The Closeby Habitable Exoplanet Survey(CHES) mission is proposed to discover habitable-zone Earth-like planets of nearby solar-type stars(～10 pc away from our solar system) via microarcsecond relative astrometry.The major scientific objectives of CHES are:to search for Earth Twins or terrestrial planets in habitable zones orbiting100 FGK nearby stars;further to conduct a comprehensive survey and extensively characterize nearby planetary systems.The primary payload is a high-quality,low-distortion,high-stability telescope.The optical subsystem is a coaxial three-mirror anastigmat(TMA) with a 1.2 m-aperture,0°.44 × 0°.44 field of view and 500 nm-900 nm working wave band.The camera focal plane is composed of a mosaic of 81 scientific CMOS detectors each with4 k × 4 k pixels.The heterodyne laser interferometric calibration technology is employed to ensure microarcsecond level(1 μas) relative astrometry precision to meet the requirements for detection of Earth-like planets.The CHES satellite operates at the Sun-Earth L2 point and observes all the target stars for 5 yr.CHES will offer the first direct measurements of true masses and inclinations of Earth Twins and super-Earths orbiting our neighbor stars based on microarcsecond astrometry from space.This will definitely enhance our understanding of the formation of diverse nearby planetary systems and the emergence of other worlds for solar-type stars,and finally provide insights to the evolution of our own solar system.

采用廉价易得的商用聚氨酯海绵(PU)为基底,通过多次浸渍涂覆的方法将迈科烯/多壁碳纳米管(MXene/MWCNT)复合材料负载在海绵基底上,制备出一种柔性压力传感器.经测试,传感器具有检测范围宽(0～50 kPa)、灵敏度高(0.16 kPa-1)等优异特性.该传感器还能实现对于微小压力、吹气以及人体指部弯曲运动信号的检测,为低成本、大规模制备柔性高性能柔性压力传感器提供了新的可能性方案.

Background Although numerous studies have been published evaluating the positive or negative effects of altitude on cardiovascular disease, many of them are conflicting. Methods and Results Data come from 2 cross‐sectional surveys using a similar method in China; and a total of 34 215 residents, aged ≥35 years, were eligible and recruited in the study. Left ventricular diastolic dysfunction (LVDD), according to the 2009 American Society of Echocardiography guidelines, was defined and evaluated. Altitude was divided into low (<1500 m), middle (1500–3500 m), and high (≥3500 m) level groups. Among the 34 215 participants (aged 55.87 years; men, 45.92%; altitude ranging from 3.1 ~ 4507 m), 15 099 (crude prevalence, 44.13%), 517 (crude prevalence, 1.51%), and 272 (crude prevalence, 0.79%) were diagnosed as having grades I, II, and LVDD, respectively. Compared with low‐level group, the odds ratios (ORs) (95% CIs) of LVDD for middle‐ and high‐level groups were 1.65 (1.49–1.82) and 1.89 (1.63–2.19), respectively (Ptrend<0.001). The ORs (95% CI) were 1.43 (1.31–1.56) and 2.03 (1.67–2.47) per 500‐m increment for middle‐ and high‐level groups. There was a nonlinear relationship (upward‐sloping “W” shape) between altitude and the risk of LVDD, assessed by the restricted cubic spline. For each LVDD grade, ORs (95% CIs) of grade I LVDD for middle‐ and high‐level groups were 1.75 (1.59–1.92) and 1.95 (1.69–2.25), respectively; for grade II, ORs (95% CIs) for middle‐ and high‐level groups were 6.19 (3.67–10.42) and 5.27 (2.18–12.74), respectively. The stratified analyses indicated that LVDD was much more remarkably influenced by elevated altitude in men (Pinteraction=0.0019). Conclusions Higher altitude is associated with increased risk of LVDD among people living over 1500 m, especially for men.

