203 research outputs found
Lattice Boltzmann modelling of bacterial colony patterns
Full text linkThe formation of branches in bacterial colonies is influenced by both chemical interactions (reactions) and the movement of substances through space (diffusion). These colonies can exhibit a variety of fascinating branching patterns due to the interplay of nutrient transport, bacterial growth, and chemotaxis. To understand this complex process, researchers have developed several mathematical models based on solving reaction-diffusion equations. In this letter, we introduce an innovative application of the lattice Boltzmann method to investigate the diverse morphological patterns observed in bacterial colonies. This method is concise, compact, and easy to implement. Our study demonstrates its effectiveness in accurately predicting various types of bacterial colony patterns, offering a new tool to obtain insights into the dynamics of bacterial growth andpattern formation
Mathematics of stable tensegrity structures
Full text linkTensegrity structures have been extensively studied over the last years due
to their potential applications in modern engineering like metamaterials,
deployable structures, planetary lander modules, etc. Many of the form-finding
methods proposed continue to produce structures with one or more soft/swinging
modes. These modes have been vividly highlighted and outlined as the grounds
for these structures to be unsuitable as engineering structures. This work
proposes a relationship between the number of rods and strings to satisfy the
full-rank convexity criterion as a part of the form-finding process. Using the
proposed form-finding process for the famous three-rod tensegrity, the work
proposes an alternative three-rod ten-string that is stable. The work
demonstrates that the stable tensegrities suitable for engineering are feasible
and can be designed
OpenFOAM v2306
No full textThis repository houses a specialized version of OpenFOAM 2306 that has been meticulously tailored and optimized for the unique needs of ajaylab. OpenFOAM, an open-source computational fluid dynamics (CFD) software, is a powerful tool for simulating and solving complex fluid flow problems. The customized version here is crafted by the experts at ajaylab to enhance performance, provide additional features, and streamline workflows to cater specifically to our research and engineering endeavors. More information on running (for users), modification (for developers), version history is available in the README-v2306.md file.
Version history
1.0.0:
openfoam-2306-arm-v100.tar.gz: Currently deprecated. Please do not us
Pointwise contact numerical models and applications
No full textYoutube link to the video: https://www.youtube.com/watch?v=3VpkVH2osxk
Abstract of the lecture
In this lecture, an overview of computational modeling of pointwise contact will be given. Beam-to-beam contact will be addressed, such as contact involving rigid/flexible bodies, modeled by beams/shells. An overview of the master-master contact strategy will be provided, presenting its pros/cons, such as numerous examples.
Related publications
Gay Neto, A.; Wriggers, P.; Master-master frictional contact and applications for beam-shell interaction. Computational Mechanics, Published Online, 2020.
Gay Neto, A.; Wriggers, P.; Numerical method for solution of pointwise contact between surfaces. Computer Methods in Applied Mechanics and Engineering, v. 365,112971, 2020.
Gay Neto, A.; Wriggers, P.; Computing pointwise contact between bodies: a class of formulations based on master-master approach. Computational Mechanics, Published Online, 2019.
Campos, P.R.R.; Gay Neto, A.; Rigid body formulation in a finite element context with contact interaction. Computational Mechanics, 62:1369, 2018.
Gay Neto, A.; Pimenta, P. M.; Wriggers, P.; Contact between spheres and general surfaces. Computer Methods in Applied Mechanics and Engineering, v. 328, p. 686-716, 2018.
Gay Neto, A.; Campello, E. M. B.; Granular materials interacting with thin flexible rods. Computational Particle Mechanics, v. 4, p. 229-247, 2017.
Gay Neto, A.; Pimento, P. M.; Wriggers, P.; A master-surface to master-surface formulation for beam to beam contact. Part II: Frictional interaction. Computer 8. Methods in Applied Mechanics and Engineering, v. 319, p. 146-174, 2017.
Gay Neto, A.; Simulation of mechanisms modeled by geometrically-exact beams using Rodrigues rotation parameters. Computational Mechanics, v. 59, p. 459-481, 2017.
