Search

The dynamic response of a micrometer-sized gallium–indium (Ga-In) jet in nitrogen subjected to intense Neodymium-doped Yttrium Aluminum Garnet (Nd: YAG) laser pulses with energy ranging from 0.35 to 5.0 mJ per pulse is investigated experimentally. The rapid deformation of the jet was visualized using timed-delayed stroboscopic shadowgraphy. The laser pulse disrupts the jet to form a gap, and the length of the gap grows according to a logarithm relationship with respect to the dimensionless time normalized a characteristic timescale τ, which is determined by the pulse energy Ep. The ablation impulse bends and flattens the jet into a thin curved film that resembles a wind-blown sail. The area of the sail increases with t6/5Ep13/15, where t is time. The sail eventually breaks up into fine mist. Additionally, we found that the laser-blast-induced initial bending velocity of the jet could be predicted using the semi-empirical laser-ablated propulsion model for an In-Sn droplet of tens of micrometers. [ABSTRACT FROM AUTHOR]

This study advances the bidirectional relationship between residents' perceived tourism impacts and subjective wellbeing, as well as examines the consequential effects on support for tourism development. The bottom-up formative and top-down reflective structural models were proposed based on the bottom-up and top-down theories of subjective wellbeing and Social Exchange Theory. The models were empirically tested with a sample of 466 residents in Macao. Partial least squares-structural equation modelling was employed in data analysis. Results reveal the co-existence of the bottom-up and top-down effects, and also confirm the significant positive impacts of tourism benefits and wellbeing on attitudes toward tourism. Findings suggest the interplay of tourism impacts and wellbeing in forming a virtuous loop, thereby driving support for tourism through mutual enhancing effects. This study validates the bidirectionality between perceived tourism impacts and subjective wellbeing under the integrative framework of the bottom-up and top-down theories. The bidirectionality signifies that subjective wellbeing should be operationalized by scales following its formative or reflective nature under investigation. Furthermore, the bilateral linkages could be exploited by promoting perceived tourism benefits, mitigating perceived tourism costs and fostering subjective wellbeing in order to uphold residents' support for tourism for its sustainable development through the social exchange mechanism. [ABSTRACT FROM AUTHOR]

The motion of millimeter gallium-indium (Ga-In) drops subject to intense Neodymium-doped Yttrium Aluminum Garnet (Nd: YAG) laser blasts in the air is investigated experimentally. The drop first experiences plasma emissions and then undergoes interfacial instabilities. The effective ablation pulse energy is quantified by the laser-induced shockwave propagation. The laser-blast-induced concave expansion and spanwise depression history is measured, and the data collapse on straight lines with proper rescaling of pulse energy and time. The propulsion speed of the drop is described by a semi-empirical model that considers the laser energy and fluence at the threshold of ablation. The data show that this propulsion speed scaling remains valid to the millimeter drop ablated by the pulsed laser with beam spot much smaller than the drop, although the original scaling was derived and verified for the indium-tin (In-Sn) droplet of tens of micrometers impacted by a laser pulse with the focal point larger than the droplet. [ABSTRACT FROM AUTHOR]

With the surge of the power conversion efficiencies (PCEs) of organic solar cells (OSCs) in recent years, the commercialization of OSCs calls for scalable and environmentally friendly manufacturing techniques. Aerosol printing is a non-contact material deposition method that is compatible with flexible or curved substrates for scaled-up OSC fabrication. Here, by introducing vibrating mesh atomization (VMA) with specific engineering, we demonstrate the first attempt of fabricating OSCs by aerosol printing with the state-of-the-art OSC material of PTQ10:Y6-BO with an environmentally friendly solvent of o-xylene in ambient air. The inks of functional organic materials are converted by VMA into tiny aerosol droplets of ∼5 micrometers, which are passed through a slit printing nozzle to increase the droplet mass flux and suppress the coffee-ring effect. In doing so, favorable arrangement/crystallization of the organic molecules in photoactive layer are realized, leading to OSC devices with PCE up to 15.65%. The VMA is also suitable for printing the hole transport layer and electron transport layer. The all-aerosol-printed OSC devices achieved a PCE of 14.78%. Notably, VMA requires as little as 100 μL solution to prime the fluid lines, making the transition from laboratory experiments to continuous production more economical and practical. To illustrate this advantage, a mini automated production line was built to demonstrate the completion of five steps (printing of three functional layers, and thermal annealing of the hole transport layer and active layer) on a conveyer belt within 30 minutes, marking a concrete step towards manufacturing of high-performance OSCs. [ABSTRACT FROM AUTHOR]

Background: Physical performance is an important healthy factor in elder people. Good living habits, which include sleep, can maintain physical strength and physical performance. The aim of the present study was to conduct a cross-sectional study to determine the association between total sleep duration and physical performance. Methods: Our study population comprised residents of the township central hospital in the suburban of Tianjin, China. We measured muscle strength, walk speed and balance function by grip, 4-m walk test and timed up and go test (TUGT). We divided sleep duration into four groups <7h, 7-8h, >8-9h, >9h. Results: A total 898 participants had completed data (392 men and 506 women, mean age 67.71 years). In man, adjusted sleep duration was associated with lower grip in > 9 h group, the mean value (95% CI) was 0.429 (0.409, 0.448), and longer TUGT time was also associated with long sleep duration, 10.46s (9.97 s, 10.95 s). In women, adjusted slower 4-m walk speed present an inverse U-shaped relation with sleep duration, by 0.93 m/s (0.86 m/s, 0.98 m/s), 0.97 m/s (0.96 m/s, 1.00 m/s), 0.97 m/s (0.95 m/s, 0.99 m/s) and 0.92 m/s (0.89 m/s, 0.96 m/s); longer TUGT time were associated with long sleep duration (> 9 h), by 11.23 s (10.70 s, 11.77 s). Conclusion: In Chinese community-dwelling elderly, lower muscle strength and lower balance function were associated with long sleep duration in men. Slower walk speed and lower balance function were associated with long sleep duration in women. [ABSTRACT FROM AUTHOR]

