具有阻隔性和导电性的聚偏二氯乙烯/石墨烯复合材料的制备

聚偏二氯乙烯(PVDC)具有优异的阻隔性能,广泛应用于包装材料。但为了满足一些特殊场合的使用要求,仍需对材料进行功能改性,进一步提升其阻隔性。文中采用胶乳共混、水合肼蒸气原位还原法成功制备了聚偏二氯乙烯/石墨烯(PVDC/r GO)复合材料。石墨烯的引入进一步提高了PVDC的阻隔性能,并赋予了复合材料优异的导电性能。当石墨烯质量分数为4. 02%时,复合材料的水汽阻隔性能提升约40%,且电导率达到3. 88 S/m,当复合材料在60℃条件下热处理7 d后,材料电导率进一步提高到8 S/m。

An infrared target intrusion detection method based on feature fusion and enhancement

Infrared target intrusion detection has significant applications in the fields of military defence and intelligent warning.In view of the characteristics of intrusion targets as well as inspection difficulties,an infrared target intrusion detection algorithm based on feature fusion and enhancement was proposed.This algorithm combines static target mode analysis and dynamic multi-frame correlation detection to extract infrared target features at different levels.Among them,LBP texture analysis can be used to effectively identify the posterior feature patterns which have been contained in the target library,while motion frame difference method can detect the moving regions of the image,improve the integrity of target regions such as camouflage,sheltering and deformation.In order to integrate the advantages of the two methods,the enhanced convolutional neural network was designed and the feature images obtained by the two methods were fused and enhanced.The enhancement module of the network strengthened and screened the targets,and realized the background suppression of infrared images.Based on the experiments,the effect of the proposed method and the comparison method on the background suppression and detection performance was evaluated,and the results showed that the SCRG and BSF values of the method in this paper had a better performance in multiple data sets,and it’s detection performance was far better than the comparison algorithm.The experiment results indicated that,compared with traditional infrared target detection methods,the proposed method could detect the infrared invasion target more accurately,and suppress the background noise more effectively.

Efficient doping modulation of monolayer WS_2 for optoelectronic applications

Transition metal dichalcogenides(TMDCs) belong to a subgroup of two-dimensional(2 D) materials which usually possess thickness-dependent band structures and semiconducting properties. Therefore, for TMDCs to be widely used in electronic and optoelectronic applications, two critical issues need to be addressed, which are thickness-controllable fabrication and doping modulation of TMDCs. In this work, we successfully obtained monolayer WS2 and achieved its efficient doping by chemical vapor deposition and chemical doping, respectively. The n-and p-type dopings of the monolayer WS2 were achieved by drop coating electron donor and acceptor solutions of triphenylphosphine(PPh3) and gold chloride(AuCl_3), respectively, on the surface, which donates and captures electrons to/from the WS2 surface through charge transfer, respectively. Both doping effects were investigated in terms of the electrical properties of the fabricated field effect transistors. After chemical doping, the calculated mobility and density of electrons/holes are around 74.6/39.5 cm^2 · V^(-1) ·s^(-1)and 1.0 x 10^(12)/4.2 x 10^(11) cm^(-2), respectively. Moreover, we fabricated a lateral WS2 p-n homojunction consisting of nondoped n-type and p-doped p-type regions, which showed great potential for photodetection with a response time of 1.5 s and responsivity of 5.8 A/W at V_G = 0 V and V_D = 1 V under 532 nm light illumination.

The effect of porosity on the mechanical properties of 3D-printed triplyperiodic minimal surface (TPMS) bioscaffold

