结合非线性CS算法的UWB-SAR运动补偿

载机飞行不稳对SAR成像质量影响很大,对超宽带SAR系统尤其如此,提出了一种结合非线性CS算法的超宽带SAR运动补偿方法。通过采用引入高次相位补偿和非正交旁瓣抑制的改进非线性CS算法,减小了超宽带SAR成像中的相位误差。通过成像前的常规一阶运动补偿和距离徙动校正后的分块二阶运动补偿,有效补偿了超宽带SAR中的方位空变运动误差,提高了飞行不稳时的成像质量。该方法在运动补偿时考虑了方位空变运动误差随距离的变化,针对载机运动误差变化较快的情况也给出了处理办法。仿真和实测数据的处理结果验证了该方法的有效性。     

基于可编程GPU的红外场景仿真实现

针对以前红外仿真方法细节差、实时性不高等技术难点,提出了一种新的红外物理模型实现方法。该方法将物理信息与物体的几何模型顶点绑定,提高了对红外场景的描述细节。该方法对物理模型的计算在CPU与GPU之间进行了分配,充分利用了可编程GPU的强大运算能力,有效提高了红外场景生成的实时性。讨论了几种典型探测器效应的添加方法。使用仿真图像来说明所提出方法的有效性,同时分析了该方法的优缺点。     

一种磁悬浮系统的降阶方法

针对电压控制的磁悬浮系统设计了时间最优控制算法以获得电流最速响应,并推导了控制系统硬件对电流响应速度的约束关系;根据跟踪误差改变控制器参数以精确地跟踪设定电流;根据在线辨识得到的线圈参数计算最终控制电压以维持理想电流。这种算法能够使电压控制取得与电流控制同样的效果,简化了控制系统分析与设计并提高了对线圈参数时变的鲁棒性。磁悬浮小球电流响应实验与悬浮实验验证了算法的有效性,该算法还可扩展到其他电压控制电流的场合。     

基于多电视台的两种无源雷达成像算法

基于外辐射源的无源雷达成像是当前新体制雷达的研究热点,给出了利用多个电视台作为外辐射源的直接二维快速傅里叶变换成像算法和极坐标成像算法。建立了多基地无源雷达成像模型,通过理论推导得到目标散射函数和雷达接收信号之间的傅里叶变换对的关系。选取15个电视台信号作为外辐射源进行了仿真实验,分析和比较了两种算法的性能,证实了算法的可行性。     

空空导弹红外成像导引头建模与仿真

红外成像导引头仿真平台是分析导引头性能的重要手段,通过分析红外成像导引头仿真系统的设计要求,建立了仿真系统的总体结构,主要包括红外图像合成系统、成像探测系统、图像处理系统和平台伺服控制系统,并描述了各子系统的功能、组成、模型原理和工作过程。它们模拟了导引头接收目标红外辐射、从背景和干扰中检测识别目标并进行跟踪的过程。给出了系统的实现途径和攻击仿真实例,验证了系统的有效性,表明系统可用于改进导引头的性能设计。     

球磨时间对NdFeBDyAlCu合金结构和磁性能的影响

采用机械合金化法制备不同球磨时间的NdFeBDyAlcu合金粉末，研究球磨时间对样品的结构和磁性能影响．随球磨时间的增加，XRD结果显示α—Fe主峰相的强度先减小后增加；SEM结果最示颗粒尺寸明显的变小；VSM结果显示合金粉末球磨5h时的磁性能最好．     

3D virtual reconstruction of the Pleistocene cheetah skull from the Tangshan, Nanjing, China

The development of computer tomography and image processing has made it possible to establish virtual 3D reconstruction and non-invasive dissection of fossil specimens. We used these methods to reconstruct a virtual 3D skull of a Pleistocene cheetah skull from the Tuozi cave, Tangshan, Nanjing, and virtually dissected it for anatomic studies, and measured the volumes of different parts of the endocranium. The endocranium of the cheetah skull has showed that its frontal sinus is beehive-like, the frontal lobe of cerebra is relatively large but the temporal lobe is relatively small, its cerebral sulcus and gyrus are more complicated than those of the domestic cat, similar to those of the domestic dog, but simpler than those of giant panda, pig, cattle and horse. The technology of virtual 3D reconstruction and non-invasive dissection of fossil specimens can extend the morphological study from the exterior to the interior, and it can also help to study fragile specimens and virtually backup rare and precious specimens.     

Magnetic fabrics in fault-related fold and its relation with finite strain: an example from Mingjiang thrust structures in Western Sichuan

The anisotropy of magnetic susceptibility (AMS) is a quick, effective and sensitive technique used to measure the weakly deformed sedimentary rocks, and also a reliable method to reveal the deforming mechanisms of fault-related folds. In Longmenshan front belt, a typical cross-section of fault-related folds is chosen to study the AMS. A total of 224 oriented specimens have been drilled at 23 different sampling sites which were distributed at the key structural positions of this structural section developed in the Xujiahe formation of the upper Triassic. Six elementary types of magnetic fabrics are recognized and established through this AMS study: 1) a sedimentary fabric; 2) an initial deformation fabric; 3) a pencil structure fabric; 4) a weak cleavage fabric; 5) a strong cleavage fabric; 6) a stretching lineation fabric. It has been found that most of magnetic fabrics are characterized by fabrics of weak deformation which belong to the pure-shear results of a pre-folding layer parallel shortening (LPS). In the fault-bend fold, almost all magnetic fabrics are the initial deformation fabrics of weak deformation, and denote that the deformation in the forelimb is stronger than that in the backlimb and no finite strain is shown in the footwall. While in the fault-propagation fold， finite strains are concentrated in the trishear zone where magnetic fabric results are approximately consistent with the estimated consequences of the kinematic model. The tectonic stress field indicated by the magnetic fabrics is basically the same along the whole structural section and shows a NW to SE compression and shortening which is accordant with the regional compressive stress field of the Longmenshan fold-thrust belt.     

Functional Materials for Catalytic and Magnetic Applications

1 Introduction Metal, metal oxide and metal compound nanoparticles (NPs) received considerable attention due to their unique properties: catalytic, magnetic, optical, electronic, etc. We believe that for different applications, there are preferable morphologies of NP-stabilizing medium composites. For example, small (1-3 nm) nanoparticles formed in micro/mesoporous hypercrosslinked polystyrene demonstrate excellent catalytic properties in various hydrogenation and oxidation reactions due to high surface...     

X射线磁性圆二色吸收谱:实验设备与初步实验

合肥国家同步揭射实验室已建立了初步的X射线磁性圆二色吸收谱（XMCD）技术，可以测量铁磁性3d过渡族元素Fe，Co和Ni的L边的XMCD，并获得它们的轨道和自旋磁矩．XMCD线站的主要技术参数为：能量范围100～1000eV，光子通量≈10^8 ph／s，能量分辨率≈1000；外磁场1500Gs.除了测量XMCD外，还可以测量C，N，O的K边近边吸收谱，以及部分元素的L边近边吸收谱．