The most simple method for solventless synthesis of supramolecular complex of CMCR·2BPY·BZP, [CMCR = C-methylcalix[4]resorcinarene, BPY = 4,4'-bipyridine, BZP = benzophenone], is proposed. Although CMCR ...The most simple method for solventless synthesis of supramolecular complex of CMCR·2BPY·BZP, [CMCR = C-methylcalix[4]resorcinarene, BPY = 4,4'-bipyridine, BZP = benzophenone], is proposed. Although CMCR by itself is high melting point compound (above 300°C), CMCR was found to be dissolved in melt mixture of BPY and BZPeven below 120°C. In the mixture of the three components, the reaction occurs to form CMCR·2BPY·BZP supramolecular complex.展开更多
The finite-difference time-domain method is used to simulate the optical characteristics of an in-plane switching blue phase liquid crystal display.Compared with the matrix optic methods and the refractive method,the ...The finite-difference time-domain method is used to simulate the optical characteristics of an in-plane switching blue phase liquid crystal display.Compared with the matrix optic methods and the refractive method,the finite-difference timedomain method,which is used to directly solve Maxwell's equations,can consider the lateral variation of the refractive index and obtain an accurate convergence effect.The simulation results show that e-rays and o-rays bend in different directions when the in-plane switching blue phase liquid crystal display is driven by the operating voltage.The finitedifference time-domain method should be used when the distribution of the liquid crystal in the liquid crystal display has a large lateral change.展开更多
A solid phase crystallizing method has been developed to grow a Si crystal at tem-peratures as low as 550 ℃. Using this method, a high-quality thin-film polycrystalline silicon (Poly-Si) was obtained. The largest gra...A solid phase crystallizing method has been developed to grow a Si crystal at tem-peratures as low as 550 ℃. Using this method, a high-quality thin-film polycrystalline silicon (Poly-Si) was obtained. The largest grain size, examined with X-ray diffraction spectroscopy and scanning electron microscopy images of recrystallized samples, is approximately 1 /μm for substrate temperature at 300 ℃ and annealed at 550℃ for 3 hours.展开更多
We report a reproducible approach in preparing high-quality overdoped Bi2 Sr2 CaCu2 08+δ (Bi2212) single crystals by annealing Bi2212 crystals in high oxygen pressure followed by a fast quenching. In this way, hig...We report a reproducible approach in preparing high-quality overdoped Bi2 Sr2 CaCu2 08+δ (Bi2212) single crystals by annealing Bi2212 crystals in high oxygen pressure followed by a fast quenching. In this way, high-quality overdoped and heavily overdoped Bi2212 single crystals are obtained by controlling the annealing oxygen pressure. We find that, beyond a limit of oxygen pressure that can achieve most heavily overdoped Bi2212 with a Tc N63 K, the annealed Bi2212 begins to decompose. This accounts for the existence of the hole-doping limit and thus the Tc limit in the heavily overdoped region of Bi2212 by the oxygen annealing process. These results provide a reliable way in preparing high-quality overdoped and heavily overdoped Bi2212 crystals that are important for studies of the physical properties, electronic structure and superconductivity mechanism of the cuprate superconductors.展开更多
This paper reports the growth and spectral assessments of Yb^(3+) ion doped MgMoO_4(Yb^(3+):MgMoO_4) crystal grown by the TSSG method. Polarized spectral properties of Yb^(3+):MgMoO_4 crystal, including a...This paper reports the growth and spectral assessments of Yb^(3+) ion doped MgMoO_4(Yb^(3+):MgMoO_4) crystal grown by the TSSG method. Polarized spectral properties of Yb^(3+):MgMoO_4 crystal, including absorption and emission cross-sections, absorption FWHM and fluorescence lifetime, have been investigated. The laser performance parameters bmin, Isat and Iminhave also been evaluated. All the investigated results show the Yb^(3+)-doped MgMoO_4 crystal is expected as a promising candidate for ultrashort pulse and tunable lasers.展开更多
We describe theoretically the grounded method of measuring the conductivity of anisotropic layered semiconductor materials. The suggested method implies the use of a four-probe testing device with a linear arrangement...We describe theoretically the grounded method of measuring the conductivity of anisotropic layered semiconductor materials. The suggested method implies the use of a four-probe testing device with a linear arrangement of probes. The final expressions for identifying the electrical conductivity are presented in the form of a series of analytic functions. The suggested method is experimentally verified, and practical recommendations of how to apply it are also provided.展开更多
