低成本改进一种简易测定水的汽化热实验装置

针对大学物理实验手动测定水的汽化热装置存在蒸汽冷凝严重、冷凝水混入量热器、蒸汽温度测量不准确从而导致较大系统误差、影响实验教学效果的问题,本文对实验装置结构进行了适当改进,通过自制四口瓶蒸汽过滤器代替传统简易蒸汽过滤器,对实际蒸汽温度进行了测定,从而降低了系统误差;通过在蒸汽输气管上加装可调温电热加热套,减少了水蒸气冷凝对实验结果的影响.实验结果表明,该改进装置稳定可靠、成本低且测定精度高,可以使测量结果与公认值的相对偏差从未改进前的10.4%降低到3%以内.     

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.     

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     

Rugate filters prepared by rapidly alternating deposition

A methodology for the fabrication of composite (Nb₂O₅)_1-x(SiO₂)_x thin-film rugate filters by using pulsed direct current magnetron sputtering is presented. The two materials are mixed using rapidly alternating deposition technology. The optical properties of the composite films varying with the composition of the material are studied in detail. Refractive indices between 1.50 and 2.14 can be realized in our coating system. Two designed rugate filters with a reflection band at the wavelength of 532 nm are fabricated using an automatic deposition process. The microstructure of the rugate filter is investigated by using scanning electron microscopy. The calculated and the measured transmittance spectra are in good agreement with each other. The causes of the slight differences between them are also analysed.