RCAAP Repository

In the present paper the project of an embeddedsolution for the realization of a floating sensor platform for themonitoring of the water and ambient quality in a flowing waterenvironment is described. First results regarding the monitoringof the water conductivity and the ambient noise level underharsh environmental conditions in a karstic river and in the finalpart of a river going towards the Mediterranean Sea arepresented. It is further discussed how this kind of system can bemodified in order to serve as urban waterway multisensoryplatform, adding important features like connectivity, energyharvesting and determination of the platform position. 

Traffic collisions, in particular high speed car accidents often result in huge damages, long traffic queues and loss of human lives. In this work we present an intelligent modular system that monitors traffic in highways and alerts drivers of sudden stops, in poor visual conditions. The system is composed of several identical modules, to be placed in the middle of a highway’s lane, that sense the lights and communicate their presence and velocity to their neighbor modules via RF. With such information, the nearby modules estimate the velocity of the passing cars. When the module ahead detects a car passing at a much slower speed than what was previously estimated, it alerts the other modules, so they produce a visual indication for the oncoming drivers, preventing accidents. The system operates autonomously using solar energy harvesting.

The relay solution in planning of mobile networks, has the aim of increasing the network coverage and/or capacity. According to the open literature, this technique will be highly used in the next Long Term Evolution (LTE) Networks. The Relay Station (RS) performance varies with its position in the cell, with the radio conditions to which RSs and User Equipments (UEs) are subjected and with the RS capacity to receive, process and forward the information. The aim of this paper is to compare the performance of the Layer 1 (L1) and Layer 3 (L3) RS types, and to determine the ideal position in which a RS should be placed, with the aim of maximizing the UE throughput.

Hydrogenated amorphous silicon thin film transistors have been used as switching elements in liquid crystal displays and large area matrix addressed sensor arrays. Later, these devices have also been used as analogue active elements in organic light emitting diode displays. However, this technology suffers from bias induced meta-stability. This issue introduces both threshold voltage and subthreshold slope shifts over time when gate bias is applied. Such instabilities jeopardize long term performance of circuits that rely on these components. Nevertheless, hydrogenated amorphous silicon thin film transistors present an exponential transfer characteristic when operating on subthreshold region and their typical power consumption is under 1 µW. This low power characteristic makes these devices ideally suited for low power electronic design.This work demonstrates, through transient analysis of a well-established simulation model for hydrogenated amorphous silicon, the viability of thin film transistors technology to perform both analogue and digital functions. Hence, these structures may be used in both application fields. To this end, two different sets of analyses have been conducted with hydrogenated amorphous silicon based thin film transistors. The first set considers a driving circuit for an active matrix of organic light emitting diodes, biased in a way to minimize the “memory effect” (increasing shift on threshold voltage) due to long term operation. The second set of analyses were conducted upon the implementation of complementary output universal gates, namely NOR/OR and XNOR/XOR elements.

In order to assess the potential of low-cost radio-over-fiber (RoF) solutions, in this paper we make a comparison of three full-duplex RoF systems. These systems are low-cost solutions that use remote modulation, with a single centralized light source used at the central station to generate a downlink wavelength that is reused at the remote location for upstream transmission. By avoiding the need for an additional light source at each remote location the cost of the solution is significantly reduced. The three systems evaluated in this paper differ by the type of optical modulation used for downlink and uplink. The first is an IM-IM system using intensity-modulation (IM) for the downlink and uplink direction. The second scheme, PM-IM, differs from the first by using phase-modulation (PM) for downlink. Finally, the third system, PM-PM, uses phase modulation for downlink and uplink.

