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81.
Stephen M. Pizer P. Thomas Fletcher Sarang Joshi Andrew Thall James Z. Chen Yonatan Fridman Daniel S. Fritsch A. Graham Gash John M. Glotzer Michael R. Jiroutek Conglin Lu Keith E. Muller Gregg Tracton Paul Yushkevich Edward L. Chaney 《International Journal of Computer Vision》2003,55(2-3):85-106
M-reps (formerly called DSLs) are a multiscale medial means for modeling and rendering 3D solid geometry. They are particularly well suited to model anatomic objects and in particular to capture prior geometric information effectively in deformable models segmentation approaches. The representation is based on figural models, which define objects at coarse scale by a hierarchy of figures—each figure generally a slab representing a solid region and its boundary simultaneously. This paper focuses on the use of single figure models to segment objects of relatively simple structure.A single figure is a sheet of medial atoms, which is interpolated from the model formed by a net, i.e., a mesh or chain, of medial atoms (hence the name m-reps), each atom modeling a solid region via not only a position and a width but also a local figural frame giving figural directions and an object angle between opposing, corresponding positions on the boundary implied by the m-rep. The special capability of an m-rep is to provide spatial and orientational correspondence between an object in two different states of deformation. This ability is central to effective measurement of both geometric typicality and geometry to image match, the two terms of the objective function optimized in segmentation by deformable models. The other ability of m-reps central to effective segmentation is their ability to support segmentation at multiple levels of scale, with successively finer precision. Objects modeled by single figures are segmented first by a similarity transform augmented by object elongation, then by adjustment of each medial atom, and finally by displacing a dense sampling of the m-rep implied boundary. While these models and approaches also exist in 2D, we focus on 3D objects.The segmentation of the kidney from CT and the hippocampus from MRI serve as the major examples in this paper. The accuracy of segmentation as compared to manual, slice-by-slice segmentation is reported. 相似文献
82.
83.
Gabriel Rosser Ruth E. Baker Judith P. Armitage Alexander G. Fletcher 《Journal of the Royal Society Interface》2014,11(97)
Most free-swimming bacteria move in approximately straight lines, interspersed with random reorientation phases. A key open question concerns varying mechanisms by which reorientation occurs. We combine mathematical modelling with analysis of a large tracking dataset to study the poorly understood reorientation mechanism in the monoflagellate species Rhodobacter sphaeroides. The flagellum on this species rotates counterclockwise to propel the bacterium, periodically ceasing rotation to enable reorientation. When rotation restarts the cell body usually points in a new direction. It has been assumed that the new direction is simply the result of Brownian rotation. We consider three variants of a self-propelled particle model of bacterial motility. The first considers rotational diffusion only, corresponding to a non-chemotactic mutant strain. Two further models incorporate stochastic reorientations, describing ‘run-and-tumble’ motility. We derive expressions for key summary statistics and simulate each model using a stochastic computational algorithm. We also discuss the effect of cell geometry on rotational diffusion. Working with a previously published tracking dataset, we compare predictions of the models with data on individual stopping events in R. sphaeroides. This provides strong evidence that this species undergoes some form of active reorientation rather than simple reorientation by Brownian rotation. 相似文献
84.
正随着IT技术的不断进步,智能手机的更新换代也正在逐渐加快,但替换下来的"旧"手机仍旧有很强的性能,如果就此放置一旁无疑是一种极大的浪费。除了将手机作为二手产品低价出售,还有什么办法能够让手机物尽其用呢?Android手机如今已经成为人们生活、工作必备的设备。相信如果你某天找不到手机,那么你一天的生活节奏一定会被弄的混乱不堪。随着IT技术的不断进步,智能手机的更新换代也正在逐渐加快,但替换下来的"旧"手机仍旧有很强的性能,如果就此放置一旁无疑是一种极大的浪费。 相似文献
85.
Sam Fletcher Mike J. S. Lowe Madis Ratassepp Colin Brett 《Journal of Nondestructive Evaluation》2012,31(1):56-64
The implementation of synthetic guided wave focusing to locate axially aligned defects in pipes has been investigated. Results
from both finite element computer models and experiments on real pipes are presented and the data show good agreement. Focusing
is necessary to improve the reflection coefficient from axially aligned defects, as the signals are very weak. The Common
Source Method (CSM) of synthetic focusing has been applied which makes it possible to apply focusing via post processing to
previously collected data. The dependence of reflection coefficient on crack length was measured for both through thickness
and part depth axially aligned defects, at a range of frequencies, using the torsional guided wave family. The results show
that the reflection coefficient is approximately doubled when focusing is employed, compared to the sensitivity for unfocused
fundamental torsional waves. However the sensitivity is still very low, so in practise this approach could only be used to
find severe defects. 相似文献
86.
