非平衡电桥的输出特性研究

研究了非平衡电桥的工作原理和输出特性,利用自组的实验装置进行了测量.     

用单片机制作交流电桥平衡指示器

1 引言交流电桥是电磁学实验仪器,它主要用来测量电容器的电容量和线圈的电感量,是电感、电容测最中精确度较高的测量方法,而且,为了提高电桥测量精度,人们进行了一些有关电桥平衡指示器的探讨性实验。     

关于自组凯尔文电桥的测量不确定度

凯尔文电桥是国内大学基础物理实验所开设的实验内容之一，且多为自组式．关于自组凯尔文电桥的测量精度与桥路参数精度之间的关系，有些实验教材已有推导，但尚未涉及与两低阻相邻电压接头间跨桥电阻的定量关系，不注意这一点，会给测量结果带来一定的误差．本文就实际中常用的等双臂凯尔文电桥从理论上定量地推出了这一关系，进而给出了跨桥电阻可忽略时的适当阻值．     

交流电桥实验中对市黾干扰信号的一种处理方法

在自搭交流电桥测量电容电感的实验中,市电干扰信号的影响不可忽略,本文给出了一种利用示波器鉴别和分市电博物坟与电桥不平衡电压的方法。     

交流电桥实验中对市电干扰信号的一种处理方法

在自搭交流电桥测量电容电感的实验中,市电干扰信号的影响不可忽略.本文给出了一种利用示波器鉴别和区分市电干扰信号电压与电桥不平衡电压的方法.     

用电阻箱自组电桥的桥臂电阻选择

本文分析了用电阻箱作桥臂电阻自组电桥的灵敏度及测量结果不确定度,给出桥臂电阻的选择原则。     

相量法在交流电桥实验中的应用

相量法是分析正弦交流电路问题的重要方法之一.它的特点是数学模型简单、直观,可操作性强.本文以交流电桥实验中的电感桥和电容桥为例,展示了相量法在交流电桥平衡的分析与求解过程中的优点.该方法用于交流电桥实验不仅有助于学生巩固相量的概念,而且能深刻地理解交流电桥的测量原理.     

讨论交流电桥测电容的误差计算方法

利用交流电桥可以精确测量电容器的电容.由于该电桥结构复杂,对测量结果的影响因素是多方面的.本文探讨了对测量结果的不确定度的评价方法,试图完善交流电桥实验的教学内容.     

用非平衡电桥测电阻抗在医学上的应用

通常用平衡交流电桥测量确定的电阻抗值,但在医学上常会遇到随时间变化的电阻抗,测量这种变化电阻抗可用非平衡交流电桥。这种变化的电阻抗可以给出许多医学信息,因而使得用电桥测电阻抗这一非常普通的物理方法,在医学上得到实际应用。     

利用李萨如图形测量交流阻抗特性

通常用交流电桥法测量电容、电感等交流阻抗的数值,由于待测的交流阻抗不一定是“纯”的电容或电感,其中总存在一定的等效电阻,所以,用交流电桥法测量的结果误差较大。本文所介绍的李萨如图形方法,直接测量通过阻抗的电流和两端电压间的相位差,通过调节电路中的电阻,使这一相位差与标     

交流电桥的调节技巧

交流电桥在电测技术中占有重要地位,而它的平衡条件和实现平衡的调节过程都比较复杂,通过对两个实验案例的电桥平衡调节方法进行对比,总结出几条有效的调节技巧,与初学者共同探讨交流。     

基于安柏AT810数字电桥的杨氏模量的测定

引入了电桥法测量杨氏模量,用自制平行板电容器对传统的实验装置进行改进,用电容的变化来表征微小位移的变化,使用数字电桥测量仪作为信号采集下位机、PC机作为上位机并使用MATLAB作为信号处理软件,减小了人工测量等因素所产生的误差,由此给出了一种测量杨氏模量更精确的方法。     

