To accurately analyze proppant transport in rough intersecting fractures and elucidate the interaction mechanisms among liquid,particles,and rough walls,this study reconstructed a numerical model of fractures in inhom...To accurately analyze proppant transport in rough intersecting fractures and elucidate the interaction mechanisms among liquid,particles,and rough walls,this study reconstructed a numerical model of fractures in inhomogeneous reservoirs with varying brittleness index(BI).Various auto-correlation Gaussian rough fracture models were created using Matlab to assess roughness through the fractal dimension method.This research innovatively combined Boolean operations to establish three-dimensional rough fracture models,incorporating(Computational Fluid Dynamics)CFD-DEM(Discrete Element Method)with a bidirectional method for cosimulation.The proppant transport in fractures was categorized into three zones based on the difference in the turbulent kinetic energy.Artificially induced fracture roughness increases fluid retention and turbulence,causing plugging effects and limiting proppant flow into branch fractures.Additionally,compared with the superior deposition and significant support effects of the spherical proppant,the low-sphericity proppant traveled farther under fracturing fluid,inducing more pronounced plugging near curved fracture intersections;the variation in fracture intersection angles primarily impacted the wall shear stress within the flow field,indicating smaller angles led to higher shear energy at the intersection.Compared with the intersection angle of 30°,the height and area deposited in the 90 branch fracture increased by 52.25%and 65.33%,respectively:notably,injecting proppant from smaller to larger particles(S:M:L)and a low velocity effectively ensured fracture conductivity near the wellbore at joint roughness coefficient(JRC)≥46 while achieving satis-factory placement in the branch fracture,making it a recommended approach.展开更多
Let Cnk denote the set of all t -subsets of an n -set. Assume A ∈ Cnk and B∈Cn.b (A,B) is called a cross-2-intersecting family if |A∩B|≥2 for any A∈A, B∈B.In this paper, the best upper bounds of the cardinalitie...Let Cnk denote the set of all t -subsets of an n -set. Assume A ∈ Cnk and B∈Cn.b (A,B) is called a cross-2-intersecting family if |A∩B|≥2 for any A∈A, B∈B.In this paper, the best upper bounds of the cardinalities for non-empty cross-2-intersecting families of a- and i- subsets are obtained for some n and b . A new proof for a Frankl-Tokushige theorem [6] is also given.展开更多
All-position robots are widely applied in the welding of complicated parts.Welding of intersecting pipes is one of the most typical tasks.The welding seam is a complicated saddle-like space curve,which puts a great ch...All-position robots are widely applied in the welding of complicated parts.Welding of intersecting pipes is one of the most typical tasks.The welding seam is a complicated saddle-like space curve,which puts a great challenge to the pose planning of end-effector.The special robots designed specifically for this kind of tasks are rare in China and lack sufficient theoretical research.In this paper,a systematic research on the pose planning for the end-effectors of robot in the welding of intersecting pipes is conducted.First,the intersecting curve of pipes is mathematically analyzed.The mathematical model of the most general intersecting curve of pipes is derived,and several special forms of this model in degraded situations are also discussed.A new pose planning approach of bisecting angle in main normal plane(BAMNP)for the welding-gun is proposed by using differential geometry and the comparison with the traditional bisecting angle in axial rotation plane(BAARP)method is also analytically conducted.The optimal pose of the welding-gun is to make the orientation posed at the center of the small space formed by the two cylinders and the intersecting curve to help the welding-pool run smoothly.The BAMNP method can make sure the pose vertical to the curve and center between the two cylinders at the same time,therefore its performance in welding-technique is superior to the BAARP method.By using the traditional BAARP method,the robot structure can become simpler and easier to be controlled,because one degree of freedom(DOF)of the robot can be reduced.For the special case of perpendicular intersecting,an index is constructed to evaluate the quality of welding technique in the process of welding.The effect of different combination of pipe size on this index is also discussed.On the basis of practical consideration,selection principle for BAARP and BAMNP is described.The simulations of those two methods for a serial joint-type robot are made in MATLAB,and the simulation results are consistent to the analysis.The mathematical model and the proposed new pose-planning method will lay a solid foundation for future researches on the control and design of all-position welding robots.展开更多
Predicting rock cracking is important for assessing the stability of underground engineering.The effects of the intersecting angle a and the distribution orientation angleβof intersecting fissures on the uniaxial com...Predicting rock cracking is important for assessing the stability of underground engineering.The effects of the intersecting angle a and the distribution orientation angleβof intersecting fissures on the uniaxial compressive strength and the failure characteristics of sandstone containing intersecting fissures are investigated through laboratory experiments and two-dimensional particle flow code(PFC2D).The relationship between the mechanical properties of sandstone and the intersecting angle a and the distribution orientation angleβis analysed.Crack initiation forms and the final failure modes are then categorised and determined via empirical methods.In addition,the cracking processes of intersecting fissures with different a andβvalues are discussed.The results show that variations in the peak stress,peak strain,average modulus,and crack initiation stress of sandstone containing intersecting fissures show a“moth”shape in the space of the a-β-mechanical parameters.Two crack initiation forms are identified:inner tip cracking(usually accompanied by one outer tip cracking)and only outer tips cracking.Two failure modes are observed:(1)the main fracture planes are created at the inner tip and one outer tip,and(2)the main fracture planes are formed at the two outer tips.Two main crack evolution processes of sandstone containing intersecting fissures under uniaxial compression are found.Approaches for quickly determining the crack initiation form and the failure mode are proposed.The combination of the determination equations for the crack initiation form and the failure mode can be used to predict the crack evolution.The approach for determining the crack evolution processes is hence proposed with acceptable precision.展开更多