We report the synthesis and characterization of a Si-based ternary semiconductor Mg_(3)Si_(2)Te_(6),which exhibits a quasitwo-dimensional structure,where the trigonal Mg_(3)Si_(2)Te_(6)layers are separated by Mg ions....We report the synthesis and characterization of a Si-based ternary semiconductor Mg_(3)Si_(2)Te_(6),which exhibits a quasitwo-dimensional structure,where the trigonal Mg_(3)Si_(2)Te_(6)layers are separated by Mg ions.Ultraviolet-visible absorption spectroscopy and density functional theory calculations were performed to investigate the electronic structure.The experimentally determined direct band gap is 1.39 eV,consistent with the value of the density function theory calculations.Our results reveal that Mg_(3)Si_(2)Te_(6)is a direct gap semiconductor,which is a potential candidate for near-infrared optoelectronic devices.展开更多
A high-contrast coronagraph for direct imaging of an Earth-like exoplanet at the visible band needs a contrast of 10^-10 at a small angular separation of 4λ/D or less. Here we report our recent laboratory experiment ...A high-contrast coronagraph for direct imaging of an Earth-like exoplanet at the visible band needs a contrast of 10^-10 at a small angular separation of 4λ/D or less. Here we report our recent laboratory experiment that approaches these lim- its. Our test of a high-contrast imaging coronagraph is based on our step-transmission apodized filter. To achieve this goal, we use a liquid crystal array as a phase correc- tor to create a dark hole based on our dedicated algorithm. We have suppressed the diffraction and speckle noise near the point image of a star to a level of 1.68 × 10^-9 at 4λ/D, which can be used for direct imaging of Jupiter-like exoplanets. This demon- strates that a telescope incorporating a high-contrast coronagraph in space has the potential to detect and characterize Earth-like planets.展开更多
We report the modulational instability (MI) analysis for the modulation equations governing the propagation of coherent polarized light through a nematic liquid crystal (NLC) slab, in the limit of low light intens...We report the modulational instability (MI) analysis for the modulation equations governing the propagation of coherent polarized light through a nematic liquid crystal (NLC) slab, in the limit of low light intensity and local material response. The linear stability analysis of the nonlinear plane wave solutions is performed by considering both the wave vectors (k,l) of the basic states and wave vectors (K,L) of the perturbations as free parameters. We compute the MI gain, and the MI gain peak is reduced and the stable bandwidth is widened with the increase of the strength of the applied electric field. Further, we invoke the extended homogeneous balance method and Exp-function method aided with symbolic computation and obtain a series of periodic solitonic humps of nematicon profiles admitting the propagation of laser light in the NLC medium.展开更多
The nano-crystalline materials with many special and super magnetic properties could be synthesized by fractional crystallization of amorphous alloys. Since this new method for preparation of nano-crystalline material...The nano-crystalline materials with many special and super magnetic properties could be synthesized by fractional crystallization of amorphous alloys. Since this new method for preparation of nano-crystalline materials was introduced, the crystallization kinetics of amorphous alloys has been studied in more and more intensive investigations. So far, almost all experiments on the crystallization kinetics are conducted by differential展开更多
A novel and efficient methodology for obtaining highly active photocatalyst of bi phase TiO 2 with small particle size and high specific surface area was developed by solvent evaporation induced crystallization (SE...A novel and efficient methodology for obtaining highly active photocatalyst of bi phase TiO 2 with small particle size and high specific surface area was developed by solvent evaporation induced crystallization (SEIC) method at low temperature. The prepared TiO 2 powder was characterized with X ray diffraction (XRD), transmission electron microscopy (TEM) and BET surface areas. The photocatalytic activity was evaluated by the photocatalytic oxidation of acetone in air. The results showed that the photocatalytic activity of the TiO 2 powder prepared by this method approached that of Degussa P25. This may be attributed to the fact that the prepared TiO 2 powder had larger specific surface areas (265 m 2·g -1 ) and smaller crystallite size (about 5 nm), but relatively low crystallinity, as compared with Degussa P25.展开更多
Microstructure-based numerical modeling of the deformation heterogeneity and ferrite recrystallization in a cold-rolled dual-phase(DP)steel has been performed by using the crystal plasticity finite element method(CPFE...Microstructure-based numerical modeling of the deformation heterogeneity and ferrite recrystallization in a cold-rolled dual-phase(DP)steel has been performed by using the crystal plasticity finite element method(CPFEM)coupled with a mesoscale cellular automaton(CA)model.The microstructural response of subsequent primary recrystallization with the deformation heterogeneity in two-phase microstructures is studied.The simulations demonstrate that the deformation of multi-phase structures leads to highly strained shear bands formed in the soft ferrite matrix,which produces grain clusters in subsequent primary recrystallization.The early impingement of recrystallization fronts among the clustered grains causes mode conversions in the recrystallization kinetics.Reliable predictions regarding the grain size,microstructure morphology and kinetics can be made by comparison with the experimental results.The influence of initial strains on the recrystallization is also obtained by the simulation approach.展开更多
