The nature of magnetic and electronic structure in double perovskite structure A2FeMoO6(A = Sr,a,Ca) was calculated using the local spin density approximation(LSDA) and the LSDA+U Coulomb interaction method of density...The nature of magnetic and electronic structure in double perovskite structure A2FeMoO6(A = Sr,a,Ca) was calculated using the local spin density approximation(LSDA) and the LSDA+U Coulomb interaction method of density functional theory. The result shows that Sr2FeMoO6 is magnetic metallic material,whereas Ba2FeMoO6 and Ca2FeMoO6 are half-metallic materials. Fe has great effect on the magnetic property of double perovskite structure A2FeMoO6 materials. Because of the orbit hybridization and polarization between the metal element and O element,the Mo element has magnetic properties. The static magnetic moment of double perovskite structure A2FeMoO6 materials,the value of the magnetic moment of these A2FeMoO6 for(A=Ca,Sr,Ba) are 3.626 43μB,2.678 64μB,3.706 17μB,respectively. The magnetic moment of Fe element in the crystal cell are,3.626 43μB,2.678 64 μB,3.706 17μB. And the energy of crystal cells are -28 540.561 907Ry,-24 268.037 272Ry,-44 106.187 179Ry. These values are in agreement with the experiment values.展开更多
The stability and electronic structures of AIN nanowires with and without N-vacancy are investigated using firstprinciples calculations. We find that there is an inverse correlation between formation energy and diamet...The stability and electronic structures of AIN nanowires with and without N-vacancy are investigated using firstprinciples calculations. We find that there is an inverse correlation between formation energy and diameter in ideal AlN nanowires. After calculating the formation energies of N-vacancy at different sites in AlN nanowires with different diameters, we find that the N-vacancy prefers to stay at the surface of the nanowires and it is easier to fabricate them under Al-rich conditions. Through studying the electronic properties of AlN nanowires with N-vacancies, we further find that there are two isolated bands in the deep part of the band gap, one of them is fully occupied and the other is half occupied. The charge density indicates that the half-fully occupied band arises from the Al at the surface, and this atom becomes an active centre.展开更多
Based on vectorial Debye theory, tight focusing of radially and azimuthally polarized vortex beams passing through a dielectric interface are studied. The intensity distribution in the focal region is illustrated by n...Based on vectorial Debye theory, tight focusing of radially and azimuthally polarized vortex beams passing through a dielectric interface are studied. The intensity distribution in the focal region is illustrated by numerical calculations. We show the influence of numerical-aperture （NA） on the full-width at half maximum （FWHM） of the focal spot or the focal hole. It has been found that compared with the azimuthally polarized Besse^Gaussian （BG） beams, the longitudinal component in the z direction of the radially polarized BG beams has no influence on the FWHM of the focal spot and hole, but enhances the total light intensity.展开更多
Dip-coated double-wall carbon nanotubes(DWCNTs) and titanium dioxide(TiO2) sol have been prepared and smeared onto the tip of a conductive iron needle which serves as the corona discharge anode in a needle-cylinder co...Dip-coated double-wall carbon nanotubes(DWCNTs) and titanium dioxide(TiO2) sol have been prepared and smeared onto the tip of a conductive iron needle which serves as the corona discharge anode in a needle-cylinder corona system.Compared with the discharge electrode of a CNT-coated needle tip, great advancements have been achieved with the TiO_2/CNT-coated electrode, including higher discharge current, ionic wind velocity, and energy conversion efficiency,together with lower corona onset voltage and power consumption.Several parameters related to the discharge have been phenomenologically and mathematically studied for comparison.Thanks to the morphology reorientation of the CNT layer and the anti-oxidation of TiO_2, better performance of corona discharge induced wind generation of the TiO2/CNT-coated electrode system has been achieved.This novel decoration may provide better thoughts about the corona discharge application and wind generation.展开更多
An efficient method is proposed to extend the bandwidth of a metamaterial absorber with multi-resonance structure.The basic unit cell of a metamaterial absorber consists of the electric ring resonator,dielectric subst...An efficient method is proposed to extend the bandwidth of a metamaterial absorber with multi-resonance structure.The basic unit cell of a metamaterial absorber consists of the electric ring resonator,dielectric substrate(FR-4)and split-wire.By assembling five sandwiched structures with different geometric dimensions into a unit cell,we obtain the superposition of five different absorption peaks.Finally the bandwidth of metamaterial absorption is extended and the full width at half maximum is up to 1.3 GHz.The simulated and experimental results are consistent.展开更多
