• 대한수학회지
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• 제46권2호
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• pp.295-311
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• 2009

The purpose of this paper is to identify the group of units of finite local rings of the types ${\mathbb{F}}_2[X]/(X^k)$ and ${\mathbb{Z}}_4[X]/I$, where I is an ideal. It turns out that they are 2-groups and we give explicit direct sum decomposition into cyclic subgroups of 2-power order and their generators.

• Restorative Dentistry and Endodontics
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• 제47권1호
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• pp.5.1-5.11
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• 2022

Objectives: This study aimed to assess the clinical longevity of a bulk-fill resin composite in Class II restorations for 3-year. Materials and Methods: Patient record files acquired from the 40 patients who were treated due to needed 2 similar sizes Class II composite restorations were used for this retrospective study. In the experimental cavity, the flowable resin composite SDR was inserted in the dentinal part as a 4 mm intermediate layer. A 2 mm coverage layer with a nano-hybrid resin composite (CeramX) was placed on SDR. The control restoration was performed by an incremental technique of 2 mm using the nano-hybrid resin composite. The restorations were blindly assessed by 2 calibrated examiners using modified United States Public Health Service criteria at baseline and 1, 2, and 3 years. The data were analyzed using non-parametric tests (p = 0.05). Results: Eighty Class II restorations were evaluated. After 3-years, 4 restorations (5%) failed, 1 SDR + CeramX, and 3 CeramX restorations. The annual failure rate (AFR) of the restorations was 1.7%. The SDR + CeramX group revealed an AFR of 0.8%, and the CeramX group an AFR of 2.5% (p > 0.05). Regarding anatomical form and marginal adaptation, significant alterations were observed in the CeramX group after 3-years (p < 0.05). The changes in the color match were observed in each group over time (p < 0.05). Conclusions: The use of SDR demonstrated good clinical durability in deep Class II resin composite restorations.

• 대한소아치과학회지
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• 제11권1호
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• pp.131-143
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• 1984

150 rats weighting about 150gm were devided into control group of 80 and experimental group of 70. Control group was subdivided into the irradiated vitamin D injection group and X-ray irradiated group. Experimental group was given 2.0mg ergocalciferol by four intramuscular injection prior to X-ray irradiation with single 800 rads and 1,500 rads respectively. Experimental animals from each group was sacrificed after 1, 3, 7, 14, and 28 days and their incisors were investigated by histopathological examination. The results were as follows; 1. In the irradiated groups, it showed dentin hypoplasia and formation of dentinoid substance caused by degeneration of odontoblast at the early stage. Especially, 1,500 rads group which was severely effected showed formation of osteoid dentin at the apical portion and severe injuries of dental papilla at the first week. 2. In the vitamin D2 administration group, it showed thinned dentin layer at the early stage but, taking time, predentin and dentin layer was thickened. At the fourth week, dentin was chiefly composed of interglobular dentin, especially in the lingual portion. 3. Using in combination of overdose vitamin D2 administration and X-ray irradiation, it effected severely odontoblast, undifferentiated mesenchymal cells around tooth germ and pulp tissue. At the early stage, dentin layer was thinned but, taking time, it was thickened and composed of interglobular dentin caused by calcification of predentin layer. 4. In 800 rads irradiation after the overdose vitamin D2 administration, it showed formation of osteoid dentin in the lingual portion at the first week. In the 1,500 rads irradiation after the overdose vitamin D2 administration, it showed formation of osteoid dentin and degeneration of ameloblast in both buccal and lingual portion at the first week, and enamel hypoplasia caused by edema and loss of polarity of ameloblasts at the second week. 5. By the entire experiment, the overdose vitamin D2 administration and X-ray irradiation effected severely odontoblasts, undifferentiated mesenchymal cells of dental papilla, and primitive cells of tooth germ among the dental tissue. Especially using combination of overdose vitamin D2 administration and X-ray irradiation also effected ameloblasts, resulting in enamel hypoplasia.

• 대한전자공학회논문지TC
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• 제43권8호
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• pp.15-24
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• 2006

본 논문에서는 다수의 소규모 그룹 멀티캐스트 통신을 위해 제안된 XMIP라는 명시적 모바일 멀티캐스트를 설계하고 구현한다. XMIP는 유니캐스트 라우팅 정보에 기초한 명시적 멀티캐스트의 특징을 상속받아 멀티캐스트 상태유지가 필요없는 간단한 멀티캐스트 메커니즘이다. 본 연구에서는 IETF Mobile IP의 각 이동 에이젼트들을 XMIP와의 연동을 고려하여 수정하고 확장한다. 확장 홈에이젼트로 전송된 XMIP 패킷들은 확장 홈에이젼트의 바인딩 테이블을 참조하여 X-in-X이라는 중첩 터널을 통해 확장 지역 에이젼트들로 전송된다. X-in-X 터널링 메커니즘은 Mobile IP 멀티캐스트 트래픽 집중 문제를 효과적으로 해결할 수 있다. 마지막으로 CDMA2000 1X EV-DO 및 무선랜을 포함하는 이종 모바일 네트워크 환경을 기반으로 XMIP 실험망을 구축하고, 소규모 그룹 통신을 위한 다중 사용자 인스턴트 메신저를 개발하여 실험함으로써 제안하는 프로토콜들의 실효성을 검증한다.

