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Articles 781 - 810 of 1876
Full-Text Articles in Physical Sciences and Mathematics
Spatial Variations In Benthic Invertebrate Assemblages In And Around The Georges Banks Closed Areas, Andrew Clayton Walker
Spatial Variations In Benthic Invertebrate Assemblages In And Around The Georges Banks Closed Areas, Andrew Clayton Walker
Dissertations, Theses, and Masters Projects
No abstract provided.
Documenting The Suspended And Bottom Sediment Dynamics Of A Two Estuarine Turbidity Maximum System Using 7be And 234th, Heidi M. Romine
Documenting The Suspended And Bottom Sediment Dynamics Of A Two Estuarine Turbidity Maximum System Using 7be And 234th, Heidi M. Romine
Dissertations, Theses, and Masters Projects
No abstract provided.
Spontaneous Pulse Formation In Bistable Systems, George A. Andrews
Spontaneous Pulse Formation In Bistable Systems, George A. Andrews
Dissertations, Theses, and Masters Projects
This thesis considers localized spontaneous pulse formation in nonlinear, dissipative systems that are far from equilibrium and which exhibit bistability. It is shown that such pulses can form in systems that are dominated by the combined effects of: (1) a saturable amplifying or gain region, (2) a saturable absorbing or loss region, and (3) cavity effects. Analysis is based upon novel models for both an inertialess material in which the absorber responds instantaneously and inertial material in which there is temporal delay in the response. Additionally, we include the situation where the material does not fully relax between pulses, i.e. …
Solid State Nmr Characterization Of Conductive Polyanilines, Yanina Anatolievna Goddard
Solid State Nmr Characterization Of Conductive Polyanilines, Yanina Anatolievna Goddard
Dissertations, Theses, and Masters Projects
Different forms of ring deuterated polyaniline with different conductivity have been characterized by solid state deuteron nuclear magnetic resonance.;Quadrupole echo (QE) spectra of all forms of polyaniline consist of a superposition of lineshapes for nearly rigid aromatic rings and a small fraction of rings which undergo fast 180?? flips. The intensity of the fast flipping component is temperature dependent and different for conductive emeraldine salt (ES) and non-conductive emeraldine base (EB). This is a manifestation of the different structure and morphology of these polymers.;Simultaneous measurements of QE lineshapes and the relaxation time anisotropies allowed an accurate description of motion in …
Structural Model Checking, Radu Siminiceanu
Structural Model Checking, Radu Siminiceanu
Dissertations, Theses, and Masters Projects
The introduction of symbolic approaches, based on Binary Decision Diagrams (BDD), to Model Checking has led to significant improvements in Formal Verification, by allowing the analysis of very large systems, such as complex circuit designs. These were previously beyond the reach of traditional, explicit methods, due to the state space explosion phenomenon. However, after the initial success, the BDD technology has peaked, due to a similar problem, the BDD explosion.;We present a new approach to symbolic Model Checking that is based on exploiting the system structure. This technique is characterized by several unique features, including an encoding of states with …
Runtime Support For Load Balancing Of Parallel Adaptive And Irregular Applications, Kevin James Barker
Runtime Support For Load Balancing Of Parallel Adaptive And Irregular Applications, Kevin James Barker
Dissertations, Theses, and Masters Projects
Applications critical to today's engineering research often must make use of the increased memory and processing power of a parallel machine. While advances in architecture design are leading to more and more powerful parallel systems, the software tools needed to realize their full potential are in a much less advanced state. In particular, efficient, robust, and high-performance runtime support software is critical in the area of dynamic load balancing. While the load balancing of loosely synchronous codes, such as field solvers, has been studied extensively for the past 15 years, there exists a class of problems, known as asynchronous and …
Building Internet Caching Systems For Streaming Media Delivery, Songqing Chen
Building Internet Caching Systems For Streaming Media Delivery, Songqing Chen
Dissertations, Theses, and Masters Projects
