Biosequence Similarity Search on the <Emphasis Type="BoldItalic">Mercury</Emphasis> System

Biosequence similarity search is an important application in modern molecular biology. Search algorithms aim to identify sets of sequences whose extensional similarity suggests a common evolutionary origin or function. The most widely used similarity search tool for biosequences is BLAST, a program designed to compare query sequences to a database. Here, we present the design of BLASTN, the version of BLAST that searches DNA sequences, on the Mercury system, an architecture that supports high-volume, high-throughput data movement off a data store and into reconfigurable hardware. An important component of application deployment on the Mercury system is the functional decomposition of the application onto both the reconfigurable hardware and the traditional processor. Both the Mercury BLASTN application design and its performance analysis are described.     

Characterization of AlxInyGa1−x−yN quaternary alloys grown on sapphire substrates by molecular-beam epitaxy

High-resolution X-ray diffraction (HR-XRD) with rocking curve, atomic force microscopy (AFM) and photoluminescence (PL) spectroscopy have been performed on high-quality quaternary Al_xIn_yGa_1−x−yN thin films at room temperature. The Al_xIn_yGa_1−x−yN films were grown on c-plane (0 0 0 1) sapphire substrates with AlN as buffer layers using a molecular beam epitaxy (MBE) technique with aluminum (Al) mole fractions x ranging from 0.0 to 0.2 and constant indium (In) mole fraction y=0.1. HR-XRD measurements confirmed the high crystalline quality of these alloys without any phase separation. The X-ray rocking curve of Al_xIn_yGa_1−x−yN films typically shows full widths at half maximum (FWHM) intensity between 14.4 and 28.8 arcmin. AFM measurements revealed a two-dimensional (2D) growth mode with a smooth surface morphology of quaternary epilayers. PL spectra exhibited both an enhancement of the integrated intensity and an increasing blueshift with increased Al content with reference to the ternary sample In_0.1Ga_0.90N. Both effects arise from Al-enhanced exciton localization. PL was used to determine the behavior of the energy band gap of the quaternary films, which was found to increase with increasing Al composition from 0.05 to 0.2. This trend is expected since the incorporation of Al increases the energy band gap of ternary In_0.1Ga_0.90N (3.004 eV). We have also investigated the bowing parameter for the variation of energy band gaps and found it to be very sensitive on the Al composition. A value of b=10.4 has been obtained for our quaternary Al_xIn_yGa_1−x−yN alloys.     

Characterizations of InxAlyGa1−x−yN alloy systems grown on GaN substrates by molecular-beam epitaxy

In_0.05Al_0.10Ga_0.85N epilayers and Al_0.10Ga_0.90N epilayers have been grown on bulk GaN single crystals and GaN templates by radio-frequency (RF) molecular-beam epitaxy (MBE). Photoluminescence (PL) spectra at different temperatures ranged from 8 to 300 K were measured for these epilayers. The decreasing rates of PL peak intensity of the In_0.05Al_0.10Ga_0.85N epilayers were smaller than those of the Al_0.10Ga_0.90N epilayers. The fluctuations of emission intensities were not observed in the In_0.05Al_0.10Ga_0.85N epilayers by cathodoluminescence observations at 77 K. Our results indicate that In-related effects exist in InAlGaN quaternary alloys on substrates with low-dislocation densities, however, expect that the localization effect related to In-segregation is weak.     

Influence of SiH4 on the WNx-PECVD process

Silane was added to an existing WN_x PECVD process in different flow ratios to the WF₆, to obtain higher thermal stability of the barrier in comparison to the WN_x. The deposition rate rises drastically with increased SiH₄/WF₆ ratios. The ternary compositions were investigated with regard to the sheet resistance and thickness. The X-ray diffraction (XRD) measurements of selected layers with low electrical resistivities in the as-deposited state show a broad amorphous peak like the WN_x barrier, indicating an amorphous structure. After characterising the as-deposited state of these samples, thermal treatments of the layers were performed at temperature of 600 °C for 1 h in vacuum.     

Effect of the Ge-molefraction on the subthreshold slope and leakage current of vertical Si/Si1−xGex MOSFETs

The effect of the Ge-concentration on the subthreshold behaviour of vertical Si/Si_1−xGe_x pMOSFETs and of complementary Si_1−xGe_x/Si nMOSFETs is investigated by using an analytical model, which includes thermionic emission across the hetero-barrier. It is shown that inclusion of Si_1−xGe_x and strained Si in the source region of the pMOSFET and nMOSFET respectively, suppresses the subthreshold slope roll-up substantially and lowers the leakage current of even the smallest devices with channel lengths down to 50 nm.     

Thin films of CoSi2 on Si1−yCy substrate layers

The reaction of Co with epitaxial Si_1−yC_y(001) films is investigated with regard to dependence on annealing temperature and C concentration y. Resistance measurements and RBS analysis reveal a small increase in the disilicide formation temperature. The electrical properties are very similar for thin CoSi₂ films grown at 650°C on Si_0.999C_0.001 and on Si. Whereas the CoSi₂ is fully polycrystalline on Si(001), partially oriented CoSi₂ has been observed on C-containing substrate layers. An increase of the number of epitaxially grown CoSi₂ crystallites has been observed with increasing C concentration.     

