157 research outputs found

    Laser sheet scattering and the cameras' positions in particle image velocimetry

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    Simulations of laser sheet scattering by microparticles, based on the generalized Lorenz-Mie theory for the case of numerous random spatial distributions of scattering particles, were done, using the novel computational time saving strategy. This type of scattering by particles immersed in a fluid flow and its recording on cameras, presents the essence of particle image velocimetry systems. The continuous and large change of the intensity of a scattered light failing on the camera causes the sequences of images of varying quality, which makes many of them useless. This paper shows how the problem could be alleviated by determining the angles of low relative standard deviation of scattered light intensity and using them for recording, as well as by avoiding the angles of high relative standard deviation of scattered light intensity

    Laser doppler velocimetry and confined flows

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    Finding the mode, in which two component laser Doppler velocimetry can be applied to flows confined in cylindrical tubes or vessels, was the aim of this study. We have identified principle issues that influence the propagation of laser beams in laser Doppler velocimetry system, applied to flow confined in cylindrical tube. Among them, the most important are influences of fluid and wall refractive indices, wall thickness and internal radius ratio and beam intersection angle. In analysis of the degrees of these influences, we have applied mathematical model, based on geometrical optics. The separation of measurement volumes, that measure different velocity components, has been recognized as the main drawback. To overcome this, we propose a lens with dual focal length primary focal length for the measurement of one velocity component and secondary focal length for the measurement of the other velocity component. We present here the procedure for calculating the optimal value of secondary focal length, depending on experimental set-up parameters. The mathematical simulation of the application of the dual focal length lens, for chosen cases presented here, confirmed the accuracy of the proposed procedure

    Influence of electromagnetic and nuclear radiation in medicine for therapy and diagnosis through processes, facts and statistical analysis

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    Contemporary medicine (biomedicine) cannot be imagined without diagnostics and therapeutic methods based on nuclear, laser, acoustical and other processes. The application of these methods is linked to common computer support, signal processing, measuring monitoring techniques, high degree of automatization, and image analyses. The paper analysed contemporary technical issues related to neonatology, ophthalmology, based on the influence of nuclear radiation and laser beams. Some statistical processing and presentations of results obtained in the IGA KCS Hospital, Belgrade, Serbia, in curing vision of prenatal type new-borns with a different degree of pathological state of retinopathy of prematurity are presented. The general conclusion is that, in spite of the good results, a multidisciplinary approach is needed for a deeper understanding of the role of lasers and laser techniques in medicine as well as possible couplings. Potential new applications of lasers important for the fields of neonatology and ophthalmology were also considered

    Lidarske metode u ranom otkrivanju i praćenju požarnih procesa i njihovoj simulaciji

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    Methods for eearly detection, dynamics monitoring and surveillance of fire processes are topics which belong to the method class where high reliability, detection rate and response imply. Although various transformation processes exist for measuring and quantification of the principal parameters of fire processes, the use of optical methods (including ultraviolet, visible and infrared ranges) is increasing. Laser - quantum generator in all three parts of optical range through various measurement methods of real atmospheric parameters or fire environment are for a long time included in this area. Operation methods are related to linear and nonlinear processes enabling different ranges of measurement uncertainty. This paper is on one hand, dedicated to the analysis of up-to-date optical methods based on lidar solutions and on the other to simulation methods and possibilities of modern software tools.Metode za rano otkrivanje, praćenje dinamike i nadgledanje požarnih procesa su problematika, koja pripada klasi metoda, gde se podrazumeva visoka pouzdanost, brzina detekcije i odziva. Iako postoje različiti procesi transformacije glavnih parametara požarnih procesa u cilju merenja i kvantifikacije, ipak su optičke metode (uključujući ultraljubičasti, vidljivi i infracrveni opseg) sve viÅ”e u upotrebi. Laseri - kvantni generatori, u sva tri dela optičkog područja, kroz različite metode merenja parametara atmosfere ili požarne okoline, su odavno uključeni u problematiku. Metode rada su vezane za linearne i nelinearne procese, koji omogućuju različite opsege mernih nesigurnosti. Rad je posvećen, sa jedne strane, analizi savremenih optičkih metoda baziranih na lidarskim reÅ”enjima, a sa druge, metodama simulacije i mogućnostima savremenih softverskih alata

    Primena Husimijeve funkcije u vremensko-frekvencijskoj analizi signala

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    Husimi function originated in phase space formulation of quantum mechanics. This function appears naturally whenever simultaneous measurement of coordinate and impulse with maximal accuracy allowed by the Heisenberg uncertainty relation is performed on a given quantum state and it represents the probability distribution for simultaneous unsharp measurement of coordinate and impulse. Husimi function may analogously be defined for any pair of conjugated variables. In analysis of time varying signals these variables are time and frequency. In this paper we consider Husimi function in time-frequency space, we derive some properties of the function and give time-frequency analysis of some characteristic signals.U ovom radu razmotrena je Husimijeva funkcija na prostoru kanonski spregnutih promenljivih vreme-frekvencija. Izvedene su neke njene nove osobine koje su ilustrovane na nekoliko analitički zadatih signala. Pokazano je da se Husimijeva funkcija može koristiti pri vremensko-frekvencijskoj analizi signala

