João Ferreira

Institute for Systems and Computer Engineering, Technology and Science (INESC TEC) | INESC TEC · CAP – Centre for Applied Photonics

The combustion of coal wastes resulting from mining is of particular environmental concern, and the importance of proper management involving real-time assessment of their status and identification of probable evolution scenarios is recognized. Continuous monitoring of the combustion temperature and emission levels of certain gases allows for the p...

This volume represents a compendium of research conducted by international scholars who participated in the 2nd Symposium on Advances in Geospatial held during “The 5th International Conference on Medical Geology” in Arlington, Virginia, USA, in 2013. The research topics dealt with here mainly focus on the new scientific field of medical geology us...

O Círculo Meridiano de Espelho (C.M.E.) é um instrumento que permite determinar a Hora, ao centésimo de segundo, através da observação astronómica. Trata-se de um instrumento que foi construído nos anos cinquenta no Observatório Astronómico da Universidade do Porto (Faculdade de Ciências) e que funcionou até meados dos anos oitenta, altura em que f...

It is presented an optical fiber sensing system projected to operate in the demanding conditions associated with coal waste piles in combustion. Distributed temperature measurement and spot gas sensing are requirements for such a system. A field prototype has been installed and is continuously gathering data, which will input a geological model of...

An ammonia sensing system based on the Wavelength Modulation Spectroscopy (WMS) principle is presented. This system uses a laser diode with an emission wavelength at 1512.21 nm, where ammonia (NH3) has a strong absorption line. Two multi-pass cells based on free space light propagation with 160 and 16 cm of optical path length were used, allowing r...

A sensing system in the near infrared region has been developed for ammonia sensing based on the wavelength modulation spectroscopy (WMS) principle. The WMS is a rather sensitive technique for detecting atomic/molecular species, presenting the advantage that it can be used in the near-infrared region by using the optical telecommunications technolo...

Coal has been for centuries a central energy source to fulfill industrial and domestic needs. Its large scale extraction produced huge amount of debris that were piled in the neighboring of the mines, quite often going into combustion triggered by events like forest fires or lightning. When in this state it can continue for years, releasing substan...

Despite the socio-economic importance of mining in Douro Coalfield, the coal exploitation and utilization originated impacts on the environment. From these stands out the S. Pedro da Cova waste pile which is self-burning since 2005. The potential environmental impacts associated with this coal waste pile include: air pollution caused by the gaseous...

We present a new and versatile sensor platform to readout the response of sensitive colorimetric films. The platform is fully self-contained and based on a switched dual-wavelength scheme. After filtering and signal processing, the system is able to provide self-referenced measures of color intensity changes in the film, while being immune to noise...

An experimental setup has been developed for different gas species sensing based on the Wavelength Modulation Spectroscopy (WMS) principle. The target is the measurement of ammonia, carbon dioxide and methane concentrations. The WMS is a rather sensitive technique for detecting atomic/molecular species presenting the advantage that it can be used i...

The combustion of coal wastes resulting from mining is of particular environmental concern and therefore the importance of the proper management involving real-time assessment of their status and identification of probable evolution scenarios is recognized. Continuous monitoring of combustion temperature and emission levels of certain gases opens t...

The pressure measured in the intervertebral discs is a response to the loads acting on the spine. External loads, such as the reaction forces resulting from locomotion, manual handling and collisions are probably the most relevant in studying spine trauma. However, the physiological functions such as breathing and hearth rate also participate in su...

The purpose of the present study was to measure the intradiscal pressure signal of an anesthetized sheep under spontaneous breathing. An ultra-miniature fiber optic high-pressure sensor was implanted into the nucleus pulposus of the fifth lumbar intervertebral using a dorsolateral transforaminal approach. Results suggested the periodicity of the in...

In this paper, we demonstrate the interrogation of fiber optic intensity sensors by using the combination of the frequency-modulated continuous wave concept with the spectral selective reflectivity of fiber Bragg gratings. Thus, we multiplex these kinds of sensors with this technique having simultaneously a referenced system. The basis of this dual...

In this work, an innovative fully integrated monitoring infrastructure based on optical fibre sensors was developed and implemented. In the framework of the research project named PROTEU [Tecnologias Avançadas para a Monitorização de Sistemas Estuarinos e Costeiros (PDCTM/P/MAR/15275/1999)], an 11km optical fibre cable with Bragg sensors each 500m...

We report on the use of a frequency-reflectometry domain technique for referencing optical intensity sensors located between two fibre Bragg gratings. The experiment combines the concept of frequency modulated continuous wave with the spectrally selective mirror proper-ties of fibre Bragg gratings to interrogate with referencing properties intensit...

In recent years the need to monitor different parameters has led to the development of several architectures able to make real time, un-attended measurements. Particularly in regard to environmental issues, it is very important that the equipment and measuring systems be small and light to avoid maximum interference of the ecosystems Studied. In th...

In recent years the need to monitor different parameters has led to the development of several architectures able to make real time, un-attended measurements. Particularly in regard to environmental issues, it is very important that the equipment and measuring systems be small and light to avoid maximum interference of the ecosystems studied. In th...

A new technique is described for the extraction of the intrinsic semiconductor parameters from intermodulation measurement of composite second-order (CSO) and composite third-order (CTB) distortion products. The effect of the parasitics elements are eliminated, by taking the distortion measurements at constant optical modulation depth, which enable...