فهرست مطالب محمد رنجبریان

Due to the nature of the Car Manufacturing Industry and the risks and incidents in such industries, organizational commitment to safety and implementation of a safety culture is essential for working in these industries. The purpose of this study is to investigate the relationship between the safety culture and its possible association with just culture in the employees of the Car Manufacturing Industry.

Metods:

 This study was a descriptive-analytical and was cross-sectionally conducted among a sample of 175 individuals who were the employees of a Car Manufacturing industry. In order to assess the safety culture and just culture, a five-dimensional Safety Culture Questionnaire with 61 items and six-dimensional Questionnaire with and 27 questions were used respectively. Linear regression analysis and chi-square test used to analyze the data, and to determine significant relationships.

The mean and standard deviation score of safety culture in workers and Supervisors were 200.8 ± 22.26 and 214.56 ± 19.4; which represents the safety culture of the organization. The results of the study showed that there is a significant relationship between safety culture and education level of supervisors as well as the incident events in both groups of workers and supervisors. A significant relationship found between five dimensions of safety Culture and six section of just culture.

The results showed the relationship between safety culture and just culture. The just culture is dependent on the safety culture. As the safety culture increases, the just culture will increase and the communication between the workers of the organization would be better

Commercial complexes are one of the most prestigious public and city-centered areas in terms of urban safety and passive defense. The purpose of this study was to determine the fire safety risk score of commercial complexes and its related factors.

 The commercial complexes of area 1 of District 12 of Tehran were studied. The characteristics of the complexes, including construction, height, activity, Occupancy Coefficient and etc in each complex were collected. fire risk assessment was performed using NFPA101 standard and CFSES software in three areas of control, Egress and general safety. In SPSS software version 21, linear regression and ANOVA tests were used to determine the relationship between variables.

Of the 79 commercial complexes studied, only 8 in control area and 4 in general area achieved acceptable risk level. None of them achieved an acceptable score in the Egress. According to the results, there was no significant relationship between risk levels and height, type and activity Coefficient of them(p>0.05). However, between Occupancy Coefficient of complexes with fire safety risk levels of control(p<0.001) and general(p= 0.013) and between construction with all risk levels ((pEgress= 0.004), (pControl & pGeneral<0.001)) There was a significant relationship.

The results showed the current situation of the studied commercial complexes is prone to cause a disaster in the 12th district of Tehran; Using the results of this study in urban planning and cross-sectoral communication to improve the safety of commercial complexes in the region is suggested.

Road traffic noise is one of the most common sources of environmental noise which has various effects on mental and physical health, impaired daily life function and cognitive performance. Vibration is another achievement of industrial development that is accompanied by noise in most work environments. Vibration transmitted from road surface to vehicles and drivers may interfere with activities, affect their comfort level and reduce attention. The purpose of this study was to compare the effect of independent and simultaneous exposure to traffic noise and whole body vibration on visual and auditory attention and control response of males using Integrated Visual Auditory Performance Test (IVA + PLUS).

