• Journal of Electrical Engineering and Technology
• /
• v.5 no.1
• /
• pp.156-162
• /
• 2010

This paper describes electrical and optical characteristics of discharge developments in water under inhomogeneous fields caused by impulse voltages. Predischarge current and discharge light images were observed for different water resistivities and applied voltages between the hemispherical water tank and the needle electrode. The electrical parameters characterizing discharge developments are analyzed based on the discharge light images and voltage-current (V-I) curves, and electrical resistances derived by voltage and current waveforms. As a result, when the streamer corona is initiated at the tip of the needle electrode, the transient resistance suddenly drops and V-I curves form a 'loop'. The length of streamer propagation is increased with increasing peak value of the applied voltage, and the streamer corona extension is enlarged with increasing water resistivity. The electrical resistances before streamer corona initiation are rarely changed by different applied voltages. On the other hand, the electrical resistances after streamer corona initiation are found to be inversely proportional to the peak value of the applied voltage, and the decreasing rates for higher water resistivities are much higher than those for lower water resistivities. The time to streamer corona initiation and the time to the second current peak become shorter as the voltage increases. Finally, the calculated resistances after streamer corona initiation are almost the same trace of measured resistances, but they are smaller than the measured values.

• The Transactions of The Korean Institute of Electrical Engineers
• /
• v.63 no.10
• /
• pp.1347-1353
• /
• 2014

This paper researches a modeling and experiment of 50kW diesel generator in grid-connected mode. The output of diesel generator can be calculated by the phase difference between voltage and current as well as the diesel generator parameter such as mutual impedance, field current and rotor angle. Considering the different d-q frame impedance, the output of diesel generator is analyzed for equation and verified by simulation. The diesel generator modeled by considering the time delay for actuator, diesel engine and exciter. The controller of diesel generator is divided into governor and exciter. The governor consists of speed controller and active power controller, where speed controller maintains frequency as 60Hz and active power tracks active power reference. On the other hand, the exciter consists of voltage controller and reactive power controller, where voltage controller controls $380V_{LL}$ and reactive power is controlled as zero. When the active power reference is changed as 0.1pu in the grid connected mode, the active power takes 10 seconds to reach the steady state and the reactive power is maintains as zero. The 50kW diesel generator is tested and experiment results are well matched with the simulation results.

• Journal of Korean Institute of Industrial Engineers
• /
• v.39 no.6
• /
• pp.546-553
• /
• 2013

A clear increase in the average annual temperature is observed worldwide, and climate changes take place in response to that increase. This affects not only the ecosystem, but also to mankind. Of all those aspects of climate change, people are especially interested in the length of each season, and people acknowledge that the duration of spring and fall has been shortened over the past several years. Still, it is difficult to observe this kind of phenomenon with the simple analysis of dividing the seasons and calculating the duration. Therefore, this study attempted to set up a more intuitive standard which well reflects the current situation. This study also divided the daily climate into 4 states using the daily maximum and minimum temperature. Moreover, using the Hidden Markov Model, this study calculated the duration of each season and analyzed its tendency based on the daily temperature data of the last 53 years (1960~2012). According to the result, the duration of spring and fall showed mild decreasing tendency over the past 53 years, and the duration of fall decreased even more during the past 30 years in the Korean peninsula. After 1960, the start of spring was advanced, which decreased the length of winter for about 11 days. On the other hand, the duration of summer increased for about 25 days, which is consistent with the worldwide tendency of temperature increase.

• KIPS Transactions on Computer and Communication Systems
• /
• v.2 no.3
• /
• pp.103-110
• /
• 2013

Logical Effort [1, 2] is a simple hand-calculated method that measures quick delay estimation. It has the advantage of reducing the design cycle time. However, it has shortcomings in designing a path for minimum area or power under a fixed-delay constraint. The method of overcoming the shortcomings is shown in [3], but it is constrained for a single logical path. This paper presents an advanced gate sizing method in multiple logical paths based on the equal delay model. According to the results of the simulation, the power dissipation for both the existing logical effort method and proposed method is almost equal. However, compared with the existing logical effort method, it is about 52 (%) more efficient in space.

• Korean Journal of Applied Biomechanics
• /
• v.17 no.3
• /
• pp.133-145
• /
• 2007

The purpose of this paper was to compare of difference between energy walking and normal walking. Subjects were selected 8 male undergraduates. The kinematic variables of a pelvis and a thorax were analysed at the take off and contact with 3d cinematography. In addition to the variables, the phase plot angle was calculated in order to definite characteristics in the phase space. The pelvic angle and angular velocity showed significant differences in the flexion/extension between two walking patterns. The pelvic angle and angular velocity were increasing when walking speed was increasing and magnitude of the variables of energy walking was larger than corresponding values for normal walking. On the other hand, the thoracic angle demonstrated significant differences in the flexion/extension and rotation between two walking patterns. The angles of energy walking were smaller in the flexion/extension and were larger in the rotation than the angle of normal walking. The kinematic characteristics of energy walking were also showed clearly significant differences in the range of motion and the relative angle of the trunk. The angle of phase plot only showed demonstrated a significant difference in the rotation at contact between the two walking patterns.

