فهرست مطالب javid zamir anvari

This research was conducted with the aim of investigating the use of metacognition on problem solving skills and academic progress of physics students in the first year of Khorram Abad city. With available random sampling, three groups of 8th grade students of Farzangan High School were selected. The first group of the control group, in the second group, the method of teaching with the metacognitive approach and in the third group, the teaching method with the metacognitive approach along with the teaching of metacognitive strategies to the students was done during the academic year. Before starting the training, the metacognition pre-test and the researcher-made physics pre-test were taken from all three groups. After the completion of the training sessions, the metacognitive state and understanding of the physics concepts of the students of all three groups were measured again using the mentioned scales. Data analysis with mixed variance method showed that the improvement of metacognitive skills of the third group was more than the second group and no significant difference was observed in the control group. The effect of improving metacognitive skills was directly related to the academic performance of the three groups.

This study evaluated the light transmission characteristics of a single modular fiber with a cylindrical microchannel using the FDTD method. To this end, various microchannel diameters (4-11μm) were explored. The SMF included a silica core (n=1.4) coated by a nanodiamond layer with a refractive index of 2.42. The impact of Fabry-Perot resonance was evidently detected in transmission features. At constant , the light transmission variations depended on the refractive index of the microchannel. A significant change was observed in the upon altering the microchannel refractive index. Based on the results, a microchannel-based SMF with different diameters can be employed for refractive index sensing. In the cases where the diameter of the microchannel largely differs from that of the core (8μm), the transmission variations were negligible. The numerical results are in good agreement with those reported in the microhole or microchannel experiment. The highest and lowest transmissions were recorded for the microchannel at diameters of 4 and 11μm, respectively. Comparing related experimental and numerical results show proper control of the microchannel diameter can enhance light transmission through the core-microchannel. The sensitivity of the refractive index to the microchannel diameter is a promising feature that can be exploited for developing various fiber optical devices.

In this article, structural stability, electronic and spectroscopic properties of zinc sulfide nanoclusters up to four atoms are studied by Density Functional Theory (DFT/B3LYP) and Hartree-Fock computational level using 6-311++G(d,p) basis set. The stable structures of these nanoclusters have been fully optimized with Gaussian 09, binding energy, energy gap, and FTIR spectra. The vibrational frequencies, Homo–Lumo energy gap, symmetry, and dipole moment are also computed for the most stable isomer of each cluster. Furthermore, NBO analysis was used for deep understanding of these interactions. The reactivity descriptors such as electronegativity are estimated for these nanoclusters to study their relative stabilities. Among nanocluster structures, the highest and lowest average binding length are related to Zn2S2 and Zn1S1, respectively. About stability of investigated structure, Zn4S4 was more stable than others (because stress of nonlinear Zn-S chains is attenuated). Both Zn1S1 and Zn3S3 nanocluster structures have a bigger dipole moment in the Hartree-Fock method. Also, increasing the number of atoms in nanoclusters has increased polarization and in the comparison, Hartree-Fock and DFT in the specimen structures, the polarization of molecules in DFT are larger rather Hartree-Fock.