711 research outputs found
Structure and Diffusion of Nanoparticle Monolayers Floating at Liquid/Vapor Interfaces: A Molecular Dynamics Study
Large-scale molecular dynamics simulations are used to simulate a layer of
nanoparticles diffusing on the surface of a liquid. Both a low viscosity
liquid, represented by Lennard-Jones monomers, and a high viscosity liquid,
represented by linear homopolymers, are studied. The organization and diffusion
of the nanoparticles are analyzed as the nanoparticle density and the contact
angle between the nanoparticles and liquid are varied. When the interaction
between the nanoparticles and liquid is reduced the contact angle increases and
the nanoparticles ride higher on the liquid surface, which enables them to
diffuse faster. In this case the short range order is also reduced as seen in
the pair correlation function. For the polymeric liquids, the out-of-layer
fluctuation is suppressed and the short range order is slightly enhanced.
However, the diffusion becomes much slower and the mean square displacement
even shows sub-linear time dependence at large times. The relation between
diffusion coefficient and viscosity is found to deviate from that in bulk
diffusion. Results are compared to simulations of the identical nanoparticles
in 2-dimensions.Comment: 8 pages, 9 figure
Development of a project level performance measurement model for improving collaborative design team work
This research explored a new direction of improving collaborative design by performance measurement. More specifically, a novel 3-dimensional performance measurement model is developed and the purpose of this model is to help project managers improve team collaboration by indicating strengths and weaknesses of team members during the project development process. Considering the complexity of collaborative design work, a multiple criteria model is proposed to reflect the design dynamics, which highlights five performance indicators: efficiency, effectiveness, collaboration, management skills and innovation. These five indicators are mostly influenced by role-based performance measurement criteria (the second dimension). Design and development process (time) is also considered (the third dimension). This 3D model allows all involved design participants to measure work performance at any time during the product development process. In order to develop this model, the role-based task analysis and industrial survey methods were utilized. Three groups of role-based product design and development performance measurement criteria were identified for measuring design performance of the top managers, middle managers and individual designers in a project team. A 3-dimensional performance measurement method was proposed to calculate final performance scores from a performance measurement matrix. The proposed model was evaluated as a tool which can support project managers to reduce potential design and collaboration risks and increase confidence in decision-making process. The model has been discussed on implementing in a web-based application for measuring design performance throughout the product design and development proces
Mechanical response of a self avoiding membrane: fold collisions and the birth of conical singularities
An elastic membrane that is forced to reside in a container smaller than its
natural size will deform and, upon further volume reduction, eventually
crumple. The crumpled state is characterized by the localization of energy in a
complex network of highly deformed crescent-like regions joined by line ridges.
Previous studies have focused on the onset of the crumpled state by analyzing
the mechanical response and stability of a conical dislocation, while others
have simulated the highly packed regime neglecting the importance of the
connectivity of the membrane. Here we show, through a combination of
experiments, numerical simulations, and analytic approach, that the emergence
of new regions of high stretching is a generic outcome when a self avoiding
membrane is subject to a severe geometrical constraint. We demonstrate that, at
moderate packing fraction, interlayer interactions produce a response
equivalent to the one of a thicker membrane that has the shape of the deformed
one. Evidence is found that friction plays a key role stabilizing the folded
structures.Comment: 10 page
A QoS-Aware Scheduling Algorithm for High-Speed Railway Communication System
With the rapid development of high-speed railway (HSR), how to provide the
passengers with multimedia services has attracted increasing attention. A key
issue is to develop an effective scheduling algorithm for multiple services
with different quality of service (QoS) requirements. In this paper, we
investigate the downlink service scheduling problem in HSR network taking
account of end-to-end deadline constraints and successfully packet delivery
ratio requirements. Firstly, by exploiting the deterministic high-speed train
trajectory, we present a time-distance mapping in order to obtain the highly
dynamic link capacity effectively. Next, a novel service model is developed for
deadline constrained services with delivery ratio requirements, which enables
us to turn the delivery ratio requirement into a single queue stability
problem. Based on the Lyapunov drift, the optimal scheduling problem is
formulated and the corresponding scheduling service algorithm is proposed by
stochastic network optimization approach. Simulation results show that the
proposed algorithm outperforms the conventional schemes in terms of QoS
requirements.Comment: 6 pages, 3 figures, accepted by IEEE ICC 2014 conferenc
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