• Journal of Welding and Joining
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• 제21권3호
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• pp.85-91
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• 2003

Narrow gap welding has many advantages over conventional V-grooved butt welding such as high productivity, small deformation and improved mechanical property of joints. With narrower groove gap, less arc heat input is expected will all the other advantages of narrow gap welding. The main defects of narrow gap welding include the lack of root fusion, convex bead surface and irregular surface, all of which have negative effects on the next welding pass. This paper suggests an up-and-down torch oscillation for ultra narrow gap welding with gap size of 5mm and investigates the proper welding conditions to fulfill the reliable and high welding quality. First, GMA welding model was suggested for ultra narrow gap welding system with Halmoy's model referenced for wire melting modeling. And the arc length in ultra narrow gap was defined. Secondly, based on the experimental results of up-and-down torch oscillation welding, phase shift of current and wire extension length were simulated for varying oscillation frequency to show that weld the bead shape in ultra narrow gap welding can be predicted. As the result, it was confirmed that reliable weld quality in ultra narrow gap welding can be achieved with up-and-down torch oscillation above 15Hz due to its ability to provide uniform heat input along the sidewall of gap.

• 대한소아치과학회지
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• 제24권1호
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• pp.173-178
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• 1997

As one of the developmental disturbances in shape of teeth, an accessory root may involve any teeth, but has very rare frequency in the deciduous teeth. Because it is possible to diagnose the accessory root only by use of the radiographs, it is important to detect this root early by carefully examining the radiographs. The accessory root produces several problems such as abnormal exfoliation of deciduous teeth, eruption abnormality of successive permanent teeth, infection due to residual root during tooth extraction, and incomplete pulp treatment, and therefore it is necessary to have a continuous follow check-up to prevent these problems.

• 대한용접접합학회:학술대회논문집
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• 대한용접접합학회 1998년도 특별강연 및 춘계학술발표 개요집
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• pp.227-229
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• 1998

• 대한원격탐사학회지
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• 제37권5_1호
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• pp.885-901
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• 2021

천리안위성 2A호의 2분 주기 고속 관측(rapid-scan) 자료를 이용하여, 가시·수증기·적외 채널의 시간 해상도와 표적의 크기가 해당 채널의 중규모 대기운동벡터 생산에 미치는 영향을 분석하였다. 중규모 대기운동벡터 산출을 위하여 2-10분의 영상 시간 간격 변화 하에서 표적의 크기를 8×8에서 40×40 화소 크기로 변환시키며, 시·공간적인 조건 변화에 따른 벡터 생산량과 평균 속력, 오차 특성의 변화 양상을 비교하였다. 그 결과, 표적의 크기가 작을수록 위성의 시간 간격 변화에 따른 벡터 개수의 변화와, 표준화된 평균 제곱근 편차(Normalized Root Mean Squared Vector Difference; NRMSVD) 값의 변화가 더욱 뚜렷해졌다. 또한 고도별 오차 특성 분석 결과에서는 평균 속력이 낮고 대기 현상의 시·공간 규모가 작은 하층(700-1000 hPa)의 경우, 짧은 시간 간격의 영상 자료와 작은 표적을 이용하는 것이 벡터 산출에 더욱 유리하게 작용하는 것을 확인할 수 있었다. 위성의 시간 간격과 표적의 크기는 대기 순환의 시·공간 규모와 밀접한 연관이 있는 요소이다. 따라서, 대기운동벡터 활용 목적에 맞게 표적 크기와 위성 시간 간격을 최적화하는 과정이 필요하며, 중규모 기상현상의 실황 분석을 위한 대기운동벡터 산출 알고리즘에서는 표적 크기와 영상 시간 간격을 각각 16×16, 4분으로 설정해주는 것이 가장 적합하다고 판단된다.

