Photonic content-addressable memory system that uses a parallel-readout optical disk

We describe a high-performance associative-memory system that can be implemented by means of an optical disk modified for parallel readout and a custom-designed silicon integrated circuit with parallel optical input. The system can achieve associative recall on 128 × 128 bit images and also on variable-size subimages. The system's behavior and performance are evaluated on the basis of experimental results on a motionless-head parallel-readout optical-disk system, logic simulations of the very-large-scale integrated chip, and a software emulation of the overall system.     

Depolarization measurements of an integrating sphere

Mueller-matrix polarimetry performed in the visible and near IR indicates that an integrating sphere acts as an ideal depolarizer to the 0.5% accuracy of the polarimeter. The integrating sphere emits unpolarized light regardless of the incident polarization state.     

资源一号02D高光谱数据大气校正及应用北大核心CSCD

针对高光谱数据大气校正耗时长和查找表构建不准确等问题,提出基于MODTRAN辐射传输模型实时创建大气校正参数查找表的方法,并应用于水体叶绿素浓度反演。首先,基于高光谱数据实时构建大气校正参数查找表;其次,根据循环迭代反演得到水汽含量和气溶胶光学厚度对查找表插值得到各个波段的大气校正参数,从而完成所有波段数据的大气校正;最后,选择植被、土壤和水体3类典型地物精度分析,并基于反演水体的叶绿素a浓度验证大气校正精度的可靠性。实验结果表明:该方法明显优于6S、FLAASH等大气校正方法;在运行效率上,在多线程并行加速后,运行效率提升了2~4倍;基于水体反射率数据反演水体叶绿素a浓度,反演模型预测集验证中ρ为0.804 7,RMSE为1.8。     

高层建筑钢结构制作问题探讨

本文以近几年上海高层钢结构制作中反映出的人们所普遍关心的厚板焊接问题,柱与柱连接的节点形式问题,钢梁与核心筒预埋件连接精度等问题进行了分析,探讨、并提出了笔者的观点和建议。     

Photorefractive Beam splitter for Free-Space Optical Interconnections

A photorefractive beam splitter (PRBS) is introduced as an alternative to a polarizing beam splitter (PBS) for coupling optical power into reflective modulators in a free-space optical interconnection system. The PRBS uses a single diffraction grating recorded in a photorefractive material to redirect the incident laser light into the first diffraction order and onto the modulators. Reflected interconnection light not matching the Bragg angle criteria transmits uncoupled through the beam splitter. Experimental results show that the PRBS provides better, more uniform transmission for off-axis beams than the currently used PBS.     

An unbiased parametric imaging algorithm for nonuniformly sampled biomedical system parameter estimation

An unbiased algorithm of generalized linear least squares (GLLS) for parameter estimation of nonuniformly sampled biomedical systems is proposed. The basic theory and detailed derivation of the algorithm are given. This algorithm removes the initial values required and computational burden of nonlinear least regression and achieves a comparable estimation quality in terms of the estimates' bias and standard deviation. Therefore, this algorithm is particular useful in image-wide (pixel-by-pixel based) parameter estimation, e.g., to generate parametric images from tracer dynamic studies with positron emission tomography. An example is presented to demonstrate the performance of this new technique. This algorithm is also generally applicable to other continuous system parameter estimation.     

Conditional-sampling spectrograph detection system for fluorescence measurements of individual airborne biological particles

We report the design and operation of a prototype conditional-sampling spectrograph detection system that can record the fluorescence spectra of individual, micrometer-sized aerosols as they traverse an intense 488-nm intracavity laser beam. The instrument's image-intensified CCD detector is gated by elastic scattering or by undispersed fluorescence from particles that enter the spectrograph's field of view. It records spectra only from particles with preselected scattering-fluorescence levels (a fiber-optic-photomultiplier subsystem provides the gating signal). This conditional-sampling procedure reduces data-handling rates and increases the signal-to-noise ratio by restricting the system's exposures to brief periods when aerosols traverse the beam. We demonstrate these advantages by reliably capturing spectra from individual fluorescent microspheres dispersed in an airstream. The conditional-sampling procedure also permits some discrimination among different types of particles, so that spectra may be recorded from the few interesting particles present in a cloud of background aerosol. We demonstrate such discrimination by measuring spectra from selected fluorescent microspheres in a mixture of two types of microspheres, and from bacterial spores in a mixture of spores and nonfluorescent kaolin particles.     

基于Lua的Linux内核测试工具开发

为减小传统的通过编写大量代码来调用Linux内核及驱动接口进行测试的编程难度,缩短测试周期,采用将Lua脚本语言载入Linux内核并使用脚本语言进行内核及驱动测试的方法,设计并实现一种简易Linux内核驱动测试工具。实验结果表明,该工具所占用的Linux内核空间小,使用灵活方便,可对内核及驱动模块进行准确有效的测试。     

Direction coding using a tactile chair

This laboratory study examined the possibility of using a car seat instrumented with a tactile display to communicate directional information to a driver. A car seat fitted with an 8 × 8 matrix of vibrators embedded in the seat pan was used to code eight different directions. Localization response time and angular accuracy were examined as a function of stimulus direction, presence of a tactile attention cue, temporal pattern, stimulus layout, age, and gender. The mean absolute angular error was 23°, and both localization accuracy and response times were superior for the back left, backward, and back right directions. Of the various temporal pattern/attention cue combinations examined, results favored the relatively fast patterns consisting of vibration bursts of 125 or 250 ms without a centrally located attention cue over 500 ms bursts that were preceded by an attention cue. Observed age and gender effects were relatively modest, suggesting that using tactile cueing to communicate direction is effective across a wide range of users. In addition, the tactile stimulus was detected by more than 90% of the participants under surprise trial conditions. Overall, these results indicate that the tactile chair provides a promising and robust method of providing directional information.     

基于Fenchel对偶的核Logistic回归并行学习算法

给出了一种大规模核Logistic回归的并行学习算法.利用凸优化中的Fenchel对偶定理, 将核Logistic回归的优化原问题转换成对偶空间的优化问题,再利用块更新迭代方法, 可以独立地在部分数据集上进行分类器训练.设计了一个简单的客户机--服务器并行计算模式, 每个客户机对部分数据优化子问题,在一次优化结束后,服务器根据各客户机传递的信息修正各子问题目标函数. 在标准数据集的实验结果表明了基于Fenchel对偶的核Logistic回归并行学习算法的可行性.