Several recent works have considered variants of the mortar-finite element method for numerical treatment of contact phenomena. The method has shown considerable promise for the spatial discretization of contact interactions, particularly for kinematically linear applications where one or both of the contacting surfaces are flat. Desirable features already demonstrated for the method in this specialized setting include passage of patch tests, preservation of convergence rates that would be obtained with a perfectly conforming mesh, and accurate resolution of contact stresses on interfaces. This paper concerns itself with the successful extension of these methods to encompass contact of geometrically noncoincident surfaces. The issue of patch test passage over curved interfaces will be discussed. It will be shown that a generalization of the mortar projection method is required to pass patch tests in this instance. Issues relating to the exact numerical integration of the mortar projection integrals will also be outlined, and a convergence study for a mortar tying application will be presented.

This paper discusses the Non-Equilibrium Zeldovich - von Neumann - Doring (NEZND) theory of self-sustaining detonation waves and the Ignition and Growth reactive flow model of shock initiation and detonation wave propagation in solid explosives. The NEZND theory identified the non-equilibrium excitation processes that precede and follow the exothermic decomposition of a large high explosive molecule into several small reaction product molecules. The thermal energy deposited by the leading shock wave must be distributed to the vibrational modes of the explosive molecule before chemical reactions can occur. The induction time for the onset of the initial endothermic reactions can be calculated using high pressure, high temperature transition state theory. Since the chemical energy is released well behind the leading shock front of a detonation wave, a physical mechanism is required for this chemical energy to reinforce the leading shock front and maintain its overall constant velocity. This mechanism is the amplification of pressure wavelets in the reaction zone by the process of de-excitation of the initially highly vibrationally excited reaction product molecules. This process leads to the development of the three-dimensional structure of detonation waves observed for all explosives. For practical predictions of shock initiation and detonation in hydrodynamic codes, …

Transparent conducting oxides (TCOs) are a group of materials that are widely used in solar cells and other optoelectronic devices. Recently, Cu-containing p-type TCOs such as MII Cu2 O2 (MIII=Mg, Ca, Sr, Ba) and CuMIII O2 (MIII=Al, Ga, In) have been proposed. Using first-principles band structure methods, we have systematically studied the electronic and optical properties of these p-type transparent oxides. For MII Cu2 O2 , we predict that adding a small amount of Ca into Sr Cu2 O2 can increase the transparency and conductivity. For CuMIII O2 , we explained the doping and band gap anomalies in this system and proposed a new approach to search for bipolar dopable wide-gap materials.

This conference paper describes Microcrystalline silicon films were grown with different thicknesses and different hydrogen dilution ratios on glass and Si substrates. Some films were deposited with a seed layer, whereas others were deposited directly on the substrate. We used atomic force microscopy, scanning electron microscopy, and X-ray diffraction to study the morphology and crystalline structure of the samples. We did not find a significant influence of the different substrates on the morphology or crystalline structure. The presence of the seed layer enhanced the crystallization process, decreasing the amount of amorphous layer present in the films. The microstructure of most films was formed by grains, with a subgrain structure. Films grown with low values of dilution ratio had (220) texture and elongated grains, whereas films deposited with high values of dilution ratio were randomly oriented and had an irregular shape.

This conference paper describes the measurement of the photovoltaic (PV) performance with respect to reference conditions requires measuring the performance with respect to a reference spectrum. Procedures were developed in the mid 1980s to correct measurements for errors relating to the spectral irradiance of the light source being different from the standard and the responsivity of the irradiance detector being different from the device under test. In principle, these procedures are exact, but require the measurement of the spectral irradiance of the light source and responsivity of the test device. This is problematic for most facilities that measure module performance. It has been suggested that a polynomial fit of the short-circuit current (I sc ) measured under natural sunlight divided by the total broadband irradiance as a function of air mass provides an accurate spectral correction factor. The polynomial correction factor is normalized to unity at an absolute air mass of 1.5.The polynomial correction factor is compared with the spectral correction factor for a variety of devices at two locations.

