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621.
Junhua Li Shoufang Kang Lixin Fu Jiming Hao 《Frontiers of Environmental Science & Engineering》2007,1(2):143-146
A highly effective Ag-Al2O3 catalyst was prepared using the in-situ sol-gel method, and characterized by surface area using nitrogen adsorption, scanning electron microscopy (SEM), and transmission electron microscopy (TEM) techniques. The catalyst performance was tested on a real lean-burn gasoline engine. Only unburned hydrocarbons and carbon monoxide in the exhaust were directly used as reductant (without any external reductant), the maximum NO x conversion could only reach 40% at 450°C. When an external reductant, ethanol was added, the average NO x conversion was greater than 60%. At exhaust gas temperature range of 350–500°C, the maximum NO x conversion reached about 90%. CO and HC could be efficiently oxidized with Pt-Al2O3 oxidation catalyst placed at the end of SCR converter. However, NO x conversion drastically decreased because of the oxidation of some intermediates to NO x again. The possible reaction mechanism was proposed as two typical processes, nitration, and reduction in HC-SCR over Ag-Al2O3. 相似文献
622.
Xiaofeng Guo Hongsheng Zhang Ling Kang Jinlin Du Wanbiao Li Yuanjing Zhu 《Environmental Fluid Mechanics》2007,7(5):421-437
Micrometeorological measurements were made over an irrigated rice paddy during the Huaihe River Basin Experiment (HUBEX) in
1999. This study addresses the quality control and gap filling strategy for the heat fluxes with the Bowen ratio energy balance
(BREB) method. It also endeavors to benefit future studies through comparing five methodologies to estimate the net water
exchange. First, a three-step quality control strategy is constructed. Its first two steps guarantee the correct flux directions
and reject suspicious data, respectively. The third step forbids supersaturation by considering the Bowen ratio ranges for
different flux combinations (termed as “scenarios”). The quality-controlled latent heat (LE) and sensible heat (H) fluxes fall in three scenarios, namely I (LE > 0, H > 0), II (LE > 0, H < 0), and IV (LE < 0, H < 0). Second, the Priestley–Taylor evaporation model (PTEM) is applied to fill the gaps of LE, while the energy balance relationship is used to gap-fill H, namely H = R
N
− G − LE (R
N
: net radiation; G: soil heat flux). Central to the success of this strategy is the idea to calibrate the Priestley–Taylor parameter (α) in
a scenario-specific manner. On average, α values are calibrated as 1.20 and 1.35 for scenario I and II, respectively. For
scenario IV, most α values lie in a narrow range, namely from 0.9 to 1.0. Then, α is calibrated as 0.97 to extend the applicability
of the PTEM to condensation (negative LE). The scenario-specific treatment explicitly explains the diurnal variation of α derived without distinguishing the scenarios.
Third, five methodologies are compared in the calculation of net water exchange, including PTEM-gap-filled BREB method (M1),
energy-balance-based eddy covariance method (M2), and three simplified models to estimate LE, respectively as R
N
− H, R
N
− G, and R
N
. A major finding is that G and H have a similar effect of about 3% in the net water exchange. Thus, if either is neglected, the net evaporation should be
slightly lowered to avoid overestimate, by 3% as a rule of thumb from this work. 相似文献
623.
624.
Competitive adsorption characteristics of Co2+, Ni2+, and Cr3+ by IRN-77 cation exchange resin in synthesized wastewater 总被引:4,自引:0,他引:4
Adsorption properties of Co2+, Ni2+, and Cr3+ on an Amberlite IRN-77 cation exchange resin were investigated in batch systems. Levels of adsorption rapidly approached an equilibrium state within 1 h. The adsorption characteristics of each metal onto the resin were accurately represented by Langmuir isotherms. Co2+ and Ni2+, which have an equivalent electrovalence, displayed similar levels of adsorption onto the resin when they coexisted in the solution. However, when Cr3+ was added to the solution it competitively replaced Co2+ and Ni2+ ions that had been previously adsorbed onto the resin, resulting in the desorption of these metals into the solution. The result was likely due to a higher adsorption affinity of Cr3+ relative to Co2+ and Ni2+. This implies that interactively competitive adsorption of multi-cations onto the resin should be thoroughly considered when contemplating the efficient operation of an ion exchange process in the treatment of industrial wastewater. 相似文献
625.
Hydroponic experiment was carried out to study the effect of three Cd levels on glutathione (GSH), free amino acids (FAA), and ascorbic acid (ASA) concentration in the different tissues of 2 barley cultivars with different Cd tolerance. Cadmium concentration in both roots and shoots increased with external Cd level, while biomass and ASA concentration declined, and Wumaoliuling, a Cd-sensitive genotype was more affected than ZAU 3, a Cd-tolerant genotype. The effect of Cd on GSH concentration was dose- and time-dependent. In the 5 d exposure, root GSH concentration increased in 0.5 microM Cd treatment compared with control, but decreased significantly in 5 microM Cd treatment, irrespective of genotypes. However, in the 10 d exposure, GSH concentration in all plant tissues decreased with increasing Cd levels in the culture medium, and Wumaoliuling was much more affected than ZAU 3. Cadmium treatment greatly altered FAA concentration and composition in plants. The effect of Cd on glutathione (Glu) concentration in roots varied with genotypes. ZAU 3 showed a steady increase in root Glu concentration in both 0.5 and 5 microM Cd treatments, while Wumaoliuling was decreased by 38.0% in 5 microM Cd treatment, compared with the control. The results indicate that GSH and ASA are attributed to Cd tolerance in barley plants, and the relative less reduction in GSH concentration in ZAU 3 under Cd stress relative to the control may account for its higher Cd tolerance. 相似文献
626.
627.
628.
岩体声发射技术在金川二矿区的应用 总被引:1,自引:0,他引:1
岩体声发射技术是利用岩体变形破坏过程中产生应力波的强弱,来监测岩体的安全状态。针对金川二矿区地压大、岩体破碎的特点,金川公司先后在二矿区1150m水平二期快进巷道、801采场、1438m水平12#采场进路等处进行了应用岩体声发射预报矿岩体和充填体安全状态的试验。在对试验过程和监测结果进行分析的基础上,初步建立了金川二矿区矿岩体和充填体安全状态与声发射参数的近似关系,为实现金川二矿区安全管理的定量化进行了有益探索。 相似文献
629.
630.
本文在数字化地下流体化学组分的观测中,认为热水井的脱气和脱气后的气体干燥是两个关键环节。我们在怀4井的气汞观测中,经过多次试验改进较好地解决了这两个环节。2004年以来,观测资料稳定,并清晰地记录到了固体潮形态。 相似文献