An accurate assessment of the evacuation efficiency in case of disasters is of vital importance to the safety design of buildings and street blocks.Hazard sources not only physically but psychologically affect the ped...An accurate assessment of the evacuation efficiency in case of disasters is of vital importance to the safety design of buildings and street blocks.Hazard sources not only physically but psychologically affect the pedestrians,which may further alter their behavioral patterns.This effect is especially significant in narrow spaces,such as corridors and alleys.This study aims to integrate a non-spreading hazard source into the social force model following the results from a previous experiment and simulation,and to simulate unidirectional pedestrian flows over various crowd densities and clarity–intensity properties of the hazard source.The integration include a virtual repulsion force from the hazard source and a decay on the social force term.The simulations reveal(i)that the hazard source creates virtual bottlenecks that suppress the flow,(ii)that the inter-pedestrian push forms a stabilisation phase on the flow-density curve within medium-to-high densities,and(iii)that the pedestrians are prone to a less orderly and stable pattern of movement in low clarity–intensity scenarios,possibly with lateral collisions passing the hazard source.展开更多
We demonstrate a method to realize unidirectional negative refraction in an acoustic parity-time(P T)-symmetric system, which is composed of a pair of metasurfaces sandwiching an air gap. The pair of metasurfaces poss...We demonstrate a method to realize unidirectional negative refraction in an acoustic parity-time(P T)-symmetric system, which is composed of a pair of metasurfaces sandwiching an air gap. The pair of metasurfaces possesses loss and gain modulations. The unidirectional negative refraction, which is strictly limited to the case of incident wave imposing on the loss end of the metasurface, is demonstrated at the exception point(EP) in this P T-symmetric system, while the incidence from the other side leads to strong reflection. Based on rigorous calculations, we explicitly show the underlying mechanism of this model to achieve unidirectional wave scatterings around the EP in the parametric space. In addition, the perfect imaging of a point source in the three-dimensional space, as a signature of negative refraction, is simulated to provide a verification of our work. We envision that this work may sharpen the understanding of P T-symmetric structures and inspire more acoustic functional devices.展开更多
Inventors:Xiujun Cai,Mingyu Chen,Chen Lu,Yifan Wang,Diyu Huang,Hepan Zhu,Yibin Zhu,Bin Zhang Applicant:Zhejiang University,Zhejiang,China Patent No.:US 10,980,541 B2 Date of Patent:Apr.20,2021 An absorbable and unidir...Inventors:Xiujun Cai,Mingyu Chen,Chen Lu,Yifan Wang,Diyu Huang,Hepan Zhu,Yibin Zhu,Bin Zhang Applicant:Zhejiang University,Zhejiang,China Patent No.:US 10,980,541 B2 Date of Patent:Apr.20,2021 An absorbable and unidirectionally compressible intestinal anastomosis device includes a first through pipe portion and a second through pipe portion including large ends and small ends,respectively;the large ends are used for fixing an intestinal canal,and the small end of the second through pipe portion is inserted into the small end of the first through pipe portion.The two large ends are drawn close to each other to achieve an intestineeintestine anastomosis.The outer sides of circular rings at the ends of the small ends of the first through pipe portion and the second through pipe portion are provided with gradually expanded elastic horn-shaped openings.The device can make two stapled intestinal canals rest relatively,thereby avoiding adjustments required in other assembly modes.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
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
The equation used to model the unidirectional flow of methane gas in coal seams is usually formulated as a nonlinear partial differential equation, which needs to be solved numerically with a computer program.Neverthe...The equation used to model the unidirectional flow of methane gas in coal seams is usually formulated as a nonlinear partial differential equation, which needs to be solved numerically with a computer program.Nevertheless, for people without access to the computer program, the conventional numerical method may be inconvenient. Thus, the objective here is to seek some method simpler than the conventional one for solving the flow problem. A commonly used model of the unidirectional methane gas flow is considered, where the methane adsorption is described by the Langmuir isotherm and the free gas is treated as real gas. By introducing the similarity solution, a simple method for solving the flow model is proposed, which can be done on a hand calculator. It is shown by two examples that the gas pressure profile obtained by the proposed method agrees well with the direct numerical solution of the flow model.展开更多
