• Journal of Information Processing Systems
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• 제14권6호
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• pp.1347-1360
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• 2018

Owing to limited energy in wireless devices power saving is very critical to prolong the lifetime of the networks. In this regard, we designed a cross-layer optimization mechanism based on power control in which source node broadcasts a Route Request Packet (RREQ) containing information such as node id, image size, end to end bit error rate (BER) and residual battery energy to its neighbor nodes to initiate a multimedia session. Each intermediate node appends its remaining battery energy, link gain, node id and average noise power to the RREQ packet. Upon receiving the RREQ packets, the sink node finds node disjoint paths and calculates the optimal power vectors for each disjoint path using cross layer optimization algorithm. Sink based cross-layer maximal minimal residual energy (MMRE) algorithm finds the number of image packets that can be sent on each path and sends the Route Reply Packet (RREP) to the source on each disjoint path which contains the information such as optimal power vector, remaining battery energy vector and number of packets that can be sent on the path by the source. Simulation results indicate that considerable energy saving can be accomplished with the proposed cross layer power control algorithm.

• 한국자동차공학회논문집
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• 제19권1호
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• pp.38-44
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• 2011

Remanufacturing is restoring or manufacturing the worn-out or discarded components of an end of life product in order to bring it to the "like new" condition. The aim is to reprocess used products in such a manner that the quality of the products is as good as or better than the new one, in terms of appearance, reliability and performance. This paper investigates the automotive remanufacturing industry in Europe. To further knowledge in this field, the paper focuses on the remanufacturing of the automotive components of end-of-life vehicles. The paper scope emphasizes key remanufacturing companies, which are identified and were surveyed in terms of their business structures. The research aims to address the potential for growth within the remanufacturing industry, with regard to various players. The state of the art in remanufacturing of automotive equipment will be identified.

• Current Optics and Photonics
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• 제7권4호
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• pp.345-353
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• 2023

We propose a turbulence-tolerant Manchester on-off keying (M-OOK) transmission for free-space optical (FSO) communication. At the transmitter end, a M-OOK signal featuring a spectrum with low-frequency components absent is modulated and transmitted into a turbulent channel. At the receiver end, a low-pass filter (LPF) -based adaptive-threshold decision (ATD) with LPF-extracted channel-state information (CSI) and a high-pass filter (HPF)-based fixed-threshold decision (FTD) are employed to compensate for the effects of turbulence, owing to the low-frequency spectral characteristics of the turbulent channel. The performance of LPF-based ATD and HPF-based FTD are evaluated for various cutoff frequencies for the LPF and HPF. Besides, the proposed M-OOK transmission is compared to conventional non-return-to-zero OOK (NRZ-OOK) for different data rates. The proposed technique is verified in simulation. The simulation results show that the proposed M-OOK detection with optimized cutoff frequencies of LPF and HPF has better bit-error-rate (BER) performance compared to NRZ-OOK, and it is close to the theoretical ATD with the knowledge of precise CSI under various degrees of turbulence effects.

• 한국음향학회지
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• 제27권7호
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• pp.342-349
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• 2008

수중통신 시 다중 음파 경로의 생성은 명확한 메시지전송을 어렵게하는 원인중 하나이다. 본 논문에서는 이러한 문제점의 해결을 위하여 각기 다른 경로에 따라 형성된 다중 경로간의 지연 시간을 계산하여 변조주파수변환구간을 생성하는 방법을 제안하였다. 송신단에서는 생성된 변조주파수변환구간의 크기에 따라 메시지를 분할하여 두 개의 주파수를 사용하여 QPSK(Quadrature Phase Shift Keying)방식을 교대로 호핑하여 메시지를 전송 하였다. 이에 대응하여 수신단에서는 수신된 메시지를 알고리즘 설계 시 구축한 프로토콜에 의하여 복조하여 원신호로 복원하는 적응 BISMO 알고리즘을 제안 하였고 모의실험을 통하여 적응적 변조주파수변환구간, 추정 오류율을 계산하였다.

