Composite materials exhibit the impressive mechanical properties of high damping and stiffness,which cannot be attained by employing conventional single materials.Along these lines,a novel material architecture is pre...Composite materials exhibit the impressive mechanical properties of high damping and stiffness,which cannot be attained by employing conventional single materials.Along these lines,a novel material architecture is presented in this work in order to fabricate composites with enhanced mechanical characteristics.More specifically,entangled metallic wire materials were used as the active matrix,whereas polyurethane was employed as the reinforcement elements.As a result,an entangled metallic wire material-polyurethane composite with high damping and stiffness was prepared by enforcing the vacuum infiltration method.On top of that,the mechanical properties(loss factor,energy consumption,and average stiffness)of the proposed composite materials were characterized by performing dynamic tests,and its fatigue characteristics were verified by the micro-interface bonding,as well as the macro-damage factor.The impact of the density,preloading spacing,loading amplitude,and exciting frequency on the mechanical properties of the composites were also thoroughly analyzed.The extracted results indicate that the mechanical properties of the composites were significantly enhanced than those of the pure materials due to the introduction of interface friction.Moreover,the average stiffness of the composites was about 10 times the respective value of the entangled metallic wire material.Interestingly,a rise in the loading period leads to some failure between the composite interfaces,which reduces the stiffness property but enhances the damping dissipation properties.Finally,a comprehensive dynamic mechanical model of the composites was established,while it was experimentally verified.The proposed composites possess higher damping features,i.e.,stiffness characteristics,and maintain better fatigue characteristics,which can broaden the application range of the composites.In addition,we provide a theoretical and experimental framework for the research and applications in the field of metal matrix composites.展开更多
Face-centered cubic (f.c.c.) high entropy alloys (HEAs) are attracting more and more attention owing to their excellent strength and ductility synergy, irradiation resistance, etc. However, the yield strength of f.c.c...Face-centered cubic (f.c.c.) high entropy alloys (HEAs) are attracting more and more attention owing to their excellent strength and ductility synergy, irradiation resistance, etc. However, the yield strength of f.c.c. HEAs is generally low, significantly limiting their practical applications. Recently, the alloying of W has been evidenced to be able to remarkably improve the mechanical properties of f.c.c. HEAs and is becoming a hot topic in the community of HEAs. To date, when W is introduced, multiple strengthening mechanisms, including solid-solution strengthening, precipitation strengthening (μphase,σphase, and b.c.c. phase), and grain-refinement strengthening, have been discovered to be activated or enhanced. Apart from mechanical properties, the addition of W improves corrosion resistance as W helps to form a dense WO_(3) film on the alloy surface. Until now, despite the extensive studies in the literature, there is no available review paper focusing on the W doping of the f.c.c. HEAs. In that context, the effects of W doping on f.c.c. HEAs were reviewed in this work from three aspects, i.e., microstructure,mechanical property, and corrosion resistance. We expect this work can advance the application of the W alloying strategy in the f.c.c. HEAs.展开更多
Understanding the adsorption interactions between carbon materials and sulfur compounds has far-reaching impacts,in addition to their well-known important role in energy storage and conversion,such as lithium-ion batt...Understanding the adsorption interactions between carbon materials and sulfur compounds has far-reaching impacts,in addition to their well-known important role in energy storage and conversion,such as lithium-ion batteries.In this paper,properties of intrinsic B or Si single-atom doped,and B-Si codoped graphene(GR)and graphdiyne(GDY)were investigated by using density functional theory-based calculations,in which the optimal doping configurations were explored for potential applications in adsorbing sulfur compounds.Results showed that both B or Si single-atom doping and B-Si codoping could substantially enhance the electron transport properties of GR and GDY,improving their surface activity.Notably,B and Si atoms displayed synergistic effects for the codoped configurations,where B-Si codoped GR/GDY exhibited much better performance in the adsorption of sulfurcontaining chemicals than single-atom doped systems.In addition,results demonstrated that,after B-Si codoping,the adsorption energy and charge transfer amounts of GDY with sulfur compounds were much larger than those of GR,indicating that B-Si codoped GDY might be a favorable material for more effectively interacting with sulfur reagents.展开更多
Thermal runaway(TR)is a critical issue hindering the large-scale application of lithium-ion batteries(LIBs).Understanding the thermal safety behavior of LIBs at the cell and module level under different state of charg...Thermal runaway(TR)is a critical issue hindering the large-scale application of lithium-ion batteries(LIBs).Understanding the thermal safety behavior of LIBs at the cell and module level under different state of charges(SOCs)has significant implications for reinforcing the thermal safety design of the lithium-ion battery module.This study first investigates the thermal safety boundary(TSB)correspondence at the cells and modules level under the guidance of a newly proposed concept,safe electric quantity boundary(SEQB).A reasonable thermal runaway propagation(TRP)judgment indicator,peak heat transfer power(PHTP),is proposed to predict whether TRP occurs.Moreover,a validated 3D model is used to quantitatively clarify the TSB at different SOCs from the perspective of PHTP,TR trigger temperature,SOC,and the full cycle life.Besides,three different TRP transfer modes are discovered.The interconversion relationship of three different TRP modes is investigated from the perspective of PHTP.This paper explores the TSB of LIBs under different SOCs at both cell and module levels for the first time,which has great significance in guiding the thermal safety design of battery systems.展开更多
