• 대한수학회보
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• 제57권3호
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• pp.763-780
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• 2020

Let R be a commutative ring. An R-module M is said to be w-flat if Tor ^R₁ (M, N) is GV -torsion for any R-module N. It is known that every flat module is w-flat, but the converse is not true in general. The w-flat dimension of a module is defined in terms of w-flat resolutions. In this paper, we study the w-flat dimension of an injective w-module. To do so, we introduce and study the so-called w-copure (resp., strongly w-copure) flat modules and the w-copure flat dimensions for modules and rings. The relations between the introduced dimensions and other (classical) homological dimensions are discussed. We also study change of rings theorems for the w-copure flat dimension in various contexts. Finally some illustrative examples regarding the introduced concepts are given.

• 대한수학회보
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• 제59권1호
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• pp.213-226
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• 2022

Let R be a ring and M an R-module. Then M is said to be regular w-flat provided that the natural homomorphism I ⊗_R M → R ⊗_R M is a w-monomorphism for any regular ideal I. We distinguish regular w-flat modules from regular flat modules and w-flat modules by idealization constructions. Then we give some characterizations of total quotient rings and Prüfer v-multiplication rings (PvMRs for short) utilizing the homological properties of regular w-flat modules.

• 대한수학회보
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• 제58권4호
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• pp.1039-1052
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• 2021

In this paper, we introduce and study the class of 𝜙-w-flat modules which are generalizations of both 𝜙-flat modules and w-flat modules. The 𝜙-w-weak global dimension 𝜙-w-w.gl.dim(R) of a commutative ring R is also introduced and studied. We show that, for a 𝜙-ring R, 𝜙-w-w.gl.dim(R) = 0 if and only if w-dim(R) = 0 if and only if R is a 𝜙-von Neumann ring. It is also proved that, for a strongly 𝜙-ring R, 𝜙-w-w.gl.dim(R) ≤ 1 if and only if each nonnil ideal of R is 𝜙-w-flat, if and only if R is a 𝜙-PvMR, if and only if R is a PvMR.

• 전력전자학회:학술대회논문집
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• 전력전자학회 1999년도 전력전자학술대회 논문집
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• pp.577-580
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• 1999

High power density on-board power supply is implemented by using flat transformer. In the high frequency switching converters, large leakage inductance increases the switching stress and duty cycle loss, which sometimes limits maximum switching frequency. The flat transformer is designed by using special core structure, which has very low profile and low temperature rise since the thermal loading is spread evenly over a larger area. 100W, 3.3V output on board supply is built and tested and 50.7W/$\textrm{inch}^{3}$ power density is achieved.

• Kyungpook Mathematical Journal
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• 제53권1호
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• pp.25-35
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• 2013

In this paper, we introduce and study the concept of "strongly $t$-linked extensions", which is a stronger version of $t$-linked extensions of integral domains. We show that for an extension of Pr$\ddot{u}$fer $v$-multiplication domains, this concept is equivalent to that of "$w$-faithfully flat".

• 대한수학회보
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• 제59권5호
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• pp.1289-1304
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• 2022

In this note, we show that a strongly 𝜙-ring R is a 𝜙-PvMR if and only if any 𝜙-torsion-free R-module is 𝜙-w-flat, if and only if any GV-torsion-free divisible R-module is nonnil-absolutely w-pure, if and only if any GV-torsion-free h-divisible R-module is nonnil-absolutely w-pure, if and only if any finitely generated nonnil ideal of R is w-projective.

• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 2009년도 춘계학술대회 논문집
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• pp.711-712
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• 2009

• 전력전자학회논문지
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• 제10권3호
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• pp.248-256
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• 2005

본 논문에서는 중$\cdot$대용량 고밀도 전원 장치에 적합한 플랫 트랜스포머(Flat Transformer)를 사용하여 다양한 출력의 DC/DC 변환장치를 설계하는 방법을 제시하였다. 플랫 트랜스포머 모듈은 다수의 트랜스포머를 병렬로 구성하여 제작하고, 이차 권선이 항상 1턴으로 구성되므로 기존의 트랜스포머에 비해 누설 인덕턴스가 크게 감소하게 되어 고주파 스위칭에 적합한 형태를 가지고 있다. 본 논문에서는 플랫 트랜스포머의 성능을 증명하기 위하여 750W급 AC/DC 변환기를 구성하여 다양한 출력을 갖는 전원 장치를 제작/실험하였다.

• 대한원격탐사학회지
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• 제27권4호
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• pp.411-420
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• 2011

본 연구는 디지털 항공사진으로부터 세계적 생태보존 지역인 순천만 갯벌의 퇴적 침식 변화를 탐지하는데 기초자료가 될 수 있는 DEM을 제작하였다. 이를 위해, 기준점으로 초점거리를 수정하고, 순천만 갯벌영상의 적합한 매칭사이즈를 제시하였으며, 불량매칭으로 인한 과대 위치오차 제거를 위해 교차거리($P_R$) 임계치 적용방법을 제안하였다. 그리고 현지 종단측량 자료를 통해 제안방법으로 제작된 DEM을 기존 상용 S/W로 제작된 DEM과 비교하였다. 그 결과 제작한 갯벌 DEM이 상용 S/W로 제작한 DEM 보다 해상도와 최대편차(-21cm)가 더 좋은 결과를 보였다. 이러한 결과를 토대로 향후, 본 연구에서 제안한 방법으로 갯벌 DEM을 제작할 수 있을 것이라 판단된다.

• 대한수학회보
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• 제52권4호
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• pp.1327-1338
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• 2015

In this paper, we introduce and study the w-weak global dimension w-w.gl.dim(R) of a commutative ring R. As an application, it is shown that an integral domain R is a $Pr\ddot{u}fer$ v-multiplication domain if and only if w-w.gl.dim(R) ${\leq}1$. We also show that there is a large class of domains in which Hilbert's syzygy Theorem for the w-weak global dimension does not hold. Namely, we prove that if R is an integral domain (but not a field) for which the polynomial ring R[x] is w-coherent, then w-w.gl.dim(R[x]) = w-w.gl.dim(R).