UWB-IR 시스템의 Internal Coding 기법을 이용한 성능 향상

李鎬京 弘益大學校 科學技術硏究所 2005 科學技術硏究論文集 Vol.16 No.-

This paper considers internal coding schemes for the Ultra wide-band impulse response (UWB-IR) communication system to improve the BER performance. Specially we introduce the interleaved super orthogonal convolutional code as an inner code and analyze its performance. The proposed system employs super-orthogonal convolutional code instead of the repetition block code. We suggest three types of interleavers, which are information-bit wise interleaver, pulse group-wise interleaver, and pulse-wise interleaver. We obtain the bit error performance of the system using transfer function bounding and some numerical methods. Simulation results are also provided to verify the theoretical analysis.

터보코드의 이론적 성능 분석

李鎬京 弘益大學校 科學技術硏究所 2001 科學技術硏究論文集 Vol.12 No.-

This paper presents a theoretical analysis of the BER (Bit Error Rate) of turbo code and explains an optimal encoder design method by applying this analysis. The ensemble bound on the BER of the optimum code is derived with the use of a so-called uniform interleaver assumption. The ensemble bound is the average BER over all possible interleavers. In order to verify the analysis results, we consider two encoders, RSC (Recursive Systematic Convolutional) (7,5) encoder and RSC (5,7) encoder with two memories. For these cases, we presents the analytic bounds, and simulation results with the practical interleavers.

정상 한국인에 있어서 하바드 프로그램을 사용한 광범위 망막전위도 검사의 측정치

이호경,주명진,김정환,박정제,배승준 인제대학교 1995 仁濟醫學 Vol.16 No.2

서울백병원에서 보다 전문적인 망막질환 환자의 진료 및 기초적인 연구목적을 위해 실시하고 있는 광범위 망막전위도 검사측정치의 정상범위를 항목별로 제시하였다. 이상의 결과를 토대로 본원의 망막전위도 검사에 대한 정량적인 분석의 기초 진단하고, 분류함에 있어 진료면에서는 물론 연구적인 차원에서도 기본적인 바탕이 마련되었다고 생각된다. Parameters of electroretinogram have not been standardized due to variations in recording techniques. This seems to be the major problem in communication among hospitals and laboratories. Examination techniques such as illuminance and amplification as well as representative recordings should be presented in literature for accurate and proper communication. Full-field electroretinograms were obtained in 87 normal Korean subjects (65 males, 22 females) under controlled conditions. Testing protocols are a modification of those developed and used in Massachusetts Eye and Ear Infirmary ERG service of Harvard Medical School. Details of recording techique were written and representative waveforms were also shown in figures. Age-matched norms were given in tables, and for the purpose of clinical appplication, range of values was given for each group. As far as we know, this is the first report of full-field ERG parameters in normal Koreans tested by the MEEI ERG protocols. The ranges are as follows. 1.Degenerative full-field electroretinogram 1) For the dim blue flash ERG, the range of b-wave amplitude and implicit time were 60㎶ - 258㎶ and 73msec - 117msec, respectively. 2) For the scotopically-matched red flash ERG, the range of a-wave amplitude and implicit time were 19㎶ - 53㎶ and 16msec - 28msec. The range of b-wave amplitude and implicit time were 99㎶ - 298㎶ and 44msec - 101msec, respectively. 3) For the white ERG, the range of a-wave amplitude and implicit time were 53㎶ - 288㎶ and 10msec - 27msec. The range of b-wave amplitude and implicit time were 190㎶- 650㎶ and 39msec - 48msec, respectively. 4) For the submaximal white ERG, the range of a-wave amplitude and implicit time were 123㎶ - 330㎶ and 20msec - 22msec. The range of b-wave amplitude and implicit time were 212㎶ - 623㎶ and 33msec - 44msec, respectively. 5) For the 30 Hz fliker ERG, the rangeof amplitude and implicit time were 23㎶ - 76㎶ and 25msec - 36msec, respectively. 2.Vascular full-field electroretinogram 1) For the bright flash ERG, the range of a-wave amplitude and implicit time were 163㎶-394㎶ and 8msec- 16msec. The range of b-wave amplitude and implicit time were 328㎶- 607㎶ and 31msec - 47msec, respectively. 2) For the absolute amplitude of oscillatory potentials, the range was 13.75㎶ -47.75㎶. For the oscillatory potentials amplitude/a-wave slope ratio, the range was 0.49 - 1.25. 3) For the mid-frequency fat amplitude, the range was 1.86㎶ -6.67㎶, and for the high-frequency fft amplitude, the range was 1.04㎶ -7.59㎶. Key Words : Electroretinography, Full-field, Rod, Cone, Blight flash ERG, Acknowledgement: Special thanks to Drs. Eliot L. Berson and Michael A. Sandberg in Harvard Medical School who made this study possible by providing the essential knowledge of electroretinography and the practical tools of recording it.

