• Journal of the Korean Ceramic Society
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• v.37 no.7
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• pp.632-637
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• 2000

Thermoelectric conversion properties of commercial Fe-Si2 and Fe-Si alloy ingots prepared by RF inductive furnace were investigated. As sintering temperature increased, density of the specimen increased and the phase transformation from metallic phases ($\varepsilon$-FeSi, ${\alpha}$-Fe2Si5) to semiconducting phase (${\beta}$-FeSi2) occurred more effectively. The FeSi phase was detected even after 100hrs of annealing treatment. For the Fesi1.95∼FeSi2.05 specimens prepared by RF inductive furnace, the thermoelectric property improved as the composition of the specimen approached to stoichiometric composition FeSi2. Electrical conductivity of the specimen increased with increasing temperatures showing typical semiconducting behavior. From the electrical conductivity measurements, activation energy in the intrinsic region (above about 700 K) was calculated to be approximately 0.46 eV. In spite of non-doping, the Seebeck coefficient for every specimen exhibited p-type conduction due to Si deficiency. Its maximum value was located at about 475 K, and then decreased abruptly with increasing temperatures. The power factor was governed by the Seebeck coefficient of the specimen more significantly than by electrical conductivity.

• Journal of Power Electronics
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• v.13 no.3
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• pp.400-408
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• 2013

This paper presents a discrete state-space controller using state feedback control and feed-forward decoupling to provide a desirable control bandwidth and control stability for dynamic voltage restorers (DVR). The paper initially discusses three typical applications of a DVR. The load-side capacitor DVR topology is preferred because of its better filtering capability. The proposed DVR controller offers almost full controllability because of the multi-feedback of state variables, including one-beat delay feedback. Feed-forward decoupling is usually employed to prevent disturbances of the load current and source voltage. Directly obtaining the feed-forward paths of the load current and source voltage in the discrete domain is a complicated process. Fortunately, the full feed-forward decoupling strategy can be easily applied to the discrete state-space controller by means of continuous transformation. Simulation and experimental results from a digital signal processor-based system are included to support theoretical analysis.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.21 no.5
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• pp.458-462
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• 2008

In this paper, we investigated the (002) preferred orientation and morphology characteristics of AlN thin film by using reactive rf sputtering. Additionally, AlN thin films grown in the range from 150 to 300 W were studied under room temperature without substrate heating and post annealing. Sputtered AlN thin films were well grown on Si substrates and the (002) main peak in XRD patterns showed the highest intensity at 300 W with $0.25^{\circ}$ degree of full width at half-maximum (FWHM). As increased RF power, the surface roughness was increased from 1.0 to 3.4 nm. In Fourier transformation infrared spectroscopy (FTIR), $A_1$ (TO) and $E_1$ (TO) mode closed to AlN thin film confirmed the changes with increasing the intensity rate. From these results, we could confirm a chance of the growth of AlN thin film by only low temperature.

• Journal of Power Electronics
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• v.13 no.6
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• pp.975-984
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• 2013

This paper proposes a robust optimal nonlinear control with an observer to reject the offset errors of position tracking for surface mounted permanent magnet synchronous motors. We provide the control method to reject offset errors and load torque for designing field oriented control (FOC) based the alternating current (AC) frame. The proposed method consists of a torque generator, a commutation scheme, an electrical controller, and a load torque observer. The mechanical controller is designed to compensate for load torque and the offset error and generate the desired torque. The commutation scheme is proposed to create the desired currents for the desired torque. The electrical controller is developed to guarantee the desired currents. The observer is designed to estimate both the velocity and the load torque. In order to obtain the robustness to parameter uncertainties and a gain tuning guide, the linear quadratic regulator method is applied to the proposed method. The closed-loop stability is proven. A detailed process for the FOC design and an analysis of the control methods based on the AC frame are presented. The performance of the proposed method was validated via experiments. The proposed method obtains the FOC based on the AC frame. Furthermore, the position tracking performance of the proposed method is superior to that of the conventional method.

• Journal of Power System Engineering
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• v.15 no.5
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• pp.91-96
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• 2011

The handling ability of containers at the terminal strongly depends on the performance of the cargo handling system such as RTGC(Rubber Tired Gantry Crane) and RMGC(Rail Mounted Gantry Crane). This paper introduces a guide line measurement system on the operating condition, in which two camera are installed to detect the guide line. Because the line tracking is the basic technique for control system design of RTGC, it is necessary to develop a useful and reliable measurement system. If the displacement and angle of the RTGC relative to a guide line as the trajectory to follow is obtained, the position of RTGC is automatically calculated. Therefore, in this paper, a camera-based measurement system is introduced. The proposed measurement system is robust against light fluctuation and cracks of the guide line. This system consists of two camera and a PC which are installed at the lower side of the RTGC. Two edges of the guide line are detected from an input image taken by the cameras in the moving state, and these positions are determined in a Hough parameter space by using the Hough transformation method. From the experimental results, the accuracy and usefulness of the proposed system is evaluated by comparing other instruments.