以4-硝基苯并-15-冠醚-5(4-NO2-B15C5)做萃取剂,苯甲醚和1-丁基-3-甲基咪唑双(三氟甲烷磺酰)亚胺盐([C4 mim][NTf2])作稀释剂和协萃剂,以1 mol/L LiCl溶液作萃取溶剂,构建高效的冠醚—离子液体/锂盐溶液的溶剂萃取体系.重点考察了有机相组成、冠醚浓度和锂盐阴离子等对锂同位素分离的影响.结果表明,4-硝基苯并-15-冠醚-5具有良好的锂同位素分离效果,在萃取CF3 COOLi时最大单级分离系数(α)可达1.043±0.01.

Pyrolysis of JP-10 hydrocarbon fuel was studied in a single-pulse shock tube over temperature range from 1150 K to 1300 K. The main decomposition products were identified by gas chromatography as ethylene, acetylene, propylene, $n$-butene, 1,3-butadiene, cyclopentadiene, cyclopentene, benzene, toluene, and a small amount of methane, ethane, xylene and 1-methylcyclopentene. By summation of all product concentrations in each run, the rate coefficient of JP-10 pyrolysis was experimentally determined. Comparative rate measurements were used to eliminate the effects of shock's non-ideality and boundary layer. A small amount of the internal standard compound, whose rate expression for decomposition is well established, was added in the test gas mixtures, and the reaction temperatures were determined according to the decomposition extents of the internal standard compound under the same experimental conditions in a shock tube. The reaction temperatures determined from the decomposition extents of the internal standard compound are usually less than those at the region 5 behind reflected shock calculated by shock velocity measurements. The temperatures determined by two methods are consistent between 1150 K and 1300 K, the difference is within 20 K, and the difference increases with the temperature increase. Based on the experimental study, kinetic modeling of JP-10 pyrolysis was carried out according to San Diego Mechanism. The yields of three main products, ethylene, acetylene and 1,3-butadiene, have a good agreement between the experimental and the simulation results,while the experimental results of cyclopentene yield are much higher than simulation,indicating that both fully and partially ring-opening reactions in JP-10 pyrolysis are important decomposition reaction pathways.

The planets with a radius < 4 R⊕ observed by the Kepler mission exhibit a unique feature, and propose a challenge for current planetary formation models. The tidal effect between a planet and its host star plays an essential role in reconfiguring the final orbits of the short-period planets. In this work, based on various initial Rayleigh distributions of the orbital elements, the final semi-major axis distributions of the planets with a radius < 4 R⊕ after suffering tidal evolutions are investigated. Our simulations have qualitatively revealed some statistical properties: the semi-major axis and its peak value all increase with the increase of the initial semi-major axis and eccentricity. For the case that the initial mean semi-major axis is less than 0.1 au and the mean eccentricity is larger than 0.25, the results of numerical simulation are approximately consistent with the observation. In addition, the effects of other parameters, such as the tidal dissipation coefficient, stellar mass and planetary mass, etc., on the final semi-major axis distribution after tidal evolution are all relatively small. Based on the simulation results, we have tried to find some clues for the formation mechanism of low-mass planets. We speculate that these low-mass planets probably form in the far place of protoplanetary disk with a moderate eccentricity via the type I migration, and it is also possible to form in situ.

在中国科学院力学研究所Φ800 mm高温低密度激波管上进行电磁波在等离子体中传输机理研究时,低密度和强激波条件下,由于气体解离和电离等非平衡过程,使得激波后2区宽度显著减小;同时由于边界层效应造成激波衰减和接触面加速,使得激波后2区长度进一步减小.这两个效应导致激波管2区实验观测时间减小,2区气体处于非平衡状态,增加了观察数据的不稳定性和数据分析的难度.本文提出在Φ800 mm高温低密度激波管中采用氩气(Ar)和空气(Air)混合气替代纯空气作为激波管实验介质气体.利用Ar不解离和难电离的特性,减小激波前后压缩比,从而增加激波后2区实验时间和气体长度.采用Langmuir静电探针和微波透射诊断技术测量激波后电子密度,同时利用探针测量激波后2区实验时间.结果显示,在Ar+Air混合气实验中,激波波后电子密度可达与纯Air同样的1013cm-3量级.在与纯Air相同的电子密度和碰撞频率条件下,采用95％Ar+5％Air和90％Ar+10％Air两种混合气,激波后2区实验时间和气体长度约为纯Air条件下的5～10倍,其中2区实验时间为300～800μs,2区气体长度1～1.5 m.在Φ800 mm激波管中采用Ar+Air介质气体进行电磁波传输实验,获得了比在纯Air介质中与理论预测更一致的结果.