The proxy has been widely and successfully used to cache the static Web objects fetched by a client so that the subsequent clients requesting the same Web objects can be served directly from the proxy instead of other sources faraway, thus reducing the server's load, the network traffic and the client response time. However, with the dramatic increase of streaming media objects emerging on the Internet, the existing proxy cannot efficiently deliver them due to their large sizes and client real time requirements.;In this dissertation, we design, implement, and evaluate cost-effective and high performance proxy-based Internet caching systems for streaming …
Lookahead Scheduling In A Real-Time Context: Models, Algorithms, And Analysis, Benjamin J. Coleman
Lookahead Scheduling In A Real-Time Context: Models, Algorithms, And Analysis, Benjamin J. Coleman
Dissertations, Theses, and Masters Projects
Our research considers job scheduling, a special type of resource assignment problem. For example, at a cross-docking facility trucks must be assigned to doors where they will be unloaded. The cargo on each truck has various destinations within the facility, and the unloading time for a truck is dependent on the distance from the assigned door to these destinations. The goal is to assign the trucks to doors while minimizing the amount of time to unload all trucks.;We study scheduling algorithms for problems like the cross-docking example that are different from traditional algorithms in two ways. First, we utilize real-time, …
Binding Studies On Molecularly Imprinted Polymers, Lucy Yue Hu
Binding Studies On Molecularly Imprinted Polymers, Lucy Yue Hu
Dissertations, Theses, and Masters Projects
Molecular imprinting is a rapidly developing technique for preparation of polymeric materials that are capable of molecular recognition for selective separation and chemical identification. to prepare molecularly imprinted polymers (MIPs), a functional monomer and a crosslinker are polymerized in the presence of a template molecule. Then the template is extracted leaving sites which are complementary in both shape and chemical functionality to those of the template. This resin then becomes capable of selectively absorbing the template species. Because of MIPs' stability, predesigned selectivity, and easy preparation, they have been used for separation, sensor, drug development and directed synthesis.;In this study, …
Optimizing Combat Capabilities By Modeling Combat As A Complex Adaptive System, Steven Mains
Optimizing Combat Capabilities By Modeling Combat As A Complex Adaptive System, Steven Mains
Dissertations, Theses, and Masters Projects
Procuring combat systems in the Department of Defense is a balancing act where many variables, only some under control of the department, shift simultaneously. Technology changes non-linearly, providing new opportunities and new challenges to the existing and potential force. Money available changes year over year to fit into the overall US Government budget. Numbers of employees change through political demands rather than by cost-effectiveness considerations. The intent is to provide the best mix of equipment to field the best force against an expected enemy while maintaining adequate capability against the unexpected. Confounding this desire is the inability of current simulations …
Files As First-Class Objects In Fault -Tolerant Concurrent Systems, Robert Edwin Matthews
Files As First-Class Objects In Fault -Tolerant Concurrent Systems, Robert Edwin Matthews
Dissertations, Theses, and Masters Projects
Concurrent systems are used in applications where multiple processors are needed to complete tasks within a reasonable amount of time, or where the data sets involved will not fit within the main memory of a single computer. Because of their reliance on multiple machines, such systems are proportionally more vulnerable to both hardware and software induced failures. Fault-tolerance schemes are used to recover some earlier consistent state of the system after such a failure.;One important technique used to achieve fault-tolerance is checkpointing and rollback-recovery. In this thesis, we present a method for efficiently and transparently incorporating the part of the …
Studies Of Pentaquarks And Of Noncommutative Field Theory, Vahagn Nazaryan
Studies Of Pentaquarks And Of Noncommutative Field Theory, Vahagn Nazaryan
Dissertations, Theses, and Masters Projects
