Researcher:
Alipour, Mohammad

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PhD Student

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Mohammad

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Alipour

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Alipour, Mohammad
Sormoli, Mohammadreza Alipour

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2017 - 201942020 - 20229

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Researcher Of Publications: search.filters.isAuthorOfPublication.5a88909c-019b-477c-b172-03963efd7d7e

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Now showing 1 - 10 of 13
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    Performance of high capacity Li-ion pouch cells over wide range of operating temperatures and discharge rates
    (Elsevier Science Sa, 2020) N/A; N/A; N/A; Department of Chemical and Biological Engineering; Alipour, Mohammad; Esen, Ekin; Varzeghani, Amir Rahimi; Kızılel, Rıza; PhD Student; PhD Student; PhD Student; Researcher; Department of Chemical and Biological Engineering; Graduate School of Sciences and Engineering; Graduate School of Sciences and Engineering; Graduate School of Sciences and Engineering; College of Engineering; N/A; N/A; N/A; 114475
    Operating temperature of Lithium-ion batteries (LIBs) significantly affects their electrochemical-thermal performance, cycle life, and cost. This study presents the thermal and electrochemical performance of 20 Ah LiFePO4 cells for 8 current rates (0.2C-5C) at 8 operating temperatures (-20 degrees C to 50 degrees C). Results show that the effects of operating temperature and current rate on cell performance differ above 10 degrees C, between 10 degrees C and 0 degrees C, and at subzero temperatures. Based on the electrochemical impedance spectroscopy (EIS) measurements, significantly higher bulk and charge-transfer resistances in conjunction with the lower diffusion coefficients results in poor battery efficiency at subzero temperatures. Optimum operating condition is 50 degrees C at a rate of 0.2C, in terms of utilized power and capacity, while a considerable power loss and capacity decrease occur below 20 degrees C. Furthermore, increasing the current rate is detrimental above 0 degrees C, whereas it improves cell performance at -10 degrees C, in terms of cell capacity. Moreover, cell temperature reaches an undesirable value at 50 degrees C and 5C rate, thus a thermal management system is necessary for high capacity LiFePO4 cells at higher temperatures and/or at higher C-rates. Additionally, temperature differences on the surface of high capacity cells reach 10 degrees C below room temperature at high current rates which can lead to nonuniform material utilization, and consequently cell failures. Finally, the cycle life of 20 Ah LiFePO4 cells decreases dramatically as discharge current rate increases. (C) 2020 Elsevier B.V. All rights reserved.
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    Design of stimuli-responsive drug delivery hydrogels synthesis and applications
    (Crc Press-Taylor and Francis Group, 2017) N/A; N/A; Department of Chemical and Biological Engineering; Aydın, Derya; Alipour, Mohammad; Kızılel, Seda; PhD Student; PhD Student; Faculty Member; Department of Chemical and Biological Engineering; Graduate School of Sciences and Engineering; Graduate School of Sciences and Engineering; College of Engineering; N/A; N/A; 28376
    Stimuli-responsive hydrogels have become popular in medicine and Polymer science as useful 'smart' devices due to their various properties such as overall biocompatibility, high drug loading capacity, and controlled molecule delivery. By tuning the polymer side chains and degree of crosslinking, these gels may exhibit swelling/shrinking behaviour in response to environmental stimuli such as light, pH, chemicals, temperature, mechanical strain, and electrical field. Sensitivity of these hydrogels enables precise control over fundamental material properties such as physical structure, porosity, swelling behaviour, mechanical strength and drug permeability. Temperature and pH alterations are examples of physiological deviations that are commonly considered for the design of responsive hydrogels, specifically for site-specific controlled drug delivery. a class of hydrogels known as multi-responsive hydrogels can respond to more than one stimuli which make them tunable and controllable with improved biomimetic properties well-suited for controlled and site specific drug delivery. Despite all these attractive properties of stimuli-responsive hydrogels, slow response time may cause some limitations in practical applications. Reduced hydrogel thickness may decrease the response time of the gel to a stimulus; however, this may lead to mechanically fragile hydrogel structures. therefore, practical applications need significant improvement in hydrogel design to improve response time considering mechanical properties, biocompatibility, and biodegradability. This chapter highlights recent progress in the field of stimuli-responsive hydrogels, focusing primarily on drug delivery vehicles.
