The high compacted density LiNi<sub>0.5-x</sub>Co<sub>0.2</sub>Mn<sub>0.3</sub>Mg<sub>x</sub>O<sub>2</sub> cathode material for lithium-ion batteries was syn...The high compacted density LiNi<sub>0.5-x</sub>Co<sub>0.2</sub>Mn<sub>0.3</sub>Mg<sub>x</sub>O<sub>2</sub> cathode material for lithium-ion batteries was synthesized by high temperature solid-state method, taking the Mg element as a doping element and the spherical Ni<sub>0.5</sub>Co<sub>0.2</sub>Mn<sub>0.3</sub> (OH)<sub>2</sub>, Li<sub>2</sub>CO<sub>3</sub> as raw materials. The effects of calcination temperature on the structure and properties of the products were investigated. The structure and morphology of cathode materials powder were analyzed by X-ray diffraction spectroscopy (XRD) and scanning electronmicroscopy (SEM). The electrochemical properties of the cathode materials were studied by charge-discharge test and cyclic properties test. The results show that LiNi<sub>0.4985</sub>Co<sub>0.2</sub>Mn<sub>0.3</sub> Mg<sub>0.0015</sub>O<sub>2</sub> cathode material prepared at calcination temperature 930°C has a good layered structure, and the compacted density of the electrode sheet is above 3.68 g/cm<sup>3</sup>. The discharge capacity retention rate is more than 97.5% after 100 cycles at a charge-discharge rate of 1C, displaying a good cyclic performance.展开更多
A new method for producing higher density PM parts, high velocity compaction (HVC), was presented in the paper. Using water atomized pure iron powder without lubricant admixed as the staring material, ring samples w...A new method for producing higher density PM parts, high velocity compaction (HVC), was presented in the paper. Using water atomized pure iron powder without lubricant admixed as the staring material, ring samples were compacted by the technique. Scanning electron microscopy (SEM) and a computer controlled universal testing machine were used to investigate the morphologies and the mechanical properties of samples, respectively. The relationships among the impact velocity, the green density, the sintered density, the bending strength and the tensile strength were discussed, The results show that with increasing impact velocity, the green density and the bending strength increase gradually, so the sintered density does. In addition, the tensile strength of sintered material is improved continuously with the sintered density enhancing. In the study, the sintered density of 7.545 g/cm^3 and the tensile strength of 190 MPa are achieved at the optimal impact velocity of 9.8 m/s.展开更多
We demonstrate a highly compact third-order elliptical micro-ring add-drop filter based on a silicon-on-insulator wafer. The elliptical micro-ring resonator has a major radius of 6μm (minor radius of 4.112μm) and ...We demonstrate a highly compact third-order elliptical micro-ring add-drop filter based on a silicon-on-insulator wafer. The elliptical micro-ring resonator has a major radius of 6μm (minor radius of 4.112μm) and a large free spectral range of 18 nm. Experimental results show a box-like channel dropping response, which has a 3 dB bandwidth of -2.7nm, high out-of-band signal rejection of around 40dB and a very low drop loss (〈0.5dB). Simulation agrees well with the experiments. The footprint of the whole chip is only 0.0003mm2.展开更多
Neutron diffraction techniques of large-volume samples at high pressure using compact opposed-anvil cells are developed at a reactor neutron source, China's Mianyang research reactor. We achieve a high-pressure condi...Neutron diffraction techniques of large-volume samples at high pressure using compact opposed-anvil cells are developed at a reactor neutron source, China's Mianyang research reactor. We achieve a high-pressure condition of in situ neutron diffraction by means of a newly designed large-volume opposed-anvil cell. This pressure calibration is based on resistance measurements of bismuth and the neutron diffraction of iron. Pressure calibration experiments are performed at room temperature for a new cell using the tungsten carbide anvils with a tapered angle of 30°, Φ4.5 mm culet diameter and the metal-nonmetal composite gasket with a thickness of 2 mm. Transitions in Bi(Ⅰ–Ⅱ 2.55 GPa, Ⅱ–V 7.7 GPa) are observed at 100 and 300 kN, respectively, by resistance measurements.The pressure measurement results of neutron diffraction are consistent with resistance measurements of bismuth.As a result, pressures up to about 7.7 GPa can routinely and stably be achieved using this apparatus, with the sample volume of 9 mm^3.展开更多
