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Application of ultrasonic vibration to shape-casting based on resonance vibration analysis

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China Foundry 2023年第4期20卷 339-346页

作者： Zong-hang Han Zhi-ming Wang Zhi-ping Sun Bing-rong Zhang wei-feng rao School of Mechanical Engineering Qilu University of Technology(Shandong Academy of Sciences)Jinan 250353China Jinan Shengquan Group Jinan 250204China

The application of ultrasonic vibration during the casting process has been proven to refine the microstructure and enhance the properties of the *** using the direct inserting method,wherein the ultrasonic horn is inserted directly into the melt,ultrasonic treatment can be utilized in the semi-continuous casting process to produce aluminum ingots with simple ***,due to the attenuation of ultrasound,it is challenging to apply the direct inserting method in the die casting process to produce complex ***,in this study,the impact of ultrasonic vibration on the microstructure of a gravity die-cast AlSi9Cu3end cap was investigated by applying ultrasonic vibration on the core(indirect method).It is found that the effect of ultrasonic vibration relies greatly on the resonance mode of the *** of ultrasonic vibration schemes mainly depends on the core structure,and only a strong vibration can significantly refine the microstructure of the *** castings with complex structures,an elaborated ultrasonic vibration design is necessary to refine the microstructure of the specified *** addition,strong vibration applied on the feeding channel can promote the feeding ability of casting by breaking the dendrites during solidification,and consequently reduce the shrinkage porosity.

关键词： resonance mode ultrasonic vibration feeding channel aluminum alloy casting

Influence of non-uniform ultrasonic vibration on casting fluidity of liquid aluminum alloy

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China Foundry 2022年第5期19卷 380-386页

作者： Zi-heng Han Zhi-ming Wang Zhi-ping Sun Bing-rong Zhang wei-feng rao School of Mechanical Engineering Qilu University of Technology(Shandong Academy of Sciences)Jinan 250353China

The application of ultrasonic vibration to the casting process can be realized through mould(die)***,the resonant vibration of the mould is always accompanied by a non-uniform vibration distribution at different parts,which may induce a complex liquid flow and affect the casting fluidity during the mould filling *** influence of non-uniform ultrasonic vibration on the fluidity of liquid AlSi9Cu3 alloy was studied by mould vibration with different vibration *** is found that ultrasonic mould vibration can generate two opposite effects on the casting fluidity:the first,ultrasonic cavitation in melt induced by mould vibration promotes the casting fluidity;the second,the non-uniform mould vibration can induce a melt flow toward the weak vibration areas and turbulence there,consequently decreasing the casting *** the melt flow and turbulence are violent enough to offset the promoting effect of cavitation on fluidity,the ultrasonic vibration will finally induce a resultant decrease of casting *** decreasing effect is proportional to the vibration gradient.

关键词： ultrasonic vibration vibration gradient aluminum alloy fluidity

Clinical application of COVID-19 vaccine in liver transplant recipients

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Hepatobiliary & Pancreatic Diseases International 2024年第4期23卷 339-343页

作者： feng-Chao Liu Man Xie wei rao Division of Hepatology Liver Disease CenterThe Affiliated Hospital of Qingdao UniversityQingdao 266000China Organ Transplantation Center The Affiliated Hospital of Qingdao UniversityQingdao 266000China Institute of Organ Donation and Transplantation of Qingdao University Qingdao 266000China Department of Gastroenterology The Affiliated Hospital of Qingdao UniversityQingdao 266000China

Background:Solid organ transplant(SOT)activities,such as liver transplant,have been greatly influenced by the pandemic of coronavirus disease 2019(COVID-19),a disease caused by severe acute respiratory syndrome coronavirus 2(SARS-CoV-2).Immunosuppressed individuals of liver transplant recipients(LTRs)tend to have a high risk of COVID-19 infection and related ***,COVID-19 vaccination has been recommended to be administered as early as possible in *** sources:The keywords“liver transplant”,“SARS-CoV-2”,and“vaccine”were used to retrieve articles published in ***:The antibody response following the 1st and 2nd doses of vaccination was disappointingly low,and the immune responses among LTRs remarkably improved after the 3rd or 4th dose of *** the 3rd or 4th dose of COVID-19 vaccine increased the antibody titer,a proportion of patients remained ***,recent studies showed that SARS-CoV-2 vaccine could trigger adverse events in LTRs,including allograft rejection and liver ***:This review provides the recently reported data on the antibody response of LTRs following various doses of vaccine,risk factors for poor serological response and adverse events after vaccination.

