超磁致伸缩换能器磁路设计及优化

为优化超磁致伸缩换能器的电磁性能,研究了线圈的几何尺寸和磁路元件的选择对换能器磁场特性和输出位移的影响,并进行了磁路损耗和气隙磁导分析.给出了合理的线圈结构参数,提出了在超磁致伸缩材料(GMM)棒两端安装高磁导率的软磁体和减少GMM棒涡流损耗的设计方案,并忽略了气隙的影响.采用有限元方法仿真了不同磁路设计方案对换能器性能的影响,并进行了试验分析.结果表明,在GMM棒两端安装电工软铁能够提高工作磁场强度,减少磁通泄漏,增加换能器输出位移并降低驱动电流,改善换能器的发热情况,从而整体改善超磁致伸缩换能器的性能     

视频处理器软硬件协同设计

为了提高视频图像处理速度与硬件资源利用,针对一种基于精简指令集处理器与数字信号处理器（RISC/DSP）混合体系结构的媒体处理器：浙大数芯（MD32）,给出了一种软硬件协同设计策略.所给策略结合视频处理核心算法,研究分析MPEG视频编码标准的处理过程,进行了视频处理指令扩展设计,提高了数据的并行处理能力,利用了指令内并行执行特性.为有效实现扩展指令,处理器执行级采用了可扩展流水级技术.实验结果表明,指令扩展硬件成本仅占MD32的2.7%,逆离散余弦变换实现性能比MMX/SSE指令集实现的性能分别提高31%和23%,运动补偿性能比MMX指令集实现的性能提高了40%.     

声发射与EMD相结合的埋地水管泄漏定位检测

针对运用水管泄漏定位方法的直接相关法受到噪声和声传播方式的影响,使其定位精度低的问题,提出了一种基于经验模态分解（empirical mode decomposition,EMD）与能量特征提取相结合的水管泄漏定位.该方法用声学传感器采集数据,通过分析噪声和声传播方式对直接相关法定位的影响,采用EMD分解将采集数据分为不同的频段,再基于能量特征的方法从其中提取有用的频段作互相关分析,通过比较相关系数来确定泄漏位置.仿真和实验表明,该方法消除了直接相关法的缺点,提高了定位精度.     

球域Bézier曲线的边界

针对几何造型和产品测量中的有效误差分析和误差控制,提出了球域Bézier曲线.借助于微分几何中空间曲面族的包络算法和变量替换方法,求得球域Bézier曲线的精确边界表示;进一步利用函数逼近论中Legendre多项式的最佳一致平方逼近方法,把球域Bézier曲线的边界曲面近似地表示为一张Bézier曲面或分片Bézier曲面的组合.利用球面族的隐式方程,得到球域Bézier曲线的边界曲面的隐式方程,进而把边界曲面参数化为显式方程.理论推导和实例运算结果表明,球域Bézier曲线是一种表达方式简洁、存储空间节省、运算速度较快的误差分析和误差控制工具.     

硬件实现基于BP神经网络设计的带阻FIR滤波器

针对带阻FIR滤波器传统设计方法的不足和缺陷,在改进BP神经网络设计带阻FIR滤波器方法的基础上,提出了BP神经网络设计FIR滤波器的硬件实现方法.通过神经网络训练使得实际滤波器的幅度响应逼近理想滤波器的幅度响应,训练得到带阻滤波器系数,再利用数字信号处理芯片(DSP),设计适当的FIR滤波器结构以及硬件结构,从硬件上实现带阻FIR滤波器.试验结果显示,用该方法设计的带阻FIR滤波器克服了传统方法的主要缺陷,具有良好的幅频特性及衰耗特性,并且边界频率控制精确.     

海底热液长期原位探测器流控系统的设计与实现

为了实现深海热液长期原位探测,设计了3套能实现深海热液传感器在线自校正与自维护功能的流控系统.在实验的基础上,针对系统结构、功耗以及流量特性3个主要方面,对3种流控系统进行了比较,最终选择采用二位二通阀配合泵工作的系统作为探测器的流控系统.针对流控系统不能在高压下工作的缺陷,借助于甲基硅油介质,采用压力补偿的方式设计了流控系统的压力补偿装置,并实验验证了在40 MPa的压力下,所设计的流控系统仍能正常工作,证实了该流控系统合理且实用,从而为深海热液长期原位探测的实现提供了技术支撑.     

有机磷农药乙酰甲胺磷的太赫兹光谱研究

为了获得有机磷农药乙酰甲胺磷在远红外波段的光学特性, 采用太赫兹时域光谱技术(THz TDS), 测量了室温下乙酰甲胺磷在0.2~2.2 THz的高分辨率吸收谱和折射率谱. 结果表明,在室温和氮气环境下,特征吸收峰位于1.58和2.10 THz处, 平均折射率为1.45. 同时运用密度泛函理论(DFT)计算了乙酰甲胺磷分子结构及其在太赫兹波段的振动频率, 并根据计算结果对实验数据进行了解析, 计算结果与实验数据吻合较好. 研究结果表明, 实验光谱的特征吸收峰是由分子的集体振动及扭转形成, 不同的吸收峰位对应分子不同的振转模式.     

