Coherence and time-frequency analysis of impulse voltage and current measurements

The aim of this paper is to point out the advantages of the use of the time-frequency analysis in the digital processing of waveforms recorded in high voltage impulse tests. Impulse voltage tests are essential to inspect and test insulation integrity of high voltage apparatus. On the other hand, generated impulse currents are used for different test applications such as investigation of high current effects, electromagnetic interference (EMI) testing, etc. Obtained voltage and current waveforms usually have some sort of interferences originated from the different sources. These interferences have to be removed from the original impulse data in order to evaluate the waveform characteristics precisely. When the interference level is high enough, it might not be possible to distinguish signal parameters from the recorded data. Conventional filtering methods cannot be useful for some interference like white noise. In that case, time-frequency filtering methods might be necessary. In this study, the wavelet analysis, which is a powerful time-frequency signal processing tool, is used to recognize the noise of impulse current and voltage data. Thus, the noise sources can be determined by short time Fourier Transform, and a coherence approach is used to determine the bandwidth of noises

Coherence and time-frequency analysis of impulse voltage and current measurements

The aim of this paper is to point out the advantages of the use of the time-frequency analysis in the digital processing of waveforms recorded in high voltage impulse tests. Impulse voltage tests are essential to inspect and test insulation integrity of high voltage apparatus. On the other hand, generated impulse currents are used for different test applications such as investigation of high current effects, electromagnetic interference (EMI) testing, etc. Obtained voltage and current waveforms usually have some sort of interferences originated from the different sources. These interferences have to be removed from the original impulse data in order to evaluate the waveform characteristics precisely. When the interference level is high enough, it might not be possible to distinguish signal parameters from the recorded data. Conventional filtering methods cannot be useful for some interference like white noise. In that case, time-frequency filtering methods might be necessary. In this study, the wavelet analysis, which is a powerful time-frequency signal processing tool, is used to recognize the noise of impulse current and voltage data. Thus, the noise sources can be determined by short time Fourier Transform, and a coherence approach is used to determine the bandwidth of noises

The Relationshıp Between Pre-Service Class Teachers' Self-Efficacy in Mathematical Literacy and Their Attitudes towards Mathematics

Teachers' perceptions of self-efficacy in mathematical literacy and their attitudes are influential in the development of cognitive and affective skills of students during the educational process. The research aims to examine the relationship between pre-service class teachers' self-efficacy in mathematical literacy and their attitudes towards math and to determine the relationship between them. The research was designed in relational screening model. The sample of the research is composed of 274 pre-service class teachers who were determined purposefully. Non-parametric analyzes were used because the scores were not normally distributed during the analysis phase of the data. In conclusion of the researchclass teachers' self-efficacy in mathematical literacy and their attitudes towards math were found to be at a medium level. There was a significant difference between self-efficacy in mathematical literacy and attitude towards mathematics and grade level, and no significant difference was found between gender and academic average. There was a high positive and significant relationship between self-efficacy in mathematical literacy and attitude towards mathematics. Keywords: Class teacher, Mathematics Education, Mathematical Literacy, Self-efficacy, Attitud

A wide-range model for surge arresters : verification analysis

This paper verifies and analyzes the proposed wide range (WR) model for surge arresters. The verification analysis of various surge arrester models is performed; 1) on the model itself independent of power systems, and 2) by considering that surge arrester models are connected to a simple power transmission system. In order to accurately verify the performance of the WR model, some of the well-known surge arrester models are utilized. Simulation results reveal the advantages of the new model compared to traditional models already available in the literature

One-year prevalence and the impact of migraine and tension-type headache in Turkey: a nationwide home-based study in adults

