2012–2014 China's Earth Observation and Earth Science Development

Human beings are now facing global and regional sustainable development challenges.In China, Earth observation data play a fundamental role in Earth system science research. The support given by Earth observation data is required by many studies, including those on Earth's limited natural resources, the rapid development of economic and social needs, global change, extreme events, food security, water resources, sustainable economic and urban development, and emergency response. Application operation systems in many ministries and departments in China have entered a stage of sustainable development, and the State Key Project of High-Resolution Earth Observation Systems has been progressing since 2006. Earth observation technology in China has entered a period of rapid development.     

Predictive Modeling and Parameter Optimization of Cutting Forces During Orbital Drilling

To optimize cutting control parameters and provide scientific evidence for controlling cutting forces,cutting force modeling and cutting control parameter optimization are researched with one tool adopted to orbital drill holes in aluminum alloy 6061.Firstly,four cutting control parameters(tool rotation speed,tool revolution speed,axial feeding pitch and tool revolution radius)and affecting cutting forces are identified after orbital drilling kinematics analysis.Secondly,hybrid level orthogonal experiment method is utilized in modeling experiment.By nonlinear regression analysis,two quadratic prediction models for axial and radial forces are established,where the above four control parameters are used as input variables.Then,model accuracy and cutting control parameters are analyzed.Upon axial and radial forces models,two optimal combinations of cutting control parameters are obtained for processing a13mm hole,corresponding to the minimum axial force and the radial force respectively.Finally,each optimal combination is applied in verification experiment.The verification experiment results of cutting force are in good agreement with prediction model,which confirms accracy of the research method in practical production.     

浅析高校房产管理存在的问题及对策

在我国市场经济快速发展的背景下,随着高校校区规模的不断扩张,高校的房产管理工作面临着管理体制改革和服务水平提升的双重挑战。对高校房产管理工作中存在的问题进行了分析,结合高校房产管理工作的实际情况,提出了改进高校房产管理的几点措施。     

扩大斜切式缓冲结构对时速400km铁路隧道口微气压波缓解研究

针对时速400?km高铁隧道口的微气压波研究,建立了基于三维可压缩非定常N?S方程和RNG?k-ε?双方程湍流模型的数值模拟方法,并通过动模型试验对计算方法进行了验证.文中分析了隧道长度、缓冲结构(带斜切的扩大段)长度和缓冲结构开孔数对微气压波的影响.研究结果表明:在一定隧道长度内,微气压波幅值随着隧道长度的增加逐渐增大;隧道口设置带斜切(30°)的等截面扩大段缓冲结构能有效缓解微气压波幅值,且随着缓冲结构的长度增加,微气压波幅值的缓解率先增大后减小,其中缓冲结构长88.56?m时缓解效果最佳,缓解率可达59.2％;该缓冲结构开孔后能进一步缓解微气压波幅值,缓冲结构开2个孔时的缓解效果最佳,缓解率可达70.9％.本文提出的缓冲结构能使得5?km及以下长度隧道的微气压波幅值达到国家规定标准,研究成果对时速400?km/h高速铁路隧道口缓冲结构的设计具有参考价值.     

基于热力耦合层合板雷击损伤特性分析

为研究复合材料层合板在雷电流作用下的烧蚀损伤力学特性,建立复合材料雷击热力耦合有限元分析模型,与文献实验结果对比验证模型的有效性。根据Hashin三维失效准则编写用户材料子程序,分别得出层合板雷击烧蚀区域周围出现的力学损伤、各层力学损伤分布以及首层在不同方向上的应力分布,分析得出层合板的烧蚀损伤随雷电流持续时间的变化规律。结果表明:由于存在较高的温度梯度,导致层合板出现较大的热膨胀应力,进而导致层合板内部产生各种力学损伤,即基体开裂、分层及纤维断裂;雷击电流施加时间、峰值电流与温度场均对层合板烧蚀面积产生较大的影响。     

