基于源项辨识的飞机座舱污染浓度动态预测

随着大型民机飞行时间的延长,座舱空气污染事故发生概率也随之增大,快速准确的污染浓度预测对保证乘客生命安全具有重要意义.座舱各污染浓度的动态预测和污染源项强度辨识是实现座舱空气质量实时预测的关键技术.污染源项散发强度辨识,如采用最小二乘算法,参数估计是静态的,一般延迟较大;如采用单模卡尔曼滤波算法,虽能实现动态辨识,但不能同时兼顾稳态和过渡过程(突发污染)的参数估计性能,导致误差较大.为解决上述难题,本文提出基于源项辨识的飞机座舱污染浓度动态预测方法,同时完成污染源散发强度动态辨识和污染浓度状态实时预测.该算法由2个滤波器组成,分别用于匹配系统的稳态和突发过渡过程特征,提高浓度方程参数估计和状态预测性能,保证飞机座舱空气质量态势预测的快速性和准确性.仿真结果证实了该算法的有效性.     

无反馈多级式多传感器组合导航系统

传统的多传感器组合导航系统大都采用集中式、分布式与混合式信息融合方法,而多级式信息融合算法是上述3种算法的发展,可完成高层次空间融合。文章首先研究了基于无反馈信息的多传感器组合导航系统的多级式信息融合算法,然后理论分析证明该算法与无反馈形式的联邦卡尔曼滤波算法等价,最后以SINS/GPS/ SST/高度表多组合导航系统为例,对上述算法及结论进行了仿真与验证。     

空间陀螺仪显式标定与隐式标定方法

针对航天器陀螺仪误差系数的标定问题,提出了显式与隐式两种标定方法。建立了显式标定与隐式标定方法的状态方程与测量方程,利用扩展Kalman滤波获得了陀螺仪误差系数的高精度估计,同时比较了显式标定与隐式标定的不同,仿真结果表明,在当前参数设置下,显式标定与隐式标定精度基本相同,两种方法得到的误差系数估计相对误差在10%以内,而隐式标定方法实现较为容易,但对航天器姿态测量精度较为敏感。     

基于特征模型的高超声速飞行器姿态控制器与自适应滤波算法的设计

提出一种基于特征模型的强跟踪无迹卡尔曼滤波（CSUKF）算法对状态和参数进行联合估计,利用特征模型参数构造时变的二阶状态转移阵,使滤波和辨识模型简化;结合强跟踪滤波（STF）的强跟踪能力和无迹卡尔曼滤波的（UKF）的非线性高逼近性对含测量噪声的高超声速飞行器系统进行参数辨识和滤波,并将其与非线性黄金分割自适应控制律相结合,对高超声速飞行器进行姿态控制.最后,将提出的CSUKF与基于特征模型的无迹卡尔曼滤波（CUKF）和基于特征模型的普通扩展卡尔曼滤波算法（CEKF）进行比较,仿真结果说明CSUKF与非线性黄金分割自适应控制律相结合可以有效改善控制的平稳性,且具有更好的滤波精度和系统输出,从而能更好地处理含测量噪声情况下的高超声速飞行器的辨识与控制问题.     

对一种特征识别算法的两点改进

 针对一类重要的特征识别算法——Falcidieno算法,做了两点较大的改进:第一,在处理显式特征时,原算法不能处理凸特征与凹特征相邻接时的情况,而改进后的算法可处理该情况,它可从既有凸边又有凹边的环识别出凸特征和凹特征;第二,指出了隐式凸特征存在的一个条件,并修改了对隐式特征的处理方法,从而可识别出更多类型的隐式凸特征.这两点改进显著地扩展了该算法的适用范围.     

基于分层随机梯度辨识算法的传感器故障检测方法

提出一种基于两阶段递推随机梯度参数辨识的传感器故障的在线检测方法.相对于最小二乘参数辨识算法,随机梯度参数辨识算法所需计算量更小.针对计算能力受限的系统,提出基于随机梯度参数辨识的检测算法.通过分析可知,参数辨识精度越高时检测精度越高.为提高精度,给出基于两阶段递推随机梯度参数辨识的检测算法并设计基于最新估计信息的残差.除此之外,还给出新的检测算法与原有的基于最小二乘检测算法计算量的对比分析,并通过仿真实例,证明新的检测算法的优越性及有效性.     

