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PurposeThe performance of the classical car-following system is easily affected by external disturbances. To enhance the performance of the classical car-following model under sudden external disturbances, a novel car-following model is established to smooth traffic flow.Design/methodology/approachThis paper proposed a Proportion Integration Differentiation (PID) control strategy based on classical control theory and developed a novel car-following model. The linear system theory and Laplace transform are used to derive a closed-loop transfer function. Then, the stability condition is obtained by using the Routh stability criterion and the small gain theorem. Finally, the validity and feasibility of the PID control strategy is proved by numerical simulations.FindingsThe analytic results and the numerical simulation results show that both the integration part and the differential part have the positive effect to suppress traffic oscillation efficiently; the collaboration of these two parts has more power to improve the stability of traffic flow. It means that the proposed model integrated with the PID control strategy has the ability of anti-interference and smooth traffic compared with the classical car-following model.Originality/valueThis paper introduces the PID control strategy into the classical car-following system, which enhances the stability of the system and also provides an efficient method for optimizing the traffic flow system.

Layered double hydroxides (LDHs) are a class of two-dimensional (2D) clay compounds that consist of positively charged host layers and exchangeable interlayer anions. The stability of their assemblies in aqueous environment is a challenge due to the extremely high hydrophilicity, which limits their use in membrane-based technologies. Here, we propose a graphene oxide (GO) armour protection strategy to substantially improve the stability of LDH membranes in aqueous solution. The sandwich structured GO/LDH/GO membranes (GLGMs) possess a negative-positive-negative charge heterojunction in the vertical direction that effectively blocks the transport of both cations and anions, i.e., NaCl, but allows the permeation of water molecules. Following this mechanism, the GLGMs are used for desalination in a forward osmosis mode. A high rejection rate of over 95.2% for NaCl and water flux of over 2.1 L m−2 h−1 are achieved with simulated seawater.

Biological hybrid catalysts have emerged as promising approaches to achieve enantioselective reactions in aqueous media. Enantioselective Michael reactions are one of the most important carbon-carbon bond formation reactions in organic synthesis, yet its aqueous-phase catalysis remains challenging. Herein, a single nucleotide-based catalyst (ATP·Cu2+) has been constructed by ATP and Cu2+ ions, which catalyzes Michael reactions in aqueous media with high reactivities and good enantioselectivities up to 83% ee. The enantioselective catalytic performances of ATP·Cu2+ are originated from specific binding between ATP and Cu2+ ions that exhibit both pH-dependent and temperature-dependent behaviors. The ATP·Cu2+ has been demonstrated to be successfully applied to a wide spectrum of enone substrates and carbon nucleophiles.

In this paper, we make an improvement on the conventional visual hull reconstruction method that runs on a single consumer graphics card. The target application is a high-precision diamond inclusion reconstruction system. One major contribution of this paper is an evaluation system of voxels for high-precision reconstruction. In contrast to existing approaches, it allows us to reconstruct the thin structure of the diamond inclusion. Based on this, we obtain a significant improvement in reconstruction precision, especially for thin inclusion.

Porous monolithic catalysts with high specific surface areas, which can not only facilitate heat/mass transfer, but also help to expose active sites, are highly desired in strongly exothermic or endothermic gas-solid phase reactions. In this work, hierarchical spinel monolithic catalysts with a porous woodpile architecture were fabricated via extrusion-based three-dimensional (3D) printing (direct ink writing, DIW in brief) of aluminate-intercalated layered double hydroxide (AI-LDH) followed by low temperature calcination. The intercalation of aluminate in LDH is found crucial to tailor the M2+/Al3+ ratio, integrate LDH nanosheets into monolithic catalyst, and enable the conversion of LDH to spinel at the temperature as low as 500 °C with high specific surface areas (> 350 m2/g). The rapid mass/heat transfer resulted from the versatile 3D network at macroscale and the highly dispersed and fully exposed active sites benefited from the porous structure at microscale endow the 3D-printed Pd loaded spinel MgAl-mixed metal oxide (3D-AI-Pd/MMO) catalyst with excellent catalytic performance in semi-hydrogenation of acetylene, achieving 100% conversion at 60 °C with more than 84% ethylene selectivity. This research was supported by the National Natural Science Foundation of China (Nos. 21935001, 22005022 and 22175012), the program for Changjiang Scholars and Innovation Research Team in the University (No. IRT1205), the starting-up foundation from Beijing University of Chemical Technology (No. BUCTRC202025), the fellowship of China Postdoctoral Science Foundation (No. 2020M670107), the Natural Science Foundation of Beijing, China (No. 2214062), the Fundamental Research Funds for the Central Universities, and the long-term subsidy mechanism from the Ministry of Finance and the Ministry of Education of PRC.

