• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2000.07a
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• pp.950-952
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• 2000

Considering the effective distribution coefficient of Ni in Fe-Ni-Co invar alloy containing a little amount of carbon, we investigated on the thermal expansion coefficient(${\alpha}$). Fe-Ni-Co invar alloy had a large thermal expansion coefficient in as-casted compared with solution treated. The thermal expansion coefficient of Fe-Ni-Co alloy increased with the carbon content in both state of as-casted and solution treated. The effective distribution coefficient(Ke$\^$Ni/) of Ni was smaller than unity in alloy of not containing carbon, but is way larger than unity in alloy of containing carbon. It was considered that the homogeneity of Ni in primary austenite affected thermal expansion coefficient.

• Journal of Industrial Technology
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• v.22 no.B
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• pp.27-34
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• 2002

3-D numerical studies are performed to investigate the effect of the air dam height and approaching air velocities on the pressure distribution of notchback road vehicle. For this purpose, the models of test vehicle with four different air dam heights are introduced and PHOENICS, a commercial CFD code, is used to simulate the flow phenomena and to estimate the values of pressure coefficients along the surface of vehicle. The standard $k-{\varepsilon}$ model is adopted for the simulation of turbulence. The numerical results show that the height variation of air dam makes almost no influence on the distribution of the value of pressure coefficient along upper and rear surface but makes strong effects on the bottom surface. That is, the value of pressure coefficient becomes smaller as the height is increased along the bottom surface. Approaching air velocity makes no differences on pressure coefficients. Through the analysis of pressure coefficient on the vehicle surface, one tries to assess aerodynamic drag and lift of vehicle. The pressure distribution on the bottom surface affects more on lift than the pressure distribution on the upper surface of the vehicle does. The increase of air dam height makes positive effects on the lift decrease but no effects on drag reduction.

• Transactions of the Korean Society of Automotive Engineers
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• v.10 no.6
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• pp.178-186
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• 2002

3-D numerical studies are performed to investigate the effect of the trunk height and approaching air velocities on the pressure distribution of notchback road vehicle. For this purpose, the models of test vehicle with four different trunk heights are introduced and PHOENICS, a commercial CFD code, is used to simulate the flow phenomena and to estimate the values of pressure coefficients along the surface of vehicle. The standard k-$\xi$ model is adopted for the simulation of turbulence. The numerical results say that the height variation of trunk makes almost no influence on the distribution of the value of pressure coefficient along upper surface but makes very strong effects on the rear surface. That is, the value of pressure coefficient becomes smaller as the height is increased along the rear surface and the bottom surface. Approaching air velocity make no differences on pressure coefficients. Through the analysis of pressure coefficient on the vehicle surfaces one tried to assess aerodynamic drag and lift of vehicle. The pressure distribution on the rear surface affected more on drag and lift than pressure distribution on the front surface of the vehicle does. The increase of trunk height makes positive effects on the lift decrease but negative effects on drag reduction.

• Wind and Structures
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• v.36 no.4
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• pp.249-261
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• 2023

Aerodynamic force coefficients are generally prescribed by an ensemble average of ten and/or twenty 10-minute samples. However, this makes it difficult to identify the exact probability distribution and exceedance probability of the prescribed values. In this study, 12,600 10-minute samples on three tall buildings were measured, and the probability distributions were first identified and the aerodynamic force coefficients corresponding to the specific non-exceedance probabilities (cumulative probabilities) of wind load were then evaluated. It was found that the probability distributions of the mean and fluctuating aerodynamic force coefficients followed a normal distribution. The ratios of aerodynamic force coefficients corresponding to the specific non-exceedance probabilities (C_f,Non) to the ensemble average of 12,600 samples (C_f,Ens), which was defined as an adjusting factor (C_f,Non/C_f,Ens), were less than 2%. The effect of coefficient of variation of wind speed on the adjusting factor is larger than that of the annual non-exceedance probability of wind load. The non-exceedance probabilities of the aerodynamic force coefficient is between P_C,nonex = 50% and 60% regardless of force components and aspect ratios. The adjusting factors from the Gumbel distribution were larger than those from the normal distribution.

• Journal of Distribution Science
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• v.13 no.12
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• pp.85-94
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• 2015

