Titanium silicalite-1(TS-1) was synthesized by a hydrothermal synthesis method with different amounts of tetrapropyl ammonium hydroxide(TPAOH) as template.The as-prepared TS-1 was characterized by scanning electron mi...Titanium silicalite-1(TS-1) was synthesized by a hydrothermal synthesis method with different amounts of tetrapropyl ammonium hydroxide(TPAOH) as template.The as-prepared TS-1 was characterized by scanning electron microscopy,X-ray powder diffraction,Fourier-transform infrared resonance spectroscopy,ultravioletvisible diffuse reflectance spectroscopy and nitrogen physical adsorption and desorption,and studied in the propylene epoxidation with hydrogen peroxide in a fixed bed reactor.The results showed that the amount of TPAOH had a strong influence on the grain morphology,the amount of framework Ti,and the average particle sizes of TS-1.With the increase of TPAOH amount in the synthesis(the molar ratio of TPAOH/SiO_2 increasing from 0.25 to 0.45),the morphology changed gradually from ellipsoids to cubes,the particle sizes of TS-1 decreased slightly,the amount of the framework Ti increased appreciably,and the catalytic stability in the propylene epoxidation increased markedly.Moreover,all the catalysts had the same selectivity to propylene epoxide.However,when the molar ratio of TPAOH/SiO_2 was further increased to 0.55,the particles became large hexagons with the size distribution in a wide range,and the catalytic stability decreased sharply although the amount of the framework Ti increased further,which can be attributed to the long diffusion paths of the reactants in the zeolite.展开更多
由于集成无源器件(IPD)工艺可与集成电路平面工艺兼容,IPD工艺设计的无源器件易集成到集成电路芯片中,有利于电子设备小型化和可靠性的提高。基于IPD工艺,采用等效电路取代14λ传输线的设计方法,分别设计了一个同相和一个反相3 d B射频...由于集成无源器件(IPD)工艺可与集成电路平面工艺兼容,IPD工艺设计的无源器件易集成到集成电路芯片中,有利于电子设备小型化和可靠性的提高。基于IPD工艺,采用等效电路取代14λ传输线的设计方法,分别设计了一个同相和一个反相3 d B射频功率分配器。同相功率分配器的实测结果显示插入损耗约为3.7 d B,隔离度约为25 d B,性能与威尔金森结构功率分配器接近,封装后的尺寸为1.6 mm×0.8 mm,小于威尔金森结构功率分配器。反相功率分配器仿真结果表明插入损耗小于4.2 d B,隔离度约为25 d B。该功率分配器可应用到移动通信终端。展开更多
For a scintillating-fiber array fast-neutron radiography system,a point-spread-function computing model was introduced,and the simulation code was developed. The results of calculation show that fast-neutron radiograp...For a scintillating-fiber array fast-neutron radiography system,a point-spread-function computing model was introduced,and the simulation code was developed. The results of calculation show that fast-neutron radiographs vary with the size of fast neutron sources,the size of fiber cross-section and the imaging geometry. The results suggest that the following qualifications are helpful for a good point spread function: The cross-section of scintillating fibers not greater than 200 μm×200 μm,the size of neutron source as small as a few millimeters,the distance between the source and the scintillating fiber array greater than 1 m,and inspected samples placed as close as possible to the array. The results give suggestions not only to experiment considerations but also to the estimation of spatial resolution for a specific system.展开更多
基金Supported by the National Natural Science Foundation of China(No.21276183)
文摘Titanium silicalite-1(TS-1) was synthesized by a hydrothermal synthesis method with different amounts of tetrapropyl ammonium hydroxide(TPAOH) as template.The as-prepared TS-1 was characterized by scanning electron microscopy,X-ray powder diffraction,Fourier-transform infrared resonance spectroscopy,ultravioletvisible diffuse reflectance spectroscopy and nitrogen physical adsorption and desorption,and studied in the propylene epoxidation with hydrogen peroxide in a fixed bed reactor.The results showed that the amount of TPAOH had a strong influence on the grain morphology,the amount of framework Ti,and the average particle sizes of TS-1.With the increase of TPAOH amount in the synthesis(the molar ratio of TPAOH/SiO_2 increasing from 0.25 to 0.45),the morphology changed gradually from ellipsoids to cubes,the particle sizes of TS-1 decreased slightly,the amount of the framework Ti increased appreciably,and the catalytic stability in the propylene epoxidation increased markedly.Moreover,all the catalysts had the same selectivity to propylene epoxide.However,when the molar ratio of TPAOH/SiO_2 was further increased to 0.55,the particles became large hexagons with the size distribution in a wide range,and the catalytic stability decreased sharply although the amount of the framework Ti increased further,which can be attributed to the long diffusion paths of the reactants in the zeolite.
文摘由于集成无源器件(IPD)工艺可与集成电路平面工艺兼容,IPD工艺设计的无源器件易集成到集成电路芯片中,有利于电子设备小型化和可靠性的提高。基于IPD工艺,采用等效电路取代14λ传输线的设计方法,分别设计了一个同相和一个反相3 d B射频功率分配器。同相功率分配器的实测结果显示插入损耗约为3.7 d B,隔离度约为25 d B,性能与威尔金森结构功率分配器接近,封装后的尺寸为1.6 mm×0.8 mm,小于威尔金森结构功率分配器。反相功率分配器仿真结果表明插入损耗小于4.2 d B,隔离度约为25 d B。该功率分配器可应用到移动通信终端。
文摘目的探讨早期生长因子(EGR-1)在大鼠小体积肝移植物早期损伤中的表达及意义。方法雄性SD大鼠随机分成3组:假手术组(SO组),小体积肝移植物组(30%供肝组),全肝移植物组(100%供肝组)。采用两袖套法建立肝移植模型,比较再灌注24 h内3组肝功能指标变化、肝脏组织病理学改变及肝移植物内EGR-1和内皮素-1(ET-1)表达的变化。结果假手术组AST水平明显低于其余两组(P<0.01),而100%供肝组AST水平低于30%供肝组,其中6,24 h时点上,两者差异具有统计学意义(P<0.01)。光镜检查显示24 h 30%供肝的肝窦明显扩张,肝窦内衬细胞崩解、分离。假手术组未见EGR-1和ET-1表达,30%供肝组EGR-1和ET-1表达明显强于100%供肝组。结论小体积肝移植物早期损伤与EGR-1高表达及受其调控的ET-1表达上调有关。
基金Supported by the Foundation of Double-Hundred Talents of China Academy of Engineering Physics (Grant No. 2004R0301)
文摘For a scintillating-fiber array fast-neutron radiography system,a point-spread-function computing model was introduced,and the simulation code was developed. The results of calculation show that fast-neutron radiographs vary with the size of fast neutron sources,the size of fiber cross-section and the imaging geometry. The results suggest that the following qualifications are helpful for a good point spread function: The cross-section of scintillating fibers not greater than 200 μm×200 μm,the size of neutron source as small as a few millimeters,the distance between the source and the scintillating fiber array greater than 1 m,and inspected samples placed as close as possible to the array. The results give suggestions not only to experiment considerations but also to the estimation of spatial resolution for a specific system.
