• 한국공간구조학회논문집
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• 제19권1호
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• pp.75-82
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• 2019

In the precedent study, the retractable-roof spatial structure was selected as the analytical model and a tuned mass damper (TMD) was installed to control the dynamic response for the earthquake loads. Also, it is analyzed that the installation location of TMD in the analytical model and the optimal number of installations. A single TMD mass installed in the analytical model was set up 1% of the mass of the whole structure, and the optimum installation location was derived according to the number of change. As a result, it was verified that most effective to install eight TMDs regardless of opening or closing. Thus, in this study, eight TMDs were installed in the retractable-roof spatial structure and the optimum mass ratio was inquired while reducing a single TMD. In addition, the optimum mass distribution ratio was identified by redistributing the TMD masses differently depending on the installation position, using the mass ratio of vibration control being the most effective for seismic load. From the analysis results, as it is possible to confirm the optimum mass distribution ratio according to the optimum mass ratio and installation location of the TMD in the the retractable-roof spatial structure, it can be used as a reference in the TMD design for large space structure.

• 제어로봇시스템학회:학술대회논문집
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• 제어로봇시스템학회 2003년도 ICCAS
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• pp.2737-2742
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• 2003

Kinematic calibration enhances absolute accuracy by compensating for the fabrication tolerances and installation errors. Effectiveness of calibration procedures depends greatly on the measurements performed. While the Cartesian postures are measured completely, all of the geometric parameters can be identified to their true values. With partial pose measurements, however, few geometric parameters may not be identifiable and effectiveness of the calibration results may vary significantly within the workspace. QR decomposition of the identification Jacobian matrix can reveal the non-identifiable parameters. Selecting postures for measurement is also an important issue for efficient calibration procedure. Typically, the condition number of the identification Jacobian is minimized to find optimum postures. This paper investigates identifiable parameters and optimum postures for four different calibration procedures - measuring postures completely with inverse kinematic residuals, measuring postures completely with forward kinematics residuals, measuring only the three position components, and restraining the mobility of the end-effector using a constraint link. The study is performed for a six degree-of-freedom fully parallel HexaSlide type paralle manipulator, HSM. Results verify that all parameters are identifiable with complete posture measurements. For the case of position measurements, one and for the case of constraint link, three parameters were found non-identifiable. Optimal postures showed the same trend of orienting themselves on the boundaries of the search space.

• 한국가스학회지
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• 제15권5호
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• pp.31-36
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• 2011

In this paper, an analytical model of a cantilever beam having a midpoint load is considered for structural optimization and design. This involves creation of the geometry through a parametric study of all design variables. For this purpose, the optimization of the cantilever beam was elaborated in order to find the optimum geometry which minimizes its volume eventually for minimum weight by FEM (finite element method) analysis. Such geometry can be obtained by different combinations of width and height, so that the beam may have the same cross-sectional area, yet different dynamic behavior. So for optimum safe design, besides minimum volume it should have minimum vibration as well. In order to predict vibration, different dynamic analyses were performed simultaneously to identify the resonant frequencies and mode shapes belonging to the lowest three modes of vibration. Next, by introducing damping effects, the tip displacement and bending stress at the fixed end was evaluated under dynamic loads of varying frequency. Investigation of the results clearly shows that only structural analysis is not enough to predict the optimum values of dimension for safe design it must be aided by dynamic analysis as well.

• Structural Engineering and Mechanics
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• 제46권1호
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• pp.19-37
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• 2013

The optimum design of base isolation system considering model parameter uncertainty is usually performed by using the unconditional response of structure obtained by the total probability theory, as the performance index. Though, the probabilistic approach is powerful, it cannot be applied when the maximum possible ranges of variations are known and can be only modelled as uncertain but bounded type. In such cases, the interval analysis method is a viable alternative. The present study focuses on the bounded optimization of base isolation system to mitigate the seismic vibration effect of structures characterized by bounded type system parameters. With this intention in view, the conditional stochastic response quantities are obtained in random vibration framework using the state space formulation. Subsequently, with the aid of matrix perturbation theory using first order Taylor series expansion of dynamic response function and its interval extension, the vibration control problem is transformed to appropriate deterministic optimization problems correspond to a lower bound and upper bound optimum solutions. A lead rubber bearing isolating a multi-storeyed building frame is considered for numerical study to elucidate the proposed bounded optimization procedure and the optimum performance of the isolation system.

• 전기전자학회논문지
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• 제11권3호
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• pp.100-107
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• 2007

무선 센서 네트워크에서 중요한 문제 중 하나는 센서 노드들의 최적 배치, 즉 측정하고자 하는 지역을 모두 커버할 수 있는 최소 센서 노드 수를 산출하고 배치 위치를 결정하는 일이다. 본 논문에서는 이러한 문제를 해결하기 위한 방법으로 제안한 Fuzzy C-Means 클러스터링을 이용하여 측정하고자 하는 지역에서의 최적의 노드 배치와 최소 노드의 수를 시뮬레이션을 통해 도출하였고, 실험을 통하여 검증하였다. 시뮬레이션은 3가지 타입의 2차원 지역을 모델로 하여 수행하였다. 모델링한 지역은 6M${\times}$10M의 직사각형, 50M${\times}$20M의 직사각형, 100M${\times}$80M의 ‘L’ 자 형태의 지역으로 하였으며, 각각 9개, 9개, 15개 노드의 위치를 결정하였다. 실제 실험결과 각 지역에 대해서 94.6%, 92.2%, 95.7%의 정확도를 가진 통신 연결을 확인할 수 있었다.

