Multi-Scale Thermohydrologic Model Sensitivity-Study Calculations in Support of the SSPA (open access)

Multi-Scale Thermohydrologic Model Sensitivity-Study Calculations in Support of the SSPA

The purpose of this calculation report is to document the thermohydrologic (TH) model calculations performed for the Supplemental Science and Performance Analysis (SSPA), Volume 1, Section 5 and Volume 2 (BSC 2001d [DIRS 155950], BSC 2001e [DIRS 154659]). The calculations are documented here in accordance with AP-3.12Q REV0 ICN4 [DIRS 154418]. The Technical Working Plan (Twp) for this document is TWP-NGRM-MD-000015 Real. These TH calculations were primarily conducted using three model types: (1) the Multiscale Thermohydrologic (MSTH) model, (2) the line-averaged-heat-source, drift-scale thermohydrologic (LDTH) model, and (3) the discrete-heat-source, drift-scale thermal (DDT) model. These TH-model calculations were conducted to improve the implementation of the scientific conceptual model, quantify previously unquantified uncertainties, and evaluate how a lower-temperature operating mode (LTOM) would affect the in-drift TH environment. Simulations for the higher-temperature operating mode (HTOM), which is similar to the base case analyzed for the Total System Performance Assessment for the Site Recommendation (TSPA-SR) (CRWMS M&O 2000j [DIRS 153246]), were also conducted for comparison with the LTOM. This Calculation Report describes (1) the improvements to the MSTH model that were implemented to reduce model uncertainty and to facilitate model validation, and (2) the sensitivity analyses conducted to better understand the influence of parameter …
Date: December 20, 2001
Creator: Glascoe, L G; Buscheck, T A; Loosmore, G A & Sun, Y
Object Type: Report
System: The UNT Digital Library
Dislocation dynamics: simulation of plastic flow of bcc metals (open access)

Dislocation dynamics: simulation of plastic flow of bcc metals

This is the final report for the LDRD strategic initiative entitled ''Dislocation Dynamic: Simulation of Plastic Flow of bcc Metals'' (tracking code: 00-SI-011). This report is comprised of 6 individual sections. The first is an executive summary of the project and describes the overall project goal, which is to establish an experimentally validated 3D dislocation dynamics simulation. This first section also gives some information of LLNL's multi-scale modeling efforts associated with the plasticity of bcc metals, and the role of this LDRD project in the multiscale modeling program. The last five sections of this report are journal articles that were produced during the course of the FY-2000 efforts.
Date: February 20, 2001
Creator: Lassila, D H
Object Type: Report
System: The UNT Digital Library
Modeling Large-Strain, High-Rate Deformation in Metals (open access)

Modeling Large-Strain, High-Rate Deformation in Metals

The large strain deformation response of 6061-T6 and Ti-6Al-4V has been evaluated over a range in strain rates from 10{sup -4} s{sup -1} to over 10{sup 4} s{sup -1}. The results have been used to critically evaluate the strength and damage components of the Johnson-Cook (JC) material model. A new model that addresses the shortcomings of the JC model was then developed and evaluated. The model is derived from the rate equations that represent deformation mechanisms active during moderate and high rate loading. Another model that accounts for the influence of void formation on yield and flow behavior of a ductile metal (the Gurson model) was also evaluated. The characteristics and predictive capabilities of these models are reviewed.
Date: July 20, 2001
Creator: Lesuer, D. R.; Kay, G. J. & LeBlanc, M. M.
Object Type: Article
System: The UNT Digital Library
Advanced Imaging Catheter: Final Project Report (open access)

