PYROMILLING SYNTHESIS OF NANOCRYSTALLINE TITANIUM CARBIDE

M. RAZAVI,S. ZAMANI,M. R. RAHIMIPOUR,P. KHATIBZADEH 성균관대학교(자연과학캠퍼스) 성균나노과학기술원 2013 NANO Vol.8 No.2

For the first time, pyromilling synthesis for production of nanocrystalline titanium carbide was presented in this research. Raw materials containing stoichiometric ratio of titanium and carbon were milled and heated simultaneously. Samplings were done at different times. Then, phase transformation, crystallite size and strain of samples were estimated by XRD technique. Microstructures of milled samples were studied by SEM and TEM. Results showed that by increasing temperature, milling time for synthesizing of titanium carbide was reduced. Crystallite size of milled samples were in nanometer scale which were reduced by increasing of milling time and decreasing of temperature while strain was intensified. Existence of created strain changed lattice parameter of synthesized titanium carbide from standard value.

Different catalytic behavior of a-amylase in response to the nitrogen substance used in the production phase

M. Hashemi,S.A. Shojaosadati,S.H. Razavi,S.M. Mousavi 한국공업화학회 2015 Journal of Industrial and Engineering Chemistry Vol.21 No.1

The impact of nitrogen substrate on the a-amylase performance at two assay conditions (pH = 4.5, 65 8C;pH = 6.8, 55 8C) was investigated. The highest a-amylase activity difference ( 38%) was related to themedium consist of dextrin, meat and yeast extracts at ( 1) levels, while the lowest variation ( 7%) wasrecorded in experiment contained the minimum amount of yeast extract followed by one with thelowest concentration ofmeat extract ( 9%). The only medium resulted in lower a-amylase activity (27%)at pH = 4.5 was the treatment with meat and yeast extracts at ( 1) levels. The effect of C/N ratio on theresponses was also investigated.

Using generalized regression neural network (GRNN) for mechanical strength prediction of lightweight mortar

S.V. Razavi,M.Z. Jumaat,E.S. Ahmed H,Mohammadi, P. 사단법인 한국계산역학회 2012 Computers and Concrete, An International Journal Vol.10 No.4

In this paper, the mechanical strength of different lightweight mortars made with 0, 5, 10, 15,20, 25, 30, 35, 40, 45, 50, 55, 60, 65, 70, 75, 80, 85, 90, 95 and 100 percentage of scoria instead of sand and 0.55 water-cement ratio and 350 kg/m3 cement content is investigated. The experimental result showed 7.9%, 16.7% and 49% decrease in compressive strength, tensile strength and mortar density, respectively, by using 100% scoria instead of sand in the mortar. The normalized compressive and tensile strength data are applied for artificial neural network (ANN) generation using generalized regression neural network (GRNN). Totally, 90 experimental data were selected randomly and applied to find the best network with minimum mean square error (MSE) and maximum correlation of determination. The created GRNN with 2 input layers, 2 output layers and a network spread of 0.1 had minimum MSE close to 0 and maximum correlation of determination close to 1.

Piezoelectric hollow cylinder with thermal gradient

M. Saadatfar,A. S. Razavi 대한기계학회 2009 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.23 No.1

The coupling nature of piezoelectric materials has acquired wide applications in electric-mechanical and electric devices. Recent advances in smart structures technology have led to a resurgence of interest in piezoelectricity, and in particular, in the solution of fundamental boundary value problems. In this paper, an analytic solution to the axisymmetric problem of a radially polarized, radially orthotropic piezoelectric hollow cylinder with thermal gradient is developed. An analytic solution to the governing equilibrium equations (a coupled system of second-order ordinary differential equations) is obtained. On application of the boundary conditions, the problem is reduced to solving a system of linear algebraic equations. The stress and potential field distributions in the cylinder are obtained numerically for two piezoceramics. It is shown that the hoop stresses in a cylinder composed of these materials can be decreased throughout the cross-section by applying an appropriate set of boundary conditions.

Accuracy of Endoscopic Ultrasonography for Determination of Tumor Invasion Depth in Gastric Cancer

Razavi, Seyed Mohsen,Khodadost, Mahmoud,Sohrabi, Masoudreza,Keshavarzi, Azam,Zamani, Farhad,Rakhshani, Naser,Ameli, Mitra,Sadeghi, Reza,Hatami, Khadijeh,Ajdarkosh, Hossein,Golmahi, Zeynab,Ranjbaran, M Asian Pacific Journal of Cancer Prevention 2015 Asian Pacific journal of cancer prevention Vol.16 No.8

Background: Gastric cancer (GC) is one the common lethal cancers in Iran. Detection of GC in the early stages would assesses to improve the survival of patients. In this study, we attempt to evaluate the accuracy of EUS in detection depth of invasion of GC among Iranian Patients. Materials and Methods: This study is a retrospective study of patients with pathologically confirmed GC. They underwent EUS before initiating the treatment. The accuracy of EUS and agreement between the two methods was evaluated by comparing pre treatment EUS finding with post operative histopathological results. Results: The overall accuracy of EUS for T and N staging was 67.9% and 75.47, respectively. Underestimation and overestimation was seen in 22 (14.2%) and 40 (25.6%) respectively. The EUS was more accurate in large tumors and the tumors located in the middle and lower parts of the stomach. The EUS was more sensitive in T3 staging. The values of weighted Kappa from the T and N staging were 0.53 and 0.66, respectively. Conclusions: EUS is a useful modality for evaluating the depth of invasion of GC. The accuracy of EUS was higher if the tumor was located in the lower parts of the stomach and the size of the tumor was more than 3 cm. Therefore, judgments made upon other criteria evaluated in this study need to be reconsidered.