Stochastic Computing has emerged as a competitive computing paradigm that produces fast and simple implementations of arithmetic operations, while offering high levels of parallelism, and graceful degradation of the results when in the presence of errors. IoT devices are often operate under limited power and area constraints and subjected to harsh environments, for which, traditional computing paradigms struggle to provide high availability and fault-tolerance. Stochastic Computing is based on the computation of pseudo-random sequences of bits, hence requiring only a single bit per signal, rather than a data-bus. Notwithstanding, we haven’t witnessed its inclusion in custom computing systems. In this direction, this work presents Stochastic Theater, a framework to specify, simulate, and test Stochastic Datapaths to perform computations using stochastic bitstreams targeting IoT systems. In virtue of the granularity of the bitstreams, the bit-level specification of circuits, high-performance characteristics and reconfigurable capabilities, FPGAs were adopted to implement and test such systems. The proposed framework creates Stochastic Machines from a set of user defined arithmetic expressions, and then tests them with the corresponding input values and specific fault injection patterns. Besides the support to create autonomous Stochastic Computing systems, the presented framework also provides generation of stochastic units, being able to produce estimates on performance, resources and power. A demonstration is presented targeting KLT, typical method for data compression in IoT applications.

Lead (Pb) is a toxic metal, which widespread use has resulted in environmental contamination, human exposure and significant public health problems. The autonomic nervous system, being a homeostatic controller, is impaired in acute and chronic lead exposure. In fact, sympathoexcitation associated to hypertension and tachypnea has been described together with baroreflex and chemoreflex dysfunction. However, up to date, no studies described the autonomic effects of an intermittent low-level lead exposure. In the present work, we addressed in vivo, autonomic behaviour in rats under chronic Pb exposure (control) and in rats under intermittent Pb exposure. For that, arterial blood pressure (BP) and ECG were recorded in 28 weeks old animal and low frequencies (LF) and high frequencies (HF) were determined (to estimate sympathetic and parasympathetic activities) using FisioSinal software with Wavelet module. Preliminary results: Rats intermittently exposed to lead showed a significant decrease in systolic BP (126 ± 4 vs 144 ± 3 mmHg) with no significant changes in LF, HF and LF/HF bands (1.5 ± 0.3 vs 1.7 ± 0.5 mmHg2, 1.9 ± 0.7 vs 2.8 ± 1.2 bpm2 and 1.2 ± 0.4 vs 1.1 ± 0.3 mmHg2/bpm2, respectively) when compared to chronically Pb exposed rats. Our data suggests that the autonomic dysfunction induced by lead exposure is similar in a chronic and intermittent Pb exposure. Nevertheless, it seems that an intermittent exposure was no effect on systolic BP values.The present study brings new insights on the environmental factors that influence autonomic and cardiovascular systems during development, which can help apprise public policy strategies to prevent and control the adverse effects of Pb toxicity.

This paper presents a baseline system for automatic acoustic scene classification based on the audio signals alone. The proposed method  is derived from classic, content-based, music classification approaches, and consists in a feature extraction phase followed by two dimensionality reduction steps (PCA and LDA) and a classification phase done using a k nearest-neighbors algorithm.This paper also reports on how our system performed  in the context of the DCASE 2016 challenge, for the acoustic scene classification task.

This paper address the implementation of a mixed-domain simulator for first-order band-pass sampling receivers, which is based on an initial frequency-domain signal treatment followed by a time-domain simulation scheme. One of the proposed applications for this type of receivers is to perform the spectrum sensing feature, which is required in actual and future cognitive radio approaches. Some details about the multi-stage modelling strategy will be given focusing in each specific component of the receiver, wherein it is considered a mixed frequency-time signal treatment. Moreover, it will be summarized the main features of the implemented simulator, as well as potential improvements. Finally, several simulation examples obtained with the implemented simulator will be shown, in which are included the impact of a CW signal excitation in a received modulated signal and a multi-carrier signal reception scenario.

