• 한국윤활학회:학술대회논문집
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• 한국윤활학회 1999년도 제30회 추계학술대회
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• pp.167-173
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• 1999

This paper suggests a method to design the deep groove ball bearing for high-load capacity by using a genetic algorithm. The design problem of ball bearings is a typical discrete/continuous optimization problem because the deep groove ball bearing has discrete variables, such as ball size and number of balls. Thus, a genetic algorithm is employed to find the optimum values from a set of discrete design variables. The ranking process is proposed to effectively deal with the constraints in genetic algorithm. Results obtained fer several 63 series deep groove ball bearings demonstrated the effectiveness of the proposed design methodology by showing that the average basic dynamic capacities of optimally designed bearings increase about 9~34% compared with the standard ones.

• 대한전기학회논문지
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• 제45권3호
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• pp.407-414
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• 1996

In this paper we consider the variable structure control for a class of discrete-time uncertain multivariable systems where the nominal system is linear. Discrete-time switching dynamics are introduced so that a new type of state trajectories called sliding mode may exist on the sliding surface by state feedback. The quantitative analysis for the matched uncertainties will show that every response of the system with the proposed switching dynamics is bounded within small neighborhoods of the state-space origin. Also, by the similarity transformation it will be shown that the eigenvalues of the closed-loop systems are composed of those of the subsystems which govern the range-space dynamics and null-space dynamics. It will be also shown that ideal sliding mode can be obtained in the absence of uncertainties due to one-step attraction to the sliding surface regardless of initial position of states. (author). 12 refs., 2 figs.

• 한국전자파학회논문지
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• 제12권7호
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• pp.1110-1114
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• 2001

그린함수의 효율적인 표현을 위하여 파수영역 웨이블릿 변환 개념을 이용하였다. 파수영역 웨이블릿 변환을 공간영역에서 가변 윈도우를 사용하여 등가적으로 구현하였다. 제안된 방법은 공간영역 그린함수에 대하여 윈도우 함수를 이용한 필터링과정, 고유함수의 전개를 통한 중심이동과정, 그리고 푸리에 변환과정으로 이루어진다. 파수영역 이산 웨이블릿 변환이 적용된 그린함수의 수식을 유도하였고, 근거리 그린함수와 원거리 그린함수를 표현하여 파수영역에서 비교하여 특성에 대하여 논의하였다.

• 대한조선학회논문집
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• 제61권3호
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• pp.152-160
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• 2024

In the event of a maritime accident, search plans have traditionally been planned using experiential methods. However, these approaches cannot guarantee safety when the scale of a maritime accident increases. Therefore, this study proposes a model utilizing discrete event simulation (DES) to predict the diving time for compartment searches of a ship located on the seabed. The discrete event simulation model was created by applying the DEVS formalism. The M/V Sewol sinking was used as an example to simulate how to effectively navigate compartments of different sizes. The simulation results showed the optimal dive time with the number of decompression chambers needed to navigate the compartment as a variable. Based on this, we propose a methodology for efficient navigation planning while ensuring diver safety.

• 조명전기설비학회논문지
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• 제15권1호
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• pp.84-89
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• 2001

본 논문은 다중 해상도 웨이브렛 변환을 이용하여 코로나 방전과 코로나방전 후 연면방전을 거치는 다중결함에 대한 방전전류펄스의 변화량을 시간 대역과 주파수 대역에서의 변화량을 분석하였다. 마더웨이브렛의 선정은 방전전류펄스의 형태를 고려하여 Daubechies 마더웨이브렛을 선정하였으며, 방전전류펄스는 이산 웨이브렛 변환을 이용하여 근사신호와 상세신호로 4단계까지 다중분해되었다. 이중 상세신호만을 이용하여 12개의 세그먼트로 나눈후 설정한 변수에 따라 그 패턴을 파악하였다. 그 결과 코로나 방전에서는 설정된 변수의 세그먼트 7, 8, 9, 10의 값이 방전의 진전에 따라 증가하였으므로 위상분포를 $210~330[^{\circ}]$분포를 특징지울 수 있고, 에폭시 절연체를 삽입한 다중결함에서는 연면방전의 특징에 기인하여 설정된 변수의 값이 대칭적인 패턴을 나타내었다.

• 제어로봇시스템학회:학술대회논문집
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• 제어로봇시스템학회 1991년도 한국자동제어학술회의논문집(국제학술편); KOEX, Seoul; 22-24 Oct. 1991
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• pp.1883-1887
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• 1991

Identification theory for linear discrete system has been presented by a great many reference, but research works for identification of continuous-time system are less than preceding identification. In fact, a great man), systems for engineering are continuous-time systems, hence, research for identification of continuous-time system has important meaning. This paper offers the following results: 1. Corresponding relations for the parameters of continuous-time model and discrete model may be shown, when single input-output system has general characteristic roots. 2. To do identification of single variable continuity linear system with stability constraints from samples of input-output data, it is necessary to use optimization with stability constraints. 3. Main results of this paper may be explained by a simple example.

• 대한전기학회논문지:전기기기및에너지변환시스템부문B
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• 제50권11호
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• pp.563-567
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• 2001

ln this paper, the designed DVSC(Discrete Variable Structure Controller) is applied to the robust control of voltage controlled APF(Active Power Filter). The voltage controlled APF has good characteristics of reducing harmonic current and harmonic voltage simultaneously. However, voltage controlled APF with large capacitor has slow dynamic response. For improving the dynamics and robustness against to disturbances, DVSC is adopted. According to the results of experiment and simulation, it is proved that the proposed system has the performance of improving dynamic response and robustness.

• 항공우주시스템공학회지
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• 제8권1호
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• pp.12-17
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• 2014

In this paper, optimal design of composite rotor blade cross-section to consider manufacturability was performed. Skin thickness, torsion box thickness and skin lay-up angle were adopted as discrete design variables and The position and width of a torsion box were considered as continuous variables. An object function of optimal design is to minimize the mass of a rotor blade, and various constraints such as failure index, center mass, shear center, natural frequency and blade minimum mass per unit length were adopted. Finally, design variables such as the thickness and lay-up angles of a skin, and the thickness, position and width of a torsion box were determined by using an in-house program developed for the optimal design of rotor blade cross-section.

• 대한화학회지
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• 제60권3호
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• pp.163-168
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• 2016

비조화진동자의 진동에너지와 파동함수를 수치적으로 간단히 계산할 수 있는 Discrete Variable Representation 방법을 요약하고, Morse 진동자를 모형으로 활용하여 실제 분자계의 기본전이 및 들뜬 전이에너지를 구하는데 적용할 수 있는 최적의 변수 범위를 예측하였다.

• East Asian mathematical journal
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• 제32권1호
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• pp.101-115
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• 2016

In this paper, we consider a semi-discrete mixed discontinuous Galerkin method with an interior penalty to approximate the solution of parabolic problems. We define an auxiliary projection to analyze the error estimate and obtain optimal error estimates in $L^{\infty}(L^2)$ for the primary variable u, optimal error estimates in $L^2(L^2)$ for ut, and suboptimal error estimates in $L^{\infty}(L^2)$ for the flux variable ${\sigma}$.