575 research outputs found
Direct numerical simulation of turbulent Couette-Poiseuille flow with zero skin friction
No full textThe near-wall scaling of mean velocity U(y) is addressed for the case of zero skin friction on one wall of a fully turbulent channel flow. The present DNS results can be added to the evidence in support of the conjecture that U is proportional to √yw in the region just above the wall at which the mean shear dU/dy = 0
Combination Of Cfd And Csd Packages For Fluid-Structure Interaction
No full textIn this article the UDF script file in the Fluent software was rewritten as the "connecting file" for the Fluent and the ANSYS/ABAQUS in order that the joined file can be used to do aero-elastic computations. In this way the fluid field is computed by solving the Navier-Stokes equations and the structure movement is integrated by the dynamics directly. An analysis of the computed results shows that this coupled method designed for simulating aero-elastic systems is workable and can be used for the other fluid-structure interaction problems
Finite-Sample Bias Propagation in Autoregressive Estimation With the Yule–Walker Method
No full textThe Yule-Walker (YW) method for autoregressive (AR) estimation uses lagged-product (LP) autocorrelation estimates to compute an AR parametric spectral model. The LP estimates only have a small triangular bias in the estimated autocorrelation function and are asymptotically unbiased. However, using them in finite samples with the YW method for AR estimation can give a strong distortion in the weak parts of the power spectral density. The distortion is shown to be influential in an example without strong spectral peaks. The true biased AR model, which is computed by applying the triangular bias to the true autocorrelation function, has an infinite order. A new objective measure is introduced to determine the smallest sample size for which the unbiased asymptotic theory can be considered as a fair approximation.Multi-Scale PhysicsApplied Science
XML approach to communication design of WebGIS
No full textXML can describe the concept model of inclusion relationship conveniently. Also, it can directly express the concept model in an understandable way, and the expression format is so flexible that no useless element will be included there. While describing communication protocols by XML, we can not only give a common format for data and control commands, but also reuse the existing XML-parsers, so as to facilitate the expansibility and integration of protocols in a system, W3C had proposed Simple Object Access Protocol (SOAP) [1], which is a light weight protocol based on XML used to build information exchange framework under distributed environments. ArcInfo's ArcIMS also used ArcXML as the fundamental command and data transmission protocols to communicate between users' web pages and backend spatial data servers [2]. Our idea of XML based communication protocols for WebGIS benefits from the SOAP model, but we basically focus on the application in WebGIS. With the aid of UML, the typical requiring and responding protocols of WebGIS are analyzed firstly. Then the mechanism of designing communication protocols following W3C's XML Schema specification is illustrated.http://gateway.webofknowledge.com/gateway/Gateway.cgi?GWVersion=2&SrcApp=PARTNER_APP&SrcAuth=LinksAMR&KeyUT=WOS:000231171300077&DestLinkType=FullRecord&DestApp=ALL_WOS&UsrCustomerID=8e1609b174ce4e31116a60747a720701Computer Science, Information SystemsComputer Science, Theory & MethodsSCI(E)CPCI-S(ISTP)
State-Space Inference and Learning with Gaussian Processes
Full text link18.10.13 KB. Ok to add author version to spiral, authors hold copyright.State-space inference and learning with Gaussian processes (GPs) is an unsolved problem. We propose a new, general methodology for inference and learning in nonlinear state-space models that are described probabilistically by non-parametric GP models. We apply the expectation maximization algorithm to iterate between inference in the latent state-space and learning the parameters of the underlying GP dynamics model. Copyright 2010 by the authors
Spatial information grid - An agent framework
