• Journal of Power Electronics
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• v.18 no.6
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• pp.1901-1911
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• 2018

This study presents a circuit model for simulating the switching transients of insulated-gate bipolar transistors (IGBTs) with inductive load switching. The modeling approach used in this study considers the behavior of IGBTs and freewheeling diodes during the transient process and ignores the complex semiconductor physics-based relationships and parameters. The proposed circuit model can accurately simulate the switching behavior due to the detailed consideration of device-circuit interactions and the nonlinear nature of model parameters, such as internal capacitances. The developed model is incorporated in an IGBT loss calculation module of an electromagnetic transient simulation program to enable the estimation of switching losses in voltage source converters embedded in large power systems.

• Nuclear Engineering and Technology
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• v.53 no.10
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• pp.3158-3163
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• 2021

Chromium material is commonly used for fusion plasma facing applications because of the low neutron activation property. The Monte Carlo method is one of the useful ways to investigate the ion-target interactions. In this study, Chromium target irradiated by protons was investigated using Monte Carlo based simulation tools. In this context, the calculations of radiation damage on Chromium material irradiated with protons at 17.9 and 22.3 MeV energies were carried out using GEANT4 and SRIM codes. Besides, the cross sections for proton interaction with Chromium target were calculated by the TALYS 1.9 code using CTM + FGM, BSFGM, and GSFM level densities. As a result, GEANT4, SRIM and TALYS 1.9 codes provide a suitable tool for the predictions of radiation damage and cross cross section with proton irradiation.

• ETRI Journal
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• v.41 no.1
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• pp.124-132
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• 2019

The energy balance (EB) model of a primary side regulation (PSR) fly-back converter in the discontinuous conduction mode (DCM) is discussed in this paper. Based on this EB model, the stability of a PSR fly-back converter in the pulse skipping mode (PSM) is analyzed, and a self-adapting modulation factor control strategy is proposed. Theoretical analysis and simulation results show that by saving an optocoupler and correlative circuits, which are necessary in traditional PSM fly-back converters, the modulation factor tolerance controlled by this method is 1.26% on average, corresponding to the ideal value. Compared with traditional fly-back PSM controllers, the power saved in the sampler/comparator modules is 87% on average for a load range of $1{\Omega}$ to $1k{\Omega}$.

• Advances in materials Research
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• v.8 no.2
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• pp.75-81
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• 2019

Through experimental and numerical studies of metal forming processes by plastic deformation, this paper represents a numerical simulation by finite element of the mechanical behavior of the material during a permanent deformation phenomenon. The main interest of this study is to optimize the shaping processes such as folding. In this context the elastic return for the folding process has been further reduced by using the design of experiments approach. In this analysis, it is proposed to consider the following factors: bending radius, metal-sheet thickness, gap and length of the fold.

• IEMEK Journal of Embedded Systems and Applications
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• v.14 no.5
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• pp.259-267
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• 2019

This paper proposes a structure of a variable impedance control system based on sensor-less external force estimator of industrial manipulators for cyber physical production systems (CPPS). To implement CPPS, a feedback system is constructed by using the robot operating system (ROS) and an external force estimator which is designed to measure the external force applied to the manipulator without a force sensor. Based on the robot dynamics, the robot-human cooperating system for the cyber physics production system is implemented through a controller that changes the impedance characteristics of the manipulator according to the situation using the external force estimator. Simulation and experimental results verify the effectiveness of the proposed control system.

• The Bulletin of The Korean Astronomical Society
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• v.43 no.2
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• pp.45.2-45.2
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• 2018

Twisted magnetic flux tubes (also called magnetic flux ropes) are believed to play a crucial role in solar eruptive phenomena. The evolution of a single flux rope with or without the influence of an overlying field of a simple geometry has been extensively studied and its physics is rather well understood. Observations show that interacting flux tubes are often involved in solar eruptions. It was Lau and Finn (1996) who intensively studied the interaction between two flux ropes, whose footpoints are anchored in two parallel planes. In this too simplified setting, the curvature of the flux rope axial fields is totally ignored. In our study, the footpoints of flux ropes are placed in a single plane containing a polarity inversion line as in the real solar active region. Our simulation study is performed for four cases: (1) co-axial field and co-axial current (co-helicity), (2) counter-axial field and co-axial current (counter-helicity), (3) co-axial field and counter-axial current (counter-helicity), and (4) counter-axial field and counter-axial current (co-helicity). Except case 3, each case is found to be related with certain eruptive features.

• Current Applied Physics
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• v.18 no.12
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• pp.1528-1533
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• 2018

The trajectories of adsorption and dissociation process of $O_2$ on the Al (111) surface were studied by the spinpolarized ab initio molecular dynamics method, and the adsorption activation energy was clarified by the NEB method with hybrid functionals. Three typical dissociation trajectories were found through simulation of $O_2$ molecule at different initial positions. When vertically approaches to the Al surface, the $O_2$ molecule tends to rotate, and the activation energy is 0.66eV. If $O_2$ molecule does not rotate, the activation energy will increase to 1.43 eV, and it makes the O atom enter the Al sublayer eventually. When the $O_2$ molecules parallel approach to the Al surface, there is no activation energy, due to the huge energy released during the adsorption process.

• Transactions of the Korean hydrogen and new energy society
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• v.32 no.6
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• pp.489-496
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• 2021

The performandce of polymer electrolyte membrane fuel cell depends on the effective management of heat and product water by the electrochemical reaction. This study is designed to investigate the parametric change of heat management along the channel of polymer electrolyte membrane. The model was developed by an aspen custom modeler that it can solve differential equation with distretization model. The model can simulate water transport through the membrane electrolyte that is coupled with heat generation. In order to verify the model, it is compared with the experimental data. The water transport behavior is then evaluated with the simulation model.

• Structural Engineering and Mechanics
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• v.83 no.5
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• pp.681-692
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• 2022

The vibrational response of the two bones in a Volleyball player's arm under ball impact is conducted. The two bones in hand, Ulna and Radius, are modeled as two cylindrical shells. The formulations associated with the shells' vibration are obtained using the energy method. Then, the results are extracted with the aid of the two-dimensional form of DQM in conjunction with Runge-Kutta. The results are validated by means of a published paper. Lastly, the role of parameters in determining vibrational frequency as well as deflection is explored through parametric studies. It was shown that the impactor speed and the time of the impact could be essential factors in determining the vibration behavior of the bones. This work can be used in the further investigation of the behavior of bones and physiological structures.

• Nuclear Engineering and Technology
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• v.55 no.1
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• pp.373-377
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• 2023

The Monte Carlo (MC) method has become an indispensable part of the nuclear radiation research field. Several widely used and well-known MC packages were developed for simulation of radiation transport and interaction with matter. All these MC packages require users to prepare an input script. The input script can become lengthy for complex models. The process of preparing these input scripts is time-consuming and error-prone. In the present work, we have developed an open-source GUI computer program for modelling radiation transport and interaction in multi-segmented slab phantoms using grid-based system for the widely used PHITS MC package. The developed tools would be useful for future users of PHITS MC package and particularly inexperienced users. The present program is distributed under GPL license and all users can freely download, modify and redistribute the program without any restrictions.