• Journal of Welding and Joining
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• 제30권6호
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• pp.42-48
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• 2012

Due to increase in demand of stable and long pipelines in natural gas industry, wide range of researches are being performed on automation welding to improved welding quality with respect to weld process parameters in real time measurement. In particular, the coupling between the pipe manufacturing process and location of the weld seam, the measured size of the gap that exists in the weld position and the weld angle depending on whether the movement of molten weld. This is due to absence of controlling welding penetration position, depending on the required size of the angle of the setting. In addition, the optimum welding conditions must be considered while selecting, the correlation between these variables and the systematic correlation has not yet been identified. Therefore, in most welded pipe root-pass weld solely depends on the experience of workers in relation to secure a stable weld quality. In this study, automation welding system is implemented to select a suitable root-pass STT (Surface Tension Transfer) welding method using the optimal welding conditions. To successfully accomplish this objective, there were various welding conditions used for welding experiment to confirm that the assessment required for construction through the pipe and automatic welding process is proposed to optimize this plan.

• 한국농림기상학회지
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• 제7권1호
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• pp.28-34
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• 2005

탄소 순환에 중요한 부분을 차지하는 토양 호흡을 뿌리와 토양 미생물에 의한 호흡으로 분리하는 세가지 연구 방법, 즉 (1) 구성 요소 직접 측정 방법, (2) 뿌리 제거 방법, (3) 동위원소 이용 방법을 검토하였다. 이 중에서,구성 요소 직접 측정 방법과 뿌리 제거 방법이 가장 널리 사용되고 있는데, 전체 토양 호흡에서 뿌리 호흡이 차지하는 부분은 뿌리 제거 방법이 다른 두 방법과 비교하여 더 높게 나타난다. 뿌리 제거 방법 중 단근처리 방법은 뿌리를 굴취하여 제거하거나 지상부 식생을 제거하는 방법과 비교해 볼 때 토양이나 관측 지면에 거의 교란을 일으키지 않는 다 동위원소 이용 방법은 다른 방법과 비교해서 토양이나 뿌리에 미치는 영향이 가장 적으나 비용이 많이 들고 복잡한 분석 기술을 필요로 한다. 관측지의 교란을 최소화하면서 발생원별 토양 호흡에 기여하는 부분을 계산하는 방법으로 단근처리 방법이 적절한 것으로 사료된다. 그러나 이 방법이 뿌리의 분해로 인해 미생물의 호흡을 과대평가함을 고려해서 뿌리의 분해를 동시에 관측하거나 큰 뿌리들을 피해서 단근처리 대상지역을 선택함으로써 현실적인 결과를 얻을 수 있을 것이다.

• Restorative Dentistry and Endodontics
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• 제46권2호
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• pp.22.1-22.12
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• 2021

Objectives: This study evaluated and compared the effects of radiation therapy on the dislocation resistance of AH Plus and BioRoot RCS applied to dentin and the sealer-dentin interface. Materials and Methods: Thirty single-rooted teeth were randomly assigned to 2 groups (n = 15 each): AH Plus (Dentsply DeTrey) and BioRoot RCS (Septodont). Each group was subdivided into control and experimental groups. The experimental group was subjected to a total radiation dose of 60 Gy. The root canals of all samples were cleaned, shaped, and obturated using the single-cone technique. Dentin slices (1 mm) were sectioned from each root third for the push-out test and scanning electron microscopy (SEM) was done to examine the sealer-dentin interface. The failure mode was determined using stereomicroscopy. Bond strength data were analyzed by the independent t-test, 1-way analysis of variance, and the Tukey post hoc test (α = 0.05). Results: Significantly lower bond strength was observed in irradiated teeth than non-irradiated teeth in the AH Plus group (p < 0.05). The BioRoot RCS group showed no significant reduction in bond strength after irradiation (p > 0.05) and showed a higher post-irradiation bond strength (209.92 ± 172.26 MPa) than the AH Plus group. SEM revealed slightly larger gap-containing regions in irradiated specimens from both groups. Conclusions: The dislocation resistance of BioRoot RCS was not significantly changed by irradiation and was higher than that of AH Plus. BioRoot RCS may be the sealer of choice for root canal treatment in patients undergoing radiation therapy.

