• 한국건설관리학회논문집
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• 제18권3호
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• pp.42-51
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• 2017

건설 프로젝트의 생산과정에서 성과를 지속적으로 측정하고 평가하는 것은 프로젝트관리의 성공적인 수행을 위한 핵심요소이다. 성과는 일반적으로 목적물에 할당 된 공정과 원가 관련 정보를 정량적으로 평가함으로써 측정되며, 객관적인 성과측정을 위해 공정과 원가가 통합적으로 계획 관리되어야 한다. 본 연구는 공정과 원가의 통합 모델을 통해 성과 측정 방법론을 제안하고 진도관리의 기반을 마련하는데 목적이 있다. 이를 위해 공정계획과 원가계획의 표준화된 업무 프로세스를 개발하였고, EVM과 기존의 통합 모델을 분석하여, 성과측정 유닛을 활용한 WBS와 CBS의 통합 방법론을 제시하였다. 플랜트 프로젝트의 시공단계를 중심으로 공통 성과측정의 대상은 공종으로 선정하여 성과측정 유닛을 규정하고 공정과 비용정보를 연계시켜 성과비율을 산정하였다. 또한 리소스의 적용시 원가요소 중 소모성자원의 비용을 배제하여 진도측정의 객관성을 향상하였다. 본 결과는 실제 플랜트 사례 프로젝트에 적용하여 실증되었으며, 개발된 방법론은 향후 프로젝트의 성과를 보다 객관적인 기준으로 평가할 수 있어 보다 효과적인 진도관리 방법이 될 것으로 판단된다.

• 대한기계학회논문집A
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• 제26권5호
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• pp.843-850
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• 2002

This paper presents a simulation method using the transmission line modeling to reduce simulation runtime of hydraulic control systems. This method is based on separating the system components each other using the transmission line elements prior to simulation, which leads to divide the simulated system into several subsystems suitable for an even more efficient integration. It can also handle nonlinearities and discontinuities without flag signal when restarting integration. By applying variable integration timestep to parallel hydraulic circuits via parallel processing, it is shown that simulation run-time can be reduced significantly compared with that of Runge Kutta method.

• Earthquakes and Structures
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• 제7권2호
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• pp.159-178
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• 2014

Although the family methods with unconditional stability and numerical dissipation have been developed for structural dynamics they all are implicit methods and thus an iterative procedure is generally involved for each time step. In this work, a new family method is proposed. It involves no nonlinear iterations in addition to unconditional stability and favorable numerical dissipation, which can be continuously controlled. In particular, it can have a zero damping ratio. The most important improvement of this family method is that it involves no nonlinear iterations for each time step and thus it can save many computationally efforts when compared to the currently available dissipative implicit integration methods.

• 대기
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• 제33권4호
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• pp.331-341
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• 2023

A numerical forecasting models usually predict future states by performing time integration considering fixed static time-steps. A time-step that is too long can cause model instability and failure of forecast simulation, and a time-step that is too short can cause unnecessary time integration calculations. Thus, in numerical models, the time-step size can be determined by the CFL (Courant-Friedrichs-Lewy)-condition, and this condition acts as a necessary condition for finding a numerical solution. A static time-step is defined as using the same fixed time-step for time integration. On the other hand, applying a different time-step for each integration while guaranteeing the stability of the solution in time advancement is called an adaptive time-step. The adaptive time-step algorithm is a method of presenting the maximum usable time-step suitable for each integration based on the CFL-condition for the adaptive time-step. In this paper, the adaptive time-step algorithm is applied for the Korean Integrated Model (KIM) to determine suitable parameters used for the adaptive time-step algorithm through the monthly verifications of 10-day simulations (during January and July 2017) at about 12 km resolution. By comparing the numerical results obtained by applying the 25 second static time-step to KIM in Supercomputer 5 (Nurion), it shows similar results in terms of forecast quality, presents the maximum available time-step for each integration, and improves the calculation efficiency by reducing the number of total time integrations by 19%.

