1,721,032 research outputs found
Determination of transition rate constants of trans-cis isomerization in a poly(malonic ester) containing disperse red 1
No full textWe suggested a simple method for obtaining the quantitative transition rate constants of trans-cis isomerization in the pseudo-stilbene-type of azobenzene molecule. The absorbances of the solution and film of a poly(malonic ester) containing disperse red 1(PDR1) were measured with the pumping beam intensity, and analyzed by the rate equation for the fractions of trans and cis conformers. The rate constants of PDR1 solution and film were successfully determined. (C) 2002 American Institute of Physics.open1122sciescopu
Development of cavitation and enhanced injector models for diesel fuel injection system simulation
No full textTo expedite the application of fuel injection equipment to diesel engines, powertrain engineers are simulating the rate of injection with computer models. Many of the simple models give quite substantial errors if fuel cavitation in the high pressure system and the variations in bulk modulus with temperature and pressure are not included. This paper discuses cavitation and a companion paper discusses the treatment of non-linear bulk modulus. Diesel fuel injection nozzle hole size has been reduced and the injection pressures have been raised, to improve combustion, and the termination of the injection has been accelerated, to reduce carbon particle mass in the exhaust. High injection pressures and rapid termination set up very large hydraulic waves in the pipes and drillings of the fuel injection system, be it pump-pipe-nozzle or accumulator/common rail in type. The fuel momentum generated in these vigorous wave actions leaves such low pressures in parts of the system that vapour bubbles form in the fuel. Cavitation changes the bulk modulus of the fuel and the collapse of the cavities imparts sudden high pressure pulses to the fuel columns in the system and changes injection characteristics significantly. When modelling devices to control injection rate, the cavitation and non-linear bulk modulus have to be incorporated into the model. To this end, the concept of 'condensation' has been useful. The cavitated pipe section is divided into liquid and liquid + vapour mixture columns and modified momentum and mass conservation equations are applied separately. The model has been validated with a particular application of a rotary distributor pump to a high speed direct injection diesel engine, which is one of the more difficult fuel injection systems to model in which cavitation occurs at several operating conditions. The simulation results show the cavitation characteristics very well. This cavitated flow calculation model may be applied to other one-dimensional flow systems. In addition, a more comprehensive injector model is introduced, which considers two loss factors at the needle seat and holes, sac volume, and viscous drag and leakage. This enhanced injector model shows some improvement at low load conditions.University of Southampton
Engine Laboratory, Combustion Engineering Research Centre, KAIST
IVECO and Royal Acamdey of Engineering for the European Chair in Automotive Engineering in the ISVR
Futhrer Financial supprot of the Korean Goverment via the National Research Laboratory BK2
UltraClean process as a package-type advanced wastewater treatment system: experiment and model assisted in investigation
No full textMorphological investigation of the microstructure, dimensions, and fractal geometry of diesel particulates
No full textThe microstructure, dimensions, and fractal geometry of diesel particulates were investigated through morphological observations. A thermophoretic particle-sampling system was developed to collect diesel particulates directly from the high-temperature exhaust stream of a 75 hp single-cylinder direct-injection diesel engine at various engine operating conditions. The morphology of die collected diesel particulates was analyzed using a high-resolution transmission electron microscope and subsequent image processing/data acquisition system. The analysis revealed that spherical primary particles were agglomerated together to form large aggregate clusters at most engine operating conditions. The particles produced at low loading conditions displayed amorphous structures, possibly containing a significant amount of soluble organic fraction, while the soot sampled at high engine load conditions mostly exhibited graphitic structures. Measured primary particle sizes ranged from 34.4 to 28.5 nm at various engine operating conditions. The smaller primary particles observed at high engine load conditions were caused by oxidation at the encountered high temperatures. A number of small and irregularly shaped particles were captured at these conditions, which identified the existence of apparent particle oxidation. Engine-speed-dependent experiments were also performed to investigate the effects of the residence time of soot particles on particle growth. A growth mechanism of diesel particulates was suggested through analyses for fractal. geometry of the cluster particles.Strong support from Dr. Sidney Diamond at the US
DOE-OHVT is greatly appreciated. The authors also thank
Dr. Russell Cook of Argonne’s Electron Microscopy Center
for his valuable advice on microscopy
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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