• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.25 no.2
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• pp.147-152
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• 2012

This paper dealt with the frequency component analysis of acoustic signals produced by corona and series-arc discharges as a diagnostic technique for closed-switchboards. Corona and series-arc discharge were simulated by a needle-plane electrode and an arc generator specified in UL1699, respectively. Acoustic signal was detected by a wideband acoustic sensor with a frequency bandwidth of 4 Hz~100 kHz (-3 dB). We analyzed frequency spectrums of the acoustic signals detected in various discharge conditions. The results showed that acoustic signals mainly exist in ranges from 30 kHz to 60 kHz. From the experimental results, an acoustic detection system which consists of a constant current power supply (CCP), a low noise amplifier (LNA) and a band pass filter was designed and fabricated. The CCP separates the signal component from the DC source of acoustic sensor, and the LNA has a gain of 40 dB in ranges of 280 Hz~320 kHz. The high and the low cut-off frequency are 30 kHz and 60 kHz, respectively. We could detect corona and series-arc discharges without any interference by the acoustic detection system, and the best frequency is considered in ranges of 30 kHz~60 kHz.

• Korean Journal of Optics and Photonics
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• v.23 no.4
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• pp.159-166
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• 2012

We have developed a daytime measuring rotational Raman LIDAR system for temperature measurement. To decrease the background signal from sunlight, we have designed and installed narrow band (0.5 nm) and high rejection ($10^{-6}$) rate band pass filter system using a grating and an interference filter. We calibrated our system by comparing our horizontal temperature profile and KMA (Korea Meteorological Administration) data. We have found that our temperature profile has a good correlation with KMA data within our theoretically expected variance. And we have used these calibration values in obtaining a vertical temperature distribution. To check our system, we also have compared our vertical temperature data with US standard atmospheric temperature profile. We also have compared our temperature profile with sonde data.

• Journal of Drive and Control
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• v.16 no.4
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• pp.1-8
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• 2019

The HPM (High-speed Power Matching) system is an electro-hydraulic control system. It directly controls the swash plate of the pump by selecting four-loop logic based on joystick signals, pump flow, and pressure signal to improve the efficiency and controllability of construction machines. In the NFC (Negative Flow Control) system, a typical pump control system using conventional open center type MCV, the loss is continuously generated by flow through the center bypass line even when the excavator is not in operation. Also, due to the slow response of the pump that indirectly controls the flow rate using the pressure regulator, peak pressure occurs at the start or stop of the operation. Conversely, the HPM system uses an MCV without center-by-pass flow path and the swash plate of a pump for the HPM is controlled by a high-speed proportional flow control valve. As a result, the HPM system minimizes energy loss in standby state of the excavator and enables peak pressure control through rapid electro-hydraulic control of a pump. In this paper, the concept of the HPM system algorithm is introduced and the hydraulic system efficiency is compared with the NFC system using the excavator SAT (System Analysis Tool).

• Korean Journal of Environmental Agriculture
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• v.33 no.2
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• pp.134-137
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• 2014

BACKGROUND: Dissipation of herbicides in paddy water varies significantly, being dependent on environmental conditions such as sunlight. The photodegradation under natural sunlight may be one of natural degradation routes of herbicides dissipation. Therefore, the aim of this study was to monitor the degradation of butachlor and pyrazosulfuron-ethyl in paddy water under natural sunlight. METHODS AND RESULTS: The 12 water sample bottles of treatment were covered by quart glass plates, which allow about 90% of UV radiation (280-2000 nm) to pass through, to minimize the UV attenuation. The other 12 water sample bottles of the control were covered by glass lids and wrapped with aluminum foils to prevent the sunlight. The concentration of butachlor and pyrazosulfuron-ethyl in paddy water samples bottles was monitored under ambient conditions with and without natural sunlight. The concentration of butachlor and pyrazosulfuron-ethyl for treatment decreased from $355.3{\mu}g/L$ to $37.8{\mu}g/L$ and from $10.5{\mu}g/L$ to $3.9{\mu}g/L$, respectively, during consecutive 21 days after herbicide application under natural sunlight. CONCLUSION: The concentration of butachlor in paddy water decreased quickly under ambient conditions with natural sunlight. The degradation of butachlor in paddy water was enhanced by the natural sunlight. However, the degradation of pyrazosulfuron-ethyl was insignificant under natural sunlight.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.21 no.12
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• pp.1423-1431
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• 2010

