• Nuclear Engineering and Technology
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• 제52권12호
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• pp.2949-2957
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• 2020

Fatigue crack growth model has been developed for dissimilar metal weld joints of a piping component under cyclic loading, where in the crack is located at the center of the weld in the circumferential direction. The fracture parameter, Stress Intensity Factor (SIF) has been computed by using principle of superposition as K_H + K_M. K_H is evaluated by assuming that, the complete specimen is made of the material containing the notch location. In second stage, the stress field ahead of the crack tip, accounting for the strength mismatch, the applied load and geometry has been characterized to evaluate SIF (K_M). For each incremental crack depth, stress field ahead of the crack tip has been quantified by using J-integral (elastic), mismatch ratio, plastic interaction factor and stress parallel to the crack surface. The associated constants for evaluation of K_M have been computed by using the quantified stress field with respect to the distance from the crack tip. Net SIF (K_H + K_M) computed, has been used for the crack growth analysis and remaining life prediction by Paris crack growth model. To validate the model, SIF and remaining life has been predicted for a pipe made up of (i) SA312 Type 304LN austenitic stainless steel and SA508 Gr. 3 Cl. 1. Low alloy carbon steel (ii) welded SA312 Type 304LN austenitic stainless-steel pipe. From the studies, it is observed that the model could predict the remaining life of DMWJ piping components with a maximum difference of 15% compared to experimental observations.

• 대한조선학회논문집
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• 제58권1호
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• pp.49-57
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• 2021

In the production power transmitting of a floating production system like a wind offshore floating, the power cable should be connected from the surface system into the subsea system. The connection between the surface and the subsea system will make the power cable get a dynamic load like current and wave forces. Based on this condition, a dynamic power cable is required to endure external physical force and vibration in the long-term condition. It needs more requirements than static power cable for mechanical fatigue properties to prevent failures during operations in marine environments where the external and internal loads work continuously. As a process to verify, the durability test of dynamic power cables under the marine operation environment condition was carried out by using domestic technology development.

• 한국융합학회논문지
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• 제12권12호
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• pp.117-123
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• 2021

본 연구의 목적은 인솔구두의 굽 높이에 따른 평발을 가진 20대 대학생의 보행 시 발목관절의 각도변화에 대해 융복합적 비교를 하는 것이다. 15명의 대학생을 대상으로 동작분석기(Qualisys Track Manager)를 이용하였다. 인솔이 장착된 기능성 구두를 제작하고, 구두의 굽 높이를 0cm, 3cm와 7cm로 셋팅하였다. 실험대상자들은 두 개의 굽 높이가 있는 구두를 신고 발목관절의 측면에 반사마커를 부착하여 보행을 실시하였다. 보행입각기에서 발목관절의 각도변화를 측정하였다. 평발을 가진 실험대상자가 인솔구두를 착용 시 구두 굽 높이가 높을수록 양측의 Heel strike, Foot flat, Midstance, Toe off에서 유의한 감소가 나타났다. 따라서 평발을 가진 대상자는 인솔구두를 착용 시 낮은 구두를 신어야만 발바닥의 피로를 감소시켜 편안한 보행을 할 것으로 사료된다.

• 한국산학기술학회논문지
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• 제20권2호
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• pp.632-637
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• 2019

해양 플랜트 전장생산설계의 케이블 트레이 설계는 구조 부재 및 각종 의장 장비들과 간섭없이 케이블이 설치될 수 있도록 3D 모델링하여 원활하게 최적 배치하는 작업으로, 대부분 PDMS(Plant design management system)를 이용하여 수행되고 있다. PDMS는 해양 플랜트 생산설계 전용 3D CAD 시스템으로 국내 조선소와 관련 설계협력업체에서 널리 사용되고 있다. 본 연구에서는 PDMS 기반 해양 플랜트 케이블 트레이 설계 지원 PML(Programmable macro language)을 개발하여, 기존 방법 대비 업무 효율성을 검토하였다. 개발된 케이블 트레이 설계 PML은 전장 템프릿 라이브러리를 이용하여 완전히 파라메트릭 설계가 가능하도록 함으로써 설계 변경으로 인한 빈번한 수정 작업에 신속히 대응할 있도록 하였고, 축적된 설계 경험를 반영하여 반복되는 작업 피로를 최소화할 수 있도록 하였다. 그리고 개발된 시스템을 해양 플랜트 구조 모듈에 적용하여 기존 방법 대비 약 50% 이상의 작업 효율성 향상이 예상됨을 확인하였다.

