Metric Structures for Riemannian and Non-Riemannian Spaces
Length Structures: Path Metric Spaces.- Degree and Dilatation.- Metric Structures on Families of Metric Spaces.- Convergence and Concentration of Metrics and Measures.- Loewner Rediscovered.- Manifolds with Bounded Ricci Curvature.- Isoperimetric Inequalities and Amenability.- Morse Theory and Minimal Models.- Pinching and Collapse.
Lattice-Gas Cellular Automata and Lattice Boltzmann Models: An Introduction
Lattice-gas cellular automata (LGCA) and lattice Boltzmann models (LBM) are relatively new andpromising methods for the numerical solution of nonlinear partial differential equations. The bookprovides an introduction for graduate students and researchers. Working knowledge of calculus isrequired and experience in PDEs and fluid dynamics is recommended. Some peculiarities of cellularautomata are outlined in Chapter 2. The properties of various LGCA and special coding techniquesare discussed in Chapter 3. Concepts from statistical mechanics (Chapter 4) provide the necessarytheoretical background for LGCA and LBM. The properties of lattice Boltzmann models and amethod for their construction are presented in Chapter 5.
Physical Adsorption on Non‐Uniform Surfaces
Analysis of adsorption on a uniform surface using the quasi‐chemical theory of interaction shows that the hypotheses of the BET theory lead to substantially no adsorption beyond the first layer if E2 = EL, and stepwise isotherms if E1>E2>E3>···>EL. For the monolayer adsorption of gases on silver, platinum, and steel, the heterogeneous nature of the adsorbing surface is clearly indicated. Cooperative adsorption on the non‐uniform surface is treated, and the cooperative analog of the Freundlich equation derived. The typical multi‐layer isotherm is shown to be composed of three regions: non‐cooperative adsorption on a strongly heterogeneous surface; cooperative adsorption on a still heterogeneous surface; and cooperative multi‐layer adsorption induced by small van der Waals perturbations some distance from the surface.The isotherm p/p0=exp{—a/θr} is derived and shown to be a good representation of adsorption data that conform to the BET Type I, II, or III shapes.
Lattice Boltzmann Modeling: An Introduction for Geoscientists and Engineers
Lattice Boltzmann models have a remarkable ability to simulate single- and multi-phase fluids and transport processes within them. A rich variety of behaviors, including higher Reynolds numbers flows, phase separation, evaporation, condensation, cavitation, buoyancy, and interactions with surfaces can readily be simulated. This book provides a basic introduction that emphasizes intuition and simplistic conceptualization of processes. It avoids the more difficult mathematics that underlies LB models. The model is viewed from a particle perspective where collisions, streaming, and particle-particle/particle-surface interactions constitute the entire conceptual framework. Beginners and those with more interest in model application than detailed mathematical foundations will find this a powerful "quick start" guide. Example simulations, exercises, and computer codes are included. Working code is provided on the Internet.
VFH+: reliable obstacle avoidance for fast mobile robots
This paper presents further improvements on the earlier vector field histogram (VFH) method developed by Borenstein-Koren (1991) for real-time mobile robot obstacle avoidance. The enhanced method, called VFH+, offers several improvements that result in smoother robot trajectories and greater reliability. VFH+ reduces some of the parameter tuning of the original VFH method by explicitly compensating for the robot width. Also added in VFH+ is a better approximation of the mobile robot trajectory, which results in higher reliability.
Real-time rendering
From the Publisher: The second edition of "Real-Time Rendering" comes three years after the release of the first. In that time computer graphics hardware has evolved at a rapid rate: it is more than ten times faster (outstripping Moore's Law) and the functionality has increased significantly in a wide range of areas. Reflecting these changes, this second edition is almost 900 pages long, 75% larger than the 512 pages of the first edition. All chapters have been updated, and new chapters added on spline and subdivision surfaces, advanced shading theory and techniques, and non-photorealistic and image-based rendering. As with the first edition, this new book is a blend of solid theory and practical advice, useful for students, professionals, and hobbyists alike.
Adsorption of Gases on Heterogeneous Surfaces
Basic principles the empirical adsorption isotherms calorimetric effects in adsorption the interpretation of empirical isotherms in terms of surface heterogeneity ideal monolayer adsorption on heterogeneous surfaces on the nature of the heterogeneity of real solid surfaces low pressure adsorption and the virial description mobile monolayer adsorption with lateral interactions localized monolayer adsorption with interactions between adsorbed molecules multilayer adsorption on heterogeneous surfaces numerical methods of evaluating the adsorption energy distribution multisite occupancy adsorption on heterogeneous solid surfaces computer simulation of adsorption on heterogeneous solid surfaces.
