• Journal of Power Electronics
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• 제17권1호
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• pp.253-261
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• 2017

For a single-phase active power filter (APF), designing a more efficient algorithm to guarantee accurate and fast harmonics extraction with a lower computing cost is still a meaningful topic. The common idea still employs a IRPT-based Park transform, which was originally designed for 3-phase applications. Therefore, an additional virtual signal generation (VSG) link is necessary when it is used in the single-phase condition. This method, with virtual signal generation and transform, is obviously not the most efficient one. Regarding this problem, this paper proposes a novel harmonics extraction algorithm to further improve efficiency. The new algorithm is based on the principle of trigonometric orthogonal functions (TOF), and its mathematical principle and physical meaning are introduced in detail. Its implementation and superiority in terms of computation efficiency are analyzed by comparing it with conventional methods. Finally, its effectiveness is well validated through detailed simulations and laboratory experiments.

• 한국수학사학회지
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• 제28권6호
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• pp.321-332
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• 2015

This paper is concerned with the convergence of double trigonometric series and Fourier series. Since the beginning of the 20th century, many authors have studied on those series. Also, Ferenc $M{\acute{o}}ricz$ has studied the convergence of double trigonometric series and double Fourier series so far. We consider $L^p(T^2)$-convergence results focused on the Ferenc $M{\acute{o}}ricz^{\prime}s$ studies from the second half of the 20th century up to now. In section 2, we reintroduce some of Ferenc $M{\acute{o}}ricz^{\prime}s$ remarkable theorems. Also we investigate his several important results. In conclusion, we investigate his research trends and the simple minor genealogy from J. B. Joseph Fourier to Ferenc $M{\acute{o}}ricz$. In addition, we present the research minor lineage of his study on $L^p(T^2)$-convergence.

• 산업기술연구
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• 제23권A호
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• pp.83-92
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• 2003

The previous control point surveying, being standardized by trigonometric point which hasn't been unified in the whole country and producing put into operation through complex calculation process, has many problems about accurate results and economic side. Because most of trigonometric points that standardize a present surveying are in situation in top of the mountain, there are many difficulties in solving sight problems. Since trigonometric points are far away from one another, Differences are created because of limitation of point distance, observatory network construction and distribution of error. In the information age, the study about acquiring three dimension surveying information that uses GPS has been processed as fast as acquiring topography information is getting important gradually. For utilizing GPS in surveying work, deciding transformation 7-Parameters that changes data about location information which is received by GPS receiver is important. In this study, it is decided transformation 7-Parameters that can be used in ka-pyoung area by using GPS surveying production that had put into operation.

• Structural Engineering and Mechanics
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• 제51권5호
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• pp.867-891
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• 2014

An equivalent single layer trigonometric shear deformation theory taking into account transverse shear deformation effect as well as transverse normal strain effect is presented for static flexure of cross-ply laminated composite and sandwich plates. The inplane displacement field uses sinusoidal function in terms of thickness coordinate to include the transverse shear deformation effect. The cosine function in thickness coordinate is used in transverse displacement to include the effect of transverse normal strain. The kinematics of the present theory is much richer than those of the other higher order shear deformation theories, because if the trigonometric term (involving thickness coordinate z) is expanded in power series, the kinematics of higher order theories (which are usually obtained by power series in thickness coordinate z) are implicitly taken into account to good deal of extent. Governing equations and boundary conditions of the theory are obtained using the principle of virtual work. The closed-form solutions of simply supported cross-ply laminated composite and sandwich plates have been obtained. The results of present theory are compared with those of the classical plate theory (CPT), first order shear deformation theory (FSDT), higher order shear deformation theory (HSDT) of Reddy and exact three dimensional elasticity theory wherever applicable. The results predicted by present theory are in good agreement with those of higher order shear deformation theory and the elasticity theory.

• 한국수학교육학회지시리즈E:수학교육논문집
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• 제23권3호
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• pp.785-801
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• 2009

본 연구에서는 제7차 수학과 교육과정 10-나 삼각함수 단원에서 구체적 조작물과 실험을 이용한 건물의 높이 너비를 측정하는 체험수학 활동을 통하여 학생들이 수학수업에 흥미를 갖고 수학의 필요성을 느낄 수 있는 방안을 제시하였다.

• Structural Engineering and Mechanics
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• 제72권3호
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• pp.329-338
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• 2019

In this paper, the magnetic field influence on the wave propagation characteristics of graphene nanosheets is examined within the frame work of a two-variable plate theory. The small-scale effect is taken into consideration based on the nonlocal strain gradient theory. For more accurate analysis of graphene sheets, the proposed theory contains two scale parameters related to the nonlocal and strain gradient effects. A derivation of the differential equation is conducted, employing extended principle of Hamilton and solved my means of analytical solution. A refined trigonometric two-variable plate theory is employed in Kinematic relations. The scattering relation of wave propagation in solid bodies which captures the relation of wave number and the resultant frequency is also investigated. According to the numerical results, it is revealed that the proposed modeling can provide accurate wave dispersion results of the graphene nanosheets as compared to some cases in the literature. It is shown that the wave dispersion characteristics of graphene sheets are influenced by magnetic field, elastic foundation and nonlocal parameters. Numerical results are presented to serve as benchmarks for future analyses of graphene nanosheets.