무선 채널을 위한 CPM 의 비동기 검출 방식에 대한 연구

金永中,李鎬京 弘益大學校 科學技術硏究所 1996 科學技術硏究論文集 Vol.7 No.2

In this paper, we consider a maximum likelihood(ML) non-coherent detection sch-me for multiple symbol continuous phase frequency shift keying (CPFSK) for the wireless communication channel. By utilizing a Gaussian approximation for Rician ra-ndom variables, we express the pairwiserror probability as a function of the equivale-nt normalized squared distance(ENSD). ENSD plays the same role as normalized sq-uared Euclidean distance when evaluation error probability performance for coherent detection. We derive an analytical approximation on the bit error probability by empl-oying ENSD for the uncoded system. For the uncoded system we show that the bit error probability of noncoherent detection approaches that of coherent symbol-by-sy-mbol detection in the limit as the symbol goes to infinity for large SNR.

초자체 절제술 관류액에 혼합된 Cefazolin 항생제의 안전농도에 관한 실험적 관찰

이호경,정해륜 고려대학교 의과대학 1988 고려대 의대 잡지 Vol.25 No.1

Management of infectious endophthalmitis presents one of the most challenging problems in ophthalmology. Retention of vision even in culture-proven cases has remained consistently poor. Recently vitrectomy is introduced into the management of endophthalmitis, often with antibiotics in the infusion 리uid, to promote intraocular drug diffusion. In this animal experiment, the author studied ultrastructural changes of the rabbit retina caused by the various concentrations of cefazolin mixed in the infusion fluid to help determine the non-toxic concentration. Pars plana core vitrectomy was performed with infustion fluid containing 40, 10, 5, and 1 ㎍/ml cefazolin on the 4 eyes of 4 rabbits respectively. Eyeballs were enucleated 2 weeks after vitrectomy and specimens were immediately processed for transmission electron microscopic examination. Same procedures were repeated using gentamicin to compare with the already known toxicity. Osmolar concentration of the each infusion fluid was checked to evaluate the possible high osmolar toxicity. The results were as follows: 1. In the 40 ㎍/ml group, pyknosis and cytoplasmic degeneration were observed in the inner and outer nuclear layer, and photoreceptor inner segment showed swelling and destruction of organelles, resulting in prominent fiber baskets of Mu¨ller cell processes. Retinal pigment epithelium also showed loss of apical microvilli, breaks in the cytoplasm, and widening of basal infolding. 2. Findings in the 10 and 5㎍/㎖ groups were similar to the 40 ㎍/㎖ group. 3. In the 1㎍/㎖ group, the changes were reduced but not as normal as in the comparison group. 4. It was confirmed that the changes noticed in the 40, 10, 5, and 1㎍/㎖ groups were not related with high osmolar concentration of the infusion fluid. In comparison with the gentamicin experiment, we may conclude, in spite of the ultrastructural changes noticed in the 1㎍/㎖ group, that these changes are reversible and functionally unharmful, provided that those additional tests such as electroretinography and fluorescein angiography be supplemented. Taking into consideration the mechanism by which cephalosporin makes retinal toxicity, we could suppose that this antibiotics might reach the enzyme-rich retinal cells and inhibit the enzyme-linked metabolism to make the morphological and functional changes in them.

