• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.35 no.2
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• pp.115-123
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• 2007

This paper presents the conceptual design of the electrical power system using Li-ion cell technology for a satellite application. Compared to a conventional NiCd cell, a Li-ion cell has a lot of advantages such as an energy density, mass and a volume. Normally, a Li-ion cell has three times than conventional NiCd cells in a capacity such as a cell voltage. The normal voltage of a NiCd cell is around +1.2V and a Li-ion cell could be in +3.6V. However, the handling procedure for a Li-ion cell in charge and discharge might be difficult than a conventional NiCd cell, which means that the charge and discharge of each cell should be monitored and controlled by electrical circuits to prevent an over-charge and over-discharge. Therefore, in this paper we propose the design consideration and the characteristics of a Li-ion cell during charging and discharging battery packs in the point of view of electrical power system.

• Journal of Korea Multimedia Society
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• v.8 no.1
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• pp.79-87
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• 2005

In e-commerce applications, a public key cryptosystem is an important and indispensible element for the basic security operations such as authentication, digital signaturing, and key distribution. In wired network environments, the public key infrastructure certificate, which is based on X.509 specification, has been widely used. On the other hand, it still remains difficult to use the certificate information in wireless network environments due to the inherent limitations of the hand-held devices such as low computational power and short battery life. In this paper, we facilitate a codesign approach by implementing a software public-key cryptosystem and classifying its internal computation overheads quantitatively using a software profiling technique. Moreover, we propose a method to analyze the profiled data and apply it to the problem of software/hardware partitioning in a codesign approach. As an illustrative example, we analyze the computational overheads of an EC-Elfagamal application and examine a critical computational path.

• Journal of the Institute of Electronics and Information Engineers
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• v.50 no.1
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• pp.239-245
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• 2013

The temperature monitoring of power cable and cable junction point is the necessary link of the safe and reliable operation of the power system. Many kinds of cables and high voltage junction points are easy to exposed continuous vibrations and momentary impulse in industry field especially power plant industries. This system can predict the overheating of the electric cable interface and the possibility of all kinds of accident, and it helps for eliminating the hazards of electric cable interface and provides the effective guarantee for the safety operation. In order to avoid the faults of the inconvenience of installation and maintenance and the high cost of application, this system used small and contactless IR sensor module. The low power consumption is used in the system. The goal of this study is the low cost and on-line reliable monitoring of power cable and junction point temperature.

• Journal of the Korean Society for Precision Engineering
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• v.29 no.3
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• pp.324-333
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• 2012

The conventional medium and large caliber gun, in general, utilize the hydro-pneumatic recoil mechanism to control the firing impulse and to return to the battery position. However, this kind of mechanism may cause the problems like the leakages and the property changes in oil and gas due to the temperature variations between low and high temperatures. Accordingly, the friction spring mechanism has recently been researched as an alternative system. The friction spring mechanism consists of a set of closed inner and outer rings with the concentric tapered contact surfaces assembled in the columnar form, and can only be used under the compression load. When the spring column is axially loaded, the tapered surfaces become overlapped, causing the outer rings to expand while the inner rings are being contracted in diameter allowing an axial displacement. Because of friction between tapered contact surfaces, much higher spring stiffness is obtained on the stroke at the increase in load than the stroke at the decrease. In this paper, the dynamic equations regarding the friction spring system and the design approach have been investigated. It is also tried for a dynamic model representing the recoil motion and the friction spring forces. And the model has been proved from firing test using a gun system with friction springs. All the results show that the recoil mechanism using friction springs can substitute for the classic hydro-pneumatic recoil system.

• Journal of Electrochemical Science and Technology
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• v.9 no.3
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• pp.163-168
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• 2018

Biomass waste-derived carbon is an attractive alternative with environmental benignity to obtain carbon material. In this study, we prepare carbon from coffee grounds as a biomass precursor using a simple, inexpensive, and environmentally friendly method through physical activation using only steam. The coffee-derived carbon, having a micropore-rich structure and a low extent of graphitization of disordered carbon, is developed and directly applied to lithium-ion battery anode material. Compared with the introduction of the Ketjenblack (KB) conducting agent (i.e., coffee-derived carbon with KB), the coffee-derived carbon itself achieves a reversible capacity of ~200 mAh/g (0.54 lithium per 6 carbons) at a current density of 100 mA/g after 100 cycles, along with excellent cycle stability. The origin of highly reversible lithium storage is attributed to the consistent diffusion-controlled intercalation/de-intercalation reaction in cycle life, which suggests that the bulk diffusion of lithium is favorable in the coffee-derived carbon itself, in the absence of a conducting agent. This study presents the preparation of carbon material through physical activation without the use of chemical activation agents and demonstrates an application of coffee-derived carbon in energy storage devices.

