Proton exchange membrane(PEM)is an integral component in fuel cells which enables proton transport for efficient energy conversion.Sulfonated Polyether Ether Ketone(SPEEK)has emerged as a cost-effective option with no...Proton exchange membrane(PEM)is an integral component in fuel cells which enables proton transport for efficient energy conversion.Sulfonated Polyether Ether Ketone(SPEEK)has emerged as a cost-effective option with non-fluorinated aromatic backbones for Proton Exchange Membrane Fuel Cell(PEMFC)applications,even though it exhibits lower proton conductivity compared to Nafion.This work aims to study the influence of Sulfonated Chitosan(SCS)concentrations on proton conductivity of SPEEK-based PEM at room temperature.SPEEK was synthesized using a sulfonation process with concentrated sulfuric acid at room temperature.SCS was synthesized via reflux of CS and 1.2 M H2SO4 with a ratio of 1:35(w/v)at 90℃ for 30 min.The composite membranes of SPEEK-SCS were formed with four different SCS concentrations,using the solution castingmethod,andDimethyl Sulfoxide(DMSO)was used as a solvent.The composite membranes synthesized include pure SPEEK(S0),SPEEK with 1%SCS(S1),SPEEK with 2%SCS(S2),and SPEEK with 3%SCS(S3).Fourier transform infrared spectroscopy(FTIR),X-ray diffraction(XRD),water uptake,degree of swelling,Ionic exchange capacity(IEC)with Electrochemical impedance spectroscopy(EIS)were used to characterize the composite membranes in terms of composition,crystallinity,water absorption,dimensional changes,number of exchangeable ions in membranes,and proton conductivity,respectively.Notably,S3 had the highest water uptake and the lowest degree of swelling.S2 had the highest proton conductivity among the SPEEK-SCS composite membranes at room temperature with 3.44×10^(−2) Scm^(-1).展开更多
With the miniaturization and high-frequency evolution of antennas in 5G/6G communications,aerospace,and transportation,polymer composite papers integrating superior wave-transparent performance and thermal conductivit...With the miniaturization and high-frequency evolution of antennas in 5G/6G communications,aerospace,and transportation,polymer composite papers integrating superior wave-transparent performance and thermal conductivity for radar antenna systems are urgently needed.Herein,a down-top strategy was employed to synthesize poly(p-phenylene benzobisoxazole)precursor nanofibers(prePNF).The prePNF was then uniformly mixed with fluorinated graphene(FG)to fabricate FG/PNF composite papers through consecutively suction filtration,hot-pressing,and thermal annealing.The hydroxyl and amino groups in prePNF enhanced the stability of FG/prePNF dispersion,while the increasedπ-πinteractions between PNF and FG after annealing improved their compatibility.The preparation time and cost of PNF paper was significantly reduced when applying this strategy,which enabled its large-scale production.Furthermore,the prepared FG/PNF composite papers exhibited excellent wave-transparent performance and thermal conductivity.When the mass fraction of FG was 40 wt%,the FG/PNF composite paper prepared via the down-top strategy achieved the wave-transparent coefficient(|T|2)of 96.3%under 10 GHz,in-plane thermal conductivity(λ_(∥))of 7.13 W m^(−1)K^(−1),and through-plane thermal conductivity(λ_(⊥))of 0.67 W m^(−1)K^(−1),outperforming FG/PNF composite paper prepared by the top-down strategy(|T|2=95.9%,λ_(∥)=5.52 W m^(−1)K^(−1),λ_(⊥)=0.52 W m^(−1)K^(−1))and pure PNF paper(|T|2=94.7%,λ_(∥)=3.04 W m^(−1)K^(−1),λ_(⊥)=0.24 W m^(−1)K^(−1)).Meanwhile,FG/PNF composite paper(with 40 wt%FG)through the down-top strategy also demonstrated outstanding mechanical properties with tensile strength and toughness reaching 197.4 MPa and 11.6 MJ m^(−3),respectively.展开更多
The thermal conductivity of nanofluids is an important property that influences the heat transfer capabilities of nanofluids.Researchers rely on experimental investigations to explore nanofluid properties,as it is a n...The thermal conductivity of nanofluids is an important property that influences the heat transfer capabilities of nanofluids.Researchers rely on experimental investigations to explore nanofluid properties,as it is a necessary step before their practical application.As these investigations are time and resource-consuming undertakings,an effective prediction model can significantly improve the efficiency of research operations.In this work,an Artificial Neural Network(ANN)model is developed to predict the thermal conductivity of metal oxide water-based nanofluid.For this,a comprehensive set of 691 data points was collected from the literature.This dataset is split into training(70%),validation(15%),and testing(15%)and used to train the ANN model.The developed model is a backpropagation artificial neural network with a 4–12–1 architecture.The performance of the developed model shows high accuracy with R values above 0.90 and rapid convergence.It shows that the developed ANN model accurately predicts the thermal conductivity of nanofluids.展开更多
The local thermal conductivity of polycrystalline aluminum nitride （A1N） ceramics is measured and imaged by using a scanning thermal microscope （SThM） and complementary scanning electron microscope （SEM） based t...The local thermal conductivity of polycrystalline aluminum nitride （A1N） ceramics is measured and imaged by using a scanning thermal microscope （SThM） and complementary scanning electron microscope （SEM） based techniques at room temperature. The quantitative thermal conductivity for the A1N sample is gained by using a SThM with a spatial resolution of sub-micrometer scale through using the 3w method. A thermal conductivity of 308 W/m-K within grains corresponding to that of high-purity single crystal A1N is obtained. The slight differences in thermal conduction between the adjacent grains are found to result from crystallographic misorientations, as demonstrated in the electron backscattered diffraction. A much lower thermal conductivity at the grain boundary is due to impurities and defects enriched in these sites, as indicated by energy dispersive X-ray spectroscopy.展开更多
A numerical simulation in real space was developed to investigate weak localization corrections to the conductivity in inhomogeneous magnetic fields created by flux lines.Both cylinder model and exponential one of flu...A numerical simulation in real space was developed to investigate weak localization corrections to the conductivity in inhomogeneous magnetic fields created by flux lines.Both cylinder model and exponential one of flux lines were studied.It was shown that the corrections are sensitive to the flux line structure.Comparing to the experiments of Bending et al.,the results show that the flux line in Pb film can be approximately described by the cylinder model.展开更多
Combining the mean field Pozhar-Gubbins(PG)theory and the weighted density approximation,a novel method for local thermal conductivity of inhomogeneous fluids is proposed.The correlation effect that is beyond the mean...Combining the mean field Pozhar-Gubbins(PG)theory and the weighted density approximation,a novel method for local thermal conductivity of inhomogeneous fluids is proposed.The correlation effect that is beyond the mean field treatment is taken into account by the simulation-based empirical correlations.The application of this method to confined argon in slit pore shows that its prediction agrees well with the simulation results,and that it performs better than the original PG theory as well as the local averaged density model(LADM).In its further application to the nano-fluidic films,the influences of fluid parameters and pore parameters on the thermal conductivity are calculated and investigated.It is found that both the local thermal conductivity and the overall thermal conductivity can be significantly modulated by these parameters.Specifically,in the supercritical states,the thermal conductivity of the confined fluid shows positive correlation to the bulk density as well as the temperature.However,when the bulk density is small,the thermal conductivity exhibits a decrease-increase transition as the temperature is increased.This is also the case in which the temperature is low.In fact,the decrease-increase transition in both the small-bulk-density and low-temperature cases arises from the capillary condensation in the pore.Furthermore,smaller pore width and/or stronger adsorption potential can raise the critical temperature for condensation,and then are beneficial to the enhancement of the thermal conductivity.These modulation behaviors of the local thermal conductivity lead immediately to the significant difference of the overall thermal conductivity in different phase regions.展开更多
