• Geomechanics and Engineering
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• 제5권6호
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• pp.595-611
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• 2013

This paper presents a three-dimensional (3D) integrated numerical model where the wave-induced pore pressures in a porous seabed around breakwater heads were investigated. Unlike previous research, the Navier-Stokes equation is solved with internal wave generation for the flow model, while Biot's dynamic seabed behaviour is considered in the seabed model. With the present model, a parametric study was conducted to examine the effects of wave and soil characteristics and breakwater configuration on the wave-induced pore pressure around breakwater heads. Based on numerical examples, it was found that the wave-induced pore pressures at breakwater heads are greater than that beneath a breakwater. The wave-induced seabed response around breakwater heads become more important with: (i) a longer wave period; (ii) a seabed with higher permeability and degree of saturation; and (iii) larger angle between the incident waves and breakwater. Furthermore, the relative difference of wave-induced pore pressure between fully-dynamic and quasi-static solutions are larger at breakwater heads than that beneath a breakwater.

• 대한전기학회논문지:전기기기및에너지변환시스템부문B
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• 제48권8호
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• pp.448-454
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• 1999

This paper describes a new dc-ac inverter system which for achieving sinusoidal ac waveform makes use of parallel loaded high frequency resonant inverter consisting of full bridge. Each one of the pair of switches in the inverter is driven to synchronous output frequency and the other is driven to PWM signal with resonant frequency proportional to magnitude of sine wave. A forced discontinuous conduction mode is used to realize the quasi-sinusoidal pulse in each switching period. Therefore the inverter generates sinusoidal modulated output voltage including carrier frequency that is resonant frequency. Carrier frequency components of modulated output voltage is filtered by low pass filter. Since current through switches is always zero at its turn-on in the proposed inverter, low stress and low switching loss is achieved. Operating characteristics of the proposed system is analyzed in per unit system using computer simulation. The output voltage of if includes low harmonics and it is almost close to sine wave. Also, the theoretical analysis is proved through the experimental test.

• Earthquakes and Structures
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• 제4권6호
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• pp.629-647
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• 2013

Loading protocols have been developed for quasi-static cyclic testing of structures and components. However, it is uncertain if protocols developed for conditions of intense ground shaking in regions of high seismicity would also be applicable to regions of low-moderate seismicity that are remote from the tectonic plate boundaries. This study presents a methodology for developing a quasi-static cyclic displacement loading protocol for experimental bracing evaluation of cold-formed steel stud shear walls. Simulations presented in the paper were based on conditions of moderate ground shaking (in Australia). The methodologies presented are generic in nature and can be applied to other regions of similar seismicity conditions (which include many parts of China, Korea, India and Malaysia). Numerous response time histories including both linear and nonlinear analyses have been generated for selected earthquake scenarios and site classes. Rain-flow cycle counting method has been used for determining the number of cycles at various ranges of normalized displacement amplitude. It is found that the number of displacement cycles of the loading protocol increases with increasing intensity of ground shaking (associated with a longer return period).

• 대기
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• 제32권1호
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• pp.39-49
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• 2022

The relationship between the Quasi-Biennial Oscillation (QBO) and the surface air temperature (SAT) in the Korean Peninsula is investigated for the period of 1979~2019. The QBO shows a statistically significant causal relationship with the Korean SAT in early spring when the El Niño-Southern Oscillation (ENSO)'s effect is relatively weak. In particular, when the QBO wind at 70 hPa is westerly, the Korean SAT becomes colder than normal in March. This relationship in March, which is statistically significant, is valid not only for March QBO but also for February QBO, indicating that the QBO is leading the Korean SAT. The Granger causality test indeed shows a causal relationship between February QBO and March Korean SAT. The QBO-Korean SAT relationship is more pronounced in the southeastern part of the Korean Peninsula. As the QBO-related circulation anomalies are evident in the North Pacific and the eastern Eurasia, they induce the horizontal temperature advection to the southeastern part of the Korean Peninsula. This result suggests that the QBO could be useful for improving seasonal prediction of the Korean SAT in March.