Fading 채널 환경에 적합한 다중 심벌 트렐리스 부호화 비동기 CPFSK 방식 연구

李鎬京,金昶中 弘益大學校 科學技術硏究所 2002 科學技術硏究論文集 Vol.13 No.-

In this paper, we introduce an encoder design technique of multiple symbol trellis coded modulation for noncoherent continuous phase frequency shift keying (MTCM/NCPFSK) on the interleaved Rician fading channel. To find dominant factors which affects the error probability of MTCM/NCPFSK, we derive the pairwise error probability (PEP) of MTCM/NCPFSK and find that the error probability mainly depends on the effective length of error event and the corresponding squared product distance for the small value of Rician paramenter K. Using this performance criteria, we search for the optimal encoder of MTCM/NCPFSK for the interleaved Rician fading channel. We also compare that encoder with the encoder designed for additive white Gaussian noise channel

비선형 채널 환경 하에서의 변조 방식의 성능 분석기법

李鎬京 弘益大學校 科學技術硏究所 2000 科學技術硏究論文集 Vol.11 No.-

In this paper we simulate the error probability of QPSK, OQPSK (offset QPSK), MSK and 8-ary PSK/TCM in the nonlinear satellite communication channel. To model the nonlinear satellite channel, we consider the nonlinearity of traveling-wave tube amplifier characteristic. For the transmitting and receiving filter we implement the root-raised cosine filter. Additive Gaussian noise environment also consiered. For 10^(-3) bit error probability, QPSK, OQPSK and MSK require 9, 7.5 and 6.8 dB E_(b)/N_(o) values, respectively. This results show the envelope deviation in the nonlinear chnnel degradate the BER performance. Trellis coded modulation applied to 8-ary PSK with 4 states gives 10^(-3) BER at 5.3 dB E_(b)/N_(o) value. This result show that the trellis coded modulation scheme could be effective in the nonlinear satellite channel.

전산화단층촬영법을 이용한 하악전돌증 호나자의 외과적 악교정술후 하악과두 위치 변화 검토

이호경 慶北大學校 齒科大學 1997 慶北齒大論文集 Vol.14 No.-

본 교실에서 악교정수술을 시행한 하악전들증 환자 37명(남자 13명, 여자 24명)을 대상으로 술전, 술직후, 장기 관찰기간동안의 전산화단층촬영법을이용하여 술전 각 항목치의 편균값 그리고 하악골의 후퇴량 및 술후의 악관절 장애 여부와하악과두의 위치변화에 따른 상관간계를 검토한 결과 다음과 같은 결과를 얻었다. 1. 두부축방향 전산화단층사진에서의 과두간 거리(MM')는 84.42±5.30mm였으며, 장축각은 우측 13.79±4.92°, 좌측 13.53±5.56°로 좌우 비슷하였으며. 기준선(AA')에 6.87m 정도 전방에 위치하였다. 관상면 전산화단층사진에서의 과두간 거리(mm')는 83.15±4.62mm였으며, 사축각은 우측 76.28±4.28°로 좌우 비슷하였다. 2. 하약골 후퇴량에 따른 술전, 술후 장기관찰에서의 과두 위치변화를 연구한 결과,. Group 1에서 하악과두의 전방내측 회전의 양상을 보였고, Group 2는 RMD, RCA'. SCA'가 감소하여 전내측의 회전 양상만이 관찰되었으며, Group 3에서는 RCA, RLD, RMD, LMD가 감소하여 우측 과두의 후방내측 회전양상을 보였다. MM' 도 감소하여 하악과두간의 거리도 좁아지는 경향을 관찰할 수 있었으며, 이 결과로 하악골의 후퇴량이 증가할수록 하악과두의 위치 변화가 많이 나타나는 것을 관찰할 수 있었다. 3. 술후에 악관절장애를 호소하는 환자 군과 증상을 호소하지 않는 환자 군과 비교시 하악과두의 위치 변화는 통계적인 유의성은 없었으나 Group A군에서는 하악과두가 전내측의 회전양상을 보였으나, Group B군의 경우는 좌측 과두의 전방외측 회전을 보였으며, 관상면상 단층면에서 LCA'가 많은 감소 양상을 보였다. 이와는 달리 Group C군에서 우측 과두의 후방내측 회전양상을 보였고 RCA'각의 감소 양상을 보였다. 따라서, 하악골의 후퇴량이 많은 군은 과두위치보존술을 이용함에도 불구하고 술후의 과두의 위치가 후방내측 회전을 보였다. 또한 장기관찰의 경우 원래의 관절 위치로 회귀하는 경우가 있었으나 술전의 과두의 위치보다는 증가와 감소의 경향을 보였다. 수술후의 악관절장애 증상을 호소한 군에서 과두 축의 변화를 관찰하였기에, 하악의 후퇴량이 많은 경우에는 더욱더 과두보존술식에 많은 주의를 하면 술후의 악관절 장애의 발생률은 감소하리라 사료된다.

