• Journal of computational fluids engineering
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• v.19 no.2
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• pp.8-16
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• 2014

Two-dimensional prediction capability of several analysis codes, such as XFOIL, MSES, and KFLOW, is compared and analyzed based on computational results of airfoil flows. To this end the transition transport equations are coupled with the Navier-Stokes equations for the prediction of the natural transition and the separation-induced transition. Experimental data of aerodynamic coefficients are used for comparison with numerical results for the transitional flows. Numerical predictions using the transition transport model show a good agreement with experimental data. Discrepancies have been found in the prediction of the pressure drag are mainly caused by the difference in the far-field circulation correction methods.

• Journal of Ocean Engineering and Technology
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• v.34 no.2
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• pp.128-135
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• 2020

When high waves and storm surge strike simultaneously, the characteristics of the fluid field change drastically from overtopping according to the wave runup height to overflow through a transition state that combines overtopping and overflows. However, an estimation model or evaluation method has not yet been established because there is not enough engineering data. This study developed a wave overtopping-overflow transition model based on a full-scale experiment involving wave overtopping and overflow transition, which appropriately reproduced the effect of waves or the temporal change in inundation flow. Using this model to perform a calculation for the wave overtopping and overflow transition process under typical circumstances, this study determined the wave runup height and features of the inundation flow under time series changes as an example.

• Advanced Composite Materials
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• v.18 no.1
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• pp.77-93
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• 2009

This paper investigated the damage transition mechanism between the fiber-breaking mode and the fiber-avoiding crack mode when the fiber-length is reduced in the unidirectional discontinuous carbon fiber-reinforced-plastics (CFRP) composites. The critical fiber-length for the transition is a key parameter for the manufacturing of flexible and high-strength CFRP composites with thermoset resin, because below this limit, we cannot take full advantage of the superior strength properties of fibers. For this discussion, we presented a numerical model for the microscopic damage and fracture of unidirectional discontinuous fiber-reinforced plastics. The model addressed the microscopic damage generated in these composites; the matrix crack with continuum damage mechanics model and the fiber breakage with the Weibull model for fiber strengths. With this numerical model, the damage transition behavior was discussed when the fiber length was varied. The comparison revealed that the length of discontinuous fibers in composites influences the formation and growth of the cluster of fiber-end damage, which causes the damage mode transition. Since the composite strength is significantly reduced below the critical fiber-length for the transition to fiber-avoiding crack mode, we should understand the damage mode transition appropriately with the analysis on the cluster growth of fiber-end damage.

• Interaction and multiscale mechanics
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• v.7 no.1
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• pp.543-561
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• 2014

We present a full energy and force formulation of the quasicontinuum method with non-local and local transition elements. Non-local transition elements are developed to transmit inhomogeneity from the atomistic to the continuum regions. Local transition elements are developed to resolve the mathematical mismatch between non-local atoms and the local continuum. The rationale behind these transition elements is provided by analyzing the energy and force transitions between atoms and continuum under the Cauchy-Born rule. We show that breakdown of the Cauchy-Born rule occurs for slaved atoms of local elements within the cutoff of non-local atoms. The inadequacy of the Cauchy-Born rule at the transition region naturally leads to the need of atomistic treatment of transition slaved and transition representative atoms. Such an atomistic treatment together with a full or cutoff sampling allows non-local transition elements containing these transition entities to transmit inhomogeneity. Different force formulations for transition representative atoms and pure local representative atoms allow the local transition elements to resolve non-local and local mismatches. The method presented herein is validated by force calculations in an unstressed perfect crystal as well as an unrelaxed grain boundary model. A nanoindentation simulation in 3D is conducted to demonstrate the accuracy and efficiency of the proposed method.

• Bulletin of the Korean Chemical Society
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• v.34 no.11
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• pp.3425-3428
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• 2013

We solve the Klein-Gordon equation with the Morse empirical potential energy model. The bound state energy equation has been obtained in terms of the supersymmetric shape invariance approach. The relativistic vibrational transition frequencies for the $X^1{\sum}^+$ state of ScI molecule have been computed by using the Morse potential model. The calculated relativistic vibrational transition frequencies are in good agreement with the experimental RKR values.

