初析足球门前空中进攻技术

随着现代足球运动的发展,“全攻全守”已明显标有“立体战”色彩,对1978年第11届世界杯赛的25场比赛录像统计结果表明:在2354次突破防线进攻总数中有二分之一是以长传高吊球方式企图在守方门前创造射门得分机会,可见在高水平的角逐中门前争夺空中球的能力是何等重要。为了深入探讨门前空中争夺能力的具体内容,着重研究门前空中进攻技术的作用与特点,初步了解中国队运用这项技术的现状,特结合1980年广州国际足球邀请赛开展了专题调研,现将前六名队十场比赛共18队次的统计结果作如下综合与分析。一、统计的内容、概念与尺度根据本题研究的需要。

浅谈足球教学中“球感”练习的设计及原则

在足球训练中,以颠球、停球为例,提出了获得“球感”练习方法,并指出了练习中应注意的原则.

颠球技巧在足球技术教学中的作用

颠球技巧在国内外的运用根据我国有关史料的记载,颠球这种技巧在距今三千多年前就已出现了,如殷代的“足球舞”相传就是民间求神祈雨的一种仪式,人们一边跳舞,一边用脚颠球,可见我国古代劳动人民已经有用脚颠球的技巧。南美型足球是以其技术准确、熟练、细腻而闻名于世的。

足球的颠球及其训练

足球运动员有目的地运用规则允许的身体某一部位,对球做连续向上的轻击,使其始终保持在自己所能控制的空间中,这样的控球方法叫颠球。颠球是一种熟悉球性、提高控球能力的有球技术练习。足球运动员进行各式各样的颠球练习,有助于很快地掌握控制球的技术,而完美娴熟的控球,又是优秀运动员必须具备的技能。球王贝利曾说过:“对正在努力掌握各种技术的年轻选手来说。

排球运动

那是1895年的事,美国马萨诸塞州霍利约克城的一个名叫莫根的体育教练,发明了一种新的游戏:在长方形场地中间,拉上一张高约2米的网,网的两边各站几个人,用双手将篮球胆托来托去,不让它落地。因为这种游戏是把球在空中打来打去,所以人们叫它“击空中球”,中文译为“排球”。排球这种新的运动从此宣告诞生。 1945年8月5日,罗马尼亚发行了1套5枚体育附捐邮票。

头顶球

头顶球是一项重要的基本技术,它在比赛中运用比较广泛,用它可以进行传球、射门和断抢高球等。人们经常把足球运动员的头称之为“第三条腿”。头顶球在进攻与防守中都起着重要的作用,它是争夺空中球的有效手段,是快速直接射门的锐利武器,因此一个优秀的足球运动员应该熟练地掌握头顶球技术。

Salt-assisted Synthesis of Hollow Bi_2WO_6 Microspheres with Superior Photocatalytic Activity for NO Removal

Hollow Bi2WO6 microspheres are successfully synthesized by a facile ultrasonic spray pyrolysis（USP） method using NaCl as a salt template.The as-prepared hollow microspheres assembled as nanoplates with dimensions of approximately 41-148 nm and are dispersed with non-uniform pores on the template surface.By swapping the salt template with KC1 or Na2SO4,different morphologies of Bi2WO6 are obtained.The experimental results demonstrate that NaCl plays a key role on the formation of Bi2WO6 with hollow structures.The specific growth mechanism of hollow microspheres was studied in detail.The Bi2WO6 hollow microspheres exhibit an excellent photocatalytic efficiency for NO removal under solar light irradiation,which is 1.73 times higher than for the Bi2WO6 obtained in the absence of any salt template.This enhancement can be ascribed to the simultaneous improvement on the surface area and visible light-harvesting ability from the hollow structures.Electron spin resonance（ESR） results suggest that both radicals of ·OH and ·O2^- are involved in the photocatalytic process over the BWO-NaCl sample.The production of ·O2^- radicals offers better durability for NO removal.

α-MnO_2 nanoneedle-based hollow microspheres coated with Pd nanoparticles as a novel catalyst for rechargeable lithium-air batteries

The hollow α-MnO2 nanoneedle-based microspheres coated with Pd nanoparticles were reported as a novel catalyst for rechargeable lithium-air batteries. The hollow microspheres are composed ofα-MnO2 nanoneedles. Pd nanoparticles are deposited on the hollow microspheres through an aqueous-solution reduction of PdCl2 with NaBH4 at room temperature. The results of TEM, XRD, and EDS show that the Pd nanoparticles are coated on the surface ofα-MnO2 nanoneedles uniformly and the mass fraction of Pd in the Pd-coated α-MnO2 catalyst is about 8.88%. Compared with the counterpart of the hollow α-MnO2 catalyst, the hollow Pd-coated α-MnO2 catalyst improves the energy conversion efficiency and the charge-discharge cycling performance of the air electrode. The initial specific discharge capacity of an air electrode composed of Super P carbon and the as-prepared Pd-coatedα-MnO2 catalyst is 1220 mA＆#183;h/g （based on the total electrode mass） at a current density of 0.1 mA/cm2, and the capacity retention rate is about 47.3% after 13 charge-discharge cycles. The results of charge-discharge cycling tests demonstrate that this novel Pd-coatedα-MnO2 catalyst with a hierarchical core-shell structure is a promising catalyst for the lithium-air battery.