连续相位调制的定时-频偏联合估计方法

针对连续相位调制信号的同步问题,研究了一种定时-频偏联合估计算法.算法分3步实现：(1）对接收基带信号差分并平方,得到四阶非线性变换值;（2）求其二阶统计量;（3）基于该统计量联合估计定时偏差和载波频偏.通过改变载波频偏值及参与二阶统计量计算的符号数,对定时同步及频偏估计性能进行研究.在加性高斯白噪声信道及Rice慢衰落信道下分别进行仿真.加性高斯白噪声信道仿真表明,算法在载波频偏达到15%符号率条件下仍有出色同步性能,当参与估计的符号数等于64时,定时偏差和频偏均方误差分别达到10－6及10－5以下;低信噪比不影响算法定时恢复性能.Rice慢衰落信道仿真表明,算法具有一定的抗衰落能力,适当改变Rice信道模型参数能提升其性能.算法采用非数据辅助方式及前馈结构,同步捕获快速,实现简单,适合于突发通信.     

一种新的基于多信息测度融合的边缘检测方法

针对高强度噪声图像, 提出了一种新的基于信息测度概念和Dempster Shafer(DS)证据理论的边缘检测算法. 利用邻域一致性、方向性和结构性3种信息测度定量描述边缘特征; 引入检测不确定性, 根据各信息测度响应分布设计基本可信度分配函数, 并利用DS合成规则加以融合; 融合后根据组合决策规则将像素分类成边缘与非边缘. 实验通过检测结果以及Pratt品质因数的分析比较, 表明该算法能够有效地区分边缘点和噪声点. 在低噪声情况下, 检测性能与传统检测方法相近; 而对于高强度噪声图像, 该方法具有较强的噪声免疫力.     

基于正交补空间的人脸识别

为了实现人脸识别免于特征提取,提出了一种基于正交补脸(OC-faces)的人脸识别方法.该方法基于空间正交分解理论,对不同类的原始训练样本进行Gram-Schmidt正交化,以正交化后的基张成各个不同的子空间,将测试样本分解为子空间投影及子空间正交补两部分.正交补的范数体现了测试样本到各类子空间的距离,并以此作为分类的依据.在Yale库和AT&T库上的实验结果表明,与主成分分析(PCA)、线性判别分析(LDA)两种经典识别手段相比,该方法有更好的识别效果.     

Sputtering preparation and magneto-optical properties of GdTbFeCo thin films

Amorphous GdTbFeCo magnetic thin films were successfully prepared on glass substrates by RF magnetron sputtering system from a mosaic target.The influences of sputtering parameters on the magneto-optical properties GdTbFeCo thin film were investigated by the variable control method.And the influence mechanism was analyzed in detail.After the sputtering parameters were optimized,it was found that when the distance between target and substrate was 72 mm,the thin film thickness was 120 nm,and the sputtering power,sputtering pressure and sputtering time was 75 W,0.5 Pa and 613 s,respectively,the coercivity with perpendicular anisotropy could be as high as 6735 Oe,and the squareness ratio of the hysteresis loop was almost equal to 1.     

Effects of Nd substitution on magnetic and magneto-optical properties of TbCo/Cr films

NdTbCo/Cr amorphous films with high perpendicular magnetic anisotropy were prepared onto glass substrates by rf magnetron sputtering. The effects of Nd substitution on the magnetic and magneto-optical properties of TbCo/Cr films were investigated. It was found that partial Tb substitution by Nd would increase the saturation magnetization and the Kerr rotation angle, change the temperature dependence of magneto-optical characteristics. These results can be explained by the ferrimagnetic structure of the rare earth-transition metal alloy. When the magnetic layer composition was （Nd0.265Tb0.735）31Co69, a saturation magnetization of 247 emu/cm^3 and a coercivity of 3.8 kOe at room temperature could be obtained.     

Preparation and Performance of Magneto-optical Glasses Doped with Tb3＋/Dy3＋

In order to increase the content of rare-earth oxides in magneto-optical glass and improve the Verdet constant, the rare-earth doped ternary Ga2O3-B2O3-SiO2(GBS) system magneto-optical glasses were prepared by the melt quenching technique. The infl uence of Tb3+ and Dy3+ ions on the structure of GBS glasses was investigated using FTIR, DSC and Faraday rotations. The experimental results showed that the content of rare-earth oxides in the glasses with the double incorporation of Tb2O3 and Dy2O3 was higher. The crystallization parameter β achieved the maximum 0.48 with Tb3+/Dy3+ content of 35mol%. Terbium oxide existed mainly in [TbO3] units in the glasses and [TbO4] units were converted into [TbO3] with increasing Tb2O3 content. As Ga3+ ion is larger than B3+ ion in radius, leading to an increasing of the glass network gap and improvement in the ability of accommodating rare earth ions, Verdet constant increased.     

