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Shedding light on the role of interfacial chemical bond in heterojunction photocatalysis

Nano Research 2022年第12期15卷 10158-10170页

作者： Yueshuang Mao Pengfei Wang Sihui Zhan moe Key laboratory of Pollution Processes and Environmental Criteria College of Environmental Science and EngineeringNankai UniversityTianjin300350China Tianjin Key lab Clean Energy&Pollutant Control School of Energy and Environmental EngineeringHebei University of TechnologyTianjin300401China

Faced with the growing consumption of fossil fuels and the consequent energy/ecological crisis,photocatalysis has become a realistic option to develop new energy source and realize the carbon neutrality.Heterojunction photocatalysts constructed by multiple semiconductors with staggered band structure can spatially separate redox reaction sites to realize synergistic oxidation and reduction reactions,and have captured broad interest.However,the undesigned heterojunctions still encounter some headache difficulties,that is the poor interfacial contact,which will block carrier mobility,thus result in inefficient and instable catalysts.Recently,researchers have been focusing on constructing chemical bonds(especially covalent bonding)between different semiconductors to induce the formation of intimate and stable interface contact.Herein,this review article presents the state-of-the-art progress on interfacial chemical bonds(ICB)in heterojunction photocatalysts and clarifies the function mechanism for enhancing photocatalysis.Given that the formation of ICB strongly depends on the surface characteristics of semiconductors,we clarify the formation mechanism and put forward rational design strategies.More importantly,the current photocatalytic applications of ICB are reviewed to have a deep understanding of structure-activity related mechanisms.Finally,our brief outlooks on the current challenges and future development trends of ICB for next-generation photocatalysts are pointed out to create brand-new strategies for optimizing photocatalytic properties and accelerate the practical applications of ICB with high-performance.

关键词： photocatalysis heterojunction interfacial chemical bond structure-activity relationships charge transfer

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Au core-PtAu alloy shell nanowires for formic acid electrolysis

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Journal of Energy Chemistry 2022年第2期31卷 94-102页

作者： Qi Xue Xin-Yu Bai Yue Zhao Ya-Nan Li Tian-Jiao Wang Hui-Ying Sun Fu-Min Li Pei Chen Pujun Jin Shi-Bin Yin Yu Chen Key laboratory of Macromolecular Science of Shaanxi Province Key Laboratory of Applied Surface and Colloid Chemistry(MOE)Shaanxi Key Laboratory for Advanced Energy DevicesShaanxi Engineering Lab for Advanced Energy TechnologySchool of Materials Science and EngineeringShaanxi Normal UniversityXi’an 710062ShaanxiChina moe Key laboratory of New Processing Technology for Non-ferrous Metals and Materials Guangxi Key Laboratory of Processing for Non-ferrous Metals and Featured MaterialsGuangxi UniversityNanning 530004GuangxiChina

Inefficient electrocatalysts and high-power consumption are two thorny problems for electrochemical hydrogen(H2)production from acidic water electrolysis.Herein we report the one-pot precise synthesis of ultrafine Au core-Pt Au alloy shell nanowires(Au@PtxAu UFNWs).Among them,Au@Pt_(0.077) Au UFNWs exhibit the best performance for formic acid oxidation reaction(FAOR)and hydrogen evolution reaction(HER),which only require applied potentials of 0.29 V and-22.6 m V to achieve a current density of 10 m A cm^(-2),respectively.The corresponding formic acid electrolyzer realizes the electrochemical H2 production at a voltage of only 0.51 V with 10 m A cm^(-2) current density.Density functional theory(DFT)calculations reveal that the Au-riched Pt Au alloy structure can facilitates the direct oxidation pathway of FAOR and consequently elevates the FAOR activity of Au@Pt_(0.077) Au UFNWs.This work provides meaningful insights into the electrochemical H_(2) production from both the construction of advanced bifunctional electrocatalysts and the replacement of OER.