The study population included 24 male students aged 18 to 30 years old in Shahid Beheshti University of Medical Sciences who had inclusion criteria for the study. The experiments were performed in 4 steps randomly in one day for each person in the acoustic room and in total, 96 experimental runs (24 runs per step) were performed. Inclusion criteria included: Students in the age group of 18-30 years, no history of underlying diseases including respiratory problems, skin disorders, sleep and cardiovascular disorders and other health problems affecting onechr('39')s muscular and brain health, no short term illnesses during the trial (colds, diarrhea and vomiting), no history of upper limb musculoskeletal disorders, hearing loss less than dBA27, visual acuity above (7/10), no smoking addiction and drugs and alcohol, no use of hypnotic drugs and CNS attenuating drugs during the test period, not  being over sensitive to sound according to Weinstein noise sensitivity questionnaire and getting a score of 22 or below in General Health Questionnaire, which reflects the health of the individuals. Exclusion criteria also included: a personchr('39')s unwillingness to continue participating because of the long studychr('39')s time and people who did not meet the above criteria. Subjects did the IVA test (data recorded including scores of total attention and response control scores) in background conditions (sound level dBA 27 and vibration acceleration zero), then they were exposed to individual and combined noise level of 55 dBA (as the permissible sound pressure level at outdoors) and the vibration acceleration of 0.65 m/s2 (as the average acceleration vibration in the Iranian vehicles). In this study, a vibration simulator was used to generate a vibration in the x, y, and z axes at different frequencies and intensities, either sinusoidal or randomly using a vibrating engine. The Italian OLI VIBRATOR MVE.440 / 2M vibrating engine was attached to the seat using a metal stand. The Ic5 inverter was used to adjust the vibration frequency and acceleration and the whole body vibration meter according to ISO 2631 was used to ensure the calibration of the vibration produced by the vibration simulator. The noise used in this study was generated by the signal software with combining the desired frequency and these computer-generated audio files were performed in the Cool edit tool software during the test. One of the features of this software is the ability to edit the sound in intensity at different frequencies, and by continuously monitoring noise in the acoustic room, the volume of the noise can be controlled at the desired frequencies. During the exposure, the intensity of noise within the individualchr('39')s hearing range, inside the acoustic room was controlled by a calibrated B&K 2238 Sound Level Meter. The IVA is an 8-minute visual and auditory continuous performance test that assesses total attention and response control scores. The task of the participant is to react when the number 1 is seen or heard and to click on the mouse once, and don’t react when the number 2 is seen or heard. The task type assigned to the participants was "simple", its physical workload was "light". Participants signed written consent form and filled demographic information form, general health questionnaire (GHQ-28), and Weinstein noise sensitivity scale. Audiometric and the E eye chart tests were done for hearing and visual acuity testing. To determine the individual and combined effect of noise and whole body vibration on attention and response control, regression analysis of repeated measures using generalized estimating equations with first order autoregressive process was used.

The mean (±SD) age of the participants were 23.41 ± 2.99 years. In the visual test and in the background vibration acceleration, the mean scores of attention has been increased with increasing traffic noise from 27 to 55 dBA and the response control score has been decreased (P = 0.79 and P = 0.1, respectively). At the background noise level, mean scores of attention and response control have been increased with increasing vibration acceleration from zero to 0.65 m/s2 (P = 0.49 and P = 0.59, respectively),). In combined exposure condition with noise level 55 dBA and vibration acceleration of 0.65 m/s2, the mean score of attention decreased compared to background ones (P= 0.95), and the response control score increased compared to background ones (P= 0.72). In the auditory test and in the background vibration acceleration, the mean scores of attention and response control have been increased by increasing the traffic noise from 27 to 55 dBA (P = 0.02 and P = 0.13, respectively), At the background noise level, mean scores of attention were significantly reduced by increasing the vibration acceleration from zero to 0.65 m/s2 (P =0.01). Mean scores of response control has been increased with increasing vibrational acceleration from zero to 0.65 m/s2 (P=0.74). In combined exposure condition, the mean scores of attention were significantly lower than background ones (P =0.01), and the response control score has been increased compared to the background ones (P= 0.09).

Similar results were found regarding the combined effect of noise level 55 dBA and vibration acceleration of 0.65 m/s2 on the total level of attention and response control in visual and auditory tests. So that the simultaneous increase in noise level and vibration acceleration relative to the background condition leaded to decrease in the total score of attention in both visual and auditory dimensions. However, in the mentioned conditions, the response control score has been increased in both visual and auditory tests.  It seems that the score of response control, which in some way expresses the ability to sustain attention and the reaction speed during the test, has been increased as a result of noise motivation theory and the positive short-term effects of vibration acceleration. In general, whole body vibration in low to moderate acceleration level and low level of noise may improve cognitive performance in a short time, however, definitive conclusions are subject to doing the systematic and comprehensive studies.

