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Rashid Saeidabadi,Mohammed S. Najafi,GholamReza Roshan,Jennifer M. Fitchett,Shoaieb Abkharabat 한국기상학회 2016 Asia-Pacific Journal of Atmospheric Sciences Vol.52 No.5
Relationships between precipitation and elevation are difficult to model for mountainous regions, due to complexities in topography and moisture sources. Attempts to model these relationships need to be tested against long-term location specific meteorological data, and hence require a case-study approach. This study uses artificial neural networks to model these relationships for the Middle of Zagros region, in semi-arid western Iran. Precipitation data for the region were collected for 1995-2007. Annual precipitation was designated as the target variable for the network, which additionally included variables significantly related to precipitation for the region, including longitude, latitude, elevation, slope, distance from the ridge, and relative distance from moisture. Long-term changes in annual precipitation for the region are investigated for 1961-2010. The artificial neural network (ANN) model explains 76% of the spatial variability of precipitation in the Middle Zagros. Precipitation predominantly increases with elevation on the windward slope, to a maximum height of 2500 m.asl, and thereafter either remains constant or decreases slowly to the ridge. Precipitation in the region has decreased significantly over the study period, with fluctuations driven by AO, NAO, ENSO and variability in the strength of pressure centers. Spectral analysis reveals significant oscillations of 2-4 and 5 yr periods, which correspond temporally with cycles in macro-scale circulation, ENSO and the Mediterranean Low pressure.
M. Rajabi,B. Mirza,K. Mahanpoor,M. Mirjalili,F. Najafi,O. Moradi,H. Sadegh,R. Shahryari-ghoshekandi,M. Asif,I. Tyagi,S. Agarwal,Vinod Kumar Gupta 한국공업화학회 2016 Journal of Industrial and Engineering Chemistry Vol.34 No.-
MWCNTs functionalized with the carboxylate group are used as efficient adsorbent for the rapid removaland fast adsorption of malachite green from the aqueous solutions. The optimized contact time and pHwere 10 min and 9, respectively. The effect of temperature revealed that the adsorption capacity ofmalachite green (MG) dye increased with increasing contact time, temperature and pH of the workingsolution. The adsorption equilibrium and kinetic data was well fitted and found to be in good agreementwith the Langmuir isotherm model and pseudo second order kinetic model respectively with highcorrelation coefficient.
M. Najafi,M. R. Vaezi,S. K. Sadrnezhaad 한양대학교 세라믹연구소 2011 Journal of Ceramic Processing Research Vol.12 No.6
In this paper, CuInSe2 nanostructures have been synthesized via a solvothermal method using diethyamine as a solvent. Various morphologies of CuInSe2 were obtained from the reaction of cupric chloride, indium chloride and selenium powder by changing the solvothermal conditions. The effect of the experimental parameters such as reaction time, temperature and concentration of the selenium powder were studied. The crystalline structures and morphologies of the products were characterized by means of X- ray diffraction (XRD) and field-emission scanning electron microscopy (FE-SEM) techniques,respectively. The results show that the morphology and dimensions of the CIS nanostructures obtained can be controlled through selective processing conditions. The optical properties and band gaps were estimated with a UV-Vis spectrophotometer. The electrical resistances of the samples were recorded by using four point probes.
Effect of Ce Addition on the Tribological Behavior of ZK60 Mg-Alloy
S. M. Banijamali,Y. Palizdar,S. Najafi,A. Sheikhani,M. Soltan Ali Nezhad,P. Valizadeh Moghaddam,H. Torkamani 대한금속·재료학회 2021 METALS AND MATERIALS International Vol.27 No.8
The present work aims to study the tribological behavior of an extruded ZK60 alloy in the presence of Ce; in a previous study, among ZK60 alloys with diferent Ce addition rates, an alloy with 3 wt% of Ce was found to exhibit the mostpromising mechanical (e.g., hardness and strengths) properties, while its wear behavior remained unknown. The results ofmicrostructural examinations by optical and electron microscopes show that Ce addition reduces the grain size from 6.1 to2.0 μm. Besides, in addition to the precipitates already distributed in the base alloy (Mg7Zn3), Ce could promote the formation of a new precipitate (MgZn2Ce), increasing the total fraction of the precipitates. These microstructural evolutionsenhance the strengths of the studied ZK60 alloy, as the yield and tensile strengths increase from 212 to 308 MPa and from297 to 354 MPa, respectively. A pin on disc tribometer was employed to study the wear behavior of the developed alloyunder diferent normal loads (5, 20, 40, and 60 N). The results show that the base and Ce-added alloys exhibit almost asimilar frictional behavior, while the wear resistance of the Ce-added alloy is higher within the load ranges applied: (i) inlow load conditions (5 and 20 N), where the abrasive wear is the active mechanism, the precipitates in the Ce-added alloycould enhance the wear resistance. (ii) Under the load of 40 N, oxidative wear is also an operative wear mechanism, leadingto a sharp increase in the wear rate of the alloys. In this condition, Ce could provide a protective oxide layer, which couldimprove the wear resistance of the alloy. (iii) At a load of 60 N, both studied alloys exhibit a similar wear rate due to a severeoxidation condition. Therefore, beyond this loading condition, the microstructural evolutions (e.g., change in precipitationbehavior) caused by Ce addition can no longer contribute to the enhancement of wear resistance.