The search for materials for hydrogen storage that are able to adsorb and desorb hydrogen molecules has received attention. Nanofibers have been studied because it has some interesting characteristics like high surface to volume ratio and the ease of producing by means of a low-cost setup. Polyacrylonitrile (PAN) has allowed the possibility of obtaining carbon nanofibers from the electrospinning process followed by a thermal treatment; moreover Pd has the capability of store hydrogen and can form a complex with dimethylformamide (DMF) so that, during the preparation of the solution of PAN and PdCl2, both present high solubility in the solvent.  Thus, the results demonstrated that as Pd can form complex with DMF the preparation method of the PAN+PdCl2 solutions influences the interaction between Pd and PAN. The decrease in dispersion viscosity and an unexpected increase in the diameter of the fibers confirm the hypothesis. The FTIRS and XPS analysis confirm that the Pd complexes with DMF by means of bonds to N.

In text classification based on the bag-of-words (BoW) or similar representations, we usually have a large number of features, many of which are irrelevant (or even detrimental) for classification tasks. Recent results show that compressed learning (CL), i.e., learning in a domain of reduced dimensionality obtained by random projections (RP), is possible, and theoretical bounds on the test set error rate have been shown. In this work, we assess the performance of CL, based on RP of BoW representations for text classification. Our experimental results show that CL significantly reduces the number of features and the training time, while simultaneously improving the classification accuracy. Rather than the mild decrease in accuracy upper bounded by the theory, we actually find an increase of accuracy. Our approach is further compared against two techniques, namely the unsupervised random subspaces method and the supervised Fisher index. The CL approach is suited for unsupervised or semi-supervised learning, without any modification, since it does not use the class labels.

Physical devices with different sensors and sampling rates distributed over several unrelated locations need to store their values over time. Applications that need the result of a set of sensors must access their data. A common and simple interface within the physical devices, monitoring stations, to store data on a database is needed; as also a simple and common retrieval interface for any application that only shows the data as it is or processes it into higher levels of significance. BlueLab IoT is a platform with libraries and an interface application to aid that development; a working implementation is provided.

This article reports on a monolithic 10 cm × 10 cm area PV module integrating an array of 72 a-Si:H n-i-p cells on a thin polyethylene-naphtalate substrate. The design optimization and device performance analysis are performed using a two-dimensional distributed circuit model of the photovoltaic cell. Experimental results show that the shunt leakage is one of the factors reducing the device performance. Using the LBIC technique, the multiple micro-shunts in the n‑i‑p cell were detected. The mechanism of electrical shunts formation is proposed and discussed.

In this work, an in-depth analysis concerning the transmission performance of IEEE802.11g/n (Wi-Fi) signals in a WDM-PON system is presented. It is considered that the optical/electrical transceivers are based on low-cost 850 nm VCSELs and PIN photodiodes. System modelling includes the impact of noise generated in the optical path, such as relative intensity noise (RIN), shot noise, photodetector thermal noise, clipping and intermodulation distortion. An analytic analysis based on Volterra series is conducted and mathematical expressions for both the EVM and SNR are derived. The theoretical analysis is also compared with experimental results. Among several conclusions, it is observed that the laser intermodulation distortion, clipping and RIN are the most relevant factors.

This paper presents the manufacturing of amicroelectrode array, on printed circuit boards (PCB) and onsilicon substrate, composed of 60 to 64 gold microelectrodes(between 4 µm and 70 µm each in diameter). The sensor has ameasurement total area of 0.5 cm in radius, one referenceelectrode (1 mm2 in area) and 28.4 mm wide and 28.4 mm long.These microelectrodes were used for checking and logging ofextracelullar local field potential of cell culture and nitritemeasurement in a phosphate buffered saline solution(electrolytical aqueous medium). In addition, an apparatus toshield from electromagnetic interference for connecting thearrays was designed to allow the capture of electrochemicalreactions or electronic signals by the microelectrodes, forexample: nitrite or cardiac potential measurement, respectively.Finally, biocompatibility tests of the array structures wereperformed. The preliminary electrical and biocompatibilitytesting, along with the collected data, has shown promisingresults pointing to the development of an accurate sensor afterthe completion of this study. The sensor has potentially abroader range of applications with only a few adaptations anddue its good accuracy it can be a very useful resource for manychemical and biological applications.