• 대한원격탐사학회지
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• 제38권5_3호
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• pp.953-966
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• 2022

에어로솔(aerosol)은 대기 질을 악화시키는 등 인체 건강에 악영향을 끼치므로 에어로솔의 분포 및 특성에 대한 정량적인 관측이 필수적이다. 최근 전 지구 규모에서의 주기적이고 정량적인 정보 획득 수단으로 위성관측 Aerosol Optical Depth (AOD) 영상이 다양한 연구에 활용되지만 광학센서 기반의 위성 AOD 영상은 구름 등의 조건을 가진 일부 지역에서 결측을 가진다. 이에 본 연구는 위성자료의 결측복원을 위하여 격자형 기상자료와 지리적 요소를 입력변수로 하여 Random Forest (RF) 기반 gap-filling 모델을 생성한 이후, gap-free GK-2A/AMI AOD hourly 영상을 산출하였다. 모델의 정확도는 -0.002의 Mean Bias Error (MBE), 0.145의 Root Mean Square Error (RMSE)로, 원자료의 목표 정확도보다 높으며 상관계수 0.714로 복원 대상이 대기변수인 점을 감안하면 상관계수 측면에서도 충분한 설명력을 갖춘 모델이다. 정지궤도 위성의 높은 시간 해상도는 일변화 관측에 적합하며 대기보정을 위한 입력, 지상 미세먼지 농도 추정, 소규모 화재 또는 오염원 분석 등 타 연구를 위한 자료 활용 측면에서 중요하다.

• 동의생리병리학회지
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• 제22권2호
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• pp.431-437
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• 2008

Sengmaek-san(Shengmai-san; SMS) is used in oriental medicine as one of the key herbal medicine for treating diverse symptoms including cardiovascular and neurological disorders. In the present study, the effects of SMS on axonal regeneration were investigated in the rat model given sciatic nerve injury. SMS treatment enhanced axonal regrowth into and the number of non-neuronal cells in the distal area after crush injury. GAP-43 protein levels were increased in the injured sciatic nerve compared to intact nerve and further upreguated by SMS treatment. GAP-43 protein was increased similarly in the dorsal root ganglion (DRG) at lumbar 4 - 6 by nerve injury and SMS treatment, suggesting GAP-43 induction at gene expression level. SMS-mediated increase in phospho-Erk1/2 protein was observed in the DRG as well as in the injured nerve implying its retrograde transport into the cell body as the process of lesion signal transmission. The present findings suggest that SMS may be involved in enhanced axonal regeneration via dynamic regulation of regeneration-associated proteins.

• Food Science and Biotechnology
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• 제16권5호
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• pp.747-752
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• 2007

This study was carried out to identify and quantify the flavonoids from 6 different plant parts of Allium victorialis var. platyphyllum (AVP), including the flower, leaf, root, stem, flower stalk, and flower seed, using liquid chromatography/ mass spectrometry. Two major flavonoids were structurally identified as quercetin (3,5,7,3'4,'-pentahydroxyflavone) and kaempferol (3,5,7,4'-tetrahydroxyflavone) at contents of 11.8-25.8 and $6.0-64.4\;{\mu}g/mL$, respectively. In particular, the flower and root plant parts contained the highest amounts of quercetin and kaempferol compared to the other parts. We also assessed the recovery effects of each plant-part extract of AVP on gap junctional intercellular communication (GJIC) in WB-F344 cells by the scrape-loading and dye transfer (SL/DT) method. According to the results, GJIC was reduced by approximately 70.2% ($62.3{\pm}12.5$ cells) compared to the control ($209{\pm}9.5$ cells, 100%) when 12-O-tetradecanoylphorbol-13-acetate (TPA) was treated alone in the WB-F344 rat liver epithelial cells. However, the stem extract (0.2 mg/mL) restored GJIC to basal levels (92%, $204{\pm}2.3$ cells, p<0.01) and the flower extract (0.2 mg/mL) stimulated GJIC to 82.5% ($172.6{\pm}8.3$ cells, p<0.05), when applied together with the TPA.