Information extraction from image sequences of real-world facial expressions

Information extraction of facial expressions deals with facial-feature detection, feature tracking, and capture of the spatiotemporal relationships among features. It is a fundamental task in facial expression analysis and will ultimately determine the performance of expression recognition. For a real-world facial expression sequence, there are three challenges: (1) detection failure of some or all facial features due to changes in illumination and rapid head movement; (2) nonrigid object tracking resulting from facial expression change; and (3) feature occlusion due to out-of-plane head rotation. In this paper, a new approach is proposed to tackle these challenges. First, we use an active infrared (IR) illumination to reliably detect pupils under variable lighting conditions and head orientations. The pupil positions are then used to guide the entire information-extraction process. The simultaneous use of a global head motion constraint and Kalman filtering can robustly track individual facial features even in condition of rapid head motion and significant expression change. To handle feature occlusion, we propose a warping-based reliability propagation method. The reliable neighbor features and the spatial semantics among these features are used to detect and infer occluded features through an interframe warping transformation. Experimental results show that accurate information extraction can be achieved for video sequences with real-world facial expressions.Received: 16 August 2003, Accepted: 20 September 2004, Published online: 20 December 2004 Correspondence to: Qiang Ji     

Appearance Sampling of Real Objects for Variable Illumination

The appearance of an object greatly changes under different lighting conditions. Even so, previous studies have demonstrated that the appearance of an object under varying illumination conditions can be represented by a linear subspace. A set of basis images spanning such a linear subspace can be obtained by applying the principal component analysis (PCA) for a large number of images taken under different lighting conditions. Since little is known about how to sample the appearance of an object in order to correctly obtain its basis images, it was a common practice to use as many input images as possible. In this study, we present a novel method for analytically obtaining a set of basis images of an object for varying illumination from input images of the object taken properly under a set of light sources, such as point light sources or extended light sources. Our proposed method incorporates the sampling theorem of spherical harmonics for determining a set of lighting directions to efficiently sample the appearance of an object. We further consider the issue of aliasing caused by insufficient sampling of the object's appearance. In particular, we investigate the effectiveness of using extended light sources for modeling the appearance of an object under varying illumination without suffering the aliasing caused by insufficient sampling of its appearance.     

面向对象分析设计方法的分析与比较

本文对国内外面向对象建模的进展情况进行了分析和对比,给出了各种建模方法中存在的问题。在此基础之上,提出了在面向对象的分析和设计中建模应该注意的问题。     

Adaptive extraction and visualization of silhouette curves from volumetric datasets

An algorithm for silhouette extraction from volumetric data is presented. Trivariate tensor product B-spline functions are used to represent the data. An offline phase that arranges the data in a lookup table is employed to improve the computation time during an interactive session. A subdivision scheme is employed to extract the silhouette curves from an implicit trivariate B-spline function. The produced results are smooth, high-quality silhouette curves when compared to voxel-based silhouette extraction schemes.     

BMP图像数据提取在分析测试中的应用

本文提出一个通用的方法,通过对Windows下BMP位图文件的格式分析,在Visual C ．Net开发环境下,提取分析测试中所需要的图像数据,使其转化为许多专业数据分析处理软件都可以兼容的文本数据文件,为后期的实验数据分析处理提供了极大的便利。实验证明,这种方法是方便、准确的,已应用于科研。     

AlGaN/GaN HEMTs on SiC and Si substrates: A review from the small‐signal‐modeling's perspective

In this article, small‐signal modeling approaches for GaN HEMTs on SiC and Si substrates have been developed. The main advantage of these approaches is their accuracy, reliability, and dependency on only cold S‐parameter measurements to extract the parasitic elements of the device. The proposed equivalent circuit model for GaN on Si HEMT considers extra effects due to parasitic conduction through substrate or buffer layers. S‐parameter measurements at different bias conditions in addition to physical based analysis have been used to validate the accuracy and reliability of the developed modeling methods. © 2013 Wiley Periodicals, Inc. Int J RF and Microwave CAE 24:389–400, 2014.     

农作物病虫害图像识别技术的研究综述

农作物病虫害的爆发往往意味着大规模的减产减质,造成不可挽回的经济损失。传统的病虫害识别方法速度慢、主观性强、误判率高,已不能满足农业生产的需要。基于图像处理技术的农作物病虫害识别具有快速、精确、实时等特点,能够协助农耕人员及时采取有效的防治措施。本文从图像分割、特征值提取和分类识别三个方面,分别阐述图像处理技术应用于农作物病虫害识别的研究现状和进展,并对今后的研究趋势和方向作了展望。     

Generative modeling and classification of dialogs by a low-level turn-taking feature

In the last few years, a growing attention has been paid to the problem of human-human communication, trying to devise artificial systems able to mediate a conversational setting between two or more people. In this paper, we propose an automatic system based on a generative structure able to classify dialog scenarios. The generative model is composed by integrating a Gaussian mixture model and a (observed) Markovian influence model, and it is fed with a novel low-level acoustic feature termed steady conversational period (SCP). SCPs are built on duration of continuous slots of silence or speech, taking also into account conversational turn-taking. The interactional dynamics built upon the transitions among SCPs provides a behavioral blueprint of conversational settings without relying on segmental or continuous phonetic features, and may be important for predicting the evolution of typical conversational situations in different dialog scenarios. The model has been tested on an extensive set of real, dyadic and multi-person conversational settings, including a recent dyadic dataset and the AMI meeting corpus. Comparative tests are made using conventional acoustic features and classification methods, showing that the proposed scheme provides superior classification performances for all conversational settings in our datasets. Moreover, we prove that our approach is able to characterize the nature of multi-person conversation (namely, the role of the participants) in a very accurate way, thus demonstrating great versatility.     

