• Transactions of the Korean Society of Automotive Engineers
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• v.22 no.4
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• pp.36-45
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• 2014

Model based control methods are widely used to improve the control performance of diesel engine air systems because the control results of the air system significantly affect the emission level and drivability. However, the model based control algorithm requires a lot of unmeasurable states which are hard to be measured in a mass production engine. In this study, an air system model of the diesel engine is proposed to estimate 11 unmeasurable states using only sensors equipped in a mass production engine. In order to improve the estimation performance in the transient condition, dynamic characteristics of the air system are analyzed and implemented as discrete filters. Turbine and compressor efficiency models are also proposed to overcome a limitation of the constant or look-up table based efficiency values. The proposed air system model was validated in steady state and transient conditions by real-time engine experiments. The maximum error of the estimation for 11 physical states was 11.7%.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.39 no.8
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• pp.796-803
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• 2011

It is called self-alignment or initial alignment that INS(Inertial Navigation System) is aligned using the measurements from the inertial sensors as an accelerometer and a gyroscope and the inserted reference navigation information in the stop state. The main purpose of self-alignment is to obtain the initial attitude of INS. The accuracy of self-alignment is determined by the performance grade of the used inertial sensors, especially horizontal attitude accuracy by the horizontal accelerometer and vertical attitude accuracy by the E-axis gyroscope. Therefore the uncertain errors in the inertial sensors cause the performance of self-alignment to degrade. In this paper, we analyze theoretically and through a simulation how the errors of inertial sensors in the temperature stabilizing state, one of the uncertain errors, affect the accuracy of self-alignment.

• Computational Structural Engineering
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• v.10 no.2
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• pp.149-160
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• 1997

Mechanical structures are composed of substructures connected by joints and boundary elements. While the finite element representation of plain substructures is well developed and reliable, joints have a lot of uncertainties in being accurately modelled and affect dynamic behavior of a total system. In order to improve the accuracy of a finite element model, a new method is proposed, in which reduced finite element model is combined with a system identification technique. After substructures except joints are modelled with finite element method and joint properties are represented by parameter states, non-linear state equation is derived in which parameter states are multiplied by physical states such as displacements and velocities. So the joint parameter identification is transformed into non-linear state estimation problem. The methods are tested and discussed numerically and the feasibility for physical application has been demonstrated through two example structures.

• Wind and Structures
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• v.22 no.2
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• pp.185-209
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• 2016

Across-wind aerodynamic damping ratios are identified from the wind-induced acceleration responses of 15 aeroelastic models of rectangular super-high-rise buildings in various simulated wind conditions by using the random decrement technique. The influences of amplitude-dependent structural damping ratio and natural frequency on the estimation of the aerodynamic damping ratio are discussed and the identifying method for aerodynamic damping is improved at first. Based on these works, effects of turbulence intensity $I_u$, aspect ratio H/B, and side ratio B/D on the across-wind aerodynamic damping ratio are investigated. The results indicate that turbulence intensity and side ratio are the most important factors that affect across-wind aerodynamic damping ratio, whereas aspect ratio indirectly affects the aerodynamic damping ratio by changing the response amplitude. Furthermore, empirical aerodynamic damping functions are proposed to estimate aerodynamic damping ratios at low and high reduced speeds for rectangular super-high-rise buildings with an aspect ratio in the range of 5 to 10, a side ratio of 1/3 to 3, and turbulence intensity varying from 1.7% to 25%.

• Preventive Nutrition and Food Science
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• v.10 no.4
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• pp.311-315
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• 2005

The antioxidant properties of methanolic extracts (PM) from the fruit of Prunus mume after liquor manufacturing were determined in a chicken breast meat system. When PM was added to chicken breast meat, 2-thiobarbituric acid-reactive substances (TBARS) value at day 3 was decreased by about $25\%$ compared to control meat without PM. PM did not significantly affect the color of chicken meat compared to the control. The amounts of volatile aldehydes and hydrocarbons were decreased by the addition of PM. Hexanal was the predominant volatile compound in the control, accounting for the majority of total volatiles; PM reduced the amount of hexanal to $81\%$of that in the control meat at 3 days.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.17 no.6
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• pp.622-632
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• 2004

We have studied how liquid crystal's rubbing direction and voltage driving method affect generation of disclination line. At first, generation of disclination line in vertical alignment(VA) cell and VA-twisted nematic(TN) cell has been examined. When liquid crystal's rubbing direction of bottom substrate was 0$^{\circ}$, the degree of generated disclination line was the smallest value. Further, the generation of disclination line above the electrode is less in the frame inversion than in the line inversion. Secondly, we have examined a generation of disclination line in reflective fringe-field switching cell. When the distance between common electrodes is over 3 ${\mu}{\textrm}{m}$ with on-state of one pixel and off-state of neighboring pixels, the reflectance appears only on-state pixel without generating reflectance in adjacent pixels.

