1,721,068 research outputs found
Multi-disciplinary design optimization of heat exchangers using Gaussian processes
No full textHeat exchangers are important equipment in many engineering systems. They are equally complex and resource-intensive to design and manufacture, requiring several hours of both simulation and experimentation budget before reaching a design freeze. Various configurations within the sub-components or their designs make the design process even more challenging, as each of those variants will require respective analysis before reaching an optimal design. The literature also reveals that such analysis are often done in isolation and not in an integrated fashion. The first aim of this work is to perform a multi-disciplinary optimization of a charge air cooler that allows us to tweak several of its design properties within the framework, as they are often necessary for design analysis. More specifically, the framework studies the impact of using corrugated tubes against smooth tubes within the multi-disciplinary framework, highlighting the importance of using such methods over traditional ones and allowing for improvement in resources required to reach a design freeze. The disciplines applied within this framework are aero-thermal and vibrations, making this approach the first of its kind in multi-disciplinary optimization for heat exchangers. Furthermore, another important component of the design process addressed in this work are the challenges posed by experimentation and the constraints it puts on the degree of freedom to explore the design space along with the time it takes to do so. This is done using surrogate-based approaches. Namely, Gaussian processes, multi-fidelity modeling, and multi-output Gaussian processes that are used to build prediction models that help swiftly explore new tube topologies (in this case, corrugated tubes), with much control and flexibility to explore the design space effectively. This work not only recommends how novel tube designs can be tested but also reduces the burden on the design process, which traditionally is resource intensive. The models constructed for tubes are then applied to a whole heat exchanger design process, providing another layer of performance for these models that cater to the entire heat exchanger design process. Lastly, an understanding about the reuse of data is formulated using multioutput Gaussian processes, where the chosen tube topologies are themselves utilized as source and target data sources. This allows us to assess when such topological decisions are helpful and when they are not
The impact of tube corrugation within the multi-disciplinary design optimization of a charge air cooler
Get PDFThe following paper explores the impact of corrugated tubes within a charge air cooler (CAC) on overall cooler performance, cost and size, for the first time. Corrugated tubes have been demonstrated to perform better in terms of heat transfer, when compared to a smooth tube, however they have not been optimized in the context of a CAC. In this study, a CAC with corrugated tubes is compared against a similar system comprising of smooth tubes as a baseline design. Both CACs have common design parameters, such as number of tubes per rows, number of rows, number of passes, fins per meter, fin material, and tube material, while two additional design parameters exist i.e., groove depth, and pitch for the CAC with corrugated tubes, that characterizes the helical corrugation. These two systems are optimized to minimize manufacturing cost where cost is a function of cooler dimensions and material selection. Feasible designs are then obtained by satisfying dimension, pressure, weight, performance and vibrations based constraints. A vibration constraint introduced here is an addition to the current state of the art, making this approach, a multi-disciplinary one and the first of its kind. Finally, the optimum is compared which signifies the importance of a multi-disciplinary analysis for bothcooler configurations
Going Beyond Counting First Authors in Author Co-citation Analysis
Get PDFThe 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
Get PDF“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
Get PDFWe 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
Get PDFWe 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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