• Journal of Electrical Engineering and Technology
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• v.10 no.2
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• pp.610-615
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• 2015

In order to study and obtain the mathematical relation between the electrification degree of transformer oil flow and the electrostatic current, a small amount of data about the electrification degree of oil flow and the corresponding electrostatic current is studied by linear regression method and grey model method. The results show that the linear correlation between the electrification degree and the electrostatic current was not good, and the relation between the electrification degree of oil flow and electrostatic current (i) could be expressed as ${\rho}(0)=0.2049\;i^{(0)}+169.4419$ according to grey model GM (0, 2) when the electrification degree of oil flow is represented by the charge number generated from transformer oil per unit volume, namely the charge density (${\rho}$).

• 한국신재생에너지학회:학술대회논문집
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• 2005.06a
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• pp.516-519
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• 2005

The pilot tidal current power plant is to be constructed at the Uldolmok between Chindo and Haenam, during next year. and extensive coastal engineering research works have been carried out. In this paper we describes some observation results of the tide and tidal current. as well as modeling work in order to investigate the tide and tidal current regime change in relation to the tidal current power plant (TCPP) construction. The special modeling skill in order to consider the turbine operation in the TCPP is developed and applied to the estimation for the flow regime change by the simple layout of the tidal current power plant.

• New & Renewable Energy
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• v.1 no.2 s.2
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• pp.73-78
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• 2005

The pilot tidal current power plant is to be constructed at the Uldolmok between Chindo and Haenam, during next year, and extensive coastal engineering research works have been carried out. In this paper we describes some observation results of the tide and tidal current, as well as modeling work in order to investigate the tide and tidal current regime change In relation to the tidal current power plant [TCPP] construction. The special modeling skill in order to consider the turbine operation in the TCPP is developed and applied to the estimation for the flow regime change by the simple layout of the tidal current power plant.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.11 no.5
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• pp.955-960
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• 2007

In this paper, the deviation of tunneling current for gate voltage has been investigated in double gate MOSFET developed to decrease the short channel effects. In device scaled to nano units, the tunneling current is very important current factor and rapidly increases,compared with thermionic emission current according to device size scaled down. We consider the change of tunneling current according to gate voltage in this study. The potential distribution is derived to observe the change of tunneling current according to gate voltage, and the deviation of off-current is derived from the relation of potential distribution and tunneling probability. The derived current is compared with the termionic emission current, and the relation of effective gate voltage to decrease tunneling current is obtained.

• Journal of the Korean Ceramic Society
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• v.33 no.5
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• pp.602-615
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• 1996

The purpose of the present study is to investigate the microstructural effect on the R-curve behavior in three aluminas with different grain size distributions by analyzing the bridging stress distribution. The crack opening displacement (COD) according to the distance behind the stationary crack tip was measured using an in situ SEM fracture method. The measured COD values in the fine-grained alumina agreed well with Wiederhorn's sollution while they deviated from Wiederhorn's solution in the two coarse-grained aluminas because of the increase of the crack closure due to the grain interface bridging in the crack wake. A numerical fitting procedure was conducted by the introduction of the power-law relation and the current theoretical model together with the measured COD's in order to obtain the bridging stress distribution. The results indicated that the bridging stress function and the R-curve computed by the current model were consistent with those computed by the power-law relation providing a reliable evidence for the bridging stress analysis of the current model. The strain-softening exponent in the power-law relation n, was calculated to be in the range from 2 to 3 and was closely related to the grain size distribution. Thus it was concluded from the current theoretical model that the grain size distribution affected greatly the bridging stress distribution thereby resulting in the quantitative analysis of microfracture of polycrystalline aluminas through correlating the local-fracture-cont-rolling microstructure.

• Journal of Korean Port Research
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• v.14 no.4
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• pp.475-479
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• 2000

A possibility of the implementation of a quartz crystal sensor to the determination of chemical oxygen demand is examined by checking the electrochemical behavior of the sensor in a glucose solution. Since the surface of a quartz crystal has to be oxidized, a relatively active metal is coated on the surface of a usual 9 MHz AT-cut crystal. The electrochemical behavior is investigated by measuring the changes of current, resonant frequency and resonant resistance while a constant potential is applied. The crystal is installed in a specially designed container, and a quartz crystal analyzer is utilized to measure the frequency and resistance simultaneously. The variations of the measurements are examined at different concentrations of glucose solution, and a proper relation between the concentrations of glucose solution, and a proper relation between the concentration and the measurements is analyzed. As a result, it is found that a linear relation between the concentration of less than 900 ppm and the peak current when a constant potential of -180 mV (SSCE) is applied. The relation can be utilized for the determination of glucose concentration in sea water, and considering a direct relation between gluose concentration and chemical oxygen demand tells a possibility of the measurement of chemical oxygen demand using quartz crystal oscillators.