Glass-forming ability and chemical stability of magneto-optical glass heavily doped with rare earth oxide

The glass-forming region of B₂O₃-Al₂O₃-SiO₂ (BAS) glass heavily doped with rare earth oxides was investigated by an effective method, and the chemical stability was investigated by powder method. Influences of rare earth oxides on the glass-forming ability and the chemical stability of the BAS glass were also discussed. The experimental results show that the BAS glass-forming region expands firstly with the increase of the Tb₂O₃ content up to 30mol% and then shrinks. The acid-resistant capacity of the BAS glass doped with rare earth oxides is the lowest, the water-resistant capacity is secondary, and the alkali-resistant capacity is the best. Besides, the glass chemical stability can be improved by doping appropriate amount of rare earth oxides. Moreover, the stronger the ionic polarization ability of the rare earth ions is, the better the chemical stability of the BAS glass will be.     

New computational treatment of optical wave propagation in lossy waveguides

In this paper, the optical wave propagation in lossy waveguides is described by the Helmholtz equation with the complex refractive-index, and the Chebyshev pseudospectral method is used to discretize t...     

纳米棒结构表面等离子体波导的光传播特性研究

用时域有限差分方法(FDTD)研究了金属平行纳米棒和π型纳米结构表面等离子体(SPs)波导的光传播特性.在调制高斯脉冲平面波入射条件下,这两种纳米棒波导结构具有形状相似、大小不同的SPs瞬态激发光谱.在高数值孔径聚焦倏逝场入射条件下,π型纳米结构能够激发纵向SPs,使得它具有更均匀的局域场增强特性和更好的远场传播能力.     

基于磁光调制的二元溶液浓度检测技术研究

根据法拉第磁光效应和某些物质本身具有的光学活性原理,利用正交交流磁光调制的方法,提出一种可以同时检测二元溶液中两种溶质浓度的光学检测方法,该方法要求溶液中有且只有一种成分具有光学活性。通过测量接收光强进而获得二元溶液两种溶质的旋光角度及维尔德常数,由于溶液的维尔德常数与浓度有一定的对应关系,因而可以得到两种溶质浓度信息。系统同时采用了双光路参比放大的方法,有效提高了系统的检测灵敏度。该方法检测原理简单,器件制作容易,成本低廉;由于采用非侵入式的检测方法,因此对溶液无污染,可以提供实时、自动检测,有望在二元溶液浓度检测中获得广泛的应用。     

混合稀土铁石榴石(HoYbBi)_3Fe_5O_12单晶磁光性能的研究

为了改善用于光隔离器中的掺铋稀土铁石榴石的法拉第旋转温度稳定性 ,采用高温溶液法 ,以Bi2 O3 /B2 O3 为助熔剂生长掺铋混合稀土铁石榴石 ( Ho Yb Bi) 3 Fe5O1 2 (简称 :Ho Yb Bi IG)单晶 .在近红外波段测量了晶体的法拉第旋转谱和光吸收损耗谱 .当 λ=1 .5 5 μm时 ,Ho Yb Bi IG单晶的比法拉第旋转角θF 和磁光优值分别为 :- 767.0 deg/cm和 4 5 deg/d B;在 1 0～ 1 1 0℃温度范围内测得 Ho Yb Bi IG单晶的法拉第旋转温度系数 ( FTC)为 1 .8%,在目前所知磁光晶体中属最小 .研究结果还表明 ,将两种法拉第旋转温度系数符号相反的石榴石型材料进行复合 ,是一种行之有效的改善晶体材料法拉第旋转温度稳定性的方法     

双层石墨烯非对称波导中导模的色散关系

从具有能隙的双层石墨烯载流子所满足的哈密顿量出发,研究了非对称外势产生的波导结构中导模的存在性．在给定不同外势区域波函数的情况下,利用势垒边界处波函数的连续性条件,解析推导出了非对称波导中导模的色散关系,讨论了双层石墨烯的能隙对导模性质的影响．该研究为基于双层石墨烯波导器件的实际应用提供了理论依据．     

Distributed parametric modeling and simulation of light polarization states using magneto-optical sensing based on the Faraday effect

To solve the problems encountered in practical processes of magneto-optical sensing, the infinitesimal distributed-parameter model and finite-element accumulation of different dielectric properties of micromaterials were used to describe the evolution of light polarization states, instead of the previously commonly used method of lumped-parameter simulation, thus essentially explaining the mechanism of sensing, magneto-optical effects, and related factors, and achieving multiphysics coupling using the COMSOL finite-element analysis method. Considering the cases of the Faraday effect without and with line birefringence, the magneto-optical effect and output characteristics of an infinitesimal magneto-optical sensor were simulated and studied. The results verified the effectiveness of the infinitesimal sensor model. Because the magnetic field, stress, and temperature changes alter the dielectric properties of magneto-optical materials, the finite-element accumulation method lays a good foundation for research on theoretical analysis and performance of magneto-optical sensors affected by factors such as the magnetic field, temperature, and stress.