Genomics,metagenomics,and microbial oceanography—A sea of opportunities

Microbial oceanography is an emerging discipline resulted from the interaction,cross-fertilization and integration of life science and ocean science.Microbial oceanography integrates the principles of marine microbiology,microbial ecology and oceanography to study the role of microorganisms in the biogeochemical dynamics of natural marine ecosystems.The application of genomics tools to study marine microbes is resulting in rapid advancements in microbial oceanography that has important implications in globa...     

Microstructure/property relations in lath martensitic steels

Many of the high strength,high toughness steels in use or under development are alloy steels with dislocated lath martensitic structures.These microstructures are visually complex,and are difficult to categorize in the detail needed to clarify the structure-property relations.However,substantial progress has been made in recent years.In particular,it is now clear that the martensite block element sets the effective grain size that must be controlled to resist brittleness by cleavage fracture.In previous papers at this conference I have discussed the nature and importance of the block structure.In this study I discuss how the block size can be controlled by thermal treatments to achieve superior properties.     

刀具创新对提高金属切削效率的作用与影响

世界范围内激烈的市场竞争迫使机械制造业降低成本以保持盈利。由于加工成本的主要部分是占用机床时间的费用,因此目前人们的注意力集中在通过提高加工生产率以缩短加工周期。机床的改进,性能更优异的零件材料的开发,新的加工方法的开发以及涉及切削液安全处理的环保法规的制订等,都给刀具行业带来了新的挑战。为了回应这些挑战,刀具行业对各种刀具材料进行了卓有成效的创新。本文重点讨论刀具技术的进步对提高金属切削生产率所起的作用。     

面向气候变化的绿色雨水基础设施设计——来自欧洲北部的经验

【目的】世界各国城市都面临着众多可能因气候变化而加剧的水问题。【方法/过程】聚焦丹麦、英国、荷兰3个受气候变化（尤其是洪水）强烈影响的欧洲北部国家,重点分析4个不同空间尺度的绿色雨水基础设施（green stormwater infrastructure, GSI）项目。这些项目是应对未来城市自然灾害和宜居性挑战的韧性解决方案的典范。之所以选择这些项目,是因为它们具有独特的创新性：如将主要机动车交通走廊更新为宜居、可步行的街区,在区域尺度创建多功能GSI以提供社会福利,利用分层种植、密集种植和生态美学的力量来产生生态系统服务等。【结果/结论】除分析项目设计外,进一步讨论促成这些项目实施及提升的关键因素,以及建成后提升公众认同和环境社会效益的关键因素。这些因素包括：对宜居性的重视、将城市更新和气候适应相结合的设计方法、跨机构合作、多重资金来源的利用,以及以扎实的公众参与获得对城市气候适应举措的支持。     

Special issue on Networked sensing,decision-making and control

Networked sensing and control has attracted signi?cant interest in recent years due to its wide applications.For example,     

Regional differences in the effects of task difficulty and motor output on blood flow response in the human anterior cingulate cortex: a review of 107 PET activation studies

We reviewed 107 blood flow activation studies carried out with positron emission tomography and published between January 1993 and November 1996. These studies had reported their findings as peaks of significant difference in cerebral blood-flow (CBF) between two scans/tasks and had located the peaks in standardized stereotaxic space. We coded each task along several dimensions, including the type and rate of input and output, the types of cognitive processes, and the relative difficulty of tasks within a study. Based on this coding, a difference score (A-B) was calculated for each subtraction. Subsequently, the frequency distributions of the difference scores for subtractions yielding a peak in the anterior cingulate region (cingulate peak) were compared with those distributions obtained from subtractions without a cingulate peak (no cingulate-peak). The cingulate peak subtractions (n = 158) differed from the no cingulate peak subtractions (n = 229) in terms of difficulty level (p = 0.001) and the presence of a remote memory component (p = 0.01). Regional differences in the frequency distribution of certain task parameters, such as difficulty level, recent memory and the use of the hand for responding, were also observed when peaks found in the anterior cingulate cortex (ACC) were further classified as located in the rostral vs caudal ACC, supracallosal vs subcallosal ACC, and limbic vs paralimbic parts of the supracallosal ACC. We conclude that task difficulty plays a major role in modulating blood-flow response in the ACC, possibly interacting with other parameters such as the nature of the response and memory demands.     

AN OPERATOR-SPLITTING ALGORITHM FOR THREE-DIMEN-SIONAL CONVECTION-DIFFUSION PROBLEMS

An operator-splitting algorithm for the three-dimensional convection-diffusion equa-tion is presented.The flow region is discretized into tetrahedronal elements which are fixed in time.The transport equation is split into two successive initial value problems:a pure convection problemand a pure diffusion problem.For the pure convection problem,solutions are found by the method ofcharacteristiCS.The solution algorithm involves tracing the characteristic lines backwards in time froma vertex of an element to an interior point.A cubic polynomial is used to interpolate the concentrationand its derivatives within each element.For the diffusion problem,an explicit finite element algorithmis employed.Numerical examples are given which agree well with the analytical solutions.     

一种GaAs/GaAlAs分别限制单量子阱锁相列阵激光器

本文描述一种由MOCVD生长的GaAs/GaAlAs 分别限制单量子阱片子制作的锁相列阵大功率激光器.由十个单横模器件耦合而成的列阵器件,其阈值电流为67mA,线性输出功率大于500mW,微分量子效率达60％.列阵器件由强耦合区和弱耦合区构成,考察了强耦合区的几何结构对耦合模即输出远场分布的影响.     

GROWTH OF THERMOELASTIC MARTENSITE

The growth of thermoelastic martensite in a Cu-29% Zn-3% Al alloy has been investigatedexperimentally and theoretically.Metallographie observations showed that the growth oc-cured thermoelastically,i.e.reversibly,in the radial direction as well as in the thickening di-rection.This is not consistent with the theories of Conhen and some others.A model has beensuggested to explain the thermoelasticity of the growth.The basic idea is:the elastic straindistribution is highly heterogeneous and the growth is controlled by the local elastic strain en-ergy at the growth frontier area.The calculated results from the model based on Eshelby'stheory are consistent with the observations.     

镍粉压坯烧结后期显微组织演变的定量体视学研究

采用体视学方法系统地定量研究了纯镍粉末压坯烧结后期(V_v~s>0.90)显微组织的量度性和拓补性两类性质的变化规律,包括烧结前压制和提高压制压力对显微组织及其演变规律的影响。