• Journal of Electrical Engineering and Technology
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• v.9 no.2
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• pp.569-575
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• 2014

A highly efficient class E power amplifier is demonstrated for application to wireless power transfer system. The amplifier is designed with an L-type matching at the output for harmonic rejection and output matching. The power loss and the effect of each component in the amplifier with the matching circuit are analyzed with the current ratio transmitted to the output load. Inductors with a quality factor of more than 120 are used in a dc feed and the matching circuit to improve transmission efficiency. The single-ended amplifier with 20 V supply voltage shows 7.7 W output power and 90.8% power added efficiency at 6.78 MHz. The wireless power transfer (WPT) system with the amplifier shows 5.4 W transmitted power and 82.3% overall efficiency. The analysis and measurements show that high-Q inductors are required for the amplifier design to realize highly efficient WPT system.

• Korean Journal of Optics and Photonics
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• v.2 no.3
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• pp.115-120
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• 1991

The effect of ZnS buffer layer on the brightness and luminous efficiency of SrS : Ce, Cl thin film EL device is investigated. The driving voltage is 210V for the cell with ZnS buffer layer, but 220V without ZnS buffer layer. The frequency range is 500 Hz-20 kHz. The. brightness is proportional to the product of the frequency and the transferred charge density within measured range. The luminous efficiency is independent on the frequency and/or driving voltage. By using the ZnS buffer layer, the luminescence characteristics of active layer is improved. The experimental data shows 0.12 Im/W of the luminous efficiency for the device with ZnS buffer layer, but 0.061m/W without ZnS buffer layer.

• Journal of the Korean Applied Science and Technology
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• v.16 no.4
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• pp.307-311
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• 1999

Interfacial properties of electrode and organic thin layer is one of the most important factor in performing a Light Emitting Diodes(LED). Phthalocyanine copper was used as a buffer layer to improve interface characteristic, so that device efficiency was improved. In this study, LEDs were fabricated as like structures of Indium-Tin-Oxide (ITO) / N,N' -Diphenyl-N,N'-di(m-tolyl)-benzidine (TPD) / 8-Hydroxyquinoline aluminum(Alq) / Aluminum(Al) and Indium-Tin-Oxide(ITO) / N,N'-Diphenyl-N,N' -di(m-tolyl)-benzidine(TPD) / 2-(4-Biphenylyl)-5(4-tert-butyl-phenyl)-1,3,4-oxadiazole(PBD) / Aluminum(Al). In these devices, CuPC was layered at electrode/organic layer interface. As position is changing and thickness is changing, devices showed characteristic luminescence efficiency and luminescence inensity respectively. We showed in this study that luminescence efficiency was improved with CuPC layer in LEDs. The efficiency of device with layer CuPC is higher than that of 2 layer CuPC. However, the luminescence of 2 layer CuPC device got higher value.

• Nuclear Engineering and Technology
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• v.53 no.4
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• pp.1284-1288
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• 2021

In this work, we propose and design a GaN-based diode with a p-doped GaN (p-GaN) multi-well structure for high efficiency betavoltaic (BV) cells. The short-circuit current density (J_SC) and opencircuit voltage (V_OC) of the devices were investigated with variations of parameters such as the doping concentration, height, width of the p-GaN well region, well-to-well gap, and number of well regions. The J_SC of the device was significantly improved by a wider depletion area, which was obtained by applying the multi-well structure. The optimized device achieved a higher output power density by 8.6% than that of the conventional diode due to the enhancement of J_SC. The proposed device structure showed a high potential for a high efficiency BV cell candidate.

• The Transactions of the Korean Institute of Power Electronics
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• v.24 no.3
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• pp.201-206
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• 2019

This study presents the design and experimental result of a GaN-based DC-DC converter with an integrated gate driver. The GaN device is attractive to power electronic applications due to its superior device performance. However, the switching loss of a GaN-based power converter is susceptible to the common source inductance, and converter efficiency is severely degraded with a large loop inductance. The objective of this study is to achieve high-efficiency power conversion and the highest power density using a multiphase integrated half-bridge GaN solution with minimized loop inductance. Before designing the converter, several GaN and Si devices were compared and loss analysis was conducted. Moreover, the impact of common source inductance from layout parasitic inductance was carefully investigated. Experimental test was conducted in buck mode operation at 48 -12 V, and results showed a peak efficiency of 97.8%.

