4 Matching Results

Search Results

Isochoric heating into the warm dense matter regime by laser-solid produced K-(alpha) x-rays

Description: The study of matter at near solid density and at temperatures of 1-10 eV is a great challenge to both experimentalists and theorists, because such matter exhibits internal energy density which is very high but insufficient to overpower the inter-atomic potentials. This form of matter, intermediate to condensed matter and plasmas, exists in many astrophysical systems. In this paper, we describe an experimental program to study solid-density matter heated to temperatures near 1 eV per atom with ultrafast pulses of x-rays. An intense, ultra-short laser pulse incident upon a thin foil produces a burst of K-{alpha} x-rays, which are used to flash heat an adjacent bulk sample. Optical interferometric probing of the sample with sub-ps time resolution allows us to measure its expansion into vacuum upon heating. K-{alpha} source target properties are optimized for irradiation of the adjacent sample. Initial results on K-{alpha} yields and heating of Al foils will be discussed.
Date: December 13, 2003
Creator: Dyer, G; Ditmire, T; Shepherd, R; Kuba, J; Price, D; Wootton, A et al.
Partner: UNT Libraries Government Documents Department

Final report on isotope tracer investigations in the Forebay of the Orange County groundwater basin.

Description: California is currently faced with some critical decisions about water resource infrastructure development in highly urbanized regions, whose outcome will dictate the future long-term viability of plentiful water. Among these is developing and safely implementing the reuse of advanced treated waste water. One of the most reliable strategies for this water resource is its indirect reuse via groundwater recharge and storage, with particular emphasis on supplementing annual water demand or during drought relief. The Orange County Water District (District) is currently implementing the first phase of a large-scale water reuse project that will advance-treat up to 60 million gallons per day of waste water and recharge it into existing percolation basins in the Forebay region of the Orange County groundwater basin. In order for the District to protect public health, the fate and potability of this recharged waste water needs to be understood. In particular, the direction and rates of flow into underlying aquifers need to be characterized so that changes in water quality can be quantified between the recharge basins and points of production. Furthermore, to ensure compliance to California Department of Health Services (DHS) draft regulations, the direction and rate of recharged waste water from these basins need to be understood to sufficient detail that small mixtures can be delineated in monitoring and production wells. Under proposed DHS guidelines, consumptive use of recycled water is permissive only if its residence time in an aquifer exceeds a specified six-month time-frame. DHS guidelines also limit the percentage of recycled water at production wells. However, attaining such detail using current hydrogeological and computer-assisted modeling tools is either cost-prohibitive or results in uncertainties too large to achieve regulatory confidence. To overcome this technical barrier, the District funded Lawrence Livermore National Laboratory (LLNL) from 1995-2001 to directly measure groundwater ages and perform two ...
Date: December 13, 2003
Creator: Davisson, M & Woodside, G
Partner: UNT Libraries Government Documents Department

Comparison of up-scaling methods in poroelasticity and its generalizations

Description: Four methods of up-scaling coupled equations at the microscale to equations valid at the mesoscale and/or macroscale for fluid-saturated and partially saturated porous media will be discussed, compared, and contrasted. The four methods are: (1) effective medium theory, (2) mixture theory, (3) two-scale and multiscale homogenization, and (4) volume averaging. All these methods have advantages for some applications and disadvantages for others. For example, effective medium theory, mixture theory, and homogenization methods can all give formulas for coefficients in the up-scaled equations, whereas volume averaging methods give the form of the up-scaled equations but generally must be supplemented with physical arguments and/or data in order to determine the coefficients. Homogenization theory requires a great deal of mathematical insight from the user in order to choose appropriate scalings for use in the resulting power-law expansions, while volume averaging requires more physical insight to motivate the steps needed to find coefficients. Homogenization often is performed on periodic models, while volume averaging does not require any assumption of periodicity and can therefore be related very directly to laboratory and/or field measurements. Validity of the homogenization process is often limited to specific ranges of frequency - in order to justify the scaling hypotheses that must be made - and therefore cannot be used easily over wide ranges of frequency. However, volume averaging methods can quite easily be used for wide band data analysis. So, we learn from these comparisons that a researcher in the theory of poroelasticity and its generalizations needs to be conversant with two or more of these methods to solve problems generally.
Date: December 13, 2003
Creator: Berryman, J G
Partner: UNT Libraries Government Documents Department

A Hidden Twelve-Dimensional SuperPoincare Symmetry In Eleven Dimensions

Description: First, we review a result in our previous paper, of how a ten-dimensional superparticle, taken off-shell, has a hidden eleven-dimensional superPoincare symmetry. Then, we show that the physical sector is defined by three first-class constraints which preserve the full eleven-dimensional symmetry. Applying the same concepts to the eleven dimensional superparticle, taken off-shell, we discover a hidden twelve dimensional superPoincare symmetry that governs the theory.
Date: December 13, 2003
Creator: Bars, Itzhak; Deliduman, Cemsinan; Pasqua, Andrea & Zumino, Bruno
Partner: UNT Libraries Government Documents Department