Non-invasive Measurement of Simulated Burn Depth Using Intensity Fluctuations of Diffusion Light

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Non-invasive Measurement of Simulated Burn Depth Using Intensity Fluctuations of Diffusion Light

The determination of burn depth is an important problem for surgeons to remedy severe skin burns. The burn can be simplified as a two-layer media model: a static layer and a dynamic layer. In this paper, the relative fluctuation of backscattering light intensity was used to determine the simulated burn depth. The experimental results show that the relative fluctuation of light intensity increases with the simulated burn depth and the depth less than 0.1 mm can be resolved. This new method may be useful for burn diagnosis.     

Velocity Fluctuations and Transport in the JET Boundary Region

A new approach for turbulent fluxes and _E×B measurements in the bulk plasma is proposed. It is based in the measurement of fluctuations in the phase velocity of fluctuations. The structure of turbulence has been investigated in the JET plasma boundary region with a fast reciprocating Langmuir probe system. Fluctuations in the radial and poloidal phase velocity have been computed from floating potential and ion saturation current measurements. The correlation between density fluctuations and fluctuations in the radial velocity of fluctuations signals show a good agreement with the turbulent transport computed from the correlation between density and poloidal electric field fluctuations. These results suggest that turbulent transport might be computed in the plasma core from measurement of density fluctuations. E×B sheared flows, both constant and varying in time, are close to the critical value to trigger the transition to improve confinement regimes below the power threshold to trigger the formation of transport barriers.     

Stress Tensor Fluctuations and Stochastic Spacetimes

The physics of the quantum stress tensor operator is discussed. Although theproblem of defining the expectation values of this operator is reasonably wellunderstood, the fluctuations around the mean value are not so well understood.It is shown that the stress tensor correlation function can be decomposed intothree parts, one of which is finite and state dependent, one which is infinite inthe coincidence limit but state independent, and a cross term which is both statedependent and infinite in the coincidence limit. Possible physical interpretationsof each part are discussed. The fluctuations of the stress tensor in turn inducefluctuations of the spacetime geometry. The terms in the correlation functionwhich are singular in the coincidence limit seem to produce drastic fluctuationsof the geometry, leading to a stochastic spacetime. Whether these fluctuationsare observable is an unanswered question.     

Black Hole Fluctuations and Backreaction in Stochastic Gravity

We present a framework for analyzing black hole backreaction from the point of view of quantum open systems using influence functional formalism. We focus on the model of a black hole described by a radially perturbed quasi-static metric and Hawking radiation by a conformally coupled massless quantum scalar field. It is shown that the closed-time-path (CTP) effective action yields a non-local dissipation term as well as a stochastic noise term in the equation of motion, the Einstein–Langevin equation. Once the thermal Green's function in a Schwarzschild background becomes available to the required accuracy, the strategy described here can be applied to obtain concrete results on backreaction. We also present an alternative derivation of the CTP effective action in terms of the Bogolyubov coefficients, thus making a connection with the interpretation of the noise term as measuring the difference in particle production in alternative histories.     

Non Equilibrium Current Fluctuations in Stochastic Lattice Gases

We study current fluctuations in lattice gases in the macroscopic limit extending the dynamic approach for density fluctuations developed in previous articles. More precisely, we establish a large deviation principle for a space-time fluctuation j of the empirical current with a rate functional I(j). We then estimate the probability of a fluctuation of the average current over a large time interval; this probability can be obtained by solving a variational problem for the functional I. We discuss several possible scenarios, interpreted as dynamical phase transitions, for this variational problem. They actually occur in specific models. We finally discuss the time reversal properties of I and derive a fluctuation relationship akin to the Gallavotti-Cohen theorem for the entropy production.     

Constancy of the Velocity of Light in Vacuum

Recently a series of papers^1-15 have been published tending to discredit Einstein's principle on the constancy of the velocity of light in vacuum and to renew theories on the propagation of light abandoned long ago. Subsequently we rediscuss some of the arguments and inconsistencies presented in Refs. 1-15.     

Stability of Decoherence-Free Subspaces under Stochastic Phase Fluctuations

We study the stability of decoherence-free subspaces under stochastic phase fluctuations by analytically and numerically evaluating the fidelity of the corresponding decoherence-free subspace bases with stochastic phase fluctuations under the evolution of environment. The environment is modeled by a bath of oscillators with infinite degrees of freedom and the register-bath coupling is chosen to be a general dissipation-decoherence form. It is found that the decoherence-free subspaces take on good stability in the case of small dissipation and small phase fluctuations.     

