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Physical Sciences and Mathematics

Old Dominion University

2001

Articles 1 - 14 of 14

Full-Text Articles in Engineering

Coherent Differential Absorption Lidar For Combined Measurement Of Wind And Trace Atmospheric Gases, Grady James Koch Apr 2001

Coherent Differential Absorption Lidar For Combined Measurement Of Wind And Trace Atmospheric Gases, Grady James Koch

Electrical & Computer Engineering Theses & Dissertations

A lidar system was developed for making combined range-resolved measurements of wind speed and direction, water vapor concentration, and carbon dioxide concentration in the atmosphere. This lidar combines the coherent Doppler technique for wind detection and the differential absorption lidar (DIAL) technique to provide a multifunctional capability. DIAL and coherent lidars have traditionally been thought of and implemented as separate instruments, but the research reported here has shown a demonstration of combining the coherent and DIAL techniques into a single instrument using solid-state lasers. The lasers used are of Ho:Tm:YLF, which operates at a wavelength of 2 μm. This wavelength …

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Future Research Vessels, Larry P. Atkinson Jan 2001

Future Research Vessels, Larry P. Atkinson

CCPO Publications

The academic research vessel fleet in the United States is embarking on a great experiment. By 2004 we will know if SWATH vessels such as the Mlo Moana and the possible built Woods Hole Oceanographic Institution coastal SWATH have such great advantages that all future vessels will be of SWATH design. Or, we will find that the two hull forms have distinct niches and the fleet will evolve with a strategic mix. Regardless of the Mure hull form research vessels will grow in size to accommodate advanced technology and the people to run and maintain it. The research vessel will …

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Xenon Excimer Emission From Pulsed Microhollow Cathode Discharges, M. Moselhy, R. H. Stark, K. H. Schoenbach, U. Kogelschatz Jan 2001

Xenon Excimer Emission From Pulsed Microhollow Cathode Discharges, M. Moselhy, R. H. Stark, K. H. Schoenbach, U. Kogelschatz

Bioelectrics Publications

By applying electrical pulses of 20 ns duration to xenon microplasmas, generated by direct current microhollow cathode discharges, we were able to increase the xenon excimer emission by more than an order of magnitude over direct current discharge excimer emission. For pulsed voltages in excess of 500 V, the optical power at 172 nm was found to increase exponentially with voltage. Largest values obtained were 2.75 W of vacuum-ultraviolet optical power emitted from a single microhollow cathode discharge in 400 Torr xenon with a 750 V pulse applied to a discharge. Highest radiative emittance was 15.2 W/cm2. The …

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Electron Cyclotron Resonance Heating In Spherical Plasmas: O-X-Ebw Mode Conversion In Mast, Josef Preinhaelter, M. A. Irzak, Linda L. Vahala, George Vahala Jan 2001

Electron Cyclotron Resonance Heating In Spherical Plasmas: O-X-Ebw Mode Conversion In Mast, Josef Preinhaelter, M. A. Irzak, Linda L. Vahala, George Vahala

Electrical & Computer Engineering Faculty Publications

Using a full wave solution, the O-X-EBW mode conversion is examined for density and magnetic profiles in MAST. The effects of magnetic shear and the sharp density pedestal for H-mode operation are considered with an eye to understanding both electron cyclotron emission (ECE) and electron cyclotron resonance heating (ECRH).

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Entropy Generation Method To Quantify Thermal Comfort, S. C. Boregowda, S. N. Tiwari, S. K. Chaturvedi Jan 2001

Entropy Generation Method To Quantify Thermal Comfort, S. C. Boregowda, S. N. Tiwari, S. K. Chaturvedi

Mechanical & Aerospace Engineering Faculty Publications

The present paper presents a thermodynamic approach to assess the quality of human-thermal environment interaction and quantify thermal comfort. The approach involves development of entropy generation term by applying second law of thermodynamics to the combined human-environment system. The entropy generation term combines both human thermal physiological responses and thermal environmental variables to provide an objective measure of thermal comfort. The original concepts and definitions form the basis for establishing the mathematical relationship between thermal comfort and entropy generation term. As a result of logic and deterministic approach, an Objective Thermal Comfort Index (OTCI) is defined and established as a …

