High(or medium)-entropy alloys(H/MEAs)are complex concentrated solid solutions prone to develop the chemical short-range orders(CSROs),as an indispensable structural constituent to make H/MEAs essentially different fr...High(or medium)-entropy alloys(H/MEAs)are complex concentrated solid solutions prone to develop the chemical short-range orders(CSROs),as an indispensable structural constituent to make H/MEAs essentially different from the traditional alloys.The CSROs are predicted to play roles in dislocation behaviors and mechanical properties.So far,the image of CSROs is built up by the theoretical modeling and computational simulations in terms of the conventional concept,i.e.,the preference/avoidance of elemental species to satisfy the short-ranged ordering in the first and the next couple of nearest-neighbor atomic shells.In these simulated CSROs,however,the structural image is missing on the atomic scale,even though the lattice periodicity does not exist in the CSROs.Further,it is pending as to the issues if and what kind of CSRO may be formed in a specific H/MEA.All these are ascribed to the challenge of experimentally seeing the CSROs.Until recently,the breakthrough does not appear to convincingly identify the CSROs in the H/MEAs by using the state-of-the-art transmission electron microscope.To be specific,the electron diffractions provide solid evidence to doubtlessly ascertain CSROs.The structure motif of CSROs is then constructed,showing both the lattice structure and species ordering occupation,along with the stereoscopic topography of the CSRO.It is suggested that the CSROs,as the first landscape along the path of development of the local chemical ordering,offer one more route to substantially develop the ordered structure on the atomic scale in the H/MEAs,parallel to the existing grain-leveled microstructure.The findings of CSROs make a step forward to understand the CSROs-oriented relationship between the microstructure and mechanical properties.This review focuses on the recent progress mainly in the experimental aspects of the identification,structure motif,and mechanical stability in CSROs,along with the chemical medium-range orders as the growing CSROs。展开更多
We propose a method to implement electromagnetically induced grating in a phaseonium medium that has been coherently generated via atomic mechanisms.Phaseonium atoms have aΛ-type structure and three distinct energy l...We propose a method to implement electromagnetically induced grating in a phaseonium medium that has been coherently generated via atomic mechanisms.Phaseonium atoms have aΛ-type structure and three distinct energy levels;such atoms are originally generated in a coherent superposition of two lower levels.The phaseonium system is comprised of three-level atoms with aΛ-type configuration,which are initially prepared in a coherent superposition of two lower levels.To accomplish this spatial modulation based on the susceptibility of phaseonium medium,a standingwave field is used.By looking at how an optical field diffracts at different relative phases,we find that the zeroth and first order diffraction intensities increase as the relative phase changes.We also investigate the impact of the Rabi frequency of the field on diffraction intensity and notice that an increasing strength of the Rabi frequency leads to amplification in the intensity of both central zeroth order and first-order diffraction.Furthermore,it has been observed that a significant rise in diffraction intensity occurs at longer interaction lengths between external fields and the atomic medium.展开更多
To study wave-current actions on 3-D bodies a time-domain numerical model was established using a higher-order boundary element method(HOBEM).By assuming small flow velocities,the velocity potential could be expressed...To study wave-current actions on 3-D bodies a time-domain numerical model was established using a higher-order boundary element method(HOBEM).By assuming small flow velocities,the velocity potential could be expressed for linear and higher order components by perturbation expansion.A 4th-order Runge-Kutta method was applied for time marching.An artificial damping layer was adopted at the outer zone of the free surface mesh to dissipate scattering waves.Validation of the numerical method was carried out on run-up,wave exciting forces,and mean drift forces for wave-currents acting on a bottom-mounted vertical cylinder.The results were in close agreement with the results of a frequency-domain method and a published time-domain method.The model was then applied to compute wave-current forces and run-up on a Seastar mini tension-leg platform.展开更多
The modification of the electron diffraction pattern(EDP) of B2 in an as rapidly quenched then short time aged Ti Ni shape memory alloy(SMA) has been studied systematically using TEM. It was found that the diffusio...The modification of the electron diffraction pattern(EDP) of B2 in an as rapidly quenched then short time aged Ti Ni shape memory alloy(SMA) has been studied systematically using TEM. It was found that the diffusion scattering rings in EDP of an as rapidly quenched Ti-Ni SMA is associated with short range order (SRO) of vancancies in parent B2. After aging at 450℃ for 5 min the diffusion scattering rings are replaced by 1/2 {001} and 1 / 4 {012} extra reflections. It indicates that the SRO of vacancies has transformed into long range order (LRO) of vacancies,moreover,the LRO of vacancies exists in microdomains.展开更多
After describing research status of super-structure for Li (Ni_(1/3)Co_(1/3)Mn_(1/3)) O_2,diffraction patterns of Li (Ni_(1/3)Co_(1/3)Mn_(1/3)) O_2 in different order parameters have been researched by Powder-cell pro...After describing research status of super-structure for Li (Ni_(1/3)Co_(1/3)Mn_(1/3)) O_2,diffraction patterns of Li (Ni_(1/3)Co_(1/3)Mn_(1/3)) O_2 in different order parameters have been researched by Powder-cell program,including crystal structure,X-ray and neutron diffraction pattern,anomalous diffraction pattern and comparison of NiCoMn in different positions. The influence of order parameters on intensity of matrix and super-lattice diffraction lines has also been analyzed and the summarization and prospect have been made lastly.展开更多
