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Light-Trapping in a-Si Solar Cells: A Summary of the Results from PV Optics

Description: This paper describes major features of a new optical software package, PV Optics, and presents a brief summary of the results of applying this program to analyze amorphous silicon solar cells. Some examples are given, mainly to demonstrate the nature of calculations that can be performed with this program for a-Si cell design.
Date: April 27, 1999
Creator: Sopori, B. L.; Madjdpour, J.; W., Chen. & Zhang, Y.
Partner: UNT Libraries Government Documents Department

PONDER: a FORTRAN code that graphically represents nuclear blackout effects

Description: The PONDER Code (Pictures of Nuclear Device Effects from RANC), which has been used at Lawrence Livermore Laboratory for performing radar blackout analyses is described. PONDER is an executive routine in which the well-known radar blackout code RANC (Radar Absorption Noise and Clutter) is a major subroutine. y a nuclear burst and that cause sufficient absorption or refraction of a signal to make the radar system under study ineffective. In general, PONDER outputs two types of data: computer-generated pictures of blackout, and calculations of blackout area in square kilometers. These computer-generated pictures consist of either a ''projection'' of blackout orto a hemispherical shell or a ''projection'' onto a constant-altitude surface or a''projection'' onto a plane. (TFD)
Date: August 1, 1973
Creator: Maples, M.D.
Partner: UNT Libraries Government Documents Department

PALLOT: a FORTRAN code that produces graphical representations of nuclear blackout effects along a reentry trajectory

Description: The PALLOT code was developed to simplify the assimilation of data relating to effects of nuclear blackout on particular reentry trajectories. This code operates in three modes: azimuth, elevation, and inline, In the azimuth and elevation modes, the PALLOT picture represents a family of trajectories that only vary, respectively, in approach azimuth and impact elevation angle. The incline mode depicts a set of reentry vehicles approaching on the same trajectory through a nuclear environment. The code, written in Fortran IV, was developed on the CDC 7600 computer; it will run on the CDC 6600 without modification although the run times may be excessively long. (auth)
Date: August 17, 1973
Creator: Maples, M.D.
Partner: UNT Libraries Government Documents Department

PMESH: A parallel mesh generator

Description: The Parallel Mesh Generation (PMESH) Project is a joint LDRD effort by A Division and Engineering to develop a unique mesh generation system that can construct large calculational meshes (of up to 10{sup 9} elements) on massively parallel computers. Such a capability will remove a critical roadblock to unleashing the power of massively parallel processors (MPPs) for physical analysis. PMESH will support a variety of LLNL 3-D physics codes in the areas of electromagnetics, structural mechanics, thermal analysis, and hydrodynamics.
Date: October 21, 1994
Creator: Hardin, D.D.
Partner: UNT Libraries Government Documents Department

Modeling delamination growth in composites

Description: A method for modeling the initiation and growth of discrete delaminations in shell-like composite structures is presented. The laminate is divided into two or more sublaminates, with each sublaminate modeled with four-noded quadrilateral shell elements. A special, eight-noded hex constraint element connects opposing sublaminate shell elements. It supplies the nodal forces and moments needed to make the two opposing shell elements act as a single shell element until a prescribed failure criterion is satisfied. Once the failure criterion is attained, the connection is broken, creating or growing a discrete delamination. This approach has been implemented in a 3D finite element code. This code uses explicit time integration, and can analyze shell-like structures subjected to large deformations and complex contact conditions. The shell elements can use existing composite material models that include in-plane laminate failure modes. This analysis capability was developed to perform crashworthiness studies of composite structures, and is useful whenever there is a need to estimate peak loads, energy absorption, or the final shape of a highly deformed composite structure. This paper describes the eight-noded hex constraint element used to model the initiation and growth of a delamination, and discusses associated implementation issues. Particular attention is focused on the delamination growth criterion, and it is verified that calculated results do not depend on element size. In addition, results for double cantilever beam and end notched flexure specimens are presented and compared to measured data to assess the ability of the present approach to model a growing delamination.
Date: December 1, 1996
Creator: Reedy, E.D. Jr. & Mello, F.J.
Partner: UNT Libraries Government Documents Department

