The adsorption process was studied for separating para-xylene from xylene mixture on modified nano-zeolite X in a breakthrough system. Nano-zeolitic adsorbent with different ratios of Si O2/Al2O3 was synthesized throu...The adsorption process was studied for separating para-xylene from xylene mixture on modified nano-zeolite X in a breakthrough system. Nano-zeolitic adsorbent with different ratios of Si O2/Al2O3 was synthesized through hydrothermal process and ion-exchanged with alkaline metal cations like lithium, sodium and potassium. The product was characterized by X-ray diffraction, scanning electron microscopy(SEM), nitrogen adsorption,transform electron microscopy(TEM) and in situ Fourier transform infrared(FTIR) spectroscopy. The influence of nano-zeolite water content and desorbent type on the selectivity of para-xylene toward other C8 aromatic isomers was studied. The optimization of adsorption process was also investigated under variable operation conditions. The isotherm for each isomer of C8 aromatics and the desorbents possess the adsorption characteristics of Langmuir type. The selectivity factor of para-xylene relative to each of meta-xylene, ortho-xylene and ethylbenzene under the optimum conditions obtained to be 5.36, 2.43 and 3.22, in the order given.展开更多
In the present paper, poly（lactide-co-glycolide） （PLGA） with high viscosity-average molecular weight was fabricated with L-lactide （LLA） and glycolide （GA） as monomers via opening-ring polymerization. Fourier ...In the present paper, poly（lactide-co-glycolide） （PLGA） with high viscosity-average molecular weight was fabricated with L-lactide （LLA） and glycolide （GA） as monomers via opening-ring polymerization. Fourier transform Infrared （FTIR） spectroscopy, ~H-NMR, X-ray diffraction （XRD） and scanning electron microscopy （SEM） were applied to characterize the products. Viscosity method was used to determine the viscosity-average molecular weight of the PLGA copolymers. Moreover, the mechanical strength of PLGA was investigated. The results showed that the highly pure LLA and GA were prepared. The as-fabricated PLGA was typical semicrystalline copolymer with the crystallinity of 18.72%. Both viscosity-average molecular weight and mechanical strength of PLGA decreased gradually with the increase of GA content. In addition, the higher the viscosity-average molecular weight was, the more the microcracks and holes on the cross-section of PLGA copolymer materials were, the smoother the cross-sections were.展开更多
A fast and accurate numerical method for solving the two dimensional Reynolds aveaged Navier Stokes is applied to calculate the internal fluid of turbines and compressors. The code is based onan explicit, time-marchin...A fast and accurate numerical method for solving the two dimensional Reynolds aveaged Navier Stokes is applied to calculate the internal fluid of turbines and compressors. The code is based onan explicit, time-marching, finite volume technique. In order to accelerate convergence, local time stepping, multigrid method is employed. Four stage Runge-Kutta method is implemented to extend the stability domain. Test cases of Hobson’s impulse cascade, NASA Rotor 37 and Sanz’s supercritical compressor cascade are presented. Results of Mach number distribution on blade surfaces and Mach number contour plots indicate good agreement with experimental data. Compared with full three 3D Navier-Stokes (N-S) codes, the two dimensional code only takes a short time to obtain predicted results. This code can be used widely in practical engineering design.展开更多
Hydrogen bonding configurations and hydrogen content in hydrogenated amorphous silicon (a-Si:H) thin films prepared at different precursor gas temperatures with undiluted silane have been investigated by means of Four...Hydrogen bonding configurations and hydrogen content in hydrogenated amorphous silicon (a-Si:H) thin films prepared at different precursor gas temperatures with undiluted silane have been investigated by means of Fourier transform infrared (FTIR) spectroscopy.The results show that the gas temperature before precursor gases entering the glow-discharge zone re-markably influences the hydrogen bonding configurations and the hydrogen content in a-Si:H thin films.The hydrogen content decreases from 18% down to 11% when increasing the gas temperature from room temperature (RT) to 433 K.Meanwhile,the clustered hydrogen at the physical film surface or at the internal surfaces of the microvoids decreases,indicating that a-Si:H thin films are densified at higher precursor gas temperatures.For a-Si:H thin films deposited at gas temperature of 433 K,the isolated silicon-hydrogen bonding configuration is predominant in the testing films.展开更多
