• Proceedings of the Korean Society of Near Infrared Spectroscopy Conference
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• 2001.06a
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• pp.1514-1514
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• 2001

In this paper a fast non-destructive analytical method to measure various nutrients in the intact tomato---Near infrared Spectrometry NIRs was introduced Using this method the content of some organic acid, vitamin C, reductive sugar, and solid soluble were determined simultaneously. Screen out four wavelengths at 916nm, 1000nm, 1004nm and 832nm to present optimum four optical terms of d$^2$ log(1/R) with second derivative spectra treating data scanned under these wavelengths. The multiple correlation coefficients between these values and those obtained on chemical analysis were 0.983, 0.990, 0.987, and 0.994, respectively, and the standard errors of prediction (SEP) were 0.007, 0.440, 0.037, and 0.057, respectively. These results indicate that NIRs is comparable to chemical methods in both accuracy and precision and is reliable method for determination of nutrients in intact tomato.

• Proceedings of the KAIS Fall Conference
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• 2010.11a
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• pp.168-171
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• 2010

본 논문에서는 GaN HEMT 소자를 이용한 고출력 고효율 특성을 가지는 광대역 SSPA의 개발을 다루고 있다. 개발한 SSPA는 8W 급과 15W 급의 GaN HEMT 소자를 사용하여 Pre-Drive 증폭단을 구성하였으며, Drive 증폭단은 50W/150W급 GaN HEMT 소자를 직/병렬구조로 사용하였다. Main 증폭단은 4-way 분배기와 결합기를 이용한 Balanced Structure를 적용하여 높은 출력을 구현하였으며, 안정적인 동작을 위하여 음(-)전원 제어 회로와 출력신호 검출 회로를 포함하고 있다. 제작된 SSPA의 사용가능 대역은 2.9GHz~3.3GHz로 단일전원을 사용하고 있으며 100us 펄스 폭, 10% Duty Cycle 조건에서 60dB의 전압이득, 1kW 출력과 약 28% 효율 특성을 가지는 것으로 측정되었다. 본 논문에서 개발한 SSPA는 S-대역을 사용하는 레이더시스템의 송신단에 적용될 수 있다.

• Computers and Concrete
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• v.7 no.4
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• pp.331-346
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• 2010

We present a quadrilateral finite element with an embedded crack that can be used to model tensile fracture in two-dimensional concrete solids and the crack growth. The element has kinematics that can represent linear jumps in both normal and tangential displacements along the crack line. The cohesive law in the crack is based on rigid-plasticity with softening. The required material data for the concrete failure analysis are the constants of isotropic elasticity and the mode I softening curve. The results of two well known tests are presented in order to illustrate very satisfying performance of the presented approach to simulate failure of concrete solids.

• Advances in Energy Research
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• v.1 no.1
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• pp.53-78
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• 2013

Methane carbon dioxide reforming (MCDR) is a promising way of utilizing greenhouse gas for hydrogen-rich fuel production. Compared with other types of reactors, Compact Reformers (CRs) are efficient for fuel processing. In a CR, a thin solid plate is placed between two porous catalyst layers to enable efficient heat transfer between the two catalyst layers. In this study, the physical and chemical processes of MCDR in a CR are studied numerically with a 2D numerical model. The model considers the multi-component gas transport and heat transfer in the fuel channel and the porous catalyst layer, and the MCDR reaction kinetics in the catalyst layer. The finite volume method (FVM) is used for discretizing the governing equations. The SIMPLEC algorithm is used to couple the pressure and the velocity. Parametrical simulations are conducted to analyze in detail the effects of various operating/structural parameters on the fuel processing behavior.

• Structural Engineering and Mechanics
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• v.62 no.6
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• pp.703-708
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• 2017

The goal of this study is to evaluate behavior uncertainties of structures by using interval finite element analysis based on interval factor method as a specific non-stochastic tool. The interval finite element method, i.e., interval FEM, is a finite element method that uses interval parameters in situations where it is not possible to get reliable probabilistic characteristics of the structure. The present method solves the uncertainty problems of a 2D solid structure, in which structural characteristics are assumed to be represented as interval parameters. An interval analysis method using interval factors is applied to obtain the solution. Numerical applications verify the intuitive effectiveness of the present method to investigate structural uncertainties such as displacement and stress without the application of probability theory.

