• The Journal of Korean Institute of Communications and Information Sciences
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• v.36 no.2C
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• pp.86-92
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• 2011

This paper details the downlink performance analysis of an multiple antennas system that combines adaptive beamforming and spatial multiplexing (SM) Multiple Input Multiple Output (MIMO). The combination of MIMO signal processing with adaptive beamforming is applied to WiBro, the South Korean Orthogonal Frequency Division Multiple Access (OFDMA) system that follows the IEEE 802.16e standard. Performance analysis is based on the results of experiments and simulations obtained from a fixed-point simulation testbed. Simulations demonstrate that the MIMO Beamforming OFDMA system improves the required signal to noise ratio (SNR) over the conventional MIMO OFDMA system by 3 dB (QPSK) / 2.5 dB (16-QAM) for the frame error rate (FER) of 1% in the WiBro signal environments. From the implementation of the fixed-point simulation testbed and its experimental results, we verify the feasibility of the MIMO Beamforming technology for realizing a practical WiBro base station.

• Proceedings of the Korea Institute of Convergence Signal Processing
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• 2005.11a
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• pp.298-301
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• 2005

모바일 기술이 발달함에 따라 모바일 기술을 이용한 다양한 컨텐츠 개발이 중요한 문제로 떠오르고 있다. 기존의 텔레매틱스 서비스는 차량 밖에 사용자가 있을 경우 안내원을 통하여 원격진단 차량 문 열림, 도난차량 추적, 내차위치확인이 있다. 본 논문에서는 WIPI를 이용하여 자동차 원격제어 시스템을 구현하였다. 자동차 원격제어 시스템은 자동차 키를 대신해야 하는 상황이나 차량의 상태 등을 자신의 모바일을 사용하여 차량을 원격제어 하는 시스템이다. 또한 차량의 손상 및 파손 여부를 SMS를 이용하여 차주에게 바로 알려주는 서비스가 가능하다. 8인의 피 실험자가 각각 12번씩 모두 96번을 실험한 결과 응답시간이 2초 이내로 나타났고 100%의 동작 성공률을 보였다. 각 이동통신사들이 모바일 플랫폼으로 많은 로얄티를 지급하던 방식에서 벗어나서 대한민국이 주도한 WIPI 플랫폼이 모바일 시장을 개척해 나간다는 점에서 WIPI 플랫폼을 기본으로 이용한 서비스는 더욱 더 발전할 것이다. 앞으로 WIPI는 모바일 산업에 주축이 될 것이며 많은 수익 창출이 예상된다.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.7 no.5
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• pp.887-892
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• 2003

In this paper, we propose a simple scaling algorithm for CDMA mobile communications where a voice traffic signals are transmitted by individual one of several data rates at every frames. The traditional method is based on using look-up table called SMT(symbol metric table), but the proposed algorithm is real-time direct scaling method through simple bit manipulations without lookup table. The bit error rate performance is calculated by computer simulation over AWGN and Rayleigh fading channels. From the results, it is shown that the proposed algorithm outperforms the traditional SMT method on Rayleigh channel by 0.3∼0.8dB, while achieving the less H/W complexity.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.30 no.7A
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• pp.568-577
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• 2005

In this paper, we propose the transmission scheme for the space-time block coded spatial multiplexing systems that have adaptive rate and power allocation per each transmit antenna through the use of feedback information related to channel state. Simulation results show that the adaptive power and rate transmission scheme gain more than 4.5 dB over conventional equal-power and rate transmission scheme.

• Transactions of the Korean Society of Mechanical Engineers
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• v.14 no.6
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• pp.1669-1678
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• 1990

The annular and coaxial swirl flows between which LPG is supplied was selected to study the swirling flames in double co-swirl flows. The objective of this study is to research into the effects of double co-swirl flow conditions on the stability limit, the reverse flow boundary, and the time mean temperature distributions of the swirling flames. The increase of swirl intensity of axial flow makes the stability limit decrease, but the annular swirl flow (SM>0.5) makes stability and swirl intensity of axial flow increase, And the existence of axial swirl flow makes flame intensive and small in size, and this may be applicable to the design of high power compact combustor.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.35 no.2C
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• pp.229-237
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• 2010

The conventional detection methods developed for spatially-multiplexed MIMO systems such as OSIC and QRD-M show performance difference for each user depending on the order of detection when they are applied to detection of multi-user signals in uplink multiuser systems based on collaborative spatial multiplexing. In this paper, a signal detection method for uplink multiuser systems based on collaborative spatial multiplexing is proposed to provide similar performance for each user while its performance is close to the case of ML detection. Compared with QRD-M method, computational complexity of the proposed signal detection method is similar in the case of QPSK, and significantly lower in the case of high modulation order with 16-QAM and 64-QAM.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.10 no.11
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• pp.3170-3175
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• 2009

In this paper, we developed u-Care service system using technologies of USN and LBS to help construct social welfare infrastructure and social safety net for lone seniors and handicapped people. This service not only monitors the in-house and outdoor activities of those disabled people but also sends the messages, whenever abnormal behaviors are detected, to the people related to them as well as the social welfare organizations and public safety institutions such as police and emergency services and etc in order to alert them.