Photonic crystal fibers (PCFs) with a stepped raised-core profile and one layer equally spaced holes in the cladding are analyzed. Using effective index method and considering a raised step refractive index differen...Photonic crystal fibers (PCFs) with a stepped raised-core profile and one layer equally spaced holes in the cladding are analyzed. Using effective index method and considering a raised step refractive index difference between the index of the core and the effective index of the cladding, we improve the characteristic parameters such as numerical aperture and V-parameter, and reduce its bending loss to about one tenth of a conventional PCF. Implementing such a structure in PCFs may be one step forward to achieve low loss PCFs for communication applications.展开更多
A highly transparent Eu3+-doped CaGdA104 (CGA) single crystal is grown by the floating zone method. The segregation coefficient, x ray diffraction, and x ray rocking curve are detected, and the results reveal that ...A highly transparent Eu3+-doped CaGdA104 (CGA) single crystal is grown by the floating zone method. The segregation coefficient, x ray diffraction, and x ray rocking curve are detected, and the results reveal that the single crystal is of high quality. The f-f transitions of Eu3+ in the host lattice are discussed. The 5D0-7F2 emis- sion transition at 621 nm (red light) is dominant over the 5D0-7F1 emission transitions at 591 and 599 nm (orange light), agreeing well with the random crystal environment of Eu3+ ions in a CGA crystal. The decay time of Eu:5D0 is measured to be 1.02 ms. All the results show that the Eu:CGA crystal has good optical char- acterization and promises to be an excellent red- fluorescence material.展开更多
The phase modulation characteristics of a reflective liquid crystal (LC) spatial light modulator (SLM) under oblique incidence are studied by using our proposed self-interference method. The experimental setup of ...The phase modulation characteristics of a reflective liquid crystal (LC) spatial light modulator (SLM) under oblique incidence are studied by using our proposed self-interference method. The experimental setup of the method is very simple and has good robustness to mechanical vibrations. By changing the gray value of the combined grayscale loaded on the LC-SLM, different sheared fringe patterns, generated by the interference between the constant phase-modulated beam and the +1-order diffracted beam of the blazed grating, can be obtained. The amount of phase modulation of the LC-SLM is obtained by subtracting the phase of the two side lobes in the frequency domain. By turning the turntable where the SLM is mounted, the phase modulation characteristics at different incident angles can be measured. The experimental results show that the phase modulation curves do not change significantly with the small angle. When the angle is large (i.e. larger than 10°), the phase modulation curves become different, especially for the high gray levels. With the increase of the incident angle, the phase modulation depth is reduced. The results indicate that the incident angle plays an important role in the performance of the phase modulation of an LC-SLM.展开更多
A uranyl compound, K_4UO_2(CO_3)_3 has been characterized by powder X-ray diffraction method. M. W.=606.46, monoclinic, C2/c (No. 15), a=1.0240(7), b=0.9198(4), c=1.2222(12)nm, β=95.12(4)°,V=1.1466(5)nm^3, Z=4, ...A uranyl compound, K_4UO_2(CO_3)_3 has been characterized by powder X-ray diffraction method. M. W.=606.46, monoclinic, C2/c (No. 15), a=1.0240(7), b=0.9198(4), c=1.2222(12)nm, β=95.12(4)°,V=1.1466(5)nm^3, Z=4, D_m=3.468g/cm^3, D_c=3.513g/cm~, λ(Cu Kα_1)=O.1540598nm, T=298K. The structure was solved by heavy atom method and Fourier synthesis, and refined by full- matrix least-squares method to R=0.1185 for 275 reflections. The uranium (Ⅵ) atom is in an eight-coordinate distorted hexagonal-bipyramidal environment with creasy fan shape. The linear uranyl group approaches to perpendicular to the equatorial plane in which three carbonate groups are chelated. U(Ⅵ) has two linear oxygen atoms closer to it (U-O=0.1767 (5) nm) than six other neighbours (U-O ranging from 0.2516 to 0.2568nm). The distances between carbon atoms and uncoordinated oxygen atoms are 0.122 (1) and 0.123(1) nm, which are distinctly different from those between carbon and coordinated oxygen atoms (mean 0.134(6) nm). This fact reveals the non-eq- uivalence of one oxygen atom to the other two in each carbonate. In K_4UO_2(CO_3)_3, the O-O dis- tance for the adjacent carbonate groups is 0.2794(4)nm approaching to the sum of Van der Waals radii of two oxygen atoms. The K-O distances vary between 0.2667 and 0.3131nm, and each anion is immediately surrounded by six potassium ions, only four of which can be considered to belong to the same structural formula unit, and they are symmetrically located above and below the equatorial plane.展开更多