    Robotics and Anthropological Research in Archaeology

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    The application of robots in anthropological research in archeology is one of the new features for the introduction of automation in the creation of databases from different periods of cultural history. In this paper, we present the analysis on basis of conservation research on artifacts from the archaeological site of Kale-KrŔevica in Serbia (fourth century BC), where, during the creation of documentation revealed the possibility for a new class of data from the field of anthropology. Bearing in mind that around the world there are a large number of pottery and artifacts on which it could be done the same study, the introduction of robots that using modern methods of diagnosis would greatly could contribute to the developing of a new paradigm in archeology

    The possibilities of application of 3D digital models in cultural heritage objects' protection and revitalisation

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    Contemporary cultural heritage protection relies on precise technical documentation obtained by new technology accomplishments in the domain of 3D digital models. Both 3D models of the existing state of object and virtual ones are equally important in reconstruction and renewal processes. Accurate, textured and detailed 3D point cloud models of various objects, i.e. cultural heritage monuments, are outcomes of contemporary photogrammetric and laser scanning methods, aided by adequate software solutions. The authors presented procedures and results of terrestrial laser scanning and 3D modelling of a cultural heritage monument the monastery church of the complex Kastaljan, located in the mountain region Kosmaj in Serbia. The first part of presented research, concerning data acquisition, carried out using laser scanner and adequate software processing, resulted in 3D dense point cloud model and further 2D plan view along with characteristic cross sections. The possibilities of 3D model presentation, measurements and additional graphic operations were explored, through various software solutions aided by adequate technical support. The second part of research elaborated on the reconstruction of the entire 3D model of the church in the complex Kastaljan, dated back to the 13th century, according to its architectural style characteristics

    The comparison of air flow LDA measurement in simple cylindrical and cylindrical tube with flat external wall

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    Primena 2D laser Dopler anemometarskih sistema je razmatrana za slučaj zatvorenog toka fluida u običnoj cilindričnoj i u cilindričnoj cevi sa ravnim spoljaÅ”njim zidom. Zakoni geometrijske optike su primenjeni na centralne linije laserskih snopova. Izvedeni su izrazi za dislokacije mernih zapremina, uglove kalibracije i rastojanja centra merne zapremine od centra vidnog polja foto-detektora. Izrazi izvedeni u ovom radu su preimenjeni na određeni vrtložni tok u cevi. To je pokazalo nekoliko prednosti koriŔćenja obične cilindrične cevi u odnosu na danas omiljenije koriŔćenje cilindrične cevi sa ravnim spoljaÅ”njim zidom. Ovi rezultati ukazuju na to da bi se sadaÅ”nje izbegavanje LDA merenja kod obične cilindrične cevi trebalo preispitati.The application of 2D laser Doppler anemometry systems is considered, in the case of fluid flow confined in simple cylindrical and in cylindrical tube with flat external surface of the wall. Geometric optics laws are applied to the central lines of laser beams. Measurement volume dislocations, calibration angles and distances of measurement volume centre from the photo-detector field of view centre are expressed. The expressions derived in this paper were applied to specific turbulent swirl flow in pipe. That revealed several advantages of use of a simple cylindrical tube over nowadays favored use of cylindrical tube with flat external surface. Those results suggest that current avoiding of laser Doppler anemometry measurements with simple cylindrical tubes should be reconsidered

    Primena Husimijeve funkcije u vremensko-frekvencijskoj analizi signala

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    Husimi function originated in phase space formulation of quantum mechanics. This function appears naturally whenever simultaneous measurement of coordinate and impulse with maximal accuracy allowed by the Heisenberg uncertainty relation is performed on a given quantum state and it represents the probability distribution for simultaneous unsharp measurement of coordinate and impulse. Husimi function may analogously be defined for any pair of conjugated variables. In analysis of time varying signals these variables are time and frequency. In this paper we consider Husimi function in time-frequency space, we derive some properties of the function and give time-frequency analysis of some characteristic signals.U ovom radu razmotrena je Husimijeva funkcija na prostoru kanonski spregnutih promenljivih vreme-frekvencija. Izvedene su neke njene nove osobine koje su ilustrovane na nekoliko analitički zadatih signala. Pokazano je da se Husimijeva funkcija može koristiti pri vremensko-frekvencijskoj analizi signala

    Some aspects of contemporary trends in civil engineering

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    In this research several topics concerning contemporary civil engineering and architecture are introduced: problems regarding structural system choice (with respect to the geometric design of the building), suitable materials search (regarding durability, reliability, technical feasibility and optimal solutions), ecological aspect of the innovative materials and constructions, aspects of the strength of chosen materials, contemporary methods for the monitoring of the materials, shapes, and tracking of the stress in critical (crack) points of the structural system, composite materials role, facade solutions, geometric design shape with respect to energy efficiency and futurism in the building context
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