in this investigation the effect of external field on the electron density of nanostructures of cds, cdse, cdte, gaas and polymeric structure of three, four, five and six units of cds as a kind of nanosolar cells has been studied theoretically. as modeling this system in nanodimension, molecular structures has used. specific properties of molecular structures permit us to consider different sym...

Presence of invasive species on rangelands is a degradation sign. The aim of this study was to evaluate the effects of invasive species Leucanthemum vulgare Lam. on the structural and functional characteristics of Fandoghlou rangelands in the Namin county of Ardabil province. The model used for sampling was the stratified random systematic. Two main sites with the presence and absence of L. vul...

مراتع حدود نیمی از خشکی های جهان را در بر دارند و پوشش گیاهی آن در نتیجه تأثیر متقابل محیط و موجودات زنده به وجود آمده است و به عنوان یک اکوسیستم طبیعی مدیریت می شوند. علاوه بر مراتع، راه ها در عصر حاضر نیز از اجزا مهم و زیرساخت های اصلی زندگی نوین و توسعه کشورها به شمار می روند. جاده ها ساخته دست بشر هستند و جوامع گیاهی کنار جاده تحت تأثیر ساخت و ساز قرار دارند. پوشش "رودرال" به مجموعه ای از پ...

Determination of factors affecting on species distribution and diversity, especially in desert areas is the most important factor in rangeland ecosystems management for encountering biological stress. In order to evaluate the effect of physiographic factors on plant biodiversity in natural ecosystems of Kakhk Gonabad, this research was conducted in spring 2014. First, by overlaying four maps of...

abstract chickpea is weak in competition of weeds that damages to it at between 40 t0 60 percent. kermanshah province is one of the most important region for chickpea fields in iran. for these reosons, weed management is necessary in this crop. in order to evaluate of herbicides and stubble control on broad leave weeds control in chickpea. experiment was conducted in agricultural research stat...

Drought and grazing rangelands play an important role in changing the structure of vegetation and losing the biodiversity of natural ecosystems. In this research, in order to determine the effects of drought and livestock grazing on the vegetation structure of rangelands located in the Nakhab Forest of South Khorasan Province, species abundance, biodiversity, and range condition and trend were ...

in this study, the effects of oleothermal modification on physical and mechanical peroperties of fir wood (abeis sp.) blocks were examined. at first, some blocks of fir wood with 5 × 20 × 120 cm dimensions were prepared. the blocks were treated in soybean oil. the effects of 3 factors such as treatments temperature (180and 200 °c), holding time (12 and 15 h) and initial moisture content of wood...