Super Twisting Sliding-Mode Control of DVR With Frequency-Adaptive Brockett Oscillator

This paper presents a super twisting sliding mode control (ST-SMC) for single-phase dynamic voltage restorers (DVRs). Unlike the conventional first-order sliding mode controller, the proposed ST-SMC technique eliminates the need for differentiating the compensation voltage in the sliding surface function while keeping the merits of first-order SMC. As a consequence of employing ST-SMC, a continuous control signal is achieved from which the pulse width modulation (PWM) signals can be generated. In this case, the inverter operates at constant switching frequency. The stability analysis of ST-SMC is also presented. The reference compensation voltage needed in ST-SMC is estimated by using Brockett oscillator based frequency-locked loop. Theoretical considerations are verified through experimental results under ideal and distorted grid voltage conditions. The obtained results show that the ST-SMC has good dynamic performance and can maintain the load voltage at desired level under voltage sag, swell and harmonically distorted grid voltages

Effects of medium range order on propagon thermal conductivity in amorphous silicon

We discuss the dependence of the propagon contribution to thermal conductivity on the medium range order (MRO) in amorphous silicon. Three different amorphous structures with the same size of 3.28 nm were studied. Among these three structures, two structures were constructed with experimentally observed MRO [Treacy and Borisenko, Science. 335, 6071 (2012)] and the other structure is from continuous random network (CRN), which lacks MRO and thus represents a randomized amorphous structure [Barkema and Mousseau, Physical Review B, 62, 8 (2000)]. Using the simulated fluctuation electron microscopy and dihedral angle distribution, we confirm that the first two structures contain MRO in the length scale of 10-20 Å while the CRN structure does not. The transport of propagons in the MRO and CRN structures are compared using the dynamic structural factor calculation and normal mode decomposition of the molecular dynamics simulation data, showing noticeably longer lifetime of propagons in the MRO structures than in the CRN structure. The propagon thermal conductivity in the MRO structures is estimated 50% larger than that in the CRN structure

Knowledge and attitude of dormitory students of Shahid Beheshti University of medical sciences about substance abuse in 2013

The increase in substance abuse among youths and its complications form one of the most pressing health problems among students as an important and vulnerable group in society. The purpose of this study is to assess the knowledge and attitude of dormitory students of Shahid Beheshti University of medical sciences  regarding substance abuse in 2013. This is a descriptive-analytic cross sectional study carried out on dormitory students of Shahid Beheshti University of medical sciences   regarding substance abuse in 2013. 604 male and female students living in the dormitories were selected via random sampling. Data were collected using a questionnaire developed by the researcher based on the questionnaire used by Dehghan, and on a review of relevant literature and expert opinion obtained from professors of the field. Data were analyzed by SPSS16 using descriptive and analytical tests (Pearson correlation, T-test and chi-square). The mean score of knowledge of dormitory students at Shahid Beheshti University of Medical Sciences was 9.86±2.13. Most students (65.6%) had moderate knowledge about drugs. The subjects' mean score on attitude was 61.99±10.10. Most students (58.3%) had moderate positive attitudes towards drugs. Students are considered as major assets of a country. Therefore, planning and developing intervention strategies to prevent and reduce substance abuse among university students is essential and plays a major role in improving their health.

A New Topology for Z-Source Inverter Based on Switched-Inductor and Boost Z-Source Inverter

In this paper, a new topology for boost Z-source inverterbased on switched-inductor cell is proposed. The operating modes of the proposed inverter are analyzed and also a suitable control method to generate the trigger signals of the inverter is presented. Having a common earth between the input source and inverter and capability to generate a higher voltage gain by using lower amounts of the duty cycles are some advantages of the proposed Z-source inverter. Comparison of the proposed inverter with conventional Z-source inverters is presented from different points of the view. Finally, the accuracy performance of the proposed inverter is reconfirmed through the simulation results in EMTDC/PSCAD software program

Subchronic effects of different doses of Zinc oxide nanoparticle on reproductive organs of female rats: An experimental study

