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Yuliang Zhou, Yuliang Zhou, Zhan Sui Zhan Sui, Yuanchao Geng Yuanchao Geng, Lixin Xu Lixin Xu et Hai Ming Hai Ming. « Using fence pulses to suppress stimulated Raman scattering effect in laser–plasma interaction ». Chinese Optics Letters 12, no 9 (2014) : 092902–92905. http://dx.doi.org/10.3788/col201412.092902.
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Pakulski, G., G. Knight, S. R. Das, T. Jones, C. Blaauw et J. K. White. « Semi-insulating buried heterostructure laser with PN fence ». Electronics Letters 38, no 25 (2002) : 1680. http://dx.doi.org/10.1049/el:20021156.
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Yang, Chuan Sen, Li Xin Cao, Ning Chen, Wei Yong Li, Li Hua Liu et Ying Zi Zhang. « Preparation and Transport Properties of Superconducting Fete Thin Film ». Advanced Materials Research 629 (décembre 2012) : 236–39. http://dx.doi.org/10.4028/www.scientific.net/amr.629.236.
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We successfully deposited the purely c-axis oriented Fete thin film, which shows superconducting transition in electrical resistivity about 12 K, by using pulsed laser deposition method. The electrical transport measurements of the thin film are studied with magnetic fields up to 14.0 T. thermally activated energy is analyzed using simple conventional Arrhenius relation and more precise relation who is closer to experimental results. Besides, the upper critical magnetic field and the vortex glass transition temperatures for the Fete thin film are studied.
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Flesch, T. K., J. D. Wilson et L. A. Harper. « Deducing Ground-to-Air Emissions from Observed Trace Gas Concentrations : A Field Trial with Wind Disturbance ». Journal of Applied Meteorology 44, no 4 (1 avril 2005) : 475–84. http://dx.doi.org/10.1175/jam2214.1.
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Abstract Inverse-dispersion techniques allow inference of a gas emission rate Q from measured air concentration. In “ideal surface layer problems,” where Monin–Obukhov similarity theory (MOST) describes the winds transporting the gas, the application of the technique can be straightforward. This study examines the accuracy of an ideal MOST-based inference, but in a nonideal setting. From a 6 m × 6 m synthetic area source surrounded by a 20 m × 20 m square border of a windbreak fence (1.25 m tall), Q is estimated. Open-path lasers gave line-averaged concentration CL at positions downwind of the source, and an idealized backward Lagrangian stochastic (bLS) dispersion model was used to infer QbLS. Despite the disturbance of the mean wind and turbulence caused by the fence, the QbLS estimates were accurate when ambient winds (measured upwind of the plot) were assumed in the bLS model. In the worst cases, with CL measured adjacent to a plot fence, QbLS overestimated Q by an average of 50%. However, if these near-fence locations are eliminated, QbLS averaged within 2% of the true Q over 61 fifteen-minute observations (with a standard deviation σQ/Q = 0.20). Poorer accuracy occurred when in-plot wind measurements were used in the bLS model. The results show that when an inverse-dispersion technique is applied to disturbed flows without accounting for the disturbance, the outcome may still be of acceptable accuracy if judgment is applied in the placement of the concentration detector.
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Dowman, Emma, Frances Wall, Peter J. Treloar et Andrew H. Rankin. « Rare-earth mobility as a result of multiple phases of fluid activity in fenite around the Chilwa Island Carbonatite, Malawi ». Mineralogical Magazine 81, no 6 (décembre 2017) : 1367–95. http://dx.doi.org/10.1180/minmag.2017.081.007.
