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1996

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Articles 2281 - 2310 of 2437

Full-Text Articles in Physical Sciences and Mathematics

Virginia Wetlands Management Handbook 2nd Edition, Wetlands Program, Virginia Institute Of Marine Science, Thomas A. Barnard Jan 1996

Virginia Wetlands Management Handbook 2nd Edition, Wetlands Program, Virginia Institute Of Marine Science, Thomas A. Barnard

Reports

No abstract provided.

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Tau Hadronic Branching Ratios, D. Buskulic, M. Thulasidas Jan 1996

Tau Hadronic Branching Ratios, D. Buskulic, M. Thulasidas

Research Collection School Of Computing and Information Systems

From 64492 selected τ-pair events, produced at the Z0 resonance, the measurement of the tau decays into hadrons from a global analysis using 1991, 1992 and 1993 ALEPH data is presented. Special emphasis is given to the reconstruction of photons and π0s, and the removal of fake photons. A detailed study of the systematics entering the π0 reconstruction is also given. A complete and consistent set of tau hadronic branching ratios is presented for 18 exclusive modes. Most measurements are more precise than the present world average. The new level of precision reached allows a stringent test τ-μ, universality in …

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On The Complexity Of Manpower Shift Scheduling, Hoong Chuin Lau Jan 1996

On The Complexity Of Manpower Shift Scheduling, Hoong Chuin Lau

Research Collection School Of Computing and Information Systems

We consider the shift assignment problem in manpower scheduling, and show that a restricted version of it is NP-hard by a reduction from 3SAT. We then present polynomial algorithms to solve special cases of the problem and show how they can be deployed to solve more complex versions of the shift assignment problem. Our work formally defines the computational intractibility of manpower shift scheduling and thus justifies existing works in developing manpower scheduling systems using combinatorial and heuristic techniques.

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Effect Of Light/Dark Transition On Carbon Translocation In Eelgrass Zostera Marina Seedlings, Richard C. Zimmerman, Randall S. Alberte Jan 1996

Effect Of Light/Dark Transition On Carbon Translocation In Eelgrass Zostera Marina Seedlings, Richard C. Zimmerman, Randall S. Alberte

OES Faculty Publications

Carbon translocation in the marine macrophyte Zostera marina L. (eelgrass) was investigated to elucidate the impact of light/dark transitions on sucrose partitioning between roots and shoots. After exposure of leaves to C-14-bicarbonate, the level of C-14-labelled photoassimilates increased monotonically in both leaves and fully aerobic roots of plants maintained in the light. Accumulation of C-14 in roots and leaves ceased abruptly when plants were transferred to darkness that induced root anaerobiosis even though C-14 levels remained high in the dark-exposed leaves. Thus, translocation of C-14 photoassimilates from shoots to roots was inhibited when roots became anoxic. Anoxia induced by light …

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Biogenic Matter Diagenesis On The Sea Floor: A Comparison Between Two Continental Margin Transects, William M. Berelson, Jim Mcmanus, Kenneth H. Coale, Kenneth S. Johnson, Tammy Kilgore, David J. Burdige, Cynthia Pilskaln Jan 1996

Biogenic Matter Diagenesis On The Sea Floor: A Comparison Between Two Continental Margin Transects, William M. Berelson, Jim Mcmanus, Kenneth H. Coale, Kenneth S. Johnson, Tammy Kilgore, David J. Burdige, Cynthia Pilskaln

OES Faculty Publications

Benthic chamber measurements of the reactants and products involved with biogenic matter diagenesis (oxygen, ammonium, nitrate, silicate, phosphate, TCO2, alkalinity) were used to define fluxes of these solutes into and out of the sediments off southern and central California. Onshore to offshore transects indicate many similarities in benthic fluxes between these regions. The pattern of benthic organic carbon oxidation as a function of water depth, combined with published sediment trap records, suggest that the supply of organic carbon from vertical rain can just meet the sedimentary carbon oxidation + burial demand for the central California region between the …

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Development And Lipid Composition Of The Harpacticoid Copepod Nitocra Spinipes Reared On Different Diets, Gregory M. Weiss, George B. Mcmanus, H. Rodger Harvey Jan 1996

Development And Lipid Composition Of The Harpacticoid Copepod Nitocra Spinipes Reared On Different Diets, Gregory M. Weiss, George B. Mcmanus, H. Rodger Harvey

