Evaluation and improvement of coastal GNSS reflectometry sea level variations from existing GNSS stations in Taiwan

Global sea level rise due to an increasingly warmer climate has begun to induce hazards, adversely affecting the lives and properties of people residing in low-lying coastal regions and islands. Therefore, it is important to monitor and understand variations in coastal sea level covering offshore regions. Signal-to-noise ratio (SNR) data of Global Navigation Satellite System (GNSS) have been successfully used to robustly derive sea level heights (SLHs). In Taiwan, there are a number of continuously operating GNSS stations, not originally installed for sea level monitoring. They were established in harbors or near coastal regions for monitoring land motion. This study utilizes existing SNR data from three GNSS stations (Kaohsiung, Suao, and TaiCOAST) in Taiwan to compute SLHs with two methods, namely, Lomb–Scargle Periodogram (LSP)-only, and LSP aided with tidal harmonic analysis developed in this study. The results of both methods are compared with co-located or nearby tide gauge records. Due to the poor quality of SNR data, the worst accuracy of SLHs derived from traditional LSP-only method exceeds 1?m at the TaiCOAST station. With our procedure, the standard deviations (STDs) of difference between GNSS-derived SLHs and tide gauge records in Kaohsiung and Suao stations decreased to 10?cm and the results show excellent agreement with tide gauge derived relative sea level records, with STD of differences of 7?cm and correlation coefficient of 0.96. In addition, the absolute GNSS-R sea level trend in Kaohsiung during 2006–2011 agrees well with that derived from satellite altimetry. We conclude that the coastal GNSS stations in Taiwan have the potential of monitoring absolute coastal sea level change accurately when our proposed methodology is used.     

基于纳米吸能流体的火工点式分离装置缓冲技术研究

运载火箭火工点式分离装置工作时具有强冲击载荷特性，为有效降低冲击峰值，提出了一种基于纳米吸能流体结构的冲击缓冲技术。首先进行纳米吸能流体的吸能原理研究，建立其本构关系，揭示影响其吸能密度的主要因素；其次开展火工装置有限空间内的纳米吸能流体缓冲结构设计；最后通过有限元仿真与试验验证其缓冲性能。试验结果表明，本文设计的基于纳米吸能流体的缓冲结构，吸能密度高达122.8 J/g，冲击力峰值较空载条件下降了59.2%，冲击加速度峰值下降了63.4%。     

新一代战斗机非定常流动数值研究综述

新一代战斗机强调超机动能力和强隐身性，其中大攻角下的静态失速、动态失速及内埋弹仓绕流是与高机动和强隐身密切相关的、极具挑战的几类典型的非定常流动，它们对数值方法提出了极高的要求。为了高精度地仿真流场、清楚地揭示流动机理，有效地控制非定常流动，非常有必要发展高精度且高效率的RANS-LES混合方法体系，包含RANS-LES混合方法本身、与RANS-LES混合方法匹配的高精度自适应耗散格式、基准湍流模式、高质量计算网格、高精度时间推进方法、非定常量的统计方法等，具有极强的紧迫性。提出、发展、验证并应用该类方法数值仿真新一代战斗机（包括单独部件、组合体、甚至全机）的非定常流动，数值预测结果与风洞实验数据吻合良好；此类方法可为新型战斗机设计提供理论依据和分析手段。     

基于经纬仪的光束平差法定向方法改进

针对基于传统经纬仪工业测量系统使用光束平差法定向精度有待提高的问题，提出一种新的定向改进方法。该方法同时结合了精确互瞄法与光束平差法，简化了测量过程，提出新的约束，消减了光束平差法中定向阶段的基准点测量累积误差，实现了在非通视条件中完成多台经纬仪高精度定向的目标。试验数据表明：该方法可在10m范围内，在误差为±3″的测点交会精度下，维持0.1mm的定向精度。     

Multi-level virtual prototyping of electromechanical actuation system for more electric aircraft

Electromechanical actuators (EMAs) are becoming increasingly attractive in the field of more electric aircraft because of their outstanding benefits, which include reduced fuel burn and maintenance cost, enhanced system flexibility, and improved management of fault detection and isolation. However, electromechanical actuation raises specific issues when being used for safety-critical aerospace applications like flight controls: huge reflected inertia to load, jamming-type failure, and increase of backlash with service due to wear and local dissipation of heat losses for thermal balance. This study proposes an incremental approach for virtual prototyping of EMAs. It is driven by a model-based system engineering process in order to enable simulation-aided design. Best practices supported by Bond graph formalism are suggested to develop a model’s structure efficiently and to make the model ready for use (or extension) by addressing the above mentioned issues. Physical effects are progressively introduced, and the realism of lumped-parameter models is increased step-by-step. In particular, multi-level component models are architected to ensure continuity between engineering activities. The models are implemented in the AMESim simulation environment, and simulation responses are given to illustrate how they can be used for preliminary sizing, control design, thermal balance verification, and faults to failure analysis. The proposed best practices intend to provide engineers with fast, reusable, and efficient means to assess performance virtually and enhance maturity, performance, and robustness.     

