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The 2.6 Angstrom resolution structure of Rhodobacter capsulatus bacterioferritin with metal-free dinuclear site and heme iron in a crystallographic 'special position' (open access)

The 2.6 Angstrom resolution structure of Rhodobacter capsulatus bacterioferritin with metal-free dinuclear site and heme iron in a crystallographic 'special position'

None
Date: October 31, 2001
Creator: Cobessi, D.; Huang, L.-S.; Ban, M.; Pon, N. G.; Daldal, F. & Berry, E. A.
System: The UNT Digital Library
Adaptive Position and Orientation Regulation for the Camera-in-hand Problem (open access)

Adaptive Position and Orientation Regulation for the Camera-in-hand Problem

None
Date: May 31, 2001
Creator: Setlur, P
System: The UNT Digital Library
CALIBRATION OF A VERTICAL-SCAN LONG TRACE PROFILER AT MSFC. (open access)

CALIBRATION OF A VERTICAL-SCAN LONG TRACE PROFILER AT MSFC.

The long trace profiler (LTP) is the instrument of choice for the surface figure measurement of grazing incidence mirrors. The modification of conventional LTP, the vertical-scan LTP, capable of measuring the surface figure of replicated shell mirrors is now in operation at Marshall Space Flight Center. A few sources of systematic error for vertical-scan LTP are discussed. Status of systematic error reduction is reported.
Date: July 31, 2001
Creator: GUBAREV,M.; KESTER,T. & TAKACS,P.Z.
System: The UNT Digital Library
The China Motor Systems Energy Conservation Program: A major national initiative to reduce motor system energy use in China (open access)

The China Motor Systems Energy Conservation Program: A major national initiative to reduce motor system energy use in China

Electric motor systems are widely used in China to power fans, pumps, blowers, air compressors, refrigeration compressors, conveyers, machinery, and many other types of equipment. Overall, electric motor systems consume more than 600 billion kWh annually, accounting for more than 50 percent of China's electricity use. There are large opportunities to improve the efficiency of motor systems. Electric motors in China are approximately 2-4 percent less efficient on average than motors in the U.S. and Canada. Fans and pumps in China are approximately 3-5 percent less efficient than in developed countries. Even more importantly, motors, fans, pumps, air compressors and other motor-driven equipment are frequently applied with little attention to system efficiency. More optimized design, including appropriate sizing and use of speed control strategies, can reduce energy use by 20 percent or more in many applications. Unfortunately, few Chinese enterprises use or even know about these energy-saving practices. Opportunities for motor system improvements are probably greater in China than in the U.S. In order to begin capturing these savings, China is establishing a China Motor Systems Energy Conservation Program. Elements of this program include work to develop minimum efficiency standards for motors, a voluntary ''green motor'' labeling program for high-efficiency …
Date: May 31, 2001
Creator: Nadel, Steven; Wang, Wanxing; Liu, Peter & McKane, Aimee T.
System: The UNT Digital Library
Conditions Around the Proton Beam Window of the Spallation Neutron Source (open access)

Conditions Around the Proton Beam Window of the Spallation Neutron Source

A proton beam window separates regions with different vacuum conditions in the last part of the path of the proton beam. Very near to the window an instrumentation box for beam diagnostics is going to be located. All components comprising the proton beam window assembly are going to be located in a box, which has to be serviced regularly through a channel perpendicular to the direction of the beam (2mA 1 GeV protons). Due to the strong effects of the proton window, the engineering design of this part of the target facility requires detailed calculations of the heating and dose distributions for beam on and off conditions as a function of the materials for the window and the shielding of the instrumentation box. A summary of the results, relevant to decisions to be taken regarding the design and operation of the facility, are presented.
Date: August 31, 2001
Creator: Difilippo, FC
System: The UNT Digital Library
Controlled Velocity Testing of an 8-kW Wind Turbine (open access)