Gay Neto, A.; Pimento, P. M.; Wriggers, P.; A master-surface to master-surface formulation for beam to beam contact. Part I: Frictionless interaction. Computer Methods in Applied Mechanics and Engineering, v. 303, p. 400–429, 2016
I-TCP: Indirect TCP for Mobile Hosts
No full textIP-based solutions to accommodate mobile hosts within existing internetworks do not address the distinctive features of wireless mobile computing. IP-based transport protocols thus suffer from poor performance when a mobile host communicates with a host on the fixed network. This is caused by frequent disruptions in network layer connectivity due to — i) mobility and ii) unreliable nature of the wireless link. We describe the design and implementation of I-TCP, which is an indirect transport layer protocol for mobile hosts. I-TCP utilizes the resources of Mobility Support Routers (MSRs) to provide transport layer communication between mobile hosts and hosts on the fixed network. With I-TCP, the problems related to mobility and the unreliability of wireless link are handled entirely within the wireless link; the TCP/IP software on the fixed hosts is not modified. Using I-TCP on our testbed, the throughput between a fixed host and a mobile host improved substantially in comparison to regular TCP.Technical report DCS-TR-31
Alleviation techniques for volumetric locking in elements based on the absolute nodal coordinate formulation
No full textThis study investigates the application of formulations employed by standard Bubnov-Galerkin Finite Elements to alleviate volumetric locking in the context of the Absolute Nodal Coordinate Formulation (ANCF). Volumetric locking is a prevalent phenomenon that occurs when linearly interpolated displacement fields are used to model incompressible phenomena. Although linear interpolations for the displacement field offer computational efficiency, their direct utilization can frequently yield erroneous solutions and slow convergence rates when applied to modeling incompressible materials. Commonly used techniques to reduce volumetric locking in classical finite elements include reduced and selective integration, mixed two/three field variational formulations, and F-bar methods. This study aims to demonstrate the efficacy of these techniques when applied to a two and three-dimensional linear ANCF-based continuum beam elements. Our findings demonstrate that most of the locking alleviation techniques yielded expected results compared to classical finite elements. Nevertheless and contrary to findings in the finite element literature, the mixed two/three field variational formulation, when used with linear ANCF-based continuum beam elements, improved the convergence rate only in the case of uniaxial tensile testing. For the bending mode, mixed ANCF elements significantly overestimated the displacements. While techniques alleviate locking for some deformation modes, the paper concludes that no definitive technique exists to completely resolve volumetric locking effects observed in linear ANCF elements, for all deformation modes.</p
ANSWER: A Semantic Approach to Film Direction
No full textIn this paper we present ANSWER, an innovative approach to film direction. Here we describe a methodology to semantically model the film domain in a way which is coherent with the director’s intent during film production. To achieve this, we are developing a system architecture which will provide the director with the necessary tools and services to author a scene description through intuitive gesture based graphical user interfaces, which will in turn populate the underlying model with a rich set of semantic descriptions. These semantic descriptions will be used to render the scene graphically through animated previsualizations. A director using the ANSWER methodology will be able to understand and assert certain film making decisions before film production begin
IP multicast extensions for mobile internetworking
No full textThis paper deals with multicasting in an internetwork with mobile hosts, particularly with regard to Mobile-IP and Distance Vector Multicast Routing (DVMRP) protocols. When the source of a multicast datagram is a mobile host (MH), the datagram may not reach all group members to which the datagram is addressed, including other mobile hosts. When the source is a static host and the multicast group includes mobile hosts, a mobile group member may receive datagrams in one cell but not in another. Further, when a MH enters a cell which contains no other member of the same group, the MH will experience a delay before it starts receiving datagrams addressed to that group. Mobility between campuses, which result in a MH acquiring an additional unicast address, also has an effect on multicast routing. We propose enhancements to DVMRP executed at the Mobility Support Routers (MSR) that ensure correct forwarding of multicast datagrams to and from mobile hosts. Our solutions do not require any change at hosts and routers unaware of mobility, i.e. the modifications are limited to MSRs and MHs. We also describe an implementation incorporating a subset of our proposals. Lastly, we show that alternate styles of multicasting or mobile networking, viz. link-state (MOSPF ) and IETF proposal, will face similar problems and our proposed solutions are still valid in their context.Technical report lcsr-tr-24
Nanoscratching on filled elastomers
No full textThis dataset include the nano scratching on polymers. Four filled elastomers (with different glass transition temperatures) were tested using scratch tests with the Agilent Nanoindenter. Tests were done at room temperature and 100-deg Celcius. The data from the tests are provided here
Design and implementation of indirect protocols for mobile wireless
No full textHost mobility within the largely stationary internetwork has been treated thus far as a routing problem, to be solved entirely within the network layer of the ISO/OSI protocol model. However, mobility of host machines from one attachment point to another affects transport and higher layer protocols as well. In addition, the use of wireless links by mobile computers for attachment to the fixed network infrastructure, gives rise to performance problems due to low bandwidth and high error rates that are typical of wireless environments. The existing network protocols do not provide any mechanism to deal with the problems arising out of host mobility and wireless access. Widespread use of mobile and wireless capable computers is also likely to create a demand for new applications that utilize the mobile user's location for accessing information sources. Applications used in mobile wireless environments may also need to adapt to the changes in the characteristics of the wireless medium.
In this dissertation, we consider the problem of supporting distributed applications on mobile wireless computers that need to communicate with peer applications and servers on the wired internetwork. We present the design and implementation of Indirect Protocols, which allow the use of specialized network protocols for the wireless medium and mobile hosts in a way that is backward compatible with the existing protocols used over the wired internetwork. Indirect protocols are based on two key ideas: i) Special treatment of wireless links and mobile computers in an internetwork and ii) Use of mobility support routers (MSRs) as multi-protocol intermediaries. Mobility support routers provide the necessary support to ensure inter-operability with the existing wired network protocols. We show that the use of indirection results in improved performance at the transport layer and provides enhanced functionality at the remote procedure call (RPC) layer.Technical report lcsr-tr-27
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