• Journal of the Korean Applied Science and Technology
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• v.28 no.4
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• pp.386-392
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• 2011

We are crystallized to the linear low density polyethylene(LLDPE) particles by a thermally induced phase separation(TIPS). TIPS process based on the phase separation mechanism was performed for the LLDPE system which undergoes liquid-solid phase separation. The linear low density polyethylene particle formation occurred by the nucleation and growth mechanism in the metastable region. Although the growth rates depended on the experimental conditions such as the polymer concentration and temperature, the particles were larger when the polymer concentration was higher or temperature was higher. The particles were observed by SEM. The LLDPE particle size distribution became broader when the polymer concentration was higher.

• Journal of the Korean Ceramic Society
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• v.30 no.7
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• pp.557-562
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• 1993

Following conclusions are made from the detalied research on the relation between the phase change of the petroleum raw cokes after ball milling and the preheat treatment temperature. The petroleum raw cokes species are preheated in the temperature range of 350~45$0^{\circ}C$. At the preheat treatment temperature of 40$0^{\circ}C$ the particles of petroleum raw cokes from ball milling become spheically shape with the almost uniform particle size distribution of 1~5${\mu}{\textrm}{m}$. At the same temperature, they became low-graphitized with the d0.02 X-ray diffraction index of 3.41$\AA$. The carbon material made from the petroleum raw cokes at 40$0^{\circ}C$ turned out to have the good modulus of rupture about 600kg/$\textrm{cm}^2$, with the bulk density around 1.8g/㎤ and the appearent porosity around 8%.

• 한국정보디스플레이학회:학술대회논문집
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• 2006.08a
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• pp.1577-1582
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• 2006

Tandem OLED structures formed by connecting two or more low-voltage electroluminescent units (stacks) are effective for achieving high efficiency at low current density as well as long operational lifetime. We have fabricated white emitting tandem structures with two or three low-voltage white-emitting stacks using transparent organic "PN"-type connectors. Three- stack white tandem structures with efficiency greater than 24 cd/A at D65 and operational stability of about 110,000 h. (extrapolated) at $1000\;cd/m^2$ have been demonstrated. With a stacked structure, the power consumption for displays using an RGBW format can be reduced by 25% compared to previously described formulations. We have also fabricated advanced white tandem structures where the color gamut (NTSC x,y ratio) has been improved to greater than 70% using standard color filters. The white OLEDs can also be used to increase the colorrendering index CRI (>80%), an important consideration for solid-state lighting.

• Proceedings of the KIEE Conference
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• 1998.07d
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• pp.1285-1287
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• 1998

Vibration measurements to monitor the condition of machinery and machine elements offers several advantages over traditional methods of nondestructive evaluation. RIST(Research Institute of Industrial Science & Technology) has established a calibration system for accelerometers that measures within a frequency range from 2Hz to 6,300Hz and a temperature range from $-40^{\circ}C$ to $180^{\circ}C$. The calibration procedures are based on the principle of the comparison method. To monitor vibration signals of machinery and machine elements, annular shear type piezoelectric accelerometers employing solid state microelectronics were fabricated. The voltage sensitivity and resonant frequency of fabricated accelerometers was 83mV/g, 23kHz, respectively. This paper discusses the method of fabrication of annular shear type piezoelectric accelerometers and the results of field tests in POSCO(Pohang Iron & Steel Co. LTD.).

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2003.06a
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• pp.925-928
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• 2003

In this paper, a precision measuring machine for large sized axial fans of cooling towers are developed. A laser sensor is used as a measuring device and aluminum profiles and stepping motors are engaged into the system as frame structure and driving devices respectively. 3-dimensional measuring data are compared to the design data to compute the distortion of the axial fans. Two distortions such as the axis of the fan and the airfoils along the axis are introduced to define the shape precision of axial fans. Genetic algorithm is used to solve the optimization problem during computing the distortion. Results of distortion are displayed 3 dimensionally in a solid-modeler as well as 2-D drawings to help users find it with case.