78,685 research outputs found
Network traffic behaviour near phase transition point
We explore packet traffic dynamics in a data network model near phase
transition point from free flow to congestion. The model of data network is an
abstraction of the Network Layer of the OSI (Open Systems Interconnection)
Reference Model of packet switching networks. The Network Layer is responsible
for routing packets across the network from their sources to their destinations
and for control of congestion in data networks. Using the model we investigate
spatio-temporal packets traffic dynamics near the phase transition point for
various network connection topologies, and static and adaptive routing
algorithms. We present selected simulation results and analyze them
Robust active heave compensated winch-driven overhead crane system for load transfer in marine operation
Active heave compensation (AHC) is important for load transfer in marine operation using the overhead crane system (OCS). The control of marine OCS aims to continuously regulate the displacement of the cart and the payload sway angle, whilst at the same time, maintaining the gap between the payload and the vessel main deck at a desirable and safe distance. As the marine OHC system is to be operated in a continuously changing environment, with plenty inevitable disturbances and undesirable loads, a robust controller, i.e., active force control (AFC) is thus greatly needed to promote accuracy and robustness features into the controllability of OCS in rough working environment. This paper highlights a novel method for controlling the payload in an OCS based on the combination of both AFC and AHC. Results from the simulation study clearly indicate that the performance of OCS can be greatly improved by the proposed robust AFC controller, as compared with the classical PID controller scheme
Moment-based analysis of biochemical networks in a heterogeneous population of communicating cells
Cells can utilize chemical communication to exchange information and
coordinate their behavior in the presence of noise. Communication can reduce
noise to shape a collective response, or amplify noise to generate distinct
phenotypic subpopulations. Here we discuss a moment-based approach to study how
cell-cell communication affects noise in biochemical networks that arises from
both intrinsic and extrinsic sources. We derive a system of approximate
differential equations that captures lower-order moments of a population of
cells, which communicate by secreting and sensing a diffusing molecule. Since
the number of obtained equations grows combinatorially with number of
considered cells, we employ a previously proposed model reduction technique,
which exploits symmetries in the underlying moment dynamics. Importantly, the
number of equations obtained in this way is independent of the number of
considered cells such that the method scales to arbitrary population sizes.
Based on this approach, we study how cell-cell communication affects population
variability in several biochemical networks. Moreover, we analyze the accuracy
and computational efficiency of the moment-based approximation by comparing it
with moments obtained from stochastic simulations.Comment: 6 pages, 5 Figure
Parrondo's games with chaotic switching
This paper investigates the different effects of chaotic switching on
Parrondo's games, as compared to random and periodic switching. The rate of
winning of Parrondo's games with chaotic switching depends on coefficient(s)
defining the chaotic generator, initial conditions of the chaotic sequence and
the proportion of Game A played. Maximum rate of winning can be obtained with
all the above mentioned factors properly set, and this occurs when chaotic
switching approaches periodic behavior.Comment: 11 pages, 9 figure
The Effective Use of Multimedia Distance Learning Technology: The Role of Technology Self-Efficacy, Attitudes, Reliability, Use and Distance in a Global Multimedia Distance Learning Classroom
According to the 1999 ASTD State of the Industry Report, the use of multimedia distance learning (MDL) technology for training delivery has increased substantially over the past few years. However, few empirical studies have been conducted that rigorously examine the factors that determine the effectiveness of MDL courses. In this study, we examine participants’ technology self-efficacy and attitudes toward technology (measured before/after training), and perceptions of technology reliability, effective use, and distance (measured after training) as antecedents to ratings of training effectiveness (general effectiveness, specific effectiveness, learning effectiveness; measured after training) in an international HRM course. In a sample of 52 participants from four countries we hypothesize that technology self-efficacy will affect participants’ attitudes toward technology; attitudes toward technology will affect participants’ perceptions of training effectiveness. In addition, we hypothesize that technology reliability and effective use will affect participants’ perceptions of classroom distance; distance perceptions will affect participants’ perceptions of training effectiveness. Finally, we hypothesize that both technology attitudes and distance perceptions will be related to participants’ perceptions of training effectiveness controlling for technology self-efficacy, reliability, and effective use.
The results indicate that attitudes toward technology completely/partially mediated the relationship between technology self-efficacy and the three measures of effectiveness. Distance perceptions completely/partially mediated the relationship between technology reliability and effectiveness. Effective technology use was not significantly related to effectiveness. Finally, attitudes toward technology and distance perceptions explained a significant or marginally significant amount of variance in the effectiveness measures after controlling for technology self-efficacy, reliability, and effective use
Building a diversity featured search system by fusing existing tools
This paper describes our diversity featured retrieval system which are built for the task
of ImageCLEFPhoto 2008. Two existing tools are used: Solr and Carrot. We have
experimented with different settings of the system to see how the performance changes.
The results suggest that the system can indeed increase diversity of the retrieved results
and keep the precision about the same
Creating a test collection to evaluate diversity in image retrieval
This paper describes the adaptation of an existing test collection
for image retrieval to enable diversity in the results set to be
measured. Previous research has shown that a more diverse set of
results often satisfies the needs of more users better than standard
document rankings. To enable diversity to be quantified, it is
necessary to classify images relevant to a given theme to one or
more sub-topics or clusters. We describe the challenges in
building (as far as we are aware) the first test collection for
evaluating diversity in image retrieval. This includes selecting
appropriate topics, creating sub-topics, and quantifying the overall
effectiveness of a retrieval system. A total of 39 topics were
augmented for cluster-based relevance and we also provide an
initial analysis of assessor agreement for grouping relevant
images into sub-topics or clusters
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