Effect of Ni-coated MoS2 on microstructure and tribological properties of(Cu−10Sn)-based composites

The(Cu−10Sn)−Ni−MoS2 composites,prepared by powder metallurgy,were studied for the effects of Ni-coated MoS2 on the microstructure,mechanical properties and lubricating properties.The mechanism of effects of Ni and MoS2 on the properties of composites was analyzed through a comparative experiment by adding Ni and MoS2 separately.The results show that the nickel wrapping around the MoS2 particles decreases the reaction rate of MoS2 with the copper matrix,and greatly improves the bonding of the matrix.The composites with 12 wt.%Ni-coated MoS2(C12)show the optimum performance including the mechanical properties and tribological behaviors.Under oil lubrication conditions,the friction coefficient is 0.0075 with a pressure of 8 MPa and a linear velocity of 0.25 m/s.The average dry friction coefficient,sliding against 40Cr steel disc,is measured to be 0.1769 when the linear velocity and pressure are 0.25 m/s and 4 MPa,respectively.

Machine learning technique for prediction of magnetocaloric effect in La(Fe,Si/Al)_(13)-based materials

Data-mining techniques using machine learning are powerful and efficient for materials design, possessing great potential for discovering new materials with good characteristics. Here, this technique has been used on composition design for La（Fe,Si/Al）（13）-based materials, which are regarded as one of the most promising magnetic refrigerants in practice. Three prediction models are built by using a machine learning algorithm called gradient boosting regression tree（GBRT） to essentially find the correlation between the Curie temperature（TC）, maximum value of magnetic entropy change（（？SM）（max））,and chemical composition, all of which yield high accuracy in the prediction of TC and（？SM）（max）. The performance metric coefficient scores of determination（R^2） for the three models are 0.96, 0.87, and 0.91. These results suggest that all of the models are well-developed predictive models on the challenging issue of generalization ability for untrained data, which can not only provide us with suggestions for real experiments but also help us gain physical insights to find proper composition for further magnetic refrigeration applications.

Comparative study of the fabrication of ultrafine Ti(C,N)-based cermets by spark plasma sintering and conventional vacuum sintering

Spark plasma sintering (SPS) and conventional vacuum sintering (VS) wereemployed to fabricate ultrafine Ti(C,N)-based cermets. The shrinkage behavior, microstracture, andporosity and mechanical properties of the samples fabricated by SPS were compared with those of thesamples sintered by VS using optical microscopy, scanning electron microscopy, universal testingmachine, and rockwell tester. The results are as follows: (1) The shrinkage process occurred mainlyin the range of 1000-1300 deg C during the VS process, and only a 0.2 percent linear shrinkage ratioappeared below 800 deg C; during the SPS process, a 60 percent dimensional change occurred below800 deg C as a result of pressure action. (2) By utilizing the SPS technique, it is difficult forobtaining fully dense Ti(C,N)-based cermets. Due to the much existence of pores and un-combinedcarbon, the mechanical properties of the sintered samples by SPS are inferior to sintered ones byVS. (3) grain size of the samples sintered by SPS is still below 0.5 urn, but not by VS; because oflow sintering temperature, there are no typical core/rim structures formed in the sintered samplesby SPS1; the main microstructures of the sintered samples by SPS2 are a white core/grey shellstructure, whereas by VS show a typical black core/grey shell structure.

A review on WO_(3)-based composite photocatalysts:synthesis,catalytic mechanism and diversified applications

Photocatalysis as an emerging "green" energy conversion technology has attracted domestic and international attention.This technology uses semiconductor photocatalysts to convert solar energy into directly usable chemical energy,showing great potential for application in environmental pollutant purification and clean energy production,with broad development prospects.Among many semiconductor materials,tungsten trioxide(WO_(3)) is favored by researchers in the field of photocatalysis because of its good visible light response and excellent valence band hole oxidation properties.Currently,a large number of photocatalysts based on WO_(3),in particular W03-based composite photocatalysts,have been reported,and their applications cover a wide range of fields.In order to promote the development of WO_(3)-based photocatalysts and provide a reference for colleagues,we present a systematic summary of the applications and research progress of W03-based composites in the field of photocatalysis in recent years.Starting from the structural properties of WO_(3)itself,this article summarizes the preparation methods and structure-activity relationships of WO_(3)-based composite photocatalysts.Subsequently,it introduces the current application status of existing WO_(3)-based composite photocatalysts in CO_(2) reduction,hydrogen production,nitrogen fixation,and pollutant removal.Finally,the development prospects were analyzed.

