基于光纤光栅传感技术的复合材料损伤检测

随着科学技术的不断进步和发展,越来越多的新型复合材料构件在工业制造过程中被采用,然而复合材料在服役过程中一旦损坏将造成巨大的损失,因此对复合材料的结构健康检测显得十分重要。将布拉格光纤光栅（FBG）传感技术应用于玻璃纤维复合材料薄板检测,采用主动冲击的方式在玻璃纤维复合材料板上激励声波,采集损伤前后的冲击响应信号,研究基于小波包能量谱的冲击响应的损伤识别。通过小波包分解,得到损伤前后的小波能量谱变化比直方图,比较图中各阶小波包能量比,能够实现复合材料的损伤识别。     

加筋复合材料板分布式光纤冲击判位

针对加筋复合材料板结构冲击损伤监测需求,提出一种基于分布式光纤光栅传感网络的冲击载荷快速判位方法。通过优化分布式光纤冲击监测网络布局,采用小波包分解方法得到冲击响应信号特征,构建了基于特定阶数能量谱幅值比的样本响应矩阵。借助BP神经网络实现对加筋类航空板结构的快速冲击判位。     

加筋复合材料板分布式光纤冲击判位

针对加筋复合材料板结构冲击损伤监测需求,提出一种基于分布式光纤光栅传感网络的冲击载荷快速判位方法。通过优化分布式光纤冲击监测网络布局,采用小波包分解方法得到冲击响应信号特征,构建了基于特定阶数能量谱幅值比的样本响应矩阵。借助BP神经网络实现对加筋类航空板结构的快速冲击判位。     

压电耦合智能板结构中微损伤识别方法研究

基于小波包能量谱分析方法,研究了压电耦合板结构中微损伤及其损伤程度的检测和识别方法。通过建立压电耦合板的谱有限元模型,数值模拟研究了金属板中微小凹陷损伤发生细微变化时传感器的动态响应;进而采用小波包分析技术对响应信号进行分解,得到一系列子信号的能量谱,分析了不同程度凹陷损伤对各节点能量谱的分布和幅值变化所产生的影响。研究结果表明,小波包能量谱能够对微小凹陷损伤及其损伤程度进行较为灵敏地识别,为实际检测工作提供了参考。     

基于深度学习网络的光通信系统非法入侵行为识别研究

为了检测多种光通信系统非法入侵行为，保障光通信系统运行安全，提出了基于深度学习网络的光通信系统非法入侵行为识别方法。采用光栅传感技术检测光栅传感器反射波长偏移量，感知光通信系统非法入侵行为频率特征信号。利用小波包分解方法将频率特征信号分解成多个频带后，提取各频带小波包能量，将其作为卷积神经网络输入。经小波包能量特征提取、处理、融合操作后，通过Softmax分类器完成光通信系统非法入侵行为数据特征的分类，实现光通信系统非法入侵行为识别。实验证明：该方法可迅速挖掘出光通信系统中非法入侵行为的时域、频域特征信号。所提取小波包能量可准确反映光通信系统中非法入侵行为特点。该方法可实现多种光通信系统非法入侵行为精准识别，助力管理人员针对入侵行为做出对应防御措施。     

光纤传感信号的模糊神经网络处理研究

为精准识别处理光纤传感振动信号、实现通信线路异常实时报警,提出了基于模糊神经网络的光纤传感信号处理方法,通过光纤传感采集异常事件振动信号,运用小波包分解对振动信号实施降噪处理,并提取到振动信号的低频与高频特征向量,对振动信号特征向量进行量化处理,将其作为输入,构建基于概率的模糊神经网络分类器,完成对光纤传感振动信号的处...     

