基于随机摄动再采样的粒子概率假设密度滤波器

作为概率假设密度滤波的典型实现方式,粒子概率假设密度滤波器无需线性高斯等先验假设,因而在多目标跟踪中得到了广泛的应用。为解决粒子退化问题并保持粒子规模,该滤波器引入了重采样机制,然而,该重采样机制易引起粒子多样性耗尽,导致粒子贫化问题产生。为解决这一问题,该文提出一种新的基于随机摄动再采样的粒子概率假设密度滤波器。首先,全面分析了粒子概率假设密度滤波因粒子贫化问题导致目标失跟的过程。然后设计了一种随机摄动再采样算法,该算法在重采样导致粒子多样性缺失时,根据源粒子的位置与复制次数随机产生相应数目的新粒子,并对源粒子进行删减,其可在保留源粒子信息的前提下保持粒子的多样性。最后,该文将该算法纳入概率假设密度滤波框架,提出了一种新的粒子概率假设密度滤波器。仿真结果表明该滤波器在不显著增加运行时间的前提下能够克服粒子贫化问题,相比标准的粒子概率假设密度滤波器具有更好的跟踪性能。     

一种高速背板用高密度数据传输连接器设计

本文从理论设计、仿真分析和产品测试三个方面对一种高速背板用高密度数据传输连接器进行了分析设计。通过对连接器差分信号的特征阻抗、串扰、插入损耗等参数的分析,对连接器的插针接触件、PCB传输线和介质体进行了设计。此外,采用电磁场与电路联合仿真的分析方法,从时域、频域和数据域三个方面对所设计的连接器进行了仿真分析。最后,通过测试夹具对所设计的连接器进行了信号完整性测试,测试结果表明：连接器具有良好在高速传输性能,在高速传输通信系统中具有良好的应用前景。     

未知噪声信息多径衰落信道的软判决度量生成

信道解码中的软判决技术需要利用信道噪声方差信息来产生软判决度量,而通常情况下,这一信息是未知和时变的。本文首先简要分析了信道噪声方差对软判决度量的影响,进而提出一种新的在多径衰落信道中估计时变噪声方差的方法,并利用该方法的估计结果为信道解码器生成软判决度量。将该算法应用于中国地面数字电视广播传输系统外接收机的仿真结果表明：与已有的信道噪声方差估计算法相比,本文算法具有收敛速度快、估计结果准确的优点,生成的软判决度量逼近于多径衰落信道的最优软判决度量。     

一种改进的CPHD多目标跟踪算法

CPHD(Cardinalized Probability Hypothesis Density)滤波是一种杂波环境下可变目标数的多目标跟踪算法,该文针对算法中存在的目标漏检问题提出一种改进算法,该算法在高斯混合框架下实现贝叶斯递归,通过对各个高斯分量进行标记,对目标进行航迹关联,在此基础上对修剪合并后各个高斯分量的权值进行两次分配。首先对超过检测门限的高斯分量权值进行分配,有效解决了目标漏检问题,然后基于一个目标只可能产生一个观测的事实进行第2次分配,改善了目标发生交叉时的算法性能。实验结果表明,所提方法在多目标状态估计和航迹维持方面均优于普通的CPHD算法。     

Effect of a changed temperature regime on the benthos of a norwegian regulated river

The lowermost 20 km of the River Surna, north-western Norway receives cool water during summer from a hypolimnetic release mountain reservoir. The benthic fauna is completely dominated by insects. Benthic densities immediately below the power station are much lower than at all other localities. Although benthic densities increase downstream of the power station, they never exceed the densities above. The dominant insect group, chironomids, can be divided into four categories according to their abundance and distribution above and below the power station: (1) rare or absent above, but common or abundant below; (2) abundant or common above but rare or absent below; (3) slightly less abundant below; (4) unchanged abundance. No major differences in the species composition were recorded for stonefilies, mayflies and caddisflies.     

高精度重力资料剩余密度反演与孔隙裂缝发育带分析

利用高精度重力资料及已具备的地质地震资料，去掉由于密度界面产生的重力场及区域重力场的影响，消除浅部干扰，求得剩余重力异常。用钻井资料作控制，反演求得剩余密度分布，以了解储层岩石孔隙裂缝发育带，从而达到直接或间接寻找油气藏的目的。理论模型试算证明方法是可行的；通过四川大足弥陀场地区实际资料的处理，推断了本区的岩性裂缝圈闭；并与已知的钻井地质资料及其它地球物理资料对比验证，说明了反演结果是可靠的。为在     

集电极扩散隔离工艺

本文介绍集电极扩散隔离工艺的特点,叙述该工艺的实验,并给出用此工艺技术制作的晶体管(β≥100,f_T>1000MHz,BV_(ceo)≥6V)和E/T转换器的结果。     

Bond strength prediction for deformed steel rebar embedded in recycled coarse aggregate concrete

This paper summarizes the results of an experimental investigation into the bond behavior between recycled aggregate concrete (RAC) and deformed steel rebars, with the main variables being the recycled coarse aggregate replacement ratio (RCAr) and water-to-cement ratio of the concrete mixture. The investigation into splitting cracking strength indicates that the degradation of the bond splitting tensile stress of the cover concrete was affected by not only the roundness of the coarse aggregate particles but also the weak interfacial transition zone (ITZ) between the cement paste and the RCA that has a more porous structure in the ITZ than normal concrete. In this study, a linear relationship between the bond strength and the density of the RCA was found, but the high compressive strength reduced the effects of the parameters. To predict the bond strength of RAC using the main parameters, a multivariable model was developed using nonlinear regression analysis. It can be inferred from this study that the degradation characteristic of the bond strength of RAC can be predicted well, whereas other empirical equations and code provisions are very conservative.     

Silicon in intericosahedra chains of boron carbide

Interaction between boron carbide and silicon was studied at 1400–1700 ℃ in a vacuum. The results at 1400 ℃ suggest that silicon substitutes a single atom of carbon per formula unit B₁₂C₃, producing a phase with increased lattice parameters. Temperature increase improves the degree of transformation, but at 1700 ℃, the product starts to lose silicon. Analysis of DFT formation energies of configurations with B₁₂C₃ and B₁₂C₂Si stoichiometries shows that B₁₂C₂Si may have two ground states with practically equal stability. The first is B₁₁Si(C-B-C) with silicon in icosahedral polar position, and the second is B₁₂(C^Si^C), where the silicon is in the middle of an angular chain. The latter is suggested to be more favorable during the synthesis, while the former is very close to equilibrium with its precursor B₁₁C(C-B-C), and its formation may be inhibited. Comparison of XRD patterns for the synthesis products and modeled structures seems to confirm this suggestion.