左手材料阶跃型光纤的模场特性

从Maxwell方程组出发,讨论纤芯为左手材料,包层为右手材料阶跃型光纤,推导了矢量解的场方程.经过数学计算,求得了左手材料阶跃型光纤矢量解的特征方程.根据矢量模的分类,找到了TE模、TM模、HE模和EH模的特征方程.根据各模的特征方程,并且与右手材料光纤相关的特征方程,在靠近截止和远离截止两种情况下进行了比较,得到了左手材料光纤的某些奇异特性.     

Some aspects on the sampling efficiency of microbial impaction air samplers

Indoor microbial monitoring is an important health issue in many sectors of society.In particular,it is important to monitor microbial concentrations in environments dealing with bio-susceptible products.Many human diseases are related to high,undesired microbial airborne concentrations.However,the lack of a standardized and well-accepted methodology for testing and ranking the performance of microbial air samplers is a source of uncertainty in such measurements.Several works clearly show that results obtained from microbial air sampling depend largely on measuring techniques,especially the air samplers’ physical parameters,such as d₅₀,as well as environmental conditions,sources,and concentrations of microbial organisms in the environment.Furthermore,personnel using cleanroom clothing can reduce the microbial burden within a clean environment.To evaluate this effect,we carried out experimental comparison tests in a cleanroom of class ISO 5 with different air samplers under various microbial concentration levels,generated by a human source dressed in different quality cleanroom clothing.Our results confirm that in addition to the measuring technique,cleanroom clothing does influence microbial contamination,affecting air sampler measurements.     

He I photoelectron spectra and valence synchrotron photoionization for XC(O)SCl (X = F, Cl) compounds

Small penta-atomic molecules like FC(O)SCl and ClC(O)SCl have been analyzed by using both photoelectron spectroscopy (PES) and results derived from the use of synchrotron radiation in the same energy range. For this second experiment total ion yield (TIY), photoelectron photoion coincidence (PEPICO), and partial ion yield (PIY) spectra have been recorded. This set of data together with results obtained by computational chemistry allow us to study electronic properties and the ionization channels of both species. Thus, whereas the photodissociation behavior of FC(O)SCl can be divided into three well-defined energy regions, the fragmentation dynamics of ClC(O)SCl seems to be more complex. Nevertheless, simultaneous evaluation of the PES and valence synchrotron photoionization studies helps to clarify the molecular ionization processes.     

Stereoselective synthesis of 2,3-unsaturated-aza-O-glycosides via new diastereoisomeric N-Cbz-imino glycal-derived allyl epoxides

Diastereoisomeric D,L-N-Cbz-imino glycal-derived allyl epoxides 5 and 6 have been synthesized, and their addition reactions with alcohols examined. The reactions lead to the corresponding 2,3-unsaturated-aza-O-glycosides through a new, completely regioselective 1,4-addition process which proceeds with complete substrate-dependent stereoselectivity.     

Artarborol, a nor-caryophyllane sesquiterpene alcohol from Artemisia arborescens. stereostructure assignment through concurrence of NMR data and computational analysis

A nor-caryophyllane derivative, artarborol, has been isolated from wormwood (Artemisia arborescens) and its stereostructure established by using a combination of chemical derivatization, NMR data, molecular modeling, and quantum-mechanical calculations. In particular, comparison of experimental 13C NMR data with a Boltzmann-weighed average of 13C NMR chemical shifts, calculated by ab initio DFT method, supported the stereochemical assignment.     

掺染料向列型液晶薄膜的光学相位共轭性质

用简并四波混频的实验手段,分析了掺染料5CB液晶分子转动的机理.给出了简明的物理图象,理论与实验是自洽的.在应用领域中将有重要的作用. 关键词：     

27Al+27Al耗散产物反应时间的提取

用发展了的Ericson统计理论,从²⁷Al+²⁷Al碰撞的耗散产物的激发函数提取了反应的相互作用时间约4.3×10^－21s.     

第52届国际物理奥林匹克竞赛理论第3题介绍与解答

第52届国际物理奥林匹克竞赛理论试题共三道,分别为永磁体(Permanent magnets)、詹姆斯韦伯太空望远镜(James Webb Space Telescope)和比例法则(Scaling laws)。考试采用远程线上形式进行。文章主要对理论第三题的命题和解答进行介绍,并对题目间的联系以及所有获奖选手的答题情况进行了简要分析。     

N80钢CO2腐蚀产物膜在水/砂两相流介质中的磨损性能

采用高温高压静态釜对N80油套钢在CO2中的腐蚀行为进行了模拟腐蚀试验;利用自制的磨损试验装置对比分析了腐蚀产物膜在水/砂两相介质中的磨损性能同成膜温度、CO2压力、流速及砂粒度之间的关系;用扫描电子显微镜分析了N80钢表面CO2腐蚀产物膜及其磨损表面形貌,用表面形貌仪测定了磨损试验前钢表面CO2腐蚀产物膜的粗糙度.结果表明:成膜温度和压力对钢表面腐蚀产物膜的表面粗糙度具有显著影响;N80钢表面CO2腐蚀产物膜磨损表面形貌沿深度方向存在差异,对应的抗磨性能亦有所不同;两相介质中的砂粒度越大或流体相对流速越大,则腐蚀膜的磨损越剧烈.