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장준복,양재경,임부국,이종윤 한국목재공학회 2004 목재공학 Vol.32 No.1
본 연구는 폐지로부터 용액화물을 제조하고, 제조된 용액화물의 성분 분리 및 성상분석을 통해 용액화물의 효율적인 이용방안을 위한 기초자료 제공에 그 연구 목적이 있다. 폐지의 액화에 있어 건식해리된 폐지보다 습식해리된 폐지의 액화가 비교적 용이하였으며, 이러한 이유는 습식해리된 폐지의 약품 침투가 비교적 용이하기 때문으로 판단된다. 폐지의 최적 액화조건은 폐지 1g에 대해 크레졸 2㎖, 물 4㎖, 인산 0.5㎖로 첨가하여 190℃에서 60분간 액화 시킨 조건이 가장 우수하였다. 폐지 액화물 중 리그닌은 용제인 크레졸 층으로, 탄수화물은 수층으로 용해되어 각각 분리되며, 두 성분의 분리·회수는 비교적 용이하였다. 액화 폐지 중의 리그닌은 80% 이상 회수되었고, 회수된 리그닌의 분자량은 1,000 정도의 저분자량을 나타냈었다. This research was carried out to investigate the component isolation method from liquefied waste paper. and isolated component was analyzed by molecular weight distribution with gel chromatography and nitrobenzene-oxidation analysis. In the aspect of liquefaction ratio, wet defibration fiber are better than dry defibration fiber because of wet defiberation fiber was easy to access of chemical solution. The optimal liquefaction condition of waste paper was treated at 190 C for 60 min(creso1 2 me, water 4 me, phosphoric acid 0.5 ㎖ based on waste paper 1 g). In the liquefied waste paper, lignin and carbohydrate were separated with two interfacial layer(creso1 layer, water layer). In the chemical analysis of isolated lignin, molecular weight distribution of isolated lignin was below 1,000.
Bandwidth-Efficient OFDM Transmission with Iterative Cyclic Prefix Reconstruction
Lim, Jong-Bu,Kim, Eung-Sun,Park, Cheol-Jin,Won, Hui-Chul,Kim, Ki-Ho,Im, Gi-Hong The Korea Institute of Information and Commucation 2008 Journal of communications and networks Vol.10 No.3
For orthogonal frequency division multiplexing (OFDM), cyclic prefix (CP) should be longer than the length of channel impulse response, resulting in a loss of bandwidth efficiency. In this paper, we describe a new technique to restore the cyclicity of the received signal when the CP is not sufficient for OFDM systems. The proposed technique efficiently restores the cyclicity of the current received symbol by adding the weighted next received symbol to the current received symbol. Iterative CP reconstruction (CPR) procedure, based on the residual intersymbol interference cancellation (RISIC) algorithm, is analyzed and compared to the RISIC. In addition, we apply the CPR method to Alamouti space-time block coded (STBC) OFDM system. It is shown that in the STBC OFDM, tail cancellation as well as cyclic reconstruction of the CPR procedure should be repeated. The computational complexities of the RISIC, the proposed CPR, the RISIC with STBC, and the proposed CPR with STBC are analyzed and their performances are evaluated in multipath fading environments. We also propose an iterative channel estimation (CE) method for OFDM with insufficient CP. Further, we discuss the CE method for the STBC OFDM system with the CPR. It is shown that the CPR technique with the proposed CE method minimizes the loss of bandwidth efficiency due to the use of CP, without sacrificing the diversity gain of the STBC OFDM system.