The double-side Tl2Ba2 CaCu2O8 （Tl-2212） superconducting thin films were fabricated on CeO2 buffered sapphire substrates. The reactive magnetron sputtering technique was used to grow CeO2 buffer thin films on sapphi...The double-side Tl2Ba2 CaCu2O8 （Tl-2212） superconducting thin films were fabricated on CeO2 buffered sapphire substrates. The reactive magnetron sputtering technique was used to grow CeO2 buffer thin films on sapphire substrates. Making use of the metal cerium as a sputtering source, the depositing rate is much higher compared with the CeO2 target. The Ti-2212 thin films on CeO2 buffered sapphire substrates were fabricated by adc magnetron sputtering and post-annealing process. The x-ray diffraction indicates that the thin film is pure Tl-2212 phase with the e-axis perpendicular to the substrate surfaces, and epitaxially grown on the CeO2 buffered sapphire. The critical transition temperature Tc is around 106K, the critical current density Jc is around 3.5 MA/cm^2 at 77K, and the microwave surface resistance R8 at 77K and 10 CHz of the film is as low as 390μ Ω.展开更多
Electroless CoFeB films with good soft magnetic properties were fabricated on polyester plastic substrate from sodium tartarate as a complexing agent.The plating rate of electroless CoFeB films is a function of concen...Electroless CoFeB films with good soft magnetic properties were fabricated on polyester plastic substrate from sodium tartarate as a complexing agent.The plating rate of electroless CoFeB films is a function of concentration of sodium tetrahydroborate,pH of the plating bath,plating temperature and the metallic ratio.The estimated regression coefficient b0-b3 confidence interval,residual error r and confidence interval rint were confirmed by a computer program.The optimal composition of the plating bath was obtained and the dynamic electromagnetic parameters of films were measured in the 2-10 GHz range.At 2 GHz,the μ＇,μ″ of the electroless CoFeB films were 304 and 76.6,respectively,as the concentration of reducer is 1 g/L.Magnetic hysteresis loop of the deposited CoFeB films show a remanence close to the saturation magnetization and coercivity of about 55.7-127.4 A/m.The loops along the hard axis display low anisotropic field Hk of 2 388-3 582 A/m.展开更多
Glass-coated amorphous FeCuNbSiB microwires were prepared by Taylor-Ulitovsky technique. X-ray diffractometry and scanning electron microscopy were used to investigate the microstructure and morphology of the glass-co...Glass-coated amorphous FeCuNbSiB microwires were prepared by Taylor-Ulitovsky technique. X-ray diffractometry and scanning electron microscopy were used to investigate the microstructure and morphology of the glass-coated microwires respectively. The vibrating sample magnetometer and vector network analyzer were used to study the magnetostatic and microwave properties of glass-coated microwires. The experimental results show that the effective anisotropy of an array of 150 microwires of 10 mm in length is large than that of one microwire of 10 mm in diameter and an array of 150 microwires of 1 mm in diameter. The natural ferromagnetic resonance takes place as the microwave magnetic component is perpendicular to the microwires axis, and the electric dipole resonance takes place as the microwire is long or the short microwire concentration is moderate. The natural ferromagnetic resonance shifts to higher frequency with the larger microwire concentration. The electric dipole resonance is governed by the microwires length and concentration. The glass-coated FeCuNbSiB microwires can be used to design EMI filters and microwave absorbing materials.展开更多
NiZn ferrite thin fihns were performed on glass substrates of 85 ℃ by spin spray plating method. X-ray diffraction patterns of the films show that the samples have a cubic spinel structure with no extra lines corresp...NiZn ferrite thin fihns were performed on glass substrates of 85 ℃ by spin spray plating method. X-ray diffraction patterns of the films show that the samples have a cubic spinel structure with no extra lines corresponding to any other phases between 75 ℃ and 85 ℃. As the pH value of oxidizing solution increases to 8.3, the saturation magnetization increases to 3.13 × 10^5 A/m and resistivity to 127 m Ω ·cm. Film deposited at pH 7.8 has a smooth surface and definite columnar structure. The large wavy flakes were observed at pH 8.3. The high real part of complex permeability μ′ up to 36.1 and the imaginary part μ″ up to 53.2 were observed at 0.5 GHz by short microstrip line perturbation method. The μ″ of thin film has values higher than 20 at the frequencies between 0.5 GHz and 2 GHz, the film is a promising anti-noise material for high frequency applications,展开更多
We propose a model of weighted networks in which the structural evolution is coupled with weight dynamics. Based on a simple merging and regeneration process, the model gives powel-law distributions of degree, strengt...We propose a model of weighted networks in which the structural evolution is coupled with weight dynamics. Based on a simple merging and regeneration process, the model gives powel-law distributions of degree, strength and weight, as observed in many real networks. It should be emphasized that, in our model, the nontrivial degree-strength correlation can be reproduced and in agreement with empirical data. Moreover, the size-growing evolution model is also presented to meet the properties of real-world systems.展开更多
