Let T:T^(d)→T^(d),defined by Tx=AX(mod 1),where A is a d×d integer matrix with eigenvalues 1<|λ_(1)|≤|λ_(2)|≤…≤|λ_(d)|,We investigate the Hausdorff dimension of the recurrence set R(ψ)={x∈T^(d):T^(n)...Let T:T^(d)→T^(d),defined by Tx=AX(mod 1),where A is a d×d integer matrix with eigenvalues 1<|λ_(1)|≤|λ_(2)|≤…≤|λ_(d)|,We investigate the Hausdorff dimension of the recurrence set R(ψ)={x∈T^(d):T^(n)x∈B(x,ψ(n))for infinitely many n}forα≥log|λ_(d)/λ_(1)|,whereψis a positive decreasing function defined onℕand its lower order at infinity isα=lim inf_(n→∞)-logψ(n)/n.In the case that A is diagonalizable overℚwith integral eigenvalues,we obtain the dimension formula.展开更多
By selecting any one limb of 3-RSR parallel robot as a research object, the paper establishes a position and orienta- tion relationship matrix between the moving platform and the base by means of Denavit-Hartenberg （...By selecting any one limb of 3-RSR parallel robot as a research object, the paper establishes a position and orienta- tion relationship matrix between the moving platform and the base by means of Denavit-Hartenberg （D-H） transformation matrix. The error mapping model is derived from original error to the error of the platform by using matrix differential method. This model contains all geometric original errors of the robot. The nonlinear implicit function relation between po- sition and orientation error of the platform and the original geometric errors is simplified as a linear explicit function rela- tion. The results provide a basis for further studying error analysis and error compensation.展开更多
This paper illustrates the crack identification method combining wavelet analysis with transform matrix. Firstly, the fundamental vibration mode was applied to wavelet analysis. The crack location was found by the pea...This paper illustrates the crack identification method combining wavelet analysis with transform matrix. Firstly, the fundamental vibration mode was applied to wavelet analysis. The crack location was found by the peaks of the wavelet coefficients. Secondly, based on the identified crack locations, a simple transform matrix method requiring only the first two tested natural frequencies was used to further identify the crack depth. The present method can be used for crack identification in a complex structure. Numerical results of crack identification of a stepped cantilever beam show that the suggested method is feasible.展开更多
Let the triangle matrix A^(ru)be a generalization of the Cesàro matrix and U∈{c_(0),c,l_(∞)}.In this study,we essentially deal with the space U(A^(ru))defined by the domain of A^(ru)in the space U and give the ...Let the triangle matrix A^(ru)be a generalization of the Cesàro matrix and U∈{c_(0),c,l_(∞)}.In this study,we essentially deal with the space U(A^(ru))defined by the domain of A^(ru)in the space U and give the bases,and determine the Kothe-Toeplitz,generalized K?theToeplitz and bounded-duals of the space U(A^(ru)).We characterize the classes(l_(∞)(A^(ru)):l_(∞)),(l_(∞)(A^(ru)):c),(c(A^(ru)):c),and(U:V(A^(ru)))of infinite matrices,where V denotes any given sequence space.Additionally,we also present a Steinhaus type theorem.As an another result of this study,we investigate the l_(p)-norm of the matrix A^(ru)and as a result obtaining a generalized version of Hardy's inequality,and some inclusion relations.Moreover,we compute the norm of well-known operators on the matrix domain l_(p)(A^(ru)).展开更多
The structures of the space switching and the wavelength switching optical cross connect (OXC) nodes which are based on the arrayed waveguide grating (AWG) multiplexer are analyzed.By the matrix transformation relatio...The structures of the space switching and the wavelength switching optical cross connect (OXC) nodes which are based on the arrayed waveguide grating (AWG) multiplexer are analyzed.By the matrix transformation relation between the input and output wavelengths of the AWG multiplexer, the wavelength transmission routings of the space switching and wavelength switching OXC nodes are determined.展开更多
The domain of generalized difference matrix B（r, s） in the classical spaces L∞, e, and co was recently studied by Kirisci and Basar in [16]. The main goal of this article is to introduce the paranormed sequence spa...The domain of generalized difference matrix B（r, s） in the classical spaces L∞, e, and co was recently studied by Kirisci and Basar in [16]. The main goal of this article is to introduce the paranormed sequence spaces L∞（B,p）, c（B,p）, and co（B,p）, which are more general and comprehensive than the corresponding consequences of the matrix domain of B（r, s）, as well as other studies in literature. Besides this, the alpha-, beta-, and gamma-duals of the spaces L∞ （B, p）, c（B, p）, and co （B, p） are computed and the bases of the spaces c（B, p） and co （B, p） are constructed. The final section of this article is devoted to the characterization of the classes （λ（B, p）： μ） and （μ：λ（B, p））, where λ ∈ {c, co, L∞ } and μ is any given sequence space. Additionally, the characterization of some other classes which are related to the space of Mmost convergent sequences is obtained by means of a given lemma.展开更多
