计算机模拟双层矩形位相光栅的实时变分束特征

双层矩形光栅随入射角的不同可得到不同数目的光束。基于这一现象,通过改变双层光栅的入射角,并对其进行优化就可得到效率高且光强分布均匀的光束。对利用双层矩形相位光栅实时变分束特征制作新型分束器的方法进行了理论探讨,并对2束、3束、4束光分束分别进行了分析。通过计算机模拟,从理论上求出了优化参数,并对结果进行了讨论。理论分析表明,通过对入射角进行优化可以得到衍射效率高且光强分布均匀的分束器。该研究为制作方便实用、造价低廉的分束器提供了理论基础。

计算机模拟双层矩形位相光栅的实时变分束特征

利用双层矩形相位光栅的实时变分束特征制作新型分束器进行了理论探讨。对2束、3束、4束光分束情况进行了分析,通过计算机模拟,从理论上求出其优化参数。

双层矩形相位光栅的变分束特性

报道双层矩形相位光栅的变分束特性。改变入射光照明方向， 由同一双层矩形相位光栅获得了光束数分别为２、３、４ 和５， 总衍射效率高于７０％ 的扇出光。

Method of variation of parameters for solving a constrained Birkhoffian system

For an in-depth study on the integration problem of the constrained mechanical systems the method of integration for the Birkhoffian system with constraints is discussed and the method of variation of parameters for solving the dynamical equations of the constrained Birkhoffian system is provided.First the differential equations of motion for the constrained Birkhoffian system as well as for the corresponding free Birkhoffian system are established.Secondly a system of auxiliary equations is constructed and the general solution of the equations is found.Finally by varying the parameters and utilizing the properties of the generalized canonical transformation of the Birkhoffian system the solution of the problem can be obtained.The proposed method reveals the inherent relationship between the solution of a free Birkhoffian system and that of a constrained Birkhoffian system. The research results are of universal significance which can be further used in a variety of constrained mechanical systems such as non-conservative systems and nonholonomic systems etc.

Variational Approach of Timoshenko Beams with Internal Elastic Restraints

An exact approach for free transverse vibrations of a Timoshenko beam with ends elastically restrained against rotation and translation and arbitrarily located internal restraints is presented. The calculus of variations is used to obtain the equations of motion, the boundary conditions and the transitions conditions which correspond to the described mechanical system. The derived differential equations are solved individually for each segment of the beam with the corresponding boundary and transitions conditions. The derived mathematical formulation generates as particular cases, and several mathematical models are used to simulate the presence of cracks. Some cases available in the literature and the presence of some errors are discussed. New results are presented for different end conditions and restraint conditions in the intermediate elastic constraints with their corresponding modal shapes.

Compliant landing of a trotting quadruped robot based on hybrid motion/force robust control

A compliant landing strategy for a trotting quadruped robot on unknown rough terrains based on contact force control is presented. Firstly, in order to lower the disturbance caused by the landing impact force, a landing phase is added between the swing phase and the stance phase, where the desired contact force is set as a small positive constant. Secondly, the joint torque optimization of the stance legs is formulated as a quadratic programming(QP) problem subject to equality and inequality/bound constraints. And a primal-dual dynamical system solver based on linear variational inequalities(LVI) is applied to solve this QP problem. Furthermore, based on the optimization results, a hybrid motion/force robust controller is designed to realize the tracking of the contact force, while the constraints of the stance feet landing angles are fulfilled simultaneously. Finally, the experiments are performed to validate the proposed methods.

A Kind of Three-Mode Entangled States of Continuum Variables Generated by Beam Splitter and Parametric Down-Conversion Amplifier

In 3-mode Fock space we find a new tripartite entangled state |α,γ 】 λ,which make up a new quantum mechanical representation. The state |α,γ 】 λ, can be generated byusing the setup composing of a beam splitter and a parametric down-conversion amplifier. Applicationof the state is briefly discussed.

Parameter Estimation with Constraints Based on Variational Method

The accuracy of parameter estimation is critical when digitally modeling a ship. A parameter estimation method with constraints was developed, based on the variational method. Performance functions and constraint equations in the variational method are constructed by analyzing input and output equations of the system. The problem of parameter estimation was transformed into a problem of least squares estimation. The parameter estimation equation was analyzed in order to get an optimized estimation of parameters based on the Lagrange multiplication operator. Simulation results showed that this method is better than the traditional least squares estimation, producing a higher precision when identifying parameters. It has very important practical value in areas of application such as system identification and parameter estimation.

Cyclic beamforming using fractional Fourier transform domain cyclostationarity

A minimum mean-squared error （MSE） beamforming algorithm employing the optimum fractional Fourier transform （Opt-FrFT） domain second-order cyclostationarity is proposed. This method can efficiently filter out the compact desired chirp signal, with a consequence that the cyclically uncorrelated interferences and stationary （colored） Gaussian noise are greatly suppressed in the Opt- FrFT domain. This improves the MSE minimization cyclic beamformer by reducing effectively the Opt-FrFY domain signal-noise cross terms in the presence of finite data length de-correlation operation. Simulation results show that the new method works well under a wide range of signal-to-noise ratio （SNR） and signal-to-interference ratio （SIR）.

