• 제어로봇시스템학회:학술대회논문집
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• 제어로봇시스템학회 2002년도 ICCAS
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• pp.62.5-62
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• 2002

The main purpose of this paper is to identify the important parameters and to examine their relations to one another while gantry crane structure was modeled. The important elements of the structural analysis are included, such as the stiffness matrix and its relations to the degrees of freedom, the displacement, and frequency responses. To investigate these relations, the parametric modeling of a dynamic system is solved by using the finite element method (ANSYS-Program). Furthermore, EXPRESS schema and C-FAR (change favorable representation) are described how to change the frame length of gantry crane which influences other elements. Since this relationship is established, the results may...

• 한국공작기계학회논문집
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• 제13권2호
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• pp.120-126
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• 2004

This study proposed the analysis of mass position detection due to the change of the mass and strifeless of structure by using the original and modified dynamic characteristics. The method is applied to examples of the cantilevers beam and the 3 degrees of freedom system by modifying the mass. The predicted detection of the mass positions and magnitudes are in good agrement with the present study from the structural reanalysis using the modified mass.

• 한국주조공학회지
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• 제16권6호
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• pp.537-549
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• 1996

This study aims at investigating the correlation of microstructure and mechanical properties of the AZ91 Mg/Al borate whisker composites fabricated by squeeze csting technique with a variation of applied pressure. Microstructure observation and in-situ fracture tests were conducted on the composites to identify the microfracture process. Detailed microstructural analyses indicated that the grain refinement could be achieved with applied pressure and the little change in volume fraction on reinforcing whiskers could be carried out. It was also found clearly from in-situ observation of crack initiation and propagation that in the composite processed by the lower applied pressure, microcracks were initiated earily at whisker/matrix interfaces, thereby resulting in the drop in strength. In the composite processed by the higher applied pressure, on the other hand, planar slip lines were well developed in the matrix, and then propagated through whiskers without whisker/matrix decohesion. Thus, the effect of the applied pressure on microstructure and mechanical properties can be explained by grain refinement, increased amounts of reinforcements, and improvement of whisker/matrix interfacial strength as the applied pressure in increased.

• 한국정밀공학회지
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• 제14권8호
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• pp.137-145
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• 1997

A two-dimensional program for the analysis of bimaterial inclusion has been developed using the bound- ary element method. In order to study the effects of circular inclusion on the stress field of the crack tip, numerical analysis was performed for the straight crack of finite length around the symmetric circular inclusion whose modulus of elasticity was different from that of the matrix material. In the case of inclusion whose stiffness was smaller than that of the matrix material, the stress intensity factor was found to increase as the crack enamated. The stress intensity factor was uninfluenced from the radial change in inclusion and remained constant for the stiffness equivalent to the matrix materials, where as it decreased for the inclusion with larger stiffness. For the vareation in the distance of the inclusion, a small increase in the stress intensity factor was observed for the case with small or equal stiffness compared with the matrix materials. The inclusion with larger stiffness showed a gradual decrease in the strss intensity factor as the crack emanated.

• 치과방사선
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• 제6권1호
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• pp.15-18
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• 1976

The authors has observed the effect of X-ray irradiation on the dentin matrix formation of the albino rat fetuses. The lower abdomen of the pregnant ratswere exposed to X-ray on the 9 1/2th day of gestation, respectively 150, 250 and 350 rads. The fetuses of the right sides of the same pregnant rats which were not exposed to X-ray were as controls. The results were as follows: 1) In the 150 rads irradiated fetuses, predentin formation was identical with control groups, but the arrangement of odontoblasts was distorted, subodontoblastic layer was condesed with pulp cells and blood capillaries were enlarged. 2) In the 250 rads irradiation, dentin matrix was imperfact or osteodentin was occured. Short columnar or cuboidal odontoblasts were presented and pulp cells were dispersed. Blood capillaries were cogested. 3) 350 rads irradiated fetuses showed osteodentin matrix and numerous degenerated odontoblasts. Their dental papilla showed reticular atrophy and enlarged capillary.

• 한국주조공학회지
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• 제24권2호
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• pp.108-114
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• 2004

$Al_2O_3$, SiC reinforced Al matrix composites were fabricated by centrifugal spray casting method and their wear resistance characteristics have been studied. Particles are generally uniformly distributed in the microstructure of as-cast specimens. In order to investigate the effect of secondary deformation, hot rolling was performed for each specimen of pure Al matrix composites with a reduction of 10, 20, 30, 40 and 50% at $400{\sim}500^{\circ}C$, respectively. Microstructure of specimen showed that particle distribution density and hardness increased because of increasing of reduction ratio. Wear test with a various sliding velocity of 1.98, 2.38, 2.88 and 3.53m/sec showed that the wear resistance characterization of composite improved remarkably compared to the normal alloy and performs without reinforced particles. Microstructural observation for the worn surface of pure Al specimens without particles showed that a change in wear mechanism seemed to separate layer by surface fatigue. In other case of Al composite reinforced with $Al_2O_3$ and SiC, the grinder type of wear mechanism was shown.