The class f of almost convergent sequences was introduced by G.G. Lorentz, using the idea of the Banach limits [A contribution to the theory of divergent sequences, Acta Math. 80（1948）, 167-190]. Let fo（B） and f（...The class f of almost convergent sequences was introduced by G.G. Lorentz, using the idea of the Banach limits [A contribution to the theory of divergent sequences, Acta Math. 80（1948）, 167-190]. Let fo（B） and f（B） be the domain of the double sequential band matrix B（r, s） in the sequence spaces f0 and f. In this article, the β- and γ-duals of the space f（B） are determined. Additionally, we give some inclusion theorems concerning with the spaces f0（B） and f（β）. Moreover, the classes （f（B） ： μ） and （μ： f（B）） of infinite matrices are characterized, and the characterizations of some other classes are also given as an application of those main results, where μ is an arbitrary sequence space.展开更多
This paper transforms combined loads, applied at an arbitrary point of a thin-walled open section beam, to the shear centre of the cross-section of the beam. Therein, a generalized transformation matrix for loads with...This paper transforms combined loads, applied at an arbitrary point of a thin-walled open section beam, to the shear centre of the cross-section of the beam. Therein, a generalized transformation matrix for loads with respect to the shear centre is derived, this accounting for the bimoments that develop due to the way the combined loads are applied. This and the authors’ earlier paper (World Journal of Mechanics 2021, 11, 205-236) provide a full solution to the theory of thin-walled, open-section structures bearing combined loading. The earlier work identified arbitrary loading with the section’s area properties that are necessary to axial and shear stress calculations within the structure’s thin walls. In the previous paper attention is paid to the relevant axes of loading and to the transformations of loading required between axes for stress calculations arising from tension/compression, bending, torsion and shear. The derivation of the general transformation matrix applies to all types of loadings including, axial tensile and compression forces, transverse shear, longitudinal bending. One application, representing all these load cases, is given of a simple channel cantilever with an eccentrically located end load.展开更多
In this paper, we research the probability theory and matrix transformation based technique to manage the data for processing and analysis. Clustering analysis research has a long history, over the decades, the import...In this paper, we research the probability theory and matrix transformation based technique to manage the data for processing and analysis. Clustering analysis research has a long history, over the decades, the importance and the cross characteristics with other research direction to get the affirmation of the people. The probability theory and linear algebra act as the powerful tool for analyzing and mining data. The experimental result illustrates the effectiveness. In the near future, we plan to conduct more theoretical analysis on the topic.展开更多
UE-Brzier （unified and extended Brzier） basis is the unified form of Brzier-like bases, including polynomial Brzier basis, trigonometric polynomial and hyperbolic polynomial Brzier basis. Similar to the original Brz...UE-Brzier （unified and extended Brzier） basis is the unified form of Brzier-like bases, including polynomial Brzier basis, trigonometric polynomial and hyperbolic polynomial Brzier basis. Similar to the original Brzier-like bases, UE-Brzier basis func-tions are not orthogonal. In this paper, a group of orthogonal basis is constructed based on UE-Brzier basis. The transformation matrices between UE-Brzier basis and the proposed orthogonal basis are also solved.展开更多
Through analysis of the basic transformation of a typical body,the error transformations of the position vector and the displacement vector are employed,a general model for positioning errors of NC machine tools by us...Through analysis of the basic transformation of a typical body,the error transformations of the position vector and the displacement vector are employed,a general model for positioning errors of NC machine tools by using kinematics of the multi body system is discussed.By means of 8031 single chip system,intelligent error compensation controller has been developed.The results of experiments on XH714 machining center show that the positioning accuracy is enhanced effectively by more than 50%.展开更多
