Rubberized concrete is one of the most studied applications of discarded tires and offers a promising approach to developing materials with enhanced properties.The rubberized concrete mixture results in a reduced modu...Rubberized concrete is one of the most studied applications of discarded tires and offers a promising approach to developing materials with enhanced properties.The rubberized concrete mixture results in a reduced modulus of elasticity and a reduced compressive and tensile strength compared to traditional concrete.This study employs finite element simulations to investigate the elastic properties of rubberized mortar(RuM),considering the influence of inclusion stiffness and interfacial debonding.Different homogenization schemes,including Voigt,Reuss,and mean-field approaches,are implemented using DIGIMAT and ANSYS.Furthermore,the influence of the interfacial transition zone(ITZ)between mortar and rubber is analyzed by periodic homogenization.Subsequently,the influence of the ITZ is examined through a linear fracture analysis with the stress intensity factor as a key parameter,using the ANSYS SMART crack growth tool.Finally,a non-linear study in FEniCS is carried out to predict the strength of the composite material through a compression test.Comparisons with high density polyethylene(HDPE)and gravel inclusions show that increasing inclusion stiffness enhances compressive strength far more effectively than simply improving the mortar/rubber bond.Indeed,when the inclusions are much softer than the surrounding matrix,any benefit gained on the elastic modulus or strength from stronger interfacial adhesion becomes almost negligible.This study provide numerical evidence that tailoring the rubber’s intrinsic stiffness—not merely strengthening the rubber/mortar interface—is a decisive factor for improving the mechanical performance of RuM.展开更多
The continuous growth in the manufacture of aerospace components such as blisks has led to an increase in the application of different hybrid materials fabricating methods,and thus the requirements for joining and str...The continuous growth in the manufacture of aerospace components such as blisks has led to an increase in the application of different hybrid materials fabricating methods,and thus the requirements for joining and strengthening of dissimilar welds.According to this goal,selective laser melted(SLM)Inconel718 was joined with forged AD730^(TM)Nickel-based superalloy through linear friction welding(LFW)in this study.Microstructure variation,specifically with respect to secondary phases precipitation was investigated.The microhardness and strengthening mechanisms of the weldment were also studied.The precipitation(volume fraction and size of particles)at different regions of both sides of the weld line was characterized.Close to the weld line,the dissolution ofγ’/γ"and Laves phases and grain refinement occurred which reveals the effects of both compression strain and high temperature on recrystallization and high degree of elemental diffusion in the weld zone(WZ).It is shown that the size,volume fraction,and shape of secondary phases increased and changed(from spherical to long-striped for Laves particles)as we went from the WZ toward the base metal.However,the measured microhardness indicated that the strength of AD730^(TM)alloy depends significantly on the grain size,while strength in SLM Inconel 718 was dominated by shape(or size)and the presence of secondary phases(γ’/γ"and Laves).展开更多
In most microfluidic applications, pressure-driven Poiseuille flow in a contained cross-section with no-slip boundary conditions is the underlying fluid-mechanical model. Solutions for this problem exist for many know...In most microfluidic applications, pressure-driven Poiseuille flow in a contained cross-section with no-slip boundary conditions is the underlying fluid-mechanical model. Solutions for this problem exist for many known cross-sections. We have recently demonstrated a simple method to solve the relevant Poisson equation using a finite difference scheme in a spreadsheet analysis tool such as Microsoft Excel. The numerical solutions obtained from such a spreadsheet are close-to-exact to the analytical solutions with errors on the order of only a few percent. However, there are numerous applications in microfluidics for which the no-slip boundary condition is not valid. Examples include drag-reducing air-retaining surfaces as well as open-channel flow. For these scenarios few to no analytical models exist. In this paper, we derive an analytical model for mixed boundary conditions (slip/no-slip) in two dimensions in a rectangular channel cross-section. We also demonstrate that the equivalent numerical solution can be derived conveniently by adaption of the spreadsheet. In general, mixed boundary-type flow scenarios are especially difficult to solve analytically whereas numerical solutions can be derived using Microsoft Excel within seconds.展开更多
A new DCG-FGT （dual-control-gate floating-gate transistor） transistor model for static and transient simulations is presented. The PSP MOS （metal-oxide-semiconductor） description is used as a basis for the formula...A new DCG-FGT （dual-control-gate floating-gate transistor） transistor model for static and transient simulations is presented. The PSP MOS （metal-oxide-semiconductor） description is used as a basis for the formulation of the conduction channel behavior. The floating gate potential is implicitly computed with an added charge neutrality relation that ensures a good convergence. The model is running under electrical simulator （ELDO） and is characterized thanks to ICCAP （integrated circuit characterization and analysis program） software. It has been validated on an advanced STMicroelectronics technology. The final objective of this work is to provide an accurate and scalable model available in design framework. This device which is derived from a flash memory cell offers many possibilities for circuit design.展开更多
Developing the railway transport sector is a challenging scientific,economic and social research topic starting with ensuring human security.The main topic that should be developed in that sense is the ballast stabili...Developing the railway transport sector is a challenging scientific,economic and social research topic starting with ensuring human security.The main topic that should be developed in that sense is the ballast stability and dynamical behaviour under external loading and environmental changes.This paper investigates the effect of particle size distribution and normal pressure on the mechanical response of a ballast bed.Grading curves of ballast layers with different sizes are illustrated to discuss their strength behaviour under various strains to deduce the significant effect on the direct shear performance of the ballast layer.Direct shear tests with different Particle Size Distribution(PSD)were reproduced using the Discrete Element Method(DEM).It is noticed that when the number of small-sized ballast increases,the shear strength and the friction angle increase to varying degrees under different normal pressures,with an average increase of 27%and 8%,respectively.When the number of large-sized ballast decreases,the shear strength and the friction angle decrease to varying degrees under different normal pressures,with an average decrease of 6%and 3%,respectively.展开更多