회암사지 막새의 특수성과 보편성

이호경,최문환 한국기와학회 2020 한국기와학회 학술대회 발표자료집 Vol.2020 No.06

하승천의 불교비판 연구

이호경 동아시아불교문화학회 2018 동아시아불교문화 Vol.0 No.36

From the end of the Late Han Dynasty to the Wei Qing Nanbei Dynasty, when Buddhism was first introduced to China, chinese society was a period of critical confusion. The theory of Causality has received high praise from the people who needed a new view of life in a turbulent period and spread rapidly. The expansion of Buddhism caused opposition of the anti-buddhist. In the Buddhist teachings, the most difficult part of understanding for chinese people was ‘Anatman and Samsara'. Chinese people at that time came to understand Causality is Buddhism, and buddhist advocates believe that although the ‘body’ is destroyed, ‘Spirit’ is immortal'. However, from the viewpoint of traditional chinese philosophy, in which the theory of divine destruction was the mainstream, it is imperative to criticize the new idea of ‘immortality'. A series of “controversies between buddhist advocates and anti-buddhist", as seen in the “Hongmingji" of Sengyou, is centered around this divine destruction and the idea of ​​the immortality of Spirit. And Hechengtian was a important figure in this early debate. He is a confucian and natural scientist who is faithful to confucian values. He is also a representative anti-buddhist who criticized the ideological aspects of Buddhism. In his “Baoyinglun", he argued that “causality of Buddhism is merely a means to alert people to good conduct." In his "Dachenglun", he states that "everything that occurs is inevitably dead, the spirit dies together when the body dies", denying the reincarnation. He was a anti-buddhist, but he accomplished as a companion to develop Buddhism as a result of disputes and academic exchanges with buddhist advocates. 불교가 중국에 전래된 이후, 후한 말로부터 위진남북조 시대까지 중국사회는 혼란의 시기였다. 불교의 인과응보론(因果應報論)은 혼란한 시대의 새로운 인생관을 필요로 하던 민중에게 높은 호응을 얻게 되었고 빠른 속도로 전파되어 갔다. 더불어 불교의 세력 확대는 기성사상의 불교에 대한 반발을 불러일으켰다. 불교의 교의 가운데 중국인들에게 있어 가장 이해가 어려웠던 부분은 바로 ‘무아와 윤회’의 모순이었다. 중국의 불교 옹호자들은 비록 ‘육체’는 멸하지만 그 ‘신’은 ‘불멸’한다는 형진신불멸론(形盡神不滅論)이란 관점을 제시하여 모순을 해결하고자 하였다. 그러나 신멸론이 주류였던 전통적 중국철학의 입장에서는 신불멸론이라는 새로운 사상에 비판을 가하지 않을 수 없게 된다. 승우의 『홍명집』에서 보이는 일련의 ‘불교옹호자와 배불론자간의 논쟁’은 이러한 신멸과 신불멸론을 중심으로 하여 전개되는데, 이 논쟁 초기의 중심적 인물이 바로 하승천(何承天)이었다. 하승천은 유교적 가치에 충실한 유학자이자 자연과학자로, 불교의 사회적 기능에 대한 우려와 비난을 넘어서 불교의 사상적 측면에도 비판을 가했다는 점에서 주목된다. 그는 「보응론」에서는 ‘불교의 인과응보설은 사람들에게 착하게 살라고 경계시키는 방편에 불과하다’고 주장하였고, 「달성론」에서는 ‘생겨나는 모든 것에는 필연적으로 죽음이 있고, 신은 육체가 죽으면 함께 사멸한다.’하여 윤회를 부정하였다. 그는 배불론자(排佛論者)였으나, 불교옹호론자들과의 논쟁을 통해서 결과적으로 불교사상을 발전시킨 동반자 역할을 수행하여, 중국 불교의 발전에 기여한 인물로 평가된다.