• Title/Summary/Keyword: Fatigue

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A Study for Durability Test of Dynamic Power Cable under Marine Operating Environment Condition (동적 파워 케이블의 해양운용환경 내구성 검증시험에 관한 연구)

  • Shim, Chunsik;Kim, Chulmin;Rho, Yuho;Lee, Jaebok;Chae, Kwangsu;Song, Hacheol;Kim, Hokyeong;Bae, Chulmin;Wi, Sungkuk;Im, Kichen
    • Journal of the Society of Naval Architects of Korea
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    • v.58 no.1
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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.

Convergence Comparison of the Angle Change of Ankle Joint while Walking according to the Heel height of Insole Shoes in 20s males with Flatfoot (평발을 가진 20대 남성이 인솔구두의 굽 높이에 따른 보행 시 발목관절의 각도변화에 대한 융복합적 비교)

  • Seo, Kyo-Chul;Park, Seung-Hwan;Kim, Hyen-Ae
    • Journal of the Korea Convergence Society
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    • v.12 no.12
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    • pp.117-123
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    • 2021
  • The purpose of this study is to convergence comparison the ankle joint angle change during walking of college students in their 20s with flat foot according to the heel height of insole shoes. Qualisys Track Manager Software ver. 2.8 (Qalisys Track Manager) was used for 15 college students. Functional shoes with insoles were manufactured, and the heel heights of the shoes were set to 3cm and 7cm. The subjects wore shoes with two high heels and gaited by attaching a reflex marker to the side of the ankle joint. The angle change of the ankle joint was measured in the gait stance phase. The angle of the ankle joint significantly decreased both heel strike, foot flat, midstance, and toe off to the heel height increased when the subjects with flat feet wore insole shoes. Therefore, it is thought that flat feet should wear low shoes when wearing insoles to reduce the fatigue of the soles and to walk comfortably.

Development of Parametric Design Tool for Offshore Plant Cable Tray Using PML (프로그램 매크로언어를 이용한 해양 플랜트 케이블 트레이의 파라메트릭 설계 도구 개발)

  • Kim, Hyun-Cheol
    • Journal of the Korea Academia-Industrial cooperation Society
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    • v.20 no.2
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    • pp.632-637
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    • 2019
  • The cable tray design of an offshore plant production design is to optimally arrange the 3D modeling so that the cable can be installed without interfering with the structural members and various outfit equipment, and it is performed using a PDMS (Plant design management system), which is a 3D CAD system for an offshore plant layout. This study reviewed the development of PML (Programmable macro language) for a PDMS supporting offshore plant cable tray design and examined the efficiency compared to the existing method. Cable tray design PML developed in this paper enables fully parametric design using electrical outfit template library, allowing a rapid response to frequent modifications due to design changes and minimizing repetitive work fatigue by reflecting the accumulated design experience. In addition, the developed system was applied to the offshore plant structure module and it improved the work efficiency by more than 50% compared to the existing method.

Design Technique for Durability Improvement of Military Vehicle Wheel (군용차량 휠 조립체 내구성 향상 방법론 연구)

  • Shin, Cheolho;Kang, Tae Woo;Kim, Seonjin;Na, Chul Ju
    • Journal of the Korea Academia-Industrial cooperation Society
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    • v.19 no.11
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    • pp.521-528
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    • 2018
  • Military vehicles use run-flat wheels for emergency situations. Run-flat wheels can run required distance in a defined duration with the pressure loss tire. For the application of a run-flat system, wheels are designed in 2 pieces, including an inner rim and outer rim. These rims are assembled using clamping bolts. Clamping bolts determine the durability of military vehicle wheels because fracture of clamping bolts account for most wheel failures. For improving wheel durability, clamping bolt durability must be improved. In this study, wheel test conditions and bolt design were investigated. Existing test standards are not sufficient to conduct endurance tests. Supplementary conditions were investigated. Using these modified test conditions, the durability of wheels including clamping bolts was tested and verified. Results found the durability of wheels improved more than 168%. This study also proposes improvements in the design process of clamping bolts.