Water atomized pure iron powder was compacted by high velocity compaction (HVC) with and without upper relaxation assist (URA) device. The influence of URA device on green density, spring back, green strength and ...Water atomized pure iron powder was compacted by high velocity compaction (HVC) with and without upper relaxation assist (URA) device. The influence of URA device on green density, spring back, green strength and hardness was studied. Morphological characteristics of the samples were observed by scanning electron microscope (SEM). Green strength of the samples was measured by computer controlled universal testing machine. The results show that as stroke length increases, the green density, green strength and hardness of the compacts increase gradually. At the identical stroke length, the green density of the compacts pressed with URA devise was 2% higher than the compacts pressed without URA device. The green strength and hardness of the compacts pressed with URA device were higher than the compacts pressed without URA device. Furthermore, the radial spring back of the compacts decreased gradually with the increment in stroke length, whilst that of compacts prepared with URA device was lower.展开更多
This work presents a numerical study on the dynamic high velocity compaction of the metal powder. The analysis of the process is based on a mesoscopic approach using multi-speed lattice Boltzmann method. The boundary ...This work presents a numerical study on the dynamic high velocity compaction of the metal powder. The analysis of the process is based on a mesoscopic approach using multi-speed lattice Boltzmann method. The boundary condition and the relaxation time are tailored to the situation. The dynamic compaction process is vividly presented and the shock wave can be easily found in the simulation. The density is analyzed in order to explore the mechanism of the high velocity compaction.展开更多
In this paper, a novel multisymplectic scheme is proposed for the coupled nonlinear Schrodinger-KdV (CNLS-KdV) equations. The CNLS-KdV equations are rewritten into the multisymplectic Hamiltonian form by introducing...In this paper, a novel multisymplectic scheme is proposed for the coupled nonlinear Schrodinger-KdV (CNLS-KdV) equations. The CNLS-KdV equations are rewritten into the multisymplectic Hamiltonian form by introducing some canonical momenta. To simulate the problem efficiently, the CNLS-KdV equations are approximated by a high order compact method in space which preserves N semi-discrete multisymplectic conservation laws. We then discretize the semi-discrete system by using a symplectic midpoint scheme in time. Thus, a full-discrete multisymplectic scheme is obtained for the CNLS-KdV equations. The conservation laws of the full-discrete scheme are analyzed. Some numerical experiments are presented to further verify the convergence and conservation laws of the new scheme.展开更多
Within the projection schemes for the incompressible Navier-Stokes equations(namely"pressure-correction"method),we consider the simplest method(of order one in time)which takes into account the pressure in b...Within the projection schemes for the incompressible Navier-Stokes equations(namely"pressure-correction"method),we consider the simplest method(of order one in time)which takes into account the pressure in both steps of the splitting scheme.For this scheme,we construct,analyze and implement a new high order compact spatial approximation on nonstaggered grids.This approach yields a fourth order accuracy in space with an optimal treatment of the boundary conditions(without error on the velocity)which could be extended to more general splitting.We prove the unconditional stability of the associated Cauchy problem via von Neumann analysis.Then we carry out a normal mode analysis so as to obtain more precise results about the behavior of the numerical solutions.Finally we present detailed numerical tests for the Stokes and the Navier-Stokes equations(including the driven cavity benchmark)to illustrate the theoretical results.展开更多
We report a simple approach to amplify Ti:sapphire femtosecond pulses to moderate energy levels by a chirped regenerative amplifier. The seed pulses are broaden naturally because of the material dispersion of system c...We report a simple approach to amplify Ti:sapphire femtosecond pulses to moderate energy levels by a chirped regenerative amplifier. The seed pulses are broaden naturally because of the material dispersion of system components in regenerative cavity. The off-focusing Ti:sapphire crystal avoids effectively the optical damage. It sustains amplification over a wavelength range from 775 nm to more than 810 nm with a birefringent filter and an oscillation bandwidth of 7.7 nm, and produces 2.1 ps chirped output pulse energy of 100 uJ at 1.1-mJ pumping energy. This system shows good performances in stability and efficiency with the benefits of two thin-film polarizers and TEMoo mode pumping laser.展开更多