The advent of Industry 4.0 has compelled businesses to adopt digital approaches that combine software toenhance production efficiency. In this rapidly evolving market, software development is an ongoing process thatmu...The advent of Industry 4.0 has compelled businesses to adopt digital approaches that combine software toenhance production efficiency. In this rapidly evolving market, software development is an ongoing process thatmust be tailored to meet the dynamic needs of enterprises. However, internal research and development can beprohibitively expensive, driving many enterprises to outsource software development and upgrades to externalservice providers. This paper presents a software upgrade outsourcing model for enterprises and service providersthat accounts for the impact of market fluctuations on software adaptability. To mitigate the risk of adverseselection due to asymmetric information about the service provider’s cost and asymmetric information aboutthe enterprise’s revenues, we propose pay-per-time and revenue-sharing contracts in two distinct informationasymmetry scenarios. These two contracts specify the time and transfer payments for software upgrades. Througha comparative analysis of the optimal solutions under the two contracts and centralized decision-making withfull-information, we examine the characteristics of the solutions under two information asymmetry scenarios andanalyze the incentive effects of the two contracts on the various stakeholders. Overall, our study offers valuableinsights for firms seeking to optimize their outsourcing strategies and maximize their returns on investment insoftware upgrades.展开更多
A new,innovative vibration cast-rolling technology of “electromagnetic stirring+dendrite breaking+asynchronous rolling” was proposed with the adoption of sinusoidal vibration of crystallization roller to prepare Ti/...A new,innovative vibration cast-rolling technology of “electromagnetic stirring+dendrite breaking+asynchronous rolling” was proposed with the adoption of sinusoidal vibration of crystallization roller to prepare Ti/Al laminated composites,and the effect of sinusoidal vibration of crystallization roller on composite microstructure was investigated in detail.The results show that the metallurgical bonding of titanium and aluminum is realized by mesh interweaving and mosaic meshing,instead of transition bonding by forming metal compound layer.The meshing depth between titanium and aluminum layers (6.6μm) of cast-rolling materials with strong vibration of crystallization roller (amplitude 0.87 mm,vibration frequency 25 Hz) is doubled compared with that of traditional cast-rolling materials (3.1μm),and the composite interfacial strength(27.0 N/mm) is twice as high as that of traditional cast-rolling materials (14.9 N/mm).This is because with the action of high-speed superposition of strong tension along the rolling direction,strong pressure along the width direction and rolling force,the composite linearity evolves from "straight line" with traditional casting-rolling to "curved line",and the depth and number of cracks in the interface increases greatly compared with those with traditional cast-rolling,which leads to the deep expansion of the meshing area between interfacial layers and promotes the stable enhancement of composite quality.展开更多
This paper presented a novel tinny motion capture system for measuring bird posture based on inertial and magnetic measurement units that are made up of micromachined gyroscopes, accelerometers, and magnetometers. Mul...This paper presented a novel tinny motion capture system for measuring bird posture based on inertial and magnetic measurement units that are made up of micromachined gyroscopes, accelerometers, and magnetometers. Multiple quaternion-based extended Kalman filters were implemented to estimate the absolute orientations to achieve high accuracy.Under the guidance of ornithology experts, the extending/contracting motions and flapping cycles were recorded using the developed motion capture system, and the orientation of each bone was also analyzed. The captured flapping gesture of the Falco peregrinus is crucial to the motion database of raptors as well as the bionic design.展开更多
In this paper, the issues of stochastic stability analysis and fault estimation are investigated for a class of continuoustime Markov jump piecewise-affine(PWA) systems against actuator and sensor faults. Firstly, a n...In this paper, the issues of stochastic stability analysis and fault estimation are investigated for a class of continuoustime Markov jump piecewise-affine(PWA) systems against actuator and sensor faults. Firstly, a novel mode-dependent PWA iterative learning observer with current feedback is designed to estimate the system states and faults, simultaneously, which contains both the previous iteration information and the current feedback mechanism. The auxiliary feedback channel optimizes the response speed of the observer, therefore the estimation error would converge to zero rapidly. Then, sufficient conditions for stochastic stability with guaranteed performance are demonstrated for the estimation error system, and the equivalence relations between the system information and the estimated information can be established via iterative accumulating representation.Finally, two illustrative examples containing a class of tunnel diode circuit systems are presented to fully demonstrate the effectiveness and superiority of the proposed iterative learning observer with current feedback.展开更多
Centrifugal pumps are widely used in the metallurgy,coal,and building sectors.In order to study the hydraulic characteristics of a closed impeller centrifugal pump during its shutdown in the so-called power frequency ...Centrifugal pumps are widely used in the metallurgy,coal,and building sectors.In order to study the hydraulic characteristics of a closed impeller centrifugal pump during its shutdown in the so-called power frequency and frequency conversion modes,experiments were carried to determine the characteristic evolution of parameters such as speed,inlet and outlet pressure,head,flow rate and shaft power.A quasi-steady-state method was also used to further investigate these transient behaviors.The results show that,compared to the power frequency input,the performance parameter curves for the frequency conversion input are less volatile and smoother.The characteristic time is longer and the response to shutdown is slower.The quasi-steady-state theoretical head-flow curves match the experimental head-flow curves more closely at low flow rates when the frequency conversion input is considered.Moreover,in this case,the similarity law predicts the hydraulic performance more accurately.展开更多
