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1.
旱灾具有出现频率高、持续时间长、波及范围广等特点,本文运用降水距平百分率、Z指数、SPI标准化降水指数,对朝阳地区50a(1969~2018)干旱特征进行分析。结果表明:Z指数与SPI标准化降水指标得到的朝阳地区干旱特征情况基本一致,能较好地反映出该地区的干旱特征,朝阳地区1969~2018年自然灾害频繁发生,严重干旱年份主要集中在1980、1981、1982 年,与实际相符。 相似文献
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《Soils and Foundations》2022,62(6):101246
This study analyzed the effect of different treatment methods in enzyme-induced carbonate precipitation (EICP) on the mechanical properties of soil. Soybean crude urease was used to catalyze the precipitation of calcium carbonate (CaCO3). A multiple-phase method was proposed and further compared with commonly practiced EICP treatment methods (including the one-phase method, two-phase method, and premix-and-compact method) from the aspects of chemical conversion efficiency, CaCO3 precipitation distribution, permeability, and unconfined compressive strength. Based on the findings, the characteristics of each method were further discussed and summarized. Although the enzymatic CaCO3 precipitation generated from all the treatment methods could potentiate the soil strength to a great or less degree, using the proposed multiple-phase method could bring about a high chemical conversion efficiency, uniform distribution of CaCO3 as well as preferable permeability retention. In addition, the multiple-phase method could significantly improve the efficiency of urease usage. 相似文献
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Pengyu Xu Hao Wang Wenjun Cui Qiangguo Chen Bingtian Tu Xiahan Sang Weimin Wang Zhengyi Fu 《Journal of the American Ceramic Society》2022,105(6):3735-3739
Here we report a transparent dual-phase ZnO·2.7Al2O3 ceramic. The composite is pore-free and consists of thin nanosheets with a spinel phase and a hexagonal phase, while the two phases match closely in both lattice and refractive index. Such features result in excellent optical transmittance (maximum value >80% in the visible spectrum) at comparable phase volume. This work may provide a new thought for the rational structural design of optical nanocomposites. 相似文献
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In the current research, a modern learning machine algorithm named “Weighted Regularized Extreme Learning Machine (WRELM)" is implemented for the first time for the simulation of the coefficient of discharge of side slots. For this purpose, an effective variable on the coefficient of discharge of side slots is firstly introduced, then five distinctive WRELM models are produced by it for the estimation of the coefficient. In the next stage, a database is created for verification of WRELM results. it should be mentioned that 70% of the data are utilized for training the WRELM models, while the rest (i.e. 30%) for testing them. After that, the optimal number of hidden layer neurons as well as the best activation function of the WRELM algorithm are chosen. In addition, the best regularization parameter and also the weight function of the WRELM are achieved. By conducting a sensitivity analysis, the most effective variable for the simulation of the coefficient of discharge along with the WRELM superior model is introduced. The WRELM superior model estimates values of the coefficient of discharge with the maximum exactness and the highest correlation. For instance, the estimations of the correlation coefficient and scatter index for this model are computed to be 0.930 and 0.051, respectively. The sensitivity analysis shows that the ratio of the side slot crest height to its length and the Froude number should be considered as the most important input variables. A comparison between the WRELM with the ELM displays that the former works much better. Furthermore, an uncertainty analysis is executed for both models. Eventually, an equation is suggested for the estimation of the coefficient of discharge and a partial derivative sensitivity analysis is performed on it. 相似文献
5.
The combined effect of resistance spot welding and precipitation hardening on the localised corrosion of A286 superalloy is studied. The specimens tested by double loop electrochemical potentiokinetic reactivation were welded in the solution treated condition, and then subjected to different precipitation hardening treatments. For both base metal and weld nugget, the maximum localised corrosion is reached when η phase is clearly observable. The fact that the localised corrosion resistance of weld nugget is different from that shown by base metal may be explained by the segregation of Ni and Ti towards the interdendritic region of weld nugget (studied by using scanning electron microscope/energy dispersive X-ray analysis). 相似文献
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During CO2 flooding, the crude oil is treated with CO2, and meanwhile it is displaced by CO2. Based on the two processes, the influence of pressure and CO2 content on the asphaltene precipitation and oil recovery efficiency are systematically investigated by indoor simulation experiment. With the increase of the pressure or CO2 content during CO2 treatment, the amount of asphaltene precipitation can be increased to a certain value. Correspondingly, the degrees of the changes of oil-water interface, the compositions of crude oil, and reservoir permeability are positively correlated with the amount of asphaltene precipitation. However, during the process, the oil recovery has an optimal value due to the combined action of asphaltene precipitation and the improvement of flow performance of the crude oil. These conclusions can provide a basis for high efficiency development of low permeability oil reservoirs by CO2 flooding. 相似文献
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本文以竹荪为原料提取多糖成分并以乙醇分级制备竹荪多糖(DPs)不同组分,通过青春双歧杆菌体外增殖试验初步评价竹荪多糖及其分级醇沉组分的益生元功效。结果显示在α-淀粉酶溶液中水解4 h后,20%、40%、50%、60%竹荪多糖醇沉组分水解度分别为9.10%、8.02%、8.88%、11.67%,与对照组菊粉(水解度13.15%)相比差异显著(P<0.05);80%竹荪多糖醇沉组分、未分级醇沉组分与菊粉对照组相比差异不显著(P>0.05)。在模拟胃液中水解6 h后,20%、40%、50%竹荪多糖醇沉组分水解度分别为17.30%、14.52%、9.61%,与对照组菊粉(水解度5.72%)相比差异显著(P<0.05);60%竹荪多糖醇沉组分、80%竹荪多糖醇沉组分、未分级醇沉组分水解度与对照组相比无显著差异(P>0.05)。随着竹荪多糖添加量的增加,青春双歧杆菌的菌体浓度呈现先增大而后不断减小的趋势。分级醇沉浓度达到80%的竹荪多糖组分和未分级的多糖组分,青春双歧杆菌体外增殖作用与pH下降显著且效果优于菊粉(P<0.05),并在20 h的发酵时间内两者表现出相似的效果。不同竹荪多糖醇沉组分对青春双歧杆菌均有增殖效果,且不同竹荪多糖醇沉组分的增殖效果和抗水解能力随乙醇浓度的增加而增强,未分级的多糖组分同样可以加强青春双歧杆菌增殖能力,具有益生元潜力。 相似文献
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