Several studies have shown that the prevalence of migraine and tension-type headache (TTH) varied between different geographical regions. Therefore, there is a need of a nationwide prevalence study for headache in our country, located between Asia and Europe. This nationwide study was designed to estimate the 1-year prevalence of migraine and TTH and analyse the clinical features, the impact as well as the demographic and socio-economic characteristics of the participant households in Turkey. We planned to investigate 6,000 representative households in 21 cities of Turkey; and a total of 5,323 households (response rate of 89%) aged between 18 and 65 years were examined for headache by 33 trained physicians at home on the basis of the diagnostic criteria of the second edition of the International Classification of Headache Disorders (ICHD-II). The electronically registered questionnaire was based on the headache features, the associated symptoms, demographic and socio-economic situation and history. Of 5,323 participants (48.8% women; mean age 35.9 ± 12 years) 44.6% reported recurrent headaches during the last 1 year and 871 were diagnosed with migraine at a prevalence rate of 16.4% (8.5% in men and 24.6% in women), whereas only 270 were diagnosed with TTH at a prevalence rate of 5.1% (5.7% in men and 4.5% in women). The 1-year prevalence of probable migraine was 12.4% and probable TTH was 9.5% additionally. The rate of migraine with aura among migraineurs was 21.5%. The prevalence of migraine was highest among 35–40-year-old women while there were no differences in age groups among men and in TTH overall. More than 2/3 of migraineurs had ever consulted a physician whereas only 1/3 of patients with TTH had ever consulted a physician. For women, the migraine prevalence was higher among the ones with a lower income, while among men, it did not show any change by income. Migraine prevalence was lower in those with a lower educational status compared to those with a high educational status. Chronic daily headache was present in 3.3% and the prevalence of medication overuse headache was 2.1% in our population. There was an important impact of migraine with a monthly frequency of 5.9 ± 6, and an attack duration of 35.1 ± 72 h, but only 4.9% were on prophylactic treatment. The one-year prevalence of migraine estimated as 16.4% was similar or even higher than world-wide reported migraine prevalence figures and identical to a previous nation-wide study conducted in 1998, whereas the TTH prevalence was much lower using the same methodology with the ICHD-II criteria

A lecture to explain endocrine disrupting chemicals to the second class students of a medical faculty

Endocrine-disrupting chemicals are the chemicals exposed at the outside, which alter the function of the endocrine system or cause adverse health effects in healthy people and in their children. These chemicals are taken mostly from plastics, detergents, pesticides, insecticides and dyes. The bisphenol A and phthalates used in the plastic, the heavy metals taken by food, respiratory, skin and transplacental ways to the human body, dioxins and several chemicals as determined in the United States, the EPA's (Environmental Protection Agency) are emphasized for their endocrine-disrupting effects. The use of Bisphenol A in polibikarbonat material of infants and children is prohibited in Turkey and the European Union. Endocrine disrupting chemicals cause mostly endometriosis, precocious puberty, nervous system disruption, immune system impairment and cancers. EPA screening program focuses on measuring estrogen, testosterone and thyroid hormones (thyroxine and triiodothyronine) for the prevention of endocrine-disrupting chemicals, and gives importance to environmental monitoring. (C) 2015 The Authors. Published by Elsevier Ltd

THE SIGNIFICANCE OF FOOD ANALYSIS IN PUBLIC HEALTH

Food poisoning is the most commonly seen acute problem among the health problems caused by foods

Nitroxide radicals appended to phthalonitriles: synthesis, structural characterization and photo-physical properties

PubMed: 33664164The syntheses of 4-[4-(4,4,5,5-tetramethyl-2-imidazoline-3-oxide-1-oxyl-2-yl)phenoxy]phthalonitrile (3, C21H19N4O3) and 4-[4-(4,4,5,5-tetramethyl-2-imidazoline-1-oxyl-2-yl)phenoxy]phthalonitrile (4) were carried out by microwaveassisted nucleophilic aromatic substitution of 4-nitrophthalonitrile (2) by the pre-formed 2-(4-hydroxyphenyl)-4,4,5,5-tetramethyl-2- imidazoline-3-oxide-1oxyl (1). Compounds 3 and 4 were characterized unambiguously by a rich array of analyses, such as melting point, FT-IR, MALDI-TOF MS, elemental analysis, UV-Vis, CV, EPR, magnetic measurements and single-crystal X-ray diffraction. Structural studies demonstrate that the C-H center dot center dot center dot X and C-X center dot center dot center dot(X = O and N) interactions in the radical nitronyl nitroxide groups play an important role in the assembly of the crystal structures. Moreover, cyclic voltammetry analyses show that the phthalonitrile substituent retains the redox properties of the Ullman radicals