• Journal of the Korean Vacuum Society
• /
• v.9 no.1
• /
• pp.7-15
• /
• 2000

An ECR-PECVD system with the characteristics of high ionization rat다 ability of plasma processing in a wide pressure range and deposition at low temperature was manufactured and characterized for the deposition of thin films. The system consists of a vacuum chamber, sample stage, vacuum gauge, vacuum pump, gas injection part, vacuum sealing valve, ECR source and a control part. The control of system is carried out by the microprocessor and the ROM program. We have investigated the vacuum characteristics of ECR-PECVD system, and also have diagnosed the characteristics of ECR microwave plasma by using the Langmuir probe. From the data of system and plasma characterization, we could confirmed the stability of pressure in the vacuum chamber according to the variation of gas flow rate and the effect of ion bombardment by the negative DC self bias voltage. The plasma density was increased with the increase of gas flow rate and ECR power. On the other hand, it was decreased with the increase of horizontal radius and distance between ECR source and probe. The calculated plasma densities were in the range of 49.7\times10^{11}\sim3.7\times10^{12}\textrm{cm}^{-3}$. It is also expected that we can estimate the thickness uniformity of film fabricated by the ECR-PECVD system from the distribution of the plasma density.

• Water for future
• /
• v.24 no.4
• /
• pp.73-84
• /
• 1991

A number of planning models that are used for preliminary design of detention ponds in urban area were compared with consideration of urbanization effects. The characteristics of hydrological parameters $\alpha$, $\gamma$ which are used in planning models wee analyzed. And a new planning model for detention ponds was suggested. The required storage volumes of the Sinjung I, Myunmock, and Hannam detention pond were calculated by the planning models with the catchment data. The applicability of planning models to estimate the required storage volume of detention pond was investigated. Mori and Rational model have the trend of overstimation of storage volumes of detention ponds, on the other hand Abt & Grigg and Kadoya model show the trend of understimated values, and the rest of the planning models show the reasonable volumes.

• Journal of Preventive Medicine and Public Health
• /
• v.45 no.1
• /
• pp.8-13
• /
• 2012

Objectives: Recently injury has become a major world-wide health problem. But studies in Korea about injuries were very few. Thus, this study was conducted to analyze the trend of major injuries from 1991 to 2006 and to provide basic data for preventing injuries. Methods: This study was based on the National Statistical Office data from 1991 to 2006 and calculated to estimate the burden of major injuries by using the standard expected years of life lost (SEYLL) and total lost earnings equation. Results: For transport accidents, mortality, SEYLL and total lost earnings were increased from 1991 to 1996 and decreased from 2000 to 2006. On the other hand, for suicides, these were increased gradually. Since 2003, falls were included in ten leading causes of death. This study showed that injury causes major social and economical losses. Conclusions: We could reduce injury related premature death through active interest in injury prevention program.

• Korean Journal of Acupuncture
• /
• v.30 no.2
• /
• pp.131-134
• /
• 2013

Objectives : This study was performed to investigate the relationship between Sasang Constitution and length of chest and abdomen region. Methods : Forty eight participants were enrolled. Weight, height, and lengths from CV22 to CV16, from CV16 to CV8, and from CV8 to CV2 were measured. Ratios of last three lengths to total CV22 to CV2 were calculated respectively. On the other hand, Sasang Constitution was analyzed with QSCCII(Questionnaire of Sasang Constitutional Classification II). The analysis of relationship between the measurements and Sasang Constitution was carried out with SPSS to compare the mean values according to Sasang Constitution. Results : All the mean values were not significantly different depending on the Sasang Constitution, except the ratio of the length from CV16 to CV8 to the length from CV22 to CV2, only in female participants. The ratio was higher in the female Soeumin participants than any other constitutional groups. Conclusions : This result showed that Soeumin could be assumed that they might have weak digestion abilities.

• Proceedings of the KIEE Conference
• /
• summer
• /
• pp.488-490
• /
• 2004

The technical data for transmission line design and maintenance are calculated by a very complicated numerical formula so it is almost impossible to solve them by hand. Therefore the TOWER+ EXPERT SYSTEM was developed to systematically support technical data for transmission line design and maintenance. This system is able to calculate technical data which is applied to all conductors in our county, - that is 12 kinds of systems with 86 numbers of standard conductors, - and is programed to be user friendly by adopting dialogue windows, menu selection functions. Moreover, it minimizes input data by automatically providing standard transmission line design data, and it includes guidance of applicable work, program usage, data input process, help, explanation of terms and automatic error recovery functions that even a beginner can easily use.