共查询到20条相似文献,搜索用时 78 毫秒
1.
A method is presented for the automated extraction of myocardial borders in M-mode echocardiograms. The successive steps of processing are: preprocessing for noise reduction, enhancement of border characteristics using a set of suitably chosen matched filters, and final extraction of border points by searching for optimal paths along the time axis. During the last step of processing, the contribution of each elementary border element is characterised by a normalized correlation coefficient. The optimal path, defined as the one that maximizes the sum of all elementary contributions, is determined efficiently using dynamic programming. An alternative approach uses a maximum tracking procedure whose performances are improved by utilizing a local model to predict the position of the next border point. Experimental examples are presented and the performance of both border extraction algorithms are compared. 相似文献
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The use of one-dimensional spatial matched filtering for identifying the left ventricular endocardial borders in human transesophageal echocardiograms recorded during surgery is investigated. A maximum-likelihood method was used to choose the endocardial intensity profiles centered within the ventricle. The computer-generated border points were compared to those identified by an experienced ultrasonographer. A 16-pixel step template located 63.2% of the border points within 2 mm of the manual border. Median prefiltering of the images reduced detection accuracy by 3% to 6%. No statistically significant difference in accuracy was found between longer and shorter templates or between data-derived and step templates. Compared to manual estimates, computer generated cross-sectional area determinations were correlated with a coefficient of 0.93. Matched filtering executes rapidly, does not require prefiltering, and performs as well as other reported methods in estimating ventricular area. 相似文献
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GuanYepeng GuWeikang YeXiuqing LiuJilin 《电子科学学刊(英文版)》2004,21(2):170-176
An algorithm for automatically extracting feature points is developed after the area of feature points in 2-dimensional (2D) image being located by probability theory, correlated methods and criterion for abnormity. Feature points in 2D image can be extracted only by calculating standard deviation of gray within sampled pixels area in our approach statically. While extracting feature points, the limitation to confirm threshold by tentative method according to some a priori information on processing image can be avoided. It is proved that the proposed algorithm is valid and reliable by extracting feature points on actual natural images with abundant and weak texture, including multi-object with complex background, respectively. It can meet the demand of extracting feature points of 2D image automatically in machine vision system. 相似文献
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在某些应用领域,常常需要得到目标的高分辨率图像,考虑到在这些应用场合中,往往可以获得对同一景物或目标的多帧图像,本文提出了一种基于亚像素级图像配准与类似于中值滤波插值的从多幅低分辨率(LR)图像中获取一幅高分辨率(HR)图像的算法。算法首先采用梯度方法计算出LR图像之间的位移量,经过图像配准后,每个HR像素点被赋予其作用域内所有LR像点值的中值。仿真结果表明,该算法简单有效,既能提高图像分辨率,又能较好地去除非线性噪声。 相似文献
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Alaa R. AL-Taee Fei Yuan Andy Ye 《Analog Integrated Circuits and Signal Processing》2013,76(1):117-128
This paper investigates the drawbacks of widely used rectangular eye-opening monitors (EOMs) and proposes a new power-efficient half hexagon EOM for Gbps serial links. The proposed EOM outperforms rectangular EOMs by providing a better control of data jitter at the edge of data eyes and by eliminating unnecessary errors flagged by rectangular EOMs. The effectiveness of the proposed EOM is evaluated using a serial link implemented in IBM 130 nm 1.2 V CMOS technology. For purpose of comparison, rectangular EOMs with the same data link are also designed and evaluated. The data links are analyzed using Spectre from Cadence Design Systems with BSIM 4 device models. Simulation results demonstrate that the proposed EOM provides a better detection of the violation of the minimum eye-opening mask over temperature range ?20 to 80 °C and at all process corners as compared with rectangular EOM, with 50 % reduction in power and silicon consumption. 相似文献
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Extensions to a 2-dimensional bipolar-transistor-modelling algorithm are described. They enable practical high-frequency silicon devices to be analysed in a time appreciably shorter than previously reported schemes. This allows device properties to be economically explored over a wide range of bias currents and voltages. 相似文献
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Numerical methods of solution to linear equations are dicussed with reference to a bipolar-transistor model. Results are presented that show the advantages of using a strongly implicit procedure (s.i.p.). A new technique for applying iteration parametrers to s.i.p. is proposed. This method is compared with both direct and other iterative methods. 相似文献
