Journal articles on the topic 'High-speed-video photography'
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KAMEDA, Masaharu, and Koichi NISHINO. "Recent Progress in High-speed Video/Camera Photography." Journal of the Visualization Society of Japan 23, no. 89 (2003): 75. http://dx.doi.org/10.3154/jvs.23.75.
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Khalid, Amir, M. Jaat, Izzuddin Zaman, B. Manshoor, and Mas Fawzi. "Effect of Pilot Injection on Mixture Formation, Ignition Process and Flame Development in Diesel Combustion." Applied Mechanics and Materials 390 (August 2013): 327–32. http://dx.doi.org/10.4028/www.scientific.net/amm.390.327.
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The alternative combustion strategies with systematic control of mixture formation have provided new opportunities and considerable improvement in the combustion process and response to meet the stringent emissions standards. Purpose of this research is to investigate the influences of pilot injection on the fuel-air premixing especially during ignition delay period. During this period, the interaction between fuel spray and surrounding gas prior to ignition which linked to the improvement of mixture formation, ignition process and initial heat recovery thus predominantly influences the combustion process and exhaust emissions. This study investigates the effects of pilot injection using a rapid compression machine together with the schlieren photography and direct photography methods. The detail behavior of mixture formation during ignition delay period was investigated using the schlieren photography system with a high speed digital video camera. This method can capture spray evaporation, spray interference and mixture formation clearly with real images. Ignition process and flame development were investigated by direct photography method using a light sensitive high-speed color digital video camera. Pilot injection promotes mixture formation during ignition delay period and slower oxidation reaction and thus leads to earlier rise and lower peak heat release rate.
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Soyama, Hitoshi. "High-Speed Observation of a Cavitating Jet in Air." Journal of Fluids Engineering 127, no. 6 (July 14, 2005): 1095–101. http://dx.doi.org/10.1115/1.2060737.
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The use of cavitation impact is a practical method for improving the fatigue strength of metals in the same way as shot peening. In the case of peening using cavitation impact, cavitation is produced by a high-speed submerged water jet with cavitation, i.e., a cavitating jet. A cavitating jet in air was successfully generated by injecting a high-speed water jet into a low-speed water jet injected into air using a concentric nozzle. In order to investigate the various appearances of cavitating jets in air, an observation was carried out using high-speed photography and high-speed video recording. In this study, periodical shading of the cavitation cloud was observed and the frequency of the shading was found to be a function of the injection pressure of the low-speed water jet. Unsteadiness of the low-speed water jet, which is related to the periodical shading of the cloud, was also observed.
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Azmi, Azwan I., R. J. T. Lin, and D. Bhattacharyya. "High-Speed Photographic Study of Chip Formation during End Milling of GFRP Composites." Advanced Materials Research 845 (December 2013): 915–19. http://dx.doi.org/10.4028/www.scientific.net/amr.845.915.
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The chip forming process during end milling of glass fibre reinforced composites has been investigated in this study. The qualitative results from a high speed video camera has showed that discontinuous and fracturing of chips has been created due to the heterogeneity and insufficient ductility of the composite materials. The high-speed photography footage has also disclosed that a layer of delaminated chip can be formed as the tool cutting edge fractured the workpiece along the fibre orientation. The fracture of chips into smaller segments accelerated as the cutting speed increases. Likewise, shorter fragment of chips were created as the tool cut at different fibre orientation or angle. This makes it difficult to denote any chip formation processes during the end milling experiments.
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Khalid, Amir, and Bukhari Manshoor. "Effect of High Swirl Velocity on Mixture Formation and Combustion Process of Diesel Spray." Applied Mechanics and Materials 229-231 (November 2012): 695–99. http://dx.doi.org/10.4028/www.scientific.net/amm.229-231.695.
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Diesel engines generate undesirable exhaust emissions during combustion process and identified as major source pollution in the worldwide ecosystem. To reduce emissions, the improvements throughout the premixing of fuel and air have been considered especially at early stage of ignition process. Purpose of this study is to clarify the effects of swirl velocity on flow fuel-air premixing mechanism and burning process in diesel combustion that strongly affects the exhaust emissions. The effects of physical factors on mixture formation and combustion process to improve exhaust emissions are discussed in detail. This study investigated diesel combustion fundamentally using a rapid compression machine (RCM) together with the schlieren photography and direct photography methods. RCM was used to simulate actual phenomenon inside the combustion chamber with changing design parameter such as swirl velocity, injection strategies and variable nozzle concept. The detail behavior of mixture formation during ignition delay period was investigated using the schlieren photography system with a high speed digital video camera. This method can capture spray evaporation, spray interference and mixture formation clearly with real images. Ignition process and flame development were investigated by direct photography method using a light sensitive high-speed color digital video camera. Moreover, the mechanism and behavior of mixture formation were analyzed by newly developed image analysis technique. Under high swirl condition, the ignition delay is extended, the higher heat losses and unutilized high-density oxygen associated with slower initial heat recovery begins might be the explanation for the longer combustion duration, reductions of pick heat release and promote combustion and soot oxidation. The real images of mixture formation and flame development reveal that the spray tip penetration is bended by the high swirl motion, fuel is mainly distributed at the center of combustion chamber, resulting that flame is only formed at the center region of the combustion chamber. It is necessary for high swirl condition to improve fuel-air premixing.
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Zhang, Chi, Zhongze Tang, Min Zhang, Bo Wang, and Lei Hou. "Developing a More Reliable Aerial Photography-Based Method for Acquiring Freeway Traffic Data." Remote Sensing 14, no. 9 (May 5, 2022): 2202. http://dx.doi.org/10.3390/rs14092202.
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Due to the widespread use of unmanned aerial vehicles (UAVs) in remote sensing, there are fully developed techniques for extracting vehicle speed and trajectory data from aerial video, using either a traditional method based on optical features or a deep learning method; however, there are few papers that discuss how to solve the issue of video shaking, and existing vehicle data are rarely linked to lane lines. To address the deficiencies in current research, in this study, we formulated a more reliable method for real traffic data acquisition that outperforms the traditional methods in terms of data accuracy and integrity. First, this method implements the scale-invariant feature transform (SIFT) algorithm to detect, describe, and match local features acquired from high-altitude fixed-point aerial photographs. Second, it applies “you only look once” version 5 (YOLOv5) and deep simple online and real-time tracking (DeepSORT) to detect and track moving vehicles. Next, it leverages the developed Python program to acquire data on vehicle speed and distance (to the marked reference line). The results show that this method achieved over 95% accuracy in speed detection and less than 20 cm tolerance in vehicle trajectory mapping. This method also addresses common problems involving the lack of quality aerial photographic data and accuracy in lane line recognition. Finally, this approach can be used to establish a Frenet coordinate system, which can further decipher driving behaviors and road traffic safety.
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Asakura, F., H. Tenjin, K. Matsumoto, S. Ueda, and M. Urano. "Digital Subtraction and Conventional Blood Flow Studies in Porcine Experimental Aneurysms." Interventional Neuroradiology 5, no. 3 (September 1999): 207–12. http://dx.doi.org/10.1177/159101999900500302.
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Flow studies are important to understanding pathogenesis and treatment of cerebral aneurysms, but have not been possible in the clinical setting. We used experimental aneurysms established in and then removed from pigs to compare and correlate flow studies by high-speed video photography of introduced particles and by clinically applicable digital subtraction angiography. Venous pouches were used to create aneurysms in incised common carotid arteries. After aneurysms and parent arteries were removed, specimens were rendered translucent with solvents so they could be studied by video photography of introduced plastic particles in addition to digital subtraction angiography with iodinated contrast material. Regions of interest were studied individually. Mean transit time for contrast in the preparation correlated with videographically measured particle flow velocity (r = 0.616). Digital subtraction angiography should be useful in evaluation of flow in the clinical assessment and treatment of cerebral aneurysms, such as in endovascular therapy.
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Bergfeld, Bastian, Alec van Herwijnen, Benjamin Reuter, Grégoire Bobillier, Jürg Dual, and Jürg Schweizer. "Dynamic crack propagation in weak snowpack layers: insights from high-resolution, high-speed photography." Cryosphere 15, no. 7 (July 30, 2021): 3539–53. http://dx.doi.org/10.5194/tc-15-3539-2021.