This is the first part of direct numerical simulation(DNS)of double-diffusive convection in a slim rectangular enclosure with horizontal temperature and concentration gradients.We consider the case with the thermal Ra...This is the first part of direct numerical simulation(DNS)of double-diffusive convection in a slim rectangular enclosure with horizontal temperature and concentration gradients.We consider the case with the thermal Rayleigh number of 105,the Pradtle number of 1,the Lewis number of 2,the buoyancy ratio of composition to temperature being in the range of[0,1],and height-to-width aspect ration of 4.A new 7thorder upwind compact scheme was developed for approximation of convective terms,and a three-stage third-order Runge-Kutta method was employed for time advancement.Our DNS suggests that with the buoyancy ratio increasing form 0 to 1,the flow of transition is a complex series changing from the steady to periodic,chaotic,periodic,quasi-periodic,and finally back to periodic.There are two types of periodic flow,one is simple periodic flow with single fundamental frequency(FF),and another is complex periodic flow with multiple FFs.This process is illustrated by using time-velocity histories,Fourier frequency spectrum analysis and the phase-space trajectories.展开更多
Polycrystalline diamond compacts(PDC), which are composed of diamond and WC/Co substrate, and synthesized at high pressure and high temperature(HPHT), are widely applied as the tooth of drilling bit. However, the ...Polycrystalline diamond compacts(PDC), which are composed of diamond and WC/Co substrate, and synthesized at high pressure and high temperature(HPHT), are widely applied as the tooth of drilling bit. However, the thermal stability of PDC will be reduced when diamond transforms into graphite due to cobalt in PDC acting as a catalyst during the drilling work. In this study, a new three-layer structured PDC with enhanced thermal stability has been successfully synthesized at pressures of 5.5–7.0 GPa and temperatures of 1650–1750?C. In this structure, the diamond-Si C composite acts as the working layer,and the diamond-Si C-Co composite and WC/Co cements are as the intermediate layer and substrate,respectively. It is found that the initial oxidizing temperature of the three-layered PDC is enhanced up to820?C, which is significantly higher than that(~780?C) of the conventional PDC counterpart.展开更多
An energy-preserving scheme is proposed for the coupled Gross-Pitaevskii equations.The scheme is constructed by high order compact method in the spatial direction and average vector field method in the temporal direct...An energy-preserving scheme is proposed for the coupled Gross-Pitaevskii equations.The scheme is constructed by high order compact method in the spatial direction and average vector field method in the temporal direction,respectively.The scheme is energy-preserving,stable,and of sixth order in space and of second order in time.Numerical experiments verify the theoretical results.The dynamic behavior modeled by the coupled Gross-Pitaevskii equations is also numerically investigated.展开更多
文摘The high compacted density LiNi<sub>0.5-x</sub>Co<sub>0.2</sub>Mn<sub>0.3</sub>Mg<sub>x</sub>O<sub>2</sub> cathode material for lithium-ion batteries was synthesized by high temperature solid-state method, taking the Mg element as a doping element and the spherical Ni<sub>0.5</sub>Co<sub>0.2</sub>Mn<sub>0.3</sub> (OH)<sub>2</sub>, Li<sub>2</sub>CO<sub>3</sub> as raw materials. The effects of calcination temperature on the structure and properties of the products were investigated. The structure and morphology of cathode materials powder were analyzed by X-ray diffraction spectroscopy (XRD) and scanning electronmicroscopy (SEM). The electrochemical properties of the cathode materials were studied by charge-discharge test and cyclic properties test. The results show that LiNi<sub>0.4985</sub>Co<sub>0.2</sub>Mn<sub>0.3</sub> Mg<sub>0.0015</sub>O<sub>2</sub> cathode material prepared at calcination temperature 930°C has a good layered structure, and the compacted density of the electrode sheet is above 3.68 g/cm<sup>3</sup>. The discharge capacity retention rate is more than 97.5% after 100 cycles at a charge-discharge rate of 1C, displaying a good cyclic performance.
基金supported by National 973 Program (No.2006CB605207)MOE Program for Changjiang Scholars and Innovative Research Team in Universityof China (No.I2P407)
文摘A new method for producing higher density PM parts, high velocity compaction (HVC), was presented in the paper. Using water atomized pure iron powder without lubricant admixed as the staring material, ring samples were compacted by the technique. Scanning electron microscopy (SEM) and a computer controlled universal testing machine were used to investigate the morphologies and the mechanical properties of samples, respectively. The relationships among the impact velocity, the green density, the sintered density, the bending strength and the tensile strength were discussed, The results show that with increasing impact velocity, the green density and the bending strength increase gradually, so the sintered density does. In addition, the tensile strength of sintered material is improved continuously with the sintered density enhancing. In the study, the sintered density of 7.545 g/cm^3 and the tensile strength of 190 MPa are achieved at the optimal impact velocity of 9.8 m/s.
