Improving the accuracy of hydrological prediction for long-term annual runoff series is important for water resources management and planning. In this study, the complementary ensemble empirical mode ...decomposition with adaptive noise (CEEMDAN) is used to decompose the runoff time series of the Tangnaihai hydrological station in the source area of the Yellow River (SAYR) from 1960 to 2017. The component reconstructions are evaluated with the Nash–Sutcliffe efficiency (NSE) coefficient, and the autoregressive moving average (ARMA) model is used to simulate and predict the runoff components at multi-time scales, which are also evaluated with the NSE coefficient. The results show that the NSE coefficient of the component simulations and predictions by ARMA are relatively high. Moreover, the NSE coefficients increase in step with the fluctuation period of the runoff component. For the runoff component-based reconstruction models at multi-time scales, the mean relative errors of simulation and prediction are low at 8.25% and 8.78%, respectively. In addition, the high-frequency components play an important role in the modal reconstruction as well as the simulation and prediction. Thus, focusing on the high-frequency components can improve the overall accuracy of runoff prediction based on the ARMA model at multi-time scales.
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CEKLJ, EMUNI, FIS, FZAB, GEOZS, GIS, IJS, IMTLJ, KILJ, KISLJ, MFDPS, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, SBMB, SBNM, UKNU, UL, UM, UPUK, VKSCE, ZAGLJ
•Polymer grouting trenchless repairing technique of drainage pipe is proposed.•Mechanical behaviour of drainage pipe repaired by polymer grouting is investigated.•The repaired effect of polymer ...grouting pipe is better than the concrete grouting.
Polymer grouting technology is an economical and efficient trenchless way to repair leakage and settlement of drainage pipeline. In this paper, the mechanical behaviours of drainage pipeline under traffic load before and after polymer grouting and cement grouting trenchless repairing are investigated through three-dimensional (3D) finite element method (FEM). Four different working conditions, including normal pipeline, disengaging pipeline, polymer-repaired pipeline, and cement-repaired pipeline are considered. The effects of load type, load location, buried depth on the mechanics of pipe are discussed in detail. The results show that the traffic load has great impact on both sides of the load position within 4 m, and the dangerous points of the pipeline are located at the bell and spigot joints. The most unfavorable condition occurs when the location of the disengaging corresponding to the load position. The greater influence on the disengaging pipeline with deeper buried depth applied. The disengaging pipeline can be repairing effectively and reliably by both the polymer and the cement grouting technology. However, the polymer material is more valuable than the cement material in terms of the Mises stresses after repairing.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK, ZRSKP
At present, researches on urban short-duration rainstorm patterns mainly focus on single-peak rainstorm patterns, and rarely involve double-peak rainstorm patterns, or convert double-peak patterns ...into single-peak patterns directly, even ignore the impact of double-peak patterns, which directly affects the urban flood planning and early warning and rescue. To scientifically and rationally deduce the urban short-duration double-peak rain pattern, this paper proposes a new function fitting rain pattern method by constructing double-peak virtual rain peak rainfall and virtual rain peak coefficient, based on the idea of convert double-peak to single-peak, then revert to the double-peak, directly deducing the double-peak rain pattern. The results show that (1) The rain pattern derived by the function fitting rain pattern method (FFRPM) can effectively improve the accuracy of the double-peak rain pattern and is also more practical; (2) The fitting degree of function fitting rainfall pattern and actual rain pattern is more than 90%, accounting for 80%, the fitting degree of main and secondary peak rainfall is more than 90%, with an average of about 95%; the accuracy of the main and secondary peak positions is also relatively high; (3) Compared with the P&C rain pattern method, whether the overall accuracy or local peak rainfall, the FFRPM has the higher accuracy, especially more accurate on rain peak rainfall.
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EMUNI, FIS, FZAB, GEOZS, GIS, IJS, IMTLJ, KILJ, KISLJ, MFDPS, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, SBMB, SBNM, UKNU, UL, UM, UPUK, VKSCE, ZAGLJ
As a substitute for pure silver nanoparticles, Cu-Ag core-shell nanoparticles (CS NPs) have received significant attention in the fields of electronic packaging and conductive inks. Shell thickness ...is one of the important factors affecting the sintering performance of CS NPs. In this work, we conduct a multi-particle molecular dynamics simulation to investigate the shell thickness effects on the sintering process of Cu-Ag CS NPs at different temperatures. The results show that the less the shell thickness, the lower the potential energy decrease during sintering. This study mainly involves two sintering mechanisms, plastic deformation mechanism, and diffusion mechanism. During the sintering process, the contribution of the plastic deformation mechanism decrease with the layer thickness decreases. As for the diffusion mechanism, the self-diffusion coefficient at 500 K is much lower than that at higher temperatures. However, the slow diffusion can increase the densification by filling the pores generated in the initial stage of sintering. The self-diffusion coefficient of surface atoms increases as the shell thickness decreases. The decrease of shell thickness can produce more lattice mismatches at the core-shell interface, which hinders crystallization during the sintering process. And we found more amorphous Ag atoms at the sintering neck. A higher sintering temperature can induce the diffusion of Cu atom near the core-shell interface, especially for the particle with thinner shell thickness. Some diffused Cu atoms were found in the neck area of sintered CS NP of Ag
5
Cu
3.5
and Ag
5
Cu
4
at 700 K. Moreover, the sintered neck partly composed of Cu atoms was observed in sintered Ag
5
Cu
4
CS NPs at 900 K.