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AbstractCarbonatites are enriched in critical raw materials such as the rare-earth elements (REE), niobium, fluorspar and phosphate. A better understanding of their fluid regimes will improve our knowledge of how to target and exploit economic deposits. This study shows that multiple fluid phases penetrated the surrounding fenite aureole during carbonatite emplacement at Chilwa Island, Malawi. The first alkaline fluids formed the main fenite assemblage and later microscopic vein networks contain the minerals of potential economic interest such as pyrochlore in high-grade fenite and rare-earth minerals throughout the aureole. Seventeen samples of fenite rock from the metasomatic aureole around the Chilwa Island carbonatite complex were chosen for study. In addition to the main fenite assemblage of feldspar and aegirine ± arfvedsonite, riebeckite and richterite, the fenite contains micro-mineral assemblages including apatite, ilmenite, rutile, magnetite, zircon, rare-earth minerals and pyrochlore in vein networks. Petrography using a scanning electron microscope in energy-dispersive spectroscopy mode showed that the rare-earth minerals (monazite, bastnäsite and parisite) formed later than the fenite feldspar, aegirine and apatite and provide evidence ofREEmobility into all grades of fenite. Fenite apatite has a distinct negative Eu anomaly (determined by laser ablation inductively coupled plasma mass spectrometry) that is rare in carbonatite-associated rocks and interpreted as related to pre-crystallization of plagioclase and co-crystallization with K-feldspar in the fenite. The fenite minerals have consistently higher midREE/lightREEratios (La/Sm ≈ 1.3 monazite, ≈ 1.9 bastnäsite, ≈ 1.2 parisite) than their counterparts in the carbonatites (La/Sm ≈ 2.5 monazite, ≈ 4.2 bastnäsite, ≈ 3.4 parisite). Quartz in the low- and medium-grade fenite hosts fluid inclusions, typically a few micrometres in diameter, secondary and extremely heterogeneous. Single phase, 2- and 3-phase, single solid and multi solid-bearing examples are present, with 2-phase the most abundant. Calcite, nahcolite, burbankite and baryte were found in the inclusions. Decrepitation of inclusions occurred at ∼200°C before homogenization but melting-temperature data indicate that the inclusions contain relatively pure CO2. A minimum salinity of ∼24 wt.% NaCl equivalent was determined. Among the trace elements in whole-rock analyses, enrichment in Ba, Mo, Nb, Pb, Sr, Th and Y and depletion in Co, Hf and V are common to carbonatite and fenite but enrichment in carbonatitic type elements (Ba, Nb, Sr, Th, YandREE) generally increases towards the inner parts of the aureole. A schematic model contains multiple fluid events, related to first and second boiling of the magma, accompanying intrusion of the carbonatites at Chilwa Island, each contributing to the mineralogy and chemistry of the fenite. The presence of distinct rare-earth mineral microassemblages in fenite at some distance from carbonatite could be developed as an exploration indicator ofREEenrichment.
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Shajid Pyari, Muhzina, Kata Vékony, Stefania Uccheddu et Péter Pongrácz. « Companion Cats Show No Effect of Trial-and-Error Learning Compared to Dogs in a Transparent-Obstacle Detour Task ». Animals 13, no 1 (21 décembre 2022) : 32. http://dx.doi.org/10.3390/ani13010032.
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We tested companion cats and dogs in similar indoor conditions using identical procedures in the classic detour task around a V-shaped transparent wire-mesh fence. Besides the control group, we used two types of laser light-pointing demonstration (moving around the fence, or pointing straight at the reward). We found that dogs reached the food reward faster than cats; across consecutive trials, only the dogs showed improvement in their speed and dogs continued to use the same side for detouring after a preceding successful attempt, while cats chose the side for detouring irrespective of their previous successful trials. In addition, ‘demonstrating’ a detour with the laser did not influence the speed or direction of the detour of the subjects; and dogs looked back to their owner more frequently than the cats did. We discuss the possibility that for dogs, detouring along a transparent obstacle represents a more problematic task than for cats; therefore, dogs strongly rely on their previous experiences. This is the first time that cats were successfully tested in this detour paradigm in direct comparison with dogs. The results are relevant from the aspect of testing cognitive performance in companion cats, which are known to be notoriously reluctant to engage with novel experimental situations.
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Tropea, C. D., et R. Gackstatter. « The Flow Over Two-Dimensional Surface-Mounted Obstacles at Low Reynolds Numbers ». Journal of Fluids Engineering 107, no 4 (1 décembre 1985) : 489–94. http://dx.doi.org/10.1115/1.3242518.