No plant and animal species protected under the ESA, candidates for such protection, or species listed by the Washington state government were observed in the vicinity of the proposed sites. Piper's daisy may still occur in some of the burial grounds. This is a Washington State Sensitive plant species, and as such is a Level III resource under the Hanford Site Biological Resources Management Plan. Compensatory mitigation is appropriate for this species when adverse impacts cannot be avoided. The Ecological Compliance Assessment Project (ECAP) staff should consulted prior to the initiation of major work activities within areas where this species has been identified (218-E-12, 218-E-10). The stalked-pod and crouching milkvetch are relatively common throughout 200 West area, therefore even if the few individuals within the active burial grounds are disturbed, it is not likely that the overall local population will be adversely affected. The Watch List is the lowest level of listing for plant species of concern in the State of Washington. No adverse impacts to species or habitats of concern are expected to occur from routine maintenance within the active portions of the 218-W-4C, 218-W-4B, 218-W-3, 218-W-3A, and 218-W-5 burial grounds, as well as the portion of 218-E-12B currently …

Atmospheric aberrations reduce the resolution and contrast in surveillance images recorded over horizontal or slant paths. This paper describes our recent horizontal and slant path imaging experiments of extended scenes as well as the results obtained using speckle imaging. The experiments were performed with an 8-inch diameter telescope placed on either a rooftop or hillside and cover ranges of interest from 0.5 km up to 10 km. The scenery includes resolution targets, people, vehicles, and other structures. The improvement in image quality using speckle imaging is dramatic in many cases, and depends significantly upon the atmospheric conditions. We quantify resolution improvement through modulation transfer function measurement comparisons.

A swift ion creates a track of electronic excitations in the target material. A net repulsion inside the track can cause a ''Coulomb Explosion'', which can lead to damage and sputtering of the material. Here we report results from molecular-dynamics (MD) simulations of Coulomb explosion for a cylindrical track as a function of charge density and neutralization/quenching time, {tau}. Screening by the free electrons is accounted for using a screened Coulomb potential for the interaction among charges. The yield exhibits a prompt component from the track core and a component, which dominates at higher excitation density, from the heated region produced. For the cases studied, the number of atoms ejected per incident ion, i.e. the sputtering yield Y, is quadratic with charge density along the track as suggested by simple models. Y({tau} = 0.2 Debye periods) is nearly 20% of the yield when there is no neutralization ({tau} {yields} {infinity}). The connections between ''Coulomb explosions'', thermal spikes and measurements of electronic sputtering are discussed.

Insulated pressure vessels are cryogenic-capable pressure vessels that can be fueled with liquid hydrogen or ambient-temperature compressed hydrogen. This flexibility results in multiple advantages with respect to compressed hydrogen tanks or low-pressure liquid hydrogen tanks. Our work is directed at verifying that commercially available aluminum-lined, fiber-wrapped pressure vessels can be safely used to store liquid hydrogen. A series of tests have been conducted, and the results indicate that no significant vessel damage has resulted from cryogenic operation. Future activities include a demonstration project in which the insulated pressure vessels will be installed and tested on two vehicles. A draft standard will also be generated for certification of insulated pressure vessels.

The Minimum Degree algorithm, one of the classical algorithms of sparse matrix computations, is widely used to order graphs to reduce the work and storage needed to solve sparse systems of linear equations. There has been extensive research involving practical implementations of this algorithm over the past two decades. However, little has been done to establish theoretical bounds on the computational complexity of these implementations. We study the Minimum Degree algorithm, and prove time complexity bounds for its widely used variants.

I will review the basic physical principles underlying the formation energy of various intrinsic defects in common photovoltaic materials. I then use the above principles to explain why doping of semiconductors is, in general, limited and which design principles can be used to circumvent such limits. This work can help design strategies of doping absorber materials as well as explain how TCOs work. Recent results on the surprising stability of polar (112)+ surfaces of CIS will also be described in this context.

The A2 LITE is a 2 liter, 2000 MPa, 750 K ultra-high pressure (UHP) vessel used to demonstrate UHP technology and to provide an air flow for wind tunnel nozzle development. It is the largest volume UHP vessel in the world. The design is based on a 100:1 pressure intensification using a hydraulic ram as a low pressure driver and a three-layer compound cylinder UHP section. Active control of the 900 mm piston stroke in the 63.5 mm bore permits pressure-time profiles ranging from static to constant pressure during flow through a 1 mm throat diameter nozzle for 1 second.

This conference paper describes the performance data for 14 photovoltaic modules deployed at fixed-latitude tilt in the field are presented and compared. Module performance is monitored continuously for optimum power characteristics. Flat-plate module technologies representative of crystalline, amorphous, and polycrystalline silicon, and cadmium telluride and copper indium diselenide, are scrutinized for energy production, effective efficiency and performance ratio-ratio of effective to reference efficiency. Most performance ratios exhibit seasonal fluctuations largely correlated to air or module temperatures, varying between 80% and 100%. These ratios tend toward larger values during winter and vise versa, except for amorphous silicon and cadmium telluride modules. In a-Si cases, the situation appears reversed: better performance ratios are exhibited during late summer. The effective efficiency and average daily and yearly energy production are analyzed and quantified.

