• 한국지진공학회논문집
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• 제23권1호
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• pp.55-70
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• 2019

The phase properties of ground acceleration records from Mw 5.5~6.5 earthquakes are analyzed. The interrelationships between phase properties and significant durations, as well as PGA, are clarified through both of theoretical and empirical approaches. The probabilistic characteristics of phase information is also discussed based on previous studies and it is shown that circular normal distribution is the most appropriate probability distribution for the phase angle and phase difference. Whereas those variates can be modeled by Gaussian random variables. From the survey results on the frequency dependency of the phase statistics, a simple model is introduced, which is possible to express the frequency dependency of phase information. It is also shown that the significant duration can be controlled by appropriately chosen standard deviation of phase difference for 4~8Hz frequency band and additional consideration of phase scattering in higher frequency band through a series of Monte Carlo simulations. The source of phase scattering effect is also pointed out and discussed.

• 대한기계학회논문집B
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• 제34권9호
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• pp.817-824
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• 2010

본 연구에서는 개선된 액막 분열 모델을 개발하였고 그에 따른 계산격자 의존성을 고찰하였다. 액막 및 액적 추적을 위해 라그랑지-오일러 액적 추적 모델을 사용하였기 때문에 계산격자의 크기에 한계가 있으므로 매우 작은 격자를 사용하는데 제약을 받는다. 또한 유동장내로의 분사기의 액막 주입 시선회유동이 존재하므로 선회 유동을 정확히 예측하기 위해서는 계산격자가 충분히 작아야 한다. 이러한 상반된 조건으로부터 두 목적을 달성하기 위해 10$\times$10mm부터 0.625$\times$0.625mm까지 다양한 계산격자를 구성하여 수치적 고찰을 수행하였고 가장 효율적인 격자의 크기는 1.25$\times$1.25mm인 것을 알 수 있었다.

• 한국건설관리학회논문집
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• 제11권5호
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• pp.65-74
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• 2010

시공단계의 경험 및 지식을 반영한 설계 결과물은 시공 효율성을 향상시키고 설계변경을 최소화하여 프로젝트의 낭비요인 제거와 전체적인 생산성 향상을 가능하게 해준다. 설계자가 설계단계에서 시공단계의 경험 및 지식을 효과적으로 활용하기 위해서는, 설계과정에서 필요한 시공성 지식을 필요한 시점에 활용할 수 있어야 한다. 설계단계에서 시공성 지식의 효과적인 활용을 위한 기존의 접근방법은 체크리스트와 같이 설계단계 별로 활용되는 시공성 지식의 구조화에 초점을 맞추고, 설계의 사결정과정의 기본단위가 되는 액티비티 수준에서 시공성 지식의 활용시점에 대한 고려가 부족하다. 하지만 적절하지 않은 시점에서 고려된 시공성 지식은 설계자에게 불필요한 재작업을 야기해 설계생산성을 저하시키는 문제를 발생시킬 수 있다. 이러한 비효율적인 정보교환을 최소화하기 위해서는, 설계 프로세스 상에서 정보흐름에 중점을 둔 설계관리를 통해 각 시공성 지식들을 요구하는 설계 액티비티가 무엇인지를 파악해야 한다. 이에 본 연구는 Dependency Structure Matrix(DSM)를 이용하여 설계의사결정과정의 기본단위가 되는 설계 익티비티와 설계과정에서 고려해야 하는 시공성 지식간의 상호관계를 고려한 정보흐름기반의 설계프로세스관리를 제안한다. 이는 설계프로세스관리를 설계단계에서의 단순한 설계검토보다 한 단계 높은, 건설프로젝트 전 과정과 연계된 포괄적인 관리활동으로 발전시켜 건설생산합리화에 크게 기여할 수 있으리라 예상된다.

• 지질공학
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• 제18권1호
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• pp.83-92
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• 2008

본 연구에서는 누적강우을 고려한 침투수 거동을 평가하기 위해 ADR 측정센서와 간극수압계를 사용하여 흙매질의 물성 변화를 측정하였다. ADR 측정센서의 측정 정밀도를 향상하기 위한 의존성 파악 및 강우조건에 따른 흙매질 특성 변화를 분석하였다. 또한, 강우/비강우조건 하에서 모형사면 내 침투수 거동 특성도 함께 검토하였다. ADR 측정센서를 활용한 체적함수비 의존성 검토 실험의 결과는 표준사와 화강풍화토에서 체적함수비 증가에 따라 측정전압도 함께 증가하였다. 온도 의존성 검토의 경우, 고함수비 조건인 체적함수비 0.15에서 0.45 범위에서는 측정 대상 매질의 온도를 고려해야만 한다 모형사면 실험에서는 누적강우조건하에서 체적함수비와 간극수압의 변화 양상을 충분히 확인하였다. 특히, ADR4와 PWP3이 설치된 모형사면 하단부에서 측정치가 높게 나타나는데, 이것은 누적강우에 의해 발생된 침투수가 사면 하단부에서 유출면으로 작용하고 있으며, 모형사면 파괴의 시작지점으로 작용함을 알 수 있다.

