Numerical Simulation and Experimental Study of the Stress Formation Mechanism of FDM with Different Printing Paths

Environmental contamination has been caused by petroleum-based polymeric materials in the melt deposition process.Nowadays biodegradable materials have been widely used in the fused deposition modeling(FDM)industry,such as polylactic acid(PLA).However,internal complex thermal stress and deformations in part caused by an uneven distribution of PLA filament deposition temperatures during FDM,which will seriously affect the geometric accuracy of the printed part.In order to reduce material waste and environmental pollution during the printing process,the accuracy of PLA part can be improved.Herein,numerical simulation was carried out to investigate the temperature field and stress field during the building and cooling process of cuboid specimens.The effects of printing path on the thermal stress and temperature field during the building process were mainly studied.The results show that the printing path has a significant effect on the stress distribution.The most uni-form stress distribution and the smallest deformation were obtained using the Zig Zag printing path.Finally,the residual stress during the cooling process was collected using strain gauges embedded at the mid-plane of the FDM built cuboid specimens.The simulation results are consistent with the experimental results.

An ADRC Parameters Self-Tuning Control Strategy of Tension System Based on RBF Neural Network

High precision control of substrate tension is the premise and guarantee for producing high-quality products in roll-to-roll precision coating machine.However,the complex relationships in tension system make the problems of decoupling control difficult to be solved,which has limited the improvement of tension control accuracy for the coating machine.Therefore,an ADRC parameters self-tuning decoupling strategy based on RBF neural network is proposed to improve the control accuracy of tension system in this paper.Firstly,a global coupling nonlinear model of the tension system is established according to the composition of the coating machine,and the global coupling model is linearized based on the first-order Taylor formula.Secondly,according to the linear model of the tension system,a parameters self-tuning decoupling algorithm of the tension system is proposed by integrating feedforward control,ADRC and RBF.Finally,the simulation results show that the proposed tension control strategy has good decoupling control performance and effectively improves the tension control accuracy for the coating machine.

Research on Printing Quality Evaluation of Decorative Paper Based on AHPEWM Model

Printing quality evaluation is an important means to check whether prints are qualfied.However,the urrent printing quality evaluation system for gravure decorative paper is not perfect.In order to solve this problem,a method for evaluating quality of decorative paper based on analytical hierarchy process(AHP)and the entropy weight method(EWM)model is proposed in this paper.So as to verify the proposed model,decorative paper of different grades was selected as the experimental objects.Firstly,the data about five indices eflecting printing quality were measured.Secondly,the evaluation model was used to assign weights to the indices,and scores in each index were calculated according to scoring tables.Finally,the evalua tion scores were statistically analyzed.The results of data analysis showed that the 95% confidence intervals and coefficients of variation were small.The average error of the evaluation system was 0.2061.It indicates that the model can stably distinguish decorative paper of diferent grades,accuracy of which is high.The research in this paper can provide reference to the quality improvement of decorative paper and the printing quality evaluation of other paper.

Preparation and Characterization of Waterborne Polyurethane/Cellulose Nanocrystal Composite Membrane from Recycling Waste Paper

Cellulose plays a key role in abundant organic natural materials meeting the increasing demand for green and biocompatible products.The highly crystalline nanoscale component of cellulose nanocrystals has recently attracted great attention due to the versatile performance as filler or matrix in producing functional materials.In this work,we prepared the waterborne polyurethane via a prepolymer process,and obtained cellulose and cellulose nanocrystals from waste paper via a facile acid hydrolysis process.After that,the cellulose nanocrystals were assembled into film and mixed with polyurethane to prepare flexible polyurethane/cellulose nanocrystals composite membrane with different soaking time.The correlation between the bulk structure and applied properties including thermal resistance and mechanical property was investigated by using Fourier transform infrared spectroscopy(FTIR),X-ray diffraction(XRD),X-ray photoelectron spectroscopy(XPS),scanning electron microscopy(SEM),thermogravimetric analysis(TGA),differential scanning calorimetry(DSC)and folding test.The structure analysis indicates that cellulose nanocrystals prepared from used paper have a quality similar to that of commercial cellulose.Meanwhile,the cellulose nanocrystals have been mixed with polyurethane uniformly.Polyurethane can significantly benefit to the thermal resistance and mechanical property of the cellulose nanocrystals film.The polyurethane/cellulose nanocrystals composite membrane present good flexibility and may hold a significantly potential application as visual and flexible material.

