• Title/Summary/Keyword: Model Equation

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Numerical Study on Pulverized Coal Combustion Applying Two-Phase WSGGM (이상 회체가스 가중합산모델을 적용한 미분탄 연소의 수치적 연구)

  • Yu, Myoung-Jong;Kang, Shin-Jae;Baek, Seung-Wook
    • Transactions of the Korean Society of Mechanical Engineers B
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    • v.24 no.10
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    • pp.1368-1379
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    • 2000
  • A numerical study on swirling pulverized coal combustion in an axisymmetric enclosure is carried out by applying the 2-phase weighted sum of gray gases model (WSGGM) approach with the discrete ordinate method (DOM) to model the radiative heat transfer equation. In the radiative transfer equation, the same polynomial equation and coefficients for weighting factors as those for gas are adopted for the coal/char particles as a function of partial pressure and particle temperature. The Eulerian balance equations for mass, momentum, energy, and species mass fractions are adopted with the standard and RNG k-${\varepsilon}$ turbulence model, whereas the Lagrangian approach is used for the particulate phase. The eddy-dissipation model is employed for the reaction rate for gaseous mixture, and the single-step and two-step first-order reaction model for the devolatilization process for coal. Special attention is given to establish the thermal boundary conditions on radiative transfer equation By comparing the numerical results with experimental ones, the radiation model used here is confirmed and found to provide an alternative for simulating the radiative transfer.

Evaluation Model for Environmentally Friendliness of Tourism Farms by LISREL Structural Equation Model (LISREL 구조방정식 모델에 의한 농촌 관광농원의 환경친화성 평가 모형 추정)

  • Eom, Boong-Hoon
    • Journal of Korean Society of Rural Planning
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    • v.5 no.2 s.10
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    • pp.56-65
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    • 1999
  • Recently, new concept and paradigm of 'Environmentally-Friendliness' is taking a growing interest in environmental planning and design. This study is to establish the evaluation model for environmentally-friendliness of 'Tourism Farms' in rural areas by LISREL structural equation model. A questionnaire survey was conducted for deputy manager group and expert group. As the Result of LISREL structural equation model, the environmentally-friendliness of tourism farms is composed of three categories. First, conservation of global environment (Low Impact), second, friendliness to surrounding nature(High Contact), and third, environmental health and amenities (Health & Amenity). Five indicators, such as (1)saving of energy and water resource, (2)reduction and reuse of garbage, (3)natural purification of sewage disposal, (4)utilization of natural energy, (5)campaign and education programs of environmentally-friendliness, were affecting the first category, i.e., conservation of global environment(Low Impact). Friendliness to surrounding nature (High Contact) is affected by 3 indicators, (1)contact to nature and diverse green areas, (2)water intimate & contact areas, (3)natural ecology observation by biotope. Finally, the dimension of environmental health and amenity is affected by 3 indicators, (1)nature affinity by farming experience, (2)environmental-friendliness of soil & crops by organic farming, (3) campaign and education programs of environmentally-friendliness. Total coefficient of determination of the structural equation model by LISREL was 0.897, which showed high explanatory power.

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Comparision Analysis of Model Test for Prediction of Uplift Resistance in the Reclaimed Land Greenhouse Foundation (간척지 온실기초 나무말뚝의 인발저항력 예측을 위한 실내모형시험 결과 비교·분석)

  • Song, Chang Seob;Kim, Myeong Hwan;Jang, Ung Hee
    • Journal of The Korean Society of Agricultural Engineers
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    • v.58 no.2
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    • pp.45-52
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    • 2016
  • The object of this paper was to evaulate modified proposed design equation in model test result in order to estimate uplift-resistance of timber pile of reclaimed land greenhouse foundation. Uplift resistance result of model test was increased to according to increased of contact area. Uplift-resistance result of field test tend to lineary increased to according to increased of embedment depth and contact area. Results of field uplift-resistance was evaluate compare with modified proposed design equation results of model test and Effective stress method. As the Effective stress method tend to underestimate, modified proposed design equation results of model test tend to similar type. As the contact area increase, difference between field uplift-resistance results and modified proposed design equation results of model test was considered uplift-speed.

Solving partial differential equation for atmospheric dispersion of radioactive material using physics-informed neural network

  • Gibeom Kim;Gyunyoung Heo
    • Nuclear Engineering and Technology
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    • v.55 no.6
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    • pp.2305-2314
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    • 2023
  • The governing equations of atmospheric dispersion most often taking the form of a second-order partial differential equation (PDE). Currently, typical computational codes for predicting atmospheric dispersion use the Gaussian plume model that is an analytic solution. A Gaussian model is simple and enables rapid simulations, but it can be difficult to apply to situations with complex model parameters. Recently, a method of solving PDEs using artificial neural networks called physics-informed neural network (PINN) has been proposed. The PINN assumes the latent (hidden) solution of a PDE as an arbitrary neural network model and approximates the solution by optimizing the model. Unlike a Gaussian model, the PINN is intuitive in that it does not require special assumptions and uses the original equation without modifications. In this paper, we describe an approach to atmospheric dispersion modeling using the PINN and show its applicability through simple case studies. The results are compared with analytic and fundamental numerical methods to assess the accuracy and other features. The proposed PINN approximates the solution with reasonable accuracy. Considering that its procedure is divided into training and prediction steps, the PINN also offers the advantage of rapid simulations once the training is over.

