Buckling analysis of embedded concrete columns armed with carbon nanotubes

Ali Jafarian Arani,Reza Kolahchi 사단법인 한국계산역학회 2016 Computers and Concrete, An International Journal Vol.17 No.5

As concrete is most usable material in construction industry it’s been required to improve its quality. Nowadays, nanotechnology offers the possibility of great advances in construction. For the first time, the nonlinear buckling of straight concrete columns armed with single-walled carbon nanotubes (SWCNTs) resting on foundation is investigated in the present study. The column is modelled with Euler-Bernoulli and Timoshenko beam theories. The characteristics of the equivalent composite being determined using mixture rule. The foundation around the column is simulated with spring and shear layer. Employing nonlinear strains-displacements, energy methods and Hamilton's principal, the governing equations are derived. Differential quadrature method (DQM) is used in order to obtain the buckling load of structure. The influences of volume percent of SWCNTs, geometrical parameters, elastic foundation and boundary conditions on the buckling of column are investigated. Numerical results indicate that reinforcing the concrete column with SWCNTs, the structure becomes stiffer and the buckling load increases with respect to concrete column armed with steel.

On the absolute maximum dynamic response of a beam subjected to a moving mass

Mohammad Ali Lotfollahi-Yaghin,Hassan Jafarian Kafshgarkolaei,Hamed Allahyari,Taher Ghazvini 국제구조공학회 2015 Structural Engineering and Mechanics, An Int'l Jou Vol.54 No.1

Taking the mid-span/center-point of the structure as the reference point of capturing the maximum dynamic response is very customary in the available literature of the moving load problems. In this article, the absolute maximum dynamic response of an Euler-Bernoulli beam subjected to a moving mass is widely investigated for various boundary conditions of the base beam. The response of the beam is obtained by utilizing a robust numerical method so-called OPSEM (Orthonormal Polynomial Series Expansion Method). It is underlined that the absolute maximum dynamic response of the beam does notnecessarily take place at the mid-span of the beam and thus the conventional analysis needs modifications. Therefore, a comprehensive parametric survey of the base beam absolute maximum dynamic response is represented in which the contribution of the velocity and weight of the moving inertial objects are scrutinized and compared to the conventional version (maximum at mid-span).

On the absolute maximum dynamic response of a beam subjected to a moving mass

Lotfollahi-Yaghin, Mohammad Ali,Kafshgarkolaei, Hassan Jafarian,Allahyari, Hamed,Ghazvini, Taher Techno-Press 2015 Structural Engineering and Mechanics, An Int'l Jou Vol.54 No.1

Taking the mid-span/center-point of the structure as the reference point of capturing the maximum dynamic response is very customary in the available literature of the moving load problems. In this article, the absolute maximum dynamic response of an Euler-Bernoulli beam subjected to a moving mass is widely investigated for various boundary conditions of the base beam. The response of the beam is obtained by utilizing a robust numerical method so-called OPSEM (Orthonormal Polynomial Series Expansion Method). It is underlined that the absolute maximum dynamic response of the beam does not necessarily take place at the mid-span of the beam and thus the conventional analysis needs modifications. Therefore, a comprehensive parametric survey of the base beam absolute maximum dynamic response is represented in which the contribution of the velocity and weight of the moving inertial objects are scrutinized and compared to the conventional version (maximum at mid-span).

Physioelectrochemical Investigation of Electrocatalytic Activity of Modified Carbon Paste Electrode in Alcohol Oxidation as Anode in Fuel Cell

Shabani-Shayeh, Javad,Ehsani, Ali,Jafarian, Majid The Korean Electrochemical Society 2014 한국전기화학회지 Vol.17 No.3

Methanol electro oxidation on the surface of carbon paste modified by $NiCl_2/6H_2O$ was studied in 1M NaOH by potentiostatic and potentiodynamic methods. Ni/C catalyst by the concentration of 5% Ni showed about twice higher electro catalytic activity than Ni metal. The amount of monolayer's on the surface of electrode is almost one order higher for Ni/C than Ni electrode. The kinetic parameters and the diffusion coefficient of methanol were derived from chronoamperometry (CA) and electrochemical impedance spectroscopy (EIS) measurements.

