Data compression for speckle correlation interferometry temporal fringe pattern analysis

Temporal fringe pattern analysis is gaining prominence in speckle correlation interferometry, in particular for transient phenomena studies. This form of analysis, nevertheless, necessitates large data storage. Current compression schemes do not facilitate efficient data retrieval and may even result in important data loss. We describe a novel compression scheme that does not result in crucial data loss and allows for the efficient retrieval of data for temporal fringe analysis. In sample tests with digital speckle interferometry on fringe patterns of a plate and of a cantilever beam subjected to temporal phase and load evolution, respectively, we achieved a compression ratio of 1.6 without filtering out any data from discontinuous and low fringe modulation spatial points. By eliminating 38% of the data from discontinuous and low fringe modulation spatial points, we attained a significant compression ratio of 2.4.     

基于自适应扰动观测器的PMSM模型预测电流控制

目的 为了实现包装自动化生产线的高性能控制，针对永磁同步包装驱动电机在模型预测电流控制中对扰动敏感性较大的问题，设计一种基于自适应扰动观测器的模型预测电流控制策略。方法 利用预测误差设计一种自适应扰动观测器，对系统遭受的内部和外部的不确定扰动，扰动观测器估计总扰动并以电流的形式进行补偿。将系统的瞬态过程和稳态过程分别进行考虑，设计一种含有动态权重因子的新型损失函数。结果 通过MATLAB/SIMULINK仿真表明，与传统的控制方法相比，文中方法可以保持瞬态下的高速动态响应和稳态下的低电流纹波，并在应对参数失配和负载突变等问题上，展现了更好的稳态性能和抗干扰能力。结论 文中方法可以有效提升系统动态性能和鲁棒性，使改进后系统更加适用于包装机的应用场景。     

A Dirichlet Process Gaussian State Machine Model for Change Detection in Transient Processes

The ability to detect incipient and critical changes in real world process—esessential for system integrity assurance—is currently impeded by the mismatch between the key assumption of stationarity underlying most change detection methods and the nonlinear and nonstationary (transient) dynamics of most real-world processes. The current approaches are slow or outright unable to detect qualitative changes in the behaviors that lead to anomalies. We present a Dirichlet process Gaussian state machine (DPGSM) model to represent dynamic intermittency, which is one of the most ubiquitous real-world transient behaviors. The DPGSM model treats a signal as a random walk among a Dirichlet process mixture of Gaussian clusters. Hypothesis tests and a numerical scheme based on this nonparametric representation were developed to detect subtle changes in the transient (intermittent) dynamics. Experimental investigations suggest that the DPGSM approach can consistently detect incipient, critical changes in intermittent signals some 50–2000 ms (20–90%) ahead of competing methods in benchmark test cases as well as a variety of real-world applications, such as in alternation patterns (e.g., ragas) in a music piece, and in the vibration signals capturing the initiation of product defects in an ultraprecision manufacturing process. A supplementary file to this article, available online, includes a Matlab implementation of the presented DPGSM.     

On the wavelet analysis of the oscillatory phenomena in He II film boiling

Continuous wavelet transform (CWT) is employed in the analysis of the pressure oscillation and the temperature oscillation in the film boiling of He II. The CWT analysis results provide the detailed time-varying frequency content, which can not be obtained in the ordinary Fourier transform. It can display the information about transient oscillatory behavior in both time and frequency domains, while Fourier transform only yields the time-averaged frequency content of the whole transient process. It could be understood from the CWT analysis results of the pressure oscillation and the temperature oscillation that the dominant frequency of the bubble oscillation is characterized by the highlighted patterns throughout the time domain. The dominant frequency varies locally in the time domain, which is directly connected with the vapor bubble behavior in the transient film boiling process.     

