MIDACO on MINLP space applications

A numerical study on two challenging mixed-integer non-linear programming (MINLP) space applications and their optimization with MIDACO, a recently developed general purpose optimization software, is presented. These applications are the optimal control of the ascent of a multiple-stage space launch vehicle and the space mission trajectory design from Earth to Jupiter using multiple gravity assists. Additionally, an NLP aerospace application, the optimal control of an F8 aircraft manoeuvre, is discussed and solved. In order to enhance the optimization performance of MIDACO a hybridization technique, coupling MIDACO with an SQP algorithm, is presented for two of these three applications. The numerical results show, that the applications can be solved to their best known solution (or even new best solution) in a reasonable time by the considered approach. Since using the concept of MINLP is still a novelty in the field of (aero)space engineering, the demonstrated capabilities are seen as very promising.     

Vibration Reduction of Open-chain Flexible Manipulators by Optimizing Independent Motions of Branch Links

In order to suppress vibration in flexible manipulators, a new type of manipulator mechanism with controllable local degrees of freedom is proposed. This mechanism consists of a main chain and some branch links. The main chain is of a flexible open-chain configuration with an end-effector installed at its tip, and the rigid branch links are able to perform active movements. It is proved by kinematics and dynamic analysis that, the branch links bear no direct kinematic relation to the main chain, but their independent motions can strongly affect the dynamic behavior and performance of the flexible manipulator. Then comes a new idea of suppressing vibration, in which independent motions of the branch links are used to suppress the undesired vibration of the flexible main chain through dynamic coupling. On this basis, an optimal method for reducing vibration of flexible manipulators is proposed. Finally, the effectiveness of this method is verified by numerical simulations.     

精密跟瞄Hexapod平台研制及其振动控制

为了实现星载光学设备的精密跟瞄,以自行研制的宏/微双重驱动复合作动器为主动元件,设计了合理的平台构型,选择并装配了铰链等关键部件,组装完成了具有振动主动控制和大幅跟瞄能力的Hexapod平台原理样机。利用牛顿-欧拉法建立了Hexapod平台线性动力学模型。采用改进的自适应振动消减器(ADC)方法进行了平台主动隔振的控制仿真与实验研究。由仿真结果可知,当Hexapod平台底部受到方向不同的双频正弦微振动干扰时,控制可以隔离干扰向平台上平面的传播;在实验中,平台上平面处于水平位置及转动一定角度时,底部微扰动引起的各杆振幅均下降了90%左右。结果表明了所研制的Hexapod平台用于主动隔振的可行性、建模的有效性以及改进的ADC方法的合理性。     

含腔复杂军事目标RCS综合计算方法

根据飞行器等含腔复杂军事目标 RCS计算的需要,改进了射线跟踪法,并针对不同高频算法的特点,将像素法、射线跟踪法和边缘等效电磁流法结合运用,不同类别散射中心采用不同的方法计算,然后将复数量叠加得出目标的RCS,并充分考虑算法的协调.结合算例对方法进行验证,并将结果与矩量法等精确算法计算得到的结果进行了对比验证;运用本文方法对美国暗星无人机RCS进行了计算和分析.     

三乙胺与硝酸-27S自燃技术研究

三乙胺和硝酸-27S作为自燃推进剂可应用于火箭发动机中。对这两种自燃推进剂的燃烧性能进行了研究,应用逐步逼近法计算其热力性质,当最佳混合比为4．1,燃烧室压力为4．5MPa时,最佳海平面比冲为2786m／s。通过试验证明了三乙胺和硝酸-27S自燃技术的可行性。     

旋翼洗流影响直升机红外辐射的计算分析

针对在旋翼洗流作用下,高速、高温的发动机喷流对直升机的红外辐射特性有着相当大影响的问题,提出了一种计算分析方法。该方法首先利用自由尾流技术对旋翼下洗流场进行计算;在此基础上,将旋翼洗流视为一种横流干扰,以计算得出的洗流速度为边界条件,进行了发动机热喷流模拟;然后,计算了喷流截面的温度涡线分布,并以此确定了旋翼洗流影响下的机体温度分布;最后,计算和分析了旋翼洗流对直升机红外辐射强度的影响。对某型直升机计算分析表明,该方法稳定可靠,结果符合实际情况,适于工程分析和预估。该方法还可用于直升机机体温度场的工程求解。     

