CCD互相关粒子图像测速及其在对抗流流场测量中的应用

在常规自相关粒子图像测速（ＰＩＶ）系统的基础上,发展了一个采用ＣＣＤ像机的互相关粒子图像测速系统。用这一新系统测量了对抗流流场的结果表明,这一技术克服了自相关粒子图像测速技术在测量具有滞止点的流场中的困难。实验说明,与自相关粒子图像测速技术相比,这一技术更快捷有效。     

目标图像的显示及后期处理技术

:通过对由图象输入设备获得的目标图象文件的分析 ,论述了利用计算机来完成此类图象的显示方法。此外还论述了利用抛物插值算法来实现目标图像的后期处理———图象局部放大显示的原理及方法。     

布鲁诺图诺尼航空展

布鲁诺（Brno)位于捷克南部邻近奥地利的位置,距离维也纳不到150公里,这是一个典型东欧城市,市内古迹众多、风景优美,在旅游旺季经常可以看到大批西方游客驻足街头,今年夏天的布鲁诺尤其热闹,美国空军的雷鸟(Thunderblrds)特技小组在欧洲巡回表演活动中造访了这个小城市,为今年的布鲁诺图谔尼航空展(Brno—Turany Airshow)大幅增加了观赏性。     

Survival and germinability of Bacillus subtilis spores exposed to simulated Mars solar radiation: implications for life detection and planetary protection

Bacterial spores have been considered as microbial life that could survive interplanetary transport by natural impact processes or human spaceflight activity. Deposition of terrestrial microbes or their biosignature molecules onto the surface of Mars could negatively impact life detection experiments and planetary protection measures. Simulated Mars solar radiation, particularly the ultraviolet component, has been shown to reduce spore viability, but its effect on spore germination and resulting production of biosignature molecules has not been explored. We examined the survival and germinability of Bacillus subtilis spores exposed to simulated martian conditions that include solar radiation. Spores of B. subtilis that contain luciferase resulting from expression of an sspB-luxAB gene fusion were deposited on aluminum coupons to simulate deposition on spacecraft surfaces and exposed to simulated Mars atmosphere and solar radiation. The equivalent of 42 min of simulated Mars solar radiation exposure reduced spore viability by nearly 3 logs, while germination-induced bioluminescence, a measure of germination metabolism, was reduced by less than 1 log. The data indicate that spores can retain the potential to initiate germination-associated metabolic processes and produce biological signature molecules after being rendered nonviable by exposure to Mars solar radiation.     

A numerical optimization of high altitude testing facility for wind tunnel experiments

High altitude test facilities are required to test the high area ratio nozzles operating at the upper stages of rocket in the nozzle full flow conditions.It is typically achieved by creating the ambient pressure equal or less than the nozzle exit pressure.On average,air/GN2is used as active gas for ejector system that is stored in the high pressure cylinders.The wind tunnel facilities are used for conducting aerodynamic simulation experiments at/under various flow velocities and operating conditions.However,constructing both of these facilities require more laboratory space and expensive instruments.Because of this demerit,a novel scheme is implemented for conducting wind tunnel experiments by using the existing infrastructure available in the high altitude testing(HAT)facility.This article presents the details about the methods implemented for suitably modifying the sub-scale HAT facility to conduct wind tunnel experiments.Hence,the design of nozzle for required area ratio A/A*,realization of test section and the optimized configuration are focused in the present analysis.Specific insights into various rocket models including high thrust cryogenic engines and their holding mechanisms to conduct wind tunnel experiments in the HAT facility are analyzed.A detailed CFD analysis is done to propose this conversion without affecting the existing functional requirements of the HAT facility.     

拉压、扭转载荷下铸铝合金的亿周疲劳性能研究

应用超声疲劳试验机对铸铝合金2-AS5U3G-Y35在扭转和拉压循环载荷下进行了超高周疲劳性能测试.介绍了超声扭转疲劳试验装置的设计.应用35 Hz常规疲劳试验机和20 kHz的超声疲劳试验机完成应力比R=-1的拉压、扭转疲劳试验,进而研究不同载荷条件、加载频率对铸铝合金超高周疲劳性能的影响.S-N曲线显示,铝合金在105～1010疲劳周次间仍发生疲劳断裂,不存在疲劳极限.断口分析表明,在超高周循环拉压载荷下,疲劳裂纹常萌生于试样次表面材料内部缩孔.与循环拉压载荷下的疲劳断裂机理不同,在循环扭转载荷下疲劳裂纹主要萌生于试样表面,疲劳断裂面为一种典型的沿试样轴向45°的螺旋面,即沿最大主应力平面断裂.扭转疲劳断面清晰的剪切条带表明扭转疲劳断裂实质上是剪切断裂.     

原子干涉陀螺仪关键技术及进展

原子作为一种微观粒子,具有波粒二象性.利用粒子的波动性,可以产生类似于光波的Sagnac效应,由此实现基于原子波干涉的原子干涉陀螺仪.其中原子干涉有内态干涉和物质波干涉两种.在围成相同面积的情况下,原子干涉陀螺仪的灵敏度将比光学陀螺仪高出10个量级以上,适宜于水下和空间等长时间惯性导航的应用.本文详细地论述了原子干涉陀...     

Sulfur-oxidizing chemolithotrophic proteobacteria dominate the microbiota in high arctic thermal springs on Svalbard

The thermal springs Trollosen and Fisosen, located on the High Arctic archipelago Svalbard, discharge saline groundwaters rich in hydrogen sulfide and ammonium through a thick layer of permafrost. Large amounts of biomass that consist of filamentous microorganisms containing sulfur granules, as analyzed with energy dispersive X-ray analysis, were found in the outflow. Prokaryotic 16S rRNA gene libraries and quantitative polymerase chain reaction (qPCR) analyses reported bacteria of the γ- and ?-proteobacterial classes as the dominant organisms in the filaments and the planktonic fractions, closely related to known chemolithoautotrophic sulfur oxidizers (Thiotrix and Sulfurovum). Archaea comprised ～1% of the microbial community, with the majority of sequences affiliated with the Thaumarchaeota. Archaeal and bacterial genes coding for a subunit of the enzyme ammonia monooxygenase (amoA) were detected, as well as 16S?rRNA genes of Nitrospira, all of which is indicative of potential complete nitrification in both springs. 16S rRNA sequences related to methanogens and methanotrophs were detected as well. This study provides evidence that the microbial communities in Trollosen and Fisosen are sustained by chemolithotrophy, mainly through the oxidation of reduced sulfur compounds, and that ammonium and methane might be minor, additional sources of energy and carbon.     

The influence of microgravity on invasive growth in Saccharomyces cerevisiae

This study investigates the effects of microgravity on colony growth and the morphological transition from single cells to short invasive filaments in the model eukaryotic organism Saccharomyces cerevisiae. Two-dimensional spreading of the yeast colonies grown on semi-solid agar medium was reduced under microgravity in the Σ1278b laboratory strain but not in the CMBSESA1 industrial strain. This was supported by the Σ1278b proteome map under microgravity conditions, which revealed upregulation of proteins linked to anaerobic conditions. The Σ1278b strain showed a reduced invasive growth in the center of the yeast colony. Bud scar distribution was slightly affected, with a switch toward more random budding. Together, microgravity conditions disturb spatially programmed budding patterns and generate strain-dependent growth differences in yeast colonies on semi-solid medium.