nd2Fe17N3 have been investigated using powder neutron diffraction techniques at pressures up to 7.3 GPa. With increasing pressure, the unit cell volume of Nd 2Fe17N3 decreases almost linearly at a rate of 6.1 Å3/GPa without undergoing a phase transformation or expelling the interstitial nitrogen atoms. The observed rate of contraction corresponds to a bulk modulus of 1.4x1011 N/m2 for Nd2Fe17N3. The unit cell volume of Nd 2Fe17N3 at 7.3 GPa is approximately equal to that of Nd2Fe17 at atmospheric pressure. Even though the unit cell of Nd2Fe17 expands anisotropically due to nitrogenation, contraction of the Nd2Fe17N3 unit …

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The Evolution Of Chiral Stationary Phases For Liquid Chromatography, Daniel W. Armstrong Jan 1998

The Evolution Of Chiral Stationary Phases For Liquid Chromatography, Daniel W. Armstrong

Chemistry Faculty Research & Creative Works

The development of effective chiral stationary phases (CSPs) and separation strategies for the liquid chromatographic (LC) resolution of enantiomers has been beneficial to many scientific disciplines. Over the last decade the number and type of CSPs has expanded tremendously. Not only have new classes of chiral selectors been introduced, but also many of the first CSPs have been changed and/or improved. The second or third generation of a CSP often can be different from the original. This can be confusing and intimidating to someone just entering the area of LC enantiomeric separations. Fortunately, all CSPs can be categorized in one …

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Kurt Mislow Honorary Issue Of Chirality, Daniel W. Armstrong Jan 1998

Kurt Mislow Honorary Issue Of Chirality, Daniel W. Armstrong

Chemistry Faculty Research & Creative Works

No abstract provided.

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Filtration Modeling Of A Plate-And-Frame Press, Scott A. Wells Jan 1998

Filtration Modeling Of A Plate-And-Frame Press, Scott A. Wells

Civil and Environmental Engineering Faculty Publications and Presentations

The porosity distribution and filtrate production during cake filtration in a plate-and-frame filter press were simulated mathematically. The model considered filtration that occurs after the filling process, not filtration that occurs as the suspension fills the cell. Governing equations for the temporal porosity distribution were developed for a plateand- frame press. The governing equations were solved numerically using an alternating-direction-implicit scheme. Appropriate initial and boundary conditions were determined based on characteristics of the plate-and-frame press and of the suspension properties. Predicted porosity and velocity distributions were calculated for assumed constitutive parameters.

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Java, Java, Java, Chaman Sabharwal Jan 1998

Java, Java, Java, Chaman Sabharwal

Computer Science Faculty Research & Creative Works

Everyone is talking about Java. The driving force for this chatter is Java''s simplicity and potential power. Java is programming language, and a language for the intranet and the World Wide Web (WWW). Java is a Write On one platform and Run on Many platforms (WORM) language. For network-friendly, platform-independent applications, Java (originally Oak) is an object oriented programming language. Java source code is compiled into a virtual machine code or bytecode. This makes the Java platform independent. It can be placed on a Web site, and executed on the client side on a PC-Intel, Mac, Motorola or UNIX-Solaris machine …

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Generalized Ultrametrics, Domains And An Application To Computational Logic, Anthony K. Seda, Pascal Hitzler Jan 1998

Generalized Ultrametrics, Domains And An Application To Computational Logic, Anthony K. Seda, Pascal Hitzler

Computer Science and Engineering Faculty Publications

Fixed points of functions and operators are of fundamental importance in programming language semantics in giving meaning to recursive definitions and to constructs which involve self-reference. It follows therefore that fixed-point theorems are also of fundamental importance in theoretical computer science. Often, order-theoretic arguments are available in which case the well-known Knaster-Tarski theorem can be used to obtain fixed-points. Sometimes, however, analytical arguments are needed involving the Banach contraction mapping theorem as is the case for example in studying concurrency and communicating systems. Situations arise also in computational logic in the presence of negation which force non-monotonicity of the operators …

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Learning To Understand: Mathematical Preparation Of Prospective Teachers, M. Hannigan, V. Preston Jan 1998

Learning To Understand: Mathematical Preparation Of Prospective Teachers, M. Hannigan, V. Preston

Journal of Mathematics and Science: Collaborative Explorations

This paper describes the development of a two-course sequence in mathematics content for prospective elementary teachers. Community college and university personnel collaborated to develop a course sequence that would prepare prospective elementary teachers to teach mathematics with an understanding of concepts to support their abstract mathematical knowledge. The strategy was to begin with a broad vision and then focus on the smaller pieces which would achieve that vision. The course changes are validated by documents published by various educational and mathematical groups advocating an increased emphasis on teaching for understanding rather than rote learning. Significant change is difficult without support …

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The Community College Of Philadelphia: Educating Teachers For A Changing World, K. Armstrong Jan 1998

The Community College Of Philadelphia: Educating Teachers For A Changing World, K. Armstrong

Journal of Mathematics and Science: Collaborative Explorations

No abstract provided.

