Comment on “Focusing of high polarization order axially-symmetric polarized beams” [Chin.Opt.Lett.7,938 (2009)]

Some mathematical and conceptual errors contained in a recent letter [Chin.Opt.Lett.7,938 （2009）] are pointed out.

Adiabatic cooling for cold polar molecules on a chip using a controllable high-efficiency electrostatic surface trap

We propose a controllable high-efficiency electrostatic surface trap for cold polar molecules on a chip by using two insulator-embedded charged rings and a grounded conductor plate. We calculate Stark energy structure pattern of ND3 molecules in an external electric field using the method of matrix diagonalization. We analyze how the voltages that are applied to the ring electrodes affect the depth of the efficient well and the controllability of the distance between the trap center and the surface of the chip. To obtain a better understanding, we simulate the dynamical loading and trapping processes of ND3 molecules in a ｜J, KM = ｜1,-1 state by using classical Monte–Carlo method. Our study shows that the loading efficiency of our trap can reach ～ 88%. Finally, we study the adiabatic cooling of cold molecules in our surface trap by linearly lowering the potential-well depth（i.e., lowering the trapping voltage）, and find that the temperature of the trapped ND3 molecules can be adiabatically cooled from 34.5 m K to ～ 5.8 m K when the trapping voltage is reduced from-35 k V to-3 k V.

Properties of One-Dimensional Highly Polarized Fermi Gases

Using both the exact Bethe ansatz method and the variational method, we study properties of the one-dimensional Fermi polaron. We focus on the binding energy, effective mass, momentum distributions, Tan contact and correlation functions. As the attraction increases, the impurity is more tightly bound and correlated with the surrounding particles, and the size of formed polaron decreases. In addition, compared with the Bethe ansatz method, the variational method is totally qualified to study the one-dimensional Fermi polaron. The intrinsic reason is that the number of particle-hole excitations in a Fermi sea, caused by a single impurity, is always rather small. The variational method can be well extended to other impurity systems.

Atomic high-order harmonic generation from a circularly polarized laser pulse

We demonstrate theoretically that the high-order harmonic of an atom can be generated by a circularly polarized laser pulse.The harmonic spectrum shows a clear cutoff with an energy Ip ＋ 2Up.In particular,the high-order harmonic generation comes from the multiple recombination of the ionized electron with non-zero initial velocity.These results are verified by the classical model theory and the time-frequency analysis of a harmonic spectrum.

High order correlation polarization potential for vibrational excitation scattering of diatomic molecules by low-energy electrons

This paper introduces a correlation-polarization potential with high order terms for vibrational excitation in electron-molecule scattering. The new polarization potential generalizes the two-term approximation so that it can better reflect the dependence of correlation and polarization effects on the position coordinate of the scattering electron. It applies the new potential on the vibrational excitation scattering from N2 in an energy range which includes the ^2Ⅱg shape resonance. The good agreement of theoretical resonant peaks with experiments shows that polarization potentials with high order terms are important and should be included in vibrational excitation scattering.

Controlling the contributions to high-order harmonic generation from different nuclei of N_2 with an orthogonally polarized two-color laser field

The generation of high-order harmonic and the attosecond pulse of the N2 molecule with an orthogonally polarized two-color laser field are investigated by the strong-field Lewenstein model.We show that the control of contributions to high-order harmonic generation（HHG） from different nuclei is realized by properly selecting the relative phase.When the relative phase is chosen to be φ= 0.4π,the contribution to HHG from one nucleus is much more than that from another.Interference between two nuclei can be suppressed greatly; a supercontinuum spectrum of HHG appears from 40 e V to125 e V.The underlying physical mechanism is well explained by the time–frequency analysis and the semi-classical threestep model with a finite initial transverse velocity.By superposing several orders of harmonics,an isolated attosecond pulse with a duration of 80 as can be generated.

Suppressing the preferential σ-polarization oscillation in a high power Nd:YVO_4 laser with wedge laser crystal

We observe the phenomenon of priority oscillation of the unexpected a-polarization in high-power Nd：YVO4 ring laser. The severe thermal lens of the a-polarized lasing, compared with the n-polarized lasing, is the only reason for the phenomenon. By designing a wedge Nd：YVO4 crystal as the gain medium, the unexpected a-polarization is completely suppressed in the entire range of pump powers, and the polarization stability of the expected zc-polarized output is enhanced. With the output power increasing from threshold to the maximum power, no a-polarization lasing is observed. As a result, 25.3 W of stable single-frequency laser output at 532 nm is experimentally demonstrated.

FSS Based Circular Polarizer for High-Speed Wireless Communication at 75 GHz

An FSS based circular polarizer for high-speed wireless communication at 75 GHz is presented. It has been designed on a low loss substrate with cross-dipole elements. Both simulation and measured results showed more than 98% circular polarization at 75 GHz. Moreover, 3 dB axial-ratio bandwidth of 6.8 GHz (Simulation) and 7.8 GHz (Measured) has been achieved. The proposed design has many advantages over the recently published research such as simplicity, low-profile, percentage bandwidth, frequency of operation and relative insertion loss.