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The flow over a fence and a block mounted in a fully developed channel flow is experimentally investigated as a function of the Reynolds number, blockage ratio and length-to-height ratio using a laser-Doppler-anemometer. The information obtained includes the location and size of the primary and secondary recirculation zones, and profiles of the mean streamwise velocity component. The experiments were carried out in a channel for a Reynolds number in the range 150 < ReH < 4500. Comparisons are drawn between the obstacle flow and the backward-facing step flow.
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Gilbreath, G. Charmaine, Paul W. Schumacher, Mark A. Davis, Edward D. Lydick et John M. Anderson. « Evaluation of the Naval Space Surveillance Fence Performance Using Satellite Laser Ranging ». Journal of Guidance, Control, and Dynamics 22, no 1 (janvier 1999) : 149–55. http://dx.doi.org/10.2514/2.4361.
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Sako, Y., et A. Kusumi. « Barriers for lateral diffusion of transferrin receptor in the plasma membrane as characterized by receptor dragging by laser tweezers : fence versus tether. » Journal of Cell Biology 129, no 6 (15 juin 1995) : 1559–74. http://dx.doi.org/10.1083/jcb.129.6.1559.
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Our previous results indicated that the plasma membrane of cultured normal rat kidney fibroblastic cell is compartmentalized for diffusion of receptor molecules, and that long-range diffusion is the result of successive intercompartmental jumps (Sako, Y. and Kusumi, A. 1994. J. Cell Biol. 125:1251-1264). In the present study, we characterized the properties of intercompartmental boundaries by tagging transferrin receptor (TR) with either 210-nm-phi latex or 40-nm-phi colloidal gold particles, and by dragging the particle-TR complexes laterally along the plasma membrane using laser tweezers. Approximately 90% of the TR-particle complexes showed confined-type diffusion with a microscopic diffusion coefficient (Dmicro) of approximately 10(-9) cm2/s and could be dragged past the intercompartmental boundaries in their path by laser tweezers at a trapping force of 0.25 pN for gold-tagged TR and 0.8 pN for latex-tagged TR. At lower dragging forces between 0.05 and 0.1 pN, particle-TR complexes tended to escape from the laser trap at the boundaries, and such escape occurred in both the forward and backward directions of dragging. The average distance dragged was half of the confined distance of TR, which further indicates that particle-TR complexes escape at the compartment boundaries. Since variation in the particle size (40 and 210 nm, the particles are on the extracellular surface of the plasma membrane) hardly affects the diffusion rate and behavior of the particle-TR complexes at the compartment boundaries, and since treatment with cytochalasin D or vinblastin affects the movements of TR (Sako and Kusumi as cited above), argument has been advanced that the boundaries are present in the cytoplasmic domain. Rebound of the particle-TR complexes when they escape from the laser tweezers at the compartment boundaries suggests that the boundaries are elastic structures. These results are consistent with the proposal that the compartment boundaries consist of membrane skeleton or a membrane-associated part of the cytoskeleton (membrane skeleton fence model). Approximately 10% of TR exhibited slower diffusion (Dmicro approximately 10(-10)-10(-11) cm2/s) and binding to elastic structures.
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Suman, Preetam, Deepak Kumar Singh, Fahad R. Albogamy et Mohammad Shibee. « Harnessing the Power of Sensors and Machine Learning to Design Smart Fence to Protect Farmlands ». Electronics 10, no 24 (13 décembre 2021) : 3094. http://dx.doi.org/10.3390/electronics10243094.
