• 천문학회보
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• 제37권2호
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• pp.78.1-78.1
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• 2012

We have studied the physical properties of X-ray point sources in galaxy clusters using ~600 Chandra archival observations. The goal of this study is to investigate the density environmental effects on the physical properties of X-ray point sources by comparing the properties of X-ray point sources in galaxy clusters to those in typical blank fields. In this presentation, we show the nature of X-ray point sources which are expected to be related with galaxy clusters with different core properties. Using ~60 galaxy clusters observed with Chandra, we investigate the physical properties of X-ray point sources in cool-core and non-cool-core clusters. The cool-core clusters are known to have short central cooling time, and are characterized by low central entropy, systematic central temperature drops, and a brightest cluster galaxy at the X-ray peak. While the non-cool-core clusters have longer central cooling time, and are characterized by large central entropies and flat or centrally rising temperature profile. We show that how central core properties of galaxy clusters affect on the physical properties of X-ray point sources.

• Annals of Clinical Neurophysiology
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• 제8권1호
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• pp.23-28
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• 2006

Background: central core disease is one of the non-progressive benign congenital myopathies characterized by the presence of cores in muscle fibers, which was originally described by Shy and Magee (1956). We describe clinical charcteristics of central core disease in a Korean family manifested by autosomal dominant pattern through three generations. Methods: Clinical, serologic, and electrophysiologic profiles were evaluated in eleven members among 22 family members through three generations. Results: Six family members were symptomatic and five were non-symptomatic. Instead of proximal muscle weakness, musculoskeletal manifestations including non-specific joint pain and stiff sense were the most frequent symptoms. Muscle biopsy performed in two symptomatic patients revealed that type I fiber showed central halo, which is charactreristics of central core disease. No remarkable findings were present in serologic study including CPK level and electromyographic findings suggesting myopathic pattern were only present in two patients among 11 symptomatic group. Conclusions: In evaluating non-specific musculoskeletal complaints from the familial members showing genetic trait, central core disease should be considered to one of the possible diagnosis.

• 한국분말야금학회:학술대회논문집
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• 한국분말야금학회 2006년도 Extended Abstracts of 2006 POWDER METALLURGY World Congress Part2
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• pp.1169-1170
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• 2006

We made a high-speed motor and a DC brush-less motor for factory automation (FA) to investigate applicability of powder magnetic core to motor application, and compared those performances with the similar motors having conventional electro magnetic steel core. Permeability and saturated magnetization of powder magnetic core are less than those of elect romagnetic steel core, however output performances of each core motor are almost the same. The FA motor with powder magnetic core using three-dimensional magnetic circuit showed higher torque than the same volume motor with electromag netic steel core.

• 대한기계학회논문집B
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• 제36권10호
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• pp.1043-1047
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• 2012

유럽지역으로의 원전 수출을 위해서는 유럽의 원전 인허가요건을 충족시켜야 하며, 이에 따르면 원전의 중대사고 대처설비로 통상 Core Catcher로 불리는 노외 노심 용융물 냉각설비를 갖출 것을 권장하고 있다. 이에 따라 본 논문에서는 노심 용융물 직접냉각방식과 간접냉각방식에 대해 각각의 개념 안의 장/단점을 비교, 검토하였으며, 그 결과 직접냉각방식은 냉각효율 측면에서, 간접냉각방식은 중대사고 사고관리 측면에서 각각 우위를 보였다.

• Journal of Magnetics
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• 제16권3호
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• pp.318-321
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• 2011

A new Fe-based amorphous compound powder was prepared from Fe-Si-B amorphous powder by crushing amorphous ribbons as the first magnetic component and Fe-Cr-Mo metallic glassy powder by water atomization as the second magnetic component. Subsequently by adding organic and inorganic binders to the compound powder and cold pressing, the new Fe-based amorphous compound powder cores were fabricated. This new Fe-based amorphous compound powder cores combine the superior DC-Bias properties and the excellent core loss. The core loss of 500 kW/$m^3$ at $B_m$ = 0.1T and f = 100 kHz was obtained When the mass ratio of FeSiB/FeCrMo equals 3:2, and meanwhile the DC-bias properties of the new Fe-based amorphous compound powder cores just decreased by 10% compared with that of the FeSiB powder cores. In addition, with the increasing of the content of the FeCrMo metallic glassy powder, the core loss tends to decrease.

• 천문학회보
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• 제45권1호
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• pp.30.2-31
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• 2020

We present the properties of circumnuclear gas associated with the AGN located in the center of Abell 1644-South. A1644-S is the main cluster in a merging system, which is also known for gas sloshing in its core as seen in X-ray. The X-ray emission of A1644-S shows a rapidly declining profile, indicating the presence of cooling gas flow. This flow of cool gas may fuel the supermassive black hole embedded in the brightest cluster galaxy, leading to the activation of the central AGN. Indeed, we find a parsec-scale bipolar jet feature in the center of A1644-S in our recent KaVA observation, which implies that its central AGN is likely to have been (re)powered quite recently. In order to verify the hypothesis that cooling gas flow in the cluster core can (re)activate the central AGN, we probe the cold gas properties of the central 1 kpc region of A1644-S using the archival VLA and ALMA data. Based on the spatially resolved morphology and kinematics of HI and CO gas, we challenge to identify inflow/outflow gas streams and clumps. We study the role of circumnuclear cool gas in fueling the centrally located cluster AGN in the cool-core environment. We also discuss how the feedback due to the (re)powered AGN affects the surrounding medium.