FePtNi films with different Ni contents were deposited on glass substrates by RF magnetron sputtering, and the L10-FePtNi films were obtained after the asdeposited samples were subjected to vacuum annealing. The magne...FePtNi films with different Ni contents were deposited on glass substrates by RF magnetron sputtering, and the L10-FePtNi films were obtained after the asdeposited samples were subjected to vacuum annealing. The magnetic properties, structures, and orientations of the L10-FePt films with Ni doping were studied. The results show that with increasing Ni content, the （001） peak position of the FePtNi films shifts to a higher angle in comparison with FePt, which suggests that there is partial Ni substitution in the L10 lattice. The perpendicular coercivity decreases from 661 to 142 kA/m and magnetization decreases from 512 to 433 kA/m with increasing Ni content. In comparison with FePt films, the FePtNi films can effectively reduce the Curie temperature, which makes FePtNi films promising media candidates in thermally assisted recording （TAR）.展开更多
We present a novel numerical model and simulate preliminarily the charging process of a polymer subjected to electron irradiation of several 10 keV. The model includes the simultaneous processes of electron scattering...We present a novel numerical model and simulate preliminarily the charging process of a polymer subjected to electron irradiation of several 10 keV. The model includes the simultaneous processes of electron scattering and ambipolar transport and the influence of a self-consistent electric field on the scattering distribution of electrons. The dynamic spatial distribution of charges is obtained and validated by existing experimental data. Our simulations show that excess negative charges are concentrated near the edge of the electron range. However, the formed region of high charge density may extend to the surface and bottom of a kapton sample, due to the effects of the electric field on electron scattering and charge transport, respectively. Charge trapping is then demonstrated to significantly influence the charge motion. The charge distribution can be extended to the bottom as the trap density decreases. Charge accumulation is therefore balanced by the appearance and increase of leakage current. Accordingly, our model and numerical simulation provide a comprehensive insight into the charging dynamics of a polymer irradiated by electrons in the complex space environment.展开更多
The alternate combinational approach of genetic algorithm and neural network （AGANN） has been presented to correct the systematic error of the density functional theory （DFT） calculation. It treats the DFT as a bl...The alternate combinational approach of genetic algorithm and neural network （AGANN） has been presented to correct the systematic error of the density functional theory （DFT） calculation. It treats the DFT as a black box and models the error through external statistical information. As a demonstration, the ACANN method has been applied in the correction of the lattice energies from the DFT calculation for 72 metal halides and hydrides. Through the AGANN correction, the mean absolute value of the relative errors of the calculated lattice energies to the experimental values decreases from 4.93% to 1.20% in the testing set. For comparison, the neural network approach reduces the mean value to 2.56%. And for the common combinational approach of genetic algorithm and neural network, the value drops to 2.15%. The multiple linear regression method almost has no correction effect here.展开更多
In this study, using a comprehensive numerical simulation of charge and discharge processes, we investigate the formation and evolution of negative charge and discharge characteristics of a grounded PMMA film irradiat...In this study, using a comprehensive numerical simulation of charge and discharge processes, we investigate the formation and evolution of negative charge and discharge characteristics of a grounded PMMA film irradiated by a non- focused electron beam. Electron scattering and transport processes in the sample are simulated with the Monte Carlo and the finite-different time-domain （FDTD） methods, respectively. The properties of charge and discharge processes are presented by the evolution of internal currents, charge quantity, surface potential, and discharge time. Internal charge accumulation in the sample may reach saturation by primary electron （PE） irradiation providing the charge duration is enough. Internal free electrons will run off to the ground in the form of leakage current due to charge diffusion and drift during the discharge process after irradiation, while trapped electrons remain. The negative surface potential determined by the charging quantity decreases to its saturation in the charge process, and then increases in the discharge process. A larger thickness of the PMMA film will result in greater charge amount and surface potential in charge saturation and in final discharge state, while the electron mobility of the material has little effects on the final discharge state. Moreover, discharge time is less for smaller thickness or larger electron mobility. The presented results can be helpful for estimating and weakening the charging of insulating samples especially under the intermittent electron beam irradiation in related surface analysis or measurement.展开更多