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Aims & Scope Jan 1998

Aims & Scope

Journal of Mathematics and Science: Collaborative Explorations

No abstract provided.

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Virtual Reality Modelling Of A Cnc Machine, Damian O'Sullivan Jan 1998

Virtual Reality Modelling Of A Cnc Machine, Damian O'Sullivan

Theses

The increasing importance of training and upgrading skills has led to the use of new interactive technologies in the development of more effective training tools. Previous techniques for training Computer Numerical Control (CNC) machine operators, while excellent for their time, varied from brief inexpensive tutorials to expensive on the job training. A CNC machine uses a computer to perform the functions of the machine using a part program stored in the memory of the computer. This thesis describes a Virtual Reality (VR) model of a CNC milling machine, implemented within a VR environment representing a CNC workshop. Its development and …

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Microscale And Nanoscale Testing Of Materials Using Scanning Probe Technologies, Mark Phelan Jan 1998

Microscale And Nanoscale Testing Of Materials Using Scanning Probe Technologies, Mark Phelan

Theses

Understanding solid surfaces and their properties is of crucial importance for many sectors of industry. This interest stems from the fact that solid surfaces are the working interface between a solid material and its environment and in many cases it is this interface which determines both the suitability and life span of a mechanical component. Furthermore the modification of surface properties using coatings and multi-layered materials has grown significantly, particularly in the case of data storage, optics and microelectronics. The demands of these and other sectors have provided the impetus for the development of material testing techniques applicable to coatings …

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Wetland Vegetation Monitoring, 1998 Survey: Gnangara Wetlands, N. E. Pettit, R. H. Froend Jan 1998

Wetland Vegetation Monitoring, 1998 Survey: Gnangara Wetlands, N. E. Pettit, R. H. Froend

Research outputs pre 2011

Water regimes, both groundwater and surface water components dil'ectly effect distribution, health and species composition of wetland fringing vegetation. In the area of the northern Swan Coastal Plain overlying the Gnangara groundwater mound, wetland water levels and therefore the vegetation can be intimately connected to underlying groundwater levels. The Water Corporation (formerly Water Authority of Western Australia) has been drawing water from the Gnangara mound for domestic water supply for a number of years. The main objective of this study is to monitor the changes in the vegetation fringing these wetlands and to determine if this is related to changes …

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Commingling Of Contrasted Magmas In Various Geodynamic Settings, Bernard Plateovet, Jean Bebien, Edilene Gomes Jan 1998

Commingling Of Contrasted Magmas In Various Geodynamic Settings, Bernard Plateovet, Jean Bebien, Edilene Gomes

Turkish Journal of Earth Sciences

Three acid-basic associations taken in various geodynamical settings are studied: the gabbro-granite association of Porto (Corsica), the associations of the Guevgueli (Greek Macedonia), and the associations of the Piracaia complex (Brazil). The diversity of field relations, the degree of mingling, the origins of the melts are debated for each association, using petrological and geochemical tools for each acid-basic association. An origin by hybridization is assumed for the intermediate rocks of the Porto association, it is tested by numerical calculation. Then, we focus on the mixing process between the comagmatic components. Mixing of melts may have happened by thorough mingling and …

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Geochemical And Petrological Characteristics Of The Eastern Pontide Eocene (?) Alkaline Volcanic Province, Ne Turkey, Cüneyt Şen, Mehmet Arslan, Ali̇ Van Jan 1998

Geochemical And Petrological Characteristics Of The Eastern Pontide Eocene (?) Alkaline Volcanic Province, Ne Turkey, Cüneyt Şen, Mehmet Arslan, Ali̇ Van

Turkish Journal of Earth Sciences

The Eastern Pontide Alkaline Volcanic Province is developed by volcanic cycles erupted in Cenozoic era. Petrographical and geochemical data suggest presence of at least two different suits of alkaline rocks (Tonya group and Trabzon group). Petrographically, both groups consist of alkali basalt, tephrite, phonolitic tephrite, basanite, nephelinite, nepheline latite and their pyroclastic rocks. Geochemically, Tonya samples have high MgO and Ni, low LREE contents and LILE/HFSE ratios compare to Trabzon group. Preliminary studies show that these two groups of rocks are related with low level differentiation and derived from a metasomatised mantle source.

