1,720,989 research outputs found
Life Cycle Assessment of Vehicle Lightweighting: A Physics-Based Model of Mass-Induced Fuel Consumption
No full textLightweighting is
a key strategy used to improve vehicle fuel economy.
Replacing conventional materials (e.g., steel) with lighter alternatives
(e.g., aluminum, magnesium, and composites) decreases energy consumption
and greenhouse gas (GHG) emissions during vehicle use, but often increases
energy consumption and GHG emissions during materials and vehicle
production. Assessing the life-cycle benefits of mass reduction requires
a quantitative description of the mass-induced fuel consumption during
vehicle use. A new physics-based method for estimating mass-induced
fuel consumption (MIF) is proposed. We illustrate the utility of this
method by using publicly available data to calculate MIF values in
the range of 0.2–0.5 L/(100 km 100 kg) based on 106 records
of fuel economy tests by the U.S. Environmental Protection Agency
for 2013 model year vehicles. Lightweighting is shown to have the
most benefit when applied to vehicles with high fuel consumption and
high power. Use of the physics-based model presented here would place
future life cycle assessment studies of vehicle lightweighting on
a firmer scientific foundation
Novel Method to Estimate the Octane Ratings of Ethanol–Gasoline Mixtures Using Base Fuel Properties
No full textEthanol blending
into gasoline yields a wide range of
octane rating responses, most frequently synergistic (i.e., greater
than expected by linear blending), but also linear or antagonistic.
A new approach to modeling ethanol octane blending, applicable for
both research octane number (RON) and motor octane number (MON), is
proposed, which predicts different
ethanol blending responses in base fuels of different compositions
and properties. The new model adds an interaction term to the linear
molar blending model with a coefficient, Z, that
quantifies the synergistic/antagonistic blending: ONblend = (1 – xe)ONg + xeONe + Zxe(1 – xe), in which xe is the molar ethanol fraction and ONg, ONe, and ONblend are the octane numbers of the base
gasoline, ethanol, and their blend, respectively. Fuel property and
hydrocarbon composition data for 299 ethanol–gasoline blends
and their 90 complex base fuels were collected from the literature,
primarily for market gasolines, blendstocks for oxygenate blending
(BOBs), and research fuels. Correlations of octane blending parameters
for several model approaches were highest for base gasoline octane
sensitivity (OSg = RONg – MONg) or saturate and aromatic fraction (Satg, Aromg). Multivariate forward-step linear regression used these same properties
to predict the octane blending response in different base fuels over
a wide range of ethanol content. For example, the two equations for
RON blending are as follows: ZRON = 15.0
– 1.76OSg + 11.3xe and ZRON = −47.8 + 64.3Satg + 24.6Aromg + 12.0xe. These models provide
greatly improved predictions as compared to generic models that do
not utilize base fuel information
Life-Cycle Energy and Greenhouse Gas Emission Benefits of Lightweighting in Automobiles: Review and Harmonization
No full textReplacing conventional materials
(steel and iron) with lighter
alternatives (e.g., aluminum, magnesium, and composites) decreases
energy consumption and greenhouse gas (GHG) emissions during vehicle
use but may increase energy consumption and GHG emissions during vehicle
production. There have been many life cycle assessment (LCA) studies
on the benefits of vehicle lightweighting, but the wide variety of
assumptions used makes it difficult to compare results from the studies.
To clarify the benefits of vehicle lightweighting we have reviewed
the available literature (43 studies). The GHG emissions and primary
energy results from 33 studies that passed a screening process were
harmonized using a common set of assumptions (lifetime distance traveled,
fuel-mass coefficient, secondary weight reduction factor, fuel consumption
allocation, recycling rate, and energy intensity of materials). After
harmonization, all studies indicate that using aluminum, glass-fiber
reinforced plastic, and high strength steel to replace conventional
steel decreases the vehicle life cycle energy use and GHG emissions.
Given the flexibility in options implied by the variety of materials
available and consensus that these materials have substantial energy
and emissions benefits, it seems likely that lightweighting will be
used increasingly to improve fuel economy and reduce life cycle GHG
emissions from vehicles
Life Cycle Assessment of Vehicle Lightweighting: A Physics-Based Model To Estimate Use-Phase Fuel Consumption of Electrified Vehicles
No full textAssessing the life-cycle benefits of vehicle lightweighting requires
a quantitative description of mass-induced fuel consumption (MIF)
and fuel reduction values (FRVs). We have extended our physics-based
model of MIF and FRVs for internal combustion engine vehicles (ICEVs)
to electrified vehicles (EVs) including hybrid electric vehicles (HEVs),
plug-in hybrid electric vehicles (PHEVs), and battery electric vehicles
(BEVs). We illustrate the utility of the model by calculating MIFs
and FRVs for 37 EVs and 13 ICEVs. BEVs have much smaller MIF and FRVs,
both in the range 0.04–0.07 Le/(100 km 100 kg),
than those for ICEVs which are in the ranges 0.19–0.32 and
0.16–0.22 L/(100 km 100 kg), respectively. The MIF and FRVs
for HEVs and PHEVs mostly lie between those for ICEVs and BEVs. Powertrain
resizing increases the FRVs for ICEVs, HEVs and PHEVs. Lightweighting
EVs is less effective in reducing greenhouse gas emissions than lightweighting
ICEVs, however the benefits differ substantially for different vehicle
models. The physics-based approach outlined here enables model specific
assessments for ICEVs, HEVs, PHEVs, and BEVs required to determine
the optimal strategy for maximizing the life-cycle benefits of lightweighting
the light-duty vehicle fleet
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
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