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Time-Resolved Structural Study Of Low-Index Surfaces Of Germanium Near Its Bulk Melting Temperature, Xinglin Zeng, H. E. Elsayed-Ali Jan 2001

Time-Resolved Structural Study Of Low-Index Surfaces Of Germanium Near Its Bulk Melting Temperature, Xinglin Zeng, H. E. Elsayed-Ali

Electrical & Computer Engineering Faculty Publications

The structure of the low-index surfaces of germanium near its bulk melting temperature is investigated using 100-ps time-resolved reflection high-energy electron diffraction. The surface is heated by 100-ps laser pulses while a synchronized electron beam probes the structure. Ge(111)was observed to remain in its incomplete melting structure up to at least Tm + 134 ± 40 K when heated by a 100-ps laser pulse. Both the Ge(100) and Ge(110) surfaces are observed to melt near the bulk melting temperature when heated with 100-ps laser pulses. Because of the low-diffraction intensity-to-background ratio at high temperatures and because of the temperature …

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Stm And Electrochemical Investigation Of Homoepitaxial Boron-Doped Cvd Diamond Films, John B. Cooper, Jason A. Moulton, Sacharia Albin, Bing Xiao Jan 2001

Stm And Electrochemical Investigation Of Homoepitaxial Boron-Doped Cvd Diamond Films, John B. Cooper, Jason A. Moulton, Sacharia Albin, Bing Xiao

Chemistry & Biochemistry Faculty Publications

Homoepitaxial growth of boron-doped CVD diamond films was carried out on (100) and (111) oriented substrates. Atomic resolution images were obtained for both (100) and (111) surfaces using scanning tunneling microscopy. STM images reveal the presence of a 2x1-monohydride reconstruction for the untreated (100) surface and a lxl reconstruction for the untreated (111) surface. No other atomically resolved reconstructions were observed under a wide range of growth conditions. Non-aqueous electrochemical investigations were carried out on the films exhibiting atomically resolved reconstructions. Evidence for potential-induced surface-reconstruction and surface chemical modification of the (100) 2xl-monohydride surface has been observed.

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A Model To Evaluate The Effect Of Organizational Adaptation, Holly A. H. Handley, Alexander H. Levis Jan 2001

A Model To Evaluate The Effect Of Organizational Adaptation, Holly A. H. Handley, Alexander H. Levis

Engineering Management & Systems Engineering Faculty Publications

When an organization’s output declines due to either internal changes or changes in its external environment, it needs to adapt. In order to evaluate the effectiveness of different adaptation strategies on organizational per- formance, an organizational model composed of individual models of a five stage interacting decision maker was designed using an object oriented design approach and implemented as a Colored Petri net. The concept of entropy is used to calculate the total activity value, a surrogate for decision maker workload, based on the functional partition and the adaptation strategy being implemented. The individual decision maker’s total activity is monitored, …

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Boron-Doped Homoepitaxial Diamond (100) Film Investigated By Scanning Tunneling Microscopy, Bing Xiao, Weihai Fu, Sacharia Albin, Jason Moulton, John Cooper Jan 2001

Boron-Doped Homoepitaxial Diamond (100) Film Investigated By Scanning Tunneling Microscopy, Bing Xiao, Weihai Fu, Sacharia Albin, Jason Moulton, John Cooper

Electrical & Computer Engineering Faculty Publications

Conducting epitaxial diamond films of high quality are essential for many diamond studies and diamond electronic device fabrication. We have grown boron-doped epitaxial diamond films on type Ila natural diamond (100) substrates by microwave plasma chemical vapor deposition. A gas mixture of H2/CH4 was used. Boron doping was done by placing solid sources of pure boron in the microwave plasma. Homoepitaxial films with atomic smoothness were achieved under the following growth conditions: substrate temperature 900 °C, gas pressure 40 Torr, and gas flow rates of H2/CH4 = 900/7.2 seem. The growth rate was 0.87 …