• Journal of Information Processing Systems
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• 제10권2호
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• pp.176-192
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• 2014

The realization of Wireless Multimedia Sensor Networks (WMSNs) has been fostered by the availability of low cost and low power CMOS devices. However, the transmission of bulk video data requires adequate bandwidth, which cannot be promised by single path communication on an intrinsically low resourced sensor network. Moreover, the distortion or artifacts in the video data and the adherence to delay threshold adds to the challenge. In this paper, we propose a two stage Quality of Service (QoS) guaranteeing scheme called Prioritized Multipath WMSN (PMW) for transmitting H.264 encoded video. Multipath selection based on QoS metrics is done in the first stage, while the second stage further prioritizes the paths for sending H.264 encoded video frames on the best available path. PMW uses two composite metrics that are comprised of hop-count, path energy, BER, and end-to-end delay. A color-coded assisted network maintenance and failure recovery scheme has also been proposed using (a) smart greedy mode, (b) walking back mode, and (c) path switchover. Moreover, feedback controlled adaptive video encoding can smartly tune the encoding parameters based on the perceived video quality. Computer simulation using OPNET validates that the proposed scheme significantly outperforms the conventional approaches on human eye perception and delay.

• 한국통신학회논문지
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• 제25권6A호
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• pp.839-847
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• 2000

최근 전송용량의 증대 및 가입자 수용용량의 증대에 따른 초고속 가입자선로 구현의 한 방안으로서 디지털가입자라인의 도입이 국내외적으로 추진되고 있는 실정이다. 이에 디지털가압자라인에 대한 국내표준화가 이루어지고 있지만, 이에 대한 성능분석은 주로 측정에 의한 실험치에 국한되고 있다. 따라서 본 연구에서는 이론해석과 시뮬레이션 기법 등을 제시하여 디지털가입자라인의 S/N 성능 및 BER 성능 등을 분석하였으며, 특히 S/N 성능으로부터 채널용량을 구해 일본에서 측정된 실험치와 비교하였다. 본 해석결과 이론치는 측정치의 상한 및 하한의 중심에 놓여 그 타당성이 입증되었으며, S/N성능은 정송길이가 길어지면 원단누화의 영향보다는 가우스잡음에 의해 지배적이고, 주파수가 높아지거나 전송거리가 길어짐에 따라 BER 성능은 상당히 열화함을 알 수 있었다. 한편, 본 해석의 결과는 향후 국내 디지털가입자라인의 표준화 제정에 기본적인 데이터로서 활용될 수 있을 것이다.

• KSII Transactions on Internet and Information Systems (TIIS)
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• 제11권3호
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• pp.1425-1440
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• 2017

In wireless communications, antenna selection (AS) is a widely used method for reducing comparable cost of multiple RF chains in MIMO systems. As is well known, most of literatures on combining AS with MIMO techniques concern linear modulations such as phase shift keying (PSK) and quadrature amplitude modulation (QAM). The combination of CPM and MIMO has been considered an optimal choice that can improve its capacity without loss of power and spectrum efficiency. The aim of this paper is to investigate joint transmit and receive antenna selection (JTRAS) in CPM MIMO systems. Specifically, modified incremental and decremental JTRAS algorithms are proposed to adapt to arbitrary number of selected transmit or receive antennas. The computational complexity of several JTRAS algorithms is analyzed from the perspective of channel capacity. As a comparison, the performances of bit error rate (BER) and spectral efficiency are evaluated via simulations. Moreover, computational complexity of the JTRAS algorithms is simulated in the end. It is inferred from discussions that both incremental JTRAS and decremental JTRAS perform close to optimal JTRAS in BER and spectral efficiency. In the sense of practical scenarios, adaptive JTRAS can be employed to well tradeoff performance and computational complexity.

