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Direct observation of the Mpemba effect with water:Probe the mysterious heat transfer

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InfoMat 2023年第2期5卷 1-10页

作者： Zhiqiang Tang Weidong Huang yagang zhang Yanxia Liu Lin Zhao School of Materials and Energy University of Electronic Science and Technology of ChinaChengduPeople's Republic of China State Key Laboratory of Electronic Thin Films and Integrated Devices University of Electronic Science and Technology of ChinaChengduPeople's Republic of China

The Mpemba effect is one of the most perplexing puzzles in nature.Although it has been discussed extensively,direct observation of the Mpemba effect is extremely challenging and rare.Herein,we report the first systematic study of the Mpemba effect with water and clearly point out the conditions required for the observation of the Mpemba effect.The results demonstrate that hot water usually has a faster cooling rate than cold water.The initial temperature,temperature difference,shape of the container,and water volume influence the heat exchange and the cooling process.Owing to the influential factors of heat exchange,the Mpemba effect can only be observed under specific conditions.This work helps to clarify doubts and confusion about the Mpemba effect and can offer alternative strategies for energy storage and transfer materials.

关键词： cooling rate energy storage and transfer heat transfer Mpemba effect

Synergistic Effect of Dual-Doped Carbon on MO_(2)C Nanocrystals Facilitates Alkaline Hydrogen Evolution

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Nano-Micro Letters 2023年第10期15卷 101-111页

作者： Min Zhou Xiaoli Jiang Weijie Kong Hangfei Li Fei Lu Xin Zhou yagang zhang School of Materials and Energy University of Electronic Science and Technology of ChinaChengdu 611731People’s Republic of China State Key Laboratory of Electronic Thin Films and Integrated Devices University of Electronic Science and Technology of ChinaChengdu 610054People’s Republic of China College of Physical Science and Technology Yangzhou UniversityYangzhou 225002People’s Republic of China Department of Chemical Engineering Polytechnique MontrealMontrealQC H3C 3A7Canada

Molybdenum carbide(MO_(2)C)materials are promising electrocatalysts with potential applications in hydrogen evolution reaction(HER)due to low cost and Pt-like electronic structures.Nevertheless,their HER activity is usually hindered by the strong hydrogen binding energy.Moreover,the lack of water-cleaving site's makes it difficult for the catalysts to work in alkaline solutions.Here,we designed and synthesized a B and N dual-doped carbon layer that encapsulated on MO_(2)C nanocrystals(MO_(2)C@BNC)for accelerating HER under alkaline condition.The electronic interactions between the MO_(2)C nanocrystals and the multiple-doped carbon layer endow a near-zero H adsorption Gibbs free energy on the defective C atoms over the carbon shell.Meanwhile,the introduced B atoms afford optimal H_2O adsorption sites for the water-cleaving step.Accordingly,the dual-doped MO_(2)C catalyst with synergistic effect of non-metal sites delivers superior HER performances of a low overpotential(99 mV@10 mA cm^(-2))and a small Tafel slope(58.1 mV dec^(-1))in 1 M KOH solution.Furthermore,it presents a remarkable activity that outperforming the commercial 10%Pt/C catalyst at large current density,demonstrating its applicability in industrial water splitting.This study provides a reasonable design strategy towards noble-metal-free HER catalysts with high activity.

关键词： Molybdenum carbide Hydrogen evolution reaction Dual-doped Synergistic effect Superior performances

Electrocatalytic oxidation of 5-hydroxymethylfurfural for sustainable 2,5-furandicarboxylic acid production-From mechanism to catalysts design

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SusMat 2023年第1期3卷 21-43页

作者： Xiaoli Jiang Wei Li Yanxia Liu Lin Zhao Zhikai Chen Lan zhang yagang zhang Sining Yun School of Materials and Energy University of Electronic Science and Technology of ChinaChengduChina State Key Laboratory of Electronic Thin Films and Integrated Devices University of Electronic Science and Technology of ChinaChengduChina Univ Lyon CNRSINSA-LyonUniversite Claude Bernard Lyon 1VilleurbanneFrance School of Materials Science and Engineering Xi’an University of Architecture and TechnologyXi’anChina