掺Er^3＋离子Sr3Y2（BO3）4晶体光谱性能的研究

研究了提拉法生长的掺Er^3＋的Sr3Y2（BO3）4晶体的吸收光谱和荧光光谱。应用J—O理论分析并计算了光谱参数,得到唯象参数Ω2、Ω4和Ω6分别为11．90×10^-20cm^2、3．44×10^-20cm^2和1．92×10^-20cm^2。在Er^3＋：Sr3Y2（BO3）4晶体中,Er^3＋在1533nm波长的发射截面为1．00×10^-20cm^2,^4I13／2→^I15／2能级跃迁的荧光寿命和辐射寿命分别为0．58ms和4．10ms,良好的光谱性能表明Er^3＋：Sr3Y2（BO3）4晶体可能成为潜在的1．55μm波段的一种激光材料。     

多角度偏振成像仪遥感图像太阳耀斑区的拖尾校正方法

为了有效校正星载偏振相机成像时太阳耀斑区产生的拖尾,以高分五号卫星多角度偏振成像仪为例,结合多角度偏振成像仪在轨成像特点,理论分析了图像获取过程中拖尾产生的机理.建立了光斑区不含饱和像元情况下能够有效对漏光拖尾进行校正的矩阵法与暗行法校正模型,以及光斑区全像元饱和情况下结合矩阵法与暗行法估计光斑区饱和像元强度的遗留拖尾校正模型,该算法充分考虑了强光饱和条件下太阳耀斑区产生的漏光拖尾与遗留拖尾.利用实验室积分球光源成像光斑模拟在轨运行时遥感图像太阳耀斑开展拖尾校正方法可行性验证实验.实验结果表明,该方法不仅能有效去除图像中的拖尾噪声,提高图像质量,而且能够对光斑饱和像元强度进行有效估计.最后,分析多角度偏振成像仪在轨成像图中耀斑区拖尾对其辐亮度测量精度的影响,分析结果表明,拖尾校正前后,灰度方差由202.69×10^6下降至2.32×10^6,平均梯度由5.08×10^-1下降至2.26×10^-1.     

Nuclear Forces in the Odd Parity Sector and the LS Forces from Lattice QCD

The first lattice QCD calculation for the spin-orbit potential as well as the central and the tensor potentials in parity odd sector is presented for the two-nucleon system. These potentials are extracted from the Nambu-Bethe-Salpeter (NBS) wave functions for total angular momenta ${J^{P}=A_1^{-}(0^-),T_1^{-}(1^-),T_2^{-}\oplus E^{-}(2^-)}$ based on the representation theory of the cubic group.     

A low-noise,high-SNR balanced homodyne detector for the bright squeezed state measurement in 1–100 kHz range

We report a low-noise, high-signal-to-noise-ratio(SNR) balanced homodyne detector based on the standard transimpedance amplifier circuit and the inductance and capacitance combination for the measurement of the bright squeezed state in the range from 1 kHz to 100 kHz. A capacitance is mounted at the input end of the AC branch to prevent the DC photocurrent from entering the AC branch and avoid AC branch saturation. By adding a switch at the DC branch,the DC branch can be flexibly turned on and off on different occasions. When the switch is on, the DC output provides a monitor signal for laser beam alignment. When the switch is off, the electronic noise of the AC branch is greatly reduced at audio-frequency band due to immunity to the impedance of the DC branch, hence the SNR of the AC branch is significantly improved. As a result, the electronic noise of the AC branch is close to -125 dBm, and the maximum SNR of the AC branch is 48 dB with the incident power of 8 mW in the range from 1 kHz to 100 kHz. The developed photodetector paves a path for measuring the bright squeezed state at audio-frequency band.     

Stochastic Averaging Principle for Spatial Birth-and-Death Evolutions in the Continuum

