共查询到20条相似文献,搜索用时 187 毫秒
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双弯曲驻波压电振子的振及其相位关系研究 总被引:1,自引:1,他引:0
对驻波驱动型双弯曲压电振子基板与凸起之间的振动及其样位关系进行了解析推导,从理论上说明了双弯曲压电振子在单一信号激励下能够生成椭圆运动并形成驱动能力。为这种振子的进上步开发应用奠定的理论基础。 相似文献
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二维弯曲矩形板压电振子型超声马达研究 总被引:4,自引:4,他引:0
提出了一种具有凸起物的单矩形板压电振子型超声波马达,利用矩形板的二维弯曲振动合成了凸起物顶部的椭圆运动,并通过制作与试验,测试了样机的速度与功率比性能,验证了其工作的可行性。 相似文献
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矩形板压电振子振动有限元分析 总被引:2,自引:0,他引:2
利用有限元法,对具有四个凸起的矩形板压电振子的振动状态进行了解析计算,并根据其振动特点,重新选择结构参数制作了超声矩形板马达,结果大大提高了这种马达的转速和效率等性能。 相似文献
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提出了一种新型纵弯超声电机振子结构,本振子分为两组进行激励,通过控制输入激励信号,实现在振子上激励出在时间上相差π/2的纵弯模态响应,纵弯模态响应叠加在振子驱动足上产生椭圆运动轨迹,进而通过驱动足和动子之间的摩擦作用,使动子产生运动。该文在分析该振子工作机理的基础上,建立了纵弯振子的参数化有限元模型,通过模态分析进行模态特征频率的结构参数灵敏度分析,最终实现振子的纵弯模态的匹配。并对振子驱动足表面质点振动轨迹进行了分析,瞬态分析得到振子驱动足表面质点运动轨迹接近理想的椭圆轨迹,分析结果为物理样机的研制提供了理论依据。 相似文献
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圆环凸起型压电振子的振动分析 总被引:2,自引:1,他引:1
利用有限元法解析并模拟了具有凸起圆环型压电振子的振动状态,给出了结构参数对振型及共振频率的影响关系,提出了有效振型的概念,测试了实际振型并制作了马达样机。 相似文献
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《Signal processing》2007,87(10):2473-2483
This paper introduces a novel Gabor-based supervised locality preserving projection (GSLPP) method for face recognition. Locality preserving projection (LPP) is a recently proposed method for unsupervised linear dimensionality reduction. LPP seeks to preserve the local structure which is usually more significant than the global structure preserved by principal component analysis (PCA) and linear discriminant analysis (LDA). In this paper, we investigate its extension, called supervised locality preserving projection (SLPP), using class labels of data points to enhance its discriminant power in their mapping into a low-dimensional space. The GSLPP method, which is robust to variations of illumination and facial expression, applies the SLPP to an augmented Gabor feature vector derived from the Gabor wavelet representation of face images. We performed comparative experiments of various face recognition schemes, including the proposed GSLPP method, PCA method, LDA method, LPP method, the combination of Gabor and PCA method (GPCA) and the combination of Gabor and LDA method (GLDA). Experimental results on AR database and CMU PIE database show superior of the novel GSLPP method. 相似文献
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采用大涡模拟方法计算了来流速度为0.4 Ma情况下球/柱形结构附近的流场,根据密度数据计算了光程差及气动相屏,并研究了尾流对激光传输的影响。结果表明:光程差空间均方根的时间平均值随发射角增大而增大,发射角从120增加到148时,其数值从0.11 m增加到0.28 m;光程差空间均方根随时间变化剧烈,发射角为148时,其时间均方根可达0.04 m;球/柱尾流对激光传输有很大影响,发射角为148情况下,Strehl比的时间平均值为0.33,并且Strehl比的时间平均值随发射角的增大而减小,发射角从120增加到148过程中,Strehl比的时间平均值减小了59%;Strehl比随时间变化剧烈,其时间均方根大于0.05。 相似文献
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由投影重建图像的对称块迭代算法 总被引:1,自引:0,他引:1
由投影重建图像的迭代算法有抑制噪声等优点,但其投影矩阵的计算量大、影响重建速度。该文利用投影线存在的几何对称结构,引入图像重建的对称块迭代算法(简写为SB-IRT),简化了投影矩阵系数的计算,调整了迭代算法的顺序相关性。对于模拟和实测数据进行了图像重建试验,结果表明:与常规算法比较,该文提出的对称块迭代算法重建速度快,重建图像精度高。 相似文献
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任务场景日趋复杂给MIMO(Mutiple-Input Mutiple-Output)雷达带来诸多挑战。为应对强散射体遮蔽干扰、阵元间波形互扰及特定频带干扰等复杂电磁环境,该文提出一种松弛迭代谱拟合交替投影算法来设计相位编码波形。该算法基于功率谱拟合及交替投影框架,并引入扩展的加速因子;首先,凭借功率谱与非周期相关函数的傅里叶变换关系,将相关特性拟合问题转化为功率谱近似问题;然后,构建理想波形频谱并利用松弛机制扩展优化投影区;最后,利用快速傅里叶变换及加速交替投影机制迭代优化。计算机仿真表明,该算法运算效率高、可有效避免局部停滞,与当前流行算法相比更适合在线波形设计。 相似文献
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Focusing on the problem of natural image retrieval, based on latent semantic analysis (LSA) and support vector machine (SVM), a novel multi-instance learning (MIL) algorithm is proposed, where a bag corresponds to an image and an instance corresponds to the low-level visual features of a segmented region. Firstly, in order to transform every bag into a single sample, a collection of “visual-word” is generated by k-means clustering method to construct a projection space, then a nonlinear mapping is defined using these “visual-word” to embed each bag as a point in the projection space, thereby obtaining every bag's projection feature. Secondly, the matrix consisted of all the projection features of training bags is regarded as a term-document matrix, and LSA method is used to obtain the latent semantic feature of each bag. As a result, the MIL problem is converted into a standard single instance learning (SIL) problem that can be solved directly by SVM method. Experimental results on the COREL data sets show that the proposed method, named LSASVM-MIL, is robust, and its performance is superior to other key existing MIL algorithms. 相似文献
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《Journal of Visual Communication and Image Representation》2008,19(5):285-298
A new method for the exact reconstruction of any gray-scale image from its projections is proposed. The original image is projected into several view angles and the projection samples are stored in an accumulator array. In order to reconstruct the image, the accumulator array is considered as an accumulation of sinusoidal contributions each one corresponding to a certain pixel of the original image. The proposed method defines conditions for the necessary number of projections and the density of ray samples on the projection axis. These conditions insure that, for each pixel, there is at least one sample in the accumulator array where only this particular pixel contributes. This characteristic projection sample is used during the reconstruction phase to determine the coordinates and the gray-scale value of the corresponding image pixel. A variation of the method is also proposed where the reconstruction is performed using a limited number of projection samples in certain view angles. Specifically, the number of necessary samples equals at most the overall number of pixels in the original image. This approach leads to a significant reduction of memory and processing time requirements since it provides exact image reconstruction using one projection sample per pixel. 相似文献