in this study a sample of bentonite obtained from semnan mines, was modified by a surfactant to prepare an organoclay with high surface area. bet analysis showed that the modification increased its surface significantly. the prepared sorbent was used for removal of dyes and other organic pollutants from a waste water obtained from ekbatan textile company. adsorption was studied in various times...

We present a system for Computer Aided Diagnosis in Virtual Colonography based on simple geometric model fitting. Our approach extends surface normal analysis and sphere fitting methods. We label locations in the volume data, which have a high probability of being colonic polyps, and present them in a user-friendly way. The method was tested on a study group of 30 patients. Using normal colonos...

This paper describes a technology for manipulating the shape of an implicitly modeled surface so that it follows a geometric flow. The proposed technology is a generalization of the method of level sets, which specifies how to manipulate the isosurfaces of greyscale functions, sampled on discrete grids. The proposed formulation projects the geometric motion of the level sets of a greyscale func...

When dealing with triangle meshes, it is often important to compute curvature information for the purposes of feature recognition, segmentation, or shape analysis. Since a triangle mesh is a piecewise linear surface, curvature has to be estimated. Several different schemes have been proposed, both discrete and continuous, i.e. based on fitting surfaces locally. This paper compares commonly used...

We consider the problem of multi-scale estimation of principal curvatures and crease lines on a surface represented with a mesh of triangles and affected by noise. We show that curvature at different scales can be efficiently and accurately estimated by modifying a fitting technique and applying it to neighborhoods of various size, depending on scale: we discard bending portions of surfaces dur...

A gradient recovery technique is proposed and analyzed for finite element solutions which provides new gradient approximations with high order of accuracy. The recovery technique is based on the method of least-squares surface fitting in a finite-dimensional space corresponding to a coarse mesh. It is proved that the recovered gradient has a high order of superconvergence for appropriately chos...

A hierarchical family of analytical Born–Oppenheimer potential energy surfaces has been developed for the H1H2 system. Ab initio calculations of near full configuration interaction ~FCI! quality ~converged to within '1 mEh! were performed for a set of 4067 configurations with the aug-cc-pVDZ, aug-cc-pVTZ, and aug-cc-pVQZ basis sets. The complete basis set ~CBS! limit energies were obtained usin...

This paper presents a physics-based approach to anatomical surface segmentation, reconstruction, and tracking in multidimensional medical images. The approach makes use of a dynamic "balloon" model--a spherical thin-plate under tension surface spline which deforms elastically to fit the image data. The fitting process is mediated by internal forces stemming from the elastic properties of the sp...

Curve and surface fitting is a relevant subject in computer vision and coordinate metrology. In this paper, we present a new fitting algorithm for implicit surfaces and plane curves which minimizes the square sum of the orthogonal error distances between the model feature and the given data points. By the new algorithm, the model feature parameters are grouped and simultaneously estimated in te...

In this paper, we propose a novel 3D free form surface matching method based on a novel key-point detector and a novel feature descriptor. The proposed detector is based on algebraic surface fitting. By global smooth fitting, our detector achieved high computational efficiency and robustness against non-rigid deformations. For the feature descriptor, we provide algorithms to compute 3D critical...