Advanced Imaging Catheter: Final Project Report

Minimally invasive surgery (MIS) is an approach whereby procedures conventionally performed with large and potentially traumatic incisions are replaced by several tiny incisions through which specialized instruments are inserted. Early MIS, often called laparoscopic surgery, used video cameras and laparoscopes to visualize and control the medical devices, which were typically cutting or stapling tools. More recently, catheter-based procedures have become a fast growing sector of all surgeries. In these procedures, small incisions are made into one of the main arteries (e.g. femoral artery in the thigh), and a long thin hollow tube is inserted and positioned near the target area. The key advantage of this technique is that recovery time can be reduced from months to a matter of days. In the United States, over 700,000 catheter procedures are performed annually representing a market of over $350 million. Further growth in this area will require significant improvements in the current catheter technology. In order to effectively navigate a catheter through the tortuous vessels of the body, two capabilities must exist: imaging and positioning. In most cases, catheter procedures rely on radiography for visualization and manual manipulation for positioning of the device. Radiography provides two-dimensional, global images of the vasculature and …
Date: July 20, 2001
Creator: Krulevitch, P.; Colston, B.; DaSilva, L.; Hilken, D.; Kluiwstra, J. U.; Lee, A. P. et al.
Object Type: Report
System: The UNT Digital Library
Processing of Prosthetic Heart Valve Sounds from Anechoic Tank Measurements (open access)

Processing of Prosthetic Heart Valve Sounds from Anechoic Tank Measurements

People with serious cardiac problems have had their life span extended with the development of the prosthetic heart valve. However, the valves operate continuously at approximately 39 million cycles per year and are therefore subject to structural failures either by faulty design or material fatigue. The development of a non-invasive technique using an acoustic contact microphone and sophisticated signal processing techniques has been proposed and demonstrated on limited data sets. In this paper we discuss an extension of the techniques to perform the heart valve tests in an anechoic like. Here the objective is to extract a ''pure'' sound or equivalently the acoustical vibration response of the prosthetic valves in a quiet environment. The goal is to demonstrate that there clearly exist differences between values which have a specific mechanical defect known as single leg separation (SLS) and non-defective valves known as intact (INT). We discuss the signal processing and results of anechoic acoustic measurements on 50 prosthetic valves in the tank. Finally, we show the results of the individual runs for each valve, point out any of the meaningful features that could be used to distinguish the SLS from INT and summarize the experiments.
Date: March 20, 2001
Creator: Candy, J V & Meyer, A W
Object Type: Article
System: The UNT Digital Library
PDE-based Non-Linear Diffusion Techniques for Denoising Scientific and Industrial Images: An Empirical Study (open access)

PDE-based Non-Linear Diffusion Techniques for Denoising Scientific and Industrial Images: An Empirical Study

Removing noise from data is often the first step in data analysis. Denoising techniques should not only reduce the noise, but do so without blurring or changing the location of the edges. Many approaches have been proposed to accomplish this; in this paper, they focus on one such approach, namely the use of non-linear diffusion operators. This approach has been studied extensively from a theoretical viewpoint ever since the 1987 work of Perona and Malik showed that non-linear filters outperformed the more traditional linear Canny edge detector. They complement this theoretical work by investigating the performance of several isotropic diffusion operators on test images from scientific domains. They explore the effects of various parameters such as the choice of diffusivity function, explicit and implicit methods for the discretization of the PDE, and approaches for the spatial discretization of the non-linear operator etc. They also compare these schemes with simple spatial filters and the more complex wavelet-based shrinkage techniques. The empirical results show that, with an appropriate choice of parameters, diffusion-based schemes can be as effective as competitive techniques.
Date: December 20, 2001
Creator: Weeratunga, S K & Kamath, C
Object Type: Article
System: The UNT Digital Library
Study of Positronium in Low-k Dielectric Films by means of 2D-Angular Correlation Experiments at a High-Intensity Slow-Positron Beam (open access)

Study of Positronium in Low-k Dielectric Films by means of 2D-Angular Correlation Experiments at a High-Intensity Slow-Positron Beam

Depth-resolved measurements of the two-dimensional angular correlation of annihilation radiation (2D-ACAR) were performed at the high-intensity slow-positron beam of Lawrence Livermore National Laboratory. We studied the formation of positronium in thin films of methyl-silsesquioxane (MSSQ) spin-on glass containing open-volume defects in the size of voids. Samples with different average void sizes were investigated and positronium formation could be found in all cases. The width of the angular correlation related to the annihilation of parapositronium increased with the void size indicating the annihilation of non-thermalized parapositronium.
Date: June 20, 2001
Creator: Gessmann, T; Petkov, M P; Weber, M H; Lynn, K G; Rodbell, K P; Asoka-Kumar, P et al.
Object Type: Article
System: The UNT Digital Library
Flow and Fracture of Bulk Metallic Glass Alloys and their Composites (open access)