A Study on the Surface Roughness Behavior of Reactor Vessel Stud Holes in APR1400 Nuclear Power Plants (APR1400 원자로 용기 스터드 홀의 표면거칠기 거동에 관한 연구)

  • Kim, Dong Il;Kim, Chang Hun;Moon, Young Jun
    • Transactions of the Korean Society of Pressure Vessels and Piping
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    • v.15 no.1
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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.

Effects of Frequency-Dependent Neuromuscular Electrical Stimulation on The Respiratory Strength, Quadriceps Muscle Activity and Quality of Life in Patients with Severe Chronic Obstructive Pulmonary Disease (주파수에 따른 신경근전기자극치료가 중증 만성폐쇄성폐질환 환자의 호흡근력, 넙다리네갈래근 활성도 및 삶의 질에 미치는 영향)

  • Kang, Jeong-Il;Jeong, Dae-Keun;Park, Jun-Su
    • Journal of the Korean Society of Physical Medicine
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    • v.14 no.3
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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.

Research Trends of Articles Published in the Journal of Korean Clinical Nursing Research from 2000 to 2017: Text Network Analysis of Keywords (텍스트 네크워크 분석을 이용한 임상간호연구 게재논문의 연구동향 분석: 2000년부터 2017년까지)

  • Kim, Yeon Hee;Moon, Seong Mi;Kwon, In Gak;Kim, Kwang Sung;Jeong, Geum Hee;Shin, Eun Suk;Oh, Hyang Soon;Kim, Soo Hyun
    • Journal of Korean Clinical Nursing Research
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    • v.25 no.1
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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.

Effects of Bu-Zhong-Yi-Qi-Tang for the treatment of functional dyspepsia: a feasibility study protocol

  • Kim, Jihye;Kim, Hyunho;Kim, Keun Ho
    • Integrative Medicine Research
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    • v.6 no.3
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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.

Identification of moving train loads on railway bridge based on strain monitoring

  • Wang, Hao;Zhu, Qingxin;Li, Jian;Mao, Jianxiao;Hu, Suoting;Zhao, Xinxin
    • Smart Structures and Systems
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    • v.23 no.3
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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.

Design and 3D-printing of titanium bone implants: brief review of approach and clinical cases

  • Popov Jr, Vladimir V.;Muller-Kamskii, Gary;Kovalevsky, Aleksey;Dzhenzhera, Georgy;Strokin, Evgeny;Kolomiets, Anastasia;Ramon, Jean
    • Biomedical Engineering Letters
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    • v.8 no.4
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    • pp.337-344
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    • 2018
  • Additive manufacturing (AM) is an alternative metal fabrication technology. The outstanding advantage of AM (3D-printing, direct manufacturing), is the ability to form shapes that cannot be formed with any other traditional technology. 3D-printing began as a new method of prototyping in plastics. Nowadays, AM in metals allows to realize not only net-shape geometry, but also high fatigue strength and corrosion resistant parts. This success of AM in metals enables new applications of the technology in important fields, such as production of medical implants. The 3D-printing of medical implants is an extremely rapidly developing application. The success of this development lies in the fact that patient-specific implants can promote patient recovery, as often it is the only alternative to amputation. The production of AM implants provides a relatively fast and effective solution for complex surgical cases. However, there are still numerous challenging open issues in medical 3D-printing. The goal of the current research review is to explain the whole technological and design chain of bio-medical bone implant production from the computed tomography that is performed by the surgeon, to conversion to a computer aided drawing file, to production of implants, including the necessary post-processing procedures and certification. The current work presents examples that were produced by joint work of Polygon Medical Engineering, Russia and by TechMed, the AM Center of Israel Institute of Metals. Polygon provided 3D-planning and 3D-modelling specifically for the implants production. TechMed were in charge of the optimization of models and they manufactured the implants by Electron-Beam Melting ($EBM^{(R)}$), using an Arcam $EBM^{(R)}$ A2X machine.