With wind energy penetration rate increasing, wind energy curtailment turns severe in some wind farms nowadays and new wind farm construction trends to aggregate this situation. Therefore the need ...for massive energy storage technology such as “Power to gas” is growing. In this study, a model of integrating curtailed wind energy with hydrogen energy storage is established based on real time data in term of 10 min avg. throughout a whole year in a wind farm. Two wind/hydrogen production scenarios via water electrolysis are given and the influence exerted on payback period by electrolyser power and hydrogen price is talked in tandem as well as the model validity is specified in the conclusion section. Our results further stress the importance of hydrogen energy storage technology on addressing wind energy curtailment and disclose some regularities from an economical perspective.
•A model of integrating wind curtailment with H2 energy storage was established.•We compared electrolyser operation with and without using grid electricity.•For the wind farm in this case, a balance hydrogen price of 0.29 $/Nm3 was found.•Over 0.29 $/Nm3, the profitability of continuous electrolyser operation was better.
•Baige landslides induced dam breaches were back-analyzed.•Two parameters (Effective dam height and Narrowing rate) were proposed to analyze geometry that influences the successive dam breaches and ...outburst floods.•Effective dam height dominates peak discharge with linear rate of 1009.4 m3/s/m.•Locally narrowing and lifting effects both promote to form subsequent dam with high effective dam height with high flood risk.
Two large landslides in October and November 2018 sequentially dammed the Jinsha river at Baige village, eastern Tibet, China. Subsequently, breaching of each dam induced massive outburst floods that posed a severe threat to downstream cities and infrastructure. Field investigation indicates volumes of the first and second landslide dam are about 24.5 × 106 m3 and 8.53 × 106 m3, respectively. However, the peak discharge of the flood generated from the second landslide (3.1 × 104 m3/s) was significantly larger than that from the first (1.0 × 104 m3/s). The second peak discharge would have been 5.15 × 104 m3/s if the dam breached naturally. In this study, we developed two geometry parameters: effective dam height He (elevation difference between overtopping level and river bottom) and a narrowing number distribution Nr(H) (measures the degree to which a river section is occupied by landslide materials to elevation H) which represents river section narrowing effects of successive landslides. Using numerical simulations, we show that He dominates peak discharge, and it has a linear relationship with peak discharge with slope of 1009.4 m2/s. Furthermore, the dam includes two sub-areas: a higher part (SB-1) and a lower part (SB-2). Two floods only eroded SB-2. However, breaching of SB-1 and breached SB-2 still narrowed the river. The narrowing effects of the first and second breached dam on the river channel are around 0.35 and 0.5, respectively. Spillway and landslide runup deposits increased the local flood risk by narrowing and lifting the local river section; the first landslide promoted the second landslide, which occupied the same area and forms a dam with high He value. Consequently, a more catastrophic flood could be triggered by a small subsequent landslide. Spatial superposition phenomenon of successive landslides increased the local flood risk. This research quantitatively analyzed the influence of the geometry of dam induced by successive landslides on the process of outburst floods and the risk.
To solve the issue of hexavalent chromium (Cr(VI)) contamination in water bodies, blue coke powder (LC) was chemically changed using potassium hydroxide to create the modified material (GLC), which ...was then used to treat a Cr(VI)-containing wastewater solution. The differences between the modified and unmodified blue coke's adsorption characteristics for Cr(VI) were studied, and the impact of pH, starting solution concentration, and adsorption period on the GLC's adsorption performance was investigated. The adsorption behavior of the GLC was analyzed using isothermal adsorption models, kinetic models, and adsorption thermodynamic analysis. The mechanism of Cr(VI) adsorption by the GLC was investigated using characterization techniques such as Fourier Transform Infrared Spectroscopy (FTIR), Field Emission Scanning Electron Microscope (FE-SEM), X-Ray Diffraction (XRD), and X-Ray Photoelectron Spectroscopy (XPS). With the biggest difference in removal rate at pH = 2, which was 2.42 times that of LC, batch adsorption experiments revealed that, under the same adsorption conditions, the GLC always performed better than LC. With a specific surface area that was three times that of LC and an average pore diameter that was 0.67 times that of LC, GLC had a more porous structure than LC. The alteration significantly increased the number of hydroxyls on the surface of GLC by altering the structural makeup of LC. The ideal pH for removing Cr(VI) was 2, and the ideal GLC adsorbent dosage was 2.0 g/L. Pseudo-second-order kinetic (PSO) model and Redlich-Peterson (RP) model can effectively describe the adsorption behavior of GLC for Cr(VI). Physical and chemical adsorption work together to remove Cr(VI) by GLC in a spontaneous, exothermic, and entropy-increasing process, with oxidation-reduction processes playing a key role. GLC is a potent adsorbent that can be used to remove Cr(VI) from aqueous solutions.
