• Interaction and multiscale mechanics
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• 제2권2호
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• pp.177-187
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• 2009

Machine or structural members subjected to fatigue loading will have a crack initiated during early part of their life. Therefore analysis of members with cracks and other discontinuities is very important. Finite element method has enjoyed widespread use in engineering, but it is not convenient for crack problems as the region very close to crack tip is to be discretized with very fine mesh. However, as the body force method (BFM), requires only the boundary of the discontinuity (crack or hole) to be discretized it is easy versatile technique to analyze such problems. In the present work fundamental solution for concentrated load x + iy acting in the semi-infinite plate at an arbitrary point $z_0=x_0+iy_0$ is considered. These fundamental solutions are in complex form ${\phi}(z)$ and ${\psi}(z)$ (England 1971). These potentials are known as Melan potentials (Ramakrishna 1994). A crack in the semi-infinite plate as shown in Fig. 1 is considered. This crack is divided into number of divisions. By applying pair of body forces on a division, the resultant forces on the remaining 'N'divisions are to be found for which ${\phi}_1(z)$ and ${\psi}_1(z)$ are derived. Body force method is applied to calculate stress intensity factor for crack in semi-infinite plate. Also for the case of crack emanating from circular hole in semi-infinite plate radial stress, hoop stress and shear stress are calculated around the hole and crack. Convergent results are obtained by body force method. These results are compared with FEM results.

• 대한간호학회지
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• 제50권5호
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• pp.658-670
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• 2020

Purpose: This study aimed to identify the predictors of blood and body fluid exposure (BBFE) in multifaceted individual (sleep disturbance and fatigue), occupational (occupational stress), and organizational (hospital safety climate) factors, as well as infection prevention behavior. We also aimed to test the mediating effect of infection prevention behavior in relation to multifaceted factors and the frequency of BBFE. Methods: This study was based on a secondary data analysis, using data of 246 nurses from the Shift Work Nurses' Health and Turnover study. Based on the characteristics of zero-inflated and over-dispersed count data of frequencies of BBFE, the data were analyzed to calculate zero-inflated negative binomial regression within a generalized linear model and to test the mediating effect using SPSS 25.0, Stata 14.1, and PROCESS macro. Results: We found that the frequency of BBFE increased in subjects with disturbed sleep (IRR = 1.87, p = .049), and the probability of non-BBFE increased in subjects showing higher infection prevention behavior (IRR = 15.05, p = .006) and a hospital safety climate (IRR = 28.46, p = .018). We also found that infection prevention behavior had mediating effects on the occupational stress-BBFE and hospital safety climate-BBFE relationships. Conclusion: Sleep disturbance is an important risk factor related to frequency of BBFE, whereas preventive factors are infection prevention behavior and hospital safety climate. We suggest individual and systemic efforts to improve sleep, occupational stress, and hospital safety climate to prevent BBFE occurrence.

• Journal of Advanced Marine Engineering and Technology
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• 제38권9호
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• pp.1075-1080
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• 2014

본 연구는 5MW급 해상풍력 하부구조물개발에 있어 설계에 필요한 다양한 해양환경 조건에 대하여 높은 안정성 확보가 요구되는 해상용 풍력발전 하부구조물과 관련, 구조물의 설계방법을 제시하고 그 안정성을 고찰하여 관련 기술 분야에 기여함을 목표로 한다. 특히, 5MW급 해상풍력발전 시스템에 대해 시험영역에서 큰 바람의 방향이 지속되고 있는 동안에 동시에 발달된 파도의 계산에 대한 정보를 제공한다. 그러므로 바람의 영역과 접근하는 파동 행열간의 관련성을 검토하여 강도, 방향 그리고 시간의 이동성을 계산할 수 있음을 확인하였다. 쇄파에서의 국부적인 압력분포를 물리적인 모델링과 수치적 모델링을 통해 조사하는 것이 가능하다. 해상 풍력 에너지 변환장치의 지지구조물들에 대해 최근 적용된 구조 및 피로에 대한 평가는 일반 설계규칙에 근거했다. 5MW 해상풍력 하부구조물은 제약조건이 많아 단일구조로 취급하는데 이는 생산에서 높은 안전계수를 고려해야함을 의미한다.

• 대한기계학회논문집A
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• 제34권2호
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• pp.161-166
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• 2010

본 논문에서는 시일 설치면에서의 마멸발생기구를 정확하게 조사하기 위한 연구의 일환으로 미세입자가 시일과 스틸면 사이에 존재하는 경우의 접촉문제를 비선형문제해석 프로그램인 MARC를 사용하여 해석하였다. 이 결과, 시일의 재질은 스틸면에서의 응력분포와 변형형상에 아주 큰 영향을 미쳤다. 특히, PTFE와 같이 탄성계수가 높은 시일인 경우에 스틸 표면은 국부적으로 항복상태에 도달할 뿐만 아니라 시일을 제거한 후에도 영구변형과 함께 상당한 크기의 압축/인장 잔류응력이 존재하였다. 따라서, 시일과 스틸면 사이에 경질입자가 존재할 경우에는 연삭마멸과 함께 피로마멸이 발생할 수 있음을 확인하였으며, 다양한 설계변수에 대한 추가연구가 요구된다.

