فهرست مطالب mohammadhosein beheshti

Accidents caused by children’s play equipment are considered a serious threat to children’s health. The aim of this study was to design slide, swing and see-saw based on national standards and children’s anthropometric data.

The present study is an applied research, in which the design of children’s play equipment, including slides, swing and see-saw was done according to national standards No. 6436-2, 6436-3 and 6436-6, as well as measuring the anthropometric dimensions. All anthropometric data of 385 children aged 2 to 12 years were measured and equipment design was performed using Minitab software.

In the national standards No. 6436-2, 6436-3 and 6436-6, the size of more dimensions required for the design of the slides, swing, and see-saw is not stated. In the present study, the ergonomic and standard design of these types of equipment is shown. Comparison of designed see-saw with see-saw available in parks showed that the length and width of the see-saw should be 0.37 and 0.25 meters, respectively. In the current study, however,  they were 0.24 and 0.35 meters, respectively. Also, the height, width and depth of the swing chair should be 0.2, 0.35 and 0.37 meters, while their actual size in the studied parks was 0.25, 0.42 and 0.31 meters, respectively.

The result of this study is helpful for standard and ergonomic designing of children’s play equipment and is very useful for urban planning. This study emphasizes the revision of national standards.

Noise pollution is a global problem causing changes in the secretion of various hormones and consequently affecting social well-being and quality of life in cities.

This study aimed to investigate the effect of noise pollution on the levels of testosterone, thyroid, and cortisol hormones in male rats.

In this experimental study, a total of 70 male Wistar rats (200 - 250 g) were randomly assigned into one control and six experimental groups, with 10 rats in each group. Experimental groups were exposed to noise with different intensity (dB) and time (min) as follows: (I) 60 dB, 30 min; (II) 60 dB, 60 min; (III) 85 dB, 30 min; (IV) 85 dB, 60 min; (V) 110 dB, 30 min; (VI) 110 dB, 60 min; (VII) controls. Animals in the experimental groups were exposed to noise in an acoustic chamber designed for this purpose for 50 days. The Noise.exe software was used to generate noise, and the sound level meter (model TES 1358) was used to determine the accuracy of the intensity and frequency of sound. To determine plasma levels of the hormones, appropriate research and commercial kits were used, which were based on the ELISA method. To determine the concentration of hormones other than TSH, human assay kits were used. All statistical tests were performed in SPSS software version 21.

Serum levels of cortisol in the 110-dB (30 and 60 min), 65-dB (60 min), and 85-dB (60 min) groups were significantly higher than the control group (P ≤ 0.05). Also, cortisol levels in the 65-dB and 85-dB (30 minutes) groups were higher than the control group; however, the increase was not significant (P > 0.05). The levels of T4, T3, and TSH in the 60-dB and 85-dB groups were significantly lower than in the control group (P ≤ 0.05). The serum levels of T4, T3, and TSH hormones in the 110-dB group were insignificantly lower than the control group (P > 0.05). The serum level of testosterone in the 110-dB group was significantly lower than the control group (P ≤ 0.05). The mean serum levels of testosterone in the 65-dB and 85-dB groups were insignificantly lower than the control group (P > 0.05).

Based on this study, exposure to noise pollution increased cortisol secretion and decreased T4, T3, TSH, and testosterone levels in rats. As this hormonal imbalance may create direct and indirect effects, studies and strategies are recommended to control the imbalance of hormones in the polluted environments.

The use of a mask is an effective measure to reduce the transmission of Covid-19. Today, due to the lack of N95 masks and medical masks with good performance, felt masks are widely used due to their ease of manufacture and low cost. The aim of this study was to determine the effectiveness of 3-layer felt masks containing polypropylene membranes in filtering particle size in the SARS-CoV-2 range.

In this study, a 3-layer felt mask was designed. For production, materials were selected that are currently available in the market and are used by manufacturers for the bulk production of the mask. Polypropylene fabric was used as the first and third layers of the outer part of the mask and the middle layer was made of felt with a pore size of about 400 nm. The efficiency of the mask in the filtration of particles of different sizes was measured according to BS EN149 standard at a flow rate of 30 liters per minute.

