Abrasion and erosion testing of materials used in power production from coal (open access)

Abrasion and erosion testing of materials used in power production from coal

The Albany Research Center (ARC) has a long history of studying abrasive wear, related to mineral testing, handling, and processing. The center has also been instrumental in the design and development of wear test procedures and equipment. Research capabilities at ARC include Pin-on-Drum, Pin-on-Disk, and Dry Sand/Rubber Wheel abrasion tests, Jaw Crusher gouging test, Ball-on-Ball Impact test, and Jet erosion tests. Abrasive and erosive wear studies have been used to develop both new alloys and improved heat treatments of commercial alloys. As part of ARC’s newest iteration on wear testing to evaluate materials for use in new and existing pulverized coal combustion and gasifier power systems, the ARC has designed and constructed a new High Temperature Hostile Atmosphere Erosion Wear Test (HAET). This new piece of test apparatus is designed for erosive particle velocities of 10-40 m/sec and temperatures from room temperature (23°C) to 800+°C, with special control over the gas atmosphere. A variable speed whirling arm design is used to vary the impact energy of the gravity fed erosive particles. The specimens are mounted at the edge of a disk and allow a full range of impingement angles to be selected. An electric furnace heats the specimens in an …
Date: September 1, 2003
Creator: Tylczak, Joseph H.; Adler, Thomas A. & Rawers, James C.
System: The UNT Digital Library
Associations of Indoor Carbon Dioxide Concentrations and Environmental Susceptibilities With Mucous Membrane and Lower Respiratory Building Related Symptoms in the Base Study: Analyses of the 100 Building Dataset (open access)

Associations of Indoor Carbon Dioxide Concentrations and Environmental Susceptibilities With Mucous Membrane and Lower Respiratory Building Related Symptoms in the Base Study: Analyses of the 100 Building Dataset

Using the US EPA 100 office-building BASE Study dataset, they conducted multivariate logistic regression analyses to quantify the relationship between indoor CO{sub 2} concentrations (dCO{sub 2}) and mucous membrane (MM) and lower respiratory system (LResp) building related symptoms, adjusting for age, sex, smoking status, presence of carpet in workspace, thermal exposure, relative humidity, and a marker for entrained automobile exhaust. In addition, they tested the hypothesis that certain environmentally-mediated health conditions (e.g., allergies and asthma) confer increased susceptibility to building related symptoms within office buildings. Adjusted odds ratios (ORs) for statistically significant, dose-dependent associations (p < 0.05) for dry eyes, sore throat, nose/sinus congestion, and wheeze symptoms with 100 ppm increases in dCO{sub 2} ranged from 1.1 to 1.2. These results suggest that increases in the ventilation rates per person among typical office buildings will, on average, reduce the prevalence of several building related symptoms by up to 70%, even when these buildings meet the existing ASHRAE ventilation standards for office buildings. Building occupants with certain environmentally-mediated health conditions are more likely to experience building related symptoms than those without these conditions (statistically significant ORs ranged from 2 to 11).
Date: September 1, 2003
Creator: Erdmann, Christine A. & Apte, Michael G.
System: The UNT Digital Library
A cadmium-zinc-telluride crystal array spectrometer (open access)

A cadmium-zinc-telluride crystal array spectrometer

This paper describes a gamma detector employing an array of eight cadmium-zinc-telluride (CZT) crystals configured as a high resolution gamma ray spectrometer. This detector is part of a more complex instrument that identifies the isotope,displays this information, and records the gamma spectrum. Various alarms and other operator features are incorporated in this battery operated rugged instrument. The CZT detector is the key component of this instrument and will be described in detail in this paper. We have made extensive spectral measurements of the usual laboratory gamma sources, common medical isotopes, and various Special Nuclear Materials (SNM) with this detector. Some of these data will be presented as spectra. We will also present energy resolution and detection efficiency for the basic 8-crystal array. Additional data will also be presented for a 32-crystal array. The basic 8-crystal array development was completed two years ago, and the system electronic design has been imp roved recently. This has resulted in significantly improved noise performance. We expect to have a much smaller detector package, using 8 crystals, in a few months. This package will use flip-chip packaging to reduce the electronics physical size by a factor of 5.
Date: September 1, 2003
Creator: McHugh, H. R.; Quam, W.; DeVore, T.; Vogle, R. & Weslowski, J.
System: The UNT Digital Library
Characterizing Shrapnel and Debris Produced in High Power Laser Experiments (open access)

