The k-nearest neighbor （k-NN） method was evaluated to predict the influent flow rate and four water qualities, namely chemical oxygen demand （COD）, suspended solid （SS）, total nitrogen （T-N） and total phosphor...The k-nearest neighbor （k-NN） method was evaluated to predict the influent flow rate and four water qualities, namely chemical oxygen demand （COD）, suspended solid （SS）, total nitrogen （T-N） and total phosphorus （T-P） at a wastewater treatment plant （WWTP）. The search range and approach for determining the number of nearest neighbors （NNs） under dry and wet weather conditions were initially optimized based on the root mean square error （RMSE）. The optimum search range for considering data size was one year. The square root-based （SR） approach was superior to the distance factor-based （DF） approach in determining the appropriate number of NNs. However, the results for both approaches varied slightly depending on the water quality and the weather conditions. The influent flow rate was accurately predicted within one standard deviation of measured values. Influent water qualities were well predicted with the mean absolute percentage error （MAPE） under both wet and dry weather conditions. For the seven-day prediction, the difference in predictive accuracy was less than 5% in dry weather conditions and slightly worse in wet weather conditions. Overall, the k-NN method was verified to be useful for predicting WWTP influent characteristics.展开更多
G-protein coupled receptors （GPCRs） are a class of seven-helix transmembrane proteins that have been used in bioinformatics as the targets to facilitate drug discovery for human diseases. Although thousands of GPCR ...G-protein coupled receptors （GPCRs） are a class of seven-helix transmembrane proteins that have been used in bioinformatics as the targets to facilitate drug discovery for human diseases. Although thousands of GPCR sequences have been collected, the ligand specificity of many GPCRs is still unknown and only one crystal structure of the rhodopsin-like family has been solved. Therefore, identifying GPCR types only from sequence data has become an important research issue. In this study, a novel technique for identifying GPCR types based on the weighted Levenshtein distance between two receptor sequences and the nearest neighbor method （NNM） is introduced, which can deal with receptor sequences with different lengths directly. In our experiments for classifying four classes （acetylcholine, adrenoceptor, dopamine, and serotonin） of the rhodopsin-like family of GPCRs, the error rates from the leave-one-out procedure and the leave-half-out procedure were 0.62% and 1.24%, respectively. These results are prior to those of the covariant discriminant algorithm, the support vector machine method, and the NNM with Euclidean distance.展开更多
This study proposes two metrics using the nearest neighbors method to improve the accuracy of time-series forecasting. These two metrics can be treated as a hybrid forecasting approach to combine linear and non-linear...This study proposes two metrics using the nearest neighbors method to improve the accuracy of time-series forecasting. These two metrics can be treated as a hybrid forecasting approach to combine linear and non-linear forecasting techniques. One metric redefines the distance in k-nearest neighbors based on the coefficients of autoregression (AR) in time series. Meanwhile, an improvement to Kulesh's adaptive metrics in the nearest neighbors is also presented. To evaluate the performance of the two proposed metrics, three types of time-series data, namely deterministic synthetic data, chaotic time-series data and real time-series data, are predicted. Experimental results show the superiority of the proposed AR-enhanced k-nearest neighbors methods to the traditional k-nearest neighbors metric and Kulesh's adaptive metrics.展开更多
Consider the regression model Y=Xβ+ g(T) + e. Here g is an unknown smoothing function on [0, 1], β is a l-dimensional parameter to be estimated, and e is an unobserved error. When data are randomly censored, the est...Consider the regression model Y=Xβ+ g(T) + e. Here g is an unknown smoothing function on [0, 1], β is a l-dimensional parameter to be estimated, and e is an unobserved error. When data are randomly censored, the estimators βn* and gn*forβ and g are obtained by using class K and the least square methods. It is shown that βn* is asymptotically normal and gn* achieves the convergent rate O(n-1/3).展开更多
