Using a field equation with a phase factor, a universal analytic potential-energy function applied to the interactions between diatoms or molecules is derived, and five kinds of potential curves of common shapes are o...Using a field equation with a phase factor, a universal analytic potential-energy function applied to the interactions between diatoms or molecules is derived, and five kinds of potential curves of common shapes are obtained adjusting the phase factors. The linear thermal expansion coefficients and Young's moduli of eleven kinds of face-centered cubic (fcc) metals - Al, Cu, Ag, etc. are calculated using the potential-energy function; the computational results are quite consistent with experimental values. Moreover, an analytic relation between the linear thermal expansion coefficients and Young's moduli of fcc metals is given using the potential-energy function. Finally, the force constants of fifty-five kinds of diatomic moleculars with low excitation state are computed using this theory, and they are quite consistent with RKR (Rydberg-Klein-Rees) experimental values.展开更多
In this paper, at large class of two-dimensional orthogonal wavelet filters, (lowpass and highpass), are presented in explicit expression. We also characterize the filters with linear phase in this case. Some examples...In this paper, at large class of two-dimensional orthogonal wavelet filters, (lowpass and highpass), are presented in explicit expression. We also characterize the filters with linear phase in this case. Some examples are also given, including non-separable filters with linear phase.展开更多
The Ti17(a+β)-Ti17(β)dual alloy-dual property blisk produced using Linear Friction Welding(LFW)is considered as high-performance component in advanced aeroengine.However,up to now,microstructure evolution and relati...The Ti17(a+β)-Ti17(β)dual alloy-dual property blisk produced using Linear Friction Welding(LFW)is considered as high-performance component in advanced aeroengine.However,up to now,microstructure evolution and relationship between microstructure and micro mechanical properties of LFWed Ti17(a+β)/Ti17(β)dissimilar joint have not been thoroughly revealed.In this work,complex analyses of the phase transformation mechanisms of the joint are conducted,and phase transformations in individual zones are correlated to their microhardness and nanohardness.Results reveal that a dissolution occurs under high temperatures encountered during LFW,which reduces microhardness of the joint to that of Ti17(a+β)and Ti17(β).In ThermoMechanically Affected Zone of Ti17(a+β)(TMAZ-(a+β))side joint,a large number of nanocrystalline a phases form with different orientations.This microstructure strengthens significantly by fine grains which balances partial softening effect of a dissolution,and increases nanohardness of a phase and microhardness of TMAZ-(a+β).Superlattice metastableβphase precipitates from metastableβin Weld Zone(WZ)during quick cooling following welding,because of short-range diffusion migration of solute atoms,especiallyβstabilizing elements Mo and Cr.The precipitation of the superlattice metastableβphase results in precipitation strengthening,which in turn increases nanohardness of metastableβand microhardness in WZ.展开更多
Dynamically controlling terahertz(THz)wavefronts in a designable fashion is highly desired in practice.However,available methods working at microwave frequencies do not work well in the THz regime due to lacking suita...Dynamically controlling terahertz(THz)wavefronts in a designable fashion is highly desired in practice.However,available methods working at microwave frequencies do not work well in the THz regime due to lacking suitable tunable elements with submicrometer sizes.Here,instead of locally controlling individual meta-atoms in a THz metasurface,we show that rotating different layers(each exhibiting a particular phase profile)in a cascaded metadevice at different speeds can dynamically change the effective Jonesmatrix property of the whole device,thus enabling extraordinary manipulations on the wavefront and polarization characteristics of a THz beam impinging on the device.After illustrating our strategy based on model calculations,we experimentally demonstrate two proof-of-concept metadevices,each consisting of two carefully designed all-silicon transmissive metasurfaces exhibiting different phase profiles.Rotating two metasurfaces inside the fabricated devices at different speeds,we experimentally demonstrate that the first metadevice can efficiently redirect a normally incident THz beam to scan over a wide solid-angle range,while the second one can dynamically manipulate both the wavefront and polarization of a THz beam.Our results pave the way to achieving dynamic control of THz beams,which is useful in many applications,such as THz radar,and bio-and chemical sensing and imaging.展开更多
基金This work was supported by the National Natural Science Foundation of China (No. 40274044).