海面温度栅格图的锋面提取与矢量化

提出一种海面温度栅格图的锋面提取方法。针对海洋表层温度(SST)锋面强度分布不均匀的特点,利用低通滤波对表温梯度图像进行平滑。再利用迭代法确定出梯度图像的分割阈值,将图像分割成目标与背景两部分。通过数学形态学中图像细化的方法,提取海洋温度锋面的骨架并对细小分枝进行修剪。经矢量化生成锋面线后,利用抹角法对折线进行光滑。最后以西太平洋为例,给出了一个表温锋面提取的实例,表明利用此方法进行海表温度锋面的提取是可行与有效的。     

一种基于单幅图像的树木深度估计与造型方法

提出了种基于单幅图像、利用光照引起的明暗效果（ｓｈａｄｉｎｇ）恢复树木枝干三维形态的方法,与传统ｓｈａｐｅ ｆｒｏｍ ｓｈａｄｉｎｇ技术相比,该方法根据树木的特殊结构,利用更稳定的明暗特征,取消了对表面、光源及拍摄条件的限制,从而将算法的鲁棒性提高到足以处理自然的树木照片．基于上述工作,提出了一种基于单幅照片的交互式树木造型方法,该方法避免用数学模型控制树木形态,独立于树木的具体种类,具有较高的普     

A robust algorithm for separation of Chinese characters from line drawings

Separating characters from graphics is an important step towards automatic document understanding. In this paper, we propose a robust algorithm to separate Chinese characters from graphics. Our approach is based on clustering the feature points in an image. Two remedy procedures are also proposed to solve the problems caused by the thinning process. This will obtain a better localization of feature points and improve the performance of the separation process. Using our algorithm, all Chinese characters can be separated from graphics without regard to the font style or orientation of the character. Furthermore, our algorithm can also handle the serious case where characters touch/cross lines. The proposed algorithm has been successfully tested on several kinds of line drawings, such as land register maps and form documents.     

基于ESD的动态系统安全性建模与实现

事件序列图(ESD)是系统安全性分析时采用的一种较新的手段,能有效地解决传统的安全性建模与分析在动态方面的不足。在对国内外动态系统安全性建模与分析方面的研究基础上,提出了一种扩展的ESD方法。对ESD的定义进行了完善,给出了ESD框架的动态逻辑图元表示形式及其数学描述,为提高其建模功能以及与系统结构关联的能力提出了层次化建模策略,并结合新的ESD算法开发了基于ESD的动态系统可视化建模与分析软件。最后,给出了一个实例以说明其有效性。     

Generating cubical complexes from image data and computation of the Euler number

A number of tasks in image processing and computer vision require the computation of certain topological characteristics of objects in a given image. In this paper, we introduce a new method based on the notion of the algebraic topology complex to compute the Euler number of a given object. First, we attach a cubical complex to the object of interest, then we associate an algebraic structure on which a number of simplifying operations preserving the topology but not necessarily the geometric nature of the complex are possible. This is a unifying dimension independent approach. We show that the Euler number can be obtained directly from the cubical structure or one can perform a collapsing operation that allows to reduce the given image to a lower dimension structure with equivalent topological properties. This reduced structure can be used in a further process, in particular, for the computation of the Euler number.     

电泳芯片分离指标的模拟分析

对电泳芯片中影响区带展宽的相关因素进行了分析，给出了分离综合效率的表达式，建立了分离指标的数学模型。以此为基础，结合实验条件，利用计算机对影响分离指标的相关因素进行了模拟分析。结果表明，以分离综合效率为分离指标，可以反映分离条件对理论塔板数和分离时间的综合影响，而且，以分离指标的模拟分析为依据，可望实现电泳芯片的优化设计，在满足分离的前提下尽快地完成样品的分离分析过程。     

Surface deformation time series and source modeling for a volcanic complex system based on satellite wide swath and image mode interferometry: The Lazufre system, central Andes

The variable spatio-temporal scales of Earth's surface deformation in potentially hazardous volcanic areas pose a challenge for observation and assessment. Here we used Envisat data acquired in Wide Swath Mode (WSM) and Image Mode (IM) from ascending and descending geometry, respectively, to study time-dependent ground uplift at the Lazufre volcanic system in Chile and Argentina. A least-squares adjustment was performed on 65 IM interferograms that covered the time period of 2003-2008. We obtained a clear trend of uplift reaching 15-16 cm in this 5-year interval. Using a joint inversion of ascending and descending interferograms, we evaluated the geometry and time-dependent progression of a horizontally extended pressurized source beneath the Lazufre volcanic system. Our results hence indicate that an extended magma body at a depth between 10 and 15 km would account for most of the ground uplift. The maximum inflation reached up to ~ 40 cm during 2003-2008. The lateral propagation velocity of the intrusion was estimated to be nearly constant at 5-10 km/yr during the observation time, which has important implications for the physical understanding of magma intrusion processes.     

基于无人机图像分形特征的油松受灾级别判定

利用无人机采集油松样地图像,提取图像中的单株样本树图像,计算单株样本树图像的多个纹理特征值,对纹理特征值进行灾害分级,与地面基于失叶率调查的灾害分级进行比对,探索能准确描述油松受灾情况的无人机图像纹理特征,实验结果表明：受灾油松图像的三种分形特征,即分形维数、缝隙量及维数升降因子能较好地反应油松的失叶率状况,可作为油松受灾级别的图像判定特征,同时上述分形特征也适用于整块油松样地的受灾级别判定。