• Transactions of the Korean Society of Mechanical Engineers
• /
• v.12 no.1
• /
• pp.1-7
• /
• 1988

Prediction performances by Einstein's equation of diffusivity, Peskin's model, Three-Equation model, Four-Equation model and Algebraic Stress Model, have been compared by analyzing twophase (air-solid) turbulent jet flow. Turbulent kinetic energy equation of dispersed phase was solved to investigate effects of turbulent kinetic energy on turbulent diffusivity. Turbulent kinetic energy dissipation rate of particles has been considered by solving turbulent kinetic energy dissipation rate equation of dispersed phase and applying it to turbulent diffusivity of dispersed phase. Results show that turbulent diffusivity of dispersed phase can be expressed by turbulent kinetic energy ratio between phases and prediction of turbulent kinetic energy was improved by considering turbulent kinetic energy dissipation rate of dispersed phase for modelling turbulent diffusivity. This investigation also show that Algebraic Stress Model is the most promising method in analyzing gas-solid two phases turbulent flow.

• Journal of the Korean Society of Safety
• /
• v.39 no.2
• /
• pp.22-27
• /
• 2024

The purpose of this study is to explore the trend in insulation resistance values according to temperature and overcurrent by conducting an investigation on the actual condition and experiments on the electrical wiring during the melting furnace process. In addition, the Arrhenius equation is used to determine whether temperatures in the furnace operating process can be applied to the actual field. In the investigation of the actual condition, the insulation resistance started to decrease seven years after replacement, even though cables in oil pump A were replaced in 2010. Both the experimental and theoretical values of the insulation resistance obtained using the Arrhenius equation decreased with an increase in temperature. Errors in insulation resistance (MΩ) values between tests and the Arrhenius equation ranged from ±2 to ±10, demonstrating a high similarity. Results revealed that when the insulation resistance cannot be measured in a manufacturing workplace (quarterly analysis), it can be estimated by partially applying the Arrhenius equation.

• Journal of the Korean Institute of Telematics and Electronics
• /
• v.11 no.4
• /
• pp.29-37
• /
• 1974

Theoretical analysis is carried out for the curtoff wavelength characteristics of rectangular waveguide containing a step-ridge. In order to obtain the cutoff wavelength of step-rigde waveguide, an transmission matriz is formulated by the method of equivalent transverse resonance. The characteristic equation, in which the wavelength is obtainable by the numerical method, is derived from the equation. An approximate determination of the dominant mode fields in step-ridge waveguides at all frequencies has been made. Using these fields, the characteristic impedance equation is derived from power considerations. Analyzing the results of the calculations, the following characteristics are noted. The values of λ /a of TE10 mode increase with decreasing gap lengths and with increasing step width S or S , or both. Experimental results of cutoff characteristics are in good agreement with the theoretical analusis. It is shown that a waveguide within which a step-ridge is placed has a lower cutoff frequency and impedance than empty guide without it. Therefore, the role of a step-ridge guide is to broadening the bandwidth 2 to 3 times more than that of an empty guide of the same demension.

• Journal of Distribution Research
• /
• v.11 no.3
• /
• pp.103-125
• /
• 2006

Recently, in-home shopping channel has become a popular shopping channel. This study develops and tests a model of the share and variety of in-home shopping channel. We explore the effects of demographic characteristics and shopping behavior characteristics to the share and variety of in-home shopping channel. As a research methodology, we choose the simultaneous equation model with selectivity to consider both sample selection and effects between dependent variables. The result of study can be summarized as follows. First, there are no effects between the share and variety of in-home shopping channel. Second, the share of in-home shopping channel decreases when consumers visit department store more than discount store. Third, the demographic characteristics and the shopping behavior characteristics don't affect the variety of in-home shopping channel. Some managerial implications for manufacturers and distributors are discussed.

• Journal of Biosystems Engineering
• /
• v.11 no.1
• /
• pp.52-63
• /
• 1986

This study was performed to find out drying characteristics and develop drying model for the design of an efficient dryer or drying system of red peper. The basic model which describes drying phenomenon of red pepper was firstly established, and drying tests were conducted at 14-different drying conditions. In this test, the effects of drying air temperature and relative humidity on the rate of drying were undertaken. Finally, a new drying model based on these experimental results was developed to describe the drying characteristics of red pepper. The results from this study may be summarized as follows. 1. Drying constant of the basic model established from Lewis' experimental model and diffusion equation was theoretically deduced as a function of moisture content and inner-temperature of red pepper. 2. From the results of drying tests, drying air temperature was found to have the greatest effect on the rate of drying. However, the effect of temperature was small for the condition of high relative humidity, and for low temperature, the effect of relative humidity was found to be large even though the range of relative humidity was low. 3. Modified Henderson equation was found to be better than Chung equation as the EMC model for the estimation of the equilibrium moisture content of red Pepper. 4. Constant-rate drying period did not exist in the red pepper drying test. And falling-rate drying period was divided into three distinct phases. Drying rate was dependent on the moisture content, the inner-temperature of red pepper and the change of physical property due to drying. 5. Drying constant increased with decrease of free moisture content, but it decreased at the end of the drying period. Also, drying constant was dependent on the drying air temperature and relative humidity. 6. The new drying model developed in this study was found to be most suitable in describing the drying characteristics of red pepper. Therefore, it may be concluded that drying time could be accurately estimated by the new drying model.

