• Title/Summary/Keyword: Mixed model scheme

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A Comparison of Two Vertical-Mixing Schemes on the Simulation of the Mixed Layer Depth and Upper Ocean Temperature in an Ocean General Circulation Model (두 가지 연직혼합방안에 따른 해양대순환모형 혼합층깊이 및 상층수온 모사 민감도 비교)

  • Yi, Dong-Won;Jang, Chan Joo;Yeh, Sang-Wook;Park, Taewook;Shin, Ho-Jeong;Kim, Donghoon;Kug, Jong-Seong
    • Ocean and Polar Research
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    • v.35 no.3
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    • pp.249-258
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    • 2013
  • Vertical and horizontal mixing processes in the ocean mixed layer determine sea surface temperature and temperature variability. Accordingly, simulating these processes properly is crucial in order to obtain more accurate climate simulations and more reliable future projections using an ocean general circulation model (OGCM). In this study, by using Modular Ocean Model version 4 (MOM4) developed by Geophysical Fluid Dynamics Laboratory, the upper ocean temperature and mixed layer depth were simulated with two different vertical mixing schemes that are most widely used and then compared. The resultant differences were analyzed to understand the underlying mechanism, especially in the Tropical Pacific Ocean where the differences appeared to be the greatest. One of the schemes was the so-called KPP scheme that uses K-Profile parameterization with nonlocal vertical mixing and the other was the N scheme that was rather recently developed based on a second-order turbulence closure. In the equatorial Pacific, the N scheme simulates the mixed layer at a deeper level than the KPP scheme. One of the reasons is that the total vertical diffusivity coefficient simulated with the N scheme is ten times larger, at maximum, in the surface layer compared to the KPP scheme. Another reason is that the zonal current simulated with the N scheme peaks at a deeper ocean level than the KPP scheme, which indicates that the vertical shear was simulated on a larger scale by the N scheme and it enhanced the mixed layer depth. It is notable that while the N scheme simulates a deeper mixed layer in the equatorial Pacific compared to the KPP scheme, the sea surface temperature (SST) simulated with the N scheme was cooler in the central Pacific and warmer in the eastern Pacific. We postulated that the reason for this is that in the central Pacific atmospheric forcing plays an important role in determining SST and so does a strong upwelling in the eastern Pacific. In conclusion, what determines SST is crucial in interpreting the relationship between SST and mixed layer depth.

Development of Hierarchical Production Planning and Control System for Mixed-Model Assembly Manufacture-an Application in Refrigerator Factory (혼류 조립 공장을 위한 계층적 생산 계획 및 통제 시스템 개발 - 냉장고 공장 사례)

  • Shin, Hyun-Joon
    • IE interfaces
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    • v.19 no.1
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    • pp.34-42
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    • 2006
  • This paper presents a scheme for a hierarchical production scheduling and control system for a refrigerator factory with mixed model assembly lines. The setting of the factory is as follows. There are three mixed-model assembly lines called main line A, B and C and two batch lines that supply parts to the main lines. For each of the main lines, three work-centers are dedicated to them. The sub-lines and work-centers produce parts in batch type. An incoming production order from the master planner is characterized by its product type, amount, and due date. Under this situation, the proposed scheme has several features to schedule and control the above mentioned factory; 1) select the starting time and the place (assembly line) for an order processing, 2) devise a way to control orders to be processed as scheduled, and 3) reschedule orders when something unexpected happen. Finally, this paper provides a case study where the proposed scheme is applied to.

A Generalized Mixed-Effects Model for Vaccination Data

  • Choi, Jae-Sung
    • Journal of the Korean Data and Information Science Society
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    • v.15 no.2
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    • pp.379-386
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    • 2004
  • This paper deals with a mixed logit model for vaccination data. The effect of a newly developed vaccine for a certain chicken disease can be evaluated by a noninfection rate after injecting chicken with the disease vaccine. But there are a lot of factors that might affect the noninfecton rate. Some of these are fixed and others are random. Random factors are sometimes coming from the sampling scheme for choosing experimental units. This paper suggests a mixed model when some fixed factors need to have different experimental sizes by an experimental design and illustrates how to estimate parameters in a suggested model.

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A Proportional Odds Mixed - Effects Model for Ordinal Data

  • Choi, Jae-Sung
    • Journal of the Korean Data and Information Science Society
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    • v.18 no.2
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    • pp.471-479
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    • 2007
  • This paper discusses about how to build up mixed-effects model for analysing ordinal response data by using cumulative logits. Random factors are assumed to be coming from the designed sampling scheme for choosing observational units. Since the observed responses of individuals are ordinal, a proportional odds model with two random effects is suggested. Estimation procedure for the unknown parameters in a suggested model is also discussed by an illustrated example.

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A Study on the Mixed Model Approach and Symbol Probability Weighting Function for Maximization of Inter-Speaker Variation (화자간 변별력 최대화를 위한 혼합 모델 방식과 심볼 확률 가중함수에 관한 연구)

  • Chin Se-Hoon;Kang Chul-Ho
    • The Journal of the Acoustical Society of Korea
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    • v.24 no.7
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    • pp.410-415
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    • 2005
  • Recently, most of the speaker verification systems are based on the pattern recognition approach method. And performance of the pattern-classifier depends on how to classify a variety of speakers' feature parameters. In order to classify feature parameters efficiently and effectively, it is of great importance to enlarge variations between speakers and effectively measure distances between feature parameters. Therefore, this paper would suggest the positively mixed model scheme that can enlarge inter-speaker variation by searching the individual model with world model at the same time. During decision procedure, we can maximize inter-speaker variation by using the proposed mixed model scheme. We also make use of a symbol probability weighting function in this system so as to reduce vector quantization errors by measuring symbol probability derived from the distance rate of between the world codebook and individual codebook. As the result of our experiment using this method, we could halve the Detection Cost Function (DCF) of the system from $2.37\%\;to\;1.16\%$.