基金Supported by the National High Technology Research and Development Program of China under Grant No 2015AA016904the National Key Research and Development Plan of China under Grant No 2016YFB0402502the National Natural Science Foundation of China under Grant No 61275065
文摘We demonstrate a highly compact third-order elliptical micro-ring add-drop filter based on a silicon-on-insulator wafer. The elliptical micro-ring resonator has a major radius of 6μm (minor radius of 4.112μm) and a large free spectral range of 18 nm. Experimental results show a box-like channel dropping response, which has a 3 dB bandwidth of -2.7nm, high out-of-band signal rejection of around 40dB and a very low drop loss (〈0.5dB). Simulation agrees well with the experiments. The footprint of the whole chip is only 0.0003mm2.
基金Supported by the National Key Research and Development Program of China under Grant No 2016YFA0401503the Science Challenge Project under Grant No TZ2016001the National Natural Science Foundation of China under Grant No 11427810
文摘Neutron diffraction techniques of large-volume samples at high pressure using compact opposed-anvil cells are developed at a reactor neutron source, China's Mianyang research reactor. We achieve a high-pressure condition of in situ neutron diffraction by means of a newly designed large-volume opposed-anvil cell. This pressure calibration is based on resistance measurements of bismuth and the neutron diffraction of iron. Pressure calibration experiments are performed at room temperature for a new cell using the tungsten carbide anvils with a tapered angle of 30°, Φ4.5 mm culet diameter and the metal-nonmetal composite gasket with a thickness of 2 mm. Transitions in Bi(Ⅰ–Ⅱ 2.55 GPa, Ⅱ–V 7.7 GPa) are observed at 100 and 300 kN, respectively, by resistance measurements.The pressure measurement results of neutron diffraction are consistent with resistance measurements of bismuth.As a result, pressures up to about 7.7 GPa can routinely and stably be achieved using this apparatus, with the sample volume of 9 mm^3.
基金financially supported by the National Natural Science Foundation of China(NSFC)(No.51172018)the National High Technical Research and Development Programme of China(No.2009BAE74B00)+1 种基金the National Basic Research Program of China(No.2006CB605207)MOE Program for Changjiang Scholars and Innovative Research Team in University of China(No.I2P407)
文摘Water atomized pure iron powder was compacted by high velocity compaction (HVC) with and without upper relaxation assist (URA) device. The influence of URA device on green density, spring back, green strength and hardness was studied. Morphological characteristics of the samples were observed by scanning electron microscope (SEM). Green strength of the samples was measured by computer controlled universal testing machine. The results show that as stroke length increases, the green density, green strength and hardness of the compacts increase gradually. At the identical stroke length, the green density of the compacts pressed with URA devise was 2% higher than the compacts pressed without URA device. The green strength and hardness of the compacts pressed with URA device were higher than the compacts pressed without URA device. Furthermore, the radial spring back of the compacts decreased gradually with the increment in stroke length, whilst that of compacts prepared with URA device was lower.
基金supported by the National Natural Science Foundation of China(Nos. 50874123 and 51174236)National Basic Research Program of China(No. 2011CB606306)
文摘This work presents a numerical study on the dynamic high velocity compaction of the metal powder. The analysis of the process is based on a mesoscopic approach using multi-speed lattice Boltzmann method. The boundary condition and the relaxation time are tailored to the situation. The dynamic compaction process is vividly presented and the shock wave can be easily found in the simulation. The density is analyzed in order to explore the mechanism of the high velocity compaction.
基金This work is supported by the NNSFC (Nos. 11771213, 41504078, 11301234, 11271171), the National Key Research and Development Project of China (No. 2016YFC0600310), the Major Projects of Natural Sciences of University in Jiangsu Province of China (No. 15KJA110002) and the Priority Academic Program Development of Jiangsu Higher Education Institutions, the Provincial Natural Science Foundation of Jiangxi (Nos. 20161ACB20006, 20142BCB23009, 20151BAB 201012).
文摘In this paper, a novel multisymplectic scheme is proposed for the coupled nonlinear Schrodinger-KdV (CNLS-KdV) equations. The CNLS-KdV equations are rewritten into the multisymplectic Hamiltonian form by introducing some canonical momenta. To simulate the problem efficiently, the CNLS-KdV equations are approximated by a high order compact method in space which preserves N semi-discrete multisymplectic conservation laws. We then discretize the semi-discrete system by using a symplectic midpoint scheme in time. Thus, a full-discrete multisymplectic scheme is obtained for the CNLS-KdV equations. The conservation laws of the full-discrete scheme are analyzed. Some numerical experiments are presented to further verify the convergence and conservation laws of the new scheme.
