2013
Authors
Romeira, B; Pessoa, LM; Salgado, HM; Ironside, CN; Figueiredo, JML;
Publication
SENSORS
Abstract
We report on photo-detectors consisting of an optical waveguide that incorporates a resonant tunneling diode (RTD). Operating at wavelengths around 1.55 m in the optical communications C band we achieve maximum sensitivities of around 0.29 A/W which is dependent on the bias voltage. This is due to the nature of RTD nonlinear current-voltage characteristic that has a negative differential resistance (NDR) region. The resonant tunneling diode photo-detector (RTD-PD) can be operated in either non-oscillating or oscillating regimes depending on the bias voltage quiescent point. The oscillating regime is apparent when the RTD-PD is biased in the NDR region giving rise to electrical gain and microwave self-sustained oscillations Taking advantage of the RTD's NDR distinctive characteristics, we demonstrate efficient detection of gigahertz (GHz) modulated optical carriers and optical control of a RTD GHz oscillator. RTD-PD based devices can have applications in generation and optical control of GHz low-phase noise oscillators, clock recovery systems, and fiber optic enabled radio frequency communication systems.
2013
Authors
Veiga, G; Silva, C; Araújo, R; Pires, N; Siciliano, B;
Publication
EXPERT SYSTEMS WITH APPLICATIONS
Abstract
This paper investigates the research profiles, collaboration patterns and research topic trends which can be identified in the proposals submitted to the ECHORD (European Clearing House for Open Robotics Development) FP7 project. On a country level, clusters were identified and characterized by patterns of proposal production per inhabitant, score and international cooperation. Belgium and Sweden constitute a cluster characterized by high proposal production, with very high scores and extensive international collaboration. Belgium also excels from another cluster analysis, being as the only country where 100% of proposals involve industry-academia cooperation and obtain scores above 10. Other findings show that single partner proposals have significantly lower quality than multi-partner proposals but, on the other hand, the number of countries involved shows no influence on the quality of the proposals. Despite the high number of industrial participants present on the proposals, it is observed that they play secondary roles in the proposals, with a very low number projects leaded by companies. Also, it is observed that partnerships between research institutions (non-universities) are the most successful. Concerning topics of the proposals, the technology human-robot interface and the product vision robot for small-scale manufacturing are the most significant. Finally, the paper shows clusters of institutions extracted from the giant network of relations obtained from the ECHORD set of proposals.
2013
Authors
Carneiro, D; Novais, P; Andrade, F; Zeleznikow, J; Neves, J;
Publication
KNOWLEDGE AND INFORMATION SYSTEMS
Abstract
The growing use of Information Technology in the commercial arena leads to an urgent need to find alternatives to traditional dispute resolution. New tools from fields such as artificial intelligence (AI) should be considered in the process of developing novel online dispute resolution (ODR) platforms, in order to make the ligation process simpler, faster and conform with the new virtual environments. In this work, we describe UMCourt, a project built around two sub-fields of AI research: Multi-agent Systems and Case-Based Reasoning, aimed at fostering the development of tools for ODR. This is then used to accomplish several objectives, from suggesting solutions to new disputes based on the observation of past similar disputes, to the improvement of the negotiation and mediation processes that may follow. The main objective of this work is to develop autonomous tools that can increase the effectiveness of the dispute resolution processes, namely by increasing the amount of meaningful information that is available for the parties.
2013
Authors
Alves, CF; Vicente, EFR;
Publication
Applied Financial Economics
Abstract
Traditionally, the Latin model of corporate governance had been a predominant model in some countries; however, this model is increasingly becoming out of fashion. Using a database of Portuguese and Brazilian firms, we investigated whether the Latin model performs worse than other models (i.e. variants of the Continental and Anglo-Saxon models) in terms of preventing earnings management. We conclude that, in general, companies that adopt the Latin model have lower levels of earnings management than other companies and that switching from the Latin model to another model does not cause a generalized decrease in the level of discretionary accruals. Additionally, firms that move away from the Latin model are not predominantly those with extremely high levels of discretionary accruals. © Taylor & Francis.
2013
Authors
Correia, A; Chiquita, S; Hussain, NS; Pirraco, R; Rosa, CC;
Publication
FIFTH EUROPEAN WORKSHOP ON OPTICAL FIBRE SENSORS
Abstract
High-precision dosimeters are needed in brachytherapy treatments to ensure safe operation and adequate working conditions, to assess the correspondence between treatment planning and dose delivery, as well as to monitor the radiation dose received by patients. In this paper we present the development of a multi-sensor dosimeter platform targeted for brachytherapy environments. The performance of different scintillating materials response is assessed. The emission bands of most common scintillator materials used in ionizing radiation detection are typically below 550 nm, thus they may be prone to stem effect response. To avoid this effect we propose the use of scintillators with longer wavelength emission. Samples of neodymium doped glasses are evaluated as new infrared radioluminescent scintillators for real-time dosimeters, namely lithium lead boron silver (LLB4Ag) and lithium bismuth boron silver (LBiB4Ag) glasses. Their response is compared with the response of organic scintillator BCF-60 with a 530nm response.
2013
Authors
Goncalves, LC; Gonzalez Aguilar, G; Frazao, O; Baptista, JM; Jorge, PAS;
Publication
REVIEW OF SCIENTIFIC INSTRUMENTS
Abstract
In this work the implementation of an optical fiber interferometric system for differential thermal analysis enabling the identification of chemical species is described. The system is based on a white light Mach-Zehnder configuration using pseudo-heterodyne demodulation to interrogate two identical fiber Bragg gratings (FBG) in a differential scheme. System performance is compared using either standard hardware or low cost virtual instrumentation for operation control and signal processing. The operation with the virtual system enabled temperature measurements with a +/-0.023 degrees C resolution nearly matching the performance of the standard hardware. The system ability to discriminate chemical species by differential thermal analysis was demonstrated. Mixed samples of acetone and methanol could be successfully identified, indicating the suitability of the system for high precision measurements using low cost instrumentation. (C) 2013 American Institute of Physics. [http://dx.doi.org/10.1063/1.4774054]
The access to the final selection minute is only available to applicants.
Please check the confirmation e-mail of your application to obtain the access code.