This article discusses Lévy diffusion as an effect of sporadic randomness.

Article discussing an ab initio study of methane activation by group IVB imido complexes.

This article discusses noise-induced transition from anomalous to ordinary diffusion and the crossover time as a function of noise intensity.

Article discussing research on chaos and thermal conductivity.

Article on mechanical deformations and coherent transport in carbon nanotubes.

Article on low-energy vibrations at the InSb(110) surface along the ΓΥ direction.

Corrections to an equation printed with a typographical error in Quantum Irreversibility and Chaos, Physical Review Letters 67, 2593 (1991).

Article on N-acylethanolamines in signal transduction of elicitor perception and the attenuation of alkalinization response and activation of defense gene expression.

Article on the degradation of the metal-cyano complex tetracyanonickelate(II) by cyanide-utilizing bacterial isolates.

Article on the spectroscopic properties of polycyclic aromatic hydrocarbons and the effect of solvent polarity on the fluorescence emission behavior of select fluoranthene, fluorenochrysene, indenochrysene, and indenopyrene derivatives.

This article provides comments on "Fluorescent Probe Studies on the Microstructure of Polystyrene-Poly (vinylpyridine) Diblock Copolymer Film," published in 'Macromolecules,' 1992.

Article on computational studies of the potential energy surface for O(¹D) + H₂S and the characterization of pathways involving H₂SO, HOSH, and H₂OS.

The second half of the twentieth century has seen major changes in computer architecture. In the early fifties to the early seventies, the word ``computes`` demanded reverence, respect and even fear. Computers, then, were almost ``untouchable``. Today, computers have become the mainstreams of communication on the rapidly expanding communication highways. They have become necessities of life. With the computers came the establishment of information centers -- tasked with the dissemination of newly developed computer codes and generated data. The Radiation Shielding Information Center (RSIC) was founded in 1962 as a valuable resource for programs and cross section data concerned with the effects of radiation. Through the years, RSIC has collected computer codes developed for the early machines (IBM 360, DEC PDP-10, CDC 660, UNIVAC 1100), to the more modern and powerful desktops (Pentium based Personal Computers, UNIX workstations like the IBM RISC 6000, DEC Alpha, SUN) and supercomputers (Cray XMP, Cray YMP, Cray C90, IBM SP2).

Three and four-layer backpropagation artificial neural networks have been used to predict the power output of a liquid metal reflux solar receiver. The networks were trained using on-sun test data recorded at Sandia National Laboratories in Albuquerque, New Mexico. The preliminary results presented in this paper are a comparison of how different size networks train on this particular data. The results give encouragement that it will be possible to predict output power of a liquid metal receiver under a variety of operating conditions using artificial neural networks.

The Radiological Environment Modeling System (REMS) quantifies dose to humans in radiation environments using the IGRIP (Interactive Graphical Robot Instruction Program) and Deneb/ERGO (Ergonomics) simulation software products. These commercially available products are augmented with custom C code to provide the radiation exposure information to and collect the radiation dose information from the workcell simulations. The emphasis of this paper is on the IGRIP and Deneb/ERGO parts of REMS, since that represents the extension to existing capabilities developed by the authors. Through the use of any radiation transport code or measured data, a radiation exposure input database may be formulated. User-specified IGRIP simulations utilize these database files to compute and accumulate dose to human devices (Deneb`s ERGO human) during simulated operations around radiation sources. Timing, distances, shielding, and human activity may be modeled accurately in the simulations. The accumulated dose is recorded in output files, and the user is able to process and view this output. REMS was developed because the proposed reduction in the yearly radiation exposure limit will preclude or require changes in many of the manual operations currently being utilized in the Weapons Complex. This is particularly relevant in the area of dismantlement activities at the Pantex Plant …

A conceptual model of shallow infiltration processes at Yucca Mountain, Nevada, was developed for use in hydrologic flow models to characterize net infiltration (the penetration of the wetting front below the zone influenced by evapotranspiration). The model categorizes the surface of the site into four infiltration zones. These zones were identified as ridgetops, sideslopes, terraces, and active channels on the basis of water-content changes with depth and time. The maximum depth of measured water-content change at a specific site is a function of surface storage capacity, the timing and magnitude of precipitation, evapotranspiration, and the degree of saturation of surficial materials overlying fractured bedrock. Measured water-content profiles for the four zones indicated that the potential for net infiltration is higher when evapotranspiration is low (i.e winter, cloudy periods), where surface concentration of water is likely to occur (i.e. depressions, channels), where surface storage capacity is low, and where fractured bedrock is close to the surface.

Creep, a potential degradation mechanism of Zircaloy cladding after repository disposal of spent nuclear fuel, has been investigated. The deformation and fracture map methodology has been used to predict maximum allowable initial storage temperatures to achieve a thousand year life without rupture as a function of spent-fuel history. Maximum allowable temperatures are 340{degree}C (613 K) for typically stressed rods (70--100 MPa) and 300{degree}C (573 K) for highly stressed rods (140--160 MPa). 10 refs., 2 figs.

