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Short Rotation Crops in the United States (open access)

Short Rotation Crops in the United States

The report is based primarily on the results of survey questions sent to approximately 60 woody and 20 herbaceous crop researchers in the United States and on information from the U.S. Department of Energy�s Bioenergy Feedstock Development Program. Responses were received from 13 individuals involved in woody crops research or industrial commercialization (with 5 of the responses coming from industry). Responses were received from 11 individuals involved in herbaceous crop research. Opinions on market incentives, technical and non-technical barriers, and highest priority research and development areas are summarized in the text. Details on research activities of the survey responders are provided as appendices to the paper. Woody crops grown as single-stem systems (primarily Populus and Eucalyptus species) are perceived to have strong pulp fiber and oriented strand board markets, and the survey responders anticipated that energy will comprise 25% or less of the utilization of single-stem short-rotation woody crops between now and 2010. The only exception was a response from California where a substantial biomass energy market does currently exist. Willows (Salix species) are only being developed for energy and only in one part of the United States at present. Responses from herbaceous crop researchers suggested frustration that markets (including …
Date: June 4, 1998
Creator: Wright, L. L.
System: The UNT Digital Library
Computational Design of High Efficiency Release Targets for Use at ISOL Facilities (open access)

Computational Design of High Efficiency Release Targets for Use at ISOL Facilities

This report describes efforts made at the Oak Ridge National Laboratory to design high-efficiency-release targets that simultaneously incorporate the short diffusion lengths, high permeabilities, controllable temperatures, and heat removal properties required for the generation of useful radioactive ion beam (RIB) intensities for nuclear physics and astrophysics research using the isotope separation on-line (ISOL) technique. Short diffusion lengths are achieved either by using thin fibrous target materials or by coating thin layers of selected target material onto low-density carbon fibers such as reticulated vitreous carbon fiber (RVCF) or carbon-bonded-carbon-fiber (CBCF) to form highly permeable composite target matrices. Computational studies which simulate the generation and removal of primary beam deposited heat from target materials have been conducted to optimize the design of target/heat-sink systems for generating RIBs. The results derived tlom diffusion release-rate simulation studies for selected targets and thermal analyses of temperature distributions within a prototype target/heat-sink system subjected to primary ion beam irradiation will be presented in this report.
Date: November 4, 1998
Creator: Alton, G. D.; Liu, Y. & Middleton, J. W.
System: The UNT Digital Library
Laser cutting of pressed explosives: Revision 1 (open access)

Laser cutting of pressed explosives: Revision 1

We have used a femtosecond laser beam to make cuts through small pressed pellets of six common explosives. The laser system, which produces 100 fs pulses of 820 nm light at a repitition rate of 1 kHz, was intitially developed for cutting metal. The advantage of using a femtosecond laser for cutting is that the cutting process transfers virtually no heat to the material that is being cut and produces almost no waste. We used LX-16 explosive (96% PETN/4% FPC 461 binder) for out intial experiments because PETN is one of the most sensitve of the secondary explosives. In some of the experiments the beam first cut through the HE pellet and then through a stainless steel substrate and in other experiments the beam first cut through the stainless steel and then through the pellet. We also cut through pellets that were not backed by a substrate. No evidence of reaction was observed in any of the LX-16 pellets. In addition to LX-16 we cut pellets of LX-14 (95.5% HMX/4.5% Estane), LX-15 (95% HNS/5% Kel-F), LX-17 (92.5% TATB/7.5% Kel-F), PBX-9407 (94% RDX/6% Exon 461), and pressed TNT with no evidence of reaction. The HE was easily cut at low power …
Date: May 4, 1998
Creator: Roeske, F., Jr.; Banks, R. E.; Armstrong, J. P.; Feit, M. D.; Lee, R. S.; Perry, M. D. et al.
System: The UNT Digital Library
Calculation of positron observables using a finite-element-based approach (open access)

