• 한국통신학회논문지
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• 제34권5C호
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• pp.527-539
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• 2009

본 논문에서는 3GPP LTE (3rd Generation Partnership Project Long Term Evolution) MIMO-OFDMA(multiple-input multiple-output-orthogonal frequency division multiple access) 시스템의 하향 링크 수신기를 위한 asynchronous ICI (Inter-Cell Interference) 완화 기법을 제안한다. Multi-cell 환경을 고려한 celluar OFDMA 시스템에서는 기본적으로 frequency reuse factor가 1로 설정되기 때문에 셀 경계에 위치한 UE (User Equipment)의 경우 ICI 영향을 받게 되며, 특히 각기 다른 셀 반경 및 nodeB 간의 거리 차이 등 현실적인 celluar 환경을 고려 할 경우에는 UE 간 타이밍 오류가 가중되어 수신 신호의 주파수 영역의 직교성이 파괴될 가능성이 있다. 따라서 이러한 인접 셀 간섭을 제거 및 완화하기 위하여 수신 OFDM 심볼에 대한 SCM (Spatial Covariance Matrix) 추정이 필요하다. 일반적으로 SCM 추정은 training symbol을 이용함을 가정하지만, 긴 시간 동안 간섭의 통계적 특성을 측정하는 것은 어려울 뿐만 아니라 training symbol이 고려되지 않는 LTE와 같은 MIMO-OFDMA 시스템에는 적합하지 않다. 또한 추정의 정확성을 높이기 위하여 noise reduction 방식이 적용된 추정 기법이 제시되고 있으나, 기존 time-domain low-pass type weighting 방식은 spectral leakage에 의한 추정 에러를 유발하는 단점이 있다. 따라서, 본 논문에서는 noise reduction 효과를 얻으면서 spectral leakage에 의한 SCM 추정 오류를 최소화할 수 있으며, 주파수 영역에의 moving average filter로 구현 가능한 time-domain sinc-type weighting 방식의 SCM 추정 기법을 제안하였으며, 다양한 환경에서의 컴퓨터 모의 실험을 통하여 제안된 방식이 기존의 방식보다 약 3dB 의 SIR (Signal to Interference Ratio) 이득을 보임을 입증하였다.

• 한국정보시스템학회:학술대회논문집
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• 한국정보시스템학회 1997년도 추계학술대회논문집 기업경쟁력 향상을 위한 정보통신 기술의 활용
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• pp.445-449
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• 1997

구조 지향적인 개발방법론(Structured Methods)에서 객체 지향적인 개발방법론 (Object Orientation)으로 개발 방법의 변경은 시스템 개발 과정의 패러다임 쉬프트 (Paradigm Shift)라고 불린다. 본 연구는 이러한 시스템 개발 도구의 변경에서 나타나는 개 발자들의 혼동을 구조 지향적 개발방법론의 객체 지향적 개발방법론에 대한 지식간섭 (Knowledge Interference)의 현상으로 간주한다. 개인의 특성에, 예를 들면 지식간섭에 영 향을 미치는 구조 지향적 개발방법론의 사용 경험과 신기술에 대한 개방성, 맞는 훈련방법 이나 정보원이 존재하는지를 규명하는 연구모형을 제시한다.

• 대한전자공학회:학술대회논문집
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• 대한전자공학회 1998년도 추계종합학술대회 논문집
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• pp.1191-1194
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• 1998

This paper presents a new computationally efficient adaptive algorithm for blind signal separation, which is able to recover the narrowband source signals in the presence of cochannel interference without a prior knowledge of array manifold. We derive a new blind signal separation algorithm using the Natural gradient 〔1〕from an information-theoretic approach. The resulting algorithm has the Bussgang property which has been widely used in blind equalization 〔12〕. Extensive computer simulation results comfirm the validity and high performance of the proposed algorithm.

• International Journal of Automotive Technology
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• 제8권3호
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• pp.327-335
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• 2007

A new optimization scheme and some key techniques are proposed in the development of a vehicle glass drop design software system. The key issues of the design system are how to regenerate the glass surface and make the vehicle glass drop down along the glass channels. To resolve these issues, a parameterized model was created at first, in which the optimizing method and Knowledge Fusion techniques were adopted the optimized process was then written into the glass drop design system by coding with C language and UGS/Open Application Programme Interface functions etc. Therefore, the designer or engineer can simulate the process of glass dropping along the channels to assess the potential interference between glass and door accessory by using this software system. All of the testing results demonstrate the validity of the optimizing scheme, and the parametric design software effectively solves the key issues on development of the door accessory package.

• 한국전자파학회논문지
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• 제27권8호
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• pp.676-683
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• 2016

본 논문에서는 단일포트시스템으로 설계된 배열안테나에서 재밍신호나 간섭신호 방향으로 방사패턴에 널(null)을 형성하는 적응 알고리즘을 제안한다. 제안한 적응 알고리즘은 재밍신호나 간섭신호의 크기나 입사방향에 대한 사전정보를 요구하지 않으며, 배열안테나의 일부 RF 경로의 위상을 제어하는 부분적응(partially adaptive) 알고리즘이다. 제안한 적응 알고리즘은 최적화 알고리즘의 한 종류인 PSO(Particle Swam Optimization) 알고리즘과 gradient-based 섭동 적응 알고리즘을 혼합하여 시간에 따라 간섭신호의 입사방향이 변화하는 이동형 재밍환경에서도 적응적으로 안정적인 널링 성능을 가진다.