The high-speed reciprocating motion of a detaching roller limits the velocity of a cotton comber and affects the quality of comber slivers. The article has proposed a controllable time-sharing unidirectional hybrid dr...The high-speed reciprocating motion of a detaching roller limits the velocity of a cotton comber and affects the quality of comber slivers. The article has proposed a controllable time-sharing unidirectional hybrid drive mechanism after analyzing detaching roller's current numerical control drive method. The analysis focuses on the detaching roller motion required according to cotton comber's velocity and process. The double-servo motors of the mechanism consists of differential gear trains. The mechanism addresses the problem of increased servo motor power,and failure of promptly responded to the positive inversion process of mechanism driven by servo motors. A velocity calculation model of the detaching roller controllable drive mechanism will be generated by using superposition method and design of differential gear trains. The accuracy of the model will be verified using the test platform. This study has presented a reliable and practical high-speed drive mechanism and can be a reference to future studies on high-speed reciprocating motion drive.展开更多
As a system using a conventional unidirectional air turbine in oscillating water column (OWC) based on a wave energy plant, a twin unidirectional impulse turbine topology has been suggested in previous studies. Howeve...As a system using a conventional unidirectional air turbine in oscillating water column (OWC) based on a wave energy plant, a twin unidirectional impulse turbine topology has been suggested in previous studies. However, the average efficiency of the suggested twin turbine is considerably lower than that of a conventional unidirectional turbine in this topology because reciprocating air flow can’t be rectified adequately by a unidirectional turbine. In order to improve the efficiency, using fluidic diode is discussed. In this study, two different fluidic diodes were discussed by computational fluid dynamics (CFD) and a wind tunnel test. Further, its usefulness is discussed from a view point of the turbine efficiency. The fluidic diode was shown to improve rectification of the topology. However, it needs more improvement in regards to its energy loss in order to enhance the turbine efficiency.展开更多
Plasmonic Bragg reflectors are essential components in plasmonic circuits.Here we propose a novel type of plasmonic Bragg reflector, which has very high reflectance for the right-side incidence and meanwhile has extre...Plasmonic Bragg reflectors are essential components in plasmonic circuits.Here we propose a novel type of plasmonic Bragg reflector, which has very high reflectance for the right-side incidence and meanwhile has extremely large absorption for the left-side incidence.This device is composed of longitudinally asymmetric nanostructures in a metal–insulator–metal waveguide.In order to efficiently analyze, design, and optimize the reflection and transmission characteristics of the proposed device, we develop a semi-analytic coupled-mode model.Results show that the reflectance extinction ratio between plasmonic modes incident from the right-side and the left-side reaches 11 dB.We expect this device with such striking unidirectional reflection performance can be used as insulators in nanoplasmonic circuits.展开更多
The solid-liquid interface morphology and solute segregation behaviour of AI-Li alloy 8090during unidirectional solidification were studied by the liquid metal quenehing method undervaried processing conditions.When s...The solid-liquid interface morphology and solute segregation behaviour of AI-Li alloy 8090during unidirectional solidification were studied by the liquid metal quenehing method undervaried processing conditions.When solidification rate,R【O.13 or】O.75 mm/min (temper-ature gradient,G_L=130℃/cm),the structure revealed of planar or dendritic interfacerespectively.With the increase of R,the interface morphology becomes cellular from planargradually,within a narrow range.And the greater the R,the,finer the dendrite.Segregationof element Cu and impurity elements Fe and Si are quite severe,the interface morphologymarkedly influences on solute segregation.During solidification at coarse dendrite interface,their segregation ratios are rather great and solidified structure is coarse.展开更多