Gas sensors based on TiO_(2) nanostructured materials for the detection of hazardous gases: A review

Hazardous gases have been strongly associated with being a detriment to human life within the environment The development of a reliable gas sensor with high response and selectivity is of great signifcance for detecting different hazardous gases.TiO_(2) nanomaterials are promising candidates with great potential and excellent per-formance in gas sensor applications,such as hydrogen,acetone,ammonia,and ethanol detection.This review begins with a detailed discussion of the di ferent dimensional morphologies of TiO_(2),whitch affect the gas sensing performance of TiO_(2) sensors.The diverse morphologies of TiO_(2) can easily be tuned by regulating the manufacturing conditions.Meanwhile,they exhibit unique characteristics for detecting gases,including large specific suface area,superior elecron tr ansport rates,extraordinary pemmeability,and active reaction sites,which offer new opportunities to improve the gas sensing properties.In addition,a variety of efforts have been made to functional TiO_(2) nanomaterials to further enhance sensing properties,including TiO_(2)-based composites and light-assisted gas sensors.The enhanced gas sensing mechanisms of multi-component composite nano-materials based on TiO_(2) include loaded noble metals,doped elements,constructed heterojunctions,and com-pounded with other functional materials.Finally,several studies have been summarized to demonstate the compar ative sensing properties of TiO_(2)-based gas sensors.

HIGH TEMPERATURE COMPOSITES

The purpose of this paper is to review the current state of development of new composite materials for advanced aircraft engines. The advantages and disadvantages of Ti-base.NiAl-base, and MoSi_2-base composites as replacements for today's Ni-base superalloys are discussed from the standpoint of key technical issues. current status, and future directions. Results describing progress in both improved understanding of the mechanisms of deformation and fracture, and improved material performance will be covered.

A Review on Metal-support Interaction in Automotive Catalysts

TWC-equipped exhausts are widely used in gasoline-fueled vehicles to meet stringent emission regulations. The main components in TWCs are precious metals such as palladium (Pd), platinum (Pt), and rhodium (Rh) as the active component, and inorganic oxides such as γ-alumina (Al 2 O 3 ), ceria (CeO 2 ), zirconia (ZrO 2 ) and ceria-zirconia (CeO 2-ZrO 2 ) are used as the support. Interaction of precious metals and support plays an important role in the thermal stability and catalytic performance of TWCs. The support can improve the dispersion of precious metals and suppress the sintering of precious metals at high temperature. In the same, precious metals can also enhance the redox performance and oxygen storage capacity of support. This paper reviews the reaction phenomenon and mechanism of precious metals (Pt, Pd, Rh) and supports such as Al 2 O 3 , CeO 2-based composite oxides.

企业境内外双循环的动态复合过程机理

从中国传统哲学深蕴的整体观与动态观出发,围绕国际化企业发展中固有的辩证性矛盾,将“境外所得”添入已有的四要素分析框架中,考察系统要素之间相生与相克关系交织中如何构成化生、催化的三元循环并结合为负反馈特性的四元循环,揭示国内大循环自主可控的稳定性之源;通过历时性考察识别出与境内循环既对立又统一的境外循环,并构建反映内—外循环“阴阳交五”的动态过程模型。借鉴动态系统观,把复合基础观拓展为动态复合观,阐明并深入解释了双循环系统以“8”字形轨迹运行的理论机制。本文尝试构建具有特色的中国式管理理论,加深了“以国内循环为主体”向“国内国际双循环相互促进”演进过程的认识,为国际化企业打通境内外循环和形成独特发展路径提供了学理依据。

VUCA时代本土管理情境特征的结构化演化研究

管理学科的实践属性决定了管理理论具有较强的时空情境依赖特征。本土情境作为中国企业成长不可分割的基本载体,也是促进管理理论与特色实践交融共生的底层影响要素。鉴于当前普遍存在“西方理论难适用”与“本土理论难开发”的共性问题,背后均指向对本土情境认知的泛化、碎片化、静态化等问题。本文通过对VUCA时代本土管理情境特征的结构化梳理,刻画了本土情境演变的动态谱系和情境要素间的复杂组合,由此呈现出兼具静态与动态、时间与空间、单一要素与多元组合等多维视角下的复合情境观。进而,在促进本土情境认知结构从离散化、架构化向谱系化与组合化演进的同时,研究进一步探索了复合情境观在本土管理理论建构过程中的嵌入角色与作用。通过明确时空情境敏感性下的“新背景-新过程”双维问题筛选机制,厘清本土情境在理论研究过程中的“嵌入”与“涤除”平衡策略,推动本土管理理论研究走向兼顾“本土特色”与“整体普适”的深度情境化阶段。

