Halbach磁阵多浮体海波发电结构功率响应研究

以Halbach磁阵多浮体海波发电结构为对象,研究了其在垂荡运动下的能量转换特性。基于线性波理论,建立了线圈浮筒的运动方程和能量转换模型,数值模拟了结构阻尼系数、弹簧刚度系数以及线圈浮筒的长度和半径,此外,数值还模拟了吃水对海波发电结构平均能量转换功率及共振频率的影响。结果表明:根据不同的海波状况,合理设计了海波发电结构的参数,将有助于其平均能量转换功率的提高。

θ短阵快速脉冲经颅磁刺激治疗抑郁症的研究进展

抑郁症作为一种心境障碍,在我国具有高复发率、高致残率等特点。θ短阵快速脉冲经颅磁刺激是一种特殊形式的重复经颅磁刺激,在治疗抑郁症方面已取得一定的研究成果,但有关θ短阵快速脉冲经颅磁刺激治疗抑郁症刺激参数的选择还存在争议。本文就θ短阵快速脉冲经颅磁刺激治疗抑郁症的刺激参数对疗效的影响进行描述及讨论,为临床应用θ短阵快速脉冲经颅磁刺激治疗抑郁症提供一定的参考依据。

金属圆形散热孔阵5G电磁屏蔽效能仿真分析

良好的电磁屏蔽和散热性能是保障电子设备稳定工作的重要因素,5G通信则对电子设备金属屏蔽散热孔阵的设计提出了更高要求。本文通过有限元法数值研究了在1 GHz^40 GHz频段正六边形周期排布金属圆形散热孔阵随散热孔径、金属厚度、入射角度和极化方式改变的屏蔽效能调控规律。结果表明,在保持散热效率不变的前提下,通过减小散热孔径或增大金属厚度可以有效提高其屏蔽效能,并且该性能对入射角度与极化方式均能保持较好的稳定性。该结论对5G通信频段电磁屏蔽设计具有一定的参考意义。

θ短阵快速脉冲经颅磁刺激治疗双相障碍患者躁狂发作的疗效和安全性观察

目的:观察θ短阵快速脉冲(TBS)重复经颅磁刺激(rTMS)治疗双相障碍躁狂发作的疗效和安全性。方法:选取30例符合DSM-Ⅴ双相障碍躁狂发作诊断标准的患者,按治疗方法不同分为研究组和对照组各15例。两组均给予丙戊酸镁缓释片治疗,在此基础上,研究组给予右额叶背外侧皮质(DLPFC)θ短阵快速脉冲(iTBS模式)rTMS刺激,对照组给予伪刺激,每天1次,共10次。采用躁狂量表(BRMS)在治疗前和治疗10 d后评估比较两组病情,治疗10 d后用副反应量表(TESS)评估比较两组不良反应。结果:治疗前BRMS评分两组差异无统计学意义(P>0.05);治疗10 d后,研究组BRMS评分明显低于对照组,差异有统计学意义(P<0.01);两组不良反应差异无统计学意义(P>0.05)。结论:在丙戊酸镁缓释片治疗基础上,采用右侧前额叶背外侧皮质θ短阵快速脉冲经颅磁刺激治疗双相障碍患者躁狂发作安全有效。

一种排斥式磁悬浮平台的磁场设计方法

提出了一种排斥式磁悬浮平台的磁场设计方法。方法选用电磁永磁混合单体,通过优化设计的排列组合方式形成产生排斥力的基底磁阵。由仿真结果可以看到均匀且成周期性的磁场分布。

一种永磁磁共振成像磁体的被动匀场方法

本文提出一种被动匀场方法,即用永磁磁片作为匀场材料,以基于函数逼近论的一套算法为指导进行匀场,所提算法已编成面向匀场工作者的软件,磁片阵则用专门设计的一套放置在磁体腔内的装置固定。此方法把磁体匀场问题提炼为函数逼近问题,每一磁片在匀场区产生的磁场函数被视为一个基函数,整个磁片阵在匀场区内张成一个函数集合。使用此方法可克服传统匀场方法低效率、不稳定的缺点,一定程度上能实现可定量的、规范的被动匀场。

注意网络功能与左侧额顶环路的经颅磁刺激研究

目的探讨注意网络功能与左侧额顶环路的关联性。方法健康受试者60人按照性别匹配原则分为顶叶组和额叶组。对左侧背外侧前额叶和后顶叶区进行持续短阵快速脉冲经颅磁刺激后,进行注意网络测试和网络效率评价。结果两组不同提示状态和靶刺激类型的平均反应时均无显著性差异。顶叶组警觉网络效率增强(P<0.05),额叶组警觉网络效率增强(P<0.05),定向网络效率受损(P<0.05)。结论左侧额顶环路神经活动抑制可以提高视空间注意警觉网络效率。

微细加工平台特性研究

通过对不同结构的微细加工平台的分析,指出采用Halbach磁阵和螺线管结构研制的微细加工平台的磁场特性比较复杂,难于建模和控制.提出了新型微细加工平台,并对它产生的磁通密度纹波进行了分析,提出以磁通纹波和驱动力为优化目的的二次序列法优化,优化结果表明,磁通纹波减小了30%,驱动力增加了10%.仿真结果表明,该系统有较好的频带宽(0～8 kHz).

