• 제어로봇시스템학회:학술대회논문집
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• 제어로봇시스템학회 1996년도 한국자동제어학술회의논문집(국내학술편); 포항공과대학교, 포항; 24-26 Oct. 1996
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• pp.427-431
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• 1996

The MRAS proposed by Schauder [8] is modified to improve robustness to the change of load torque and/or the variation of the stator resistance. The difference between the voltage and the current model is fed into the current model via proportional and integral gains. In order to generalize the MRAS, supposing that the rotor speed is time varying, we add a compensating term to the current model. It does not alter the Popov's integral inequality condition. Also, the asymptotic stability of the modified MRAS (MMRAS) is shown with the stability proof technique as in the original paper. By the simulation works, it is verified that the MMRAS obtains improved performance than the original MRAS.

• Structural Engineering and Mechanics
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• 제75권6호
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• pp.685-699
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• 2020

Polygonal finite element provides a great flexibility in mesh generation of crack propagation problems where the topology of the domain changes significantly. However, the control of the discretization error in such problems is a main concern. In this paper, a polygonal-FEM is presented in modeling of crack propagation problems via an automatic adaptive mesh refinement procedure. The adaptive mesh refinement is accomplished based on the Zienkiewicz-Zhu error estimator in conjunction with a weighted SPR technique. Adaptive mesh refinement is employed in some steps for reduction of the discretization error and not for tracking the crack. In the steps that no adaptive mesh refinement is required, local modifications are applied on the mesh to prevent poor polygonal element shapes. Finally, several numerical examples are analyzed to demonstrate the efficiency, accuracy and robustness of the proposed computational algorithm in crack propagation problems.

• 한국전산구조공학회:학술대회논문집
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• 한국전산구조공학회 2003년도 봄 학술발표회 논문집
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• pp.288-295
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• 2003

An adaptive procedure in finite element analysis is presented by p-refinement of meshes in conjunction with a posteriori error estimator that is based on the recovery technique. In case of the recovery technique, the SPR(superconvergent patch recovery) approach has been modified for p-adaptive mesh refinement. The strategy of finding a nearly optimal distribution of polynomial degrees on a fixed finite element mesh is discussed such that a particular element has to be refined automatically to obtain an acceptable level of accuracy by increasing p-levels non-uniformly. To verify the proposed algorithm, the limit value approach is proposed which utilizes the exact strain energy computed from the extrapolation equation. A new pre-processor is developed for the p-version finite element program in which the vector graphic editor is used for the automatic generation of node connection and coordinate by halfedge solid data structure according to uniform or nonuniform p-distribution. The general 2-D algorithm is also developed to generate face modes and internal modes in accordance with different mesh types. The quality of the error estimator is investigated with the help of two mumerical examples. The results show that the sequences of p-distributions obtained by the proposed error indicator closely follow the optimal trajectory.

• 대한기계학회논문집A
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• 제25권6호
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• pp.1004-1014
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• 2001

The fully automatic algorithm from initial finite element mesh generation to remeshing in two dimensional geometry is introduced using bubble packing method (BPM) for finite element analysis. BPM determines the node placement by force-balancing configuration of bubbles and the triangular meshes are made by Delaunay triangulation with advancing front concept. In BPM, we suggest two node-search algorithms and the adaptive/recursive bubble controls to search the optimal nodal position. To use the automatically generated mesh information in FEA, the new enhanced bandwidth minimization scheme with high efficiency in CPU time is developed. In the remeshing stage, the mesh refinement is incorporated by the control of bubble size using two parameters. And Superconvergent Patch Recovery (SPR) technique is used for error estimation. To verify the capability of this algorithm, we consider two elasticity problems, one is the bending problem of short cantilever beam and the tension problem of infinite plate with hole. The numerical results indicate that the algorithm by BPM is able to refine the mesh based on a posteriori error and control the mesh size easily by two parameters.

• Journal of Microbiology and Biotechnology
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• 제16권1호
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• pp.141-144
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• 2006

An antibody layer was fabricated to detect Escherichia coli O157:H7. The micropattern of 16-mercaptohexadecanoic acid (16-MHDA) as alkylthiolate was formed on the gold surface by using the PDMS stamp with microcontact printing $({\mu}CP)$ techniques. In order to form antibody patterns on the template, protein G was chemically bound to the 16-MHDA patterns, and antibody was adsorbed on a self-assembled protein G layer. The formation of the 16-MHDA micropattern, self-assembled protein G layer and antibody pattern on Au substrate was confirmed by surface plasmon resonance (SPR) spectroscopy. Finally, the micropatterning method was applied to fabricate the antibody probe for detection of E. coli O157:H7, and monitoring of antigen by using this probe was successfully achieved.

