1,720,983 research outputs found
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
Environmental and economic assessment of transportation fuels from municipal solid waste
No full textThesis: S.M., Massachusetts Institute of Technology, Department of Aeronautics and Astronautics, 2016.This electronic version was submitted by the student author. The certified thesis is available in the Institute Archives and Special Collections.Cataloged from student-submitted PDF version of thesis.Includes bibliographical references (pages 76-86).Municipal solid waste (MSW), comprising food waste, residential rubbish and commercial waste, has been identified as a potential feedstock for the production of alternative fuels. Conversion of MSW to fuel could displace petroleum-derived fuels to mitigate greenhouse gas (GHG) emissions from transportation, and also avoid the GHG emissions associated with existing waste management strategies such as landfilling. This thesis quantifies the lifecycle GHG emissions and economic feasibility of middle distillate (MD) fuel, including diesel and jet fuel, derived from MSW in the United States via three thermochemical conversion pathways: conventional gasification and Fischer-Tropsch (FT MD), plasma gasification and Fischer-Tropsch (Plasma FT MD) and, conventional gasification, catalytic alcohol synthesis and alcohol-to-jet upgrading (ATJ MD). Expanded system boundaries are used to capture the change in existing MSW use and disposal, and parameter uncertainty is accounted for with Monte Carlo simulations. The median lifecycle GHG emissions are calculated to be 32.9, 62.3 and 52.7 gCO2e/MJ with standard deviations of 7.2, 9.5 and 13.2 gCO2e/MJ for FT, Plasma FT and ATJ MD fuels, respectively, compared to a baseline of 90 gCO2e/MJ for conventional MD fuels. These results are found to be sensitive to MSW composition, the waste management strategy displaced, plant scale and associated fuel yield, feedstock transportation distance and the co-product allocation method. Median minimum selling prices are estimated at 0.99, 1.78 and 1.20 per litre with the probability of achieving a positive net present value of fuel production at market prices of 14%, 0.1% and 7% for FT, Plasma FT and ATJ MD fuels, respectively. The sensitivity of these results to the discount rate, income tax rate, implementation of carbon price, feedstock cost, scale and process efficiency indicate that policy measures, MSW tipping fees and technological advancements can improve the economic viability of MSW fuels. Considering a societal perspective (e.g. social opportunity cost of capital, social costs of GHG emissions) increases the probability of positive net present value of fuel production to 93%, 67% and 92.5% for the FT, Plasma FT, and ATJ MD fuels, respectively.by Pooja Suresh.S.M
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
Attribution of PM₂.₅ Health Impacts in Asia-Pacific
No full textThesis: S.M., Massachusetts Institute of Technology, Department of Aeronautics and Astronautics, 2018.This electronic version was submitted by the student author. The certified thesis is available in the Institute Archives and Special Collections.Cataloged from student-submitted PDF version of thesis.Includes bibliographical references (pages 57-63).Asia-Pacific anthropogenic emissions have changed rapidly in recent years due to industrialization, increasing mobility, and emissions controls. Although these changes have altered the region's burden of premature mortalities due to ambient fine particulate matter (PM₂.₅), the contribution of each sector and effectiveness of different policy measures has not yet been quantified. Such data would inform future decision-making on both policy effectiveness and the relative importance of controlling emissions from different sectors. This study estimates changes in regional anthropogenic emissions by industrial sector between 2010 and 2015, based on sector-level activity indicators and enacted emission controls. These factors are applied to an existing high-resolution emissions inventory for 2010 to estimate emissions up to 2015. Using a chemical transport model, the effects of changes in each sector's contribution to total PM₂.₅-driven premature mortalities are calculated for 2010 - 2015, in addition to the total contribution of each sector to premature mortality in 2015. 2,000,000 (95% CI: 1,740,000-2,260,000) annual global PM₂.₅-driven premature mortalities are attributed to Asia-Pacific anthropogenic sectoral emissions in 2015. The agricultural, industrial, and residential sectors constitute the top three sources of these total impacts. Between 2010 and 2015, sustained economic and activity growth, particularly in South and Southeast Asia, have led to 129,000 (95% CI: 106,000-166,000) additional annual premature mortalities, primarily across India, Indonesia, and Bangladesh. The energy and industrial sectors, in particular, cause 38,000 and 45,000 additional annual premature mortalities across these three countries respectively. Simultaneously, falling activity rates in other countries due to structural changes such as electrification of railroads, as well as newly introduced abatement measures over this period, including China's Action Plan on the Prevention and Control of Air Pollution as well as region-wide adoption of Euro IV/V/VI-compliant road vehicle emission and fuel quality standards have led to a total reduction of 95,000 (95% CI: 76,000-129,000) annual premature mortalities, primarily across East Asia, including China and Japan. These opposing drivers result in a net change of an additional 34,000 (95% CI: 23,000-47,000) PM2.5-driven annual premature mortalities between 2010 and 2015 due to Asia-Pacific anthropogenic emissions.by Kingshuk Dasadhikari.S.M
Reducing the air quality impacts of aircraft activity at airports
No full textThesis: Ph. D., Massachusetts Institute of Technology, Department of Aeronautics and Astronautics, 2016.This electronic version was submitted by the student author. The certified thesis is available in the Institute Archives and Special Collections.Cataloged from student-submitted PDF version of thesis.Includes bibliographical references (pages 140-161).Air transportation is an integral part of the economy and the transportation infrastructure. However, aircraft activity at airports generates CO2 emissions that affect the climate and other pollutants that affect air quality and human health. The focus of this thesis is to enable the reduction of the air quality impacts of aircraft operations at airports by (1) advancing the understanding of the relationship between aircraft activity and its air quality impacts and (2) evaluating the air quality benefits of controlling aircraft operations. There are atmospheric conditions where decreasing fuel burn (which is directly proportional to CO2 emissions) results in increased population exposure to fine particulate matter (PM2.5) and ozone (O3). This thesis quantifies the duration and magnitude of the tradeoffs between CO2 emissions and population exposure. The research complements current studies that optimize aircraft operations at airports for CO2 emissions but have not quantified the air quality implications of doing so. This raises the possibility of reducing the air quality impacts of airports beyond focusing only on minimizing fuel burn. Next, this thesis characterizes the atmospheric conditions that give rise to tradeoffs between emissions and population exposure to ozone. The ozone exposure response to nitrogen oxide (NOx) and Volatile Organic Compound (VOC) emissions is quantified as a function of ambient NOx and VOC concentrations using ozone exposure isopleths. This is the first time that ozone exposure isopleths are created for all locations in the US, using emission sensitivities from the adjoint of an air quality model. Metrics are calculated based on the isopleths which can be used to determine whether NOx and VOC emission reductions will improve ozone exposure or be counter-productive and the optimal NOx/VOC reduction ratio. Finally, this thesis calculates, for the first time, the air quality and climate benefits of pushback control and de-rated takeoffs for simulated aircraft operations at the Detroit Metropolitan Wayne County Airport (DTW). Operations are also optimized for minimum air quality, environmental and fuel combustion-related costs. The results show that the gate holding strategy is effective in mitigating the environmental impacts of taxi operations at airports, reducing CO2 emissions and air quality impacts by 35-40% relative to a baseline without gate holds. De-rated takeoffs at 75% thrust are effective in reducing the air quality impacts of takeoff operations by 19% but increase fuel burn by 3% relative to full-thrust takeoffs. Environmental costs are minimized with average optimal thrust setting of 81%, while maintenance cost savings are estimated to be 2 orders of magnitude larger than the increase in fuel costs from de-rated takeoffs.by Akshay Ashok.Ph. D
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