Calculation of positron observables using a finite-element-based approach

We report the development of a new method for calculating positron observables using a finite-element approach for the solution of the Schrodinger equation. This method combines the advantages of both basis-set and real-space-grid approaches. The strict locality in real space of the finite element basis functions results in a method that is well suited for calculating large systems of a thousand or more atoms, as required for calculations of extended defects such as dislocations. In addition, the method is variational in nature and its convergence can be controlled systematically. The calculation of positron observables is straightforward due to the real-space nature of this method. We illustrate the power of this method with positron lifetime calculations on defects and defect-free materials, using overlapping atomic charge densities.
Date: November 4, 1998
Creator: Klein, B. M.; Pask, J. E. & Sterne, P.
System: The UNT Digital Library
Investigation of range extension with a genetic algorithm (open access)

Investigation of range extension with a genetic algorithm

Range optimization is one of the tasks associated with the development of cost- effective, stand-off, air-to-surface munitions systems. The search for the optimal input parameters that will result in the maximum achievable range often employ conventional Monte Carlo techniques. Monte Carlo approaches can be time-consuming, costly, and insensitive to mutually dependent parameters and epistatic parameter effects. An alternative search and optimization technique is available in genetic algorithms. In the experiments discussed in this report, a simplified platform motion simulator was the fitness function for a genetic algorithm. The parameters to be optimized were the inputs to this motion generator and the simulator`s output (terminal range) was the fitness measure. The parameters of interest were initial launch altitude, initial launch speed, wing angle-of-attack, and engine ignition time. The parameter values the GA produced were validated by Monte Carlo investigations employing a full-scale six-degree-of-freedom (6 DOF) simulation. The best results produced by Monte Carlo processes using values based on the GA derived parameters were within - 1% of the ranges generated by the simplified model using the evolved parameter values. This report has five sections. Section 2 discusses the motivation for the range extension investigation and reviews the surrogate flight model developed …
Date: March 4, 1998
Creator: Austin, A. S., LLNL
System: The UNT Digital Library
Heat capacity disk laser (open access)

Heat capacity disk laser

In this paper we describe the concept, and the basic scaling relation ships of solid state heat capacity lasers. Intermediate between single shot and average power systems, the heat capacity concept scales solid state lasers to MW levels of burst power.
Date: June 4, 1998
Creator: Albrecht, G. F.
System: The UNT Digital Library
New Horizons and New Strategies in Arms Control (open access)

New Horizons and New Strategies in Arms Control

In the last ten years, since the break-up of the Soviet Union, remarkable progress in arms control and disarmament has occurred. The Nuclear Non-Proliferation Treaty (NPT), the completion of the Comprehensive Test Ban Treaty (CTBT), and the Chemical Weapons Treaty (CWC) are indicative of the great strides made in the non- proliferation arena. Simultaneously, the Intermediate Nuclear Forces Treaty (INF), the Conventional Forces Treaty in Europe (CFE), and the Strategic Arms Reduction Treaties (START), all associated with US-Soviet Union (now Russia) relations have assisted in redefining European relations and the security landscape. Finally, it now appears that progress is in the offing in developing enhanced compliance measures for the Biological and Toxin Weapons Convention (BTWC). In sum, all of these achievements have set the stage for the next round of arms control activities, which may lead to a much broader, and perhaps more diffused multilateral agenda. In this new and somewhat unpredictable international setting, arms control and disarmament issues will require solutions that are both more creative and innovative than heretofore.
Date: December 4, 1998
Creator: Brown, J. editor
System: The UNT Digital Library
Automatic generation of warehouse mediators using an ontology engine (open access)