A dynamic compression test was performed on α+β dual-phase titanium alloy Ti20C using a split Hopkinson pressure bar.The formation of adiabatic shear bands generated during the compression process was studied by com...A dynamic compression test was performed on α+β dual-phase titanium alloy Ti20C using a split Hopkinson pressure bar.The formation of adiabatic shear bands generated during the compression process was studied by combining the proposed multi-scale crystal plasticity finite element method with experimental measurements.The complex local micro region load was progressively extracted from the simulation results of a macro model and applied to an established three-dimensional multi-grain microstructure model.Subsequently,the evolution histories of the grain shape,size,and orientation inside the adiabatic shear band were quantitatively simulated.The results corresponded closely to the experimental results obtained via transmission electron microscopy and precession electron diffraction.Furthermore,by calculating the grain rotation and temperature rise inside the adiabatic shear band,the microstructural softening and thermal softening effects of typical heavily-deformed α grains were successfully decoupled.The results revealed that the microstructural softening stress was triggered and then stabilized(in general)at a relatively high value.This indicated that the mechanical strength was lowered mainly by the grain orientation evolution or dynamic recrystallization occurring during early plastic deformation.Subsequently,thermal softening increased linearly and became the main softening mechanism.Noticeably,in the final stage,the thermal softening stress accounted for 78.4% of the total softening stress due to the sharp temperature increase,which inevitably leads to the stress collapse and potential failure of the alloy.展开更多
By inserting an air cavity into a one-dimensional photonic crystal of LiF/GaSb, a tunable filter covering the whole visible range is proposed. Following consideration of the dispersion of the materials, through modula...By inserting an air cavity into a one-dimensional photonic crystal of LiF/GaSb, a tunable filter covering the whole visible range is proposed. Following consideration of the dispersion of the materials, through modulating the thickness of the air cavity, we demonstrate that a single resonant peak can shift from 416.1 to 667.3 nm in the band gap at normal incidence by means of the transfer matrix method. The research also shows that the transmittance of the channel can be maximized when the number of periodic Li F/Ga Sb layers on one side of the air defect layer is equal to that of the other side. When adding a period to both sides respectively, the full width at half maximum of the defect mode is reduced by one order of magnitude. This structure will provide a promising approach to fabricate practical tunable filters in the visible region with ultra-wide tuning range.展开更多
F321 austenitic stainless steel,well known for its excellent corrosion and oxidation resistance,is widely used as a structural component in the pipelines and pumps of light water reactors(LWRs)and generation IV(GenlV)...F321 austenitic stainless steel,well known for its excellent corrosion and oxidation resistance,is widely used as a structural component in the pipelines and pumps of light water reactors(LWRs)and generation IV(GenlV)reactors.However,the material failure arising from the high-temperature softening of the 300 series austenitic stainless steels has recently received significant attention.In this study,we conducted uniaxial tensile tests on F321 stainless steel at different temperatures.P\irthermore,we developed a face-centered cubic(FCC)crystal plasticity method emphasizing the temperature factor of the evolution of dislocations inferred by the physical mechanisms at the microscopic level to simulate the polycrystalline mechanical response and model the high-temperature softening phenomenon of F321 austenitic stainless steel.Subsequently,this model was implemented using the ABAQUS finite-element platform.On this basis,the crystal plastic finite-element method(CPFEM)of F321 stainless steel was established.The calculated results were in good agreement with the experimental results,which validated the effectiveness of this numerical method.展开更多
文摘The most simple method for solventless synthesis of supramolecular complex of CMCR·2BPY·BZP, [CMCR = C-methylcalix[4]resorcinarene, BPY = 4,4'-bipyridine, BZP = benzophenone], is proposed. Although CMCR by itself is high melting point compound (above 300°C), CMCR was found to be dissolved in melt mixture of BPY and BZPeven below 120°C. In the mixture of the three components, the reaction occurs to form CMCR·2BPY·BZP supramolecular complex.
