• Journal of applied mathematics & informatics
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• v.20 no.1_2
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• pp.445-454
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• 2006

We describe a solution to the Ornstein-Uhlenbeck equation $\frac{dI}{dt}-\frac{1}{\tau}$I(t)=cV(t) where V(t) is a constant multiple of a Gaussian white noise. Our solution is based on a discrete set of Gaussian white noise obtained by taking sample points from a sum of single frequency harmonics that have random amplitudes, random frequencies, and random phases. Hence, it is different from the solution by the standard random walk using random numbers generated by the Box-Mueller algorithm. We prove that the power of the signal has the additive property, from which we derive that the Lyapunov characteristic exponent for our solution is positive. This compares with the solution by other methods where the noise is kept to be in an error range so that its Lyapunov exponent is negative.

• Proceedings of the Korean Operations and Management Science Society Conference
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• 2006.05a
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• pp.1085-1092
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• 2006

Response surface methodology(RSM) is a useful collection of experimentation techniques for developing, improving, and optimizing products and processes. When we are to estimate second-order regression model and optimize quality characteristic by RSM, central composite designs and Box-Behnken designs are widely in use. However, in developing cutting-edge products, it is very crucial to reduce the time of experimentation as much as possible. In this paper small-sized second-order designs are introduced and their estimation abilities are compared in terms of D-optimality, A-optimality, and variance of regression coefficients. The result of this study will be beneficial to experimenters who face experiments which are expensive, difficult, or time-consuming.

• Journal of the Korean Society for Precision Engineering
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• v.22 no.7 s.172
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• pp.54-61
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• 2005

A simulator for virtual laser machining is developed to help understanding and predicting the effects of machining parameters on the final machined results. Main program is based on the model for polymer ablation with short pulse excimer lasers. Version f of the simulator is built using Visual Fortran to make the user work under visual environment such as Windows on PC, where the important machining parameters can be input via dialog box and the calculated results for machined shape, beam fluence, and temperature distribution can be plotted through the 2-D graphics windows. Version II of the simulator is built using HTML, CGI and JAVA languages, allowing the user to control the input parameters and to see the results plot through the internet.

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 2008.05a
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• pp.543-546
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• 2008

In the present study, the effect of cold reduction ratio on the spherodization rate of SK85 high carbon steel sheet was investigated. High carbon steel sheet fabricated by POSCO was soaked at $800^{\circ}C$ for 2 hr in a box furnace and then treated at $570^{\circ}C$ for 5 min in a salt bath furnace followed by water quenching to obtain a fine pearlite structure. Cold rolling was conducted on the sheets of fine pearlite by reduction ratios of 20, 30, and 40 % and heat treatment for spheroidization was carried out at $720^{\circ}C$ for the various time intervals from 0.1 to 32 hrs. Area fraction of spheroidized cementite was measured with an image analyzer as a function of cold reduction ratios and duration times.

• Journal of the military operations research society of Korea
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• v.27 no.2
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• pp.134-148
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• 2001

In this paper, air-defense simulation model, called "DADSim", will be introduced. DADSim(Distributed Air Defense Simulation Model) was developed by Modeling&Simulation Lab of K.N.D.U.(Korea National Defence Univ) Weapon Systems Department. This model is an analysis-purpose model in the engagement-level. DADSim can simulate not only the global air-defense or Korean Peninsula but also the local air-defense or a battle field. DADSim uses the DTED(digital terrain elevation data) LeveII it for the representation of peninsula terrain characteristics. The weapon systems cooperated in the model are low/medium-range missile systems such as HAWK, NIKE, SAM. DADSim was designed in the way of object-oriented development method, implemented by C++ language. The simulation view is an event-sequenced object-orientation. For the convenience of input, output analysis, GUI(Graphic User Interface) of menu, window, dialog box, etc. are provided to the user, For the execution of DADSim, Silicon Graphic IRIX 6.3 or high version is required. DADSim can be used for the effectiveness analysis of­defence systems. Some illustrative examples will be shown in this paper.

• Bulletin of the Korean Chemical Society
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• v.6 no.1
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• pp.29-32
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• 1985

Normal modes of crystalline orthorhombic sulfur belonging to the space group $D_{2h}$-Fddd, have been evaluated by taking the lowest temperature phase in the solid. Normal modes are obtained by the valence force field with modified force constants and a quantitative description of the mode is adjusted by the potential energy distribution. Since the full crystal system of orthorhombic sulfur is so large, we intended to calculate the normal modes simply by constructing the imaginary box made by the infinite mass boundary. And the Raman experiment is done by using the more powerful Ar-Kr gas laser with lowering the temperature to ${\sim}10^{\circ}K$.