The relation between the Black hole mass and the Bulge mass for low redshift AGNs. Part I: Ground-based observations

Using the bulge data from AGN image decomposition with ground-based observations, we calculate the ratios of the central supermassive black hole mass(SMBH) to the Bulge mass (_Mbh/_Mbulge$M_{\text{bh}}/M_{\text{bulge}}$) in a sample of X-ray selected AGNs, including 15 Narrow-line Seyfert 1 galaxies (NLS1s) and 18 broad-line Seyfert 1 galaxies (BLS1s). We found that the mean value of log(_Mbh/_Mbulge)$\log (M_{\text{bh}}/M_{\text{bulge}})$ is -3.81±0.11$-3.81\pm 0.11$ for 15 NLS1s, and -2.91±0.13$-2.91\pm 0.13$ for 18 BLS1s, showing the lower _Mbh/_Mbulge$M_{\text{bh}}/M_{\text{bulge}}$ in NLS1s relative to BLS1s. The calculation shows that the Bulge mass from the host image decomposition in NLS1s is statistically smaller than that from Hubble-type correction method, and a linear mass relation is suggested for NLS1s and a nonlinear mass relation for BLS1s. The studying of host galaxies with ground-based observations strongly limited by the atmospheric seeing. We need to do the decomposition of host images for NLS1s with Hubble Space Telescope observation in the future.     

Searching for life on Mars: selection of molecular targets for ESA's aurora ExoMars mission

The European Space Agency's ExoMars mission will seek evidence of organic compounds of biological and non-biological origin at the martian surface. One of the instruments in the Pasteur payload may be a Life Marker Chip that utilizes an immunoassay approach to detect specific organic molecules or classes of molecules. Therefore, it is necessary to define and prioritize specific molecular targets for antibody development. Target compounds have been selected to represent meteoritic input, fossil organic matter, extant (living, recently dead) organic matter, and contamination. Once organic molecules are detected on Mars, further information is likely to derive from the detailed distribution of compounds rather than from single molecular identification. This will include concentration gradients beneath the surface and gradients from generic to specific compounds. The choice of biomarkers is informed by terrestrial biology but is wide ranging, and nonterrestrial biology may be evident from unexpected molecular distributions. One of the most important requirements is to sample where irradiation and oxidation are minimized, either by drilling or by using naturally excavated exposures. Analyzing regolith samples will allow for the search of both extant and fossil biomarkers, but sequential extraction would be required to optimize the analysis of each of these in turn.     

Biomarker and stable isotope characterization of coastal pond-derived organic matter, McMurdo Dry Valleys, Antarctica

Small coastal ponds that contain photosynthetic microbial mat communities represent an extreme environment where a potentially significant source of labile organic carbon can be found within the McMurdo Dry Valleys, Antarctica. To distinguish coastal pond-derived organic matter from other sources of organic matter in the Dry Valleys, bulk organic carbon, nitrogen, and sulfur isotope signatures and phospholipid fatty acid (PLFA) profiles of benthic microbial mats located at two sites--Hjorth Hill coast and Garwood Valley--were investigated. The average isotope values at Hjorth Hill coast and Garwood Valley are, respectively, -10.9 per thousand and -10.2 per thousand for delta(13) C, 3.7 per thousand and -1.3 per thousand for delta(15)N, and 8.1 per thousand and 16.7 per thousand for delta(34)S. Microbial mats from all ponds are dominated by monounsaturated PLFAs (indicative of Gram-negative bacteria) and polyunsaturated PLFAs (indicative of microeukaryotes). Biomarkers specific to aerobic prokaryotes, eukaryotes, and photoautotrophic microeukaryotes, as well as sulfur-reducing bacteria, are present in all samples. Benthic mats at Garwood Valley are thicker and more laminated, have a higher biomass, and have a greater carbon and nitrogen content, which suggests greater productivity than mats at Hjorth Hill coast. Greater productivity is supported, as well, by higher dissolved oxygen contents likely derived from heightened photosynthetic productivity. More productivity at Garwood Valley likely results from a larger influx of terrestrial surface waters together with a concomitant nutrient loading.