Characterizing Shrapnel and Debris Produced in High Power Laser Experiments

As large laser facilities increase in beam energy and target size, the propensity to produce shrapnel and debris that may impact target-facing optics lifetimes also increases. We present techniques and results using silica aerogel and thin glass plates to characterize the number, velocity, size, and spatial distribution of shrapnel and mass distribution of debris. We have conducted experiments on the HELEN laser to develop these techniques and provide data to support computer modeling of shrapnel and debris generation. We have begun to measure shrapnel and debris generation on Omega and are evolving plans to make similar measurements on NIF. These techniques appear viable for measuring shrapnel and debris with sufficient resolution to quantify their asymmetric deposition within the target chamber. These passive measurements can confirm improved target designs that reduce target shrapnel and debris effects and therefore aid in extending optics lifetime. Ultimately, these data support the most efficient use of optics in executing experimental campaigns on large laser facilities.
Date: September 1, 2003
Creator: Tobin, Mike; Andrew, Jim; Eder, David; Haupt, David; Johannes, Andrew & Brown, Bill
System: The UNT Digital Library
The development of ultrahigh and extreme high vacuum technology for physics research (open access)

The development of ultrahigh and extreme high vacuum technology for physics research

Over the last 50 years increasingly large and more sophisticated devices have been designed and put into operation for the study of particle and nuclear physics, magnetic confinement of high temperature plasmas for thermonuclear fusion research, and gravity wave observatories based on laser interferometers. The evolution of these devices has generated many developments in ultrahigh and extreme high vacuum technology that were required for these devices to meet their operational goals. The technologies that were developed included unique ultrahigh vacuum vessel structures, ultrahigh vacuum compatible materials, surface conditioning techniques, specialized vacuum pumps and vacuum diagnostics. Associated with these technological developments are scientific advancements in the understanding of outgassing limits of UHV-compatible materials and particle-induced desorption effects.
Date: September 1, 2003
Creator: Dylla, Fred
System: The UNT Digital Library
Durability of Polymeric Glazing Materials for Solar Applications (open access)

Durability of Polymeric Glazing Materials for Solar Applications

The economic viability of solar collector systems for domestic hot water (DHW) generation is strongly linked to the cost of such systems. Installation and hardware costs must be reduced by 50% to allow significant market penetration[1]. An attractive approach to cost reduction is to replace glass and metal parts with less expensive, lighter-weight polymeric components. Weight reduction decreases the cost of shipping, handling, and installation. The use of polymeric materials also allows the benefits and cost savings associated with well established manufacturing processes, along with savings associated with improved fastening, reduced part count, and overall assembly refinements. A key challenge is to maintain adequate system performance and assure requisite durability for extended lifetimes. Results of preliminary and ongoing screening tests for a large number of candidate polymeric glazing materials are presented. Based on these results, two specific glazings are selected to demonstrate how a service lifetime methodology can be applied to accurately predict the optical performance of these materials during in-service use.
Date: September 1, 2003
Creator: Jorgensen, G.; Brunold, S.; Carlsson, B.; Heck, M.; Kohl, M. & Moller, K.
System: The UNT Digital Library
Experimental Target Injection and Tracking System Construction and Single Shot Testing (open access)

Experimental Target Injection and Tracking System Construction and Single Shot Testing

