The first aim of this study was to synthesize poly vinyl chloride (PVC) nanocomposites, consisting of various additive nanoparticles, including Silica, Zinc oxide (ZnO), and Zeolite A nanoparticles. The size of Silica, ZnO, and Zeolite A nanoparticles were near 30±2, 45±5, and 100±5 nm, respectively. The second aim was to investigate the effect of these nanoparticles on sound absorption, density, heat change, expansion, and contraction. This study was an experimental one . In this study, three nanoparticles were used, including Silica, ZnO, and Zeolite A. This study showed that PVC/Silica: 0.51%, PVC/Silica: 0.29%, PVC/Zeolite A: 6.1%, and PVC/Silica: 0.51% had the highest sound adsorption coefficient at frequency of 250, 500, 1000, and 2000 Hz, respectively. Moreover, the increase of Zeolite A and ZnO nanoparticles led to increase of density. In case of Silica nanoparticles, the increase of content of nanoparticles led to decrease of density. The heat change experiment showed that the increase of Zeolite A led to decrease of heat change, but the increase of Silica led to increase of heat change. It was found that PVC/Silica: 0.51% had minimum contraction and expansion. Taken together, PVC/Silica: 0.51%, PVC/Silica: 0.29%, PVC/Zeolite A: 6.1%, and PVC/Silica: 0.51% nanocomposite had highest sound adsorption coefficient at frequency of 250, 500, 1000, and 2000 Hz, respectively.

Due to technology improvement particularly telecommunication technology, the use of mobile phones has increased in recent years. Service providers have increasingly installed more BTS antennas inside the cities and villages to meet the growing demand. However, there is a concern about the level of exposure to microwave waves from these antennas. It is due to this concern that the current study seeks to investigate the horizontal pattern of microwave radiation from BTS antennas considering the type of antennas and surrounding buildings in Maragheh city, East Azerbaijan Province, Iran. The required information was collected through the interview with the city telecommunications organization company and field observations. Then, measurements were performed based on the IEEE STD C95.1 standard method via SPECTRAN 4060 handheld RF spectrum analyzer device. Kolmogorov-Smirnov and Mann-Whitney tests were adopted to analyze data using SPSS software. The results of the study showed that the BTS antenna installation and the amount of wave propagation on surrounding buildings vary from service provider to service provider. It is recommended to pay more attention prior to installation process specifically in highly populated areas. However, all the measurements were within the acceptable range of the ICNIRP allowable limits.

The aim of this article was to present a model for measuring and managing the risk of using hot mineral spas, based on structural safety with environmental approach. A conceptual model of risk was prepared in four stages: 1) determining the general outline of the model, 2) identifying spa structure safety indicators, 3) evaluating and scoring the indicators and 4) determining the quantitative and qualitative categories of the model and providing solutions. In this study, 30 spa structure safety indicators were extracted, and the weight of each indicator was obtained based on the amount of risk for users. Moreover, a questionnaire was prepared by analytic hierarchy process analysis method. According to the standard level allowed for each indicator, spa structure safety risk categories were prepared in five ranges for each indicator based on the obtained weights and the opinions of health experts. The results of the risk associated with each spa were obtained by combining 30 spa structure safety indicators. To assess the risk of using hot mineral spas by the method invented in this study, first, the extracted model indicators were scored in six spas of Iran. Then, risk level of the six spas was evaluated. According to the risk scores, hot spas named Gavmishgoli and Qotoursoo had an unacceptable level of risk. Qinarjeh, Shabil, and Sabalan had a high level of risk. Borjloo had a moderate level of risk. The proposed risk model provides a framework for a standard and safe mineral spa.

Air dispersion modeling is an important tool to improve air quality. The main objective of this research was focused on the simulation of CO emission from stacks at the Tehran Oil Refinery Complex, Iran. The AMS/EPA Regulatory Model (AERMOD) was developed to simulate the CO dispersion from stacks between the years 2018 and 2019. The results of the model on the maximum volume of CO concentration at 1hr and 8hr for hot and cold temperature were equal to 109 μg/m3, 32 μg/m3, 360 μg/m3, 254 μg/m3, respectively. Simulated values of CO emissions were compared to those obtained area measurement campaign at 4 receptors. Maximum concentration of CO in cold period of times was more than hot period of times. This can be attributed to low air turbulence. Our analysis demonstrated that the AERMOD modeling system is applicable for air quality simulation in the near future for CO. Simulation output showed that were all centered in against mountain and  the middle of simulation area where the emission sources concentrated, and it is probably because the air pollutions were topography and source oriented. Finally, study results indicate that the simulated concentration of CO based on AERMOD, does not exceed concentration limit, set by the Iranian Ambient Air Quality Standard. It verified that CO release from oil refinery stacks don't have any significant impact on nearby communities.