Fourier-transform method of data compression and temporal fringe pattern analysis

Temporal fringe pattern analysis is invaluable in studies of transient phenomena but necessitates large data storage for two essential sets of data, i.e., fringe pattern intensity and deformation phase. We describe a compression scheme based on the Fourier-transform method for temporal fringe data storage that permits retrieval of both the intensity and the deformation phase. When the scheme was used with simulated temporal wavefront interferometry intensity fringe patterns, a high compression ratio of 10.77 was achieved, with a significant useful data ratio of 0.859. The average root-mean-square error in phase value restored was a low 0.0015 rad. With simulated temporal speckle interferometry intensity fringe patterns, the important paremeters varied with the modulation cutoff value applied. For a zero modulation cutoff value, the ratio of data points and the compression ratio values obtained were roughly the same as in wavelength interferometry, albeit the average root-mean-square error in the phase value restored was far higher. By increasing the modulation cutoff value we attained significant reduction and increase in the ratio of data points and the compression ratio, respectively, whereas the average root-mean-square error in the restored phase values was reduced only slightly.     

Influence of laser deposition patterns on part distortion, interior quality and mechanical properties by laser solid forming (LSF)

Present work applied a kind of new deposition pattern, fractal deposition pattern, in the LSF process. The influences of different depositing patterns (fractal, offset and raster) on the parts’ deformation, interior quality and mechanical properties are also investigated. The finite element method (FEM) simulation results show that the offsetout (the offset from the outside to the inside) and fractal deposition patterns generate the temperature distribution with the circular and eccentric circle symmetry at the end of deposition process, respectively. There are smaller temperature gradients using these two kinds of deposition patterns than those by the raster and offsetin (the offset from the inside to the outside) deposition patterns. It is also found that the magnitude of the transient temperature gradient has a critical effect on part distortion during LSF process. The fractal deposition pattern generates the smallest parts’ deformation, followed by offsetout. The parts interior quality investigation with fractal and offsetout deposition patterns shows that the overlap should be increased to 50% to avoid pore defects. Moreover, we find that adopting arc path instead of square path at the corner locations and “semi-spot vibration” strategy for the offset and fractal deposition patterns respectively can produce better LSFed parts’ quality.     

Wavelet-based SPC procedure for complicated functional data

Functional data characterize the quality or reliability performance of many manufacturing processes. As can be seen in the literature, such data are informative in process monitoring and control for nanomachining, for ultra-thin semiconductor fabrication, and for antenna, steel-stamping, or chemical manufacturing processes. Many functional data in manufacturing applications show complicated transient patterns such as peaks representing important process characteristics. Wavelet transforms are popular in the computing and engineering fields for handling these types of complicated functional data. This article develops a wavelet-based statistical process control (SPC) procedure for detecting ‘out-of-control’ events that signal process abnormalities. Simulation-based evaluations of average run length indicate that our new procedure performs better than extensions from well-known methods in the literature. More importantly, unlike recent SPC research on linear profile data for monitoring global changes of data patterns, our methods focus on local changes in data segments. In contrast to most of the SPC procedures developed for detecting a known type of process change, our idea of updating the selected parameters adaptively can handle many types of process changes whether known or unknown. Finally, due to the data-reduction efficiency of wavelet thresholding, our procedure can deal effectively with large data sets.     

Derivation of temperature and pressure from submillimetric limb observations

We demonstrate the feasibility of retrieval of temperature and pressure profiles from spaceborne limb-sounding spectroscopic measurements in the submillimetric region. Whether these profiles can be retrieved determines whether a submillimetric instrument can be self-sufficient as far as the atmospheric model is concerned or whether complementary sensors in other spectral regions, dedicated to temperature and pressure measurements, are needed. Molecular-oxygen transitions are selected for the purpose of temperature and pressure retrieval on the basis of realistic observational parameters. We use a mathematical model of the retrieval process to evaluate the information content of the spectral features and to study the trade-off between the uncertainty of the retrieved profiles and their vertical resolution. It is shown that, using only one oxygen transition and without any constraint, one can achieve uncertainties of 5% for both temperature and pressure from 10 to ~40 km of altitude with a vertical resolution of 3 km; above 40 km the vertical resolution needs to be degraded to limit the uncertainties. The possibility of exploiting a priori information is discussed, as well as the effects of external constraints that can be used to improve the quality of the retrieved profiles. The sources of systematic error that need to be considered for the compilation of the total error budget are also evaluated.     

