Skin collagen fiber-based radar absorbing materials

By using skin collagen fiber (CF) as raw material,Schiff base structure containing CF (Sa-CF) was synthesized through CF-salicylaldehyde reaction.Then a novel radar absorbing material (Fe-Sa-CF) was prepared by chelating reaction between Sa-CF and Fe 3+.The coaxial transmission and reflection method was used to analyze the complex permittivity and complex magnetic permeability of these CF-based materials,and the radar cross section (RCS) method was used to investigate their radar absorbing properties in the frequency range of 1.0-18.0 GHz.Experimental results indicated that the conductivity of CF increased from initial 1.08×10-11 to 2.86×10-6 S/cm after being transferred into Fe-Sa-CF,and its dielectric loss tangent (tanδ) in the frequency range of 1.0-17.0 GHz also increased.These facts suggest that the Fe-Sa-CF is electric-loss type radar absorbing material.In the frequency range of 3.0-18.0 GHz,Sa-CF (1.0 mm in thickness) exhibited somewhat radar absorbing property with maximum radar reflection loss (RL) of-4.73 dB.As for Fe-Sa-CF,the absorbing bandwidth was broadened,and the absorbing intensity significantly increased in the frequency range of 1.0-18.0 GHz where a maximum radar RL of-9.23 dB was observed.In addition,the radar absorbing intensity of Fe-Sa-CF can be further improved by increasing membrane thickness.When the thickness reached to 2.0 mm,the RL values of Fe-Sa-CF were-15.0-18.0 dB in the frequency range of 7.0-18.0 GHz.Consequently,a kind of novel radar absorbing material can be prepared by chemical modification of collagen fiber,which is characterized by thin thickness,low density,broad absorption bandwidth and high absorption intensity.     

基于智能手机Tango传感器的室内三维场景实时感知

室内三维场景实时感知是室内增强现实、三维测图和机器人自主定位与导航的关键技术之一。利用智能手机Tango传感器搭载的单目摄像头和深度相机,根据实时获取的彩色图像和深度信息,研究并提出了一种实时的室内三维场景感知方法;该方法首先根据智能手机Tango传感器获取的彩色图像存在的问题,采用多项式函数对彩色相机进行校正。接着,使用ORB(oriented FAST and rotated BRIEF)算子对彩色图像进行特征提取,利用RANSAC算法剔除误匹配点;并根据优化后的匹配点对采用ICP算法对手机姿态进行初步估计。最后,基于融合空间关系的视觉词典(SDBo W2)对感知的初步室内场景进行闭环检测;并通过图优化得到实时感知的室内三维场景模型。实验表明,方法能利用Tango传感器高效地获取室内场景完整的三维结构信息与纹理。     

实景三维模型缺陷修复关键技术

为了有效提高实景三维模型反映各类型地理要素的准确度和精细度以充分支撑实景三维中国建设工作,本文首先将当前无人机倾斜摄影三维重建后的三维模型中存在的模型缺陷系统性分为四大类型,并分析其产生的原因。随后,本文针对性地提出了三种关键技术：一是基于连通性和欧氏距离聚类的交互式悬浮物去除,利用图割理论和随机一致性抽样算法识别和删除悬浮物;二是基于图割理论的水面半自动整平,在利用Grabcut算法提取水面区域的同时为其赋予统一高程以实现水面的平整;三是基于深度网络模型的水体纹理inpainting填充,利用卷积神经网络和深度对抗训练以获得水体纹理的特征和结构从而实现水体缺失纹理的修复。最后,本文利用湖北省宜昌市的实际生产数据进行了修复实验,实验结果表明本文提出的各项关键技术能够有效修复三维模型缺陷,从而使实景三维模型具备更精细的地理实体和地理景观还原度。     

滑带土抗剪强度特性的环剪试验研究

以黄土坡滑坡滑带土为研究对象,采用环剪仪研究了天然含水率的滑带土在不同法向应力与剪切速率下的抗剪强度特性。试验结果表明:滑带土的峰值强度和残余强度均随着法向应力的增大而增大,并呈现出较强的线性关系;0.1~10mm/min范围内的剪切速率对滑带土的残余剪切强度影响不明显,变化幅度在±6%以内;但剪切速率越大,滑带土需要更多的变形以达到残余强度;随着剪切速率地增大残余黏聚力不断地减小,残余内摩擦角逐渐地增大,峰值强度及峰值黏聚力、内摩擦角均增大;剪切速率对滑带土的软化特性影响明显,并且较大的剪切速率使得剪切过程中从剪切盒侧壁流失的黏粒与孔隙水增多,因此在进行滑带土排水环剪时,宜采用较小的剪切速率。     

GPS载体姿态测量技术研究

本文首先介绍了ＧＰＳ姿态测量技术的原理,包括坐标转换、相位干涉等,并在此基础上重点讨论了基线矢量解算过程中存在的相位模糊问题。在低精度基线较短时可采用搜索方法,并推导了模糊空间的大小和搜索检验方法;在高精度基线较长时,可采用多天线辅助解相位模糊,并推导了为满足给定的整周模糊错误概率和一定精度要求时,所需的相邻基线长度比及所需的天线阵元总数,同时给出了实例。本文的研究对ＧＰＳ姿态测量的工程应用具有一定的参考价值。     

Target location with signal fitting and sub-aperture tracking for airborne multi-channel radar

The location of a moving target based on signal fitting and sub-aperture tracking from an airborne multi-channel radar is dealt with. The proposed approach is applied in two steps: first, the ambiguous slant-range velocity is derived with a modified single-snapshot multiple direction of arrival estimation method, and second, the unambiguous slant-range velocity is found using a track-based criterion. The prominent advantage of the proposed approach is that the unambiguous slant-range velocity can be very large. Besides, the first stage is carried out at the determinate range-Doppler test cell by azimuth searching for fitting best to the moving target signal, therefore, the location performance would not be sacrificed in order to suppress clutter and/or interference. The effectiveness and efficiency of the proposed method are validated with a set of airborne experimental data.     

军队技术干部队伍结构预测模型及应用

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作物品种区域试验的评价体系及评价方法

从作物品种区域试验的实际需要出发,提出了区域试验的试验评价和品种评价的体系,并对具体评价方法和指标作了概述和比较,指出了其中尚待解决的难点,同时论述了区域试验中应注意的问题.表1,参29.     

1SQ-250型全方位深松机性能分析

通过介绍１ＳＱ－２５０型全方位深松机结构特点,对全方位深松部件的松土原理以及深松后的土壤理化性质变化进行了研究分析。并指出全方位深松部件深松土壤的同时在耕层底部形成鼠道的作用。提出了全方位深松机与其它土壤耕作机具配合使用新的土壤耕作技术措施。图１,参３。     

On the complexity of the normal bases via prime Gauss period over finite fields

A formula on the complexity of the normal bases generated by prime Gauss period over finite fields is presented in terms of cyclotomic numbers. Then, the authors determine explicitly the complexity of such normal bases and their dual bases in several cases where the related cyclotomic numbers have been calculated. Particularly, the authors ˉnd several series of such normal bases with low complexity. This research is supported by the National Fundamental Science Research Program 973 of China under Grant No. 2004 CB3180000 and the State Key Lab. (Information Security) of China.