The C.oleifera oil processing industry generates large amounts of solid wastes,including C.oleifera shell(COS)and C.oleifera cake(COC).Distinct from generally acknowledged lignocellulosic biomass(corn stover,bamboo,bi...The C.oleifera oil processing industry generates large amounts of solid wastes,including C.oleifera shell(COS)and C.oleifera cake(COC).Distinct from generally acknowledged lignocellulosic biomass(corn stover,bamboo,birch,etc.),Camellia wastes contain diverse bioactive substances in addition to the abundant lignocellulosic components,and thus,the biorefinery utilization of C.oleifera processing byproducts involves complicated processing technologies.This reviewfirst summarizes various technologies for extracting and converting the main components in C.oleifera oil processing byproducts into value-added chemicals and biobased materials,as well as their potential applications.Microwave,ultrasound,and Soxhlet extractions are compared for the extraction of functional bioactive components(tannin,flavonoid,saponin,etc.),while solvothermal conversion and pyrolysis are discussed for the conversion of lignocellulosic components into value-added chemicals.The application areas of these chemicals according to their properties are introduced in detail,including utilizing antioxidant and anti-in-flammatory properties of the bioactive substances for the specific application,as well as drop-in chemicals for the substitution of unrenewable fossil fuel-derived products.In addition to chemical production,biochar fabricated from COS and its applications in thefields of adsorption,supercapacitor,soil remediation and wood composites are comprehensively reviewed and discussed.Finally,based on the compositions and structural characteristics of C.oleifera byproducts,the development of full-component valorization strategies and the expansion of the appli-cationfields are proposed.展开更多
This paper discussed the experimental results of the performance of an organic Rankine cycle(ORC)system with an ultra-low temperature heat source.The low boiling point working medium R134a was adopted in the system.Th...This paper discussed the experimental results of the performance of an organic Rankine cycle(ORC)system with an ultra-low temperature heat source.The low boiling point working medium R134a was adopted in the system.The simulated heat source temperature(SHST)in this work was set from 39.51°C to 48.60°C by the simulated heat source module.The influence of load percentage of simulated heat source(LPSHS)between 50%and 70%,the rotary valve opening(RVO)between 20%and 100%,the resistive load between 36Ωand 180Ωor the no-load of the generator,as well as the autumn and winter ambient temperature on the system performance were studied.The results showed that the stability of the system was promoted when the generator had a resistive load.The power generation(PG)and generator speed(GS)of the system in autumn were better than in winter,but the expander pressure ratio(EPR)was lower than in winter.Keep RVO unchanged,the SHST,the mass flow rate(MFR)of the working medium,GS,and the PG of the system increased with the increasing of LPSHS for different generator resistance load values.When the RVO was 60%,LPSHS was 70%,the SHST was 44.15°C and the resistive load was 72Ω,the highest PG reached 15.11 W.Finally,a simulation formula was obtained for LPSHS,resistance load,and PG,and its correlation coefficient was between 0.9818 and 0.9901.The formula can accurately predict the PG.The experimental results showed that the standard deviation between the experimental and simulated values was below 0.0792,and the relative error was within±5%.展开更多
On the basis of the traditional mechanical model of a grinding wheel rotor and the mechanical-electric coupling model with ideal sinusoidal supply,taking high-frequency converting current of inverter power switches in...On the basis of the traditional mechanical model of a grinding wheel rotor and the mechanical-electric coupling model with ideal sinusoidal supply,taking high-frequency converting current of inverter power switches into further consideration,a modified mechanical-electric coupling model is created.The created model consists of an inverter,a motorized spindle,a grinding wheel and grinding loads.Some typical non-stationary processes of the grinding system with two different supplies,including the starting,the speed rising and the break in grinding loads,are compared by making use of the created model.One supply is an ideal sinusoida]voltage source,the other is an inverter.The theoretical analysis of the high-order harmonic is also compared with the experimental result.The material strategy of suppressing high-order harmonic mechanical-electric coupling vibration by optimizing inverter operating parameters is proposed.展开更多
In order to establish the rolling process parameters of grade-2 commercially pure titanium(CP-Ti),it is necessary to understand the transformation mechanism and mechanical properties of this material.The β→α transf...In order to establish the rolling process parameters of grade-2 commercially pure titanium(CP-Ti),it is necessary to understand the transformation mechanism and mechanical properties of this material.The β→α transformation kinetics of the grade-2 CP-Ti during continuous cooling was measured and its hot compression behavior was investigated using Gleeble-1500 thermal mechanical simulator.Dynamic CCT diagram confirms that cooling rate has an obvious effect on the start and finishing transformation and microstructures at room temperature.The critical cooling rate for β-phase transforms to α phase is about 15 °C/s.When the cooling rate is higher than 15 °C/s,some β phases with fine granular shape remain residually into plate-like structure.The plate-like α phase forms at cooling rate lower than 2 °C/s,serrate α phase forms at medium cooling rates,about 5-15 °C/s.The flow stress behavior of grade-2 CP-Ti was investigated in a temperature range of 700-900 °C and strain rate of 3.6-40 mm/min.The results show that dynamic recrystallization,dynamic recovery and work-hardening obviously occur during hot deformation.Constitutive equation of grade-2 CP-Ti was established by analyzing the relationship of the deformation temperature,strain rate,deformation degree and deformation resistance.展开更多
ZA 27 alloys reinforced by Mn containing intermetallic compounds were prepared and the effect of Mn content on their mechanical properties were examined. By adding Mn, rare earth elements(RE) and Ti into ZA 27, experi...ZA 27 alloys reinforced by Mn containing intermetallic compounds were prepared and the effect of Mn content on their mechanical properties were examined. By adding Mn, rare earth elements(RE) and Ti into ZA 27, experimental alloys were fabricated by sand casting. The volume fraction, grain size and morphology of the Mn containing intermetallic compound phases vary with the changing of Mn content. Mechanical properties of the reinforced ZA 27 alloys at elevated temperatures were measured. The results show that the hardness, compressive strength and compressibility of experimental alloys increase with increasing Mn content until they reach a maximum at 0.5% Mn. Excessive and coarse hard phases would act as crack origins instead of dispersion strengthening particles. Best tensile properties of these alloys at elevated temperature can be achieved at a Mn content of 0.18 %.展开更多
