• 한국정보디스플레이학회:학술대회논문집
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• 2003.07a
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• pp.362-364
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• 2003

In this study, sintering behavior of closed-cell type barrier ribs formed via capillary molding route was examined. Sintering of the molded barrier ribs revealed asymmetric shrinkage, leading to distortion of the cells. The effects of the parameters such as solid loading in the paste, presintering temperature, and morphology of the barrier ribs on the sintering shrinkage of the barrier ribs were investigated.

• YAKHAK HOEJI
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• v.30 no.6
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• pp.306-310
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• 1986

The release of heparin from monolithic devices composed of different ratios of polyethylene oxide(PEO MW 20,000) and polydimethylsiloxane was investigated. Water soluble PEO plended into the polydimethylsiloxane proved a controlled release of heparin. The release rate of heparin could be controlled by varying the content of PEO and loading dose of heparin. The release rate of heparin from the devices increased as the content of PEO and heparin in the devices increased. The release rate of heparin from devices were related to nature of solute(ionic strength) and temperature. The release mechanism may be associated with the creation of pore or domine through the devices the water-uptake and the change in the physical structure of the polydimethysiloxane network.

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 1999.03b
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• pp.86-89
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• 1999

Structural analysis of die set in cold forging is conducted by the finite element method and the results are introduced in this paper. The problem formulation is introduced in detail. In the approach, amount of shrink fit is controlled by thermal load, i.e., temperature difference between die insert and shrink fits. The loading conditions are extracted automatically from a forging simulator. An application example is given.

• Proceedings of the KSME Conference
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• 2000.11a
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• pp.426-431
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• 2000

A decoupled thermo-piezoelectric-mechanical model of composite laminates with surface bonded piezoelectric actuators, subjected to externally applied load, temperature change load, electric field load is developed. The governing differential equations are obtained by applying the principle of free energy and variational techniques. A higher order zigzag theory displacement field is employed to accurately capture the transverse shear and normal effects in laminated composite plates of arbitrary thickness.

• Journal of Electrical Engineering and Technology
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• v.9 no.5
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• pp.1724-1728
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• 2014

Heat sink has been used to help an electrical device operate in normal temperature condition. But heat sink radiates unwanted electromagnetic wave, which may cause electromagnetic interference problem. A resistance loaded grounding technique is proposed to reduce electromagnetic wave radiation by a heat sink. Numerical simulations are accomplished to find optimal loading resistance. Also electromagnetic fields radiated by from a heat sink are measured and compared with the simulation results. The test results verify the usefulness of the proposed technique.

• Animal cells and systems
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• v.7 no.4
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• pp.289-294
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• 2003

To quantify nutrient loading from emergent macrophytes through leaching in the littoral zones of Paldang Reservoir, we conducted incubation experiments using leaf litter of the emergent macrophyte, Zizaniz latifolia. To separate the leaching process from microbial decay, we used $HgCl_2$ to suppress microbial activity during the experiment. We measured electric conductivity, absorbance at 280nm, total nitrogen and dissolved inorganic nitrogen, total phosphorus and soluble reactive phosphorus, Na, K, Mg and Ca amounts in leaf litter and in water. In addition, we examined the effects of water temperature and ion concentrations of ambient water on the leaching process. A total of 6% of the initial ash-free dry mass of leaf litter was lost due to leaching during incubation (four days). Electric conductivity and A280 continued to increase and saturate during the incubation. To compare reaching rates of different nutrients, we fitted leaching dynamics with a hyperbolic saturation function [Y=AㆍX/(B+X)]. From these fittings, we found that ratios of leaching amounts to nutrient concentration in the litter were in the order of K > Na > Mg > P > Ca > N. Leaching from leaf litter of Z. latifolia was dependent on water temperature while it was not related with ion concentrations in the ambient water. Our results suggest that the leaching process of nutrients, especially phosphorus, from aquatic macrophytes provides considerable contribution to the eutrophication of the Paldang Reservoir ecosystem.

