Tracking of facial deformations in multi-image sequences with elimination of rigid motion of the head

The paper deals with measurement of human facial deformations from synchronized image sequences taken with multiple calibrated cameras from different viewpoints. SIFT (Scale Invariant Feature Transform) keypoints are utilized as image feature points in the first place to determine spatial and temporal correspondences between images. If no temporal match is found for an image point by keypoint matching, then the tracking of the point is switched to least squares matching provided the point has one or more spatial corresponding points in the other views of the previous frame. For this purpose, a new method based on affine multi-image least squares matching is proposed where multiple spatial and temporal template images are simultaneously matched against each search image and part of the spatial template images also change during adjustment. A new method based on analyzing temporal changes in the image coordinates of the tracked points in multiple views is then presented for detecting the 3-D points which move only rigidly between consecutive frames. These points are used to eliminate the effect of rigid motion of the head and to obtain the changes in the 3-D points and in the corresponding image points due to pure deformation of the face. The methods are thoroughly tested with three multi-image sequences of four cameras including also quite large changes of facial deformations. The test results prove that the proposed affine multi-image least squares matching yields better results than another method using only fixed templates of the previous frame. The elimination of the effect of rigid motion works well and the points where the face is deforming can be correctly detected and the true deformation estimated. A method based on a novel adaptive threshold is also proposed for automated extraction and tracking of circular targets on a moving calibration object.     

Riegl VZ-400三维激光扫描仪数据的建模的研究

三维激光扫描技术是近年来发展起来的一门新技术,其在众多领域中有非常广阔的应用前景。本文介绍了三维激光扫描仪目前的应用现状,以及原理和数据后处理方法。最后通过青海玉树山体建模实例叙述了Riegl VZ-400扫描仪如何获取数据、点云数据的拼接及三维模型的建立。     

基于改进White方法的地下水蒸散发研究

在依赖地下水的植被广泛分布的干旱半干旱地区,蒸散发是地下水排泄的主要方式,因而准确计算地下水蒸散发量,对地下水资源评价具有重要意义。目前水量残差法、地下水极限埋深法和地下水水位日动态法可以用于计算地下水蒸散发量,由于地下水动态信息容易获取,长期以来得到广泛关注。分析了利用地下水动态信息的White方法在计算地下水净补给量方面的不足之处,提出了改进的White方法,即利用相邻两天地下水位上升段的平均斜率计算地下水的净补给量,并利用数值模拟方法对改进的White方法的计算精度进行了评价,表明改进后的方法较原始方法精度提高了16%。最后利用苏贝淖流域实测的地下水动态数据,采用改进的White方法计算了地下水蒸散发量。研究成果对干旱区水资源可持续开发利用具有一定的科学意义和应用价值。     

实时精密单点定位精度与收敛性分析

介绍了目前国际全球定位系统服务（IGS）组织提供的实时精密轨道和精密钟差改正系数（ROCC）的基本参数以及能够进行实时精密单点定位软件（BNC）（即BKG Ntrip Client,由BKG开发的一款用于实时同步接收、解码及转换的GNSS数据流管理软件）。选取了25个全球IGS跟踪站,并基于BNC软件分析了IGS提供的15种ROCC产品对测站实时精密单点定位精度与收敛性的影响。实验结果表明：采用BNC软件,15种ROCC产品均能在平均15min的时间收敛,并且在N、E方向达到6～8cm,U方向10～20cm的定位精度;且不同ROCC产品其收敛时间和定位精度都存在一定的差异。     

Volcanic emissions of metals and halogens from White Island (New Zealand) and Erebus volcano (Antarctica) determined with chemical traps

Volcanic emission rates of As, Sb, Pb, Hg, Se, Cl, and F were determined at Erebus volcano, Antarctica and White Island, New Zealand, using chemical traps. The trace metal fluxes were determined by combining the species to S ratios in the solutions with SO₂ emission rates measured by correlation spectrometry at the two volcanoes. At Erebus volcano, fluxes for the metals Pb and Hg were 2.0 × 10^− 4 and 8.1 × 10^− 6 kg s^− 11, respectively. Fluxes for Cl, F, As, Sb and Se (0.35, 0.15, 2.5 × 10^− 4, 1.2 × 10^− 5, and 4.5 × 10^− 6 kg s^− 1, respectively) agreed within error limits for values determined previously by the LiOH impregnated filter method [Zreda-Gostynska, G., Kyle, P., Finnegan, D., Prestbo, K., 1997. Volcanic gas emissions from Mount Erebus and their impact on the Antarctic environment. Journal of Geophysical Research, 102(B7): 15039–15055.], demonstrating the utility of the chemical trap method. A fall in the As/S ratio from 7 × 10^− 4 in 1997/1999 to 3 × 10^− 4 in 2000 at Erebus coincided with a change in the frequency and style of eruptive activity that may have been due to injection of magma into the system. At White Island, chemical trap data indicated fluxes of Cl = 0.90, F = 0.0079, Pb = 2.7 × 10^− 4, Hg = 1.1 × 10^− 5, As = 1.3 × 10^− 4, Sb = 1.9 × 10^− 5 and Se = 1.5 × 10^− 5 kg s^− 1. Samples collected 600 m downwind of the active crater were comparable to samples collected adjacent to the main gas vent, showing that this method can still be used at some distance from a degassing vent.     