Several experiments reported seeing evidence in their data of a new particle, the strangeness +1 Theta+ pentaquark made of four quarks and an antiquark. In the first few chapters of this dissertation we study four-quark-antiquark systems within the framework of a constituent quark model. We describe the Theta+ as a member of a spin-½ pentaquark antidecuplet. For both parity-odd, and parity-even antidecuplets we derive useful decompositions of the quark model wave functions that allow for easy computation of color-flavor-spin-orbital matrix elements, and we compute mass splittings within the antidecuplet. We study parity-even antidecuplet in an effective theory with dominant flavor-spin …
Ultraviolet Sources For Advanced Applications In The Vacuum Uv And Near Uv, Sheng Peng
Ultraviolet Sources For Advanced Applications In The Vacuum Uv And Near Uv, Sheng Peng
Dissertations, Theses, and Masters Projects
This dissertation documents a systematic study consisting of experimental investigations and theoretical analyses of intense ultraviolet sources in VUV and near-UV. Some engineering issues regarding two prototypes of electrodeless lamps using rf and microwave are discussed.;Various excimers that produce intense UV light are investigated, including: (1) A benchmark Xe2 excimer which has been proven to be very efficient in our novel rf capacitively coupled discharge lamp; (2) A rarely studied excimer, KrI, which suffers from predissociation and was reported to be very weak or invisible by most of other studies; (3) XeI excimer whose emission dominates around 253 nm and …
Efficient Caching Algorithms For Memory Management In Computer Systems, Song Jiang
Efficient Caching Algorithms For Memory Management In Computer Systems, Song Jiang
Dissertations, Theses, and Masters Projects
As disk performance continues to lag behind that of memory systems and processors, fully utilizing memory to reduce disk accesses is a highly effective effort to improve the entire system performance. Furthermore, to serve the applications running on a computer in distributed systems, not only the local memory but also the memory on remote servers must be effectively managed to minimize I/O operations. The critical challenges in an effective memory cache management include: (1) Insightfully understanding and quantifying the locality inherent in the memory access requests; (2) Effectively utilizing the locality information in replacement algorithms; (3) Intelligently placing and replacing …
Stability At Hydrothermal-Vent Mussel Beds: Dynamics At Hydrothermal Vents: Evidence For Stable Macrofaunal Communities In Mussel Beds On The Northern East Pacific Rise, Jennifer Carolyn Dreyer
Stability At Hydrothermal-Vent Mussel Beds: Dynamics At Hydrothermal Vents: Evidence For Stable Macrofaunal Communities In Mussel Beds On The Northern East Pacific Rise, Jennifer Carolyn Dreyer
Dissertations, Theses, and Masters Projects
No abstract provided.
Diet Of The Sandbar Shark, Carcharhinus Plumbeus, In Chesapeake Bay And Adjacent Waters, Julia K. Ellis
Diet Of The Sandbar Shark, Carcharhinus Plumbeus, In Chesapeake Bay And Adjacent Waters, Julia K. Ellis
Dissertations, Theses, and Masters Projects
The sandbar shark, Carcharhinus plumbeus, is the most abundant large coastal shark in the temperate and tropical waters of the northwest Atlantic Ocean. The Chesapeake Bay, Virginia and adjacent waters serve as a nursery ground for C. plumbeus as well as many other fauna. Characterizing the diet of a higher trophic level predator such as the sandbar shark sheds light on a small portion of the temporally and spatially complex food web in the Bay. This study describes the diet of the sandbar shark, highlighting differences in diet within various portions of the nursery area, as well as ontogenetic changes …
Persistent Organic Pollutants At The Base Of The Antarctic Marine Food Web, Amy Lee Chiuchiolo
Persistent Organic Pollutants At The Base Of The Antarctic Marine Food Web, Amy Lee Chiuchiolo
Dissertations, Theses, and Masters Projects
No abstract provided.
Bioavailability Of Polybrominated Diphenyl Ethers (Pbdes) In Biosolids And Spiked Sediment To The Aquatic Worm Lumbriculus Variegatus, Serena Ciparis
Bioavailability Of Polybrominated Diphenyl Ethers (Pbdes) In Biosolids And Spiked Sediment To The Aquatic Worm Lumbriculus Variegatus, Serena Ciparis
Dissertations, Theses, and Masters Projects
No abstract provided.