月面远程运输飞行轨迹优化设计

针对月球表面不同区域之间的载人或载货运输问题,设计了一种基于上升-巡航-下降模式的燃料最省飞行轨迹。首先通过求解不同飞行时间的Lambert问题确定了最佳飞行时间,并获得了对应的双脉冲解,然后利用有限推力替代两次速度脉冲,建立了非线性规划问题,求解得到了有限推力燃料最省飞行轨迹。优化设计过程中主要研究了两个主要难点:bang-bang控制与飞行高度约束。这两个问题通过推力加速度与飞行时间的数值延拓得以解决,同时揭示了月面飞行的基本原理。最后给出了3种不同应用场景的仿真算例,仿真结果表明,当飞行时间为小时量级时,上升-巡航-下降飞行模式下的优化解即为燃料最优解,如果飞行距离较远,则还需要适当增加飞行时间从而满足飞行高度约束。     

热力学排气系统中节流效应及其冷量利用分析

为更好地理解热力学排气系统(TVS)的运行机理，优化其运行参数，针对节流装置，建立了热力学模型，讨论了节流过程中状态参数的变化规律，对比了单相气体、单相液体节流的性能特性，进一步揭示了焦汤节流效应的原理，分析了不同节流背压下节流前低温工质(液氢和液氧)压力和温度对节流性能的影响，并结合TVS实际应用，阐述了节流最大制冷量的利用效果，提出了优化的TVS工作区间。研究表明：在节流过程不发生相变情况下单相气体节流制冷效应要比单相液体节流制冷效应更加显著；而在节流过程发生相变情况下液体节流至两相后，由于空化吸热导致流体温度降低，对于液氢，0.5MPa的压降可产生接近3 K的温降。对于液体节流，节流前压力对节流过程影响可忽略，〖JP2〗而节流前温度和节流背压对节流过程起主导作用；对于液氢在在轨运行工况下，考虑到节流制冷量的充分利用，同时保证换热过程体积含气率不高于90%，推荐TVS系统中节流背压范围为75～143 kPa。     

PIP工艺制备SiC晶须增强SiCf/SiC复合材料的性能

以不同界面层厚度的SiC纤维为增强相,采用先驱体浸渍裂解工艺(PIP)制备SiC_f(PyC)/SiC复合材料,并在复合材料基体中引入SiC晶须,对其性能进行研究。结果表明:热解碳(PyC)界面层厚度约为230 nm时,SiC纤维拔出明显,SiC_f/SiC复合材料拉伸强度、弯曲强度和断裂韧度分别达到192.3 MPa、446.9 MPa和11.4 MPa?m^1/2;在SiC_f/SiC复合材料基体中引入SiC晶须后,晶须的拔出、桥连及裂纹偏转等增韧机制增加了裂纹在基体中传递时的能量消耗,使复合材料的断裂韧度和弯曲强度分别提高了22.9%和9.1%。     

黄渤海晴空像元下雾霾识别的机器学习算法

为实时有效地识别和监测雾霾，选取2013年10月4日与10月5日的两景MODIS遥感图像，利用不同类型像元的光谱差异，基于神经网络模型，建立海上雾霾的遥感识别机器学习算法。经检验表明，在晴空条件下，机器学习算法反演精度相对较高，已超过98%，利用算法可以实现对中国近海上空雾霾的监测。     

质量矩导弹固定时间二阶滑模控制方法

针对三轴稳定的双滑块质量矩导弹，基于动态系统零点配置原理提出一种快速固定时间二阶滑模控制方法。首先建立具有完整耦合动力学特征的质量矩导弹姿态动力学模型；其次，基于典型动态系统进行零点配置原理分析和收敛时间估计；在此基础上，提出动态过程可调节的固定时间二阶滑模控制方法，并对系统收敛时间的上界进行估计；最后，针对质量矩导弹的仿真校验了设计方法的有效性。