• 한국음향학회지
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• 제32권3호
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• pp.199-207
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• 2013

본 논문에서는 압전단결정으로 구성된 $64{\times}8$ 채널 1.75D 초음파 트랜스듀서의 설계, 제작 및 평가를 하였다. 우선, 평면 배열된 독립소자에 전기적 연결이 가능한 트랜스듀서의 구조를 선정하고 구조에 맞게 구성소자를 제작하였다. 그리고 유한요소 해석을 통해 트랜스듀서의 세부 구조를 설계하였다. 트랜스듀서의 주요 성능요소로서, 치폭의 너비와 재료를 조절하여 소자간 상호간섭의 영향을 줄이고, 압전단결정 및 정합층의 최적 두께를 설계함으로써 트랜스듀서의 원하는 대역폭을 구현하였다. 설계에 맞게 트랜스듀서 시편을 제작하고 실험적으로 그 특성을 측정한 후, 그 결과를 유한요소 해석 결과와 비교함으로써 개발된 트랜스듀서의 성능을 평가하였다.

• International Journal of Automotive Technology
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• 제3권4호
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• pp.157-163
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• 2002

It is well recognized that the ultrasonic method is one of the most common and reliable nondestructive testing (NDT) methods for the quantitative estimation of defects in welded structures. However, NDT techniques applying for adhesively bonded joints have not been clearly established yet. In this paper, the detection of interface crack by the ultrasonic method was applied for the measurement of interfacial crack length in the adhesively bonded joints of double-cantilever beam (DCB). An optimal condition of transmission coefficients and experimental accuracy by the ultrasonic method in the adhesively bonded joints have been investigated and discussed. The experimental values are in good agreement with the computed results by boundary element method (BEM) and Ripling's equation.

• 오토저널
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• 제14권3호
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• pp.57-70
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• 1992

As automobile industry develope, design techniques to satisfy light weight and high efficiency in automobile parts is demanded. In this study modal analysis is performed using transfer matrix method to identify dynamic characteristics of exhaust system. It is estimated the theoretical transfer function by Pestel-Leckey method and the mode shapes in 3-D graphic. the validity of developed program is verified by comparing with the experimental results of exhaust system. Estimated modal parameters(natural frequency, vibrational mode, transfer function) are in accord with the experimental results. From the developed program, we can predict a location of the hanger which is determined by the lowest RMS value point, when displacement is given as an input at the engine side. We can find that attachment of spring modelled hanger at the hanger location bring vibration level down.

• 대한산업공학회지
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• 제34권1호
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• pp.49-56
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• 2008

Reliability has been considered as an important design measure in various industrial systems. We discuss a reliability optimization problem with component choices (ROP-CC) subject to a budget constraint. This problem has been known as a NP-hard problem in the reliability design fields. Several researchers have been working to find the optimal solution through different heuristic methods. In this paper, we describe our development of simulated annealing (SA) and tabu search (TS) algorithms and a reoptimization procedure of the two algorithms for solving the problem. Experimental results for some examples are shown to evaluate the performance of these methods. We compare the results with the solutions of a previous study which used ant system (AS) and the global optimal solution of each example obtained through an optimization package, CPLEX 9.1. The computational results indicate that the developed algorithms outperform the previous results.

• 한국소음진동공학회논문집
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• 제17권11호
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• pp.1050-1055
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• 2007

P.A.(public address) system is considered as an useful active soundscape appliance which can gives a place identity and vitality by introducing conventional musics, environmental musics, bird singing sounds etc. In this study, the main aim is to know the optimistic distance from the speaker and sound pressure level range of introducing sound. So, the sound pressure level of P.A. system due to distances were measured and subjects' responses with level variations were checked. The main results are as follows. Level range from 64 dB to 71 dB is comfortable for subjects. And the optimal level of introducing sound is related with sound source characteristics. The results of this study could be used for street furniture location design and P.A. system output level.

