• International Journal of Aeronautical and Space Sciences
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• 제11권2호
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• pp.131-135
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• 2010

We report on the design of a three-axis missile autopilot using multi-objective control synthesis via linear matrix inequality techniques. This autopilot design guarantees $H_2/H_{\infty}$ performance criteria for a set of finite linear models. These models are linearized at different aerodynamic roll angle conditions over the flight envelope to capture uncertainties that occur in the high-angle-of-attack regime. Simulation results are presented for different aerodynamic roll angle variations and show that the performance of the controller is very satisfactory.

• 제어로봇시스템학회논문지
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• 제14권7호
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• pp.615-623
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• 2008

This paper proposes an $H_{\infty}$ controller design method for Takagi-Sugeno (T-S) fuzzy systems using a fuzzy basis-function-dependent Lyapunov function. Sufficient conditions for the guaranteed $H_{\infty}$ performance of the T-S fuzzy control system are given in terms of linear matrix inequalities (LMIs). These LMI conditions are further used for a convex optimization problem in which the $H_{\infty}-norm$ of the closed-loop system is to be minimized. To facilitate the basis-function-dependent Lyapunov function approach and thus improve the closed-loop system performance, additional decision variables are introduced in the optimization problem, which provide an additional degree-of-freedom and thus can enlarge the solution space of the problem. Numerical examples show the effectiveness of the proposed method.

• 한국세라믹학회지
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• 제29권4호
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• pp.283-292
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• 1992

Duplex composites such as Y-TZP/Y-TZP-20 wt.% Al2O3 and Y-TZP/Y-TZP- 40 wt.% Al2O3 were made by mixing the sieve-shaked granules followed by isostatic pressing and sintering at 150$0^{\circ}C$ for 1 hour. So Y-TZP became matrix region and Y-TZP-20 wt.% Al2O3 or Y-TZP-40 wt.% Al2O3 became dispersed regions. In these composites, propagating cracks due to thermal shock always run into the dispersed region because these regions act as compressive zone due to low thermal expansion than matrix region. So duplexes having dispersed regions of Y-TZP-40 wt.% Al2O3 showed higher retained strength after thermal shock than matrix only composites because crack propagations were stopped more or less in the dispersed region. But when crack propagations were much more easy than matrix like Y-TZP-20 wt.% Al2O3 region, retained strength was decreased than the matrix only composites despite of the low initial strength.

• Membrane and Water Treatment
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• 제11권2호
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• pp.131-139
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• 2020

The current study focused on the preparation of low-cost PVC-based adsorbing membrane. Metakaolin, as available adsorbent, was embedded into the PVC matrix via solution blending method. The as-prepared PVC/metakaolin mixed matrix membranes were characterized using scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDS), attenuated total reflectance-Fourier transform infrared (ATR-FTIR) spectroscopy, atomic force microscopy (AFM), pure water permeability and contact angle measurements. The results confirmed the improvement of PWP and hydrophilicity due to the presence of metakaolin in the PVC matrix. Additionally the structure of PVC membrane was changed due to the incorporation of metakaolin in the polymer matrix. The static adsorption capacity of all samples was determined through dye removal. The effect of metakaolin dosage (0-7%) and pH (4, 8, 12) on dye adsorption capacity was investigated. The results depicted that the highest adsorption capacity was achieved at pH of 4 for all samples. Additionally, adsorption data were fitted on Langmuir, Freundlich, and Temkin models to determine the appropriate governing isotherm model. Finally, the dynamic adsorption capacity of the optimum PVC/metakaolin membrane was studied using dead-end filtration cell. The dye removal efficiency was determined for pure PVC and PVC/metakaolin membrane. The results demonstrated that PVC/metakaolin mixed matrix membrane had a high adsorption capacity for dye removal from aqueous solution.

• 한국수소및신에너지학회논문집
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• 제33권5호
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• pp.598-606
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• 2022

With the advancement of industry, the use of various sustainable energy sources and solutions to problems affecting the environment are being actively requested. From this point of view, it is intended to directly burn unused biogas to use it as energy and to solve environmental problems such as greenhouse gases. In this study, a new type of cavity matrix combustor capable of low-emission complete combustion without complex facilities such as separation or purification of biogas produced in small and medium-sized facilities was proposed, and CFD numerical calculation was performed to understand the performance characteristics of this combustor. The cavity matrix combustor consists of a burner with a rectangular porous microwave receptor at the center inside a 3D cavity that maintains a rectangular parallelepiped shape composed of a porous plate that can store heat in the combustor chamber. As a result of numerical calculation, the biogas supplied to the inlet of the combustor is converted to CO and H₂, which are intermediate products, on the surface of the 3D matrix porous burner. And then the optimal combustion process was achieved through complete combustion into CO₂ and H₂O due to increased combustibility by receiving heat energy from the microwave heating receptor.

