Bayesian estimation of Dirichlet mixture model with variational inference

In statistical modeling, parameter estimation is an essential and challengeable task. Estimation of the parameters in the Dirichlet mixture model (DMM) is analytically intractable, due to the integral expressions of the gamma function and its corresponding derivatives. We introduce a Bayesian estimation strategy to estimate the posterior distribution of the parameters in DMM. By assuming the gamma distribution as the prior to each parameter, we approximate both the prior and the posterior distribution of the parameters with a product of several mutually independent gamma distributions. The extended factorized approximation method is applied to introduce a single lower-bound to the variational objective function and an analytically tractable estimation solution is derived. Moreover, there is only one function that is maximized during iterations and, therefore, the convergence of the proposed algorithm is theoretically guaranteed. With synthesized data, the proposed method shows the advantages over the EM-based method and the previously proposed Bayesian estimation method. With two important multimedia signal processing applications, the good performance of the proposed Bayesian estimation method is demonstrated.     

泄水建筑物下游冲刷坑二维数值模拟

对巨亭水电站泄水建筑物下游局部冲刷过程进行了二维数值模拟。采用RNG k-ε湍流模型封闭N-S方程、有限体积法在计算网格上离散求解、VOF方法追踪自由水面;采用C语言编写用户自定义函数,以泥沙起动切应力作为床面泥沙起动判别标准,通过分析比较水流剪切力与泥沙起动切应力大小,用以控制冲刷坑底部边界变化;采用局部重构模型和弹簧光顺模型更新计算区域和网格质量,藉以模拟和追踪局部冲刷坑边界变化。研究表明,模拟结果与实测资料符合良好。在冲刷坑的冲刷过程中,床面剪切应力随着冲刷的进程急剧减小,湍动能随着冲刷的进程减小缓慢;床面剪切应力和湍动能沿程变化均较为剧烈,床面剪切应力沿程先增大后减小,床面湍动能则沿程减小。冲刷坑的纵向平衡形态或床面泥沙起动主要决定于床面剪切应力,床面湍动能对泥沙起动也具有重要影响。     

产品艺术形式的深度创新

文章对产品设计艺术形式的深度创新进行了分析与探索。选取家电、家居产品、五金产品、交通产品、数码电子产品中典型的中外设计案例,结合比较学的方法对优秀产品的深层创新与其它产品中的浅层创新做了比较分析。论述了产品设计中艺术形式创新应包含的本质内容。艺术形式深度创新的本质包括：为解决平凡生活中的某个问题而设计的形式;作为新技术的先导而设计的形式。研究的结论对减少资源浪费,提高人的生活质量,正确引导未来的设计走向具有重要意义。     

单幅图像多尺度小波深度提取算法

针对浅景深图像中平滑前景区域深度提取误差大的问题,基于像素点分类思想对深度值进行修正,提出一种基于多尺度小波线索的、可同时面向单幅浅景深图像和广角图像的深度图提取算法.首先使用小波分析法在多个尺度下提取图像深度信息;然后提出自适应分类法并根据尺度与深度变化规律对像素点做深度修正,得到深度图;最后结合区域生长与边缘分割算法对深度图进行区域优化.为了加快深度计算,还提出了快速zerocount法以及多尺度加速法来满足标清视频实时处理要求.实验结果证明,采用文中算法获得的深度图相对深度正确,前景和背景区域深度一致性好.     

kinect深度数据随机跳变误差分析及修正算法研究

采用微软空间扫描设备kinect的测距数据会产生随机跳变误差现象。通过分析误差原因及实验验证了跳变误差随距离增加曲线上升的特点。为修正该误差设计了一个基于像素滤波技术的误差修正算法。在kinect有效距离内连续观测三个待测物的空间深度数据和滤波数据。经实验验证在使用10帧深度数据可以将跳变误差在1.5m以内的跳变误差控制在5mm以内;1.5~3m以内的随机跳变误差控制大部分在10mm以内;超过3m的随机误差均匀分布在25mm以内。     