In this paper, the dual-band compact broad bandpass filter using parallel coupled line is proposed. The proposed filter has reduced size and can be controlled bandwidth. And it is also possible to operate in the dual-band purpose. Futhermore, the inserted bandstop fiilter with T-type configuration is also possible to operate in the same purpose. The dual-band bandpass filter has the first operating frequencies and its bandwidth which are 5.8 GHz and 60 % respectively and the second operating frequency and the bandwidth are 16.2 GHz and 60 % respectively. The insertion loss and the return loss of the first frequency has 0.4 dB and 17.4 dB and the insertion loss and the return loss of the second frequency has 0.62 dB and 19.8 dB, respectively.

• Korean Journal of Metals and Materials
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• v.47 no.3
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• pp.139-146
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• 2009

The heat-affected zone (HAZ) of SA508 Gr.4N Ni-Mo-Cr low alloy steel, which has higher Ni and Cr contents than SA508 Gr.3 Mn-Mo-Ni low alloy steel, was investigated on the microstructure and mechanical properties. The HAZ was categorized into seven characteristic zones (CGCG, FGCG, ICCG, SCCG, FGFG, ICIC and SCSC-HAZ) according to the peak temperature from the thermal cycle experienced during multi-pass welding. Post Weld Heat Treatment (PWHT) was conducted in the temperature range of $550{\sim}610^{\circ}C$ for 30 hours to evaluate the effect of PWHT conditions on the microstructure and mechanical properties. Before PWHT, CGHAZ and FGFGHAZ showed high yield strength (YS) ranging from 1000 to 1250 MPa, while YS of SCSCHAZ decreased from 607 MPa (observed for base metal) to 501 MPa. The Charpy impact energies of sub-HAZs fell below 100J at $-29^{\circ}C$, except in the SCSCHAZ. By applying PWHT to sub-HAZ specimens, YS decreased as the PWHT temperature increased. In the case of CGHAZs and FGFGHAZ heat-treated at $610^{\circ}C$, YS dropped drastically to the range of 654~686 MPa. From the Charpy impact test, the upper-shelf energy (USE) increased to approximately 250J and Index temperature ($T_{68J}$) decreased below $-50^{\circ}C$. Specifically, in FGFG, ICIC and SCSC-HAZ, $T_{68J}$ was below -110, which was lower than the case of base metal.

• Neonatal Medicine
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• v.25 no.1
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• pp.37-43
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• 2018

Purpose: Meconium-related ileus is common in preterm infants. Without proper management, it can cause necrotizing enterocolitis and perforation requiring emergent operation. This study was conducted to describe the efficacy and safety of ultrasound-guided Gastrografin enema at bedside for preterm infants with meconium-related ileus. Methods: Between March 2013 and December 2014, this study enrolled preterm infants with birth weight <1,500 g, who were diagnosed with meconium-related ileus requiring ultrasound-guided Gastrografin enema refractory to glycerin or warm saline enemas. Gastrografin was infused until it passed the ileocecal valve with ultrasound guidance at bedside. Results: A total of 13 preterm infants were enrolled. Gestational age and birth weight were 28.6 weeks (range, 23.9-34.3 weeks) and 893 g (range, 610-1,440 g), respectively. Gastrografin enema was performed around postnatal day 8 (range, day 3-11). The success rate was 84.6% (11 of 13 cases). Three of these 11 infants received a second procedure, which was successful. Among 2 unsuccessful cases, one failed to pass meconium while the other required surgery due to perforation. The time required to pass meconium was $2.8{\pm}1.5hours$ (range, 1-6 hours). The time until radiographic improvement was $2.8{\pm}3.4days$ (range, 1-14 days) after the procedure. Conclusion: Ultrasound-guided Gastrografin enema at bedside as a first-line treatment to relieve meconium-related ileus was effective and safe for very low birth weight infants. We could avoid unnecessary emergent operation in preterm infants who have high postoperative morbidity and mortality. This could also avoid transporting small preterm infants to fluoroscopy suite.

