非线性RL电路的暂态特性

对一个可解的非线性ＲＬ电路模型的暂态过程进行了研究，得到非线性ＲＬ电路的一些普遍特性，加深了加ＲＬ电路中的有关概念的理解，对教学有一定的参考价值。     

关于RL-C并联谐振特性曲线的讨论

从理论上导出了ＲＬ－Ｃ并联谐振电路的阻抗公式，由此分析谐振特性曲线的性质，并得出献中引用的ＲＬ－Ｃ谐振特性曲线成立的充分条件。     

RLC串联电路暂态过程的演示

介绍一种能显示ＲＬＣ串联电路暂态过程中三种不同情况下Ｒ和Ｃ上的电压波形的演示实验．     

RLC串联电路暂态过程中的几个问题

本文讨论了以周期性方波为电源的ＲＬＣ串联电路暂态过程中的几个问题．主要是给出了ＲＣ电路时间常数大于、小于或等于方波半周期的几种情况下电路微分方程的解和相应的实验结果，还讨论了ＲＬＣ串联电路临界电阻的测量方法和影响测量准确度的原因．     

RLC串联谐振教学实验的研究

ＲＬＣ串联谐振教学实验的研究陆申龙，曹正东（复旦大学上海２００４３３）（同济大学上海２０００９２）在物理实验教材中，ＲＬＣ串联谐振实验的教学重点是通过做ＲＬＣ串联谐振实验，使学生学习该谐振电路的电流随频率变化的特性，并掌握测量电路谐振曲线的方法．由谐...     

一种修正RLC串联电路暂态过程τ值的方法

对ＲＬＣ串联电路暂态过程提出一种测量方法,较好的解决了驰豫时间τ的测量值与计算值偏离较大的问题。     

RL-C并联谐振态量与Q的几个关系式

对ＲＬ－Ｃ并联谐振电路中的几个谐振态量与Ｑ之间的关系作了详尽的推导。     

介观电路的量子效应

本用涨落耗散定理证明了一个有源ＲＬＣ电路，在温度接近绝对零度时，存在量子效应；而当温度升高时，这一量子效应被热力学涨落淹没，并给出了绝对零度时，该电路的量子噪声的大小，以及电荷，电流的测不准点系。     

关于有源RLC电路的量子化

提出一种将有源ＲＬＣ电路量子化的方法,修正了有关文献中的错误。     

RLC电路非线性现象的演示

非线性现象的研究在电子线路、化学反应及非 平衡热力学等各个领域都有重要的理论和实际意义． 本文介绍用普通的白炽灯泡、变压器线圈和电容组成的 ＲＬＣ非线性电路，可以演示单稳、双稳、无稳等各种 现象．     

截止阀启闭过程内部瞬态流动特性

为分析截止阀启闭过程内部的瞬态流动特性,基于N-S方程和标准的κ-ε湍流模型,通过自定义函数(UDF)和C++语言编程给定阀芯的运动规律,采用动网格技术对截止阀进行了瞬态的全三维湍流数值模拟,得到阀芯在不同运动时刻的瞬态流场,阀芯在运动过程中受到的流体挤压效应是影响截止阀性能的主要原因。截止阀瞬态的全三维数值研究具有较高的可靠性,数值结果为进一步研究截止阀的性能提供重要理论依据。     

ESTIMATION OF THERMAL CONTACT CONDUCTANCE DURING RESISTANCE SPOT WELDING

This article describes an experimental procedure conducted to estimate and investigate the transient thermal contact conductance (or thermal contact resistance) between the electrodes and workpieces during resistance spot welding. A fine thermal metrology was developed to collect thermal histories near the welding region. Indeed, the electrode tip was instrumented with several interior microthermocouples for measuring the transient temperature response during the welding process. A simple mathematical model, using an inverse heat transfer method, was built for the estimation of the transient heat transfer coefficient from interior transient temperature measurements. A simple resistance welding case of two steel sheets was investigated. The initial transient values of thermal contact conductance were found to be in agreement with those observed in the dry copper–steel solid contact case. At the end of the process, the transient heat transfer coefficient reaches a high value corresponding to the best heat transfer phenomenon at the interface during the welding process. When the metal is melted, the contact quality increases due to the high-applied electrode force. Higher electrode force and heating temperatures produce lower thermal contact resistance. The results obtained show the capabilities and the power of the coupled thermal metrology and transient inverse technique developed to investigate thermal history of resistance spot welding.     

