محمدرضا روشنی

The most fundamental element of any organization, to achieve its high goals, is the presence of an expert and committed human force. The main asset of any organization is its human force, and to protect this factor is very important and vital for the organization ׳s life. Based on the mentioned goal, health risk was assessed regarding human approach in olefin unit of Polymeraryasasol company using a risk detection and risk assessment method. Regarding the widespread and diversity of the personnel exposing to the hazardous factors at the workplace and in order to control these factors effectively, firstly, the hazards were identified and assessed, then the prevention and elimination techniques were given. Finally, it is suggested as how to encounter with probable human damages and minimize the hazards in a case exposed. The most important proposed techniques referred here are: setting up the health objectives based on the policies of the company; providing an occupational ID based on the results of measurements related to hazardous factors of workplace, issuing the modifying actions for controlling these factors; visiting the unit and preparing a health check list as well as exercising the response at emergency times.

One of the best indicators of the geological and environmental events in the Quaternary is the alternation of loess-paleosol. In this study, for paleoenvironmental identification of buried paleosols in loess sequences, 14 sections located between 36˚ 49′ 6˝ to 36˚ 49′ 20˝ northern latitude and 54˚ 26′ 45˝ to 54˚ 26′ 52˝ eastern longitude in the southern part of Gorgan (Kharazmi town) were studied. The disturbed soil samples for physico-chemical analysis and clay mineralogy and undisturbed samples for prepration of thin sections were collected. The physico-chemical results (calcium carbonate content, particle size distribution, cationexchangable capacity and Feo/Fed) indicated that the soils had experienced several pedogenic periods. The result of mineralogy showed that a high amount of smectite, vermiculite and mixed layer mica-smectite in paleosols compared to loess deposits probably indicates moister regims through interglacial compared to glacial periods. The micromorphological observations revealed many evidences on the occurance of pedogenic processes. One of the most important index of pedogenesis, clay coating and hypocoating around void are presented only in buried paleosols, which is the evidence for moist climate conditions, enough for leaching and translocation of clay. Formation of the studied loess and paleosols, probably took place in glacial and interglacial cycles with different climate condition, respectively.

One of the most common facilities utilized in supersonic wind tunnels is multi-stage ejector system. In this system high speed air blowing with specified Mach numbers into the wind tunnel at predetermined points, helps to obtain the desired Mach number in the test section. In this study, according to characteristics of test section including Mach number, static temperature and stagnation pressure, relevant prominent features of the single-stage, two-stage and three-stage ejectors such as mass flow, velocity and stagnation pressure are computed. Two different aspects are implemented in solving governing equations of ejectors; first one is to assume the same Mach number for all ejectors and second one is based on assumption of the same stagnation pressure for the ejectors. It will be revealed that the later one is more optimal in comparison with the former criteria. Validation of the developed computational code results is performed via comparison with the experimental data of a wind tunnel operating at Mach number 2, which resulted in a difference of 5 to 7 percent. At the earlier section, design parameters of single ejector versus different mach numbers of the test section are presented and then effect of outlet static pressure reduction as a means of vacuum generation at the exhaust of the wind tunnel is discussed. Furthermore design of two-stage ejector according to both methods of equal Mach number and the same stagnation pressure is completed and in the last section three-stage ejector is studied base on the same stagnation pressure for comprising ejectors.