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Spatiotemporal variations of parameters of internal solitary waves in the northern South China Sea

Journal of Oceanology and Limnology 2024年第2期42卷 421-438页

作者： yu’ang liu Yifei JIANG Xiaojiang ZHANG Zhiyuan WANG yu CAO Huizan WANG College of Meteorology and Oceanography National University of Defense TechnologyChangsha 410000China

The dynamic parameters for internal solitary waves(ISWs)derived from the extended Korteweg-de Vries(eKdV)equation play an important role in the understanding and prediction of *** spatiotemporal variations of the dynamic parameters of the ISWs in the northern South China Sea(SCS)were studied based on the reanalysis of long-term temperature and salinity *** results for spectrum analysis show that there are definite geographical differences for the periodic variation of the parameters:in shallow water,all parameters vary with a wave period of one year,while in deep water wave components of the parameters at other frequencies *** wavelet analysis,the wavelet power spectral densities in deep water exhibited an inter-annual variation *** example,the wave component of the dispersion coefficient with a wave period of about half a year reached its power peak once every two *** on previous work,this inter-annual variation pattern was deduced to be caused by dynamic *** further work on the regulatory mechanisms,empirical orthogonal function(EOF)decomposition was *** was found that the modes of the dispersion coefficient have different geographical distributions,explaining the reason why the wave components in different frequencies appeared in different *** numerical simulation results confirm that the variations in the parameters of the ISWs derived from the eKdV equation could affect the waveforms significantly because of changes in the polarity of the ***,the periodic variations of the dynamic parameters are related to the geographical location because of dynamic processes operating.

关键词： internal solitary waves(ISWs) dynamic parameters eKdV equation spatiotemporal variation polarity empirical orthogonal function(EOF)decomposition

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Donor-acceptor covalent organic frameworks-confined ultrafine bimetallic Pt-based nanoclusters for enhanced photocatalytic H_(2)generation

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Nano Research 2024年第7期17卷 5835-5844页

作者： yu liu Yawen Shi Hua Wang Shengbo Zhang Collaborative Innovation Center of Chemical Science and Engineering(Tianjin) Key Laboratory for Green Chemical Technology of the Ministry of EducationSchool of Chemical Engineering and TechnologyTianjin UniversityTianjin 300350China School of Environmental Science and Engineering Tianjin Key Laboratory of Biomass/Wastes UtilizationTianjin UniversityTianjin 300350China

Photocatalytic hydrogen generation from hydrogen storage media is an effective and promising approach for the green hydrogen industry as well as for achieving carbon neutrality ***,the lower photocatalytic efficiency due to the limited light trapping capacity,low electron transfer rate,and severe aggregation of nanoparticles caused by high surface energy seriously restricts their practical ***,we constructed a series of donor–acceptor(D–A)type covalent organic frameworks to confine ultrafine bimetallic Pt-based nanoclusters for photocatalytic hydrogen generation from ammonia borane(AB)*** visible light irradiation at 20℃,PtCo_(2)@covalent organic framework(COF)showed the highest photocatalytic activity with a turnover frequency(TOF)of 486 min−*** and density functional theory(DFT)calculations reveal that the high catalytic activity is mainly attributed to the strong electronic interactions between D–A type COF and ultrafine PtCo_(2)***,the D–A type COF can significantly enhance the light-trapping ability by fine-tuning the electron-acceptor type in the framework,and accelerate the photogenerated electron transfer from D–A type COF to PtCo_(2)nanocluster,which promotes the adsorption and activation of H_(2)O and AB molecules and accelerates hydrogen ***,PtCo_(2)@COF also exhibited ultra-high durability due to the significantly enhanced resistance to nanocluster aggregation caused by the nanopore confinement effect of D–A type *** believe that this work will provide a theoretical guide for the rational design of efficient D–A COFbased catalysts for photocatalysis.