Phase modulation of transient evolution of atomic response in open lambda-type system with spontaneously generated coherence

We study the effects of the relative phase, Φ, between the probe and driving fields on the transient evolution of the atomic response from different respects in an open lambda-type system with spontaneously generated coherence. We find that: variation of value of Φ will obviously change the transient evolution process, transient and stationary values of gain, absorption and dispersion but has no any effect on the transient evolution of populations. For the same value of Φ, the stationary gain without inversion (GWI) when the incoherent pumping exists is much larger than that when the incoherent pumping is absent, the time needed to reach at the stationary state when the incoherent pumping exists is much shorter than that when the incoherent pumping is absent. The initial condition varying has remarkable effects on the phase-dependent transient evolution process, transient value of GWI but doesn’t vary size of stationary value of GWI. Varying the ratio C of the atomic injection rates and exit rate γ₀ has evident effects on the phase-dependent transient evolution process, transient and stationary values of GWI. Our study result shows that the transient evolution of the atomic response in the open system presents some considerable difference from that in the corresponding closed system, specially in the open system we can get much larger GWI than that in the corresponding closed system. In addition, we give a brief discussion about effects of the relative phase on the transient evolution of the atomic response in the open system without SGC, and obtain some results much different from those obtained in the open system with SGC.     

开放V型系统相对位相对LWI增益瞬态演化的影响

数值计算具有自发辐射诱导相干性的开放V型三能级原子系统密度矩阵运动方程,分析无反转激光(LWI)增益的瞬态演化.结果表明:无论是否存在非相干抽运,探测场和驱动场间的相对位相(Ф)对增益的瞬态演化都有显著的影响;通过选择的取值可以获得更大的瞬态和稳定增益;不存在非相干抽运时,系统达到瞬态增益最大值及获得增益稳定值所需要的时间更长,演化过程中振荡幅度更大,获得的增益更大;原子退出速率r0(原子注入速率比S)的变化将使增益瞬态演化的具体过程发生改变,在r0(S)的一定取值范围内,瞬态和稳定增益随S(r0)的增大而增大.     

Effects of Vacuum-Induced Coherence on One- and Two-Photon Absorption Spectra of Transient Process in a Y-Type System

We investigate the influence of the vacuum-induced coherence on one- and two-photon absorption of the transient process in a four-level Y-type atomic system. We find that the one- and two-photon transient absorption and amplification properties are quite sensitive to the vacuum-induced coherence. It is also shown that the one- and two-photon absorption spectra of the transient process can be dramatically affected by modulating the relative phase of the applied fields. By appropriately choosing the relative phase, the amplification of the probe field can be achieved.     

TRANSIENT OPTICAL VORTICES IN THE PROCESS OF PATTERN FORMATION IN A KERR SLICE SYSTEM WITH SINGLE FEEDBACK

The transient process of the optical pattern formation in a Kerr medium is numerically studied. We find that the process is accompanied by transient optical vortices in the far field. The temporal evolutions of the appearance and disappearance of the vortices are presented. All vortices will vanish when the system approaches its steady state. The number of vortices versus time is given.     

Asymptotic Behaviour of Randomly Reflecting Billiards in Unbounded Tubular Domains

We study stochastic billiards in infinite planar domains with curvilinear boundaries: that is, piecewise deterministic motion with randomness introduced via random reflections at the domain boundary. Physical motivation for the process originates with ideal gas models in the Knudsen regime, with particles reflecting off microscopically rough surfaces. We classify the process into recurrent and transient cases. We also give almost-sure results on the long-term behaviour of the location of the particle, including a super-diffusive rate of escape in the transient case. A key step in obtaining our results is to relate our process to an instance of a one-dimensional stochastic process with asymptotically zero drift, for which we prove some new almost-sure bounds of independent interest. We obtain some of these bounds via an application of general semimartingale criteria, also of some independent interest.     

开放Ⅴ型系统相对位相对LWI增益瞬态演化的影响

数值计算具有自发辐射诱导相干性的开放V型三能级原子系统密度矩阵运动方程,分析无反转激光(LWI)增益的瞬态演化.结果表明:无论是否存在非相干抽运,探测场和驱动场间的相对位相(Ф)对增益的瞬态演化都有显著的影响;通过选择Ф的取值可以获得更大的瞬态和稳定增益;不存在非相干抽运时,系统达到瞬态增益最大值及获得增益稳定值所需要的时间更长,演化过程中振荡幅度更大,获得的增益更大;原子退出速率r₀(原子注入速率比S)的变化将使增益瞬态演化的具体过程发生改变,在r₀(S)的一定取值范围内,瞬态和稳定增益随S(r₀)的增大而增大.     

High-resolution positron lifetime spectrometer with BaF2 scintillators

A transient negative photoconductivity phenomenon observed in silicon doped with gold atoms by an appropriate diffusion condition has been investigated. The transient negative photoconductivity could be observed with a diode doped with gold atoms under intrinsic light-pulse illumination. In the recovery process of the transient negative photoconductivity to a steady-state dark level, two kind of time constants were observed, which may be related with the emission of electrons from gold level. A dependence of the magnitude of the peak value on the ambient temperature was observed; a qualitative explanation is given.     

Regional business cycle synchronization through expectations

This paper provides an example in which regional business cycles may synchronize via producers’ expectations, even though there is no interregional trade, by means of a system of globally coupled, noninvertible maps. We concentrate on the dependence of the dynamics on a parameter η which denotes the inverse of price elasticity of demand. Simulation results show that several phases (the short transient, the complete asynchronous, the long transient and the intermediate transient) appear one after another as η increases. In the long transient phase, the intermittent clustering process with a long chaotic transient appears repeatedly.