• 전산구조공학
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• 제4권4호
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• pp.97-106
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• 1991

주-부 구조물의 진동 특성을 파악하기 위한 새로운 방법인 frequency window method를 다중 지지되고 구조물간의 커플링이 강한 주-부 구조물을 해석하였다. 다항식의 합으로 표현된 특성 방정식과 이 식의 해는 기존의 고유치 해석 방법의 결과와는 다른 새로운 것으로 frequency window method의 주된 장점으로는 공진과 커플링 현상을 정량적으로 파악할 수 있는 피라미터의 정의, 전체 주-부 구조물의 모드특성을 나타내는 해석적인 식과 반복 기법의 도입으로 인한 해석 결과의 정확성등이 있다.

• KEPCO Journal on Electric Power and Energy
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• 제4권2호
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• pp.107-114
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• 2018

In recent years, ESS (Energy Storage System) has been widely used in various parts of a power system. Especially, due to its fast response time and high ramp rate, ESS is known to play an important role in regulating grid frequency and providing rotational inertia. As the number of installed and commercially operating ESSs increases, the reliability becomes an important issue. This paper introduces control schemes and presents its test method for grid-connected ESS for primary frequency regulation. The test method allows to verify the control operation in the individual operation mode and state. A validation of the method through actual ESS test in a electrical substation is presented in the case study section.

• Clinics in Shoulder and Elbow
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• 제8권2호
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• pp.88-96
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• 2005

Purpose: To compare and analyze the outcome of primary clavicular lateral end resection method and conventional acromioclavicular (AC) joint reduction method in type III AC dislocation patients over 45 years. Materials and Methods: This study was performed on selected 24 cases of type III AC dislocation patients, over 45 years of age, operated at our hospital from 1998 to 2002. Group I consist of 12 patients who underwent primary clavicular lateral end resection methods (average age: 54.3 years$(45{\sim}72)$). Group II consist of 7 patients using Bosworth methods and 5 patients using Phemister methods (average age: 54.4 years$(45{\sim}71)$). Clinical outcome was evaluated by Weaver and Dunn method. Radiological results were compared by measuring coracoclavicular distance between normal and injured side. Results: As clinical outcome, good was 10 cases(83%); fair 2(17%) in Group I, and good 6(50%); fair 3(25%); poor 3(25%) in Group II. In contrast, the difference of coracoclavicular distance was not statistically significant between two groups before or after surgery, and last follow up. At the last follow up, there was no special correlation between the difference of coracoclavicular distance and clinical outcome. Conclusion: We considered that primary clavicular lateral end resection may be effective for prevention of arthrosis in AC joint in type III AC dislocation patients over 45 years.

• Journal of Welding and Joining
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• 제17권2호
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• pp.97-103
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• 1999

The dynamic resistance monitoring in primary circuit is one of the important issues. Because in-process and real time quality assurance of resistance spot weld is needed to increase the product reliability. In this study, new dynamic resistance detecting method is proposed as a practical manner of weld quality assurance using instantaneous current and voltage measured at the primary circuit. and also, various patterns of primary dynamic resistance curve are characterized with the macro photograph and the weldability lobe curve. It is found that the primary dynamic resistance patterns are basically similar to those of the secondary, but there is evident advantage such as no extra devices are needed to obtain the quality information and eventually real time feedback control will be possible.

• 한국초등과학교육학회지:초등과학교육
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• 제17권1호
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• pp.11-21
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• 1998

Portfolio assessment provides many opportunities to foster children's creativity and to increase their responsibility for learning. few research study has been conducted in this area, and this assessment method has scarcely been administered in primary science class, Proper and effective use of portfolio assessment in our primary science class requires basic research on how to design and administer the method. Based on the earlier study on typical structures and components of portfolio assessment, the assessment instrument was developed on various primary science topics, The development team was consisted of one science education specialist and nine pre-service elementary school teachers. It takes ten months to develop instruments for 27 class hours. The development process was reciprocal in that development and revision cycle was repeated more than 7 times. The portfolio assessment instruments consist of instructional objectives, developers' evidence for the objectives, and assessment criteria. Adopting a new way of assessment into science class inevitably causes lots of confusions to teachers and children. The absence of basic research studies must be a critical barrier for successful administration of a new assessment method such as portfolio assessment. further research is required in the preparation and administration of portfolio assessment in our primary science classroom.

• 한국보육지원학회지
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• 제15권4호
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• pp.21-36
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• 2019

Objective: Using data from the Panel Study on Korean Children, this study investigated the influence of teacher'thoughts about the transition from ECEC to primary school in relation to learner-centered teaching methods and children's school adjustment. Methods: We analyzed the longitudinal data of 658 seven-year-olds from the 8th and 9th waves of the panel study of Korean children collected by the Korea Institute of Child Care and Education in 2015 and 2016. The main analysis method was Structural Equation Modeling(SEM). Results: First, theachers' thoughts about the transition from ECEC to primary school was noteworthy. Second, the more concern a theacher' had about transition, the higher their learner-centered teaching method. Third, teacher' concern about transition influenced children's school adjustment. Fourth, a teacher's learner-centered teaching method mediated concern about children's transition and school adjustment in the first year and the second year. Conclusion/Implications: According to the results of this study, 1st grade teachers' concern about the transition from ECEC to primary school has been found to be predictors of children's school adjustment.