关键词： light trapping electron transfer donor-acceptor covalent organic frameworks(D-A COFs) bimetallic nanoclusters photocatalysis

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Biomass-based materials for advanced supercapacitor:principles,progress,and perspectives

Aggregate

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Aggregate 2024年第1期5卷 95-114页

作者： Yaxuan Wang Ting Xu Kun liu Meng Zhang Xu-Min Cai Chuanling si State Key Laboratory of Biobased Fiber Manufacturing Technology Tianjin Key Laboratory of Pulp and PaperTianjin University of Science and TechnologyTianjinChina Jiangsu Co-Innovation Center of Efficient Processing and Utilization of Forest Resources College of Chemical EngineeringNanjing Forestry UniversityNanjingChina

Supercapacitors exhibit considerable potential as energy storage devices due to their high power density,fast charging and discharging abilities,long cycle life,and *** the increasing environmental concerns associated with synthetic compounds,the use of environment friendly biopolymers to replace conventional petroleum-based materials has been widely ***-based materials are biodegradable,renewable,environment friendly and *** unique hierarchical nanostructure,excellent mechanical properties and hydrophilicity allow them to be used to create functional conductive materials with precisely controlled structures and different *** this review,the latest development of biomass-based supercapacitor materials is reviewed and *** paper describes the physical and chemical properties of various biopolymers and their impact on supercapacitors,as well as the classification and basic principles of ***,a comprehensive discussion is presented on the utilization of biomass-based materials in supercapacitors and their recent applications across a range of supercapacitor ***,an overview of the future prospects and challenges pertaining to the utilization of biomass-based materials in supercapacitors is provided.

关键词： biomass electrodes electrolyte energy storage supercapacitor

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Vibration Control of the Rail Grinding Vehicle with Abrasive Belt Based on Structural Optimization and Lightweight Design

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Chinese Journal of Mechanical Engineering 2024年第3期37卷 311-337页

作者： Wengang Fan Shuai Zhang Zhiwei Wu Yi liu Jiangnan yu School of Mechanical Electronic and Control EngineeringBeijing Jiaotong UniversityBeijing 100044China Key Laboratory of Vehicle Advanced Manufacturing Measuring and Control TechnologyMinistry of EducationBeijing 100044China China Railway Materials Operation and Maintenance Technology Co. LtdBeijing 100036China

As a new grinding and maintenance technology,rail belt grinding shows significant advantages in many applications The dynamic characteristics of the rail belt grinding vehicle largely determines its grinding performance and service *** order to explore the vibration control method of the rail grinding vehicle with abrasive belt,the vibration response changes in structural optimization and lightweight design are respectively analyzed through transient response and random vibration simulations in this ***,the transient response simulation analysis of the rail grinding vehicle with abrasive belt is carried out under operating conditions and non-operating ***,the vibration control of the grinding vehicle is implemented by setting vibration isolation elements,optimizing the structure,and increasing ***,in order to further explore the dynamic characteristics of the rail grinding vehicle,the random vibration simulation analysis of the grinding vehicle is carried out under the condition of the horizontal irregularity of the American AAR6 ***,by replacing the Q235 steel frame material with 7075 aluminum alloy and LA43M magnesium alloy,both vibration control and lightweight design can be achieved *** results of transient dynamic response analysis show that the acceleration of most positions in the two working conditions exceeds the standard value in GB/T 17426-1998 *** optimizing the structure of the grinding vehicle in three ways,the average vibration acceleration of the whole car is reduced by about 55.1%from 15.6 m/s^(2) to 7.0 m/s^(2).The results of random vibration analysis show that the grinding vehicle with Q235 steel frame does not meet the safety conditions of 3σ.By changing frame material,the maximum vibration stress of the vehicle can be reduced from 240.7 MPa to 160.0 MPa and the weight of the grinding vehicle is reduced by about 21.7%from 1500 kg to 1175 *** modal analysis results indic

关键词： Vibration control Dynamic characteristics Structural optimization Lightweight design Modal analysis