Size-controlled preparation of hollow silica spheres and glyphosate release

Different-sized hollow SiO2 spheres of 249–1348 nm in diameter were successfully prepared by using Na2SiO3 as the precursor and using polystyrene and polystyrene-methyl acrylic acid latexes as the templates. The diameter and shell thickness of the hollow SiO2 spheres increase with increasing the latex template diameter at a given mass ratio of SiO2 to latex template. The diameter and shell thickness of the hollow SiO2 spheres also increase with increasing the mass ratios of SiO2 to latex template. The presence of carboxylic acid groups on the surfaces of polystyrene-methyl acrylic acid latex templates favors the formation of dense and uniform SiO2 shells. The hollow SiO2 sphere is constructed by mesoporous shell with large specific surface area. When glyphosate is used as a release model chemical, glyphosate release rate is tuned by varying the shell thickness.

对两个物理实验的双语尝试

通过对两个有趣实验双语描述的尝试,旨在培养学生的实验兴趣,同时也为大家传递一种新的教改理念.

Simultaneous formation of a C/N-TiO_2 hollow photocatalyst with efficient photocatalytic performance and recyclability

Herein,we report a unique approach towards the preparation of C-modified and N-doped TiO2 hollow spheres(C/N-TiO2).TEM,SEM,and XPS analyses were used to confirm that the carbon and nitrogen co-decorated TiO2 photocatalyst was formed.Carbon-decoration improves the visible-light absorption and speeds up the separation of the photo-generated electron-hole pairs.C/N-TiO2 not only narrows the band gap of TiO2,but also exhibits excellent photocatalytic activity for the degradation of tetracycline and tetracycline hydrochloride.In addition,the C/N-TiO2 photocatalyst shows excellent recyclability for water decontamination,making it a promising candidate to purify aquatic contaminants.

Controllable preparation of hierarchical NiO hollow microspheres with high pseudo-capacitance

Nickel oxide(NiO)hollow microspheres with hierarchical structure were fabricated through a process consisting of a self-assembling,hydrothermal reaction and calcination.The prepared NiO hollow microspheres composed of many nanoflakes,are about 2-3μm in diameter.The length of the NiO flakes,having clear edges,is about 500-700 nm,while the thickness is only about 40-50 nm.This indicates that the NiO microspheres possess a hierarchical structure that can provide porous channels to facilitate the transmission of both electrons and electrolyte ions.NiO microspheres exhibit a high specific capacitance of about 1340 F/g at a current density of 1 A/g and high capacitance retention about 96.5%after 1000 cycles.What’s more,the conductive mechanism of nickel oxide for electrochemical capacitor electrodes was also studied.

Specific Heat of Hollow Nanosphere Coupled to Substrate： Quantum Size Effects

With the help of the elastic wave theory in the perturbed approximation the density-of-states for vibrational modes and the specific heat are studied for different hollow Si nanospheres, coupled with a semi-infinite substrate. We find that the modes of such coupled hollow spheres are significantly broadened and shifted toward low frequencies. The specific heat of the coupled hollow nanosphere is bigger than an isolated one due to the coupling interaction and quantum size effects. The predicted coupling and size enhancements on specific heat are probed in thermal experiments.

Precipitation Type Estimation and Validation in China

The results from three methods aimed at improving precipitation type （e.g., rain, sleet, and snow） estimation are presented and compared in this paper. The methods include the threshold air temperature （AT）, threshold wet bulb temperature （WBT） and Koistinen and Saltikoff （KSS） methods. Dot graphs are plotted to acquire the threshold air temperature or the threshold wet bulb temperature using daily averaged air temperature, wet bulb temperature and precipitation data at 643 stations from 1961 to 1979 （precipitation types are not labeled in the database from 1980 to present） in China. The results indicate that the threshold AT or WBT methods are not able to differentiate rain, sleet and snow in the most regions in China; sleet is difficult to differentiate from other precipitation types based on the two threshold methods. Therefore, one threshold AT and WBT method was used in this study to differentiate rain and snow. Based on Gaussian- Kriging interpolation of threshold air temperature （To） and wet bulb temperature （Tw）, the To and Tw contour lines and contour surfaces are calculated for China. Finally, a comparison between the KSS, AT and WBT methods are provided in which the KSS method is calculated based on air temperature and relative humidity. The results suggest that the KSS method is more appropriate for water phase estimation than are the other methods; the maximum precision for rain and snow is 99% and 94%, respectively. The AT method performs better than the WBT method when the critical air temperature is 2℃.

