改进的强跟踪UKF算法及其在INS/GPS组合导航中的应用

针对标准UKF缺乏对系统状态异常的自适应调整能力,导致滤波精度降低的问题,提出一种改进的强跟踪UKF算法。该算法采用假设检验的方法对异常状态进行检测,当系统状态发生异常时,对预测协方差阵引入次优渐消因子自适应的调整滤波增益,实现对系统真实状态的强跟踪。该算法中次优渐消因子的确定无需计算系统模型的雅克比矩阵,提高了传统强跟踪UKF的实用性。将提出的算法应用于INS/GPS组合导航系统进行仿真验证,并与标准UKF进行比较,结果表明,在系统状态存在异常时,提出的带单重次优渐消因子的强跟踪UKF得到的东向、北向位置误差在[-13.7 m,14.9 m]以内,带多重次优渐消因子的强跟踪UKF得到的东向、北向位置误差在[-10.0 m,12.1 m]以内,滤波性能明显优于标准UKF,提高了组合导航系统的解算精度。     

科普图书“再加工”的有益尝试——以《彩绘名著科普阅读》和《闪电球探长》为例

引进版科普图书近年来大有跃增之势。简单地将原书照搬照译无可厚非,但考虑到中外文化的背景差异等因素,有时进行适当的"再加工"也很有必要,而且会给原书增色不少。以知识之链应对"拦路虎"科学普及出版社最近引进了由英国DK公司组织改写的《彩绘名著科普阅读》丛书。     

High Temperature Melting Curve of Basaltic Glass by Laser Flash Heating

Basalt is an igneous rock originating from the cooling and solidification of magma and covers approximately 70% of Earth’s surface. Basaltic glass melting in the deep Earth is a fundamental subject of research for understanding geophysics, geochemistry, and geodynamic processes. In this study, we design a laser flash heating system using two-dimensional, four-color multi-wavelength imaging radiometry to measure the basaltic glass melting temperature under high pressure conditions in diamond anvi...     

用于真空紫外探测器标定的光学斩波器研究北大核心CSCD

为了满足基于低温辐射计的115 nm~400 nm波段探测器绝对光谱响应度高精度标定的需求,研制了一种由斩波片、转轴、伺服电机、U型光电开关、降温组件、支架和控制电路等组成的适用于真空环境的光学斩波器,使其在真空低温环境下将微弱的真空紫外-紫外辐射信号调制为频率已知的交变辐射信号,并由锁相放大器进行测量。实验结果表明,该光学斩波器的频率在80 Hz时的稳定性为±0.05 Hz,满足115 nm~400 nm波段探测器绝对光谱响应度标定对斩波器在10^(-4) Pa的真空环境下的使用要求。     

New experimental measurement of natSe(n, γ) cross section between 1 eV to 1 keV at the CSNS Back-n facility

The ⁷⁴Se is one of 35 p-nuclei, and ⁸²Se is a r-process only nucleus, and their (n, γ) cross sections are vital input parameters for nuclear astrophysics reaction network calculations. The neutron capture cross section in the resonance range of isotopes and even natural selenium samples has not been measured. Prompt γ-rays originating from neutron-induced capture events were detected by four C₆D₆ liquid scintillator detectors at the Back-n facility of China Spallation Neutron Source (CSNS). The pulse height weighting technique (PHWT) was used to analyze the data in the 1 eV to 100 keV region. The deduced neutron capture cross section was compared with ENDF/B-VIII.0, JEFF-3.2, and JENDL-4.0, and some differences were found. Resonance parameters were extracted by the R-matrix code SAMMY in the 1 eV-1 keV region. All the cross sections of ^natSe and resonance parameters are given in the datasets. The datasets are openly available at http://www.doi.org/10.11922/sciencedb.j00113.00019.     

