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991.
Cu/SiO2 catalysts with different bimodal pore structures adjusted by the ratio of HMS and silica sol were prepared via modified impregnation method. Structure evolutions of the catalyst were systematically characterized by N2-physisorption, X-ray diffraction, H2 temperature-programmed reduction, N2O titration and X-ray photoelectron spectroscopy. The results show that the composite silica supported copper catalysts showed remarkably enhanced catalytic performance in the selective hydrogenation of dimethyl oxalate to ethylene glycol compared to the individual silica supported ones obtained by the same method. The dimethyl oxalate conversion and the ethylene glycol selectivity can reach 100% and 98% at 473 K with 2.5 MPa H2 pressure and 1.5 h−1 liquid hour space velocity of dimethyl oxalate over the optimized Cu/SiO2 catalyst. The remarkably enhanced catalytic performance of Cu/SiO2 catalysts might be attributed to the homogeneous dispersion and uniformity of the active copper species and to the larger copper surface areas attained on the HMS supports with large pore diameters and surface areas. 相似文献
992.
Yueli Wen Wei Huang Bin Wang Jinchuan FanZhihua Gao Lihua Yin 《Applied Surface Science》2011,258(2):946-949
Cuboid copper nanocrystals were synthesized by thermal treatment in liquid paraffin without any inert gas protection with salicylaldehyde Schiff base copper (II) (Cu (II)-Salen) complex as precursor. Liquid paraffin was used as solvent and reductant. The obtained copper nanocrystals are morphology-controlled and stable when exposed to air for one year. The nanocrystals were characterized by X-ray diffraction measurements (XRD), UV-visible spectroscopy (UV-vis), transmission electron microscope (TEM), and Fourier transform infrared spectroscopy (FT-IR). The results showed that the stable cuboid copper nanocrystals are synthesized by using Salen as capping agents. 相似文献
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996.
A thermal control system (TCS) based on the resistance heating method is designed for the High Energy Detector (HED) on the Hard X-ray Modulation Telescope (HXMT). The ground-based experiments of the active thermal control for the HED with the TCS are performed in the ambient temperature range from -15 to 20 ℃ by utilizing the pulse width to monitor the interior temperature of a NaI(Tl) crystal. Experimental results show that the NaI(Tl) crystal's interior temperature is from 17.4 to 21.7 ℃ when the temperature of the PMT shell is controlled within (20±3) ℃ with the TCS in the interesting temperature range, and the energy resolution of the HED is maintained at 16.2% @ 122 keV, only a little worse than that of 16.0% obtained at 20 ℃. The average power consumption of the TCS for the HED with a low-emissivity shell is about 4.3 W, which is consistent with the simulation. 相似文献
997.
The construction of China Spallation Neutron Source (CSNS) has been initiated in Dongguan, Guangdong, China. Thus a detailed radiation transport analysis of the shutter neutron beam stop is of vital importance. The analyses are performed using the coupled Monte Carlo and multi-dimensional discrete ordinates method. The target of calculations is to optimize the neutron beamline shielding design to guarantee personal safety and minimize cost. Successful elimination of the primary ray effects via the two-dimensional uncollided flux and the first collision source methodology is also illustrated. Two-dimensional dose distribution is calculated. The dose at the end of the neutron beam line is less than 2.5 μSv/h. The models have ensured that the doses received by the hall staff members are below the standard limit required. 相似文献
998.
The design, fabrication and field measurement of 11 DC curved dipole magnets for the PEFP Beam Line have been completed. In this paper, a design method for a complex end chamfer using OPERA-3D is proposed. The conventional method for estimating chamfer shape is extended and applied to a curved dipole magnet by a coordinate transformation. Using the interface with CAD software, the complex end chamfer is modeled and fully determined by 3D simulation to meet the field uniformity requirement. The magnetic field measurement results are in good agreement with the simulation. The design considerations, field simulation results, end chamfer development process and measurement results are presented in detail. 相似文献
999.
In this paper, we investigate in detail the interactions of solitary waves in lattice systems with interaction potential V(q)=qn/n, where n is 4,6,8…, through their all possible collision types, and establish a quantitative connection between the scattering property of solitary waves and the chaotic dynamics of the systems. Kink and antikink are excited in such lattice systems and the variation of their scattering effect with n is concerned. After a kink-antikink collision, the dominant interaction in the systems, if n is small, is that solitary waves pass through each other and the scattering effect increases with n; if n is large, solitary waves reflect back sometimes due to the influence of phase and this leads to a decrease of the scattering effect with n. The largest Lyapunov exponents of systems at fixed energy density first increase and then decrease with n, which is consistent with a variation of the scattering effect. The application of the special scattering behaviors between kink and antikink in information propagation is also discussed. 相似文献
1000.
激光剥蚀-电感耦合等离子体质谱测定植物样品中的元素 总被引:2,自引:0,他引:2
采用193 nm准分子激光剥蚀-电感耦合等离子体质谱(LA-ICP-MS)对标准植物粉末样品(GBW07602-GBW07603灌木枝叶、GBW07604杨树叶、GBW07605茶叶、GBW08514烟草)中13种元素(Li,B,Na,Mg,Al,K,Ca,Cr,Mn,Fe,Ni,Cu,Ba)进行定量测试.向植物粉末样... 相似文献