OES Faculty Publications

We reared the harpacticoid copepod Nitocra spinipes on diets of bacteria, a diatom, or a macroalga, evaluating survivorship and growth in short-term (≤ 1 generation) experiments. Lipid content of the copepods and their diets was measured and used as an index of nutrition. Although growth, survivorship and lipid content of N. spinipes were significantly greater when fed the diatom, which had the highest lipid content of the 3 diets, the copepod was able to develop from egg to adult when fed a lipid- poor bacterial diet. Furthermore, this species was able to go through developmental molts without the addition of …

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The Effect Of Atomic Hydrogen On The Growth Of Gallium Nitride By Molecular Beam Epitaxy, Zhonghai Yu, S. L. Buczkowski, N. C. Giles, T. H. Myers, Michelle Richards-Babb Jan 1996

The Effect Of Atomic Hydrogen On The Growth Of Gallium Nitride By Molecular Beam Epitaxy, Zhonghai Yu, S. L. Buczkowski, N. C. Giles, T. H. Myers, Michelle Richards-Babb

Faculty & Staff Scholarship

GaN was grown by molecular beam epitaxy using an rf plasma source. Growth under gallium‐rich conditions at 730 °C was required to produce high quality layers as indicated by photoluminescence, Hall effect, atomic force microscopy, and x‐ray diffraction measurements. Atomic hydrogen has a significant effect for Ga‐rich growth, increasing growth rates by as much as a factor of 2.

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Combinatorial Approaches For Hard Problems In Manpower Scheduling, Hoong Chuin Lau Jan 1996

Combinatorial Approaches For Hard Problems In Manpower Scheduling, Hoong Chuin Lau

Research Collection School Of Computing and Information Systems

Manpower scheduling is concerned with the construction of a workers' schedule which meets demands while satisfying given constraints. We consider a manpower scheduling Problem, called the Change Shift Assignment Problem(CSAP). In previous work, we proved that CSAP is NP-hard and presented greedy methods to solve some restricted versions. In this paper, we present combinatorial algorithms to solve more general and realistic versions of CSAP which are unlikely solvable by greedy methods. First, we model CSAP as a fixed-charge network and show that a feasible schedule can be obtained by finding disjoint paths in the network, which can be derived from …

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Tau Leptonic Branching Ratios, D. Buskulic, M. Thulasidas Jan 1996

Tau Leptonic Branching Ratios, D. Buskulic, M. Thulasidas

Research Collection School Of Computing and Information Systems

A sample of 62249 τ-pair events is selected from data taken with the ALEPH detector in 1991, 1992 and 1993. The measurement of the branching fractions for τ decays into electrons and muons is presented with emphasis on the study of systematic effects from selection, particle identification and decay classification. The results obtained are: B e = 17.79±0.12(stat)±0.06(syst)(%) and Bμ = 17.31±0.11(stat)±0.05(syst)(%). Combined with the most recent ALEPH determination of the τ lifetime, these results provide a relative measurement of the leptonic couplings in the weak charged current for transverse W bosons: ${cal G}_{ώ}/{cal G}_{e}=1.0002pm 0.0051$ and ${cal G}_{∢u}/{cal G}_{u}=0.9943pm …

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Time- And Cost-Optimal Parallel Algorithms For The Dominance And Visibility Graphs, D. Bhagavathi, H. Gurla, S. Olariu, J. L. Schwing, J. Zhang Jan 1996

Time- And Cost-Optimal Parallel Algorithms For The Dominance And Visibility Graphs, D. Bhagavathi, H. Gurla, S. Olariu, J. L. Schwing, J. Zhang

Computer Science Faculty Publications

The compaction step of integrated circuit design motivates associating several kinds of graphs with a collection of non-overlapping rectangles in the plane. These graphs are intended to capture various visibility relations amongst the rectangles in the collection. The contribution of this paper is to propose time- and cost-optimal algorithms to construct two such graphs, namely, the dominance graph (DG, for short) and the visibility graph (VG, for short). Specifically, we show that with a collection of n non-overlapping rectangles as input, both these structures can be constructed in θ (log n) time using n processors in the CREW model.