• Advances in nano research
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• 제10권3호
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• pp.235-251
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• 2021

In the current study, the free vibrational behavior of a Porous Micro (PM) beam which is integrated with Functionally Graded Piezoelectric (FGP) layers with initial curvature is considered based on the two trigonometric shear deformation theories namely SSDBT and Tan-SDBT. The structure's mechanical properties are varied through its thicknesses following the given functions. The curved microbeam is exposed to electro-mechanical preload and also is rested on a Pasternak type of elastic foundation. Hamilton's principle is used to extract the motion equations and the MCST is used to capture the size effect. Navier's solution method is selected as an analytical method to solve the motion equations for a simply supported ends case and by validating the results for a simpler state with previously published works, effects of different important parameters on the behavior of the structure are considered. It is found that although increasing the porosity reduces the natural frequency, but enhancing the volume fraction of CNTs increasing it. Also, by increasing the central angle of the curved beam the vibrations of the structure increases. Designing and manufacturing more efficient smart structures such as sensors and actuators are of the aims of this study.

• Advances in aircraft and spacecraft science
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• 제10권3호
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• pp.281-302
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• 2023

In this paper, bending analysis of exponentially varying functionally graded (FG) plate is presented using trigonometric shear deformation theory (TSDT) considering both transverse shear and normal deformation effects. The in-plane displacement field consists of sinusoidal functions in thickness direction to include transverse shear strains and transverse displacement include the effect of transverse normal strain using the cosine function in thickness coordinate. The governing equations and boundary conditions of the theory are derived using the virtual work principle. System of governing equations, for simply supported conditions, Navier's solution technique is used to obtain results. Plate material properties vary across thickness direction according to exponential distribution law. In the current theory, transverse shear stresses are distributed accurately through the plate thickness, hence obviates the need for a shear correction factor. TSDT results are compared with those from other theories to ensure the accuracy and effectiveness of the present theory. The current theory is in excellent agreement with the semi-analytical theory.

• 한국수학교육학회지시리즈E:수학교육논문집
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• 제34권3호
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• pp.393-419
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• 2020

삼각법은 수학의 유용성을 인식하도록 하며 삼각함수와의 연계를 통해 고등 수학 개념의 기반을 다진다. 본 연구는 호주와 핀란드를 비교 대상 국가로 정하여 Charalambous 외(2010)가 제시한 수평적 및 수직적 분석을 통해 교육과정과 교과서를 분석하였다. 세 국가가 삼각비에서 다루는 각을 확장한 학습 순서가 유사하며 삼각함수의 도입 시기 및 학습의 연속성에 차이가 있다. 삼각비의 정의 방법에 대한 학습경로는 공통적으로 삼각형 방법, 단위원 방법, 삼각함수 순서로 나타났는데 우리나라는 제 1사분면의 단위원에서 삼각비를 정의한 후 바로 일반각과 삼각함수가 전개된다는 차이점이 나타났다. 위장 맥락 문제와 인위적 맥락 문제는 우리나라가 호주나 핀란드에 비해 높은 비율을 보였다. 이를 통해 우리나라의 학습경로에서 생략되었던 단위원 방법을 제시하는 것, 실생활 맥락을 강조하는 문제를 제시하고 공학적 도구를 활용할 것, 삼각법을 다루는 교육과정 방식과 영역에 대해 재고할 것을 제안한다.

• 한국수학교육학회지시리즈A:수학교육
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• 제63권1호
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• pp.63-83
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• 2024

본 연구의 목적은 2015 개정 수학과 교육과정의 중3 교과서 삼각비 단원에 포함된 과제의 수학적 연결성 구성요소를 분석하고 이에 대한 교사의 인식 및 실천적 방안을 조사하는 것이다. 이를 위하여 중학교 3학년 수학교과서 9종을 대상으로 삼각비 단원에 포함된 수학적 연결성 과제의 특징을 분석하고, 이에 대한 인식과 실천적 방안을 조사하기 위해 예비 연구에서 현직 수학 교사 1인, 본 연구에서 현직 수학 교사 2인을 대상으로 설문지 조사와 인터뷰를 진행하였다. 연구 결과, 중학교 3학년 삼각비 단원에서는 외적 연결성의 과제가 내적 연결성의 과제보다 적은 것으로 나타났다. 또한 교사의 인식 및 실천적 방안에서는 교사의 관점에 따라 과제에 포함된 수학적 연결성에 대한 분석이 다르게 나타났으며, 이에 따른 실천적 방안 또한 다양하게 나타났다. 이러한 연구 결과는 학생들의 효과적인 수학적 연결성 함양을 위해 수학 과제, 교사의 인식, 교사의 실천적 방안 사이의 관계성을 밝혔다는 점에서 의의가 있다고 볼 수 있다.