Role of heterogenous microstructure and deformation behavior in achieving superior strength-ductility synergy in zinc fabricated via laser powder bed fusion

Zinc(Zn)is considered a promising biodegradable metal for implant applications due to its appropriate degradability and favorable osteogenesis properties.In this work,laser powder bed fusion(LPBF)additive manufacturing was employed to fabricate pure Zn with a heterogeneous microstructure and exceptional strength-ductility synergy.An optimized processing window of LPBF was established for printing Zn samples with relative densities greater than 99%using a laser power range of 80∼90 W and a scanning speed of 900 mm s−1.The Zn sample printed with a power of 80 W at a speed of 900 mm s−1 exhibited a hierarchical heterogeneous microstructure consisting of millimeter-scale molten pool boundaries,micrometer-scale bimodal grains,and nanometer-scale pre-existing dislocations,due to rapid cooling rates and significant thermal gradients formed in the molten pools.The printed sample exhibited the highest ductility of∼12.1%among all reported LPBF-printed pure Zn to date with appreciable ultimate tensile strength(∼128.7 MPa).Such superior strength-ductility synergy can be attributed to the presence of multiple deformation mechanisms that are primarily governed by heterogeneous deformation-induced hardening resulting from the alternative arrangement of bimodal Zn grains with pre-existing dislocations.Additionally,continuous strain hardening was facilitated through the interactions between deformation twins,grains and dislocations as strain accumulated,further contributing to the superior strength-ductility synergy.These findings provide valuable insights into the deformation behavior and mechanisms underlying exceptional mechanical properties of LPBF-printed Zn and its alloys for implant applications.

A rolled Mg-8Al-0.5Zn-0.8Ce alloy with high strength-ductility synergy via engineering high-density low angle boundaries

Developing low-cost rolled Mg alloys with both high strength and ductility is desirable,while the improved strength is generally accompanied with decreased ductility.Here,by using rotated hard-plate rolling(RHPR)with a total thickness reduction of~85%,we obtained a Mg-8Al-0.5Zn-0.8Ce(wt.%,AZ80-0.8Ce)alloy with a high strength-ductility synergy,i.e.,the yield strength(YS),ultimate tensile strength(UTS)and elongation-to-failure(EF)are~308 MPa,~360 MPa and~13.8%,respectively.It reveals that the high YS is mainly originated from grain boundary strengthening(~212 MPa),followed by dislocation strengthening(~43 MPa)and precipitation hardening(~25 MPa).It is found that a relatively homogeneous fine grain structure containing a large fraction(~62%)of low angle boundaries(LABs)is achieved in the RHPRed alloy,which is benefit for the high tensile EF value.It demonstrates that LABs have important contributions to strengthening and homogenizing tensile deformation process,leading to the simultaneous high strength and high EF.Our work provides a new insight for fabrication of low-cost high performance Mg alloys with an excellent strength-ductility synergy.

The Description of Oil Displacement Mechanism in Steam Injection of Multi-Field Synergy with Exergy Transfer

Steam injection is a most effective way for improving heavy oil recovery efficiency, and it has academic and practical significance for the mechanism of multi-field synergy oil displacement. Mechanism of “diversified” oil displacement which is obtained by traditional study methods in the exploitation territory of oil and gas fields has both respective roles and mutual cross shortages. To describe and analyze the displacement process of multi-field coupling with exergy transfer can simplify this kind of problem by introducing a unified goal-driving exergy. It needs to use the method of theoretical modeling, numerical simulation and experimental validation to study the basic law of exergy transfer in the oil displacement process of multi-field synergy, make a thorough research for the flooding process of steam injection with exergy transfer theory and reveal the oil displacement mechanism in steam injection of multi-field synergy. Thus the theory instruction and technical support can be provided to improve reservoirs producing degree and extraction ratio.

Study on the Coordination Mechanism Between Higher Vocational Students’Career Development Planning and School Management

The coordination mechanism between the career development planning of vocational students and the management of vocational colleges is an important means to improve the quality of education and students’vocational competitiveness.The application of synergy theory in the field of education emphasizes the interaction and coordination of various elements in the system and pursues the optimization of overall efficiency.Based on the theory of coordination and its relevance to the management of higher vocational colleges,this paper analyzes the current development status and problems of the coordination mechanism and puts forward the strategy of building an efficient coordination mechanism designed to enhance the students’employment competitiveness,promote the all-round development,and provide theoretical and practical support for the reform and development of higher vocational education.