Iterative Multiuser Detection for Single-Carrier Modulation with Frequency-Domain Equalization
Jong-Bu Lim,Chan-Ho Choi,Tae-Won Yune,Gi-Hong Im IEEE 2007 IEEE communications letters Vol.11 No.6
<P>In this letter, we propose a new multiuser detection scheme for single-carrier modulation with frequency-domain equalization (SC-FDE). We first present mathematical formulations of multiuser detection for the SC-FDE system with user- specific interleaving. The proposed structure employs spreader and different interleaver for each user at the transmitter, and re moves multiuser interference with an iterative detection method in the frequency domain at the receiver. Simulation results show that the proposed scheme outperforms the interleave- division multiple-access (IDMA) scheme in the block error rate even for severely frequency-selective channel, while providing considerably lower computational complexity.</P>
Bandwidth-Efficient OFDM Transmission with Iterative Cyclic Prefix Reconstruction
Jong-Bu Lim,Eung-Sun Kim,박철진,Hui-Chul Won,Ki-Ho Kim,임기홍 한국통신학회 2008 Journal of communications and networks Vol.10 No.3
For orthogonal frequency divisionmultiplexing (OFDM), cyclic prefix (CP) should be longer than the length of channel impulse response, resulting in a loss of bandwidth efficiency. In this paper, we describe a new technique to restore the cyclicity of the received signal when the CP is not sufficient for OFDM systems. The proposed technique efficiently restores the cyclicity of the current received symbol by adding the weighted next received symbol to the current received symbol. Iterative CP reconstruction (CPR) procedure, based on the residual intersymbol interference cancellation (RISIC) algorithm, is analyzed and compared to the RISIC. In addition, we apply the CPR method to Alamouti space-time block coded (STBC)OFDMsystem. It is shown that in the STBCOFDM, tail cancellation as well as cyclic reconstruction of the CPR procedure should be repeated. The computational complexities of the RISIC, the proposed CPR, the RISIC with STBC, and the proposed CPR with STBC are analyzed and their performances are evaluated in multipath fading environments. We also propose an iterative channel estimation (CE) method for OFDMwith insufficient CP. Further, we discuss the CE method for the STBC OFDM system with the CPR. It is shown that the CPR technique with the proposed CE method minimizes the loss of bandwidth efficiency due to the use of CP, without sacrificing the diversity gain of the STBC OFDM system.
A Novel Low-Cost Fiber In-Line-Type Bidirectional Optical Subassembly
Lim, Kwon-Seob,Lee, Jong Jin,Lee, Seihyoung,Yoon, Shinyoung,Yu, Chong Hee,Sohn, Ik-Bu,Kang, Hyun Seo IEEE 2007 IEEE photonics technology letters Vol.19 No.13-16
<P> A novel low-cost fiber in-line-type bidirectional optical subassembly using a tilted fiber Bragg grating has been developed for fiber-to-the-home applications. We successfully realized a low-cost subassembly by reducing the number of components and simplifying the packaging process. The extinction ratio of 14.8 dB, receiver minimum sensitivity of <TEX>${-}$</TEX>26.5 dBm at a bit-error rate of <TEX>$10^{-12}$</TEX> and frequency response of 2.7 GHz were experimentally obtained. The electrical crosstalk between transmitter and receiver part was less than <TEX>${-}$</TEX>86 dB up to 2.5 GHz. </P>
Preparation of Cellulose Acetate Produced from Lignocellulosic Biomass
Jong-soo Jo,Ji Young Jung,Ji-hye Byun,Bu-kug Lim,Jae-kyung Yang 한국목재공학회 2016 목재공학 Vol.44 No.2
Cellulose acetate is one of well-known industrial materials which have various commercial uses. We treated the lignocellulosic biomass using two-step (steam explosion-chemical) reaction followed by acetylation to get the cellulose acetate in this study. The two-step treatment was done to improve the yields of acetylation of the substrates. The yields of the cellulose acetate were about 88.4, 88.1, and 151.7% in barley straw, rice straw, and oak tree, respectively. Also the degree of substitution (DS) of the acetates was 2.1 to 2.5 in the biomass. We found that the biomass were valuable cellulosic sources, including their derivatives, in this study. This means that the biomass can be converted into the high-valued cellulosic stuff.