• Polymer(Korea)
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• v.26 no.6
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• pp.792-802
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• 2002

In this study, hydrogels from mixtures of poly (vinyl alcohol) (PVA)/poly(N-vinylpyrrolidone) (PVP)/glycerin/chitosan were prepared by γ-ray irradiation and the mechanical properties such as gelation, water absorptivity, and gel strength were examined to evaluate the applicability of these for wound dressing. Then PVA:PVP was weight ratio of 6 : 4, the concentration of chitosan was 0.3 wt%, the concentration of glycerin was in the range of 0∼5 wt%t. The solid concentration of PVA/PVP/glycerin/chitosan solution was 15 wt%. Gamma irradiation doses of 25, 35, 50, and 60 kGy were exposed to a mixture of PVA/PVP/glycerin/chitosan to evaluate the effect of irradiation dose. Gel content and gel strength increased as glycerin concentration in PVA/PVP/glycerin/chitosan decreased, and as irradiation dose increased. Swelling degree increased as glycerin concentration in PVA/PVP/glycerin/chitosan increased, and as irradiation dose decreased. The glycerin in PVA/PVP/glycerini/chitosan hydrogel prevented the transformation of shape. These hydrogel dressings had better curing effect than vaseline gauge.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.35 no.7A
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• pp.669-681
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• 2010

In this paper, we analyze the active RFID system ISO/IEC 18000-7. In order to apply to USN, which consists active RFID tags and sensor nodes, we propose UWB-based Class 4 active RFID protocol using active RFID relay tag as relay AP. To compare the performance between the existing ISO/IEC 18000-7 system and the proposed system, we introduce sensitivity-based measurement of achieved coverage and system efficiency. Also, we analyze the performance of the proposed system and compare it with that of the existing system through MCL analysis and SLS analysis.

• JSTS:Journal of Semiconductor Technology and Science
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• v.8 no.2
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• pp.143-149
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• 2008

A novel compact model for a five-port transformer balun is proposed for the efficient circuit design of hybrid balun. Compared to the conventional model, the proposed model provides much faster computation time and more reasonable values for the extracted parameters. The hybrid balun, realized in $0.18\;{\mu}m$ CMOS, achieves 2.8 dB higher gain and 1.9 dB lower noise figure than its passive counterpart only at a current consumption of 0.67 mA from 1.2 V supply. By employing the hybrid balun, a differential zero-IF receiver is designed in $0.18\;{\mu}m$ CMOS for IEEE 802.15.4 ZigBee applications. It is composed of a differential cascode LNA, passive mixers, and active RC filters. Comparative investigations on the three receiver designs, each employing the hybrid balun, a simple transformer balun, and an ideal balun, clearly demonstrate the advantages of the hybrid balun in fully differential CMOS RF receivers. The simulated results of the receiver with the hybrid balun show 33 dB of conversion gain, 4.2 dB of noise figure with 20 kHz of 1/f noise corner frequency, and -17.5 dBm of IIP3 at a current consumption of 5 mA from 1.8 V supply.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.11 no.6
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• pp.2263-2268
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• 2010

In this paper, the hybrid compensation algorithm($A_{HB}$) for localization using the Compensation Algorithm distance($CA_d$) and the Algorithm of Equivalent Distance Rate(AEDR) in SDS-TWR(Symmetric Double-Sided Two-Way Ranging) is suggested and the performance of the proposed algorithm is analyzed by practical experimentations. From experimentations, it is confirmed that the errors are reduced in 28 coordinates of total 32 coordinates in the experimental region and the errors are reduced about above 70% in the assigned 3 type error level ranges by $A_{HB}$. Also, it is analyzed that the average localization error is reduced from 2.67m to 1.19m as 55.4% in total 32 coordinates by $A_{HB}$ and the error compensation capability of $A_{HB}$ is very excellent as above 90%. From above results, we have seen that the error reduction ratio and error compensation capability of $A_{HB}$ is more excellent than each $CA_d$ or AEDR.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2008.05a
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• pp.849-852
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• 2008

현대 사회의 급속한 발전 속에 네트워크 분야는 급속한 발전을 이루고 있다. 급변하는 네트워크 시장에서 홈 네트워크 분야는 일반인들에게 많은 관심을 증대시키고 있으며, 보다 안락한 생활을 위한 욕구의 충족을 위하여 자신의 주거지에 홈 네트워크를 구축하거나 홈 네트워크가 구현된 주거지를 선택하는 현상이 두드러지게 증대하고 있다. 이러한 현상에 발맞추어 홈 네트워크 시장의 규모는 빠른 속도로 증가하고 있는 실정이며, 이를 위한 여러 분야에 걸친 연구와 상업성을 기반으로 발전하고 그 적용범위를 확장하고 있다. 이러한 홈 네트워크의 구현은 점점 기술의 발달함에 따라 그 기능 또한 점점 복잡하고 다양한 프로세서의 처리를 필요로 하는 경향이 두드러지고 있다. 홈 네트워크 시스템은 여러 가지 요소에 의해 영향을 받기 때문에 시스템의 설계는 상당히 중요한 과정에 해당된다. 이에 본 논문에서는 임베디드 계발장비와 STR710F칩을 이용하여 확장성을 고려하여 홈 네트워크 시스템 노드를 구성하고, 이를 활용한 홈 네트워크 시스템을 설계하였다.