Recycling Spent LiCoO_(2)Battery as a High-efficient Lithiumdoped Graphitic Carbon Nitride/Co_(3)O_(4)Composite Photocatalyst and Its Synergistic Photocatalytic Mechanism

The ever-increasing quantity of spent lithium-ion batteries(LIBs)is both a potential environmental pollutant and a valuable resource.The spent LIBs recycling mainly aimed at the separation of valuable elements.Some issues still exist in these processes such as high energy consumption and complex separation procedures.This study avoided element separation and proposed a facile approach to transform spent LiCoO_(2) electrode into a lithium(Li)-doped graphitic carbon nitride(g-C_(3)N_(4))/Co_(3)O_(4) composite photocatalyst through one-pot in situ thermal reduction.During the thermal process,melamine served as the reductant for LiCoO_(2) decomposition and the raw material for g-C_(3)N_(4) production.Li was in situ doped in g-C_(3)N_(4) and the generated Co_(3)O_(4) was in situ integrated,forming a Li-doped g-C_(3)N_(4)/Co_(3)O_(4) composite photocatalyst.This special composite exhibited an enhanced photocatalytic performance,and its photocatalytic H2 production and RhB degradation rates were 8.7 and 6.8 times higher than those of g-C_(3)N_(4).The experiments combined with DFT calculation revealed that such enhanced photocatalytic efficiency was ascribed to the synergy effect of Li doping and Co_(3)O_(4) integrating,which extended the visible light absorption(450-900 nm)and facilitated the charge transfer and separation.This study transforms waste into a high-efficient catalyst,realizing high-valued utilization of waste and environmental protection.

Optimizing mechanical properties of magnesium alloys by philosophy of thermo-kinetic synergy:Review and outlook

Although several strategies(including grain refinement,texture adjustment,precipitation hardening,etc.)have been verified to effectively improve the mechanical properties of lightweight magnesium(Mg)alloys,considerable efforts are still needed to be made to comprehensively understand the potential mechanisms controlling complex microstructures and deformation behaviors exhibited by the hexagonal close-packed host lattice of Mg,thus assisting the rational design of materials at a more physical level.As the cornerstone of this review,a universal rule,the so-called synergy of thermodynamics and kinetics(i.e.,thermo-kinetic diversity,correlation and connectivity),including a recently proposed theory of generalized stability(GS),is introduced to deepen our understanding on common behaviors in Mg alloys(i.e.,deformations(slip and twining modes),phase transformations(especially for precipitations)and interactions in between)at a new perspective.Guided by the GS theory,typical cases for Mg alloys design are qualitatively evaluated to reemphasize the traditional strengthening and toughening strategies mentioned above and to illuminate their exquisite coordination for breaking through the trade-off relationship between strength and ductility,corresponding to a typical thermo-kinetic pair(i.e.,high driving force(ΔG)-high GS).To produce the Mg alloys with superior strength-ductility balances,the potential capacity of this GS theory for guiding processing path design is discussed,finally。

Gradient microstructure and superior strength-ductility synergy of AZ61 magnesium alloy bars processed by radial forging with different deformation temperatures

Gradient microstructure modification is a cost-efficient strategy for high strength without compromising ductility,which is urgently needed in the fundamental science of engineering materials.In this study,heterogeneous structures of AZ61 alloy bars with anisotropic gradients(with different grain size distributions from the surface to the center)were observed to exhibit strong strength-ductility synergies under different deformation tem peratures.The results reveal that the grain refinement process under mediumlow temperature deformation conditions(≤350℃)consists of four transition stages along the radial direction,i.e.,twin activations and deformation band formations,dislocation cells and pile-ups,ultrafine sub-grains,and randomly orientated quasi-micron grains.Different deformation temperatures have a great influence on twin activations and deformation band formations,and the high temperature can easily provoke the initiation of non-basal slip.The deformation bands were determined as a primary nucleation site due to their highly unstable dislocation hindrance ability.Analysis in combination with the Radial forging(RF)deformation process,the differences of dynamic precipitates can be attributed to microstructural difference and solubility limit of Al at different tem peratures.By summarizing the tensile test results,the sample forged at 350℃exhibited the best strength-ductility synergy,exhibiting the highest elongation(EL)of 23.2%with a 251 MPa yield strength(YS)and 394 MPa ultimate tensile strength(UTS)in center region,and combined with the highest strength value of 256 MPa YS and 420 MPa UTS in the center region,while the EL was slightly degraded to 19.8%.