• 한국산학기술학회논문지
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• 제19권11호
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• pp.521-528
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• 2018

전투목적으로 개발된 군용차량은 타이어 압력이 손실되더라도 일정시간동안 일정거리를 달릴 수 있도록 런플랫시스템을 도입하였다. 런플랫을 적용하기 위하여 휠을 외측림과 내측림으로 구성된 2개의 부분으로 구성하고, 클램핑 볼트를 체결함으로써 외측림과 내측림을 조립한다. 이 클램핑 볼트는 휠의 내구성을 결정하는 중요 부품이다. 실제로 휠의 내측림과 외측림의 파손보다는 클램핑볼트의 파손이 발생되어 휠을 사용하지 못하는 빈도가 높다. 따라서, 클램핑 볼트의 내구성능이 휠의 내구성능과 연관이 크다고 할 수 있다. 본 연구는 휠의 내구성을 향상시키기 위하여 휠조립체를 시험하고 클램핑 볼트를 개발하는 과정을 다루었다. 기존에 정립된 내구시험 조건의 불충분성을 식별하였으며, 휠조립체의 내구성을 보다 정확히 확인할 수 있도록 통제해야 하는 시험조건을 제시하였다. 정립된 시험조건을 기반으로, 성능이 개선된 클램핑 볼트를 시험하였다. 시험조건을 확인한 결과 기존 제품보다 최소 168% 내구성이 향상됨을 확인할 수 있었다. 본 연구는 휠 조립체의 내구시험 방법과 클램핑 볼트를 개발하는 과정에서 고려해야 할 요소를 제시한 것에 의미가 있다 할 수 있다.

• 한국압력기기공학회 논문집
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• 제15권1호
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• pp.62-70
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• 2019

The APR1400 reactor may be operated for a long time under high temperature and pressure conditions, causing damage to the stud holes and causing stud bolts and holes to stick. The present practice is to manually remove the anti-sticking agent and foreign matter remaining in the APR1400 reactor stud hole and to visually check the surface condition of the thread to check the damage status of the threads. In the case of the APR1400 reactor stud holes, manually cleaning the threads increases the risk of radiation exposure and operator's fatigue. To avoid this, the autonomous mobile robot is used to automatically clean the reactor stud holes. The purpose of this study is to optimize the cleaning performance of the mobile robot by looking at the behavior of the surface roughness of the stud surface cleaned by the brush attached to the mobile robot due to changes in brush material, thickness of wire, and rotation speed. A microscopic approach to the surface roughness of the flank is needed to investigate the effects of the newly proposed brush of the autonomous mobile robot on the thread holes. According to this experiment, it is reasonable to use STS brush rather than Carbon one. Optimal operating conditions are derived and the safety of APR1400 reactor stud holes maintenance can be improved.

• 대한물리의학회지
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• 제14권3호
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• pp.81-89
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• 2019

PURPOSE: To solve the problems of chronic obstructive pulmonary disease (COPD) patients complaining of muscle fatigue and having limited motor abilities, this study provided the clinical basic data for pulmonary rehabilitation by examining the effects of High Low-Frequency Neuromuscular Electrical Stimulation (NMES) on the respiratory muscle strength, quadriceps muscle activity, and life quality. METHODS: Samples were collected from 20 COPD patients and placed randomly in a low-frequency group (n=10) and high-frequency group (n=10). For a pretest, the respiratory muscle strength (MIP, MEP), quadriceps muscle activity (LF, VM, VL), and life quality (SGRQ) were measured. After applying NMES to each group for 30 minutes at a time, five times a week, for four weeks, a posttest was conducted in the same way as the pretest. RESULTS: Both groups showed significant differences in the respiratory muscle strength, quadriceps muscle activity, and quality of life within the groups and there were significant differences in the quadriceps muscle activity between the groups. CONCLUSION: The four-weeks NMES positively influenced the respiratory muscle strength and life quality by enhancing the function of the quadriceps and exercise tolerance. In particular, high-frequency(75 Hz) NMES was more effective than low-frequency (15 Hz) NMES. This result can be an alternative means to improve the physical functions of COPD patients clinically in the future.

