• Title/Summary/Keyword: Homogeneous Mixture Model

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Clustering In Tied Mixture HMM Using Homogeneous Centroid Neural Network (Homogeneous Centroid Neural Network에 의한 Tied Mixture HMM의 군집화)

  • Park Dong-Chul;Kim Woo-Sung
    • The Journal of Korean Institute of Communications and Information Sciences
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    • v.31 no.9C
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    • pp.853-858
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    • 2006
  • TMHMM(Tied Mixture Hidden Markov Model) is an important approach to reduce the number of free parameters in speech recognition. However, this model suffers from a degradation in recognition accuracy due to its GPDF (Gaussian Probability Density Function) clustering error. This paper proposes a clustering algorithm, called HCNN(Homogeneous Centroid Neural network), to cluster acoustic feature vectors in TMHMM. Moreover, the HCNN uses the heterogeneous distance measure to allocate more code vectors in the heterogeneous areas where probability densities of different states overlap each other. When applied to Korean digit isolated word recognition, the HCNN reduces the error rate by 9.39% over CNN clustering, and 14.63% over the traditional K-means clustering.

CAVITATING FLOW ANALYSIS OF CONVERGING-DIVERGING CHANNEL (수축-확대 채널내부의 캐비테이션 유동해석)

  • Jin, M.S.;Ha, K.T.;Park, W.G.
    • 한국전산유체공학회:학술대회논문집
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    • 2011.05a
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    • pp.14-19
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    • 2011
  • Two difference cavitation models based on the homogeneous mixture model are used to study cavitating flows through converging-diverging channel. Here, the cloud cavities, pressure distributions and other results have been obtained and compared to evaluate two cavitation models. What's more, differences are observed in the simulated results, due to the differences in characteristics of each model. Analytical results shows that the new improvement cavitation model is validated to have better effects on simulating cavitating flows

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CAVITATION FLOW ANALYSIS OF 2-D HYDROFOIL USING A HOMOGENEOUS MIXTURE MODEL ON UNSTRUCTURED MESHES (비정렬 격자계에서 균질혼합 모델을 이용한 2차원 수중익형 주위의 캐비테이션 유동 해석)

  • An, S.J.;Kwon, O.J.
    • 한국전산유체공학회:학술대회논문집
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    • 2011.05a
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    • pp.20-24
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    • 2011
  • In this paper, numerical simulation of cavitation flow for modified NACA66 hydrofoil was made by using the multi-phase RANS equation based on pseudo-compressibility. The Homogeneous mixture model comprised of the mixture continuity, mixture momentum and liquid volume fraction equations was utilized. A vertex-centered finite-volume method was used in conjunction 2nd-order Roe's FDS to discretize the inviscid fluxes. The viscous fluxes were computed based on central differencing The Spalart-Allmaras one equation model was employed for the closure of turbulence. Reasonable agreements were obtained between the calculation results and the experiment for pressure coefficients on the hydrofoil surface.

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CAVITATION FLOW SIMULATION FOR A 2-D HYDROFOIL USING A HOMOGENEOUS MIXTURE MODEL ON UNSTRUCTURED MESHES (비정렬 격자계에서 균질혼합 모델을 이용한 2차원 수중익형 주위의 캐비테이션 유동 해석)

  • Ahn, S.J.;Kwon, O.J.
    • Journal of computational fluids engineering
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    • v.17 no.1
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    • pp.94-100
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    • 2012
  • In this paper, the cavitating flows around a hydrofoil have been numerically investigated by using a 2-d multi-phase RANS flow solver based on pseudo-compressibility and a homogeneous mixture model on unstructured meshes. For this purpose, a vertex-centered finite-volume method was utilized in conjunction with 2nd-order Roe's FDS to discretize the inviscid fluxes. The viscous fluxes were computed based on central differencing. The Spalart-Allmaras one equation model was employed for the closure of turbulence. A dual-time stepping method and the Gauss-Seidel iteration were used for unsteady time integration. The phase change rate between the liquid and vapor phases was determined by Merkle's cavitation model based on the difference between local and vapor pressure. Steady state calculations were made for the modified NACA66 hydrofoil at several flow conditions. Good agreements were obtained between the present results and the experiment for the pressure coefficient on a hydrofoil surface. Additional calculation was made for cloud cavitation around the hydrofoil. The observation of the vapor structure, such as cavity size and shape, was made, and the flow characteristics around the cavity were analyzed. Good agreements were obtained between the present results and the experiment for the frequency and the Strouhal number of cavity oscillation.

A Study on Pressure Drop Characteristics of Refrigerant in Heat Exchanger for Automobile (자동차용 열교환기 냉매의 압력 강하 특성에 관한 연구)

  • 임태우;박종운
    • Transactions of the Korean Society of Automotive Engineers
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    • v.11 no.2
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    • pp.119-125
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    • 2003
  • An experiment study on pressure drop was carried out for both an adiabatic and a diabatic two-phase flow with pure refrigerants R134a and Rl23 and their mixtures as test fluids in a uniformly heated horizontal tube. The frictional pressure drop during flow boiling is predicted by using two models; the homogeneous model that assumes equal phase velocity and the separate flow model that allows a slip velocity between two phases. The measured frictional pressure drop was compared to a few available correlations. Homogeneous model considerally underpredicted the present data for mixture as well as pure component in the entire mass velocity ranges employed in the present study, while Friedel correlation was found to satisfactorily correlate the frictional pressure drop data as compared to other correlation.

