• Korean Chemical Engineering Research
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• 제56권3호
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• pp.416-420
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• 2018

A comprehensive kinetic study has been conducted on dimethyl carbonate synthesis by transesterification reaction of ethylene carbonate with methanol. An alkali base metal (KOH) was used as catalyst in the synthesis of DMC, and its catalytic ability was investigated in terms of kinetics. The experiment was performed in a batch reactor at atmospheric pressure. The reaction orders, the activation energy and the rate constants were determined for both forward and backward reactions. The reaction order for forward and backward reactions was 0.87 and 2.15, and the activation energy was 12.73 and 29.28 kJ/mol, respectively. Using the general factor analysis in the design of experiments, we analyzed the main effects and interactions according to the MeOH/EC, reaction temperature and KOH concentration. DMC yield with various reaction conditions was presented for all ranges using surface and contour plot. Furthermore, the optimal conditions for DMC yield were determined using response surface method.

• 동력기계공학회지
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• 제18권3호
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• pp.20-28
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• 2014

Most washing machines are now produced as a drum-type, where a washing drum mounted on a suspension system with springs and dampers, to minimize the transmittance of the vibration from the drum to the cabinet. The purpose of this paper is to develop optimized suspension system of the drum washing machine which minimizes transmission of disturbing vibration and force. In this paper, a method for optimizing suspension system of the drum washing machine is presented using ADAMS. The design variables to optimize are extracted using Sequential Quadratic Programming(SQP) in ADAMS. To evaluate optimized spring constants and damping coefficients of the drum washing machine, simulation was done to compare the vibration attenuation performances before and after the optimization. The results of simulation show that the optimized suspension system has better performance than before the optimization.

• 대한전기학회논문지:전력기술부문A
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• 제49권5호
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• pp.205-211
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• 2000

This paper presents an optimal design method for fuzzy logic controller (FLC) of HVDC using an Adaptive Evolutionary Algorithm(AEA). We have proposed the AEA which uses a genetic algorithm (GA) and an evolution strategy (ES) in an adaptive manner in order to take merits of two different evolutionary algorithms. The AEA is used for tuning fuzzy membership functions and scaling constants. Simulation results show that disturbances are well damped and the dynamic performances of FLC have better responses than those of PD controller when AC system load changes suddenly.

• 대한전기학회:학술대회논문집
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• 대한전기학회 1999년도 추계학술대회 논문집 학회본부 A
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• pp.160-162
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• 1999

This paper presents an optimal design method for fuzzy controllers of HVDC system using adaptive evolutionary algorithm(AEA). We have proposed an adaptive evolutionary algorithm which uses a genetic algorithm and an evolution strategy in an adaptive manner in order to take merits of two different evolutionary computations. AEA is used for tuning fuzzy membership functions, scaling constants and PD gains. The simulation results show that the disturbances are well damped by both controllers and the dynamic performances of fuzzy controllers have better responses than those of PD controllers when mechanical torque changes suddenly.

• Journal of Biosystems Engineering
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• 제29권5호
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• pp.385-394
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• 2004

The objectives of this study were to investigate the effectiveness of rubber as an engine mount of walking-type cultivators and to determine its optimal spring constant and damping coefficient using a dynamic simulation of the engine mount system. Four different types of rubber mounts were tested to determine their spring constants and damping coefficients, and the best type was selected for the isolation of the engine vibrations transmitted to the handle. The total vibration levels transmitted to the handle when the rubber mounts weren't installed were 17.52 $m/s^2$. The total vibration levels transmitted to the handle when the rubber mounts were installed were 10.69 $m/s^2$ for Stripe 1, 11.33$m/s^2$ for Stripe 2, 10.92$m/s^2$ for Stripe 3 and 14.19$m/s^2$ for Hive, respectively, resulting in an average of $30\%$ reduction when compared with that without the engine mount. A dynamic model of the cultivator's engine-mount system and its simulation program were developed and verified. A method was proposed to determine the optimal spring constant and damping coefficient of the engine-mount system. It was found from the simulation that a spring constant of 4,100 kN/m and the largest damping coefficient were the most effective for the vibration isolation.