Application of Acoustic Emission to the Study on Cathodic Polarization and SCC for High Strength Steels

The ambiguous effect of cathodic polarization on SCC of two high strength steels in 0.1 M Na_2HPO_4 and 0.1 M NaNO_3 has been investigated by means of meas- uring electric resistance(R)and recording acoustic emis- sion(AE)signals simultaneously.Results showed that AE sensitivity strongly depends on K value in different solu- tions.Both anodic and cathodic polarization can acceler- ate crack growth rate at high K values,but it appears that there are only subtle differences in their AE characteristics.AE signals only reflect the macroprocesses of crack growth rather than the elementary ones and can not be used for identification of the micro-mechanisms of SCC.

High-Resolution Simulation and Analysis of the Mature Structure of a Polar Low over the Sea of Japan on 21 January 1997

This paper presents a high-resolution simulation of a remarkable polar low observed over the Sea of Japan on 21 January 1997 by using a 5-km mesh non-hydrostatic model MRI-NHM (Meteorological Research Institute Non-Hydrostatic Model). A 24-hour simulation starting from 0000 UTC 21 January 1997 successfully reproduced the observed features of the polar low such as the wrapping of western part of an initial E-W orientation vortex, the spiral-shaped bands, the cloud-free 'eye', and the warm core structure at its mature stage. The 'eye' of the simulated polar low was relatively dry, and was associated with a strong downdraft. A thermodynamic budget analysis indicates that the 'warm core' in the 'eye' region was mainly caused by the adiabatic warming associated with the downdraft. The relationship among the condensational diabatic heating, the vertical velocity, the convergence of the moisture flux, and the circulation averaged within a 50 km×50 km square area around the polar low center shows that they form a positive feedback loop, and this loop is not inconsistent with the CISK (Conditional Instability of the Second Kind) mechanism during the developing stage of the polar low.

Focusing of elliptically polarized Gaussian beams through an annular high numerical aperture

Based on the vectorial Debye theory, the focusing properties of the Gaussian beam through an annular high numerical aperture are studied numerically, including the intensity, the phase and the orbital angular momentum properties. Then the influence of certain parameters on the focusing properties is also investigated. It is shown that sub-wavelength elliptical light spots can be obtained. And there exists a vortex in the longitudinal component of the focused field even though the incident beam is Gaussian beam, indicating that the spin angular momentum of the elliptically polarized Gaussian beam is converted into the orbital angular momentum by the focusing.

High-Order Finite Difference Method for Helmholtz Equation in Polar Coordinates

We present a fourth-order finite difference scheme for the Helmholtz equation in polar coordinates. We employ the finite difference format in the interior of the region and derive a nine-point fourth-order scheme. Specially, ghost points outside the region are applied to obtain the approximation for the Neumann boundary condition. We obtain the matrix form of the linear system and the sparsity of the coefficient matrix is favorable for the computation of the Helmholtz equation. The feasibility and accuracy of the method are validated by two test examples which have exact solutions.

High-order harmonic generation of N2molecule in two-color circularly polarized laser fields

The generation of high-order harmonics and the attosecond pulse of the N2 molecule in two-color circularly polarized laser fields are investigated by the strong-field Lewenstein model. We show that the plateau of spectra is dramatically extended and a continuous harmonic spectrum with the bandwidth of 113 eV is obtained. When a static field is added to the x direction, the quantum path control is realized and a supercontinuum spectrum can be obtained, which is beneficial to obtain a shorter attosecond pulse. The underlying physical mechanism is well explained by the time-frequency analysis and the semi-classical three-step model with a finite initial transverse velocity. By superposing several orders of harmonics in the combination of two-color circularly polarized laser fields and a static field, an isolated attosecond pulse with a duration of 30 as can be generated.

A novel variable polarity welding power based on high-frequency pulse modulation

A new type of variable polarity welding power modulated with high-frequency pulse current is developed. Series of high-frequency pulse current is superimposed on direct-current-electrode-negative （DCEN）, which can improve the crystallization process in the weld bead as a result of the electromagnetic force generated by pulse current. Digital signal processor （DSP） is used to realize the closed-loop control of the first inverter, variable polarity output of the second inverter and high-frequency pulse current superposition.

