查看更多>>摘要：A low-cost and portable reflectometric system was described to correlate the water content inside building material with the resonance frequency of a planar probe. An inexpensive planar patch resonator was realized, and a high sensitivity load cell was developed to investigate the external force effect on the resonance frequency shift. Regarding the material under test, four stones commonly employed in Italy Cultural Heritage buildings were used: Pietra Gentile, Leccese, Carparo, and Tuff. Measurements were carried out at different water content values and were performed using a portable vector network analyzer. Two different trials were carried out ten times for each moisture level: with an unknown handheld force exerted on the probe and using the load cell to ensure a repeatable force. Results showed that a repeatable applied force guaranteed more reproducible mea-surements. The achieved humidity/frequency calibration curves can be used, in practice, for non-invasive on-site water content monitoring of historic structures.
查看更多>>摘要：In this paper, a piezoelectric-sensor-based free-field shock-wave test method for measuring the muzzle overpressure of a meteorological air is proposed. The test system is described, and the measurement-point layout is introduced. Experimental verification of the results from Autodyn numerical simulations based on the Sadowski formula was conducted, and the distributions of pressure, density, and velocity of the muzzle flow field were simulated as references for the free-field shock-wave pressure for the actual tests. The experimental results from different models of air cannons demonstrate that the proposed method can accurately measure the peak of the free-field shock-wave overpressure. Considering the location of each sensor and the time interval between the shock-wave overpressure peak reaching adjacent test points, the propagation speed can be obtained, and the muzzle-pressure propagation law can be established. This work has certain guiding significance for the development and design of meteorological air cannons.
查看更多>>摘要：Compressed Sensing (CS) is an effective method for improving the real-time performance of crack-induced acoustic emission (AE) signals analysis in Structural Health Monitoring (SHM) of rails. Aiming to promote the reconstruction accuracy and speed of CS, a reconstruction method is proposed based on improved Sparsity Adaptive Matching Pursuit (SAMP) and modular dictionary update. In the proposed method, a multiscalemodular dictionary is devised based on a multiscale dataset to enhance the real-time performance of reconstruction. Meanwhile, the step size of the SAMP is adaptively adjusted by the kurtosis residuals, which promotes the reconstruction accuracy. Furthermore, to optimize the adaptability of the dictionary, kurtosis-deviation is utilized to update the dictionary adaptively and modularly. The proposed method was verified by tensile tests. The results demonstrate that the proposed method has a higher reconstruction accuracy and speed than other methods, which can guide real-time crack-induced signal analysis in the SHM of rails.
查看更多>>摘要：In this research, an effective, selective and accurate method for determining the isoniazid (INH) residues is presented based on screen printed carbon electrode (SPCE) modified with graphene oxide/gold nanourchin/layer molecular imprinted polymer. The morphological properties of the suggested sensor were explored by FESEM, FTIR, EDX techniques as well as its electrochemical characteristics versus isoniazid were invigilated in detail. The proposed sensor was capable of measuring the isoniazid in the linear range of 2.5-850.0 nM with a detection limit of 0.85 nM. One of the excellent features of this sensor is its good selectivity to INH in the presence of anionic species from these families of drugs. This sensor has an acceptable price, speed, detection limit, selectivity, reproducibility and fast response time compared to other isoniazid quantification sensors. The proposed sensor was used to measure the INH values in biological samples such as blood and urine with appropriate recovery percentage.
查看更多>>摘要：Technological development of remote sensing and computer graphic techniques resulted in various methods of documenting heritage sites. This paper presents validation of point clouds produced using different measurement techniques: SfM (based on images taken with a hand-held digital camera and from a UAV) and TLS and its products - a textured 3D vector model and a reality mesh. The study area is the ruins of the Church of the Annunciation of the Blessed Virgin Mary of Mount Carmel in Zag ' orz, Poland. The obtained results allowed for formulating general conclusions regarding the usage of particular methods for documenting heritage sites, achievable measurement accuracies and data quality. Possible further applications of produced models in VR and BIM were discussed. Based on the analyses, the research also proposes workflow for inventory of heritage sites, which may become useful during documentation surveys and modelling planning.