This study examines hemodynamic behavior in particular cases of pulmonary hypertension without treatment. Pulmonary hypertension represents an anomalous hemodynamic state and is characterized by an excessively high bl...This study examines hemodynamic behavior in particular cases of pulmonary hypertension without treatment. Pulmonary hypertension represents an anomalous hemodynamic state and is characterized by an excessively high blood pressure in the pulmonary artery. To simulate the hemodynamic abnormalities in pulmonary hypertension under different causes and pathologies, we construct a localized parameter circuit model governed by nonlinear ordinary derivative equations of the human circulatory system. Thus, two special cases are considered, namely pulmonary the artery stenosis and the left ventricular diastolic dysfunction. For each case of pulmonary hypertension development, we determine the relationships between blood pressure and chamber and vessel pressure-volume. When the pulmonary hypertension is due to pulmonary artery stenosis, it appears that the right ventricular pressure increases up to 90 mm Hg, likewise the rise in pulmonary artery resistance induces direct increment in pulmonary artery pressure. However, when the pulmonary hypertension is due to left ventricular diastolic dysfunction, we note that the left atrial pressure and the pulmonary vein pressure augment, leading to the growth of the pulmonary artery blood pressure. The established results within this paper are useful for understanding the hemodynamic mechanism of particular pulmonary hypertension.展开更多
Carbonaceous mudstone is a potential embankment filler in mountainous regions with limited high-quality materials;however,its engineering performance in highway embankments under complex environmental conditions remai...Carbonaceous mudstone is a potential embankment filler in mountainous regions with limited high-quality materials;however,its engineering performance in highway embankments under complex environmental conditions remains poorly understood.This study aimed to investigate the mechanical properties and failure mechanisms of carbonaceous mudstone filler under different temperature-moisture coupled conditions.Triaxial shear tests were conducted under four temperaturemoisture coupled conditions:dry-heat to dry-cold(DHDC),wet-cold to wet-heat(WCWH),dry-cold to wet-heat(DCWH),and dry-heat to wet-cold(DHWC).The effects of these conditions on the strength characteristics,relative breakage ratio,failure mode,and microscopic morphology were examined.A segmented prediction model based on the DuncanChang model was applied to validate the experimental results under the DHWC condition.The failure mechanisms under different conditions were also analyzed.The results indicate that the degradation of carbonaceous mudstone increases in the following order:DHDC,WCWH,DCWH,and DHWC.Under the DHDC condition,the stress-strain curves exhibit strain-softening behavior,while other conditions show strain-hardening behavior,with peak deviatoric stress occurring at 2%and 4%axial strains,respectively.The shear strength decreases by up to 40%under the DHWC condition but remains nearly unchanged under the DHDC condition,showing a positive correlation with particle breakage.As the number of cycles increases,the failure surfaces gradually move downward.Higher confining pressure shifts failure mode from shear failure to shear slip or localized compression,and eventually to overall compression or expansion failure.The modified Duncan-Chang model accurately predicts the experimental results.These findings provide important guidance for the application of carbonaceous mudstone filler in highway embankment construction in humid mountainous regions.展开更多
Dry reforming of methane(DRM)over Ni-based catalysts is an economically reasonable technology for large-scale CO_(2)utilization.However,prolonged Ni sintering and carbon deposition reduce the durability and efficiency...Dry reforming of methane(DRM)over Ni-based catalysts is an economically reasonable technology for large-scale CO_(2)utilization.However,prolonged Ni sintering and carbon deposition reduce the durability and efficiency of DRM,hindering its engineering application.Herein,we propose a facile approach by combining continuous microscale coprecipitation with solid-state reactions to construct a BaAl_(2)O_(4)-overlayer-confined Ni catalyst.The 5-wt%-Ni@BaAl_(2)O_(4)catalyst exhibited advanced CO_(2)and CH_(4)conversions of 96% and 86% at 800℃ and a GHSV of 144 L g_(cat)^(-1).h^(-1).Moreover,the k_(d)-CO_(2)and k_(d)-CH_(4)of Ni@BaAl_(2)O_(4)were 0.0063 and 0.0029 h^(-1);which are approximately half and one-thirds of those of Ni/BaAl_(2)O_(4)and slightly better than those of Ni@MgAl_(2)O_(4),underscoring the versatility of the proposed synthesis protocol for constructing core-shell structures.XAS,HAADF-STEM-EDS,and CO transmission-IR characterizations confirmed the SMSI of~2-nm amorphous BaAl_(2)O_(4)-overlaid~10 nm Ni with an overall mesoporous structure.After a long-term test,the sintering and coking inhibition effects of Ni@BaAl_(2)O_(4)(10→11 nm,0.55 mgCg_(cat)^(-1).h^(-1))outperformed Ni/BaAl_(2)O_(4)(13→22 nm,1.90 mgCg_(cat)^(-1).h^(-1))and Ni@MgAl_(2)O_(4).In situ time-resolved CH4→CO_(2)transient response,DRIFTS experiments,and DFT calculations suggested that Ni@BaAl_(2)O_(4)and Ni/BaAl_(2)O_(4)followed the Mars-van Krevelen and Langmuir-Hinshelwood redox mechanisms,respectively.The functional interfacial lattice oxygen promoted the removal of C_(ads)^(*)on Ni and core-shell structure induced fast CO_(2)adsorption and CO desorption.The present study provides a facile approach for constructing a stable and active Ni-based core-shell catalyst.Furthermore,it offers novel insights into the functionalities of non-reducible spinel overlayers in the DRM process.展开更多