Targets must be injected into an IFE power plant at a rate of approximately 5 to 10 Hz. Targets must be tracked very accurately to allow driver beams to be aligned with defined points on the targets with accuracy {+-} 150 {micro}m for indirect drive and {+-} 20 {micro}m for direct drive. An experimental target injection and tracking system has been constructed at General Atomics. The injector system will be used as a tool for testing the survivability of various target designs and provide feedback to the target designers. Helium gas propels the targets down an 8 m gun barrel up to 400 m/s. Direct-drive targets are protected in the barrel by sabots that are spring loaded to separate into two halves after acceleration. A sabot deflector directs the sabot halves away from the target injection path. Targets will be optically tracked with laser beams and line-scan cameras. Target position and arrival time will be predicted in real time based on early target position measurements. The system installation will be described. System testing to overcome excessive projectile wear and debris in the gun barrel is presented.
Date: September 1, 2003
Creator: Petzoldt, R. W.; Alexander, N. B.; Drake, T. J.; Goodin, D. T.; Jonestrack, K. & Vermillion, B. A.
System: The UNT Digital Library
A fully coupled three-dimensional THM analysis of the FEBEX in situ test with the ROCMAS Code: Prediction of THM behavior in a bentonite barrier (open access)

A fully coupled three-dimensional THM analysis of the FEBEX in situ test with the ROCMAS Code: Prediction of THM behavior in a bentonite barrier

This paper presents a fully coupled thermal-hydrological-mechanical analysis of FEBEX--a large underground heater test conducted in a bentonite and fractured rock system. System responses predicted by the numerical analysis--including temperature, moisture content, and bentonite-swelling stress--were compared to field measurements at sensors located in the bentonite. An overall good agreement between predicted and measured system responses shows that coupled thermal-hydrological-mechanical processes in a bentonite barrier are well represented by the numerical model. The most challenging aspect of this particular analysis was modeling of the bentonite's mechanical behavior, which at FEBEX turned out to be affected by gaps between prefabricated bentonite blocks. At FEBEX, the swelling pressure did not develop until a few months into the experiment when moisture swelling of bentonite blocks had closed the gaps completely. Moreover, the wetting of the bentonite took place uniformly from the rock and was not impacted by the permeability difference between the Lamprophyres dykes and surrounding rock.
Date: September 1, 2003
Creator: Rutqvist, J. & Tsang, C-F.
System: The UNT Digital Library
Homoclinic Tangle Bifurcations and Edge Stochasticity in Diverted Tokamaks (open access)

Homoclinic Tangle Bifurcations and Edge Stochasticity in Diverted Tokamaks

OAK-B135 The boundary and pedestal region of a poloidally diverted tokamak is particularly susceptible to the onset of vacuum magnetic field stochasticity due to small non-axisymmetric resonant perturbations. Recent calculations of the separatrix topology in diverted tokamaks, when subjected to small magnetic perturbations, show the existence of complex invariant manifold structures known as homoclinic tangles. These structures appear above a relatively low perturbation threshold that depends on certain equilibrium shape parameters. Homoclinic tangles represent a splitting of the unperturbed separatrix into stable and unstable invariant manifolds associated with each X-point (hyperbolic point). The manifolds that make up homoclinic tangles set the boundaries that prescribe how stochastic field line trajectories are organized i.e., how field lines from the inner domain of the unperturbed separatrix mix and are transported to plasma facing surfaces such as divertor target plates and protruding baffle structures. Thus, the topology of these tangles determines which plasma facing components are most likely to interact with escaping magnetic field lines and the parallel heat and particle flux they carry.
Date: September 1, 2003
Creator: Evans, T. E.; Roeder, R. K. W.; Carter, J. A. & Rapoport, B. I.
System: The UNT Digital Library
Hydration dynamics near a model protein surface (open access)

