this study investigated the effects of manipulating the cognitive complexity of tasks along +/- few elements and the time limits on l2 learners writing performance. to conduct the study, 60 iranian efl learners with two levels of proficiency, low and high intermediate, were selected and assigned to three groups based on the time devoted to task completion. the participants performed both a simp...

in civil engineering concrete is a material combined of hydraulic cement, sand, gravel and water. gravel and sand compose 60 to 70 percent of concrete. these aggregates support compression force of concrete. cement paste acts as glue to stick grain together. in bushehr factories producing aggregates do not operate according to astm standards, so that fineness modulus (fm) of the produced sands ...

abstract: mineral scaling in oil and gas production equipment is one of the most important problem that occurs while water injection and it has been recognized to be a major operational problem. the incompatibility between injected and formation waters may result in inorganic scale precipitation in the equipment and reservoir and then reduction of oil production rate and water injection rate. ...

Extended abstract 1- Introduction A dust storm is one of the biggest serious environmental problems in the arid and semi-arid regions of the world, causing irreparable damages to farms, facilities, roads, traffic and transportation every year and respitory problems by contaminating the air. Due to the geographic location of Iran which is  in the arid and semi-arid belt of the world, the count...

Introduction: In recent years, frequency and intensity of dust storms have been increased because of human destructive activities and caused significant loss in different aspects of hygienic and health, environmental and socio-economic sections. Therefore, detection and trace of dust storms in shortest time is the first effective step in preparation and implementation of strategic and operation...

Introduction: Physical, chemical and ecological changes on dust deposition sites are one of the many problems caused by the occurrence of dust phenomena in arid areas. The entrance of additional salts to the ecosystem by dust, makes increased salinity and imbalanced of salts in the growth environment of plants. The purpose of this study is to determine the seasonal variations in the amount of s...

today the image of a permanent skeletal space of cities affected by some forces or mechanisms is put in time with social-economic development and while imposes a new face and perspective to physical anatomy of cities, and prepares field to changes in content and social- economic structures of cities too. simultaneously with quitting villages in order to settle in cities by villagers, the phen...