Ruddlesden-Popper Phase in Two-Dimensional Inorganic Halide Perovskites: A Plausible Model and the Supporting Observations.

A Ruddlesden-Popper (RP) type structure is well-known in oxide perovskites and is related to many interesting properties such as superconductivity and ferroelectricity. However, the RP phase has not yet been discovered in inorganic halide perovskites. Here, we report the direct observation of unusual structure in two-dimensional CsPbBr3 nanosheets which could be interpreted as the RP phase based on model simulations. Structural details of the plausible RP domains and domain boundaries between the RP and conventional perovskite phases have been revealed on the atomic level using aberration-corrected scanning transmission electron microscopy. The finding marks a major advance toward future inorganic halide RP phase synthesis and theoretical modeling, as well as unraveling their structure-property relationship

Facile synthesis and enhanced visible light photocatalytic activity of N and Zr co-doped TiO2 nanostructures from nanotubular titanic acid precursors

Zr/N co-doped TiO2 nanostructures were successfully synthesized using nanotubular titanic acid (NTA) as precursors by a facile wet chemical route and subsequent calcination. These Zr/N-doped TiO2 nanostructures made by NTA precursors show significantly enhanced visible light absorption and much higher photocatalytic performance than the Zr/N-doped P25 TiO2 nanoparticles. Impacts of Zr/N co-doping on the morphologies, optical properties, and photocatalytic activities of the NTA precursor-based TiO2 were thoroughly investigated. The origin of the enhanced visible light photocatalytic activity is discussed in detail.Comment: 8 pages, 7 figure

Yielding and hardening of flexible fiber packings during triaxial compression

This paper examines the mechanical response of flexible fiber packings subject to triaxial compression. Short fibers yield in a manner similar to typical granular materials in which the deviatoric stress remains nearly constant with increasing strain after reaching a peak value. Interestingly, long fibers exhibit a hardening behavior, where the stress increases rapidly with increasing strain at large strains and the packing density continuously increases. Phase diagrams for classifying the bulk mechanical response as yielding, hardening, or a transition regime are generated as a function of the fiber aspect ratio, fiber-fiber friction coefficient, and confining pressure. Large fiber aspect ratio, large fiber-fiber friction coefficient, and large confining pressure promote hardening behavior. The hardening packings can support much larger loads than the yielding packings contributing to the stability and consolidation of the granular structure, but larger internal axial forces occur within fibers.Comment: 14 pages, 4 figure

Effects of match forms and outcomes on phase-based elite male table tennis match performance

The aim of the study was to explore the service round technical-tactical performance indicators of three phases discriminating the match result and the two match forms. The statistics of 72 professional men’s singles matches of the 2018 international competitions were collected. A chi-square test was used to assess the relationship between match form, match outcome and service round result. Afterwards, a two-way ANOVA was performed to evaluate the effect of match form (SHM: match between players of the same handedness and OHM: match between players of the opposite handedness) and match result on three evaluation indices of thirteen technical-tactical indicators. The results displayed that: (1) there was a weak relationship between the service round outcome and match form for both the winning and losing players (p<0.001, ES=0.12); (2) the winners outperformed the defeated players by a higher technical effectiveness in all three phases with small to moderate effects (p<0.05, ES:0.50-1.00) at both match forms; (3) the usage rate of performance indicators of the first four strokes phase and six strokes above phase distinguished the SHM matches from the OHM matches by small to large effects (p<0.05, ES:0.50-1.26). This study offers insights for practitioners to comprehend the technical-tactical aspects that are deciding for performance when competing against different types of opponents and to make effective training plans and match strategies

Construction of evaluation index system of ecological civilized city

Ecological civilization city evaluation is the driving force and main means to promote the construction of urban ecological civilization. The establishment of evaluation index system is the key to the scientific and accuracy of ecological civilization city evaluation. The element structure method is adopted to build the evaluation index model according to the functions of urban government in economy, culture, society and environment. Build an evaluation index system for urban ecological economy, ecological culture, ecological society and ecological environment

Simulation-Based Dynamic Passenger Flow Assignment Modelling for a Schedule-Based Transit Network

The online operation management and the offline policy evaluation in complex transit networks require an effective dynamic traffic assignment (DTA) method that can capture the temporal-spatial nature of traffic flows. The objective of this work is to propose a simulation-based dynamic passenger assignment framework and models for such applications in the context of schedule-based rail transit systems. In the simulation framework, travellers are regarded as individual agents who are able to obtain complete information on the current traffic conditions. A combined route selection model integrated with pretrip route selection and entrip route switch is established for achieving the dynamic network flow equilibrium status. The train agent is operated strictly with the timetable and its capacity limitation is considered. A continuous time-driven simulator based on the proposed framework and models is developed, whose performance is illustrated through a large-scale network of Beijing subway. The results indicate that more than 0.8 million individual passengers and thousands of trains can be simulated simultaneously at a speed ten times faster than real time. This study provides an efficient approach to analyze the dynamic demand-supply relationship for large schedule-based transit networks

Evolution of H9N2 influenza viruses from domestic poultry in Mainland China

AbstractH9N2 viruses have circulated in domestic poultry in Mainland China since 1994, and an inactivated vaccine has been used in chickens to control the disease since 1998. The present study analyzed 27 H9N2 avian influenza viruses that were isolated from chickens and ducks from 1996 to 2002. Infection studies indicated that most of the viruses replicate efficiently but none of them is lethal for SPF chickens. However, these viruses exhibit different phenotypes of replication in a mouse model. Five viruses, including 4 early isolates and one 2000 isolate, are not able to replicate in mice; 14 viruses replicate to moderate titers in mouse lungs and cause less than 5% weight loss, while other 8 viruses could replicate to high titers in the lungs and 7 of them induce 10–20% weight loss of the mice on day 5 after inoculation. Most of the viruses isolated after 1996 are antigenically different from the vaccine strain that is currently used in China. Three viruses isolated in central China in 1998 are resistant to adamantanes. Phylogenetic analysis revealed that all of the viruses originated from CK/BJ/1/94-like virus and formed multiple genotypes through complicated reassortment with QA/HK/G1/97-, CK/HK/G9/97-, CK/SH/F/98-, and TY/WI/66-like viruses. This study is a description of the previously uncharacterized H9N2 avian influenza viruses recently circulating in chickens and ducks in Mainland China. Our findings suggest that urgent attention should be paid to the control of H9N2 influenza viruses in animals and to the human's influenza pandemic preparedness