对大学英语四级统考题型改革的思考

本文分析了原四级统考题型的利与弊及题型改革的作用和意义，说明了采用新题型是积极和进步的，它对体现《大纲》精神，促进英语教学有积极的指导作用。     

考虑用户体验的动态共乘系统设计

动态共乘系统是一种新兴的智能出行系统,它通过实时动态地将司机和乘客进行匹配,达到有效整合路网运力资源、缓解交通拥堵和减少环境污染的目的.用户体验的优劣对动态共乘系统的可持续发展至关重要,传统的系统设计只重视运行效率,而忽略了用户心理.为此,本文引入实时反馈、优先权分配以及不动匹配对移除三大机制,提出了一个新的考虑用户体验的动态共乘系统.系统的决策过程分为三个阶段:1)建立基于优先权分配的最大权重双向图匹配模型,以确定当前最优匹配方案;2)基于实时反馈机制,将匹配结果告知出行者;3)基于不动匹配对和最晚出发时刻,进行方案评估.最后,通过数值算例将提出的动态共乘系统与传统系统进行了对比.结果表明,本文提出的系统可以大幅度缩短用户的等待时间,改善用户体验,同时有效地提高系统的运行效率.     

Temperature Control System for Biochemical Reactions in Microchip-Based Devices

IntroductionIn recent years,the development of miniaturizedsystems for chemical and biochemical reactions hasrapidly progressed[1] .Most of the microdevices forconducting these reactions are made of silicon orglass using conventional microfabrication methodsused in the microelectronic industry or bymodifying the processing technologies for microelectromechanical systems ( MEMS) . Severalresearch groups have developed polymerase chainreactions ( PCR) chips with various features toperform sim…     

福建福鼎银硐层控铅锌矿床成矿机制探讨

银碉矿区位于浙、闽、粤沿海中生代火山岩分布区中段。富含铅、锌的硅质灰岩为矿源层,对矿床形成提供了相当数量的铅锌。矿石矿物主要是闪锌矿、方铅矿、黄铁矿,伴生少量的黄锕矿、磁黄铁矿、毒砂及辉银矿。脉石矿物主要是石英、石榴石、方解石、绿泥石、硅灰石、透辉石、阳起石及萤石。矿体主要呈层状、似层状或透镜状产于典型地槽复理石建造中,它们严格受中石炭纪硅质灰岩控制。本矿的形成过程,起源于晚古生代冒地槽环境下,由同生沉积作用形成初步富集的含矿层(C_2)。在后期地质事件中,该初始富集的胚胎矿遭受到构造、岩浆及热卤水的作用,活化、转移改造成为现有的工业矿床。     

层状仿生生物活性人工软骨植入体的数字散斑相关分析

制备了一种仿生层状人工软骨/骨复合植入体,可将软骨植入体与宿主软骨的连接转变为骨-骨的界面结合,提高植入软骨固定效果.采用数字散斑等方法对仿生层状人工关节软骨/骨复合植入体的生物力学性能进行研究,比较了松质骨,PVA/骨复合体以及PVA-BG复合体在不同载荷作用下的位移变化,并从微观变形角度探讨了人工软骨/骨复合植入体中软骨层厚度对缓冲内部应力的作用.     

Inhibitory effect of the adenovirus type 5 E1A protein expressed in the yeast system on the human tumor cell growth

Adenovirus 5 type E1A as a tumor suppressor gene can inhibit tumor growth and enhance the sensitivity of chemotherapy and radiotherapy. E1A have the ability to integrate into the host genome, resulting in long-time expression that induces Rb gene inactivation and animal cells immortalization. This prompted us to select the E1A protein for treatment of cancer in order to overcome the limitations of E1A gene therapy. Thus, we firstly constructed E1A eucaryotic expression vector (pPIC9/E1A), transformated the pichia pastoris yeast cells (GS115) and screened the high-expressing recombinant strains. The positive yeast strains were cultured in the shake flask, and induced for 3 d. The crude E1A protein was purified using two steps of column chromatography on HiTrap Q and HiTrap SP. The purified E1A protein was identified by SDS-PAGE and Western blot. E1A protein was mostly located at cellular nuclear when Chariot delivered E1A protein into cells. The analysis in vitro indicated that the E1A protein arrested LN686 cell cycle at G2/M phase, and significantly inhibited the growth of LN686 tumor cells. The current studies firstly provided an experimental basis to further develop E1A protein for tumor treatment.     

AUTOMATED REASONING IN DIFFERENTIAL GEOMETRY AND MECHANICS USING THE CHARACTERISTIC METHOD Ⅳ. Bertrand Curves

This paper reports the study of properties of the curve pairs of the Bertrandtypes using our automated reasoning program based on Wu's method of mechanical the-orem proving for differential geometry. A complete list of results about Bertrand curvesin metric and affine spaces is derived mechanically. The list includes most of the knownresults of various Bertrand curves. We also derive some new results about Bertrand curves.     

THE PROPER PARAMETRIZATION OF A SPECIAL CLASS OF RATIONAL PARAMETRIC EQUATIONS

We give a proper reparametrization theorem for a set of rational parametric equationswhich is proper for all but one of its parameters.We also give an algorithm to determine whether aset of rational parametric equations belongs to this class,and if it does,we reparametrize it such thatthe new parametric equations are proper.