In this paper,the application of an algorithm for precipitation retrieval based on Himawari-8 (H8) satellite infrared data is studied.Based on GPM precipitation data and H8 Infrared spectrum channel brightness tempera...In this paper,the application of an algorithm for precipitation retrieval based on Himawari-8 (H8) satellite infrared data is studied.Based on GPM precipitation data and H8 Infrared spectrum channel brightness temperature data,corresponding "precipitation field dictionary" and "channel brightness temperature dictionary" are formed.The retrieval of precipitation field based on brightness temperature data is studied through the classification rule of k-nearest neighbor domain (KNN) and regularization constraint.Firstly,the corresponding "dictionary" is constructed according to the training sample database of the matched GPM precipitation data and H8 brightness temperature data.Secondly,according to the fact that precipitation characteristics in small organizations in different storm environments are often repeated,KNN is used to identify the spectral brightness temperature signal of "precipitation" and "non-precipitation" based on "the dictionary".Finally,the precipitation field retrieval is carried out in the precipitation signal "subspace" based on the regular term constraint method.In the process of retrieval,the contribution rate of brightness temperature retrieval of different channels was determined by Bayesian model averaging (BMA) model.The preliminary experimental results based on the "quantitative" evaluation indexes show that the precipitation of H8 retrieval has a good correlation with the GPM truth value,with a small error and similar structure.展开更多
针对配电台区复杂拓扑结构识别,以及统计数据缺失造成的识别准确率低的问题,融合最长公共子序列(longest common subsequence,LCSS)与动态时间规整(dynamic time warping,DTW)方法,提出了基于最长公共子序列动态时间规整距离(LCSS-DTW)...针对配电台区复杂拓扑结构识别,以及统计数据缺失造成的识别准确率低的问题,融合最长公共子序列(longest common subsequence,LCSS)与动态时间规整(dynamic time warping,DTW)方法,提出了基于最长公共子序列动态时间规整距离(LCSS-DTW)的低压配电台区拓扑结构识别方法。依据在低压配电台区中,分布在同一电压相别的用户之间存在相似的电压波动,计算低压配电台区内用户之间的距离矩阵。利用LCSS的局部动态对齐的特性,结合DTW全局对齐的方式,能够更准确地捕捉到用户时序电压数据的相似性,以及确保时序数据的完整性,通过聚类算法,成功识别了配电台区用户的相序归属,并引入了随机数据缺失和异常数据干扰进行验证,结果表明,本方法具有较强的鲁棒性。在不同数据缺失和异常数据干扰条件下,方法的识别准确率保持在95%以上,较传统方法有明显提高,有效解决了数据缺失对拓扑结构识别准确率的影响。展开更多
密度峰值聚类(density peaks clustering,DPC)算法通过考虑局部密度和相对距离来识别簇中心以实现聚类.然而,该算法在处理密度分布不均匀和类簇大小不平衡的数据时容易忽视低密度区域的类簇中心,需要人为设定类簇数量,并且其分配策略中...密度峰值聚类(density peaks clustering,DPC)算法通过考虑局部密度和相对距离来识别簇中心以实现聚类.然而,该算法在处理密度分布不均匀和类簇大小不平衡的数据时容易忽视低密度区域的类簇中心,需要人为设定类簇数量,并且其分配策略中一个数据点分配错误会导致后续点的错误分配.为了解决上述问题,本文提出一种自适应稀疏感知密度峰值聚类算法.首先,引入模糊点概念以降低对子簇合并过程的影响;其次,利用减法聚类方法识别低密度区域的中心;然后,根据新的局部密度和反向最近邻数来识别噪声并更新子簇中心;最后,给出改进的全局交叠度,结合全局可分度指导子簇融合,并在这些度量下自动确定聚类结果.实验结果表明,在合成数据集和UCI数据集上,与DPC及其改进算法相比,本文提出的算法能够更好地识别稀疏簇、减少非中心分配带来的连锁反应,自动确定最优类簇数目并获得更加准确的聚类结果.展开更多
文摘The k-nearest neighbor （k-NN） method was evaluated to predict the influent flow rate and four water qualities, namely chemical oxygen demand （COD）, suspended solid （SS）, total nitrogen （T-N） and total phosphorus （T-P） at a wastewater treatment plant （WWTP）. The search range and approach for determining the number of nearest neighbors （NNs） under dry and wet weather conditions were initially optimized based on the root mean square error （RMSE）. The optimum search range for considering data size was one year. The square root-based （SR） approach was superior to the distance factor-based （DF） approach in determining the appropriate number of NNs. However, the results for both approaches varied slightly depending on the water quality and the weather conditions. The influent flow rate was accurately predicted within one standard deviation of measured values. Influent water qualities were well predicted with the mean absolute percentage error （MAPE） under both wet and dry weather conditions. For the seven-day prediction, the difference in predictive accuracy was less than 5% in dry weather conditions and slightly worse in wet weather conditions. Overall, the k-NN method was verified to be useful for predicting WWTP influent characteristics.
基金supported by the Natural Science Foundation of Jiangsu Province(No.BK2004142)partly by the National Natural Science Foundation of China(No.60275007).
文摘G-protein coupled receptors （GPCRs） are a class of seven-helix transmembrane proteins that have been used in bioinformatics as the targets to facilitate drug discovery for human diseases. Although thousands of GPCR sequences have been collected, the ligand specificity of many GPCRs is still unknown and only one crystal structure of the rhodopsin-like family has been solved. Therefore, identifying GPCR types only from sequence data has become an important research issue. In this study, a novel technique for identifying GPCR types based on the weighted Levenshtein distance between two receptor sequences and the nearest neighbor method （NNM） is introduced, which can deal with receptor sequences with different lengths directly. In our experiments for classifying four classes （acetylcholine, adrenoceptor, dopamine, and serotonin） of the rhodopsin-like family of GPCRs, the error rates from the leave-one-out procedure and the leave-half-out procedure were 0.62% and 1.24%, respectively. These results are prior to those of the covariant discriminant algorithm, the support vector machine method, and the NNM with Euclidean distance.
