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31.
离散傅里叶变换扩频正交频分复用(DFT-S-OFDM)作为一种单载波调制方案,与传统正交频分复用相比具有较小的峰均功率比(PAPR),并且已被3GPP采用作为其长期演进项目(LTE)的上行调制方案。针对该方案,提出了一种改进的基于局部最大似然(ML)的DFT-S-OFDM检测算法,首先挑选一阶最小均方误差-最大似然(MMSE-ML)检测后最有可能的2个星座符号位置,进而在这2个位置上做最大似然检测。仿真结果表明,提出的算法相比二阶MMSE-ML,在大幅度降低计算复杂度的基础上,性能损失很小;相比一阶MMSE-ML,能获得0.5 dB~0.7 dB的增益,而所需的额外计算量较少。 相似文献
32.
《Journal of Visual Communication and Image Representation》2014,25(3):586-595
The proposed work aims at analyzing the quality perceived by the user when streaming video on tablet devices. The contributions of this paper are: (i) to analyze the results of subjective quality assessments to determine which Quality of Service (QoS) parameters mainly affect the users’ Quality of Experience (QoE) in video streaming over tablet devices; (ii) to define a parametric quality model useful in system control and optimization for the considered scenarios; (iii) to compare the performance of the proposed model with subjective quality results obtained in alternative state-of-the-art studies and investigate whether other models could be applied to our case and vice versa. 相似文献
33.
在实际工程机械所产生的滚动轴承故障信号十分复杂,有效的故障信号和特征信息极易被噪声信号所干扰,针对工程中振动信号的特点,提出了一种基于局部均值分解(LMD)结合核独立分量分析(KICA)的方法提取故障信号特征。首先将源信号进行LMD分解,根据相关系数准则提取相关程度高的PF分量并构建新信号,对新构建的故障信号运用KICA进行噪声分离,进而获得故障信号特征。先通过构造信号仿真分析方法有效性,再通过西储大学轴承实验数据对比分析,验证该方法适用于提取滚动轴承的故障特征。 相似文献
34.
针对FH算法(Felzenszwalb和Huttenloch提出的图像分割算法)中存在的欠合并现象,在L*u*v*彩色空间,结合Mean Shift算法,提出了一种改进FH图像分割方法,即IFH(Improved FH)。该方法首先采用Mean Shift算法获得均值漂移图像,再将图像由RGB空间转换到L*u*v*颜色空间;然后,结合L*u*v*彩色空间,采用FH算法构造带权无向图,基于图像的颜色特征进行分割。实验证明,与原算法相比,该方法在分割精度与分割质量上有了很大程度的提高。 相似文献
35.
36.
T. Sekercioglu 《Materialwissenschaft und Werkstofftechnik》2009,40(9):713-717
The Gerber, modified Goodman, Soderberg, Bagci, ASME‐elliptic and Clemson diagrams are proposed for estimating mechanical element fatigue strength under positive mean and alternating stresses. However, all of these diagrams are either conservative or have fields containing stress greater than yield strength of mechanical element materials. The aim of this study was to propose a new simple diagram with an exponential power k for various types of mechanical element materials. Exponential power k values of steel and Al‐alloy materials were about 0.80 and 0.45, respectively. The proposed diagram (Sekercioglu line) had a minimum average absolute deviation (Xm) of 8.56 %, lower than the Bagci, ASME‐elliptic and Clemson diagrams. The Sekercioglu line can be successfully used in fatigue design processes because of its simple structure and its less conservative nature. 相似文献
37.
Dominik M. Wittmann Daniel Schmidl Florian Blchl Fabian J. Theis 《Theoretical computer science》2009,410(38-40):3826-3838
The analysis of complex networks is of major interest in various fields of science. In many applications we face the challenge that the exact topology of a network is unknown but we are instead given information about distances within this network. The theoretical approaches to this problem have so far been focusing on the reconstruction of graphs from shortest path distance matrices. Often, however, movements in networks do not follow shortest paths but occur in a random fashion. In these cases an appropriate distance measure can be defined as the mean length of a random walk between two nodes — a quantity known as the mean first hitting time.In this contribution we investigate whether a graph can be reconstructed from its mean first hitting time matrix and put forward an algorithm for solving this problem. A heuristic method to reduce the computational effort is described and analyzed. In the case of trees we can even give an algorithm for reconstructing graphs from incomplete random walk distance matrices. 相似文献
38.
This work studies the problem of recovering a complex signal (source) from an underdetermined linear mixture of bounded sources. We assume some a priori information of the desired signal in the form of a training sequence and complete absence of knowledge from the other sources, except for their bounded character. The main contribution of this letter is the proposal of a bounded component analysis of the training error that tries to condense the relevant information of the observations in a linear estimate of the desired signal. This subspace can be later used for subsequent refined estimation of the signal of interest. Simulations corroborate the good performance of the proposed method in high SNR scenarios. 相似文献
39.
A recent model for electrolysis with forced convection in a channel and an excess of dilute supporting electrolyte is extended using concentrated solution theory. Mean Spherical Approximation theory is used to calculate the necessary Onsager coefficients and ionic activities. Using asymptotic methods, we demonstrate the surprising similarities between the leading order equations for the dilute and concentrated theories. In addition, in deriving the extension, certain omissions in the original work are highlighted: an oversight in the Butler-Volmer law used in the original work is corrected, and the systematic use of similarity-like variables in electrochemical problems that do not have a similarity solution along the entire length of the diffusion layer adjacent to an electrode is demonstrated. This helps to explain the manner in which the solutions for the anode and cathode boundary layers and the bulk region decouple from each other at limiting current, enabling a much simpler solution strategy. 相似文献
40.
Minye Liu 《Chemical engineering science》2011,66(13):3045
The degree of mixing was first proposed by Danckwerts and further discussed by Zwietering more than 50 years ago to measure mixing performance of a continuous flow system. Although the measure has been widely discussed in mixing literature, there has never been a method to compute its value for a general continuous flow. In this paper, a method is developed to compute this measure for a general steady continuous flow system for the first time. The method is based on the recently developed mean age theory. The governing equations for the mean age and higher moments of age are also derived for different types of tracer introduction other than pulse input in the current mean age theory. 相似文献