• Proceedings of the Korean Vacuum Society Conference
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• 2014.02a
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• pp.471.1-471.1
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• 2014

염료감응형 태양전지(DSSC)는 다양한 태양전지 중, 가장 환경친화적이고, 생산단가도 낮을 뿐만 아니라 다양한 색상과 투광성을 확보할 수 있어 많은 연구가 진행되어왔다. 하지만 액체전해질을 사용하는 기존 염료감응형 태양전지는 높은 휘발성과 열 팽창 수축에 따른 전해질 누액의 문제점으로 인하여 최근에는 고체전해질을 이용한 염료감응형 태양전지의 개발이 활발히 이루어지고 있다. 또한 기존 염료보다 높은 흡광계수와 넓은 흡수스펙트럼을 지닌 페로브스카이트가 개발되어 현재 많은 관심이 주목되고 있다. 본 연구에서는 $TiO_2$ 제조상의 중간생성물인 Metatitanic acid (MTA)를 이용하여 광전극을 형성하고 열처리 온도에 따른 나노입자의 소성거동평가을 평가하였고 시차열중량 분석, 결정상 확인을 하고 염료감응 태양전지에 적용하였다. MTA 나노입자를 Field Emission Transmission Electron Microscopy (FE-TEM), Barrett-Joyner-Halenda (BJH pore size distribution)과 Brunauer-Emmet-Teller (BET) 분석을 통해 소성거동을 평가하고, Thermogravimetry and differential thermal analysis (TG-DTA)를 통해 열중량 측정을 하였으며, X-ray Diffraction (XRD) 분석을 통해 결정상을 확인하였다. 또한 Fourier-transform infrared (FT-IR) spectroscopy를 통해 MTA 나노입자의 표면분석을 하였다. 형성된 MTA 광전극을 페로브스카이트 염료에 적용하여 5%의 효율을 달성하였다.

• International Journal of Highway Engineering
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• v.4 no.1 s.11
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• pp.161-170
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• 2002

This study is a fundamental research for recycling waste polyethylene film(WPF) in asphalt concrete for roadway pavement. The objective of this study is to develop technology of making waste polyethylene asphalt mixture and evaluate properties of the asphalt concrete containing WPF. Asphalt concrete for surface course of pavement was produced through an appropriate mix-design using dense-graded and gap-graded aggregates. Marshall mix design, indirect tensile strength test, wheel tracking test and tensile fatigue test were performed. Test result showed that some WPF asphalt mixtures had a high tensile property and good resistances against rutting and fatigue cracking, compared with normal asphalt mixture.

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 2005.10a
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• pp.344-349
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• 2005

This paper is studied on the effect of TiAlN coated ball end mill on cutting characteristic of high hardness steels in dry cutting condition without coolant. KP4 steels[HRC32] and STD11[HRC60] heat treated steels wert: used as the workpiece and WC-Co ball end mill and single and multi layer TiAlN coated ball end mill were utilized. Results showed that TiAlN coated ball end mill were increased the cutting length than WC-Co ball end mill in the cutting speed$[245\~320m/min]$ about $2\~5$ times for KP4 steels and about $2.7\~4.3$ times for STD11 heat treated steels. The multi layer TiAlN coated ball end mill is good about $1.2\~1.7$ times for KP4 steels and STD11 steels than single layer coated.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2008.06a
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• pp.56-56
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• 2008