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A High-Linear Radio Frequency Quadrature Modulator with Improved sideband Suppression and Carrier Leakage Performance

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Tsinghua Science and Technology 2024年第3期29卷 635-643页

作者： Yingdan Jiang Zongguang yu Shutong Wu Li Li Xuelian liu School of Electronic Science and Engineering Nanjing UniversityNanjing 210093China The 58th Research Institute of China Electronic Technology Group Corporation Wuxi 214072China

The quadrature modulator is a crucial block in transmitters that upconverts baseband signals to theRadio Frequency(RF)band of interest using local oscillator *** this paper,non-ideal factors thatinfluence the performance of the quadrature modulator are considered,and solutions are accordingly taken inthe quadrature modulator design.A high-linear RF quadrature modulator with improved sideband suppressionand carrier leakage performance is presented in this *** quadrature modulator implemented in the0.18-μm siGe process uses the current bleeding technique to improve the general performance of the doublebalanced active Gilbert *** on-chip prescaler followed by two cascaded limiting amplifiers is designed toprovide accurate quadrature local oscillator *** at quadrature baseband signal input ports areproposed to eliminate DC *** measured sideband suppression achieves a performance of better than−43 dBc and carrier leakage is less than−38 dBm over the output RF frequency range of 30 MHz to 2.15 *** output 1 dB compression point equals 11.4 dBm at 800 MHz.

关键词： Radio Frequency(RF) quadrature modulator sideband suppression carrier leakage linearity

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Ru-doped functional porous materials for electrocatalytic water splitting

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Nano Research 2024年第3期17卷 982-1002页

作者： Chongao Tian Rui liu yu Zhang Wenxiu Yang Bo Wang Beijing Key Laboratory of Photoelectronic/Electrophotonic Conversion Materials Advanced Technology Research Institute(Jinan)Advanced Research Institute of Multidisciplinary ScienceSchool of Chemistry and Chemical EngineeringBeijing Institute of TechnologyBeijing 100081China Beijing Institute of Technology Library Beijing Institute of TechnologyBeijing 100081China

Electrolytic water splitting(EWS)is an attractive and promising technique for the production of hydrogen ***,the sluggish kinetic rate of hydrogen/oxygen evolution reactions leads to a high overpotential and low energy *** to date,Pt/Ir-based nanocatalysts have become the state-of-the-art EWS catalysts,but disadvantages such as high cost and low earth abundance greatly limit their applications in EWS *** an attractive candidate for the Pt/Ir catalysts,series of Ru-based nanomaterials have aroused much attention for their low price,Pt-like hydrogen bond strength,and high EWS *** particular,Ru-doped functional porous materials have been becoming one of the most representative EWS catalysts,which can not only achieve the dispersion and adjustment for active Ru sites,but also simultaneously solve the problems of mass transfer and catalytic conversion in *** this review,the design and preparation strategies of Ru-doped functional porous materials toward EWS in recent years are summarized,including Ru-doped metal organic frameworks(MOFs),Ru-doped porous organic polymers(POPs),and their ***,detailed structure–activity relationships induced by the tuned geometric/electronic structures of Ru-doped functional porous materials are further depicted in this *** but not least,the challenges and perspectives of Ru-doped functional porous materials catalysts are reasonably proposed to provide fresh ideas for the design of Ru-based EWS catalysts.

关键词： Ru-based catalyst functional porous materials electrolytic water splitting oxygen evolution reaction hydrogen evolution reaction

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Impact of climate change on food security in the Central Asian countries

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Science China Earth Sciences 2024年第1期67卷 268-280页

作者： Fang SU yu liu Lvfan CHEN Rustam OROZBAEV Liangcheng TAN School of Economics and Management Northwest UniversityXi’an 710127China School of Economics and Management Shaanxi University of Science and TechnologyXi’an 710021China State Key Laboratory of Loess and Quaternary Geology Institute of Earth EnvironmentChinese Academy of SciencesXi’an 710061China Institute of Geology National Academy of Sciences of Kyrgyz RepublicBishkek 720040Kyrgyzstan Institute of Global Environmental Change Xi’an Jiaotong UniversityXi’an 710049China

