oalib

Publish in OALib Journal

ISSN: 2333-9721

APC: Only $99

Submit

Any time

2019 ( 3 )

2018 ( 10 )

2017 ( 13 )

2016 ( 11 )

Custom range...

Search Results: 1 - 10 of 1587 matches for " Saber Mohammadi "
All listed articles are free for downloading (OA Articles)
Page 1 /1587
Display every page Item
Pyroelectric Energy Harvesting: With Thermodynamic-Based Cycles
Saber Mohammadi,Akram Khodayari
Smart Materials Research , 2012, DOI: 10.1155/2012/160956
Abstract: This work deals with energy harvesting from temperature variations using ferroelectric materials as a microgenerator. The previous researches show that direct pyroelectric energy harvesting is not effective, whereas thermodynamic-based cycles give higher energy. Also, at different temperatures some thermodynamic cycles exhibit different behaviours. In this paper pyroelectric energy harvesting using Lenoir and Ericsson thermodynamic cycles has been studied numerically and the two cycles were compared with each other. The material used is the PMN-25?PT single crystal that is a very interesting material in the framework of energy harvesting and sensor applications. 1. Introduction Small, portable, and lightweight power generation systems are currently in very high demand in commercial markets, due to a dramatic increase in the use of personal electronics and communication equipments. The simple way to satisfy these demands is to utilize batteries; however, nonrechargeable batteries are becoming useless upon discharging, and rechargeable batteries require portable power generation units to recharge them. Thus, a portable small-scale power generation system that can either replace batteries entirely or recharge them to extend their lifetime is of considerable interest. There are several different classes of small-scale power generators currently being researched. The power generation technique that is investigated in this study is the thermodielectric power generation system, which is somewhat similar to thermoelectric power generation [1]. Some possible ambient energy sources are thermal energy, solar energy, or mechanical energy. Harvesting energy from such renewable sources has stimulated important research efforts over the past years [2–5]. Thermal energy is a source available everywhere. Also, electronics advances directed the researchers towards completely autonomous microchips embedding their own energy source. Furthermore, proposing self-powered devices opens new application possibilities for the systems with limited accessibility such as biomedical implants, structure embedded microsensors, or safety monitoring devices. Thermodielectric power generation utilizes the pyroelectric effect to convert heat to useful electricity. Pyroelectricity has been observed in different crystals and ceramics [6]. Materials with high pyroelectric activity or those exhibiting a transition can be used for energy harvesting [7, 8]. The pyroelectric effect may be used for temperature/heat sensors or energy harvesting; on the contrary the electrocaloric effect may be used
Damping Analyses of Structural Vibrations and Shunted Piezoelectric Transducers
Saber Mohammadi,Akram Khodayari
Smart Materials Research , 2012, DOI: 10.1155/2012/431790
Abstract: Piezoelectric transducers in conjunction with appropriate electric networks can be used as a mechanical energy dissipation device. Alternatively, undesired mechanical energy of a structure could be converted into electrical energy that can be dissipated through a shunt network in the form of Joule heating. This paper presents an experimental method to calculate damping energy in mechanical systems. However, the mathematical description of damping mechanism is much more complicated, and any process responsible for the occurrence of damping is very intricate. Structural and piezoelectric damping are calculated and analysed in the case of pulse switching or SSDI semiactive vibration control technique. This technique which was developed in the field of piezoelectric damping consists in triggering the inverting switch on each extremum of the piezoelectric voltage which induces an increase of the electromechanical energy conversion. 1. Introduction Vibration damping is one of the manifestations of mechanical energy dissipation related to motion in mechanical systems. Damping processes have been studied for a long time. Damping forces are small compared to the other interactions in a mechanical system and yet their mathematical description remains much more complicated. Actually, any process responsible for the occurrence of damping is very intricate and the knowledge of it is insufficient. Sometimes just changing the system’s stiffness or mass to alter the resonance frequencies can reduce the unwanted vibration as long as the excitation frequencies do not change. But in most cases, the vibrations need to be dissipated using damping materials or devices that are tuneable with vibration. Several methods have