International Labor Organization (ILO) 2015 report shows that about 40% of the all total compensation for work-related diseases and accidents in the world is due to musculoskeletal disorders. According to UK Health and Safety Executive (2019) 41% of all registered Work related Musculoskeletal Disorders (WMSDs) are due to upper limbs. Barr et al. (2004) reported that most absence from work in the United States was due to musculoskeletal injuries to the hand and wrist. Hand, arm, and forearm are most important limbs of human body to work. Hand tools, especially non-powered hand tools, are responsible for a significant portion of damages. Many different types of hand tools are used in industrial, services, and domestic activities including wrenches, pliers, screwdrivers, clamps, snips, saws, etc. The use of hand tools is accompanied by repetitive movements and previous studies have shown that inappropriate design of hand tool can damage human joints, tendons and muscles. Repetitive movements are one of main causes of musculoskeletal injuries. In order to achieve high levels of comfort, safety, and efficiency of hand tools, physical abilities and limitations of users must be taken into account in design phase. Also, women and left-handed people must be considered in design of hand tools due to their different body dimensions and abilities. These factors are directly influences the trading of hand tools. Handle design is an important factor in the safe, convenient and ease of use of non-powered hand tools. Socket wrench is a single-wrench that is widely used to open and close the bolts and nuts that require high force and high speed operation. Due to wide usage of socket wrench this study aimed to investigate the relationship between physical parameters of length and diameter of handle, and weight of different models of socket wrench with electrical activity of two selected forearm muscles. We examined the correlation between three physical parameters of six trade model of socket wrenches. 

This descriptive-analytical study performed among 58 male workers of the installation and maintenance unit staff of a university. Their ages ranged from 25 to 45 years.  All participants were right-handed, healthy, and without history of upper limb injury or musculoskeletal disorders. They had at least one year of job experience in maintenance unit of university, and their body mass index was between 20-30. Six different types of socket wrench were selected and named with alphabetic codes A, B, C, D, E, F. Selected wrenches were differed in length and diameter of handle, and weight (Table 1). Table 1. Characteristics of the Socket wrenches Type of socket wrench Handle length  (mm) Handle diameter  (mm) Weight  (gr) A 225.52 25.76 439.77 B 158.30 18.14 240.21 C 235.16 37.82 570.58 D 228.78 18.36 592.08 E 186.68 29/20 348.90 F 185.70 33.56 235.21   A simulated task were designed according to usual usage of wrench users. This task was consist of opening the bolts using 6 types of wrenches. For this purpose, a wooden plate was fitted on a table with 12 fitted bolts and nuts of size 10. All bolts and nuts were fastened on the plate using a torque meter with 8 Nm. The height of task surface was in 95 percentile of elbow height of males (104 cm). However, it was possible to adjust the height of the table with the elbow height of each participant. Participants were asked to stand behind the desk and perform the activity of opening the bolts with each of six wrenches. The order of use of wrenches for each participant was random. The steps of each trial were as follows: steps 1) select the right socket; step 2) attach the socket to the handle; step 3) check turning direction; step 4) open the bolts.Surface Electromyography (SEMG) was applied to record the electrical activity of forearm muscles. The flexing muscle of the fingers and wrist extensor muscles play important role in gripping the wrench handle and using it to perform the simulated task. Therefore, the Flexor Digitorum Superficialis (FDS) and Extensor Carpi Radialis (ECR) muscles were considered for the recording the surface EMG signals. The steps of recording EMG signals were as follows: step 1) finding the flexor digitorum superficialis and extensor carpi radialis muscles on participant’s forearm; step 2) preparing the skin to conncet the electrodes; and step 3) connecting the electrodes. A surface EMG apparatus made by Biometrics Ltd. was used in this experiment. Since the independent (length and diameter of handle and weight of wrench) and dependent variables (EMG signals) were both quantitative, linear regression model was used to examine the relationship between the two quantitative variables and the data were analyzed by SPSS® 21 software. 

