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[IEEE 2018 25th IEEE International Conference on Image Processing (ICIP) - Athens, Greece (2018.10.7-2018.10.10)] 2018 25th IEEE International Conference on Image Processing (ICIP) - A Retina-Inspired Encoder: An Innovative Step on Image Coding Using Leaky Integrate-and-Fire Neurons
摘要： This paper aims to build an image coding system based on a model of the mammalian retina. The retina is the light-sensitive layer of tissue located on the inner coat of the eye and it is responsible for vision. Inspired by the way the retina handles and compresses visual information and based on previous studies we aim to build and analytically study a retinal-inspired image quantizer, based on the Leaky Integrate-and-Fire (LIF) model, a neural model approximating the behavior of the ganglion cells of the Ganglionic retinal layer that is responsible for visual data compression. In order to have a more concrete view of the encoder's behavior, in our experiments, we make use of the spatiotemporal decomposition layers provided by extensive studies on a previous retinal layer, the Outer Plexiform Layer (OPL). The decomposition layers produced by the OPL, are being encoded using our LIF image encoder and then, they are reconstructed to observe the encoder's efficiency.
关键词： weighted difference of Gaussians,neural coding,Leaky Integrate-and-Fire (LIF) model,Ganglion cells,image coding,Retina
更新于2025-09-23 15:22:29
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Ambient Tracer-LIF for 2-D quantitative measurement of fuel concentration in gas jets
摘要： A novel ambient tracer LIF technique with addition of tracer into ambient gas is proposed in this study to quantitatively measure the two dimensional (2-D) fuel concentration distribution in high-pressure gas jets. Firstly, the fundamental principle of the ambient tracer-LIF technique is described, and the equation of fuel concentration in a jet is deduced from the ambient fluorescence intensity. In the ambient tracer-LIF technique, the on-site calibration can be performed, and much more degrees of freedom in selection of tracers or target fuels can be achieved in principle. Then, the experiments are carried out with the high pressure gas injected into the environment doped with acetone in an optical accessible constant volume vessel. The fluorescence in the ambient is induced by using the 266 nm laser, and is recorded by the ICCD camera. The dedicated image processing is implemented to reduce the uncertainty and obtain the quantitative fuel concentration distribution in the jet. The uncertainties of the measurement results are evaluated, including both the systematic and random errors. The uncertainty propagation analysis shows that the measurement uncertainty increases with the local fuel concentration decreasing, and at the boundary regions of the jet, where the mixture is over lean, the relative uncertainty goes up to 26%. Finally, the temporal variations of the fuel concentration distribution in the gas jet are presented, and the effects of injection pressure are discussed. These results are believed to be valuable for development of numerical models and combustion system designs.
关键词： 2-D quantitative concentration measurement,On-site calibration,Ambient tracer-LIF,Natural gas direct injection
更新于2025-09-23 15:22:29
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Machine learning for improved data analysis of biological aerosol using the WIBS
摘要： Primary biological aerosol including bacteria, fungal spores and pollen have important implications for public health and the environment. Such particles may have different concentrations of chemical fluorophores and will respond differently in the presence of ultraviolet light, potentially allowing for different types of biological aerosol to be discriminated. Development of ultraviolet light induced fluorescence (UV-LIF) instruments such as the Wideband Integrated Bioaerosol Sensor (WIBS) has allowed for size, morphology and fluorescence measurements to be collected in real-time. However, it is unclear without studying instrument responses in the laboratory, the extent to which different types of particles can be discriminated. Collection of laboratory data is vital to validate any approach used to analyse data and ensure that the data available is utilized as effectively as possible.
关键词： biological aerosol,UV-LIF,WIBS,clustering,machine learning
更新于2025-09-23 15:21:21
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Attosecond transient-absorption spectroscopy of polar molecules
摘要： We apply attosecond transient absorption spectroscopy (ATAS) to explore the effects of a nonzero permanent dipole on electron dynamics at the subfemtosecond scale, exemplified in the polar LiF molecule. In contrast with nonpolar systems, a familiar feature of the ATA spectra—the light-induced structures—are observed adjacent to a bright state. Moreover, a previously unobserved ladder structure is identified. The observations are analyzed in the context of a model based on fixed-nuclei adiabatic states, supported by full numerical simulations. Analytic calculations originating in the adiabatic model shed light on the nature and origins of the findings.
