844 research outputs found
Complex Agent Networks explaining the HIV epidemic among homosexual men in Amsterdam
Simulating the evolution of the Human Immunodeficiency Virus (HIV) epidemic
requires a detailed description of the population network, especially for small
populations in which individuals can be represented in detail and accuracy. In
this paper, we introduce the concept of a Complex Agent Network(CAN) to model
the HIV epidemics by combining agent-based modelling and complex networks, in
which agents represent individuals that have sexual interactions. The
applicability of CANs is demonstrated by constructing and executing a detailed
HIV epidemic model for men who have sex with men (MSM) in Amsterdam, including
a distinction between steady and casual relationships. We focus on MSM contacts
because they play an important role in HIV epidemics and have been tracked in
Amsterdam for a long time. Our experiments show good correspondence between the
historical data of the Amsterdam cohort and the simulation results.Comment: 21 pages, 4 figures, Mathematics and Computers in Simulation, added
reference
Optomechanical preparation of photon number-squeezed states with a pair of thermal reservoirs of opposite temperatures
Photon number-squeezed states are of significant value in fundamental quantum
research and have a wide range of applications in quantum metrology. Most of
their preparation mechanisms require precise control of quantum dynamics and
are less tolerant to dissipation. We propose a mechanism that is not subject to
these restraints. In contrast to common approaches, we exploit the
self-balancing between two types of dissipation induced by positive- and
negative-temperature reservoirs to generate steady states with sub-Poissonian
statistical distributions of photon numbers. We also show how to implement this
mechanism with cavity optomechanical systems. The quality of the prepared
photon number-squeezed state is estimated by our theoretical model combined
with realistic parameters for various typical optomechanical systems.Comment: 10 pages, 3 figures, 90 referances
Quantum tunneling time of a Bose-Einstein condensate traversing through a laser-induced potential barrier
We theoretically study the effect of atomic nonlinearity on the tunneling
time in the case of an atomic Bose-Einstein condensate (BEC) traversing the
laser-induced potential barrier. The atomic nonlinearity is controlled to
appear only in the region of the barrier by employing the Feshbach resonance
technique to tune interatomic interaction in the tunneling process. Numerical
simulation shows that the atomic nonlinear effect dramatically changes the
tunneling behavior of the BEC matter wave packet, and results in the violation
of Hartman effect and the occurrence of negative tunneling time.Comment: 4 pages, 5 figure
Fabrication of Nanostructured Electroforming Copper Layer by Means of an Ultrasonic-assisted Mechanical Treatment
AbstractElectroformed copper layer with nanostructure is obtained using a subsequent mechanical treatment under the conditions of ultrasonic vibration according to the demand of high performance material in aeronautics. The microstructure of the electroformed copper layer is observed by optical microscope (OM), scanning electron microscope (SEM) and transmission electron microscope (TEM). The tensile strength is evaluated with a tensile tester. It is found that bulk crystal of electroformed copper's surface layer is changed to nanocrystals (about 10 nm in size) after the ultrasonic-assisted mechanical treatment (UMT) but the whole monocrystalline structure still remains. The tensile strength exhibited by the new copper layer is two times better than the regular electroformed copper layer, while the fracture strain remains constant. In addition, the strengthening mechanism of UMT process is proved to be dislocation strengthening mechanism
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