In recent years,there has been a growing global demand for carbon neutrality and energy efficiency,which are expected to become long-term trends.In the field of architecture,an effective approach to achieve this is to...In recent years,there has been a growing global demand for carbon neutrality and energy efficiency,which are expected to become long-term trends.In the field of architecture,an effective approach to achieve this is to reduce heat loss in buildings.Vacuum insulation panels(VIPs),a type of high-performance insulation material,have been increasingly utilised in the construction industry and have played an increa-singly important role as their performance and manufacturing processes continue to improve.This paper provides a review of the factors affecting the thermal conductivity of VIPs and presents a detailed overview of the research progress on core materials,barrier films,and getters.The current research status of VIPs is summarised,including their thermal conductivity,service life,and thermal bridging effects,as well as their applications in the field of architecture.This review aims to provide a comprehensive understanding for relevant practitioners on the factors influencing the thermal conductivity of VIPs,and based on which,measures can be taken to produce VIPs with lower thermal conductivity and longer service life.展开更多
The thermal conductivity of the soil skeletonλ;is an essential parameter from the point of view of the correct assessment of soil overall/effective conductivity.This work introduces the concept of“local thermal cond...The thermal conductivity of the soil skeletonλ;is an essential parameter from the point of view of the correct assessment of soil overall/effective conductivity.This work introduces the concept of“local thermal conductivity fluctuation”which characterizes the microscale variation of conductivity within the solid phase.It is proposed to link the“local fluctuation”of thermal conductivityλwith the soil texture-the information that is available at the scale of engineering applications.It was possible to relate the skeleton thermal conductivity with the grain size distribution of the soil.Finally,based on a large series of numerical simulations,the paper provides four triangle diagrams(at different organic matter contents:0%,2%,4%and 6%)relating the value ofλ;with volume fraction of individual soil separates.This result is extremely important from the practical point of view.One can quickly evaluateλ;value provided that information on the grain size distribution and organic matter content is available.展开更多
Improving and optimizing the target properties of ceramics via the high entropy strategy has attracted significant attention.Rare earth niobate is a potential thermal barrier coating(TBCs)material,but its poor high-te...Improving and optimizing the target properties of ceramics via the high entropy strategy has attracted significant attention.Rare earth niobate is a potential thermal barrier coating(TBCs)material,but its poor high-temperature phase stability limits its further application.In this work,four sets of TBCs high-entropy ceramics,(Sm_(1/5)Dy_(1/5)Ho_(1/5)Er_(1/5)Yb_(1/5))(Nb_(1/2)Ta_(1/2))O_(4)(5NbTa),(Sm_(1/6)Dy_(1/6)Ho_(1/6)Er_(1/6)Yb_(1/6)Lu_(1/6))(Nb_(1/2)Ta_(1/2))O_(4)(6NbTa),(Sm_(1/7)Gd_(1/7)Dy_(1/7)Ho_(1/7)Er_(1/7)Yb_(1/7)Lu_(1/7))(Nb_(1/2)Ta_(1/2))O_(4)(7NbTa),(Sm_(1/8)Gd_(1/8)Dy_(1/8)Ho_(1/8)Er_(1/8)Tm_(1/8)Yb_(1/8)Lu_(1/8))(Nb_(1/2)Ta_(1/2))O_(4)(8NbTa)are synthesized using a solid-state reaction method at 1650℃for 6 h.Firstly,the X-ray diffractometer(XRD)patterns display that the samples are all single-phase solid solution structures(space group C 2/c).Differential scanning calorimetry(DSC)and the high-temperature XRD of 8NbTa cross-check that the addition of Ta element in 8HERN increases the phase transition temperature above 1400℃,which can be attributed to that the Ta/Nb co-doping at B site introduces the fluctuation of the bond strength of Ta-O and Nb-O.Secondly,compared to high-entropy rare-earth niobates,the introduction of Ta atoms at B site substantially reduce thermal conductivity(re-duced by 44%,800℃)with the seven components high entropy ceramic as an example.The low thermal conductivity means strong phonon scattering,which may originate from the softening acoustic mode and flattened phonon dispersion in 5–8 principal element high entropy rare earth niobium tantalates(5–8NbTa)revealed by the first-principles calculations.Thirdly,the Ta/Nb co-doping in 5–8NbTa systems can further optimize the insulation performance of oxygen ions.The oxygen-ion conductivity of 8NbTa(3.31×10^(−6)S cm^(−1),900℃)is about 5 times lower than that of 8HERN(15.8×10^(−6)S cm^(−1),900℃)because of the sluggish diffusion effect,providing better oxygen barrier capacity in 5–8NbTa systems to inhibit the overgrowth of the thermal growth oxide(TGO)of TBCs.In addition,influenced by lattice dis-tortion and solid solution strengthening,the samples possess higher hardness(7.51–8.15 GPa)and TECs(9.78×10^(−6)K−1^(-1)0.78×10^(−6)K^(−1),1500℃)than the single rare-earth niobates and tantalates.Based on their excellent overall properties,it is considered that 5–8NbTa can be used as auspicious TBCs.展开更多
In this paper,we present local functional law of the iterated logarithm for Cs?rg?-Révész type increments of fractional Brownian motion.The results obtained extend works of Gantert[Ann.Probab.,1993,21(2):104...In this paper,we present local functional law of the iterated logarithm for Cs?rg?-Révész type increments of fractional Brownian motion.The results obtained extend works of Gantert[Ann.Probab.,1993,21(2):1045-1049]and Monrad and Rootzén[Probab.Theory Related Fields,1995,101(2):173-192].展开更多
Water content, whether as free or lattice-bound water, is a crucial factor in determining the Earth's internal thermal state and plays a key role in volcanic eruptions, melting phenomena, and mantle convection rat...Water content, whether as free or lattice-bound water, is a crucial factor in determining the Earth's internal thermal state and plays a key role in volcanic eruptions, melting phenomena, and mantle convection rates. As electrical conductivity in the Earth's interior is highly sensitive to water content, it is an important geophysical parameter for understanding the deep Earth water content. Since its launch on May 21, 2023, the MSS-1(Macao Science Satellite-1) mission has operated for nearly one year, with its magnetometer achieving a precision of higher than 0.5 nT after orbital testing and calibration. Orbiting at 450 kilometers with a unique 41-degree inclination, the satellite enables high-density observations across multiple local times, allowing detailed monitoring of low-latitude regions and enhancing data for global conductivity imaging. To better understand the global distribution of water within the Earth's interior, it is crucial to study internal conductivity structure and water content distribution. To this aim, we introduce a method for using MSS-1 data to estamate induced magnetic fields related to magnetospheric currents. We then develop a trans-dimensional Bayesian approach to reveal Earth's internal conductivity, providing probable conductivity structure with an uncertainty analysis. Finally, by integrating known mineral composition, pressure, and temperature distribution within the mantle, we estimate the water content range in the mantle transition zone, concluding that this region may contain the equivalent of up to 3.0 oceans of water, providing compelling evidence that supports the hypothesis of a deep water cycle within the Earth's interior.展开更多