Availability Of Humic Nitrogen To Phytoplankton, Jason Holt See
Availability Of Humic Nitrogen To Phytoplankton, Jason Holt See
Dissertations, Theses, and Masters Projects
The chemical, physical, and biological factors affecting the bioavailability of humic nitrogen (N) to coastal phytoplankton were examined. Historically, humic substances have largely been considered biologically refractory, and humic-N is though to be unavailable biologically without prior oxidation via photochemical cleavage or remineralization by bacteria. This is due in part to the high aromaticity and low N content of humic substances. This dissertation investigates whether these assumptions are valid, and whether humic substances may be a more important source of N to the coastal phytoplankton community than previously believed. The research consisted of four main parts. First, changes in the …
A Parallel Two Dimensional Delaunay Decoupling Method, Leonidas Linardakis
A Parallel Two Dimensional Delaunay Decoupling Method, Leonidas Linardakis
Dissertations, Theses, and Masters Projects
No abstract provided.
Chemical Bonding In Hard And Elastic Amorphous Carbon-Nitride Films, W. Jason Gammon
Chemical Bonding In Hard And Elastic Amorphous Carbon-Nitride Films, W. Jason Gammon
Dissertations, Theses, and Masters Projects
In this study, the chemical bonding in hard and elastic amorphous carbon nitride (a-CNx) films is investigated with x-ray photoelectron spectroscopy (XPS) and 15N, 13C, and 1H nuclear magnetic resonance (NMR) spectroscopy. The films were deposited by DC Magnetron sputtering in a pure nitrogen discharge on Si(001) substrates at 300--400??C. Nanoindentation measurements reveal an elastic modulus of ∼50 GPa and a hardness of ∼5 GPa, thus confirming our films are highly elastic but resist plastic deformation.;Our 13C NMR study demonstrates the absence of sp 3-bonded carbon in this material. Collectively, our N(1s) XPS, 13C NMR, and 15N NMR data suggest …
Microbial Dynamics And Biogeochemistry In The North Pacific Subtropical Gyre, Matthew J. Church
Microbial Dynamics And Biogeochemistry In The North Pacific Subtropical Gyre, Matthew J. Church
Dissertations, Theses, and Masters Projects
The research presented in this dissertation describes the influence of planktonic bacterial growth on upper ocean organic matter dynamics in the North Pacific Subtropical Gyre (NPSG). Examination of the temporal dynamics in dissolved organic matter (DOM) was coupled with investigations that targeted the influence of heterotrophic bacterial production (HBP) on organic matter fluxes in the NPSG. Nine cruises to the Hawaii Ocean Time-series field site Station ALOHA revealed that HBP accounted for a large flux of organic carbon in the upper ocean of the NPSG. HBP was significantly enhanced by sunlight, with photoenhancement of HBP accounting for 3.2 mol C …
Effects Of Sediment Characteristics On The Distribution Of Fiddler Crabs (Uca Spp) At Goodwin Island, Virginia, Landon Alan Ward
Effects Of Sediment Characteristics On The Distribution Of Fiddler Crabs (Uca Spp) At Goodwin Island, Virginia, Landon Alan Ward
Dissertations, Theses, and Masters Projects
No abstract provided.
