轴类零件内部缺陷超声检测与重构方法研究

为了探究轴类零件内部缺陷的无损检测方法,本文以曲轴为研究对象,基于超声ALOK技术对其内部多个小孔进行了无损检测实验,并建立了相应的声学仿真有限元模型,提出利用声程—角度散点图中的趋势线,可快速判别内部缺陷特征和位置的方法。并且改进了ALOK算法,即采用邻近探头构建的方程或曲线重构缺陷,模拟和实验结果表明使用改进的算法提高了缺陷位置和尺寸的检测精度,通过实验数据重构所得的缺陷位置误差和半径误差分别在2 mm和0.5 mm左右。研究结论对于轴类零件内部缺陷精确定量化无损检测提供了理论和技术指导。     

Hepatic stellate cells: Three-dimensional structure,localization, heterogeneity and development

Hepatic stellate cells (HSCs) are vitamin-A storing collagen-producing cells in hepatic lobules. The three-dimensional structure of HSCs has been demonstrated with the Golgi method, the maceration method for scanning electron microscopy, and confocal laser scanning microscopy. Many thorn-like microprojections or spines extend from the subendothelial processes and make contacts with hepatocytes. One HSC entwines two or more sinusoids and about 20–40 hepatocytes to create a cellular unit, ‘the stellate cell unit’ or ‘stellon’. The Space of Disse is defined as the space between stellate cell-endothelial cell complex and hepatocytes. Intralobular heterogeneity of HSCs is assessed. HSCs develop from mesenchymal cells in the septum transversum. The developmental process of HSCs is reproduced partly in culture. In the lamprey abundant vitamin A is stored not only in HSCs, but in the fibroblast-like cells in the various other splanchnic organs. In vertebrates, the existence of both conventional fibroblast system in somatic tissues and vitamin A-storing cell system in splanchnic organs is suggested.     

The ultrasonic probe for the investigating of internal object structure by ultrasound transmission tomography

The main component of every device used for investigating internal object structure by Ultrasound Transmission Tomography (UTT) is a special ultrasonic probe. This paper presents the structure of model multielement ring probe for examining objects using this method in divergent ray projection geometry. The probe is made up of 1024 rectangular separate piezoelectric transducers working at frequency f=1.7 MHz, placed inside a ring with diameter D=30 cm and height h=9 cm. Each element of the probe is equipped with a quarter-wave matching layer. All the transducers function as transmitters and receivers, and can be joined in groups both during transmitting and during receiving. Some examples of admittance characteristics of a single piezoelectric transducer and examples of shapes of pulses generated and received by particular transducers were presented. Important factors affecting the measurement resolution are the sizes of the active surface of the transducers.     

Pseudo-three-dimensional reconstruction of ultrasonic images of the tongue

The purpose of the present investigation was to develop a method for the three-dimensional reconstruction of the surface of the tongue using serial ultrasonic images gathered during the production of the sustained fricative /s/. Using a phased linear array ultrasonic monitoring system, transducer position, subject position, and ultrasonic scan data were recorded simultaneously on composite video for off-line analysis. Reconstruction of a series of ultrasound images was completed using a microcomputer programmed to transform the ultrasonic image contours into three-dimensional space. Additional transformations converting the three-dimensional tongue contours into two dimensions for screen plotting were also developed. Results are discussed in light of previously reported models of the tongue surface.     

Algorithms for suppressing ultrasonic backscattering from material structure

In pulse-echo ultrasonic inspection the backscattering from the material structure appears in the received ultrasonic images as clutter, often referred to as grain noise, which impairs the inspection results. A toolbox including algorithms for suppressing ultrasonic clutter is presented in the paper. Several processing algorithms capable of suppressing grain noise have been proposed, of which the split spectrum processing (SSP) probably is the most renowned. The classical SSP technique applies a filter bank to some frequency band that has to be precisely known in advance, to obtain a set of narrow-band signals that are tested for mutual correlation using some statistical operation. A number of SSP algorithms with different statistical operations are included in the toolbox. A completely different approach is to use explicit statistical models of grain noise and defects and to design an optimal filter based on those models. A simple such algorithm, based on noncoherent detection (NCD) known from communications, is also included in the toolbox. The toolbox, implemented in Matlab, is provided with a user-friendly graphical interface facilitating comparison of the algorithms.     

