Multi-Wavelength vs. Binary Code Pattern Unwrapping in Fringe Projection Method

Phase extraction, phase unwrapping and phase to height conversion are consecutive steps within the fringe projection method for reconstruction of 3D objects. The procedure of determining discontinuities on the wrapped phase, resolving them and achieving the unwrapped phase is called phase unwrapping. A software system was developed that provides the ability to create many kinds of patterns with a verity of desirable properties suitable for different demands in fringe projection systems. In our previous work, an experimental study was reported based on a multi-wavelength unwrapping approach. In the following work, we implemented a new method called binary code pattern unwrapping that is based on time analysis. A comparison of the two unwrapping approaches in terms of resolution, quality, noise, depth accuracy, and computational cost is provided.     

用两个形状指数表征粉煤灰颗粒形貌的研究

引用两个形状指数表征颗粒形状的概念,即先将颗粒形状近似为椭圆,再将椭圆图像分离:以圆为基准的颗粒宏观形状指数δ;以光滑椭圆为基准的颗粒轮廓凹凸度,即微观形状指数ζ。分析和发展了近似椭圆模型。并运用图像分析仪对粉煤灰、水泥样品进行实验。结果表明,粉煤灰颗粒的两个形状指数δ和ζ都大于水泥颗粒。证明粉煤灰颗粒的球形度、表面光滑度优于水泥,而且,随着粒径增大,δ和ζ呈下降趋势,表明磨制颗粒越粗。(?)粒形状越不规则。文中还运用近似椭圆模型再现了颗粒的模拟图像。     

Markov随机场与Gaussian曲线在MR图像分割中的应用

针对扫描的人脑组织MR图像边缘分辨率低、模糊性大的特点,本文提出了一种基于模糊Markov随机场和Gaussian曲线相结合的MR图像最佳阈值分割方法。该方法通过对图像的像素邻域属性的统计将模糊论引入其中,建立模糊Markov随机场,并利用Gaussian曲线对二维直方图最佳一维投影进行拟合,确定出图像中各脑组织的二维阈值点,在二维直方图上实现对脑组织的分割。通过实验表明,本算法能够有效提高脑组织的分辨率,对噪声的鲁棒性、结果区域的连通性相对于一维Otsu和二维Otsu算法都有了很大的提高。     

基于梯度投影法与随机优化算法的约束优化方法

针对带有线性等式和不等式约束的无确定函数形式的约束优化问题,提出一种利用梯度投影法与遗传算法、同时扰动随机逼近等随机算法相结合的优化方法。该方法利用遗传算法进行全局搜索,利用同时扰动随机逼近算法进行局部搜索,算法在每次进化时根据线性约束计算父个体处的梯度投影方向,以产生新个体,从而能够严格保证新个体满足全部约束条件。将上述约束优化算法应用于典型约束优化问题,其仿真结果表明了所提出算法的可行性和收敛性。     

基于压缩感知的图像重构算法

在图像压缩感知中,梯度投影恢复算法存在收敛速度慢、迭代次数多、对数据稀疏度过分敏感的问题。为此,提出一种基于压缩感知的图像重构算法。将拟牛顿法引入稀疏梯度投影算法中,利用拟牛顿法的估计校正机制以及其全局超线性收敛性,通过对目标函数的校正,获得更精确的搜索方向,从而减少迭代次数,构成有效收敛的图像恢复算法。实验结果表明,与传统梯度投影恢复算法相比,该算法在保证较好图像恢复效果的同时具有较好的抗噪性能,并且在减少迭代次数的基础上能有效降低重构误差,得到稳定收敛的重构结果。     

区间数信息下的多属性群决策研究

随着决策系统的不断扩大以及复杂化,评价指标以实数值描述稍显欠妥。研究属性权重为实数值、区间数信息下的多属性群决策问题,建立集结区间数信息的非线性规划模型,采用模拟植物生长算法集结各方案中多位专家给出的区间数偏好,并利用得到的偏好区间数构成群决策偏好矩阵。结合已知权重,引入投影理论得到各方案的综合评价值,从而选出最优决策方案。算例结果表明,模拟植物生长算法不仅计算简便、灵活,并且尊重每个专家的意见,较好地保留了信息的完整性,显示出人工智能算法在信息集结方面的有效性。     

PROJECTION MODULUS: A NEW DIRECTION FOR SELECTING SUBSET AUTOREGRESSIVE MODELS

Selecting a parsimonious subset autoregressive time series model is a valuable objective particularly where there is or may be evidence that a time series may have some form of periodic or quasi-periodic behaviour. An efficient model selection procedure is essential because of the large number of possible alternative models involved. The explanation of an increase in residual variance due to excluding a lag is examined in Hilbert space. As a result, a new statistic, the projection modulus , and its derivatives are developed to assess the significance of any lag in a model. The impact of deleting a lag, as measured by these statistics, helps to produce a selection procedure where true lags have less chance of being removed. We then assess an efficient subset autoregressive model selection procedure employing these statistics. The success of the proposed procedure is illustrated by its efficiency in identifying the true model for simulated and real data.     

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.     

考虑空气阻力的抛体最大射程和最佳抛射角研究

为了研究抛体在什么抛射角抛出时具有最大射程,利用拉格朗日乘子法,推导出存在空气阻力并且起点和终点不在同一高度时,在某一斜面上抛出的抛体的最大射程和最佳抛射角.通过计算机编程,以计算投掷手榴弹时的最大射程和最佳抛射角为例进行验证,并对物理教学中抛体运动的动力学过程进行了进一步的分析和讨论,有利于提高教学效果.     

基于球门检测的足球视频精彩事件提取

为了提高足球视频精彩事件检测效率,提出了一种基于双投影法的球门镜头检测算法,并在此基础上提出了基于球门检测的精彩事件提取算法.实验结果表明,该算法比常规算法取得了更好的检测效果,生成的精彩视频摘要大约为原视频的5%.