• 설비공학논문집
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• 제25권7호
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• pp.398-405
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• 2013

Small and medium-size buildings employ a multi-distributed individual air-conditioning system that utilizes package air conditioners instead of centralized cooling systems, which can allow easier building management and maintenance, along with a diversification of facility use. Inverter driven system heat pumps have been developed to achieve not only an easy distribution control, allowing free combination of indoor units with different models and different capacities, but also wide applications to intelligent air conditioning. However, the control algorithms of the system heat pump are limited in the open literature, due to complicated operating conditions. In this paper, an inverter-driven system heat pump having two indoor units with electronic expansion valves (EEV) was simulated in the cooling mode. An integral optimum regulating controller employing the state space control method was also simulated, and applied to the system-heat pump system, to obtain efficient control of the MIMO (multi input multi output) system. The simulation model for the controller yielded satisfactory prediction results. The new control model can be successfully utilized as a basic tool in controller design.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2003년도 추계학술대회
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• pp.1476-1481
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• 2003

Kinematic calibration enhances absolute accuracy by compensating for the fabrication tolerances and installation errors. Effectiveness of calibration procedures depends greatly on the measurements performed. This paper investigates identifiable parameters and optimum postures for four different calibration procedures - measuring postures completely with inverse kinematic residuals, measuring postures completely with forward kinematics residuals, measuring only the three position components, and restraining the mobility of the end-effector using a constraint link. The study is performed for a six degree-of-freedom fully parallel HexaSlide type parallel manipulator, HSM. Results verify that all parameters are identifiable with complete posture measurements. For the case of position measurements, one and for the case of constraint link, three parameters were found non-identifiable. Selecting postures for measurement is also an important issue for efficient calibration procedure. Typically, the condition number of the identification Jacobian is minimized to find optimum postures. Optimal postures showed the same trend of orienting themselves on the boundaries of the search space.

• 대한토목학회논문집
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• 제12권3호
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• pp.1-15
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• 1992

본 논문에서는 열 두가지의 가능한 지지조건을 갖는 연속 곡평면 2방향 슬래브 시스템에 대하여 실용적이고 간편한 수치해석과 최적 설계 방법을 제시하였다. 얇은 곡평판의 탄성이론에 의하여 유도된 설계모멘트 계수를 이용하여, 구조해석을 하는 수치해석 방법을 본 연구에서는 사용하였다. 최적화의 결과는 한계상태 설계법에 의해서 정의된 feasible 영역내에서 결정되도록 유도하였으며 슬래브의 주재료 경비함수를 변형시켜 유도한 목적함수는 한계상태 설계의 규정에 따라 역학적 거동의 문제와 사용성 제약조건을 모두 만족하연서 최적화에 이르도록 하였다. 형성된 최적화 문제는 고차의 비선형 문제로 유도 되었으며 이 비선형 최적화 문제를 연속 선형계획법을 이용하여 해석하므서 슬래브의 유효깊이와 중간대 및 주열대의 단위폭당 변형시킨 철근비들의 최적 설계변수들을 구하였다.

• 환경영향평가
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• 제22권1호
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• pp.19-26
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• 2013

The propose of this study is to analyze the optimum spatial resolution of the urban spatial thermal environment structure and to evaluate of the possibility detection using aerial photographs and thermal satellite images. The proper techniques of the optimum spatial resolution for the urban spatial thermal environment structure were analyzed. Thermal infrared satellite image of Seoul city were used for the change rate of surface temperature variation and suggested to the spatial extent and effects of urban surface characteristics and spatial data was interpreted as regions. To extract the surface temperature, Landsat thermal infrared satellite image compared with an automatic weather station data and in the field of the measured temperature and surface temperature by thermal environment affects, the spatial domain has been verified. The surface temperature of the satellite images to extract after adjusting surface temperature isotherms were constructed. The changes in surface temperature from 2008 to 2012 the average surface temperature observation images of changing areas were divided into space. The results of this study are as follows: Through analysis of satellite imagery, Seoul city surface temperature change due to extraction comfort indices were classified into four grades. The comfort index indicative of the temperature of Gangnam-gu, $23.7{\sim}27.2(^{\circ}C)$ range and Songpagu, a $22.7{\sim}30.6(^{\circ}C)$ respectively, the surface temperature of Yeouido $25.8{\sim}32.6(^{\circ}C)$ were in the range.

• International Journal of Reliability and Applications
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• 제13권1호
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• pp.19-35
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• 2012

This paper presents an optimum design of step-stress partially accelerated life test (PALT) plan which allows the test condition to be changed from use to accelerated condition on the occurrence of fixed number of failures. Various life distribution models such as exponential, Weibull, log-logistic, Burr type-Xii, etc have been used in the literature to analyze the PALT data. The need of different life distribution models is necessitated as in the presence of a limited source of data as typically occurs with modern devices having high reliability, the use of correct life distribution model helps in preventing the choice of unnecessary and expensive planned replacements. Truncated distributions arise when sample selection is not possible in some sub-region of sample space. In this paper it is assumed that the lifetimes of the items follow Truncated Logistic distribution truncated at point zero since time to failure of an item cannot be negative. Optimum step-stress PALT plan that finds the optimal proportion of units failed at normal use condition is determined by using the D-optimality criterion. The method developed has been explained using a numerical example. Sensitivity analysis and comparative study have also been carried out.