Blood volume regulating hormones, fluid and electrolyte modifications during 21 and 198-day space flights (Altair-MIR 1993)

During the Altair MIR' 93 mission we studied several parameters involved in blood volume regulation. The experiment was done on two cosmonauts before (B-60, B-30), during (D6, D12, D18 for French and D7, D12, D17 for Russian) and after the flight (R+1, R+3 and R+7). Space flight durations were different for two cosmonauts: for the Russian the flight duration was 198 days and for the French 21 days. On board the MIR station only urinary (volume and electrolytes, atrial natriuretic peptide (ANP), cyclic guanosine monophosphate (cGMP) and catecholamines) and salivary (cGMP and cortisol) samples were collected, centrifuged and stored in freezer. Lithium was used as a tracer to know exactly the 24 h urine output (CNES urine collection Kit). Before and after flight, blood was drawn with an epicite needle and vacutainer system for hormonal assays (renin, antidiuretic hormone, cGMP, ANP and aldosterone) in two positions: after 30 min rest in upright seated position and after 90 min of supine position. Salivary samples were collected simultaneously. During flight a decrease of diuresis and ANP and an increase of osmolality were found. No modifications of hematocrit, but an increase of salivary cGMP and cortisol were also observed. The decrease of urinary ANP is in favor of hypovolemia as described in previous flights. The postflight examinations revealed changes in fluid-electrolyte metabolism which indicate a hypohydration status and a stimulation of hormonal system responsible for water and electrolyte retention in order to readapt to the normal gravity.     

再入飞行器迎风面边界层转捩的数值预估

基于求解三维Ｎａｖｉｅｒ－Ｓｔｏｋｅｓ方程,首先数值预估了高超声速三维流动的边界层特性;采用已有的高超声速三维边界层转捩准则,即在转捩位置Ｒｅθ／Ｍｅ＝常数,以及通过修正由ＯＮＥＲＡ提出的代数转捩模型,建立了预估三维边界层转捩的半经验数值技术并应用于三维Ｎａｖｉｅｒ－Ｓｔｏｋｅｓ方程的求解。利用ＨＡＬＩＳ模型及相关的实验数据,首次进行了在Ｍ∞＝６时不同雷诺数及迎角的验证试验。预估结果表明：在不考虑     

视函数法分析卫星覆盖研究

通过所建立的视函数法,得到了星座中每一颗卫星对地面的覆盖区和间隙区出现的时刻,各覆盖区和间隙区的长度、最大间隙出现的时刻等覆盖的详细信息;讨论了星座的覆盖性能指标,并建立了各项覆盖性能指标的计算方法。最后,对ＧＰＳ星座的覆盖性能进行了数值仿真,给出了ＧＰＳ星座的视函数图,并得到了ＧＰＳ星座在不同纬度的覆盖性能。     

星座的发射规划研究

卫星的组网发射规划就是确定从地面把多颗卫星发射到所需求的轨道平面的适当时间问题.在保证组网卫星之间相位要求和发射单颗卫星限制条件的情况下,给出了一个轨道高度为800km、轨道倾角为45°的12颗星Wallker星座的发射窗口.其研究思路可为确定卫星群发射窗口提供参考.      

Drilling systems for extraterrestrial subsurface exploration

Drilling consists of 2 processes: breaking the formation with a bit and removing the drilled cuttings. In rotary drilling, rotational speed and weight on bit are used to control drilling, and the optimization of these parameters can markedly improve drilling performance. Although fluids are used for cuttings removal in terrestrial drilling, most planetary drilling systems conduct dry drilling with an auger. Chip removal via water-ice sublimation (when excavating water-ice-bound formations at pressure below the triple point of water) and pneumatic systems are also possible. Pneumatic systems use the gas or vaporization products of a high-density liquid brought from Earth, gas provided by an in situ compressor, or combustion products of a monopropellant. Drill bits can be divided into coring bits, which excavate an annular shaped hole, and full-faced bits. While cylindrical cores are generally superior as scientific samples, and coring drills have better performance characteristics, full-faced bits are simpler systems because the handling of a core requires a very complex robotic mechanism. The greatest constraints to extraterrestrial drilling are (1) the extreme environmental conditions, such as temperature, dust, and pressure; (2) the light-time communications delay, which necessitates highly autonomous systems; and (3) the mission and science constraints, such as mass and power budgets and the types of drilled samples needed for scientific analysis. A classification scheme based on drilling depth is proposed. Each of the 4 depth categories (surface drills, 1-meter class drills, 10-meter class drills, and deep drills) has distinct technological profiles and scientific ramifications.     

