Reproductivity Study of Metal Oxide Gas Sensors Using Two Different Temperature Setups

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A Comparative Analysis Between Customized and Commercial Systems for Complex Permittivity Measurements on Liquid Samples at Microwave Frequencies

In this paper, different customized systems for microwave permittivity measurements on liquid samples, based on reflectometric measurements, are presented and analyzed. Their performance is compared against the one deriving from the most widely adopted commercial measurement setup. The systems are designed with the aim of providing less expensive solutions without compromising measurement accuracy. The purpose of the first proposed solution is to replace the commercial measurement software exploiting a reformulation of the classical theory. Based on this alternative formulation, a "homemade" probe is built by properly modifying an N-type coaxial connector, thus providing a system requiring a lower quantity of liquid under test. Moreover, a different experimental approach which uses time-domain reflectometry (TDR) instrumentation is presented. Such solution is by far the least expensive, as it allows avoiding the use of costly instrumentation (such as a vector network analyzer). In order to metrologically characterize the proposed solutions, a series of repeated measurements is performed on a set of well-referenced liquids. After extracting the Cole-Cole parameters through each of the considered measurement methods, the resulting type A uncertainty is evaluated. Finally, comparison with literature data allows the estimation of measurement bias. The analysis evidences that custom solutions generally exhibit an accuracy comparable to the one of the commercial solution, with a slight degradation of performance for the TDR-based setup, which, however, compensates for this drawback with its appealing low cost

Reproductivity Study of Metal Oxide Gas Sensors Using Two Different Temperature Setups

The use of the electronic nose as a screening device is of great interest in various types of applications, including food quality control and environmental monitoring. It is an easy-to-use device and produces a much faster response than that obtained by classical chemical and microbiological techniques. The reproductivity of nominally identical electronic noses and sensors is critical. Four identical MOX sensors were compared using two different working methods, namely, the temperature modulation mode and isothermal mode. Each sensor was tested with two standard compounds, water and lactic acid, often identified in food matrices, which are potential applications of the electronic nose

Position and speed control of a low-cost two-wheeled, self-balancing inverted pendulum vehicle

International audienceIn this paper we present a low-cost prototype of a two-wheeled, self-balancing inverted pendulum realized at the mechatronics laboratory of the University of Trento. This vehicle lends itself to represent a class of control problems that arise in many educational robotic devices custom built and assembled with low-end market components. We provide a detailed description of the equipment and describe the strategies adopted to suitably address backlash of the low-cost DC motors and disturbances arising from the voltage controlled hardware. Then we propose a nested control paradigm where an inner loop provides regulation of a virtual control requested by an outer loop that uses the pitch angle to regulate the longitudinal displacement and speed. Three saturation-based control laws are proposed for the outer loop, all of them allowing the designer to adjust the maximum pitch angle. Experimental results illustrate the effectiveness of the proposed control laws and the operation of the developed prototype

Detection of chlorinated compounds in ground water by a novel electronic nose

n this work we present the use of the electronic nose EOS 835 (EN) for the screening of chlorinated substances into groundwater. Pollution of the groundwater to be analysed (Rho, Milan) reaches levels of contamination up to 0.1 g/l. The EOS835 is a tool equipped with a chamber with 6 different MOX sensors. It provided excellent results in terms of screeIn this work we present the use of the electronic nose EOS 835 (EN) for the screening of chlorinated substances into groundwater. Pollution of the groundwater to be analysed (Rho, Milan) reaches levels of contamination up to 0.1 g/l. The EOS835 is a tool equipped with a chamber with 6 different MOX sensors. It provided excellent results in terms of screening capabilities, in fact EN detected trichloroethylene in to the water up to 0.03 mg/ml. We can be concluded that the electronic nose could be used as a tool to assist the development of pollution remediation

Impaired cerebral and systemic hemodynamics under cognitive load in young hypotensives: a transcranial Doppler study