基于声学黑洞效应的直升机驾驶舱宽带降噪

声学黑洞（ABH）效应是利用结构阻抗的变化，使结构中传播的波相速度和群速度发生变化，在结构局部区域实现波的聚集，进而通过少量阻尼将能量耗损。该方法具有高效、轻质、宽频等优点，为结构振动噪声控制提供了新的思路，具有较强的潜能和应用前景。本文针对直升机驾驶舱复杂的噪声问题，根据噪声源和传递路径，提出基于ABH效应的内嵌式和附加式2种减振降噪设计方案。利用有限元软件建立了结构声振耦合模型，分析了直升机驾驶舱模型的声振特性，解释了ABH效应有助于降低舱室噪声的机理，并搭建了实验平台，开展了效果测试和性能评估。结果表明，内嵌式ABH结构可以有效降低舱内的中高频噪声，而低频控制能力略显不足。附加式ABH结构可以弥补这一局限性，拓宽有效频带。结合内嵌式和附加式ABH 2种控制方案，相比传统结构在总质量不增加甚至略有降低的前提下，舱室平均噪声水平在1/3倍频程内降低3~10 dB。该研究成果有助于推进ABH新技术在未来直升机工程减振降噪中的应用。     

不同喷铝参数对复合材料雷击防护性能模拟

为了研究复合材料不同的雷击防护(lightning strike protection,LSP)系统在雷电流作用下的损伤规律,对雷击损伤过程和烧蚀机理进行分析,建立复合材料层合板雷击防护的能量平衡数学模型。在此基础上,在ABAQUS中建立复合材料基准件、全喷铝和局部喷铝防护系统的碳纤维增强复合材料(carbon fiber reinforced polymer,CFRP)层合板电-热耦合有限元模型,和实验结果对比验证模型的有效性,对雷击烧蚀损伤特征进行分析,并引入雷击烧蚀损伤指数DI,得出三种不同模型在不同铝涂层厚度、不同峰值雷电流作用下的烧蚀损伤规律,并对两种不同的局部喷铝防护系统下复合材料的损伤特征进行对比分析。结果表明:雷击防护系统下复合材料的烧蚀损伤面积和铝涂层厚度关系进行函数拟合,两者均满足幂函数关系。     

Command filtered sliding mode trajectory tracking control for unmanned airships based on RBFNN approximation

This paper presents two sliding mode controllers to address the trajectory tracking problem of unmanned airships in the presence of unknown wind disturbance. The sliding mode controller proposed first is designed by a fast power rate reaching law(FPRRL). The disturbance is compensated by a radial basis function neural network (RBFNN). To avoid the aggressive adaptation, the controller is augmented by a command filter. The controller provides good robustness and tracking performance with no chattering under the hypothesis of ideal wind field. However, serious chattering occurs when simulation is performed under discontinuous wind field. To simulate the wind in practice, the wind field employed in the simulation is generated by the combination of a constant field and white noise. The controller is improved subsequently with an extended model to suppress the chattering induced by the white noise. The enhanced controller manipulates the derivation of system input, thus attenuating the chattering. Stability analysis shows that both controllers drive the tracking error into a controllable small region near zero. Simulations are provided to validate the performance of the proposed controllers under different wind hypothesis.     

复合材料MMB试件I-II混合型层间裂纹扩展分析

基于经典层合板理论及双线性黏聚区本构关系，建立了含一般分层裂纹层合板的理论模型，对I-Ⅱ混合型弯曲（MMB）断裂试件进行了裂纹扩展理论分析。提出了一种I-Ⅱ混合型断裂叠加模型，引入I型裂纹分量的刚体转动位移，同时考虑了裂纹长度超过试件半长后中部载荷分量对裂纹扩展的闭合效应，并根据黏聚区力学响应，分段获得了位移函数通解。结合叠加模型的边界条件与连续性条件，分析了MMB试件的裂纹扩展过程，求解获得了载荷-位移曲线。通过与梁模型预测以及试验结果进行对比，验证了本文模型对I-Ⅱ混合型裂纹扩展预测的有效性和准确性，并讨论了初始断裂模式混合比及闭合效应对裂纹扩展过程的影响。结果表明：初始Ⅱ型裂纹比重较大时，中部载荷的闭合效应更为明显，可能出现I型裂纹完全闭合的情况；裂纹扩展过程中，当裂纹长度小于试件半长时，断裂混合比基本保持常数；当裂纹扩展超过试件半长后，闭合效应明显，混合裂纹形式逐渐向单一型断裂模式退化。