Showing 3 results for M. Raz
M. K. Jafari, M. Davoodi and M. Razzaghi,
Volume 22, Issue 1 (7-2003)
Abstract
There is a worldwide interest in the proper design of embankment dams to resist earthquake loadings. For the first time in Iran, a complete ambient vibration survey due to low-level loads such as wind, machinery activities, low level tectonic activities, and water exit from bottom outlet was performed on Marun embankment dam. These kinds of ambient vibration tests are suitable for manifesting the lower vibration modes of the dam body. Using different signal processing methods such as Power Spectra Density, the results of in-situ tests have been used to evaluate the natural frequencies, mode shapes and modal damping of the dam body. Besides ambient vibration tests, the 3-D modal analysis of the dam body was performed using ANSYS software. The foundation and abutment flexibility effects on dynamic characteristics of the dam body was investigated and the dynamic soil properties were used from Engineer’s report and some empirical relations. Also initial shear modulus of the dam body and foundation materials were evaluated by refraction survey. In this paper, the test procedures, related signal processing results, numerical analysis results and its comparison with the dynamic characteristics of the dam body obtained from the full-scale dynamic tests will be presented. Finally, calibrating procedures of the numerical model (based on increasing the accuracy of dam body geometry, soil and rock material parameters and foundation and abutment flexibility) will be discussed.
Keywords: Embankment Dam, Dynamic Characteristics, Ambient Vibration Test, Modal Analysis
M.tahriri, F. Moztarzadeh, M. Raz , M. Ashuri,
Volume 32, Issue 1 (Jun 2013)
Abstract
In this study, magnetite (Fe3O4) nanoparticles were synthesized by chemical co-precipitation from the solution containing iron salts in alkaline medium under N2 gas and room temperature. Magnetite nanoparticles were characterized by X- ray diffraction (XRD), Fourier transform infrared spectrometer (FTIR), scanning electron microscopy (SEM), transmission electron microscopy (TEM), thermal gravimetric analysis (TGA), differential thermal analysis (DTA), Brunauer-Emmet-Teller (BET), and vibrating-sample magnetometer (VSM). The rheological properties of magnetite ferrofluid were examined by rheology apparatus. The biocompatibility and cytotoxity of magnetite nanoparticles were evaluated by 3T3 and fibroblast cells. The results showed that the Fe3O4 magnetite nanoparticles coated by polyvinyl alcohol (PVA) could be an appropriate candidate for biomedical applications.
M. Raz, F. Moztarzadeh, M.a. Shokrgozar, M. Ashuri, M. Tahriri,
Volume 32, Issue 2 (Dec 2013)
Abstract
In this project, we prepared biomimetic nanocomposite scaffolds from gelatin and chitosan and hydroxyapatite and subsequently the scaffolds were evaluated by common used bulk technique. For this purpose, the nanocomposite hydrogel/apatite bone tissue engineering scaffolds were fabricated using applied biomimetic method accompanied with freeze drying technique. The apatite was precipitated using double diffusion mechanism within gelatin hydrogel in similar pH and temperature to the human body. Chitosan initial percentage (20, 30 and 40%) was set as variables. Nanocomposites were soaked in glutaraldehyde solution in order to enhance mechanical properties and make them insoluble in water. Diffusion of calcium and phosphate from lateral hydrogel into the middle hydrogel caused formation of parallel white layer-formed precipitate. Analysis of precipitates formed within middle hydrogel for the samples, showed that detected materials are composed of carbonated hydroxyapatite and dicalcium phosphate dihydrate (DCPD, brushite). Also, mechanical behavior obtained for the scaffolds were comparable with spongy bone. With increasing chitosan in the composite scaffold, the water up-take was increased from 379 to 661%. Phase composition, microstructure and structural groups in the composite samples were also characterized by X-Ray Diffraction (XRD), scanning electron microscopy (SEM) and Fourier transform infra-red (FTIR) analyses. Eventually, the obtained results showed that the composite contains 20% chitosan had appropriate properties for fabricating bone scaffold.