Prevailing tissue degeneration caused by musculoskeletal maladies poses a great demand on bioscaffolds,which are artificial,biocompatible structures implanted into human bodies with appropriate mechanical properties.Recent advances in additive manufacturing,i.e.,3D printing,facilitated the fabrication of bioscaffolds with unprecedented geometrical complexity and size flexibility and allowed for the fabrication of topologies that would not have been achieved otherwise.In our work,we explored the effect of porosity on themechanical properties of a periodic cellular structure.The structure was derived from the mathematically created triply periodic minimal surface(TPMS),namely the Sheet-Diamond topology.First,we employed a series of software including MathMod,Meshmixer,Netfabb and Cura to design the model.Then,we utilized additive manufacturing technology to fabricate the cellular structures with designated scale.Finally,we performed compressive testing to deduce the mechanical properties of each cellular structure.Results showed that,in comparison with the highporosity group,the yield strength of the low-porosity group was 3 times higher,and the modulus was 2.5 times larger.Our experiments revealed a specific relationship between porosity and Young’s modulus of PLA-made Sheet-Diamond TPMS structure.Moreover,it was observed that the high-and low-porosity structures failed through distinctive mechanisms,with the former breaking down via buckling and the latter via micro-fracturing.

Laboratory studies on the infectivity of human respiratory viruses:Experimental conditions,detections,and resistance to the atmospheric environment

The environmental stability of infectious viruses in the laboratory setting is crucial to the transmission potential of human respiratory viruses.Different experimental techniques or conditions used in studies over the past decades have led to diverse understandings and predictions for the stability of viral infectivity in the atmospheric environment.In this paper,we review the current knowledge on the effect of simulated atmospheric conditions on the infectivity of respiratory viruses,mainly focusing on influenza viruses and coronaviruses,including severe acute respiratory syndrome coronavirus 2 and Middle East respiratory syndrome coronavirus.First,we summarize the impact of the experimental conditions on viral stability;these involve the methods of viral aerosol generation,storage during aging and collection,the virus types and strains,the suspension matrixes,the initial inoculum volumes and concentrations,and the drying process.Second,we summarize and discuss the detection methods of viral infectivity and their disadvantages.Finally,we integrate the results from the reviewed studies to obtain an overall understanding of the effects of atmospheric environmental conditions on the decay of infectious viruses,especially aerosolized viruses.Overall,this review highlights the knowledge gaps in predicting the ability of viruses to maintain infectivity during airborne transmission.

Anisotropic photoresponse of layered rhenium disulfide synaptic transistors

Layered ReS_(2) with direct bandgap and strong in-plane anisotropy shows great potential to develop high-performance angle-resolved photodetectors and optoelectronic devices.However,systematic characterizations of the angle-dependent photoresponse of ReS_(2) are still very limited.Here,we studied the anisotropic photoresponse of layered ReS_(2) phototransistors in depth.Angel-resolved Raman spectrum and field-effect mobility are tested to confirm the inconsistency between its electrical and optical anisotropies,which are along 120°and 90°,respectively.We further measured the angle-resolved photoresponse of a ReS_(2) transistor with 6 diagonally paired electrodes.The maximum photoresponsivity exceeds 0.515 A·W^(-1) along b-axis,which is around 3.8 times larger than that along the direction perpendicular to b axis,which is consistent with the optical anisotropic directions.The incident wavelength-and power-dependent photoresponse measurement along two anisotropic axes further demonstrates that b axis has stronger light-ReS_(2) interaction,which explains the anisotropic photoresponse.We also observed angle-dependent photoresistive switching behavior of the ReS_(2) transistor,which leads to the formation of angle-resolved phototransistor memory.It has simplified structure to create dynamic optoelectronic resistive random access memory controlled spatially through polarized light.This capability has great potential for real-time pattern recognition and photoconfiguration of artificial neural networks(ANN)in a wide spectral range of sensitivity provided by polarized light.

A lateral super-resolution imaging method using structured illumination without phase shift

Structured illumination microscopy has been a useful method for achieving lateral super-resolution,but it typically requires at least three precise phase shifts per orientation.In this paper,we propose a super-resolution method that utilizes structured illumination without phase shift.The reconstruction process requires only a conventionally illuminated image and an image with structured illumination.This method achieves the same effect as the traditional phase shift method,and more than doubles the resolution by synthesizing a few reconstructions at different illumination frequencies.We verify the resolution improvement process using a combination of theoretical derivations and diagrams,and demonstrate its effectiveness with numerical simulations.

