• Kyungpook Mathematical Journal
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• 제54권2호
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• pp.203-209
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• 2014

We assume that the existence and termination conjecture for flips holds. A complex projective manifold is said to be of almost general type if the intersection number of the canonical divisor with every very general curve is strictly positive. Let f be an algebraic fiber space from X to Y. Then the manifold X is of almost general type if every very general fiber F and the base space Y of f are of almost general type.

• 대한수학회보
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• 제35권4호
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• pp.625-627
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• 1998

Let f: S$\rightarrow$ C be a fiber space with connected fibers. We may have an information about a surface S from the fiber space structure. The result we have is ${\chi}({\mathcal O}_C){\chi}({\mathcal O}_F){\leq}{\chi}({\mathcal O}_S)$.

• 대한수학회논문집
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• 제12권3호
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• pp.539-541
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• 1997

Let X be a smooth projective threefold. Let C be a smooth projective curve and let $f : X \to C$ be a fiber space with connected fiber S. Assume that $q_1(S) = 0$. Then we have $-X(O_C)X(O_S) \leq -X(O_X)$.

• 항공우주산업기술동향
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• 제8권2호
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• pp.76-85
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• 2010

본 논문에서는 우주환경에 사용되는 광섬유자이로(FOG)의 최근 개발동향에 대해 기술하고자 한다. 광섬유자이로는 샤냑효과를 이용하여 각속도를 측정하는 장치로 링레이저자이로(RLG)에 비해 짧은 개발역사를 가지고 있지만, 관련 소자 및 신호처리 방법의 발전으로 인해 고성능의 우주용 관성항법장치로 링레이저자이로를 대체하기에 충분한 것으로 알려져 왔다. 본 논문에서는 광섬유자이로의 개발동향을 현재까지 개발된 광섬유자이로 제품을 바탕으로 각각의 성능과 특징에 대해 알아보고, 앞으로 고성능 우주용 관성항법장치로서의 광섬유자이로의 발전 방향에 대해 살펴보기로 한다.

• Nuclear Engineering and Technology
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• 제55권8호
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• pp.3039-3045
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• 2023

Fiber-reinforced polymer (FRP) composites are considered suitable candidates for structural materials of spacecrafts due to their excellent properties of high strength, light weight, and corrosion resistance. An online health monitoring method for FRP composites must be applied to space structures. However, the application of existing health monitoring methods to space structures is limited due to the harsh space environment. Here, carbon fiber-reinforced polymer (CFRP) composites embedded with fiber Bragg grating (FBG) sensors were prepared to explore the feasibility of strain monitoring using embedded FBG sensors in γ-radiation environment. The analysis of the influence of radiation on the strain monitoring demonstrated that the embedded FBG can be successfully applied to the health monitoring of FRP composites in radiation environment.

• Restorative Dentistry and Endodontics
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• 제45권2호
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• pp.19.1-19.8
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• 2020

Objective: This study aimed to evaluate the effect of ultrasonic cleaning of the intracanal post space on the bond strength of fiber posts in oval canals filled with a premixed bioceramic (Bio-C Sealer [BIOC]) root canal sealer. Materials and Methods: Fifty premolars were endodontically prepared and divided into 5 groups (n = 10), based on the type of root canal filling material used and the post space cleaning protocol. A1: gutta-percha + AH Plus (AHP) and post space preparation with ultrasonic cleaning, A2: gutta-percha + BIOC and post space preparation with ultrasonic cleaning, B1: gutta-percha + AHP and post space preparation, B2: gutta-percha + BIOC and post space preparation, C: control group. Fiber posts were cemented with a self-adhesive luting material, and 1 mm thick slices were sectioned from the middle and cervical third to evaluate the remaining filling material microscopically. The samples were subjected to a push-out test to analyze the bond strength of the fiber post, and the results were analyzed with the Shapiro-Wilk, Bonferroni, Kruskal-Wallis, and Mann-Whitney tests (p < 0.05). Failure modes were evaluated using optical microscopy. Results: The results showed that the fiber posts cemented in canals sealed with BIOC had lower bond strength than those sealed with AHP. The ultrasonic cleaning of the post space improved the bond strength of fiber posts in canals sealed with AHP, but not with BIOC. Conclusions: BIOC decreased the bond strength of fiber posts in oval canals, regardless of ultrasonic cleaning.

• 대한수학회지
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• 제42권4호
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• pp.621-634
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• 2005

Let$P{\rightarrow}M$ be an oriented $S^2-fiber$ bundle over a closed manifold M and let Q be its associated SO(3)-bundle, then we investigate the ring structure of the cohomology of the total space P by constructing the coupling form TA induced from an SO(3) connection A. We show that the cohomology ring of total space splits into those of the base space and the fiber space if and only if the Pontrjangin class $p_1(Q)\;{\in}\;H^4(M;\mathbb{Z})$ vanishes. We apply this result to the twistor spaces of 4-manifolds.

• 대한수학회보
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• 제38권4호
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• pp.787-795
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• 2001

For the generalized nilpotent spaces, e.g. the locally nilpotent space, the residually locally nilpotent space and the space satisfying the condition ($T^{*}$) or ($T^{**}$), we find the pullback property of them. Furthermore we investigate some fiber properties of the space satisfying the condition ($T^{*}$) or ($T^{**}$), especially locally nilpotent space.

• Current Optics and Photonics
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• 제2권3호
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• pp.226-232
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• 2018

We propose a triangular-multicore hollow optical fiber (TMC-HOF) design for uncoupled mode-division and space-division multiplexing. The TMC-HOF has three triangular cores, and each core has three modes: $LP_{01}$ and two split $LP_{11}$ modes. The asymmetric structure of the triangular core can split the $LP_{11}$ modes. Using the proposed structures, nine independent modes can propagate in a fiber. We use a fully vectorial finite-element method to estimate effective index, chromatic dispersion, differential group delay (DGD), and confinement loss by controlling the parameters of the TMC-HOF structure. We confirm that the proposed TMC-HOF shows flattened chromatic dispersion, low DGD, low confinement loss, low core-to-core crosstalk, and low crosstalk between adjacent modes. The proposed TMC-HOF can provide a common platform for MDM and SDM applications.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 1999년도 춘계학술대회 논문집
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• pp.536-539
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• 1999

Physical properties of glass fiber-reinforced nylon 6,6 and ionomer blends were investigated in variation of ionomer and glass fiber content. With the increase of ionomer content, tensile strength, impact strength and flexural strength decreased, whereas increasing glass fiber content, these properties were improves. Both permittivity and tan $\delta$ remain unchanged. Space charge distribution was investigated by PEA (Pulsed electroacoustic) method. Heterocharge was found in nylon 6,6 and 히ass fiber composites, whereas composites, whereas when ionomer is blended.