IT设备监控死角的低成本解决方案研究

IT设备监控死角,是指未直接进行监控、相对稳定、故障几率低的设备。当前IT存储设备,存在机房地理位置分散、依靠人工巡查、全方位监控代价大等问题。针对早期设备存在监控死角以及代价大的问题,通过唤醒以存储设备为主体的IT设备扫除死角的方式,采用新颖而科学的管理方法,打破存储管理的黑匣子,透明化管理,分布式架构,统一化监控,将存储管理纳入综合监控体系,最大化地保障了业务的稳定性与安全性。

Geomagnetic jerk extraction based on the covariance matrix

We normalize data from 43 Chinese observatories and select data from ten Chinese observatories with most continuous records to assess the secular variations(SVs)and geomagnetic jerks by calculating the deviations between annual observed and CHAOS-6 model monthly means.The variations in the north,east,and vertical eigendirections are studied by using the covariance matrix of the residuals,and we find that the vertical direction is strongly affected by magnetospheric ring currents.To obtain noise-free data,we rely on the covariance matrix of the residuals to remove the noise contributions from the largest eigenvalue or vectors owing to ring currents.Finally,we compare the data from the ten Chinese observatories to seven European observatories.Clearly,the covariance matrix method can simulate the SVs of Dst,the jerk of the northward component in 2014 and that of the eastward component in 2003.5 in China are highly agree with that of Vertically downward component in Europe,compare to CHAOS-6,covariance matrix method can show more details of SVs.

Preparation and Characterization of Fe Nanowire Arrays Embedded in Porous Anodic Aluminum Oxide Templates

Fe nanowire arrays are prepared by electrodeposition in porous anodic aluminum oxide template from a composite electrolyte solution. These nanowires have an uniform diameter of approximate 25 nm and a length in excess of 2.5 μm. The micrographs and crystal structures of Fe nanowires are studied by transmission electron microscopy (TEM), selected-area electron diffraction (SAED), and X-ray diffraction(XRD). It is found that each nanowire is essentially a single crystal and has a different orientation in each array. Hysteresis loops of Fe nanowire array show that its easy magnetization direction is perpendicular to the sample plane.

A Second-Order Method for the Electromagnetic Scattering from a Large Cavity

In this paper,we study the electromagnetic scattering from a two dimen- sional large rectangular open cavity embedded in an infinite ground plane,which is modelled by Helmholtz equations.By introducing nonlocal transparent boundary con- ditions,the problem in the open cavity is reduced to a bounded domain problem.A hypersingular integral operator and a weakly singular integral operator are involved in the TM and TE cases,respectively.A new second-order Toeplitz type approximation and a second-order finite difference scheme are proposed for approximating the hyper- singular integral operator on the aperture and the Helmholtz in the cavity,respectively. The existence and uniqueness of the numerical solution in the TE case are established for arbitrary wavenumbers.A fast algorithm for the second-order approximation is pro- posed for solving the cavity model with layered media.Numerical results show the second-order accuracy and efficiency of the fast algorithm.More important is that the algorithm is easy to implement as a preconditioner for cavity models with more general media.

Phase Diagram for Ashkin-Teller Model on Bethe Lattice

Using- the recursion method, we study the phase transitions of theAshkin-Teller model on the Bethe lattice, restricting ourselves to the case of ferromagneticinteractions. The isotropic Ashkin-Teller model and the anisotropic one are respectivelyinvestigated, and exact expressions for the free energy and the magnetization are obtained. It canbe found that each of the three varieties of phase diagrams, for the anisotropic Ashkin-Tellermodel, consists of four phases, i.e., the fully disordered paramagnetic phase Para, the fullyordered ferromagnetic phase Ferro, and two partially ordered ferromagnetic phases 【 σ 】 and 【 σs】, while the phase diagram, for the isotropic Ashkin-Teller model, contains three phases, i.e., thefully disordered paramagnetic phase Para, the fully ordered ferromagnetic phase Baxter Phase, andthe partially ordered ferromagnetic phase 【 σs 】.

