• 한국구조물진단유지관리공학회 논문집
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• 제27권6호
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• pp.22-29
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• 2023

재료 및 부재의 내진성능평가 실험 시 재하속도와 수직하중은 성능에 중대한 영향을 미칠 수 있다. 반복 가력 및 하이브리드 실험 시 재하속도는 입력 변위와 출력 변위 사이의 시간 지연현상으로 인해 고속으로 제어하기 어려우며 횡방향 변위에 의해 수직하중을 일정하게 유지하는 것이 어려워 일정한 수직하중이 유지되는 고속 및 실시간 실험은 거의 이루어지지 않았다. 본 연구에서는 면진받침의 속도 의존성과 수직하중의 영향을 조사하기 위해 저속 및 고속 반복 가력 실험과 실시간 하이브리드 실험을 수행하였다. 실험에서 수평 변위와 수직 하중의 실시간 제어를 위해 Adaptive Time Series(ATS) 보정 방법과 State estimator가 포함된 FLB System을 구축하였다. 고속 또는 실시간으로 재하되는 수평 변위 제어 속도와 상부구조물에 의한 수직하중은 면진받침의 강도 및 지진 시 거동에 상당한 영향을 미칠 수 있음을 확인하였으며 내진성능평가를 위한 실험 시 실제와 유사하도록 구현되어야함을 알 수 있었다. 본 연구는 내진성능평가를 위해 구축하고 사용된 시스템의 우수한 성능을 보여주며 정확하고 효율적인 내진성능평가가 가능하도록 하였다.

• 한국전자파학회논문지
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• 제24권4호
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• pp.436-447
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• 2013

본 논문에서는 IC(Integrated Circuit) 전자파 전도내성 시험 방법인 BCI(Bulk Current Injection)와 DPI(Direct Power Injection)를 이용하여 1.8 V I/O 버퍼에 대한 IC 전자파 전도내성을 시험하였다. IC 전자파 전도내성 시험을 회로 해석기를 사용하여 시뮬레이션 할 수 있는 등가회로 모델(model)을 개발하고 검증하였다. BCI와 DPI의 주파수에 따른 forward 전력을 비교한 결과는 주파수 성분에 따라 실제 IC에 도달하는 전자파(electromagnetic, EM) 노이즈의 양이 제한됨을 보여준다. 시뮬레이션을 통해, 가해지는 RF(Radio Frequency) 노이즈가 전달되는 경로의 삽입손실을 구하여, 하나의 시험 방법만으로는 넓은 주파수 영역에서 실질적인 IC 전자파 내성시험의 어려움을 발견하였다. 따라서 규정된 시험 방법을 보완하여 넓은 주파수 영역의 노이즈에 대해 신뢰도 높은 IC 전자파 전도내성 시험 방법을 제안한다.

• 대한기계학회논문집A
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• 제38권1호
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• pp.45-50
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• 2014

인쇄회로기판 위에 9개의 PBGA (Plastic Ball Grid Array) 패키지를 SnPb 솔더로 실장하여 진동시편을 제작하고 랜덤진동시험을 수행하였다. 진동에 대한 각 패키지 솔더의 내구수명을 분석한 결과, 패키지의 인쇄회로기판 배치 위치에 따라 솔더의 내구수명이 결정됨을 보였다. 이 위치에 따른 내구수명 의존성을 규명하기 위하여 유한요소모델을 작성하고, 모델의 모든 요소에 대해서 응력응답함수로부터 정의되는 등가응력을 분석하였다. 분석결과로부터 랜덤진동시험에서 패키지를 연결하는 솔더 중 코너에 위치한 솔더에서 최대 등가응력이 발생함을 보였다. 마지막으로, 각 패키지별 코너 솔더의 최대 등가응력값을 파괴등가응력으로 정의하고 파괴등가응력과 각 패키지의 내구수명간에 직접적인 연관관계가 있음을 제시하였다.

• Tribology and Lubricants
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• 제40권1호
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• pp.28-37
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• 2024

This paper presents the development of a squeeze film damper (SFD) test rig and experimental identification of the effects of clearance, damper length, journal eccentricity ratio, excitation amplitude, oil supply pressure, and oil flow rate on the damping coefficients of a test SFD with open ends and a central groove. Test data are compared with predictions from a simple model developed for short SFDs with open ends and a central groove. The test results show a significant decrease in the damping coefficient with increasing clearance and a dramatic increase with damper length, which are in good agreement with the simple model predictions. According to the simple model, the damping coefficient is inversely proportional to the cube of the clearance and directly proportional to the cube of the length. An increase in the journal eccentricity ratio results in a dramatic increase in the damping coefficient by as much as 15 times that of the concentric case, particularly at low excitation frequencies. By contrast, the measured damping coefficient remains almost constant with changes in the excitation amplitude and supply pressure, which are not major factors in the damper design. In general, the test data agree well with the simple model predictions, excluding cases that show increases in the SFD length and journal eccentricity, which indicate significant dependency on the excitation frequency.

• Journal of Power Electronics
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• 제12권1호
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• pp.40-48
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• 2012

This paper proposes the State-of-charge (SOC) estimator of a LiPB Battery using the Extended Kalman Filter (EKF). EKF can work properly only with an accurate model. Therefore, the high accuracy electrical battery model for EKF state is discussed in this paper, which is focused on high-capacity LiPB batteries. The battery model is extracted from a single cell of LiPB 40Ah, 3.7V. The dynamic behavior of single cell battery is modeled using a bulk capacitance, two series RC networks, and a series resistance. The bulk capacitance voltage represents the Open Circuit Voltage (OCV) of battery and other components represent the transient response of battery voltage. The experimental results show the strong relationship between OCV and SOC without any dependency on the current rates. Therefore, EKF is proposed to work by estimating OCV, and then is converted it to SOC. EKF is tested with the experimental data. To increase the estimation accuracy, EKF is improved with a single dominant varying parameter of bulk capacitance which follows the SOC value. Full region of SOC test is done to verify the effectiveness of EKF algorithm. The test results show the error of estimation can be reduced up to max 5%SOC.