• Proceedings of the Computational Structural Engineering Institute Conference
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• 2009.04a
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• pp.467-470
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• 2009

본 논문에서는 유비쿼터스 기반 인프라를 이용한 실시간 유괴방지 시스템을 구축하였다. 급속한 사회 발전과 더불어 강력사건이 증가되고 있으며 그중에서 어린이 유괴 범죄 같이 질적으로 흉악한 범죄가 해마다 증가되고 있는 실정이다. 이러한 유괴 범죄를 예방하기 위하여 현재 GPS(Global Positioning System)을 이용한 위치인식 기술 및 이동통신 기지국을 이용한 위치인식 기술이 사용되고 있다. 단순히 위치인식 기술은 위험상황이 발생하였을 때, 상황을 정확히 인지하기 어려워 유괴된 어린이 44%가 1시간 이내 사망하고 74%가 3시간 이내 사망 한다는 통계를 감안하면 기존 시스템은 어린이 생명 보호 능력에 한계가 있다. 본 연구에서는 유비쿼터스 도시 기반 인프라를 구축하여 WPAN(Wireless Personal Area Network)환경에서 RF만으로 거리 측정이 가능한 IEEE 802.15.4a의 ISM Band CSS(Chirp Spread Spectrum)방식을 이용하여 보다 저 전력으로 정확한 위치정보 시스템을 적용하였다. 이에 CSS방식을 통하여 얻은 위치정보를 지능형 CCTV와 융합하여 CCTV가 단말기 위치로 자동 초점하는 시스템을 구성하였다. 도시통합운영센터에서 상황을 정확히 인지하고 신속하게 출동할 수 있도록 단말기 위치를 지속적으로 요원의 PDA 및 핸드폰으로 통보하고 현장 주변의 미디어 보드 표시와 음성 경고로 경찰의 적절한 대응 및 주변의 도움을 받을 수 있는 시스템을 구성하였다.

• 한국HCI학회:학술대회논문집
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• 2008.02a
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• pp.274-279
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• 2008

In this paper, we will presents the join procedure for efficient network performance in the ZigBee Sensor Network. In existing network, new devices join procedure is performed base on the participating in the already Coordinator and Router beacon information. However, beacon has insufficient information network. Thus, the concentration of traffic and inefficient use of resources, address the problem that occurs. To solve these problems, the Coordinator and router on the network, depending on their location and the ability to transfer a beacon. This algorithm is proposed in the paper, the transmission time by using the beacon, network configuration control of the network to improve performance.

• Proceedings of the Korea Society of Information Technology Applications Conference
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• 2005.11a
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• pp.339-342
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• 2005

In order to support ultrawide-band signal generation for low rate WPAN, several types of signal generation mechanisms are suggested such as Chaos, Impluse, and Chirp signals by the activity of IEEE 802.15.4a. The communication system applied chaos theory may have ultrawide-band characteristics with spread spectrum and immunity from multipath effect. In order to use the advantage of chaotic signal generation, we introduce the system implementation of communication and networking systems with the chaos UWB signal. This system may be composed of mainly three parts in hardware architecture : RF transmission with chaotic signal generation, signal receiver using amplifiers and filters, and 8051 & FPGA unit. The most difficult part is to implement the chaotic signal generator and build transceiver with it. The implementation of the system is devidced into two parts i.e. RF blocks and digital blocks with amplifiers, filters, ADC, 8051 processor, and FPGA. In this paper, we introduce the system block diagram for chaotic communications. Mainly the RF block is important for the system to have good performance based on the chaotic signal generator. And the main control board functions for controlling RF blocks, processing Tx and Rx data, and networking in MAC layer.

• Proceedings of the Korean Society of Broadcast Engineers Conference
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• 2006.11a
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• pp.207-211
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• 2006

IEEE 802.15.4a에서는 첩(Chirp)신호을 이용한 UWB(Ultra Wide Band) 시스템으로서 DBO(Differential Bi-Orthogonal)-CSS(Chirp Spread Spectrum) 기술을 선택적 표준안으로 정하였다. 기존 DBO-CSS에서는 다중 피코넷 간섭(MPI; Multiple Piconets Interference)을 피하기 위하여 각 피코넷 별로 Different Time-Gap을 할당하고 있다 하지만 완벽한 직교성이 존재하지 않는다는 특성을 가지고 있어서 간섭의 영향에 민감할 수 밖에 없고, 무선통신시스템의 성능 저하를 야기시킨다. 본 논문에서는 각 피코넷 별로 보다 완전한 직교성을 확보하기 위하여, 확산코드기법을 적용한 CSS 변복조 알고리즘을 제안하고, 또한 일정한 시간 구간동안 연속적인 직교특성을 가지는 이진 ZCD(Zero Correlation Duration) 코드를 사용하여 BER(Bit Error Rate) 성능 분석을 통해 SOP(Simultaneously Operating Piconets) 환경에서 다중 피코넷 간섭 등의 영향을 효과적으로 제거함을 확인하였다.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.13 no.4
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• pp.813-820
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• 2009

This paper describes the realization of ubiquitous healthcare monitoring system using wearable pulse oximeter based on a wireless sensor network. In order to obtain information of oxygen saturation from a patient, a small size and low power consumption wearable pulse oximeter was designed. Information of oxygen saturation collected by wireless sensor node was transmitted wirelessly to a base-station for storage and display purposes via wireless sensor network. Wireless sensor nodes were programmed by TinyOS application to perform data acquisition and transmission. Lab VIEW server program was designed to monitor information of oxygen saturation and process the measured PPG (photo plethysmogram) signals to APG(Accelerated plethysmogram) signals by appling second order derivatives. PPG signals are simple and cost effective technique to measure blood volume change.