The efficiency of the felt mask for particle filtration with a size of 300 nm, which is approximately equal to the size of the SARS-CoV-2, is in the range of 11 to 25%. While the efficiency of the mask in the filtration of particles with a size of 500 nm is about 13 to 32%. The efficiency of this mask in filtering particles with a diameter of 10 microns increased by an average of 83%. The average efficiency of the mask in particle filtration with sizes of 0.3, 0.5, 1, 2.5, 5 and 10 micrometers is equal to 18, 22, 33, 50, 66 and 83%, respectively, and the average pressure drop is equal to 4 Pascal.

The findings of the present study showed that the use of a felt mask with such a design and structure to prevent Covid-19 is not effective enough and may even increase the prevalence of the disease by creating false confidence in individuals. Due to the widespread use of felt masks in the community, improving the filtration capability of this mask for particles smaller than 500 nm and also modifying the surface and structure of the mask by hydrophilizing polypropylene fibers inside the mask can play an important role in reducing the prevalence of Covid-19.

In humans, the reaction time limit is associated with several factors. It includes the time that takes to stimulate the sensory member, the stimulus effect is transmitted to the brain, then is perceived and the decision is made; consequently, the command resulting from the decision of the brain is sent from the brain to the functional member, and the member operates. Failure to respond at the right time may result in human error and the occurrence of incoming incidents. There are important factors that affect the reaction time. Attention is one of the important factors affecting the speed of the reaction. Selective attention and correct perception of several stimuli among the other stimuli is one of the effective factors in promoting productivity and safety. Additionally, various environmental factors may be effective in determining selective attention, increasing the number of errors and the human response time in detecting triggers. Environmental lighting is one of the factors affecting the processing mechanisms of the brain. In the design of indoor and outdoor lighting systems, the quality parameters of the lighting system are usually less considered. Color temperature is one of the most important qualitative parameters of light, which is measured by the Kelvin unit and is an indicator for the brightness and color of the light. The aim of this study was to investigate the effect of color of light temperature on selective attention, error rate and reaction time.

This research is an interventional and laboratory study in order to determine the effect of the color of light temperature on human error, selective attention, and reaction time of students in Tarbiat Modares University (TMU) of Tehran during the fall of 2018. All students were in the same age range. The inclusion criteria for the study were; not having any eye-related diseases, such as diminished vision and subtlety, and mental-psychiatric disorders. On the day before performing the test, individuals were urged to have enough sleep and rest, to adhere to a regular diet, and to avoid taking medicines, coffee and caffeinated drinks. In this interventional study, 92 students (36 female and 56 male) from Tarbiat Modarres University of Tehran with an average age of 28.33 years were recruited as subjects. The measurements and tests related to selective attention and reaction time of individuals were performed in 4 locations with an equal lighting system and different color temperatures (3500, 4000, 5000, or 6500 degrees Kelvin). In the first stage of the study, in order to determine the effect of the color of light temperature on the studied parameters, the participants were randomly divided into four groups with 24 subjects in each group. Before the main test was being performed, the subjects were kept in rooms adjusted to a brightness of 3500° K to rest for at least 5 minutes in order to be adapted to the situation, and then, in the same conditions, to become familiar with the test method they were studied with the Stroup software. In the second step, each group was placed in a separate room where the levels of brightness had been designed with one of the lighting systems to yield a color temperature of 3500, 4000, 5000, and 6500° K. Cognitive performance tests including reaction time, accuracy and selective attention were measured using Stroop tests. Measurement of interference score and interruption time, which are indicators of selective attention, were calculated by measuring the difference in the error rate and the reaction time in detecting incongruent and consonant words. Stroop test was used to determine the reaction time, error and other parameters. This test consists of two parts; the practice and the main test, each of which has 3 stages. The first step is to name the color in which circular shapes appears in green, blue and red colors and the participant, upon viewing the image, applies pressure on keyboard buttons which are labeled with colors corresponding to the ones on the screen. The second step is to name the word which appears in a white box. The names of the colors appear, and as soon as the correct word is recognized, the person being tested should press the color word associated to the word on the keyboard. The third step, which is the main stage of the test, is a non-consistent word (red-green-blue) shown randomly and sequentially on the monitor's screen. The subject must only press the keyboard button with the same color, only emphasizing the color and regardless of its connotation. In this test, 48 matching colored words (the color of the word is identical with the meaning of the word; red, yellow, green and blue) and 48 non-consistent colored words (the color of the word is not the same as the word meaning; for example, the blue word shown in red). The time lap between the stimulants was 800 milliseconds and the duration of each of them was 2000 milliseconds. The subject's task was to select the correct color only. Finally, the data were analyzed using SPSS software.

