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991.
本文应用图论法研究光泵激光气体分子的波谱特性。假定了:1.分子与外来信号场相互作用输运过程中只涉及到六个能级;2.泵场强远大于探测场强。在这些假定下求解密度矩阵方程,获得一套反映受激分子波谱特性的解析表达式。应用这些表达式,可求得不同频率的泵场作用下分子气体的远红外波谱特性。本文特别叙述分子振动基态远红外光谱的AC aStark效应。结果表明:在谐振点AC aStark分裂的值与C.H.Townes所得结果基本相同,在受激发射和吸收共存的情况下,特性曲线的总趋向与他的结果基本一致。调谐曲线有些部份反映发射特性,有些部份反映吸收特性,在发射和吸收的过渡部份,吸收和发射都很小,而且具有特殊的过渡特性。 相似文献
992.
Neumann随机有限元的一种推广形式 总被引:1,自引:0,他引:1
针对Monte—Carlo随机有限元,研究在多样本环境下如何提高单样本计算效率的问题。证明了关于线性问题Neumann随机有限元法的算法与线性系统的等刚度迭代法是一致的;在此基础上,将迭代效率更高的算法一预处理共轭梯度法引入线性Monte—Carlo随机有限元系统,建立了相应的有限元列式;最后,利用两个算例比较了本方法与Neumann随机有限元法,结果显示随着随机变量离散度的增大,Neumann法的计算效率急剧下降,而本方法的计算效率表现稳定;对于离散度不太大的随机变量,Neumann法已经不收敛,而本方法在随机变量离散度很大的情况下,仍然保持很好的收敛性。 相似文献
993.
Lin Ziyang Jue Shi Xiang Ying L. P. Shi Wang Jian Z. X. Liang Z. R. Qiu 《Physics letters. A》2000,270(6):207-330
We observed an azo-isomerization-induced Freedericksz transition of the 5CB liquid crystal doped with 1% double-azo. In experiment, we found that the Freedericksz transition threshold occurred at optical intensity level of 0.3 mW/mm2 for the 12.5 μm-thickness planar alignment doped 5CB, which is four orders of magnitude lower as that for the pure 5CB. Using optical phase retardation, we measured the relations between the Freedericksz transition threshold and the pump beam polarization. The maximum twist angle of liquid crystal molecules under different pump beam intensity is given. The experiment indicated that trans–cis isomerization plays an important role in the decrease of the Freedericksz transition threshold. 相似文献
994.
995.
我们采用直流四引线法对银包套的Bi2-xPbxSr2Ca2Cu3Oy,(Ag-Bi2223)带材进行了临界电流的测量研究了外加磁场和电流扫描速度对临界电流的影响结果表明,电流扫描速度和磁场增加使临界电流减小,并且磁场增加使V-I曲线对加电流速度的敏感程度发生变化利用电动力学方程和磁通玻璃态蠕动机制对实验结果进行了解释,将磁场、温度、磁通钉扎强度对约化临界电流的影响归结成单一的临界电流参数n的影响,和实验结果符合得比较满意.1引言 临界电流密度Jc是表征技术应用超导材料性能的主要参量之一,也是表征… 相似文献
996.
Miao Yang Fenglei Qiu El-Sayed M. El-Sayed Wenjing Wang Shunfu Du Kongzhao Su Daqiang Yuan 《Chemical science》2021,12(40):13307
Although porous organic cages (POCs), particularly imine-linked (C N) ones, have advanced significantly over the last few decades, the reversible nature of imine linkages makes them prone to hydrolysis and structural collapse, severely limiting their applications under moist or water conditions. Herein, seven water-stable hydrazone-linked (C N–N) POCs are prepared through a simple coupling of the same supramolecular tetraformylresorcin[4]arene cavitand with different dihydrazide linkers. Their structures are all determined by single-crystal X-ray crystallography, demonstrating rich structural diversity from the [2 + 4] lantern, [3 + 6] triangular prism, and unprecedented [4 + 8] square prism to the extra-large [6 + 12] octahedron. In addition, they respectively exhibit tunable window diameters and cavity volumes ranging from about 5.4 to 11.1 nm and 580 to 6800 Å3. Moreover, their application in the water environment for pollutant removal was explored, indicating that they can effectively eliminate various types of contaminants from water, including radionuclide waste, toxic heavy metal ions, and organic micropollutants. This work demonstrates a convenient method for rationally constructing versatile robust POCs and presents their great application potentialities in water medium.A convenient method for constructing water-stable hydrazone-linked porous organic cages (POCs) with tunable structures has been reported, and such POCs can be used as robust adsorbents for effective removal of various pollutants from water. 相似文献
997.
