• 대한기계학회논문집
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• 제18권11호
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• pp.3098-3107
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• 1994

The central burst defects, so-called chevroning, in wire drawing are analyzed by the rigid-plastic finite element method. The occurrence of central burst defects in wire drawing is estimated by the distribution of the hydrostatic pressure around the central part of the workpiece. It has been possible to obtain numerical boundaries which, in reduction in area vs. semicone angle plane, divide the safe and the danger zones, depending on friction factors and material properties. Based on the results of the analysis, it is suggested that the previous criterion derived from the upper bound analysis should be modified for better prediction of the defects. The back tension and the billet with a spherical hole on the central axis are also included in the analysis of the defects.

• 한국건축시공학회:학술대회논문집
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• 한국건축시공학회 2001년도 학술논문발표회
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• pp.130-135
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• 2001

In this study, I have researched into the causes of defects in apartment house, The results of this study are listed below. (1) Water leakages which result from land sinking and cracks, results of misuse of back filling method, are the main reason of defects in civil engineering work and architectural work. (2) Inexperience and unwillingness are the main reason of defects in plaster work. (3) In windows work and painting work, the main reasons are lacks of precision construction and efflorescence resulting from outdoor air, respectively. (4) Defects in waterproofing work and electric work result from fault construction by low unit Costs. (5) Equipment work requires uses of standardized construction materials and management, and landscape architecture work requires minimizing human mistakes, for instance, degin carelessness. For the reasons stated above, the causes of defects in apartment house are insufficient construction labors, inferior construction materials, urgent construction process time, and conscientiousless industrialists who only seek after a profit margin.

• Journal of Magnetics
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• 제18권3호
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• pp.357-360
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• 2013

A modified SQI method using magnetic leakage flux (MFL) signal for underground gas pipelines' defect detection and characterization is presented in this paper. Raw signals gathered using MFL signals include many unexpected noises and high frequency signals, uneven background signals, signals caused by real defects, etc. The MFL signals of defect free pipelines primarily consist of two kinds of signals, uneven low frequency signals and uncertain high frequency noises. Leakage flux signals caused by defects are added to the case of pipelines having defects. Even though the SQI (Self Quotient Image) is a useful tool to gradually remove the varying backgrounds as well as to characterize the defects, it uses the division and floating point operations. A modified SQI having low computational complexity without time-consuming division operations is presented in this paper. By using defects carved in real pipelines in the pipeline simulation facility (PSF) and real MFL data, the performance of the proposed method is compared with that of the original SQI.

• Nuclear Engineering and Technology
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• 제51권3호
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• pp.769-775
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• 2019

The tensile strength of irradiated 3C-SiC, SiC with artificial point defects, SiC with symmetric tilt grain boundaries (GBs), irradiated SiC with GBs are investigated using molecular dynamics simulations at 300 K. For an irradiated SiC sample, the tensile strength decreases with the increase of irradiation dose. The Young's modulus decreases with the increase of irradiation dose which agrees well with experiment and simulation data. For artificial point defects, the designed point defects dramatically decrease the tensile strength of SiC at low concentration. Among the point defects studied in this work, the vacancies drop the strength the most seriously. SiC symmetric tilt GBs decrease the tensile strength of pure SiC. Under irradiated condition, the tensile strengths of all SiC samples with grain boundaries decrease and converge to certain value because the structures become amorphous and the grain boundaries disappear after high dose irradiation.

• 방사성폐기물학회지
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• 제19권2호
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• pp.215-223
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• 2021

The domestic CANDU nuclear power plants have been operated for a long time and various unforeseen spent fuel defects have been discovered. As the spent fuel defects are important factors in the safety of the nuclear power plant, a study on the analysis of the spent fuel defects to prevent their recurrence is necessary. However, in cases where the fuel rods inside the fuel assembly are defected, it is difficult to dismantle the fuel assembly owing to their welded structure and the facility conditions of the plant. Therefore, it is impossible to analyze the spent fuel defect because it is difficult to visually check the shape of the fuel defect. To resolve these problems, an analysis technology that can predict the number of defected fuel rods and defect size was developed. In this study, we developed a methodology for investigating the root cause of spent fuel defects using a database of the earlier fuel defects in the plants. It is anticipated that in the future this analysis technology will be applied when spent fuel defects occur.

• 무역학회지
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• 제45권2호
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• pp.67-86
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• 2020

This study analyzes the buyer's remedies for defects in title under DCFR, and it is compared with those of CISG. DCFR adopts a unitary concept of 'non-performance' which is any failure and includes delayed performance and any other performance which is not conformed with the contract. In terms of defects in title, any remedies for non-performance are available under DCFR. Thus. under DCFR, the buyer is entitled to enforce specific performance of obligations, to withhold performance, to terminate for fundamental non-performance, to reduce price, to damage for loss, to require repair, or to deliver a replacement. But under CISG, whether or not defects in title constitute 'non-conformity' is not clear and the majority understands 'non-conformity' does not include title defects. Therefore, the buyer may not has rights to require repair and delivery of replacement unlike DCFR.

