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Liu, B.

Publications and source records attributed to Liu, B..

At least 19 records
All sourcesNASA NTRSDOE OSTI
DOE OSTI2024

The Beta-decay Paul Trap Mk IV: Design and commissioning

Here, the Beta-decay Paul Trap is an open-geometry, linear trap used to measure the decays of 8 Li and 8 B to search for a tensor contribution to the weak interaction. In the latest 8 Li measurement of Burkey et al. (2022), β scattering was the dominant experimental systematic uncertainty. The Beta-decay Paul Trap Mk IV reduces the prevalence of β scattering by a factor of 4 through a redesigned electrode geometry and the use of glassy carbon and graphite as electrode materials. The trap has been constructed and successfully commissioned with 8 Li in a new data campaign that collected 2.6 million triple coincidence events, an increase in statistics by 30% with 4 times less β scattering compared to the previous 8 Li data set.

46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND ↗
NASA NTRS2002

Solid State Electrolytes Prepared from PEO (360) Silanated Silica

All solid state composite electrolytes were prepared using fumed silica (SiO2) silanated with an oligomeric polyethylene oxide (PEO) silane containing 6-9 ethylene oxide repeat units, a PEO matrix and LiClO4 (8/1 O/Li). The PEO-silane covalently attached to the silica was amorphous, with a T(sub g) that increased from -90 C to -53 C after attachment. The conductivity of films prepared using the PEO-silanated silica increased to approx. 6 x 10(exp -5) S/cm at RT compared with approx. 1 x 10(-5) S/cm for films prepared with unsilanated SiO2.

Maitra, P.↗
NASA NTRS2002

Preparation and Characterization of Single Ion Conductors from High Surface Area Fumed Silica

Anions that can form dissociative salts with Li(+) have been prepared and covalently attached to high surface area fumed silica. When blended with polyethylene oxide (PEO), the functionalized fumed silica suppresses the crystallization of the PEO, provides dimensional stability, and serves as a single ion conductor. Since functionalized fumed silica is easily dispersed in common polar solvents, it can be incorporated in both the polymer electrolyte and the electrodes.

Zhang, H.↗
NASA NTRS2000

Overview of the Preliminary Design of the Optical Communication Demonstration and High-Rate Link Facility

Tlis paper presents an overview of the preliminary design of both the flight and ground systems of the Optical Communication Demonstration and High-Rate Link Facility which will demonstrate optical communication from the International Space Station to ground after its deployment in October 2002. The overview of the preliminary design of the Flight System proceeds by contrasting it with the design of the laboratory-model unit, emphasizing key changes and the rationale behind the design choices. After presenting the preliminary design of the Ground System, the timetable for the construction and deployment of the flight and ground systems is outlined.

Sandusky, John V.↗
NASA NTRS1988

The C4H7+ cation. A theoretical investigation

The potential energy surface of the C4H7+ cation has been investigated with ab initio quantum chemical theory. Extended basis set calculations, including electronic correlation, show that cyclobutyl and cyclopropylcarbinyl cation are equally stable isomers. The saddle point connecting these isomers lies 0.6 kcal/mol above the minima. The global C4H7+ minimum corresponds to the 1-methylallyl cation, which is 9.0 kcal/mol more stable than the cyclobutyl and the cyclopropylcarbinyl cation and 9.5 kcal/mol below the 2-methylallyl cation. These results are in excellent agreement with experimental data.

NASA Discipline Number 52-10↗
NASA NTRS1983

Theoretical study of the AlO blue-green (B2Sigma + - X2Sigma +) band system

Two independent, extensive theoretical calculations are reported for the relative band strengths of the AlO (B2Sigma + - X2Sigma +) blue-green system and for the radiative lifetimes of the lowest few vibrational levels of the B2Sigma(+) state. The theoretical lifetimes, which include a small (less than -.5 percent) contribution from bound-bound transitions into the A2Pi state, are in excellent agreement with laser fluorescence studies. The theoretical lifetimes increase monotonically and very slowly with increasing vibrational quantum number. The relative band strengths for the blue-green system derived from the two theoretical calculations are in excellent agreement, but differ systematically from the relative band strengths of Linton and Nicholls (1969). The present results suggest that their self-absorption corrections are not large enough, resulting in relative intensities that are too large, especially for the weak bands with r centroids less than 1.5 A.

Partridge, H.↗
NASA NTRS1983

An ab initio study of core-valence correlation

Especially in the cases of the first two columns of the periodic table, the inclusion of core-valence correlation in ab initio CI calculations yields a contraction of the atomic valence shell and improves both calculated atomic ionization potentials and atomic energy separations. For the alkali dimers Na2, K2, and Rb2, the presently calculated bond lengths are in excellent agreement with experiments when core-valence is included. In addition, the valence dissociation energies are accurate.

Partridge, H.↗
NASA NTRS1983

Theoretical study of NH2 - Potential curves, transition moments, and photodissociation cross sections

Photodissociation cross sections from the ground state of NH2 have been calculated using a pseudodiatomic model. The potential curves needed in these calculations, functions of one NH bond length, were obtained by ab initio MCSCF calculations on the five lowest doublet states of NH2 using a contracted Gaussian basis set of double zeta quality augmented by polarization and Rydberg functions. Transition dipole moments between the ground and excited states were evaluated using MCSCF wave functions.

Saxon, R. P.↗
NASA NTRS1982

Advanced digital SAR processing study

A highly programmable, land based, real time synthetic aperture radar (SAR) processor requiring a processed pixel rate of 2.75 MHz or more in a four look system was designed. Variations in range and azimuth compression, number of looks, range swath, range migration and SR mode were specified. Alternative range and azimuth processing algorithms were examined in conjunction with projected integrated circuit, digital architecture, and software technologies. The advaced digital SAR processor (ADSP) employs an FFT convolver algorithm for both range and azimuth processing in a parallel architecture configuration. Algorithm performace comparisons, design system design, implementation tradeoffs and the results of a supporting survey of integrated circuit and digital architecture technologies are reported. Cost tradeoffs and projections with alternate implementation plans are presented.

Martinson, L. W.↗
NASA NTRS1979

A Study of Linear Approximation Techniques for SAR Azimuth Processing

The application of the step transform subarray processing techniques to synthetic aperture radar (SAR) was studied. The subarray technique permits the application of efficient digital transform computational techniques such as the fast Fourier transform to be applied while offering an effective tool for range migration compensation. Range migration compensation is applied at the subarray level, and with the subarray size based on worst case range migration conditions, a minimum control system is achieved. A baseline processor was designed for a four-look SAR system covering approximately 4096 by 4096 SAR sample field every 2.5 seconds. Implementation of the baseline system was projected using advanced low power technologies. A 20 swath is implemented with approximately 1000 circuits having a power dissipation of from 70 to 195 watts. The baseline batch step transform processor is compared to a continuous strip processor, and variations of the baseline are developed for a wide range of SAR parameters.

Martinson, L. W.↗