Charged-particle telescope experiment on Clementine

The charged-particle telescope (CPT) onboard the Clementine spacecraft measured the fluxes of energetic protons emitted in solar energetic particle events. Protons in the energy range from 10 to 80 MeV were of greatest interest for radiation effects such as total dose and single event upsets. Energetic electrons were also of interest for spacecraft charging and their contribution to total dose. The lower-energy CPT electron channels (25-500 keV) were mainly of geophysical interest. While orbiting the moon, the CPT observed the wake created by the moon when it blocked the flow of energetic particles in the magnetotail region. The CPT provided opportunities to observe energetic electron bursts during magnetic storms and magnetospheric substorms. CPT data are particularly useful in multispacecraft studies of interplanetary disturbances and their interaction with the magnetosphere. The proton channels on the CPT provided data on solar energetic protons and storm-time protons associated with the passage of an interplanetary shock at 0903 UT on Feb. 21, 1994. Results are compared with those from GOES-7, SAMPEX, and GEOTAIL.     

Effects of sublethal irradiation with helium ions (300 MeV/nucleon) on basic hematological parameters of mice

The aim of the experiment was to obtain new knowledge on the biological effectiveness of high-energy (300 MeV/nucleon) helium ions, which represent a part of the spectrum of cosmic rays. Male (CBA x C57BL)F1 mice, 4 months old, were exposed to a dose of 4 Gy helium ions (exposure rate 0.05 Gy/min). As a comparative standard irradiation the same dose of 4 Gy of 137Cs gamma-rays (exposure rate 0.07 Gy/min) was used. Material sampling was performed 6-8 h, 4 days and 9 days after irradiation for both experimental groups mentioned above. There were 7 animals in each group including the control group of non-irradiated mice. Eight basic hematological parameters of peripheral blood, bone marrow, spleen and thymus were studied. On day 4 after the irradiation with helium ions, the values of leukocyte counts in peripheral blood, bone marrow cellularity and spleen cellularity were reduced to about 10% of the respective control values while the decline after irradiation with gamma-rays amounted to about 50%. These and other results presented reflect a high relative biological effectiveness of 300 MeV/nucleon helium ions.     

An assessment of the impact of radiofrequency interference on microwave SETI searches

Investigations are carried out at JPL on radiofrequency interferences at very low levels (-130 to -180 dBm) in various bands, especially the 1-2 GHz band. Extrapolation of interferences in the years to come is attempted.     

Influence of Fast Global Variations of Solar Magnetic Fields on Space Weather in Cycle 23

It is established that the large-scale and global magnetic fields in the Sun's atmosphere do not change smoothly, and long-lasting periods of gradual variations are superseded by fast structural changes of the global magnetic field. Periods of fast global changes on the Sun are accompanied by anomalous manifestations in the interplanetary space and in the geomagnetic field. There is a regular recurrence of these periods in each cycle of solar activity, and the periods are characterized by enhanced flaring activity that reflects fast changes in magnetic structures. Is demonstrated, that the fast changes have essential influencing on a condition of space weather, as most strong geophysical disturbances are connected to sporadic phenomena on the Sun. An explanation has been offered for the origin of anomalous geomagnetic disturbances that are unidentifiable in traditionally used solar activity indices. Is shown, main physical mechanism that leads to fast variations of the magnetic fields in the Sun's atmosphere is the reconnection process.     

NUMERICAL SIMULATION OF FLOW PATTERNS IN PLANAR JETS

INTRODUCTIONTurbulent jet flow is the most widely usedflow type in engineering applications especiallyfor combustion engines which provide most ener-gy sources for industrial production and trans-portation,and a large proportion of energy trans-portation and conversion processes is dominatedby transient evolution of large- scale structures,or so called coherent structures,in turbulentjets.As the flow control and optimization pro-cesses are closely related to the understanding ofdetailed in…     

无剪切湍流混合层中被动标量扩散的实验研究

研究被动标量在无剪切湍流混合层中的扩散。实验在风洞中进行,用大小网格尺度比为2∶1的网格实现无剪切湍流混合层,用烟粒子作为测量用的示踪粒子同时作为被动标量形成浓度场,用PIV测量得到速度场同时用Mie散射测量得到高施密特数的浓度场,由此可以计算得到速度和浓度相关,并用实验数据直接检验大涡模拟中亚格子应力Smagorinsky模式和亚格子质量通量梯度模式。     

从聚硫到丁羧—固体推进剂粘合剂化学的主要变化

从1945年到1949年,液体聚硫粘合剂的复合同体推进剂,由于它在硫化前易于加工,在硫化后具有良好的机械性能和粘合强度,因而达到了可以扩大生产的工艺水平。这些发展导致了浇注——壳体粘结方法,在五十年代成功的用在一些火箭发动机上。到1954年,开始合成含有可固化官能团的液体聚丁二烯粘合剂。聚丁二烯最终取代聚硫粘合剂,有如下几个原因:较高的比冲、优良的老化性能及较好的高、低温机械性能。本文评述了这些配方的发展历史,并介绍了从乙基缩甲醛、丁基缩甲醛、丁醚聚硫到聚丁二烯丙烯酸(PBAA)、聚丁二烯丙烯腈(PBAN)和端羧聚丁二烯(CTPB)的变革原因。给出了典型配方实例、性能及其存在的问题。     

使用连续流动法测量高氯酸铵表面积

1、引言为了予测复合固体推进剂的弹道性能,必须要知道推进剂中各组份的粒度或表面积。在塑料型推进剂的制造过程中固体粒子会发生机械破碎,尽管如此,仍发现高氯酸铵的初始表面积与推进剂的弹道性能有关。爆炸物研制公司(ERDE)测量高氯酸铵表面积的作法是采用以空气渗透法为基础的菲希尔(Fisher)筛分机。由于塑料型推进剂中使用的高氯酸铵的比表面积范围通常为1000～9000cm~2/cm~3(0.051～0.46m~2/g),因此,菲希尔法完全能满足这一要求。为了生产较高燃速的推进剂,爆炸物研制公司最近研究的推进剂配方中含有更细的高氯酸铵(9000～10000cm~2/cm~3)。在端羧基聚丁二烯和端羟基聚丁二烯两种橡胶型推进剂中,即     

中国空军的志愿队

空中作战出现有志愿队 ,乃起自西班牙的佛朗哥内战时代 ,当时双方参与作战的飞行员 ,有来自英、美、苏联、德、意、法等国 ,他们参与的动机 ,多少与其本国的政治背景有关。彼此使用不同的机种 ,互相在空中逞强逞勇 ,借机表演一场国际性的空中比武而已 ,反正胜负都是西班牙人自己的事。我国自七七芦沟桥对日抗战之后 ,于翌年春中国空军已成立一志愿队 ,名为十四队 ,直属于航空委员会。当时航委会的主任是钱大钧将军。队部设在汉口公园内 ,队中的飞行员与地勤人员 ,中外国藉皆有 ,队长是美人史密斯( SMITH) ,年近四十 ,机务员是英人司密时 ,…     

三元乙丙橡胶/蒙脱土纳米复合材料的制备和性能研究

以马来酸酐接枝的EPDM齐聚物(EPDM-g-MAH)作为相容剂,用熔体插层的方法成功制备了EPDM／蒙脱土纳米复合材料,研究了材料形成的机理。X射线衍射(XRD)和透射电子显微镜(TEM)观测的结果表明,所制备的纳米复合材料为剥离型结构。与微米级复合材料相比。其力学性能和耐热性能提高。