14642729
Flow simulation with locally-refined LBM
We simulate 3D fluid flow by a locally-refined lattice Boltzmann method (LBM) on graphics hardware. A low resolution LBM simulation running on a coarse grid models global flow behavior of the entire domain with low consumption of computational resources. For regions of interest where small visual details are desired, LBM simulations are performed on fine grids, which are separate grids superposed on the coarse one. The flow properties on boundaries of the fine grids are determined by the global simulation on the coarse grid. Thus, the locally refined fine-grid simulations follow the global fluid behavior, and model the desired small-scale and turbulent flow motion with their denser numerical discretization. A fine grid can be initiated and terminated at any time while the global simulation is running. It can also move inside the domain with a moving object to capture small-scale vortices caused by the object. Besides the performance improvement due to the adaptive simulation, the locally-refined LBM is suitable for acceleration on contemporary graphics hardware (GPU), since it involves only local and linear computations. Therefore, our approach achieves fast and adaptive 3D flow simulation for computer games and other interactive applications.
14038172
Visual Simulation of Heat Shimmering and Mirage
We provide a physically-based framework for simulating the natural phenomena related to heat interaction between objects and the surrounding air. We introduce a heat transfer model between the heat source objects and the ambient flow environment, which includes conduction, convection, and radiation. The heat distribution of the objects is represented by a novel temperature texture. We simulate the thermal flow dynamics that models the air flow interacting with the heat by a hybrid thermal lattice Boltzmann model (HTLBM). The computational approach couples a multiple-relaxation-time LBM (MRTLBM) with a finite difference discretization of a standard advection-diffusion equation for temperature. In heat shimmering and mirage, the changes in the index of refraction of the surrounding air are attributed to temperature variation. A nonlinear ray tracing method is used for rendering. Interactive performance is achieved by accelerating the computation of both the MRTLBM and the heat transfer, as well as the rendering on contemporary graphics hardware (GPU)
2480088
Melting and flowing in multiphase environment
Abstract This paper presents a method to simulate the melting and flowing phenomena with different materials in multiple phases. In such a multiphase environment, solid objects are melted because of heating and the melted liquid flows while interacting with the ambient air flow. Our simulation is based on a modified lattice Boltzmann method (LBM), where the fluid dynamics of the air flow and the melted liquid is modeled within a common lattice framework. Therefore, no particular front tracking methods are required for the liquid–air interface. The liquid–solid and air–solid interfaces are implemented as curved boundaries in the LBM, which can accommodate arbitrarily shaped solid objects. Heat transfer is incorporated with a finite difference discretization of a standard diffusion–advection equation simulating the temperature evolution. The temperature and body forces (gravity and surface tension) are easily applied by adopting a new version of the LBM: multiple-relaxation-time LBM (MRTLBM). The melting and flowing behavior is controlled by the heat source, the viscosity and the body forces. All the numerical computations in our method are local and parallelizable, therefore, interactive speed is achieved by hardware acceleration on the contemporary graphics hardware (GPU).
15795709
Lattice-based flow field modeling
We present an approach for simulating the natural dynamics that emerge from the interaction between a flow field and immersed objects. We model the flow field using the lattice Boltzmann model (LBM) with boundary conditions appropriate for moving objects and accelerate the computation on commodity graphics hardware (GPU) to achieve real-time performance. The boundary conditions mediate the exchange of momentum between the flow field and the moving objects resulting in forces exerted by the flow on the objects as well as the back-coupling on the flow. We demonstrate our approach using soap bubbles and a feather. The soap bubbles illustrate Fresnel reflection, reveal the dynamics of the unseen flow field in which they travel, and display spherical harmonics in their undulations. Our simulation allows the user to directly interact with the flow field to influence the dynamics in real time. The free feather flutters and gyrates in response to lift and drag forces created by its motion relative to the flow. Vortices are created as the free feather falls in an otherwise quiescent flow.
