The influences of ambiguity phase aberration profiles on focusing quality in the very near field--part I: single range focusing on transmission

Most phase aberration measurement algorithms have an ambiguity for constant and tilted phase aberration profiles. Based on the Fresnel (near field) approximation with single range focusing and the Fraunhofer (far field) approximation, constant and tilted phase aberration profiles change the position of the focal point only and do not influence the image focusing quality. Therefore, ambiguity phase aberration profiles are generally considered to be harmless and ignored in those algorithms and related theoretical analyses. However, Fresnel and Fraunhofer approximations may become invalid under many medical ultrasound imaging situations, e.g., when the imaging field is in the very near field (f-number ~1). In the very near field, although it is known that constant and tilted phase aberration profiles may degrade the focusing quality, it seems that there is a lack of quantitative analysis results in the literature about their influences, and this is the purpose of the current paper. A quantitative analysis with a very near field approximation is performed for single range focusing on transmission, which is a commonly used transmission focusing method in medical ultrasound imaging. The tolerable levels of constant and tilted phase aberration profiles are derived as a function of the imaging system's f-number and wavelength. Because some phase aberration measurement algorithms may also have an ambiguity for quadratic phase aberration profiles, they are also included in the analysis. The theoretical results are compared with numerical and simulation results. These results have shown that the influences of tilted and quadratic phase-aberration profiles can be ignored only under certain conditions in the very near field     

Computation of the range of feasible solutions in self-modeling curve resolution algorithms

Self-modeling curve resolution (SMCR) describes a set of mathematical tools for estimating pure-component spectra and composition profiles from mixture spectra. The source of mixture spectra may be overlapped chromatography peaks, composition profiles from equilibrium studies, kinetic profiles from chemical reactions and batch industrial processes, depth profiles of treated surfaces, and many other types of materials and processes. Mathematical solutions are produced under the assumption that pure-component profiles and spectra should be nonnegative and composition profiles should be unimodal. In many cases, SMCR may be the only method available for resolving the composition profiles and pure-component spectra from these measurements. Under ideal circumstances, the SMCR results are accurate quantitative estimates of the true underlying profiles. Although SMCR tools are finding wider use, it is not widely known or appreciated that, in most circumstances, SMCR techniques produce a family of solutions that obey nonnegativity constraints. In this paper, we present a new method for computation of the range of feasible solutions and use it to study the effect of chromatographic resolution, peak height, spectral dissimilarity, and signal-to-noise ratios on the magnitude of feasible solutions. An illustration of its use in resolving composition profiles from a batch reaction is also given.     

扰流流场对超声流量计积分误差的影响分析

对若干典型扰流流场条件下的超声流量计积分误差进行了系统推算,在分析流场结构对积分误差影响的基础上,研究了声路数量对积分误差的统计规律。流量计的积分误差与流场的复杂程度直接相关,流场越复杂积分误差也越大。在统计意义上流量计声路越多则积分误差越小,但对于某特定流场则不存在这种单调性。OWICS积分方案要优于Gauss-Jaccobi方案,尤其在声路数量受限时具有明显优势。     

一种估计吊放声呐工作深度的简易方法

反潜战中,吊放声呐的工作深度对探测效果影响较大,研究如何根据不同声速剖面确定最佳工作深度使探测距离达到最远,可有效提高探测效率。先将声速剖面划分为典型的几类,然后设计了一种使计算机能够自动识别其类型的方法,再在此基础上利用Bellhop模型找出不同声速剖面下的最佳工作深度规律。仿真结果证明快速算法在一定条件下可替代逐深度计算声呐作用距离,再通过比较选出最佳工作深度的传统算法的。     

Coil impedance due to a sphere of arbitrary radial conductivity andpermeability profiles

This paper presents analytical expressions for coil impedance due to a spherical workpiece consisting of concentric spherical shells. The expressions are used to simulate the nondestructive inspection of a sphere having arbitrary radial conductivity and magnetic permeability profiles by a circular coil of rectangular cross section. The simulation replaces continuous profiles with piecewise constant profiles. The paper compares the results to published experimental measurements and the results of other analytical solutions     