Exploration and mitigation of protrusion behavior in Ga-ion doped h-BN memristors

Using hexagonal boron nitride(h-BN)to prepare resistive switching devices is a promising strategy.Various doping methods have aroused great interest in the semiconductor field in recent years,but many researchers have overlooked the various repetitive anomalies that occur during the testing process.In this study,the basic electrical properties and additive protrusion behavior of Ga-ion-doped h-BN memristors at micro–nanoscale during the voltage scanning process are investigated via atomic force microscopy(AFM)and energy dispersive spectroscopy.The additive protrusion behavior is subjected to exploratory research,and it is concluded that it is caused by anodic oxidation.An approach is proposed that involves filling the AFM chamber with nitrogen gas to improve the stability of memristor testing,and this method provides a solution for enhanced testing stability of memristors.

On the four-dimensional lattice spring model for geomechanics

Recently, a four-dimensional lattice spring model(4D-LSM) was developed to overcome the Poisson’s ratio limitation of the classical LSM by introducing the fourth-dimensional spatial interaction. In this work, some aspects of the 4D-LSM on solving problems in geomechanics are investigated, such as the ability to reproduce elastic properties of geomaterials, the capability of solving heterogeneous problems,the accuracy on modelling stress wave propagation, the ability to solve dynamic fracturing and the parallel computational efficiency. Our results indicate that the 4D-LSM is promising to deal with problems in geomechanics.

THE CONDITIONAL DIAGNOSABILITY OF SHUFFLE-CUBES

In the application of multiple-processor systems some processors or links in a system maynot function properly,thus the fault diagnosis is one of the most important issues in the analysisand maintenance of those systems.For the practical fault diagnosis systems,the probability that allneighboring processors of a processor are faulty simultaneously is very small.Thus,the conditionaldiagnosability,which is a new metric for evaluating such systems,assumes that every fault set doesnot contain all neighbors of any processor in the system.In this paper,the authors show that then-dimensional shuffle-cube has the conditional diagnosability of 4n-15 for n = 2 (mod 4) and n ≥ 10.

一种结构化的化工系统人因失误概率评估方法

化工生产系统高度非线性且复杂耦合化,使现有人因可靠性分析(HRA)技术难以直接应用,且分析结果的有效性和准确性差。为此,本工作将人因-危险和可操作性分析(人因HAZOP)与贝叶斯网络(BN)相融合,提出了一种结构化的化工系统人因失误概率评估方法。通过概述人因HAZOP的作业任务,筛选引导词和偏差,形成结构化的人因HAZOP报告,并据此构建BN模型,求解化工系统人因失误概率。以丙烯酸甲酯虚拟仿真工厂的酯化反应为例,人因失误概率的计算结果为0.0004,且主要人误行为是维护人员遗漏。对该化工系统进行传统CREAM分析,人因失误概率结果为0.0001~0.01。与传统CREAM相比,这种结构化方法能够高效且精确地评估化工系统人因失误概率。

Occurrence and risk assessment of azole fungicides during the urban water cycle:A year-long study along the Yangtze River,China

Azole fungicides(AFs)play an important role in the prevention and treatment of fungal diseases in agricultural crops.However,limited studies are addressing the fate and ecological risk of AFs in the urban water cycle at a large watershed scale.To address this gap,we investigated the spatiotemporal distribution and ecological risk of twenty AFs in the lower reaches of the Yangtze River across four seasons.Carbendazim(CBA),tebuconazole(TBA),tricyclazole(TCA),and propiconazole(PPA)were found to be the dominant compounds.Their highest concentrations were measured in January(188.3 ng/L),and November(2197.1 ng/L),July(162.0 ng/L),and November(1801.9 ng/L),respectively.The comparison between wastewater treatment plants(WWTPs)effluents and surface water suggested that industrial WWTPs are major sources of AFs in the Yangtze River.In particular,TBA and PPA were found to be the most recalcitrant AFs in industrial WWTPs,while difenoconazole(DFA)was found to be the most potent pollutant in municipal WWTPs,with an average removal rate of less than60%.The average risk quotient(RQ)for the entire AFs was 6.45 in the fall,which was higher than in January(0.98),April(0.61),and July(0.40).This indicates that AFs in surface water posed higher environmental risks during the dry season.Additionally,the exposure risk of AFs via drinking water for sensitive populations deserves more attention.This study provides benchmark data on the occurrence of AFs in the lower reaches of the Yangtze River,and offers suggestions for better reduction of AFs.