• Geomechanics and Engineering
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• 제24권4호
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• pp.359-370
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• 2021

Joint roughness is combination of primary and secondary roughness. Ordinarily primary roughness is a geostatistical part of a joint surface that has a periodic nature but secondary roughness or unevenness is a statistical part of that which have a random nature. Using roughness generating algorithms is a useful method for evaluation of joint roughness. In this paper after determining geostatistical parameters of the joint profile, were presented two roughness generating algorithms using Mount-Carlo method for evaluation of primary (GJRGAP) and secondary (GJRGAS) roughness. These based on geostatistical parameters (range and sill) and statistical parameters (standard deviation of asperities height, SDH, and standard deviation of asperities angle, SDA) for generation two-dimensional joint roughness profiles. In this study different geostatistical regions were defined depending on the range and SDH. As SDH increases, the height of the generated asperities increases and asperities become sharper and at a specific range (a specific curve) relation between SDH and SDA is linear. As the range in GJRGAP becomes larger (the base of the asperities) the shape of asperities becomes flatter. The results illustrate that joint profiles have larger SDA with increase of SDH and decrease of range. Consequencely increase of SDA leads to joint roughness parameters such Z2, Z3 and RP increases. The results showed that secondary roughness or unevenness has a great influence on roughness values. In general, it can be concluded that the shape and size of asperities are appropriate parameters to approach the field scale from the laboratory scale.

• Nuclear Engineering and Technology
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• 제47권7호
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• pp.895-906
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• 2015

Background: Mitigation of primary water stress corrosion cracking (PWSCC) is a significant issue in the nuclear industry. Advanced nickel-based alloys with lower susceptibility have been adopted, although they do not seem to be entirely immune from PWSCC during normal operation. With regard to structural integrity assessments of the relevant components, an accurate evaluation of crack growth rate (CGR) is important. Methods: For the present study, the extended finite element method was adopted from among diverse meshless methods because of its advantages in arbitrary crack analysis. A user-subroutine based on the strain rate damage model was developed and incorporated into the crack growth evaluation. Results: The proposed method was verified by using the well-known Alloy 600 material with a reference CGR curve. The analyzed CGR curve of the alternative Alloy 690 material was then newly estimated by applying the proven method over a practical range of stress intensity factors. Conclusion: Reliable CGR curves were obtained without complex environmental facilities or a high degree of experimental effort. The proposed method may be used to assess the PWSCC resistance of nuclear components subjected to high residual stresses such as those resulting from dissimilar metal welding parts.

• 한국추진공학회:학술대회논문집
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• 한국추진공학회 2004년도 제22회 춘계학술대회논문집
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• pp.192-197
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• 2004

Recently, fluidic thrust vectoring methods have been preferably employed to control the movement of propulsive systems due to relatively simpler design and lower cost than mechanical thrust vectoring methods. For An application of the thrust vectoring to flight bodies, it is necessary to understand very complicated exhaust flows which are often subject to shock waves and boundary layer separation. But researches for the thrust vector control using counterflow have been few. In the present study, experiments have been performed to investigate the characteristics of supersonic jets controlled by a thrust vectoring method using counterflow. The primary jet is expanded through a two-dimensional primary nozzle shrouded by collars, and is deflected by the suction of the air near nozzle into an upper slot placed between the primary nozzle and the upper collar. A shadowgraph method is used to visualize the supersonic jet flowfields. Primary nozzle pressure ratios and suction nozzle pressure ratios are varied from 3.0 to 5.0, and from 0.2 to 1.0 respectively. The present experimental results showed that, for a given primary nozzle pressure ratio, a decrease in the suction nozzle pressure ratio produced an increased thrust vector angle. As the suction nozzle pressure ratios were increased and decreased, the hysteresis of the thrust vectoring was observed through the wall pressure distributions

• 한국안전학회지
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• 제15권3호
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• pp.30-39
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• 2000

The present paper deals with the numerical simulation for the spray characteristics with swirling turbulent flows and dilution flows from swirl injectors in a simplified can type of gas turbine combustor. The main objective is to investigate the characteristics of swirling turbulent flows with dilution flows and to provide the qualitative results for the spray characteristics such as the droplet distribution and Sauter Mean Diameter(SMD). The gas-phase equations based on Eulerian approach were discretized by Finite Volume Method, together with SIMPLE algorithm and the Reynolds -Stress-Model. The liquid-phase equations based on Lagrangian method were used to predict the droplet behavior. The results of preliminary test are generally in good agreement with experimental data, and show that the anisotropy exists in the primary zone due to swirl velocity and injected air from primary injector, and then gradually decays due to turbulent mixing and consequently near-isotropy occurs in the region between primary and dilution zones. For the spray characteristics, it is indicated that the swirling flows of primary jet region increase the droplet atomization. In addition, it is showed that the swirling flows at the inlet region lead the air-fuel mixture to be distributed near the igniter and can significantly affect the spray behavior in the primary jet region.