• Korean Journal of Chemical Engineering
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• 제36권6호
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• pp.975-980
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• 2019

Infrared (IR) spectroscopy is a powerful technique for observing organic molecules, as it combines sensitive vibrational excitations with a non-destructive probe. However, gaseous volatile compounds in the air are challenging to detect, as they are not easy to immobilize in a sensing device and give enough signal by themselves. In this study, we fabricated a thin nanocrystalline metal-organic framework (nMOF) film on a surface plasmon resonance (SPR) substrate to enhance the IR vibration signal of the gaseous volatile compounds captured within the nMOF pores. Specifically, we synthesized nanocrystalline HKUST-1 (nHKUST-1) particles of ca. 80 nm diameter and used a colloidal dispersion of these particles to fabricate nHKUST-1 films by a spin-coating process. After finding that benzene was readily adsorbed onto nHKUST-1, an nHKUST-1 film deposited on a plasmonic Au substrate was successfully applied to the IR detection of gaseous benzene in air using surface-enhanced IR spectroscopy.

• 한국방사선학회논문지
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• 제12권5호
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• pp.549-555
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• 2018

방사선 영상 기술은 피사체의 조성 및 두께에 따라 변화되는 X선의 흡수계수 차이를 기반으로 형성되는 대조도를 영상화하는 기술로서 영상 검출기에 입사하는 1차선 뿐 만 아니라 산란선이 영상 품질에 큰 영향을 미친다. 이에 본 연구에서는 피사체 두께, 조사야 변화에 따라 발생하는 산란선이 영상 품질에 미치는 영향을 고찰하고자 몬테카를로 시뮬레이션을 통하여 FSR 및 SPR 분석을 수행하였다. 연구 결과, 피사체 두께에 따른 FSR은 최대 15.3%p, SPR은 2.00 ~ 4.54로 분석되었으나, 조사야 변화에 대해서는 일정한 값을 유지하는 것으로 분석되었다. 이러한 결과를 바탕으로 피사체 두께는 영상 품질에 영향을 미치는 인자로서 고려되어야 하지만, 조사야는 영상 품질에 영향을 미치지 못하는 인자임을 검증하였다. 이러한 본 연구 결과는 영상 품질 개선을 위한 산란선에 대한 기초 자료로서 활용할 수 있을 것으로 사료된다.

• 한국전산구조공학회논문집
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• 제20권5호
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• pp.533-541
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• 2007

계층적 p-세분화를 위해 Zienkiewicz-Zhu 오차평가법이 약간 수정되었으며, 이 방법의 유효성을 보이기 위해 휨을 받는 개구부를 갖는 Reinssner-Mindlin $C^{\circ}$-평판에 적용하였다. 유한요소해석상의 적응적 체눈을 결정하는 단계는 초수렴 팻취 복구기법에 기초를 둔 사후오차평가자와 연계된 p-세분화에 의해 제안되었다. 요소내의 변위장을 정의하기 위해 적분형 르장드르 고차 형상함수가 사용되는 반면 복구응력을 보간하기 위해 파스칼의 삼각수에 기초를 둔 같은 차수의 고차다항식이 사용되는 이유로 수정 Z/Z 오차평가는 종래의 방법과 다소 차이를 보여준다. 가우스 적분점에서의 응력을 최적화하기 위해 필요한 다항식으로 표현되는 응력함수를 얻기 위해 최소제곱법이 사용되었다. 고정된 요소망에 거의 최적의 형상함수 차수의 분배를 찾기 위한 전략이 논의되었는데, 허용되는 정확도를 얻을 수 있을 때까지 각 요소마다 형상함수의 차수를 불균등하게 증가시키는 방법으로, 소위 최적의 선택적 p-분배를 자동으로 결정하도록 되어있다. 위의 사항들을 L-형 평판 해석에 적용한 결과, 적응적 p-체눈설계 단계가 진행됨에 따라 자유도의 증가에 따라 오차량은 급격히 감소되는 것을 알 수 있었고, 제안된 오차 지시자에 의한 적응적 p-체눈 세분화는 최적 p-분배 진행방향에 근접하는 것을 볼 수 있었다.