A scheme based on irregular V-shaped silicon nanoantennas is proposed to optimize transverse unidirectional scattering under plane wave irradiation.Traditional methods of designing regular shapes offer fewer parameter...A scheme based on irregular V-shaped silicon nanoantennas is proposed to optimize transverse unidirectional scattering under plane wave irradiation.Traditional methods of designing regular shapes offer fewer parameters and higher search efficiency.However,due to the limitations of regular shapes,it is challenging to meet high-precision design requirements.Irregular shape design allows for a broader range of adjustments,but the complexity of shape parameters leads to lower search efficiency and a higher likelihood of converging to local optima.展开更多
Sudden temperature drops cause soils in natural environments to freeze unidirectionally,resulting in soil expansion and deformation that can lead to damage to engineering structures.The impact of temperature-induced f...Sudden temperature drops cause soils in natural environments to freeze unidirectionally,resulting in soil expansion and deformation that can lead to damage to engineering structures.The impact of temperature-induced freezing on deformation and solute migration in saline soils,especially under extended freezing,is not well understood due to the lack of knowledge regarding the microscopic mechanisms involved.This study investigated the expansion,deformation,and water-salt migration in chlorinated saline soils,materials commonly used for canal foundations in cold and arid regions,under different roof temperatures and soil compaction levels through unidirectional freezing experiments.The microscopic structures of saline soils were observed using scanning electron microscopy(SEM)and optical microscopy.A quantitative analysis of the microstructural data was conducted before and after freezing to elucidate the microscopic mechanisms of water-salt migration and deformation.The results indicate that soil swelling is enhanced by elevated roof temperatures approaching the soil's freezing point and soil compaction,which prolongs the duration and accelerates the rate of water-salt migration.The unidirectional freezing altered the microstructure of saline soils due to the continuous temperature gradients,leading to four distinct zones:natural frozen zone,peak frozen zone,gradual frozen zone,and unfrozen zone,each exhibiting significant changes in pore types and fractal dimensions.Vacuum suction at the colder end of the soil structure facilitates the upward migration of salt and water,which subsequently undergoes crystallization.This process expands the internal pore structure and causes swelling.The findings provide a theoretical basis for understanding the evolution of soil microstructure in cold and arid regions and for the management of saline soil engineering.展开更多
Ferrimagnetic materials exhibiting remanence can be used to achieve unidirectional electromagnetic-field propagation in the form of magnetoplasmons(MPs)in the subwavelength regime.This study investigates the MP proper...Ferrimagnetic materials exhibiting remanence can be used to achieve unidirectional electromagnetic-field propagation in the form of magnetoplasmons(MPs)in the subwavelength regime.This study investigates the MP properties and various guiding modes in a hollow cylindrical waveguide made of materials that exhibit remanence.Pattern analysis and numerical simulations are used to demonstrate that dispersion relationships and electromagnetic-field distribution are strongly affected by the operating frequency and physical dimensions of the structure.In addition,the existence of two different guiding modes is proved,namely regular and surface-wave modes.By adjusting the operating frequency and reducing the diameter of the hollow cylinder,the regular mode can be suppressed so as to only retain the surface-wave mode,which enables unidirectional MP propagation in the cylindrical waveguide.Moreover,the unidirectional surface-wave mode is robust to backscattering due to surface roughness and defects,which makes it very useful for application in field-enhancement devices.展开更多
The fexible strain sensor has found widespread application due to its excellent fexibility,extensibility,and adaptability to various scenarios.This type of sensors face challenges in direction identification owing to ...The fexible strain sensor has found widespread application due to its excellent fexibility,extensibility,and adaptability to various scenarios.This type of sensors face challenges in direction identification owing to strong coupling between the principal strain and transverse resistance.In this study,a silver nanowires(Ag-NWs)/polydimethylsiloxane(PDMS)strain sensor was developed,using a filtration method for preparing the AgNWs film which was then combined with PDMS to create a unidirectional,highly sensitive,fast-responsive,and linear fexible strain sensor.When the grid width is 0.25 mm,the AgNWs/PDMS strain sensor demonstrates an outstanding unidirectional sensitivity,with a strain response solely along the parallel direction of the grid lines(noise ratioα≈8%),and a fast reaction time of roughly 106.99 ms.In the end,this sensor's ability to detect curvature was also demonstrated through LEDs,demonstrating its potential applications in various fields,including automotive,medical,and wearable devices.展开更多