初始缺陷对非均质SFRCC单向受拉特性影响细观分析

初始缺陷会对钢纤维增强水泥基复合材料(SFRCC)的力学性能产生较大影响。通过参数化语言,建立了由钢纤维、水泥砂浆基体及界面过渡区构成的二维SFRCC模型,布置了界面、砂浆、表面和三处同时存在的四种初始缺陷类型,并结合Weibull分布函数建立非均质模型,模拟了不同初始缺陷下非均质SFRCC试件单轴拉伸破坏的过程。结果表明:不同类型初始缺陷对不同平均方向效应系数SFRCC材料抗拉强度影响程度不同;探究了不同类型初始缺陷对SFRCC材料细观单元力学性能的影响;揭示了非均质SFRCC材料存在不同初始缺陷时的拉伸损伤过程及破坏机理。

MoS2-based anode materials for lithium-ion batteries:Developments and perspectives

In recent years,significant progress has been achieved in the creation of innovative functional materials for energy storage and conversion.Due to their distinct physicochemical characteristics,ultrathin nanosheets composed of common layered transition metal sulfide materials(MoS2)have demonstrated promise as high-capacity anode materials for lithium-ion batteries(LIBs).Nevertheless,their practical application is severely limited by the tendency of monolayer nanosheets to restack due to strong van der Waals forces,dramatic volume changes during successive cycles,and low intrinsic conductivity.Recent research advances have shown that composite structures and nanowire morphologies with specific morphologies effectively overcome these issues.This paper reviews the recent research progress on molybdenum disulfide-based composites as anode materials for LIBs and discusses in detail the struc-tural characteristics of pure molybdenum disulfide and other composite forms of molybdenum disulfide.In addition,the phase engineering,defect engineering,and lithium storage mechanisms of molybdenum disulfide and the synthesis of molybdenum disulfide-based nanocomposites by different preparation methods are focused on.Finally,we review the design(structure),recent developments,and challenges of novel anode materials and consider their electrochemical performance in Li-ion batteries.

观演建筑空间复合化设计研究

随着人们审美标准的变化,传统观演建筑已无法满足多样化的文化活动和观众体验的需求,需对观演建筑进行空间复合化设计。基于此,文章以建筑空间复合化设计为研究对象,分析观演建筑功能组成,并从空间布局设计、使用时间复合化设计及科技应用设计等方面入手,优化观演建筑空间复合化设计,以期打造出符合当代人们观演需求的建筑。

基于数据服务的数据组合视图的优化更新

数据服务为实现跨域数据集成提供了统一的数据模型,并且可通过组合的方式支持用户定义数据视图,当底层的数据服务发生数据更新时,数据更新需要自下而上经过多个中间复合数据服务传播到顶层的数据视图.一类挑战性问题是,如何在这个传播的过程中保障数据视图的更新效率.为此,文中规范化数据服务的操作及其性质,并且根据用户的组合结果,通过复合数据服务的等价变换,生成运行效果相同的多种数据服务组合方案.同时,建立复合数据服务的更新代价模型,该模型能够利用底层数据服务的更新频率和请求频率,衡量复合数据服务的更新代价.基于该模型,文中提出最小化更新代价的数据视图的更新优化算法,利用该算法可以为用户推荐优化的数据服务组合方案.实验表明,该方法能够提高数据视图的更新效率.

中国物流企业成长的战略思路研究——基于复合基础观的新视角

现有关于"企业成长"的研究主要包括企业外生成长论和企业内生成长论,文章认为现有研究对"企业成长"的认识并没有摆脱"资源基础观"的窠臼。以此为切入点,通过引入"复合基础观"的视角,构建了基于复合式能力、复合式提供和复合式竞争的中国物流企业成长的理论框架。进而,依托复合基础观提出了中国物流企业成长的战略思路,中国物流企业成长的范式转变:资源基础观转变为复合基础观;中国物流企业成长的思维转变:独占思维转变为整合思维;中国物流企业成长的创新转变:被动创新转变为主导创新;中国物流企业成长的方式转变:单独成长转变为协同成长。