Controlled Velocity Testing of an 8-kW Wind Turbine

This paper describes a case study of the controlled-velocity test of an 8-kW wind turbine. The turbine was developed in response to the U.S. Department of Energy's small wind turbine program. As background, the prototype development is discussed. The turbine mechanical and electrical components are described. The turbine was tested on a flatbed truck and driven down an airfield runway at constant relative wind speed. Horizontal furling was used to control over-speed. Various parameters were changed to determine their effects on furling. The testing showed that the machine had insufficient rotor offset for adequate furling. Also, a rotor resonance problem was discovered and remedied. Problems associated with taking the measurements made it difficult to determine if the truck test was a suitable method for code validation. However, qualitative observations gleaned from the testing justified the effort.
Date: July 31, 2001
Creator: Larwood, S.; Sencenbaugh, J. & Acker, B.
System: The UNT Digital Library
CYP1B1 expression, a potential risk factor for breast cancer (open access)

CYP1B1 expression, a potential risk factor for breast cancer

CYP1B1 expression in non-tumor breast tissue from breast cancer patients and cancer-free individuals was determined to test the hypothesis that high CYP1B1 expression is a risk factor for breast cancer. Large interindividual variations in CYP1B1 expression were found with CYP1B1 levels notably higher in breast cancer patients than cancer-free individuals. The results indicate that CYP1B1 might play a role in breast cancer either through increased PAH activation or through metabolism of endogenous estrogen to a carcinogenic derivative.
Date: May 31, 2001
Creator: Goth-Goldstein, Regine; Erdmann, Christine A. & Russell, Marion
System: The UNT Digital Library
The D-Zero Run II Detector and physics prospects (open access)

The D-Zero Run II Detector and physics prospects

The DO Detector at Fermilab is currently undergoing an extensive upgrade to participate in the Run II data taking which shall begin on March 1, 2001. The design of the detector meets the requirements of the high luminosity environment provided by the accelerator. This paper describes the upgraded detector subsystems and gives a brief outline of the physics prospects associated with the upgrade.
Date: May 31, 2001
Creator: Parashar, Neeti
System: The UNT Digital Library
Development of a Sub-Picosecond Tunable X-Ray Source at the LLNL Electron Linac (open access)

Development of a Sub-Picosecond Tunable X-Ray Source at the LLNL Electron Linac

The use of ultrafast laser pulses to generate very high brightness, ultra short (fs to ps) pulses of x-rays is a topic of great interest to the x-ray user community. In principle, femtosecond-scale pump-probe experiments can be used to temporally resolve structural dynamics of materials on the time scale of atomic motion. The development of sub-ps x-ray pulses will make possible a wide range of materials and plasma physics studies with unprecedented time resolution. A current project at LLNL will provide such a novel x-ray source based on Thomson scattering of high power, short laser pulses with a high peak brightness, relativistic electron bunch. The system is based on a 5 mm-mrad normalized emittance photoinjector, a 100 MeV electron RF linac, and a 300 mJ, 35 fs solid-state laser system. The Thomson x-ray source produces ultra fast pulses with x-ray energies capable of probing into high-Z metals, and a high flux per pulse enabling single shot experiments. The system will also operate at a high repetition rate ({approx} 10 Hz).
Date: August 31, 2001
Creator: Slaughter, D; Springer, P; Le Sage, G; Crane, J; Ditmire, T; Cowan, T et al.
System: The UNT Digital Library
Development of Interfacial Structure in a Confined Air-Water Cap-Turbulent and Churn-Turbulent Flow (open access)

Development of Interfacial Structure in a Confined Air-Water Cap-Turbulent and Churn-Turbulent Flow

The objective of the present work is to study and model the interfacial structure development of air-water two-phase flow in a confined test section. Experiments of a total of 9 flow conditions in a cap-turbulent and churn-turbulent flow regimes are carried out in a vertical air-water upward two-phase flow experimental loop with a test section of 20-cm in width and 1-cm in gap. The miniaturized four-sensor conductivity probes are used to measure local two-phase parameters at three different elevations for each flow condition. The bubbles captured by the probes are categorized into two groups in view of the two-group interfacial area transport equation, i.e., spherical/distorted bubbles as Group 1 and cap/churn-turbulent bubbles as Group 2. The acquired parameters are time-averaged local void fraction, interfacial velocity, bubble number frequency, interfacial area concentration, and bubble Sauter mean diameter for both groups of bubbles. Also, the line-averaged and area-averaged data are presented and discussed. The comparisons of these parameters at different elevations demonstrate the development of interfacial structure along the flow direction due to bubble interactions.
Date: October 31, 2001
Creator: Sun, X.; Kim, S.; Cheng, L.; Ishii, M. & Beus, S.G.
System: The UNT Digital Library
Equivalence Ratio-EGR Control of HCCI Engine Operation and the Potential for Transition to Spark-Ignited Operation (open access)

