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  • Open access
  • 111 Reads
Integration of Autonomous Wireless Sensor Networks in Academic School Gardens

In this work, the combination of capabilities provided by Wireless Sensor Networks with parameter observation in a school garden is employed in order to provide a comprehensive environment for school garden integration as a complementary educational activity in primary schools. Wireless transceivers with energy harvesting capabilities are employed in order to provide autonomous system operation, combined with an ad-hoc implemented application called MySchoolGardenApp. The system enables direct parameter observation as well as data analysis and processing capabilities, which can be further employed with students in a cloud based platform. Providing remote data access allows the adaptation of content to specific classroom needs. The proposed WSN for monitoring the orchard located in the schoolyard of a primary school has been built with EnOcean’s energy harvesting modules, operating at 868.3 MHz with a data rate of 125 kbps and transmitting between 5-8 dBm of power. These wireless modules have incorporated a temperature sensor and there is the possibility of equipping them with a humidity sensor. Each module communicates only with a central module connected to a PC or laptop via USB, in a star topology. For the assessment of the wireless link quality and the deployment of the modules, especially the central module which needs to receive directly the signals of all the sensor modules, simulation results obtained by an in-house developed 3D Ray Launching deterministic method have been used. Preliminary trials with MySchoolGardenApp have been performed, showing the feasibility of the proposed platform as an educational resource in schools.

  • Open access
  • 52 Reads
Influence of particle size in the characterization of street dust by proximal soil sensing

Urban road dust can be enriched in different elements and hence it can pose a threat to human and environmental health. Proximal soil sensing allows the swift monitoring of such particles in order to drive attention to any possible risks. The goal of this study is to find the variation in concentrations found when using a portable X-ray fluorescence (XRF) proximal sensor for the determination of metals in road dust as the particle size of the samples decreases. In general, readings decrease as the particles are larger. The maximum reading occurs when particles are sieved to 100 µm but a particle size of 250 µm maintain a 90% accuracy. This study can help field workers to define an expected accuracy when using such type of sensors in street dust analysis.

  • Open access
  • 71 Reads
A 3D Visual Attention Model to Guide Tactile Data Acquisition for Object Recognition

Drawing inspiration from the human vision-touch interaction that demonstrates the ability of vision in assisting tactile manipulation tasks, this paper addresses the issue of 3D object recognition from tactile data whose acquisition is guided by visual information. An improved computational visual attention model is initially applied on images collected from multiple viewpoints over the surface of an object to identify regions that attract visual attention. Information about color, intensity, orientation, symmetry, curvature, contrast and entropy are advantageously combined for this purpose. Interest points are then extracted from these regions of interest using an innovative iterative technique that takes into consideration the best viewpoint of the object. As the movement and positioning of the tactile sensor to probe the object surface at the identified interest points take generally a long time, the local data acquisition is first simulated to choose the most promising approach to interpret it. To enable the object recognition, the tactile images are analyzed with the help of various classifiers. A method based on similarity is employed to select the best candidate tactile images to train the classifier. Among the tested algorithms, the best performance is achieved using the k-nearest neighbor classifier (87.89% for 4 objects and 75.82% for 6 objects). The proposed solution is then validated on real tactile data collected using a piezo-resistive tactile sensor array. The best performance obtained using the same classifier is of 72.25% for 4 objects and of 67.23% for 6 objects.

  • Open access
  • 47 Reads
Combining Water Indices for Water and Background Threshold in Landsat Image

Accurate and frequent update of surface water has been made possible by remote sensing technology. Index methods are mostly used for surface water estimation which seprates the water and nonwater bodies based on a threshold. Generally thresholds have fixed value but are challenging in case of shades, hills, forest and urban areas. In such case, determination of threshold is done manually which is subjective and can cause a lot variation in area. In order to widen the difference between water and non water class and ease the threshold selection, a combination of muntiple water index can be used. This could widen the gap between classes and the threshold sensitivity can be minimized. In this study, we combined Normalized Difference Water Index (NDWI), Modified NDWI, Water Ratio Index and Normalized Difference Vegetation Index to form a new raster and explore the efficiencty of thresholding compared to individual indices on Landsat 8 Operational Land Imager (OLI) image of Nepal. The combined index shows much better separation of water with it is background and can be further used for automated binary classification of surface water. The process could be very useful in mapping surface water accurately.