一种用户为中心、基于多视图合成的服务组合方法

用户为中心的服务组合旨在直接地反映用户需求、提高建模灵活性和降低应用构建成本.然而,当前的用户编程方法仍然存在挑战:一方面传统方法以服务为基本元素,忽视了应用背后的业务数据,用户难以从熟知的业务数据角度表达建模需求;另一方面传统方法以控制流为中心,需要精确描述组合细节,非专业的用户不易理解和操作且难以表达业务约束.文中提出一种用户为中心、基于多视图合成的服务组合方法,通过体征数据模型显式建模业务数据,将服务组合的需求转化为在多个视图编程操作;并给出一种候选流程的构造算法,参照用户的视图操作合成服务组合流程.案例和实验分析表明,文中方法可降低用户构造服务组合的复杂性并提高建模的效率.

一种光栅普适的LCD多视点立体图像合成方法

多视点立体图像合成很大程度上取决于多视点立体显示设备的类型。当前,基于光栅的LCD多视点自由立体显示设备最为常见,但目前缺乏针对这类显示器的通用合成方法。因此,提出了一种通用的多视点立体视频图像合成新方法,主要分为子像素判断准则、各视点子像素的子采样、子像素排列合成三部分。该方法从原理上考虑了光栅LCD多视点自由立体显示的各种可能情况,具有普适性和实用价值。通过具体实例验证了所提方法的正确性和可行性。

基于X-RESTORE查询XML视图

基于转换 XML文档到关系数据库中进行存储与查询的策略 ,研究了 XML视图查询的有效计算问题 .提出了XML 视图查询的合成重写技术 ,它能够消除视图查询中所有在视图结构上的路径导航操作 ,并将视图查询中所有在原文档结构上的路径导航操作以及所有谓词操作下推到视图定义中去 ,与视图定义中的路径导航操作相结合 ,形成统一的在原文档结构上的路径导航操作 .视图合成重写不仅避免了对视图中不出现在最后结果中的中间 XML 片段的构造 ,而且允许将查询中的所有内存密集型或数据密集型操作尽量下推到关系引擎中去执行 ,从而提高

数据服务依赖图模型及自动组合方法研究

数据服务是一种提供数据资源访问的软件服务,为跨域数据集成提供了统一的数据模型.一类挑战性问题是,如何快速自动组合数据服务并生成满足用户数据需求的数据视图.为此,根据内在的数据依赖关系,将数据服务构建为能够描述全局逻辑结构的数据服务依赖图,将数据组合问题建模为基于依赖图模型的数据服务搜索问题,根据数据需求自动搜索依赖图得到最优的复合数据服务,并通过执行复合数据服务生成可视化数据视图.实验结果表明,所提出的数据服务组合算法具有较高的组合效率和良好的组合质量,并能够准确生成满足用户需求的数据视图.

新型复合多视场光学敏感器及其导航方法

基于利用四面镜结构实现的复合多视场光学敏感器,给出了一种高精度天文导航方法,即通过四面镜同时观测地球、导航星和折射星,利用卫星、地球、恒星之间的位置关系,实现自主导航。通过研究导航量测信息的获取途径,给出了复合多视场光学敏感器的5种实用工作方式。结合卡尔曼滤波算法,建立了自主天文导航的仿真模型,并对5种工作方式进行了仿真与比较。仿真结果表明:双组直接敏感地平与单组间接敏感地平结合的导航方式精度最高,位置精度达到了10 m量级。

基于增量日志的数据组合视图定位更新方法

数据服务作为一种面向跨域异构数据源的统一数据模型,能够将数据资源以服务的形式进行发布,并根据用户的数据需求,通过组合若干个数据服务生成数据组合视图。然而,由于数据源是自治的,当数据发生变化时,如何以最小的代价实时更新数据组合视图是数据服务技术需要解决的关键问题。为此,提出一种基于增量日志的数据组合视图定位更新方法,先根据数据源日志的增量变化获取最新变更数据,然后通过定位属性计算组合视图中差异元组的索引号,并根据变更类型直接对组合视图中的差异元组执行数据更新操作,最终给出了基于日志的更新数据实时获取算法和数据组合视图定位更新算法。在跨域异构电梯数据服务系统中对本更新方法进行了评价,结果表明,当变更元组数量所占比例远小于元组总数或数据组合视图的属性个数较多时,定位更新方法的更新效率比现有方法高。