Numerical simulations of unsteady flow problems with moving boundaries commonly require the use of geometric conservation law(GCL).However,in cases of unidirectional large mesh deformation,the cumulative error caused ...Numerical simulations of unsteady flow problems with moving boundaries commonly require the use of geometric conservation law(GCL).However,in cases of unidirectional large mesh deformation,the cumulative error caused by the discrete procedure in GCL can significantly increase,and a direct consequence is that the calculated cell volume may become negative.To control the cumulative error,a new discrete GCL(D-GCL)is proposed.Unlike the original D-GCL,the proposed method uses the control volume analytically evaluated according to the grid motion at the time level n,instead of using the calculated value from the D-GCL itself.Error analysis indicates that the truncation error of the numerical scheme is guaranteed to be the same order as that obtained from the original D-GCL,while the accumulated error is greatly reduced.For validation,two challenging large deformation cases including a rotating circular cylinder case and a descending GAW-(1)two-element airfoil case are selected to be investigated.Good agreements are found between the calculated results and some other literature data,demonstrating the feasibility of the proposed D-GCL for unidirectional motions with large displacements.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
Carbon Fiber Reinforced Polymer(CFRP) has such characteristics as light weight, high strength and corrosion resistance, so it is suitable for corrosive environment and large-span structures. This study investigated th...Carbon Fiber Reinforced Polymer(CFRP) has such characteristics as light weight, high strength and corrosion resistance, so it is suitable for corrosive environment and large-span structures. This study investigated the stability of CFRP slender column, whose slenderness is greater than Euler’s critical load. The columns in this study were formed by a two-step process and the fiber direction was along the same direction of column axis. Firstly, we obtained the basic mechanical properties of the material by tensile experiment. Then, we studied the critical force of 10 CFRP columns with different lengths and widths by axial compression test. Finally, by comparing Euler’s formula with the modified Euler formula and combining with existing literature and experimental result of this paper, we proposed a modified Perry formula which could well predict the critical force of unidirectional CFRP extruded column and could be used for CFRP extruded column research and engineering design.展开更多
A unidirectional reaction for synthesis of the high T<sub>c</sub> superconductor YBa<sub>2</sub>Cu<sub>3</sub>O<sub>x</sub> has beenproposed, Its T<sub>c</sub&g...A unidirectional reaction for synthesis of the high T<sub>c</sub> superconductor YBa<sub>2</sub>Cu<sub>3</sub>O<sub>x</sub> has beenproposed, Its T<sub>c</sub> is 90-94.5 K and △T is 1 K. The phase relationships in the systemY<sub>2</sub>BaCuO<sub>5</sub>-Y<sub>2</sub>Cu<sub>2</sub>O<sub>5</sub>-CuO-YBa<sub>2</sub>Cu<sub>3</sub>O<sub>x</sub> were studied and discussed.展开更多
The dynamics of two-dimensional rigid circles filled with chiral active particles are investigated by employing the overdamped Langevin dynamics simulations. Unidirectional rotation of rigid circles is observed, and t...The dynamics of two-dimensional rigid circles filled with chiral active particles are investigated by employing the overdamped Langevin dynamics simulations. Unidirectional rotation of rigid circles is observed, and the rotational angular velocity(ω) relies mainly on the length(l), the number(nB), and tilt angle(γ) of boards, and the angular velocity(ω)and area fraction(ρ) of chiral active particles. There are optimum values for these parameters at which the average angular velocity of circle reaches its maximum. The center-of-mass mean square displacement for circles drops by about two orders of magnitude for large angular velocity ω of chiral active particles with oscillations in the short-time regime. Our work demonstrates that nanofabricated objects with suitable designs immersed in a bath of chiral active particles can extract and rectify energy in a unidirectional motion.展开更多
This paper considers the unsteady unidirectional flow of a micropolar fluid, produced by the sudden application of an arbitrary time dependent pressure gradient, between two parallel plates. The no-slip and the no-spi...This paper considers the unsteady unidirectional flow of a micropolar fluid, produced by the sudden application of an arbitrary time dependent pressure gradient, between two parallel plates. The no-slip and the no-spin boundary conditions are used. Exact solutions for the velocity and microrotation distributions are obtained based on the use of the complex inversion formula of Laplace transform. The solution of the problem is also considered if the upper boundary of the flow is a free surface. The particular cases of a constant and a harmonically oscillating pressure gradient are then examined and some numerical results are illustrated graphically.展开更多
