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膜的动电特性研究中,往往采用流动电位方法。该方法中,Ag-Ag Cl测试电极的质量是影响测试准确性的关键要素。本文采用正交试验设计和方差分析,着重考察电解法制备Ag-Ag Cl电极过程中,电流强度(I)、氯化时间(t)、电解质溶液浓度(CHCl)、电极来源(n)、烘烤温度(T)、活化电极溶液浓度(CKCl)等因素对Ag-Ag Cl电极稳定性的影响。得到Ag-Ag Cl电极的最优制备参数为:电流密度3.0m A/cm2,氯化时间50min,盐酸浓度0.1mol·L-1,烘烤温度120℃,活化电极溶液(KCl)浓度0.001mol·L-1;最显著影响因素为电极来源,显著影响因素为氯化时间和烘烤温度。对最优条件组合下制备的AgAg Cl电极,进行了稳定性实验,结果表明:制备的电极具有较好的稳定性,24h内电极电位漂移量小于0.10mv,7天内电极电位漂移量小于0.2mv;在聚偏氟乙烯中空纤维超滤膜流动电位测试中,流动电位与流动压差具有良好的线性和可重复性,回归曲线R20.99,变化规律符合Helmholtz-Smoluehowski公式,可以较好满足膜的流动电位测试要求。 相似文献
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以4-氯-7-硝基苯并-2-氧杂-1,3-二唑、乙二胺和溴乙酸乙酯等为原料,合成4-氨基-7-硝基苯并-2-氧杂-1,3-二唑类衍生物(NBD-OEt),通过IR、NMR和MS对其进行结构表征。研究NBD-OEt的吸收光谱和荧光光谱性质,探讨其在H2O/EtOH(60/40, V/V) pH 7.40的HEPES缓冲体系中对Hg2 的响应,以及NBD-OEt与Hg2 的结合模式。结果表明, 随Hg2 的不断加入可诱使NBD-OEt在476nm的吸收峰红移至514nm,并有两个等吸收点(347nm、482nm);其荧光发射峰由536nm红移至559nm,且在525nm出现等发射点;通过Job plot法测定NBD-OEt与Hg2 以1:1的计量比结合。 相似文献
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The ultrasonic signals in long bones contain multiple guided modes which are mutual superposed.The velocities of guided waves in long bones are very sensitive to cortical thickness (CTh).In this paper,Hilbert-Huang transform(HHT) was proposed to analyze multi-mode guided waves,which can decompose superposed waves into many independent modes.Then the group velocity of each mode was obtained at corresponding frequency,which was compared with the results of short time Fourier transform(STFT).The CTh was also obtained by comparing with the theoretical calculation.The results showed that the experimental determined thickness was in agreement with the actual CTh,indicating that measuring the velocity of the guided mode can be used to estimate the CTh.The HHT is an effective method to identify multimode guided waves. 相似文献
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采用共沉淀法成功地合成了不同Mg掺杂量的Ce1-xMgxO2(x=0.05、0.10、0.15、0.20)固溶体催化材料,并运用透射电子显微镜(TEM)、X射线衍射(XRD)、氮气吸附-脱附测试、拉曼光谱、X射线光电子能谱(XPS)、CO2程序升温脱附(CO2-TPD)等技术对这些材料进行了表征。结果发现,通过调控CeO2晶格中Mg的含量,可以调控所制备的Ce1-xMgxO2催化材料的粒径、比表面积、表面缺陷等。其中Ce0.90Mg0.10O2展现了最佳的表面性质,具有最小的平均粒径(约5.8 nm),最大的比表面积(约136 m2·g-1)以及最高的表面氧含量(31.98%)。将Ce1-xMgxO2催化材料涂覆在堇青石蜂窝陶瓷上制成整体催化剂,考察其对CO2和CH3OH直接合成碳酸二甲酯的催化性能。在140℃、2.4 MPa、反应2 h的条件下,Ce0.90Mg0.10O2整体催化剂上碳酸二甲酯的收率高达20.21%,催化效果明显优于CeO2和其余的Ce1-xMgxO2(x=0.05、0.15、0.20)催化材料。 相似文献
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The mechanism of the copper-mediated disproportionation of aromatic imine disulfides to benzothiazoles in the gas phase is investigated by experimental and theoretical methods. Application of infrared multiphoton dissociation and hydrogen/deuterium exchange experiments combined with density functional theory (DFT) calculations of the relevant molecular structures and the associated infrared spectra allows the identification of the observed ionic intermediates. The theoretical investigation of the possible reaction pathways supported by collision-induced dissociation experiments provides a consistent mechanistic picture of the reaction catalyzed by a single copper(I) ion. Activation of the substrate proceeds via homolytic sulfur-sulfur bond cleavage, yielding metal complexes in the formal +3 oxidation state; carbon-sulfur coupling and hydrogen-atom transfer complete the transformation to the products. Exploratory studies demonstrate that in the gas phase, the disproportionation of the imine disulfide can also be mediated by other metal ions via different either homo- or heterolytic mechanisms without involving high-valent intermediates. 相似文献
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Abstract A model of sustainable economic growth in an economy with two types of exhaustible resources is analyzed. The resources are assumed to be perfect substitutes with marginal rate of substitution varying over time. The optimal control framework is used to characterize the optimal paths under the maximin criterion. It is shown that the resource with increasing productivity is not used before the constant productivity resource is depleted. Afterwards the resource with an increasing productivity is asymptotically depleted as well. The results are based on an assumption that transversality conditions hold. A new sufficient condition for the transversality conditions is derived. Finally, an analogue of Hartwick’s rule for this non‐autonomous case is established. 相似文献
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This study examined how the signals of interest (SOI) effect on the backscattering measurement numerically based on 3-D finite-difference time-domain (FDTD) method. High resolution microstructure mappings of bovine cancellous bones provided by micro-CT were used as the input geometry for simulations. Backscatter coefficient (BSC), integrated backscatter coefficient (IBC) and apparent integrated backscatter (AIB) were calculated with changing the start (L1) and duration (L2) of the SOI. The results demonstrated that BSC and IBC decrease as L1 increases, and AIB decreases more rapidly as L1 increases. The backscattering parameters increase with fluctuations as a function of L2 when L2 is less than 6 mm. However, BSC and IBC change little as L2 continues to increase, while AIB slowly decreases as L2 continues to increase. The results showed how the selections of the SOI effect on the backscattering measurement. An explicit standard for SOI selection was proposed in this study and short L1 (about 1.5 mm) and appropriate L2 (6 mm-12 mm) were recommended for the calculations of backscattering parameters. 相似文献