关键词： LiF molecule,attosecond transient absorption spectroscopy,electron dynamics,polar molecules,ladder structure,light-induced structures
更新于2025-09-23 15:21:01
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On the role of magnesium in LiF:Mg,Ti thermoluminescent dosimeter
摘要： LiF doped with Mg and Ti is the most widely used thermoluminescent (TL) dosimeter for a large variety of applications. It has been argued that the Mg dopant is the most important defect in the TL process. Besides the common F-centre defects in LiF, optical absorption measurements have suggested the presence of Mg-related absorption bands at 380 nm (3.26 eV), and 310 nm (4.0 eV) when LiF:Mg is exposed to ionizing radiation, whose origin is not yet well understood. This work presents an investigation of the role of defects induced by Mg in LiF through electronic structure calculations. The calculations show that Mg interstitials induce a local lattice distortion characterized by the displacement of two opposite fluorine atoms, adjacent to the magnesium, away from their original sites by an average distance of 0.6 ? each, while the closest Li atoms are displaced by 0.1 ?. This defect introduces electronic states in the band-gap that can trap excess electrons produced during irradiation, thus enhancing the efficiency of the detector. Holes, on the other hand, are created and trapped in orbitals of mainly Mg-3s character. Additionally, the results suggest that irradiation can simultaneously remove a Li atom nearby a Mg interstitial; substitute a Li by a Mg atom or create a Li vacancy plus a Mg substitutional, giving rise to defects within the LiF gap that are more stable thermodynamically than the Mg interstitial itself.
关键词： magnesium dopant,LiF:Mg,Ti,thermoluminescent dosimeter,electronic structure calculations,defect states
更新于2025-09-23 15:21:01
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Rapid analysis of marble treatments by laser induced fluorescence
摘要： Nowadays scientific study of Cultural Heritage accompanies most of the time historical artistic evaluation and an assessment of the conservation state by humanistic experts and restorers. Several laboratory methods with high sensitivity are well established (ICP-MS, FTIR,…), and many methods for in situ rough characterization of large surface are widely diffused (thermovision, UV photography,…), in addition to instrumentation for punctual analysis to be applied also in field (XRF, colorimetry,…). However, the request for systems that can provide rapid detailed characterization on large surface in any storage conditions is still a hot topic. This is combined with the ever-increasing demand for digital material for documentation, fruition and study. Laser-based systems, and in particular Laser Induced Fluorescence (LIF), Laser Induced Breakdown Spectroscopy and Raman spectroscopy, due to the characteristics of these sources and the detectors to which they can be coupled, respond well to these needs. The TECFIS-DIM (Diagnostic and Metrology) Laboratory of the ENEA center of Frascati (Rome, Italy) in the last decade has put an effort to develop more and more compact and efficient laser systems for in situ material characterization on cultural heritage surfaces. Here two prototypal LIF systems have been used to characterize marble surfaces treated with ancient and modern materials and a rapid recognition and mapping method has been developed and tested thanks to the individuation of discriminant spectral features. Results are reported on test samples created in lab with known substances and in situ on real artworks.
关键词： Patinas,Marble,Polymers,Laser spectroscopies,Laser induced fluorescence (LIF)
更新于2025-09-23 15:19:57
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Luminescence interference to two-colour toluene laser-induced fluorescence thermometry in a particle-laden flow
摘要： We present the use of two-colour toluene planar laser-induced fluorescence (LIF) to obtain spatially resolved measurements of the gas temperature ( T g ) in a particle-laden turbulent flow under sufficiently dense particle loading that the interference from laser interactions with the particles is significant. The effect of the ratio of volumetric flow rates of the particle phase to the gas phase ( ?? ) on the accuracy and precision of two-colour toluene LIF thermometry was systematically investigated for three particle materials, alumina, zinc activated zinc oxide (ZnO:Zn) and polymethyl methacrylate (PMMA), each of which has differing interactions with the excitation laser. The PMMA particles were spherical and mono-disperse with diameters of 6 to 40 μm , while the alumina and ZnO:Zn particles had diameters in the range 1–40? μm and 2–200?μm, respectively. The results show that the accuracy of the gas temperature measurement is insensitive to particle size for the PMMA particles, but dependent on the instantaneous particle loading. Importantly, reliable measurements can be performed in the dense two-way coupling regime, with the measurement being accurate to within 5?°C for ???<?2.5 × 10?4 for the PMMA particles and for ?? < 7.6 × 10?4 for the alumina and ZnO:Zn particles.