• Bulletin of the Korean Chemical Society
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• v.16 no.11
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• pp.1119-1121
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• 1995

The method for the Schlo"gl model with the first order transition is extended to the Scho;gl model with the second order transition for a photochemical reaction. We obtain the explicit results of the time-dependent average and the time correlation function at the unstable steady state of the model in the neighborhood of the Gaussian white noise and then discuss the effect of noise on the dynamic properties.

• Proceedings of the Korean Operations and Management Science Society Conference
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• 2005.10a
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• pp.213-216
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• 2005

In this research, we explore how to manage the transition of technology generations considering incremental innovation of the existing technology generation. Firms can slow down decaying of the existing technology by continuous incremental improvements rather than introducing a new generation technology at the first time if the former strategy is better. We characterize optimal technology transition problem by setting up an optimal control model. The model which is originally designed and solved by Thompson(1968) as a ‘Machine maintenance problem’ has been cited to build the main body of our model. With this analytical model, we derive optimal ‘incremental innovation’ strategy which is considering transition to the next technology. Our analysis indicates that there exists an unique ‘stopping incremental innovation timing’. Before the point of time, the decision maker should make his effort at a maximum level to enhance the current technology. However from the stopping timing to the final time horizon where the new technology is introduced, it is found that not to invest to the current technology any more is optimal.

• Journal of Korea Planning Association
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• v.53 no.7
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• pp.67-86
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• 2018

This paper attempted to analyze impacts of transition in electricity generation system on a national economy and environmental level in Korea using a recursive computable general equilibrium(CGE) model. In particular, the paper presented a hybrid model combining the top-down CGE model with the bottom-up model which describes the structure of electricity production in detail. The impacts were analyzed by two policy scenarios base on the basic plan for electricity supply and demand proposed by the Korean government. As a result, the paper specifically showed that there exists a trade-off relationship in the policy-making between economic efficiency and environmental level. The paper also suggested that the transition in electricity generation system should be done more gradually and carefully.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.24 no.4 s.175
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• pp.824-829
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• 2000

The industries use polymer materials for many purposes because they have many merits. But these materials' costs take up too much proportion in overall cost of products that use these materials as their major material. So it is very economical for polymer industries to reduce these costs. Microcellular foaming process appeared in 1980's to solve this problem and it proved to be quite successful. This process uses inert gases such as CO2, N2. As these gases are dissolved into polymer matrices. many properties are changed. Glass transition temperature is one of these properties. DSC, DMA are devices that measures this temperature, but these are not sufficient to measure the temperature of polymer containing gas. In this paper, we devised a new tester that uses magnetism. We used this device to acquire data of the change of glass transition temperature and made Cha-Yoon model that can predict the change of glass transition temperature. Using this model, the change of this temperature can be estimated as a function of weight gain of gas. Cha-Yoon model proved that Chow's model is inappropriate to predict the change of glass transition temperature of polymer matrices containing gas.

• Korean Journal of Hydrosciences
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• v.7
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• pp.1-8
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• 1996

The location and the shape of a freshwater transition zone in a coastal aquifer are affected by many hydraulic variables. To data most works to determine the effects of these variables are limited to qualitative comparison of transiton zones. In this work characteristics of transition zones are analyzed quantitatively. The investigation is limited to a steady-state transition zones. Three dimensionless variables are defined to represent characteristics of steady-state transition zones. They are maximum introsion length, thickness, and degree of stratification. Effects of principal hydraulic variables (velocity and dispersivity) on these characteristics are studied using a numerical model. Dimensional analysis is used to systematically analyze entire model results. Effects of velocity and dispersivity are seem clearly. From this study, increase in velocity is found to cause shrinkage of transition zones. This observation contradicts claims by some that, because dispersion is proportional to velocity, increase in velocity would cause expansion of transition zones.