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• A robust and efficient joint sensor registration and multi-object tracking method for PHD filter to address the distributed fusion in networks where the relative positions of sensors are unknown. • The pairwise registration strategy which can transform the high-dimension optimization to low-dimension optimization for computationally efficient. • The two-step optimization method which can transform the formulated non-convex problem of the proposed method to a convex one. This paper addresses the joint sensor registration and multi-object tracking in distributed sensor networks wherein the accurate positions of sensors are unknown. Each local sensor runs the probability hypothesis density filter (PHD) in its local coordinate system, having no knowledge about the relative positions of other sensors in the network. The generalized covariance intersection (GCI) fusion rule is employed to fuse the local densities. To tackle the sensor registration problem, a cost function expressing the information discrepancy between local densities is constructed based on the GCI divergence, then the relative positions of sensors are estimated by minimizing such a cost function. As the constructed cost function leads to a high-dimension optimization problem, for computational efficiency, a pairwise sensor registration strategy is proposed which is proved equally sound with the high-dimension registration method but more computationally efficient. Lastly, we demonstrate that the formulated registration method involves a non-convex problem. To solve such a non-convex problem, a two-step optimization method is proposed which can transform the non-convex problem into a convex one. The efficacy of the proposed method is demonstrated in a challenging tracking scenario via numerical experiments. [ABSTRACT FROM AUTHOR]

Silicon thin-film is one of the most promising silicon anode materials for lithium-ion batteries, with the advantages of high cycle stability and initial coulombic efficiency. The excellent performance of silicon thin-films is due to their ultra-thin thickness (< 200 nm), but this results in their areal capacity too low to be compatible with commercial cathode materials, and only films thicker than 500 nm are practical. However, frequent volume changes in non-ultra-thin silicon films during cycling may cause layer misalignment and separation of the film from substrate. In this paper, silicon films with a thickness of ∼700 nm are prepared by magnetron sputtering on the inhomogeneous surface of a copper foil. The properties of the silicon films and mechanisms involved in the cycling process is investigated by combining experimental means during cycling with calculations of the atomic-scale amorphous lithium-silicon Zintl Phases' structural volumes before and after cycling. The results show that the volume of silicon doesn't recover after delithiation and there is still significant swelling. The cyclic process causes a superimposed expansion of the volume, but the non-uniform film substrate causes the lateral expansion stresses to offset each other, thereby retaining a relatively stable structure. At the end of 100 cycles, the specific capacity of the silicon film electrode is 1461.5 mAh g −1 (areal capacity 0.242 mAh cm−2), with a capacity retention of 64.35%, and the silicon film thickness becomes 8.5 μm. We believe that by reducing the longitudinal expansion volume or stress of the silicon film, the cycle life of the silicon film can be further optimized. [Display omitted] [ABSTRACT FROM AUTHOR]

Considerable research has established the harmful impacts of the COVID-19 pandemic on children's and adolescents' health and well-being. However, the literature has been constrained by studies using less representative samples, hindering the generalization of the findings. This study aimed to investigate the associations of employment disruption and school closures during the pandemic with suicidal ideation and behavior in children and adolescents—and to consider the potential mediating effects of child psychological and physical abuse and subsequent mental health conditions. This study used the Adolescent Behaviors and Experiences data (n = 4692) — a nationally representative survey administered by the CDC of the United States from January to June 2021. Logistic regression models were conducted to investigate the associations. A series of multiple mediation models were performed. School closures directly reduced child psychological and physical abuse and suicidal ideation and behavior. Employment disruption did not directly predict suicidal ideation and behavior but primarily through child abuse. Mental health's mediation role was significant in the associations between child psychological abuse and suicidal ideation and behavior, but no evidence suggested the same mediating pattern for the physical abuse-suicidal ideation and behavior relationship. Within the covariates, sexual orientation was the most consistent and highest risk factor. This study contributes to current knowledge on disaster impact, child abuse, and suicidal ideation and behavior, and it can also provide policy and intervention awareness for social workers. • The most recent national representative survey in the United States about children and adolescents was analyzed. • The associations between COVID-19 impacts, child abuse, mental health and four suicidality measures were investigated. • School disruptions directly reduced child psychological and physical abuse experience and suicidal ideation and behaviors. • Employment disruption did not directly predict suicidal ideation and behavior but primarily through child abuse. • Mental health's mediation role was significant between psychological abuse and suicidality but not for physical abuse. [ABSTRACT FROM AUTHOR]

