• International Journal of Highway Engineering
• /
• v.9 no.4
• /
• pp.21-32
• /
• 2007

The linear traffic model(Vertical queueing model) that is adopted widely in traffic flow estimation assumes that all vehicles have the identical motion before joining a queue at the stop-line. Thus, a queue is supposed to form vertically not horizontally. Due to the simplicity of this model, the departure time of the leading vehicle is assumed to coincide with the start of effective green time. Thus, the delay estimates given by the Vertical queueing model is not always realistic. This paper explores a microscopic traffic model(a Kinematic Car-following model at Signalised intersections: a KCS traffic model) based on the one dimensional Kinematic equations in physics. A comparative evaluation in delay and sensitivity of delay difference between the KCS traffic model and the previously known Vertical queueing model is presented. The results show that the delay estimate in the Vertical queueing model is always greater than or equal to the KCS traffic model; however, the sensitivity of delay in the KCS traffic model is greater than the Vertical queueing model.

• Journal of Korean Society of Steel Construction
• /
• v.18 no.2
• /
• pp.123-135
• /
• 2006

This paper investigates the design equations and the strength behavior of the diaphragm for steel box beams and circular-column connections. The strength of the connection is decided by the strength of the diaphragm and the strength of the beam and the column, because the connection diaphragm supports the concentration forces from the box beam's lower flange. In previous researches, however, the calculation procedure of the diaphragm stress from the indeterminate curved-beam model is to complicated to apply in process of the equation. Moreover, no reasonable design has yet ben made because the diaphragm's effect on the strength of the connection has not ben considered. Therefore, through nonlinear FEM analysis of the connection diaphragm, this study examines the strength behavior of a connection with diaphragm details. In addition, a great difference is confirmed between the theoretical and analytic behaviors. Fi naly, considering the strength of the connection and the rigidity capacity of the diaphragm, the diaphragm design method is proposed.

• Membrane Journal
• /
• v.16 no.4
• /
• pp.252-258
• /
• 2006

A numerical analysis was performed for a separation process of carbon dioxide from a flue gas stream using polyethersulfone hollow fiber membranes. Countercurrent flow governing equations were regarded to be two point boundary-value problem and the nonlinear ordinary differential equation were simultaneously solved using the finite- difference method. A computer program was developed using the Compaq Visual Fortran 6.6 software. The carbon dioxide permeate driving force and the fred gas residence time at the inside of membrane were found to be very important factors affecting the permeation characteristics of carbon dioxide. The carbon dioxide concentration in the permeate and the flow rate of the permeate were found to be slightly larger by a few percent with a countercurrent flow analysis than those with a cocurrent flow analysis.

• Water for future
• /
• v.24 no.4
• /
• pp.41-48
• /
• 1991

This paper describes the characteristics of tidal currents in the Gamag Bay by using the two-dimensional nonlinear hydrodynamic euation. The basic equations are derived by Navier-Stokes momentum equation and continuity equation and its characteristics critically are reviewed, and they are analysed by the implicit finite difference method. The numerical model is constructed two-dimensional(depth-averaged) simple layer model. This paper investigates the stability of solution and convergence of solution in application of the method to Gamag Bay, and the reproducibility of the simulation is also discussed in comparison with the results of field survey. The following items are clarifide through the numerical investigation; i)the reproduc-ibility of tidal range and currents are quite acceptable, comparing with the results of model tests and field data, and ii) tidal cycle for convergent solution is four tidal cycle, also, iii) bottom friction is successfully represented as c=(1/n))$h^{1/6}$.

• Korean Journal of Veterinary Research
• /
• v.25 no.1
• /
• pp.33-40
• /
• 1985

The inhibitory action of oxymetazoline on the spontaneous movements of isolated intestinal strips of the rabbit and the effects of antagonists upon the oxymetazoline actions were assessed with recordings through both isometric and isotonic transducers, and comparisons were made between both methods of recording. There were significant differences between the slopes of regression equations calculated from log dose response curves of oxymetazoline obtained from jejunum and those from ileum. But no difference was noted between both recordings either through isotonic transducer or through isometric transducer. The $ID_{50}$ of oxymetazoline obtained from the recording through isotonic transducer was $6.31{\times}10^{-7}M$ in jejunum and $3.16{\times}10^{-8}M$ in ileum. The recording through isometric transducer gave the values of $5.01{\times}10^{-7}M$ in jejunum and $1.07{\times}10^{-8}M$ in ileum. The $pA_2$-values of prazosin to oxymetazoline calculated from the recording through isotonic transducer were 8.13 in jejunum and 8.31 in ileum and the recording through isometric transducer gave the values of 7.29 and 8.26 in jejunum and ileum, respectively. The $pA_2$-values of phentolamine to oxymetazoline obtained from the recording through isotonic transducer were 8.18 in Jejunum and 9.31 in ileum and those from the recording through isometric transducer were 7.75 and 8.13 in jejunum and ileum, respectively. These results indicate that there are no significant differences between recordings either through isotonic transducer or through isometric transducer in assessing inhibitory responses of intestinal movement to certain drugs.