超声应变重建的仿真研究

本文提出了一种基于匹配滤波器的用于估计生物组织内部应变的方法,并且为了检验这一技术的可行性,本文还详细介绍了一线超声弹性散射回波模型的建立方法.计算机仿真的结果揭示了这种估计内部应变的方法在人体组织弹性定征领域的应用前景。     

The reconstruction of the relaxation matrix from an incomplete set of nuclear overhauser effects

Internal motions in a macromolecule and indirect magnetization transfers (spin diffusion) prevent simple interpretation of NOE values in terms of structural and dynamic parameters in the course of the study of a macromolecule. A method for separating these two problems by first analyzing the NOES with respect to the relaxation rate constants is proposed. NOE values for 1 D or 2D experiments are obtained as nonlinear functions of the ϱ and σ parameters by solving the Bloch equations. A general least-squares minimization routine that makes use of the Hessian matrix of second derivatives was found to be efficient in determining iteratively the set of parameters that statistically correlates the corresponding calculated NOEs to a set of experimental NOES. The procedure was applied to probe the internal mobility of the deoxyriboses in a self-complementary hexamer, d(CGTACG)₂. It was found that H_2′-H_2″ and H_1′-H_2″-vectors are subject to internal motions whose amplitudes vary as we move along the sequence.     

脱粘界面超声检测信号的小波多分辨率分析与重构

针对钢-橡胶分层粘接结构的超声检测回波信号,利用小波变换的多分辨率时频特性提出了小波特征参数提取算法,据此在对检测信号进行的时间-尺度分布分析基础上,重构出脱粘界面回波信号的时域和频域特征。实验检测结果表明本文方法在现代工业NDT&E中的应用有着可喜的前景。     

Temperature dependent ultrasonic characterization of biological media

Quantitative ultrasound (QUS) is an imaging technique that can be used to quantify tissue microstructure giving rise to scattered ultrasound. Other ultrasonic properties, e.g., sound speed and attenuation, of tissues have been estimated versus temperature elevation and found to have a dependence with temperature. Therefore, it is hypothesized that QUS parameters may be sensitive to changes in tissue microstructure due to temperature elevation. Ultrasonic backscatter experiments were performed on tissue-mimicking phantoms and freshly excised rabbit and beef liver samples. The phantoms were made of agar and contained either mouse mammary carcinoma cells (4T1) or chinese hamster ovary cells (CHO) as scatterers. All scatterers were uniformly distributed spatially at random throughout the phantoms. All the samples were scanned using a 20-MHz single-element f/3 transducer. Quantitative ultrasound parameters were estimated from the samples versus increases in temperature from 37 °C to 50 °C in 1 °C increments. Two QUS parameters were estimated from the backscatter coefficient [effective scatterer diameter (ESD) and effective acoustic concentration (EAC)] using a spherical Gaussian scattering model. Significant increases in ESD and decreases in EAC of 20%-40% were observed in the samples over the range of temperatures examined. The results of this study indicate that QUS parameters are sensitive to changes in temperature.     

Tomographic reconstruction of asymmetric soot structure from multi-angular scanning

A tomographic deconvolution technique using the Fourier transformation has been applied for the reconstruction of asymmetric soot structure. Local soot volume fraction distribution can be identified from line-of-sight integrated data using light extinction measurements with multi-angular scanning. A peak-following interpolation technique was adopted to effectively increase the number of scanning angles. The results showed that the peak-following interpolation has improved the accuracy of reconstruction compared to the arithmetic interpolation in determining the local soot volume fraction. The measurement from a laser-induced incandescence technique substantiated the validity of the reconstruction technique.     

On the information completeness of quantum tomograms

We address the problem of information completeness of quantum measurements in connection to quantum state tomography and with particular concern to quantum symplectic tomography. We put forward some non-trivial situations where informatively incomplete set of tomograms allows as well the state reconstruction provided to have some a priori information on the state or its dynamics. We then introduce a measure of information completeness and apply it to symplectic quantum tomograms.     

Three-dimensional image reconstruction of V-grooves for damage analysis

In this paper, a novel method for the analysis of damaged V-grooves is presented. An optical sectioning system and image processing software were developed to determine the width of V-grooves at various heights. We succeeded in constructing a three-dimensional (3D) topographic image, which enabled the estimation of damage in each region of the V-groove. The necessity of replacing damaged wire guide rollers can be determined according to whether the damage in the V-grooves exceeds a given threshold. By altering the sampling rate, the proposed system can achieve an optimal balance between resolution and measurement speed. The proposed innovations represent a novel solution for engineering inspection technology and related applications.     

