V型微通道热沉的 流体流动与传热问题研究

V型微通道热沉具有体积小、流速小、散热效率高等优点,是将多个DL线阵组装为面阵并实现高性能冷却封装的良好解决方案.本文采用计算流体力学软件Fluent建立了V型微通道的数值模型,研究了其中的流体流动与传热问题.仿真结果表明,设计的V型微通道可满足激光二极管线阵的散热要求.仿真分析结果与V型微通道热沉样品的模拟热源加载实验测试数据对比,吻合较好,证明了数值仿真的有效性.     

光纤通信中的MOEMS光开关

光开关是一种重要的全光通信器件。MOEMS光开关阵列因其串扰小、插入损耗小、消光比高、对波长和偏振不敏感、且稳定性好、造价低等突出优点得到了国内外的广泛研究。本文介绍了MOEMS光开关的国内外研究进展。并对我国MOEMS光开关的研究提出建议。     

基于微流控光开关的波导结构分析与优化

光开关是全光网的关键器件,提出一种全新基于微流控技术的波导型光开关设计。通过电控方法改变光波导结构,实现光路变化。基于有限元方法,重点研究了光开关插入损耗、串扰、透过率等参数,对波导层光传输性能进行评价。优化结果表明,当波导层以一定角度斜交叉时,透过率提高,插入损耗降低,最低降到0.18dB,实现了光开关的结构优化。由于采用微流控技术和有机光学材料,这类开关体积小、结构简单、成本低,易于集成大规模光开关阵列。     

Nonlinear Features of a Fluid Flow in an Elastic Pipeline

Mathematical Models and Computer Simulations - The process of a fluid flow in an elastic pipeline with fixed ends is considered. It is shown that in such a pipeline auto-oscillations of the wall...     

High Performance Computations for Large Scale Simulations of Subsurface Multiphase Fluid and Heat Flow

TOUGH2 is a widely used reservoir simulator for solving subsurface flow related problems such as nuclear waste geologic isolation, environmental remediation of soil and groundwater contamination, and geothermal reservoir engineering. It solves a set of coupled mass and energy balance equations using a finite volume method. This contribution presents the design and analysis of a parallel version of TOUGH2. The parallel implementation first partitions the unstructured computational domain. For each time step, a set of coupled non-linear equations is solved with Newton iteration. In each Newton step, a Jacobian matrix is calculated and an ill-conditioned non-symmetric linear system is solved using a preconditioned iterative solver. Communication is required for convergence tests and data exchange across partitioning borders. Parallel performance results on Cray T3E-900 are presented for two real application problems arising in the Yucca Mountain nuclear waste site study. The execution time is reduced from 7504 seconds on two processors to 126 seconds on 128 processors for a 2D problem involving 52,752 equations. For a larger 3D problem with 293,928 equations the time decreases from 10,055 seconds on 16 processors to 329 seconds on 512 processors.     

MEMS光开关研究

光开关是光通信网络的重要功能器件,MEMS光开关是最具发展前景的光开关之一.在简介不同种类光开关原理特点的基础上,详细分析了当前主要的MEMS光开关的分类、结构、工艺与性能特点,并给出这一领域的研究与发展状况.     

光开关产品市场研究

研究一种基于继电器式透射形机械式光开关,这种光开关除了具备常规机械式结构简单、指标优良等特点外,还具有结构紧凑、便于集成安装的特点。介绍光网络和无源光器件的现状和关键技术,描绘光开关器件使用的背景和环境。描述一些主要光开关器件的技术特点。并重点解析机械式光开关的技术特定、反射式光开关和透射式光开关的技术对比等。     

Real-Time Stabilization of an Eight-Rotor UAV Using Optical Flow

An original configuration of a small aerial vehicle having eight rotors is presented. Four rotors are devoted to the stabilization of the orientation of the helicopter, and the other four are used to drive the lateral displacements. A precompensation on the roll and pitch angles has been introduced so that the attitude dynamics is practically independent of the translational dynamics. This compensation is directly related to the velocity of the lateral motors. The dynamical model is obtained using the Euler–Lagrange approach. The proposed configuration is particularly useful for image processing since the the camera orientation is held constant. The eight-rotor rotorcraft is simpler to pilot than other rotorcrafts. A control strategy is proposed that uses the optical flow measurements to achieve a hover flight that is robust with respect to perturbations like wind. The new aerial configuration and control strategy have been tested in real-time experiments.      

以太网交换控制电路流量控制研究与实现

针对以太网交换控制电路帧丢失问题，研究了以太网交换的流量控制技术，在以太网交换控制电路设计中采用了流量控制机制，实现了基于数据缓冲策略的流量控制功能，解决了数据缓冲区可用容量不足造成的数据帧丢失问题。     

智能光网络及其发展方向

本文介绍了智能光网络的产生、分层体系结构及其研究进展。     

环网中的维度气泡流控与自适应路由算法

介绍了一个称为环网维度气泡流控(TDBFC)的新型流控策略和称为环网维度气泡路由(TADBR)算法的新型自适应路由算法.在Bubble流控和DBFC流控的基础上设计了适合于环网的维度气泡流控.在环网中,如果采用TDBFC流控策略,设计的TADBR自适应路由算法可实现无死锁的最短距离的路由.对于以上结论,提供了详细的证明.最后,介绍了自行设计的模拟工具RingNetSim,该模拟器实现了TDBFC流控策略和TADBR算法.在RingNetSim上分析了TADBR算法的性能,结果显示环网维度气泡路由算法拥有较好的性能.     

