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991.
West W.C. Whitacre J.F. Brandon E.J. Ratnakumar B.V. 《Aerospace and Electronic Systems Magazine, IEEE》2001,16(8):31-33
Recent successes in the effort to miniaturize spacecraft components using MEMS technology, integrated passive components, and low power electronics have driven the need for very low power, low profile, low mass micro-power sources for micro/nanospacecraft applications. Recent work at JPL has focused upon developing thin film/micro-batteries compatible with temperature sensitive substrates. A process to prepare crystalline LiCoO2 films with RF sputtering and moderate (<700°C) annealing temperature has been developed. Thin film batteries with cathode films prepared with this process have specific capacities approaching the practical limit for LiCoO2, with acceptable rate capabilities and discharge voltage profiles. Solid-state micro-scale batteries have also been fabricated with feature sizes on the order of 50 microns 相似文献
992.
R F Strayer B W Finger M P Alazraki 《Advances in Space Research (includes Cospar's Information Bulletin, Space Research Today)》1997,20(10):2023-2028
The focus of resource recovery research at the KSC-CELSS Breadboard Project has been the evaluation of microbiologically mediated biodegradation of crop residues by manipulation of bioreactor process and environmental variables. We will present results from over 3 years of studies that used laboratory- and breadboard-scale (8 and 120 L working volumes, respectively) aerobic, fed-batch, continuous stirred tank reactors (CSTR) for recovery of carbon and minerals from breadboard grown wheat and white potato residues. The paper will focus on the effects of a key process variable--bioreactor retention time--on response variables indicative of bioreactor performance. The goal is to determine the shortest retention time that is feasible for processing CELSS crop residues, thereby reducing bioreactor volume and weight requirements. Pushing the lower limits of bioreactor retention times will provide useful data for engineers who need to compare biological and physicochemical components. Bioreactor retention times were manipulated to range between 0.25 and 48 days. Results indicate that increases in retention time lead to a 4-fold increase in crop residue biodegradation, as measured by both dry weight losses and CO2 production. A similar overall trend was also observed for crop residue fiber (cellulose and hemicellulose), with a noticeable jump in cellulose degradation between the 5.3 day and 10.7 day retention times. Water-soluble organic compounds (measured as soluble TOC) were appreciably reduced by more than 4-fold at all retention times tested. Results from a study of even shorter retention times (down to 0.25 days), in progress, will also be presented. 相似文献
993.
G. I. Pugacheva A. A. Gusev U. B. Jayanthi I. M. Martin W. N. Spjeldvik 《Advances in Space Research (includes Cospar's Information Bulletin, Space Research Today)》2001,28(12):1759-1762
We report a study of the numeric solution to the diffusive transport equation for energetic protons magnetically trapped in the Earth's equatorial magnetosphere. The analysis takes into account the pertinent physical processes in this region, including deceleration of protons by Coulomb collisional interactions with free and bound electrons, the charge exchange process, cosmic ray albedo neutron decay source, and electric and magnetic radial diffusion. These results were obtained using the Finite Element Method with magnetic moment and geomagnetic L-shell as free variables. Steady state boundary conditions were imposed at L=1 as zero distribution function and at L=7 with proton distribution function extracted from ATS 6 satellite observations. The FEM-code yields unidirectional proton flux in the energy range of 0.1–1000 MeV at the equatorial top of the geomagnetic lines, and the results are found to be in satisfactorily agreement with the empirical NASA AP-8 model proton flux within the energy range of 0.5–100 MeV. Below 500 keV, the empirical AP-8 model proton fluxes are several orders of magnitude greater than those computed with the FEM-code at L<3. This discrepancy is difficult to explain by uncertainties of boundary spectrum parameters or transport coefficients. 相似文献
994.
C F Johnson T W Dreschel C S Brown R M Wheeler 《Advances in Space Research (includes Cospar's Information Bulletin, Space Research Today)》1996,18(4-5):239-242
The Porous Tube Plant Nutrient Delivery System (PTPNDS), a hydrophilic, microporous ceramic tube hydroponic system designed for microgravity, will be tested in a middeck locker of the Space Shuttle. The flight experiment will focus on hardware operation and assess its ability to support seed germination and early seedling growth in microgravity. The water controlling system of the PTPNDS hardware has been successfully tested during the parabolic flight of the KC-135. One challenge to the development of the space flight experiment was to devise a method of holding seeds to the cylindrical porous tube. The seed-holder must provide water and air to the seed, absorb water from the porous tube, withstand sterilization, provide a clear path for shoots and roots to emerge, and be composed of flight qualified materials. In preparation for the flight experiment, a wheat seed-holder has been designed that utilizes a cellulose acetate plug to facilitate imbibition and to hold the wheat seeds in contact with the porous tube in the correct orientation during the vibration of launch and the microgravity environment of orbit. Germination and growth studies with wheat at a range of temperatures showed that optimal moisture was 78% (by weight) in the cellulose acetate seed holders. These and other design considerations are discussed. 相似文献
995.
