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1.
Development ofPostgraduate Education There were only postgraduates were honored master degree from the year to in old China. While after the establishment of new China the postgraduate educationhas developed in a certain degree there were postgraduates were enrolled from to there were no postgraduates during the period of to due to the"culture revolution".…… 《广西师范大学学报(自然科学版)》2003,21(Z1):231-232
1 Development of Postgraduate Education
There were only 200 postgraduates were honored master degree from the year 1935 to 1949 in old China. While, after the establishment of new China, the postgraduate education has developed in a certain degree, there were 23,000 postgraduates were enrolled from 1950 to 1965, and there were no postgraduates during the period of 1966 to 1977 due to the "culture revolution". 相似文献
2.
In modernindustry thin film on the substratc has much important role to decide the properties ofproduct especially for electrical optical wear-resistant etc production. There aresome technical methods to prepare thin film including plasma spray physical vapordeposition 《广西师范大学学报(自然科学版)》2003,21(Z4):284-285
In modern industry,thin film on the substratc has much important role to decide the properties of product, especially for electrical, optical and wear-resistant etc, production. There are some technical methods to prepare thin film,including plasma spray,physical vapor deposition (PVD),chemical vapor deposition (CVD) and sol-gel,etc. Among of them,sol-gel method has been developed a popular tech nique for preparing thin films. 相似文献
3.
针对采用码相位循环移位获得的M元扩频需要额外同步信息的问题,提出一种改进型扩频通信算法.该算法采用m序列及其倒序序列构成系统扩频码集;在同相支路上利用扩频码的码极性调制进行传输,同时在正交支路利用扩频码码相位调制,实现M元扩频.该算法利用2种扩频方式的自身特点可快速准确地获取载波相位信息,具有不需要额外提供同步资源的优势.仿真结果表明,该算法可有效提高系统资源的利用率. 相似文献
4.
平板流固耦合振动的数值分析 总被引:2,自引:0,他引:2
采用了一种基于紧耦合的流固耦合算法,对流场与柔性平板之间的耦合运动进行了数值模拟.流场部分通过有限体积法求解任意拉格朗日 欧拉描述下的不可压缩N-S方程,而结构则由有限元法离散求解拉格朗日坐标下的弹性动力学方程.在一个时间步内,流场与结构计算区域的交界面上进行多次的数据传递和插值,以保证满足耦合面边界条件.计算了在静止流场中弹性板的自由振动和方柱后部平板的涡激振动现象,监测了平板的振幅和频率以及水动力载荷.通过与前人结果的比较,验证了所采用的流固耦合算法的可靠性.同时,分析了不同的材料参数对于平板耦合运动的影响.流体黏性越大对平板振动的阻尼作用越明显,而流体密度的增加会加速振动的衰减,并降低振动的频率.对于具有较低固有频率的结构,在耦合运动中的振动幅度和频率也较小.
相似文献
5.
Five advanced high-strength transformation-induced plasticity(TRIP) steels with different chemical compositions were studied to correlate the retained austenite and nonmetallic inclusion content with their physical properties and the characteristics of the resistance spot welding nuggets. Electrical and thermal properties and equilibrium phases of TRIP steels were predicted using the JMatPro? software. Retained austenite and nonmetallic inclusions were quantified by X-ray diffraction and saturation magnetization techniques. The nonmetallic inclusions were characterized by scanning electron microscopy. The results show that the contents of Si, C, Al, and Mn in TRIP steels increase both the retained austenite and the nonmetallic inclusion contents. We found that nonmetallic inclusions affect the thermal and electrical properties of the TRIP steels and that the differences between these properties tend to result in different cooling rates during the welding process. The results are discussed in terms of the electrical and thermal properties determined from the chemical composition and their impact on the resistance spot welding nuggets. 相似文献
6.
7.
Cdk1 is sufficient to drive the mammalian cell cycle 总被引:1,自引:0,他引:1
Santamaría D Barrière C Cerqueira A Hunt S Tardy C Newton K Cáceres JF Dubus P Malumbres M Barbacid M 《Nature》2007,448(7155):811-815
8.