Modeling of transverse welds formation during liquid-solid extrusion directly following vacuum infiltration of magnesium matrix composite

Liquid-solid extrusion directly following vacuum infiltration(LSEVI)is an infiltration-extrusion integrated forming technique,and transverse weld between upper residual magnesium alloy and magnesium matrix composites is a common internal defect,which can severely reduce the yield of composite products.To improve current understanding on the mechanism of transverse welding phenomenon,a thermo-mechanical numerical model of LSEVI for magnesium matrix composites was developed.The formation of transverse weld during extrusion was visualized using finite element simulation method,and the formation mechanism was discussed from the aspect of velocity field using a point tracking technique.The simulation results were verified by the experimental results in term of weld shape.

Preparation and Characterization of Waterborne Polyurethane with Unique Nanoparticles by Controlling Water

A facile method,focusing on emulsification,chain extension and dispersion process in preparing waterborne polyurethane,was developed to prepare emulsion with rod-like nanoparticles.The facile method involves a water addition procedure by in situ generated water to react with polyurethane prepolymer instead of the external water addition process.As a comparison,waterborne polyurethane was synthesized through the external water addition process.According to the characterization methods including FTIR,1H-NMR,TEM and water swelling experiments,it is suggested there are two kinds of hydrogen bonds interactions in hard/soft domain of the novel polyurethane,and the phase separation of hard/soft domains increases significantly.The morphology of the two polyurethanes was quite different(nanorods and spherical particles,respectively),presenting a different surface property.In addition,the water swelling of the novel polyurethane indicates that it holds significant potential application as degradable material.

Fabrication of triangular Cu_(3)P nanorods on Cu nanosheets as electrocatalyst for boosted electrocatalytic water splitting

Non-precious electro catalysts with high-efficiency, cheapness and stablility are of great significance to replace noble metal electro catalysts in the hydrogen evolution reaction(HER) and oxygen evolution reaction(OER). In this work, triangular Cu@CuO nanorods on Cu nanosheets were fabricated by a novel in-situ oxidation approach using Cu nanosheets as self-template and conductive nano-substrate in an aqueous solution of NaOH/H2O2, and then by lowtemperature phosphorization treatments. The experimental results show that the phosphating temperature has a significant effect on the morphology, composition and number of active sites of Cu@Cu_(3)P nanorods. The Cu@Cu_(3)P-280 electrode exhibits a good HER catalytic activity of achieving a current density of 10 mA/cm^(2) at 252 mV in acid electrolyte. After catalysis for 14 h, the current density can still reach 72% of the initial value. Moreover, the Cu@Cu_(3)P-280 electrode also shows an excellent OER catalytic activity in basic electrolyte, reaching a current density of 10 mA/cm^(2) at the overpotential value of 200 mV. After catalysis for 12 h, the current density remained more than 93% of the initial value. This work provides a theoretical basis for the directional design and preparation of sustainable, low-cost, bifunctional electrocatalytic materials.

Effect of Components on the Performance of Asphalt Modified by Waste Packaging Polyethylene

Waste packaging polyethylene（WPE） was used to modify raw asphalt by melt blending the components at 190 ℃ for 1 h in a simple mixer and subsequently machining them at 120 ℃ for 1 h in a highspeed shearing machine.The effect of modification on the degree of the penetration,the softening point and the ductility of the asphalt was studied using fluorescent microscopy,infrared spectrometry,component changes and various other techniques.The experimental results showed that no chemical reactions took place in the components themselves（saturate,aromatic,asphaltene and resin） during the modifications.The softening point and penetration of the asphalt were found to be closely related to the resulting contents of the asphaltene,saturate and resin components.In addition,aromatics were identified as having the greatest impact on the ductility of the asphalt.