Hydration dynamics near a model protein surface

The evolution of water dynamics from dilute to very high concentration solutions of a prototypical hydrophobic amino acid with its polar backbone, N-acetyl-leucine-methylamide (NALMA), is studied by quasi-elastic neutron scattering and molecular dynamics simulation for both the completely deuterated and completely hydrogenated leucine monomer. We observe several unexpected features in the dynamics of these biological solutions under ambient conditions. The NALMA dynamics shows evidence of de Gennes narrowing, an indication of coherent long timescale structural relaxation dynamics. The translational water dynamics are analyzed in a first approximation with a jump diffusion model. At the highest solute concentrations, the hydration water dynamics is significantly suppressed and characterized by a long residential time and a slow diffusion coefficient. The analysis of the more dilute concentration solutions takes into account the results of the 2.0M solution as a model of the first hydration shell. Subtracting the first hydration layer based on the 2.0M spectra, the translational diffusion dynamics is still suppressed, although the rotational relaxation time and residential time are converged to bulk-water values. Molecular dynamics analysis shows spatially heterogeneous dynamics at high concentration that becomes homogeneous at more dilute concentrations. We discuss the hydration dynamics results of this model protein system in …
Date: September 1, 2003
Creator: Russo, Daniela; Hura, Greg & Head-Gordon, Teresa
System: The UNT Digital Library
Hydrodynamic Issues in PAMS Mandrel Target Fabrication (open access)

Hydrodynamic Issues in PAMS Mandrel Target Fabrication

OAK-B135 Imperfections in PAMS mandrels critically govern the quality of final ICF targets. Imperfections in the mandrels can have a wide range of origins. Here, they present observations of 3 types of imperfections, and data to support the proposal that hydrodynamic factors during the curing of the mandrel are potential causes of these imperfections.
Date: September 1, 2003
Creator: McQuillan, B. W.; Paguio, R.; Subramanian, P.; Takagi, M. & Zebib, A.
System: The UNT Digital Library
Hydrogen Storage in Wind Turbine Towers: Cost Analysis and Conceptual Design; Preprint (open access)

Hydrogen Storage in Wind Turbine Towers: Cost Analysis and Conceptual Design; Preprint

Low-cost hydrogen storage is recognized as a cornerstone of a renewables-hydrogen economy. Modern utility-scale wind turbine towers are typically conical steel structures that, in addition to supporting the rotor, could be used to store hydrogen. The most cost-effective hydrogen tower design would use substantially all of its volume for hydrogen storage and be designed at its crossover pressure. An 84-m tall hydrogen tower for a 1.5-MW turbine would cost an additional $84,000 (beyond the cost of the conventional tower) and would store 950 kg of hydrogen. The resulting incremental storage cost of $88/kg is approximately 30% of that for conventional pressure vessels.
Date: September 1, 2003
Creator: Kottenstette, R. & Cotrell, J.
System: The UNT Digital Library
Hydrogen Storage in Wind Turbine Towers: Design Considerations; Preprint (open access)

Hydrogen Storage in Wind Turbine Towers: Design Considerations; Preprint

The paramount considerations associated with a hydrogen tower are corrosion (in the form of hydrogen embrittlement) and structural failure (through bursting or fatigue life degradation). Although hydrogen embrittlement (HE) requires more research and experimentation, it does not appear to prohibit the use of turbine towers for hydrogen storage. Furthermore, the structural modifications required to store hydrogen in a tower are technically feasible. We discovered that hydrogen towers have a''crossover pressure'' at which their critical mode of failure crosses over from fatigue to bursting. The crossover pressure for many turbine towers is between 10 and 15 atm. The cost of hydrogen storage per unit of storage capacity is lowest near the crossover pressure. Above the crossover pressure, however, storage costs rise quickly.
Date: September 1, 2003
Creator: Kottenstette, R. & Cotrell, J.
System: The UNT Digital Library
IEEE 1547 Series of Standards: Interconnection Issues; Preprint (open access)

IEEE 1547 Series of Standards: Interconnection Issues; Preprint

IEEE 1547TM 2003 Standard for Interconnecting Distributed Resources With Electric Power Systems is the first in the 1547 series of planned interconnection standards. Major issues and a wealth of constructive dialogue arose during 1547 development. There was also a perceived increased vitality in updating complementary IEEE standards and developing additional standards to accommodate modern electrical and electronics systems and improved grid communications and operations. Power engineers and other stakeholders looking to the future are poised to incorporate 1547 into their knowledge base to help transform our nation's aging distribution systems while alleviating some of the burden on existing transmission systems.
Date: September 1, 2003
Creator: Basso, T. & DeBlasio, R.
System: The UNT Digital Library
The integrated beam experiment - A next step experiment for heavy ion fusion (open access)

