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This work investigates the effects of interlayer hybrid fiber dispersion on the impact response of carbon-flax epoxy hybrid laminates at low carbon volume fractions, and benchmarks the mechanical performance enhancement against the non-hybrid flax epoxy. Five hybrid laminate stacking sequences with similar carbon-to-flax weight ratio were fabricated and subjected to low-velocity impact at three different energy values, generating non-perforated and perforated damage states. A virtual drop-weight impact test that models intralaminar failure based on continuum damage mechanics approach, and delamination using cohesive elements, was also implemented to evaluate the material behavior and damage development in the composites. Simulation results were then verified against experimental data. Results suggested that positioning stiffer carbon plies at the impact face does not necessarily lead to enhancement of the hybrid's impact properties. On the contrary, flax plies at the impacted side lead to significant improvement in impact resistance compared to the non-hybrid flax composite with similar thickness. Results of finite element analysis showed that carbon plies play a significant role in the hybrid laminate's energy absorption characteristics due to lower failure strain.

Background and aims: Nowadays, artificial insulators such as fiberglass and rock wool are used as sound absorbers in developing countries. The present study is performed to introduce new sound absorbing materials used in developed countries and discuss their acoustical characteristics. It also aims to look at the efficiency of sound absorber natural materials (green materials) as an alternative to commercial materials with a synthetic base used in different places. Methods: In order to identify new porous absorbents, their mechanism of action and various applications, a search was conducted by using keywords such as "Sound Absorbent", "Natural Noise Absorbent" and "Passive Absorber" in PubMed, Scopus, Science Direct, ProQuest, Springer, Web of Knowledge, Magiran, SID, IranMedex and Google Scholar. We selected 48 review and original research papers that were about natural and recycled absorbents. Results: Most recent research includes production and optimization of sound absorbers using natural and recycled materials. The aim of all of these researches was producing green absorber materials in accordance with environmental regulations. In order to properly use these materials, in addition to knowing the benefits and suitability of absorbers for use in the intended environment, the effective factors in sound absorption such as fiber size, air flow resistance, porosity, curve, thickness and density of absorbers were considered. Conclusion: In comparison to old absorbents, new materials are safer and lighter and enjoy a more efficient technology. It seems like environmental friendly, degradable, recyclable and green noise absorbents will play on important role in the market of noise absorbents in the future. Also because of the place and different uses of absorbent materials, specialists should consider the limitations of the environment and the acoustic characteristics of the absorbents.

Background and aimWork-related injuries are among the most important health problems in developing countries, such as Iran. The purpose of this study was to determine the epidemiology of work-related injuries among construction workers who had been insured by the Iranian Social Security Organization (ISSO).MethodsThis is a cross-sectional study. The population included all construction workers who had a work- related accident during 2012 in Iran, which were recorded in the ISSO database after inspection. The effects of independent variables on injuries were estimated by logistic regression. SPSS software version 18 was used for analyzing the data.ResultsOverall, 5352 work-related injuries were investigated. The incidence rate of fatal and nonfatal injuries was 0.07 in 1000 and 11.18 in 1000 workers, respectively. More than half of these accidents were due to careless activities. A younger age at the time of the accident (OR=0.98, CI: 0.97–0.99, p=0.001), being married (OR=1.37, CI: 1.04–1.79, p=0.02), place of accident (OR=1.86, CI: 1.18–2.92, p=0.007), lack of information (OR=5.28, CI: 1.57–17.75, p=0.007), disrespect of safety regulations (OR=3.11, CI: 1.87–5.17, p=0.001), non-use of protective equipment (OR=2.98, CI: 1.62–5.50, p=0.001), and defective equipment (OR=2.22, CI: 1.18–4.20, p=0.01) had a significant effect on the incidence of work-related injury.ConclusionsThe pattern of work-related injury in Iran was almost similar in regard to age, gender, cause and type of the accident, with other parts of the world.

Background: The sound is an environmental and occupational pollutant and can cause a number of reactions in human body, in which hearing loss is one of the most important effects. Cement industry is one of the industries with noise induced hazards. The aim of this study was to evaluate the noise level in different parts of Kerman Cement Plant. Materials and Methods: This descriptive cross-sectional study was done in Kerman Cement Plant in 2009. The sound level was measured according to the standard ISO 9612:1997 (E) in workers main commuting spots. Noise levels were measured by the testo SLM device (Model CEL-815) in network A and calibrator model IEC942/90 claa2. Data were analyzed by the EXCEL software. Results: The highest sound pressure level in the Cement Plant (106 db) was recorded in the stone crushing units and the grinding units (mills); 14 units had a mean sound level above the permissible 85 db noise level. Conclusion: There are specific units with high noise exposure in the Kerman Cement plant. Thus systematic noise evaluation in the working units, worker education, noise control, distributing proper standard noise protection equipment among the workers, performing annual audiometries, and evaluating and updating noise control programs are necessary.