Janus Silica Nanoparticles at Three-Phase Interface of Oil–Calcite–Electrolyte Water: Molecular Dynamics Simulation

Tohidi Zahra,Jafari Arezou,Omidkhah Mohammadreza 한국화학공학회 2024 Korean Journal of Chemical Engineering Vol.41 No.4

Nanofl uid injection into oil reservoirs is a novel chemical enhanced oil recovery (EOR) method and has been the subject of many researches in recent years. Despite its increasing applications, there is not enough information on the mechanisms and microscopic aspects of nanoparticle performance in EOR processes. Among nanoparticles, Janus nanoparticles (JNPs), which have two distinct hydrophilic and hydrophobic sides, can play an eff ective role in oil recovery enhancement applications. In the present study, molecular dynamics (MD) simulations were performed to provide a molecular-scale insight into the working mechanisms of silica Janus nanoparticles in oil recovery enhancement by considering the presence of sodium, chlorine, magnesium and sulfate ions. The calcite surface interacts with the mixture of heptane, decane, and toluene as the oil phase. Based on the simulation results, the mechanism of oil detachment from the calcite surface involves several steps. Due to the electrostatic interactions between the nanofl uid and the calcite, the formation of a water channel towards the calcite surface begins, and the nanofl uid reaches and spreads over the calcite surface, which is infl uenced by two factors: hydrogen bonds between water and calcite; the presence of ions in the nanofl uid, which can increase the hydrophilicity of the calcite surface. Thus, the oil molecules remain as a droplet on the rock surface. Subsequently, the JNPs approach to the oil–water interface near the calcite surface and push the oil droplet upward so that the oil phase completely detaches from the surface. The presence of ionic compounds around the JNPs increases their electrostatic interactions with each other and also increases the probability agglomeration of JNPs, which is a negative factor. On the other hand, they increase the electrostatic interactions of JNPs with calcite, which is a positive factor. Therefore, it is necessary to choose the optimal concentration of the ionic compounds in the injected nanofl uid. According to the simulation results, JNPs could increase the viscosity of the water phase by 60% and reduce the surface tension of water–oil by 33%. Under the reservoir temperature and pressure conditions, the diff usion coeffi cient of 1nm JNPs has increased from 3.33 × 10 –10 to 6.67 × 10 –10 m 2 /s. The results of this study may be useful for designing favorable conditions for nanofl uid injection in the EOR applications.

Dynamic stability of FG-CNT-reinforced viscoelastic micro cylindrical shells resting on nonhomogeneous orthotropic viscoelastic medium subjected to harmonic temperature distribution and 2D magnetic field

Tohidi, H.,Hosseini-Hashemi, S.H.,Maghsoudpour, A.,Etemadi, S. Techno-Press 2017 Wind and Structures, An International Journal (WAS Vol.25 No.2

This paper deals with the dynamic stability of embedded functionally graded (FG)-carbon nanotubes (CNTs)-reinforced micro cylindrical shells. The structure is subjected to harmonic non-uniform temperature distribution and 2D magnetic field. The CNT reinforcement is either uniformly distributed or FG along the thickness direction where the effective properties of nano-composite structure are estimated through Mixture low. The viscoelastic properties of structure are captured based on the Kelvin-Voigt theory. The surrounding viscoelastic medium is considered nonhomogeneous with the spring, orthotropic shear and damper constants. The material properties of cylindrical shell and the viscoelastic medium constants are assumed temperature-dependent. The first order shear deformation theory (FSDT) or Mindlin theory in conjunction with Hamilton's principle is utilized for deriving the motion equations where the size effects are considered based on Eringen's nonlocal theory. Based on differential quadrature (DQ) and Bolotin methods, the dynamic instability region (DIR) of structure is obtained for different boundary conditions. The effects of different parameters such as volume percent and distribution type of CNTs, mode number, viscoelastic medium type, temperature, boundary conditions, magnetic field, nonlocal parameter and structural damping constant are shown on the DIR of system. Numerical results indicate that the FGX distribution of CNTs is better than other considered cases. In addition, considering structural damping of system reduces the resonance frequency.

Size-dependent forced vibration response of embedded micro cylindrical shells reinforced with agglomerated CNTs using strain gradient theory

Tohidi, H.,Hosseini-Hashemi, S.H.,Maghsoudpour, A. Techno-Press 2018 Smart Structures and Systems, An International Jou Vol.22 No.5

This article presents an analysis into the nonlinear forced vibration of a micro cylindrical shell reinforced by carbon nanotubes (CNTs) with considering agglomeration effects. The structure is subjected to magnetic field and transverse harmonic mechanical load. Mindlin theory is employed to model the structure and the strain gradient theory (SGT) is also used to capture the size effect. Mori-Tanaka approach is used to estimate the equivalent material properties of the nanocomposite cylindrical shell and consider the CNTs agglomeration effect. The motion equations are derived using Hamilton's principle and the differential quadrature method (DQM) is employed to solve them for obtaining nonlinear frequency response of the cylindrical shells. The effect of different parameters including magnetic field, CNTs volume percent and agglomeration effect, boundary conditions, size effect and length to thickness ratio on the nonlinear forced vibrational characteristic of the of the system is studied. Numerical results indicate that by enhancing the CNTs volume percent, the amplitude of system decreases while considering the CNTs agglomeration effect has an inverse effect.