Atmospheric simulation chambers,are unique tools for investigating atmospheric processes in the gas and heterogeneous phases.They can provide a controlled yet realistic environment that simulates atmospheric condition...Atmospheric simulation chambers,are unique tools for investigating atmospheric processes in the gas and heterogeneous phases.They can provide a controlled yet realistic environment that simulates atmospheric conditions.In the current study,a Teflon atmospheric simulation chamber of 600 L,named THALAMOS(thermally regulated atmospheric simulation chamber) has been developed and cross-validated.THALAMOS can be operated over the temperature range 233 to 373 K under both static and flow conditions.It is equipped with state of the art instrumentation(selective ion flow tube mass spectrometry(SIFT-MS),long path Fourier transform infrared spectroscopy(FTIR),gas chromatography-mass spectrometry(GC-MS),various analyzers) for the in-line monitoring of both reactants and products.THALAMOS was validated by measuring the rate coefficients of well documented reactions,i.e.the reaction of ethanol with OH radicals and the reaction of dichloromethane with Cl atoms,in a wide temperature range.Two different detection techniques were used in parallel,FTIR and SIFT-MS,to internally cross-validate the obtained results.The measured rate coefficients are in excellent agreement,both between each other and with the literature recommended values.Furthermore,the gas phase oxidation of toluene by Cl atoms(kinetics and product yields) was studied in the temperature range of 253 to 333 K.To the best of our knowledge,THALAMOS is a unique facility on national level and among a few smog chambers internationally that can be operated in such a wide temperature range providing the scientific community with a versatile tool to simulate both outdoor and indoor physicochemical processes.展开更多
The effects of accelerated photooxidation on the molecular weight and thermal and mechanical properties of Cast PHBV and PHBV/Cloisite 30B(3 wt%)bionanocomposites are investigated herein.Through size exclusion chromat...The effects of accelerated photooxidation on the molecular weight and thermal and mechanical properties of Cast PHBV and PHBV/Cloisite 30B(3 wt%)bionanocomposites are investigated herein.Through size exclusion chromatography(SEC)analysis,a significant decrease in both weight and number average molecular weights was observed for all irradiated samples over time,resulting from the chain scission mechanism.Differential scanning calorimetry(DSC)data indicated a decrease in degree of crystallinity and melting temperature after UV exposure,with the appearance of double melting peaks related to the changes in the crystal structure of PHBV.Thermal stability,tensile and thermo-mechanical properties were also reduced consecutively in photooxidation,being more pronounced for Cast PHBV.This study shows that the incorporation of Cloisite 30B in PHBV provides a better resistance to photooxidation in comparison with the neat polymer.展开更多
In this paper,we consider solving the topology optimization for steady-state incompressibleNavier-Stokes problems via a new topology optimization method called parameterized level set method,which can maintain a relat...In this paper,we consider solving the topology optimization for steady-state incompressibleNavier-Stokes problems via a new topology optimization method called parameterized level set method,which can maintain a relatively smooth level set function with a local optimality condition.The objective of topology optimization is tond an optimal conguration of theuid and solid materials that minimizes power dissipation under a prescribeduid volume fraction constraint.An articial friction force is added to the Navier-Stokes equations to apply the no-slip boundary condition.Although a great deal of work has been carried out for topology optimization ofuidow in recent years,there are few researches on the topology optimization ofuidow with physical body forces.To simulate theuidow in reality,the constant body force(e.g.,gravity)is considered in this paper.Several 2D numerical examples are presented to discuss the relationships between the proposed method with Reynolds number and initial design,and demonstrate the feasibility and superiority of the proposed method in dealing with unstructuredmesh problems.Three 3D numerical examples demonstrate the proposedmethod is feasible in three-dimensional.展开更多
Innovative catalysts based on a "porous glass" support material were developed and investigated for the reduction of benzalace-tophenone. The easy preparation conditions and possibility to use different meta...Innovative catalysts based on a "porous glass" support material were developed and investigated for the reduction of benzalace-tophenone. The easy preparation conditions and possibility to use different metals (e.g. Pd, Pt, Rh) for impregnation gave a broad variety of these catalysts. Hydrogenation experiments with these supported catalysts were carried out under different hydrogen pressures and temperatures. Porous glass catalysts with Pd as the active component gave chemoselective hydrogenation of benzalacetophenone, while Pt- and Rh-catalysts tended to further reduce the carbonyl group, especially at elevated hydrogen pressures and temperatures. Kinetic analysis of the reactions revealed these had zero order kinetics, which was independent of the type of porous glass support and solvent used.展开更多
Indeed,polymeric materials have thrived in worldwide sectors over the last five decades due to their versatility and durability,to the point that we can no longer envisage a product that does not contain them.However,...Indeed,polymeric materials have thrived in worldwide sectors over the last five decades due to their versatility and durability,to the point that we can no longer envisage a product that does not contain them.However,many synthetic polymers that have been produced are mostly sourced from petroleum and coal as raw materials,making them environmentally incompatible because they cannot be integrated with what is a natural recycling system.One of the most important aspects of the transition to a circular bioeconomy(CBE)is the provision of more sustainable strategies for resource and waste management.Considering the environmental consequences associated with petroleum-based polymers(PBPs),natural biopolymers,originating from biomass,can be conceived as a promising solution to gradually replace the PBPs,and address,and resolve the potential challenges and prevailing research gaps in the PBPs.The biopolymers have significant advantages over PBPs in terms of low-cost/zero-cost precursors,environmental friendliness,and user-friendliness.The present review dissects the sources,synthesis pathways,structures,characterization,and employment of biopolymers and their composites in water and wastew-ater treatment applications via different scenarios.Furthermore,the CBE model framework proposes potential approaches to applying CBE principles in the wastewater management sector,with a heavy emphasis on not only technology but also organizational and societal reforms.To sum up,the reliance on biopolymers can be considered a crucial tool for assessing the global progress toward CBE,as well as future environmental management and planning.展开更多
