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  • Open access
  • 74 Reads
Evaluation of sensor performance for harmful compounds by using photo-induced electron transfer from photosynthetic membranes to electrodes

The effect of harmful compounds such as KCN, phenol and herbicides such as 3-(3,4-dichlorophenyl)-1,1-dimethylurea (DCMU), 1-chloro-3-ethylamino-5-isopropylamino-2,4,6-triazine (atrazine) and 2-N-tert-butyl-4-N-ethyl-6-methylsulfanyl-1,3,5-triazine-2,4-diamine (terbtryne) on the photocurrent of photosynthetic membranes (so-called chromatophores) was investigated by using the carbon paste electrode. The amperometric curve (photocurrent-time curve) due to the photo-induced electron transfer from chromatophores of the purple photosynthetic bacterium Rhodobacter sphaeroides to the electrode via an exogenous electron acceptor was composed of characteristic two phases: the abrupt increased current immediately after illumination (I0), and the constant current with time (Ic). 2,5-Dichloro-1,4-benzoquinone (DCBQ) was found to be most useful exogenous electron acceptor for this system than other redox compounds. Photo-reduction of DCBQ was observed as a Michaelis-Menten type kinetics, and reduction rates were dependent on the amount of DCBQ and photon flux intensity. In the presence of KCN, the only Ic decreased depending on the concentration of KCN higher than 0.05 μM (= μmol dm-3). The I0 decreased selectively by addition of phenol at the concentration higher than 20 μM. Terbtryne also affected only Ic when the concentration of terbtryne was higher than 10 μM. On the other hand, DCMU and atrazine did not affect both I0 and Ic. The utility of this electrode system as the detection of harmful compounds will be discussed in the conference.

  • Open access
  • 80 Reads
Greenhouse Monitoring System based on a Wireless Sensor Network

Wireless sensor networks are considered an important dimension of the modern information and communication technology-based solutions for greenhouse monitoring. Several sensing and communication technologies are already available and have been used both in pilot and commercial installations. Their attractiveness is based on their deployment flexibility and low cost. In this paper we present the implementation features of a greenhouse monitoring system that is based on a ZigBee wireless sensor network. The system is composed of various sensor nodes that collect environmental conditions' data and transmit them to a remote database. A web application enables the growers to setup electronic cultivation records and monitor the greenhouse conditions as indicated by the collected WSN data. We also present the outcomes of an experimental study in the context of which the implemented system was deployed and operated in a greenhouse complex with hydroponic cultivation of tomato crops. This experimentation intended to explore the level of heterogeneity of the microclimate conditions in the greenhouse environment. The study revealed non negligible differences on the levels of temperature and humidity even across different sectors of compact greenhouse compartments and highlights the importance of dynamic management of the climate conditions on the basis of real time microclimate observations, with an ultimate objective to achieve greenhouse production of high quality and quantity, while using less input resources.

  • Open access
  • 74 Reads
An Initial Study of Commercial Piezoelectric Diaphragms for Damage Detection Based on the Electromechanical Impedance Principle

Piezoelectric transducers have been extensively used in various applications in recent decades, such as in the non-destructive testing (NDT) of materials and structures. A piezoelectric transducer commonly used in NDT applications is lead zirconate titanate (PZT) ceramic, which is thin, lightweight, and minimally invasive to the structure. In this study, we analyzed the use of commercial piezoelectric diaphragms for damage detection based on the electromechanical impedance (EMI) method, which is an NDT technique used in structural health monitoring (SHM) applications. The commercial diaphragms have the advantages of being low cost and readily available. To assess their feasibility for damage detection, a low-cost diaphragm was compared with a conventional PZT ceramic with similar shape and dimensions. Tests were performed on aluminum beams, in which damage was simulated by placing a metallic bolt at different distances from the transducers. The sensitivity to damage was estimated using the correlation coefficient deviation (CCD) damage index, which was calculated using the electrical impedance signatures obtained from each transducer. The experimental results indicate that the piezoelectric diaphragms are able to detect damage; therefore, this study provides an important contribution to the field of SHM systems based on the EMI method.

  • Open access
  • 79 Reads
Detecting Layered Liquids Using Long Period Fiber Grating Sensors

Layers occur when insoluble liquids meet each other such as water and oil. The monitoring of the interfaces among various liquid layers are of paramount importance for chemistry purifications, liquids storage in reservoirs, oil transportation, and chemical engineering. However, studies for layered liquid detection are limited. Visible examination has been used as a common practice to distinguish liquid layers, which is rough and in most cases hard to operate for chemical processing. In this paper, a long-period fiber grating (LPFG) based optical fiber sensor was investigated to detect the boundaries between layered liquids. The LPFG sensor when placed among the boundary of liquids will respond to the change of the refractive index between various liquid layers. Laboratory experiments showed that the refractive index difference between layers will induce a sudden change of the LPFG’s resonant wavelength if the LPFG sensor is bonded on an object when moving through the layer boundary. The LPFG sensor will have a higher sensitivity to detect the liquid layers when there is a bigger refractive index difference between the layered liquids. With further approval, the LPFG sensors could be potentially use for accurate liquid layer sensing which is highly demanded for chemical processing and liquid storage.