To better understand the changes in the atmospheric evaporative demand (AED) in the context of global warming, the anomaly contribution analysis is presented to estimate mid‐long term contributions ...of meteorological factors to the AED. The Pearson correlation coefficient (RP) between the total contribution (ψ) of meteorological factors and the relative variation (ϕ) of the AED, and the Sen's trend slope (βS) of (ϕ, ψ) scatters are used to evaluate the applicability of the method. The smaller the values of |1 − RP| and |1 − βS|, the more applicable the method is. To validate the method, the reference crop evapotranspiration is employed as a proxy for the AED. The multi‐year contribution analysis is used as a comparison approach, which can only investigate the dominant meteorological factors of the AED in long term. Moreover, the Huaihe River basin of China is taken as a case study. Results show that (a) the values of |1 − RP| and |1 − βS| in mid‐long term are less than 0.1 in most cases when applying the anomaly contribution analysis, and the mid‐long term contribution processes of meteorological factors to the AED are clearly demonstrated; and (b) the wind speed and sunshine hours are the two most dominant factors (the total absolute contribution exceeds 60%) in long term, but they are not always the dominant factors in mid‐long term (e.g., wind speed in summer, and sunshine hours in winter). Therefore, the anomaly contribution analysis is a reasonable and effective method, which can help to gain insights into the changes in the AED.
Key Points
Anomaly contribution analysis can identify the dominant meteorological factors
Anomaly contribution analysis is better than multi‐year contribution analysis
Dominant meteorological factors may not be consistent across time scales
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BFBNIB, FZAB, GIS, IJS, KILJ, NLZOH, NUK, OILJ, SAZU, SBCE, SBMB, UL, UM, UPUK
In this work, an Al-Zn aluminum alloy was welded using friction stir welding (FSW) and metal inert gas (MIG) welding methods. The comparison between microstructure and mechanical properties of the ...two different joints was mainly discussed. Results showed that defect-free joints can be obtained using both the two welding methods. Due to much less heat input, grains of the stir zone (SZ) of the FSW joint are finer than those of the MIG joint, resulting into higher hardness. Tensile strength of the MIG and FSW joints respectively reaches 68.6 and 73.2% of the BM. The FSW joints own much better fatigue properties than the MIG joints and reach its infinite life at using 90 MPa. The FSW joint owns two cracks during the fatigue test.
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DOBA, EMUNI, FIS, FZAB, GEOZS, GIS, IJS, IMTLJ, IZUM, KILJ, KISLJ, MFDPS, NLZOH, NUK, OBVAL, OILJ, PILJ, PNG, SAZU, SBCE, SBJE, SBMB, SBNM, SIK, UILJ, UKNU, UL, UM, UPUK, VKSCE, ZAGLJ
Carbon nanomaterials, predominantly carbon nanofibers, carbon nanotubes, graphene, graphene nanoplates, graphene oxide and reduced graphene oxide, possess superior chemical, physical and mechanical ...properties. They have been successfully introduced into ordinary Portland cement to give enhancements in terms of mechanical properties, durability and electrical/thermal conductivity, and to modify the functional properties, converting conventional cement-based materials into stronger, smarter and more durable composites. This paper provides a comprehensive review of the properties of carbon nanomaterials, current developments and novel techniques in carbon nanomaterials enhanced cement-based composites (CN-CBCs). Further study of the applications of CN-CBCs at industrial scale is also discussed.
Understanding mechanical behavior at the soil–structure interface is fundamental for safety in engineering and is therefore an important consideration in structural design. Buildings can be deformed ...or severely damaged by shear forces from the action of earthquakes, waves, or winds. It is therefore necessary to understand the conditions which lead to structural failure at the soil–structure interface under shear action. We investigated the strain and displacement of bentonite–polymer specimens at various moisture contents. Shear failure was investigated using novel shear test equipment consisting of a two-dimensional soil fracture test device and computerized digital image correlation (DIC) technology. Analysis of the shear test results revealed the mechanical properties of bentonite–polymer composite structure under shear stress. Experiments showed that there were four stages in the failure of the bentonite–polymer samples: an increasing stress stage, a pre-damage stage, an abrupt damage stage, and a stable stage. At the instant the shear stress reaches peak value, the strain in the bentonite was greater than that in the polymer at the same position. In the failure stage, the bentonite at the middle and upper levels of the bentonite–polymer interface cracked first. Increased moisture content in the bentonite weakens the shear performance at the bentonite–polymer interface, and brittle failure was most significant when the moisture content was optimal.
•A novel type of shear observation equipment was used in this work.•The four stages of shear failure of bentonite-polymer specimens were observed.•The influence of water content on the shear failure mode of bentonite-polymer composite specimens has been deeply studied.•It is found for the first time that the bentonite-polymer specimens exhibit brittle failure under the optimal water content.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
An evaluation method is proposed for determining the full fatigue life of aluminum alloy cruciform joint, including the crack initiation and propagation with welding residual stress. The results of ...simulations have shown that the boundary between the initiation and propagation stage is not constant, but a variable value. The residual stress leads to a significant reduction in both stages, which is more severe on initiation. With considering residual stress, the ratio of crack initiation to total life is below 7%. The effect of residual stress varies with external loading; when external load is lower, the residual stress has a greater effect.
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IZUM, KILJ, NUK, PILJ, PNG, SAZU, UL, UM, UPUK
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