• Proceedings of the KIPE Conference
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• 2019.07a
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• pp.6-7
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• 2019

본 논문에서는 양방향 전력 전송을 가능케 해주는 Dual-active-bridge (DAB) 컨버터에서, 고주파 변압기 대신 무선 전력 전송 코일을 이용한 시스템을 제안한다. 기존의 DAB 컨버터에서 주로 사용되는 고주파 변압기는 Core-type 또는 shell-type으로 만들어지며, 1차 측 권선과 2차 측 권선이 자기적으로 강하게 결합되어 높은 전력 전달 효율을 가지도록 만든다. 이런 DAB 컨버터를 직/병렬 연결해 MV-DC to LV-DC로 변환하는 반도체 변압기 등을 구성할 때, 1차 측 권선과 2차 측 권선 사이에는 절연 문제와 1차 측 스위치 회로와 2차 측 스위치 회로, 그리고 고주파 변압기가 각각 따로 절연해야 하는 문제점이 있다. 본 논문에서 제안하는 DAB 컨버터는 1차 측과 2차 측이 수 cm 이격되어 있어 1차 측과 2차 측 사이의 자기적 결합이 굉장히 약하다. 따라서 1차 측과 2차 측 코일을 커패시터로 공진시켜 전력을 전달하는 무선전력전송(Loosely Coupled Inductive Wireless Power Transfer)을 이용한다. 무선전력전송의 공진 topology는 Parallel-Series로 선택했고, impedance transformation 회로를 추가했다.

• Nonlinear Functional Analysis and Applications
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• v.27 no.1
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• pp.169-187
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• 2022

There have been provided a surprisingly large number of summation formulae for generalized hypergeometric functions and series incorporating a variety of elementary and special functions in their various combinations. In this paper, we aim to consider certain generalized hypergeometric function ₃F₂ with particular arguments, through which a number of summation formulas for _p+1F_p(1) are provided. We then establish a power series whose coefficients are involved in generalized hypergeometric functions with unit argument. Also, we demonstrate that the generalized hypergeometric functions with unit argument mentioned before may be expressed in terms of Bell polynomials. Further, we explore several special instances of our primary identities, among numerous others, and raise a problem that naturally emerges throughout the course of this investigation.

• Asia pacific journal of information systems
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• v.31 no.1
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• pp.102-120
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• 2021

E-learning is a planned effort towards providing interactive and experiential learning having flexibility in terms of time, place, pace, participation and accessibility. Globalization has set the stage for a social transformation of the world economy driven by technological innovation, emphasizing knowledge-based processes. While the tertiary education enrolments in wealthy nations have gone up incrementally, the same cannot be said to be right about developing economies. E-Learning can streamline enrolments to higher education, in developing nations by being a cost-effective and flexible alternative. The objective of this paper is to draw attention to the similarities in the national culture of these two countries and compare students' perception on e-learning in India and Sri Lanka along eight dimensions viz., viability, dependability, flexibility, inclusivity, power, pertinence, challenge and equitability. The results reveal that e-learning is equally popular among students from both countries, and they have a high perception score towards e-learning on each of the measured eight dimensions. Hence results are indicative of an opportunity of tapping the potential of e-learning in reaching out to a broader audience of underprivileged students and onboarding them into the knowledge economy.

• Journal of the Daesoon Academy of Sciences
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• v.29
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• pp.1-36
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• 2017

The purpose of this article is to investigate the future prospects for establishing the True Donghak phase of Daesoon Thought. The True Donghak refers to 'the future prospect of having a true life, true thinking, and true living' in which enjoying the world in a state of good fortune became a true reality after the death of Suwun, according to faith in Gucheon Sangje. The correlation between "Attending to the Lord of Heaven" in Donghak, and "The Reordering Works of Heaven and Earth" in Daesoon shows the prospect of achieving the Daesoonist transformation into energy to gain true life and re-creation. The correlation between "Nourishing the Lord of Heaven" in Donghak and "Attending to Study and Attending to Law" in Daesoon show the transformation of Daesoon-reason into true thinking and renewing. The correlation between "Humanity is Divine" in Donghak and "The Salvation of Humanity is the Will of Heaven" in Daesoon show transformation into the practice of Daesoon for the true living and renewing. This investigation utilizes the literature review and the generation theory of life-philosophy to examine revelations regarding the conversation between Spirit and Mind. This is the future prospect for the establishing the True Donghak phase of Daesoon thought. It consists of a threefold connection among life, thinking, and living. The "public-centered spirituality of Daesoon Truth" which connects and mediates among people appears in three aspects. Firstly, it is thought to be the vision of the true life through the 'renewal of active, energetic power' bestowed by Gucheon Sangje. Secondly, it is thought to be the vision of true thinking through the "renewal via freedom from delusion". Thirdly, it is thought to be the vision of true living through the "renewal of true mind". To bring about the creation of true Donghak, Gucheon Sangje incarnated to the Korean peninsula instead of Suwun and the salvation of the world salvation now centers on Korea with regards to the threefold connection future prospect. Gucheon Sangje's revelation addresses and solves the postscript problem of Chosun and further establishes a Utopia. Suwun established Donghak but failed later on due to his lankiness. At last the true Donghak has been opened for the future by Gucheon Sangje and Jeongsan's fifty years of religious accomplishments. In the long run, it has been developed further by Woodang's Daesoon Jinrihoe.

• Transactions of the Korean hydrogen and new energy society
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• v.16 no.3
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• pp.277-283
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• 2005

Pretreatment procedure was investigated into brucite powders for mineral carbonation materials. Higher magnesium content was found from brucite powders and weight loss due to hydroxy group(-OH) elimination, explained by FT-IR spectra, was found after pretreatment. X-ray diffraction results showed that the crystallographic changing of brucite into magnesium oxides during pretreatment. XPS core spectra also showed chemical transformation of magnesium ingredient from hydroxides to oxide.