Flow and Fracture of Bulk Metallic Glass Alloys and their Composites

The fracture and plastic deformation mechanisms of a Zr-Ti-Ni-Cu-Be bulk metallic glass and a composite utilizing a crystalline reinforcement phase are reviewed. The relationship between stress state, free volume and shear band formation are discussed. Positron annihilation techniques were used to confirm the predicted increase in free volume after plastic straining. Strain localization and failure were examined for a wide range of stress states. Finally, methods for toughening metallic glasses are considered. Significant increases in toughness are demonstrated for a composite bulk metallic glass containing a ductile second phase which stabilizes shear band formation and distributes plastic deformation.
Date: June 20, 2001
Creator: Flores, K M; Suh, D; Howell, R; Asoka-Kumar, P & Dauskardt, R H
Object Type: Article
System: The UNT Digital Library
Polarization Studies in Fast-Ion Beam Spectroscopy (open access)

Polarization Studies in Fast-Ion Beam Spectroscopy

In a historical review, the observations and the insight gained from polarization studies of fast ions interacting with solid targets are presented. These began with J. Macek's recognition of zero-field quantum beats in beam-foil spectroscopy as indicating alignment, and D.G. Ellis' density operator analysis that suggested the observability of orientation when using tilted foils. Lastly H. Winter's studies of the ion-beam surface interaction at grazing incidence yielded the means to produce a high degree of nuclear orientation in ion beams.
Date: December 20, 2001
Creator: Trabert, E
Object Type: Article
System: The UNT Digital Library
High-Efficiency Steam Electrolyzer (open access)

High-Efficiency Steam Electrolyzer

We are developing a novel high-efficiency, high-temperature steam electrolyzer. Although water or steam electrolysis is well known to be one of the cleanest ways to produce hydrogen, widespread utilization is hindered by high operational costs because of high electricity consumption. To decrease the electrical power input requirements in electrolysis, our approach uses natural gas as an anode depolarizer. This approach essentially replaces one unit of electricity with one equivalent-energy unit of natural gas at much lower cost. The direct use of natural gas on the electrolyzer enables very high system efficiency with respect to primary energy. Experiments performed on single cells have shown a voltage reduction as much as 1 V when compared to conventional electrolyzers. System efficiency has been estimated to be 50 to 80%, depending on the electrolytic current. A 200-W prototype unit is being developed.
Date: June 20, 2001
Creator: Pham, A. Q.
Object Type: Report
System: The UNT Digital Library
UV Laser Conditioning for Reduction of 351-nm Damage Initiation in Fused Silica (open access)

UV Laser Conditioning for Reduction of 351-nm Damage Initiation in Fused Silica

This paper describes the effect of 355-nm laser conditioning on the concentration of UV-laser-induced surface damage sites on large-aperture fused silica optics. We will show the effect of various 355-nm laser conditioning methodologies on the reduction of surface-damage initiation in fused silica samples that have varying qualities of polishing. With the best, generally available fused silica optic, we have demonstrated that 355-nm laser conditioning can achieve up to 10x reduction in surface damage initiation concentration in the fluence range of 10-14 J/cm{sup 2} (355-nm {at} 3 ns).
Date: December 20, 2001
Creator: Brusasco, R. M.; Penetrante, B. M.; Peterson, J. E.; Maricle, S. M. & Menapace, J. A.
Object Type: Article
System: The UNT Digital Library
Teller Medal Lecture IFSA2001: Problems and Solutions in the Design and Analysis of Early Laser Driven High Energy Density and ICF Target Physics Experiments (open access)

Teller Medal Lecture IFSA2001: Problems and Solutions in the Design and Analysis of Early Laser Driven High Energy Density and ICF Target Physics Experiments