최근, 비납 또는 납의 함량을 줄인 압전 세라믹에 대한 관심이 증가하고 있고, 그에 따른 여러 연구가 활발히 이루어지고 있다. 납을 포함하는 세라믹은 높은 소성온도에서 납의 휘발로 인한 특성저하와 환경오염 등이 문제가 된다는 것을 우리는 익히 알고 있다. 그렇기 때문에 PZT계 세라믹스를 대체할 우수한 특성을 가지는 새로운 비납 세리믹스의 조성개발이 시급하다. 비납계 세라믹스 중에서 NKN계를 바탕으로 하는 세라믹스는 가장 기대되는 재료이다. 일반적인 소성에서 순수한 NKN 세라믹은 가장 높은 압전 $d_{33}$상수가 100 pC/N이 넘지 않는다. 그런데 페로브스카이트 구조로된 NKN세라믹스의 A-site에 $Li^{1+}$이온을 치환하면 압전 특성을 향상시킬 수 있다. 그리고, 압전세라믹에서 분극처리는 필수적인데 분극처리는 압전성을 부여할 뿐 아니라 다른 물성도 변화시킴은 잘 알려져 있다. 그러므로 그에 대한 연구 또한 중요한 의미를 갖는다. 따라서 이번 연구에서는 NKN세라믹스에 $Li_2CO_3$를 소결조제로 첨가하여 시편을 제작하였고, 제작된 시편의 특성을 분극전계에 따라 조사하였다.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2009.11a
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• pp.83-83
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• 2009

우수한 압전성을 가지는 PZT는 인체에 유해한 다량의 PbO을 함유하여 심각한 환경문제를 야기함은 물론 제조 공정 중 PbO 휘발 억제 시설 구비에 따른 경제적 부담 등 문제점이 지적되었다. 따라서 환경오염 및 가격경쟁력을 갖추기 위해 현재 무연 조성 세라믹스에 대한 많은 연구가 진행되고 있다. 최근 비납계 압전 세라믹의 연구는 비스무스 레이어형과 페로브스카이트 형 비납계 세라믹스의 연구가 활발히 진행되고 있다. 특히 $(Na,K)NbO_3$ 계는 페로브스카이트 구조를 가지는 비납계 세라믹으로 현재 많은 연구가 진행되고 있다. 이 물질은 PZT계와 유사하게 상전이(morphotropic phase boundary:MPB)영역을 가지고 있 으며 이 영역에서 높은 압전 특성을 보여주고 있다. 최근 $Na_{0.5}K_{0.5}NbO_3$에 $LiTaO_3$를 치환하여 우수한 압전 특성을 지니는 조성이 개발되고 있지만, 보통 소성법으로 제조된 세라믹스는 PZT계 세라믹스와 비교하여 특성이 떨어진다. 본 연구에서는 압전성이 우수한 $(Na_{0.44}K_{0.52}Li_{0.44})(Nb_{0.90}Sb_{0.06}Ta_{0.04})O_3$ 조성에 도너 도핑과 억셉터 도핑을 한 다음 전기기계결합계수, 압전상수, 유전상수의 변화를 평가하고, hardener 와 softener 특성이 본조성에서 나타나는지를 관찰하였다. 실험방법은 보통 소성법을 사용하였으며, 분쇄와 혼합은 직경 3 mm zirconia ball을 사용하여 볼밀 하였다. $850^{\circ}C$ 에서 5h 하소 후 $1100{\sim}1200^{\circ}C$ 에서 소결하고, 두께 1 mm로 연마한 다음 silver paste를 $650^{\circ}C$ 에서 소부하여 전극을 형성하였다. 제작된 시편은 $90^{\circ}C$의 실리콘유에서 3~4 kV/mm의 전계를 가해 20분간 분극 처리를 수행하였다. 제작된 시편의 압전전하 상수 값은 d33-meter(APC-8000)를 이용하여 측정하였고, 유전율, 전기기계결합계수 및 기계적품질계수 등은 임피던스 분석기 (impedance/gain phase analyzer)를 이용하여 특성을 측정 하였다. 또한 전압-분극 특성의 평가에는 강유전특성 측정기(ferroelectric tester: Precision-LC, Radiant Technologies, USA)를 이용하였다.

• Journal of the Korean GEO-environmental Society
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• v.2 no.4
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• pp.51-61
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• 2001

A series of model tests and analyses by load transfer function were performed to study load-settlement behaviour with relative compaction ratio of soil and embeded depth of pile. In the model tests, embeded depth ratio(L/D) of pile were installed 15, 20, 25 and relative compaction of soil(RC) is 85%, 95% and then cement were injected at around perimeter of pile. For analysis of embedded pile, the paper were compared results of model tests with analysis results by Vijayvergiya model and Castelli model, Gwizdala model of elastic plasticity-perfect plastic model and then the fitness load transfer mechanism was proposed to predict load-settlement behaviour of embeded pile. The analysis results of predicted bearing capacity by load transfer function, ultimate bearing capacity of embeded pile were approached to measured value and behaviour of initial load-settlement curve were estimated that load transfer function by Castelli were similar to measured value. The result of axial load analysis of bored pile shows that skin friction estimated by load transfer mechanism is investigated more a little than that of measured values.