The generation and propagation of partially coherent vortex beams have been investigated experimentally.It is found that a vortex beam with more uniform intensity distribution can be obtained by decreasing the coheren...The generation and propagation of partially coherent vortex beams have been investigated experimentally.It is found that a vortex beam with more uniform intensity distribution can be obtained by decreasing the coherence of the beam.We find that the beam shape of a completely coherent beam will keep hollow profile invariant during its propagation in free space.However,the center of the beam turns to be blurred for a partially coherent vortex beam on propagation.It is also found that the beam spreads more rapidly for the vortex beam with lower coherence,and this influence can be decreased by increasing the topological charge of the vortex beam.展开更多
Measuring accuracy of inclinometer based on accelerometer is mainly influenced by the adopted accelerometer sensor.To improve the measuring accuracy of the inclinometer,the structure of the measuring system is given a...Measuring accuracy of inclinometer based on accelerometer is mainly influenced by the adopted accelerometer sensor.To improve the measuring accuracy of the inclinometer,the structure of the measuring system is given and measuring principle is analyzed,and the error model is established in this paper.Furthermore,the model is verified by simulation and experiment,which not only gives the smallest errors of the measured pitch and roll,but also lays foundation for sensor selection,error analysis and error compensation.The results show that the error model is of practical value.展开更多
The principle of a novel orthogonal modulation format of differential 8-1evel phase-shift keying amplitude-shift keying （D8PSK/ASK） with differential bi-phase encoding （DBC） is introduced. Based on it, an optical ...The principle of a novel orthogonal modulation format of differential 8-1evel phase-shift keying amplitude-shift keying （D8PSK/ASK） with differential bi-phase encoding （DBC） is introduced. Based on it, an optical labeling scheme, in which the payload is 100 Gbit/s D8PSK signal and the label is 10 Gbit/s DBC-ASK signal, is proposed and simulated. The results arc compared with other current schemes, and the effects of transmission range, modulation extinction ratio （ER） and received power on system performance are analyzed, respectively. The results show that the spectrum efficiency and bit error rate （BER） are improved greatly, and when the modulation ER is increased to 11 dB, the balanced performance between the payload and label is achieved.展开更多
Spinel NiZn ferrite thin films were prepared on glass substrates by spray plating method. Adding cetyltrimethylammoniumchloride （CTAC）, adsorptive energy of substrate surface increased, and smooth surface and unifor...Spinel NiZn ferrite thin films were prepared on glass substrates by spray plating method. Adding cetyltrimethylammoniumchloride （CTAC）, adsorptive energy of substrate surface increased, and smooth surface and uniform columnar film structures were observed. The optimum reaction temperature up to 85℃ and pH up to 7.5 were obtained. As the solution pH value increases from 6.5 to 7.5, the film saturation magnetization increases to 36.1 and the imaginary part μ″ up to 53.2 for NiZn ferrite film at 500 MHz were achieved, and higher magnetic resonance at 508 MHz was observed. As the ferrite plate thickness is 50 μm, the attenuating characteristics for reflection loss ≤-0.8 dB can be obtained in the wide frequency ranging from 0.5 to 2.7 GHz. Theμ″ of thin film has values higher than 20 at the frequencies between 0.5 and 2 GHz, and the thin film can be applied as shielding material in GHz range.展开更多
The focusing properties of a partially coherent and partially polarized beam focused by a high numerical aperture(NA) objective are investigated.The influence of the degree of polarization and the correlation length o...The focusing properties of a partially coherent and partially polarized beam focused by a high numerical aperture(NA) objective are investigated.The influence of the degree of polarization and the correlation length of the incident beam and the numerical aperture of the objective on the intensity and degree of polarization in the focal region is studied.It is shown that the intensity and degree of polarization in the focal region change with the degree of polarization and the correlation length of the incident beam.展开更多
