• 한국지반공학회지:지반
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• 제14권6호
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• pp.127-138
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• 1998

신선한 쓰레기 매립지에서는 쓰레기에 포함되어 있는 유기물의 분해로 인하여 장기간에 걸쳐 상당한 양의 침하가 유발되는 것으로 알려져 있다. 본 연구에서는 여러 신선한 쓰레기 매립지들의 침하자료에 대하여 기존에 제안된 몇몇 침하모델들을 적용하였으며. 얻어진 침하예측곡선과 장기침하량을 분석함으로써 분해로 의한 침하양상이 장기침하량 예측에 미치는 영향을 살펴보았다. 사용된 모델과는 상관없이 선정된 모델변수 값들이 분해효과를 포함하지 않는 한 장기침하를 적절히 평가할 수 없었다. 몇몇 예측방법 가운데 Gibson & Lo 모델과 쌍곡선 모델은 쓰레기 매립지의 장기침하 거동특성을 비교적 타당성 있게 예측한 반면에 power creep law는 상당히 과다예측하는 것으로 나타났다.

• Journal of Power Electronics
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• 제16권3호
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• pp.1025-1035
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• 2016

Luenberger observer (LO)-based sensorless multi-loop control of a converter requires an iterative trial-and-error design process, considering that many parameters should be determined, and loop gains are indirectly related to the closed-loop characteristics. Robust H∞ control adopts a compact sensorless controller. The algebraic Riccati equation (ARE)-based and linear matrix inequality (LMI)-based H∞ approaches need an exhaustive procedure, particularly for a low-order controller. Therefore, in this study, a novel robust H∞ synthesis approach is proposed to design a low-order sensorless controller for boost converters, which need not solve any ARE or LMI, and to parameterize the controller by an adjustable parameter behaving like a "knob" on the closed-loop characteristics. Simulation results show the straightforward closed-loop characteristics evaluation and better dynamic performance by the proposed H∞ approach, compared with the LO-based sensorless multi-loop control. Practical experiments on a digital processor confirmed the simulation results.

• 제어로봇시스템학회:학술대회논문집
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• 제어로봇시스템학회 2004년도 ICCAS
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• pp.1694-1700
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• 2004

In this paper, we propose the AWLS/MFT (Adaptive Weighed Least Squares/ Modulation Function Technique) devised by A. E. Pearson et al. for the transfer function estimation of a modal system and investigate the performance of several algorithms, the Gram matrix method, a Luenberger Observer (LO), Least Squares (LS), and Recursive Least Squares (RLS), for the estimation of initial conditions. With the benefit of the Modulation Function Technique (MFT), we can separate the estimation problem into two phases: the transfer function parameters are estimated in the first phase, and the initial conditions are estimated in the second phase. The LO method produces excellent IC estimates in the noise free case, but the other three methods show better performance in the noisy case. Finally, we compared our result with the Prony based method. In the noisy case, the AWLS and one of the three methods - Gram matrix, LS, and RLS- show better performance in the output Signal to Error Ratio (SER) aspect than the Prony based method under the same simulation conditions.

• 한국정보통신설비학회:학술대회논문집
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• 한국정보통신설비학회 2007년도 학술대회
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• pp.279-282
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• 2007

Typically a wireless sensor network consists of a number of nodes that sense surrounding environment and collaboratively work to process and route the sensing data to a sink or gateway node. We propose an architecture with support of multiple routers in IPv6-based Low-power Wireless Personal Area Network (6LoWPAN). Our architecture provides traffic load balancing and increases network lifetime as well as self-healing mechanism so that in case of a router failure the network still can remain operational. Each router sends its own Router Advertisement message to nodes and all the nodes receiving the messages can select which router is the best router with the minimum hop-count and link information. We have implemented the architecture and assert our architecture helps in traffic load balancing and reducing data transmission delay for 6LoWPAN.

• 정보와 통신
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• 제32권4호
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• pp.16-22
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• 2015

유비쿼터스 정보 기술을 기반으로 다양한 업무 지원 기기간 네트워크를 형성하여 업무 처리를 지원하는 u-Office와, 지능화된 다양한 사물에 인터넷 연결성을 제공하여 지능적 서비스를 제공하는 Internet of Things(IoT)는 기하급수적으로 증가하는 다수의 객체간 통신을 수행하므로 네트워킹 자원의 최적화 기술이 필수로 뒷받침되어야 한다. 데이터 패킷의 오버헤드를 줄이고 통신 자원을 절약하기 위한 기술 연구는 다방면으로 진행되고 있으며, 특히 패킷의 오버헤드를 줄이고 통신 자원을 절약하는 패킷 헤더 압축 기술은 다양한 국제 표준이 개발되어 모바일 와이맥스(Mobile WiMAX), Long Term Evolution(LTE), IPv6 over Low power Wireless Personal Area Network(6LoWPAN) 등의 네트워크에 활용되고 있다. 본 고에서는 모바일 와이맥스, LTE, 6LoWPAN에서 각각 사용되는 패킷 헤더 압축 기술인 Payload Header Suppression(PHS), Robust Header Compression(ROHC), Header Compression(HC), Improved Header Compression(IPHC)의 개발 동향을 제시하고 각 기술의 특징을 비교 분석한다.

