• Journal of the Institute of Electronics Engineers of Korea TC
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• v.49 no.4
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• pp.9-17
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• 2012

In this paper, we show the memory effect of the high-power amplifiers for wied-band signals, present a compensation method for the nonlinearity combined with memory effect, and analyze its performance. For the modeling and the compensation of the nonlinear high-power amplifier with memory effect, we investigate the Volterra series model, the Wiener model, and the Hammerstein model. As a compensator scheme, we propose a digital feedforward technique. Compared to analog feed-forward scheme, the proposed scheme has better stability and adaptability to the environmental changes. It has a simpler structure than the conventional digital nonlinear compensation schemes. The result of computer simulations using ADS of the Agilent shows that spectral re-growth is suppressed by more than 20 dB, which amounts to at least 10 dB back-off. Considering the compensation performance, implementation complexity, and convergence rate, we could conclude the Wiener model is most suitable for the proposed scheme.

• The Inventors News
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• no.50
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• pp.1-16
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• 2006

'제1회 여대생 발명캠프' 성황리에 마쳐/'발명으로 풍성한 가을을 맞이하시길'/IT기업, 국내 특허 30% 이상 넘었다/레이저 프린터 특허출원, 프린터 분야 중 최다/피부 보호하는 자외선 차단제, 특허출원 꾸준히 증가/액정표시장치 관련 특허 지속적 증가/진공청소기, 첨단 기술로 혁신 꾀해/소멸특허정보, 온.오프라인 제공/발명 지도자 양성 연수, 온라인에서 이루어진다/검색율증가로 활발한 지재권 활동 기대/'2006상표-디자인 전시회'/표준기술특허로 신제품 개발 쉬워져/김광림 전 차관, 세명대 총장에 취임/영양 살린 '기능성 국수' 눈길 끌어/특허청, 포스코와 혁신 파트너십 체결/한국특허정보원, 성과 관리제 도입으로 경영 성과 극대화/특허청, 상반기 미국 국제특허출원 심사 1백18건 유치/중소기업 48%, 고액 기술이전비 '지불 가능'/특허청, 고객눈높이 맞춘 민원서비스 제공/모범명세서 첨부제도로 특허 받기 쉬워져/'여성 발명인의 축제' 개최/'제5회 전국 대학발명 경진대회'/'미스터 차우' 둘러싼 상표권 분쟁 치열/외환은행, 외국인 근로자 해외송금서비스 특허 획득/재난 방지 시스템 구축 핵심기술, 특허출원 증가/비밀디자인 청구기간 확대/이젠, 여름용품 정리할 때/역사 속의 발명품/하루 10분 발명교실/특허Q&A/한경희 (주)한경희 생활과학 대표이사/특허청, 수해복구에 두 팔 걷고 나서/무선환경에서의 저작권보호 관련 외국인출원 급증/아이디어 착상 및 발명 기법/다림질 편하게 하는 요령 10가지/발명을 통한 사업화, 시대의 흐름과 인간의 마음을 담아야/스텐서의 전자레인지/3차원 구조물 만들수 있는 나노종이 개발/애플, 크리에이티브에 1억불 지급/흰 우유에 꽂으면 딸기맛 나는 '퍼니스토로우'/한올제약, 씹는 비만 치료제 특허 취득/음성군, 기술로 복숭아 털 알레르기 잡았다/향기로 소비자 마음을 사로잡는다/'독일 국제 아이디어.발명.신제품 전시회'/한국여성발명협회 회원사 발명품 가이드/코네쥬얼리, 우선심사 통해 특허등록/

• Journal of KIISE:Information Networking
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• v.30 no.3
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• pp.316-328
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• 2003

In this paper, we propose and analyze two adaptive channel allocation schemes for supporting multimedia traffics in hierarchical cellular systems. It is guaranteed to satisfy the required quality of service of multimedia traffics according to their characteristics such as a mobile velocity for voice calls and a delay tolerance for multimedia calls. In the scheme 1, only slow-speed voice calls are allowed to overflow from macrocell to microcell and only adaptive multimedia calls can overflow from microcell to macrocell after reducing its bandwidth to the minimum channel bandwidth. In the scheme II, in addition to the first scheme, non-adaptive multimedia calls can occupy the required channel bandwidth through reducing the channel bandwidth of adaptive multimedia calls. The proposed scheme I is analyzed using 2-dimensional Markov model. Through computer simulations, the analysis model and the proposed schemes are compared with the fixed system and two previous studies. In the simulation result, it is shown that the proposed schemes yield a significant improvement in terms of the forced termination probability of handoff calls and the efficiency of channel usage.

• Journal of the Institute of Electronics and Information Engineers
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• v.52 no.11
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• pp.12-19
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• 2015

In network-centric warfare, the communication network has played a significant role in defeating an enemy. Especially, the urgent and important data should be preferentially delivered in time. Thus, we proposed a priority MAC protocol based on CSMA/CA with Binary Exponential Back-off for tactical wireless networks. This MAC protocol suggested a PCW(Prioritized Contention Window) with differentiated back-off time by priority and a RBR(Repetitive Back-off Reset) to reset the remaining back-off time. The results showed that this proposed MAC has higher performance than those of DCF(Distributed Coordination Function) in the transmission success rate and the number of control packet transmission by reducing the packet collision. Thus, it produced more effective power consumption. In comparison with DCF, this proposed protocol is more suitable in high-traffic network.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.19 no.12
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• pp.532-540
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• 2018