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Agriculture and animals are two crucial factors for ecological balance. Human–wildlife conflict is increasing day-by-day due to crop damage and livestock depredation by wild animals, causing local farmer’s economic loss resulting in the deepening of poverty. Techniques are needed to stop the crop damage caused by animals. The most prominent technique used to protect crops from animals is fencing, but somehow, it is not a full-proof solution. Most fencing techniques are harmful to animals. Thousands of animals die due to the side effects of fencing techniques, such as electrocution. This paper introduces a virtual fence to solve these issues. The proposed virtual fence is invisible to everyone, because it is an optical fiber sensor cable, which is laid 12-inches-deep in soil. A laser light is used at the start of the fiber sensor cable, and a detector detects at the end of the cable. The technique is based on the reflection of light inside the fiber optic cable. The interferometric technique is used to predict the changes in the pattern of the laser light. The fiber cable sensors are connected to a microprocessor, which can predict the intrusion of any animal. The use of machine learning techniques to pattern detection makes this technique highly efficient. The machine learning algorithms developed for the identification of animals can also classify the animal. The paper proposes an economical and feasible machine-learning-based solution to save crops from animals and to save animals from dangerous fencing. The description of the complete setup of optical fiber sensors, methodology, and machine learning algorithms are covered in this paper. This concept was implemented and regressive tests were carried out. Tests were performed on the data, which were not used for training purposes. Sets of people (50 people in each set) were randomly moved into the fiber optic cable sensor in order to test the effectiveness of the detection. There have been very few instances where the algorithm has been unable to categorize the detections into different animal classes. Three datasets were tested for configuration effectiveness. The complete setup was also tested in a zoo to test the identification of elephants and tigers. The efficiency of identification is 94% for human, 80% for tiger, and 75% for elephant.
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Šafář, Václav, Markéta Potůčková, Jakub Karas, Jan Tlustý, Eva Štefanová, Marián Jančovič et Drahomíra Cígler Žofková. « The Use of UAV in Cadastral Mapping of the Czech Republic ». ISPRS International Journal of Geo-Information 10, no 6 (3 juin 2021) : 380. http://dx.doi.org/10.3390/ijgi10060380.
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The main challenge in the renewal and updating of the Cadastre of Real Estate of the Czech Republic is to achieve maximum efficiency but to retain the required accuracy of all points in the register. The paper discusses the possibility of using UAV photogrammetry and laser scanning for cadastral mapping in the Czech Republic. Point clouds from images and laser scans together with orthoimages were derived over twelve test areas. Control and check points were measured using geodetic methods (RTK-GNSS and total stations). The accuracy of the detailed survey based on UAV technologies was checked on hundreds of points, mainly building corners and fence foundations. The results show that the required accuracy of 0.14 m was achieved on more than 80% and 98% of points in the case of the image point clouds and orthoimages and the case of the LiDAR point cloud, respectively. Nevertheless, the methods lack completeness of the performed survey that must be supplied by geodetic measurements. The paper also provides a comparison of the costs connected to traditional and UAV-based cadastral mapping, and it addresses the necessary changes in the organisational and technological processes in order to utilise the UAV based technologies.
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Hao, Yi, Ping Song, Xuanquan Wang et Zhikang Pan. « A Spectrum Correction Algorithm Based on Beat Signal of FMCW Laser Ranging System ». Sensors 21, no 15 (26 juillet 2021) : 5057. http://dx.doi.org/10.3390/s21155057.
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The accuracy of target distance obtained by a frequency modulated continuous wave (FMCW) laser ranging system is often affected by factors such as white Gaussian noise (WGN), spectrum leakage, and the picket fence effect. There are some traditional spectrum correction algorithms to solve the problem above, but the results are unsatisfactory. In this article, a decomposition filtering-based dual-window correction (DFBDWC) algorithm is proposed to alleviate the problem caused by these factors. This algorithm reduces the influence of these factors by utilizing a decomposition filtering, dual-window in time domain and two phase values of spectral peak in the frequency domain, respectively. With the comparison of DFBDWC and these traditional algorithms in simulation and experiment on a built platform, the results show a superior performance of DFBDWC based on this platform. The maximum absolute error of target distance calculated by this algorithm is reduced from 0.7937 m of discrete Fourier transform (DFT) algorithm to 0.0407 m, which is the best among all mentioned spectrum correction algorithms. A high performance FMCW laser ranging system can be realized with the proposed algorithm, which has attractive potential in a wide scope of applications.
