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Coarsening rate of microstructure in semi-solid aluminium alloys

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Transactions of Nonferrous Metals Society of China 2010年第9期20卷 1672-1676页

作者： h.v.atkinson D.LIU Mechanics of Materials Research Group Department of EngineeringUniversity of LeicesterUniversity Rd. Now with Wolfson Microelectronics PLC.

The rate of microstructural coarsening of recrystallisation and partial melting (RAP) and cooling slope (CS) processed materials in the semi-solid state is compared with rates found in the *** rate of coarsening depended on the liquid fraction but RAP route 2014 alloy with 37% liquid coarsened slightly more slowly than the CS route 2014 alloy with a lower liquid fraction of 17%, contrary to *** the CS route, an increase in liquid fraction resulted in faster coarsening.A modified 2014 alloy with Fe, Mn and Zn stripped out of the composition gave a relatively high coarsening *** coarsening rate was also relatively high for CS 201 alloy in comparison with either RAP 2014 or CS *** coarsening rates are thought to be associated with the presence of particles which inhibit the migration of liquid film grain *** could be the result of pinning or of the liquid film impeding diffusion at the boundary.

关键词： coarsening semi-solid metal 2014 alloy recrystallisation and partial melting cooling slope

Microstructure and Mechanical Properties of 7005 Aluminum Alloy Components Formed by Thixoforming

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Journal of Materials Science & Technology 2017年第4期33卷 379-388页

作者： Jufu Jiang h.v.atkinson Ying Wang School of Materials Science and Engineering Harbin Institute of Technology Harbin 150001 China Department of Engineering University of Leicester University Road Leices-ter LE1 7RH UK School of Mechatronics Engineering Harbin Institute of Technology Harbin 150001 China

In the present research, semisolid billet of 7005 aluminum alloy was fabricated by using recrystallization and partial remelting（RAP）, then thixoformed at different isothermal temperatures, preheating temperatures and load routes. Mechanical properties and microstructure of the thixoformed product were investigated. The results showed that microstructure achieved by three-step induction heating warm extruded 7005 aluminum alloy consists of a uniform and spheroidal microstructure suitable for *** temperature of the die affected significantly the filling status of semisolid billet of 7005 aluminum alloy. Complete filling status with good surface quality was obtained at a preheating temperature of 365 ℃. Thixoformed microstructures consisting of relatively spheroidal grains illustrate the dependence of filling process on the sliding and rotating of solid grains rather than plastic deformation of solid grains. A non-uniform distribution of liquid phase was found in the different regions of the thixoformed product due to the slower adjustable velocity of solid grains as compared with liquid phase. Increase of isothermal temperatures led to a slight decrease of mechanical properties of the thixoformed product due to coarsening of solid grains. The highest yield strength, ultimate tensile strength and elongation of thixoformed components with T6 heat treatment are 237 MPa, 361 MPa and 16.8%, respectively, which were achieved at the isothermal temperature of 605℃. Load route has a significant effect on mechanical properties and microstructure of the thixoformed product. Defects, such as crack and microporosity occurred in the microstructure of the thixoformed product obtained under load route 2. It led to an obvious reduction of mechanical properties as compared with route 1. A better compatibility of deformation caused by more liquid fraction at the isothermal temperature of 612℃ is beneficial to reducing nonuniformity of liquid phase in the different r

关键词： 7005 aluminum alloy Microstructure Mechanical properties Semisolid billet Thixoforming

Experimental and numerical investigation on alternatives to sandy gravel

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Defence Technology（防务技术） 2024年第1期31卷 130-141页

作者： v.Denefeld h.Aurich Fraunhofer Institute for high-Speed Dynamics Ernst-Mach-Institut(EMI)Ernst-Zermelo-Str.479104FreiburgGermany Fraunhofer Institute for high-Speed Dynamics Ernst-Mach-Institut(EMI)Am Christianswuhr 279400KandernGermany

The NATO agreement STANAG 4569 defines the protection levels for the occupants of logistic and light armored *** Allied Engineering Publication,AEP-55,volume 2 document outlines the test conditions for underbelly improvised explosive device(IEDs),which must be buried in water-saturated sandy *** use of sandy gravel has some drawbacks,for instance reproducibility,time consumption,and *** paper focuses on the investigation of four alternatives to sandy gravel,which could produce similar specific and cumulative impulses:a concrete pot filled with water,a concrete pot filled with quartz sand,a steel pot without filling and a concrete pot filled with glass spheres(diameter 200μm—300μm)and different water *** impulses are measured with a ring technology developed at the Fraunhofer EMI.A numerical soil model based on the work of Marrs,2014 and Fi serov a,2006 and considering the soil moisture was used to simulate the experiments with glass spheres at different water contents,showing much better agreement with the experiments than the classical Laine&Sandvik model,even for high saturation *** results can be used to create new test conditions at original scale that are more cost-effective,more reproducible and simpler to manage in comparison to the current tests carried out with STANAG sandy gravel.