Enhanced strength-ductility synergy of magnesium alloy fabricated by ultrasound assisted directed energy deposition

Investigations on the fabrication of large-size lightweight Mg alloy components by wire-arc directed en-ergy deposition(DED)are steadily flourishing.Nevertheless,most of these components still suffer from inferior performance due to internal defects and inherent columnar grains.Herein,external ultrasound fields with different powers were successfully introduced into the wire-arc DED of AZ31 Mg alloy.The microstructure,defects,and mechanical properties of the fabricated components were carefully charac-terized and compared.The results show that the external ultrasound fields lead to decreased porosity,complete columnar to equiaxed transition(CET),and enhanced performance.Consequently,the UA90 samples exhibited a remarkable increase of~30%,~45%,and~189%in yield strength,ultimate tensile strength,and elongation,respectively.The dominant mechanisms of enhanced strength-ductility synergy were analyzed in detail.This study thus sheds new light on wire-arc DED of Mg alloy components with excellent performance via external ultrasound fields.

A new high-pressure die casting Mg-Gd-Sm-Al alloy with high strength-ductility synergy

A high-pressure die casting(HPDC)Mg-5Gd-1.5Sm-0.7Al alloy was newly developed and exhibits outstanding strength-ductility synergy,with the yield strength and the tensile elongation to fracture being approximately 200 MPa and 8.5%,respectively.This alloy has two types of a-Mg grains:coarse a_(1)-Mg((46±18)μm)and fine a_(2)-Mg((9.2±2.3)μm)grains,and various Al-GS(GS=Gd and Sm)particles located at grain boundaries while clear solute-atom segregation near grain boundaries with limited or free intermetallic particles.Characterizations using Cs-corrected high-angle annular dark-field scanning transmission electron microscopy(HAADF-STEM)indicate the crystal structures of Al-GS phases.After aging,denseβ'precipitates and chain-shapedβ''-like structures precipitated near grain boundaries while a high density of ultrafineβ''-(Mg,Al)3Sm precipitates and Al-GS clusters formed in grain center.Relatively fine grains,Al-GS primary particles,solute-atom segregation near grain boundaries,and/or multiple precipitates contribute to the high strength of the studied alloy,while the multi-scale a-Mg grains,variety of intermetallic particles but discontinuous skeleton,and the multi-typed precipitated lead to its satisfactory ductility.

Synergistic Effect of Nonionic Surfacants(Nonethoxylated Sorbitan Esters)on Herbicides in Paddy Fields

An uneven herbicide distribution can lead to reduced efficacy,and the release of herbicide residues and their transformation products into the environment through runoff increases their potential use risk.Understanding the water distribution dynamics of commonly used paddy field herbicides,for example,oxadiazon,is imperative for the long-term management of weeds in paddy fields.To clarify the diffusion and sedimentation ability of oxadiazon with the addition of a nonionic surfactant—diffusion and settling agent(DSA)for subsequent commercial use in paddy field water layers,the synergistic mechanisms of DSA with butachlor and bensulfuron-methyl in paddy fields were studied.Bioassays,instrumental analysis and field experiments were conducted in this research to provide a relevant basis for improving the efficacy of paddy field herbicides.The field experiment results indicated that DSA could increase the plant and fresh weight control effects of oxadiazon(450 g a.i.·hm^(-2)),butachlor and bensulfuron-methyl to different degrees.These findings demonstrated that DSA could not only effectively improve oxadiazon diffusion and settling in water layers and significantly increase the control effects of butachlor and bensulfuron-methyl,but also promote crop growth and development to different degrees.