Catalytic conversion of biomass-based platform chemicals is one of the significant approaches to utilize renewable biomass resources.2,5-Furandicarboxylic acid(FDCA),obtained by an electrocatalytic oxidation of 5-hydroxymethylfurfural(HMF),has attracted extensive attention due to the potential of replacing terephthalic acid to synthesize high-performance polymeric materials for commercialization.In the present work,the pHdependent reaction pathways and factors influencing the degree of functional group oxidation are first discussed.Then the reaction mechanism of HMF oxidation is further elucidated using the representative examples.In addition,the emerging catalyst design strategies(defects,interface engineering)used in HMF oxidation are generalized,and structure-activity relationships between the abovementioned strategies and catalysts performance are analyzed.Furthermore,cathode pairing reactions,such as hydrogen evolution reaction,CO_(2) reduction reaction(CO_(2)RR),oxygen reduction reaction,and thermodynamically favorable organic reactions to lower the cell voltage of the electrolysis system,are discussed.Finally,the challenges and prospects of the electrochemical oxidation of HMF for FDCA are presented,focusing on deeply investigated reaction mechanism,coupling reaction,reactor design,and downstream product separation/purification.

关键词： 5-hydroxymethylfurfural catalysts design strategies electrocatalytic oxidation pairing reactions reaction mechanism

A logic-based controller for the mitigation of ventilation air methane in a catalytic flow reversal reactor

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Frontiers of Chemical Science and Engineering 2013年第3期7卷 347-356页

作者： Zhikai LI zhangfeng QIN yagang zhang Zhiwei WU Hui WANG Shuna LI Mei DONG Weibin FAN Jianguo WANG State Key Laboratory of Coal Conversion Institute of Coal Chemistry Chinese Academy of Sciences Taiyuan 030001 China University of the Chinese Academy of Sciences Beijing 100049 China

The control system of a catalytic flow reversal reactor （CFRR） for the mitigation of ventilation air methane was investigated. A one-dimensional heteroge- neous model with a logic-based controller was applied to simulate the CFRR. The simulation results indicated that the controller developed in this work performs well under normal conditions. Air dilution and auxiliary methane injection are effective to avoid the catalyst overheating and reaction extinction caused by prolonged rich and lean feed conditions, respectively. In contrast, the reactor is prone to lose control by adjusting the switching time solely. Air dilution exhibits the effects of two contradictory aspects on the operation of CFRR, i.e., cooling the bed and accumulating heat, though the former is in general more prominent. Lowering the reference temperature for flow reversal can decrease the bed temperature and benefit stable operation under rich methane feed condition.

关键词： ventilation airlean methane combustion,matical modelingmethane reverse flow reactor,logic-based controller mathe-

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绝缘子引线腐蚀断裂研究

电镀与涂饰 2024年第1期43卷 50-58页

作者：高明起徐玉娟张亚刚董东王强中国电子科技集团公司第二十九研究所四川成都610000 电子科技大学四川成都611731 中国电子科技集团公司第四十研究所安徽蚌埠233010

[目的]绝缘子作为微波组件内、外部的连接器件,其引线与玻璃封接处容易断裂。[方法]采用金相显微镜、扫描电镜、能谱仪等手段对上述断裂的原因进行分析。[结果]通过机理探讨与现场观察相结合,确定症结在于应力腐蚀开裂。绝缘子引线断裂... 详细信息

[目的]绝缘子作为微波组件内、外部的连接器件,其引线与玻璃封接处容易断裂。[方法]采用金相显微镜、扫描电镜、能谱仪等手段对上述断裂的原因进行分析。[结果]通过机理探讨与现场观察相结合,确定症结在于应力腐蚀开裂。绝缘子引线断裂分为3个阶段:点蚀过程及裂纹萌生,裂纹扩展,以及纯力学快速断裂。[结论]采用化学抛光与机械研磨相结合、镍金交叉镀覆的新工艺可以消除绝缘子引线封接处镀层应力敏感性和应力条件,令镀层的结合力、耐盐雾性能及焊接性能均达到工艺要求。

关键词：绝缘子引线断裂应力腐蚀化学抛光镍金交叉镀覆

Fault Detection Based on Hierarchical Cluster Analysis in Wide Area Backup Protection System

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Energy and Power Engineering 2009年第1期1卷 21-27页

