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  • Open access
  • 108 Reads
Numerical Study of A Multi-Layered Strain Sensor for Structural Health Monitoring of Asphalt Pavement

Crack initiation and propagation affect the mechanical properties of asphalt pavement and significantly limit its design life. To assess the structural health of asphalt, knowledge of the strain condition has proven to be useful and optical fibers, conventional strain gauge, metal-foil-type gauges, can be used for this purpose. The high cost of optical fibers has limited their use in this application and although conventional strain gauges have an excellent capability of assessing even large strains, they are rarely used because asphalt paving has high temperature (up to 150 ℃) and pressure (around 290ksi) during installation. A new multi-layered strain sensor has been proposed to overcome the installation challenges in asphalt pavement and provide a reliable structural health monitoring of capability. In this proof-of-concept study, a finite element model was created to simulate the pavement–sensor interaction for the proposed strain sensor in order to optimize its design and potential.

The core of the strain sensor is an H-shaped Araldite GY-6010 epoxy structure with a set of PVDF piezoelectric transducer in its center beam and a polyurethane foam layer at its external surface. An extra thin layer of urethane casting resin is then coated at the external surface of the polyurethane foam to prevent the sensor from being damaged under harsh installation condition. During the life of the pavement, traffic loads deform the embedded sensor. The sensor deflection variations register as voltage amplitude changes by the piezoelectric transducers that are later recorded as strain changes. When a crack initiates and propagates in the pavement, sensor deflection increases dramatically as the pavement fails to maintain its designed tensile and flexural strength.

The simulation of the pavement–sensor interaction resulted in a modification of several key elements of the original design. The internal Araldite epoxy structure, and outer foam layer were optimized with thicknesses of 11mm, and 2.5mm, respectively. Two design parameters for the sensor, side wing length/middle beam length ratio, and pavement thickness, were also adjusted for optimal design and location of the sensor. The numerical model was created and the simulation performed using COMSOL. Using a fixed traffic load, and varying the side wing length between 20mm-50mm, and the middle beam length between 80mm-200mm, with the best ratio of side wing to middle beam length of 0.3125 was determined as a result of this study.

  • Open access
  • 55 Reads
Spectro-temporal Analysis of the Ionospheric Sounding of an NVIS HF Sensor

In communications, channel models are useful approximations to the performance of a real channel, which most of the times is not available for repeated tests. In this work we present the problem over the real NVIS ionospheric scenario channel sounding, evaluating the channel propagation characteristics in terms of frequency spread and time spread, with the final goal to design a channel model. A NVIS channel model can be obtained from the evaluated channel parameters, but on one hand, there is the problem of missing data due to bad channel performance in some frequencies, and on the other hand, the measured parameters have strong dependencies between them that cannot be evinced directly. In this work, we conduct a first set of analysis to the soundings to determine the dependencies in terms of quality of the channel propagation but referring mainly to the Doppler spread and the time spread in the sensor. This classification approach will allow us to face the second part of the research, with the focus on the design of the channel model for the ionospheric communication of remote sensors.

  • Open access
  • 55 Reads
Monitoring of the Ceramic Kerf During the Laser Cutting Process through Piezoelectric Transducer

Advanced ceramics are widely used in industry due to their unique properties. However, the machining of ceramic components by conventional methods is difficult due to their high hardness and brittleness. In this sense, laser beam machining (LBM) is presented as an alternative to conventional methods, enabling the machining of workpieces through more accurate and less invasive techniques. Despite the advantages of laser machining, the process still needs to be studied in detail, as advanced ceramic machining is considered a stochastic process. Thus, real-time monitoring systems are required in order to optimize the ceramic laser machining. Therefore, this paper proposes a novel method for monitoring the cutting kerf in the laser cutting process of ceramic components using low-cost piezoelectric transducer (PZT) and digital signal processing. Tests were performed on the surface of an alumina ceramic workpiece under different machining conditions. The cutting kerf was measured by a digital microscope and the raw signals from the PZT transducer were collected at a sampling rate of 2 MHz. Time domain and frequency domain analyzes were performed in order to find a frequency band that best correlates with the process conditions. Finally, a linear regression was calculated in order to correlate the PZT signal and the measured kerf. The results showed that the piezoelectric transducer was sensitive to the acoustic activity generated during the process, allowing the real-time monitoring of the cutting kerf. Thus, the approach proposed in this paper can be used efficiently in the monitoring of the laser cutting process.

  • Open access
  • 64 Reads
On-line digitalization technologies for monitoring activities in the marine environment.