• 한국BIM학회 논문집
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• 제5권2호
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• pp.34-45
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• 2015

As buildings become larger and more complicated, construction costs have increased with a considerable effect on buildings' Life Cycle Cost (LCC). However, there has been little consideration on economic aspects in the selection of construction materials due to limited information on the materials and dependency in architects' experience and inefficiency in cost estimation, causing design changes, increase in maintenance cost, difficulty in budgeting, and decrease in building performance. To solve these problems, this study proposed a BIM-based material selection model which reflects the comprehensive economic efficiency of building materials. Our cost prediction model can estimates the material-related cost during the entire building life cycle. Furthermore, we implemented the proposed model in connection with BIM, which can analyze and compare LCC by material. Through the validation of the model, we could confirm the necessity of LCC-based material selection in comparison with the conventional cost-centered material selection.

• Advances in materials Research
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• 제7권1호
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• pp.1-16
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• 2018

Thermal bifurcation buckling behavior of fully clamped Euler-Bernoulli nanobeam built of a through thickness functionally graded material is explored for the first time in the present paper. The variation of material properties of the FG nanobeam are graded along the thickness by a power-law form. Temperature dependency of the material constituents is also taken into consideration. Eringen's nonlocal elasticity model is employed to define the small-scale effects and long-range connections between the particles. The stability equations of the thermally induced FG nanobeam are derived via the principal of the minimum total potential energy and solved analytically for clamped boundary conditions, which lead for more accurate results. Moreover, the obtained buckling loads of FG nanobeam are validated with those existing works. Parametric studies are performed to examine the influences of various parameters such as power-law exponent, small scale effects and beam thickness on the critical thermal buckling load of the temperature-dependent FG nanobeams.

• KSII Transactions on Internet and Information Systems (TIIS)
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• 제4권6호
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• pp.1209-1221
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• 2010

Three dimensional (3D) video is expected to be an important application for broadcast and IP streaming services. One of the main limitations for the transmission of 3D video over IP networks is network bandwidth mismatch due to the large size of 3D data, which causes fatal decoding errors and mosaic-like damage. This paper presents a novel selective frame discard method to address the problem. The main idea of the proposed method is the symmetrical discard of the two dimensional (2D) video frame and the depth map frame. Also, the frames to be discarded are selected after additional consideration of the playback deadline, the network bandwidth, and the inter-frame dependency relationship within a group of pictures (GOP). It enables the efficient utilization of the network bandwidth and high quality 3D IPTV service. The simulation results demonstrate that the proposed method enhances the media quality of 3D video streaming even in the case of bad network conditions.

• 대한전기학회:학술대회논문집
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• 대한전기학회 1999년도 하계학술대회 논문집 E
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• pp.2161-2163
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• 1999

Generally, ZnO varistors have dynamic characteristics that the cut-off voltage increases as the time to crest of the varistor current decreases. Dynamic characteristics of ZnO varistor are the most important factor in region of the steep front discharge current particularly. Also, V-I characteristics of ZnO varistor have hysterisis loop in time domain and frequency dependency. This paper deals with ZnO varistor numerical equation and modeling method which takes the behavior of varying clamping voltage into consideration during the time to crest, in range of $1{\mu}m{\sim}50{\mu}m$, of impulse current applied to a ZnO varistor. The simulated results by the proposed model are compared with experimental results for each of the impulse current.

• 한국군사과학기술학회지
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• 제13권5호
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• pp.734-738
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• 2010

Object Generator is a software to provide simulation object data(aircraft, ship, submarine, missile, torpedo) for sumulators in LBTS(Land Based Test System). but there is a burden to the system, because Object generator needs to send many object's data, display objects in a tactical screen, show object's information in a list in 1 second. This paper suggests a parallel software structure taking a few factors(deadlock, dependency) into consideration. At last, the paper shows the performance of the parallel structure's software compared with the former structure's software.

• 열처리공학회지
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• 제7권2호
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• pp.103-110
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• 1994

It is well-known that the analysis of temperature distribution is substantilly important in optimal design of quenching process. The unsteady state temperature gradients generated during the quenching process were numerically calculated by the Finite Element Method(F. E. M.). Formulations of F. E. M. based weighted residural method were presented for the analysis of the two dimensional heat conduction problem. In the process of calculation, the temperature dependency of physical properties of the material was in consideration. At early stage of the quenching process, the abrupt temperature gradient has been shown in the surface of the carbon steel(SM45C).