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Abstract. Dynamic crack propagation in snow is of key importance for avalanche release. Nevertheless, it has received very little experimental attention. With the introduction of the propagation saw test (PST) in the mid-2000s, a number of studies have used particle tracking analysis of high-speed video recordings of PST experiments to study crack propagation processes in snow. However, due to methodological limitations, these studies have provided limited insight into dynamical processes such as the evolution of crack speed within a PST or the touchdown distance, i.e. the length from the crack tip to the trailing point where the slab comes to rest on the crushed weak layer. To study such dynamical effects, we recorded PST experiments using a portable high-speed camera with a horizontal resolution of 1280 pixels at rates of up to 20 000 frames s−1. We then used digital image correlation (DIC) to derive high-resolution displacement and strain fields in the slab, weak layer and substrate. The high frame rates enabled us to calculate time derivatives to obtain velocity and acceleration fields. We demonstrate the versatility and accuracy of the DIC method by showing measurements from three PST experiments, resulting in slab fracture, crack arrest and full propagation. We also present a methodology to determine relevant characteristics of crack propagation, namely the crack speed (20–30 m s−1), its temporal evolution along the column and touchdown distance (2.7 m) within a PST, and the specific fracture energy of the weak layer (0.3–1.7 J m−2). To estimate the effective elastic modulus of the slab and weak layer as well as the weak layer specific fracture energy, we used a recently proposed mechanical model. A comparison to already-established methods showed good agreement. Furthermore, our methodology provides insight into the three different propagation results found with the PST and reveals intricate dynamics that are otherwise not accessible.
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Maines, B., and R. E. A. Arndt. "The Case of the Singing Vortex." Journal of Fluids Engineering 119, no. 2 (June 1, 1997): 271–76. http://dx.doi.org/10.1115/1.2819130.
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A relatively high amplitude, discrete tone is radiated from fully developed tip vortex cavitation under certain conditions. The phenomenon of the “singing vortex” was first reported by Higuchi et al. (1989). This study more closely examines the singing phenomenon by varying the hydrofoil cross-section, scale, angle of attack, water quality, and cavitation number in two different facilities. Noise data were collected for each condition with visual documentation using both still photography and high speed video in an effort to explain the mechanism of vortex singing. The theory of Kelvin (1880) provides a framework for correlating all the data obtained.
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Srichai, Prathan, Chinda Chareonphonphanich, Preechar Karin, and Nuwong Chollacoop. "Spray Visualization of Biodiesel and Diesel in a High Pressure Chamber." Advanced Materials Research 931-932 (May 2014): 1043–47. http://dx.doi.org/10.4028/www.scientific.net/amr.931-932.1043.
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The present research attempted to characterize fuel spray pattern, such as spray angle, spray penetration and their mixture formation by recourse to images analysis. Diesel and biodiesel were used to investigate via a single hole injector (solinoild type) in a constant volume high-pressure chamber. In this experimental study, the spray characteristics of diesel and biodiesel fuel were comparatively evaluated. Initial conditions were ambient temperature, ambient density of 21 kg/m3, injection durations varied from 0.5 and 1 ms and rail pressure of 400 and 800 bar. The series of images were captured by high speed video camera with resolution of 7,500 frames per second and shutter speed of 1/10,000 sec under Schlieren photography technique. The result showed the biodiesel spray penetration was longer than that of the diesel, and spray angle of biodiesel in start injection was larger than biodiesel. From the results, it can be concluded that the higher the density and viscosity of biodiesel, the stronger the effect on the spray mixture formation.
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Audira, Gilbert, Ting-Wei Hsu, Kelvin H. C. Chen, Jong-Chin Huang, Ming-Der Lin, Tzong-Rong Ger, and Chung-Der Hsiao. "A Fast and Cost-Effective (FACE) Instrument Setting to Construct Focus-Extended Images." Inventions 7, no. 4 (November 29, 2022): 110. http://dx.doi.org/10.3390/inventions7040110.
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Image stacking is a crucial method for micro or macro photography. It captures images at different focal planes and then merges them into a single, all-in-focus image with extended focus. This method has been extensively used for digital documentation by scientists working at museums or research institutions. However, the traditional image stacking method relies on expensive instruments to conduct precise image stacking using a computer-based stepper motor controller. In this study, we reported how to conduct image focus extensions with comparable quality to those done by a motorized stepper using a cost-effective instrument setting and an efficient manual stacking method. This method provides a shorter operation time and capability to capture images of living objects and high flexibility in obtaining the images of objects from cm to mm scale. However, it also has some limitations, including the inability to control aperture and exposure time, relatively short working distance at high magnification, requires additional steps to convert the video into images, and heavily relies on the user’s manual observation prior to a video recording. Nevertheless, the authors believe that the current method can be applied as an alternative method to conduct image stacking. The development of such an instrument and method offers a promising avenue for scientists to perform image stacking with greater flexibility and speed in macro photography.
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Hurst, W. J., J. M. Cormier, J. D. Stitzel, M. V. Jernigan, D. M. Moorcroft, I. P. Herring, and S. M. Duma. "A new methodology for investigating airbag-induced skin abrasions." Proceedings of the Institution of Mechanical Engineers, Part D: Journal of Automobile Engineering 219, no. 5 (May 1, 2005): 599–605. http://dx.doi.org/10.1243/095440705x11158.
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Although airbags have been shown to reduce the incidence of life-threatening injuries, they have increased the risk of minor injuries such as those to the skin. Based on the distribution of injuries that can be directly attributed to the airbag itself, it is believed that shear loading exists as a mechanism for these skin injuries. The purpose of this study was to develop a new methodology designed to assess the injury potential from different types of airbag with respect to shear loading. This new methodology utilized a high-speed impactor to accelerate the airbag fabric past a sample of skin. Contact normal forces were monitored by the use of pressure sensors, and fabric velocity was determined from a high-speed video. The abraded skin samples were analysed using light microscopic analysis and ultraviolet light source photography. A new abrasion rating method was developed called the total abrasion score, which allows for quantifiable differentiation between the abrasions caused by different airbag fabric and seam types.
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Wang, Zhi Dong. "Research on the Model of Sports Action Features Based on the Computer Image Processing and Multimedia Databases Technology." Advanced Materials Research 1049-1050 (October 2014): 1947–49. http://dx.doi.org/10.4028/www.scientific.net/amr.1049-1050.1947.
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As we all known, the physical education and sports training are inseparable from the sports action, and the standardization of action is the key to raise the standard of sports. Meantime, in the scientific training process, the analysis and comparison of technical movements’ morphology are essential. And traditional motion analysis technology uses high-speed photography and video image analysis, which cannot accurately determine the action features, therefore cannot meet the needs of quantitative analysis and morphological analysis. In this paper, using the computer image processing and multimedia databases and other computer technology to do quantitative research on sports action characteristics, and establishing the motion feature model, all these will provide a scientific basis and action paradigm for sports teaching and training.
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Spielbauer, T. M., and C. K. Aidun. "The Wave-Thinning and Breakup of Liquid Sheets." Journal of Fluids Engineering 116, no. 4 (December 1, 1994): 728–34. http://dx.doi.org/10.1115/1.2911842.
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In this study, the radially thinning liquid sheets formed by a simple splash plate nozzle were investigated. These sheets, observed using high-speed video and 16 mm photography, were found to breakup by way of a localized rupture mechanism. The sheet is thinned by geometric distortion due to the radial expansion of the sheet, and by stretching caused by the presence of large amplitude sinuous waves. The downstream sheet thickness in the wave-thinned region was calculated from experimentally measured perforation growth rates. These thicknesses were found to be about 12 percent of the predicted value for an undisturbed sheet. Trends in the downstream position at which significant thinning due to sinuous waves is predicted to occur agree with trends in experimentally measured rates of hole formation.
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Trabold, Thomas A., and Ranganathan Kumar. "High Pressure Annular Two-Phase Flow in a Narrow Duct: Part I—Local Measurements in the Droplet Field." Journal of Fluids Engineering 122, no. 2 (January 25, 2000): 364–74. http://dx.doi.org/10.1115/1.483266.