The interplay between 2a_(0)×2a_(0)charge density wave(CDW),nematicity and superconductivity in AV_(3)Sb_(5)(A=K,Rb,Cs)compounds gives rise to a rich landscape of intriguing physical phenomena.In addition to the ...The interplay between 2a_(0)×2a_(0)charge density wave(CDW),nematicity and superconductivity in AV_(3)Sb_(5)(A=K,Rb,Cs)compounds gives rise to a rich landscape of intriguing physical phenomena.In addition to the 2a_(0)×2a_(0)CDW,a unidirectional 4a_(0)stripe CDW is also observed on the Sb surface of RbV3Sb5and CsV3Sb5.However,reports of stripe-like CDWs in KV3Sb5have been limited.Here,we report the first observation of a long-range unidirectional stripe order with a 6a_(0)modulation period on the Sb surface of KV_(3)Sb_(5),coexisting with the 2a_(0)×2a_(0)CDW.Notably,the intensity of the6a_(0)stripes in STM topographies exhibits pronounced contrast reversal between opposite bias voltages.Additionally,the wave vector of the 6a_(0)modulation shows no energy-dependent dispersion,confirming its CDW origin.Furthermore,the6a_(0)CDW is robust under a 7 T out-of-plane magnetic field and persists over a temperature range from 215 mK to 720 mK.These results provide compelling evidence for the emergence of a long-range unidirectional CDW in KV_(3)Sb_(5).展开更多
Structural uniformity is an important parameter influencing physical and mechanical properties of lotus-type porous metals prepared by directional solidification of metal-gas eutectic (Gasar). The effect of superheat ...Structural uniformity is an important parameter influencing physical and mechanical properties of lotus-type porous metals prepared by directional solidification of metal-gas eutectic (Gasar). The effect of superheat on structural uniformity as well as average porosity, pore morphology of porous metals was studied. The experimental results show that, when the superheat is higher than a critical value (ΔTc), the bubbling or boiling phenomenon will occur and the gas bubbles will form in the melt and float out of the melt. As a result, the final porosity will decrease. In addition, a higher superheat will simultaneously cause a non-uniform porous structure due to the pores coalescence and bubbling phenomenon. Finally, a theoretical model was developed to predict the critical superheat for the hydrogen to escape from the melt and the corresponding escapement ratio of hydrogen content. Considering the escapement of hydrogen, the predicted porosities are in good agreement with the experimental results.展开更多
In this paper two set of GFRP specimens are manufactured and tested to investigate the relaxation behaviour under cyclic loading in the longitudinal and transversel direction. The relaxation of GFRP unidirectional la...In this paper two set of GFRP specimens are manufactured and tested to investigate the relaxation behaviour under cyclic loading in the longitudinal and transversel direction. The relaxation of GFRP unidirectional laminates is evident for both cyclic loadings. Under longitudinal cyclic loading the relaxation is dependent on the number of loading cycles. Under transverse loading the relaxation depends on the loading cycles as well as the time of loading. Two expressions are set up to describe the relaxation for the longitudinal and transverse loading, and the predictions agree well with the experimental data.展开更多
Based on the solid-gas eutectic unidirectional solidification technique and the principle of unidirectional solidification of single-phase alloy, a new method for evaluating the diffusion coefficient of hydrogen in li...Based on the solid-gas eutectic unidirectional solidification technique and the principle of unidirectional solidification of single-phase alloy, a new method for evaluating the diffusion coefficient of hydrogen in liquid metals was proposed. Taking Cu-H2 system for example, the influences of argon partial pressure and superheat degree of melt on the diffusion coefficient of hydrogen in liquid metal were studied and the predicted values were similar to each other. The obtained temperature-dependent equation for diffusion coefficient of hydrogen in liquid copper is comparable with experimental data in literature, which validates the effectiveness of this method. The temperature-dependent equations for diffusion coefficient of hydrogen in liquid Mg, Si and Cu-34.6%Mn alloy were also evaluated by this method, along with the values at the melting point of each metal and alloy.展开更多
In this paper, repeated unidirectional bending （RUB）, was applied to improve the texture of AZ31B magnesium alloy sheets so as to enhance their stamping properties. The samples undergoing RUB were annealed at differ...In this paper, repeated unidirectional bending （RUB）, was applied to improve the texture of AZ31B magnesium alloy sheets so as to enhance their stamping properties. The samples undergoing RUB were annealed at different temperatures. The mechanical properties, formability, textural components and microstructure of the samples before and after RUB were characterized and compared. It was found that the basal textural component was reduced dramatically by RUB, and that （1212） and （1211） textural components appeared. Annealing has a great effect on the mechanical properties of samples undergoing RUB. The plasticity and stamping formability of samples were greatly improved by RUB and annealing at 260℃ for 1 h, and elongation to fracture and Erichsen value were increased to 38% and 67%, respectively.展开更多
A continuous unidirectional solidification equipment with the advantages of electric slag remelting, induction heating, continuous casting and unidirectional solidification was built to study the QAl9 4 Cu Al alloy. T...A continuous unidirectional solidification equipment with the advantages of electric slag remelting, induction heating, continuous casting and unidirectional solidification was built to study the QAl9 4 Cu Al alloy. The results show that the electro slag induction continuous unidirectional solidification process can be used for the steady continuous unidirectional solidification of QAl9 4, and revitalizes the down pulling continuous unidirectional solidification process; that the temperature distribution in the mold wall reflects that of the molten metal in the mold, thus the temperature distribution in the mold wall can be used to control the electric slag induction continuous unidirectional solidification process; and that the mutual matching of the technological parameters is the key to stabilize the solidification process.展开更多
