谈“相对论”教学中遇到的几个问题的处理

根据狭义相对性原理,惯性系是完全等价的,在同一个惯性系中,存在统一的时间,称为同时性,而相对论证明,在不同的惯性系中,却没有统一的同时性,也就是两个事件(时空点)在一个惯性系内同时,在另一个惯性系内就可能不同时,这就是同时的相对性,在惯性系中,同一物理过程的时间进程是完全相同的,如果用同一物理过程来度量时间,就可在整个惯性系中得到统一的时间.非惯性系中,时空是不均匀的,也就是说,在同一非惯性系中,没有统一的时间,因此不能建立统一的同时性.由此从下面几个问题来说明,值得一起商榷. 一.对于人教版3-4课本P109图15.2-3如何解释?     

“探究:牛顿第一定律”的教学案例

1教学设计1.1教学思想本节包含牛顿第一定律和惯性两部分.教材内容较多,《课程标准》要求较高,而学生的"前概念"根深蒂固,自制力弱,课堂注意力集中时间较短,在规定时间完成学习任务难度较大.所以,教学设计采用"五让"教学法,充分发挥学生的主体地位和教师     

关于牛顿定律和质量定义

在质量问题的讨论中,有些同志对质量是惯性的量度这一说法提出了反对意见。他们认为:根据惯性的定义,惯性是任一物体在没有外界作用迫使它改变状态之前保持其匀速直线运动或静止状态的性质,因此不管什么物体在没有受外界作用时,都毫无差别地显示出这种性质;这样惯性就无大小可言,就不能把质量和惯性联系起来,质量当然也就不能是惯性的     

热惯性对热弹性行为影响的渐近分析

当热作用时间或受热器件结构尺寸呈现微尺度特征时, 热流运动的惯性效应将对热量的传递过程产生显著地影响. 基于热质的概念, 依据牛顿力学原理引入用于描述热质运动的热波方程, 结合各向同性材料的本构关系, 构建了计及热流运动惯性效应的广义热弹性动力学模型. 利用超常传热的微尺度特征, 采用解析的方法对半无限大体外表面受热冲击作用的一维问题进行了渐近求解. 通过对热波、热弹性波的传播和各物理场分布的分析以及与已有广义热弹性理论预测结果的对比, 揭示了热流运动的惯性效应对热弹性行为的影响. 结果表明：热量的传递除了受到热流加速的时间惯性影响之外, 热流运动的空间惯性也对传热行为产生影响, 当计及空间惯性时, 热波、热弹性波的波速、波前位置, 各物理场的建立时间、阶跃峰值及阶跃间隔均受到不同程度的影响. 关键词： 热惯性 热质运动 广义热弹性动力学模型 渐近分析     

关于运动的钟变慢的讨论

"运动的钟变慢"是相互的.通过这个结论,本文进一步论证处在两个不同惯性系的两个时钟,它们的读数与观察者所处的惯性系无关.     

《广义相对论入门讲座》连载②——广义相对论的物理基础

1狭义相对论的困难洛伦兹变换表明,时间和空间存在内在联系."能量动量张量"的表达式和"质能关系式"等表明,质量和运动不可分割.光速不变原理和相对性原理告诉我们,一切惯性系都是平权的,不可能测出相对     

乒乓球的“反常”运动

我们知道,由于惯性,物体运动状态发生变化时,看起来好像呈"相反"的运动状态;比如刹车时乘客向前倾倒,车启动时乘客向后倾倒.在教学中还有这样一个惯性"反常"的问题引起了学生的兴趣:在一个密闭、充满水的长方体容器的顶部和底部分别系一个铁球和一个乒乓球,如图1(a)所示.刚开     

脉冲管制冷机调相惯性管的设计理论及通用图表

本文介绍一种针对纯惯性管以及惯性管加无限大气库的选型图表.系统介绍了其设计理论.通过与实验值的对比,采用了符合较好的简化湍流模型进行计算.为了使图表易于使用,本文提出了一组更实用的无量纲参数和计算"无限大"气库体积的方法.最终,通过两个实例,给出了应用该表的使用方法和应注意的问题.     

惯性颗粒所见流场拓扑结构

本文采用直接数值模拟的方法从颗粒所见的流场拓扑结构这一角度探讨了颗粒在不同拓扑结构下速度统计特性.结果表明,不同惯性的颗粒所见流体的速度特性类似,在Top1和Top2结构中,随时间演化而减少,而在Top3和Top4结构中随时间有波浪性的增长;由于颗粒惯性的差异引起的轨道交叉效应不同,颗粒与颗粒所见流体速度的关联随颗粒增大而衰减加剧,在颗粒与流体相之间的能量传递中,不同拓扑结构明显不同,从颗粒加入时能量由颗粒相向流体传递,各拓扑结构的相对强度为Top2>Top4>Top1>Top3,演化到后期能量由流体相向颗粒相传递,相对强度为Top1>Top2>Top3>Top4;st=1.0和st=10.0的颗粒差别在于演化后期Top2和Top3相对强度的转变.     

时间间隔的正确理解

在狭义相对论框架中研究不同惯性参照系时间间隔问题并讨论了两个典型的问题,通过讨论,明确时间膨胀和固有时的严格意义.     

Proposal of a dual-ball atomic fountain clock

A simple improved structure is designed to trap and launch two cold atomic balls vertically at the same time,which works like"two fountains",but is more compact since most components of the"two fountains" are shared.It is expected to improve the stability of the fountain markedly.     

