• Nuclear Engineering and Technology
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• 제30권6호
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• pp.609-616
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• 1998

Cast duplex stainless steels are extensively used for primary pressure boundary components. These components are, however, embrittled due to the precipitation of $\alpha$' phase by spinodal decomposition and other processes when exposed to reactor operating temperature for a design lifetime or life extension conditions. This report presents a procedure for estimating the current condition and the residual life of safety-related stainless steel components by using ANL database and correlations. The database of Charpy impact energy suggests that CF-8M grade is the most susceptible to thermal aging and CF-3 grade is the least. Thus, the integrity of CF-8M alleys may be degraded seriously and the degree of deterioration may exceed acceptance limit after several years of service in the nuclear reactors.

• 한국가정과학회지
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• 제6권2호
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• pp.27-40
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• 2003

The Purpose of this paper was to study the uses of the extra activity classroom of elementary school and the satisfaction of the students. The SPSS 10.0 for windows was used to analyze data collected from 397 elementary school students in Kunsan and Seocheon. The results were as follows: (1) More than 2/3 students have experienced special activities. The extra activity classroom was not effectively used showing less than one or two hours use a week for the lecture and extra activities. (2) Generally the students were satisfied at the condition of extra activity classroom, but dissatisfied with the degree of the independence, of deterioration, and of safety while moving. That is because the building and its equipment were old, and soundproofing and safety establishments were not well equipped. (3) There was difference between schools. Students at city had more satisfaction than at county. (4) The most important item of extra activity classroom was esthetics followed by function, safeness. and healthiness. It shows that the important item is being moved to esthetics and healthiness from function of extra activity classroom.

• International Journal of Naval Architecture and Ocean Engineering
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• 제12권1호
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• pp.699-710
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• 2020

Pitting corrosion commonly shaped in hull structure due to marine corrosive environment seriously causes the deterioration of structural performance. This paper deals with the ultimate strength behaviors of stiffened ship panels damaged by the pits subjected to uniaxial compression. A series of no-linear finite element analyses are carried out for three stiffened panels using ABAQUS software. Influences of the investigated typical parameters of pit degree (DOP), depth, location and distribution on the ultimate strength strength are discussed in detail. It is found that the ultimate strength is significantly reduced with increasing the DOP and pit depth and severely affected by the distribution. In addition, the pits including their distributions on the web have a slight effect on the ultimate strength. Compared with regular distribution, random one on the panel result in a change of collapse mode. Finally, an empirical formula as a function of corrosion volume loss is proposed for predicting the ultimate strength of stiffened panel.

• 열처리공학회지
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• 제35권5호
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• pp.239-245
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• 2022

The purpose of this study is to evaluate the degree of microstructural change of materials using ultrasonic nonlinear parameters. For microstructure change, isothermal heat-treated ferritic 2.25Cr steel and low-cycle fatigue-damage copper alloy were prepared. The variation in ultrasonic nonlinearity was analyzed and evaluated through changes in hardness, ductile-brittle transition temperature, electron microscopy, and X-ray diffraction tests. Ultrasonic nonlinearity of 2.25Cr steel increased rapidly during the first 1,000 hours of deterioration and then gradually increased thereafter. The variation in non-linear parameters was shown to be coarsening of carbides and an increase in the volume fraction of stable M6C carbides during heat treatment. Due to the low-cycle fatigue deformation of oxygen-free copper, the dislocation that causes lattice deformation developed in the material, distorting the propagating ultrasonic waves, and causing an increase in the ultrasonic nonlinear parameters.

• Journal of Periodontal and Implant Science
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• 제32권1호
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• pp.51-59
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• 2002

The aim of the present study was to investigate the distribution of periodontally hopeless teeth in patients who had not been treated. Five hundred nineteen teeth of 163 patients who had visited at the Department of Periodontology, Chonbuk National University Hospital during the period from January 1999 to July 2001 were selected as a periodontally hopeless tooth. Selection criteria were as follows: 1) probing pocket depth more than 8mm, 2) tooth mobility of degree III, 3) radiographic bone loss more than 75%. The contralateral tooth to a hopeless tooth (experimental tooth) was designated as a control tooth. Between the experimental and control tooth, differences in probing pocket depth, tooth mobility and amount of radiographic bone loss were examined as well as correlation. The results showed that hopeless teeth were most frequently found in the maxillary first molar position and least frequently in the maxillary canine position. Differences between experimental and control teeth were 2mm in probing depth, 1 degree in tooth mobility, and 20% in amount of bone loss (p<0.01). The periodontal conditions between the experimental and control teeth showed correlation in general, however, statistical significances were found in posterior teeth positions. Within limitations of this study, it can be concluded that local factors may play a role in deterioration of periodontal disease along with symmetrical character of periodontal disease.

• 한국식생활문화학회지
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• 제22권1호
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• pp.115-126
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• 2007

This study was conducted to preserve the quality of Gangjung (Traditional Korean cookies) during storage with the addition of sorbitol in Gangjung dough. Sorbitol was added with different levels (0, 1.5, 3%) in the Gangjung dough and the Gangjung samples were stored for different periods (1, 16, and 31 days). Compared to the control group, the Gangjung samples with sorbitol groups had higher moisture content, expansion ratio, and ceil size. As the storage was extended, peroxide values, hardness, fracturability, chewiness and stickiness to teeth were increased, while cohesiveness, moistness, and degree of melting were decreased. From the PCA in the sensory analysis, Gangjung with addition of 3% sorbitol stored for 1, 16, and 31 days showed high levels in moistness, cohesiveness, degree of expansion, cell size, and degree of melting, whiie Gangjung in control group stored for 16 and 31 days showed high levels in fracturability, heated oil flavor, chewiness, and stickiness to teeth. The moisture content of Gangjung was significantly increased as the level of sorbitol was increased. The changes of physicochemical and sensory characteristics by storage were increased in control groups the most, 1.5% sorbitol groups the next, and 3% sorbitol groups the least. Therefore, the sorbitol added groups could be delayed in the quality deterioration during storage, especially in the texture, and could be increased in the preservation of Gangjung.