• Restorative Dentistry and Endodontics
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• 제40권3호
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• pp.229-235
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• 2015

Objectives: To determine and compare the fracture resistance of endodontically treated maxillary central incisors restored with different posts and cores. Materials and Methods: Forty-eight upper central incisors were randomly divided into four groups: cast post and core (group 1), fiber-reinforced composite (FRC) post and composite core (group 2), composite post and core (group 3), and controls (group 4). Mesio-distal and bucco-lingual dimensions at 7 and 14 mm from the apex were compared to ensure standardization among the groups. Twelve teeth were prepared for crown restoration (group 4). Teeth in other groups were endodontically treated, decoronated at 14 mm from the apex, and prepared for posts and cores. Resin-based materials were used for cementation in groups 1 and 2. In group 3, composite was used directly to fill the post space and for core build-up. All samples were restored by standard metal crowns using glass ionomer cement, mounted at $135^{\circ}$ vertical angle, subjected to thermo-mechanical aging, and then fractured using a universal testing machine. Kruskal-Wallis and Mann-Whitney U tests were used to analyze the data. Results: Fracture resistance of the groups was as follows: Control (group 4) > cast post and core (group 1) > fiber post and composite core (group 2) > composite post and core (group 3). All samples in groups 2 and 3 fractured in restorable patterns, whereas most (58%) in group 1 were non-restorable. Conclusions: Within the limitations of this study, FRC posts showed acceptable fracture resistance with favorable fracture patterns for reconstruction of upper central incisors.

• 한국멀티미디어학회논문지
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• 제5권6호
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• pp.616-624
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• 2002

본 논문에서는 영상에 포함된 중심 객체를 추출하는 방법에 대해 제시한다. 중심 객체는 촬영의 중심이 되어 영상의 중앙 부분에 비교적 큰 면적을 차지하는 객체로 정의하는데 영상 내용에 대한 중요한 정보를 제공한다. 중심 객체 추출을 위해 우선 입력 영상에 대해 해상도를 줄여가며 영상 분할하고 분할된 결과에 대해 계층적 영역 병합을 수행함으로써 객체가 많은 수의 영역으로 세분화되어 영상 분할되는 것을 방지할 수 있도록 하였다. 분할된 각 영역은 영상의 경계와 접하는 경계 영역과 그 외의 비경계 영역으로 분류하였다. 비경계 영역은 중심 객체에 해당될 가능성이 있는 영역으로써, 이들 중에서 영상 중심 부근에서 가장 큰 크기를 차지하는 영역이 핵심객체영역으로 선택된다. 또한 경계 영역 중에서 영상의 네 모서리에 인접하는 영역은 핵심배경영역으로 선택되어 핵심객체영역과 함께 중심 객체 추출에 이용된다. 각 비경계 영역은 핵심 배경영역및 핵심객체영역과 칼라 분포 유사도출 비교하여 배경영역과 전경영역으로 분류된다. 핵심객체영역 및 핵심객체영역과 연결성을 가지는 전경영역이 최종 중심 객체로 선택된다. 본 논문에서 제안된 방법은 비교적 복잡한 배경을 갖는 영상에 대해서도 어느 정도 만족할 만한 결과를 얻을 수 있었다.

• Restorative Dentistry and Endodontics
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• 제21권1호
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• pp.70-86
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• 1996

The purpose of this study was to analyze the stress distribution in mandibular second premolars restored with different post and core techniques. Sixteen two-dimensional finite element model of mandibular second premolars restored with post and core and complete crown were developed according to the diameter, length, and material of post and core. Vertical force, 10N in magnitude, was applied first to the central fossa and then $45^{\circ}$ oblique force of same magnitude was applied to the buccal contact surface of buccal cusp. The obtained results were as follows : 1. Stress distribution within the dentin 1) Regardless of the material of the post and core and the diameter and length of the post, the pattern of stress distribution within the dentin was similar. 2) Maximum dentinal stress was observed on the lingual root surface of alveolar crest level with oblique loading and on lingual side of root dentin at the crown margin on vertical loading. 3) Cast post and cores produced the lowest dentinal stress concentrations and the highest stress concentration was observed in composite resin post and cores. 2. Stress distribution within the post and core 1) Within the amalgam and composite resin post and core, the patterns and maximum values of stress were similar. Maximum stress located at the central fossa of core portion on vertical loading and at the lingual junction of post and core with oblique loading. 2) Among the all post and cores, the cast post and core registered the highest stress concentration and maximum stress value within the post. Maximum stress located at the post apex on vertical loading and at lingual half of the post surface with oblique loading. 3) In case of Para-post and amalgam core, maximum stress located at the central fossa of core portion and lingual tip of the post head on vertical loading. With oblique loading, maximum stress located at the lingual half of the post surface.

• 천문학회지
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• 제27권1호
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• pp.1-11
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• 1994

We have observed the emission of $HC_3N$ J=4-3, 5-4,10-9 and 12-11 transitions toward the Sgr B2 central region in an area of $150'\times150'$ with resolutions of 16'-48'. The intensities and central velocities of line profiles show significant variations with positions. In contrast to the intensities of the low J-level transitions which gradually increase from the central source toward the outside region, the $HC_3N$ emission of the high J-level transition become stronger toward 'the central radio continuum source MD5. Systematic change in the radial velocity of each line profile occurs along north-south direction. There are a few peaks in most line profiles, and these indicate that there are multiple velocity components along the line of sight. Distributions of excitation temperature and column density which were estimated from the excitation calculations show the existence of a small $(1\times2pc),\;hot\;(T_{ex}>50K)$ core which contains two temperature peaks at-15' east and north of MD5. The column density of $HC_3N\;is\;(1-3)\times10^{14}cm^{-2}$ Column density at distant position from MD5 is larger than that in the central region. We have deduced that this 'hot-core' has a mass of 105M 0, which is about an order of magnitude larger than those obtained by previous studies.