Ni-doped ZnO nanopowder （Zn0.98Ni0.2O） was synthesized by improved coprecipitation method. The average particle size of the powder was estimated to be 50 nm. The powder was then processed by thermal treatment. Sampl...Ni-doped ZnO nanopowder （Zn0.98Ni0.2O） was synthesized by improved coprecipitation method. The average particle size of the powder was estimated to be 50 nm. The powder was then processed by thermal treatment. Samples were annealed at 1 073, 1 273, and 1 473 K, respectively. The solubility of NiO in ZnO and the lattice parameters of ZnO both increased with the temperature. The magnetic property of the doped samples was examined, and hysteresis loops were got. The results showed all the samples were ferromagnetic, while powder processed at 1 273 K for 4 h got a highest saturation magnetization （Ms） of 0.0457 emu/g. Also, magnetic properties were related to the grain size of the powder.展开更多
基金Project(NCET-04-0702) supported by the New Century Excellent Talents in University of ChinaProject(50771047) supported by the National Natural Science Foundation of China
文摘The nature of magnetic and electronic structure in double perovskite structure A2FeMoO6(A = Sr,a,Ca) was calculated using the local spin density approximation(LSDA) and the LSDA+U Coulomb interaction method of density functional theory. The result shows that Sr2FeMoO6 is magnetic metallic material,whereas Ba2FeMoO6 and Ca2FeMoO6 are half-metallic materials. Fe has great effect on the magnetic property of double perovskite structure A2FeMoO6 materials. Because of the orbit hybridization and polarization between the metal element and O element,the Mo element has magnetic properties. The static magnetic moment of double perovskite structure A2FeMoO6 materials,the value of the magnetic moment of these A2FeMoO6 for(A=Ca,Sr,Ba) are 3.626 43μB,2.678 64μB,3.706 17μB,respectively. The magnetic moment of Fe element in the crystal cell are,3.626 43μB,2.678 64 μB,3.706 17μB. And the energy of crystal cells are -28 540.561 907Ry,-24 268.037 272Ry,-44 106.187 179Ry. These values are in agreement with the experiment values.
基金Project supported by the National Natural Science Foundation of China (Grant Nos. 11074200 and 61176079)the Natural Science Fund of Shaanxi Province,China (Grant No. 2009JM1005)
文摘The stability and electronic structures of AIN nanowires with and without N-vacancy are investigated using firstprinciples calculations. We find that there is an inverse correlation between formation energy and diameter in ideal AlN nanowires. After calculating the formation energies of N-vacancy at different sites in AlN nanowires with different diameters, we find that the N-vacancy prefers to stay at the surface of the nanowires and it is easier to fabricate them under Al-rich conditions. Through studying the electronic properties of AlN nanowires with N-vacancies, we further find that there are two isolated bands in the deep part of the band gap, one of them is fully occupied and the other is half occupied. The charge density indicates that the half-fully occupied band arises from the Al at the surface, and this atom becomes an active centre.
基金Supported by the National Natural Science Foundation of China under Grant No 60477041, the Key Project of Science and Technology of Fujian Province under Grant No 2007H0027, and the Foundation of Science and Technology Development of Southwest Jiaotong University of China under Grant No 2006B01.
文摘Based on vectorial Debye theory, tight focusing of radially and azimuthally polarized vortex beams passing through a dielectric interface are studied. The intensity distribution in the focal region is illustrated by numerical calculations. We show the influence of numerical-aperture （NA） on the full-width at half maximum （FWHM） of the focal spot or the focal hole. It has been found that compared with the azimuthally polarized Besse^Gaussian （BG） beams, the longitudinal component in the z direction of the radially polarized BG beams has no influence on the FWHM of the focal spot and hole, but enhances the total light intensity.
基金Project supported by the National Natural Science Foundation of China(Grant Nos.61504042,61504098,and 61771198)the Natural Science Foundation of Shanghai,China(Grant No.17ZR1447000)the Fundamental Research Funds for the Central Universities,China
文摘Dip-coated double-wall carbon nanotubes(DWCNTs) and titanium dioxide(TiO2) sol have been prepared and smeared onto the tip of a conductive iron needle which serves as the corona discharge anode in a needle-cylinder corona system.Compared with the discharge electrode of a CNT-coated needle tip, great advancements have been achieved with the TiO_2/CNT-coated electrode, including higher discharge current, ionic wind velocity, and energy conversion efficiency,together with lower corona onset voltage and power consumption.Several parameters related to the discharge have been phenomenologically and mathematically studied for comparison.Thanks to the morphology reorientation of the CNT layer and the anti-oxidation of TiO_2, better performance of corona discharge induced wind generation of the TiO2/CNT-coated electrode system has been achieved.This novel decoration may provide better thoughts about the corona discharge application and wind generation.
