共查询到20条相似文献,搜索用时 78 毫秒
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大气信道对垂直发收模式紫外光散射通信性能影响的仿真 总被引:3,自引:3,他引:0
介绍了非直视单散射信道模型及其在椭球坐标系下的求解方法.在此基础上,针对垂直发收模式,研究了大气信道对紫外光通信系统的影响.对不同天气、不同通信距离条件下,大气信道所产生的能量损耗、时间延迟和脉冲展宽等进行了定量分析和仿真.仿真结果表明:能量衰减随能见度变化曲线存在拐点,即并不是天气越好,能见度越高,系统接收能量越大;通信距离1km时,能见度18km处出现能量衰减最小值;能量衰减随通信距离非线性递增,通信距离1km时,能量衰减近100dB;随着通信距离的增加,时间延迟和脉冲展宽都近似呈线性增长,通信距离1km时,时间延迟接近5μs,脉冲展宽大于10μs. 相似文献
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大气信道对垂直发收模式紫外光散射通信性能影响的仿真 总被引:1,自引:0,他引:1
介绍了非直视单散射信道模型及其在椭球坐标系下的求解方法.在此基础上,针对垂直发收模式,研究了大气信道对紫外光通信系统的影响.对不同天气、不同通信距离条件下,大气信道所产生的能量损耗、时间延迟和脉冲展宽等进行了定量分析和仿真.仿真结果表明:能量衰减随能见度变化曲线存在拐点,即并不是天气越好,能见度越高,系统接收能量越大|通信距离1 km时,能见度18 km处出现能量衰减最小值|能量衰减随通信距离非线性递增,通信距离1 km时,能量衰减近100 dB|随着通信距离的增加,时间延迟和脉冲展宽都近似呈线性增长,通信距离1 km时,时间延迟接近5 μs,脉冲展宽大于10 μs. 相似文献
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分析了楔形镜和中性玻璃衰减片组对光束的衰减原理,采用反射式楔形镜作为无像差定量衰减器,并同时使用中性玻璃衰减片组微调光束能量。实验测量了LD泵浦激光模式发生器基模和高阶模条件下激光束的M2因子,结果表明:楔形镜反射式衰减器对光束质量无显著影响,将楔形镜第一次表面反射作为无像差定量衰减,入射角在0~55°范围内,单棱镜表面反射光束能量为入射光能量的4.3%,通过多块组合可以得到更大的衰减;可采用中性玻璃衰减片组对激光光束的衰减进行精细控制,使其满足CCD探测器动态范围要求。该结论可为高精度激光参数测量装置光衰减系统的研制提供理论依据。 相似文献
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为了精确计算早期核辐射,建立了中子及次级γ在大气中输运的蒙特卡罗计算模型,并利用几何分裂算法与时间分裂算法等减方差技巧提高计算效率,计算得到了距源点不同距离球面上中子与中子次级γ的信息,给出了不同位置不同时间的氮俘获γ能量释放率。开展了氮俘获γ能量释放率的规律性研究,并分析了中子能量对氮俘获γ的影响。结果表明,氮俘获γ能量释放率先随源点的距离增加而增大,在距源点约500 m达到峰值,而后随距离增加指数衰减。氮俘获γ能量释放率在时间上服从指数衰减规律,衰减时间在0.1 s左右。引入表征氮俘获γ辐射强度参数a和特征衰减时间参数τ,拟合得到了不同距离不同时间氮俘获γ能量释放率的快速计算公式。研究表明,氮俘获γ辐射强度、衰减时间及其空间分布均与中子能量密切相关。 相似文献
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针对反射式GaN光电阴极长波段量子效率衰减较大, 短波段量子效率衰减较小的实验现象, 在考虑谷间散射的情况下, 利用玻尓兹曼分布和基于Airy函数的传递矩阵法, 计算了发射电子能量分布, 分析了表面势垒变化对量子效率衰减的影响, 理论与实验符合较好. 激活层有效偶极子数的减少使表面势垒宽度和高度增加, 引起长波光子激发产生的发射电子能量分布衰减较大, 短波光子激发产生的发射电子能量分布衰减较小, 这是量子效率在长波段衰减较大, 短波段衰减较小的根本原因. 相似文献
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N. G. Kanev 《Acoustical Physics》2013,59(5):559-564
The problem of sound decay in a trapezoidal room with a nonuniform distribution of wall absorption is considered. It is shown that the sound energy decay may be either anomalously slow, obeying the law ~1/t, or fast, obeying an exponential law. It is found that the type of the decay law depends on the presence of stable ray trajectories in the room. Manifestations of stable ray trajectories in both laboratory and field experiments are demonstrated. 相似文献
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Joachim Petzold 《Zeitschrift für Physik A Hadrons and Nuclei》1959,157(1):122-129
The probability of decay of a quantum mechanical system is completely determined by the energy spectrum of the initial state. An exponential law of decay is obtained only if the spectrum has a long tail. Since the initial state is spatially localized, the decay energy and decay constant are fixed by the poles of theS-function. 相似文献
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The limitations in the use of the Impulse Precision Sound Level Meter for the assessment of the sound energy of recurrent impact noise have been investigated. For repetition rates above 30 impacts per second the meter reading and level predicted by an energy law agree to within ±2 dB. Below 30 impacts per second, for pulses with decay times in the range 2 to 28 msec, a simple empirical correction applied to the meter reading will produce results that follow the energy law. For decay times in excess of 28 msec simple corrections are not adequate and therefore the Impulse Sound Level Meter cannot be used in practice. 相似文献
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Hansen K Andersen JU Hvelplund P Møller SP Pedersen UV Petrunin VV 《Physical review letters》2001,87(12):123401
The exponential law is valid both for decay from a single quantum state into a continuum and for an ensemble maintained in thermal equilibrium. For statistical decay of an ensemble of isolated systems with a broad energy distribution, the exponential decay is replaced by a 1/t distribution. We present confirmation of this decay law by experiments with cluster anions in a small electrostatic storage ring. Deviations from the 1/t law for such an ensemble give important information on the dynamics of the systems. As examples, we present measurements revealing strong radiative cooling of anions of both metal clusters and fullerenes. 相似文献
