22,896 research outputs found
Implications of Color Gauge Symmetry For Nucleon Spin Structure
We study the chromodynamical gauge symmetry in relation to the internal spin
structure of the nucleon. We show that 1) even in the helicity eigenstates the
gauge-dependent spin and orbital angular momentum operators do not have
gauge-independent matrix element; 2) the evolution equations for the gluon spin
take very different forms in the Feynman and axial gauges, but yield the same
leading behavior in the asymptotic limit; 3) the complete evolution of the
gauge-dependent orbital angular momenta appears intractable in the light-cone
gauge. We define a new gluon orbital angular momentum distribution
which {\it is} an experimental observable and has a simple scale evolution.
However, its physical interpretation makes sense only in the light-cone gauge
just like the gluon helicity distribution y.Comment: Minor corrections are made in the tex
Global supply chain of biomass use and the shift of environmental welfare from primary exploiters to final consumers
With the increasingly frequent interregional trade that leads to the geographical separation of production and consumption, the invisible shift of the environmental welfare bestowed by biomass use is brought to attention. Using a systems embodiment accounting model, this study tracked the dynamic process of interregional transfer of biomass use from primary supply to final consumption via the global supply chain. The results reveal that biomass use embodied in global trade is 87% of total global biomass exploitation. Moreover, the intermediate trade volume is 1.7 times higher than the final trade volume. In terms of biomass use, the United States, South Korea, mainland China, Japan, and the United Kingdom are revealed as the five leading net importers and also the main final consumers. Brazil, India, Cyprus, Indonesia, and Latvia are demonstrated to be the top five net exporters and also the main exploiters of biomass resources. The biomass self-sufficiency rate by source and that by sink for each country are then discussed. The outcome shows that through the channels of global supply chain, the shift of environmental welfare from biomass-exporting nations to biomass-importing nations occurs along with interregional trade. For Brazil and India, we suggest that they should strike a balance between economic revenues and long-term sustainability. Regarding the consumption-oriented nations such as the United States, an increase in the energy efficiency of high value-added industries is recommended
Reactor Fuel Fraction Information on the Antineutrino Anomaly
We analyzed the evolution data of the Daya Bay reactor neutrino experiment in
terms of short-baseline active-sterile neutrino oscillations taking into
account the theoretical uncertainties of the reactor antineutrino fluxes. We
found that oscillations are disfavored at with respect to a
suppression of the reactor antineutrino flux and at
with respect to variations of the and
fluxes. On the other hand, the analysis of the rates of the
short-baseline reactor neutrino experiments favor active-sterile neutrino
oscillations and disfavor the suppression of the flux at
and variations of the and fluxes
at . We also found that both the Daya Bay evolution data and the
global rate data are well-fitted with composite hypotheses including variations
of the or fluxes in addition to
active-sterile neutrino oscillations. A combined analysis of the Daya Bay
evolution data and the global rate data shows a slight preference for
oscillations with respect to variations of the and
fluxes. However, the best fits of the combined data are given
by the composite models, with a preference for the model with an enhancement of
the flux and relatively large oscillations.Comment: 9 page
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Molecular dynamics simulation for microscope insight of liquid evaporation on a heated surface
This paper was presented at the 2nd Micro and Nano Flows Conference (MNF2009), which was held at Brunel University, West London, UK. The conference was organised by Brunel University and supported by the Institution of Mechanical Engineers, IPEM, the Italian Union of Thermofluid dynamics, the Process Intensification Network, HEXAG - the Heat Exchange Action Group and the Institute of Mathematics and its Applications.Molecular dynamics (MD) simulation is a very effective tool that gives a microscopic insight into the mechanisms of complex physical phenomena. This paper uses MD simulation to study the evaporation of a liquid from a heated surface. As for the argon/platinum model, a group of simulations starts from a fixed lower wall with the temperature of 110K. In this system, argon molecule numbers of 784, 1200, 1440 are
simulated respectively. Additional simulations for argon models are based on superheat conditions, which indicate that the variation of ultra-thin liquid film thickness is very small with the different numbers of argon molecules. Also, it shows that if the argon molecule numbers increase, the extra molecules accumulate near the cooling wall. In terms of the MD simulation for the water/magnesium model, water evaporates from a magnesium heating wall at different temperatures and an initial study has been carried out. Moreover, further
and more accurate simulations will be improved in the near future
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