Focal shift and focal switch of Bessel–Gaussian beams passing through a lens system with or without aperture

The focal shift and focal switch of Bessel–Gaussian (B–G) beams passing through a lens system with or without aperture is studied in detail. For the unapertured case, the necessary condition for the focal switch and the expression for the amplitude of the focal switch are derived. It is shown that if the truncation parameter δδ_c or beam parameter ββ_c (δ_c, β_c are the corresponding critical values), there exits only one axial intensity maximum, and the focusing without focal shift can be achieved for u/f=1 (u is the separation between the aperture and lens, f is the focal length of the lens); if δ>δ_c and β>β_c, there exist two axial intensity maxima, and the focal switch can take place at the turning point u/f=1 for both apertured and unapertured cases. The dependence of the amplitude of focal switch and normalized axial intensity minimum on the truncation parameter, beam parameter and Fresnel number is also studied.     

A DFT/TDDFT study on the structures, trend in DNA-binding and spectral properties of molecular “light switch” complexes [Ru(phen)2(L)](L = dppz, taptp, phehat)

Theoretical studies on a series of molecular “light switch” complexes [Ru(phen)₂L]²⁺ (phen = 1,10-phenanthroline; L: dppz = dipyrido [3,2-a:2′,3′-c]phenazine; taptp = 4,5,9,18-tetraazaphenanthreno-[9,10-b]triphenylene; phehat = 1,10-phenanthrolino[5,6-b]1,4,5,8,9,12-hexaazatriphenylene) 1-3 have been carried out applying DFT/TDDFT (density functional theory and time-dependent DFT) methods. The geometric and electric structure-characteristics of these complexes have been revealed, and the trend in their DNA-binding constants (K_b), i.e., K_b (2) < K_b (3) < K_b (1), which closely relates to the luminescence properties of the complexes in DNA, has been reasonably explained. The results show that simply increasing the planar area of intercalative ligand may be ineffective on improvement of DNA-binding of resulting complex because of going with the increase in the LUMO (and LUMO + x) energy, but introducing some heteroatoms (e.g., N atom) with stronger electronegativity into the ring skeleton of intercalative ligand should be effective because of the decrease in the LUMO (and LUMO + x) energy to a certain extent. In addition, the spectra of this series of complexes in vacuo are also computed, simulated, and minutely discussed by the DFT/TDDFT methods, and it is interesting to find that the symmetries of the excited and accepting orbitals of the transition with the largest f value are the same.     

光接枝法制备新型pH开关核孔膜

用表面光接枝方法制备了具有pH开关特性的丙烯酸接枝PET核孔膜 .XPS、SEM和AFM的表征结果证明 ,接枝膜具有非对称结构 ,丙烯酸接枝层主要在膜的向光侧表面 ,膜背侧和膜孔内没有变化 .膜孔周围的接枝链在湿态下沉入膜孔 ,接枝层对膜孔顶部产生封盖 .接枝链的体积随环境pH值的不同而变化 ,从而控制接枝膜的滤过特性 .在低接枝程度时 ,接枝链体积变化对膜孔径的影响小 ,不具有pH开关特性 ,但是接枝提高了膜的亲水性 ,通量得到提高 ;接枝程度达到一定程度时 (如 0 5 %) ,膜孔径受接枝链体积变化的影响显著 ,接枝膜表现出pH开关效应 .在pH大于 5时 ,接枝膜通量恒定 ,基本不受溶液pH值影响 .当pH值小于 4时 ,膜通量随溶液酸性的增加迅速升高 .接枝膜的开关幅度JpH =2 JpH =6 8,随接枝程度的增加而增加 .膜的通量和开关幅度可以通过接枝程度来调节     

金属箔断路开关电爆性能的研究

给出了在单纯断路开关调节电路（Ｆ型）、断路开关－变压器调节电路（ＦＴ型）和变压器－断路开关调节电路（ＴＦ型）三种类型的电爆炸断路开关的理论模型和数值模拟结果,并对其性能进行对比和分析。     

Traps for charge carriers in molecular materials formed by dipolar species: towards light-driven molecular switch

The influence of polar species on the transport and trapping of charge carriers is discussed. Calculations performed on a model molecular lattice demonstrate that polar dopants locally modify the polarization energy thus creating traps for charge carriers in the vicinity of the dipole. The presence of polar dopants in disordered solids gives rise to a broadening of the density-of-states function. A scheme of a molecular switch has been put forward, based on electrostatic interactions between photochromic moieties and charge carriers travelling on a molecular wire (conjugated polymer chain).     

