Islamic Azad University North Tehran Branch

About: Islamic Azad University North Tehran Branch is a education organization based out in Tehran, Iran. It is known for research contribution in the topics: Adsorption & Catalysis. The organization has 868 authors who have published 968 publications receiving 9987 citations.

Influence of thickness error on the operation of adjustable magneto-optical isolators

Abstract: We have performed a theoretical study on the case of transmission-type one-dimensional magnetophotonic crystals (MPCs) to establish a practical magneto-optical isolator (MOI) that operates properly even in the presence of construction errors. We have introduced a very thin MPC structure with high transmittance and a large Faraday rotation, with the capability of adjusting to a perfect MOI. A minor thickness error for the individual layers of this MOI may take it from being a perfect MOI; however, its adjustability can provide a stable operation against fabrication errors.

Synthesis and Crystal Structure of Mn(II) and Hg(II) Compounds and Solution Studies of Mn(II), Zn(II), Cd(II) and Hg(II) Compounds Based on Piperazinediium Pyridine-2,3-dicarboxylate

Abstract: Novel metal organic frameworks including {(pipzH2)[Mn(py-2,3-dc)2]·7.75H2O}n, 1, {(pipzH2)[Zn(py-2,3-dc)2]·4H2O}n, 2, [Cd(py-2,3-dc)(H2O)3]n, 3 and {(pipzH2)[Hg4Cl10]}n, 4, in which pipz is piperazine and py-2,3-dcH2 is pyridine-2,3-dicarboxylic acid were synthesized applying a proton transfer ion pair i.e. (pipzH2)(py-2,3-dcH)2 and corresponding metallic salts and studied by IR, 1H NMR, 13C NMR spectroscopy and single crystal X-ray diffractometry. The space group of compounds 1 and 4 are P21/c and C2/c of monoclinic system, respectively. The crystal dimensions are a = 20.108(2) A, b = 19.910(2) A, c = 12.997(1) A, β = 94.354(2)° for 1 and a = 15.940(1) A, b = 11.2690(9) A, c = 11.1307(9) A, β = 90.685(2)° for 4. The crystal structures of 2 and 3 have been reported previously. However, their solution studies are discussed here. The compounds had all polymeric structures. Although ZnII, CdII and HgII were elements of the same group, their behavior against the ion pair was essentially different. Various supramolecular interactions mainly hydrogen bonds of the type O-H⋯O, N-H⋯O, C-H⋯O, N-H…Cl and C-H⋯Cl were observed in the structures. There was an unusual and huge water cluster in the structure of compound 1. The solution states of compounds 1–4 were studied and reported. The protonation constants of pipz and py-2,3-dc, the py-2,3-dc/pipz proton transfer equilibrium constants and stoichiometry and stability of the system with Mn2+, Zn2+, Cd2+ and Hg2+ ions in aqueous solution were investigated by potentiometric pH titrations.

Behavior of semi-rigid connections and semi-rigid frames

Abstract: SUMMARY Semi-rigid connections are widely used in different countries. These connections are usually used in semi-rigid frames with bracing system. Considering the frequent use of these connections, studying their behavior as an individual connection or as a frame with a semi-rigid connection is of great importance. In this paper, moment–rotation behavior of bolted angle connection as a usual semi-rigid connection is studied, and the affecting factors on there are investigated. Finite element connection models are developed. These models are verified by comparing the results of finite element analyses with the results of experimental test, and the verified models are used to investigate the behavior of the connections. The behavior of semi-rigid frame with bolted angle connection is then studied conducting time-history analyses. The results show that the increase in shear stiffness of angle bolted connections significantly decreases the lateral drift and increase the frame stability against lateral loading. Copyright © 2012 John Wiley & Sons, Ltd.

The impact of task-based activities on the reading skill of iranian efl young learners at the beginner level

Abstract: Task-based learning and teaching in the realm of teaching young learners is still considered an adventure since very few experimental studies to date have tackled its applicability in that age group. The present research was an attempt to find out whether using task-based reading activities has any impact on the development of text comprehension in Iranian young learners studying English as a foreign language at the beginner level. Two groups of 25 students, aged 11 to 13, were the participants of the study. Through a reading pretest, it was ensured that the two groups were at the same level and belonged to the same population in terms of the reading skill. Having instructed the experimental group with four task types and the control group with classical reading activities, the researcher compared the reading performance of the two groups through a t-test which, not surprisingly, manifested the better performance of the experimental group. A follow-up reading test also showed that the experimental group still enjoyed a higher level of reading skill after one month. Furthermore, the scores gained from the four task types were compared and it was concluded that the students performed better in tasks which involved creativity and gave them the experience of playing.