基金Project supported by the National Natural Science Foundation of China(Grant Nos.11304074,61475042,and 11274088)the Natural Science Foundation of Hebei Province,China(Grant Nos.A2015202320 and GCC2014048)the Key Subject Construction Project of Hebei Province University,China
文摘The finite-difference time-domain method is used to simulate the optical characteristics of an in-plane switching blue phase liquid crystal display.Compared with the matrix optic methods and the refractive method,the finite-difference timedomain method,which is used to directly solve Maxwell's equations,can consider the lateral variation of the refractive index and obtain an accurate convergence effect.The simulation results show that e-rays and o-rays bend in different directions when the in-plane switching blue phase liquid crystal display is driven by the operating voltage.The finitedifference time-domain method should be used when the distribution of the liquid crystal in the liquid crystal display has a large lateral change.
基金This work was supported by the Guangdong Provincial Natural Science Foundation of China No.990781.
文摘A solid phase crystallizing method has been developed to grow a Si crystal at tem-peratures as low as 550 ℃. Using this method, a high-quality thin-film polycrystalline silicon (Poly-Si) was obtained. The largest grain size, examined with X-ray diffraction spectroscopy and scanning electron microscopy images of recrystallized samples, is approximately 1 /μm for substrate temperature at 300 ℃ and annealed at 550℃ for 3 hours.
基金Supported by the National Natural Science Foundation of China under Grant Nos 11190022,11334010 and 11534007the National Basic Research Program of China under Grant No 2015CB921000the Strategic Priority Research Program(B)of Chinese Academy of Sciences under Grant No XDB07020300
文摘We report a reproducible approach in preparing high-quality overdoped Bi2 Sr2 CaCu2 08+δ (Bi2212) single crystals by annealing Bi2212 crystals in high oxygen pressure followed by a fast quenching. In this way, high-quality overdoped and heavily overdoped Bi2212 single crystals are obtained by controlling the annealing oxygen pressure. We find that, beyond a limit of oxygen pressure that can achieve most heavily overdoped Bi2212 with a Tc N63 K, the annealed Bi2212 begins to decompose. This accounts for the existence of the hole-doping limit and thus the Tc limit in the heavily overdoped region of Bi2212 by the oxygen annealing process. These results provide a reliable way in preparing high-quality overdoped and heavily overdoped Bi2212 crystals that are important for studies of the physical properties, electronic structure and superconductivity mechanism of the cuprate superconductors.
基金supported by the National Natural Science Foundation of China(No.61308085,51102047,51472050 and 11404072)Fund of Key Laboratory of Optoelectronic Materials Chemistry and Physics,Chinese Academy of Sciences(2008DP173016)the Natural Science Foundation of Fujian Province(2017J01746)
文摘This paper reports the growth and spectral assessments of Yb^(3+) ion doped MgMoO_4(Yb^(3+):MgMoO_4) crystal grown by the TSSG method. Polarized spectral properties of Yb^(3+):MgMoO_4 crystal, including absorption and emission cross-sections, absorption FWHM and fluorescence lifetime, have been investigated. The laser performance parameters bmin, Isat and Iminhave also been evaluated. All the investigated results show the Yb^(3+)-doped MgMoO_4 crystal is expected as a promising candidate for ultrashort pulse and tunable lasers.