• Journal of the Korean Home Economics Association
• /
• v.47 no.7
• /
• pp.97-107
• /
• 2009

This study investigated the impact of long-term relationship orientation on emotional characteristic in fashion stores and relationship characteristic between middle-aged and senior women and salespeople. This study employed survey method with questionnaire. Data were collected from 579 women who were from the age of forty to seventy. The data were analyzed using statistic methods(SPSS 15.0 and Amos 5.0) such as frequency analysis, cronbach $\alpha$, exploratory factor analysis, second-order confirmatory factor analysis, confirmatory factor analysis and structural equation modelling. The findings of this study were concluded as follows; Firstly, the income significantly affected on emotional characteristics(p < 0.01), but had no significant effect on long-term relationship orientation(p < 0.05). The higher income, the more respondents exhibited positive attitude and sensitive emotional characteristics as a sense of sight, hearing, smell, tactile and feeling to salespeople in the fashion stores. The path of structural equation was implemented as income variables $\rightarrow$ emotional characteristics $\rightarrow$ (relationship with salespeople variables $\rightarrow$ )commitment $\rightarrow$ long-term relationship orientation which turned out to be statistically significant at the 95% confidence level. Secondly, senior group(55~70yrs) was more positive relationship with salespeople compared to middle-aged group(40~54yrs). The precondition of get satisfaction and feeling of being cared from the salespeople were critical for long-term relationship orientation. The path of structural equation was carried out as age variables $\rightarrow$ relationship with salespeople variables $\rightarrow$ commitment $\rightarrow$ long-term relationship orientation which turned out to be statistically significant at the 95% confidence level.

• Journal of the Institute of Electronics and Information Engineers
• /
• v.50 no.10
• /
• pp.245-251
• /
• 2013

An impedance of ground electrode for information and communication facilities has a significant relationship with the electrical characteristics of soil where the ground electrode is buried. Especially, the impedance of ground electrode is directly affected by the characteristics of permittivity and conductivity in soil as a function of a frequency of an applied electric field. The program based on the electromagnetic field model was developed in MATLAB. Because both permittivity and conductivity can not be modified in commercial programs. The permittivity of soil was applied with the Debye equation which is a model of dielectric relaxation. And the empirical equation of the conductivity in soil was quoted in other paper. In order to confirm the reliability of proposed program, the impedance measurement of ground electrode was carried out, which were compared with the results of simulation in commercial program. In result, it was confirmed that the impedance and phase different simulated by appling the characteristics of permittivity and conductivity in soil are in good agreement with the measured values than results of NEC.

• Journal of Korean Port Research
• /
• v.13 no.2
• /
• pp.399-408
• /
• 1999

Copeland’s(1985) hyperbolic mild-slope equation including diffraction refraction and reflection in the wave field is used as a governing equation in this study. The result of Maruyama & Kajima(1985) is used to calculate wave direction and that of Watanabe & Maruyama(1986) is used as a energy dissipation formula. Numerical solutions are obtained by the Leap-Frog scheme and compared with Watanabe & Maruyama’s (1984) hydraulic experimental results and numerical simulation results for the detached breakwater. This wave model is applied to a detached breakwater and compared with Watanabe and Maruyama’s (1984) hydraulic model results to check the characteristics of reflected wave field around a detached breakwater. The distribution of wave height and we phase in front of a detached breakwater is more accurate than the Watanabe and Maruyama’s numerical results. The results from our wave model show good agreements with the others and also show nonlinear effects around the detached breakwater. This model is applied to the Gamcheon harbor of pusan. the field observations were carried out at Pusan harbor wave station in 1986-1995 and the results were accepted as a design wave condition in this study. The wave height and wave period was measured by Dong-A university at one station in the Gamcheon harbor in 1996-1997 and used as a calibration criterion. The measured data were used as input data for the numerical simulation and also compared with simulated results. The numerical simulation shows a fairly good results which considering the effect of topographic characteristics and effect of narrow entrance due to two separated breakwaters in Gamcheon harbor. The wave distribution characteristics inside Gamcheon harbor is quite different with the offshore wave direction and wave period.

• Journal of Ocean Engineering and Technology
• /
• v.28 no.5
• /
• pp.371-377
• /
• 2014

In this study, the hydrodynamic characteristics of various types of jack-up legs for a wind turbine installation vessel were analyzed. Using the modified Morison equation, the wave and current excitation forces on the jack-up legs were calculated. A modal analysis was performed to predict the dynamic responses for various types of jack-up legs. The Newmark-beta time integration scheme was used to solve the equation of motion in waves in the time domain. The maximum displacement and maximum bending stress were computed for four different types of legs, and their results were compared to select an optimum leg type. Finally, a six-leg jack-up rig with the selected optimal legs was modeled, and its natural period and hydrodynamic behaviors were evaluated.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
• /
• v.27 no.1
• /
• pp.8-13
• /
• 2015

The objective of this paper is to provide design data of fin-tube heat exchanger which have a large diameter oval tube for dryer application. In this study, the heat transfer and pressure drop performance characteristics of the fin-tube heat exchanger were compared with Dittus-Boelter and a new correlation equation using Wilson plot method. The simulation results based on section by section method were compared with experimental results. These results showed that a new correlation equation using Wilson plot method provided better prediction, about 3 to 12%, than the Dittus-Boelter equation, from the experiment comparison. Also, the pressure drop of simulation results showed much more deviation with the experimental results.