Automatic EEG signal classification for epilepsy diagnosis with Relevance Vector Machines

In this paper, we investigate the potentials of applying a kernel-based learning machine, the Relevance Vector Machine (RVM), to the task of epilepsy detection through automatic electroencephalogram (EEG) signal classification. For this purpose, some experiments have been conducted over publicly available data, contrasting the performance levels exhibited by RVM models with those achieved with Support Vector Machines (SVMs), both in terms of predictive accuracy and sensitivity to the choice of the kernel function. Four settings of both types of kernel machine were considered in this study, which vary in accord with the type of input data they receive, either raw EEG signal or some statistical features extracted from the wavelet-transformed data. The empirical results indicate that: (1) in terms of accuracy, the best-calibrated RVM models have shown very satisfactory performance levels, which are rather comparable to those of SVMs; (2) an increase of accuracy is sometimes accompanied by loss of sparseness in the resulting RVM models; (3) both types of machines present similar sensitivity profiles to the kernel functions considered, having some kernel parameter values clearly associated with better accuracy rate; (4) when not making use of a feature extraction technique, the choice of the kernel function seems to be very relevant for significantly leveraging the performance of RVMs; and (5) when making use of derived features, the choice of the feature extraction technique seems to be an important factor to one take into account.     

Modeling and Prediction of Shell-Side Fouling in Shell-and-Tube Heat Exchangers

Fouling is a challenging, longstanding, and costly problem affecting a variety of heat transfer applications in industry. Mathematical models that aim at capturing and predicting fouling trends in shell-and-tube heat exchangers typically focus on fouling inside the tubes, while fouling on the shell side has generally been neglected. However, fouling deposition on the shell side may be significant in practice, impairing heat transfer, increasing pressure drops, and modifying flow paths. In this paper, a new model formulation is presented that enables capturing fouling on the shell side of shell-and-tube heat exchangers including the effect of occlusion of the shell-side clearances. It is demonstrated by means of an industrial case study in a crude oil refinery application. The model, implemented in an advanced simulation environment, is fitted to plant data. It is shown to capture the complex thermal and hydraulic interactions between fouling growth inside and outside of the tubes, the effect of fouling on the occlusion of the shell-side construction clearances, and to unveil the impact on shell-side flow patterns, heat transfer coefficient, pressure drops, and overall exchanger performance. The model is shown to predict the fouling behavior in a seamless dynamic simulation of both deposition and cleaning operations, with excellent results.     

A Mechanistic Study on Alcohol Oxidations with Oxygen Catalysed by TPAP‐Doped Ormosils in Supercritical Carbon Dioxide

The heterogeneous oxidation of various alcohols with oxygen catalysed by TPAP‐doped ormosils in scCO₂ at 75 °C and 22.0 MPa has been studied in detail. Sol‐gel segregation of TPAP into the inner porosity of an organically modified silica (ormosil) xerogel along with the use of a reaction medium which does not dissolve the catalyst, prevents aggregation of oxidation‐inactive ruthenium derivatives without the need of chemical tethering. Thus, at least 140 TONs may be obtained in the oxidation of primary alcohols with the formation of aldehydes as sole reaction products. Investigation of the oxidation mechanism shows that the catalytic process exhibits a first‐order dependence on the amount of catalyst, a fractional order on the alcohol concentration and a negative order for oxygen pressures higher than 0.2 bar. Evidence is presented for an associative oxidation mechanism simultaneously involving TPAP, organic substrate and oxygen.     

Steady change: the 200 largest US manufacturing firms throughout the 20th century

This paper discusses the existence of structural change in businessactivity and technological competence among the 200 largestUS manufacturing companies throughout the 20th century. Thedata were taken from Chandler (Scale and Scope, 1990) and Fortunemagazine. The analysis of corporate evolution in used to assesscontinuity versus turbulence of business organizations in thecontext of the neo-Schumpeterian long-wave hypothesis. The empiricalresults show that the giants of the late 20th century are notthe same as those at the beginning of that period. Persistencein the sample is very limited. Moreover, turbulence is not smooth,but rather occurs by impulses that affect specific industries,and it has increased over time. Overall, the pattern of corporateentry and industry development is very indicative of the newopportunities emerging with information and communication technologies.This process of open-ended continuous transformation supportsthe case for putting change at the centre of economic analysis.     

