46,491 research outputs found
Measures to enforce mandatory civil building energy efficiency codes in China
Mandatory civil building energy efficiency codes strictly govern the energy consumption of new buildings in China. As the promotion of building energy efficiency in China has increased in recent years, compliance with mandatory civil building energy efficiency codes has also improved, increasing from less than 10% in 2000 to nearly 100% in 2012, a remarkable achievement. However, because the promotion of energy efficiency strategies in China has followed a unique pattern, some researchers doubt these statistics. In response to these doubts, this paper summarises and analyses the framework of measures implemented by the Chinese government to enforce mandatory building energy efficiency codes. First, the development and implementation of China's mandatory civil building energy efficiency code system is summarised. Second, the building supervision and inspection systems used to assess energy efficiency are introduced and analysed in detail in order to provide a framework for the development of energy policies in other countries. Third, the assessment and reporting processes used to determine compliance rates are reviewed. Finally, the improvement of compliance rates and its impact on building energy savings in China are discussed. Along with the increase in compliance rates in the construction stage from 71% in 2007 to 100% in 2012, the energy savings of new buildings per increased floor area per year increased from 20.4 kWh/m2 to 28.4 kWh/m2. The supervision and inspection systems reported in this paper are the keys to enforcing building energy efficiency codes
Intrinsic spin Hall effect in platinum metal
Spin Hall effect in metallic Pt is studied with first-principles relativistic
band calculations. It is found that intrinsic spin Hall conductivity (SHC) is
as large as at low temperature, and
decreases down to at room
temperature. It is due to the resonant contribution from the spin-orbit
splitting of the doubly degenerated -bands at high-symmetry and
points near the Fermi level. By modeling these near degeneracies by effective
Hamiltonian, we show that SHC has a peak near the Fermi energy and that the
vertex correction due to impurity scattering vanishes. We therefore argue that
the large spin Hall effect observed experimentally in platinum is of intrinsic
nature.Comment: Accepted for publication in Phys. Rev. Let
Flavor-twisted boundary condition for simulations of quantum many-body systems
We present an approximative simulation method for quantum many-body systems
based on coarse graining the space of the momentum transferred between
interacting particles, which leads to effective Hamiltonians of reduced size
with the flavor-twisted boundary condition. A rapid, accurate, and fast
convergent computation of the ground-state energy is demonstrated on the
spin-1/2 quantum antiferromagnet of any dimension by employing only two sites.
The method is expected to be useful for future simulations and quick estimates
on other strongly correlated systems.Comment: 6 pages, 2 figure
Factors of sums and alternating sums involving binomial coefficients and powers of integers
We study divisibility properties of certain sums and alternating sums
involving binomial coefficients and powers of integers. For example, we prove
that for all positive integers , , and any
nonnegative integer , there holds {align*} \sum_{k=0}^{n_1}\epsilon^k
(2k+1)^{2r+1}\prod_{i=1}^{m} {n_i+n_{i+1}+1\choose n_i-k} \equiv 0 \mod
(n_1+n_m+1){n_1+n_m\choose n_1}, {align*} and conjecture that for any
nonnegative integer and positive integer such that is odd, where .Comment: 14 pages, to appear in Int. J. Number Theor
Metastable helium molecules as tracers in superfluid liquid He
Metastable helium molecules generated in a discharge near a sharp tungsten
tip operated in either pulsed mode or continuous field-emission mode in
superfluid liquid He are imaged using a laser-induced-fluorescence
technique. By pulsing the tip, a small cloud of He molecules is
produced. At 2.0 K, the molecules in the liquid follow the motion of the normal
fluid. We can determine the normal-fluid velocity in a heat-induced counterflow
by tracing the position of a single molecule cloud. As we run the tip in
continuous field-emission mode, a normal-fluid jet from the tip is generated
and molecules are entrained in the jet. A focused 910 nm pump laser pulse is
used to drive a small group of molecules to the vibrational state.
Subsequent imaging of the tagged molecules with an expanded 925 nm probe
laser pulse allows us to measure the velocity of the normal fluid. The
techniques we developed demonstrate for the first time the ability to trace the
normal-fluid component in superfluid helium using angstrom-sized particles.Comment: 4 pages, 7 figures. Submitted to Phys. Rev. Let
Transverse force generated by an electric field and transverse charge imbalance in spin-orbit coupled systems
We use linear response theory to study the transverse force generated by an
external electric field and hence possible charge Hall effect in spin-orbit
coupled systems. In addition to the Lorentz force that is parallel to the
electric field, we find that the transverse force perpendicular to the applied
electric field may not vanish in a system with an anisotropic energy
dispersion. Surprisingly, in contrast to the previous results, the transverse
force generated by the electric field does not depend on the spin current, but
in general, it is related to the second derivative of energy dispersion only.
Furthermore, we find that the transverse force does not vanish in the
Rashba-Dresselhaus system. Therefore, the non-vanishing transverse force acts
as a driving force and results in charge imbalance at the edges of the sample.
The estimated ratio of the Hall voltage to the longitudinal voltage is . The disorder effect is also considered in the study of the
Rashba-Dresselhaus system. We find that the transverse force vanishes in the
presence of impurities in this system because the vertex correction and the
anomalous velocity of the electron accidently cancel each other
Proof of two conjectures of Z.-W. Sun on congruences for Franel numbers
For all nonnegative integers n, the Franel numbers are defined as We confirm two conjectures of Z.-W. Sun on
congruences for Franel numbers: \sum_{k=0}^{n-1}(3k+2)(-1)^k f_k &\equiv 0
\pmod{2n^2}, \sum_{k=0}^{p-1}(3k+2)(-1)^k f_k &\equiv 2p^2 (2^p-1)^2
\pmod{p^5}, where n is a positive integer and p>3 is a prime.Comment: 8 pages, minor changes, to appear in Integral Transforms Spec. Func
Monotonicity results and bounds for the inverse hyperbolic sine
In this note, we present monotonicity results of a function involving to the
inverse hyperbolic sine. From these, we derive some inequalities for bounding
the inverse hyperbolic sine.Comment: 3 page
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