Torus网络中移动气泡流控及其自适应路由实现

在torus网络中气泡流控是一种有效、实用的死锁避免技术.关键气泡机制使用虚跨步技术,只需要使用一个报文缓冲区就可以避免torus网络中的环内死锁,但是可能存在阻塞.首先提出了伪报文协议,然后结合伪报文协议设计了移动气泡流控策略,克服了关键气泡不能移动时引起的阻塞.伪报文协议基于简单的请求-应答,移动气泡流控则使用传统的信用传输方法.采用该机制,路由器只需要最少两条虚通道,每条虚通道最少一个报文空间就可以实现无死锁完全自适应路由.通过对经典路由器进行适当修改,给出了实现移动气泡流控的方法.采用模拟器比较了各种气泡流控的性能,结果表明,移动气泡流控性能超出传统的气泡机制,而加入自适应机制后的性能明显高于其他非自适应方法,不仅降低了延迟,吞吐率也提高20%以上,最大幅度甚至达100%.     

Variational-Bayes Optical Flow

The Horn-Schunck (HS) optical flow method is widely employed to initialize many motion estimation algorithms. In this work, a variational Bayesian approach of the HS method is presented, where the motion vectors are considered to be spatially varying Student’s t-distributed unobserved random variables, i.e., the prior is a multivariate Student’s t-distribution, while the only observations available is the temporal and spatial image difference. The proposed model takes into account the residual resulting from the linearization of the brightness constancy constraint by Taylor series approximation, which is also assumed to be a spatially varying Student’s t-distributed observation noise. To infer the model variables and parameters we recur to variational inference methodology leading to an expectation-maximization (EM) framework with update equations analogous to the Horn-Schunck approach. This is accomplished in a principled probabilistic framework where all of the model parameters are estimated automatically from the data. Experimental results show the improvement obtained by the proposed model which may substitute the standard algorithm in the initialization of more sophisticated optical flow schemes.     

Optical Flow Rendering

This paper proposes a new approach to image-based rendering that generates an image viewed from an arbitrary camera position and orientation by rendering optical flows extracted from reference images. To derive valid optical flows, we develop an analysis technique that improves the quality of stereo matching. Without using any special equipments such as range cameras, this technique constructs reliable optical flows from a sequence of matching results between reference images. We also derive validity conditions of optical flows and show that the obtained flows satisfy those conditions. Since environment geometry is inferred from the optical flows, we are able to generate more accurate images with this additional geometric information. Our approach makes it possible to combine an image rendered from optical flows with an image generated by a conventional rendering technique through a simple Z-buffer algorithm.     

Exploiting Discontinuities in Optical Flow

Most optical flow estimation techniques have substantial difficulties dealing with flow discontinuities. Methods which simultaneously detect flow boundaries and use the detected boundaries to aid in flow estimation can produce significantly improved results. Current approaches to implementing these methods still have important limitations, however. We demonstrate three such problems: errors due to the mixture of image properties across boundaries, an intrinsic ambiguity in boundary location when only short sequences are considered, and difficulties insuring that the motion of a boundary aids in flow estimation for the surface to which it is attached without corrupting the flow estimates for the occluded surface on the other side. The first problem can be fixed by basing flow estimation only on image changes at edges. The second requires an analysis of longer time intervals. The third can be aided by using a boundary detection mechanism which classifies the sides of boundaries as occluding and occluded at the same time as the boundaries are detected.     

FPGA在光开关模块控制电路中的应用

基于光开关在光传输交换中所起的重要作用,本文简要介绍光开关驱动电路的硬件连接,重点阐述光开关工作时序的FPGA实现方法。     

不同错开位置锯齿翅片热力特性的三维仿真

对通道壁面沿流动方向周期性地错开而在横向上通道壁面有几组不同错开位置的强化换热翅片的层流流动和传热情况进行了三维仿真分析。这类翅片经常被应用在汽车和电子设备的冷却系统中。三维有限元方法用来模拟Re数在100-1500范围时翅片的速度场和温度场，考虑了通道壁面的不同错开位置(SSP)对翅片传热性能的影响。仿真结果与以前的试验数据也进行了比较研究。     

Over-Parameterized Variational Optical Flow

A novel optical flow estimation process based on a spatio-temporal model with varying coefficients multiplying a set of basis functions at each pixel is introduced. Previous optical flow estimation methodologies did not use such an over parameterized representation of the flow field as the problem is ill-posed even without introducing any additional parameters: Neighborhood based methods of the Lucas–Kanade type determine the flow at each pixel by constraining the flow to be described by a few parameters in small neighborhoods. Modern variational methods represent the optic flow directly via the flow field components at each pixel. The benefit of over-parametrization becomes evident in the smoothness term, which instead of directly penalizing for changes in the optic flow, accumulates a cost of deviating from the assumed optic flow model. Our proposed method is very general and the classical variational optical flow techniques are special cases of it, when used in conjunction with constant basis functions. Experimental results with the novel flow estimation process yield significant improvements with respect to the best results published so far.     

光纤流量传感器

讨论了典型光纤流量传感器结构及原理,介绍了实际测试系统实验方案。     

Communication Models for a Free-Space Optical Cross-Connect Switch

We design and analyze communication algorithms for an optical switch based on the electroholographic effect, that provides capabilities for configuration changes and a limited multicast. As configuration changes incur a high overhead, we suggest the use of a high-speed forwarding unit as part of the network interface. We develop broadcast algorithms that trade off the number of configuration changes and forwarding operations in order to achieve the minimal completion time. For general point- to-point communication, we use the limited multicast to create a spanning topology along which messages can be forwarded. This requires care to avoid collisions, but is still preferable to using configuration changes if the topology is rich enough but still has a low degree.