• 한국지진공학회:학술대회논문집
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• 한국지진공학회 2001년도 춘계학술대회 논문집
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• pp.387-393
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• 2001

Installing vibration control devices in the structure rises as a solution instead of increasing structural strength considering construction cost. Especially, viscoelastic dampers show excellent vibration control performance at low cost and are easy to install in existing structures compared with other control devices. Therefore, cost-effectiveness of structure with viscoelastic dampers needs to be evaluated. Previous cost-effectiveness evaluation method for the seismically isolated structure(Koh et al., 1999;2000)is applied on the building structure with viscoelastic dampers, which combines optimal design and cost-effectiveness evaluation for seismically isolated structures based on minimum life-cycle cost concept. Input ground motion is modeled in the form of spectral density function to take into account acceleration and site coefficients. Damping of the viscoelastic damper is considered by modal strain energy method. Stiffness of shear building and shear area of viscoelastic damper are adopted as design variables for optimization. For the estimation of failure probability, transfer function of the structure with viscoelastic damper for spectral analysis is derived from the equation of motion. Results reveal that cost-effectiveness of the structure with viscoelastic dampers is relatively high in how seismic region and stiff soil condition.

• 전자공학회논문지SC
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• 제49권3호
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• pp.47-52
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• 2012

본 논문은 Ku대역에서 동작하는 레이더용 원형편파안테나에 대한 설계 및 실험에 관한 것으로 선형안테나를 이용하여 원형편파안테나를 만들기 위해 Post를 이용함으로 안테나의 구조적 크기를 줄일 수 있었다. 원형편파 안테나의 축비 Bandwidth을 넓히기 위해 3개의 Post을 사용하였으며, 축비 최적화를 위해 Post사이 거리와 길이를 적절하게 선정하여 설계하였다. 또한 축비 최적화를 위해 반응표면법을 이용하여 최적화를 하였으며, 구현된 안테나는 12.7%의 Impedance Bandwidth와 설계 대역 내에서 2dB 이하의 축비 특성 및 7.8dBi 이상의 이득을 확인할 수 있었다.

• 대한기계학회논문집A
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• 제30권8호
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• pp.1001-1007
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• 2006

In this paper we present robust optimal supporting positions for large glass panels used for TFT-LCD monitors when they are stored in a cassette during manufacturing process. The criterion taken is to minimize their maximum deflection. Since they are supported by some supports and have large deformations, contact analysis with a geometrically nonlinear effect is necessary. In addition, the center of a panel can not be positioned exactly as intended and should be considered as uncertainties. To take into account of these effects, the mean and the standard deviation of system response functions, particularly the deflection of the panels, need be calculated. A function approximation moment method (FAMM) is utilized to estimate them. It is a special type of response surface methodology for structural reliability analysis and can be efficiently used to estimate the two stochastic properties, that is, the system performance and the perturbations caused by uncertainties. For a design purpose, they are to be minimized simultaneously by some optimization algorithm to obtain robust optimal supporting positions.

• 한국해양공학회지
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• 제29권5호
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• pp.351-358
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• 2015

This paper presents an effective damage detection method using a meta model. A meta model is an approximation model that uses the relations between the design and response variables. It eliminates the need for repetitive analyses of computationally expensive models during the optimization process. In this study, a response surface model was employed as the meta model. The surface model was estimated using the correlation of the stiffness and natural frequencies of the structures. The locations and values of the damages were identified using a meta model-based damage detection method. Two numerical examples (a cantilever beam and jacket structure) were considered to verify the performance of the proposed method. As a result, the damages to the structures were accurately detected.

• Structural Engineering and Mechanics
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• 제67권1호
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• pp.33-43
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• 2018

The dynamic output-feedback robust control method based on linear matrix inequality (LMI) method is presented for suppressing vibration response of a functionally graded material (FGM) beam with piezoelectric actuator/sensor layers in this paper. Based on the reduced model obtained by using direct mode truncation, the linear fractional state space representation of a piezoelectric FGM beam with material properties varying through the thickness is developed by considering both the inherent uncertainties in constitution material properties as well as material distribution and the model error due to mode truncation. The dynamic output-feedback robust H-infinity control law is implemented to suppress the vibration response of the piezoelectric FGM beam and the LMI method is utilized to convert control problem into convex optimization problem for efficient computation. In numerical studies, the flexural vibration control of a cantilever piezoelectric FGM beam is considered to investigate the accuracy and efficiency of the proposed control method. Compared with the efficient linear quadratic regulator (LQR) widely employed in literatures, the proposed robust control method requires less control voltage applied to the piezoelectric actuator in the case of same control performance for the controlled closed-loop system.

