A method for improving the accuracy of data mining classification algorithms

In this paper we introduce a method called CL.E.D.M. (CLassification through ELECTRE and Data Mining), that employs aspects of the methodological framework of the ELECTRE I outranking method, and aims at increasing the accuracy of existing data mining classification algorithms. In particular, the method chooses the best decision rules extracted from the training process of the data mining classification algorithms, and then it assigns the classes that correspond to these rules, to the objects that must be classified. Three well known data mining classification algorithms are tested in five different widely used databases to verify the robustness of the proposed method.     

Multi-temporal land-cover classification and change analysis with conditional probability networks: the case of Lesvos Island (Greece)

This study uses a series of Landsat images to map the main land-cover types on the Mediterranean island of Lesvos, Greece. We compare a single-year maximum likelihood classification (MLC) with a multi-temporal maximum likelihood classification (MTMLC) approach, with time-series class labels modelled using a first-order hidden Markov model comprising continuous and discrete variables. A rigorous validation scheme shows statistically significant higher accuracy figures for the multi-temporal approach. Land-cover change accuracies were also greatly improved by the proposed methodology: from 46% to 70%. The results show that when only two dates are used, the mapping of land use/cover is unreliable and a large number of the changes identified are due to the individual-year commission and omission errors.     

Stable indirect adaptive switching control for fuzzy dynamical systems based on T–S multiple models

A new indirect adaptive switching fuzzy control method for fuzzy dynamical systems, based on Takagi–Sugeno (T–S) multiple models is proposed in this article. Motivated by the fact that indirect adaptive control techniques suffer from poor transient response, especially when the initialisation of the estimation model is highly inaccurate and the region of uncertainty for the plant parameters is very large, we present a fuzzy control method that utilises the advantages of multiple models strategy. The dynamical system is expressed using the T–S method in order to cope with the nonlinearities. T–S adaptive multiple models of the system to be controlled are constructed using different initial estimations for the parameters while one feedback linearisation controller corresponds to each model according to a specified reference model. The controller to be applied is determined at every time instant by the model which best approximates the plant using a switching rule with a suitable performance index. Lyapunov stability theory is used in order to obtain the adaptive law for the multiple models parameters, ensuring the asymptotic stability of the system while a modification in this law keeps the control input away from singularities. Also, by introducing the next best controller logic, we avoid possible infeasibilities in the control signal. Simulation results are presented, indicating the effectiveness and the advantages of the proposed method.     

Semi-supervised vision-based maritime surveillance system using fused visual attention maps

This paper presents a vision-based system for maritime surveillance, using moving PTZ cameras. The proposed methodology fuses a visual attention method that exploits low-level image features appropriately selected for maritime environment, with appropriate tracker, without making any assumptions about environmental or visual conditions. The offline initialization is based on large graph semi-supervised technique. System’s performance was evaluated with videos from cameras placed at Limassol port and Venetian port of Chania. Results suggest high detection ability, despite dynamically changing visual conditions and different kinds of vessels, all in real time.     

Scalable playback rate control in P2P live streaming systems

Current commercial live video streaming systems are based either on a typical client–server (cloud) or on a peer-to-peer (P2P) architecture. The former architecture is preferred for stability and QoS, provided that the system is not stretched beyond its bandwidth capacity, while the latter is scalable with small bandwidth and management cost. In this paper, we propose a P2P live streaming architecture in which by adapting dynamically the playback rate we guarantee that peers receive the stream even in cases where the total upload bandwidth changes very abruptly. In order to achieve this we develop a scalable mechanism that by probing only a small subset of peers monitors dynamically the total available bandwidth resources and a playback rate control mechanism that dynamically adapts playback rate to the aforementioned resources. We model analytically the relationship between the playback rate and the available bandwidth resources by using difference equations and in this way we are able to apply a control theoretical approach. We also quantify monitoring inaccuracies and dynamic bandwidth changes and we calculate dynamically, as a function of these, the maximum playback rate for which the proposed system able to guarantee the uninterrupted and complete distribution of the stream. Finally, we evaluate the control strategy and the theoretical model in a packet level simulator of a complete P2P live streaming system that we designed in OPNET Modeler. Our evaluation results show the uninterrupted and complete stream delivery (every peer receives more than 99 % of video blocks in every scenario) even in very adverse bandwidth changes.     