been investigated in case of vibration damping. These methods have the forms of passive, semiactive, and active treatments which can be used for sound/vibration cancellation. Active control involves the use of active elements (actuators) along with sensors and controllers (analogue or digital) to produce an out-of-phase actuation to cancel the disturbance causing the noise/vibration [1]. All other methods that do not include a real-time active algorithm can be grouped under the passive control option. Passive damping refers to energy dissipation within the structure by add-on damping devices. Viscous dampers (dashpots), viscoelastic damping, tuned-mass dampers, dynamic absorbers, and shunted piezoelectric dampers are the mechanisms of passive vibration control. The most common types of passive damping treatments of viscoelastic materials were described by
Interaction of smoking and occupational noise exposure on hearing loss: a cross-sectional study
Gholamreza Pouryaghoub, Ramin Mehrdad, Saber Mohammadi
BMC Public Health , 2007, DOI: 10.1186/1471-2458-7-137
Abstract: A cross-sectional study was designed to study the effect of smoking on NIHL in 206 male smoker workers and 206 male non-smoker workers in a large food-producing factory, in which workers were exposed to noise levels exceeding 85dBA. To determine noise exposure level, we used sound level measurements reported by industrial hygienists.A qualified audiologist assessed hearing acuity by using standardized audiometric procedures assuring at least 14 h of noise avoidance.We observed that the percentage of workers with hearing threshold differences of greater than or equal to 30 dB between 4000 Hz and 1000 Hz in both ears were 49.5% and 11.2% in smoker and non smoker groups, respectively (Odds ratio = 7.8, 95% CI = 4.7 – 13), and the percentage of workers with a hearing threshold of greater than 25dB at 4000 Hz in the better ear were 63.6% and 18.4% in smoker and non smoker groups, respectively. This difference was statistically significant after adjustment for age and exposure duration.It can be concluded that smoking can accelerate noise induced hearing loss, but more research is needed to understand the underlying mechanisms. Accurate follow up of smoker workers who are exposed to noise levels exceeding 85 dBA is suggested. Smokers should periodically attend educational courses on "smoking cessation", especially in noisy workplaces.Noise is the most pervasive hazardous agent at workplaces [1,2]. Approximately 30 million American workers are exposed to hazardous noise on their jobs [3,4], and it is estimated that approximately 600 million workers are exposed to occupational noise worldwide [5].Generally, NIHL (Noise- Induced Hearing loss) is a sensorineural hearing deficit which begins at higher frequencies (3,000 to 6,000 Hz) and develops gradually as a result of chronic exposure to excessive sound levels [6]. The mechanism by which the sensory cells are lost is probably a combination of physical and metabolic stress. There are large number of studies that suggest the p
Induction of programmed cell death by Prangos uloptera, a medicinal plant
ZAHRI,SABER; RAZAVI,SEYED MEHDI; NIRI,FARSHAD HASSANZADEH; MOHAMMADI,SARIEH;
Biological Research , 2009, DOI: 10.4067/S0716-97602009000400013
Abstract: inhibition of the cell growth or induction of cell death is the most promising area in cancer therapy. the induction of apoptosis by dichloromethane extract of prangos uloptera was evaluated on the mccoy cell line. this plant's roots, aerial parts and fruit have medicinal value. cell growth inhibitory and cell cytotoxicity effects of the extract were assayed by mtt and trypan-blue tests, respectively. morphological changes and dna fragmentation were also evaluated. the viability tests showed 0.49 and 0.3 mg/ml as 50% inhibition concentration and 50% cytotoxicity concentration after 24 hours of treatment, respectively. fluorescent microscopy analysis revealed chromatin fragmentation and scanning electron microscopy showed cell shrinkage and cytoplasmic blebbing. these findings were confirmed by dna fragmentation analysis. the results demonstrated efficient induction of apoptosis by the plant extract in moderate concentrations, but administration of higher concentrations showed that the primary manner of cell death was necrosis.
FAAS DETERMINATION OF THALLIUM AFTER PRECONCENTRATION USING NITROSO-S AND TDBA ONTO BENZOPHENONE
Mohammad Ali Taher*, Sayed Ziae Mohammadi Mobarakeh, Fatameh Saber Mahani
Bulletin of the Chemical Society of Ethiopia , 2005,