基金the National Natural Science Foundation of China(No.61203337)the Natural Science Foundation of Shanghai(No.12ZR1440200)
文摘This study proposes two metrics using the nearest neighbors method to improve the accuracy of time-series forecasting. These two metrics can be treated as a hybrid forecasting approach to combine linear and non-linear forecasting techniques. One metric redefines the distance in k-nearest neighbors based on the coefficients of autoregression (AR) in time series. Meanwhile, an improvement to Kulesh's adaptive metrics in the nearest neighbors is also presented. To evaluate the performance of the two proposed metrics, three types of time-series data, namely deterministic synthetic data, chaotic time-series data and real time-series data, are predicted. Experimental results show the superiority of the proposed AR-enhanced k-nearest neighbors methods to the traditional k-nearest neighbors metric and Kulesh's adaptive metrics.
文摘Consider the regression model Y=Xβ+ g(T) + e. Here g is an unknown smoothing function on [0, 1], β is a l-dimensional parameter to be estimated, and e is an unobserved error. When data are randomly censored, the estimators βn* and gn*forβ and g are obtained by using class K and the least square methods. It is shown that βn* is asymptotically normal and gn* achieves the convergent rate O(n-1/3).
基金Supported by National Natural Science Foundation of China(41805080)Natural Science Foundation of Anhui Province,China(1708085QD89)+1 种基金Key Research and Development Program Projects of Anhui Province,China(201904a07020099)Open Foundation Project Shenyang Institute of Atmospheric Environment,China Meteorological Administration(2016SYIAE14)
文摘In this paper,the application of an algorithm for precipitation retrieval based on Himawari-8 (H8) satellite infrared data is studied.Based on GPM precipitation data and H8 Infrared spectrum channel brightness temperature data,corresponding "precipitation field dictionary" and "channel brightness temperature dictionary" are formed.The retrieval of precipitation field based on brightness temperature data is studied through the classification rule of k-nearest neighbor domain (KNN) and regularization constraint.Firstly,the corresponding "dictionary" is constructed according to the training sample database of the matched GPM precipitation data and H8 brightness temperature data.Secondly,according to the fact that precipitation characteristics in small organizations in different storm environments are often repeated,KNN is used to identify the spectral brightness temperature signal of "precipitation" and "non-precipitation" based on "the dictionary".Finally,the precipitation field retrieval is carried out in the precipitation signal "subspace" based on the regular term constraint method.In the process of retrieval,the contribution rate of brightness temperature retrieval of different channels was determined by Bayesian model averaging (BMA) model.The preliminary experimental results based on the "quantitative" evaluation indexes show that the precipitation of H8 retrieval has a good correlation with the GPM truth value,with a small error and similar structure.
文摘针对配电台区复杂拓扑结构识别,以及统计数据缺失造成的识别准确率低的问题,融合最长公共子序列(longest common subsequence,LCSS)与动态时间规整(dynamic time warping,DTW)方法,提出了基于最长公共子序列动态时间规整距离(LCSS-DTW)的低压配电台区拓扑结构识别方法。依据在低压配电台区中,分布在同一电压相别的用户之间存在相似的电压波动,计算低压配电台区内用户之间的距离矩阵。利用LCSS的局部动态对齐的特性,结合DTW全局对齐的方式,能够更准确地捕捉到用户时序电压数据的相似性,以及确保时序数据的完整性,通过聚类算法,成功识别了配电台区用户的相序归属,并引入了随机数据缺失和异常数据干扰进行验证,结果表明,本方法具有较强的鲁棒性。在不同数据缺失和异常数据干扰条件下,方法的识别准确率保持在95%以上,较传统方法有明显提高,有效解决了数据缺失对拓扑结构识别准确率的影响。
文摘密度峰值聚类(density peaks clustering,DPC)算法通过考虑局部密度和相对距离来识别簇中心以实现聚类.然而,该算法在处理密度分布不均匀和类簇大小不平衡的数据时容易忽视低密度区域的类簇中心,需要人为设定类簇数量,并且其分配策略中一个数据点分配错误会导致后续点的错误分配.为了解决上述问题,本文提出一种自适应稀疏感知密度峰值聚类算法.首先,引入模糊点概念以降低对子簇合并过程的影响;其次,利用减法聚类方法识别低密度区域的中心;然后,根据新的局部密度和反向最近邻数来识别噪声并更新子簇中心;最后,给出改进的全局交叠度,结合全局可分度指导子簇融合,并在这些度量下自动确定聚类结果.实验结果表明,在合成数据集和UCI数据集上,与DPC及其改进算法相比,本文提出的算法能够更好地识别稀疏簇、减少非中心分配带来的连锁反应,自动确定最优类簇数目并获得更加准确的聚类结果.
