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Experiment summary for n/y attenuation through materials (Environments 1A)

Depriest, Kendall R.

The Radiation Effects Sciences (RES) program is responsible for conducting Neutron Gamma Energy Transport (NuGET) code validation. In support of this task, a series of experiments were conducted in the annular core research reactor (ACRR) to investigate the modification of the incident neutron/gamma environment by aluminum (Al6061) and high-density polyethylene (HDPE) spheres with 4-in and 7-in-diameter. The experiment series described in this report addresses several NuGET validation concerns. The validation experiment series also addresses the design and execution of proper reactor testing to match the hostile radiation environments and to match the component stresses that arise from the hostile radiation environments. This report summarizes the RES Validation: n/{gamma} Attenuation through Materials, Environments 1A, experiments conducted at the ACRR in FY 2003 using ACRR Experiment Plans 933 and 949.

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TYPE SAND Report YEAR 2006
DOIOSTI

Survey of the hypervelocity impact technology and applications

Chhabildas, L.C.

HVIS 2005 was a clear success. The Symposium brought together nearly two hundred active researchers and students from thirteen countries around the world. The 84 papers presented at HVIS 2005 constitute an ''update'' on current research and the state-of-the-art of hypervelocity science. Combined with the over 7000 pages of technical papers from the eight previous Symposia, beginning in 1986, all published in the International Journal of Impact Engineering, the papers from HVIS 2005 add to the growing body of knowledge and the progressing state-of-the-art of hypervelocity science. It is encouraging to report that even with the limited funding resources compared to two decades ago, creativity and ingenuity in hypervelocity science are alive and well. There is considerable overlap in different disciplines that allows researchers to leverage. Experimentally, higher velocities are now available in the laboratory and are ideally suited for space applications that can be tied to both civilian (NASA) and DoD military applications. Computationally, there is considerable advancement both in computer and modeling technologies. Higher computing speeds and techniques such as parallel processing allow system level type applications to be addressed directly today, much in contrast to the situation only a few years ago. Needless to say, both experimentally and computationally, the ultimate utility will depend on the curiosity and the probing questions that will be incumbent upon the individual researcher. It is quite satisfying that over two dozen students attended the symposium. Hopefully this is indicative of a good pool of future researchers that will be needed both in the government and civilian industries. It is also gratifying to note that novel thrust areas exploring different and new material phenomenology relevant to hypervelocity impact, but a number of other applications as well, are being pursued. In conclusion, considerable progress is still being made that is beneficial for continuous development of hypervelocity impact technology and applications even with the relatively limited resources that are being directed in this field.

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TYPE SAND Report YEAR 2006
DOIOSTI

Self-assembling holographic biosensors and biocomputers

Schoeniger, Joseph S.; Light, Yooli K.; Trent, Amanda M.; Bachand, George D.

We present concepts for self-assembly of diffractive optics with potential uses in biosensors and biocomputers. The simplest such optics, diffraction gratings, can potentially be made from chemically-stabilized microtubules migrating on nanopatterned tracks of the motor protein kinesin. We discuss the fabrication challenges involved in patterning sub-micron-scale structures with proteins that must be maintained in aqueous buffers to preserve their activity. A novel strategy is presented that employs dry contact printing onto glass-supported amino-silane monolayers of heterobifunctional crosslinkers, followed by solid-state reactions of these cross-linkers, to graft patterns of reactive groups onto the surface. Successive solution-phase addition of cysteine-mutant proteins and amine-reactive polyethylene glycol allows assembly of features onto the printed patterns. We present data from initial experiments showing successful micro- and nanopatterning of lines of single-cysteine mutants of kinesin interleaved with lines of polyethylene, indicating that this strategy can be employed to arrays of features with resolutions suitable for gratings.

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TYPE SAND Report YEAR 2006
DOIOSTI

Micropower chemical fuel-to-electric conversion : a "regenerative flip" hydrogen concentration cell promising near carnot efficiency

Wally, Karl W.

Although battery technology is relatively mature, power sources continue to impose serious limitations for small, portable, mobile, or remote applications. A potentially attractive alternative to batteries is chemical fuel-to-electric conversion. Chemical fuels have volumetric energy densities 4 to 10 times those of batteries. However, realizing this advantage requires efficient chemical fuel-to-electric conversion. Direct electrochemical conversion would be the ideal, but, for most fuels, is generally not within the state-of-the-science. Next best, chemical-to-thermal-to-electric conversion can be attractive if efficiencies can be kept high. This small investigative project was an exploration into the feasibility of a novel hybrid (i.e., thermal-electrochemical) micropower converter of high theoretical performance whose demonstration was thought to be within near-term reach. The system is comprised of a hydrogen concentration electrochemical cell with physically identical hydrogen electrodes as anode and cathode, with each electrode connected to physically identical hydride beds each containing the same low-enthalpy-of-formation metal hydride. In operation, electrical power is generated by a hydrogen concentration differential across the electrochemical cell. This differential is established via coordinated heating and passive cooling of the corresponding hydride source and sink. Heating is provided by the exothermic combustion (i.e., either flame combustion or catalytic combustion) of a chemical fuel. Upon hydride source depletion, the role of source and sink are reversed, heating and cooling reversed, electrodes commutatively reversed, cell operation reversed, while power delivery continues unchanged. This 'regenerative flip' of source and sink hydride beds can be cycled continuously until all available heating fuel is consumed. Electricity is efficiently generated electrochemically, but hydrogen is not consumed, rather the hydrogen is regeneratively cycled as an electrochemical 'working fluid'.

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TYPE SAND Report YEAR 2006
DOIOSTI

Geochemical chaos: Periodic and nonperiodic growth of mixed-layer phyllosilicates

Geochimica et Cosmochimica Acta

Wang, Yifeng; Xu, Huifang

Interstratification-periodic or nonperiodic stacking of two different silicate layers along a c*-axis-is common in phyllosilicates. Published evidence indicates that some interstratified minerals precipitate directly from aqueous solutions. In this paper, we have demonstrated, based on chaos theory, that both periodic and nonperiodic interstratification can autonomously arise from simple kinetics of mineral growth from a solution. Growth of a mixed-layer mineral is assumed to proceed layer by layer, and each layer starts with the formation of a base (Si, Al)-O tetrahedral sheet, whose structural configuration in a-b dimensions determines the type of new layer that forms. The sequence of layer stacking can be described by a one-dimensional map (i.e., a difference equation), which accounts for two competing factors: (1) the affinity of each end-member structural component for attaching to the surface of the preceding layer, and (2) the strain energy created by stacking next to each other two silicate layers with different structural configurations. Chaotic (or nonperiodic) interstratification emerges when the contacting solution becomes slightly supersaturated with respect to both structural components. The transition from one interstratification pattern to another reflects a change in chemical environment during mineral crystallization. Our model can successfully predict the occurrence of mixed-layer phyllosilicates and the associated layer stacking sequences observed in both hydrothermal alteration and sediment diagenesis. The model suggests that the diagenetic transition of smectite → nonperiodic illite/smectite → ordered illite/smectite → illite may reflect relative changes in the saturation degree of pore water with respect to two end-member phases as a result of increasing burial temperatures. © 2006 Elsevier Inc. All rights reserved.

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TYPE Conference YEAR 2006
ScopusOSTI
Results 84501–84600 of 99,299
Results 84501–84600 of 99,299