基金Supported by the Ministry of Education and Science of the Russian Federation under Grant No 2271
文摘We describe theoretically the grounded method of measuring the conductivity of anisotropic layered semiconductor materials. The suggested method implies the use of a four-probe testing device with a linear arrangement of probes. The final expressions for identifying the electrical conductivity are presented in the form of a series of analytic functions. The suggested method is experimentally verified, and practical recommendations of how to apply it are also provided.
基金the National Natural Science Foundation of China(Grant Nos.12174454,11904414,11904416,and 12104427)the Guangdong Basic and Applied Basic Research Foundation,China(Grant No.2021B1515120015)+1 种基金the Guangzhou Basic and Applied Basic Research Foundation(Grant No.202201011123)the National Key Research and Development Program of China(Grant No.2019YFA0705702).
文摘We report the synthesis and characterization of a Si-based ternary semiconductor Mg_(3)Si_(2)Te_(6),which exhibits a quasitwo-dimensional structure,where the trigonal Mg_(3)Si_(2)Te_(6)layers are separated by Mg ions.Ultraviolet-visible absorption spectroscopy and density functional theory calculations were performed to investigate the electronic structure.The experimentally determined direct band gap is 1.39 eV,consistent with the value of the density function theory calculations.Our results reveal that Mg_(3)Si_(2)Te_(6)is a direct gap semiconductor,which is a potential candidate for near-infrared optoelectronic devices.
基金Supported by the National Natural Science Foundation of China
文摘A high-contrast coronagraph for direct imaging of an Earth-like exoplanet at the visible band needs a contrast of 10^-10 at a small angular separation of 4λ/D or less. Here we report our recent laboratory experiment that approaches these lim- its. Our test of a high-contrast imaging coronagraph is based on our step-transmission apodized filter. To achieve this goal, we use a liquid crystal array as a phase correc- tor to create a dark hole based on our dedicated algorithm. We have suppressed the diffraction and speckle noise near the point image of a star to a level of 1.68 × 10^-9 at 4λ/D, which can be used for direct imaging of Jupiter-like exoplanets. This demon- strates that a telescope incorporating a high-contrast coronagraph in space has the potential to detect and characterize Earth-like planets.
基金One of the authors (L. Kavitha) gratefully acknowledges the financial support from NBHM, India in the form of major research project, BRNS, India in the form of Young Scientist Research Award and ICTP, Italy in the form of Junior AssociateshipUGC, India for financial assistance in the form of Research Award+1 种基金M. Venkatesh acknowledges BSR-Research Fellowship under UGC Non-SAP Scheme, IndiaS. Dhamayanthi thanks the University Research Fellowship (URF) given by Periyar Uni- versity, India.
文摘We report the modulational instability (MI) analysis for the modulation equations governing the propagation of coherent polarized light through a nematic liquid crystal (NLC) slab, in the limit of low light intensity and local material response. The linear stability analysis of the nonlinear plane wave solutions is performed by considering both the wave vectors (k,l) of the basic states and wave vectors (K,L) of the perturbations as free parameters. We compute the MI gain, and the MI gain peak is reduced and the stable bandwidth is widened with the increase of the strength of the applied electric field. Further, we invoke the extended homogeneous balance method and Exp-function method aided with symbolic computation and obtain a series of periodic solitonic humps of nematicon profiles admitting the propagation of laser light in the NLC medium.
文摘The nano-crystalline materials with many special and super magnetic properties could be synthesized by fractional crystallization of amorphous alloys. Since this new method for preparation of nano-crystalline materials was introduced, the crystallization kinetics of amorphous alloys has been studied in more and more intensive investigations. So far, almost all experiments on the crystallization kinetics are conducted by differential
基金theNationalNaturalScienceFoundationofChina (No .5 0 2 72 0 49)
文摘A novel and efficient methodology for obtaining highly active photocatalyst of bi phase TiO 2 with small particle size and high specific surface area was developed by solvent evaporation induced crystallization (SEIC) method at low temperature. The prepared TiO 2 powder was characterized with X ray diffraction (XRD), transmission electron microscopy (TEM) and BET surface areas. The photocatalytic activity was evaluated by the photocatalytic oxidation of acetone in air. The results showed that the photocatalytic activity of the TiO 2 powder prepared by this method approached that of Degussa P25. This may be attributed to the fact that the prepared TiO 2 powder had larger specific surface areas (265 m 2·g -1 ) and smaller crystallite size (about 5 nm), but relatively low crystallinity, as compared with Degussa P25.