Project Records Information System (PRIS) user`s manual. Revision 3

Description: The Project Records Information System (PRIS) is an interactive system developed for the Information Management Services (IMS) of Martin Marietta Energy Systems, Inc., to perform indexing, maintenance, and retrieval of information about Engineering project record documents for which they are responsible. This PRIS User`s Manual provides instruction on the use of this system. Section 2.0 of this manual presents an overview of PRIS, describing the system`s purpose; the data that it handles; functions it performs; hardware, software, and access; and help and error functions. Section 3.0 describes the interactive menu-driven operation of PRIS. Appendixes A, B, and C contain help screens, report descriptions, and the data dictionary, respectively.
Date: January 1, 1995
Creator: Schwarz, R.K.; Cline, B.E. & Smith, P.S.
Partner: UNT Libraries Government Documents Department

PCx user guide

Description: We describe the code PCx, a primal-dual interior-point code for linear programming. Information is given about problem formulation and the underlying algorithm, along with instructions for installing, invoking, and using the code. Computational results on standard test problems are tabulated. The current version number is 1.0.
Date: March 1, 1997
Creator: Czyzyk, J.; Mehrotra, S. & Wright, S.J.
Partner: UNT Libraries Government Documents Department

Linac design algorithm with symmetric segments

Description: The cell lengths in linacs of traditional design are typically graded as a function of particle velocity. By making groups of cells and individual cells symmetric in both the CCDTL AND CCL, the cavity design as well as mechanical design and fabrication is simplified without compromising the performance. We have implemented a design algorithm in the PARMILA code in which cells and multi-cavity segments are made symmetric, significantly reducing the number of unique components. Using the symmetric algorithm, a sample linac design was generated and its performance compared with a similar one of conventional design.
Date: September 1996
Creator: Takeda, Harunori; Young, L. M.; Nath, S.; Billen, J. H. & Stovall, J. E.
Partner: UNT Libraries Government Documents Department

Testing of PVODE, a parallel ODE solver

Description: The purpose of this paper is to discuss the issues involved with, and the results from, testing of two example programs that use PVODE: pvkx and pvnx. These two programs are intended to provide a template for users for follow when writing their own code. However, we also used them (primarily pvkx) to do performance testing and visualization. This work was done on a Cray T3D, a Sparc 10, and a Sparc 5.
Date: August 9, 1996
Creator: Wittman, M. R.
Partner: UNT Libraries Government Documents Department

Density effect of inspection data points in as-built modeling of parts

Description: At Los Alamos National Laboratory, the use of inspection data generated at various stages of the life cycle of a product is being investigated in a feedback process to the design engineers and physicists. This data will be used to determine through analysis how to optimize assembly, mitigate nominal deviations, and confront aging issues. This as-built engineering philosophy characterizes a system through the topographical data generated through inspection. Through intricate modeling techniques, the topographical definition gives rise to a solid model in a Computer Aided Engineering (CAE) software package such as Parametric Technologies Pro/ENGINEER{trademark}. Once a solid model has been built, the definition can be used for a variety of analytical purposes including mass property calculations, finite element model generation, and virtual environment generation. A strictly analytical approach was used to exercise the as-built engineering method in characterizing components. A hypothetical component was used and mass properties were calculated analytically to provide nominal definition. This was then compared to mass properties calculated as a result of modeling theoretical inspection data in two formats; manual-collected data such as that obtained from a Coordinate Measuring Machine (specifically the Brown and Sharp) inspection process and automated-collected data such as obtained from a Sheffield inspection process. Mass properties calculated from a solid model generated using the Pro/ENGINEER{trademark} modeling operations were also compared with the nominal definition.
Date: December 31, 1998
Creator: Hefele, J. & Dolin, R.M.
Partner: UNT Libraries Government Documents Department