• 한국패류학회지
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• 제3권1호
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• pp.3-14
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• 1987

The electrophoretic and innunological cnalyses of organic matrices in the shells of freshwater bivalves were made in order to dlucidate the biochemical characteristics and species-specific differinces of the applied shells, The water-soluble and insoluble matrices of four species of freshwater bivalves, Andodonta fukudai, Unio douglasiae, Lanceolaria and Chrbicula fluminea, were used as analytical materials, There was non-identity in immuno affinity between anti soluble matrix(anti-Sm) and anti insoluble matrix(anti-ISM)sera against the organic matrix of Andodnta fukudai. The SMs of four species (S. fukudai, U.douglasiae, L. acrorhyncha, and C. fluminea) showed the differences in the precipitate arcs at the level of family, though ISMs did mot show differences. In the electrophoretic analysis, all foru species had two SDS-electrophoretic bands of SM, of which molecular wights appeared to be lower than 55,000, shereas the native organic matrices of foru speceis had higher molecular weighrs than those from SDS-dldctrophoresis. Only calcium ion among many ions in extrapallial fluid(EPF) caused SM to change into insoluble molecules, thus the EPF pretreated with Ca++did not form the precipitate arc when did the immuno diffusion whth anti SM serum. ISM precursor may be polymerized into macromolecules like periostracin, a precusor of periostracum, judging from the similat polymerization patterns in 0.1M Tris formate buffer(pH 3); they may be made insoluble macromolecules due to their strong natrue of hydrophobicity.

• 한국전산구조공학회논문집
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• 제17권4호
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• pp.351-363
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• 2004

비보존력을 받는 보-부재의 질량행렬, 탄성강도행릴, circulatory비보존력의 방향변화로 인한 load correction강도행력, 그리고 Winkler 및 Pasternak지반강도행렬을 고려한 운동방정식을 유도하고 divergence 및 flutter에 의한 안정성 해석을 수행한다. 또한 내적 및 외적 감쇠계수를 운동방정식에 포함시킴으로써 감쇠효과를 고려하고, 2차 고유치문제의 해법(quadratic eigen problem solution)을 적용하여 flutter에 미치는 영향을 조사한 후, Beck's column, Leipholz's column 및 Hauger's column에 대하여 비보존력의 방향파라미터 ${\alpha}$에 대한 임계하중의 영향, 내적 및 외적 감쇠계수 및 Winkler 및 Pasternak지반에 의한 임계하중의 영향을 각각 조사한다.

• 제어로봇시스템학회논문지
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• 제22권6호
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• pp.411-416
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• 2016

This paper presents the design methodology of an unknown input observer for Lipschitz nonlinear systems with unknown inputs in the framework of convex optimization. We use an unknown input observer (UIO) to consider both nonlinearity and disturbance. By deriving a sufficient condition for exponential stability in the linear matrix inequality (LMI) form, existence of a stabilizing observer gain matrix of UIO will be assured by checking whether the quadratic stability margin of the error dynamics is greater than the Lipschitz constant or not. If quadratic stability margin is less than a Lipschitz constant, the coordinate transformation may be used to reduce the Lipschitz constant in the new coordinates. Furthermore, to reduce the maximum singular value of the observer gain matrix elements, an object function to minimize it will be optimally designed by modifying its magnitude so that amplification of sensor measurement noise is minimized via multi-objective optimization algorithm. The performance of UIO is compared to a nonlinear observer (Luenberger-like) with an application to a flexible joint robot system considering a change of load and disturbance. Finally, it is validated via simulations that the estimated angular position and velocity provide true values even in the presence of unknown inputs.

• Journal of Pharmaceutical Investigation
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• 제20권2호
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• pp.79-88
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• 1990

A numerical model for diffusion and dissolution controlled transport from dispersed matrix is presented. The rate controlling process for transport is considered to be diffusion of drug through a concentration gradient coupled with time-dependent surface change and/or disappearance of the dispersed drug in response to the dissolution. The transport behavior of drug was explained in terms of ${\nu}$ parameter: ${\nu}$ value means a ratio of diffusion time constant and dissolution time constant. This general model has wide range of application from where release is controlled by the diffusion rate to where release is governed by the dissolution rate. Based on this model, theoretical drug concentration, particle size distributions in the polymer matrix system and the resulting release rate were also investigated.