• 대한전기학회논문지:전기기기및에너지변환시스템부문B
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• 제53권12호
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• pp.725-731
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• 2004

In this study, the three type hybrid interrupters according to the arrangement of the thermal expansion chamber and the puffer cylinder(they are called 'serial type', 'parallel/exchanged type', and 'parallel/separated type' respectively in this work) were designed and manufactured. This paper presents the tested results of the thermal recovery characteristics on the interrupters using a simplified synthetic test facility. The 'serial type' hybrid interrupter which is to obtain more easily the pressure rise for the thermal recovery compared with the others has the best capability in the thermal recovery characteristics. In order to investigate the stress on the operating mechanism, the distortion of the stroke wave in on-load test was examined to the stroke curve in no-load test. The biggest distortion was occurred in the 'parallel/exchanged type' hybrid interrupter. Finally, the small interruption capability on the three type interrupters was estimated by a theoretical form and the 'parallel/separated type' hybrid interrupter has the advantage of the others in the view of structure.

• 한국아동복지학
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• 제56호
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• pp.101-132
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• 2016

팬덤 문화는 오늘날 한국 청소년 문화의 중요한 측면을 나타내는 의미있는 사회적 현상이다. 그러나 기존 연구들에서는 팬덤 활동을 일종의 일탈적 현상으로 여겨, 청소년들의 팬덤 활동에 대하여 부정적인 태도를 보이는 경우가 많았으며, 팬덤 활동의 긍정적인 영향에 초점을 둔 연구는 부족한 상황이다. 이에 본 연구에서는 팬덤 활동을 오프라인과 온라인 팬덤 활동으로 구분하여 팬덤 활동 빈도가 청소년 학습시간 관리능력에 미치는 영향을 살펴보고, 그 영향이 시간의 따라 다른지에 대해 분석하였다. 분석 자료로 한국청소년정책연구원(NYPI)에서 실시하는 한국아동 청소년 패널조사(KCYPS)의 중학교 1학년 패널의 1차 년도(2010) 데이터(N = 2,206), 3차 년도(2012) 데이터(N = 2,150), 5차 년도(2014) 데이터(N = 1,911)를 활용하였다. 종속변수를 학습시간 관리능력으로 설정하고, 독립변수를 오프라인 팬덤 활동 빈도와 온라인 팬덤 활동 빈도로, 통제변수를 보호자의 최종학력, 가구 연간소득, 성별, 자아존중감, 학교적응으로 설정한 뒤 다층성장모형을 적용하여 변인간의 관계를 종단적으로 살펴 본 결과는 다음과 같다. 첫째, 팬덤 활동에 참여하는 학생들이 과반수가 넘으며, 오프라인 팬덤 활동과 온라인 팬덤 활동을 병행하는 청소년의 비율이 가장 높은 것을 알 수 있었다. 둘째, 청소년의 학습시간 관리능력은 시간의 흐름에 따라 정적 변화가 있는 것으로 나타났다. 셋째, 초깃값에서 청소년의 오프라인 팬덤 활동 빈도와 온라인 팬덤 활동 빈도는 학습시간 관리능력과 정적 관계가 있는 것으로 나타났다. 그러나 중학교 1학년에서 중학교 3학년, 그리고 고등학교 2학년으로 학년이 증가함에 따라 팬덤 활동이 학습시간 관리능력에 미치는 정적 영향 크기는 감소하는 것으로 나타났다. 이러한 연구 결과를 바탕으로 청소년들의 주요한 문화인 팬덤 활동 및 팬덤 활동의 긍정적 측면에 대한 성인들의 이해와 적절한 개입을 강조하였으며, 학습시간 관리능력 교육의 실천적 제언을 제시하였다.

