New model for shrinkage compensation in selective laser sintering

This paper presents a new model for shrinkage and a new approach for shrinkage compensation to enhance the accuracy of parts produced by selective laser sintering (SLS)–a solid freeform fabrication process. The present prevailing approach as proposed by machine manufacturers is simple but not accurate. A new shrinkage model which accounts for part geometry as well as beam offset is proposed in this work. A new compensation scheme which accounts for nonlinear shrinkage is proposed, implemented and validated. The proposed compensation scheme compensates for shrinkage at every layer and at every hatch length, unlike a uniform compensation scheme applied to entire part. A new algorithm which accounts for this is developed and implemented. Experiments carried out with the new shrinkage model as well as with the new compensation scheme have shown significant improvement in the accuracy of the parts produced which establishes the effectiveness of the proposed methodology.     

基于有理逼近和灵敏度分析的结构动力重分析方法

提出了一种新的结合特征灵敏度直接法和向量值函数有理逼近的结构动力重分析方法。给出了直接法简单特征对n阶灵敏度分析的一般表达式。利用向量值函数有理逼近，减小固有振型n阶Taylor展开的截断误差。数值算例表明，对结构设计参数作大修改时，该方法能够给出高精度的逼近结果。新方法不需要系统的全部模态，因此，适用于大型复杂结构的动力重分析。     

Fault diagnosis of batch processes using discriminant model

A new statistical online diagnosis method for a batch process is proposed. The proposed method consists of two phases: offline model building and online diagnosis. The offline model building phase constructs an empirical model, called a discriminant model, using various past batch runs. When a fault of a new batch is detected, the online diagnosis phase is initiated. The behaviour of the new batch is referenced against the model, developed in the offline model building phase, to make a diagnostic decision. The diagnosis performance of the proposed method is tested using a dataset from a PVC batch process. It has been shown that the proposed method outperforms existing PCA-based diagnosis methods, especially at the onset of a fault.     

Performance analysis of a new hybrid token‐CSMA/CD protocol

Abstract

A new hybrid token‐CSMA/CD protocol is proposed and analyzed in this paper. The new hybrid protocol is suitable for bus‐structured local area networks. Basically, the new hybrid protocol is a modification of the one proposed by Gopal and Wong [3]. In our new hybrid protocol, the first time slot after the channel changes state from busy to idle, is reserved for the exclusive use of the priority user who possesses the token. Results show that, by this simple modification, our new hybrid protocol has a better performance than the one proposed in [3], especially when the time wasted in detecting a collision is large. The reason is that most of the packet collisions will be avoided by reserving one time slot for the exclusive use of the priority user.     

用杂交法改善应力解的新型复合材料层合板单元

本文给出一种基于一阶剪切变形理论(FSDT)新型的、无闭锁的位移型四边形复合材料层合板单元TMQ20的列式;并根据Hellinger-Reissner变分原理,针对位移型复合材料板单元提出了一种新型应力杂交化后处理方法来改善单元计算应力的能力,使位移型单元可以简单和正确地预测层合板的应力,特别是层间横向剪应力的解。数值算例表明,经过改善的TMQ20单元具有位移型和杂交型有限元的双重优点,它不仅自由度少,列式简单,而且对位移和应力都可以得到高精度的结果,适用于从薄到中等厚度的复合材料层合板的计算。本文所提出的杂交化后处理方法的概念适用于改善任何种类的位移型单元的应力解。     

统计圆度公差及其误差评定的研究

在分析几何圆度公差及其误差评定方法存在问题的基础上,指出现有圆度误差的各种测量评定方法都是基于几何公差的概念。提出应以统计圆度公差作为几何圆度公差的补充与发展。论述了统计圆度误差的意义及其测量评定方法。     

A New Two-Sided Cumulative Sum Quality Control Scheme

A new two-sided cumulative sum quality control scheme is proposed. The new scheme was developed specifically to be generalized to a multivariate cumulative sum quality control scheme. The multivariate version will be examined in a subsequent paper; this article evaluates the univariate version. A comparison of the conventional two-sided cumulative sum scheme and the proposed scheme indicates that the new scheme has slightly better properties (ratio of on-aim to off-aim average run lengths) than the conventional scheme. Steady state average run lengths are discussed. The new scheme and the conventional two-sided cumulative sum scheme have equivalent steady state average run lengths. Methods for implementing the fast initial response feature for the new cumulative sum scheme are given. A comparison of average run lengths for the conventional and proposed schemes with fast initial response features is also favorable to the new scheme. A Markov chain approximation is used to calculate the average run lengths of the new scheme.     

