Zn添加对铸造Mg-Gd-Y-Zr合金组织和力学性能的影响（英文）

研究Zn添加对Mg-10Gd-3Y-0.6Zr(wt.%)合金在铸态、固溶态和峰时效态下显微组织和力学性能的影响。实验结果表明,不含Zn的铸态合金由α-Mg和Mg_(24)(Gd,Y)_5相组成,而含0.5wt.%Zn的铸态合金由α-Mg、(Mg,Zn)_3(Gd,Y)和Mg_(24)(Gd,Y,Zn)_5相组成。随着Zn含量增加到1 wt.%,Mg_(24)(Gd,Y,Zn)_5相消失,一些针状堆垛层错沿晶界分布。此外,在含2wt.%Zn的铸态合金中观察到18R型长周期结构相。固溶处理后,Mg_(24)(Gd,Y)_5和Mg_(24)(Gd,Y,Zn)_5共晶相完全溶解,(Mg,Zn)_3(Gd,Y)相、针状堆垛层错和18R型长周期结构相均转化为14H型长周期结构相。适当体积分数的14H型长周期结构相和细小的椭球状β′相共同赋予峰时效态下含0.5 wt.%Zn合金优良的综合力学性能,该合金的抗拉强度、屈服强度和伸长率分别为338 MPa、201 MPa和6.8%。

Al添加对Mg-Gd-Zn合金显微组织和力学性能的影响

研究不同Al含量(0,0.4%,0.7%和1.0%,质量分数)Mg−15.3Gd−1Zn合金的显微组织演变和力学性能。显微组织分析表明,添加0.4%Al有利于Mg−Gd−Zn合金中18R-LPSO相(Mg12Gd(Al,Zn))的形成。随着Al含量的增加,Al11Gd3和Al2Gd相含量增加,同时(Mg,Zn)_(3)Gd相含量减少。均匀化处理后,(Mg,Zn)_(3)Gd、18R-LPSO和部分Al11Gd3相转变为高温稳定的14H-LPSO相。颗粒状Al−Gd相可通过粒子激发形核(PSN)机制促进动态再结晶的形核。由于晶粒的细化和纤维状长程堆垛有序(LPSO)相的强化,轧制态合金的抗拉强度得到显著提高。峰时效态合金中的β′析出相能显著提高合金的强度。峰时效态下含0.4%Al的合金具有优异的力学性能,该合金的抗拉强度、屈服强度和伸长率分别为458 MPa、375 MPa和6.2%。

晶体相场法模拟晶界预熔区液相熔池的演化

预熔是指晶体在低于熔点温度时,晶界处预先出现类似液体而块体仍为晶体状的现象。采用晶体相场法研究原子密度对晶界预熔的影响。结果表明:晶界处液相熔池的早期演化主要涉及4个形态特征:固-固状态→小液滴状态→较大的液相熔池→均质熔融层。通过对比不同平均原子密度下的微观结构和能量变化,表明平均原子密度对液相池的形态特征敏感。二维与三维模拟结果表明,平均原子密度的降低能抑制刃型位错聚集区域中原子的结晶相特征,这有助于液相熔池的形成。从热力学的角度验证平均原子密度与液相熔池宽度之间的关系,在一定程度上为后续施加高温应变提供前提条件。

Application of AI and IoT in Clinical Medicine:Summary and Challenges

The application of artificial intelligence(AI)technology in the medical field has experienced a long history of development.In turn,some long-standing points and challenges in the medical field have also prompted diverse research teams to continue to explore AI in depth.With the development of advanced technologies such as the Internet of Things(IoT),cloud computing,big data,and 5G mobile networks,AI technology has been more widely adopted in the medical field.In addition,the in-depth integration of AI and IoT technology enables the gradual improvement of medical diagnosis and treatment capabilities so as to provide services to the public in a more effective way.In this work,we examine the technical basis of IoT,cloud computing,big data analysis and machine learning involved in clinical medicine,combined with concepts of specific algorithms such as activity recognition,behavior recognition,anomaly detection,assistant decision-making system,to describe the scenario-based applications of remote diagnosis and treatment collaboration,neonatal intensive care unit,cardiology intensive care unit,emergency first aid,venous thromboembolism,monitoring nursing,image-assisted diagnosis,etc.We also systematically summarize the application of AI and IoT in clinical medicine,analyze the main challenges thereof,and comment on the trends and future developments in this field.

Phase-Field Lattice-Boltzmann Study for α-Mg Dendrite Growth of Mg-5wt%Zn Alloy with Forced Convection

Melt flow can significantly change the transport of heat and solute,dendrite growth.In this work,a phase-field lattice-Boltzmann model was developed to studyα-Mg dendrite growth of Mg-5wt%Zn alloy with forced convection.Results show that the existence of forced convection and overlap of thermal and solute fields makes thermal and solute fields distribution nonuniform.Thus,the symmetry of dendrite morphology is destroyed.The solid temperature and concentration of the downstream dendrite tip front with forced convection are higher than that without forced convection,while the concentration of the upstream dendrite tip front is lower.The solute transport through melt flow will be hindered by developed sidebranching.With flow velocity increase,the upstream temperature gradient and thickness of the downstream solute enrichment layer increase gradually,while the downstream temperature gradient and thickness of the upstream solute enrichment layer decrease gradually.Meanwhile,the upstream dendrite tip velocity will increase gradually,while the downstream dendrite tip velocity will decrease at first and then unchanged.This study is helpful to establish the relationship betweenα-Mg dendrite growth and melt flow,which is beneficial to understand the role of melt flow on dendrite morphologies.

