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- 저자 : Nasrollahi, Vahid (검색결과 15 건)
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Nasrollahi, Vahid,Penchev, Pavel,Jwad, Tahseen,Dimov, Stefan,Kim, Kyunghan,Im, Changmin Elsevier 2018 Optics and lasers in engineering Vol.110 No.-
<P><B>Abstract</B></P> <P>Micro drilling employing ultra-short pulsed lasers is a promising manufacturing technology for producing high aspect ratio holes, particularly on ceramic substrates due to the growing range of application in electronic industry. Controlling the morphology and quality of the holes is an important factor in fulfilling the requirements of such applications. In this research, the effects of a wide fluence spectrum associated with the use of femto-second lasers on achievable aspect ratios were investigated by employing lenses with different focal distances. The holes’ morphology and quality were analysed utilising a high resolution X-ray tomography (XCT). It was demonstrated that the achievable aspect ratio can be increased from 3 to 25 just by varying the lenses focal distances. In addition, the quality of produced holes in terms of taper angle and cylindricity was investigated and the results showed that the quality would be improved by increasing the fluence and/or decreasing the focal distance. At the same time, the limitations of drilling holes with low focal distance lenses were discussed, i.e. sensitivity to defocusing and increased risks of recast formations inside the holes and bending effects, that should be considered in designing processes for high aspect ratio percussion drilling.</P> <P><B>Highlights</B></P> <P> <UL> <LI> The effects of different focal distance lenses and fluence on achievable holes’ aspect ratio in percussion drilling with femto-second lasers are investigated. </LI> <LI> The achievable holes’ aspect ratio can be increased significantly by employing lower focal distance lenses. </LI> <LI> Holes’ morphologies, cylindricity and taper angle improve by employing smaller focal distance lenses. </LI> <LI> The use of high fluence and high pulse energy in percussion drilling leads to a high penetration depth. </LI> <LI> Key limitations in using lenses with smaller focal distances are a higher sensitivity to defocusing, risks of recast formations and bending effects. </LI> </UL> </P>
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Investigation of pipe shear connectors using push out test
Saeed Nasrollahi,Shervin Maleki,Mahdi Shariati,Aminaton Marto,Majid Khorami 국제구조공학회 2018 Steel and Composite Structures, An International J Vol.27 No.5
Mechanical shear connectors are commonly used to transfer longitudinal shear forces across the steel-concrete interface in composite beams. Steel pipe as a new shear connector is proposed in this research and its performance to achieve composite strength is investigated. Experimental monotonic push-out tests were carried out for this connector. Then, a nonlinear finite element model of the push-out specimens is developed and verified against test results. Further, the finite element model is used to investigate the effects of pipe thickness, length and diameter on the shear strength of the connectors. The ultimate strengths of these connectors are reported and their respective failure modes are discussed. This paper comprises of the push-out tests of ten specimens on this shear connector in both the vertical and horizontal positions in different reinforced concretes. The results of experimental tests are given as load-deformation plots. It is concluded that the use of these connectors is very effective and economical in the medium shear demand range of 150-350 KN. The dominant failure modes observed were either failure of concrete block (crushing and splitting) or shear failure of pipe connector. It is shown that the horizontal pipe is not as effective as vertical pipe shear connector and is not recommended for practical use. It is shown that pipe connectors are more effective in transferring shear forces than channel and stud connectors. Moreover, based on the parametric study, a formula is presented to predict the pipe shear connectors' capacity.
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Nazanin Nasrollahi,Maryam Yousefpoor,Alireza Khataee,Vahid Vatanpour 한국공업화학회 2022 Journal of Industrial and Engineering Chemistry Vol.116 No.-
Nowadays, reaching a membrane with good mechanical/thermal properties, biocompatibility, and industrialapplication is a big challenge in science and technology. Polyurethane (PU) has been known as apolymer with excellent and distinct properties, such as biodegradability, biocompatibility, and also exclusivechemistry can be considered an important part of a membrane, especially in polymeric ones. Therefore, this review aims to introduce polyurethane and urea bond properties, structures, and chemistryand then review studies related to the polymeric separation of membranes. It is expected thatthe versatility of polyurethane in various states from flexible to rigid and from compact to foamed, whichcan be produced easily through selecting various starting materials, makes it a suitable target to be usedin various membrane applications. This review also highlights the synthesis methods of polyurethane andrelated membranes and considers the role of chain extenders and some fillers in changing the propertiesof polyurethane polymeric membranes in various categories such as exchange membranes, distillationmembranes, thin-film composite membranes, gas separation membranes, and ultrafiltration, nanofiltrationand microfiltration membranes. Other synthesized polyurethane-based membranes are introducedbriefly and some prospective about the future of polyurethane is mentioned in the end.
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Photocatalytic-membrane technology: a critical review for membrane fouling mitigation
Nazanin Nasrollahi,Leila Ghalamchi,Vahid Vatanpour,Alireza Khataee 한국공업화학회 2021 Journal of Industrial and Engineering Chemistry Vol.93 No.-
The present paper provides an overview of the hybrid photocatalytic-membrane process and its newproperties such as permeability, hydrophilicity, rejection, antifouling and photodegradation efficiency. The integration of photocatalysts and membranes could be occurred in three major stepsfirstlyphotocatalysts mixed matrix membranes, secondly photocatalysts immobilized on the surface ofmembranes, and thirdly membranes for the separation of photocatalysts from their suspensions. Different combinations of photocatalysts (TiO2, CuO or ZnO) and membrane processes are presented andcharacterized in the review paper. Positive or negative effect of different configurations of photocatalysisand membrane processes are discussed on the antifouling and antibacterial properties of themembranes. This review outlines the coupling of photocatalysts with the membranes can reduce thefouling of the membranes due to three mechanisms: elevation of membrane hydrophilicity, induction ofantibacterial properties and degradation of foulants by produced radicals. However, reactive radicals candestroy polymeric membranes. Moreover, a short introduction to the photoelectrocatalysts is presentedcombined with membrane processes.
