Given the conflicts over the proposed formation mechanisms of Xiashu loess, the question of the provenance of sediments comprising the Xiashu loess in the Yangtze River Delta has not been satisfactorily resolved. In t...Given the conflicts over the proposed formation mechanisms of Xiashu loess, the question of the provenance of sediments comprising the Xiashu loess in the Yangtze River Delta has not been satisfactorily resolved. In this study, the provenance of aeolian sediments of the Yangtze River Delta, China was examined by applying the detrial zircon U–Pb dating technique, Sr–Nd isotopic and trace element compositional analysis. U-Pb dating analysis was conducted on the Xiashu loess at three locations over the Yangtze River Delta, including Huangnishan(HNS) hill, Shengshan(SS) island and the Xuancheng(XC) area. The Xiashu loess and the sediments of the Yangtze River Valley share considerable similarity in their zircon U-Pb age spectra with the same main age peak and comparable age distribution. By contrast, significant differences in the age spectra, existbetween the Xiashu loess and loess deposits of Chinese Loess Plateau(CLP). Coarse grains of the Yangtze River Delta loess may have a proximal material source identical to the sediments from the Yangtze River valley. Sr–Nd isotopic values of the Xiashu loess match those from the northern margin of the Tibetan Plateau. Rare earth element ratios independent of grain size illustrate that the values from loess of the Yangtze River Delta mostly overlap with those of CLP loess. This feature implies that loess from the Yangtze River Delta has a dominant source of distant material similar as the CLP loess. As such, we conclude that multi-proxy analysis of sediments can shed new light on tracing the provenance of aeolian loess in the Yangtze River Delta.展开更多
Lithium metal batteries(LMBs) promise ultrahigh energy density,yet their advancement is impeded by dendritic lithium growth and unstable interfacial behavior.Herein,for the first time,we present novel lithiophilic CoN...Lithium metal batteries(LMBs) promise ultrahigh energy density,yet their advancement is impeded by dendritic lithium growth and unstable interfacial behavior.Herein,for the first time,we present novel lithiophilic CoNiB quantum dots embedded in nitrogen-doped hollow carbon nanorods(CoNiB@NC) as a multifunctional interlayer on a polypropylene separator for dendrite-free and stable lithium metal batteries.The CoNiB@NC interlayer has several advantages:The uniformly distributed CoNiB quantum dots serve as highly lithiophilic nucleation centers to induce homogeneous lithium plating/stripping and form stable SEI to inhibit the growth of Li dendrites but also act as a lithiophilic layer and a strengthened physical barrier to enhance the electrolyte wettability and mechanicalhermal stability;the N-doped porous carbon scaffold ensures fast ion/electron transport and accommodates interfacial volume changes;and the boride-rich interface further enhances interfacial stability by modulating local electronic distribution.Benefiting from the merits mentioned above,symmetric Li//Li cells exhibit stable cycling over 500 h at 1 mA cm-2,whereas Li//LiFePO4 full cells maintain a high initial capacity of 144.7 mAh g-1 and a reversible capacity of 104.4 mAh g-1 at 1C over 200 cycles.This work provides new insight into the rational design,facile fabrication,and performance enhancement mechanisms of multifunctional interlayers for dendrite-free and stable LMBs.展开更多
Jacket-type offshore structures consist of tubular members joined by welding,where the weld geometry plays a crucial role in determining hot-spot stresses and,consequently,the fatigue strength of the joints.The weld g...Jacket-type offshore structures consist of tubular members joined by welding,where the weld geometry plays a crucial role in determining hot-spot stresses and,consequently,the fatigue strength of the joints.The weld geometry can be modeled using the finite element(FE)method;however,FE models usually employ assumed weld geometry.It is of interest to investigate the effect of the modeling options related to the weld geometry on the hot-spot stress.The weld geometry of a T-shaped tubular joint was measured using 3D scanning.Different from conventional industry practices,this approach captures the actual shape of the weld joints and toes.An FE model was generated based on the coordinates of the weld toe points,which can lead to more accurate hot-spot stress predictions.In addition,one FE model without welds and two FE models with assumed weld geometry,based on the specifications of the American Welding Society(AWS),were constructed.The hot-spot stresses of these models were compared,and significant deviations were observed.These findings highlight that model uncertainty in hot-spot stress should be considered in fatigue strength assessment to enhance the reliability of offshore structural designs.展开更多