• 한국유체기계학회 논문집
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• 제19권1호
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• pp.37-44
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• 2016

In this study, a parametric study of a centrifugal pump with double volute has been performed numerically using three-dimensional Reynolds-averaged Navier-Stokes equations. The shear stress transport model was selected as turbulence closure through turbulence model test. The finite volume method and unstructured grid system were used for the numerical analysis. The optimal grid system in the computational domain was determined through a grid dependency test. The expansion coefficient, circumferential and radial starting positions and length of divider were selected as the geometric parameters to be tested. And, the hydraulic efficiency and the radial thrust coefficient were considered as performance parameters. It was found that the radial thrust and hydrualic efficiency are more sensitive to the expansion angle and circumferential starting position of the divider than the other geometrical parameters.

• Child Health Nursing Research
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• 제24권4호
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• pp.383-392
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• 2018

Purpose: The purpose of this study was to identify factors associated with smartphone overdependency in preschool children based on an analysis of mother, child, and their mutual dyadic relationships. Methods: Data were collected from 171 mothers of preschool children enrolled at daycare centers and kindergartens from January to March 2018. The data were analyzed by descriptive statistics, the t-test, analysis of variance with $Scheff{\acute{e}}$ post hoc test, Pearson correlation coefficient, and hierarchical regression analysis using SPSS version 24. Results: The self regulation of preschool children (${\beta}=-.358$, p<.001) was the factor most closely associated with smartphone overdependency. The second most closely associated factor was children's use of a smartphone 0.5-1 hour daily (${\beta}=-.249$, p=.005). Additional associated factors were mothers' use of a smartphone for 3-4 hours daily (${\beta}=.217$, p=.002), children's use of a smartphone for less than 0.5 hour daily (${\beta}=-.212$, p=.006), and children's use of a smartphone for 1-2 days per week (${\beta}=-.205$, p=.026). Conclusion: Based on the results of this study, it is necessary to try to develop guidelines and programs to prevent smart phone overdependency in preschool children.

• 대한간호학회지
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• 제40권1호
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• pp.110-118
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• 2010

Purpose: To develop outcome indicators of urinary incontinence to measure quality of care in long term care hospitals in Korea. Methods: The draft indicators of urinary incontinence were developed from a literature review and clinical expert panel. A survey of medical records of 280 patients in 20 hospitals was conducted to test inter-rater reliability. Statistical analysis was done to test risk adjustment criteria, variation between hospitals, and stability of indicators, using assessment data from 77,918 patients in 623 hospitals. Results: The inter-rater reliability of items was high (Kappa range: 0.66- 0.92). Severe cognitive impairment (odds ratio [OR]: 3.15, confidence interval [CI]: 3.03-3.26) and total mobility activities of daily living (ADLs) dependency (OR: 4.85, CI: 4.72-4.98) increased the prevalence of urinary incontinence, thus they proved to be significant criteria to stratify high and low risk groups. The prevalence for low risk showed more substantial variation than the high risk group. The indicators were stable over one month. Conclusion: This study demonstrated the feasibility of outcome indicators of urinary incontinence. Improving the reliability of the patient assessment tool and refining the indicators through validation study is a must for future study.

• 대한가정학회지
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• 제47권2호
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• pp.97-110
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• 2009

The purpose of this study was to exam the effects of sociocultural attitude toward appearance on perceptual attitudinal body images and clothing behaviors. The research method was survey and the subjects were 447 male and female adolescents in Daejeon. The questionnaire consisted of 4 measuring instruments; sociocultural attitude toward appearance, perceptual and attitudinal body images, clothing behaviors, and subject’s demographic attributions. The data were analyzed by Cronbach's $\alpah$, x$^2$ test, t-test, factor analysis, cluster analysis, using SPSS program. The results were as follows. Adolescents had relatively high level recognition and internalization of sociocultural value toward appearance, and they perceived very thin body type as ideal body and had high interest of their appearance and weight. Sociocultural attitude toward appearance had important effects on adolescents' perceptual and attitudinal body images and clothing behaviors. The adolescents who are receptive to sociocultural value toward appearance had the tendency to distort their body as fat, showed high interest of their appearance and weight, and also showed high clothing interest & psychological dependency, clothing ostentation, and clothing conformity, but low clothing comfort than those who are not receptive to sociocultural value toward appearance.

• 지역사회간호학회지
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• 제20권4호
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• pp.433-442
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• 2009

Purpose: The purpose of this study was to identify factors affecting on the successful cessation of smoking for six months in the smoking cessation clinic of a public health center. Methods: The subjects of this study were 568 adult smokers who had registered in the smoking cessation clinic of a public health center in B City. Data were analyzed through $x^2$-test, t-test, and logistic regression using the SPSS/WIN 12.0 program. Results: Identified factors affecting the successful cessation of smoking for six months were service type, number of counseling, alcohol problem, previous quit-smoking trial, dependency on nicotine, CO level in expiration at the first visit time, self-reevaluation, helping relationship, negative/affective situational temptation, and Cons. Conclusion: Trans-theoretical Model variables were confirmed as factors affecting the success of smoking cessation. Based on the results of this study, a smoking cessation program was suggested, which uses Trans-theoretical Model variables affecting smoking cessation for six months in a public health center.