Physioelectrochemical Investigation of Electrocatalytic Activity of Modified Carbon Paste Electrode in Alcohol Oxidation as Anode in Fuel Cell

Javad Shabani-Shayeh,Ali Ehsani,Majid Jafarian 한국전기화학회 2014 한국전기화학회지 Vol.17 No.3

Methanol electro oxidation on the surface of carbon paste modified by NiCl2/6H2Owas studied in 1M NaOH by potentiostatic and potentiodynamic methods. Ni/C catalyst bythe concentration of 5% Ni showed about twice higher electro catalytic activity than Ni metal. The amount of monolayer’s on the surface of electrode is almost one order higher for Ni/Cthan Ni electrode. The kinetic parameters and the diffusion coefficient of methanol were derivedfrom chronoamperometry (CA) and electrochemical impedance spectroscopy (EIS) measurements

Numerical optimization of a vertical axis wind turbine: case study at TMU campus

Seyed Kourosh Mirfazli,Mohammad Hossein Giahi,Ali Jafarian Dehkordi 한국풍공학회 2019 Wind and Structures, An International Journal (WAS Vol.28 No.3

In this paper, the aerodynamic analysis of a vertical axis wind turbine was carried out by CFD approach to optimize the turbine performance. To perform numerical simulation, SST-Transition turbulence model was used, which demonstrated more precise results compared to non-transition models. A parametric study was conducted to optimize the VAWT performance based on the selected model. The investigation of pitch angle changes showed that the highest power produced by the turbine occurs at 2º angle. Considering the effect of the rotor’s arm junction to the airfoil showed that by increasing the distance of the junction from the edge of the airfoil from 25 cm to 40 cm, the power of the turbine increases by 60%. However, further increase in this distance results in power decrease. Based on the proposed numerical model, a case study was conducted to consider the installation of four VAWTs in the southwest corner of the medical science building at TMU campus with a height of 42m. The results of the simulation showed that 8.27 MWh energy is obtainable annually.

Comparison the effect of MQL, wet and dry turning on surface topography, cylindricity tolerances and sustainability

Soroush Masoudi,Mohammad Javad Esfahani,Farshid Jafarian,Seyed Ali Mirsoleimani 한국정밀공학회 2023 International Journal of Precision Engineering and Vol.10 No.1

The increasing needs for the production of high quality parts require the use of new techniques to produce parts with higher precision. One of these modern techniques is minimum quantity lubricant (MQL) machining. In this paper, the effects of MQL, wet and dry machining on surface characteristic and geometric tolerances in turning of parts made of AISI 1045 steel were investigated. The influences of machining parameters i.e. feed rate and cutting speed as well as MQL parameters, namely air pressure and flow rate on surface topography, cutting force and cylindricity tolerance were studied. In addition, dry, wet, and MQL machining were compared to study the performance of different cooling systems. In the final step, the Pugh matrix approach was implemented to compare different cooling strategies in terms of sustainable production. According to the obtained results, MQL machining significantly improved the output parameters in AISI 1045 steel turning. By using MQL system, not only was the topography of machined surfaces improved and parts with tighter tolerances produced, but sustainability criteria were also improved. Based on sustainability assessment results, MQL turning was superior to wet and dry conditions in terms of the environmental impact, operator heath, manufacturing economy and production efficiency.

Enhanced recovery after hepatopancreaticobiliary surgery: A single-center case control study

Fakhar Nasir,Zeeshan Hyder,Amir Kasraianfard,Ali Sharifi,Abdolhamid Chavoshi Khamneh,Seyed Yahya Zarghami,Ali Jafarian 한국간담췌외과학회 2021 Annals of hepato-biliary-pancreatic surgery Vol.25 No.1

Backgrounds/Aims: The aim of this study was to find the safety and effectiveness of enhanced recovery after surgery (ERAS) in patients who undergo hepatopancreaticobiliary (HPB) surgeries and its association with the postoperative complications and survival rate of the patients. Methods: This study was conducted on patients who underwent HPB surgeries in Imam Khomeini Hospital Complex, Iran from 2018 to 2020. Patients who underwent surgery after from 2019 to February 2020 considered as the ERAS group (n=47) in which ERAS was implemented postoperatively including removing nasogastric tube and initiating surgical diet at 6 hours post operation, and removing intraabdominal drains and Foley catheter at postoperative day one. Other patients (n=43) were considered as the control group in which conventional postoperative care was implemented. Results: Ninety patients with the mean age of 47.3±13.3 yrs/old (range=17-76) including 39 females were enrolled into the study. There were no significant differences between the demographic and preoperative comorbidities between the two groups. Pain severity of the patients in the ERAS group was significantly lower than the control group (visual analogue scales of 3.4±0.77 vs. 4.47±0.88, p<0.001). However, there were no significant differences between the other postoperative data between the two groups. One patient in each group died during hospitalization period due to myocardial infarction. Conclusions: ERAS may be safe and effective in patients who undergo HPB surgery and may be associated with less severe postoperative pain.