Miniaturized thermal flow sensors have opened the doors for a large variety of new applications due to their small size, high sensitivity and low power consumption. Theoretically, very small detection limits of air velocity of some micrometers per second are achievable. However, the superimposed free convection is the main obstacle which prevents reaching these expected limits. Furthermore, experimental investigations are an additional challenge since it is difficult to generate very low flows. In this paper, we introduce a physical method, capable of generating very low flow values in the mixed convection region. Additionally, we present the sensor characteristic curves at the zero flow case and in the mixed convection region. Results show that the estimated minimum detectable air velocity by the presented method is 0.8 mm/s. The equivalent air velocity to the noise level of the sensor at the zero flow case is about 0.13 mm/s.
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http://dx.doi.org/10.3390/s130810944 | DOI Listing |
Sensors (Basel)
January 2025
Department of Electronics Engineering, Kaunas University of Technology, 51368 Kaunas, Lithuania.
The application of spread-spectrum signals (arbitrary pulse width and position (APWP) sequences) in air-coupled resonant ultrasound spectroscopy is studied. It was hypothesized that spread-spectrum signal optimization should be based on te signal to noise ratio (SNR). Six APWP signal optimization criteria were proposed for this purpose.
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December 2024
Faculty of Management, Lublin University of Technology, 20-618 Lublin, Poland.
This article presents the results of experimental studies on the influence of the geometry of high-voltage plasma actuator electrodes on the change in flow in the boundary layer and their influence on the change in the lift coefficient. The plasma actuator used in the described experimental studies has a completely different structure. The experimental model of the plasma actuator uses a large mesh ground electrode and different geometries of the high-voltage electrodes, namely copper solid electrodes and mesh electrodes (the use of mesh electrodes, large GND and HV is a new solution).
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December 2024
Faculty of Food Technology and Biotechnology, University of Zagreb, Pierottijeva 6, 10 000 Zagreb, Croatia.
Considering the short shelf life of fresh pumpkin due to its high water content and the extensive use of dried pumpkin in the food industry, it is necessary to find an efficient drying method that minimizes water activity and preserves nutritional properties. In this study, the effects of hot air drying (HAD), vacuum drying (VAD), and conductive drying (CD) at 50, 60, and 70 °C on fatty acid profiles were investigated to determine optimal drying conditions that preserve fatty acid (FA) quality and associated nutritional benefits. Results showed that drying methods had a significant effect ( < 0.
View Article and Find Full Text PDFWater Res
December 2024
School of Energy and Environment, City University of Hong Kong, Hong Kong SAR, China; State Key Laboratory of Marine Pollution, City University of Hong Kong, Hong Kong SAR, China. Electronic address:
Airflow models are powerful tools for ventilation design to achieve odour and corrosion mitigation in sewer networks. Currently, there lacks a model able to efficiently predict in-sewer dynamic airflows, as all available dynamic models with an acceptable accuracy are computationally demanding. In this study, a swift dynamic airflow model based on an ordinary differential equation (ODE) is derived by simplifying the one-dimensional Navier Stokes Equations (NSE), supported by the observation that the NSE solutions always display negligible spatial variations in air velocity when applied to a sewer conduit.
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December 2024
Kotelnikov Institute of Radio Engineering and Electronics of RAS, Moscow 125009, Russia.
An important technical task is to develop methods for recording the phase transitions of water to ice. At present, many sensors based on various types of acoustic waves are suggested for solving this challenge. This paper focuses on the theoretical and experimental study of the effect of water-to-ice phase transition on the properties of Lamb and quasi shear horizontal (QSH) acoustic waves of a higher order propagating in different directions in piezoelectric plates with strong anisotropy.
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