基金supported by the National Natural Science Foundation of China (Grant Nos. 41371032, 41671003, 41601189, 41672349)
摘要Given the conflicts over the proposed formation mechanisms of Xiashu loess, the question of the provenance of sediments comprising the Xiashu loess in the Yangtze River Delta has not been satisfactorily resolved. In this study, the provenance of aeolian sediments of the Yangtze River Delta, China was examined by applying the detrial zircon U–Pb dating technique, Sr–Nd isotopic and trace element compositional analysis. U-Pb dating analysis was conducted on the Xiashu loess at three locations over the Yangtze River Delta, including Huangnishan(HNS) hill, Shengshan(SS) island and the Xuancheng(XC) area. The Xiashu loess and the sediments of the Yangtze River Valley share considerable similarity in their zircon U-Pb age spectra with the same main age peak and comparable age distribution. By contrast, significant differences in the age spectra, existbetween the Xiashu loess and loess deposits of Chinese Loess Plateau(CLP). Coarse grains of the Yangtze River Delta loess may have a proximal material source identical to the sediments from the Yangtze River valley. Sr–Nd isotopic values of the Xiashu loess match those from the northern margin of the Tibetan Plateau. Rare earth element ratios independent of grain size illustrate that the values from loess of the Yangtze River Delta mostly overlap with those of CLP loess. This feature implies that loess from the Yangtze River Delta has a dominant source of distant material similar as the CLP loess. As such, we conclude that multi-proxy analysis of sediments can shed new light on tracing the provenance of aeolian loess in the Yangtze River Delta.
基金financially supported by the National Natural Science Foundation of China(Grant No.52572207)the open research fund of Songshan Lake Materials Laboratory(Grant No.2022SLABFN26)。
摘要Lithium metal batteries(LMBs) promise ultrahigh energy density,yet their advancement is impeded by dendritic lithium growth and unstable interfacial behavior.Herein,for the first time,we present novel lithiophilic CoNiB quantum dots embedded in nitrogen-doped hollow carbon nanorods(CoNiB@NC) as a multifunctional interlayer on a polypropylene separator for dendrite-free and stable lithium metal batteries.The CoNiB@NC interlayer has several advantages:The uniformly distributed CoNiB quantum dots serve as highly lithiophilic nucleation centers to induce homogeneous lithium plating/stripping and form stable SEI to inhibit the growth of Li dendrites but also act as a lithiophilic layer and a strengthened physical barrier to enhance the electrolyte wettability and mechanicalhermal stability;the N-doped porous carbon scaffold ensures fast ion/electron transport and accommodates interfacial volume changes;and the boride-rich interface further enhances interfacial stability by modulating local electronic distribution.Benefiting from the merits mentioned above,symmetric Li//Li cells exhibit stable cycling over 500 h at 1 mA cm-2,whereas Li//LiFePO4 full cells maintain a high initial capacity of 144.7 mAh g-1 and a reversible capacity of 104.4 mAh g-1 at 1C over 200 cycles.This work provides new insight into the rational design,facile fabrication,and performance enhancement mechanisms of multifunctional interlayers for dendrite-free and stable LMBs.
基金supported by the National Natural Science Foundation of China(No.52101350).
摘要Jacket-type offshore structures consist of tubular members joined by welding,where the weld geometry plays a crucial role in determining hot-spot stresses and,consequently,the fatigue strength of the joints.The weld geometry can be modeled using the finite element(FE)method;however,FE models usually employ assumed weld geometry.It is of interest to investigate the effect of the modeling options related to the weld geometry on the hot-spot stress.The weld geometry of a T-shaped tubular joint was measured using 3D scanning.Different from conventional industry practices,this approach captures the actual shape of the weld joints and toes.An FE model was generated based on the coordinates of the weld toe points,which can lead to more accurate hot-spot stress predictions.In addition,one FE model without welds and two FE models with assumed weld geometry,based on the specifications of the American Welding Society(AWS),were constructed.The hot-spot stresses of these models were compared,and significant deviations were observed.These findings highlight that model uncertainty in hot-spot stress should be considered in fatigue strength assessment to enhance the reliability of offshore structural designs.