• Journal of Pharmaceutical Investigation
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• 제22권2호
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• pp.149-153
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• 1992

The applicability of sodium alginate as a carrier of 5-fluorouracil as an oral delivery system was investigated. Hydrophobicity of sodium alginate was controlled by introducing cetyl group to this polymer. The effects of degree of esterification for n-cetyl partial ester on the rate of release of 5-fluorouracil in artificial gastric juice and artificial intestinal juice were examined. The release rete of the drug in the gastric juice was mainly affected by the diffusion of the drug. The release rate of the drug in the intestinal juice could be controlled by the degree of esterification. The alginate matrices may be a valuable addition as the carrier of 5-fluorouracil for an oral delivery system.

• 제어로봇시스템학회:학술대회논문집
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• 제어로봇시스템학회 1994년도 Proceedings of the Korea Automatic Control Conference, 9th (KACC) ; Taejeon, Korea; 17-20 Oct. 1994
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• pp.162-167
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• 1994

An effective and disturbance suppressible controller can be obtained by assigning the left eigenstructure (eigenvalues/left eigenvectors) of a system. However, the disturbance decouplability is governed by the right eigenstructure(eigenvalues/right eigenvectors) of the system. In this paper, in order to obtain a disturbance decouplable as well as effective and disturbance suppressible controller, the concurrent assignment scheme of the left and right eigenstructure is proposed. The biorthogonality property between the left and right modal matrices of a system well as the relations between the achievable right modal matrix and states selection matrices are used to develop the scheme. The proposed concurrent eigenstructure assignment scheme guarantees that the desired eigenvalues are achieved exactly and the desired left and right eigenvectors are assigned to the best possible(achievable) sets of eigenvectors in the least square sense, respectively. A numerical example is presented to illustrate the usefulness of the proposed scheme.

• 제어로봇시스템학회논문지
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• 제15권8호
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• pp.812-817
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• 2009

In this paper, a new method to design sliding surfaces using eigenstructure assignment is proposed. Most conventional methods for constructing the surfaces require special form like canonical or regular canonical form of system matrices. But the proposed method can be applied to arbitrary system matrices. Futhermore, the surface matrix, C can be decided for the matrix multiplication, CB to have a designated form. SVD is used to decide desirable eigenvectors explicitly. To verify the proposed algorithm, a sliding mode controller for a multivariable system with matched uncertainty is constructed. The controller is designed to guarantee minimum approach velocity to the sliding surface.

• Journal of Advanced Marine Engineering and Technology
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• 제22권2호
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• pp.174-180
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• 1998

Robust stability of discrete-time regulators which utilize state predictors to compensate computation delays is considered. Novel expressions for the return difference matrices and the complementary sensitivity matrices at the input and the output of the regulator are found to obtain simple bounds for unstructured perturbations. Robust stability for pertubations of the system matrix and /or the gain matrix is also considered. under certain restriction on the nominal system simple bounds for the pertubations are obtained directly from the characteristic equation. It is shown that as far as the effect of the computation delays concerns these bounds have explicit relation to those for the unstructured pertubations.

• The Journal of the Acoustical Society of Korea
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• 제18권4E호
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• pp.20-25
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• 1999

To get accurate natural frequencies of an engine crankshafts, finite element equations of motion are developed, taking real geometries of the shaft into account. For the crankshaft with wide crank webs, a specialized rotating web element is developed. This includes the effects of rotary inertia, gyroscopic moment, and shear. After the finite element equations are constructed, eigenvalues are extracted from the system equations to get natural frequencies, based on the Sturm sequence method which exploits the banded forms of the system matrices to reduce computations. The scheme developed can be used for the free vibration analysis of any type of spinning structures which include skew symmetric gyroscopic moment matrix in the system matrices. The results are compared with experimental data in order to confirm the study.

• Structural Engineering and Mechanics
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• 제33권3호
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• pp.307-323
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• 2009

This article presents the differential system that governs the mechanical behaviour of a curved-beam element, with varying cross-section area, subjected to generalized load. This system is solved by an exact procedure or by the application of a new numerical recurrence scheme relating the internal forces and displacements at the two end-points of an increase in its centroid-line. This solution has a transfer matrix structure. Both the stiffness matrix and the equivalent load vector are obtained arranging the transfer matrix. New structural matrices have been defined, which permit to determine directly the unknown values of internal forces and displacements at the two supported ends of the curved-beam element. Examples are included for verification.