The aim of this study was to simulate the solidification process of beam blank continuous casting, and then find the reasons for the typical defects of the beam blank. A two-dimensional transient coupled finite elemen...The aim of this study was to simulate the solidification process of beam blank continuous casting, and then find the reasons for the typical defects of the beam blank. A two-dimensional transient coupled finite element model has been developed to compute the temperature and stress profile in beam blank continuous casting. The enthalpy method was used in the heat conduction equation. The thermo-mechanical property in the mushy zone was taken into consideration in this calculation. It is shown that at the mold exit the thickness of the shell had its maximum value at the flange tip and its minimum value at the fillet. The temperature had a great fluctuation on the surface of the beam blank in the secondary cooling zone. At the unbending point, the surface temperature of the web was in the brittleness temperature range under the present condition. To ensure the quality, it is necessary to weaken the intensity of secondary cooling. At the mold exit the equivalent stress and strain have higher values at the flange tip and at the web. From the spray 1 to the unbending point, the maximum values of stress and strain gradually moved to the internal section of the flange tip and the web. However, whenever, there were bigger stress and strain values near the flange tip and the web than in the other parts, it must be very easy to generate cracks at those positions. Now, online verification of this simulation has been developed, which has proved to be very useful and efficient to instruct the practical production of beam blank continuous casting.展开更多
gradient aluminum alloy was prepared by semi-continuous casting using double-stream-pouring technique. The microstructures of the as-cast, pressed and heat-treated alloys were analyzed by scanning electron microscope ...gradient aluminum alloy was prepared by semi-continuous casting using double-stream-pouring technique. The microstructures of the as-cast, pressed and heat-treated alloys were analyzed by scanning electron microscope and transmission electron microscope. And the mechanical properties of the alloy in pressed and heat-treated states were studied. The results show that the ingots with diameter of 65 mm and external thickness （about） 5.5 mm are obtained when the temperatures of the melt in the internal and external ladles are 1 023 and 1 003 K, respectively, and the nozzle diameter is 2.0 mm. The microstructures of the as-cast alloy consist of α（Al）+（θ（CuAl2））+S（Al2CuMg） in the internal region and （α（Al）+MnAl6） in the external region. The phases found in the internal and external layers coexist in the transition zone. The transition layer is maintained after plastic deformation and heat treatment of the alloy. The tensile strength, yield strength and elongation of the alloy are 300 MPa, 132 MPa and 16.0%, respectively, after T6 treatment. The tensile and yield strength are increased by 150.0% and （94.1%,） respectively, compared with that of 3003 aluminum alloy. The maximum hardness in the internal region of 2024/3003 gradient aluminum alloy can be increased from HRF 55 in the pressed state to HRF 70 in the heat-treated state.展开更多
Mechanical properties and tribological behavior of a novel cast heat resisting copper based alloy are investigated. The corresponding properties of a commercial aluminum bronze C95500 (ASTM B30) are compared with the ...Mechanical properties and tribological behavior of a novel cast heat resisting copper based alloy are investigated. The corresponding properties of a commercial aluminum bronze C95500 (ASTM B30) are compared with the alloy. The results show that the alloy possesses better mechanical properties and tribological behaviors than that of C95500 at elevated temperature. The tensile strength, elongation and hardness at 500℃ are 470MPa, 2.5% and HB220, respectively. The wear rate of the developed alloy at ambient and elevated temperature is about one sixth and one fortieth of that of C95500, respectively. The alloy is very suitable for ma nufacturing heat resisting and wear resisting parts. Major strengthening mechanisms for the alloy are solution strengthening and the second phase strengthening.展开更多
A diamond-like carbon(DLC) film was deposited on YT14 substrate using magnetron sputtering(MS). The surface morphologies, roughness and bonding spectra of obtained film were characterized using scanning electron micro...A diamond-like carbon(DLC) film was deposited on YT14 substrate using magnetron sputtering(MS). The surface morphologies, roughness and bonding spectra of obtained film were characterized using scanning electron microscopy(SEM), atomic force microscopy(AFM), and X-ray photoelectron spectroscopy(XPS), respectively, and its mechanical property and bonding strength were measured using a nanoindentation and scratch tester, respectively. The results show that the C-enriched DLC film exhibits a denser microstructure and smoother surface with lower surface roughness of 21.8 nm. The ratio of C sp2 at 284.4 e V that corresponds to the diamond(111) and the C sp3 at 285.3 e V that corresponds to the diamond(220) plane for the as-received film is 0.36: 0.64, showing that the C sp3 has the high content. The hardness and Young's modulus of DLC film by nanoindentation are 8.534 41 and 142.158 1 GPa, respectively, and the corresponding bonding strength is 74.55 N by scratch test.展开更多
Warm compaction process of pure iron powder was investigated. Due to the existence of elastic, plastic and thermal strains, a coupled mechanical and thermal model was applied. The elasto-plastic constitutive equations...Warm compaction process of pure iron powder was investigated. Due to the existence of elastic, plastic and thermal strains, a coupled mechanical and thermal model was applied. The elasto-plastic constitutive equations for powder material were developed based on ellipsoidal yield criterion and continuum theory. The constitutive equations were integrated into the constitutive integral arithmetic and solved employing incremental iterative solution strategy. The yield strength of iron powder was obtained according to the tensile experiments. When the compaction temperature was raised to 130 ℃, the yield strength of iron powder metal drops to 85% of room temperature value. Modified coulomb friction law is applied and the simulation results show that friction was an important factor resulting in the inhomogeneous relative density and reverse-density distribution phenomena in the regions near the die wall and the symmetrical axis.展开更多
