586 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
Shape Memory Actuator: thermomechanical training and surface optimization of shape memory wires embedded in a polymeric matrix
No full textIn the first part of my work I studied the mechanical and thermal behaviour of NiTi wires and
strips in order to find the best training cycle to achieve a good compromise between
transformation temperatures, recovery forces and phase reversibility. Other parameters such as
the stress-rate and maximum recovery deformations, useful to realize smart composites, were
evaluated. DSC and DMTA analyses were performed on NiTi thin strips that were cold rolled
with different thickness reductions. DSC is a well-known technique used to find the
transformation temperatures of SMAs. Contrary to DSC, DMTA is not a traditional
characterization method for shape memory alloys. Therefore, in this work I tried to find a
correlation between the results of DSC and DMTA analysis, according to different hardenings
induced by cold rolling.
In the second part I dealt with the interface bonding optimization between polymer matrices and
NiTi wires. Smart composites take advantage of the adhesion between the NiTi wires and the
polymer matrix. Their mechanical properties depend strongly on the efficiency of stresses and
deformations transfer at the interface between the wires and the surrounding matrix. This way,
adhesion must be improved to avoid the degradation or premature failure of the actuation. I
focused on the evaluation of the interface strength between NiTi wires and two kinds of
thermosetting resins: polyester and vinylester. Different surface treatments were performed on
the NiTi wires in order to increase the performance of the wire-resin interface adhesion. In
particular, chemical passivation by using acid solution and functionalization by using silane
coupling agents, were considered. Pull-out tests were carried out to quantify the improvement of
the interface adhesion.
Moreover, during my PhD I also dealt with the theoretical modeling of SMA materials and the
mechanical behavior of smart composites during activation, but this topic is not discussed in this
thesis
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
A framework for designing an immersive language learning environment integrated with educational robots and IoT-based toys
No full textIn view of the benefits of and success in acquiring multiple languages in an immersive learning environment while young, this research aims to create an immersive language learning environment for young children to acquire multiple languages utilizing robots and IoT (Internet of Things) -based toys. This paper presents the results from the first two stages of this project aiming to develop a design framework to guide the development of such an immersive environment. Our extensive review of the relevant literature indicates that the framework should, at least, consist of five main pedagogical considerations: language input, activity design, interaction design, toy design and robot design. In each of the five dimensions, a number of key factors should also be addressed in creating an effective learning environment. The development of the design framework is to serve as a road map providing design principles and guidelines for educators and researcher to create an immersive learning environment.Full Tex
A framework for a consumer-end energy management system in smart grid
No full textHome appliances, smartphones, smart meters, dynamic pricing, and a data center employing cloud-computing technologies are combined to construct a consumer-end energy management system. In the proposed framework, a power user in a grid can use a smartphone to adjust the power consumption of their home appliances and other electronic devices based on the ambient environment and pricing signals. Consequently, the proposed system can facilitate reducing power consumption and improving energy efficiency
Pearl millet yields and climate evolution across the last 20 years in central Senegal. A yield gap study. [P93]
No full textThe study focuses on the evolution of yield of pearl millet in central Senegal between the early 1990s (P1) and present time (P2). Mean air temperature and total annual rainfall both increased between P1 and P2. To avoid confounding effects due to these differences in climate with other possible causes, yields measured in farmers' fields (Ya) in the two periods were compared with estimates of potential (Yp) and water-limited (Yw) yields obtained using a crop model. Ya were extremely variable across fields whatever the period (100 to 1937 Kg.ha-1) and much lower than simulated Yw (1343 to 3251 Kg.ha-1). Resulting from interactions between changes in sowing dates, the photoperiod sensitive nature of the cultivars used, and the distribution of changes in temperature across the rainy season (increasing in June and July, and decreasing in August and September), cycle durations were slightly but significantly increased between P1 and P2, whereas solar radiation decreased concomitantly with the increase in rainfall (from 377 to 614 mm). This provoked a decrease in Yp (3076±14 Kg.ha-1 in P1 against 2843±37 Kg.ha-1 in P2), whereas Yw increased (1959±92 Kg.ha-1 in P1 against 2571±72 Kg.ha-1 in P2). With the change in Ya, passing from 835±105 Kg.ha-1 for P1 to 525±43 Kg.ha-1 for P2, the resulting yield gap Yw-Ya significantly increased (1124±140 Kg.ha-1 in P1 against 2045±77 Kg.ha-1 in P2). Field management did not significantly change between P1 and P2. It is concluded that the low yields and their stability across climate variations were due to the non-intensive nature of the cropping system. The impact of climate change on agricultural systems of the region should be studied accounting for complex interactions between rainfall, temperature, and radiation and for possible changes in cropping systems in response to changes in the economic environment of farms, that would likely change the crop's sensitivity to climate variables. (Texte intégral
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
No full text18.10.13 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)
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