Synthetic And Mechanistic Studies Of Poly(Vinyl Chloride) And Some Other Chlorinated Polymers, Xianlong Ge
Synthetic And Mechanistic Studies Of Poly(Vinyl Chloride) And Some Other Chlorinated Polymers, Xianlong Ge
Dissertations, Theses, and Masters Projects
Unlike vinyl chloride, 1,2-dichloroethylene (DCE) experienced dimerization under free-radical conditions. Chain transfer to DCE by beta-Cl elimination was shown to be the major reason for its nonpolymerization.;During the chlorination of alkyl chlorides with molecular chlorine, the involvement of a bridged intermediate led to the formation of vicinal chlorides as the major products. The yields of geminal chlorides increased significantly in the presence of solvents that form complexes with chlorine atoms, but such solvents also decreased the reactivity of the chlorination. Thus the chlorination of poly(vinyl chloride) (PVC) in the presence of complexing solvents was not a useful method for the …
Domain And Type Enforcement In Linux, Serge Edward Hallyn
Domain And Type Enforcement In Linux, Serge Edward Hallyn
Dissertations, Theses, and Masters Projects
Domain and Type Enforcement (DTE) is a simple and well-known access control system, which has been used at the microkernel level in SPIN, the kernel level in Unix, and the user-space library level in CORBA. This work implements DTE as a Linux Security Module, and provides tools for the composition and analysis of policies. The goal is to bring Mandatory Access Control in Linux to the level of ease of use of cryptography tools and libraries.;Tools have been created to edit DTE policies and query transitions through different privilege levels. A subtle modification of the Bell LaPadula (BLP) access control …
Relationships Between Watershed Characteristics And Base Flow Nutrient Discharges To Eastern Shore Coastal Lagoons, Virginia, Jennifer Wu Stanhope
Relationships Between Watershed Characteristics And Base Flow Nutrient Discharges To Eastern Shore Coastal Lagoons, Virginia, Jennifer Wu Stanhope
Dissertations, Theses, and Masters Projects
No abstract provided.
A Genetic Analysis Of The Intraspecific Relationships Of Tropical Marine Shorefishes Common To Bermuda And The Southeastern Atlantic Coast Of The United States, Kelly R. Johnson
A Genetic Analysis Of The Intraspecific Relationships Of Tropical Marine Shorefishes Common To Bermuda And The Southeastern Atlantic Coast Of The United States, Kelly R. Johnson
Dissertations, Theses, and Masters Projects
No abstract provided.
Controls On The Delivery Of Fluvial Sediment To The Coastal Ocean: The Salinas River, California, Katherine L. Farnsworth
Controls On The Delivery Of Fluvial Sediment To The Coastal Ocean: The Salinas River, California, Katherine L. Farnsworth
Dissertations, Theses, and Masters Projects
To estimate delivery to the coastal ocean, a global river database was assembled. An estimated 35,000 km3 of freshwater, 4 * 10 6 tonnes of dissolved solids and 18.6 * 106 tonnes of suspended sediment are delivered annually. The global delivery of fluvial water and sediment, both suspended and dissolved, is dominated by Southeast Asia, due to the unique climatic, geologic and geomorphic character of the rivers in this region. Over 30% of the global freshwater and dissolved solid discharge, and an astounding 70% of the suspended sediment originate in this region. The Salinas River, central California, was the focus …
Location Management In A Mobile Object Runtime Environment, Andriy Fedorov
Location Management In A Mobile Object Runtime Environment, Andriy Fedorov
Dissertations, Theses, and Masters Projects
No abstract provided.
Measurement Of The Neutron (Helium-3) Spin Structure Functions At Low 4-Momentum: A Connection Between The Bjorken And Gerasimov-Drell-Hearn Sum Rule, Pibero Kisa Djawotho
Measurement Of The Neutron (Helium-3) Spin Structure Functions At Low 4-Momentum: A Connection Between The Bjorken And Gerasimov-Drell-Hearn Sum Rule, Pibero Kisa Djawotho
Dissertations, Theses, and Masters Projects
This dissertation presents results of experiment E94-010 performed at Jefferson Laboratory (simply known as JLab) in Hall A.;The experiment aimed to measure the low Q2 evolution of the Gerasimov-DrellHearn (GDH) integral from Q 2 = 0.1 to 0.9 GeV2. The GDH sum rule at the real photon point provides an important test of Quantum Chromodynamics (QCD). The low Q2 evolution of the GDH integral contests various resonance models, Chiral Perturbation Theory (chiPT) and lattice QCD calculations, but more importantly, it helps us understand the transition between partonic and hadronic degrees of freedom. at high Q2, beyond 1 GeV2, the difference …