4,627 research outputs found
Placement solutions for multiple versions of a multimedia object
Transcoding is an important technology which adapts the same multimedia object to diverse mobile appliances; thus, users' requests for a specified version of a multimedia object could be served by a more detailed version cached according to transcoding. Therefore, it is of particularly theoretical and practical necessity to determine the proper versions to be cached at a node such that the specified objective is achieved. In this paper, we address the problem of multimedia object placement. The performance objective is to minimize the total access cost by considering both transmission cost and transcoding cost. We present an optimal dynamic programming-based solution for this problem. The performance of the proposed solutions is evaluated with a set of carefully designed simulation experiments for various performance metrics over a wide range of system parameters. The simulation results show that our solution consistently and significantly outperforms comparison solutions in terms of all the performance metrics considered.Keqiu Li, Hong Shen, Francis Y. L. Chi
Protein mechanical unfolding: importance of non-native interactions
Mechanical unfolding of the fourth domain of Distyostelium discoideum filamin
(DDFLN4) was studied by all-atom molecular dynamics simulations, using the
GROMOS96 force field 43a1 and the simple point charge explicit water solvent.
Our study reveals an important role of non-native interactions in the unfolding
process. Namely, the existence of a peak centered at the end-to-end extension
22 nm in the force-extension curve, is associated with breaking of non-native
hydrogen bonds. Such a peak has been observed in experiments but not in Go
models, where non-native interactions are neglected. We predict that an
additional peak occurs at 2 nm using not only GROMOS96 force field 43a1 but
also Amber 94 and OPLS force fields. This result would stimulate further
experimental studies on elastic properties of DDFLN4.Comment: 27 pages, 15 figure
Dynamical Effects from Asteroid Belts for Planetary Systems
The orbital evolution and stability of planetary systems with interaction
from the belts is studied using the standard phase-plane analysis. In addition
to the fixed point which corresponds to the Keplerian orbit, there are other
fixed points around the inner and outer edges of the belt. Our results show
that for the planets, the probability to move stably around the inner edge is
larger than the one to move around the outer edge. It is also interesting that
there is a limit cycle of semi-attractor for a particular case. Applying our
results to the Solar System, we find that our results could provide a natural
mechanism to do the orbit rearrangement for the larger Kuiper Belt Objects and
thus successfully explain the absence of these objects beyond 50 AU.Comment: accepted by International Journal of Bifurcation and Chaos in Aug.
2003, AAS Latex, 27 pages with 6 color figure
On the Mass-Period Distributions and Correlations of Extrasolar Planets
In addition to fitting the data of 233 extra-solar planets with power laws,
we construct a correlated mass-period distribution function of extrasolar
planets, as the first time in this field. The algorithm to generate a pair of
positively correlated beta-distributed random variables is introduced and used
for the construction of correlated distribution functions. We investigate the
mass-period correlations of extrasolar planets both in the linear and logarithm
spaces, determine the confidence intervals of the correlation coefficients, and
confirm that there is a positive mass-period correlation for the extrasolar
planets. In addition to the paucity of massive close-in planets, which makes
the main contribution on this correlation, there are other fine structures for
the data in the mass-period plane.Comment: to be published in AJ, tentatively in December 200
Multimedia object placement for hybrid transparent data replication
In this paper, we address present an optimal solution for the problem of multimedia object placement for hybrid transparent data replication. The performance objective is to minimize the total access cost by considering both transmission cost and transcoding cost. The performance of the proposed solution is evaluated with a set of carefully designed simulation experiments for various performance metrics over a wide range of system parameters. The simulation results show that our solution consistently and significantly outperforms comparison solutions in terms of all the performance metrics considered. © 2005 IEEE.published_or_final_versio
Multimedia object placement for hybrid transparent data replication
© 2005 IEEEIn this paper, we address present an optimal solution for the problem of multimedia object placement for hybrid transparent data replication. The performance objective is to minimize the total access cost by considering both transmission cost and transcoding cost. The performance of the proposed solution is evaluated with a set of carefully designed simulation experiments for various performance metrics over a wide range of system parameters. The simulation results show that our solution consistently and significantly outperforms comparison solutions in terms of all the performance metrics considered
The impact of alerting design on air traffic controllers' response to conflict detection and resolution
Purposes: The research aim is to develop a better design of auditory alerts that can improve air traffic controllers’ situation awareness.
Method: Participants are seventy-seven qualified Air Traffic Controllers. The experiment was conducted in the Air Traffic Control operational rooms of the Irish Aviation Authority at Shannon and Dublin. Participants were advised that the trials were in relation to the COOPANS Air Traffic Control. ANOVA with two between-subject factors (alerting designs and experience levels) were conducted to analyze the ATCO’s response time for three critical events. Bonferroni test was performed for post-hoc analysis on mean differences of response time.
Results: There is a significant difference in ATCO’s response time between acoustic alert and semantic alert across STCA, APW and MSAW. No significant main effect of controllers’ experience on ATCO’s response time for STCA and APW. Also, there is no significant interaction between alerting design and experience level on ATCO’s response time across STCA, APW and MSAW.
Conclusion: The results demonstrated that the acoustic alert deployed within the COOPANS ATM system provides level-1 Situational Awareness to ATCO’s compared with an semantic alert which provides not only level-1 of situational awareness for perceived alerts, but also level-2 and level-3 of situational awareness to assist ATCO understanding of critical events and therefore develop more suitable solutions. Consequently, human-centered design of a semantic alert can significantly speed up ATCO’s response to STCA, and APW. Furthermore, the sematic alert could alleviate expertise differences by promoting quicker response times for both novice and experienced air traffic controllers
Effect of lycium barbarum (wolfberry) polysaccharides on preserving retinal function after partial optic nerve transection
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