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Atomistic Simulations of the Mechanical Deformation of Irradiation-amorphized Silicon Carbide

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Chinese Journal of Mechanical Engineering 2010年第6期23卷 671-676页

作者： xue kun NIU Lisha SHI Huiji Department of Engineering Mechanics Tsinghua University Beijing 100084 China

Irradiation-induced atomic-scale defects and lattice disorder in Silicon Carbide （SIC） can significantly affect the material＇s mechanical properties. Currently there lacks a unified physical model capable of describing the law in which the properties of SiC scale with the accumulation of defects, especially in terms of the underlying physical mechanism. To develop fundamental models that are capable of describing the various physical properties of SiC as a function of microstructural change, molecular dynamics simulations of uniaxial tension were performed on a series of irradiation-amorphized SiC （a-SiC） samples with a range of imposed chemical disorder, which is defined as the ratio between the number of homonuclear bonds and heteronuclear bonds （x = Nc-c / Nsi-c）. With increasing chemical disorder, significant alternation of mechanical response of a-SiC has been detected in terms of increasingly pronounced plastic flow. Meanwhile relevant mechanical properties, including Young＇s modulus, strength, yield stress and strain, as well as failure strain scale monotonically with chemical disorder while in distinct manners. Specifically slight chemical disorder （x = 0.045） could induce substantial reduction of Young＇s modulus up to -2%, whereas strength basically linearly varies with chemical disorder until x≈0.5 upon which the variations in mechanical properties tend to saturate. Further examination of the evolution of atomic structure of a-SiC reveals a crossover of deformation mechanisms from homogeneous elastic deformation to localized plastic flow, which accounts for the strong chemical disorder dependence of the mechanical properties as well as mechanical responses of amorphous SiC. This crossover is also manifested in switching of fracture mode from brittle failure dominated by lattice instability in the ligaments between topological disordered clusters to nanoductile failure preceded by percolation of nanocavities. Employing chemical disorder to measure the defec

关键词： silicon carbide irradiation-amorphization molecular dynamics modeling tensile test chemical disorder

Pressure evolution in shock-compacted granular media

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Petroleum Science 2023年第6期20卷 3736-3751页

作者： Jia-Rui Li Jun-Sheng Zeng kun xue State Key Laboratory of Explosive Science and Technology Beijing Institute of TechnologyBeijing100081China Institute of Applied Physics and Computational Mathematics Beijing100094China

The pressure evolution associated with the transient shock-induced infiltration of gas flow through granular media consisting of mobile particles is numerically investigated using a coupled Eulerian–Lagrangian *** coupling between shock compaction and interstitial flow has been revealed.A distinctive two-stage diffusing pressure field with deflection occurring at the tail of the compaction front is found,with corresponding spikes in both gaseous velocity and temperature profiles emerging within the width of the compaction *** compaction front,together with the deflection pressure,reaches a steady state during the later *** analytical prediction of the steady deflection pressure that considers the contributions of porosity and the non-isothermal effect is *** isothermal single-phase method we developed,combining the porosity jump condition across the compaction front,shows consistent pressure evolution with the non-isothermal CMP-PIC one under weak shock strength and low column ***,the microscale mechanism governing the formation of not only pressure deflection but also gaseous velocity and temperature spikes within the width of the compaction front has been *** aforementioned evolutions of the flow field are shown to arise from the nozzling effects associated with the particle-scale variations in the volume fraction.

关键词： Shock compaction Pressure evolution Transport in porous media Transient gas infiltration Mobile granular column

Incoherent scatter spectra from plasma of a 13-moment approximation distribution function

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Science China(Technological Sciences) 2008年第5期51卷 624-631页

作者： XU Bin xue kun WU Jian WU ZhenSen School of Science Xidian UniversityXi’an 710071China National Key Laboratory of Electromagnetic Environment China Research Institute of Radiowave PropagationBeijing 102206China

The function and physical mechanism of heat flow and the viscous stress in the velocity distribution function expanded by Maxwellian distribution are presented. With the introduction of effective temperature Tf, incoherent scatter spectra from plasma for electromagnetic wave in arbitrary line of sight are given. The effect of asymmetry and anisotropy provided by heat flow and the viscous stress on power spectra is discussed. Radar spectra are calculated for different cases of electric field, direction, collision frequency and temperature. The effect of heat flow and the viscous stress on inversion results is analyzed. With a large electric field, the character of non-Maxwellian must be considered.

关键词： power spectra incoherent radar spectra Boltzmann equation non-Maxwellian distribution function

Incoherent scatter spectra due to HF heating in the low ionosphere region

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Science China(Technological Sciences) 2009年第4期52卷 1112-1116页

作者： XU Bin WU ZhenSen WU Jian xue kun School of Science Xidian UniversityXi’an 710071China State Key Laboratory of Electromagnetic Environment China Research Institute of Radiowave PropagationBeijing 102206China

The electron velocity distribution function and the incoherent scatter spectra during ionospheric heating in low ionosphere region are presented with consideration of the elastic collision between electrons and neural particles and the excitation of rotation energy level. The effects of pump frequency and electric fields on the spectra are discussed. With the increase of electric field, the non-Maxwellian feature is enhanced, and with the increase of heating frequency, the non-Maxwellian feature is weak- ened. The non-Maxwellian factor will bring a large error in ionosphere parameters, which must be con- sidered in the inversion.

