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Tuning optical properties of cadmium thiourea acetate nonlinear optical crystal exploiting organic ligand of L-proline
摘要： Modifying optical properties of crystal is very fundamental need for designing various photonic devices, hence in the current investigation, the L-proline (LP) has been firstly doped in cadmium thiourea acetate (CTA) crystal with the aim to optimize the UV–Visible, second harmonic generation (SHG) efficiency, luminescence and third-order nonlinear optical (TONLO) properties of CTA crystal. The pure and doped CTA crystals have been grown by slow solvent evaporation technique at 35°C. The structural parameters of grown crystals have been determined using the single crystal X-ray diffraction technique. The incorporation of LP in CTA crystal matrix has been confirmed by Fourier transforms infrared analysis. The UV–Visible studies have been employed within the wavelength range of 200–900 nm to explore the enhancing impact of LP on CTA crystal. The LP doped CTA crystals were subjected to Kurtz–Perry test and Z-scan analysis to identify the nonlinear nature of studied crystals. The SHG efficiency of LP-CTA crystal shows significant increase owing to enhanced charge transfer over the organic ligand of LP. The laser-induced TONLO properties of LP-doped CTA crystal have been determined at 632.8 nm. The nature of nonlinear refraction and absorption has been explored by close and open aperture Z-scan configuration. The magnitude of nonlinear refraction (n2), absorption coefficient (β), cubic susceptibility (χ3) and figure of merit has been determined using the transmittance data. The color-centered luminescence studies have been carried out which established the prominent redshift in peak maxima of emission wavelength of CTA crystal due to doping of LP. Comparative analysis of pure and doped crystal confirmed the dominance of LP doping.
关键词： optical studies,TONLO parameters,Crystal growth,Z-scan analysis
更新于2025-09-23 15:22:29
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Growth, optical, mechanical and nonlinear optical properties of Furfurylaminium 2-chloro-5-nitrobenzoate single crystal
摘要： The furfurylaminium 2-chloro-5-nitrobenzoate (FC) is a modernized organic material possessing enhanced order three nonlinearity. The crystals of FC of dimensions 17 × 4 × 2 mm3 were yielded on slow evaporation with the usage of ethanol-water mixed solvent (1:1). The precise peaks in powder XRD analysis reveal the crystalline property of the compound. The lattice parameters was estimated (a = 11.77 ± 0.012 ?, b = 6.84 ± 0.012 ? and c = 16.33 ± 0.028 ? and volume = 1342 ?3) from powder XRD using XRDA software. The FC crystal corresponds to the system of monoclinic with the space group P21/c. The UV-visible spectrum of FC crystal sample furnishes the lower cut off wavelength (325 nm) and the band gap (3.57 eV) for FC crystal. The dispersion factors Eo and Ed was calculated to be 4.24 eV and 15.20 eV respectively from Wemple and Di Domenico single oscillator model. Using these values, the oscillator strength value was calculated to be 64.5134 (eV) 2 and the moments of optical spectra was estimated to be M -1 = 3.580 (eV) 2 and M -3= 0.198 (eV) 2. The optical conductivity (σ) value of FC crystal at 532 nm was found out to be 0.21 ×1010 s-1. A red emission peak at 691 nm was obtained in photoluminescence spectra when the FC sample was excited at 325 nm. Single shot LDT value for FC crystal was calculated to be 14.40 GW/ cm2. The third order optical susceptibility (χ(3)) of the molecule was enumerated as 4.02 ×10-6 esu from Z-scan technique and the second order hyperpolarizability (γ) value is calculated to be 2.64 × 10-35 esu. The coupling factor (ρ*) is estimated to be 0.047, on utilizing the calculated values of (Re χ(3) = 0.19 × 10-6 esu) and (Im χ(3) =0.19 × 10-6 esu) from Z scan technique. The specific heat capacity (Cp) at 50°C was calculated as 1.5810 (Jg-1 K-1) and thermal diffusivity (α) as 1.750 ×10-6 m2/s. Thus using α the thermo-optic coefficient was deliberated to be 5.34 × 10-6 K-1. The maximum output power of FC indicates its optical limiting behaviour.
关键词： third order susceptibility,optical limiting,Solution growth,Optical materials,Z-scan
更新于2025-09-23 15:22:29
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Use of graph algorithms in the processing and analysis of images with focus on the biomedical data
摘要： INTRODUCTION: Image segmentation is a known problem in the field of image processing. A great number of methods based on different approaches to this issue was created. One of these approaches utilizes the findings of the graph theory. METHODS: Our work focuses on segmentation using shortest paths in a graph. Specifically, we deal with methods of “Intelligent Scissors,” which use Dijkstra’s algorithm to find the shortest paths. RESULTS: We created a new software in Microsoft Visual Studio 2013 integrated development environment Visual C++ in the language C++/CLI. We created a format application with a graphical users development environment for system Windows, with using the platform .Net (version 4.5). The program was used for handling and processing the original medical data. CONCLUSION: The major disadvantage of the method of “Intelligent Scissors” is the computational time length of Dijkstra’s algorithm. However, after the implementation of a more efficient priority queue, this problem could be alleviated. The main advantage of this method we see in training that enables to adapt to a particular kind of edge, which we need to segment. The user involvement has a significant influence on the process of segmentation, which enormously aids to achieve high-quality results (Fig. 7, Ref. 13). Text in PDF www.elis.sk.