Challenges for coring deep permafrost on Earth and Mars

A scientific drilling expedition to the High Lake region of Nunavut, Canada, was recently completed with the goals of collecting samples and delineating gradients in salinity, gas composition, pH, pe, and microbial abundance in a 400 m thick permafrost zone and accessing the underlying pristine subpermafrost brine. With a triple-barrel wireline tool and the use of stringent quality assurance and quality control (QA/QC) protocols, 200 m of frozen, Archean, mafic volcanic rock was collected from the lower boundary that separates the permafrost layer and subpermafrost saline water. Hot water was used to remove cuttings and prevent the drill rods from freezing in place. No cryopegs were detected during penetration through the permafrost. Coring stopped at the 535 m depth, and the drill water was bailed from the hole while saline water replaced it. Within 24 hours, the borehole iced closed at 125 m depth due to vapor condensation from atmospheric moisture and, initially, warm water leaking through the casing, which blocked further access. Preliminary data suggest that the recovered cores contain viable anaerobic microorganisms that are not contaminants even though isotopic analyses of the saline borehole water suggests that it is a residue of the drilling brine used to remove the ice from the upper, older portion of the borehole. Any proposed coring mission to Mars that seeks to access subpermafrost brine will not only require borehole stability but also a means by which to generate substantial heating along the borehole string to prevent closure of the borehole from condensation of water vapor generated by drilling.     

Spectral signatures of photosynthesis. II. Coevolution with other stars and the atmosphere on extrasolar worlds

As photosynthesis on Earth produces the primary signatures of life that can be detected astronomically at the global scale, a strong focus of the search for extrasolar life will be photosynthesis, particularly photosynthesis that has evolved with a different parent star. We take previously simulated planetary atmospheric compositions for Earth-like planets around observed F2V and K2V, modeled M1V and M5V stars, and around the active M4.5V star AD Leo; our scenarios use Earth's atmospheric composition as well as very low O2 content in case anoxygenic photosynthesis dominates. With a line-by-line radiative transfer model, we calculate the incident spectral photon flux densities at the surface of the planet and under water. We identify bands of available photosynthetically relevant radiation and find that photosynthetic pigments on planets around F2V stars may peak in absorbance in the blue, K2V in the red-orange, and M stars in the near-infrared, in bands at 0.93-1.1 microm, 1.1-1.4 microm, 1.5-1.8 microm, and 1.8-2.5 microm. However, underwater organisms will be restricted to wavelengths shorter than 1.4 microm and more likely below 1.1 microm. M star planets without oxygenic photosynthesis will have photon fluxes above 1.6 microm curtailed by methane. Longer-wavelength, multi-photo-system series would reduce the quantum yield but could allow for oxygenic photosystems at longer wavelengths. A wavelength of 1.1 microm is a possible upper cutoff for electronic transitions versus only vibrational energy; however, this cutoff is not strict, since such energetics depend on molecular configuration. M star planets could be a half to a tenth as productive as Earth in the visible, but exceed Earth if useful photons extend to 1.1 microm for anoxygenic photosynthesis. Under water, organisms would still be able to survive ultraviolet flares from young M stars and acquire adequate light for growth.     

AZ91D镁合金表面浸锌工艺研究

为使AZ91D镁合金表面浸锌时无需采用氢氟酸进行前处理,采用百格试验和盐雾试验等方法对浸锌液主要成份及工艺参数对所得浸锌层性能的影响进行了研究。结果表明:浸锌液中硫酸锌和焦磷酸钾的浓度、浸锌液的温度、pH值以及浸锌时间均对浸锌层的质量有很大影响;最佳浸锌液的组成为:硫酸锌40g/L,焦磷酸钾125g/L,抑制剂20g/L,添加剂80g/L,与工艺参数温度75±5℃,pH值10.5±0.5,时间2~3min;在最佳浸锌条件下可在AZ91D镁合金表面获得浸锌层的结合力良好,耐盐雾时在最佳浸锌条件下可在AZ91D镁合金表面获得浸锌层的结合力良发好,耐盐雾时间为28min,将浸锌后的镁合金进行电镀铜试验,铜镀层结合力与耐蚀性均良好。     

现代航空发动机液压机械控制器仿真研究

利用先进的计算机技术和数字仿真技术进行现代航空发动机的液压机械控制器的精确仿真.在Matlab/Simulink环境下,建立了一套元件模型库,并将航空发动机控制系统部件利用此模型库进行数学建模.对某型发动机控制器进行了仿真验证,仿真结果与试验数据吻合.      

基于POD降阶模型的气动弹性快速预测方法研究

CFD/CSD耦合数值模拟是解决复杂气动弹性问题精度最高的方法,但同时也是计算效率最低的方法。研究了气动弹性系统的时域POD降阶模型方法,并引入平衡截断技术进一步降低时域POD/ROM的阶数,从而有效克服了时域POD/ROM阶数过高的缺点。以AGARD445.6机翼为例,说明了时域POD/ROM建模的各个细节,并将其用于气动弹性动响应及颤振边界的预测。计算结果表明,POD/ROM具有接近CFD/CSD耦合计算的精度,同时又大大提高了计算效率约1到2个量级。