The current and potential impacts of global warming have generated widespread concerns about food security among all sectors of *** Asian countries located deep in the interior of Asia with fragile ecological environments and lower agricultural technology are particularly more prone to severe threats from climate *** on panel data acquired in five Central Asian countries from 1990 to 2019,a C-D-C model was developed to study how climate change affects food security in the region and to predict future *** study found that the level of food security has generally increased for these five Central Asian countries over the past 30 years,with Kazakhstan and Tajikistan having the highest and lowest food security levels,*** average annual temperature and precipitation exhibit an inverted U-shaped relationship with the region’s food security,with the most positive effect on the food security of *** high and low temperatures have significantly affected food security in the studied region,with Turkmenistan experiencing the most significant negative *** number of frost days had no significant effect on food *** analysis of future climate showed that the temperature and precipitation in Central Asia will continue to increase from 2030 to 2090,which will negatively impact the food security of these *** is recommended that the Central Asian countries enhance their understanding of climate risks,strengthen scientific climate research,and develop multiple adaptation strategies in ***,they are encouraged to consolidate international cooperation,reducing greenhouse gas emissions effectively and maintaining the ability to ensure food security.

关键词： Global warming Extreme climate Food security Future forecasts Five Central Asian countries

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Cu,N codoped carbon nanosheets encapsulating ultrasmall Cu nanoparticles for enhancing selective 1,2-propanediol oxidation

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Journal of Energy Chemistry 2024年第4期91卷 27-35页

作者： Yonghai Feng Min yu Minjia Meng Lei liu Dewei Rao Institute for Advanced Materials School of Materials Science and EngineeringJiangsu UniversityZhenjiang 212013JiangsuChina School of Chemistry and Chemical Engineering Jiangsu UniversityZhenjiang 212013JiangsuChina

In the selective oxidation of biomass-based 1,2-propanediol(PDO)with oxygen as the terminal oxidant,it is challenging to improve the lactic acid(LA)selectivity for nonnoble metal nanoparticles(NPs)due to their limited oxygen reduction rate and easy C-C *** the high economic feasibility of nonnoble metals,i.e.,Cu,in this work,copper and nitrogen codoped porous carbon nanosheets encapsulating ultrafine Cu nanoparticles(Cu@Cu-N-C)were developed to realize highly selective of PDO oxidation to *** carbon-encapsulated ultrasmall Cu^(0)NPs in Cu@Cu-N-C have high PDO dehydrogenation activity while N-coordinated Cu(Cu-N)sites are responsible for the high oxygen reduction ***,the performance of catalytic PDO conversion to LA is optimized by a proposed pathway of PDO→hydroxylacetone→lactaldehyde→***,the enhanced LA selectivity is 88.5%,and the PDO conversion is up to 75.1%in an O_(2)-pressurized reaction system(1.0 MPa O_(2)),superior to other Cu-based catalysts,while in a milder nonpressurized system(O_(2)flow rate of 100 mL min-1),a remarkable LA selectivity(94.2%)is obtained with 39.8%PDO conversion,2.2 times higher than that of supported Au nanoparticles(1%Au/C).Moreover,carbon encapsulation offers Cu@Cu-N-C with strong leaching resistance for better recycling.

