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

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Journal of Magnesium and Alloys 2022年第2期10卷 346-383页

作者： Tianle Wang feng liu State Key Laboratory of Solidification Processing Northwestern Polytechnical UniversityXi’anShaanxi 710072China Analytical&Testing Center Northwestern Polytechnical UniversityXi’anShaanxi 710072China

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 *** 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 *** 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。

关键词： Magnesium alloys Synergy of thermodynamics and kinetics Generalized stability Superior strength-ductility balance

Prediction of giant and ideal Rashba-type splitting in ordered alloy monolayers grown on a polar surface

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National Science Review 2021年第4期8卷 100-106页

作者： Mingxing Chen feng liu Key Laboratory for Matter Microstructure and Function of Hunan Province Key Laboratory of Low-Dimensional Quantum Structures and Quantum Control of Ministry of Education Synergetic Innovation Center for Quantum Effects and Applications(SICQEA)School of Physics and Electronics Hunan Normal University Department of Materials Science and Engineering University of Utah

A large and ideal Rashba-type spin-orbit splitting is desired for the applications of materials in spintronic devices and the detection of Majorana fermions in solids. Here, we propose an approach to achieve giant and ideal spin-orbit splittings through a combination of ordered surface alloying and interface engineering,that is, growing alloy monolayers on an insulating polar surface. We illustrate this unique strategy by means of first-principle calculations of buckled hexagonal monolayers of Sb Bi and Pb Bi supported on Al2O3(0001). Both systems display ideal Rashba-type states with giant spin-orbit splittings, characterized with energy offsets over 600 meV and momentum offsets over 0.3 ?-1, respectively. Our study thus points to an effective way of tuning spin-orbit splitting in low-dimensional materials to draw immediate experimental interest.

关键词： Rashba effect interface spin-orbit coupling

Higher-order topology induced by structural buckling

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National Science Review 2022年第8期9卷 55-61页

作者： Huaqing Huang feng liu School of Physics Peking University Collaborative Innovation Center of Quantum Matter Center for High Energy Physics Peking University Department of Materials Science and Engineering University of Utah

Higher-order topological insulator(HOTI) states, such as two-dimension(2D) HOTI featured with topologically protected corner modes at the intersection of two gapped crystalline boundaries, have attracted much recent interest. However, the physical mechanism underlying the formation of HOTI states is not fully understood, which has hindered our fundamental understanding and discovery of HOTI materials. Here we propose a mechanistic approach to induce higher-order topological phases via structural buckling of 2D topological crystalline insulators(TCIs). While in-plane mirror symmetry is broken by structural buckling, which destroys the TCI state, the combination of mirror and rotation symmetry is preserved in the buckled system, which gives rise to the HOTI state. We demonstrate that this approach is generally applicable to various 2D lattices with different symmetries and buckling patterns, opening a horizon of possible materials to realize 2D HOTIs. The HOTIs so generated are also shown to be robust against buckling height fluctuation and in-plane displacement. A concrete example is given for the buckledβ-Sb monolayer from first-principles calculations. Our finding not only enriches our fundamental understanding of higher-order topology, but also opens a new route to discovering HOTI materials.

关键词： higher-order topological insulators structural buckling rotation-reflection symmetry buckled honeycomb antimony monolayer

The multi-functional roles of the cGAS-STING signaling pathway in health and diseases

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Journal of Molecular Cell Biology 2022年第9期14卷 1-2页

作者： feng liu National Clinical Research Center for Metabolic Diseases and the Metabolic Syndrome Research Center The Second Xiangya Hospital of Central South UniversityChangsha 410011China

The innate immune system provides an important first line of defense against invading pathogens or harmful *** the past decade,our understanding on the recognition of pathogenic nucleic acids by innate immunity has advanced considerably by the discovery of the DNA-sensing receptor cyclic guanosine monophosphateadenosine monophosphate(cGAMP)synthase(cGAS)and its downstream effector stimulator of interferon genes(STING).The cGAS-STING signaling pathway is activated by various DNA microbes,leading to increased cytokine production and upregulation of type I interferon(IFN)gene *** studies reveal that the cGAS-STING signaling pathway is also activated by host DNAs such as mitochondrial and nuclear DNAs aberrantly localized in the cytosol,which has become an important mechanism triggering chronic inflammatory diseases,e.g.

关键词： interferon diseases immunity

ELASTIC-PLASTIC DYNAMIC RESPONSE OF A CANTILEVER BEAM SUBJECTED TO OBLIQUE IMPACT AT ITS TIP

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Acta Mechanica Solida Sinica 2005年第4期18卷 316-325页

作者： Xi feng liu feng Shandong Institute of Architecture and Engineering Jinan 250101 China