• 임상간호연구
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• 제25권1호
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• pp.80-90
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• 2019

Purpose: The aim of this study was to identify the research trends of articles published in the Journal of Korean Clinical Nursing Research from 2000 to 2017 by a text network analysis using keywords. Methods: This study analyzed 600 articles. The R program was used for text mining that extracted frequency, centrality rank, and keyword network. Results: From 2000 to 2009, keywords with high-frequency were 'nurse', 'pain', 'anxiety', 'knowledge', 'attitude', and so on. 'Pain', 'nurse', and 'knowledge' showed a high centrality. 'Fatigue' showed no high frequency but a high centrality. Keywords such as 'nurse', 'knowledge', and 'pain' also showed high frequency and centrality between 2010 and 2017. 'Hemodialysis' and 'intensive care unit' were added to keywords with high frequency and centrality during the period. Conclusion: The frequency and centrality of keywords such as 'nurse', 'pain', 'knowledge', 'hemodialysis', and 'intensive care unit' reflect the research trends in clinical nursing between 2000 and 2017. Further studies need to expand the keyword networks by connecting the main keywords.

• Integrative Medicine Research
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• 제6권3호
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• pp.317-324
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• 2017

Background: Bu-Zhong-Yi-Qi-Tang (BZYQT) has long been used for the treatment of severe weakness caused by general fatigue, loss of appetite, or indigestion. The aim of this feasibility study is to assess the effectiveness and safety of BZYQT for the treatment of functional dyspepsia (FD) with spleen qi deficiency. Methods: This study will be conducted at a single center as a prospective, nonrandomized, nonblinded, single-arm feasibility study. A total of 30 participants diagnosed with FD in accordance with the Rome III criteria will be enrolled. All patients will receive BZYQT for 4 weeks. The primary outcome is the change in the Nepean Dyspepsia Index-Korean version (NDI-K) scores between the baseline and 4-week images. The secondary outcomes include the tongue coating thickness, blood parameters, and BZYQT Questionnaire score. The NDI-K score will be acquired four times, at Weeks 0 (baseline), 2 (during treatment), 4 (after treatment), and 8 (after follow-up). Written informed consent will be obtained from all study participants prior to enrollment. This study has been approved by the Institutional Review Board of Kyung Hee University Korean Medicine Hospital. This study protocol is registered with the national clinical trial registry of the World Health Organization International Clinical Trials Registry Platform. Results will be published in a journal and will be disseminated both electronically and in print. Discussion: The results of this study may serve as a guide for researchers seeking to effectively evaluate the effects of BZYQT.

• Smart Structures and Systems
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• 제23권3호
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• pp.263-278
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• 2019

Moving train load parameters, including train speed, axle spacing, gross train weight and axle weights, are identified based on strain-monitoring data. In this paper, according to influence line theory, the classic moving force identification method is enhanced to handle time-varying velocity of the train. First, the moments that the axles move through a set of fixed points are identified from a series of pulses extracted from the second derivative of the structural strain response. Subsequently, the train speed and axle spacing are identified. In addition, based on the fact that the integral area of the structural strain response is a constant under a unit force at a unit speed, the gross train weight can be obtained from the integral area of the measured strain response. Meanwhile, the corrected second derivative peak values, in which the effect of time-varying velocity is eliminated, are selected to distribute the gross train weight. Hence the axle weights could be identified. Afterwards, numerical simulations are employed to verify the proposed method and investigate the effect of the sampling frequency on the identification accuracy. Eventually, the method is verified using the real-time strain data of a continuous steel truss railway bridge. Results show that train speed, axle spacing and gross train weight can be accurately identified in the time domain. However, only the approximate values of the axle weights could be obtained with the updated method. The identified results can provide reliable reference for determining fatigue deterioration and predicting the remaining service life of railway bridges.