• 한국디지털정책학회:학술대회논문집
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• 한국디지털정책학회 2005년도 춘계학술대회
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• pp.605-615
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• 2005

This paper represent a method of U-Learning based on advanced e-Learning. Ubiquitous computing configuration and advanced Information technology. As we know well, the 21th century is called knowledge based informational society. Many scholar stress that the improved 21th century's educational paradigm be able to success based on advanced educational paradigm. Therefore, we discuss the material for e-Learning fields including with necessity, vision, law, quality authorization etc. Also, we discuss the relational technologies including with meta data, standardization, identification etc. Finally, we propose a method for constructing the U-Learning based on advanced e-Learning and Ubiquitous computing configuration.

• E2M - 전기 전자와 첨단 소재
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• 제16권9호
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• pp.61.1-61
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• 2003

Stoichiometric, uniform, amorphous ZrO$_2$ films with an equivalent oxide thickness of ∼1.5nm and a dielectric constant of ∼18 were deposited by an atomic layer controlled deposition process on silicon for potential application in meta-oxide-semiconductor(MOS) devices. The conduction mechanism is identified as Schottky emission at low electric fields and as Poole-Frenkel emission at high electric fields. the MOS devices showed low leakage current, small hysteresis(〈50mV), and low interface state density(∼2*10e11/cm2eV). Microdiffraction and high-resolution transmission electron microscopy showed a localized monoclinic phase of ${\alpha}$-ZrO$_2$ and an amorphous interfacial ZrSi$\_$x/O$\_$y/ layer which has a correspondign dielectric constant of 11

• 한국세라믹학회지
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• 제17권4호
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• pp.213-216
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• 1980

A glass-ceramics material of composition %SiO_2$: 38.50, $Al_2O_3$: 26.00, $Na_2O$: 18.00, CaO: 6.00, MgO: 4.00, $TiO_2$: 7.50 was strengthened by coating a series of glazes$(SiO_2-B_2O_3-Al_2O_3-CaO-PbO-Na_2O-)$, which has lower thermal expansion coefficient than that of the glass-ceramics. The thermal expansion coefficient of the glazes ranges $80~90{\times}10^{-7}$cm/cm/$^{\circ}C$, whereas that of the glass-ceramics is $115{\times}10^{-7}$cm/cm/$^{\circ}C$. The glass-ceramics was identified to be composed of nepheline, carnegieite low form, and meta sodium silicate crystal by X-ray diffraction phase analysis. The glaze, having lower melting point and appropriate thermal expansion coefficient, was tried to be stable and good at secondary heat treatment.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2007년도 춘계학술대회A
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• pp.654-659
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• 2007

In this paper, the fatigue load spectrum for tilt rotor UAV is developed and fatigue analysis is achieved for flaperon joint. Tilt rotor UAV has two modes which are helicopter mode when UAV is taking off and landing and fixed wing mode when UAV is cruising. To make fatigue load spectrum, FELIX for helicopter mode and TWIST for fixed wing mode are used. And Fatigue analysis of flaperon joint is achieved using fatigue load spectrum we obtained. When S-N test data are analyzed, we use the Kriging meta model to get probability S-N curve for whole range of material life. The result which is life of flaperon joint obtained by suggested fatigue analysis procedure in this paper is compared with that obtained by MSC/Fatigue.

• 소성∙가공
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• 제16권6호
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• pp.438-442
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• 2007

Sidewall curl is the curvature that results from non-uniform through-thickness strain present in the sheet stamping process which involves material flow over a die radius. In order to understand and control curl for tight fit-up tolerances, an analytical model that can provide a reliable measure for the amount of curl would be very helpful. In this study, a model is developed based on the moment-curvature relationship during bending-under-tension operations. For the verification of analytical model, sidewall curl is experimentally measured after deformation of a strip using a bending-under-tension test system. The results show a consistent relationship between the theoretically predicted value and the experimentally obtained one, especially in regions of high curl.