Zahid Hussain Shar Mary T. Fletcher Gul Amer Sumbal Syed Tufail Hussain Sherazi Cindy Giles Muhammad Iqbal Bhanger 《Food additives & contaminants. Part A, Chemistry, analysis, control, exposure & risk assessment》2016,33(5):849-860
This work reports the application of banana peel as a novel bioadsorbent for in vitro removal of five mycotoxins (aflatoxins (AFB1, AFB2, AFG1, AFG2) and ochratoxin A). The effect of operational parameters including initial pH, adsorbent dose, contact time and temperature were studied in batch adsorption experiments. Scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FTIR) and point of zero charge (pHpzc) analysis were used to characterise the adsorbent material. Aflatoxins’ adsorption equilibrium was achieved in 15 min, with highest adsorption at alkaline pH (6–8), while ochratoxin has not shown any significant adsorption due to surface charge repulsion. The experimental equilibrium data were tested by Langmuir, Freundlich and Hill isotherms. The Langmuir isotherm was found to be the best fitted model for aflatoxins, and the maximum monolayer coverage (Q0) was determined to be 8.4, 9.5, 0.4 and 1.1 ng mg?1 for AFB1, AFB2, AFG1 and AFG2 respectively. Thermodynamic parameters including changes in free energy (ΔG), enthalpy (ΔH) and entropy (ΔS) were determined for the four aflatoxins. Free energy change and enthalpy change demonstrated that the adsorption process was exothermic and spontaneous. Adsorption and desorption study at different pH further demonstrated that the sorption of toxins was strong enough to sustain pH changes that would be experienced in the gastrointestinal tract. This study suggests that biosorption of aflatoxins by dried banana peel may be an effective low-cost decontamination method for incorporation in animal feed diets. 相似文献
87.
P. Thomas Fletcher 《International Journal of Computer Vision》2013,105(2):171-185
This paper develops the theory of geodesic regression and least-squares estimation on Riemannian manifolds. Geodesic regression is a method for finding the relationship between a real-valued independent variable and a manifold-valued dependent random variable, where this relationship is modeled as a geodesic curve on the manifold. Least-squares estimation is formulated intrinsically as a minimization of the sum-of-squared geodesic distances of the data to the estimated model. Geodesic regression is a direct generalization of linear regression to the manifold setting, and it provides a simple parameterization of the estimated relationship as an initial point and velocity, analogous to the intercept and slope. A nonparametric permutation test for determining the significance of the trend is also given. For the case of symmetric spaces, two main theoretical results are established. First, conditions for existence and uniqueness of the least-squares problem are provided. Second, a maximum likelihood criteria is developed for a suitable definition of Gaussian errors on the manifold. While the method can be generally applied to data on any manifold, specific examples are given for a set of synthetically generated rotation data and an application to analyzing shape changes in the corpus callosum due to age. 相似文献
88.
ANTHONY DOMANICO 《微电脑世界》2014,(9):36-37
今年秋天,当iOS 8最终到来的时候,苹果iPhone和iPad的用户们将有大把的新功能等待学习。作为最新的手机操作系统,苹果公司承诺提供一系列的新功能及对现有功能的增强,以及更好的通讯,更好的分享。这里列出苹果公司最近不断鼓吹的12项:1.通知iOs 8中的全新“交互式”通知,让你无需离开现有的应用,即可处理各种通知或警告信息。获取日历邀请,将无需你中断手头正在写的电子邮件,也无需你退出手头正在玩的游戏。你还可以通过移动设备的锁屏界面直接处理通知, 相似文献
89.
This paper illustrates how hidden details in garment design may reveal important clues about the motives of the wearer or designer that are of considerable cultural relevance. We suggest these hidden design features may reflect key psychological factors previously not considered. We illustrate this by doing a multilevel analysis of two important sixteenth century examples of Ottoman court clothing from the Topkapi Palace Museum. We show that these garments contain early examples of the use of “enclothed cognition” where the designs themselves are likely to have influenced the mind of the wearer. We suggest that the historical-social analysis of clothing may benefit from considering the concealed, as well as the explicit, psychologically relevant design features. We suggest that psychosocial interpretations of clothing may help further our understanding of textile and apparel design more generally, even within an historical context. 相似文献
90.
He Yang Thomas H. Fletcher Yang Li Lijun Jin Sufen Li Yan Shang Haoquan Hu 《American Institute of Chemical Engineers》2020,66(2):e16834
The influence of changes in aliphatic structure on char surface area during coal pyrolysis was modeled, and the effect was introduced to a previous char surface area model for lignite pyrolysis established based on the chemical percolation devolatilization (CPD) model. The modified model can predict not only the N2 and CO2 char surface area during rapid pyrolysis of three lignites but also the CO2 char surface area of two high-volatile bituminous coals; the agreement of the modified model with experiments is improved at high temperatures. The decrease in aliphatic chain length can reduce adsorption positions around aromatic core, and decrease char surface area. When mass release is more than 55% at about 1,100 K, the predicted N2 char surface area starts to decrease with further generation of volatiles, and the increase of predicted CO2 char surface area with increasing generation of volatiles also become slow at the end of mass release. 相似文献