李衍达
长期从事信号处理理论方法及应用的研究,如利用部分数据重构信号、小波分析、分形信号处理以及这些方法在油气勘探与开发中的应用。近年来,主要从事智能信号处理的方法及系统的研究,如人工神经元网络、模糊系统、专家系统、进化算法的理论模型及其在信息网络智能控制中的应用。
个性化签名
- 姓名:李衍达
- 目前身份:
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- 学位:
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学术头衔:
博士生导师, 中国科学院院士
- 职称:-
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学科领域:
水声工程
- 研究兴趣:长期从事信号处理理论方法及应用的研究,如利用部分数据重构信号、小波分析、分形信号处理以及这些方法在油气勘探与开发中的应用。近年来,主要从事智能信号处理的方法及系统的研究,如人工神经元网络、模糊系统、专家系统、进化算法的理论模型及其在信息网络智能控制中的应用。
李衍达院士生于1936年10月,1959年毕业于清华大学,1979-1981年作为中国第一批赴美访问学者在麻省理工学院访问。现为中国科学院院士、国务院学位委员会委员、中国自动化学会副理事长、清华大学校学术委员会主任、教授,博士生导师。李衍达院士长期从事长期从事信号处理理论方法及应用的研究,如利用部分数据重构信号、小波分析、分形信号处理以及这些方法在油气勘探与开发中的应用。近年来,主要从事智能信号处理的方法及系统的研究,如人工神经元网络、模糊系统、专家系统、进化算法的理论模型及其在信息网络智能控制中的应用。研究了高速网络环境下信息的发掘、提取与多媒体数据的压缩和组织,以及工业生产过程及设备的智能控制。此外,更致力于生物信息学的研究,将复杂系统的信息处理方法应用在分子生物学中;在基因组序列的信息结构研究,基因调控网络的建模和仿真等方面的研究中也取得了开拓性成果,推动了信息科学与生物学的结合,既有重要的学术价值又有极高的应用价值。李衍达院士发表了《信号重构理论及应用》、《神经网络信号处理》等多部著作及一百余篇论文;曾主持自然科学基金重大项目,先后获国家自然科学奖(四等奖)、四次获国家教委科技进步奖(三次一等奖,一次二等奖)、北京市科技进步奖、国家优秀科技图书奖、电子部优秀教材奖及国家教委优秀教学成果特等奖。
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主页访问
2791
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关注数
0
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成果阅读
510
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成果数
10
【期刊论文】AsMamDB: an alternative splice database of mammals
李衍达, Hongkai Ji*, Qing Zhou, Fang Wen, Huiyu Xia, Xin Lu, and Yanda Li
260-263 Nucleic Acids Research, 2001, Vol. 29, No.1,-0001,():
-1年11月30日
The objective of database AsMamDB is to facilitate the systematic study of alternatively spliced genes of mammals. Version 1.0 of AsMamDB contains 1563 alternatively spliced genes of human, mouse and rat, each associated with a cluster of nucleotide sequences. The main information provided by AsMamDB includes gene alternative splicing patterns, gene structures, locations in chromosomes, products of genes and tissues where they express. Alternative splicing patterns are represented by multiple alignments of various gene transcripts and by graphs of their topological structures. Gene structures are illustrated by exon, intron and various regulatory elements distributions. There are 4204 DNAs, 3977 mRNAs, 8989 CDSs and 126 931 ESTs in the current database. More than 130000 GenBank entries are covered and 4443 MEDLINE records are linked. DNA, mRNA, exon, intron and relevant regulatory element sequences are provided in FASTA format. More information can be obtained by using the web-based multiple alignment tool Asalign and various category lists. AsMamDB can be accessed at http://166.111.30.65/ASMAMDB. html.
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李衍达, Fang Wen, *, Fei Li, Huiyu Xia, Xin Lu, , Xuegong Zhang, and Yanda Li
,-0001,():
-1年11月30日
-loop structure and have an important influence on protein functions, as shown by the predicted 3D structure of human IL-4δ2. The observed VSAS events can be classified into two groups depending on whether they insert new structure domains in the proteins, and they might be of different evolutionary status.
