共查询到20条相似文献,搜索用时 103 毫秒
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从π介子核子散射振幅出发,根据Mandelstam表示和么正条件,对于奇异量子数为零、重子数为1的费米子Regge轨迹,求得了下列结果:(1)位置参数α(s)的解析性,只有右方物理割而无左方动力割,但是左方有从s=0到-∞的运动学割。(2)当s<0时α(s)取复数值,并且还有一条同它成复共轭(在s<0范围内)的Regge轨迹。这一对轨迹它们的J-宇称相同,但是空间宇称相反。02时,α(s)为实数。不同宇称的轨迹对s的依赖不同。(3)讨论了费米子Regge迹在阈能(W0=M+μ)附近的行为。凡是与共振态、束缚态有关的Regge轨迹,α(W0)≠0。求得了在阈附近的表示,定性方面同玻色子轨迹相同。(4)还有一大类Regge轨迹,它们同共振态、束缚态无关,α(W0)=0。这类轨迹在能量趋近阈能时,有无穷多个极点趋于ReJ=0(即我们在费米子情况下得到Gribov-Pomeranchuk极点凝聚现象),这类轨迹当能量由阈下趋于阈时,从J平面左半平面共轭成对趋于ReJ=0;当能量从阈上趋于阈时,成对地从第一和第三象限趋于ReJ=0。所有这些极点实数部分Reα→0比虚数部分Imα→0快一或二个数量级。J平面原点是一个凝聚点,这类“非动力”的Regge轨迹阈行为,无论对玻色子、费米子,以至非相对论势散射,定性都相似(只是凝聚的轴线和点不同)。它们实际上是s矩阵在阈的普遍性质的反映。 相似文献
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砂土的突破压力与渗透率实验 总被引:2,自引:0,他引:2
符号表A截面积,m2p压力,PaV体积流量,m3/sd颗粒平均粒径,mpc毛细压力,pa孔隙率dth突破直径,mPth突破压力,Pa黏度,kg/(m.s)k渗透率,m2,半径,表面张力,N/mL长度,m1前言三参数模型曾经再现了某种意义的毛细滞后现象[1],但对于存在边界影响的典型重力脱湿和毛细吸湿过程始终未能模拟[2]。重要的原因是边界上的两相流体如何处于平衡并不十分清楚。窄筛分沙水中自然沉积的表层实验表明,气体进入湿饱和多孔介质存在一个压力阈值Pth。低于突破阈值时,气体与湿介质处于随遇平衡,只有达到这个值时,气体才能突破表层阻挠进人… 相似文献
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Coherent transitions of charge carriers between the conduction and valence bands of a semiconductor medium are essential for the operation of a semiconductor laser. In this paper, we study how such interband coherence can be set up by an injection current and a coherent pump-field. In the absence of the pump-field, the injection current is the only source to establish the interband coherence in a semiconductor laser system. A laser threshold is obtained, which shows that a strongly coupled high-Q microcavity has a low threshold value. However, when an external pump-field serving as another mechanism to create the interband coherence is applied, the threshold value of the injection current can be lowered and it vanishes for sufficiently strong field. Besides, if the pump-field exceeds a threshold value, it is even possible to achieve a bistability in the inversionless region. Some fundamental macroscopic properties, including polarization, absorption and dispersion for the semicoductor system, are also obtained analytically. 相似文献
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微光成像系统的阈值探测理论和视距探测方程的研究 总被引:8,自引:2,他引:6
研究目前文献中常见的18种微光成像系统探测方程之间的内在联系和异同之处,分析论证各种阈值探测理论和探测方程存在的问题和不足。在此基础上,从人眼的视觉理论和阈值特性出发,建立微光成像系统新的阈值探测理论模型,并分别导出微光直视系统和微光电视系统的视距探测方程。应用所导出的理论公式计算的数据与各种实际系统的实测数据进行了比较,证明新的阈值探测理论和视距探测方程是正确可靠的,且具有很高的精度。 相似文献
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Li Taihua An Zhu Luo Zhengming Center for Radiation Physics Institute of Nuclear Science Technology Sichuan Union University Chengdu 《原子与分子物理学报》1997,(1)
MEASUREMENTSOFFeANDCuK-ShelIONIZATIONCROSSSECTIONSBYSLOWELECTRONIMPACTLiTaihuaAnZhuLuoZhengmingCenterforRadiationPhysics,Ins... 相似文献
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M. A. Sakhbetdinov P. F. Kartsev 《Bulletin of the Russian Academy of Sciences: Physics》2007,71(8):1115-1117
Schemes and calculated characteristics of effective logic elements with two inputs for classical ground-state computations are reported. These elements have a high threshold (0.48) and perform a desired logical operation in a wide range of input signals. 相似文献
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我们着重研究了高压H2气Q(1)振动跃迁(4155cm-1)受激喇曼散射(SRS)中,参与非线性相互作用的几个参数(介质分子密度、跃迁线宽、泵浦光子密度以及非线性作用长度)对受激阈值与能量转换效率的影响。给出了自零到24atmH2气压范围内阈值随H2气压变化的实验结果,它与根据Dicke-Doppler展宽和碰撞展宽的联合效应的分析是一致的。讨论了由于受激喇曼过程(SRP)和四波混频参量过程(FWPP)共同影响下能量转换效率、压力-色散效应对高阶反斯托克斯的能量输出的重要影响。
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LINEAR AND NONLINEAR SEMICLASSICAL THEORY OF WHISPERING-GALLERY-MODE MICROSPHERE LASER 总被引:1,自引:0,他引:1 下载免费PDF全文
A complete whispering-gallery-mode microsphere laser theory is developed, which combines usual laser semiclassical theory with Lorenz-Mie theory. The linear and nonlinear problems of the microsphere lasing are dealt with in the universal mode picture. The threshold condition, average amplitude of the steady state and frequency effect are obtained. A comparison between the theory and experiments is also made. 相似文献
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The nonlinear effects of large amplitude ion acoustic wave are studied theoretically and experimentally, so as to obtain the amplitude threshold for producing the nonlinear effects, the half width of the trapped region and the transitional region width caused by collisions. The experimental results are in good agreement with the theoretical predictions. 相似文献
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用聚焦的紫外XeCl准分子激光器轰击高分子聚合物薄膜(涤纶薄膜),由OMA系统接收其发射光谱.发现谱线主要为C2的Swan带和CN的红带,并与高压汞灯照射后的聚合物薄膜的发射谱进行了比较,在我们的实验精度内,没有发现区别.实验显示,每个光脉冲能刻蚀掉几分之一到几个微米的薄膜.激光的刻蚀效应存在波长和能量密度两个阈值.对于涤纶薄膜,能量密度的阈值约为40mJ/cm2.同时还作了紫外吸收光谱和SEM照片的分析. 相似文献
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Temperature dependence of the threshold of pure and impurity-doped blue bronzes has been studied. It is found that for pare blue bronzes the threshold field near 100K has an anomalous peak, but for impurity-doped samples no anomaly is observed in the range of liquid nitrogen temperature, and the value of the threshold field gradu-ally increases with the decrease of temperature. The results show that in the high-quality pure blue bronzes, there may exist an incommensurate to quasi-commensurate transition near 100K. But for the impurity-doped or "dirty" pure samples, such an incommensurate to quasi-commensurate transition near 100K can be extensively re-strained by impurities or defects, which leads to a pure incommensurate CDW in a wide temperature range. 相似文献
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