A Novel Prediction Method for Hardness Using Auto-regressive Spectrum of Barkhausen Noise

In this study, a novel method for predicting hardness of ferromagnetic alloy based on the magnetic Barkhausen noise (MBN) is proposed. A set of new frequency features of MBN and a new hardness prediction method are proposed. The new features are derived from the first and second derivative of the auto-regressive spectrum of MBN signal. The new automatic hardness prediction method include Bag-of-Words, principal component analysis and back propagate neural network optimized by ensemble learning. The experimental results of the hardness classification show that the new features are superior to the previous features—the misclassification rate using the new features is less than 0.67%, while the misclassification rate using the previous features is about 2%. The efficiency of the new method is also proved by hardness classification experiment. Compared with the traditional time-domain method and the previous frequency domain method, the misclassification rate of the new method decreased significantly from 25% to less than 1%. In addition, the new method is highly automatic, so it is more versatile than manual algorithms. The above characteristics make the proposed new method suitable for predicting the hardness of ferromagnetic alloys in practice.     

插入软管的低频宽带共振吸声机理与实验研究

提出了一种新型的宽频带共振吸声结构，该结构基于赫姆霍兹共振吸声机理，并充分利用了软管在长度上的优势，易于实现对低频噪声的控制。论文通过分域处理并建立不同区域声学边界条件的方法，考虑了软管的管壁特性，从理论上给出了这种结构的吸声特性。实验证明本文提出的新型宽带共振吸声机理正确，利用本文提供的分析方法可以精确计算系列共振频率及其吸声系数，利用本文提出的增加软管长度和系列软管组合的方法可有效拓宽吸声频带。这种新型吸声结构的提出，为低频宽带噪声控制提供了新的途径，为对次声和极低频噪声的防护提供了技术基础。     

Edge detection using Chebyshev's orthogonal polynomial and brain extraction from magnetic resonance images of human head

In this article, we propose a new edge detecting method based on the transform coefficients obtained by a point spread function constructed out of Chebyshev's orthogonal polynomials. This edge detector finds edges similar to that of Prewitt and Roberts but is robust against additive and multiplicative noises. We also propose a new scheme to extract brain portion from the magnetic resonance images (MRI) of human head scan by making use of the of the new edge detector. The proposed scheme involves edge detection, morphological operations, and largest connected component analysis. Experiments conducted by applying the proposed scheme on 19 volumes of MRI collected from Internet Brain Segmentation Repository (IBSR) show that the proposed brain extraction scheme performed better than the popular Brain Extraction Tool (BET). The performance of the proposed scheme is measured by computing the Dice coefficient (D) and Jaccard similarity index (J). The proposed method produced a value of 0.9068 for D and 0.8321 for J.     

一类组合优化问题的新解法及其收敛性

混合LT法是一种解组合优化问题的新方法,这种方法将约束分为两部分,其一用Lagrange方法来处理,另一部分用罚函数来处理。与现存的Hopfield网络比较,这种方法有几个优点：它既能用于二次函数,还能用于非二次函数：且在控制人为的加权参数时,它减少了对外部的依赖。本文提出了一种新的混合LT法．使用它,能更快找到更准确的解,并且对这种方法作了收敛性分析,给出了收敛性的必要条件和充分条件。从而说明这种方法是可行的和有效的,可用于很多组合优化问题。     

Scheduling in flowshops to minimize total tardiness of jobs

The problem of scheduling in static flowshops is considered with the objective of minimizing mean or total tardiness of jobs. A heuristic algorithm based on the simulated annealing (SA) technique is developed. The salient features of the proposed SA algorithm are the development of two new perturbation schemes for use in the proposed SA algorithm and a new improvement scheme to improve the quality of the solutions. The proposed algorithm is evaluated by using the benchmark problems available in the literature. The performance of the proposed SA algorithm is found to be very good, and the proposed heuristic performs better than the existing heuristics.     

A new reliability analysis method for repairable systems with closed‐loop feedback links

A new reliability analysis method for repairable systems with closed‐loop feedback link (CLFL) is proposed based on GO methodology. A method for creating new function GO operators is used to describe the CLFL. Next, methods for deducing the formulae of the new GO function are proposed. In addition, a 2‐level GO model is proposed for the GO operation of repairable systems with CLFL. And then, quantitative and qualitative analysis methods for repairable systems with CLFL based on the GO method are proposed, and a process for analyzing repairable systems with CLFL based on the new GO method is formulated. Finally, we used this new GO method to analyze the reliability of an electro‐hydraulic servo speed control system and a power‐shift steering transmission control system for a heavy vehicle. To verify the feasibility, advantages, and reasonability of the new GO method, we compared our results with those obtained by fault tree analysis, Monte Carlo Simulation, and an existing GO method using serial and parallel structures to represent the CLFL. All in all, the proposed method overcomes the limitations of the existing methods as well as increasing its applicability. And it provides a new approach for reliability analysis of repairable systems with CLFL.     