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李衍达, Q Xu, , Y-B Jia, B-Y Zhang, K Zou, Y-B Tao, Y-P Wang, B-Q Qiang, G-Y Wu, Y Shen, H-K Ji, Y Huang, X-Q Sun, L Ji, Y-D Li, Y-B Yuan, L Shu, X Yu, Y-C Shen, Y-Q Yu, G-Z Ju, Chinese Schizophrenia Consortium*
,-0001,():
-1年11月30日
Schizophrenia is a common mental disorder with a complex pattern of inheritance. Despite a large number of studies in the past decades, its molecular etiology remains unknown. In this study, we proposed a 'system-thinking' strategy in seeking the combined effect of susceptibility genes for a complex disorder by using paranoid schizophrenia as an example. We genotyped 85 reported single-nucleotide polymorphisms (SNPs) present in 23 genes for the dopamine (DA) metabolism pathway among 83 paranoid schizophrenics and 108 normal controls with detailed clinical and genetic information. We developed two novel multilocus approaches-the potential effective SNP combination pattern and potential effective dynamic effects analysis, by which three susceptibility genotype combinations were found to be associated with schizophrenia. These results were also validated in a family-based cohort consisting of 95 family trios of paranoid schizophrenia. The present findings suggest that the COMT and ALDH3 combination may be the most common type involved in predisposing to schizophrenia. Since the combination blocks the whole pathways for the breakdown of DA and noradrenaline, it is very likely to play a central role in developing paranoid schizophrenia.
schizophrenia, complex disorder, susceptibility genotype combinations, single nucleotide polymophism, dopamine metabolic pathway, clinial subgroup, effective SNP combination pattern, potential effective dynamic effects
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【期刊论文】Simulation of the evolution of genomic complexity☆
李衍达, Xin Lu*, Yanda Li
BioSystems 61(2001)83-94,-0001,():
-1年11月30日
A general evolutionary trend is the generation of organisms of increasing complexity, notwithstanding that reduction and simplification phenomena do occur in the evolutionary process. This paper proposes an evolutionary model incorporating the mechanisms of gene amplification and deletion. The evolutionary process leading to genomic complexity and the coexistence of simpler organisms with complicated ones were both simulated using the proposed model. The model was also used to investigate the influence of various factors on the evolution of complexity. The simulations indicated that the evolution of complexity is largely influenced by adaptation to complicated environments. Nevertheless, complex organisms require relatively more resources for survival and replication, which limits the on going tendency towards complexity. Moreover, the analysis showed that if the environment varies rapidly and the profit obtained from complexity is greater than the resources consumed, selection will tend to favor complexity. However, high living cost will tend to limit the trend of complexity and if the environment is relatively stable, reduction and simplification will become the dominant trends.
Genomic complexity, Gene amplification/, deletion, Simulated evolution
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【期刊论文】Classifying G-protein coupled receptors with bagging classification tree
李衍达, Ying Huang*, Jun Cai, Liang Ji, Yanda Li
Computational Biology and Chemistry 28(2004)275-280,-0001,():
-1年11月30日
G-protein coupled receptors (GPCRs) play a key role in different biological processes, such as regulation of growth, death and metabolism of cells. They are major therapeutic targets of numerous prescribed drugs. However, the ligand specificity of many receptors is unknown and there is little structural information available. Bioinformatics may offer one approach to bridge the gap between sequence data and functional knowledge of a receptor. In this paper, we use a bagging classification tree algorithm to predict the type of the receptor based on its amino acid composition. The prediction is performed for GPCR at the sub-family and sub-sub-family level. In a cross-validation test, we achieved an overall predictive accuracy of 91.1% for GPCR sub-family classification, and 82.4% for sub-sub-family classification. These results demonstrate the applicability of this relative simple method and its potential for improving prediction accuracy.
