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At least 109 records · Page 6

Energy yields for hydrogen cyanide and formaldehyde syntheses - The HCN and amino acid concentrations in the primitive ocean

Simulated prebiotic atmospheres containing either CH4, CO, or CO2, in addition to N2, H2O, and variable amounts of H2, were subjected to the spark from a high-frequency Tesla coil, and the energy yields for the syntheses of HCN and H2CO were estimated from periodic (every two days) measurements of the compound concentrations. The mixtures with CH4 were found to yield the highest amounts of HCN, whereas the CO mixtures produced the highest yields of H2CO. These results model atmospheric corona discharges. From the yearly energy yields calculated and the corona discharge available on the earth, the yearly production rate of HCN was estimated; using data on the HCN production rates and the experimental rates of decomposition of amino acids through the submarine vents, the steady state amino acid production rate in the primitive ocean was calculated to be about 10 nmoles/sq cm per year.

Stribling, Roscoe↗

A detailed investigation of proposed gas-phase syntheses of ammonia in dense interstellar clouds

The initial reactions of the Herbst and Klemperer (1973) and the Dalgarno (1974) schemes (I and II, respectively) for the gas-phase synthesis of ammonia in dense interstellar clouds were investigated. The rate of the slightly endothermic reaction between N(+) and H2 to yield NH(+) and H (scheme I) under interstellar conditions was reinvestigated under thermal and nonthermal conditions based on laboratory data. It was found that the relative importance of this reaction in synthesizing ammonia is determined by how the laboratory data at low temperature are interpreted. On the other hand, the exothermic reaction between N and H3(+) to form NH2(+) + H (scheme II) was calculated to possess significant activation energy and, therefore, to have a negligible rate coefficient under interstellar conditions. Consequently, this reaction cannot take place appreciably in interstellar clouds.

Herbst, Eric↗

A system for evaluating Ada implementations using synthesized benchmarks

A system is described that allows project designers to evaluate the suitability of an Ada implementation for a particular application using tailored benchmarks. Specification of the load that an application is expected to generate is written in an Ada-like notation. An Ada program is then synthesized that generates the specified load. Studies of the way in which performance varies with various parameters of the application can be performed by the system automatically.

Knight, John C.↗

Digital frequency synthesizer for radar astronomy

The digital frequency synthesizer (DFS) is an integral part of the programmable local oscillator (PLO) which is being developed for the NASA's Deep Space Network (DSN) and radar astronomy. Here, the theory of operation and the design of the DFS are discussed, and the design parameters in application for the Goldstone Solar System Radar (GSSR) are specified. The spectral purity of the DFS is evaluated by analytically evaluating the output spectrum of the DFS. A novel architecture is proposed for the design of the DFS with a frequency resolution of 1/2(exp 48) of the clock frequency (0.35 mu Hz at 100 MHz), a phase resolution of 0.0056 degrees (16 bits), and a frequency spur attenuation of -96 dBc.

Sadr, R.↗

Analog synthesized fast-variable linear load

A several kilowatt power level, fast-variable linear resistor was synthesized by using analog components to control the conductance of power MOSFETs. Risetimes observed have been as short as 500 ns with respect to the control signal and 1 to 2 microseconds with respect to the power source voltage. A variant configuration of this load that dissipates a constant power set by a control signal is indicated. Replacement of the MOSFETs by static induction transistors (SITs) to increase power handling, speed and radiation hardness is discussed.

Niedra, Janis M.↗

Studies of proton irradiated H2O + CO2 and H2O + CO ices and analysis of synthesized molecules

Infrared spectra of H2O + CO2 and H2O + CO ices before and after proton irradiation showed that a major reaction in both mixtures was the interconversion of CO2 yields CO. Radiation synthesized organic compounds such as carbonic acid were identified in the H2O + CO2 ice. Different chemical pathways dominate in the H2O + CO ice in which formaldehyde, methanol, ethanol, and methane were identified. Sublimed material was also analyzed using a mass spectrometer. Implications of these results are discussed in reference to comets.

