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奈奎斯特采样定理；亚奈奎斯特采样；最小欧式距离；欠定线性问题；时变维特比算法 1

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Evaluation of the ecological status with benthic indices in the coastal system: the case of Bohai Bay (China)

Wenqian CAI,Wei MENG,Lusan LIU,Kuixuan LIN

《环境科学与工程前沿（英文）》 2014年 第8卷 第5期   页码 737-746 doi: 10.1007/s11783-013-0617-x

摘要： Based on biologic and environmental materials collected from coastal areas of Bohai Bay (China) in April, 2008, three biotic indices (AZTI’s Marine Biotic Index (AMBI), Shannon–Wiener Index and -statistic) were applied together to evaluate the ecological status of the sampling area. The results showed a clear spatial gradient from a worse ecological status in the near-shore areas (especially around Haihe and Jiyun River Estuaries) to a better status in the offshore areas. While all the three indices could assist decision makers in visualizing spatial changes of organic pollutants in Bohai Bay, two indices, i.e., AMBI and Shannon-Wiener index, were effective in distinguishing sites from Haihe River Estuary, Jiyun River Estuary and other area. However, -statistic can’t tell the differences between estuaries and other area. It would be explained that organic pollutants and/or other environmental stresses in Bohai Bay were not strong enough to reduce the size of macrozoobenthos, which may cause both of the abundance and biomass curves crossed. To our knowledge, this is the first time that several benthic indices were used to assess the benthic ecological status in Bohai Bay, which gave the similar results. Furthermore, there is indication that the ecological status is related to excess input of wastewater along main rivers and outlets. In a word, AMBI, Shannon–Wiener Index and -statistic could be able to assess the benthic ecological status of Bohai Bay under the organic pollutants pressure.

关键词： AZTI’s Marine Biotic Index     Shannon-Wiener Index     W-statistic     ecological status     coastal system     Bohai Bay (China)    

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Ecological assessment of lakeshore wetland rehabilitation on eastern route of South-to-North Water Transfer Project

ZHANG Jian, Lu Yifeng, JING Yuming, ZHANG Bo, ZHANG Chenglu, MENG Fei, ZHANG Huayong

《环境科学与工程前沿（英文）》 2008年 第2卷 第3期   页码 306-310 doi: 10.1007/s11783-008-0057-1

摘要： To evaluate the ecological effects of lakeshore wetland rehabilitation on the eastern route of the South-to-North Water Transfer Project, species composition, coverage, height, and biomass of wetland communities at 22 sites of the study area on the shore of Nansi Lake in April and May 2007 were investigated. The wetlands under investigation were divided into platform fields, transition zones, and shallow water zones according to differences in elevations, water levels, and human activities. The species richness index, Shannon-Wiener index, Simpson index, and Pielou Evenness index were adopted to delineate and discuss the ecological effects of lakeshore wetland rehabilitation in 22 quadrates. Results showed that the species richness of the wetland areas after 2 years’ rehabilitation amounted to 47 of 24 families, higher than 25 of 20 families in areas without rehabilitation. The biodiversity index and abundance index of rehabilitated areas were also higher than those of platform fields and fish ponds where there was no rehabilitation. In addition, the Shannon-Wiener index, Simpson index, and community evenness index of platform fields in rehabilitated wetland areas were 1.619, 0.745, and 0.860, respectively, higher than those of the platform fields before rehabilitating. The results suggested that the constructed lakeshore wetland played an important role in protecting the diversity of species.

关键词： community     South-to-North     Shannon-Wiener     Evenness     addition    

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Sequential degradation-based burn-in test with multiple periodic inspections

《工程管理前沿（英文）》 2021年 第8卷 第4期   页码 519-530 doi: 10.1007/s42524-021-0166-0

摘要： Burn-in has been proven effective in identifying and removing defective products before they are delivered to customers. Most existing burn-in models adopt a one-shot scheme, which may not be sufficient enough for identification. Borrowing the idea from sequential inspections for remaining useful life prediction and accelerated lifetime test, this study proposes a sequential degradation-based burn-in model with multiple periodic inspections. At each inspection epoch, the posterior probability that a product belongs to a normal one is updated with the inspected degradation level. Based on the degradation level and the updated posterior probability, a product can be disposed, put into field use, or kept in the test till the next inspection epoch. We cast the problem into a partially observed Markov decision process to minimize the expected total burn-in cost of a product, and derive some interesting structures of the optimal policy. Then, algorithms are provided to find the joint optimal inspection period and number of inspections in steps. A numerical study is also provided to illustrate the effectiveness of our proposed model.