Beyond plain weave fabrics – I. Geometrical model

In response to the large variety of weaving styles offered by the textile industry, a new general approach for the geometrical modeling of 2D biaxial orthogonal woven fabric reinforcements for composite materials is proposed here. New geometrical parameters are introduced in order to describe general families of twill and satin woven patterns, and a new classification of woven fabrics is proposed based on these parameters. Generation of the 3D internal geometry of the woven fabric families is achieved based on new geometrical functions that consider the actual configuration of the composite material in all its complexity. The proposed geometrical model is intended as the foundation for further analytical or numerical modeling of the mechanical properties of the composite materials reinforced with these fabrics.     

A new hybrid real-coded genetic algorithm and its application to parameters identification of soils

Inverse analysis using an optimization method based on a genetic algorithm (GA) is a useful tool for obtaining soil parameters in geotechnical fields. However, the performance of the optimization in identifying soil parameters mainly depends on the search ability of the GA used. This study aims to develop a new efficient hybrid real-coded genetic algorithm (RCGA) being applied to identify parameters of soils. In this new RCGA, a new hybrid strategy is proposed by adopting two crossovers with outstanding ability, namely the Simulated Binary Crossover and the simplex crossover. In order to increase the convergence speed, a chaotic local search technique is used conditionally. The performance of the proposed RCGA is first validated by optimizing mathematical benchmark functions. The results demonstrate that the RCGA has an outstanding search ability and faster convergence speed compared to other hybrid RCGAs. The proposed new hybrid RCGA is then further evaluated by identifying soil parameters based on both laboratory tests and field tests, for different soil models. All the comparisons demonstrate that the proposed RCGA has an excellent performance of inverse analysis in identifying soil parameters, and is thus recommended for use based on all the evaluations carried out in this paper.     

基于Kriging代理模型的多点加点序列优化方法

基于Kriging 代理模型提出了一种同时考虑预测响应值及其不确定性的多点加点准则,并基于该准则发展了一套序列近似优化方法。多点加点准则基于初始样本信息和所预测的对象函数特征增加新样本集,以在寻优迭代过程中自适应地提高代理模型的精度。该文方法依据多点加点准则在一次迭代中增加多个空间无关的新样本点,适用于多机同时计算或并行计算,从而提高计算效率。以两个经典的数学函数为例,将该优化方法与期望提高准则方法进行了比较,结果表明该文提出的优化方法能够有效地提高最优解的全局性。将方法用于一盒式注塑件的成型工艺优化设计,优化结果也表明了该方法的有效性。     

A bioinspired path planning approach for mobile robots based on improved sparrow search algorithm

In this paper, a bioinspired path planning approach for mobile robots is proposed. The approach is based on the sparrow search algorithm, which is an intelligent optimization algorithm inspired by the group wisdom, foraging, and anti-predation behaviors of sparrows. To obtain high-quality paths and fast convergence, an improved sparrow search algorithm is proposed with three new strategies. First, a linear path strategy is proposed, which can transform the polyline in the corner of the path into a smooth line, to enable the robot to reach the goal faster. Then, a new neighborhood search strategy is used to improve the fitness value of the global optimal individual, and a new position update function is used to speed up the convergence. Finally, a new multi-index comprehensive evaluation method is designed to evaluate these algorithms. Experimental results show that the proposed algorithm has a shorter path and faster convergence than other state-of-the-art studies.The full text can be downloaded at https://link.springer.com/article/10.1007/s40436-021-00366-x     

基于神经网络的质量控制图模式识别技术的研究

提出了一种用于质量控制图模式识别的新的神经网络模型，它与以往的神经网络模型相比，具有较强的识别能力和较短的训练时间。     

Actuation and sensing of piezolaminated sandwich type structures

A new piezolaminated sandwich type structure to be eventually used as a smart wall for active control of sound radiated by harmonically excited thin walled structures is proposed. The present study presents the equations of motion of the new adaptive sandwich structures in a sufficiently accurate model in a form readily for solution either in closed-form or by approximate methods. The theoretical natural frequencies are compared with an approximate evaluation and test results yielding a good correlation. It also yields the axial strains and the curvature of the composite beam leading to the calculation of equivalent mechanical loads produced by the piezoceramic actuator for inclusion in a finite element code. The numerical results are compared with experimental ones obtained during a test series on a cantilever sandwich beam equipped with piezoceramic sensors and actuators and constructed according to the new proposed concept. The influence of the input voltage on the performance of the new sandwich structure is investigated. The beam tip deflection induced by the piezoceramic actuators is measured and compared with numerical and finite element predictions to yield a very good match. Both the numerical and the experimental results show the applicability of the new proposed concept.     

基于时频滤波的时变模态分解方法

应用非平稳信号的时频滤波进行多自由度时变线性系统的模态分解。将基于Gabor展开的时频滤波 方法引入多自由度线性时变结构模态参数辨识中,提取单模态响应分量。对线性时变系统在白噪声激励下振动响 应的单模态响应进行提取,通过对附加质量随时间连续变化的悬臂梁的单模态响应分离来验证分解方法韵有效 性。实验研究结果和理论计算结果表明:方法为参数时变的线性系统的模态分解提供了一条新的途径。