Moore, M. H.↗

Bandwidth-Synthesizing FM Radar

Proposed frequency-modulation (FM) radar system uses sawtooth-wave-form linear frequency sweeps and return-signal-processing scheme in which samples of signals from N consecutive sweep periods are combined to multiply range resolution by factor of N. System "synthesizes" bandwith N times that of transmitted signal in sense that to increase resolution of ordinary radar system where consecutive samples are not combined, it is necessary to increase bandwidth of transmitted signal by same factor. Used in FM radar altimeters.

Wu, Chialin↗

Digital Frequency Synthesizer For Radar Astronomy

Report discusses conceptual digital frequency synthesizer part of programmable local oscillator in radar-astronomy system. Phase must remain continuous during adjustments of frequency, phase noise must be low, and spectral purity must be high. Discusses theory of operation in some mathematical detail and presents new analysis of spectral purity of output.

Sadr, Ramin↗

Thermal Synthesizer System - An integrated approach to spacecraft thermal analysis

The Thermal Synthesizer System (TSS), which is being developed to meet the thermal analysis needs of Space Station Freedom and of the proposed Space Exploration Initiative missions, is examined. The key requirements and design goals to be met by TSS are summarized, and the software engineering and user interface design philosophy are reviewed. The basic architecture for all applications within TSS is described. An overview is given of the main features of each of the applications of TSS.

Panczak, Tim↗

Precise laser frequency scanning using frequency-synthesized optical frequency sidebands - Application to isotope shifts and hyperfine structure of mercury

Based on an efficient broadband electrooptic modulator producing RF optical sidebands locked to a stable cavity, a tunable dye laser can be scanned under computer control with frequency-synthesizer precision. Cavity drift is suppressed in software by using a strong feature in the spectrum for stabilization. Mercury isotope shifts are measured with a reproducibility of about 50 kHz. This accuracy of about 1/300 of the linewidth illustrates the power of the technique. Derived hyperfine-structure constants are compared with previous atomic-beam data.

Rayman, M. D.↗

Analog synthesized fast-variable linear load

A several-kilowatt power level, fast-variable linear resistor has been synthesized by using analog components to control the conductance of power MOSFETs. Risetimes observed have been as short as 500 ns with respect to the control signal and 1 to 2 microsec with respect to the power source voltage. A variant configuration of this load that dissipates a constant power set by a control signal is indicated. Replacement of the MOSFETs by static induction transistors to increase power handling, speed, and radiation hardness is discussed.

Niedra, Janis M.↗

Synthesizing Diacetylenes With Nonlinear Optical Properties

Diacetylene compounds being investigated to determine whether they have nonlinear optical properties making them useful for four-wave mixing, generation of third harmonics, phase conjugation, and like. Diacetylene monomers synthesized by sequences of chemical reactions. Monomers polymerized by ultraviolet light, forming potentially useful nonlinear optical materials.

Mcmanus, Samuel P.↗

Synthesizing Friction In A Force-Reflecting Hand Controller

Algorithm synthesizes frictionlike limited reaction force in force-reflecting hand controller. Synthetic friction enhances operator's feel and improves control characteristics in two ways: handle of controller retains setting when operator releases it, and in case of multiple-axis controller, synthetic frictional force helps to hold control setting on one axis when handle pushed to command movement along another axis.

Kauffman, James↗

Horizontal axis wind turbine post stall airfoil characteristics synthesization

Blade-element/momentum performance prediction codes are routinely used for wind turbine design and analysis. A weakness of these codes is their inability to consistently predict peak power upon which the machine structural design and cost are strongly dependent. The purpose of this study was to compare post-stall airfoil characteristics synthesization theory to a systematically acquired wind tunnel data set in which the effects of aspect ratio, airfoil thickness, and Reynolds number were investigated. The results of this comparison identified discrepancies between current theory and the wind tunnel data which could not be resolved. Other factors not previously investigated may account for these discrepancies and have a significant effect on peak power prediction.