基金Supported by the Specialized Research Fund for the Doctoral Program of Higher Education of China under Grant No 20090142120003.
文摘An efficient method is proposed to extend the bandwidth of a metamaterial absorber with multi-resonance structure.The basic unit cell of a metamaterial absorber consists of the electric ring resonator,dielectric substrate(FR-4)and split-wire.By assembling five sandwiched structures with different geometric dimensions into a unit cell,we obtain the superposition of five different absorption peaks.Finally the bandwidth of metamaterial absorption is extended and the full width at half maximum is up to 1.3 GHz.The simulated and experimental results are consistent.
文摘The double-side Tl2Ba2 CaCu2O8 （Tl-2212） superconducting thin films were fabricated on CeO2 buffered sapphire substrates. The reactive magnetron sputtering technique was used to grow CeO2 buffer thin films on sapphire substrates. Making use of the metal cerium as a sputtering source, the depositing rate is much higher compared with the CeO2 target. The Ti-2212 thin films on CeO2 buffered sapphire substrates were fabricated by adc magnetron sputtering and post-annealing process. The x-ray diffraction indicates that the thin film is pure Tl-2212 phase with the e-axis perpendicular to the substrate surfaces, and epitaxially grown on the CeO2 buffered sapphire. The critical transition temperature Tc is around 106K, the critical current density Jc is around 3.5 MA/cm^2 at 77K, and the microwave surface resistance R8 at 77K and 10 CHz of the film is as low as 390μ Ω.
文摘Electroless CoFeB films with good soft magnetic properties were fabricated on polyester plastic substrate from sodium tartarate as a complexing agent.The plating rate of electroless CoFeB films is a function of concentration of sodium tetrahydroborate,pH of the plating bath,plating temperature and the metallic ratio.The estimated regression coefficient b0-b3 confidence interval,residual error r and confidence interval rint were confirmed by a computer program.The optimal composition of the plating bath was obtained and the dynamic electromagnetic parameters of films were measured in the 2-10 GHz range.At 2 GHz,the μ＇,μ″ of the electroless CoFeB films were 304 and 76.6,respectively,as the concentration of reducer is 1 g/L.Magnetic hysteresis loop of the deposited CoFeB films show a remanence close to the saturation magnetization and coercivity of about 55.7-127.4 A/m.The loops along the hard axis display low anisotropic field Hk of 2 388-3 582 A/m.
基金Project(50371029) supported by the National Natural Science Foundation of ChinaProject(NCET-04-0702) supported by the New Century Excellent Talents in University, China
文摘Glass-coated amorphous FeCuNbSiB microwires were prepared by Taylor-Ulitovsky technique. X-ray diffractometry and scanning electron microscopy were used to investigate the microstructure and morphology of the glass-coated microwires respectively. The vibrating sample magnetometer and vector network analyzer were used to study the magnetostatic and microwave properties of glass-coated microwires. The experimental results show that the effective anisotropy of an array of 150 microwires of 10 mm in length is large than that of one microwire of 10 mm in diameter and an array of 150 microwires of 1 mm in diameter. The natural ferromagnetic resonance takes place as the microwave magnetic component is perpendicular to the microwires axis, and the electric dipole resonance takes place as the microwire is long or the short microwire concentration is moderate. The natural ferromagnetic resonance shifts to higher frequency with the larger microwire concentration. The electric dipole resonance is governed by the microwires length and concentration. The glass-coated FeCuNbSiB microwires can be used to design EMI filters and microwave absorbing materials.
基金the Advanced Research Project of the General Armament De-partment of China
文摘NiZn ferrite thin fihns were performed on glass substrates of 85 ℃ by spin spray plating method. X-ray diffraction patterns of the films show that the samples have a cubic spinel structure with no extra lines corresponding to any other phases between 75 ℃ and 85 ℃. As the pH value of oxidizing solution increases to 8.3, the saturation magnetization increases to 3.13 × 10^5 A/m and resistivity to 127 m Ω ·cm. Film deposited at pH 7.8 has a smooth surface and definite columnar structure. The large wavy flakes were observed at pH 8.3. The high real part of complex permeability μ′ up to 36.1 and the imaginary part μ″ up to 53.2 were observed at 0.5 GHz by short microstrip line perturbation method. The μ″ of thin film has values higher than 20 at the frequencies between 0.5 GHz and 2 GHz, the film is a promising anti-noise material for high frequency applications,
基金Supported by the National 0utstanding Young Investigator Foundation of China under Grant No 70225005, the National Natural Science Foundation of China under Grant No 70471088.