Equivalence Ratio-EGR Control of HCCI Engine Operation and the Potential for Transition to Spark-Ignited Operation

This research investigates a control system for HCCI engines, where equivalence ratio, fraction of EGR and intake pressure are adjusted as needed to obtain satisfactory combustion. HCCI engine operation is analyzed with a detailed chemical kinetics code, HCT (Hydrodynamics, Chemistry and Transport), that has been extensively modified for application to engines. HCT is linked to an optimizer that determines the operating conditions that result in maximum brake thermal efficiency, while meeting the peak cylinder pressure restriction. The results show the values of the operating conditions that yield optimum efficiency as a function of torque and rpm. The engine has high NO{sub x} emissions for high power operation, so the possibility of switching to stoichiometric operation for high torque conditions is considered. Stoichiometric operation would allow the use of a three-way catalyst to reduce NO{sub x} emissions to acceptable levels. Finally, the paper discusses the possibility of transitioning from HCCI operation to SI operation to achieve high power output.
Date: July 31, 2001
Creator: Martinez-Frias, J; Aceves, S M; Flowers, D L; Smith, J R & Dibble, R
System: The UNT Digital Library
Evaluation of MOSFETS and IGBTS for Pulsed Power Applications (open access)

Evaluation of MOSFETS and IGBTS for Pulsed Power Applications

Single solid-state devices or arrays of solid-state devices are being incorporated into many pulsed power applications as a means of generating fast, high-power, high repetition-rate pulses and ultimately replacing hard tubes and thyratrons. While vendors' data sheets provide a starting point for selecting solid-state devices, most data sheets do not have sufficient information to determine performance in a pulsed application. To obtain this relevant information, MOSFET's and IGBT's from a number of vendors have been tested to determine rise times, fall times and current handling capabilities. The emphasis is on the evaluation of devices that can perform in the range of 100ns pulse widths and the test devices must be capable of switching 1000 volts or greater at a pulsed current of at least 25 amperes. Additionally, some devices were retest with a series magnetic switch to evaluate the effects on switching parameters and specifically rise times. All devices were evaluated under identical conditions and the complete test results are presented.
Date: May 31, 2001
Creator: Hickman, B. & Cook, E.
System: The UNT Digital Library
Experimental and numerical simulation of dissolution andprecipitation: Implications for fracture sealing at Yucca Mountain,Nevada (open access)

Experimental and numerical simulation of dissolution andprecipitation: Implications for fracture sealing at Yucca Mountain,Nevada

Plugging of flow paths caused by mineral precipitation in fractures above the potential repository at Yucca Mountain, Nevada, would reduce the probability of water seeping into the repository. As part of an ongoing effort to evaluate thermal-hydrologic-chemical (THC) effects on flow in fractured media, we performed a laboratory experiment and numerical simulations to investigate mineral dissolution and precipitation under anticipated temperature and pressure conditions in the repository. To replicate mineral dissolution by vapor condensate in fractured tuff, water was flowed through crushed Yucca Mountain tuff at 94 C. The resulting steady-state fluid composition had a total dissolved solids content of about 140 mg/L; silica was the dominant dissolved constituent. A portion of the steady-state mineralized water was flowed into a vertically oriented planar fracture in a block of welded Topopah Spring Tuff that was maintained at 80 C at the top and 130 C at the bottom. The fracture began to seal with amorphous silica within five days. A 1-D plug-flow numerical model was used to simulate mineral dissolution, and a similar model was developed to simulate the flow of mineralized water through a planar fracture, where boiling conditions led to mineral precipitation. Predicted concentrations of the major dissolved constituents …
Date: August 31, 2001
Creator: Dobson, Patrick F.; Kneafsey, Timothy J.; Sonnenthal, Eric L.; Spycher, Nicolas & Apps, John A.
System: The UNT Digital Library
A Germanium-Based, Coded Aperture Imager (open access)