• 한국환경복원기술학회지
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• 제23권3호
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• pp.91-104
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• 2020

This study was conducted to analyze the characteristics of defects according to the type of block and spatial type by quantitatively examining defects occurring in block pavement in apartment complex. According to the research results, depending on the type of block, defects have occurred 1,394.3ea/100㎡ in interlocking paver blocks, 464.8ea/100㎡ in clay brick paver blocks, and 235.1ea/100㎡ in shot blasted paver blocks. By space type, the defects were occurred 1,576.0ea/100㎡ on the access road paved by interlocking paver blocks and the defects were found 1,139.6ea/100㎡ in interlocking paver blocks, 235.1ea/100㎡ in shot blasted paver blocks, and 797.1ea/100㎡ in clay brick paver blocks, on the sidewalk. Also the defects are occurred 455.6ea/100㎡ on the resting space and 403.2ea/100㎡ on the gym space paved by clay brick paver blocks. Through the size analysis of the defects in the block paver, in the case 'peeling', the largest volume of 2,539.0㎣ on the sidewalk paved with shot blasted paver blocks, and 'Subsidence' occurred at the widest area of 2,096.0㎠ on the sidewalk where interlocking paver block was constructed. The difference in defect occurrence according to the type of block is considered to be influenced by the block production process, and the space type is considered to be caused the difference in the occurrence of defects according to the cause of construction and the usage pattern of residents. This study conducted a survey on defects in block and analyzed the defect characteristic according to paver material and space type. Base on this, it is judged that it can be used as an efficient basic data for material replacement, improvement, paver planning and construction in the future.

• 대한기계학회논문집A
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• 제37권9호
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• pp.1175-1182
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• 2013

위상잠금모드가 적용된 적외선열화상 시험법은 열전도도가 큰 재료에서 결함의 검출능력을 향상시키기 위해 개발되었으며, 기존의 적외선열화상 기법에 비해 우수한 결함 검출능력을 보이는 것으로 알려져 있다. 따라서, 본 연구에서는 원전 배관 감육결함 검출에서 위상잠금모드 기법의 적용 효과를 살펴보기 위해서, 감육결함이 가공된 배관 시편을 대상으로 위상잠금모드를 적용하여 적외선열화상 시험을 수행하였다. 시험 결과로부터 감육결함에 대한 위상이미지를 얻고, 이것을 기존의 적외선열화상시험법으로 구한 열화상이미지와 비교하였다. 비교 결과, 위상잠금모드의 적용이 감육결함에 대한 형상 결정 능력을 향상시키는 것을 확인하였다. 이러한 개선 효과는 폭과 길이가 작거나 경계가 경사진 감육결함에서 뚜렷하였다. 그러나, 깊이가 얕은 감육결함의 검출능력은 크게 향상되지 않았다.

• Restorative Dentistry and Endodontics
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• 제45권4호
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• pp.53.1-53.11
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• 2020

Objectives: This study investigated the incidence of root dentin defects after the use of different post space preparation (PSP) drills. Materials and Methods: Seventy-two bovine incisors were selected and obtained 14-mm-long root sections. Twelve roots served as controls with no intervention (G1). The 60 root canals remaining were instrumented using the crown-down technique with the ProTaper Next system and obturated using the lateral condensation technique. Specimens were randomly distributed into 5 groups (n = 12) according to the operative steps performed: G2, root canal instrumentation and filling (I+F); G3, I+F and PSP with Gates-Glidden drills; G4, I+FI+F and PSP with Largo-Peeso reamers; G5, I+F and PSP with Exacto drill; and G6, I+F and PSP with WhitePost drill. Roots were sectioned at 3, 6, 9, and 12 mm from the apex, and digital images were captured. The presence of root dentin defects was recorded. Data were analyzed by the χ² test, with p < 0.05 considered to indicate statistical significance. Results: Root dentin defects were observed in 39.6% of the root sections. No defects were observed in G1. G5 had significantly more cracks and craze lines than G1, G2, and G3 (p < 0.05), and more fractures than G1, G2, G3, and G4 (p < 0.05). When all root sections were analyzed together, significantly more defects were observed at the 12-mm level than at the 3-mm level (p < 0.05). Conclusions: PSP drills caused defects in the root dentin. Gates-Glidden drills caused fewer root defects than Largo-Peeso reamers and Exacto drills.

• 한국산학기술학회논문지
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• 제15권6호
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• pp.3376-3382
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• 2014

전자내시경을 이용하여 양극처리된 알루미늄 실린더튜브 내면의 결함을 자동으로 검사하는 시스템을 개발하였다. 이 시스템은 크게 자동 결함검사 소프트웨어, 전자내시경 및 이송장치 등으로 구성되어 있다. 실험을 통하여 자동 결함검사의 최적검출 조건을 도출하여 실린더튜브 내면의 결함 검사에 적용한 결과 주요 결함 요소인 스크래치, 산화물, 라인, 웰드라인의 인식률을 99%로서 만족하였다. 자동 결함검사 시스템을 생산현장에 적용하면 기존의 육안 검사 시 작업자가 가지는 육체적인 피로도 줄여 작업효율을 증가시키며, 결함검출 자료를 바탕으로 제품의 품질을 향상시킬 수 있다.