• Transactions of the Korean Society of Mechanical Engineers
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• v.17 no.7 s.94
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• pp.1772-1782
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• 1993

The characteristics of metal matrix composite under dynamic tension at high strain rates up to the order of $10^3/sec$ is studied by using newly developed apparatus. The composite material processed in this research is aluminum-alumina metal matrix composites, arid fabricated by compocasting with the fiber volume fraction from 5 to 20%. The whisker and matrix material used in this paper were ${\delta}-Al_2O_3$ and Al-6061, respectively. The mechanical tests performed in this research are low and high strain rate tensile test. At low strain-rate tensile test, the modulus of elasticity and the ultimate tensile strength of the composites were improved about 77 pct. and 55 pct., respectively comparing with the unreinforced materials. At strain-rate from $10^{-3}\;to\;10^3/s$, the effect of strain-rate on the modulus, ultimate strength, flow stress is determined. Also the effect of strain rate on the modulus, ultimate tensile strength, flow stress and elongation to failures were investigated.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2014.10a
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• pp.288-291
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• 2014

MRE(Magneto-rheological Elastomer) is a material which shows reversible and various modulus in magnetic field. Comparing to conventional rubber vibration isolator, MREs are able to absorb broader frequency range of vibration. These characteristic phenomena result from the orientation of magnetic particle (i.e., chain-like formation) in rubber matrix. In this study, Silicon was used as a matrix in order to manufacture MREs. Magnetic reactive powder(MRP), having rapid magnetic reaction, was selected as a magnetic particle to give magnetic field reactive modulus. The mechanical properties of manufactured MREs were measured with the application of magnetic field. The analysis of MR effect was carried out by FFT analyzer with various induced magnetic field. As the addition of CIP and induced magnetic field intensity increased, increment of MR effect was observed.

• Restorative Dentistry and Endodontics
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• v.38 no.4
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• pp.194-203
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• 2013

Objectives: To investigate the effect of enamel matrix derivative (EMD) on periodontal healing of replanted teeth in animal models. Materials and Methods: The authors searched MEDLINE, PubMed, EMBASE, Cochrane Library, Web of Knowledge and Scopus for articles published up to Oct 2012. Animal studies in which EMD was applied in transplanted or replanted teeth with adequate controls and histological data were considered. Normal periodontal healing or root resorption determined by histology after EMD was applied in replanted teeth with adequate controls was used as outcome measures. The following search strategy was used: ('Emdogain' OR 'enamel matrix proteins' OR 'enamel matrix derivative') AND ('avulsion' OR 'transplantion' OR 'autotransplantation' OR 'replantation'). Results: Six animal studies were included in the final review. There was great heterogeneity in study design among included studies. Two studies with similar study designs were identified and analyzed by a meta-analysis. The pooled estimates showed a significantly higher normal healing and surface resorption and significantly less inflammatory and replacement resorption in EMD-treated groups compared with non-EMD-treated groups. Conclusions: With the limitations of this systematic review, the use of EMD led to greater normal periodontal healing and surface root resorption and less inflammatory and replacement root resorption in the presence of periodontal ligaments. However, no definite conclusion could be drawn with regard to the effect of EMD on periodontal healing and root resorption when no periodontal ligaments exist.

• Bulletin of the Korean Chemical Society
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• v.34 no.5
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• pp.1435-1440
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• 2013

To investigate the influence of the carbon matrix on the electrochemical performance of Si/C composites, four types of Si/C composites were prepared using graphite, petroleum coke, pitch and sucrose as carbon precursors. A ball mill was used to prepare Si/C blends from graphite and petroleum coke, whereas a dispersion technique was used to fabricate Si/C composites where Si was embedded in disordered carbon matrix derived from pitch or sucrose. The Si/pitch-based carbon composite showed superior Si utilization (96% in the first cycle) and excellent cycle retention (70% after 40 cycles), which was attributed to the effective encapsulation of Si and the buffering effect of the surrounding carbon matrix on the silicon particles.

