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911.
912.
K. Hornung Yu.G. Malama K. Thoma 《Advances in Space Research (includes Cospar's Information Bulletin, Space Research Today)》1996,17(12):77-86
This overview deals with very high impact velocities, where complete vaporization of an impacting cosmic dust particle is to be expected upon expansion from the high pressure high temperature state behind the stopping shock (v > 15 km/s). The topics discussed are the mechanics and thermodynamics of compression, adiabatic release, equation of state and nonequilibrium states upon expansion. The case of very high particle porosity (ρ 1 g/cm3) and the case of very small dust masses (m < 10−17 g) are discussed from what one presently knows. The possibility of three body collisions in the expanding gas phase is discussed briefly. The effect of oblique impact is discussed with respect to its relevance to the ionization process. The numbers communicated are up to the highest “experimental” impact velocities (80 km/s, Halley mission). As one goes to lower impact velocities (20 < v < 30 km/s) there is still complete vaporization of the dust particle but ionization out of the bulk of the particle becomes low. Other than thermal processes may become important. Ideas are outlined to understand their physical nature. 相似文献
913.
多媒体煤矿安全监测管理系统研究 总被引:1,自引:0,他引:1
介绍了现有的煤矿安全监测和安全考勤管理系统的特点及缺陷,探讨了如何将多媒体计算机技术应用于煤矿安全监测管理系统。该系统具有实时监视、紧急救援和事故分析三大特点。 相似文献
914.
保证高校教职工、大学生的身心健康,是高校医院义不容辞的责任.为此,应探索一条更适合高校实际情况的医疗模式.本文就高校医院应如何为师生员工提供全方位的医疗保健服务进行了初步探讨. 相似文献
915.
A N Boyandin T I Lobova L Yu Popova N S Pechurkin 《Advances in Space Research (includes Cospar's Information Bulletin, Space Research Today)》2003,31(7):1763-1768
It has been demonstrated that the transgenic microorganism Escherichia coli Z905/pPHL7 (AprLux+) can exist for a long time at an elevated concentration of mineral salts. The microorganism was introduced into microcosms with sterile brackish water (salinity variable from 21 to 22 g l-1) taken from Lake Shira (Khakasia, Russia). The survival of the microorganism was estimated both by measuring the growth of the colonies on solid nutrient media and by the bioluminescence exhibited by the transgenic strain in samples from the microcosms and in the enrichment culture with the added selective factor-ampicillin (50 micrograms/ml). In the enrichment culture, the bioluminescent signal was registered through the 160-day experiment. It has been shown that in the closed microcosms with brackish water the E. coli strain becomes heterogeneous in its ampicillin resistance. The populations of the transgenic strain were mainly represented by isolates able to persist in the medium containing 50 micrograms/ml, but there were also the cells (about 10%) with the threshold of ampicillin resistance not more than 0.05 micrograms/ml. Thus, it was shown that in the microcosms with brackish water and in the absence of the selective factor the transgenic strain survives and retails the recombinant plasmid. 相似文献
916.
917.
E.I. Daibog Yu.I. Logachev S. Kahler K. Kecskemty S. McKenna-Lawlor 《Advances in Space Research (includes Cospar's Information Bulletin, Space Research Today)》2003,32(12):2661-2666
The values of the characteristic decay time of particle fluxes in SEP events vary, as a rule, considerably from event to event. We point out, however, that at times sequences of events having similar decay times were observed over long time intervals (up to one month, and even longer in a few cases). The values of the decay times, however, differed among different sequences. The constancy of the decay phase in each consecutive event of these series suggests that the interplanetary medium was in steady state during the event series, and, because of solar rotation, its uniformity within sectors extended to 90–180° in heliolongitude. The very rarely observed long series (up to 2–3 solar rotations) indicate the steadiness and homogeneity of the plasma and the interplanetary magnetic field (IMF) in the entire inner solar system in the course of this time span. It is pointed out that the neutral current sheet of the IMF does not represent a substantial obstacle for energetic charged particles. Both hemispheres are (above and below the current sheet), at least during the series of solar events, invariant with time, uniform and alike from the viewpoint of the propagation of charged particles. The investigation of such sequences of events can also be useful for forecasting characteristics of SEP events. 相似文献
918.
I. Yu. Skriabysheva 《Cosmic Research》2005,43(6):432-441
The main problems concerning the electric polarization of low-orbit spacecraft are considered, including the results of studying the structure of the Earth's upper ionosphere, the methods of calculating the electrophysical characteristics of construction materials for spacecraft, and the elaboration of recommendations to mitigate the negative effects due to processes of charging and discharging. 相似文献
919.
V. I. Badin Yu. V. Dumin 《Advances in Space Research (includes Cospar's Information Bulletin, Space Research Today)》1995,15(12):119-122
The initial reduction of the electron density after the injection explosion is shown to be associated with recombination at the adiabatic cooling under the cloud expansion. Primordial thermal ions can disappear in triple collisions almost entirely. Nevertheless, a minor amount of ions is conserved due to the freezing effect. The further rapid increase in the electron concentration may be attributed to the secondary ionization process. It is shown that the cumulative electronic ionization can account for the observed electron density elevation. The modified two-stream instability can provide a longitudinal (anomalous) resistance for the longitudinal electric field required for an avalanche. The electric field and longitudinal currents arise owing to the polarization with ions entrained by the neutral gas across the magnetic field and magnetized electrons moving along the field. 相似文献
920.
本文介绍了采用ANDOVER楼宇自控系统中,自行研制开发的数据采集器的硬件设计原理及与上位机接口软件的原理,该系统已用于实际,效果良好。 相似文献