This proceeding shows the results of the investigation of techniques of integration, management and visualization of massive data from the digitalization of environmental and procedural parameters of facilities that operate in the marine environment. The work focuses on three main lines: (1) research on the development of a Cloud-based system for Big Data that allows the hosting of the data generated by the different devices to be monitored (GPS, sounds, vibrations, video, temperature, emissions, consumption, power, etc.). (2) Implement a first layer of analysis and visualization of information. Thus, there is a first intelligent layer that addresses one of the four pillars of Web 4.0: machine-to-machine (M2M) communication. (3) BigData analytics research for post-processing of information. Depending on the context of the data source (marine environment or vessel), different analyzes of the recorded data are performed. With this, progress is made in another of the pillars of Web 4.0: use of context information, since the application is in charge of intelligently processing the data of the different variables together although they are not, in principle, directly related.

  • Open access
  • 106 Reads
A Statistical Method for Area Coverage Estimation and Loss Probability Analysis on Mobile Sensor Networks

Sensor networks are formed by fixed or mobile sensor nodes and their functions are to capture the events that occur within a certain area and then relay to a central node. Normally sensor nodes are not able to transmit or receive information over long distances due to the need to use less energy and thus extend their useful life. Therefore, the number of sensor nodes in a given area directly influences the coverage of this area and the ability of information to be relayed by several sensors to the central node. If there are many missed messages the application will have its performance compromised. In this paper we used a statistical method-based on Monte Carlo approach to estimate the probability of message loss and area coverage. The position and proper motion of the sensors are randomly chosen and from that we estimate how many nodes can communicate with the central node directly or through another sensor working as relay. The free variables in our analysis are node density, node displacement velocity and sensor quantity. The results obtained are compared analytically with simple cases in order to validate the results obtained by the simulations performed.

  • Open access
  • 42 Reads
Geometrical optimization of piezoelectric sensors for acoustical monitoring in proton therapy treatment.

The hadrontherapy has been in constant evolution by leaps and bounds since the fifties, when the use of heavy particles was proposed as an alternative treatment to radiotherapy with gamma rays or electrons. The main objective of this treatment is to maximize the dose applied to the tumour avoiding damage to the surrounding tissue. One of the keys to the success of the hadrontherapy is to achieve an instantaneous monitoring of this energy deposition in the environment. Since the energy deposition leads to the generation of a thermoacoustic pulse, acoustic technologies have been tested with successful results. However, for this purpose, it is essential to increase the sensitivity of the sensors for the acoustical signal and, therefore, to optimize their geometry as a function of the beam that would be used. We have studied a PTZ material in volumetric and surface volumes through experimental measures and FEM methods. In this text, we start with numerical studies which determine the dependence of the thermoacoustic signal frequency with the energy and duration of the hadron beam.

  • Open access
  • 39 Reads
Acoustic Bragg peak localization in proton therapy treatment: Simulation studies

A full chain simulation of the acoustic handontherapy monitoring for brain tumors is presented in this work. For the study, a proton beam of 100 MeV is considered. In the first stage, Geant4 is used to simulate the energy deposition and to study the behavior of the Bragg peak. The energy deposition in the medium produces local heating that can be considered instantaneous with respect to the hydrodynamic time scale producing a sound pressure wave. The resulting thermoacoustic signal has been subsequently obtained by solving the thermoacoustic equation. The acoustic propagation has been simulated by FEM methods in the brain and the skull, where a set of piezoelectric sensors are placed. Last, the final received signals in the sensors have been processed in order to reconstruct the position of the thermal source and, thus, to determine the feasibility and accuracy of acoustic beam monitoring in handontherapy.

  • Open access
  • 48 Reads
Analysis and Design of IoT Enabled Low Cost Distributed Angle Measurement System

Linear Fresnel Reflector (LFR) is a recent technology that have a good potential in small scale solar power applications. It is arranged from many long row segments of mirrors that focus the sunlight onto a fixed elevated tubular receiver. Mirror segments are aligned horizontally and track the sun such that the receiver is illuminated without the need of being moved. The efficiency at which LFR can convert solar to thermal energy depends on the accuracy of the sun tracking system. To maximize the degree of sunlight capture, a precise solar tracking is needed with the goal of capturing solar radiation as much as possible. The tilt angles of each raw are a crucial information that are necessary for the tracking controller to whether or not correct positioning is achieved. Encoders generally are employed in the closed-loop tracking systems as feedback signals used to inform the controller with the actual position of collector mirrors. Recently inclinometers have begun to largely replace encoders as the most viable and cost-effective sensor technology solution which offer the capacity for simpler and precise feedback, as they measure the angle of tilt with respect to gravity and provides the ability to adjust system to the optimal angle for maximizing output. This paper presents the research results on the development of remote measurements for the precise control of LFR tracking system, by using distributed angle measurements. The applied methodology enables the precision measurement LFR inclination angles through the fusion of data from multiple accelerometers, supported by low cost wireless transceivers in a wireless sensor network, capable of exchanging information in cloud infrastructure.

