Enhanced oil recovery (EOR) methods assisted by gravity drainage mechanism and application of sophisticated horizontal wells bring new hope for heavy oil extraction. Variety of thermal and ...non-thermal EOR techniques inject an external source of energy and materials such as steam, solvent vapor, or gas through a horizontal well at the top of the reservoir to reduce in-situ heavy oil viscosity. So, the diluted oil becomes mobile and flows downwards by gravity drainage to a horizontal producer located at the bottom of the reservoir.
In this paper, a sector model of an Iranian fractured carbonate heavy oil reservoir was provided to simulate and evaluate capability of some EOR techniques such as Vapor Extraction (VAPEX), Steam Assisted Gravity Drainage (SAGD), Combustion Assisted Gravity Drainage (CAGD), and Toe to Heel Air Injection (THAI) at its reservoir conditions and fluid properties. The simulation results demonstrated that wet CAGD in comparison with other nominated methods could improve heavy oil recovery factor to around 19% much more than each of SAGD, THAI, and VAPEX techniques. It could also reduce the total energy to produced oil ratio index up to 82% with respect to SAGD process in a year.
Although lower oil recovery has been gained by VAPEX process, but using a proper vaporized solvent could produce a kind of de-asphalted and upgraded oil with increased API gravity up to 29°API with no considerable solvent loss.
•The open question given by Sederberg’s research team is answered.•The linear independence of the blending functions of T-splines without multiple knots is proved.•A necessary condition for the ...linear dependence of a T-spline’s blending functions is also deduced.
The purpose of the present paper is to answer the following open question given by Sederberg’s research team: are there T-splines with linearly dependent blending functions that do not have multiple knots? First, the mathematical properties of the blending functions of T-splines without multiple knots are analyzed. Then, the linear independence of them is proved, and meanwhile a necessary condition is deduced for the linear dependence of T-spline blending functions. Finally, the answer to the open question is obtained: there are no T-splines with linearly dependent blending functions that do not have multiple knots.
•Aiming at the problem that how to classify T-splines this paper gives a mathematical analysis, and a sufficient condition of standard T-splines is also given.•Then this paper presents an algorithm ...of determining the T-spline classification, and we can get the inherently mathematical properties of T-splines by the algorithm.
T-splines are a new surface modeling technology, whose theoretical framework is not still well founded. Aiming at the problem that how to classify T-splines this paper gives a mathematical analysis, and a sufficient condition of standard T-splines is also given. Then this paper presents an algorithm of determining the T-spline classification, and we can get the inherently mathematical properties of T-splines by the algorithm. At last, the experimental results verify the effectiveness of our algorithm. The results in this paper play an important role in the research on T-spline theory and T-spline modeling algorithms.
Pathogenic strains of Helicobacter pylori use a type IV secretion system (T4SS) to deliver the toxin CagA into human host cells. The T4SS, along with the toxin itself, is coded into a genomic insert, ...which is termed the cag pathogenicity island. The cag pathogenicity island contains about 30 open-reading frames, for most of which the exact function is not well characterized or totally unknown. We have determined the crystal structure of one of the proteins coded by the cag genes, CagD, in two crystal forms. We show that the protein is a covalent dimer in which each monomer folds as a single domain that is composed of five β-strands and three α-helices. Our data show that in addition to a cytosolic pool, CagD partially associates with the inner membrane, where it may be exposed to the periplasmic space. Furthermore, CagA tyrosine phosphorylation and interleukin-8 assays identified CagD as a crucial component of the T4SS that is involved in CagA translocation into host epithelial cells; however, it does not seem absolutely necessary for pilus assembly. We have also identified significant amounts of CagD in culture supernatants, which are not a result of general bacterial lysis. Since this localization was independent of the various tested cag mutants, our findings may indicate that CagD is released into the supernatant during host cell infection and then binds to the host cell surface or is incorporated in the pilus structure. Overall, our results suggest that CagD may serve as a unique multifunctional component of the T4SS that may be involved in CagA secretion at the inner membrane and may localize outside the bacteria to promote additional effects on the host cell.