System Level Hardware/Software Partitioning Based on Simulated Annealing and Tabu Search

This paper presents two heuristics for automatic hardware/software partitioning of system level specifications. Partitioning is performed at the granularity of blocks, loops, subprograms, and processes with the objective of performance optimization with a limited hardware and software cost. We define the metric values for partitioning and develop a cost function that guides partitioning towards the desired objective. We consider minimization of communication cost and improvement of the overall parallelism as essential criteria during partitioning. Two heuristics for hardware/software partitioning, formulated as a graph partitioning problem, are presented: one based on simulated annealing and the other on tabu search. Results of extensive experiments, including real-life examples, show the clear superiority of the tabu search based algorithm.     

基于无人机定位搜索系统的研究

无人机具备无人员驾驶的优点,对野外搜救提供了有利条件。该文利用无线通信技术．配合无人机飞行平台,提出了无人机定位搜索系统的概念。搜索系统通过低功耗处理器MSP430F149和短距离无线传输芯片nRF905构建机载探测器和救援信标机的硬件平台,并通过制定搜索系统的无线通信协议．为快速地搜索地理位置信息并提供给管理部门提供了可能。     

基于平均交互信息量的DNA序列相似性分析

序列相似性分析是生物信息学中一个重要问题,对于研究物种的进化起源有着重要的意义。序列相似性算法包括基于序列比对的方法及非比对方法两种。基于比对的方法对于序列整体的衡量略有欠缺;非比对算法中有DNA曲线化方法以及比较序列各自整体碱基分布间的信息量差异的方法,只是考虑了序列整体信息间的差异,但未考虑序列各个位点间的差异。因此,提出了一种基于信息熵的相似性度量模型,把序列比对与信息量差异结合起来,将两条比对后的序列间的平均交互信息量与其联合熵之比作为两条序列的相似性度量。使用该度量构建了11个物种的相似性矩阵,对各物种间的相似性进行了分析,结果在一定程度上与生物分类学相契合。通过距离矩阵所构建的进化树,也反映了各物种间的进化关系,表明该模型的设计具有合理性。     

Melt growth and stoichiometry control of (Cd1−xZnx)1+yTe single crystals

Growth of (Cd_1−xZn_x)_1+yTe(CZT) single crystals is tried by a modified Bridgman method using a reservoir chamber containing Cd and Zn metals with a fixed mole ratio. The aim of this method is to obtain the single crystals with controlled deviation y from stoichiometry and homogeneous target composition x. A suitable growth condition was examined experimentally and the effectiveness of this method for controlling the deviation y from stoichiometry and the composition x is confirmed.     

Fabrication of strained Si channel PMOSFET on thin relaxed Si1−xGex virtual substrate

A novel MBE-grown method using low-temperature Si technology is introduced into the fabrication of strained Si channel PMOSFETs. The thickness of relaxed Si_1−xGe_x epitaxy layer on bulk silicon is reduced to approximate 400 nm (x=0.2). The Ge fraction and relaxation of Si_1−xGe_x film are confirmed by DCXRD (double crystal X-ray diffraction) and the DC characteristics of strined Si channel PMOSFET measured by HP 4155B indicate that hole mobility μ_p has an maximum enhancement of 25% compared to similarly processed bulk Si PMOSFET.     

On the InGaP/InxGa1−xAs pseudomorphic high electron-mobility transistors for high-temperature operations

The high-temperature characteristics of a novel InGaP/In_xGa_1−xAs pseudomorphic transistor with an inverted delta-doped channel are reported. Due to the presented wide-gap InGaP Schottky layer and the V-shaped In_xGa_1−xAs channel structure, the degradation of device performance with increasing the temperature is not so significant. Experimentally, for a 1×100 μm² device, the gate–drain voltages at a gate leakage current of 260 μA/mm and the maximum transconductances g_m,max are 30 (22.2) V and 201 (169) mS/mm at the temperature of 300 (450) K, respectively. Meanwhile, broad and flat drain current operation regimes for g_m, f_T and f_max are obtained.     

The effect of single-phonon and plasmon recombination on the lifetime in n-Hg1−xCdxTe with magnetically tuned bandgap

Theoretical investigations have predicted a great enhancement of electron-hole recombinations by adjusting the bandgap of narrow-gap semiconductors to the energy of elementary excitation in solids such as phonons or plasmons. Such an enhancement of the recombination rate of excess carriers is very important in constructing far-I.R. devices and might be used to generate high densities of LO-phonons and plasmons. We report experimental evidence of the influence of these recombination channels on the photoconductivity and the excess carrier lifetime in semimetallic n-Hg_1−xCd_xTe alloys, whose induced bandgap is magnetically tuned through the relevant energies of the elementary excitations. Both from a comparison of theoretically estimated lifetimes with Auger lifetimes and from experimental observations the new recombination channels prove to be very efficient and dominate the behaviour near their resonance with the band-gap.     