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    Tactile feedback displayed through touchscreens via electrovibration
    (IEEE, 2020) N/A; N/A; N/A; N/A; Department of Mechanical Engineering; Özdamar, İdil; Alipour, Mohammad; Chehrehzad, Mohammadreza; Başdoğan, Çağatay; Master Student; PhD Student; PhD Student; Faculty Member; Department of Mechanical Engineering; Graduate School of Sciences and Engineering; Graduate School of Sciences and Engineering; Graduate School of Sciences and Engineering; College of Engineering; N/A; N/A; N/A; 125489
    Displaying tactile feedback through a touchscreen via electrovibration has many potential applications in mobile devices, consumer electronics, home appliances and automotive industry. However, this area of research is new and the electromechanical interactions between human finger and the touchscreen under electrovibration as well as the effect of frictional forces arising from these interactions on our haptic perception have not been fully understood yet. The aim of this study is to investigate the electro-mechanical interactions between human finger and a touchscreen under electrovibration in depth. In particular, we investigate the effect of following factors on the frictional force acting on the finger and the finger contact area; a) the amplitude and signal type (AC or DC) of voltage signal applied to the conductive layer of touchscreen, b) the magnitude of normal force applied by finger on touchscreen, and c) effect of finger speed. The results of this study enable us to better understand the physics of contact interactions between human finger and a touchscreen actuated by electrostatic forces.
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    Nanogel-integrated pH-responsive composite hydrogels for controlled drug delivery
    (Amer Chemical Soc, 2017) Hashimoto, Yoshihide; Sasaki, Yoshihiro; Akiyosh, Kazunari; N/A; N/A; N/A; Department of Chemical and Biological Engineering; Cinay, Günce Ezgi; Erkoç, Pelin; Alipour, Mohammad; Kızılel, Seda; Master Student; PhD Student; PhD Student; Faculty Member; Department of Chemical and Biological Engineering; Graduate School of Sciences and Engineering; Graduate School of Sciences and Engineering; Graduate School of Sciences and Engineering; College of Engineering; N/A; N/A; N/A; 28376
    A novel pH-sensitive hydrogel system consisting of poly(methacrylic acid-g-ethylene glycol) (P(MAA-gEG)) and acryloyl group modified-cholesterol-bearing pullulan (CHPOA) nanogels was developed for the controlled delivery of an anticonvulsant drug, pregabalin (PGB). Here, the hydrophilic hydrogel network provides the pH-sensitive swelling behavior, whereas nanogel components form separate reservoirs for the delivery of drugs with different hydro-phobicities. These nanocarrier-integrated hybrid gels were synthesized through both surface-initiated and bulk photo polymerization approaches. The swelling and drug release behavior of these pH-responsive hydrogels synthesized by different photopolymerization approaches at visible and UV light wavelenghts were studied at acidic and basic pH values. Nanogel-integrated hydrogels exhibited higher swelling behavior compared to plain hydrogels in reversible swelling experiments. Similarly, the presence of nanogels in hydrogel network enhanced the loading and release percentages of PGB and the release was analyzed to describe the mode of transport through the network. In vitro cytotoxicity assay suggests that hydrogels in altered groups are nontoxic. This is the first report about the visible light-induced synthesis of a pH-responsive network incorporated CHPOA nanogels. Responsive and multifunctional properties of this system could be used for pH-triggered release of therapeutic molecules for clinical applications.
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    Design of stimuli-responsive drug delivery hydrogels
    (CRC Press, 2017) N/A; N/A; Department of Chemical and Biological Engineering; Aydın, Derya; Alipour, Mohammad; Kızılel, Seda; PhD Student; PhD Student; Faculty Member; Department of Chemical and Biological Engineering; Koç University Tüpraş Energy Center (KUTEM) / Koç Üniversitesi Tüpraş Enerji Merkezi (KÜTEM); Graduate School of Sciences and Engineering; Graduate School of Sciences and Engineering; College of Engineering; N/A; N/A; 28376
    Stimuli-responsive hydrogels have become popular in medicine and polymer science as useful ‘smart’ devices due to their various properties such as overall biocompatibility, high drug loading capacity, and controlled molecule delivery. By tuning the polymer side chains and degree of crosslinking, these gels may exhibit swelling/shrinking behaviour in response to environmental stimuli such as light, pH, chemicals, temperature, mechanical strain, and electrical field. Sensitivity of these hydrogels enables precise control over fundamental material properties such as physical structure, porosity, swelling behaviour, mechanical strength and drug permeability. Temperature and pH alterations are examples of physiological deviations that are commonly considered for the design of responsive hydrogels, specifically for site-specific controlled drug delivery. A class of hydrogels known as