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The Effects Of A Regulatory Gear Restriction On The Harvest Of The Recruiting Year Class In The Offshore Sea Scallop, Placopecten Magellanicus, Fishery, Jeffrey C. Brust Jan 1996

The Effects Of A Regulatory Gear Restriction On The Harvest Of The Recruiting Year Class In The Offshore Sea Scallop, Placopecten Magellanicus, Fishery, Jeffrey C. Brust

Dissertations, Theses, and Masters Projects

No abstract provided.

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Contributions To The Life History Of Juvenile Blueback Herring (Alosa Aestivalis): Phototactic Behavior And Population Dynamics, Douglas A. Dixon Jan 1996

Contributions To The Life History Of Juvenile Blueback Herring (Alosa Aestivalis): Phototactic Behavior And Population Dynamics, Douglas A. Dixon

Dissertations, Theses, and Masters Projects

This research investigated the relationship between juvenile abundance indexes (JAIs) for anadromous blueback herring (Alosa aestivalis) and abiotic factors (river flow and temperature) during the spawning and nursery period in the tidal freshwater areas of James, Pamunkey, Mattaponi, and Rappahannock Rivers in Virginia. Accomplishing this objective required the evaluation of the JAI methodology, specifically the effect of phototactic behavior on diel changes in the surface availability to the pushnet sampling gear, and obtaining population dynamics information (hatch dates, growth, natural mortality) during early life history from otolith microstructure of samples collected in 1991 and 1992. Mean catch-per-unit effort (CPUE) at …

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Temporal Variablity Of The Pycnocline In The Mid-Chesapeake Bay, Linda Jane Frizzell-Makowski Jan 1996

Temporal Variablity Of The Pycnocline In The Mid-Chesapeake Bay, Linda Jane Frizzell-Makowski

Dissertations, Theses, and Masters Projects

Mixing and dispersion in a partially mixed estuary are driven by, among other processes, the gravitational circulation, wind-events and tides. These processes are important in the vertical and horizontal distribution and exchange of salinity, oxygen, nutrients, and organisms. The objective of this research was to examine the temporal variability of the pycnocline in the mid-Chesapeake Bay in response to forcing at subtidal and higher frequencies as observed in the spring of 1993. The largest change in the pycnocline was associated with meteorological forcing. Up-Bay wind stress and subsequent abatement of the wind stress produced a 5 meter displacement of the …

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Gaseous Flux And Distribution Of Polycyclic Aromatic Hydrocarbons Across The Air-Water Interface Of Southern Chesapeake Bay, Kurt E. Gustafson Jan 1996

Gaseous Flux And Distribution Of Polycyclic Aromatic Hydrocarbons Across The Air-Water Interface Of Southern Chesapeake Bay, Kurt E. Gustafson

Dissertations, Theses, and Masters Projects

Gaseous fluxes of polycyclic aromatic hydrocarbons (PAHs) across the air-water interface of Southern Chesapeake Bay were calculated for the period January 1994 through May 1995 using a modified two-film model. Additionally, the distributions of PAHs between the vapor and aerosol phase in the atmosphere, and between the freely dissolved and suspended particulate phase in the water column were investigated. Net instantaneous gaseous fluxes of PAHs were determined to vary in direction and magnitude both spatially and temporally across the air-water interface of Southern Chesapeake Bay at four sites ranging from remote to urban and highly industrialized. The magnitude of gas …

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Modeling Storm-Induced Sediment Transport On The Inner Shelf: Effects Of Bed Microstratigraphy, Baeck Oon Kim Jan 1996

Modeling Storm-Induced Sediment Transport On The Inner Shelf: Effects Of Bed Microstratigraphy, Baeck Oon Kim

Dissertations, Theses, and Masters Projects

Sediment transport during a storm event on the inner continental shelf was detailed through the development of models based on field experiments conducted at Duck, North Carolina in October 1994. A vertical one-dimensional model (1DV model) was developed by coupling the Grant and Madsen (1986) model with bed stratigraphy to consider real seabeds. Sediment was divided into seven size classes and fractional transport was estimated. Mixing depth and total depth from a simplified sediment conservation equation provided the basis for changing bottom sediment, sediment availability for transport, and armoring processes. These processes involve a feedback between hydrodynamics and bed stratigraphy. …

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Demersal Predator Exposure To Toxic Organic Contaminants: Direct Effects Of Macrofauna In Trophic Transfer, Patrick Winfield Lay Jan 1996

