• Nuclear Engineering and Technology
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• 제53권5호
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• pp.1416-1428
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• 2021

Pebble flow characteristics can be significantly affected by the configuration of pebble bed, especially for HTGR pebble beds. How to achieve a desired uniform flow pattern without stagnation is the top priority for reactor design. Pebbles flows inside some specially designed pebble bed with arc-shaped contraction configurations at the bottom, including both concave-inward and convex-outward shapes are explored based on discrete element method. Flow characteristics including pebble retention, residence-time frequency density, flow uniformity as well as axial velocity are investigated. The results show that the traditionally designed pebble bed with cone-shape bottom is not the most preferred structure with respect to flow pattern for reactor design. By improving the contraction configuration, the flow performance can be significantly enhanced. The flow in the convex-shape configuration featured by uniformity, consistency and less stagnation, is much more desirable for pebble bed design. In contrast, when the shape is from convex-forward to concave-inward, the flow shows more nonuniformity and stagnation in the corner although the average cross-section axial velocity is the largest due to the dominant middle pebbles.

• 대한치과의사협회지
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• 제16권1호통권104호
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• pp.37-42
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• 1978

A study on the impacted teeth of the anterior segment was carried out. The data for this study were compiled form 1739 outpatients of the Department of Orthodontics, College of Dentistry, Seoul National University. The following conclusions were obtained; 1. The frequency of the impacted teeth of the anterior segment was 2.8% and the frequency of male was 4.0%, that of female was 2.1%., respectively. 2. The order of occurrence of the impacted teeth in the anterior segment was maxillary canine mesiodens, maxillary central incisor, maxillary lateral incisor, mandibular canine. 3. The etiologic factors of the impaction were the space deficiency for eruption, cleft palate, the prolonged retention of deciduous teeth, dentigerous cyst. 4. The favorable results of treatment and prognosis were obtained from the impacted teeth of the normal shape after surgical exposure and adhered the plastic attachment and inducted them into the dental arch.

• 대한용접접합학회:학술대회논문집
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• 대한용접접합학회 2004년도 춘계 학술발표대회 개요집
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• pp.305-307
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• 2004

One set of rotor coils is required per each large generator rotor assembly, Rotors consist of two directly opposing poles. Each pole requires from 5 to 9 coils. Each coil is made up of two halves identified on the connection end. These coil halves will be joined together by butt brazing process during subsequent rotor assembly. Each half coil is made up of typically 4 to 9 layers of copper conductors. Because of Generator rotor is rotated very high speed with 3,600RPM, the quality soundness of brazed joints is very important at each coil. But, it is very difficult to be optimized non-destructive evaluation, because c-coil has the long shape and evaluation is to be done assembled condition. In this paper introduce newly developed inspection process and acceptance standards for the ultrasonic inspection of " C" coil butt braze. This inspection system is a semi-automatic ultrasonic flaw detector with data acquisition and retention capable of assessing the relative lack of bond of brazed butt joints

• 한국감성과학회:학술대회논문집
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• 한국감성과학회 1998년도 추계학술발표 논문집
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• pp.256-260
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• 1998

1스포츠 양말의 쾌적성과 항균성에 영향을 주는 인자 중에서 특히 양말의 항균성은 위생적인 쾌적감에 중요한 요소이고, 반복되는 착용과 관리도중 에 발생하는 양말의 형태변화는 착용자의 Fit감에 영향을 준다. 본 연구에서는 20종류의 양말시료를 섬유종류, 실의 굵기, 편성조직, 가공처리를 실험조건에 맞게 고려하여 직접 편성하거나 구입하여 사용하였다. 항균가공된 시판 양말의 항균성과 내세탁성, 양말의 착용과 관리 중에 문제가 되는 형태안정성에 관한 실험결과로서 얻은 결론은 다음과 같다. 1. 시판되는 항균가공양말의 항균성과 내세탁성은 모든 시료에서 매우 우수하게 나타나, 위생적인 의생활을 원하는 소비자들의 쾌적감을 충족시킬 수 있다. 2. 양말의 착용 중 또는 관리 중에 형태안정성을 결과를 보면, 섬유의 종류 편성조직에 영향을 받는데, 특히 면양말의 제작 시에는 착용 중에 발생하는 폭방향의 이완현상과 관리 중에 발생하는 길이수축현상을 고려하여 부위별 크기를 조절해야, Fit 감을 유지하며 이수축에 의한 문제발생을 줄일 수 있다.

