机械阻抗测量的一种新方法

本文介绍了一种新的机械阻抗测量方法－声强法，由定义出发将机械阻抗表为功率流和加速度响应谱的函数，应用结构声强技术测量功率流，声强法不需要测量作用力信号，可以用于测量任意结构中的各类机械阻抗，实验结果表明，声强获得的测量值与直接获得的测量值相近，声强法能较准确地测量一维和二维匀质结构中机械阻抗。     

Optical-heterodyne method for measuring surface strain

A new form of optical heterodyne method for measuring surface strain is proposed. In this method we detect the phase difference between two beat signals obtained from the light waves scattered by two neighboring points on a rough surface. Each of the two points is illuminated by two laser beams with different frequencies: totally there are four laser beams. The detected beat signals which are obtained at the two points have different phases. This phase difference is measured by an electrical circuit. The deviation of the measured phase difference is proportional to the difference of displacement at the two points: that is surface strain. Strains of a thin plate have been measured as a verification experiment. The experiment confirmed the theory for 10^-4 to 10^-5 strain.     

相对法测量表面张力系数

从细管缓慢流出的液体,并不是呈现连续的液流,而是一些继续的液滴。通过对不同液体液滴大小的比较,可测得表面张力系数。     

A direct method for measuring acoustic ground impedance in long-range propagation experiments

A method is reported for determining ground impedance in long-range propagation experiments by using the definition of impedance directly. The method is envisioned as way of measuring the impedence at multiple locations along the propagation path, using the signals broadcast during the experiment itself. In a short-range (10 m) test, the direct method was in good agreement with a more conventional model-based least-squares method. The utility of the direct method was demonstrated in a 400 m propagation experiment in a agricultural field. The resulting impedance was consistent with the impedance measured previously in the same field.     

On the theory of surface impedance of metals placed in a magnetic field

The smooth non-monotonous dependence of the metal surface impedance upon the magnetic field H is investigated theoretically for the cases of diffuse and specular reflection of electrons from the specimen boundary. The type of the electron-surface interaction has been found to have very little effect on the magnitude of the impedance Z_α(H) in the range of weak magnetic fields [equation (1)]. In a strong field [equation (2)] the surface impedance behaves differently for diffuse and specular reflection. The form of the Z_α(H) function depends essentially on the ratio of the electromagnetic wave frequency ω and the collision frequency of electrons ν. This provides a possibility of establishing experimentally the frequency of electron collisions with volume scatterers.     

An impulse method of measuring normal impedance at oblique incidence

An experimental method of determining the oblique incidence behaviour of sound absorbing materials is given. The method involves the measurement of acoustic impulses at the surface of an absorbing material and comparing the complex frequency components with those of a reference signal recorded remote from the surface. Amplitude and phase characteristics of the reflected signal are thus obtained and hence the normal impedance of the material is found. Comparison between measurements made by the “surface” method and standing wave tube measurements shows good agreement for normal incidence. However, at very oblique angles of incidence the method is in obvious error, the accuracy being limited by a sphericity effect.     

Optical method for measuring the coupling constant of surface acoustic waves

The coupling constant of common or thin-layered-piezoelectric interdigital transducers for surface acoustic waves up to the highest frequencies can be determined in an optical way with reproducibility better than 3%. Being a nondestructive and noncontact method one can apply it in the technological process for fabricating uniform piezoelectric layered transducers.     

一种检测减影(DSA)图像中肺癌肿瘤大小的新方法

当肺癌被胸水淹没时 ,无法用常规X胸片测量肺癌肿瘤的大小。提出了采用形态算子滤波和广义模糊算子 (GFO)检测边缘 ,从而获得支气管动脉减影图中的肺癌肿瘤的边缘轮廓 ,进而计算得到肿瘤的大小。该方法为肺癌介入病人提供了一种新的肿瘤检测手段 ,且拓展了数学形态学和广义模糊算子的应用领域 ,具有一定的的实用价值和理论价值。     

Optical method for measuring the amplitude response of surface acoustic wave devices

The amplitude response of acoustic surface wave (SAW) devices up to the highest frequencies can be determined in an optical way without electric shielding. This makes it possible to use the method for fast nondestructive testing and control in SAW-device production as well.     

Role of specular reflection of electrons in the radio frequency surface magneto impedance of metals

The effect of a parallel magnetic field on the 10-mHz surface resistance of gallium single crystals is reported. We suggest that the observed structure can be interpreted in terms of an angular dependence of the probability of specular reflection of the electron at the crystal surface. This model allows a quantitative determination from the data of the temperature-dependent electron mean free path for electron wave vectors with a narrow range that is determined by the magnetic field and crystal orientation.     