POET (parallel object-oriented environment and toolkit) and frameworks for scientific distributed computing

Description: Frameworks for parallel computing have recently become popular as a means for preserving parallel algorithms as reusable components. Frameworks for parallel computing in general, and POET in particular, focus on finding ways to orchestrate and facilitate cooperation between components that implement the parallel algorithms. Since performance is a key requirement for POET applications, CORBA or CORBA-like systems are eschewed for a SPMD message-passing architecture common to the world of distributed-parallel computing. Though the system is written in C++ for portability, the behavior of POET is more like a classical framework, such as Smalltalk. POET seeks to be a general platform for scientific parallel algorithm components which can be modified, linked, mixed and matched to a user`s specification. The purpose of this work is to identify a means for parallel code reuse and to make parallel computing more accessible to scientists whose expertise is outside the field of parallel computing. The POET framework provides two things: (1) an object model for parallel components that allows cooperation without being restrictive; (2) services that allow components to access and manage user data and message-passing facilities, etc. This work has evolved through application of a series of real distributed-parallel scientific problems. The paper focuses on what is required for parallel components to cooperate and at the same time remain ``black-boxes`` that users can drop into the frame without having to know the exquisite details of message-passing, data layout, etc. The paper walks through a specific example of a chemically reacting flow application. The example is implemented in POET and the authors identify component cooperation, usability and reusability in an anecdotal fashion.
Date: January 1, 1997
Creator: Armstrong, R. & Cheung, A.
Partner: UNT Libraries Government Documents Department

Preliminary calculations of ballistic bunch compression with thermionic cathode rf guns

Description: Preliminary calculations using the computer code PARMELA indicate that it is possible to achieve peak currents on the order of 1 kA using a thermionic-cathode rf gun and ballistic bunch compression. In contrast to traditional magnetic bunching schemes, ballistic bunch compression uses a series of rf cavities to modify the energy profile of the beam and properly chosen drifts to allow the bunching to occur naturally. The method, suitably modified, should also be directly applicable to photoinjector rf guns. Present work is focusing on simultaneously compressing the bunch while reducing the emittance of the electron beam. At present, the calculated normalized rms emittance is in the neighborhood of 6.8 {pi} mm mrad with a peak current of 0.88 kA, and a peak bunch charge of 0.28 nC from a thermionic-cathode gun.
Date: September 1, 1997
Creator: Lewellen, J.W. & Milton, S.
Partner: UNT Libraries Government Documents Department

Simulation of the SRI International test Gun-27 using the PAGOSA code

Description: SRI International conducted a set of impact tests with flat disks hitting water-filled chemical submunitions. One of these tests, called Gun-27, involved a 595 gram disk hitting the side of a submunition at 200 m/s. This test was simulated using the PAGOSA code with a materials model that was a good overall match to the data, and with a sequence of five mesh sizes. It was found that when a mesh was used which had at least five cells across the wall of the submunition, PAGOSA was able to provide reasonably satisfactory agreement with the test results, except for the partial fracture of a welded joint. One feature of the test that was reproduced very well by the simulation that used the finest mesh was the fracture of the diaphragm around its edge. Results are compared for all five simulations so that trends can be seen.
Date: June 23, 1997
Creator: Jacoby, J.J.
Partner: UNT Libraries Government Documents Department

Computational experience with a dense column feature for interior-point methods

Description: Most software that implements interior-point methods for linear programming formulates the linear algebra at each iteration as a system of normal equations. This approach can be extremely inefficient when the constraint matrix has dense columns, because the density of the normal equations matrix is much greater than the constraint matrix and the system is expensive to solve. In this report the authors describe a more efficient approach for this case, that involves handling the dense columns by using a Schur-complement method and conjugate gradient interaction. The authors report numerical results with the code PCx, into which the technique now has been incorporated.
Date: August 1, 1997
Creator: Wenzel, M.; Czyzyk, J. & Wright, S.
Partner: UNT Libraries Government Documents Department

