Landweber iterative regularization for nearfield acoustic holography

In the past twenty years, nearfield acoustic holography (NAH) has become an efficient tool for noise source identification, noise source localization and acoustic field visualization. By measuring the complex pressure or particle velocity on a hologram su…     

An event-related potential study of working memory in children

Working memory refers to temporary storage and manipulation of “on-line” information in the brain,which is central to a large range of cognitive capabili- ties[1]. Visual working memory involves processes such as maintaining, updating and manipulating b…     

ESeal Calculus: A secure mobile calculus

0　IntroductionAdvancesincomputercommunicationsandcomputerhard warearechangingthelandscapeofcomputation .Mobilecomputationisnowpervasive .Theπ calculus[1 ] isatypicalcalcu lusofmobilecomputation .Manyworksextenditinmanyas pects.Forexample ,Ref.[2 ,3]extendthebasictypesystemsforπ calculusasgivingmoreinformativetypestoprocesses.YoshidaandHennessyproposeinRef.[4 ]atypesystemforahigher orderπ calculusthatcanbeusedtocontroltheeffectsofmigratingcodeonlocalenvironments.Thesealcalculus[5] canber…     

Unravelling angiosperm genome evolution by phylogenetic analysis of chromosomal duplication events

Conservation of gene order in vertebrates is evident after hundreds of millions of years of divergence, but comparisons of the Arabidopsis thaliana sequence to partial gene orders of other angiosperms (flowering plants) sharing common ancestry approximately 170-235 million years ago yield conflicting results. This difference may be largely due to the propensity of angiosperms to undergo chromosomal duplication ('polyploidization') and subsequent gene loss ('diploidization'); these evolutionary mechanisms have profound consequences for comparative biology. Here we integrate a phylogenetic approach (relating chromosomal duplications to the tree of life) with a genomic approach (mitigating information lost to diploidization) to show that a genome-wide duplication post-dates the divergence of Arabidopsis from most dicots. We also show that an inferred ancestral gene order for Arabidopsis reveals more synteny with other dicots (exemplified by cotton), and that additional, more ancient duplication events affect more distant taxonomic comparisons. By using partial sequence data for many diverse taxa to better relate the evolutionary history of completely sequenced genomes to the tree of life, we foster comparative approaches to the study of genome organization, consequences of polyploidy, and the molecular basis of quantitative traits.     

LETTER TO CSB

From new experiments in our laboratory, we found out thatwe need to make the following corrections in one of our paperspublished in your journal, namely, Novel method for accuratedetermination of the orientational angle of interfacial chemicalgroups, by Lǖ Rong, Gan Wei and Wang Hongfei, Chin. Sci.Bull., 2003, 48(20): 2183—2187.     

三阶线性方程的稳定性

本文对三阶变系数线性方程,在比较一般的条件下,用变换技巧和李雅普诺夫函数方法,研究了它的稳定性问题,得到了一些充分性准则,并对其适用范围作了若干讨论。     

铈盐引发丙烯酰胺在棉纤维上接枝共聚合反应研究

采用铈盐－棉氧化还原体系引发丙烯酰胺在天然纤维素纤维上接枝共聚，探讨了酸预自理和接枝反应条件对产物平衡接枝率的影响及接枝共聚机理。ＩＲ表征产物具有预期的结构。     

Fluorite Ce0.8Sm0.2O2-δ porous layer coating to enhance the oxygen permeation behavior of a BaCo0.7Fe0.2Nb0.1O3-δ mixed conductor

Fluorite Ce_0.8Sm_0.2O_2-δ (SDC) nanopowder with a crystallite size of 15 nm was synthesized by a co-precipitation method. An SDC porous layer was coated onto a BaCo_0.7Fe_0.2Nb_0.1O_3-δ (BCFN) mixed conductor to improve its oxygen transport behavior. The results show that the SDC-coated BCFN membrane exhibits a remarkably higher oxygen permeation flux (J_O2) than the uncoated BCFN in the partial oxidation of coke oven gas (COG). The maximum (J_O2) value of the SDC-coated BCFN is 18.28 mL·min-1·cm-2 under a COG/air flux of 177 mL·min-1/353 mL·min-1 at 875℃ when the thickness of the BCFN membrane is 1 mm; this (J_O2) value is 23% higher than that of the uncoated BCFN membrane. This enhancement is likely because of the higher oxygen ionic conductivity of SDC, which supplies oxygen vacancies and accelerates oxygen exchange on the membrane/coating layer/gas three-phase boundary.     

Path planning based on sliding window and variant A*algorithm for quadruped robot

In order to improve the adaptability of the quadruped robot in complex environments , a path planning method based on sliding window and variant A * algorithm for quadruped robot is presen-ted .To improve the path planning efficiency and robot security , an incremental A*search algorithm ( IA*) and the A*algorithm having obstacle grids extending ( EA*) are proposed respectively .The IA* algorithm firstly searches an optimal path based on A * algorithm, then a new route from the current path to the new goal projection is added to generate a suboptimum route incrementally .In comparison with traditional method solving path planning problem from scratch , the IA* enables the robot to plan path more efficiently .EA* extends the obstacle by means of increasing grid g-value, which makes the route far away from the obstacle and avoids blocking the narrow passage .To navi-gate the robot running smoothly , a quadratic B-spline interpolation is applied to smooth the path . Simulation results illustrate that the IA* algorithm can increase the re-planning efficiency more than 5 times and demonstrate the effectiveness of the EA * algorithm.