The metallic bump-assisted resistance spot welding (MBaRSW) weld formed between Al and steel had higher strength and better ductility than the RSW welds. The fracture behavior was investigated for ...both the RSW weld and MBaRSW/Al weld by printing metallic bumps on an Al sheet prior to welding. The results showed that a larger nugget size, thinner intermetallic compounds (IMC) layer and smaller thinning of the base metal (BM) yielded MBaRSW/Al welds with better properties. With increasing welding current, the nugget size, thickness of the IMC layer and thinning of the BM all increased, causing the weld strength to first increase and then decrease. During lap-shear tests, all RSW welds fractured by the interfacial failure (IF) mode and exhibited poor properties, resulting from its thick IMC layer, interfacial defects and large thinning of the BM. The MBaRSW/Al welds failed by the IF mode, mixed failure (MF) mode and partial button pull-out failure (PBF) mode with the increasing welding currents. As a result, the nugget size and the thickness of the IMC layer determined the MBaRSW/Al weld property and failure mode, and the thinning of the Al sheet had a large effect on the properties and failure mode of the MBaRSW/Al welds at high welding currents,
e.g.
, 11 kA.
•The temperature and pressure distributions are not consistent inside the porous bearing.•The circumferential velocity is the major contributor to the temperature rise.•Oil film shearing is the heat ...source of the bearing system.•The heat is gradually transferred from oil film to porous medium through the heat conduction and convection.
Circular porous bearing is a widely used self-lubricating bearing structure but it exhibits higher temperature rise in bearing system — heat produced cannot be dissipated in time — which leads to poorer lubricating performance and makes it difficult to use in complex working conditions. We establish the thermo-hydrodynamic lubrication model of circular bilayer porous bearing in polar coordinates coupling with the fluid pressure and heat transfer equations, and reveal the fundamental origin of the heat generating and its transfer mechanism. The results indicate that the circumferential velocity is the major contributor to determine the temperature distribution, and the oil film shearing causes temperature rise of the bearing system which is gradually transferred from oil film to porous medium through the heat conduction of porous metal and the convection of fluid. Thus, the temperature in the oil film region is higher than that in the porous bearing. In the vertical direction, the temperature rises first and then decreases from the bearing bottom face to the counterpart surface, While in the radial direction, the temperature increases gradually from the inner radius to the outer radius. We find that the highest temperature of the bearing system occurs at the minimum film thickness of the external ring face in the oil film region. The numerical model is verified by comparing the experimental and numerical results, and the numerical accuracy of the lubrication performance has been improved after considering the thermal effect. Our results can be employed to control the oil film temperature and exert a better lubricating performance.
•A novel dimensionless index (MLSDR) was proposed to efficiently assess the post-earthquake landslides sediment supply capacity (SSC) for debris flows.•The 1 km2 threshold between hillslopes and ...channels in Wenchuan Earhquake-affected area is distinguished using logarithmic slope–area diagram.•Catchments with higher active debris flow in Wenchuan Earhquake-affected area are identified based on the values of 0.2 ≤ MLSDRout ≤ 2.25 and 0.3 ≤ MLSDRchannel ≤ 4.5.•Short- and long-term changes in post- Wenchuan earthquake SSC are dominated by the strong earthquakes and precipitation, respectively.
