فهرست مطالب m parniani

Early childhood caries is one of the most common health problems, and numerous factors play a role in its onset and progression. Investigating these factors and providing timely training for parents can play an important role in controlling the disease. The present study aimed at determining the prevalence of early childhood caries and its related factors in children aged 3-6 years in Kohgiluyeh and Boyer-Ahmad province in 2019.

In the present cross-sectional descriptive-analytical, 565 children aged 3 to 6 years from kindergartens and preschool centers in the cities of Yasuj, Dehdasht and Gachsaran located at Kohgiluyeh and Boyer-Ahmad province, Iran, were selected and included in the study using a multi-stage cluster random sampling method. The caries diagnosis was done by 3 dental students (one dentist in each city). Collecting demographic data and factors related to premature dental caries was done using a checklist. The collected data were analyzed using Chi-square statistical tests and logistic regression.

Mean age of children was 5.03± 0.94. Out of 565 children, 306(54.2%) were boy and 259(45.8%) were girl. 75% of children had early childhood dental caries. Mean of dmft was 5.13 ± 3.69. There was a statistically significant relationship between early childhood dental caries and employment status of mothers (p<0.0001), and fathers (p<0.0001). Early childhood dental caries was less frequent in children whose mothers were housewives and more frequent in children with unemployed fathers. There was correspondingly a significant relationship between early childhood dental caries and the onset of brushing in a child (p = 0.001), doing or not failing to do fluoride therapy (p = 0.0001), frequency of feeding with sweets between meals (p = 0.04), the time of the first dental visit (p = 0.002), and mothers’ education (p = 0.01). In logistic regression analysis, it was indicated that the father’s age (OR = 1.12, CI95% OR = 1.04-1.24, p=0.003), fluoride therapy status (OR = 4.26, CI95% OR = 1.97-9.18, p=0.0001), and dmft (OR = 2.05, CI95% OR = 1.76-2.4, p=0.0001) were predictors of early childhood dental caries.

Considering the high prevalence of early childhood caries in children aged 3-6 years, conducting educational interventions to increase parents' awareness of how to prevent early childhood carries, including the use of fluoride varnish, toothpaste containing fluoride, the correct way to brush teeth under the supervision of parents, counseling Diet, proper feeding of the child and avoiding excessive feeding of the child during the night and the first dental visit of the child are necessary.

Excitation Controlled Synchronous Generator-based Wind Turbine (ECSG WT) is a recently proposed wind turbine scheme which has not been fully investigated in detail. This paper is devoted to analyze performance of the ECSG WT scheme and to compare it with two mainstream wind turbine schemes based on electrically excited synchronous generator, i.e. VSC-based full converter wind turbine and diode bridge rectifier-based wind turbine equipped with boost converter on its DC link. The aim of this comparison is to demonstrate great potentials of ECSG WT for being considered in wind industry. To do so, two successful WT schemes at the market which are structurally close to ECSG WT are selected. The comparison includes different technical and economic aspects of the three schemes, assuming DC grid connection for the wind turbines. In addition, another comparison is made between the recently introduced Siemens 2nd generation DC Grid Access Offshore wind farm and a wind farm with similar structure, but using ECSG WTs. The results of these comparisons declare that ECSG WT scheme has promising characteristics, especially regarding economic, reliability and efficiency aspects.

Balancing between demand and supply of grids is the most important task of the power systems operators and control systems. Otherwise, the possibility of frequency instability and severe damages to equipment are present. Primary frequency control (PFC) is the first and main control action in the grid in front of the active power imbalance disturbances. In this paper, the effects of the spinning reserve characteristics and the grid dynamic parameters, on PFC performance and maximum frequency decline (frequency nadir), are investigated. Then, a comprehensive equation is presented to determine the maximum frequency deviation after a large power imbalance in the grid. This equation considers all effective factors such as volume and speed of the primary frequency reserve (PFR), grid inertia constant, grid load level, and the frequency-dependent loads. The correctness of the presented equation is verified through different simulations. Finally, a comprehensive scheme is proposed for the primary frequency control reserve allocation in the grid, in the form of a few equations and instructions.