Automatic generation of warehouse mediators using an ontology engine

The Data Foundry research project at LLNL is investigating data warehousing in highly dynamic scientific environments. Specifically, we are developing a data warehouse to aid structural biologists in genetics research. Upon completion, this warehouse will present a uniform view of data obtained from several heterogeneous data sources containing distinct but related data from various genetics domains. Our warehouse uses a mediated data warehouse architecture in which only some data is represented explicitly in the warehouse; remote access is required to obtain the non-materialized data. Mediators are used to convert data from the data source representation to the warehouse representation and make it available to the warehouse. The major challenge we face is reducing the impact of source schema changes on warehouse availability and reliability: based upon previous efforts, we anticipate one source schema modification every 2-4 weeks once all of the desired sources have been integrated. Incorporating these modifications into the mediators using brute force results in an unacceptable amount of warehouse down-time. We believe that extensive use of a carefully designed ontology will allow us to overcome this problem, while providing a useful knowledge base for other applications. In addition to automatically generating the transformation between the data sources …
Date: March 4, 1998
Creator: Critchlow, T.
System: The UNT Digital Library
Solutions to Defect-Related Problems in Implanted Silicon by Controlled Injection of Vacancies by High-Energy Ion Irradiation (open access)

Solutions to Defect-Related Problems in Implanted Silicon by Controlled Injection of Vacancies by High-Energy Ion Irradiation

Amorphization and a dual implant technique have been used to manipulate residual defects that persist following implantation and post-implant thermal treatments. Residual defects can often be attributed to ion-induced defect excesses. A defect is considered to be excess when it occurs in a localized region at a concentration greater than its complement. Sources of excess defects include spatially separated Frenkel pairs, excess interstitials resulting from the implanted atoms, and sputtering. Pre-amorphizing prior to dopant implantation has been proposed to eliminate dopant broadening due to ion channeling as well as dopant diffusion during subsequent annealing. However, transient-enhanced diffusion (TED) of implanted boron has been observed in pre-amorphized Si. The defects driving this enhanced boron diffusion are thought to be the extended interstitial-type defects that form below the amorphous-crystalline interface during implantation. A dual implantation process was applied in an attempt to reduce or eliminate this interfacial defect band. High-energy, ion implantation is known to inject a vacancy excess in this region. Vacancies were implanted at a concentration coincident with the excess interstitials below the a-c interface to promote recombination between the two defect species. Preliminary results indicate that a critical fluence, i.e., a sufficient vacancy concentration, will eliminate the interstitial defects. …
Date: November 4, 1998
Creator: Duggan, J.L.; Holland, O.W. & Roth, E.
System: The UNT Digital Library
Prospects for fluorescence based imaging/visualization of hydrodynamic systems on the National Ignition Facility (open access)

Prospects for fluorescence based imaging/visualization of hydrodynamic systems on the National Ignition Facility

The next generation of large, high power lasers, such as the National Ignition Facility (NIF) [1] in the United States, Laser Mega Joule [2] in France or Helen Successor [3] in the United Kingdom offer the prospect of x-ray fluorescence based diagnosis of hydrodynamic experiments The x-ray fluorescence could be pumped by at least two techniques One technique is to use a sizable fraction of these facilities` high power to efficiently make multi-kilovolt x-rays which, in turn, causes dopants placed in experimental packages to fluoresce We call this ``externally pumped x-ray fluorescence`` The second technique is to use the sizable multi-kilovolt photon background that we expect to be present in many hohlraum based experiments, while the driving laser is on, to pump x-ray fluorescence The fluorescing medium could be a dopant in an experimental package or, possibly, a relatively thick slab of material in the hohlraum wall which could serve as a backlighter We call this ``hohlraum hot-corona pumped fluorescence``.
Date: June 4, 1998
Creator: Suter, L. J., LLNL
System: The UNT Digital Library
Clean Cities Ozone Air Quality Attainment and Maintenance Strategies That Employ Alternative Fuel Vehicles, With Special Emphasis on Natural Gas and Propane (open access)

Clean Cities Ozone Air Quality Attainment and Maintenance Strategies That Employ Alternative Fuel Vehicles, With Special Emphasis on Natural Gas and Propane