The concept of metamorphic mechanism is put forward according to the changeof configurations from one state to another. Different configurations of metamorphic mechanism aredescribed through the method of Huston lower...The concept of metamorphic mechanism is put forward according to the changeof configurations from one state to another. Different configurations of metamorphic mechanism aredescribed through the method of Huston lower body arrays. Kinematics analyses for metamorphicmechanism with generalized topological structure, including the velocity, angular velocity,acceleration and angular acceleration, are given. Dynamic equations for an arbitrary configuration,including close-loop constraints, are formed by using Kane's equations. For an arbitrary metamorphicmechanism, the transformation matrix of generalized speeds between configuration zeta and zeta+1 isobtained for the first time. Furthermore, configuration-complete dynamic modeling of metamorphicmechanism including all configurations is completely established.展开更多
We consider the problem of the two-point resistance on an m ×n cobweb network with a 2r boundary, which has never been solved before. Up to now researchers just only solved the cases with free boundary or null re...We consider the problem of the two-point resistance on an m ×n cobweb network with a 2r boundary, which has never been solved before. Up to now researchers just only solved the cases with free boundary or null resistor boundary. This paper gives the general formulae of the resistance between any two nodes in both tinite and infinite cases using a method of direct summation pioneered by Tan [Z. Z. Tan, et al., J. Phys. A 46 （2013） 195202], which is simpler and can be easier to use in practice. This method contrasts the Green＇s function technique and the Laplacian matrix approach, which is difllcult to apply to the geometry of a cobweb with a 2r boundary. We deduce several interesting results according to our genera/formula. In the end we compare and illuminate our formulae with two examples. Our analysis gives the result directly as a single summation, and the result is mainly composed of the characteristic roots.展开更多
Aiming at the workspace calculation problem of multi-joint serial manipulators,a surface enveloping and overlaying (SEO) method is presented to identify and visualize the manipulator workspace.The SEO method is compos...Aiming at the workspace calculation problem of multi-joint serial manipulators,a surface enveloping and overlaying (SEO) method is presented to identify and visualize the manipulator workspace.The SEO method is composed of two stages:the first stage is to choose reference points of the manipulator and calculate their boundary surfaces using the nth enveloping method;the second stage is to overlay these boundary surfaces to identify the final workspace.The SEO method is basically a combination of the analytic method and the numerical method.By delineating the graphic representation of the workspace step by step,the SEO method is easy to analyze the existence and the shape of voids and holes.The basic theory of the SEO method and formulas for workspace calculation are presented based on a 6R serial manipulator.By showing the workspace calculation results,the SEO method is proved working correctly.展开更多
Corrosion re sistance of Zircaloy-4 alloy tube in superheated steam at 673 K/10.3 MPa is anisotropic.A part of the surface undergoes uniform corrosion while the other suffers nodular corrosion.Narrow and wide nodules ...Corrosion re sistance of Zircaloy-4 alloy tube in superheated steam at 673 K/10.3 MPa is anisotropic.A part of the surface undergoes uniform corrosion while the other suffers nodular corrosion.Narrow and wide nodules are observed after an exposure period of 3 and 30 days,respectively.A new matrix transformation method is established in order to study the formation mechanism of nodules in the cross-section(CS) of Zircaloy-4 alloy tube using the EBSD technique,while the CS perpendicular to axial direction(AD).The results reveal that the microtexture is a key factor behind the two types of corrosion.Furthermore,the oxide layers grow anisotropically over the corroded surface.A thick oxide layer forms over the nodular corrosion region on the grains with c-axis oriented in the range of 40° around tangential direction(TD),whereas a thin oxide layer over the uniform corrosion region is detected on the grains with c-axis oriented in the range of 68° around TD.In short,the anisotropic growth of oxide layer was caused by the change of microtexture of the Zr-4 alloy tube,and this anisotropic growth of oxide layer contributed to the nodules formation.展开更多
Fatigue strength assessment of a horizontal axis wind turbine(HAWT)composite blade is considered.Fatigue load cases are identified,and loads are calculated by the GH Bladed software which is specified at the IEC61400 ...Fatigue strength assessment of a horizontal axis wind turbine(HAWT)composite blade is considered.Fatigue load cases are identified,and loads are calculated by the GH Bladed software which is specified at the IEC61400 international specification and GL(Germanisher Lloyd)regulations for the wind energy conversion system.Stress analysis is performed with a 3-D finite element method(FEM).Considering Saint-Venant′s principle,a uniform cross section FEM model is built at each critical zone.Stress transformation matrixes(STM)are set up by applied six unit load components on the FEM model separately.STM can be used to convert the external load into stresses in the