multi-responsive hydrogels can respond to more than one stimuli which make them tunable and controllable with improved biomimetic properties well-suited for controlled and site specific drug delivery. Despite all these attractive properties of stimuli-responsive hydrogels, slow response time may cause some limitations in practical applications. Reduced hydrogel thickness may decrease the response time of the gel to a stimulus; however, this 2may lead to mechanically fragile hydrogel structures. Therefore, practical applications need significant improvement in hydrogel design to improve response time considering mechanical properties, biocompatibility, and biodegradability. This chapter highlights recent progress in the field of stimuli-responsive hydrogels, focusing primarily on drug delivery vehicles.
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    Numerical investigation of design parameters effects on performance of cooling system designed for a lithium-ion cell
    (Yildiz Technical University, 2020) N/A; Department of Chemical and Biological Engineering; Alipour, Mohammad; Kızılel, Rıza; PhD Student; Researcher; Department of Chemical and Biological Engineering; Graduate School of Sciences and Engineering; College of Engineering; N/A; 114475
    A 3D numerical approach using the Finite Element Method (FEM) is applied to model the thermal behavior of multilayer 20Ah LiFePO4/Graphite cell and to design a cooling system. A three-dimensional multilayer cell model with heterogeneous thermal properties for the various cell layers is developed to study the effects of design parameters on cooling performance of mini-channel aluminum plates. As design parameters, effects of channel width, a number of channel passes, inlet mass flow rate, and heat transfer medium were considered. Using the optimized parameters, the cooling performance of water-cooling and air-cooling systems were compared. The results showed that the designed cooling system provided good cooling performance in controlling the temperature rise and uniformity. Inlet mass flow rate was the main influential parameter in controlling the cooling performance. The optimum number of channel passes was found to be seven passes. Channel width mainly controlled the pressure drop and had minor effects on temperature. At higher discharge current rates, the water-cooling system showed better cooling performance in dropping the maximum temperature and making uniform surface and inner temperature profile. Moreover, pressure drop, and power consumption rates become significantly lower for water cooling system.
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    Investigation of 3-D multilayer approach in predicting the thermal behavior of 20 Ah Li-ion cells
    (Pergamon-Elsevier Science Ltd, 2019) N/A; N/A; Department of Chemical and Biological Engineering; Alipour, Mohammad; Esen, Ekin; Kızılel, Rıza; PhD Student; PhD Student; Researcher; Department of Chemical and Biological Engineering; Koç University Tüpraş Energy Center (KUTEM) / Koç Üniversitesi Tüpraş Enerji Merkezi (KÜTEM); Graduate School of Sciences and Engineering; Graduate School of Sciences and Engineering; College of Engineering; N/A; N/A; 114475
    Numerous research groups have adopted a 1D single-layer cell approach to model the thermal behavior of the Li-ion battery systems. However, as the size of a Li-ion cell increases, the 1D single-layer approach is not enough to determine the thermal behavior of the high capacity batteries. In this study, a multilayer approach is proposed to consider the effects of the number of layers on the thermal behavior of the cell. 3D electrochemical-thermal model with multilayer approach is designed and temperature predictions at various discharge rates are calculated. The results are validated at 30 degrees C for various discharge rates. Thermal behavior of the single-layer and multilayer cell approaches are compared with the experimental measurements. The results show that the error of estimates is halved if multilayer approach is applied. The proposed model is also used to study the effects of the number of layers on the temperature non-uniformity of the large sized Li-ion batteries. The results showed that multilayer cell approach represents the thermal behavior of the Li-ion cell more accurately. The study is promising for the development of an efficient thermal management system with a better prediction of the potential hot spots on the single cells and battery packs.
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    Modeling sliding friction between human finger and touchscreen under electroadhesion
    (Ieee Computer Soc, 2020) Department of Mechanical Engineering; N/A; Başdoğan, Çağatay; Alipour, Mohammad; Şirin, Ömer; Faculty Member; PhD Student; PhD Student; Department of Mechanical Engineering; College of Engineering; Graduate School of Sciences and Engineering; Graduate School of Sciences and Engineering; 125489; N/A; N/A
