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The Sensor Optimization Unit (SOU) is a tool, meant to be used by HVAC engineer, for the optimization of temperature sensors placement in large sports spaces, where the HVAC system usually maintains climate conditions actuating control rules based on one temperature sensor, installed in the return air duct or in a single point of the space, without taking into account the indoor air temperature distribution. The SOU characterizes the indoor horizontal air temperature distribution which can be retrieved with a simulation model or field measurement. A dedicated measurement performance index is calculated to determine the optimal sensors location that provides the maximum accuracy with the minimum number of sensors to be deployed. The application and validation of the tool in a real indoor swimming pool outlined that the measurement uncertainty due to the incorrect location of the existing thermostat was higher than ± 0.5 °C (thermostat uncertainty datasheet) for the 42% of the period considered. The optimized placement determined with the SOU decreased that period to 1.5% of the overall time. [ABSTRACT FROM AUTHOR]

Highlights: [•] A new characterization technique for air-coupled ultrasound probes is presented. [•] A dedicated shock tube is designed to generate a controlled pressure wave. [•] A shock wave with low pressure and high frequency content is generated. [•] A quantitative transfer function for air-coupled ultrasound probe is measured. [Copyright &y& Elsevier]

Abstract: Nowadays there are several direct or indirect measurement methods for the determination of the surface velocity in vibrating structures, but two of them seem to be the most promising and interesting, in particular for vibro-acoustic problems: laser Doppler vibrometry (LDV) and near-field acoustic holography (NAH). While LDV is a direct laser-based vibration measurement technique, NAH allows the determination of the particle surface velocity starting from simultaneous microphone measurements performed on a plane array positioned near the vibrating object, although with some limitations. In this work the two structural and acoustic techniques are compared on a simple laboratory case, specifically a plate, in order to carefully and quantitatively assess the measurement uncertainty in the indirect NAH method used to estimate the vibration velocity. Advantages and disadvantages of the two methods are discussed briefly. This study was conducted within the European Growth Project “ACES” (Optimal Acoustic Equivalent Source Descriptors for Automotive Noise Problems) GRD1-1999-11202. [Copyright &y& Elsevier]

The attention is focused on the experimental evaluation of uncertainty sources in modal parameter measurement, when high-energy laser pulses are used to excite the vibration of the structure. The tests were performed on a cantilever beam excited firstly with a hammer and then with laser pulses from a Nd-YAG source (532 nm, 100 mJ/pulse). This paper consider the problem of the lack of knowledge on laser-induced input force that makes the precise quantitative measurement of the mobility functions (FRF) and of the damping ratio difficult. To calculate the FRF an “equivalent” input force was estimated by solving an inverse problem: the “equivalent” force is useful to determine the features of the laser-induced impulsive excitation. The achieved results are in complete agreement with other characterisations presented in previous studies, in particular in terms of specific impulse, time duration and characteristic frequencies. The paper reports several suggestions useful for minimising the effect connected to the use of laser pulse excitation, in particular concerning the limited energy given to the structure under investigation. Two typical applications (modal analysis and vibrational analysis) are reported as example. [Copyright &y& Elsevier]

Elaborates a study which examined advances in laser Doppler vibrometry. Background on the measurement and analysis of mechanical vibrations; Basic principles; Limitations.

A fine-grained regulation of the HVAC emitters, capable of providing heat and cool only where effectively needed, can lead to a significant energy saving. This paper presents the results from an experimental test of an energy-efficient sub-zonal heating management system, based on an innovative comfort sensor. The objective is to demonstrate how the real-time PMV (Predicted Mean Vote) measurement of different positions in a room can be used to apply optimal rules for the climate control. The case study is an office, located in Central Italy, equipped with two separately controllable electrical heaters. The heating system has been coupled with a low-cost, IR-based comfort sensor, named Comfort Eye, to regulate the heating output of each heater in function of the local comfort conditions. A PID (Proportional–integral–derivative) controller, tuned by fuzzy logic, uses the PMV measured in the respective sub-zone as controlled variable, regulates the power of each heater. The system ran for one winter day and results have been compared with a reference condition, representative of the typical ON/OFF control of the room. The reference condition has been created with the same heating system, but without the sub-zonal division. The comparison, considering the specific application presented, turned out that the sub-zonal control system could achieve an energy saving up to 17% with respect to the typical ON/OFF control with a slight improvement of thermal comfort, reduced deviation from the neutral condition (PMV = 0). This shows that the possibility of measuring comfort distributions is crucial to achieve optimal environmental control. [ABSTRACT FROM AUTHOR]

