17,295 research outputs found
Evaluation of anchor bolt effects on the thermal performance of building insulation materials
For Near-zero-energy buildings, the application of building insulation materials is widely used. Anchor bolts, as a fixing element of insulators, have been applied to increase the safety of insulators; however, due to their high thermal conductivity they can cause point thermal bridges and lead to a negative effect on the insulation function of building envelopes. Very few studies, though, have systematically explored the issuer. This study therefore proposes a prediction approach, with a 3D model developed by MATLAB, to investigate the effect of anchors on thermal performance of building envelopes with insulation layers fixed by anchors. It also provides a new indicator, namely the equivalent effective thermal conductivity of insulators which can be used in many popular building energy prediction packages. Simulation results reveal a complicated thermal impact of anchor bolts on an external building envelope, which would be affected by many parameters of different envelope contents. For example, for glass fiber insulation materials with aluminum alloy anchor bolts, the effective thermal conductivity would rise by up to 18 times, and the corresponding envelope thermal transmittance would increase by 33%. This novel model can provide an accurate and easy method to evaluate the thermal effect of anchor bolts, and it is applicable to anchors made of any material. The proposed method could be a reference in energy performance prediction for high-performance buildings
Strong decays of heavy baryons in Bethe-Salpeter formalism
In this paper we study the properties of diquarks (composed of and/or
quarks) in the Bethe-Salpeter formalism under the covariant instantaneous
approximation. We calculate their BS wave functions and study their effective
interaction with the pion. Using the effective coupling constant among the
diquarks and the pion, in the heavy quark limit , we calculate
the decay widths of () in the BS formalism under the
covariant instantaneous approximation and then give predictions of the decay
widths .Comment: 41 pages, 1 figure, LaTex2e, typos correcte
Local Operations in qubit arrays via global but periodic Manipulation
We provide a scheme for quantum computation in lattice systems via global but
periodic manipulation, in which only effective periodic magnetic fields and
global nearest neighbor interaction are required. All operations in our scheme
are attainable in optical lattice or solid state systems. We also investigate
universal quantum operations and quantum simulation in 2 dimensional lattice.
We find global manipulations are superior in simulating some nontrivial many
body Hamiltonians.Comment: 5 pages, 2 figures, to appear in Phys. Rev.
Stability of Pairwise Entanglement in a Decoherent Environment
Consider the dynamics of a two-qubit entangled system in the decoherence
environment, we investigate the stability of pairwise entanglement under
decoherence. We find that for different decoherence models, there exist some
special class of entangled states of which the pairwise entanglement is the
most stable. The lifetime of the entanglement in these states is larger than
other states with the same initial entanglement. In addition, we also
investigate the dynamics of pairwise entanglement in the ground state of spin
models such as Heisenberg and XXY models.Comment: accepted by Physical Review A, references updated and minor change
Relationship between High-Energy Absorption Cross Section and Strong Gravitational Lensing for Black Hole
In this paper, we obtain a relation between the high-energy absorption cross
section and the strong gravitational lensing for a static and spherically
symmetric black hole. It provides us a possible way to measure the high-energy
absorption cross section for a black hole from strong gravitational lensing
through astronomical observation. More importantly, it allows us to compute the
total energy emission rate for high-energy particles emitted from the black
hole acting as a gravitational lens. It could tell us the range of the
frequency, among which the black hole emits the most of its energy and the
gravitational waves are most likely to be observed. We also apply it to the
Janis-Newman-Winicour solution. The results suggest that we can test the cosmic
censorship hypothesis through the observation of gravitational lensing by the
weakly naked singularities acting as gravitational lenses.Comment: 6 pages, 2 figures, improved version, accepted for publication as a
Rapid Communication in Physical Review
Performance of various correlation measures in quantum renormalization-group method: A case study of quantum phase transition
We have investigated quantum phase transition employing the quantum
renormalization group (QRG) method while in most previous literature barely
entanglement (concurrence) has been demonstrated. However, it is now well known
that entanglement is not the only signature of quantum correlations and a
variety of computable measures have been developed to characterize quantum
correlations in the composite systems. As an illustration, two cases are
elaborated: one dimensional anisotropic (i) XXZ model and (ii) XY model, with
various measures of quantum correlations, including quantum discord (QD),
geometric discord (GD), measure-induced disturbance (MID), measure-induced
nonlocality (MIN) and violation of Bell inequalities (eg. CHSH inequality). We
have proved that all these correlation measures can effectively detect the
quantum critical points associated with quantum phase transitions (QPT) after
several iterations of the renormalization in both cases. Nonetheless, it is
shown that some of their dynamical behaviors are not totally similar with
entanglement and even when concurrence vanishes there still exists some kind of
quantum correlations which is not captured by entanglement. Intriguingly, CHSH
inequality can never be violated in the whole iteration procedure, which
indicates block-block entanglement can not revealed by the CHSH inequality.
Moreover, the nonanalytic and scaling behaviors of Bell violation have also
been discussed in detail. As a byproduct, we verify that measure-induced
disturbance is exactly equal to the quantum discord measured by \sigma_z for
general X-structured states.Comment: Published version. 10 pages, 8 figure
Realization of All-or-nothing-type Kochen-Specker Experiment with Single Photons
Using the spontaneous parametric down-conversion process in a type-I phase
matching BBO crystal as single photon source, we perform an all-or-nothing-type
Kochen-Specker experiment proposed by Simon \QTR{it}{et al}. [Phys. Rev. Lett.
\QTR{bf}{85}, 1783 (2000)] to verify whether noncontextual hidden variables or
quantum mechanics is right. The results strongly agree with quantum mechanics.Comment: 3 figure
Determining the Solution Space of Vertex-Cover by Interactions and Backbones
To solve the combinatorial optimization problems especially the minimal
Vertex-cover problem with high efficiency, is a significant task in theoretical
computer science and many other subjects. Aiming at detecting the solution
space of Vertex-cover, a new structure named interaction between nodes is
defined and discovered for random graph, which results in the emergence of the
frustration and long-range correlation phenomenon. Based on the backbones and
interactions with a node adding process, we propose an Interaction and Backbone
Evolution Algorithm to achieve the reduced solution graph, which has a direct
correspondence to the solution space of Vertex-cover. By this algorithm, the
whole solution space can be obtained strictly when there is no leaf-removal
core on the graph and the odd cycles of unfrozen nodes bring great obstacles to
its efficiency. Besides, this algorithm possesses favorable exactness and has
good performance on random instances even with high average degrees. The
interaction with the algorithm provides a new viewpoint to solve Vertex-cover,
which will have a wide range of applications to different types of graphs,
better usage of which can lower the computational complexity for solving
Vertex-cover
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