En modelación geométrica o en aplicaciones de diseño gráfico, la manipulación interactiva de propiedades geométricas, tales como la posición, la tangencia o la curvatura es crucial. Citando a 12, los ...métodos convencionales no proveen un control directo de estas propiedades en un punto arbitrario sobre la curva. Los usuarios pueden tener algún control sobre unos pocos puntos y este control depende fuertemente de la representación de la curva. Por ejemplo, las curvas de Bezier ofrecen un control directo sobre la posición y los vectores tangentes en los extremos de cada sección de la curva, pero no sobre sus puntos interiores. Los usuarios controlan las propiedades sobre los puntos interiores indirectamente, bien manipulando los vértices del polígono de control o complicando la curva haciendo subdivisiones. En este trabajo se introducen dos métodos que aportan un control más directo e intuitivo de una curva A-spline cúbica. El primero de ellos permite la asignación de una dirección tangente a un punto interior prescrito en tanto, el segundo asigna una recta prescrita como la recta tangente a algún punto interior. Estas son tareas básicas en la manipulación de una curva basada en restricciones y se demuestra que las mismas pueden ser resueltas eficientemente usando curvas A-spline cúbicas. In geometric modeling or graphic design applications the interactive manipulation of geometric properties, such as position, tangency and curvature is crucial. Qupting 12, the conventional methods do not provide direct control at arbitrary points on the curve. Users may have some control at a few specific points and this control strongly depends on the representation of the curve. For instance, Bezier curves offer direct representational control of position and tangency at the endpoints of its sections, but not at its interior points. Users control properties on the interior of the curves indirectly by manipulating the control vertices or by complicating the curves through subdivisions. In this work, we introduce methods to provide a more direct and intuitive control of a cubic A-spline curve: the first method permits to assign a tangent direction to a prescribed interior point, while the second assigns a prescribed line as the tangent line at some interior point. These are basic tasks in the constraint-based curve manipulation and in the present work we demonstrate that they may be efficiently solved using cubic A-spline curves. KEY WORDS: A-spline curve, constrain based curve manipulation, free design, geometric modeling, graphic design, CAGD. MSC: 65D07, 41A29, 65D17, 68U07
A complex geometric shape is often a composition of a set of simple ones, which may differ from each other in terms of their mathematical representations and the ways in which they are constructed. ...One of the necessary requirements in combining these simple shapes is that their original shapes can be preserved as much as possible. In this paper, a set of partial shape-preserving (PSP) spline basis functions is introduced to smoothly combine a collection of shape primitives with flexible blending range control. These spline basis functions can be considered as a kind of generalization of traditional
B
-spline basis functions, where the shape primitives used are control points or control polygons. The PSP-spline basis functions have all the advantages of the conventional
B
-spline technique in the sense that they are nonnegative, piecewise polynomial and of property of partition of unity. However, PSP-spline is a more powerful freeform geometric shape design technique in the sense that it is also a kind of shape-preserving spline. In addition, the PSP-spline technique implicitly integrates the weights of shape control primitives into its basis functions, which allows users to design a required geometric shape based on weighted control primitives. Though its basis functions are simply piecewise polynomial functions, it has the same shape design strengths as the rational piecewise polynomial based spline techniques such as NURBS. In particular, when control shape primitives are specified as a set of control points, PSP-spline behaves like a polygon smoother, with which a shape can be designed to approximate the specified control polygon or control mesh smoothly with any required precision. Consequently, a richer set of geometric shapes can be built using a relatively smaller set of control points.
► A kind of partial shape-preserving (PSP) spline technique is developed. ► PSP-spline is only piecewise polynomial but it is more powerful than NURBS. ► The 2D PSP-spline basis functions can be constructed from any given polygonal net. ► Numerous experiments are presented to demonstrate the versatility of PSP-splines.
Recently, a new extension of the standard neural networks, the so-called
functional networks, has been described E. Castillo, Functional networks, Neural Process. Lett. 7 (1998) 151–159. This ...approach has been successfully applied to the reconstruction of a surface from a given set of 3D data points assumed to lie on unknown Bézier A. Iglesias, A. Gálvez, Applying functional networks to CAGD: the tensor-product surface problem, in: D. Plemenos (Ed.), Proceedings of the International Conference on Computer Graphics and Artificial Intelligence, 3IA’2000, 2000, pp. 105–115; A. Iglesias, A. Gálvez, A new artificial intelligence paradigm for computer-aided geometric design, in: Artificial Intelligence and Symbolic Computation, J.A. Campbell, E. Roanes-Lozano (Eds.), Lectures Notes in Artificial Intelligence, Berlin, Heidelberg, Springer-Verlag, vol. 1930, 2001, pp. 200–213 and B-spline tensor-product surfaces A. Iglesias, A. Gálvez, Applying functional networks to fit data points from B-spline surfaces, in: H.H.S. Ip, N. Magnenat-Thalmann, R.W.H. Lau, T.S. Chua (Eds.), Proceedings of the Computer Graphics International, CGI’2001, IEEE Computer Society Press, Los Alamitos, CA, 2001, pp. 329–332. In both cases the sets of data were fitted using Bézier surfaces. However, in general, the Bézier scheme is no longer used for practical applications. In this paper, the use of B-spline surfaces (by far the most common family of surfaces in surface modeling and industry) for the surface reconstruction problem is proposed instead. The performance of this method is discussed by means of several illustrative examples. A careful analysis of the errors makes it possible to determine the number of B-spline surface fitting control points that best fit the data points. This analysis also includes the use of two sets of data (the training and the testing data) to check for overfitting, which does not occur here.