Analysis of transient processes with the method of linear prediction

We describe a method for determining the dynamic parameters of instruments or processes by representing the transient process of a model with several complex exponents. The nonlinear problem of finding the parameters of exponentials is replaced by the simpler problem of determining the coefficients of a linear predictive filter. Computer simulation shows that the error in determining the dynamic parameters is substantially reduced. Translated from Izmeritel'naya Tekhnika, No. 10, pp. 11–13, October, 1997.     

Fabricating functional circuits on 3D freeform surfaces via intense pulsed light-induced zinc mass transfer

Deployment of functional circuits on a 3D freeform surface is of significant interest to wearable devices on curvilinear skin/tissue surfaces or smart Internet-of-Things with sensors on 3D objects. Here we present a new fabrication strategy that can directly print functional circuits either transient or long-lasting onto freeform surfaces by intense pulsed light-induced mass transfer of zinc nanoparticles (Zn NPs). The intense pulsed light can locally raise the temperature of Zn NPs to cause evaporation. Lamination of a kirigami-patterned soft semi-transparent polymer film with Zn NPs conforming to a 3D surface results in condensation of Zn NPs to form conductive yet degradable Zn patterns onto a 3D freeform surface for constructing transient electronics. Immersing the Zn patterns into a copper sulfate or silver nitrate solution can further convert the transient device to a long-lasting device with copper or silver. Functional circuits with integrated sensors and a wireless communication component on 3D glass beakers and seashells with complex surface geometries demonstrate the viability of this manufacturing strategy.     

Premature transition to stable film boiling initiated by power transients in liquid nitrogen

We have investigated transient pool boiling in liquid nitrogen for a process in which the boiling is initiated by a step-function application of power to a thin wire immersed in the liquid. For such a process we find that a transition to stable film boiling can be observed for power values as low as about 40% of the steady-state peak heat flux. Such a ‘premature transition’ to stable film boiling can occur, even though the maximum observed values attained by the transient heat flux may lie substantially below the steady-state peak heat flux. Heating wires of platinum, copper, and constantan were employed in this investigation. Steady-state measurements are presented for comparison with the transient results, and a demonstration of the inhibition of the premature transition is described using a form of forced convection around the test wire.     

基于改进几何哈希法的矢量图形检索

针对图形文件以矢量方式记录几何实体的特点,提出了一种基于改进几何哈希法的图形检索算法。与图像的对应处理方式相比,该算法充分利用图形的矢量信息,以实体基准点和实体的准确几何形式描述几何实体;在检索过程中,每个图形实体仅有基准点参与排序和查询,哈希表数据组织形式简单,查询速度快;通过验证图形实体属性,保证了查询结果的准确性。最后以矢量图形文件为图例,验证了方法的有效性。     

基于粒子群-向量机的汽车加速噪声评价

以乘用车由50 km/h加速到100 km/h时的噪声信号为评价对象,用成对比较法对车内加速噪声品质偏好性进行主观评价实验,获得每个样本的偏好性评价值。计算各噪声样本的主要心理声学客观参数并进行相关分析。鉴于评价者对非稳态噪声主观评价过程的复杂性,建立支持向量机(Support Vector Machine,SVM)的主客观评价模型,并利用粒子群优化算法(Particle Swarm Optimization,PSO)对模型参数进行优化。为对比优化后预测效果,建立BP神经网络回归模型。结果表明,优化后的粒子群-向量机回归模型用于噪声声品质评价能获得更好的预测效果,可较大程度提高声品质预测精度。     

Analysing bullwhip and backlash effects in supply chains with phase space trajectories

We will investigate demand and supply variations in supply chains commonly known as bullwhip and backlash effects. The main goal of this paper is to detect bullwhip and backlash effects and its interactions by measuring only a few supply chain variables. To do so, we consider a multistage supply chain and analyse it with the aid of phase space trajectories. An examination of the geometrical structures of trajectories can reveal the dynamics of the bullwhip and backlash behaviour in supply chains. Therefore, we use a physical analogy to wave theory and describe order and delivery oscillations as a process of wave reflection. The proposed methodology systematically provides the basis for analysing a number of dynamic and transient behaviours that supplement the traditional analysis. These behaviour patterns include supply chain stability, compactness and bullwhip/backlash trade-offs, which have important consequences for the design, operation and control of supply chains.     