This study presents a numerical investigation on a cascaded shell-and-tube 3PCMs latent heat thermal storage unit filled with three types of phase-change materials namely, C24H50, C21H44, and C18H38. The mathematical model is based on the enthalpy method and considers the effect of the natural convection of liquid phase-change material during melting. The transient heat transfer and thermal storage characteristic of the 3PCMs unit are analyzed and compared with those of a 1PCM unit that utilizes C24H50. The influences of heat transfer fluid flow rate and inlet temperature on the efficiency, accumulated energy, and exergy of the latent heat thermal storage unit are studied. Results show that the 3PCMs unit can improve the heat transfer rate greatly and shorten the heat storage time effectively, as much as 58% more energy can be stored than the 1PCM unit at the same charging time. The increase of both inlet temperature and flow rate of the heat transfer fluid will lead to a shorter charging time, whereas the advantage of the 3PCMs unit on storage performance over the 1PCM unit becomes more insignificant. [ABSTRACT FROM AUTHOR]

To examine the fluid flow and heat transfer characteristics in a microchannel with fan-shaped reentrant cavities, the numerical investigations were conducted, and the results were compared with the conventional rectangular microchannel data. The SIMPLEX method was used for the computation. The effects of volumetric flow rate, heat flux on the pressure drop and thermal resistance were investigated in detail. The numerical simulation results indicate that a microchannel with fan-shaped reentrant cavities can improve heat transfer performance with an acceptable pressure drop when the Reynolds numbers are larger, and the fluid flow and heat transfer mechanism can be attributed to the interaction of the redeveloping of hydraulic and thermal boundary layers, the effect of jet and throttling and the stagnation zone of laminar flow. [ABSTRACT FROM AUTHOR]

To estimate spatial distribution, source analysis and uncertainty of heavy metals (Pb, Cd, Cr, Hg, As, Cu, Zn, and Ni) based on geographic information system (GIS), positive matrix factorization model (PMF) and bootstrap (BS) using 382 soil samples collected from cultivated soils in Lanzhou. The mean contents of Cd, Hg, Cu, Zn and Ni were high as 1.7,1.7, 2.1, 1.5 and 1.3 times local background values, mean contents of Pb, Cr and As were lower than local background values. However, the mean contents of eight heavy metals were lower environmental quality risk control standard for soil contamination of agricultural soil. Proportions of four sources were identified: Cr was predominantly contributed by natural sources (29.14%), Cu, Zn and Ni was primarily from industrial sources (25.26%), Hg and As were mainly of agricultural sources (27.49%), Pb and Cd mainly came from traffic source and smelting-related activities (18.09%). Uncertainties analysis contained three aspects: bootstrap runs, factor contributions in the PMF solution, and coefficient of variation (CV) values. By combining the four pollution source factors with bootstrap runs, the accuracy of the four pollution source factors were reliable based on PMF model. The median values in the BS runs was considered the most true factor contribution, and the 5th–95th quartile interval represents the variability of each factor, Factor 4 (traffic source) R2 was 0.70 and lower variability. The highest CV value usually means a significantly deviation degree. In this study, the CV values of Cr in Factor 1, Cu, Zn, and Ni in Factor 2, Hg, and As in Factor 3, Pb, and Cd in Factor 4 were lower, indicates a lower deviation degree. and with the lowest content among heavy metals usually was also with the greatest uncertainties. In this study improves understanding of the reduction of heavy metal pollution in cultivated soil, and also serves as reference for pollution source apportionment in other regions. [Display omitted] • Four sources were identified and natural sources and agricultural sources were the largest. • Combination with Bootstrap can help improve the accuracy of the four pollution source factors. • The determination coefficient (R2) of the four factors was between 0.52 and 0.70. • The lowest concentrations heavy metals usually became with higher uncertainties. [ABSTRACT FROM AUTHOR]

