信号调制下色噪声间关联的周期调制对单模激光随机共振的影响

在色噪声间的关联程度受时间周期调制的激光系统中,研究噪声受信号调制情况下的随机共振.用线性化近似的方法计算了光强关联函数及信噪比.具体讨论信噪比随噪声强度、噪声自关联时间、信号频率以及时间周期调制频率的变化关系.发现一种新的随机共振：信噪比随时间周期调制频率的变化出现周期振荡型随机共振;发现广义随机共振：信噪比随抽运噪声自关联时间的变化、随信号频率的变化出现随机共振;同时也存在典型的信噪比随噪声强度的变化而出现的随机共振.而信噪比随量子噪声自关联时间的变化表现为抑制. 关键词： 信号调制 时间周期调制 噪声间关联程度 周期振荡型随机共振     

小孔流速实验中的排水时间和流量系数的研究

本文以水作为理想流体,考虑到水头损失和孔口缩流效应,对小孔流速实验涉及的容器排水问题进行了系统的理论和实验研究.从理论上推导得出了圆柱形容器排水时间的解析解,分析了排水时间和自由液面速度、流量系数之间的规律,提出了排水时间的等效性.实验上,加工了底部开有不同小孔的大型圆柱形容器,测量了容器排水时间随液面高度的变化关系,借助实验结果计算了流量系数值,验证了容器排水时间的等效性关系,实验结果与理论计算符合较好.     

On the concept of time and the origin of the cosmological temperature

Time arises in the theory of gravity through the semiclassical approximation of the gravitational part of the solution of the Wheeler-De Witt equation in the manner shown by Banks (SCAG). We generalize Banks' procedure by grafting a Born-Oppenheimer type approximation onto SCAG. This allows for the feedback of matter onto gravity, wherein the latter is driven by the (quantum) mean energy-momentum tensor of matter. The wave function is nonvanishing in classically forbidden configurations of gravity. In SCAG this is described by the evolution of matter in imaginary time. This is interpreted as an inverse temperature, and the norm of the matter wave function, no longer conserved for these gravitational configurations, is a partition function. A simple cosmological model is worked out to illustrate these ideas. In this model it is shown that the temperature of the matter which emerges into the classically permitted region is the inverse bounce time of the bounce executed by the system in the forbidden region (behind the horizon).Time present and time past are both perhaps present in time future. And time future contained in time past. If all time is eternally present All time is unredeemable.—T. S. Eliot, Burnt Norton,Four Quartets, 1943.In honor of Ilya Prigogine on the occasion of his 70th birthday.     

Hierarchy of Times for the Establishment of the Gibbs Distribution

Doklady Physics - It is shown that there are three characteristic time scales for the establishment of thermodynamic equilibrium: the time for the thermalization of the system; the time for...     

On the delay time of the total signal from a set of transmitters

The time dependence of the total signal from a group of closely spaced acoustic or electromagnetic transmitters radiating the same (up to an amplitude factor) signals is considered. If the duration of the partial signal is sufficiently long, the time dependence of the signal from the set of transmitters turns out to be close to that of the signal from a single transmitter up to a delay time. This delay does not necessarily coincide with the time it takes for an optical (or acoustic) signal to pass from the transmitters to the observation point. At different points of the space, this delay time may exceed, or be shorter than, the light (sound) delay time and also may be positive or negative. This follows from the backward or forward extrapolation of the time dependence of the signal when variously delayed and attenuated copies of the same signal that are produced by different transmitters are added up (i.e., interfere). One result of such an extrapolation, which arises upon transmitting a signal with its leading or trailing edge cut off, is the reconstruction of its time dependence, i.e., the detection of the nontransmitted part of the signal.     

Time and temperature dependence of the specific heat of non-crystalline solids within the tunneling model

We propose a new way to introduce the measuring time in the Tunneling Model of non-crystalline solids. We have obtained a time dependent relation for the specific heat which can be used without limits in time or temperature. We prove that under the usual assumptions of the standard Tunneling Model and without free parameters one can understand quantitatively the experimentally observed time and temperature dependence of the specific heat and heat release experiments on vitreous silica over ten orders of magnitude in time. We also discuss the influence of conductions electrons on the time dependent specific heat. Time dependent experiments could provide useful information on the interaction of Tunneling Systems with conduction electrons.     

