• 대한수학회보
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• 제56권6호
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• pp.1617-1642
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• 2019

In this paper, we study a theory for the structure of ${\tau}_w$-Loewy series of modules over commutative rings, where ${\tau}_w$ is the hereditary torsion theory induced by the so-called w-operation, and explore the relationship between ${\tau}_w$-Loewy modules and w-Artinian modules.

• 대한수학회보
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• 제59권1호
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• pp.141-154
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• 2022

Let R be a commutative ring with identity. Denote by w𝒫_w the class of weak w-projective R-modules and by w𝒫_w^⊥ the right orthogonal complement of w𝒫_w. It is shown that (w𝒫_w, w𝒫_w^⊥) is a hereditary and complete cotorsion theory, and so every R-module has a special weak w-projective precover. We also give some necessary and sufficient conditions for weak w-projective modules to be w-projective. Finally it is shown that when we discuss the existence of a weak w-projective cover of a module, it is enough to consider the w-envelope of the module.

• 대한전기학회:학술대회논문집
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• 대한전기학회 1990년도 추계학술대회 논문집 학회본부
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• pp.231-234
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• 1990

This paper shows real-time control technique of voltage-reactive power using the fuzzy theory. Here, major benefits of applying the fuzzy set theory as follow. First, heuristic knowledge of operator has been used in the operation and control of power system. Second, difficulties in traditional multi-objective numerical solution methods have been solved. Also, to achieve optimizing process on the voltage-reactive power control conventional search method have been used.

• East Asian mathematical journal
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• 제19권1호
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• pp.63-71
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• 2003

In his invited lecture presented during the First Conference of the Mathematical Society of the Republic of Moldova($Chi\c{s}in\v{a}u$, August 2001) W. A. Dudek posed several open problems on the role and properties of the skew element in the theory of n-ary groups. In this note we give the partial solutions of some of these problems.

• 전기학회논문지
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• 제56권3호
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• pp.524-530
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• 2007

This paper presents a new and simple method for sensorless operation of matrix converter drives using a constant air-gap flux and the imaginary power flowing to the motor. To improve low-speed sensorless performance, the non-linearities of a matrix converter drive such as commutation delays, turn-on and turn-off times of switching devices, and on-state switching device voltage drop are modelled using PQR transformation and compensated using a reference power control scheme. The proposed compensation method is applied for high performance induction motor drives using a 3 kW matrix converter system. Experimental results are shown to illustrate the feasibility of the proposed strategy.

• 대한전기학회:학술대회논문집
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• 대한전기학회 1998년도 하계학술대회 논문집 B
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• pp.737-739
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• 1998

This presentation describes an experiment to intergrated control, protection and measurement system configulation at KOWACO's Yongdam hydro-power station currently constructed by discrete electronic and electromechenical devices. The experiment is designed to exploit existing microcomputer technologies, digital signal processors, m/w&fiber optic communications. The theory of operation and advantages of the intergrated approach are discussed.

• Journal of Biosystems Engineering
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• 제34권2호
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• pp.89-94
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• 2009

Aerial application using an agricultural unmanned helicopter was suggested for an alternative against current pesticide application methods. Centrifugal clutches play important roles in the performance and safety of the helicopter operation. A previous study analyzed and verified the power transfer theory of the guide type centrifugal clutch. Based on the clutch theory, optimal designs of the clutch became possible and feasible using a simulation method. Design criteria of the clutch were the power transfer capacity of 24.66 kW(33.5 PS) at the rated engine speed and the engaging range speed of 3,000${\sim}$3,500 rpm. Various designs were accomplished using the simulation. An optimal clutch was simulated by determining the values of spring constant and mass of friction sector, which were 94,700 N/m and 123.7 g, respectively. The design performed the power capacity of 24.86 kW(33.8 PS) and engagement speed of 3,069 rpm, meeting the design criteria. Using the designed clutch, an efficient transfer of the power would be possible for the unmanned agricultural helicopter.

• 유통과학연구
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• 제18권8호
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• pp.75-87
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• 2020

Purpose: This study uses the protection motivation theory and information processing theory to discuss the high number of fraud phenomenon in Indonesia which causes worries to the internet users. The second problem is the large amount of information transparency in e-commerce which actually hinders the users in making decisions so it causes a negative behavior pattern, namely discontinue usage intention. Design/methodology: Therefore, this research hopes to provide insight to the online or e-commerce business community, especially for Tokopedia, to develop its business from understanding the factors influencing consumer attitude when shopping online. The sample are students from Universitas Indonesia, Institut Teknologi Bandung, Institut Pertanian Bogor, Universitas Gadjah Mada and Institut Teknologi Surabaya, with total 900 respondents. Result: The results of this research indicate that ubiquitous connectivity (UC) variable significantly affects variables such as the privacy concern (PC), information transparency (IT) and information overload (IO). PC and IO variables also significantly affect Discontinue Usage Intention (DUI). Conclusion: This study gives a new perspective that despite the phenomenon, the millennial generation especially are not entirely concerned about the privacy concern, however, this study clearly shows that the privacy issue in the digital word continues to be something that needs to be cared for.

• Journal of Power Electronics
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• 제13권6호
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• pp.919-927
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• 2013

This paper proposes a Boundary Current Mode (BCM) control scheme to realize soft switching on a conventional single phase full bridge DC/AC inverter. This technique with the advantages of no auxiliary components, low cost, high efficiency, and simple in control, is attractive for micro-inverter applications. The operation principle and characteristic waveforms of the proposed soft switching technique are analyzed in theory. A digital controller is provided based on that theory. To balance the requirements of efficiency, switching frequency, and inductor size, the design considerations are discussed in detail to guide in BCM inverter construction. A 150W prototype is built under these guidelines to implement the BCM control scheme. Simulation and experiment results demonstrate the feasibilities of the proposed soft switching technique.

• 한국광학회지
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• 제10권4호
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• pp.311-317
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• 1999

다이오드 레이저 펌핑 Nd:YAG 레이저를 평면 반일체 고리형 공진기를 이용하여 1064 nm 파장에서 단방향, 단일 모드로 발진시켰다. 실험에 사용된 반일체 고리형 공진기는 자기장 내에 놓여진 Nd:YAG 레이저 활성매질, 결정 석영판, 출력경으로 구성되어 전체적으로 광 다이오드로서 작용한다. 이에 대한 고유편광 이론 연구가 수행되었으며, 고유편광 모드에 대한 광손실이 계산되었다. 1.2 W, 809 nm 다이오드 레이저로 펌핑하여 155 mW의 단일 모드 출력을 얻었으며, 이때의 기울기 효율은 17%이었다. 동일한 두 레이저 시스템이 제작되었는데, 그 출력들의 맥놀이 주파수 스펙트럼으로부터 100 kHz 이하의 레이저 선폭을 갖는 것으로 측정되었고, 2 GHz 이상의 영역에서 연속적인 주파수 튜닝이 관측되었다.