• 콘크리트학회논문집
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• 제22권4호
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• pp.499-510
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• 2010

이 연구의 목적은 Bayesian 통계법을 통하여 얻어진 만족도 곡선을 활용하여 체계적으로 콘크리트 재료성능을 평가하고 배합설계를 하는 것이다. 단일변수 만족도 곡선은 콘크리트 성능기준을 만족할 확률을 콘크리트 재료변수 함수로서 나타낸다. 여러 개의 만족도 곡선을 결합해 하나의 만족도 곡선으로 나타내기 위하여 Importance Factor와 Goodness value라는 신규개념을 도입하여 서로 다른 재료변수들이 콘크리트성능에 미치는 영향을 정량화하고 서로 다른 재료변수들을 공통된 하나의 변수로 통합하는 것을 가능하도록 하였다. 또한 PBMD 과정에 의한 설계예제를 제시함으로써 목표지향적 콘크리트배합설계의 한 방법을 제시하고 그 유효성에 대해 증명하였다. 마지막으로, 실제 구조물에 대한 적용 가능성을 확인하기 위해 PBMD과정에 의한 콘크리트의 기대성능 결과값과 ACI 기준에 의한 결과값을 비교하였다.

• 한국정밀공학회지
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• 제29권2호
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• pp.193-200
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• 2012

Wheel loader is one of the construction machinery capable of variety of tasks and the demand on functional diversity and structural reliability is growing. As a study on the optimal shape design of front axle for wheel loader through the design of experiments, this paper assessed the design parameters affecting the maximum stress. As a result, a value of 126.77 MPa of minimum stress was obtained, and optimal factors showed the values of w = 100.0 mm, ${\theta}=40^{\circ}$ and R = 118 mm. It showed an accuracy of 98.7% compared with the structural analysis.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2014년도 추계학술대회 논문집
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• pp.467-471
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• 2014

The natural frequencies of a mechanical system are determined by the system parameters such as masses and stiffness of the system. Since material irregularities and manufacturing tolerances always exist in most of practical engineering situations, the system parameters always have uncertainties. As the uncertainties of the parameters increase, the uncertainties of the system natural frequencies also increases. Then, the reliability of the system deteriorates. So, the uncertainty of the system natural frequencies should be analyzed accurately and considered in the design of the system. In order to analyze the uncertainty of the system natural frequencies employing most of existing uncertainty analysis methods, the probability distributions of the uncertain system parameters should be identified. In most practical situations, however, identification of the probability distributions is almost impossible because of limited time and cost. For that case, the reliability should be estimated based on finite samples of the system parameters. In this paper, sample based reliability estimation method employing extreme value theory was proposed. Using the proposed estimation method, sample based reliability design of the system natural frequencies was conducted.

• Journal of Magnetics
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• 제21권2호
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• pp.209-214
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• 2016

This paper analyzes the magnetic property according to the machined shape of steel material with non-oriented silicon steel (50PN470/50A470), that is most commonly used in the design of electrical equipment. Toward this end, specimens were produced and divided into Bar-Specimen (Epstein Frame Tester) and Ring-Specimen (Toroidal Ring Tester). The characteristics of the electrical Silicon steel were measured using the instruments solely dedicated to measuring each specimen. The core loss of the Bar-Specimen, which is commonly used, was found to be less than that of the Ring-Specimen. This is a very important design factor in achieving the objectives of improving the product efficiency and predicting the performance of electrical equipment. It serves as a critical point of view in order to reduce the error between design value and product value. A comparative analysis was conducted regarding various characteristics (Hysteresis, B-H characteristic, Iron loss, Minor loop, Coercive force, Residual magnetic flux density, etc.) of the electrical silicon steel considered in the design of the electrical equipment according to the specimen.

• Structural Engineering and Mechanics
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• 제34권6호
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• pp.739-753
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• 2010

Pointing to the design requirement of prestressed space grid structure being the target cable force, the pretension scheme decision analysis method is studied when there's great difference between structural actual state and the analytical model. Based on recursive formulation of cable forces, the simulative recursive system for pretension process is established from the systematic viewpoint, including four kinds of parameters, i.e., system initial value (structural initial state), system input value (tensioning control force scheme), system state parameters (influence matrix of cable forces), system output value (pretension accomplishment). The system controllability depends on the system state parameters. Based on cable force observation values, the influence matrix for system state parameters can be calculated, making the system controllable. Next, the pretension scheme decision method based on cable force observation values can be formed on the basis of iterative calculation for recursive system. In this way, the tensioning control force scheme that can meet the design requirement when next cyclic supplemental tension finished is obtained. Engineering example analysis results show that the proposed method in this paper can reduce a lot of cyclic tensioning work and meanwhile the design requirement can be met.