Efficient and stable organic solar cells enabled by a poly(carbazole phosphonic acid)hole transporter

Conventional self-assembled monolayer(SAM)hole transporters in organic solar cells(OSCs)generally suffer from poor uniformity and limited thickness tolerance,hindering their large-scale production.To overcome these limitations,we introduce a novel polymeric hole transporter synthesized by polymerizing carbazole phosphonic acid(PACz).The resultant Poly-2PACz material exhibits exceptional conductivity,high tolerance for variations in layer thickness,and improved film uniformity compared with conventional SAMs.Consequently,the OSCs utilizing Poly-2PACz achieve a remarkable power conversion efficiency of 19.1%and a high fill factor of 81.2%,surpassing the devices based on 2PACz.Moreover,Poly-2PACz-based OSCs demonstrate excellent operational stability,retaining over 80%of their initial efficiency after 1,400 h of continuous light exposure in ambient conditions.This work presents a novel strategy for designing hole transporters,paving the way for more efficient and stable OSCs.

Evaluating a river's ecological health: A multidimensional approach

Evaluating the health of river surface water is essential,as rivers support significant biological resources and serve as vital drinking water sources.While the Water Quality Index(WQI)is commonly employed to evaluate surface water quality,it fails to consider biodiversity and does not fully capture the ecological health of rivers.Here we show a comprehensive assessment of the ecological health of surface water in the lower Yangtze River(LYR),integrating chemical and biological metrics.According to traditional WQI metrics,the LYR's surface water generally meets China's Class II standards.However,it also contains 43 high-risk emerging contaminants;nitrobenzenes are found at the highest concentrations,representing 25e90%of total detections,while polycyclic aromatic hydrocarbons present the most substantial environmental risks,accounting for 81e93%of the total risk quotient.Notably,the plankton-based index of biological integrity(P-IBI)rates the ecological health of the majority of LYR water samples(59.7%)as‘fair’,with significantly better health observed in autumn compared to other seasons(p<0.01).Our findings suggest that including emerging contaminants and P-IBI as additional metrics can enhance the traditional WQI analysis in evaluating surface water's ecological health.These results highlight the need for a multidimensional assessment approach and call for improvements to LYR's ecological health,focusing on emerging contaminants and biodiversity rather than solely on reducing conventional indicators.

MRI and CT compatible asymmetric bilayer hydrogel electrodes for EEG-based brain activity monitoring

The exploration of multi-dimensional brain activity with high temporal and spatial resolution is of great significance in the diagnosis of neurological disease and the study of brain science.Although the integration of electroencephalo-gram(EEG)with magnetic resonance imaging(MRI)and computed tomography(CT)provides a potential solution to achieve a brain-functional image with high spatiotemporal resolution,the critical issues of interface stability and magnetic compatibility remain challenging.Therefore,in this research,we proposed a conductive hydrogel EEG electrode with an asymmetrical bilayer structure,which shows the potential to overcome the challenges.Benefting from the bilayer structure with different moduli,the hydrogel electrode exhibits high biological and mechanical compatibility with the heterogeneous brain-electrode interface.As a result,the impedance can be reduced compared with conventional metal electrodes.In addition,the hydrogel-based ionic conductive electrodes,which are free from metal conductors,are compatible with MRl and CT.Therefore,they can obtain high spatiotemporal resolution multi-dimensional brain information in clinical settings.The research outcome provides a new approach for establishing a platform for early diagnosis of brain diseases and the study of brain science.

