善待科技

时值今日,人类文明正一步一步演变得日益发达,人类社会在不断进步,作为推动社会发展的最活跃、最具活力的因素--科学技术,其本身也在努力交织、渗透、完善。以相对论、量子论、DNA双螺旋结构的发现、计算机与互联网的发明为标志的科学技术革命,为现代世界的发展构建了崭新的科学技术基础。迈入21世纪,以物质科学、生命科学和信息科学为先导的科学技术的迅速发展,正在带动一个世纪的科学技术的持续进步,同时也在不断促进经济繁荣和人类文明的变革,实现人类的未来之梦。当我们在为科学技术的成就而欢欣的同时,却不得不遗憾地看到当今科学技…     

IS γα≤δ FOR GRAPHS WHICH HAVE DIAMETER TWO?

A subset of S of the vertex set of a graph G is called acyclic if the subgraph it induces in G contains no cycles. S is called an acyclic dominating set of G if it. is both acyclic and dominating. The minimum cardinality of an acyclic dominating set, denoted by 7a(G), is called the acyclic domination number of G. S. M. Hedetniemi et al. on 2000 introduced the concept of acyclic domination and posed the following open problem: Is -ya(G) < <5(G) for any graph whose diameter is two? In this paper, we give a counterexample which disproves the problem.     

FROM MANUFACTURING SCHEDULING TO SUPPLY CHAIN COORDINATION：THE CONTROL OF COMPLEXITY AND UNCERTAINTY

With time-based competition and rapid technology advancements, effective manufacturingscheduling and supply chain coordination are critical to quickly respond to changing marketconditions. These problems, however, are difficult in view of inherent complexity and variousuncertainties involved. Based on a series of results by the authors, decomposition and coordination byusing Lagrangian relaxation is identified in this paper as an effective way to control complexity anduncertainty.A manufacturing scheduling problem is first formulated within the job shop context withuncertain order arrivals, processing times, due dates, and part priorities as a separable optimizationproblem. A solution methodology that combines Lagrangian relaxation, stochastic dynamicprogramming, and heuristics is developed. Method improvements to effectively solve large problemsare also highlighted. To extend manufacturing scheduling within a factory to coordinate autonomicmembers across chains of suppliers, a decentralized supply chai     

保护好我们的家园

有一首老歌曾这样赞美我们的家园:蓝蓝的天上白云飘,白云下面马儿跑,挥动着鞭儿响四方,百鸟任飞翔……然而,不知从什么时候开始,我们头顶的天空不再蔚蓝,变成了沉重的灰色,更难得见鸟儿飞翔;广袤肥沃的土地不再松软,变得越来越板结,甚至荒芜;河里的流水不再清澈,变得越来越浑浊,而且动辄大发脾气,冲走人们的财物,夺去人们的生命;古老的森林一天天萎缩,而沙漠却一天天扩大,一步步向我们逼近……去冬今春突如其来的SARS,更是让我们人类付出了数百条生命和几百亿金钱的沉重代价。毫无疑问,这都是我们人类目光短浅、一味追求享受造成的恶果。…     

Radar Imaging Based on Iterative Algorithms

It has long been realized that the problem of radar imaging is a special case of image reconstruction in which the data are incomplete and noisy. In other fields, iterative reconstruction algorithms have been used successfully to improve the image quality. This paper studies the application of iterative algorithms in radar imaging. A discrete model is first derived, and the iterative algorithms are then adapted to radar imaging. Although such algorithms are usually time consuming, this paper shows that, if the algorithms are appropriately simplified, it is possible to realize them even in real time. The efficiency of iterative algorithms is shown through computer simulations.     

Abnormal dielectric characteristics of PMN-32%PT single crystal under dc bias

It has been reported that the single crystal of relaxor ferroelectrics (1-x)Pb(Mg1/3Nb2/3)O3-xPbTiO3 (PMN-xPT) with the compositions near the morphotropic phase boundary (MPB, 0.28相似文献   

Researching on quadrature conversion structures For an UWB demonstrative receiver

1. INTRODUCTION As the development of technologies of digital signal processing and integrated circuits, the structure of wireless communication system has been improved. Many schemes for software defined radio (SDR) systems have been developed since 1995, and they can be divided into five tiers of solutions according to their developing history and their definitions[1]. The five tiers are conventional hardware-implemented scheme; software-controlled radio scheme; SDR, that implements m…     

建筑节能:安全与环保新概念

安得广厦千万间,大庇天下寒士俱欢颜。杜甫忧国忧民的诗感染了几代代人。而今,杜甫的梦想早已成为现实,神州大地一座座高楼大厦拔地而起,国民告别了严寒,拥有了温馨的家。然而,也许大家未想到,我国建筑能耗十分惊人,建造和使用建筑直接、间接消耗的能源占全社会总能源的46.7%,也就是说,我国全社会总能耗的近一半被建筑“吞噬”。人们在充分享受现代文明的同时,现代建筑对社会造成了沉重的能源负担和严重的环境污染,已成为制约我国可持续发展的突出问题之一。     

投稿须知

1稿件形式及篇幅1.1研究论文:报道学术价值显著、实验数据完整、具有原始性和创造性的研究成果,全文一般不超过8000字。1.2综述文章:对当前有关学科领域的研究热点和前沿问题进行总结、概括和评价,全文一般不超过6000字。1.3卷首寄语:仅接受院士就某一科技问题、现象、事件等发表的个人见解、意见、希望等寄语性文章,全文要求控制在1300~1500字之间。1.4科技动态:简要并迅速报道有关学科领域发展动向及最新研究成果,全文一般不超过1000字。1.5图书评论:仅接受新近出版的理工类学术专著、高校教材以及高级科普类图书评论,全文要求控制在1500~…     

Self-assembling Characteristics of Amphiphilic Star Block Copolymers with a Polyelectrolyte Shell

1 Results Amphiphilic block copolymers are capable of forming supramolecular assemblies resembling those observed in nature,such as spherical micelles,worm micelles,and vesicles.Changing the solvent composition,ionic strength or pH of the polymer solution may induce the self-assembly of block copolymers or trigger the transition between the geometries of noncovalent assemblies.In the current work,we have synthesised starlike amphiphilic block copolymers having hydrophobic poly(methyl methacrylate),PMMA,core,and hydrophilic poly(acrylic acid),PAA,shell.The self-assembling characteristics of these polymers have been investigated in aqueous solutions by light scattering and direct visualisation by cryo-transmission electron microscopy (cryoTEM)[1]. Computer simulations along with the theoretical predictions made for the star-like system based on mean-field theory have been used to support the experimental observations[2]. The association of the starlike macromolecules resembles that of charged biopolymers,such as actin,since a balance between attractive and repulsive forces is required for the formation of cylindrical assemblies and can be manipulated by changing the pH or the ionic strength of the solvent[3].