Variation in the biological characteristics of BAC during ultrasonic regeneration

Ultrasonic treatment has been shown to have a favorable effect on the regeneration of spent biological activated carbon (BAC) from drinking water treatment plants. In this study, the use of ultrasound as a regeneration method had a significant effect on the recovery of spent BAC after 7.5 years of use; it effectively increased the iodine value from 300 mg/g to 600 mg/g and restored the specific surface area and pore volume of BAC. Ultrasound effectively changed the structure of the biofilm inside and on the surfaces of BAC particles, on the basis of confocal laser scanning microscopy (CLSM) images. The thickness of the surface biofilm attached to BAC reached an “active” level (about 100 μm) at the regeneration frequency of 40 kHz. The dehydrogenase activity significantly improved from 4.50 mg TF/g BAC to 9.13 mg TF/g BAC, and the content of adenosine-triphosphate (ATP) in regenerated BAC was maintained at a high level (2.501 × 10⁻⁶g ATP/g BAC), thus allowing the development of microbial growth. The production of soluble microbial products (SMPs) from regenerated BAC decreased during the reuse process. The removal efficiency of DOC, COD_Mn, NH₄⁺ and NO₃^– control increased by approximately 78%, 71%, 50% and 20%, respectively.     

超声检测中的结构噪声

结构噪声是超声脉冲在介质结构上激发产生的一种特殊噪声，它严重妨碍超声检测，是超声检测的基本限制因素之一；但也可被利用进行某些检测。本文综述了有关结构噪声的基本研究，抑制或降低结构噪声的方法，以及在结构噪声背景下进行超声检测和利用结构噪声进行超声检测的有关工作。     

Three-dimensional display of ultrasonic images using a fly's-eye lens.

In order to form a three-dimensional image from a set of two-dimensional cross-sectional ultrasonic images, a simple method making use of a fly's-eye lens in proposed. The depth perception obtained from the reconstructed image using the fly's-eye lens is analysed and an optical configuration that maximizes the depth perception is devised. With this configuration, the synthesis of a three-dimensional image is performed by using a simple object. Results of the experiment show clearly the three-dimensional aspect of the reconstructed image.     

Application of stochastic analysis to ultrasonic echoes--estimation of attenuation and tissue heterogeneity from peaks of echo envelope

A study of the statistics of ultrasound speckle indicates that the noise-to-signal ratio (NSR) of the echo envelope peaks (EEP) in a B scan is monotonically related to the variance of the mean power of the backscattered echoes. If it is assumed that the backscattered echoes all have the same mean power, the NSR of the EEP's in a B scan will be expected to reach a theoretical minimum value NSR0 (0.40 approximately 0.42). In practical situations, the variance of the mean power of the echoes is increased due to the presence of both attenuation (including beam spreading) and the spatial variation in the backscattering cross section (BCS) of the tissue. Accordingly, the measured value of the NSR of the EEP's is expected to be greater than the NSR0. In principle, the effects of beam pattern and the attenuation can be compensated for by system calibration and a depth-related gain function, respectively. The attenuation coefficient of the tissue may then be obtained by adjusting the gain function to minimize the NSR of the EEP's. Due to the random nature of the heterogeneity of diseased tissue, the effect of the variation in the BCS, however, cannot be compensated for by the depth-related gain function. Therefore, the minimum value of the NSR indicates the spatial variation in the BCS and may finally correlate to the disease state of the tissue.     

Self-action of ultrasonic beams for biological applications.

Theoretical and experimental investigations of powerful ultrasonic beams self-focusing in liquids are described. Calculations of the conditions to observe self-action as a result of sound-induced heating of liquids are reported. The effects of controlled self-action of ultrasonic waves in high-viscosity liquids are demonstrated in experiments. A hydrodynamic mechanism of the acoustic dispersion technique is developed. The rate of this process, as a function of ultrasound intensity, including the effects of self-focusing and self-transparency, is evaluated.     

Determination of the internal structure of valons

We determine the internal structure functions of the valons introduced by Hwa and coworkers, using low-p _t data and Regge model constraints. Our calibration reaction is the fragmentation processp→π^? observed in 70 GeV/cK ⁺ p interactions. The fitted valon structure parameters are used to make successful predictions for various other fragmentation processes (p→π⁺ andp→K ⁺). A comparison with experimental data of the DISvW ₂ (x)-values implied by this same fit, indicates that soft processes probe the nucleon typically at aQ ²-value of ～1 GeV². This finding supports the hypothesis that soft hadronic reactions are useful (and often unique) tools to learn about hadron quark structure.     

Three-dimensional structure of low-density nuclear matter

We numerically explore the pasta structures and properties of low-density nuclear matter without any assumption on the geometry. We observe conventional pasta structures, while a mixture of the pasta structures appears as a metastable state at some transient densities. We also discuss the lattice structure of droplets.