A novel non-destructive testing procedure for delamination detection based on the exploitation of the simultaneous time and spatial sampling provided by Continuous Scanning Laser Doppler Vibrometry (CSLDV) and the feature extraction capability of Multi-Level wavelet-based processing is presented in this paper. The processing procedure consists in a multi-step approach. Once the optimal mother-wavelet is selected as the one maximizing the Energy to Shannon Entropy Ratio criterion among the mother-wavelet space, a pruning operation aiming at identifying the best combination of nodes inside the full-binary tree given by Wavelet Packet Decomposition (WPD) is performed. The pruning algorithm exploits, in double step way, a measure of the randomness of the point pattern distribution on the damage map space with an analysis of the energy concentration of the wavelet coefficients on those nodes provided by the first pruning operation. A combination of the point pattern distributions provided by each node of the ensemble node set from the pruning algorithm allows for setting a Damage Reliability Index associated to the final damage map. The effectiveness of the whole approach is proven on both simulated and real test cases. A sensitivity analysis related to the influence of noise on the CSLDV signal provided to the algorithm is also discussed, showing that the processing developed is robust enough to measurement noise. The method is promising: damages are well identified on different materials and for different damage-structure varieties. [ABSTRACT FROM AUTHOR]

• Biochar (BCH) and recycled carbon fibres (RCF) were used as conductive additions. • The combined use of BCH and RCF lowered the electrical impedance of mortar/concrete. • BCH increased compressive and tensile splitting strength of concrete. • BCH and RCF increased capillary water absorption and carbonation of concrete. • BCH and RCF reduced the chlorides penetration depth thanks to the "barrier effect". Biochar (BCH) and recycled carbon fibres (RCF) were used as carbonaceous additions in low-resistive mortars/concretes. Their effects on mechanical, electrical, and durability properties were investigated. Tests were performed both during curing and accelerated degradation. The combined use of RCF and BCH decreased the electrical impedance of cement-based matrices, enabling the use of low-cost monitoring instrumentation, and improved their mechanical performance. Recycled carbon fibres and biochar additions increased carbonation and capillary water absorption but acting as a barrier they made water and chlorides penetrate less deeply. [ABSTRACT FROM AUTHOR]

The integrity of the wheel is very important for the safety of railway. In this paper a laser-ultrasonic diagnostic measurement procedure has been designed for the inspection of the train wheels with the aid of a FE-model simulating the ultrasound propagation within the wheel itself. The laser-ultrasonic method exploits an air-coupled ultrasonic probe that detects the ultrasonic waves generated by a high-energy pulsed laser. As a result, the measurement chain is completely non-contact, from generation to detection, this making it possible to considerably speed up the testing set-up time and make it more flexible. This is an important advantage with respect to the conventional NDT technologies currently applied to train component diagnostics, as contact phase array methods. Laser ultrasonics is a complete remote technique since both the laser source and the receiving probe are installed in the proximity of the wheel directly on the bogie and therefore it is a more flexible technology with respect to standard techniques applied for wheel train diagnostics, as phased array. The applications of laser-ultrasonic technique available in the state-of-the-art work with high energy ultrasonic waves to guarantee good signal to noise ratio. Therefore, conventional laser-ultrasonic systems operates under ablative regime that assures high energy ultrasonic waves generation. On the other hand, the ablation produces damages on the surface of the component inspected. In this paper, it has been demonstrated that it is possible to work with lower energy waves, i.e. in the limit between ablative and thermo-elastic regime, if the experiment is properly designed on the basis of a numerical model. This operation regime allowed to guarantee a material removal below the threshold admitted in rail wheel application. The diagnostic procedure developed has been applied for the inspection of train wheels provided by the Italian railway company Trenitalia, on which dominant wheel failure cracks have been expressly created. [ABSTRACT FROM AUTHOR]

The present paper demonstrates the applicability of a laser-ultrasonic procedure to improve the performances of train axle ultrasonic inspection. The method exploits an air-coupled ultrasonic probe that detects the ultrasonic waves generated by a high-power pulsed laser. As a result, the measurement chain is completely non-contact, from generation to detection, this making it possible to considerably speed up inspection time and make the set-up more flexible. The main advantage of the technique developed is that it works in thermo-elastic regime and it therefore can be considered as a non-destructive method. The laser-ultrasonic procedure investigated has been applied for the inspection of a real high speed train axle provided by the Italian railway company (Trenitalia), on which typical fatigue defects have been expressly created according to standard specifications. A dedicated test bench has been developed so as to rotate the axle with the angle control and to speed up the inspection of the axle surface. The laser-ultrasonic procedure proposed can be automated and is potentially suitable for regular inspection of train axles. The main achievements of the activity described in this paper are: – the study of the effective applicability of laser-ultrasonics for the diagnostic of train hollow axles with variable sections by means of a numerical FE model, – the carrying out of an automated experiment on a real train axle, – the analysis of the sensitivity to experimental parameters, like laser source – receiving probe distance and receiving probe angular position, – the demonstration that the technique is suitable for the detection of surface defects purposely created on the train axle. [ABSTRACT FROM AUTHOR]