• 대한전기학회논문지:시스템및제어부문D
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• 제53권5호
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• pp.338-344
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• 2004

This paper presents a sensorless speed control of a DC servo motor using a fuzzy-sliding observer in the presences of load disturbances. A fuzzy-sliding observer is proposed in order to estimate the speed of a motor rotor. First, a sliding observer is used to estimate the derivative of the armature current directly using the armature current mesured in the DC servo motor. Second, the optimal gain of the Luenberger observer is set up using the fuzzy control. Experimental results show the good performance in the DC servo motor system with the proposed fuzzy-sliding observer.

• 산업경영시스템학회지
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• 제12권19호
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• pp.39-47
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• 1989

This paper considers a multi-stage flowshop scheduling Problem where the setup times of jots depend on immediately preceding jobs. Three heuristics algorithms, CAMPBELL, PEIDAN and CAMRING are proposed. The performance measure is a minimization of makespan. The parameters of simulation model are PS(ratio of the processing times to setup times), M(number of machines), and N(number of job). This simulation model for each algorithm is a 4$\times$3$\times$3 factorial design with 360 observations. The makespan of the proposed heuristic algorithms is compared with the optimal makespan obtained by the complete enumeration of schedules. This yardstick of comparison is defined as a relative error. The mean relative error of CAMPBELL, PEIDAN, and CAMRING algorithms are 4.353%, 7.908%, and 8.578% respectively. The SPSS, is used to analyse emphirical results. The experimental results show that the three factors are statistically significant at 5% level.

• 한국철도학회:학술대회논문집
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• 한국철도학회 2004년도 춘계학술대회 논문집
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• pp.589-594
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• 2004

In design of suspension system for KHST, it was applied the approximated optimization method using meta-models which called Response Surface Model and Neural Network Model for 29 design variables and 46 performance index. These models was coded using correlation between design variables and performance indices that is made by the 66 times iterative execution through the design of experimental table consisted orthogonal array L32 and D-Optimal design table. The results show that the optimization process is very efficient and simply applicable for complex mechanical system such as railway vehicle system. Also it was compared with the sensitivity of some design variables in order to know the characteristics of two models. This paper describes the general method for dynamic analysis and design process of railway vehicle system applied to KHST development, and proposed the efficient methods for vibration mode analysis process dealing with test data and the function based approximation method using meta-model applicable for a complex mechanical system. This method will be able to apply to the other railway vehicle system in oder to systematize and generalize the design process of railway vehicle dynamic system.

• 대한전자공학회:학술대회논문집
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• 대한전자공학회 2000년도 하계종합학술대회 논문집(1)
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• pp.69-72
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• 2000

This paper shows the more improved design of MRI receiver compared to conventional one based on Elscint Spectrometer. At first, the low-cost ADC is 16 bits, 3MHz sampling A/D converter Comparing to conventional one with signal bits of 14 bits, this device with those of 16 bits helps getting Improved the image resolution improved. If frequency is designed centering around 7.6 MHz to be satisfied in 10 MHz of maximum input bandwidth of ADC. For 1st demodulation, fixed IF is used for the purpose of the implementing multi nuclei system. Control parts & partial digital parts are integrated on one chip(FPGA). In DDC(Digital Down Converter), we got required bandwidth of LPF by controlling its decimation rate. With above considerations, we designed optimal receiver for high resolution imaging to be implemented through PC interface & experimental test of receiver of MRI after receiver's fabrication.

• 산업기술연구
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• 제22권A호
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• pp.83-87
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• 2002

Many industrial products such as paints, ink and adhesives are composed of the ingredients of a mixture. In mixture experiments, the characteristics of quality(response) depends only on the proportions of the ingredients and does not depend on the total amount of the mixture. This article discusses the constrained mixture experimental design, the data analysis, and the optimum formulation of ingredients based on the two quality characteristics - taste and flavor. It IS shown that efficient designs can be constructed from D-optimal criterion. Special cubic models were selected as the final mixture response surfaces for both reponses. The desirability function was used for the optimization of the two responses.