Introduction: Firefighting is one of the occupations that requires high physical and aerobic power due to the nature of the job and the physical demands of this profession. Therefore, the present study aimed to investigate the relationship among Workability index (WAI), mental workload, musculoskeletal disorders (MSDs) and their effective factors in firefighters. Methods: This descriptive-analytical study was carried out on 250 firefighters in Tehran in 2019. Data were collected using WAI, NASA-TLX and Body Discomfort Chart (BDC). Data analysis was carried out using descriptive statistics, linear regression, Pearson, and Spearman correlations Results: The mean (SD) of total mental load was 70. 07 (6. 58). Also, the mean (standard deviation) of the total WAI score was 38. 85 (1. 17). Physical workload dimension had the highest value among mental workload dimensions 93. 49 (8. 93). The results showed that WAI is increased by 0. 14 by augmentation of one unit at the academic level of firefighters (p = 0. 03). The most common discomfort was reported in the lower (50 people (20%)) and upper (42 people (16. 8%)) regions of the back. The total WAI relationship with total mental workload was positive and insignificant (p>0. 05). There was a significant and reverse association between WAI and discomfort in the wrist, leg, and ankle. Conclusion: Despite the low rate of MSDs, even mild symptoms of musculoskeletal pain should be considered. Given the high level of mental workload, improving physical, psychosocial and social working conditions is important in increasing the ability of employees and augmenting the ability of their occupational activity.

In the last decades, the development of nanotechnology has been rising and nanomaterials have been widely used in combination with many traditional materials. The prominent chemical and physical properties of nanomaterials enable them to play an important role in various applications such as modifying the structure of materials, improving the properties of composites, and manufacturing new multifunctional products. Many studies have been carried out on the effect of nanoparticles on concrete performance and most of them demonstrated the improvement of concrete properties. There are a lot of studies on the effect of nanoclay on cement composites. However, there are little researches on the halloysite nanotube (HNT) effect, as subcategories of nanoclay, on the properties of cement composites. Halloysites are a kind of mineral clay which are often produced by air-induced erosion or by thermal transformation of ultramafic rocks, volcanic glasses, and pumice. They are chemically similar to kaolinite but, unit layers in halloysites are separated by a monolayer of water molecules. In general, halloysites have different shapes and exist in the plate, spherical, and tubular forms. The tubular structure is the dominant form of halloysite in nature. Chemically, the outer surface of the HNTs has properties similar to SiO2 while the inner cylinder core is related to Al2O3. Due to the tubular geometry, HNTs like carbon nanotubes could be classified as one-dimensional nanoparticles. Halloysite can grow into long multi-walled tubules, which morphologically resemble to multi-walled carbon nanotubes. In terms of dimensional characteristics, HNTs have an external diameter of about 30 to 190 nm, an inner diameter of about 10 to 100 nm and a length between 3 to 30 μ m. Halloysite characteristics could be sum up as high length to diameter (L/D) ratio, high specific surface, large pore volume, low density in surface, and pozzolanic properties. Mechanical properties of HNTs could make them an ideal reinforcing additive to improve the mechanical properties of cement composites. In addition, due to the nano scale size of HNTs, they can play the role of filler and make a denser and stronger microstructure. Therefore, in this research, the effect of HNTs on the performance of cement mortar was evaluated and the Workability and permeability of mortar samples containing 3% halloysite nanotubes were presented. The results indicated an increase of more than 28% of electrical resistance, a decrease of approximately 26% of water absorption rate, 23% reduction in water repellent, a decrease in the Workability, and an increment in the rate of hydration of cement mortar due to the incorporation of 3% halloysite nanotube. These results indicate that halloysite nanotubes can be used as an appropriate nanoparticle to improve the properties of cementitious composites. The pozzolanic properties of HNTs enable them to decrease the permeability of cementitious matrices. This could lead to an enhancement in the durability of cementitious matrices.

Nowadays, concrete is one of the most important and widely used human product. Improving concrete characteristics have always been one of the fundamental subjects for engineers. Improve the physical properties of water, as one of the main elements of concrete, is one way to improve the characteristics of the concrete. When water passes through the magnetic field, its physical quality has changed, it is called Magnetic water. This study examines the effect of the use of magnetized water (MW) with a solenoid current-carrying, on the compressive strength and Workability of high performance concrete. The variables of this study were the intensity of magnetic field, the silica fume replacement level and water to cement ratio in different mixes. The results show that using MW increases the Workability of concrete about 36% in average.MW in combination with super plasticizer is more effective than MW on Workability and compressive strength of concrete. MW had more positive effects on the samples without silica fume. Increasing the intensity of magnetic field improved the Workability, 28 and 90 days compressive strength concrete.

