104,791 research outputs found
NOx Emission Prediction Based on Measurement of in-Cylinder Pressure for CI Engine Running with Diesel and Biodiesel
No full textNOx is one of the major toxic emissions that needs to be regulated stringently in both EU and USA emission regulations. The engine designer is keen to get an accurate, reliable and cost effective NOx measurement system. In this paper, the application of the cylinder pressure for predicting the NOx emission of compression ignition (CI) engine fuelled with diesel and biodiesel during steady state operations is carried out. To address the problem, an experimental work was conducted on four-cylinder, turbo-charged, four-stroke and direct-injection CI engine which was fuelled with diesel and biodiesel blends. During the experiment, the main parameters consisting of in-cylinder pressure, fuel flow rate, air flow rate, and the NOx emission, were measured. The temperature within the cylinder was predicted using the cylinder pressure and air flow rate. Using the temperature values, the NOx emission was simulated in the Zeldovich extended mechanism. The simulation result was then compared with the measured one for a range of engine operating conditions. The models were shown to produce consistent results with the measured one for a range of engine working speeds and loads
Prediction of metal pm emission in rail tracks for condition monitoring application
No full textExposure to particulate material (PM) is a major health concern in megacities across the world which use trains as a primary public transport. PM emissions caused by railway traffic have hardly been investigated in the past, due to their obviously minor influence on the atmospheric air quality compared to automotive transport. However, the electrical train releases particles mainly originate from wear of rails track, brakes, wheels and carbon contact stripe which are the main causes of cardio-pulmonary and lung cancer. In previous reports most of the researchers have focused on case studies based PM emission investigation. However, the PM emission measured in this way doesn’t show separately the metal PM emission to the environment. In this study a generic PM emission model is developed using rail wheel-track wear model to quantify and characterise the metal emissions. The modelling has based on Archard’s wear model. The prediction models estimated the passenger train of one set emits 6.6mg/km-train at 60m/s speed. The effects of train speed on the PM emission has been also investigated and resulted in when the train speed increase the metal PM emission decrease. Using the model the metal PM emission has been studied for the train line between Leeds and Manchester to show potential emissions produced each day. This PM emission characteristics can be used to monitor the brakes, the wheels and the rail tracks conditions in future
Investigations into the Performance and Emission Characteristics of a Biodiesel Fuelled CI Engine under Steady and Transient Operating Conditions
No full textThe stringent emission laws, the depletion of petroleum reserves and the relation of fuels with politics have forced the world to find alternatives to fossil fuels. Biodiesel is one of the biofuels which is renewable and environmentally friendly and can be used in diesel engines with little or no modifications. For the last two decades, many researchers have reported extensive work on the performance and emission characteristics of engines running with biodiesel during steady state operation. However, there are numbers of knowledge gaps that have been identified which include limited information on biodiesel physio-chemical properties and their effects on combustion behaviour and performance and emission characteristics of the engine. In this study after an exhaustive literature review, the following four research areas have been identified and investigated extensively using available numerical and experimental means.
The initial focus was to investigate the most important properties of biodiesel such as density, viscosity and lower heating value using experimental and numerical techniques. The effects of biodiesel blend content on the physical properties were analysed. For each property, prediction models were developed and compared with current models available in literature. New density and viscosity prediction models were developed by considering the combined effect of biodiesel content and temperature. All the empirical models have showed a fair degree of accuracy in estimating the physical properties of biodiesel in comparison to the experimental results. Finally, the effects of density and viscosity on the fuel supply system were investigated. This system includes the fuel filter, fuel pump and the engine combustion chamber in which air-fuel mixing behaviour was studied numerically. These models can be used to understand the effects of changes in the physical properties of the fuel on the fuel supply system. In addition, the fuel supply system analysis can be carried out during the design stage of fuel pump, fuel filter and injection system.
The second research objective was the investigation into a CI engine’s combustion characteristics as well as performance and emissions characteristics under both the steady and transient conditions when fuelled with biodiesel blends. The effects of biodiesel content on the CI engine’s in-cylinder pressure, brake specific fuel consumption, thermal efficiency and emissions (CO2, NOx, CO, THC) were evaluated based on experimental results. It has been seen that the CI engine running with the biodiesel resulted in acceptable engine performance as well as reduction in main emissions (except NOx). Following this study, a detailed analysis on the transient performance and emission output of the CI engine has been carried out. During this analysis, the emission changing rate is investigated during speed transient and torque transition stages. Further to this, a transient emission prediction model has been developed using associated steady and transient emission data. The model has been shown to predict the transient emission reasonably accurately.
The third research objective was to develop a method for on-line measurement of NOx emission. For this purpose the in-cylinder pressure generated within a CI engine has been measured experimentally along with mass air flow and these parameters have been used in the development of a NOx prediction model. This model has been validated using experimental data obtained from a NOx emission analyzer. The predicted data obtained from NOx prediction model has been compared with measured data and has shown that the deviation is within acceptable range.