一种对磁电式速度传感器进行动态补偿的新方法

在已知磁电式速度传感器传递函数的情况下,采用优化技术设计了动态数字滤波器。在不改变传感器高频特性的情况下,扩展了传感器的低频工作范围。该设计方法基于系统辨识,一切算法都在时间域内完成,可全部借助于计算机进行处理。实践证明,采用该方法可以有效地改善传感器及其它测量系统的动念特性。文中的模型定阶准则是在设计磁电式速度传感器的动态补偿数字滤波器时,采用其它准则都不易实现的情况下提出来的,具有一定的通用性。最后,计算了一个设计实例。     

数值模拟高超音速化学非平衡流的隐式格式

针对高超音速化学非平衡流提出了两种隐式格式.一种是近似因子分解算法对角化形式在隐式TVD(全变差递减)格式上的推广,另一种可视为隐式TVD格式的LU分解形式.数值试验表明,本文给出的算法保持了TVD格式的高分辨率特性,同时计算量大大减少,是高超音速化学非平衡流数值模拟的有效方法.     

反射器夹层面板精密成形原理

对高精度、大面积不可展双曲反射面的制造问题,提出了基于"离散钉模、真空负压、蜂窝夹层、应力释放、回弹补偿"的高精度反射面板成形原理;建立了四边自由面内多点约束的薄板大挠度弯曲解法及夹层板成形过程仿真模型,用于确定成形工艺参数;利用动力显式和静力隐式算法相结合的方法实现成形过程仿真;通过开缝和开槽方法释放面内压应力,确定了面板开缝和开槽方案;通过逆向修正离散模包络面,使其与成形模拟得到的夹层板型面误差最小,得到模具修正因子,补偿回弹误差.在此基础上开发了夹层板精密成形CAE系统.该方法制造的面板型面精度RMS达到25 μm以下,已成功地应用于多项大型紧缩场和毫米波天线的制造.      

板料冲压成形回弹的数值模拟

回弹是板料成形过程中不可避免的现象.回弹的数值模拟作为解决回弹问题的有效方法,越来越受到工业界和学术界的重视.完整的回弹数值模拟分为2步,即冲头加载成形过程模拟和冲头卸载回弹过程模拟.本文比较了静力隐式和动力显式2种算法在计算回弹问题时的优劣,采用静力隐式算法建立了计算冲头加载成形过程模拟和冲头卸载回弹过程模拟的有限元模型,并利用自行开发的软件给出了计算实例.      

Volatile organic compounds detected in the atmosphere of NASA's Biomass Production Chamber.

Atmospheres of enclosed environments in which 20 m2 stands of wheat, potato, and lettuce were grown were characterized and quantified by gas chromatography-mass spectrometry. A large number (in excess of 90) of volatile organic compounds (VOCs) were identified in the chambers. Twenty eight VOC's were assumed to be of biogenic origin for these were not found in the chamber atmosphere when air samples were analyzed in the absence of plants. Some of the compounds found were unique to a single crop. For example, only 35% of the biogenic compounds detected in the wheat atmosphere were unique to wheat, while 36% were unique to potato and 26% were unique to lettuce. The number of compounds detected in the wheat (20 compounds) atmosphere was greater than that of potato (11) and lettuce (15) and concentration levels of biogenic and non-biogenic VOC's were similar.     

The potential of the lichen symbiosis to cope with the extreme conditions of outer space II: germination capacity of lichen ascospores in response to simulated space conditions.

Complementary to the already well-studied microorganisms, lichens, symbiotic organisms of the mycobiont (fungi) and the photobiont (algae), were used as "model systems" in which to examine the ecological potential to resist to extreme environments of outer space. Ascospores (sexual propagules of the mycobiont) of the lichens Fulgensia bracteata, Xanthoria elegans and Xanthoria parietina were exposed to selected space-simulating conditions (up to 16 h of space vacuum at 10(-3) Pa and UV radiation at 160 nm < or = lambda < or = 400 nm), while embedded in the lichen fruiting bodies. After exposure, the ascospores were discharged and their viability was tested as germination capacity on different culture media including those containing Mars regolith simulant. It was found that (i) the germination rate on media containing Mars regolith simulant was as high as on other mineral-containing media, (ii) if enclosed in the ascocarps, the ascospores survived the vacuum exposure, the UV-irradiation as well as the combined treatment of vacuum and UV to a high degree. In general, 50 % or more viable spores were recovered, with ascospores of X. elegans showing the highest survival. It is suggested that ascospores inside the ascocarps are well protected by the anatomical structure, the gelatinous layer and the pigments (parietin and carotene) against the space parameters tested.     