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Rothenberg, Joshua E. « Ultrafast picket fence pulse trains to enhance frequency conversion of shaped inertial confinement fusion laser pulses ». Applied Optics 39, no 36 (20 décembre 2000) : 6931. http://dx.doi.org/10.1364/ao.39.006931.
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Leroux, Nicolas R., Julie M. Thériault et Roy Rasmussen. « Improvement of Snow Gauge Collection Efficiency through a Knowledge of Solid Precipitation Fall Speed ». Journal of Hydrometeorology 22, no 4 (avril 2021) : 997–1006. http://dx.doi.org/10.1175/jhm-d-20-0147.1.
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AbstractThe collection efficiency of a typical precipitation gauge-shield configuration decreases with increasing wind speed, with a high scatter for a given wind speed. The high scatter in the collection efficiency for a given wind speed arises in part from the variability in the characteristics of falling snow and atmospheric turbulence. This study uses weighing gauge data collected at the Marshall Field Site near Boulder, Colorado, during the WMO Solid Precipitation Intercomparison Experiment (SPICE). Particle diameter and fall speed data from a laser disdrometer were used to show that the scatter in the collection efficiency can be reduced by considering the fall speed of solid precipitation particles. The collection efficiency was divided into two classes depending on the measured mean-event particle fall speed during precipitation events. Slower-falling particles were associated with a lower collection efficiency. A new transfer function (i.e., the relationship between collection efficiency and other meteorological variables, such as wind speed or air temperature) that includes the fall speed of the hydrometeors was developed. The root-mean-square error of the adjusted precipitation with the new transfer function with respect to a weighing gauge placed in a double fence intercomparison reference was lower than using previously developed transfer functions that only consider wind speed and air temperature. This shows that the measured fall speed of solid precipitation with a laser disdrometer accounts for a large amount of the observed scatter in weighing gauge collection efficiency.
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OKUDA, Satoshi, Akinori NAKAMURA, Atsushi TAKANO, Akiyoshi KATANO et Keitaro KABE. « FIELD MEASUREMENT OF SAND ACCUMULATION FORMS AROUND THE SAND FENCE WITH DISCONNECTED WING TYPE BY USING 3D LASER SCANNER ». Journal of Japan Society of Civil Engineers, Ser. B2 (Coastal Engineering) 74, no 2 (2018) : I_967—I_972. http://dx.doi.org/10.2208/kaigan.74.i_967.
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Matsuzawa, Tomonori, et Ryo Kohsaka. « Preliminary Experimental Trial of Effects of Lattice Fence Installation on Honey Bee Flight Height as Implications for Urban Beekeeping Regulations ». Land 11, no 1 (23 décembre 2021) : 19. http://dx.doi.org/10.3390/land11010019.
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Urban beekeeping has gained salience because of its significance in biodiversity conservation and community building. Despite this, beekeeping practices in urban areas have received negative perceptions from residents, which stem from public safety concerns. There is, therefore, a need to enhance and/or work on appropriate rules for maximizing the profits while minimizing the risks. Amongst the present regulations, the installation of barriers and setbacks is the most common rule for public safety. However, only a limited number of empirical studies have reported on their effective location and height. Thus, in this study, an experimental apiary was set up with different types of barriers installed with varying distances to observe and measure flyway patterns of honey bees. We used a 3D laser scanner, which obtained 8529 points of highly accurate flight location data in about five hours. Results showed that the heights (1.8 and 0.9 m) of the barriers installed were effective in increasing the flight altitudes. The distance of the fence, which was installed as close as 1 m from the hives, was effective as well. These findings, which showed that barriers and setbacks are effective, can have regulatory implications in designing apiaries in urban spaces, where location is often restricted.
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Bertolini-Cestari, Clara, Filiberto Chiabrando, Stefano Invernizzi, Tanja Marzi et Antonia Spanò. « Terrestrial Laser Scanning and Settled Techniques : A Support to Detect Pathologies and Safety Conditions of Timber Structures ». Advanced Materials Research 778 (septembre 2013) : 350–57. http://dx.doi.org/10.4028/www.scientific.net/amr.778.350.