We investigate the construction of four-family N= 1 supersymmetric Pati-Salam models from Type IIA T^(6)×Z_(2) Z_(2) orientifold with intersecting D6-branes. Utilizing the deterministic algorithm introduced in He...We investigate the construction of four-family N= 1 supersymmetric Pati-Salam models from Type IIA T^(6)×Z_(2) Z_(2) orientifold with intersecting D6-branes. Utilizing the deterministic algorithm introduced in He W, Li T and Sun R(2021 ar Xiv: hep-th/2112.09632), we obtain 274 types of models with three rectangular tori and distinct gauge coupling relations at string scale,while 6 types of models with two rectangular tori and one tilted torus. In both cases, there exists a class of models with gauge coupling unification at string scale. In particular, for the models with two rectangular tori, one tilted torus and gauge coupling unification, the gaugino condensations are allowed, and thus supersymmetry breaking and moduli stabilization are possible for further phenomenological study.展开更多
We construct two conical surfaces which take non-coplanar lines as generatrix and rational Bezier curve as ridge-line, and prove that the intersecting line of conical surface has similar properties to Bezier curve. Th...We construct two conical surfaces which take non-coplanar lines as generatrix and rational Bezier curve as ridge-line, and prove that the intersecting line of conical surface has similar properties to Bezier curve. Then, the smoothly blending of two cylinders whose axes are non-coplanar is realized by taking intersecting line of conical surface as axes.展开更多
This paper focuses on the simulation analysis of stripe formation and dynamic features of intersecting pedestrian flows.The intersecting flows consist of two streams of pedestrians and each pedestrian stream has a des...This paper focuses on the simulation analysis of stripe formation and dynamic features of intersecting pedestrian flows.The intersecting flows consist of two streams of pedestrians and each pedestrian stream has a desired walking direction.The model adopted in the simulations is the social force model, which can reproduce the self-organization phenomena successfully. Three scenarios of different cross angles are established. The simulations confirm the empirical observations that there is a stripe formation when two streams of pedestrians intersect and the direction of the stripes is perpendicular to the sum of the directional vectors of the two streams. It can be concluded from the numerical simulation results that smaller cross angle results in higher mean speed and lower level of speed fluctuation. Moreover, the detailed pictures of pedestrians＇ moving behavior at intersections are given as well.展开更多
In order to establish the groove model for intersecting structures of circular tubes,mathematical model of the intersecting line is established by the method of analytic geometry,and parametric equations are thus dete...In order to establish the groove model for intersecting structures of circular tubes,mathematical model of the intersecting line is established by the method of analytic geometry,and parametric equations are thus determined.The dihedral angle,groove angle and actual cutting angle for any position of the intersecting line are derived as well.In order to identify groove vectors for two pipes,a new analytical method,i.e.coplanarity of vectors,is further proposed to complete the groove model.The established model is virtually verified by programming and simulation calculation in the MATLAB environment.The results show that groove vectors of intersecting structures simulated by MATLAB are consistent with the theoretical groove model,indicating that the theoretical groove model established in this paper is accurate,and further proves that the proposed coplanarity of vectors for solving groove vectors is correct and feasible.Finally,a graphical user interface(GUI)is developed by MATLAB software to independently realize functions such as model drawing,variable calculation and data output.The research outcome provides a theoretical foundation for the actual welding of circular intersecting structures,and lays an essential basis for weld bead layout and path planning.展开更多
The celebrated Erdos-Ko-Rado theorem states that given n≥2k,every intersecting k-uni-n-1 form hypergraph G on n vertices has at most(n-1 k-1)edges.This paper states spectral versions of the Erd6s-_Ko--Rado theorem:le...The celebrated Erdos-Ko-Rado theorem states that given n≥2k,every intersecting k-uni-n-1 form hypergraph G on n vertices has at most(n-1 k-1)edges.This paper states spectral versions of the Erd6s-_Ko--Rado theorem:let G be an intersecting k-uniform hypergraph on n vertices with n≥2k.Then,the sharp upper bounds for the spectral radius of Aα(G)and 2*(G)are presented,where Aα(G)=αD(G)+(1-α).A(G)is a convex linear combination of the degree diagonal tensor D(G)and the adjacency tensor A(G)for 0≤α<1,and Q^(*)(G)is the incidence Q-tensor,respectively.Furthermore,when n>2k,the extremal hypergraphs which attain the sharp upper bounds are characterized.The proof mainly relies on the Perron-Frobenius theorem for nonnegative tensor and the property of the maximizing connected hypergraphs.展开更多
This paper presents an approach for recognizing both isolated and intersecting geometric features of freeform surface models of parts,for the purpose of automating the process planning of sheet metal forming.The devel...This paper presents an approach for recognizing both isolated and intersecting geometric features of freeform surface models of parts,for the purpose of automating the process planning of sheet metal forming.The developed methodology has three major steps:subdivision of B-spline surfaces,detection of protrusions and depressions,and recognition of geometric features for sheet metal forming domain.The input geometry data format of the part is based on an IGES CAD surface model represented in the form of trimmed B-spline surfaces.Each surface is classified or subdivided into different curvature regions with the aid of curvature property surfaces obtained by using symbolic computation of B-spline surfaces.Those regions satisfying a particular geometry and topology relation are recognized as protrusion and depression(DP) shapes.The DP shapes are then classified into different geometric features using a rule-based approach.A verified feasibility study of the developed method is also presented.展开更多
The analytic expression of the special points on the intersection of two cones with their axes intersecting(ITCTAI) is given. It also presents a method to construct the special points graphically according to the anal...The analytic expression of the special points on the intersection of two cones with their axes intersecting(ITCTAI) is given. It also presents a method to construct the special points graphically according to the analytic expression of them. Finally, with computer programming language, it gives a program to generate the intersection in several different cases.展开更多