The integrated beam experiment - A next step experiment for heavy ion fusion

The U.S. Heavy Ion Fusion Virtual National Laboratory is proposing as its next experiment the Integrated Beam Experiment (IBX). All experiments in the U.S. Heavy Ion Fusion (HIF) program up to this time have been of modest scale and have studied the physics of selected parts of a heavy ion driver. The mission of the IBX, a proof-of-principle experiment, is to demonstrate in one integrated experiment the transport from source to focus of a single heavy ion beam with driver-relevant parameters--i.e., the production, acceleration, compression, neutralization, and final focus of such a beam. Present preconceptual designs for the IBX envision a 5-10 MeV induction linac accelerating one K{sup +} beam. At injection (1.7 MeV) the beam current is approximately 500 mA, with pulse length of 300 ns. Design flexibility allows for several different acceleration and compression schedules, including the possibility of longitudinal (unneutralized) drift compression by a factor of up to ten in pulse length after acceleration, and neutralized drift compression. Physics requirements for the IBX, and preliminary physics and engineering design work are discussed in this paper.
Date: September 1, 2003
Creator: Celata, C. M.; Kwan, J. W.; Lee, E. P.; Leitner, M. A.; Logan, B. G.; Vay, J. L. et al.
System: The UNT Digital Library
New capabilities for modeling intense beams in heavy ion fusiondrivers (open access)

New capabilities for modeling intense beams in heavy ion fusiondrivers

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Date: September 1, 2003
Creator: Friedman, A.; Barnard, J. J.; Bieniosek, F. M.; Celata, C. M.; Cohen, R. H.; Davidson, R. C. et al.
System: The UNT Digital Library
A New Numerical Treatment of Hohlraum Boundaries for ALE RAD/Hydro Codes (open access)

A New Numerical Treatment of Hohlraum Boundaries for ALE RAD/Hydro Codes

Numerical treatment of the Laser Entrance Hole (LEH) region in hohlraums and halfraums with Arbitrary Lagrangian Eulerian (ALE) or pure Lagrangian codes is difficult near the Lagrangian boundary interface. For example, recent studies have focused on ALE methods for boundaries with rezoning to simulate the LEH window motion and the sliding contact between the window and the LEH edge. We propose a technique for handling such boundary complications based on the inclusion of a wrap around very-low density mesh structure. Additional ALE rezoning features such as material zone weighting are included to preserve numerical accuracy. We demonstrate the ability of ALE simulations using our technique to run to late time with very little user intervention. We benchmark our simulation results with experimental data from both two and three-dimensional halfraum experiments shots on the Helen and Omega Lasers.
Date: September 1, 2003
Creator: Koniges, A. E.; Tipton, R. & Marinak, M. M.
System: The UNT Digital Library
A Parametric Study of the Thermal-Hydraulic Response of Supercritical Light Water Reactors During Loss-of-Feedwater and Turbine-Trip Events (open access)

A Parametric Study of the Thermal-Hydraulic Response of Supercritical Light Water Reactors During Loss-of-Feedwater and Turbine-Trip Events

The Idaho National Engineering and Environmental Laboratory in investigating the feasibility of supercritical light water reactors for low-cost electric power production through a Nuclear Energy Research Initiative Project sponsored by the United State Department of Energy. The project is evaluating a variety of technical issues related to the fuel and reactor design, material corrosion, and safety characteristics. This paper presents the results of parametric calculations using the RELAP5 computer code to characterize the thermal-hydraulic response of supercritical reactors to transients initiated by loss-of-feedwater and turbine-trip events. The purpose of the calculations was to aid in the design of the safety systems by determining the time available for the safety systems to respond and their required capacities.
Date: September 1, 2003
Creator: Davis, Cliff B.; Buongiorno, Jacopo & MacDonald, Philip E.
System: The UNT Digital Library
Passive measurement of nitrogen oxides to assess traffic-related pollutant exposure for the East Bay Children's Respiratory Health Study (open access)

