• Journal of the Korea Institute of Information and Communication Engineering
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• v.16 no.8
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• pp.1747-1752
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• 2012

The SiOC film of carbon centered system was prepared using bistrimethylsilylmethane (BTMSM) and oxygen mixed precursor by the chemical vapor deposition. The dielectric constant is measured by MIS(metal/insulator/Si) structure, but it could decrease the reliability because the uniformity is not assured. To research the dielectric constant of SiOC film, the range of low polarization was researched in SiOC film using the optical analysis and hardness, and then calculated the dielectric constant of SiOC film with amorphous structure of high degree. After annealing, the dielectric constant of SiOC film was decreased owing to the lowering of polarization, and FTIR spectra of the main bond was shifted to higher wave number. The main bond of 950~1200 cm-1 was composed of the Si-C and Si-O bonds. The intensity increases in Si-O bond infers the bonding strength became stronger than that of deposited film. Annealed SiOC film showed 2.06 in dielectric constant.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2002.11a
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• pp.95-98
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• 2002

전력선 통신 blocking filter용 자심 재료를 개발하기 위해서 MnO 24 mol%, ZnO 25 mol% and $Fe_{2}O_{3}$ 51 mol% 의 기본조성에 $MoO_{3}$, $SiO_{2}$, CaO를 첨가하여 $1350^{\circ}C$에서 대기압 상수 A를 7.8롤 고정하고 소결하여 미세구조를 제어하였으며 기본 조성에 $MoO_{3}$ 400 ppm, $SiO_{2}$ 100 ppm and CaO 200 ppm을 첨가한 경우 평균 입경 $25{\mu}m$ 의 균일한 결정립으로 구성된 미세구조를 얻었고 기공의 감소에 의한 치밀화로 $4.98g/cm^{2}$의 고밀도화가 이루어 졌다. 또한 소결체의 균일한 미세구조와 고밀도화로 인해서 8221(${25^{\circ}C}$, 1 KHz) 의 가장 높은 투자율 특성을 나타냈다. 시편의 온도가 증가함에 따라 투자율이 증가되어 ${110^{\circ}C}$에서 13904의 거대 투자융이 측정되었고, 코일의 인가주파수가 1 KHz에서 1 MHz까지 증가됨에 따라 최고 ${102^{\circ}C}$까지 시편 온도가 상승하였다. 가장 높은 투자율 특성을 나타낸 ferrite 코어를 사용하여 단상 및 3상용 블로킹 필터의 감쇄율을 측정한 결과 현재 국내의 전력선 통신용 주파수 대역으로 규정되어 있는 10 KHz ~ 450 KHz 대역에서 각각 -46.46 dB와 -73.9 dB의 최고 값을 얻었다.

• Journal of Korea Water Resources Association
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• v.51 no.1
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• pp.19-33
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• 2018

This study proposed a rainfall-runoff model for the purpose of real-time flood warning in urban basins. The proposed model was based on the shot noise process, which is expressed as a sum of shot noises determined independently with the peak value, decay parameter and time delay of each sub-basin. The proposed model was different from other rainfall-runoff models from the point that the runoff from each sub-basin reaches the basin outlet independently. The model parameters can be easily determined by the empirical formulas for the concentration time and storage coefficient of a basin and those of the pipe flow. The proposed model was applied to the total of three rainfall events observed at the Jungdong, Guro 1 and Daerim 2 pumping stations to evaluate its applicability. Summarizing the results is as follows. (1) The unit response function of the proposed model, different from other rainfall-runoff models, has the same shape regardless of the rainfall duration. (2) The proposed model shows a convergent shape as the calculation time interval becomes smaller. As the proposed model was proposed to be applied to urban basins, one-minute of calculation time interval would be most appropriate. (3) Application of the one-minute unit response function to the observed rainfall events showed that the simulated runoff hydrographs were very similar to those observed. This result indicates that the proposed model has a good application potential for the rainfall-runoff analysis in urban basins.

• Proceedings of the Korea Institute of Applied Superconductivity and Cryogenics Conference
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• 2002.02a
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• pp.294-296
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• 2002

Considering the application of high temperature superconductor to MRI, the loss at conductor joint would be very important. Therefore, we have carried out a measurement of joint resistance of Bi-2223/Ag tapes at 77 K. A pancake coil was wound by Bi-2223/Ag tape. Both ends the tape were overlapped and soldered to each other. The DC current is induced in the pancake coil by energizing the excitation coil wound by copper wire closely located to the pancake coil. The decay behaviour of the current in coils was clearly separated in two regimes, and initial fast decay of the order of minutes followed by a slow logarithmic-like decay, From this data, the resistance of the joint was evaluated as 2.74 n$\Omega$.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.12 no.3
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• pp.285-291
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• 1987

Seismic waves are attenuated by losses of energy as they propagate through the earth. One way to model this numerically is to make the velocity a complex number, the real part giving the phase velocity and the imaginary part the attenuation. This models wave propagation in a medium for which the logarithmic decrement is independent of frequency(attenuation coefficient is proportional to frequncy). The aim is to modify forward and inverse numerical modeling so that attenuation can be specified as a function of position.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.21 no.5
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• pp.486-493
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• 2010