Fast beam migration(FBM),characterized by its super-high efficiency in velocity model building,consists of three main steps:beam forming,beam propagation,and image forming.The super-high efficiency is achieved by beam...Fast beam migration(FBM),characterized by its super-high efficiency in velocity model building,consists of three main steps:beam forming,beam propagation,and image forming.The super-high efficiency is achieved by beam forming,as it needs only to be performed once for one dataset and is independent of velocity,and the other two steps take relatively little time.However,compared to the beam-propagation and image-forming steps,the beam-forming step is still quite time-consuming owing to the high-dimensional computing problem of estimating the source and receiver slope orientation of a beam.Furthermore,previous methods for estimating the source and receiver slope orientation of a beam struggled to deal with intersecting events,leading to poor imaging results for complex subsurface structures,such as unconformities or faults,where events often intersect.We propose the use of a three-step multimodal optimization method based on the neighborhood crowding differential evolution(NCDE)algorithm to estimate the source and receiver slope orientation of a beam during the beam-forming step,which can quickly and accurately obtain slope orientations when events intersect.We first test the three-step multimodal optimization algorithm on a 3D super-gather and provide the parameter criteria.We then apply the FBM based on the three-step multimodal optimization algorithm to the Marmousi 2 and 3D SEG/EAGE salt models.Both results demonstrate that the proposed method can image intersecting events well and that the imaging quality of complex zones is improved.We also apply the proposed method to a 2D offshore seismic dataset containing abundant intersecting events,which validates the practicality of the proposed method.展开更多
When two trains going through a tunnel pass each other,the difference of the surrounding space between a train’s both sides rises,which induces abrupt aerodynamic force variations on the trains,resulting in the pheno...When two trains going through a tunnel pass each other,the difference of the surrounding space between a train’s both sides rises,which induces abrupt aerodynamic force variations on the trains,resulting in the phenomenon of sudden swaying.This study employs the unsteady Reynolds-averaged Navier-Stokes(URANS)method of numerical simulation to analyse the effects of two terrain conditions,that is,a tunnel with and without asymmetric mountain structures at its portals,on the aerodynamic characteristics of two trains during their intersections.The results indicate that during two trains’intersections at tunnel portals,the rear car suffers the highest risk of swaying.The presence of asymmetric mountain structures at tunnel portals reduces the risk of swaying the train adjacent to the mountains but increases the risk for trains farther away from the mountains.When trains intersect at the exit(for the train adjacent to the mountain)of the tunnel,the presence of mountain structures at the portal reduces the peak-to-peak lateral force values by 12.7%for the front car of the train adjacent to the mountain and increases by 16.5%for the rear car of the train away from the mountain.The impact of the mountain structures on the peak-to-peak values of a train’s lateral force is minimal when two trains intersect at the midpoint of the tunnel.Therefore,it is suggested to consider the placement of symmetrical buffer structures or the modification of existing mountain structures at appropriate locations near tunnel portals to mitigate the abrupt lateral force variations experienced by passing trains.展开更多
The stress analysis based on the theory of a thin shell is carried out for cylindrical shells with normally intersecting nozzles subjected to external moment loads on the ends of shells with a large diameter ratio(ρ ...The stress analysis based on the theory of a thin shell is carried out for cylindrical shells with normally intersecting nozzles subjected to external moment loads on the ends of shells with a large diameter ratio(ρ 0 ?0. 8). Instead of the Donnell shallow shell equation, the modified Morley equation, which is applicable toρ 0(R/T)1/2 ?1, is used for the analysis of the shell with cutout. The solution in terms of displacement function for the nozzle with a nonplanar end is based on the Goldenveizer equation. The boundary forces and displacements at the intersection are all transformed from Gaussian coordinates (α, β) on the shell, or Gaussian coordinates (ζ, θ) on the nozzle into three-di-mensional cylindrical coordinates(ρ,θ, z). Their expressions on the intersecting curve are periodic functions ofθ and expanded in Fourier series. Every harmonic of Fourier coefficients of boundary forces and displacements are obtained by numerical quadrature. The results obtained are in agreement with those from the three-dimensional finite element method and experiments.展开更多
The vertex-arboricity a(G)of a graph G is the minimum number of colors required for a vertex coloring of G such that no cycle is monochromatic.The list vertex-arboricity al(G)is the list-coloring version of this conce...The vertex-arboricity a(G)of a graph G is the minimum number of colors required for a vertex coloring of G such that no cycle is monochromatic.The list vertex-arboricity al(G)is the list-coloring version of this concept.In this paper,we prove that every planar graph G without intersecting 5-cycles has al(G)≤2.This extends a result by Raspaud and Wang[On the vertex-arboricity of planar graphs,European J.Combin.29(2008),1064-1075]that every planar graph G without 5-cycles has a(G)≤2.展开更多
Intersecting connection plays an important role in the new diagrid structural system for high-rise buildings.To investigate the static behavior of the intersecting connection of concrete-filled steel tubular(CFST)colu...Intersecting connection plays an important role in the new diagrid structural system for high-rise buildings.To investigate the static behavior of the intersecting connection of concrete-filled steel tubular(CFST)columns,a typical reduced-scale planner connection specimen is tested under monotonic axial compression.The failure modes,force mechanism and bearing capacity of intersecting CFST connections are analyzed further in the follow-up numerical simulation,considering influences of intersecting angle,elliptical plate and ring plate.Test and simulation results prove that,intersecting connection can develop fully plastic deformation and provide sufficient bearing capacity.Parametric analysis indicates that bearing capacity of planar intersecting CFST connection mainly depends on intersecting angle and thickness of elliptical plate,while the ring plate affects that little.Capacity estimation method for planar intersecting CFST connection is proposed basing on the capacity of the critical section which is located near intersecting center for a distance of steel tube radius,and the design suggestions is provided in the end of this paper.展开更多
