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We use atom-tracking scanning tunneling microscopy to study the diffusion of Pd in the Pd/Cu(001) surface alloy. By following the motion of individual Pd atoms incorporated in the surface, we show that Pd diffuses by a vacancy-exchange, mechanism. We measure an effective activation energy for the diffusion of incorporated Pd atoms of 0.88 eV, which is consistent with an ab initio calculated barrier of 0.94 eV.

This paper investigates the questions of what statistical information about a memory request sequence is useful to have in making page replacement decisions: Our starting point is the Markov Request Model for page request sequences. Although the utility of modeling page request sequences by the Markov model has been recently put into doubt, we find that two previously suggested algorithms (Maximum Hitting Time and Dominating Distribution) which are based on the Markov model work well on the trace data used in this study. Interestingly, both of these algorithms perform equally well despite the fact that the theoretical results for these two algorithms differ dramatically. We then develop succinct characteristics of memory access patterns in an attempt to approximate the simpler of the two algorithms. Finally, we investigate how to collect these characteristics in an online manner in order to have a purely online algorithm.

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Correspondence issued by the General Accounting Office with an abstract that begins "Allegations of favoritism were raised about the Department of Labor's Office of Inspector General's (OIG) payment of relocation allowances to certain employees. GAO investigated the transfers of six OIG employees between or within its New York and New Jersey district offices from 1995 to November 2000. GAO found that decisions to grant or deny permanent change of station (PCS) and related relocation allowances were based on the needs of OIG and the availability of funds and do not appear to result from favoritism. Furthermore, the reimbursement associated with the PCS was in accordance with the Federal Travel Regulations."

The US DOE must provide a reasonable assurance that the performance objectives for the Yucca Mountain Project (YMP) potential radioactive-waste repository can be achieved for a 10,000-year post-closure period. The guidance that mandates this direction is under the provisions of 10 CFR Part 63 and the US Department of Energy's ''Revised Interim Guidance Pending Issuance of New US Nuclear Regulatory Commission (NRC) Regulations (Revision 01, July 22, 1999), for Yucca Mountain, Nevada'' (Dyer 1999 and herein referred to as DOE's Interim Guidance). This assurance must be demonstrated in the form of a performance assessment that: (1) identifies the features, events, and processes (FEPs) that might affect the performance of the potential geologic repository; (2) examines the effects of such FEPs on the performance of the potential geologic repository; (3) estimates the expected annual dose to a specified receptor group; and (4) provides the technical basis for inclusion or exclusion of specific FEPs.

Advanced thin film processing and packaging technologies are employed in the fabrication of new planar thin-film multifunction thermal converters. The processing, packaging, and design features build on experience gained from prior NIST demonstrations of thin-film converters and are optimized for improved sensitivity, bandwidth, manufacturability, and reliability.

A letter report issued by the General Accounting Office with an abstract that begins "The Quality Housing and Work Responsibility Act of 1998 was intended to give the nation's public housing agencies greater flexibility to manage their public housing or tenant-based section 8 programs. In the two years since the legislation was passed, the Department of Housing and Urban Development has provided sufficient guidance for housing agencies to begin making use of their expanded discretionary authority. In GAO's view, the agencies appear to be tailoring their policies to fit their own perceived needs and priorities, adopting only those provisions that fit their particular circumstances."

New standards for ac current and voltage measurements, thin-film multifunction thermal converters (MJTCS), have been fabricated using thin-film and micro-electro-mechanical systems (MEMS) technology. Improved sensitivity and accuracy over single-junction thermoelements and targeted performance will allow new measurement approaches in traditionally troublesome areas such as the low frequency and high current regimes. A review is presented of new microfabrication techniques and packaging methods that have resulted from a collaborative effort at Sandia National Laboratories and the National Institute of Standards and Technology (MHZ).