Earthquake-triggered landslides provide sufficient loose material for the formation of subsequent debris flow events in earthquake-affected catchments. The landslides sediment supply capacity (SSC) for debris flows plays an important role in post-earthquake sediment transportation, which is influenced by landslide location during different post-earthquake periods. In this study, the logarithmic slope–area diagram was used to distinguish hillslope and channel processes in catchments affected by the Wenchuan earthquake, adopting a threshold between hillslopes and channels set at 1 km2. In comparison with the existing structural sediment delivery ratio (SDR), it was found that the SSC assessed using the SDR showed a decreasing trend of power exponent as distance increased, effectively eliminating the impact of earthquake-triggered sediment supply. To efficiently assess the SSC of post-earthquake landslides for debris flows, we proposed a novel dimensionless index, namely Mean Landslide Sediment Delivery Ratio (MLSDR), by considering the impact of earthquakes and eliminating the impact of catchment area. It was found that, the SSC of coseismic landslides assessed by the MLSDR in catchments affected by the Wenchuan earthquake could better reflect seismic impact, with higher values concentrated along the seismogenic fault of the earthquake, thereby highlighting the satisfactory applicability of the method in the Wenchuan earthquake-affected area. Moreover, it was found that the proposed index had a reasonable corresponding relationship with debris flow development in Wenchuan earthquake-affected catchments, mainly for values of 0.2 ≤ MLSDRout ≤ 2.25 and 0.3 ≤ MLSDRchannel ≤ 4.5, which could help identify potential debris flow development. The controlling factors of long-term changes in coseismic and post-earthquake SSC in the Wenchuan earthquake-affected region were assessed. It was found that SSC was controlled by earthquakes during first three years and subsequently controlled by precipitation and grain composition. This study will strengthen the understandings of the long-term evolution of post-earthquake debris flow.
River confluences are pivotal junctions that have vital influences on hydraulic characteristics and sediment particle distributions as well as on hyporheic water exchange. However, hyporheic water ...exchange is poorly understood because of the complicated river morphology within a river confluence. Therefore, the river confluence between the Juehe River and Haohe River located in arid and semi-arid areas of northwestern China was selected to evaluate the hyporheic water exchange processes, and the temperatures of different depth sediment were measured on July 11th and 12th, 2016 by an instrument equipped with five temperature sensors. The patterns and magnitudes of hyporheic water exchange were estimated using a one-dimensional heat transport model coupled with temperature data. Meanwhile, terrain points elevations and sediment particle distributions in this river confluence were collected to determine the confluence riverbed morphology. Furthermore, the river confluence morphology effects on hyporheic water exchange were investigated in this study. The different riverbed morphology and hydrodynamic zone locations were observed, which were controlled by the planform geometry with low river confluence flux momentum during the test period. Meanwhile, the upwelling flow dominated in the test area, and the downwelling occurred at three of the 23 total test points, which was induced by the complicated riverbed morphology and hydraulic characteristics. Additionally, the magnitudes of the upwelling flow were significantly influenced by the sediment heterogeneity subjected to the erosional and depositional processes. Hyporheic water exchange is a vital hydrological process in arid and semi-arid areas, where it significantly impacts the ecological environment of rivers. This study provides a valuable guideline for water quality and quantity management in arid and semi-arid areas.
The microstructure evolution of Q&P 980 steel resistance spot welds under two different welding conditions,
i.e
., single pulse and dual pulse, and the influence of the welding process on the ...mechanical strength and fracture behavior of welds were investigated. The welds had a softening zone inside the subcritical heat-affected zone (SC-HAZ) for both welding conditions. Moreover, a Mn-free zone (approximately 20
μ
m in width) leading to the formation of a banded bainite microstructure with a lower microhardness between the fusion zone (FZ) and the HAZ was observed, causing cracks to initiate under single pulse welding. Compared to the single pulse process, the dual pulse process with a suitable secondary current and an
in situ
post-weld heat treatment effect leads to an enhancement in tensile-shear and cross-tensile mechanical properties. By establishing the relationship between the microstructure of the failure path, including the FZ, Mn-free zone, and HAZ, and the mechanical properties, the mechanism of mechanical property improvement was revealed. After introducing the post-weld current, three strengthening mechanisms for the FZ were observed,
i.e
., tempered martensite, refined martensite, and remelted nugget. Moreover,
in situ
pulse welding caused a new softening phenomenon in the HAZ and led to the transformation of the banded bainite into martensite in the Mn-free zone, causing changes in the fracture mode and improvement in the mechanical properties.