Unidirectional liquid transport without any need of external energy has drawn worldwide attention for its potential applications in various fields such as microfluidics,biomedicine and mechanical engineering.In nature...Unidirectional liquid transport without any need of external energy has drawn worldwide attention for its potential applications in various fields such as microfluidics,biomedicine and mechanical engineering.In nature,numerous creatures have evolved such extraordinary unidirectional liquid transport ability such as spider sik,Sarracenia's trichomes,and Nepenthes alata's peristome,etc.This review summarizes the current progresses of natural unidirectional liquid transport on 1-Dimensional(1D)linear structure and 2-Dimensional(2D)surface stucture.The driving force of unidirectional liquid transport which is determined by unique structure exist distinct differences in physics.The fundamental understanding of 1D and 2D unidirectionaliquid transport especially about hierarchical structural characteristics and their transport mechanism were concentrated,and various bioinspired fabrication methods are also introduced.The applications of bioinspired directional liquid transport are demonstrated especially in fields of microfluidies,biomedical devices and anti-icing surfaces.With newly developed smart materials,various liquid transport regulation strategies are also summarized for the control of transport speed,direction guiding,etc.Finally,we provide new insights and future perspectives of the directional transport materials.展开更多
Repeatedly unidirectional bending(RUB) was applied to the magnesium alloy sheet to improve the basal texture.The effect of RUB temperature on resulting structure and room temperature properties was investigated.The te...Repeatedly unidirectional bending(RUB) was applied to the magnesium alloy sheet to improve the basal texture.The effect of RUB temperature on resulting structure and room temperature properties was investigated.The texture components of the sheet undergoing RUB at recovery temperature were similar to those of the sheet undergoing RUB at room temperature(RT).As the RUB temperature increased to above recrystallization temperature,the texture components became more disperse and the pyramidal components increased.With the increase of RUB temperature,the grain size near the surface of the sheets undergoing RUB tended to grow up.When the sheets were processed by RUB at medium-high temperature followed by annealing at 533 K,the yield strength and fracture elongation were lower than those of the cold rolled sheet;however,the Erichsen value was slightly higher than that of the cold rolled sheet.The sheet undergoing RUB at RT followed by annealing at 533 K represented the best mechanical properties.展开更多
A 2D micro-mechanical model was proposed to study the compressive failure of Uni Directional（UD） carbon/epoxy composite. Considering the initial imperfection and strength distribution of the fiber, the plasticity an...A 2D micro-mechanical model was proposed to study the compressive failure of Uni Directional（UD） carbon/epoxy composite. Considering the initial imperfection and strength distribution of the fiber, the plasticity and ductile damage of the matrix, the failure of T300/914 UD composite under longitudinal compression and in-plane combined loads was simulated by this model. Simulation results show that the longitudinal compressive failure of the UD composite is caused by the plastic yielding of the matrix in kink band, and the fiber initial imperfection is the main reason for it. Under in-plane combined loads, the stress state of the matrix in kink band is changed, which affects the longitudinal compressive failure modes and strength of UD composite.The failure envelope of r_1–s_（12） and r_1–r_2 are obtained by the micro-mechanical model. Meanwhile,the compressive failure mechanism of the UD composite is analyzed. Numerical results agree well with the experimental data, which verifies the validity of the micro-mechanical model.展开更多
An unidirectional and bidirectional hybrid connective star network model with coupling time-delay is constructed in this paper. According to synchronization error systems, adaptive controllers for each node are struct...An unidirectional and bidirectional hybrid connective star network model with coupling time-delay is constructed in this paper. According to synchronization error systems, adaptive controllers for each node are structured by using the linear system stability method and the Lyapunov stability method. These adaptive controllers can realize the modified functional projective synchronization between each node of star network and an isolated node by argument and analysis. Finally, the corrective and effective of the adaptive controllers are illustrated by some numerical examples.展开更多
Considering the S L interface morphology stability, the S L interface energy, the Joule heat produced by electric current at the S L interface, and the change of solute concentration at the S L interface indirectly ca...Considering the S L interface morphology stability, the S L interface energy, the Joule heat produced by electric current at the S L interface, and the change of solute concentration at the S L interface indirectly caused by electric current, the mechanism of reduction of columnar dendrite spacing in unidirectional solidification caused by electric current passing through solid liquid interface was studied. The following conclusions can be drawn that: 1) under sub rapid solidification condition, increasing electric current density will improve the stability of S L interface, thus decreasing the columnar dendrite spacing; 2)there are two ways by which the increase of electric current decreases the columnar dendrite spacing, one is promoting the splitting of the protruding tips at the S L interface, the other is promoting the forming of new convex parts at the bottom of the concave interface.[展开更多
