Fabry-Perot microcavity modes observed in the micro-photoluminescence spectra of the single nanowire with InGaAs/GaAs heterostructure

We report on the fabrication of the nanowires with InGaAs/GaAs heterostructures on the GaAs(111) B substrate using selective-area metal organic vapor phase epitaxy. Fabry-Perot microcavity modes were observed in the nanowires with perfect end facets dispersed onto the silicon substrate and not observed in the free-standing nanowires. We find that the calculated group refractive indices only considering the material dispersion do not agree with the experimentally determined values although this method was used by some researchers. The calculated group refractive indices considering both the material dispersion and the waveguide dispersion agree with the experimentally determined values well. We also find that Fabry-Perot microcavity modes are not observable in the nanowires with the width less than about 180 nm, which is mainly caused by their poor reflectivity at the end facets due to their weak confinement to the optical field. (C) 2009 Optical Society of America

Magnetic field switching in parallel quantum dots

We show that the Coulomb blockade in parallel dots pierced by magnetic flux Phi completely blocks the resonant current for any value of Phi except for integer multiples of the flux quantum Phi(0). This non-analytic (switching) dependence of the current on Phi arises only when the dot states that carry the current are of the same energy. The time needed to reach the steady state, however, diverges when Phi -> n Phi(0). Copyright (C) EPLA, 2009

Evolution of mosaic structure in InN grown by metalorganic chemical vapor deposition

Mosaic structure in InN layers grown by metalorganic chemical vapor deposition at various temperatures has been investigated by X-ray diffraction (XRD). With a combination of Williamson-Hall measurement and fitting of twist angles, it was found that variation of growth temperature from 450 to 550 degrees C leads to the variation of the lateral coherence length, vertical coherence length, tilt and twist of mosaic blocks in InN films in a, respectively, monotonic way. In particular, mosaic tilt increases whereas mosaic twist decreases with elevating temperature. Atomic force microscopy shows the morphological difference of the InN nucleation layers grown at 450 and 550 degrees C. Different coalescence thickness and temperature-dependent in-plane rotation of InN nuclei are considered to account for the XRD results. (c) 2006 Elsevier B.V. All rights reserved.

Design and Verification of the Programming Circuit in an Application-Specific FPGA

In this paper we present a methodology and its implementation for the design and verification of programming circuit used in a family of application-specific FPGAs that share a common architecture. Each member of the family is different either in the types of functional blocks contained or in the number of blocks of each type. The parametrized design methodology is presented here to achieve this goal. Even though our focus is on the programming circuitry that provides the interface between the FPGA core circuit and the external programming hardware, the parametrized design method can be generalized to the design of entire chip for all members in the FPGA family. The method presented here covers the generation of the design RTL files and the support files for synthesis, place-and-route layout and simulations. The proposed method is proven to work smoothly within the complete chip design methodology. We will describe the implementation of this method to the design of the programming circuit in details including the design flow from the behavioral-level design to the final layout as well as the verification. Different package options and different programming modes are included in the description of the design. The circuit design implementation is based on SMIC 0.13-micron CMOS technology.

基于重叠分块的FM-index性能研究与分析

FM-index压缩查询方法结合压缩技术和索引技术,其最大优势是能够在不解开压缩文件的情况下对源文件进行查询。该文通过理论分析和详细的测试数据研究重叠分块对FM-index压缩查询性能的改善。对改进后的FM-index和压缩软件Winrar在压缩时间和文件占用空间上进行分析和比较,进一步证明了重叠分块对FM-index压缩查询性能的改善。

一种分块包标记的IP追踪方案

DDoS攻击以其高发性、高破坏力和难以防范的特点，近年来成为互联网的主要安全威胁之一．研究者们提出了多种对抗DDoS攻击的方法．：乓中，Savage等人提出的概率包标记方案以其易于实施、消耗资源小等优点，引起人们的重视．然而概率包标记方案存在两个明显缺陷：多攻击路径重构时的高误报率和高计算复杂度．在概率包标记的基础上，提出了一种分块包标记方案，该方案与概率包标记方案相比具有较低的误报率和较低的计算复杂度，因而具有更高的实际应用意义．

structuring and manipulating hand-drawn concept maps

Concept maps are an important tool to knowledge organization,representation, and sharing. Most current concept map tools do not provide full support for hand-drawn concept map creation and manipulation, largely due to the lack of methods to recognize hand-drawn concept maps. This paper proposes a structure recognition method. Our algorithm can extract node blocks and link blocks of a hand-drawn concept map by combining dynamic programming and graph partitioning and then build a concept-map structure by relating extracted nodes and links. We also introduce structure-based intelligent manipulation technique of hand-drawn concept maps. Evaluation shows that our method has high structure recognition accuracy in real time, and the intelligent manipulation technique is efficient and effective.

