8,739 research outputs found
Nonlinear Schr\"odinger Equation for Superconductors
Using the Hartree-Fock-Bogoliubov factorization of the density matrix and the
Born-Oppenheimer approximation we show that the motion of the condensate
satisfies a nonlinear Schr\"odinger equation in the zero temperature limit. The
Galilean invariance of the equation is explicitly manifested. {}From this
equation some general properties of a superconductor, such as Josephson
effects, the Magnus force, and the Bogoliubov-Anderson mode can be obtained
readily.Comment: Latex, 12 page
On the "Security analysis and improvements of arbitrated quantum signature schemes"
Recently, Zou et al. [Phys. Rev. A 82, 042325 (2010)] pointed out that two
arbitrated quantum signature (AQS) schemes are not secure, because an
arbitrator cannot arbitrate the dispute between two users when a receiver
repudiates the integrity of a signature. By using a public board, they try to
propose two AQS schemes to solve the problem. This work shows that the same
security problem may exist in their schemes and also a malicious party can
reveal the other party's secret key without being detected by using the
Trojan-horse attacks. Accordingly, two basic properties of a quantum signature,
i.e. unforgeability and undeniability, may not be satisfied in their scheme
The analysis of barriers to bim implementation for industrialized building construction: a China study
The emerging Building Information Modeling (BIM) can better promote the development of building industrialization, with data integration between information-rich building models and business processes. However, the practical implementation of BIM still faces barriers. Existing studies have discussed these barriers extensively, but the research on the barriers to the implementation of BIM amid building industrialization in China is inadequate. In this study, 23 barriers were identified through literature review. A questionnaire survey approach was used to collect data from various parties. Factor analysis methods were used to process and rank barrier factors for BIM applications in the context of industrialized building. Based on the analysis of each factor, analytic hierarchy process was adopted to identify the key barriers to the implementation of BIM for industrialized building construction. The study concluded that the main barriers for BIM implementation for industrialized building were capital-related factors and the lack of support from owners. This study proposes that in addition to governmental policy support for BIM and multi-stakeholder engagement, companies should also organize experts to effectively evaluate the risks of applying BIM. Overall, this study provides suggestions on construction organizational transformations in the roadmap of moving towards digital-driven building industrialization
Molecular Dynamics Simulation of Strong Shock Waves Propagating in Dense Deuterium With the Effect of Excited Electrons
We present a molecular dynamics simulation of shock waves propagating in
dense deuterium with the electron force field method [J. T. Su and W. A.
Goddard, Phys. Rev. Lett. 99, 185003 (2007)], which explicitly takes the
excitation of electrons into consideration. Non-equilibrium features associated
with the excitation of electrons are systematically investigated. We show that
chemical bonds in D molecules lead to a more complicated shock wave
structure near the shock front, compared with the results of classical
molecular dynamics simulation. Charge separation can bring about accumulation
of net charges on the large scale, instead of the formation of a localized
dipole layer, which might cause extra energy for the shock wave to propagate.
In addition, the simulations also display that molecular dissociation at the
shock front is the major factor corresponding to the "bump" structure in the
principal Hugoniot. These results could help to build a more realistic picture
of shock wave propagation in fuel materials commonly used in the inertial
confinement fusion
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