Shock excitations are normally random process realizations, and most of our efforts to represent them either directly or indirectly reflect this fact. The most common indirect representation of shock sources is the shock response spectrum. It seeks to establish the damage-causing potential of random shocks in terms of responses excited in linear, single-degree-of-freedom systems. This paper shows that shock sources can be represented directly by developing the probabilistic and statistical structure that underlies the random shock source. Confidence bounds on process statistics and probabilities of specific excitation levels can be established from the model. Some numerical examples are presented.

The long-term performance of Department of Energy (DOE) spent nuclear fuel (SNF) in a mined geologic disposal system depends highly on fuel oxidation and subsequent radionuclide release. The oxidation rates of nuclear fuels are reviewed in this two-volume report to provide a baseline for comparison with release rate data and technical rationale for predicting general corrosion behavior of DOE SNF. The oxidation rates of nuclear fuels in the DOE SNF inventory were organized according to metallic, Part 1, and non-metallic, Part 2, spent nuclear fuels. This Part 1 of the report reviews the oxidation behavior of three fuel types prototypic of metallic fuel in the DOE SNF inventory: uranium metal, uranium alloys and aluminum-based dispersion fuels. The oxidation rates of these fuels were evaluated in oxygen, water vapor, and water. The water data were limited to pure water corrosion as this represents baseline corrosion kinetics. Since the oxidation processes and kinetics discussed in this report are limited to pure water, they are not directly applicable to corrosion rates of SNF in water chemistry that is significantly different (such as may occur in the repository). Linear kinetics adequately described the oxidation rates of metallic fuels in long-term corrosion. Temperature dependent oxidation …

Between 1965 and 1979 there were five documented and one or more inferred attempts to stimulate the production from hydrocarbon reservoirs by detonating nuclear devices in reservoir strata. Of the five documented tests, three were carried out by the US in low-permeability, natural-gas bearing, sandstone-shale formations, and two were done in the USSR within oil-bearing carbonates. The objectives of the US stimulation efforts were to increase porosity and permeability in a reservoir around a specific well by creating a chimney of rock rubble with fractures extending beyond it, and to connect superimposed reservoir layers. In the USSR, the intent was to extensively fracture an existing reservoir in the more general vicinity of producing wells, again increasing overall permeability and porosity. In both countries, the ultimate goals were to increase production rates and ultimate recovery from the reservoirs. Subsurface explosive devices ranging from 2.3 to about 100 kilotons were used at depths ranging from 1208 m (3963 ft) to 2568 m (8427 ft). Post-shot problems were encountered, including smaller-than-calculated fracture zones, formation damage, radioactivity of the product, and dilution of the BTU value of tie natural gas with inflammable gases created by the explosion. Reports also suggest that production-enhancement factors from …

Ion Beam Induced Luminescence (IBIL) and Ion Beam Induced Charge Collection (IBICC) have been applied in the study of the luminescence emission efficiency and investigation of the homogeneity of the luminescence emission in phosphors. The IBIL imaging was performed by using sharply focused ion beams or broad/partially-focused ion beams. The luminescence emission homogeneity in samples was examined to reveal possible distributed crystal-defects that may lead to the inhomogeneity of the luminescence emission in samples.The purpose of the study is to search for suitable luminescent thin films that have high homogeneity of luminescence emission, large IBIL efficiency under heavy ion excitation, and can be placed as a thin layer on the top of microelectronic devices to be analyzed with Ion Photon Emission Microscopy (IPEM). The emission yield was found to be low for organic materials, due to saturation of the light output dependence on the energy deposition of heavy ions. The emission yield of a typical Bicron plastic scintillator is about 70 photons/ion/micron. Inorganic materials may have higher IBIL yield under high-energy and heavy-ion excitation, but the challenging problem is the inhomogeneity of the IBIL emission. The IBIL image techniques are applied in the investigation of the homogeneity of a GaN …

A weekly publication, the Texas Register serves as the journal of state agency rulemaking for Texas. Information published in the Texas Register includes proposed, adopted, withdrawn and emergency rule actions, notices of state agency review of agency rules, governor's appointments, attorney general opinions, and miscellaneous documents such as requests for proposals. After adoption, these rulemaking actions are codified into the Texas Administrative Code.