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Nowadays, there is an increasing demand for detailed geometrical representation of the existing cultural heritage, in particular to improve the comprehension of interactions between different phenomena and to allow a better decisional and planning process. The LiDAR technology (Light Detection and Ranging) can be adopted in different fields, ranging from aerial applications to mobile and terrestrial mapping systems. One of the main target of this study is to propose an integration of innovative and settled inquiring techniques, ranging from the reading of the technological system, to non-destructive tools for diagnosis and 3D metric modeling of buildings heritage. Many inquiring techniques, including Terrestrial Laser Scanner (TLS) method, have been exploited to study the main room of the Valentino Castle in Torino. The so-called “Salone delle Feste”, conceived in the XVIIth century under the guidance of Carlo di Castellamonte, has been selected as a test area. The beautiful frescos and stuccoes of the domical vault are sustained by a typical Delorme carpentry, whose span is among the largest of their kind. The dome suffered from degradation during the years, and a series of interventions were put into place. A survey has revealed that the suspender cables above the vault in the region close to the abutments have lost their tension. This may indicate an increase of the vault deformation; therefore a structural assessment of the dome is mandatory. The high detailed metric survey, carried out with integrated laser scanning and digital close range photogrammetry, reinforced the structural hypothesis of damages and revealed the deformation effects. In addition, the correlation between the survey-model of the intrados and of the extrados allowed a non-destructive and extensive determination of the dome thickness. The photogram-metrical survey of frescos, with the re-projection of images on vault surface model (texture mapping), is purposed to exactly localize formers restoration and their signs on frescos continuity. The present paper illustrates the generation of the 3D high-resolution model and its relations with the results of the structural survey; both of them support the Finite Element numerical simulation of the dome.
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Devenport, William J., et Edward J. Smith. « The diode-array velocimeter ». Journal of Fluid Mechanics 259 (25 janvier 1994) : 167–89. http://dx.doi.org/10.1017/s002211209400008x.
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Diode-array velocimetry is an optical technique for measuring turbulent flows. It involves timing the passage of seed particles through a small section of a light beam by imaging the light they scatter onto one or more photodiode arrays. The arrays have a few carefully shaped elements, the shapes and positions of which are used to control the measurement-volume geometry and thus select the measurement made. Measurement volumes sensitive to velocity, position and acceleration may be designed. Measurements in highly turbulent and reversing flows are possible.A diode-array velocimeter (DAV) for one-component velocity measurements has been developed to demonstrate this concept. This uses a single laser beam to illuminate particles and a photodiode array with two rectangular elements to sense their motion. The sensitivity of this DAV to electrical noise in the photodiode circuitry decreases with reduction in measurement-volume size. The angle response is closely cosinusoidal to about 60°. Changes to the photodiode-array design could substantially increase this limit.Measurements of mean velocity, normal turbulence stress and velocity skewness made with this DAV in two attached boundary-layer flows compare well with hot-wire measurements. Useful DAV measurements were made as close as 0.2 mm from the wall. DAV measurements made in a separated flow formed downstream of a fence are also presented. These show all the expected features of the separated shear layer and recirculation including the sub-boundary layer formed beneath the backflow. Histograms measured in the reversing part of this flow show a hole near zero velocity that is a consequence of the imperfections in the DAV angle response and limitations on the maximum transit time. These are not fundamental problems, however, and the hole could be minimized or eliminated by using a different photodiode array design and/or measurement strategy.
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Keller, Matthew D., Bryan J. Norton, David J. Farrar, Phil Rutschman, Maclen Marvit et Arty Makagon. « Optical tracking and laser-induced mortality of insects during flight ». Scientific Reports 10, no 1 (9 septembre 2020). http://dx.doi.org/10.1038/s41598-020-71824-y.
