检索结果-南通市图书馆

Cooperative effects of Mo,V and Zr additions on the microstructure and properties of multi-elemental Nb-Si based alloys

在线全文

维普期刊数据库

学校读者我要写书评

暂无评论

Journal of materials Science & Technology 2023年第1期132卷 27-41页

作者： Rui Ma Xiping Guo State Key Laboratory of Solidification Processing Northwestern Polytechnical UniversityXi’an 710072China

Eight multi-elemental Nb-Si-based alloys with various Mo,V and Zr contents were prepared by vacuum non-consumable arc melting.The cooperative alloying effects of Mo,V and Zr on the arc-melted and heat-treated microstructure,mechanical properties as well as oxidation resistance at 1250°C of the alloys were evaluated systematically.The results show that except for adding Mo solely,additions of Mo,V and Zr change the microstructure from eutectic to hypereutectic.The additions of Mo,V and Zr suppress the formation ofα(Nb,X)5 Si 3(“X”represents the alloying elements that substitute for Nb in the lattices),whilst promoting the formation ofγ(Nb,X)5 Si 3.The heat treatment at 1450°C for 50 h promotes the formation of(Nb,X)3 Si phase in the Zr-containing alloys.Alloying with either Mo or Zr improves,and their composite additions more obviously improve the compressive yield strength at 1250°C as well as the microhardness ofγ(Nb,X)5 Si 3.The room temperature fracture toughness of the alloys is enhanced by sole and composite additions of V and Zr,while it is deteriorated by the addition of Mo.The sole addition of Mo,V or Zr improves the oxidation resistance at 1250°C,the composite additions of V with Mo/Zr(especially V-Mo-Zr)degrade the oxidation resistance at 1250°C.

关键词： Multi-elemental Nb-Si based ultrahigh temperature alloy Alloying effect Microhardness Room temperature fracture toughness High-temperature compressive yield strength Oxidation resistance

在线全文

维普期刊数据库

学校读者我要写书评

暂无评论

设计师马蕊

传播力研究 2020年第7期4卷 F0002-F0002页

作者： Rui Ma 不详

美国硕士毕业,高级设计师马蕊,来自中国哈尔滨。2008年由哈市六中考入北京航空航天大学"新媒体艺术设计专业"。毕业以后又很幸运的被美国罗彻斯特理工大学影像艺术与科学学院"平面设计硕士专业"录取。2015年硕士研究生毕业即进入Sid Le... 详细信息

美国硕士毕业,高级设计师马蕊,来自中国哈尔滨。2008年由哈市六中考入北京航空航天大学"新媒体艺术设计专业"。毕业以后又很幸运的被美国罗彻斯特理工大学影像艺术与科学学院"平面设计硕士专业"录取。2015年硕士研究生毕业即进入Sid Lee公司从事她心爱的设计工作。在公司高级专家精心培育下,马蕊通过自身的不懈努力,现在已由一个初出校门的见习设计师成长为优秀的高级设计师。

关键词：硕士研究生罗彻斯特艺术与科学新媒体艺术设计硕士毕业平面设计北京航空航天大学设计师

Springs Emerging along the Elevation Gradient Indicate Intensive Groundwater-Surface Water Exchange in an Alpine Headwater Catchment, Northwestern China

在线全文

维普期刊数据库

学校读者我要写书评

暂无评论

Journal of Earth Science 2023年第1期34卷 181-193页

作者： Yalu Hu Ziyong Sun Rui Ma School of Environmental Studies China University of GeosciencesWuhan430078China Laboratory of Basin Hydrology and Wetland Eco-Restoration China University of GeosciencesWuhan430078China State Environmental Protection Key Laboratory of Source Apportionment and Control of Aquatic Pollution Ministry of Ecology and EnvironmentWuhan430078China Hubei Key Laboratory of Yangtze Catchment Environmental Aquatic Science China University of GeosciencesWuhan430078China

Groundwater plays an important role in sustaining the streamflow in cold alpine area, but is poorly understood due to a lack of direct access. About 98 groups of springs are observed at the upper reaches of Heihe River Basin, which provide an opportunity to explore the main aquifers. Springs are clustered in three groups according to locations:(1) springs on the moraine and talus deposits;(2) springs at the end of alluvial plain in lower topography;(3) springs along the river bank. The hydrometric, geochemical and isotopic data of springs in a representative catchment were integrated and used to elucidate the groundwater flow paths. Results indicate the Quaternary porous aquifers in the alpine catchment have a profound influence on the regional groundwater flow paths and the groundwater and surface water(GW-SW) interactions. The aquifer consisting of alluvial-pluvial deposits has a great capacity of groundwater storage and plays a vital role in regulating discharge by attenuating the seasonal variation and maintaining the main stream in cold seasons. This is different from the fast recharge and discharge mode of the moraine and talus deposits. Our work highlights the importance of loose deposits in controlling the GW-SW interactions in the cold alpine area.