An operation scheme for the mixed model assembly lines scheduling (혼류 조립 생산 라인 계획 운영 구조)

  • Shin, Hyeon-Jun;Chun, Jin;Kim, Seong-Sik
    • Proceedings of the Korean Operations and Management Science Society Conference
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    • 1996.04a
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    • pp.365-368
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    • 1996
  • The setting of the factory under this study is as the following. There are multiple assembly lines. Each line can handle any of given set of products. Furthermore each line is capable of assembling several products concurrently, i.e. mixed model assembly line. An incoming production order is characterized by its due-date, product type and quantity. Under this setting we first have to select the starting time and the place(assembly line) for an order to be processed. We also have to devise a way to control orders to be manufactured as scheduled. Finally there should be a mean to reschedule orders when something unexpected happens. This paper offers a scheme that provides the above mentioned necessities. It also provides a case where the scheme is applied.

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Unsteady cascade flow calculations of using dual time stepping and the k-$\omega$ turbulence model (이중시간전진법과 k-$\omega$ 난류모델을 이용한 익렬 내부 비정상 유동해석)

  • Choe, Chang-Ho;Yu, Jeong-Yeol
    • Transactions of the Korean Society of Mechanical Engineers B
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    • v.21 no.12
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    • pp.1624-1634
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    • 1997
  • A numerical study on two-dimensional unsteady transonic cascade flow has been performed by adopting dual time stepping and the k-.omega. turbulence model. An explicit 4 stage Runge-Kutta scheme for the compressible Navier-Stokes equations and an implicit Gauss-Seidel iteration scheme for the k-.omega. turbulence model are proposed for fictitious time stepping. This mixed time stepping scheme ensures the stability of numerical computation and exhibits a good convergence property with less computation time. Typical steady-state convergence accelerating schemes such as local time stepping, residual smoothing and multigrid combined with dual time stepping shows good convergence properties. Numerical results are presented for unsteady laminar flow past a cylinder and turbulent shock buffeting problem for bicircular arc cascade flow is discussed.

Design of On-line Process Control with Variable Measurement Interval

  • Park, Changsoon
    • Journal of the Korean Statistical Society
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    • v.29 no.3
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    • pp.319-336
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    • 2000
  • A mixed model with a white noise process and an IMA(0,1,1) process is considered as a process model. It is assumed that the process is a white noise in the absence of a special cause and the process changes to an IMA(0,1,1) due to a special cause. One useful scheme in measuring the process level is to use the variable measurement interval (VMI) between measurement times according to the value of the previous chart statistic. The advantage of the VMI scheme is to measure the process level infrequently when in control to save the measurement cost and to measure frequently when out of control to save the off-target cost. This paper considers the VMI scheme in order to detect changes in the process model from a white noise to an IMA(0,1,1). The VMI scheme is shown to be effective compared to the standard fixed measurement interval (FMI) scheme in both statistical and economic contexts.

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Cavitating Flow Simulation Using Two-Fluid Two-Phase Flow Model and HLL Scheme (이유체 이상유동 모델과 HLL 스킴을 이용한 캐비테이션 유동 해석)

  • Yeom Geum-Su;Chang Keun-Shik
    • 한국전산유체공학회:학술대회논문집
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    • 2005.04a
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    • pp.219-222
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    • 2005
  • A compressible two-fluid two-phase flow computation model using the stiffened-gas equation of state is formulated. Since the conservation equation system is of mixed type, it gives complex eigenvalues. The sonic speeds obtained from the individual single phase have been simply used in the literature for the fastest wave speeds necessary in the HLL scheme. This method has worked fine but proved to be quite diffusive according to our test. To improve the accuracy, we here propose to utilize the analytic eigenvalues evaluated from an approximate Jacobian matrix lot the fastest wave speeds. The interfacial transfer terms were dropped in constituting the Jacobian matrix for this purpose. The present scheme proved efficient, robust and accurate in comparison with other existing methods. We solved the cavitating flow problem using the present scheme. The result shows more detailed wave structure in the cavitating process caused by the strong expansion waves.

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A batch scheduling scheme for the workcenters that supply parts to mixed-model assembly lines (혼류 조립 라인에 batch 단위로 부품을 공급하는 단위 작업장의 생산계획 수립)

  • 백종관;백준걸;김성식
    • Proceedings of the Korean Operations and Management Science Society Conference
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    • 1996.04a
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    • pp.369-372
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    • 1996
  • The factory under this study consists of mixed-model assembly lines and workcenters which provide parts to the main lines. Parts produced by the workcenter have different specifications for different product models. The workcenters fabricate parts in batches, and they are divided into two types. A type 1 center supplies parts only to the main line that is designated to the center while type 2 center provides parts to all the main lines. The purpose of this study is to develop a scheduling scheme for the workcenter, and the main objective of the schedules is to provide parts for the main lines without delay. The facts that make the scheduling challengeable are that 1) the different models existing together on a main line request different parts, 2) the spaces for part inventories are limited and 3) set up times are sequence dependent and long in some cases. This study presents developed scheduling schemes for the type 1 center and explains the scheduling and control structure used.

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