This paper discusses the thermal influence on long-distance and noncontact measurement of suspension bridge three-dimensional displacement by the use of an optical system composed of a digital ...camera, infrared active targets, and computational support. In this type of measurement method, the optical propagation path of light through the air can range from 250 m up to 750 m, making its measurement accuracy strongly dependent on atmospheric refraction and turbulence, phenomena that are linked to the vertical temperature gradient between the camera and targets. In addition, the adopted measurement geometrical configuration can lead to a height difference between these two elements (camera and targets) above 50 m. The paper describes the experimental setup and procedure followed for the determination of local temperature vertical gradients in the 25th of April Bridge in Lisbon (Portugal), where an optical measurement system was applied. The obtained thermal measurements are presented and applied in the evaluation of the systematic refraction vertical deviation, based on appropriate mathematical models mentioned in the paper, and for the identification of stable or unstable observation thermal conditions related to turbulence.
A variety of polymers or surfactant mixtures or aeration of a number of liquids could generate mixtures of liquid and foam. Therefore, characterizing the properties of liquid/foam mixtures has ...important applications in the chemical process industry. The lack of a robust automated method for characterization within limited time and with high accuracy, however, has made this task difficult. In this work, we propose a new method based on image analysis for quantifying the geometric and statistical properties of such liquid/foam mixtures using images captured by an optical camera. The method can reliably achieve automated segmentation of liquid and foam layers. It can also find the boundaries of individual bubbles in the foam layer. At first, the region of interest, the foam region, is segmented from the input raw image. Then, the foam region is partitioned into two types of subregions, namely, loose foam or dense foam, according to local texture feature analysis. In the next step, to segment bubbles within the foam to obtain quantitative characterization, we apply two image processing algorithms, namely, Canny edge detection and K-means clustering, each specific to a different type of foam (loose or dense). The results show that the proposed automated segmentation and characterization method is robust and applicable to the processing of foam/liquid mixtures under many conditions.
An image processing technique was used to predict the size distribution of the high speed, fine droplets at downstream of an air blast atomizer. The spray visualization setup consisted of UV lamps as ...light source, a stroboscope for slowing down the droplet motion, and a digital camera to capture the droplet images. The experiments were carried out at different liquid flow rates with various nozzle diameters. Two key unknown parameters (spray half angle and dispersion angle) of the air blast atomizer model in Fluent were obtained from these experiments. Using the obtained parameters and other structural parameters, the spray modeling was performed, and the Rosin-Rammler distribution was obtained and compared with those obtained from image processing technique through a diagnostic matrix. Regarding the kappa value, the agreement between predictions of the Fluent model and the image processing technique was moderate.
Environment perception with cameras is an important requirement for many applications for autonomous vehicles and robots. This work presents a stereoscopic omnidirectional camera system for ...autonomous vehicles which resolves the problem of a limited field of view and provides a 360° panoramic view of the environment. We present a new projection model for these cameras and show that the camera setup overcomes major drawbacks of traditional perspective cameras in many applications.
Unmanned Aerial Vehicles (UAVs) equipped with video cameras are a flexible support to ensure civil and military safety and security. In this thesis, a video processing chain is presented for moving ...object detection in aerial video surveillance. A Track-Before-Detect (TBD) algorithm is applied to detect motion that is independent of the camera motion. Novel robust and fast object detection and segmentation approaches improve the baseline TBD and outperform current state-of-the-art methods.
The mechanism of the thermospray formed at low flow rates using a peristaltic pump in thermospray flame furnace atomic absorption spectrometry (TS-FF-AAS) is described here for the first time. The ...study was based on magnified images of the thermospray formed inside the hot tube furnace by using a high-speed CMOS camera. For this purpose different image acquisition speeds were used (from 1000 to 18000 frames/s), revealing that the thermospray obtained under such conditions is quite different from those already reported. The frames of the thermospray evolution indicate that the Leindenfrost effect plays an important role and allow us to propose a mechanism for its formation. The analysis of the images contributed to calculation of parameters related to thermospray formation, such as pulse incidence average (110 ± 10, 320 ± 50, and 1200 ± 150 pulses per second) and pulse speed (6 ± 1, 10 ± 1, and 14 ± 2 m s-1) for 0.1, 0.4, and 1.0 mL min-1 flow rate, respectively, for both parameters. Additionally, the evaporation constant (λ) of 10-4 m2 s-1 was estimated, and the present thermospray was correlated to the conventional sprays using the Sauter mean diameter (SMD) parameter, which ranged from ca. 2 to 44 μm. In order to correlate the information obtained through images with analytical parameters employing the thermospray, the sensitivities for cadmium determination at each condition (0.12, 0.11, and 0.069 s L μg-1 for 0.1, 0.4, and 1.0 mL min-1 flow rate, respectively) were taken into account.
Several properties of ceramic foams render them promising substrates for various industrial processes. For automotive applications, the foam properties that need to be further studied include the ...substrate impact on the exhaust gas flow, in terms of pressure drop and flow uniformity. In this paper, pressure drop measurements are performed with different honeycomb and ceramic foam substrates, and pressure drop correlations are discussed. The flow uniformity upstream and downstream of the substrates is evaluated using particle image velocimetry. The results show that ceramic foam substrates induce higher pressure drop, while increasing the uniformity of the flow. In contrast to honeycomb monoliths, the flow uniformity downstream of ceramic foams does not decrease with increasing flow velocity. The higher flow uniformity of ceramic foams is not only caused by their higher pressure drop, but also by flow homogenization that occurs inside the ceramic foam structure, as a result of the momentum exchange perpendicular to the main flow direction.
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