• Korean Journal of Agricultural Science
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• v.42 no.1
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• pp.53-61
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• 2015

Development of highly efficient and energy-saving tractors has been one of the issues in agricultural machinery. For design of such tractors, measurement and analysis of load on major power transmission parts of the tractors are the most important pre-requisite tasks. Objective of this study was to perform pre-processing procedures before effective analysis of load data of agricultural tractors (30, 75, and 82 kW) during major field operations such as plow tillage, rotary tillage, baling, bale wrapping, and to select the suitable pre-processing method for the analysis. A load measurement systems, equipped in the tractors, were consisted of strain-gauge, encoder, hydraulic pressure, and radar speed sensors to measure torque and rotational speed levels of transmission input shaft, PTO shaft, and driving axle shafts, pressure of the hydraulic inlet line, and travel speed, respectively. The entire sensor data were collected at a 200-Hz rate. Plow tillage, rotary tillage, baling, wrapping, and loader operations were selected as major field operations of agricultural tractors. Same or different farm works and driving levels were set differently for each of the load measuring experiment. Before load data analysis, pre-processing procedures such as outlier removal, low-pass filtering, and data division were performed. Data beyond the scope of the measuring range of the sensors and the operating range of the power transmission parts were removed. Considering engine and PTO rotational speeds, frequency components greater than 90, 60, and 60 Hz cut off frequencies were low-pass filtered for plow tillage, rotary tillage, and baler operations, respectively. Measured load data were divided into five parts: driving, working, implement up, implement down, and turning. Results of the study would provide useful information for load characteristics of tractors on major field operations.

• Journal of Bio-Environment Control
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• v.15 no.1
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• pp.8-20
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• 2006

This research was conducted to determine the plant growth and nutrient contents of potted chrysanthemum 'Lima Honey' as influenced by application rate of dolomite in three root media, peatmoss+vermiculite (1:1, v/v), peatmoss+composted rice hall (1:1, v/v), and peatmoss+composted pine bark (1:1, v/v). All root media contained polyacrylic acid sodium salt (PASS) at a rate of $4.5g L^{-1}$. In crop growth at 40 and 80 days after transplanting, elevated application rates of dolomite up to $6.0g L^{-1}$ in three root media increased fresh and dry weights per plant. But the treatment of $9.0g L^{-1}$ had less fresh and dry weights than those of $6.0g L^{-1}$. Tissue phosphorus content decreased and those of Ca and Mg increased by the elevated application rates of dolomite. Elevated application rates of dolomite in three root media resulted in the increase of pH, EC, and the concentrations of K, Ca, and Mg at 43 days after transplanting. Those at 80 days after transplanting were also increased, but the differences among treatments were less significant as compared to those at 43 days after transplanting. From the results of dry weight in potted chrysanthemum 'Lima Honey', the proper application rate of dolomite to three root media containing PASS at a rate of $4.5g L^{-1}$ were $6.0g L^{-1}$.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.25 no.9B
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• pp.1551-1562
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• 2000

In the using of FBG developed in home land, we designed and manufactured three types of FBG sound transducers the first in Korea. On FBG transducers manufactured we made an demonstrated on respective frequency response peculiarties in the water and analyzed the special characters. As the experimental result on frequency response peculiarities, we made t possible underwater acoustic detection on C type to maximum 18kHz, And for the purpose of realization on multi-point signal detection on wide scope in the water, in the using of WDM(Wavelength Division Multiplexing) method and passive band-pass filter system, established arrays system and succeeded in multi-point underwater acoustic signal detection to the frequency 1.3KHz out of the two B type FBG transducers. Additionally, it would be possible directivity detection for the objects of its source as the intensity of detection signal varies with the sound source's direction and angle. From now on we prepared a new moment on the practical used study on FBG hydrophone.