• Fashion & Textile Research Journal
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• v.13 no.5
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• pp.806-814
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• 2011

A solar jacket, which utilizes solar energy for generating electricity, is an example of clothing developed by the fusion of multiple technologies; such fusion of technologies can lead to further developments in the clothing industry and other industries in general. Many research institutes and garment manufacturing companies in Europe and America are developing solar garments; various solar-based products manufactured using solar cells, photovoltaic batteries, etc. are being sold at high prices. The purpose of this study was to investigate the development status of solar garments and their application for generating photovoltaic energy; the study also identified the type of design and upper body clothing preferred by Korean in their early 20s. The survey participants were 188 university students aged between 20 and 25. The design of the proposed six types of solar clothing was evaluated and rated; they were then ranked on the basis of the ratings. A survey on the management of solar garments was conducted, and ratings were assigned according to a 5-point Likert scale, with 5 indicating the strong affirmation. The survey results showed that among the six types of clothing, protective clothing (50%) and sportswear (22%) were more preferable than the others (working clothes (16%), casual clothes (3%), everyday wear(6%), and suits(1%)). Among the six proposed designs, the jumper design (22%) and jean jacket design (21%) were preferred over the others (casual jacket (19%), casual jacket I (15%), classic suit (14%), and climbing jacket (9%)). Factorial analysis of the management of solar garments revealed that the most important factors were the properties of the solar cell and time required for battery charging, and the second important factors were clothing weight and comfort.

• The Journal of the Korea Contents Association
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• v.5 no.5
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• pp.107-114
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• 2005

The next generation of 3D mobile games market is becoming increasingly active, more as a result of improvement in the CPU speed of hardware phone, embarkation of 3D engines and high memory capacity, In response to this trend, popular 3D games of PS2 (PlayStation2) and popular online games are being launched as mobile games. However, mobile units have different hardware characteristics compared to those of other platforms such as the PC or the game console. Therefore, mobile game versions of the popular PC games face many limitations in many aspects such as in battery capacity, size of display, capacity of the game, and other user interface issues. Among these many limitations, study for allowing low capacity storage of the game is becoming important. In addition, realistic animation of the 3D character on the small screen of the mobile unit is more important than any other matter. The purpose of this study is to find a solution to providing realistic 3D character animation, and for decreasing the storage capacity of character animation for application in 3D mobile games.

• Journal of Electrical Engineering and Technology
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• v.9 no.1
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• pp.143-153
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• 2014

This paper presents a novel application of LCC resonant converter for 60kW EV fast charger and describes development of the high efficiency 60kW EV fast charger. The proposed converter has the advantage of improving the system efficiency especially at the rated load condition because it can reduce the conduction loss by improving the resonance current shape as well as the switching loss by increasing lossless snubber capacitance. Additionally, the simple gate driver circuit suitable for proposed topology is designed. Distinctive features of the proposed converter were analyzed depending on the operation modes and detail design procedure of the 10kW EV fast charger converter module using proposed converter topology were described. The proposed converter and the gate driver were identified through PSpice simulation. The 60kW EV fast charger which generates output voltage ranges from 50V to 500V and maximum 150A of output currents using six parallel operated 10kW converter modules were designed and implemented. Using 60kW fast charger, the charging experiments for three types of high-capacity batteries were performed which have a different charging voltage and current. From the simulation and experimental results, it is verified that the proposed converter topology can be effectively used as main converter topology for EV fast charger.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.40 no.8
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• pp.1606-1612
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• 2015

In this paper, a portable high efficiency nondispersive infrared(NDIR) $CO_2$ sensor module with a smart device interface is developed. For low power consumption design, an IR LED was used instead of tungsten lamp for light source and an optical waveguide optimized to the sensor module is designed. With the smart device interface, power of the sensor module is applied from the battery of smart phone. The measured data of the sensor module such as $CO_2$ concentration, temperature, and humidity are displayed on the smart phone using android application. From measured results, the developed sensor module shows ${\pm}60ppm$ tolerance error from 0 to 3,000ppm $CO_2$ concentration range among $-10^{\circ}C$ and $50^{\circ}C$ ranges.

• Journal of KIISE:Computing Practices and Letters
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• v.14 no.4
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• pp.352-362
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• 2008

In the mobile ad hoc network, network nodes are continuously capable of movement, but have battery limitations and these characteristics of MANET cause network link failure. Therefore, when performing ubiquitous services with the application of MANET, a technique is required to improve the packet transmission rates as to enable continuous packet transmission while flexibly adapting to topology changes caused by the mobility of nodes. In this paper, we are proposing PAOMDV(Possibility based AOMDV) and OLSR-ME(OLSR with Modified Energy Efficiency) which are mixed-type protocols to solve the problem for design a more efficient protocol. Especially by classifying mobile ad hoc networks as clusters, OLSR-ME protocol is implemented on communication within the clusters, while PAOMDV is used in protocols between clusters. In addition, a selection algorithm for forwarding nodes that responding packet relays in the case of increased hops was proposed for designing a more efficient protocol than existing protocols. We verified the performance of the proposed protocols through a comparative experiment with AODV, AOMDV, ZRP, and the existing protocols. We confirmed the results of the experiment revealed that the proposed protocol had the best packet transmission rate, the shortest delay between nodes, and showed better results in routing overhead.