A Germanium-Based, Coded Aperture Imager

We describe a coded-aperture based, gamma-ray imager that uses a unique hybrid germanium detector system. A planar, germanium strip detector, eleven millimeters thick is followed by a coaxial detector. The 19 x 19 strip detector (2 mm pitch) is used to determine the location and energy of low energy events. The location of high energy events are determined from the location of the Compton scatter in the planar detector and the energy is determined from the sum of the coaxial and planar energies. With this geometry, we obtain useful quantum efficiency in a position-sensitive mode out to 500 keV. The detector is used with a 19 x 17 URA coded aperture to obtain spectrally resolved images in the gamma-ray band. We discuss the performance of the planar detector, the hybrid system and present images taken of laboratory sources.
Date: October 31, 2001
Creator: Ziock, K P; Madden, N; Hull, E; William, C; Lavietes, T & Cork, C
System: The UNT Digital Library
Grid technologies and applications : architecture and achievements. (open access)

Grid technologies and applications : architecture and achievements.

None
Date: October 31, 2001
Creator: Foster, I.
System: The UNT Digital Library
Influence of microstructure on electrical properties of diluted GaNxAs1-x formed by nitrogen implantation (open access)

Influence of microstructure on electrical properties of diluted GaNxAs1-x formed by nitrogen implantation

None
Date: May 31, 2001
Creator: Jasinski, J.; Yu, K. M.; Walukiewicz, W.; Washburn, J. & Liliental-Weber, Z.
System: The UNT Digital Library
A Load Balanced Domain Decomposition Method Using Wavelet Analysis (open access)

A Load Balanced Domain Decomposition Method Using Wavelet Analysis

Wavelet Analysis provides an orthogonal basis set which is localized in both the physical space and the Fourier transform space. We present here a domain decomposition method that uses wavelet analysis to maintain roughly uniform error throughout the computation domain while keeping the computational work balanced in a parallel computing environment.
Date: May 31, 2001
Creator: Jameson, L; Johnson, J & Hesthaven, J
System: The UNT Digital Library
Making industrial energy efficiency mainstream and profitable: Where public benefit and private interests intersect (open access)

Making industrial energy efficiency mainstream and profitable: Where public benefit and private interests intersect

In 1996, the US Department of Energy s Office of Industrial Technologies (OIT) Motor Challenge program began a unique collaboration with industry called the Allied Partner program. Partnerships were sought with equipment suppliers and manufacturers, utilities, consultants, and state agencies that had extensive existing relationships with industrial customers. Partners were neither paid nor charged a fee for participation. The assumption was that these relationships could serve as the foundation for conveying a motor system efficiency message to many more industrial facilities than could be reached through a typical government-to-end-user program model. A substantial effort was made to engage industrial suppliers in delivering program information as part of their customer interactions. A recent independent evaluation of the Motor Challenge program attributes $16.9 million or nearly 67 percent of the total annual program energy savings to the efforts of Allied Partners in the first three years of operation.In 1997, the Compressed Air Challenge(R) (CAC) was developed as an outgrowth of the partnership concept. In this model, OIT is one of 15 sponsors who collaborated to create a national program of compressed air system training. The CAC has gone a step further by setting up a development and deployment model based on shared …
Date: May 31, 2001
Creator: McKane, Aimee T.; Tutterow, Vestal & Cockrill, Chris
System: The UNT Digital Library
Many-Body Correlations in Nuclei and Quantum Dots (open access)

Many-Body Correlations in Nuclei and Quantum Dots

Confined quantum many-body systems of a given particle number exhibit a variety of intrinsic shape characteristics as a function of increasing external field and internal thermal excitation. The shell model is an important tool for the theoretical description of these various structures and transitions in nuclei. Another system in which correlations beyond the mean field may play an important role is semiconductor quantum dots. In this Proceedings, the author compares nuclei and quantum dots and their various deformation properties. The author reports on shell-model calculations in nuclei and some recent mean-field calculations of the thermal properties of quantum dots.
Date: August 31, 2001
Creator: Dean, D. J.
System: The UNT Digital Library
Massively parallel computing simulation of fluid flow in the unsaturated zone of Yucca Mountain, Nevada (open access)