关键词： Selective oxidation Copper and nitrogen doped carbon 1,2-Propanediol Ultrasmall Cu nanoparticles Lactic acid

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Atomic Ni directional-substitution on ZnIn_(2)S_(4) nanosheet to achieve the equilibrium of elevated redox capacity and efficient carrier-kinetics performance in photocatalysis

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Journal of Energy Chemistry 2024年第1期88卷 272-281,I0007页

作者： Haibin Huang Guiyang yu Xingze Zhao Boce Cui Jinshi yu Chenyang Zhao Heyuan liu Xiyou Li School of Materials Science and Engineering China University of Petroleum(East China)Qingdao 266580ShandongChina Key Laboratory of Optic-electric Sensing and Analytical Chemistry for Life Science(MOE) College of Chemistry and Molecular EngineeringQingdao University of Science and TechnologyQingdao 266042ShandongChina College of New Energy China University of Petroleum(East China)Qingdao 266580ShandongChina

It is a challenge to coordinate carrier-kinetics performance and the redox capacity of photogenerated charges synchronously at the atomic level for boosting photocatalytic ***,the atomic Ni was introduced into the lattice of hexagonal ZnIn_(2)S_(4) nanosheets(Ni/ZnIn_(2)S_(4))via directionalsubstituting Zn atom with the facile hydrothermal *** electronic structure calculations indicate that the introduction of Ni atom effectively extracts more electrons and acts as active site for subsequent reduction *** the optimized light absorption range,the elevation of Efand ECBendows Ni/ZnIn_(2)S_(4) photocatalyst with the increased electron concentration and the enhanced reduction ability for surface ***,ultrafast transient absorption spectroscopy,as well as a series of electrochemical tests,demonstrates that Ni/ZnIn_(2)S_(4) possesses 2.15 times longer lifetime of the excited charge carriers and an order of magnitude increase for carrier mobility and separation efficiency compared with pristine ZnIn_(2)S_(4).These efficient kinetics performances of charge carriers and enhanced redox capacity synergistically boost photocatalytic activity,in which a 3-times higher conversion efficiency of nitrobenzene reduction was achieved upon Ni/ZnIn_(2)S_(4).Our study not only provides in-depth insights into the effect of atomic directional-substitution on the kinetic behavior of photogenerated charges,but also opens an avenue to the synchronous optimization of redox capacity and carrier-kinetics performance for efficient solar energy conversion.

关键词： ZnIn_(2)S_(4) Substitution Carrier kinetics Redox capacity Photocatalysis

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Suppression of current-induced membrane discharge of bipolar membranes by regulating ion crossover transport

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Journal of Energy Chemistry 2024年第9期96卷 387-395页

作者： Tingting yu Haolan Tao Jingkun Li Cheng Lian Honglai liu State Key Laboratory of Chemical Engineering Shanghai Engineering Research Center of Hierarchical NanomaterialsSchool of Chemical EngineeringEast China University of Science and TechnologyShanghai 200237China School of Chemistry and Molecular Engineering East China University of Science and TechnologyShanghai 200237China

Bipolar membranes(BPMs)exhibit the unique capability to regulate the operating environment of electrochemical system through the water dissociation-combination ***,the industrial utilization of BPMs is limited by instability and serious energy *** current-induced membrane discharge(CIMD)at high-current conditions has a negative influence on the performance of anion-exchange membranes,but the underlying ion transport mechanisms in the BPMs remain ***,the CIMD-coupled Poisson-Nernst-Planck(PNP)equations are used to explore the ion transport mechanisms in the BPMs for both reverse bias and forward bias at neutral and acid-base *** is demonstrated that the CIMD effect in the reverse-bias mode can be suppressed by enhancing the diffusive transport of salt counter-ions(Na^(+)and Cl^(−))into the BPMs,and that in the forward-bias mode with acid-base electrolytes can be suppressed by matching the transport rate of water counter-ions(H_(3)O^(+)and OH^(−)).Suppressing the CIMD can promote the water dissociation in the reverse-bias mode,as well as overcome the plateau of limiting current density and reduce the interfacial blockage of salt co-ions(Cl^(−))in the anion-exchange layer in the forward-bias mode with acid-base *** work highlights the importance of regulating ion crossover transport on improving the performance of BPMs.

关键词： Bipolar membranes Current-induced membrane discharge Salt ion crossover Diffusion-migration-reaction process

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