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91.
92.
针对目前网络地理信息系统体系结构难以实现Internet环境下的异构空间信息的互操作问题,深入分析其主要原因,在对现有网络地理信息系统的三层体系结构进行深入分析的基础上,提出一种基于Web services的网络地理信息系统体系结构(Web-based geographical information services visualization architecture,WebGISVisA).WebGISVisA体系结构通过Web services对各个地理信息系统组件进行包装,实现各个组件的跨平台操作,从技术上使得客户端和服务端达到了负载平衡,完成了WebGIS三维的虚拟现实,实现了在Internet下空间数据互操作和跨平台的功能,最大限度地达到数据共享. 相似文献
93.
群签名使得群中任何一个成员均可以代表该群进行签名,而不会暴露签名者的身份.当争议发生时,签名者的身份可以通过群管理员公开.基于身份的签名与群签名有许多相似性,给出了一个由基于身份的签名转换而来的群签名,并给出了它在电子选举中的应用实例. 相似文献
94.
95.
By the virtue of their olfactory, physicochemical, and biological characteristics, essential oils (EOs) have drawn wide attention as additives in daily chemicals like perfume or personal care products. Nevertheless, they are physicochemically unstable and susceptible to degradation or loss. Microencapsulation offers a feasible strategy to stabilize and prolong release of EO. This review summarizes the recognized benefits and functional properties of various preparation and characterization methods, wherein innovative fabrication strategies and their formation mechanisms are especially emphasized. Progress in combining detecting/measuring technologies with kinetic modelling are discussed, to give an integral approach of controlling the dynamic release of encapsulated EOs. Moreover, new development trends of EOs capsules are also highlighted. 相似文献
96.
97.
用普通反应热压方法(RHP)和反应放电等离子体方法(R-SPS)原位反应制备了ZrB2-SiC,ZrB2-SiC—ZrC,ZrB2-SiC-ZrN,以及ZrB2-SiC-AIN4种复合材料。从密度,物相以及显微结构等方面比较了两种烧结方式之间的差别,对于升温速度较慢的普通热压方法,反应分步进行,显微结构不均匀;对于升温速度快的放电等离子体烧结,原料间的自蔓延反应被点着,反应速度快,显微结构均匀。同时以红外灯的热量为点火源,引发了Zr,Si及B4C间在空气气氛下的自蔓延反应,制备了较纯及粒径约为1μm的活性粉体。 相似文献
98.
《Microporous and mesoporous materials》2007,98(1-3):174-181
This article describes a novel citric acid treatment method for realuminating dealuminated HZSM-5 zeolite and its application in enhancing the performance of the zeolite derived FCC gasoline hydro-upgrading catalysts. A series of modified HZSM-5 zeolites were prepared by streaming and/or acid treatments and the influences of the different modification methods on the acidity, pore structure and catalytic performance of the modified HZSM-5 zeolite supported catalysts were compared in the present investigation. The results showed that compared with the single HCl or citric acid treatment, the steaming treatment, and the steaming/HCl treatments, the citric acid treatment after steaming exclusively increased the amount of framework Al species due to its realumination effect on the steamed HZSM-5 zeolite. This realumination effect of the citric acid treatment could optimize the ratio of framework Al to extra-framework Al in the steamed HZSM-5 zeolite and thus greatly improve the acidity distribution and pore structure of the corresponding catalyst. The catalytic performance assessments of the different zeolite supported catalysts for FCC gasoline hydro-upgrading revealed that the catalyst supported on the steaming/citric acid treated HZSM-5 zeolite had balanced initial and long-term activities in hydrodesulfurization, hydroisomerization and aromatization, high liquid yield and improved gasoline road octane number. The superior catalytic performance of the catalyst could be closely related to its suitable ratio of framework Al to extra-framework Al achieved by the combinational use of the steaming dealumination and the citric acid realumination, fully demonstrating the effectiveness of the steaming and citric acid treatments in optimizing the physicochemical properties and catalytic performance of HZSM-5 zeolite supported catalysts. 相似文献
99.
The epoxidation of β-ionone over the Pt/MCM-41 catalyst using molecular oxygen in the liquid phase had been studied. The results
indicated that the β-ionone was catalytically oxidized to 5,6-epoxy-β-ionone, 4-oxo-β-ionone, 4-hydroxy-β-ionone and dihydroactinidiolide
using molecular oxygen as the sole oxidant. The effects of solvent, content of Pt, reaction temperature and time on the catalytic
activity and product selectivity had also been investigated in detail. 相似文献
100.
Benzene alkylation with propane has been studied over HZSM-5 loading 3.1–15.4 wt% Mo in continuous-flow microreactor under
350 °C and atmospheric pressure with the highest activity obtained at 6.7 wt% Mo loading. C7–9 aromatics were obtained as main products while the total amount of benzene rings kept unchanged. i-Propylbenzene and n-propylbenzene are formed primarily, while toluene, ethylbenzene, and ethyl-toluene are formed secondly from the propylbenzenes.
Catalytic performance of 6.7 wt% Mo/HZSM-5(38) partially poisoned by NH3 shows that the strong acid sites play a crucial role in the alkylation. Low SiO2/Al2O3 ratio of HZSM-5 in the Mo modified catalysts gives high propane conversion. Two hydrothermal treatment methods were applied
to the 6.7 wt% Mo/HZSM-5(38) catalyst, caused decrease of propane conversion but result in different product distribution.
A possible reaction mechanism concerning bifunctional active centers resulted from combination of loaded Mo species and strong
acid centers on HZSM-5 is proposed. 相似文献