• 융합신호처리학회논문지
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• 제24권1호
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• pp.1-14
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• 2023

Underwater images carry information that is useful in the fields of aquaculture, underwater military security, navigation, transportation, and so on. In this research, we transmitted an underwater image through various underwater mediums in the presence of underwater turbulence and beam attenuation effects using a high-speed visible optical carrier signal. The optical beam undergoes scintillation because of the turbulence and attenuation effects; therefore, distorted images were observed at the receiver end. To understand the behavior of the communication media, we obtained the bit error rate (BER) performance of the system with respect to the average signal-to-noise ratio (SNR). Also, the structural similarity index (SSI) and peak SNR (PSNR) metrics of the received image were evaluated. Based on the received images, we employed suitable nonlinear filters to recover the distorted images and enhance them further. The BER, SSI, and PSNR metrics of the specific nonlinear filters were also evaluated and compared with the unfiltered metrics. These metrics were evaluated using the on-off keying and binary phase-shift keying modulation techniques for the 50-m and 100-m links for beam attenuation resulting from pure seawater, clear ocean water, and coastal ocean water mediums.

• KSII Transactions on Internet and Information Systems (TIIS)
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• 제10권1호
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• pp.200-220
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• 2016

Orthogonal frequency division multiplexing (OFDM) signals suffer from the problem of large peak-to-average power ratio (PAPR) which complicates the design of the analog front-end of the system. Companding is a well-known PAPR reduction technique that reduces the PAPR by transforming the signal amplitude using a deterministic function. In this paper, a novel piecewise linear companding transform is proposed. The design criteria for the proposed transform is developed by investigating the relationships between the compander and decompander's profile and parameters with the system's performance metrics. Using analysis and simulations, we relate the companding parameters with the bit error rate (BER), out-of-band interference (OBI), amount of companding noise, computational complexity and average power. Based on a set of criteria developed thereof, we formulate the design of the proposed transform. The main aim is to preserve the signal's attributes as much as possible for a predetermined amount of PAPR reduction. Simulations are carried out to evaluate and compare the proposed scheme with the existing companding transforms to demonstrate the enhancement in PAPR, BER and OBI performances.

• 원예과학기술지
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• 제30권1호
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• pp.27-33
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• 2012

본 연구는 착색단고추 수경재배 시 배양액 내 Ca과 길항하는 세 가지 양이온(K, Mg 및 $NH_4$)의 이온비율에 따른 착색단고추의 생육과 배꼽썩음과 발생에 미치는 영향을 밝히고자 수행하였다. 배양액 내 K, Mg 및 Ca과 같은 세가지 양이온의 종류와 비율은 착색단고추의 생육에 영향을 미치기는 하나 줄기와 잎의 생육보다는 착색단고추 과실의 생육과 품질에 더 큰 영향을 미치는 것으로 나타났다. 특히 배꼽 썩음과 발생과 이로 인한 상품과율은 양이온의 종류와 비율에 따라 큰 영향을 받는 것으로 나타났다. Ca:K = 1:2 처리와 Ca:(K + Mg + $NH_4$) = 1:2 처리에서 각각 70.3%와 86.3%의 가장 높은 배꼽썩음과 발생률이 관찰되었고, 상품과율도 각각 19%와 13.7%로 가장 낮았다. 배꼽썩음과 발생과 배양액 내 K이온의 상관성(r = $0.82^{**}$)이 가장 높았고 그 다음이 $NH_4$-N(r = $0.65^{**}$)이었으며, Mg은 본 실험에서 배꼽썩음과 발생에 영향을 미치지 않는 것으로 나타났다. 두가지 이상의 양이온을 혼합하여 처리한 경우 K + Mg은 r = $0.46^*$이었고 K + Mg + $NH_4$는 r = $0.92^{**}$로 배꼽썩음과 발생에 가장 큰 영향을 미쳤다.