A Multi-Directional Search technique for image annotation propagation

Image annotation has attracted lots of attention due to its importance in image understanding and search areas. In this paper, we propose a novel Multi-Directional Search framework for semi-automatic annotation propagation. In this system, the user interacts with the system to provide example images and the corresponding annotations during the annotation propagation process. In each iteration, the example images are clustered and the corresponding annotations are propagated separately to each cluster: images in the local neighborhood are annotated. Furthermore, some of those images are returned to the user for further annotation. As the user marks more images, the annotation process goes into multiple directions in the feature space. The query movements can be treated as multiple path navigation. Each path could be further split based on the user’s input. In this manner, the system provides accurate annotation assistance to the user - images with the same semantic meaning but different visual characteristics can be handled effectively. From comprehensive experiments on Corel and U. of Washington image databases, the proposed technique shows accuracy and efficiency on annotating image databases.     

Influence of tellurium impurity on the Properties of Ga1?XInXAsYSb1?Y (X>0.22) solid solutions

The influence of tellurium impurity on the electrical properties of Ga_1−X In_XAs_YSb_1−Y (X=0.22 and X=0.24) solid solutions grown by liquid-phase epitaxy from lead-containing solution-melts was studied. Defect healing was shown to take place at low tellurium doping levels (X _Te ^L <2×10⁻⁵ at. %) in inhomogeneous highly compensated p-type solid solutions. Thus, it is possible to produce slightly compensated p-type materials with a low density of impurities and structural defects. High doping levels allow production of n-type materials with the electron density n=10¹⁷–10¹⁹ cm⁻³. Electroluminescence spectra of n-GaInAsSb/p-GaSb heterostructures are promising for the development of light-emitting diodes with a wavelength λ=2.0–2.5 μm. __________ Translated from Fizika i Tekhnika Poluprovodnikov, Vol. 36, No. 8, 2002, pp. 917–924. Original Russian Text Copyright ? 2002 by Voronina, Lagunova, Kunitsyna, Parkhomenko, Sipovskaya, Yakovlev.     

Recrystallization and dielectric properties of CaHfOx films on Si

The recrystallization and dielectric behavior for amorphous CaHfO_x films on Si substrates has been investigated. Upon conventional annealing in air, the CaHfO_x films remain amorphous up to an annealing temperature of 800 °C for annealing times of 1 h. This recrystallization temperature is significantly higher than that reported for HfO₂ subjected to rapid thermal annealing. Metal–insulator–semiconductor structures with Pt gate electrodes were fabricated with various CaHfO_x film thickness for capacitance–voltage and leakage current measurements. From this, the permittivity of CaHfO_x was determined, along with interface layer capacitance for films on Si. The enhanced stability against polycrystalline grain growth, along with the thermodynamic stability of both CaO and HfO₂ in contact with Si, suggests that CaHfO_x may be an attractive gate dielectric for future generation metal–oxide–semiconductor field-effect transistor applications.     

基于S系统和Patentics的联合检索

S系统是功能强大的检索系统,审查员习惯于利用S系统进行检索,但已无法应对不断增长的专利数据;Patentics是基于智能语义搜索技术的检索系统,其在分析现有技术、检索公知常识以及追踪检索方面具有其优势.Patentics是S系统的一种有益补充.在检索过程中应将S系统和Patentics的优势进行整合,以提高检索的效率.结合三个实际案例,介绍了基于S系统和Patentics的联合检索技巧,提供了新的检索思路.     

MIMO OFDM系统中小区搜索技术

本文在OFDMA技术研究的基础上,基于LTE基本帧结构,通过对小区搜索原理的详细分析,提出了OFDMA系统的小区搜索方案和实现流程,并且通过仿真给出了多天线模式下算法的仿真曲线和性能分析,验证了算法的可实现性.     

Dispersion characteristics of the Hm,n and Em,n modes in a multilayer metal-dielectric waveguide

Dispersion equations for the H _m,n and E _m,n modes in a three-layer metal-dielectric waveguide with odd and even field variations over the thickness of two basic layers are analyzed analytically and numerically. For the first time, the effects of interaction between even cophasal H _n ^s modes and antiphase H _n ^p modes in the double-thickness basic layer and the odd E _m ^s and E _m ^p modes in the single-thickness basic layer are found. The realizability of high-power microwave power dividers on the basis of the considered waveguides is shown.     

嵌入式系统中电子地图的路径寻优

最优路径算法是地理信息科学与计算机科学等领域的研究热点。由于嵌入式系统的特点,其中电子地图的最优路径规划算法,要求快速而高效,为此对一些最优路径搜索算法进行了分析,提出了用基于人工智能的A*算法对电子地图进行最优路径寻优,实现了准确而高效的最优路径搜索。最后给出了一个基于Linux嵌入式系统中的电子地图的路径寻优实例。