• Nuclear Engineering and Technology
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• 제27권5호
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• pp.730-742
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• 1995

증기발생기의 급수 및 수위조절 시스템과 관련하여 전체 시스템을 급수 서보시스템과 궤환제어기로 나누어 설계하였다. 급수 시스템의 설계에는 최적제어이론을 사용하였으며 시스템의 강인성을 위하여 다시 LTR 기법을 이용하였다. 중기발생기의 제어특성은 열수력학적인 이유에 의하여 출력에 따라 계속적으로 변하게 되므로 궤환제어기가 이러한 변화를 동적으로 반영할 수 있도록 하였다. 모든 설계는 연속시스템에서 이루어졌으며 적절한 샘플링 주기를 선정하여 디지탈화 하였다. 이같은 시스템을 이용하여 출력증가 및 감소의 두 가지에 대해 검토한 결과, 출력의 증가시에는 제어상수를 고정시키는 것이 바람직하나 출력의 감소시에는 시스템의 안정을 위하여 제어상수가 출력에 따라 동적으로 변화해야함을 알 수 있었다.

• Composites Research
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• 제15권2호
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• pp.18-23
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• 2002

군사적 목적뿐만 아니라 상업적 목적에서도 레이더나 기타 전자파를 방출하는 기기들로부터 생성되는 전자파의 흡수 또는 차폐는 매우 중요한 일이다. 본 연구에서는 다른 유전적 성질을 가지는 복합재층을 배열하여 전자기파의 반사를 최소화하는 연구를 수행하였다. Glass fabric/epoxy에 전도성을 가지는 카본블랙 분체를 혼합한 복합재와 Carbon fabric/epoxy 복합재 대만 유전성질을 측정하였고, 이를 이용하여 X-band(8.2 GHz-l2.4GHz)에 대한 전자기파 반사의 최소화 구조를 구성하였다. 두께2.6mm의 다층 구조로 최대 30dB 이상의 반사 손실과 최대 흡수 주파수로부터 2GHz 주파수 대역에 걸쳐 10dB이상의 반사손실을 일으킬 수 있었다.

• 전산구조공학
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• 제1권1호
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• pp.87-94
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• 1988

반복 비선형 계획법의 하나인 선형화 기법을 절대수렴의 전제아래 합성 구조물의 최적 설계에 응용한다. 선형화 기법은 설계문제의 제약조건을 선형화된 등가 제약조건으로 변형시키며 active-set 정책을 구사한다. 결과, 매 설계단계에서 풀어야 할 상태 및 수반 방정식의 수를 줄임으로써 실질적인 계산의 절감을 기한다. 기둥으로 받쳐진 판-보 구조물은 최적화 기법의 능력을 시험키 위한 합성구조물의 좋은 예로서, 설계결과 선형화 기법은 만족할만한 수렴치로써 최적해를 산출함을 알 수 있고 나아가 이 방법은 모든 종류의 최적화 문제에 적용될 수 있을 것으로 보인다.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2000년도 하계학술대회 논문집 D
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• pp.2977-2979
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• 2000

A Fuzzy Hybrid-Multilayer Perceptron (FH-MLP) Structure is proposed in this paper. proposed FH-MLP is not a fixed architecture. that is to say. the number of layers and the number of nodes in each layer of FH-MLP can be generated to adapt to the changing environment. FH-MLP consists of two parts. one is fuzzy nodes which each node is operated as a small fuzzy system with fuzzy implication rules. and its fuzzy system operates with Gaussian or Triangular membership functions in premise part and constants or regression polynomial equation in consequence part. the other is polynomial nodes which several types of high-order polynomial such as linear. quadratic. and cubic form are used and is connected as various kinds of multi-variable inputs. To demonstrate the effectiveness of the proposed method. time series data for gas furnace process has been applied.

• 산업식품공학
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• 제21권4호
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• pp.303-311
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• 2017

To automate cooking processes, quantitative descriptions are needed on how quality parameters, such as texture change during heating. Understanding mechanical property changes in foods during thermal treatment due to changes in chemical composition or physical structure is important in the context of engineering models and in precise control of quality in general. Texture degradation of food materials has been studied widely and softening kinetic parameters have been reported in many studies. For a better understanding of kinetic parameters, applied kinetic models were investigated, then rate constants at $100^{\circ}C$ and activation energy from previous kinetic studies were compared. The food materials are hardly classified into similar softening kinetics. The range of parameters is wide regardless of food types due to the complexity of food material, different testing methods, sample size, and geometry. Kinetic parameters are essential for optimal process design. For broad and reliable applications, kinetic parameters should be generated by a more consistent manner so that those of foods could be compared or grouped.