Background Video anomaly detection has always been a hot topic and has attracted increasing attention.Many of the existing methods for video anomaly detection depend on processing the entire video rather than consider...Background Video anomaly detection has always been a hot topic and has attracted increasing attention.Many of the existing methods for video anomaly detection depend on processing the entire video rather than considering only the significant context. Method This paper proposes a novel video anomaly detection method called COVAD that mainly focuses on the region of interest in the video instead of the entire video. Our proposed COVAD method is based on an autoencoded convolutional neural network and a coordinated attention mechanism,which can effectively capture meaningful objects in the video and dependencies among different objects. Relying on the existing memory-guided video frame prediction network, our algorithm can significantly predict the future motion and appearance of objects in a video more effectively. Result The proposed algorithm obtained better experimental results on multiple datasets and outperformed the baseline models considered in our analysis. Simultaneously, we provide an improved visual test that can provide pixel-level anomaly explanations.展开更多
Data assimilation(DA)and uncertainty quantification(UQ)are extensively used in analysing and reducing error propagation in high-dimensional spatial-temporal dynamics.Typical applications span from computational fluid ...Data assimilation(DA)and uncertainty quantification(UQ)are extensively used in analysing and reducing error propagation in high-dimensional spatial-temporal dynamics.Typical applications span from computational fluid dynamics(CFD)to geoscience and climate systems.Recently,much effort has been given in combining DA,UQ and machine learning(ML)techniques.These research efforts seek to address some critical challenges in high-dimensional dynamical systems,including but not limited to dynamical system identification,reduced order surrogate modelling,error covariance specification and model error correction.A large number of developed techniques and methodologies exhibit a broad applicability across numerous domains,resulting in the necessity for a comprehensive guide.This paper provides the first overview of state-of-the-art researches in this interdisciplinary field,covering a wide range of applications.This review is aimed at ML scientists who attempt to apply DA and UQ techniques to improve the accuracy and the interpretability of their models,but also at DA and UQ experts who intend to integrate cutting-edge ML approaches to their systems.Therefore,this article has a special focus on how ML methods can overcome the existing limits of DA and UQ,and vice versa.Some exciting perspectives of this rapidly developing research field are also discussed.Index Terms-Data assimilation(DA),deep learning,machine learning(ML),reduced-order-modelling,uncertainty quantification(UQ).展开更多
In this paper,the effects of gamma irradiation on Cast poly(3-hydroxybutyrate-co-3-hydroxyvalerate)(PHBV)and PHBV/Cloisite 30B(C30B)(3 wt%)bionanocomposite prepared by melt compounding,were evaluated at various doses,...In this paper,the effects of gamma irradiation on Cast poly(3-hydroxybutyrate-co-3-hydroxyvalerate)(PHBV)and PHBV/Cloisite 30B(C30B)(3 wt%)bionanocomposite prepared by melt compounding,were evaluated at various doses,i.e.,5,15,20,50 and 100 kGy at room temperature in air.Changes in molecular weight,morphology and physical properties were investigated.The study showed that the main degradation mechanism occurring in gamma irradiation in both Cast PHBV and C-PHBV/3C30B bionanocomposite is chain scission,responsible for the decrease of molecular weight.Differential scanning calorimetry(DSC)data indicated a regular decrease in crystallization temperature,melting temperature and crystallinity index for all irradiated samples with increasing the dose.Further,DSC thermograms of both Cast PHBV and PHBV bionanocomposite exhibited double melting peaks due probably to changes in the PHBV crystal structure.Tensile and DMA data showed a reduction in Young’s modulus,strength,elongation at break and storage modulus with the radiation dose;the decrease was however more pronounced for Cast PHBV.The morphological damages were much less pronounced for the PHBV bionanocomposite sample compared to Cast PHBV,for which some irregularities and defects were observed at 100 kGy.This study highlighted the ability of C30B to counterbalance the detrimental effect of radiolytic degradation on the functional properties of PHBV up to 100 kGy,thus acting as a potential anti-rad.展开更多
The return to old building methods by mixing crop by-products with mineral binders is arousing great interest in Europe since about 25 years.The use of these bio-aggregates based materials for the design of building e...The return to old building methods by mixing crop by-products with mineral binders is arousing great interest in Europe since about 25 years.The use of these bio-aggregates based materials for the design of building envelopes is a valuable opportunity to deal with increasingly demanding thermal regulations.In addition,the regulatory framework is moving towards reducing the overall car-bon footprint of new buildings.Some traditional and historic buildings are based on timber framing with earth-straw as infill material for instance.Hemp concrete is a bio-based material that can be manually tamped in timber stud walls or more recently in the form of precast blocks.Owing to their low compressive strength,bio-based concretes using a large volume fraction of plant-derived aggregates are only considered as thermal and sound insulation materials.The structural design practice of wood frame walls does not assume any mechanical contribution of hemp concrete whereas it may contribute to the racking strength of the structure.In this context,more research is needed regarding the shear behavior of crop by-products and bio-based concretes.In this case,the objective of the study was to perform direct shear tests under three levels of normal pressure on hemp shiv and rice husk as unbound crop by-products.The results showed that the friction angle of the granular skeleton based on rice husk for a given relative displacement was significantly lower than that measured on hemp shiv.This is in accordance with what had been observed on bio-based concretes cast by mixing aggregates with lime and shear strength parameters measured by means of triaxial compression.展开更多
基金financial support from the Chilean National Agency for Research and Development(ANID),National Doctorate No.21212028financial support from ANID,FONDECYT Regular Research Project No.1221793.