• Proceedings of the KIEE Conference
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• 2003.07c
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• pp.1903-1905
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• 2003

전자기력을 이용하여 탐침형 정보저장장치의 미디어를 제어할 수 있는 초정밀 구동기를 제작하였다. 탐침형 정보저장장치는 데이터 비트의 크기가 10nm 수준이고, 단일 캔틸레버가 점유하는 영역의 크기가 수십 ${\mu}m$${\times}$수십${\mu}m$ 수준이므로, 미디인 구동기는 수 nm의 위치 정확도 및 수십 ${\mu}m$ 수준의 변위 그리고 100Hz이상의 공진 주파수를 확보하여야한다. 본 연구에서 제작한 탐침형 정보저장장치의 미디어 구동기는 고저항 Si wafer 표면을 Deep RIE로 patterning한 후 그 내부를 도금으로 채워 구리 코일을 형성하고 이를 영구자석과 결합시킨 후, 구리 코일에 전류를 흘려 미디어를 구동하는 방식이다. 사용된 영구자석은 SmCo 자석이며 코일의 폭은 $100{\mu}m$이고 간격은 $20{\mu}m$, 높이는 $70{\mu}m$로 결정하였으며, 100Hz 이상의 공진 주파수를 확보하기 위하여 스프링 재질은 구리보다 상대적으로 stiff한 Si을 사용하였다. 미디어의 크기는 $20{\times}20mm^2$, 전체 구동기의 크기는 $30{\times}30mm^2$이며 측정결과 최대변위는 140mA 인가 시 약 ${\pm}127{\mu}m$이다.

• Journal of Intelligence and Information Systems
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• v.14 no.2
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• pp.137-156
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• 2008

The purpose of this study is to implement evaluation on domestic cyber University web site to analyze web usability and web accessibility in order to present how much cyber University provides various personalized services and qualitative contents to users on web site. And also with this result, I hope to contribute in qualitative development of web site and reliability of remote education. For this purpose, I developed checklist suitable to remote University by applying SM-ABCDE assessment method of Moonhyeongnam, the professor in Sookmyung Women's University, and implemented evaluation on web sites of 17 cyber University over the five aspects of attraction, business, contents, design, and engineering. As the result of this study, it was found that Busan Digital University was best in the respect of attraction, both Kyunghee Cyber University and Cyber University of foreign studies were best in the respect of business, Kyunghee University was best in the respect of contents, and Hanyang Cyber University was best in the respect of design. It was also evaluated in the comprehensive view and the order was found that Kyunghee Cyber University, Busan Cyber University, and Hanyang Cyber University. However in the respect of engineering, it came out that all the sites did not observe the regulation on web accessibility. If domestic Cyber Universities are to observe the regulation on web accessibility with the long term view, on the base of this study, web usability would be increasing. Then they can secure various classes of customers as well as ordinary people so that they will be able to take the real place of educational institution orienting the most advanced educational method in the society of knowledge and information in addition to advance in themselves.

• Journal of the Korean Applied Science and Technology
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• v.34 no.2
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• pp.327-337
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• 2017

A continuous low temperature ($510^{\circ}C{\sim}530^{\circ}C$) pyrolysis experiment in a pilot-scale of 85.3 kg/hr was carried out by the mixed feedstock of half dried digested sewage sludge and waste plastics. As a result, the amount of pyrolysis gas generated was maximum 68.3% of input dry mass and scored $40.9MJ/Nm^3$ of lower heating value (LHV), and the percentage of air inflow caused by continuous pyrolysis was 19.6%. The oil was produced 4.2% of the input dry mass, and the LHV was 32.5 MJ/kg. The sulfur and chlorine contents, which could cause corrosion of the facility, were found to be 0.2% or more respectively. The carbide generated was 27.5% of the input dry mass which shows LHV of 10.2 MJ/kg, and did not fall under designated waste from the elution test. The concentration of carbon monoxide, sulfur oxides and hydrogen cyanide of emitted flu gas from pyrolysis gas combustion was especially high, and dioxin (PCDDs/DFs) was within the legal standards as $0.034ng-TEQ/Sm^3$. Among the 47 water pollutant contents of waste water generated from dry flue gas condensation, several contents such as total nitrogen, n-H extract and cyanide showed high concentration. Therefore, the merge treatment in the sewage treatment plants after pre-treatment could be considered.