In ground tests of hypersonic scramjet,the high-enthalpy airstream produced by burning hydro?carbon fuels often contains contaminants H2O and CO2. The contaminants may cause the ignition characteristics of fuels to become discrepant between ground tests and real flights. In order to properly assess the influence of the contaminants on ignition characteristics of hydrocarbon fuels,the effects of H2O and CO2 on ignition characteris?tics of RP-3 aviation kerosene were investigated in a preheated shock tube. To meet the needs of scramjet ground tests based on the ignition delay times of RP-3 aviation kerosene in clean gas, comparative experiments were conducted with clean and vitiated gases. At pressure of 0.05,0.1 and 0.2MPa,and equivalence ratios of 0.5 and 1,respectively,ignition delay times of kerosene were measured for four cases:(1) clean gas,(2) gas vitiat?ed with 4%and 25%H2O by mole,(3) gas vitiated with 3%and 10%CO2 by mole,and (4) gas vitiated with 15%H2O and 10%CO2 by mole fraction. The experimental results show that water vapor or/and carbon dioxide have almost no effect at pressure of 0.1 MPa. However,at pressure of 0.05MPa and 0.2MPa,respectively,wa? ter vapor appears to accelerate the ignition process, whereas carbon dioxide produces an inhibiting effect. At pressure of 0.05MPa and 0.2MPa, an obvious promoting effect appears over a wide temperature range when wa?ter vapor and carbon dioxide exist together. The results were also discussed preliminarily by considering both the combustion reaction mechanism and the thermophysic properties of the test mixtures.

In ground tests of hypersonic scramjet, the high-enthalpy airstream produced by burning hydrocarbon fuels often contains contaminants of water vapor and carbon dioxide. The contaminants may change the ignition characteristics of fuels between ground tests and real flights. In order to properly assess the influence of the contaminants on ignition characteristics of hydrocarbon fuels, the effect of water vapor and carbon dioxide on the ignition delay times of China RP-3 kerosene was studied behind reflected shock waves in a preheated shock tube. Experiments were conducted over a wider temperature range of 800–1 500K, at a pressure of 0.3 MPa, equivalence ratios of 0.5 and 1, and oxygen concentration of 20%. Ignition delay times were determined from the onset of the excited radical OH emission together with the pressure profile. Ignition delay times were measured for four cases: (1) clean gas, (2) gas vitiated with 10% and 20% water vapor in mole, (3) gas vitiated with 10% carbon dioxide in mole, and (4) gas vitiated with 10% water vapor and 10% carbon dioxide, 20% water vapor and 10% carbon dioxide in mole. The results show that carbon dioxide produces an inhibiting effect at temperatures below 1 300 K when ϕ = 0.5, whereas water vapor appears to accelerate the ignition process below a critical temperature of about 1 000 K when ϕ = 0.5. When both water vapor and carbon dioxide exist together, a minor inhibiting effect is observed at ϕ = 0.5, while no effect is found at ϕ = 1.0. The results are also discussed preliminary by considering both the combustion reaction mechanism and the thermophysics properties of the fuel mixtures. The current measurements demonstrate vitiation effects of water vapor and carbon dioxide on the autoignition characteristics of China RP-3 kerosene at air-like O2 concentration. It is important to account for such effects when data are extrapolated from ground testing to real flight conditions.

