工业过程对象的实用辨识

本文从实际应用出发讨论了两种过程控制中的系统对象的辨识方法，在生产过程中这种辨识方法可直接得到实际的对象模型，测试时间短，编程简单易操作。     

机电产品的响应与两种运输试验的振动情况

本文分析了一般机构产品结构对不同外加振动过程的响应规律,测试并总结了我国部分地区汽车和火车运输过程的振动情况,并用部分国家的汽车与火车运输的振动情况进行了对比。     

On the meausurement of the material response of linear photoviscoelastic polymers

The basic relations between the temporary birefringence effects, the strain and stress state and the optical response of linear photoviscoelastic materials are derived. According to the theoretical considerations proper procedures are described to measure the time-dependent optical response and to evaluate the optical creep compliance and the optical relaxation function. Finally, results are given for some different photoviscoelastic materials.     

Second order inverse response process identification from transient step response

Simple algorithms for identification of inverse response models from step response are difficult to obtain because analytically the solution of a system of coupled nonlinear equations is required. In this article we propose a simple identification procedure for second order inverse response processes, based on the plant step response. The algorithm provides the model parameters in a sequential way, thus avoiding the solution of a nonlinear equation system. Moreover the algorithm is flexible because it can be suited to user requirements, thus modifying the algorithm performance. Finally error bounds on the identified parameters are provided which are useful if the model is used for control design purposes.     

PCB布线产生的串扰及其解决办法

介绍了电磁耦合的基本原理,定性地分析了串扰的形成机理,重点分析了串扰的主要因素即后向串扰,给出了串扰的估算公式,阐述了PCB设计中解决串扰问题的具体策略。     

Generalized solution for predicting relaxation from creep in soft tissue: Application to ligament

Creep and relaxation are two viscoelastic phenomena that are easily interrelated for a linearly viscoelastic material, but interrelationships are complex for nonlinearly viscoelastic materials. We use a single-integral nonlinear superposition principle to relate creep and relaxation, where the kernel is assumed to be a nonseparable product of strain and time. Herein, we develop time dependence as general power laws with up to four terms for creep compliance and relaxation modulus. Higher-order formulations give better results for ligament in terms of curve fitting and prediction of relaxation from creep. This is illustrated by a comparison between a two- and a three-term formulation on the experimental data of rabbit medial collateral ligaments. Also, an interrelation between several aspects of creep and relaxation is presented for arbitrarily high order, and the nature of high-order interrelation is discussed. The generality of the method makes it suitable to phenomenologically model many complex materials, to predict complex behaviors and to therefore reduce the amount of testing for robust material characterization.     

机载相干激光雷达收发机

相干激光雷达系统建立在固态激光技术上,以对眼安全的波长工作。它已在衫的传感器方面得到飞速发展,这些传感器只在一些地面雷达和机载对风远距离探测上得到应用,而没有在众的飞机上得到应用,这是由于它们的价值、体积、重量、需要大功率的冷却器以使系统温度稳定这些因素所阻制。     

光学系统探测器上的辐照度的偏振分析

推导出了光学系统探测器上的辐照度误差与入射光以及光学系统的偏振特性之间关系的公式,分析了入射光以及光学系统的线偏振灵敏度对光学系统的探测器上的辐照度的影响,并计算了卡氏望远镜的探测器上的辐照度误差。     

Theoretical estimation for correlations of diffraction patterns from objects differently oriented in space

Coherent diffraction imaging of single biomolecules is expected to open unique opportunities for studies of non-crystalline samples. There are, however, still many technical and physical issues that need to be resolved in a more quantitative manner, especially if one aims for structural information at high resolution. Signal recorded from an object after a single shot is low. As primarily proposed in Spence and Doak (2004) and Huldt et al. (2003) [1] and [2], averaging over the diffraction patterns from many different shots is necessary, in order to achieve a signal-to-noise ratio sufficient for image reconstruction. The images of the randomly oriented molecules have to be sorted out in order to identify those corresponding to the similar spatial orientations of the objects. This procedure is called the classification of diffraction images. Here we approach the classification in the framework of pattern-to-pattern correlations, and analyse theoretically the correlations between diffraction images of differently oriented objects.     

An experimental study of nonlinear viscoelastic bushing model for axial mode

A bushing is a device used in automotive suspension systems to cushion the force transmitted from the wheel to the frame of the vehicle. A bushing is essentially a hollow cylinder which is bonded to a solid metal shaft at its inner surface and a metal sleeve at its outer surface. The shaft is connected to the suspension and the sleeve is connected to the frame. The cylinder provides the cushion when it deforms due to relative motion between the shaft and sleeve. The relation between the force applied to the shaft or sleeve and its deformation is nonlinear and exhibits features of viscoelasticity. An explicit force-displacement relation has been introduced for multi-body dynamics simulations. The relation is expressed in terms of a force relaxation function and a method of determination by experiments on bushings has been developed. Solutions allow for comparison between the force-displacement behavior by experiments and that predicted by the proposed method. It is shown that the predictions by the proposed force-displacement relation are in very good agreement with the experimental results.     

Transient suppression in FRF measurement: Comparison and analysis of four state-of-the-art methods

This paper compares four well selected methods for computing the non-parametric Frequency Response Function (FRF) of a periodically excited linear time invariant system. The suppression of the transient is mandatory when its influence in the data is large. Better suppression of the transient leads to a better non-parametric FRF estimate. A good non-parametric FRF estimate can be used to validate the parametric transfer function model in a second step. The suppression of the transient will be highlighted using the mean squared error of the non-parametric FRF estimate. Temperature transients caused by heat diffusion are used as example. The selected methods consist of two standard windowing methods and two methods based on the Local Polynomial Method (LPM). LPM was designed to find a non-parametric FRF estimate in the presence of nonlinearities. This paper will modify LPM to find a non-parametric FRF estimate for linear systems using a single experiment. The mean squared error of the four non-parametric FRF estimates will be compared and analyzed, based on a simulation and a measurement example.     