Air quality administrators across the nation are coming under greater pressure to find new strategies for further reducing automotive generated non-methane hydrocarbon (NMHC) and nitrogen oxide (NOx) emissions. The US Environmental Protection Agency (EPA) has established stringent emission reduction requirements for ozone non-attainment areas that have driven the vehicle industry to engineer vehicles meeting dramatically tightened standards. This paper describes an interim method for including alternative-fueled vehicles (AFVs) in the mix of strategies to achieve local and regional improvements in ozone air quality. This method could be used until EPA can develop the Mobile series of emissions estimation models to include AFVs and until such time that detailed work on AFV emissions totals by air quality planners and emissions inventory builders is warranted. The paper first describes the challenges confronting almost every effort to include AFVs in targeted emissions reduction programs, but points out that within these challenges resides an opportunity. Next, it discusses some basic relationships in the formation of ambient ozone from precursor emissions. It then describes several of the salient provisions of EPA`s new voluntary emissions initiative, which is called the Voluntary Mobile Source Emissions Reduction Program (VMEP). Recent emissions test data comparing gaseous-fuel light-duty AFVs with …
Date: August 4, 1998
Creator: Santini, D. J. & Saricks, C. L.
System: The UNT Digital Library
Sns Accumulator Ring Design and Space Charge Considerations (open access)

Sns Accumulator Ring Design and Space Charge Considerations

The goal of the proposed Spallation Neutron Source (SNS) is to provide a short pulse proton beam of about 0.5{micro}s with average beam power of 1MW. To achieve such purpose, a proton storage ring operated at 60Hz with 1 x 10{sup 14} protons per pulse at 1GeV is required. The Accumulator Ring (AR) receives 1msec long H{sup {minus}} beam bunches of 28mA from a 1GeV linac. Scope and design performance goals of the AR are presented. About 1,200 turns of charge exchange injection is needed to accumulate 1mA in the ring. After a brief description of the lattice design and machine performance parameters, space charge related issues, such as: tune shifts, stopband corrections, halo generation and beam collimation etc. is discussed.
Date: May 4, 1998
Creator: Weng, W. T.
System: The UNT Digital Library
Neutron Capture Measurements on Unstable Nuclei at LANSCE (open access)

Neutron Capture Measurements on Unstable Nuclei at LANSCE

Although neutron capture by stable isotopes has been extensively measured, there are very few measurements on unstable isotopes. The intense neutron flux at the Manual Lujan Jr. Neutron Scattering Center at LANSCE enables us to measure capture on targets with masses of about 1 mg over the energy range from 1 eV to 100 keV. These measurements are important not only for understanding the basic physics, but also for calculations of stellar nucleosynthesis and Science-Based Stockpile Stewardship. Preliminary measurements on {sup 169}Tm and {sup 171}Tm have been made with deuterated benzene detectors. A new detector array at the Lujan center and a new radioactive isotope separator will combine to give Los Alamos a unique capability for making these measurements.
Date: November 4, 1998
Creator: Ullmann, J.; Haight, R.; Wilhelmy, J.; Fowler, M.; Rundberg, R. & Miller, G.
System: The UNT Digital Library
Measurement of the Parity Violating Asymmetry A (open access)

Measurement of the Parity Violating Asymmetry A

The weak pion-nucleon coupling constant H{sub {pi}}{sup 1} remains poorly determined, despite many years of effort. The recent measurement of the {sup 133}Cs anapole moment has been interpreted to give a value of H{sub {pi}}{sup 1} almost an order of magnitude larger than the limit established in the {sup 18}F parity doublet experiments. A measurement of the gamma ray directional asymmetry A{sub {gamma}} for the capture of polarized neutrons by hydrogen has been proposed at Los Alamos National Laboratory. This experiment will determine H{sub {pi}}{sup 1} independent of nuclear structure effects. However, since the predicted asymmetry is small, A{sub {gamma}} {approximately} 5 x 10{sup {minus}8}, systematic effects must be reduced to < 5 x 10{sup {minus}9}. The design of the experiment will is presented, with an emphasis on the techniques used for controlling systematic errors.
Date: December 4, 1998
Creator: Wilburn, W. S.; Bazhenov, A.; Blessinger, C. S.; Bowman, J. D.; Chupp, T. E.; Coulter, K. P. et al.
System: The UNT Digital Library
Copper Mountain Conference on Iterative Methods 1998 (open access)

