• Journal of the Korean Chemical Society
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• v.59 no.6
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• pp.493-498
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• 2015

The reductive amination of cyclohexanone with ammonia over Cu-Cr-a/γ-Al₂O₃ was investigated. It was found that a proper solvent with high solubility of ammonia and 4Å molecular sieves for the elimination of generated water contributed to the formation of cyclohexylamine in the premixing process. In addition, the addition of ammonia in the fixedbed reactor could obviously improve the conversion of cyclohexanone to cyclohexylamine. Finally, reaction conditions including reaction temperature, hydrogen pressure and charging rate of the premix were optimized. Under the optimized conditions, cyclohexylamine was obtained in 83.06% yield.

• Aerospace Engineering and Technology
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• v.12 no.2
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• pp.7-13
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• 2013

Power system in satellite shall produce stable outputs for successful mission accomplishment. However, unstability in overall electrical system is caused in a case where a load having a power profile with high-powered and micro-cycled pulse shape is connected to a satellite power system. In order to resolve this anomaly, "power system stabilization method using a battery" featured with simplicity can be applied, but there is a constraint to operate a battery in its normal operational conditions. In this paper, an effective interface structure for "power system stabilization method using a battery" is suggested and a battery protection algorithm for preventing over-charging and over-discharging is discussed.

• Proceedings of the KIPE Conference
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• 2008.10a
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• pp.13-15
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• 2008

Charging or discharging secondary batteries such as a lithium-ion battery is essential in the stage of production and takes long time over two hours. And the charge/discharge system is operated with high switching frequency over several tens kHz. Therefore, to simulate such a system in the conventional way takes very long time and huge files are produced. Finally, the simulation would be unable with general PC class. In this paper, the lithium-ion battery charge/discharge system is analyzed by using state space averaging method. As a result, the simulation time is reduced dramatically and the charge/- discharge characteristics of the lithium-ion battery can be observed.

• Proceedings of the KIPE Conference
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• 2016.11a
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• pp.59-60
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• 2016

Flooded lead acid batteries are still very popular in the industry because of their low cost as compared to their counterparts. State of Charge (SOC) estimation is of great importance for a flooded lead acid battery to ensure its safe working and to prevent it from over-charging or over-discharging. Different types of Kalman Filters are widely used for SOC estimation of batteries. The values of process and measurement noise covariance of a filter are usually calculated by trial and error method and taken as constant throughout the estimation process. While in practical cases, these values can vary as well depending upon the dynamics of the system. Therefore an Adaptive Unscented Kalman Filter (AUKF) is introduced in which the values of the process and measurement noise covariance are updated in each iteration based on the residual system error. A comparison of traditional and Adaptive Unscented Kalman Filter is presented in the paper. The results show that SOC estimation error by the proposed method is further reduced by 3 % as compared to traditional Unscented Kalman Filter.

• Applied Microscopy
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• v.43 no.1
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• pp.9-13
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• 2013

The helium ion microscope (HIM) has recently emerged as a novel tool for imaging and analysis. Based on a bright ion source and small probe, the HIM offers advantages over the conventional field emission scanning electron microscope. The key features of the HIM include (1) high resolution (ca. 0.25 nm), (2) great surface sensitivity, (3) great contrast, (4) large depth-of-field, (5) efficient charge control, (6) reduced specimen damage, and (7) nanomachining capability. Due to the charge neutralization by flood electron beam, there is no need for conductive metal coating for the observation of insulating biological specimens by HIM. There is growing evidence that the HIM has substantial potential for high-resolution imaging of uncoated insulating biological specimens at the nanoscale.

• Journal of the Korean Society for Precision Engineering
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• v.23 no.6 s.183
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• pp.64-71
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• 2006

A target of this paper is to study on the usefulness of the adaptive piezoelectric energy harvesting device as a wireless electrical power supply when it is driven by mechanical vibrations of low frequency. For this purpose, an adaptive control technique and a step-down converter are used. A THUNDER series a piezoelectric material (TH7-R), which has been developed by a NASA engineer is selected for this study. In order to provide a mechanical energy to the piezoelectric material, a mechanical motion vibrator is designed. The adaptive controller is implemented using a dSPACE DS1104 controller board. The do-dc converter with an adaptive control technique harvests energy at over five times the rate of direct charging without a converter.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.23 no.9
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• pp.718-723
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• 2010

In this paper, the following results were obtained from the experiment in which electrification voltage of silicone rubber specimen for thermal bonding were measured under various time, temperature ($10{\sim}40^{\circ}C$), and humidity (30~90%) conditions and different amount of carbon additives (0~15 phr (per hundred resin)). Electrostatics electrification voltage decreased when carbon is up to 10 phr, and there was no electrification voltage in 15 phr condition. The electrostatics electrification voltage did not change over time. When the temperature was constant, electrostatics electrification voltage sharply dropped when the humidity was around 70%. That means, this condition might be appropriate for prevention of charging. The electrification voltage decreased as humidity and amount of carbon increased.

• East Asian Economic Review
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• v.16 no.3
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• pp.249-272
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• 2012

This paper examines how a Korean automobile firm price-discriminates between the Korean and the U.S. markets. We argue that a Korean automobile firm's pricing behavior depends on the differences in price elasticity over the segmented markets between the countries. Our findings are that differences in price elasticity may help explain why a medium-class car's price is higher in Korea than that in the U.S. while a small-sized car's price is higher in the U.S. than in Korea, which implies that a Korean automobile firm $3^{rd}$ degree price-discriminates on the same or similar products between Korea and the U.S. This type of $3^{rd}$ degree price discrimination differs from a typical home-bias effect (charging higher prices to domestic consumers) because a small-sized car which is produced domestically sells at higher price abroad. This finding can be added as a source that violates the law of one price.

• Proceedings of the KIPE Conference
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• 2017.11a
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• pp.111-112
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• 2017

This paper presents a novel three-port converter for the OnBoard Charger of Electric Vehicles by using an impedance control network. The proposed concept is suitable for charging a main battery and an auxiliary battery of an electric vehicle at the same time due to its power handling capability of the converter without additional switches. The power flow is managed by the phase angle (${\Theta}$) between the ports whereas voltage at each port is controlled by the asymmetric duty cycle and the phase shift (${\Phi}$) between the inverter lags controlled by the impedance control network. The proposed system has a capability of achieving zero voltage switching (ZVS) and zero current switching (ZCS) at all the switches over the wide range of input voltage, output voltage and output power. The feasibility of the proposed system is verified by the PSIM simulation.

• Transactions of the Korean Society of Automotive Engineers
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• v.2 no.2
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• pp.42-48
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• 1994

Turbocharging is one of the best methods to improve the performance of diesel engines, because of its merits,-power ratio, fuel consumption and exhaust emissions. Most of them in small and medium diesel engines have adopted the pulse turbocharging method with twin entry vaneless radial turbines to maximize the energy utility of exhaust gas. This method requires the high performance of turbine under unsteady flow, and also the matching between turbine and diesel engine is most important. However, it is difficult to match properly between them. Because the steady flow data are usually used for it. Accordingly, it is necessary to catch the characteristics of turbine performance correctly over the wide range of the operation conditions under unsteady flow. In this paper, the characteristics of turbine performance under unsteady flow are represented at varying conditions, such as inlet pressure amplitude, turbine speed and frequence.