Pure copper rods containing continuous columnar crystals were fabricatedusing the downward CUS (Continuous Unidirectional Solidification) equipment. When the technologicalparameters were set as the ranges of mould tem...Pure copper rods containing continuous columnar crystals were fabricatedusing the downward CUS (Continuous Unidirectional Solidification) equipment. When the technologicalparameters were set as the ranges of mould temperature 1100-1300℃, cooling distance (the distancefrom the exit of the cast mould to the start point of cooling) 10-20 mm, casting speed 0.2-2.5 mm/s,cooling water (20-25℃) volume 1000-1320 L/h, and when these parameters matched reasonably, the CUSprocess was performed stably, and pure copper rods containing continuous columnar crystals withbright and smooth surface were produced. The dendritic arm spacing of the crystals in copper rodsdecreased with increasing the casting speed. The results of the texture by X-ray diffractionanalysis showed that the rods has strong <100> fiber texture.展开更多
Cohesive non-swelling soil(CNS)cushion technology is widely used to solve swelling deformation problems in expansive soil areas.However,the swelling inhibition mechanism is still not fully understood.In this study,the...Cohesive non-swelling soil(CNS)cushion technology is widely used to solve swelling deformation problems in expansive soil areas.However,the swelling inhibition mechanism is still not fully understood.In this study,the inhibition effect on expansive soil using a CNS layer was studied by performing five types of laboratory model tests under unidirectional seepage.The results showed that CNS cushion technology produced a sound inhibition effect on the swelling characteristics of expansive soil.It was shown that the cations in the CNS layer moved downward and accumulated on the surface of solids and produced an electrical environment inside the expansive soil.In this process,the adsorbed hydrated cations participated in ion exchange with the expansive soil,leading to the modification effect on its swelling potential.Meanwhile,the adsorbed water membrane surrounding the expansive soil aggregates formed by the hydrated cations obstructed further adsorption of water molecules,which inhibited the swelling development of expansive soil.Therefore,the swelling inhibition mechanism can be attributed to three factors:(i)modification effect,(ii)electrical environment,and(iii)deadweight of the CNS layer.The combined contribution of modification effect and electrical environment can be considered as an electric charge effect,which mainly controls the swelling characteristics of expansive soil.展开更多
The present study focused on the formation and crystallographic orientation of twinned dendrites coexisting with equiaxed grains in unidirectional solidification of Al-32%Zn(mass fraction)alloy.The morphology was inve...The present study focused on the formation and crystallographic orientation of twinned dendrites coexisting with equiaxed grains in unidirectional solidification of Al-32%Zn(mass fraction)alloy.The morphology was investigated by optical metallograph and electron back-scattered diffraction technique.Results showed that the macrostructure of the alloy exhibited a typical feathery and fan-like structure while the microstructures were elongated lamellas,which were separated by coherent and incoherent twin boundaries.Both the primary trunk and all lateral arms of twinned dendrites grew along〈110〉directions,unlike regular〈100〉α(Al)dendrites.The facet growth of crystals at solid/liquid interface was responsible for the origin of twinned dendrites during the weak local convection,and high thermal gradient and medium solidification velocity had significant contribution to the formation of twinned dendrites.The formation mechanism of twinned dendrites which consisted of three multiplication ways of new twin boundaries formation and one way of dendrite evolution in twin plane was shown schematically.展开更多
Copper rods with diameter of 17.0 mm have been fabricated by Continuous Unidirectional Solidification (CUS) process. The metallographic results show that the microstructures of the rods are longitudinal columnar cryst...Copper rods with diameter of 17.0 mm have been fabricated by Continuous Unidirectional Solidification (CUS) process. The metallographic results show that the microstructures of the rods are longitudinal columnar crystals and the crystal sizes range roughly among 100-200 μm. The copper rod can be worked to ultra-fine wires 19.7 μm diameter at room temperature without any heat treatments, and the size of the microstructure of the wires obtains nanometer scale. During working process, the elongation multiple of the rod is as high as 740 000 and total deformation true strain over 13.5. The copper rod containing continuous columnar crystals has exhibited excellent cold elongation deformation ability. The results of the texture tests show that the rod has strong <100> fiber texture. After worked at room temperature, texture variants of strong <100> and less strong <111> evolve in the copper wires. With increasing deformation level, the contour of <100> fiber texture decreases while <111> increases. The excellent cold elongation deformation ability and high strength of copper wires is considered to be a result of the strong <100> fiber texture, work hardening and a small quantity of <111>展开更多
基金supported by the National Natural Science Foundation of China(Nos.62475121 and 62335012)。
文摘A scheme based on irregular V-shaped silicon nanoantennas is proposed to optimize transverse unidirectional scattering under plane wave irradiation.Traditional methods of designing regular shapes offer fewer parameters and higher search efficiency.However,due to the limitations of regular shapes,it is challenging to meet high-precision design requirements.Irregular shape design allows for a broader range of adjustments,but the complexity of shape parameters leads to lower search efficiency and a higher likelihood of converging to local optima.