Treatment of patient-dependent beam modifiers in photon treatments by the Monte Carlo dose calculation code PEREGRINE

Description: The goal of the PEREGRINE Monte Carlo Dose Calculation Project is to deliver a Monte Carlo package that is both accurate and sufficiently fast for routine clinical use. One of the operational requirements for photon-treatment plans is a fast, accurate method of describing the photon phase-space distribution at the surface of the patient. The open-field case is computationally the most tractable; we know, a priori, for a given machine and energy, the locations and compositions of the relevant accelerator components (i.e., target, primary collimator, flattening filter, and monitor chamber). Therefore, we can precalculate and store the expected photon distributions. For any open-field treatment plan, we then evaluate these existing photon phase-space distributions at the patient`s surface, and pass the obtained photons to the dose calculation routines within PEREGRINE. We neglect any effect of the intervening air column, including attenuation of the photons and production of contaminant electrons. In principle, for treatment plans requiring jaws, blocks, and wedges, we could precalculate and store photon phase-space distributions for various combinations of field sizes and wedges. This has the disadvantage that we would have to anticipate those combinations and that subsequently PEREGRINE would not be able to treat other plans. Therefore, PEREGRINE tracks photons through the patient-dependent beam modifiers. The geometric and physics methods used to do this are described here. 4 refs., 8 figs.
Date: March 1, 1997
Creator: Schach von Wittenau, A.E.; Cox, L.J.; Bergstrom, P.M. Jr.; Hornstein, S.M.; Mohan, R.; Libby, B. et al.
Partner: UNT Libraries Government Documents Department

Users guide to the PGAPack parallel genetic algorithm library

Description: PGAPack is a parallel genetic algorithm library that is intended to provide most capabilities desired in a genetic algorithm package, in an integrated, seamless, and portable manner. Key features of PGAPack are as follows: Ability to be called from Fortran or C. Executable on uniprocessors, multiprocessors, multicomputers, and workstation networks. Binary-, integer-, real-, and character-valued native data types. Object-oriented data structure neutral design. Parameterized population replacement. Multiple choices for selection, crossover, and mutation operators. Easy integration of hill-climbing heuristics. Easy-to-use interface for novice and application users. Multiple levels of access for expert users. Full extensibility to support custom operators and new data types. Extensive debugging facilities. Large set of example problems.
Date: January 1, 1996
Creator: Levine, D.
Partner: UNT Libraries Government Documents Department

PC/FRAM, Version 3.2 User Manual

Description: This manual describes the use of version 3.2 of the PC/FRAM plutonium isotopic analysis software developed in the Safeguards Science and Technology Group, NE-5, Nonproliferation and International Security Division Los Alamos National Laboratory. The software analyzes the gamma ray spectrum from plutonium-bearing items and determines the isotopic distribution of the plutonium 241Am content and concentration of other isotopes in the item. The software can also determine the isotopic distribution of uranium isotopes in items containing only uranium. The body of this manual descnies the generic version of the code. Special facility-specific enhancements, if they apply, will be described in the appendices. The information in this manual applies equally well to version 3.3, which has been licensed to ORTEC. The software can analyze data that is stored in a file on disk. It understands several storage formats including Canberra's S1OO format, ORTEC'S `chn' and `SPC' formats, and several ASCII text formats. The software can also control data acquisition using an MCA and then store the results in a file on disk for later analysis or analyze the spectrum directly after the acquisition. The software currently only supports the control of ORTEC MCB'S. Support for Canbema's Genie-2000 Spectroscopy Systems will be added in the future. Support for reading and writing CAM files will also be forthcoming. A versatile parameter fde database structure governs all facets of the data analysis. User editing of the parameter sets allows great flexibility in handling data with different isotopic distributions, interfering isotopes, and different acquisition parameters such as energy calibration, and detector type. This manual is intended for the system supervisor or the local user who is to be the resident expert. Excerpts from this manual may also be appropriate for the system operator who will routinely use the instrument.
Date: February 23, 1999
Creator: Kelley, T.A. & Sampson, T.E.
Partner: UNT Libraries Government Documents Department