关键词： incoherent scatter spectra non-Maxwellian distribution ionospheric heating

Flotation evaluation and adsorption mechanism of medialan collector to wolframite

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Rare Metals 2013年第6期32卷 636-641页

作者： Xian-Ping Luo Li-Ying Luo Li Gao xue-kun Tang College of Resource and Environmental Engineering Jiangxi University of Science and Technology

Medialan has preferable flotation performance to wolframite,under the conditions of the best flotation pH value 7.0 and low dosage,wolframite recovery is up to80%.Medialan shows poor flotation performance to quartz,but better to fluorite and ***,fluorite and calcite are inhibited in a certain degree by adding medialan mixed with sodium *** mechanism of medialan collector on wolfram surface was also studied by using infrared(IR)radiation spectrum,adsorption volume,and zeta *** results show that medialan can adsorb on wolfram surface in the form of chemistry adsorption,and as medialan collector dosage changes,change law of adsorption volume is similar with that of wolfram pure mineral *** potential results prove that zeta potential of wolfram surface moves negatively after adsorbing medialan collector.

关键词： Medialan Wolframite Flotation performance IR spectrum measurement Adsorbance Zeta potential

Preparation of spatially uniform monolayer FeSexTe1−x(0

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Nano Research 2023年第1期16卷 1712-1716页

作者： Zhongxu Wei Cui Ding Yujie Sun Lili Wang Qi-kun xue Department of Physics Southern University of Science and TechnologyShenzhen 518055China State Key Laboratory of Low-Dimensional Quantum Physics Department of PhysicsTsinghua UniversityBeijing 10008China Beijing Academy of Quantum Information Sciences Beijing 100193China

Spatially uniform high-temperature superconducting films are highly desirable for exploring novel properties and popularizing *** improve the uniformity,we fabricate monolayer FeSexTe1−x(0 详细信息

Spatially uniform high-temperature superconducting films are highly desirable for exploring novel properties and popularizing *** improve the uniformity,we fabricate monolayer FeSexTe1−x(0

关键词： monolayer FeSexTe1−x interface superconductivity topotactic reaction scanning tunneling microscopy

Asymmetric hydroazidation ofα-substituted vinyl ketones catalyzed by chiral primary amine

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Chinese Chemical Letters 2017年第5期28卷 1083-1086页

作者： Zai-kun xue Nian-Kai Fu San-Zhong Luo Beijing National Laboratory for Molecular Sciences(BNLMS) CAS Key Laboratory of Molecular Recognition and FunctionInstitute of ChemistryChinese Academy of SdencesBeijing 100190China

We report herein the first example of asymmetric hydroazidation of α-substituted vinyl ketones by using chiral primary amines as the catalysts.A simple chiral primary-tertiary diamine catalyst derived from lphenylalanine was found to readily promote this aza-Michael addition reaction with enamine protonation as the key stereogenic step,thus enabling the effective synthesis of α-chiral β-azido ketones with good yields and moderate enantioselectivities.

关键词： Chiral primary amine catalysis Hydroazidation Enamine protonation α-Substituted vinyl ketones Aza-Michael addition Chiral β-azido ketones

Obtaining tetragonal FeAs layer and superconducting K_(x)Fe_(2)As_(2)by molecular beam epitaxy

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Nano Research 2023年第2期16卷 3040-3045页

作者： Cui Ding Yuanzhao Li Shuaihua Ji Ke He Lili Wang Qi-kun xue State Key Laboratory of Low-Dimensional Quantum Physics Department of PhysicsTsinghua UniversityBeijing 100084China Beijing Academy of Quantum Information Sciences Beijing 100193China Collaborative Innovation Center of Quantum Matter Beijing 100084China Department of Physics Southern University of Science and TechnologyShenzhen 518055China

Atomic characterization on tetragonal FeAs layer and engineering FeAs superlattices is highly desirable to get deep insight into the multi-band superconductivity in *** fabricate the tetragonal FeAs layer by topotactic reaction of FeTe films with arsenic and then obtain KxFe_(2)As_(2)upon potassium intercalation using molecular beam *** in-situ low-temperature√2×√2scanning tunneling microscopy/spectroscopy investigations demonstrate characteristic reconstruction of the FeAs layer and stripe pattern of KxFe_(2)As_(2),accompanied by the development of a superconducting-like *** ex-situ transport measurement with FeTe capping layers shows a superconducting transition with an onset temperature of 10 *** work provides a promising way to characterize the FeAs layer directly and explore rich emergent physics with epitaxial superlattice design.

关键词： tetragonal FeAs KxFe_(2)As_(2) interface enhanced superconductivity topotactic reaction molecular beam epitaxy

Topological dynamical decoupling

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Science China(Physics,Mechanics & Astronomy) 2019年第12期62卷 2-9页

作者： Jiang Zhang Xiao-Dong Yu Gui-Lu Long Qi-kun xue State Key Laboratory of Low-Dimensional Quantum Physics and Department of Physics Tsinghua UniversityBeijing 100084China Beijing Academy of Quantum Information Sciences Beijing 100193China Naturwissenschaftlich-Technische Fakultcit Universitat SiegenWaiter-Flex-Strafie 357068 SiegenGermany Beijing National Research Center for Information Science and Technology Beijing 100084China Collaborative Innovation Center of Quantum Matter Beijing 100084China

We show that topological equivalence classes of circles in a two-dimensional square lattice can be used to design dynamical decoupling procedures to protect qubits attached on the edges of the lattice. Based on the circles of the topologically trivial class in the original and the dual lattices, we devise a procedure which removes all kinds of local Hamiltonians from the dynamics of the qubits while keeping information stored in the homological degrees of freedom unchanged. If only the linearly independent interaction and nearest-neighbor two-qubit interactions are concerned, a much simpler procedure which involves the four equivalence classes of circles can be designed. This procedure is compatible with Eulerian and concatenated dynamical decouplings,which make it possible to implement the procedure with bounded-strength controls and for a long time period. As an application,it is shown that our method can be directly generalized to finite square lattices to suppress uncorrectable errors in surface codes.

关键词： dynamical decoupling surface codes topological quantum computation