This article introduces a novel ultra wideband(UWB) bandpass filter(BPF) with sharp roll-off characteristics in stripline structure. The UWB characteristic is basically obtained from capacitive coupled cross resonator. The resonator has ${\lambda}/2$ length. And at the center of the resonator, two stubs are loaded, one is a ${\lambda}/8$ short-circuited stub and the other is a ${\lambda}/8$ open-circuited stub. The two stubs provide two attenuation poles at lower and upper cutoff frequencies. For input and output lines, two identical capacitively coupled lines have been installed to suppress the unwanted signals in the lower and upper stopbands. The filter has been designed for the U.S. UWB band(3.1~10.6 GHz) with two transmission zeros at 2.4 and 11.1 GHz. The filter has been realized with Low Temperature Core-fired Ceramic(LTCC) green tape which has the dielectric constant of 7.8. Measurement results agree well with HFSS simulation results. Insertion loss less than 0.7 dB and return loss better than 14 dB in the pass band have been measured. The group delay in the center frequency is 0.27 ns and the group delay variation within pass band is less than 0.5 ns. The size of the filter is $6{\times}18{\times}0.6\;mm^3$.

• Korean Journal of Agricultural and Forest Meteorology
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• v.18 no.2
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• pp.88-98
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• 2016

The storage variation in the vadose zone at a hillslope is important to understand the hydrological process. This study explores seasonal changes of soil water storage at a hillslope scale. The study was conducted on a hillslope of Beomrunsa, located in the Seolma-cheon river basin in Paju-si, Gyeonggi-do. Using soil moisture measurements through Time Domain Reflectometry (TDR), storage, discharge, and response constant were calculated for all monitoring points on a hillslope between March and November, 2010. This study found that temporal changes in storage are resulted from the rainfall distribution patterns. Analysis of the spatial changes in storage indicated that the soil water storage tends to increase towards the downslope direction. The discharges calculated based on the soil water measurements exhibited a high correlation with observation discharge. The storage response constant was high during the autumn which demonstrates the increased contribution from upslope is responsible for the occurrence of soil water recharge during autumn.

• Fire Science and Engineering
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• v.30 no.2
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• pp.62-67
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• 2016

In this study, the optical depth is analyzed with the effects of droplet size distribution of the water curtain nozzle to attenuate the radiative heat transfer. The HELOS/VARIO equipment is used for the measurement of the droplet size distributions. The spray characteristics are quantified by the investigation of Deirmenjian's modified gamma distribution function. The distribution constant of the nozzle can be obtained as ${\alpha}=1$ and ${\gamma}=5.2$. The generalized equation of the optical depth related with the droplet size distribution is introduced. These results will be applicable to the analysis of the design condition of the water curtain nozzle.

• Journal of the Korean Solar Energy Society
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• v.31 no.6
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• pp.57-65
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• 2011

The wake generated by a wind turbine has an effect on performance of a downstream wind turbine as well as mechanical loads. This paper investigated characteristics of fatigue load at the blade root due to the wake effects and quantitatively analyzed its effects at operating condition of a 5MW tripod offshore wind turbine using Bladed 4.1 software. The wake effects was studied the way the wake's center position move from the rotor center to the blade tip to the far-away position where the wake doesn't affect the wind turbine. When wake's center was located on the blade tip or the rotor center, damage equivalent fatigue load was higher than other positions. It was up to 10~14% compared to those of non-wake case. Results of this study would be helpful to design wind turbines and wind farms to have lifetimes more than 20 years of the wind turbine.

• Journal of Applied Biological Chemistry
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• v.63 no.3
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• pp.267-274
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• 2020

The dissipation characteristics and kinetics of fungicide mandipropamid and insecticide thiamethoxam in lettuce under greenhouse conditions were investigated at three different lettuce-growing fields for estimating the pre-harvest residue limits (PHRLs). The analytical methods were fully validated for the quantitation of pesticide residues using High-Performance Liquid Chromatography-Photo Diode Array detector or Ultraviolet-Visible Detector and applied to real samples. The lettuces suitable for shipment were harvested during 10 days including pre-harvest interval after treatment at the recommended dose by safe-use guidelines. The initial mean residues in different fields were 6.68-17.87 and 4.96-8.31 mg/kg for mandipropamid and thiamethoxam, respectively, which decreased to 16-54 and 14-44% in 10 days. The clothianidin, a metabolite of thiamethoxam, was detected in <0.02 to 0.37 mg/kg. The dissipation of both pesticides followed first-order kinetics over a period of 10 days after application. Based on the residue data, the mean dissipation rate constant (λ) and biological half-lives (T_1/2) were estimated to be -0.1060 and 6.5 days of mandipropamid and -0.1236 and 5.6 days of thiamethoxam. The PHRLs for lettuce on the 10th and 5th day before harvesting were calculated to be 63.24 and 43.56 mg/kg for mandipropamid, and 44.66 and 25.88 mg/kg for thiamethoxam, with -0.0746 and -0.1091 of the upper 95% confidence intervals of dissipation rate constant, respectively. This work would be useful as guidance for adjusting the shipment date and contribute to stabilizing the income of farmers in Korea.