文摘Rubberized concrete is one of the most studied applications of discarded tires and offers a promising approach to developing materials with enhanced properties.The rubberized concrete mixture results in a reduced modulus of elasticity and a reduced compressive and tensile strength compared to traditional concrete.This study employs finite element simulations to investigate the elastic properties of rubberized mortar(RuM),considering the influence of inclusion stiffness and interfacial debonding.Different homogenization schemes,including Voigt,Reuss,and mean-field approaches,are implemented using DIGIMAT and ANSYS.Furthermore,the influence of the interfacial transition zone(ITZ)between mortar and rubber is analyzed by periodic homogenization.Subsequently,the influence of the ITZ is examined through a linear fracture analysis with the stress intensity factor as a key parameter,using the ANSYS SMART crack growth tool.Finally,a non-linear study in FEniCS is carried out to predict the strength of the composite material through a compression test.Comparisons with high density polyethylene(HDPE)and gravel inclusions show that increasing inclusion stiffness enhances compressive strength far more effectively than simply improving the mortar/rubber bond.Indeed,when the inclusions are much softer than the surrounding matrix,any benefit gained on the elastic modulus or strength from stronger interfacial adhesion becomes almost negligible.This study provide numerical evidence that tailoring the rubber’s intrinsic stiffness—not merely strengthening the rubber/mortar interface—is a decisive factor for improving the mechanical performance of RuM.
基金The authors gratefully acknowledge the support from the Natural Sciences and Engineering Research Council of Canada(NSERC)2018–03889 through a Discovery Grant.Thanks to Mr.Adrien Lieurey(IMT-Mines Albi ICA-site Albi)for his involvement and fabrication of SLM parts.They would also like to express their gratitude to Aubert&Duval Co.,Dr.Alexandre Devaux,and Prof.Cormier for providing forged AD730™samples and discussions on the definition of the scope of the project.Special thanks to TWI Ltd.for carrying out the LFW of the samples.
文摘The continuous growth in the manufacture of aerospace components such as blisks has led to an increase in the application of different hybrid materials fabricating methods,and thus the requirements for joining and strengthening of dissimilar welds.According to this goal,selective laser melted(SLM)Inconel718 was joined with forged AD730^(TM)Nickel-based superalloy through linear friction welding(LFW)in this study.Microstructure variation,specifically with respect to secondary phases precipitation was investigated.The microhardness and strengthening mechanisms of the weldment were also studied.The precipitation(volume fraction and size of particles)at different regions of both sides of the weld line was characterized.Close to the weld line,the dissolution ofγ’/γ"and Laves phases and grain refinement occurred which reveals the effects of both compression strain and high temperature on recrystallization and high degree of elemental diffusion in the weld zone(WZ).It is shown that the size,volume fraction,and shape of secondary phases increased and changed(from spherical to long-striped for Laves particles)as we went from the WZ toward the base metal.However,the measured microhardness indicated that the strength of AD730^(TM)alloy depends significantly on the grain size,while strength in SLM Inconel 718 was dominated by shape(or size)and the presence of secondary phases(γ’/γ"and Laves).
文摘In most microfluidic applications, pressure-driven Poiseuille flow in a contained cross-section with no-slip boundary conditions is the underlying fluid-mechanical model. Solutions for this problem exist for many known cross-sections. We have recently demonstrated a simple method to solve the relevant Poisson equation using a finite difference scheme in a spreadsheet analysis tool such as Microsoft Excel. The numerical solutions obtained from such a spreadsheet are close-to-exact to the analytical solutions with errors on the order of only a few percent. However, there are numerous applications in microfluidics for which the no-slip boundary condition is not valid. Examples include drag-reducing air-retaining surfaces as well as open-channel flow. For these scenarios few to no analytical models exist. In this paper, we derive an analytical model for mixed boundary conditions (slip/no-slip) in two dimensions in a rectangular channel cross-section. We also demonstrate that the equivalent numerical solution can be derived conveniently by adaption of the spreadsheet. In general, mixed boundary-type flow scenarios are especially difficult to solve analytically whereas numerical solutions can be derived using Microsoft Excel within seconds.
文摘A new DCG-FGT （dual-control-gate floating-gate transistor） transistor model for static and transient simulations is presented. The PSP MOS （metal-oxide-semiconductor） description is used as a basis for the formulation of the conduction channel behavior. The floating gate potential is implicitly computed with an added charge neutrality relation that ensures a good convergence. The model is running under electrical simulator （ELDO） and is characterized thanks to ICCAP （integrated circuit characterization and analysis program） software. It has been validated on an advanced STMicroelectronics technology. The final objective of this work is to provide an accurate and scalable model available in design framework. This device which is derived from a flash memory cell offers many possibilities for circuit design.
基金"PSPC Régions n°2"("Projets Structurants des Pôles de Compétitivitéen région")funded by Conseil Régional Hauts-de-France and BPI.
文摘Developing the railway transport sector is a challenging scientific,economic and social research topic starting with ensuring human security.The main topic that should be developed in that sense is the ballast stability and dynamical behaviour under external loading and environmental changes.This paper investigates the effect of particle size distribution and normal pressure on the mechanical response of a ballast bed.Grading curves of ballast layers with different sizes are illustrated to discuss their strength behaviour under various strains to deduce the significant effect on the direct shear performance of the ballast layer.Direct shear tests with different Particle Size Distribution(PSD)were reproduced using the Discrete Element Method(DEM).It is noticed that when the number of small-sized ballast increases,the shear strength and the friction angle increase to varying degrees under different normal pressures,with an average increase of 27%and 8%,respectively.When the number of large-sized ballast decreases,the shear strength and the friction angle decrease to varying degrees under different normal pressures,with an average decrease of 6%and 3%,respectively.