• Advances in aircraft and spacecraft science
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• v.5 no.1
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• pp.141-164
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• 2018

In this paper, the thermal effect on buckling and free vibration characteristics of functionally graded (FG) size-dependent Timoshenko nanobeams subjected to an in-plane thermal loading are investigated by presenting a Navier type solution for the first time. Material properties of FG nanobeam are supposed to vary continuously along the thickness according to the power-law form and the material properties are assumed to be temperature-dependent. The small scale effect is taken into consideration based on nonlocal elasticity theory of Eringen. The nonlocal equations of motion are derived based on Timoshenko beam theory through Hamilton's principle and they are solved applying analytical solution. According to the numerical results, it is revealed that the proposed modeling can provide accurate frequency results of the FG nanobeams as compared to some cases in the literature. The detailed mathematical derivations are presented and numerical investigations are performed while the emphasis is placed on investigating the effect of the several parameters such as thermal effect, material distribution profile, small scale effects, aspect ratio and mode number on the critical buckling temperature and normalized natural frequencies of the temperature-dependent FG nanobeams in detail. It is explicitly shown that the thermal buckling and vibration behaviour of a FG nanobeams is significantly influenced by these effects. Numerical results are presented to serve as benchmarks for future analyses of FG nanobeams.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.26 no.6
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• pp.1069-1076
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• 2002

The high temperature creep behavior of heat machine systems such as aircraft engines, boilers and turbines in power plants and nuclear reactor components have been considered as an important and needful fact. There are considerable research results available for the design of high temperature tube materials in power plants. However, few studies on the Initial Strain Method (ISM) capable of securing repair, maintenance, cost loss and life loss have been made. In this method, 3 long time prediction Of high temperature creep characteristics can be dramatically induced through a short time experiment. The purpose of present study is to investigate the high temperature creep lift of Udimet 720, SCM 440-STD61 and 1Cr-0.5Mo steel using the ISM. The creep test was performed at 40$0^{\circ}C$ to $700^{\circ}C$ under a pure loading. In the prediction of creep life for each materials, the equation of ISM was superior of Larson-Miller Parameter(LMP). Especially, the long time prediction of creep life was identified to improve the reliability.

• Journal of Mechanical Science and Technology
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• v.18 no.9
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• pp.1604-1613
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• 2004

This paper presents an effective and reliable evaluation method for fracture strength and material degradation of the micro-structure of high temperature service steel weldment using advanced small punch (ASP) test developed from conventional small punch (CSP) test. For the purpose of the ASP test, a lower die with a minimized ${\Phi}$1.5 mm diameter loading ball and an optimized deformation guide hole of ${\Phi}$3 mm diameter were designed. The behaviors of fracture energy (E$\_$sp/), ductile-brittle transition temperature (DBTT) and material degradation from the ASP test showed a definite dependency on the micro-structure of weldment. Results obtained from ASP test were compared and reviewed with results from CSP test, Charpy impact test, and hardness test. The utility and reliability of the proposed ASP test were verified by investigating fracture strength, behavior of DBTT, and fracture location of each micro-structure of steel weldment for test specimen in ASP test. It was observed that the fracture toughness in the micro-structure of FL＋CGHAZ and ICHAZ decreased remarkably with increasing aging time. From studies of all micro-structures, it was observed that FGHAZ microstructure has the most excellent fracture toughness, and it showed absence of material degradation.

• Transactions of the Korean Society of Mechanical Engineers
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• v.18 no.11
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• pp.2860-2870
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• 1994

When crack are detected in aged turbine rotors of power plants, information on fracture resistance of the aged material at operating temperature is needed for determination of critical loading condition and residual life of the turbine. In this study, fracture toughness (J$_lc$) and tearing modulus(T$_mat$) of virgin and thermally degraded 1Cr-1Mo-0.25V steel, which is one of the most widely used rotor steels, were measured at 538.deg. C according to ASTM E813 and ASTM E1152, respectively. Five kinds of specimen with different degradation levels were prepared by isothermal aging heat treatment at $630^{\circ}C.$ It was observed that J$_lc$ and T$_mat$ value decreased as the degradation level increased. Analysis of microstructures using a scanning electron microscope showed that the decrement of J$_lc$ is related to segregation of impurities at grain boundaries. It was also verified that the DC electric potential drop method is accurate and reliable for crack length monitoring at elevated temperature.