Estudi de la zona de finalització més eficaç per guanyar el punt mitjançant l'atac de dreta en el tennis de taula

Curs 2011-2012L’objectiu d’aquest estudi és determinar la zona més efectiva per guanyar el punt mitjançant l’atac de dreta en el tennis de taula. S’utilitza una adaptació del sistema d’anàlisi dels tres nivells d’habilitat, proposat pels acadèmics xinesos Wu i Li (1990) per tal de classificar els punts de la forma que ens permetin analitzar les zones de finalització i les formes com s’obtenen els punts. L’estudi analitza cinc partits dels sis millors jugadors del rànquing mundial de la ITTF. El resultat de l’estudi és que la zona de finalització més eficaç per obtenir el punt mitjançant l’atac de dreta és la zona 1 de la taula del rival.The goal of this study is to determine the most effective zone to win the point with a forehand attack in table tennis. Used an adaptation of the three-stage skill analysis, proposed by Chinese scholars Wu and Li (1990) to classify the points of the form that will allow us to analyze the end zone and the ways we get the point. The study examines five games of the six best players in the ITTF world ranking. The result of the study is that the most effective end zone to win the point with a forehand attack is zone 1 of the table opponents

Campus News January 15, 2010

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Surface Instability and Surface Charge Orders in the Kagome Metal TbV6_6Sn6_6

The ideal kagome lattice shows an electronic structure with intriguing correlated and topological electronic states. In realistic materials, however, the kagome atomic layer is generally buried inside a bulk while little is known about the kagome layer on a surface. In this work, we reveal that the kagome layer of the recently discovered kagome metals $R$V$_6$Sn$_6$ ($R$ = Y and rare-earth elements) exhibits strong lattice instabilities when exposed on the surface, despite that it is stable inside the bulk. Exemplified by TbV$_6$Sn$_6$ without bulk charge density waves, surface kagome layers present $\sqrt 3 \times \sqrt 3$ and $2 \times 2$ surface charge orders (SCOs). In contrast, SCOs disappear when kagome surfaces are covered by a Sn or TbSn atomic layer. These SCOs exhibit clover-like patterns with trimers of V atoms, different from known bulk CDWs. Furthermore, we find that SCOs are generally present (absent) in thin films of $R$V$_6$Sn$_6$ terminated with kagome (non-kagome) sublattices, indicating its surface origin. The SCOs distort the kagome lattice and sensitively modify kagome surface bands. Our work reveals unexpected surface instability of kagome materials and calls for surface-sensitive measurements such as scanning tunneling microscopy.Comment: Supplementary is included. 4 figures + 1 tabl

Spin excitations in K2_{2}Fe4+x_{4+x}Se5_{5}: linear response approach

Using \emph{ab initio} linear response techniques we calculate spin wave spectra in K$_{2}$Fe$_{4+x}$Se$_{5}$, and find it to be in excellent agreement with a recent experiment. The spectrum can be alternatively described rather well by localized spin Hamiltonian restricted to first and second nearest neighbor couplings. We confirm that exchange coupling between nearest neighbor Fe magnetic moments is strongly anisotropic, and show directly that in the ideal system this anisotropy has itinerant nature which can be imitated by introducing higher order terms in effective localized spin Hamiltonian (biquadratic coupling). In the real system, structural relaxation provides an additional source of the exchange anisotropy of approximately the same magnitude. The dependence of spin wave spectra on filling of Fe vacancy sites is also discussed

Growth of Thin Oxidation-Resistive Crystalline Si Nanostructures on Graphene

We report the growth of Si nanostructures, either as thin films or nanoparticles, on graphene substrates. The Si nanostructures are shown to be single crystalline, air stable and oxidation resistive, as indicated by the observation of a single crystalline Si Raman mode at around 520 cm-1, a STM image of an ordered surface structure under ambient condition, and a Schottky junction with graphite. Ultra-thin silicon regions exhibit silicene-like behavior, including a Raman mode at around 550 cm-1, a triangular lattice structure in STM that has distinctly different lattice spacing from that of either graphene or thicker Si, and metallic conductivity of up to 500 times higher than that of graphite. This work suggests a bottom-up approach to forming a Si nanostructure array on a large scale patterned graphene substrate for fabricating nanoscale Si electronic devices

Research on the Dynamic Change of Comparative Advantage of China’s Service Trade

The service trade develops quickly in China and the scale of which is increased. The main body of China’s service trade is transportation and travel. Meanwhile, the deficit in China\u27s balance of service trade is widened and China’ service trade lags behind the China’s goods trade and the service trade in some country. It’s important to assess the dynamic change of the comparative advantage of China’s service trade for improving the competitive of China’s service trade. The TC index and RCA index are used to evaluate the dynamic change of the comparative advantage of China’s service trade. The conclusions are drawn that China’s service trade in whole has comparative disadvantage, the comparative advantage of transportation is biggest in all service sectors, the comparative advantages in new services sectors such as financial service and insurance service are smaller than other service sector, the comparative advantages in transportation and travel are decreasing. Some measures should be taken to enhance the comparative advantages of China’s service trade, which consist of perfecting the rules and laws of China’s service trade, promoting science and technology innovation, opening more China’s service sectors