On the influence of viscosity on the characteristic time of the instability of a charged drop

A nonlinear integral equation describing the evolution of spheroidal deformation of a drop that is unstable with respect to its intrinsic charge is derived and solved for arbitrary values of viscosity. It was shown that, due to an essentially nonlinear character of the phenomenon, the characteristic time of instability develop-ment equals the time of tenfold increase in the amplitude of an initial, physically infinitesimal spheroidal deformation of an unstable drop. The dependence of the instability characteristic time on the drop viscosity is described by an increasing linear function.     

Computation of the far-field time domain solution of the scattering problem.

This paper presents a new technique for calculating the time domain (transient) far-field scattered pressure. The scattering problem is divided in two steps; the first step evaluates the field distribution inside the scatterer, and the second step generates the far-field scattered pressure by 3-D Radon transform of these data for each time step and summing over time. The algorithm results in considerable saving in CPU time and memory by simplifying the calculation along the path from scatterer to receiver. This technique can also be used in two dimensions.     

Dependence of the time of the appearance of a Stark echo response on irreversible relaxation of a system

The dependence of the time of the appearance of a Stark (gradient) echo response on the irreversible transverse relaxation time of a system in the nanosecond range and on the width of the excitation region of an inhomogeneously broadened line has been investigated. It has been shown that the use of nonresonant laser pulses with an artificially created spatial inhomogeneity makes it possible to determine the relaxation time in the nanosecond range from the time of the appearance of a Stark (gradient) echo response, which is a more accurate method than the method of determining the relaxation time from the decay of the intensity by varying time intervals of the exposure to inhomogeneous electromagnetic fields.     

微生物培养法推断纸张的相对生产时间

利用微生物培养法检测两种制浆方式的纸张,观察随着生产时间的不同,纸张上细菌和霉菌数量上的变化,根据其纸张上细菌和霉菌的变化规律,推断纸张的相对生产时间。该方法利用现代生物技术,对文件制成时间的检验提供一种新的思路和方法。     

Origin of the usefulness of the natural-time representation of complex time series

The concept of natural time turned out to be useful in revealing dynamical features behind complex time series including electrocardiograms, ionic current fluctuations of membrane channels, seismic electric signals, and seismic event correlation. However, the origin of this empirical usefulness is yet to be clarified. Here, it is shown that this time domain is in fact optimal for enhancing the signals in time-frequency space by employing the Wigner function and measuring its localization property.     

群速度色散对于纠缠光场二阶关联函数影响的研究

HBT干涉是量子测量中的一种重要手段, 其通过计算光场的二阶关联函数而得到测量结果. 在长距离测距中, 光场的二阶关联函数会受到光纤中群速度色散的影响而发生展宽和平移, 从而在一定程度上影响测量精度. 本文主要针对二阶关联函数半高宽受群速度色散的影响, 给出了半高宽与测量距离与群速度色散系数的关系.     

卤化银材料光作用过程的时间分辨谱测量

卤化银材料是重要的光信息材料，对于信息科学与技术的发展具有非常重要的作用。光作用过程的时间特性在很大程度上决定了卤化银材料性能的优劣。本文采用微波吸收技术来测量卤化银材料光作用过程的时间特性。卤化银材料样品被放入微波谐振腔中，在准分子激光的作用下，卤化银材料中生成了光生载流子，光生载流子的产生改变了卤化银材料的介电函数。因此，介电函数的变化体现光生载流子时间特性的信息，同时，介电函数的变化引起微波谐振腔品质因数的改变，品质因数的改变使腔输出了一个反射波，反射波包含卤化银材料光作用时间特性的信息，通过测量反射波、我们能获得卤化银材材料光作用过程的时间分辨谱并研究光作用过程的时间特性。本文获得了卤化银材料光作用过程的时间分辨谱，并对黑白、彩色和X－光片的光作用时间特性进行了分析。     

Determination of the scintillator decay time by the autocorrelation method

An autocorrelation method is developed for determining the composition and decay time of scintillators. This method also allows studying the spatial distribution of nuclear radiation and controlling the amount of the dopants introduced in the scintillator. The decay time is measured from a few nanoseconds to microseconds. It is found out that the decay time increases in plastic scintillators with a wavelength shifter and a Gd doped.     