Aggregation-induced emission luminogens(AIEgens)are typically largeπ-conjugated molecules,but their low affinity and noninvasiveness toward analytes limit practical applications.To address this,smaller,more planar AI...Aggregation-induced emission luminogens(AIEgens)are typically largeπ-conjugated molecules,but their low affinity and noninvasiveness toward analytes limit practical applications.To address this,smaller,more planar AIEgens are needed.Stilbene,though structurally suitable,lacks visible luminescence.Here,we report a minimally modified stilbene-based AIEgen-4-dipropylamino-4'-cyano-bridged stilbene(DpCBS[7])-that exhibits fluorescence solvatochromism and efficient AIE across a broad polarity range in the visible region.DpCBS[7]exhibits low quantum yields(Φ_(fl)=0.010.04)in solvents from nonpolar n-hexane to polar dimethyl sulfoxide,with large Stokes shifts,viscosity-sensitive luminescence,and highly efficient solid-state luminescence(Φ_(fl)=0.70).To elucidate its dual solvatochromic and AiE behavior,femtosecond transient absorption spectroscopy was conducted.In solution,DpCBS[7]displays transient absorption with lifetimes of 21 ps(toluene)and 56 ps(acetonitrile)at 293 K,indicating ultrafast nonradiative decay leading to low Φ_(fl).Arrhenius analysis over the temperature range of 263-313 K revealed activation energies(ΔE_(a))of 9.90kJ/mol in toluene and 12.8 kJ/mol in acetonitrile for the S_(1)→S_(0) decay of DpCBS[7].The ΔE_(a) values show no clear systematic dependence on solvent polarity.In contrast,pre-exponential factor A remains consistently high regardless of solvent polarity,indicating that the striking photophysical response is governed primarily by the pre-exponential factor rather than by modulation of the activation energy.These findings highlight the fundamental importance of tailoring the distribution function through structural modification as a robust strategy to control AiE characteristics.展开更多
Traffic at urban intersections frequently encounters unexpected obstructions,resulting in congestion due to uncooperative and priority-based driving behavior.This paper presents an optimal right-turn coordination syst...Traffic at urban intersections frequently encounters unexpected obstructions,resulting in congestion due to uncooperative and priority-based driving behavior.This paper presents an optimal right-turn coordination system for Connected and Automated Vehicles(CAVs)at single-lane intersections,particularly in the context of left-hand side driving on roads.The goal is to facilitate smooth right turns for certain vehicles without creating bottlenecks.We consider that all approaching vehicles share relevant information through vehicular communications.The Intersection Coordination Unit(ICU)processes this information and communicates the optimal crossing or turning times to the vehicles.The primary objective of this coordination is to minimize overall traffic delays,which also helps improve the fuel consumption of vehicles.By considering information from upcoming vehicles at the intersection,the coordination system solves an optimization problem to determine the best timing for executing right turns,ultimately minimizing the total delay for all vehicles.The proposed coordination system is evaluated at a typical urban intersection,and its performance is compared to traditional traffic systems.Numerical simulation results indicate that the proposed coordination system significantly enhances the average traffic speed and fuel consumption compared to the traditional traffic system in various scenarios.展开更多
Let l>r≥3.Given a 2-graph F,the expansion E^((r))of F is an r-graph obtained from F by adding r-2 new vertices into each edge.When F is a clique of order l,the Turán number ex(n,F^((r)))was first asymptotical...Let l>r≥3.Given a 2-graph F,the expansion E^((r))of F is an r-graph obtained from F by adding r-2 new vertices into each edge.When F is a clique of order l,the Turán number ex(n,F^((r)))was first asymptotically determined by Mubayi(J Comb Theory Ser B 96:122–134,2006)and exactly computed by Pikhurko(J Comb Theory Ser B 103:220–225,2013).Let F_(k,l)be the 2-graph on(l-1)k+1 vertices consisting of k cliques of order l intersecting at exactly one vertex.We determine the exact Turán number ex(n,F_(k,l)^((3)))for all l>3,k≥1,and sufficiently large n,as well as the corresponding extremal graphs.展开更多
At a time when humanity grapples with intersecting deficits in peace,development,security and governance,civilizations stand at a crossroads.As traditional Western-led solutions falter,China’s Global Civilization Ini...At a time when humanity grapples with intersecting deficits in peace,development,security and governance,civilizations stand at a crossroads.As traditional Western-led solutions falter,China’s Global Civilization Initiative(GCI)emerges as a transformative framework,translating historical wisdom into actionable strategies.Recent forums like the 11th Nishan Forum on World Civilizations and the Global Civilizations Dialogue Ministerial Meeting underscore growing consensus on core principles:equality,mutual learning,inclusive dialogue,and collaborative response to global challenges.As Chinese President Xi Jinping pointed out in his congratulatory letter to the Global Civilizations Dialogue Ministerial Meeting,“History shows that exchanges and mutual learning among civilizations are essential for civilizations to flourish and for human progress to be made.”展开更多
文摘To accurately analyze proppant transport in rough intersecting fractures and elucidate the interaction mechanisms among liquid,particles,and rough walls,this study reconstructed a numerical model of fractures in inhomogeneous reservoirs with varying brittleness index(BI).Various auto-correlation Gaussian rough fracture models were created using Matlab to assess roughness through the fractal dimension method.This research innovatively combined Boolean operations to establish three-dimensional rough fracture models,incorporating(Computational Fluid Dynamics)CFD-DEM(Discrete Element Method)with a bidirectional method for cosimulation.The proppant transport in fractures was categorized into three zones based on the difference in the turbulent kinetic energy.Artificially induced fracture roughness increases fluid retention and turbulence,causing plugging effects and limiting proppant flow into branch fractures.Additionally,compared with the superior deposition and significant support effects of the spherical proppant,the low-sphericity proppant traveled farther under fracturing fluid,inducing more pronounced plugging near curved fracture intersections;the variation in fracture intersection angles primarily impacted the wall shear stress within the flow field,indicating smaller angles led to higher shear energy at the intersection.Compared with the intersection angle of 30°,the height and area deposited in the 90 branch fracture increased by 52.25%and 65.33%,respectively:notably,injecting proppant from smaller to larger particles(S:M:L)and a low velocity effectively ensured fracture conductivity near the wellbore at joint roughness coefficient(JRC)≥46 while achieving satis-factory placement in the branch fracture,making it a recommended approach.