铝合金隔热型材隔热性能检测方法及测量不确定度评定

传热系数测试是评价铝合金隔热型材隔热性能指标的重要途径,建立了铝合金隔热型材检测方法,分析了影响铝合金隔热型材传热系数测量的不确定度来源,对隔热型材传热系数测量不确定度进行评定分析,结果表明在（2．90—0．06）至（2．90＋0．06）W·m-2·K-1的区间包含了传热系数K测量结果可能值的95％,并提出了测量传热系数的注意事项。     

Derivatives of scattering profiles: tools for nanoparticle characterization

This paper presents a new approach to characterize nanoparticles using derivatives of scattering profiles of evanescent waves/surface plasmons. We start the procedure using the scattering profiles for an unknown configuration of nanoparticles, either from physical experiments or numerical simulations conducted for different nanoparticles on surfaces. We apply the statistical technique of compound estimation to recover the derivatives of scattering profiles. The L(1) discrepancies with the corresponding curves from known configurations are used to identify the most plausible configuration of particles that could yield the "experimental" profiles. We conduct a simulation study to see how often the new procedure correctly recovers the agglomeration level for gold spherical nanoparticles on a thin gold film. The results suggest that first derivatives are much more effective for characterization than undifferentiated profiles and that M(33) is the most useful element for distinguishing among configurations. The proposed compound estimation technique is more effective than typical inverse analyses based on look-up tables and can be used effectively in nanoparticle characterization platforms.     

Investigation of distribution of lithium atoms in the boundary layer of the flow of combustion products

The results are given of measurements of the profiles of temperature and concentration of lithium in the cross section of the boundary layer formed under conditions of flow of combustion products of propaneair flame past the surface of a flat metal plate. A model of chemically nonequilibrium laminar boundary layer is used to perform numerical simulation of various components of the combustion products. A comparison of the measured profiles of lithium concentration and profiles of hydrogen atoms obtained from the experimental data with the predicted results on a cooled and uncooled plate demonstrates that the suggested model of chemical kinetics describes the measurement results with good accuracy.     

泵用直谷转子的参数化造型与尺寸优选

为实现罗茨泵直谷转子型线的造型参数化与尺寸最优化。基于直谷型线与峰型线的共轭关系,通过法线法的旋转和平移的矩阵变换,构建出实际型线最简洁的全参数化的坐标方程与3D模型;其次,以节圆半径为设计变量,转子副所占方体空间的最小体积为目标函数,构建单变量优化模型和实例分析。结果表明:直谷转子的最大谷部尺寸以容积利用率最小化为代价,多适用于有粗轴需求的特定场合。转子叶数对泵体积的影响很大,3叶是2叶的1.84倍;4叶是2叶的3.04倍;直谷型多适用2叶转子。参数化转子副的实例造型和节圆半径的优选结果,说明型线方程正确,优选结果可靠。为泵用其它型线的转子,提供一种全参数的造型和设计方法。     

Quantification of ageing of ultracapacitors during cycling tests with current profile characteristics of hybrid and electric vehicles applications

The ageing quantification of ultracapacitors in cycle-life tests has been studied. Current profiles and the characteristics of the ultracapacitors used in hybrid and electric vehicle applications are specified and validated. With these profiles, significant self-heating occurs but without exceeding the manufacturers' limits. Thus, ultracapacitors are aged in a short time with the same degradation mechanisms observed in normal use. Ageing evaluation is based on the measurement of the electrical parameter changes. A particular phenomenon is performance recovery during rest periods when power-cycling is interrupted for electrical characterisation. Therefore, an online characterisation procedure was added for more accurate evaluation of the ultracapacitors' ageing. A number of devices from two manufacturers are cycled with different current profiles. The obtained results are presented and discussed.     

Determination of slope in lidar data using a duplicate of the inverted function

An iterative method for determining slope in noisy lidar data is considered based on the use of a corrected ('shaped') inverted function and an assumed behavior of the unknown function of interest (an 'image function'). The method is utilized for extracting extinction- coefficient profiles from data of multiangle measurements. The sequence and specifics of the retrieval procedure, results of simulations, and essentials of the practical retrieval of particulate extinction-coefficient profiles from signals of the elastic scanning lidar are considered. The methodology may be applicable when extracting the extinction-coefficient profiles from an elastic lidar operating in a multiangle scanning mode, a combined Raman elastic-backscatter lidar, or a high spectral resolution lidar operating in a fixed angular position.     