Demersal Predator Exposure To Toxic Organic Contaminants: Direct Effects Of Macrofauna In Trophic Transfer, Patrick Winfield Lay

Dissertations, Theses, and Masters Projects

The bioaccumulation and metabolism of organic contaminants (PAH, PCB) by three estuarine polychaetes, Nereis succinea (Frey and Leuckart 1847), Paraprionospio pinnata (Ehlers 1901) and Polydora ligni (Webster 1879), and by the fish predator, spot (Leiostomus xanthurus Lacepede 1802), were examined in laboratory experiments. Variations in trophic transfer of these contaminants resulting from differences in prey and contaminant type were also investigated. Toxicokinetic modeling reveals that metabolism of organic contaminants by invertebrate species result in variations in uptake, metabolism and elimination rate constants. Incorporation of prey metabolism potential in kinetic models increases the latter's predictability of biota-sediment accumulation factors (BSAFs), or …

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The Development Of Affinity Maturation In Rainbow Trout Oncorhynchus Mykiss, Ing Wei Khor Jan 1996

The Development Of Affinity Maturation In Rainbow Trout Oncorhynchus Mykiss, Ing Wei Khor

Dissertations, Theses, and Masters Projects

No abstract provided.

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Lipid Class Composition Of Oysters, Crassostrea Virginica, Exposed To Sediment-Associated Pahs, Tong Li Jan 1996

Lipid Class Composition Of Oysters, Crassostrea Virginica, Exposed To Sediment-Associated Pahs, Tong Li

Dissertations, Theses, and Masters Projects

No abstract provided.

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The Influence Of Location, Seagrass Species And Water Depth On The Settlement And Distribution Of Early Stage Blue Crabs, Renee A. Pardieck Jan 1996

The Influence Of Location, Seagrass Species And Water Depth On The Settlement And Distribution Of Early Stage Blue Crabs, Renee A. Pardieck

Dissertations, Theses, and Masters Projects

No abstract provided.

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Growth Dynamics Of A York River Estuary Heterotrophic Dinoflagellate Grazing Katodinium Rotundatum, Angela Denise Smith Jan 1996

Growth Dynamics Of A York River Estuary Heterotrophic Dinoflagellate Grazing Katodinium Rotundatum, Angela Denise Smith

Dissertations, Theses, and Masters Projects

No abstract provided.

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Exchanges Of Dissolved Inorganic Nitrogen And Dissolved Organic Carbon Between Salt Marsh Sediments And Overlying Tidal Water, Betty Berry Neikirk Jan 1996

Exchanges Of Dissolved Inorganic Nitrogen And Dissolved Organic Carbon Between Salt Marsh Sediments And Overlying Tidal Water, Betty Berry Neikirk

Dissertations, Theses, and Masters Projects

No abstract provided.

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Synthesis And Characterization Of Boron-Containing Polymeric Materials For Neutron Shielding Applications, Michael B. Glasgow Jan 1996

Synthesis And Characterization Of Boron-Containing Polymeric Materials For Neutron Shielding Applications, Michael B. Glasgow

Dissertations, Theses, and Masters Projects

The development of boron-containing polymeric materials for neutron shielding applications was undertaken. Three types of materials were characterized for physical and thermal properties: boron powder-filled epoxy composites, carborane polyamides having boron chemically bonded into the polymer, and boron-loaded polyimide thin films. Addition of amorphous submicron boron powder did not affect significantly the thermal performance of the epoxy. The 17% boron loading produced a 26% increase in compressive failure strength and a 68% increase in the compressive modulus. 0.125 inch thick specimens containing 17% boron absorbed 92% of incident neutrons from a 5-Curie Pu/Be source compared with {dollar}<{dollar}1% for the neat epoxy. Dispersion of the boron in the epoxy was improved with the addition of larger size crystalline boron powders. Carborane polyamides containing up to 35% boron were thermally stable up to 400{dollar}\sp\circ{dollar}C in air. The polymers had hydrogen/boron ratios from 2.0 to 3.8 and were soluble in several organic solvents. Polymer solutions were processed into clear, colored thin films. Boron-filled polyamic acid solutions of a PMDA-ODA polyimide containing up to 10% boron were processed into thin films. Neutron absorption of the opaque films measured in a 5-Curie Pu/Be neutron source was linear with boron concentration and film thickness. The fraction of neutrons absorbed varied linearly with boron concentration and film thickness. The applicability of boron-containing materials to the aerospace, nuclear power and accelerator industries was investigated.