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Detailed measurements have been made in a high pressure, adiabatic (boiled at the inlet) annular flow in a narrow, high aspect ratio duct using a gamma densitometer, hot-film anemometer and high-speed video photography. Measurements of void fraction, droplet frequency, velocity, drop size, and interfacial area concentration have been made to support the three-field computational capability. An important aspect of this testing is the use of a modeling fluid (R-134a) in a vertical duct which permits visual access in annular flow. This modeling fluid accurately simulates the low liquid-to-vapor density ratio of steam-water flows at high pressures. These measurements have been taken in a narrow duct of hydraulic diameter 4.85 mm, and a cross-section aspect ratio of 22.5. However, the flow displays profiles of various shapes not only in the narrow dimension, but also in the width dimension. In particular, the shape of the void profiles depends on the entrained droplet flux from the edges in the vapor core. The average diameter from these profiles compare well with the models developed in the literature. Interfacial area concentration for these low density ratio flows is higher than the highest concentration reported for air-water flows. Video records show that along with the bow-shaped waves, three-dimensional λ-shaped waves appear in annular flows for high flow rates. [S0098-2202(00)00902-0]
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Randolph, Kaylan, Heidi M. Dierssen, Alejandro Cifuentes-Lorenzen, William M. Balch, Edward C. Monahan, Christopher J. Zappa, Dave T. Drapeau, and Bruce Bowler. "Novel Methods for Optically Measuring Whitecaps under Natural Wave-Breaking Conditions in the Southern Ocean." Journal of Atmospheric and Oceanic Technology 34, no. 3 (March 2017): 533–54. http://dx.doi.org/10.1175/jtech-d-16-0086.1.
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AbstractTraditional methods for measuring whitecap coverage using digital video systems mounted to measure a large footprint can miss features that do not produce a high enough contrast to the background. Here, a method for accurately measuring the fractional coverage, intensity, and decay time of whitecaps using above-water radiometry is presented. The methodology was developed using data collected in the Southern Ocean under a wide range of wind and wave conditions. Whitecap quantities were obtained by employing a magnitude threshold based on the interquartile range of the radiance or reflectance signal from a single channel. Breaking intensity and decay time were produced from the integration of and the exponential fit to radiance or reflectance over the lifetime of the whitecap. When using the lowest magnitude threshold possible, radiometric fractional whitecap coverage retrievals were consistently higher than fractional coverage from high-resolution digital images, perhaps because the radiometer captures more of the decaying bubble plume area that is difficult to detect with photography. Radiometrically obtained whitecap measurements are presented in the context of concurrently measured meteorological (e.g., wind speed) and oceanographic (e.g., wave) data. The optimal fit of the radiometrically estimated whitecap coverage to the instantaneous wind speed, determined using robust linear least squares, showed a near-cubic dependence. Increasing the magnitude threshold for whitecap detection from 2 to 4 times the interquartile range produced a wind speed–whitecap relationship most comparable to the concurrently collected fractional coverage from digital imagery and previously published wind speed–whitecap parameterizations.
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Merati, P., M. J. Macelt, and R. B. Erickson. "Flow Investigation Around a V-Sector Ball Valve." Journal of Fluids Engineering 123, no. 3 (February 9, 2001): 662–71. http://dx.doi.org/10.1115/1.1385831.
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Experimental and computational methods were used to study the structure and behavior of the shedded vortices around a V-ball valve. Strouhal frequency for shedded vortices around the valve over a range of operating conditions and flow rates using water as the medium were measured. The information gathered in this study would help to predict at what operating conditions pipe ruptures might occur. A dynamic pressure transducer was used to determine the Strouhal frequency. LDV was used to measure the mean velocity and turbulence magnitudes. FLUENT was used to develop a two dimensional fluid dynamics model. Flow was visualized using high-speed video photography. A dominant large three-dimensional vortex downstream of the valve was detected. The centerline of this vortex is a shadow of the valve lip. A fifth degree polynomial describing the relationship between the Strouhal number and Reynolds number is obtained.
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SKEWS, BERIC W., and HARALD KLEINE. "Flow features resulting from shock wave impact on a cylindrical cavity." Journal of Fluid Mechanics 580 (May 21, 2007): 481–93. http://dx.doi.org/10.1017/s0022112007005757.
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The complex flow features that arise from the impact of a shock wave on a concave cavity are determined by means of high-speed video photography. Besides additional information on features that have previously been encountered in specific studies, such as those relating to shock wave reflection from a cylindrical wall and those associated with shock wave focusing, a number of new features become apparent when the interaction is studied over longer times using time-resolved imaging. The most notable of these new features occurs when two strong shear layers meet that have been generated earlier in the motion. Two jets can be formed, one facing forward and the other backward, with the first one folding back on itself. The shear layers themselves develop a Kelvin–Helmholtz instability which can be triggered by interaction with weak shear layers developed earlier in the motion. Movies are available with the online version of the paper.
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Mustafa M Amami, Ali M El-Turki, Asim I Rustum, Ibrahim M El-Amaari, and Tariq A Jabir. "Topographic Surveying using Low-Cost Amateur Drones & 4K Ultra-High-Definition Videos." Open Access Research Journal of Science and Technology 4, no. 2 (April 30, 2022): 072–82. http://dx.doi.org/10.53022/oarjst.2022.4.2.0040.
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These days, the science of photogrammetry is frequently used in a wide range of applications, including engineering geology, medication, security, navigation, and topographic surveying works. Drones have gradually become an effectual and frequent technique for obtaining a number of photogrammetric products, such as ortho-mosaics, Digital Elevation Model (DEM), and land detailed topographic maps. This paper investigates the possibility of employing low-cost amateur drones with 4K Ultra-High-Definition (UHD) video for topographic surveying works and creating DEM's. DJI Mavic 2 PRO drone with Hasselblad L1D-20C 20 MP camera has been used for covering an expected gas & oil pipeline route in the South of Libya with length of nearly 15 km and width of 200 m. 60 well-distributed high-quality 3D ground points, divided as 30 Ground Control Points (GCP's) and 30 check points, have been used for more stable and robust photogrammetric processing and for reliable evaluation, respectively. The camera has been calibrated twice, before and after executing the flight mission for trustworthy Interior Orientation Elements (IOE's). The recorded video has been split into smaller videos based on the capturing time of the required frames, and the small videos have been extracted to individual UHD photos using Matlab image tools. Leica Photogrammetric Suite (LPS) software has been used for all processing steps, except the automatic filtration of the generated tie points, which has been carried out using self-developed Matlab algorithm for epipolar geometry and 2D transformation based filters. Results show that DEM's with quality of nearly 1.2 to 2 decimeter in plane and elevation, respectively can be obtained using DJI Mavic 2 PRO drone, 4K UHD video taken by Hasselblad L1D-20C 20 MP camera, pixel ground footprint of 8 cm, and flight height of 350 m. This level of accuracy is appropriate for many engineering applications, such as initial-planning projects stretched on huge areas, urban development plans, GIS data collection, inventory of earth works materials, and 3D modeling. The obtained quality of the generated DEM depends on the flight height and the camera quality, IOE's, and resolution. Tests show that using 4K UHD video for photogrammetric applications can provide UHD extracted frames, similar to that captured singly, especially with fit flight speed and camera settings, namely: ISO sensitivity, shatter speed, and aperture size. Also, using video facilitates the aerial photography process, overcoming the difficulties of determining the suitable capturing time and location of individual photos in site. The other advantage is the ability of taking alternative frames if the selected images are not suitable for photogrammetric works in terms of tilting and blurring. The opportunity of changing the overlapping rates across the route is another important advantage of using video, especially for curvy routes. Moreover, using different groups of overlapped images for the same route helps for creating different DEM's for the same area, resulting more precise and dense topographic surveying works.
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Dong, Ping, Dong Cheng, Huixiang Jing, Guanghua Li, Bingju Lu, and Ximeng Wang. "Flow Structures of Submerged Gas Jet in Liquid Currents." E3S Web of Conferences 299 (2021): 03011. http://dx.doi.org/10.1051/e3sconf/202129903011.
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The flow structure of the submerged gas jet in liquid currents is important to engineering applications. In the present study, the development of a submerged gas jet subjected to liquid current is experimentally investigated to evaluate the effects of the current on the underwater gas jet evolution. A full-scale experimental setup is designed for submerged gas jet release and dispersion in the liquid currents with different velocities. The flow structures of the gas jet are captured by shadow photography combined with a high speed video camera. The experimental images are processed to extract the parameters and perform Proper Orthogonal Decomposition (POD) analysis to reveal the characteristics of different modes standing for different flow structures. It turns out that the flow structures of the gas jets submerged in liquid currents with different velocities are affected by the liquid currents and gas jet pulsation, and the analysis will provide credible assessment and opportunity to take prompt response to control potential accidents caused by the submerged gas jet release in liquid current.
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Wang, Haiying. "Recognition of Wrong Sports Movements Based on Deep Neural Network." Revue d'Intelligence Artificielle 34, no. 5 (November 20, 2020): 663–71. http://dx.doi.org/10.18280/ria.340518.