Spectral diagnosis of radiation from laser plasma interaction and monochromation of radiation source are hot and important topics recently. Grating is one of the primary optical elements to do this job. Although easy ...Spectral diagnosis of radiation from laser plasma interaction and monochromation of radiation source are hot and important topics recently. Grating is one of the primary optical elements to do this job. Although easy to fabricate, traditional diffraction grating suffers from multi-order diffraction contamination. On the other hand, sinusoidal amplitude grating has the nonharmonic diffraction property, but it is too difficult to fabricate, especially for x-ray application. A novel nonharmonic diffraction grating named random position rectangle grating（RPRG） is proposed in this paper. Theoretical analysis and experiment results show that the RPRG is both higher order diffraction suppressing and not difficult to fabricate. Additionally, it is highly efficient; its first order absolute theoretical diffraction efficiency reaches 4.1%. Our result shows that RPRG is a novel tool for radiation diagnosis and monochromation.展开更多
A single-order diffraction transmission grating named spectroscopic photon sieve(SPS)for soft x-ray region is proposed and demonstrated in this paper.The SPS consists of many circular pinholes located randomly,and can...A single-order diffraction transmission grating named spectroscopic photon sieve(SPS)for soft x-ray region is proposed and demonstrated in this paper.The SPS consists of many circular pinholes located randomly,and can realize both free-standing diffractions and the suppression of higher-order differations.In this paper,the basic concept,numerical simulations,and calibration results of a 1000-lines/mm SPS for soft x-ray synchrotron radiation are presented.As predicted by theoretical calculations,the calibration results of a 1000-lines/mm SPS verify that the higher-order diffractions can be significantly suppressed along the symmetry axis.With the current nanofabrication technique,the SPS can potentially have a higher line density,and can be widely used in synchrotron radiation,laser-induced plasma diagnostics,and astrophysics.展开更多
基金supported by the National Key Research and Development Program of the Ministry of Science and Technology of China(No.2019YFA0209902)the National Natural Science Foundation of China(Nos.11998102,11972350,and 11790293)the Strategic Priority Research Program of the Chinese Academy of Sciences(No.XDB22040503).
文摘High(or medium)-entropy alloys(H/MEAs)are complex concentrated solid solutions prone to develop the chemical short-range orders(CSROs),as an indispensable structural constituent to make H/MEAs essentially different from the traditional alloys.The CSROs are predicted to play roles in dislocation behaviors and mechanical properties.So far,the image of CSROs is built up by the theoretical modeling and computational simulations in terms of the conventional concept,i.e.,the preference/avoidance of elemental species to satisfy the short-ranged ordering in the first and the next couple of nearest-neighbor atomic shells.In these simulated CSROs,however,the structural image is missing on the atomic scale,even though the lattice periodicity does not exist in the CSROs.Further,it is pending as to the issues if and what kind of CSRO may be formed in a specific H/MEA.All these are ascribed to the challenge of experimentally seeing the CSROs.Until recently,the breakthrough does not appear to convincingly identify the CSROs in the H/MEAs by using the state-of-the-art transmission electron microscope.To be specific,the electron diffractions provide solid evidence to doubtlessly ascertain CSROs.The structure motif of CSROs is then constructed,showing both the lattice structure and species ordering occupation,along with the stereoscopic topography of the CSRO.It is suggested that the CSROs,as the first landscape along the path of development of the local chemical ordering,offer one more route to substantially develop the ordered structure on the atomic scale in the H/MEAs,parallel to the existing grain-leveled microstructure.The findings of CSROs make a step forward to understand the CSROs-oriented relationship between the microstructure and mechanical properties.This review focuses on the recent progress mainly in the experimental aspects of the identification,structure motif,and mechanical stability in CSROs,along with the chemical medium-range orders as the growing CSROs。
基金the financial support provided by Hubei University of Automotive Technology in the form of a startup research grant(BK202212)。
文摘We propose a method to implement electromagnetically induced grating in a phaseonium medium that has been coherently generated via atomic mechanisms.Phaseonium atoms have aΛ-type structure and three distinct energy levels;such atoms are originally generated in a coherent superposition of two lower levels.The phaseonium system is comprised of three-level atoms with aΛ-type configuration,which are initially prepared in a coherent superposition of two lower levels.To accomplish this spatial modulation based on the susceptibility of phaseonium medium,a standingwave field is used.By looking at how an optical field diffracts at different relative phases,we find that the zeroth and first order diffraction intensities increase as the relative phase changes.We also investigate the impact of the Rabi frequency of the field on diffraction intensity and notice that an increasing strength of the Rabi frequency leads to amplification in the intensity of both central zeroth order and first-order diffraction.Furthermore,it has been observed that a significant rise in diffraction intensity occurs at longer interaction lengths between external fields and the atomic medium.