The high energy density (HED) and inertial confinement fusion (ICF) physics community relies on increasingly sophisticated high power laser driven experiments to advance the field. We review early work in the design and analysis of such experiments, and discuss the problems encountered. By finding solutions to those problems we put the field on firmer ground, allowing the community to develop it to the exciting stage it is in today. Specific examples include: drive and preheat in complex hohlraum geometries with the complicating effects of sample motion; and issues in the successful design of laboratory soft x-ray lasers and in the invention of methods to reduce the required optical laser driver energy by several orders of magnitude.
Date: August 20, 2001
Creator: Rosen, M D
Object Type: Article
System: The UNT Digital Library
Partial Data Traces: Efficient Generation and Representation (open access)

Partial Data Traces: Efficient Generation and Representation

Binary manipulation techniques are increasing in popularity. They support program transformations tailored toward certain program inputs, and these transformations have been shown to yield performance gains beyond the scope of static code optimizations without profile-directed feedback. They even deliver moderate gains in the presence of profile-guided optimizations. In addition, transformations can be performed on the entire executable, including library routines. This work focuses on program instrumentation, yet another application of binary manipulation. This paper reports preliminary results on generating partial data traces through dynamic binary rewriting. The contributions are threefold. First, a portable method for extracting precise data traces for partial executions of arbitrary applications is developed. Second, a set of hierarchical structures for compactly representing these accesses is developed. Third, an efficient online algorithm to detect regular accesses is introduced. The authors utilize dynamic binary rewriting to selectively collect partial address traces of regions within a program. This allows partial tracing of hot paths for only a short time during program execution in contrast to static rewriting techniques that lack hot path detection and also lack facilities to limit the duration of data collection. Preliminary results show reductions of three orders of a magnitude of inline instrumentation over a …
Date: August 20, 2001
Creator: Mueller, F; De Supinski, B R; McKee, S A & Yoo, A
Object Type: Article
System: The UNT Digital Library
Geologic and Wireline Borehole Summary from the Second ILAW Borehole (299-E24-21) (open access)

Geologic and Wireline Borehole Summary from the Second ILAW Borehole (299-E24-21)

The second borehole for the Immobilized Low-Activity Waste Disposal site Performance Assessment (PA) was drilled in March 2001. Continuous core samples were obtained for characterization activities in support of the PA. The borehole was drilled to a depth of 335 feet below ground surface and completed as a groundwater monitoring well. Only sediments of the Hanford formation were penetrated further defining the paleochannel that trends northwest southeast through the 200 East Area. Open-framework gravel was encountered from 335 feet drilled depth to 270 feet. From 270 feet to the surface, sands dominate the stratigraphy with minor amounts of gravel. The stratigraphic section can be divided into three layers defined by paleosols at the top. The water table is at 312.45 feet below ground surface. Aquifer testing indicates that a lower bounding value for hydraulic conductivity of the gravels comprising the paleochannel is 75 m/day.
Date: September 20, 2001
Creator: Reidel, Steve P.; Horton, Duane G. & Valenta, Michelle M.
Object Type: Report
System: The UNT Digital Library
X-Ray Spectropolarimetry Studies at the Nevada Terawatt Facility and LLNL EBIT (open access)

X-Ray Spectropolarimetry Studies at the Nevada Terawatt Facility and LLNL EBIT

Recent results from x-pinches at the NTF provide experimental evidence for the existence of strong electron beams in x-pinch plasmas and motivate the development of a new diagnostic, x-ray spectropolarimetry, for investigating the anisotropy of such plasmas. This diagnostic is based on theoretical modeling of polarization-dependent spectra measured simultaneously by spectrometers with different sensitivity to polarization. Results of the first polarization-sensitive experiments at the NTF are presented. K-shell emission from Ti x-pinches is recorded simultaneously by two identical spectrometers with the dispersion plane perpendicular and parallel to the discharge axis. The spectroscopic analysis of more than eight Ti x-pinch shots show how spectropolarimetry complements the usual diagnostics of a z-pinch plasma. The polarization-sensitive spectra, generated by a Maxwellian electron beam at LLNL EBIT have been collected and analyzed. These data make an important contribution to the plasma polarization spectroscopy program at the NTF. In particular, the study of multiply-charged Ti ion spectra help in the interpretation of the polarization-sensitive spectra from Ti x-pinches at the NTF.
Date: October 20, 2001
Creator: Shlyaptseva, A S; Kantsyrev, V L; Bauer, B S; Neill, P; Harris, C; Fedin, D A et al.
Object Type: Article
System: The UNT Digital Library
Simulating Intense Ion Beams for Inertial Fusion Energy (open access)