数据跨境流动安全管理协同研究

[目的/意义]数据跨境流动推动了数字经济发展和国际交流合作,探索数据跨境流动安全管理协同问题,有利于维护数据安全和国家安全,促进数据利用体系与能力建设。[方法/过程]运用Nvivo软件,分析我国数据跨境流动安全管理协同存在的问题与产生的原因,基于协同理论和霍尔三维模型,构建数据跨境流动安全管理协同三维模型。[结果/结论]构建以组织协同机制、法制协同机制和资源协同机制3个子机制构成的数据跨境流动安全管理协同机制,并从知识共享、技术实力、文化环境3方面提出数据跨境流动安全管理协同机制运行保障措施,实现数据跨境流动安全管理协同效果。

数据要素在现代经济中引领创新发展的作用机制与挑战

为了深入理解数据要素的概念、特性及其在现代经济中的多重作用,特别是如何通过数据要素乘数效应推动经济创新与发展,通过文献综述和理论探讨,详细分析了数据要素与传统生产要素的相互作用,数据在决策支持、资源优化、创新推动和提高生产效率方面的关键作用,探讨了数据要素应用中的挑战,包括数据安全、隐私保护、数据管理和数据质量等问题。研究发现,数据要素能够显著提升企业和经济体的创新能力和生产效率;通过数据分析和应用,企业可以更好地理解市场需求、优化产品与服务、降低运营成本,并提高决策的精准度。研究表明,面对数据安全和隐私保护等挑战,应该强化数据保护法律政策、建立全面的数据治理框架、鼓励数据的开放共享以及增加对数据技术研发的投资,推动经济的持续健康发展。

食品减盐策略研究进展

高血压及心脑血管疾病等慢性非传染性疾病成为威胁人类的首要危险因素,减少食盐摄入被认为是最经济的预防手段之一。该文首先阐述全球减盐的必要性,然后在介绍人体咸味感受机制的基础上,综述不同研究视角下减盐措施的研究进展,如替代盐、咸味肽及咸味增强肽、其他增咸物质、人体多感官协同、食盐结构优化、食品结构优化、高新加工技术等,并对各减盐措施的应用前景和挑战进行总结,旨在为食品工业的减盐实践提供理论依据。

长江经济带数字经济的减污降碳效应及作用机制研究——基于市级数据的分析

基于2011~2021年长江经济带104个城市的面板数据,采用公式法测算碳污排放强度,运用固定效应模型与机制检验模型,分析数字经济对减污降碳的影响效应及作用机制,构建减污降碳协同效应模型,探究数字经济的减污降碳协同效应与长江经济带减污降碳协同度的时空演变趋势。研究发现,数字经济对长江经济带城市的碳污排放产生显著的抑制作用;能够通过促进产业结构升级、提升绿色技术创新和增强公众环境关注度,促进长江经济带减污降碳的协同治理。

基于“岗课赛证创”五位一体的校企协同金课建设机制研究

建设金课是职业教育“课堂革命”的应有之义,而“岗课赛证创”融通的育人模式则是金课建设的必由之路。基于“岗课赛证创”融通逻辑,梳理“岗课赛证创”五要素在课程建设中的内在关系,揭示职业教育金课课程体系先进性、课程标准高阶性、课程目标创新性、人才评价实效性的内涵;从校企双主体角度构建“岗课赛证创”融通的金课建设机制。通过以岗定课、以赛定标、以创促学、以证促评实现人才培养与需求对接,课程标准与大赛标准匹配,专业教学与双创教育融合,职业证书考核与人才评价融通,最终实现岗位、大赛、双创、证书融入金课五位一体。

以行政协同治理推动区域协同发展——成渝地区双城经济圈协同推进机关事务标准化工作范例

随着区域协同发展政策战略地位的不断提高,区域协同研究正如火如荼,但现阶段学界尚有待阐明区域协同瓶颈之因并提出解决之法及相应的区域协同新机制。本研究试图聚焦于此,在理论层面梳理区域协同瓶颈产生机制与区域协同新机制,并对成渝地区双城经济圈协同推进机关事务标准化工作进行案例分析与问卷调查,在实证层面检验本研究的两个理论框架。案例分析发现,以机关事务为例,成渝地区双城经济圈存在治理尺度差异,这与中央政策调控共同构成协同的内外动机,驱动成渝地区深化合作意愿,卷入区域协同;与此同时,地方保护主义现象在两地机关事务标准化协同工作中亦有所披露,并阻碍了成渝地区双城经济圈建设的协同发展。问卷调查数据进一步验证案例分析结果:推进协同地区加强行政治理协同、推进治理尺度统一具有紧要性,成渝地区双城经济圈建设推进标准化执行助推区域协同发展,标准化的行政治理协同增强了成渝地区双城经济圈协同互信意识,在一定程度上消解行政壁垒和地方保护主义;此外,当前成渝地区双城经济圈建设干部协同卷入的奖惩机制不完善,行政治理协同还需大力推进,两地协同仍有较强的地方本位意识。基于此,本研究认为,地方保护现象是长久以来中国实行区域分治所衍生的治理产物,消弭地方保护主义、强化区域一体化思维成为协同瓶颈破局之必然要求,而基于行政尺度视角出发的行政协同治理则可能通过为地区卷入协同建构与区域空间相适配的治理尺度,从而成为区域协同必然的路径选择。并且,协同是基于时间矢量上不断发展变换的过程,地方政府应当通过牢牢把握不同阶段中区域协同“动机—路径—目的”三核心元素以寻求合理的区域协同合作。