• Journal of Pharmaceutical Investigation
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• 제26권4호
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• pp.281-289
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• 1996

In our previous work, we have studied the effect of lactose and sodium alginate (SA) on the rate of release of 5-fluorouracil (5-FU) from ethylene-vinyl acetate (EVA) matrix. These hydrophilic additives promoted the rate of 5-FU release and the increase in rate was larger when SA was used. Both additives showed better ability to increase the rate than 5-FU itself. In this paper, we extended our study to another hydrophilic additive, Carbopol 940 (CP). Compared to SA or lactose, CP increased the rate of 5-FU release markedly. Release rate increased as the loading amount and the pH of the release medium increased. After release experiment, matrix volume increased up to 15 times of that before release experiment, depending on the amount of CP dispersed in the matrix and the pH of the release medium. On the other hand, the volume of the matrix containing lactose or SA decreased. The weight changes of the dry matrix before and after release experiment imply that CP is not released out of the matrix, to the contrary of lactose and SA. Scanning electron microscope study clearly showed that large cavities and pores are generated on the surface and the inside of the matrix. These results indicate that the mechanism by which CP increases the release rate is quite different from that of monomeric additives such as lactose or SA.

• 대한수학회논문집
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• 제7권1호
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• pp.123-128
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• 1992

• Bulletin of the Korean Chemical Society
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• 제16권9호
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• pp.894-896
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• 1995

• 한국응용과학기술학회지
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• 제30권4호
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• pp.656-663
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• 2013

본 연구는 식품으로 사용하고 있는 유산균의 보존성과 안정성을 높이고, 맛과 시각적인 차별화를 주기 위한 방법으로 더블매트릭스 캡슐화에 대한 제조방법에 대하여 기술하였다. 일차캡슐화방법으로 5wt%의 슈크로스에스터를 이용하여 부드럽고 촉촉한 크림을 만들었다. 더블매트릭스캡슐화는 키토산과 아르긴산을 1:3의 비율로 혼합하여 제조하였을 때 가장 안정한 캡슐이 형성되었다. 더블매트릭스 캡슐입자의 크기는 지름이 3mm이었다. 유산균의 pH변화에 대한 활성은 산성($pH=4.3{\pm}0.3$)이나 중성($pH=7.12{\pm}0.2$)상태에서보다 알칼리성 ($pH=10.5{\pm}0.3$)에서 더욱 우수한 활성을 보였다. 1개월 경과 후에서도 살아있는 유산균의 활성을 확인할 수 있었다. 식품산업에 응용으로 요거트안에 유산균캡슐이 함유된 제형과 5가지의 색상을 입힌 더블매트릭스캡슐을 개발하였다. 이상의 결과로 볼 때, 유산균을 안정화시키는 방법의 하나의 도구로써, 더블매트릭스캡슐이 식품산업에 크게 기여할 것으로 기대된다. 더 나아가 의약품산업에서 인슐린 등의 캡슐화를 통한 약물전달시스템 (drug delivery system) 및 화장품산업에서의 활성성분의 안정화 기술에 응용이 가능할 것으로 기대한다.

• 전자공학회논문지
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• 제52권12호
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• pp.89-98
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• 2015

본 논문에서는 임의적으로 발생하는 폴리토프 불확실성과 외란을 고려한 시간지연시스템의 강인비약성 $H_{\infty}$ 제어기설계 알고리듬을 다룬다. 먼저 임의적으로 발생하는 불확실성과 외란을 가지는 시간지연시스템을 설계하고, Lyapunov 안정성 분석과 $H_{\infty}$ 성능지수를 기반으로 강인비약성 $H_{\infty}$ 제어기가 존재하기 위한 충분조건을 선형행렬부등식(LMI, linear matrix inequality)의 형태로 제시한다. 구한 충분조건은 변수치환과 슈어 여수(Schur complement) 정리를 바탕으로 파라미터의 함수를 포함한 파라미터화 선형행렬부등식(PLMI, parameterized linear matrix inequality)으로 표현할 수 있으므로 PLMI의 모든 해로부터 제어기이득과 비약성을 만족하는 제어기 섭동영역 및 $H_{\infty}$ 성능을 만족하는 노옴 한계치 ${\gamma}$를 한번에 구할 수 있다. 마지막으로 예제와 모의실험에서 제안한 강인비약성 $H_{\infty}$ 제어기가 임의적으로 발생하는 불확실성 및 외란, 시간지연이 있더라도 폐루프시스템을 안정화시키고 $H_{\infty}$ 성능을 보장함을 확인하고 확정적인 불확실성을 기반으로 설계한 제어기와 성능을 비교한다.