Three-Dimentional Surface Light Irradiance Reconstruction in Bioluminescence Tomography

Reconstruction of 3D surface irradiance distribution using multiple views captured by charged coupled device(CCD)camera is the basis of solving the light source in bioluminescence tomography(BLT).A simple and convenient mapping technique based on the pin-hole imaging model and Lambert′s cosine law was presented to establish the relationship between gray levels and irradiance intensities.Compared with previous integrating sphere camera calibration used in BLT,the proposed method can effectively avoid heavy burden of simulation experiment to obtain the corresponding relationship of gray levels and irradiance intensities.The accuracy and feasibility of the proposed method are validated with no more than 1mm location error by different types of phantom experiments.The mapping approach is also applicable to other noncontact optical imaging system.     

A prediction model of short-term ionospheric foF2 based on AdaBoost

In this paper, the AdaBoost-BP algorithm is used to construct a new model to predict the critical frequency of the ionospheric F2-layer (foF2) one hour ahead. Different indices were used to characterize ionospheric diurnal and seasonal variations and their dependence on solar and geomagnetic activity. These indices, together with the current observed foF2 value, were input into the prediction model and the foF2 value at one hour ahead was output. We analyzed twenty-two years’ foF2 data from nine ionosonde stations in the East-Asian sector in this work. The first eleven years’ data were used as a training dataset and the second eleven years’ data were used as a testing dataset. The results show that the performance of AdaBoost-BP is better than those of BP Neural Network (BPNN), Support Vector Regression (SVR) and the IRI model. For example, the AdaBoost-BP prediction absolute error of foF2 at Irkutsk station (a middle latitude station) is 0.32 MHz, which is better than 0.34 MHz from BPNN, 0.35 MHz from SVR and also significantly outperforms the IRI model whose absolute error is 0.64 MHz. Meanwhile, AdaBoost-BP prediction absolute error at Taipei station from the low latitude is 0.78 MHz, which is better than 0.81 MHz from BPNN, 0.81 MHz from SVR and 1.37 MHz from the IRI model. Finally, the variety characteristics of the AdaBoost-BP prediction error along with seasonal variation, solar activity and latitude variation were also discussed in the paper.     

自然形高空气球上升过程形状预测

为研究高空气球在上升过程中的形状变化以及蒙皮应力分布情况，并给气球的结构设计以及强度设计提供一定依据，本文建立了气球上升过程中的热力学模型，同时基于高空气球蒙皮材料具有非线性、黏弹性、各向异性和不能抗压等特点，通过简化气球几何模型，采用最小势能法预测自然形高空气球上升过程中的形状，并分析了气球上升过程中的应力分布情况，气球的应力极值出现在气球顶部和底部，而经向应力的数量级远大于纬向应力；还对比了不同充气量下、不同时刻下气球形状及应力分布情况，为气球设计及工程应用提供了有效计算 方法。     

多维磁悬浮隔振系统动力学模型与控制策略

磁悬浮隔振系统具有非线性、强耦合、高响应、宽频带等特点，系统的隔振控制目标与其定子和浮子之间的位置约束相互制约，这对系统的精密控制提出了较大的挑战。为解决该问题，建立了面向控制的六自由度磁悬浮隔振系统非线性动力学模型，并提出了双闭环控制策略，使系统在低频到中高频带内实现隔振控制，在极低频带内实现跟踪控制。采用PD定点控制算法，在MATLAB/Simulink环境中开发了控制系统仿真程序，通过分析不同扰动频率下浮子的绝对运动响应以及定子与浮子之间的相对运动响应，获得了系统的隔振控制与跟踪控制仿真结果。搭建了磁悬浮隔振平台样机测试系统，验证了动力学模型的正确性和控制策略的有效性。     

China to Build and Launch Cambodia's First Communications Satellite

正On January 11,2018,CGWIC and Royal Group of Cambodia signed a Framework Agreement for the TECHO1 Communications Satellite Project in the Peach Palace,Phnom Penh,witnessed by Chinese Premier LI Keqiang and Cambodian Prime Minister Samdech Techo Hun Sen.As a prime contractor of the project,     

新一代总线技术AFDX在箭载测量系统设计中的应用研究

传统的箭载测量系统数据传输由点到点的电缆完成,存在布线复杂、占用空间大、质量大、通信速率低等方面的不足,为此提出将新一代总线AFDX应用于箭载测量系统的设计思路。介绍了新一代基于以太网的总线技术AFDX,研究、比较了其技术特点和关键技术,并对基于AFDX的箭载测量系统数据综合网络拓扑结构进行了设计,为设计更高可靠性、更快通信速率、更强灵活性的箭载测量系统提供参考依据。     

某机翼的安全预测载荷模型建立

基于试飞阶段全V-N包线的实测飞行载荷，将改进遗传算法、线性回归与BP神经网络融合，给出了一种适用于全寿命周期的自适应安全预测载荷模型建立方法。将该方法应用于某飞机机翼的安全预测载荷模型建立，并对所建立的载荷模型进行了全V-N包线的验证。分析了样本空间与载荷模型精度的关系。结果表明：建立的弯矩预测载荷全包线最大误差为10.6%、平均误差为1.0%，剪力的最大误差为9.1%、平均误差为0.4%，比优化线性和分段线性的误差小，比神经网络的收敛性好。随着建模数据从全样本、1/2、1/3、…、1/10样本的变化，弯矩和剪力方程的全V-N包线的最大误差整体呈增大趋势，弯矩最大误差变化范围为10.6%~19.6%，最大剪力误差变化范围为9.1%~27.9%。     

一种适合星载多光谱图像的压缩算法研究

文章提出了一种适合星载多光谱（4个谱段）图像压缩方法,根据多光谱图像之间相关性较强和卫星对地通道传输速率有限的特点,利用谱段变换,调整各谱段之间的信息量分配,形成新的谱段数据,并对新谱段数据压缩比进行适当调整,完成多光谱图像数据压缩。采用此算法后,可以使平均压缩比不变的情况下,4个谱段恢复的多光谱图像大部分峰值信噪比（Peak Signal Noise Ratio,PSNR）与直接压缩图像后的PSNR值相比有所提高。     

受损反辐射导引头的跟踪性能仿真分析

在定向能硬损伤反导背景下,推导出反辐射导弹导引头受硬损伤引起馈入性能变化下的振幅测向法和相位干涉测向法的数学模型,建立了受损导引头的跟踪场景,分别以该两种测向模型进行了跟踪性能的仿真分析。结果表明,导引头受硬损伤下会导致跟踪性能下降,视损伤程度仍有可能在上靶区域命中目标。     

地月系低能转移轨道设计

分析了不同转移轨道间的性能指标,以黄道面与白道面交线作为庞加莱截面实现不同系统轨道的拼接,利用其中耗能最小的日地系稳定流形和地月系的不稳定流形设计了一条低能耗转移轨道.最后对不同轨 道进行了能量分析和对比,优化了国内提出的低能探月轨道.仿真结果表明,文中方法比直接通过霍曼转移节约21.1%的能量,对探月工程的轨道设计具...