Aeschlimann M Bauer M Bayer D Brixner T García de Abajo FJ Pfeiffer W Rohmer M Spindler C Steeb F 《Nature》2007,446(7133):301-304
Adaptive shaping of the phase and amplitude of femtosecond laser pulses has been developed into an efficient tool for the directed manipulation of interference phenomena, thus providing coherent control over various quantum-mechanical systems. Temporal resolution in the femtosecond or even attosecond range has been demonstrated, but spatial resolution is limited by diffraction to approximately half the wavelength of the light field (that is, several hundred nanometres). Theory has indicated that the spatial limitation to coherent control can be overcome with the illumination of nanostructures: the spatial near-field distribution was shown to depend on the linear chirp of an irradiating laser pulse. An extension of this idea to adaptive control, combining multiparameter pulse shaping with a learning algorithm, demonstrated the generation of user-specified optical near-field distributions in an optimal and flexible fashion. Shaping of the polarization of the laser pulse provides a particularly efficient and versatile nano-optical manipulation method. Here we demonstrate the feasibility of this concept experimentally, by tailoring the optical near field in the vicinity of silver nanostructures through adaptive polarization shaping of femtosecond laser pulses and then probing the lateral field distribution by two-photon photoemission electron microscopy. In this combination of adaptive control and nano-optics, we achieve subwavelength dynamic localization of electromagnetic intensity on the nanometre scale and thus overcome the spatial restrictions of conventional optics. This experimental realization of theoretical suggestions opens a number of perspectives in coherent control, nano-optics, nonlinear spectroscopy, and other research fields in which optical investigations are carried out with spatial or temporal resolution. 相似文献
9.
Bedding TR Mosser B Huber D Montalbán J Beck P Christensen-Dalsgaard J Elsworth YP García RA Miglio A Stello D White TR De Ridder J Hekker S Aerts C Barban C Belkacem K Broomhall AM Brown TM Buzasi DL Carrier F Chaplin WJ Di Mauro MP Dupret MA Frandsen S Gilliland RL Goupil MJ Jenkins JM Kallinger T Kawaler S Kjeldsen H Mathur S Noels A Aguirre VS Ventura P 《Nature》2011,471(7340):608-611
Red giants are evolved stars that have exhausted the supply of hydrogen in their cores and instead burn hydrogen in a surrounding shell. Once a red giant is sufficiently evolved, the helium in the core also undergoes fusion. Outstanding issues in our understanding of red giants include uncertainties in the amount of mass lost at the surface before helium ignition and the amount of internal mixing from rotation and other processes. Progress is hampered by our inability to distinguish between red giants burning helium in the core and those still only burning hydrogen in a shell. Asteroseismology offers a way forward, being a powerful tool for probing the internal structures of stars using their natural oscillation frequencies. Here we report observations of gravity-mode period spacings in red giants that permit a distinction between evolutionary stages to be made. We use high-precision photometry obtained by the Kepler spacecraft over more than a year to measure oscillations in several hundred red giants. We find many stars whose dipole modes show sequences with approximately regular period spacings. These stars fall into two clear groups, allowing us to distinguish unambiguously between hydrogen-shell-burning stars (period spacing mostly ~ 50 seconds) and those that are also burning helium (period spacing ~ 100 to 300 seconds). 相似文献
10.
Spin-orbit (SO) coupling--the interaction between a quantum particle's spin and its momentum--is ubiquitous in physical systems. In condensed matter systems, SO coupling is crucial for the spin-Hall effect and topological insulators; it contributes to the electronic properties of materials such as GaAs, and is important for spintronic devices. Quantum many-body systems of ultracold atoms can be precisely controlled experimentally, and would therefore seem to provide an ideal platform on which to study SO coupling. Although an atom's intrinsic SO coupling affects its electronic structure, it does not lead to coupling between the spin and the centre-of-mass motion of the atom. Here, we engineer SO coupling (with equal Rashba and Dresselhaus strengths) in a neutral atomic Bose-Einstein condensate by dressing two atomic spin states with a pair of lasers. Such coupling has not been realized previously for ultracold atomic gases, or indeed any bosonic system. Furthermore, in the presence of the laser coupling, the interactions between the two dressed atomic spin states are modified, driving a quantum phase transition from a spatially spin-mixed state (lasers off) to a phase-separated state (above a critical laser intensity). We develop a many-body theory that provides quantitative agreement with the observed location of the transition. The engineered SO coupling--equally applicable for bosons and fermions--sets the stage for the realization of topological insulators in fermionic neutral atom systems. 相似文献