对现代足球比赛进球策略分析

通过对第12届欧洲杯、第18届世界杯足球赛的224个进球的发动方式、进球成功率、进球前传球次数的分析,证实抢断球、任意球、点球、角球、界外球、球门球是现代足球进球的主要发动方式,进一步验证了查理.休斯的进球前传球次数越少,进球机率就越大的理论,并对“直接打法”提出新的观点和看法.     

A heat-driven thermoacoustic cryocooler capable of reaching below liquid hydrogen temperature

A "double-gas acoustic amplifier" is introduced to couple a thermoacoustic heat engine and a two-stage pulse tube cooler in this paper. Compared with previous acoustic amplifiers, this new acoustic amplifier maintains the function of amplification for pressure amplitude. In particular, the novel acoustic amplifier with a reservoir makes it possible to install an acoustic transparent but gas blocking elastic membrane between the engine and the cooler. Thus, the engine can use nitrogen as the working gas to work at low frequency; and meanwhile, the cooler can still use helium as the working gas to maintain its high performance. With this new amplifier, the cooling temperature of a two-stage pulse tube cooler driven by an energy-focused thermoacoustic engine reached 18.7 K.     

试论国外施工风险管理及对策

在集团公司“走出去”战略的指导下，施工企业积极开拓国外市场，承揽了多个施工项目。如何在复杂多变的国际市场中防范和控制工程施工风险是每个施工企业非常关注的问题。文章重点就国外施工的常见风险及应对策略做了概述。     

Morphology and contact mechanics influence adhesive characteristics of Dung Beetle’s bristle and Gecko’s setae

Geckos (Gekko gecko) use their hairy setae to adhere on various solid surfaces and dung beetles (Copris ochus Motschulsky) use their hairy bristles to anti-adhere in sticky environments. We study why two hairy systems express a conflict in functions by using SEM, histological approaches and functional experiments. Adhesion models and various parameters were collected and analyzed. Based on the morphological data and functional experimental results carried out by natural and denatured gecko setae and beetle bristles, we first demonstrated that the stiffness along the hair is 1000 to 30000 times that perpendicular to the hair. This stiffness difference is the key factor leading to the two hairy systems’ functional differences. Slope of gecko setae reduces contact stiffness, increases contact points and real contact area that results in amazing adhesive abilities. On the other hand, stiff bristles in a beetle have higher contact stiffness, which reduces the real contact area and decreases the adhesion between two contact surfaces. Deformation of gecko setae destroys the hierarchical structure, increases the contact stiffness and results in a decrease of adhesion forces. Similarly, deformation of beetle bristles destroys the erect structure of the hair, interconnects the separated bristles and thus decreases the anti-adhesive functions. These observations inspire us in designing anti-adhesive and adhesive biomimetic systems.     

Water-vapor source shift of Xinjiang region during the recent twenty years

The aim of this paper is to investigate the climate water-vapor sources of Xinjiang region and their shifts during the past 20 years. First, the principle and steps are roughly regulated to seek the water-vapor sources. Second, the climate stationary water-vapor transport in troposphere is calculated to distinguish where the water vapor comes from by ERA-40 reanalysis. In addition, the collocation between the transport and the atmospheric column water vapor content is analyzed. The results show that the major vapor comes from the west side of Xinjiang for mid-month of seasons, apart from July while the water vapor comes from the north or northwest direction. The water vapor sources are different for different seasons, for example, the Caspian Sea and Mediterranean are the sources in January and April, the North Atlantic and the Arctic sea in July, and the Black Sea and Caspian Sea in October, respectively. In recent ten years more water vapor above Xinjiang comes from the high latitudes and the Arctic sea with global warming, and less from Mediterranean in comparison with the case of 1973—1986. In fact, the air over subtropics becomes dry and the anomalous water vapor transport direction turns to west or southwest during 1987—2000. By contrast, the air over middle and high latitudes is warmer and wetter than 14 years ago.     

Sinorhizobium meliloti nifA gene exerts a pleiotropic effect on nodulation through the enhanced plant defense response

Sinorhizobium meliloti nifA gene is required for the expression of a bunch of nif and fix genes. Here, we report its pleiotropic effects on the nodule formation. Compared with wild type strain, nifA mutant sig- nificantly reduced nodule suppression rate in split-root system. The plants inoculated with mutant strain produced lower amount of daidzein and less necrotic cells on their roots. In addition, the defense genes failed to be evoked by nifA mutant at the early nodulation stage. These findings indicated that host defense response was one of the mechanisms mediated by nifA gene to regulate nodule formation during symbiosis. Even though nifA mutant could increase the number of nodules in host plant, it synthesized lower Nod factors than wild type. This suggested that nifA gene mediated multiple and diverse instances in nodulation formation.     

集艺术与科学于一身的巨人--纪念达·芬奇诞辰55O周年

2002年4月15日,是意大利文艺复兴先驱列奥那多·达·芬奇(Leonardo da Vinci)①诞辰550周年纪念日,中国中央电视台此前所做的街头随机采访显示,多数人知道达·芬奇是一位著名画家,对名画<蒙娜丽莎>、<最后的晚餐>有较深的印象;有些中小学生从课外读物中还知道少年达·芬奇刻苦画蛋等故事.不过,从采访中看到,许多人除达·芬奇的艺术作品和逸闻趣事外,对达·芬奇在科学和工程技术方面的成就了解得很少,也有人甚至对达·芬奇的名字全然陌生.     

推广的遗忘因子递推最小二乘算法在GPS中的应用

作者将推广的遗忘因子递推最小二乘算法应用到GPS以确定动态目标的轨迹，并与推广的Kalman滤波进行比较，发现两种算法在GPS中具有各自的优点，当噪声相关性较大又不能准确地得到其方差时，推广的遗忘因子递推最小二乘算法好于推广的Kalman滤波算法。     

含ZrO2硅溶胶制备及烧成性能的研究

研究含ZrO2硅溶胶的制备工艺，胶凝条件，溶胶的热性能和烧成。通过X射线衍射分析证实，恰当地控制工艺条件可以使含ZrO2硅溶胶仅析出ZrO2晶体，而不析出SiO2晶体和ZrSiO4晶体。通过SEM观察分析，烧成工艺制度不仅决定那种晶体析出，而且对析出晶体的显效结构和晶体形貌影响很大。对使用含ZrO4硅溶胶增韧石英玻璃陶瓷有非常重要意义。     

用PB实现基于TCP/IP协议的通信设计方法

针对当前国际流行的TCP／IP网络协议，阐述了基于此的网络通信机制，根据目前PC机上主流操作系统提供的网络通信接口－－WinSock，描述了用PB实现基于TCP／IP协议的网络通信的设计方法和编程原理。