• 한국축산식품학회:학술대회논문집
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• 한국축산식품학회 2006년도 정기총회 및 제37차 춘계 국제학술발표대회
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• pp.272-276
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• 2006

In this research, storage temperature and periods had significant influence on the physical properties of ice cream. Lower storage temperature reduced the ice re-crystallization and discoloration of ice cream. Increased melt resistance was observed at the lower storage temperature, inducing a good shape retention of ice cream.

• 한국동물위생학회지
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• 제16권1호
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• pp.11-19
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• 1993

This experiment was carried out to detect the residues of sulfonamides in raw milk. Raw milks which does not contain sulfonamides was collected from one of the farm and fortified with 5 sulfonamides (sulfamerazine, sulfamethazine, sulfamonomethoxine, sulfadimethoxine, sulfaqinoxaline). The sulfonamides in the fortified sample were extracted and detected by High Performance Liquid Chromatography. UV /vis detector was used in this experiment. The results obtained were summarized as follows : 1. Chloroform was good as a extracting solution. 2. 15.5% methanol in PDP as a mobile phase solution was best detective condition for SMR, SMT, SMM. But for SDM and SQN the best condition was 23% methanol. 3. The detectable limits of SMR, SMT, SMM were 2ppb. but SDM and SQN were 20ppb because of delayed retention time and relatively low recovery rate. 4. The peaks of SMR, SMT, SMM and SDM were erected at baseline and the apexes were sharp but SQN was round shape.

• Bulletin of the Korean Chemical Society
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• 제16권4호
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• pp.305-309
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• 1995

The enantiomeric separation of several amino acid derivatives by reversed-phase liquid chromatography using two (R)-and (S)-naphthylethylcarbamate-β-cyclodextrin(NEC-β-CD) bonded stationary phases was studied to illustrate the chiral recognition model of the enantiomeric separation. The retention and enantioselectivity of the chiral separations with (R)-and (S)-NEC-β-CD bonded phases were compared with similar separations with the native β-CD stationary phases. Especially, the enantioselectivity and elution orders between the derivatized amino acid enantiomers are carefully examined. These results can be illustrated by the chiral recognition models involving inclusion complexation, π-π interaction, and/or hydrophobic interaction. Inclusion complexation and hydrophobic interaction of the naphthyl group of the NEC moiety seem to be major chiral recognition components in the enantiomeric separation of 2,4-dinitrophenyl amino acids and dabsyl amino acids on (R)-and (S)-NEC-β-CD columns. For dansyl amino acids, only the inclusion complexation is the dominant factor. Three different chiral recognition models containing π-π interaction, inclusion complexation and hydrogen bonding were proposed for the separation of the 3,5-dinitrobenzoyl amino acid enantiomers, depending on the size and shape of amino acids.

• 대한치과보철학회지
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• 제51권3호
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• pp.221-225
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• 2013

임시 보철물의 적절한 관리는 보철의 성공에 있어서 중요한 요소이다. 상악 전치 결손부 임시 보철물은 장경간의 결손부가 존재하거나, 타원형의 악궁을 가진 환자에서 자주 탈락하게 된다. 이는 상악 전치부가 구치부에 비해서 수평적인 힘에 더 많이 노출되며, 부가적으로 전방 캔틸레버 효과가 임시 보철물의 유지를 저해하고, 상악 전치부 임시 보철물은 하악의 기능 운동시 적절한 전방 유도를 제공하여야 하기 때문이다. 또한 임시 보철물의 최대 감합위에서 교합접촉은 지점선의 반대편에 위치하게 되어 그 자체로 임시 보철물의 탈락을 야기한다. 본 증례에서는 임시 임플란트를 이용하여 상악 전치부 보철물에 대한 전술한 유해 작용을 피할 수 있었고, 발치 후 치유기간 동안 환자에게 편안함과 만족감을 부여하였으므로 이를 보고하는 바이다.