文摘Within the projection schemes for the incompressible Navier-Stokes equations(namely"pressure-correction"method),we consider the simplest method(of order one in time)which takes into account the pressure in both steps of the splitting scheme.For this scheme,we construct,analyze and implement a new high order compact spatial approximation on nonstaggered grids.This approach yields a fourth order accuracy in space with an optimal treatment of the boundary conditions(without error on the velocity)which could be extended to more general splitting.We prove the unconditional stability of the associated Cauchy problem via von Neumann analysis.Then we carry out a normal mode analysis so as to obtain more precise results about the behavior of the numerical solutions.Finally we present detailed numerical tests for the Stokes and the Navier-Stokes equations(including the driven cavity benchmark)to illustrate the theoretical results.
基金This work was supported by innovation foundation of Chinese Academy of Sciences and the National Natural Science Foundation of China under Grant No. 60078004. G. Cheng's e-mail address is guanghuacheng@163.com.
文摘We report a simple approach to amplify Ti:sapphire femtosecond pulses to moderate energy levels by a chirped regenerative amplifier. The seed pulses are broaden naturally because of the material dispersion of system components in regenerative cavity. The off-focusing Ti:sapphire crystal avoids effectively the optical damage. It sustains amplification over a wavelength range from 775 nm to more than 810 nm with a birefringent filter and an oscillation bandwidth of 7.7 nm, and produces 2.1 ps chirped output pulse energy of 100 uJ at 1.1-mJ pumping energy. This system shows good performances in stability and efficiency with the benefits of two thin-film polarizers and TEMoo mode pumping laser.
基金The authors thank Shanghai Supercomputer Center(SSC)for providing computer timeThis work was supported by National Natural Science Foundation of China(Grant Nos.10632050,10502052).
文摘This is the first part of direct numerical simulation(DNS)of double-diffusive convection in a slim rectangular enclosure with horizontal temperature and concentration gradients.We consider the case with the thermal Rayleigh number of 105,the Pradtle number of 1,the Lewis number of 2,the buoyancy ratio of composition to temperature being in the range of[0,1],and height-to-width aspect ration of 4.A new 7thorder upwind compact scheme was developed for approximation of convective terms,and a three-stage third-order Runge-Kutta method was employed for time advancement.Our DNS suggests that with the buoyancy ratio increasing form 0 to 1,the flow of transition is a complex series changing from the steady to periodic,chaotic,periodic,quasi-periodic,and finally back to periodic.There are two types of periodic flow,one is simple periodic flow with single fundamental frequency(FF),and another is complex periodic flow with multiple FFs.This process is illustrated by using time-velocity histories,Fourier frequency spectrum analysis and the phase-space trajectories.
基金financial supports from the National Natural Science Foundation of China (No. 41572357)
文摘Polycrystalline diamond compacts(PDC), which are composed of diamond and WC/Co substrate, and synthesized at high pressure and high temperature(HPHT), are widely applied as the tooth of drilling bit. However, the thermal stability of PDC will be reduced when diamond transforms into graphite due to cobalt in PDC acting as a catalyst during the drilling work. In this study, a new three-layer structured PDC with enhanced thermal stability has been successfully synthesized at pressures of 5.5–7.0 GPa and temperatures of 1650–1750?C. In this structure, the diamond-Si C composite acts as the working layer,and the diamond-Si C-Co composite and WC/Co cements are as the intermediate layer and substrate,respectively. It is found that the initial oxidizing temperature of the three-layered PDC is enhanced up to820?C, which is significantly higher than that(~780?C) of the conventional PDC counterpart.
基金supported by the National Natural Science Foundation of China(Nos.11771213,and 11961036)the Natural Science Foundation of Jiangxi Province(Nos.20161ACB20006,20142BCB23009,and 20181BAB201008).
文摘An energy-preserving scheme is proposed for the coupled Gross-Pitaevskii equations.The scheme is constructed by high order compact method in the spatial direction and average vector field method in the temporal direction,respectively.The scheme is energy-preserving,stable,and of sixth order in space and of second order in time.Numerical experiments verify the theoretical results.The dynamic behavior modeled by the coupled Gross-Pitaevskii equations is also numerically investigated.