基金Supported by the National Natural Science Foundation of China under (Grant No.107 72040,50709005 and 50921001)the Major National Science and Technology Projects of China under (Grant No.2008ZX05026-02)the Open Fund of State Key Laboratory of Ocean Engineering
文摘To study wave-current actions on 3-D bodies a time-domain numerical model was established using a higher-order boundary element method(HOBEM).By assuming small flow velocities,the velocity potential could be expressed for linear and higher order components by perturbation expansion.A 4th-order Runge-Kutta method was applied for time marching.An artificial damping layer was adopted at the outer zone of the free surface mesh to dissipate scattering waves.Validation of the numerical method was carried out on run-up,wave exciting forces,and mean drift forces for wave-currents acting on a bottom-mounted vertical cylinder.The results were in close agreement with the results of a frequency-domain method and a published time-domain method.The model was then applied to compute wave-current forces and run-up on a Seastar mini tension-leg platform.
文摘The modification of the electron diffraction pattern(EDP) of B2 in an as rapidly quenched then short time aged Ti Ni shape memory alloy(SMA) has been studied systematically using TEM. It was found that the diffusion scattering rings in EDP of an as rapidly quenched Ti-Ni SMA is associated with short range order (SRO) of vancancies in parent B2. After aging at 450℃ for 5 min the diffusion scattering rings are replaced by 1/2 {001} and 1 / 4 {012} extra reflections. It indicates that the SRO of vacancies has transformed into long range order (LRO) of vacancies,moreover,the LRO of vacancies exists in microdomains.
基金Sponsored by the National Key Research and Development Program(Grant No.2016YFB0100500)
文摘After describing research status of super-structure for Li (Ni_(1/3)Co_(1/3)Mn_(1/3)) O_2,diffraction patterns of Li (Ni_(1/3)Co_(1/3)Mn_(1/3)) O_2 in different order parameters have been researched by Powder-cell program,including crystal structure,X-ray and neutron diffraction pattern,anomalous diffraction pattern and comparison of NiCoMn in different positions. The influence of order parameters on intensity of matrix and super-lattice diffraction lines has also been analyzed and the summarization and prospect have been made lastly.
基金Project supported by the National Natural Science Foundation of China(Grant No.11375160)the National Science Instruments Major Project of China(Grant No.2012YQ130125)
文摘Spectral diagnosis of radiation from laser plasma interaction and monochromation of radiation source are hot and important topics recently. Grating is one of the primary optical elements to do this job. Although easy to fabricate, traditional diffraction grating suffers from multi-order diffraction contamination. On the other hand, sinusoidal amplitude grating has the nonharmonic diffraction property, but it is too difficult to fabricate, especially for x-ray application. A novel nonharmonic diffraction grating named random position rectangle grating（RPRG） is proposed in this paper. Theoretical analysis and experiment results show that the RPRG is both higher order diffraction suppressing and not difficult to fabricate. Additionally, it is highly efficient; its first order absolute theoretical diffraction efficiency reaches 4.1%. Our result shows that RPRG is a novel tool for radiation diagnosis and monochromation.
基金Project supported by the National Natural Science Foundation for Young Scientists of China(Grant No.11805179).
文摘A single-order diffraction transmission grating named spectroscopic photon sieve(SPS)for soft x-ray region is proposed and demonstrated in this paper.The SPS consists of many circular pinholes located randomly,and can realize both free-standing diffractions and the suppression of higher-order differations.In this paper,the basic concept,numerical simulations,and calibration results of a 1000-lines/mm SPS for soft x-ray synchrotron radiation are presented.As predicted by theoretical calculations,the calibration results of a 1000-lines/mm SPS verify that the higher-order diffractions can be significantly suppressed along the symmetry axis.With the current nanofabrication technique,the SPS can potentially have a higher line density,and can be widely used in synchrotron radiation,laser-induced plasma diagnostics,and astrophysics.