• E2M - 전기 전자와 첨단 소재
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• 제7권2호
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• pp.94-99
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• 1994

The purpose of this work is to investigate the interface characteristics of hydrogenated amorphous silicon thin films prepared by PECVD and photo-induced CVD and to examine the annealing effects of ultraviolet irradiation on hydrogenated amorphous silicon thin films which were degraded by visible light illumination. The interface layer thickness of films deposited by photo-induced CVD was about 600-900.angs. while that by PECVD was about 1000-1300.angs.. These results can show that the quality of interface layer in photo induced CVD film is better than that in PECVD sample. The electrical properties are improved by ultraviolet irradiation on visible light soaked a-Si:H films using photo-CVD light sources, probably due to the fact that UV generates phonons in a-Si:H films and anneal the meta stable defects.

• 한국세라믹학회지
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• 제14권2호
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• pp.82-87
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• 1977

The material used in this experiment is Ha-Dong kaolin whichis composed of almost crystallographically pure meta-halloysite. It was grinded and passed through 250 mesh and 325 mesh. It was treated with oxalic acids and EDTA which are different in concentration. The samples in conical beaker were kept in laboratory incubator at $25^{\circ}C$ for a certain hours. The treated samples were stirred twice a day. The sample in the conditions as A-7 was kept in an autoclave under the pressure of 3 atmospheric. The samples suspended in each solution were kept for 1.5, 3 and 6 months. The transformation of crystals was detected by X-ray spectrometer, electron microscopy, and infrared spectrometer. The sample through 325 mesh compared with one through 250 mesh was transformed much more. It took for 6 months to transfer from halloysite to kaolinite in EDTA, and 3~4 months under 3 atms in autoclave at the same condition. In oxalic acids it took more than 6 months.

• Structural Engineering and Mechanics
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• 제58권6호
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• pp.1109-1126
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• 2016

The present paper focuses on size optimization of double layer barrel vaults considering nonlinear behavior. In order to tackle the optimization problem an improved colliding bodies optimization (ICBO) algorithm is proposed. The important task that should be achieved before optimization of structural systems is to determine the best form having the least cost. In this study, an attempt is done to find the best form then it is optimized considering linear and non-linear behaviors. In the optimization process based on nonlinear behavior, the geometrical and material nonlinearity effects are included. A large-scale double layer barrel vault is presented as the numerical example of this study and the obtained results indicate that the proposed ICBO has better computational performance compared with other algorithms.

• 한국소성가공학회:학술대회논문집
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• 한국소성가공학회 2000년도 춘계학술대회논문집
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• pp.40-43
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• 2000

A process optimal design methodology applicable to steady-state forming with a strain-hardening material is presented. in this approach the optimal design problem is formulated on the basis of a rigid-viscoplastic finite element process model and a derivative based approach is adopted as an optimization technique The process model the schemes for the evaluation of the design sensitivity considering the effect of strain-hardening and an iterative procedure for design optimization are described. the validity of the proposed approach is demonstrated through application to die shape optimal design in extrusion.

• 대한전기학회논문지
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• 제35권1호
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• pp.17-25
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• 1986

Discussions on this paper are related to the effects of organic materials to treeing phenomena of low density polyethylene. As additives, 11 kinds of organic compounds are selected by considering the respective features such as melting point, boiling point, electron affinity as well as molecular structure, and then the specimens of low density polyethylene are prepared by blending with 10wt% of the selected additives. For the comparison of effectiveness of treeing resistance and interpretation of the mechanism of compounds as treeing retardants, several investigations such as the tree acceleration test, the prestressed test and the measurement of internally occurred partial discharge are carried out. As the results, meta-Cresol is regard as the most effective retardant among those, and it is supposed that this aromatic compound to be comprised of radical having large electron affinity has strong capability to accept energetic electron to prevent or delay the growth of discharge streamer. Furthermore, by activating partial discharge at the wall of tree pit through the function of trapped electron at this material, the gas pressure in the pit is increased up to prevent the growth of streamer.