Background: Zinc performs many biochemical and physiological functions; however, toxicological studies demonstrate that Nano-zinc oxide has harmful effects on human health and environmental species in high concentrations. Objective: The aim of this study was to investigate the toxicity of zinc oxide nanoparticles on reproductive tissues of female rat. Materials and Methods: Eighty female Wistar adult rats weighing 180–200 gr, divided into eight groups (n= 10 in each group) including control, sham (treated with saline), and six groups injected with different doses of zinc oxide nanoparticle with 10–30 nanometer size (4, 8, 25, 50, 100, and 200 mg/kg) twice a week for four weeks. At the end of the study, the rats were bled and slaughtered; the Ovary and Uterus were taken for histopathology studies and blood samples were transferred to the laboratory for biochemical analysis. Results: Microscopic diagnoses in ovary tissue were included; increase in the corpus luteum, follicular cysts, inflammatory cells infiltration and fibrosis. Histopathological changes in ovary in a dose-dependent manner. In uterus tissue the lesions consisted; epithelial destruction, hyperplasia of endometrial glands. The Estrogen and Progesterone level in the serum of rats increased in low doses and reduced in a dose-dependent manner at high doses. Conclusion: The results of the current study proved the toxicity of zinc oxide nanoparticles on the ovary and uterus organs at high concentrations, so further investigation is needed to reduce these effects. Key words: Zinc oxide, Nanoparticles, Ovary, Uterus, Toxicity

Study the status of job stress and work-related stressors among the employees of a Spinning industry

Background and Aims: Job stress is one of the most important professional issues that poses high costs on organizations. It may result in reducing efficiency, feeling fatigue, which subsequently leads to employee dissatisfaction in him/her workplace. This study was designed to assess the employees’ job stress in a Spinningindustry.Materials and Methods: The present cross-sectional descriptive-analytic study was performed on 230 workers at a spinning industry. The standard job stress questionnaire of England HSE Institute was used to determine job stress. The employees were requested permission and their answers were treated as strictly confidential. The obtained data were analyzed by SPSS (version19), using descriptive statistics and Spearman & Pearson correlation coefficient, independent t-test, Kruskal-Wallis, ANOVA and Mann-Whitney Tests.Results: Statistically meaningful relationship (p >0.05) was observed between job stress and education level, the more education the less job stress. Age factors and working units indeed showed a similar relationship. There was only limited and not statistically significant (p>0.05) evidence for an increased job stress and sex, marital status, as well as job experience. The current study further found that the different job opportunities have high stress for 29.2 % employees, average stress for 69.5% employees and low stress for 1.3%.Conclusion: Considering the harmful physical and emotional responses of job stress, managing and controlling¬ of work-related stressors is recommended. This may worked out through identifying resources to significantly reduce the stress level and increase productivity in the workplace.Key words: Job Stress, Questionnaire, HSE, Mental Health, Spinning Industry Employee

The Study of Knowledge, attitude and practice towards physical activity and its Related Factorsof College Students Living on Campus in Shahid Beheshti University of medical science

Regular physical activity has a positive effect on physical, mental, and social aspects of individual and community health. Regarding prevalence of non-communicable diseases such as primary hypertension, osteoporosis, and cardiovascular diseases that sedentary is responsible for them; health policy makers plan to encourage people to do more physical activity. In this study, knowledge, attitude and practice towards physical activity and its related factors of students living on campus at Shahid Beheshti university of medical science were determined.In this descriptive analytic survey, 665 individuals college students living on campus at Shahid Beheshti university of medical science were selected by clustering sampling method. Data collected using  questionnaires and analyzed by SPSS16 software.54.9% of the subjects were female and 45.1% male. Mean age of participants was 21.82 years for female and 22.76 years for male. Mean scores of knowledge was 73±1.72 for male and 78.90 ±1.66 for female. In addition mean scores of attitude was 79.18 for male and 74.33 for female and mean scores of practice was 228.78 minute per week for male and 174.41minute per week for female.Results indicated that students had no optimal practice towards physical activity. Thus, more attention is necessary to be paid by authorities to this specific topic and some measures are essential in training students

Perceived social support, depression, and perceived stress in university students

