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921.
M Suzuki M Watanabe T Kanai Y Kase F Yatagai T Kato S Matsubara 《Advances in Space Research (includes Cospar's Information Bulletin, Space Research Today)》1996,18(1-2):127-136
We investigated the LET dependence of cell death, mutation induction and chromatin break induction in human embryo (HE) cells irradiated by accelerated carbon-ion beams. The results showed that cell death, mutation induction and induction of non-rejoining chromatin breaks detected by the premature chromosome condensation (PCC) technique had the same LET dependence. Carbon ions of 110 to 124keV/micrometer were the most effective at all endpoints. However, the number of initially induced chromatin breaks was independent of LET. About 10 to 15 chromatin breaks per Gy per cell were induced in the LET range of 22 to 230 keV/micrometer. The deletion pattern of exons in the HPRT locus, analyzed by the polymerase chain reaction (PCR), was LET-specific. Almost all of the mutants induced by 124 keV/micrometer beams showed deletion of the entire gene, while all mutants induced by 230keV/micrometer carbon-ion beams showed no deletion. These results suggest that the difference in the density distribution of carbon-ion track and secondary electron with various LET is responsible for the LET dependency of biological effects. 相似文献
922.
F. P. Keenan 《Space Science Reviews》1996,75(3-4):537-550
A bibliography is provided of the most reliable emission and absorption line ratio diagnostic calculations currently available for application to the spectra of astrophysical sources in the UV and EUV wavelength region (50–3000 Å). References are listed containing diagnostics for species in the Li through P isoelectronic sequences, as well as the iron ions Feii-Fexxiii and nickel ions Nixvii-Nixxv. Also given is the wavelength range for which diagnostic calculations are presented in each reference, along with the type of diagnostic considered. These include, for example, emission line ratios for determining electron temperatures and densities, and absorption line diagnostics for evaluating hydrogen densities. 相似文献
923.
Fundamental questions that arise in the certification of readiness for dedicated test and evaluation of software-intensive systems are addressed. They concern what comprises production-representative or production software, what are the software impacts on dedicated system operational test readiness, how software impacts should be considered in the certification process, and what are the retest/recertification requirements associated with software changes/modifications. A paradigm is proposed that answers these questions and outlines guidelines for implementing a solution to these issues. The paradigm is based on existing test and evaluation events and uses a combination of defense and commercial standards and definitions to propose criteria for software certification and retest or regression test 相似文献
924.
I. F. Clarke 《Space Policy》1991,7(4):328-331
During the last 40 years — the merest blip in world history — talk about Homo astronauticus has signalled a growing awareness that the passengers on planet Earth can, if they want, take off for other destinations. If the scale of past advances is a satisfactory measure of future possibilities, then the wish will be father of the achievement. 相似文献
925.
926.
B. Biran F. de Schryver F. Dubois 《Advances in Space Research (includes Cospar's Information Bulletin, Space Research Today)》1988,8(12):133-136
A new type of differential interferometer based on holographic optical elements is developed, which allows the exact determination of a refractive index gradient field in two orthogonal directions. This interferometer will be used in TEXUS experiments to determine the temperature field in a convective liquid cell in which the temperature may be known at only one point. 相似文献
927.
Woodbury R.F. Oppenheim I.J. 《IEEE transactions on aerospace and electronic systems》1988,24(5):630-646
Anticipating the use of knowledge-based expert systems for robot task planning, a geometric reasoning is envisioned for the representation and manipulation of geometric information in a manner uniform with other knowledge. The general requirements for such a reasoner are outlined and a proposed architecture is described, built on four concepts: a class structure of spatial sets, features as subsets of those spatial sets, geometric abstractions as partial representations of features, and constraints as a mechanism for reasoning. An example implementation is built in an object-oriented environment and uses an underlying solids modeler, transparent to the end user 相似文献
928.
F Guerrin K Bousson L Steyer JPhTrave-Massuyes 《Advances in Space Research (includes Cospar's Information Bulletin, Space Research Today)》1994,14(11):307-312
Qualitative Reasoning (QR) is a branch of Artificial Intelligence that arose from research on engineering problem solving. This paper describes the major QR methods and techniques, which, we believe, are capable of addressing some of the problems that are emphasized in the literature and posed by CELSS modeling, simulation, and control at the supervisory level. 相似文献
929.
V.P. Ageev A.I. Barchukov F.V. Bunkin V.I. Konov V.P. Korobeinikov B.V. Putjatin V.M. Hudjakov 《Acta Astronautica》1980,7(1):79-90
Some schemes of laser propulsive systems are discussed. The question concerned with a body acceleration due to series of air blast waves generated by laser sparks is studied. For this purpose the numerical solutions of gasdynamic equations are found under appropriate initial conditions corresponding to the real ones. Radiative losses and spatial effects at the nozzle exit are taken into account. Theoretical results presented as coupling coefficients (equivalent to reciprocal thrust cost realizing under periodical pulse laser operation) are compared with the experiment. Using conical and parabolic nozzles irradiated by pulsed CO2 laser the thrust cost about 2000 W/N is achieved which is close to the minimum possible one for the air blast wave-nozzle wall interaction. The main characteristics of laser propulsive jet are presented. Experimental results on recoil momentum transfered to solids under their evaporation by the pulsed CO2-laser are presented as well. The question of plasma shielding effects on the momentum transfer under the vapour optical breakdown conditions is touched on. 相似文献
930.
Mauricio F. Araya 《Advances in Space Research (includes Cospar's Information Bulletin, Space Research Today)》1984,4(11):235-240
Pilot experiments developed in Los Andes Range, Central Zone of Chile, have obtained significant snd positive preliminary results on the use of multispectral and multitemporal satellite images to prepare snowmelt runoff forecasts by measuring snowcovered area in Andean watersheds. The same information is also very useful for studying regional and semi-regional geothermal activity along Los Andes in Chile. These results will be improved with the new satellite data to be available in the next years. 相似文献