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Analysis Of (Iso)Surface Reconstructions: Quantitative Metrics And Methods, Tracey Allen Beauchat Jan 1996

Analysis Of (Iso)Surface Reconstructions: Quantitative Metrics And Methods, Tracey Allen Beauchat

Dissertations, Theses, and Masters Projects

Due to sampling processes volumetric data is inherently discrete and most often knowledge of the underlying continuous model is not available. Surface rendering techniques attempt to reconstruct the continuous model, using isosurfaces, from the discrete data. Therefore, it natural to ask how accurate the reconstructed isosurfaces are with respect to the underlying continuous model. A reconstructed isosurface may look impressive when rendered ("photorealism"), but how well does it reflect reality ("physical realism")?;The users of volume visualization packages must be aware of the short-comings of the algorithms used to produce the images so that they may properly interpret, and interact with, …

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Surface Reflection Hyperthermal Neutral Stream Source, Christopher A. Nichols Jan 1996

Surface Reflection Hyperthermal Neutral Stream Source, Christopher A. Nichols

Dissertations, Theses, and Masters Projects

A novel source of hyperthermal (1-30 eV) reactive neutrals based on the surface-reflection-neutralization technique is described. This source is potentially capable of minimizing the charge-induced damage associated with plasma based semiconductor processing steps. The goal of this thesis is to investigate the issues involved in scale-up of this technology for processing of 8{dollar}\sp{lcub}\prime\prime{rcub}{dollar} diameter wafers used today in the semiconductor industry. This includes modeling the plasma ion source and trajectory simulations of the reflected neutral flux. A prototype source was constructed for experimental verification of the plasma model.;An inductively coupled plasma (ICP) source is used to provide a source of …

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A Grammar-Based Technique For Genetic Search And Optimization, Clayton Matthew Johnson Jan 1996

A Grammar-Based Technique For Genetic Search And Optimization, Clayton Matthew Johnson

Dissertations, Theses, and Masters Projects

The genetic algorithm (GA) is a robust search technique which has been theoretically and empirically proven to provide efficient search for a variety of problems. Due largely to the semantic and expressive limitations of adopting a bitstring representation, however, the traditional GA has not found wide acceptance in the Artificial Intelligence community. In addition, binary chromosones can unevenly weight genetic search, reduce the effectiveness of recombination operators, make it difficult to solve problems whose solution schemata are of high order and defining length, and hinder new schema discovery in cases where chromosome-wide changes are required.;The research presented in this dissertation …

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The Meteorological Effects Of The Kuwait Oil Fires, Patrick Kevin Dowling Jan 1996

The Meteorological Effects Of The Kuwait Oil Fires, Patrick Kevin Dowling

Dissertations, Theses, and Masters Projects

No abstract provided.

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Synthesis And Characterization Of Cyclic Arylene Ether Oligomers, David Lewis Eldridge Jan 1996

Synthesis And Characterization Of Cyclic Arylene Ether Oligomers, David Lewis Eldridge

Dissertations, Theses, and Masters Projects

No abstract provided.

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Low-Valent Metal Complexes As Reductive Coupling Agents For Smoke Suppression In Poly(Vinyl Chloride), Panagiotis Ioannou Kourtesis Jan 1996

Low-Valent Metal Complexes As Reductive Coupling Agents For Smoke Suppression In Poly(Vinyl Chloride), Panagiotis Ioannou Kourtesis

Dissertations, Theses, and Masters Projects

No abstract provided.

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Spectroscopic Characterization Of Hg(Ii) Coordination Complexes, Sharon Rosemary Fitzhenry Jan 1996

Spectroscopic Characterization Of Hg(Ii) Coordination Complexes, Sharon Rosemary Fitzhenry

Dissertations, Theses, and Masters Projects

No abstract provided.

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Synthesis And Characterization Of Poly(Carborane-Sulfone), Beth Le Ogura Jan 1996

Synthesis And Characterization Of Poly(Carborane-Sulfone), Beth Le Ogura

Dissertations, Theses, and Masters Projects

No abstract provided.

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