Fiber Bragg grating hydrophone with high sensitivity

A fiber Bragg grating (FBG) hydrophone with high sensitivity was demonstrated. This hydrophone used a rubber diaphragm and a copper hard core as the sensing element. To compensate the hydrostatic pressure, a capillary tube was fixed at the end of the hydrophone. Theoretical analysis of the acoustic pressure sensitivity was given in this letter. Experiments were carried out to test the frequency response of the hydrophone. The result shows that when the Young's modulus of the diaphragm is higher, a flatter frequency response will be obtained.

Polarization dependence of absorption in strongly vertically coupled InAs/GaAs quantum dots for two-color far-infrared photodetector

Strongly vertically coupled InAs/GaAs quantum dots (QDs) with modulation doping are investigated, and polarization dependence of two-color absorptions was observed. Analysis of photoluminescence (PL) and absorption spectra shows that s-polarized absorptions at. 10.0 and 13.4 mu m, stem from the first excited state E-1 and the second excited state E-2 in the QDs to the bound state E-InGaAs in the InGaAs spacer, respectively, whereas p-polarized absorptions at 10.0 and 8.2 mu m stem from the first excited state E-1 and the ground E-g in the QDs to the bound state E-InGaAs in the InGaAs spacer, respectively. These measurements illustrate that transitions from excited states are more sensitive to normal incidence, which are very important in designing QD infrared detector. (C) 2007 Elsevier B.V. All rights reserved.

Effect of counterpart on the tribological behavior and tribo-induced phase transformation of Si

The tribological behaviors and phase transformation of single crystal silicon against Si3N4, Ruby and steel were investigated in this study. It was found that the strong chemical action between silicon and Fe was the key factor to the tribological behavior of silicon as slid against steel. SEM and Raman spectroscopy indicated that phase transformation of single crystal silicon occurred during the running-in period at low sliding velocity as slid against Si3N4 and Ruby. and gave birth to single or a mixture phase of Si-III, Si-XII and amorphous silicon. The high hardness of counterpart and the absence of chemical action between silicon and counterpart facilitated the phase transformation of single crystal silicon. (C) 2008 Elsevier Ltd. All rights reserved.

Kinetic Monte Carlo simulation of spatially ordered growth of quantum dots on patterned substrate

We report the growth of well-ordered InAs QD chains by molecular beam epitaxy system. In order to analyze and extend the results of our experiment, a detailed kinetic Monte Carlo simulation is developed to investigate the effects of different growth conditions to the selective growth of InAs quantum dots (QDs). We find that growth temperature plays a more important role than growth rate in the spatial ordering of the QDs. We also investigate the effect of periodic stress on the shape of QDs in simulation. The simulation results are in good qualitative agreement with our experiment. (c) 2006 Elsevier Ltd. All rights reserved.

笔式几何学习系统的设计与实现

基于现有的几何学习软件存在着交互方式不自然，不智能的缺点，设计并实现了一个笔式几何学习系统，用以模拟初中几何教学过程中，教师出题，学生答题的情境。笔式几何学习系统运用约束求解技术动态展示几何属性，运用草图识别技术将草图识别为几何图形，通过笔手势帮助用户更加方便地操作使用软件。评估表明，用户以笔交互的方式进行书写，绘图和操作，体现了和谐自然的人机交互模式．

基于混合自动机的Post-WIMP界面的建模

Post- WIMP界面作为继当前的主流界面范式—— WIMP界面后的下一代界面范式 ,它和 WIMP界面有着很大的不同 ,通过使用虚拟现实、语音交互、手势交互等技术 ,它能够提供更加自然高效的交互方式 .然而 ,它却难以构造 .为了有效地构造 Post- WIMP界面 ,在构造之前不考虑实现细节 ,而在一个抽象的层次上描述它是一个较好的方法 .首先 ,分析了 Post- WIMP界面的交互本质 ,交互混合性是 Post- WIMP界面一个最为重要的特点 .从形式化系统的角度分析 Post- WIMP界面 ,通过将 Post- WIMP界面抽象为混合系统能够更为准确和严格地分析Post- WIMP界面的特性 .混合自动机是用于描述混合系统的形式化工具 ,将 Post- WIMP界面建模为一组相互协作的混合自动机 .设计了一基于混合自动机理论的半形式化语言 L EAFF作为 Post- WIMP界面的描述工具 .LEAFF通过结合文本描述和图形描述描述 Post- WIMP界面中的交互行为 ,能够准确地反映交互中的控制关系、时序关系 .给出了对两个典型 Post- WIMP界面——虚拟现实交互和笔式交互的描述实例 ,同时讨论了 Post- WIMP界面中交互并行性的描述、交互实时性的验证和从描述到实际交互系统构造的转换 .

Polarization holographic high-density optical data storage in bacteriorhodopsin film

Optical films containing the genetic variant bacteriorhodopsin BR-D96N were experimentally studied in view of their properties as media for holographic storage. Different polarization recording schemes were tested and compared. The influence of the polarization states of the recording and readout waves on the retrieved diffractive image's intensity and its signal-to-noise ratio were analyzed. The experimental results showed that, compared with the other tested polarization relations during holographic recording, the discrimination between the polarization states of diffracted and scattered light is optimized with orthogonal circular polarization of the recording beams, and thus a high signal-to-noise ratio and a high diffraction efficiency are obtained. Using a He-Ne laser (633 nm, 3 mW) for recording and readout, a spatial light modulator as a data input element, and a 2D-CCD sensor for data capture in a Fourier-transform holographic setup, a storage density of 2 x 10(8) bits/cm(2) was obtained on a 60 x 42 mu m(2) area in the BR-D96N film. The readout of encoded binary data was possible with a zero-error rate at the tested storage density. (c) 2005 Optical Society of America.

Bleaching kinetics of indoly-benzylfulgimide in PMMA

Indoly-benzlfulgimide belongs to the photochromic fulgide family and follows photochemical first order kinetics. Its bleaching kinetics is investigated at 633 nm and 640 nm by spectroscopy, by the time dependence of transmission and of diffraction from holographically induced gratings. The non-exponential decay law resulting for diffraction experiments with a Gaussian beam profile is calculated and verified experimentally. For a quasi-homogeneous beam profile the time constant determined from diffraction decay is half the one for absorbance decay. The photochemical reaction rate of indoly-benzylfulgimide in PMMA is (3.9 +/- 0.3) cm(2)/J at 650 nm. (c) 2007 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

PCA在语音检测中的应用研究

提出主元分析PCA(Principal Component Analysis)用于语音检测的方法研究．用主元分析法在多维空间中建立坐标轴，将待处理信号投影到该坐标轴中，通过分析投影结果判断是否为语音信号．通过将语音和非语音分别建立子空间，来区分语音和非语音信号．该方法不同于常规的语音时域、频域处理方法，而是在多维空间中对信号进行分析·实验结果表明，该方法准确率高、简单、容易实现，而且能区分多种非语音信号．