• Journal of information and communication convergence engineering
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• v.11 no.1
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• pp.7-11
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• 2013

Wearable computer systems use the wireless universal serial bus (WUSB), which refers to USB technology that is merged with WiMedia physical layer and medium access control layer (PHY/MAC) technical specifications. WUSB can be applied to wireless personal area network (WPAN) applications as well as wired USB applications such as PAN. WUSB specifications have defined high-speed connections between a WUSB host and WUSB devices for compatibility with USB 2.0 specifications. In this paper, we focus on an integrated system with a WUSB over an IEEE 802.15.6 wireless body area network (WBAN) for wireless wearable computer systems. Due to the portable and wearable nature of wearable computer systems, the WUSB over IEEE 802.15.6 hierarchical medium access control (MAC) protocol has to support power saving operations and integrate WUSB transactions with WBAN traffic efficiently. In this paper, we propose a low-power hibernation technique (LHT) for WUSB over IEEE 802.15.6 hierarchical MAC to improve its energy efficiency. Simulation results show that the LHT also integrates WUSB transactions and WBAN traffic efficiently while it achieves high energy efficiency.

• New & Renewable Energy
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• v.18 no.4
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• pp.64-69
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• 2022

Double-sided photovoltaic (PV) modules have received significant attention in recent years as a technology that can achieve higher annual energy production rates than single-sided modules. The shingled technology is a promising method for manufacturing high-density and high-power modules. These modules are divided by laser and joined with electrically conductive adhesives. The output efficiency of the divided cells depends on the division pattern and the electrode pattern, making it important to understand the output characteristics. In this study, the output characteristics of large-area double-sided light-receiving shingled cells with different split patterns and electrode patterns were investigated. The M6 size, with 6 divisions in the electrode pattern, had the highest efficiency when using 142 front fingers and 146 rear fingers. The M10 size, with 7 divisions, had the highest output when using 150 fingers equally in the front and rear. The M12 size, also with 7 divisions, showed the highest output characteristics when using 192 front fingers and 208 rear fingers.

• Korean Chemical Engineering Research
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• v.61 no.4
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• pp.627-634
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• 2023

Graphitic carbon nitride (g-C₃N₄) has attracted considerable attention since its discovery for its catalysis of water splitting to hydrogen and oxygen under visible light irradiation. However, pristine g-C₃N₄ confers only low photocatalytic efficiency and requires surface cocatalysts to reach moderate activity due to a lack of accessible surface active sites. Inspired by the high specific surface area and superior electron transfer of graphene, we developed a strongly coupled binary structure of graphene and g-C₃N₄ aerogel with 3D porous skeleton. The as-prepared 3D structure photocatalysts achieve a high surface area that favors efficient photogenerated charge separation and transfer, enhances the light-harvesting efficiency, and significantly improves the photocatalytic hydrogen evolution rate as well. The photocatalyst performance is observed to be optimized at the ratio 3:7 (g-C₃N₄:GO), leading to photocatalytic H₂ evolution of 16125.1 mmol. g^-1. h^-1 under visible light irradiation, more than 161 times higher than the rate achieved by bulk g-C₃N₄.

• 한국ITS학회:학술대회논문집
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• 2008.11a
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• pp.189-192
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• 2008

• 한국정보디스플레이학회:학술대회논문집
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• 2004.08a
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• pp.272-276
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• 2004

Great strides in organic light emitting device (OLED) technology have resulted in a number of commercial products. To continue this growth into large area displays, for example televisions, an understanding of the mechanisms that drive the OLED device efficiency and lifetime performance is critical. In this work, we consider maximizing the efficiency lifetime product based on phosphorescent OLED ($PHOLED^{TM}$) technology. We report green PHOLEDs with luminous efficiency of 82 cd/A, 5.7 V and 10,000 hours lifetime at 1,000 cd/$m^2$,red PHOLEDs with CIE of (0.67,0.33), 11 cd/A and 35,000 hours lifetime at 500 cd/$m^2$ and recent progress in blue demonstrating efficiencies of 18 cd/A at 200 cd/$m^2$.

• Journal of Information Management
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• v.41 no.3
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• pp.67-84
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• 2010

The purpose of this paper is to measure and analyse the relative efficiency of 17 public libraries in Daejeon metropolitan city using Data Envelopment Analysis. In this paper, total staffs, total area, total holdings are used as library inputs and total circulations, total user visits are used as library outputs. The estimated results show that libraries operate at 64.15% efficiency and only 4 libraries are relatively efficient. Inefficiency of the public libraries was due to small use of outputs compared to inputs.

• Journal of the Korea Institute of Military Science and Technology
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• v.5 no.4
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• pp.9-18
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• 2002

In this paper, we have studied the characteristics of a perforated muzzle brake. The main purpose of a muzzle brake is to reduce the momentum being applied to the recoil system. Muzzle brake redirect a portion of the exiting gases to the side exerting a forward force on the brake, thus reducing recoil. So it also reduces the recoil force which acts on the turret and vehicle. First of all, we analyzed the flow-field characteristics of muzzle brake using RAMPANT software. Then we investigated the influence of design parameters of perforated muzzle brake. Sixteen muzzle brakes were tested and evaluated for analyzing their influence on the muzzle brake efficiency. The muzzle brakes were designed to fit on a 40mm gun barrel. The strong dependent parameters of muzzle brake efficiency were the wall thickness(L/d ratio) and the area ratio AR. We designed the perforated muzzle brakes which have 10-20% efficiency. And we proposed a design method of perforated muzzle brake.

• Journal of the Korean Society for Precision Engineering
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• v.14 no.1
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• pp.84-89
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• 1997

Recentely, a compact and small size air-cleaning Electrostatic Precipitator(ESP) is needed to develop for air conditioning devices. From Deutsch formula for ESP efficiency, collection efficiency is affected not only the structure of collection section but also the charge rate of dust. In terms of collection area, the most useful type is a scroll type ESP. In this work, we investigated experimentally aptimum design factor of scroll type ESP by application of Taguchi method. And we developed the scroll type ESP by using optimal condition of control factor.

• Journal of Electrical Engineering and Technology
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• v.12 no.4
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• pp.1593-1599
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• 2017

This paper presents a multi-channel light-emitting diode (LED) driver IC with a current-mode current regulator. The proposed current regulator replaces resistors for current sensing with a sequentially controlled single current sensor and a single regulation loop for sensing and regulating all LED channel currents. This minimizes the current mismatch among the LED channels and increases voltage headroom or, equivalently, power efficiency. The proposed LED driver IC was fabricated in a $0.35-{\mu}m$ BCD 60-V high voltage process, and the chip area is $1.06mm^2$. The measured maximum power efficiency is 93.4 % from a 12-V input, and the inter-channel current error is smaller than as low as ${\pm}1.3%$ in overall operating region.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.65 no.4
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• pp.561-566
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• 2016

In this paper, effective design method of linear induction motor(LIM) for Maglev is proposed in order to maximize system efficiency of Maglev. For the high system efficiency of Maglev, it is important to minimize weight of traction motor. Light weight design by changing materials of core and winding is conducted without changing volume of LIM. For the silicon steel core of primary part for magnetic flux path, iron-cobalt alloy steel with high magnetic saturation characteristic compared to silicon steel is suggested. Moreover, aluminium winding with light weight instead of copper winding is wounded in the widen slot area due to the high magnetic saturation level. For the verification of performance of proposed model, the characteristics are analyzed by using finite element method(FEM).