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During physical education (PE), the teaching quality is severely affected by problems like nonstandard technical movements or wrong demonstrative movements. High-speed photography can capture instantaneous movements that cannot be recognized with naked eyes. Therefore, this technology has been widely used to judge the sprint movements in track and field competitions, and assess the quality of artistic gymnastics. Inspired by three-dimensional (3D) image analysis, this paper proposes a method to recognize the standard and wrong demonstrative sports movements, based on 3D convolutional neural network (CNN) and graph theory. Firstly, a 3D posture perception strategy for demonstrative sports movements was constructed based on video sequence. Next, the authors provided the framework of the recognition system for standard and wrong demonstrative sports movements. After that, a 3D CNN was stablished to distinguish between standard and wrong demonstrative sports movements. The proposed method was proved effective and superior through experiments. The research results provide a good reference for the application of 3D image analysis in the recognition of other body behaviors and movements.
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Lebedeva, V. V., and I. V. Lebedev. "Algorithms for Calculating the Trajectory of Unmanned Aerial Vehicles for Solving Agricultural Problems." Agricultural Machinery and Technologies 16, no. 3 (October 2, 2022): 40–47. http://dx.doi.org/10.22314/2073-7599-2022-16-3-40-47.
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The relevance of using unmanned aerial vehicles (UAV) is substantiated in comparison with other methods of aerospace survey. The paper provides examples of tasks requiring the use of UAVs for aerial photography from different heights. It is shown that the introduction of agricultural robots, including UAVs, increases the speed of fi eld work, allows obtaining unique data necessary for the assessment of agricultural territories, crops processing and plant growth stimulation. It is noted that the problem of constructing the movement trajectories of a multirotor UAV for performing agricultural tasks within a minimum time limit remains unresolved. (Research purpose) To reduce the length of the trajectory covering a given area and reduce the flight time of a multirotor UAV, taking into account the analysis of possible obstacles and land plots that are beyond the task scope. (Materials and methods) Geometric methods have been used to calculate the UAV flight trajectory covering a given section, the trajectory of movement in an environment with obstacles to the designated point. Photogrammetry methods have been used for processing aerial photography images when forming an orthophotoplane and a terrain map. (Results and discussion) The trajectory calculated by the developed algorithm proves to meet all the requirements: it is continuous, has a minimum number of turns, it is smoothed, and feasible for a multirotor UAV. (Conclusions) It was determined that according to the proposed algorithm it takes less than 0.05 seconds to calculate the trajectory covering a rectangular section with the sides of 200 by 30 meters. It was found that the trajectory in the fi rst 10,200-square-meter section decreased by 9 percent, and in the second 950,000-square-meter section it reduced by 6 percent, compared with the length of the trajectory built using standard algorithms. The flight time reduced by 32 and 10 percent, respectively. The paper presents the key advantages of using UAV for video shooting such as: guaranteed high resolution of photographic materials and the ability to shoot at a given time, allowing for the crop condition assessment.
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Stamatellou, Antiopi-Malvina, and Anestis I. Kalfas. "On the Efficiency of a Piezoelectric Energy Harvester under Combined Aeroelastic and Base Excitation." Micromachines 12, no. 8 (August 14, 2021): 962. http://dx.doi.org/10.3390/mi12080962.
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A flutter-type, nonlinear piezoelectric energy harvester was tested in various combinations of aerodynamic and harmonic base excitation to study its power output and efficiency. The commercial polyvinylidene fluoride film transducer LDT1-028K was used in 33 excitation mode. The aerodynamic excitation was created by a centrifugal fan and the base excitation by a cone speaker. The excitations were produced by varying independently the mean airflow velocity and the frequency of base vibration. A capacitive load was used to store the harvested energy. A line laser was employed along with long exposure photography and high-speed video, for the visualization of the piezo film’s mode shapes and the measurement of maximum tip deflection. The harvested power was mapped along with the maximum tip deflection of the piezo-film, and a process of optimally combining the two excitation sources for maximum power harvesting is demonstrated. The energy conversion efficiency is defined by means of electrical power output divided by the elastic strain energy rate of change during oscillations. The efficiency was mapped and correlated with resonance conditions and results from other studies. It was observed that the conversion efficiency is related to the phase difference between excitation and response and tends to decrease as the excitation frequency rises.
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Luo, Xisheng, Yu Liang, Ting Si, and Zhigang Zhai. "Effects of non-periodic portions of interface on Richtmyer–Meshkov instability." Journal of Fluid Mechanics 861 (December 20, 2018): 309–27. http://dx.doi.org/10.1017/jfm.2018.923.
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The development of a non-periodic $\text{air}\text{/}\text{SF}_{6}$ gaseous interface subjected to a planar shock wave is investigated experimentally and theoretically to evaluate the effects of the non-periodic portions of the interface on the Richtmyer–Meshkov instability. Experimentally, five kinds of discontinuous chevron-shaped interfaces with or without non-periodic portions are created by the extended soap film technique. The post-shock flows and the interface morphologies are captured by schlieren photography combined with a high-speed video camera. A periodic chevron-shaped interface, which is multi-modal (81 % fundamental mode and 19 % high-order modes), is first considered to evaluate the impulsive linear model and several typical nonlinear models. Then, the non-periodic chevron-shaped interfaces are investigated and the results show that the existence of non-periodic portions significantly changes the balanced position of the initial interface, and subsequently disables the nonlinear model which is applicable to the periodic chevron-shaped interface. A modified nonlinear model is proposed to consider the effects of the non-periodic portions. It turns out that the new model can predict the growth of the shocked non-periodic interface well. Finally, a method is established using spectrum analysis on the initial shape of the interface to separate its bubble structure and spike structure such that the new model can apply to any random perturbed interface. These findings can facilitate the understanding of the evolution of non-periodic interfaces which are more common in reality.
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Jiang, Fan, Cheng Li, Bin Xu, Shinichi Tashiro, Manabu Tanaka, and Shujun Chen. "Study on the Decoupled Transfer of Heat and Mass in Wire Variable Polarity Plasma Arc Welding." Materials 13, no. 5 (February 28, 2020): 1073. http://dx.doi.org/10.3390/ma13051073.
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A hybrid arc-wire welding method based on the variable polarity plasma arc (VPPA) and variable polarity pulse metal inert-gas (VP-PMIG) was proposed for manufacturing aluminum alloys. This paper aims to clarify the decoupling control process of heat and mass transfer in the hybrid welding process. To understand the arc physics and analyze the mass transfer behavior, the hybrid arc shape and droplet cross-sectional area with different parameters were obtained by high speed video photography. Further, the melting area of the base metal was analyzed by macro-metallography of the weld bead cross-section to study the heat transfer. It is found that the hybrid arc shape changes with time. The VPPA main arc is deflected to one side by the VP-PMIG, making the temperature distribution asymmetric, and during the VP-PMIG pulse necking occurs. The cross-sectional area of the droplet is more obviously affected by the VP-PMIG current than the VPPA current. Meanwhile, the VPPA current dominates the melting area of the base metal. Therefore, we conclude that heat transfer to the base metal is from the VPPA, while droplet transfer is mainly controlled by the VP-PMIG arc. These conclusions are confirmed by analyzing the decoupling degree of heat and mass transfer of the base metal by the VPPA and VP-PMIG arc.
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Mendeluk, Gabriela Ruth, Sergio López Costa, Sergio Scigliano, Guillermo Menga, Sergio Demiceu, and Luis Alberto Palaoro. "A Rare Case of Respiratory Disorders Associated with Two Autosomal Recessive Diseases and Male Infertility." Allergy & Rhinology 4, no. 1 (January 2013): ar.2013.4.0038. http://dx.doi.org/10.2500/ar.2013.4.0038.
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The study of nasal ciliary beat frequency (CBF) and ultrastructure may contribute to the understanding of pathognomonic cases of male infertility associated with defects in sperm motility. This study was designed to report a particular case of male infertility, characterized by the association of two respiratory autosomal recessive genetic diseases (alpha-1-antitrypsin deficiency [AAT-D] and primary ciliary dyskinesia [PCD]). A 39-year-old patient with complete sperm immotility, AAT-D, and bronchiectasis was studied in the Laboratory of Male Fertility, the Department of Urology, the Respiratory Center of a Pediatric Hospital, and in the Department of Clinical Medicine of a Rehabilitation Respiratory Hospital. Family history, physical examination, hormonal analysis, microbial assays, semen analysis, nasal ciliary function, and structure study by digital high-speed video photography and transmission electron microscopy are described. A noninvasive nasal biopsy to retrieve ciliated epithelium lining the inferior surface of the inferior nasal turbinates was performed and CBF was determined. Beat pattern was slightly curved and rigid, not wide, and metacronic in all the observed fields analyzed. CBF was 8.2 Hz in average (reference value, 10–15 Hz) Ultrastructural assay revealed absence of the inner dynein arms in 97% of the cilia observed. The final infertility accurate diagnosis was achieved by the study of nasal CBF and ultrastructure contributing to the patient health management and genetic counseling while deciding fatherhood. Beyond this particular case, the present report may open a new field of studies in male infertility, mainly in cases of asthenozoospermia.