No full textSpatial information grid (SIG) is a spatial information infrastructure that has the capability of providing services on-demand. In this paper, agent technology is adopted to construct a SIG framework, which contains three layers: users/applications layer, agent services layer and information layer. Different applications can get their spatial information via agent services, and agent services make the procedure of navigating and accessing spatial information transparent to users. Also, the implementation issues of the framework are discussed.Computer Science, Artificial IntelligenceComputer Science, Information SystemsComputer Science, Theory & MethodsSCI(E)CPCI-S(ISTP)
A component-based WebGIS Geo-Union
No full textA component-based WebGIS system Geo-Union is introduced, including its architecture, functional partition and web application mode.http://gateway.webofknowledge.com/gateway/Gateway.cgi?GWVersion=2&SrcApp=PARTNER_APP&SrcAuth=LinksAMR&KeyUT=WOS:000223024600075&DestLinkType=FullRecord&DestApp=ALL_WOS&UsrCustomerID=8e1609b174ce4e31116a60747a720701Computer Science, Information SystemsComputer Science, Software EngineeringComputer Science, Theory & MethodsSCI(E)CPCI-S(ISTP)
A cache mechanism for component-based WebGIS
No full textFirst, a component-based WebGIS system Geo-Union is introduced, then the architecture and the web application mode of Geo-Union are discussed. After that, a spatial cache framework is designed and adopted in Geo-Union to improve its performance in network environment. There are three levels of spatial cache: spatial database cache, network spatial cache and spatial data proxy server, and they play different roles in different situations to improve spatial data access performance of Geo-Union.http://gateway.webofknowledge.com/gateway/Gateway.cgi?GWVersion=2&SrcApp=PARTNER_APP&SrcAuth=LinksAMR&KeyUT=WOS:000223079700121&DestLinkType=FullRecord&DestApp=ALL_WOS&UsrCustomerID=8e1609b174ce4e31116a60747a720701Computer Science, Interdisciplinary ApplicationsComputer Science, Theory & MethodsSCI(E)CPCI-S(ISTP)
SOM: A novel model for defining topological line-region relations
No full textTopological line-region relations are generally defined by the Ninth-Intersection Model (9IM) or the Dimensionally Extended Ninth-Intersection Model (DE-9IM) in GIS. In the paper, Segment Operator Model (SOM) is introduced to solve the same problem. Let a simple region R filter a simple curve L and produce a set of curve segments within the exterior, the interior or the borders of R. The topological relations between curve segments and R are mapped into seven categories: across, stabsin, along, bowsto, sticksto, inside and disjoint. SOM is based on counting the curve segments that belong to each of the seven categories. Any topological relations defined in 9IM or DE-9IM can be expressed in SOM. In SOM, L is atomic to R when only a single curve segment is produced, simplex to R when no more than three curve segments are produced, otherwise, L is complex to R. L is uniform to R when only one kind of curve segments are produced.http://gateway.webofknowledge.com/gateway/Gateway.cgi?GWVersion=2&SrcApp=PARTNER_APP&SrcAuth=LinksAMR&KeyUT=WOS:000221852900035&DestLinkType=FullRecord&DestApp=ALL_WOS&UsrCustomerID=8e1609b174ce4e31116a60747a720701Computer Science, Interdisciplinary ApplicationsComputer Science, Software EngineeringComputer Science, Theory & MethodsSCI(E)CPCI-S(ISTP)
Load analysis and load control in geo-agents
No full textGeo-Agents is an agent-based distributed Geographic Information System (GIS), which is a multi-agent system and consists of four types of GIS agent: GuServer, Facilitator, interface agent and GIS function agent. For a multi-agent system, there contains many distributed agents in different environments, which form a complex distributed system. In order to improve the performance, load control should be a keystone in a multi-agent system. Firstly, the load problems in Geo-Agents are analyzed, and then two load control strategies are discussed in detail.http://gateway.webofknowledge.com/gateway/Gateway.cgi?GWVersion=2&SrcApp=PARTNER_APP&SrcAuth=LinksAMR&KeyUT=WOS:000223079700128&DestLinkType=FullRecord&DestApp=ALL_WOS&UsrCustomerID=8e1609b174ce4e31116a60747a720701Computer Science, Interdisciplinary ApplicationsComputer Science, Theory & MethodsSCI(E)CPCI-S(ISTP)
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