Abstract: Thallium is quantitatively retained by 2-nitroso-1-naphthol-4-sulfonic acid (nitroso-S) and tetradecyldimethylbenzylammonium chloride (TDBA) onto benzophenone in the pH range 10.0-11.5 from large volumes of aqueous solutions of various samples. After filtration, each solid mass consisting of thallium complex and benzophenone is dissolved with 5 mL of dimethylformamide and the metal was determined by flame atomic absorption spectrophotometry (FAAS). Eight replicate determinations of 10.0 mg/mL of thallium in final dimethylformamide (DMF) solution gave a mean absorbance of 0.150 with a relative standard deviation of 1.9%. The sensitivity for 1% absorption was 0.293 mg/mL. The method of extraction and preconcentration is economical, rapid, sensitive, highly selective and satisfactory. The interference of a number of anions and cations has been studied and the optimized conditions developed were utilized for the trace determination of thallium in various samples. KEY WORDS: Flame atomic absorption spectrophotometry, Thallium determination, Nitroso-S, Tetradecyldimethylbenzylammonium chloride (TDBA), Benzophenone Bull. Chem. Soc. Ethiop. 2005, 19(1), 17-22.
Induction of programmed cell death by Prangos uloptera, a medicinal plant
SABER ZAHRI,SEYED MEHDI RAZAVI,FARSHAD HASSANZADEH NIRI,SARIEH MOHAMMADI
Biological Research , 2009,
Abstract: Inhibition of the cell growth or induction of cell death is the most promising area in cancer therapy. The induction of apoptosis by dichloromethane extract of Prangos uloptera was evaluated on the McCoy cell line. This plant's roots, aerial parts and fruit have medicinal value. Cell growth inhibitory and cell cytotoxicity effects of the extract were assayed by MTT and Trypan-blue tests, respectively. Morphological changes and DNA fragmentation were also evaluated. The viability tests showed 0.49 and 0.3 mg/ml as 50% inhibition concentration and 50% cytotoxicity concentration after 24 hours of treatment, respectively. Fluorescent microscopy analysis revealed chromatin fragmentation and scanning electron microscopy showed cell shrinkage and cytoplasmic blebbing. These findings were confirmed by DNA fragmentation analysis. The results demonstrated efficient induction of apoptosis by the plant extract in moderate concentrations, but administration of higher concentrations showed that the primary manner of cell death was necrosis.
Knowledge and Practice Assessment of Workers in a Pharmaceutical Company about Prevention of Coronary Artery Disease
Mirsaeed Attarchi,Saber Mohammadi,Marzieh Nojomi,Yasser Labbafinejad
Acta Medica Iranica , 2012,
Abstract: Coronary artery disease is one of the most common reasons of death around the world. Also, according to previous studies, the incidence of coronary artery disease is rapidly increasing in developing countries such as Iran. The aim of this study was to evaluate the knowledge and practice of pharmaceutical company workers towards the prevention of cardiovascular disease. In this cross sectional study that was conducted in Tehran, 1223 workers of a pharmaceutical company were enrolled. Data was collected using a questionnaire that assessed the level of knowledge and practice of the participants towards coronary artery disease. Regression analysis was used to evaluate the relationship between study variables and the workers knowledge level. The results of this study showed that 49% of the workers were in a good level of knowledge and according to the regression analysis, the female gender, age above 28, education level higher than high school diploma, body mass index above 25 kilograms per square meters, history of hyperlipidemia, history of diabetes, history of hypertension, history of myocardial infarction, daily activity and exercise, were significantly related to a good knowledge towards coronary artery disease. In addition, the mean score of the participants' performance in preventing coronary artery disease was 4.66 out of 9. The results of this study showed that increasing level of knowledge of labors in order to prevent missing specialized work force, leads to imposition of health costs to the industry and the labor society.
Effect of Contemporary Exposure to Mixed Organic Solvents and Occupational Noise on Hearing Thresholds of Workers
Mohammadi Saber,Labbafinejad Yaser,Amiri Rigi Azadeh,Attarchi Mir Saeid
Zahedan Journal of Research in Medical Sciences , 2010,
Abstract: Background: Mixed organic solvent exposure, as well as noise, has a wide spread in different industries. In recent years it has been propounded that simultaneous exposure to mixed organic solvents and occupational noise can establish a hearing loss that is more severe than hearing loss due to exposure to each of them separately.Materials & Methods: A descriptive- analytic study was conducted during 2008 in an automobile industry on 441 employees in three different groups. First group were assembly workers that only exposed to noise. The second group included employees in new painting saloon that exposed not only to noise but also to permissible levels of mixed organic solvents and the third group were employees in old painting saloon that exposed to noise and mixed organic solvents in more than threshold limit value (TLV) level. The prevalence of hearing loss was compared between three groups on the basis of model 1 (mean hearing