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1.
目前,光折变非线性元件在光学并行图像处理中有着非常广泛的应用。光折变晶体用于图像边缘增强,图像加、减运算,非相干—相干转换(PICOC),图像相关和卷积运算等研究已取得显著成果。本文研究了Cu;KNSBN晶体中多重图像的存贮问题,指出可以利用这种技术实现光学目标识别并给出了一些初步实验结果。此外,还从理论上分析了具有相同衍射效率的多重全息信息记录技术。 相似文献
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The geometry, energy, internal rotation, vibrational spectra, dipole moments and molecular polarizabilities of poly(vinylidene fluoride-trifluoroethylene) (P(VDF-TrFE)) of α- and β-chain models were studied with density functional theory at B3PW91/6-31G(d) level and compared with those of the poly(vinylidene fluoride) (PVDF) homopolymer. The chain length and the trifluoroethylene (TrFE) concentration were examined to discuss the copolymer chain stabilities, chain conformations and electric properties. The asymmetrical internal-rotation potential energy curve shows that the angles for the g and g′ conformations in the α-chain (tg and tg′) models are 53° and −70°, respectively, and the β-chain (ttt) conformation is a slightly distorted all-trans plane with dihedral angle at 177°. The energy differences, Eβ − Eα(g) and Eβ − Eα(g′), between the β- and the α-conformation are 2.1 and 7.8 kJ/mol, respectively. These values are smaller than that in PVDF (8.4 kJ/mol), suggesting that the β-conformation in the copolymer will be more stable than in PVDF. The energy barriers for β → α(g) and β → α(g′) transitions are 16.2 and 5.8 kJ/mol, respectively. The former is almost twice of the energy barrier in PVDF by 8.2 kJ/mol and the latter is slightly smaller (by 2.4 kJ/mol) than that in PVDF. The respective energy barriers for α(g) → β and α(g′) → β transitions are 18.3 and 13.6 kJ/mol compared with the value 16.3 kJ/mol in PVDF. The asymmetrical energy barriers may be one of the reasons for the copolymers with 0.5-0.6 (mole fraction) VDF exhibiting complicated phase transition behavior. The conformation of α-chain P(VDF-TrFE) exhibits from a helical (containing higher TrFE) to a nearly beeline (containing lower TrFE). This behavior is different from that in the PVDF and the nearly beeline conformation might be responsible for the increasing crystallizability. The helical might also be associated with the complicated phase transition behavior and the larger lattice strain in the P(VDF-TrFE)s with higher TrFE concentration. The energy difference per monomer unit between the β- and α-chain decreases with increasing TrFE content. The ideal β-chain is curved with a radius of about 30 Å, which is similar to that in PVDF. The chain curvature and the TrFE content will affect the dipole moment contribution per monomer. The chain length and TrFE content will not significantly affect the mean polarizability. The calculations indicated that there are some additional characteristic vibrational modes that may be used in identification of the α- or β-phase P(VDF-TrFE)s with different TrFE contents. 相似文献
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多径干扰信号会导致GNSS接收机伪距、载波相位和多普勒等测量精度降低,多径信号对GNSS接收机观测数据的影响与多径信号的延迟、幅度、相位等特性参数有关,造成的伪距测量误差高于载波相位测量误差2个数量级。多径抑制是GNSS接收机关键性能指标之一,GNSS接收机主要从试验室模拟环境和实际工作环境两方面检测多径抑制性能,多径误差包络检测技术利用模拟导航信号源完成多径抑制性能检测,码减载波和多径误差分析都是通过接收观测卫星导航信号并进行数据分析完成多径抑制性能的检测。 相似文献
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FANG Min ZHOU Shuyue CHEN Yongmei WANG Hongchun QIU Zheng ZHANG Zhendong XIAO Chenguang 《西安电子科技大学学报(自然科学版)》2017,44(6):20
The dynamic fault tree does not have the ability of fault calculation when analyzing the reliability of the system, so it needs to be modeled and analyzed by means of multi-valued decision diagrams and so on. The dynamic fault tree is translated into a multi-valued decision diagram according to the ordering of variables of basic events which affects the size of the generated multi-valued decision diagram and the cost of traversal to get cut sequences. An adjustment method of the dynamic fault tree structure is proposed based on the importance degree of repeated events, dynamic gates and the locations of events of the dynamic fault tree. By taking the fact that the basic events at the same level are equally important into account, an improved dynamic variable ordering method and ordering generation algorithm for the multi-valued decision diagram are presented in this paper. The result analysis of an example shows that the improved dynamic variable ordering method can reduce the size of the multi-valued decision diagram and space and time complexity of the reliability calculation compared to the similar methods. 相似文献
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Under the centralized cognitive radio network architecture, considering the network performance and users' demands. We propose an optimized dynamic spectrum access algorithm based on Q-learning. The proposed algorithm has two steps, which consist of user request according to Q-learning and the application process according to the overall system performance. Simulation results show that the proposed scheme can improve the overall system performance obviously, and that the user requirements could be satisfied at the same time. 相似文献
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赵丽维 《电脑编程技巧与维护》2009,(18):25-27
系统以英语教育为背景进行设计,旨在提供一个适合形成性测试和阶段性测试的自动组卷系统,能快速方便地提供各种要求的试卷,帮助教师把握教学的进度,及时地反馈教学中的问题,以使改进教学方法和调整教学重点。 相似文献
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原生XML数据库(NXD)的事务处理机制是保障数据库正常运行的核心机制,是当前研究的一个重点.在分析了现事务处理机制的基础上,结合关系数据库中成熟的封锁理论,提出基于XPath的XPL四种锁封锁机制,对数据库的操作和事务做出了明确的定义,并给出了实例进行验证说明. 相似文献
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