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Investigation of change in surface morphology of heated surfaces upon pool boiling of magnetic fluids under magnetic actuation

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Materials Research Express 2016年第9期3卷

作者： Shojaeian, Mostafa Yildizhan, Melike-Mercan Cokun, Ömer Ozkalay, Ebrar Teken, Yiit Gulgun, Mehmet Ali Acar, Havva Funda Yagci Koar, Ali Mechatronics Engineering Program Faculty of Engineering and Natural Sciences Sabanci University Tuzla Istanbul34956 Turkey Materials Science and Nanoengineering Program Faculty of Engineering and Natural Sciences Sabanci University Tuzla Istanbul34956 Turkey Departmet of Chemistry Faculty of Natural Sciences Koc University Sariyer Istanbul34450 Turkey

Nanofluids are becoming a significant candidate for new generation coolants to be used in industrial applications. In order to reduce clustering and sedimentation of nanoparticles and improve the heat transfer performance simultaneously, magnetic fluids prepared with magnetic Fe3O4 nanoparticles dispersed in water, which were placed in a pool and were exposed to varying magnetic fields to actuate nanoparticles in the system. The effect of magnetic actuation on boiling heat transfer characteristics and on the surface morphology of the pool was examined. An average enhancement of 29% in boiling heat transfer was achieved via magnetic actuation with rather low magnetic field (magnetic flux densities up to 11 mT) densities. Furthermore, it was observed that magnetic actuation significantly prevented the deposition and sedimentation of the nanoparticles in the pool. Otherwise, significant destabilization of nanoparticles causing aggregation and heavy sedimentation was present as a result of the performed surface analysis. Even though magnetic actuation reduced the sedimentation on the macroscale, the deposition of a thick and porous film occurred onto the pool floor, increasing the surface roughness. © 2016 IOP Publishing Ltd.

关键词： Nanoparticles

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Design of a robust cascaded controller for Cuk converter

Design of a robust cascaded controller for Cuk converter

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International (EPE-PEMC) Power Electronics and Motion Control Conference

作者： Fiaz Ahmad Akhtar Rasool Emre Ozsoy Asif Sabanovic M. Elitas Mechatronics Faculty of Engineering and Natural Sciences Sabanci University Tuzla Istanbul

ISBN: (纸本)9781509017997

In this paper, design of a robust cascade controller for a Cuk converter is investigated. The controller contains two loop cascaded structure. The external voltage loop, which is the slow loop, contains the continuous proportionalintegral( PI) voltage controller whereas the internal current loop, which is the fast loop, contains the continuous sliding mode controller(CSMC). The controller effectiveness is validated by simulating the Cuk converter in SimPowerSystems ® toolbox of MATLAB/Simulink ®. The simulation is done for six different cases including ideal case, sudden variation of input supply voltage, load resistance, reference voltage, for noise disturbance and parametric variation. It is shown that the performance of the proposed controller is satisfactory and the ultimate goal of tracking the reference by the converter output voltage and the inductor current is achieved with little or no sensitivity to the uncertainties simulated.

关键词： Voltage control Inductors Robustness Resistance Uncertainty Switches Pulse width modulation

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Vision Based Cone Angle Estimation of Bubbly Cavitating Flow and Analysis of Scattered Bubbles using Micro Imaging Techniques

Vision Based Cone Angle Estimation of Bubbly Cavitating Flow...

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Annual Conference of the IEEE Industrial Electronics Society

作者： Gokhan Alcan Morteza Ghorbani Ali Kosar Mustafa Unel Mechatronics Engineering Program Faculty of Engineering and Natural Sciences Sabanci University

ISBN: (纸本)9781479917631

Hydrodynamic cavitation is an effective and alternative treatment method in various biomedical applications such as kidney stone erosion, ablation of benign prostatic hyperplasia tissues and annihilation of detrimental cells. In order to effectively position the orifice of bubbly cavitating flow generator towards the target and control the destructive cavitation effect, cone angle of multi-phase bubbly flow and distributions of scattered bubble swarms around main flow must be determined. This paper presents two vision based solutions to determine these quantities. 3D Gaussian modeling of multi-phase flow and edge slopes of cross-section are used to estimate the cone angle in a Kalman filter framework. Scattered bubble swarm distributions around main flow were assumed as a normal distribution and analyzed with the help of covariance matrix of the bubble position data. Hydrodynamical cavitating bubbles were generated from 0.45 cm long micro probe with 152μm inner diameter under 10 to 120 bars pressures and monitored via Particle Shadow Sizing technique. Proposed methods enabled to quantize the increasing inlet pressure effect on bubbly cavitating multi-phase flow.

关键词： cone angle Sparkling wine Sight multiphase flow bubbles supercavitating flow Scattering Gaussian distribution variance covariance matrix

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Fuzzy PID Controller Design Using Q-Learning Algorithm with a Manipulated Reward Function

Fuzzy PID Controller Design Using Q-Learning Algorithm with ...

