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991.
Hong-jun Liu Wei Zhao Guo-fu Chen Yi-shan Wang Lian-jun Yu Chi Ruan Xue-feng Li 《Optics & Laser Technology》2004,36(4):3482-314
Experimental investigations of a type-I noncollinear phase-matched optical parametric amplification based on lithium triborate, which was pumped by a 5-ns second-harmonic pulses from a Q-switched Nd:YAG, seeded by a cw Ti:sapphire laser at 800 nm, was presented. The experiments generated 2-ns signal output pulses at 800 nm, the maximum signal output pulse energy reached 19 μJ, the corresponding parametric gain was 44 dB. Furthermore, the experiments demonstrate that the 65 nm-FWHM parametric fluorescence gain spectrum could also be observed. A quantitative account of the ultrabroadband parametric fluorescence gain spectrum was given with our theory. The experimental measurements are in agreement with theoretical calculations. 相似文献
992.
By means of a new force sensor based on optical beam deflection (OBD), the mechanical effects of laser-matter interaction underwater at different incident laser energy are investigated in detail. The experimental results show that a target underwater is impacted in turn by laser-plasma ablation force and high-speed liquid-jet impulse induced by bubbles collapse in the vicinity of a solid boundary. Furthermore, the amplitudes of the two forces increase monotonously with laser energy. According to the ablation force detected by the experiment and the theoretical relationship between laser intensity and ablation pressure, the value of liquid-jet impact against a solid boundary can be easily obtained. In addition, based on the model of a collapsing bubble, some characteristic parameters, such as the liquid-jet impact velocity, the maximum bubble radius, the bubble energy can also be obtained at different laser energy, which are valuable in the corresponding research fields. 相似文献
993.
A central problem that arises in evolutionary biology is that of displaying partitions of subsets of a finite set X on a tree whose vertices are partially labelled with the elements of X. Such a tree is called an X-tree and, for a collection of partitions of subsets of X, characterisations for the existence and uniqueness of an X-tree that displays have been previously given in terms of chordal graphs. In this paper, we obtain two closely related characterisations also in terms of chordal graphs. The first describes when identifies an X-tree, and the second describes when a compatible subset of is of maximum size. 相似文献
994.
Y. Gu Igor L. Kuskovsky R.D. Robinson G.F. Neumark S.P. Guo M.C. Tamargo 《Solid State Communications》2005,134(10):677-681
The composition and size of optically active CdxZn1−xSe/ZnSe quantum dots are estimated with a previously developed method. The results are then compared with those obtained for CdxZn1−xSe/Zn0.97Be0.03Se QDs. We show that introducing Be into the barrier material enhances both Cd composition and quantum size effect of optically active quantum dots. 相似文献
995.
A polarization-insensitive 40-Gb/s time-division demultiplexer was demonstrated in a polarization-diversity loop configuration. The power penalty was measured to be 2.3 dB at a bit error rates of 10-9 for 10 Gb/s output signals. 相似文献
996.
S. V. Bobashev R. V. Vasil’eva A. V. Erofeev T. A. Lapushkina S. A. Poniaev D. M. Van Wie 《Technical Physics》2003,48(2):177-184
Effective ways for controlling shock wave configurations by means of external actions are sought. One such way is a local effect of electric and magnetic fields. In this paper, the local effect of external fields is implemented by current localization in a limited region of a diffuser. The experiment is carried out in a diffuser providing the complete internal compression of the gas with a Mach number at the inlet M=4.3. As a working medium, a xenon plasma is used. The plasma flow is formed in a shock tube equipped with an accelerating nozzle. Two ways of current localization are tested. In the first one, the diffuser inlet is a short channel of Faraday generator type. In this case, the ponderomotive force basically decelerates or accelerates the flow depending on the direction of the electric field. In the second way, the current flows through a narrow near-wall region between adjacent electrodes. In this case, the ponderomotive force compresses or expands the gas. In both cases, it is shown that the angle of an attached shock due to MHD interaction can be both decreased and increased. The central problem with the MHD control of shock waves is near-electrode and near-wall phenomena. 相似文献
997.
