小阻尼封闭空间声压级灵敏度分析与优化设计

本文研究了小阻尼界面封闭空间低频声学有限元分析、灵敏度分析和优化设计问题。分别用模态法和直接法计算了封闭空间内声压级响应，并推导了声压级响应对声空间边界形状控制参数的灵敏度分析公式，在此基础上建立了小阻尼空间声学问题的优化模型，同时给出了优化求解算法，并在JIFEX软件中进行了程序实现。本文提出的灵敏度分析和优化设计方法可以使声场的边界布局更为合理，从而达到改进小阻尼界面封闭空间声学性能的目的。数值算例验证了本文提出的灵敏度分析和优化算法的有效性。     

Determination of the sound power levels emitted by various vehicles using a novel testing method

This paper presents a new and efficient method to determine sound power levels (PWLs). PWLs, generally used for modeling outdoor sound simulations, are obtained from sounds that are emitted by various types of vehicles and cause road traffic noise. Other models, such as HARMONOISE and the ASJ Model, are also based on PWLs. However, a more efficient method is required for determining PWLs from sound pressure levels (SPLs) that typically are measured by field testing and evaluating the influence of different vehicles and road surfaces. The statistical pass-by (SPB) of ISO 11819-1 is used for SPL measurements; however, numerous SPBs must be carried out to reduce measurement uncertainty as well as to satisfy requirements related to meteorological conditions and background noise. In order to alleviate this problem and to make the determination of PWLS more efficient, a testing approach is presented that uses both the novel close proximity (NCPX) method and the pass-by method to determine PWLs.     

Analysis of sound absorption by periodic structures using a hybrid-boundary element/mode expansion method

An improved hybrid method is proposed for analyzing sound scattering by a periodic structure. Part of the scattered field formulated with the mode expansion method is combined with other components of the field formulated with the boundary integration method in one period of the structure. Structures treated by this method can have arbitrary periodic forms made of locally reactive boundaries and porous materials. The oblique incident absorption coefficient of the structure is obtained simply from the reflection factor calculated for each elemental wave of the scattered field. The accuracy of the method is demonstrated by the agreement between calculated and measured values of the normal absorption coefficient of some test structures.     

用于测量流量和含沙量的超声波液位测定系统

本文介绍了实验室内用于测量流量和含沙量的超声波液位测定系统，此系统采用气介式方案，选用复合材料高频换能器作为超声波发射／接收器件，结构简单，静态测量时测量误差在１５０ｍｍ范围内不超过１ｍｍ，并可与微机进行远距离通讯。     

Non-contact method for measuring solution concentration using surface plasmon resonance apparatus and heterodyne interferometry

A simple non-contact method is proposed for measuring the concentration of solutions. Using the significant phase difference between p- and s-polarizations of the reflected light of a surface plasmon resonance apparatus, the variation in the phase difference, which is caused by a variation in the concentration of a test solution, can be accurately measured by common path heterodyne interferometry. Then, by substituting the corresponding variation in the incident angle of light at the base of the SPR prism in a specially derived equation, the concentration of the test solution can be determined. The validity of this method was demonstrated experimentally. This method is characterized by the advantages of the device having a simple non-contact structure; it being easy to operate; and its high accuracy, stability, and resolution.     

Control of stochastic resonance in bistable system by using periodic signal

<正>According to the characteristic structure of double wells in bistable systems,this paper analyses stochastic fluctuations in the single potential well and probability transitions between the two potential wells and proposes a method of controlling stochastic resonance by using a periodic signal.Results of theoretical analysis and numerical simulation show that the phenomenon of stochastic resonance happens when the time scales of the periodic signal and the noise-induced probability transitions between the two potential wells achieve stochastic synchronization.By adding a bistable system with a controllable periodic signal,fluctuations in the single potential well can be effectively controlled,thus affecting the probability transitions between the two potential wells.In this way,an effective control can be achieved which allows one to either enhance or realize stochastic resonance.     

Resonance suppression and electromagnetic shielding effectiveness improvement of an apertured rectangular cavity by using wall losses

The cavity-mode resonance effect could result in significant degradation of the shielding effectiveness （SE） of a shielding enclosure around its resonance frequencies. In this paper, the influence of coated wall loss on the suppression of the resonance effect is investigated. For this purpose, an equivalent circuit model is employed to analyze the SE of an apertured rectangular cavity coated with an inside layer of resistive material. The model is developed by extending Robinson＇s equivalent circuit model through incorporating the effect of the wall loss into both the propagation constant and the characteristic impedance of the waveguide. Calculation results show that the wall loss could lead to great improvement on the SE for frequencies near the resonance but almost no effect on the SE for frequencies far away from the resonance.     

