1,940 research outputs found
The Energy and CO2 Emissions Impact of Renewable Energy Development in China
China’s recently-adopted targets for developing renewable electricity—wind, solar, and biomass—would require expansion on an unprecedented scale in China and relative to existing global installations. An important question is how far this deployment will go toward achieving China’s low carbon development goals, which include a carbon intensity reduction target of 40–45% relative to 2005 and a non-fossil primary energy target of 15% by 2020. During the period from 2010 to 2020, we find that current renewable electricity targets result in significant additional renewable energy installation and a reduction in cumulative CO2 emissions of 1.2% relative to a no policy baseline. After 2020, the role of renewables is sensitive to both economic growth and technology cost assumptions. Importantly, we find that CO2 emissions reductions due to increased renewables are offset in each year by emissions increases in non-covered sectors through 2050. By increasing reliance on renewable energy sources in the electricity sector, fossil fuel demand in the power sector falls, resulting in lower fossil fuel prices, which in turn leads to greater demand for these fuels in unconstrained sectors. We consider sensitivity to renewable electricity cost after 2020 and find that if cost falls due to policy or other reasons, renewable electricity share increases and results in slightly higher economic growth through 2050. However, regardless of the cost assumption, projected CO2 emissions reductions are very modest under a policy that only targets the supply side in the electricity sector. A policy approach that covers all sectors and allows flexibility to reduce CO2 at lowest cost—such as an emissions trading system—will prevent this emissions leakage and ensure targeted reductions in CO2 emissions are achieved over the long term.The authors are grateful for the support provided by the National Key Technology R&D Program
from Ministry of Science and Technology of Grant NO. 2012BAC20B07. We acknowledge the
support of the National Key Technology R&D Program and the Institute for Energy,
Environment, and Economy at Tsinghua University, which is supporting Tianyu Qi’s doctoral
research as a visiting scholar at the Massachusetts Institute of Technology. We acknowledge the
support of ENI, ICF and Shell, initial Founding sponsors of the China Energy and Climate
Project. This consortium of sponsors has provided support for researchers in the MIT Joint
Program to engage in a five-year program of research focused on China. None of the sponsoring
organizations played a role in the study design, collection, analysis, or interpretation of the data
used for this study, nor did they influence our decisions to submit the article for publication, and
all errors are our own
Nonlinear interaction between electromagnetic fields at high temperature
The electron-positron `box' diagram produces an effective action which is
fourth order in the electromagnetic field. We examine the behaviour of this
effective action at high-temperature (in analytically continued imaginary-time
thermal perturbation theory). We argue that there is a finite, nonzero limit as
(where is the temperature). We calculate this limit
in the nonrelativistic static case, and in the long-wavelength limit. We also
briefly discuss the self-energy in 2-dimensional QED, which is similar in some
respects.Comment: 13 pages, DAMTP 94/3
Collapse of Randomly Self-Interacting Polymers
We use complete enumeration and Monte Carlo techniques to study
self--avoiding walks with random nearest--neighbor interactions described by
, where is a quenched sequence of ``charges'' on the
chain. For equal numbers of positive and negative charges (), the
polymer with undergoes a transition from self--avoiding behavior to a
compact state at a temperature . The collapse temperature
decreases with the asymmetry Comment: 8 pages, TeX, 4 uuencoded postscript figures, MIT-CMT-
One Loop Multiphoton Helicity Amplitudes
We use the solutions to the recursion relations for double-off-shell fermion
currents to compute helicity amplitudes for -photon scattering and
electron-positron annihilation to photons in the massless limit of QED. The
form of these solutions is simple enough to allow {\it all}\ of the
integrations to be performed explicitly. For -photon scattering, we find
that unless , the amplitudes for the helicity configurations (+++...+) and
(-++...+) vanish to one-loop order.Comment: 27 pages + 4 uuencoded figures (included), Fermilab-Pub-93/327-T,
RevTe
Quantum Electrodynamics of the Helium Atom
Using singlet S states of the helium atom as an example, I describe precise
calculation of energy levels in few-electron atoms. In particular, a complete
set of effective operators is derived which generates O(m*alpha^6) relativistic
and radiative corrections to the Schr"odinger energy. Average values of these
operators can be calculated using a variational Schr"odinger wave function.Comment: 23 pages, revte
Conformations of Proteins in Equilibrium
We introduce a simple theoretical approach for an equilibrium study of
proteins with known native state structures. We test our approach with results
on well-studied globular proteins, Chymotrypsin Inhibitor (2ci2), Barnase and
the alpha spectrin SH3 domain and present evidence for a hierarchical onset of
order on lowering the temperature with significant organization at the local
level even at high temperatures. A further application to the folding process
of HIV-1 protease shows that the model can be reliably used to identify key
folding sites that are responsible for the development of drug resistance .Comment: 6 pages, 3 eps figure
Topological spin-Hall current in waveguided zinc-blende semiconductors with Dresselhaus spin-orbit coupling
We describe an intrinsic spin-Hall effect in -type bulk zinc-blende
semiconductors with topological origin. When electron transport is confined to
a waveguide structure, and the applied electric field is such that the spins of
electrons remain as eigenstates of the Dresselhaus spin-orbit field with
negligible subband mixing, a gauge structure appears in the momentum space of
the system. In particular, the momentum space exhibits a non-trivial Berry
curvature which affects the transverse motion of electrons anisotropically in
spin, thereby producing a finite spin-Hall effect. The effect should be
detectable using standard techniques in the literature such as Kerr rotation,
and be readily distinguishable from other mechanisms of the spin-Hall effect.Comment: 6 pages, 3 figure
NRQED and Next-to-Leading Hyperfine Splitting in Positronium
We compute the next-to-leading, O(m alpha^5), contribution to the hyperfine
splitting in positronium within the framework of NRQED. When applied to the
ground state, our calculation reproduces known results, providing a further
test of NRQED techniques. Besides providing a very simple method of calculation
of the standard result, we also obtain new expressions for excited states of
positronium with negligible additional effort. Our calculation requires the
complete next-to-leading matching of the lowest-dimension NRQED four-fermi
couplings, which we publish here for the first time.Comment: 24 pages, plain TeX, 6 figures included using eps
Theory of Anomalous Hall Effect in a Heavy fermion System with a Strong Anisotropic Crystal Field
In a heavy fermion system, there exists the anomalous Hall effect caused by
localized -orbital freedom, in addition to the normal Hall effect due to the
Lorentz force. In 1994, we found that the Hall coefficient caused by the
anomalous Hall effect () is predominant and the relation ( is the electrical resistivity) holds at low
temperatures in many compounds. In this work, we study the system where the
magnetic susceptibility is highly anisotropic due to the strong crystalline
electric field on -orbitals. Interestingly, we find that is
nearly isotropic in general. This tendency is frequently observed
experimentally, which has casted suspicion that the anomalous Hall effect may
be irrelevant in real materials. Our theory corresponds to corrections and
generalizations of the pioneering work on ferromagnetic metals by Karplus and
Luttinger.Comment: 4 pages, revtex, to be published in J. Phys. Soc. Jpn. (No.8
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