Fault-tolerant Cooperative Tasking for Multi-agent Systems

A natural way for cooperative tasking in multi-agent systems is through a top-down design by decomposing a global task into sub-tasks for each individual agent such that the accomplishments of these sub-tasks will guarantee the achievement of the global task. In our previous works [1], [2] we presented necessary and sufficient conditions on the decomposability of a global task automaton between cooperative agents. As a follow-up work, this paper deals with the robustness issues of the proposed top-down design approach with respect to event failures in the multi-agent systems. The main concern under event failure is whether a previously decomposable task can still be achieved collectively by the agents, and if not, we would like to investigate that under what conditions the global task could be robustly accomplished. This is actually the fault-tolerance issue of the top-down design, and the results provide designers with hints on which events are fragile with respect to failures, and whether redundancies are needed. The main objective of this paper is to identify necessary and sufficient conditions on failed events under which a decomposable global task can still be achieved successfully. For such a purpose, a notion called passivity is introduced to characterize the type of event failures. The passivity is found to reflect the redundancy of communication links over shared events, based on which necessary and sufficient conditions for the reliability of cooperative tasking under event failures are derived, followed by illustrative examples and remarks for the derived conditions.Comment: Preprint, Submitted for publicatio

Performance evaluation of DASH rate adaptation algorithms [DASH Hiz Uyarlama Algoritmalarinin Performans De?erlendirmesi]

2015 23rd Signal Processing and Communications Applications Conference, SIU 2015 -- 16 May 2015 through 19 May 2015 -- 113052MPEG group has recently proposed Dynamic Adaptive HTTP Streaming (DASH) standard. Various rate adaptation algorithms were proposed in the literature in order to maximize the Quality of Experience (QoE) in DASH clients. In this paper, the performances of pioneer DASH clients, which implement rate adaptation algorithm by taking the bandwidth measurements, buffer level, and both parameters into account, are examined. For this purpose, QoE parameters according to the different buffer sizes are observed under variable network conditions in a simulation environment. The results enlighten that which type of approach in which circumstances can be used in order to obtain best performance in terms of QoE. © 2015 IEEE

The determination of seed yield and yield components in some bean (Ph. vulgaris) Cultivars and Correlations between These Characters under the Çukurova Conditions [Çukurova koşullarinda bazi fasulye (Phaseolus vulgaris L.) çeşitlerinde tane verimi ve verimle i·lgili özellikler ile bu özellikler arasi i·lişkilerin saptanmasi]

This research was conducted to determine suitable bean cultivars under Çukurova conditions, as well as to find out the correlations between seed yield and yield components. According to the experiment years' average, the seed yield of bean cultivars varied from 57.4 to 119.6 kg/da and from 16.5 to 97.5 kg/da in dwarf and climbing beans respectively şehirali-90 and Yalova-5 in dwarf beans and Dermason-Malatya and Horoz-Tokat in climbing beans had the high seed yield in both experiment years. Positive correlation cofficients were found between seed yield and 100 seed number in dwarf beans. Also, there were positive correlation coefficients between seed yield and total pod number, filled pod number, seed weight per plant and seed number per plant in twining beans

Genetic variability, correlation and path analysis of yield, and yield components in chickpea (Cicer arietinum L.)

This study was conducted to determine variability, heritability, and correlations between yield and yield components in 15 kabuli chickpea (Cicer arietinum L.) genotypes for 2 years. Direct and indirect effects of yield components on seed yield per plant were investigated. Genotypic variance was the highest for 1000 seed weight, followed by seed number per plant. Broad-sense heritabilities ranged from 5.47% (days to flowering) to 51.66% (seed number per plant). Heritabilities for seed number, 1000 seed weight, and number of full pods were greater than those for the other traits. Positive and significant (P < 0.05) relationships were determined between seed yield per plant and plant height, first pod height, secondary branch, total pod, and number of full pods and seeds per plant. The path coefficient analysis based on seed yield per plant, as a dependent variable, revealed that all of the other traits, except days to flowering, first pod height, and total pod number, exhibited high positive direct effects. Number of seeds and full pods showed the highest direct influence with 47.49% and 44.73%, respectively. Therefore, this research suggests that seed and full pod numbers can be good selection criteria for improving seed yield per plant in kabuli winter chickpea. © TÜBITAK

Design of Observers for Hybrid Systems

A methodology for the design of dynamical observers for hybrid plants is proposed. The hybrid observer consists of two parts: a location observer and a continuous observer. The former identifies the current location of the hybrid plant, while the latter produces an estimate of the evolution of the continuous state of the hybrid plant. A synthesis procedure is offered when a set of properties on the hybrid plant is satisfied

Optimal Communication Algorithms for Hypercubes

We consider the following basic communication problems in a hypercube network of processors: the problem of a single processor sending a different packet to each of the other processors, the problem of simultaneous broadcast of the same packet from every processor to all other processors, and the problem of simultaneous exchange of different packets between every pair of processors. The algorithms proposed for these problems are optimal in terms of execution time and communication resource requirements; that is, they require the minimum possible number of time steps and packet transmissions. In contrast, algorithms in the literature are optimal only within an additive or multiplicative factor

Observability of Linear Hybrid Systems

We analyze the observability of the continuous and discrete states of a class of continuous-time linear hybrid systems. We derive necessary and sufficient conditions that the structural parameters of the model must satisfy in order for filtering and smoothing algorithms to operate correctly. Our conditions are simple rank tests that exploit the geometry of the observability subspaces generated by the output of a linear hybrid system. We also derive weaker rank conditions that guarantee the uniqueness of the reconstruction of the state trajectory from a specific output, even when the hybrid system is unobservable