We study a spatial birth-and-death process on the phase space of locally finite configurations \({\varGamma }^+ \times {\varGamma }^-\) over \({\mathbb {R}}^d\). Dynamics is described by an non-equilibrium evolution of states obtained from the Fokker-Planck equation and associated with the Markov operator \(L^+(\gamma ^-) + \frac{1}{\varepsilon }L^-\), \(\varepsilon > 0\). Here \(L^-\) describes the environment process on \({\varGamma }^-\) and \(L^+(\gamma ^-)\) describes the system process on \({\varGamma }^+\), where \(\gamma ^-\) indicates that the corresponding birth-and-death rates depend on another locally finite configuration \(\gamma ^- \in {\varGamma }^-\). We prove that, for a certain class of birth-and-death rates, the corresponding Fokker-Planck equation is well-posed, i.e. there exists a unique evolution of states \(\mu _t^{\varepsilon }\) on \({\varGamma }^+ \times {\varGamma }^-\). Moreover, we give a sufficient condition such that the environment is ergodic with exponential rate. Let \(\mu _{\mathrm {inv}}\) be the invariant measure for the environment process on \({\varGamma }^-\). In the main part of this work we establish the stochastic averaging principle, i.e. we prove that the marginal of \(\mu _t^{\varepsilon }\) onto \({\varGamma }^+\) converges weakly to an evolution of states on \({\varGamma }^+\) associated with the averaged Markov birth-and-death operator \({\overline{L}} = \int _{{\varGamma }^-}L^+(\gamma ^-)d \mu _{\mathrm {inv}}(\gamma ^-)\).     

Study of spin and decay-plane correlations of W bosons in the e + e$^-\rightarrow$ W + W- process at LEP

Data collected at LEP at centre-of-mass energies GeV are used to study correlations of the spin of W bosons using events. Spin correlations are favoured by data, and found to agree with the Standard Model predictions. In addition, correlations between the W-boson decay planes are studied in and events. Decay-plane correlations are measured to be consistent with the Standard Model predictions.Received: 26 October 2004, Revised: 15 January 2005, Published online: 3 March 2005     

AlN-Si(111)异质结构界面陷阱态研究

利用Al_AlN_Si(111) MIS结构电容_频率谱研究了金属有机化学气相沉积法生长的 Si 基AlN的AlN_Si异质结构中的电荷陷阱态. 揭示了AlN_Si异质结构界面电荷陷阱态以及A lN层中的分立陷阱中心. 结果指出：AlN层中存在E_t-E_v=2.55eV的分立陷阱中心；AlN_Si界面陷阱态在Si能隙范围内呈连续分布，带中央态密度最低，N_ss为8×10^11eＶ^-1cm^-2，对应的时间常数τ为8×10^-4s ，俘获截面σn为1.58×10^-14cm^2；在AlN界面层存在三种陷阱 态，导致Al_AlN_Si异质结构积累区电容的频散. 关键词： 界面陷阱态 AlN-Si 电容-频率谱     

SU(3) symmetry breaking in charmed baryon decays

We explore the breaking effects of the SU(3) flavor symmetry in the singly Cabibbo-suppressed anti-triplet charmed baryon decays of \(\mathbf{B}_c\rightarrow \mathbf{B}_n M\), with \(\mathbf{B}_c=(\Xi _c^0,\Xi _c^+,\Lambda _c^+)\) and \(\mathbf{B}_n(M)\) the baryon (pseudo-scalar) octets. We find that these breaking effects can be used to account for the experimental data on the decay branching ratios of \({\mathcal {B}}(\Lambda _c^+\rightarrow \Sigma ^{0} K^{+},\Lambda ^{0} K^{+})\) and \(R'_{K/\pi }={\mathcal {B}}(\Xi ^0_c \rightarrow \Xi ^- K^+)\)/\({\mathcal {B}}(\Xi ^0_c \rightarrow \Xi ^- \pi ^+)\). In addition, we obtain that \({\mathcal {B}}(\Xi _{c}^{0} \rightarrow \Xi ^{-} K^{+},\Sigma ^{-} \pi ^{+})=(4.6 \pm 1.7,12.8 \pm 3.1)\times 10^{-4}\), \({\mathcal {B}}(\Xi _c^0\rightarrow pK^-,\Sigma ^+\pi ^-)=(3.0 \pm 1.0, 5.2 \pm 1.6)\times 10^{-4}\) and \({\mathcal {B}}(\Xi _c^+\rightarrow \Sigma ^{0(+)} \pi ^{+(0)})=(10.3 \pm 1.7)\times 10^{-4}\), which all receive significant contributions from the breaking effects, and can be tested by the BESIII and LHCb experiments.