  • Open access
  • 73 Reads
Wireless monitoring of pavement temperature based on low cost computing platform

Nowadays, preservation, maintenance, rehabilitation and improvement of the road network is a fundamental issue. Many of the parameters that define the road surface conditions are conditioned by various environmental factors, mainly temperature. Hence the importance of having databases that allow a meticulous analysis of the properties of the road. The fundamental goal of the work is the design and development of a road monitoring system based on temperature measurement at different pavement depths, capable of transmitting the information to a moving vehicle. Therefore, it is necessary a modular device, of easy installation, low cost and reduced energy consumption that enables the optimizing of the auscultation procedure, improving the reliability of the measures collected and the process of obtaining them, which, in turn is the basement to estimate the useful life of the pavement. The results of the tests and validation of the proposed prototype in either static system with two types of pavement (asphalt and concrete), and in real driving situations, demonstrate the good performance and accuracy of the proposed system.

  • Open access
  • 96 Reads
UV Total Dose Nonvolatile Sensor Using Fluorine-Treated SOHOS capacitor

The fluorine-treated silicon–silicon oxide–hafnium oxide–silicon oxide–silicon capacitor device (hereafter F-SOHOS) could be candidate for UV radiation total dose (hereafter TD) nonvolatile sensor. UV radiation induces a significant increase in the threshold voltage VT of the F-SOHOS. The experimental results indicate that the UV radiation-induced increase of VT for the F-SOHOS capacitor device under gate positive bias stress (hereafter PVS) is nearly 4 volts after 100mW.sec/cm2 TD UV radiation. The change in VT for F-SOHOS capacitor after UV irradiation also has a strong correlation to UV TD up to 100mW.sec/cm2 irradiation. The charge-retention loss of the nonvolatile F-SOHOS capacitor after 10 years retention is below 15%. The UV TD information can be permanently stored and accumulated in the non-volatile F-SOHOS capacitor devices. In order to erase the UV TD data, data in the F-SOHOS capacitor devices can be erased to original null state by positive charges injection under gate negative bias stress (hereafter NVS). The F-SOHOS capacitor device in this study has demonstrated the feasibility of non-volatile UV TD radiation sensing.

  • Open access
  • 55 Reads
Optimal Robot Path Selection Using Fuzzy Analytical Hierarchical Process

Robot path planning is an integral process of mobile robots. A service mobile robots needs to plan a path from its current location to the goal (service) location. Many algorithms like A-star, D-star, Probabilistic Roadmap, Rapidly-exploring random tree, Dijkstra, and other planners have successfully been used for path planning. Most of these planners generate a shortest path from the start location to the goal location. However, the shortest path is not necessarily the best (for ex. safest) path. Apart from the distance between the start and goal locations, a robot must consider several other factors like the bumpiness, steepness, and crowd on the path. Depending on the sensors used by the robots, other factors like the brightness of the path, for ex. in case of vision sensors, must also be considered. There could be different paths between the same start and goal locations, and the robot must select the optimal path from many paths. The factors which influence the generation of such paths can be dynamic. Moreover, each factor has a varying degree of influence on the selection of path by the robot which also varies from robot to robot. In such situations, selecting a particular path based on a rigorous mathematical analysis which validates the particular selection becomes necessary. In this paper we propose to use Fuzzy Analytical Hierarchical Process (Fuzzy-AHP) to make the optimal selection of the path considering multiple factors. We propose two navigational approaches, namely, defensive and offensive approaches which can be taken by mobile robots to complete a task. We test the results of the proposed method and show comparison with other approaches in simulations.

  • Open access
  • 50 Reads
Theoretical study of quasi-longitudinal Lamb modes in SiN/c-AlN thin composite plates for liquid sensing applications

The propagation of longitudinally polarized acoustic modes along thin piezoelectric plates has been previously reported [1], aiming at the design of high frequency and low loss electroacoustic devices suitable for working in liquids. The investigation of the acoustic field profile across the plate revealed the presence of higher order quasi-longitudinally polarized Lamb modes, traveling at velocities close to that of the longitudinal bulk acoustic wave propagating in the same direction. The commonly used fundamental anti-symmetric Lamb modes Ao is suitable for liquid sensing only for very small plate thickness-to-wavelength ratio h/l corresponding to a phase velocity lower than that of the liquid to be tested (v<1400 m/s), which results in low sensor operating frequencies and sensitivity. The fundamental symmetric mode S0 is much faster than A0 (thus allowing higher operating frequencies) but it is suitable for liquid sensing application only for a limited h/l range (up to 0.1) corresponding to predominant longitudinal polarization. This latter limitation can be overcome by investigating the propagation of higher order quasi-longitudinal modes with close-to-zero transverse particle displacement component at the surface of the plate contacting the liquid environment. The zero-surface transverse component will prevent attenuation of acoustic energy into the liquid. Disperse, McGill and COMSOL Multiphysics simulations were used to study the dispersion curves and the acoustic field profile of the fundamental and higher order modes traveling in SiN/AlN thin suspended membranes, for fixed SiN thickness (200 nm) and variable AlN thickness. Two higher order modes, qS1 and qS2, were found that are slowly dispersive and have dominant longitudinal particle displacement component, at hAlN/l = 0.8 and 1.6 respectively. The acoustic field profile shows that the modes have close to zero out-of-plane particle displacement at the surface of the thin film. The electroacoustic coupling coefficient K2 dispersion curves were studied for four different electroacoustic coupling configurations, based on interdigital transducers (IDTs) positioned at the AlN surface, with or without a metal floating electrode at the opposite layer surface. The theoretical sensitivity to the density-viscosity product of a Newtonian liquid was calculated for the two modes. In order to verify the technological feasibility of such device and to test the technological complexity, Cr/Au IDTs were implemented onto the bare Silicon Nitride (Si3N4) thin suspended membrane (200 nm thick, and with the area equal to 1.5 mm x 1.5 mm) by electron beam lithography (EBL) technology. Then a c-AlN layer was deposited by rf magnetron sputtering technique onto the suspended membrane. The IDTs width of 0.5 mm (equal to l/4) was achieved with EBL resolution of 500 nm onto the Si3N4 suspended membrane (wavelength l = 2 μm). The piezoelectric AlN thin film was deposited onto a reduced area of the surface of the Si3N4 suspended membrane by using a shadow mask with an opening area of 1 mm x 1 mm, thus an AlN layer was sputtered having an “island-like” structure, with the thickness of 1.4 μm and 3 μm. The use of a mask is a method that offers the remarkable advantage to reduce the complexity of the device fabrication process based on several technological steps, including the silicon substrate surface or bulk micromachining and the etching of a sacrificial layer to release the membrane.


