Low light intensity effects on the growth,photosynthetic characteristics,antioxidant capacity,yield and quality of wheat (Triticum aestivum L.) at different growth stages in BLSS

Minimizing energy consumption and maximizing crop productivity are major challenges to growing plants in Bioregenerative Life Support System (BLSS) for future long-term space mission. As a primary source of energy, light is one of the most important environmental factors for plant growth. The purpose of this study is to investigate the effects of low light intensity at different stages on growth, pigment composition, photosynthetic efficiency, biological production and antioxidant defence systems of wheat (Triticum aestivum L.) cultivars during ontogenesis. Experiments were divided into 3 intensity-controlled stages according to growth period (a total of 65 days): seedling stage (first 20 days), heading and flowering stage (middle 30 days) and grain filling stage (last 15 days). Initial light condition of the control was 420 μmol m⁻² s⁻¹ and the light intensity increased with the growth of wheat plants. The light intensities of group I and II at the first stage and the last stage were adjusted to the half level of the control respectively. For group III, the first and the last stage were both adjusted to half level of the control. During the middle 30 days, all treatments were kept the same intensity. The results indicated that low-light treatment at seedling stage, biomass, nutritional contents, components of inedible biomass and healthy index (including peroxidase (POD) activity, malondialdehyde (MDA) and proline content) of wheat plants have no significant difference to the control. Furthermore, unit kilojoule yield of group I reached 0.591 × 10⁻³ g/kJ and induced the highest energy efficiency. However, low-light treatment at grain filling stage affected the final production significantly.     

Dry Grinding of Titanium Alloy Using Brazed Monolayer cBN Wheels Coated with Graphite Lubricant

The purpose of this study is to investigate the effect of graphite lubricant on the dry grinding performance of Ti-6Al-4Valloy,using graphite-coated,brazed monolayer,cubic boron nitride(cBN)wheels.Brazed monolayer cBN wheels both with and without a coating of polymer-based graphite lubricant are fabricated and subsequently compared for grinding performance based on measurements of grinding temperature,surface microstructure and grinding.In terms of grinding temperature,considerable improvement in dry grinding performance of titanium alloy is achieved using coated brazed monolayer cBN wheels,with 42%—47%reduction in grinding temperature as opposed to uncoated wheels.The grinding force ratio with the coated wheels is observed to remain between 1.45to1.85despite material removal rates reaching up to 1 950mm3/mm.No tangible change in ground titanium surface microstructure is noted as a result of grinding with the graphite coated wheels as opposed to the uncoated ones.     

电动静液作动器的新型变阻尼级联滑模控制

为改善电动静液作动器（EHA）的动态性能，提出了一种基于新型准自适应变阻尼滑模控制（DV-SMC）和PID控制的级联控制（CC）算法。所提算法将高阶EHA分为液压和机械2个低阶系统，分别对2个低阶系统采用了DV-SMC和双环PID控制策略。DV-SMC方法能够自适应调整滑模面阻尼。在起始阶段采用欠阻尼、末段自适应调节为过阻尼，从而在保证EHA快速性的同时也能够完全抑制超调现象。通过仿真验证了所提算法的有效性，并讨论给出了DV-SMC滑模面最优参数。      

基于改进HHT的一体化电液作动器故障诊断

介绍了机载变排量变转速一体化电动静液作动器(EHA-VPVM,Electro-Hydrostatic Actuator with Variable Pump displacement and Variable Motor speed)的系统结构,根据EHA-VPVM早期故障信号非平稳、时变等特点,采用一种新的时频分析方法希尔伯特黄变换(HHT,Hilbert-Huang Transform)进行信号分析.针对HHT方法的模态混叠和虚假本征模态函数问题,提出两点改进:通过集合经验模式分解算法抑制模态混叠的发生;采用相关系数法保留真实本征模态函数.对EHA-VPVM工程样机进行早期故障诊断实验,用Hilbert边际谱和HHT谱分析永磁无刷直流电机两种工作状态下的振动信号.实验结果表明:改进HHT方法较好解决了HHT的模态混叠和虚假本征模态函数问题,能准确提取研究对象的早期故障特征,对EHA-VPVM早期故障具有良好的诊断效果.     

微量润滑系统的喷射雾化特性研究

为了揭示微量润滑系统的喷射雾化规律,采用基于激光多普勒效应的三维粒子动态分析仪测量了油滴雾化特性.针对3种可降解绿色润滑油——三羟甲基丙烷三油酸酯、植物油6000和聚乙二醇400,测试得到了不同的油量、空气流量和截距条件下的雾化锥角及油滴大小、速度、数量的分布规律.试验表明,喷雾锥角主要由喷嘴结构决定,油滴数量基本符合...     

柔性转子-挤压油膜阻尼器系统突加不平衡响应试验研究

关于柔性转子、无定心弹簧的挤压油膜阻尼支承系统的突加不平衡响应实验研究,在国内尚未见公开报导,而探讨其一般规律性的论文却不少见,其原因可能是这种试验较难逼真地实现,并且因为要释放一块旋转质量而带有一定的危险性。 挤压油膜阻尼器已经过二十余年的研究和使用,日趋完善,但是大多数阻尼器是设计在正常不平衡量范围内工作的,而在航空发动机上却常因某种原因发生诸如叶片折断或丢失一     

计算机飞行计划系统的设计与实现

介绍了计算机飞行计划系统的设计和实现过程,给出了实现该系统的软硬件环境,说明了其中的一些关键技术和解决方案,同时,还介绍了该系统的主要功能,并对进一步的工作和这项技术的应用前景作了展望。     

基于非测地线理论的回转体缠绕成型的数学模型

根据非测地线缠绕的有关理论，详细分析了微机控制纤维缠绕机的丝嘴运动规律，推导出了丝嘴运动方程和芯模的转角方程，为复杂芯模的缠绕以及微机控制纤维缠绕机的推广应用奠定了基础。     

舰船空气尾流场特性研究

舰船空气尾流场是舰载直升机在非航空型舰船上起降或者在这类舰船附近作业时的主要环境条件，是危及舰载直升机飞行安全的主要因素之一。现以机－舰动态干扰为研究目的。通过各种试验结果的相互比较，验证，综合分析了舰船空气尾流场特性。着重研究了尾流场中涡流区的及变化规律，下洗速度的大小、下洗范围及变化规律，为机－舰动态配合的试验提供了可靠的依据，另外，还结合飞行实践简要地分析了直升机进入尾流场后的反应。     

HRS定向凝固过程中固/液界面位置控制

 本文通过在计算机上模拟固/液界面位置受到控制的整个HRS定向凝固过程、求出使固/液界面稳定在隔热板及其附近时抽拉速度的调节规律。依此规律,利用一个以TP 801 B单板机为核心的控制系统对铸件的HRS定向凝固过程进行实时控制。用Al—4.5％Cu合金试样进行了验证试验。结果表明:受控HRS定向中、固/液界面很快趋近于隔热板并在定向过程中稳定在隔热板附近。对界面位置实行控制能有效提高固/液界面前沿温度梯度及其稳定性明显改善定向凝固显微组织。