查看更多>>摘要：Six Italian non-accredited laboratories participated to an interlaboratory study aimed at measuring Differential Pressure (DP) and Bacterial Filtration Efficiency (BFE) of three face-mask models using methods in-line with EN 14683 standard. Methodological non-conformities were annotated. Repeatability and reproducibility on quintuplicate samples were calculated according to ISO 5725-2. Sample stability was also assessed. Laboratories were ranked according to the total standard deviation over all samples and proficiency was evaluated using z-score according to ISO 13528. Although some non-conformities were present, performances for the DP measurements were always acceptable. One laboratory had to revise the bacterial suspension preparation for the BFE test. Overall, non-accredited laboratories working during pandemic emergency performed satisfactorily. Sample-to-sample variability impacted measurement repeatability. BFE values above 98% showed good repeatability (<1.0%) and reproducibility (<6.1%), but high BFE uncertainty was associated to community masks. Our findings suggest that relevant face-mask conformity standards should consider uncertainty of BFE and DP measurements.
查看更多>>摘要：In this paper, we propose an on-chip wideband microwave interferometry sensor to measure minute variations in the dielectric properties of chemical liquids with a marginal volume (5 ul). The device is based on coplanar waveguide (CPW) and slot-line technology. It consists of two uniplanar broadband hybrid ring couplers and two branches. Each branch is loaded with an electrically small discontinuity (ESD), which is the sensing region. If the sensor is unloaded or loaded with the same material under test (MUT), we obtain a transmission-zero. When different MUTs are loaded into the two microfluidic channels, new interference frequencies occur. Variations in transmission-zeros are employed to express variations in the dielectric properties or concentrations of the MUT. Experiments show that the sensitivity of the ESD-inspired interference sensor is higher (average value from 13 GHz to 17 GHz) than that of the wideband interference sensor by 1.2 times.
查看更多>>摘要：Optical measurement methods are being increasingly used in the profile measurement field, but optical highprecision measurements of gear tooth profiles have not been achieved. Therefore, a high-precision profile measurement method that uses incoherent line structured light was proposed and a corresponding measurement system was developed in this paper. To calibrate the accuracy of this system, profile measurement experiments using roughness comparison specimens were conducted. Finally, the tooth profile measurement experiments using an involute master were performed. The results indicated that the incoherent line structured light method was less affected by speckle noise and had higher measurement resolution than the line laser method. The tooth profile error for the involute master measured by the incoherent line structured light method was +/- 2.2 mu m. This study provides a new method for the industrial application of optical high-precision measurement of gear tooth profiles.
查看更多>>摘要：Wire arc additive manufacturing technology (WAAM) has become a very promising alternative for large-scale metal components manufacturing. Due to the unsatisfactory performance in solidification, surface quality monitoring has been a critical issue for WAAM. In this study, we set up a non-contact in-situ 3D laser profilometer inspection (3D-LPI) system to automatically monitor the visual surface defects. The 3D surface point cloud was converted to a 2D topography image firstly. Then the surface defects were identified after the classification of pixels using a support vector machine (SVM) model. The availability of the system was validated in the building process of different aluminum components. The results illustrated that the proposed novel methods can detect not only widespread bulge and collapsing defects but also small pore defects with pixel-level accuracy, which has great significance for the automatic quality evaluation and process control in WAAM.
Carmen Manjabacas-Tendero, MariaMiguel-Eguia, ValentinGarcia-Martinez, EnriqueMartinez-Martinez, Alberto...
11页
查看更多>>摘要：Although it is essential to know the cutting temperature in turning operations, it is very complex to measure it by direct procedures because of the contact tool-workpiece is not accessible. In this research, a methodology consisting of a natural thermocouple, built from the contact tool-workpiece, has been validated. For that, it was necessary to measure the temperature of a reference point on the tool rake face and to probe the results by FEM. Three different materials were experimented getting to a good agreement between the real values of the temperature and those obtained by simulation. Particularly, the range of measurement was defined for the Tialuminides machining by uncoated WC inserts. In addition, taking into consideration the correlations obtained between the temperatures of the flank contact tool-workpiece and of the tool rake face and the wearing in the flank, the evolution of this last variable would be known.
NSTL
Elsevier