• 한국항해항만학회:학술대회논문집
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• 한국항해항만학회 2006년도 International Symposium on GPS/GNSS Vol.2
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• pp.107-112
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• 2006

The previous acquisition method of GPS receiver for reference station adopts not only the coherent integration method but also the non-coherent integration method in order to enhance sensitivity under noisy environment. However, under noisy environment, the previous GPS signal acquisition method causes the non-coherent integration loss which is a major factor among losses that can be caused during GPS signal acquisition. The non-coherent integration loss also increases with the strength of the received noise. This paper has intention of analyzing the performance of the GPS signal acquisition method proposed to effectively enhance sensitivity of DGPS reference receiver under noisy environment. This paper presents that the proposed GPS signal acquisition method suppresses the non-coherent integration loss through post-processing simulation. Furthermore, with regard to the mean acquisition time, it is shown that the number of search cells of the proposed GPS signal acquisition method is much fewer than that of the previous GPS signal acquisition method.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2004년도 추계학술대회
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• pp.453-458
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• 2004

This study proposes a new two-level condensation scheme for the construction of a reduced system. In the first step, the candidate area is selected for the construction of the reduced system by energy estimation in element-level. In the second step, primary degrees of freedom are selected by sequential elimination from the candidate degrees of freedom linked to the selected elements. Numerical examples demonstrate that the proposed method saves the computational cost effectively and provides a reduced system which predicts the eigenvalues accurately. Moreover, the well-constructed reduced system can present the reliable behavior of the structure under arbitrary dynamic loads comparing to that of global system. Time integration in a reduced system can save the computing time remarkably. Through a few numerical examples, the efficiency and reliability of the proposed scheme are verified.

• 한국소성가공학회:학술대회논문집
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• 한국소성가공학회 1998년도 제2회 박판성형심포지엄 논문집 박판성형기술의 현재와 미래
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• pp.1-8
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• 1998

The explicit and implicit time integration methods are applied effectively to analyze sheet metal stamping processes, which include the forming stage and the springback stage consecutively. The explicit time integration method has better merits in the forming stage including highly complicated three-dimensional contact conditions. By contrary, the implicit time integration method is better for analyzing springback since the complicated contact conditions are removd and the computing time to get the final static state is short. In this work, brief descriptions of the formulation and the factor study for springback simulations are presented. Further, the simulated results for the S-rail and the roof pannel stamping processes are shown and discussed.

• 한국건설관리학회:학술대회논문집
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• 한국건설관리학회 2001년도 학술대회지
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• pp.379-382
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• 2001

국내 건설프로젝트는 공정관리와 원가관리의 이원적 관리체계를 가지고 있으며, 공정관리는 아직 그 체계가 미흡하고 상대적으로 관리의 중요도가 낮게 평가되고 있는 현실이다. 현재의 원가위주의 관리체계로는 프로젝트 진행과정상의 수행성과를 정확히 파악하기 어려우며, 이에 따라 공기지연, 공사비초과, 생산성저하 둥의 문제가 야기되고 있다. 따라서 프로젝트를 계획된 기간과 비용안에 효율적으로 완성하기 위해서는 비용과 일정의 통합관리를 통한 정확한 실적관리기법의 도입이 요구된다. 이에 본 연구에서는 실공정을 중심으로 한 실적관리를 통해 프로젝트의 성과를 정확히 파악하여 성공적 프로젝트 수행을 위한 방안으로 비용과 일정의 통합관리를 통한 실적관리 모델을 제시하였다.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2001년도 춘계학술대회논문집C
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• pp.402-407
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• 2001

Sensitivity analysis scheme is developed in the elasto-plastic finite element method with explicit time integration using direct differentiation method. The direct differentiation is concerned with the time integration, constitutive relation, shell element with reduced integration and the contact scheme. Sensitivity analysis results are mainly examined with the highly nonlinear and quasi-static problem with the complicated contact condition. The result shows stable sensitivity especially in the sheet metal forming analysis.

• Structural Engineering and Mechanics
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• 제28권5호
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• pp.549-570
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• 2008

Numerical integration is an efficient approach for nonlinear dynamic analysis. In this paper, general category of the implicit integration errors will be discussed. In order to decrease the errors, Dynamic Relaxation method with modified time step (MFT) will be used. This procedure leads to an alternative algorithm which is very general and can be utilized with any implicit integration scheme. For numerical verification of the proposed technique, some single and multi degrees of freedom nonlinear dynamic systems will be analyzed. Moreover, results are compared with both exact and other available solutions. Suitable accuracy, high efficiency, simplicity, vector operations and automatic procedures are the main merits of the new algorithm in solving nonlinear dynamic problems.