基于二维彩色靶标的结构光三维测量系统快速标定方法

系统标定是基于结构光投影的主动式光学三维面形测量的关键技术之一,同时也是一项复杂和耗时的工作。提出了一种基于RGB彩色模型的系统快速标定新方法。利用一个彩色的二维平面靶标和由投影仪投影的彩色标记特征图像实现了摄像机和投影仪的同时快速标定,对靶标的每个标定姿态位置只需要拍摄一幅图像即可得到该位置的特征参数。与传统方法相比,标定过程简单快捷,所需的数据量较少。利用该方法对一个结构光三维测量系统进行了现场标定,并测量了一个平面和一个半圆柱物体,实验结果中点到拟合平面的最大距离为0.8039mm,平均误差为0.1693mm。利用该系统恢复半圆柱物体的面形与传统标定方法的测量结果符合得很好。实验表明,由该方法获得的结果准确可用,且标定速度快。     

A novel method of partial coherence measuring for the illumination system and its defocus performance analysis

Partial coherence (generally represented by σ) is one of the important parameters of lithographic tool to assess the performance of pupil fill. In this paper, a novel method of partial coherence measurement for the illumination system is proposed. Statistical results of measured σ by the proposed method are analyzed. The dependence of partial coherence on the defocus, which is the distance from the measuring position to the best image plane, is also investigated. The simulation results prove the effectiveness of this method, and with the defocus increasing, the measured partial coherence decreases. Generally, if three times of the standard deviation is required to be 1 × 10⁻³, the amount of defocus should be less than 96 μm.     

位相测量轮廓术中的相位修正及系统标定的新方法

介绍了在位相测量轮廓术中的一种相位修正及系统参数标定的新方法。对参考面(标定面)上点的位置_相位关系进行全场拟合,并根据该相互关系对参考面相位进行修正,能够非常有效地去除相位误差;提出的参数标定方法能精确得到投影系统参数的组合。实验证明了此方法具有良好的实用性和测量精度。     

A novel scheme of hybrid entanglement swapping and teleportation using cavity QED in the small and large detuning regimes and quasi-Bell state measurement method

We outline a scheme for entanglement swapping based on cavity QED as well as quasi-Bell state measurement(quasiBSM) methods. The atom–field interaction in the cavity QED method is performed in small and large detuning regimes.We assume two atoms are initially entangled together and, distinctly two cavities are prepared in an entangled coherent–coherent state. In this scheme, we want to transform entanglement to the atom-field system. It is observed that, the fidelities of the swapped entangled state in the quasi-BSM method can be compatible with those obtained in the small and large detuning regimes in the cavity QED method(the condition of this compatibility will be discussed). In addition, in the large detuning regime, the swapped entangled state is obtained by detecting and quasi-BSM approaches. In the continuation,by making use of the atom–field entangled state obtained in both approaches in a large detuning regime, we show that the atomic as well as field states teleportation with complete fidelity can be achieved.     

一种把三角法应用于中、短距离测量的方法

三角法测距的原理公式中因变量、自变量及系统结构参数之间具有非线性关系,并且在系统结构确定之后,距离越远,单位距离变化在接收器件上的对应变化量越小,即测量分辨精度越低,测量精度与测量范围之间存在矛盾。通过采用一种新的距离分段的改进三角测距法,使远近距离都有一个比较适中的测量精度,较好地解决了测量精度与测量范围之间的矛盾。并给出其应用实例。     

A theoretical model for the evaluation of measurement uncertainty of a sound level meter calibration by comparison method in an anechoic room

A theoretical model for the evaluation of measurement uncertainty of a sound level meter (hereafter as `SLM') calibration by comparison method in an anechoic room was developed. Through this model, the uncertainties in the semi-automatic calibration and that in the full-automatic calibration were estimated for the recently developed SLM calibration system. In order to estimate the standard uncertainty against the SLM positioning, which is a significant uncertainty component, the sound field curve-fitting formulae were adopted. The validity of the curve-fitting method was proven by the similarity of the spatial distributions of radiation sound field produced by the plane circular piston source and that by the cone shape source. A linear equation was used to fit the measurements of the sound field distribution along the radiation axis. A quadratic equation was used to fit the measurements along the radial axis normal to the radiation axis. The fitting parameters gave us the sensitivity coefficients of the propagation of the uncertainty. In addition, one of the quadratic fitting parameters was found to be a positional uncertainty itself. Using this model, the expanded uncertainties were evaluated for the semi-automatic and full-automatic calibration of SLM.     