基金supported by the Open Fund of State Key Laboratory of Frozen Soil Engineering (Grant No.SKLFSE201806)the National Natural Science Foundation of China (Grant No.42177155).
文摘Sudden temperature drops cause soils in natural environments to freeze unidirectionally,resulting in soil expansion and deformation that can lead to damage to engineering structures.The impact of temperature-induced freezing on deformation and solute migration in saline soils,especially under extended freezing,is not well understood due to the lack of knowledge regarding the microscopic mechanisms involved.This study investigated the expansion,deformation,and water-salt migration in chlorinated saline soils,materials commonly used for canal foundations in cold and arid regions,under different roof temperatures and soil compaction levels through unidirectional freezing experiments.The microscopic structures of saline soils were observed using scanning electron microscopy(SEM)and optical microscopy.A quantitative analysis of the microstructural data was conducted before and after freezing to elucidate the microscopic mechanisms of water-salt migration and deformation.The results indicate that soil swelling is enhanced by elevated roof temperatures approaching the soil's freezing point and soil compaction,which prolongs the duration and accelerates the rate of water-salt migration.The unidirectional freezing altered the microstructure of saline soils due to the continuous temperature gradients,leading to four distinct zones:natural frozen zone,peak frozen zone,gradual frozen zone,and unfrozen zone,each exhibiting significant changes in pore types and fractal dimensions.Vacuum suction at the colder end of the soil structure facilitates the upward migration of salt and water,which subsequently undergoes crystallization.This process expands the internal pore structure and causes swelling.The findings provide a theoretical basis for understanding the evolution of soil microstructure in cold and arid regions and for the management of saline soil engineering.
文摘Ferrimagnetic materials exhibiting remanence can be used to achieve unidirectional electromagnetic-field propagation in the form of magnetoplasmons(MPs)in the subwavelength regime.This study investigates the MP properties and various guiding modes in a hollow cylindrical waveguide made of materials that exhibit remanence.Pattern analysis and numerical simulations are used to demonstrate that dispersion relationships and electromagnetic-field distribution are strongly affected by the operating frequency and physical dimensions of the structure.In addition,the existence of two different guiding modes is proved,namely regular and surface-wave modes.By adjusting the operating frequency and reducing the diameter of the hollow cylinder,the regular mode can be suppressed so as to only retain the surface-wave mode,which enables unidirectional MP propagation in the cylindrical waveguide.Moreover,the unidirectional surface-wave mode is robust to backscattering due to surface roughness and defects,which makes it very useful for application in field-enhancement devices.
基金the Open Foundation of the State Key Laboratory of Fluid Power and Mechatronic Systems(No.GZKF-202219)the Belt and Road Joint Laboratory on Measurement and Control Technology(No.MCT202306)。
文摘The fexible strain sensor has found widespread application due to its excellent fexibility,extensibility,and adaptability to various scenarios.This type of sensors face challenges in direction identification owing to strong coupling between the principal strain and transverse resistance.In this study,a silver nanowires(Ag-NWs)/polydimethylsiloxane(PDMS)strain sensor was developed,using a filtration method for preparing the AgNWs film which was then combined with PDMS to create a unidirectional,highly sensitive,fast-responsive,and linear fexible strain sensor.When the grid width is 0.25 mm,the AgNWs/PDMS strain sensor demonstrates an outstanding unidirectional sensitivity,with a strain response solely along the parallel direction of the grid lines(noise ratioα≈8%),and a fast reaction time of roughly 106.99 ms.In the end,this sensor's ability to detect curvature was also demonstrated through LEDs,demonstrating its potential applications in various fields,including automotive,medical,and wearable devices.
