1,720,976 research outputs found
Experimental Study of Capillary-Assisted Solution Wetting And Heat Transfer Using A Micro-Scale, Porous-Layer Coating On Horizontal-Tube, Falling-Film Heat Exchanger
No full textThe horizontal-tube falling-film heat exchangers have many different applications ranging from large refrigeration systems to desalination due to their high heat transfer coefficients with low liquid inventory. However, the problem of partial solution wetting severely deteriorates the heat transfer capability of the falling-film evaporators. Therefore, an experimental study was conducted to investigate the effects of a micro-scale porous-layer coating and tube row on solution fluid wetting and evaporation heat transfer of a horizontal-tube, falling-film heat exchanger. Micro-scale copper particles were directly bonded onto plain copper tubes by sintering to create a uniform, porous-layer coating on the tubes. Distilled water was used as solution and heating fluids. The visual observation performed in open ambient condition revealed that when the solution fluid was dripped onto the horizontal tubes from a solution dispenser, conventional plain tubes were partially wetted while the porous-layer coated tubes were completely wetted due to capillary action, even at very low solution flow rates. It was shown from the comparison of the evaporation heat transfer results of the plain and porous-layer coated tubes tested in a closed chamber under saturated conditions that the porous-layer coated tubes exhibited a superior evaporation heat transfer rate (around 100% overall improvement at low solution flow rates) due to the complete solution wetting and thin film formation. It was also observed that the evaporation heat transfer and surface wetting are greatly affected by both the flow mode of the solution fluid between the tubes and tube wall superheat. The effect of the tube row on the solution wetting and heat transfer was significant, especially for downstream tubes
Shock Tube and Mid-infrared Laser Absorption Measurements of Ignition Delay Times and Species Time-histories
Get PDFEnergy consumption has increased dramatically as the world advances and becomes more industrialized. Over the next twenty five years, the U.S. Department of Energy expects the energy demand to increase by 29% with majority of the new energy coming from natural gas (methane). Another promising fuel source for power generation and transportation is the biofuels. The biofuel use in the US is shown to have increased substantially in the last decade. There are serious environmental concerns associated with greenhouse (e.g. carbon-dioxide) and toxic gas emissions (e.g. nitrogen oxides and aldehydes such as propanal) due to deriving energy from natural gas and biofuel combustion. In this doctoral study, a shock tube experimental setup was designed, assembled, and tested in order to study the ignition as well as thermal decomposition characteristics of two types of fuels: methane (the major natural gas component, which is also a major intermediate during higher order hydrocarbon ignition and pyrolysis) and propanal (an oxygenated hydrocarbon found in the exhaust emissions of biofuels). A laser diagnostics using semi-conductor type laser diodes in the infrared region for measurements of methane and propanal gas concentrations was developed and used with the shock tube. This diagnostics also enabled the interference-free detection of methane during the course of propanal pyrolysis. The experimental measurements highlighted the areas in which refinement of reaction kinetic models was required. The current research provided information on the ignition delay times as well as concentration time-histories of fuels (e.g. propanal or methane) and intermediates (e.g. methane). The knowledge gained during this doctoral study is vital for the accurate modeling of emissions due to combustion of fuels. The dissertation discusses the details of the four following items: 1) design, assembly, and testing of a shock tube setup as well as a laser diagnostics apparatus for studying ignition characteristics of fuels and associated reaction rates, 2) measurements of methane and propanal infrared spectra at room and high temperatures using a Fourier Transformed Infrared Spectrometer (FTIR) and a shock tube , 3) measurements of ignition delay times and reaction rates during propanal thermal decomposition and ignition, and 4) investigation of ignition characteristics of methane during its combustion in carbon-dioxide diluted bath gas. The main benefit and application of this work is the experimental data which can be used in future studies to constrain reaction mechanism development
Gas phase chemical evolution of uranium, aluminum, and iron oxides
Get PDFWe use a recently developed plasma-flow reactor to experimentally investigate the formation of oxide nanoparticles from gas phase metal atoms during oxidation, homogeneous nucleation, condensation, and agglomeration processes. Gas phase uranium, aluminum, and iron atoms were cooled from 5000 K to 1000 K over short-time scales (σt < 30 ms) at atmospheric pressures in the presence of excess oxygen. In-situ emission spectroscopy is used to measure the variation in monoxide/atomic emission intensity ratios as a function of temperature and oxygen fugacity. Condensed oxide nanoparticles are collected inside the reactor for ex-situ analyses using scanning and transmission electron microscopy (SEM, TEM) to determine their structural compositions and sizes. A chemical kinetics model is also developed to describe the gas phase reactions of iron and aluminum metals. The resulting sizes and forms of the crystalline nanoparticles (FeO-wustite, eta-Al2O3, UO2, and alpha-UO3) depend on the thermodynamic properties, kinetically-limited gas phase chemical reactions, and local redox conditions. This work shows the nucleation and growth of metal oxide particles in rapidly-cooling gas is closely coupled to the kinetically-controlled chemical pathways for vapor-phase oxide formation
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
koamabayili/VECTRON-author-checklist: VECTRON author checklist
No full textWe have done our best to complete the author checklist relating to the use of animals in the hut study. Note that the objective for the hut study was to evaluate the IRS treatment applications for residual efficacy against Anopheles mosquitoes, including the local An. coluzzii mosquito population. Cows were only used to attract mosquitoes into the huts and no tests were carried out directly on the cows. The author checklist is intended for use with studies where experiments are carried out on animals, which is why we have had such difficulty in completing this for the hut study, as many of the questions do not relate to how the cows were used
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