• Journal of the Institute of Electronics Engineers of Korea SD
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• v.37 no.1
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• pp.29-35
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• 2000

Luminescent characteristics of SrS:Cu,X TFeL devices fabricated by electron-beam deposition system were studied. The SrS powders were used as the host materials and Cu, $CuF_2,\;Cu_2S$ or CuCl powders were added as the luminescent center. The emission spectra of the SrS:Cu,X TFEL devices strongly depended on coactivators. The luminance($L_{40}$) and efficiency(${\eta}_{20}$) of SrS:$Cu_2S$ TFEL device were 1443 cd/$m^2$ and 2.44 lm/w, respectively. Green color was observed from this TFEL device. The luminous efficiency of SrS:$Cu_2S$ TFEL device was higher than that of ZnS:Tb TFEL device, and it also could be good green phosphors for TFEL devices. The luminance($L_{40}$) and efficiency(${\eta}_{20}$) of SrS:CuCl TFEL device were 262 cd/$m^2$ and 0.26 lm/w, respectively. Blue color was emitted from this TFEL device.

• Journal of The Korean Society of Agricultural Engineers
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• v.60 no.1
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• pp.31-36
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• 2018

A rainwater harvesting device was developed for runoff flow harvesting in a small stream or channel and its performance was evaluated in small fields. The rainwater harvesting device has slits on its side of cylindrical volume in 15 cm diameter and 70 cm length, which is designed to increase its water flow harvesting capacity. The maximum collectable water quantity was about 0.0022 ton/sec (130 L/min). Rainwater harvesting device were installed in two locations (P1, P2). P1 is a point for rainfall runoff flow harvesting. P2 is a point for ordinary flow harvesting. During this study, total rainfall depth was 334.5 mm. Runoff of 1,722 ton and 7,984 ton occurred in P1 and P2, and 273 ton and 125 ton were collected by this rainwater harvesting device. Harvesting efficiency was calculated as 15.85 % and 1.57 % in P1 and P2. Clogging of screen filter media in the cylinder due to soil and suspended solids has lowered the harvesting efficiency. However, it was possible to harvest 30 ton/month of rainwater harvesting and it is expected that it will help to solve short-term water shortage.

• Journal of Climate Change Research
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• v.9 no.1
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• pp.75-80
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• 2018

The problem of water shortages and water related disasters caused by climate change has increased the seriousness of water problems and the importance of water treatment technology capable of securing clean water is expanding. In this study, we analyzed not only the water pollutant generated by the filtration system technology of various water treatment technologies but also the indirect greenhouse gas emissions generation, and analyzed the influence on the environment. The subjects of study are Fabric Filter, Reverse Osmosis System and Pressurized Microfiltration Device which are widely used for water treatment and we analyzed the impact on the environment using the Life Cycle Assessment (LCA) method using the electricity amount necessary for use, the water purification efficiency, the throughput per ton and the cost. The amount of greenhouse gas generated when the Pressurized Microfiltration Device operates for 1 year is $2.15E+04kg\;CO_2-eq$., Fabric Filter is $3.29E+04kg\;CO_2-eq$., and Reverse Osmosis System is $1.68E+05kg\;CO_2-eq$. As a result of analyzing the amount of greenhouse gas generated at the time of purifying 1 ton of the Pressurized Microfiltration Device and the conventional filtration system, the Pressurized Microfiltration Device was $20.5g\;CO_2-eq$., Fabric Filter was $34.7g\;CO_2-eq$., and Reverse Osmosis System was $191.7g\;CO_2-eq$. The amount of greenhouse gas generated was calculated to be 41.0% less than that of the Fabric Filter by the Pressurized Microfiltration Device and 89.3% less than the Reverse Osmosis System. From the viewpoint of climate change, it is necessary to select a filtration system that takes climate change into account, not from the viewpoint of water quality removal efficiency and economic efficiency according to future water treatment applications, and it is necessary to select a water treatment filtration system more researches and improvements will be made for.

• 한국정보디스플레이학회:학술대회논문집
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• 2006.08a
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• pp.1591-1594
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• 2006

In this work, we fabricated efficient white organic light emitting device (WOLED) by the stack of complementary fluorescent dye-doped layers, Effect of dye-doping ratio and thickness of each layers on WOLED efficiency and emission spectrum was investigated. Moreover, out-coupling efficiency enhancement using microlens array was analyzed for bottom and top-emitting device architecture, leading to higher light extraction properties.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 1997.10a
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• pp.171-174
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• 1997

The great development of semiconductor industry demands the high efficiency and performance of related device, but the pick and place system of semiconductor packaging device can load a few units until nowdays. Although the system can load a lot of units, it can work multiple sort operation. The defect like that causes a low efficiency. Therefore, this paper represents the development of pick and place system which can work multiple sort operation.