Aging and availability of binocular disparity and pictorial depth cues in 3D graphics contents

Some stereoblind observers do not perceive depth of 3D stimuli that depends on binocular disparity. These individuals, who have no disabilities, comprise over 5% of the general population. In addition, 17–30% of nonstereoblind young and young–middle people do not use disparity information in certain 3D environments, a phenomenon known as pseudo‐stereoblindness. This study aimed to investigate the relationship between aging and the proportion of pseudo‐stereoblindness in the general population. In an experiment, 134 nonstereoblind participants, ranging in age from 17 to 83 years, judged subjective depth of 3D stimuli containing binocular disparity and pictorial depth cues. Results showed that the proportion of pseudo‐stereoblindness among young (17–24 years old) and young–middle aged observers (25–39 years old) was 29%, in both cases. However, the proportion of pseudo‐stereoblind observers increased in older populations: 65% and 82% in the middle (40–54 years old) and senior (55–83 years old) age groups, respectively. These results suggest that a number of people, especially in elderly populations, have trouble perceiving depth from binocular disparity in 3D graphic contents despite their essential ability to use disparity information.     

Visual experience for autostereoscopic 3D projection display

In order to investigate visual experience for watching the autostereoscopic three‐dimensional (3D) projection display, we conduct a subjective evaluation experiment by a questionnaire when viewing video clips. Factor analysis is adopted to classify the evaluation items for the perpetual constructs of visual experience. Then a mixed design with repeated measurement analysis of variance with dimension and display duration as factors is carried out on the evaluation data to check the factorial effects and interactions for statistical significance. The results of factor analysis extract five factors including visual comfort, image quality, distortion, naturalness, and presence, which can be used as comprehensive indicators to evaluate the autostereoscopic 3D projection display. The results of analysis of variance indicate that image quality, which is used to assess two‐dimensional contents, is no longer applicable. It is necessary to give consideration to depth when evaluating 3D visual experience. Although 3D scenes enhance the overall subjective performance such as naturalness and presence, the health issues and stereoscopic distortion related to the introduction of depth cannot be ignored.     

Crack elongation and its width of large depth reinforced concrete beams

In order to meet the requirement of structural inspection,the crack spacing and crack width at various heights in the tensile zone of six large depth reinforced concrete beams were measured under several loading levels of serviceability state.The effects of the depth of normal section beams on the crack spacing and crack width were analyzed,and the modified model is proposed for calculating the average crack spacing by thinking about the depth of normal section,the reinforcement arrangement and the effective reinforcement ratio.The relationships of crack widths at any position in the tensile zone and at the reinforcement level on the side surface of beam were studied.By theoretical and statistical analysis,a method is proposed to calculate the ratios of crack widths between any position and the reinforcement level on the side surface of large depth reinforced concrete beams.     

湿陷性黄土地基强夯有效加固深度预测

对强夯有效加固深度主要影响因素进行分析,考虑能量的转化,综合运用量纲守恒和最小二乘原理,结合一定量的湿陷性黄土地基强夯加固实例,推导了有效加固深度估算公式,并与其他公式进行比较;再结合另外两组湿陷性黄土地基实例,进一步探讨了本文公式的估算效果。新的公式反映了含水量与有效加固深度呈非线性相关,能使得计算效果更好,参数选用方便,对湿陷性黄土地基有一定参考价值。     

旅行商问题的较优可行解的搜索算法的设计

利用问题本身的特点和相关的已有结论,结合最近邻法和深度优先搜索算法设计了产生旅行商问题较优可行解的方法。首先,将与每个城市关联的城市由近到远排序,并将城市之间距离较远的边删除。然后选择一个城市作为出发地,按排序利用深度优先搜索算法在有限步内搜索可行解。若搜索到多个可行解,从中选择较优的作为以该城市为出发地的可行解;否则,重新选择出发地开始新的搜索。对经典的st70、a280问题依次将每个城市作为出发地进行实验,该方法产生的可行解的性能明显优于随机搜索算法。但仍不及最近邻法。