  • Open access
  • 68 Reads
Communication Range Dynamics Using an Energy Saving Self-Adaptive Transmission Power Controller in a Wireless Sensor Network

The deployment of the nodes in a Wireless Sensors and Actuators Network (WSAN) is typically restricted by the sensing and acting coverage. This implies that the locations of the nodes may be, and usually are, not optimal from the point of view of the radio communication. And also when the transmission power is tuned for those locations, there are other unpredictable factors that can cause connectivity failures, like interferences, signal fading due to passing objects, and of course, radio irregularities.
A control based self-adaptive system is a typical solution to improve the energy consumption while keeping a good connectivity. In this paper, we explore how the communication range for each node evolves along the iterations of an energy saving self-adaptive transmission power controller when using different parameter sets in an outdoor scenario, providing a WSAN that automatically adapts to surrounding changes keeping a good connectivity.
The results obtained in this paper show how the parameters with the best performance keep a k-connected network, where k is in the range of the desired node degree plus or minus a specified tolerance value. In addition, the worst performance shows how a bad parameters choice can create isolated islands, groups of nodes disconnected from the rest of the network.

  • Open access
  • 84 Reads
New design of an acoustic array calibrator for underwater neutrino telescopes

A short bipolar pressure pulse with ‘pancake’ directivity is produced and propagated when an Ultra-High Energy (UHE) neutrino interacts with a nucleus in water. Nowadays, several acoustic sensors are deployed in deep sea trying to detect the phenomena as first step to build a neutrino telescope. In order to study its feasibility, it is critical to have a calibrator able to mimic the neutrino ‘signature’. In previous works we developed  a first compact array calibrator prototype that validated the possibility of using the acoustic parametric technique for this aim, but due to limitations in terms of power efficiency, transducer properties and electronics matching, the application was not fully fulfilled. In this paper, we describe a new proposed design of a compact calibrator composed of an array of piezo ceramic tube transducers emitting in axial direction, and new specific electronics adapted to the transducers to feed it more efficiently. The array is operated at high-frequency and, by means of the parametric effect, the emission of the low-frequency acoustic bipolar pulse is generated permitting to mimic the UHE neutrino acoustic pulse with the required power. All the design processes involved and the results are presented: ceramic characterization, signal processing, simulations, tests, etc.

  • Open access
  • 61 Reads
Firefighter and victims protecting solution based on Wireless Body Area Network nodes

Interconnectivity between Web systems and sensor networks is used to provide smart services for the Internet of Things. These services are based on data collection and processing to obtain useful information about the supervised environment. With this information it is possible to provide smart services, but some of them must be considered as protected by the legislation regarding privacy of personal data. In order to face this issue, security and privacy mechanisms must be used. So as to deal with the limited resources in sensor networks, these mechanisms must be as lightweight as possible to preserve the enough Quality of Service. However, these mechanisms must fulfill security and privacy requirements defined by the regulations. This paper describes a Wireless Body Area Network application providing services to protect firefighter work in hazardous environments. The firefighter wears a special shirt with sensors embedded. These sensors are able to monitor not only the firefighter health status, but also they can be connected to external sensors in order to monitor the health status of the victims. These external sensors are part of the equipment carried by the firefighter to face the emergencies and save lives. Thus, they are able to obtain external medical aid.

  • Open access
  • 82 Reads
R&D studies for the development of acoustic sensors for dark matter bubble chamber detectors

PICO Dark Matter bubble chamber detectors use piezoelectricsensors in order to detect and discriminate the acoustic signals emitted by the bubbles grown within the superheated fluid from a nuclear recoil produced by a particle interaction. These sensors are attached on the outside walls of the vessel containing the superheated fluid. The acoustic discrimination depends strongly of the properties of the complete sensor and there are constrains as well in the size and radiopurity of the piezoelectric ceramics. With the aim of understanding the complete acoustic process and optimising the sensor system, a test bench for the characterization of the sensors glued to the vessel has been developed. The sensor response for different piezoelectric materials, geometries, matching layers and experimental designs has been measured and contrasted with FEM simulations and analytical models. The results of these studies and designs lead us to have a design criterion for the construction of specific sensors for next generation of PICO detectors (250 L bubble chambers).

  • Open access
  • 72 Reads
Singular Value Decomposition Applied to Non-Cooperative Target Identification

Since High Resolution Radar provides the ability to recognize targets at long distance and under any weather condition, Non-Cooperative Target Identification based on High Resolution Range Profiles has become a key research domain in the Defense industry. According to that, to face this problem, an approach to Non-Cooperative Target Identification based on the exploitation of Singular Value Decomposition applied to a matrix of range profiles is presented. The method compares a collection of profiles of a given target, namely test set, with the profiles included in a database, namely training set. The classification is improved by using the decomposition, since it allows to model each aircraft as a subspace and to accomplish recognition in a transformed domain where the main features are easier to extract hence, reducing unwanted information. In order to evaluate the performance, range profiles are obtained through numerical simulation of seven civil aircraft at defined trajectories taken from an actual measurement campaign. Taking into account the nature of the datasets, the main drawback of using simulated profiles instead of actual measured profiles is that the former implies an ideal identification scenario, while measured profiles suffer from unsought information. So as to confirm the feasibility of the approach the addition of noise has been considered before the creation of the test set. Identification experiments of profiles are conducted for demonstrating which methodology provides the best robustness against noise in an actual possible scenario. Future experiments with larger sets are expected to be conducted with the aim of finally using actual profiles as test sets in a real hostile situation.

  • Open access
  • 108 Reads
Real-time self adaptable Prediction system for Mine Equipment 

Identifying failure signatures of machines and modeling them to predict problems well before failure occur has been of great interest to reliability and maintenance engineers, primarily because of the unparalleled advantages like improved equipment up-time, lower maintenance cost, and reduced safety risk. Production critical machinery often requires intelligent real time monitoring and an unplanned interruption can have high cost implications. To address this, we utilize the on-board sensor data and develop a near-real time prediction system to identify anomalies and failure patterns of assets. Development of such data driven system will help improve reliability engineering strategies by modeling system dynamics and predicting equipment health problems.