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Stability assessment of tunnel face in a layered soil using upper bound theorem of limit analysis
Khezri, Nima,Mohamad, Hisham,Fatahi, Behzad Techno-Press 2016 Geomechanics & engineering Vol.11 No.4
Underground tunnelling is one of the sustainable construction methods which can facilitate the increasing passenger transportation in the urban areas and benefit the community in the long term. Tunnelling in various ground conditions requires careful consideration of the stability factor. This paper investigates three dimensional stability of a shallow circular tunnel in a layered soil. Upper bound theorem of limit analysis was utilised to solve the tunnel face stability problem. A three dimensional kinematic admissible failure mechanism was improved to model a layered soil and limiting assumptions of the previous studies were resolved. The study includes calculation of the minimum support pressure acting on the face of the excavation in closed-face excavations. The effects of the characteristics of the layers on the minimum support pressure were examined. It was found that the ratio of the thickness of cover layers particularly when a weak layer is overlying a stronger layer, has the most significant influence on the minimum tunnel support pressure. Comparisons have been made with the results of the numerical modelling using FLAC3D software. Results of the current study were in a remarkable agreement with those of numerical modelling.
Khezri, A.,Rezayazdi, K.,Mesgaran, M. Danesh,Moradi-Sharbabk, M. Asian Australasian Association of Animal Productio 2009 Animal Bioscience Vol.22 No.5
Four multiparous lactating Holstein cows fitted with rumen cannulae were fed diets varying in the amount and source of rumen-degradable carbohydrates (starch vs. sucrose) to examine their effects on rumen fermentation, nitrogen metabolism and lactation performance. A $4{\times}4$ Latin square with four diets and four periods of 28 days each was employed. Corn starch and sucrose were added to diets and corn starch was replaced with sucrose at 0 (0 S), 2.5 (2.5 S), 5.0 (5.0 S) 7.5% (7.5 S) of diet dry matter in a total mixed ration (TMR) containing 60% concentrate and 40% forage (DM basis). Replacing corn starch with sucrose did not affect (p>0.05) ruminal pH which averaged 6.41, but the ruminal pH for 7.5 S decreased more rapidly at 2 h after morning feeding compared with other treatments. Sucrose reduced ($p{\leq}0.05$) ruminal $NH_3-N$ concentration (13.90 vs. 17.09 mg/dl) but did not affect peptide-N concentration. There was no dietary effect on total volatile fatty acids (110.53 mmol/L) or the acetate to propionate ratio (2.72). No differences (p>0.05) in molar proportion of most of the individual VFA were found among diets, except for the molar proportion of butyrate that was increased ($p{\leq}0.05$) with the inclusion of sucrose. Total branched chain volatile fatty acids tended to increase ($p{\geq}0.051$) for the control treatment (0 S) compared with the 7.5 S treatment. Dry matter intake, body weight changes and digestibility of DM, OM, CP, NDF and ADF were not affected by treatments. Sucrose inclusion in the total mixed ration did not affect milk yield, but increased milk fat and total solid percentage ($p{\leq}0.05$). Sucrose tended ($p{\geq}0.063$) to increase milk protein percentage (3.28 vs. 3.05) and reduced ($p{\leq}0.05$) milk urea nitrogen concentration (12.75 vs. 15.48 mg/dl), suggesting a more efficient utilization of the rapidly available nitrogen components in the diet and hence improving nitrogen metabolism in the rumen.
Performance enhancement through parameter optimization for a rechargeable zinc-air flow battery
Ramin Khezri,Amir Parnianifard,Shiva Rezaei Motlagh,Mohammad Etesami,Woranunt Lao-atiman,Ali Abbasi,Amornchai Arpornwichanop,Ahmad Azmin Mohamad,Sorin Olaru,Soorathep Kheawhoma 한국공업화학회 2022 Journal of Industrial and Engineering Chemistry Vol.115 No.-
Owing to their large specific energy density and eco-friendliness, zinc-air batteries (ZABs) are seen to bepotential large-scale rechargeable batteries. In recent years, numerous attempts have been made todevelop zinc-air flow batteries (ZAFBs) with the premise that a flowing electrolyte can alleviate the shortcomingsof zinc electrodes. Herein, the effects of electrolyte flow rate, current density, initial ZnO concentration,and electrolyte temperature on the performance and efficiency of a ZAFB are systematicallyexplored. In addition, the paper discusses the morphological evolution of a zinc electrode with respectto different levels of parameters as well as gravity. Optimal parameters are determined by employinga combination of orthogonal array (OA) sampling and response surface methodology. Results demonstratethat a two-factor interaction regression model can effectively predict actual results with quitean acceptable accuracy. Applying optimal conditions, the battery obtains 99.27 % charge efficiency,97.65 % discharge efficiency, 73.52 % overall round-trip efficiency, and charge and discharge overpotentialsas low as 0.36 V and 0.09 V, respectively. The optimized ZAFB is able to attain superior performancewith enhanced round-trip efficiency, making it appropriate for large-scale development.