Smoothing of contact surfaces can be used to eliminate the chatter typically seen with node on facet contact and give a better representation of the actual contact surface. The latter affect is well demonstrated for problems with interference fits. In this work we present two methods for the smoothing of contact surfaces for 3D finite element contact. In the first method, we employ Gregory patches to smooth the faceted surface in a node on facet implementation. In the second method, we employ a Bezier interpolation of the faceted surface in a mortar method implementation of contact. As is well known, node on facet approaches can exhibit locking due to the failure of the Babuska-Brezzi condition and in some instances fail the patch test. The mortar method implementation is stable and provides optimal convergence in the energy of error. In the this work we demonstrate the superiority of the smoothed versus the non-smoothed node on facet implementations. We also show where the node on facet method fails and some results from the smoothed mortar method implementation.

Traces of tritiated water (HTO) were determined at World Trade Center (WTC) ground zero after the 9/11/01 terrorist attack. A method of ultralow-background liquid scintillation counting was used after distilling HTO from the samples. A water sample from the WTC sewer, collected on 9/13/01, contained 0.174{plus_minus}0.074 (2{sigma}) nCi/L of HTO. A split water sample, collected on 9/21/01 from the basement of WTC Building 6, contained 3.53{plus_minus}0.17 and 2.83{plus_minus}0.15 nCi/L, respectively. Several water and vegetation samples were analyzed from areas outside the ground zero, located in Manhattan, Brooklyn, Queens, and Kensico Reservoir. No HTO above the background was found in those samples. All these results are well below the levels of concern to human exposure. Several tritium radioluminescent (RL) devices were investigated as possible sources of the traces of tritium at ground zero. Tritium is used in self-luminescent emergency EXIT signs. No such signs were present inside the WTC buildings. However, it was determined that Boeing 767-222 aircraft operated by the United Airlines that hit WTC Tower 2 as well as Boeing 767-223ER operated by the American Airlines, that hit WTC Tower 1, had a combined 34.3 Ci of tritium at the time of impact. Other possible sources of tritium include …

The corrosion resistance of Alloy 22 (UNS No.: N06022) was studied in 5 M CaCl{sub 2} electrolyte at various temperatures. Potentiodynamic polarization was used to examine the electrochemical behavior and measure the key potentials. Alloy 22 was found to be susceptible to localized corrosion in this high chloride [10M Cl{sup -}] environment at temperatures as low as 6O C.

Releasing the energy stored in an isomeric nuclear state in a controlled way with an atomic or electromagnetic trigger is an attractive speculation: the energy gain may be on the order of the ratio of nuclear/atomic energies - MeV/keV. (Nuclear isomers are loosely defined as excited nuclear states with lifetimes longer than 10{sup -9} s.) Nuclear isomers, therefore, represent an opportunity for a stand-alone energy source if suitable schemes for trigger and control of the energy release can be found. Potential applications include space drive, as well as very bright {gamma}-ray sources. The nucleus {sup 178}Hf has a nuclear isomer with excitation energy E{sub x} = 2.447 MeV. The 2.447-MeV isomeric state decays slowly (t{sub 1/2} = 31 y) to the nearby state at 2.433 MeV. The J{sup {pi}} = 13{sup -} state loses energy in a rapid (t {approx} 10{sup -12} s) {gamma}-ray cascade ending at the 8{sup -} rotational band head which in turn decays via the ground-state rotational band cascade. The {gamma}-ray cascade is delayed at the 8{sup -} state at 1.147 MeV, since the 8{sup -} state is also isomeric, with t{sub 1/2} = 4 s. Very scarce quantities of the 16{sup +}, 31-yr isomer are …

A new collegiate competition, called the Solar Decathlon, is under way. Fourteen teams from colleges and universities across the United States, including Puerto Rico, will assemble on the National Mall in Washington, DC, in late September 2002. They will compete to capture, convert, store, and use enough solar energy to power small, solar-powered, energy-efficient homes that they have designed, built, and transported to the site. Solar Decathletes will be required to provide all the energy for an entire household, including a home-based business and the transportation needs of the household and business. During the event, only the solar energy available within the perimeter of each house may be used to generate the power needed to compete in the ten Solar Decathlon contests. The event is sponsored by the U.S. Department of Energy, National Renewable Energy Laboratory, and private-sector partners BP Solar, American Institute of Architects, Electronic Data Systems, and Home Depot.