The purpose of this study is to develop a training program for teachers to improve their entrepreneurial education competency for teenager entrepreneurship education. In order to achieve this objective, the training program was developed through a literature review and input from professionals. In addition, to verify field appropriateness of the entrepreneurship program for teachers, teachers participated in the program and a satisfaction survey was conducted. Results of this study are as follows. First, this study developed teaching contents and methods for entrepreneurship education which included 4 hours of online education and 26 hours of off-line education, for a total of 30 hours. Second, for verifying the applicability to schools and its effects, the satisfaction of training was examined using 88 teachers that participated in the entrepreneurship education program. Results found the satisfaction level was rated 4.58 for the curriculum suitability and 4.67 for the effectiveness of class contents, indicating that teachers were very satisfied with the training program and contents.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.20 no.8
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• pp.813-822
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• 2009

We have investigated operation of a 1:2:2 asymmetric 3-stage Doherty PA(Power Amplifier) and implemented using the Freescale's 4 W, 10 W PEP LDMOSFETS at 1 GHz. By employing the three peak efficiency characteristics, compared to the two peak N-way Doherty PA, the asymmetric 3-stage Doherty can overcome the serious efficiency degradation along the backed-off output power region and maximize the average efficiency for the modulation signal. To maximize the efficiency characteristic, the inverse class F PA has been designed as carrier and peaking amplifiers. Furthermore, to extract the proper load modulation operation, the adaptive gate bias control signal has been applied to the two peaking PAs based on the envelope tracking technique. For the 802.16e Mobile WiMAX(World Interoperability for Microwave Access) signal with 8.5 dB PAPR(Peak to Average Power Ratio), the proposed Doherty PA has shown 55.46 % of high efficiency at an average output power of 36.85 dBm while maintaining the -37.23 dB of excellent RCE(Relative Constellation Error) characteristic. This is the first time demonstration of applying the saturated PA and adaptive gate bias control technique to the asymmetric 3-stage Doherty PA for the highly efficient transmitter of the base-station application.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.20 no.1
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• pp.21-28
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• 2009

DFT-spread OFDM(Discrete Fourier Transform-Spread Orthogonal Frequency Division Multiplexing) is very effective for solving the PAPR(Peak-to-Average Power Ratio) problem. Therefore, the SC-FDMA(Single Carrier-Frequency Division Multiple Access) which is basically same to the DFT spread OFDM was adopted as the uplink standard of the 3GPP LTE ($3^{rd}$ Generation Partnership Project Long Term Evolution). Unlike the ordinary OFDM system, the SC-FDMA using DFT spreading method is vulnerable to the ICI(Inter-Carrier Interference) problem caused by the phase noise and IQ(In-phase/Quadrature) imbalance and effected FDE(Frequency Domain Equalizer). In this paper, the ICI effects from the phase noise and IQ imbalance which can be problems in uplink transmission are analyzed according the back-off level of HPA. Next, we propose the equalizer algorithm to remove the ICI effects. This proposed equalizer based on the FDE can be considered as up-graded and improved version of PNS(Phase Noise Suppression) algorithm. This proposed equalizer effectively compensates the ICI resulting from the phase noise and IQ imbalance. Finally, through the computer simulation, it can be shown that about SNR=14 dB is required for the $BER=10^{-4}$ after ICI compensation when the back-off is 4.5 dB, $\varepsilon=0.005$, $\phi=5^{\circ}$, and $pn=0.06\;rad^2$.

• The KIPS Transactions:PartB
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• v.14B no.7
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• pp.493-502
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• 2007

An on-line registration technique is presented to register multi-view range images for the 3D reconstruction of real objects. Using a range camera, we first acquire range images and photometric images continuously. In the range images, we divide object and background regions using a predefined threshold value. For the coarse registration of the range images, the centroid of the images are used. After refining the registration of range images using a projection-based technique, we use a modified KLT(Kanade-Lucas-Tomasi) tracker to match photometric features in the object images. Using the modified KLT tracker, we can track image features fast and accurately. If a range image fails to register, we acquire new range images and try to register them continuously until the registration process resumes. After enough range images are registered, they are integrated into a 3D model in offline step. Experimental results and error analysis show that the proposed method can be used to reconstruct 3D model very fast and accurately.

• Journal of the Institute of Electronics Engineers of Korea CI
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• v.45 no.4
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• pp.53-63
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• 2008

Reader collision may occur when neighboring RFID readers use the same channel at the same time. Especially when the readers are operated in dense mode, even though many channels are available, because of frequent reader collisions we can not guarantee the performance of RFID readers. Conventional solutions such as FH(Frequency Hopping) or LBT(Listen Before Talk) are not effective in this situation because they can not schedule RFID readers effectively when RFID readers are operated in multi-channel, dense reader mode, In this paper, we propose a new RFID reader anti-collision algorithm which employs LBT, random backoff before channel access, and probabilistic channel hopping at the same time. While LBT and Random backoff before channel access reduces collisions between competing readers, probabilistic channel hopping increases channel utilization by adaptively changing the hopping probability by reflecting the reader density and utilization. Simulation results shows that our algorithm outperforms conventional methods.

• Archives of design research
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• v.15 no.2
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• pp.253-266
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• 2002

Web Based Instruction has its theoretical background in constructivism paradigm of education. According to social changes called information era and thanks to the sophisticated internet mechanism the constructivism in education has been dominant paradigm. In this paradigm information and knowledge are not merely given by a instructor facing the loaners. This system of instruction has n almost every field of discipline introduced. This article aims to examine how far WBI and constructivism are applicable for design education. Richard Branchia predicted that the learner oriented instruction method would become the dominant education system. He stressed an interactivity of the teacher and students. Upon this can the applicability of WBI for design education be affirmed. Furthermore, there is a dozen of successful cases like www.cyberartcenter.com) (www.digitalyeil.co.kr)', http://www.schooleweb.co.kr/, htp://www.startstudy.co.kr/among many others. This article suggests several ways to solve the problems web based design education faces, including the lesson should inevitably combine the outline and of online study.