陶瓷和金属微波烧结在线实验及微观机理分析

为研究陶瓷和金属微波烧结时的微观演化机理,从而为优化不同材料的烧结过程提供依据,本文采用同步辐射技术对陶瓷(SiC)和金属(Al)的微波烧结微结构演化过程进行实时、无损的观测,并结合有限元模拟分析两者的微结构演化特征及微观机理。通过滤波反投影等数字图像处理技术得到烧结过程中样品内部的二维、三维重建图像,清晰地观察到SiC和Al在颗粒表面和界面演化上存在差异。定量地统计了陶瓷和金属烧结颈相对尺寸与时间的双对数关系,并与陶瓷和金属双球模型的微波烧结模拟结果进行了对比。运用模拟分别对实验中的烧结颈和微观形貌演化进行分析,得出结论:陶瓷和金属微波烧结时的加热机制不同,分别为整体介质损耗加热和表面涡流损耗加热。陶瓷的整体加热将会在材料内部特别是界面产生较高的温度,而金属的表面加热使颗粒表面温度高于界面。由相应的加热机制产生的温度分布差异,将会对材料的物质扩散过程产生不同程度的影响,进而产生不同的微结构。     

基于Android的SIP远程视频监控系统的设计

本文利用SIP协议建立组呼来控制监控摄像头,从而建立多路远程视频监控系统。论文介绍了基于Android系统的SIP协议栈JAIN-SIP和远程视频监控系统架构,阐述了利用SIP扩展消息完成组呼控制,从而实现监控中心对远端监控摄像头的呼叫控制。     

急性心肌梗死患者D-二聚体、cTnT及心肌酶谱联合检测的临床意义

为探讨急性心肌梗死患者D-二聚体、肌钙蛋白及心肌酶谱联合检测的临床意义,选择30例健康者（对照组）和100例患者（病例组）进行D-二聚体、肌钙蛋白及心肌酶谱（AST、LDH、CK、CK-MB）检测,并把100例患者（病例组）分为3组,分别为36例AMI组,34例不稳定型心绞痛（UAP）组,30例稳定型心绞痛（SAP）组。结果表明,AMI组及UAP组中D-二聚体、肌钙蛋白及心肌酶谱（AST、LDH、CK、CK—MB）的升高程度较SAP组和健康对照组显著增高（P〈0．05）;AMI组肌钙蛋白（cTnT）较UAP组明显增高（P〈0．05）;UAP组肌钙蛋白（cTnT）较对照组明显增高（P〈0．05）;D-二聚体、肌钙蛋白及心肌酶谱（AST、LDH、CK、CK—MB）的升高程度与心肌梗死的面积正相关（P〈0．01）。提示D-二聚体、肌钙蛋白及心肌酶谱（AST、LDH、CK、CK—MB）联合检测有助于急性心肌梗死诊断的提高。     

带官能团的双有机碘化锌试剂与酰氯的反应研究

探索了带醚键、酯基、羰基的双有机锌试剂的制备及其在CuCN 2LiCl存在下和酰氯的反应,得到了带官能团的二酮类化合物.该方法条件温和,操作简便,产率中等,提供了合成带官能团的长链二酮类化合物的一种简便方法.     

Ferroferric oxide/chitosan scaffolds with three-dimensional oriented structure

A facile approach to construct ferroferric oxide/chitosan composite scaffolds with three-dimensional oriented structure has been explored in this research.Chitosan and ferroferric oxide are co-precipitated by using an in situ precipitation method,and then lyophilized to get the composite scaffolds.XRD indicated that Fe₃O₄ was generated during the gel formation process,and increasing the content of magnetic particles could destruct the crystal structure of chitosan. When the content of magnetic particles is lower than 10%,the layer-by-layer structure and wheel spoke structure arc coexisting in the scaffolds.Increasing the content of magnetic particles,just layer-by-layer structure could be observed in the scaffolds.Ferroferric oxide particles were uniformly distributed in the matrix,the size of which was about 0.48μm in diameter,2μm in length.Porosity of magnetic chitosan composite scaffolds is about 90%.When the ratio of ferroferric oxide to chitosan is 5/100,the compressive strength of the material is 0.4367 MPa,which is much higher than that of pure chitosan scaffolds,indicating that the layer-by-layer and wheel spokes complex structure is beneficial for the improvement of the mechanical properties of chitosan scaffolds.However,increasing the content of ferroferric oxide,the compressive strength of scaffolds decreased,because of the decreasing of chitosan crystallization and aggregation of magnetic particles as stress centralized body.Another reason is that the layer-by-layer and wheel spokes complex structure makes bigger contributions for the compressive strength than the layer-by-layer structure does.Three-dimensional ferroferric oxide/chitosan scaffolds could be used as hyperthermia generator system,improving the local circulation of blood, promoting the aggradation of calcium salt and stimulating bone tissue regeneration.