Laser-welded Ti-6Al-4 V is prone to severe residual stresses,microstructural variation,and structural de-fects which are known detrimental to the mechanical properties of weld joints.Residual stress removal is typical...Laser-welded Ti-6Al-4 V is prone to severe residual stresses,microstructural variation,and structural de-fects which are known detrimental to the mechanical properties of weld joints.Residual stress removal is typically applied to weld joints for engineering purposes via heat treatment,in order to avoid prema-ture failure and performance degradation.In the present work,we found that proper welding residual stresses in laser-welded Ti-6Al-4 V sheets can maintain better ductility during uniaxial tension,as op-posed to the stress-relieved counterparts.A detailed experimental investigation has been performed on the deformation behaviours of Ti-6Al-4 V butt welds,including residual stress distribution characteriza-tions by focused ion beam ring-coring coupled with digital image correlation(FIB-DIC),X-ray comput-erized tomography(CT)for internal voids,and in-situ DIC analysis of the subregional strain evolutions.It was found that the pores preferentially distributed near the fusion zone(FZ)boundary,where the compressive residual stress was up to-330 MPa.The removal of residual stress resulted in a changed failure initiation site from the base material to the FZ boundary,the former with ductile and the latter with brittle fracture characteristics under tensile deformation.The combined effects of residual stresses,microstructures,and internal pores on the mechanical responses are discussed in detail.This work high-lights the importance of inevitable residual stress and pores in laser weld pieces,leading to key insights for post-welding treatment and service performance evaluations.展开更多
Neurons are highly polarized cells with axons reaching over a meter long in adult humans.To survive and maintain their proper function,neurons depend on specific mechanisms that regulate spatiotemporal signaling and m...Neurons are highly polarized cells with axons reaching over a meter long in adult humans.To survive and maintain their proper function,neurons depend on specific mechanisms that regulate spatiotemporal signaling and metabolic events,which need to be carried out at the right place,time,and intensity.Such mechanisms include axonal transport,local synthesis,and liquid-liquid phase separations.Alterations and malfunctions in these processes are correlated to neurodegenerative diseases such as amyotrophic lateral sclerosis(ALS).展开更多
High thermal conductivity and high strength Mg-1.5Mn-2.5Ce alloy with a tensile yield strength of 387.0 MPa,ultimate tensile strength of 395.8 MPa,and thermal conductivity of 142.1 W/(m·K)was successfully fabrica...High thermal conductivity and high strength Mg-1.5Mn-2.5Ce alloy with a tensile yield strength of 387.0 MPa,ultimate tensile strength of 395.8 MPa,and thermal conductivity of 142.1 W/(m·K)was successfully fabricated via hot extrusion.The effects of La and Ce additions on the microstructure,thermal conductivity,and mechanical properties of the Mg-1.5Mn alloy were investigated.The results indicated that both the as-extruded Mg-1.5Mn-2.5La and Mg-1.5Mn-2.5Ce alloys exhibited a bimodal grain structure,with dynamically precipitated nano-scaleα-Mn phases.In comparison with La,the addition of Ce enhanced the dynamic precipitation more effectively during hot extrusion,while its influence on promoting the dynamic recrystallization was relatively weaker.The high tensile strength obtained in the as-extruded Mg-1.5Mn-2.5RE alloys can be attributed to the combined influence of the bimodal grain structure(with fine dynamic recrystallized(DRXed)grain size and high proportion of un-dynamic recrystallized(unDRXed)grains),dense nano-scale precipitates,and broken Mg12RE phases,while the remarkable thermal conductivity was due to the precipitation of Mn-rich phases from the Mg matrix.展开更多
Polymer dielectrics possessing excellent electrical insulation and high thermal conductivity are pivotal for dielectric capacitors at elevated temperatures.However,the integration of electrical insulation and thermal ...Polymer dielectrics possessing excellent electrical insulation and high thermal conductivity are pivotal for dielectric capacitors at elevated temperatures.However,the integration of electrical insulation and thermal conductivity in polymers remains a challenge.In this work,we present a feasible strategy to integrate high electrical insulation and high thermal conductivity by bonding carbon quantum dots(CQDs)with the diamine monomer of polyetherimide(PEI).The CQDs with Coulomb blockade effect serve as traps for the migrating of electrons in the dielectrics,while the bonding networks formed by CQDs and PEI further deepen the traps and augment trap density.As a result,the hybrid dielectrics(PEI-NH_(2)-CQDs)exhibit nearly an order of magnitude higher electrical resistivity than that of pure PEI,leading to an 80%increase in discharge energy density with an energy efficiency of 90%at 200℃ compared to pure counterpart.Additionally,this all-organic dielectric achieves a significantly increased thermal conductivity of 0.65 W m^(-1) K^(-1) compared to 0.26 W m^(-1) K^(-1) of PEI,which supports its cyclic stability at elevated temperatures.We also demonstrate the kilogram-scale production of CQDs,synthesizing over 8 kg in a single batch,paving the way for large-scale production of reliable PEI-NH_(2)-CQDs dielectrics.展开更多
Solid-state electrolytes(SSEs),as the core component within the next generation of key energy storage technologies-solid-state lithium batteries(SSLBs)-are significantly leading the development of future energy storag...Solid-state electrolytes(SSEs),as the core component within the next generation of key energy storage technologies-solid-state lithium batteries(SSLBs)-are significantly leading the development of future energy storage systems.Among the numerous types of SSEs,inorganic oxide garnet-structured superionic conductors Li7La3Zr2O12(LLZO)crystallized with the cubic Iaˉ3d space group have received considerable attention owing to their highly advantageous intrinsic properties encompassing reasonable lithium-ion conductivity,wide electrochemical voltage window,high shear modulus,and excellent chemical stability with electrodes.However,no SSEs possess all the properties necessary for SSLBs,thus both the ionic conductivity at room temperature and stability in ambient air regarding cubic garnet-based electrolytes are still subject to further improvement.Hence,this review comprehensively covers the nine key structural factors affecting the ion conductivity of garnet-based electrolytes comprising Li concentration,Li vacancy concentration,Li carrier concentration and mobility,Li occupancy at available sites,lattice constant,triangle bottleneck size,oxygen vacancy defects,and Li-O bonding interactions.Furthermore,the general illustration of structures and fundamental features being crucial to chemical stability is examined,including Li concentration,Li-site occupation behavior,and Li-O bonding interactions.Insights into the composition-structure-property relations among cubic garnet-based oxide ionic conductors from the perspective of their crystal structures,revealing the potential compatibility conflicts between ionic transportation and chemical stability resulting from Li-O bonding interactions.We believe that this review will lay the foundation for future reasonable structural design of oxide-based or even other types of superionic conductors,thus assisting in promoting the rapid development of alternative green and sustainable technologies.展开更多