• Journal of the Korean Society of Combustion
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• v.19 no.3
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• pp.44-52
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• 2014

Solid oxide fuel cell(SOFC) makes electric power using hydrogen or reformed from methane and emits high temperature products that contain flammable species like hydrogen, carbon monoxide and methane which varies with operation condition. SOFC/gas turbine integrated system which uses thermal and chemical energy of the discharges is more efficient than SOFC itself. Burning character of the SOFC products will affect the efficiency and stability of the system. Experiments were conducted to know the characteristics of the flame for two typical composition of SOFC products, i.e. start-up and steady state composition. When coflowing air temperature was higher than $600^{\circ}C$, auto-ignitin occurred for both fuels. Though start-up fuel has higher contents of hydrogen, it makes longer flame than steady state composition. It was inferred that the amount of oxidizer necessary to burn makes this phenomenon. Steady state composition fuel was unstable since it contains lots of water. Nozzle that had 6 holes, distance between each hole was 16.7 times of hole diameter, improved the stability of the flame.

• Journal of Electrical Engineering and Technology
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• v.9 no.2
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• pp.635-642
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• 2014

The space charge behaviors of oil-paper insulation affect the stability and security of oil-filled converter transformers of traditional and new energies. This paper presents the results of the electrical aging of oil-impregnated paper under AC-DC combined voltages by the pulsed electro-acoustic technique. Data mining and feature extractions were performed on the influence of electrical aging on charge dynamics based on the experiment results in the first stage. Characteristic parameters such as total charge injection and apparent charge mobility were calculated. The influences of electrical aging on the trap energy distribution of an oil-paper insulation system were analyzed and discussed. Longer electrical aging time would increase the depth and energy density of charge trap, which decelerates the apparent charge mobility and increases the probability of hot electron formation. This mechanism would accelerate damage to the cellulose and the formation of discharge channels, enhance the acceleration of the electric field distortion, and shorten insulation lifetime under AC-DC combined voltages.

• The Journal of Asian Finance, Economics and Business
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• v.8 no.12
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• pp.353-361
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• 2021

An economic system is a means by which societies or governments organize and distribute available resources, services, and goods across a geographic region or country. The Islamic financial system faces a number of challenges as part of its role as a tool for developing economic activities. This study intends to advance research by Lassoued (2018) by expanding the research population to include Islamic banks in Asia and adding new dimensions - the size of the independent commissioner and corporate governance. The population of this study is the 100 largest Islamic banks in Asia. Statistical calculations with the STATA application is used for data analysis. Based on the test results, it was found that the size of the sharia board and the independent board of directors did not affect the financial stability of Islamic banking companies. Another finding is that the size of the independent commissioner affects financial stability. This finding shows that commissioners have played an active role in the company, indicating that if the sharia banking company has an ideal number of independent commissioners, it will be advantageous to the company's stability and business sustainability.

• Korea Trade Review
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• v.44 no.6
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• pp.345-361
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• 2019

In recent years, Chinese firms have explosively increased outward foreign direct investment (oFDI). While state-owned enterprises (SOEs) are still dominant in Chinese oFDI, privately-owned enterprises (POEs) are also accelerating their internationalization. These two types of Chinese firms differ in their behavior regarding oFDI. The objective of this paper is to analyze the differences in the choice of oFDI locations between Chinese SOEs and POEs by considering host country factors. By integrating the literature on Chinese firms' oFDI and on FDI locations, we developed six hypotheses concerning how host country factors affect their choice of location. We tested our hypotheses by conducting multiple regression analysis with recent secondary data on 413 Chinese MNEs in 88 countries between 2005 and 2016. The results of the test show that in selecting oFDI locations, Chinese SOEs invest relatively more in countries with richer natural resources, more abundant strategic assets, less production efficiency, higher political risk, and lower institutional quality compared with Chinese POEs. It is our hope that the empirical results of this paper will contribute to research on Chinese oFDI.