Geometric phase and entanglement for massive spin-1 particles

The cyclic evolution of a spin-1 system is studied under the spin-spin interaction between the transverse and the longitudinal states. The eigenstates of the systems are obtained by generalized and extended Jordan-Wigner transformation with an angle described the path of particle propagation. According to the wave functions of time evaluation for many-particle systems, the entanglement effects and geometric phase are observed. The systems with more than two particles, in contrast to the two particle system, evolve in time with two parameters.     

The combination of dual waveband (3～5um and 8～12um) thermal image

For the two colour (35um and 812um) sensor fusion, an optical method can replace the electric time delay and integration (TDI) circuit. During the fusion process, there exits an optimal relative gain setting between the two preamplifiers of the sensors. The optical method can provide a real time (30 frames) single enhanced dual band thermal image with an improved signal to noise ratio and better system performance.     

基因转录调控系统中的色噪声诱导转化研究

研究了基因转录调控系统中的色噪声诱导蛋白质浓度转换现象. 据Novikov定理和Fox近似方法得到相应的Fokker-Planck方程, 给出稳态概率分布函数、蛋白质浓度平均值及其平均首通时间的近似表达式, 分析了噪声的自关联时间对稳态概率、平均值和平均首通时间的影响. 研究表明, 分解率的噪声的自关联时间引起蛋白质的浓度经历了“关”→“开”的转换; 合成率的噪声的自关联时间引起蛋白质的浓度经历了“开”→“关”转换. 然而, 随着两种自关联时间的增大, 平均首通时间增大, 即蛋白质浓度之间的转换变得困难. 数值模拟结果与理论预测基本符合. 关键词： 色噪声 基因转录调节系统 转换     

Interpretation of the curious results of the new quantum formalism of pre- and post-selected systems

The analysis, with the use of two state vectors, of a quantum system, during the time interval between two measurements, leads to some amazing results, which seem to contradict our usual quantum common sense. We explore the questions of compatibility with the conventional quantum theory, uniqueness of pre- and post-selected ensembles, commutativity, simultaneity and reality of strong and weak values in the intermediate time, and the meaning of the weak value. Common criticisms are shown to be unfounded.     

Theoretical Study on Grating Formation in Photovoltaic Photorefractive LiNbO<Subscript>3</Subscript> Crystal with Short Light Pulses

Based on Valley’s quasi-cw approximation, the grating formation in materials exhibiting bulk photovoltaic effect on illumination with short light pulses (such as ns pulses) is investigated. We give the expression of the space-charge field, and find that it has two time constants. When considering and not considering the photovoltaic effect, the diagrams of two time constants as a function of irradiance in units of are the same. The energy required to erase a grating to 1/e of its initial value is also studied in the two cases. The two results are also the same.     

Speech detection in spatial and nonspatial speech maskers

The effect of perceived spatial differences on masking release was examined using a 4AFC speech detection paradigm. Targets were 20 words produced by a female talker. Maskers were recordings of continuous streams of nonsense sentences spoken by two female talkers and mixed into each of two channels (two talker, and the same masker time reversed). Two masker spatial conditions were employed: "RF" with a 4 ms time lead to the loudspeaker 60 degrees horizontally to the right, and "FR" with the time lead to the front (0 degrees ) loudspeaker. The reference nonspatial "F" masker was presented from the front loudspeaker only. Target presentation was always from the front loudspeaker. In Experiment 1, target detection threshold for both natural and time-reversed spatial maskers was 17-20 dB lower than that for the nonspatial masker, suggesting that significant release from informational masking occurs with spatial speech maskers regardless of masker understandability. In Experiment 2, the effectiveness of the FR and RF maskers was evaluated as the right loudspeaker output was attenuated until the two-source maskers were indistinguishable from the F masker, as measured independently in a discrimination task. Results indicated that spatial release from masking can be observed with barely noticeable target-masker spatial differences.     

Discrimination of symmetric time-intensity traded binaural stimuli

Experiments were conducted to determine the extent to which listeners can discriminate between different combinations of interaural time and intensity for binaural stimulus configurations which eliminate loudness, lateralization, and image-diffuseness cues. A two-interval forced choice paradigm was used, and the task of the subject was to determine the order of two stimuli, each of which was a slowly gated 500-Hz tone with a combination of interaural time and intensity differences that resulted in a centered primary spatial image. The two stimuli to be discriminated were symmetric in that they differed only in the polarity of their interaural differences. Also, in order to reduce artifacts introduced by variations in the coupling of the earphones to the head, acoustic monitoring and compensation was performed both before and after each experimental run. The performance of the two most highly trained subjects is consistent with previous experimental results that indicate an incomplete trading of interaural time and intensity information. The subjective perceptions of these observers are not consistent with previous studies that describe a "time image" and a "time-intensity traded" spatial image.     

Interruptedz-pinch filamentary structure

The longitudinalz-pinch time evolution study between two conical electrodes was carried out by means of the interferometric and the schlieren methods, the discharge basic parameters time development (namely geometry, filamentary structure and electron density) was investigated.     

Stochastic models of firstorder nonequilibrium phase transitions in chemical reactions

The steady states of a simple nonlinear chemical system kept far from equilibrium are analyzed. A standard macroscopic analysis shows that the nonlinearity introduces an instability causing a transition analogous to a thermodynamic first-order phase transition. Near this transition the system exhibits hysteresis between two alternative steady states. Fluctuations are introduced into this model using a stochastic master equation. The solution of this master equation is unique, preventing two alternative exactly stable states. However, a quasi-hysteresis occurs involving transitions between alternative metastable steady states on a time scale that is longer than that of the fluctuations around the mean steady state values by a factor of the forme , where ø is the height of a generalized thermodynamic potential barrier between the two states. In the thermodynamic limit this time scale tends to infinity and we have essentially two alternative stable steady states.