Simultaneous measurement of H

Interspecies coaggregation promotes transcriptional changes in oral bacteria, affecting bacterial pathogenicity. Streptococcus gordonii (S. gordonii) and Fusobacterium nucleatum (F. nucleatum) are common oral inhabitants. The present study investigated the transcriptional profiling of S. gordonii and F. nucleatum subsp. polymorphum in response to the dual-species coaggregation using RNA-seq. Macrophages were infected with both species to explore the influence of bacterial coaggregation on both species’ abilities to survive within macrophages and induce inflammatory responses. Results indicated that, after the 30-min dual-species coaggregation, 116 genes were significantly up-regulated, and 151 genes were significantly down-regulated in S. gordonii; 97 genes were significantly down-regulated, and 114 genes were significantly up-regulated in F. nucleatum subsp. polymorphum. Multiple S. gordonii genes were involved in the biosynthesis and export of cell-wall proteins and carbohydrate metabolism. F. nucleatum subsp. polymorphum genes were mostly associated with translation and protein export. The coaggregation led to decreased expression levels of genes associated with lipopolysaccharide and peptidoglycan biosynthesis. Coaggregation between S. gordonii and F. nucleatum subsp. polymorphum significantly promoted both species’ intracellular survival within macrophages and attenuated the production of pro-inflammatory cytokines IL-6 and IL-1β. Physical interactions between these two species promoted a symbiotic lifestyle and repressed macrophage’s killing and pro-inflammatory responses.

Sustainable water-splitting hydrogen production has long been considered one of the most promising energy conversion technologies, but enormous challenges remain: for instance, water electrolysis suffers from high overpotential and over energy consumption under neutral pH conditions. Here, taking advantage of the memory effect of layered double hydroxide (LDH), we report an energy-efficient neutral water electrolyzer material based on LDH with multiple vacancy defects. Benefiting from the improved electrical conductivity, larger electrochemical surface area (ECSA), and faster charge transfer, the NiFe LDH with O, Ni, and Fe vacancies exhibits a low overpotential of 87 mV at 10 mA/cm2 for hydrogen evolution reaction (HER) in a pH 7 buffer electrolyte. Impressively, the as-fabricated vacancy-containing NiFe LDH (v-NiFe LDH) splits water with a current density of 10 mA/cm2 at ∼1.60 V in a two-electrode device, outperforming most other water-splitting catalysts in neutral media. Such an electrolyzer setup cou...

Considering practical applications in electronic devices, we studied the growth of In 2 O 3 thin films on amorphous glasses by magnetron sputtering at room temperature and annealing effect on the structural and electrical properties. The vacuum annealed In 2 O 3 thin films display a grain size enlargement and preferential orientation. Electrical characterization shows that the vacuum annealed In 2 O 3 thin films exhibit a significant enhancement of both electron density and mobility, while air ambient annealing leads to a remarkable drop. The mechanism of the electrical characteristic changes in In 2 O 3 thin films by annealing is explored by using different scattering mechanisms. Finally, a thin film transistor device using vacuum annealed In 2 O 3 nano-meter thin films as active channel material is demonstrated.

A combination of studies on photoluminescence and resonant Raman scattering in N-doped ZnO thin films were carried out at room temperature. In the photoluminescence spectra, a transformation of radiative recombination mechanism from free-exciton to donor–acceptor-pair transition was observed. An enhancement of resonant Raman scattering processes as well as longitudinal optical (LO) phonon overtones up to the sixth order were observed in the Raman spectra. Also, the nature of the 1LO phonon underwent a transformation from a pure A1(LO) mode to a quasimode with mixed A1 and E1 symmetry. The underlying mechanisms accounting for the influences of N doping on the optical properties of ZnO were related to the incorporation of extrinsic defects in the crystal lattice.

