• Title/Summary/Keyword: Numerical Calculation

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Methodological study on the High Dynamic Range Imaging Processing (채광·조명설비시스템의 광학 분석을 위한 이미지 프로세싱 기법에 관한 연구)

  • Lim, Hong Soo;Kim, Gon
    • KIEAE Journal
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    • v.10 no.4
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    • pp.3-8
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    • 2010
  • Recently, various daylight evaluation methods for visual environment have been developed; simulation analysis methods, numerical calculation, and data monitoring methods. However, it is impossible for simulation analysis to make real scenes and visualize real images exactly. Also, a numerical calculation is considered as an out of date and time-consuming mean. Therefore, for acquisition of accurate results, many studies often use the monitoring data methods. Especially, most studies regarding discomfort glare are evaluated by measuring the physical quantity of luminance through traditional measuring Minolta Luminance meters as an instrument. But, this method has a difficulty in measuring several points at the same time because of the limitation of spaces and time when mapping. So, this study focused on the potential usefulness of High Dynamic Range photography technique as a luminance mapping tool. In order to evaluate the accuracy of proposed programs such as webHDR, Photomatix and PHOTOLUX, this paper has conducted an experiment by using Canon EOS 5D and NICON Coolpix8400 digital camera.

A Study on the Numerical Calculation of the Electron Density in Organic Semiconductors (유기반도체에서 전자 밀도의 수치적 계산에 관한 연구)

  • Yeom, Keesoo
    • Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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    • 2016.10a
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    • pp.161-163
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    • 2016
  • Organic semiconductors, in contrast with inorganic semiconductors, have DOS of the Gaussian distribution function which leads to difficulties to obtain the electron density with a closed equation. For this reason, the prediction of the device operation is extremely difficult in the development of OLED and the repetitive trial-and-error is required to find the appropriate electrical and optical properties of the devices. In this paper, the standard to analyze organic semiconductor is proposed by the optimization of the time and the accuracy which is necessary for the numerical calculation of the electron density in organic semiconductors.

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A New Groutability Criterion of Cement-based Grout with Consideration of Viscosity and Filtration Phenomenon (점도변화와 흡착현상을 고려한 시멘트계 그라우트재의 새로운 침투 기준)

  • Kim, Jong-Sun;Lee, In-Mo;Lee, Mun-Seon;Choi, Hang-Seok
    • Proceedings of the Korean Geotechical Society Conference
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    • 2009.03a
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    • pp.154-163
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    • 2009
  • The groutability depends on the properties of the grout, its injection processes, and on the mechanical properties of the soil formation. During the process of pouring cement-based grouting into a porous medium, a variation with time occurs in the viscosity of grout suspension. In addition the particle filtration phenomenon will limit the expansion of the grouted zone because cement particles are progressively stagnant within the soil matrix. In this paper, a closed-form solution was derived by implementing the mass balance equations and the generalized phenomenological filtration law, which can be used to evaluate the deposition of cement-based grout in the soil matrix. The closed-form solution relevant to a particular spherical flow was modified by a step-wise numerical calculation, considering the variable viscosity caused by a chemical reaction, and the decrease in porosity resulting from grout particle deposition in the soil pores. A series of pilot-scale chamber injection tests was performed to verify that the developed step-wise numerical calculation is able to evaluate the injectable volume of grout and the deposition of grout particles. The results of the chamber injection tests concurred well with that of the step-wise numerical calculation. Based on the filtration phenomenon, a new groutability criterion of cement-based grout in a porous medium was proposed, which might facilitate a new insight in the design of the grouting process.

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Numerical Analysis on the Beat and Mass Transport in Horizontal MOCVD Reactor for the Growth of GaN Epitaxy (수평형 MOCVD에 의한 GaN 에피층 성장시 반응로내의 열 및 물질전달에 관한 수치해석 연구)

  • 신창용;윤정모;이철로;백병준
    • Journal of the Korean Vacuum Society
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    • v.10 no.3
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    • pp.341-349
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    • 2001
  • Numerical calculation has been performed to investigate the fluid flow, heat transfer and local mass fraction of chemical species in the MOCVD(metalorganic chemical vapor deposition) manufacturing process. The mixing of reactants (trimethylgallium with hydrogen gas and ammonia) was presented by the concentration of each reactant to predict the uniformity of film growth. Effects of inlet size, location, mass flow rate and susceptor/cold wall tilt angle on the concentration were reported. From the numerical calculation, the concentration of reactants could be qualitatively predicted by the Nusselt number(heat transfer) and the optimum mass flow rate, wall tilt angle and inlet condition were considered.