Hyperspectral anomaly detection via memory‐augmented autoencoders

Recently,the autoencoder(AE)based method plays a critical role in the hyperspectral anomaly detection domain.However,due to the strong generalised capacity of AE,the abnormal samples are usually reconstructed well along with the normal background samples.Thus,in order to separate anomalies from the background by calculating reconstruction errors,it can be greatly beneficial to reduce the AE capability for abnormal sample reconstruction while maintaining the background reconstruction performance.A memory‐augmented autoencoder for hyperspectral anomaly detection(MAENet)is proposed to address this challenging problem.Specifically,the proposed MAENet mainly consists of an encoder,a memory module,and a decoder.First,the encoder transforms the original hyperspectral data into the low‐dimensional latent representation.Then,the latent representation is utilised to retrieve the most relevant matrix items in the memory matrix,and the retrieved matrix items will be used to replace the latent representation from the encoder.Finally,the decoder is used to reconstruct the input hyperspectral data using the retrieved memory items.With this strategy,the background can still be reconstructed well while the abnormal samples cannot.Experiments conducted on five real hyperspectral anomaly data sets demonstrate the superiority of the proposed method.

Recycling Carbon Resources from Waste PET to Reduce Carbon Dioxide Emission:Carbonization Technology Review and Perspective

Greenhouse gas emissions from waste plastics have caused global warming all over the world,which has been a central threat to the ecological environment for humans,flora and fauna.Among waste plastics,waste polyethylene terephthalate(PET)is attractive due to its excellent stability and degradation-resistant.Therefore,merging China’s carbon peak and carbon neutrality goals would be beneficial.In this review,we summarize the current state-of-the-art of carbon emission decrease from a multi-scale perspective technologically.We suggest that the carbon peak for waste PET can be achieved by employing the closed-loop supply chain,including recycling,biomass utilization,carbon capture and utilization.Waste PET can be a valuable and renewable resource in the whole life cycle.Undoubtedly,all kinds of PET plastics can be ultimately converted into CO_(2),which can also be feedstock for various kinds of chemical products,including ethyl alcohol,formic acid,soda ash,PU,starch and so on.As a result,the closed-loop supply chain can help the PET plastics industry drastically reduce its carbon footprint.

Self-assembled gel-assisted preparation of high-performance hydrophobic PDMS@MWCNTs/PEDOT:PSS composite aerogels for wearable piezoresistive sensors

The conductive polymer poly(3,4-thylenedioxythiophene):poly(styrenesulfonate)(PEDOT:PSS)exhibits po-tential in the development of flexible devices due to its unique conjugated structure and water-solubility characteristics.To address the incompressibility of the original PEDOT:PSS aerogel without compromis-ing its high conductivity,a stable interpenetrating polymer network(IPN)was self-assembled by guiding the molecular motion within PEDOT:PSS and introducing multi-walled carbon nanotubes(MWCNTs).By combining critical surface removal,directional freeze-drying,and polydimethylsiloxane(PDMS)reinforce-ment processes,a hydrophobic PDMS@MWCNTs/PP aerogel with a highly oriented porous structure and high strength was prepared.Under the synergistic effect of MWCNTs/PEDOT:PSS electroactive scaffold,the composite aerogel exhibited a high sensitivity of up to 16.603 kPa^(-1) at 0-2 kPa,a fast response time of 74 ms,and excellent repeatability.Moreover,the sensor possessed hydrophobicity with a good water contact angle of 137°The sensor could serve as a wearable electronic monitoring device to achieve ac-curate and sensitive detection of human motion including large-scale human activities and tiny muscle movements.Therefore,our findings provide a new direction to fabricate high-performance piezoresistive sensors based on three-dimensional(3D)conductive polymer active scaffolds,demonstrating their great potential for flexible electronics,human-computer interaction,and a wide range of applications under special working conditions.