KHEZROLLAH KHEZRI,VAHID HADDADI-ASL,HOSSEIN ROGHANI-MAMAQANI 성균관대학교(자연과학캠퍼스) 성균나노과학기술원 2014 NANO Vol.9 No.2
Mesoporous silica nanoparticles (MCM-41) surface was functionalized with 3-(trimethoxysilyl)propyl methacrylate (MPS). Then, the resultant double bond containing nanoparticles were usedin grafting through simultaneous reverse and normal initiation technique for atom transferradical polymerization (SR&NI ATRP) of styrene to synthesize well-de¯ned polystyrene nano-composites with twofold chains. Nitrogen adsorption/desorption isotherm and X-ray di®ractionanalysis were used to evaluate characteristics of spherical MCM-41 nanoparticles. Morphologicalstudies were also performed by scanning and transmission electron microscopy. Conversion andmolecular weight determinations were carried out using gas and size exclusion chromatographyrespectively. Addition of MCM-41 nanoparticles by 3 wt.% results in a decrease of conversionfrom 93% to 82%. Molecular weight of the free and attached polystyrene chains decreases byadding 3 wt.% MCM-41 nanoparticles; however, PDI values increases from 1.27 to 1.78 for freechains and 1.87 to 2.48 for attached chains. A peak around 4.1 ppm which originates fromhydrogen atom of terminal units of polystyrene chains in proton nuclear magnetic resonancespectra in combination with low PDI values can appropriately demonstrate the living nature ofthe polymerization. Increasing thermal stability of the nanocomposites is demonstrated byThermogravimetric analysis. Di®erential scanning calorimetry also shows a decrease in glasstransition temperature by increasing MCM-41 nanoparticles.
Effect of characteristics of media on cobalt and iron nanoparticles prepared by arc discharge method
S. Hosseynizadeh Khezri,A. Yazdani,R. Khordad 한국공업화학회 2014 Journal of Industrial and Engineering Chemistry Vol.20 No.2
Above a critical size, cobalt (Co) and iron (Fe) nanoparticles (NPs) aggregate due to magnetic dipole–dipole interaction into chains. In this paper, the effect of liquid environment on nucleation, growth andaggregation of Fe and Co nanoparticles is reported. The iron NPs were prepared by novel arc dischargemethod in ethylene glycol and 1-propanol and the cobalt NPs were prepared by that method in five liquidenvironments: ethylene glycol, 1-propanol, ethanol, methanol, and deionized water. SEM and FE-SEMobservations were employed for morphology of the NPs. Meanwhile, in this case, the effect of media wasdiscussed by considering the characteristics of the solution such as size, shape and dipole moment of itsmolecules. Preparation of Fe results shows that compared to 1-propanol a denser agglomeration can beseen among the NPs dispersed in ethylene glycol and the NPs possess a broader size distribution. Preparation of Co NPs in five solvent results if a solvent has large molecules with small dipole momentthen the NPs will be larger in size. When three different amounts of surfactant PVP is added to preparedFe nanofluid, it can be concluded that a low PVP content leads to more uniform NPs with rather clearboundaries.
Intelligent Robust Automotive Engine Control
Mostafa Mirzadeh,Saeed Khezri,Adel Darveshi,Mohammad Haghighi,Gholam Hossein Ahrami 보안공학연구지원센터 2015 International Journal of Hybrid Information Techno Vol.8 No.2
In this research, manage the Internal Combustion (IC) engine modeling and a multi-input-multi-output artificial intelligence baseline sliding mode methodology scheme is developed with guaranteed stability to simultaneously control fuel ratios to desired levels under various air flow disturbances by regulating the mass flow rates of engine PFI and DI injection systems. Analytical dynamic nonlinear modeling of internal combustion engine is carried out using elegant Euler-Lagrange method compromising accuracy and complexity. A baseline estimator with varying parameter gain is designed with guaranteed stability to allow implementation of the proposed state feedback sliding mode methodology into a MATLAB simulation environment, where the sliding mode strategy is implemented into a model engine control module (“software”). To estimate the dynamic model of IC engine fuzzy inference engine is applied to baseline sliding mode methodology. The proposed tracking method is designed to optimally track the desired FR by minimizing the error between the trapped in-cylinder mass and the product of the desired FR and fuel mass over a given time interval.