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Si, Ting, Zhigang Zhai, and Xisheng Luo. "Experimental study of Richtmyer-Meshkov instability in a cylindrical converging shock tube." Laser and Particle Beams 32, no. 3 (June 6, 2014): 343–51. http://dx.doi.org/10.1017/s0263034614000202.
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AbstractThe interaction of a cylindrical converging shock wave with an initially perturbed gaseous interface is studied experimentally. The cylindrical converging shock is generated in an ordinary shock tube but with a specially designed test section, in which the incident planar shock wave is directly converted into a cylindrical one. Two kinds of typical initial interfaces involving gas bubble and gas cylinder are employed. A high-speed video camera combined with schlieren or planar Mie scattering photography is utilized to capture the evolution process of flow structures. The distribution of baroclinic vorticity on the interface induced by the cylindrical shock and the reflected shock from the center of convergence results in distinct phenomena. In the gas bubble case, the shock focusing and the jet formation are observed and the turbulent mixing of two fluids is promoted because of the gradually changed shock strength and complex shock structures in the converging part. In the gas cylinder case, a counter-rotating vortex pair is formed after the impact of the converging shock and its rotating direction may be changed when interacting with the reflected shock for a relatively long reflection distance. The variations of the interface displacements and structural dimensions with time are further measured. It is found that these quantities are different from those in the planar counterpart because of the shock curvature, the Mach number effect and the complex shock reflection within the converging shock tube test section. Therefore, the experiments reported here exhibit the great potential of this experimental method in study of the Richtmyer-Meshkov instability induced by converging shock waves.
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Bilous, V. V., and O. P. Bilous. "INNOVATIVE APPROACHES TO PERPETUATION OF MONEY AS MATERIAL EVIDENCE IN CRIMINAL PROCEEDINGS." Theory and Practice of Forensic Science and Criminalistics 17 (November 29, 2017): 55–69. http://dx.doi.org/10.32353/khrife.2017.07.
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The paper is devoted to the actual problems of innovative technologies introduction into the activity on crimes investigation. Based on the analysis of the state ofperpetuation by the bodies ofpre-trial investigation of money, acquired by criminally wrongful way or obtained by a legal entity as a result of a criminal offense commission, the authors distinguished typical violations of procedural orders and criminalistical recommendations in dealing with monetary notes as material evidence during the conduct of investigative (search) actions.
With the purpose of equipping the bodies of pre-trial investigation with modern scientific and technical means of field criminalistics, there was proposed the concept of a unique technical and criminalistic tool in the form of a manyfunctional multicurrency software and hardware complex, that in the processing of monetary notes - material evidence when carrying out investigative (search) actions, would ensure high-speed automated performance of such functions as: 1) detection of the validity of a large number of banknotes in national andforeign currencies ofdifferent denominations and years of issue, with recognition ofvarious types of falsifications, as well as souvenir products and special imitation means; 2) sorting; 3) recalculation with the determination of the total quantity and quantity by each note and total amount; 4) scanning and perpetuation by compiling and printing a detailed written description (appendix to the inspection protocol), andfull- colour digital photography and high-resolution video recording of not only the general form and machine-readable mandatory requisites of banknotes, but also various acquired criminalistic important signs (inscriptions, fingerprints, microparticles, spots of various substances of natural and synthetic origin, etc.); 5) data exchange in real time with databases of the National Bank of Ukraine and various criminalistics registrations, first of all, with a database of criminalistic accounting of monetary notes; 6) packing and sealing of seized monetary notes.
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Lundberg, Jan, Jan Ove Östensen, and Henrik Åström. "High-speed video photographs of lubrication breakdown in squeeze-sliding contact." Wear 157, no. 2 (September 1992): 427–33. http://dx.doi.org/10.1016/0043-1648(92)90079-n.
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Roberts, A., N. A. Hill, and R. Hicks. "Simple mechanisms organise orientation of escape swimming in embryos and hatchling tadpoles of Xenopus laevis." Journal of Experimental Biology 203, no. 12 (June 15, 2000): 1869–85. http://dx.doi.org/10.1242/jeb.203.12.1869.
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Many amphibian tadpoles hatch and swim before their inner ears and sense of spatial orientation differentiate. We describe upward and downward swimming responses in hatchling Xenopus laevis tadpoles from stages 32 to 37/38 in which the body rotates about its longitudinal axis. Tadpoles are heavier than water and, if touched while lying on the substratum, they reliably swim upwards, often in a tight spiral. This response has been observed using stroboscopic photography and high-speed video recordings. The sense of the spiral is not fixed for individual tadpoles. In ‘more horizontal swimming’ (i.e. in directions within +/−30 degrees of the horizontal), the tadpoles usually swim belly-down, but this position is not a prerequisite for subsequent upward spiral swimming. Newly hatched tadpoles spend 99 % of their time hanging tail-down from mucus secreted by a cement gland on the head. When suspended in mid-water by a mucus strand, tadpoles from stage 31 to 37/38 tend to swim spirally down when touched on the head and up when touched on the tail. The three-dimensional swimming paths of stage 33/34 tadpoles were plotted using simultaneous video images recorded from the side and from above. Tadpoles spiralled for 70 % of the swimming time, and the probability of spiralling increased to 1 as swim path angles became more vertical. Tadpoles were neutrally buoyant in Percoll/water mixtures at 1.05 g cm(−)(3), in which anaesthetised tadpoles floated belly-down and head-up at 30 degrees. In water, their centre of mass was ventral to the muscles in the yolk mass. A simple mathematical model suggests that the orientation of tadpoles during swimming is governed by the action of two torques, one of which raises the head (i.e. increases the pitch) and the other rotates (rolls) the body. Consequently, tadpoles (i) swim belly-down when the body is approximately horizontal because the body is ballasted by dense yolk, and (ii) swim spirally at more vertical orientations when the ballasting no longer stabilises orientation. Measurements in tethered tadpoles show that dorsal body flexion, which could produce a dorsal pitch torque, is present during swimming and increases with tailbeat frequency. We discuss how much of the tadpole's behaviour can be explained by our mathematical model and suggest that, at this stage of development, oriented swimming responses may depend on simple touch reflexes, the organisation of the muscles and physical features of the body, rather than on vestibular reflexes.
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Mandal, Sandip, and D. V. Khakhar. "Granular surface flow on an asymmetric conical heap." Journal of Fluid Mechanics 865 (February 18, 2019): 41–59. http://dx.doi.org/10.1017/jfm.2019.26.
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We carry out an experimental study of the granular surface flow of nearly monodisperse glass beads on a conical heap formed on a rough circular disc by a narrow stream of the particles from a hopper, with the pouring point displaced from the centre of the disc. During the growth phase, an axisymmetric heap is formed, which grows either by periodic avalanches or by non-periodic avalanches that occur randomly over the azimuthal location of the heap, depending on the operating conditions and system properties. The dynamics of heap growth is characterized by the variation of the heap height, angle of repose and the angular velocity of the periodic avalanche with time, for different mass flow rates from the hopper. When the base of the heap reaches the edge of the disc closest to the pouring point, the heap stops growing and a steady surface flow of particles is developed on the heap surface, with particles flowing over the edge of the disc into a collection tray. The geometry is a unique example of a granular flow on an erodible bed without any bounding side walls. The corresponding steady state geometry of the asymmetric heap is characterized by means of surface contours and angles of repose. The streamwise and transverse surface velocities are measured using high-speed video photography and image analysis for different mass flow rates. The flowing layer thickness is measured by immersing a coated needle in the flow at different positions on the mid-line of the flow. The surface angle of the flowing layer is found to be significantly smaller than the angle of repose and to be independent of the mass flow rate. The velocity profiles at different streamwise positions for different mass flow rates are found to be geometrically similar and are well described by Gaussian functions. The flowing layer thickness is calculated from a model using the measured surface velocities. The predicted values match the measured values quite well.