Stability of Decoherence-Free Subspaces under Stochastic Phase Fluctuations

We study the stability of decoherence-free subspaces under stochastic phase fluctuations by analytically and numerically evaluating the fidelity of the corresponding decoherence-free subspace bases with stochastic phase fluctuations under the evolution of environment. The environment is modeled by a bath of oscillators with infinite degrees of freedom and the register-bath coupling is chosen to be a general dissipation-decoherence form. It is found that the decoherence-free subspaces take on good stability in the case of small dissipation and small phase fluctuations.     

用统计的方法研究光拍法测光速实验中的电流表达式

根据光电子具有泊松分布的特点得到一定光强的光入射到光电探测器后,光电流的表达式,并对光电流的起伏误差进行了分析。     

基于双光导纤维延时法测量光速

介绍了利用光波在已知长度差的两段不同长度的光导纤维中传输时间延时差测量光速的基本原理。时钟方波信号通过LED调制电路转变为光信号在一段光导纤维中传输,后经SPD再生电路重新转变为方波再生信号,将原始方波信号与再生方波信号同时输入示波器中测量延时τ1,采用相同的方法测量另一端光导纤维传输延时τ2,通过已知的长度差和延时计算出光导纤维中的光速VZ,最终计算出光速c。     

The International Atomic Time and the Velocity of Light

Atomic clocks distributed around the world communicate with one another by means of radio signals. The synchronization signals sent by a transmitting station always reach the receiving station on time, at any hour of the day and in any season, despite the motion of the Earth. For some authors this means that these signals propagate isotropically (with one way velocity c), even with respect to the Earth's surface. In fact this may not be so; we show that the proper working of the network says nothing about the one-way velocity, as it is consistent with another theory, empirically (almost) equivalent to special relativity, in which the one-way speed of light has a directional dependence in moving frames.     

Radar Testing of the Relative Velocity of Light in Space

Published interplanetary radar do to presents evidence that the relative velocity of light in space is c+v and not c.     

Phase Transitions and Spatio-Temporal Fluctuations in Stochastic Lattice Lotka–Volterra Models

We study the general properties of stochastic two-species models for predator-prey competition and coexistence with Lotka–Volterra type interactions defined on a d-dimensional lattice. Introducing spatial degrees of freedom and allowing for stochastic fluctuations generically invalidates the classical, deterministic mean-field picture. Already within mean-field theory, however, spatial constraints, modeling locally limited resources, lead to the emergence of a continuous active-to-absorbing state phase transition. Field-theoretic arguments, supported by Monte Carlo simulation results, indicate that this transition, which represents an extinction threshold for the predator population, is governed by the directed percolation universality class. In the active state, where predators and prey coexist, the classical center singularities with associated population cycles are replaced by either nodes or foci. In the vicinity of the stable nodes, the system is characterized by essentially stationary localized clusters of predators in a sea of prey. Near the stable foci, however, the stochastic lattice Lotka–Volterra system displays complex, correlated spatio-temporal patterns of competing activity fronts. Correspondingly, the population densities in our numerical simulations turn out to oscillate irregularly in time, with amplitudes that tend to zero in the thermodynamic limit. Yet in finite systems these oscillatory fluctuations are quite persistent, and their features are determined by the intrinsic interaction rates rather than the initial conditions. We emphasize the robustness of this scenario with respect to various model perturbations.     

随机对流扩散方程的数值仿真

本文针对对流一扩散随机过程在随机输入（即随机输运和源项）,作用下进行数值仿真。我们先将对流扩散随机微分方程中的随机函数采用有限项截断的多项式浑沌展开（Polynomial Chaos Expansion）展开,再由Galerkin映射法得到求解浑沌展开系数的确定性方程组。这是一个在物理空间包含多尺度解的大方程组。为此我...     

光速测量仪中的远程光光程测量方法的改进

通过对大学物理实验光速测量仪测量光速中的远程光光程测量方法的改进,得到影响测量精度的主要误差来源于远程光光程的测量误差,并进行了分析计算,提出了控制误差的方法和措施。     

Nonequilibrium Fluctuations of Light Scattering Intensity in the Neighborhood of the Phase Transition Temperature

Optics and Spectroscopy - Light scattering in a 3% aqueous solution of hydroxypropyl methylcellulose (metolose) is studied under nonequilibrium conditions within a temperature range of...