Dong Xiang

A review of mechanochemistry applications in waste management

Mechanochemistry is defined to describe the chemical and physicochemical transformation of substances during the aggregation caused by the mechanical energy. Mechanochemical technology has several advantages, such as simple process, ecological safety and the possibility of obtaining a product in the metastable state. It potentially has a prospective application in pollution remediation and waste management. Therefore, this paper aims to give an overall review of the mechanochemistry applications in waste management and the related mechanisms. Based on our study, the modification of fly ash and asbestos-containing wastes (ACWs) can be achieved by mechanochemical technology. Waste metal oxides can be transformed into easily recyclable sulfide by mechanochemical sulfidization. Besides, the waste plastics and rubbers, which are usually very difficult to be recycled, can also be recycled by mechanochemical technology.

Mechanical assembly planning using ant colony optimization

In mechanical assembly planning research, many intelligent methods have already been reported over the past two decades. However, those methods mainly focus on the optimal assembly solution search while another important problem, the generation of solution space, has received little attention. This paper proposes a new methodology for the assembly planning problem. On the basis of a disassembly information model which has been developed to represent all theoretical assembly/disassembly sequences, two decoupled problems, generating the solution space and searching for the best result, are integrated into one computation framework. In this framework, using an ant colony optimization algorithm, the solution space of disassembly plans can be generated synchronously during the search process for best solutions. Finally, the new methods validity is verified by a case study.

Intelligent disassembly planning: a review on its fundamental methodology

Purpose – The purpose of this paper is to review the fundamental methodology and its development of intelligent disassembly planning research.Design/methodology/approach – Following a brief introduction, this paper first discusses the fundamental problems associated with disassembly planning and analysis. And then considers the role of intelligent optimization methods in the disassembly planning field. This is followed by a summary and conclusion.Findings – Many advances have been made in computerized intelligent disassembly planning research, which is a natural evolutionary result of both traditional solving methodology and much research effort over past two decades. But as yet, some fundamental limitations are also rooted in this computational model‐based methodology.Originality/value – The paper provides a fundamental review on the development of computerized intelligent disassembly planning research.

Subassembly identification based on grey clustering

Nowadays discarded electromechanical products are more and more common, and have done much harm to the ecological environment, human health and natural resources. In order to recycle discarded products effectively, it is necessary to disassemble them properly in an integrated consideration of economic returns and environmental protection. Therefore Disassembly Process Planning has become a key part in Environmentally Conscious Design. Because there may be a combination explosion when the disassembly process of a product with a large number of parts is planned, subassembly identification is often adopted to divide the product into some reasonable subassemblies. This paper uses a method of grey clustering based on grey system theory to perform subassembly identification. The clustered objects are part pairs with adjacency relation in a product, and the clustering indices consist of energy consumption of disassembly, disassembly time, disassemblable direction and diameter of part pair. The indices can be obtained by detailed estimate or direct input from a CAD system via secondary development. After five grey clusters are set up, their whitening weight functions are presented in detail. Several other key problems in subassembly identification based on grey clustering are also expounded, such as obtaining the nondimensional matrix of sample values, determining the weight of clustering index relative to grey cluster. A heat-sealing machine with 80 components is selected as an example to validate the method of subassembly identification based on grey clustering. The identification result of the example is feasible according to experiences, and at the same time it satisfies the requirement of Disassembly Process Planning.

Disassembly AND/OR graph model for "disassembly for recycling"

There exists combination explosion during the course of modeling of AND/OR graph for disassembly planning for recycling, which makes it nearly impossible to handle a product with numerous parts. To conquer the difficulty, set AND/OR graph (SAOG) is defined, and with the mapping from SAOG to product, complete disassembly AND/OR graph (DAOG) is presented. In order to ensure the validity and applicability of DAOG, several sieves are designed to delete most of the vertexes and edges. These sieves are successively applied to DAOG, and finally the complete DAOG becomes sieved DAOG which is the model used for disassembly planning. DAOG contains all possible disassembly actions, thus it provides a suitable basis for generation and evaluation of all possible disassembly sequences of an end-of-life product.