基金National Natural Science Foundation of China(Grant No.52175162,51805086 and 51975123)Natural Science Foundation of Fujian Province(Grant No.2019J01210)Health education joint project of Fujian Province(Grant No.2019-WJ-01)。
文摘Composite materials exhibit the impressive mechanical properties of high damping and stiffness,which cannot be attained by employing conventional single materials.Along these lines,a novel material architecture is presented in this work in order to fabricate composites with enhanced mechanical characteristics.More specifically,entangled metallic wire materials were used as the active matrix,whereas polyurethane was employed as the reinforcement elements.As a result,an entangled metallic wire material-polyurethane composite with high damping and stiffness was prepared by enforcing the vacuum infiltration method.On top of that,the mechanical properties(loss factor,energy consumption,and average stiffness)of the proposed composite materials were characterized by performing dynamic tests,and its fatigue characteristics were verified by the micro-interface bonding,as well as the macro-damage factor.The impact of the density,preloading spacing,loading amplitude,and exciting frequency on the mechanical properties of the composites were also thoroughly analyzed.The extracted results indicate that the mechanical properties of the composites were significantly enhanced than those of the pure materials due to the introduction of interface friction.Moreover,the average stiffness of the composites was about 10 times the respective value of the entangled metallic wire material.Interestingly,a rise in the loading period leads to some failure between the composite interfaces,which reduces the stiffness property but enhances the damping dissipation properties.Finally,a comprehensive dynamic mechanical model of the composites was established,while it was experimentally verified.The proposed composites possess higher damping features,i.e.,stiffness characteristics,and maintain better fatigue characteristics,which can broaden the application range of the composites.In addition,we provide a theoretical and experimental framework for the research and applications in the field of metal matrix composites.
基金financially supported by the National Key R&D Program of China (No.2021YFA1200203)the National Natural Science Foundation of China (Nos.51922026 and 51975111)+1 种基金the Fundamental Research Funds for the Central Universities (No.N2202015,N2002005,and N2105001)the 111 Project of China (No.BP0719037 and B20029)。
文摘Face-centered cubic (f.c.c.) high entropy alloys (HEAs) are attracting more and more attention owing to their excellent strength and ductility synergy, irradiation resistance, etc. However, the yield strength of f.c.c. HEAs is generally low, significantly limiting their practical applications. Recently, the alloying of W has been evidenced to be able to remarkably improve the mechanical properties of f.c.c. HEAs and is becoming a hot topic in the community of HEAs. To date, when W is introduced, multiple strengthening mechanisms, including solid-solution strengthening, precipitation strengthening (μphase,σphase, and b.c.c. phase), and grain-refinement strengthening, have been discovered to be activated or enhanced. Apart from mechanical properties, the addition of W improves corrosion resistance as W helps to form a dense WO_(3) film on the alloy surface. Until now, despite the extensive studies in the literature, there is no available review paper focusing on the W doping of the f.c.c. HEAs. In that context, the effects of W doping on f.c.c. HEAs were reviewed in this work from three aspects, i.e., microstructure,mechanical property, and corrosion resistance. We expect this work can advance the application of the W alloying strategy in the f.c.c. HEAs.
基金the support of the National Natural Science Foundation of China(Grant No.51472074).
文摘Understanding the adsorption interactions between carbon materials and sulfur compounds has far-reaching impacts,in addition to their well-known important role in energy storage and conversion,such as lithium-ion batteries.In this paper,properties of intrinsic B or Si single-atom doped,and B-Si codoped graphene(GR)and graphdiyne(GDY)were investigated by using density functional theory-based calculations,in which the optimal doping configurations were explored for potential applications in adsorbing sulfur compounds.Results showed that both B or Si single-atom doping and B-Si codoping could substantially enhance the electron transport properties of GR and GDY,improving their surface activity.Notably,B and Si atoms displayed synergistic effects for the codoped configurations,where B-Si codoped GR/GDY exhibited much better performance in the adsorption of sulfurcontaining chemicals than single-atom doped systems.In addition,results demonstrated that,after B-Si codoping,the adsorption energy and charge transfer amounts of GDY with sulfur compounds were much larger than those of GR,indicating that B-Si codoped GDY might be a favorable material for more effectively interacting with sulfur reagents.
基金supported by the National Natural Science Foundation of China(No.U20A20310 and No.52176199)sponsored by the Program of Shanghai Academic/Technology Research Leader(No.22XD1423800)。
文摘Thermal runaway(TR)is a critical issue hindering the large-scale application of lithium-ion batteries(LIBs).Understanding the thermal safety behavior of LIBs at the cell and module level under different state of charges(SOCs)has significant implications for reinforcing the thermal safety design of the lithium-ion battery module.This study first investigates the thermal safety boundary(TSB)correspondence at the cells and modules level under the guidance of a newly proposed concept,safe electric quantity boundary(SEQB).A reasonable thermal runaway propagation(TRP)judgment indicator,peak heat transfer power(PHTP),is proposed to predict whether TRP occurs.Moreover,a validated 3D model is used to quantitatively clarify the TSB at different SOCs from the perspective of PHTP,TR trigger temperature,SOC,and the full cycle life.Besides,three different TRP transfer modes are discovered.The interconversion relationship of three different TRP modes is investigated from the perspective of PHTP.This paper explores the TSB of LIBs under different SOCs at both cell and module levels for the first time,which has great significance in guiding the thermal safety design of battery systems.