• Journal of the Korean GEO-environmental Society
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• v.2 no.3
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• pp.81-88
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• 2001

The behavior of porous medium is modeled by linear thermoporoelastic behavior, linear poroviscoelastic behavior, poroplastic behavior, and poroviscoplastic behavior, etc. The behavior has, in general, a complicated aspect which makes a mechanical description of the problem with time. Constitutive modeling for deformation behavior of porous medium with coupling effects is needed since there is interaction between the constituents in pores with a relative velocity to each other. In this work, it is explained 3-dimensional behavior depending on degree of saturation for porous medium composed of homogeneous, isotropic materials. It is obtained the governing equations based on continuum porous mechanics. In addition, it is developed constitutive model which can be understood of behavior for porous medium which can be understood, analysed behavior of porous medium. It can be accomplished exact analysis and prediction of behavior in porous medium. The behavior for porous medium is analysed exactly, and the prediction of deformation behavior is accomplished. Consequently, it will be basis to analyze 3-dimensional behavior in municipal solid waste landfill, and the practical using of porous medium ground which are composed of nonhomogeneous, anisotropic materials can be done widely.

• Journal of Korean Society of Environmental Engineers
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• v.32 no.10
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• pp.928-935
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• 2010

A bag filter system was partially burnt down during a trial run of waste wood incineration boiler. This brought about unburned hydrocarbon which caused a rapid deactivation of low temperature SCR catalyst set up in two stage after the bag filter. The deactivated catalyst was investigated in order to trace the origin by several characterization methods such as XRD, EDX, BET, TGA, SEM. The deactivated catalyst was regenerated by different methods such as acid washing, water washing in ultrasonication, and calcination treatment under air condition. It is found the calcination treatment under air condition at $450^{\circ}C$ for 2 hours to be the best regeneration method. The catalytic activity was measured in the form of 2 cm ${\times}$ 2 cm ${\times}$ 10 cm (catalyst weight 10 g) honeycomb type. A deNOx efficiency of the regenerated catalyst showed 100% at $180^{\circ}C$ which is the same level of fresh one.

• Journal of the Korean Geotechnical Society
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• v.35 no.2
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• pp.37-51
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• 2019

This study focuses on the numerical simulations of the cone penetration tests in a sand ground. The mechanical responses of sand were described using the modified Mohr Coulomb plasticity model based on the critical state soil mechanics. In the plasticity model, the dilatancy angle was not a constant, but a function of the distance to the critical state line from the current state of void ratio and mean effective stress. To simulate cone penetration tests numerically, this study relied on Lagrangian finite element method under the axisymmetric condition. To enable penetration of the cone penetrometer without tearing elements along the symmetric axis, the penetration guide concept was adopted in this study. The results of numerical simulations on the calibration chamber cone penetration tests had good agreement with the experimental results.

• Journal of the Korea institute for structural maintenance and inspection
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• v.26 no.6
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• pp.204-211
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• 2022

In this study, Hollow Concrete Filled FRP Tube Pile(HCFFT Pile) was proposed as a model to utilize the advantages of composite piles and solve the problem of corrosion, which is a disadvantage of CFT piles, and a numerical analysis model was developed to analyze their behavior. The strain compatibility method was applied considering the damage plastic behavior of concrete, the yield plastic behavior of steel, and the elastic behavior of FRP. The flexural strength calculation equation of HCFFT piles was proposed considering the change of the FRP tube section according to the distance from the neutral axis. The flexural strength calculation equation, numerical analysis results, and experimental results were compared and analyzed to verify their adequacy. The results of this study can be used as basic data for the optimal design of various HCFFT piles using FRP.