• 한국산업융합학회 논문집
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• 제26권6_2호
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• pp.1055-1062
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• 2023

Globally, the need for remanufacturing or reusing ships and various mechanical parts continues to increase due to environmental problems including global warming. Research on remanufacturing is being carried out in many areas. However, research on inspection and classification to identify the performance or degree of wear of mechanical parts is insufficient. In particular, studies on the inspection-ability and classification-ability of mechanical parts equipped with various materials and complex forms are highly required. Remanufacturing must be considered from the stage of design to extend the life cycle of mechanical parts. Particularly, it is very important to perform research for evaluating the degree of ease to inspect and classify various sorts of wear or deterioration of parts caused by long-term use easily. In this study, the degree of ease in inspecting or classifying mechanical parts for remanufacturing is defined as inspection-ability and classification-ability. In fact, to remanufacture old parts, inspection-ability and classification-ability should be reflected from the stage of design. The purpose of this study is to evaluate the inspection-ability and classification-ability of ships and various mechanical parts. This researcher has presented the quantitative evaluation procedure of inspection-ability and classification-ability, derived the factors and ranges that influence each of the details of easiness, assigned scores according to the ranges of the factors, and calculated weights. Lastly, this study presents the procedure of scoring to evaluate the overall weights of inspection-ability and classification-ability and also inspection-ability and classification-ability quantitatively.

• 펄프종이기술
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• 제44권6호
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• pp.70-78
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• 2012

The Annals of Joseon Dynasty, which recorded governmental affairs for 472 years (AD 1392-1863) during the Joseon dynasty is an representative paper cultural heritage in Korea. Being recognised their authenticity and values they were designated as the No 151 national treasure of Korea in 1973 and registered as 'The Memories of the World' by UNESCO in 1997. Unusually, some volumes of the Annals were treated by beeswax for the permanent preservation. However, the examinations on the deterioration of the beeswax-treated volumes had been exposed the serious damage than the untreated volumes. In particular, the larger amount of beeswax were worst in deterioration condition. In order to solve these problems, NRICH(National Research Institute of Cultural Heritage) of Korea launched the investigation study for the conservation of beeswax-treated volumes of the Annals. Now then, the five study areas have been set up; 1) to understand the damaged condition of the Annals; 2) to analyse the raw materials and production techniques; 3) to test the degradation degree using the duplication samples for understanding the aging factors and mechanism; 4) to develop the conservation techniques through dewaxing and thereafter strengthening the base paper of Hanji; 5) to develop the long-term storage technique using inert gases. On the basis of outcomes from this study, NRICH will plan to establish the systematic conservation and management plan for the beeswax-treated volumes of the Annals in future.

• 한국강구조학회 논문집
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• 제24권1호
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• pp.81-89
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• 2012

콘크리트 충전강관 기둥은 내부의 콘크리트에 의해 축열효과로 인해 철골기둥에 비해 내화성능이 우수하며, 기둥 단면 내 철근 및 강관을 보강하여 구조적내력 및 내화성능 향상연구가 이루어져 오고 있다. 실제로 보강된 CFT기둥은 고축력을 요구하는 기둥부재로 사용 빈도 수가 증가되고 있는 추세이다. 이러한 상황에서 CFT기둥을 사용한 건축물에 화재가 발생하여 손상을 입게 되었을 경우 성능 저하정도를 정밀하게 측정할 수 있는 기법이 필요하다. 본 연구에서는 화재 발생시 CFT기둥에 대한 내부 온도 분포를 평가 하고, 단면내부의 온도분포에 따라 내부 충전콘크리트와 보강재의 내력 저하 정도를 파악하여 CFT기둥의 전체적인 잔존강도를 평가하고자 한다.

• Journal of Korean Neurosurgical Society
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• 제29권7호
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• pp.904-909
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• 2000

Objectives : Most cases of cervical ossification of the posterior longitudinal ligament(OPLL) present with myelopathy or myeloradiculopathy, which sometimes is further complicated by minor trauma to the spinal cord. The main purpose of surgery in these patients is the alleviation symptoms but also as protection against further deterioration. The purpose of this study is to analyze the influence of trauma on the surgical outcome in patients with cervical OPLL. Methods : Over the past 13 years, we have operated on 123 patients with myelopathy associated with cevical OPLL. Among these, thirty patients had cervical cord injury associated with major or minor trauma and their clinical and radiographic data were reviewed retrosepctively. Results : As to cause of trauma, seventeen were related with traffic accident and 13 were related with minor slipping injury. The pre- and post-operative motor power were significantly weaker in the patients with trauma, but the degree of motor improvement was significantly higher(trauma group : $0.90{\pm}1.49$, non-trauma group : $0.41{\pm}0.80$). Conclusion : These results indicate that even indirect minor trauma to the cervical spine can cause irreversible changes to the spinal cord if this is associated with underlying cervical stenosis with OPLL. Although less favorable results may be anticipated in patients with trauma, operative decompression could improve motor power and protect further deterioration.