Passive measurement of nitrogen oxides to assess traffic-related pollutant exposure for the East Bay Children's Respiratory Health Study

This paper provides an overview of software interoperability as it relates to the energy simulation of buildings. The paper begins with a discussion of the difficulties in using sophisticated analysis tools like energy simulation at various stages in the building life cycle, and the potential for interoperability to help overcome these difficulties. An overview of the Industry Foundation Classes (IFC), a common data model for supporting interoperability under continuing development by the International Alliance for Interoperability (IAI) is then given. The process of creating interoperable software is described next, followed by specific details for energy simulation tools. The paper closes with the current status of, and future plans for, the ongoing efforts to achieve software interoperability.
Date: September 1, 2003
Creator: Singer, Brett C.; Hodgson, Alfred T.; Hotchi, Toshifumi & Kim, Janice J.
System: The UNT Digital Library
Patterns of cowbird parasitism in the Southern Atlantic Coastal Plain and Piedmont. (open access)

Patterns of cowbird parasitism in the Southern Atlantic Coastal Plain and Piedmont.

Until recently, little information was available on patterns of brood parasitism by Brownheaded Cowbirds (Molothrus ater) in the southeastern United States, a region into which cowbirds expanded their range only during the last half of the Twentieth Century and where their abundance is relatively low. We compiled parasitism data from several published and unpublished studies conducted in Georgia and South Carolina from 1993-2000 to examine levels of brood parasitism and determine frequent host species. The combined dataset included 1,372 nests of 24 species reported in the literature to have been parasitized by cowbirds. The parasitism rate on all species combined was 8.2%. Considering only those species that served as hosts in these studies (n = I2), the parasitism rate was 9.3%. Seven species were parasitized at rates 2 10%. Based on the extent of parasitism (among studies and locations), their relative abundance, and the sample size of nests, Prairie Warblers (Dendroicta discolor), Hooded Warblers (Wilsonia citrina), Yellow-breasted Chats (Icteria virens), and Indigo Buntings (Passerina cyanea), all shrub nesters, appear to be the most important cowbird hosts in the region. Parasitism on some species reported as frequent hosts elsewhere was extremely low or not documented. We conclude that the impact of …
Date: September 1, 2003
Creator: Kilgo, J.C. & Moorman, C.E.
System: The UNT Digital Library
Power and capacity fade mechanism of LiNi0.8Co0.15Al0.0502composite cathodes in high-power lithium-ion batteries (open access)

Power and capacity fade mechanism of LiNi0.8Co0.15Al0.0502composite cathodes in high-power lithium-ion batteries

High-power Li-ion cells that were tested at elevatedtemperatures showed a significant impedance rise, which was associatedprimarily with the LiNi0.8Co0.15Al0.05O2 cathode. By systematicallycollecting thousands of Raman spectra from 50 x 80 mm areas at 0.9 mmspatial resolution, and integrating the respective bands of the cathodecomponents for each spectrum, we were able to produce color-coded,semi-quantitative composition maps of cathode surfaces. Raman microscopyimages of cathodes from tested cells revealed that cell cycling orstorage at elevated temperatures led to significant changes in theLiNi0.8Co0.15Al0.05O2/elemental-carbon surface concentration ratio. Theloss of conductive carbon correlated with the power and capacity fade ofthe tested cathodes. The cathode surface state of charge (SOC) variedbetween individual grains of active material, and at some locations thespectra indicated the presence of fully charged material, despite thedeep cell discharge at the end of testing.
Date: September 1, 2003
Creator: Kostecki, Robert & McLarnon, Frank
System: The UNT Digital Library
SAFETY FACTOR SCALING OF ENERGY TRANSPORT IN L-MODE PLASMAS ON THE DIII-D TOKAMAK (open access)