• Journal of Pharmaceutical Investigation
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• v.30 no.2
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• pp.93-98
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• 2000

In order to evaluate the effect of fabrication methods on the controlled release of an antibiotic from a polymeric device, two types of polyurethane-cefadroxil matrix were prepared by the solvent casting method or the freeze drying method, using bovine serum albumin as a pore former. The amount of cefadroxil released from various formulations at $37^{\circ}C$ was measured by HPLC. The duration of antimicrobial activity of matrices against S. aureus was evaluated by measuring the diameters of the inhibition zone. The morphology of the matrices was investigated by scanning electron microscopy (SEM). Changing the fabrication method could alter the release rate of cefadroxil from the matrix. The matrix fabricated by the freeze drying method had more porous inner structure and showed higher release rate than that prepared by the solvent casting method. However, the duration of antimicrobial activity was shorter when the matrix was fabricated by the freeze drying method.

• Korean Journal of Optics and Photonics
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• v.9 no.1
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• pp.5-8
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• 1998

In calculating the light propagation in inhomogeneous uniaxial materials by using a conventional $4{\times}4$ matrix method, Fabry-Perot effect is caused by inherent multiple internal reflections at interfaces for monochromatic light source. In this paper we propose an apodization method by which we can eliminate in negligible time the interference fringe in the $4{\times}4$ matrix optics. For a cell with k abrupt interfaces, the new apodization method can be implemented simply by, at maximum, (k+1) addtional $4{\times}4$ matrix multiplications in calculating the complete transfer matrix of the cell.

• International Journal of Control, Automation, and Systems
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• v.3 no.2
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• pp.159-165
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• 2005

This paper designs observers for matrix second-order linear systems on the basis of generalized eigenstructure assignment via unified parametric approach. It is shown that the problem is closely related with a type of so-called generalized matrix second-order Sylvester matrix equations. Through establishing two general parametric solutions to this type of matrix equations, two unified complete parametric methods for the proposed observer design problem are presented. Both methods give simple complete parametric expressions for the observer gain matrices. The first one mainly depends on a series of singular value decompositions, and is thus numerically simple and reliable; the second one utilizes the right factorization of the system, and allows eigenvalues of the error system to be set undetermined and sought via certain optimization procedures. A spring-mass system is utilized to show the effect of the proposed approaches.

• YAKHAK HOEJI
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• v.31 no.1
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• pp.25-32
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• 1987

The effect of loading dose, plasticiser and PVA molecular weight on naproxen release from hydrophilic polymer matrix was examined. Hydrophilic polymer matrix was prepared with PVA and PVP by adding glycerine as plasticiser. The release of naproxen from polymer matrix was determined in phosphate buffer medium. The release rate of naproxen from the polymer matrix increased as drug loading dose and plasticiser percentage increased. Raproxen released from the polymer matrix showed the time square root kinetics. Without changing the release-pattern, the release rate of naproxen could not be changed by varying molecular weight of PVA. Linearly released time range increased as drug loading dose increased, whereas decreased as plasticiser percentage increased up to 30%.

• Carbon letters
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• v.19
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• pp.47-56
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• 2016

In this study, the fracture behavior of a thermoplastic-modified epoxy resin reinforced with continuous carbon fibers for two levels of fiber-matrix adhesion was performed. A carbon fiber with commercial sizing was used and also treated with a known silane, (3-glycidoxy propyl trimethoxysilane) coupling agent. Toughness was determined using the double cantilever test, together with surface analysis after failure using scanning electron microscope. The presence of polysulfone particles improved the fracture behavior of the composite, but fiber-matrix adhesion seemed to play a very important role in the performance of the composite material. There appeared to be a synergy between the matrix modifier and the fiber-matrix adhesion coupling agent.

• Transactions of the Korean Society of Mechanical Engineers
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• v.17 no.8
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• pp.1963-1970
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• 1993

A simple technique to decouple the modal equations of motion of a linear nonclassically damped system is to neglect the off-diagonal elements of the modal damping matrix. This is called the decoupling approximation. It has generally been conceived that smallness of off-diagonal elements relative to the diagonal ones would validate its use. In this study, the relationship between elements of the modal damping matrix and the error arising from the decoupling approximation is explored. It is shown that the enhanced diagonal dominance of the modal damping matrix need not diminish the error. In fact, the error may even increase. Moreover, the error is found to be strongly dependent on the exitation. Therefore, within the practical range of engineering applications, diagonal dominance of the modal damping matrix would not be sufficient to supress the effect of modal coupling.