基于小波包与神经网络的海底电缆故障诊断北大核心

针对海底电缆的故障诊断问题,提出了一种基于小波包与神经网络的诊断新方法。该方法将海缆中光纤的布里渊频移转换成温度和应变数据,首先使用六层小波分解对监测信号降噪,然后对故障数据进行三层小波包分解和重构,再通过提取能量、标准差和Shannon熵等构造特征向量并输入BP(反向传播)神经网络进行训练和测试。实验分析表明,在海底电缆故障诊断中,采用标准差作为特征向量输入BP神经网络中的诊断方法性能最佳。     

基于类脑脉冲神经网络的光纤油气管道监测

为了提高光纤油气管道监测效果,采用类脑脉冲神经网络算法。首先通过累加平均法对光纤传感器振动信号进行消噪;接着利用小波包对振动信号频带分解,将信号在频域上平均分为８个频段,把各频段的能量占比作为神经网络训练输入;然后基于脉冲响应对类脑神经元设计,神经元连接的强度与前、后神经元激活时间差函数关系非线性设计,振动输入数据与神经元脉冲转换;最后给出了算法流程。实验仿真显示本文算对单一振动信号识别准确率在9587左右,两种振动混合信号识别准确率在9052左右,指标优于其他算法,同时定位误差小于其他算法。     

直升机声信号的检测和识别

详细介绍了一种基于小波包和神经网络的新算法，用于对直升机声音信号检测并且识别机型。具体方法是对采集到的声音样本利用小波包分析提取特征向量，把这些特征向量输入反向误差传播（Back Propagation，BP）神经网络训练，用训练好的检测神经网络进行直升机的检测。检测完毕，证实是直升飞机声信号后，再通过识别神经网络区分不同型号直升机。实验表明，此方法能利用小波包时频局部聚焦分析能力和BP神经网络的自适应能力，较好地对不同型号的直升机声信号进行有效地检测和识别。因此。基于小波包和神经网络的直升机检测和识别算法不仅可靠而且是可行的。     

基于光纤阵列的气流传感方法研究

提出了一种基于光纤光栅阵列的光纤气流传感器。单模光纤光栅的栅区长度为10 mm,将三根光纤光栅均匀环绕布设于硅胶基体。传感器外界环境温度以及气流流速的改变都会引起传感器反射谱的变化。通过监测反射谱可以实现对外界物理量的测量。实验分析可知,硅胶基体与光纤光栅有着很好的耦合效果,通过改变硅胶基体的长度使得传感器的传感特性得到有效改善。实验研究结果表明,在正常室温情况下,传感器的中心波长漂移量与流速成二次函数关系且传感器具有方向传感特性。本文提出的光纤阵列气流传感器结构紧凑、制作工艺简单、可靠性高。     

Resolution Enhancement Technology:Integrated Process Solutions using OPC

DUV lithography, using the 248 nm wavelength, is a viable manufacturing option for devices with features at 130 nm and less. Given the low kl value of the lithography, integrated process development is a necessary method for achieving acceptable process latitude. The application of assist features for rule based OPC requires the simultaneous optimization of the mask, illumination optics and the resist.Described in this paper are the details involved in optimizing each of these aspects for line and space imaging.A reference pitch is first chosen to determine how the optics will be set. The ideal sigma setting is determined by a simple geometrically derived expression. The inner and outer machine settings are determined, in turn,with the simulation of a figure of merit. The maximum value of the response surface of this FOM occurs at the optimal sigma settings. Experimental confirmation of this is shown in the paper.Assist features are used to modify the aerial image of the more isolated images on the mask. The effect that the diffraction of the scattering bars (SBs) has on the image intensity distribution is explained. Rules for determining the size and placement of SBs are also given.Resist is optimized for use with off-axis illumination and assist features. A general explanation of the material' s effect is discussed along with the affect on the through-pitch bias. The paper culminates with the showing of the lithographic results from the fully optimized system.     

Cost-effective test solutions for smart card and other integrated flash applications

From its emergence in the late 1980s as a lower cost alternative to early EEPROM technologies, flash memory has evolved to higher densities and speedsand rapidly growing acceptance in mobile applications.In the process, flash memory devices have placed increased test requirements on manufacturers. Today, as flash device test grows in importance in China, manufacturers face growing pressure for reduced cost-oftest, increased throughput and greater return on investment for test equipment. At the same time, the move to integrated flash packages for contactless smart card applications adds a significant further challenge to manufacturers seeking rapid, low-cost test.     

