• Nuclear Engineering and Technology
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• v.53 no.5
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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.

• The Journal of the Korean dental association
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• v.16 no.1 s.104
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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.

• Proceedings of the KWS Conference
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• 2004.05a
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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

• Proceedings of the Korean Society for Emotion and Sensibility Conference
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• 1998.11a
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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.

• Proceedings of the Korean Society for Food Science of Animal Resources Conference
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• 2006.05a
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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.

• Korean Journal of Veterinary Service
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• v.16 no.1
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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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• v.16 no.4
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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.

• The Journal of Korean Academy of Prosthodontics
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• v.51 no.3
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• pp.221-225
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• 2013

Proper management of provisional prosthesis is key to success in prosthodontics. Provisional restoration on maxillary anterior missing area frequently come across a incident of falling off especially in patients with long span pontics and oval arch shape. This is because maxillary anterior teeth are more exposed to horizontal force than the posterior teeth and additional anterior cantilever effect will negatively affect to the retention of provisional prosthesis. Beside that maxillary anterior provisional prosthesis should provide proper incisal guidance during the mandibular functional movements. However occlusal contacts on the prosthesis in maximum intercuspal position are located on opposite side of fulcrum line of prosthesis which will cause removing force against the provisional prosthesis. This case report present that provisional implant prevent pre-described harmful effect on maxillary anterior fixed provisional prosthesis and provide comfort and satisfactory result during post-extraction healing period.

• Journal of the Korean Wood Science and Technology
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• v.23 no.4
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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.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.28 no.5B
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• pp.535-546
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• 2008

Urbanization results in increased runoff volume and flowrate and shortening in time of concentration, which may cause frequent flooding downstream. The retardation structures are used to eliminate adverse downstream effects of urban stormwater runoff. There are various types of flow retardation measures include detention basin, retention basin, and infiltration basin. In this study, to present a rough standard about location of detention pond for attenuating peak flow of urban area, the runoff reduction effect is analyzed at outlet point when detention pond is located to upstream drainage than outlet. The runoff reduction effects are analyzed under the three assumed basins. These basins have longitudinal shape (SF = 0. 204), concentration shape (SF = 0. 782), and middle shape (SF = 0.567). Numerous variables in connection with the storage effect of detention pond and the runoff reduction effects are analyzed by changing the location of detention pond. To analyze runoff reduction effect by location of single detention pond, Dimensionless Upstream Area Ratio (DUAR) is changed to 20%, 40%, 60%, and 80% according to the basin shape. In case of multiple detention pond, DUAR is changed to 60%, 80%, 100%, 120%, and 140% only under the middle shape basin (SF = 0.567). Related figures and regression equations to determine the location of detention pond are obtained from above analysis of two cases in this study. These results can be used to determine the location of appropriate detention pond corresponding to the any runoff reduction such as storage ratio and peak flow ratio in urban watershed.