测量液体和气体折射率的集成光学技术单侧和双侧漏模法

由单侧和双侧漏模法,测量了液体和气体的折射率,将液体或气体滴入或充入棱镜和衬底之间,使这三层介质组成单侧或双侧漏波导.用棱镜耦合器测量共振漏模的模折射率,并由相应的模方程确定液体或气体的折射率.测量结果表明,折射率的误差为1～3×10~(-4).并在理论上对测量精度作了分析和讨论.     

对超声复合振动系统中“局部共振”现象的一种解释

对超声复合振动系统中的“局部共振”现象,基于熟知的棒或管中声波产生和传播的理论,提出一种机理解释。     

中子共振谱测温的研究和应用

本文简要回顾了中子共振测温技术发展的过程,介绍了该技术在测温特别是冲击加载条件下材料内部测温方面的进展和应用。论述了该技术的理论模型与数据分析方法,探讨了测温共振位选择,测温实验中子源选择,测温数据分析软件等多方面内容。     

A novel method for measuring the coma of a lithographic projection system by use of mirror-symmetry marks

A novel method for measuring the coma of a lithographic projection system is proposed and the principle of the method is described. By utilizing mirror-symmetry marks, the adverse effects of axial aberrations on the coma measurement are avoided. Experimental results demonstrated that the method has high accuracy. Compared with TAMIS, the conventional technique used for coma measurement, the method is more reliable because the influences of the process factors on the lateral displacements have been considered.     

高炉送风系统力学行为的数字散斑相关法实验研究

研究高炉送风系统在燃烧、送风、切换状态时热风炉壳的力学性能。首次在热风炉炉壳测试中采用了高精度的数字散斑相关技术,利用自然光对热风炉壳进行了非接触式测量,得到了由于温度引起的轴向和环向的变形、应变及热应力等力学参量,光测结果与电测结果吻合较好。表明数字散斑相关测量技术应用于测量恶劣环境下力学参量有效,方法实用,较好地解决了热风炉壳的力学测试工作。     

Stochastic resonance and nonequilibrium dynamic phase transition of Ising spin system driven by a joint external field

The dynamic response and stochastic resonance of a kinetic Ising spin system （ISS） subject to the joint action of an external field of weak sinusoidal modulation and stochastic white-nolse are studied by solving the mean-field equation of motion based on Glauber dynamics. The periodically driven stochastic ISS shows that the characteristic stochastic resonance as well as nonequilibrium dynamic phase transition （NDPT） occurs when the frequency ω and amplitude h0 of driving field, the temperature t of the system and noise intensity D are all specifically in accordance with each other in quantity. There exist in the system two typical dynamic phases, referred to as dynamic disordered paramagnetic and ordered ferromagnetic phases respectively, corresponding to a zero- and a unit-dynamic order parameter. The NDPT boundary surface of the system which separates the dynamic paramagnetic phase from the dynamic ferromagnetic phase in the 3D parameter space of ho-t-D is also investigated. An interesting dynamical ferromagnetic phase with an intermediate order parameter of 0.66 is revealed for the first time in the ISS subject to the perturbation of a joint determinant and stochastic field. The intermediate order dynamical ferromagnetic phase is dynamically metastable in nature and owns a peculiar characteristic in its stability as well as the response to external driving field as compared with a fully order dynamic ferromagnetic phase.     

A design of novel type superconducting magnet for super—high field functional magnetic resonance imaging by using the harmonic analysis method of magnetic vector potentials

The approach of expanding the magnetic scalar potential in a series of Legendre polynomials is suitable for designing a conventional superconducting magnetic resonance imaging magnet of distributed solenoidal configuration. Whereas the approach of expanding the magnetic vector potential in associated Legendre harmonics is suitable for designing a single-solenoid magnet that has multiple tiers, in which each tier may have multiple layers with different winding lengths. A set of three equations to suppress some of the lowest higher-order harmonics is found. As an example, a 4T single-solenoid magnetic resonance imaging magnet with 4×6 layers of superconducting wires is designed. The degree of homogeneity in the 0.5m diameter sphere volume is better than 5.8 ppm. The same degree of homogeneity is retained after optimal integralization of turns in each correction layer. The ratio B_m/B₀ in the single-solenoid magnet is 30% lower than that in the conventional six-solenoid magnet. This tolerates higher rated superconducting current in the coil. The Lorentz force of the coil in the single-solenoid system is also much lower than in the six-solenoid system. This novel type of magnet possesses significant advantage over conventional magnets, especially when used as a super-high field functional magnetic resonance imaging magnet.