Massively parallel computing simulation of fluid flow in the unsaturated zone of Yucca Mountain, Nevada

This paper presents the application of parallel computing techniques to large-scale modeling of fluid flow in the unsaturated zone (UZ) at Yucca Mountain, Nevada. In this study, parallel computing techniques, as implemented into the TOUGH2 code, are applied in large-scale numerical simulations on a distributed-memory parallel computer. The modeling study has been conducted using an over-one-million-cell three-dimensional numerical model, which incorporates a wide variety of field data for the highly heterogeneous fractured formation at Yucca Mountain. The objective of this study is to analyze the impact of various surface infiltration scenarios (under current and possible future climates) on flow through the UZ system, using various hydrogeological conceptual models with refined grids. The results indicate that the one-million-cell models produce better resolution results and reveal some flow patterns that cannot be obtained using coarse-grid modeling models.
Date: August 31, 2001
Creator: Zhang, Keni; Wu, Yu-Shu & Bodvarsson, G. S.
System: The UNT Digital Library
Measurement of Low Level Explosives Reaction in Gauged Multi-Dimensional Steven Impact Tests (open access)

Measurement of Low Level Explosives Reaction in Gauged Multi-Dimensional Steven Impact Tests

The Steven Test was developed to determine relative impact sensitivity of metal encased solid high explosives and also be amenable to two-dimensional modeling. Low level reaction thresholds occur at impact velocities below those required for shock initiation. To assist in understanding this test, multi-dimensional gauge techniques utilizing carbon foil and carbon resistor gauges were used to measure pressure and event times. Carbon resistor gauges indicated late time low level reactions 200-540 {micro}s after projectile impact, creating 0.39-2.00 kb peak shocks centered in PBX 9501 explosives discs and a 0.60 kb peak shock in a LX-04 disk. Steven Test modeling results, based on ignition and growth criteria, are presented for two PBX 9501 scenarios: one with projectile impact velocity just under threshold (51 m/s) and one with projectile impact velocity just over threshold (55 m/s). Modeling results are presented and compared to experimental data.
Date: May 31, 2001
Creator: Niles, A M; Garcia, F; Greenwood, D W; Forbes, J W; Tarver, C M; Chidester, S K et al.
System: The UNT Digital Library
The phylogeny of Nudibranchia (Opisthobranchia, Gastropoda, Mollusca) reconstructed by three molecular markers (open access)

The phylogeny of Nudibranchia (Opisthobranchia, Gastropoda, Mollusca) reconstructed by three molecular markers

None
Date: December 31, 2001
Creator: Wollscheid-Lengeling, Evi; Boore, Jeffrey L.; Brown, Wesley M. & Wagele, Heike
System: The UNT Digital Library
Pressure Wave Measurements from Thermal Cook-Off of an HMX Based High Explosive PBX 9501 (open access)

Pressure Wave Measurements from Thermal Cook-Off of an HMX Based High Explosive PBX 9501

A better understanding of thermal cook-off is important for safe handling and storing explosive devices. A number of safety issues exist about what occurs when a cased explosive thermally cooks off. For example, violence of the events as a function of confinement are important for predictions of collateral damage. This paper demonstrates how adjacent materials can be gauged to measure the resulting pressure wave and how this wave propagates in this adjacent material. The output pulse from the thermal cook-off explosive containing fixture is of obvious interest for assessing many scenarios.
Date: May 31, 2001
Creator: Garcia, F.; Forbes, J. W.; Tarver, Craig M.; Urtiew, P. A.; Greenwood, D. W. & Vandersall, K. S.
System: The UNT Digital Library
Quantum Algorithm for Continuous Global Optimization (open access)

Quantum Algorithm for Continuous Global Optimization

We investigate the entwined roles of information and quantum algorithms in reducing the complexity of the global optimization problem (GOP). We show that: (1) a modest amount of additional information is sufficient to map the general continuous GOP into the (discrete) Grover problem; (2) while this additional information is actually available in some classes of GOPs, it cannot be taken advantage of within classical optimization algorithms; (3) on the contrary, quantum algorithms over a natural framework for the efficient use of this information resulting in a speed-up of the solution of the GOP.
Date: October 31, 2001
Creator: Protopopescu, V
System: The UNT Digital Library