Processing map for hot working of Ti-IF steel has been developed in the temperature range of 750 to 1100 °C and strain rate of 0.01 to 100 s-1. This map in the austenite region exhibits a single domain with a peak efficiency of 45% occurring at 1025 °C and strain rate of 0.02 s-1. The domain extends over the temperature range of 1000 to 1100 °C and strain rate range of 0.01 to 1 s-1. The true stress-strain curves and microstructural observations show the occurrence of dynamic recrystallization in this domain. In two phase regions, where austenite and ferrite are present together, flow localization occurs in the form of bands with a fine grained structure as a result of dynamic recrystallization in the bands. These deformation bands are formed at 45° with respect to axial direction of compression. The processing map in ferrite region exhibits a domain with a peak efficiency of 38% occurring at 825 °C and strain rate of 0.02 s-1, so this domain extends over the temperature range of 800 to 850 °C and strain rate range of 0.01 to 0.5 s-1. The true stress-strain curves and microstructural results confirm the occurrence of partially dynamic recrystallization in this domain.

The aim of the present study is to investigate the effects of thermomechanical parameters such as hot deformation temperature and strain rate on the hot Workability of 2024 aluminum alloy by using hot compression tests. These tests were conducted on the solutionized specimens with strain rates of 0.00l-1s-1 at the temperature range of 350-480.C. By plotting true strain-true stress curves, the amounts of flow stresses were found. For the various conditions, study of these curves confirmed the existence of dynamic recovery phenomenon. The activation energy was found to be between 127-140KJ/mol, showing that dislocation climb controlled dynamic recovery. Dynamic recrystallization phenomenon was not observed in this work. At temperatures of 350.C and 400.C with strain rate of 0.001s-1 and temperature of 400.C with strain rate of 0.01s-1, flow softening was revealed. This behaviour can be attributed to a precipitation coarsening. Furthermore, it was found that the strain-rate sensivity increases with increasing the deformation temperature.      

Background and aims: Sleep disorders are among the most prevalent disorders today and especially in the industrial and developed countries. Their prevalence have been varied in different populations. The occurrence of these disorders in working population can cause occupational injuries and reduces the performance of the employees. It also can be hazardous. In this article, the association between sleep disorders and the work ability index are considered.Methods: This is a cross-sectional study performed in a dairy company on all the employees in the year 2013. In this study, the Stop Bang questionnaire for assessment of the sleep apnea, Epworth Sleepiness Scale (ESS) questionnaire for assessment of sleepiness, and the work ability index (WAI) for assessment of work ability were used. The gathered data from these questionnaires were analyzed in conjunction with the demographic data.Results: In this study, 215 workers were finally considered. The associations between the three questionnaires (WAI, ESS, and STOP Bang) were statistically significant. There were also significant associations between age and WAI and STOP Bang; the level of education and ESS; work history and STOP Bang; smoking and all three questionnaires; pack-years of smoking and STOP Bang; and also the employee's body mass index (BMI) and STOP Bang. There was positive correlation between ESS and STOP Bang and both these questionnaires were negatively correlated with WAI.Conclusion: The results showed a strong correlation between sleep disorders (sleepiness and sleep apnea) and the work ability index. It is important to consider the sleep hygiene and performance of screening for sleep disorders in the employees to reduce the irreversible injuries and associated problems and also reduce the problem of lowered productivity.

Introduction: Recently appropriate Workability is widely considered in organizations. Developing appropriate Workability in hospitals leads to many positive achievements for nurses and patients and totally for the whole health and treatment system. According to the researches, Workability levels of persons are strongly related to their working places' conditions. So, this study was conducted to evaluate the level of working abilities of nurses in selected educational-medical centers of the Tehran University of Medical Sciences in 2012.Methods: In this cross-sectional study, 150 nurses working in selected educational medical centers of the Tehran University of Medical Sciences were selected by the random sampling method. Data were collected using the demographic information and Workability indicator questionnaire. Then, the data were analyzed by descriptive and inferential statistic tests and the SPSS 16 software.Results: Workability of 44.7% of the nurses was in an appropriate level. There was a linear and meaningful relation between the educational level and Workability of the nurses (P=0.003). A negative and meaningful statistical relation was found between diseases diagnosed by physicians and Workability of the nurses (P<0.001). Also, a negative and meaningful relation was found between Workability and interest in working in extra hours.Conclusions: Considering the good Workability level of almost half of the nurses, maintaining this level of Workability and improving it in nurses should be noticed more than before by nursing managers of the country and hospitals.