文摘We propose a model of weighted networks in which the structural evolution is coupled with weight dynamics. Based on a simple merging and regeneration process, the model gives powel-law distributions of degree, strength and weight, as observed in many real networks. It should be emphasized that, in our model, the nontrivial degree-strength correlation can be reproduced and in agreement with empirical data. Moreover, the size-growing evolution model is also presented to meet the properties of real-world systems.
基金supported by the National Natural Science Foundation of China (No. 60571010)the Natural Science Foundation of Hubei Province,China (No. 2007ABD001)
文摘FePtNi films with different Ni contents were deposited on glass substrates by RF magnetron sputtering, and the L10-FePtNi films were obtained after the asdeposited samples were subjected to vacuum annealing. The magnetic properties, structures, and orientations of the L10-FePt films with Ni doping were studied. The results show that with increasing Ni content, the （001） peak position of the FePtNi films shifts to a higher angle in comparison with FePt, which suggests that there is partial Ni substitution in the L10 lattice. The perpendicular coercivity decreases from 661 to 142 kA/m and magnetization decreases from 512 to 433 kA/m with increasing Ni content. In comparison with FePt films, the FePtNi films can effectively reduce the Curie temperature, which makes FePtNi films promising media candidates in thermally assisted recording （TAR）.
基金Project supported by the National Natural Science Foundation of China(Grant No.11175140)the Fundamental Research Funds for the Central Universities
文摘We present a novel numerical model and simulate preliminarily the charging process of a polymer subjected to electron irradiation of several 10 keV. The model includes the simultaneous processes of electron scattering and ambipolar transport and the influence of a self-consistent electric field on the scattering distribution of electrons. The dynamic spatial distribution of charges is obtained and validated by existing experimental data. Our simulations show that excess negative charges are concentrated near the edge of the electron range. However, the formed region of high charge density may extend to the surface and bottom of a kapton sample, due to the effects of the electric field on electron scattering and charge transport, respectively. Charge trapping is then demonstrated to significantly influence the charge motion. The charge distribution can be extended to the bottom as the trap density decreases. Charge accumulation is therefore balanced by the appearance and increase of leakage current. Accordingly, our model and numerical simulation provide a comprehensive insight into the charging dynamics of a polymer irradiated by electrons in the complex space environment.
基金supported by the National Basic Research Program of China (973 Program) (Grant No. G2009CB929300)the National Natural Science Foundation of China (Grant No. 60521001 and 60925016)
文摘The alternate combinational approach of genetic algorithm and neural network （AGANN） has been presented to correct the systematic error of the density functional theory （DFT） calculation. It treats the DFT as a black box and models the error through external statistical information. As a demonstration, the ACANN method has been applied in the correction of the lattice energies from the DFT calculation for 72 metal halides and hydrides. Through the AGANN correction, the mean absolute value of the relative errors of the calculated lattice energies to the experimental values decreases from 4.93% to 1.20% in the testing set. For comparison, the neural network approach reduces the mean value to 2.56%. And for the common combinational approach of genetic algorithm and neural network, the value drops to 2.15%. The multiple linear regression method almost has no correction effect here.
基金supported by the National Natural Science Foundation of China(Grant Nos.11175140 and 11004157)the Foundation of National Key Laboratory of Space Microwave Technology of China(Grant No.9140C530101130C53013)
文摘In this study, using a comprehensive numerical simulation of charge and discharge processes, we investigate the formation and evolution of negative charge and discharge characteristics of a grounded PMMA film irradiated by a non- focused electron beam. Electron scattering and transport processes in the sample are simulated with the Monte Carlo and the finite-different time-domain （FDTD） methods, respectively. The properties of charge and discharge processes are presented by the evolution of internal currents, charge quantity, surface potential, and discharge time. Internal charge accumulation in the sample may reach saturation by primary electron （PE） irradiation providing the charge duration is enough. Internal free electrons will run off to the ground in the form of leakage current due to charge diffusion and drift during the discharge process after irradiation, while trapped electrons remain. The negative surface potential determined by the charging quantity decreases to its saturation in the charge process, and then increases in the discharge process. A larger thickness of the PMMA film will result in greater charge amount and surface potential in charge saturation and in final discharge state, while the electron mobility of the material has little effects on the final discharge state. Moreover, discharge time is less for smaller thickness or larger electron mobility. The presented results can be helpful for estimating and weakening the charging of insulating samples especially under the intermittent electron beam irradiation in related surface analysis or measurement.
