101,045 research outputs found
Competent genetic-evolutionary optimization of water distribution systems
A genetic algorithm has been applied to the optimal design and rehabilitation of a water distribution system. Many of the previous applications have been limited to small water distribution systems, where the computer time used for solving the problem has been relatively small. In order to apply genetic and evolutionary optimization technique to a large-scale water distribution system, this paper employs one of competent genetic-evolutionary algorithms - a messy genetic algorithm to enhance the efficiency of an optimization procedure. A maximum flexibility is ensured by the formulation of a string and solution representation scheme, a fitness definition, and the integration of a well-developed hydraulic network solver that facilitate the application of a genetic algorithm to the optimization of a water distribution system. Two benchmark problems of water pipeline design and a real water distribution system are presented to demonstrate the application of the improved technique. The results obtained show that the number of the design trials required by the messy genetic algorithm is consistently fewer than the other genetic algorithms
Level sequence and splitting identification of closely-spaced energy levels by angle-resolved analysis of the fluorescence light
The angular distribution and linear polarization of the fluorescence light
following the resonant photoexcitation is investigated within the framework of
the density matrix and second-order perturbation theory. Emphasis has been
placed on "signatures" for determining the level sequence and splitting of
intermediate (partially) overlapping resonances, if analyzed as a function of
the photon energy of the incident light. Detailed computations within the
multiconfiguration Dirac-Fock method have been performed especially for the
photoexcitation and subsequent fluorescence emission of atomic sodium. A
remarkably strong dependence of the angular distribution and linear
polarization of the fluorescence emission is found upon the level
sequence and splitting of the intermediate overlapping resonances owing to their finite lifetime
(linewidth). We therefore suggest that accurate measurements of the angular
distribution and linear polarization might help identify the sequence and small
splittings of closely-spaced energy levels, even if they can not be
spectroscopically resolved.Comment: 9 pages, 7 figure
Authorization and access control of application data in Workflow systems
Workflow Management Systems (WfMSs) are used to support the modeling and coordinated execution of business processes within an organization or across organizational boundaries. Although some research efforts have addressed requirements for authorization and access control for workflow systems, little attention has been paid to the requirements as they apply to application data accessed or managed by WfMSs. In this paper, we discuss key access control requirements for application data in workflow applications using examples from the healthcare domain, introduce a classification of application data used in workflow systems by analyzing their sources, and then propose a comprehensive data authorization and access control mechanism for WfMSs. This involves four aspects: role, task, process instance-based user group, and data content. For implementation, a predicate-based access control method is used. We believe that the proposed model is applicable to workflow applications and WfMSs with diverse access control requirements
Theory of the Magnetic Moment in Iron Pnictides
We show that the combined effects of spin-orbit, monoclinic distortion, and
p-d hybridization in tetrahedrally coordinated Fe in LaOFeAs invalidates the
naive Hund's rule filling of the Fe d-levels. The two highest occupied levels
have one electron each but as a result of the p-d hybridization have very
different on-site repulsions. As a result, electrons in the upper level are
more itinerant while those in the lower level are more localized. It is the
xy-projection of the spin in the lower level that orders antiferromagnetically
as the z-components of the spins in the two levels is shown to be vanishingly
small in the ground state. The resulting magnetic moment is highly anisotropic
with an in-plane value of per Fe and a z-projection of
, both of which are in agreement with experiment. As a consequence,
we arrive the minimal model that describes the electronic properties of
LaOFeAs.Comment: Published Versio
Aqua MODIS Electronic Crosstalk on SMWIR Bands 20 to 26
Aqua MODIS Moon images obtained with bands 20 to 26 (3.66 - 4.55 and 1.36 -
1.39 m) during scheduled lunar events show evidence of electronic
crosstalk contamination of the response of detector 1. In this work, we
determined the sending bands for each receiving band. We found that the
contaminating signal originates, in all cases, from the detector 10 of the
corresponding sending band and that the signals registered by the receiving and
sending detectors are always read out in immediate sequence. We used the lunar
images to derive the crosstalk coefficients, which were then applied in the
correction of electronic crosstalk striping artifacts present in L1B images,
successfully restoring product quality.Comment: Accepted to be published in the IEEE 2017 International Geoscience &
Remote Sensing Symposium (IGARSS 2017), scheduled for July 23-28, 2017 in
Fort Worth, Texas, US
Making new connections towards cooperation in the prisoner's dilemma game
Evolution of cooperation in the prisoner's dilemma game is studied where
initially all players are linked via a regular graph, having four neighbors
each. Simultaneously with the strategy evolution, players are allowed to make
new connections and thus permanently extend their neighborhoods, provided they
have been successful in passing their strategy to the opponents. We show that
this simple coevolutionary rule shifts the survival barrier of cooperators
towards high temptations to defect and results in highly heterogeneous
interaction networks with an exponential fit best characterizing their degree
distributions. In particular, there exist an optimal maximal degree for the
promotion of cooperation, warranting the best exchange of information between
influential players.Comment: 6 two-column pages, 7 figures; accepted for publication in
Europhysics Letter
X-ray Polarization Signatures of Compton Scattering in Magnetic Cataclysmic Variables
Compton scattering within the accretion column of magnetic cataclysmic
variables (mCVs) can induce a net polarization in the X-ray emission. We
investigate this process using Monte Carlo simulations and find that
significant polarization can arise as a result of the stratified flow structure
in the shock-ionized column. We find that the degree of linear polarization can
reach levels up to ~8% for systems with high accretion rates and low
white-dwarf masses, when viewed at large inclination angles with respect to the
accretion column axis. These levels are substantially higher than previously
predicted estimates using an accretion column model with uniform density and
temperature. We also find that for systems with a relatively low-mass white
dwarf accreting at a high accretion rate, the polarization properties may be
insensitive to the magnetic field, since most of the scattering occurs at the
base of the accretion column where the density structure is determined mainly
by bremsstrahlung cooling instead of cyclotron cooling.Comment: 7 pages, 8 figures, accepted by MNRA
Field study on adaptive thermal comfort in typical air conditioned classrooms
This study investigates adaptive thermal comfort in air conditioned classrooms in Hong Kong. A field survey was conducted in several typical classrooms at the City University of Hong Kong. This survey covered objective measurement of thermal environment parameters and subjective human thermal responses. A total of 982 student volunteers participated in the investigation. The results indicate that students in light clothing (0.42 clo) have adapted to the cooler classroom environments. The neutral temperature is very close to the preferred temperature of approximately 24 °C. Based on the MTSV ranging between −0.5 and + 0.5, the comfort range is between 21.56 °C and 26.75 °C. The lower limit is below that of the ASHRAE standard. Of the predicted mean vote (PMV) and the University of California, Berkeley (UCB) model, the UCB model predictions agree better with the mean thermal sensation vote (MTSV). Also, the respective fit regression models of the MTSV versus each of the following: operative temperature (Top), PMV, and UCB were obtained. This study provides a better understanding of acceptable classroom temperatures
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