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Zhang X.,Shanghai University | Zhang X.,State Key Laboratory of Digital Manufacturing Equipment and Technology | Li C.,Shanghai University
Guangxue Xuebao/Acta Optica Sinica | Year: 2014

The light field imaging with microlens array is modeled through analyzing three fundamental factors, such as space, lens, and sensor. The spatial multiplexing is explained and the relationship between the light field and the pixel in raw image is described. Based on the phase shifting, a calibration method is proposed to determine the centers of microlens, the corresponding relationship between the pixel and the microlens, and the character of the microlens vignetting. The experiment is conducted on a commercial light field camera, Lytro. The light field is decoded from the raw image and the refocus image and all-focus image is created from the obtained light field. The experiment results confirm the proposed model and calibration method is valid. ©, 2014, Chinese Optical Society. All right reserved.


Wen J.,Jiangnan University | Peng L.,Jiangnan University | Peng L.,State Key Laboratory of Digital Manufacturing Equipment and Technology | Nguang S.K.,University of Auckland
Signal Processing | Year: 2014

This work studies the asynchronous H∞ filtering problem for a class of discrete-time switched time-delay systems. The word "asynchronous" means that the switching of the filters has a lag to the switching of system modes due to the network induced random occurrences, which includes both the sensor saturations and the missing measurements. First, new results on the regional stability and l2 gain analysis for the underlying system are given by allowing the Lyapunov-like function (LLF) to increase with a random probability during the unmatched period of the switching mode and the filter. Then, a regional H∞ filter with a modified mode dependent ellipsoid constraint is designed such that the filtering error dynamics is asymptotically stable in the mean square sense with a given disturbance attenuation level. Finally, a numerical example is given to verify the efficiency of the proposed method. © 2013 Elsevier B.V.


Rao Y.-Q.,State Key Laboratory of Digital Manufacturing Equipment and Technology | Rao Y.-Q.,Huazhong University of Science and Technology | Wang M.-C.,State Key Laboratory of Digital Manufacturing Equipment and Technology | Wang M.-C.,Huazhong University of Science and Technology | And 3 more authors.
Computers and Operations Research | Year: 2013

This paper focuses on the scheduling of a single vehicle, which delivers parts from a storage centre to workstations in a mixed-model assembly line. In order to avoid part shortage and to cut down total inventory holding and travelling costs, the destination workstation, the part quantity and the departure time of each delivery have to be specified properly according to predetermined assembly sequences. In this paper, an optimisation model is established for the configuration that only one destination workstation is involved within each delivery. Four specific properties of the problem are deduced, then a backward-backtracking approach and a hybrid GASA (genetic algorithm and simulated annealing) approach are developed based on these properties. Both two approaches are applied to several groups of instances with real-world data, and results show that the GASA approach is efficient even in large instances. Furthermore, the existence of feasible solutions (EOFS) is analysed via instances with different problem settings, which are obtained by an orthodox experimental design (ODE). An analysis of variance (ANOVA) shows that the buffer capacity is the most significant factor influencing the EOFS. Besides this, both the assembly sequence length and distances to workstations also have noticeable impacts. © 2013 Elsevier Ltd.


Yan L.,Huazhong University of Science and Technology | Yan L.,State Key Laboratory of Digital Manufacturing Equipment and Technology | Yang W.,Huazhong University of Science and Technology | Yang W.,State Key Laboratory of Digital Manufacturing Equipment and Technology | And 2 more authors.
International Journal of Advanced Manufacturing Technology | Year: 2012

In the machining of hard machined materials, microstructure changes in the machined surface must be taken into account to improve product performance. Therefore, a large number of experimental and finite element method investigations have been carried out to investigate these microstructure changes. However, until now, only a few studies have reported the analytical modelling of microstructure changes. This paper presents a hardness-based analytical model that accounts for both mechanical and thermal effects in predicting microstructure changes during the machining of 304 stainless steel. The model was also validated for a range of cutting speeds, feed rates, and wear widths. The predicted results are in good agreement with the experimentally measured results. Thus, with the analytical model, an accurate prediction of microstructure changes is achieved, which reduces experimental expense and finite element method computational time. © Springer-Verlag London Limited 2011.


Liu F.-M.,Hunan University of Science and Technology | Zhu H.-P.,State Key Laboratory of Digital Manufacturing Equipment and Technology | Liu B.-X.,State Key Laboratory of Digital Manufacturing Equipment and Technology
Journal of Central South University | Year: 2013

A cost-based selective maintenance decision-making method was presented. The purpose of this method was to find an optimal choice of maintenance actions to be performed on a selected group of machines for manufacturing systems. The arithmetic reduction of intensity model was introduced to describe the influence on machine failure intensity by different maintenance actions (preventive maintenance, minimal repair and overhaul). In the meantime, a resolution algorithm combining the greedy heuristic rules with genetic algorithm was provided. Finally, a case study of the maintenance decision-making problem of automobile workshop was given. Furthermore, the case study demonstrates the practicability of this method. © 2013 Central South University Press and Springer-Verlag Berlin Heidelberg.


