• 반도체디스플레이기술학회지
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• 제19권4호
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• pp.99-104
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• 2020

In this paper, efficiency and loss characteristics of GaN FET were reported by applying it into the QR flyback converter. In particular, for the comparison of efficiency characteristics, QR flyback converter experimental circuits with Si FET and with GaN FET were separately produced in 12W class. As a result of the experiment, the experimental circuit of the QR flyback converter using GaN FET reached a high efficiency of 90% or more when the load power was 2W or more, and the maximum efficiency was observed to be about 92%, and the maximum loss power was about 1.1W. Meanwhile, the efficiency of the experimental circuit with Si FET increased as the input voltage increased, and the maximum efficiency was observed to be about 82% when the load power was 9W or higher, and the maximum loss power was about 2.8W. From the results, it is estimated that that in the case of the experimental circuit applying the GaN FET switch, the power conversion efficiency was improved as the switching loss and conduction loss due to on-resistance were reduced, and the internal loss due to the synchronous rectifier was minimized. Consequently, it is concluded that the GaN FET is suitable for under 20W class power supply unit as a high efficiency power switch.

• Applied Biological Chemistry
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• 제43권2호
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• pp.124-129
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• 2000

농업유역에서 영양원소들은 시비 후 강우에 의해 지표 유출이 생기면 용해되거나 토사에 흡착된 상태로 하천에 유입되어 부영양화의 주요한 요인이 되고 있다. 농경지로부터의 영양염류 유실 정도를 평가하기 위해 경북 영천군 임고천 유역의 대표적 영농형태인 과수원 토양에 $14.3{\times}24.8\;m$면적의 유출 시험포를 설치하고 1999년 3월부터 11월 사이에 발생한 26개의 강우 사상에 대하여 지표 유출수량과 토양 유실량을 측정하였으며 이들과 함께 발생하는 질소와 인의 유실량을 조사하였다. 시험 포장에는 화학비료와 혼합유박비료로 질소와 인이 각각 112, 46kg/ha씩 처리되었다 조사 기간 동안 발생한 총 표면 유출수량은 $421.5\;m^3/ha$이었고 토양 유실량은 1,989kg/ha이었다. 유출수중의 T-N, $NO_3-N$, $NH_4-N$, T-P 및 $PO_4-P$의 농도는 각각 $4.7{\sim}171.0,\;0.1{\sim}188.0,\;0.13{\sim}3.36,\;0.58{\sim}4.99$ 및 $0.05{\sim}3.71\;mg/l$ 범위였다 강우에 의해 지표면으로 유실된 총 질소량은 16.39 kg/ha였으며 이중 질산태 질소와 암모늄태 질소가 각각 75%와 3%를 차지하였다. 인의 유실량은 총 16.39 kg/ha였으며 이 중에서 이온형태의 인이 47%였으며 토사와 함께 유실되는 인은 27% 정도였다. 질소와 인의 총 유실량은 각각 총 시비량의 9.5% 및 2.3%였다.

• 전력전자학회논문지
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• 제22권4호
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• pp.297-304
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• 2017

The purpose of this paper is to analyze losses because of switching devices and the secondary side circuit diodes of 500 W full bridge dc-dc converter by applying gallium nitride (GaN) field-effect transistor (FET), which is one of the wide band gap devices. For the detailed device analysis, we translate the specific resistance relation caused by the GaN FET material property into algebraic expression, and investigate the influence of the GaN FET structure and characteristic on efficiency and system specifications. In addition, we mathematically compare the diode rectifier circuit loss, which is a full bridge dc-dc converter secondary side circuit, with the synchronous rectifier circuit loss using silicon metal-oxide semiconductor (Si MOSFET) or GaN FET, which produce the full bridge dc-dc converter analytical value validity to derive the final efficiency and loss. We also design the heat sink based on the mathematically derived loss value, and suggest the heat sink size by purpose and the heat divergence degree through simulation.