关键词： springs alpine catchments groundwater groundwater-surface water interactions alluvial plain

Effect of Crystallization and Entropy Contribution Upon the Mechanical Response of Polymer Nano-fibers:A Steered Molecular Dynamics Study

在线全文

学校读者我要写书评

暂无评论

Chinese Journal of Polymer Science 2023年第3期41卷 465-474,I0011页

作者： Rui Ma Dan Xu Chuan-Fu Luo Xinjiang Laboratory of Phase Transitions and Microstructures in Condensed matters College of Physical Science and TechnologyYili Normal UniversityYining 835000China State Key Laboratory of Polymer Physics and Chemistry Changchun Institute of Applied ChemistryChinese Academy of SciencesChangchun 130022China University of Science and Technology of China School of Applied Chemistry and EngineeringHefei 230026China

The mechanical response of polyethylene nano-fibers with the same chain length but different chain numbers are studied by using steered molecular dynamics simulations.The shrinking or stretching forces acted on the chain ends are investigated according to the chain-end distance and temperature under isothermal or continuous warming-cooling conditions,respectively.An inflection point is found in the ForceDistance response when temperature is below 500 K.This inflection point is related to the balance between entropy force and inter-monomer interaction and it reflects the strong effect of crystallization on the mechanical response of the nano-fibers.The force at inflection point is also affected by the buckling effect due to increased stiffness when crystallization occurs.The two stages found in the Force-Temperature response and the difference between the shrinking and stretching forces indicate the hysteresis of crystallization and melting.The forces at different shrinking and stretching rates reveal the entropy contribution upon the mechanical response,indicated by the Ramachandran plot of dihedrals.The chain-conformation entropy is majorly contributed by dihedrals and is quantified by the information entropy of dihedrals,which has a highly similarity to the mechanical Force-Temperature response.The enlarged forces in multiple chains over a single chain are attributed to the enhanced dihedral-conformation entropy.Our study provides a new insight to the dynamically mechanical response of polymer nano-fibers according to the effect of crystallization and entropy contribution.

关键词： Polymer fibers Crystallization Entropy contribution Mechanical response

Assessing urban resilience to public health disaster using the rough analytic hierarchy process method:A regional study in China

在线全文

学校读者我要写书评

暂无评论

Journal of Safety Science and Resilience 2022年第2期3卷 93-104页

作者： Zezhao Liu Rui Ma HuiJia Wang School of Public Administration and Sociology Jiangsu Normal UniversityXuzhou 221116China School of Government Nanjing UniversityNanjing 210023China People’s Procuratorate in Tongshan District Xuzhou 221116China

In the context of frequent occurrences of disasters worldwide,disaster-coping capability is imperative for risk reduction and contemporary emergency management.The global COVID-19 pandemic since 2020 has further highlighted the significance of resilience construction at different geographical scales.Overall,the conceptual cognition of resilience in disaster management covers multiple elements and has diverse yielding on regional assessment.This study assesses the local resilience to the public health disaster in the prefecture-level cities,focusing on two dimensions consisting of vulnerability and capability in the targeted provincial region of Jiangsu in China.To this end,based on the vulnerability-capability framework,the Rough Analytic Hierarchy Process(Rough AHP)method was applied to the resilience assessment.Drawing upon the criteria derived from literature,the criteria weights were determined with the RAHP method and we assessed urban resilience with census data.In addition,the hierarchical factors contributing to urban resilience were determined using robustness analysis.This research provides constructive ideas for regional disaster reduction and contributes to the government’s capability to improve urban resilience.

关键词： Urban resilience Vulnerability-capability Public health disaster Rough Analytic Hierarchy Process Jiangsu Province China

Optimal Dispatch for Battery Energy Storage Station in Distribution Network Considering Voltage Distribution Improvement and Peak Load Shifting

在线全文

维普期刊数据库

学校读者我要写书评

暂无评论

Journal of Modern Power Systems and Clean Energy 2022年第1期10卷 131-139页

作者： Xiangjun Li Rui Ma Wei Gan Shijie Yan State Key Laboratory of Control and Operation of Renewable Energy and Storage Systems China Electric Power Research InstituteBeijingChina College of Information and Engineering Northeastern UniversityShenyangChina

Distribution networks are commonly used to demonstrate low-voltage problems.A new method to improve voltage quality is using battery energy storage stations(BESSs),which has a four-quadrant regulating capacity.In this paper,an optimal dispatching model of a distributed BESS considering peak load shifting is proposed to improve the voltage distribution in a distribution network.The objective function is to minimize the power exchange cost between the distribution network and the transmission network and the penalty cost of the voltage deviation.In the process,various constraints are considered,including the node power balance,single/two-way power flow,peak load shifting,line capacity,voltage deviation,photovoltaic station operation,main transformer capacity,and power factor of the distribution network.The big M method is used to linearize the nonlinear variables in the objective function and constraints,and the model is transformed into a mixed-integer linear programming problem,which significantly improves the model accuracy.Simulations are performed using the modified IEEE 33-node system.A typical time period is selected to analyze the node voltage variation,and the results show that the maximum voltage deviation can be reduced from 14.06%to 4.54%.The maximum peak-valley difference of the system can be reduced from 8.83 to 4.23 MW,and the voltage qualification rate can be significantly improved.Moreover,the validity of the proposed model is verified through simulations.

