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981.
本文针对处于信息化起步阶段的企业 ,提出一种符合中国国情的、面向整个企业信息集成的系统框架及实施方案 ,使企业信息化发展绕过“信息孤岛”阶段 ,从以往的无序化变成有序化、合理化 ,减少了由于缺乏规划而产生的投资浪费 . 相似文献
982.
合成了系列溴代烷烃修饰的尾式锌卟啉,以此为主体,研究了尾式卟啉对含氮类客体吡啶、DABCO 和吡嗪的轴向配位反应,测定了这些轴配反应的缔合常数.结果表明:四个主体对同一客体的平衡常数顺序为 Kθ(ZnTPP)>Kθ(ZnPC2Br)>Kθ(ZnPC4Br)>Kθ(ZnPC6Br);而三个含氮类客体对于同一主体平衡常数顺序为 Kθ(pyridine)>Kθ(DABCO)>Kθ(pyrazine).主体与所有客体的配位数均为1.不同主体体系缔合常数的顺序与主客体结构均有关,是电子效应和空间效应的综合结果.研究了温度对缔合常数的影响,发现各类配位反应的平衡常数均随温度的升高而降低.根据不同温度下的Kθ,确定了配位过程的热力学函数△rHθm,△rSθm,发现反应均为放热、熵减过程. 相似文献
983.
984.
Xiying Ma Weilin Shi Zhijun Yan Baoping Shen 《Applied physics. B, Lasers and optics》2007,88(2):245-248
We have fabricated three-dimensional ZnO photonic crystals by the self-assembly of SiO2/ZnO core–shell microspheres of diameter 180–220 nm by means of a vertical deposition method. The organized crystals adopt
a uniform close-packed hexagonal structure with long-range order and a high filling fraction. They exhibit strong partial
photonic band gaps at 565–688 nm in the transmission spectrum and a broadened band edge emission at 383 nm in the photoluminescence
spectrum. For comparison with these ZnO photonic crystals, we have also prepared pure silica crystals of the same dimensions.
The photonic band gaps of the former have been found to be shifted to a longer wavelength by about 200 nm compared to those
of the latter as a result of the higher refractive index of ZnO. This approach provides an efficient, economical alternative
means of obtaining other, more complicated photonic crystals.
PACS 82.70.D; 61.46.w; 61.82.Rx; 68.37.Hk 相似文献
985.
986.
Chalcogenide glass photonic crystals 总被引:1,自引:0,他引:1
Darren Freeman Christian Grillet Michael W. Lee Cameron L.C. Smith Yinlan Ruan Andrei Rode Maryla Krolikowska Snjezana Tomljenovic-Hanic C.Martijn de Sterke Michael J. Steel Barry Luther-Davies Steve Madden David J. Moss Yong-Hee Lee Benjamin J. Eggleton 《Photonics and Nanostructures》2008,6(1):3-VII
All-optical switching devices are based on a material possessing a nonlinear optical response, enabling light to control light, and are enjoying renewed interest. Photonic crystals are a promising platform for realizing compact all-optical switches operating at very low power and integrated on an optical integrated circuit. In this review, we show that by making photonic crystals from a highly nonlinear chalcogenide glass, we have the potential to integrate a variety of active devices into a photonic chip. We describe the fabrication and testing of two-dimensional Ge33As12 Se55 chalcogenide glass photonic crystal membrane devices (waveguides and microcavities). We then demonstrate the ability to post-tune the devices using the material photosensitivity. In one proposal we hope to introduce a double-heterostructure microcavity using the photosensitivity alone. 相似文献
987.
Real-time, continuous-wave terahertz (THz) imaging is demonstrated. A 1.89-THz optically-pumped farinfrared laser is used as the illumination source, and a 124 × 124 element room-temperature pyroelectric camera is adopted as the detector. With this setup, THz images through various wrapping materials are shown. The results show that this imaging system has the potential applications in real-time mail and security inspection. 相似文献
988.
In this paper, by using the stability theory of stochastic
differential equations, the average-consensus problem with noise
perturbation is investigated. It is analytically proved that the
consensus could be achieved with a probability of one. Furthermore,
numerical examples are taken to illustrate the effectiveness of the
theoretical result. 相似文献
989.
The multi-phase particle swarm optimization (MPPSO) technique is applied to retrieve the particle size distribution (PSD) under dependent model.Based on the Mie theory and the Lambert-Beer theory, three PSDs, i.e., the Rosin-Rammer (R-R) distribution, the normal distribution, and the logarithmic normal distribution, are estimated by MPPSO algorithm.The results confirm the potential of the proposed approach and show its effectiveness.It may provide a new technique to improve the accuracy and reliability of the PSD inverse calculation. 相似文献
990.
An approach of open-path gas sensor based on tunable diode laser absorption spectroscopy 总被引:1,自引:0,他引:1
Hui Xia Wenqing Liu Yujun Zhang Ruifeng Kan Min Wang Ying He Yiben Cui Jun Ruan Hui Geng 《中国光学快报(英文版)》2008,6(6)
Tunable diode laser absorption spectroscopy (TDLAS) is a new method to detect trace-gas qualitatively or quantificationally based on the scan characteristic of the diode laser to obtain the absorption spectroscopy in the characteristic absorption region. A time-sharing scanning open-path TDLAS system using two near infrared distributed feedback (DFB) tunable diode lasers is designed to detect CH4 and H2S in leakage of natural gas. A low-cost Fresnel lens is used in this system as receiving optics which receives the laser beam reflected by a solid corner cube reflector with a distance of up to about 60 m. High sensitivity is achieved by means of wavelength-modulation spectroscopy with second-harmonic detection. The minimum detection limits of 1.1 ppm·m for CH4 and 15 ppm·m for H2S are demonstrated with a total optical path of 120 m. The simulation monitoring experiment of nature gas leakage was carried out with this system. According to the receiving light efficiency of optical system and detectable minimum light intensity of detection, the detectable optical path of the system can achieve 1 - 2 km. The sensor is suitable for natural gas leakage monitoring application. 相似文献