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971.
Kinsey G.S. King R.R. Edmondson K.M. Stavrides A.P. Hojun Yoon Fetzer C.M. Colter P.C. Ermer J.H. Gillanders M.S. Hebert P. Granata J.E. Karam N.H. 《Aerospace and Electronic Systems Magazine, IEEE》2003,18(3):8-10
Solar cells suitable for the space environment must combine high-efficiency, high energy density, and radiation hardness in a manufacturable design. As improvement in one performance parameter usually results in degradation in one or more of the remaining parameters, careful optimization is required to enhance overall performance. The ultra triple-junction cell developed builds upon the established success of the fully qualified improved triple-junction cell currently in production. In the ultra triple-junction cell configuration, improved robustness and efficiency after radiation exposure augment a cell design expected to deliver 28% beginning-of-life efficiency in production. 相似文献
972.
Examples of solar microwave precursors and estimates of their energetic characteristics are discussed based on spectral investigations of the preflare activity. 相似文献
973.
N. A. Porter 《Space Science Reviews》1996,75(1-2):67-69
Searches for primordial black holes are reviewed. 相似文献
974.
C Chun C A Mitchell 《Advances in Space Research (includes Cospar's Information Bulletin, Space Research Today)》1997,20(10):1855-1860
A procedure for dynamic optimization of net photosynthetic rate (Pn) for crop production in Controlled Ecological Life-Support Systems (CELSS) was developed using leaf lettuce as a model crop. Canopy Pn was measured in real time and fed back for environmental control. Setpoints of photosynthetic photon flux (PPF) and CO2 concentration for each hour of the crop-growth cycle were decided by computer to reach a targeted Pn each day. Decision making was based on empirical mathematical models combined with rule sets developed from recent experimental data. Comparisons showed that dynamic control resulted in better yield per unit energy input to the growth system than did static control. With comparable productivity parameters and potential for significant energy savings, dynamic control strategies will contribute greatly to the sustainability of space-deployed CELSS. 相似文献
975.
F A Waldman C R Davis 《Advances in Space Research (includes Cospar's Information Bulletin, Space Research Today)》1994,14(11):217-222
A novel dielectric sensor technology has been developed for monitoring and control of plant nutrient delivery systems as part of NASA's Controlled Ecological Life Support System (CELSS) program. A unique measurement phenomenon was discovered in which the electrostatic field is shunted to a third terminal of the sensor, resulting in a much greater sensitivity to changes in the complex dielectric properties of the nutrient solution. Based on this phenomenon, a small, flexible, thin-film shunting dielectric sensor (SDS) was designed to provide low-frequency, non-invasive measurement of both the thickness and nutrient concentration of the layer of solution on a plant growth surface. Test results indicate a sensitivity of +/- 0.05mm in layer thickness while characterization of the ability to measure nutrient concentration continues. The development plan for this sensor is presented and other applications are discussed. 相似文献
976.
We studied solar wind observations of five different spacecraft: Helios 1, Helios 2, IMP-8, Voyager 1 and Voyager 2, from November 1977 to February 1978. In this period the large-scale dynamics of the solar wind near of the ecliptic plane
was characterized by transient forward shocks (TFSs), ejecta, unstable corotating interaction regions (CIRs), and complex
and variable magnetic sector structures. We identified 12 forward shock events of different origin. We did not find any clear
tendency of the shock parameters with heliocentric distance nor longitudinal angle, but comparing the observations of each
shock event we found local variations in the shock strength and the mean propagation velocities from one spacecraft to another.
These unsystematic variations indicate that there were local deformations of the shock fronts, which we attribute to the inhomogenuos
solar wind structure that affects the shock propagation.
This revised version was published online in August 2006 with corrections to the Cover Date. 相似文献
977.
Kaminer I. Wei Kang Yakimenko O. Pascoal A. 《IEEE transactions on aerospace and electronic systems》2001,37(1):158-172
The problem of navigation system design for autonomous aircraft landing is addressed. New nonlinear filter structures are introduced to estimate the position and velocity of an aircraft with respect to a possibly moving landing site, such as a naval vessel, based on measurements provided by airborne vision and inertial sensors. By exploring the geometry of the navigation problem, the navigation filter dynamics are cast in the framework of linear parametrically varying systems (LPVs). Using this set-up, filter performance and stability are studied in an H∞ setting by resorting to the theory of linear matrix inequalities (LMIs). The design of nonlinear, regionally stable filters to meet adequate H∞ performance measures is thus converted into that of determining the feasibility of a related set of LMIs and finding a solution to them, if it exists. This is done by using-widely available numerical tools that borrow from convex optimization techniques. The mathematical framework that is required for integrated vision/inertial navigation system design is developed and a design example for an air vehicle landing on an aircraft carrier is detailed 相似文献
978.
I.A. Daglis 《Space Science Reviews》2001,98(3-4):343-363
In this paper I am reviewing recent advances and open disputes in the study of the terrestrial ring current, with emphasis on its storm-time dynamics. The ring current is carried by energetic charged particles flowing toroidally around the Earth, and creating a ring of westward electric current, centered at the equatorial plane and extending from geocentric distances of about 2 R
E to roughly 9 R
E. This current has a permanent existence due to the natural properties of charged particles in the geospace environment, yet its intensity is variable. It becomes more intense during global electromagnetic disturbances in the near-Earth space, which are known as space (or magnetic or geomagnetic) storms. Changes in this current are responsible for global decreases in the Earth's surface magnetic field, which is the defining feature of geomagnetic storms. The ring current is a critical element in understanding the onset and development of space weather disturbances in geospace. Ring current physics has long been driven by several paradigms, similarly to other disciplines of space physics: the solar origin paradigm, the substorm-driver paradigm, the large-scale symmetry paradigm, the charge-exchange decay paradigm. The paper addresses these paradigms through older and recent important investigations. 相似文献
979.
980.
W F Blakely A C Miller M B Grace C B McLeland L Luo J M Muderhwa V L Miner P G Prasanna 《Advances in Space Research (includes Cospar's Information Bulletin, Space Research Today)》2003,31(6):1487-1493
The multiparametric dosimetry system that we are developing for medical radiological defense applications could be adapted for spaceflight environments. The system complements the internationally accepted personnel dosimeters and cytogenetic analysis of chromosome aberrations, considered the best means of documenting radiation doses for health records. Our system consists of a portable hematology analyzer, molecular biodosimetry using nucleic acid and antigen-based diagnostic equipment, and a dose assessment management software application. A dry-capillary tube reagent-based centrifuge blood cell counter (QBC Autoread Plus, Becton [correction of Beckon] Dickinson Bioscience) measures peripheral blood lymphocytes and monocytes, which could determine radiation dose based on the kinetics of blood cell depletion. Molecular biomarkers for ionizing radiation exposure (gene expression changes, blood proteins) can be measured in real time using such diagnostic detection technologies as miniaturized nucleic acid sequences and antigen-based biosensors, but they require validation of dose-dependent targets and development of optimized protocols and analysis systems. The Biodosimetry Assessment Tool, a software application, calculates radiation dose based on a patient's physical signs and symptoms and blood cell count analysis. It also annotates location of personnel dosimeters, displays a summary of a patient's dosimetric information to healthcare professionals, and archives the data for further use. These radiation assessment diagnostic technologies can have dual-use applications supporting general medical-related care. 相似文献