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Analysis of transport current loss considering the conductive layer of YBCO wires (도전성이 높은 안정화층을 고려한 YBCO 선재의 전송전류 손실 해석)

  • Kang, Myung-Hun;Han, Byung-Wook;Jung, Du-Young;Lim, Hee-Hyun;Lim, Hyoung-Woo;Cha, Guee-Soo;Lee, Hee-Joon
    • Proceedings of the KIEE Conference
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    • 2006.10d
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    • pp.191-193
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    • 2006
  • YBCO wire has a metal substrate to improve the texture structure and highly conductive layers to increase the cryogenic stability. When AC current flows in the YBCO wire, magnetic field which is generated by the AC current magnetizes the metal substrate and induces the eddy current in the stabilizing layer. To examine the effect of the metal substrate and the conducting layer on the transport current loss of YBCO wire, this paper presents the transport current loss of YBCO wire which has metal substrate and conductive layer. YBCO wire with Ni-W substrate and copper layer were chosen as the model HTS wire for numerical calculation. Finite element method has been used to calculate the transport loss and the results of numerical calculation was compared with analytic calculation suggested by Norris.

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An Application of the Acoustic Similarity Law to Centrifugal Fan Noise by Numerical Calculation (수치기법을 이용한 원심홴 소음의 음향학적 상사법칙 적용)

  • 전완호;이덕주
    • Journal of KSNVE
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    • v.9 no.5
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    • pp.955-965
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    • 1999
  • Centrifugal fans are widely used and the noise generated by the these machines causes one of the most serious problems. In general, the centrifugal fan noise is often dominated by tones at BPF(blade passage frequency) and its higher harmonics. This is a consequence of the strong interaction between the flow discharged form the impeller and the cutoff in the casing. However, only a few researches have been carried out on predicting the noise because of the difficulty in obtaining detailed information about the flow field and casing effects on noise radiation. The objective of this study is to understand the generation mechanism of sound and to develop a prediction method for the unsteady flow field and the acoustic pressure field of a centrifugal fan. We assume that the impeller rotates with a constant angular velocity and the flow field of the impeller is incompressible and inviscid. So, a discrete vortex method (DVM) is used to model the centrifugal by the unsteady Bernoulli equation. Lowson's method is used to predict the acoustic source. A centrifugal impeller and wedge introduced by Weidemann are used in the numerical calculation and the results are compared with the experimental data. Reasonable results are obtained not only for the peak frequencies but also for the amplitudes of the tonal sound.

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Numerical calculation of torque converter flow using interrow mixing model (익렬간 혼합모델을 이용한 토크 컨버터 유동장의 수치계산)

  • Park, Jae-In;Jo, Gang-Rae
    • Transactions of the Korean Society of Mechanical Engineers B
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    • v.22 no.3
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    • pp.326-335
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    • 1998
  • In this study, a steady three-dimensional incompressible turbulent flow within a torque converter was numerically analyzed with the introduction of interrow mixing model. Mixing planes were introduced to exchange the flow informations between two adjacent elements of the torque converter. The mixing planes were installed among three elements of the torque converter. Therefore, in the present method, it could be possible to calculate the flow-filed within the torque converter without any assumption of circulating flow rates or any extension of boundaries toward the upstream and the downstream for each element. The numerically calculated performances of the torque converter were in good agreement with experimental results, and the complex flow patterns were be observed according to design and off-design condition. As a conclusion, it was found that the present numerical method was very effective in the steady flow analysis of torque converters.

Two-position alignment of strapdown inertia navigation system

  • Lee, Jang-Gyu;Kim, Jin-Won;Park, Heong-won;Park, Chan-Gook
    • 제어로봇시스템학회:학술대회논문집
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    • 1994.10a
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    • pp.665-671
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    • 1994
  • Some extended results in the study of two-position alignment for strapdown inertial navigation system are presented. In [1], an observability analysis for two-position alignment was done by analytic rank test of the stripped observability matrix and numerical calculation of the error covariance propagation using ten-state error model. In this paper, it is done by an analytic approach which utilizes the nonsingular condition of the determinant of simplified stripped observability matrix and by numerical calculation of the error covariance propagation accomplished in more cases than [1], and the twelve-state error model including vertical channel is used instead of ten-state error model. In addition, it is confirmed that this approach more clearly produces the same result as shown in the original work in terms of complete observability and there exist some better two-position configurations than [1] using the twelve-state error model.

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Numerical Investigation of Internal Flow Field for Diffuser Passage Compressor

  • Yamagami, Mai;Tsuchiya, Naoki;Kato, Dai;Kodama, Hidekazu;Yamamoto, Kazuomi;Enomoto, Shunji;Horiguchi, Yasuo;Outa, Eisuke
    • Proceedings of the Korean Society of Propulsion Engineers Conference
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    • 2008.03a
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    • pp.136-142
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    • 2008
  • The influence of different grids on numerical prediction of subsonic compressor performance and stall was investigated. Two types of grids were examined, structured H type grid and structured O-H type grid. Evaluations were conducted by comparing the numerical results with experimental results obtained from a low-speed single-stage rig test for a new concept compressor, called diffuser passage compressor, aiming at improving tip clearance sensitivity. At low mass flow operating conditions, the numerical calculation with O-H type grid showed that the lowest mass flow operating point for which the calculation was able to converge was almost the same as the lowest steady mass flow obtained from the rig test. On the other hand, the numerical calculation with structured H type grid diverged at higher mass flow operating point. It was found that this difference was attributed to the effect of double-valuedness of H type grid that existed at leading edge on the boundary layer development on the blade surface.

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