Theoretical analysis of the relationship between the Brillouin gain coefficient and the strain in the optical-fiber sensors

The relation between the power of the Brillouin signal and the strain is one of the bases of the distributed fiber sensors of temperature and strain. The coefficient of the Bfillouin gain can be changed by the temperature and the strain that will affect the power of the Brillouin scattering. The relation between the change of the Brillouin gain coefficient and the strain is thought to be linear by many researchers. However, it is not always linear based on the theoretical analysis and numerical simulation. Therefore, errors will be caused if the relation between the change of the Brillouin gain coefficient and the strain is regarded as to be linear approximately for measuring the temperature and the strain. For this reason, the influence of the parameters on the Brillouin gain coefficient is proposed through theoretical analysis and numerical simulation.     

An improved parallel thinning algorithm with two subiterations

The parallel thinning algorithm with two subiterations is improved in this paper. By analyzing the notions of connected components and passes, a conclusion is drawn that the number of passes and the number of eight-connected components are equal. Then the expression of the number of eight-connected components is obtained which replaces the old one in the algorithm. And a reserving condition is proposed by experiments, which alleviates the excess deletion where a diagonal line and a beeline intersect. The experimental results demonstrate that the thinned curve is almost located in the middle of the original curve connectivelv with single pixel width and the processing speed is high.     

Novel fiber-optical interferometer with miniaturized probe for in-hole measurements

Today, micro-system technology and the development of new MEMS （Micro-Electro-Mechanical Systems） are emerging rapidly. In order for this development to become a success in the long run, measurement systems have to ensure product quality. Most often, MEMS have to be tested by means of functionality or destructive tests. One reason for this is that there are no suitable systems or sensing probes available which can be used for the measurement of quasi inaccessible features like small holes or cavities. We present a measurement system that could be used for these kinds of measurements. The system combines a fiber optical, miniaturized sensing probe with low-coherence interferometry, so that absolute distance measurements with nanometer accuracy are possible.     

Study of waveguide coupling efficiency in hybrid silicon lasers

This paper presents a new method to increase the waveguide coupling efficiency in hybrid silicon lasers. We find that the propagation constant of the InGaAsP emitting layer can be equal to that of the Si resonant layer through improving the design size of the InP waveguide. The coupling power achieves 42% of the total power in the hybrid lasers when the thickness of the bonding layer is 100 nm. Our result is very close to 50% of the total power reported by Intel when the thickness of the thin bonding layer is less than 5 nm. Therefore, our invariable coupling power technique is simpler than Intel＇s.     

Teleportation of an arbitrary unknown N-qubit entangled state under the controlling of M controllers

A new quantum protocol to teleport an arbitrary unknown N-qubit entangled state from a sender to a fixed receiver under M controllers(M < N) is proposed. The quantum resources required are M non-maximally entangled Greenberger-Home-Zeilinger (GHZ) state and N-M non-maximally entangled Einstein-Podolsky-Rosen (EPR) pairs. The sender performs N generalized Bell-state measurements on the 2N particles. Controllers take M single-particle measurement along x-axis, and the receiver needs to introduce one auxiliary two-level particle to extract quantum information probabilistically with the fidelity unit if controllers cooperate with it.     

Diode-end-pumped Nd:YVO4/LBO lasers with 4.2W continuous-wave output at 457 nm

A continuous-wave (CW) 457 nm blue laser operating at the power of 4.2 W is demonstrated by using a fiber coupled laser diode module pumped Nd: YVO4 and using LBO as the intra-cavity SHG crystal With the optimization of laser cavity and crystal parameters, the laser operates at a very high efficiency. When the pumping power is about 31 W, the output at 457nm reaches 4.2 W, and the optical to optical conversion efficiency is about 13.5% accordingly. The stability of the out putpower is better than 1.2% for 8 h continuously working.     

A rigorous proof of MIMO channel capacity’s increase with antenna number

It is well known that adding more antennas at the transmitter or at the receiver may offer larger channel capacity in the multiple-input multiple-output（MIMO） communication systems. In this letter, a simple proof is presented for the fact that the channel capacity increases with an increase in the number of receiving antennas. The proof is based on the famous capacity formula of Foschini and Gans with matrix theory.     

Call for Papers

正Wireless Body-area Networks The last decade has witnessed the convergence of three giant worlds:electronics,computer science and telecommunications.The next decade should follow this convergence in most of our activities with the generalization of sensor networks.In particular with the progress in medicine,people live longer and the aging of population will push the development of wireless personal networks