Copper Mountain Conference on Iterative Methods 1998

None
Date: April 4, 1998
Creator: unknown
System: The UNT Digital Library
Economic Analysis of Energy Crop Production in the U.S. - Location, Quantities, Price, and Impacts on Traditional Agricultural Crops (open access)

Economic Analysis of Energy Crop Production in the U.S. - Location, Quantities, Price, and Impacts on Traditional Agricultural Crops

POLYSYS is used to estimate US locations where, for any given energy crop price, energy crop production can be economically competitive with conventional crops. POLYSYS is a multi-crop, multi-sector agricultural model developed and maintained by the University of Tennessee and used by the USDA-Economic Research Service. It includes 305 agricultural statistical districts (ASD) which can be aggregated to provide state, regional, and national information. POLYSYS is being modified to include switchgrass, hybrid poplar, and willow on all land suitable for their production. This paper summarizes the preliminary national level results of the POLYSYS analysis for selected energy crop prices for the year 2007 and presents the corresponding maps (for the same prices) of energy crop production locations by ASD. Summarized results include: (1) estimates of energy crop hectares (acres) and quantities (dry Mg, dry tons), (2) identification of traditional crops allocated to energy crop production and calculation of changes in their prices and hectares (acres) of production, and (3) changes in total net farm returns for traditional agricultural crops. The information is useful for identifying areas of the US where large quantities of lowest cost energy crops can most likely be produced.
Date: October 4, 1998
Creator: Walsh, M.E.; De La Torre Ugarte, D.; Slinsky, S.; Graham, R.L.; Shapouri, H. & Ray, D.
System: The UNT Digital Library
A PERSPECTIVE FROM THE AGS. (open access)

A PERSPECTIVE FROM THE AGS.

A working model for the proposed JHF project is the AGS facility at BNL. Research that is being planned at the JHF represent extensions of present AGS experiments. The AGS presently holds the record for beam intensity from a synchrotron. Experience gained and lessons learned over the years from operation of the AGS is invaluable to a new facility like JHF. Presented here is a brief description of the AGS facility with emphasis on the separated particle beam lines that are presently being used for studying strangeness -1 and -2 systems.
Date: March 4, 1998
Creator: PILE,P.H.
System: The UNT Digital Library
A perspective from the AGS (open access)

A perspective from the AGS

A working model for the proposed SHF project is the AGS facility at BNL. Research that is being planned at the JHF represent extensions of present AGS experiments. The AGS presently holds the record for beam intensity from a synchrotron. Experience gained and lessons learned over the years from operation of the AGS is invaluable to a new facility like JHF. Presented here is a brief description of the AGS facility with emphasis on the separated particle beam lines that are presently being used for studying strangeness {minus}1 and {minus}2 systems.
Date: March 4, 1998
Creator: Pile, P.H.
System: The UNT Digital Library
''Magic'' Energies for Detecting Light Elements with Resonant Alpha Particle Backscattering (open access)

''Magic'' Energies for Detecting Light Elements with Resonant Alpha Particle Backscattering

Resonant backscattering is widely used to improve the detection limit of the light elements such as B, C, N and O. One disadvantage, however, is that several incident energies are normally needed if the sample contains a number of the light elements. There are ''magic'' energies at which several light elements can be detected simultaneously with suitable sensitivities. When these energies are used along with the elastic recoil detection of hydrogen, multiple elements can be detected without changing the beam energy, and the analysis time is greatly reduced. These reactions along with examples will be discussed.
Date: November 4, 1998
Creator: Wetteland, C.J.; Maggiore, C.J.; Tesmer, J.R.; He, X-M. & Lee, D-H.
System: The UNT Digital Library
High Intensity Performance and Upgrades at the Brookhaven AGS (open access)

