• 대한치과기공학회지
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• 제35권4호
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• pp.359-364
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• 2013

Purpose: This study was to observe characteristic of metal oxidation and bonding strength according to composition of Ni-Cr alloy for porcelain fused to metal crown. The three kinds of Ni-Cr alloy with different composition ratio of parent metal were observed general properties and chemical properties of each alloy surface and measured the shear bonding strength between ceramic and each alloys. The aim of study was to suggest the material for design of parent metal's composition ratio to development of alloy for porcelain fused to metal crown. Methods: The three kinds of alloy as test specimen was Ni(59wt%)-Cr(24wt%), Ni(67wt.%)-Cr(16wt.%) alloy and Ni(71wt%)-Cr(12wt%)alloy. The oxide on surface was observed by EDX. And the shear test was performed by MTS. Results: The surface property and oxide characteristic analysis of oxide layer, weight percentage of Element O within $Ni_{59}Cr_{24}$ alloy measured 23.03wt%, $Ni_{67}Cr_{16}$ alloy measured 21.13wt% and $Ni_{71}Cr_{12}$ alloy was measured 48.55wt%. And the maximum shear bonding strength was measured 58.02Mpa between $Ni_{59}Cr_{24}$ alloy and vintage halo(H2 group). Conclusion: The surface property and oxide characteristic three kind of Ni-Cr alloy was similar. and shear bonding strength showed the highest bonding strength in H2 specimens.

• 치위생과학회지
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• 제2권1호
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• pp.11-14
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• 2002

본 연구에서는 천연항균제인 Citrex와 대표적인 치과영역의 항균물질로 사용되어 오고 있는 CPC를 복합적으로 처방하고 사용감이 좋은 양치액을 개발하기 위해 정밀구강검사를 통하여 특이한 구강질환이 없는 41명을 대상으로 하여 양치액의 기포 형성능력에서 사용감에 이르기까지 6개 항목의 관능평가와 개량 구강환경관리능력지수(M-PHP)를 평가하였으며, 또한 구강질환유발 미생물 Streptococcus mutans, Staphylococcus aureus, Candida albicans을 대상으로 항균 효능평가를 수행하고 아래와 같은 결론을 얻었다. 1. 복합 양치액의 관능평가는 비교적 우수하게 나타났으며, 특히 사용감이 좋고 수렴감이 있는 것으로 나타났다. 2. Citrex와 CPC 복합처방 양치액의 구강질환 유발 미생물에 대한 효능은 분명하였으며, 이들 미생물 3종에 대한 항균효과는 Streptococcus mutans, Staphylococcus aureus, Candida albicans 순이었다. 3. 복합 처방된 양치액에 의한 5일간 M-PHP 변화는 첫째날 대조군과 실험군에서 약간의 차이는 인정되었으나, 이후 4일 동안 두 그룹간의 유의한 차이는 없는 것으로 나타났다.

• Journal of Microbiology and Biotechnology
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• 제13권3호
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• pp.415-421
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• 2003

A bacterium, Pseudomonas fluorescens 2112, that is antagonistic against a red-pepper blight-causing fungus, Phytophthora capsici, was isolated from the local soil of Gyongju, Korea. This strain formed an orange-colored clear halo zone on chrome azurol S (CAS) blue agar, suggesting the production of a siderophore in addition to an antifungal antibiotic. The optimal culture conditions for siderophore production by P. fluorescens 2112 were 30-h cultivation at $25^{\circ}C$ and pH 6.5 in King's B medium. The presence of $20{\mu}g/ml\;of\;Fe^3+$ ion or EDDHA promoted the production of siderophore in King's B medium. The siderophore was purified from culture broth by CM-Sephadex C-25 and Sephadex G-25 column chromatographies. The UV spectra of the purified siderophore was the same as that of pyoverdins or pseudobactins. The molecular mass was 1,958 Da determined by FAB-rlass spectrometer, and the amino acid composition analysis showed that the purified siderophore consisted of glycine/threonine/serine/glutamic acid/alanine/lysine with the molar ratio of 3:2:1:1:1:1, DL-Threo-${\beta}$-hydroxyaspartic acid and $N^{\delta}$-hydroxyornithine, two of the essential constituents of pyoverdin, were also found. The purified siderophore pyoverdin showed strong in vitro and in vivo antagonistic activities against phytophthora blight-causing P. capsici. Especially in an in vivo pot test, the siderophore protected red-pepper Capsicum annum L. very well from the attack of P. capsici. These results indicated that the purified siderophore of P. fluorescens 2112 played a critical role in the biocontrol of the red-pepper blight disease, equivalent to treatment by P.fluorescens 2112 cells.