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European Control Conference

作者： Vahid Tavakol Aghaei Ahmet Onat Ibrahim Eksin Mujde Guzelkaya Faculty of Engineering and Natural Sciences Mechatronics Engineering Sabanci University Faculty of Electrical and Electronics Engineering Control Engineering Program Istanbul Technical University

ISBN: (纸本)9781467371605

In this paper we propose a manipulated reward function for the Q-learning algorithm which is a reinforcement learning technique and utilize the proposed algorithm to tune the parameters of the input-output membership functions of fuzzy logic controllers. The use of a reward signal to formalize the idea of a goal is one of the most distinctive features of reinforcement learning. To improve both the performance and convergence criteria of the mentioned algorithm we propose a fuzzy structure for the reward function. In order to demonstrate the effectiveness of the algorithm we apply it to two second order linear systems with and without time delay and finally a nonlinear system will be examined.

关键词： Reward fuzzy PID controller learning (artificial intelligence) convergence criterion algorithms Linear system

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Single cell analysis on the role of TGF-β1 in autophagy of tumor cell-interacted stroma fibroblasts 19

Single cell analysis on the role of TGF-β1 in autophagy of ...

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19th International Conference on Miniaturized Systems for Chemistry and Life sciences, MicroTAS 2015

作者： Kim, Junyoung Karakas, Hacer Ezgi Gozuacik, Devrim Cho, Yoon-Kyoung UNIST-gil 50 Ulsan689-798 Korea Republic of Molecular Biology Genetics and Bioengineering Program Sabanci University Faculty of Engineering and Natural Sciences Orhanli-Tuzla Istanbul34956 Turkey UNIST-gil 50 Ulsan689-798 Korea Republic of

ISBN: (纸本)9780979806483

The communication between carcinoma associated fibroblast cells (CAFs) and tumor cells and autophagy activation mechanism during this interaction are important in the survival, proliferation and metastasis of cancer. Here we introduce a single cell-based screening platform consisted of PDMS porous membrane. In this paper, single cell-based screening platform is used (1) to trap single tumor cells by using gravitation force and agitation, (2) to monitor the autophagy of fibroblasts after interaction, and (3) to study paracrine factors from the heterogenic tumor cells inducing autophagy activation in fibroblasts. Our study highlights the role of TGF-β1 secreted by tumor cells in the autophagy activation in fibroblast using a novel screening system. © 15CBMS-0001.

关键词： Tumors

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Visualization and image processing of spray structure under the effect of cavitation phenomenon

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Journal of Physics: Conference Series 2015年第1期656卷

作者： M Ghorbani G Alcan D Yilmaz M Unel A Kosar Mechatronics Engineering Program Faculty of Engineering and Natural Sciences Sabanci University Orhanli Tuzla Istanbul Turkey Manufacturing Systems Program Faculty of Engineering and Natural Sciences Sabanci University Orhanli Tuzla Istanbul Turkey

This paper presents visualization and image processing of spray structure affected by cavitation bubbles and cavitating flow patterns. Experiments were conducted for a better understanding of cavitation and resulting flow regimes. Cavitation is generated with sudden pressure drop across a 4.5 mm long short micro-channel with an inner diameter of 152 μm connected to the setup using proper fittings. Generated cavitation bubbles and fluid flow patterns were observed by using a high speed camera. The spray structure was observed in four different segments and mainly the droplet evaluation in the lower segments for low upstream pressures was analyzed using several image processing techniques including contrast adjustments and morphological operators. Moreover, fluid flow regimes for different upstream pressures were investigated, and the flow patterns were analyzed in the separated regions of the spray.

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The effect of radiative heat transfer on slip flow through parallel-plate microchannels 15

The effect of radiative heat transfer on slip flow through p...

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15th International Heat Transfer Conference, IHTC 2014

作者： Shojaeian, Mostafa Zamanian, Rahim Kosar, Ali Mechatronics Engineering Program Faculty of Engineering and Natural Sciences Sabanci University Tuzla Istanbul34956 Turkey International Campus Mechanical Engineering Group Amirkabir University of Technology Tehran Iran

A wide range of applications in Micro-Electro-Mechanical systems (MEMS) has attracted many investigators in fluid flow and heat transfer in micro scale. As a continuation of ongoing research on this field, in the current study, thermal analysis of steady-state fully developed laminar gaseous flow in a parallel plate macro- and microchannel with two different constant heat fluxes at walls (asymmetrically heated walls) was considered. The rarefaction and viscous heating effects were also taken into consideration. The radiative heat transfer effect was examined through the inclusion of Rosseland approximation term in the energy equation. The first order slip velocity and temperature jump boundary conditions were implemented at the wall. Closed-form expressions were analytically obtained for temperature distributions and Nusselt number. The results indicate that increasing either Brinkman number or radiation parameter causes a decrease in heat transfer rate for the symmetrical wall heating case. Furthermore, when the wall is exposed to asymmetric wall heating, in contrast to heat fluxes ratio, increasing the radiation parameter decreases Nusselt number of lower wall. Also, increasing either the radiation parameter or heat fluxes ratio results in a reduction in Nusselt number of upper wall beyond singularity points existing in this case, whereas the opposite behavior is observed for Nusselt number of upper wall prior to these points.

