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상관 페이딩 채널에서 사전스위칭 다이버시티를 갖는 트렐리스 부호화 변조
Hahm, Young-Kwon 한국전자파학회 1996 한국전자파학회논문지 Vol.7 No.4
페이딩 채널에 적합하도록 설계된 TCM은 채널으이 페이딩 상관을 없애는 이상적인 인터리버를 사용한다는 가정하에 설계된방식으로, 저속 페이딩 채널에서 유한 크기의 인터리버를 사용할 수 경우에 페이딩을 잘 분산시킬 수 없기 때문에 부호화 변조 시스템의 성능이 급격히 떨어진다. 이런한 성능 저하를 개선하기 위하여 송신 안테나의 사전 스위칭에 의하여 인터리빙 효과를 얻을 수 있는 방식을 제안하였으며, 이러한 방식의 성능 개선을 해석과 시뮬레이션에 의하여 보여 준다. 결고를 보면 느린 페이딩 환경에서 상당한 성능 개선이 있었으며, 페이딩이 빨라지면 기존의 방식과 같은 성능을 갖는다. The existing coders used in the fading channels are designed under the assumption that the ideal interleaver, which removes the fading correlation of the channel, is used. With the non-ideal interleaver of finite size, however, the performance of the coded modulation system degrades rapidly when the fading is very slow. A new method which achieves interleaving effects by switching the transmitter antennas is suggested to improve the performance even in the slow fading. The performance of the new system is analyzed. The results show significant performance improvement in the slow fading and at least no deterioration in the fast fading over the existing systems.
Trellis-coded 16-QAM with base station antenna switching in slow Rayleigh fading channel
Hahm, Young Kwon 대한전자공학회 1996 APCCAS:Asia Pacific Conference on Circuits And Sys Vol.1 No.1
The existing coders used in the fading channels are designed under the assumption that the ideal interleaver , which removes the fading correlation of the channel, is used. With the non-ideal interleaver of finite size, however, the performance of the coded modulation system degrades rapidly when the fading is very slow. So author propose a scheme to get inerleaving effects by switching base station antennas in a forward link, without additional software or hardware in small handset. We derive the theoretical upper bound on the pairwise error probability and do computer simulations for BER performance. The results show significant performance improvement in the slow fading and at least no deterioration in the fast fading over the existing systems.
Effect of Nb Doping on Chemical Sensing Performance of Two-Dimensional Layered MoSe<sub>2</sub>
Choi, Sun Young,Kim, Yonghun,Chung, Hee-Suk,Kim, Ah Ra,Kwon, Jung-Dae,Park, Jucheol,Kim, Young Lae,Kwon, Se-Hun,Hahm, Myung Gwan,Cho, Byungjin American Chemical Society 2017 ACS APPLIED MATERIALS & INTERFACES Vol.9 No.4
<P>Here, we report that Nb doping of two-dimensional (2D) MoSe2 layered nanomaterials is a promising approach to improve their gas sensing performance. In this study, Nb atoms were incorporated into a 2D MoSe2 host matrix, and the Nb doping concentration could be precisely controlled by varying the number of Nb2O5 deposition cycles in the plasma enhanced atomic layer deposition process. At relatively low Nb dopant concentrations, MoSe2 showed enhanced device durability as well as NO2 gas response, attributed to its small grains and stabilized grain boundaries. Meanwhile, an increase in the Nb doping concentration deteriorated the NO2 gas response. This might be attributed to a considerable increase in the number of metallic NbSe2 regions, which do not respond to gas molecules. This novel method of doping 2D transition metal dichalcogenide-based nanomaterials with metal atoms is a promising approach to improve the performance such as stability and gas response of 2D gas sensors.</P>
A Nutritional Evaluation on Whole Cottonseed Removed Germination Ability by Heat-treatment
Hahm, Sahng-Wook,Son, Heyin,Baek, Seong-Gwang,Kwon, Hyeok,Kim, Wook,Oh, Young-Kyoon,Son, Yong-Suk The Korean Society of Grassland and Forage Science 2013 한국초지조사료학회지 Vol.33 No.1
In Korea, wide spread use of whole cottonseed, which is primarily a GMO plant imported from foreign countries and being fed to animals as raw state, has aroused concern that it may disturb the existing ecology of the country unless dispersion of the seed is under proper control. The objective of this study was to elucidate the changes in various nutritive parameters due to heat treatment and to determine the effective condition for removing germination ability of whole cottonseed (WCS). Of the various temperatures applied (76, 78, 80, 85, $100^{\circ}C$/30 min) $85^{\circ}C$ for 30 min was confirmed to be the lowest temperature treatment which resulted in a complete removal of the germination ability of WCS. Therefore, based on the determined temperature condition ($85^{\circ}C$ 30 min) we tried to examine the changes of various nutritional parameters, including nutrient composition, in vitro digestibilities and ruminal protein degradabilities, comparing raw whole cotton seed (RWCS) and heated whole cotton seed (HWCS). Some changes in amino acid composition were observed with heat treatment of WCS, but these were regarded to originate from the variation in plant quality and seed morphology, which are usually affected by different environmental factors during the vegetation period. As for fatty acid composition, no significant differences were observed to occur during heat treatment. However, WCS heated at $85^{\circ}C$ for 30 min in a circulating oven showed a significant decrease (p<0.05) of in situ rumen degradability in both dry matter (DM) and crude protein (CP), as compared to raw WCS. Overall results obtained in the study indicate that the heating condition used in this study, which was proven to be the most appropriate and economic to remove germination ability of WCS, may also improve the nutritional value of the ruminant with regard to reducing its protein degradability within the rumen.
CDMA Mobile System Testbed and Field Test
Kwon, Dong-Seung,Hahm, Young-Kwon,Jeong, In-Myoung,Im, Duck-Bin Electronics and Telecommunications Research Instit 1997 ETRI Journal Vol.19 No.3
This paper briefly explains the configuration of CDMA Mobile System (CMS) test bed. The measured fading and delay results of CDMA signal in Taejon area are shown. In comparison to other cellular systems, there are more parameters in the CDMA systems that affect system performance and capacity. We performed the optimization test of the selected parameters and present the effect of each parameter on the performance. This paper presents the capacity and performance test results of CMS. The capacity test was performed on ETRI site of three sectors in Taejon area. The performance tests include call completion rate, busy hour call attempt, and the delay characteristics of voice.