Axisymmetric transient waves in transversely isotropic half-space

A transversely isotropic material in the sense of Green is considered. Using a series of potential functions proposed in [Eskandari-Ghadi M. A complete solution of the wave equations for transversely isotropic media. J Elasticity 2005; 81:1–19], the solutions of the transient wave equations within a half-space under surface load are obtained in the Laplace–Hankel domain for axisymmetric problems. The solutions are investigated in detail in the special case of a surface point force pulse varying with time as Heaviside function. Using Cagniard–De Hoop method, the inverse Laplace transform and inverse Hankel transform of the solutions are then obtained in the form of integrals with finite limits. For validity of the analytical results, the final formulations for surface waves are degenerated for an isotropic material and compared with the existing formulation obtained by Pekeris [The seismic surface pulse. Proc Natl Acad Sci USA 1955;41:469–80], to show that they are exactly the same. The numerical evaluations of the integrals for some transversely isotropic materials as well as an isotropic one are obtained. The present approach is then numerically verified by comparing a particular case of displacements for the surface of an isotropic half-space subjected to a point load of Heaviside function with the solutions obtained by Pekeris [The seismic surface pulse. Proc Natl Acad Sci USA 1955;41:469–80]. In addition, the wave equations for the mentioned medium are obtained on the vertical line directly under the applied surface load. The final formulations are degenerated for an isotropic material and compared with the existing formulation given in Graff [Wave motion in elastic solids. New York: Dover Publications Inc; 1975 [New Ed edition, November 1991]], to show that they are also exactly the same. Then equations are presented in graphical forms using an appropriate numerical evaluation.     

三维观测系统中横向覆盖次数及CDP间隔的计算方法

总结了三维观测系统中横向覆盖次数及CDP间隔计算的综合平面图法、坐标法、Z变换公式法,指出了3种方法各自的优、缺点和适用性。     

火山岩地震屏蔽层的转换波叠前时间偏移成像

在反射地震转换波资料处理中,准确求取共转换点一直是一个难题,采用叠前时间偏移技术能避免共转换点道集的抽取,而且能够使转换波归位到真正的反射点上,实现准确成像.本文针对火山岩地震屏蔽层的转换波成像问题,通过对转换波共近似转换点道集进行速度分析,建立了转换波叠前时间偏移的初始速度场,通过速度扫描和纵、横波速度比值扫描确定最佳的偏移速度场和纵、横波速度比值,实现了在火山岩高速层覆盖区域的转换波偏移成像.实际资料的成像结果表明,本文采用的近似转换点计算以及转换波叠前时间偏移方法是有效的.     

场地土的随机地震反应分析

研究了剪切模量随深度呈线性变化时场地土的随机地震反应分析方法, 分别建立了基岩输入地震动加速度功率谱函数为白噪声和过滤白噪声时场地土的随机地震反应分析理论。     

运城市2010年4月13日强霜冻过程分析

利用常规天气资料和数值预报产品,应用天气分析和诊断分析方法,对2010年4月13日运城市出现的近40年最严重的强霜冻天气过程进行分析,并与历史个例进行比较,结果表明,此次过程是在前期升温明显的基础上,有强冷空气在西伯利亚及贝加尔湖堆积并向南侵袭造成的;此次过程亚洲中高纬环流表现为“一脊一槽”型,动力机制为横槽转竖促使冷空气向南爆发;冷空气爆发后,本地上空由强盛的冷平流控制,地面冷高压进入关键区并达到寒潮强度。由于每次强降温发生的环流背景、影响系统及冷空气的强度、发展、移动路径不同,所以造成的降温幅度和影响也不同。在此基础上,总结出强霜冻预报的着眼点。