II-VI binary thin-film solar cells based on cadmium telluride (CdTe) and I-III-VI ternary thin-film solar cells based on copper indium diselenide (CIS) and related materials have been the subject of intense research and development in the past few years. Substantial progress has been made thus far in the area of materials research, device fabrication, and technology development, and numerous applications based on CdTe and CIS have been deployed worldwide. World record efficiency of 16.5% has been achieved by NREL scientists for a thin-film CdTe solar cell using a modified device structure. Also, NREL scientists achieved world-record efficiency of 21.1% for a thin-film CIGS solar cell under a 14X concentration and AM1.5 global spectrum. When measured under a AM1.5 direct spectrum, the efficiency increases to 21.5%. Pathways for achieving 25% efficiency for tandem polycrystalline thin-film solar cells are elucidated. R&D issues relating to CdTe and CIS are reported in this paper, such as contact stability and accelerated life testing in CdTe, and effects of moisture ingress in thin-film CIS devices. Substantial technology development is currently under way, with various groups reporting power module efficiencies in the range of 7.0% to 12.1% and power output of 40.0 to 92.5 W. A number …

The Department of Energy (DOE) Distributed Power Program (DPP) is conducting work to complete, validate in the field, and support the development of a national interconnection standard for distributed energy resources (DER), and to address the institutional and regulatory barriers slowing the commercial adoption of DER systems. This work includes support for the IEEE standards, including P1547 Standard for Interconnecting Distributed Resources with Electric Power Systems, P1589 Standard for Conformance Test Procedures for Equipment Interconnecting Distributed Resources with Electric Power Systems, and the P1608 Application Guide. Work is also in progress on system integration research and development (R&D) on the interface and control of DER with local energy systems. Additional efforts are supporting high-reliability power for industry, evaluating innovative concepts for DER applications, and exploring plug-and-play interface and control technologies for intelligent autonomous interconnection systems. This paper summarizes (1) the current status of the IEEE interconnection standards and application guides in support of DER, and (2) the R&D in progress at the National Renewable Energy Laboratory (NREL) for interconnection and system integration and application of distributed energy resources.

We have performed a series of experiments examining shock propagation in low density aerogels. High-pressure ({approx}100 kbar) shock waves are produced by detonating high explosives. Radiography is used to obtain a time sequence imaging of the shocks as they enter and traverse the aerogel. We compress the aerogel by impinging shocks waves on either one or both sides of an aerogel slab. The shock wave initially transmitted to the aerogel is very narrow and flat, but disperses and curves as it propagates. Optical images of the shock front reveal the initial formation of a hot dense region that cools and evolves into a well-defined microstructure. Structures observed in the shock front are examined in the framework of hydrodynamic instabilities generated as the shock traverses the low-density aerogel. The primary features of shock propagation are compared to simulations, which also include modeling the detonation of the high explosive, with a 2-D Arbitrary Lagrange Eulerian hydrodynamics code The code includes a detailed thermochemical equation of state and rate law kinetics. We will present an analysis of the data from the time resolved imaging diagnostics and form a consistent picture of the shock transmission, propagation and instability structure.

The effect of texture on enhancement and losses in photocurrent in a-Si solar cells is explored using PVOPTICS software and measurements on a-Si device structures. The texture angle has a major impact on light trapping and internal reflection. Increasing the angle causes better internal trapping in the i-layer, but also higher SnO2/a-Si reflection losses, as well as SnO2 and metal absorption losses. Parasitic absorption in the textured SnO2 due to back reflected light is 1-2 mA/cm2 for typical designs. N-i-p cells have a fundamental advantage over p-i-n cells since the textured TCO is at the rear of the device leading to lower losses.

Linear coupling is one of the factors that determine beam lifetime in RHIC. The traditional method of measuring the minimum tune separation requires a tune scan and can't be done parasitically or during the acceleration ramp. A new technique of using ac dipoles to measure linear coupling resonance has been developed at RHIC. This method measures the degree of coupling by comparing the amplitude of the horizontal coherent excitation with the amplitude of the vertical coherent excitation if the beam is excited by the vertical AC dipole and vice versa. One advantage of this method is that it can be done without changing tunes from the normal machine working points. In principle, this method can also localize the coupling source by mapping out the coupling driving terms throughout the ring. This is very useful for local decoupling the interaction regions in RHIC. A beam experiment of measuring linear coupling has been performed in RHIC during its 2003 run, and the analysis of the experimental data is discussed in this paper.

In this note, we describe the first of two updates to the uranium isotopes in Livermore's Evaluated Neutron Data Library, ENDL99. Here, we concentrate on improving the (n, f) and (n, {gamma}) evaluations for a limited set of uranium isotopes. The first improvement consisted of creating an evaluation for {sup 232}U using a combination of fission and capture cross sections from the JENDL-3.2 database and the outgoing particle distributions from the exiting ENDL99 {sup 234}U evaluation. The second improvement consisted of updating existing (n, f) and (n, {gamma}) evaluations for uranium isotopes with A=233-238. These improvements are particularly apparent in the neutron resonance region as ENDL99 often contains gross averages over the resonances. We have propagated these updates into various Livermore application libraries.