826 research outputs found
Analysis of performance ratings for tires
This study analyzed two sets of performance ratings for light-duty-vehicle tires. The aim was to ascertain whether some of the ratings in either set convey redundant information. The first set included the Uniform Tire Quality Grade (UTQG) ratings for 2,734 tires, published by the U.S. National Highway Traffic Safety Administration. The second set consisted of ratings for 49 tires published by Consumer Reports. The approach consisted of using factor analysis to determine whether the number of variables in the two sets (3 in UTQG, and 11 in Consumer Reports) can be reduced to a smaller number of independent factors.
The results indicate that the three UTQG variables form two factors. The first is dominated by tread properties, while the second factor reflects tread-abrasion resistance. The two factors accounted for 83% of the variance.
The 11 Consumer Reports variables form four factors. These factors are dominated, in turn, by tread properties, the tire (and especially belt) construction, tread-band flexibility (particularly in the longitudinal direction), and tread-abrasion resistance. Each of the 11 variables loaded highly on at least one factor. The four factors accounted for 68% of the variance.
The examination of the factors in each analysis suggests that each factor that is highly loaded by more than one variable represents richer and more complex information than what smaller subsets of variables could capture. Therefore, none of the variables could be excluded if one wants to provide the same information conveyed by the full sets of the variables.The University of Michigan Sustainable Worldwide Transportationhttp://deepblue.lib.umich.edu/bitstream/2027.42/90513/1/102852.pd
Carbon capture in vehicles: a review of general support, available mechanisms, and consumer acceptance issues
This survey of the feasibility of introducing carbon capture and storage (CCS) into light vehicles started by reviewing the level of international support for CCS in general. While there have been encouraging signs that CCS is gaining acceptance as a means to reduce carbon emissions, the overall
outlook looks somewhat mixed. Recent developments in the US, the UK, Germany, India, and China are discussed to obtain an indication of how likely it is that CCS technologies will gain acceptance in each respective country.
Fossil fuels continue to be a versatile means of energy storage, especially compared with
many low-emissions alternatives. This is noted because CCS technology is the only method that
can directly reduce the CO2 emissions produced by the continued use of fossil fuels in
transportation.
Primary focus in this review was placed on post-combustion-capture technologies because
these mechanisms are most easily adapted for use with the existing fleet of internal combustion
engines. Three post-combustion-capture mechanisms were described: absorption, membrane
separation, and adsorption.
Considerations about the consumer’s operational costs were discussed, including storage
management of captured CO2, additional energy costs to support separation and storage,
discharge procedures, and vehicle maintenance costs. Models of consumer inclination to adopt
new technologies were also reviewed. An important component of a consumer’s motivation to
adopt eco-friendly transport is perceived financial benefit. This suggests that incentives beyond
reduced emissions may be required to motivate consumer adoption of vehicle-based CCS because
the link between emissions and fuel consumption may change.The University of Michigan Sustainable Worldwide Transportationhttp://deepblue.lib.umich.edu/bitstream/2027.42/90951/3/102855.pd
Effect of external stresses on efficiency of dislocation sinks in BCC (Fe, V) and FCC (Cu) crystals
The efficiency of linear sinks for selfpoint defects (SPDs) elastically interacting (dislocations) and not interacting with sinks with the density of 3 × 1014 m–2 is calculated for BCC (Fe, V) and FCC (Cu) crystals at the temperature 293 K using the object kinetic Monte Carlo technique, depending on type and value of applied mechanical load (up to 200 MPa) and types of linear sinks. Full straight dislocations in slip systems [111](1 0), [111](11 ), [100](001), and [100](011) for Fe and V and [100](001) for Cu are considered for dislocation sinks (DSs). Orientations of noninteracting linear sinks (NILSs) coincide with those of DSs. Interaction of SPDs with internal (dislocation) and external stress fields is calculated within the framework of anisotropic linear theory of elasticity. Relative changes in efficiency of different codirectional linear sinks (either interacting or not interacting with SPDs) under action of applied stress are approximately identical under low stress. Radiation creep rates are calculated for the considered crystals under uniaxial stress in the stationary regime of Frenkel pairs generation. The creep rate strongly depends on the loading direction and Burgers vector of dislocations in Fe and V, and it is almost independent of these parameters in Cu. At the same generation rate of Frenkel pairs, the radiation creep rate averaged over all loading directions is significantly higher in BCC (Fe, V) crystals containing dislocations with the Burgers vector a/2〈111〉 than in FCC (Cu) crystals
Dislocation sinks efficiency for self-point defects in iron and vanadium crystals
The effect of the dislocations stress fields on their sink efficiency for self-point defects (interstitial atoms and vacancies) is studied in the temperature range of 293–1000 K and at the dislocation density values of 1 × 1012–3 × 1014 m−2 in body-centered cubic (BCC) iron and vanadium crystals. Straight screw and edge dislocations in 〈111〉{110}, 〈111〉{112}, 〈100〉{100}, and 〈100〉{110} slip systems are considered. Defect diffusion is simulated via the object kinetic Monte Carlo method. The energies of the interaction of defects with dislocations are calculated within the anisotropic linear theory of elasticity. The dislocation sink efficiency is analytically represented as a function of temperature and dislocation density
Pharmacologic inhibition of reactive gliosis blocks TNF-α-mediated neuronal apoptosis.