The mean of participants’ age, height and weight were 39.95 year, 175.7 cm, and 72.9 kg, respectively. Mean and standard deviation of normalized electrical activity of FDS and ECR muscles are shown in Table 2. Table 2. Mean (SD) of normalized electrical activity of flexor digitorum superficialis and extensor carpi radialismuscles Type of socket wrench Mean (SD) of electrical activity of muscles (mv/s) FDS muscle ECR muscle A 0.45(0.21) 0.47(0.22) B 0.61(0.25) 0.48(0.23) C 0.43(0.23) 0.46(0.24) D 0.55(0.24) 0.45(0.21) E 0.48(0.23) 0.44(0.21) F 0.50(0.22) 0.43(0.22)  The results showed that the lowest level of electrical activity of FDS muscle was belonged to type C wrench, which had the longest handle length and largest handle diameter. On the opposite side, the highest level of electrical activity of FDS muscle was belonged to type B wrench with shortest handle length and smallest handle diameter. Lowest and highest levels of electrical activity of ECR muscle were belonged to type F and B wrenches, respectively.A linear regression test was used to examine the relationship between the electrical activity of Flexor Digitorum Superficialis muscle and the physical parameters of the socket wrenches. The results showed that there is a significant relationship between the electrical activity of FDS muscle and the wrenches’ handle length and diameter (p-value<0.001). Based on regression models, for one millimeter increase in handle length and diameter, the level of electrical activity of the flexor muscles decreased by 0.001 and 0.007 mV, respectively. Simple and multiple regression models showed no significant relationship between the electrical activity of ECR muscle and physical parameters of wrenches (p-value>0.001). Discussion and

In the present study, relationship between three physical parameters (handle length, handle diameter and weight of wrench) of six type of socket wrenches with electrical activity of two important muscles involved in using this hand tool was investigated. The results showed that increasing or decreasing socket wrench length, handle diameter, and weight were associated with changes in the electrical activity level of FDS muscle. However, no relationship found for ECR muscle. The findings showed that lowest and highest muscle force for opening the bolts were applied in using wrench type C (maximum length) and wrench type B (lowest length), respectively.Li (2002) showed that new designs of handle for powered and non-powered hand tools can decrease the unnatural postures, including flexion, extension, radial deviation, and ulnar deviation. He showed that flexor digitorum superficialis and the flexor carpi ulnaris of the right forearm may be significantly reduced when using the new designs of pliers. Dong et al (2006) and Ozawa (2001) reported similar finding. They showed that physical characteristics of hand tools can strongly effect the muscular effort required to work with hand tools used by dentists.The present study showed that there is no significant relationship between the weight of the wrench and the electrical activity level of the Flexor Digitorum Superficialis muscle. This indicates that muscles other than FDS are involved in controlling the weight of hand tool.In power grip tasks (such as working with a wrenches), the handle diameter and length of the tool are important parameters. Therefore, wrenches with a longer handle length and a larger handle diameter provide the lowest level of electrical activity of the FDS muscle to open the bolts. This results to lower levels of muscle fatigue. Therefore, the force required to open the bolts can be reduced by choosing a longer handle and a larger handle diameter (near to optimum diameter). The findings of this study can be used by hand tools manufacturers to improve tool design. Also, differences in the ergonomic characteristics of different types of a hand tool can be well documented using electromyography. The generalization of the findings of this study should be considered to its limitations. In this study, the performance of Flexor Digitorum Superficialis muscle and Extensor Carpi Radialis muscle were recorded for a short time task. Therefore, the level of muscle fatigue that occurs in participants may vary in actual and long-term conditions. Also, the effect of roughness and softness of the handle on the grip power and electrical activity of the muscles were not examined in this study. Thus, it is suggested that the effect of this variables along with other physical factors be investigated in future studies.

Recent industrial developments have led to the rapid development of electricity production successively; it leads to power grids and high voltage utilization. The effects of electromagnetic fields have been investigated on the organism by researchers. In many cases, it is not possible to conclusively comment, because of the slowness impact of fields of life-cycle processes and the long-term studies. According to the harmful effects of exposure to electromagnetic waves, this study was conducted to investigate the electric field intensity and magnetic field at high voltage substations (230 kv) in Golestan province.

This Cross-sectional study (descriptive-analytical) was performed at 230 kv substations in Golestan Province (1396). The electric field and the magnetic field density were measured by instrument model TM-190 at 5 posts in Golestan province and compared with the standards.