threshold in frequencies 0.5, 1 and 2 KHz more than 25dB) and model 2 (mean hearing threshold in frequencies 3, 4, 6 and 8 KHz more than 25dB). Results: According to model 2, in workers exposed to noise in addition to mixed organic solvents, the rate of hearing loss, was significantly higher than workers exposed to noise alone (P<0.05), even after adjusting for confounding variables using logistic regression analysis (OR= 4.12 , P<0.001).Conclusion: In workers with simultaneous exposure to mixed organic solvents and noise, special attention must be paid to accurate accomplishment of hearing conservation programs including doing audiometric exams in shorter periods and take advantage of hearing protection devices with higher noise reduction rate (NRR).
FAAS determination of thallium after preconcentration using nitroso-S and TDBA onto benzophenone
Mohammad Ali Taher,Sayed Ziae Mohammadi Mobarakeh,Fatameh Saber Mahani
Bulletin of the Chemical Society of Ethiopia , 2005,
Abstract: Thallium is quantitatively retained by 2-nitroso-1-naphthol-4-sulfonic acid (nitroso-S) and tetradecyldimethylbenzylammonium chloride (TDBA) onto benzophenone in the pH range 10.0-11.5 from large volumes of aqueous solutions of various samples. After filtration, each solid mass consisting of thallium complex and benzophenone is dissolved with 5 mL of dimethylformamide and the metal was determined by flame atomic absorption spectrophotometry (FAAS). Eight replicate determinations of 10.0 μg/mL of thallium in final dimethylformamide (DMF) solution gave a mean absorbance of 0.150 with a relative standard deviation of 1.9%. The sensitivity for 1% absorption was 0.293 μg/mL. The method of extraction and preconcentration is economical, rapid, sensitive, highly selective and satisfactory. The interference of a number of anions and cations has been studied and the optimized conditions developed were utilized for the trace determination of thallium in various samples.
"Assessment Of Knowledge And Satifaction Of Information Given In Cancer Patients Referred To Imam Khomeini Hospital 1382-1383 And Itss Assossiation With Anxiety and Depression In These Patients "
G. Tarighat Saber,S. Zarei.,A. Etemadi,MR. Mohammadi G. Shams
Tehran University Medical Journal , 2006,
Abstract: Background and Aim: Anxiety is the most common psychological distress in cancer patients. Many studies have been conducted to assess the prevalence of anxiety and depression and the predisposing factors of psychological morbidity in cancr patients. Patients knowledge of disease, their desire for more information, their satisfaction of given information and their attitudes’ towards communication of information about cancer are among issues that have not been well anddressed in assessment of psychological morbidity of cancer patients in Iran. Materials and Methods: 250 cancer patients of 15-75 age group who were referred to Cancer Institute entered the study. The patients’ knowledge of disease, their desire for more information, their attitude and satisfaction were assessed by Questionnaire n1. patients’ anxiety and depression scores were assessed by Hospital Anxiety and Depression Scale (HADS). Results: 30 of patients had severe anxiety symptoms and 17% suffered severe depression most patients’ knowledge of disease was “low” (32%) and “intermediate” (54%). There was no significant correlation between knowledge and anxiety and depression. Most patients (69%) believed that the information given by physicians had been “insufficient”. Depression score was significantly higher in this group of patients compared to other patients. Most patients (59%) had a high level of desire for gaining more information and 64% believed that physicians should inform patients of different aspects of disease as much as possible. There was no significant correlation between patients’ desire and attitude and anxiety and depression. Level of satisfaction was “low” in 29% of patients and “intermediate” in 39%. Depression and anxiety scores were significantly higher in patients who were less satisfied with given information. Conclusion: Low level of knowledge in most cancer patients, their high desire for gaining more information, their dissatisfaction of given information and their positive attitudes towards full disclosure of information about cancer in this study, all indicate that complete and honest disclosure of information to cancer patients by physicians should be improved and encouraged. Although it seems that amount of information given doesn’t influence the psychological morbidity in cancer patients; the patients’ satisfaction of given information, which has implications for the quality of patient-physician communication, plays a far more important role in occurance of psychological morbidity in cancer patients. Meanwhile, negative public opinion of cancer and its progno
Page 1 /1587
Display every page Item


Home
Copyright © 2008-2017 Open Access Library. All rights reserved.