3140808
Voxels on Fire
We introduce a method for the animation of fire propagation and the burning consumption of objects represented as volumetric data sets. Our method uses a volumetric fire propagation model based on an enhanced distance field. It can simulate the spreading of multiple fire fronts over a specified isosurface without actually having to create that isosurface. The distance field is generated from a specific shell volume that rapidly creates narrow spatial bands around the virtual surface of any given isovalue. The complete distance field is then obtained by propagation from the initial bands. At each step multiple fire fronts can evolve simultaneously on the volumetric object. The flames of the fire are constructed from streams of particles whose movement is regulated by a velocity field generated with the hardware-accelerated Lattice Boltzmann Model (LBM). The LBM provides a physically-based simulation of the air flow around the burning object. The object voxels and the splats associated with the flame particles are rendered in the same pipeline so that the volume data with its external and internal structures can be displayed along with the fire.
7249461
Equilibrium probability calculations for a discrete-time bulk queue model
Many problems in management science and telecommunications can be solved by the analysis of aDX/Dm/1 queueing model. In this paper, we use the zeros, both inside and outside the unit circle, of the denominator of the generating function of the model to obtain an explicit closed-form solution for the equilibrium probabilities of the number of customers in the system. The moments of the number of customers in the queue or in the system are also studied. When there are infinitely many zeros outside the unit circle, we propose an approximation method using polynomials. This method yields correct values for a finite number of the probabilities, the number depending on the degree of the polynomial approximation.
29045473
On Reduct Construction Algorithms
This paper critically analyzes reduct construction methods at two levels. At a high level, one can abstract commonalities from the existing algorithms, and classify them into three basic groups based on the underlying control structures. At a low level, by adopting different heuristics or fitness functions for attribute selection, one is able to derive most of the existing algorithms. The analysis brings new insights into the problem of reduct construction, and provides guidelines for the design of new algorithms
10708118
Fault modeling and simulation for crosstalk in system-on-chip interconnects
System-on-chips (SOCs) using ultra deep sub-micron (DSM) technologies and GHz clock frequencies have been predicted by the 1997 SIA Road Map. Recent studies, as well as experiments reported in this paper, show significant crosstalk effects in long on-chip interconnects of GHz DSM chips. Recognizing the importance of high-speed, reliable interconnects in GHz SOCs, we address in this paper the problem of testing for glitch and delay errors caused by crosstalk in buses and interconnects between components of a SOC. Since it is not possible to explicitly test for all the possible process variations and defects that can lead to crosstalk errors in SOC interconnects, we present an abstract model, Maximum Aggressor (MA) fault model, and its test requirements. The attractiveness of the model is that it can abstract crosstalk defects in interconnects with a linear number of faults, while the corresponding MA tests provide complete coverage for all level defects related to cross-coupling capacitance the interconnects. A SPICE-level fault simulation methodology is presented which allows simulation of a small subset of the potentially exponential number of defects. The simulation methodology also enables validation of the proposed fault model and the resulting test set.
5956143
Fast Update Algorithm for IP Forwarding Table Using Independent Sets
This paper describes a new update algorithm for Internet Protocol (IP) forwarding tables. The update algorithm is so general that it can be combined with many IP address lookup algorithms for fast update. This is done by partitioning the IP forwarding table into independent sets. Each independent set can be looked as a set of disjoint ranges, therefore any data structure for disjoint ranges search can be combined with this algorithm to support fast update. This algorithm achieves fast update by avoiding the worst-case update scenario. The number of independent sets is small, hence, the number of parallel data structures is small.
184418
Self-adaptive clock synchronization for computational grid
This paper presents an innovative method to synchronize physical clocks for a computational grid, in particular for a computational grid linked through the asynchronous Intranet or Internet environments. The method discussed is an asynchronous self-adaptive clock synchronization mechanism. Two strategies for clock synchronisationare introduced. (1), Use continuous time intervals to calculate the precision of clocks, which can reduce the effect of network delay efficiently. (2) Every node synchronizes its clock, with its leader actively. In addition, a node self-adaptive model is presented, and the relationship between the clock precision and synchronization time is induced, hence a node can predict when it should begin the synchronization process. Detailed simulation and extension of this issue are provided at the end of the paper. The presented model is both practical and feasible.