M.S. Aghakhani,A.A. Khodadadi,Sh. Najafi,Y. Mortazavi 한국공업화학회 2014 Journal of Industrial and Engineering Chemistry Vol.20 No.5
Catalytic composites of Y-zeolite-amorphous silica–alumina (ASA) were prepared by four different methods to enhance pre-cracking and cracking of triisopropylbenzene (TIPB). TIPB cracking on composite catalysts were compared with a conventionally prepared catalyst. The samples were characterized by FESEM, XRD, N2-adsorption and NH3-TPD. The catalysts performance was evaluated by triisopropylbenzene cracking at 350˚ C in a fixed bed reactor. The coke content of the catalysts was measured by TPO. Compared to the conventional catalyst, significantly deeper cracking to benzene of about 117% higher, up to 62% lower amount of coke, and lower deactivation rate are observed for the composite catalysts.
Salt Tolerance in Transgenic Pea (Pisum sativum L.) Plants by P5CS Gene Transfer
Najafi F.,Rastgar-jazii F.,Khavari-Nejad R. A.,Sticklen M. The Korean Society of Plant Biotechnology 2005 Plant molecular biology and biotechnology research Vol.7 No.4
Slices of embryonic axis of mature pea (Pisum sativum L. cv. Green Arrow) seeds were used as explant. Transformation of explants was done via Agrobacterium tumefaciens bearing vector pBI-P5CS construct. The best results for inoculation of explants were obtained when they were immersed for 90 s at a concentration of $6{\times}10^8$ cell $ml^(-1)$ of bacterial suspension. Transformed pea plants were selected on $50\;mg\;l^(-1)$ kanamycin and successful transformants were confirmed by PCR and blotting. Transgenic plants were further analyzed with RT-PCR to confirm the expression of P5CS. Transgenic plants and non-transgenic plants were treated with different concentrations of NaCl 0 (control), 100, 150 and 200 mM in culture medium. Measurement of proline content indicated that transgenic plants produced more amino acid proline in response to salt in comparison with non-transgenic plants. Photosynthetic efficiency in transgenic plants under salt-stress was more than that of non-transgenic plants.
Simulating three dimensional wave run-up over breakwaters covered by antifer units
Najafi-Jilani, A.,Niri, M. Zakiri,Naderi, Nader The Society of Naval Architects of Korea 2014 International Journal of Naval Architecture and Oc Vol.6 No.2
The paper presents the numerical analysis of wave run-up over rubble-mound breakwaters covered by antifer units using a technique integrating Computer-Aided Design (CAD) and Computational Fluid Dynamics (CFD) software. Direct application of Navier-Stokes equations within armour blocks, is used to provide a more reliable approach to simulate wave run-up over breakwaters. A well-tested Reynolds-averaged Navier-Stokes (RANS) Volume of Fluid (VOF) code (Flow-3D) was adopted for CFD computations. The computed results were compared with experimental data to check the validity of the model. Numerical results showed that the direct three dimensional (3D) simulation method can deliver accurate results for wave run-up over rubble mound breakwaters. The results showed that the placement pattern of antifer units had a great impact on values of wave run-up so that by changing the placement pattern from regular to double pyramid can reduce the wave run-up by approximately 30%. Analysis was done to investigate the influences of surface roughness, energy dissipation in the pores of the armour layer and reduced wave run-up due to inflow into the armour and stone layer.
Simulating three dimensional wave run-up over breakwaters covered by antifer units
A. Najafi-Jilani,M. Zakiri Niri,Nader Naderi 대한조선학회 2014 International Journal of Naval Architecture and Oc Vol.6 No.2
The paper presents the numerical analysis of wave run-up over rubble-mound breakwaters covered by antifer units using a technique integrating Computer-Aided Design (CAD) and Computational Fluid Dynamics (CFD) software. Direct application of Navier-Stokes equations within armour blocks, is used to provide a more reliable approach to simulate wave run-up over breakwaters. A well-tested Reynolds-averaged Navier-Stokes (RANS) Volume of Fluid (VOF) code (Flow-3D) was adopted for CFD computations. The computed results were compared with experimental data to check the validity of the model. Numerical results showed that the direct three dimensional (3D) simulation method can deliver accurate results for wave run-up over rubble mound breakwaters. The results showed that the placement pattern of antifer units had a great impact on values of wave run-up so that by changing the placement pattern from regular to double pyramid can reduce the wave run-up by approximately 30%. Analysis was done to investigate the influences of surface roughness, energy dissipation in the pores of the armour layer and reduced wave run-up due to inflow into the armour and stone layer.