223,579 research outputs found
A proposed case for the cloud software engineering in security
This paper presents Cloud Software Engineering in Security (CSES) proposal that combines the benefits from each of good software engineering process and security. While other literature does not provide a proposal for Cloud security as yet, we use Business Process Modeling Notation (BPMN) to illustrate the concept of CSES from its design, implementation and test phases. BPMN can be used to raise alarm for protecting Cloud security in a real case scenario in real-time. Results from BPMN simulations show that a long execution time of 60 hours is required to protect real-time security of 2 petabytes (PB). When data is not in use, BPMN simulations show that the execution time for all data security rapidly falls off. We demonstrate a proposal to deal with Cloud security and aim to improve its current performance for Big Data
Высшее образование в Китае и России: сходство и отличие
В статье дана сравнительная характеристика высшего образования в странах Китай и Россия.The article gives a comparative description of higher education in China and Russia
Local Density of States and Level Width for Wannier-Stark Ladders
The local density of states \rho(x,E) is calculated for a Bloch electron in
an electric field. Depending on the system size, we can see one or more
sequences of Wannier-Stark ladders in \rho(x,E), with Lorentz type level widths
and apparent spatial localization of the states. Our model is a chain of delta
function potential barriers plus a step-like electric potential, with open
boundary condition at both ends of the system. Using a wave tunneling picture,
we find that the level widths shrink to zero as an inverse power as the system
size approaches infinity, confirming an earlier result.Comment: 14 pages, plain TeX, 9 figures not included, available on request, to
be published in Phys.Rev.B4
Gas-grain chemistry in cold interstellar cloud cores with a microscopic Monte Carlo approach to surface chemistry
AIM: We have recently developed a microscopic Monte Carlo approach to study
surface chemistry on interstellar grains and the morphology of ice mantles. The
method is designed to eliminate the problems inherent in the rate-equation
formalism to surface chemistry. Here we report the first use of this method in
a chemical model of cold interstellar cloud cores that includes both gas-phase
and surface chemistry. The surface chemical network consists of a small number
of diffusive reactions that can produce molecular oxygen, water, carbon
dioxide, formaldehyde, methanol and assorted radicals. METHOD: The simulation
is started by running a gas-phase model including accretion onto grains but no
surface chemistry or evaporation. The starting surface consists of either flat
or rough olivine. We introduce the surface chemistry of the three species H, O
and CO in an iterative manner using our stochastic technique. Under the
conditions of the simulation, only atomic hydrogen can evaporate to a
significant extent. Although it has little effect on other gas-phase species,
the evaporation of atomic hydrogen changes its gas-phase abundance, which in
turn changes the flux of atomic hydrogen onto grains. The effect on the surface
chemistry is treated until convergence occurs. We neglect all non-thermal
desorptive processes. RESULTS: We determine the mantle abundances of assorted
molecules as a function of time through 2x10^5 yr. Our method also allows
determination of the abundance of each molecule in specific monolayers. The
mantle results can be compared with observations of water, carbon dioxide,
carbon monoxide, and methanol ices in the sources W33A and Elias 16. Other than
a slight underproduction of mantle CO, our results are in very good agreement
with observations.Comment: 13 pages, 7 figures, to be published in A. &
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