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Ammerman, C. N., and S. M. You. "Consecutive-Photo Method to Measure Vapor Volume Flow Rate During Boiling From a Wire Immersed in Saturated Liquid." Journal of Heat Transfer 120, no. 3 (August 1, 1998): 561–67. http://dx.doi.org/10.1115/1.2824311.
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A photographic measurement technique is developed to quantify the vapor volume flow rate departing from a wire during boiling. The vapor flow rate is determined by measuring the volume of bubbles after departure from the boiling surface in consecutive frames of high-speed video. The measurement technique is more accurate and easier to implement than a previously developed photographic/laser Doppler anemometry (LDA) method. Use of the high-speed camera in place of a standard video camera eliminates the requirement for LDA-acquired bubble velocity measurements. The consecutive-photo method requires relatively few video images to be analyzed to obtain steady-state vapor volume flow rates. The volumetric flow rate data are used to calculate the latent heat transfer and, indirectly, sensible heat transfer which comprise the nucleate boiling heat flux. The measurement technique is applied to a 75-μm diameter platinum wire immersed in saturated FC-72.
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Lamb, Jordan E., Robert Fitzsimmons, Anjana Sevagamoorthy, Carrie L. Kovarik, Daniel B. Shin, and Junko Takeshita. "Patient Factors Associated With Teledermatology Visit Type and Submission of Photographs During the COVID-19 Pandemic: Cross-sectional Analysis." JMIR Dermatology 5, no. 4 (November 8, 2022): e38694. http://dx.doi.org/10.2196/38694.
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Background The COVID-19 pandemic necessitated the widespread adoption of teledermatology, and this continues to account for a significant proportion of dermatology visits after clinics have reopened for in-person care. Delivery of high-quality teledermatology care requires adequate visualization of the patient’s skin, with photographs being preferred over live video for remote skin examination. It remains unknown which patients face the greatest barriers to participating in a teledermatology visit with photographs. Objective The aim of this study was to identify patient characteristics associated with type of telemedicine visit and the factors associated with participating in teledermatology visits with digital photographs versus those without photographs. Methods We performed a cross-sectional analysis of the University of Pennsylvania Health System electronic health record data for adult patients who participated in at least 1 teledermatology appointment between March 1, 2020, and June 30, 2020. The primary outcomes were participation in a live-interactive video visit versus a telephone visit and participation in any teledermatology visit with photographs versus one without photographs. Multivariable logistic regression was performed to evaluate the associations between patient characteristics and the primary outcomes. Results In total, 5717 unique patients completed at least 1 teledermatology visit during the study period; 68.25% (n=3902) of patients participated in a video visit, and 31.75% (n=1815) participated in a telephone visit. A minority of patients (n=1815, 31.75%) submitted photographs for their video or telephone appointment. Patients who submitted photographs for their teledermatology visit were more likely to be White, have commercial insurance, and live in areas with higher income, better education, and greater access to a computer and high-speed internet (P<.001 for all). In adjusted analysis, older age (age group >75 years: odds ratio [OR] 0.60, 95% CI 0.44-0.82), male sex (OR 0.85, 95% CI 0.75-0.97), Black race (OR 0.79, 95% CI 0.65-0.96), and Medicaid insurance (OR 0.81, 95% CI 0.66-0.99) were each associated with lower odds of a patient submitting photographs for their video or telephone visit. Older age (age group >75 years: OR 0.37, 95% CI 0.27-0.50) and Black race (OR 0.82, 95% CI 0.68-0.98) were also associated with lower odds of a patient participating in a video visit versus telephone visit. Conclusions Patients who were older, male, or Black, or who had Medicaid insurance were less likely to participate in teledermatology visits with photographs and may be particularly vulnerable to disparities in teledermatology care. Further research is necessary to identify the barriers to patients providing photographs for remote dermatology visits and to develop targeted interventions to facilitate equitable participation in teledermatology care.
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Tarafder, Kamrul Hassan, M. Alamgir Chowdhury, and Ahmed Tariq. "Video Laryngostroboscopy." Bangladesh Journal of Otorhinolaryngology 18, no. 2 (November 24, 2012): 171–78. http://dx.doi.org/10.3329/bjo.v18i2.12010.
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Stroboscopy has improved our understanding of the vocal cord function and has become an important tool in the diagnosis of voice disorders. It has led to changes in diagnosis in approximately 30% of cases when compared to examination with continuous light and mirror. It is important to understand the normal microscopic anatomy of the vocal folds- the plane of movement of the mucosal wave is the superficial layer (Reinkes space) of lamina propria. Opening and closing of the vocal cords during phonation can be easily seen in mirror examination. The use of high speed motion photography demonstrates additional movements. The equipment required includes stroboscope, camera, recorder, monitor and 90 degree telescope. The following parameters are routinely noted -fundamental frequency, periodicity, amplitude, symmetry, glottic closure, mucosal wave, non vibrating portion, supraglottic activity of larynx. Videostroboscopy helps in differentiating superficial lesions of the epithelium from the deeper lesions involving the muscle. It is useful in diagnosis of early malignancy, vocal nodule, differentiating unilateral paralysis from ankylosis of the cricoarytenoid joint, planning and evaluating phonosurgery. The stroboscopy images can be recorded and stored for future medicolegal purposes in professional voice users and monitoring their treatment. DOI: http://dx.doi.org/10.3329/bjo.v18i2.12010 Bangladesh J Otorhinolaryngol 2012; 18(2): 171-178
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Chen, Yong, Rong Hua Li, and Jin Wei Liu. "Exoskeleton Robot Walking on Slope Terrain." Applied Mechanics and Materials 367 (August 2013): 422–26. http://dx.doi.org/10.4028/www.scientific.net/amm.367.422.
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The walking procedure of the human on slope terrain was captured with a high-speed video camera. The geometrical configurations and motion postures of the human walking on slope terrain were analyzed from the high-speed photographs. Based on the biological observation, a dynamic model was put forward to aid the design of the exoskeleton robot. The hip angle, knee angle, hip moment and knee moment of the exoskeleton robot during walking on slope terrain were shown in figures. The results would provide some theoretical and practical references for the biomimetic design of the exoskeleton robot. This work may provide the basic theory in developing the structural design of the exoskeleton robot to help old people. Besides, it provides an important reference to study the other exoskeleton robots.
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Chen, Yong. "Jumping Mechanism Analysis of the Humanoid Robot." Applied Mechanics and Materials 29-32 (August 2010): 1562–66. http://dx.doi.org/10.4028/www.scientific.net/amm.29-32.1562.
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The jumping procedure of the human in the standing long jump was captured with a high-speed video camera. The geometrical configurations and motion postures of the human during jumping were analyzed from the high-speed photographs. By biological observation, the human jump was divided into stance phase, flight phase and land phase. The dynamic model of the humanoid jumping robot was established by the technology of virtual prototype. The joint angles of the robot during jumping were analyzed. The results would provide some theoretical and practical references for the biomimetic design to improve the reasonable motion of the humanoid jumping robot. This work may provide the basic theory in developing humanoid jumping robot in structural design. Besides, it provides an important reference to study the other bionic robots.
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Yin, Hong, Zanyao Yan, and Randall R. Bresee. "Experimental Study of the Meltblowing Process." International Nonwovens Journal os-8, no. 1 (March 1999): 1558925099OS—80. http://dx.doi.org/10.1177/1558925099os-800122.