Simulation-Based Optimization of a Vector Showerhead System for the Control of Flow Field Profile in a Vertical Reactor Chamber

Optimization of a vector showerhead in a vertical reactor involves thousands of holes on the showerhead face plate and the spatial distribution of physical fields, so parameterizing the geometry configuration of the holes in high resolution is very difficult, which makes the conventional optimization methods hard to deal with. To solve this problem, a profile error feedback (PEF) optimization solution was proposed to optimize a vector showerhead gas delivery system for the control of mass transport. The gas velocity profile in the reactor and the continuous-feature impedance distribution profile on the showerhead face plate are defined as design objective and variables, respectively. A cyclic iterative approximation idea was implemented in this solution. The algorithm was started from a guessed initial design model and then cyclically adjusted the design variables by the constructed PEF iterative formula to generate a better model and to make the gas velocity profile in the critical domain of the new model continually approximate to the expected profile, until it could be accepted. Finally, the optimized impedance profile was mapped to the holes geometry configuration through the established equivalent impedance model for the showerhead face plate.

The Recycle Model of Printed Circuit Board and Its Economy Evaluation

The rational reclamation of the waste printed circuit board (PCB) plays the key portion in the solution of electronic waste. The evaluation of the feasibility and rationality of the reclamation mostly consists of technicality and economical efficiency. Current research inclines to the former factor. And the study on the economical efficiency of the reclamation is insufficient. Thus, this paper presents a new technique of waste PCB recycle, based on which an economical model of the recycle is elaborated. Aiming at the specific conditional of a Hong Kong plant, we perfect the economical model, and make the evaluation of the economical efficiency and feasibility of the waste PCB recycle process conducted by that plant. Finally, we offer quantitative analysis for the rational production of that plant.

Ant Colony Optimization for Disassembly Sequence Planning

In this paper, to solve disassembly sequence planning problem efficiently, Disassembly Feasibility Information Graph (DFIG) is presented firstly. Based on this graph, the problem of disassembly sequence planning is converted into a problem of searching optimal path in this directed and weighted graph. Then, an ant colony optimization algorithm is presented, integrated with part moving planner in 3D system, to build the DFIG, and search optimum solution(s). The tour of ant represents a possible product disassembly solution. The pheromone trail laid on edge by ant is related with the quality of its tour. It is by two steps to get heuristic information: calculating heuristic vector — representing the feasibility of solution — and then, calculating heuristic information-representing the quality of solution. Finally, by a case study, the well performance of the proposed method is shown.© 2006 ASME

A Hybrid Heuristic Approach for Disassembly/Recycle Applications

Over the past several years, heuristic methods are often used to find optimal solution(s) of disassembly/recycle sequencing problem, for it is a NP-hard combinatorial optimization problem. In the proposed research, first, we present a method: product disassembly sequence planning problem could map onto a problem of searching the optimal tour in the disassembly feasibility information graph (DFIG). Then a genetic algorithm is proposed to search the optimal solution of disassembly/recycle problem. Optimization objective is the performance of a solution, which is mainly related with three factors: disassembling process, environment impact and disassembly & recycle line. In particular, scheduling disassembly & recycle line is also a NP-hard problem. Therefore, a heuristic genetic operator, combined with disassembly & recycle processes tree, is also presented to schedule the disassembly & recycle line

The segmented non-uniform dielectric module design for uniformity control of plasma profile in a capacitively coupled plasma chamber

Low-temperature plasma technique is one of the critical techniques in IC manufacturing process, such as etching and thin-film deposition, and the uniformity greatly impacts the process quality, so the design for the plasma uniformity control is very important but difficult. It is hard to finely and flexibly regulate the spatial distribution of the plasma in the chamber via controlling the discharge parameters or modifying the structure in zero-dimensional space, and it just can adjust the overall level of the process factors. In the view of this problem, a segmented non-uniform dielectric module design solution is proposed for the regulation of the plasma profile in a CCP chamber. The solution achieves refined and flexible regulation of the plasma profile in the radial direction via configuring the relative permittivity and the width of each segment. In order to solve this design problem, a novel simulation-based auto-design approach is proposed, which can automatically design the positional sequence with multi independent variables to make the output target profile in the parameterized simulation model approximate the one that users preset. This approach employs an idea of quasi-closed-loop control system, and works in an iterative mode. It starts from initial values of the design variable sequences, and predicts better sequences via the feedback of the profile error between the output target profile and the expected one. It never stops until the profile error is narrowed in the preset tolerance.