• Structural Engineering and Mechanics
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• 제11권6호
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• pp.591-604
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• 2001

In this paper, a finite element with embedded displacement discontinuity which eliminates the need for remeshing of elements in the discrete crack approach is applied for the progressive fracture analysis of concrete structures. A finite element formulation is implemented with the extension of the principle of virtual work to a continuum which contains internal displacement discontinuity. By introducing a discontinuous displacement shape function into the finite element formulation, the displacement discontinuity is obtained within an element. By applying either a nonlinear or an idealized linear softening curve representing the fracture process zone (FPZ) of concrete as a constitutive equation to the displacement discontinuity, progressive fracture analysis of concrete structures is performed. In this analysis, localized progressive fracture simultaneous with crack closure in concrete structures under mixed mode loading is simulated by adopting the unloading path in the softening curve. Several examples demonstrate the capability of the analytical technique for the progressive fracture analysis of concrete structures.

• 대한산업공학회지
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• 제42권5호
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• pp.337-351
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• 2016

As technologies' life-cycle shortens and their development directions are uncertain, firms' technology planning capability becomes increasingly important. Prior patent-based studies using technology growth curves identify developmental stages of technologies, thereby formulating technology development directions from an overall perspective. However, a technology generally consists of multiple sub-technologies and accordingly their development stages are likely various. In this regard, the prior studies failed to identify core sub-technologies and their specific development directions. Therefore, we suggest an approach consisting of 1) identifying core sub-technologies of a given technology using patent co-classifications and social network analysis, and 2) identifying each sub-technology's development stage and thereby determining its further development direction. We apply our approach to patents related to augmented reality to examine its applicability. It is expected that our approach will help identify evolving development stages for the core sub-technologies of a given technology, thereby effectively assisting technology experts in technology planning processes.

• 대한기계학회논문집A
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• 제22권2호
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• pp.428-436
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• 1998

A TCS slip control system improves acceleration capability and steerability on slippery roads through engine torgue and/or brake torque control. This research mainly deals with the engine control algorithm via the adjustment of the engine throttle angle. The following new control strategy is proposed and investigated ; the TCS slip controller whose input is the difference between the desired driving wheel speed corresponding to the optimum slip ratio and the actual speed yields the target engine torque and then estimates the throttle angle based on the engine performance curve. Various simulation and hardware-in-the-loop simulation have been carried out. The results show the proposed strategy may compensate for the inherent nonlinearity between variation of the throttle angle and variation of the engine torque and produce better performance than the previous strategies without the engine map, especially in the high speed region.

• 대한한방소아과학회지
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• 제12권1호
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• pp.145-162
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• 1998

The purpose of this study was to determine the effects of oriental medical care on growth deficiency children. These cases were collected to investigate the effects of oriental medical care on growth deficiency children. So the cases were divided into 5 groups. The growth velocity was compared to a normal growth curve, and the results are as follows: 1. Oriental medical care was efficient when the epiphysial plates were not closed. 2. In female middle school beyond 1st grade students and in male middle school 3rd grade students who had almost closed epiphysial plates, the oriental medical care was not efficient and did not promote growth velocity. endothelium were used for the experiment using organ bath. 3. In the cases where the parent were very short, the effects of the oriental medical care to promote growth velocity was not efficient. 4. when we treated children of normal height, their growth velocity was over the normal growth curve. 5. In preschool aged children, oriental medical care was very efficient to promote children's growth. 6. The principle oriental medical care was to make balanced their body and digestive organs by using herb medicines that have the capability to promote the growth of the bones, and build strong muscles.

• 한국생산제조학회지
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• 제19권2호
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• pp.198-203
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• 2010

In this paper, study on the mode characteristics analysis of the SH-EMAT (shear horizontal, electromagnetic acoustic transducer) waves for evaluating the thickness reduction in plates such as corrosion and friction is presented. Noncontact methods for ultrasonic wave generation and detection have been a great concern and highly demanded due to their capability of wave generation and reception on surface of high temperature or on rough surface. Mode identification of the SH-EMAT wave is carried out in an aluminum plate with thinning defects using time frequency analysis method such as wavelet transform, compared with theoretically calculated group velocity dispersion curve. The changes of various wave features such as the amplitude and the time-of-flight have been observed and the correlations with the thickness reduction have been investigated. Firstly, experiments have been conducted to confirm that it is possible to selectively generate and receive specific desired SH modes. These modes have then been analyzed to select the parameters that are sensitive to the thickness change. The results show that the mode cutoff and the time-of-flight changes are feasible as key parameters to evaluate the thickness reduction.