Highly polar CoP/Co_(2)P heterojunction composite as efficient cathode electrocatalyst for Li-air battery

In order to advance the commercialization of rechargeable Li-air batteries,it is of importance to explore cathode catalyst with efficient catalytic activity.Transition metal oxides have poor electrical conductivity,while cobalt phosphide has excellent electrical conductivity and large specific surface area.Nevertheless,its application in organic Li-air batteries has been much less studied,and the electrocatalytic activity desires to be further elevated.Here,CoP/Co_(2)P heterojunction composite with higher polarity was fabricated.The discharge product of high-polarity CoP/Co_(2)P had a new porous box-like morphology,which was easy to be decomposed and exposed more active sites.The highly polar CoP/Co_(2)P heterostructure composite had homogeneous pores,the synergistic effect existed between CoP and Co_(2)P,and the discharge product was porous box mixed with Li_(2)O_(2)and LiOH,which made CoP/Co_(2)P achieve high specific capacity of14632 m Ah/g and cycle stably 161 times when used as air electrode cathode catalyst.This work furnished a thought for the construction of cathode catalysts with efficient catalytic activity for Li-air batteries.

偶极子对激发的宽带平面端射高增益天线

文中提出了一款单向辐射特性的微带缝隙结构双偶极子宽带天线。该天线由阶梯型缝隙结构、共面双偶极子和5组引向器构成。阶梯型缝隙结构用于改善阻抗匹配,拓展了天线的带宽;共面双偶极子改善了天线的辐射特性;引向器提高了天线的增益。仿真和实测表明,该天线的相对带宽为66.4%(5.78 GHz~11.53 GHz),带内前后比为15.7 dB~27.4 dB、增益为8.4 dBi~11.9 dBi,并且天线的交叉极化低、辐射方向图稳定。该天线的良好性能使其在无线通信和雷达领域的应用具有极强的吸引力。

基于宽带极化纯度估计的极化测量定标修正

对扩展目标极化散射特性进行测量时,通常期望精确获得宽带高分辨条件下目标各散射中心的极化特征信息,但由于各极化分量散射的信号对测试系统的正交极化通道存在能量泄漏,会严重影响较弱的极化散射分量的测量准确性。基于极化散射测量定标原理与宽带高分辨极化测量表征模型,分析了干扰量的产生原因以及对散射中心测试结果的影响机理,提出了一种基于宽带正交极化纯度估计进而修正复杂目标极化测量结果的方法,并通过对金属球、金属二面角组合和类弹头金属模型3类典型目标的实测,验证了其有效性。

外贸是否会带来工资差距及技能极化?——来自中国家庭追踪调查(CFPS)数据的经验证据

本文研究在应对贸易一体化时我国不同技能劳动者之间的工资差距和技能分布如何作出相应的反应。利用2010—2020年期间中国家庭追踪调查(CFPS)数据、联合国贸易数据(UNComtrade)等构造面板,在控制内生性问题的基础上,估计结果表明贸易对以所受教育为基准的中级和初级技能劳动者之间的工资差距有负面影响,对高级和中级技能组间的工资差距则有积极影响。且前者对于劳动技能的均值和分布具有负向作用,后者则有正向作用。因此,外贸活动会诱发技能极化,而工资差距解释了由贸易导致技能极化作用的50%。此外,在中年工人组以及高技术密集型行业中,收入差距特别是高中级技能组间的收入差距所带来的技能极化问题更为突出。鉴于一国的技能分配会长远地影响到未来的经济增长和不平等,因此,了解工资收入分配的变化并在政策设计中予以充分考虑至关重要,本文在劳动保障和教育支持等方面提出了相关的政策建议。

小口径弹载遥测系统天线设计

天线是弹载遥测系统的核心器件。针对小口径弹载遥测系统的特殊需求,开展弹载天线设计。采用圆极化模式消除炮弹飞行过程中自旋对遥测信号的影响;通过扩展天线的波束宽度适应炮弹的曲线弹道;为满足小口径炮弹对天线小尺寸的需求,通过采用高介电常数介质基板并对辐射单元开槽实现天线小型化;天线和弹载遥测系统板卡之间采用插针相连以实现天线的抗过载要求。对所设计的天线进行试制加工,并测得其阻抗带宽为24 MHz,沿轴线±80°内的轴比均小于3 dB,且其顶点处增益为2.18 dBi。测试结果表明此天线的性能够满足实际使用需求。

Resolving multi-orbital effects on high harmonic generation from aligned N2 molecules in linearly and elliptically polarized intense laser fields

We perform an experimental study of the multi-orbital effect on the high-order harmonic generation(HHG) from aligned N_2 molecules in both linearly and elliptically polarized intense laser fields.Measured by a home-built extreme ultraviolet(XUV) flat grating spectrometer with the pump-probe method, the angular distributions of different orders of HHG are obtained, which show distinctive behaviors for harmonics in the plateau and the cut-off regions.The ellipticity dependence of HHG is investigated by aligning the molecular axis parallel or perpendicular to the laser polarization.Our results indicate that both the highest occupied molecular orbital(HOMO) as well as the lower one(HOMO-1) contribute to the HHG of N2 molecules, in either linearly or elliptically polarized intense laser field.The study paves the way for understanding the ultrafast electron dynamics of molecules exposed to an intense laser field.