72,756 research outputs found
Robust mean absolute deviation problems on networks with linear vertex weights
This article deals with incorporating the mean absolute
deviation objective function in several robust single facility
location models on networks with dynamic evolution
of node weights, which are modeled by means of linear
functions of a parameter. Specifically, we have considered
two robustness criteria applied to the mean absolute
deviation problem: the MinMax criterion, and the MinMax
regret criterion. For solving the corresponding optimization
problems, exact algorithms have been proposed and
their complexities have been also analyzed.Ministerio de Ciencia e Innovación MTM2007-67433-C02-(01,02)Ministerio de Ciencia e Innovación MTM2009-14243Ministerio de Ciencia e Innovación MTM2010-19576-C02-(01,02)Ministerio de Ciencia e Innovación DE2009-0057Junta de Andalucía P09-TEP-5022Junta de Andalucía FQM-584
The Focal plane Detector Package on the TUNL Split-pole Spectrograph
A focal plane detector for the Enge Split-pole Spectrograph at Triangle
Universities Nuclear Laboratory has been designed. The detector package
consists of two position sensitive gas avalanche counters, a gas
proportionality energy loss section, and a residual energy scintillator. This
setup allows both particle identification and focal plane reconstruction. In
this paper we will detail the construction of each section along with their
accompanying electronics and data acquisition. Effects of energy loss
throughout the detector, ray tracing procedures, and resolution as a function
of fill pressure and bias voltage are also investigated. A measurement of the
Al reaction is used to demonstrate detector performance and to
illustrate a Bayesian method of energy calibration
Coordination of Mobile Mules via Facility Location Strategies
In this paper, we study the problem of wireless sensor network (WSN)
maintenance using mobile entities called mules. The mules are deployed in the
area of the WSN in such a way that would minimize the time it takes them to
reach a failed sensor and fix it. The mules must constantly optimize their
collective deployment to account for occupied mules. The objective is to define
the optimal deployment and task allocation strategy for the mules, so that the
sensors' downtime and the mules' traveling distance are minimized. Our
solutions are inspired by research in the field of computational geometry and
the design of our algorithms is based on state of the art approximation
algorithms for the classical problem of facility location. Our empirical
results demonstrate how cooperation enhances the team's performance, and
indicate that a combination of k-Median based deployment with closest-available
task allocation provides the best results in terms of minimizing the sensors'
downtime but is inefficient in terms of the mules' travel distance. A
k-Centroid based deployment produces good results in both criteria.Comment: 12 pages, 6 figures, conferenc
Median problems in networks
The P-median problem is a classical location model “par excellence”. In this paper we, first examine the early origins of the problem, formulated independently by Louis Hakimi and Charles ReVelle, two of the fathers of the burgeoning multidisciplinary field of research known today as Facility Location Theory and Modelling. We then examine some of the traditional heuristic and exact methods developed to solve the problem. In the third section we analyze the impact of the model in the field. We end the paper by proposing new lines of research related to such a classical problem.P-median, location modelling
Use of the Long Duration Exposure Facility's thermal measurement system for the verification of thermal models
The Long Duration Exposure Facility (LDEF) postflight thermal model predicted temperatures were matched to flight temperature data recorded by the Thermal Measurement System (THERM), LDEF experiment P0003. Flight temperatures, recorded at intervals of approximately 112 minutes for the first 390 days of LDEF's 2105 day mission were compared with predictions using the thermal mathematical model (TMM). This model was unverified prior to flight. The postflight analysis has reduced the thermal model uncertainty at the temperature sensor locations from +/- 40 F to +/- 18 F. The improved temperature predictions will be used by the LDEF's principal investigators to calculate improved flight temperatures experienced by 57 experiments located on 86 trays of the facility
Demonstration of rapid-scan two-dimensional laser velocimetry in the Langley Vortex Research Facility for research in aerial applications
Tests were conducted to demonstrate a rapid scan two dimensional laser velocimeter (LV) measurement technique for aerial applications research. The LV system is capable of simultaneously measuring both vertical and axial flow velocity components in a near or far field vortex system. Velocity profiles were successfully measured in the wake vortex of a representative agricultural aircraft model, with the vortex system rapidly transporting in ground effect. Results indicate that the laser velocimetry technique can provide quantitative information of wake vortex characteristics in ground effect
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