关键词： Liver transplant COVID-19 SARS-CoV-2 Vaccine Antibody response

Nanoembryonic thermoelastic equilibrium and enhanced properties of defected pretransitional materials

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npj Computational Materials 2018年第1期4卷 178-184页

作者： Ye-Chuan Xu wei-feng rao John W.Morris Jr. Armen G.Khachaturyan Department of Materials Physics and IEMMNanjing University of Information Science and TechnologyNanjing 210044China Department of Materials Science and Engineering University of CaliforniaBerkeleyCA 94720USA Department of Materials Science and Engineering Rutgers UniversityPiscatawayNJ 08854USA

Behaviors of displacive phase-transforming materials above the temperature of transformation,where abnormal thermal,elastic,magnetic properties are often observed,are mostly explained by intrinsic peculiarities in electronic/atomic ***,we show these properties may also be attributed to extrinsic effects caused by a thermoelastic equilibrium in highly defected pretransitional *** demonstrate that the stress concentration near stress-generating defects such as dislocations and coherent precipitates could result in the stress-induced transformation within nanoscale regions,producing equilibrium embryos of the product *** nanoembryos in thermoelastic equilibrium could anhysteretically change their equilibrium size in response to changes in applied stress or magnetic fields leading to superelasticity or *** response to cooling may explain the observed diffuse phase transformation,changes in the coefficient of thermal expansion and effective elastic modulus,which,in turn,may explain the invar and elinvar behaviors.

关键词： transformation equilibrium transitional

On the reverse leakage current of Schottky contacts on free-standing GaN at high reverse biases

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Chinese Physics B 2017年第2期26卷 403-405页

作者： Yong Lei Jing Su Hong-Yan Wu Cui-Hong Yang wei-feng rao Department of Materials Physics School of Physics and Optoelectronic Engineering Nanjing University of Information Science and Technology Nanjing 210044 China

In this work, a dislocation-related tunneling leakage current model is developed to explain the temperature-dependent reverse current–voltage（I–V –T） characteristics of a Schottky barrier diode fabricated on free-standing GaN substrate for reverse-bias voltages up to-150 V. The model suggests that the reverse leakage current is dominated by the direct tunneling of electrons from Schottky contact metal into a continuum of states associated with conductive dislocations in GaN epilayer.A reverse leakage current ideality factor, which originates from the scattering effect at metal/GaN interface, is introduced into the model. Good agreement between the experimental data and the simulated I–V curves is obtained.

关键词： homoepitaxial GaN Schottky contact leakage current tunneling dislocations ideality factor

Magnetic properties of L1_0 FePt thin film influenced by recoverable strains stemmed from the polarization of Pb(Mg_(1/3)Nb_(2/3))O_3–PbTiO_3 substrate

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Chinese Physics B 2018年第7期27卷 515-520页

作者： Li-Wang Liu Cheng-Chao Hu Ye-Chuan Xu Hou-Bing Huang Jiang-wei Cao Linyun Liang wei-feng rao Department of Materials Physics and IEMMNanjing University of Information Science and TechnologyNanfing 210044China College of Materials Science and Engineering Liaocheng UniversityLiaocheng 252059China Department of Physics University of Science and Technology BeijingBeijing 100083China Key Laboratory for Magnetism and Magnetic Materials of the Ministry of Education Lanzhou UniversityLanzhou 730000China Mathematics and Computer Science Division Argonne National LaboratoryArgonneIllinois 60439USA