基金Project supported by the National Key Research and Development Project of China(Grant Nos.2024YFA1207700 and 2022YFA1204100)the National Natural Science Foundation of China(Grant No.62488201)+2 种基金the CAS Project for Young Scientists in Basic Research(Grant No.YSBR-003)the Youth Innovation Promotion Association(Grant No.2023005)the Innovation Program of Quantum Science and Technology(Grant No.2021ZD0302700)。
文摘The interplay between 2a_(0)×2a_(0)charge density wave(CDW),nematicity and superconductivity in AV_(3)Sb_(5)(A=K,Rb,Cs)compounds gives rise to a rich landscape of intriguing physical phenomena.In addition to the 2a_(0)×2a_(0)CDW,a unidirectional 4a_(0)stripe CDW is also observed on the Sb surface of RbV3Sb5and CsV3Sb5.However,reports of stripe-like CDWs in KV3Sb5have been limited.Here,we report the first observation of a long-range unidirectional stripe order with a 6a_(0)modulation period on the Sb surface of KV_(3)Sb_(5),coexisting with the 2a_(0)×2a_(0)CDW.Notably,the intensity of the6a_(0)stripes in STM topographies exhibits pronounced contrast reversal between opposite bias voltages.Additionally,the wave vector of the 6a_(0)modulation shows no energy-dependent dispersion,confirming its CDW origin.Furthermore,the6a_(0)CDW is robust under a 7 T out-of-plane magnetic field and persists over a temperature range from 215 mK to 720 mK.These results provide compelling evidence for the emergence of a long-range unidirectional CDW in KV_(3)Sb_(5).
基金Project(51271096)supported by the National Natural Science Foundation of ChinaProject(NCET-12-0310)supported by the Program for New Century Excellent Talents in University,Ministry of Education,China
文摘Structural uniformity is an important parameter influencing physical and mechanical properties of lotus-type porous metals prepared by directional solidification of metal-gas eutectic (Gasar). The effect of superheat on structural uniformity as well as average porosity, pore morphology of porous metals was studied. The experimental results show that, when the superheat is higher than a critical value (ΔTc), the bubbling or boiling phenomenon will occur and the gas bubbles will form in the melt and float out of the melt. As a result, the final porosity will decrease. In addition, a higher superheat will simultaneously cause a non-uniform porous structure due to the pores coalescence and bubbling phenomenon. Finally, a theoretical model was developed to predict the critical superheat for the hydrogen to escape from the melt and the corresponding escapement ratio of hydrogen content. Considering the escapement of hydrogen, the predicted porosities are in good agreement with the experimental results.
文摘In this paper two set of GFRP specimens are manufactured and tested to investigate the relaxation behaviour under cyclic loading in the longitudinal and transversel direction. The relaxation of GFRP unidirectional laminates is evident for both cyclic loadings. Under longitudinal cyclic loading the relaxation is dependent on the number of loading cycles. Under transverse loading the relaxation depends on the loading cycles as well as the time of loading. Two expressions are set up to describe the relaxation for the longitudinal and transverse loading, and the predictions agree well with the experimental data.
基金Project(51271096)supported by the National Natural Science Foundation of ChinaProject(NCET-12-0310)supported by Program for New Century Excellent Talents in University,China
文摘Based on the solid-gas eutectic unidirectional solidification technique and the principle of unidirectional solidification of single-phase alloy, a new method for evaluating the diffusion coefficient of hydrogen in liquid metals was proposed. Taking Cu-H2 system for example, the influences of argon partial pressure and superheat degree of melt on the diffusion coefficient of hydrogen in liquid metal were studied and the predicted values were similar to each other. The obtained temperature-dependent equation for diffusion coefficient of hydrogen in liquid copper is comparable with experimental data in literature, which validates the effectiveness of this method. The temperature-dependent equations for diffusion coefficient of hydrogen in liquid Mg, Si and Cu-34.6%Mn alloy were also evaluated by this method, along with the values at the melting point of each metal and alloy.
基金supported by the National Natural Science Foundation of China under Grant No. 50504019Natural Science Foundation Project of CQ CSTC under Grant No. 2008BB4040
文摘In this paper, repeated unidirectional bending （RUB）, was applied to improve the texture of AZ31B magnesium alloy sheets so as to enhance their stamping properties. The samples undergoing RUB were annealed at different temperatures. The mechanical properties, formability, textural components and microstructure of the samples before and after RUB were characterized and compared. It was found that the basal textural component was reduced dramatically by RUB, and that （1212） and （1211） textural components appeared. Annealing has a great effect on the mechanical properties of samples undergoing RUB. The plasticity and stamping formability of samples were greatly improved by RUB and annealing at 260℃ for 1 h, and elongation to fracture and Erichsen value were increased to 38% and 67%, respectively.