Identification of Staphylococcus aureus and determination of its methicillin resistance by matrix-assisted laser desorption/ionization time-of-flight mass spectrometry

To evaluate the performance of matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF MS) in identifying Staphylococcus aureus and in determining its methicillin resistance, we analyzed 76 S. aureus clinical isolates using a linear MALDI-TOF MS. Spectral profile data obtained were compared with the database provided with the instrument, and 74% of the isolates were identified as S. aureus, as confirmed by a nuc-based PCR test. The determination of the methicillin resistance in S. aureus is based on the fact that the spectral profiles of methicillin-susceptible S. aureus (MSSA) and methicillin-resistant S. aureus (MRSA) differ greatly from each other. Replicate spectral profiles obtained from each isolate were combined to be a representative spectrum of it, and representative spectral profiles from all the isolates constitute a user's self-established database. All the spectral profiles in the database were classified into two groups based on clustering analysis, and one is for MSSA and another MRSA. There was a little discrepancy between the results from MALDI-TOF MS and from PCR. Seven isolates that are negative for the mecA gene by PCR were identified as MRSA by MALDI-TOF MS. The discrepancy may be partially explained by the heterogeneous nature of methicillin resistance in S. aureus. Our results suggested that comparison of MALDI-TOF MS spectral profiles of microorganism could serve as a simple and rapid method for bacterial identification and antibiotic susceptibility analysis.     

高速车辆车轮磨耗与轮轨接触几何关系的研究

根据线路实际测量的高速车辆车轮踏面外形,分析了不同磨耗里程下的S1002G踏面的轮轨接触几何关系的变化规律。研究结果表明S1002G踏面随着运营里程的增加,等效锥度逐渐增大,特别是在轮对横移量2mm以内表现最明显。随着轮对横移量的增加等效锥度呈现先减小后增大的变化趋势,这说明S1002G踏面在京沪线实际运营过程中以凹形磨耗为主。通过建立高速动车组单车动力学模型,采用磨耗前后的轮轨型面,分析了三种不同类型转向架车辆模型的运动稳定性。分析结果表明磨耗导致轮轨匹配关系发生变化从而大大降低了车辆的临界速度;而一系纵向定位刚度无论是磨耗前还是磨耗后都会对车辆稳定性造成重要的影响,相对来说柔性转向架更有利于车辆的运动稳定性。轨道参数对轮轨接触几何关系有着非常重要的影响,因此研究车辆稳定性问题必须要考虑轨道几何参数的作用。     

Multiaxial fatigue life modelling using hybrid approach of critical plane and genetic algorithm

This paper presents a new hybrid approach for multiaxial fatigue life estimation, based on continuum damage mechanics theory and a genetic algorithm with critical plane model formulation. The hybrid model employs a genetic algorithm based setup for calibration with standard proportional and non‐proportional profiles to predict fatigue life for complex loading profiles. The model is evaluated using experimental fatigue life data for SS304 steel. Calibration using simplified profiles is in agreement with the requirement for cost‐effective experimental fatigue life testing. In‐phase and out‐of‐phase loads are used for calibration, and fatigue life is predicted for more complicated profiles. The results show good agreement between the estimated and experimental fatigue life, and calibration through simple loading histories to predict fatigue life for complex histories appears to be an effective solution using the proposed model. A brief comparison is presented with fatigue life estimation performance of the proposed model with models available in commercial codes. Proposed model found to be more consistent in fatigue life prediction against various loading conditions.     

