排序方式: 共有94条查询结果,搜索用时 31 毫秒
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采用数值模拟方法和实验研究了兰姆波在搭接焊缝上的反射和透射。数值模拟了频率500 kHz的兰姆波S0与.A0模态,分别在2 mm厚不锈钢板上的不同宽度搭接焊缝模型上的反射和透射,并计算了相应的反射系数和透射系数。发现:当搭接焊缝宽度小于4 mm时,S0模态的反射系数和焊缝宽度具有近似的线性关系,而焊缝余高和两板之间的间隙对S0模态反射系数的影响很小。基于兰姆波S0模态反射系数与焊缝宽度的线性关系。提出了通过测量S0模态反射系数快速测量搭接焊缝宽度的方法。实验测得的2 mm厚不锈钢板上不同宽度搭接焊缝对500 kHz的入射兰姆波S0模态的反射系数,验证了上述线性关系,说明了可用兰姆波反射回波测量搭接焊缝宽度。 相似文献
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Caixia Lin Min Zhang Xiquan Yan Ruiqi Zhang Xiaojie He Yaofeng Yuan 《无机化学与普通化学杂志》2020,646(23-24):1892-1899
In this work, we reported a simple coumarin-boronic acid ester fluorescent probe 1 , which displayed very high “ON-OFF” fluorescence response for Hg2+ in an aqueous environment (H2O/CH3CN = 1:1, v/v) or in a PBS solution (pH = 7.4). With the addition of Hg2+ to the solution of probe, a color change from light yellow to orange could be observed by naked eye. The detection limits were lower than the permitted level of Hg2+ in drinking water defined by WHO. Infrared spectroscopy, mass spectroscopy and 1H NMR titration studies showed that probe 1 formed a 1:1 complex with Hg2+. In addition, the probe was non-toxic to cells and could stain specifically the membrane region surrounding the HeLa cell. 相似文献
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Cheng Yang Yan Hu Ruiqi Shen Yinghua Ye Shouxu Wang Tianli Hua 《Applied Physics A: Materials Science & Processing》2014,114(2):459-464
Al/Ni multilayer bridge films, which were composed of alternate Al and Ni layers with bilayer thicknesses of 50, 100 and 200 nm, were prepared by RF magnetron sputtering. In each bilayer, the thickness ratio of Al to Ni was maintained at 3:2 to obtain an overall 1:1 atomic composition. The total thickness of Al/Ni multilayer films was 2 μm. XRD measurements show that the compound of AlNi is the final product of the exothermic reactions. DSC curves show that the values of heat release in Al/Ni multilayer films with bilayer thicknesses of 50, 100 and 200 nm are 389.43, 396.69 and 409.92 J?g?1, respectively. The temperatures of Al/Ni multilayer films were obviously higher than those of Al bridge film and Ni bridge film. Al/Ni multilayer films with modulation of 50 nm had the highest electrical explosion temperature of 7000 K. The exothermic reaction in Al/Ni multilayer films leads to a more intense electric explosion. Al/Ni multilayer bridge films with modulation period of 50 nm explode more rapidly and intensely than other bridge films because decreasing the bilayer thickness results in an increased reaction velocity. 相似文献
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Water-soluble PEGylated lignin polymers were efficiently synthesized by macromolecular azo coupling reaction between alkali lignin and PEG based macromolecular diazonium salts in alkaline water. 相似文献
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Zhang R Hirakawa K Seto D Soh N Nakano K Masadome T Nagata K Sakamoto K Imato T 《Talanta》2005,68(2):231-238
A rapid and sensitive immunoassay for the determination of linear alkylbenzene sulfonates (LAS) is described. The method involves a sequential injection analysis (SIA) system equipped with a chemiluminescence detector and a neodymium magnet. Magnetic beads, to which an anti-LAS monoclonal antibody was immobilized, were used as a solid support in an immunoassay. The introduction, trapping and release of the magnetic beads in the flow cell were controlled by means of a neodymium magnet and adjusting the flow of the carrier solution. The immunoassay was based on an indirect competitive immunoreaction of an anti-LAS monoclonal antibody on the magnetic beads and the LAS sample and horseradish peroxidase (HRP)-labeled LAS, and was based on the subsequent chemiluminscence reaction of HRP with hydrogen peroxide and p-iodophenol, in a luminol solution. The anti-LAS antibody was immobilized on the beads by coupling the antibody with the magnetic beads after activation of a carboxylate moiety on the surface of magnetic beads that had been coated with a polylactic acid film. The antibody immobilized magnetic beads were introduced, and trapped in the flow cell equipped with the neodymium magnet, an LAS solution containing HRP-labeled LAS at constant concentration and the luminol solution were sequentially introduced into the flow cell based on an SIA programmed sequence. Chemiluminescence emission was monitored by means of a photon counting unit located at the upper side of the flow cell by collecting the emitted light with a lens. A typical sigmoid calibration curve was obtained, when the logarithm of the concentration of LAS was plotted against the chemiluminescence intensity using various concentrations of standard LAS samples (0-500 ppb) under optimum conditions. The time required for analysis is less than 15 min. 相似文献
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Cubic ZrW2−xMoxO8 (c-ZrW2−xMoxO8) (x=0-1.3) solid solutions were prepared by a novel polymorphous precursor transition route. X-ray diffraction (XRD) analysis reveals that the solid solutions are single phase with α- and β-ZrW2O8 structure for 0?x?0.8 and 0.9?x?1.3, respectively. The optimum synthesis conditions of ZrWMoO8 are obtained from differential scanning calorimetry-thermal gravimetric analysis (DSC-TGA), XRD and mass loss-temperature/time curves. Following the above experience, the stoichiometric solid solutions of c-ZrW2−xMoxO8 (x=0-1) are obtained within 1 wt% of mass loss. The relationships of lattice parameters (a), phase transition temperatures (Tc) and instantaneous coefficients of thermal expansion (αi) against the content x of Mo are discussed based on the variation of order degree parameters of ZrW2−xMoxO8. 相似文献
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质子辐照对有机硅树脂增强甲基硅橡胶的性能损伤及机理 总被引:3,自引:0,他引:3
硅橡胶具有优良的电绝缘性以及耐高低温、耐电晕、耐化学腐蚀、耐大气老化、耐臭氧和耐辐射等性能,近年来在航天领域得到了广泛应用.在宇宙空间的带电粒子如质子、电子等的辐照作用下,硅橡胶会发生性能退化,其质损率上升,产生析气现象,从而直接影响航天器的可靠性和寿命.自80年代以来,人们就对不同辐照源及不同粒子注量对硅橡胶材料的影响进行了研究,但直到近几年才将研究热点转向辐照场中硅橡胶的性能退化及微观结构的演变规律,其辐照环境大多集中于γ射线、Si^+和F^+离子、He^2+离子等.对于空间环境下带电粒子辐照对硅橡胶材料的影响,国外由于相应的研究工作保密性强,报道甚少;国内哈尔滨工业大学则对我国自行研制的白炭黑增强空间级甲基硅橡胶质子辐照作用后的性能与微观结构的变化做了较为深入的研究。 相似文献