• Journal of the Korean Institute of Landscape Architecture
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• v.40 no.6
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• pp.190-197
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• 2012

The purpose of this study was to evaluate thermal environment and heat budget of light thin layer green roof through an experiment in order to quantify its heat budget. Two concrete model boxes($1.2m(W){\times}1.2m(D){\times}1.0m(H)$) were constructed: One experiment box with Zoysia japonica planted on substrate depth of 10cm and one control box without any plant. Between June 6th and 7th, 2012, outside climatic conditions(air temperature, relative humidity, wind direction, wind speed), evapotranspiration, surface and ceiling temperature, heat flux, and heat budget of the boxes were measured. Daily maximum temperature of those two days was $29.4^{\circ}C$ and $30^{\circ}C$, and daily evapotranspiration was $2,686.1g/m^2$ and $3,312.8g/m^2$, respectively. It was found that evapotranspiration increased as the quantity of solar radiation increased. A surface and ceiling temperature of those two boxes was compared when outside air temperature was the greatest. and control box showed a greater temperature in both cases. Thus it was found that green roof was effective in reducing temperature. As results of heat budget analysis, heat budget of a green roof showed a greater proportion of net radiation and latent heat while heat budget of the control box showed a greater proportion of sensible heat and conduction heat. The significance of this study was to analyze heat budget of green roof temperature reduction. As substrate depth and types, species and seasonal changes may have influences on temperature reduction of green roof, further study is necessary.

• Proceedings of the Computational Structural Engineering Institute Conference
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• 2009.04a
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• pp.360-363
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• 2009

토목구조물의 설계 패러다임이 2차원에서 3차원으로 전환될 때 효율성과 재활용성의 관건이 되는 기술적 제약사항이 호환성이다. 대부분의 캐드 엔진이 형상모델 수준에서 호환성 혹은 연계성을 지원하고 있지만 3차원 정보모델에서 요구하는 정보모델의 호환성은 지원하고 있지 않은 실정이다. 이 논문에서는 콘크리트 박스 교량에 대해서 3차원 교량 정보 모델을 구성하고 건설 프로세서에서 이를 활용할 수 있는 방안을 시범적으로 적용한 사례를 정리하였다. 적용 대상 구조물은 FSM 공법으로 시공되는 경간 40미터의 콘크리트 박스거더 교량이다. 견적, 시공시뮬레이션, 해석 등의 프로세서의 요구사항을 반영한 분류체계에 따라 형상모델의 체계를 정의하고 각각의 형상모델 단위에 정보를 부여하는 방식을 사용하였다. 개별 프로세서를 위한 솔류션에서 이러한 형상과 정보가 연계된 내용을 받아들이거나 캐드 엔진에서 필요한 형태로 내보내는 방식을 모두 시도하였다. 3차원 형상 모델과 시간이 부여된 4D 시뮬레이션을 활용하여 공사 스케쥴에 따라 모델 레이어 분류 작업으로 공사 진행 단계가 가상으로 보여진다. 시범 적용을 통해서 가상건설 시스템의 구성하는 개별 솔류션 혹은 정보체계에 대한 문제점과 개선사항을 도출하였다.

• Proceeding of EDISON Challenge
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• 2017.03a
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• pp.241-250
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• 2017

Auxetic is a structure that behave as negative Poisson's ratio. It is known for high mechanical property like energy absorption and destruction toughness so far. In this paper, we aimed to design auxetic structure which has small internal energy when force is applied and high NPR and over 50N/mm stiffness by using optimization method. We defined length(L), thickness(t), angle(${\theta}_1$, ${\theta}_2$) as design factors and also von-Mises stress, NPR, stiffness as reaction factors. We used Box-Behnken method and conducted 4factors - 3levels experiment design. We also analyzed each models by using CSD_EPLAST, Edison program, and did extra analysis for more accurate results. Finally, we found out the optimal design factors which is satisfied aimed value and increased reliability through factor analysis and validity verification.

• Journal of the Korean Electrochemical Society
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• v.13 no.3
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• pp.175-180
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• 2010

The highly conductive polyaniline was synthesized and investigated on the properties of its thin film electrode fabricated by solution process. The transmittance and sheet resistance of the polyaniline thin film of 200 nm thickness were observed in 85% in absorption range above 450 nm and $380P{\Omega}/{\Box}$, respectively. The sheet resistance of the polyaniline was largely varied above $130^{\circ}C$ annealing temperature.