基金Suppored by Postdoctral Fellowship Foundation of China
文摘Let Cnk denote the set of all t -subsets of an n -set. Assume A ∈ Cnk and B∈Cn.b (A,B) is called a cross-2-intersecting family if |A∩B|≥2 for any A∈A, B∈B.In this paper, the best upper bounds of the cardinalities for non-empty cross-2-intersecting families of a- and i- subsets are obtained for some n and b . A new proof for a Frankl-Tokushige theorem [6] is also given.
基金supported by National Nautural Science Foundation of China(Grant No.50775002)Key Science and Technology Research Program of Beijing Municipal Commission of Education of China(Grant No.KZ200910005003)
文摘All-position robots are widely applied in the welding of complicated parts.Welding of intersecting pipes is one of the most typical tasks.The welding seam is a complicated saddle-like space curve,which puts a great challenge to the pose planning of end-effector.The special robots designed specifically for this kind of tasks are rare in China and lack sufficient theoretical research.In this paper,a systematic research on the pose planning for the end-effectors of robot in the welding of intersecting pipes is conducted.First,the intersecting curve of pipes is mathematically analyzed.The mathematical model of the most general intersecting curve of pipes is derived,and several special forms of this model in degraded situations are also discussed.A new pose planning approach of bisecting angle in main normal plane(BAMNP)for the welding-gun is proposed by using differential geometry and the comparison with the traditional bisecting angle in axial rotation plane(BAARP)method is also analytically conducted.The optimal pose of the welding-gun is to make the orientation posed at the center of the small space formed by the two cylinders and the intersecting curve to help the welding-pool run smoothly.The BAMNP method can make sure the pose vertical to the curve and center between the two cylinders at the same time,therefore its performance in welding-technique is superior to the BAARP method.By using the traditional BAARP method,the robot structure can become simpler and easier to be controlled,because one degree of freedom(DOF)of the robot can be reduced.For the special case of perpendicular intersecting,an index is constructed to evaluate the quality of welding technique in the process of welding.The effect of different combination of pipe size on this index is also discussed.On the basis of practical consideration,selection principle for BAARP and BAMNP is described.The simulations of those two methods for a serial joint-type robot are made in MATLAB,and the simulation results are consistent to the analysis.The mathematical model and the proposed new pose-planning method will lay a solid foundation for future researches on the control and design of all-position welding robots.
基金supported by the National Key R&D Program of China(Grant No.2018YFC1504802)the National Natural Science Foundation of China(Grant No.52074042)the Basic Research and Frontier Exploration Project of Chongqing,China in 2018(Grant No.cstc2018jcyj AX0453)。
文摘Predicting rock cracking is important for assessing the stability of underground engineering.The effects of the intersecting angle a and the distribution orientation angleβof intersecting fissures on the uniaxial compressive strength and the failure characteristics of sandstone containing intersecting fissures are investigated through laboratory experiments and two-dimensional particle flow code(PFC2D).The relationship between the mechanical properties of sandstone and the intersecting angle a and the distribution orientation angleβis analysed.Crack initiation forms and the final failure modes are then categorised and determined via empirical methods.In addition,the cracking processes of intersecting fissures with different a andβvalues are discussed.The results show that variations in the peak stress,peak strain,average modulus,and crack initiation stress of sandstone containing intersecting fissures show a“moth”shape in the space of the a-β-mechanical parameters.Two crack initiation forms are identified:inner tip cracking(usually accompanied by one outer tip cracking)and only outer tips cracking.Two failure modes are observed:(1)the main fracture planes are created at the inner tip and one outer tip,and(2)the main fracture planes are formed at the two outer tips.Two main crack evolution processes of sandstone containing intersecting fissures under uniaxial compression are found.Approaches for quickly determining the crack initiation form and the failure mode are proposed.The combination of the determination equations for the crack initiation form and the failure mode can be used to predict the crack evolution.The approach for determining the crack evolution processes is hence proposed with acceptable precision.
