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排序方式: 共有460条查询结果,搜索用时 31 毫秒
61.
A lower bound approach to the yield loci of porous materials 总被引:1,自引:0,他引:1
A lower bound approach is proposed for the first time to solve the macroscopic yield loci of porous materials. The results
are then compared with Gurson's upper bound yield loci and those of the experiments. It is shown that the present analysis
is much more in accordance with the experimental results than the Gurson's. 相似文献
62.
提出了栅控X射线源作为发射器和基于微通道板的X射线单光子探测器作为接收器的X射线通信方案. 搭建了基于X射线的空间语音通信系统, 详细介绍了信号调制发射器、基于微通道板的X射线单光子探测器及信号接收解调器的设计及工作原理. 报道了基于X射线的空间语音通信系统的初步实验结果, 实现了优于20 kbit/s的基于语音信号调制的X射线通信. 实验分析了在不同X射线强度、信号整形时间和阈值设置下通信性能影响, 得出了X射线发射功率限制X射线通信速率的结论, 提出了下一步提高X射线通信性能的改进方案.
关键词:
X射线通信
X射线源
探测器 相似文献
63.
Twenty‐eight novel ferrocenyl ionic compounds, composed of mononuclear 1‐ferrocenylmethylalkyldimethylammoniums, 1‐ferrocenylmethyl‐3‐alkylimidazoliums, or their dinuclear analogs and [Fe(CN)6]3– anion, were designed and synthesized to tackle significant volatility and migration tendency of ferrocene‐based burning rate catalysts (BRCs) used currently in the composite solid propellants. The new compounds were characterized by UV/Vis, FT‐IR, and elementary analysis. The crystal structures of compounds 2· 5H2O and 3· CH2Cl2 · 4H2O verified the successful preparation of the desired ionic compounds. The TG tests at 70 °C for 24 h revealed that the new compounds exhibit lower volatility than catocene. The cyclic‐voltammetry results suggested that new compounds are quasi‐reversible or irreversible redox systems. TheTG/DSC analyses exhibited that the compounds are of highly thermal stability. Their catalytic effects on the thermal degradation of ammonium perchlorate (AP), 1,3,5‐trinitro‐1,3,5‐triazacyclohexane (RDX), and 1,3,5,7‐tetranitro‐1,3,5,7‐tetrazacyclooctane (HMX) were investigated. The results showed that most of the compounds exert great effects on the thermal degradation of AP and RDX during combustion. 11 and 2 are comparable to catocene in the thermal decomposition of AP and RDX, respectively, and can therefore be used as alternatives of catocene in a composite solid propellant. Some new compounds are unexpectedly active in promoting the thermal disintegration of HMX. 相似文献
64.
Hailong Zhang Wei Liu Ao Li Duo Zhang Xiaoyan Li Fuwan Zhai Lanhua Chen Long Chen Yanlong Wang Shuao Wang 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2019,131(45):16256-16260
The design and synthesis of uranium sorbent materials with high uptake efficiency, capacity and selectivity, as well as excellent hydrolytic stability and radiation resistance remains a challenge. Herein, a polyoxometalate (POM)–organic framework material ( SCU‐19 ) with a rare inclined polycatenation structure was designed, synthesized through a solvothermal method, and tested for uranium separation. Under dark conditions, SCU‐19 can efficiently capture uranium through ligand complexation using its exposed oxo atoms and partial chemical reduction from UVI to UIV by the low‐valent Mo atoms in the POM. An additional UVI photocatalytic reduction mechanism can occur under visible light irradiation, leading to a higher uranium removal without saturation and faster sorption kinetics. SCU‐19 is the only uranium sorbent material with three distinct sorption mechanisms, as further demonstrated by X‐ray photoelectron spectroscopy (XPS) and X‐ray absorption near edge structure (XANES) analysis. 相似文献
65.
Tiantian Si Lei Liu Xiaojing Liang Huixiao Duo Licheng Wang Shuai Wang 《Journal of separation science》2019,42(12):2148-2154
A zirconium(IV)‐based metal–organic framework material (MOF‐808) has been synthesized in a simple way and used for the extraction of phenoxyacetic acids in complex samples. The material has good thermal and chemical stability, large specific surface area (905.36 m²/g), and high pore size (22.18 Å). Besides, it contains a large amount of Zr‐O groups, easy‐to‐form Zr‐O‐H bond with carboxyl groups of phenoxyacetic acids, and possesses biphenyl skeleton structure, easy to interact with compounds through π‐π and hydrophobic interactions. These characteristics make the material very suitable for the extraction of certain compounds with a high extraction efficiency and excellent selectivity. The extraction conditions were optimized, and then an analytical method was successfully established and applied for analysis of actual samples. The solid‐phase extraction method based on prepared material had a wide linear range of 0.2–250 μg/L and a low detection limit of 0.1–0.5 μg/L for four phenoxyacetic acid compounds including 2,4‐dichlorophenoxyacetic acid, 2‐(2,4‐dichlorophenoxy) propionic acid, 4‐chlorophenoxyacetic acid, and dicamba. The relative standard deviations of intra‐ and interday precision were 1.8–3.8 and 4.3–6.9%, and the recoveries after spiking were between 77.1 and 109.3%. The results showed that the material is a desired substituent for the extraction of compounds with benzene ring structure containing carboxyl groups. 相似文献
66.
Xin‐Yi Huang Xia Zhang Dong Pei Jian‐Fei Liu Yuan Gong Haji Akber Aisa Duo‐Long Di 《Journal of separation science》2019,42(11):2080-2088
In this work, a continuous high‐speed countercurrent chromatography method has been developed on the basis of elution‐extrusion mode and this method was successfully applied to the separation of maslinic and oleanolic acid from the extract of olive pulp. In the process of ‘elution’, the sample solution was continuously loaded into the column and the maslinic acid was steadily eluted out in this step while highly retained oleanlic acid always stayed in the column. In the process of ‘extrusion’, the oleanlic acid was pushed out of the column with the stationary phase. In this way, we achieved a large sample loading. A total of 120 mL sample solution (about 89.55% of the column volume) which contains 600 mg olive pulp extract was pumped in the apparatus by a constant‐flow pump and the maslinic and oleanolic acids were largely separated within 120 min. Both of these two compounds presented high yields and high purities (271.6 mg for maslinic acid with 86.7% and 83.9 mg oleanolic acids with 83.4%). 相似文献
67.
68.
69.
Jianlong Ma Chaoxian Yan Yijing Li Huixiao Duo Qiang Li Xiaofeng Lu Prof. Yong Guo 《Chemistry (Weinheim an der Bergstrasse, Germany)》2019,25(29):7168-7176
One of the most important endogenous reactive oxygen species, hypochlorous acid (HClO), is involved in numerous pathological and physiological processes. Herein, a near-infrared fluorescence probe (CyHR) was designed and synthesized for ultrafast (within 0.2 s), sensitive (limit of detection=39.44 nm ), and selective response to HClO. The reaction mechanism was systematically analyzed by MS, 1H NMR spectroscopy, HPLC-MS techniques, and theoretical calculations. The results indicated that HClO can be recognized by CyHR, which is based on chlorine–oxygen (Cl−O) bond formation. To the best of our knowledge, this study is the first to find Cl−O bonds among organic aromatic compounds, given that Cl−O bonds are common among inorganics. Through biological experiments, CyHR was successfully applied to image exogenous and endogenous HClO in macrophage cells (RAW 264.7). Thus, CyHR is a promising tool for HClO-related physiological and pathological studies and may provide a means for designing HClO-specific fluorescence probes. 相似文献
70.