Dielectrophoresis (DEP) is a very popular technique for microfluidic bio-particle manipulation. For the design of a DEP-based microfluidic device, simulation of the particle trajectory within the microchannel network is crucial. There are basically two approaches: (i) point-particle approach and (ii) finite-sized particle approach. In this study, many aspects of both approaches are discussed for the simulation of direct current DEP, alternating current DEP, and traveling-wave DEP applications. Point-particle approach is implemented using Lagrangian tracking method, and finite-sized particle is implemented using boundary element method. The comparison of the point-particle approach and finite-sized particle approach is presented for different DEP applications. Moreover, the effect of particle-particle interaction is explored by simulating the motion of closely packed multiple particles for the same applications, and anomalous-DEP, which is a result of particle-wall interaction at the close vicinity of electrode surface, is illustrated.
A multi-domain direct boundary element formulation for particulate flow in microchannels By Alper Topuz August 2021We certify that we have read this thesis and that in our opinion it is fully adequate, in scope and in quality, as a thesis for the degree of Master of Science.
Oil well drilling towers have different operating modes during a real operation, like drilling, tripping, and reaming. Each mode involves certain external disturbances and uncertainties. In this study, using the nonlinear model for the modes of the operation, robust and/or adaptive control systems are designed based on the models. These control strategies include five types of controllers: cascaded proportional–integral–derivative, active disturbance rejection controller, loop shaping, feedback error learning, and sliding mode controller. The study presents the design process of these controllers and evaluates the performances of the proposed control systems to track the reference signal and reject the uncertain forces including the parametric uncertainties and the external disturbances. This comparison is based on the mathematical performance measures and energy consumption. In addition, three architectures are presented to control the weight on bit during drilling process, and also to maintain a preset constant weight on bit, two control approaches are designed and presented.
Design and implementation of electromagnetic forming system Induction heating system design Experimental results of electromagnetic pulse forming systems preheated by induction High speed forming is a trending technique in sheet metal forming processes. Electromagnetic forming is one of the methods in high speed forming which is mostly employed in forming of sheet metal and pipes. For brittle materials, to increase formability, heating is employed, which would slow down the forming process if performed externally. Induction heating provides a proper option where the heating and forming processes can be sequentially applied. Induction heating is currently employed in many heating processes, both for industrial and domestic use. Its advantages such as efficiency, fast heating, safety, cleanness and accurate control makes it appropriate for such purposes. In this study, an electromagnetic forming system combined with induction heating is designed and constructed. This way, a controlled heating can be performed which is followed by the electromagnetic forming process. Figure A. Induction heating system circuit diagram and forming system circuit design Purpose: To combine the heating and forming process in an induction heating/electromagnetic forming system to improve the formability of brittle materials. Theory and Methods: Induction heating and electromagnetic forming methods are employed within the study. The material is first heated and then formed with the coil-die set system. Results: The combined induction heating/electromagnetic forming system is utilized to bulge Al7075 sheets of 0.75 mm thickness. It has been seen that the forming can be done effectively. The material that is used in the tests (Al7075) does not have an improved formability in the temperature regions tested; therefore, the system, although worked with good precision, did not lead to better forming results for the tested material. Conclusion: The combined induction heating and electromagnetic forming system that utilizes the coil-die set system is successfully operated and tested. The system is shown to perform well in forming of Al7075 sheet samples.
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