• Laser Ultrasonics NDT for train wheelset inspection. • Axle standard defects investigated. • FEM model developed to drive experiments and set optimal measurement set-up. • Experimental parameters identified to improve the contrast between sound and damaged area. Laser-Ultrasonics Testing (LUT) is a Non-Destructive Technique (NDT) with good potential for application in the railway sector, nevertheless this technique is not yet used in practice because there are some practical difficulties to overcome. The possibility of measuring on a complete wheelset by bypassing the keying of the wheel will allow drastically reducing the inspection time but it has not yet been demonstrated. In fact, the attenuation of the signal in the path makes complex the interpretation of the generated waves. This paper aims at illustrating how the combination of simulated and experimental data allows to optimize the test setup for having output data of unambiguous interpretation. The main innovations presented in this paper are: (i) the possibility to work with low energy waves in the thermoelastic-ablative limit while maintaining satisfactory contrast levels for the purpose of defect detection and (ii) the implementation of a complete Finite Element Model (FEM) including the generation and propagation of waves in the solid domain and the propagation in air. This last step has not considered before in previous papers. The model allows to define the optimal experimental conditions to have a measured signal with an adequate signal-to-noise ratio (SNR > 6 dB) and to define an experimental procedure for defect detection reliable and comparable with current standards. This study lays the foundations for an innovative approach for train axle diagnostics which can be used during train extraordinary maintenance interventions. The laser ultrasonics system presented in this paper can be likely integrated in the pit lathe and exploited to monitor the railway wheels during their re-profiling phase, without having to remove them from the vehicle. [ABSTRACT FROM AUTHOR]

• An automated system for standard carbonation depth measurements is proposed. • Processing algorithm provides average and maximum carbonation depths. • Computer vision, image processing, and Convolutional Neural Networks are used. • Convolutional Neural Networks separate carbonated aggregates from paste. • The measurement system is challenged in terms of repeatability and reproducibility. This paper aims at discussing an automated measurement system for detecting carbonation depth in concrete sprayed with phenolphthalein. Image processing and Convolutional Neural Networks strategies are exploited to accurately separate the carbonated and non-carbonated areas and to remove those aggregates on the carbonation front that could bring to a wrong evaluation of the carbonation depth. Very strong correlation (R2 = 0.96) is found between results provided by the proposed approach and the method suggested by the EN 13295 standard. The expanded uncertainty (coverage factor k = 2) of this novel approach is 0.08 mm. ANOVA analysis performed in multi-operator tests proved that the highest source of uncertainty is the measurement system, which, on the other hand, is robust to changes in the operator performing the measurement. [ABSTRACT FROM AUTHOR]

• Electrical impedance is used as NDT for concrete health status assessment. • Three concrete compositions were subjected to accelerated degradation tests. • Wenner's method is used for measuring electrical impedance in AC configuration. • Electrical impedance decreases with water/chlorides penetration. • Low-clinker cements help in increasing detectability of aggressive agents. This paper discusses the electrical impedance behaviour, measured according to the Wenner's method, of three different concrete mixes during accelerated degradation tests. Being a first attempt to move from laboratory to in-field applications targeted to long-term monitoring, the same electrode array configuration and set-up (AC current at 10 kHz) is used. Results show that electrical impedance decreases down to 24% in capillary water absorption tests, 77% and 86% in salt-spray chamber and wet/dry cycles with 3.5% NaCl solution, respectively. The two new low-clinker cements adopted seem to improve the measurement sensitivity towards contaminants ingress with respect to the commercial one (reference). [ABSTRACT FROM AUTHOR]

Development of a compact beam intensity monitor using gas amplified sample current measurement is described. The monitor can be a powerful tool for x-ray spectroscopy and microscopy when the beam is defined by a small pinhole or slits and when the workspace around the sample is limited. The thickness of the monitor is as small as approximately 3 mm, and the dimension is 10 mm square. The photon flux is monitored by measuring x-ray excited current from an Al foil under atmospheric conditions. Emitted electrons from the Al foil can ionize surrounding air molecules, and the gas amplified current can be measured with the use of a biased grid that prevents created ion pairs from recombination. © 2000 American Institute of Physics. [ABSTRACT FROM AUTHOR]