    When an alternating voltage is applied to the conductive layer of a capacitive touchscreen, an oscillating electroadhesive force (also known as electrovibration) is generated between the human finger and its surface in the normal direction. This electroadhesive force causes an increase in friction between the sliding finger and the touchscreen. Although the practical implementation of this technology is quite straightforward, the physics behind voltage-induced electroadhesion and the resulting contact interactions between human finger and the touchscreen are still under investigation. In this article, we first present the results of our experimental study conducted with a custom-made tribometer to investigate the effect of input voltage on the tangential forces acting on the finger due to electroadhesion during sliding. We then support our experimental results with a contact mechanics model developed for estimating voltage-induced frictional forces between human finger and a touchscreen as a function of the applied normal force. The unknown parameters of the model were estimated via optimization by minimizing the error between the measured tangential forces and the ones generated by the model. The estimated model parameters show a good agreement with the ones reported in the literature.
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    PublicationOpen Access
    Step-change in friction under electrovibration
    (Institute of Electrical and Electronics Engineers (IEEE), 2020) Delhaye, Benoit P.; Lefevre, Philippe; Department of Mechanical Engineering; Başdoğan, Çağatay; Özdamar, İdil; Alipour, Mohammad; Faculty Member; Department of Mechanical Engineering; College of Engineering; Graduate School of Sciences and Engineering; 125489; N/A; N/A
    Rendering tactile effects on a touch screen via electrovibration has many potential applications. However, our knowledge on tactile perception of change in friction and the underlying contact mechanics are both very limited. In this article, we investigate the tactile perception and the contact mechanics for a step change in friction under electrovibration during a relative sliding between a finger and the surface of a capacitive touch screen. First, we conduct magnitude estimation experiments to investigate the role of normal force and sliding velocity on the perceived tactile intensity for a step increase and decrease in friction, called rising friction (RF) and falling friction (FF). To investigate the contact mechanics involved in RF and FF, we then measure the frictional force, the apparent contact area, and the strains acting on the fingerpad during sliding at a constant velocity under three different normal loads using a custom-made experimental set-up. The results show that the participants perceived RF stronger than FF, and both the normal force and sliding velocity significantly influenced their perception. These results are supported by our mechanical measurements; the relative change in friction, the apparent contact area, and the strain in the sliding direction were all higher for RF than those for FF, especially for low normal forces. Taken together, our results suggest that different contact mechanics take place during RF and FF due to the viscoelastic behavior of fingerpad skin, and those differences influence our tactile perception of a step change in friction.
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    PublicationOpen Access
    Frequency-dependent behavior of electrostatic forces between human finger and touch screen under electroadhesion
    (Institute of Electrical and Electronics Engineers (IEEE), 2022) Department of Mechanical Engineering; Başdoğan, Çağatay; Aliabbasi, Easa; Alipour, Mohammad; Faculty Member; Department of Mechanical Engineering; College of Engineering; Graduate School of Sciences and Engineering; 125489; N/A; N/A
    The existing lumped parameter circuit models do not capture the true (experimentally observed) behavior of electrostatic forces between human finger and a touch screen under electroadhesion, changing as a function of stimulation frequency. In order to address this problem, we first conducted an experiment to measure the voltage-induced frictional forces acting on the finger of a user sliding on a touch screen under constant normal force for stimulation frequencies ranging from 1 to 106 Hz. The steady-state values of coefficient of sliding friction for those frequencies and the value for voltage-free sliding (no electroadhesion) were utilized to estimate the magnitude of electrostatic force as a function of frequency. The experimental data shows that electrostatic force follows an inverted parabolic curve with a peak value around 250 Hz. Following the experimental characterization of electrostatic forces, an electromechanical model based on the fundamental laws of electric fields and Persson's multi-scale contact mechanics theory was developed. Compared to the existing ones in the literature, the proposed model takes into account the charge accumulation and transfer at the interfaces of finger and touch screen. The model is in good agreement with the experimental data and shows that the change in magnitude of electrostatic force is mainly due to the leakage of charge from the Stratum Corneum (SC) to the touch screen at frequencies lower than 250 Hz and electrical properties of the SC at frequencies higher than 250 Hz.