A Study on Optimal Release Time for Software Systems based on Mixture Weibull NHPP Model (혼합 와이블 NHPP 모형에 근거한 소프트웨어 최적방출시기에 관한 연구)

  • Lee, Sang Sik;Kim, Hee Cheul
    • Journal of Korea Society of Digital Industry and Information Management
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    • v.6 no.2
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    • pp.183-191
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    • 2010
  • Decision problem called an optimal release policies, after testing a software system in development phase and transfer it to the user, is studied. The applied model of release time exploited infinite non-homogeneous Poisson process. This infinite non-homogeneous Poisson process is a model which reflects the possibility of introducing new faults when correcting or modifying the software. The failure life-cycle distribution used mixture which has various intensity, if the system is complicated. Thus, software release policies which minimize a total average software cost of development and maintenance under the constraint of satisfying a software reliability requirement becomes an optimal release policies. In a numerical example, after trend test applied and estimated the parameters using maximum likelihood estimation of inter-failure time data, estimated software optimal release time.

Does mudcake change the results of modeling gamma-gamma well-logging?

  • Rasouli, Fatemeh S.
    • Nuclear Engineering and Technology
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    • v.54 no.9
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    • pp.3390-3397
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    • 2022
  • Among the different techniques available, nuclear methods, including gamma-gamma logging tools, are of special importance. Though the real environment which surrounds the drilled borehole is a complex fractured medium which the fluid can flow through the porosities, simulation studies generally use the traditional model of a homogeneous mixture of formation and the liquid. Considering a previously published study, which shows that modeling of fluid flow in fractured reservoirs and simulating the formation as an inhomogeneous fractured medium leads to different results compared with those of homogeneous mixture, here we study the effect of the presence of drilling fluid (mudcake) on the response of the detectors in both the models. To study this effect, a typical gamma-gamma logging tool was modeled by using the MCNPX Monte Carlo code. The results show that the responses of the detectors in the mixture model in the presence of various thicknesses of mudcake are sensitive to the density of the formation material. However, this effect is not notable in the inhomogeneous fractured medium. These results emphasize the importance of the model employed for simulation of the medium in gamma-gamma well-logging.

SIMULATION OF THE DESIGN METHODOLOGY FOR HIGH PERFORMANCE AND EFFICIENT CAVITATOR (측류유동을 고려한 실린더 주위의 캐비테이션 유동 현상 해석)

  • Lee, B.W.;Park, S.I.;Park, W.G.;Lee, K.C.
    • 한국전산유체공학회:학술대회논문집
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    • 2009.11a
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    • pp.177-184
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    • 2009
  • Cavitating flow simulation is of practical importance for many engineering systems, such as marine propellers, pump impellers, nozzles, injectors, torpedoes, etc. The present work has focused on the simulation of cavitating flow past cylinders with strong side flows. The governing equation is the Navier-Stokes equation based on the homogeneous mixture model. The momentum and energy equation is in the mixture phase while the continuity equation is solved liquid and vapor phase, separately. An implicit dual time and preconditioning method are employed for computational analysis. For the code validation, the results from the present solver have been compared with experiments and other numerical results. A fairly good agreement with the experimental data and other numerical results have been obtained. After the code validation, the strong side flow was applied to include the wake flow effects of the submarine or ocean tide.

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SIMULATION OF CAVITATING FLOW PAST CYLINDERS WITH STRONG SIDE FLOW (측류유동을 고려한 실린더 주위의 캐비테이션 유동 현상 해석)

  • Lee, B.W.;Park, W.G.;Lee, K.C.
    • 한국전산유체공학회:학술대회논문집
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    • 2009.04a
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    • pp.149-154
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    • 2009
  • The cavitating flow simulation is of practical importance for many engineering systems, such as marine propellers, pump impellers, nozzles, injectors, torpedoes, etc. The present work has focused on the simulation of cavitating flow past cylinders with strong side flow. The governing equation is the Navier-Stokes equation based on homogeneous mixture model. The momentum and energy equation is in the mixture phase while the continuity equation is solved liquid and vapor phase, separately. An implicit dual time and preconditioning method are employed for computational analysis. The results from the present solver have been in a fairly good agreement with the experimental data and other numerical results. After the code validation the strong side flow was applied to include the wake flow effect of the submarine.

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Numerical simulation of cavitating flow past cylinders

  • Park, Warn-Gyu;Koo, Tae-Kyoung;Jung, Chul-Min;Lee, Kurn-Chul
    • 한국전산유체공학회:학술대회논문집
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    • 2008.03a
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    • pp.327-333
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    • 2008
  • The cavitating flow simulation is of practical importance for many engineering systems, such as marine propellers, pump impellers, nozzles, injectors, torpedoes, etc. The present work has developed a base code for simulating cavitating flows past cylinders and hydrofoils. The governing equation is the Navier-Stokes equation based on homogeneous mixture model. The momentum and energy equation is in the mixture phase while the continuity equation is solved in liquid and vapor phase, separately. The solver employs an implicit preconditioning algorithm in curvilinear coordinates. The computations have been carried out for the cylinders with spherical, 1- and 0-caliber forebody and hydrofoil of ALE and NACA cross-section and, then, compared with experiments and other numerical results. Fairly good agreements with experiments and numerical results have been achieved. The present base code has shown the feasibility to solve the cavitating flow past supercavitating torpedo after the improvement for compressibility effects and interactions with hot exhaust gas of propulsive rocket.

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