• 한국기계가공학회지
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• 제18권4호
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• pp.34-40
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• 2019

We performed shape optimization of an anti-vibration rubber assembly which is used in the field option cabin of agricultural tractors to improve the vibration isolation capability. To characterize the hyper-elastic material property of rubber, we performed uniaxial and biaxial tension tests and used the data to calibrate the material model applied in the finite element analyses. We conducted a field test to characterize the input excitation from the tractor and the output response at the cabin frame. To account for the nonlinear behavior of rubber, we performed static analyses to derive the load-displacement curve of the anti-vibration rubber assembly. The stiffness of the rubber assembly could be calculated from this curve and was input to the harmonic analyses of the cabin. We compared the results with the test data for verification. We utilized Taguchi's parameter design method to determine the optimal shape of the anti-vibration rubber assembly and found two distinct shapes with reduced stiffness. Results show that the vibration at the cabin frame was reduced by approximately 35% or 47.6% compared with the initial design using the two optimized models.

• Structural Engineering and Mechanics
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• 제73권6호
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• pp.613-620
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• 2020

The research study is focuses on a form of all-bolted joint with the external ring stiffening plate in the prefabricated steel structure. The components are bolted at site after being fabricated in the factory. Six specimens were tested under cyclic loading, and the effects of column axial compression ratio, concrete-filled column, beam flange sub plate, beam web angle cleats, and spliced column on the failure mode, hysteretic behavior and ductility of the joints were analyzed. The results shown that the proposed all-bolted joint with external ring stiffening plate performed high bearing capability, stable inflexibility degradation, high ductility and plump hysteretic curve. The primary failure modes were bucking at beam end, cracking at the variable section of the external ring stiffening plate, and finally welds fracturing between external ring stiffening plate and column wall. The bearing capability of the joints reduced with the axial compression ratio increased. The use of concrete-filled steel tube column can increase the bearing capability of joints. The existence of the beam flange sub plate, and beam web angle cleat improves the energy dissipation, ductility, bearing capacity and original rigidity of the joint, but also increase the stress concentration at the variable section of the external reinforcing ring plate. The proposed joints with spliced column also performed desirable integrity, large bearing capacity, initial stiffness and energy dissipation capacity for engineering application by reasonable design.

• 한국수자원학회논문집
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• 제31권1호
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• pp.95-103
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• 1998

댐 퇴사량 예측방법은 수리학적 메커니즘을 이용하는 방법과 실측자료를 설계치로 적용하는 경험적 방법으로 구분할 수 있다. 전자는 물리적 해석방법으로 단기간에 이루어지는 현상을 규명하는데 적용할 수 있으며, 후자는 댐사수량 결정등 장기적인 설계변수 추정에 용이하게 이용할 수 있다. 이중 경험적 자료인 배사비 곡선식을 이용하면 월단위의 저수지 운영이 가능하며, 저류량에 대응하는 퇴사량을 정보변수로 추적하면 퇴사관리의 최적운영이 가능하다. 이와 같은 접근방법은 퇴사량에 의하여 시간적으로 변하는 댐 유효저수용량을 최적으로 관리할 수 있는 운영방안을 제공할 수 있다. 본 연구는 배사비 곡선을 이용한 장기 댐 퇴사량 예측방법을 제시하고 잇다. 개발된 방법을 중국 황하유역에 위치한 분하댐을 대상으로 장기간의 댐 운영을 모의하여 예상되는 퇴사량과 용수공급능력 분석에 적용하였다.