The Sun–Earth connection is studied using long-term measurements from the Sun and from the Earth. The auroral activity is shown to correlate to high accuracy with the smoothed sunspot numbers. Similarly, both geomagnetic activity and global surface temperature anomaly can be linked to cyclic changes in the solar activity. The interlinked variations in the solar magnetic activity and in the solar irradiance cause effects that can be observed both in the Earth's biosphere and in the electromagnetic environment. The long-term data sets suggest that the increase in geomagnetic activity and surface temperatures are related (at least partially) to longer-term solar variations, which probably include an increasing trend superposed with a cyclic behavior with a period of about 90 years. 相似文献
996.
Within the framework of the Space Weather program, 25-year data sets for solar X-ray observations, measurements of plasma and magnetic field parameters in the solar wind, and D
st index variations are analyzed to reveal the factors that have had the greatest influence on the development of magnetospheric storms. The correlation between solar flares and magnetic storms practically does not exceed a level of correlation for random processes. In particular, no relation was found between the importance of solar flares and the minimum of the D
st index for storms that could be connected with considered flares by their time delay. The coronal mass ejections (CME; data on these phenomena cover a small part of the interval) result in storms with D
st < –60 nT only in half of the cases. The most geoeffective interplanetary phenomena are the magnetic clouds (MC), which many believe to be interplanetary manifestations of CMEs, and compressions in the region of interaction of slow and fast streams in the solar wind (the so-called Corotating Interaction Region, CIR). They correspond to about two-thirds of all observed magnetic storms. For storms with –100 < D
st < –60 nT, the frequencies of storms from MC and CIR being approximately equal. For strong storms with D
st < – 100 nT, the fraction of storms from MC is considerably higher. The problems of reliable prediction of geomagnetic disturbances from observations of the Sun and conditions in interplanetary space are discussed. 相似文献
997.
J Birn M Hesse K Schindler 《Advances in Space Research (includes Cospar's Information Bulletin, Space Research Today)》1997,19(12):1763-1771
Magnetic reconnection in traditional, two-dimensional theory can be closely associated with topological properties of the magnetic field, separatrices, neutral lines, or separators. Such well-defined topological properties may no longer exist, or become hopelessly complicated, in more general three-dimensional configurations, that otherwise behave physically quite similarly to the two-dimensional configurations. We discuss generalized definitions of reconnection applied to such situations and illustrate typical properties with simulations of three-dimensional reconnection in the magnetotail. 相似文献
998.
M B Simakov E A Kuzicheva I L Malko 《Advances in Space Research (includes Cospar's Information Bulletin, Space Research Today)》1997,19(7):1059-1062
The abiogenic synthesis of pyrimidine nucleotides in solid state has been investigated. Our experiment indicates that natural nucleotides are produced in thin films prepared from nucleoside and inorganic phosphate by irradiating with vacuum ultraviolet light (VUV, lambda=100-200 nm). We have investigated the influence of the type of nucleic acids base (thymidine, cytosine, uracil) and the structure of sugar moiety (ribose or deoxyribose) on the course and yield of reaction. We compared the action of vacuum ultraviolet light with action of gamma-radiation, heat and biology significant UV (254 nm) which have been investigated earlier. The occurrence of these reaction in open space is discussed. 相似文献
999.
C. S. Zerefos D. S. Balis P. Zanis C. Meleti A. F. Bais K. Tourpali D. Melas I. Ziomas E. Galani K. Kourtidis A. Papayannis Z. Gogosheva 《Advances in Space Research (includes Cospar's Information Bulletin, Space Research Today)》2001,27(12):1955-1963
Intensive measurements of UV solar irradiance, total ozone and surface ozone were carried out during the solar eclipse of 11 August 1999 at Thessaloniki, Greece and Stara Zagora, Bulgaria, located very close to the footprint of the moon's shadow during the solar eclipse with the maximum coverage of the solar disk reaching about 90% and 96% respectively. It is shown that during the eclipse the diffuse component is reduced less compared to the decline of the direct solar irradiance at the shorter wavelengths. A 20-minute oscillation of erythemal UV-B solar irradiance was observed before and after the time of the eclipse maximum under clear skies, indicating a possible 20-minute fluctuation in total ozone presumably caused by the eclipse induced gravity waves. The surface ozone measurements at Thessaloniki display a decrease of around 10–15 ppbv during the solar eclipse. Similarly, ozone profile measurements with a lidar system indicate a decrease of ozone up to 2 km during the solar eclipse. The eclipse offered the opportunity to test our understanding of tropospheric ozone chemistry. The use of a chemical box model suggested that photochemistry can account for a significant portion of the observed surface ozone decrease. 相似文献