• 한국건설관리학회논문집
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• 제23권5호
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• pp.98-107
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• 2022

본 연구의 목적은 플랜트 건설사업에서 모듈러 설계대안에 대한 위험기반의 평가지수를 도출하는 모델을 제안하는 것이다. 이에 따라 ① 기초사업비와 모듈을 적용하는 대상과 범위를 설정하는 단계, ② 설계, 구매, 제작, 운송, 시공업무에 대한 중요도, 편리성, 효율성 지수를 평가하는 단계, ③ 중요 위험사건의 영향에 따른 경제적 손실을 예방하기 위해서 필요한 예비비를 분석하여 총사업비를 추정하는 단계, ④ 모듈 설계대안별로 평가된 관리업무의 효율성 지수와 총사업비를 비교하여 RVI를 도출하는 단계로 구성하였다. 그리고 모델의 사용성을 검증하기 위해서 Module Plan-A는 Pipe Rack을 모듈로 적용하는 경우, Module Plan-B는 Steel Structure, Pipe Rack, Process Module을 모듈로 적용하는 경우로 설정하여 관리업무의 중요도, 편리성, 효율성 지수를 평가하고 위험예비비를 포함하여 총사업비를 추정하였다. 이와 같은 과정으로 모델을 검증한 결과, 1개의 공종에 모듈을 적용한 Module Plan-A 보다 3개의 공종에 모듈을 적용한 Module Plan-B가 관리업무의 효율성은 낮은 것으로 나타났지만, 기초사업비에서 간접비가 절감되어 종합적인 RVI는 높게 평가되었다.

• Journal of Electrical Engineering and Technology
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• 제11권4호
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• pp.921-930
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• 2016

This paper proposes a design and control method for a high-voltage direction current modular multilevel converter (HVDC-MMC) considering the capacitor voltage ripple of the submodule (SM). The capacitor voltage ripple consists of the line frequency and double-line-frequency components. The double line- frequency component does not fluctuate according to the active power, whereas the line-frequency component is highly influenced by the grid-side voltage and current. If the grid voltage drops, a conventional converter increases the current to maintain the active power. A grid voltage drops, current increment, or both occur with a capacitor voltage ripple higher than the limit value. In order to reliably control an MMC within a limit value, the SM capacitor should be designed on the basis of the capacitor voltage ripple. In this paper, the capacitor voltage ripple according to the grid voltage and current are analyzed, and the proposed control method includes a current limitation method considering the capacitor voltage ripple. The proposed design and control method are verified through simulation using PSCAD/EMTDC.

• Geomechanics and Engineering
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• 제18권4호
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• pp.339-352
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• 2019

Rockmass parameters are used in the design of engineering structures built in rock and soil. One of the most important of these parameters is the rockmass Emass (Emass). Determination of the Emass of rockmass is a long, hard and expensive job. Therefore, empirical formulas developed by different researchers are used. These formulas use the elastic modulus of the material as a parameter. This value is a constant value in the design. However, engineering structures remain under different loads depending on many factors, such as topography, geometry of the structure, rock / soil properties. Time is other important parameter for rock/soil structure. With the start of the excavation, the loads that the structure is exposed to will change and remain constant at one level. In the new proposed method, the use of different Emass calculated from empirical formulas using the different material elastic modulus, which has different values under different loads as time dependent, was investigated in rock/soil structures during design. The performance of the stability analysis using different deformation modules was questioned by numerical modeling method. For this query, a sub-routine which can be integrated into the numerical modeling software has been developed. The integrated sub-routine contains the formula for the Emass, which is calculated from the material elasticity modules under time dependent and different constant loads in the laboratory. As a result of investigations conducted in 12 different field studies, the new proposed method is very sensitive.

• 대한전기학회:학술대회논문집
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• 대한전기학회 1997년도 하계학술대회 논문집 F
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• pp.2207-2209
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• 1997

This Paper Presents the design automation for isolated DC-DC converters. Isolated DC-DC converts have many advantages such as protection, wide range variation, and multiple output. Prosedures consist of several steps. There are the selection of converter topology, the selection of switching devices. the calculation for the value of inductances and capacitances, and the design of transformers. We verified it with many practical examples from databooks.

• 한국공작기계학회:학술대회논문집
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• 한국공작기계학회 2000년도 춘계학술대회논문집 - 한국공작기계학회
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• pp.355-360
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• 2000

There are many changed while a design is completed. Therefore, if the impact of the design changes is estimated, it may result in the improvement of design efficiency. But, the design changes have various types and affect other parts of the design system. Hence, it is difficult to deal with design changes directly. The purpose of this research is to develop a systematic change propagation tracing algorithm and a method of change impact analysis and then, to implement a change impact analysis system. Process based design is set up for the field of this research. Also the design, composed of design parameters and constraints, is set up for the subject of the research. Change propagation tracing algorithm traces change propagation based on the following concept : If the design parameters are changed, other parameters within the constrains including them may be changed. Using the result of change propagation tracing algorithm, changeable parameters, constraints and tasks can be found. The method of change impact analysis, to calculate change impact value from this changeable tasks, is developed. Change propagation tracing algorithm and the method of change impact analysis are implemented into change impact analysis system and it is applied to the redesign of 2 stage gear drives. It can support different kinds of design activities systematically. especially, at the redesign step, where many design change alternatives exist, change impact value of each alternative exist, change impact value of each alternative is calculated and design change is performed toward direction to minimize the impact of design change. Consequently, it is expected to improve the efficiency of the whole design.