28,766 research outputs found
Structuring and sampling complex conformation space: Weighted ensemble dynamics simulations
Based on multiple simulation trajectories, which started from dispersively
selected initial conformations, the weighted ensemble dynamics method is
designed to robustly and systematically explore the hierarchical structure of
complex conformational space through the spectral analysis of the
variance-covariance matrix of trajectory-mapped vectors. Non-degenerate ground
state of the matrix directly predicts the ergodicity of simulation data. The
ground state could be adopted as statistical weights of trajectories to
correctly reconstruct the equilibrium properties, even though each trajectory
only explores part of the conformational space. Otherwise, the degree of
degeneracy simply gives the number of meta-stable states of the system under
the time scale of individual trajectory. Manipulation on the eigenvectors leads
to the classification of trajectories into non-transition ones within the
states and transition ones between them. The transition states may also be
predicted without a priori knowledge of the system. We demonstrate the
application of the general method both to the system with a one-dimensional
glassy potential and with the one of alanine dipeptide in explicit solvent.Comment: 13 pages, 7 figures. Phys Rev E 2009 (in press
Energy-Efficient Antenna Selection and Power Allocation for Large-Scale Multiple Antenna Systems with Hybrid Energy Supply
The combination of energy harvesting and large-scale multiple antenna
technologies provides a promising solution for improving the energy efficiency
(EE) by exploiting renewable energy sources and reducing the transmission power
per user and per antenna. However, the introduction of energy harvesting
capabilities into large-scale multiple antenna systems poses many new
challenges for energy-efficient system design due to the intermittent
characteristics of renewable energy sources and limited battery capacity.
Furthermore, the total manufacture cost and the sum power of a large number of
radio frequency (RF) chains can not be ignored, and it would be impractical to
use all the antennas for transmission. In this paper, we propose an
energy-efficient antenna selection and power allocation algorithm to maximize
the EE subject to the constraint of user's quality of service (QoS). An
iterative offline optimization algorithm is proposed to solve the non-convex EE
optimization problem by exploiting the properties of nonlinear fractional
programming. The relationships among maximum EE, selected antenna number,
battery capacity, and EE-SE tradeoff are analyzed and verified through computer
simulations.Comment: IEEE Globecom 2014 Selected Areas in Communications Symposium-Green
Communications and Computing Trac
The silicate model and carbon rich model of CoRoT-7b, Kepler-9d and Kepler-10b
Possible bulk compositions of the super-Earth exoplanets, CoRoT-7b,
Kepler-9d, and Kepler-10b are investigated by applying a commonly used silicate
and a non-standard carbon model. Their internal structures are deduced using
the suitable equation of state of the materials. The degeneracy problems of
their compositions can be partly overcome, based on the fact that all three
planets are extremely close to their host stars. By analyzing the numerical
results, we conclude: 1) The iron core of CoRoT-7b is not more than 27% of its
total mass within 1 mass-radius error bars, so an Earth-like
composition is less likely, but its carbon rich model can be compatible with an
Earth-like core/mantle mass fraction; 2) Kepler-10b is more likely with a
Mercury-like composition, its old age implies that its high iron content may be
a result of strong solar wind or giant impact; 3) the transiting-only
super-Earth Kepler-9d is also discussed. Combining its possible composition
with the formation theory, we can place some constraints on its mass and bulk
composition.Comment: 20 pages, 8figures, accepted for publication in RAA. arXiv admin
note: text overlap with arXiv:0707.289
- …