The sirtuin family in health and disease

Sirtuins(SIRTs)are nicotine adenine dinucleotide(+)-dependent histone deacetylases regulating critical signaling pathways in prokaryotes and eukaryotes,and are involved in numerous biological processes.Currently,seven mammalian homologs of yeast Sir2 named SIRT1 to SIRT7 have been identified.Increasing evidence has suggested the vital roles of seven members of the SIRT family in health and disease conditions.Notably,this protein family plays a variety of important roles in cellular biology such as inflammation,metabolism,oxidative stress,and apoptosis,etc.,thus,it is considered a potential therapeutic target for different kinds of pathologies including cancer,cardiovascular disease,respiratory disease,and other conditions.Moreover,identification of SIRT modulators and exploring the functions of these different modulators have prompted increased efforts to discover new small molecules,which can modify SIRT activity.Furthermore,several randomized controlled trials have indicated that different interventions might affect the expression of SIRT protein in human samples,and supplementation of SIRT modulators might have diverse impact on physiological function in different participants.In this review,we introduce the history and structure of the SIRT protein family,discuss the molecular mechanisms and biological functions of seven members of the SIRT protein family,elaborate on the regulatory roles of SIRTs in human disease,summarize SIRT inhibitors and activators,and review related clinical studies.

Microalloying Effect of Sn on Phase Transformation During Heat Treatment in Mg–Y–Zn–Zr Alloys

The microstructure and mechanical properties of the as-cast and heat-treated Mg-4.6 Y-2.5 Zn-0.6 Zr-x Sn(x = 0, 0.2 and0.5 wt%) alloys were investigated in this work. The results showed that the eutectics have been refined with 0.2% Sn addition and it has no effect on the phase category of the alloys. However, Sn3 Y5 phase was found in 0.5% Sn-added alloy.After heat treatment at 520 °C, the transformation of the long-period stacking ordered(LPSO) phase takes place in the Mg-Y-Zn-Zr alloy, but the transition is not completed in the alloys containing Sn. In addition, during the heat treatment, the mechanical properties of Sn-free alloys are significantly improved, and the strength of alloys containing Sn does not change much. Through observation and analysis of the microstructure and mechanical properties, it is found that Sn addition hinders the process of a0-Mg ? a-Mg ? 14 H and the process is the key to the transition of 18 H-LPSO to 14 H-LPSO.

Microscopic Phase-Field Simulation for the Influence of Interatomic Potential on the Precipitation Process of Ni_(75)Al_(14)Mo_(11) Alloy

Abstract The process of γ＇ phase precipitating from Ni75Al14MO11 is studied by a computational simulation technique based on microscopic phase-field kinetics model. We studied the phase transformation with the purpose of clarifying the influence of the nearest interatomic potential V Ni-Al （the nearest interatomic potential） on the precipitation process of γ＇ phase. The result demonstrates that there are two kinds of ordered phases, respective Llo and L12 in the early stage, and Llo phase transforms into L12 phase subsequently. For L12 phase, Ni atoms mainly occupy α site （face center positions）, while Al and Mo atoms occupy fl sites （the vertex positions）. When VNi-Al is increased by 10 MeV, the occupation probability of Ni atoms on α sites and Al atoms on β sites are enhanced. Enhanced VNi-Al facilitates clustering and ordering of Al atom, which promotes the formation of the γ＇ phase. At last, the simulation result was discussed by employing the thermodynamic stability.

Phase-field simulation of tip splitting in dendritic growth of Fe-C alloy

Two types of dendrite tip splitting including dendrite orientation transition and twinned-like dendrites in Fe-C alloys were investigated by phase-field method. In equiaxed growth, the possible dendrite growth directions and the effect of supersaturation on tip splitting were discussed; the dendrite orientation transition was observed, and it was found that the orientation regions of anisotropy parameters were reduced from three to two with increasing the supersaturation, which was due to the effect of interracial anisotropy controlled by the solute in front of S/L interface changing with the increase of supersaturation. In directional solidification, it was found that the twinned like dendrites were formed with the fixed anisotropy couples and no seaweed dendrites were observed; these were concluded from the results of competition between process anisotropy and inherent anisotropy. The formation process of twinned-like dendrite was investigated by tip splitting phenomenon, which was related to the chan ges of dendrite tips growth velocity. Then, the critical speed of tips splitting and solute concentration of twinned-like dendrites were investigated, and a new type of microsegregation in Fe-C alloys was proposed to supplement the dendrite growth theories.

Global Pediatric Pulmonology Alliance recommendation to strengthen prevention of pediatric seasonal influenza under COVID-19 pandemic

The World Health Organization(WHO)announced COVID-19 as a global pandemic in March of 2020[1].The COVID-19 pandemic may persist for a long period of time.Global prevention and control becomes a complex and challenging task,and such efforts should be sustained.Although general measures,such as social distancing,face masks,respiratory hygiene and hand sanitization,will bear fruits for decreasing spread of other respiratory illnesses including influenza,the specific prevention through vaccination is a key focus especially in the upcoming winter and spring seasons[2].