Hypersonic laminar boundary layers around slender bodies

Compressible laminar boundary layer equations considered for hypersonic flow around slender bodie

Integration of tools for the Design and Assessment of High-Performance, Highly Reliable Computing Systems (DAHPHRS), phase 1

Systems for Space Defense Initiative (SDI) space applications typically require both high performance and very high reliability. These requirements present the systems engineer evaluating such systems with the extremely difficult problem of conducting performance and reliability trade-offs over large design spaces. A controlled development process supported by appropriate automated tools must be used to assure that the system will meet design objectives. This report describes an investigation of methods, tools, and techniques necessary to support performance and reliability modeling for SDI systems development. Models of the JPL Hypercubes, the Encore Multimax, and the C.S. Draper Lab Fault-Tolerant Parallel Processor (FTPP) parallel-computing architectures using candidate SDI weapons-to-target assignment algorithms as workloads were built and analyzed as a means of identifying the necessary system models, how the models interact, and what experiments and analyses should be performed. As a result of this effort, weaknesses in the existing methods and tools were revealed and capabilities that will be required for both individual tools and an integrated toolset were identified

Water at interfaces - some recent experimental results from surface spectroscopy

Journal ArticleFundamental aspects of interfacial phenomena in aqueous systems are determined by the properties of interfacial water It has become evident that interfacial water must be characterized spectroscopically in order to explain the recently identified non DLVO forces observed by atomic force microscopy and with the surface force apparatus. In the past little information was available regarding the spectroscopic characteristics of interfacial water due to the difficulty in differentiating between bulk and interfacial water. However, with the advent of FTIR and Raman internal reflection spectroscopy (IRS) and the recent non-linear optical technique, sum frequency generation (SFG), more information on interfacial water is now available as is evident from the results of recent spectroscopic studies. Thus the non DLVO forces eventually may be explained by the extent of hydrogen bonding as revealed by surface spectroscopic techniques

Characterization of interfacial water at hydrophilic and hydrophobic surfaces by in situ FTIR/internal reflection spectroscopy

Journal ArticleIn-situ FTIR/internal reflection spectroscopy (FTIR/IRS) has been used to spectroscopically characterize interfacial water near hydrophilic (silicon single crystal) and hydrophobic (polymer-coated germanium single crystal) surfaces. Interfacial water was examined spectroscopically over certain distances from the surface by appropriate design of the geometry and optics of the internal reflection system. The in-situ FTIR/IRS spectra were characterized by consideration of the OH stretching region (3000-3800 cm"1) associated with the vibrational spectra of the interfacial water. Preliminary spectral results indicate the prevalence of an ice-like structure at the hydrophilic silicon surface, whereas at the hydrophobic surface the ice like structure is not so prevalent and there appears to be a significant decrease in hydrogen bonding

Inference of gene-phenotype associations via protein-protein interaction and orthology

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Effectively Transparent Front Contacts for Optoelectronic Devices

Effectively transparent front contacts for optoelectronic devices achieve a measured transparency of up to 99.9% and a measured sheet resistance of 4.8 Ω sq^(−1). The 3D microscale triangular cross-section grid fingers redirect incoming photons efficiently to the active semiconductor area and can replace standard grid fingers as well as transparent conductive oxide layers in optoelectronic devices

Shocks in supersonic sand

We measure time-averaged velocity, density, and temperature fields for steady granular flow past a wedge and calculate a speed of granular pressure disturbances (sound speed) equal to 10% of the flow speed. The flow is supersonic, forming shocks nearly identical to those in a supersonic gas. Molecular dynamics simulations of Newton's laws and Monte Carlo simulations of the Boltzmann equation yield fields in quantitative agreement with experiment. A numerical solution of Navier-Stokes-like equations agrees with a molecular dynamics simulation for experimental conditions excluding wall friction.Comment: 4 pages, 5 figure

High Broadband Light Transmission for Solar Fuels Production Using Dielectric Optical Waveguides in TiO₂ Nanocone Arrays

We describe the fabrication and use of arrays of TiO₂ nanocones to yield high optical transmission into semiconductor photoelectrodes covered with high surface loadings of light-absorbing electrocatalysts. Covering over 50% of the surface of a light absorber with an array of high-refractive-index TiO₂ nanocones imparted antireflective behavior ( 85% transmission of broadband light to the underlying Si, even when thick metal contacts or opaque catalyst coatings were deposited on areas of the light-facing surface that were not directly beneath a nanocone. Three-dimensional full-field electromagnetic simulations for the 400 – 1100 nm spectral range showed that incident broadband illumination couples to multiple waveguide modes in the TiO₂ nanocones, reducing interactions of the light with the metal layer. A proof-of-concept experimental demonstration of light-driven water oxidation was performed using a p⁺n-Si photoanode decorated with an array of TiO₂ nanocones additionally having a Ni catalyst layer electrodeposited onto the areas of the p⁺n-Si surface left uncovered by the TiO₂ nanocones. This photoanode produced a light-limited photocurrent density of ~ 28 mA cm⁻² under 100 mW cm⁻² of simulated Air Mass 1.5 illumination, equivalent to the photocurrent density expected for a bare planar Si surface even though 54% of the front surface of the Si was covered by an ~ 70 nm thick Ni metal layer

Effectively Transparent Front Contacts for Optoelectronic Devices

Effectively transparent front contacts for optoelectronic devices achieve a measured transparency of up to 99.9% and a measured sheet resistance of 4.8 Ω sq^(−1). The 3D microscale triangular cross-section grid fingers redirect incoming photons efficiently to the active semiconductor area and can replace standard grid fingers as well as transparent conductive oxide layers in optoelectronic devices