We have performed a thermal mechanical analysis of the Drift Scale Test (DST) currently underway at Yucca Mountain. The Yucca Mountain Site Characterization Project is investigating Yucca Mountain, Nevada, as a potential repository for high-level nuclear waste. The purpose of the DST is to acquire a more in-depth understanding of coupled Thermal-Mechanical-Hydrological-Chemical (TMHC) processes likely to exist in the rock mass surrounding a potential geologic repository at Yucca Mountain. Moreover, the DST is located in a highly fractured and densely welded ash-flow tuff, and movement of fluids in this rock is thought to occur primarily through the fractures. Our work is concerned with describing fracture deformation due to thermal mechanical effects, as normal and shear deformation of fractures can substantially change the fracture permeability, and affect the coupled TMHC behavior. We modeled the DST by defining a rectangular rock mass 50m x 50m x 100m in size. The rock mass was formed by an assemblage of discrete, elastic blocks. Excavations within the DST were closely simulated, and discrete fractures mapped from video logs of several boreholes in the DST test block were incorporated. Stress boundary conditions were used on the top and sides of the rock mass, while the bottom …

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The Xyce{trademark} Parallel Electronic Simulator has been written to support the simulation needs of the Sandia National Laboratories electrical designers. As such, the development has focused on providing the capability to solve extremely large circuit problems by supporting large-scale parallel computing platforms (up to thousands of processors). In addition, they are providing improved performance for numerical kernels using state-of-the-art algorithms, support for modeling circuit phenomena at a variety of abstraction levels and using object-oriented and modern coding-practices that ensure the code will be maintainable and extensible far into the future. The code is a parallel code in the most general sense of the phrase--a message passing parallel implementation--which allows it to run efficiently on the widest possible number of computing platforms. These include serial, shared-memory and distributed-memory parallel as well as heterogeneous platforms. Furthermore, careful attention has been paid to the specific nature of circuit-simulation problems to ensure that optimal parallel efficiency is achieved even as the number of processors grows.

AMBER is a Particle-In-Cell (PIC) code which models the evolution of a representative slice of a relativistic electron beam in a linear accelerator. The beam is modeled as a steady flow and therefore no electromagnetic waves: all the fields (external and self-fields) are electrostatic and magnetostatic fields (for a complete description, see chapter 5). The possible elements describing the accelerator lattice are solenoids, accelerating gaps, pipes and apertures. Several kinds of beam distribution can be loaded: KV, gaussian, semi-gaussian, etc. Alternatively, the user can reconstruct (or load) a distribution from the output of another codefile, for example, an interface generating the beam distribution from output produced from EGUN or LSP codes is available as an option. This documentation first describes in detail the input files needed to run AMBER and the procedure to start the executable. The possible data files and graphical output are explained in the two following chapters. The last chapter describes the physics model and numerical techniques used. An example of input files and the result obtained with these inputs are also given in the Appendix.

Correspondence issued by the General Accounting Office with an abstract that begins "This report discusses bank regulators' evaluation of electronic signature systems. Financial institutions use signature systems to verify or authenticate the identity of customers conducting financial and nonfinancial transactions over the Internet and other open electronic networks. Officials at the Office of the Comptroller of the Currency (OCC) and the Federal Reserve told GAO that they are developing an examination strategy for Identrus LLC, which is an entity that provides services to financial institutions to authenticate electronic signatures. OCCofficials have not determined what role they will play in assessing Identrus' operations, but they believe that financial institutions should take an active role in assessing the risks associated with electronic signatures."

