‘Long autonomy or long delay?’ The importance of domain in opinion mining

Nowadays, people do not only navigate the web, but they also contribute contents to the Internet. Among other things, they write their thoughts and opinions in review sites, forums, social networks, blogs and other websites. These opinions constitute a valuable resource for businesses, governments and consumers. In the last years, some researchers have proposed opinion extraction systems, mostly domain-independent ones, to automatically extract structured representations of opinions contained in those texts. In this work, we tackle this task in a domain-oriented approach, defining a set of domain-specific resources which capture valuable knowledge about how people express opinions on a given domain. These resources are automatically induced from a set of annotated documents. Some experiments were carried out on three different domains (user-generated reviews of headphones, hotels and cars), comparing our approach to other state-of-the-art, domain-independent techniques. The results confirm the importance of the domain in order to build accurate opinion extraction systems. Some experiments on the influence of the dataset size and an example of aggregation and visualization of the extracted opinions are also shown.     

Models and emerging trends of concurrent constraint programming

Concurrent Constraint Programming (CCP) has been used over the last two decades as an elegant and expressive model for concurrent systems. It models systems of agents communicating by posting and querying partial information, represented as constraints over the variables of the system. This covers a vast variety of systems as those arising in biological phenomena, reactive systems, net-centric computing and the advent of social networks and cloud computing. In this paper we survey the main applications, developments and current trends of CCP.     

Analysis of the gate current as a suitable indicator for FET degradation under nonlinear dynamic regime

Electron device degradation, although not directly accounted for, represents a key issue in microwave circuit design. This is especially true when the particular applications involved (e.g., satellite, military, consumer) do not allow or strongly discourage any kind of maintenance. As a matter of fact, in order to account for device degradation in circuit design, a suitable electron device model is needed which is able to predict the performance degradation as a function of the actual electrical regime involved in the device operation. Such a kind of model is not available in literature. In this paper, quantitative results are provided for device degradation indicators which correlate DC and RF stress experiments. These results can be considered an important step toward the definition of a nonlinear model accounting for device degradation.     

Three-dimensional effects induced by FRP-from-masonry delamination

In this study, delamination of a perfectly-adherent FRP reinforcement from a masonry pillar is investigated by means of a fully three-dimensional finite element model. It is shown that the width of the FRP reinforcement governs the propagation of damage through the brick bulk starting from the anchorage of the strip, and influences significantly the overall response in terms of peak strength, ductility and fracture energy. The resulting failure mechanisms are specified. A critical comparison with formulae provided by Italian design code is also provided, for which mechanically-based improvements are suggested, taking into account three-dimensional effects.     

Variable-gain up-converter with current reuse for 5-GHz WLAN applications

A variable-gain up-conversion mixer for 5-GHz WLAN applications is presented, whose input stage is based on a novel variable gain transconductor. The proposed topology features reduced power consumption by exploiting dc current reuse for mixer biasing. Moreover, a new low-consumption control circuit is introduced, which achieves a temperature-stable and linear-in-dB characteristic, providing a 40-dB dynamic range within ±1 dB gain error.     

Analysis of supercritical carbon dioxide extracts from cones and leaves of a Humulus lupulus L cultivar

Extracts obtained by supercritical carbon dioxide extraction of cones and leaves of hop (Humulus lupulus L) at different combinations of temperature and pressure were analysed for their α- and β-acids and volatiles, using HPLC and GC respectively. The yield and composition of the mixtures of bitter compounds from the cones were largely influenced by the temperature and pressure applied during the extraction. Bitter compounds could not be detected in the extracts from the leaves. The most important volatile components identified were β-myrcene, β-caryophyllene and α-humulene. The extraction parameters also influenced the composition of the mixture of volatiles from the cones and leaves, 40°C and 20.0 MPa being optimum for the extraction of both bitter compounds and volatiles, which are thought to be important for the aroma of beer.     

Biological tissue characterization by magnetic induction spectroscopy (MIS): requirements and limitations

Magnetic induction spectroscopy (MIS) aims at the contactless measurement of the passive electrical properties (PEP) sigma, epsilon, and mu of biological tissues via magnetic fields at multiple frequencies. Whereas previous publications focus on either the conductive or the magnetic aspect of inductive measurements, this article provides a synthesis of both concepts by discussing two different applications with the same measurement system: 1) monitoring of brain edema and 2) the estimation of hepatic iron stores in certain pathologies. We derived the equations to estimate the sensitivity of MIS as a function of the PEP of biological objects. The system requirements and possible systematic errors are analyzed for a MIS-channel using a planar gradiometer (PGRAD) as detector. We studied 4 important error sources: 1) moving conductors near the PGRAD; 2) thermal drifts of the PGRAD-parameters; 3) lateral displacements of the PGRAD; and 4) phase drifts in the receiver. All errors were compared with the desirable resolution. All errors affect the detected imaginary part (mainly related to sigma) of the measured complex field much less than the real part (mainly related to epsilon and mu). Hence, the presented technique renders possible the resolution of (patho-) physiological changes of the electrical conductivity when applying highly resolving hardware and elaborate signal processing. Changes of the magnetic permeability and permittivity in biological tissues are more complicated to deal with and may require chopping techniques, e.g., periodic movement of the object.     

Design methodology for the optimization of transformer-loaded RF circuits

In this paper, a design methodology for the optimization of transformer-loaded RF circuits is presented. The optimization procedure is based on a novel figure of merit for the integrated transformer (namely the transformer characteristic resistance), which was introduced to quantify its performance when operated as a tuned load. Using the proposed approach, a highly linear up-converter for 5-GHz wireless LAN applications was implemented in a 45-GHz-f/sub T/ SiGe HBT technology. The circuit achieved an output 1-dB compression point of 4.5 dBm and a power gain of 18 dB, while drawing only 34 mA from a 3-V power supply.