关键词： Au core-PtAu alloy shell nanowires Formic acid oxidation reaction Reaction pathway Hydrogen evolution reaction Acidic water electrolysis

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Composite Quantile Estimation for Kink Model with Longitudinal Data

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Acta Mathematica Sinica,English Series 2023年第3期39卷 412-438页

作者： Chuang WAN Wei ZHONG Ying FANG School of Statistics and Data Science Nankai UniversityTianjin 300071P.R.China moe Key lab of Econometrics WISEDepartment of Statistics and Data ScienceSchool of EconomicsXiamen UniversityXiamen 361000P.R.China

Kink model is developed to analyze the data where the regression function is two-stage piecewise linear with respect to the threshold covariate but continuous at an unknown kink point.In quantile regression for longitudinal data,kink point where the kink effect happens is often assumed to be heterogeneous across different quantiles.However,the kink point tends to be the same across different quantiles,especially in a region of neighboring quantile levels.Incorporating such homogeneity information could increase the estimation efficiency of the common kink point.In this paper,we propose a composite quantile estimation approach for the common kink point by combining information from multiple neighboring quantiles.Asymptotic normality of the proposed estimator is studied.In addition,we also develop a sup-likelihood-ratio test to check the existence of the kink effect at a given quantile level.A test-inversion confidence interval for the common kink point is also developed based on the quantile rank score test.The simulation studies show that the proposed composite kink estimator is more efficient than the single quantile regression estimator.We also illustrate the proposed method via an application to a longitudinal data set on blood pressure and body mass index.

关键词： Asymptotical normality composite quantile estimation estimation efficiency kink design model longitudinal data

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Computational dynamics of soft machines

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Acta Mechanica Sinica 2017年第3期33卷 516-528页

作者： Haiyan Hu Qiang Tian Cheng Liu moe Key lab of Dynamics and Control of Flight Vehicles School of Aerospace Engineering Beijing Institute of Technology

Soft machine refers to a kind of mechanical system made of soft materials to complete sophisticated missions, such as handling a fragile object and crawling along a narrow tunnel corner, under low cost control and actuation. Hence, soft machines have raised great challenges to computational dynamics. In this review article, recent studies of the authors on the dynamic modeling, numerical simulation, and experimental validation of soft machines are summarized in the framework of multibody system dynamics. The dynamic modeling approaches are presented first for the geometric nonlinearities of coupled overall motions and large deformations of a soft component, the physical nonlinearities of a soft component made of hyperelastic or elastoplastic materials, and the frictional contacts/impacts of soft components, respectively. Then the computation approach is outlined for the dynamic simulation of soft machines governed by a set of differential-algebraic equations of very high dimensions, with an emphasis on the efficient computations of the nonlinear elastic force vector of finite elements. The validations of the proposed approaches are given via three case studies, including the locomotion of a soft quadrupedal robot, the spinning deployment of a solar sail of a spacecraft, and the deployment of a mesh reflector of a satellite antenna, as well as the corresponding experimental studies. Finally, some remarks are made for future studies.

关键词： Computational dynamics Multibody system dynamics Absolute nodal coordinate formulation Contact and impact Soft machine Soft robot Deployable space structure

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Extending attributes page:a scheme for enhancing the reliability of storage system metadata

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Journal of Zhejiang University-Science A(Applied Physics & Engineering) 2009年第8期10卷 1106-1113页

作者： Juan WANG Dan FENG Fang WANG Cheng-tao LU moe Key lab of Data Storage System Huazhong University of Science and Technology Wuhan 430074 China

In an object-based storage system,a novel scheme named EAP(extending attributes page) is presented to enhance the metadata reliability of the system by adding the user object file information attributes page for each user object and storing the file-related attributes of each user object in object-based storage devices.The EAP scheme requires no additional hardware equipments compared to a general method which uses backup metadata servers to improve the metadata reliability.Leveraging a Markov chain,this paper compares the metadata reliability of the system using the EAP scheme with that using only metadata servers to offer the file metadata service.Our results demonstrate that the EAP scheme can dramatically enhance the reliability of storage system metadata.

