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961.
稳定受迫振动中的能量转换 总被引:2,自引:0,他引:2
将强迫分解成超前位移π/2和位移相同或反相的两个分量,通过对两分力作功的定量计算,可以方便地讨论受迫振动中的能量转换,并能对共振作出较的物理解释。 相似文献
963.
Guo H. Wu D.S. Liu G. Miao Y.H. Qian S.Z. Qin W.Z. 《IEEE transactions on plasma science. IEEE Nuclear and Plasma Sciences Society》1990,18(3):326-333
A theory is proposed for the special complex cavity; it is in the form of a single resonant circuit having a TE0n&lrarr2;TE0,n+p mode converter and it features excellent mode selectivity, high power capability, and an asymmetric triangle profile of the RF field that is favourable to efficient operation for a 35-GHz second-harmonic gyromonotron employing this complex cavity with TE03 mode output are numerically illustrated and experimentally demonstrated. Power as high as 200 kW and efficiency as high as 30% have been obtained. These experimental results are record values for a gyrotron operating at the second-harmonic millimeter wavelength. Implications of the single-resonant complex cavity for the fundamental harmonic and third-harmonic high-average-power gyrotron design are discussed 相似文献
964.
We propose a 4-velocity unidimensional discrete Boltzmann model with two different speeds 2, 1 and two different masses 1, 2. With the three conservation laws of mass, momentum, and energy satisfied, we can introduce a nontrivial temperature. First, we determine the similarity shock waves satisfying physical properties: positivity, shock stability, inequalities of the subsonic and supersonic flows, increase or decrease of both mass and temperature across the shock. It results that either the speed of the shock front is higher than the speed 1 of the slow particles and the shocks are compressive or less than 1 and the shocks are rarefactive. We observe overshoots of the temperature, across the shock, with bumps higher and higher as the shock front speed increases. Second, we study the (1+1)-dimensional shock waves. They represent the superposition and collision of two compressive shocks traveling in opposite directions and we observe temperature overshoots for not too large times. 相似文献
965.
2003年8月开始,我应邀参加了物理通报教材研究中心组织的高中物理改革教材的编写工作.在编写过程中,如何领会与掌握“坚持时代性与基础性相结合原则”一直是大家关注的一个热点问题.本文介绍一下我对这一问题的思考与认识以及在教材编写中的一些具体做法.抛砖引玉,希望更多同志参与探讨. 相似文献
966.
CH2?CHCH2CpTiCl3 (1), CH2?CHCH2CH2CpTiCl3 (2) and CH3CH2CH3CpTiCl3 (3) have been synthesized and characterized. The influence of the alkenyl substituent groups on the catalyst activities in the syndiotactic polymerization of styrene was investigated. The catalyst activities decreased in the order CH2?CHCH2CH2CpTiCl3 > CH3CH2CH2CH2CpTiCl3 > CH3CH2CH2CpTiCl3 > CH2?CHCH2CpTiCl3 (Cp?C5H4). By using complex 1, the dependence of the activity on the concentration of methylaluminoxane, triisobutylaluminum and diisobutylaluminum hydride was investigated. Copyright © 2003 John Wiley & Sons, Ltd. 相似文献
967.
Justin T. Russell Yao Lin Alexander Bker Long Su Philippe Carl Heiko Zettl Jinbo He Kevin Sill Ravisubhash Tangirala Todd Emrick Kenneth Littrell Pappannan Thiyagarajan David Cookson Andreas Fery Qian Wang Thomas P. Russell 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2005,117(16):2472-2478
968.
Summary. The dynamical behavior of the damped sine-Gordon equation with homogeneous Neumann boundary condition is studied. It is shown
that the equation has an unbounded one-dimensional global attractor in a suitable functional space when the ``damping' and
the ``diffusing' are not very small.
Received March 16, 1999; accepted December 10, 1999 相似文献
969.
Yihua Jiang Yaochuan Wang Jianli Hua Sanyin Qu Shiqiong Qian He Tian 《Journal of polymer science. Part A, Polymer chemistry》2009,47(17):4400-4408
A novel hyperbranched polyyne (hb‐ DPP ) with triphenylamine as the core, 2,5‐dioctylpyrrolo [3,4‐c]pyrrole‐1,4 (2H,5H)‐dione ( DPP ) as the connecting unit has been designed and synthesized by Glaser‐Hay oxidative coupling reaction, which was characterized by IR, NMR, UV‐vis, FL, and GPC. The polymer exhibits high molecular weight (Mw up to ~6.55 × 104 Da) and is readily soluble in common organic solvents such as toluene, chloroform, tetrahydrofuran, N,N‐dimethyl formamide and so on. The one‐ and two‐photon absorption (TPA) properties have been investigated. The TPA cross section of the polymer was measured by open‐aperture Z‐scan experiment using 140 femtosecond (fs) pulse, and the TPA cross section for hb‐ DPP was determined to be 579 GM per repeating unit at wavelength of 800 nm. In tetrahydrofuran, hb‐ DPP exhibits intense frequency up‐converted fluorescence with the peak located at 584 nm under the excitation of 800 nm fs pulses. © 2009 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 47: 4400–4408, 2009 相似文献
970.
Xinde Tang Xiaochao Liang Qian Yang Xinghe Fan Zhihao Shen Qifeng Zhou 《Journal of polymer science. Part A, Polymer chemistry》2009,47(17):4420-4427
Novel AB2‐type amphiphilic block copolymers of poly(ethylene glycol) and poly(N‐isopropylacrylamide), PEG‐b‐(PNIPAM)2, were successfully synthesized through single‐electron transfer living radical polymerization (SET‐LRP). A difunctional macroinitiator was prepared by esterification of 2,2‐dichloroacetyl chloride with poly(ethylene glycol) monomethyl ether (PEG). The copolymers were obtained via the SET‐LRP of N‐isopropylacrylamide (NIPAM) with CuCl/tris(2‐(dimethylamino)ethyl)amine (Me6TREN) as catalytic system and DMF/H2O (v/v = 3:1) mixture as solvent. The resulting copolymers were characterized by gel permeation chromatography and 1H NMR. These block copolymers show controllable molecular weights and narrow molecular weight distributions (PDI < 1.15). Their phase transition temperatures and the corresponding enthalpy changes in aqueous solution were measured by differential scanning calorimetry. As a result, the phase transition temperature of PEG44‐b‐(PNIPAM55)2 is similar to that in the case of PEG44‐b‐PNIPAM110; however, the corresponding enthalpy change is much lower, indicating the significant influence of the macromolecular architecture on the phase transition. This is the first study into the effect of macromolecular architecture on the phase transition using AB2‐type amphiphilic block copolymer composed of PEG and PNIPAM. © 2009 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 47: 4420–4427, 2009 相似文献