Evaluation of Coloring Potential of Dietzia natronolimnaea Biomass as Source of Canthaxanthin for Egg Yolk Pigmentation

Esfahani-Mashhour, M.,Moravej, H.,Mehrabani-Yeganeh, H.,Razavi, S.H. Asian Australasian Association of Animal Productio 2009 Animal Bioscience Vol.22 No.2

An experiment was conducted to evaluate the effect of different levels of extracted pigment from Dietzia natronolimnaea biomass as a source of canthaxanthin in comparison with synthetic canthaxanthin on egg yolk pigmentation. The experiment used a completely randomized design (CRD). A total of 63 laying hens, 68 weeks old, were used and the birds were allotted to 7 dietary treatments with each treatment replicated three times with three hens per replicate. Treatments consisted of 3 levels of synthetic canthaxanthin (4, 8 and 16 ppm), 3 levels of extracted pigment from D. natronolimnaea biomass (4, 8 and 16 ppm) and control. Changes in yolk color were determined in 2 eggs taken at random, during the four week experimental period from each replicate. Supplementation of extracted pigment from D. natronolimnaea biomass had a significant effect on the color of egg yolks (p<0.05). Yolk color score of the control group was 6.83 in BASF color fan and the yolk color score of different extracted pigment levels was 11.00, 12.50 and 14.50, respectively. The yolk colors of different levels of synthetic canthaxanthin were 12.00, 14.00 and 15.00, respectively. The effect of pigment supplementation on egg yolk color was better explained by polynomial response curves. The $R_{2}$ indicated that for 3 supplementation levels of each pigment studied, over 90% of the color variation could be explained by the pigment concentration. The egg yolk color after 15 and 30 days of storage was not significantly different, but boiling reduced egg yolk color significantly (p<0.05).

Microstructure and mechanical properties of spark plasma sintered aluminabased composites reinforced with WC

D. Ghahremani,I. Mobasherpour,M. RAZAVI,H. Eslami Shahed,H. Rajaei 한양대학교 세라믹연구소 2016 Journal of Ceramic Processing Research Vol.17 No.11

Alumina-based composites reinforced with WC were fabricated by powder processing techniques and consolidated by sparkplasma sintering. Microstructure, strength, hardness and fracture toughness of the Al2O3-WC composites were studied. TheAl2O3-WC composite containing 5-20 wt% WC reached over 95% theoretical density at 1650 oC and nearly full density at1700 oC. The strength, Vickers hardness and fracture toughness of Al2O3-(10 wt. %)WC composite sintered at 1700 oC reacheda maximum value of 463 MPa, 2208 HV, and 4.15 MPa.m1/2 respectively.

Averaged strain energy density to assess mixed mode I/III fracture of U-notched GPPS samples

Saboori, Behnam,Torabi, A.R.,Berto, F.,Razavi, S.M.J. Techno-Press 2018 Structural Engineering and Mechanics, An Int'l Jou Vol.65 No.6

In the present contribution, fracture resistance of U-notched GPPS members under mixed mode I/III loading conditions is assessed by using the Averaged Strain Energy Density (ASED) criterion. This criterion has been founded based on the ASED parameter averaged over a well-defined control volume embracing the notch edge. The validation of the theoretical criterion predictions is evaluated through comparing with the results of a series of mixed mode I/III fracture tests conducted on rectangular-shaped GPPS specimens weakened by a single edge U-notch. A recently developed apparatus for mixed mode I/III fracture experiments is employed for measuring the fracture loads of the specimens. The test samples are fabricated with different notch tip radii with the aim of evaluating the influence of this major feature of the U-notched components on the mixed mode I/III fracture behavior. It is shown that the onset of brittle fracture in U-notched GPPS specimens under various combinations of tension and out-of-plane shear can well be predicted by means of the ASED criterion.

Averaged strain energy density to assess mixed mode I/III fracture of U-notched GPPS samples

Behnam Saboori,A. R. Torabi,F. Berto,S. M. J. Razavi 국제구조공학회 2018 Structural Engineering and Mechanics, An Int'l Jou Vol.65 No.6

In the present contribution, fracture resistance of U-notched GPPS members under mixed mode I/III loading conditions is assessed by using the Averaged Strain Energy Density (ASED) criterion. This criterion has been founded based on the ASED parameter averaged over a well-defined control volume embracing the notch edge. The validation of the theoretical criterion predictions is evaluated through comparing with the results of a series of mixed mode I/III fracture tests conducted on rectangular-shaped GPPS specimens weakened by a single edge U-notch. A recently developed apparatus for mixed mode I/III fracture experiments is employed for measuring the fracture loads of the specimens. The test samples are fabricated with different notch tip radii with the aim of evaluating the influence of this major feature of the U-notched components on the mixed mode I/III fracture behavior. It is shown that the onset of brittle fracture in U-notched GPPS specimens under various combinations of tension and out-of-plane shear can well be predicted by means of the ASED criterion.