Melt flow has an important influence on the microstructure formation of alloys. In this paper the growth behaviour of constrained crystals is systematically studied. It is discovered that the constrained crystals have...Melt flow has an important influence on the microstructure formation of alloys. In this paper the growth behaviour of constrained crystals is systematically studied. It is discovered that the constrained crystals have a quite complicated response to melt flow. It may grow upstream or downstream or keep its growth direction unchanged with the influence of melt flow. Also low growth velocity and high flow velocity favour the formation of spike-like crystal. A new model is suggested to explain these experimental展开更多
Directional fluid transport is of significan</span><span style="font-family:Verdana;">ce</span><span style="font-family:Verdana;"> to many physical processes in nature. How ...Directional fluid transport is of significan</span><span style="font-family:Verdana;">ce</span><span style="font-family:Verdana;"> to many physical processes in nature. How to manipulate this process by man-made material is still a key challenge to scientists. In this study, Janus fabric was constructed by electrospinning a layer of polyvinylidene fluoride (PVDF) nanofibers on woven cotton or gauze. The chemical composition, morphology and surface wettability of two sides of Janus fabric were characterized by infrared spectroscopy, scanning electron microscope (SEM) and contact angle measurement. By controlling the PVDF electrospinning time, the maximum hydrostatic pressure of Janus fabric with different PVDF thickness was measured. It was found that PVDF/gauze is more favorable for unidirectional water transportation, and the moisture also can transfer from hydrophobic side to hydrophilic side. With the advantages of facile preparation, low-cost and one-way water/moisture transportation, the Janus fabric prepared in this study can be applied for water separation, humidity transfer and water collection from the air.展开更多
In this work, flexural properties and failure behavior of unidirectional (UD) carbon fiber reinforced polyamide 6 (CF/Nylon 6) and epoxy resin (CF/ Epoxy) laminates were investigated through three-point bending test. ...In this work, flexural properties and failure behavior of unidirectional (UD) carbon fiber reinforced polyamide 6 (CF/Nylon 6) and epoxy resin (CF/ Epoxy) laminates were investigated through three-point bending test. The mechanical properties and failure behavior of 0 and 90 degree CF/Nylon 6 and CF/Epoxy laminates were discussed based on the fiber volume fraction, fiber distribution, void content, interfacial properties, transversal tensile strength and fracture toughness. The effects of fiber volume fraction, fiber distribution, void content and their hybrid effect on the flexural properties were investigated. Step-by-step observation and scanning electron microscope observation of laminates after flexural tests were employed to analyze the fracture process.展开更多
基金Project supported by National Key Research and Development Program of China(Grant Nos.2022YFC3320800 and 2021YFC1523500)the National Natural Science Foundation of China(Grant Nos.71971126,71673163,72304165,72204136,and 72104123).
文摘An accurate assessment of the evacuation efficiency in case of disasters is of vital importance to the safety design of buildings and street blocks.Hazard sources not only physically but psychologically affect the pedestrians,which may further alter their behavioral patterns.This effect is especially significant in narrow spaces,such as corridors and alleys.This study aims to integrate a non-spreading hazard source into the social force model following the results from a previous experiment and simulation,and to simulate unidirectional pedestrian flows over various crowd densities and clarity–intensity properties of the hazard source.The integration include a virtual repulsion force from the hazard source and a decay on the social force term.The simulations reveal(i)that the hazard source creates virtual bottlenecks that suppress the flow,(ii)that the inter-pedestrian push forms a stabilisation phase on the flow-density curve within medium-to-high densities,and(iii)that the pedestrians are prone to a less orderly and stable pattern of movement in low clarity–intensity scenarios,possibly with lateral collisions passing the hazard source.