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If an exponential decay law is measured (which clearly need not be found in every case) it cannot be concluded that the line shape must be lorentzian. To show that the possible energy spectra may differ from a Lorentz shape by a well measurable amount an example of such a spectrum is constructed, leading to an exponential decay law in an even better approximation than a lorentzian spectrum. Hereafter various facts about decaying systems are discussed in connection with scattering theory. Finally it is shown that ordinary Mößbauer experiments are not suited for line shape measurements and modified experiments are proposed. 相似文献
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PENZhong-Zhou TAIFei SHENWen-Qing 《理论物理通讯》2003,40(2):191-194
We systematically analyze the experimental data of alpha decay in even-even heavy nuclei far from stability and find that the Geiger-Nuttall law brea~s for an isotopic chain when its neutron number is across a marc number or there is a deformed subshell. This break can be used to identify new magic numbers of superheavy nuclei. It is also discovered that there is a new linear relation between the logarithm of half-life and the reciprocal of the square root of decay energy for N = 126 and N = 152 isotones. It could be a new law of alpha decay for nuclei with magic neutron numbers but the physics behind it is to be explored. The significance of these researches for the search of new elements is discussed. 相似文献
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P. Závada 《Czechoslovak Journal of Physics》1975,25(11):1261-1278
Thermally stimulated process is discussed as a superposition of components with equal activation energy and a distribution of frequency factors. Changes of concentrations of individual components of this process proceed according to first order rate law. A relationship between Laplace transformation of the distribution of frequency factors and the law governing the resulting changes of the concentration is studied. An application on the thermal decay of F-centers indicates that actual activation energy tends to be greater than the energy resulting e.g. from Urbach analysis. Experimental procedures are proposed allowing the actual activation energy and the distribution of frequency factors to be determined. 相似文献
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The results of investigations of delayed luminescence decay are presented for disordered phenanthrene in the microsecond, millisecond, and second time ranges. At liquid nitrogen temperature, the highly non-exponential decay of both the phosphorescence and the annihilation delayed fluorescence is observed. This character of decay is caused by the relaxation of the electron-excitation energy in the system of energy-disordered centers when a quantity kT is much less than the width of the distribution for the excited-state energy. At the same time, the analysis of the time dependence for the triplet-triplet-annihilation rate exhibits two time intervals in which different kinetics is observed for the triplet excitations annihilation. In the microsecond range, the classical relationship between the phosphorescence and the delayed fluorescence takes place for the system under investigation; i.e., the triplet-triplet-annihilation rate is constant. At large times, the reaction-rate time dependence is described by the power law characteristic of inhomogeneous and low-dimensional systems. When the temperature increases, a transition to the classical behavior is observed throughout the entire time interval. 相似文献
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We systematically analyze the experimental data of alpha decay in even-even heavy nuclei far from stabilityand find that the Geiger-Nuttall law breaks for an isotopic chain when its neutron number is across a magic numberor there is a deformed subshell. This break can be used to identify new magic numbers of superheavy nuclei. It is alsodiscovered that there is a new linear relation between the logarithm of half-life and the reciprocal of the square root ofdecay energy for N = 126 and N = 152 isotones. It could be a new law of alpha decay for nuclei with magic neutronnumbers but the physics behind it is to be explored. The significance of these researches for the search of new elementsis discussed. 相似文献