Based on the results of this study, the highest mean of correct selection (474.49 ± 10.65) and the lowest mean of the correct ones (654.49 ± 11.77) were assigned to the color temperature of 6500 and 3500 ° K, respectively. Also, the highest mean, the error (15.65 ± 9.77) and the lowest mean error (10.94 ± 9.4) were reported at a color temperature of 3500 and 6500 ° K, respectively. According to the results of this study, with an increase in the level of color temperature from 3500 to 5000° Kelvin, the number of questions that were not responded decreased. Likewise, the number of unanswered questions for the color temperature of 6500 °K slightly increased compared to the color temperature of 5000 and 4000 °K. The results also indicated that, with an increase in color temperature from 3500 to 6500 °K, the reaction time to visual stimuli also decreased. The highest interference score was in the light color temperature of 3500 °K which suggests that the number of faults in subjects in naming inconsistent words relative to consonant words at a color temperature of 3500° K was high compared to the other color temperatures. Also, according to Fig. 3, the maximum interference time at light color temperature is 6500 ° K. This suggests that the performance time of the subjects in naming incoherent words relative to consonants at a color temperature of 6,500° K compared to other color temperatures was more significant. Although the average response time under lighting condition with color temperature of 6500° K (718.95 ± 65.33) was less than the color temperature of 3500° K (728.58 ± 43.48), according to the results of the study, with a decrease in color temperature, the increase in mean response time was observed, but this difference was not significant (p <0.05). In the present study, we compared the mean of the studied variables (interference score, interference time, correct number, number of errors, unanswered items and response time) among classified groups tested under different lighting conditions with color temperatures (3000, 4000, 5000, and 6500 degrees Kelvin). One-way ANOVA was used for data analysis. Based on the results of Tukey's post-test, the mean of correct responses under lighting conditions with a color temperature of 6,500 ° K was significantly higher than the other color temperatures, and the average for the number of correct responses at the color temperature of 5000 was significantly higher than 3500 and 4000° K (p <0.05). The average light error rate with a color temperature of 6500 ° K was significantly lower than the mean error at color temperature of 3500 and 4000 ° K, and also the average error under lighting condition with a color temperature of 5000 K was significantly lower than 3500 and 4000 ° K. 0> p). Also, based on independent t-test (Table 2), there was a significant relationship between subjects’ gender and variables such as interference score, interruption time and number of unanswered questions. For all of these three variables (interference score, interruption time and number of unanswered questions) mean in men was significantly lower than women (p <0.05). Based on subjects’ gender, the average response time under different color temperatures showed that the response time (or reaction time) of female students under lighting conditions with 3000 and 5,000 ° K was higher than that of male students, while under lighting conditions with 4000 and 6500° K the response time of male students was higher than that of female students. Although the average response time under different color temperatures was different between male and female subjects, based on the results from independent t-test, such difference was not significant.