By employing large deformation governing equations expressed in the form of finite difference, the dynamic responses of an elastic, perfectly plastic cantilever subjected to an oblique impact at its tip was numerically studied. Through analyzing the instantaneous distribution of the yield function （φ = ｜M/Mo｜＋（N/No）^2）, bending moment and axial force during the early stage of the response, the elastic-plastic deformation mechanism and the influence of axial component of an oblique impact on the dynamic response of a cantilever beam were discussed. The present analysis shows that the deformation mechanism of an elastic-plastic cantilever subjected to an oblique impact consists of four phases, i.e. ‘the expanding compressed plastic region＇ mode; the ‘generalized traveling plastic hinge＇ and ‘shrinking plastic region＇ mixed mode; the ‘stationary plastic hinge＇ mode and ‘elastic vibration＇ mode. Compared with the two-phase deformation mode obtained by using the rigid, perfectly plastic approach, the mode of shrinking plastic region that occurred instantly after the oblique impact and the mode of stationary hinge were both confirmed. The primary features of the deformation mechanism are captured by both analysis methods. It has also been found that the beam＇s deformation is mainly controlled by the axial component of the oblique impact in the early phase of the dynamic response, the deformation mechanism is obviously different from the case of a transverse impact. With further development of the response, the axial component attenuates rapidly and gives negligible contribution to the yielding of the beam cross-section. At the same time, the bending moments along the cantilever develop gradually and dominate the beam＇s deformation. The numerical results indicate that the mass, impact speed and oblique angle are the important factors that influence the elastic-plastic dynamic response of a cantilever beam.

关键词： oblique impact elastoplasticity large deformation dynamic response cantilever

Pulse laser induced graphite-to-diamond phase transition： the role of quantum electronic stress

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Science China(Physics,Mechanics & Astronomy) 2017年第2期60卷 38-48页

作者： ZhengFei Wang feng liu Hefei National Laboratory for Physical Sciences at the Microscale Synergetic Innovation Center of Quantum Information and Quantum Physics University of Science and Technology of China Hefei 230026 China Department of Materials Science and Engineering University of Utah Salt Lake City UT84112 USA Collaborative Innovation Center of Quantum Matter Beijing 100084 China

First-principles calculations show that the pulse laser induced graphite-to-diamond phase transition is related to the lattice stress generated by the excited carriers,termed as "quantum electronic stress(QES)".We found that the excited carriers in graphite generate a large anisotropic QES that increases linearly with the increasing carrier *** the QES as a guiding parameter,structural relaxation spontaneously transforms the graphite phase into the diamond phase,as the QES is reduced and *** results suggest that the concept of QES can be generally applied as a good measure to characterize the pulse laser induced phase transitions,in analogy to pressure induced phase transitions.

关键词： graphite quantum electronic stress phase transition

Joint sparsity and fidelity regularization for segmentation-driven CT image preprocessing

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Science China(Information Sciences) 2016年第3期59卷 146-152页

作者： feng liu Huibin LI School of Mathematics and Statistics Xi'an Jiaotong University

In this paper, we propose a novel segmentation-driven computed tomography(CT) image preprocessing approach. The proposed approach, namely, joint sparsity and fidelity regularization(JSFR) model can be regarded as a generalized total variation(TV) denoising model or a generalized sparse representation denoising model by adding an additional gradient fidelity regularizer and a stronger gradient sparsity ***, JSFR model consists of three terms: intensity fidelity term, gradient fidelity term, and gradient sparsity term. The interactions and counterbalance of these terms make JSFR model has the ability to reduce intensity inhomogeneities and improve edge ambiguities of a given image. Experimental results carried out on the real dental cone-beam CT data demonstrate the effectiveness and usefulness of JSFR model for CT image intensity homogenization, edge enhancement, as well as tissue segmentation.

关键词： CT image homogenization enhancement tissue segmentation gradient fidelity gradient sparsity

Regularity of discrete multisublinear fractional maximal functions

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Science China Mathematics 2017年第8期60卷 1461-1476页

作者： liu feng WU HuoXiong College of Mathematics and Systems Science Shandong University of Science and Technology School of Mathematical Sciences Xiamen University

We investigate the regularity properties of discrete multisublinear fractional maximal operators,both in the centered and uncentered *** prove that these operators are bounded and continuous from l^1（Z^d）×l^1（Z^d）×…×l^1（Z^d）to BV（Z^d）,where BV（Z^d）is the set of functions of bounded variation defined on ***,two pointwise estimates for the partial derivatives of discrete multisublinear fractional maximal functions are also *** applications,we present the regularity properties for discrete fractional maximal operator,which are new even in the linear case.

关键词： discrete multisublinear fractional maximal operator discrete fractional maximal operator bounded variation continuity

Total energy equation leading to exchange-correlation functional

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Science China(Physics,Mechanics & Astronomy) 2015年第5期58卷 93-98页

作者： liu feng WANG TzuChiang State Key Laboratory of Nonlinear Mechanics Institute of Mechanics Chinese Academy of Sciences

By solving the total energy equation, we obtain the formula of exchange-correlation functional for the first time. This functional is usually determined by fitting experimental data or the numerical results of models. In the uniform electron gas limit, our exchangecorrelation functional can exactly reproduce the results of Perdew-Zunger parameterization from the jellium model. By making use of a particular solution, our exchange-correlation functional could take into accotmt the case of non-uniform electron density, and its validity can be confirmed through comparisons of the band structure, equilibrium lattice constant, and bulk modulus of aluminum and silicon. The absence of mechanical prescriptions for the systematic improvement of exchange-correlation functional hinders further development of density-functional theory （DFT）, and the formula of exchange-correlation functional given in this study might provide a new perspective to help DFT out of this awkward situation.

关键词： Density-functional theory exchange-correlation functional bulk modulus band structure aluminum silicon