SAFETY FACTOR SCALING OF ENERGY TRANSPORT IN L-MODE PLASMAS ON THE DIII-D TOKAMAK

OAK-B135 The scaling of energy transport with safety factor (q) at fixed magnetic shear has been measured on the DIII-D tokamak [Nucl. Fusion 42, 614 (2002)] for low confinement (L) mode discharges. At constant density, temperature, and toroidal magnetic field strength, such that the toroidal dimensionless parameters other than q are held fixed, the one-fluid thermal diffusivity is found to scale like {chi} {proportional_to} q{sup 0.84{+-}0.15}, with the ion channel having a stronger q dependence than the electron channel in the outer half of the plasma. The measured q scaling is in good agreement with the predicted scaling by the GLF23 transport model for the ion temperature gradient and trapped electron modes, but it is significantly weaker than the inferred scaling from empirically-derived confinement scaling relations.
Date: September 1, 2003
Creator: PETTY,CC; KINSEY,JE & LUCE,TC
System: The UNT Digital Library
Seasonal trend of photosynthetic parameters and stomatal conductance of blue oak (Quercus douglasii) under prolonged summer drought and high temperature (open access)

Seasonal trend of photosynthetic parameters and stomatal conductance of blue oak (Quercus douglasii) under prolonged summer drought and high temperature

OAK-B135 Understanding seasonal changes in photosynthetic parameters and stomatal conductance is crucial for modeling long-term carbon uptake and energy fluxes of ecosystems. Gas exchange measurements of CO{sub 2} and light response curves on blue oak leaves (Quercus douglasii H. & A.) were conducted weekly throughout the growing season to study the seasonality of photosynthetic capacity (V{sub cmax}) and Ball-Berry slope (m) under prolonged summer drought and high temperature. A leaf photosynthetic model was used to determine V{sub cmax}. There was a pronounced seasonal pattern in V{sub cmax}. The maximum value of V{sub cmax}, 127 {micro}molm{sup -2} s{sup -1},was reached shortly after leaf expansion in early summer, when air temperature was moderate and soil water availability was high. Thereafter, V{sub cmax} declined as the soil water profile became depleted and the trees experienced extreme air temperatures, exceeding 40 C. The decline in V{sub cmax} was gradual in midsummer, however, despite extremely low predawn leaf water potentials ({Psi}{sub pd}, {approx} -4.0 MPa). Overall, temporal changes in V{sub cmax} were well correlated with changes in leaf nitrogen content. During spring leaf development, high rates of leaf dark respiration (R{sub d}, 5-6 {micro}mol m{sup -2} s{sup -1}) were observed. Once a leaf reached maturity, …
Date: September 1, 2003
Creator: Xu, Liukang & Baldocchi, Dennis D.
System: The UNT Digital Library
Simulation of Shrapnel to Aid in the Design of NIF/LMJ Target-Diagnostic Configurations (open access)

Simulation of Shrapnel to Aid in the Design of NIF/LMJ Target-Diagnostic Configurations

Shrapnel fragments, produced when target/diagnostic components are impulse loaded, can reduce the lifetime of final optical components. The authors give simulations results of shrapnel generation in thin metal plates loaded by laser heating. They discuss two approaches to predicting the size and velocity distribution of the shrapnel fragments. The first uses the 2D LASNEX code to calculate energy absorption, shock propagation, and material response. The calculated strain rates combined with hydrodynamic quantities are used to determine properties of the fragments. The second uses the 1D DELPOR code to calculate energy absorption with the results coupled to the 3D HESIONE code to calculate dynamic fragmentation. They show results of varying the incident laser energy and the plate material. They compare with data obtained using low-density aerogel to capture shrapnel fragments.
Date: September 1, 2003
Creator: Eder, D.; Koniges, A.; Bonneua, F.; Vierne, J.; Combis, P.; Tobin, M. et al.
System: The UNT Digital Library