 [1] Caliendo, Cinzia. "Longitudinal Modes along Thin Piezoelectric Waveguides for Liquid Sensing Applications." Sensors 15.6 (2015): 12841-12856.

  • Open access
  • 50 Reads
Underwater communication using acoustic parametric arrays

The underwater channel is a hard environment for acoustic communications, in addition to suffering a huge loss of energy, the acoustic waves are affected by the agitation of the waves and the mass of water that cause the signal to fluctuate erratically, being able to fade at short intervals of time. Ultrasonic communications are more exposed to its effects. Therefore you are proposing new methods of communicaction, based on non-linear propagation efect that allow to avoid some of these problems in which the high frequencies are emitted and the low ones are obtained in the medium, allowing the design of more compact transducers.

In general, if the emitted wave has a high carrier frequency (primary beam), it interferes and is rapidly absorbed in the medium allowing the low frequencies formed (secondary beam) to propagate at greater distances. As is well known, high frequencies tend to be very directional, unlike with low frequencies, which are more omnidirectional. However, one of the fundamental characteristics of the parametric effect is that the low frequencies that are generated have a rather narrow directivity, comparable to that of the primary beam.

This paper presents a study of different types of parametric signals with application to submarine acoustic telecommunications. In all of them, the carrier frequency is 200 kHz, which corresponds to that resonates the transducer under study, while they differ by the different modulations they present. In this sense, we study modulations with sweeps (2 to 20 kHz), and signals with information contained in binary code (zeros and ones), getting closer to the application in acoustic telecommunications. The different properties of the transmitting signals in terms of communication speed, directivity, efficiency and power needed are discussed as well.


  • Open access
  • 51 Reads
An integrated framework for users’ well-being

The hygro-thermal comfort (ICQ) is defined as the psychophysical state in which the subject expresses a condition of well-being with respect to environmental variables, a condition known as thermal neutrality. Furthermore, the ICQ represents one pillar of the holistic concept of the Indoor Environmental Quality (IEQ). The methods for the assessment of ICQ and recognized at international level are mainly two. The former, based on a steady-state approach, described by the EN ISO 7730:2005 and applied to Fully Mechanically Controlled buildings (FMC) equipped with an active conditioning system. This method is based on the studies conducted by the Danish researcher Fanger in some climatic chambers, conditioned and insulated from the external environment, in which the users were considered as passive subjects that exchange thermal energy on the base of the equation of the human’s energy balance. The latter, based on and adaptive approach, as defined trough in field activities and described by the technical standard ASHRAE 55 ans EN 15251, instead, considers the users as active subjects that interact with surrounding environment and are influenced in their comfort perception by external conditions. In this case, the thermal comfort concept is not just defined depending on physical, but also psychological, social, economic and cultural aspects. The technical standards provides that this method could be applied in middle seasons when the control of comfort is handled by passive technological methods, i.e. in the so calledNatural Ventilated or Free Running buildings (FR). In this approach, methodologies providing the direct involvement of the end user are consolidating, through the collection of physiological, psychological and behavioral personal data as to obtain the better assessment of the comfort conditions. Placing in this field, the article describes the results of a field investigation in a office aimed at defining a framework for the assessment of the thermal comfort based on the two approaches through the use of low cost technology solutions, parametric and freeware models.

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