  In general, the results of the study showed that when subjects are exposed to a light color temperature of 6,500 ° K, the number of correct responses by them is higher than those exposed to other color temperatures, and with increasing the color temperature of the light source the number of correct answers increases. Also, according to the results of this study, the levels of error decrease by increasing color temperature of light source. Based on the results of this study, it is suggested to make use of light sources with a color temperature of 6,500 ° K in designing the lighting system of the places where human reaction time and error are of great importance. Accordingly, it is recommended to repeat this study in other demographic groups, as well as taking into account the qualitative parameters of the lighting system in addition to its quantitative parameters.

Accidents caused by children’s play equipment are a severe health threat to them. Implementing the requirements of the safety standards is necessary to ensure the safety of such equipment. The current study aimed to determine the general safety of playground equipment in general parks in Gonabad City, Iran. We also compared the level of the general safety of this equipment with national standards. 

This cross-sectional and analytical study was conducted in all the parks of Gonabad City during the autumn and winter of 2017. The required information on the playgrounds in the public parks of this city was collected by a checklist. The checklist was designed based on the general safety of playgrounds standards (national standard 1-6436) in 124 items. 

On average, 9.55 of standard requirements were not implemented in examined parks. Moreover, none of the studied parks fully complied with current standards. We observed fractures, cracks, or deformation in equipment, rough surfaces with the risk of injury, hazardous conditions due to inappropriate design that could harm children, as well as the lack of middle aggressors. These were non-compliant components observed at least 70% of the studied parks. 

Removing points with fracture and defective points, and improving the level of children’s playground is essential. The obtained data also emphasized the need for periodic safety audits and the improvement of the safety level of children’s playground equipment.

Sound is one of the most effective exogenous factors affecting human brain processing mechanisms and audio disturbance, which play a major role in human error and occupational accidents. The purpose of this study was to evaluate the effect of sound frequency on human noise annoyance. This research is an interventional study that was carried out on 60 students of Gonabad University of Medical Sciences in 2017 that 30 were female and 30 were male. Measurements and tests to determine the degree of noise annoyance was performed during exposure to sound at various frequencies of 500, 1000, 2000, 4000 and 8000 Hz. Sound.exe software was used to determine the sound with different frequencies and noise annoyance were determined based on the acoustic questionnaire “Acoustics -- Assessment of noise annoyance by means of social and socio-acoustic surveys” which is available in the ISO / TS 15666 standard. Data analysis was performed using SPSS.
The mean age of males was 21.12 years with a standard deviation of 0.13 and the mean age of females was 19.19 years with a standard deviation of 0.5. According to the results of this study, in female subjects, the maximum degree of noise annoyance is at 4000 Hz, and the frequency of previous and subsequent frequencies of 4000 Hz decreases the degree of noise annoyance. Also, in male subjects, the highest degree of noise annoyance is at 8000 Hz. And from 500 to 8000 Hz, the frequency of noise annoyance increases, respectively. The results of ANOVA test showed that there is a significant relationship between noise annoyances with different frequencies. The results of t - test showed that there is a significant difference between male and female dissonance. According to the results of the study, the highest degree of sound irritation is at 4000 and 8000 Hz. In this study, the gender variable as one of the factors affecting anxiety was studied Because of individual differences in overall sensitivity to sound and sound sensitivity with different frequencies, also because there are other environmental factors that may affect cognitive functions in addition to sound, it is suggested these factors investigate in future studies.
Keywords: noise, frequency noise, annoyance