• 성인간호학회지
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• 제26권4호
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• pp.424-433
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• 2014

Purpose: This study was to test the effects of the positional change on low back pain, discomfort, and bleeding complications during the period of bed rest following transarterial chemoembolization (TACE). Methods: The research design for this study was a non-equivalent control group quasi-experimental design. The participants were 23 patients for the experimental group, and 23 patients for the control group. The experimental group received positional change of taking the semi-Fowler's position and the 30-degree lateral position alternatively during the period of bed rest after TACE for 4 hours at one-hour intervals. The control group maintained the supine position continuously during the period of bed rest after TACE. Results: There were statistically significant differences in low back pain and discomfort between the experimental and the control group after intervention. And no significant difference was found in bleeding complication between two groups. Conclusion: The results of the study suggest that the positional change is an effective nursing intervention to reduce low back pain and discomfort without increasing the risk of bleeding after TACE.

• 여성건강간호학회지
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• 제19권3호
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• pp.129-141
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• 2013

Purpose: The purpose of this study was to determine the current state of nursing intervention for maternal adaptation and its' effectiveness in Korea by utilizing a systematic review. Methods: The PICO(Population-Intervention-Compar ator-Outcome) strategy was established, and 1,720 pieces of literature published during the last ten-year period from four electronic databases were reviewed. Eighteen references that met inclusion and exclusion criteria were finally selected for systematic review. The quality of references using critical appraisal checklist for experimental studies were evaluated, and then systematic review and meta-analysis were conducted. Results: All 18 references were quasi-experimental research design. Most interventions were provided at the hospital and postpartum care center. Maternal adaptation interventions appeared to be of many types, and particularly maternal role education programs were the most common. Confidence in maternal role was used as the most common variable for the maternal adaptati on. Various interventions for helping maternal adaptation in the postnatal period improved maternal confidence, moth er-infant attachment, maternal satisfaction and mother-infant interaction effectively. Conclusion: A diversity of nursin g interventions in postnatal period improved various aspects of maternal adaptation. Randomized controlled trials and longitudinal studies are needed in order to verify the effect of interventions for maternal adaptation more clearly.

• 한국해안·해양공학회논문집
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• 제21권4호
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• pp.290-300
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• 2009

연직 막체방파제에 대한 기존의 수치해석에서는 막체의 운동 중 발생하는 변동장력성분이 초기장력에 비하여 미미하다는 가정 하에 운동 중의 막체 장력을 초기장력으로 대체하는 선형해석을 수행하였다. 본 수치해 석에서는 막체장력의 비선형 변화를 한 주기 동안의 평균장력으로 대체하며 이 평균장력을 반복계산을 통하여 구해나가는 준 비선형 해석을 수행하였다. 상기 선형해석 결과와 비교하여 입사파 주기가 증가할수록 반사율은 증가하며 전달율은 감소하는 것으로 나타났다. 아울러, 본 준 비선형해석을 계류형태를 달리하는 두 구조물에 적용한 결과, 막체의 수평변위의 제어가 방파성능에 밀접한 효과가 있는 것으로 나타났다. 막체의 수평변위를 억제하기 위해서는 막체의 초기장력을 증가시키거나 막체의 중간부에 계류라인을 추가 결속시키는 방법들이 있으나 이를 위해서는 연직 하향 계류력을 지지하기 위한 대형 수면 부표의 설치가 요구된다.

• 한국학교ㆍ지역보건교육학회지
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• 제6권
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• pp.35-48
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• 2005