Zhang Xun Zhang Hongjie Zhang Ping Chen Weibin Luo Xizhang 《International Journal of Infrared and Millimeter Waves》2003,24(11):1967-1976
Based on the basic theory of molecular vibration relaxation and semi-classical density matrix theory, operating parameters optimization of buffer gas in the process of miniature pulsed optically pumped submillimeter wave laser was systemically studied and the theoretical calculated result was tested by experiments. The result would do favor to develop and study high-power and wide-range tunable miniature and high-efficient pulsed optically pumped submillimeter wave laser and also had some instruction to its application. 相似文献
998.
A. F. G. Monte M. A. G. Soler S. W. da Silva B. B. D. Rodrigues P. C. Morais A. A. Quivy J. R. Leite 《Physica E: Low-dimensional Systems and Nanostructures》2004,23(3-4):466
We have investigated the influence of vicinal GaAs substrates on the optical and electronic properties of InGaAs/GaAs quantum wells (QWs). A single In0.10Ga0.90As QW was grown by molecular-beam epitaxy on a vicinal GaAs(0 0 1) substrate with a miscut angle of 0° (nominal), 2°, 4° and 6° towards [1 1 0]. The carrier diffusion was obtained by a micro-photoluminescence scan technique that permits to observe the effective diffusion length characterized by the lateral spread of carriers in the QW followed by radiative recombination. The carrier diffusion length was obtained parallel (L||) and perpendicular (L) to the atomic steps. The diffusion length decreases as the temperature increases up to 100 K. Above this temperature we found different behaviours that depend on the sample miscut angle. 相似文献
999.
The purpose of this work was to investigate the effects of physical aging on the kinetics of yielding in polycarbonate. PC samples were annealed over a wide range of aging times and temperatures. Both tensile and compressive tests were performed over various loading rates and temperatures to analyze the effects of aging time and aging temperature on yielding kinetics. Two grades of polycarbonate, Makrolon, of different molecular weights, PC-2608 (low Mw), and PC-3208 (high Mw), supplied by Bayer were analyzed. In unaged condition, PC is hard and tough, but after aging, it becomes more brittle. In terms of molecular movement, the yielding process is a thermally activated process involving inter- and intra-molecular motions. The time–temperature dependence of yielding behavior can be separated into two regions. Aging does not affect localized molecular motions of the β process during yielding. Physical aging in PC results in a slower jump rate of the main segments of macromolecules between two equilibrium positions. It reduces the flexibility of the macromolecules and thus, makes the polymer more brittle. Heat aging also causes a decrease of the entropy (ΔS) in polycarbonate, and this decrease is more important when the molecular weight is reduced. Increasing the annealing time and temperature results in a continuous reduction of ΔS. The rate of aging decreases with decreasing annealing temperature and below about 30 °C, no aging takes place. Annealing also strongly affects the excess of enthalpy in PC. However the effect of physical aging on yielding differs to that on enthalpy excess. The kinetics of yielding and aging processes in polycarbonate are also different. An increase in the strain rate does not have the same effect on the yield stress as an increase in the aging time by a same factor. 相似文献
1000.
T. N. Shilkin 《Journal of Mathematical Sciences》2004,123(6):4668-4677
In this paper, we study the smoothness of weak solutions of the three-dimensional stationary Boussinesq system describing steady-state motion of viscous heat-convergent Newtonian fluid whose viscosity may depend on the temperature of the fluid. The principal feature of the system under consideration is the occurrence of the dissipative term in the equation of energy balance. This term is equal to the product of the stress and the strain velocity tensors and has a quadratic growth with respect to the gradient of the velocity field. We prove the partial regularity of solutions to this system and give an estimate of the Hausdorff measure of the singular set. Bibliography: 14 titles. 相似文献