Equations of state in a lattice Boltzmann model
In this paper we consider the incorporation of various equations of state into the single-component multiphase lattice Boltzmann model. Several cubic equations of state, including the van der Waals, Redlich-Kwong, and Peng-Robinson, as well as a noncubic equation of state (Carnahan-Starling), are incorporated into the lattice Boltzmann model. The details of phase separation in these nonideal single-component systems are presented by comparing the numerical simulation results in terms of density ratios, spurious currents, and temperature ranges. A comparison with a real fluid system, i.e., the properties of saturated water and steam, is also presented.
Grid Refinement for Lattice-BGK Models
Lattice?Boltzmann models, proposed at the end of the 1980s as the noise-free version of lattice?gas models, are based on gas-kinetic representation of fluid flow. Their recent modifications, the lattice BGK models, provide especially simple, effective and stable algorithms for the solution of hydrodynamical problems. A local second-order grid refinement scheme for the lattice?BGK model is proposed in this work. The refinement scheme and a boundary-fitting scheme for complicated geometries are applied to simulate a benchmark problem of flow past a cylinder in a channel with small and moderate Reynolds numbers.
Lattice Boltzmann model for simulation of magnetohydrodynamics.
A numerical method, based on a discrete Boltzmann equation, is presented for solving the equations of magnetohydrodynamics (MHD). The algorithm provides advantages similar to the cellular automaton method in that it is local and easily adapted to parallel computing environments. Because of much lower noise levels and less stringent requirements on lattice size, the method appears to be more competitive with traditional solution methods. Examples show that the model accurately reproduces both linear and nonlinear MHD phenomena.
Multicomponent lattice-Boltzmann model with interparticle interaction
A lattice Boltzmann model for simulating fluids with multiple components and interparticle forces proposed by Shan and Chen is described in detail. Macroscopic equations governing the motion of each component are derived by using the Chapman-Enskog method. The mutual diffusivity in a binary mixture is calculated analytically and confirment by numerical simulation. The diffusivity is generally a function of the concentrations of the two components but independent of the fluid velocity, so that the diffusion is Galilean invariant. The analytically calculated shear kinematic viscosity of this model is also confiremoed numerically.
Real-time volume graphics
The tremendous evolution of programmable graphics hardware has made high-quality real-time volume graphics a reality. In addition to the traditional application of rendering volume data in scientific visualization, the interest in applying these techniques for real-time rendering of atmospheric phenomena and participating media such as fire, smoke, and clouds is growing rapidly. This course covers both applications in scientific visualization, e.g., medical volume data, and real-time rendering, such as advanced effects and illumination in computer games, in detail. Course participants will learn techniques for harnessing the power of consumer graphics hardware and high-level shading languages for real-time rendering of volumetric data and effects. Beginning with basic texture-based approaches including hardware ray casting, the algorithms are improved and expanded incrementally, covering local and global illumination, scattering, pre-integration, implicit surfaces and non-polygonal isosurfaces, transfer function design, volume animation and deformation, dealing with large volumes, high-quality volume clipping, rendering segmented volumes, higher-order filtering, and non-photorealistic volume rendering. Course participants are provided with documented source code covering details usually omitted in publications.
Theory of the lattice Boltzmann method: acoustic and thermal properties in two and three dimensions.
The focus of the present work is to provide an analysis for the acoustic and thermal properties of the energy-conserving lattice Boltzmann models, and a solution to the numerical defects and instability associated with these models in two and three dimensions. We discover that a spurious algebraic coupling between the shear and energy modes of the linearized evolution operator is a defect universal to the energy-conserving Boltzmann models in two and three dimensions. This spurious mode coupling is highly anisotropic and may occur at small values of wave number k along certain directions, and it is a direct consequence of the following key features of the lattice Boltzmann equation: (1) its simple spatial-temporal dynamics, (2) the linearity of the relaxation modeling for collision operator, and (3) the energy-conservation constraint. To eliminate the spurious mode coupling, we propose a hybrid thermal lattice Boltzmann equation (HTLBE) in which the mass and momentum conservation equations are solved by using the multiple-relaxation-time model due to d'Humières, whereas the diffusion-advection equation for the temperature is solved separately by using finite-difference technique (or other means). Through the Chapman-Enskog analysis we show that the hydrodynamic equations derived from the proposed HTLBE model include the equivalent effect of gamma=C(P)/C(V) in both the speed and attenuation of sound. Appropriate coupling between the energy and velocity field is introduced to attain correct acoustics in the model. The numerical stability of the HTLBE scheme is analyzed by solving the dispersion equation of the linearized collision operator. We find that the numerical stability of the lattice Boltzmann scheme improves drastically once the spurious mode coupling is removed. It is shown that the HTLBE scheme is far superior to the existing thermal LBE schemes in terms of numerical stability, flexibility, and possible generalization for complex fluids. We also present the simulation results of the convective flow in a rectangular cavity with different temperatures on two opposite vertical walls and under the influence of gravity. Our numerical results agree well with the pseudospectral result.