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Resonant Energy Transfer From Argon Dimers To Atomic Oxygen In Microhollow Cathode Discharges, M. Moselhy, R. H. Stark, K. H. Schoenbach, U. Kogelschatz Jan 2001

Resonant Energy Transfer From Argon Dimers To Atomic Oxygen In Microhollow Cathode Discharges, M. Moselhy, R. H. Stark, K. H. Schoenbach, U. Kogelschatz

Bioelectrics Publications

The emission of atomic oxygen lines at 130.2 and 130.5 nm from a microhollow cathode discharge in argon with oxygen added indicates resonant energy transfer from argon dimers to oxygen atoms. The internal efficiency of the vacuum-ultraviolet (VUV) radiation was measured as 0.7% for a discharge in 1100 Torr argon with 0.1% oxygen added. The direct current VUV point source operates at voltages below 300 V and at current levels of milliamperes.

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Arc - An Oai Service Provider For Digital Library Federation, Xiaoming Liu, Kurt Maly, Mohammad Zubair, Michael L. Nelson Jan 2001

Arc - An Oai Service Provider For Digital Library Federation, Xiaoming Liu, Kurt Maly, Mohammad Zubair, Michael L. Nelson

Computer Science Faculty Publications

The usefulness of the many on-line journals and scientific digital libraries that exist today is limited by the inability to federate these resources through a unified interface. The Open Archive Initiative (OAI) is one major effort to address technical interoperability among distributed archives. The objective of OAI is to develop a framework to facilitate the discovery of content in distributed archives. In this paper, we describe our experience and lessons learned in building Arc, the first federated searching service based on the OAI protocol. Arc harvests metadata from several OAI compliant archives, normalizes them, and stores them in a search …

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Buckets: Smart Objects For Digital Libraries, Michael L. Nelson Jan 2001

Buckets: Smart Objects For Digital Libraries, Michael L. Nelson

Computer Science Faculty Publications

Current discussion of digital libraries (DLs) is often dominated by the merits of the respective storage, search and retrieval functionality of archives, repositories, search engines, search interfaces and database systems. While these technologies are necessary for information management, the information content is more important than the systems used for its storage and retrieval. Digital information should have the same long-term survivability prospects as traditional hardcopy information and should be protected to the extent possible from evolving search engine technologies and vendor vagaries in database management systems. Information content and information retrieval systems should progress on independent paths and make limited …

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A New Compensating Element For A Femtosecond Photoelectron Gun, Bao-Liang Qian, Hani E. Elsayed-Ali Jan 2001

A New Compensating Element For A Femtosecond Photoelectron Gun, Bao-Liang Qian, Hani E. Elsayed-Ali

Electrical & Computer Engineering Faculty Publications

Design and analysis of a new compensating element for improving the electron pulse front and compressing the pulse duration in a femtosecond photoelectron gun are described. The compensating element is a small metallic cylindrical cavity in which an external voltage is applied in such a way that a special electric field forms and interacts with the electron pulse. This electric field reduces the distances between the faster and slower electrons inside the cavity and efficiently compensates for electron pulse broadening caused by the photoelectron energy spread and space charge effects. Poisson's equation and the equation of motion are solved to …

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Smart Objects And Open Archives, Michael L. Nelson, Kurt Maly Jan 2001

Smart Objects And Open Archives, Michael L. Nelson, Kurt Maly

Computer Science Faculty Publications

Within the context of digital libraries (DLs), we are making information objects "first-class citizens". We decouple information objects from the systems used for their storage and retrieval, allowing the technology for both DLs and information content to progress independently. We believe dismantling the stovepipe of "DL-archive-content" is the first step in building richer DL experiences for users and insuring the long-term survivability of digital information. To demonstrate this partitioning between DLs, archives and information content, we introduce "buckets": aggregative, intelligent, object-oriented constructs for publishing in digital libraries. Buckets exist within the "Smart Object, Dumb Archive" (SODA) DL model, which promotes …

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