732 research outputs found

    Modeling of Power Losses Caused by Hidden Tree-Related High Impedance Faults

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    The great majority of overhead distribution systems in urban and rural areas of countries such as Australia, Iran and etc., are in interfering with vegetation. This phenomena leads to high impedance faults (HIFs) which not produce enough fault current to be detectable and consequently causes electrical energy losses. In this paper, according to experimental data obtained from measurements, the effective factors in power losses caused by trees are studied and a new numerical model of power loss is presented so as to reflect the effects of environmental conditions and biological classification. The base of this method is according to Samuelson theory. In proposed algorithm, the impacts of species, short-term environmental conditions (temperature and humidity) and long-term environmental conditions (Seasonal variations in physiology) on the power loss estimation are fully considered. Experimental investigations on a real low voltage (380 V) and medium voltage (20 kV) distribution network verify the algorithm\u27s operation

    Experimental And Theoretical Study Of The Substitution Mechanism In The W6+: Litao3 Correlated With The Ferroelectric Properties

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    The purpose of the present work is to report the latest results of our experimental and theoretical non-stoichiometry investigations of solid solutions isolated close to LiTaO3 inside the ternary system Li2O-Ta2O5-(WO3)2 correlated with the ferroelectrics transitions. Dielectric measurements performed on ceramic samples have shown that ferro-paraelectric temperatures transitions TC varied along the solids solutions, as the stoichiometry deviates from LiTaO3. A Safaryan’s theory of ferroelectric transition and the various vacancy models in this work reproduce well the experimental results by explaining the substitution nature of Tungsten hexavalent (W6+) in LiTaO3.The purpose of the present work is to report the latest results of our experimental and theoretical non-stoichiometry investigations of solid solutions isolated close to LiTaO3 inside the ternary system Li2O-Ta2O5-(WO3)2 correlated with the ferroelectrics transitions. Dielectric measurements performed on ceramic samples have shown that ferro-paraelectric temperatures transitions TC varied along the solids solutions, as the stoichiometry deviates from LiTaO3. A Safaryan’s theory of ferroelectric transition and the various vacancy models in this work reproduce well the experimental results by explaining the substitution nature of Tungsten hexavalent (W6+) in LiTaO3

    On the Wang-Landau Method for Off-Lattice Simulations in the "Uniform" Ensemble

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    We present a rigorous derivation for off-lattice implementations of the so-called "random-walk" algorithm recently introduced by Wang and Landau [PRL 86, 2050 (2001)]. Originally developed for discrete systems, the algorithm samples configurations according to their inverse density of states using Monte-Carlo moves; the estimate for the density of states is refined at each simulation step and is ultimately used to calculate thermodynamic properties. We present an implementation for atomic systems based on a rigorous separation of kinetic and configurational contributions to the density of states. By constructing a "uniform" ensemble for configurational degrees of freedom--in which all potential energies, volumes, and numbers of particles are equally probable--we establish a framework for the correct implementation of simulation acceptance criteria and calculation of thermodynamic averages in the continuum case. To demonstrate the generality of our approach, we perform sample calculations for the Lennard-Jones fluid using two implementation variants and in both cases find good agreement with established literature values for the vapor-liquid coexistence locus.Comment: 21 pages, 4 figure

    The impact of variability and distribution of practice on student’s learning of basketball throw skill

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    Purpose: The practice organization is an important factor in sports environment and education. This study aimed to investigate the impact of variability and distribution of practice on basketball throw skill learning among female elementary school students. Material: Based on the pre-test scores of 15 attempts (5 throw from any distances of 3, 3.5, and 4 meters), 90 volunteer participants were distributed in 6 homogeneous groups of 15 participants (three massed practice groups and three distributed practice groups with blocked, increasing, and decreasing practice arrangements). In acquisition stage, the participants practiced for 9 sessions. After 72 hours, all participants conducted the retention test. Changing the angle at a distance of 3.5 meters, the transfer test was conducted at the same day. Results: The findings showed that the variability and distribution of practice did not impact on participants’ performance in acquisition, retention, and transfer stages. Conclusions: For development of contextual interference effect, the variability in parameters of a motor program is not enough

    Serum level of interleukin-6 in patients with oral tongue squamous cell carcinoma

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    Introduction: The clinical outcome of patients with squamous cell carcinoma (SCC) located in the head and neck has remained poor despite ongoing advances in diagnosis and management. Interleukin-6(IL-6) is a multi-functional cytokine that plays an important role in the process of cell differentiation and is increased in several malignancies. The aim of this study was to investigate the serum levels of interleukin-6 in patients with oral tongue SCC. Materials and Methods: In a cross-sectional study, 17 patients with oral tongue SCC were compared with the same number of age- and gender-matched healthy subjects. Serum IL-6 level fluctuation was determined using an immunological technique, before detecting its possible association with the subjects' age, gender, drinking and smoking history, cancer site, and disease severity. Results: The intensity of serum IL-6 in patients with oral tongue SCC was statistically significantly higher than that in healthy subjects (P<0.001). Serum IL-6 level was independent of the patients' age, gender, smoking and drinking history as well as cancer stage. Conclusion: IL-6 is a valuable biomarker in the diagnosis of oral tongue SCC. Its high sensitivity makes prediction of this condition possible, while this biomarker can also be used to screen high-risk patients
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