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911.
Performance of gain-switched all-solid-state quasi-continuous-wave tunable Ti:sapphire laser system 下载免费PDF全文
We have made a gain-switched all-solid-state quasi-continuous-wave (QCW) tunable Ti:sapphire laser system, which is pumped by a 532 nm intracavity frequency-doubled Nd:YAG laser. Based on the theory of gain-switching and the study on the influencing factors of the output pulse width, an effective method for obtaining high power and narrow pulse width output is proposed. Through deliberately designing the pump source and the resonator of the Ti:sapphire laser, when the repetition rate is 6 kHz and the length of the cavity is 220 mm, at an incident pump power of 22 W, the tunable Ti:sapphire laser from 700 to 950nm can be achieved. It has a maximum average output power of 5.6W at 800nm and the pulse width of 13.2 ns, giving an optical conversion efficiency of 25.5% from the 532 mn pump laser to the Ti:sapphire laser. 相似文献
912.
Kulbaba K Cheng A Bartole A Greenberg S Resendes R Coombs N Safa-Sefat A Greedan JE Stöver HD Ozin GA Manners I 《Journal of the American Chemical Society》2002,124(42):12522-12534
Pt(0)-catalyzed ring-opening precipitation copolymerization of [1]silaferrocenophanes fcSiMe(2) (3) and the spirocyclic cross-linker fcSi(CH(2))(3) (4) (fc = Fe(eta(5)-C(5)H(4))(2)) was used to prepare polyferrocenylsilane microspheres (PFSMSs) under mild conditions. By varying the reaction conditions, a wide variety of other morphologies was obtained. The effects of temperature, monomer ratio, solvent composition, catalyst concentration, and time on the observed morphology were investigated and interpreted in terms of a mechanism for microsphere formation. The most well-defined particles were formed using equimolar amounts of 3 and 4, in a 50:50 mixture of xylenes and decane at 60 degrees C with gentle agitation. Chemical oxidation of the polymeric microspheres led to positively charged particles (OPFSMSs) which underwent electrostatically driven self-assembly with negatively charged silica microspheres to form core-corona composite particles. Redox titration with controlled amounts of the one-electron oxidant [N(C(6)H(4)Br-p)(3)][PF(6)] in acetonitrile led to the oxidation of the outer 0.15 microm (ca. 32%) of the PFSMSs. The resulting OPFSMSs were reduced back to their neutral form by reaction with hydrazine in methanol. Pyrolysis of the PFSMSs led to spherical magnetic ceramic replicas with tunable magnetic properties that organize into ordered 2-D arrays at the air-water interface under the influence of a magnetic field. 相似文献
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REN Ping-Da PAN Shi-Feng DONG Ting-Wei WU Shi-HuiDepartment of Chemistry Pudan University Shanghai China 《中国化学》1996,14(5):462-466
In the presence of active metal bismuth (Bi) which was prepared from the combination of bismuth trichloride and sodium borohydride,aldehydes have been found to react with allyl bromide in aqueous media,and the corresponding homoallylic alcohols were obtained in excellent yields with high chemo-and stereoselectivity. 相似文献
916.
XIANG Shiqing LOU Qihong DONG Jingxing MANG Yanping WEI Yunrong 《Chinese Journal of Lasers》1996,5(5):385-390
Generationof2-10nsExcimerLaserPulsebyOpticalSynchronizingWave-clippingXIANGShiqing;LOUQihong;DONGJingxing;MANGYanping;WEIYunr... 相似文献
917.
SOLUTE REDISTRIBUTION IN THE INITIAL TRANSIENT REGION OF DIRECTIONAL SOLIDIFICATION SPECIMEN 下载免费PDF全文
The solute redistribution during initial transient process of directional solidification of a binary alloy is associated with the solid-liquid interface advancing velocity which will pass a hysteretic process approaching to the externally imposed velocity. In the present paper, a new accelerated growth equation, dV/dt = μG[m/G·(dGL*)/dt+Ve-V] is deduced, based on which a new formula for the initial transient solute redistribution is obtained with the reasonable assumption that the solid-liquid interface advancing velocity changes exponentially during solidification. It shows that the kinematic effect dominates solidification at high velocity while the coupling effect of thermal and mass transportation controls that at lower velocity.In addition, another new equation to calculate the time required for a planar interface to lose stability is also found. Since the effects of the imposed thermal gradient are taken into account in the new equations, they are more reasonable and satisfactory than those given by Tiller et al. and by Smith et al. 相似文献
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本文讨论了Yamabe方程的摄动方程解的收敛性质,由此给出Aubin的结果一个新证明,证明不需要用带最好常数的Sobolev不等式.并且给出了一个未被Aubin结果所包括的存在定理。最有趣的是,文中所获得的解一般是非极小的。 相似文献