Thermal Anomalies and Earthquakes:Evidence from Wenchuan,China

Earthquake prediction is a difficult problem in Earth sciences.Unsuccessful predictions one after another urged people to explore more synthetic and comprehensive methods for earthquake prediction.The Lithosphere-Atmosphere-Ionosphere(LAI)coupling theory pays great attention to the processes taking place within the near ground layer of atmosphere.It has achieved great results recently,and can enlighten us about the nature of an earthquake's precursor.Based on the NCEP reanalysis dataset,this paper attempts to track the anomalies of the surface's upward long wave radiation flux(ULWRF),the temperature at the depth of 10cm～20cm below ground surface layer(BGL)and the air temperature at 2 meters above ground surface(AIR)around the time of the strong Wenchuan earthquake.Thermal anomalies were observed before and after May 12,2008,the time of the Wenchuan earthquake.Perhaps the thermal anomaly that occurred prior to the earthquake can be taken as indicators of the earthquake,but in view of the complexity of the earthquake phenomena,using thermal anomaly as a precursor should be done with caution.

Impacts of Global Warming on Patterns of Temperature Change in China

Global climate change has a wide range ofimpacts,and this paper presents an investigation onhow global warming has changed the relationshipbetween air temperature and latitude & altitude usingthe meteorological data obtained from 160 stations inChina. The investigation indicates that there are verydistinct seasonal differences in patterns of tempera-ture variation as a function of latitude and altitude:avery significant latitude effect in winter and a verysignificant altitude effect in summer. However,withglobal warming,the latitude effect in winter isweakening and the altitude effect in summer isstrengthening. This pattern of change in therelationship between temperature and latitude &altitude is helpful in efforts to reconstruct and explainthe past temperature patterns and variations.

Earth Observations in China and the World: History and Development in 50 Years

Remote sensing, which came into being at the first International Symposium on Remote Sensing of Environment (ISRSE) 50 years ago, has enabled people to obtain objecive and realistic spatial and temporal information through the application of Earth observation technologies and analyze and understand the macro-level changes of the Earth system from a spaial view. The technology of Earth observaion from space has incomparable advantages in the study of the Earth. This aricle introduces the 50-year development of Earth observaion in the world and the 30-year development of Earth observaion in China and reflects on the building of China's Earth observaion system.

A New Upsurge in Global Seismicity

This paper studies the temporal and spatial distribution of great global earthquakes （Mw i〉 8.0） since 1900. We compare the two periods of upsurges of great earthquakes occurring in the middle of last century and beginning of this century. The former period took place between 1950 and 1965 during which 13 great earthquakes （Mw I〉 8.0） occurred, including three events with moment magnitude greater than 9. 0. The largest magnitude in this period reached 9.6. The latter period starts from the beginning of this century. In less than 12 years, 15 great earthquakes have attacked the world with the largest magnitude being Mw 9. 1. On the basis of comparison between these two upsurges of global earthquake activity, we infer that the ongoing high level of earthquake activity may continue for another five years or so. Numerous great earthquakes （Mw I〉8. 0） and many large earthquakes （Mw6.0 ~ 7. 0） will occur globally in these five years. In addition, this paper also discusses the relationships between earthquake activity along the Sumatra segment of the Indian-Australia plate boundary and that in the Bayankala block in the middle of Qinghai-Tibetan plateau as well as in the blocks of the southern plateau. The results indicate that the Qinghai-Tibetan plateau, in particular its middle and southern parts, is a likely place for future earthquakes of magnitude over 7.0.

射门

一、射門的意义一場足球比賽的胜負决定于得失球的多少,此賽的进攻与防守过程,就是双方爭取射門和阻止射門的过程。足球此賽中一切的技术和战术,它的最終目的也是为了完成射門。由此可見射門在足球比賽中的意义,在一場比賽中无論技术发揮多好,战术配合得多么成功,但由于缺乏“射門”,而全功尽弃。近几年来由于足球防守技术的大发展,一般都采用盯人結合区域的混合防守,使前鋒既不能在无阻撓下从容射門,也不容易在禁区內获得射門机会。

我国女子足球技术的现状及特点

我国女子足球运动在1981年楚雄邀请赛之后,像雨后春笋,在全国各地迅速的开展了起来。两年多来,女子足球技术水平有了一定的提高。为了在最短的时间内赶上和超过世界先进水平,我们对1983年中国女子足球锦标赛的各场比赛进行了技术统计和分析。