اَبَر بتن خودمتراکم (high performance high strength self compacting concrete, hphsscc)، بتن نسبتا جدیدی است بدون نیاز به ویبره و با مقاومتی حدود 800 kg/cm2 که در صورت استفاده از آن در سیستم های پس تنیده، صرفه جوئی های بیشتری نسبت به چنین بتن هائی با نیاز به ویبره را بدست خواهد داد.

abstract the present study was conducted to examine the effect of proficiency on students interaction while carrying out the grammar-based task(s) in collaboration. in particular, the study examines whether the level of proficiency affects the learners’ focus of attention to grammatical and lexical features. the study takes a further step and examines whether there is any difference in the use...

building on previous studies on the effectiveness of different types of written corrective feedback, the present study aimed at investigating whether direct focused corrective feedback and direct unfocused corrective feedback produced any differential effects on the accurate use of english articles by efl learners across two different proficiency levels (low and high). in current study, the par...

the following question poped up: is there any relationship between iranian high school efl learners reading comprehension and listening comprehension? then the following null hypothesis (ho) was developed to the test the above, mentioned question. "there is no relationship between high school efl learners reading comprehension and listening comprehension. for nearly 16 weeks, the experimental g...

heteropoly acids (hpa) and their salts have advantages as catalysts which make them both economically and environmentally attractive, strong br?nsted acidity, exhibiting fast reversible multi-electron redox transformations under rather mild conditions, very high solubility in polar solvents, fairly high thermal stability in the solid states, and efficient oxidizing ability, so that they are imp...

this study aimed at examining the effects of iranian efl learners’ anxiety, ambiguity tolerance, and gender on their preferences for corrective feedback (cf, henceforth). the effects were sought with regard to the necessity, frequency, and timing of cf, types of errors that need to be treated, types of cf, and choice of correctors. seventy-five iranian efl students, twenty-eight males and forty...