• Journal of the Korean Wood Science and Technology
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• 제23권4호
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• pp.60-66
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• 1995

The treatability of Japanese larch heartwood was assessed by pressure treatment of non-incised dimension material with CCA or CCFZ. The effectiveness of incising(conventional, high density, and needle incising) for improving CCA treatability on refractory Japanese larch heartwood was also investigated. Preservative retention and penetration were somewhat greater with CCFZ treatment, although those was generally poor in both preservatives. The retention gradients for both CCA and CCFZ-treated stock were essentially the same shape. Treatment of non-incised material with CCA acheived the recommended treatability for using treated wood at the regions of hazard class H2 in the Japanese Agricultural Standards. However, Japanese larch heartwood would require incising as a pretreatment for enhancing treatability, if CCA-treated larch is intended to be used at the regions of hazard class H3 and H4. As expected, incising resulted in a considerable improvement of preservative treatability, particularly penetration, and the effect of incising on the improvement of treatability was excellent at the sequence of needle incising, high density incising, and conventional incising. Among incising techniques investigated in this study, high density and needle incising enhanced CCA treatability beyond the point where it did meet a minimum requirements specified by the Japanese Agricultural Standards for using CCA-treated Japanese larch at the regions of hazard class H3 and even H4.

• 대한토목학회논문집
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• 제28권5B호
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• pp.535-546
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• 2008

도시화는 유출량의 증가와 도달시간의 감소에 영향을 미치고 있으며, 이는 하류 지점의 빈번한 범람을 야기시키고 있다. 따라서 유역내에 침투시설과 저류시설 등 유출저감효과를 기대할 수 있는 여러 가지 시설을 이용하여 유출량을 저감시킬 수 있는 각종 규모의 지체저류시설을 활용하게 되었다. 본 연구에서는 세가지의 형태(세장형(SF=0.204), 집중형(SF=0.782), 중간형(SF=0.567))로 유역을 가정하여 일반적으로 유역 말단에 설치하던 유수지(저류지)를 유역내의 임의의 위치에 설치하여 단일저류지와 복수 저류지에 대해 각각 유출저감효과를 분석하고, 이들 저류지의 위치관련변수와 수문학적으로 분석하였다. 단일 저류지의 위치에 따른 유출저감효과를 분석하기 위해 유역의 형상에 따라 저류지의 위치는 전체 유역면적에 대한 저류지 상류부 면적의 비(이하 저류지 상류부 면적비, DUAR(Dimensionless Upstream Area Ratio)이라 한다)를 20%, 40%, 60%, 80%로 변동시키면서 모의분석을 수행하였으며, 복수 저류지의 위치에 따른 유출저감효과를 분석하기 위해 단일 저류지 분석시 적용한 유역형상 중 중간형 유역을 대상으로 하여 방류구조와 유역의 제반사항은 단일 저류지의 모의시와 동일하게 가정하였고, 저류지가 분담하는 유역의 면적비를 바탕으로 하여 DUAR 60%, 80%, 100%, 120%, 140%의 경우에 대해 분석하였다. 이 때 저류지 바닥면적(Ab)의 크기는 유역면적에 대해 각각 1%와 0.5%를 취하는 경우의 두 가지로 구분지어 모의분석을 실시하였다. 저류지의 위치에 따른 유출저감효과를 분석한 결과 세장형의 유역이 적은 저류량에 대해 유출저감효과가 우수하였으며, 저류지의 위치 관련변수의 관계도 및 관계식을 제시하였고, 이를 시험유역에 적용시켜 검증하였다. 저류지 위치 관련변수의 관계도 및 관계식을 이용하여 단일 저류지와 복수 저류지의 개략적인 위치선정 기준을 제안하였다.