文摘The advent of Industry 4.0 has compelled businesses to adopt digital approaches that combine software toenhance production efficiency. In this rapidly evolving market, software development is an ongoing process thatmust be tailored to meet the dynamic needs of enterprises. However, internal research and development can beprohibitively expensive, driving many enterprises to outsource software development and upgrades to externalservice providers. This paper presents a software upgrade outsourcing model for enterprises and service providersthat accounts for the impact of market fluctuations on software adaptability. To mitigate the risk of adverseselection due to asymmetric information about the service provider’s cost and asymmetric information aboutthe enterprise’s revenues, we propose pay-per-time and revenue-sharing contracts in two distinct informationasymmetry scenarios. These two contracts specify the time and transfer payments for software upgrades. Througha comparative analysis of the optimal solutions under the two contracts and centralized decision-making withfull-information, we examine the characteristics of the solutions under two information asymmetry scenarios andanalyze the incentive effects of the two contracts on the various stakeholders. Overall, our study offers valuableinsights for firms seeking to optimize their outsourcing strategies and maximize their returns on investment insoftware upgrades.
基金Funded by the Hebei Province Natural Science Foundation (No.E2017203043)National Natural Science Foundation of China(No.U1604251)。
文摘A new,innovative vibration cast-rolling technology of “electromagnetic stirring+dendrite breaking+asynchronous rolling” was proposed with the adoption of sinusoidal vibration of crystallization roller to prepare Ti/Al laminated composites,and the effect of sinusoidal vibration of crystallization roller on composite microstructure was investigated in detail.The results show that the metallurgical bonding of titanium and aluminum is realized by mesh interweaving and mosaic meshing,instead of transition bonding by forming metal compound layer.The meshing depth between titanium and aluminum layers (6.6μm) of cast-rolling materials with strong vibration of crystallization roller (amplitude 0.87 mm,vibration frequency 25 Hz) is doubled compared with that of traditional cast-rolling materials (3.1μm),and the composite interfacial strength(27.0 N/mm) is twice as high as that of traditional cast-rolling materials (14.9 N/mm).This is because with the action of high-speed superposition of strong tension along the rolling direction,strong pressure along the width direction and rolling force,the composite linearity evolves from "straight line" with traditional casting-rolling to "curved line",and the depth and number of cracks in the interface increases greatly compared with those with traditional cast-rolling,which leads to the deep expansion of the meshing area between interfacial layers and promotes the stable enhancement of composite quality.
基金Project supported by the National Natural Science Foundation of China (Grant Nos.52175279 and 51705459)the Natural Science Foundation of Zhejiang Province,China (Grant No.LY20E050022)the Key Research and Development Projects of Zhejiang Provincial Science and Technology Department (Grant No.2021C03122)。
文摘This paper presented a novel tinny motion capture system for measuring bird posture based on inertial and magnetic measurement units that are made up of micromachined gyroscopes, accelerometers, and magnetometers. Multiple quaternion-based extended Kalman filters were implemented to estimate the absolute orientations to achieve high accuracy.Under the guidance of ornithology experts, the extending/contracting motions and flapping cycles were recorded using the developed motion capture system, and the orientation of each bone was also analyzed. The captured flapping gesture of the Falco peregrinus is crucial to the motion database of raptors as well as the bionic design.
基金supported in part by the National Natural Science Foundation of China (62222310, U1813201, 61973131, 62033008)the Research Fund for the Taishan Scholar Project of Shandong Province of China+2 种基金the NSFSD(ZR2022ZD34)Japan Society for the Promotion of Science (21K04129)Fujian Outstanding Youth Science Fund (2020J06022)。
文摘In this paper, the issues of stochastic stability analysis and fault estimation are investigated for a class of continuoustime Markov jump piecewise-affine(PWA) systems against actuator and sensor faults. Firstly, a novel mode-dependent PWA iterative learning observer with current feedback is designed to estimate the system states and faults, simultaneously, which contains both the previous iteration information and the current feedback mechanism. The auxiliary feedback channel optimizes the response speed of the observer, therefore the estimation error would converge to zero rapidly. Then, sufficient conditions for stochastic stability with guaranteed performance are demonstrated for the estimation error system, and the equivalence relations between the system information and the estimated information can be established via iterative accumulating representation.Finally, two illustrative examples containing a class of tunnel diode circuit systems are presented to fully demonstrate the effectiveness and superiority of the proposed iterative learning observer with current feedback.
基金supported by the“Pioneer”and“Leading Goose”R&D Program of Zhejiang(Grant No.2022C03170)Science and Technology Project of Quzhou(Grant No.2022K98)Hunan Province Key Field R&D Plan Project(Grant No.2022GK2068).
文摘Centrifugal pumps are widely used in the metallurgy,coal,and building sectors.In order to study the hydraulic characteristics of a closed impeller centrifugal pump during its shutdown in the so-called power frequency and frequency conversion modes,experiments were carried to determine the characteristic evolution of parameters such as speed,inlet and outlet pressure,head,flow rate and shaft power.A quasi-steady-state method was also used to further investigate these transient behaviors.The results show that,compared to the power frequency input,the performance parameter curves for the frequency conversion input are less volatile and smoother.The characteristic time is longer and the response to shutdown is slower.The quasi-steady-state theoretical head-flow curves match the experimental head-flow curves more closely at low flow rates when the frequency conversion input is considered.Moreover,in this case,the similarity law predicts the hydraulic performance more accurately.