A multi-phase heterogeneous FeCoNi-based high-entropy alloy is developed to overcome the trade-off between strength and ductility.By alloying with a small amount of Cu and employing a rapid recrystalliza-tion process,...A multi-phase heterogeneous FeCoNi-based high-entropy alloy is developed to overcome the trade-off between strength and ductility.By alloying with a small amount of Cu and employing a rapid recrystalliza-tion process,it exhibits a good combination of yield strength(roughly 1300 MPa)and ductility(approach-ing 20%).Firstly,a multi-phase heterogeneous structure is tailored ranging from nano to micron.Cu is efficiently precipitated as nanoscale clusters(4.2 nm),high-density cuboidal L1_(2) particles(20-40 nm)and L2_(1) particles(500-800 nm)are found to be embedded in the matrix and a bimodal heterogeneous grain structure(1-40μm)is constructed.Secondly,the introduction of Cu effectively suppresses the pre-cipitation of coarse L21 phase at grain boundaries,reducing its volume fraction by 80%and replaced by smaller-scale continuous precipitations within the grains.Thirdly,the high mixing enthalpy gap of Cu and the matrix leads to the formation of local chemical fluctuation and the consequential rugged topog-raphy in the matrix,which result in retarded dislocation motion and promotes dislocation plugging and interlocking during strain,enhancing yield stress and work hardening rate.This study provides a valuable perspective to enhance strength and ductility via enlarged local chemical fluctuation-tailored multi-phase heterogeneous structures.展开更多
Spectrum-based fault localization (SBFL) generates a ranked list of suspicious elements by using the program execution spectrum, but the excessive number of elements ranked in parallel results in low localization accu...Spectrum-based fault localization (SBFL) generates a ranked list of suspicious elements by using the program execution spectrum, but the excessive number of elements ranked in parallel results in low localization accuracy. Most researchers consider intra-class dependencies to improve localization accuracy. However, some studies show that inter-class method call type faults account for more than 20%, which means such methods still have certain limitations. To solve the above problems, this paper proposes a two-phase software fault localization based on relational graph convolutional neural networks (Two-RGCNFL). Firstly, in Phase 1, the method call dependence graph (MCDG) of the program is constructed, the intra-class and inter-class dependencies in MCDG are extracted by using the relational graph convolutional neural network, and the classifier is used to identify the faulty methods. Then, the GraphSMOTE algorithm is improved to alleviate the impact of class imbalance on classification accuracy. Aiming at the problem of parallel ranking of element suspicious values in traditional SBFL technology, in Phase 2, Doc2Vec is used to learn static features, while spectrum information serves as dynamic features. A RankNet model based on siamese multi-layer perceptron is constructed to score and rank statements in the faulty method. This work conducts experiments on 5 real projects of Defects4J benchmark. Experimental results show that, compared with the traditional SBFL technique and two baseline methods, our approach improves the Top-1 accuracy by 262.86%, 29.59% and 53.01%, respectively, which verifies the effectiveness of Two-RGCNFL. Furthermore, this work verifies the importance of inter-class dependencies through ablation experiments.展开更多
Heat dissipation performance is critical to the design of high-end equipment,such as integrated chips and high-precision machine tools.Owing to the advantages of artificial intelligence in solving complex tasks involv...Heat dissipation performance is critical to the design of high-end equipment,such as integrated chips and high-precision machine tools.Owing to the advantages of artificial intelligence in solving complex tasks involving a large number of variables,researchers have exploited deep learning to expedite the optimization of material properties,such as the heat dissipation of solid isotropic materials with penalization(SIMP).However,because the approach is limited by discrete datasets and labeled training forms,ensuring the continuous adaptation of the condition domain and maintaining the stability of the design structure remain major challenges in the current intelligent design methodology for thermally conductive structures.In this study,we propose an innovative intelligent design fram-ework integrating Conditional Deep Convolutional Generative Adversarial Networks(CDCGAN)with SIMP,capable of creating topology structures that meet prescribed thermal conduction performance.This proposed design strategy significantly reduces the computational time required to solve symmetric and random heat sink problems compared with existing design approaches and is approximately 98%faster than standard SIMP methods and 55.5%faster than conventional deep-learning-based methods.In addition,we benchmarked the design performance of the proposed framework against theoretical structural designs via experimental measurements.We observed a 50.1%reduction in the average temperature and a 28.2%reduction in the highest temperature in our designed topology compared with those theoretical structure designs.展开更多
The fast growth of mobile autonomous machines from traditional equipment to unmanned autonomous vehicles has fueled the demand for accurate and reliable localization solutions in diverse application domains.Ultra Wide...The fast growth of mobile autonomous machines from traditional equipment to unmanned autonomous vehicles has fueled the demand for accurate and reliable localization solutions in diverse application domains.Ultra Wide Band(UWB)technology has emerged as a promising candidate for addressing this need,offering high precision,immunity to multipath interference,and robust performance in challenging environments.In this comprehensive survey,we systematically explore UWB-based localization for mobile autonomous machines,spanning from fundamental principles to future trends.To the best of our knowledge,this review paper stands as the pioneer in systematically dissecting the algorithms of UWB-based localization for mobile autonomous machines,covering a spectrum from bottom-ranging schemes to advanced sensor fusion,error mitigation,and optimization techniques.By synthesizing existing knowledge,evaluating current methodologies,and highlighting future trends,this review aims to catalyze progress and innovation in the field,unlocking new opportunities for mobile autonomous machine applications across diverse industries and domains.Thus,it serves as a valuable resource for researchers,practitioners,and stakeholders interested in advancing the state-of-the-art UWB-based localization for mobile autonomous machines.展开更多
文摘Proton exchange membrane(PEM)is an integral component in fuel cells which enables proton transport for efficient energy conversion.Sulfonated Polyether Ether Ketone(SPEEK)has emerged as a cost-effective option with non-fluorinated aromatic backbones for Proton Exchange Membrane Fuel Cell(PEMFC)applications,even though it exhibits lower proton conductivity compared to Nafion.This work aims to study the influence of Sulfonated Chitosan(SCS)concentrations on proton conductivity of SPEEK-based PEM at room temperature.SPEEK was synthesized using a sulfonation process with concentrated sulfuric acid at room temperature.SCS was synthesized via reflux of CS and 1.2 M H2SO4 with a ratio of 1:35(w/v)at 90℃ for 30 min.The composite membranes of SPEEK-SCS were formed with four different SCS concentrations,using the solution castingmethod,andDimethyl Sulfoxide(DMSO)was used as a solvent.The composite membranes synthesized include pure SPEEK(S0),SPEEK with 1%SCS(S1),SPEEK with 2%SCS(S2),and SPEEK with 3%SCS(S3).Fourier transform infrared spectroscopy(FTIR),X-ray diffraction(XRD),water uptake,degree of swelling,Ionic exchange capacity(IEC)with Electrochemical impedance spectroscopy(EIS)were used to characterize the composite membranes in terms of composition,crystallinity,water absorption,dimensional changes,number of exchangeable ions in membranes,and proton conductivity,respectively.Notably,S3 had the highest water uptake and the lowest degree of swelling.S2 had the highest proton conductivity among the SPEEK-SCS composite membranes at room temperature with 3.44×10^(−2) Scm^(-1).