Fluorescent Switch Behavior of 1, 2-Bis（4-pyridyl） Ethylene Controlled by pH in Aqueous Solution

With the decrease of pH value from 8.45 to -1.0, the UV-Vis absorption and fluorescent spectra of 1,2-bis（4-pyridyl） ethylene（BPE） took on the same changing trend at four different successive pH stages： 8.45--7.20, 7.20--5.62, 5.62--2.60, and 2.60--1.0, namely, no change, decrease, increase, and decrease again. Among these, in a range of 7.20--5.62, the fluorescence wavelength blueshifted from 418 to 359 nm, but the UV-Vis absorption wavelength, in contrast, redshifted from 285 to 298 nm. The fluorescence intensity of BPE had a drop even to quench upon a decline in the pH value from 2.60 to -1.0 probably owing to its cation-re interaction to reduce the π electron cloud density of BPE. Two dissociation constants, pKa1（4.30±0.01） and PKa2（5.65±0.04）, were obtained based on fluorescence data. The changes of fluorescence spectra indicate that BPE has ＂oft-on-off＂ switch behavior. The fluorescent spectra of BPE were nearly independent on the presence of α- and β-cyclodextrins.     

Electrochemical Characterizations of Nitro-styrene Derivatives

The redox behaviour of three electron donor-acceptor compounds, nitro-styrene derivatives was investigated by means of cyclic voltammetry. The results indicate that (1) these compounds can be considered as a good electron donor-acceptor material, and its electrodeposition film can be formed by electro-oxidation; (2) the oxidation of donor is related to the reduction of acceptor closely. and it can be used to prepare redox switch film.     

固态化高功率长脉冲驱动源关键技术

基于固态化磁开关、低阻抗脉冲形成网络和感应电压叠加等关键技术, 提出了一种固态化高功率长脉冲驱动源技术方案, 该方案充分利用了绝缘规律, 可实现模块化设计, 具备提高系统稳定性、可靠性、重复频率和长时间运行的潜在优势。目前, 针对系统方案进行了电路模拟计算, 研制了各关键子系统, 开展了全系统的初步联合实验, 在假负载上输出了功率2.1 GW、脉宽约170 ns的高压脉冲, 验证了技术方案的合理性。     

衰减振荡电流下火花电阻的光谱诊断

气体开关是脉冲功率系统的关键部件,开关的火花通道阻抗直接影响负载电压的陡度及其能量传输效率。提出一种光谱学诊断方法,通过对火花通道成像光谱的时空分辨测量,获得通道半径及电导率,从而计算时变的火花电阻。光谱测量结果表明, 氮气间隙火花放电通道电子温度为2~3 eV,通道电导率先增大后减小,最大值约16 000 S,随着放电发展,火花通道电阻从绝缘状态快速跌落并趋于稳定值,时变趋势与电学计算结果基本吻合。3~100 kPa范围内,随着气压增大,放电通道半径减小,火花通道电阻增大。     

高频高变比脉冲变压器耦合固态刚管调制器

调制器输出脉冲宽度存在两种模式,输出脉冲宽度为10 s时,工作频率0~8 kHz可调,输出脉冲宽度为200 s时,工作频率0~400 Hz可调。为了实现了调制器的小型化,初级电压设计为700 V,初级储能电容可采用高储能密度的电解电容,且可降低绝缘栅双极晶体管(IGBT)串联的风险,次级输出电压为70 kV,采用变比为100的脉冲变压器。概述其各个组成部分及其工作原理,重点对IGBT固态开关的驱动、保护电路、损耗和吸收回路进行了分析讨论,并对高变比的变压器进行了理论分析。对调制器进行了实验测试,脉冲前沿2.2 s,脉冲后沿1.65 s,过冲小于7%,脉冲顶降小于1%。