On the electrospinning of PVDF: influence of the experimental conditions on the nanofiber properties

The characteristics of poly(vinylidene fluoride) (PVDF) nanofibers, prepared by applying the electrospinning technique from N,N‐dimethylformamide/acetone mixtures, were studied by varying the experimental conditions. The nanofiber morphology was assessed by scanning electron microscopy, while wide angle X‐ray diffraction and infrared spectroscopy were performed to study the crystallinity. The influence of the electrospinning conditions, such as kind of solvent mixture, polymer concentration, voltage tension, airflow and humidity, on nanofiber morphology was studied. In particular, the latter parameter, generally not considered, was found to modify the electrospun mat structure in a relevant way. Generally, the above technique turns out to be capable of strongly affecting the polymorphism of the polymer, namely β phase formation was higher in the electrospun mats compared with cast films, which displayed a non‐polar α crystal phase. As far as the influence of the electrospinning conditions on PVDF crystal structure is concerned, modification of the experimental parameters did not affect the α/β ratio. Nevertheless, comparing the behavior of two commercial PVDF samples with similar molecular masses, our results show that the polymer which forms a higher content of β phase in its cast films allowed electrospun mats characterized by almost complete formation of β phase to be obtained. Copyright © 2012 Society of Chemical Industry     

Predicting time series of railway speed restrictions with time-dependent machine learning techniques

In this paper, a hybrid approach to combine conditional restricted Boltzmann machines (CRBM) and echo state networks (ESN) for binary time series prediction is proposed. Both methods have demonstrated their ability to extract complex dynamic patterns from time-dependent data in several applications and benchmark studies. To the authors’ knowledge, it is the first time that the proposed combination of algorithms is applied for reliability prediction.The proposed approach is verified on a case study predicting the occurrence of railway operation disruptions based on discrete-event data, which is represented by a binary time series. The case study concerns speed restrictions affecting railway operations, caused by failures of tilting systems of railway vehicles. The overall prediction accuracy of the algorithm is 99.93%; the prediction accuracy for occurrence of speed restrictions within the foresight period is 98% (which corresponds to the sensitivity of the algorithm). The prediction results of the case study are compared to the prediction with a MLP trained with a Newton conjugate gradient algorithm. The proposed approach proves to be superior to MLP.     

Exploring free-energy profiles through ion channels: Comparison on a test case

The calculation of free-energy profiles in proteins, and, more specifically, in ion channels, is a challenge for modern numerical simulations due both to the convergence problems associated with the electrostatics of the environment and to the difficulties in modeling the fields acting on the permeating ions. The present study is aims at comparing three different simulation techniques available in the literature on a nanometric channel protein chosen as a test case, with the purpose of establishing their real predictivity and limits.     

Comparison of two sealing coupling geometries for a direct fuel injector

The present paper describes some Finite Elements simulations carried out in order to investigate the contact problem in the sealing region of a direct fuel injector. In particular two different design solutions have been analyzed, both patent pending, one characterized by a conformal contact of two conic surfaces and the other one by a non-conformal contact between a cone and a sphere. Pressure distribution, contact width and von Mises equivalent stress have been calculated and employed as comparison parameters. Two different loading conditions have been considered: nominal loads and nominal loads plus undesired effects. Also deviations from the nominal geometry, obtained from profile detection of 40 samples, have been introduced for considering a real-like case. Numerical results stress the robustness of the non-conformal solution with respect to geometrical tolerances and real loading conditions.     

Shoot cuttings propagation of giant reed (Arundo donax L.) in water and moist soil: The path forward?

Giant reed (Arundo donax L.) is a perennial rhizomatous grass that can be regarded as an ideal crop for bioenergy production, owing to several intrinsic characteristics. Despite to the promising yield results obtained in many plot experiments, the cultivation of giant reed at field scale is still a challenge. Owing to the floral sterility of the species, rhizome propagation has been predominantly used to establish field plots experiments, although this method is unpractical and monetarily expensive. Giant reed is a hydrophytic plant that typically spread in riparian systems by flood-mediated fragmentation and dispersal of vegetative propagules. Since giant reed propagation is strictly dependent on temporary abundance of water, this plant characteristic might be exploited for fostering the diffusion of giant reed as a bioenergy field crop. The objectives of this paper were: i) to disseminate some techniques for shoot cutting propagation of giant reed in water and in moist soil; ii) to address the critical points that remain to be solved for a widespread diffusion of this species as a bioenergy field crop.     

A Framework for Engineering Interactions in Java-based Component Systems

This paper describes a Java-based framework for the development of component-based software systems supporting the specification of the logic of component interactions as a first-class aspect. Java is used as the reference development language.On the one side, the framework makes it possible to specify the logic of interaction at the component-level, in terms of input and output interfaces, the events generated and observed by a component, and related information about the management of the control flow. On the other side, it is possible to specify the logic of interaction at the inter-component level, providing a modelling and linguistic support for designing and (dynamically) programming the glue among the components, enabling general forms of observation, control and construction of the interaction space.As a result, the framework supports the coordination of components at different levels: from interoperability among heterogeneous and unknown components, to the support for dynamic introduction, removal and update of components, to general coordination patterns, such as workflow. The framework adopts first-order logic as the reference computational model for describing and defining the logic of interaction: the modalities adopted by components to interact, the coordination laws gluing the components and the interaction events occurring in the system are expressed as facts and rules. They compose the (evolving) logic theories describing and defining the interaction at the system level, and can be observed and controlled at runtime to allow dynamic re-configurability.     

Characterization of the loss allocation techniques for radial systems with distributed generation

In the restructured electricity industry, meaningful loss allocation methods are required in order to send correct signals to the market taking into account the location and characteristics of loads and generations, including the local sources forming the distributed generation (DG). This paper addresses the issues related to loss allocation in radial distribution systems with DG, with a three-fold focus. First, the key differences in the formulation of the loss allocation problem for radial distribution systems with respect to transmission systems are discussed, specifying the modeling and computational issues concerning the treatment of the slack node in radial distribution systems. Then, the characteristics of derivative-based and circuit-based loss allocation techniques are presented and compared, illustrating the arrangements used for adapting the various techniques to be applied to radial distribution systems with DG. Finally, the effects of introducing voltage-controllable local generation on the calculation of the loss allocation coefficients are discussed, proposing the adoption of a “reduced” representation of the system capable of taking into proper account the characteristics of the nodes containing voltage-controllable DG units. Numerical results are provided to show the time evolution of the loss allocation coefficients for distribution systems with variable load and local generation patterns.     

Reliable and efficient forwarding in ad hoc networks

This paper focuses on packet forwarding in ad hoc networks and proposes a new approach to improve performance of nodes communication. In particular, we present a lightweight mechanism for REliable and Efficient Forwarding (REEF), which mitigates the effects of adverse situations caused by cooperation misbehavior or network fault conditions. It exploits nodes’ local knowledge to estimates route reliability, and multi-path routing to forward packets on the most reliable route. REEF becomes also a security mechanism in case of a security association established between the communication parties. This additional feature makes the mechanism robust, guaranteeing trustworthiness of the reliability estimator and security of data transmission.A new approach to cooperation enforcing is also proposed. The classical method denies service to misbehaving nodes by, for example, not serving their forwarding requests. We approach the problem less drastically, differentiating the quality of service provided to nodes according to their behavior. In other words, traffic of misbehaving nodes will flow through the network slower than that one of reliable nodes.