8,632 research outputs found
Simulation and experimental evaluation of a flexible time triggered ethernet architecture applied in satellite nano/micro launchers
The success of small satellites has led to the study of new technologies for the realization of Nano and Micro Launch Vehicle (NMLV) in order to make competitive launch costs. The paper has the objective to define and experimentally investigate the performance of a communication system for NMLV interconnecting the End Systems as On-Board Computer (OBC), telemetry apparatus, Navigation Unit...we propose a low cost Ethernet-based solution able to provide the devices with high interconnection bandwidth. To guarantee hard delays to the Guide, Navigation and Control applications we propose some architectural changes of the traditional Ethernet network with the introduction of a layer implemented in the End Systems and allow for the lack of any contention on the network links. We show how the proposed solution has comparable performance to the one of TTEthernet standard that is a very expensive solution. An experimental test-bed equipped with Ethernet switches and Hercules boards by Texas Instruments is also provided to prove the feasibility of the proposed solution
An Exact Approach to Early/Tardy Scheduling with Release Dates
In this paper we consider the single machine earliness/tardiness scheduling problem with di?erent release dates and no unforced idle time. The problem is decomposed into a weighted earliness subproblem and a weighted tardiness subproblem. Lower bounding procedures are proposed for each of these subproblems, and the lower bound for the original problem is then simply the sum of the lower bounds for the two subproblems. The lower bounds and several versions of a branch-and-bound algorithm are then tested on a set of randomly generated problems, and instances with up to 30 jobs are solved to optimality. To the best of our knowledge, this is the first exact approach for the early/tardy scheduling problem with release dates and no unforced idle time.scheduling, early/tardy, release dates, lower bounds, branch-and-bound
Heuristics for the Early/Tardy Scheduling Problem with Release Dates
In this paper we consider the single machine earliness/tardiness scheduling problem with di?erent release dates and no unforced idle time. We analyse the performance of several dispatch rules, a greedy procedure and a decision theory local search heuristic. The dispatch rules use a lookahead parameter whose value must be specified. We perform some experiments to determine an appropriate value for this parameter. The use of dominance rules to improve the solutions obtained by these heuristics is also considered. The computational results show that the use of the dominance rules can indeed improve the solution quality with little additional computational e?ort. To the best of our knowledge, this is the first analysis of heuristic performance for the early/tardy scheduling problem with release dates and no unforced idle time.scheduling, early/tardy, release dates, heuristics
Improved Lower Bounds for the Early/Tardy Scheduling Problem with No Idle Time
In this paper we consider the single machine earliness/tardiness scheduling problem with no idle time. Two of the lower bounds previously developed for this problem are based on lagrangean relaxation and the multiplier adjustment method, and require an initial sequence. We investigate the sensitivity of the lower bounds to the initial sequence, and experiment with di?erent dispatch rules and some dominance conditions. The computational results show that it is possible to obtain improved lower bounds by using a better initial sequence. The lower bounds are also incorporated in a branch-and-bound algorithm, and the computational tests show that one of the new lower bounds has the best performance for larger instances.scheduling, early/tardy, lower bound
Improved Heuristics for the Early/Tardy Scheduling Problem with No Idle Time
In this paper we consider the single machine earliness/tardiness scheduling problem with no idle time. We present two new heuristics, a dispatch rule and a greedy procedure, and also consider the best of the existing dispatch rules. Both dispatch rules use a lookahead parameter that had previously been set at a fixed value. We develop functions that map some instance statistics into appropriate values for that parameter. We also consider the use of dominance rules to improve the solutions obtained by the heuristics. The computational results show that the function-based versions of the heuristics outperform their fixed value counterparts and that the use of the dominance rules can indeed improve solution quality with little additional computational effort.scheduling, early/tardy, heuristics, dispatch rules, dominance rules
Beam search algorithms for the early/tardy scheduling problem with release dates
In this paper we consider the single machine earliness/tardiness scheduling problem with di?erent release dates and no unforced idle time. We present several heuristic algorithms based on the beam search technique. These algorithms include classical beam search procedures, with both priority and total cost evaluation functions, as well as the filtered and recovering variants. Both priority evaluation functions and problem-specific properties were considered for the filtering step used in the filtered and recovering beam search heuristics. Extensive preliminary tests were performed to determine appropriate values for the parameters used by each algorithm. The computational results show that the recovering beam search algorithms outperform their filtered counterparts in both solution quality and computational requirements, while the priority-based filtering procedure proves superior to the rules-based alternative. The beam search procedure with a total cost evaluation function provides very good results, but is computationally expensive and can therefore only be applied to small or medium size instances. The recovering algorithm is quite close in solution quality and is significantly faster, so it can be used to solve even large instances.scheduling, early/tardy, beam search, heuristics
Optimal irreversible stimulated emission
We studied the dynamics of an initially inverted atom in a semi-infinite
waveguide, in the presence of a single propagating photon. We show that atomic
relaxation is enhanced by a factor of 2, leading to maximal bunching in the
output field. This optimal irreversible stimulated emission is a novel
phenomenon that can be observed with state-of-the-art solid-state atoms and
waveguides. When the atom interacts with two one-dimensional electromagnetic
environments, the preferential emission in the stimulated field can be
exploited to efficiently amplify a classical or a quantum state.Comment: 9 pages, 6 figure
A Fabry-Perot interferometer with quantum mirrors: nonlinear light transport and rectification
Optical transport represents a natural route towards fast communications, and
it is currently used in large scale data transfer. The progressive
miniaturization of devices for information processing calls for the microscopic
tailoring of light transport and confinement at length scales appropriate for
the upcoming technologies. With this goal in mind, we present a theoretical
analysis of a one-dimensional Fabry-Perot interferometer built with two highly
saturable nonlinear mirrors: a pair of two-level systems. Our approach captures
non-linear and non-reciprocal effects of light transport that were not reported
previously. Remarkably, we show that such an elementary device can operate as a
microscopic integrated optical rectifier
Additive Manufacturing Tools to Improve the Performance of Chromatographic Approaches
Chromatography is widely applied industrially. However, some limitations are associated with its common supports, and the impossibility to fully control their structural features is particularly restrictive. Additive manufacturing (AM) is emerging as a fast, highly precise, and reproducible technology for producing chromatographic supports that can improve its performance.info:eu-repo/semantics/publishedVersio
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