• 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.

• The Journal of Korean Academic Society of Nursing Education
• /
• v.20 no.4
• /
• pp.596-605
• /
• 2014

Purpose: This study aims to understand the influence of college entrance system-related factors and scores of college scholastic ability test on a first year nursing student's academic achievement. Method: Data collected include both a descriptive survey designed to assess college entrance system-related factors with respect to 182 nursing students attending a 4-year nursing college program and their test scores in the first year. The data were analyzed via descriptive statistics, Mann-Whitney U test, Kruskal-Wallis test with Bonferroni's correction, and Spearman's rank correlation coefficient through an SPSS 18.0 program. Results: Student academic achievement with regard to college entrance system-related factors exhibited significant divergence from first year grade point averages (hereafter GPA) and natural science grades. Conclusion: This study confirmed the existence of significant differences, depending on the factors regarding the college entrance system. As a result, conducting assessment to evaluate the level of basic knowledge before college entrance is highly recommended. Also recommended is the development of a support program for students projected to have difficulties with respect to their academic achievement.

• Transactions of the Korean Society of Automotive Engineers
• /
• v.5 no.2
• /
• pp.50-59
• /
• 1997

When a front head of train enters a tunnel at a high speed, compression wave is generated at tunnel entrance due to the confinement effect and propagated along the tunnel with sound of speed. The propagated compression wave is reflected at tunnel exit due to abrupt pressure change at passage. The reflected wave is expansion pressure wave. And when the rear head of train goes through the tunnel entrance, another expansion pressure wave is generated and propagated along the tunnel. The pressure drop occurs seriously around train when the two expansion pressure waves come cross on train in the tunnel. In order to reduce the pressure drop, the compression wave front must be controlled because the intensity and magnitude of pressure drop is nearly proportional to that of compression wave at tunnel entrance. This study relates to reduction of the pressure wave gradient with respect to tunnel entrance shape change with various kind of angle and rounding. The results show characteristics of wave propagation in tunnel, usefulness of characteristic curve to estimate proper time domain size in numerical study and measuring time in actual experiment. Also rounding is contributed to improve pressure wave front even if its radius is very small at tunnel entrance. In order to improve of pressure wave front at tunnel entrance, proper angle is prefered to rounding with big radius and an angle of around 14$^{\circ}$ is recommended according to this simulations, And it is expected to reduce additional pressure drop in tunnel when the location and the size of the internal space for attendant equipment are considered in advance.

• Journal of The Korean Association For Science Education
• /
• v.36 no.4
• /
• pp.693-704
• /
• 2016

The aim of this study was to investigate the conditions and strategies of interaction for the school adjustment for the early entrance students of science academy for the gifted. To know their concerns and process of school adjustment, we interviewed six early entrance gifted students of the science academy and two gifted students preparing for their early entrance with a semi-structured questions. Using the grounded theory, a paradigm model was organized and a core category was abstracted through the open, axial, and selective coding. Based on the open coding analysis, 75 concepts, 21 sub-categories, and 10 categories were derived. In the axial coding, the paradigm model was organized by the link between 10 categories derived from open coding. Through the selective coding, this study discovered the core category about early entrance student's school adjustment was overcoming difficulties by using academic, social, and emotional strategy for school adjustment. Through this, we understand the school adjustment process of the students of early entrance to science academy for the gifted.

• Transactions of the Korean Society of Mechanical Engineers
• /
• v.12 no.5
• /
• pp.1189-1196
• /
• 1988

Thermal entrance lengths of turbulent tube flow for viscoelastic polymer solutions are investigated experimentally in the recirculating flow system with tubes of inside diameters 8.5mm(L/D=710) and 10.3mm(L/D=1158), respectively. In the present system, the hydrodynamic and thermal boundary layers develop simultaneously from the beginning of the test section. To provide the boundary condition of constant heat flux at the wall, the test tubes are heated directly by electricity. The polymer solution used in the current study is 1000 wppm aqueous solution of polyacrylamide(Separan AP-273). The apparent viscosity of the polymer solutions circulating in the flow system are measured by the capillary tube viscometer at regular time intervals. Thermal entrance lengths vary due to the rate of degradation. The entrance lengths of degraded polymer solutions are about 500~600 times the diameter. However, the entrance lengths of fresh polymer solutions are greater than the lengths of the test tubes used in this study suggesting that thermal entrance lengths for viscoelastic polymer solutions are greater than 1100 tube times the diameters. Friction factor is almost insensitive to the degradation, but the heat transfer $j_{H}$-factor is affected seriously by degradation. Based on the present experimental data of fresh solutions a correlation for the heat transfer $j_{H}$-factor is presented.ted.

