1,720,966 research outputs found
Two-stage approach for nesting in two-dimensional cutting problems using neural network and simulated annealing
No full textNesting of two-dimensional patterns on a given raw sheet has applications in a number of industries. It is a common problem often faced by designers in the shipbuilding, garment making, blanking die design, glass and wood industries. This paper presents a new two-stage layout approach for nesting two-dimensional patterns by using the self-organization assisted layout and simulated annealing. The proposed nesting approach consists of two stages: initial layout stage and layout improvement stage. This heuristic algorithm generates a 'good' initial layout by using the self-organization assisted layout (SOAL) algorithm and then improves the layout by using the simulated annealing (SA) algorithm. Some examples are treated for showing the effectiveness of this approach in nesting the two-dimensional irregular patterns with and without holes
A study on torch path planning in laser cutting processes - Part 1: Calculation of heat flow in contour laser beam cutting
No full textConductive heat transfer in contour laser beam cutting is analyzed by using a transient, two-dimensional finite difference model, and the result is combined with a simple analytic model. From the calculation results, the correlation is derived between workpiece temperature and opening angles at a corner in contour cutting. As a result, a modified analytic solution is developed to predict if excessive workpiece heating occurs for given cutting contours in a nested plate. The main objective is to use the computation results in the optimization of torch path planning to provide fully automated CNC programming software for laser cutting. To efficiently apply the analytic model in torch path planning, the critical temperature that should be avoided during the cutting sequence is considered. This leads to an improvement of the cutting quality in the automatic cutting process
Global torch path generation for 2-D laser cutting process using simulated annealing
No full textRecently the major objective of laser processing in production line is the precision or shape cutting of sheet metals. This paper addresses the problem of a torch path generation for the 2D laser cutting of a stock plate nested with irregular parts. In this paper, the basic object is a polygon(a many-sided figure) with holes. Under the constraint of the relative positions of parts enforced by nesting, the developed torch path algorithm generates feasible cutting paths. The objective of this work is to traverse this cutting contours with a minimum path length. The proposed torch path algorithm is based on a simulated annealing, that is an improved version of previously suggested TSP models. Since every piercing point of parts is not fixed in advance, the algorithm solves an relaxed optimization problem with constraints. For solving the torch path optimization problem an efficient generation mechanism of neighborhood structure and annealing schedule were presented. In this way, a global solution can be obtained in a reasonable time. Several examples are represented to illustrate the method
A study on heat flow and temperature monitoring in the laser brazing of a pin-to-plate joint
No full textAn advantage offered by laser brazing over fusion welding is that strong joints can be produced at a relatively low heat input. To minimize the thermal effects and maintain the designed dimension of assemblies, the CO2 laser beam was applied to the brazing of joints between a pin and a hole as a micro heat source. The heat flow and temperature distribution of the brazed parts were calculated using the finite element method with a two-dimensional axisymmetric model and the surface temperature of the brazed joint was measured with laser brazing by using a infrared radiation sensor system. The laser beam mode was considered as a process parameter and its influence was predicted with respect to the temperature distribution and joint quality through finite element analysis. The measured and calculated results were compared with each other, showing fairly good agreement. Based on these results, the proper process parameters were selected to obtain a good joint quality. (C) 1998 Elsevier Science S.A. All rights reserved
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Variations on the Author
Full text link“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
Appropriate Similarity Measures for Author Cocitation Analysis
Full text linkWe provide a number of new insights into the methodological discussion about author cocitation analysis. We first argue that the use of the Pearson correlation for measuring the similarity between authors’ cocitation profiles is not very satisfactory. We then discuss what kind of similarity measures may be used as an alternative to the Pearson correlation. We consider three similarity measures in particular. One is the well-known cosine. The other two similarity measures have not been used before in the bibliometric literature. Finally, we show by means of an example that our findings have a high practical relevance.information science;Pearson correlation;cosine;similarity measure;author cocitation analysis
Dispelling the Myths Behind First-author Citation Counts
Full text linkWe conducted a full-scale evaluative citation analysis study of scholars in the XML research field to explore just how different from each other author rankings resulting from different citation counting methods actually are, and to demonstrate the capability of emerging data and tools on the Web in supporting more realistic citation counting methods. Our results contest some common arguments for the continued
use of first-author citation counts in the evaluation of scholars, such as high correlations between author rankings by first-author citation counts and other citation
counting methods, and high costs of using more realistic citation counting methods that are not well-supported by the ISI databases. It is argued that increasingly available digital full text research papers make it possible for citation analysis studies to go beyond what the ISI databases have directly supported and to employ more
sophisticated methods
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