文摘This study examines hemodynamic behavior in particular cases of pulmonary hypertension without treatment. Pulmonary hypertension represents an anomalous hemodynamic state and is characterized by an excessively high blood pressure in the pulmonary artery. To simulate the hemodynamic abnormalities in pulmonary hypertension under different causes and pathologies, we construct a localized parameter circuit model governed by nonlinear ordinary derivative equations of the human circulatory system. Thus, two special cases are considered, namely pulmonary the artery stenosis and the left ventricular diastolic dysfunction. For each case of pulmonary hypertension development, we determine the relationships between blood pressure and chamber and vessel pressure-volume. When the pulmonary hypertension is due to pulmonary artery stenosis, it appears that the right ventricular pressure increases up to 90 mm Hg, likewise the rise in pulmonary artery resistance induces direct increment in pulmonary artery pressure. However, when the pulmonary hypertension is due to left ventricular diastolic dysfunction, we note that the left atrial pressure and the pulmonary vein pressure augment, leading to the growth of the pulmonary artery blood pressure. The established results within this paper are useful for understanding the hemodynamic mechanism of particular pulmonary hypertension.
基金the financial support by the National Natural Science Foundation of China(52378440,42477143)the Key Science and Technology Program in the Transportation Industry(2022-MS1-032,2022-MS5-125)+2 种基金the Postgraduate Scientific Research Innovation Project of Hunan Province(CX20251302)the Science and Technology Innovation Program of Hunan Province(2024RC3166)the Guangxi Key Research and Development Program(AB23075184)。
文摘Carbonaceous mudstone is a potential embankment filler in mountainous regions with limited high-quality materials;however,its engineering performance in highway embankments under complex environmental conditions remains poorly understood.This study aimed to investigate the mechanical properties and failure mechanisms of carbonaceous mudstone filler under different temperature-moisture coupled conditions.Triaxial shear tests were conducted under four temperaturemoisture coupled conditions:dry-heat to dry-cold(DHDC),wet-cold to wet-heat(WCWH),dry-cold to wet-heat(DCWH),and dry-heat to wet-cold(DHWC).The effects of these conditions on the strength characteristics,relative breakage ratio,failure mode,and microscopic morphology were examined.A segmented prediction model based on the DuncanChang model was applied to validate the experimental results under the DHWC condition.The failure mechanisms under different conditions were also analyzed.The results indicate that the degradation of carbonaceous mudstone increases in the following order:DHDC,WCWH,DCWH,and DHWC.Under the DHDC condition,the stress-strain curves exhibit strain-softening behavior,while other conditions show strain-hardening behavior,with peak deviatoric stress occurring at 2%and 4%axial strains,respectively.The shear strength decreases by up to 40%under the DHWC condition but remains nearly unchanged under the DHDC condition,showing a positive correlation with particle breakage.As the number of cycles increases,the failure surfaces gradually move downward.Higher confining pressure shifts failure mode from shear failure to shear slip or localized compression,and eventually to overall compression or expansion failure.The modified Duncan-Chang model accurately predicts the experimental results.These findings provide important guidance for the application of carbonaceous mudstone filler in highway embankment construction in humid mountainous regions.
基金financially supported by the National Natural Science Foundation of China(22378227)the National Research Foundation,Singapore,and A*STAR under its Low-Carbon Energy Research(LCER)Funding Initiative(FI)Project(U2102d2011,WBS:A-8000278-00-00)the Medium Energy X-ray Absorption Spectroscopy beamline at the Australian Synchrotron,part of ANSTO。
文摘Dry reforming of methane(DRM)over Ni-based catalysts is an economically reasonable technology for large-scale CO_(2)utilization.However,prolonged Ni sintering and carbon deposition reduce the durability and efficiency of DRM,hindering its engineering application.Herein,we propose a facile approach by combining continuous microscale coprecipitation with solid-state reactions to construct a BaAl_(2)O_(4)-overlayer-confined Ni catalyst.The 5-wt%-Ni@BaAl_(2)O_(4)catalyst exhibited advanced CO_(2)and CH_(4)conversions of 96% and 86% at 800℃ and a GHSV of 144 L g_(cat)^(-1).h^(-1).Moreover,the k_(d)-CO_(2)and k_(d)-CH_(4)of Ni@BaAl_(2)O_(4)were 0.0063 and 0.0029 h^(-1);which are approximately half and one-thirds of those of Ni/BaAl_(2)O_(4)and slightly better than those of Ni@MgAl_(2)O_(4),underscoring the versatility of the proposed synthesis protocol for constructing core-shell structures.XAS,HAADF-STEM-EDS,and CO transmission-IR characterizations confirmed the SMSI of~2-nm amorphous BaAl_(2)O_(4)-overlaid~10 nm Ni with an overall mesoporous structure.After a long-term test,the sintering and coking inhibition effects of Ni@BaAl_(2)O_(4)(10→11 nm,0.55 mgCg_(cat)^(-1).h^(-1))outperformed Ni/BaAl_(2)O_(4)(13→22 nm,1.90 mgCg_(cat)^(-1).h^(-1))and Ni@MgAl_(2)O_(4).In situ time-resolved CH4→CO_(2)transient response,DRIFTS experiments,and DFT calculations suggested that Ni@BaAl_(2)O_(4)and Ni/BaAl_(2)O_(4)followed the Mars-van Krevelen and Langmuir-Hinshelwood redox mechanisms,respectively.The functional interfacial lattice oxygen promoted the removal of C_(ads)^(*)on Ni and core-shell structure induced fast CO_(2)adsorption and CO desorption.The present study provides a facile approach for constructing a stable and active Ni-based core-shell catalyst.Furthermore,it offers novel insights into the functionalities of non-reducible spinel overlayers in the DRM process.
