1,398 research outputs found
The Glass Transition in Driven Granular Fluids: A Mode-Coupling Approach
We consider the stationary state of a fluid comprised of inelastic hard
spheres or disks under the influence of a random, momentum-conserving external
force. Starting from the microscopic description of the dynamics, we derive a
nonlinear equation of motion for the coherent scattering function in two and
three space dimensions. A glass transition is observed for all coefficients of
restitution, epsilon, at a critical packing fraction, phi_c(epsilon), below
random close packing. The divergence of timescales at the glass-transition
implies a dependence on compression rate upon further increase of the density -
similar to the cooling rate dependence of a thermal glass. The critical
dynamics for coherent motion as well as tagged particle dynamics is analyzed
and shown to be non-universal with exponents depending on space dimension and
degree of dissipation.Comment: 16 pages, 9 figure
Electric road vehicles - overview, concepts and research at Reutlingen university
The paper details the architecture of fully electrified vehicles as well as their new electronic systems. Examples of up-to-date electrical passenger cars are given. A very important question, that is the environmental foot-print of electrical vehicles compared to conventional ones, is examined. A research project is introduced where a fleet of two-wheeled vehicles is available for day-to-day use. Research on vehicles, software for fleet management and battery range prediction is described.В данной статье привeдены подробные сведения о принципе работы электрифицированных транспортных средств, а также описаны их новые электрические системы. Показан примеры уже существующих электрических пассажирских транспортных средств. Рассмотрено влияние электрифицированного транспорта на окружающую среду в сравнении с обычными видами транспорта. Приведен проект исследований, в рамках которого для ежедневного использования существует парк двух колесных электрифицированных транспортных средств. Описаны исследования, непосредственно связанные с электрифицированным транспортом,
определением точного времени разряда батареи, а также программным обеспечением, позволяющим управлять парком таких транспортных средств.У статті наведено докладні відомості щодо принципів роботи електрифікованих транспортних засобів, а також описано їх нові електричні системи. Показано приклади вже існуючих електричних пасажирських транспортних засобів. Розглянуто вплив електрифікованого транспорту на навколишнє середовище у порівнянні із звичайними видами транспорту. На-
ведено проект досліджень, у рамках якого існує парк двоколісних електрифікованих транспортних засобів для щоденного використання. Описано дослідження, безпосередньо пов'язані із електрифікованим транспортом, визначенням точного часу розряду батареї, а також програмним забезпеченням, що дозволяє керувати парком таких транспортних засобів
Partitioning of energy in highly polydisperse granular gases
A highly polydisperse granular gas is modeled by a continuous distribution of
particle sizes, a, giving rise to a corresponding continuous temperature
profile, T(a), which we compute approximately, generalizing previous results
for binary or multicomponent mixtures. If the system is driven, it evolves
towards a stationary temperature profile, which is discussed for several
driving mechanisms in dependence on the variance of the size distribution. For
a uniform distribution of sizes, the stationary temperature profile is
nonuniform with either hot small particles (constant force driving) or hot
large particles (constant velocity or constant energy driving). Polydispersity
always gives rise to non-Gaussian velocity distributions. Depending on the
driving mechanism the tails can be either overpopulated or underpopulated as
compared to the molecular gas. The deviations are mainly due to small
particles. In the case of free cooling the decay rate depends continuously on
particle size, while all partial temperatures decay according to Haff's law.