100 % of the measured electric field intensity and magnetic field of the 230 kv substations in Golestan Province is less than the standard.

The magnitude of the electric and magnetic fields is in the occupational limits.

Today the rate of human beings exposed to electromagnetic fields is increasing deliriously and human beings are being more drowned in the ocean of electromagnetic fields each day. It has been a long time that the effects of electromagnetic fields on organisms has been studied by researchers and due to the long-term researches and the slow impact of fields on life-cycle processes, in a lot of cases a final opinion is impossible. Considering the detrimental effects of being exposed to electromagnetic radiations, this study aimed to determine the relation between electromagnetic radiations and the level of Melatonin and Cortisol hormones of serum (blood) of the male employees of the 230kV substations in Golestan Province.

this study has been accomplished with the cross sectional method (descriptive-analytic) on male employees of the 230 kilo-Volt substations in Golestan Province(1396). The results achieved from the serum sample of the case and control groups have been compared, and the measurements and the relation between them has been analyzed, using Spss22 software.

100 % of the measured electric field intensity and magnetic flux density of the 230kV substations in Golestan Province is less than Iran’s occupational limits. There was no significant difference between the average of the level of Cortisol hormone in the case and control groups. The average of the level of Cortisol in the substation job group was not significantly different. There is no significant difference in the average of Cortisol level and age category and work place

Electromagnetic radiations do not affect the level of Cortisol hormones of the male employees of the 230 kV substations in Golestan province and the electric and magnetic fields intensity of substations is in the occupational limits of Iran.

There are various models of socket wrench in the market varying in the length and diameter of handle and weight. Each of these features alone can modify the force applied by the hand and affect how comfortable the user is. The purpose of this study was to investigate the relationship between dimensional properties and weight of several models of socket wrench with their usability index score.  

58 male technicians from maintenance units of Shahid Beheshti University of Medical Sciences performed the task of opening 12 bolts with 8 N/m of torque using 6 models of socket wrench with different physical properties. The sample size was selected based on proposed figures for usability studies.  The System Usability Index (SUS) validated questionnaire was used to determine the usability score of each model after the experiment. The study was conducted in 2017. SPSS 21 was used for data analysis.

The results showed that there was a significant relationship between usability index score and dimensional properties and weight of wrenches (P<0.001). Wrench models with longer handle and diameter size close to optimum range of diameter of hand tools for male users had a higher usability score, and participants reported a better test experience with these models.

Using the System Usability Index (SUS Questionnaire) to measure the quality of human-centered design of hand tools is a good way to evaluate and select the hand tools that are widely used by technical staff. The results of this study are valid for short-term applications of wrenches. However, for long time activities, epidemiological and physiological evidences such as EMG should also be used.
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Background and

Exposure to formaldehyde (FA), a highly-used chemical in industries, can induce serious health problems.Aim of this study was to explorethestatus of oxidant and antioxidant parameters in liver tissue of rats exposed to FAinhalation

Twenty-one male albino Wistar rats divided into 3 separate groups randomly (n=7). Rats in groups 1 and 2 were respectively exposed to atmospheres containing6 and 12 PPM FA continuously (8 hours/day, 14 days), whileanimals in group 3 which served as control group were not exposed to any stress source.The animals were anesthetized by CO2 and after decapitation, liver samples were collected and processed for estimation of MDA and GSHlevels in the supernatant by spectrophotometric methodin control and exposed groups. Data were analyzed bynonparametric tests and significance was expressedas P<0.05.

The present research findings showed statistically significant body weight loss in FA (12ppm) exposed group compared to the control and also FA (6ppm) exposed groups. However, a statistically significant decrease in liver weight and liver/body weight ratio was observed in the exposed groups compared to the control group (P<0.05). FA exposed groups showed a statistically significant decrease in GSH levelin liver tissue and statistically significant increase in MDA level in liver tissue (P<0.05). However, the levels of changes inbiochemical parametersin FA exposed groups were not dose-dependent.

The results of present study show that exposure to formaldehyde is toxic to liver tissue. Further research for exploring the toxicity of FA in occupationally exposed groups is recommended.