文摘The adsorption process was studied for separating para-xylene from xylene mixture on modified nano-zeolite X in a breakthrough system. Nano-zeolitic adsorbent with different ratios of Si O2/Al2O3 was synthesized through hydrothermal process and ion-exchanged with alkaline metal cations like lithium, sodium and potassium. The product was characterized by X-ray diffraction, scanning electron microscopy(SEM), nitrogen adsorption,transform electron microscopy(TEM) and in situ Fourier transform infrared(FTIR) spectroscopy. The influence of nano-zeolite water content and desorbent type on the selectivity of para-xylene toward other C8 aromatic isomers was studied. The optimization of adsorption process was also investigated under variable operation conditions. The isotherm for each isomer of C8 aromatics and the desorbents possess the adsorption characteristics of Langmuir type. The selectivity factor of para-xylene relative to each of meta-xylene, ortho-xylene and ethylbenzene under the optimum conditions obtained to be 5.36, 2.43 and 3.22, in the order given.
文摘In the present paper, poly（lactide-co-glycolide） （PLGA） with high viscosity-average molecular weight was fabricated with L-lactide （LLA） and glycolide （GA） as monomers via opening-ring polymerization. Fourier transform Infrared （FTIR） spectroscopy, ~H-NMR, X-ray diffraction （XRD） and scanning electron microscopy （SEM） were applied to characterize the products. Viscosity method was used to determine the viscosity-average molecular weight of the PLGA copolymers. Moreover, the mechanical strength of PLGA was investigated. The results showed that the highly pure LLA and GA were prepared. The as-fabricated PLGA was typical semicrystalline copolymer with the crystallinity of 18.72%. Both viscosity-average molecular weight and mechanical strength of PLGA decreased gradually with the increase of GA content. In addition, the higher the viscosity-average molecular weight was, the more the microcracks and holes on the cross-section of PLGA copolymer materials were, the smoother the cross-sections were.
文摘A fast and accurate numerical method for solving the two dimensional Reynolds aveaged Navier Stokes is applied to calculate the internal fluid of turbines and compressors. The code is based onan explicit, time-marching, finite volume technique. In order to accelerate convergence, local time stepping, multigrid method is employed. Four stage Runge-Kutta method is implemented to extend the stability domain. Test cases of Hobson’s impulse cascade, NASA Rotor 37 and Sanz’s supercritical compressor cascade are presented. Results of Mach number distribution on blade surfaces and Mach number contour plots indicate good agreement with experimental data. Compared with full three 3D Navier-Stokes (N-S) codes, the two dimensional code only takes a short time to obtain predicted results. This code can be used widely in practical engineering design.
基金supported by the Ministry of Education of People’s Republic of China (Grant No. J2009JBPY003)
文摘Hydrogen bonding configurations and hydrogen content in hydrogenated amorphous silicon (a-Si:H) thin films prepared at different precursor gas temperatures with undiluted silane have been investigated by means of Fourier transform infrared (FTIR) spectroscopy.The results show that the gas temperature before precursor gases entering the glow-discharge zone re-markably influences the hydrogen bonding configurations and the hydrogen content in a-Si:H thin films.The hydrogen content decreases from 18% down to 11% when increasing the gas temperature from room temperature (RT) to 433 K.Meanwhile,the clustered hydrogen at the physical film surface or at the internal surfaces of the microvoids decreases,indicating that a-Si:H thin films are densified at higher precursor gas temperatures.For a-Si:H thin films deposited at gas temperature of 433 K,the isolated silicon-hydrogen bonding configuration is predominant in the testing films.