• JSTS:Journal of Semiconductor Technology and Science
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• 제9권3호
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• pp.153-159
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• 2009

A CMOS frequency synthesizer for $5{\sim}6$ GHz UNII-band sub-harmonic direct-conversion receiver has been developed. For quadrature down-conversion with sub-harmonic mixing, octa-phase local oscillator (LO) signals are generated by an integer-N type phase-locked loop (PLL) frequency synthesizer. The complex timing issue of feedback divider of the PLL with large division ratio is solved by using multimodulus prescaler. Phase noise of the local oscillator signal is improved by employing the ring-type LC-tank oscillator and switching its tail current source. Implemented in a $0.18{\mu}m$ CMOS technology, the phase noise of the LO signal is lower than -80 dBc/Hz and -113 dBc/Hz at 100 kHz and 1MHz offset, respect-tively. The measured reference spur is lower than -70 dBc and the power consumption is 40 m W from a 1.8 V supply voltage.

• 한국전자파학회논문지
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• 제11권2호
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• pp.197-205
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• 2000

매우 높은 선형성을 요구하는 혼합기의 설계는 입력 전력의 back-off로 얻어지는 것이 일반적이다. 본 논문에 서는 혼합기의 비선형 특성을 보상하기 위해 혼합기의 입력 단에 역 비선형 특성을 갖는 전치왜곡 회로를 부착 하여 비선형 특성을 개선시키는 방볍을 제안하였다. 이 제안된 방법으로 주파수 성분이 1852.5 MHz와 1857.5 MHz인 2 2 -tone 엽력 RF 선호와 2015 MHz인 LO 선호를 혼합기에 입력하여 혼합기의 ell비를 IF 출력이 -20dBm/tone 일 때 22 dB. - 17 dBm/tone일 때 21.7 dB를 개선시켰다.

• 전자공학회논문지T
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• 제35T권1호
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• pp.22-28
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• 1998

A new type of FET source mixer with a single bias voltage has been presented. It is designed to operate at Vds=0 [V] with only one positive supply voltage, which makes mixer circuits simple. The proposed mixer has shown improved stability and less sensitivity to both bias and LO power compared with conventional active mixers. It also shows lower conversion loss than that of diode mixers. The minimum conversion loss measured at RF frequency of 5.6㎓ is 0.6㏈ for a LO frequency of 5.8㎓.

• ETRI Journal
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• 제33권5호
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• pp.818-821
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• 2011

A D-band subharmonically-pumped resistive mixer has been designed, processed, and experimentally tested. The circuit is based on a $180^{\circ}$ power divider structure consisting of a Lange coupler followed by a ${\lambda}$/4 transmission line (at local oscillator (LO) frequency). This monolithic microwave integrated circuit (MMIC) has been realized in coplanar waveguide technology by using an InAlAs/InGaAs-based metamorphic high electron mobility transistor process with 100-nm gate length. The MMIC achieves a measured conversion loss between 12.5 dB and 16 dB in the radio frequency bandwidth from 120 GHz to 150 GHz with 4-dBm LO drive and an intermediate frequency of 100 MHz. The input 1-dB compression point and IIP3 were simulated to be 2 dBm and 13 dBm, respectively.

• Journal of electromagnetic engineering and science
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• 제6권1호
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• pp.18-23
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• 2006

In this paper, we demonstrate a fully integrated X-band image rejection down converter, which was developed using InGaP/GaAs HBT MMIC technology, consists of two single-balanced mixers, a differential buffer amplifier, a differential YCO, an LO quadratue generator, a three-stage polyphase filter, and a differential intermediate frequency(IF) amplifier. The X-band image rejection downconverter yields an image rejection ratio of over 25 dB, a conversion gain of over 2.5 dB, and an output-referred 1-dB compression power$(P_{1dB,OUT})$ of - 10 dBm. This downconverter achieves broadband image rejection characteristics over a frequency range of 1.1 GHz with a current consumption of 60 mA from a 3-V supply.