Use of post-processing to increase the order of accuracy of the trapezoidal rule at time integration of linear elastodynamics problems

In this paper, we suggest a very simple and effective post-processing procedure to increase the order of accuracy in time for numerical results obtained by the trapezoidal rule. We first derive a new exact, closed-form, a-priori error estimator for time integration of linear elastodynamics equations by the trapezoidal rule with non-uniform time increments. Based on this error estimator, we suggest a new post-processing procedure (containing additional time integration of elastodynamics equations by the trapezoidal rule with few time increments) that systematically improves the order of accuracy of numerical results, with the increase in the number of additional time increments used for post-processing. For example, the use of just one additional time increment for post-processing after time integration with any number of uniform time increments, renders the order of accuracy of numerical results equal to 10/3. Numerical examples of the application of the new techniques to a system with a single degree of freedom and to a multi-degree system confirm the corresponding increase in the order of convergence of numerical results after post-processing. Because the same trapezoidal rule is used for basic computations and post-processing, the new technique retains all of the properties of the trapezoidal rule, requires no writing of a new computer program for its implementation, and can be easily used with any existing commercial and research codes for elastodynamics.     

Multifractal analysis of the Korean agricultural market

We have studied the long-term memory effects of the Korean agricultural market using the detrended fluctuation analysis (DFA) method. In general, the return time series of various financial data, including stock indices, foreign exchange rates, and commodity prices, are uncorrelated in time, while the volatility time series are strongly correlated. However, we found that the return time series of Korean agricultural commodity prices are anti-correlated in time, while the volatility time series are correlated. The $n$-point correlations of time series were also examined, and it was found that a multifractal structure exists in Korean agricultural market prices.     

On the propagation of hydrodynamic interactions

We present explicit expressions in real space and time for the equilibrium correlation functions of the density and velocity fields in a compressible fluid. This allows to discuss the time scales involved in the propagation of hydrodynamic interactions and its relevance on the dynamics of suspended colloidal particles. We show that hydrodynamic interactions develop in a sonic time scale, not in a vorticity time scale.     

Study of the time for ground state recovery of the dye BDN in the nematic liquid crystal 5CB

The recovery time of the ground state of the dye BDN in the liquid crystal 5CB has been measured as a function of temperature. We found that the recovery time decreases significantly with temperature and has an abrupt change near the transition point from mesomorphic to isotropic phase, which suggest that the recovery time of a saturable absorber is dependent on the molecular order.     

Intensity thresholds and the statistics of the temporal occurrence of solar flares

Introducing thresholds to analyze time series of emission from the Sun enables a new and simple definition of solar flare events and their interoccurrence times. Rescaling time by the rate of events, the waiting and quiet time distributions both conform to scaling functions that are independent of the intensity threshold over a wide range. The scaling functions are well-described by a two-parameter function, with parameters that depend on the phase of the solar cycle. For flares identified according to the current, standard definition, similar behavior is found.     

储存环HIAF-SRing等时性模式的非线性磁场影响研究

高精度环形谱仪SRing（Spectrometer Ring）是强流重离子加速器装置（HIAF）的重要组成部分,其等时性模式为远离β稳定线的短寿命原子核质量和寿命的精确测量提供国际领先的科研条件。为了扩大短寿命原子核质量测量精度和范围,SRing等时性模式设计了两种光学:γ_t=1.43和1.67。质量分辨是衡量等时性储存环的最重要参数。二极磁铁的高阶场以及磁铁的边缘场能强烈地引起束流光学高阶畸变,对质量分辨产生影响,因此需要高极磁铁对其进行校正。介绍了SRing等时性模式的线性计算,对非线性磁场的影响进行了详细研究。应用六极磁铁和八极磁铁对非线性场和发射度的影响进行了校正后,离子的循环时间标准偏差σ（T）/T达到3.5×10-7,质量分辨△m/m达到1×106。The isochronous mode of the Spectrometer Ring at the High Intensity heavy-ion Accelerator Facility (HIAF) project in China offers the capacity of measuring the mass and half-life of short-lived nuclides. The transition energy settings of the SRing are 1.43 and 1.67, which have been calculated in the same injection scheme. The resolution of mass or revolution time is the most important parameter of the isochronous mode design of a storage ring. The nonlinear magnetic field errors, including high-order magnet field of dipole, fringe field of magnets, have strongly effect to the resolution of revolution time. High-order corrections are required to improve the resolution of revolution time and mass. In this paper, the SRing linear isochronous optical were shown. The influence of nonlinear magnetic field errors on the revolution time resolving power were investigated. With 3 sextupole families and 1 octupole family corrections, the relative variation of revolution time reaches 4.6×10-7 with the momentum spread of ±0.2%. The relation of the relative standard revolution time deviation σ(T)/T and revolution turns was researched. With corrections of high-order isochronous condition and emittance influence by 3 sextupole families and 1 octupole family, one can reach a resolution of up to σ(T)/T=3.5×10-7, which corresponds to the mass resolution of △m/m=1×106.