基金supported by grants from The National Natural Science Foundation of China(61575025)the fund of the State Key Laboratory of Information Photonics and Optical Communications(IPOC2016ZZ02)~~
基金part of the chemical and physical properties of the atmosphere(Ca PPA)project funded by the Agence Nationale de la Recherhe(ANR)through the programme d’investissements d’avenir PIA(No.ANR-11-LABX0005-01)the“Hauts-de-France”Regional Council and the European Regional Development Fund(ERDF)+4 种基金the Institut National des Sciences de L’univers(INSU)les Enveloppes Fluides et L’environnement Chimie de L’atmosphère(LEFE-CHAT)program for financial supportsupport from Labex Ca PPA for his graduate fellowshipsupport from Labex Ca PPA for his short term visit at the institute mines telecom(IMT)Lille Douaisupport from the project make our planet great again(MOPGA)for her short term visit at IMT Lille Douaithe Greek sate scholarships foundation(IKY)program that funds her PhD
文摘Atmospheric simulation chambers,are unique tools for investigating atmospheric processes in the gas and heterogeneous phases.They can provide a controlled yet realistic environment that simulates atmospheric conditions.In the current study,a Teflon atmospheric simulation chamber of 600 L,named THALAMOS(thermally regulated atmospheric simulation chamber) has been developed and cross-validated.THALAMOS can be operated over the temperature range 233 to 373 K under both static and flow conditions.It is equipped with state of the art instrumentation(selective ion flow tube mass spectrometry(SIFT-MS),long path Fourier transform infrared spectroscopy(FTIR),gas chromatography-mass spectrometry(GC-MS),various analyzers) for the in-line monitoring of both reactants and products.THALAMOS was validated by measuring the rate coefficients of well documented reactions,i.e.the reaction of ethanol with OH radicals and the reaction of dichloromethane with Cl atoms,in a wide temperature range.Two different detection techniques were used in parallel,FTIR and SIFT-MS,to internally cross-validate the obtained results.The measured rate coefficients are in excellent agreement,both between each other and with the literature recommended values.Furthermore,the gas phase oxidation of toluene by Cl atoms(kinetics and product yields) was studied in the temperature range of 253 to 333 K.To the best of our knowledge,THALAMOS is a unique facility on national level and among a few smog chambers internationally that can be operated in such a wide temperature range providing the scientific community with a versatile tool to simulate both outdoor and indoor physicochemical processes.
文摘The effects of accelerated photooxidation on the molecular weight and thermal and mechanical properties of Cast PHBV and PHBV/Cloisite 30B(3 wt%)bionanocomposites are investigated herein.Through size exclusion chromatography(SEC)analysis,a significant decrease in both weight and number average molecular weights was observed for all irradiated samples over time,resulting from the chain scission mechanism.Differential scanning calorimetry(DSC)data indicated a decrease in degree of crystallinity and melting temperature after UV exposure,with the appearance of double melting peaks related to the changes in the crystal structure of PHBV.Thermal stability,tensile and thermo-mechanical properties were also reduced consecutively in photooxidation,being more pronounced for Cast PHBV.This study shows that the incorporation of Cloisite 30B in PHBV provides a better resistance to photooxidation in comparison with the neat polymer.
基金supported by the National Natural Science Foundation of China (Grant No.12072114)the National Key Research and Development Plan (Grant No.2020YFB1709401)the Guangdong Provincial Key Laboratory of Modern Civil Engineering Technology (2021B1212040003).
文摘In this paper,we consider solving the topology optimization for steady-state incompressibleNavier-Stokes problems via a new topology optimization method called parameterized level set method,which can maintain a relatively smooth level set function with a local optimality condition.The objective of topology optimization is tond an optimal conguration of theuid and solid materials that minimizes power dissipation under a prescribeduid volume fraction constraint.An articial friction force is added to the Navier-Stokes equations to apply the no-slip boundary condition.Although a great deal of work has been carried out for topology optimization ofuidow in recent years,there are few researches on the topology optimization ofuidow with physical body forces.To simulate theuidow in reality,the constant body force(e.g.,gravity)is considered in this paper.Several 2D numerical examples are presented to discuss the relationships between the proposed method with Reynolds number and initial design,and demonstrate the feasibility and superiority of the proposed method in dealing with unstructuredmesh problems.Three 3D numerical examples demonstrate the proposedmethod is feasible in three-dimensional.
文摘Innovative catalysts based on a "porous glass" support material were developed and investigated for the reduction of benzalace-tophenone. The easy preparation conditions and possibility to use different metals (e.g. Pd, Pt, Rh) for impregnation gave a broad variety of these catalysts. Hydrogenation experiments with these supported catalysts were carried out under different hydrogen pressures and temperatures. Porous glass catalysts with Pd as the active component gave chemoselective hydrogenation of benzalacetophenone, while Pt- and Rh-catalysts tended to further reduce the carbonyl group, especially at elevated hydrogen pressures and temperatures. Kinetic analysis of the reactions revealed these had zero order kinetics, which was independent of the type of porous glass support and solvent used.
文摘Indeed,polymeric materials have thrived in worldwide sectors over the last five decades due to their versatility and durability,to the point that we can no longer envisage a product that does not contain them.However,many synthetic polymers that have been produced are mostly sourced from petroleum and coal as raw materials,making them environmentally incompatible because they cannot be integrated with what is a natural recycling system.One of the most important aspects of the transition to a circular bioeconomy(CBE)is the provision of more sustainable strategies for resource and waste management.Considering the environmental consequences associated with petroleum-based polymers(PBPs),natural biopolymers,originating from biomass,can be conceived as a promising solution to gradually replace the PBPs,and address,and resolve the potential challenges and prevailing research gaps in the PBPs.The biopolymers have significant advantages over PBPs in terms of low-cost/zero-cost precursors,environmental friendliness,and user-friendliness.The present review dissects the sources,synthesis pathways,structures,characterization,and employment of biopolymers and their composites in water and wastew-ater treatment applications via different scenarios.Furthermore,the CBE model framework proposes potential approaches to applying CBE principles in the wastewater management sector,with a heavy emphasis on not only technology but also organizational and societal reforms.To sum up,the reliance on biopolymers can be considered a crucial tool for assessing the global progress toward CBE,as well as future environmental management and planning.