基金financially supported by the National Science Foundation of China under Grant Nos. 51771192, 51371169 and U1708252。
文摘Microstructure-based numerical modeling of the deformation heterogeneity and ferrite recrystallization in a cold-rolled dual-phase(DP)steel has been performed by using the crystal plasticity finite element method(CPFEM)coupled with a mesoscale cellular automaton(CA)model.The microstructural response of subsequent primary recrystallization with the deformation heterogeneity in two-phase microstructures is studied.The simulations demonstrate that the deformation of multi-phase structures leads to highly strained shear bands formed in the soft ferrite matrix,which produces grain clusters in subsequent primary recrystallization.The early impingement of recrystallization fronts among the clustered grains causes mode conversions in the recrystallization kinetics.Reliable predictions regarding the grain size,microstructure morphology and kinetics can be made by comparison with the experimental results.The influence of initial strains on the recrystallization is also obtained by the simulation approach.
文摘Photonic crystal fibers (PCFs) with a stepped raised-core profile and one layer equally spaced holes in the cladding are analyzed. Using effective index method and considering a raised step refractive index difference between the index of the core and the effective index of the cladding, we improve the characteristic parameters such as numerical aperture and V-parameter, and reduce its bending loss to about one tenth of a conventional PCF. Implementing such a structure in PCFs may be one step forward to achieve low loss PCFs for communication applications.
基金supported by the Natural Science Foundation of Shanghai under Grant No.15ZR1444700
文摘A highly transparent Eu3+-doped CaGdA104 (CGA) single crystal is grown by the floating zone method. The segregation coefficient, x ray diffraction, and x ray rocking curve are detected, and the results reveal that the single crystal is of high quality. The f-f transitions of Eu3+ in the host lattice are discussed. The 5D0-7F2 emis- sion transition at 621 nm (red light) is dominant over the 5D0-7F1 emission transitions at 591 and 599 nm (orange light), agreeing well with the random crystal environment of Eu3+ ions in a CGA crystal. The decay time of Eu:5D0 is measured to be 1.02 ms. All the results show that the Eu:CGA crystal has good optical char- acterization and promises to be an excellent red- fluorescence material.
基金financially supported by the National Natural Science Foundation of China(No.51705404)the China Postdoctoral Science Foundation(No.2016M602806)the Fundamental Research Funds for the Central Universities(No.xjj2017093)
文摘The phase modulation characteristics of a reflective liquid crystal (LC) spatial light modulator (SLM) under oblique incidence are studied by using our proposed self-interference method. The experimental setup of the method is very simple and has good robustness to mechanical vibrations. By changing the gray value of the combined grayscale loaded on the LC-SLM, different sheared fringe patterns, generated by the interference between the constant phase-modulated beam and the +1-order diffracted beam of the blazed grating, can be obtained. The amount of phase modulation of the LC-SLM is obtained by subtracting the phase of the two side lobes in the frequency domain. By turning the turntable where the SLM is mounted, the phase modulation characteristics at different incident angles can be measured. The experimental results show that the phase modulation curves do not change significantly with the small angle. When the angle is large (i.e. larger than 10°), the phase modulation curves become different, especially for the high gray levels. With the increase of the incident angle, the phase modulation depth is reduced. The results indicate that the incident angle plays an important role in the performance of the phase modulation of an LC-SLM.
基金This work was supported by the National Natural Science Foundation of China.