文摘A continuous unidirectional solidification equipment with the advantages of electric slag remelting, induction heating, continuous casting and unidirectional solidification was built to study the QAl9 4 Cu Al alloy. The results show that the electro slag induction continuous unidirectional solidification process can be used for the steady continuous unidirectional solidification of QAl9 4, and revitalizes the down pulling continuous unidirectional solidification process; that the temperature distribution in the mold wall reflects that of the molten metal in the mold, thus the temperature distribution in the mold wall can be used to control the electric slag induction continuous unidirectional solidification process; and that the mutual matching of the technological parameters is the key to stabilize the solidification process.
基金the National Key R&D Program of China(No.2019YFB1309702)the National Natural Science Foundation of China(Nos.51935001,51725501 and 51905022).
文摘Unidirectional liquid transport without any need of external energy has drawn worldwide attention for its potential applications in various fields such as microfluidics,biomedicine and mechanical engineering.In nature,numerous creatures have evolved such extraordinary unidirectional liquid transport ability such as spider sik,Sarracenia's trichomes,and Nepenthes alata's peristome,etc.This review summarizes the current progresses of natural unidirectional liquid transport on 1-Dimensional(1D)linear structure and 2-Dimensional(2D)surface stucture.The driving force of unidirectional liquid transport which is determined by unique structure exist distinct differences in physics.The fundamental understanding of 1D and 2D unidirectionaliquid transport especially about hierarchical structural characteristics and their transport mechanism were concentrated,and various bioinspired fabrication methods are also introduced.The applications of bioinspired directional liquid transport are demonstrated especially in fields of microfluidies,biomedical devices and anti-icing surfaces.With newly developed smart materials,various liquid transport regulation strategies are also summarized for the control of transport speed,direction guiding,etc.Finally,we provide new insights and future perspectives of the directional transport materials.
基金Project(50504019) supported by the National Natural Science Foundation of ChinaProject(2008BB4040) supported by the Science Foundation of Chongqing, ChinaProject(2008AA4028) supported by Scientific and Technological Project of Chongqing Science and Technology Commission, China
文摘Repeatedly unidirectional bending(RUB) was applied to the magnesium alloy sheet to improve the basal texture.The effect of RUB temperature on resulting structure and room temperature properties was investigated.The texture components of the sheet undergoing RUB at recovery temperature were similar to those of the sheet undergoing RUB at room temperature(RT).As the RUB temperature increased to above recrystallization temperature,the texture components became more disperse and the pyramidal components increased.With the increase of RUB temperature,the grain size near the surface of the sheets undergoing RUB tended to grow up.When the sheets were processed by RUB at medium-high temperature followed by annealing at 533 K,the yield strength and fracture elongation were lower than those of the cold rolled sheet;however,the Erichsen value was slightly higher than that of the cold rolled sheet.The sheet undergoing RUB at RT followed by annealing at 533 K represented the best mechanical properties.
文摘A 2D micro-mechanical model was proposed to study the compressive failure of Uni Directional（UD） carbon/epoxy composite. Considering the initial imperfection and strength distribution of the fiber, the plasticity and ductile damage of the matrix, the failure of T300/914 UD composite under longitudinal compression and in-plane combined loads was simulated by this model. Simulation results show that the longitudinal compressive failure of the UD composite is caused by the plastic yielding of the matrix in kink band, and the fiber initial imperfection is the main reason for it. Under in-plane combined loads, the stress state of the matrix in kink band is changed, which affects the longitudinal compressive failure modes and strength of UD composite.The failure envelope of r_1–s_（12） and r_1–r_2 are obtained by the micro-mechanical model. Meanwhile,the compressive failure mechanism of the UD composite is analyzed. Numerical results agree well with the experimental data, which verifies the validity of the micro-mechanical model.
基金Supported by the National Natural Science Foundation of China(11161027)Natural Science Foundation of Gansu Province(1610RJZA080)the Foundation of Gansu Education Bureau(2017A-155)
文摘An unidirectional and bidirectional hybrid connective star network model with coupling time-delay is constructed in this paper. According to synchronization error systems, adaptive controllers for each node are structured by using the linear system stability method and the Lyapunov stability method. These adaptive controllers can realize the modified functional projective synchronization between each node of star network and an isolated node by argument and analysis. Finally, the corrective and effective of the adaptive controllers are illustrated by some numerical examples.