Model predictive torque control of permanent magnet synchronous motor system driven by matrix converter

Employing matrix converter （MC） as driving mode, the strategy of model predictive torque control （MPTC） is proposed for three phase permanent magnet synchronous motor （PMSM） system. MC is applied instead of conventional AC DC AC converter to increase the power factor （PF） of the system input side. MPTC is used to select optimal voltage space vector to enable the system to have satisfactory torque and flux control effect. The resultant MPTC strategy not only makes the MC fed PMSM system operate reliably and have perfect control performance, but also makes the PF of the system input side be 1. Compared with direct torque control （DTC）, the proposed MPTC strategy guarantees that MC fed PMSM has better command following characteristics in the presence of variation of load torque and tracking reference speed. Simulation results verify the feasibility and effectiveness of the proposed strategy.

A novel fuzzy logic direct torque controller for a permanent magnet synchronous motor with a field programmable gate array

A high-performance digital servo system built on the platform of a field programmable gate array (FPGA),a fully digitized hardware design scheme of a direct torque control (DTC) and a low speed permanent magnet synchronous motor (PMSM) is proposed. The DTC strategy of PMSM is described with Verilog hardware description language and is employed on-chip FPGA in accordance with the electronic design automation design methodology. Due to large torque ripples in low speed PMSM,the hysteresis controller in a conventional PMSM DTC was replaced by a fuzzy controller. This FPGA scheme integrates the direct torque controller strategy,the time speed measurement algorithm,the fuzzy regulating technique and the space vector pulse width modulation principle. Experimental results indicate the fuzzy controller can provide a controllable speed at 20 r min-1 and torque at 330 N m with satisfactory dynamic and static performance. Furthermore,the results show that this new control strategy decreases the torque ripple drastically and enhances control performance.

Description of the Mueller Matrix for Multiple Scatteringat 90°

Mueller matrix elements are presented represen ting scatter to 90° from an incident polarized laser beam. The cases considered include five particle sizes (such as l.24 μm, 0.494 μm, 0.36 μm, 0.123 μm, and 0.065 μm), two concentr ations (such as 0.002 5% and 0.005% by volume), and three detector depths (such as 0, l.5 cm, and 3 cm into the scat tering volume). If the magnitudes of the elements can be rounded off to the near est 0.01, a particle size dependence is described by the resulting average mat rices, which is only two matrices for d >0.22 μm and d <0.22 μm which are nonsingular and asymmetric, respectively.

Theoretical Calculation of Energy Spectrum of YGG:Cr^(3+)and Thermal Shifts of Its R-Lines

With the strong-field scheme and trigonal bases, the complete d3 energy matrix in a trigonally distorted cubic-field has been constructed. By diagonalizing this matrix, the energy spectrum of YGG：Cr^3＋ at normal pressure and low temperature has been calculated. The g factor of the ground-state has been evaluated in terms of the energy spectrum. At the same time, by using the wavefunctions obtained from diagonalizing the complete d^3 energy matrix and Thermal Shifts theory, we calculate the thermal shifts of the sharp lines of YGG：Cr^3＋ and determine the relevant parameters. The calculated results are all in good agreement with the optical-spectrum and EPR experimental data. It is demonstrated that the obtained wavefunctions and the values of parameters are reasonable.

A Negative Donor D^- in a Magnetic Field

Using the method of numerical matrix diagonalization within the effective-mass approximation, we investigated a D^--center quantum dot system subjected to a Gaussian potential confinement. We obtain the dependence of binding energies of the ground-states of the D^--center on the depth of Gaussian potential and the magnetic field strength. The result shows clearly that the binding energies of the ground-states of the D^--center are rather sensitive to the depth of potential and the strength of magnetic field.

Binding Energies of D^- Centers Trapped by a Quantum Dot in a Magnetic Field

A investigation of the properties of the bound states of D^- centers confined in a parabolic quantum dot has been performed for the case with the presence of a perpendicular magnetic field. Calculations are carried out by using the method of numerical diagonalization of Hamiltonian matrix within the effective-mass approximation. The binding energies of the ground and some bound-excited states are obtained as a function of the applied magnetic field strength. Detailed calculations of the binding energies for a number of low-lying states show that for field strength less than B = 2.1 T, the D center confined in a quantum dot possesses two bound states, for 2.1 〈 B 〈 2.4 T, there exist three bound states, etc. Further relevant characteristics of the D- center quantum dots in magnetic fields are provided.

Two Interacting Electrons in a Vertically Coupled Quantum Dot

We study a two-electron system in a double-layer quantum dot under a magnetic field by means of the exact diagonalization of the Hamiltonian matrix.We find that discontinuous ground-state energy transitions are induced by an external magnetic field in the case of strong coupling.However,in the case of weak coupling,the angular momentum L of the true ground state does not change in accordance with the change of the magnetic field B and remains L=0.