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Nazanin Nasrollahi,Leila Ghalamchi,Vahid Vatanpour,Alireza Khataee,Maryam Yousefpoor 한국공업화학회 2022 Journal of Industrial and Engineering Chemistry Vol.109 No.-
One of the basic challenges in polymeric membrane fabrication is the control of pore size and the porosityof the membranes. In this review paper, the role of polymeric additives is overviewed in membrane fabricationprocesses, such as the formation of pores in membranes, increasing permeability, hydrophilicityand even the creation of a desirable property such as antifouling and antibacterial properties. The polymericadditives could dissolve in water during the phase inversion process (a pore forming agent) orremain in the membrane matrix (hydrophilic and antifouling agent) or could have both roles. The additivescould also act as proton exchanger and gas transport facilitating agents. This review concentrates onthe introduction of new polymeric additives. In the blended membranes, the miscibility of chosen polymericadditives at the molecular levels make it a challenge to use the modification method. Molecularinteractions between polymers such as hydrogen bonding and charge transfer play the main roles ofthe quality of blending. Different methods of polymer/co-polymer addition to the polymeric matrix ofmembranes are investigated to identify the best polymeric additives in various types of polymeric membranesincluding: pervaporation, contactor membrane, distillation membrane, etc. Moreover, the mixabilityof the additive polymer with the matrix polymer solution and the effectiveness of somefunctional additives are described in this review.
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A new hybrid meta-heuristic for structural design: ranked particles optimization
Kaveh, A.,Nasrollahi, A. Techno-Press 2014 Structural Engineering and Mechanics, An Int'l Jou Vol.52 No.2
In this paper, a new meta-heuristic algorithm named Ranked Particles Optimization (RPO), is presented. This algorithm is not inspired from natural or physical phenomena. However, it is based on numerous researches in the field of meta-heuristic optimization algorithms. In this algorithm, like other meta-heuristic algorithms, optimization process starts with by producing a population of random solutions, Particles, located in the feasible search space. In the next step, cost functions corresponding to all random particles are evaluated and some of those having minimum cost functions are stored. These particles are ranked and their weighted average is calculated and named Ranked Center. New solutions are produced by moving each particle along its previous motion, the ranked center, and the best particle found thus far. The robustness of this algorithm is verified by solving some mathematical and structural optimization problems. Simplicity of implementation and reaching to desired solution are two main characteristics of this algorithm.
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Asadollahfardi, Gholamreza,Nasrollahi, Mostafa,Rezaee, Milad,Darban, Ahmad Khodadadi Techno-Press 2017 Advances in environmental research Vol.6 No.2
This paper represents a set of experimental tests on remediation of nickel-contaminated kaolin by Electrokinetic method. For this purpose, we conducted unenhanced and EDTA-enhanced Electrokinetic tests in one, three, and five days of treatment. In unenhanced tests, we used deionized water as an electrolyte in the anode and the cathode compartments. In the EDTA-enhance tests, we used ethylenediaaminetetra acetic acid 0.1 Molar in the cathode and sodium hydroxide 0.1 Molar in the anode. The average nickel removal for unenhanced tests after three and five days of treatment was 19 and 23 percent, respectively. High buffer capacity of the soil is responsible for low removal efficiency in the unenhanced tests, which maintained pH close to the initial amount that restrained nickel as an adsorbed or precipitated forms. The average nickel removal for EDTA-unenhanced tests after three and five days of treatment was 22 and 12 percent, respectively. Lower ionic mobility of EDTA-Ni complex in comparison with $Ni^{+2}$, which is the main transportation mechanism for this complex, could be responsible for less removal efficiency in EDTA-enhanced test.
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A new hybrid meta-heuristic for structural design: ranked particles optimization
A. Kaveh,A. Nasrollahi 국제구조공학회 2014 Structural Engineering and Mechanics, An Int'l Jou Vol.52 No.2
In this paper, a new meta-heuristic algorithm named Ranked Particles Optimization (RPO), is presented. This algorithm is not inspired from natural or physical phenomena. However, it is based on numerous researches in the field of meta-heuristic optimization algorithms. In this algorithm, like other meta-heuristic algorithms, optimization process starts with by producing a population of random solutions, Particles, located in the feasible search space. In the next step, cost functions corresponding to all random particles are evaluated and some of those having minimum cost functions are stored. These particles are ranked and their weighted average is calculated and named Ranked Center. New solutions are produced by moving each particle along its previous motion, the ranked center, and the best particle found thus far. The robustness of this algorithm is verified by solving some mathematical and structural optimization problems. Simplicity of implementation and reaching to desired solution are two main characteristics of this algorithm.
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Development of a model for dimethyl ether non-adiabatic reactors to improve methanol conversion
Gholamreza Bakeri,Fatemeh Nasrollahi,Ahmad Fauzi Ismail,Mostafa Rahimnejad,Mahdi Imanian 한국화학공학회 2013 Korean Journal of Chemical Engineering Vol.30 No.10
The modeling of adiabatic and non-adiabatic reactors, using three cooling mediums in the shell side of a shell and tube reactor in cocurrent and countercurrent flow regimes has been conducted. The cooling mediums used in this research are saturated water and methanol feed gas to a reactor which is preheated in the shell side and a special type of oil. The results of adiabatic reactor modeling show good compatibility with the data received from a commercial plant. The results of non-adiabatic reactor modeling showed that more methanol conversion can be achieved in a lower length of reactor, even though in some cases the maximum temperature in the tube side of the reactor is more than the deactivation temperature of the catalyst.
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