基金The authors acknowledge the financial support from the National Natural Science Foundation of China(Grant No.32201509)Hunan Science and Technology Xiaohe Talent Support Project(2022 TJ-XH 013)+6 种基金Science and Technology Innovation Program of Hunan Province(2022RC1156,2021RC2100)State Key Laboratory of Woody Oil Resource Utilization Common Key Technology Innovation for the Green Transformation of Woody Oil(XLKY202205)State Key Laboratory of Woody Oil Resource Utilization Project(2019XK2002)Key Research and Development Program of the State Forestry and Grassland Administration(GLM[2021]95)Hunan Forestry Outstanding Youth Project(XLK202108-1)Changsha Science and Technology Project(kq2202325,kq2107022)Science and Technology Innovation Leading Talent of Hunan Province(2020RC4026).
文摘The C.oleifera oil processing industry generates large amounts of solid wastes,including C.oleifera shell(COS)and C.oleifera cake(COC).Distinct from generally acknowledged lignocellulosic biomass(corn stover,bamboo,birch,etc.),Camellia wastes contain diverse bioactive substances in addition to the abundant lignocellulosic components,and thus,the biorefinery utilization of C.oleifera processing byproducts involves complicated processing technologies.This reviewfirst summarizes various technologies for extracting and converting the main components in C.oleifera oil processing byproducts into value-added chemicals and biobased materials,as well as their potential applications.Microwave,ultrasound,and Soxhlet extractions are compared for the extraction of functional bioactive components(tannin,flavonoid,saponin,etc.),while solvothermal conversion and pyrolysis are discussed for the conversion of lignocellulosic components into value-added chemicals.The application areas of these chemicals according to their properties are introduced in detail,including utilizing antioxidant and anti-in-flammatory properties of the bioactive substances for the specific application,as well as drop-in chemicals for the substitution of unrenewable fossil fuel-derived products.In addition to chemical production,biochar fabricated from COS and its applications in thefields of adsorption,supercapacitor,soil remediation and wood composites are comprehensively reviewed and discussed.Finally,based on the compositions and structural characteristics of C.oleifera byproducts,the development of full-component valorization strategies and the expansion of the appli-cationfields are proposed.
基金This work was supported by Tianjin Natural Science Foundation(No.21JCZDJC00750).
文摘This paper discussed the experimental results of the performance of an organic Rankine cycle(ORC)system with an ultra-low temperature heat source.The low boiling point working medium R134a was adopted in the system.The simulated heat source temperature(SHST)in this work was set from 39.51°C to 48.60°C by the simulated heat source module.The influence of load percentage of simulated heat source(LPSHS)between 50%and 70%,the rotary valve opening(RVO)between 20%and 100%,the resistive load between 36Ωand 180Ωor the no-load of the generator,as well as the autumn and winter ambient temperature on the system performance were studied.The results showed that the stability of the system was promoted when the generator had a resistive load.The power generation(PG)and generator speed(GS)of the system in autumn were better than in winter,but the expander pressure ratio(EPR)was lower than in winter.Keep RVO unchanged,the SHST,the mass flow rate(MFR)of the working medium,GS,and the PG of the system increased with the increasing of LPSHS for different generator resistance load values.When the RVO was 60%,LPSHS was 70%,the SHST was 44.15°C and the resistive load was 72Ω,the highest PG reached 15.11 W.Finally,a simulation formula was obtained for LPSHS,resistance load,and PG,and its correlation coefficient was between 0.9818 and 0.9901.The formula can accurately predict the PG.The experimental results showed that the standard deviation between the experimental and simulated values was below 0.0792,and the relative error was within±5%.
基金National Hi-tech Research and Development Program of China(863 Program,No.2008AA04Z116)and Natural Science Foundation of Hunan Province,China.
文摘On the basis of the traditional mechanical model of a grinding wheel rotor and the mechanical-electric coupling model with ideal sinusoidal supply,taking high-frequency converting current of inverter power switches into further consideration,a modified mechanical-electric coupling model is created.The created model consists of an inverter,a motorized spindle,a grinding wheel and grinding loads.Some typical non-stationary processes of the grinding system with two different supplies,including the starting,the speed rising and the break in grinding loads,are compared by making use of the created model.One supply is an ideal sinusoida]voltage source,the other is an inverter.The theoretical analysis of the high-order harmonic is also compared with the experimental result.The material strategy of suppressing high-order harmonic mechanical-electric coupling vibration by optimizing inverter operating parameters is proposed.
基金Project(J51504) supported by Shanghai Leading Academic Discipline Project,China
文摘In order to establish the rolling process parameters of grade-2 commercially pure titanium(CP-Ti),it is necessary to understand the transformation mechanism and mechanical properties of this material.The β→α transformation kinetics of the grade-2 CP-Ti during continuous cooling was measured and its hot compression behavior was investigated using Gleeble-1500 thermal mechanical simulator.Dynamic CCT diagram confirms that cooling rate has an obvious effect on the start and finishing transformation and microstructures at room temperature.The critical cooling rate for β-phase transforms to α phase is about 15 °C/s.When the cooling rate is higher than 15 °C/s,some β phases with fine granular shape remain residually into plate-like structure.The plate-like α phase forms at cooling rate lower than 2 °C/s,serrate α phase forms at medium cooling rates,about 5-15 °C/s.The flow stress behavior of grade-2 CP-Ti was investigated in a temperature range of 700-900 °C and strain rate of 3.6-40 mm/min.The results show that dynamic recrystallization,dynamic recovery and work-hardening obviously occur during hot deformation.Constitutive equation of grade-2 CP-Ti was established by analyzing the relationship of the deformation temperature,strain rate,deformation degree and deformation resistance.