文摘Using a field equation with a phase factor, a universal analytic potential-energy function applied to the interactions between diatoms or molecules is derived, and five kinds of potential curves of common shapes are obtained adjusting the phase factors. The linear thermal expansion coefficients and Young's moduli of eleven kinds of face-centered cubic (fcc) metals - Al, Cu, Ag, etc. are calculated using the potential-energy function; the computational results are quite consistent with experimental values. Moreover, an analytic relation between the linear thermal expansion coefficients and Young's moduli of fcc metals is given using the potential-energy function. Finally, the force constants of fifty-five kinds of diatomic moleculars with low excitation state are computed using this theory, and they are quite consistent with RKR (Rydberg-Klein-Rees) experimental values.
文摘In this paper, at large class of two-dimensional orthogonal wavelet filters, (lowpass and highpass), are presented in explicit expression. We also characterize the filters with linear phase in this case. Some examples are also given, including non-separable filters with linear phase.
基金supported by the National Science and Technology Major Project,China(No.2017-VII-0005-0098)the National Natural Science Foundation of China(No.52105400)+1 种基金the State Key Laboratory of Solidification Processing,China(No.2021-TS-07)the Innovation Foundation for Doctor Dissertation of Northwestern Polytechnical University,China(No.CX2023008)。
文摘The Ti17(a+β)-Ti17(β)dual alloy-dual property blisk produced using Linear Friction Welding(LFW)is considered as high-performance component in advanced aeroengine.However,up to now,microstructure evolution and relationship between microstructure and micro mechanical properties of LFWed Ti17(a+β)/Ti17(β)dissimilar joint have not been thoroughly revealed.In this work,complex analyses of the phase transformation mechanisms of the joint are conducted,and phase transformations in individual zones are correlated to their microhardness and nanohardness.Results reveal that a dissolution occurs under high temperatures encountered during LFW,which reduces microhardness of the joint to that of Ti17(a+β)and Ti17(β).In ThermoMechanically Affected Zone of Ti17(a+β)(TMAZ-(a+β))side joint,a large number of nanocrystalline a phases form with different orientations.This microstructure strengthens significantly by fine grains which balances partial softening effect of a dissolution,and increases nanohardness of a phase and microhardness of TMAZ-(a+β).Superlattice metastableβphase precipitates from metastableβin Weld Zone(WZ)during quick cooling following welding,because of short-range diffusion migration of solute atoms,especiallyβstabilizing elements Mo and Cr.The precipitation of the superlattice metastableβphase results in precipitation strengthening,which in turn increases nanohardness of metastableβand microhardness in WZ.
基金This work was financially supported by the National Natural Science Foundation of China(Grant Nos.11704240,11734007,and 91850101)the National Key Research and Development Program of China(Grant Nos.2017YFA0303504 and 2017YFA0700201)+1 种基金the Shanghai Science and Technology Committee(Grant Nos.18QA1401800,20JC1414601,and 20JC1414602)the Shanghai East Scholar Plan,Fudan University-CIOMP Joint Fund(No.FC2018-006)。
文摘Dynamically controlling terahertz(THz)wavefronts in a designable fashion is highly desired in practice.However,available methods working at microwave frequencies do not work well in the THz regime due to lacking suitable tunable elements with submicrometer sizes.Here,instead of locally controlling individual meta-atoms in a THz metasurface,we show that rotating different layers(each exhibiting a particular phase profile)in a cascaded metadevice at different speeds can dynamically change the effective Jonesmatrix property of the whole device,thus enabling extraordinary manipulations on the wavefront and polarization characteristics of a THz beam impinging on the device.After illustrating our strategy based on model calculations,we experimentally demonstrate two proof-of-concept metadevices,each consisting of two carefully designed all-silicon transmissive metasurfaces exhibiting different phase profiles.Rotating two metasurfaces inside the fabricated devices at different speeds,we experimentally demonstrate that the first metadevice can efficiently redirect a normally incident THz beam to scan over a wide solid-angle range,while the second one can dynamically manipulate both the wavefront and polarization of a THz beam.Our results pave the way to achieving dynamic control of THz beams,which is useful in many applications,such as THz radar,and bio-and chemical sensing and imaging.