Simulating Intense Ion Beams for Inertial Fusion Energy

The Heavy Ion Fusion (HIF) program's goal is the development of the body of knowledge needed for Inertial Fusion Energy (IFE) to realize its promise. The intense ion beams that will drive HIF targets are nonneutral plasmas and exhibit collective, nonlinear dynamics which must be understood using the kinetic models of plasma physics. This beam physics is both rich and subtle: a wide range in spatial and temporal scales is involved, and effects associated with both instabilities and non-ideal processes must be understood. Ion beams have a ''long memory'', and initialization of a beam at mid-system with an idealized particle distribution introduces uncertainties; thus, it will be crucial to develop, and to extensively use, an integrated and detailed ''source-to-target'' HIF beam simulation capability. We begin with an overview of major issues.
Date: February 20, 2001
Creator: Friedman, A
Object Type: Article
System: The UNT Digital Library
Laser Science & Technology Program Annual Report - 2000 (open access)

Laser Science & Technology Program Annual Report - 2000

The Laser Science and Technology (LS&T) Program Annual Report 2001 provides documentation of the achievements of the LLNL LS&T Program during the April 2001 to March 2002 period using three formats: (1) an Overview that is a narrative summary of important results for the year; (2) brief summaries of research and development activity highlights within the four Program elements: Advanced Lasers and Components (AL&C), Laser Optics and Materials (LO&M), Short Pulse Laser Applications and Technologies (SPLAT), and High-Energy Laser System and Tests (HELST); and (3) a compilation of selected articles and technical reports published in reputable scientific or technology journals in this period. All three elements (Annual Overview, Activity Highlights, and Technical Reports) are also on the Web: http://laser.llnl.gov/lasers/pubs/icfq.html. The underlying mission for the LS&T Program is to develop advanced lasers, optics, and materials technologies and applications to solve problems and create new capabilities of importance to the Laboratory and the nation. This mission statement has been our guide for defining work appropriate for our Program. A major new focus of LS&T beginning this past year has been the development of high peak power short-pulse capability for the National Ignition Facility (NIF). LS&T is committed to this activity.
Date: March 20, 2001
Creator: Chen, H. L.
Object Type: Report
System: The UNT Digital Library
The Performance of PFS, the Compaq Sierra Product's Parallel File System (open access)

The Performance of PFS, the Compaq Sierra Product's Parallel File System

In FY 2000 Livermore Computing took delivery of serial number one of the Compaq Sierra high performance cluster product. The Sierra product employs a derivative of the Tru64 UNIX operating system called Tru-Cluster, which provides a cluster-wide parallel file system called PFS. This report documents the observed performance of PFS along with the performance of some of the underlying file system components. Testing reveals that the underlying AdvFS file system does a good job of read-ahead and write-behind I/O performance enhancement at the expense of a high CPU utilization. On the other hand, PFS performs at only a fraction of the speed that the underlying I/O and communication hardware allow.
Date: June 20, 2001
Creator: Uselton, A C
Object Type: Report
System: The UNT Digital Library
Isotopic Tracing of Fuel Components in Particulate Matter from a Compression Ignition Engine Fueled with Ethanol-In-Diesel Blends (open access)

Isotopic Tracing of Fuel Components in Particulate Matter from a Compression Ignition Engine Fueled with Ethanol-In-Diesel Blends