linear elastic range.The main material of composite wind turbine blade is fiber reinforced plastics(FRP).In order to evaluate the degree of fatigue damage of FRP,the stresses of fiber direction are extracted and the well-known strength criterion-Puck theory is used.The total fatigue damage of each laminate on the critical point is counted by the rain-flow counting method and Miner′s damage law based on general S-N curves.Several sections of a 45.3mblade of a 2 MW wind turbine are studied using the fatigue evaluation method.The performance of this method is compared with far more costly business software FOCUS.The results show that the fatigue damage of multi-axis FRP can be assessed conveniently by the FEM-STM method.And the proposed method gives a reliable and efficient method to analyze the fatigue damage of slender composite structure with variable cross-sections.展开更多
Because of the range-angle dependency in random log frequency diverse array(RD-log-FDA) radar, a method for designing beamspace transformation matrix in angle and range based on the receive signal has been proposed.It...Because of the range-angle dependency in random log frequency diverse array(RD-log-FDA) radar, a method for designing beamspace transformation matrix in angle and range based on the receive signal has been proposed.It is demonstrated that the designed beamspace transformation matrix basically meets the requirements of beam gain.However, there are some problems in the transformation matrix designed, such as unstable beam gain and high sidelobe.Hence, we propose an optimization method by adjusting array element spacing and random number in frequency offset to get the optimum beam gain.Therefore, particle swarm optimization(PSO) is used to find the optimal solution.The beam gain comparison before and after the optimization is obtained by simulation, and the results show that the optimized array after beamspace preprocessing has more stable beam gain, lower sidelobe, and higher resolution in parameter estimation.In conclusion, the RD-log-FDA is capable of forming desired beam gain in angle and distance through beamspace preprocessing, and suppressing interference signals in other areas.展开更多
This paper proposes a novel control approach for fault-tolerant control of dual three-phase permanent magnet synchronous motor(PMSM) under one-phase open-circuit fault.A modified six-phase static coordinate transforma...This paper proposes a novel control approach for fault-tolerant control of dual three-phase permanent magnet synchronous motor(PMSM) under one-phase open-circuit fault.A modified six-phase static coordinate transformation matrix and an extended rotating coordinate transformation matrix are investigated considering the influence of the fifth harmonic space on fault-tolerant control. These mathematical models are further analyzed in the fundamental space and the fifth harmonic space after the fault and to eliminate the coupling between the d-q axis voltage equation in the fundamental wave space and the d-q axis voltage equation in the fifth harmonic space, a secondary rotation coordinate transformation matrix is proposed. To achieve the purpose of reducing torque ripple, the fault-tolerant control method proposed in this paper not only takes the minimum copper loss as the constraint condition, but also injects the fifth harmonic current. The experimental result of current and torque is used to verify the accuracy of fault-tolerant control.展开更多
基金supported by the Science Foundation of China University of Petroleum,Beijing(2462023SZBH013)the China Postdoctoral Science Foundation(2023M743878)+2 种基金the Postdoctoral Fellowship Program of CPSF(GZB20240848)supported partially by the NSFC(12271176)the Guangdong Natural Science Foundation(2024A1515010946).
文摘Let T:T^(d)→T^(d),defined by Tx=AX(mod 1),where A is a d×d integer matrix with eigenvalues 1<|λ_(1)|≤|λ_(2)|≤…≤|λ_(d)|,We investigate the Hausdorff dimension of the recurrence set R(ψ)={x∈T^(d):T^(n)x∈B(x,ψ(n))for infinitely many n}forα≥log|λ_(d)/λ_(1)|,whereψis a positive decreasing function defined onℕand its lower order at infinity isα=lim inf_(n→∞)-logψ(n)/n.In the case that A is diagonalizable overℚwith integral eigenvalues,we obtain the dimension formula.
基金National Natural Science Foundation of China(No.51275486)the Specialized Research Fund for the Doctoral Program of Higher Education(No.20111420110005)
文摘By selecting any one limb of 3-RSR parallel robot as a research object, the paper establishes a position and orienta- tion relationship matrix between the moving platform and the base by means of Denavit-Hartenberg （D-H） transformation matrix. The error mapping model is derived from original error to the error of the platform by using matrix differential method. This model contains all geometric original errors of the robot. The nonlinear implicit function relation between po- sition and orientation error of the platform and the original geometric errors is simplified as a linear explicit function rela- tion. The results provide a basis for further studying error analysis and error compensation.