• 대한전자공학회:학술대회논문집
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• 대한전자공학회 2006년도 하계종합학술대회
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• pp.391-392
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• 2006

In x-ray imaging system, twokinds of noises are involved. First, the charge generated from the radiation interaction with the detector during exposure is modeled by Poisson process. Second, the signal is then added by readout electronics noise, which is modeled by Gaussian distribution. In this paper, we applied Wiener filter and Wavelet to remove noise from medical X-ray image, the result shows that wavelet yield better segmentation results than the wiener filter.

• Korean Journal of Mathematics
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• 제7권1호
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• pp.131-138
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• 1999

We introduce an extended Jiang subgroup $J(f,x_0,G)$ of the fundamental group of a transformation group as a generalization of the Jiang subgroup $J(f,x_0)$ and show some properties of this extended Jiang subgroup.

• Journal of the Optical Society of Korea
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• 제20권2호
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• pp.283-290
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• 2016

This study presents an 8x four-group inner-focus zoom lens with one-moving group for a compact camera by use of a focus tunable lens (FTL). In the initial design stage, we obtained the powers of lens groups by paraxial design based on thin lens theory, and then set up the zoom system composed of four lens modules. Instead of numerically analytic analysis for the zoom locus, we suggest simple analysis for that using lens modules optimized. After replacing four groups with equivalent thick lens modules, the power of the fourth group, which includes a focus tunable lens, is designed to be changed to fix the image plane at all positions. From this design process, we can realize an 8x four-group zoom system having one moving group by employing a focus tunable lens. The final designed zoom lens has focal lengths of 4 mm to 32 mm and apertures of F/3.5 to F/4.5 at wide and tele positions, respectively.

• 한국방사선학회논문지
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• 제17권1호
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• pp.149-156
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• 2023

보리의 생산년도에 따른 생장과 광합성 차이를 알아보고자 질병의 진단 및 치료에 가장 많이 이용하는 고에너지 X-선을 묵은보리씨앗과 햇보리씨앗에 조사하여 연구를 수행하였다. 묵은보리와 햇보리 종자가 싹이 튼 것을 확인 후, 대조군을 제외한 실험군에 대해 방사선종양학과의 선형가속기(Clinac IS, VERIAN, USA, 2011)를 이용하여 30 Gy X-선을 조사하였다. 조사 조건은 6 MV X-ray, 조사거리(Source-surface distance) 100 cm, 조사면적(field size) 18 × 10 cm², 선량률(dose rate) 600 MU/min 에서 실시하였다. 보리의 생장은 종자별로 X-선 조사 후 4일차 부터 1일 간격으로 9일차 까지 줄기의 길이를 측정하였다. X-선이 보리 싹의 엽록소 형성에 미치는 영향을 알아보기 위하여 분광광도법을 이용하여 클로로필 a 농도를 측정하였다. 통계분석은 SPSS ver 26.0(Chicago, IL, USA)을 사용하여 독립표본 T-검정(Independent T-test)을 실시하였다. 대조군에서는 햇보리가 묵은보리 보다 성장이 빨랐지만, 실험군에서는 묵은보리가 햇보리 보다 빠른 성장을 보였다. 묵은보리에서 대조군의 길이가 실험군 보다 모든 일차에서 유의하게 큰 것으로 나타났다. 대조군에서는 묵은보리 보다 햇보리의 무게가 무거웠지만, 실험군에서는 묵은보리의 무게가 햇보리 무게 보다 높았다. 클로로필 농도를 측정하여 비교한 결과, 대조군 실험군 모두 묵은보리 보다 햇보리가 높은 결과를 보였고, 대조군 보다 실험군이 높게 나타났다. X-선은 햇보리 보다 묵은보리의 성장과 무게를 촉진시켰고, 클로로필 농도에는 햇보리에게 더 큰 영향을 미치는 것으로 나타났다. 이와 같은 결과는 향후 X-선이 새싹보리에 미치는 영향에 대한 연구의 기초 자료로 사용될 수 있을 것이다.

• 대한수학회보
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• 제48권5호
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• pp.1015-1021
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• 2011

A point of a Riemann surface X is said to be its fixed point if it is a fixed point of one of its nontrivial holomorphic automorphisms. We start this note by proving that the set Fix(X) of fixed points of Riemann surface X of genus g${\geq}$2 has at most 82(g-1) elements and this bound is attained just for X having a Hurwitz group of automorphisms, i.e., a group of order 84(g-1). The set of such points is invariant under the group of holomorphic automorphisms of X and we study the corresponding symmetric representation. We show that its algebraic type is an essential invariant of the topological type of the holomorphic action and we study its kernel, to find in particular some sufficient condition for its faithfulness.

• 한국세라믹학회지
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• 제35권10호
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• pp.1113-1119
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• 1998

Crystal structure of needle-shaped maghemite(${\gamma}$-{{{{ { {Fe }_{2 }O }_{3 } }}) has been studied by the Rieveld analysis of powder X-ray diffraction patterns. The tetragonal space group P41,.3212 and cubic space group P41,.32 have been have been used for the refinement of X-ray diffraction patterns. The crystal system of maghemite is closed to tetragonal more than cubic. The tetragonal lattice parameters are a=8.3460$\AA$ and c=25.034$\AA$ The standard X-ray diffraction pattern of the tetragonal maghemite analyzed with space group P41,.3212 is proposed.