A new breed of innovative ground water modeling

Description: Sparse data is a critical obstacle in every ground water remediation project. Lack of data necessitates non-unique interpolations that can distort modeled distributions of contaminants and essential physical properties (e.g., permeability, porosity). These properties largely determine the rates and paths that contaminants may take in migrating from sources to receptor locations. We apply both forward and inverse model estimates to resolve this problem because coupled modeling provides the only way to obtain constitutive property distributions that simultaneously simulate the flow and transport behavior observed in borehole measurements. Innovations in multidimensional modeling are a key to achieving more effective subsurface characterizations, remedial designs, risk assessments, and compliance monitoring in efforts to accelerate cleanup and reduce costs in national environmental remediations. Fundamentally new modeling concepts and novel software have emerged recently from two decades of research on self-adaptive solvers of partial differential equations (PDEs). We have tested a revolutionary software product, PDEase, applying it to coupled forward and inverse flow problems. In the Superfund cleanup effort at Lawrence Livermore National Laboratory`s (LLNL) Livermore Site, the new modeling paradigm of PDEase enables ground water professionals to simply provide the flow equations, site geometry, sources, sinks, constitutive parameters, and boundary conditions. Its symbolic processors then construct the actual numerical solution code and solve it automatically. Powerful grid refinements that conform adaptively to evolving flow features are executed dynamically with iterative finite-element solutions that minimize numerical errors to user-specified limits. Numerical solution accuracy can be tested easily with the diagnostic information and interactive graphical displays that appear as the solutions are generated.
Date: July 1, 1995
Creator: Gelinas, R.J.; Doss, S.K.; Ziagos, J.; McKereghan, P.; Vogele, T. & Nelson, R.G.
Partner: UNT Libraries Government Documents Department

A facility for creating Python extensions in C++

Description: Python extensions are usually created by writing the glue that connects Python to the desired new functionality in the C language. While simple extensions do not require much effort, to do the job correctly with full error checking is tedious and prone to errors in reference counting and to memory leaks, especially when errors occur. The resulting program is difficult to read and maintain. By designing suitable C++ classes to wrap the Python C API, we are able to produce extensions that are correct and which clean up after themselves correctly when errors occur. This facility also integrates the C++ and Python exception facilities. This paper briefly describes our package for this purpose, named CXX. The emphasis is on our design choices and the way these contribute to the construction of accurate Python extensions. We also briefly relate the way CXX's facilities for sequence classes allow use of C++'s Standard Template Library (STL) algorithms on C++ sequences.
Date: July 14, 1998
Creator: Dubois, P F
Partner: UNT Libraries Government Documents Department

Modeling of ablation by photospallation using the computer program PUFF/DFRACT

Description: In general, macroscopic material failure is a manifestation of irreversible changes at the microscopic level. Many tissues, which may appear to be macroscopically homogeneous, are, at a fundamental microscopic level, a composite material. For example, cornea is composed of a hyaluronic acid matrix in which layers of collagen fibers are overlaid in a crossing pattern. The points where the collagen fibers intersect are potential nucleation sites for microscopic defects, which under the action of tensile stress, nucleate, grow and coalesce to form macroscopic failure planes, or spall planes. Using a model based on microstructural evolution, this paper examines the failure process during photoablation. Specifically, the paper describes a physically motivated, micromechanical model based on the nucleation and growth of spherical voids. This model is then used to simulate photoablation of cornea. Potential for using this model to predict the stress wave and material damage measured by experiment is discussed.
Date: March 1, 1995
Creator: Antoun, T.; Seaman, L. & Glinsky, M.E.
Partner: UNT Libraries Government Documents Department