人机决策融合复杂性机理及应用研究

在雷达组网探测群协同运用中,指战员一直难以快速正确地决策构群形态与管控预案,也就带来敏捷构群难与精准管控难问题,制约了空天新威胁的协同探测效能。文中在简述人机决策融合原理与复杂性的基础上,揭示了人机决策融合技术生成协同探测复杂性与破解空天新威胁突防复杂性的机理,建立了人机融合决策在协同探测全过程中的作用模型,设计了生成协同探测复杂性的应用流程,使雷达组网探测群具备“决策优化、构群敏捷、管控精准”等协同探测能力及“设变、知变、应变、求变”智能化博弈能力,能实现“基于任务敏捷构群、基于预案精准管控、基于情景快准微调”的协同探测。

多元协同育人视域下机械类专业创新人才培养的模式探索

分析了当前机械类专业高校教育在创新能力培养方面存在的问题,在多元协同育视域下,分别讨论了校内协同、校企协同、校地协同以及国际协同4种不同的人才创新能力培养模式,通过4种模式的协同并举,有助于高校机械类专业人才创新能力的培养。

边疆民族地区输入型公共卫生安全风险的制度协同治理机制研究

公共卫生安全风险是非传统安全风险的组成部分,一定情况下会威胁到国家总体安全。我国边疆民族地区多处于边境地带,既是境外公共卫生安全风险向国内输入的脆弱性空间,又是防范化解境外公共卫生安全风险的安全屏障。那么,如何有效治理边疆民族地区输入型公共卫生安全风险是当前亟须解决的重要问题。从输入型公共卫生安全风险的生成缘由、影响因素、发展态势等方面分析,边疆民族地区输入型公共卫生安全风险治理需遵循出入境制度、婚育制度、就业制度、反走私制度、公共卫生安全制度与社会公共安全制度。基于协同治理理论,在审视各项制度的基础上,通过制度建设协同、制度运行协同、制度保障协同构建边疆民族地区输入型公共卫生安全风险的制度协同治理机制,为边疆民族地区输入型公共卫生安全风险治理提供可行方案。

退耕区域生态系统服务作用关系尺度效应及分异机制——以安塞区为例

生态系统服务的形成依赖于一定时空尺度上的生态过程。因此,探究生态系统服务在不同空间尺度的特征、关联和效应对于丰富生态系统服务的可持续管理具有重要的理论价值和实践意义。以典型退耕县域安塞区作为研究对象,基于生态模型定量评估了6项重要的生态系统服务,采用相关系数法、双变量空间自相关以及地理探测器揭示了不同空间尺度上生态系统服务作用关系的尺度效应及分异机制。研究结果显示:(1)退耕区域内,生态系统服务之间以协同关系为主,其中调节服务与支持服务的协同关系最强(|r|≥0.5),而权衡关系发生在文化服务与其他服务之间。从时间序列来看,调节服务与支持服务的作用关系较为稳定,在研究期间保持为协同关系,且协同度在退耕还林后有所提升;(2)生态系统服务作用关系的空间尺度效应主要表现在作用关系的方向变化与空间显著性的差异。在网格尺度中,生态系统服务之间的关系较为稳健,作用方向的变化主要发生在网格尺度与行政单元之间,且随研究尺度的加大,服务之间作用关系的空间显著性降低;(3)生态系统服务的权衡与协同是自然因子和社会因子共同作用的结果。退耕区人类活动干扰较小,自然因子的解释力(q均值0.1507)高于社会因子(q均值0.0148),且影响某类生态系统服务的关键因子对生态系统服务的作用关系起到重要作用。其中,土地利用程度和地形因子的共同作用是进行生态系统服务管理的主要关注点。