A redundant manipulator that can online clamp pipe was developed to track along a cylinder intersection curve. With an ultrasonic transducer mounted on its end-effector, the manipulator can perform welding seam inspec...A redundant manipulator that can online clamp pipe was developed to track along a cylinder intersection curve. With an ultrasonic transducer mounted on its end-effector, the manipulator can perform welding seam inspection at pipe joint in nuclear industry. An inverse kinematics solution expressed in joint space was solved based on the combination of geometric method and D-H matrix transformation. Expression about joints variables was obtained based on the scanning parameters of pipeline. The analysis method and results can be widely applied for online trajectory planning of intersection curve scanning manipulators.展开更多
The contour of the slices of SLA parts is composed of a great deal of small lines. When offsetting the contour to compensate for the radius of laser spot, many self-intersection contours come into being, which decreas...The contour of the slices of SLA parts is composed of a great deal of small lines. When offsetting the contour to compensate for the radius of laser spot, many self-intersection contours come into being, which decrease the precision of formed parts. A new lemma to judge the local self-intersection contour and the global self-intersection contour separately is put forward, according to which self-intersection contour can be removed reliably. Meanwhile, a new beam offsetting algorithm for SLA parts is described, which brings about good resuits in the practical manufacturing process.展开更多
A new kind of k-quantum nonlinear coherent states,i.e.,the k eigenstates of the k-th power~k (k≥3) of the generalized annihilation operator=1/f() of f-oscillators,are obtained and their properties are discussed.The c...A new kind of k-quantum nonlinear coherent states,i.e.,the k eigenstates of the k-th power~k (k≥3) of the generalized annihilation operator=1/f() of f-oscillators,are obtained and their properties are discussed.The completeness of the k states is investigated.An alternative method to construct them is proposed.It is shown that these states may form a complete Hilbert space,and all of them can be generated by a linear superposition of k Roy-type nonlinear coherent states.Physically,they can be generated by a linear superposition of the time-dependent Roy-type nonlinear coherent states at different instants.展开更多
Research on the stress gradient hypothesis recognizes that positive(i.e. facilitative) and negative(i.e. competitive) plant interactions change in intensity and effect relative to abiotic stress experienced on a gradi...Research on the stress gradient hypothesis recognizes that positive(i.e. facilitative) and negative(i.e. competitive) plant interactions change in intensity and effect relative to abiotic stress experienced on a gradient. Motivated by observations of alpine treeline ecotones, we suggest that this switch in interaction could operate along a gradient of relative size of individual plants. We propose that as neighbors increase in size relative to a focal plant they improve the environment for that plant up to a critical point. After this critical point is surpassed, however, increasing relative size of neighbors will degrade the environment such that the net interaction intensity becomes negative. We developed a conceptual(not site or species specific) individual based model to simulate a single species with recruitment, growth, and mortality dependent on the environment mediated by the relative size of neighbors. Growth and size form a feedback. Simulation results show that the size gradient model produces metrics similar to that of a stress gradient model. Visualizations reveal that the size gradient model produces spatial patterns that are similar to the complex ones observed at alpine treelines. Size-mediated interaction could be a mechanism of the stress gradient hypothesis or it could operate independent of abiotic stress.展开更多
We study the geometry and the period map of nodal complex prime Fano threefolds with index 1 and degree 10.We show that these threefolds are birationally isomorphic to Verra threefolds,i.e.,hypersurfaces of bidegree (...We study the geometry and the period map of nodal complex prime Fano threefolds with index 1 and degree 10.We show that these threefolds are birationally isomorphic to Verra threefolds,i.e.,hypersurfaces of bidegree (2,2) in P2 × P2.Using Verra's results on the period map for these threefolds and on the Prym map for double tale covers of plane sextic curves,we prove that the fiber of the period map for our nodal threefolds is the union of two disjoint surfaces,for which we give several descriptions.This result is the analog in the nodal case of a result of Debarre O,Iliev A,Manivel L (arXiv:0812.3670) in the smooth case.展开更多
In this paper, we establish a Second Main Theorem for an algebraically degenerate holomorphic curve f : C → Pn(C) intersecting hypersurfaces in general position. The related Diophantine problems are also considered.