A High-Accuracy Technique for Re-outputting Scratched Paintings

A method of restoring scratches on old paintings is proposed,and the corresponding high-accuracy output workflow is also developed.Firstly the scanner is selected as an input device to get the RGB(red,green,blue)image of the painting,and for the purpose of capturing high-quality image,scanner characterization is done by using neural network.And then the scratches on the RGB image are restored with the technology of digital inpainting,while the inpainting algorithm is mainly based on gradient vector and fast marching method.Finally the restored image is output with a printer,which is calibrated by using the high order polynomial regression method.In experiment the new replicated painting is well restored in the scratched areas,as well as keeps high resemblance with the original painting.

Aging phenomena of backsheet materials of photovoltaic systems for future zero-carbon energy and the improvement pathway

The insulation degradation in polymeric backsheets has been identified as a main cause of catastrophic accidents induced by short circuit or ground faults in photovoltaic module.To ensure quality,the photovoltaic industry is therefore faced with urgent demand in discovering degradation mechanisms.Moreover,the development of environmental-friendly backsheets and the establishment of backsheets recycling specifications are vital to fulfilling the requirements of a future reliable photovoltaic system with improved productivity.In this review,we innovatively summarize the detection methods of insulation deterioration from the viewpoints of spectroscopic,thermal and mechanical approaches.The corresponding ambient conditions in measurement and their accelerating effect on the degradation of photovoltaic backsheets are discussed.Subsequently,emerging novel materials and structures for enhancing insula-tion properties,antiaging performance and optical-electrical energy conversion efficiency of photovoltaic cell are summarized.It offers a comprehensive strategy to design materials with optimal structures in photovoltaic module for a future zero-carbon energy system.

Recent Progress in Cellulose-Based Flexible Sensors

Flexible sensors are attractive due to potential applications in body exercise and ambient gas monitoring systems.Cellulose and its derivatives have combined superiorities such as intrinsic and structural flexibility,ease of chemical functionalization,moisture sensitivity,and mechanical stability,enabling them to be promising candidates as flexible supporting substrates and flexible sensitive materials.Significant progress consequently has been achieved to improve mechanical,electrical,and chemical performance.The latest advance in materials synthesis,structure design,fabrication control,and working mechanism of novel cellulose-based flexible sensors are reviewed and discussed,including strain sensors,humidity sensors,and harmful gas sensors.Various strategies were summarized to enhance sensor performance by surface group modifications,inorganic and organic conducting fillers optimization,multilayer structure design.Newly emerged processing techniques of self-assembly,vacuum filtration,and 3D printing were introduced as well to construct multiscale microstructures.The integration of multiple sensors toward smart and healthy exercise monitoring system is briefly reviewed.The facing challenges and future opportunities of cellulose-based flexible sensors were discussed and proposed at the end.This review provides inspiration and guidelines on how to design and fabricate cellulose-based flexible sensors.

Enhancement of permittivity and energy storage efficiency of poly (vinylidene fluoride-chlorotrifluoroethylene) by uniaxial stretching

Dielectric polymer film capacitors with a high-power density as well as efficient charge and discharge rates have great potential for application to fulfill the miniaturized and lightweight requirements of the electronic and stationary power systems.It was reported that the elastic recovery rate and energy storage density of poly(vinylidene fluoride-chlorotrifluoroethylene)[P(VDF-CTFE)]polymer film can be enhanced through thermostatic uniaxial stretching.But it is unknown about the relationship between the stretching rate and above properties.In this study,we investigated the effect of different stretching rates on the conformation,elastic recovery,dielectric constant,and energy storage density of stretched P(VDF-CTFE)polymer films.It was found that the stretching rate significantly affected the formation of polarβ-crystal phase,causing different dielectric properties.The degrees of elastic recovery of P(VDF-CTFE)film vary with stretching rates.Among them,the elastic recovery rate of the P(VDF-CTFE)94/6 film is 46.5%at a stretching rate of 15 mm/min,the dielectric constant is 12.25 at 100 Hz,and the energy density reaches 3.95 J/cm^(3) with the energy loss of 39%at 200 MV/m field.