G-protein coupled receptors, Amino acid composition, Bagging classification tree, Proteomics
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【期刊论文】Identifying splicing sites in eukaryotic RNA: support vector machine approach
李衍达, Ying-Fei Sun*, Xiao-Dan Fan, Yan-Da Li
Computers in Biology and Medicine 33(2003)17-29,-0001,():
-1年11月30日
We introduce a new method for splicing sites prediction based on the theory of support vector machines (SVM). The SVM represents a new approach to supervised pattern classification and has been successfully applied to a wide range of pattern recognition problems. In the process of splicing sites prediction, the statistical information of RNA secondary structure in the vicinity of splice sites, e.g. donor and acceptor sites, is introduced in order to compare recognition ratio of true positive and true negative. From the results of comparison, addition of structural information has brought no significant benefit for the recognition of splice sites and had even lowered the rate of recognition. Our results suggest that, through three cross validation, the SVM method can achieve a good performance for splice sites identi7cation.
Support vector machines (, SVM), , Neural network, Sensitivity, Speci7city, Splice site, RNA secondary structure
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【期刊论文】Directed Variation in Evolution Strategies
李衍达, Qing Zhou, and Yanda Li, Senior Member, IEEE
IEEE TRANSACTIONS ON EVOLUTIONARY COMPUTATION, VOL. 7, NO.4, AUGUST 2003,-0001,():
-1年11月30日
Biological evolution gives rise to self-organizing phenomena. Inspired by this theory, directed variation is added to the (μ,λ) evolution strategies (ES) algorithm and it is called directed variation ES (DVES). In DVES, some neighboring individuals in the population mutate correlatively according to the distribution of the whole population. Experimental results showed that, with the same number of function evaluations, directed variation ES reached better optimization results for different generally used strategies under the ES framework. Experimental analysis showed that the application of directed variation could increase the expected fitness improvement and the probability of fitness improvement. From a biological perspective, directed variation can be regarded as a result of self-organizing evolution.
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【期刊论文】Performance Model of IEEE 802.11 DCF With Variable Packet Length
李衍达, Hongyuan Chen and Yanda Li, Senior Member, IEEE
IEEE COMMUNICATIONS LETTERS, VOL. 8, NO.3, MARCH 2004,-0001,():
-1年11月30日
Abstract-Few analytical models have been proposed to evaluate the hybrid of the basic and the RTS/CTS access mechanisms up to now. The main reason is that it is very difficult to study a scheme with variable packet length. In this letter, we propose a model to evaluate the saturation throughput performance of the hybrid access mechanism, assuming that the packet lengths are sampled from a general distribution function f(χ). Index Terms-IEEE 802.11, performance model, WLAN.
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【期刊论文】Characterizing self-similarity in bacteria DNA sequences
李衍达, Xin Lu, , *, Zhirong Sun, Huimin Chen, and Yanda Li
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-1年11月30日
In this paper some parametric methods are introduced to characterize the self-similarity of DNA sequences. Compared with Fourier analysis, these methods perform statistically more stably and yield more reliable results. Using these methods, eight whole genomes of bacteria provided by NCBI are analyzed. Long-range correlation properties in the nucleotide density distribution along these DNA sequences are explored. Estimation results show that the long-range correlation structure prevails through the entire molecule of DNA. Higher order statistics through coarse graining reveal that rather than multifractal, there are only monofractal phenomena presented in the sequences. Hence, the nucleotide density distribution can be modeled asymptotically as fractional Gaussian noise. This result points to a new direction for analyzing and understanding the intrinsic structures of DNA sequences.
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【期刊论文】Prediction of protein subcellular locations using fuzzy k-NN method
李衍达, Ying Huang*, and Yanda Li
,-0001,():
-1年11月30日
Motivation: Protein localization data are a valuable information resource helpful in elucidating protein functions. It is highly desirable to predict a protein's subcellular locations automatically from its sequence. Results: In this paper, fuzzy k-nearest neighbors (k-NN) algorithm has been introduced to predict proteins' subcellular locations from their dipeptide composition. The prediction is performed with a new data set derived from version 41.0 SWISS-PROT databank, the overall predictive accuracy about 80% has been achieved in a jackknife test. The result demonstrates the applicability of this relative simple method and possible improvement of prediction accuracy for the protein subcellular locations. We also applied this method to annotate six entirely sequenced proteomes, namely Saccharomyces cerevisiae, Caenorhabditis elegans, Drosophila melanogaster, Oryza sativa, Arabidopsis thaliana and a subset of all human proteins.
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