Size-dependent forced vibration response of embedded micro cylindrical shells reinforced with agglomerated CNTs using strain gradient theory

H. Tohidi,S.H. Hosseini-Hashemi,A. Maghsoudpour 국제구조공학회 2018 Smart Structures and Systems, An International Jou Vol.22 No.5

This article presents an analysis into the nonlinear forced vibration of a micro cylindrical shell reinforced by carbon nanotubes (CNTs) with considering agglomeration effects. The structure is subjected to magnetic field and transverse harmonic mechanical load. Mindlin theory is employed to model the structure and the strain gradient theory (SGT) is also used to capture the size effect. Mori-Tanaka approach is used to estimate the equivalent material properties of the nanocomposite cylindrical shell and consider the CNTs agglomeration effect. The motion equations are derived using Hamilton’s principle and the differential quadrature method (DQM) is employed to solve them for obtaining nonlinear frequency response of the cylindrical shells. The effect of different parameters including magnetic field, CNTs volume percent and agglomeration effect, boundary conditions, size effect and length to thickness ratio on the nonlinear forced vibrational characteristic of the of the system is studied. Numerical results indicate that by enhancing the CNTs volume percent, the amplitude of system decreases while considering the CNTs agglomeration effect has an inverse effect.

Strain gradient theory for vibration analysis of embedded CNT-reinforced micro Mindlin cylindrical shells considering agglomeration effects

H. Tohidi,S.H. Hosseini-Hashemi,A. Maghsoudpour,S. Etemadi 국제구조공학회 2017 Structural Engineering and Mechanics, An Int'l Jou Vol.62 No.5

Based on the strain gradient theory (SGT), vibration analysis of an embedded micro cylindrical shell reinforced with agglomerated carbon nanotubes (CNTs) is investigated. The elastic medium is simulated by the orthotropic Pasternak foundation. The structure is subjected to magnetic field in the axial direction. For obtaining the equivalent material properties of structure and considering agglomeration effects, the Mori-Tanaka model is applied. The motion equations are derived on the basis of Mindlin cylindrical shell theory, energy method and Hamilton’s principal. Differential quadrature method (DQM) is proposed to evaluate the frequency of system for different boundary conditions. The effects of different parameters such as CNTs volume percent, agglomeration of CNTs, elastic medium, magnetic field, boundary conditions, length to radius ratio and small scale parameter are shown on the frequency of the structure. The results indicate that the effect of CNTs agglomeration plays an important role in the frequency of system so that considering agglomeration leads to lower frequency. Furthermore, the frequency of structure increases with enhancing the small scale parameter.

A new interleaved high step up converter with low voltage stress on the main switches

Babak Tohidi,Majid Delshad,Hadi Saghafi 국제구조공학회 2020 Smart Structures and Systems, An International Jou Vol.26 No.4

In this paper, a new interleaved high step-up converter with low voltage stress on the switches is proposed. In the proposed converter, soft switching is provided for all switches by just one auxiliary switch, which decreases the conduction loss of auxiliary circuit. Also, the auxiliary circuit is expanded on the converter with more input branches. In the converter all main switches operate under zero voltage switching condition and auxiliary switch operate under zero current switching condition. Because of the interleaved structure, the reliability of converter increases and input current ripples decreases. The clamp capacitor in the converter not only absorb the voltage spikes across the switch due to leakage inductance, but also improve voltage gain. The proposed converter is fully analyzed and to verify the theoretical analysis, a 100 W prototype was implemented. Also, to show the effectiveness of auxiliary circuit on conduction EMI, EMI of the proposed converter comprised with hard switching counterpart.

Effects of Iron Supplementation on Attention Deficit Hyperactivity Disorder in Children Treated with Methylphenidate

Sepehr Tohidi,Elham Bidabadi,Mohammad-Javad Khosousi,Melika Amoukhteh,Maryam Kousha,Parham Mashouf,Tamkin Shahraki 대한정신약물학회 2021 CLINICAL PSYCHOPHARMACOLOGY AND NEUROSCIENCE Vol.19 No.4

Objective: To evaluate the effect of iron on the attention deficit hyperactivity disorder, treated with methylphenidate. Methods: This double-blind, randomized placebo-controlled clinical trial was performed on 50 children with attention deficit hyperactivity disorder under the treatment of methylphenidate, with ferritin levels below 30 ng/ml and absence of anemia. They were randomly assigned into two groups of ferrous sulfate and placebo, for 12 weeks. Conners' Parent Rating Scale (CPRS) was used to assess the outcome in the first, sixth, and twelfth weeks. Results: Almost all CPRS subscales improved in the ferrous sulfate group from the baseline to the endpoint, although only the changes in conduct subscale scores were significant (p = 0.003). There was no significant difference in score changes between two groups in intergroup comparison. Also, the score of learning problems (p = 0.007) in the first six weeks, and conduct (p = 0.023) and psychosomatic (p = 0.018) subscales in the second six weeks were improved in the ferrous sulfate group compared with the placebo group. Conclusion: Our study showed promising effects of iron supplementation in the improvement of subscales of the CPRS.