Coherent electron emission from point sources

We study the electron emission and propagation in ultrasharp tips field-emission experiments. The intensity-voltage characteristics as well as the angular spreading of the electron beam is analysed. We show that non-coherent emission cannot explain the very narrow experimental electron beams. The properties of coherent electron sources and the beam spatial coherence width are discussed. The quantum mechanical current distribution of field-emitted electrons from tubes seems to explain the experimental beam widths.     

基于混合全息算法的多源相干声场分离方法

当空间声场中存在多个相干声源时,运用常规的近场声全息算法无法重建和预测每个相干声源的声场分布,限制了声全息的应用范围和对相干声场的分析。在针对该问题的现有方法中,基于傅里叶变换的声场分离技术只能用于相干声源位于全息面两侧的情况,而分布源边界点法、联合波叠加法等虽然可解决相干声源位于全息面同侧的分离问题,但在应用时必须预先知道声源的位置以及几何形状等先验知识。针对相干声源在全息面同侧的情况,提出一种新的多源相干声场分离方法。该方法只需全息面声压,不需要其他先验知识就可以实现相干声场分离,能很好地弥补现有方法的缺点,并为相干声场的分析提供有力手段。数值仿真和试验验证该方法的正确性、可行性和有效性。     

A method for correcting the effect of specimen drift on coherent diffractive imaging

Coherent diffractive imaging involves the inversion of a diffraction pattern to find the wave function at the exit-surface plane of the specimen. It is a promising technique for imaging, for example, nanoparticles with electrons and biological molecules with X-rays. If the illumination is not a plane wave of infinite extent, then a relative drift between the illumination and the object introduces errors into the diffraction pattern; an issue which is often overlooked. This may be of particular importance for applications with electron microscopes which use nanoscale probes. Here we show that beams which are uniform over a sufficiently large region can be used to pose a phase retrieval problem that is immune from specimen drift, provided suitable analysis of the diffraction data is undertaken. The method only applies to objects contained within a support that is smaller than a uniform region of the beam.     

Chemically specific imaging of cryptosporidium oocysts using coherent anti-Stokes Raman scattering (CARS) microscopy

We demonstrate the application of coherent anti-Stokes Raman scattering microscopy for the rapid, label-free chemical imaging of waterborne pathogens. Chemically selective images of cryptosporidium were acquired in just a few seconds using coherent anti-Stokes Raman scattering microscopy, demonstrating its capability for the rapid detection of cryptosporidium at the single oocyst level. We discuss the applicability of such a technique in a near-real time automated water testing system.     

In vivo coherent anti-Stokes Raman scattering imaging of sciatic nerve tissue

We report in vivo nonlinear optical imaging of mouse sciatic nerve tissue by epidetected coherent anti‐Stokes Raman scattering and second harmonic generation microscopy. Following a minimally invasive surgery to open the skin, coherent anti‐Stokes Raman scattering imaging of myelinated axons and second harmonic generation imaging of the surrounding collagen fibres were demonstrated with high signal‐to‐background ratio, three‐dimensional spatial resolution, and no need for labelling. The underlying contrast mechanisms of in vivo coherent anti‐Stokes Raman scattering were explored by three‐dimensional imaging of fat cells that surround the nerve. The epidetected coherent anti‐Stokes Raman scattering signals from the nerve tissues were found to arise from interfaces as well as back reflection of forward coherent anti‐Stokes Raman scattering.     

Improved (non-)parametric identification of dynamic systems excited by periodic signals—The multivariate case

Recently [1] a method has been developed to suppress nonparametrically the noise (and system) transients (leakage errors) in frequency response function and noise (co-)variance estimates of single-input, single-output systems excited by periodic signals. This paper extends the results of [1] to multiple-input, multiple-output systems where all inputs and outputs are disturbed by noise (i.e. an errors-in-variables framework). Two methods are presented: the first starts from multiple experiments with uncorrelated sets of inputs, and makes no assumption about the frequency response matrix (FRM); while the second only requires one single experiment, but assumes that the FRM can locally be approximated by a polynomial. Both methods estimate simultaneously the FRM, the noise level, and the level of the nonlinear distortions. For lightly damped systems, the proposed methods either significantly reduce the experiment duration or, for a given measurement time, significantly increase the frequency resolution of the FRM estimate. If the noise (and/or system) transients are the dominant error sources, then the proposed methods also significantly reduce the covariance matrix of the FRM estimates. The use of the nonparametric noise covariance estimates for parametric transfer function modelling is also discussed in detail.     

Improved (non-)parametric identification of dynamic systems excited by periodic signals

The steady state response of a system to a periodic input is still subject to noise transients. For lightly damped systems these noise transients can significantly increase the variance of the estimated frequency response function (FRF). This paper presents a method that suppresses the influence of the noise transients (leakage errors) in nonparametric FRF and noise (co-)variance estimates of dynamic systems excited by periodic signals. The method is based on a local polynomial approximation of the noise leakage errors on the FRF. Compared with the classical approaches, the proposed procedure is more robust and needs less measurement time (two signal periods are sufficient). The theory is supported by simulation and real measurement examples.