关键词： volumetric flow rates,gas temperature measurement,particle-laden flow,two-colour toluene LIF,particle materials
更新于2025-09-23 15:19:57
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Crystallization and spectroscopic characterizations of binary SrO-B2O3 glasses doped with LiF, NaF, CaF2, or TiO2
摘要： Glasses based on the basic chemical composition of binary strontium borate (SrO 50-B2O350 mol%) together with samples containing dopant (2%) with one of the fluorides (LiF, NaF, CaF2) or TiO2 have been synthesized through the routinely melting and annealing technique. Collective structural, optical, and thermal properties have been measured for the prepared glasses. X-ray diffraction and SEM measurements were carried out for their corresponding glass-ceramics which were synthesized by controlled thermal heat treatment with two-step regime. FT infrared absorption spectra reveal composite vibrational modes in the mid-range 400–1600 cm?1 which are related to the co-presence of both triangular and tetrahedral borate building units in their particular different wavenumber sites. The low dopant level did not make any distinct variations in the IR spectra. X-ray diffraction patterns elucidate the formed crystal phases after crystallization mainly strontium metaborate and other related borate phase and the LiF shows no distinct variation while NaF2 and CaF2 induce the formation of additional crystalline Na-containing or Ca-containing phases besides the formation of NaF or fluorite (CaF2). TiO2 acts as a nucleating agent and also separate as rutile. The crystallization behavior has been correlated with the assumption of the tendency of SrO to induce phase separation in the host binary borate glass and controlled heat treatment initiates the separation of strontium metaborate crystalline phase in the base binary SrO-B2O3 in accordance with its composition and the role of dopants is found to be varying with the type of dopant. The measured thermal expansion parameters of the prepared glasses reveal variations in their values for transformation and softening temperatures depending on the type of added dopant. The changes in the thermal expansion coefficients in the different parts of the thermal curves are related to the ability of the network to absorb lattice expansion through bending of the bonds. The uniform observed ultraviolet absorption bands are related to traces of iron (Fe3+) ions present as impurities.
关键词： LiF,CaF2,NaF,Thermal expansion,FTIR optical spectra,SrO.B2O3 glass,Glass-ceramics,TiO2
更新于2025-09-19 17:15:36
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LIF study of temporal and spatial fluid mixing in an annular downcomer
摘要： In possible accident scenarios of the reactor coolant system, the convection and mixing characteristics of borated water have a great influence on reactivity variations in the reactor, and then impact the reactor safety. The mixing and diffusion characteristics of the boric acid solution in the annular downcomer is studied by laser-induced fluorescence (LIF). An aqueous solution of Rhodamine B (RhB) fluorescence dye, which is used to simulate boron solution, was injected in the coolant inlet to visualize the fluid mixing process in the annular volume. Laser sheet was formed by optical system to emit the fluorescence, a high-speed camera was used to capture the fluorescence information for reconstructing the concentration distribution of dye. In order to guarantee the experimental accuracy, LIF image processing and a calibration technology are applied. The concentration profiles were implemented to illuminate the fluid mixing between dye solution and diluted water in the downcomer. The coefficient of variation (COV) was conducted to quantify the spatial and temporal transport of dye in the annular downcomer. The results indicate that a higher flow improves the transport ability of dye in the transverse direction, and shortens the distance and time to uniform. The mass force can accelerate the dye transport in the vertical direction. The whole-field measurement technique implemented in this study is expected to provide an insight in the research of flow mixing in the complex geometry. The experimental results can provide a better understanding of mixing phenomena in annular downcomer, and it is also useful for the annular downcomer CFD validation.
关键词： Annular downcomer,Concentration distribution,LIF,Fluid mixing,Transport ability
更新于2025-09-19 17:15:36
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Particle dynamics in a gas assisted coal combustion chamber using advanced laser diagnostics
摘要： Coal combustion is strongly influenced by the interaction of gas phase turbulence, particle dynamics and chemistry. To advance the understanding of these mutually coupled processes, experiments under well-controlled inflow and boundary conditions are needed that provide access to non-intrusive multi-parameter measurement techniques. Following this idea, in this work gas-assisted coal flames with power up to 40 kWth are investigated in an optically accessible combustion chamber including a quartz glass quarl of the swirl burner assembly. A Two-phase particle image/tracking velocimetry (PIV-PTV) technique is applied for the first time in coal combustion to measure simultaneously velocities of small and large particles. Due to the wide particle size distribution of the grinded coal small particles can be used as tracers for the gas flow while the velocity of large particles can be measured with particle tracking velocimetry (PTV) simultaneously. For this purpose Mie-scattering is imaged by a single camera. Large and small particles are separated in the post-processing based on apparent size and signal intensity of each particle individually. By measuring quasi-simultaneously laser-induced fluorescence of intermediate hydrocarbons released from coal particles during their devolatilization process, regions of intense pyrolysis are identified. Flames operated with different coal types and thermal powers in air and oxy-fuel atmospheres are compared to each other. Additionally, advantages and limits of the measurement techniques are discussed in the context of coal combustion.
关键词： PIV,LIF,PTV,Coal,Two phase,Oxy-fuel
更新于2025-09-19 17:13:59