A New Predictive Model for Restrained Distortional Buckling Strength of Half-through Bridge Girders using Artificial Neural Network

Sajjad Tohidi,Yasser Sharifi 대한토목학회 2016 KSCE JOURNAL OF CIVIL ENGINEERING Vol.20 No.4

Half-through girders are not affected by conventional lateral-torsional buckling. I-section beams of simply supported half-through girders experience compression in their top flanges and tension in their bottom flanges. In this condition, the compression flange is restrained only by the stiffness of the web, and the buckling mode is generally restrained distortional. In this study, new and efficient model is derived to predict the Restrained Distortional Buckling (RDB) strength of half-through I-section bridge girders utilizing an Artificial Neural Network (ANN). The model is developed based on a reliable database obtained from the nonlinear finite element (FE) method. To verify the accuracy of the derived model, it is applied to estimate the RDB strength of parts of the FE analysis results that were not included in the modeling process. A sensitivity analysis has been also developed to determine the importance of each input parameters. ANN model is further compared to the some existing design codes. The results indicate that the proposed model is effectively capable of evaluating the RDB load of the half-through girders. The prediction performance of the ANN model is markedly better than prediction of the AISC/LRFD and the AS4100 specifications. The ANN-based design equation can reliably be employed for pre-design applications.

Introduction of a chaotic dough mixer, part A: mathematical modeling and numerical simulation

Seyed Mostafa Hosseinalipour,Amir Tohidi,Mahnaz Shokrpour,Norouz Mohammad Nouri 대한기계학회 2013 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.27 No.5

The motivation of this work is to propose a special dough mixer with chaotic advection to take advantage of high performance mixing in chaotic mixers and to develop typical dough mixers. In order to prevent common difficulties encountered due to the dynamic mesh, a mathematical model was employed based on neglecting the transient term of the momentum equation using conceptual features from creeping flow. Then, the numerical simulation was performed using the bird Carreau dough model of Dhanasekharan. The mathematical model was further developed to complete the numerical procedure in order to find the required material point trajectories for assessing the presence of chaotic advection in the proposed mixer. In this approach, Lyapunov exponents were also calculated which quantify the exponential divergence of the initially close state-space trajectories and identify chaotic behavior of the system as well. The results indicated that the flow field was a combination of both chaotic and non-chaotic zones.

The effect of heavy metals on the nutritional value of Alfalfa: comparison of nutrients and heavy metals of Alfalfa (Medicago sativa) in industrial and non‑industrial areas

Mohammad Rezaeian,Mahmoud Tohidi Moghadam,Mohammad Mehdi Kiaei,Homayoun Mahmuod Zadeh 한국독성학회 2020 Toxicological Research Vol.36 No.2

The aim of this study is to compare the nutritional value of Alfalfa and accumulation of heavy metals in the farms near and far from the industrial regions. Three regions were considered located at 2, 32 and 65 km distances from an industrial region, and the nutrient content of the Alfalfa including crude protein, crude fiber, crude fat, nitrogen-free extract, and Ash as well as soil and plant heavy metals was determined. The results showed no significant difference in the value of nutrients in the three regions except nitrogen-free extract (mainly starch and sugars). A positive correlation was observed between nitrogen-free extract and lead, chromium, and arsenic (p ≤ 0.05). In addition, the highest accumulations of heavy metals such as arsenic, chromium, lead and cadmium were found in soil and Alfalfa produced at 2 km distance from the industrial area. The lead and cadmium concentrations were higher than the maximum allowable agricultural soil concentration in the areas near industrial region; the accumulation of these metals in the Alfalfa was however lower than the cattle and plant risk levels. The distribution of heavy metals in the Alfalfa cultivated in these three areas (zinc > copper > lead > chromium > arsenic > cadmium) did not coincide with the average of these metals in the soils (lead > zinc > chromium > copper > cadmium > arsenic). The positive correlation was also recorded between electrical conductivity of agricultural soils and copper, lead, chromium and arsenic content of Alfalfa. The highest translocation factors of arsenic, chromium and lead elements were detected in industrial areas. For copper and zinc, the highest translocation factor was found in non- industrial areas. The results of this study can be applied as an important control program in different areas.