The final research objective was to develop a simple, reliable and low-cost novel method to reduce the NOx emission of the CI engine when using biodiesel blends. A potential solution to this problem has been found to be in the form of direct water injection which has shown to be capable to reduce NOx emission. Using a water injection technique, the performance and emission(NOx and CO) characteristics of a CI engine fuelled with biodiesel has been investigated at varying water injection flow rates. Intake manifold water injection reduces NOx emission by up to 40% over the entire operating range without compromising the performance characteristics of the CI engin
Going Beyond Counting First Authors in Author Co-citation Analysis
No full textThe 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
Appropriate Similarity Measures for Author Cocitation Analysis
No full textWe 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
No full textWe 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
The construction of Karen Karnak: The multi-author-function
No full textThis thesis is situated within the comparatively recent developments of Web 2.0 and the emergence of interactive WikiMedia, and explores the mode of authorship within a Read/Write culture compared to that of a Read/Only tradition. The hypothesis of this study is that the role of the audience has become merged with the author, and as such, represents new functions and attributes, distinct from a more conventional concept of authorship, in which the roles of audience and author are more separate. Read/Write and participatory culture, as defined by this study, is focused on collaboration, and includes the influences of D.I.Y. culture, Open-Source practices and the production of text by multiple authors. Multi-authorship presents a re-thinking of several concepts which support the notion of the individual author, since the focus of multi-authorship is not on attribution and ownership of a finished text, but on the continued malleability of a text. Modes of multi-authorship, demonstrated in the use of the pseudonyms Alan Smithee and Karen Eliot, represent declarative authors whose names signify multiple origins, whilst concurrently indicating a distinct body of work. The function of these names form an important context to this study, since primary research involves the construction of an experimental mode of multi-authorship utilising WikiMedia technology and the interaction of thirty nine participants, who are invited to create a body of work under the collective pseudonym Karen Karnak. The data generated by this experiment is analysed using aspects of Michel Foucault's author-function to identify and determine power structures inherent in the WikiMedia context. The interplay of power structures, including concepts such as identity, ownership and the body of work, affect the resulting mode of authorship and contribute to the construction of Karen Karnak, suggesting further areas of research into the emerging multi-author
Contribution of Information and Communication Technology (ICT) in Country’S H-Index
No full textThe aim of this study is to examine the effect of Information and Communication Technology (ICT) development on country’s scientific ranking as measured by H-index. Moreover, this study applies ICT development sub-indices including ICT Use, ICT Access and ICT skill to find the distinct effect of these sub-indices on country’s H-index. To this purpose, required data for the panel of 14 Middle East countries over the period 1995 to 2009 is collected. Findings of the current study show that ICT development increases the H-index of the sample countries. The results also indicate that ICT Use and ICT Skill sub-indices positively contribute to higher H-index but the effect of ICT access on country’s H-index is not clear
Fully Turbulent Mean Velocity Profile for Purely Viscous non-Newtonian Fluids
No full textThe characteristic near wall behavior of turbulent flow of purely-viscous non-Newtonian fluids is discussed for both power-law (P.-L.) and Herschel-Bulkley (H.-B.) rheological models. A proper scaling is presented for H.-B. fluids to establish an analogy with power-law fluids with same flow index. To provide reference data for turbulent flow of non-Newtonian fluids, DNS simulations of power-law fluids are conducted in a rectangular channel for a large range of power-law indices ( = 0.5, 0.69, 0.75, 0.9, 1, 1.2). The DNS data show that the mean velocity profile in the viscous and logarithmic layers follow expressions of the form and respectively, where shows a logarithmic dependency on the flow index.Comparison with some experimental data shows the above formulation to be valid for Reynolds numbers (based on shear velocity) as high as 1000
H-index and research evaluation: A suggested set of components for developing a comprehensive author-level index
No full textThe H-index has been investigated in various studies; this index has many strengths that have made it popular. However, it also has weaknesses, due to which other indicators have been developed. This study aims to identify the strengths and weaknesses of the H-index and provide the minimum set of necessary components for developing a comprehensive author-level index. In this systematic literature review, Scopus, PubMed, Web of Science, Emerald, and ProQuest databases were searched to identify relevant studies. From the number of 14,253 retrieved studies, after two stages of screening, 81 studies were selected according to the eligibility criteria for data extraction. The findings of the study led to the identification of 15 strengths in the three categories of Quality Features, Simplicity, and Suitability, and 13 weaknesses in the six categories of Publications, Citations, Academic Age, Author Credit Allocation, Variety of Fields, and mathematical calculation for H-index. Finally, 28 components were identified as the minimum set of necessary components to develop a comprehensive author-level index to help evaluate researchers more realistically and fairly. The minimum components that need to be considered in developing a comprehensive author-level index can be proposed as follows: Quality Features, Simplicity, Suitability, Publications, Citations, Academic Age, Author Credit Allocation, Variety of Fields, and mathematical calculation
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