This paper analyses the Alamouti scheme for different antenna configurations and different modulation types,namely BPSK, QPSK and QAM. All configurations were modeled and simulated in MATLAB. A MIMOreceiver for a 21 antenna configuration and BPSK modulation was implemented in a FPGA. The FPGAresults indicate that the Alamouti scheme is a good design option for hardware implementation of a MIMOreceiver. The receiver uses only about 10% of the resources of a medium-sized FPGA and achieves almost300 Msymbols per second.

The emerging concept of smart cities demands for a large number of electronic devices, like sensors and actuators, distributed over several public spaces and buildings. The Internet of Things (IoT) has a key role in connecting devices to the Internet. However, the significant number of devices makes the maintenance task of the entire network difficult and expensive. To mitigate this problem, considerable research efforts have been made to develop energy-aware devices capable of self-sustainable operation, by harvesting their energy from various sources. In this paper, we study the possibility of harvesting energy from the light flowing in the Gigabit Passive Optics Network (GPON) to supply low-power devices. Since most cities already have a working GPON installation, using this installation to interconnect and power IoT devices can be a viable and less expensive solution, instead of installing new dedicated networks. This is also an interesting solution to convey communications and energy to low-power applications where access to the power grid is unfeasible. This study is focused in the 1550 nm wavelength, whose available optical power, in residential premises, is between -7 dBm and +2 dBm. With this range of optical power, and with a 30% efficiency photodiode, we show, for the worst-case scenario of the GPON, how it is possible to harvest 62 µW of energy at the Maximum Power Point (MPP).

This paper presents a new single cell multi-objectiveoptimization algorithm. The objective is to optimize areas oflow coverage and high interference simultaneously, through theadjustment of the antenna tilts and/or antenna orientation. Theprocess is achieved using a specific implementation of a ParticleSwarm Optimization (PSO) algorithm. Both the detection ofsub-optimal performance areas and its subsequent optimizationare supported by Drive Test (DT) data and network topologyinformation. The antenna optimization algorithm was tested withreal data in 3rd Generation (3G)/4th Generation (4G) networks.In this work, a 3G urban scenario is highlighted, achieving anaverage optimization gain of 78%.

This work presents fully automated plasma-enhanced reactive thermal evaporation system (rf-PERTE) that can be used for the deposition of transparent metal oxide films with high reproducibility of their electrical and optical properties. The developed hardware/software platform enables the full control over the critical deposition conditions such as mass flow of oxygen, process pressure, current flowing through crucible and rf-power. For indium oxide films on glass substrates a resistivity of 9×10-4 Ω-cm and a transmittance of 90% in the visible spectral range were achieved without substrate heating. The system is also suitable for the deposition of transparent conducting coatings in a wide range of plastic substrates, for applications in the field of flexible sensors or solar cells. In particular, we have successfully deposited indium oxide on PEN (polyethylene naphthalate) sheets with electrical and optical properties approaching the ones of the films deposited on glass substrates.

In this paper we report the use of a monolithic system that combines the demultiplexing operation with the simultaneous photodetection and self amplification of the signal. The device is a double pi’n/pin a-SiC:H heterostructure with optical gate connections for light triggering in different spectral regions. Results show that when a polychromatic combination of different pulsed channels impinges on the device the output signal has a strong nonlinear dependence on the light absorption profile, (wavelength, bit rate and intensity). This effect is due to the self biasing of the junctions under unbalanced light generation of carriers. Self optical bias amplification under uniform irradiation and transient conditions is achieved. An optoelectronic model based on four essential elements: a voltage supply, a monolithic double pin photodiode, optical connections for light triggering, and optical power sources for light bias explains the operation of the optical system.