The age of the very first smoking is a significant indicator of life-long health status. Smoking prevention intervention was actively conducted based in middle and high schools with the support of the Korean Act for Health Promotion since 1998. These governmental supports became large and various smoking prevention programs were developed and conducted in diverse standards and perspectives. This study made a comprehensive descriptive literature review on smoking prevention educational programs for youth in Korea to identify the intervention quality and effectiveness of them for future smoking prevention program development. A total of 28 peer-reviewed journal articles published between May, 1995 and May 2005 (for the last 10 years) were finally included in this review process. The study participants should be adolescences in middle or high schools in Korea and the intervention types of the review studies should be smoking prevention or cessation educational programs. The outcomes of the reviewed studies were reanalyzed by the participants' characteristics, theory basement, evaluation design, intervention period, evaluation outcomes, and program effectiveness Most smoking intervention programs were not specified by sex and smoking status. Largely most intervention programs focused on male students although female students' smoking percent is increasing including both smokers and nonsmokers. Based on the school grades, the large percents of smoking intervention were conducted to the first grade of middle school and the first grade of high school. Almost 70% of the reviewed studies did not apply any health behavior change theories and the Transtheoretical model and social cognitive theory were utilized in 7 studies among the last reviewed 30%. The theory-based intervention studies had greater effectiveness than the non-theory based studies. More than 90% had quasi-experimental evaluation design and the effectiveness of the non-experimental designed study seemed over estimated than the quasi-experimental or experimental designed studies. More than 60% of the reviewed studies made their education for less than j days, over a short period and the evaluation factors were knowledge and attitude in general which can be obtained in short intervention period. Therefore, smoking intervention programs for youth in Korea need to be modified in terms of research design such as the intervention period, intervention-evaluation design, theory-based approach, and population-focused intervention specification.

• 여성건강간호학회지
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• 제4권3호
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• pp.322-331
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• 1998

The postpartum is a period of transition to motherhood where a childless woman transforms into a woman with children. Parents, especially mothers must perform an essential role of implementing instrumental and emotional care behaviors on part of the helpless, dependent, and immature infant. First-time mothers, however, suddenly face the responsibility of round the clock duty without neither parenting training during pregnancy, nor a time to gradually adapt to growing responsibilities after birth, with confusion and frustration as a result. Thus, after providing first-time mothers with childcare education as maternal role preparation, this study will try to examine its effects on childcare behaviors and confidence in maternal role during the early postpartum period. This quasi-experimental study using a nonequivalent control group non-synchronized design, was carried out from March 1995 to May 1996 to verify the effects of a childcare education program with first-time mothers who had vaginal delivery in Ewha University Hospital, Seoul, Korea, and collected data from 60 subjects who consented to the study. The education was given in the early postpartum period(48-72 hours after delivery) and to measure its effects, a posttest was done 4 weeks later with the results analyzed by SPSS shown in the following : 1. The childcare behavior score of the experimental group that had received the newborn care education was higher than the control group(t=3.5, P=.001). 2. The control group and the experimental group which had received the education showed no difference in degree of confidence in maternal role. 3. The higher the childcare behavior score, the higher the degree of confidence in maternal role was among the subjects(r=.56, P=.001). The preceding results are significant in that childcare practices can be promoted by providing child-care education to first-time mothers in the early postpartum period. Thus, this education can be used as a nursing intervention strategy in the early postpartum period.

• Structural Engineering and Mechanics
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• 제50권5호
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• pp.589-603
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• 2014

Expressions for determining the value of the impact force as reported in the literature and incorporated into code provisions are essentially quasi-static forces for emulating deflection. Quasi-static forces are not to be confused with contact force which is generated in the vicinity of the point of contact between the impactor and target, and contact force is responsible for damage featuring perforation and denting. The distinction between the two types of forces in the context of impact actions is not widely understood and few guidelines have been developed for their estimation. The value of the contact force can be many times higher than that of the quasi-static force and lasts for a matter of a few milli-seconds whereas the deflection of the target can evolve over a much longer time span. The stiffer the impactor the shorter the period of time to deliver the impulsive action onto the target and consequently the higher the peak value of the contact force. This phenomenon is not taken into account by any contemporary codified method of modelling impact actions which are mostly based on the considerations of momentum and energy principles. Computer software such as LS-DYNA has the capability of predicting contact force but the dynamic stiffness parameters of the impactor material which is required for input into the program has not been documented for debris materials. The alternative, direct, approach for an accurate evaluation of the damage potential of an impact scenario is by physical experimentation. However, it can be difficult to extrapolate observations from laboratory testings to behaviour in real scenarios when the underlying principles have not been established. Contact force is also difficult to measure. Thus, the amount of useful information that can be retrieved from isolated impact experiments to guide design and to quantify risk is very limited. In this paper, practical methods for estimating the amount of contact force that can be generated by the impact of a fallen debris object are introduced along with the governing principles. An experimental-calibration procedure forming part of the assessment procedure has also been verified.