关键词： Improvised explosive device(IED) Specific impulse Momentum transfer Sandy gravel Glass spheres Numerical model Soil moisture

Investigation of crack segmentation and fast evaluation of crack propagation, based on deep learning

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Frontiers of Structural and Civil Engineering 2024年第4期18卷 516-535页

作者： Than v.TRAN h.NGUYEN-XUAN Xiaoying ZhUANG Institute of Photonics Leibniz University HannoverHannover 30167Germany CIRTech Institute HUTECH UniversityHo Chi Minh City 700000Vietnam College of Civil Engineering Tongji UniversityShanghai 200092China

Identifying crack and predicting crack propagation are critical processes for the risk assessment of engineering *** traditional approaches to crack modeling are faced with issues of high computational costs and excessive computing *** address this issue,we explore the potential of deep learning(DL)to increase the efficiency of crack detection and forecasting crack ***,there is no single algorithm that can fit all data sets well or can apply in all cases since specific tasks *** the paper,we present DL models for identifying cracks,especially on concrete surface images,and for predicting crack ***,SegNet and U-Net networks are used to identify concrete *** gradient descent(SGD)and adaptive moment estimation(Adam)algorithms are applied to minimize loss function during ***,time series algorithms including gated recurrent unit(GRU)and long short-term memory(LSTM)are used to predict crack *** experimental findings indicate that the U-Net is more robust and efficient than the SegNet for identifying crack segmentation and achieves the most outstanding *** evaluation of crack propagation,GRU and LSTM are used as DL models and results show good agreement with the experimental data.

关键词： deep learning crack segmentation crack propagation encoder−decoder recurrent neural network

The multi-impurity system in CdSe nanoplatelets:electronic structure and thermodynamic properties

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Communications in Theoretical Physics 2024年第3期76卷 165-173页

作者： D A Baghdasaryan v A harutynyan E M Kazaryan h A Sarkisyan Russian-Armenian University H Emin 1230051YerevanArmenia Institute of Applied Problems of Physics 25 Nersisyan St0014YerevanArmenia

This paper theoretically studies the impurity states and the effects of impurity concentration and configuration on the optical,electrical,and statistical properties of CdSe nanoplatelets(NPLs).An image charge-based model of electron-impurity interaction is *** charge-carrier energy spectra and corresponding wave functions depending on the impurity number and configuration are *** electron binding energies are calculated for different NPL *** is shown that the image charge-based interaction potential that arises due to the dielectric constants mismatch is much stronger than the interaction potential that does not take such a mismatch into ***,it is demonstrated that the binding energies are increasing with the number of *** calculate the canonical partition function using the energy levels of the electron,which in turn is used to obtain the mean energy,heat capacity,and entropy of the non-interacting electron *** thermodynamic properties of the non-interacting electron gas that depend on the geometric parameters of the NPL,impurity number,configuration,and temperature are studied.

关键词： nanoplateletes thermodynamic properties impurity states

Exploring one material for dual applications:A red-emitting Mg_(2)GeO_(4):Eu^(3+)nanophosphor for future generation energy efficient WLEDs and dosimetric applications

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Journal of Rare Earths 2024年第10期42卷 1835-1845页

作者： Akshay Arjun G.P.Darshan S.C.Sharma h.Nagabhushana D.v.Sunitha h.B.Premkumar Department of Physics Faculty of Mathematical and Physical SciencesM.S.Ramaiah University of Applied SciencesBengaluru560054India honorary Professor of Law and Forensic Materials Jain UniversityBengaluru560069India C.N.R.Rao Centre for Advanced Materials Tumkur UniversityTumkur572103India School of Applied Sciences(Physics) REVA UniversityBengaluru560064India