• 대한후두음성언어의학회지
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• 제11권1호
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• pp.51-60
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• 2000

Background and Objectives : Quality of life(QOL) is a construct representing physical, mental and social well-being. QOL has been used as a device for measuring the severity of health-related condition and treatment outcomes. As the social welfare system develops, the attention to QOL increases as well. The aims of this study was to examine whether the patients with voice disorder perceived significantly more the effects of voice disorder on QOL than nonpatient group did and if any, identify the sociodemographic risk factors influencing QOL of patients. Materials and Methods : This study asked 113 adults with voice disorders who were enrolled in Voice Clinic in the Department of Otolaryngology, Kangbuk Samsung Hospital between lune 1998 and January 1999 and 111 nonpatients to complete a questionnaire designed to elicit information about the effete of voice disorders on quality of lift. The questionnaire included items concerning sociodemographic areas, voice symptoms, job, effects of voice disorders on QOL domains(work, social, psychological, physical, and communication areas), potential risk factors to exposures, familial and medical history of voice disorders. Results : The sociodemographic characteristics of the patient group are as follows : (1) 75.2% of total patient group were female and the rest were male. (2) Age of total patient group ranged from 20 to 65 years. Hoarseness was the most commonly reported complaints, followed by complaints of high note difficulties during singing and voice fatigue. The patient group perceived effects of voice disorders on the areas of work, social, psychological, physical and communication more adversely than the comparison group did (p＜0.05). QOL impairments were evaluated as a function of age, gender, education, and income, controlling other independent effects. The results were that (1) age was significantly associated with work problems and (2) gender and income were significantly associated with psychological problems. Conclusions : The findings indicated that the patients with voice disorders would perceive markedly adverse effect on all QOL domains, that is, work, social, psychological, physical, communicational areas. Therefore, the results of study suggest that lurker investigations about the nature of voice disorders, the prevention, treatment, and coping strategies are needed in the future.

• 동의신경정신과학회지
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• 제11권2호
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• pp.63-78
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• 2000

Headache is one of the most common medical complaints. It is not so easy to manage headache. especially if it is chronic although it seldom cause serious problem. There are many psychological factor known to induce, maintain an aggravate symptom in patients with chronic headache. The purpose of this study is to investigate clinical characteristics with ABR-2000 was carried out for 57 patients who had been suffered from headache for 6 months from march to August 2000.The results were as follows:1. According to the statics, on the whole woman's rate was higher than man's, and the mean duration of the headache was 8.06 years.2. Common associated symptoms were nausea. dyspepsia, dizziness, palpitation, fatigue, depression, etc.3. According to oriental medical differentiation of symptoms and signs, the rate of stagnation of the liver-qi's fire-transmission(肝變化火), deficiency of blood(血虛) and plegm syncope (痰厥), these three types were hghest.4. Result of analyzing ABR-2000 is that the rate of low response is higher than high response's on each item. But result of Graph A is that the rate of high response in higher than that of low response only in deficiency of Yin(陰虛) and the rate of high response in stagnation of the liver-qi's fire-transmission(肝變化火) and deficiency of blood (血虛) is comparatively high. Result of Graph R is that the rate of high response in wind-heat(風熱), deficiency of blood(血虛) and plegm syncope(痰厥) is comparatively higher than in others.

• 동의신경정신과학회지
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• 제15권2호
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• pp.89-101
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• 2004