浅谈甲状腺无功能良性结节的规范化管理策略

甲状腺结节在人群中发病率呈持续上升趋势,约90%为无功能良性结节,临床关注不足,存在管理不规范甚至过度治疗。本文简要介绍甲状腺无功能良性结节的临床诊断和治疗,以期提高广大基层医生的规范化诊疗水平。

大气环境对新型冠状病毒传播影响的研究进展

新型冠状病毒(SARS-CoV-2)引发的肺炎疫情全球大流行引起了学术界对病毒传播机制的广泛关注.流行病学研究的结果表明,大气环境条件(包括太阳辐射、温湿度、风速、气溶胶颗粒物、气态污染物等)对SARS-CoV-2的传播有一定影响.然而,不同的研究得到的结论不尽相同.本文总结了有关大气环境对SARS-CoV-2传播影响的流行病学研究结果,并分析了其中的作用机制.从SARS-CoV-2的排放和大气赋存状态、存活特性等几个方面,评述了大气环境条件对病毒传播的直接影响;进而,从宿主细胞易感性的角度,分析了大气环境条件对病毒传播的间接影响.最后指出当前还亟须解决的相关科学问题.

GaN-based substrates and optoelectronic materials and devices

In order to solve the problems of GaN heteroepitaxy on sapphire substrate,some techniques were explored.Freestanding GaN substrates have been made by hydride vapor phase epitaxy(HVPE),laser lift-off(LLO),and chemical mechanical polishing techniques.Wafer bending and cracking in the HVPE growth were partly settled by pulsed flow modulation method.High-crystal quality was established for 1.2 mm thick GaN substrate by X-ray diffraction measurement,in which the full width of half maximum values were 72,110 arcsec for(102),(002)peaks.A novel micro-size patterned sapphire substrate(PSS)and a nano PSS were also fabricated.High-power vertical structure light emitting diodes(VSLEDs)have been developed by Au–Sn eutectic wafer bonding,homemade micro-area LLO,and light extraction structure preparation.The high-injection-level active region with low temperature GaN sandwiched layers was used for lowefficiency droop.The light output power of VSLED was achieved as 400 mW driven at 350 mA,and the dominant wavelength is about 460 nm.The structures and properties of strain modulated superlattices(SLs)and quantum wells as well as advanced simulation of carriers transport across the electron blocking layer were investigated in laser diodes.The hole concentration was achieved as high as1.6 9 1018cm-3in AlGaN/GaN SLs:Mg by inserting an AlN layer.High-quality AlGaN epilayers and structures were grown by MOCVD.Some device structures of UV LEDs and detectors were demonstrated.The emission wavelength of 262 nm UV LED has been successfully fabricated.At last,high-quality InN and InGaN materials for solar cell were grown by boundary-temperature-controlled epitaxy and growth-temperature-controlled epitaxy.Hall-effect measurement showed a recorded electron mobility of 3,280 cm2/(V s)and a residual electron concentration of 1.47 9 1017cm-3at 300 K.

Open-pore LiFePO_4/C microspheres with high volumetric energy density for lithium ion batteries

LiFePO4/C microspheres with different surface morphologies and porosities were prepared from different carbon sources. The effects of the surface morphology and pore structure of the microspheres on their electrochemical properties and electrode density were investigated. The electrochemical performance and electrode density depended on the morphology and pore structure of the LiFePO4/C microspheres. Open-pore LiFePO4/C microspheres with rough surfaces exhibited good adhesion with current collectors and a high electrode density （2.6g/cm3）. They also exhibited high performance in a half cell and full battery with a high volumetric energy density.

A Decoupling Control Model on Perturbation Method for Twin-Roll Casting Magnesium Alloy Sheet

To better understand the twin-roll casting process,based on the analysis of the solidification phenomenon,the geometry shape of the molten metal pool,the continuity of metal and the balance of energy and momentum,five critical partial equations were established separately including the equations of pool level,solidification process,roll separating force,roll gap and casting speed.Meanwhile,to obtain a uniform sheet thickness and keep a constant roll separating force,a decoupling control model was built on the perturbation method to eliminate the interference of process parameters.The simulation results show that the control model is valuable to quickly and accurately determine the control parameters.Moreover,Mg alloy sheets with high quality were cast by applying this model.