文摘ZA 27 alloys reinforced by Mn containing intermetallic compounds were prepared and the effect of Mn content on their mechanical properties were examined. By adding Mn, rare earth elements(RE) and Ti into ZA 27, experimental alloys were fabricated by sand casting. The volume fraction, grain size and morphology of the Mn containing intermetallic compound phases vary with the changing of Mn content. Mechanical properties of the reinforced ZA 27 alloys at elevated temperatures were measured. The results show that the hardness, compressive strength and compressibility of experimental alloys increase with increasing Mn content until they reach a maximum at 0.5% Mn. Excessive and coarse hard phases would act as crack origins instead of dispersion strengthening particles. Best tensile properties of these alloys at elevated temperature can be achieved at a Mn content of 0.18 %.
基金supported by the Hebei Provincial Natural Science Foundation of China(No.E2007000591).
文摘The aim of this study was to simulate the solidification process of beam blank continuous casting, and then find the reasons for the typical defects of the beam blank. A two-dimensional transient coupled finite element model has been developed to compute the temperature and stress profile in beam blank continuous casting. The enthalpy method was used in the heat conduction equation. The thermo-mechanical property in the mushy zone was taken into consideration in this calculation. It is shown that at the mold exit the thickness of the shell had its maximum value at the flange tip and its minimum value at the fillet. The temperature had a great fluctuation on the surface of the beam blank in the secondary cooling zone. At the unbending point, the surface temperature of the web was in the brittleness temperature range under the present condition. To ensure the quality, it is necessary to weaken the intensity of secondary cooling. At the mold exit the equivalent stress and strain have higher values at the flange tip and at the web. From the spray 1 to the unbending point, the maximum values of stress and strain gradually moved to the internal section of the flange tip and the web. However, whenever, there were bigger stress and strain values near the flange tip and the web than in the other parts, it must be very easy to generate cracks at those positions. Now, online verification of this simulation has been developed, which has proved to be very useful and efficient to instruct the practical production of beam blank continuous casting.
文摘gradient aluminum alloy was prepared by semi-continuous casting using double-stream-pouring technique. The microstructures of the as-cast, pressed and heat-treated alloys were analyzed by scanning electron microscope and transmission electron microscope. And the mechanical properties of the alloy in pressed and heat-treated states were studied. The results show that the ingots with diameter of 65 mm and external thickness （about） 5.5 mm are obtained when the temperatures of the melt in the internal and external ladles are 1 023 and 1 003 K, respectively, and the nozzle diameter is 2.0 mm. The microstructures of the as-cast alloy consist of α（Al）+（θ（CuAl2））+S（Al2CuMg） in the internal region and （α（Al）+MnAl6） in the external region. The phases found in the internal and external layers coexist in the transition zone. The transition layer is maintained after plastic deformation and heat treatment of the alloy. The tensile strength, yield strength and elongation of the alloy are 300 MPa, 132 MPa and 16.0%, respectively, after T6 treatment. The tensile and yield strength are increased by 150.0% and （94.1%,） respectively, compared with that of 3003 aluminum alloy. The maximum hardness in the internal region of 2024/3003 gradient aluminum alloy can be increased from HRF 55 in the pressed state to HRF 70 in the heat-treated state.
文摘Mechanical properties and tribological behavior of a novel cast heat resisting copper based alloy are investigated. The corresponding properties of a commercial aluminum bronze C95500 (ASTM B30) are compared with the alloy. The results show that the alloy possesses better mechanical properties and tribological behaviors than that of C95500 at elevated temperature. The tensile strength, elongation and hardness at 500℃ are 470MPa, 2.5% and HB220, respectively. The wear rate of the developed alloy at ambient and elevated temperature is about one sixth and one fortieth of that of C95500, respectively. The alloy is very suitable for ma nufacturing heat resisting and wear resisting parts. Major strengthening mechanisms for the alloy are solution strengthening and the second phase strengthening.
基金Funded by the Jiangsu Province Science and Technology Support Program(Industry)(No.BE2014818)
文摘A diamond-like carbon(DLC) film was deposited on YT14 substrate using magnetron sputtering(MS). The surface morphologies, roughness and bonding spectra of obtained film were characterized using scanning electron microscopy(SEM), atomic force microscopy(AFM), and X-ray photoelectron spectroscopy(XPS), respectively, and its mechanical property and bonding strength were measured using a nanoindentation and scratch tester, respectively. The results show that the C-enriched DLC film exhibits a denser microstructure and smoother surface with lower surface roughness of 21.8 nm. The ratio of C sp2 at 284.4 e V that corresponds to the diamond(111) and the C sp3 at 285.3 e V that corresponds to the diamond(220) plane for the as-received film is 0.36: 0.64, showing that the C sp3 has the high content. The hardness and Young's modulus of DLC film by nanoindentation are 8.534 41 and 142.158 1 GPa, respectively, and the corresponding bonding strength is 74.55 N by scratch test.
基金Project(50325516) supported by the National Foundation of China for Outstanding Young Scientists Project(50135020) supported by the National Natural Science Foundation of China Project(CG2003-GA005) supported by China Education and Research Grid (China Grid)
文摘Warm compaction process of pure iron powder was investigated. Due to the existence of elastic, plastic and thermal strains, a coupled mechanical and thermal model was applied. The elasto-plastic constitutive equations for powder material were developed based on ellipsoidal yield criterion and continuum theory. The constitutive equations were integrated into the constitutive integral arithmetic and solved employing incremental iterative solution strategy. The yield strength of iron powder was obtained according to the tensile experiments. When the compaction temperature was raised to 130 ℃, the yield strength of iron powder metal drops to 85% of room temperature value. Modified coulomb friction law is applied and the simulation results show that friction was an important factor resulting in the inhomogeneous relative density and reverse-density distribution phenomena in the regions near the die wall and the symmetrical axis.