• 한국기계가공학회지
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• 제19권1호
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• pp.108-113
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• 2020

Pinions are generally heavy and integrated with a shaft. Thus, fabricating a pinion is a material- and machining-intensive task characterized by low productivity. Contact of the output pinion with a sliding surface or a cloud contact causes loss of power because of friction. Consequently, the output pinion undergoes considerable wear and tear at its ends, which adversely affects the overall transmission efficiency of decelerators. To improve transmission efficiency and extend gear life, an optimum output pinion design is required. To this end, in this study, an output pinion for worm gear decelerators was designed and optimized by means of product verification through prototyping and performance evaluation to improve gear life and productivity. The optimized design was validated and subjected to structural analysis.

• Smart Structures and Systems
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• 제26권5호
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• pp.591-603
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• 2020

Dynamic deflection monitoring is an essential and critical part of structural health monitoring for high-speed railway bridges. Two critical problems need to be addressed when using inclinometer sensors for such applications. These include constructing a general representation model of inclination-deflection and addressing the ill-posed inverse problem to obtain the accurate dynamic deflection. This paper provides a dynamic deflection monitoring method with the placement of optimal inclinometer sensors for high-speed railway bridges. The deflection shapes are reconstructed using the inclination-deflection transformation model based on the differential relationship between the inclination and displacement mode shape matrix. The proposed optimal sensor configuration can be used to select inclination-deflection transformation models that meet the required accuracy and stability from all possible sensor locations. In this study, the condition number and information entropy are employed to measure the ill-condition of the selected mode shape matrix and evaluate the prediction performance of different sensor configurations. The particle swarm optimization algorithm, genetic algorithm, and artificial fish swarm algorithm are used to optimize the sensor position placement. Numerical simulation and experimental validation results of a 5-span high-speed railway bridge show that the reconstructed deflection shapes agree well with those of the real bridge.

• 동력기계공학회지
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• 제3권3호
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• pp.83-90
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• 1999

제어이론분야에서의 발전은 그러한 이론을 다방면으로 응요할 수 있는 분야를 더더욱 폭넓게 제공해 주고 있다. 자동화와 관련된 분야뿐만 아니라, 건축 및 토목분야에서도 고도의 제어어이론을 응용한 예를 쉽게 접할 수 있게 되었으며, 지진동에 의한 구조물의 진동을 억제하려는 방책이 그 ??ㅣ다. 이에 관한 많은 연구에서도 알 수 있듯이, 일반적으로 구조물의 수학적 모델에만 의존하여, 즉 구조물의 설계파라미터는 이미 설계되어져 있다는 가정하에 제어계를 설계하고 있다. 그러나 이러한 설계법에 있어서는 설계자로 하여금 구조물의 설계파라미터를 조정할 수 있는 자유도는 전혀 주어지지 않게 되며 단지 제어계의 파라미터를 조정하는 자유도만 허용된다. 이러한 문제점을 극복하기 위해 구조계 및 제어기의 설계파라미터를 동시에 조절할 수 있는 자유도가 허용되는 '구조계/제어계의 동시 최적화' 기법이 있다. 따라서 본 논문에서는 교량의 주탑 및 해양구조물 등의 진동제어 문제에 이러한 설계기법을 이용하여 주어진 설계사양을 만족하도록 구조계 및 제어계의 파라미터를 최적화 한다. 특히 본 논문에서는 제어계 설계 문제에 있어서의 일반적인 경우를 고려하여 상태의 일부가 관측된다고 가정하고 출력피드백의 경우에 대해 고찰하고 있다. 이때의 설계사양은 선형행렬부등식(LMI)으로 주어지며, 실험을 통하여 본 논문에서 소개하는 설계기법의 유효성을 검증한다.

• 한국정밀공학회지
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• 제28권4호
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• pp.490-495
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• 2011

A slide-rail system is widely used in home appliances, furniture, mechanical rigs, and so many other applications; due to its high strength and performance for easy moving heavy objectives. In general, a pair of side slide-rails is set on both sides of a drawer to support and move it. So an unbalanced sliding motion can occur during opening and closing a drawer with pull and push force. To settle this problem, single central slide-rail having three collapsible rail-bodies was firstly proposed in this work. 'H'-beam shaped rail-body was newly designed to have enough bending and twisting strength. The experimental test showed that the proposed rail could be applied to large-size home appliances for easy moving drawer with heavy weight.

• 한국도로학회논문집
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• 제17권3호
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• pp.13-25
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• 2015

PURPOSES : This paper aims at the implementation of a balanced scorecard that can be widely applied to modern business management for use in the public road management sector. METHODS : This study applied the newly developed LOS-based balanced scorecard system instead of a traditional Key Performance Index (KPI) for better decision making in asset management planning. As an evaluation technique, a" hierarchical alignment and cascading method" is also suggested. Finally, the suggested system has been empirically applied to a regional government. RESULTS : To provide stable and sustainable road services, the balanced scorecard informs the regional government of needed improvements in its asset management plans regarding budget optimization, structural management, the development of inner-business processes, and human resources. CONCLUSIONS : An LOS-based balanced scorecard for managing road services and organizations in a quantitative manner has been successfully developed and tested through a field study. The developed scorecard is a timely topic and a useful analytical tool for coping with the new phases of an aging infrastructure, tighter budgets, and demand for greater public accountability.