• 천문학회지
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• 제48권1호
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• pp.21-55
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• 2015

If the Universe is dominated by cold dark matter and dark energy as in the currently popular ${\Lambda}CDM$ cosmology, it is expected that large scale structures form gradually, with galaxy clusters of mass $M{\geq}10^{14}M_{\odot}$ appearing at around 6 Gyrs after the Big Bang (z ~ 1). Here, we report the discovery of 59 massive structures of galaxies with masses greater than a few times $10^{13}M_{\odot}$ at redshifts between z = 0.6 and 4.5 in the Great Observatories Origins Deep Survey fields. The massive structures are identified by running top-hat filters on the two dimensional spatial distribution of magnitude-limited samples of galaxies using a combination of spectroscopic and photometric redshifts. We analyze the Millennium simulation data in a similar way to the analysis of the observational data in order to test the ${\Lambda}CDM$ cosmology. We find that there are too many massive structures (M > $7{\times}10^{13}M_{\odot}$) observed at z > 2 in comparison with the simulation predictions by a factor of a few, giving a probability of < 1/2500 of the observed data being consistent with the simulation. Our result suggests that massive structures have emerged early, but the reason for the discrepancy with the simulation is unclear. It could be due to the limitation of the simulation such as the lack of key, unrecognized ingredients (strong non-Gaussianity or other baryonic physics), or simply a difficulty in the halo mass estimation from observation, or a fundamental problem of the ${\Lambda}CDM$ cosmology. On the other hand, the over-abundance of massive structures at high redshifts does not favor heavy neutrino mass of ~ 0.3 eV or larger, as heavy neutrinos make the discrepancy between the observation and the simulation more pronounced by a factor of 3 or more.

• 천문학회지
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• 제48권2호
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• pp.155-164
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• 2015

In Kang (2015) we calculated the acceleration of cosmic-ray electrons at weak spherical shocks that are expected to form in the cluster outskirts, and estimated the diffuse synchrotron radiation emitted by those electrons. There we demonstrated that, at decelerating spherical shocks, the volume integrated spectra of both electrons and radiation deviate significantly from the test-particle power-laws predicted for constant planar shocks, because the shock compression ratio and the flux of inject electrons decrease in time. In this study, we consider spherical blast waves propagating through a constant density core surrounded by an isothermal halo with ρ ∝ r⁻ⁿ in order to explore how the deceleration of the shock affects the radio emission from accelerated electrons. The surface brightness profile and the volumeintegrated radio spectrum of the model shocks are calculated by assuming a ribbon-like shock surface on a spherical shell and the associated downstream region of relativistic electrons. If the postshock magnetic field strength is about 0.7 or 7 µG, at the shock age of ∼ 50 Myr, the volume-integrated radio spectrum steepens gradually with the spectral index from α_inj to α_inj + 0.5 over 0.1–10 GHz, where α_inj is the injection index at the shock position expected from the diffusive shock acceleration theory. Such gradual steepening could explain the curved radio spectrum of the radio relic in cluster A2266, which was interpreted as a broken power-law by Trasatti et al. (2015), if the relic shock is young enough so that the break frequency is around 1 GHz.