Vehicle detection is an essential part of an intelligent traffic system, which is an important research field in drone application. Because unmanned aerial vehicles (UAVs) are rarely configured with stable camera platforms, aerial images are easily blurred. There is a challenge for detectors to accurately locate vehicles in blurred images in the target detection process. To improve the detection performance of blurred images, an end-to-end adaptive vehicle detection algorithm (DCNet) for drones is proposed in this article. First, the clarity evaluation module is used to determine adaptively whether the input image is a blurred image using improved information entropy. An improved GAN called Drone-GAN is proposed to enhance the vehicle features of blurred images. Extensive experiments were performed, the results of which show that the proposed method can detect both blurred and clear images well in poor environments (complex illumination and occlusion). The detector proposed achieves larger gains compared with SOTA detectors. The proposed method can enhance the vehicle feature details in blurred images effectively and improve the detection accuracy of blurred aerial images, which shows good performance with regard to resistance to shake. 相似文献
998.
聚[吡咯-2,5-二(3-羟基-4-甲氧基苯甲烷)]的吸附性能研究 总被引:1,自引:0,他引:1
合成了具有类似开环卟啉结构的高分子——聚[吡咯-2,5-二(3-羟基-4-甲氧基苯甲烷)]。研究了该聚合物对Cu^2 和Mg^2 的吸附性能,讨论了吸附时间、吸附温度和体系pH对吸附量的影响。通过红外光谱分析对聚合物-金属络合物的结构进行了表征。 相似文献
999.
In this paper four families of orthogonal wavelets are applied to analyze the turbulent counter gradient transport phenomena in fully developed asymmetric channel flows. The results show that: (1) In the instance of counter gradient transport, the principal scale of the coherent structure is responsible for the strong local counter gradient transport; (2) Counter gradient transport phenomena have a strong effect on the intermittency of turbulence; (3) Non-Gaussian part of the principal coherent structure is essential for counter gradient transport phenomena.The project supported by the National Natural Science Foundation of China (10272071, 10472063) 相似文献
1000.
Liewei Qiu Yongkang Zhang Xueli Long Zhi Ye Zhangmingzu Qu Xiaowu Yang Chen Wang 《Molecules (Basel, Switzerland)》2021,26(21)
The O/W isocyanate emulsion can be used as a sizing agent to improve the waterproof performance of paper. However, the -NCO content in the emulsion diminishes with the prolongation of standing time. What is happening to this seemingly stable emulsion, especially concerning its microstructure evolution? We propose to monitor the emulsions deteriorative process by combining freeze-drying technique and SEM. Thus, the emulsion containing -NCO active group was obtained by the synthetic polymer emulsification of HDI trimers. The results of SEM demonstrate that the emulsion deteriorative process actually represents the collapsing and fusion of stable honeycomb structure with the prolongation of standing time and increasing temperature. This is possibly due to the fact that the inner aggregative HDI trimers are reacting with outside water to form urethane macromolecules, and this results in the collapsing and fusion of the honeycomb structure, as observed in SEM images. Moreover, the measurement results of -NCO content and FT-IR spectroscopy present the -NCO content as reducing with increasing standing time and temperature. This conclusion further proves our hypotheses. Additionally, the emulsions are used to treat the paper by site-directed reaction. The results show that the with the increase of the standing time and temperature, the contact angles and surface free energy show a decrease and an increase, respectively, whereas surface free energy appeared at a minimum of 29.19 mJ·m−2 when the standing time and temperature was 1 h and 25 °C. 相似文献