关键词：数据存储系统可靠性属性页元数据服务器用户对象存储文件基于对象经济活动

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Experimental and modeling investigations on the unexpected hydrogen sulfide rebound in a sewer receiving nitrate addition: Mechanism and solution

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Journal of Environmental Sciences 2023年第3期125卷 630-640页

作者： Zhensheng Liang Dongping Wu Guibiao Li Jianliang Sun Feng Jiang Yu Li School of Environment Guangdong Provincial Key Laboratory of Chemical Pollution and Environmental Safety&MOE Key Laboratory of Theoretical Chemistry of EnvironmentSouth China Normal UniversityGuangzhou 510006China Guangdong Provincial Key lab of Environmental Pollution Control and Redemidation Technology School of Environmental Science&EngineeringSun Yat-sen UniversityGuangzhou 510275China

Biogenic hydrogen sulfide is an odorous, toxic and corrosive gas released from sewage in sewers. To control sulfide generation and emission, nitrate is extensively applied in sewer systems for decades. However, the unexpected sulfide rebound after nitrate addition is being questioned in recent studies. Possible reasons for the sulfide rebounds have been studied,but the mechanism is still unclear, so the countermeasure is not yet proposed. In this study, a lab-scale sewer system was developed for investigating the unexpected sulfide rebounds via the traditional strategy of nitrate addition during 195-days of operation. It was observed that the sulfide pollution was even severe in a sewer receiving nitrate addition. The mechanism for the sulfide rebound can be differentiated into short-term and long-term effects based on the dominant contribution. The accumulation of intermediate elemental sulfur in biofilm resulted in a rapid sulfide rebound via the high-rate sulfur reduction after the depletion of nitrate in a short period. The presence of nitrate in sewer promoted the microorganism proliferation in biofilm, increased the biofilm thickness, re-shaped the microbial community and enhanced biological denitrification and sulfur production, which further weakened the effect of nitrate on sulfide control during the long-term operation. An optimized biofilminitiated sewer process model demonstrated that neither the intermittent nitrate addition nor the continuous nitrate addition was a sustainable strategy for the sulfide control. To minimize the negative impact from sulfide rebounds, a(bi)monthly routine maintenance(e.g., hydraulic flushing with nitrate spike) to remove the proliferative microorganism in biofilm is necessary.

关键词： Hydrogen sulfide control Nitrate addition Sewer modelling Sewer management

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Theoretical and experimental investigations of flexural wave propagation in periodic grid structures designed with the idea of phononic crystals

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Chinese Physics B 2009年第6期18卷 2404-2411页

作者：温激鸿郁殿龙刘竞文肖勇温熙森 Institute of Mechatronical Engineering National University of Defense Technology Key lab of Photonic and Phononic Crystals (moe)

The propagation characteristics of flexural waves in periodic grid structures designed with the idea of phononic crystals are investigated by combining the Bloch theorem with the finite element method. This combined analysis yields phase constant surfaces, which predict the location and the extension of band gaps, as well as the directions and the regions of wave propagation at assigned frequencies. The predictions are validated by computation and experimental analysis of the harmonic responses of a finite structure with 11 × 11 unit cells. The flexural wave is localized at the point of excitation in band gaps, while the directional behaviour occurs at particular frequencies in pass bands. These studies provide guidelines to designing periodic structures for vibration attenuation.