Timed high-level nets

Petri nets have been widely used for modeling and analyzing concurrent systems. Several reasons contribute to their success: the simplicity of the model, the immediate graphical representation, the easy modeling of asynchronous aspects, the possibility of reasoning about important properties such as reachability, liveness, boundedness. However, the original model fails in representing two important features: complex functional aspects, such as conditions which rule the flow of control, and time. Due to that, two different classes of extensions of Petri nets have been proposed: high-level nets and timed Petri nets. High-level nets allow the representation of functional aspects in full details, but do not provide a means for representing time; on the other hand, timed Petri nets have been thought for time representation, but they do not provide a means for representing detailed functinal aspects. Thus, these two important aspects cannot be mastered together. In particular, it is difficult to express relationships between time and functional aspects.This paper investigates the relationships between high-level nets and timed Petri nets, thus extending a first set of results published in a previous paper, where a unifying Petri net based model for time representation has been proposed. It first recalls how time can be represented in a Petri net extension called ER nets, and assesses its generality. It then investigates the relationships of ER nets with the best known high-level nets. In particular it shows the overall equivalence of ER nets, Colored Petri nets and Predicate/Transition nets, and extends the mechanism for time representation introduced in ER nets to both Colored Petri nets and Predicate/Transition nets. It also shows that these models cannot be simplified without significantly constraining the timing aspects that can be modeled.     

Mechanical and leakage behaviour of the dentin – adhesive interface

Dentine bonding systems (DBS) have been developed in order to bond restorative materials (i.e. composite) to the inner walls of the tissues when function and integrity as to be restored. Adhesion to dentine results from the penetration of DBS into the demineralised substrate constituted by a swollen collagen network. The short-term stability of a restored tooth is mainly affected by the presence of defects which act as stress raiser, while the long-term stability of a restored tooth is mainly affected by the seal of the restorative material on the dental structures. In order to determine the properties of the material interface, bonding to dentine is analysed using micro-tensile static and dynamic tests, assisted by the finite element modelling (FEM) and by the X-ray computed microtomography (micro-CT). The effect of voids and porosity in the composite layer of the DBS on the stress distribution has been investigated. Tensile adhesive strength for a particular DBS was measured on cylindrical specimens. The dual energy absorption technique, with the synchrotron beam light, has been developed to investigate, in a non-destructive manner, the leakage at the dentine-DBS interface of a silver nitrate staining solution as a function of mechanical cycling. The results indicate that leakage occurs radially through the dentine-adhesive interface and is influenced by the porosity in the adhesive and composite layers.     

2D residual generation and dead-beat observers

In this paper we consider the 2D residual generation problem in an algebraic context. An algorithmic method that provides a complete family of residual generators is presented and some connections between 2D residual generation and 2D dead-beat observer synthesis are investigated.     

Symbolic execution of concurrent systems using Petri nets

Techniques for analyzing sequential programs in order to improve their reliability have been widely studied in the past. Among the most interesting analysis techniques, we consider symbolic execution. However, analysis techniques for concurrent programs, and in particular symbolic execution, are still an open research area. In this paper, we define a method for symbolic execution of concurrent systems, based on an extension of the Petri net formalism, called EF nets. EF nets are a powerful, highly expressive and general formalism. Depending on the level of abstraction of actions and predicates that one associates to the transitions of the net, EF nets can be used as a high-level specification formalism for concurrent systems, or as a lower level internal representation of concurrent programs. Thus, the model is not dependent on a particular concurrent programming language, but it is flexible enough to be the kernel model for the representation of a wide set of systems and programming languages. In the paper, in order to support the analysis of a concurrent system or program, at first a general algorithm for symbolically executing an EF net is defined. Then, a more efficient algorithm is given for the particular, though important, subclass of EF nets, defined as safe EF nets. Such algorithm is proved to significantly help in reducing the amount of information needed to characterize a symbolic execution. Both the modelling power of the EF nets and the usefulness of the concurrent symbolic execution algorithms defined are illustrated by means of a case study.