• 전자공학회논문지A
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• 제32A권1호
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• pp.89-96
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• 1995

Lateral p-i-n photodiodes have been fabricated, electrically tested, and incorporated into microwave control circuits such as an optically excited microwave atttenuator and reflection type phase shifter. Circuit design procedures for the loaded-line phase shifter with the optically controlled p-i-n photodiode are presented. The equal loss loading mode presented for the first time for the phase shifter circuits with lossy load allows an equal insertion loss of the phase shifter in both of its phase states. It is found that the insertion loss of the equal loss loading mode phase shifter constructed with the fabricated p-i-n photodiode load are about 3dB for 11.25$^{\circ}$ bit and 1dB for 5.625$^{\circ}$ bit for the frequency range of 2GHz to 11GHz.

• 아시안잔디학회지
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• 제6권1호
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• pp.23-28
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• 1992

Urea, the major N source of world agriculture involves a serious urea-N loss through NH$_3$volatilization. Approaches to decrease N loss include using urease inhibitors in view of the environmental protection and the increase of urea-N efficiency. The purpose of laboratory researches was toassess the potential value of urease inhibitors to increase urea-N efficiency in soil and Kentucky blue-grass(Poa Pratensis L.) turf. The activity of urease inhibitors Phenyiphosphorodiamjdate(ppD) and N-(n-butyl) thiophosphoric triamjde(NBPT) measured to break-down ammonia volatilization. The soil and turf used in this project were from the fairway in one of the Korean gof course. The researches were carried out for two weeks to measure the urease activities on urea hydrolysis under four temperatures (10~ 40$^{\circ}C$) and for one week on turfgrass using forced-draft system. Results indicated that Urea-N involves considerable loss through gaseous NH$_3$ by urease activities in plant-soil systems. Urease inhibitors PPD and NBPT have potential value for increasing N use efficiency by reduing NH$_3$ volatilization. NBPT deserves futher evaluation as fertilizer amendment than PPD use of urea in turf industries.

• 한국토양비료학회지
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• 제49권6호
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• pp.669-676
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• 2016

A field study was conducted to determine the runoff loss of N and P in small scale of red pepper field plots (10% slope), consisting of three different plots with black polyethylene vinyl mulching (mulching), ridge without mulching (ridge), and flat without ridge and mulching (flat). Composted manure and urea as a basal application were applied at rates of $20MT\;ha^{-1}$ and $93kg\;N\;ha^{-1}$, respectively. Urea at $189kg\;N\;ha^{-1}$ and fused phosphate at $67kg\;P_2O_5\;ha^{-1}$ were additionally applied on June 25 with different fertilization methods, broadcast application in flat plot and hole injection in ridge and mulching plots. Plant uptake of N and P was positively correlated with their respective concentrations in surface soil: mulching > ridge > flat plots. The runoff loss by soil erosion was higher in flat plot than ridge and mulching plot with contour line. Nitrate loss by the runoff water had no significant differences among three surface management practices, but the higher average value in ridge and mulching plots than flat plot. Especially, the flat plot had no phosphate loss during summer season. This is probably due to low labile P content in surface soil of flat plot. In the summation of soil and water loss, flat plot was higher in N and P loss than ridge and mulching plot with contour line. Nevertheless, the nitrate and phosphate loss by runoff water could be more important for non-point source management because the water could meet the river easier than eroded soil because of re-deposition around slope land.

• 공업화학
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• 제5권1호
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• pp.63-73
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• 1994

n-Tetradecyldimethylbenzylammonium chloride(TDAC)와 n-tetradecyltrimethylammonium methyl sulfate (TTAM)를 합성하고 각각에 물을 가하여 감량촉진제 용액 TDACW와 TTAMW를 각각 제조하였다. 제조된 TDACW와 TTAMW 각각을 NaOH와 병용하여 PET섬유를 감량가공처리한 결과, 감량률은 TDACW가 TTAMW보다 훨씬 높게 나타났으며, 적정 처리농도는 약 $8g/{\ell}$, 처리시간은 60~90분 및 처리액량비는 1:40~1:50이었다. 밀도와 결정화도는 감량률이 증가할수록 상승하였고, 인장강도는 역으로 감량률이 증가될수록 저하되었다. 또한 감량촉진제와 PET섬유와의 반응메카니즘을 고찰하여 감량촉진제가 촉매로서 작용함을 밝혔으며, SEM으로 감량가공된 PET섬유의 표면형태를 관찰하였다.