基金supported by the National Key R&D Program of China (Grant Nos. 2022YFA1404400 and 2022YFA1404403)the National Natural Science Foundation of China (Grant No. 92263208)+3 种基金the Natural Science Foundation of Jiangsu Province (Grant No. BK20210541)the Natural Science Foundation of the Jiangsu Higher Education Institutions of China (Grant No. 21KJB140003)the Fundamental Research Funds for the Central Universitiesthe Open Fund of State Key Laboratory of Acoustics (Grant No. SKLA202313)。
文摘We demonstrate a method to realize unidirectional negative refraction in an acoustic parity-time(P T)-symmetric system, which is composed of a pair of metasurfaces sandwiching an air gap. The pair of metasurfaces possesses loss and gain modulations. The unidirectional negative refraction, which is strictly limited to the case of incident wave imposing on the loss end of the metasurface, is demonstrated at the exception point(EP) in this P T-symmetric system, while the incidence from the other side leads to strong reflection. Based on rigorous calculations, we explicitly show the underlying mechanism of this model to achieve unidirectional wave scatterings around the EP in the parametric space. In addition, the perfect imaging of a point source in the three-dimensional space, as a signature of negative refraction, is simulated to provide a verification of our work. We envision that this work may sharpen the understanding of P T-symmetric structures and inspire more acoustic functional devices.
文摘Inventors:Xiujun Cai,Mingyu Chen,Chen Lu,Yifan Wang,Diyu Huang,Hepan Zhu,Yibin Zhu,Bin Zhang Applicant:Zhejiang University,Zhejiang,China Patent No.:US 10,980,541 B2 Date of Patent:Apr.20,2021 An absorbable and unidirectionally compressible intestinal anastomosis device includes a first through pipe portion and a second through pipe portion including large ends and small ends,respectively;the large ends are used for fixing an intestinal canal,and the small end of the second through pipe portion is inserted into the small end of the first through pipe portion.The two large ends are drawn close to each other to achieve an intestineeintestine anastomosis.The outer sides of circular rings at the ends of the small ends of the first through pipe portion and the second through pipe portion are provided with gradually expanded elastic horn-shaped openings.The device can make two stapled intestinal canals rest relatively,thereby avoiding adjustments required in other assembly modes.
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.
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provided by the Priority Academic Program Development of Jiangsu Higher Education Institutions (PAPD)
文摘The equation used to model the unidirectional flow of methane gas in coal seams is usually formulated as a nonlinear partial differential equation, which needs to be solved numerically with a computer program.Nevertheless, for people without access to the computer program, the conventional numerical method may be inconvenient. Thus, the objective here is to seek some method simpler than the conventional one for solving the flow problem. A commonly used model of the unidirectional methane gas flow is considered, where the methane adsorption is described by the Langmuir isotherm and the free gas is treated as real gas. By introducing the similarity solution, a simple method for solving the flow model is proposed, which can be done on a hand calculator. It is shown by two examples that the gas pressure profile obtained by the proposed method agrees well with the direct numerical solution of the flow model.
基金National Basic Research Program of China(973 Program)(No.2010CB334711)the Applied Basic Research of China National Textile and Apparel Council (Textile Vision Science and Education Fund of China in 2012)
文摘The high-speed reciprocating motion of a detaching roller limits the velocity of a cotton comber and affects the quality of comber slivers. The article has proposed a controllable time-sharing unidirectional hybrid drive mechanism after analyzing detaching roller's current numerical control drive method. The analysis focuses on the detaching roller motion required according to cotton comber's velocity and process. The double-servo motors of the mechanism consists of differential gear trains. The mechanism addresses the problem of increased servo motor power,and failure of promptly responded to the positive inversion process of mechanism driven by servo motors. A velocity calculation model of the detaching roller controllable drive mechanism will be generated by using superposition method and design of differential gear trains. The accuracy of the model will be verified using the test platform. This study has presented a reliable and practical high-speed drive mechanism and can be a reference to future studies on high-speed reciprocating motion drive.