• Perovskite film modified by PVP/PEG mixture was prepared by a two-step method in air. • The cell with 1.5 wt%PVP/0.5 wt%PEG shows 30% PCE increasement compared with pure one. • The cell with 1.5 wt% PVP/0.5 wt%PEG retains 76% of its initial PCE value for 30 days. • The interactions between CH 3 NH 3 PbI 3 and PVP/PEG improve film quality and stability. • The bondings between perovskite and PVP/PEG increase cell efficiency and stability. The synergistic effect including the strong attraction between the C˭O in PVP and Pb2+ in perovskite, and the intense hydrogen bond between O atoms from PEG and H atoms in CH 3 NH 3 + results in the improved photoelectric conversion efficiency and air stability of PVP/PEG mixture added perovskite solar cell based on ZnO-TiO 2 nanorod arrays compared to those of the pristine one and single polymer added perovskite solar cells. ga1 The key to commercialization of organic‐inorganic lead halide perovskite solar cells (PSCs) is to achieve high photoelectric conversion efficiency (PCE) and long-term stability under ambient condition. In this paper, polymer mixture of polyvinylpyrrolidone (PVP) and polyethylene glycol (PEG) with appropriate mass ratio are incorporated into PbI 2 precursor solution in the preparation process of perovskite film via two-step sequential deposition method in air. The PCE of polymer mixture modified PSC based on ZnO@TiO 2 nanorod arrays is better than those of the PSC with single polymer（PVP or PEG）and the pristine one, and the PCE of 1.5 wt%PVP/0.5 wt%PEG modified device increased by 30% compared with that of the unmodified one, which is mainly a consequence of the better quality of perovskite film caused by the synergistic effect including the strong attraction between the C=O in PVP and Pb2+ in perovskite, and the intense hydrogen bond between O atoms from PEG and H atoms in CH 3 NH 3 +. Moreover, polymer mixture modified PSC also represents better air stability compared with the device with single polymer or the pristine one，which is largely attributed to the exceptional hygroscopicity of PVP/PEG mixture, the synergistic stabilization of perovskite structure and inhibition of ion migration by the bondings between polymer mixture and perovskite. Furthermore, the mechanism of the interaction between PVP/PEG mixture and CH 3 NH 3 PbI 3 to increase the efficiency and stability of the PSC was also studied. Our work offers an effective additive to simultaneously improve the efficiency and stability of the PSCs in high humidity environment for further commercial application. [ABSTRACT FROM AUTHOR]

Using a nationally representative survey of urban areas from China, the present study examines three research questions: (1) how are alcohol and tobacco use associated with academic performance among Chinese children and adolescents? (2) how does skipping class mediate those associations? And (3) do any observed patterns differ for boys and girls? Our results show that alcohol and tobacco use are associated with poor academic performance. However, alcohol use fully accounts for the detrimental effect of tobacco use on academic performance. Moreover, skipping class partially and fully mediates the effects of alcohol and tobacco use on poor academic performance. The adverse effect of tobacco use on academic performance is stronger for girls than boys. To improve children's and adolescents' academic performance, it is important to document the potential contributing factors. [ABSTRACT FROM AUTHOR]

Using a nationally representative survey of urban areas from China collected in 2016, we examine two research questions: (1) how is school bullying victimization associated with self-rated health and life satisfaction; and (2) how do relationships with parents, teachers, and peers mediate those associations? We find that, among students of higher primary, middle, high, and vocational schools, bullying victims are more likely to report poor self-rated health and life satisfaction, regardless of whether the victims experience traditional bullying or cyberbullying. In addition, both traditional bullying and cyberbullying victims are associated with poor relationships with parents, teachers, and peers, which, in turn, partially mediate the effect of bullying victimization on poor self-rated health and life satisfaction. The present study underscores that the impact of adults and peers might be an important mechanism contributing to the health and well-being disparities by school bullying victimization. [ABSTRACT FROM AUTHOR]