Exposure to noise is an important safety and health problem in many industries. The rail transport industry is one of the industries involved with this problem due to the variety of equipment and its scope.  The present study aimed to evaluate noise pollution and determine the sources of noise at Mashhad railway station. In this descriptive-analytic study in 2014, the departments with noise pollution were identified and studied based on an initial assessment of all parts of the railway station. Noise was measured in ten departments and units. The environmental and local noise was measured by calibrated sound level meter Model CEL485 in A and C networks according to ISO9612 and ISO 11200 standards. Then the collected data entered and analyzed in Surfer V.10 and Excel software. The results of noise measurement showed that the average sound pressure level in units of Diesel GM, repair shop, refueling station, Diesel Siemens, and platform 3 was in hazard range. The results of measurement of the average sound pressure level in departments and units and the isosonic mappings drawn by Surfer V.10 software as well as the results of the average noise level in GM diesel showed that GM diesel (with LP=87.60 dB (A)) is the main source of noise at Mashhad railway station. The results of this study showed that diesel engines, gearboxes, moving trains, and beeps are the main noise generator components in GM diesel. The highest mean sound pressure level among these components was related to the diesel engine with an average sound pressure level of 87.60 dB (A). In general, the average sound pressure level of this diesel was 95.45 dB in the dominant frequency of 63 Hz. Based on the result of this study, GM diesel plays a major role in transporting at Mashhad railway station, accordingly the design and implementation of technical control measures such as chamber and enclosure of noise generator components are essential to reduce the average sound pressure level.

The purpose of this study was to assess the contrast perception of obstacles in a tunnel entrance which was placed in Ilam Province, Iran. An obstacle with the reflection coefficient of 20% was mounted at the entrance of thetunnel and then, the car was placed near the tunnel entrance and the intrinsic luminance of the road (Lr,intrinsic) and obstacle (Lo,intrinsic) were measured inside the car using the luminance meter. Intrinsic luminance of obstacle and road at the entrance of the tunnel were measured as 41 and 17 cd/m2, respectively. The contrast perception of obstacle in deriver’s eyes and in the safe stopping distance (SSD) from the tunnel entrance was determined as 2.79 cd/m2. At the entrance of the studied tunnel, the contrast perception of obstacles with the reflection coefficient of 20% was lower than the minimum contrast perception (28%) recommended by International Commission on Illumination. The main conclusion that can be drawn from it, is that this obstacle in the SSD from the tunnel entrance cannot be conceived by the drivers, which may lead to higher rate of road traffic crashes

Sound is one of the most effective exogenous factors affecting brain processing mechanisms, including attention that affecting human error and occupational accidents. The purpose of this study was to investigate the effect of sound frequency on noise annoiance, selective attention and human response time. This research is an interventional study that was conducted in 2017 on 60 students of Gonabad University of Medical Sciences. Measurements and tests were performed at two positions of before and during exposure to noise at various frequencies of 500, 1000, 2000, 4000 and 8000 Hz. To determine the sound with different frequencies, noise.exe software was used and to determine the accuracy of the intensity and frequency of sound, the TES 1358 TES sounding device was used. In the next step, cognitive performance tests including reaction time, accuracy and attention were measured by the test Stroop Complex. Data analysis was performed using spss. The mean age of males was 21.12 with a standard deviation of 0.13 and the mean age of females was 19.19 years with a standard deviation of 0.5. The highest degree of noise is at a frequency of 4000 and 8000 Hz The results of ANOVA showed that there is a significant relationship between noise anniance with different frequencies. By increasing the frequency from 500 to 4000 Hz, the reaction time is reduced and from 4000 to 8000 Hz, the reaction time increases. There is no meaningful relationship between the reaction time and the various frequencies.in both male and female groups, exposure to sound at all frequencies increases the number of errors and the highest error rate is at 1000 Hz, there is a significant difference between the interference score and the interference time with different frequencies. Due to the significance relationship between frequency of sound and interference score and interference time of individuals, by changing these factors, the reaction time and the time for mental tests and the degree of error of individuals are changed. In job posts and sensitive occupational tasks requiring the use of cognitive functions such as precision and reaction time the frequency of the sound should be considered

This study investigated the accidents recorded at the Gonabad Hospital Management Center for Hospital Management from 2014 to 2016, and identified important causes or parameters that influenced the incidence of accidents using the Pareto chart.
This descriptive and analytic study examined 25,414 incidents recorded at the Gonabad Hospital Management Center. The key variables such as the types of accident, age, time, types of lesion, and treatment, were collected for transport and non-transport accident. Data analysis was performed using Pareto chart as well as Minitabver v.16 and SPSS v.21 software.
Based on the results, the highest rate of the accidents (39.79%) were among people aged between 0-10 years. Transport accidents (17.61%) and heart attacks (10.92%) were the most common that occurred during the study. The spring had the highest rate of accidents, while the winter had the lowest.
Transportation accidents had the highest rate of incidents and injuries; therefore, the safety of transportation and vehicles should be taken more seriously.