• The Journal of Korean Medicine
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• v.22 no.4
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• pp.69-78
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• 2001

Objectives : It is known that cigarette smoking is associated with increased risk of both thrombotic and hemorrhagic stroke. However, in Korea, especially in the academic world of Korean Medicine, there is a lack of study about the relation between cigarette smoking and stroke. We carried out a case-control study to clarify the relation between cigarette smoking and stroke. Method : We interviewed 441 stroke patients (236 men, 205 women) as a case group and 432 non-stroke patients (208 men, 224 women) as a control group. We investigated the smoking pattern of all patients and stroke-subtype of the case group. Smoking pattern is classed into two (Class I), four (Class II) and five groups (Class III). Class I consists of current non-smokers and current smokers. Class II consists of non-smokers, former smokers, current light smokers and current heavy smokers. Class III consists of never smoked, secondhand smokers, former smokers, Current light smokers and current heavy smokers. Stroke-subtype consists of cerebral infarction and cerebral hemorrhage. Results : The percentage of current smokers of case group is higher significantly than that of control group. The number of cigarettes smoked per day is associated positively with the risk of stroke. According to our study, generally cigarette smoking is related with ischemic stroke. The percentage of secondhand smokers of the case group is lower than that of the control group. According to our study, characteristically secondhand smoking is associated with hemorrhagic stroke. Conclusions : From the above results we found that cigarette smoking is an important risk factor of stroke - especially cerebral infarction - and the number of cigarettes smoked per day is associated positively with the risk of stroke. Characteristically according to our study, secondhand smoking is associated with hemorrhagic stroke. Overall we conclude that cigarette smoking may be an important preventable factor for stroke.

• The Korean Journal of Elementary Counseling
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• v.7 no.1
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• pp.37-66
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• 2008

This study has been carried out with the aims of developing a comprehensive inventory of peer relation problems, which is based on the Korean Inventory of Interpersonal Problems Circumplex scales (KIIP-C). It also aims to examine reliability and validity of the inventory, and provide a preliminary norms. For the current study, inventory items were culled from the following sources: the Korean Inventory of Interpersonal Problems Circumplex scales (KIIP-C), various current scales dealing with peer relations of children, and a survey of children's peer relation problems. The preliminary items for each scale were administered to 220 fourth through sixth graders. The resulting skewness of distribution, kurtosis, mean and standard deviation, item-total correlation, internal consistency, and meanings of the items were comprehensively considered in selecting the final 64 items. In order to check on reliability, internal consistency, convergence and discrimination reliability of the final items and scales, the data were collected from 1,046 fourth through sixth graders currently attending four elementary schools. The study results can be summarized as follows. Internal consistency of the inventory of peer relation problems showed the range between .70-.94 (median value of .75), split-half reliability between .67-.83 (median value of .75), and test-retest reliability between .69-.88 (median value of .81). Inter-correlation of 8 scale scores and factor analysis results of individual ipsative scores showed that the circumplex property of inventory of peer relation problems is appropriate. Regarding correlations between various existing indices and scales related to peer relation problems, both convergence reliability and discrimination reliability were found to be fair. When the scale scores for the inventory of peer relation problems compared according to the factors of gender and grade, the primary effects of gender and grade were statistically meaningful whereas effects of interaction between gender and grade were not. This study can be considered meaningful in that it constructed an inventory for a comprehensive evaluation of peer relation problems specific for children and provided preliminary norms.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.10 no.9
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• pp.1648-1653
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• 2006

In this paper, transport characteristics have been investigated using analytical current-voltage model for double gate MOSFET(DGMOSFET). Scaling down to 100nm of gate length for MOSFET can bring about various problems such as a threshold voltage roll-off and increasing off current by tunneling since thickness of oxide is down by 1.fnm and doping concentration is increased. A current-voltage characteristics have been calculated according to changing of channel length,using analytical current-voltage relation. The analytical model has been verified by calculating I-V relation according to changing of oxide thickness and channel thickness as well as channel length. A current-voltage characteristics also have been compared and analyzed for operating temperature. When gate voltage is 2V, it is shown that a current-voltage characteristic in 77K is superior to in room temperature.

• Journal of the Korean Institute of Telematics and Electronics A
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• v.32A no.7
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• pp.51-57
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• 1995

The theoretical analysis for AlInAs/GaInAs resonant tunneling diodes (RTDs), which have shown the improved negative differential resistance (NDR) characteristics, has scarcely been made in comparison with AlGaAS/GaAs RTDs. In this paper, the static current-voltage relation of Al$_{0.48}In_{0.52}As/Ga_{0.47}In_{0.53}$As RTDs were numerically estimated by using a self-consistent method. Assuming a simplified RTD with single quantum well structure and spacer layers, the peak current density (J$_{P}$) and the peak-to-valley current ratio (PVCR) were analysed as the function of the thickness of the well, the barrier and the spacer layer, and temperature. As the results, the peak current density and the peak-to-valley current ratio indicated a reciprocal relation roughly in respect to the thicknesses of the well and the barrier, and it was theoretically predicted that it be not attainable to provide a high peak current desity (J$_{P}$) over 1${\times}10^{5}A/cm^{2}$ as well as the large peak-to-valley current ratio (PVCR) over 10 that were the the critical conditions for the practical use.