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Abstract Addressing the need for novel insect observation and control tools, the Photonic Fence detects and tracks mosquitoes and other flying insects and can apply lethal doses of laser light to them. Previously, we determined lethal exposure levels for a variety of lasers and pulse conditions on anesthetized Anopheles stephensi mosquitoes. In this work, similar studies were performed while the subjects were freely flying within transparent cages two meters from the optical system; a proof-of-principle demonstration of a 30 m system was also performed. From the dose–response curves of mortality data created as a function of various beam diameter, pulse width, and power conditions at visible and near-infrared wavelengths, the visible wavelengths required significantly lower laser exposure than near infrared wavelengths to disable subjects, though near infrared sources remain attractive given their cost and retina safety. The flight behavior of the subjects and the performance of the tracking system were found to have no impact on the mortality outcomes for pulse durations up to 25 ms, which appears to be the ideal duration to minimize required laser power. The results of this study affirm the practicality of using optical approaches to protect people and crops from pestilent flying insects.
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Patt, Joseph M., Arty Makagon, Bryan Norton, Maclen Marvit, Phillip Rutschman, Matt Neligeorge et Jeremy Salesin. « An optical system to detect, surveil, and kill flying insect vectors of human and crop pathogens ». Scientific Reports 14, no 1 (8 avril 2024). http://dx.doi.org/10.1038/s41598-024-57804-6.
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AbstractSustainable and effective means to control flying insect vectors are critically needed, especially with widespread insecticide resistance and global climate change. Understanding and controlling vectors requires accurate information about their movement and activity, which is often lacking. The Photonic Fence (PF) is an optical system that uses machine vision, infrared light, and lasers to identify, track, and interdict vectors in flight. The PF examines an insect’s outline, flight speed, and other flight parameters and if these match those of a targeted vector species, then a low-power, retina-safe laser kills it. We report on proof-of-concept tests of a large, field-sized PF (30 mL × 3 mH) conducted with Aedes aegypti, a mosquito that transmits dangerous arboviruses, and Diaphorina citri, a psyllid which transmits the fatal huanglongbing disease of citrus. In tests with the laser engaged, < 1% and 3% of A. aegypti and D. citri, respectfully, were recovered versus a 38% and 19% recovery when the lacer was silenced. The PF tracked, but did not intercept the orchid bee, Euglossa dilemma. The system effectively intercepted flying vectors, but not bees, at a distance of 30 m, heralding the use of photonic energy, rather than chemicals, to control flying vectors.
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Eichmanns, Christiane, et Holger Schüttrumpf. « A Nature-Based Solution for Coastal Protection : Wind Tunnel Investigations on the Influence of Sand-Trapping Fences on Sediment Accretion ». Frontiers in Built Environment 8 (14 avril 2022). http://dx.doi.org/10.3389/fbuil.2022.878197.
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Sand-trapping fences are a frequently used nature-based solution in coastal protection for initiating and facilitating coastal dune toe growth. However, only a few researchers have evaluated the trap efficiency of sand-trapping fences based on their porosity and height. Subsequently, the design of their properties has only been based on empirical knowledge, to date. However, for restoring and maintaining coastal beach–dune systems, exact knowledge of sand-trapping fence’s optimal properties is essential. Thus, we conducted physical model tests focusing on the most crucial parameters: fence height (h = 40, 80, 120 mm) and fence porosity (ε = 22.6, 41.6, and 56.5%). These tests were conducted in an indoor subsonic, blowing-sand wind tunnel equipped with a moveable sediment bed (d50 ∼ 212 µm). The experimental mean wind velocities were u1 = 6.1 m/s, u2 = 7.4 m/s, and u3 = 9.3 m/s. We used a hot-wire anemometer to measure the flow fields, a vertical mesh sand trap to determine the sediment fluxes, and a 2D laser scanner to record the sediment accretion around the sand-trapping fences over time. The study results provide substantial theoretical and practical support for the installation and configuration of trapping fences and improving their design. The fence porosity, for example, should be chosen depending on the installation purpose. While denser fence porosities (ε1 = 22.6% and ε2 = 41.6%) can be used for initiating and facilitating the dune toe growth, fences with higher porosity (ε3 = 56.5%) are more suitable to favor the sediment accretion between foredunes and white dunes as they allow further dune growth downwind.