Heat stress is one of the harmful factors in workplaces. Asphalt workers are exposed to thermal stress due to the open environment and process. The aim of this study was to assess the heat stress and strain in asphalt workers. This study was conducted on 29 employees of asphalt workstation. The heat stress was measured based on Wet-Bulb Globe Temperature (WBGT). Also, physiological parameters such as blood pressure and heart rate of asphalt workers were measured. The mean of WBGT index for drivers of asphalt machinery, trowels, shovels people and burner servicemen were 27.77, 27.77 and 29.61°C respectively whereas this value was 29.81, 29.85 and 3.23°C for workers of asphalt workstations respectively. The process of asphalting has significant effect on heat stress and physiological parameters of individuals. The pearson correlation between WBGT and heart rate, systolic blood pressure and diastolic blood pressure was significant. Asphalt workers are exposed to heat stress caused by different sources which may generate a host of heat strains in these people so special attention should be paid to control heat stress.

Aims: Due to their work type, the bakery workers undergo musculoskeletal disorders caused by the ergonomics factors. The aim of this study was to study the risk factors of musculoskeletal disorders in the bakery.
Instrument & In the cross-sectional descriptive-analytical study, 28 bakeries of Gonabad were studied in 2015. The bakeries were selected by census method. Data was collected by 3 methods including observation information (to analyze works and tasks with repetitive movements), interviews (to ask about work type and its complexity), and the ergonomics assessment of the upper limb (OCRA and JSI technics to determine and assess the actual risk levels of repetitive tasks). Data was analyzed using descriptive statistics and Spearman correlational non-parametric analysis.
Findings: OCRA index in kneaders and bakers was more than 3 (the red criteria) in Lavash, Sangak, and Taftoon bakeries. Alongside the kneader task in Sangak bakery, the scores of the right hand strain index of all tasks in Lavash, Taftoon, and Sangak bakeries were more than 7 (the red criteria). There were significant correlations between the results of OCRA index and JSI method in the determination of ergonomics statuses of the bakery workers in three bakery types including Lavash (p Based on the results of OCRA and JSI, there is a high risk level of musculoskeletal damages in the bakery workers.

Workers in wood industry are exposed to vibration and its damages. The purpose of this study was to evaluate exposure to hand-arm and whole body vibration in the wood industry. In this study, the parameters of whole body and hand-arm vibrations such as effective acceleration, overall equivalent acceleration, Vibration Dose Value and crest factor were studied on two Thicknessing planes, two sliding panel saw machines, two orbital sander, and three operators of perforate procedure. Assessments were done by the use of an oscillator and an analyzer of Svantak Co. Evaluating Hand-arm and whole body vibrations were conducted based on ISO 5349-1, ISO 5349-2 and ISO 2631-1 standards, respectively, and the findings/ the evaluated data were analyzed.The mean amount of daily exposure to hand-arm vibration (RMS) in Thicknessing plane, Orbital Sander and Sliding panel saw machine operators are respectively 5.56, 5.49 and 3.37 m/s2. In addition, the average crest factor of the 3 jobs is higher than 6. Mean of daily Exposure to whole body vibration in 3 machine operators of Thicknessing plane, perforate procedure and Sliding panel saw is respectively, 0.28, 0.24 and 0.17 meters per square second. The crest factor for all the exposures was to be less than 6 and the mean of the calculated daily vibration dose equaled 5.83 with the standard deviation of 0.87(m)⁄s^1.75. In further measured situations, exposure to hand-arm vibration is more than the standard level, so engineering and management measures are required to reduce the amount of exposure and support the health of the operators and the equipment.