Reactive gliosis is an early pathological feature common to most neurodegenerative diseases, yet its regulation and impact remain poorly understood. Normally astrocytes maintain a critical homeostatic balance. After stress or injury they undergo rapid parainflammatory activation, characterized by hypertrophy, and increased polymerization of type III intermediate filaments (IFs), particularly glial fibrillary acidic protein and vimentin. However, the consequences of IF dynamics in the adult CNS remains unclear, and no pharmacologic tools have been available to target this mechanism in vivo. The mammalian retina is an accessible model to study the regulation of astrocyte stress responses, and their influence on retinal neuronal homeostasis. In particular, our work and others have implicated p38 mitogen-activated protein kinase (MAPK) signaling as a key regulator of glutamate recycling, antioxidant activity and cytokine secretion by astrocytes and related Müller glia, with potent influences on neighboring neurons. Here we report experiments with the small molecule inhibitor, withaferin A (WFA), to specifically block type III IF dynamics in vivo. WFA was administered in a model of metabolic retinal injury induced by kainic acid, and in combination with a recent model of debridement-induced astrocyte reactivity. We show that WFA specifically targets IFs and reduces astrocyte and Müller glial reactivity in vivo. Inhibition of glial IF polymerization blocked p38 MAPK-dependent secretion of TNF-α, resulting in markedly reduced neuronal apoptosis. To our knowledge this is the first study to demonstrate that pharmacologic inhibition of IF dynamics in reactive glia protects neurons in vivo
George C. Marshall Space Flight Center Research and Technology Report 2014
Many of NASA's missions would not be possible if it were not for the investments made in research advancements and technology development efforts. The technologies developed at Marshall Space Flight Center contribute to NASA's strategic array of missions through technology development and accomplishments. The scientists, researchers, and technologists of Marshall Space Flight Center who are working these enabling technology efforts are facilitating NASA's ability to fulfill the ambitious goals of innovation, exploration, and discovery
The geometry of thermodynamic control
A deeper understanding of nonequilibrium phenomena is needed to reveal the
principles governing natural and synthetic molecular machines. Recent work has
shown that when a thermodynamic system is driven from equilibrium then, in the
linear response regime, the space of controllable parameters has a Riemannian
geometry induced by a generalized friction tensor. We exploit this geometric
insight to construct closed-form expressions for minimal-dissipation protocols
for a particle diffusing in a one dimensional harmonic potential, where the
spring constant, inverse temperature, and trap location are adjusted
simultaneously. These optimal protocols are geodesics on the Riemannian
manifold, and reveal that this simple model has a surprisingly rich geometry.
We test these optimal protocols via a numerical implementation of the
Fokker-Planck equation and demonstrate that the friction tensor arises
naturally from a first order expansion in temporal derivatives of the control
parameters, without appealing directly to linear response theory
Thermodynamic metrics and optimal paths
A fundamental problem in modern thermodynamics is how a molecular-scale
machine performs useful work, while operating away from thermal equilibrium
without excessive dissipation. To this end, we derive a friction tensor that
induces a Riemannian manifold on the space of thermodynamic states. Within the
linear-response regime, this metric structure controls the dissipation of
finite-time transformations, and bestows optimal protocols with many useful
properties. We discuss the connection to the existing thermodynamic length
formalism, and demonstrate the utility of this metric by solving for optimal
control parameter protocols in a simple nonequilibrium model.Comment: 5 page
Neutrino pair synchrotron radiation from relativistic electrons in strong magnetic fields
The emissivity for the neutrino pair synchrotron radiation in strong magnetic
fields has been calculated both analytically and numerically for high densities
and moderate temperatures, as can be found in neutron stars. Under these
conditions, the electrons are relativistic and degenerate. We give here our
results in terms of an universal function of a single variable. For two
different regimes of the electron gas we present a simplified calculation and
compare our results to those of Kaminker et al. Agreement is found for the
classical region, where many Landau levels contribute to the emissivity , but
some differences arise in the quantum regime. One finds that the emissivity for
neutrino pair synchrotron radiation is competitive, and can be dominant, with
other neutrino processes for magnetic fields of the order .This indicates the relevance of this process for some astrophysical
scenarios, such as neutron stars and supernovae.Comment: 19 pages, AAS latex, 6 figures on a separate file. Accepted for
publication in Ap.
The thermodynamics of prediction
A system responding to a stochastic driving signal can be interpreted as
computing, by means of its dynamics, an implicit model of the environmental
variables. The system's state retains information about past environmental
fluctuations, and a fraction of this information is predictive of future ones.
The remaining nonpredictive information reflects model complexity that does not
improve predictive power, and thus represents the ineffectiveness of the model.
We expose the fundamental equivalence between this model inefficiency and
thermodynamic inefficiency, measured by dissipation. Our results hold
arbitrarily far from thermodynamic equilibrium and are applicable to a wide
range of systems, including biomolecular machines. They highlight a profound
connection between the effective use of information and efficient thermodynamic
operation: any system constructed to keep memory about its environment and to
operate with maximal energetic efficiency has to be predictive.Comment: 5 pages, 1 figur
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