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In this paper, a residual-type a posteriori error estimator is proposed and analyzed for a weak Galerkin finite element method for solving linear elasticity problems. The error estimator is proven to be both reliable and efficient, and be used for adaptive refinement. Numerical experiments are presented to illustrate the effectiveness of this error estimator. [ABSTRACT FROM AUTHOR]

• We conducted the binary cross-lagged model combines the subject-object reciprocity model and the longitudinal cross-lagged model by constructing structural equations to test the potential bidirectional effects over time. • Husband's sleep quality may be a predictor of his wife's depressive symptoms. Wives' nighttime sleep duration may be a predictor of husbands' depressive symptoms. • Husband's depressive symptoms were a significant negative predictor of both the wife's sleep quality and sleep duration. • A significant negative predictive effect of wives' depressive symptoms on husbands' nighttime sleep duration. Although there are many studies analysing the relationship between sleep and depression in individuals, there is currently no bi-directional causal relationship between sleep and depression between older couples analysed from a binary perspective.Thus, this study used the CHARLS database to analyse the relationship between sleep and depression among older couples. A binary cross-lagged model was used to analyse the data.The study found an interaction between nighttime sleep duration and depression among older couples. Wife's depressive symptoms were significant predictors of husband's nocturnal sleep duration. Husband's depression and sleep quality predicted wife's sleep quality and depression, respectively. Therefore, when screening community-dwelling older adults for depressive symptoms, we need to be aware of the impact of different sleep profiles of older adults of different genders on spousal depressive symptoms. In addition, when dealing with patients with depressive symptoms, we need to consider not only the patient but also the impact of their depressive symptoms on their spouse. [ABSTRACT FROM AUTHOR]

Clean energy hydrogen is a promising substitute for traditional fossil fuels. Hydrogen production via electrocatalytic and photocatalytic water splitting is attracting much attention due to its environmental friendliness. Platinum-based materials are used to promote the kinetic rate for hydrogen evolution reaction (HER). However, the Pt usage is limited by their high price and low content. Much efforts have been put to replace them by non-precious metals. With low melting point and widest liquid temperature range, gallium is easily coupled with other metals or non-metals for constructing composite material for HER, However, systematic research on constructing gallium-based materials for HER is rare and this review could fill in certain gaps of related field. In this work, the preparation method and HER performance of gallium-based materials including gallium alloy, gallium phosphide and their composites, are summarized systematically. This review provides a comprehensive understanding of the structure influences of these gallium-based materials on electrocatalytic and photocatalytic HER performance. Moreover, possible challenges and prospects are also proposed for inspiring people to design excellent gallium-based materials for HER. [ABSTRACT FROM AUTHOR]

In the free-bending process, the tube undergoes bending and deformation due to the action of a guide mechanism and bending die. The plastic deformation zone of the bent tube is less constrained by the die, and the quality of the formed tube is significantly affected by the friction between the tube and the die. To assess the impact of friction between tube and die on the formability of the bent tube, the theoretical modeling that considers the friction coefficient is conducted. Afterward, the free-bending experiments and finite element simulations are performed using Cr12MoV and ceramic bushing. The theoretical and experimental results are compared with those obtained from finite element simulation under different friction conditions to confirm the validity of finite element simulation. The influence of friction on the arc radius, wall thickness variation, and cross-section deformation of the curved tube is explored and discussed. With the increase of friction coefficient, the arc radius decreases gradually, the wall thickness thickens more obviously, and the cross-sectional distortion becomes more serious. Furthermore, the effect of different bushing materials on the surface quality of aluminum alloy and stainless-steel bent tubes is experimentally investigated. Those findings expand our understanding of the influence of tube-die friction on deformation behavior and it is necessary to first determine the friction condition during the actual free-bending forming process. [Display omitted] • The increase of friction coefficient introduces the improvement of axial force. • Shift of strain-neutral layer is verified by simulation and theoretical deduction. • The bending radius of bent tube decreases with increasing friction coefficient. • The surface quality of bent tube is improved by using the ceramic bushing. [ABSTRACT FROM AUTHOR]

To link to full-text access for this article, visit this link: http://dx.doi.org/10.1016/j.comnet.2004.08.002 Byline: Chunmei Liu, Eytan Modiano Keywords: AIMD protocol; TCP; ARQ; Hybrid networks; Interactions Abstract: It is well known that TCP does not perform well in networks with large propagation delay and high link loss probability, which are typical in hybrid space-terrestrial networks. Implementing Automatic-Repeat-Request (ARQ) retransmission over satellite links in hybrid networks has been proposed to enhance TCP performance by hiding the link losses from TCP. This paper analyzes the impact of implementing ARQ over satellite links on TCP performance. In particular, this paper focuses on the window flow control mechanism of TCP, and provides an exact model for a hybrid space-terrestrial system with transport layer Additive-Increase-Multiplicative-Decrease (AIMD) protocols and satellite link layer ARQ. Both Go-Back-N (GBN) and Selective-Repeat (SRP) are considered, and the delay of acknowledgements (ACKs) of ARQ are taken into account. The numerical solutions for the throughput as a function of different protocol and packet loss parameters are presented. Both the analysis and numerical results show that in most cases, implementing ARQ over satellite links can significantly improve TCP performance, and that proper choices of the protocol parameters can significantly improve the system performance as well. Although the paper focuses on hybrid space-terrestrial networks, the analysis and results are also applicable to other networks with large bandwidth-delay product and one error-prone bottleneck link. Author Affiliation: Massachusetts Institute of Technology, Cambridge, MA 02139, United States Article Note: (footnote) [star] This work was supported by NASA Space Communication Project grant number NAG3-2835.

Two neutral tetrahedral cuprous complexes have been synthesized, which exhibit blue TADF emission at 462 nm for 1 and 472 nm for 2 , respectively. Remarkably, both complexes simultaneously exhibit high PLQY (1 , 52% and 2 , 85%) and short emission lifetimes (1 , 4.2 μs and 2 , 7.5 μs) at ambient temperature. [Display omitted] Endowing thermally activated delayed fluorescence (TADF) emitters simultaneously with high emission quantum yields and short radiative lifetimes is of fundamental significance in optoelectronic field. In this contribution, two neutral tetrahedral Cu(I) complexes (1 and 2) have been developed, which realize blue-TADF with photoluminescent quantum yield of up to 85 % due to the high structural rigidity. Meanwhile, short TADF lifetimes (<10 μs) of the Cu(I) complexes suggest that the synergistic effects of small ΔE(S 1 -T 1) gap and relatively large SOC value introduced by the copper ion could facilitate fast reverse ISC processes compared to the typical organic-TADF materials. [ABSTRACT FROM AUTHOR]