文摘Considering the S L interface morphology stability, the S L interface energy, the Joule heat produced by electric current at the S L interface, and the change of solute concentration at the S L interface indirectly caused by electric current, the mechanism of reduction of columnar dendrite spacing in unidirectional solidification caused by electric current passing through solid liquid interface was studied. The following conclusions can be drawn that: 1) under sub rapid solidification condition, increasing electric current density will improve the stability of S L interface, thus decreasing the columnar dendrite spacing; 2)there are two ways by which the increase of electric current decreases the columnar dendrite spacing, one is promoting the splitting of the protruding tips at the S L interface, the other is promoting the forming of new convex parts at the bottom of the concave interface.[
基金This work was financially supported by the Major State Basic Research Project of China (G2000067206) and the National Science Fund for Distinguished Young Scientists of China (No.50125415).
文摘Pure copper rods containing continuous columnar crystals were fabricatedusing the downward CUS (Continuous Unidirectional Solidification) equipment. When the technologicalparameters were set as the ranges of mould temperature 1100-1300℃, cooling distance (the distancefrom the exit of the cast mould to the start point of cooling) 10-20 mm, casting speed 0.2-2.5 mm/s,cooling water (20-25℃) volume 1000-1320 L/h, and when these parameters matched reasonably, the CUSprocess was performed stably, and pure copper rods containing continuous columnar crystals withbright and smooth surface were produced. The dendritic arm spacing of the crystals in copper rodsdecreased with increasing the casting speed. The results of the texture by X-ray diffractionanalysis showed that the rods has strong <100> fiber texture.
基金supported by the Outstanding Youth Foundation of Hubei Province,China(Grant No.2017CFA056)the National Natural Science Foundation of China(Grant Nos.41672312 and 41972294).
文摘Cohesive non-swelling soil(CNS)cushion technology is widely used to solve swelling deformation problems in expansive soil areas.However,the swelling inhibition mechanism is still not fully understood.In this study,the inhibition effect on expansive soil using a CNS layer was studied by performing five types of laboratory model tests under unidirectional seepage.The results showed that CNS cushion technology produced a sound inhibition effect on the swelling characteristics of expansive soil.It was shown that the cations in the CNS layer moved downward and accumulated on the surface of solids and produced an electrical environment inside the expansive soil.In this process,the adsorbed hydrated cations participated in ion exchange with the expansive soil,leading to the modification effect on its swelling potential.Meanwhile,the adsorbed water membrane surrounding the expansive soil aggregates formed by the hydrated cations obstructed further adsorption of water molecules,which inhibited the swelling development of expansive soil.Therefore,the swelling inhibition mechanism can be attributed to three factors:(i)modification effect,(ii)electrical environment,and(iii)deadweight of the CNS layer.The combined contribution of modification effect and electrical environment can be considered as an electric charge effect,which mainly controls the swelling characteristics of expansive soil.
基金Project(51674204)supported by the National Natural Science Foundation of ChinaProject(2016GY-219)supported by Shaanxi Provincial Science and Technology Research and Development Program of China
文摘The present study focused on the formation and crystallographic orientation of twinned dendrites coexisting with equiaxed grains in unidirectional solidification of Al-32%Zn(mass fraction)alloy.The morphology was investigated by optical metallograph and electron back-scattered diffraction technique.Results showed that the macrostructure of the alloy exhibited a typical feathery and fan-like structure while the microstructures were elongated lamellas,which were separated by coherent and incoherent twin boundaries.Both the primary trunk and all lateral arms of twinned dendrites grew along〈110〉directions,unlike regular〈100〉α(Al)dendrites.The facet growth of crystals at solid/liquid interface was responsible for the origin of twinned dendrites during the weak local convection,and high thermal gradient and medium solidification velocity had significant contribution to the formation of twinned dendrites.The formation mechanism of twinned dendrites which consisted of three multiplication ways of new twin boundaries formation and one way of dendrite evolution in twin plane was shown schematically.
基金National Natural Science Foundation of China (5090400510972030)
文摘Copper rods with diameter of 17.0 mm have been fabricated by Continuous Unidirectional Solidification (CUS) process. The metallographic results show that the microstructures of the rods are longitudinal columnar crystals and the crystal sizes range roughly among 100-200 μm. The copper rod can be worked to ultra-fine wires 19.7 μm diameter at room temperature without any heat treatments, and the size of the microstructure of the wires obtains nanometer scale. During working process, the elongation multiple of the rod is as high as 740 000 and total deformation true strain over 13.5. The copper rod containing continuous columnar crystals has exhibited excellent cold elongation deformation ability. The results of the texture tests show that the rod has strong <100> fiber texture. After worked at room temperature, texture variants of strong <100> and less strong <111> evolve in the copper wires. With increasing deformation level, the contour of <100> fiber texture decreases while <111> increases. The excellent cold elongation deformation ability and high strength of copper wires is considered to be a result of the strong <100> fiber texture, work hardening and a small quantity of <111>