Accelerator Mass Spectrometry (AMs) was used to investigate the relative contribution to diesel engine particulate matter (PM) from the ethanol and diesel fractions of blended fuels. Four test fuel blends and a control diesel fuel baseline were investigated. The test fuels were comprised of {sup 14}C depleted diesel fuel mixed with contemporary grain ethanol ({approx}400 the {sup 14}C concentration of diesel). An emulsifier (Span 85) or cosolvent (butyl alcohol) was used to facilitate mixing. The experimental test engine was a 1993 Cummins B5.9 diesel rated at 175 hp at 2500 rpm. Test fuels were run at steady-state conditions of 1600 rpm and 210 ft-lbs, and PM samples were collected on quartz filters following dilution of engine exhaust in a mini-dilution tunnel. AMs analysis of the filter samples showed that the ethanol contributed less to PM relative to its fraction in the fuel blend. For the emulsified blends, 6.4% and 10.3% contributions to PM were observed for 11.5% and 23.0% ethanol fuels, respectively. For the cosolvent blends, even lower contributions were observed (3.8% and 6.3% contributions to PM for 12.5% and 25.0.% ethanol fuels, respectively). The distribution of the oxygen, not just the quantity, was an important factor in reducing PM …
Date: March 20, 2001
Creator: Buchholz, B. A.; Cheng, A. S. & Dibble, R. W.
Object Type: Article
System: The UNT Digital Library
Chemical Kinetic Characterization of Combustion Toluene (open access)

Chemical Kinetic Characterization of Combustion Toluene

A study is performed to elucidate the chemical kinetic mechanism of combustion of toluene. A detailed chemical kinetic mechanism for toluene was improved by adding a more accurate description of the phenyl + O{sub 2} reaction channels. Results of the chemical kinetic mechanism are compared with experimental data obtained from premixed and nonpremixed systems. Under premixed conditions, predicted ignition delay times are compared with new experimental data obtained in shock tube. Also, calculated species concentration histories are compared to experimental flow reactor data from the literature. Critical conditions of extinction and ignition were measured in strained laminar flows under nonpremixed conditions in the counterflow configuration. Numerical calculations are performed using the chemical kinetic mechanism at conditions corresponding to those in the experiments. Critical conditions of extinction and ignition are predicted and compared with the experimental data. For both premixed and nonpremixed systems, sensitivity analysis was used to identify the reaction rate constants that control the overall rate of oxidation in each of the systems considered.
Date: March 20, 2001
Creator: Pitz, W. J.; Seiser, R.; Bozzelli, J. W.; Da Costa, I.; Fournet, R.; Billaud, F. et al.
Object Type: Article
System: The UNT Digital Library
Supplemental Analysis to Support Postulated Events in Process Hazards Analysis for the HEAF (open access)

Supplemental Analysis to Support Postulated Events in Process Hazards Analysis for the HEAF

The purpose of this report is to conduct a limit scope risk assessment by generating event trees for the accident scenarios described in table 4-2 of the HEAF SAR, ref 1. Table 4-2 lists the postulated event/scenario descriptions for non-industrial hazards for HEAF. The event tree analysis decomposes accident scenarios into basic causes that appear as branches on the event tree. Bold downward branches indicate paths leading to the accident. The basic causes include conditions, failure of administrative controls (procedural or human error events) or failure of engineered controls (hardware, software or equipment failure) that singly or in combination can cause an accident to occur. Event tree analysis is useful since it can display the minimum number of events to cause an accident. Event trees can address statistical dependency of events such as a sequence of human error events conducted by the same operator. In this case, dependent probabilities are used. Probabilities/frequencies are assigned to each branch. Another example of dependency would be when the same software is used to conduct separate actions such as activating a hard and soft crow bar for grounding detonator circuits. Generally, the first event considered in the event tree describes the annual frequency at …
Date: July 20, 2001
Creator: Lambert, H & Johnson, G
Object Type: Report
System: The UNT Digital Library
West Valley Tank 8D-1 and 8D-2 Inventory Estimation Methodology (open access)

