2,493 research outputs found
Robust Radio Interferometric Calibration Using the t-Distribution
A major stage of radio interferometric data processing is calibration or the
estimation of systematic errors in the data and the correction for such errors.
A stochastic error (noise) model is assumed, and in most cases, this underlying
model is assumed to be Gaussian. However, outliers in the data due to
interference or due to errors in the sky model would have adverse effects on
processing based on a Gaussian noise model. Most of the shortcomings of
calibration such as the loss in flux or coherence, and the appearance of
spurious sources, could be attributed to the deviations of the underlying noise
model. In this paper, we propose to improve the robustness of calibration by
using a noise model based on Student's t distribution. Student's t noise is a
special case of Gaussian noise when the variance is unknown. Unlike Gaussian
noise model based calibration, traditional least squares minimization would not
directly extend to a case when we have a Student's t noise model. Therefore, we
use a variant of the Expectation Maximization (EM) algorithm, called the
Expectation-Conditional Maximization Either (ECME) algorithm when we have a
Student's t noise model and use the Levenberg-Marquardt algorithm in the
maximization step. We give simulation results to show the robustness of the
proposed calibration method as opposed to traditional Gaussian noise model
based calibration, especially in preserving the flux of weaker sources that are
not included in the calibration model.Comment: MNRAS accepte
Design comparison of experimental storm water detention systems treating concentrated road runoff
The aim was to assess the treatment efficiencies of experimental storm water detention (extended
storage) systems based on the Atlantis Water Management Limited detention cells receiving concentrated
runoff that has been primary treated by filtration with different inert aggregates. Randomly collected gully
pot liquor was used in stead of road runoff. To test for a 'worst case scenario', the experimental system
received higher volumes and pollutant concentrations in comparison to real detention systems under real
(frequently longer but diluted) runoff events. Gravel (6 and 20 mm), sand (1.5 mm), Ecosoil (inert 2 mm
aggregate provided by Atlantis Water Management Limited), block paving and turf were tested in terms of
their influence on the water quality. Concentrations of five-day @ 20� C ATU biochemical oxygen demand
(BOD) in contrast to suspended solids (SS) were frequently reduced to below international secondary
wastewater treatment standards. The denitrification process was not completed. This resulted in higher
outflow than inflow nitrate-nitrogen concentrations. An analysis of variance indicated that some systems
were similar in terms of most of their treatment performance variables including BOD and SS. It follows that
there is no advantage in using additional aggregates with high adsorption capacities in the primary treatment
stage
Perfect transfer of coherent state-based qubits via coupled cavities
Motivated by the need for communication of coherent state-based qubits in
quantum computers, we introduce a method for perfect transferring of an
arbitrary superposition of coherent states between two distant nodes of a
linear array of three semiconductor QDs. The QDs trapped in a system of coupled
cavities. In this method, the field mode of the cavities, as the resource of
transferring of quantum states, are only virtually excited which minimizes the
effect of decoherence due to photon loss.Comment: 10 pages, 3 figures. arXiv admin note: text overlap with
arXiv:quant-ph/0211055 by other author
Perfect routing of quantum information in regular cavity QED networks
We introduce a scheme for perfect routing of quantum states and entanglement
in regular cavity QED networks. The couplings between the cavities are
quasi-uniform and each cavity is doped with a two-level atom. Quasi-uniform
couplings leads the system to evolve in invariant subspaces. Combination the
evolutions of the system in its invariant subspaces with quite simple local
operations on atoms in the networks, gives the perfect routing of quantum
states and entanglement through the network. To provide the protocol be robust
due to decoherence arisen from photon loss, the field mode of the cavities are
only virtually excited
Redefinition of the genus Scarabacariphis Masan and new morphological data for S. geotrupes comb. nov. (Ishikawa) (Acari: Mesostigmata: Eviphididae)
International audienceHerein, Alliphis geotrupes Ishikawa, 1979 is transferred to the genus Scarabacariphis Masan, 1994 because of its free peritrematal shield (i.e. separated from the dorsal shield). The genus Scarabacariphis is redefined, and a key to the species of Scarabacariphis is provided, as well as additional morphological information for Scarabacariphis geotrupes comb. nov