基金supported by the Key Natural Science Research of Guangdong Province,China P.R(Grant No.05Z003)the Project of Tackling Key Problem of Guangdong Province,China P.R(Grant No.2006B12401008)the National Natural Science Foundation of China(Grant No.10672067).
文摘This paper illustrates the crack identification method combining wavelet analysis with transform matrix. Firstly, the fundamental vibration mode was applied to wavelet analysis. The crack location was found by the peaks of the wavelet coefficients. Secondly, based on the identified crack locations, a simple transform matrix method requiring only the first two tested natural frequencies was used to further identify the crack depth. The present method can be used for crack identification in a complex structure. Numerical results of crack identification of a stepped cantilever beam show that the suggested method is feasible.
文摘Let the triangle matrix A^(ru)be a generalization of the Cesàro matrix and U∈{c_(0),c,l_(∞)}.In this study,we essentially deal with the space U(A^(ru))defined by the domain of A^(ru)in the space U and give the bases,and determine the Kothe-Toeplitz,generalized K?theToeplitz and bounded-duals of the space U(A^(ru)).We characterize the classes(l_(∞)(A^(ru)):l_(∞)),(l_(∞)(A^(ru)):c),(c(A^(ru)):c),and(U:V(A^(ru)))of infinite matrices,where V denotes any given sequence space.Additionally,we also present a Steinhaus type theorem.As an another result of this study,we investigate the l_(p)-norm of the matrix A^(ru)and as a result obtaining a generalized version of Hardy's inequality,and some inclusion relations.Moreover,we compute the norm of well-known operators on the matrix domain l_(p)(A^(ru)).
基金NationalKeyLabofBroadBandFiberTransmissionandCommunicatonSystemTechnology ElectronicUniversityofScienceandTechnology China
文摘The structures of the space switching and the wavelength switching optical cross connect (OXC) nodes which are based on the arrayed waveguide grating (AWG) multiplexer are analyzed.By the matrix transformation relation between the input and output wavelengths of the AWG multiplexer, the wavelength transmission routings of the space switching and wavelength switching OXC nodes are determined.
基金Supported by Natural Science Foundations of China (11101108, 11171301, 10771191 and 10471124)Natural Science Foundation of Zhejiang Province of China (Y6090105)
文摘Let X and Y be Banach spaces, 0 〈 q 〈 ＋∞, i ≤ p 〈 ＋∞. In this paper, we characterize matrix transformations of lq （ X ） to lp （ Y ）.
文摘The domain of generalized difference matrix B（r, s） in the classical spaces L∞, e, and co was recently studied by Kirisci and Basar in [16]. The main goal of this article is to introduce the paranormed sequence spaces L∞（B,p）, c（B,p）, and co（B,p）, which are more general and comprehensive than the corresponding consequences of the matrix domain of B（r, s）, as well as other studies in literature. Besides this, the alpha-, beta-, and gamma-duals of the spaces L∞ （B, p）, c（B, p）, and co （B, p） are computed and the bases of the spaces c（B, p） and co （B, p） are constructed. The final section of this article is devoted to the characterization of the classes （λ（B, p）： μ） and （μ：λ（B, p））, where λ ∈ {c, co, L∞ } and μ is any given sequence space. Additionally, the characterization of some other classes which are related to the space of Mmost convergent sequences is obtained by means of a given lemma.
文摘The class f of almost convergent sequences was introduced by G.G. Lorentz, using the idea of the Banach limits [A contribution to the theory of divergent sequences, Acta Math. 80（1948）, 167-190]. Let fo（B） and f（B） be the domain of the double sequential band matrix B（r, s） in the sequence spaces f0 and f. In this article, the β- and γ-duals of the space f（B） are determined. Additionally, we give some inclusion theorems concerning with the spaces f0（B） and f（β）. Moreover, the classes （f（B） ： μ） and （μ： f（B）） of infinite matrices are characterized, and the characterizations of some other classes are also given as an application of those main results, where μ is an arbitrary sequence space.