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干扰角度估计是数字阵列雷达抗干扰的基础,本文针对实际数字阵列天线阵元间距大于半波长导致大角度估计时阵元相位出现模糊问题,提出一种新的基于时空DOA矩阵的多目标高性能二维角度估计算法。该算法首先计算时空DOA矩阵并进行特征值分解,接着利用空时矩阵特征向量与来波导向矢量匹配特性,对估计得到的各导向矢量分别进行相位解模糊,进而利用导向矢量联立方程组,得到各来波角度信息的最小二乘解。相位解模糊过程主要通过计算多组模糊解对应的导向矢量与实际估计得到的导向矢量的相关性,选取相关值最大的一组模糊解作为真实解来实现。仿真与数字阵列天线实测结果表明,与时空DOA矩阵法相比,本文算法具有更高的测角精度和更加稳健的输出性能。 相似文献
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多线圈采集技术与并行成像算法通过降低磁共振成像所必需的梯度编码步数有效提高了成像的扫描速度.但是在数据采集过程中,运动常常会使线圈数据发生异常,从而对最终重建图像质量产生很大影响.本文提出了一种新的重建算法去消除重建图像中产生的伪影.算法把破坏数据看成观测数据样本中的异常值,应用了AM鲁棒估计进行数据修正,很好的抑制了异常值对数据集造成的影响.本研究分别对多线圈并行采集的体模数据与真实脑部数据进行了实验,结果显示算法可以有效消除破坏数据在重建图像中产生的伪影,并通过对比实验充分显示了本算法的优越性. 相似文献
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一种快速有效的自适应算术编码 总被引:1,自引:0,他引:1
介绍了算术编码的原理和基于模型的自适应算术编码算法,并利用二进制索引树这样一个高效率的数据结构对传统的0阶自适应算术编码进行了改进。实验表明,无论对于高度集中的数据集还是对于分布较为均匀的数据集,在运行时间上新算法都有较大的改进。 相似文献
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消息传递机制是影响LDPC码解码性能的重要因素。简要介绍了Gallager提出的LDPC码和基于洪水消息传递机制的和积解码算法。在此基础上引入基于校验节点的串行消息传递机制并提出具体可实现的解码算法模型。该串行解码算法按照校验节点一定的顺序进行消息处理和传递,保证更新的消息能够马上进入迭代过程,从而改善消息传递的收敛特性;同时充分利用消息间相互关联的特点,融合消息传递步骤,可以降低所需的存储容量,简化解码复杂度。分别应用洪水解码算法和串行解码算法在AWGN信道下进行性能仿真。仿真结果表明串行解码算法使解码性能得到明显提高。 相似文献
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The transition from 2-dimensional line analysis to the 1-dimensional model is examined on the basis of a suitable series expansion of the voltage equation. It is shown that 1-dimensional equations can be derived from a 2-dimensional analysis with proper approximations for certain operators. A consistence procedure is outlined and applied to an exponential taper. 相似文献
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We propose a new efficient serial architecture to implement the Berlekamp-Massey (1968, 1969) algorithm, which is frequently used in BCH and Reed-Solomon (1960) decoders. An inversionless Berlekamp-Massey algorithm is adopted which not only eliminates the finite-field inverter but also introduces additional parallelism. We discover a clever scheduling of three finite-field multipliers to implement the algorithm very efficiently. Compared to a previously proposed serial Berlekamp-Massey architecture, our technique significantly reduces the latency 相似文献
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An effective and efficient compression algorithm for ECG signals with irregular periods 总被引:1,自引:0,他引:1
This paper presents an effective and efficient preprocessing algorithm for two-dimensional (2-D) electrocardiogram (ECG) compression to better compress irregular ECG signals by exploiting their inter- and intra-beat correlations. To better reveal the correlation structure, we first convert the ECG signal into a proper 2-D representation, or image. This involves a few steps including QRS detection and alignment, period sorting, and length equalization. The resulting 2-D ECG representation is then ready to be compressed by an appropriate image compression algorithm. We choose the state-of-the-art JPEG2000 for its high efficiency and flexibility. In this way, the proposed algorithm is shown to outperform some existing arts in the literature by simultaneously achieving high compression ratio (CR), low percent root mean squared difference (PRD), low maximum error (MaxErr), and low standard derivation of errors (StdErr). In particular, because the proposed period sorting method rearranges the detected heartbeats into a smoother image that is easier to compress, this algorithm is insensitive to irregular ECG periods. Thus either the irregular ECG signals or the QRS false-detection cases can be better compressed. This is a significant improvement over existing 2-D ECG compression methods. Moreover, this algorithm is not tied exclusively to JPEG2000. It can also be combined with other 2-D preprocessing methods or appropriate codecs to enhance the compression performance in irregular ECG cases. 相似文献
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A. Ortiz-Conde J. J. Liou F. J. García Snchez E. Gouveia Fernandes O. Montilla Castillo M. D. Rofiqul Hassan G. De Mercato 《Microelectronics Reliability》1998,38(12):1867-1870
A new and simple method to extract the effective channel length Leff of metal-oxide superconductor field effect transistor (MOSFET)s is presented. The method, which is developed based on an auxiliary integral function, has the advantage of determining the value of Leff not influenced by the series resistances of the MOSFET. The method is tested in the environments of device simulation and measurements. In addition, comparison is made between the results obtained from the present method and a widely used Leff extraction method. 相似文献
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By a transformation of variables, the equations of Gummel's algorithm achieve a form which avoids the recurrent calculation of exponentials that usually characterises the method. The transformation results in tractable equations and a reduction in computational labour compared with previous methods. 相似文献