文摘A uranyl compound, K_4UO_2(CO_3)_3 has been characterized by powder X-ray diffraction method. M. W.=606.46, monoclinic, C2/c (No. 15), a=1.0240(7), b=0.9198(4), c=1.2222(12)nm, β=95.12(4)°,V=1.1466(5)nm^3, Z=4, D_m=3.468g/cm^3, D_c=3.513g/cm~, λ(Cu Kα_1)=O.1540598nm, T=298K. The structure was solved by heavy atom method and Fourier synthesis, and refined by full- matrix least-squares method to R=0.1185 for 275 reflections. The uranium (Ⅵ) atom is in an eight-coordinate distorted hexagonal-bipyramidal environment with creasy fan shape. The linear uranyl group approaches to perpendicular to the equatorial plane in which three carbonate groups are chelated. U(Ⅵ) has two linear oxygen atoms closer to it (U-O=0.1767 (5) nm) than six other neighbours (U-O ranging from 0.2516 to 0.2568nm). The distances between carbon atoms and uncoordinated oxygen atoms are 0.122 (1) and 0.123(1) nm, which are distinctly different from those between carbon and coordinated oxygen atoms (mean 0.134(6) nm). This fact reveals the non-eq- uivalence of one oxygen atom to the other two in each carbonate. In K_4UO_2(CO_3)_3, the O-O dis- tance for the adjacent carbonate groups is 0.2794(4)nm approaching to the sum of Van der Waals radii of two oxygen atoms. The K-O distances vary between 0.2667 and 0.3131nm, and each anion is immediately surrounded by six potassium ions, only four of which can be considered to belong to the same structural formula unit, and they are symmetrically located above and below the equatorial plane.
基金financially supported by the National Natural Science Foundation of China(No.51571031)。
文摘A dynamic compression test was performed on α+β dual-phase titanium alloy Ti20C using a split Hopkinson pressure bar.The formation of adiabatic shear bands generated during the compression process was studied by combining the proposed multi-scale crystal plasticity finite element method with experimental measurements.The complex local micro region load was progressively extracted from the simulation results of a macro model and applied to an established three-dimensional multi-grain microstructure model.Subsequently,the evolution histories of the grain shape,size,and orientation inside the adiabatic shear band were quantitatively simulated.The results corresponded closely to the experimental results obtained via transmission electron microscopy and precession electron diffraction.Furthermore,by calculating the grain rotation and temperature rise inside the adiabatic shear band,the microstructural softening and thermal softening effects of typical heavily-deformed α grains were successfully decoupled.The results revealed that the microstructural softening stress was triggered and then stabilized(in general)at a relatively high value.This indicated that the mechanical strength was lowered mainly by the grain orientation evolution or dynamic recrystallization occurring during early plastic deformation.Subsequently,thermal softening increased linearly and became the main softening mechanism.Noticeably,in the final stage,the thermal softening stress accounted for 78.4% of the total softening stress due to the sharp temperature increase,which inevitably leads to the stress collapse and potential failure of the alloy.
基金Project supported by the National Natural Science Foundation of China(Nos.61575138,61307069,51205273)the Top Young Academic Leaders and the Outstanding Innovative Teams of Higher Learning Institutions of Shanxi
文摘By inserting an air cavity into a one-dimensional photonic crystal of LiF/GaSb, a tunable filter covering the whole visible range is proposed. Following consideration of the dispersion of the materials, through modulating the thickness of the air cavity, we demonstrate that a single resonant peak can shift from 416.1 to 667.3 nm in the band gap at normal incidence by means of the transfer matrix method. The research also shows that the transmittance of the channel can be maximized when the number of periodic Li F/Ga Sb layers on one side of the air defect layer is equal to that of the other side. When adding a period to both sides respectively, the full width at half maximum of the defect mode is reduced by one order of magnitude. This structure will provide a promising approach to fabricate practical tunable filters in the visible region with ultra-wide tuning range.
文摘F321 austenitic stainless steel,well known for its excellent corrosion and oxidation resistance,is widely used as a structural component in the pipelines and pumps of light water reactors(LWRs)and generation IV(GenlV)reactors.However,the material failure arising from the high-temperature softening of the 300 series austenitic stainless steels has recently received significant attention.In this study,we conducted uniaxial tensile tests on F321 stainless steel at different temperatures.P\irthermore,we developed a face-centered cubic(FCC)crystal plasticity method emphasizing the temperature factor of the evolution of dislocations inferred by the physical mechanisms at the microscopic level to simulate the polycrystalline mechanical response and model the high-temperature softening phenomenon of F321 austenitic stainless steel.Subsequently,this model was implemented using the ABAQUS finite-element platform.On this basis,the crystal plastic finite-element method(CPFEM)of F321 stainless steel was established.The calculated results were in good agreement with the experimental results,which validated the effectiveness of this numerical method.