基金supported by the National Key Research and Development Program of China Grant No. 2020YFC2201504by the Projects No. 11875062, No. 11947302, and No. 12047 503 supported by the National Natural Science Foundation of China+1 种基金by the Key Research Program of the Chinese Academy of Sciences, Grant NO. XDPB15supported by KIAS Individual Grant PG080701。
文摘We investigate the construction of four-family N= 1 supersymmetric Pati-Salam models from Type IIA T^(6)×Z_(2) Z_(2) orientifold with intersecting D6-branes. Utilizing the deterministic algorithm introduced in He W, Li T and Sun R(2021 ar Xiv: hep-th/2112.09632), we obtain 274 types of models with three rectangular tori and distinct gauge coupling relations at string scale,while 6 types of models with two rectangular tori and one tilted torus. In both cases, there exists a class of models with gauge coupling unification at string scale. In particular, for the models with two rectangular tori, one tilted torus and gauge coupling unification, the gaugino condensations are allowed, and thus supersymmetry breaking and moduli stabilization are possible for further phenomenological study.
文摘We construct two conical surfaces which take non-coplanar lines as generatrix and rational Bezier curve as ridge-line, and prove that the intersecting line of conical surface has similar properties to Bezier curve. Then, the smoothly blending of two cylinders whose axes are non-coplanar is realized by taking intersecting line of conical surface as axes.
基金Project supported by the National Natural Science Foundation of China(Grant No.61233001)the Fundamental Research Funds for the Central Universities,China(Grant No.2017JBM014)
文摘This paper focuses on the simulation analysis of stripe formation and dynamic features of intersecting pedestrian flows.The intersecting flows consist of two streams of pedestrians and each pedestrian stream has a desired walking direction.The model adopted in the simulations is the social force model, which can reproduce the self-organization phenomena successfully. Three scenarios of different cross angles are established. The simulations confirm the empirical observations that there is a stripe formation when two streams of pedestrians intersect and the direction of the stripes is perpendicular to the sum of the directional vectors of the two streams. It can be concluded from the numerical simulation results that smaller cross angle results in higher mean speed and lower level of speed fluctuation. Moreover, the detailed pictures of pedestrians＇ moving behavior at intersections are given as well.
基金This work was supported by Natural Science Foundation of Fujian Province(Grant No.2020J01873)Science and Technology Major Project of Fujian Province(Grant No.2020HZ03018).
文摘In order to establish the groove model for intersecting structures of circular tubes,mathematical model of the intersecting line is established by the method of analytic geometry,and parametric equations are thus determined.The dihedral angle,groove angle and actual cutting angle for any position of the intersecting line are derived as well.In order to identify groove vectors for two pipes,a new analytical method,i.e.coplanarity of vectors,is further proposed to complete the groove model.The established model is virtually verified by programming and simulation calculation in the MATLAB environment.The results show that groove vectors of intersecting structures simulated by MATLAB are consistent with the theoretical groove model,indicating that the theoretical groove model established in this paper is accurate,and further proves that the proposed coplanarity of vectors for solving groove vectors is correct and feasible.Finally,a graphical user interface(GUI)is developed by MATLAB software to independently realize functions such as model drawing,variable calculation and data output.The research outcome provides a theoretical foundation for the actual welding of circular intersecting structures,and lays an essential basis for weld bead layout and path planning.
基金the National Natural Science Foundation of China(Nos.11971311,11531001)the Montenegrin-Chinese Science and Technology Cooperation Project(No.3-12).
文摘The celebrated Erdos-Ko-Rado theorem states that given n≥2k,every intersecting k-uni-n-1 form hypergraph G on n vertices has at most(n-1 k-1)edges.This paper states spectral versions of the Erd6s-_Ko--Rado theorem:let G be an intersecting k-uniform hypergraph on n vertices with n≥2k.Then,the sharp upper bounds for the spectral radius of Aα(G)and 2*(G)are presented,where Aα(G)=αD(G)+(1-α).A(G)is a convex linear combination of the degree diagonal tensor D(G)and the adjacency tensor A(G)for 0≤α<1,and Q^(*)(G)is the incidence Q-tensor,respectively.Furthermore,when n>2k,the extremal hypergraphs which attain the sharp upper bounds are characterized.The proof mainly relies on the Perron-Frobenius theorem for nonnegative tensor and the property of the maximizing connected hypergraphs.
文摘This paper presents an approach for recognizing both isolated and intersecting geometric features of freeform surface models of parts,for the purpose of automating the process planning of sheet metal forming.The developed methodology has three major steps:subdivision of B-spline surfaces,detection of protrusions and depressions,and recognition of geometric features for sheet metal forming domain.The input geometry data format of the part is based on an IGES CAD surface model represented in the form of trimmed B-spline surfaces.Each surface is classified or subdivided into different curvature regions with the aid of curvature property surfaces obtained by using symbolic computation of B-spline surfaces.Those regions satisfying a particular geometry and topology relation are recognized as protrusion and depression(DP) shapes.The DP shapes are then classified into different geometric features using a rule-based approach.A verified feasibility study of the developed method is also presented.
文摘The analytic expression of the special points on the intersection of two cones with their axes intersecting(ITCTAI) is given. It also presents a method to construct the special points graphically according to the analytic expression of them. Finally, with computer programming language, it gives a program to generate the intersection in several different cases.