An experimental study on flow patterns and heat transfer characteristics during cryogenic chilldown in a vertical pipe

In the present paper, the experimental results of a cryogenic chilldown process are reported. The physical phenomena involve unsteady two-phase vapor–liquid flow and intense boiling heat transfer of the cryogenic fluid that is coupled with the transient heat conduction inside pipe walls. The objective for the present study is to compare the chilldown rates and flow patterns between the upward flow and downward flow in a vertical pipe. Liquid nitrogen is employed as the working fluid and the test section is a vertical straight segment of a Pyrex glass pipe with an inner diameter of 8 mm. The effects of mass flow rate on the flow patterns, heat transfer characteristics and interface movement were determined through experiments performed under several different mass flow rates. Through flow visualization, measurement and analysis on the flow patterns and temperature variations, a physical explanation of the vertical chilldown is given. By observing the process and analyzing the results, it is concluded that pipe chilldown in a vertical flow is similar to that in microgravity to some extent.     

Design of diffractive phase elements that produce focal annuli: a new method

A new optimization method based on the general theory of amplitude-phase retrieval is proposed for designing the diffractive phase elements (DPE's) that produce focal annular patterns. A set of equations for determining the phase distribution of the DPE is given. The profile of a surface-relief DPE can be designed with an iterative algorithm. Numerical calculations are carried out for several examples. A comparison of the performance of the DPE's designed with the Gerchberg-Saxton algorithm and the new algorithm is presented. The effect of quantization of the phase distribution of the DPE's on the results is also investigated. The results show that the new algorithm can successfully achieve the design of the DPE's that convert the uniform incident beam into the focal annular patterns.     

Analysis of self-calibrated field aligned starting (FAS) at mains connection

Field aligned starting (FAS) is a technique for starting three-phase cage induction motors on either three-phase or single-phase supply lines under varying load conditions with minimal inrush currents. The technique starts the motor independent of the mains supply with a high transient torque before connecting the spinning motor to the mains. It is imperative to the operation of FAS that the spinning motor be connected to the mains at the correct time. Incorrectly timed mains connection can result in negative transient torques with the severity to slow, or possibly stall the already started motor. As the implementation of FAS is not possible without a predictive mechanism by which the correct moment of mains connection can be found in advance, this paper proposes a simple, low cost, yet effective self-calibrating method which ensures that the timing of the mains connection is correct under all starting conditions. Critical issues vital to a successful self-calibration under transient and varying starting conditions are investigated and presented with both experimental and simulated results to show that self-calibration is an indispensable part of FAS technique.     

苗绣纹样搜索中草图和文本检索的认知负荷对比研究

目的 为了探究一种更高效的苗绣纹样检索方式,通过对手绘草图检索及文本检索过程中的认知负荷来进行对比研究。方法 首先通过构建认知负荷信息检索过程模型,对5个认知阶段的平均认知负荷及所需时间进行实验对比;其次通过眼动指标(持续注视时间、眼球扫视振幅、眼球直径)及NASA-TLX评估对两种检索过程的认知负荷进行分析;最后基于眼动追踪得到可视化眼动数据(热点图、注视轨迹)验证是否符合检索任务需求。结论 基于手绘草图的图形检索方式更适合于苗绣纹样检索,通过主、客观融合对比实验验证了草图检索的高效性,同时也验证了眼动追踪和NASA_TLX具有相关性,能更有效地进行认知负荷测量。     

Contextual paradigm for ad hoc retrieval of user-centric web data

The choice of the term-weighting technique and the combination of term weights during retrieval is an important aspect of the Web information retrieval (WebIR) system. At their heart, most WebIR models utilise some form of term frequency-based term-weighting technique. The notion is that the more often a query term occurs in a document, the more likely it is that the document meets an information need. We examine an alternative. We propose a model, which assesses the presence of a term in a document not by looking at the actual occurrence of that term, but by a set of non-independent supporting terms, that is context. We expound contextual proximity model (CPM), a novel context-based paradigm, which when used as a part of the Web retrieval process, will improve retrieval effectiveness in response to a given multi-term input query. This work is concerned with a non-iterative retrieval process, that is one without query refinement or relevance feedback.