关键词： phononic crystal phase constant surface grid structure

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Idealized Numerical Simulation Study of the Potential Vorticity Banners over a Mesoscale Mountain: Dry Adiabatic Process

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Advances in Atmospheric Sciences 2009年第5期26卷 906-922页

作者：王其伟谈哲敏 Key lab of Mesoscale Severe Weather/moe School of Atmospheric Sciences Nanjing University

Topography-induced potential vorticity （PV） banners over a mesoscale topography （Dabie Mountain, hereafter DM） in eastern China, under an idealized dry adiabatic flow, are studied with a mesoscale numerical model, ARPS. PV banners generate over the leeside of the DM with a maximal intensity of ～1.5 PVU, and extend more than 100 km downstream, while the width varies from several to tens of kilometers, which contrasts with the half-width of the peaks along the ridge of the DM. Wave breaking occurs near the leeside surface of the DM, and leads to a strong PV generation. Combining with the PV generation, due to the friction and the flow splitting upstream, the PV is advected downstream, and then forms the PV banners over the DM. The PV banners are sensitive to the model resolution, Coriolis force, friction, subgrid turbulent mixing, stratification, the upstream wind speed and wind direction. The negative PV banners have a more compact connection with the low level turbulent kinetic energy. The PV banners are built up by the baroclinic and barotropic components. The barotropic-associated PV can identify the distribution of the PV banners, while the baroclinic one only has important contributions on the flanks and on the leeside near the topography. PV fluxes are diagnosed to investigate the influence of friction on the PV banners. Similar patterns are found between the total PV flux and the advective PV flux, except near the surface and inside the dipole of the PV banners, where the nonadvective PV flux associated with the friction has a net negative contribution.

关键词： potential vorticity banners surface friction turbulent kinetic energy Dabie Mountain

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Mesoscale Moist Adjoint Sensitivity Study of a Mei-yu Heavy Rainfall Event

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Advances in Atmospheric Sciences 2010年第6期27卷 1415-1424页

作者：储可宽谈哲敏 Key lab of Mesoscale Severe Weather/moe and School of Atmospheric SciencesNanjing University

The mesoscale moist adjoint sensitivities related to the initiation of mesoscale convective systems （MCSs） are evaluated for a mei-yu heavy rainfall event. The sensitivities were calculated on a realistic background gained from a four-dimensional variational data assimilation of precipitation experiment to make the sensitivity computation possible and reasonable within a strong moist convective event at the mesoscale. The results show that the computed sensitivities at the mesoscale were capable of capturing the factors affecting MCS initiation. The sensitivities to the initial temperature and moisture are enhanced greatly by diabatic processes, especially at lower levels, and these sensitivities are much larger than those stemming from the horizontal winds, which implies that initiation of MCSs is more sensitive to low-level temperature and moisture perturbations rather than the horizontal winds. Moreover, concentration of sensitivities at low levels reflects the characteristics of the mei-yu front. The results provide some hints about how to improve quantitative precipitation forecasts of mei-yu heavy rainfall, such as by conducting mesoscale targetted observations via the adjoint-based method to reduce the low-level errors in the initial temperature and moisture.

关键词： adjoint sensitivity analysis mei-yu heavy rainfall mesoscale

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A review of distributed statistical inference

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Statistical Theory and Related Fields 2022年第2期6卷 89-99页

作者： Yuan Gao Weidong Liu Hansheng Wang Xiaozhou Wang Yibo Yan Riquan Zhang School of Statistics and Key laboratory of Advanced Theory and Application in Statistics and Data Science–moe East China Normal UniversityShanghaiPeople’s Republic of China School of Mathematical Sciences and Key lab of Articial Intelligence–moe Shanghai Jiao Tong UniversityShanghaiPeople’s Republic of China Guanghua School of Management Peking UniversityBeijingPeople’s Republic of China

The rapid emergence of massive datasets in various fields poses a serious challenge to tra-ditional statistical methods.Meanwhile,it provides opportunities for researchers to develop novel algorithms.Inspired by the idea of divide-and-conquer,various distributed frameworks for statistical estimation and inference have been proposed.They were developed to deal with large-scale statistical optimization problems.This paper aims to provide a comprehensive review for related literature.It includes parametric models,nonparametric models,and other frequently used models.Their key ideas and theoretical properties are summarized.The trade-off between communication cost and estimate precision together with other concerns is discussed.

关键词： Distributed computing divide-and-conquer communication-efficiency shrinkage methods nonparametric estimation principal component analysis feature screening bootstrap

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