Objective : The present experiments were designed to study on the immune-enhancing effect of Mountain grown ginseng, Mountain cultivated ginseng, and Panax ginseng Method : In order to compare the immune-enhancing effect of moutain grown ginseng, moutain cultivated ginseng and Panax ginseng, the study was done through the forced swimming test (FST), measurement of T helper Th1, Th2 cytokines and fatigue related factors. Result : Moutain grown ginseng and panax ginseng decreased the immobility time in the FST compared to the control. Glucose, blood urea nitrogen (BUN), creatinine, lactate dehydrogenase (LDH) and Total-protein (T-protein) in serum were investigated. The serum achieved from ginseng administered mouse showed higher BUN, T-protein than the control. moutain grown ginseng administered group showed lower LDH than the control group. moutain grown ginseng administered mouse showed higher glucose than the control. Creatinine was same in either experimental or control group. Ginseng-induced cytokine production in human T-cell line, MOLT-4 cells and mouse peritoneal macrophages were compared. Moutain cultivated ginseng (10-4 dilution) and panax ginseng (10-3 dilution) were increased the interferon $IFN-{\gamma}$ production compared with media control (about 1.6-fold P<0.05) at 48 h. Moutain grown ginseng (10-4 dilution) was increased the $IFN-{\gamma}$ and interleukin IL-4 production compared with media control (about l.4-fold for $IFN-{\gamma}$ and 1.6-fold for IL-4 P<0.05) at 48 h. Moutain grown ginseng (10-3 dilution) and moutain cultivated ginseng (10-4 dilution) were increased the turmor necrosis factor $TNF-{\alpha}$ production compared with $rIFN-{\gamma}$ treated cells (about 1.9-fold for $TNF-{\alpha}$ P<0.05), respectively. Moutain cultivated ginseng (10-3 dilution) was increased the IL-12 production compared with $rIFN-{\gamma}$ treated cell (about 1.7-fold for IL-12 P<0.05). Conclusion : These data suggest that three different three kinds of ginseng act on immune responses in different aspects.

• 한국해안·해양공학회논문집
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• 제22권5호
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• pp.326-332
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• 2010

해수 임펠러샤프트의 각종 하중에 의한 파단과 이를 개선하기위한 재설계는 정적, 동적 해석을 통한 원인분석과 유한요소법을 이용하여 효과적으로 수행할 수 있다. 본 논문에서는 전형적인 임펠러 샤프트의 파손에 대한 원인 분석을 수행하고 관련된 재설계기법을 제시하였다. 일차적으로 정적구조해석을 수행하였고 다음으로 구조물의 외력과의 공진문제를 포함한 동적해석을 수행하였다. 구조해석은 ANSYS코드를 사용하였으며, 결과적으로 파단원인을 찾아 분석하였다. 주된 파단원인은 과도한 굽힘모멘트의 발생과 응력집중, 구조물의 외력과의 공진에 의한 것으로 분석되었다. 해수 임펠러샤프트의 파단과 관련된 재설계기법의 이론적 배경을 정립하였으며, 재설계기법의 적용성과 정적, 동적 샤프트 재설계에 대한 유용성을 제시하였다.

• 한국해양환경ㆍ에너지학회지
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• 제19권2호
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• pp.129-136
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• 2016

부유식 해양 구조물은 계류선을 이용하여 다양한 종류의 환경하중에 따른 표류를 방지하게 된다. 따라서 구조물의 초기 설계 단계에서 신뢰성 있는 계류선의 설계는 매우 중요한 요소라 할 수 있다. 하지만 다양한 해양의 하중 조건을 견딜 수 있도록 설계된 계류선이라 하더라도 극한 조건의 하중이나 오랜시간 반복된 피로 하중으로 인하여 파손되는 경우가 발생하기도 한다. 일부 계류선의 파손은 잔여 계류선의 장력 변화를 야기하여 경우에 따라서는 전체 구조물의 점진적인 파손을 초래한다. 본 연구에서는 10 MW급 부유식 파력-해상풍력 복합발전 구조물에 연결된 12개의 계류선 중 일부가 손상된 경우의 구조물의 과도 응답을 시간 영역의 수치 시뮬레이션을 통하여 해석하였다. 이를 통하여 일부 계류선 손상 시 전체적인 구조물의 거동 변화 및 잔여 계류선의 장력 변화를 확인하였다.

• Tribology and Lubricants
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• 제32권4호
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• pp.132-139
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• 2016

The piston of a marine diesel engine works under severe conditions, including a combustion pressure of over 180 bar, high thermal load, and high speed. Therefore, the analyses of the fatigue strength, thermal load, clamping (bolting) system and lubrication performance are important in achieving a robust piston design. Designing the surface profile and the skirt ovality carefully is important to prevent severe wear and reduce frictional loss for engine efficiency. This study performs flexible multi-body dynamic and elasto-hydrodynamic (EHD) analyses using AVL/EXCITE/PU are performed to evaluate tribological characteristics. The numerical techniques employed to perform the EHD analysis are as follows: (1) averaged Reynolds equation considering the surface roughness; (2) Greenwood_Tripp model considering the solid_to_solid contact using the statistical values of the summit roughness; and (3) flow factor considering the surface topology. This study also compares two cases of skirt shapes with minimum oil film thickness, peak oil film pressure, asperity contact pressure, wear rate using the Archard model and friction power loss (i.e., frictional loss mean effective pressure (FMEP)). Accordingly, the study compares the calculated wear pattern with the field test result of the piston operating for 12,000h to verify the quantitative integrity of the numerical analysis. The results show that the selected profile and the piston skirt ovality reduce friction power loss and peak oil film pressure by 7% and 57%, respectively. They also increase the minimum oil film thickness by 34%.