Model-independent reconstruction of the equation of state of dark energy

  • Hwang, Seung-gyu;L'Huillier, Benjamin
    • The Bulletin of The Korean Astronomical Society
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    • v.45 no.1
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    • pp.69.1-69.1
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    • 2020
  • While Dark Energy is one of the explanations for the accelerating expansion of the Universe, its nature remains a mystery. The standard (flat) ΛCDM model is consistent with cosmological observations: type Ia Supernova, BAO, CMB, and so on. However, the analysis of observations assuming a model, model-dependent approach, is likely to bias the results towards the assumed model. In this poster, I will introduce model-independent approach with Gaussian process and the application of Gaussian process regression to reconstruct the equation of state of dark energy.

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Prediction of Longshore Current with Set-up/down Effect on a Plane Beach (일정경사 수심단면에서 평균수위의 상승/저하 효과를 고려한 해빈류의 예측)

  • Lee, Cheol-Eung;Kim, Young-Jung;Choi, Han-Kyu
    • Journal of Industrial Technology
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    • v.17
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    • pp.277-289
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    • 1997
  • The numerical model for prediction of longshore current with set-up/down effect on a plane beach is developed using the longshore component of the depth-integrated momentum balance equation. To predict the longshore current, the wave height model should first be formulated because the longshore current depends on the wave height directly. Two wave model, regular wave model and random wave model, are developed based on the energy flux balance equation. Also, the numerical model estimating the set-up inside the shoreline is developed using both the on-offshore momentum equation and the moving boundary technique. The numerical models are verified by the analytical solution, and compared with laboratory data. It is found from the comparison that developed models may be predicted accurately the longshore current with set-up/down effect on a plane beach.

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Interrelationship Between the Drift-flux Model and the Two-fluid Model (드리프트 플럭스 모델과 2-유체 모델 사이의 상관 관계)

  • No, Hee-Cheon
    • Nuclear Engineering and Technology
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    • v.25 no.2
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    • pp.233-236
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    • 1993
  • For one-dimensional two-phase flow without phase change and without axially-temporally rapid change of pressure, the interrelationship between the drift-flux model and the two-fluid model is studied. It is derived on the basis of the fact that the vapor conservation equation is related to the momentum equation by the drift flux. Starting from the two-fluid model, we obtain the interfacial friction expressed in terms of drift-flux parameter. Also, by deriving the void propagation equation, the drift-flux is shown to have jnterrelationship with forces in the two-fluid model.

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Analytic model to determine the unknown parameters of JWL++ rate equation (JWL++ 반응속도식의 미정상수 결정을 위한 화약의 이론적 모델)

  • Kim, Bohoon;Yoh, Jai-ick
    • 한국연소학회:학술대회논문집
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    • 2012.04a
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    • pp.283-286
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    • 2012
  • The analytical model determining the unknown parameters of reaction rate equation which is necessary to simulate the combustion phenomena of energetic materials is proposed. The relationship between detonation velocity and size effect of energetic materials is derived from simplified JWL++ model. Theoretical model is used to investigate the combustion characteristics of certain energetic materials before running Hydrocode by pre-determination of unknown parameter, b. When b=0.8, the behavior of HANFO gunpowder is in the form of concave-up and ANFO explosives has the concave-down form in case of b=1.5. The analytical model provides efficient and highly accurate results rather than previous method which simulated the unconfined-rate-stick via the numerical means.

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Simulation of Miniaturized n-MOSFET based Non-Isothermal Non-Equilibrium Transport Model (디바이스 시뮬레이션 기술을 이용한 미세 n-MOSFET의 비등온 비형형장에 있어서의 특성해석)

  • Choi, Won-Cheol
    • Journal of the Korean Society of Industry Convergence
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    • v.4 no.3
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    • pp.329-337
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    • 2001
  • This simulator is developed for the analysis of a MOSFET based on Thermally Coupled Energy Transport Model(TCETM). The simulator has the ability to calculate not only stationary characteristics but also non - stationary characteristics of a MOSFET. It solves basic semiconductor devices equations including Possion equation, current continuity equations for electrons and holes, energy balance equation for electrons and heat flow equation, using finite difference method. The conventional semiconductor device simulation technique, based on the Drift-Diffusion Model (DDM), neglects the thermal and other energy-related properties of a miniaturized device. I, therefore, developed a simulator based on the Thermally Coupled Energy Transport Model (TCETM) which treats not only steady-state but also transient phenomena of such a small-size MOSFET. In particular, the present paper investigates the breakdown characteristics in transient conditions. As a result, we found that the breakdown voltage has been largely underestimated by the DDM in transient conditions.

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Lumped Modeling of Thermal Inkjet Print Head (열 잉크젯 프린트헤드의 집중질량 모델링)

  • Lee You-Seop
    • Transactions of the Korean Society of Mechanical Engineers B
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    • v.30 no.10 s.253
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    • pp.942-949
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    • 2006
  • A lumped model is proposed to predict liquid ejection characteristics of a thermally driven inkjet print head. The model is based on a two-dimensional heat conduction equation, an empirical pressure-temperature equation and a nonlinear hydraulic flow-pressure equation. It has been simulated through the construction of an equivalent R-C circuit, and subsequently analyzed using SIMULINK and a circuit simulation tool, PLECS. Using the model, heating and cooling characteristics of the head are predicted to be in agreement with the IR temperature measurements. The effects of the head geometry on the drop ejection are also analyzed using the nonlinear hydraulic model. The present model can be used as a design tool for a better design of thermal inkjet print heads.