Zhong F.,State Key Laboratory of Digital Manufacturing Equipment and Technology | He S.,State Key Laboratory of Digital Manufacturing Equipment and Technology | Li B.,State Key Laboratory of Digital Manufacturing Equipment and Technology
International Journal of Advanced Manufacturing Technology | Year: 2015

During the testing and sorting of LED chips, traditional methods do not exclude the polycrystalline and fragmentary LED chips from the normal chips well. The purpose of this paper is to propose a new algorithm to solve this problem. The algorithm consists of three steps. Firstly, present a simple but efficient image segmentation method to get blobs. Secondly, analyze the blobs to exclude abnormal blobs and predict the pose (position and orientation) of the potential object based on the pose of the minimum enclosing rectangle (MER) of each remained blob. Finally, according to the predicted poses, locate the LED chips precisely in the originally captured image based on gradient orientation features. Experiments show that the algorithm is not only robust to illumination variation but also can locate the LED chips and exclude the polycrystalline and fragmentary chips efficiently. © 2015 Springer-Verlag London


Huang B.,State Key Laboratory of Digital Manufacturing Equipment and Technology | Huang B.,Huazhong University of Science and Technology | Yang W.,Huazhong University of Science and Technology | Wen Y.,Huazhong University of Science and Technology | And 2 more authors.
ACS Applied Materials and Interfaces | Year: 2015

Composite Co3O4/TiO2 nanotube arrays (NTs) were fabricated via atomic layer deposition (ALD) of Co3O4 thin film onto well-aligned anodized TiO2 NTs. The microscopic morphology, composition, and interfacial plane of the composite structure were characterized by scanning electron microscopy, energy dispersion mapping, X-ray photoelectron spectra, and high-resolution transmission electron microscopy. It was shown that the ultrathin Co3O4 film uniformly coat onto the inner wall of the high aspect ratio (>100:1) TiO2 NTs with film thickness precisely controlled by the number of ALD deposition cycles. The composite structure with ∼4 nm Co3O4 coating revealed optimal photoelectrochemical (PEC) performance in the visible-light range (Î" > 420 nm). The photocurrent density reaches as high as 90.4 ÎA/cm2, which is ∼14 times that of the pristine TiO2 NTs and 3 times that of the impregnation method. The enhanced PEC performance could be attributed to the finely controlled Co3O4 coating layer that enhances the visible-light absorption, maintains large specific surface area to the electrolyte interface, and facilitates the charge transfer. © 2014 American Chemical Society.


Wu T.,Huazhong University of Science and Technology | Pei X.,Huazhong University of Science and Technology | Lu Y.,Huazhong University of Science and Technology | Chen C.,Huazhong University of Science and Technology | Gao L.,State Key Laboratory of Digital Manufacturing Equipment and Technology
Journal of Network and Computer Applications | Year: 2013

With the boom of Internet Technology, it becomes possible to combine designers from different disciplines into one team to support product design globally. In this paper, a distributed collaborative product design environment is presented to support top-down process oriented product design. In conceptual design stage, the artifact is managed by semantic norm model (SNM). In SNM, the designers can define virtual components at early design stage and instantiate those components at later detailed design stage. By role-based access control (RBAC), different roles with corresponding permissions could be assigned to distributed designers, and the designers could concurrently modify different components of the product relevant to his or her roles. Based on the SNM and RBAC system, a distributed collaborative product design environment is developed and the top-down oriented product design process is demonstrated. © 2013 Elsevier Ltd. All rights reserved.


Yan L.,Huazhong University of Science and Technology | Yang W.,Huazhong University of Science and Technology | Yang W.,State Key Laboratory of Digital Manufacturing Equipment and Technology | Jin H.,Huazhong University of Science and Technology | Wang Z.,Huazhong University of Science and Technology
Machining Science and Technology | Year: 2012

Tool flank wear has significant effects on the cutting process, as it affects cutting forces, temperature and residual stresses. In this article, analytical models are developed to predict the cutting temperature and residual stresses in the orthogonal machining of a worn tool. In these models, measured forces, cutting conditions, tool geometry, and material properties are used as inputs. Stresses resulting from thermal stresses, fresh tool stresses and stresses due to tool flank wear are used in this analytical elasto-plastic model, and the residual stresses are determined by a relaxation procedure. The analytical model is verified experimentally with X-ray diffraction measurements. With the analytical model presented here, accurate residual stress profiles in worn tools are shown, while the computational time is significantly reduced from days, typical for finite-element method (FEM) models, to seconds. © 2012 Copyright Taylor and Francis Group, LLC.


PubMed | State Key Laboratory of Digital Manufacturing Equipment and Technology and Huazhong University of Science and Technology
Type: | Journal: Scientific reports | Year: 2015

We report an atomic scale controllable synthesis of Pd/Pt core shell nanoparticles (NPs) via area-selective atomic layer deposition (ALD) on a modified surface. The method involves utilizing octadecyltrichlorosilane (ODTS) self-assembled monolayers (SAMs) to modify the surface. Take the usage of pinholes on SAMs as active sites for the initial core nucleation, and subsequent selective deposition of the second metal as the shell layer. Since new nucleation sites can be effectively blocked by surface ODTS SAMs in the second deposition stage, we demonstrate the successful growth of Pd/Pt and Pt/Pd NPs with uniform core shell structures and narrow size distribution. The size, shell thickness and composition of the NPs can be controlled precisely by varying the ALD cycles. Such core shell structures can be realized by using regular ALD recipes without special adjustment. This SAMs assisted area-selective ALD method of core shell structure fabrication greatly expands the applicability of ALD in fabricating novel structures and can be readily applied to the growth of NPs with other compositions.

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