883 research outputs found

    A Study of the Impact of Squirrel-Cage Rotor Faults on the Stator Current Signature

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    The present paper considers the impact of the degree of damage to a squirrel-cage rotor of an induction motor on the spectrum of the stator current. The study is based on the motor current signature analysis. Performed, for this purpose, were scientific experiments on eight samples of squirrel-cage rotors, seven of which with pre-inflicted faults using Dynamic Motor Analyser. The obtained results are herein presented in graphical and tabular form and are further compared with the ones acquired from an induction motor with an intact rotor winding. It can be clearly ascertained that the larger the number of damaged rotor bars, the more significant the increase in the current amplitude as correspondent to the side band amplitude

    Online System for Monitoring and Analysis of the Operation of a Small Photovoltaic Plant

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    This article proposes an integrated system for monitoring and analysis of the operation of a small photovoltaic plant with the possibility of remote access via the Internet. The system has been built on the territory of Varna Technical University and is based on a mini computer Raspberry Pi 3B + using a Linux operating system. The monitoring is performed by keeping track of the environmental parameters and the input-output parameters of the photovoltaic inverter. Data are presented for a period of three months: October 1, 2020 to December 31, 2020. The results are visualized by appropriate graphs, demonstrating the change in the observed indicators, both for the entire specified period and for a randomly selected day

    Experimental Study of the Characteristic of a PEM Reversible Fuel Cell

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    Renewable energy sources are the proper way to protect and preserve the natural resources of the only planet we inhabit. The fuel cell is an interesting solution in the field of renewable energy sources. These devices convert the chemical energy from hydrogen and oxygen into electrical and thermal energy.  The present paper, therefore, focuses exclusively on their ability to generate electricity, their energy efficiency, quiet mode of operation, and environmental compatibility.  The polymer electrolyte membrane fuel cell coverts the energy at high density of power. The weight and cost of this cells are lower than the other kind of fuel cell. A reversible proton exchange membrane fuel cell is a kind of PEM fuel cell. It can operate in two modes - fuel cell mode and electrolyzer mode. Presented in the current paper are the experimental studies conducted into the operation of the fuel cell in electrolyzer and fuel cell mode. The relevant parameters and characteristics obtained from experiments are analyzed in relation to the mode of operation

    Linguistic Validation and Cultural Adaptation of Bulgarian Version of Hospital Survey on Patient Safety Culture (HSOPSC)

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    BACKGROUND: Patient safety (PS) is one of the essential elements of health care quality and a priority of healthcare systems in most countries. Thus the creation of validated instruments and the implementation of systems that measure patient safety are considered to be of great importance worldwide.AIM: The present paper aims to illustrate the process of linguistic validation, cross-cultural verification and adaptation of the Bulgarian version of the Hospital Survey on Patient Safety Culture (B-HSOPSC) and its test-retest reliability.METHODS: The study design is cross-sectional. The HSOPSC questionnaire consists of 42 questions, grouped in 12 different subscales that measure patient safety culture. Internal con­sistency was assessed using Cronbachñ€ℱs alpha. The Wilcoxon signed-rank test and the split-half method were used; the Spear­man-Brown coefficient was calculated.RESULTS: The overall Cronbachñ€ℱs alpha for B-HSOPSC is 0.918. Subscales 7 Staffing and 12 Overall perceptions of safety had the lowest coefficients. The high reliability of the instrument was confirmed by the Split-half method (0.97) and ICC-coefficient (0.95).  The lowest values of Spearmen-Broun coefficients were found in items A13 and A14.CONCLUSION: The study offers an analysis of the results of the linguistic validation of the B-HSOPSC and its test-retest reliability. The psychometric characteristics of the questions revealed good validity and reliability, except two questions. In the future, the instrument will be administered to the target population in the main study so that the psychometric properties of the instrument can be verified

    Measurement of the top quark forward-backward production asymmetry and the anomalous chromoelectric and chromomagnetic moments in pp collisions at √s = 13 TeV

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    Abstract The parton-level top quark (t) forward-backward asymmetry and the anomalous chromoelectric (d̂ t) and chromomagnetic (Ό̂ t) moments have been measured using LHC pp collisions at a center-of-mass energy of 13 TeV, collected in the CMS detector in a data sample corresponding to an integrated luminosity of 35.9 fb−1. The linearized variable AFB(1) is used to approximate the asymmetry. Candidate t t ÂŻ events decaying to a muon or electron and jets in final states with low and high Lorentz boosts are selected and reconstructed using a fit of the kinematic distributions of the decay products to those expected for t t ÂŻ final states. The values found for the parameters are AFB(1)=0.048−0.087+0.095(stat)−0.029+0.020(syst),Ό̂t=−0.024−0.009+0.013(stat)−0.011+0.016(syst), and a limit is placed on the magnitude of | d̂ t| < 0.03 at 95% confidence level. [Figure not available: see fulltext.

    Measurement of t(t)over-bar normalised multi-differential cross sections in pp collisions at root s=13 TeV, and simultaneous determination of the strong coupling strength, top quark pole mass, and parton distribution functions