Previous works investigated particle trajectories in hard disk drives (HDDs) with the actuator arm and the head gimbals assembly at a fixed position. Actually, internal fluid field characteristics of HDDs can be greatly changed by the arm swing during track-seeking operations, which can affect particle trajectories and trapping status. In this paper, using the dynamic mesh method in a 2.5 in HDD for the first time considers the arm swing in the computational fluid dynamics (CFD) simulation. Al2O3 particle trajectories in this HDD are studied by the CFD solver FLUENT with user-defined functions. The trapping criterion for Al2O3 particles is used as a boundary condition for colliding surfaces. Simulation results reveal that the particle undergoes a larger number of collisions with the disk surface for the average seek time of 12 ms than for the average seek time of 6 ms. In addition, the faster the arm swings, the larger the number of particles that gather near the arm, and the shorter time it will take for particles to be trapped. Moreover, particle-surface collisions can successively take place many times in the helium flow. Furthermore, the particles are trapped slower in the helium-filled drive than in the air-filled drive. [ABSTRACT FROM AUTHOR]

The lubricant bridge connecting the slider and the disk will significantly deteriorate the read–write stability of the hard disk drive. This paper builds a model of disk-lubricant-slider system. The coarse-grained bead-spring model is used to represent perfluoropolyethers molecules. And the molecular dynamic method is used to study the formation time and the molecule number of the lubricant bridge under different disk rotation speeds and slider flying heights. Furthermore, the influence of lubricant bridge on the pressure acting on the slider pad is also studied. [ABSTRACT FROM AUTHOR]

Understanding the temperature-dependent shear behavior of rock joints is significant for the design, construction and maintenance of deep rock engineering. However, the shear characteristics of healed rock joints under high temperatures are still poorly understood. In this paper, to capture the thermal effect on the shear behavior of healed rock joints, a series of direct shear tests are performed with the aid of X-ray diffraction and scanning electron microscope techniques. The testing results demonstrate that the shear resistance of the healed joints is slightly lower than that of the intact rock, but much greater than that of clean joints. Compared with intact rocks, the ductile failure characteristics of the healed joints after high temperature thermal treatment are more significant. The peak shear strength, shear stiffness and dilation angle of healed joints are greatly influenced by thermal treatment temperature, while the ultimate shear strength is almost independent on with temperatures. The influence of thermal treatment on shear resistance is attributed to the physical and chemical changes. The thermal decomposition of the filling minerals at around 400 °C is believed to be the main cause of the change in thermal-induced shear behavior of the healed joints. The findings of this work are useful to understand the mechanical behavior of jointed rock mass under high temperatures. [ABSTRACT FROM AUTHOR]

Entrepreneurs' live streaming (ELS) is an important tool for marketing, and it can increase consumer engagement, especially during the COVID-19 pandemic. Previous live streaming literature mainly focused on third-party live streaming, targeted at professional streamers and online celebrities. This study aims to discuss the factors underlying consumer engagement in the ELS. Using a mixed method of a quasi-experiment and an online survey, we analyzed the impact of the ELS on consumer engagement and the factors that drive consumer engagement in the ELS in each of 231 samples. In the enterprises' live streaming, the ELS has a significantly higher influence on consumer engagement compared with the employees' live streaming. In the ELS, based on source credibility theory and signaling theory, this study concludes that factors of ELS's credibility consist of internal factors (reputation, expertise, and interactivity) and external factors (guarantee, authenticity, and money-saving). The authors demonstrate that both internal and external factors positively affect trust in activities. Trust in activities positively affects consumer engagement and mediates the effects of reputation, expertise, interactivity, guarantee, and authenticity on consumer engagement. Moreover, reputation and expertise positively improve consumers' admiration toward the entrepreneur streamer and in turn, positively increase consumer engagement. Interactivity and expertise shorten the psychological distance. Psychological distance negatively affects consumer engagement and only helps increase the positive effect of interactivity on consumer engagement. These findings have theoretical and practical implications for live streaming e-commerce., Competing Interests: The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest., (Copyright © 2022 Jiang, Wang, Xue and Zhai.)

Scalable and roll-to-roll compatible processing methods have become pressing needs to transfer organic solar cells (OSCs) to realistic energy sources. Herein a new fabrication method of flexible microcomb printing is proposed. The microcomb is based on a PET sheet micromachined into comb teeth by a laser marker. A computational fluid mechanics simulation shows that the fluid flow around the microcomb teeth induces high shear as well as extensional strain rates, which enhance the molecular alignment and lateral mass transport. The PTQ10:Y6-BO OSCs printed by the flexible microcomb demonstrate a substantially increased degree of crystallinity and phase separation with a suitable domain size. Devices printed by the flexible microcomb in air achieve PCEs of up to 15.93%, higher than those of control devices spin-coated in the N 2 glovebox. The flexibility of the PET film makes the microcomb teeth contact directly with the substrate without a suspended liquid meniscus, thus facilitating printing on soft or curved substrates. Printing of flexible OSCs and large-area devices are demonstrated. The flexible OSCs exhibit PCEs of up to 13.62%, which is the highest for flexible OSCs made by scalable printing techniques to date. These results make flexible microcomb printing a feasible and promising strategy toward the manufacture of efficient OSCs.