Music and anxiety in hospitalized children
Purpose: Music is a method of stress reduction and could be used as a non-invasive therapeutic tool to relieve the pain and anxiety of patient. This study is designed to evaluate the role of music therapy on the level of anxiety in children aged 912 yearsold, in an academic hospital in Gorgan, northeast of Iran. Methods: Sixty hospitalized children were categorized into the intervention (case=30) and the control groups (N=30) by using a simple randomized method. The data gathering instruments were questionnaires which included demographic information and a trait anxiety inventory for children, the Spielberger test (STAIC). For the intervention group, for 2 days, 20 minutes (3 am-6 pm), the soothing rhythmic music of Johann Sebastian Bach was released through a tape recorder which was equipped with a headphone and then, the Spielberger questionnaires were refilled by each patient. The control group did not receive any intervention. Results: The results showed that the anxiety scores between the control and the intervention groups had no significant difference before the application of the music. The mean anxiety after the application of music in the control group was 49.4±7.2 and in the intervention group, it was 30.7±7.5. The results showed a significant difference between the mean anxiety in the control and the intervention groups (p<0.05). Conclusions: Our results showed that in hospitalized children, music therapy reduced the anxiety level
The comparison of under-5-year nutritional status among Fars-native, Turkman and Sistani ethnic groups in the north of Iran
Background: Under nutrition is a health problem in developing countries and the main aim of this study was determine of the nutritional status and some sociodemographic factors among rural under-5-year children in the North of Iran in 2013. Methods: This was a descriptive, cross-sectional study, which carried out on 2530 children (637 = Fars-native, 1002 = Turkman and 891 = Sistani) from 21 villages in the North of Iran. Villages were chosen by random sampling among 118, and all of under-five children were chosen by simple sampling. For all of cases, a questionnaire with contain questions on the socialdemographic condition was completed and anthropometric indexes were measured by a learned team. Anthropometric data were compared with those in Centers for Disease Control and Prevention reference population. SPSS 18.0 software was used for statistical data analysis and P value under 0.05 included significations. Results: Generally, under nutrition (Z-score ≤ −2) was observed in 6.6%, 18.5% and 3.3% based on underweight, stunting and wasting, respectively and there were in boys more than girls and in Sistani more than other ethnic groups. Based on underweight and stunting, under nutrition was seen in Sistani more than other ethnic groups. Among three ethnic groups, stunting was significant both in boys (P = 0.013) and in girls (P = 0.004), but wasting was significant only in girls (P = 0.001). The estimated odds ratio (OR) with 95% confidence interval of under nutrition was obtained from logistic regression. Compared with good economic group, the OR was 1.831 in poor economic groups (P = 0.001). The risk of under nutrition in Sistanish ethnic group was 1.754 times more than Fars-native group (P = 0.001). Conclusions: Under nutrition is a health problem among under-5-year children in rural area in the North of Iran and stunting was seen in an alarming rate among them. Among ethnic groups, Sistanish children more than others were under nourished. Poor economic status is a risk factor for under nutrition in this area. © 2015 Veghari G
Classification of the Structural Behavior of Tall Buildings with a Diagrid Structure: A Machine Learning-Based Approach
We study the relationship between the architectural form of tall buildings and their structural response to a conventional seismic load. A series of models are generated by varying the top and bottom plan geometries of the buildings, and a steel diagrid structure is mapped onto their skin. A supervised machine learning approach is then adopted to learn the features of the aforementioned relationship. Six different classifiers, namely k-nearest neighbour, support vector machine, decision tree, ensemble method, discriminant analysis, and naive Bayes, are adopted to this aim, targeting the structural response as the building drift, i.e., the lateral displacement at its top under the considered external excitation. By focusing on the classification of the structural response, it is shown that some classifiers, like, e.g., decision tree, k-nearest neighbour and the ensemble method, can learn well the structural behavior, and can therefore help design teams to select more efficient structural solutions
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