文摘This paper transforms combined loads, applied at an arbitrary point of a thin-walled open section beam, to the shear centre of the cross-section of the beam. Therein, a generalized transformation matrix for loads with respect to the shear centre is derived, this accounting for the bimoments that develop due to the way the combined loads are applied. This and the authors’ earlier paper (World Journal of Mechanics 2021, 11, 205-236) provide a full solution to the theory of thin-walled, open-section structures bearing combined loading. The earlier work identified arbitrary loading with the section’s area properties that are necessary to axial and shear stress calculations within the structure’s thin walls. In the previous paper attention is paid to the relevant axes of loading and to the transformations of loading required between axes for stress calculations arising from tension/compression, bending, torsion and shear. The derivation of the general transformation matrix applies to all types of loadings including, axial tensile and compression forces, transverse shear, longitudinal bending. One application, representing all these load cases, is given of a simple channel cantilever with an eccentrically located end load.
文摘In this paper, we research the probability theory and matrix transformation based technique to manage the data for processing and analysis. Clustering analysis research has a long history, over the decades, the importance and the cross characteristics with other research direction to get the affirmation of the people. The probability theory and linear algebra act as the powerful tool for analyzing and mining data. The experimental result illustrates the effectiveness. In the near future, we plan to conduct more theoretical analysis on the topic.
基金Supported by National Science Foundation of China(No.60904070,61272032)the Natural Science Foundation of Zhejiang Province(No.LY12F02002,Y1111101)
文摘UE-Brzier （unified and extended Brzier） basis is the unified form of Brzier-like bases, including polynomial Brzier basis, trigonometric polynomial and hyperbolic polynomial Brzier basis. Similar to the original Brzier-like bases, UE-Brzier basis func-tions are not orthogonal. In this paper, a group of orthogonal basis is constructed based on UE-Brzier basis. The transformation matrices between UE-Brzier basis and the proposed orthogonal basis are also solved.
文摘Through analysis of the basic transformation of a typical body,the error transformations of the position vector and the displacement vector are employed,a general model for positioning errors of NC machine tools by using kinematics of the multi body system is discussed.By means of 8031 single chip system,intelligent error compensation controller has been developed.The results of experiments on XH714 machining center show that the positioning accuracy is enhanced effectively by more than 50%.
基金This project is supported by National Natural Science Foundation of China (No.50075009)Postdoctoral Science Foundation of China.
文摘The concept of metamorphic mechanism is put forward according to the changeof configurations from one state to another. Different configurations of metamorphic mechanism aredescribed through the method of Huston lower body arrays. Kinematics analyses for metamorphicmechanism with generalized topological structure, including the velocity, angular velocity,acceleration and angular acceleration, are given. Dynamic equations for an arbitrary configuration,including close-loop constraints, are formed by using Kane's equations. For an arbitrary metamorphicmechanism, the transformation matrix of generalized speeds between configuration zeta and zeta+1 isobtained for the first time. Furthermore, configuration-complete dynamic modeling of metamorphicmechanism including all configurations is completely established.
文摘We consider the problem of the two-point resistance on an m ×n cobweb network with a 2r boundary, which has never been solved before. Up to now researchers just only solved the cases with free boundary or null resistor boundary. This paper gives the general formulae of the resistance between any two nodes in both tinite and infinite cases using a method of direct summation pioneered by Tan [Z. Z. Tan, et al., J. Phys. A 46 （2013） 195202], which is simpler and can be easier to use in practice. This method contrasts the Green＇s function technique and the Laplacian matrix approach, which is difllcult to apply to the geometry of a cobweb with a 2r boundary. We deduce several interesting results according to our genera/formula. In the end we compare and illuminate our formulae with two examples. Our analysis gives the result directly as a single summation, and the result is mainly composed of the characteristic roots.
文摘Aiming at the workspace calculation problem of multi-joint serial manipulators,a surface enveloping and overlaying (SEO) method is presented to identify and visualize the manipulator workspace.The SEO method is composed of two stages:the first stage is to choose reference points of the manipulator and calculate their boundary surfaces using the nth enveloping method;the second stage is to overlay these boundary surfaces to identify the final workspace.The SEO method is basically a combination of the analytic method and the numerical method.By delineating the graphic representation of the workspace step by step,the SEO method is easy to analyze the existence and the shape of voids and holes.The basic theory of the SEO method and formulas for workspace calculation are presented based on a 6R serial manipulator.By showing the workspace calculation results,the SEO method is proved working correctly.