Purpose - The purpose of this paper is to provide a political registration point for analyzing the economic impacts on the national economy from the REITs distribution industry in our country. The REITs distribution industry was introduced in 2001 to accelerate the corporate restructuring process and advance the real estate market. During its establishment, the REITs distribution industry faced difficulties; however, the industry grew rapidly through interest from institutional investors, thus mitigating the establishment problems by 2006. In Korea, more than 108 REITs were operating as of the end of June 2015. REITs contribute significantly to the national economy. The economic impacts on the national economy of the REITs distribution industry was analyzed using input-output (I-O) analysis with respect to production, imports, value-added, and employment. Research design, data, and methodology - The research used an I-O analysis of the activities of the REITs distribution industry in the national economy. The I-O analysis methodology analyzes the economic effects that influence other industries with respect to one unit of external investment. The data for this analysis were the I-O table of 2013 as published by the Bank of Korea in 2014. Results - The findings of this study are as follows. First, if an external input to the REITs distribution industry is 1 won, the overall impact of the product is 1.3869 won, the import induction is 0.0002 won, and the value-added induction is 0.7656 won. A new investment of 659.9 billion won into the REITs industry was estimated to produce a gross effect of 915.2 billion won. Second, if an external input to the REITs distribution industry is 1 billion won, the employment-inducing effects are estimated at 19.6394 individuals. The employment-inducing coefficient of 19.6394 for the REITs distribution industry indicates that the industry created significant employment-more than other industries-because the coefficient was 2.2 times the 2013 industry average employment-inducing coefficient of 8.8. Third, the investment effects of the REITs distribution industry on production induction, value-added induction, and employment induction are assumed to be large in business support services, financing, communications and broadcasting, and professional, scientific, and technical services. Conclusions - The REITs distribution industry was analyzed as having a strong employment inducing, high value added effect. The REITs distribution industry is an excellent alternative for the government authority to create multilateral jobs. Because the REITs distribution industry has a significant positive impact on the national economy, it should be developed. However, the I-O methodology has restrictions with respect to the fixation and timing of the input coefficient. Follow-up research is expected to supplement the analysis method at a specific point in time.

• Proceedings of the Korea Concrete Institute Conference
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• 2004.05a
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• pp.148-151
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• 2004

The hardening of concrete after setting is accompanied with nonlinear temperature distribution caused by development of hydration heat of cement. Especially at early ages, this nonlinear distribution has a large influence on the tensile cracking. As a result, in order to predict the exact temperature distribution in concrete structures it is required to examine thermal properties of concrete. In this study, the coefficient of air convection for concrete mix of nuclear power plant, which presents thermal transfer between surface of concrete and air, was experimentally investigated with variables such as velocity of wind and types of form. The coefficient of air convection obtained from experiment increases with velocity of wind, and its dependance on wind velocity is varied with types of form. This tendency is due to a combined heat transfer system of conduction through form and convection to air. The coefficient of air convection for concrete mix of nuclear power plant obtained from this study was well agreed with the existing models.

• Journal of Korean Society for Quality Management
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• v.34 no.3
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• pp.19-30
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• 2006

For highly reliable products, it is difficult to assess the lifetime of the products with traditional life tests. Accordingly, a recent approach is to observe the performance degradation of product during the test rather than regular failure time. This study compares performances of three methods(i.e. the approximation, analytical and numerical methods) to estimate the parameters and quantiles of the lifetime when the time-to-failure distribution follows Weibull and lognormal distributions under a random coefficient degradation rate model. Numerical experiments are also conducted to investigate the effects of model error such as measurements in a random coefficient model.

• Journal of Bio-Environment Control
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• v.4 no.1
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• pp.1-8
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• 1995

One of the most destructive forces around greenhouses is wind. Wind loads can be obtained by multiplying velocity pressure by dimensionless wind force coefficient. Generally, wind force coefficients can be determined by wind tunnel experiments. The wind force coefficient distribution on a single - span arched greenhouse was estimated using experimental data and compared with reported values from various countries. The results obtained are as follows : 1. The coefficients obtained from this study agree with the values proposed by G. L. Nelson except about 0.5 of difference in the middle region of roof section. This discrepancy is mainly attributed to the dissimilarity of experimental conditions (or wind tunnel test such as Reynolds number, type of terrain, surface roughness of model, location of the lapping and measuring methods. 2. Considering that the wind force coefficients are varied along the height of a wall at wind direction perpendicular to wall, structural analysis using subdivided wind force coefficient distribution is more resonable for wall. 3. It is recommendable that wind force coefficient distribution on a roof should take more subdivision than the existing four equal divisions for more accurate structural design. 4. Structural design using wind forces close to real values is more advantageous in safety and expense.

• Journal of Korean Society for Atmospheric Environment
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• v.4 no.2
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• pp.28-37
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• 1988

Light scattering coefficient of visible light by atmospheric aerosol over the size range 0.01-10$\mu$m is determined from scattering efficiency and aerosol size distribution. Aerosol number distribution as a function of particle diameter dN/dlog D decreases rapidly as increasing particle size. Distribution of scattering coefficient d$\sigma_s/dlog$ D is mostly accumulated in diameter 0.1-2.0 $\mu$m showing its maximum in the vicinity of 0.6$\mu$m. This means that the visible light in the atmosphere is mainly scattered by these particles. Diurnal variation of scattering coefficient $\sigma_s$ appears its maximum in the morning, while minimum in the afternoon which agrees with the aerosol number distribution in the size range 0.1-2.0 $\mu$m.

• Proceedings of the KSME Conference
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• 2001.11a
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• pp.272-277
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• 2001

In order to evaluate variation of fatigue data of the LP steam turbine blade steel, it is important to estimate P - S - N curves to accurately define the probability distributions. In this study, new procedure is introduced to determine the expression of P - S - N curves. For this purpose, 3-parameter Weibull distribution was found to be most appropriate among assumed distributions when the probability distributions of the fatigue life were examined by the proposed analysis. Furthermore, parameter estimation for P - S - N curves was performed using various optimization to maximize the correlation coefficient. As a result of this, sequential linear programing method is used for estimation of P - S - N curves.