In the paper,we give two conditions that the Heegaard splitting admits the disjoint curve property.The main result is that for a genus g(g■2)strongly irreducible Heegaard splitting(C_1,C_2;F),let D_i be an essential ...In the paper,we give two conditions that the Heegaard splitting admits the disjoint curve property.The main result is that for a genus g(g■2)strongly irreducible Heegaard splitting(C_1,C_2;F),let D_i be an essential disk in C_i,i=1,2,satisfying(1)at least one of ■D_1 and ■D_2 is separating in F and|■D_1∩■D_2|■2g-1;or(2)both ■D_1 and ■D_2 are non-separating in F and|■D_1∩■D_2|■2g-2,then(C_1,C_2;F)has the disjoint curve property.展开更多
This article presents the results of experimental investigation of heat transfer process, carded out using the model of heat exchanger. Two-phase statically stable foam flow was used as a heat transfer fluid. Heat exc...This article presents the results of experimental investigation of heat transfer process, carded out using the model of heat exchanger. Two-phase statically stable foam flow was used as a heat transfer fluid. Heat exchanger model consisted of staggered tube bank. Experimental results are presented with the focus on influence of tube position in the line of the bank, volumetric void component and velocity of gas component of the foam. The phenomena of liquid draining in cellular foam flow and its influence on heat transfer rate has also been discussed. The experi- mental results have been generalized by relationship between Nusselt, Reynolds and Prandtl numbers.展开更多
By constructing an auxiliary function and using Hopf 's maximum principles onit, existence theorems of blow-up solutions, upper bound of 'blow-up time' and upper estimates of'blow-up rate' are give...By constructing an auxiliary function and using Hopf 's maximum principles onit, existence theorems of blow-up solutions, upper bound of 'blow-up time' and upper estimates of'blow-up rate' are given under suitable assumptions on a, b, f, g, σ and initial date u_0(x). Theobtained results are applied to some examples in which a, b, f, g and σ are power functions orexponential functions.展开更多
The line segment intersection problem is one of the basic problems in computational geometry and has been widely used in spatial analysis in Geographic Information Systems （GIS）. Lots of traditional algorithms study...The line segment intersection problem is one of the basic problems in computational geometry and has been widely used in spatial analysis in Geographic Information Systems （GIS）. Lots of traditional algorithms study the problem in a serial environment. However, in GIS, a spatial object is much more complicated and is considered to be always composed of multiple line segments, and one line segment connects another line segment at its endpoint. On the other hand, along with the advances made in computer hardware, more and more personal computers have multiple cores or CPUs equipped. Thus, to make full use of the increasing computing resources, parallel technique is applied as one of the most available methods. Apparently, the traditional algorithms should be improved to take advantage of the technologies. Under these circumstances, based on the modified uniform grid algorithm, which is adapted to dealing with spatial objects in GIS, this paper proposes a parallel strategy in a shared memory architecture. Also, experimental results are given in the final part of this paper to demonstrate the efficiency this strategy brings.展开更多
We consider the extended trust-region subproblem with two linear inequalities. In the "nonintersecting" case of this problem, Burer and Yang(2015) have proved that its semi-definite programming relaxation wi...We consider the extended trust-region subproblem with two linear inequalities. In the "nonintersecting" case of this problem, Burer and Yang(2015) have proved that its semi-definite programming relaxation with second-order-cone reformulation(SDPR-SOCR) is a tight relaxation. In the more complicated "intersecting" case, which is discussed in this paper, so far there is no result except for a counterexample for the SDPR-SOCR. We present a necessary and sufficient condition for the SDPR-SOCR to be a tight relaxation in both the "nonintersecting" and "intersecting" cases. As an application of this condition, it is verified easily that the "nonintersecting" SDPR-SOCR is a tight relaxation indeed. Furthermore, as another application of the condition, we prove that there exist at least three regions among the four regions in the trust-region ball divided by the two intersecting linear cuts, on which the SDPR-SOCR must be a tight relaxation. Finally, the results of numerical experiments show that the SDPR-SOCR can work efficiently in decreasing or even eliminating the duality gap of the nonconvex extended trust-region subproblem with two intersecting linear inequalities indeed.展开更多