High Intensity Performance and Upgrades at the Brookhaven AGS

Fig. 1 shows the present layout of the AGS-RHIC accelerator complex. The high intensity proton beam of the AGS is used both for the slow-extracted-beam (SEB) area with many target station to produce secondary beams and the fast-extracted-beam (FEB) line used for the production of muons for the g-2 experiment and for high intensity target testing for the spallation neutron sources and muon production targets for the muon collider. The same FEB line will also be used for the transfer of beam to RHIC. The proton beam intensity in the AGS has increased steadily over the 35 year existence of the AGS, but the most dramatic increase occurred over the last couple of years with the addition of the new AGS Booster[1]. In Fig. 2 the history of the AGS intensity improvements is shown and the major upgrades are indicated. The AGS Booster has one quarter the circumference of the AGS and therefore allows four Booster beam pulses to be stacked in the AGS at an injection energy of 1.5--1.9 GeV. At this increased energy, space charge forces are much reduced and this in turn allows for the dramatic increase in the AGS beam intensity. The 200 MeV LINAC is …
Date: May 4, 1998
Creator: Roser, T.
System: The UNT Digital Library
Plasma Signatures of Radial Field Power Dropouts (open access)

Plasma Signatures of Radial Field Power Dropouts

A class of small scale structures, with a near-radial magnetic field and a drop in magnetic field fluctuation power, have recently been identified in the polar solar wind. An earlier study of 24 events, each lasting for 6 hours or more, identified no clear plasma signature. In an extension of that work, radial intervals lasting for 4 hours or more (89 in total), have been used to search for a statistically significant plasma signature. It was found that, despite considerable variations between intervals, there was a small but significant drop, on average, in plasma temperature, density and {beta} during these events.
Date: October 4, 1998
Creator: Lucek, E.A.; Horbury, T.S.; Balogh, A. & McComas, D.J.
System: The UNT Digital Library
HRIBF Tandem Accelerator Radiation Safety System Upgrade (open access)

HRIBF Tandem Accelerator Radiation Safety System Upgrade

The HRIBF Tandem Accelerator Radiation Safety System was designed to permit experimenters and operations staff controlled access to beam transport and experiment areas with accelerated beam present. Neutron-Gamma detectors are mounted in eaeh area at points of maximum dose rate and the resulting signals are integrated by redundan~ circuitry; beam is stopped if dose rate or integrated dose exceeds established limits. This paper will describe the system, in use for several vears at the HRIBF, and discuss changes recently made to modernize the system and to make the system compliant with DOE Order 5480.25 and related ORNL updated safety rules.
Date: November 4, 1998
Creator: Blankenship, J. L. & Juras, R. C.
System: The UNT Digital Library
Stress and Defect Control in GaN Using Low Temperature Interlayers (open access)

Stress and Defect Control in GaN Using Low Temperature Interlayers

In organometallic vapor phase epitaxial growth of Gail on sapphire, the role of the low- temperature-deposited interlayers inserted between high-temperature-grown GaN layers was investigated by in situ stress measurement, X-ray diffraction, and transmission electron microscopy. Insertion of a series of low temperature GaN interlayers reduces the density of threading dislocations while simultaneously increasing the tensile stress during growth, ultimately resulting in cracking of the GaN film. Low temperature AIN interlayers were found to be effective in suppressing cracking by reducing tensile stress. The intedayer approach permits tailoring of the film stress to optimize film structure and properties.
Date: December 4, 1998
Creator: Akasaki, I.; Amano, H.; Chason, E.; Figiel, J.; Floro, J.A.; Han, J. et al.
System: The UNT Digital Library
Three-Dimensional Silicon Photonic Crystals (open access)

Three-Dimensional Silicon Photonic Crystals

In this work, we report the realization of a series of silicon 3D photonic crystals operating in the infrared (IR), mid-IR and most importantly the near-IR (k= 1 -2pm) wavelengths. The structure maintains its crystal symmetry throughout the entire 6-inches wafer and holds a complete photonic bandgap.
Date: December 4, 1998
Creator: Biswas, R.; Fleming, J.G.; Hetherington, D.L.; Ho, K.M.; Lin, S.; Sigalas, M.M. et al.
System: The UNT Digital Library