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High-speed digital imaging techniques and web measurements were used to investigate the meltblowing (MB) process. We evaluated fiber diameter, fiber orientation, fiber entanglement, fiber velocity and fiber acceleration between the die and collector. Three processing variables were studied: primary air pressure, die-to-collector distance and collector surface speed. Although results of this investigation are somewhat preliminary, they provide fundamental information about the MB process and increase our understanding of it. Introduction Meltblowing (MB) is a fast, chaotic and complicated process. These features make it difficult to study the MB process theoretically as well as experimentally and most researchers have simply studied the effects of resin and process variables on web structure or web properties. Some researchers, however, have reported on-line measurements during MB [1–9]. Bansal and Shambaugh measured fiber temperature during single-hole MB using an infrared camera [1]. Wu and Shambaugh measured fiber velocity using laser Doppler velocimetry during single-hole MB [2]. Shambaugh and others reported experimental measurements of fiber motion and fiber diameter using a single-hole die [1–7]. Multiple-exposed photographs using conventional film were produced with a strobe light in a dark room to study fiber motion and single-exposed photographs were used to estimate fiber diameter. The exposure duration of the strobe light (50 μs), however, was not short enough to eliminate image blur and obtain sharp images so the primary air velocity used during MB was low (17–55 m/s). Milligan and Utsman used a similar film-based photographic technique to investigate MB using a 30-hole die [8]. Bresee and Yan used a video imaging technique to investigate the dynamics of web formation at the collector of a 600-hole MB line [9]. Measurements of the dynamics between the die and collector of a high-speed commercial-like MB process would be expected to be especially desirable for understanding MB. To directly observe dynamic motions during this fast process, it is necessary to use a short exposure time to freeze motion in each image and a high framing rate to resolve fast fiber motions. We used a high-speed digital camera from Vision Research Inc. to acquire images as rapidly as 1,000 frames/s. The camera produced image frames with a spatial resolution as great as 512×512 pixels and 8-bit gray level resolution (256 gray levels). Electronic shuttering of the camera provided exposure times as short as 50 μs/frame. To obtain exposure times shorter than 50 μs or to obtain multiple-exposed images, a high-speed pulsed laser from Oxford Lasers, Inc. was used for illumination. The laser produced 100 watt peak power at 805 nm and pulse durations as short as 1 μs were synchronized with the camera.
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Kimura, Satoshi, Hidehiro Hata, Tetsuyuki Hiroe, Kazuhito Fujiwara, and Hideaki Kusano. "Analysis of Explosion Combustion Phenomenon with Ammonium Nitrate." Materials Science Forum 566 (November 2007): 213–18. http://dx.doi.org/10.4028/www.scientific.net/msf.566.213.
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In this study, an explosion combustion phenomenon of ammonium nitrate (ρ=1.7kg/cm3) was used instead of the explosive PETN and the ultra-high-speed destruction phenomenon of aluminum cylinder was analyzed. The mix powder obtained by mixing aluminum powder (ρ=2.7kg/cm3) and ammonium nitrate was used instead of the explosive PETN, and an explosive combustion phenomenon was generated using copper wire explosion by high-voltage capacitor bank (40kV, 12.5 /F). Ammonium nitrate and aluminum powder are kneaded in a combination ratio of 5 : 1 in mass. An aluminum cylinder was destroyed by the phenomenon. The experiments were conducted using various diameters of ammonium nitrate particle and the photographs of the phenomenon were taken by the high-speed camera (IMACON468) and the high-speed video camera (HPV-1). The fragments of aluminum cylinder were collected and their dimensions were measured. The explosion phenomenon and fragments were compared with the result by explosive PETN. This paper presents these experiments and analysis result. And, hydro codes have been applied to simulate the deformation behavior of the aluminum cylinder.
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Chen, Yong. "Jumping Mechanism and Simulation of the Humanoid Robot." Applied Mechanics and Materials 80-81 (July 2011): 1176–79. http://dx.doi.org/10.4028/www.scientific.net/amm.80-81.1176.
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The jumping procedure of the human was captured with a high-speed video camera. The geometrical configurations and motion postures of the human during jumping were analyzed from the high-speed photographs. Based on the biological observation, the human jump was simplified and a mechanical model was put forward. The height and vertical velocity of COM of the human were analyzed. The angular velocity of the shoulder joint, hip joint, knee joint and ankle joint were shown in figure.It was shown that the arm swing was able to help increase the takeoff velocity. The results would provide some theoretical and practical references for biomimetic design for improving the reasonable motion of the jumping robot. This work may provide the basic theory in developing human jumping robot in structural design. Besides, it provides an important reference to study the other bionic robots.
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Płaczkowski, Krzysztof, Mirosław Grabowski, and Mieczysław E. Poniewski. "Novel Twofold Use of Photographic Technique for Simultaneous Flow Boiling Image Recording and Void Fraction Computation in a Mini-Channel Experiment." Energies 14, no. 15 (July 24, 2021): 4478. http://dx.doi.org/10.3390/en14154478.
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The paper presents a novel twofold use of the photographic technique for flow boiling heat transfer investigation in the horizontal mini-channel. The dedicated measurement system was constructed to record basic thermal and flow parameters, i.e., boiling liquid inlet and outlet temperatures and pressures, and also temperatures inside the heating block to calculate heat flux going into the liquid. A high-speed video camera equipped with synchronous movement system was applied to combine the recording of two-phase flow images with simultaneous local void fraction measurements both based on the same photographic data set. The data were collected, managed, and refined with the scripts developed in the MathWorks Matlab 2019b environment. The synchronous use of two intelligent techniques in the scripts, i.e., the background subtraction technique and the statistical analysis of individual pictures allowed obtaining reliable experimental results. The proposed method of the void fraction determination ensures high measurement accuracy.
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Zeitoun, O., and M. Shoukri. "Bubble Behavior and Mean Diameter in Subcooled Flow Boiling." Journal of Heat Transfer 118, no. 1 (February 1, 1996): 110–16. http://dx.doi.org/10.1115/1.2824023.
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Bubble behavior and mean bubble diameter in subcooled upward flow boiling in a vertical annular channel were investigated under low pressure and mass flux conditions. A high-speed video system was used to visualize the subcooled flow boiling phenomenon. The high-speed photographic results indicated that, contrary to the common understanding, bubbles tend to detach from the heating surface upstream of the net vapor generation point. Digital image processing technique was used to measure the mean bubble diameter along the subcooled flow boiling region. Data on the axial area-averaged void fraction distributions were also obtained using a single-beam gamma densitometer. Effects of the liquid subcooling, applied heat flux, and mass flux on the mean bubble size were investigated. A correlation for the mean bubble diameter as a function of the local subcooling, heat flux, and mass flux was obtained.
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Chen, Yong, Sheng Lin, Rong Hua Li, and Lian Dong Zhang. "Kinematics Characteristic of Exoskeleton Walking Robot for Older People." Applied Mechanics and Materials 644-650 (September 2014): 167–70. http://dx.doi.org/10.4028/www.scientific.net/amm.644-650.167.
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The movement processes of the older people during walking on level ground were captured by the high-speed video camera with the speed of 500 frames per second. The gait parameters of the older people during walking on level ground were obtained by the quantitative analysis of the successive photographs captured by the high-speed video camera. Kinematics features of the older people during walking on level ground were discussed. Along with the growth of the age, step velocity, step frequency and step length were reduced, and gait cycle was rising. According to the morphology of the older people during walking on level ground, a mechanical model was put forward to aid the design of the exoskeleton walking robot. The couple walking characteristics between the older wearer and the exoskeleton walking robot was studied. In the single support phase of the exoskeleton walking robot, the change of the hip joint was gradually decreased to provide the driving force for the stable walk, the change of the knee joint was increased and following decreased and then increased to forward the older people's body center of gravity, and the change of the ankle joint was gradually increased to reduce the impact force of the ground. The results would provide the basic theory to bionic references for improving the reasonable properties of the exoskeleton walking robot. This work would provide certain theoretical and practical base in developing the exoskeleton walking robot on bionic structural design.
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Леонов, Евгений, Evgeny Leonov, Юрий Леонов, Yuriy Leonov, Андрей Аверченков, Andrey Averchenkov, Юрий Казаков, Yuriy Kazakov, Анастасия Зуева, and Anastasiya Zueva. "RECOGNITION METHOD OF ELLIPTIC FORMS OBJECTS ON THE IMAGES." Automation and modeling in design and management 2019, no. 3 (November 24, 2019): 4–8. http://dx.doi.org/10.30987/article_5d8d113d478348.62159890.
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The article briefly describes the methodology and suggests the method for recognizing any elliptic forms objects on the images. This method is universal and can be applied in any intelligent recognition systems, for example, recognition system of the road signs from video camera images. The proposed method has proven itself in solving various practical problems, such as searching for signs in photographs, detecting circles on charts and diagrams, searching for the boundaries of ovals of faces, etc. The main advantage of the method is its extreme ease of implementation and high speed, which makes it possible to use not only on modern stationary computers, but also on mobile devices with low computing power.
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Andre´s, Luis San, and Sergio E. Diaz. "Flow Visualization and Forces From a Squeeze Film Damper Operating With Natural Air Entrainment." Journal of Tribology 125, no. 2 (March 19, 2003): 325–33. http://dx.doi.org/10.1115/1.1510878.