文摘As a system using a conventional unidirectional air turbine in oscillating water column (OWC) based on a wave energy plant, a twin unidirectional impulse turbine topology has been suggested in previous studies. However, the average efficiency of the suggested twin turbine is considerably lower than that of a conventional unidirectional turbine in this topology because reciprocating air flow can’t be rectified adequately by a unidirectional turbine. In order to improve the efficiency, using fluidic diode is discussed. In this study, two different fluidic diodes were discussed by computational fluid dynamics (CFD) and a wind tunnel test. Further, its usefulness is discussed from a view point of the turbine efficiency. The fluidic diode was shown to improve rectification of the topology. However, it needs more improvement in regards to its energy loss in order to enhance the turbine efficiency.
基金Project supported by the Shenzhen Research Foundation,China(Grant Nos.JCYJ20160608153308846,JSGG20170822093953679,and JCYJ20180507182444250)the National Key Research and Development Program of China(Grant No.2017YFC0803506)+1 种基金the National Natural Science Foundation of China(Grant Nos.61261033 and 61162007)the Youth Innovation Promotion Association of Chinese Academy of Sciences(Grant No.20160320)
文摘Plasmonic Bragg reflectors are essential components in plasmonic circuits.Here we propose a novel type of plasmonic Bragg reflector, which has very high reflectance for the right-side incidence and meanwhile has extremely large absorption for the left-side incidence.This device is composed of longitudinally asymmetric nanostructures in a metal–insulator–metal waveguide.In order to efficiently analyze, design, and optimize the reflection and transmission characteristics of the proposed device, we develop a semi-analytic coupled-mode model.Results show that the reflectance extinction ratio between plasmonic modes incident from the right-side and the left-side reaches 11 dB.We expect this device with such striking unidirectional reflection performance can be used as insulators in nanoplasmonic circuits.
文摘The solid-liquid interface morphology and solute segregation behaviour of AI-Li alloy 8090during unidirectional solidification were studied by the liquid metal quenehing method undervaried processing conditions.When solidification rate,R【O.13 or】O.75 mm/min (temper-ature gradient,G_L=130℃/cm),the structure revealed of planar or dendritic interfacerespectively.With the increase of R,the interface morphology becomes cellular from planargradually,within a narrow range.And the greater the R,the,finer the dendrite.Segregationof element Cu and impurity elements Fe and Si are quite severe,the interface morphologymarkedly influences on solute segregation.During solidification at coarse dendrite interface,their segregation ratios are rather great and solidified structure is coarse.
基金supported by the National Basic Research Program of China(″973″Project)(No.2014CB046200)
文摘Numerical simulations of unsteady flow problems with moving boundaries commonly require the use of geometric conservation law(GCL).However,in cases of unidirectional large mesh deformation,the cumulative error caused by the discrete procedure in GCL can significantly increase,and a direct consequence is that the calculated cell volume may become negative.To control the cumulative error,a new discrete GCL(D-GCL)is proposed.Unlike the original D-GCL,the proposed method uses the control volume analytically evaluated according to the grid motion at the time level n,instead of using the calculated value from the D-GCL itself.Error analysis indicates that the truncation error of the numerical scheme is guaranteed to be the same order as that obtained from the original D-GCL,while the accumulated error is greatly reduced.For validation,two challenging large deformation cases including a rotating circular cylinder case and a descending GAW-(1)two-element airfoil case are selected to be investigated.Good agreements are found between the calculated results and some other literature data,demonstrating the feasibility of the proposed D-GCL for unidirectional motions with large displacements.
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Sponsored by the Shandong Provincial Natural Science Foundation,China(Grant No.ZR2018MA029)
文摘Carbon Fiber Reinforced Polymer(CFRP) has such characteristics as light weight, high strength and corrosion resistance, so it is suitable for corrosive environment and large-span structures. This study investigated the stability of CFRP slender column, whose slenderness is greater than Euler’s critical load. The columns in this study were formed by a two-step process and the fiber direction was along the same direction of column axis. Firstly, we obtained the basic mechanical properties of the material by tensile experiment. Then, we studied the critical force of 10 CFRP columns with different lengths and widths by axial compression test. Finally, by comparing Euler’s formula with the modified Euler formula and combining with existing literature and experimental result of this paper, we proposed a modified Perry formula which could well predict the critical force of unidirectional CFRP extruded column and could be used for CFRP extruded column research and engineering design.