We present evidence for a change in electron--phonon coupling across a bulk phase transition. Below the lattice stiffening transition at around 160 K, there is a change in the diffracted peak width observed by neutron and X-ray scattering techniques. Also, the electronic band structure of the copolymer is shifting in binding energy below 160 K, decreasing the density of states near the Fermi level. The value of the effective Debye temperature above the transition temperature is approximately 50 K, while below 160 K, the value of the Debye parameter is 245 K. We postulate that the coupling between electrons and phonons results in a static distortion of the lattice (below 160 K), and this distortion ''melts'' above 160 K.

The purpose of this analysis is to document the Quality Assurance (QA) classification of the Monitored Geologic Repository (MGR) waste emplacement/retrieved system structures, systems and components (SSCs) performed by the MGR Preclosure Safety and Systems Engineering Section. This analysis also provides the basis for revision of YMP/90-55Q, Q-List (YMP 2000). The Q-List identifies those MGR SSCs subject to the requirements of DOE/RW-0333P, Quality Assurance Requirements and Description (QARD) (DOE 2000). This QA classification incorporates the current MGR design and the results of the ''Design Basis Event Frequency and Dose Calculation for Site Recommendation'' (CRWMS M&O 2000a). The content and technical approach of this analysis is in accordance with the development plan ''QA Classification of MGR Structures, Systems, and Components'' (CRWMS M&O 1999b).

The magnetic field and temperature dependence of the magnetic susceptibility and magnetization is studied for the ferromagnetic layered manganites SrO(La{sub t{minus}x}Sr{sub x}MnO{sub 3}){sub 2} in the composition range x = 0.32-0.40. In the paramagnetic phase, the susceptibility exhibits an anomalous maximum at an intermediate magnetic field value. The size of this field-induced susceptibility enhancement increases dramatically with x from 10% for x = 0.32 to 160% for x = 0.40. The temperature dependence of the effect shows a maximum at T {approx} 1.1 T{sub c} for all x. Quantitative analysis in terms of the Landau theory of phase transitions enables us to identify a distortion of the free energy F in the paramagnetic phase that is associated with the susceptibility anomaly. This free energy distortion corresponds to a magnetic system that approaches a first order magnetic phase transition as the temperature is lowered towards T{sub c}. Such a behavior is indicative of a second, competing order parameter, which is identified as the recently observed charge density wave. In the immediate vicinity of T{sub c}, the anomaly disappears and the system seems to undergo a more conventional second order paramagnetic-ferromagnetic phase transition.

A new enhanced, visual version of DART code is presented. DART is a mechanistic model based code, developed for the performance calculation and assessment of aluminum dispersion fuel. Major issues of this new version are the development of a new, time saving calculation routine, able to be run on PC, a friendly visual input interface and a plotting facility. This version, available for silicide and U-Mo fuels,adds to the classical accuracy of DART models for fuel performance prediction, a faster execution and visual interfaces. It is part of a collaboration agreement between ANL and CNEA in the area of Low Enriched Uranium Advanced Fuels, held by the Implementation Arrangement for Technical Exchange and Cooperation in the Area of Peaceful Uses of Nuclear Energy.

A letter report issued by the General Accounting Office with an abstract that begins "The Forest Service manages about 192 million acres of land that make up the National Forest System. The agency has proposed to make ecological sustainability its top priority in an attempt to sustain a flow of products, services, and values from the national forests and grasslands. One of the most debated issues is the role of roads, especially in areas that are now roadless. This report summarizes GAO's findings on how the potential roadless rule will affect the Forest Service's ability to meet its goals of restoring and maintaining ecological sustainability. GAO found that building roads in national forests can have both positive and negative effects. Road construction can alter a forest's ecosystem by facilitating timber harvesting and disturbing wildlife. However, roads can be used to repair environmental damage done by other activities. Forest Service officials at the 10 National forests that GAO reviewed provided general observations on the proposed rule. In GAO's view, the proposed rule would have little effect on forest management efforts because there was no plan to build roads in roadless areas unless it was determined that doing so would restore the …