Fractional Fourier transform of Lorentz-Gauss vortex beams

An analytical expression for a Lorentz-Gauss vortex beam passing through a fractional Fourier transform (FRFT) system is derived. The influences of the order of the FRFT and the topological charge on the normalized intensity distribution, the phase distribution, and the orbital angular momentum density of a Lorentz-Gauss vortex beam in the FRFT plane are examined. The order of the FRFT controls the beam spot size, the orientation of the beam spot, the spiral direction of the phase distribution, the spatial orientation of the two peaks in the orbital angular momentum density distribution, and the magnitude of the orbital angular momentum density. The increase of the topological charge not only results in the dark-hollow region becoming large, but also brings about detail changes in the beam profile. The spatial orientation of the two peaks in the orbital angular momentum density distribution and the phase distribution also depend on the topological charge.

A three-stage method with efficient calculation for lot streaming flow-shop scheduling

An important production planning problem is how to best schedule jobs(or lots)when each job consists of a large number of identical parts.This problem is often approached by breaking each job/lot into sublots(termed lot streaming).When the total number of transfer sublots in lot streaming is large,the computational effort to calculate job completion time can be significant.However,researchers have largely neglected this computation time issue.To provide a practical method for production scheduling for this situation,we propose a method to address the n-job,m-machine,and lot streaming flow-shop scheduling problem.We consider the variable sublot sizes,setup time,and the possibility that transfer sublot sizes may be bounded because of capacity constrained transportation activities.The proposed method has three stages:initial lot splitting,job sequencing optimization with efficient calculation of the makespan/total flow time criterion,and transfer adjustment.Computational experiments are conducted to confirm the effectiveness of the three-stage method.The experiments reveal that relative to results reported on lot streaming problems for five standard datasets,the proposed method saves substantial computation time and provides better solutions,especially for large-size problems.

Study of metamorphic InGaAs/GaAs quantum well laser materials grown on GaAs substrate by molecular beam epitaxy

The GaAs based InGaAs metamorphic structures and their growth by molecular beam epitaxy (MBE) are investigated. The controlling of the source temperature is improved to realize the linearly graded InGaAs metamorphic structure precisely. The threading dislocations are reduced. We also optimize the growth and annealing parameters of the InGaAs quantum well (QW). The 1.3-μm GaAs based metamorphic InGaAs QW is completed. A 1.3-μm GaAs based metamorphic laser is reported.

Onset of the Meissner effect at 65 K in Fe Se thin film grown on Nb-doped Sr TiO_3 substrate

We report the Meissner effect studies on an Fe Se thin film grown on Nb-doped Sr Ti O3 substrate by molecular beam epitaxy. Two-coil mutual inductance measurement clearly demonstrates the onset of diamagnetic screening at 65 K, which is consistent with the gap opening temperature determined by previous angle-resolved photoemission spectroscopy results. The applied magnetic field causes a broadening of the superconducting transition near the onset temperature, which is the typical behavior for quasi-two-dimensional superconductors. Our results provide direct evidence that Fe Se thin film grown on Nb-doped Sr Ti O3 substrate has an onset TC* 65 K,which is the highest among all iron-based superconductors discovered so far.

η-Invariant and Flat Vector Bundles

We present an alternate definition of the mod Z component of the Atiyah-Patodi-Singer η invariant associated to（not necessary unitary ）flat vector bundles,which identifies explicitly its realandimaginary parts.This is done by combining a deformation of flatconnections introduced in a previous paper with the analytic continuation procedure appearing in the original article of Atiyah Patodi and Singer.

Predicting the D_(s)(*)D_(s)(*)bound states as the partners of X(3872)

In this work,we investigate the SU(3)flavor symmetry,heavy quark spin symmetry and their breaking effects in the di-meson systems.We prove the existence of the[D_(s)(*)D_(s)(*)]^(0++),[D_(s)(*)D_(s)(*)]^(1++),and[D_(s)(*)D_(s)(*)]^(1++)bound states as the consequence of two prerequisites in the SU(3)flavor symmetry and heavy quark spin symmetry.The first prerequisite,the X(3872)as the weakly D*D=DD*bound state is supported by its mass and decay branching ratios.The second prerequisite,the existence of the DsDs[D_(s)(*)D_(s)(*)]^(0++)bound state is supported by the lattice QCD calculation and the observation of X_(c0)(3930)by the LHCb Collaboration.We hope the future experimental analyses can search for these bound states in the B→[D_(s)(*)D_(s)(*)]h processes(h denotes the light hadrons).The[D_(s)(*)D_(s)(*)]^(0++)bound state is also expected to be reconstructed in the J/ψФinal state in the B→//ψФK decay.