• The Transactions of the Korean Institute of Electrical Engineers P
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• v.58 no.4
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• pp.592-596
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• 2009

DAFC(direct alcohol fuel cell) takes the same structure and operational principle with PEMFC(Proton exchange membrane fuel cell). However, DAFC, which uses liquid alcohol instead of hydrogen as fuel, is able to be used as a portable power for small-scaled electronic devices such as MP3, PMP, and mobile phone because alcohol is quite convenient steady-state compound to carry and store it. This paper presents the OCV(open circuit voltage) characteristics of the cases which are alcohol species and different weight rate of ethanol, respectively. The OCV of methanol fuel cell is slightly higher 0.2V than ethanol one, and 8% wt. rate ethanol is rated as the most appropriate fuel for DAFC.

• Proceedings of the IEEK Conference
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• 2008.06a
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• pp.474-475
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• 2008

Portable device is powered by the battery. To use portable devices longer time without replacing the battery, you should maximize the lifetime of the battery. If you use efficient DC-DC converter, You can maximize the lifetime of the battery.

• Proceedings of the Korea Information Processing Society Conference
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• 2005.05a
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• pp.863-866
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• 2005

Low-power design is one of the most important challenges encountered in maximizing battery life in portable devices as well as saving energy during system operation. In this paper we propose a low-power DCT (Discrete Cosine Transform) architecture using a modified Computation Sharing Multiplication (CSHM). The overall rate of power consume is reduced during DCT: the proposed architecture does not perform arithmetic operations on unnecessary bits during the Computation Sharing Multiplication calculations. Experimental results show that it is possible to reduce power dissipation up to about $7{\sim}8%$ without compromising the final DCT results. The proposed lowpower DCT architecture can be applied to consumer electronics as well as portable multimedia systems requiring high throughput and low-power.

• International Journal of Aeronautical and Space Sciences
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• v.12 no.4
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• pp.385-395
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• 2011

An ejector was developed for man-portable missiles. The ejector can be separated from the missile after the completion of the ejection function even without any additional separation devices. This paper introduces the particular separation mechanism of the ejector and presents the methodology, based on a probabilistic design method, to predict the ejection-and-separation reliability. This approach using Monte Carlo simulation can also be applicable to the reliability prediction of one-shot items suffering from difficulties in estimating or in demonstrating their reliability due to the lack of the number of tests available.

• Electronics and Telecommunications Trends
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• v.35 no.2
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• pp.69-78
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• 2020

Small portable devices such as mobile phones and laptops currently display a trend of high power consumption owing to their characteristics of high speed and multifunctionality. Low-power SoC design is one of the important factors that must be considered to increase portable time at limited battery capacities. Popular low power SoC design techniques include clock gating, multi-threshold voltage, power gating, and multi-voltage design. With a decreasing semiconductor process technology size, leakage power can surpass dynamic power in total power consumption; therefore, appropriate low-power SoC design techniques must be combined to reduce power consumption to meet the power specifications. This study examines several low-power SoC design trends that reduce semiconductor SoC dynamic and static power using EDA tools. Low-power SoC design technology can be a competitive advantage, especially in the IoT and AI edge environments, where power usage is typically limited.

• Journal of the Korea Society of Computer and Information
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• v.21 no.6
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• pp.71-76
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• 2016

In this paper, we propose the mobile visual inspection information system using DGPS and portable range finder for levee safety inspection. Instead of existing visual inspection management method that is stored hand-written data, this system is designed to manage directly the visual inspection information using mobile devices in the field of levee. And through extracting accurate DGPS coordinates information about damage location of levee, this system is developed to ensure efficiency for the main task arising from the levee site such as inspection, maintenance and reinforcement. Furthermore, when damage has occurred at the point that inspector is not able to approach, this system can record the damage site data correctly, by converting data such as position, orientation and height of the damage point into the World Geodetic System coordinates. The position, orientation and height data was extracted automatically through the DGPS and portable range finder. And by applying the augmented reality method, this system was implemented for inspector to revisit the point of damage easily in order to perform the management, maintenance and reinforcement of the levee later.