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Measurements of dynamic film pressures and high-speed photographs of the flow field in an open-ended Squeeze Film Damper (SFD) operating with natural free air entrainment are presented for increasing whirl frequencies (8.33–50 Hz), and a range of feed pressures to 250 kPa (37 psig). The flow conditions range from lubricant starvation (air ingestion) to a fully flooded discharge operation. The test dynamic pressures and video recordings show that air entrainment leads to large and irregular gas fingering and striation patterns. This is a natural phenomenon in SFDs operating with low levels of external pressurization (reduced lubricant through flow rates). Air ingestion and entrapment becomes more prevalent as the whirl frequency raises, and increasing the feed pressure aids little to ameliorate the loss in dynamic forced performance. As a result of the severity of air entrainment, experimentally estimated damping forces decrease steadily as the whirl frequency (operating speed) increases.
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Płaczkowski, Krzysztof, Mieczysław Poniewski, Mirosław Grabowski, and Sławomir Alabrudziński. "Photographic Technique Application to the Determination of Void Fraction in Two-Phase Flow Boiling in Mini Channels." Applied Mechanics and Materials 797 (November 2015): 299–306. http://dx.doi.org/10.4028/www.scientific.net/amm.797.299.
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The study deals with experimental investigations into heat transfer flow boiling in rectangular, vertical and horizontal mini-channels. The dedicated measurement system was designed to observe flow boiling in the mini-channel. The main task of the system is to record images of two-phase flow with a high-speed video camera, which is equipped with the synchronous movement system. The data, in the form of the footage of two-phase flow structures, were subjected to the analysis with the scripts, developed for that purpose in the MathWorks Matlab 2010b environment. The scripts allowed the determination of void fraction for each pattern of two-phase flow structures observed, at various heat fluxes and various volume fluxes, for two spatial orientations of the mini-channel: vertical and horizontal.
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Park, Jongdoc, Katsuya Fukuda, and Qiusheng Liu. "CHF Phenomena by Photographic Study of Boiling Behavior due to Transient Heat Inputs." Science and Technology of Nuclear Installations 2012 (2012): 1–12. http://dx.doi.org/10.1155/2012/248923.
Full textAbstract:
The transient boiling heat transfer characteristics in a pool of water and highly wetting liquids such as ethanol and FC-72 due to an exponentially increasing heat input of various rates were investigated using the 1.0 mm diameter experimental heater shaped in a horizontal cylinder for wide ranges of pressure and subcooling. The trend of critical heat flux (CHF) values in relation to the periods was divided into three groups. The CHF belonging to the 1st group with a longer period occurs with a fully developed nucleate boiling (FDNB) heat transfer process. For the 2nd group with shorter periods, the direct transition to film boiling from non boiling occurs as an explosive boiling. The direct boiling transition at the CHF from non-boiling regime to film boiling occurred without a heat flux increase. It was confirmed that the initial boiling behavior is significantly affected by the property and the wettability of the liquid. The photographic observations on the vapor bubble behavior during transitions to film boiling were performed using a high-speed video camera system.
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Deng, Guojun, Zhixiang Zhou, Shuai Shao, Xi Chu, and Peng Du. "NOVEL APPROACH TO EXTRACT DENSE FULL-FIELD DYNAMIC PARAMETERS OF LARGE-SCALE BRIDGES USING SPATIAL SEQUENCE VIDEO." JOURNAL OF CIVIL ENGINEERING AND MANAGEMENT 27, no. 8 (November 10, 2021): 617–36. http://dx.doi.org/10.3846/jcem.2021.15797.
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This study proposes the use of a high-speed camera as a holographic visual sensor to obtain the dense full-field dynamic parameters of the main beam of a bridge by the field of view through uniaxial rotation photography. Based on the basic principle that the frequency and mode of a structure are inherent characteristics, the mode coordinates obtained from each field of view are unified, normalized, and matched according to the same name pixels to obtain the dense fullfield dynamic parameters of the entire bridge. The frequency and first three order modes of a self-anchored suspension test bridge are collected by the method proposed in this study. The frequency comparison between the accelerometers and dial gauges is within 3%, and the mode shapes are more holographic and more realistic than those obtained by limited measuring points. In addition, the difference in the curvature mode under various damage conditions obtained by limited measurement points is compared with that obtained by the method proposed in this study. Results shows that the dense full-field modal curvature difference can reflect the change in the damage location even in a low order, which means the sensitivity of the change of damage location in low-order modal.
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Yeh, Wei Ming. "The Study of New Trend for DSC Scene Effects Technology." Advanced Materials Research 225-226 (April 2011): 1284–87. http://dx.doi.org/10.4028/www.scientific.net/amr.225-226.1284.
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Since early 2007, many ambitious DSC manufactures in Japan have paid special attention for built in digital effects, in order to create better quality of picture, such as: Face Detection, Smile Shutter Mode, Full frame CCD, Anti Shake system, Live View, CMOS sensor..., which were highly appreciated by many photo fans around the world, and created hot-selling record on favorite model. In fact, these fancy “Digital Technologies” could be standardized in selected new cameras right now. In late 2009, new artificial intelligence image chips such as: back-illuminated CMOS image sensor, 30x Optical Zoom (or more), Full HD Video, Sweep Panorama, Interchangeable Unit Camera System,Super High Speed ISO, Super Steady, Motion Remover.., have been promoted in new generation of camera. It could change not only the performance of new camera (DSC/DC) but to challenge the current DV market seriously, and may inspire new record-high selling again. In our experiment, we collect more than 300 cases from the telephone survey during Sep, 2010 and Dec, 2010. Total of 220 cases comply with the conditions. To probe mainly into the relationship between new generation DC Confidence level and 3 potential customers: Amateur Photographer (AP), Senior Photographer (SP), and college student (CS). That is the reason what we are probe into this highly competitively market with brilliant creative design, and hope to offer an objective suggestion for both industry and education administers.
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Mooney, P. E., G. Y. Fan, C. E. Meyer, K. V. Truong, D. B. Bui, and O. L. Krivanek. "Slow-Scan CCD Camera for Transmission Electron Microscopy." Proceedings, annual meeting, Electron Microscopy Society of America 48, no. 1 (August 12, 1990): 164–65. http://dx.doi.org/10.1017/s0424820100179579.
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Transmission electron microscopes aretraditionally equipped with three imaging devices: 1) the main viewing screen, which shows a large portion of the specimen in real time, 2) the focussing screen, which is viewed through binoculars and shows a small area of the specimen at a high magnification also in real time, and 3) a film camera, which permits time-integrated images to be recorded with a large number of pixels and a good detective quantum efficiency (DQE). In many laboratories, TV cameras have replaced the real-time viewing devices 1 and 2. The slow-scan CCD technology now promises to replace the photographic film.Slow-scan charge coupled device (CCD) sensors differ from the CCDs found in home video cameras in several aspects: their pixels are typically 10x larger in area, there is no frame-transfer buffer which would enable the CCD to function at TV rate, and the CCDs are optimized for operation at low temperature and slow readout speed. The increased size permits more electrons to be stored per pixel, which increases the dynamic range of the CCD. The elimination of the frame-transfer buffer allows the whole area of the CCD to be used for image detection. The low temperature and slow readout speed minimize the CCD dark current and readout noise.
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Fang, Jingxin, and Xuwei Li. "Object Detection Related to Irregular Behaviors of Substation Personnel Based on Improved YOLOv4." Applied Sciences 12, no. 9 (April 24, 2022): 4301. http://dx.doi.org/10.3390/app12094301.
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The accurate and timely detection of irregular behavior of substation personnel plays an important role in maintaining personal safety and preventing power outage accidents. This paper proposes a method for irregular behaviors detection (IBD) of substation personnel based on an improved YOLOv4 which uses MobileNetV3 to replace the CSPDarkNet53 feature extraction network, depthwise separable convolution and efficient channel attention (ECA) to optimize the SPP and PANet networks, and four scales of feature maps to fuse to improve the detection accuracy. First, an image dataset was constructed using video data and still photographs preprocessed by the gamma correction method. Then, the improved YOLOv4 model was trained by combining Mosaic data enhancement, cosine annealing, and label smoothing skills. Several detection cases were carried out, and the experimental results showed that the proposed improved YOLOv4 model has high accuracy, with a mean average precision (mAP) of 83.51%, as well as a fast detection speed, with a frames per second (FPS) of 38.06 pictures/s. This represents better performance than other object detection methods, including Faster RCNN, SSD, YOLOv3, and YOLOv4. This study offers a reference for the IBD of substation personnel and provides an automated intelligent monitoring method.