Density-functional method for surface properties of two-component plasmas of liquid metals

A general density-functional formalism for an inhomogeneous two-component liquid metal is described. The expression for the free energy is obtained and the gradient approximation is used for its simplification. Both electronic and ionic gradients are present in the theory.     

探讨测量液体表面张力系数的优化方法

针对用拉脱法测液体表面张力系数的系统误差较大的系列问题,提出了自动降拉双π丝补偿法.用自动化降拉代替手动提拉,提高了操作过程的稳定性;用双π丝代替π丝,消除了拉膜丝的不光滑点;用突变初态和补偿态作为测量状态,有效地排除了浮力、膜重以及侧丝上的表面张力对实验结果的影响.自动降拉双π丝补偿法得到的实验结果,其精度比拉脱法提高3％.     

测量精磨玻璃表面破坏层深度的侧面观测法

本文主要介绍用侧面观测法测量精磨玻璃表面破坏层深度的试件制做、测试仪器；对精磨裂纹也做了一定的分析。     

Resonance method for IR sensing

A highly sensitive method for infrared radiation detection based on thermal resonance in an active bolometer is set forth. An active bolometer is a self-oscillating system consisting of an IR-sensitive cell in a feedback circuit of an adjustable proportional controller. The analysis of an active bolometer autonomous (dark) dynamics reveals that with a generalized gain factor A variation the system evolves from relaxation type towards oscillating and self-oscillating type. When A=A_c, where A_c is a critical value of the generalized gain factor A, the steady state loses stability through self-excited thermal oscillations. The resonance in a system weakly perturbed by IR radiation modulated at self-oscillation frequency q₀[1+exp(iω_ct)] is considered. It is shown that in a small precritical vicinity =(A−A_c)/A_c of the gain factor the amplitude of forced thermal oscillations is proportional to q₀/A_c. The D^* calculation reveals that the detection power of a passive (A=0) bolometer increases with feedback introduction by a factor of 1/||. The detection powers of feasible versions of an active bolometer are compared.     

Comparison of the surface wave method and the indentation method for measuring the elasticity of gelatin phantoms of different concentrations

The speed of the surface Rayleigh wave, which is related to the viscoelastic properties of the medium, can be measured by noninvasive and noncontact methods. This technique has been applied in biomedical applications such as detecting skin diseases. Static spherical indentation, which quantifies material elasticity through the relationship between loading force and displacement, has been applied in various areas including a number of biomedical applications. This paper compares the results obtained from these two methods on five gelatin phantoms of different concentrations (5%, 7.5%, 10%, 12.5% and 15%). The concentrations are chosen because the elasticity of such gelatin phantoms is close to that of tissue types such as skin. The results show that both the surface wave method and the static spherical indentation method produce the same values for shear elasticity. For example, the shear elasticities measured by the surface wave method are 1.51, 2.75, 5.34, 6.90 and 8.40 kPa on the five phantoms, respectively. In addition, by studying the dispersion curve of the surface wave speed, shear viscosity can be extracted. The measured shear viscosities are 0.00, 0.00, 0.13, 0.39 and 1.22 Pa.s on the five phantoms, respectively. The results also show that the shear elasticity of the gelatin phantoms increases linearly with their prepared concentrations. The linear regressions between concentration and shear elasticity have R² values larger than 0.98 for both methods.     

配光镜柱面半径光电检测方法的研究

本文介绍一种测量柱面镜曲率半径的基本原理和检测系统结构。该测量技术利用激光束折射原理，采用线阵ＣＣＤ光电探测器件和单片机数据处理系统，通过测量激光束散开的宽度，计算出柱面镜的曲率半径。将这种方法应用到配光镜柱面单位曲率半径测量，整个测试过程在微机控制下自动完成，并具有高的测试精度。     

An improved method for measuring the surface sound energy diffusion coefficient in a room

The partly specular reflection and partly diffusion reflection model is a convenient way to express the phenomena of surface sound energy scattering in room acoustics. Sound energy diffusion coefficient becomes a key factor to study surface scattering. But there have been very few methods for determining the average sound energy diffusion coefficient. Vorliinder proposed such an easy one based on the correlation principle. However, his method ignored the correlation from direct sound, in which defect is present. A new approximate method for calculating sound energy diffusion coefficient, including direct sound and first strong reflectionsis presented. Therefore, Vorlaender‘‘‘‘‘‘‘‘s defect is overcome. In addition, with the aid of digitalmeasuring technology, a relevant measuring system was developed. The experiment resultshows that the method is improved than Vorlaender‘s.