作者： yagang zhang Jinfang zhang Jing MA Zengping WANG 不详

In wide area backup protection of electric power systems, the prerequisite of protection device's accurate, fast and reliable performance is its corresponding fault type and fault location can be discriminated quickly and defined exactly. In our study, global information will be introduced into the backup protection system. By analyzing and computing real-time PMU measurements, basing on cluster analysis theory, we are using mainly hierarchical cluster analysis to search after the statistical laws of electrical quantities' marked changes. Then we carry out fast and exact detection of fault components and fault sections, and finally accomplish fault isolation. The facts show that the fault detection of fault component (fault section) can be performed successfully by hierarchical cluster analysis and calculation. The results of hierarchical cluster analysis are accurate and reliable, and the dendrograms of hierarchical cluster analysis are in intuition.

关键词： wide area backup protection phasor measurement unit PMU wide area measurement system WAMS fault detection cluster analysis

Fault Diagnosis Based on Graph Theory and Linear Discriminant Principle in Electric Power Network

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Wireless Sensor Network 2010年第1期2卷 62-69页

作者： yagang zhang Qian MA Jinfang zhang Jing MA Zengping WANG 不详

In this paper, we adopt a novel topological approach to fault diagnosis. In our researches, global information will be introduced into electric power network, we are using mainly BFS of graph theory algorithms and linear discriminant principle to resolve fast and exact analysis of faulty components and faulty sections, and finally accomplish fault diagnosis. The results of BFS and linear discriminant are identical. The main technical contributions and innovations in this paper include, introducing global information into electric power network, developing a novel topological analysis to fault diagnosis. Graph theory algorithms can be used to model many different physical and abstract systems such as transportation and communication networks, models for business administration, political science, and psychology and so on. And the linear discriminant is a procedure used to classify an object into one of several a priori groupings dependent on the individual characteristics of the object. In the study of fault diagnosis in electric power network, graph theory algorithms and linear discriminant technology must also have a good prospect of application.

关键词： Fault Diagnosis Graph Theory BFS Linear Discriminant Principle Electric Power Network

CT70低合金高强度油管用钢激光焊接接头残余应力有限元模拟

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焊管 2024年第6期47卷 28-33页

作者：张阿昱王建张亚刚毕宗岳余晗中国石油宝鸡石油钢管有限责任公司陕西宝鸡721008 中油国家石油天然气管材工程技术研究中心有限公司西安710018 中国石油渤海钻探第四钻井工程公司河北沧州062450

针对CT70级连续管用钢激光焊焊接接头,考虑试板、焊缝、热源的轴对称性,应用有限元软件建立了1/2轴对称有限元分析模型,对激光焊接接头的温度场、变形场与应力场进行了模拟分析。结果表明,有限元模拟焊缝尺寸与实际基本一致;残余应力主... 详细信息

针对CT70级连续管用钢激光焊焊接接头,考虑试板、焊缝、热源的轴对称性,应用有限元软件建立了1/2轴对称有限元分析模型,对激光焊接接头的温度场、变形场与应力场进行了模拟分析。结果表明,有限元模拟焊缝尺寸与实际基本一致;残余应力主要集中在焊缝周围,在远离焊缝区域残余应力逐渐减小,且焊缝中心为拉应力;变形在焊缝周围最大,距离焊缝越远变形越小。将有限元模拟结果与实际测试结果对比,激光焊焊缝中心为拉应力,与有限元计算结果相同。

关键词：低合金高强度油管激光焊焊接接头残余应力

Applications of Data Mining Theory in Electrical Engineering

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Engineering（科研） 2009年第3期1卷 211-215页

作者： yagang zhang Jing MA Jinfang zhang Zengping WANG 不详

In this paper, we adopt a novel applied approach to fault analysis based on data mining theory. In our researches, global information will be introduced into the electric power system, we are using mainly cluster analysis technology of data mining theory to resolve quickly and exactly detection of fault components and fault sections, and finally accomplish fault analysis. The main technical contributions and innovations in this paper include, introducing global information into electrical engineering, developing a new application to fault analysis in electrical engineering. Data mining theory is defined as the process of automatically extracting valid, novel, potentially useful and ultimately comprehensive information from large databases. It has been widely utilized in both academic and applied scientific researches in which the data sets are generated by experiments. Data mining theory will contribute a lot in the study of electrical engineering.

关键词： Fault Analysis Data Mining Theory Classification Electrical Engineering