Wavelength multiplexing and tuning in nano-Ag/dielectric multilayers

Multicolored optical active planes have been fabricated with magnetron sputter method coupled with selective masking technique. The plane is multilayer structured with Ag nanoparticles and TiO2 thin layer as the building blocks. It was found that the formed multilayer can be readily wavelength multiplexed by simply overlapping several nano-Ag/TiO2 layered structures, each of which may have different surface plasmon resonance wavelength. Unlike high order multiple resonances of large particles each of the multiplexing wavelengths in such a system is separately tunable. Importantly, it reveals that modification of the TiO2 layer thickness generates a fine tuning of the resonance wavelength.

Wavelength multiplexing and tuning in nano-Ag/dielectric multilayers

Multicolored optical active planes have been fabricated with magnetron sputter method coupled with selective masking technique. The plane is multilayer structured with Ag nanoparticles and TiO2 thin layer as the building blocks. It was found that the formed multilayer can be readily wavelength multiplexed by simply overlapping several nano-Ag/TiO2 layered structures, each of which may have different surface plasmon resonance wavelength. Unlike high order multiple resonances of large particles each of the multiplexing wavelengths in such a system is separately tunable. Importantly, it reveals that modification of the TiO2 layer thickness generates a fine tuning of the resonance wavelength.

Low power design in 100 MHz embedded SRAM

Low power design method is used in a 100MHz embedded SRAM. The embedded SRAM used in a FFT chip is divided into 16 blocks. Two-level decoders are used and only one block can be selected at one time by tristate control circuits, while other blocks are set stand-by. The SRAM cell has been optimized and the cell area has been minimized at the same time.

基于基本块的控制流检错方法优化研究

系统的高可靠性是研究航空航天领域的一个重要指标. 由于太空环境的特殊性, 辐射和高能粒子会造成计算机系统的出现瞬时性错误, 这种错误被称作软错误, 它对航空航天器件造成了很大的影响, 严重降低系统的可靠性. 检测和防护这种软错误是航空航天系统中的重要研究方向之一. 软错误的检测和防护包括硬件防护与检错, 软硬件混合检错以及纯软件检错等. 随着商用器件的广泛使用, 与之相配合的各种软错误软件检错方法开始得到深入的研究, 在各种软件检错方法中, 控制流检测是抵御单粒子事件的有效手段之一.目前的主流方法是采用嵌入式签名技术, 但是该技术引入的检测指令过多, 导致程序效率低下. 本文从总结控制流检测技术的共同点出发, 分析该技术导致效率低下的原因：由于基本块定义的约束导致程序中基本块过多, 进而在代码注入过程中引入过多的判断及跳转指令, 导致程序效率低下. 本文针对这种情况, 提出了一种基于源代码分析的基本块规约的方法. 该方法通过修改基本块定义的约束, 使在新的基本块定义下每个基本块能够容纳更多的指令, 减少检测指令的注入, 提高效率；并且在新的基本块定义下, 原来的控制流检错方法仍可以不加修改的直接应用于新的基本块定义上. 该方法能在不修改benchmark源代码以及控制流检测方法的基础上, 选择合适的约束量重新划分基本块, 减少引入的检测指令. 本文中使用该方法以ECCA, CFCSS和RSCFC三个控制流检错方法作为验证对象, 使用这3种控制流检错方法, 在不同的约束量作用下, 对8个常见算法的benchmark进行了软错误覆盖率测试和效率测试. 多次实验数据表明, 该方法在提高检错算法效率的同时, 能够保持软错误检错的覆盖率基本不变. 在对控制流检错算法进行优化的同时, 本文还完成了相应的控制流分析工具, 基于模拟器的错误注入和代码片段执行时间检测工具等. 有效的对优化算法进行了评估和测试.