      Psychological disorders are universally common problems. Social support contributes much to the health of individuals. Focusing upon social support and upon vicissitudes of life can help prevent the depression-induced disorders. The present paper investigated the relationship between perceived social support, depression and perceived stress in university students.The descriptive-analytical study was carried out on 390 students living in Shahid Beheshti University of Medical Sceince campus, whom were selected based on a simple random selection method. The related questionnaires of multidimensional scales of perceived social support, Beck’s depression, and perceived stress then were distributed during midterm among students to collect the necessary data. Data was fed into SPSS 16 and analysed using ANOVA, Pearson correlation coefficient, independent t-test, Chi-square, and Fisher exact test.Our results indicated that 49.7 per cent of students suffered from specific degrees of depression. 30.5 per cent of students had given educational progress and employment as sources of stress in living in the campus. The perceived social support scores were 28.32±9.56, depression, 12.10±9.02, and for perceived stress was 26.84±8.27. A significant relationship was shown to be between perceived social support, depression, and perceived stress (p<0.001) The conclusion made in the paper is that considering depression and stress is crucial to the health of the students. Also, forming workgroups to increase social support for students can help alleviates depression and stress in university students

بررسى وضعيت استرس شغلى و عوامل استر سزاى مرتبط با كار بين كاركنان شاغل در يكى از كارخانجات ريسندگى كشور

Background and Aims: Job stress is one of the most important professional issues that poses high costs on organizations. It may result in reducing efficiency, feeling fatigue, which subsequently leads to employee dissatisfaction in him/her workplace. This study was designed to assess the employees’ job stress in a Spinningindustry.Materials and Methods: The present cross-sectional descriptive-analytic study was performed on 230 workers at a spinning industry. The standard job stress questionnaire of England HSE Institute was used to determine job stress. The employees were requested permission and their answers were treated as strictly confidential. The obtained data were analyzed by SPSS (version19), using descriptive statistics and Spearman & Pearson correlation coefficient, independent t-test, Kruskal-Wallis, ANOVA and Mann-Whitney Tests.Results: Statistically meaningful relationship (p >0.05) was observed between job stress and education level, the more education the less job stress. Age factors and working units indeed showed a similar relationship. There was only limited and not statistically significant (p>0.05) evidence for an increased job stress and sex, marital status, as well as job experience. The current study further found that the different job opportunities have high stress for 29.2 % employees, average stress for 69.5% employees and low stress for 1.3%.Conclusion: Considering the harmful physical and emotional responses of job stress, managing and controlling¬ of work-related stressors is recommended. This may worked out through identifying resources to significantly reduce the stress level and increase productivity in the workplace.زمينه و هدف: استرس شغلی یکی از مهمترین مشکلات حرفه‌ای است که هزینه چشمگیری را به سازمان‌ها اعمال می‌کند به طوری که در کارکنان باعث کاهش بازده کاری، احساس خستگی و متعاقباً نارضایتی کارکنان صنعت می‌شود. لذا مطالعه حاضر با هدف بررسی ميزان استرس شغلی کارکنان در یک شرکت ریسندگی انجام شد. مواد و روش‌ها: این مطالعه توصیفی-تحلیلی، بصورت مقطعی روی دویست و سی نفر از کارکنان شاغل در یک شرکت ریسندگی انجام شد. جهت تعیین استرس شغلی از پرسشنامه استرس شغلی HSE انگلستان استفاده گردید. از تمام کارکنان رضایت آگاهانه گرفته شد و پاسخ‌های آنان محرمانه باقی ماند. تجزیه و تحلیل داده‌ها با استفاده از نرم افزار SPSS نسخه نوزده با محاسبه آمار توصیفی و آزمون‌های ضریب همبستگی اسپیرمن، T-Test، Kruskal-Wallis، ANOVA و Mann-Whitney انجام شد. يافته‌ها: از نظر آماری ارتباط معناداری بین استرس شغلی با متغیرهای سن، تحصیلات و واحدهای کاری مشاهده گردید (05/0>p)، بین متغیر استرس شغلی با متغیرهای جنس، تاهل و سابقه شغلی ارتباط آماری معناداری دیده نشد (05/0<p). یافته‌های این مطالعه نشان داد  که 20/29 درصد کارکنان از استرس زیاد، 50/69 درصد از استرس متوسط و تنها 30/1 درصد افراد از استرس کم برخوردار بودند. نتيجه گيري: با توجه به اثرات زیان آور استرس شغلی در کارکنان صنایع ریسندگی، با مدیریت و کنترل استرس شغلی از طریق شناسایی منابع و کنترل آنها، می‌توان به میزان قابل توجهی از میزان استرس در محیط‌های شغلی کاهش داد و بهره وری و تولید در محیط کار را افزایش داد. &nbsp