• Korean Journal of Radiology
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• 제21권4호
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• pp.494-500
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• 2020

Objective: This study presents a preliminary report on the chest radiographic and computed tomography (CT) findings of the 2019 novel coronavirus disease (COVID-19) pneumonia in Korea. Materials and Methods: As part of a multi-institutional collaboration coordinated by the Korean Society of Thoracic Radiology, we collected nine patients with COVID-19 infections who had undergone chest radiography and CT scans. We analyzed the radiographic and CT findings of COVID-19 pneumonia at baseline. Fisher's exact test was used to compare CT findings depending on the shape of pulmonary lesions. Results: Three of the nine patients (33.3%) had parenchymal abnormalities detected by chest radiography, and most of the abnormalities were peripheral consolidations. Chest CT images showed bilateral involvement in eight of the nine patients, and a unilobar reversed halo sign in the other patient. In total, 77 pulmonary lesions were found, including patchy lesions (39%), large confluent lesions (13%), and small nodular lesions (48%). The peripheral and posterior lung fields were involved in 78% and 67% of the lesions, respectively. The lesions were typically ill-defined and were composed of mixed ground-glass opacities and consolidation or pure ground-glass opacities. Patchy to confluent lesions were primarily distributed in the lower lobes (p = 0.040) and along the pleura (p < 0.001), whereas nodular lesions were primarily distributed along the bronchovascular bundles (p = 0.006). Conclusion: COVID-19 pneumonia in Korea primarily manifested as pure to mixed ground-glass opacities with a patchy to confluent or nodular shape in the bilateral peripheral posterior lungs. A considerable proportion of patients with COVID-19 pneumonia had normal chest radiographs.

• Journal of Astronomy and Space Sciences
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• 제24권1호
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• pp.79-90
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• 2007

지구와 태양 사이의 중력 평형점에서 혜일로 궤도로 운용되며, 심우주 반사율(albedo)을 측정코자 하는 EARTHSHINE 미션의 과학적 목적에 최적화된 아몬라 가시광 채널의 성능 인증 모델용 광학 시스템 개발을 완료하였다. 아몬라 광학계 설계 요구사항에 부합하는 설계안과 공차분석 결과를 바탕으로 광학 시스템의 설계, 부품 제작, 결합, 정렬, 성능 검증까지의 전 공정을 순수 국내 개발하였으며 특히 측정된 부품들의 광파면 오차를 결합 및 성능 평가 공정에 역투입하는 신 공법에 의하여 성능 검증을 실시하였다. 최종 결합 및 정렬이 완료되어 측정한 아몬라 광학계의 광파면 오차는 중심 시야에서 RMS 0.091 wave(기준 파장: 632.8nin)이며, Ensquared Energy(EE) 성능은 61.7%($14{\mu}m$ 이내), 변조전달함수(MTF) 성능은 35.3%(기준 주파수: $35.7mm^{-1}$)이다. 위 결과들은 아몬라 가시광 채널의 요구사항을 모두 만족시킴으로써 개발된 아몬라 가시광 채널 광학계가 EARTHSHINE 미션의 과학목적을 완수할 수 있음을 증명하였다.

• 대한전자공학회논문지SP
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• 제43권6호
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• pp.65-84
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• 2006

본 논문에서는 개선된 영상 생성 모델을 제시하고, 제시된 모델에 기반한 칼라 영상 향상을 제안한다. 제시된 영상 생성 모델에서는 입력 영상을 전역 조명 성분과 국부 조명 성분, 그리고 반사율 성분의 곱으로 표현한다. 제안된 칼라 영상 향상에서는 RGB 입력 칼라 영상을 HSV 칼라 영상으로 변환한 다음, 백색광 조명 상태라는 가정 하에 개선된 영상 생성 모델에 근거하여 V 성분 영상만을 향상한다. 전역 조명 성분은 입력 V 성분 영상에 유효 영역이 넓은 선형 저대역 필터를 적용하여 추정하고, 국부 조명 성분은 입력 V 성분 영상에서 추정된 전역 조명 성분이 제거된 영상에 유효 영역이 좁은 JND (just noticeable difference) 기반의 비선형 저대역 필터를 적용하여 추정한다. 그리고 반사율 성분은 입력 V 성분 영상에 추정된 전역 조명 성분과 국부 조명 성분을 나누어 추정한다. 이어서 이들 추정된 성분에 감마 수정을 각각 적용하고 그 결과들을 곱하여 출력 V 성분 영상을 얻은 다음 히스토그램 모델링을 적용하여 최종 출력 V 성분 영상을 얻는다. 마지막으로 최종 출력 V 성분 영상과 입력 H 성분 영상 및 S 성분 영상으로부터 출력 RGB 칼라 영상을 얻는다. 실험 결과 제안된 방법은 NASA 홈 페이지로부터 다운받은 칼라 영상과 MPEG-7 CCD 칼라 영상으로 구축한 시험 영상 데이터 베이스에 대하여 후광 효과가 거의 억제되고 색상 변화가 거의 없으면서 전역 대비와 국부 대비를 동시에 잘 증가시키는 것을 확인하였다.