The envisaged design and developme nt of individual mate rials to excavate a broader spectrum of desired properties and offer multiple applications are highly *** this in mind,a series of forsterite-structured Mg_(2)GeO_(4):Eu^(3+)(1 mol%-9 mol%)nanophosphors was synthesized via a solution combustion method using oxalyl dihydrazide as a *** X-ray diffraction patterns confirm the orthorhombic crystal system with a Puma space *** results clearly show irregularly shaped cluster-like structures with aggregation of the *** diffuse reflectance spectra,the optical energy band gap of the Mg_2GeO_4:Eu^(3+)(1 mol%-9 mol%)nanophosphors was estimated and obtained to be~4.12-4.32 *** photoluminescence emission spectra exhibit intense peaks at~579,589,610,661,and 707 nm,which are due to characteristic~5D_(0)→~7F_(0),~5D_(0)→~7F_(1),~5Do→~7F_(2),~5D_(0)→~7F_(3)and~5D_(0)→~7F_(4)transitions of Eu^(3+)ions,*** Commission International de L'Eclairage color coordinates are gradually tuned from pale red(0.5980,0.4012)to a pure red(0.6385,0.3611)*** glow peaks showcase excellent super-linear response at low doses ofγ-irradiations,indicating that the prepared phosphor can be used in thermoluminescent personal dosimetry which is a biological tissue *** aforementioned results demonstrate that the prepared Mg_2GeO_4:Eu^(3+)(1 mol%-9 mol%)nanophosphors are considered an excellent candidate for dual applications,i.e.,red component in future generation white-light-emitting diodes(WLEDs)and personal dosimetric applications.

关键词： Nanophosphors Photoluminescence Thermoluminescence Dosimetry Photometric properties Rare earths

Charge qubits based on ultra-thin topological insulator films

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Frontiers of physics 2024年第3期19卷 71-81页

作者： Kexin Zhang hugo v.Lepage Ying Dong Crispin h.W.Barnes Research Center for Quantum Sensing Intelligent Perception Research InstituteZhejiang LabHangzhou 311121China Cavendish Laboratory Department of PhysicsUniversity of CambridgeCambridge CB30HEUnited Kingdom

We study how to use the surface states in a Bi2Se3 topological insulator ultra-thin film that are affected by finite size effects for the purpose of quantum *** demonstrate that:(i)surface states under the finite size effect can effectively form a two-level system where their energy levels lie in between the bulk energy gap and a logic qubit can be constructed,(ii)the qubit can be initialized and manipulated using electric pulses of simple forms,(iii)two-qubit entanglement is achieved through a√SWAP operation when the two qubits are in a parallel setup,and(iv)alternatively,a Floquet state can be exploited to construct a qubit and two Floquet qubits can be entangled through a Controlled-NOT *** Floquet qubit offers robustness to background noise since there is always an oscillating electric field applied,and the single qubit operations are controlled by amplitude modulation of the oscillating field,which is convenient experimentally.

关键词： topological insulator quantum computing nanodevices

B-L model with D_(4)×Z_(4)×Z_(2)symmetry for fermion mass hierarchies and mixings

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Chinese Physics C 2024年第6期48卷 11-30页

作者： v.v.vien Department of Physics Tay Nguyen UniversityDaklakVietnam

We constructed a gauge B-L model with D_(4)×Z_(4)×Z_(2)symmetry to explain the quark and lepton mass hierarchies and their mixings with realistic CP phases via the type-I seesaw *** quark mases,three quark mixing angles,and the CP phase in the quark sector take the central values whereas Yukawa couplings in the quark sector are diluted in a range of difference of three orders of magnitude by the perturbation theory at the first *** the neutrino sector,a small neutrino mass is achieved by the type-I seesaw *** inverted and normal neutrino mass hierarchies are consistent with the experimental *** predicted sum of neutrino masses for normal and inverted hierarchies,the effective neutrino masses,and the Dirac CP phase are also consistent with recently reported limits.

关键词： flavor symmetries quark and lepton masses and mixing extensions of electroweak gauge sector neutrino mass and mixing non-standard-model neutrinos right-handed neutrinos D4 discrete symmetry

Kinetics of dense plasma in the field of short laser pulses:A generalized approach

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Matter and Radiation at Extremes 2024年第5期9卷 87-92页

作者： v.A.Astapenko v.S.Lisitsa Moscow Institute of Physics and Technology(National Research University) Institutskii per.9141701 DolgoprudnyiRussia National Research Centre“Kurchatov Institute ”123182 MoscowRussia National Research Nuclear University MEPhI 115409 MoscowRussia

A generalized kinetic model of atomic level populations in an optically dense plasma excited by laser pulses of arbitrary duration is formulated and *** model is based on a nonstationary expression for the probability of excitation of an atomic transition and takes into account the effects of laser pulse penetration into an optically dense medium.A universal formula for the excitation probability as a function of time and propagation length is derived and applied to the case of a Lorentzian spectral profile of an atomic transition excited by a laser pulse with a Gaussian *** features of nonstationary excitation probabilities are presented for different optical depths of the plasma,laser pulse durations,and carrier *** formulas derived here will be useful for the description of atomic populations excited by laser pulses under realistic conditions of dense plasmas.

关键词： laser excitation excited