• Journal of Korean Society for Quality Management
• /
• v.47 no.3
• /
• pp.615-630
• /
• 2019

Purpose: Based on the theory of "Stimulus-Organism-Response" (S-O-R), this thesis takes customer forgiveness as a medium variable to explore the impact of merchant service remedy on customer behavior intention in the context of online shopping service failure. This thesis divides the merchant service remedy into two dimensions: spiritual recovery and material recovery, and reveals the influence difference of different merchant service remedy methods on customer behavior intention and the mediating role of customer forgiveness. Methods : 325 questionnaires were distributed and 307 valid questionnaires were collected for data analysis. The relationship between potential variables is proposed by using Structural Equations Modeling. Results : The two dimensions of service recovery have significant positive impact on customer forgiveness, and physical recovery has greater impact on customer forgiveness. In the influence of physical recovery on customer behavior intention, customer forgiveness is a partial mediating effect. However, in the influence of spiritual recovery on customer behavior intention, customer forgiveness is a complete mediating effect. Conclusion : In case of service faults, merchants should take the initiative to provide appropriate physical recovery and provide spiritual recovery sincerely and patiently. Only in this way can they regain good impression in the hearts of consumers and promote them to improve the quality of service recovery, so as to increase their willingness to repurchase Intention and positive word of mouth.

• Proceedings of the Korean Society of Propulsion Engineers Conference
• /
• 2008.11a
• /
• pp.299-304
• /
• 2008

Starting characteristics of the axi-symmetric second throat exhaust diffuser (STED) with zero-secondary flows are numerically investigated. Renolds-Average Navier-Stokes equations with a standard ${\kappa}-{\varepsilon}$ turbulence model incorporated with enhanced wall treatment are solved to simulate the diffusing evolutions of the nozzle plume. Minimum (optimum) starting pressure difference of 20$\sim$25% between 1-D theory and the measured data validated from previous results[5] is also applied to predict the range of an effective diffuser expansion ratio (Ad/At) in this system.

• Journal of the Korean Society of Marine Environment & Safety
• /
• v.20 no.6
• /
• pp.746-751
• /
• 2014

In this paper, ship performance prediction solver was developed using open source computational fluid dynamics (CFD) libraries. The mass- and momentum-conservation equations and turbulent model with a wall function for the turbulent closer were considered. The volume fraction transport equation with a high-resolution interface capturing scheme were selected for free-surface simulation. The predicted wave pattern around KRISO container ship (KCS) using developed program showed good agreement against existing experimental data. For the revolution of a propeller in the propulsive test, general grid interface (GGI) library was used. The predicted propulsive performance showed 7 % difference against experimental data. Two-phase mixture model was developed to simulate a cavitation and applied to a propeller. The sheet cavitation on the propeller was predicted well. From results, the potential of the numerical tank developed by open source libraries was verified by applying it to KCS.

• Journal of Ship and Ocean Technology
• /
• v.10 no.4
• /
• pp.1-11
• /
• 2006

The finite volume based multi-block RANS code, WAVIS developed at MOERI is applied to the numerical self-propulsion test. WAVIS uses the cell-centered finite volume method for discretization of the governing equations. The realizable $k-{\epsilon}$ turbulence model with a wall function is employed for the turbulence closure. The free surface is captured with the two-phase level set method and body forces are used to model the effects of a propeller without resolving the detail blade flow. The propeller forces are obtained using an unsteady lifting surface method based on potential flow theory. The numerical procedure followed the self-propulsion model experiment based on the 1978 ITTC performance prediction method. The self-propulsion point is obtained iteratively through balancing the propeller thrust, the ship hull resistance and towing force that is correction for Reynolds number difference between the model and full scale. The unsteady lifting surface code is also iterated until the propeller induced velocity is converged in order to obtain the propeller force. The self-propulsion characteristics such as thrust deduction, wake fraction, propeller efficiency, and hull efficiency are compared with the experimental data of the practical container ship. The present paper shows that hybrid RANS and potential flow based numerical method is promising to predict the self-propulsion parameters of practical ships as a useful tool for the hull form and propeller design.

• Korea journal of population studies
• /
• v.11 no.1
• /
• pp.87-96
• /
• 1988

The subjects used in this study were chosen from self-employed women in Taegu City, Korea, Data for 415 respondents were collected by face-to-face interviews conducted during the period of November 10 through 23, 1987. There are three major purposes in this study : first, to describe the general characteristics of self-employed Korean women's fertility behavior ; second, to examine the determinants of fertility behavior among self-employed women : third, to explore the relative importance of the fertility determinants among the women. Regression analyses were introduced to test hypotheses. Nine variables, such as household income, educational attainment, mass media, abortion, the period of contraception practice, contraceptive expenses, the number of infant, deaths marital period, and age at first marriage were introduced as indicators in the regression. The results of this study show that there are negative relationships between the dependent variable of fertility and abortion, and the period of contraception practice. On the other hand, positive relationships between the dependent variable of fertility and the number of infant deaths, and marital period and age at first marriage are shown in this study. However, the results of this study show that there are insignificant relationships between socioeconomic variables and fertility. From the results of the F test to evaluate the significance of difference in $R^2$between two different regression equations, we have found that the regression equation including both socioeconomic variables and intermediate variables is misspecified to examine the determinants of fertility behavior among self-employed Korean women. That is, the F test shows that the regression equation including only intermediate variables as indicators is the best model for this study. Finally, the relative importance of the fertility determinants among self-employed women is found as follows : Age at the first marriage is the most influential variable in the fertility, and the next important factors are abortion, the period of contraception practice, the number of infant deaths, and marital period, in that order.