• Journal of Ocean Engineering and Technology
• /
• v.27 no.6
• /
• pp.32-42
• /
• 2013

In this paper, a wave-induced swirl water chamber (SWC) for breakwater and wave power generation is introduced and its applicability to wave power generation in the coastal waters of Korea is investigated. The SWC type of wave power generation is a way to drive a turbine using the unidirectional swirl flow that is induced in the back of a curtain wall of a breakwater due to incident waves. The typical wave characteristics are obtained by analyzing the annual statistical wave data from KHOA (Korea Hydrographic and Oceanographic Administration). A numerical analysis is carried out on the variations in the SWC entrance height, wave height, and different installation conditions. For the numerical analysis, a commercial code, Fluent based on FVM, is used. As the entrance height decreases, the mass flow rate through the entrance is rarely changed, whereas the magnitude of the flow velocity of the smaller entrance height is greater than the other ones, which is better for the formation of an SWC swirl flow inside and the flow kinetic energy at the entrance. In cases of installation conditions where a wall is place behind and under SWC, it has been shown that the mass flow rate through the entrance is greater than that in the open condition, and sufficient flow kinetic energy is generated in the entrance for wave power generation. However, the swirl flow kinetic energy is relatively small. Thus, in the future, it is necessary to study the swirl flow generation, which is affected by the SWC shape.

• Journal of Korean Society of Occupational and Environmental Hygiene
• /
• v.24 no.4
• /
• pp.471-477
• /
• 2014

Objectives: This study was conducted to evaluate area exposure of airborne dust and organic gas during entrance and shipment of chicken in poultry farms Methods: Total dust was measured with NIOSH method 0500. The volume of distributed dust and organic gas(Ammonia, TVOC, Hydrogen Sulfide) were measured using direct reading instrument. Results: The range of concentrations of total dust in area sample was $0.07{\sim}4.91mg/m^3$ during the entrance of chicks and $4.37{\sim}9.4mg/m^3$ during shipment respectively. Concentration of ammonia reached approximately 9 ppm during shipment. There was a difference of concentration of total dust in the area sample between shipment and entrance tasks. Conclusions: It was found that the development of a special intervention program by type of task should be considered for reducing respiratory health effects among poultry farmers.

• Journal of Biosystems Engineering
• /
• v.18 no.3
• /
• pp.275-287
• /
• 1993

The flow characteristics of the transitional oscillatory flows are investigated analytically and experimentally in the entrance region of a square duct. The systems of conservation equations are analytically solved by linearizing the non-linear convective terms for the developing transitional oscillatory flows in a square duct. The analytical solutions are obtained in the form of infinite series for the velocity profiles. The experimental study for the air flow in a square duct is carried out to measure the velocity profiles and waveforms by using a hot-wire anemometer with the data acquisition and processing systems. The theoretical and experimental results provide the major characteristics of the developing transitional oscillatory flows, such as velocity profiles, velocity waveforms, and entrance length. The velocity profiles in the decelerating phase are larger than those in the accelerating phase for the developing transitional oscillatory flows. The correlations of the entrance length of the transitional oscillatory flows in a square duct are found to be $Le/Dh=K{\cdot}Re_{os}/2({\omega}^+)^2$, where K is 1.23 of an experimental constant.

• 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.

• Korean Management Science Review
• /
• v.7 no.2
• /
• pp.22-42
• /
• 1990

This paper deals with enhancement of the high school equalization assignment system to be executed by the allied entrance examination after the applicants graduated from their middle schools. In prevailing opinion, because educational demander's will has not been considered under the current system, it whose merits have been covered is required to be improved. If the application system of the entrance examination for the high schools will be returned, a situation that it will result in irregularity of the middle school education and in overheating entrance examination seems to appear explicitly. Since the averages of the allied entrance examination score of all the high schools, achieved by the equalization-application nearest assignment system which is named by writers of this paper, are equal, our system is good for maintaining the merits of the current system. More than 50% educational demander's will has been reflected by our system, so that we come to the conclusion that our system is excellent in all the systems verified up to now. Assigning students to the high school to make an average difference between three and five score, we expect that relection rate of the educational demander's will be increased more than 60%.