among the low–dimensional allotropes of carbon, nanotubes and graphene have attracted very much attention from nano–science and nanotechnology specialists. they have been proposed as building blocks in nanometer device engineering. however, these structures are not defect–free. in this thesis, we focused on defective carbon nanotubes and graphene, and studied the effect of couple of very common...

in this research we have studied the effect of some transition-metals (cu, ag and au) substitutions on two-electron reduction potential of flavins by application of dft method. all geometries have been optimized at blyp level of theory and “6-31+g** + lanl2dz” mixed basis set. the frequency job at the same method and basis sets has been performed to obtain gibbs free energy of compounds. it h...

fluorescence chemical sensors for the highly sensitive and selective determination of pb2+ , hg2+, co2+ and fe3+ ions in aqueous solutions are described. the ion sensing system was prepared by incorporating lipophilic ligand (l) as a neutral ion-selective fluoroionophore in the plasticized pvc membrane containing sodium tetraphenylborate or potasium tetrakis (p-chlorophenyl) borate as a liphoph...

چکیده اساسی ترین منبع استراتژیک هر سازمان یا جامعه،منابع انسانی می باشد.جوامع موفق،جوامعی هستند که بتوانند منابع انسانی خود را به طور صحیح پرورش و توسعه دهند. در اقتصاد امروز، دانش به عنوان مهمترین سرمایه، جایگزین سرمایه مالی و فیزیکی شده است . دانش و اطلاعات به رشد اقتصادی کمک می کند.این امر موجب افزایش اهمیّت سرمایه فکری به عنوان مقوله ای پژوهشی شده است. مدیریت منابع انسانی یعنی مدیریت و ادار...

هدف پژوهش حاضر، تحلیل استنادی پایان نامه های دانشجویان کارشناسی ارشد رشته های علوم پایه دانشگاه بیرجند از ابتدا تا پایان سال 1388 است. پژوهش از نوع کاربردی و با استفاده از روش تحلیل استنادی انجام گرفته است. روش های آماری این پژوهش، از نوع توصیفی(جداول و درصد فراوانی) و استنباطی(ضریب همبستگی پیرسون) می باشد. نتایج نشان داد میانگین استنادها در پایان نامه های چهار گرایش رشته شیمی، 74 استناد است. ه...

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 ...

the application of e-learning systems - as one of the solutions to the issue of anywhere and anytime learning – is increasingly spreading in the area of education. content management - one of the most important parts of any e-learning system- is in the concern of tutors and teachers through which they can obtain means and paths to achieve the goals of the course and learning objectives. e-learn...