Due to the negative influence of manual load handling on the lower back, it leads to low back disorders and high mechanical loads. The present study was aimed to investigate forces exerted on the lower back during manual handling in young workers in selected block-making workshops. This descriptive, cross-sectional study was carried out on 40 young workers with an average age of 31 years old in several block-making industries in 2020. 3DSSPP Software was used for biomechanical analysis of the forces exerted on the lower back. The prevalence of musculoskeletal disorders was assessed using the Standard Cornell Questionnaires. Spearman, Friedman, and ANOVA correlation tests via SPSS software version19 were used to determine the relationship between demographic variables, the prevalence of musculoskeletal disorders, the relationship between the prevalence of musculoskeletal disorders, the amount of compressive, and shear forces on workers' backs. The results showed that the mean compressive and shear forces exerted to the lumbosacral joint (L5/S1) were 3194.85 ± 1064.326 and 473.17 ± 89.451 N, the intervertebral disc (L4/L5) were 3924.78  ±4344.87  and 383.18 ± 154.554. The findings also indicated that the highest prevalence of pain was related to the lower back 45% and right knee 30%. There was a significant relationship between the mean score of musculoskeletal disorders obtained from the Cornell questionnaire with age, work experience, and weight and body mass (0.001> P). The shear forces exerted to the lower back were higher than the permissible levels by 30% to 37% of respondents, and on average 42.5% of them experienced compressive forces. Thus, it can cause a lot of injuries to the back if lasts for a long time. The results showed that manual load handling was dangerous for this group's ages. Consequently, people may suffer serious injuries and disorders particularly lower back disorders.

A safety and engineering related survey has been conducted to identify infrastructure problems in an undeveloped neighborhood. The studied neighborhood has lacked so many modern and updated infrastructures. NNS (Near Northside) neighborhood infrastructure is failing or becoming older because of lack of engineering and safety knowledge among the community people to have awareness to improve the infrastructure. There exists a need to understand the infrastructure deficiencies that currently is apparent within the community of Near Northside. This work addressed those issues and would encourage the people to have a better infrastructure which could help to improve their neighborhood.

Despite all technological improvement and automation in the production process, a majority of tasks are still performing by workers. Due to this challenge, the occurrence of musculoskeletal disorders (MSDs) is an expected common result of manual tasks. Fatigue is one of the common causes resulting MSDs. Hence, one of the strategies for resolving this issue is to schedule rest time to provide a recovery time for workforce from the physiological consequences of exertion. This study was aimed to suggest a pre-planned rest allowance at MAPNA Company, Tehran, Iran. Therefore, we designed an experiment in a workstation to obtain input data (postures and forces). Then, the collected data was used to simulate the working condition for all workers using 3DSSPP software. We considered maximum voluntary contraction (MVC) of involved muscles. So, the critical muscle was determined for all workers based on specific tasks. The rest time for a critical muscle of each worker was calculated using the Rohmert model. Results showed that optimally work time schedule based on the task specification and subsequent rest time could reduce MSDs. This approach provides a comprehensive view of workers and their tasks (for both sources p-value was less than 0.05). This approach can be used for any workstation to suggest pre-planned rest allowances.

Ultrasonic testing (UT) for medical examination as well as metal flaw detection is a popular method. From the beginning of ultrasonic testing conducted by Mulhauser in 1931, a lot of new things and technologies emerged in UT testing. This review paper deals with progress in detecting human organs as well as materials flaws and future prospects of UT for metal flaw detection. Study on components of UT system is conducted. Then typical UT inspection system is determined. After that advantages and disadvantages of UT have been reviewed. Major types of waves in ultrasound with considering UT instruments have been reviewed as well. Progress in different areas of UT have been discussed extensively with more emphasis on progress in composite piezoelectric materials, variations of probes, EMAT (Electromagnetic Acoustic Transducer), focused probe, focusing axicon probe, focused phased arrays, LASER (Light Amplification by Stimulated Emission of Radiation) generation of ultrasound, acoustic holography, and ultrasonic microscopy. At the end future prospects of UT have been reviewed as well as recommendations have been provided.