关键词： Energy storage station distribution network voltage regulation peak load shifting mixed integer programming

Assessing the Connectivity of a Regional Fractured Aquifer Based on a Hydraulic Conductivity Field Reversed by Multi-Well Pumping Tests and Numerical Groundwater Flow Modeling

在线全文

学校读者我要写书评

暂无评论

Journal of Earth Science 2023年第6期34卷 1926-1939页

作者： Jingjing Lin Rui Ma Ziyong Sun Liansong Tang School of Environmental Studies State Key Laboratory of Biogeology and Environmental GeologyChina University of GeosciencesWuhan 430078China Yangtze River Basin Ecological Environment Monitoring and Scientific Research Center Yangtze River Basin Ecological Environment Supervision and Administration BureauMinistry of Ecological EnvironmentWuhan 430010China

Aquifer connectivity could greatly affect groundwater flow and further control the contaminant transport in fractured medium.However,assessing connectivity of fractured aquifer at regional scales is still a challenge because such connectivity is difficult to be measured directly.This study proposes a framework for assessing connectivity of a fractured aquifer,with Qitaihe area,Heilongjiang Province,northeastern China as an illustrating study area.The 3-D finite difference numerical models were established to interpret the results of three multi-well pumping tests and inversely estimate the distribution of hydraulic conductivity(K)in the fractured aquifer.A static connectivity metric of the minimum hydraulic resistance(MHR)was calculated,based on the optimized K-field,to evaluate the hydraulic connectivity in the aquifer,and the corresponding least resistance paths(LRPs)were identified.The results indicate a better horizontal connectivity in the fractured aquifer in the northeastern and middle parts than in the southwestern part of the study area.The identified LRP indicated that the preferential flow channels at regional scales were controlled mainly by aquifer connectivity instead of local high-K zones.The results of this study can provide a method for aquifer connectivity estimation at regional scales.

关键词： numerical modeling aquifer connectivity groundwater flow hydraulic conductivity minimum hydraulic resistance least resistance paths

Within-day travel speed pattern unsupervised classification——A data driven case study of the State of Alabama during the COVID-19 pandemic

在线全文

学校读者我要写书评

暂无评论

Journal of Traffic and Transportation Engineering(English Edition) 2021年第2期8卷 170-185页

作者： Niloufar Shirani-bidabadi Rui Ma Michael Anderson Connecticut Transportation Institute University of ConnecticutStorrs-MansfieldCT 06269USA Department of Civil and Environmental Engineering University of Alabama in HuntsvilleHuntsuilleAL 35899USA

Recent comparative studies on mobility patterns are emerging to describe the changes in mobility patterns due to the COVID-19 pandemic.Most of the current studies utilize travel volume per day as the critical indicator and identify the impacted period by the dates of governmental lockdown or stay-at-home orders,which however may not accurately present the actual impacted dates.The objective of this study is to provide an alternative perspective to identify the normal and pandemic-influenced daily traffic patterns.Instead of only using traffic volumes per day or assuming the impacted travel pattern began with the stay-at-home order,the methodology in this study investigates the within-day timedependent travel speed as time series,and then applies dynamic time warping algorithm and hierarchical clustering unsupervised classification methods to classify days into various groups without assuming a start date for any group.Using the state-wide travel speed data in Alabama,these study measures dissimilarities among within-day travel speed time series.By incorporating the dissimilarities/distance matrix,various agglomerative hierarchical clustering(AHC)methods(average,complete,Ward’s)are tested to conduct proper unsupervised classification.The Ward’s AHC classification results show that within-day travel speed pattern in Alabama shifted more than two weeks before the issuance of the State stay-at-home order.The results further show that a new travel speed pattern appears at the end of stay-at-home order,which is different from either the normal pattern before the pandemic or the initial pandemic-influenced pattern,which leads to a conclusion that a’new normal’within-day travel pattern emerges.

关键词： COVID-19 Within-day traffic dynamics Dynamic time warping Hierarchical clustering Unsupervised classification

Willingness of the General Public to Receive the COVID-19 Vaccine During a Second-Level Alert——Beijing Municipality,China,may 2020

在线全文

学校读者我要写书评

暂无评论

China CDC weekly 2021年第25期3卷 531-537页

作者： Rui Ma Luodan Suo Li Lu Xinghuo Pang Division of Expanded Program of Immunization(EPI) Beijing Center for Disease Control and Prevention/Beijing Center for Preventive Medicine ResearchBeijingChina

Summary What is already known on this topic?Preclinical trials showed the effectiveness of domestic inactivated vaccine candidates for coronavirus disease 2019(COVID-19).However,it is necessary to evaluate the willingness of the public to receive future domestic vaccines and to understand factors associated with willingness at the early stages of vaccine development.

关键词： COV Public Summary