The influences of ambiguity phase aberration profiles on focusing quality in the very near field part II: dynamic range focusing on reception

For pt. I see ibid., vol. 49, no. 1, p. 57-71 (2002). The influences of ambiguity phase aberration profiles, including constant, tilted, and quadratic profiles, on focusing quality have been quantitatively analyzed with the very near field approximation for single range focusing on transmission. In this paper, their influences are analyzed in a very different situation: dynamic range focusing on reception, which is commonly used in medical ultrasound imaging for beam formation on reception. It is shown that the results for dynamic range focusing on reception are dramatically different from those for single range focusing on transmission. For example, constant phase aberration profiles are harmless to focusing quality for single range focusing on transmission but become harmful for dynamic range focusing on reception. The analysis also shows that, compared with single range focusing on transmission, dynamic range focusing on reception is much more sensitive to ambiguity phase aberration profiles, which have adverse effects on focusing quality even in the near field and far field. These significant differences are caused by the fundamental differences between single range focusing and dynamic range focusing as well as between transmission and reception. Numerical and simulation results are also derived to test the correctness and accuracy of the theoretical results     

Calculation of radiation modes by the Lanczos-Fourier expansion

For construction of the TE radiation modes of planar waveguides several methods are employed that are based on collocation techniques. The field representation in the core is based on the Lanczos-Fourier sinusoidal series. The numerical codes are very simple and give accurate results. The validity of these methods is checked for constant refractive-index profiles, while numerical results are also given for parabolic profiles. Furthermore, the validity of the orthogonality condition between the guided and the radiation modes is checked. These methods are demonstrated to be effective and can also be employed to study the TM case and waveguides of lossy media, as well as anisotropic and chiral structures.     

Hydrocode results for the penetration of continuous, segmented and hybrid rods compared with ballistic experiments

Hydrocode calculations of the penetration of various tungsten alloy and stainless steel rod penetrators into semi-infinite steel and aluminum targets are presented and compared with results from ballistic experiments. Good agreement with experimental results is seen for penetration depth, penetration with time, and crater size and profile. The rod penetrator configurations investigated in the calculations include: idealized segmented rods with various segment spacings, the corresponding hybrid rods with axial spacers, and continuous rods of various dimensions. The Eulerian hydrocode results show enhanced penetration performance for idealized segmented rods compared with the parent continuous rods. Penetration performance for the corresponding hybrid segmented rods is significantly greater, even after accounting for the added mass of axial spacers. Results for long rod penetrators of the same mass and length as the hybrid rods, provide evidence that the axial spacers contribute to penetration. Both calculations and experiment show significant differences between the crater profiles of continuous versus ideal segmented or hybrid rods. The profiles generated by continuous rods are smooth, while those by segmented and hybrid rods are scalloped. Hydrocode results show that the scalloped crater profiles arise from successive impacts of rod segments.     

An iterative solution of the two-dimensional electromagnetic inverse scattering problem

A new method, based on an iterative procedure, for solving the two-dimensional inverse scattering problem is presented. This method employs an equivalent Neumann series solution in each iteration step. The purpose of the algorithm is to provide a general method to solve the two-dimensional imaging problem when the Born and the Rytov approximations break down. Numerical simulations were calculated for several cases where the conditions for the first order Born approximation were not satisfied. The results show that in both high and low frequency cases, good reconstructed profiles and smoothed versions of the original profiles can be obtained for smoothly varying permittivity profiles (lossless) and discontinuous profiles (lossless), respectively. A limited number of measurements around the object at a single frequency with four to eight plane incident waves from different directions are used. The method proposed in this article could easily be applied to the three-dimensional inverse scattering problem, if computational resources are available.     

Laser sensing of a subsurface oceanic layer. I. Effect of the atmosphere and wind-driven sea waves

Depth profiles and polarization characteristics of airborne lidar return signals have been calculated by the Monte Carlo method. We analyze some peculiarities of depth profiles of lidar return signals for a rough air-water interface. The distorting effect of the atmosphere on the lidar return signal structure is evaluated as a function of the geometry of the observations. Calculated results are compared with the data of airborne lidar measurements for lambda = 0.53 mum.     

Generation of partially coherent diffraction-free fields with tunable geometry

The synthesis of diffraction-free fields with different profiles is described. The synthesis is done by illuminating a screen containing a circular slit with a cosine beam. The treatment is equivalent to the modulation of the slit transfer characteristics and makes possible a tunable interference interaction of Bessel beams with noncommon axes. These results are generalized, and it is shown that coherent diffraction-free fields with arbitrary profiles can be expressed as the superposition of shifted zero-order Bessel beams and temporary parametric representations of the shifted functions. Diffraction-free fields with partially coherent features can be obtained. Experimental results are shown for each case.