关键词： burn-in     degradation     multiple inspections     Wiener process     partially observed Markov decision process    

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Bayes estimation of residual life by fusing multisource information

Qian ZHAO, Xiang JIA, Zhi-jun CHENG, Bo GUO

《工程管理前沿（英文）》 2018年 第5卷 第4期   页码 524-532 doi: 10.15302/J-FEM-2018034

摘要：

Residual life estimation is essential for reliability engineering. Traditional methods may experience difficulties in estimating the residual life of products with high reliability, long life, and small sample. The Bayes model provides a feasible solution and can be a useful tool for fusing multisource information. In this study, a Bayes model is proposed to estimate the residual life of products by fusing expert knowledge, degradation data, and lifetime data. The linear Wiener process is used to model degradation data, whereas lifetime data are described via the inverse Gaussian distribution. Therefore, the joint maximum likelihood (ML) function can be obtained by combining lifetime and degradation data. Expert knowledge is used according to the maximum entropy method to determine the prior distributions of parameters, thereby making this work different from existing studies that use non-informative prior. The discussion and analysis of different types of expert knowledge also distinguish our research from others. Expert knowledge can be classified into three categories according to practical engineering. Methods for determining prior distribution by using the aforementioned three types of data are presented. The Markov chain Monte Carlo is applied to obtain samples of the parameters and to estimate the residual life of products due to the complexity of the joint ML function and the posterior distribution of parameters. Finally, a numerical example is presented. The effectiveness and practicability of the proposed method are validated by comparing it with residual life estimation that uses non-informative prior. Then, its accuracy and correctness are proven via simulation experiments.

关键词： residual life estimation     Bayes model     linear Wiener process    

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亚奈奎斯特采样的数据恢复：性能极限与恢复算法

罗茜倩,张朝阳

《信息与电子工程前沿（英文）》 2021年 第22卷 第2期   页码 141-286 doi: 10.1631/FITEE.1900320

摘要： 奈奎斯特频率是一般带限信号进行无损采样的采样率下界，然而在某些情景中，亚奈奎斯特频率也足以进行无损采样和信号恢复。以往对亚奈奎斯特采样的研究主要集中在利用信号变换来降低信号维度，但是亚奈奎斯特采样信号的结构并没有得到充分研究。本文针对线性调制基带信号的亚奈奎斯特采样，研究其信号恢复性能极限与算法。该问题中，原信号维度无法降低，因此亚奈奎斯特采样不可避免会带来信息损失，信号恢复也变成一个欠定线性问题。本文采用两种亚奈奎斯特采样方法对线性调制基带信号进行采样，分别研究了两种采样方法下的性能极限和信号恢复算法。首先，针对两种亚奈奎斯特采样方法，分别计算了采样序列之间的最小归一化欧氏距离，以此作为最优性能的指标。然后，在基带信号有限符号集的限制条件下，采用改进的时变维特比算法从亚奈奎斯特采样序列中恢复原信号。将仿真得到的亚奈奎斯特采样的误比特率与其性能的理论极限比较，并与奈奎斯特采样性能对比，验证了时变维特比算法在信号恢复问题中的优良性能。

关键词： 奈奎斯特采样定理；亚奈奎斯特采样；最小欧式距离；欠定线性问题；时变维特比算法    

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标题 作者 时间 类型 操作

Evaluation of the ecological status with benthic indices in the coastal system: the case of Bohai Bay (China)

Wenqian CAI,Wei MENG,Lusan LIU,Kuixuan LIN

期刊论文

Ecological assessment of lakeshore wetland rehabilitation on eastern route of South-to-North Water Transfer Project

ZHANG Jian, Lu Yifeng, JING Yuming, ZHANG Bo, ZHANG Chenglu, MENG Fei, ZHANG Huayong

期刊论文

Sequential degradation-based burn-in test with multiple periodic inspections

期刊论文

Bayes estimation of residual life by fusing multisource information

Qian ZHAO, Xiang JIA, Zhi-jun CHENG, Bo GUO

期刊论文

亚奈奎斯特采样的数据恢复：性能极限与恢复算法

罗茜倩,张朝阳

期刊论文