Cathode dissolution into the electrolyte matrix and endurance of current collector/separator plate materials are the main life-limiting factors of the state-of-the art MCFC. These components are also major contributors to the total system cost. Therefore, to reduce capital cost, it is necessary to minimize hardware corrosion and increase cell life. This study consists of experimental evaluation of corrosion processes with the objective to further practical; understanding of corrosion behavior of alloys and alloy components under cathodic gas conditions. Nickel, iron, cobalt and stainless steels 310 and 316L are analyzed. The experimental study consists of: (1) Observation of open circuit potential (OCP) changes. Surface reactions occurring without net passage of current are proposed based on this measurement. (2) Applying cyclic voltammetry, which provides information about the possible electrode reactions at different stages of polarization. (3) Applying AC impedance to support the result of tasks 1 and 2 at different stages of oxidation, and data analysis by means of equivalent circuits. Open circuit conditions as well as positive and negative polarization are used in the impedance measurements. (4) Surface analysis of the electrodes by SEM-EDX and X-ray diffraction. To obtain more information from electrochemical measurements a novel approach has been applied in …

ARIES (Autonomous Robotic Inspection Experimental System) is under development for the Department of Energy (DOE) to survey and inspect drums containing low-level radioactive waste stored in warehouses at DOE facilities. This paper focuses on the mechanical deployment system-referred to as the camera positioning system (CPS)-used in the project. The CPS is used for positioning four identical but separate camera packages consisting of vision cameras and other required sensors such as bar-code readers and light stripe projectors. The CPS is attached to the top of a mobile robot and consists of two mechanisms. The first is a lift mechanism composed of 5 interlocking rail-elements which starts from a retracted position and extends upward to simultaneously position 3 separate camera packages to inspect the top three drums of a column of four drums. The second is a parallelogram special case Grashof four-bar mechanism which is used for positioning a camera package on drums on the floor. Both mechanisms are the subject of this paper, where the lift mechanism is discussed in detail.

The results from a performance test of a {gamma}- and neutron-radiation measurement instrument used to provide two-dimensional radiation field maps are reported. The performance test was conducted at the Transuranic Storage Area of the Radioactive Waste Management Complex (RWMC) where interim storage is provided for 55-gal. drums of TRU waste from the Department of Energy`s Rocky Flats Plant. The performance test consisted of scanning drums stacked five high and five wide to identify high radiation areas and possible discrepancies with the waste manifest. Scans were taken at standoff distances of 15 cm, 30 cm, 45 cm and 90 cm. Data were acquired at scan speeds of 7.5 cm/s and 15 cm/s. The results of these scans are presented as one, two and three dimensional contour plots of the radiation fields. A comparison of these results with manifests of these drums are compared and discussed. While the T-radiation fields as measured by the Health Physicist and by the radiation maps are in general in agreement, the TRU content as given in the manifest did not often correlate with the neutron map.

We report two aspects of a computational molecular dynamics study of large-scale problems on a distributed-memory MIMD parallel computer: (1) efficiency and scalability results on Intel Paragon parallel computers with up to 512 nodes and (2) a new method for dynamic load balancing.

Fracture-mechanics crack growth tests were conducted on 25.4-mm-thick compact tension specimens of Types 304L and 316L Stainless steel and Incoloy 825 at 93{degrees}C and 1 atmosphere of pressure in simulated J-13 well water, which is representative of the groundwater at the Yucca Mountain site in Nevada that is proposed for a high-level nuclear waste repository. Crack growth rates were measured under various load conditions: load ratios of 0.2--1.0, frequencies of 2 {times} 10{sup {minus}4}{minus}1 Hz, rise times of 1--5000 s, and peak stress intensities of 25--40 MPa{center_dot}m{sup {1/2}}. The measured crack growthrates are bounded by the predicted rates from the current ASME Section 11 correlation for fatigue crack growth rates of austenitic stainless steel in air. Environmentally accelerated crack growth was not evident in any of the three materials under the test conditions investigated.

Reaction-bonded silicon carbide ({alpha}-SiC) armor tiles were annealed at 2100{degree}C using microwave radiation at 2.45 GHz. Ultrasonic velocity measurements showed that the longitudinal and shear velocities, acoustic impedances, and acoustic moduli of the post-annealed tiles were statistically higher than for the unannealed tiles. However, the exposed surfaces of the annealed tiles experienced slight degradation, which was attributed to the high annealing temperatures.

Scaling laser systems to large sizes for power beaming and other applications can sometimes be simplified by combing a number of smaller lasers. However, to fully utilize this scaling, coherent beam combination is necessary. This requires measuring and controlling each beam`s pointing and phase relative to adjacent beams using an adaptive optical system. We have built a sub-scale brass-board to evaluate various methods for beam-combining. It includes a segmented adaptive optic and several different specialized wavefront sensors that are fabricated using diffractive optics methods. We have evaluated a number of different phasing algorithms, including hierarchical and matrix methods, and have demonstrated phasing of several elements. The system is currently extended to a large number of segments to evaluate various scaling methodologies.