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排序方式: 共有1916条查询结果,搜索用时 15 毫秒
91.
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Angel Kirchev Florence Mattera Elisabeth Lemaire Kien Dong 《Journal of power sources》2009,191(1):82-90
The paper discusses the influence of the state of charge and pulse charge frequency on the mechanism of the lead-acid battery recharge with pulse current. The data from the pulse charge transients of the negative plate potential at various frequencies show that a decrease of the pulse charge frequency keeping constant average pulse current can impede the charge reaction leading to earlier start of the hydrogen evolution reaction. The dependence of the electrochemical double layer (EDL) capacitance on the state of charge was estimated both during the charge and the discharge using electrochemical impedance spectroscopy measurements at open circuit, followed by equivalent circuit modelling. These data were used to derive the dependence of the average double layer current on SOC and pulse charge frequency. The results show that in the end of the charge almost all of the charge proceeds with the participation of EDL in a certain pulse frequency domain. Using the data from the impedance measurements the optimal pulse charge frequencies were predicted, considering the existence of “electrochemical resonance”. The latter appears when the pulse charge frequency approaches the characteristic frequency of the Pb electrodeposition process, given by the product between EDL capacitance and the charge transfer resistance. 相似文献
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Titania nanotube array sensitised with lead sulphide (PbS) were synthesised using a successive ionic layer adsorption and reaction (SILAR) method. The PbS sensitation gives visible light sensitivity to the titania nanotube arrays. The PbS sensitised titania nanotube were characterised using X-ray diffraction, UV–visible spectroscopy and scanning electron microscopy. The stability of the PbS sensitised titania nanotube were monitored through the X-ray photoelectron spectroscopy (XPS). The photocatalytic activity of the titania sensitised with PbS were studied by monitoring the degradation of methylene blue under visible light irradiation. The photocatalytic activity and solar cell efficiency is found to be highly depended on the number of SILAR cycle used for the sensitisation of PbS on titania nanotube. The sample coated for 3 SILAR cycle of PbS shows highest solar cell efficiency and photocatalytic activity under visible light. The photocatalytic activity drastically decreased in the samples after the Ist cycle of photocatalytic reaction. The drastic decrease in the photoactivity is due to the dissolution of PbS nanoparticle on the surface of titania nanotube after the first cycle of photocatalytic reaction. XPS was employed as a tool to probe the dissolution of PbS nanoparticles. 相似文献
97.
We report the fluorescence properties of Sm3+-doped lead telluroborate glasses of composition PbF2.TeO2.H3BO3.Sm2O3 as a function of Sm3+ concentration. A Judd-Ofelt scheme was used to determine the intensity parameters and radiative properties of Sm3+ ion. The emission and decay measurements were carried out at 402 nm excitation. Beyond 1.0 mol% Sm3+ concentration, the luminescence quenching is observed. The decay curves of 4G5/2 level are well fitted to a single exponential function. The evaluated radiative properties suggest that the 4G5/2 → 6H7/2 transition is responsible for reddish-orange luminescence which might be used in the development of visible lasers. 相似文献
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In this study, the lead concentrations of chewing gum samples having different compositions were determined by solid sampling electrothermal atomic absorption spectrometry. In order to optimise the experimental conditions, the effects of pyrolysis temperature, atomization temperature, sample amount and sample thermal pre-treatment, on the analyte sensitivity were investigated. The samples were ashed at 400 °C for 2 h prior to directly determined by SS-ETAAS applying 600 °C of pyrolysis and 1600 °C of atomization temperatures without to add a modifier, acid and/or surfactant. The relationship between sample mass and integrated absorbance was linear up to 1.2 mg of sample; for higher sample mass the relationship was no longer linear, irrespective of the lead content. In addition, the thermally treated chewing gum samples were digested using concentrated HNO3. The lead concentrations found by the two methods in 27 different kinds of samples were not significantly different at 95% confidence level. The proposed solid sampling technique was fast, simple, the risks of contamination and analyte loss were low. Detection limit (3σ) for lead was 0.017 ng/g. 相似文献
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岭西隧道在下穿浅埋、地表河流水量大的红线渠全~强安山玢岩地段时,先以超前地质预报对前方围岩状况进行预判,后以洞身超前大管棚注浆预支护、环形开挖预留核心土法开挖、全断面径向注浆辅以监控量测,成功穿过浅埋、地表河流水量大的全~强安山玢岩地段,获得良好的效果。 相似文献
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