Construction of a few-layer g-C_3N_4/α-MoO_3 nanoneedles all-solid-state Z-scheme photocatalytic system for photocatalytic degradation

The suppression of the recombination of electrons and holes(e–h) and the enhancement of the light absorption of semiconductors are two key points toward efficient photocatalytic degradation.Here,we report a few-layer g-C_3N_4/α-MoO_3 nanoneedles(flg-C_3N_4/α-MoO_3 NNs) all-solid-state Z-scheme mechanism photocatalyst synthesized via a typical hydrothermal method in a controlled manner.The recombination of the photo-induced e–h pairs could be effectively restrained by the Z-scheme passageway between the flg-C_3N_4 and α-MoO_3 NNs in the composite,which could also promise a high redox ability to degrade pollutants.And it became possible for the prepared photocatalyst to absorb light in a wide range of wavelengths.The detailed mechanism was studied by electron spin-resonance spectroscopy(ESR).The low-dimensional nanostructure of the two constituents(α-MoO_3 NNs with one-dimensional structure and flg-C_3N_4 with two-dimensional structure) endowed the composite with varieties of excellent physicochemical properties,which facilitated the transfer and diffusion of the photoelectrons and increased the specific surface area and the active sites.The 10 wt% flg-C_3N_4/α-MoO_3 NNs showed the best photocatalytic performance toward RhB degradation,the rate of which was 71.86%,～2.6 times higher than that ofα-MoO_3 NNs.

Stability Investigation and Improvement for DC Cascade Systems with Simplified Impedance-based Stability Criterion

In DC distributed power systems(DPSs),the complex impedance interactions possibly lead to DC bus voltage oscillation or collapse.In previous research,the stability analysis of DPSs is implemented based on mathematical analysis in control theory.The specific mechanisms of the instability of the cascade system have not been intuitively clarified.In this paper,the stability analysis of DPSs based on the traditional Nyquist criterion is simplified to the resonance analysis of the seriesconnected port impedance(Z=R+jX)of source and load converters.It reveals that the essential reason for impedance instability of a DC cascade system is that the negative damping characteristic(R<0)of the port the overall impedance amplifies the internal resonance source at reactance zero-crossing frequency.The simplified stability criterion for DC cascade systems can be concluded as:in the negative damping frequency ranges(R<0),there exists no zero-crossing point of the reactance component(i.e.,X=0).According to the proposed stability criterion,the oscillation modes of cascade systems are classified.A typical one is the internal impedance instability excited by the negative damping,and the other one is that the external disturbance amplified by negativity in a low stability margin.Thus,the impedance reshaping method for stability improvement of the system can be further specified.The validity of the simplified criterion is verified theoretically and experimentally by a positive damping reshaping method.

Experimental study on the acoustic roughness spectrum of high-speed railway rails

Purpose–This study aims to investigate the acoustic roughness of rails on China’s high-speed railways,with a focus on short-wavelength irregularities(less than 80 cm),which are known to significantly contribute to noise.The goal is to develop a specific acoustic roughness spectrum tailored for China’s high-speed railway system,as no such spectrum currently exists.Design/methodology/approach–A long-term tracking study was conducted on major railway lines in China,monitoring rail roughness throughout the initial operational period and the rails’service life.Data preprocessing techniques such as peak removal and curvature correction were applied for acoustic adjustments.A spatial-wavelength domain transformation was performed,providing the distribution patterns and statistical characteristics of acoustic roughness on China’s high-speed rails.Based on these analyses,a model for constructing the acoustic roughness spectrum was developed.Findings–The study found that the acoustic roughness of China’s high-speed railway rails follows aχ2 distribution with six degrees of freedom.For wavelengths greater than 8 cm,the acoustic roughness spectrum remains below the ISO specified limits.In the wavelength range of 3.2 cm to 6.3 cm,the roughness is comparable to or within the limits specified by ISO 3095:2005 and ISO 3095:2013.However,for wavelengths shorter than 2.5 cm,the roughness exceeds ISO limits.Originality/value–This research fills the gap in the lack of a specific acoustic roughness spectrum for China’s high-speed railways.By establishing a tailored spectrum based on long-term data analysis,the findings provide valuable insights for noise control and rail maintenance in the context of China’s high-speed rail system.

基于群体影响力的网络传播关键节点选择策略

网络中的少量关键节点对政务舆情、病毒等信息扩散具有重要影响,因此关键节点挖掘是网络科学的关键问题之一.经典方法通过单个节点重要性指标选择关键节点,而多个重要节点的综合影响力更值得讨论.基于此,本文从多节点的综合影响力角度出发,基于Rayleigh熵机制,首先分析了个体影响力和多节点的综合影响力之间的关系,指出多节点的综合影响力小于单节点的影响力之和.然后提出了一个指标刻画多节点的综合影响力,并设计了一个高效的贪婪算法选择一组关键节点,从而最大化多节点的综合影响力.4个真实网络上的信息传播实验验证了新算法的有效性.

Visualizing large-scale high-dimensional data via hierarchical embedding of KNN graphs

Visualizing intrinsic structures of high-dimensional data is an essential task in data analysis.Over the past decades,a large number of methods have been proposed.Among all solutions,one promising way for enabling effective visual exploration is to construct a k-nearest neighbor(KNN)graph and visualize the graph in a low-dimensional space.Yet,state-of-the-art methods such as the LargeVis still suffer from two main problems when applied to large-scale data:(1)they may produce unappealing visualizations due to the non-convexity of the cost function;(2)visualizing the KNN graph is still time-consuming.In this work,we propose a novel visualization algorithm that leverages a multilevel representation to achieve a high-quality graph layout and employs a cluster-based approximation scheme to accelerate the KNN graph layout.Experiments on various large-scale datasets indicate that our approach achieves a speedup by a factor of five for KNN graph visualization compared to LargeVis and yields aesthetically pleasing visualization results.

