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1,064 results on '"Liu, Hai-Yang"'

28. Random Shapelet Forest Algorithm Embedded with Canonical Time Series Features

Author

GAO Zhen-zhuo, WANG Zhi-hai, LIU Hai-yang

Subjects
time series, classification, shapelet, canonical time series features, random forest, Computer software, QA76.75-76.765, Technology (General), T1-995
Abstract

In recent years,the research on the classification of time series has attracted more and more attention.Advanced time series classification methods are usually based on great feature representations.Shapelet refers to the discriminative subsequences in time series,which can effectively express the local shape characteristics of time series.However,the high computational cost greatly limits the practicability of the Shapelet-based time series classification methods.In addition,traditional Shapelet can only describe the overall shape characteristics of the subsequence under Euclidean distance metric,so it is easy to be disturbed by noise and is difficult to mine other types of discriminative information contained in the subsequence.To deal with the aforementioned problems,a new time series classification algorithm,named random Shapelet forest embedded with canonical time series features,is proposed in this paper.The proposed algorithm is based on the following three key strategies:1)randomly select Shapelet and limit the scope of Shapelet to improve efficiency;2)embed multiple canonical time series features in Shapelet to improve the adaptability of the algorithm to different classification problems and make up for the accuracy loss caused by the random selection of Shapelet;3)build a random forest classifier based on the new feature representations to ensure the generalization ability of the algorithm.Experimental results on 112 UCR time series datasets show that the proposed algorithm is more accurate than the STC algorithm which is based on Shapelet exact search and the Shapelet transform technique,as well as many other types of state-of-the-art time series classification algorithms.Moreover,extensive experimental comparisons verify the significant advantages of the proposed algorithm in terms of efficiency.

Published
2022
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46. Electrocatalytic Hydrogen Evolution Reaction of Cobalt Triaryl Corrole Bearing Nitro Group.

Author

Zeng, Jie, Cao, Xu-You, Xu, Shi-Yin, Qiu, Yi-Feng, Chen, Jun-Ying, Si, Li-Ping, and Liu, Hai-Yang

Subjects
GROUP 15 elements, CHARGE exchange, TRIFLUOROACETIC acid, ENERGY conservation, ENVIRONMENTAL protection
Abstract

The use of non–precious metals for electrocatalytic hydrogen reaction (HER) is particularly important for energy conservation and environmental protection. In this work, three new cobalt corroles containing o−, m−, and p−nitrobenzyl (1, 2, 3) at the meso 10−position of the corrole macrocycle were synthesized, and their electrocatalytic hydrogen evolution reaction in organic and neutral aqueous systems was also investigated. The results show that these three cobalt corroles have significant catalytic HER activity in both systems, and the catalytic efficiency follows 1 > 3 > 2, which indicates that the position of the nitro group can affect the catalytic property of the complexes. In the organic phase, when using trifluoroacetic acid or p−toluenesulfonic acid as the proton source, the electrocatalytic HER may undergo an EECC (E: electron transfer, C: proton coupling) pathway. In a neutral aqueous system, the HER turnover frequency value of 1 is up to 137.4 h−1 at 938 mV overpotential. [ABSTRACT FROM AUTHOR]

Published
2024
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47. First Application of Non‐Metallic A2B Type Silicon Corrole Complexes in Electrocatalytic Hydrogen Evolution.

Author

Liu, Zhen‐Wu, Yang, Gang, Xu, Shi‐Yin, Xie, Wan‐Yue, Yao, Yan‐Fang, Xiao, Xin‐Yan, Si, Li‐Ping, and Liu, Hai‐Yang

Subjects
HYDROGEN evolution reactions, SILICON, CHARGE exchange, CATALYTIC activity, HYDROGEN, CYANO group, MACROCYCLIC compounds
Abstract

In this study, we have successfully synthesized two non‐metallic‐based silicon corrole complexes (F10C−Si, F10C−CN−Si) and used them as HER electrocatalysts for the first time. Electrochemical studies indicate the electrocatalytic HER may go via EE‐CEEC (E: electron transfer step, C: chemical step) pathway. Notably, it can be seen that the introduction of electron‐withdrawing cyano group on the meso‐phenyl of the corrole macrocycle may enhance the catalytic activity of silicon corrole complexes. In DMF with TsOH as the proton source, F10C−CN−Si exhibits a turnover frequency (TOF) of 331.48 s−1 and a high catalytic efficiency (C.E) of 1.29. Furthermore, the catalytic prowess of the silicon corrole complexes extends to neutral aqueous solution, with F10C−CN−Si achieving a TOF of 52.72 h−1 at an overpotential of 1188 mV. This study extends the application of non‐metallic‐based silicon corrole molecular catalysts in the electrocatalytic HER field. [ABSTRACT FROM AUTHOR]

Published
2024
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