• The Journal of Advanced Prosthodontics
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• 제1권2호
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• pp.102-106
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• 2009

STATEMENT OF PROBLEM. Screw loosening has been a common complication and still reported frequently. PURPOSE. The purpose of this study was to evaluate abrasion of the implant fixture and TiN coated abutment screw after repeated delivery and removal with universal measuring microscope. MATERIAL AND METHODS. Implant systems used for this study were Osstem and 3i. Seven pairs of implant fixtures, abutments and abutment screws for each system were selected and all the fixtures were perpendicularly mounted in liquid unsaturated poly-esther with dental surveyor. After 20 times of repeated closing and opening test, the evaluation for the change of inner surface of implant and TiN-coated abutment screw, and weight loss were measured. Mann-Whitney test with SPSS statistical software for Window was applied to analyze the measurement of weight loss. RESULTS. TiN-coated abutment screws of Osstem and 3i showed lesser loss of weight than non-coated those of Osstem and 3i (P < .05, Mann-Whitney test). CONCLUSION. Conclusively, TiN coating of abutment screw showed better resistance to abrasion than titanium abutment screw. It was concluded that TiN coating of abutment screw would reduce the loss of preload with good abrasion resistance and low coefficient of friction, and help to maintain screw joint stability.

• 한국작물학회지
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• 제44권3호
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• pp.230-235
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• 1999

To study the effects of an urease inhibitor, N-(n-butyl)-thiophosphoric triamide (NBPT), and a nitrification inhibitor, dicyandiamide (DCD), on nitrogen losses and nitrogen use efficiency, urea fertilizer with or without inhibitors and slowrelease fertilizer (synthetic thermoplastic resins coated urea) were applied to direct-seeded flooded rice fields in 1998. In the urea and the urea+DCD treatments, NH$_4$$^{+}$ -N concentrations reached 50 mg N L$^{-1}$ after application. Urea+NBPT and urea+ NBPT+DCD treatments maintained NH$_4$$^{+}$ -N concentrations below 10 mg N L$^{-1}$ in the floodwater, while the slow-release fertilizer application maintained the lowest concentration of NH$_4$$^{+}$ -N in floodwater. The ammonia losses of urea+NBPT and urea+NBPT+DCD treatments were lower than those of urea and urea+DCD treatments during the 30 days after fertilizer application. It was found that N loss due to ammonia volatilization was minimized in the treatments of NBPT with urea and the slow-release fertilizer. The volatile loss of urea+DCD treatment was not significantly different from that of urea surface application. It was found that NBPT delayed urea hydrolysis and then decreased losses due to ammonia volatilization. DCD, a nitrification inhibitor, had no significant effect on ammonia loss under flooded conditions. The slow-release fertilizer application reduced ammonia volatilization loss most effectively. As N0$_3$$^{[-10]}$ -N concentrations in the soil water indicated that leaching losses of N were negligible, DCD was not effective in inhibiting nitrification in the flooded soil. The amount of N in plants was especially low in the slow-release fertilizer treatment during the early growth stage for 15 days after fertilization. The amount of N in the rice plants, however, was higher in the slow-release fertilizer treatment than in other treatments at harvest. Grain yields in the treatments of slow-release fertilizer, urea+NBPT+ DCD and urea+NBPT were significantly higher than those in the treatments of urea and urea+DCD. NBPT treatment with urea and the slow-release fertilizer application were effective in both reducing nitrogen losses and increasing grain yield by improving N use efficiency in direct-seeded flooded rice field.field.

• 한국유기농업학회지
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• 제8권2호
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• pp.89-96
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• 2000

To reduce loss of nitrogen and generation of ammonia gas during composting, poultry manure and sawdust were mixed at the equivalent ratio and calcium chloride, fused superphosphate and vermiculite were added. Ammonia and sulfurous gas during composting, and NH4-N and NO3-N contents of composts were periodically measured. With the treatments of 0.5∼3% calcium chloride and 3% fused superphosphate, ammonia and sulfurous gas during composting significantly decreased, and especially generation of gases sharply reduced and a increase of calcium chlorde. Extractable NH4-N content in composts treasted with calcium chloride and fused superphosphate were high but extractable NO3-N markedly decreased. In conclusion, the results suggest that it is necessary the additon of 1∼3% calcium chloride or 3% fused superphosphate to reduce loss of nirogen and generation of offensive odor during composting of poultry manure mixed with sawdust.