TiO2/EDTA-rich carbon composites： Synthesis, characterization and visible-light-driven photocatalytic reduction of Cr(Ⅵ)

TiO2/EDTA-rich carbon composites （TiO2/EDTA-RC） have been successfully synthesized via a low temperature carbonization process. TiO2/EDTA-RC exhibits marked absorption of visible light and excellent photoreduction of Cr（Ⅵ） activity under visible light irradiation （λ 〉 420 nm）. Due to the high carboxyl group content and strong coordination ability of EDTA, TiO2-EDTA complex can be easily fabricated between EDTA incorporated in carbon sheet and titanol group on the surface of TiO2. TiO2- EDTA complexes on the surface of TiO2/EDTA-RC, the LMCT complex, are responsible for the prominent photoreduction of Cr（Ⅵ） properties of TiO2/EDTA-RC under visible light irradiation. In addition, the unique structure of TiO2/EDTA-RC is also propitious to the visible-light photocatalytic reduction of Cr（Ⅵ）. Carbon sheet of TiO2/EDTA-RC acts as a supporter. Tio2 nanoparticles and EDTA homogeneously disperse into the carbon sheet supporter and form the TiO2-EDTA complexes, which can avoid the aggregation of TiO2 nanoparticles in the aqueous solution and provide more photocatalytic reaction points for the reduction of Cr（Ⅵ）.

Potential dissemination mechanism of the tetC gene in Aeromonas media from the aerobic biofilm reactor under oxytetracycline stresses

The tet C gene has been found to be one of the most widely distributed tetracycline resistance( tet) genes in various environmental niches, but the detailed dissemination mechanisms are still largely unknown. In the present study, 11 tet C-containing Aeromonas media strains were isolated from an aerobic biofilm reactor under oxytetracycline stresses, and the genome of one strain was sequenced using the Pac Bio RSII sequencing approach to reveal the genetic environment of tet C. The tet C gene was carried by an IS 26 composite transposon, named Tn 6434. The tet C-carrying Tn 6434 structure was detected in all of the A. media strains either in a novel plasmid p Aeme2( n = 9) or other DNA molecules( n = 2) by PCR screening. The NCBI database searching result shows that this structure was also present in the plasmids or chromosomes of other 13 genera, indicating the transferability of Tn 6434. Inverse PCR and sequencing confirmed that Tn 6434 can form a circular intermediate and is able to incorporate into a preexisting IS 26 element, suggesting that Tn 6434 might be responsible for the dissemination of tet C between different DNA molecules. This study will be helpful in uncovering the spread mechanism of tet genes in water environments.

In-suit fabricating an efficient electronic transport channels via S-scheme polyaniline/Cd_(0.5)Zn_(0.5)S heterojunction for rapid removal of tetracycline hydrochloride and hydrogen production

The development of highly efficient catalyst is the key for photocatalytic technology to deal with water pollution and energy problems.In this work,the S-scheme polyaniline/Cd_(0.5)Zn_(0.5)S(PANI/CZS)nanocomposites were elaborately prepared for the first time by in-situ oxidation polymerization.Compared to pure PANI and Cd_(0.5)Zn_(0.5)S,this PANI/CZS hybrid displayed outstanding photocatalytic performance in removing tetracycline hydrochloride(TCH)and hydrogen evolution under light irradiation.Among them,15 PANI/CZS sample could achieve 84.9%TCH degradation efficiency within 25 min,and the degradation rate(0.06931 min−1)was 5.13 times than that of Cd_(0.5)Zn_(0.5)S(0.0135 min^(−1)).The optimal photocatalytic H_(2) evolution rate of 30 PANI/CZS sample was 15.57 mmol g^(-1) h^(-1),which was twice that of Cd_(0.5)Zn_(0.5)S(7.34 mmol g^(-1) h^(-1)).These results were mainly attributed to the efficient electronic transport channels provided by S-scheme heterojunction structure.The density functional theory(DFT)calculation proved that the difference of work function resulted in band bending and forming built-in electric field on the contact interface of PANI/CZS,which facilitated the migration and separation of interfacial photogener-ated charge carriers for the strengthened photocatalytic performance.Further,the degradation interme-diate products and pathways of TCH were also put forwarded in depth based on MS experiment.At last,the S-scheme electron transport model and the photocatalytic reaction mechanism in PANI/CZS hetero-junction structure were studied.This work provided an innovative vision in developing high-performance S-scheme heterojunction multifunctional photocatalysts.

A Stochastic Optimization Approach for Dynamic Adaptive Streaming over NDN

Nowadays,video streaming counts for the major part of network traffic over the Internet.However,on account of the host-to-host mechanism of the traditional IP network,video distribution over IP-based Internet encounters bottlenecks.Fortunately,a new proposed future Internet architecture,named data networking(NDN)can improve the performance of video distribution by its features such as in-network storage,multi-path forwarding,etc.In this paper,we design an adaptive bitrate algorithm based on Lyapunov optimization theory over NDN to optimize the long-term quality-of-experience(QoE)of video distribution while ensuring the stability of the whole system.When the network condition is abundant and stable,the problem can be simplified by approximating to a fixed-slot queuing model,but the theoretical performance will degrade when the network status is poor and fluctuate fiercely.Therefore,we divide the problem into two models of fixed time slot and non-fixed time slot and design two Lyapunov optimization algorithms to adapt different network scenarios.The proposed algorithms do not require prior knowledge of the network bandwidth and are capable of running online with the client’s available information.Simulation and realistic experiment results demonstrate that our algorithms perform better than others in NDN.