Reduced sympathetic outflow and deficits in cerebral hemodynamics have been considered as possible factors mediating the impaired cognitive performance in essential hypotension. However, the relationship between systemic blood pressure (BP), cerebral blood flow and cognitive functioning is still poorly understood. The present study was aimed at clarifying the physiological processes underlying cerebral and systemic hemodynamics in young hypotensives during cognitive engagement. Doppler sonography blood flow velocities in both middle cerebral arteries were measured from 17 hypotensives and 15 normotensives during a working memory task. Impedance cardiographic and BP measures were also recorded continuously. Lower increases in systolic and diastolic BP were observed in hypotensives. However, no evidence of lower sympathetic control was found for this group, as assessed by pre-ejection period. Flow velocity in middle cerebral arteries showed a lower increase in hypotensives throughout the task. Moreover, significant positive correlations between BP changes and blood flow velocities in middle cerebral arteries during the task were obtained for this group only, suggesting a less effective cerebral autoregulation. No difference was found between groups in task performance. Results suggest that during cognitive challenge hypotensives show impaired hemodynamic adjustments, both central and peripheral. However, such alterations do not directly affect cognitive performance, at least under moderate cognitive load

Rapid diagnosis of Enterobacteriaceae in vegetable soups by a metal oxide sensor based electronic nose

A rapid protocol for the early diagnosis of microbial contamination of commercial food products by Electronic Nose is presented. Mixed vegetable soup samples are artificially contaminated by Enterobacter hormaechei and Escherichia coli and a large dataset of 584 samples, over two experimental campaigns, was analyzed by the electronic nose EOS507C based on a four metal oxide sensors array. Diagnosis of the contamination is obtained after 21 h and 18 h from the inoculation of E. hormaechei and E. coli respectively

Fast Identification of Microbiological Contamination in Vegetable Soup by Electronic Nose

Microbial contamination, either before or during food production phases, is one of the major concerns of food manufacturers. In this work we present the EOS507C Electronic Nose (EN) for early screening of Enterobacter hormaechei type strain (ATCC 49162) contamination in vegetable soup. The EOS507C, based on an array of metal oxide semiconductor (MOX) sensors, is a rather innovative system equipped with dynamic headspace autosampler and new functionalities such as real-time sample humidity compensation, sensor response linearization and automated periodic calibration. The EOS507C has provided excellent results in terms of screening capabilities: E.hormaechei contamination was detected in 24 hours

Synthesis and thermal evolution of polysilazane-derived SiCN(O)aerogels with variable C content stable at 1600°C

Ceramic aerogels possess intriguing thermophysical properties which make them excellent candidates for high temperature thermal insulators. However, their properties can degrade at high temperature because of crystallization phenomena or because of densification (causing a sensible reduction of their specific surface area and porosity). The polymer derived ceramic (PDC) route is a relatively new way of developing ceramic aerogels. Several aspects influence the properties of the final product when dealing with preceramic polymers, among them their chemical composition and molecular architecture. In this work, we investigated the possibility of producing aerogels belonging to the SiCN system from polysilazanes mixtures, namely perhydropolysilazane (PHPS) and a methyl/vinyl-containing polysilazane, namely Durazane 1800®, thus changing the C/Si ratio of the amorphous pyrolyzed products. It is shown that the chemical composition of the ceramic aerogel affects the main properties of the porous materials, such as thermal stability and specific surface area (SSA). Results show that the presence of carbon in the aerogels inhibits crystallization of Si3N4 up to 1600 °C in N2 and allows to maintain a SSA of ~90 m2/g up to this temperature

Effect of ultra-fast pyrolysis on polymer-derived SiOC aerogels and their application as anodes for Na-ion batteries

In the last decade, Sodium-Ion-Batteries (SIB) started to gain interest as a possible complementary candidate to support the overburdened lithium technology, but the manufacturing of a proper anode material is one of the challenging factors for the development of performing SIB. Among others, porous polymer-derived ceramics have been widely explored as suitable anodes despite the production of such materials being time and energy-consuming. In this work, we investigate the feasibility of adopting a low-cost ultra-fast high-temperature pyrolysis for the ceramic conversion of a polymer-derived SiOC aerogel to be employed as anode material. A comprehensive study including N2 physisorption, 29Si MAS NMR and Raman spectroscopy provides the insights of the effect of ultra-fast and conventional heating rates (i.e., 200 °C·s−1 vs. 5 °C·min−1) on the microstructural features and ceramic yield of the SiOC aerogels. As a consequence of the ultra-fast heating rate, a compositional drift towards oxygen-rich SiOC is observed and discussed. The electrochemical performance of both ceramics has been tested and related to the observed compositional differences, revealing a stable capacity of 103 mAh·g−1 for the ultra-fast pyrolyzed SiOC anode, and 152 mAh·g−1 for SiOC ceramized at 5 °C·min−1