A survey on smart metering and smart grid communication
The smart metering and communication methods used in smart grid are being extensively studied owing to widespread applications of smart grid. Although the monitoring and control processes are widely used in industrial systems, the energy management requirements at both service supplier and consumer side for individuals promoted the evolution of smart grid. In this paper, it is aimed to disclose in a clear and clean way that what smart grid is and what kind of communication methods are used. All components of a smart grid are introduced in a logical way to facilitate the understanding, and communication methods are presented regarding to their improvements, advantages, and lacking feature. The developing generation, transmission, distribution and customer appliances are surveyed in terms of smart grid integration. The communication technologies are introduced as wireline and wireless classification where the key features are also tabulated. The security requirements of hardware and software in a smart grid are presented according to their cyber and physical structures.
Lattice Boltzmann Method for 3-D Flows with Curved Boundary
In this work, we investigate two issues that are important to computational efficiency and reliability in fluid dynamic applications of the lattice Boltzmann equation (LBE): (1) Computational stability and accuracy of different lattice Boltzmann models and (2) the treatment of the boundary conditions on curved solid boundaries and their 3-D implementations. Three athermal 3-D LBE models (Q15D3, Q19D3, and Q27D3) are studied and compared in terms of efficiency, accuracy, and robustness. The boundary treatment recently developed by Filippova and Hanel (1998, J. Comp. Phys.147, 219) and Mei et al. (1999, J. Comp. Phys.155, 307) in 2-D is extended to and implemented for 3-D. The convergence, stability, and computational efficiency of the 3-D LBE models with the boundary treatment for curved boundaries were tested in simulations of four 3-D flows: (1) Fully developed flows in a square duct, (2) flow in a 3-D lid-driven cavity, (3) fully developed flows in a circular pipe, and (4) a uniform flow over a sphere. We found that while the 15-velocity 3-D (Q15D3) model is more prone to numerical instability and the Q27D3 is more computationally intensive, the Q19D3 model provides a balance between computational reliability and efficiency. Through numerical simulations, we demonstrated that the boundary treatment for 3-D arbitrary curved geometry has second-order accuracy and possesses satisfactory stability characteristics.
A lattice Boltzmann model for multiphase flows with large density ratio
a lattice Boltzmann model for simulating multiphase flows with large density ratios is described in this paper. The method is easily implemented. It does not require solving the Poisson equation and does not involve the complex treatments of derivative terms. The interface capturing equation is recovered without any additional terms as compared to other methods [M.R. Swift, W.R. Osborn, J.M. Yeomans, Lattice Boltzmann simulation of liquid-gas and binary fluid systems, Phys. Rev. E 54 (1996) 5041-5052; T. Inamuro, T. Ogata, S. Tajima, N. Konishi, A lattice Boltzmann method for incompressible two-phase flows with large density differences, J. Comput. Phys. 198 (2004) 628-644; T. Lee, C.-L. Lin, A stable discretization of the lattice Boltzmann equation for simulation of incompressible two-phase flows at high density ratio, J. Comput. Phys. 206 (2005) 16-47]. Besides, it requires less discrete velocities. As a result, its efficiency could be greatly improved, especially in 3D applications. It is validated by several cases: a bubble in a stationary flow and the capillary wave. The numerical surface tension obtained from the Laplace law and the interface profile agrees very well with the respective analytical solution. The method is further verified by its application to capillary wave and the bubble rising under buoyancy with comparison to other methods. All the numerical experiments show that the present approach can be used to model multiphase flows with large density ratios.
Accuracy of Magnetic Resonance Imaging for Local Staging of Prostate Cancer: A Diagnostic Meta-analysis.