狭长型封闭舱室内非定常流动模拟的湍流模型比较

针对狭长型封闭舱室内非定常流动模拟的湍流模型选择问题，以飞机舱室为典型环境，使用相似准则为依据的热缩比法搭建了实验平台。将实验结果与RNG k-ε、DES、LES三种湍流模型的数值模拟结果进行对比和分析，评估狭长型封闭舱室内非定常流动特征研究中合适的湍流模型。结果显示，RNG k-ε和DES模型可以定性描述流动变化趋势，但是LES模型在流场非定常性和不稳定性捕捉更为准确，其流场结构更接近实验结果。模拟结果与实验结果对比显示，LES模型能更加真实地反映狭长型封闭舱室非定常流动的情况。     

细水雾喷头喷射压力影响灭火性能的实验

为了研究细水雾喷头在不同喷射压力情况下针对油盘火的灭火效果,采用正庚烷为火灾燃料,在4.6m×3.3m×4m(长×宽×高)的空间内,针对同一型号的细水雾喷头在不同喷射压力下进行了灭火实验,在实验过程中采用热电偶树和气体分析仪对火焰温度及火场氧浓度进行了测量,得到了不同喷射压力下细水雾灭火的影响规律,为细水雾灭火设计、检验标准制定及细水雾灭火产品的开发提供了相应的实验依据.     

油面距油盘沿口高度对细水雾灭火效果的影响

油盘火是细水雾灭火效果检验的标准实验火灾模型,为了确定细水雾针对油盘火模型的实验方法,采用正庚烷为火灾燃料,在长4.6m,宽3.2m,高4m的空间内,对油面距油盘沿口高度进行了灭火实验,在实验过程中采用热电偶树和气体分析仪对火焰温度及火场氧浓度进行了测量,得到了油面距油盘沿口高度对细水雾灭火效果的影响规律,为细水雾灭火设计、检验标准制定及细水雾灭火产品的开发提供了相应的实验依据.      

电离辐射对部分耗尽SOI器件关态电流的影响

针对辐射前后环栅与条栅结构部分耗尽绝缘体上硅(SOI,Silicon On Insulator)器件关态电流的变化展开实验,研究结果表明辐射诱使关态电流增加主要取决于侧壁泄漏电流、背栅寄生晶体管导通、带-带隧穿与背栅泄漏电流的耦合效应.在条栅结构器件中,辐射诱生场氧化层固定电荷将使得器件侧壁泄漏电流增加,器件前、背栅关态电流随总剂量变化明显;在环栅结构器件中,辐射诱使背栅晶体管开启将使得前栅器件关态电流变大,而带-带隧穿与背栅泄漏电流的耦合效应将使得器件关态电流随前栅电压减小而迅速增加.基于以上结果,可通过改良版图结构以提高SOI器件的抗总剂量电离辐射能力.     

DFR腐蚀影响系数及其试验测定

为使腐蚀环境下民机结构疲劳分析的细节疲劳额定值(DFR)方法具有更广泛适用性,对DFR腐蚀影响系数与腐蚀环境的关系进行了研究,将DFR的腐蚀影响系数分解为地面停放腐蚀影响系数和空中腐蚀疲劳影响系数,建立了地面停放腐蚀影响系数与地面停放腐蚀时间的关系,以及空中复杂综合环境腐蚀疲劳影响系数与单一介质环境腐蚀影响系数的关系.通过试验测定了各种典型情况的DFR腐蚀影响系数,试验结果说明DFR腐蚀影响系数随着地面停放腐蚀时间的增加和环境腐蚀性的增强而降低,腐蚀疲劳的影响较停放腐蚀的影响更严重.分析实例具体说明了腐蚀条件下DFR方法的具体步骤和所需数据,并体现出疲劳分析中计及腐蚀影响的必要性.      

Pigment composition and concentrations within the plant (Ceratophyllum demersum L.) component of the STS-89 C.E.B.A.S. Mini-Module spaceflight experiment.

The Closed Equilibrated Biological Aquatic System (C.E.B.A.S.) Mini-Module, a Space Shuttle middeck locker payload which supports a variety of aquatic inhabitants (fish, snails, plants and bacteria) in an enclosed 8.6 L chamber, was tested for its biological stability in microgravity. The aquatic plant, Ceratophyllum demersum L., was critical for the vitality and functioning of this artificial mini-ecosystem. Its photosynthetic pigment concentrations were of interest due to their light harvesting and protective functions. "Post-flight" chlorophyll and carotenoid concentrations within Ceratophyllum apical segments were directly related to the quantities of light received in the experiments, with microgravity exposure (STS-89) failing to account for any significant deviation from ground control studies.     

X-ray populations in galaxies

High-resolution Chandra observations have allowed the detection of populations of X-ray sources in galaxies of all morphological types. The X-ray Luminosity Functions (XLFs) of these X-ray source populations have been derived and studied to uncover the drivers for the formation and evolution of binaries in different stellar populations and environments. These XLFs also provide a tool for identifying the nature of the X-ray source population, since different XLFs characterize X-ray sources belonging to young and old stellar populations. Similarly, X-ray colors can be used for identifying different types of X-ray sources. Ultra-Luminous X-ray sources (ULXs, L_X > 10³⁹ ergs s⁻¹) are found to be associated with star-forming stellar populations. The study of the ULX population of the Antennae galaxies points to compact accreting binaries.