• Korean Chemical Engineering Research
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• v.49 no.1
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• pp.69-74
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• 2011

In this study, it was prepared for nanofiber with high impact polystyrene(HIPS). HIPS is able to crosslinking after electrospinning with crosslinking agent and it could overcome brittle characteristics of polystyrene(PS). After thermal crosslinking, HIPS nanofiber was sulfonated by sulfuric acid. It was investigated FT-IR, XPS, water uptake, ion exchange capacity(IEC), SEM, and contact angle. According to the result of FT-IR and XPS, it was increased due to introduce the hydrophilic group($SO_3H$) in the HIPS nanofiber. The highest water uptake and IEC were 75.6%, 2.67 meq/ g at 120 min sulfonation time with 7.5 wt% DVB.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.16 no.8
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• pp.1631-1641
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• 2012

A TDMA system in satellite communication has been utilized. Especially DVB-S2 was standardized and now operated in satellite broadcasting system. In this paper, we propose a TDMA frame structure appropriate for special purpose which has the good reliablilty in a poor RF environment even if frequency efficiency is decreased. TDMA frame duration is 12 seconds which is long duration in comparison with general TDMA system with several ms. Designing the frame structure, time and frequency shift in single frame duration are considered. Simulation results show that the proposed frame structure and synchronization method has robust synchronization performance when the terminal is even in low SNR as well as 25 kHz frequency offsets.

• Membrane Journal
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• v.18 no.2
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• pp.138-145
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• 2008

A series of anion exchange composite membranes were prepared and characterized for electro-dialysis process used in the removal of toxic anion and cation polutants in groundwater or wastewater. The membranes were prepared as follows; first, porous poly(ethylene) (PE) substrates were fully impregnated with monomer mixtures with various ratio of vinylbenzylchloride (VBC), divinylbenzene (DVB) and ${\alpha},\;{\alpha}$-azobis(isobutyronitrile) (AIBN). Second, they were thermally polymerized to yield crosslinked poly(VBC-DVB)/PE composite membranes. Finally, the membranes were treated in trimethylamine (TMA)/acetone to give $-N^+(CH_3)_3$-containing poly(VBC-DVB)/PE membranes. The basic membrane properties such as ion exchange capacity (IEC), electric resistance and water content of the resulting membranes were measured as a function of VBC/DVB and TMA/Acetone content. As a result, the composite membranes showed lower electric resistance, lower water content and higher IEC than commercial anion exchange membranes (AMX, Astom) due to thin PE substrates, indicating that the composite membranes could be successfully applied to the electrodialysis for water treatment.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.14 no.1
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• pp.205-212
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• 2010

This paper describes a core generator (FCore_Gen) which generates Verilog-HDL models of 640 different FFT/IFFT cores with selected parameter value for OFDM-based communication systems. The generated FFT/IFFT cores are based on in-place single memory architecture and use a hybrid structure of radix-4 and radix-2 DIF algorithm to accommodate various FFT lengths. To achieve both memory reduction and the improved SQNR, a conditional scaling technique is adopted, which conditionally scales the intermediate results of each computational stage. The cores synthesized with a $0.35-{\mu}m$ CMOS standard cell library can operate with 75-MHz@3.3-V, and a 8,192-point FFT can be computed m $762.7-{\mu}s$, thus the cores satisfy the specifications of wireless LAN, DMB, and DVB systems.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.8 no.2
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• pp.430-439
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• 2004

This paper describes a design of 8192/2048-point FFT/IFFT processor (CFFT8k2k), which performs multi-carrier modulation/demodulation in OFDM-based DVB-T receiver. Since a large size FFT requires a large buffer memory, two design techniques are considered to achieve memory-efficient implementation of 8192-point FFT/IFFT. A hybrid structure, which is composed of radix-4 single-path delay feedback (R4SDF) and radix-4 single-path delay commutator (R4SDC), reduces its memory by 20% compared to R4SDC structure. In addition, a memory reduction of about 24% is achieved by a novel two-step convergent block floating-point scaling. As a result, it requires only 57% of memory used in conventional design, reducing chip area and power consumption. The CFFT8k2k core is designed in Verilog-HDL, and has about 102,000 Bates, RAM of 292k bits, and ROM of 39k bits. Using gate-level netlist with SDF which is synthesized using a $0.25-{\um}m$ CMOS library, timing simulation show that it can safely operate with 50-MHz clock at 2.5-V supply, resulting that a 8192-point FFT/IFFT can be computed every 164-${\mu}\textrm{s}$. The functionality of the core is fully verified by FPGA implementation, and the average SQNR of 60-㏈ is achieved.

• Journal of the Institute of Electronics Engineers of Korea TC
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• v.43 no.12 s.354
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• pp.1-8
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• 2006

In this paper, we propose carrier phase synchronization algorithm which are base on turbo coded system for DVB-RCS. There have been two categories of phase estimator, single estimator outside turbo code decoder and multiple estimators inside turbo code decoder. In single estimator, we use the estimation algorithm that ML(Maximum Likelihood) and LMS(Least Mean Square), also three different soft decision methods are proposed. Multiple estimator apply PSP(Per Survivor Processing) algorithm additionally. We compared performance between single estimator and Multiple estimator in AWGN channel. We presented the two methods of PSP algorithm for performance elevation. First is the Bi-directional channel estimation and second is binding method.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2016.10a
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• pp.913-914
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• 2016

This paper analyzes the impact of the satellite TWTA non-linearity charateristics for shared band transmission technology to improve spectral efficiency in satellite communication system. In shared band transmission technology for star network, a hub and terminals use same frequency band. In order to receive terminals's signal a hub have to remove the its own DVB-S2 carrier. In this paper the non-linearity impact of satellite TWTA is analyzed for self-interference cancellation.

• IT SoC Magazine
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• s.19
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• pp.37-42
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• 2007

이 글은 당사에서 개발 진행한 TDMB,ISDB-T등의 Moblie TV Receiver단의 Analog Front-End SIP들의 Test H/W, S/W제작 경험을 바탕으로 보다 효율적이고 성공적인 SIP 개발이 될 수 있도록 도움을 주고자 기술 하였다.

• Journal of Satellite, Information and Communications
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• v.8 no.4
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• pp.12-16
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• 2013

This paper we introduce operated public test-bed satellite system configuration for satellite communications and usage for services via COMS(Communication, Ocean and Meteorological Satellite). According to trial public test-bed operation, the broadband multimedia services are expected to be available at the next generation VSAT services due to the increasing of Ka-band utilization. In addition, UHD broadcasting services via satellite is expected to improve the universal accessibility of broadcast services.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.14 no.10
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• pp.2207-2214
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• 2010

Underwater acoustic(UWA) communication has multipath error because of reflection by sea-level and sea-bottom. The multipath of UWA channel causes signal distortion and error floor. In this paper, we proposed split input bits of channel decoder using method of maximum value, average value, LLR value for optimal estimation. Channel coding method is LDPC(N size=16000) standard in DVB-S2. As shown in simulation results, the performance of LLR value method is better than other methods.