基金supported by the Key Project of Science and Technology (2007H0027) of Fujin Provincethe Natural Science Founation of Fujin Province (A0810012)
文摘The generation and propagation of partially coherent vortex beams have been investigated experimentally.It is found that a vortex beam with more uniform intensity distribution can be obtained by decreasing the coherence of the beam.We find that the beam shape of a completely coherent beam will keep hollow profile invariant during its propagation in free space.However,the center of the beam turns to be blurred for a partially coherent vortex beam on propagation.It is also found that the beam spreads more rapidly for the vortex beam with lower coherence,and this influence can be decreased by increasing the topological charge of the vortex beam.
文摘Measuring accuracy of inclinometer based on accelerometer is mainly influenced by the adopted accelerometer sensor.To improve the measuring accuracy of the inclinometer,the structure of the measuring system is given and measuring principle is analyzed,and the error model is established in this paper.Furthermore,the model is verified by simulation and experiment,which not only gives the smallest errors of the measured pitch and roll,but also lays foundation for sensor selection,error analysis and error compensation.The results show that the error model is of practical value.
基金supported by the National Basic Research Program of China (No.2010CB328300)the National Natural Science Foundation of China (Nos.61077050, 61077014 and 60932004)+2 种基金the Foundation of State Key Laboratory of Optical Communication Technologies and Networks (WRI) (No.2010OCTN-02)the Fundamental Research Funds for the Central Universities (Nos.2011RC0307 and 2009 RC0314)the Natural Science Foundation of Hebei Province (No.F2010001045)
文摘The principle of a novel orthogonal modulation format of differential 8-1evel phase-shift keying amplitude-shift keying （D8PSK/ASK） with differential bi-phase encoding （DBC） is introduced. Based on it, an optical labeling scheme, in which the payload is 100 Gbit/s D8PSK signal and the label is 10 Gbit/s DBC-ASK signal, is proposed and simulated. The results arc compared with other current schemes, and the effects of transmission range, modulation extinction ratio （ER） and received power on system performance are analyzed, respectively. The results show that the spectrum efficiency and bit error rate （BER） are improved greatly, and when the modulation ER is increased to 11 dB, the balanced performance between the payload and label is achieved.
文摘Spinel NiZn ferrite thin films were prepared on glass substrates by spray plating method. Adding cetyltrimethylammoniumchloride （CTAC）, adsorptive energy of substrate surface increased, and smooth surface and uniform columnar film structures were observed. The optimum reaction temperature up to 85℃ and pH up to 7.5 were obtained. As the solution pH value increases from 6.5 to 7.5, the film saturation magnetization increases to 36.1 and the imaginary part μ″ up to 53.2 for NiZn ferrite film at 500 MHz were achieved, and higher magnetic resonance at 508 MHz was observed. As the ferrite plate thickness is 50 μm, the attenuating characteristics for reflection loss ≤-0.8 dB can be obtained in the wide frequency ranging from 0.5 to 2.7 GHz. Theμ″ of thin film has values higher than 20 at the frequencies between 0.5 and 2 GHz, and the thin film can be applied as shielding material in GHz range.
基金supported by the National Natural Science Foundation of China (No.60977068)the Natural Science Foundation of Fujian Province (No.A0810012)the Natural Science Foundation of Huaqiao University (No.08HZR14)
文摘The focusing properties of a partially coherent and partially polarized beam focused by a high numerical aperture(NA) objective are investigated.The influence of the degree of polarization and the correlation length of the incident beam and the numerical aperture of the objective on the intensity and degree of polarization in the focal region is studied.It is shown that the intensity and degree of polarization in the focal region change with the degree of polarization and the correlation length of the incident beam.
文摘Ni-doped ZnO nanopowder （Zn0.98Ni0.2O） was synthesized by improved coprecipitation method. The average particle size of the powder was estimated to be 50 nm. The powder was then processed by thermal treatment. Samples were annealed at 1 073, 1 273, and 1 473 K, respectively. The solubility of NiO in ZnO and the lattice parameters of ZnO both increased with the temperature. The magnetic property of the doped samples was examined, and hysteresis loops were got. The results showed all the samples were ferromagnetic, while powder processed at 1 273 K for 4 h got a highest saturation magnetization （Ms） of 0.0457 emu/g. Also, magnetic properties were related to the grain size of the powder.