• International journal of advanced smart convergence
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• v.8 no.1
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• pp.58-64
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• 2019

In recent years, small mobile devices called personal mobility or smart mobility have attracted attention. Personal mobility refers to electric-driven personal transportation that can travel at close range and medium distance, including small electric vehicles, electric bicycles, electric motorcycles and electric scooters. Most of the electric scooters used in Korea are mainly imported from China. This is due to the fact that the price competitiveness of major components of electric scooters is owned in China. At this point, the domestic research direction is preferable for the composition and design of the electric scooter body rather than cost reduction for the components. In this study, we propose a new model of portable folding structure that is easy to use for electric scooters, which are personal vehicles using electric energy. We also made a prototype for practical use.

• Journal of the Korean Society of Industry Convergence
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• v.21 no.6
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• pp.265-271
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• 2018

DC-DC buck converter is a critical building block in the power management integrated circuit (PMIC) architecture for the portable devices such as cellular phone, personal digital assistance (PDA) because of its power efficiency over a wide range of conversion ratio. To ensure a safe operation, avoid unexpected damages and enhance the reliability of the converter, fully-integrated protection circuits such as over voltage protection (OVP), under voltage lock out (UVLO), startup, and thermal shutdown (TSD) blocks are designed. In this paper, these three fully-integrated protection circuit blocks are proposed for use in the DC-DC buck converter. The buck converter with proposed protection blocks is operated with a switching frequency of 1 MHz in continuous conduction mode (CCM). In order to verify the proposed scheme, the buck converter has been designed using a 180 nm CMOS technology. The UVLO circuit is designed to track the input voltage and turns on/off the buck converter when the input voltage is higher/lower than 2.6 V, respectively. The OVP circuit blocks the buck converter's operation when the input voltage is over 3.3 V, thereby preventing the destruction of the devices inside the controller IC. The TSD circuit shuts down the converter's operation when the temperature is over $85^{\circ}C$. In order to verify the proposed scheme, these protection circuits were firstly verified through the simulation in SPICE. The proposed protection circuits were then fabricated and the measured results showed a good matching with the simulation results.

• Journal of Internet Computing and Services
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• v.19 no.6
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• pp.53-62
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• 2018

As the performance of computer hardware has been increased in recent years, more realistic computer generated objects can be created and presented in personal computers and portable digital devices as well. For this reason, digital contents, including computer graphics, require virtual objects that are more realistic and representable in real-time on various devices, thus it requires more computational costs. In order to support the production of contents including computer graphics, games, and animations on multi-platform, Unity or unreal engines are mainly used. To represent more realistic behavior of virtual objects in a simulation, a virtual object must collide with other virtual objects and present the plausible interaction, as in the real world. However, such dynamic simulation requires a large amount of computational cost, and most portable devices cannot provide these dynamic simulations in real-time. In this paper, we proposed a GPGPU computation based dynamic cloth simulation to represent collision and response with spherical object in real-time. We believe that the proposed method can be useful for readily producing realistic digital contents.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.26 no.1D
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• pp.89-94
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• 2006

Premature failures in pavements are frequently reported due to rapid increasement in traffic volume, heavy vehicles, and high temperature in the summer. Based on this concept in mind, Korea Highway Corporation established the Test Road Operation Center to estimate the pavement performance. To evaluate the pavement performance effectively using the field data, wandering is an important topic in pavement analysis. In this study, portable wandering system was developed and analyzed to investigate the pavement responses due to the dynamic truck passes, and analyzed the wandering to dynamic load test. The test results revealed that the advantages of laser devices were noticeable compare to the other measuring ones. To understand the behavioral characteristics of pavements using the wandering measurement devices, dynamic truck tests were conducted in the field. Test results showed that the effects of wandering on asphalt pavement were significant. The data analysis using this wandering effect is considered as an important tool in performance analysis of asphalt concrete pavement.