基金the support from the National Natural Science Foundation of China(52473083,52373089,52403085)Natural Science Basic Research Program of Shaanxi(2024JC-TBZC-04)+2 种基金the Innovation Capability Support Program of Shaanxi(2024RS-CXTD-57)Natural Science Basic Research Plan in Shaanxi Province of China(2024JC-YBMS-279)Natural Science Foundation of Chongqing,China(2023NSCQMSX2547)
文摘With the miniaturization and high-frequency evolution of antennas in 5G/6G communications,aerospace,and transportation,polymer composite papers integrating superior wave-transparent performance and thermal conductivity for radar antenna systems are urgently needed.Herein,a down-top strategy was employed to synthesize poly(p-phenylene benzobisoxazole)precursor nanofibers(prePNF).The prePNF was then uniformly mixed with fluorinated graphene(FG)to fabricate FG/PNF composite papers through consecutively suction filtration,hot-pressing,and thermal annealing.The hydroxyl and amino groups in prePNF enhanced the stability of FG/prePNF dispersion,while the increasedπ-πinteractions between PNF and FG after annealing improved their compatibility.The preparation time and cost of PNF paper was significantly reduced when applying this strategy,which enabled its large-scale production.Furthermore,the prepared FG/PNF composite papers exhibited excellent wave-transparent performance and thermal conductivity.When the mass fraction of FG was 40 wt%,the FG/PNF composite paper prepared via the down-top strategy achieved the wave-transparent coefficient(|T|2)of 96.3%under 10 GHz,in-plane thermal conductivity(λ_(∥))of 7.13 W m^(−1)K^(−1),and through-plane thermal conductivity(λ_(⊥))of 0.67 W m^(−1)K^(−1),outperforming FG/PNF composite paper prepared by the top-down strategy(|T|2=95.9%,λ_(∥)=5.52 W m^(−1)K^(−1),λ_(⊥)=0.52 W m^(−1)K^(−1))and pure PNF paper(|T|2=94.7%,λ_(∥)=3.04 W m^(−1)K^(−1),λ_(⊥)=0.24 W m^(−1)K^(−1)).Meanwhile,FG/PNF composite paper(with 40 wt%FG)through the down-top strategy also demonstrated outstanding mechanical properties with tensile strength and toughness reaching 197.4 MPa and 11.6 MJ m^(−3),respectively.
基金supported by Basic Science Research Program through the National Research Foundation of Korea(NRF)funded by the Ministry of Education(2021R1A6A1A10044950).
文摘The thermal conductivity of nanofluids is an important property that influences the heat transfer capabilities of nanofluids.Researchers rely on experimental investigations to explore nanofluid properties,as it is a necessary step before their practical application.As these investigations are time and resource-consuming undertakings,an effective prediction model can significantly improve the efficiency of research operations.In this work,an Artificial Neural Network(ANN)model is developed to predict the thermal conductivity of metal oxide water-based nanofluid.For this,a comprehensive set of 691 data points was collected from the literature.This dataset is split into training(70%),validation(15%),and testing(15%)and used to train the ANN model.The developed model is a backpropagation artificial neural network with a 4–12–1 architecture.The performance of the developed model shows high accuracy with R values above 0.90 and rapid convergence.It shows that the developed ANN model accurately predicts the thermal conductivity of nanofluids.
基金Project supported by the National Basic Research Program of China(Grant No.2009CB623702)the National Natural Science Foundation of China(Grant No.10904001)the Key Project Funding Scheme of Beijing Municipal Education Committee,China(Grant No.KZ201010005002)
文摘The local thermal conductivity of polycrystalline aluminum nitride （A1N） ceramics is measured and imaged by using a scanning thermal microscope （SThM） and complementary scanning electron microscope （SEM） based techniques at room temperature. The quantitative thermal conductivity for the A1N sample is gained by using a SThM with a spatial resolution of sub-micrometer scale through using the 3w method. A thermal conductivity of 308 W/m-K within grains corresponding to that of high-purity single crystal A1N is obtained. The slight differences in thermal conduction between the adjacent grains are found to result from crystallographic misorientations, as demonstrated in the electron backscattered diffraction. A much lower thermal conductivity at the grain boundary is due to impurities and defects enriched in these sites, as indicated by energy dispersive X-ray spectroscopy.
基金Supported by the National Natural Science Foundation of Chinathe National Fundamental Science Research Program.
文摘A numerical simulation in real space was developed to investigate weak localization corrections to the conductivity in inhomogeneous magnetic fields created by flux lines.Both cylinder model and exponential one of flux lines were studied.It was shown that the corrections are sensitive to the flux line structure.Comparing to the experiments of Bending et al.,the results show that the flux line in Pb film can be approximately described by the cylinder model.
基金Project supported by the Fundamental Research Fund for the Central Universities of Chinathe Research Project for Independently Cultivate Talents of Hebei Agricultural University (Grant No.ZY2023007)。
文摘Combining the mean field Pozhar-Gubbins(PG)theory and the weighted density approximation,a novel method for local thermal conductivity of inhomogeneous fluids is proposed.The correlation effect that is beyond the mean field treatment is taken into account by the simulation-based empirical correlations.The application of this method to confined argon in slit pore shows that its prediction agrees well with the simulation results,and that it performs better than the original PG theory as well as the local averaged density model(LADM).In its further application to the nano-fluidic films,the influences of fluid parameters and pore parameters on the thermal conductivity are calculated and investigated.It is found that both the local thermal conductivity and the overall thermal conductivity can be significantly modulated by these parameters.Specifically,in the supercritical states,the thermal conductivity of the confined fluid shows positive correlation to the bulk density as well as the temperature.However,when the bulk density is small,the thermal conductivity exhibits a decrease-increase transition as the temperature is increased.This is also the case in which the temperature is low.In fact,the decrease-increase transition in both the small-bulk-density and low-temperature cases arises from the capillary condensation in the pore.Furthermore,smaller pore width and/or stronger adsorption potential can raise the critical temperature for condensation,and then are beneficial to the enhancement of the thermal conductivity.These modulation behaviors of the local thermal conductivity lead immediately to the significant difference of the overall thermal conductivity in different phase regions.
