1,721,059 research outputs found
Experimental analysis of the influence of wall axial conduction on gas-to-gas micro heat exchanger effectiveness
No full textIn this paper an experimental investigation of the thermal performances of gas-to-gas micro heat
exchangers operating under different flow configurations (co-current, counter-current, cross flow) is presented
and the results are compared with the predictions of the conventional correlations developed for
the design of the conventional-sized heat exchangers. A double-layered microchannel heat exchanger has
been specifically designed in order to be able to reproduce co-current, counter-current and cross flow gas
arrangements. The core is housed in a shell made of polymer; on the contrary, the foil between the hot
and cold flow is exchangeable; several foils made with different materials (copper, peek, stainless steel
and aluminum) and with different thickness have been investigated in order to put in evidence the effect
due to the axial wall-fluid conjugate heat transfer on the thermal efficiency of the micro heat exchanger.
The results show that the conjugate heat transfer can be very strong in micro heat exchangers and it
tends to reduce the effectiveness of counter-current micro heat exchangers and to increase the effectiveness
of cross flow micro heat exchangers. In the case of a co-current arrangement with balanced flows the
role of the wall axial conduction can be considered negligible
Design of a Temperature Micro-Sensor with a Gaseous Fluid Flow
Get PDFNon-intrusive Liquid Crystal Thermography technique (LCT) has been proven as a powerful tool for lowtemperature
application in micro-scale systems. It provides high-spatial resolution temperature maps
dependent on colour response of heated thermo-chromic liquid crystal material (TLC). Different types of
TLCs have been widely used in form of coated paints or water-based droplets in aqueous carrier fluid. Up to
now, suitable designs of micro-devices with specific features optimized for their use in the presence of gas
micro-flows has still not being proposed. Therefore, the study of a design of single channel micro-device for
liquid-gas mixing is presented here. Research work has been performed experimentally and/or numerically to
investigate the effect of various geometric designs of micro-devices to provide uniformly distributed TLC
particles along a gas flow and to avoid their sedimentation. Beside the geometric design, material and heating
systems are of high importance in order to achieve desirable observation of temperature gradients along the
channel. Moreover, the flow rate and shear stress inside the channel were set to be minimal due to suspected
high sensitivity of TLCs.
This paper is intended to bring new insights and fresh perspectives to the development of temperature microscale
sensors for practical implementation in the future
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
Design and Experimental Investigation of A Gas-to-Gas Counter Flow Micro Heat Exchanger
No full textIn this work a double-layered microchannel heat exchanger is designed for investigation on gas to gas heat transfer.
The micro-device contains 133 parallel microchannels machined into polished PEEK plate for both hot side and cold
side. The microchannels are 200 μm high, 200 μm wide and 39.8 mm long. The design of the micro device allows tests
with partition foils in different materials and of flexible thickness. A test rig is developed with the integration of
customized pressure and temperature sensors for in-situ measurements. Experimental tests have been carried out for
five different partition foils and various mass flow rates. The experimental results, in terms of pressure drop, heat
transfer coefficients and heat exchanger effectiveness, are discussed and compared with the predictions of the classic
theory for conventionally sized heat exchangers
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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