基金Natural Science Foundation of China(42304128 and 42074150)the National Key Research and Development Program of China(2023YFC2906704-5 and 2023YFC370790)+1 种基金the Mount Tai Industry Leading Talent Project Special Fund Support(tscx202312018)the Jinan Science and Technology Innovation Development Plan(Social Livelihood Special Project)(202131001)。
文摘Fast beam migration(FBM),characterized by its super-high efficiency in velocity model building,consists of three main steps:beam forming,beam propagation,and image forming.The super-high efficiency is achieved by beam forming,as it needs only to be performed once for one dataset and is independent of velocity,and the other two steps take relatively little time.However,compared to the beam-propagation and image-forming steps,the beam-forming step is still quite time-consuming owing to the high-dimensional computing problem of estimating the source and receiver slope orientation of a beam.Furthermore,previous methods for estimating the source and receiver slope orientation of a beam struggled to deal with intersecting events,leading to poor imaging results for complex subsurface structures,such as unconformities or faults,where events often intersect.We propose the use of a three-step multimodal optimization method based on the neighborhood crowding differential evolution(NCDE)algorithm to estimate the source and receiver slope orientation of a beam during the beam-forming step,which can quickly and accurately obtain slope orientations when events intersect.We first test the three-step multimodal optimization algorithm on a 3D super-gather and provide the parameter criteria.We then apply the FBM based on the three-step multimodal optimization algorithm to the Marmousi 2 and 3D SEG/EAGE salt models.Both results demonstrate that the proposed method can image intersecting events well and that the imaging quality of complex zones is improved.We also apply the proposed method to a 2D offshore seismic dataset containing abundant intersecting events,which validates the practicality of the proposed method.
基金supported by the Science and Technology Research and Development Program of China Railway(Grant No.N2023J016)the Science and Technology Innovation Program of Hunan Province,China(Grant No.2022RC3040)+1 种基金the Natural Science Foundation of Hunan Province,China(Grant No.2022JJ30727)the Major Project of China Railway Design Corporation(Project No.2022A02480004).
文摘When two trains going through a tunnel pass each other,the difference of the surrounding space between a train’s both sides rises,which induces abrupt aerodynamic force variations on the trains,resulting in the phenomenon of sudden swaying.This study employs the unsteady Reynolds-averaged Navier-Stokes(URANS)method of numerical simulation to analyse the effects of two terrain conditions,that is,a tunnel with and without asymmetric mountain structures at its portals,on the aerodynamic characteristics of two trains during their intersections.The results indicate that during two trains’intersections at tunnel portals,the rear car suffers the highest risk of swaying.The presence of asymmetric mountain structures at tunnel portals reduces the risk of swaying the train adjacent to the mountains but increases the risk for trains farther away from the mountains.When trains intersect at the exit(for the train adjacent to the mountain)of the tunnel,the presence of mountain structures at the portal reduces the peak-to-peak lateral force values by 12.7%for the front car of the train adjacent to the mountain and increases by 16.5%for the rear car of the train away from the mountain.The impact of the mountain structures on the peak-to-peak values of a train’s lateral force is minimal when two trains intersect at the midpoint of the tunnel.Therefore,it is suggested to consider the placement of symmetrical buffer structures or the modification of existing mountain structures at appropriate locations near tunnel portals to mitigate the abrupt lateral force variations experienced by passing trains.
文摘The stress analysis based on the theory of a thin shell is carried out for cylindrical shells with normally intersecting nozzles subjected to external moment loads on the ends of shells with a large diameter ratio(ρ 0 ?0. 8). Instead of the Donnell shallow shell equation, the modified Morley equation, which is applicable toρ 0(R/T)1/2 ?1, is used for the analysis of the shell with cutout. The solution in terms of displacement function for the nozzle with a nonplanar end is based on the Goldenveizer equation. The boundary forces and displacements at the intersection are all transformed from Gaussian coordinates (α, β) on the shell, or Gaussian coordinates (ζ, θ) on the nozzle into three-di-mensional cylindrical coordinates(ρ,θ, z). Their expressions on the intersecting curve are periodic functions ofθ and expanded in Fourier series. Every harmonic of Fourier coefficients of boundary forces and displacements are obtained by numerical quadrature. The results obtained are in agreement with those from the three-dimensional finite element method and experiments.
基金supported by the National Natural Science Foundation of China(Nos.11971437,11771402)the Natural Science Foundation of Zhejiang Province(No.LY19A010015).
文摘The vertex-arboricity a(G)of a graph G is the minimum number of colors required for a vertex coloring of G such that no cycle is monochromatic.The list vertex-arboricity al(G)is the list-coloring version of this concept.In this paper,we prove that every planar graph G without intersecting 5-cycles has al(G)≤2.This extends a result by Raspaud and Wang[On the vertex-arboricity of planar graphs,European J.Combin.29(2008),1064-1075]that every planar graph G without 5-cycles has a(G)≤2.
基金The presented work is financially supported by National Science Foundation(NSF,USA)project 90815029 and SLDRCE08-A-04.
文摘Intersecting connection plays an important role in the new diagrid structural system for high-rise buildings.To investigate the static behavior of the intersecting connection of concrete-filled steel tubular(CFST)columns,a typical reduced-scale planner connection specimen is tested under monotonic axial compression.The failure modes,force mechanism and bearing capacity of intersecting CFST connections are analyzed further in the follow-up numerical simulation,considering influences of intersecting angle,elliptical plate and ring plate.Test and simulation results prove that,intersecting connection can develop fully plastic deformation and provide sufficient bearing capacity.Parametric analysis indicates that bearing capacity of planar intersecting CFST connection mainly depends on intersecting angle and thickness of elliptical plate,while the ring plate affects that little.Capacity estimation method for planar intersecting CFST connection is proposed basing on the capacity of the critical section which is located near intersecting center for a distance of steel tube radius,and the design suggestions is provided in the end of this paper.