• 대한전기학회:학술대회논문집
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• 대한전기학회 1983년도 하계학술회의강연.논문초록집
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• pp.135-138
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• 1983

This paper studies a variable structure adaptive model following control system which can control a plant in which the parameters of the controlled plant can not be estimated because they vary with time and in which the controlled plant has noise. The values of the feedback gain matrices for given states are obtained the equivalent control law, and the adaptive controller has been designed using the adaptive mechanism which switches the matrices. The adaptive controller minimizes the state error vector, that is, the difference between the state vector of the model and the state vector of the controlled plant. A controlled plant which has time varying parameters, a controlled plant which has only noise, and a controlled plant which has both have been controlled by the designed adaptive controller. The continuous single input-output system has been analysed by computer. This control system may be used to control practical systems by the addition of a microcomputer.

• 한국해양공학회지
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• 제14권2호
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• pp.7-12
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• 2000

This paper presents a non-regressor based adaptive control scheme for the trajectory tracking of underwater vehicle-mounted manipulator systems(UVMS). The adaptive control system includes a class of unmodeled effects is applied to the trajectory control of an UVMS. The only information required to implement this scheme ios the upper bound and lowe bound of the system parameter matrices the upper bound of unmodeled effects the number of joints the position and attitude of the vehicle and trajectory commands. The adaptive control law estimates control gains defined by the combinations of the bounded constants of system parameter matrices and of a filtered error equation. To evaluate the performance of the non-regressor based adaptive controller computer simulation was performed with a two-link planar robot model mounted on an underwater vehicle. The hydrodynamic effects acting on the manipulator are included. It is assumed that the vehicle's motion is slow and can be predicted with a proper compensator.

• 한국통신학회논문지
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• 제27권10C호
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• pp.887-901
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• 2002

소프트웨어 관리 모델은 크게 소프트웨어 프로젝트 견적 모델과 소프트웨어 설계평가 모델, 소프트웨어 복잡성 모델, 소프트웨어 신뢰도 성장 모델, 소프트웨어 프로세스 개선 모델 등으로 나누어진다. 그 중에서도 개발된 소프트웨어를 정량적으로 분석하여 평가하는 모델이 소프트웨어 복잡도 모델이다. 즉, 소프트웨어를 객관적으로 관리하는데 있어서 정량적인 판단 기준이 필요하다. 그렇기 때문에 소프트웨어 복잡성 모델(software complexity model)은 소프트웨어의 복잡성에 대한 정량적인 평가에 응용할 목적으로 도입되었으며, 소프트웨어 복잡성 측정시 이 결과를 소프트웨어 관리(software management)의 기준에 이용하는데 있어서 품질이나 생산성에 대한 영향을 제공할 때 정량적이고 명확히 할 필요가 있기 때문이다. 다시 말해서 복잡한 프로그램에는 에러가 많이 포함될 가능성이 높고 또 개발비용(source cost)도 높다는 것을 경험적으로 알 수 있다. 이러한 관계가 성립되지 않는 경우에는 소프트웨어의 효과적인 관리가 곤란하다. 본 논문은 이런 관점에서 대표적인 소프트웨어 복잡성 모델에 대한 적용법에 대해 기술하고 개발중인 교환시스템의 소프트웨어에 대해 volume metrics와 process complexity metrics 방법, 제어구조 및 인터페이스 구조 방법에 대한 분석 결과와 시스템 개발을 수행하는 과정에서 발생되고 있는 문제점들에 대해 다각도로 분석을 하여 이를 유사한 시스템 연구개발 및 프로젝트 관리에 활용하고자 한다.

• Journal of Pharmaceutical Investigation
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• 제34권6호
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• pp.471-475
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• 2004

Tamsulosin has been frequently used for the treatment of benign prostatic hyperplasia. To avoid dose-dependent side effects of tamsulosin upon oral administration, the development of sustained-release delivery system is required, that can maintain therapeutic drug levels for a longer period of time. The aim of this study was therefore to formulate sustained-release tamsulosin matrix tablets and assess their formulation variables. We designed enteric coated sustained-release tamsulosin matrices to fulfill above statement. Aqueous microchannels in the enteric film need to be formed in order to obtain tamsulosin release even in an acidic environment such as gastric region. In the sustained-release tamsulosin matrix, low viscosity hydroxypropylmethylcellulose was used as a rate controller. Povidone K30 was also added to the matrices to facilitate water uptake so that a decrease in the release rate of tamsulosin as time elapses was prevented, possibly leading to pseudo zero-order release of the drug. The matrices were enteric-coated with hydroxypropylmethylcellulose phthalate (HPMCP), along with povidone K30 as an aqueous microchannel former. With the aqueous microchannels formed within the enteric film, tamsulosin could be released in an acidic condition. The release of tamsulosin decreased with increasing thickness of HPMCP membrane while the release rates of tamsulosin from those having different HPMCP thickness in pH 7.2 aqueous media were not considerably different, indicating that the enteric film was promptly dissolved at pH 7.2. These results clearly suggest that the sustained-release oral delivery system for tamsulosin could be designed with satisfying drug release profile approved by the KFDA.