文摘In recent years,there has been a growing global demand for carbon neutrality and energy efficiency,which are expected to become long-term trends.In the field of architecture,an effective approach to achieve this is to reduce heat loss in buildings.Vacuum insulation panels(VIPs),a type of high-performance insulation material,have been increasingly utilised in the construction industry and have played an increa-singly important role as their performance and manufacturing processes continue to improve.This paper provides a review of the factors affecting the thermal conductivity of VIPs and presents a detailed overview of the research progress on core materials,barrier films,and getters.The current research status of VIPs is summarised,including their thermal conductivity,service life,and thermal bridging effects,as well as their applications in the field of architecture.This review aims to provide a comprehensive understanding for relevant practitioners on the factors influencing the thermal conductivity of VIPs,and based on which,measures can be taken to produce VIPs with lower thermal conductivity and longer service life.
文摘The thermal conductivity of the soil skeletonλ;is an essential parameter from the point of view of the correct assessment of soil overall/effective conductivity.This work introduces the concept of“local thermal conductivity fluctuation”which characterizes the microscale variation of conductivity within the solid phase.It is proposed to link the“local fluctuation”of thermal conductivityλwith the soil texture-the information that is available at the scale of engineering applications.It was possible to relate the skeleton thermal conductivity with the grain size distribution of the soil.Finally,based on a large series of numerical simulations,the paper provides four triangle diagrams(at different organic matter contents:0%,2%,4%and 6%)relating the value ofλ;with volume fraction of individual soil separates.This result is extremely important from the practical point of view.One can quickly evaluateλ;value provided that information on the grain size distribution and organic matter content is available.
基金support from Yunnan Major Scientific and Technological Projects(No.202302AG050010)Yunnan Fundamental Research Projects(Nos.202101AW070011 and202101BE070001–015)+1 种基金National Natural Science Foundation of China(No.52303295)Project Funds of“Xingdian Talent Support Program”.
文摘Improving and optimizing the target properties of ceramics via the high entropy strategy has attracted significant attention.Rare earth niobate is a potential thermal barrier coating(TBCs)material,but its poor high-temperature phase stability limits its further application.In this work,four sets of TBCs high-entropy ceramics,(Sm_(1/5)Dy_(1/5)Ho_(1/5)Er_(1/5)Yb_(1/5))(Nb_(1/2)Ta_(1/2))O_(4)(5NbTa),(Sm_(1/6)Dy_(1/6)Ho_(1/6)Er_(1/6)Yb_(1/6)Lu_(1/6))(Nb_(1/2)Ta_(1/2))O_(4)(6NbTa),(Sm_(1/7)Gd_(1/7)Dy_(1/7)Ho_(1/7)Er_(1/7)Yb_(1/7)Lu_(1/7))(Nb_(1/2)Ta_(1/2))O_(4)(7NbTa),(Sm_(1/8)Gd_(1/8)Dy_(1/8)Ho_(1/8)Er_(1/8)Tm_(1/8)Yb_(1/8)Lu_(1/8))(Nb_(1/2)Ta_(1/2))O_(4)(8NbTa)are synthesized using a solid-state reaction method at 1650℃for 6 h.Firstly,the X-ray diffractometer(XRD)patterns display that the samples are all single-phase solid solution structures(space group C 2/c).Differential scanning calorimetry(DSC)and the high-temperature XRD of 8NbTa cross-check that the addition of Ta element in 8HERN increases the phase transition temperature above 1400℃,which can be attributed to that the Ta/Nb co-doping at B site introduces the fluctuation of the bond strength of Ta-O and Nb-O.Secondly,compared to high-entropy rare-earth niobates,the introduction of Ta atoms at B site substantially reduce thermal conductivity(re-duced by 44%,800℃)with the seven components high entropy ceramic as an example.The low thermal conductivity means strong phonon scattering,which may originate from the softening acoustic mode and flattened phonon dispersion in 5–8 principal element high entropy rare earth niobium tantalates(5–8NbTa)revealed by the first-principles calculations.Thirdly,the Ta/Nb co-doping in 5–8NbTa systems can further optimize the insulation performance of oxygen ions.The oxygen-ion conductivity of 8NbTa(3.31×10^(−6)S cm^(−1),900℃)is about 5 times lower than that of 8HERN(15.8×10^(−6)S cm^(−1),900℃)because of the sluggish diffusion effect,providing better oxygen barrier capacity in 5–8NbTa systems to inhibit the overgrowth of the thermal growth oxide(TGO)of TBCs.In addition,influenced by lattice dis-tortion and solid solution strengthening,the samples possess higher hardness(7.51–8.15 GPa)and TECs(9.78×10^(−6)K−1^(-1)0.78×10^(−6)K^(−1),1500℃)than the single rare-earth niobates and tantalates.Based on their excellent overall properties,it is considered that 5–8NbTa can be used as auspicious TBCs.
基金Supported by NSFC(Nos.11661025,12161024)Natural Science Foundation of Guangxi(Nos.2020GXNSFAA159118,2021GXNSFAA196045)+2 种基金Guangxi Science and Technology Project(No.Guike AD20297006)Training Program for 1000 Young and Middle-aged Cadre Teachers in Universities of GuangxiNational College Student's Innovation and Entrepreneurship Training Program(No.202110595049)。
文摘In this paper,we present local functional law of the iterated logarithm for Cs?rg?-Révész type increments of fractional Brownian motion.The results obtained extend works of Gantert[Ann.Probab.,1993,21(2):1045-1049]and Monrad and Rootzén[Probab.Theory Related Fields,1995,101(2):173-192].
基金financially supported by the National Natural Science Foundation of China(42250102,42250101)the Macao Foundation.