The magnetic properties and magnetization reversible processes of Llo FePt （3 nm）/Pb（Mg1/3Nb2/3）O3-PbTiO3 （PMN-PT） heterostructure were investigated by using the phase field model. The simulation results show that the magnetic coercivities and magnetic domains evolution in the Llo FePt thin film are significantly influenced by the compressive strains stemming from the polarization of single crystal PMN-PT substrate under an applied electric field. It is found that the magnetic coercivities increase with increasing of the compressive strain. A large compressive strain is beneficial to aligning the magnetic moments along the out-of-plane direction and to the enhancement of perpendicular magnetic anisotropy. The variations of magnetic energy densities show that when compressive strains are different at the magnetization reversible processes, the magnetic anisotropy energies and the magnetic exchange energies firstly increase and then decrease, the negative demagnetization energy peaks appear at coercivities fields, and the magnetoelastic energies are invariable at large external magnetic field with the energy maximum appearing at coercivities fields. The variations of the magnetoelastic energies bring about the perpendicular magnetic anisotropy so that the magnetoelastic energy is lower at the large external magnetic fields, whereas the appearance of magnetoelastic energy peaks is due to the magnetization-altered direction from the normal direction of the plane of the Llo FePt thin film at coercivities fields.

关键词： FePt strain magnetoelastic energy phase field

Recent progress of vanadium-based alloys for fusion application

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Tungsten 2021年第4期3卷 382-392页

作者： Shao-Ning Jiang Fu-Jie Zhou Gao-wei Zhang Xiao-Ou Yi Chang-Wang Yu Xiu-Jie Wang wei-feng rao School of Mechanical and Automotive Engineering Qilu University of Technology(Shandong Academy of Sciences)Jinan 250353China Shandong Institute of Mechanical Design and Research Jinan 250353China School of Materials Science and Engineering University of Science and Technology BeijingBeijing 100083China

Low-activation vanadium alloys,with the reference composition of V-4Cr-4Ti have been considered as one of the most promising candidate materials for structural components such as the blanket in future fusion reactors,thanks to their excellent neutron irradiation resistance,superior high-temperature mechanical properties,and high compatibility with liquid lithium *** self-cooled liquid lithium blanket using structural materials of vanadium alloys is an attractive concept because of the high heat transfer and high tritium breeding *** more than 2 decades of research,technological progress has been made in reducing the number of critical issues for application of vanadium alloys to fusion *** this paper,the recent research and development activities of vanadium alloys are summarized,including significant progress achieved on fabrication technology and composition optimization,coating and corrosion,improved understanding of irradiation effects upon microstructure and material properties,retention of hydrogen isotopes,as well as advancements in joining and *** particular,the fact that recent products from China,Japan,US and France showed similar properties which meant the fabrication technology has been almost standardized.

关键词： Vanadium alloy Fabrication Coating and corrosion Irradiation damage Hydrogen retention

Computer simulation of super-magnetoelastic behavior near critical region of magnetic materials based on phase-field method

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稀有金属:英文版 2023年第8期42卷 2477-2488页

作者： Zhao Zhang Cheng-Chao Hu An-Hang Zhou Yu-Xin Xu Yuan-Yuan Wu Hai-Hua Huang Hou-Bing Huang Jun-Jie Ni wei Li wei-feng rao School of Materials Science and Engineering Liaocheng UniversityLiaocheng 252059China Advanced Research Institute of Multidisciplinary Science Beijing Institute of TechnologyBeijing 100081China School of Mechanical Engineering Qilu University of Technology(Shandong Academy of Sciences)Jinan 250353China Shandong Institute of Mechanical Design and Research Jinan 250031China

Since the discovery of ferromagnetic morphotropic phase boundary(MPB)in 2010,the connotation and extension of MPB have been becoming more and more *** the last dozen years,much experimental work has been done to design magnetostrictive materials based on the MPB ***,due to the difficulty in direct experimental observations and the complexity of theoretical treatments,the insight into the microstructure property relationships and underlying mechanisms near the ferromagnetic MPB has not been fully ***,we have reviewed our recent computer simulation work about the super-magnetoelastic behavior near the critical region of several typical ***-field modeling and simulation are employed to explore the domain configuration and engineering in single crystals as well as the grain size effect in ***,a general nano-embryonic mechanism for superelasticity is also ***,some future perspectives and challenges are presented to stimulate a deeper consideration of the research paradigm between multiscale modeling and material development.

关键词： Super-magnetoelastic behavior Phase-field simulation Morphotropic phase boundary(MPB)

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