Tangler, James L.↗

TSS-Thermal Synthesizer System

Thermal Synthesizer System (TSS) is integrated set of thermal-analysis application programs designed to solve problems encountered by thermal engineers. Combines functionality of Systems Improved Numerical Differencing Analyzer/Fluid Integrator (SINDA/FLUINT) and radiation analysis with friendly and easily understood user-interface environment coupled with powerful interactive color graphics and geometric modeling capability. Enables thermal engineers to spend more time solving engineering problems instead of laboriously constructing and verifying math models. Written in FORTRAN and C language.

Chimenti, Edward↗

Syntheses and Degradations of Fluorinated Heterocyclics: Perfluoroalkyl and Perfluoroalkylether-1,3,4-Oxadiazoles - 3

2,5-Bis(perfluoro-n-heptyl)-, 2-perfluoroalkylether-5-perfluoro-n- heptyl- , and 2 , 5-bisperfluoroalkylether-1,3,4-oxadiazoles were synthesized and characterized. 2,5-Bis(perfluoro-n-heptyl)-1,3,4-oxadiazole was thermally and hydrolytically stable at 325 C; however, in the presence of air, degradation took place at 235 C. The perfluoroalkylether analogue exhibited thermal and hydrolytic stability at 325 C; it was found to be unaffected by jet-A fuel and air at 235 C. At 325 C in air some degradation occurred as evidenced by volatiles production, oxygen consumption, and 96% starting material recovery.

Paciorek, K. J. L.↗

Syntheses and Degradations of Fluorinated Heterocyclics: Perfluoroalkyl and Perfluroalkylether-1,2,4-Oxadiazoles - 2

3-Perfluoroalkylether-5-perfluoro-n-heptyl-1,2,4-oxadiazole and 3,S-bis(perfluoroalkylether)-1,2,4-oxadiazole were synthesized and characterized. The 3, 5-bis(perfluoroalkylether)-l, 2,4-oxadiazole was subjected to thermal, thermal oxidative, and hydrolytic degradations at 235 and 325 C and was found to be stable under these conditions as evidenced by practically quantitative recovery of the test samples. In the presence of Jet-A fuel at 235 C a low degree of degradation, approximately 4%, was observed. 3,5-Bis(perfluoro-n-heptyl)-1,2,4-oxadiazole was found to be stable to attack by water at 325 C; however in air in the presence of jet-A at 235 C the extent of degradation was in excess of 10%.

Paciorek, K. J. L.↗

Morphology and Structure of ZnO Films Synthesized by Off-Axis Sputtering Deposition

ZnO is a wide-band-gap oxide material that has many applications. A new potential application of ZnO material is for light emitting devices since its structure and electrical properties are similar to that of the GaN material (a blue laser candidate). It also is a good substrate for fabricating GaN-based devices. Off-axis sputtering technique has revealed great potential in synthesizing excellent oxide materials because the negative ion bombardment is greatly reduced when adatoms condense on substrates. The surface of films grown by off-axis sputtering will be much smoother than that produced in a regular sputtering configuration. A growth mechanism is studied by investigating the morphology and structure of ZnO films under different growth conditions and orientations. ZnO films are deposited on (0001) sapphire and quartz substrates by off- axis sputtering deposition at various oxygen/argon mixture ratios and pressures and at different temperatures. All films reveal highly textured structures on quartz substrates and epitaxial growth on sapphire substrates. Two off-axis configurations, vertical and horizontal orientations are conducted to study the process of film growth, surface morphology, and film structure. X-ray diffraction, scanning probe microscopy, and electrical measurements are used to characterize these films. Detailed results will be discussed in the presentation. Keywords: ZnO, Photonic material, Off-axis sputtering, Growth mechanism

Zhu, Shen↗