文摘Water content, whether as free or lattice-bound water, is a crucial factor in determining the Earth's internal thermal state and plays a key role in volcanic eruptions, melting phenomena, and mantle convection rates. As electrical conductivity in the Earth's interior is highly sensitive to water content, it is an important geophysical parameter for understanding the deep Earth water content. Since its launch on May 21, 2023, the MSS-1(Macao Science Satellite-1) mission has operated for nearly one year, with its magnetometer achieving a precision of higher than 0.5 nT after orbital testing and calibration. Orbiting at 450 kilometers with a unique 41-degree inclination, the satellite enables high-density observations across multiple local times, allowing detailed monitoring of low-latitude regions and enhancing data for global conductivity imaging. To better understand the global distribution of water within the Earth's interior, it is crucial to study internal conductivity structure and water content distribution. To this aim, we introduce a method for using MSS-1 data to estamate induced magnetic fields related to magnetospheric currents. We then develop a trans-dimensional Bayesian approach to reveal Earth's internal conductivity, providing probable conductivity structure with an uncertainty analysis. Finally, by integrating known mineral composition, pressure, and temperature distribution within the mantle, we estimate the water content range in the mantle transition zone, concluding that this region may contain the equivalent of up to 3.0 oceans of water, providing compelling evidence that supports the hypothesis of a deep water cycle within the Earth's interior.
基金supported by the National Key Re-search&Development Plan of China(No.2020YFA0405900)the Major Research Plan of the National Natural Science Foundation of China(No.92263201)Y.P.Xia would like to thank the support by the Jiangsu Funding Program for Excellent Postdoctoral Talent.All authors thank the Advanced Material Research Institute of Jiangsu Industrial Technology Research Institute(JITRI,Suzhou,China)for the experimental support.
文摘Laser-welded Ti-6Al-4 V is prone to severe residual stresses,microstructural variation,and structural de-fects which are known detrimental to the mechanical properties of weld joints.Residual stress removal is typically applied to weld joints for engineering purposes via heat treatment,in order to avoid prema-ture failure and performance degradation.In the present work,we found that proper welding residual stresses in laser-welded Ti-6Al-4 V sheets can maintain better ductility during uniaxial tension,as op-posed to the stress-relieved counterparts.A detailed experimental investigation has been performed on the deformation behaviours of Ti-6Al-4 V butt welds,including residual stress distribution characteriza-tions by focused ion beam ring-coring coupled with digital image correlation(FIB-DIC),X-ray comput-erized tomography(CT)for internal voids,and in-situ DIC analysis of the subregional strain evolutions.It was found that the pores preferentially distributed near the fusion zone(FZ)boundary,where the compressive residual stress was up to-330 MPa.The removal of residual stress resulted in a changed failure initiation site from the base material to the FZ boundary,the former with ductile and the latter with brittle fracture characteristics under tensile deformation.The combined effects of residual stresses,microstructures,and internal pores on the mechanical responses are discussed in detail.This work high-lights the importance of inevitable residual stress and pores in laser weld pieces,leading to key insights for post-welding treatment and service performance evaluations.
文摘Neurons are highly polarized cells with axons reaching over a meter long in adult humans.To survive and maintain their proper function,neurons depend on specific mechanisms that regulate spatiotemporal signaling and metabolic events,which need to be carried out at the right place,time,and intensity.Such mechanisms include axonal transport,local synthesis,and liquid-liquid phase separations.Alterations and malfunctions in these processes are correlated to neurodegenerative diseases such as amyotrophic lateral sclerosis(ALS).
基金supported by National Key Research&Development Program of China(Grant Nos.2021YFB3703300,2021YFE010016 and 2020YFA0405900)National Natural Science Foundation(Grant Nos.52220105003 and 51971075)+2 种基金the Fundamental Research Funds for the Central Universities(Grant No.FRFCU5710000918)Natural Science Foundation of Heilongjiang Province-Outstanding Youth Fund(Grant No.YQ2020E006)JSPS KAKENHI(Grant No.JP21H01669).
文摘High thermal conductivity and high strength Mg-1.5Mn-2.5Ce alloy with a tensile yield strength of 387.0 MPa,ultimate tensile strength of 395.8 MPa,and thermal conductivity of 142.1 W/(m·K)was successfully fabricated via hot extrusion.The effects of La and Ce additions on the microstructure,thermal conductivity,and mechanical properties of the Mg-1.5Mn alloy were investigated.The results indicated that both the as-extruded Mg-1.5Mn-2.5La and Mg-1.5Mn-2.5Ce alloys exhibited a bimodal grain structure,with dynamically precipitated nano-scaleα-Mn phases.In comparison with La,the addition of Ce enhanced the dynamic precipitation more effectively during hot extrusion,while its influence on promoting the dynamic recrystallization was relatively weaker.The high tensile strength obtained in the as-extruded Mg-1.5Mn-2.5RE alloys can be attributed to the combined influence of the bimodal grain structure(with fine dynamic recrystallized(DRXed)grain size and high proportion of un-dynamic recrystallized(unDRXed)grains),dense nano-scale precipitates,and broken Mg12RE phases,while the remarkable thermal conductivity was due to the precipitation of Mn-rich phases from the Mg matrix.
基金supported by the National Natural Science Foundation of China(52172265)Excellent Youth Science Foundation of Hunan Province(2022JJ20067)+1 种基金The Science and Technology Innovation Program of Hunan Province(2022RC1074)Central South University Innovation-Driven Research Program(2023CXQD010).
文摘Polymer dielectrics possessing excellent electrical insulation and high thermal conductivity are pivotal for dielectric capacitors at elevated temperatures.However,the integration of electrical insulation and thermal conductivity in polymers remains a challenge.In this work,we present a feasible strategy to integrate high electrical insulation and high thermal conductivity by bonding carbon quantum dots(CQDs)with the diamine monomer of polyetherimide(PEI).The CQDs with Coulomb blockade effect serve as traps for the migrating of electrons in the dielectrics,while the bonding networks formed by CQDs and PEI further deepen the traps and augment trap density.As a result,the hybrid dielectrics(PEI-NH_(2)-CQDs)exhibit nearly an order of magnitude higher electrical resistivity than that of pure PEI,leading to an 80%increase in discharge energy density with an energy efficiency of 90%at 200℃ compared to pure counterpart.Additionally,this all-organic dielectric achieves a significantly increased thermal conductivity of 0.65 W m^(-1) K^(-1) compared to 0.26 W m^(-1) K^(-1) of PEI,which supports its cyclic stability at elevated temperatures.We also demonstrate the kilogram-scale production of CQDs,synthesizing over 8 kg in a single batch,paving the way for large-scale production of reliable PEI-NH_(2)-CQDs dielectrics.
基金supported by the National Natural Science Foundation of China(Nos.22171102 and 22090044)the National Key R&D Program of China(Nos.2021YFF0500502 and 2023YFA1506304)+2 种基金the Jilin Province Science and Technology Development Plan(No.20230101024JC)the"Medicine+X"crossinnovation team of Bethune Medical Department of Jilin University"Leading the Charge with Open Competition"construction project(No.2022JBGS04)the Jilin University Graduate Training Office(Nos.2021JGZ08 and 2022YJSJIP20).
