Impact forces of water drops falling on superhydrophobic surfaces

A falling liquid drop, after impact on a rigid substrate, deforms and spreads, owing to the normal reaction force. Subsequently, if the substrate is non-wetting, the drop retracts and then jumps off. As we show here, not only is the impact itself associated with a distinct peak in the temporal evolution of the normal force, but also the jump-off, which was hitherto unknown. We characterize both peaks and elucidate how they relate to the different stages of the drop impact process. The time at which the second peak appears coincides with the formation of a Worthington jet, emerging through flow-focusing, and it is independent of the impact velocity. However, the magnitude of this peak is dictated by the drop's inertia and surface tension. We show that even low-velocity impacts can lead to a surprisingly high peak in the normal force, namely when a more pronounced singular Worthington jet occurs due to the collapse of an air cavity in the drop.Comment: Please find the supplemental movies here: https://youtube.com/playlist?list=PLf5C5HCrvhLGmlYTF1Gg2WviZ-Bkmy2q

The Role of Relative Deprivation and Attribution Style in the Relationship between Organizational Fairness and Employees’ Service Innovation Behavior

The basis of organizational innovation is employee innovation, which is of great significance for organizations to gain a competitive advantage. At present, the research on the influencing factors of employee service innovation behavior is increasing. This study, based on the social cognitive theory, with relative deprivation as the mediator and attribution style as the moderator, explores the mechanism of the effect of organizational fairness on employee service innovation behavior. Taking 342 employees of service-oriented enterprises as the subjects of investigation, this paper empirically tests the theoretical model by using Amos and SPSS. The results indicated the following, organizational fairness was positively related to employees’ service innovation behavior. Relative deprivation partially mediated the relationship between organizational fairness and service innovation behavior. An external attribution style positively moderated the relationship between relative deprivation and employee service innovation behavior. An external attribution style also positively moderated the mediation effect of the relationship between organizational fairness and service innovation behavior. The internal attribution style negatively moderated the relationship between relative deprivation and employee service innovation behavior. The internal attribution style also negatively moderated the mediation effect of the relationship between organizational fairness and service innovation behavior. The conclusion of this study has managerial implications on how to promote employee service innovation behavior in service-oriented enterprises

A PET Fluorescent Probe for Dynamic Pd²⁺ Tracking with Imaging Applications in the Nanofiber and Living Cells

Constructed on the moiety of a lactam screw ring, a near-infrared fluorescent probe RCya for Pd2+ was designed under the PET mechanism and synthesized by incorporating 2,4-dihydroxybenzaldehyde as the recognition group. Dynamic detection of aqueous Pd2+ by the probe RCya could be accomplished through ion competition, linear response, fluorescence-pH/time stabilities, and other optical tests. Moreover, the high selectivity, low cytotoxicity, cell permeability, and lysosome accumulation properties of RCya enabled the imaging applications on solid-state RCya–PAN composite nanofibers and in living cells. The recognition mechanism of probe RCya toward Pd2+ was further studied through simulation calculation and MS analysis

Effect of Cold Expansion on Fatigue Life of Hole Structure of TC17 Titanium Alloy

In order to improve the fatigue performance of TC17 central hole specimen, the hole wall surface integrity was characterized by scanning electron microscopy (SEM), roughness meter, X-ray diffraction, and the influence of hole cold expansion(HCE) parameter on the fatigue performance of the hole specimens was investigated. The results show that the minimum fatigue life (14718 cycle) of the HCE specimens with an expansion value of 0.18 mm is higher than the original specimen (13965 cycle). Compared to the specimens with the expansion values of 0.28 mm and 0.38 mm, the fatigue life dispersion is less, no obvious stress concentration phenomenon is found, and it has the best fatigue performance than the other two. The surface roughness value of hole wall is the lowest after the HCE with 0.18 mm, the inner hole wall forms a certain depth of strengthened layer, the residual compressive stress produced in the hole side effectively suppresses the produce of fatigue cracks in the inner hole wall, so the fatigue performance of hole structure is improved

Rapid Estimation of Decameter FPAR from Sentinel-2 Imagery on the Google Earth Engine

