Hybrid three-dimensional variation and particle filtering for nonlinear systems

This work addresses the problem of estimating the states of nonlinear dynamic systems with sparse observations.We present a hybrid three-dimensional variation(3DVar) and particle piltering(PF) method,which combines the advantages of 3DVar and particle-based filters.By minimizing the cost function,this approach will produce a better proposal distribution of the state.Afterwards the stochastic resampling step in standard PF can be avoided through a deterministic scheme.The simulation results show that the performance of the new method is superior to the traditional ensemble Kalman filtering(EnKF) and the standard PF,especially in highly nonlinear systems.     

Independently tunable multichannel terahertz filters

We numerically demonstrate terahertz multichannel filters with independently tunable defect modes based on fractal photonic crystals. Single defect and multiple defects models are proposed to fabricate the multichannel terahertz filters. The facts that the wave functions of the defect states do not overlap and their bases are orthogonal lead to the independency among the defect modes. The simulated results theoretically provide the principle for fabricating independently tunable multichannel terahertz filters by utilizing one-dimensional photonic crystals with defects.     

多功能针式过滤器净化超高效液相色谱法测定大米和花生中玉米赤霉烯酮

建立了一种基于多功能针式过滤器净化的超高效液相色谱测定大米和花生中玉米赤霉烯酮的方法。样品经乙腈提取,采用多功能针式过滤器通过式净化,以超高效液相色谱法测定其中的玉米赤霉烯酮,色谱柱为ACQUITY UPLC BEH C18柱（100 mm×2.1 mm,1.7μm）,以甲醇-乙腈-水（体积比为8∶46∶46）为流动相等度洗脱,流量为0.3 mL/min,用荧光检测器检测,色谱峰面积外标法定量。玉米赤霉烯酮的质量浓度在2.5～500 ng/mL范围内与色谱峰面积线性关系良好,相关系数不小于0.999 5。大米和花生样品的方法检出限分别为15.0、30.0μg/kg,定量限分别为50.0、100.0μg/kg。样品加标回收率为77.11%～93.65%,测定结果的相对标准偏差为0.49%～4.95%(n=6)。该方法简便快速,适用于大米和花生中玉米赤霉烯酮的日常检测。     

俄罗斯研发“激光盾牌”防止军用光学元件被摧毁

正俄罗斯科学家已经研发了一种特殊的过滤器,可以使俄军光学设备的敏感元件免遭激光束的摧毁。据西伯利亚国家大地测量学院纳米技术实验室主任德梅·切斯诺科夫介绍,已经有许多国家研发了多种高能激光武器,可摧毁夜视设备和光学导航系统等仪器的光学传感器。俄罗斯军队可能需要面对这样的问题,为此该实验室设计了一种特制的过滤器来抵御激光束的攻     

Perfect Spin-Filtering in 4H-TAHDI-Based Molecular Devices： the Effect of N-Substitution

Based on the non-equilibrium Green＇s function formalism and spin-polarized density functional theory calcula- tions, we investigate the spin transport properties of HDI and terahydrotetraazahexaeene diimide （4H-TAHDI） with two ferromagnetic zigzag-edge graphene nanoribbon electrodes. Compared with ttDI, four carbon atoms in the hexacene part of 4H-TAHDI are substituted by nitrogen atoms. The results show that the nitrogen substitu- tion can improve significantly the spin-filtering performance and 4H-TAHDI can be used as a perfect spin filter. Our study indicates that suitable chemical substitution is a possible way to realize high-efficiency spin filters.     

生物过滤器中非均匀性流动的数值研究

生物过滤技术因其具有有效性、低成本和环境友好等优点引起了人们的广泛关注.该技术主要通过生物过滤器去除含有H2S等废气的有毒有害气体.运用格子Boltzmann方法对三种生物过滤器模型中多孔介质的非均匀性流动进行了数值模拟.数值模拟结果表明,多孔介质的性质和进口流动条件对临界Rayleigh数有显著影响,临界Rayleigh数随着多孔介质的孔隙度和Darcy数的增大而逐渐变小,并随着进口Reynolds数的增大而逐渐变大.所得结果可望为生物过滤器的优化设计提供一个合理的理论依据.     

Track-before-detect algorithm for maneuvering infrared weak multiple targets via particle filter

We present a particle filter （PF）-based algorithm to detect and track maneuvering infrared weak multiple targets at different signal-to-noise ratios for the scenes with the multiple targets number unknown and vary- ing. A detecting filter and a tracking filter based on sequential likelihood ratio （LR） testing with fixed sample size are designed, respectively, for capturing new target and tracking confirmed targets. The algorithm is optimized with selectively particles sampling and adaptive process noise. Targets birth and death time are accurately estimated according to the change degree of the LR along with the corresponding state amended through PF backward recursion. Simulation results show that it is positive to detect and track maneuvering infrared weak multiple targets with the appearance and disappearance of more than one, which also achieves a significant improvement in state estimation especially for the time targets which appear and disappear.     

HIRFL装置主动式点扫描束流配送系统的Monte Carlo模拟优化

为获得适用于HIRFL 装置主动式点扫描束流配送系统配送的碳离子束,利用Monte Carlo (MC) 工具SHIELD-HIT12A 研究了配送距离和微型脊形过滤器结构周期对治疗室等中心处束斑半高宽(FWHM) 和剂量平坦度的影响。模拟研究发现:束流配送距离越短,束斑FWHM越小,但剂量平坦度越差;微型脊形滤器结构周期是影响剂量平坦度的关键因素,周期越小,剂量平坦度越好。通过模拟研究得出:在HIRFL装置重离子治疗终端将真空窗设置在距等中心距离小于125 cm 时,采用结构周期为2 mm微型脊形过滤器可以满足主动式点扫描照射对束斑FWHM和剂量平坦度的要求。To obtain carbon ion beams suitable for the active spot scanning beam delivery system at the Heavy Ion Research Facility in Lanzhou (HIRFL), the Monte Carlo program SHIELD-HIT12A was used to study the influences of beam delivery distance and structure period of mini ridge filter on full width at the half maximum (FWHM) of beam spot and dose flatness at the isocenter of the treatment room. The present simulation study shows that the shorter was the beam delivery distance, the smaller was the FWHM of beam spot, but the worse was the dose flatness. The structure period of mini ridge filter was a key factor to account for the dose flatness at the isocenter. The smaller was the structure period of mini ridge filter, the better was the dose flatness. Based on the simulation results, we conclude that 2 mm structure period for a mini ridge filter statisfies the requirements on the FWHM of beam spot and dose flatness at the isocenter for the active spot scanning beam delivery system at HIRFL when the distance between the vacuum window and the isocenter is set shorter than 125 cm in the nozzle.