• Restorative Dentistry and Endodontics
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• 제27권6호
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• pp.561-568
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• 2002

Purpose of this research is estimating polymerization depth of different source of light. XL 3000 for halo-gen light, Apollo 95E for plasma arc light and Easy cure for LED light source were used in this study. Different shade (B1 & A3) resin composites (Esthet-X, Dentsply, U.S.A.) were used to measure depth of cure. 1, 2, and 3 mm thick samples were light cured for three seconds, six seconds or 10 seconds with Apollo 95E and they were light cured with XL-3000 and Easy cure for 10 seconds, 20 seconds, or 40 seconds. Vicker's hardness test carried out after store samples for 24 hours in distilled water. Results were as following. 1. Curing time increases from al1 source of lights, oui$.$ing depth increased(p<0.05). 2. Depth (that except 1mm group and 2mm group which lighten to halogen source of light) deepens in all groups, Vickers hardness decreased(p<0.05). 3. Vicker's hardness of A3 shade composite was lower in all depths more than B1 shade composites in group that do polymerization for 10 seconds and 20 seconds using halogen source of light(p<0.05), but group that do polymerization lot 40 seconds did not show difference(p>0.05). 4. Groups that do polymerization using Plasma arc and LED source of light did not show Vicker's hardness difference according to color at surface and 1mm depth(p>0.05), but showed difference according to color at 2mm and 3mm depth(p<0.05). The results showed that Apollo 95E need more polymerization times than manufacturer's recommendation (3 seconds), and Easy cure need polymerization time of XL-3000 at least.

• 식물병연구
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• 제22권3호
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• pp.158-167
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• 2016

육묘장과 재배포장의 애호박에서 새롭게 발생한 병원균의 특성을 분석하여 동정하였다. 병징은 잎에 수침상의 병반과 강한 노란색의 둘레무리를 가진 점무늬, 꽃에서 갈색 병반, 열매에 노란색의 점무늬였다. 잎의 점무늬로부터 분리된 세균은 박과작물 8개의 식물체, 흑종호박, 애호박, 쥬키니호박, 풋호박, 참박, 참외, 멜론, 오이에 병원성이 있었지만 수박과 밤호박에서는 병을 일으키지 못했다. 분리세균은 다발모를 가진 막대형으로 그람음성이며 King's B 배지에서 형광성이었으며, LOPAT 1a 그룹에 속했다. 그들의 Biolog 기질이용성은 Biolog database의 P. syringae pv. syringae 이용성과 유사하였다. 16S rRNA 유전자 염기서열을 이용한 계통수와 4개의 항존유전자(gapA, gltA, gyrB, rpoD)의 염기서열과 PAMDB에 있는 P. syringae균주들의 염기서열을 이용한 MLST는 애호박 분리균주들이 P. syringae pv. syringae 균주들과 동일한 그룹(clade)으로 그룹화되었고, MLST 계통수에서 애호박 분리균주들의 그룹(clade)은 genomospecies 1에 속하였다. 표현형적, 유전적 특성은 애호박 분리균이 P. syringae pv. syringae임을 제시하였다.