CONTEXT Correct assessment of tumour stage is crucial for prostate cancer (PCa) management. OBJECTIVE To assess the diagnostic accuracy of magnetic resonance imaging (MRI) for local PCa staging and explore the influence of different imaging protocols. EVIDENCE ACQUISITION We searched the PubMed, Embase, and Cochrane databases from 2000 up to August 2014. We included studies that used MRI for detection of extracapsular extension (ECE; T3a), seminal vesicle invasion (SVI; T3b), or overall stage T3 PCa, with prostatectomy as the reference standard. Methodologic quality was assessed using the Quality Assessment of Diagnostic Accuracy Studies tool by two independent reviewers. Data necessary to complete 2×2 tables were obtained, and patient, study, and imaging characteristics were extracted. Accuracy was reported for the most experienced or first reader. Results were pooled and plotted in summary receiver operating characteristics plots. EVIDENCE SYNTHESIS A total of 75 studies (9796 patients) could be analysed. Pooled data for ECE (45 studies, 5681 patients), SVI (34 studies, 5677 patients), and overall stage T3 detection (38 studies, 4001 patients) showed sensitivity and specificity of 0.57 (95% confidence interval [CI] 0.49-0.64) and 0.91 (95% CI 0.88-0.93), 0.58 (95% CI 0.47-0.68) and 0.96 (95% CI 0.95-0.97), and 0.61 (95% CI 0.54-0.67) and 0.88 (95% CI 0.85-0.91), respectively. Functional imaging in addition to T2-weighted imaging and use of higher field strengths (3 T) improved sensitivity for ECE and SVI. ECE sensitivity was not improved by endorectal coil use. CONCLUSIONS MRI has high specificity but poor and heterogeneous sensitivity for local PCa staging. An endorectal coil showed no additional benefit for ECE detection, but slightly improved sensitivity for SVI detection. Higher field strengths and the use of functional imaging techniques can slightly improve sensitivity. PATIENT SUMMARY We pooled the results from all previous studies that evaluated magnetic resonance imaging (MRI) for detection of tumour growth outside the prostate. MRI is not sensitive enough to find all tumours with extraprostatic growth.
Dynamic Contribution of DFIG-Based Wind Plants to System Frequency Disturbances
The paper investigates contribution of doubly fed induction generator (DFIG) to system frequency responses. Impact of different governor settings and system inertia are investigated. Three distinct cases are simulated in order to illustrate the influence of DFIG penetration on frequency regulation. Provision of inertial response by DFIG through artificial speed coupling is also presented. The effects of the inertial response on the machine behavior and its significance for frequency regulation are discussed. The influence of converter current limits and auxiliary loop parameters on the inertial response are illustrated and a novel control algorithm is developed for extracting maximum energy from the turbine in a stable manner. The results of the study are illustrated on the example of an isolated power system consisting of a diesel generator and a DFIG.
Lattice Boltzmann Method for 3-D Flows with Curved Boundary
In this work, we investigate two issues that are important to computational efficiency and reliability in fluid dynamic applications of the lattice Boltzmann equation (LBE): (1) Computational stability and accuracy of different lattice Boltzmann models and (2) the treatment of the boundary conditions on curved solid boundaries and their 3-D implementations. Three athermal 3-D LBE models (Q15D3, Q19D3, and Q27D3) are studied and compared in terms of efficiency, accuracy, and robustness. The boundary treatment recently developed by Filippova and Hanel (1998, J. Comp. Phys.147, 219) and Mei et al. (1999, J. Comp. Phys.155, 307) in 2-D is extended to and implemented for 3-D. The convergence, stability, and computational efficiency of the 3-D LBE models with the boundary treatment for curved boundaries were tested in simulations of four 3-D flows: (1) Fully developed flows in a square duct, (2) flow in a 3-D lid-driven cavity, (3) fully developed flows in a circular pipe, and (4) a uniform flow over a sphere. We found that while the 15-velocity 3-D (Q15D3) model is more prone to numerical instability and the Q27D3 is more computationally intensive, the Q19D3 model provides a balance between computational reliability and efficiency. Through numerical simulations, we demonstrated that the boundary treatment for 3-D arbitrary curved geometry has second-order accuracy and possesses satisfactory stability characteristics.
JAsCo: an aspect-oriented approach tailored for component based software development
In this paper we introduce a novel aspect oriented implementation language, called JAsCo. JAsCo is tailored for component based development and the Java Beans component model in particular. The JAsCo language introduces two concepts: aspect beans and connectors. An aspect bean describes behavior that interferes with the execution of a component by using a special kind of inner class, called a hook. The specification of a hook is context independent and therefore reusable. A connector on the other hand, is used for deploying one or more hooks within a specific context. To implement the JAsCo language, we propose a new "aspect-enabled' component model, which contains build-in traps that enable to interfere with the normal execution of a component. The JAsCo component model is backward-compatible with the Java Beans component model. Furthermore, the JAsCo component model allows very flexible aspect application, adaptation and removal at run-time. The necessary tool support for the JAsCo approach has been implemented. In addition, we present a performance assessment of our current implementation.
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