The analytical results are supported by event driven simulations for a large,
but discrete number of species.Comment: 10 pages; 5 figure
Irrigation-Yield Production Functions and Irrigation Water Use Effciency Response of Drought-Tolerant and Non-Drought-Tolerant Maize Hybrids under Different Irrigation Levels, Population Densities, and Environments
Irrigation-yield production functions (IYPFs), irrigation water use effciency (IWUE), and grain production per unit of applied irrigation of non-drought-tolerant (NDT) and drought-tolerant (DT) maize (Zea mays L.) hybrids were quantified in four locations with different climates in Nebraska [Concord (sub-humid), Clay Center (transition zone between sub-humid and semi-arid); North Platte (semi-arid); and, Scottsbluff (semi-arid)] during three growing seasons (2010, 2011, and 2012) at three irrigation levels (fully-irrigated treatment (FIT), early cut-off (ECOT), and rainfed (RFT)) under two plant population densities (PPDs) (low-PPD; 59,300 plants ha-1; and, high-PPD, 84,000 plants ha-1). Overall, DT hybrids’ performance was superior to NDT hybrid at RFT, ECT, and FIT conditions, as confirmed by the yield response, IYPF and IWUE when all locations, years, and PPDs were averaged. The yield response to water was greater with the high-PPD than the low-PPD in most cases. The magnitude of the highest yields for DT hybrids ranged from 7.3 (low-PPD) to 8.5% (high-PPD) under RFT, 3.7 (low-PPD) to 9.6% (high-PPD) under ECOT, and 3.9% (high-PPD) under FIT higher than NDT hybrid. Relatively, DT hybrids can resist drought-stress conditions longer than NDT hybrid with fewer penalties in yield reduction and maintain comparable or even higher yield production at non-stress-water conditions
Feasibility of fuel switching in Boston
This report develops a simple physical model that predicts that the
nighttime dispersion of S2 from the largest sources in Boston is different
than the dispersion of S2 from small, low level sources. Diurnal variations in S02 levels measured in Boston over the last seven years are analyzed
in the light of this theory. The comparison between theory and observation
is favorable. A simple, unambiguous, criteria for defining a large source
is developed. The results are used to predict the fraction of the time
large sources could burn high sulfur fuels while still meeting the state
standards for sulfur dioxide
Grain yield, crop and basal evapotranspiration, production functions and water productivity response of drought-tolerant and non-drought-tolerant maize hybrids under different irrigation levels, population densities and environments: Part II. In south-central and northeast Nebraska\u27s transition zone and sub-humid environments
Information and data on newer drought-tolerant maize hybrid response to water in different climates are extremely scarce. This research quantified the performance of non-drought-tolerant (NDT) (H1) and drought-tolerant (DT) (H2, H3, and H4) maize (Zea mays L.) hybrids response to grain yield, crop evapotranspiration (ETc), basal evapotranspiration (ETb), ETc-yield production functions (ETYPF), and crop water use efficiency (CWUE) at three irrigation levels and two plant population densities (PPDs) at two locations (transition zone between sub-humid and semiarid climates at Clay Center (SCAL), Nebraska, in 2010 and 2012; and in a sub-humid climate at Concord (HAL), Nebraska, in 2010, 2011, and 2012). Irrigation treatments were: fully irrigated (FIT), early cutoff (ECOT) (i.e., no irrigation after blister stage), and rainfed (RFT) under two PPDs of 59,300 plants ha-1 (low PPD), and 84,000 plants ha-1 (high PPD). Generally, DT hybrids performed superior to NDT hybrid consistently at both locations, treatments, and years. DT H3 and DT H4 had highest grain yield consistently at SCAL and HAL, respectively. DT H3 and H4 hybrids’ productivity was not only superior in the RFT, but also in FIT. The highest yield of 16.3, and 15.3 Mg ha-1 were achieved by DT H3 (high PPD) and DT H2 (high PPD), respectively, associated with 471 and 590 mm of ETc in the FIT in 2012 at SCAL, and HAL, respectively. In most cases, all hybrids had highest grain yield under low PPD than high PPD at the RFT. All hybrids exhibited a linear yield response to increasing ETc in all years at both locations with positive slopes in all cases. The individual ETYPF response for individual hybrids had inter-annual variation in slopes between the hybrids and for the same hybrids between the years and location for both low and high PPDs. The ETYPF slopes ranged from 0.004 to 0.102 Mg ha-1 mm-,1 including all treatments (i.e., irrigation and PPDs) at SCAL for 2010 and 2012; and they ranged from 0.008 to 0.057 Mg ha-1 mm-1 including all treatments at HAL for 2010, 2011, and 2012. The ETb values exhibited inter-annual variation for the same hybrid between the irrigation levels, PPDs, and locations and they also exhibited an inner-annual variation between the hybrids and treatments in a given year with DT hybrids having consistently lower ETb values than the NDT hybrid. The greatest CWUE values were found in DT hybrids consistently at both locations. The DT hybrids can significantly increase yield productivity as well as crop water productivity per unit of ETc with respect to conventional hybrids not only in dry conditions, but also in average or above average years in terms of precipitation
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