• Journal of Labour Economics
• /
• v.34 no.1
• /
• pp.1-32
• /
• 2011

This paper explores the effect of relative age at elementary school entry, which is determined by birth date and school entrance law, on college entrance. First, I compare the college entrance rate between students born in January or February and those born in other months. Second, I estimate the effect of age at school entry on college entrance. Relatively older students at school entry are likely to have better educational outcomes during the first college entrance. However, these differences in educational outcomes seem to decrease the more that younger students repeat taking the college entrance exam.

• Tunnel and Underground Space
• /
• v.6 no.3
• /
• pp.245-249
• /
• 1996

In this study, the flow field and the recirculation phenomena are investigated numerically for the model around a tunnel entrance and exit. It turns out that the air entering to the tunnel entrance comes mostly from the upper region of the entrance implying that maintaining the air clear in that region is important for the inside-tunnel ventilation. We also found that the recirculation of the exhaust gas from the exit to the entrance has a maximum effect when the flow velocity at the exit is somewhat lower than that of the entrance.

• Transactions of the Korean Society of Mechanical Engineers B
• /
• v.23 no.1
• /
• pp.58-68
• /
• 1999

The entry compression wave, which forms at the entrance of a high-speed railway tunnel, is closely related to the pressure transients in the train/tunnel systems as well as an impulsive noise appearing at the exit of the tunnel. In order to alleviate such undesirable phenomena, some control strategies have been applied to the compression wave propagating inside the tunnel. The objective of the current work is to investigate the effect of tunnel entrance hoods on the entry compression wave at the vicinity of the tunnel entrance. Three types of entrance hoods were tested by the numerical method using the characteristics of method for a wide range of train speeds. The results show that the maximum pressure gradient of compression wave can be considerably reduced by the tunnel entrance hood. Optimum hood shape necessary to reduce the pressure transients and impulsive noise was found to be of an abrupt type hood with its cross-sectional area 2.5 times the tunnel area. It is believed that the current results are highly useful in predicting the effects of entrance hoods and in choosing the shape of proper hood.

• Journal of Korean Society of Industrial and Systems Engineering
• /
• v.21 no.47
• /
• pp.125-138
• /
• 1998

In this paper, we investigate the effect of re-entrance to the same work station in a job shop with multiple identical machines. System A is defined as the system in which re-entrance is not permitted, and system B is defined as the system in which re-entrance is permitted. By the analytical result of the queueing network, we find that the two systems have the same queue length distributions and utilizations under FIFO dispatching rule when all parameters are same. Simulation models are developed for various comparisons between the two systems, and simulation experiments are conducted for the combinations of five dispatching rules, two average workloads and two due date allowances. Five performance measures are selected for the comparison. The simulation results show that permitting re-entrance affects for some combinations of system environments.

• Journal of the Korea Academia-Industrial cooperation Society
• /
• v.14 no.6
• /
• pp.2660-2666
• /
• 2013

Education is important in Korea and English education takes a huge part of it. Korean Education can be divided into public and private. A number of households expend money on private education. Therefore this study examines the relationship between private education expense and the grade of college entrance examination. As results, there is a positive effect between them and also a positive effect between the total mount of time of private education and the grade of college entrance examination.

• Journal of Korean Tunnelling and Underground Space Association
• /
• v.9 no.4
• /
• pp.377-385
• /
• 2007

Drivers passing through a tunnel fare some difficulties caused by the visual differences between outside and inside of the tunnel. The blackhole phenomenon at a tunnel entrance lone severely decreases the driver's visibility during the daytime. A counterbeam lighting is generally recommended for the prevention of it. This paper simulates an entrance zone with a blackhole phenomenon to verify the effect of counterbeam lighting. Even though the tunnel lighting is important, It Is not easy to consider many lighting alternatives at the stage of tunnel design due to the complexity of tunnel renditions. This paper is expected to contribute improving the visibility in tunnels, especially at the entrance zone.

• Proceedings of the SAREK Conference
• /
• 2009.06a
• /
• pp.1031-1036
• /
• 2009

This study is intended to identify how quick disconnect coupling which connects with refrigerant piping of air-conditioner using R-22 refrigerant has effect on characteristics of flux. in the case where the air-conditioner installs utilizes quick disconnect coupling, COP has an effect on the quantity of cooling load because of changing flow rate and physical properties of refrigerant which flow into an entrance of expansion valve from coupling. Variation of flow rate can be regulated by changing expansion-contraction angle; $\alpha$ of an entrance and an exit of coupling. In this study, quick disconnect coupling is presented flow of coupling by using FLUENT as heat flow program. To have an effect on the expansion entrance valve, and by changing expansion-contraction angle; $\alpha$ of an entrance and an exit

• Journal of Ocean Engineering and Technology
• /
• v.10 no.1
• /
• pp.100-107
• /
• 1996

In this paper, we report the results of the experimental study on the flow and the mass transport around a square harbor driven by a tidal effect. The model harbor is composed of a uniform water-depth with a straight breakwater. The harbor is connected to the outer ocean by an entrance region having the same shape as the harbor. We investigated two cases, one having another breakwater in the place between the entrance region and the outer ocean, and the other without it, The surface and bottom flow patterns of the model container are visualized by using light particles and dye, respectively. It was shown that the inner harbor and the entrance region have well-organized, large vortical residual flows, and the material transport between the entrance and outer region is however significantly different for two cases; when the breakwater is built between the two regions, the transport is far better than that without it, which is clearly contrary to our common sense that the breakwater would block the dispersion of the materials between the harbor and the outer ocean.

• International Journal of Contents
• /
• v.14 no.4
• /
• pp.65-69
• /
• 2018

The objective of this study was to conduct a radiation shielding analysis for the facility equipped with radiation generator. The analysis was carried out in two aspects. First, from the aspect of the effect caused by primary and leakage radiation. Second, effect of scattered radiation was evaluated by applying a simple calculation method based on a scattering rate concept since effect of scattered radiation is significantly important at maze entrance of the radiation facility. The calculated results obtained using the simple method were compared to the results calculated using Geant4 code and the measured values. The results calculated by the suggested method indicate that slight error exists in a radiation shielding analysis done at the maze entrance comparing to other two results, while the results evaluated at the outside of the maze entrance door are relatively consistent with other values.

• Transactions of the Korean Society of Mechanical Engineers B
• /
• v.26 no.3
• /
• pp.439-447
• /
• 2002

The microchannel flow in miniature TCDs (thermal conductivity detectors) is investigated numerically. The solutions based on the boundary layer approximation are not very accurate in the region of the duct inlet for low Reynolds numbers. In this study, two-dimensional Navier-Stokes equations are considered to analyze the gas flow in a miniature TCD. Effects of channel size, inlet and boundary conditions on the heat transfer rate are examined. When the gas stream is not preheated, the distances for a miniature TCD to reach the conduction-dominant region for duct flow are found to be approximately two and three times the thermal entry length for duct flow with constant properties, respectively, leer constant wall temperature and constant wall heat flux boundary conditions. If the gas temperature at the channel inlet is close to the mean gas temperature in the conduction-dominant region, the entrance region is much shorter compared to other cases considered in this study.