Portable visual and electrochemical detection of hydrogen peroxide release from living cells based on dual-functional Pt-Ni hydrogels

It is important to monitor the intra-/extracellular concentration of hydrogen peroxide(H_(2)O_(2))in biological processes.However,miniaturized devices that enable portable and accurate H_(2)O_(2)measurement are still in their infancy because of the difficulty of developing facile sensing strategies and highly integrated sensing devices.In this work,portable H_(2)O_(2)sensors based on Pt-Ni hydrogels with excellent peroxidase-like and electrocatalytic activities are demonstrated.Thus,simple and sensitive H_(2)O_(2)sensing is achieved through both colorimetric and electrochemical strategies.The as-fabricated H_(2)O_(2)sensing chips exhibit favorable performance,with low detection limits(0.030μM&0.15μM),wide linearity ranges(0.10μM-10.0 mM&0.50μM-5.0 mM),outstanding long-term stability(up to 60 days),and excellent selectivity.With the aid of an M5stack development board,portable visual and electrochemical H_(2)O_(2)sensors are successfully constructed without complicated and expensive equipment or professional operators.When applied to the detection of H_(2)O_(2)released from HeLa cells,the results obtained by the developed sensors are in good agreement with those from an ultraviolet‒visible spectrophotometer(UV‒vis)(1.97μM vs.2.08μM)and electrochemical station(1.77μM vs.1.84μM).

High-areal-capacity/power lithium metal microbattery configuration based on the mechanically flexible,ultra-lightweight,nanocellulose framework

The ubiquitous implementation of integrated microelectronics requires the on-chip power sources featured with the lightweight configuration design,high areal-capacity-loadings as well as facile reaction kinetics that beyond the current available microbattery prototypes.Herein,this study constructs a mechanically flexible,nanocellulose fiber(NCF)reinforced microbattery configuration,which consists of metal-organic frameworks(ZIF-8)modified NCF as the separator(MOF@NCF),the carbonized MOF@NCF as the metallic deposition substrate(c-MOF@NCF)as well as gradient-structured LiFePO4 particles infiltrated in the NCF matrix(LFP@NCF)as the cathode.The film-stacked,integrated NCF-based microbattery prototype not only achieves the facile reaction kinetics with homogenized,dendrite-free Li metal deposition at high-capacity-loadings(2 mAh·cm^(-2)),but also eliminates the necessary use of metallic current collector to maximize the electroactive mass ratio,which therefore enables the high energy density of 6.8 mWh·cm^(-2)at the power output of 1.36 mW·cm^(-2)as well as the robust cyclability upon various geometric flexing states.This study presents a quantum leap towards the facile reaction kinetics and multi-scale interfacial stability for the flexible microbattery construction that based on the sustainable utilization of bio-scaffolds.

Discoloration mechanism,structures and recent applications of thermochromic materials via different methods:A review

Thermochromic material is a kind of smart material whose color will vary as the result of the phase transition caused by the temperature change. The characteristics of thermochromic materials are the memory functions to the temperature, having great potential applications in aerospace, military, anticounterfeiting technology, construction and other fields. In recent years, many kinds of thermochromic materials have been prepared by different methods and their discoloration mechanisms are various according to published literatures. In this paper, the classification, discoloration mechanism, preparation methods, application fields and development trend of thermochromic materials are reviewed.