In the ground tests of hypersonic scramjet,the high-enthalpy airstream produced by burning hydrocarbon fuels often contains contaminants H 2 O and CO 2. The contaminants may cause the ignition characteristics of the fuel to become discrepant between ground tests and real flights. In order to properly assess the effects of the contaminants on ignition characteristics of hydrocarbon fuels,the effects of H 2 O and CO 2 on ignition charateristics of ethylene were investigated in a preheated shock tube. Based on the ignition delay time of ethylene in clean gas,comparative experiments with clean and vitiated gases were conducted. At pressure of 0. 2 MPa,equivalence ratios of 1 and 0. 5,ignition delay time of ethylene were measured for four cases:( 1) clean gas,( 2) gas vitiated with 7. 5%,15% and 25% H 2 O by mole,( 3) gas vitiated with 10% CO 2 by mole,and( 4) gas vitiated with 25% H 2 O and 10% CO 2 by mole. The experimental results show that water vapor and carbon dioxide have almost no effects at equivalence ratio of 0. 5,but an inhibiting effect appears at equivalence ratio of 1. An obviously inhibiting effect appears over a wide temperature range when water vapor and carbon dioxide exist together. The results were also discussed preliminarilyby considering both the combustion reaction mechanism and the thermophysics properties of the test mixtures.

在激波管中利用反射激波后高温环境加热燃料,以燃料点火过程中氢氧自由基特征发射光谱强度的急剧变化作为点火发生的标志,在温度范围800～1 650K,压力0.2 MPa,0.7 MPa,1.2 MPa,化学当量比为0.5,1,2,O2浓度为空气含量20％的条件下,进行了C2H4/O2/Ar混合气在低稀释度条件下点火特性的实验研究.获得了乙烯点火延时随温度、压力、化学当量比、燃料以及氧化剂浓度等参数变化的拟合关系式.对乙烯点火转爆轰现象进行了初步观察,考察了初始温度对乙烯点火特性以及点火转爆轰的影响.

在预加热到135℃的激波管反射激波后5区,以点火过程中OH自由基在306.5 nm处特征发射光谱强度的急剧变化作为点火发生的标志,进行了RP-3航空煤油点火特性的实验研究.实验温度范围为800～1450K,当量比为0.5,1,1.5,压力为0.05,0.1,0.2 MPa,O2的摩尔浓度为空气含量20％.实验获得了低压条件下(0.05,0.1,0.2 MPa) RP-3航空煤油点火延时与点火温度、压力、当量比以及煤油和氧气浓度的依赖关系.将低压实验结果与高压(0.55,1.1,2.2 MPa)条件下煤油点火特性进行了对比.结果显示,当量比对煤油点火特性的影响存在一个临界温度.在临界温度以上的高温区,煤油点火延时随当量比增加而增长;在临界温度以下的低温区,煤油点火延时随当量比增加而缩短;这一临界温度随点火压力的降低而升高.采用3种煤油燃烧反应动力学机理对煤油点火过程进行了动力学数值模拟,并与实验结果进行了对比.结果显示,Honnet等提出的煤油反应机理在高压(2.2 MPa)下与实验结果吻合得很好,而在低压下有一些差异.对不同压力条件下的点火过程进行敏感度分析表明,三体反应H+O2+M=HO2+M在高压时对煤油点火起轻微抑制作用,而在低压时对煤油点火起促进作用.

Ignition delay times of China No. 3 aviation kerosene were measured behind reflected shock waves using a heated high-pressure shock tube. Experimental conditions covered a wider temperature range of 820–1500 K, at pressures of 5.5, 11 and 22 atm, equivalence ratios of 0.5, 1.0 and 1.5, and oxygen concentration of 20%. Adsorption of kerosene on the shock tube wall was taken into account. Ignition delay times were determined from the onset of the excited radical OH emission in conjunction with the pressure profiles. The experimental results of ignition delay time were correlated with the equations: τ = 3.2 × 10−11[Kerosene]0.22[O2]−1.09 exp(69941/RT) and τ = 4.72×10−7 P −0.88 ϕ 0.23 exp(62092/RT). The current measurements provide the ignition delay behavior of China No. 3 aviation kerosene at high pressures and air-like O2 concentration.

