一种基于‘E’型梁结构的光纤光栅振动传感器

为了提高梁式结构光纤光栅振动传感器的测量灵敏度,设计并提出了一种悬臂梁结构 的光纤光栅振动传感器。首先对悬臂梁结构的光纤光栅振动传感器的工作原理进行理论上的 分析,其次对结构中悬臂梁长度和光纤光栅有效长度与固有频率和灵敏度的关系进行了仿真 ,以便传感器获得较高的灵敏度。仿真结果表明,固有频率随光纤光栅有效长度的增加而逐 渐减小,但灵敏度随悬臂梁长度的增加而增大。而当光纤光栅有效长度增大时,光纤的固有 频率和灵敏度有减小的趋势。根据理论上分析和仿真结果,最终确定了‘E’型梁结构的最 佳参数和光纤的有效长度,这一点在实验中得到了很好验证。实验结果表明,传感器的平坦 区域为15 Hz~60 Hz,其固有频率为83Hz,灵 敏度高达481.32 pm/g。该振动传感 器在振动信号检测中的良好表现,这将在桥梁、建筑等振动传感领域具有重要的研究意义。     

基于对称悬臂梁的小型化低频FBG加速度传感器研究

提出了一种基于对称悬臂梁的小型化低频光纤布拉格光栅(FBG)加速度传感器。首先根据传感器结构的力学模型,推导出传感器的灵敏度和固有频率表达式;然后对传感器进行结构参数优化,采用ANSYS Workbench对传感器进行静应力与模态分析;最后根据分析结果制作传感器,并实验研究了传感器的幅频响应、灵敏度特性、横向抗干扰能力和冲击响应。结果表明,该传感器固有频率为72 Hz,灵敏度为681.7 pm/g,抗横向干扰度小于4.9%,且体积仅为6.48 cm^(3),可用于50 Hz以下的低频微弱振动信号的实时监测。     

一种新型滑动杆式光纤光栅振动传感器研究

为了提高振动传感器对加速度信号测量的灵敏度 ,本文提出了一种新型的基于悬臂梁和滑动杆结 合的光纤光栅振动加速度传感器。详细阐述了传感器的结构和工作原理,并推导了传感器固 有频率和灵敏 度的理论公式。最后通过振动台测试了传感器的固有频率和灵敏度,并和光纤光栅仅沿光纤 轴向上受力的 实验数据进行了比较。实验结果表明,传感器频率响应曲线的平坦区域在10～38Hz之间,传感器的固有频 率为62Hz,灵敏度为52.8pm/g。与光纤光栅 仅沿光纤轴向受力的实验相比较,加速度灵敏度提高了70.8%。     

基于L型悬臂梁的光纤光栅加速度传感器

为了测量低频小信号,提出了一种基于L型悬臂梁的光纤光栅(FBG)加速度传感器, 并进行了理论分析,推导出了其灵敏度及谐振频率表达公式。为了得出结构的最优参数,根 据理论公式进行了仿真分析得出仿真曲线。根据仿真曲线,选定传感器各个参数,制作出传 感器实物,分别对传感器灵敏度幅频响应,线性响应及横向抗干扰性进行了实验测试,实验 测试出传感器谐振频率280 Hz,在充装硅油阻尼后测量带宽为1Hz－ 240 Hz,测量带宽内响应 曲线平坦度在±1.5 dB以内,灵敏度可达到52 pm/g,线性相关性为99.97%,与理论谐振频 率290 Hz,灵敏度59 pm/g较吻合,表明了理 论分析的正确性,同时传感器具有较好的横向 抗干扰性,横向抗干扰性为4.2%,研究表明此传感器可以应用于低频 小信号场合的振动测试。     

基于等强度悬臂梁的低频高灵敏度FBG加速度传感器研究

针对桥梁低频振动监测灵敏度低的问题,提出了一种基于等强度悬臂梁的低频高灵敏度光纤光栅(fiber Bragg grating,FBG)加速度传感器。以悬臂梁厚度与质量块质量为主要参数设计了12组FBG加速度传感器,通过激振器对传感器进行幅频特性、灵敏度及横向抗干扰试验,得到较适合监测桥梁振动的一组传感器,其固有频率为49 Hz,工作频带为0—34 Hz,灵敏度高达664.53 pm/g,线 性 度为99.9%,且横向抗干扰能力强。通过理论推导到试验验证,为桥梁振动提供一种新型有效的监测手段。     

高灵敏抗冲击光纤光栅微振动传感器

针对高灵敏度的光纤布拉格光栅（FBG）振动传感器的抗冲击可靠性,设计了一种具有限振结构的双悬臂梁型FBG振动传感器,理论分析了结构参数与灵敏度和振动位移的关系,进行了结构优化,确定了限振幅度。制作了限振幅度约为90m的传感器样品,对传感器的加速度灵敏、频率响应、抗冲击性能进行了测试,结果表明,传感器的加速度灵敏度达到525 pm/g,谐振频率约为66 Hz,传感器经过50 g反复冲击,频响特性具有良好重复性,表明传感器具有较高的可靠性。     

基于双等强度悬臂梁的光纤光栅加速度振动传感器

研制了一种基于双等强度悬臂梁式光纤布 拉格光栅(FBG)振动传感器。首先采用ANSYS软件对 传感器进行数值计算与仿真,得到在各个阻尼比下传感器的幅频特性曲线和相频特性曲 线,不断变化 传感器结构参数,寻找最优谐振频率与加速度灵敏度,从而得到传感器最优结构参数;根据 仿真所得的最 优结构参数,进行传感器加工;利用所加工的振动传感器进行振动台试验研究并对所得实验 数据进行处理, 将处理后的数据与ANSYS软件仿真得到的数据进行比较,结果表明,振动平台所测得的 实验结果与ANSYS 软件仿真结果相吻合,传感器的谐振频率为80.74Hz,可实现50Hz以下低 频振动信号的实时监测,在5～50Hz之间的加速度灵敏度约为20.85pm/m·s－2。     