文摘Corrosion re sistance of Zircaloy-4 alloy tube in superheated steam at 673 K/10.3 MPa is anisotropic.A part of the surface undergoes uniform corrosion while the other suffers nodular corrosion.Narrow and wide nodules are observed after an exposure period of 3 and 30 days,respectively.A new matrix transformation method is established in order to study the formation mechanism of nodules in the cross-section(CS) of Zircaloy-4 alloy tube using the EBSD technique,while the CS perpendicular to axial direction(AD).The results reveal that the microtexture is a key factor behind the two types of corrosion.Furthermore,the oxide layers grow anisotropically over the corroded surface.A thick oxide layer forms over the nodular corrosion region on the grains with c-axis oriented in the range of 40° around tangential direction(TD),whereas a thin oxide layer over the uniform corrosion region is detected on the grains with c-axis oriented in the range of 68° around TD.In short,the anisotropic growth of oxide layer was caused by the change of microtexture of the Zr-4 alloy tube,and this anisotropic growth of oxide layer contributed to the nodules formation.
基金supported jointly by the National Basic Research Program of China(″973″Program)(No.2014CB046200)the Natural Science Foundation of Jiangsu Province(No.BK2014059)+1 种基金the Priority Academic Program Development of Jiangsu Higher Education Institutionsthe National Natural Science Foundation of China(No.11172135)
文摘Fatigue strength assessment of a horizontal axis wind turbine(HAWT)composite blade is considered.Fatigue load cases are identified,and loads are calculated by the GH Bladed software which is specified at the IEC61400 international specification and GL(Germanisher Lloyd)regulations for the wind energy conversion system.Stress analysis is performed with a 3-D finite element method(FEM).Considering Saint-Venant′s principle,a uniform cross section FEM model is built at each critical zone.Stress transformation matrixes(STM)are set up by applied six unit load components on the FEM model separately.STM can be used to convert the external load into stresses in the linear elastic range.The main material of composite wind turbine blade is fiber reinforced plastics(FRP).In order to evaluate the degree of fatigue damage of FRP,the stresses of fiber direction are extracted and the well-known strength criterion-Puck theory is used.The total fatigue damage of each laminate on the critical point is counted by the rain-flow counting method and Miner′s damage law based on general S-N curves.Several sections of a 45.3mblade of a 2 MW wind turbine are studied using the fatigue evaluation method.The performance of this method is compared with far more costly business software FOCUS.The results show that the fatigue damage of multi-axis FRP can be assessed conveniently by the FEM-STM method.And the proposed method gives a reliable and efficient method to analyze the fatigue damage of slender composite structure with variable cross-sections.
基金supported by the National Natural Science Foundation of China (62001506)。
文摘Because of the range-angle dependency in random log frequency diverse array(RD-log-FDA) radar, a method for designing beamspace transformation matrix in angle and range based on the receive signal has been proposed.It is demonstrated that the designed beamspace transformation matrix basically meets the requirements of beam gain.However, there are some problems in the transformation matrix designed, such as unstable beam gain and high sidelobe.Hence, we propose an optimization method by adjusting array element spacing and random number in frequency offset to get the optimum beam gain.Therefore, particle swarm optimization(PSO) is used to find the optimal solution.The beam gain comparison before and after the optimization is obtained by simulation, and the results show that the optimized array after beamspace preprocessing has more stable beam gain, lower sidelobe, and higher resolution in parameter estimation.In conclusion, the RD-log-FDA is capable of forming desired beam gain in angle and distance through beamspace preprocessing, and suppressing interference signals in other areas.
基金supported by the National Natural Science Foundation of China under Grant 61603263。
文摘This paper proposes a novel control approach for fault-tolerant control of dual three-phase permanent magnet synchronous motor(PMSM) under one-phase open-circuit fault.A modified six-phase static coordinate transformation matrix and an extended rotating coordinate transformation matrix are investigated considering the influence of the fifth harmonic space on fault-tolerant control. These mathematical models are further analyzed in the fundamental space and the fifth harmonic space after the fault and to eliminate the coupling between the d-q axis voltage equation in the fundamental wave space and the d-q axis voltage equation in the fifth harmonic space, a secondary rotation coordinate transformation matrix is proposed. To achieve the purpose of reducing torque ripple, the fault-tolerant control method proposed in this paper not only takes the minimum copper loss as the constraint condition, but also injects the fifth harmonic current. The experimental result of current and torque is used to verify the accuracy of fault-tolerant control.