Accelerated corrosion exposure in ultra thin sheets of 2024 aircraft aluminium alloy for GLARE applications

The effect of corrosion exposure on ultra thin (t < 0.4 mm) 2024-T3 aluminium sheet thickness is investigated. Microstructural analysis showed that for low accelerated corrosion exposure times, no surface deterioration existed and hence corresponding mechanical properties degradation was assumed to be incited by hydrogen diffusion and subsequent embrittlement. Medium exposure times resulted in cross-section reduction due to formation of sub-surface corrosion products, while crevice corrosion was evident for higher exposure times. Tensile specimens were pre-corroded for single or double sides and then mechanically tested. Decrease in mechanical properties was noticed for both L and T sheet rolling directions, even after a few minutes exposure, with transverse rolling direction having higher degradation values for same exposure times. It was noticed that a single sided corroded specimen needs approximately double exposure time to reach the same ductility decrease of a double sided specimen. Quantitative tensile properties degradation results are discussed; the results were correlated to observed corrosion degradation mechanisms. The stepwise ductile-to-brittle transition of tensile fracture mechanism with increasing corrosion exposure time was denoted via analysis of the ‘un-corroded’ region of tensile fracture surface. Single sided specimens exhibited quasi-cleavage fracture surfaces at the region below protected surface to corrosion.     

Interconnection of geographically distributed wireless mesh testbeds: Resource sharing on a large scale

Creating large scale testbeds for evaluating wireless mesh technologies and protocols, and for testing their ability to support real world applications in realistic environments, is a crucial step towards the ultimate success of the WMN paradigm. In this paper we suggest the hierarchical federation of a planetary scale infrastructure, such as PlanetLab, with a number of local OMF-based wireless testbeds as a viable approach towards this goal. Along such direction, we present an architectural model for integrating at the technical level these two kinds of infrastructures and our initial implementation of such a model. We also present some test case experiments we run on our initial implementation of the integrated architecture, to illustrate how an experiment on peer-to-peer traffic optimization can be executed by combining both wireless nodes of a OMF-based testbed and PlanetLab nodes located across Europe. The possibility of running this kind of experiments in such a hybrid experimental scenario highlighted several real-world issues that are worth to be further investigated.     

A structured autopsy-based audit of 370 firearm fatalities: Contribution to inform policy decisions and the probability of the injured arriving alive at a hospital and receiving definitive care

The objectives of this autopsy-based audit of firearm-related fatalities were to acquire data to inform policy decisions and to assess the probability of the injured arriving alive at a hospital and receiving definitive care.     

Effect of chromium(VI) on bacterial kinetics of heterotrophic biomass of activated sludge

The effect of hexavalent chromium, Cr(VI), on the maximum specific growth rate, mu(m) and biomass yield, Y(H), of heterotrophic biomass was studied in batch tests conducted under high (= 10) and low (= 1.5) substrate-to-biomass ratios (S0/X0). The effects of sludge age and biomass acclimatization to Cr(VI) on the bacterial kinetics were also studied. The mu(m) values were determined by measuring oxygen uptake rate (OUR) and volatile suspended solids (VSS) increase. Cr(VI) concentrations equal or greater than 10 mg l(-1) inhibited the growth of unacclimatized activated sludge and caused a significant decrease in mu(m) and Y(H) values. The acclimatization of biomass and the selection of a high operating sludge age reduced the inhibitory effect of Cr(VI). At a sludge age of 20 days, Cr(VI) concentrations of <10 mg l(-1) stimulated bacterial growth as evidenced by an increase in both the mu(m) and Y(H) values. Determining mu(m) values by OUR and VSS methods, revealed that the presence of Cr(VI) in unacclimatized biomass caused an inhibitory effect mostly on substrate oxidation, while in acclimatized biomass, anabolic pathways were inhibited more.