文摘Background Video anomaly detection has always been a hot topic and has attracted increasing attention.Many of the existing methods for video anomaly detection depend on processing the entire video rather than considering only the significant context. Method This paper proposes a novel video anomaly detection method called COVAD that mainly focuses on the region of interest in the video instead of the entire video. Our proposed COVAD method is based on an autoencoded convolutional neural network and a coordinated attention mechanism,which can effectively capture meaningful objects in the video and dependencies among different objects. Relying on the existing memory-guided video frame prediction network, our algorithm can significantly predict the future motion and appearance of objects in a video more effectively. Result The proposed algorithm obtained better experimental results on multiple datasets and outperformed the baseline models considered in our analysis. Simultaneously, we provide an improved visual test that can provide pixel-level anomaly explanations.
基金the support of the Leverhulme Centre for Wildfires,Environment and Society through the Leverhulme Trust(RC-2018-023)Sibo Cheng,César Quilodran-Casas,and Rossella Arcucci acknowledge the support of the PREMIERE project(EP/T000414/1)+5 种基金the support of EPSRC grant:PURIFY(EP/V000756/1)the Fundamental Research Funds for the Central Universitiesthe support of the SASIP project(353)funded by Schmidt Futures–a philanthropic initiative that seeks to improve societal outcomes through the development of emerging science and technologiesDFG for the Heisenberg Programm Award(JA 1077/4-1)the National Natural Science Foundation of China(61976120)the Natural Science Key Foundat ion of Jiangsu Education Department(21KJA510004)。
文摘Data assimilation(DA)and uncertainty quantification(UQ)are extensively used in analysing and reducing error propagation in high-dimensional spatial-temporal dynamics.Typical applications span from computational fluid dynamics(CFD)to geoscience and climate systems.Recently,much effort has been given in combining DA,UQ and machine learning(ML)techniques.These research efforts seek to address some critical challenges in high-dimensional dynamical systems,including but not limited to dynamical system identification,reduced order surrogate modelling,error covariance specification and model error correction.A large number of developed techniques and methodologies exhibit a broad applicability across numerous domains,resulting in the necessity for a comprehensive guide.This paper provides the first overview of state-of-the-art researches in this interdisciplinary field,covering a wide range of applications.This review is aimed at ML scientists who attempt to apply DA and UQ techniques to improve the accuracy and the interpretability of their models,but also at DA and UQ experts who intend to integrate cutting-edge ML approaches to their systems.Therefore,this article has a special focus on how ML methods can overcome the existing limits of DA and UQ,and vice versa.Some exciting perspectives of this rapidly developing research field are also discussed.Index Terms-Data assimilation(DA),deep learning,machine learning(ML),reduced-order-modelling,uncertainty quantification(UQ).
文摘In this paper,the effects of gamma irradiation on Cast poly(3-hydroxybutyrate-co-3-hydroxyvalerate)(PHBV)and PHBV/Cloisite 30B(C30B)(3 wt%)bionanocomposite prepared by melt compounding,were evaluated at various doses,i.e.,5,15,20,50 and 100 kGy at room temperature in air.Changes in molecular weight,morphology and physical properties were investigated.The study showed that the main degradation mechanism occurring in gamma irradiation in both Cast PHBV and C-PHBV/3C30B bionanocomposite is chain scission,responsible for the decrease of molecular weight.Differential scanning calorimetry(DSC)data indicated a regular decrease in crystallization temperature,melting temperature and crystallinity index for all irradiated samples with increasing the dose.Further,DSC thermograms of both Cast PHBV and PHBV bionanocomposite exhibited double melting peaks due probably to changes in the PHBV crystal structure.Tensile and DMA data showed a reduction in Young’s modulus,strength,elongation at break and storage modulus with the radiation dose;the decrease was however more pronounced for Cast PHBV.The morphological damages were much less pronounced for the PHBV bionanocomposite sample compared to Cast PHBV,for which some irregularities and defects were observed at 100 kGy.This study highlighted the ability of C30B to counterbalance the detrimental effect of radiolytic degradation on the functional properties of PHBV up to 100 kGy,thus acting as a potential anti-rad.
文摘The return to old building methods by mixing crop by-products with mineral binders is arousing great interest in Europe since about 25 years.The use of these bio-aggregates based materials for the design of building envelopes is a valuable opportunity to deal with increasingly demanding thermal regulations.In addition,the regulatory framework is moving towards reducing the overall car-bon footprint of new buildings.Some traditional and historic buildings are based on timber framing with earth-straw as infill material for instance.Hemp concrete is a bio-based material that can be manually tamped in timber stud walls or more recently in the form of precast blocks.Owing to their low compressive strength,bio-based concretes using a large volume fraction of plant-derived aggregates are only considered as thermal and sound insulation materials.The structural design practice of wood frame walls does not assume any mechanical contribution of hemp concrete whereas it may contribute to the racking strength of the structure.In this context,more research is needed regarding the shear behavior of crop by-products and bio-based concretes.In this case,the objective of the study was to perform direct shear tests under three levels of normal pressure on hemp shiv and rice husk as unbound crop by-products.The results showed that the friction angle of the granular skeleton based on rice husk for a given relative displacement was significantly lower than that measured on hemp shiv.This is in accordance with what had been observed on bio-based concretes cast by mixing aggregates with lime and shear strength parameters measured by means of triaxial compression.