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Temporal Variability In Dissolved Organic Carbon And Radiocarbon In The Eastern North Pacific Ocean, James E. Bauer Jan 1998

Temporal Variability In Dissolved Organic Carbon And Radiocarbon In The Eastern North Pacific Ocean, James E. Bauer

VIMS Articles

The factors regulating the steady state inventories and residence times of dissolved organic carbon (DOG) in the deep ocean are not well established. Previous studies of DOC have been limited to single time-point profiles that provide general information on the potential role of vertical advective-diffusive processes in controlling DOC distributions and mean apparent ages. We present results from a 2-year time series station in the eastern North Pacific (station M) where short-term (months) changes in inventories and Delta(14)C signatures of DOC as measured in deep profiles were examined in conjunction with changes in particulate organic carbon (POC) pools. Significant long-term …

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Nano-Engineering Of Molecular Films By Self-Assembly And Langmuir-Blodgett Techniques, Erwin P. Enriquez Jan 1998

Nano-Engineering Of Molecular Films By Self-Assembly And Langmuir-Blodgett Techniques, Erwin P. Enriquez

Chemistry Faculty Publications

The availability of sophisticated and ultra-sensitive analytical tools and the maturity of organic synthesis have opened new possibilities for fabrication of molecular materials designed at the nanometer scale. Presently, the most promising and widely investigated methodologies are the self-assembly and Langmuir-Blodgett procedures. The former relies on the strong, preferential affinity of specific functional groups to solid surfaces, whereas the latter involves transfer of pre-formed mono layers at the air-water interface onto solid substrates. These techniques and their recent applications are reviewed.

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Solute And Bacterial Transport Through Partially-Saturated Intact Soil Blocks, Edmund Perfect, Mark S. Coyne, Michael C. Sukop, Gerald R. Haszler, Virgil L. Quisenberry, Ligia Bejat Jan 1998

Solute And Bacterial Transport Through Partially-Saturated Intact Soil Blocks, Edmund Perfect, Mark S. Coyne, Michael C. Sukop, Gerald R. Haszler, Virgil L. Quisenberry, Ligia Bejat

KWRRI Research Reports

Steady-state transport of water, chloride and bacteria was measured through intact blocks of Maury and Cecil soils, under partially saturated conditions. Major objectives were to determine if transport occurs uniformly or via preferential flow paths, and if soil physical properties could be used to predict breakthrough. The blocks were instrumented with TDR probes and mounted on a vacuum chamber containing 100 cells that collected eflluent. After each experiment the blocks were sampled for soil physical properties. The fluxes showed no spatial autocorrelation and the eflluent variance was not statistically different between soils. Less than 3% of the influent bacteria appeared …

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Spatial And Temporal Variability In Seepage Between A Contaminated Aquifer And Tributaries To The Ohio River, Alan E. Fryar, David L. Brown, David B. Wenner, Todd C. Rasmussen, Eric J. Wallin Jan 1998

Spatial And Temporal Variability In Seepage Between A Contaminated Aquifer And Tributaries To The Ohio River, Alan E. Fryar, David L. Brown, David B. Wenner, Todd C. Rasmussen, Eric J. Wallin

KWRRI Research Reports

Because interactions between ground water and tributaries may influence contaminant loading to rivers, we delineated seepage along Little Bayou and Bayou Creeks in McCracken County, Kentucky, during a two-year period. From the Paducah Gaseous Diffusion Plant, on the divide between the creeks, trichloroethene and technetium-99 plumes extend several km toward the Ohio River. Gaining conditions occur where the creeks are incised into coarse sediments in the river's flood plain. Such conditions were marked by upward hydraulic gradients within the bed; maximum specific discharge (q) > 0.24 m d-1; relatively narrow ranges of stream, piezometer, and bed temperatures; relatively cool …

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A Review Of Research On The Kentucky River Ecosystem: Biota And Human Impacts, R. M. Waltman, R. J. Stevenson Jan 1998

A Review Of Research On The Kentucky River Ecosystem: Biota And Human Impacts, R. M. Waltman, R. J. Stevenson

KWRRI Research Reports

This report provides information about the water conditions in the Kentucky River Basin, through collection of previous studies.

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Kentucky River Modeling And Monitoring Needs Assessment, L. Ormsbee, L. Jarrett, B. Perkins Jan 1998

Kentucky River Modeling And Monitoring Needs Assessment, L. Ormsbee, L. Jarrett, B. Perkins

KWRRI Research Reports

This report outlines the responsibilities of the Kentucky River Authority in the planning, operation, and management of river monitoring.

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Finite Direct Sums Of (D1)-Modules, Derya Keskin Jan 1998

Finite Direct Sums Of (D1)-Modules, Derya Keskin

Turkish Journal of Mathematics

In this paper we give necessary conditions for a finite direct sum of (D1)--modules to be a (D1)--module.

