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991.
通过构造适当的关联函数,计算B→π跃迁形状因子fB+π(q2),fBπ(q2)和标量形状因子f0(q2),从而就能研究轻子质量对B0→π-+ν(l=e,μ,τ)衰变过程的影响.首次分别计算B0→π-e+νe,B0→π-μ+νμ,B0→π-τ+ντ衰变过程的分支比,并发现轻子质量me,mμ可以忽略,但重轻子质量mτ不能忽略,它对分支比计算有一定的贡献.把计算结果与最近的实验数据进行比较,发现理论结果与实验数据基本符合. 相似文献
992.
This work investigated the effect of infusion of a self-made ultrasound contrast agent with long persistence (named ZHIFUXIAN) on rat right ventricular pressure and made a preliminary evaluation on the relative safety of the novel microbubbles. Normal saline, SonoVue and ZHIFUXIAN were injected through caudal vein at the total volume of 0.5 ml for each injection. The right ventricular systolic pressure (RVSP) and end-diastolic pressure (RVEDP) were monitored and the changes of the pressure were compared with baseline readings. RVSP increased when saline, SonoVue or ZHIFUXIAN were injected, the greatest change being after SonoVue (about 2 mm Hg), but there was no statistical significance compared with baseline (P > 0.05). There was no significant difference in RVSP between saline, SonoVue and ZHIFUXIAN at any time point. Also, there was no significant difference in RVEDP between groups at each time point and between different time points in each group. The results indicate that the self-made microbubbles effect on right ventricular hemodynamics is equivalent to that of normal saline at the same volume needed for effective enhanced imaging, demonstrating that it does not produce changes in right ventricular blood pressure under the study conditions. Pathological examination also showed it had no obvious influence on lung, liver and kidney. 相似文献
993.
We report pulse-shaper-assisted phase control of a broad spectrum, aiming to synthesize nonsinusoidal waveforms. We first generate multiple-order coherent Raman sidebands by focusing two laser beams into a piece of diamond. Then we combine five sidebands into a single beam by using a prism. Our setup allows for both coarse, manual phase adjustments and fine tuning of the spectral phases. A flat spectral phase across these five frequency-separated sub-bands is achieved, which implies generation of two to three optical-cycle pulses. 相似文献
994.
DENG Kai WU Yunfei LI Hua FANG Deming ZHONG Yingjie 《声学学报:英文版》2011,(4):417-426
Based on the energy conservation relationship,nonlinear thermo-acoustic effects of Rijke tube including instability range,saturation processes and higher harmonics modes were investigated.With coupling between the external flow and the inner space of a Rijke tube, the acoustic characteristics of self-excited oscillation were simulated.The experimental study was also carried out and the results were compared with those from simulation.The nonlinear factors which distort the acoustic waveform distortion were analyzed.From the results,it is seen that varying size of the nozzle outlet changes the acoustic impedance in the boundary, and leads to reduction of the nonlinear effects.The results show that the modes of self-excited oscillation could be influenced by the position of higher harmonics.In the large amplitude oscillation,the distortion of pressure wave within Rijke tube could be induced by the acoustic losses due to vortices on nozzle.It is found that the waveform distortion could be avoided by the shrinkage of nozzle. 相似文献
995.
Yanfeng Wang Li ZhengxianDu Jihong Hua YunfengWang Baoyun 《Applied Surface Science》2011,258(1):456-460
Materials’ surface service property could be enhanced by transition metal nitride hard coatings due to their high hardness, wear and high temperature oxidation resistance, but the higher friction coefficient (0.4-0.9) of which aroused terrible abrasion. In this work, quinternary (Ti,Al,Si,C)N hard coating 3-4 μm was synthesized at 300 °C using plasma enhanced magnetron sputtering system. It was found that the coating's columnar crystals structure was restrained obviously with the increase of C content and a non-columnar crystals growth mode was indicated at the C content of 33.5 at.%. Both the XRD and TEM showed that the (Ti,Al,Si,C)N hard coatings had unique nanocomposite structures composed of nanocrystalline and amorphous nc-(Ti,Al)(C,N)/nc-AlN/a-Si3N4/a-Si/a-C. However, the coatings were still super hard with the highest hardness of 41 GPa in spite of the carbon incorporation. That a-C could facilitate the graphitization process during the friction process which could improve the coating's tribological performance. Therefore, that nanocomposite (Ti,Al,Si,C)N coatings with higher hardness (>36 GPa) and a lower friction coefficient (<0.2) could be synthesized and enhance the tribological performance and surface properties profoundly. 相似文献
996.
997.
The evolution of inter-device leakage current with total ionizing dose in transistors in 180 nm generation technologies is studied with an N-type poly-gate field device (PFD) that uses the shallow trench isolation as an effective gate oxide. The overall radiation response of these structures is determined by the trapped charge in the oxide. The impacts of different bias conditions during irradiation on the inter-device leakage current are studied for the first time in this work, which demonstrates that the worst condition is the same as traditional NMOS transistors. Moreover, the two-dimensional technology computer-aided design simulation is used to understand the bias dependence. 相似文献
998.
The authors construct a solution Ut(x) associated with a vector field on the Wiener space for all initial values except in a 1-slim set and obtain the 1-quasi-sure flow property where the vector field is a sum of a skew-adjoint operator not necessarily bounded and a nonlinear part with low regularity, namely one-fold differentiability. Besides, the equivalence of capacities under the transformations of the Wiener space induced by the solutions is obtained. 相似文献
999.
1000.
Hua‐Huai Chern María‐Inés Fernández‐Camacho Hsien‐Kuei Hwang Conrado Martínez 《Random Structures and Algorithms》2014,44(1):67-108
An unusual and surprising expansion of the form as , is derived for the probability pn that two randomly chosen binary search trees are identical (in shape, hence in labels of all corresponding nodes). A quantity arising in the analysis of phylogenetic trees is also proved to have a similar asymptotic expansion. Our method of proof is new in the literature of discrete probability and the analysis of algorithms, and it is based on the logarithmic psi‐series expansions for nonlinear differential equations. Such an approach is very general and applicable to many other problems involving nonlinear differential equations; many examples are discussed in this article and several attractive phenomena are discovered.Copyright © 2012 Wiley Periodicals, Inc. Random Struct. Alg., 44, 67–108, 2014 相似文献