• Journal of the Korean Society of Safety
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• v.8 no.2
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• pp.51-57
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• 1993

This study was done by ultrasonic testing. The proves used in this study were 5Z10$\times$10A70. The useful fatigue life of structural components is determined by the sum of the elapsed load cycles required to initiate a fatigue crack and to propagate the crack from subcritical size to critical dimensions. Thus, to predict the service life of many steel structures and to establish safe inspection intervals, an understanding of the Fatigue Crack Initiation and Fatigue Crack Propagation behavior in the steel is required. In the present study, the Fatigue Crack Initiation Life in SPS 5A steel was investigated by testing specimens having widely varying notch acuities. The variation in the notch acuity covered the range from notch root raidus 0.5mm to 2.5mm, and Fatigue Crack Initiation Life data were obtained in that range.

• Journal of the Korean Society of Safety
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• v.5 no.3
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• pp.27-32
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• 1990

Standardization of solar collector test method is desirable for improvement solar collector quality and Valuation of collector thermal performance. In the present work, test loop proposed by Chun, is modified for convenience of test and obtained accurate collector thermal performance. An experimental investigation hat been carried out with a modified collector test loop under a real sun condition in order to confirm the utility of modified test loop and study the effect of variation of flow rate on thermal efficiency, the range of optimum flow rate and critical incident angle.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2000.07a
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• pp.132-135
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• 2000

This paper present the results of measured Thermally Stimulated Current of EPR(Ethylene Propylene Rubber) sheet material with variation of bias temperature range of -35~80[$^{\circ}C$], the quality of the material of electrode, condition. The origins of these peaks are that, low temperature peak seems to result from dipole, and high temperature peak from the orientation electronic trap.

• Korean Journal of Agricultural and Forest Meteorology
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• v.19 no.3
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• pp.93-101
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• 2017

The distribution of inter-annual variation in temperature would help evaluate the likelihood of a climatic risk and assess suitable zones of crops under climate change. In this study, we evaluated two methods to estimate the standard deviation of temperature in the areas where weather information is limited. We calculated the monthly standard deviation of temperature by collecting temperature at 0600 and 1500 local standard time from 10 automated weather stations (AWS). These weather stations were installed in the range of 8 to 1,073m above sea level within a mountainous catchment for 2011-2015. The observed values were compared with estimates, which were calculated using a geospatial correction scheme to derive the site-specific temperature. Those estimates explained 88 and 86% of the temperature variations at 0600 and 1500 LST, respectively. However, it often underestimated the temperatures. In the spring and fall, it tended to had different variance (e.g., increasing or decreasing pattern) from lower to higher elevation with the observed values. A regression analysis was also conducted to quantify the relationship between the standard deviation in temperature and the topography. The regression equation explained a relatively large variation of the monthly standard deviation when lapse-rate corrected temperature, basic topographical variables (e.g., slope, and aspect) and topographical variables related to temperature (e.g., thermal belt, cold air drainage, and brightness index) were used. The coefficient of determination for the regression analysis ranged between 0.46 and 0.98. It was expected that the regression model could account for 70% of the spatial variation of the standard deviation when the monthly standard deviation was predicted by using the minimum-maximum effective range of topographical variables for the area.

• Proceedings of the Korea Electromagnetic Engineering Society Conference
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• 2005.11a
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• pp.39-44
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• 2005

A broadband DC to 40 GHz 5-bit MMIC digital attenuator has been developed. The ultra broadband attenuator has been achieved by newly inserted the transmission lines in conventional Switched-T attenuator and the optimization of the transmission line parameters. Momentum was employed in design for an accurate performance prediction at high frequencies and Monte Carlo analysis was applied to verify performance stability against the MMIC process variation. The attenuator has been fabricated with 0.15 $\mu$m GaAs pHEMT process. This attenuator has 1 dB resolution and 23 dB dynamic range. High attenuation accuracy has been achieved over all attenuation range and full 40 GHz bandwidth with the reference state insertion loss of less than 6 dB at 20 GHz. The input and output return losses of the attenuator are better than 14 dB over all attenuation states and frequencies.

• Biomedical Science Letters
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• v.23 no.3
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• pp.208-214
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• 2017

To investigate the effects of strenuous physical exercise on commonly used hematological markers in subjects the intensive long running. Blood samples were obtained from nineteen participants in a 622 km ultra-marathon race before, 300 km and immediately after completion of the 622 km ultra-marathon. Samples were analyzed for total white cell count (WBC) and differential, total red cell count (RBC), hemoglobin, hematocrit, mean corpuscular volume (MCV), mean corpuscular hemoglobin (MCH), mean corpuscular hemoglobin concentration (MCHC), red cell distribution width (RDW), platelets, mean platelets volume (MPV), platelets distribution width (PDW). Significant increases were found in WBC, neutrophil and platelets at 622 km compared to the pre-race. RBC, hemoglobin and hematocrit decreased statistically significantly the race at 300 km and 622 km compared to pre-race. A wide range of hematological perturbations occur during 622 km ultra-marathon running but it was physiological changes within a reference range. The 622 km ultra-marathon is less likely to cause clinically significant hematologic changes in athletes.

• Proceedings of the KIEE Conference
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• 2015.07a
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• pp.83-84
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• 2015

In order to use the high-speed range of Interior Permanent Magnet Synchronous Motor(same as IPMSM above), the motor should be at flux weakening control status. High-speed range is called field weakening control region or constant power region, and explain the basic theory of flux weakening control used in the constant power region. Back electromotive force of IPMSM is measured. and field weakening conrtrol driving characteristics is configurated verification test. Through experimentation speed-torque characteristic curve, the efficiency variation corresponding to the current phase angl,the efficiency map were produced.

• Journal of the Korean Society of Safety
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• v.15 no.4
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• pp.41-46
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• 2000

Silicone rubbers are elastomeric materials and organic copolymers, of which backbone is siloxane with high bonding strength. Silicone rubbers have been used as an power insulator because they are well weather proof, ozone proof and have excellent electric characteristics, thermal stability, cold resistance and low surface energy. Especially, it is known that they have very excellent characteristics at 200[$^{\circ}C$]. For this study, we made silicone rubbers as specimens and measured volume resistivity due to applied voltage and a variation of temperature 25[$^{\circ}C$] to 180[$^{\circ}C$]. Also we measured dielectric loss tangent due to applied voltage at temperature range 25[$^{\circ}C$] to 180[$^{\circ}C$] and frequency range 20[Hz] to 1${\times}10^6$[Hz].

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2010.05a
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• pp.226-230
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• 2010

In this paper, the performance of an electric powered small Unmanned Aerial Vehicle which has a battery and electric motor is analysed. Aerodynamic data is obtained through flight test and flight performance is predicted. As a result, we present the optimum flight speed for the maximum endurance and predict endurance and range according to the variation of flight speed.

• Proceedings of the KIEE Conference
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• 1997.07f
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• pp.2207-2209
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• 1997

This Paper Presents the design automation for isolated DC-DC converters. Isolated DC-DC converts have many advantages such as protection, wide range variation, and multiple output. Prosedures consist of several steps. There are the selection of converter topology, the selection of switching devices. the calculation for the value of inductances and capacitances, and the design of transformers. We verified it with many practical examples from databooks.