In recent years, many new CCD observations of Phoebe, the ninth Saturnian satellite, were published. In this paper, we have used all the observations of Phoebe available until 2009 to update Phoebe's orbit. These observations represent a total number of 2994 positions, spread over a time-interval of 105 years, from 1904 to 2009. The accuracy of the updated orbit of Phoebe presented here has been improved to about 0.1 arcsec as it has been fitted to a large number of new high-accuracy observations. However, the accuracy of the orbit remains limited by the accuracy of the observations. Moreover, we have shown that the new orbit is in quite good agreement with the very reliable JPL ephemeris, within less than 20 mas.

The pyrolysis of phenolic resin was studied in a single-pulse shock tube at high temperatures between 1100 K and 1800 K. Considering the very high temperature and short duration time in a shock tube, the heat transfer process of sample particles in high temperature gas was analyzed and the heat equilibrium conditions between the phenolic resin powder and the ambient high temperature gas was also discussed. The pyrolysis product distribution and the pyrolysis rate constants of phenolic resin were determined using gas chromatograph and mass spectrometry. The major pyrolysis products were identified as water, carbon monoxide, hydrogen, acetylene and benzene. The pyrolysis process was divided into the lower and higher temperature regions at the temperature of 1400 K. The different dependency relationships of the pyrolysis rate constant with temperature for the lower and higher temperature regions were obtained.

The vibrational temperature and electron number density behind strong shock waves were measured in shock tubes, and the shock stand - off distance was measured in a ballistic range. The results were compared with those of theoretical calculations. The vibrational temperature was derived by measuring the radiation of (0,0) and ( 1,2) bands of N_2~+ first negative system. According to the experimental results, the electronic energy of N_2~+ can be excited faster than its vibrational energy, and there are periodic fluctuations in the measured vibrational temperature. In the measurement of electron number densitiy behind strong shock waves (P_1 =0. 01mmHg, V_s =7.65～7.85km/s) in could not reach the peak in such a short time. The agreement between measurement and calculation are good during the effective test region, which length is about 10 times of freestream mean - free - molecular path. The resolution of shock stand - off distance measurement is 5%, which is the best in China at present.

A method used for the study of thermal decomposition kinetics by peak analysis was developed. This method needs only a few eigenvalues of the thermogravimetric mass loss curves for the determination of kinetic parameters. A peak separation was performed to separate the thermal decomposition of phenolic resin into three stages according to the characteristic of the experimental differential mass loss curve. Kinetic parameters for each stage were determined using peak analysis method. A decomposition kinetic model, which was shown to accurately describe the decomposition process of phenolic resin, was obtained by the combination of these three stages.

The pyrolysis behavior of phenolic formaldehyde resin was studied in a shock tube at high temperatures between 1200K and 1800K.The major hydrocarbon products were identified as methane,ethene,acetylene,benzene and toluene.The variation of the major products distribution with pyrolysis temperature was obtained.It was found that the thermal decomposition of phenolic formaldehyde resin mainly took place at the methylene bridges at the temperatures below 1400K,while the cracking of aromatic framework became the major pyrolysis pathway at the temperatures above 1400K,which gave birth to large amount of acetylene.

The pyrolysis kinetics of phenolic-formaldehyde resin was studied at the temperature range from 1400 to 1700 K using a shock tube. Shock tube experiment can provide a rapid heating rate, which breaks through the limit of traditional heating rate. The major hydrocarbon products were identified as methane, ethene, acetylene and benzne. The effect of diffusion on the pyrolysis process was investigated through analyzing the reaction-diffusion process. It was found that in this experiment the reaction-diffusion process got constant rapidly, and the effect of diffusion was neglectable. The pyrolysis rate constant of phenolic resin under the pyrolysis mechanism of aromatic framework cracking was obtained for the first time.