Combustion Assisted Gravity Drainage (CAGD) is a new EOR process that uses dual horizontal wells for the injection of air and the production of heavy oil. One of the important features of CAGD is the ...properly oriented dual horizontal wells, similar to SAGD, which assists in the development of combustion chamber and stable growth of the combustion front in the reservoir.
This research evaluates the potential of CAGD as an attractive alternative to conventional in-situ combustion (ISC). A 3D laboratory model was designed and constructed to study the CAGD process. The combustion cell was fitted with 48 thermocouples. A horizontal producer was placed near the base of the model with a horizontal injector in the upper part. The CAGD process combines the advantages of both gravity drainage and the conventional ISC. Experimental results showed the combustion chamber developed in the wide area of the porous media around the horizontal injector. This combustion chamber consisted of flue gases, injected air and hot oil. The gravity drainage is the main mechanism for oil production and extracting the flue gases from reservoir. Recorded temperatures reached up to 650°C at the combustion front, with oil recovery more than 82% OOIP. Experimental data showed that improper well distance could cause severe plugging in production well perforations and terminate the process prematurely.
► New air injection technology proposed and related experiments have been conducted. ► Effect of vertical inter-well spacing on CAGD and coke formation was investigated. ► Stable combustion is due to coke seal formation between injector and producer. ► Gravity drainage ensures stable sweep which results in recovery up to 82%. ► Significant thermal upgrading is observed during the experiment.
► We develop a geometrically accurate model of cotton leaves and crop canopies. ► Leaf structure includes three-dimensional folding and orientation with age and cultivar. ► Dynamic changes in leaf ...shape and canopy position are based on in situ measurements. ► Simulated leaves populate a canopy element of 1
m
×
1
m for different heights. ► Canopy elements are designed on statistical distributions of measured crop canopies.
The research presented here develops a geometrically accurate model of cotton crop canopies that can be used to explore changes in canopy microenvironment and physiological function with leaf structure. We develop an accurate representation of the leaves, including changes in three-dimensional folding and orientation with age and cultivar. Photogrammetrical analysis of leaf surfaces is used to generate measured points at known positions. Interpolation of points located on the surface of the cotton leaves is then performed with a tensor product interpolants model that generates a generic leaf shape. Dynamic changes in leaf shape and canopy position over the growing season are based on measurements of cotton canopies in the field, and are used to modulate the generic leaf shape. The simulated leaves populate a canopy element based on statistical distributions from measured crop canopies. The simulation is found to give a good representation of cotton canopy leaves, adequately capturing the three-dimensional structure of the leaves and changes in leaf shape and size over the growing season. The simulated canopy accurately estimates leaf area index, except for the earliest measurement period prior to canopy closure. The application of the CAGD algorithm for representing cotton leaf and canopy geometry, and the technique for changing the leaves’ spatial position, size and shape through time of four representative cotton canopies is found to be a useful tool for developing a realistic crop canopy. We use leaf area index (LAI) as a measure of the accuracy of model-predicted LAI values in comparison to LAI in crop canopies in situ, obtaining
r
2 values ranging from 0.82 to 0.92. The level of detail captured in the model could contribute greatly to future studies of physiological function and biophysical dynamics within a crop canopy.
In this paper, we presented a constrained multi-degree reduction algorithm of DP curves based on the transformation between the DP and Bézier curves. We first correct the conversion formula between ...Bernstein basis and DP basis. And then, we deal with multi-degree reduction of NP curves by degree reduction of Bézier curve.