基金supported in part by MEXT/JSPS KAK-ENHI grants 23H02036(G.K.)JP23H04631,JP23K26670,JP23H03833,JP24K01471,JP24K01515(K.M.)+8 种基金JP23K01977,JP23K20039,JP25K01678(K.O.)24K08341(S.S.)Toyota Riken Scholar(K.M.)the Yoshida Aca-demic and Educational Promotion Foundation(K.M.)the Environment Research and Technology Development Fund(grant number 3RA-2502)of the Environmental Restoration and Conservation Agency provided by Ministry of the Environment of Japan(K.M.)Kyushu University Platform of Inter-/Transdisciplinary Energy Research(Q-PIT)Module-Research Program(K.M.)Kyushu University Integrated Initiative for Designing Future Society(K.M.)JST SPRING,Grant Number JPMJSP2180(T.T.)Network Joint Research Center for Materials and Devices(20253036)(K.I.)The Creative Research Encouragement Award,School of Materials and Chemical Technology,Institute of Science Tokyo(G.K.)。
文摘Aggregation-induced emission luminogens(AIEgens)are typically largeπ-conjugated molecules,but their low affinity and noninvasiveness toward analytes limit practical applications.To address this,smaller,more planar AIEgens are needed.Stilbene,though structurally suitable,lacks visible luminescence.Here,we report a minimally modified stilbene-based AIEgen-4-dipropylamino-4'-cyano-bridged stilbene(DpCBS[7])-that exhibits fluorescence solvatochromism and efficient AIE across a broad polarity range in the visible region.DpCBS[7]exhibits low quantum yields(Φ_(fl)=0.010.04)in solvents from nonpolar n-hexane to polar dimethyl sulfoxide,with large Stokes shifts,viscosity-sensitive luminescence,and highly efficient solid-state luminescence(Φ_(fl)=0.70).To elucidate its dual solvatochromic and AiE behavior,femtosecond transient absorption spectroscopy was conducted.In solution,DpCBS[7]displays transient absorption with lifetimes of 21 ps(toluene)and 56 ps(acetonitrile)at 293 K,indicating ultrafast nonradiative decay leading to low Φ_(fl).Arrhenius analysis over the temperature range of 263-313 K revealed activation energies(ΔE_(a))of 9.90kJ/mol in toluene and 12.8 kJ/mol in acetonitrile for the S_(1)→S_(0) decay of DpCBS[7].The ΔE_(a) values show no clear systematic dependence on solvent polarity.In contrast,pre-exponential factor A remains consistently high regardless of solvent polarity,indicating that the striking photophysical response is governed primarily by the pre-exponential factor rather than by modulation of the activation energy.These findings highlight the fundamental importance of tailoring the distribution function through structural modification as a robust strategy to control AiE characteristics.
基金supported by the Japan Society for the Promotion of Science(JSPS)Grants-in-Aid for Scientific Research(C)23K03898.
文摘Traffic at urban intersections frequently encounters unexpected obstructions,resulting in congestion due to uncooperative and priority-based driving behavior.This paper presents an optimal right-turn coordination system for Connected and Automated Vehicles(CAVs)at single-lane intersections,particularly in the context of left-hand side driving on roads.The goal is to facilitate smooth right turns for certain vehicles without creating bottlenecks.We consider that all approaching vehicles share relevant information through vehicular communications.The Intersection Coordination Unit(ICU)processes this information and communicates the optimal crossing or turning times to the vehicles.The primary objective of this coordination is to minimize overall traffic delays,which also helps improve the fuel consumption of vehicles.By considering information from upcoming vehicles at the intersection,the coordination system solves an optimization problem to determine the best timing for executing right turns,ultimately minimizing the total delay for all vehicles.The proposed coordination system is evaluated at a typical urban intersection,and its performance is compared to traditional traffic systems.Numerical simulation results indicate that the proposed coordination system significantly enhances the average traffic speed and fuel consumption compared to the traditional traffic system in various scenarios.
基金supported in part by the National Natural Science Foundation of China(Nos.11901292,11631014).
文摘Let l>r≥3.Given a 2-graph F,the expansion E^((r))of F is an r-graph obtained from F by adding r-2 new vertices into each edge.When F is a clique of order l,the Turán number ex(n,F^((r)))was first asymptotically determined by Mubayi(J Comb Theory Ser B 96:122–134,2006)and exactly computed by Pikhurko(J Comb Theory Ser B 103:220–225,2013).Let F_(k,l)be the 2-graph on(l-1)k+1 vertices consisting of k cliques of order l intersecting at exactly one vertex.We determine the exact Turán number ex(n,F_(k,l)^((3)))for all l>3,k≥1,and sufficiently large n,as well as the corresponding extremal graphs.
文摘At a time when humanity grapples with intersecting deficits in peace,development,security and governance,civilizations stand at a crossroads.As traditional Western-led solutions falter,China’s Global Civilization Initiative(GCI)emerges as a transformative framework,translating historical wisdom into actionable strategies.Recent forums like the 11th Nishan Forum on World Civilizations and the Global Civilizations Dialogue Ministerial Meeting underscore growing consensus on core principles:equality,mutual learning,inclusive dialogue,and collaborative response to global challenges.As Chinese President Xi Jinping pointed out in his congratulatory letter to the Global Civilizations Dialogue Ministerial Meeting,“History shows that exchanges and mutual learning among civilizations are essential for civilizations to flourish and for human progress to be made.”