Understanding the spatiotemporal characteristics of flash floods is important for reasonable and accurate identification of high-risk regions and for prediction of future hydrological regimes. ...Therefore, using time series datasets (1979–2015) of historical flash flood events, rainfall, and land use in the Hengduan Mountains region (HMR) of China, this study analyzed the effects of changes in precipitation and land use on spatiotemporal variation of flash floods. Analysis of the linear trend revealed that flash floods increased by 12 events/10 years and that 82% of events occurred in the flood season (June–August). The increase in flash flood events was found closely correlated with the increased frequency (rainstorm days increased by 3.5 d/10 years) and magnitude (rainstorm amount increased by 10.2 mm/10 years) of heavy rainfall as well as the expansion of the area of artificial surfaces (increase of 999 km
2
). Morlet wavelet analysis revealed significant periodic variation in the occurrence of flash floods on scales of 3–7, 8–15, and 21–31 years. On the basis of the standard elliptical difference, we identified displacement of the center of gravity of flash flooding from the northwest toward the southeast. Generally, more disasters were recorded in southern parts of the HMR owing to the frequent occurrence of rainstorms and the increase in area of both cultivated land and artificial surfaces with higher runoff potential. These findings improve understanding regarding the spatiotemporal dynamics of flash floods in the HMR and could support policymakers in identifying high-risk areas in mountainous watershed.
Ice dammed glacial lake outburst floods (GLOFs) associated with surge glaciers are increasing in response to climate change. Predicting the phenomenon to protect downstream communities remains ...challenging around the globe. Surge-type glaciers are characterized by unsteady movements and frequent frontal advances, which cause natural hazards by obstructing river channels, forming ice-dammed lakes, which can cause GLOFs, posing threats downstream. The determination of the surge characteristics, timing and evolution of lakes and GLOFs is fundamental to flood control and disaster management. In this study, the case of the Khurdopin Glacier (Karakoram) is used to elucidate key behavioral characteristics of surging glaciers that usefully can be applied to understand the GLOF hazard from glaciers worldwide. Seven surge periodical cycles associated with the Khurdopin Glacier that occurred at intervals of 19–20 years between 1880 and 2020 were investigated using a GLOF dataset. The ice flow dynamics of three surge events that occurred between 1970 and 2020 were analyzed using high-resolution satellite imagery. The results indicate that the maximum and minimum surge velocities control the conduit development that drains lakes resulting in a number of GLOFs. A surge between 1998 and 2002 generated six GLOFs. A subglacial drainage model was developed to estimate the timing of the peak discharge in GLOF hydrographs. The results show that conduit melt enlargement becomes the dominant drainage process at one-third of the rising limb. These floods' high peak discharges and short durations are primarily due to the higher lake water temperature, which controls the conduit enlargement rate. Based on the current study results, the proposed model can be adopted worldwide for surge-type glaciers. The initiation of the main surge period, which leads to lake formation, can be anticipated, as the pre-surge period can be identified using remote-sensing analysis. The timing of ice-dammed lake formation and GLOFs can be estimated, providing residents and authorities time to take precautionary measures and thus limiting damage downstream.
•The study presents the development of the reoccurrence surge cycle between 1880 and 2020 using a GLOF dataset.•Seven reoccurring surge cycles with the interval of 19-20 years developed at the Khurdopin Glacier.•The ice flow dynamics of three surge cycles between 1970-2020 were analyzed using high-resolution satellite imagery.•The glacier ice flow dynamics indicate that the maximum and minimum surge velocities control the number of GLOFs.•Results from the Khurdopin Glacier system can be applied to other surge-type glaciers, both regionally and globally.•Where models of glacier surging, lake formation and GLOFs require detection and prediction.
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