双光纤-悬臂梁FBG加速度传感器研究

针对现有悬臂梁FBG加速度传感器光纤表面粘贴会造成FBG受力不均匀,并且无法在温度变化和振动等复杂的环境中工作的问题,提出一种双光纤-悬臂梁结构的FBG加速度传感器。理论分析了结构参数对传感器灵敏度和固有频率的影响,并采用ANSYS有限元分析软件进行了静应力和模态仿真分析,最后搭建了测试系统对传感器进行性能测试。结果表明,加速度传感器的固有频率为84.86Hz,在15~60Hz的低频段具有平坦的灵敏度响应,双光纤在增加传感器的灵敏度的同时有效消除了温度变化的影响,加速度灵敏度为156.70pm/g,线性度为99.38%,刚性梁有效增加了结构的稳定性,在工作频段内的横向串扰为-26.97dB。     

基于光纤光栅的杆型二维振动传感器

为了实现两个方向的振动信号检测,提出了一种以杆为弹性结构的二维光纤光栅振动传感器。首先对该传感器进行了理论分析,并推导出其固有频率和灵敏度公式。然后对传感器结构进行了优化仿真,确定各个参数的最终值。最后通过实验研究了传感器的各项性能。实验结果表明,该传感器在x方向上的固有频率为493 Hz,灵敏度为54 pm/g,线性度为99.9%;在y方向上的固有频率为466 Hz,灵敏度为5 pm/g,线性度为97.5%。此外,采用双光纤光栅消除了温度对振动信号测量的影响,温度灵敏度为0.1 pm/°C。该传感器结构简单,可检测两个方向的振动信号,消除了温度的影响,在振动信号检测中表现良好,因此在多维振动信号检测领域具有重要研究意义。     

基于双悬臂梁结构的光纤加速度传感器

为消除悬臂梁结构加速度传感器由于光纤表面粘贴产生的啁啾现象,增强横向抗干扰能力,提高共振频率,提出了一种基于双悬臂梁结构的光纤加速度传感器。给出了理论分析结果,建立了有限元模型,得到了加速度灵敏度表达式,并且探讨了在共振频率不变的情况下提高加速度灵敏度的方法。实验结果表明,该传感器在6～50 Hz内频响平坦,加速度灵敏度为14pm/g,抗横向干扰能力达20dB,与理论计算较好地吻合。     

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.     

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.     

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.     

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.     

Curved crystal spectrometer for the measurement of X-ray lines from laser-produced plasmas

In order to diagnose the laser-produced plasmas, a focusing curved crystal spectrometer has been developed for measuring the X-ray lines radiated from a laser-produced plasmas. The design is based on the fact that the ray emitted from a source located at one focus of an ellipse will converge on the other focus by the reflection of the elliptical surface. The focal length and the eccentricity of the ellipse are 1350 mm and 0.9586, respectively. The spectrometer can be used to measure the X- ray lines in the wavelength range of 0.2-0.37 nm, and a LiF crystal （200） （2d = 0.4027 nm） is used as dispersive element covering Bragg angle from 30° to 67.5°. The spectrometer was tested on Shengnang- Ⅱ which can deliver laser energy of 60-80 J/pulse and the laser wavelength is 0.35 μm. Photographs of spectra including the 1 s2p ^1P1-1s^2 ^1S0 resonance line（w）, the 1s2p ^3P2-1s^2 1S0 magnetic quadrupole line（x）, the 1s2p ^3P1-1 s^2 ^1S0 intercombination lines（y）, the 1 s2p ^3S~1-1 s^2 ^1S0 forbidden line（z） in helium-like Ti Ⅹ Ⅺ and the 1 s2s2p ^2P3/2-1 s622s ^2S1/2 line（q） in lithium-like Ti Ⅹ Ⅹhave been recorded with a X-ray CCD camera. The experimental result shows that the wavelength resolution（λ/△ 2） is above 1000 and the elliptical crystal spectrometer is suitable for X-ray spectroscopy.     

Preparation and Characterization of TaN ALD Precursors

High purity organic-tantalum precursors for thin film ALD TaN were synthesized and characterized.Vapor pressure and thermal stability of these precursors were studied.From the vapor pressure analysis,it was found that TBTEMT has a higher vapor pressure than any other published liquid TaN precursor,including TBTDET,TAITMATA,and IPTDET.Thermal stability of the alkyl groups on the precursors was investigated using a 1H NMR technique.The results indicated that the tertbutylimino group is the most stable group on TBTDET and TBTEMT as compared to the dialkylamido groups.Thermal stability of TaN precursors decreased in the following order:TBTDET ＞ PDMAT ＞ TBTEMT.In conclusion,precursor vapor pressure and thermal stability were tuned by making slight variations in the ligand sphere around the metal center.     

Electronic Structure of Semiconductor Nanocrystals

This paper reviews our recent development of the use of the large-scale pseudopotential method to calculate the electronic structure of semiconductor nanocrystals, such as quantum dots and wires, which often contain tens of thousands of atoms. The calculated size-dependent exciton energies and absorption spectra of quantum dots and wires are in good agreement with experiments. We show that the electronic structure of a nanocrystal can be tuned not only by its size,but also by its shape. Finally,we show that defect properties in quantum dots can be significantly different from those in bulk semiconductors.     

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.