关键词： Microchannels

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Alteration in Autophagic-lysosomal Potential During Aging and Neurological Diseases: The microRNA Perspective

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Current Pathobiology Reports 2013年第4期1卷 247-261页

作者： Tekirdag, Kumsal Ayse Ozturk, Deniz Gulfem Gozuacik, Devrim SABANCI University Faculty of Engineering and Natural Sciences Biological Sciences and Bioengineering Program Orhanli-Tuzla Istanbul 34956 Turkey

Macroautophagy (hereafter referred to as autophagy) is an evolutionary conserved degradation pathway that targets cytoplasmic substrates, including long-lived proteins, protein aggregates and damaged organelles, and leads to their degradation in lysosomes. Beyond its role in adaptation to cellular stresses, such as nutrient deprivation, hypoxia and toxins, recent studies attributed a central role to autophagy in aging and life span determination. Moreover, alterations and abnormalities of autophagy may contribute to a number of important health problems, including cancer, myopathies, metabolic disorders and, the focus of this review, aging-related neurodegenerative diseases. Some disease-related, mutant and aggregation-prone proteins may be cleared by autophagy;on the other hand, disregulation of the autophagy pathways may also contribute to neurotoxicity observed in degenerative pathologies. microRNAs (miRNAs) are endogenous regulators of gene expression, and their deregulation was reported in several aging-related conditions. Studies in the last few years introduced miRNAs as novel and potent regulators of autophagy. In this review article, we will summarize the connection between autophagy, aging and Alzheimer’s, Parkinson’s and Huntington’s diseases, and discuss the role of autophagy-related miRNAs in this context. © 2013, Springer Science+Business Media New York.

关键词： Ageing Autophagy microRNA Mitophagy Neurodegenerative diseases Pathobiology

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In-Channel Experiments on Vertical Swimming with Bacteria-Like Robots

In-Channel Experiments on Vertical Swimming with Bacteria-Li...

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IEEE/RSJ International Conference on Intelligent Robots and Systems

作者： Ahmet Fatih Tabak Serhat Yesilyurt Department of Mechatronics Engineering Faculty of Engineering and Design Istanbul Commerce University 34840 Istanbul Turkey Department of Mechatronics Engineering Faculty of Engineering and Natural Sciences Sabanci University 34956 Istanbul Turkey

ISBN: (纸本)9781467363563

Bio-inspired micro-robots are of great importance as to implement versatile microsystems for a variety of in vivo and in vitro applications in medicine and biology. Accurate models are necessary to understand the swimming and rigid-body dynamics of such systems. In this study, a series of experiments are conducted with a two-link cm-scale bio-inspired robot moving vertically without a tether, in silicone-filled narrow cylindrical glass channels. Swimming velocities are obtained for a set of varying tail and wave geometries, and employed to validate a resistive force theory (RFT) model using modified resistance coefficients based on measured forward velocity and body rotation rates.

关键词： Robot Swimming bacteria swimming speed waveforms Rotational behavior Medicine experimentation vertical

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Answer Set programming for reasoning with semantic knowledge in collaborative housekeeping robotics

Answer Set Programming for reasoning with semantic knowledge...

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10th IFAC Symposium on Robot Control, SYROCO 2012

作者： Aker, Erdi Patoglu, Volkan Erdem, Esra Computer Science and Engineering Faculty of Engineering and Natural Sciences Sabanci University Istanbul Turkey Mechatronics Faculty of Engineering and Natural Sciences Sabanci University Istanbul Turkey

ISBN: (纸本)9783902823113

Answer Set programming (ASP) is a knowledge representation and reasoning paradigm with high-level expressive logic-based formalism, and efficient solvers;it is applied to solve hard problems in various domains, such as, systems biology, wire routing, space shuttle control. In this paper, we present an application of ASP to housekeeping robotics, by showing how the following problems are addressed using computational methods/tools of ASP: 1) embedding commonsense knowledge automatically extracted from the commonsense knowledge base ConceptNet, into high-level representation, 2) embedding (continuous) geometric reasoning and temporal reasoning about durations of actions, into (discrete) high-level reasoning. We illustrate the applicability of ASP on several housekeeping robotics problems, and report on the computational efficiency in terms of CPU time and memory. © 2012 IFAC.

关键词： Knowledge representation

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