• The Journal of the Acoustical Society of Korea
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• 제23권2E호
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• pp.56-67
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• 2004

Despite abundant research outcomes of blind source separation (BSS) in many types of simulated environments, their performances are still not satisfactory to be applied to the real environments. The major obstacle may seem the finite filter length of the assumed mixing model and the nonlinear sensor noises. This paper presents a two-step speech enhancement method with multiple microphone inputs. The first step performs a frequency-domain BSS algorithm to produce multiple outputs without any prior knowledge of the mixed source signals. The second step further removes the remaining cross-channel interference by a spectral cancellation approach using a probabilistic source absence/presence detection technique. The desired primary source is detected every frame of the signal, and the secondary source is estimated in the power spectral domain using the other BSS output as a reference interfering source. Then the estimated secondary source is subtracted to reduce the cross-channel interference. Our experimental results show good separation enhancement performances on the real recordings of speech and music signals compared to the conventional BSS methods.

• 한국추진공학회지
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• 제10권2호
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• pp.87-94
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• 2006

모델 표면의 임의 영역에서 나타나는 이차원 전단응력의 분포를 측정하는 실험적 연구가 수행되었다. 오일막 위에 형성된 간섭영상을 이용한 이 측정법은 시험부 표면에 있는 오일막의 국소 기울기의 분포로부터 오일 윤활이론을 적용하여 전단응력의 분포를 얻어낼 수 있다. 평판 위에 수직으로 설치된 원형 실린더 전방의 박리영역에 이 측정법을 적용되어 전단응력의 이차원 분포가 측정되었다. 실험에서 관찰된 전단응력 분포는 유사한 유동조건에서 얻어진 과거 실험 및 수치결과와 비교분석 되었으며, 연구에서 전단응력 분포가 다른 연구결과들과 서로 잘 일치하고 있음이 관찰되어 이 측정법의 응용성이 검증되었다.

• Journal of Communications and Networks
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• 제8권3호
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• pp.290-296
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• 2006

In this paper, a generalized blind adaptive algorithm is introduced for multi-user detection of direct sequence code division multiple access (OS-COMA) wireless communication systems. The main property of the proposed algorithm is its ability to resolve the multipath fading channel resulting in inter symbol interference (ISI) as well as multiple access interference (MAI). Other remarkable properties are its low complexity and mitigation to the near-far problem as well as its insensitivity to asynchronous transmission. The proposed system is based on the minimization of the output energy and convergence to the minimum mean square error (MMSE) detector. It is blind in the sense that it needs no knowledge of the other users' signatures, only the intended user signature and timing are required. Furthermore, the convergence of the minimum output energy (MOE) detector to the MMSE detector is analytically proven in case of M-ary PSK. Depicted results show that the performance of the generalized system dominates those previously considered. Further improvements are obtained when multiple input multiple output (MIMO) technique is employed.

• Journal of Communications and Networks
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• 제11권3호
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• pp.240-247
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• 2009

The results of performance analysis by adopting the channel scenarios characterized as Weibull fading for an multicarrierdirect sequence-coded division multiple access (MC-DS-CDMA) system are proposed in this investigation. On the other hand, an approximate simple expression with the criterion of bit error rate (BER) versus signal-to-noise ratio (SNR) method is derived for an MC-DS-CDMA system combining with maximal ratio combining (MRC) diversity based on the moment generating function (MGF) formula of Weibull statistics, and it associates with an alternative expression of Gaussian Q-function. Besides, the other point of view on the BER performance evaluation of an MC-DS-CDMA system is not only the assumption of both single-user and multi-user cases applied, but the phenomena of partial band interference (PBI) is also included. Moreover, in order to validate the accuracy in the derived formulas, some of the system parameters, such as Weibull fading parameter (${\beta}$), user number (K), spreading chip number (N), branch number (L), and the PBI (JSR) values, etc., are compared with each other in the numerical results. To the best of author's knowledge, it is a brand new idea which proposes the evaluation of the system performance for an MC-DS-CDMA system over the point of view with Weibull fading channel.

• The Plant Pathology Journal
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• 제40권1호
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• pp.59-72
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• 2024

A comprehensive survey of mungbean-growing areas was conducted to observe leaf spot disease caused by Alternaria alternata. Alternaria leaf spot symptoms were observed on the leaves. Diversity of 50 genotypes of mungbean was assessed against A. alternata and data on pathological traits was subjected to cluster analysis. The results showed that genotypes of mungbean were grouped into four clusters based on resistance parameters under the influence of disease. The principal component biplot demonstrated that all the disease-related parameters (% disease incidence, % disease intensity, lesion area, and % of infection) were strongly correlated with each other. Alt a 1 gene that is precisely found in Alternaria species and is responsible for virulence and pathogenicity. Alt a 1 gene was amplified using gene specific primers. The isolated pathogen produced similar symptoms when inoculated on mungbean and tobacco. The sequence analysis of the internal transcribed spacer (ITS) region, a 600 bp fragment amplified using specific primers, ITS1 and ITS2 showed 100% identity with A. alternata. Potato virus X (PVX) -based silencing vector expressing Alt a 1 gene was constructed to control this pathogen through RNA interference in tobacco. Out of 50 inoculated plants, 9 showed delayed onset of disease. Furthermore, to confirm our findings at molecular level semi-quantitative reverse transcriptase polymerase chain reaction was used. Both phenotypic and molecular investigation indicated that RNAi induced through the VIGS vector was efficacious in resisting the pathogen in the model host, Tobacco (Nicotiana tabacum). To the best of our knowledge, this study has been reported for the first time.