Polycrystalline lead salt photoconductive (PC) detectors have been widely used for applications in the 1-5μm spectral range because of their low cost, room temperature operation and high detectivity. However, the physical mechanism of such detectors had not been un-ambiguously understood. In order to improve the performance, we proposed a charge separation junction (CSJ) model to analyze and guide our material synthesis process, which has led to PbSe PC detectors with record high detectivity. On the other hand, the performance of photovoltaic (PV) detectors using Pb-salt epitaxial films on Si substrates has been limited by their high defect density even though the ideal performance of the PbSe PV detector was theoretically proven to be higher than the most popular HgCdTe PV detectors at near room temperature, due to its low Auger recombination property. Inspired by the high material quality of self-assembled lead salt microcrystals, we developed a novel method to produce PV detectors using PbSe micro-crystals based on our studies on the PC detector research that showed promising preliminary results.

We introduce a charge separation model in this work to explain the mechanism of enhanced photoconductivity of polycrystalline lead salt photoconductors. Our results show that this model could clarify the heuristic fabrication processes of such lead salt detectors that were not well understood and often considered mysterious for nearly a century. The improved lifetime and performance of the device, e.g., responsivity, are attributed to the spatial separation of holes and electrons, hence less possibility of carrier recombination. This model shows that in addition to crystal quality the size of crystallites, the depth of outer conversion layer, and doping concentration could all affect detector performance. The simulation results agree well with experimental results and thus offer a very useful tool for further improvement of lead salt detectors. The model was developed with lead salt family of photoconductors in mind, but may well be applicable to a wider class of semiconducting films.

The CaF2 nano-structures grown by thermal vapor deposition are presented. Significant responsivity improvement (>200%) of mid-infrared PbSe detectors incorporating a 200 nm nano-structured CaF2 coating was observed. The detector provides a detectivity of 4.2 × 1010 cm · Hz1/2/W at 3.8 μm, which outperforms all the reported un-cooled PbSe detectors. Structural investigations show that the coating is constructed by tapered-shape nanostructures, which creates a gradient refractive-index profile. Analogy to moth-eye antireflective mechanism, the gradient refractive-index nanostructures play the major roles for this antireflection effect. Some other possible mechanisms that help enhance the device performance are also discussed in the work.

For nearly a century, oxygen has been widely accepted as the key element that triggers photo-response in polycrystalline PbSe photoconductive detectors. Our photoluminescence and responsivity studies on PbSe samples, however, suggest that oxygen only serves as an effective sensitization improver and it is iodine rather than oxygen that plays the key role in triggering the photo-response. These studies shed light on the sensitization process for detector applications and ways to passivate defects in IV–VI semiconductors. As a result, high peak detectivity of 2.8 × 1010 cm·Hz1/2·W−1 was achieved at room temperature.

A novel three-dimensional branched double-shelled TiO2 nanotube network (3DNTNs) structure was constructed on transparent conducting oxide substrates (TCO) by using a ZnO-nanorod array template-assisted method. Various morphological features, such as branch length and population density, could be easily tailored by simply modifying the growth time. The performances of dye-sensitized solar cells (DSCs) fabricated with TiO2 3DNTNs are higher than those assembled with 1-dimensional nanotube arrays. The hollow branches filling in the spaces between the double-shelled stem nanotubes increase the amount of dye-loading, resulting in an enhanced light-harvesting ability.

We report the construction of In(2)O(3)/Ag/In(2)O(3) sandwich nanostructures and realization of effective coupling with surface plasmon (SP) modes. An enhancement of photoluminescence as large as 278-fold is achieved for the new nanostructures, while only eightfold is obtained from bilayer structures. The advancement of the nanostructures is that both the frequency of incidence photons and the in-plane wavevector of the excited SP modes along each side of the sandwiched nanometer metal layer are identical, thus the momenta mismatch between two SP modes which inevitably occurs in commonly used metal/dielectric bilayer structures is no longer a problem. The fulfillment of the cross coupling and resonance conditions of the two SP modes leads to the tremendous amplification of light emission. Such sandwich nanostructures can be readily extended to other dielectric/metal/dielectric nanomaterial combinations and identified as technologically useful for SP mediated light emitting devices.