As a direct indicator of vegetation photosynthesis, the fraction of absorbed photosynthetically active radiation (FPAR) serves as a critical input in a series of land surface models. While existing satellite FPAR products are generally at coarse resolutions ranging from 250 m to 1 km, operational FPAR products at fine resolution are urgently needed in studying land surface processes at the plot scale. However, existing methods for estimating fine-resolution FPAR were mainly designed for Landsat data, and few studies have attempted to develop algorithms for Sentinel-2 data. In particular, the operational estimation of decameter FPAR has a higher requirement for the algorithms in terms of generalizability, efficiency, accuracy, and adaptability to Sentinel-2 data. In this paper, we developed a retrieval chain on the Google Earth Engine (GEE) platform to estimate FPAR by learning the relationship between MODIS FPAR and Sentinel-2 surface reflectance. Scale-consistent multilinear models were used to model the relationship between MODIS FPAR and Sentinel-2 surface reflectance, and the model coefficients were regressed from the selected training samples. To account for the spectral and spatial characteristics of the Sentinel-2 data, we designed criteria for selecting training samples and compared different band combinations. Three strategies for band combination were used: (1) green, red, and near infrared (NIR) bands at 10 m resolution (i.e., three bands); (2) green, red, NIR, and red edge (RE) 1, RE2, and RE3 bands at 20 m resolution (i.e., five bands); and (3) green, red, NIR, RE1, RE2, RE3, shortwave infrared1 (SWIR1) and SWIR2 bands at 20 m resolution (i.e., eight bands). Meanwhile, the official Sentinel Application Platform (SNAP) method has also been implemented to estimate the Sentinel FPAR at 10 m and 20 m resolutions for comparison. Both methods were applied to the western Guanzhong area, Shaanxi Province, China, for FPAR estimation of all cloud-free Sentinel-2 images in 2021. The results show that the scaling-based method using five bands at 20 m resolution was the most accurate compared to the in situ measurements (RMSE = 0.076 and R² = 0.626), which outperformed the SNAP method at 10 m and 20 m resolutions and the scaling-based method using other strategies. The results of the scaling-based method using all three strategies were highly consistent with the MODIS FPAR product, while the SNAP method systematically underestimated FPAR values compared to the MODIS FPAR products. The proposed method is more ready-to-use and more efficient than SNAP software. Considering that the service of the MODIS sensor is overdue, the proposed method can be extended to alternatives to MODIS products, such as VIIRS and Sentinel-3 data

Effect of Double Cold Expansion of Hole on Fatigue Property of TB6 Titanium Alloy

To improve the fatigue resistance of the bolt connecting hole, the effect of double cold expansion (DCE) of the hole on the fatigue life of TB6 titanium alloy was investigated. The fatigue fracture, surface roughness, residual stress, hardness and microstructure of the hole wall were characterized by scanning electron microscopy (SEM), roughmeter, X-ray diffraction (XRD), microhardness tester and optical microscopy. The mechanism of DCE on the fatigue life of the hole was also investigated. The results show that the mean value of the fatigue life of DCE specimen is much higher than that of the interference fit specimen. The surface integrity of the hole wall is improved after DCE. The roughness decreases remarkably. The deep surface-strengthen-layer with high hardness and deep residual compressive stress field are formed around the hole through severe plastic deformation of the microstructure of the hole wall. It is considered that the improvement of surface integrity plays an important role on the enhancement of fretting fatigue life

Impact Forces of Water Drops Falling on Superhydrophobic Surfaces

A falling liquid drop, after impact on a rigid substrate, deforms and spreads, owing to the normal reaction force. Subsequently, if the substrate is nonwetting, the drop retracts and then jumps off. As we show here, not only is the impact itself associated with a distinct peak in the temporal evolution of the normal force, but also the jump-off, which was hitherto unknown. We characterize both peaks and elucidate how they relate to the different stages of the drop impact process. The time at which the second peak appears coincides with the formation of a Worthington jet, emerging through flow focusing. Even low-velocity impacts can lead to a surprisingly high second peak in the normal force, even larger than the first one, namely when the Worthington jet becomes singular due to the collapse of an air cavity in the drop