1,721,006 research outputs found
Monitoring the gas metal arc additive manufacturing process using unsupervised machine learning
No full textInfluence of reflected arc light on vision sensor in automatic welding system for height-varing weldments
No full textProcess monitoring and adaptive quality control for robotic gas metal arc welding
Full text linkThe aim of this research was to develop an adaptive quality control strategy for robotic
gas metal arc welding of thin steel sheets. Statistical methods were used to monitor and
control the quality of welds produced.
The quality of welds cannot be directly measured during welding. It can however be
estimated by correlating weld quality parameters to relevant process variables. It was
found sufficient to do this using welding current and voltage transient signals only.
The strategy developed was problem solving oriented with emphasis on quality
assurance, defect detection and prevention. It was based on simple algorithms developed
using multiple regression models, fuzzy regression models and subjective rules derived
from experimental trials.
The resulting algorithms were used to
control weld bead geometry;
prevent inadequate penetration;
detect and control metal transfer;
assess welding arc stability;
optimise welding procedure;
prevent undercut;
detect joint geometry variations.
Modelling was an integral part of this work, and as a feasibility study, some of the
models developed for process control were remodelled using "Backpropagation"
Artificial Neural Networks. The neural network models were found to offer no
significant improvement over regression models when used for estimating weld quality
from welding parameters and predicting optimum welding parameter.
As a result of the work a multilevel quality control strategy involving preweld parameter
optimisation, on line control and post weld analysis was developed and demonstrated
in a production environment. The main emphasis of the work carried out was on
developing control models and means of monitoring the process on-line; the
implementation of robotic control was outside the scope of this work. The control
strategy proposed was however validated by using post weld analysis and simulation in
software
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
The prediction of risk of welding defects at the procedure stage using computer knowledge based systems.
Full text linkThe purpose of this research was to develop a methodology to evaluate the
likelihood of defective welds as a procedure proposal is entered into a computerised
database system. The approach developed was assessed for hydrogen induced cold
cracking (HICC) since this defect is a major problem in welding technology. An
expert system was used to implement the methodology.
The information for the expert system knowledge base was partly gathered
from previous work in this area. The technique necessary to analyze and incorporate
knowledge was organized in a structured form including the major area to be
attacked.
The final system was implemented using an expert system shell. The global
task of analyzing a welding procedure was broken-down into three different stages. A
welding procedure specification comprised the first stage. In the second stage, an
interface between the expert system software and a database was implemented.
Having proved the feasibility and advantages of integrating the expert system shell
with a relational database the remainder of the work was devoted to the development
of a strategy for operating the expert system and in particular dealing with
uncertainty.
Detailed validation of the knowledge base and the system as a whole were
confined to a single defect type in the belief that the modularity of the system would
allow extension to other defect types and the strategies developed in the present work
should it be applicable. Results have shown that the system performs well in the
specified area. Validation trials using simulated welding conditions generated by the
expert system have shown a very good correlation with practical results for different
classes of steels. The integration between approved welding procedure records and
procedure qualification records could be the basis for a complete welding database
management. Practical application of this system could be extended for educational
purpose and training facilities
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
- …