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Derivation Of Separable Amplitude Equations By Multiple Scales Method, Mehmet Naci̇ Özer, Dursun Eser Jan 1998

Derivation Of Separable Amplitude Equations By Multiple Scales Method, Mehmet Naci̇ Özer, Dursun Eser

Turkish Journal of Mathematics

The method of multiple scales is used to derive separable nonlinear Schrödinger equations as amplitude equation from three component 2D nonlinear Klein-Gordon Equation. We further discuss the integrability of the derived separable amplitude equations and reduce them into finite dimensional Hamiltonian systems. Finally we give first integrals for the reduced systems.

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Exponential Dichotomy And Mild Solutions Of Nonautonomous Equations In Banach Spaces, Y. Latushkin, Timothy W. Randolph, R. Schnaubelt Jan 1998

Exponential Dichotomy And Mild Solutions Of Nonautonomous Equations In Banach Spaces, Y. Latushkin, Timothy W. Randolph, R. Schnaubelt

Mathematics and Statistics Faculty Research & Creative Works

We prove that the exponential dichotomy of a strongly continuous evolution family on a Banach space is equivalent to the existence and uniqueness of continuous bounded mild solutions of the corresponding inhomogeneous equation. This result addresses nonautonomous abstract Cauchy problems with unbounded coefficients. The technique used involves evolution semigroups. Some applications are given to evolution families on scales of Banach spaces arising in center manifolds theory. © 1998 Plenum Publishing Corporation.

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Some Harmonic N-Slit Mappings, Michael Dorff Jan 1998

Some Harmonic N-Slit Mappings, Michael Dorff

Mathematics and Statistics Faculty Research & Creative Works

The class SH consists of univalent, harmonic, and sense-preserving functions f in the unit disk, Δ, such that f = h+ḡ where h(z) = z + ∑2∞ akzk g(z) = ∑1∞ bkzk. SHO will denote the subclass with b1 = 0. We present a collection of n-slit mappings (n ≥ 2) and prove that the 2-slit mappings are in SH while for n ≥ 3 the mappings are in SHO. Finally, we show that these mappings establish the sharpness of a previous theorem by Clunie and Sheil-Small while disproving a conjecture about the inner mapping radius. ©1998 American Mathematical Society.

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Some Necessary And Sufficient Conditions For Two Variable Orthogonal Designs In Order 44, Christos Koukouvinos, M. Mitrouli, Jennifer Seberry Jan 1998

Some Necessary And Sufficient Conditions For Two Variable Orthogonal Designs In Order 44, Christos Koukouvinos, M. Mitrouli, Jennifer Seberry

Faculty of Informatics - Papers (Archive)

We give a new algorithm which allows us to construct new sets of sequences with entries from the commuting variables 0, ±a, ±b, ±c, ±d with zero autocorrelation function. We show that for twelve cases if the designs exist they cannot be constracted using four circulant matrices in the Goethals-Seidel array. Further we show that the necessary conditions for the existence of an OD(44;s1,s2) are sufficient except possibly for the following 7 cases. (7,32) (8,31) (9,30) (9,33) (11,30) (13,29) (15,26) which could not be found because of the large size of the search space for a …

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Letter To The Editor, Noel A. Cressie Jan 1998

Letter To The Editor, Noel A. Cressie

Faculty of Informatics - Papers (Archive)

No abstract provided.

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Cover - Table Of Contents Jan 1998

Cover - Table Of Contents

Journal of the Iowa Academy of Science: JIAS

No abstract provided.

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Front Matter Jan 1998

Front Matter

Journal of the Iowa Academy of Science: JIAS

No abstract provided.

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Managing Seedling Emergence Of Cuphea In Iowa, W. W. Roath Jan 1998

Managing Seedling Emergence Of Cuphea In Iowa, W. W. Roath

Journal of the Iowa Academy of Science: JIAS

Cuphea, a western hemisphere genus of some 260 species, has been proposed as a domestic source of medium-chain fatty acids. These fatty acids are used primarily in soap and detergent manufacture and are presently extracted from imported tropical oils or from petroleum. Considerable difficulty in obtaining consistent plant stands with direct seeding has been experienced at two Iowa locations. Trials were initiated in 1987 and continued through 1994 to test various treatments upon seedling emergence of C. laminuligera Koehne, C lanceolata Ait., and hybrid C. viscosissima Jacq. X C. lanceolata. These treatments included planting depths from 1.3 to 6.4 cm, …

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Book Review - The Iowa Breeding Bird Atlas, Louis B. Best Jan 1998

Book Review - The Iowa Breeding Bird Atlas, Louis B. Best

Journal of the Iowa Academy of Science: JIAS

The Iowa Breeding Bird Atlas is the first comprehensive statewide survey of Iowa's breeding birds. Through the efforts of over 500 people, every county in the state was sampled to provide a record of the composition and distribution of the bird life in Iowa. The project entailed dividing the state into 861 atlas blocks; 83% received at least some coverage and 71 % were completed. Information known through 1995 is included in the text, although the atlas project ended in 1990.

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