文摘Solid-state electrolytes(SSEs),as the core component within the next generation of key energy storage technologies-solid-state lithium batteries(SSLBs)-are significantly leading the development of future energy storage systems.Among the numerous types of SSEs,inorganic oxide garnet-structured superionic conductors Li7La3Zr2O12(LLZO)crystallized with the cubic Iaˉ3d space group have received considerable attention owing to their highly advantageous intrinsic properties encompassing reasonable lithium-ion conductivity,wide electrochemical voltage window,high shear modulus,and excellent chemical stability with electrodes.However,no SSEs possess all the properties necessary for SSLBs,thus both the ionic conductivity at room temperature and stability in ambient air regarding cubic garnet-based electrolytes are still subject to further improvement.Hence,this review comprehensively covers the nine key structural factors affecting the ion conductivity of garnet-based electrolytes comprising Li concentration,Li vacancy concentration,Li carrier concentration and mobility,Li occupancy at available sites,lattice constant,triangle bottleneck size,oxygen vacancy defects,and Li-O bonding interactions.Furthermore,the general illustration of structures and fundamental features being crucial to chemical stability is examined,including Li concentration,Li-site occupation behavior,and Li-O bonding interactions.Insights into the composition-structure-property relations among cubic garnet-based oxide ionic conductors from the perspective of their crystal structures,revealing the potential compatibility conflicts between ionic transportation and chemical stability resulting from Li-O bonding interactions.We believe that this review will lay the foundation for future reasonable structural design of oxide-based or even other types of superionic conductors,thus assisting in promoting the rapid development of alternative green and sustainable technologies.
基金financial support from the National Natural Science Foundation of China(Nos.52104306,52274301,52334009)the Aeronautical Science Foundation of China(No.2023Z0530S6005)+3 种基金the National Key Research and Development Program of China(No.2023YFB3712401)the Science and Technology Commission of Shanghai Municipality(No.21DZ1208900)the Academician Workstation of Kunming University of Science and Technology(2024),the Ningbo Yongjiang Talent-Introduction Programme(No.2022A-023-C)the Zhejiang Phenomenological Materials Technology Co.,Ltd.,China.
文摘A multi-phase heterogeneous FeCoNi-based high-entropy alloy is developed to overcome the trade-off between strength and ductility.By alloying with a small amount of Cu and employing a rapid recrystalliza-tion process,it exhibits a good combination of yield strength(roughly 1300 MPa)and ductility(approach-ing 20%).Firstly,a multi-phase heterogeneous structure is tailored ranging from nano to micron.Cu is efficiently precipitated as nanoscale clusters(4.2 nm),high-density cuboidal L1_(2) particles(20-40 nm)and L2_(1) particles(500-800 nm)are found to be embedded in the matrix and a bimodal heterogeneous grain structure(1-40μm)is constructed.Secondly,the introduction of Cu effectively suppresses the pre-cipitation of coarse L21 phase at grain boundaries,reducing its volume fraction by 80%and replaced by smaller-scale continuous precipitations within the grains.Thirdly,the high mixing enthalpy gap of Cu and the matrix leads to the formation of local chemical fluctuation and the consequential rugged topog-raphy in the matrix,which result in retarded dislocation motion and promotes dislocation plugging and interlocking during strain,enhancing yield stress and work hardening rate.This study provides a valuable perspective to enhance strength and ductility via enlarged local chemical fluctuation-tailored multi-phase heterogeneous structures.
基金funded by the Youth Fund of the National Natural Science Foundation of China(Grant No.42261070).
文摘Spectrum-based fault localization (SBFL) generates a ranked list of suspicious elements by using the program execution spectrum, but the excessive number of elements ranked in parallel results in low localization accuracy. Most researchers consider intra-class dependencies to improve localization accuracy. However, some studies show that inter-class method call type faults account for more than 20%, which means such methods still have certain limitations. To solve the above problems, this paper proposes a two-phase software fault localization based on relational graph convolutional neural networks (Two-RGCNFL). Firstly, in Phase 1, the method call dependence graph (MCDG) of the program is constructed, the intra-class and inter-class dependencies in MCDG are extracted by using the relational graph convolutional neural network, and the classifier is used to identify the faulty methods. Then, the GraphSMOTE algorithm is improved to alleviate the impact of class imbalance on classification accuracy. Aiming at the problem of parallel ranking of element suspicious values in traditional SBFL technology, in Phase 2, Doc2Vec is used to learn static features, while spectrum information serves as dynamic features. A RankNet model based on siamese multi-layer perceptron is constructed to score and rank statements in the faulty method. This work conducts experiments on 5 real projects of Defects4J benchmark. Experimental results show that, compared with the traditional SBFL technique and two baseline methods, our approach improves the Top-1 accuracy by 262.86%, 29.59% and 53.01%, respectively, which verifies the effectiveness of Two-RGCNFL. Furthermore, this work verifies the importance of inter-class dependencies through ablation experiments.
基金Supported by National Natural Science Foundation of China(Grant Nos.52222508 and 52335011)。
文摘Heat dissipation performance is critical to the design of high-end equipment,such as integrated chips and high-precision machine tools.Owing to the advantages of artificial intelligence in solving complex tasks involving a large number of variables,researchers have exploited deep learning to expedite the optimization of material properties,such as the heat dissipation of solid isotropic materials with penalization(SIMP).However,because the approach is limited by discrete datasets and labeled training forms,ensuring the continuous adaptation of the condition domain and maintaining the stability of the design structure remain major challenges in the current intelligent design methodology for thermally conductive structures.In this study,we propose an innovative intelligent design fram-ework integrating Conditional Deep Convolutional Generative Adversarial Networks(CDCGAN)with SIMP,capable of creating topology structures that meet prescribed thermal conduction performance.This proposed design strategy significantly reduces the computational time required to solve symmetric and random heat sink problems compared with existing design approaches and is approximately 98%faster than standard SIMP methods and 55.5%faster than conventional deep-learning-based methods.In addition,we benchmarked the design performance of the proposed framework against theoretical structural designs via experimental measurements.We observed a 50.1%reduction in the average temperature and a 28.2%reduction in the highest temperature in our designed topology compared with those theoretical structure designs.
文摘The fast growth of mobile autonomous machines from traditional equipment to unmanned autonomous vehicles has fueled the demand for accurate and reliable localization solutions in diverse application domains.Ultra Wide Band(UWB)technology has emerged as a promising candidate for addressing this need,offering high precision,immunity to multipath interference,and robust performance in challenging environments.In this comprehensive survey,we systematically explore UWB-based localization for mobile autonomous machines,spanning from fundamental principles to future trends.To the best of our knowledge,this review paper stands as the pioneer in systematically dissecting the algorithms of UWB-based localization for mobile autonomous machines,covering a spectrum from bottom-ranging schemes to advanced sensor fusion,error mitigation,and optimization techniques.By synthesizing existing knowledge,evaluating current methodologies,and highlighting future trends,this review aims to catalyze progress and innovation in the field,unlocking new opportunities for mobile autonomous machine applications across diverse industries and domains.Thus,it serves as a valuable resource for researchers,practitioners,and stakeholders interested in advancing the state-of-the-art UWB-based localization for mobile autonomous machines.