West Valley Tank 8D-1 and 8D-2 Inventory Estimation Methodology

This report details work funded by the West Valley Support Project (WVSP) and the Tanks Focus Area Retrieval and Closure Program. The work was conducted by the Pacific Northwest National Laboratory (PNNL) and is in support of the West Valley Demonstration Project (WVDP). The WVDP site in New York was originally the site of a commercial nuclear fuel reprocessing plant. The high-level waste (HLW), approximately 2 million liters, produced during plutonium-uranium extraction (PUREX) and thorium extraction (THOREX) reprocessing campaigns at the plant and subsequent HLW preprocessing, was stored on site in three tanks identified as 8D-1, 8D-2, and 8D-4. Waste from the PUREX process was neutralized with NaOH for storage in a carbon steel tank designated as 8D-2. Neutralization resulted in a precipitated hydroxide sludge that settled to the bottom of the tank and was covered by a supernatant salt solution. The acidic THOREX waste, approximately 55,000 L, was first stored in a stainless steel tank (8D-4) and then added to the PUREX waste in Tank 8D-2. Supernatant decontamination, primarily cesium removal, was conducted by ion-exchange using in-tank columns suspended in Tank 8D-1. The cesium-loaded zeolite, resulting from the supernatant decontamination process, was dumped to the bottom of Tank 8D-1. …
Date: July 20, 2001
Creator: O'Brien, Robert F.; Heasler, Patrick G. & Rowell, Laurene
Object Type: Report
System: The UNT Digital Library
Memory Benchmarks for SMP-Based High Performance Parallel Computers (open access)

Memory Benchmarks for SMP-Based High Performance Parallel Computers

As the speed gap between CPU and main memory continues to grow, memory accesses increasingly dominates the performance of many applications. The problem is particularly acute for symmetric multiprocessor (SMP) systems, where the shared memory may be accessed concurrently by a group of threads running on separate CPUs. Unfortunately, several key issues governing memory system performance in current systems are not well understood. Complex interactions between the levels of the memory hierarchy, buses or switches, DRAM back-ends, system software, and application access patterns can make it difficult to pinpoint bottlenecks and determine appropriate optimizations, and the situation is even more complex for SMP systems. To partially address this problem, we formulated a set of multi-threaded microbenchmarks for characterizing and measuring the performance of the underlying memory system in SMP-based high-performance computers. We report our use of these microbenchmarks on two important SMP-based machines. This paper has four primary contributions. First, we introduce a microbenchmark suite to systematically assess and compare the performance of different levels in SMP memory hierarchies. Second, we present a new tool based on hardware performance monitors to determine a wide array of memory system characteristics, such as cache sizes, quickly and easily; by using this tool, …
Date: November 20, 2001
Creator: Yoo, A. B.; de Supinski, B.; Mueller, F. & Mckee, S. A.
Object Type: Article
System: The UNT Digital Library
ARF1 Frequency and Amplitude Curve Calibration (open access)

ARF1 Frequency and Amplitude Curve Calibration

ARF1 was calibrated and checked on 4/18/01. The technique used was to set the start/stop timers (A:R1LLT1 and A:R1LLT2) for duration of 200 msec. Driving the cavities for longer than 200 msec at full voltage could put some stress on the Hipotronics anode supply. The Camac curve generator card was substituted with a precision DC voltage source. Data for both amplitude and frequency were taken with the DC source. A HP 8563A spectrum analyzer in zero span with resolution bandwidth of 1 MHz at a center frequency of 52.818 MHz was used to take the amplitude data. The dynamic curve was a triangle waveform provided by a triggered HP3213A function generator. Frequency was measured on the Fluke frequency counter mounted in the rack in AP50 (with the high level RF off). The attached data and graph contain the current calibration. ARF1-1 is slightly lower voltage than ARF1-2, but well within spec. The calibration was made with the Anode supply at 9 Kvolts, the bend busses were off due to an access that was in progress. Due to the unregulated Anode supply, the voltage levels observed may be slightly higher than with bend busses on. The dynamic performance with the triangle …
Date: April 20, 2001
Creator: Pasquinelli, Ralph J.
Object Type: Report
System: The UNT Digital Library