This paper proposes a kind of modulation architecture for wavelength-division-multiplexing passive optical network （WDM- PON） employing optical differentia/quadrature phase shift keying （DQPSK） downstream signals ...This paper proposes a kind of modulation architecture for wavelength-division-multiplexing passive optical network （WDM- PON） employing optical differentia/quadrature phase shift keying （DQPSK） downstream signals and two different modulation formats of re-modulated upstream signals. At the optical line terminal （OLT）, 10 Gbit/s signal is modulated with DQPSK. At the optical network unit （ONU）, part of the downstream signal is re-modulated with on-offkeying （0OK） or inverse-return-to-zero （IRZ）. Simulation results show the impact on the system employing NRZ, RZ and carrier-suppressed return-to-zero （CSRZ）. The analyses also reflect that the architecture can restrain chromatic dispersion and channel crosstalk, which makes it the best architecture of access network in the future.展开更多
Using an adaptive split-step Fourier method,the coupled nonlinear Schrdinger equations have been numerically solved in this paper.The nonlinear propagation of an ultrashort optical pulse in the birefringent photonic c...Using an adaptive split-step Fourier method,the coupled nonlinear Schrdinger equations have been numerically solved in this paper.The nonlinear propagation of an ultrashort optical pulse in the birefringent photonic crystal fibers is investigated numerically.It is found that the phenomenon of pulse trapping occurs when the incident pulse is deviating from the principal axis of the fiber with some angle.Owing to the birefringence effect,the incident pulse can be regarded as two orthogonal polarized pulses.The phenomenon of pulse trapping occurs because of the cross phase modulation(XPM) between the two components.As a result,the bandwidth of the supercontinuum(SC) decreases compared with the case that the incident pulse is input along the principal axis.When the polarization direction of the incident pulse is parallel to the fast axis,the bandwidth of the supercontinuum is maximal.展开更多
In this paper, a dynamic optical arbitrary waveform generator(OAWG) based on cross phase modulation(XPM) is proposed. According to the characteristics of XPM, the nonlinear phase shift of signal can be changed along w...In this paper, a dynamic optical arbitrary waveform generator(OAWG) based on cross phase modulation(XPM) is proposed. According to the characteristics of XPM, the nonlinear phase shift of signal can be changed along with the pump power. The amplitude of signal can be changed by controlling the phase shift at one arm of a Mach-Zehnder interferometer(MZI) using XPM effect between signal and pump. Therefore, the phase and amplitude of the optical frequency comb(OFC) can be controlled by two pump arrays. As a result, different kinds of waveforms can be synthesized. Due to the ultrafast response of XPM, the generated waveform could be dynamically updated with an ultrafast frequency. The waveform fidelity is affected by the updating frequency.展开更多
基金Foundation Program Conducted by Science&Technology Committee of National Defence ( T0 12 0 0 1A0 0 1)
文摘A redundant manipulator that can online clamp pipe was developed to track along a cylinder intersection curve. With an ultrasonic transducer mounted on its end-effector, the manipulator can perform welding seam inspection at pipe joint in nuclear industry. An inverse kinematics solution expressed in joint space was solved based on the combination of geometric method and D-H matrix transformation. Expression about joints variables was obtained based on the scanning parameters of pipeline. The analysis method and results can be widely applied for online trajectory planning of intersection curve scanning manipulators.
文摘The contour of the slices of SLA parts is composed of a great deal of small lines. When offsetting the contour to compensate for the radius of laser spot, many self-intersection contours come into being, which decrease the precision of formed parts. A new lemma to judge the local self-intersection contour and the global self-intersection contour separately is put forward, according to which self-intersection contour can be removed reliably. Meanwhile, a new beam offsetting algorithm for SLA parts is described, which brings about good resuits in the practical manufacturing process.
基金The project supported by National Natural Science Foundation of China under Grant No.10074072the Natural Science Foundation of Shandong Province of China under Grant No.Y2002A05
文摘A new kind of k-quantum nonlinear coherent states,i.e.,the k eigenstates of the k-th power~k (k≥3) of the generalized annihilation operator=1/f() of f-oscillators,are obtained and their properties are discussed.The completeness of the k states is investigated.An alternative method to construct them is proposed.It is shown that these states may form a complete Hilbert space,and all of them can be generated by a linear superposition of k Roy-type nonlinear coherent states.Physically,they can be generated by a linear superposition of the time-dependent Roy-type nonlinear coherent states at different instants.