文摘A unidirectional reaction for synthesis of the high T<sub>c</sub> superconductor YBa<sub>2</sub>Cu<sub>3</sub>O<sub>x</sub> has beenproposed, Its T<sub>c</sub> is 90-94.5 K and △T is 1 K. The phase relationships in the systemY<sub>2</sub>BaCuO<sub>5</sub>-Y<sub>2</sub>Cu<sub>2</sub>O<sub>5</sub>-CuO-YBa<sub>2</sub>Cu<sub>3</sub>O<sub>x</sub> were studied and discussed.
基金Project supported by the National Natural Science Foundation of China(Grant Nos.21674096 and 21873082)
文摘The dynamics of two-dimensional rigid circles filled with chiral active particles are investigated by employing the overdamped Langevin dynamics simulations. Unidirectional rotation of rigid circles is observed, and the rotational angular velocity(ω) relies mainly on the length(l), the number(nB), and tilt angle(γ) of boards, and the angular velocity(ω)and area fraction(ρ) of chiral active particles. There are optimum values for these parameters at which the average angular velocity of circle reaches its maximum. The center-of-mass mean square displacement for circles drops by about two orders of magnitude for large angular velocity ω of chiral active particles with oscillations in the short-time regime. Our work demonstrates that nanofabricated objects with suitable designs immersed in a bath of chiral active particles can extract and rectify energy in a unidirectional motion.
文摘This paper considers the unsteady unidirectional flow of a micropolar fluid, produced by the sudden application of an arbitrary time dependent pressure gradient, between two parallel plates. The no-slip and the no-spin boundary conditions are used. Exact solutions for the velocity and microrotation distributions are obtained based on the use of the complex inversion formula of Laplace transform. The solution of the problem is also considered if the upper boundary of the flow is a free surface. The particular cases of a constant and a harmonically oscillating pressure gradient are then examined and some numerical results are illustrated graphically.
文摘Melt flow has an important influence on the microstructure formation of alloys. In this paper the growth behaviour of constrained crystals is systematically studied. It is discovered that the constrained crystals have a quite complicated response to melt flow. It may grow upstream or downstream or keep its growth direction unchanged with the influence of melt flow. Also low growth velocity and high flow velocity favour the formation of spike-like crystal. A new model is suggested to explain these experimental
文摘Directional fluid transport is of significan</span><span style="font-family:Verdana;">ce</span><span style="font-family:Verdana;"> to many physical processes in nature. How to manipulate this process by man-made material is still a key challenge to scientists. In this study, Janus fabric was constructed by electrospinning a layer of polyvinylidene fluoride (PVDF) nanofibers on woven cotton or gauze. The chemical composition, morphology and surface wettability of two sides of Janus fabric were characterized by infrared spectroscopy, scanning electron microscope (SEM) and contact angle measurement. By controlling the PVDF electrospinning time, the maximum hydrostatic pressure of Janus fabric with different PVDF thickness was measured. It was found that PVDF/gauze is more favorable for unidirectional water transportation, and the moisture also can transfer from hydrophobic side to hydrophilic side. With the advantages of facile preparation, low-cost and one-way water/moisture transportation, the Janus fabric prepared in this study can be applied for water separation, humidity transfer and water collection from the air.
文摘In this work, flexural properties and failure behavior of unidirectional (UD) carbon fiber reinforced polyamide 6 (CF/Nylon 6) and epoxy resin (CF/ Epoxy) laminates were investigated through three-point bending test. The mechanical properties and failure behavior of 0 and 90 degree CF/Nylon 6 and CF/Epoxy laminates were discussed based on the fiber volume fraction, fiber distribution, void content, interfacial properties, transversal tensile strength and fracture toughness. The effects of fiber volume fraction, fiber distribution, void content and their hybrid effect on the flexural properties were investigated. Step-by-step observation and scanning electron microscope observation of laminates after flexural tests were employed to analyze the fracture process.