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Tian, Zhenhua, Zhaoyun Ma, Wenfeng Xiao et Lingyu Yu. « Noncontact laser vibrometry-based fence-like arrays with wavefield filtering-assisted adaptive imaging algorithms for detecting multiple pits in a compact cluster ». Structural Health Monitoring, 15 décembre 2020, 147592172097692. http://dx.doi.org/10.1177/1475921720976926.
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Pitting corrosion presents challenges for ultrasonic nondestructive evaluation due to the small pit dimension. Few Lamb wave-based techniques have achieved the identification of individual pits as subwavelength wave scatterers that are densely packed in a small cluster. In this article, noncontact laser vibrometry-based fence-like arrays with wavefield filtering-assisted adaptive imaging algorithms are developed for detecting and identifying small pits in a cluster. Signals of back scattering waves induced by a cluster of subwavelength scatterers are acquired by noncontact laser Doppler vibrometry at sensing points and form a fence-like array surrounding the area of inspection. The signals are then processed by our array imaging algorithms to construct inspection images which take advantage of three techniques, including the wave mode and wave direction filters to extract single-mode back scattering Lamb waves induced by subwavelength scatterers, the pseudo-reversal propagation of back scattering waves to address the dispersion effect and improve the radial imaging resolution, and the adaptive weighting to improve the angular imaging resolution. Moreover, this work introduces the wave diffraction-related Rayleigh and Abbe limits that are conventionally used for characterizing optic lenses, for characterizing the resolution limit of Lamb wave-based arrays, and optimizing the array configuration. To validate our array imaging approach, a proof-of-concept experiment has been performed to detect a cluster of 3 × 3 pits with the pit diameter of 2 mm and the interval of 2 mm in a 3.2-mm thick aluminum plate; the experimental imaging result shows that our method can identify most pits except the one at the center of the pit cluster. We believe this study will benefit the design, characterization, and optimization of Lamb wave-based arrays for subwavelength resolution imaging and enable potential applications for the noncontact inspection of hidden pitting corrosion in civil, petrochemical, nuclear, and aerospace structures.
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Agarkov, I. B., I. M. Ignatenko, V. A. Dunaev et I. S. Kryuchkov. « Estimate of change in specific cohesion between fracture surfaces by back-calculation : A case study of open pit mine Zhelezny of Kovdor Mining and Processing Plant ». Gornyi Zhurnal, 30 octobre 2020, 68–73. http://dx.doi.org/10.17580/gzh.2020.10.06.
Texte intégralRésumé :
This article presents the back-calculation data on bench deformations in open pit mine Zhelezny of Kovdor Mining and Processing Plant. The calculations are performed for 105 rock falls divided into six groups with respect to volume (m3): 0–200 is group 1; >200–500 is group 2; >500–1000 is group 3; >1000–5000 is group 4; >5000–10000 is group 5; >10000 is group 6. The computational method was the single-factor analysis of change in specific cohesion between the surfaces of deformation-limiting fractures. The internal friction angle is assumed to be constant as it is the least of all changeable and is correlatable with laboratory test data. Actual rock falls were simulated in GIS GEOMIX. The simulation correctness was ensured by the high-accuracy referencing and orientation measurements of fractures using 3D models constructed based on laser scanning and drone photography. For all sampled rocks, it is found that specific cohesion between fracture surfaces grows with increasing volume of rock falls. Specific cohesion in case of small volume rock falls (0–200 м3) in all types of rocks, except for olivinite, is approximately the same and ranges as 0.0021–0.011 MPa; for olivinite, this value is higher by 20 % at least. Higher rate slipping along fractures is typical of fenite (almost in all groups, specific cohesion is lower by 10–90 % than in other rock types), which is governed by supergene mineralization of fenites and by down water flow in fractures. The low and approximately equal values of specific cohesion (0.0058–0.0094 MPa) are observed in group 0–200 m3, which is conditioned by the action of blasting on deformation of benches. The study is carried out under State Contract No. 075-03-2020-474/1 от 05.03.2020.