基金based upon work while an author served at the National Science Foundation(USA)
文摘Research on the stress gradient hypothesis recognizes that positive(i.e. facilitative) and negative(i.e. competitive) plant interactions change in intensity and effect relative to abiotic stress experienced on a gradient. Motivated by observations of alpine treeline ecotones, we suggest that this switch in interaction could operate along a gradient of relative size of individual plants. We propose that as neighbors increase in size relative to a focal plant they improve the environment for that plant up to a critical point. After this critical point is surpassed, however, increasing relative size of neighbors will degrade the environment such that the net interaction intensity becomes negative. We developed a conceptual(not site or species specific) individual based model to simulate a single species with recruitment, growth, and mortality dependent on the environment mediated by the relative size of neighbors. Growth and size form a feedback. Simulation results show that the size gradient model produces metrics similar to that of a stress gradient model. Visualizations reveal that the size gradient model produces spatial patterns that are similar to the complex ones observed at alpine treelines. Size-mediated interaction could be a mechanism of the stress gradient hypothesis or it could operate independent of abiotic stress.
基金supported by the project VSHMOD-2009 ANR-09-BLAN-0104-01
文摘We study the geometry and the period map of nodal complex prime Fano threefolds with index 1 and degree 10.We show that these threefolds are birationally isomorphic to Verra threefolds,i.e.,hypersurfaces of bidegree (2,2) in P2 × P2.Using Verra's results on the period map for these threefolds and on the Prym map for double tale covers of plane sextic curves,we prove that the fiber of the period map for our nodal threefolds is the union of two disjoint surfaces,for which we give several descriptions.This result is the analog in the nodal case of a result of Debarre O,Iliev A,Manivel L (arXiv:0812.3670) in the smooth case.
基金supported by National Natural Science Foundation of China (Grant Nos. 11171255, 10901120)Doctoral Program Foundation of the Ministry of Education of China (Grant No.20090072110053)US National Security Agency (Grant Nos. H98230-09-1-0004, H98230-11-1-0201)
文摘In this paper, we establish a Second Main Theorem for an algebraically degenerate holomorphic curve f : C → Pn(C) intersecting hypersurfaces in general position. The related Diophantine problems are also considered.
基金Foundation item： the National Natural Science Foundation of China （No. 10571034）
文摘In the paper,we give two conditions that the Heegaard splitting admits the disjoint curve property.The main result is that for a genus g(g■2)strongly irreducible Heegaard splitting(C_1,C_2;F),let D_i be an essential disk in C_i,i=1,2,satisfying(1)at least one of ■D_1 and ■D_2 is separating in F and|■D_1∩■D_2|■2g-1;or(2)both ■D_1 and ■D_2 are non-separating in F and|■D_1∩■D_2|■2g-2,then(C_1,C_2;F)has the disjoint curve property.
文摘This article presents the results of experimental investigation of heat transfer process, carded out using the model of heat exchanger. Two-phase statically stable foam flow was used as a heat transfer fluid. Heat exchanger model consisted of staggered tube bank. Experimental results are presented with the focus on influence of tube position in the line of the bank, volumetric void component and velocity of gas component of the foam. The phenomena of liquid draining in cellular foam flow and its influence on heat transfer rate has also been discussed. The experi- mental results have been generalized by relationship between Nusselt, Reynolds and Prandtl numbers.
基金This research is partially supported by the National Natural Science Foundation of China under project 60174007and by the Shanxi Province Natural Science Foundation of China.
文摘By constructing an auxiliary function and using Hopf 's maximum principles onit, existence theorems of blow-up solutions, upper bound of 'blow-up time' and upper estimates of'blow-up rate' are given under suitable assumptions on a, b, f, g, σ and initial date u_0(x). Theobtained results are applied to some examples in which a, b, f, g and σ are power functions orexponential functions.
文摘The line segment intersection problem is one of the basic problems in computational geometry and has been widely used in spatial analysis in Geographic Information Systems （GIS）. Lots of traditional algorithms study the problem in a serial environment. However, in GIS, a spatial object is much more complicated and is considered to be always composed of multiple line segments, and one line segment connects another line segment at its endpoint. On the other hand, along with the advances made in computer hardware, more and more personal computers have multiple cores or CPUs equipped. Thus, to make full use of the increasing computing resources, parallel technique is applied as one of the most available methods. Apparently, the traditional algorithms should be improved to take advantage of the technologies. Under these circumstances, based on the modified uniform grid algorithm, which is adapted to dealing with spatial objects in GIS, this paper proposes a parallel strategy in a shared memory architecture. Also, experimental results are given in the final part of this paper to demonstrate the efficiency this strategy brings.