  • Open access
  • 69 Reads
Use of Optical Fiber Sensor for Monitoring the Degradation of Ac-Dex Biopolymeric Nanoparticles

Acetalated Dextran (Ac-Dex) is a promising pH-sensitive biocompatible and biodegradable polymer for nanomedicine applications. In this work, Ac-Dex nanoparticles were synthesized by two different solvent evaporation methods, the single nanoemulsion and the double nanoemulsion. The Ac-Dex particles were characterized by Scanning Electron Microscopy and the synthesis of highly homogeneous spherical particles was verified. Then, an optical fiber sensor based on quasi-elastic light scattering and comprised of only single-mode optical fibers and standard telecommunication devices showed sensitivity regarding the nanoparticles concentrations and was used for monitoring their degradation over 12 hours under pH and temperature conditions of cancerous tissues. The results revealed a well-controlled degradation pattern, corroborating the suitability of the modified polymer to the release of active compounds in a sustainable manner and also demonstrating the applicability of the sensor for the in-situ evaluation of the degradation.

  • Open access
  • 76 Reads
Different approaches to FT-IR microspectroscopy on X-ray exposed human cells.

Fourier-Transform Infrared microspectroscopy (microFT-IR) is nowadays considered a valuable tool for investigating biochemical changes occurring in cells during the interaction with external agents [1]. In particular, microFT-IR has been usefully applied in the analysis of the complex biological processes occurring during X-ray radiation-cell interaction [2, 3].

Different experimental approaches are available for FT-IR spectra collection (transmission, attenuated total reflection (ATR) and transflection modes) on cells samples. Transflection-mode FTIR spectroscopy has become particularly used for this kind of samples due to the relatively low cost of substrates compared to transmission windows, and a higher absorbance due to a double pass through the same sample approximately doubling the effective path length. Recently, some questions have been raised about the role of transmitted and reflected components of the infrared beam in transflection mode [4,5].

For this reason, we investigated two different transreflection approaches for collecting spectra from cells samples exposed to X-ray. In the former approach, cells were grown on MirrIR slides (25x25 mm2) (Kevley Technologies, Chesterland, Ohio), a specific reflection FT-IR spectroscopy microscope slide; for the second approach cell pellets were prepared.

In both cases, SH-SY5Y neuroblastoma (American Type Culture Collection, Manassas, VA, USA) cells were used. X-ray exposure was performed at room temperature using a Gilardoni MGL 200/8D machine operating at 250 kVp and 6 mA (dose rate 60 cGy / min) at doses of 2 and 4 Gy.

After X-ray exposure, the cells grown on MirrIR slides were fixed in a 3.7% formaldehyde PBS solution for 20 min at room temperature, and, then, briefly washed in distilled water for 3 s to remove the residue PBS from the surface of the cells. Subsequently, the samples were dried under ambient conditions and stored in a desiccator until analysis. To obtain cell pellets, X-ray irradiated cells were centrifuged for 8 minutes at 1,500 rpm. The supernatant was aspirated and the pellet resuspended in 300 μl of NaCl 0.9% until spectra acquisition.

For the acquisition of the IR absorption spectra a Spectrum One FTIR (PerkinElmer, Shelton, CT, USA) spectrometer, equipped with a Perkin Elmer Multiscope system infrared microscope and an MCT (mercury cadmium telluride) detector was used.

Significant spectra were obtained by using both the approaches in the 4000 - 600 cm-1 spectral range from exposed and not-exposed samples. The main contribution from proteins, lipids, carbohydrates and DNA were clearly evidenced and assigned. Particular care has paid in considering how the transmission and reflection infrared beam component can affect the obtained spectra.

The results of this investigation can be particularly useful in evaluating the effective reliability of low-cost metallic substrates that can really contribute to significantly spread the use of microFT-IR.


[1] Baker MJ, Trevisan J, Bassan P, Bhargava R, Butler HJ, Dorling KM, Fielden PR, Fogarty SW, Fullwood NJ, Heys KA, Hughes C, Lasch P, Martin-Hirsch PL, Obinaju B, Sockalingum GD, Sulé-Suso J, Strong RJ, Walsh MJ, Wood BR, Gardner P, Martin FL. 2014. Using Fourier transform IR spectroscopy to analyze biological material. Nat Protoc. 9:1771–1791.

[2] Gault N, Lefaix JL. 2003. Infrared microspectroscopic characteristics of radiation-induced apoptosis in human lymphocytes. Radiation Research. 160:238-250.

[3] Meade A, Clarke C, Byrne H, Lyng F. 2010. Fourier transform infrared microspectroscopy and multivariate methods for radiobiological dosimetry. Radiation Research. 173:225-237.

[4] Bassan P, Lee J, Sachdeva A, Pissardini J, Dorling KM, Fletcher JS, Henderson A, Gardner P. 2013 The inherent problem of transflection-mode infrared spectroscopic microscopy and the ramifications for biomedical single point and imaging applications. Analyst. 138: 144-157

[5] Mayerhöfer TG, Pahlow S, Hübner U, Popp J. 2018 Removing interference-based effects from the infrared transflectance spectra of thin films on metallic substrates: a fast and wave optics conform solution. Analyst. 143: 3164-3175