基金supported by National Natural Science Foundation of China(Grant Nos.11471052,11171040,11001030 and 61375066)the Grant of China Scholarship Council
文摘We consider the extended trust-region subproblem with two linear inequalities. In the "nonintersecting" case of this problem, Burer and Yang(2015) have proved that its semi-definite programming relaxation with second-order-cone reformulation(SDPR-SOCR) is a tight relaxation. In the more complicated "intersecting" case, which is discussed in this paper, so far there is no result except for a counterexample for the SDPR-SOCR. We present a necessary and sufficient condition for the SDPR-SOCR to be a tight relaxation in both the "nonintersecting" and "intersecting" cases. As an application of this condition, it is verified easily that the "nonintersecting" SDPR-SOCR is a tight relaxation indeed. Furthermore, as another application of the condition, we prove that there exist at least three regions among the four regions in the trust-region ball divided by the two intersecting linear cuts, on which the SDPR-SOCR must be a tight relaxation. Finally, the results of numerical experiments show that the SDPR-SOCR can work efficiently in decreasing or even eliminating the duality gap of the nonconvex extended trust-region subproblem with two intersecting linear inequalities indeed.
基金supported by the National Internation Technology Cooperration(No.2012DFG12110)the National Natural Science Foundation of China(Nos.61077050and61077014)the Open Foundation of State Key Laboratory of Optical Communication Technologies and Networks(No.2010OCTN-02)
文摘This paper proposes a kind of modulation architecture for wavelength-division-multiplexing passive optical network （WDM- PON） employing optical differentia/quadrature phase shift keying （DQPSK） downstream signals and two different modulation formats of re-modulated upstream signals. At the optical line terminal （OLT）, 10 Gbit/s signal is modulated with DQPSK. At the optical network unit （ONU）, part of the downstream signal is re-modulated with on-offkeying （0OK） or inverse-return-to-zero （IRZ）. Simulation results show the impact on the system employing NRZ, RZ and carrier-suppressed return-to-zero （CSRZ）. The analyses also reflect that the architecture can restrain chromatic dispersion and channel crosstalk, which makes it the best architecture of access network in the future.
基金supported by the National Natural Science Foundation of China (No.10874145)the Natural Science Foundation of Hebei Province of China (No.F2009000481)the China Postdoctoral Science Foundation (No.20080440014)
文摘Using an adaptive split-step Fourier method,the coupled nonlinear Schrdinger equations have been numerically solved in this paper.The nonlinear propagation of an ultrashort optical pulse in the birefringent photonic crystal fibers is investigated numerically.It is found that the phenomenon of pulse trapping occurs when the incident pulse is deviating from the principal axis of the fiber with some angle.Owing to the birefringence effect,the incident pulse can be regarded as two orthogonal polarized pulses.The phenomenon of pulse trapping occurs because of the cross phase modulation(XPM) between the two components.As a result,the bandwidth of the supercontinuum(SC) decreases compared with the case that the incident pulse is input along the principal axis.When the polarization direction of the incident pulse is parallel to the fast axis,the bandwidth of the supercontinuum is maximal.
基金supported by the National Natural Science Foundation of China(No.61377075)Program for New Century Excellent Talents in University(No.NCET-07-0611)
文摘In this paper, a dynamic optical arbitrary waveform generator(OAWG) based on cross phase modulation(XPM) is proposed. According to the characteristics of XPM, the nonlinear phase shift of signal can be changed along with the pump power. The amplitude of signal can be changed by controlling the phase shift at one arm of a Mach-Zehnder interferometer(MZI) using XPM effect between signal and pump. Therefore, the phase and amplitude of the optical frequency comb(OFC) can be controlled by two pump arrays. As a result, different kinds of waveforms can be synthesized. Due to the ultrafast response of XPM, the generated waveform could be dynamically updated with an ultrafast frequency. The waveform fidelity is affected by the updating frequency.