关键词： image analysis,CT image,intelligent scissors,MRI scan,medical data
更新于2025-09-23 15:22:29
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Atenuación del artefacto metálico post cirugía de columna lumbar mediante protocolo de obtención de imagen en tomografía computarizada multicorte: estudio de cohortes
摘要： background. In postoperative patients with metallic implants, CT scans can become less effective due to metal-related artifacts. The purpose of our study was to evaluate the effectiveness of a specific metal artifact reduction image protocol, in order to reduce the metal artifact caused by titanium pedicular screws in patients undergoing lumbar pathology by lumbar fusion. This enables surgeons to make an accurate diagnosis of the exact placement of inserted pedicle screws, making this the preferred image modality for assessing screw position after surgery. Methods. In the first part of the study, CT scans were performed on 23 patients (103 titanium alloy pedicle screws) undergoing a lumbar instrumented fusion for treatment for degenerative disease with a standard image acquisition protocol evaluating the possible overdimension caused by the artifact. In the second part, a prospective study was performed using 64-slice multidetector-row computed tomography (MDCT) on 18 patients (104 titanium alloy pedicle screws) undergoing a lumbar instrumented fusion using a specific image acquisition protocol. results. Our results show that in the sequential CT scan group, mean overdimension (on each side) due to brightness was 1.045 mm (SD 0.45). In the 64-slice multichannel CT group, mean overdimension (on each side) due to brightness was 0.005 mm at the proximal part of the screw and 0.025 mm at the distal part of the screw. conclusions. The use of a specific metal artifact reduction image protocol in MDCT produces a minimal artifact following lumbar fusion with pedicle screws.
关键词： Screw,CT scan,Lumbar spine,Artifact
更新于2025-09-23 15:22:29
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Transition from Two-photon Absorption to Saturable Absorption in Gold Patterned Ruby Thin Film
摘要： Nonlinear behaviour of gold micro disks patterned Ruby film has been investigated via Z-scan technique. Open Z-scan was performed for Ruby and Ruby/gold thin film using 532 nm Laser source. Two-photon absorption (TPA) and Saturable absorption (SA) have been observed in pure Ruby and Ruby/gold thin film respectively. The expression for normalized transmittance in open Z-scan was obtained by Gaussian decomposition method for fitting the open. The values for nonlinear absorption coefficient (β) for Ruby/gold (7.41 × 10?7??/??) was two orders of magnitude higher than that of Ruby (1.41 × 10?9??/??). Further, TPA and SA were confirmed by open Z-scan on these films, performed by 633 nm Laser source.
关键词： Surface Plasmon Resonance,Ruby,Z-scan,Two-photon absorption,Saturable absorption
更新于2025-09-23 15:22:29
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DIAMAGNETO-DIELECTRIC ANISOTROPIC WIDE ANGLE IMPEDANCE MATCHING LAYERS FOR ACTIVE PHASED ARRAYS
摘要： In this paper, we present the full process of designing anisotropic metamaterial (MM) wide angle impedance matching (WAIM) layers. These layers are used to reduce the scan losses that occur in active phased arrays for large scanning angles. Numerical results are provided to show the improvement in performances that such layers can ensure. The proposed anisotropic MM-WAIM layers achieve an improvement of about 1 dB of more radiated power at θ = 70? from broadside, in a 13% of fractional bandwidth on the azimuthal plane φ = 90?. Weaker improvements are obtained in the other azimuthal planes, however keeping the active re?ection coe?cient below ?9 dB for all azimuthal planes up to θ = 60? and up to θ = 70? o?-axis for planes φ = 45?, 90? in the whole operational band.
关键词： scan losses,wide angle impedance matching,anisotropic metamaterial,active phased arrays,impedance matching
更新于2025-09-23 15:21:21
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A Novel Multi-Level Security Technique Based on IRIS Image Encoding
摘要： Providing highly secured access to restricted or private areas has become highly required these days, mainly due to terrorism threats. One method of security is no longer sufficient, hence the term and technology of a “multi-level” security system was developed by integrating more than one security procedure, on both hardware and software levels. This research provides a simple, cheap, easily achievable, yet highly secured multi-level security system to control access through doors. The system integrates IRIS scan authentication, innovative IRIS image encoding, encrypted of mobile communication, and multipoint Control Unit (MCU) Security as main procedures of security. The system’s novelty shows in the encoding and encryption of IRIS image data that is acquired by a mobile phone before it is sent to the authentication site, where it is decrypted by a cheap and fast MCU to retrieve the IRIS image that is fed into a Neural Network in order to grant authorization to the user.
关键词： multipoint Control Unit (MCU),Near Field Communication (NFC),authorization,image Encoding,IRIS scan
更新于2025-09-23 15:21:21
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Preparation of composite Ag@Au core–shell nanoparticles and their linear and nonlinear optical properties
摘要： We herein report the preparation of composite Ag@Au core–shell nanoparticles (NPs) through galvanic replacement reaction and the investigations of linear and nonlinear optical properties. TEM micrographs envisage the formation of core–shell NPs. EDS elemental mapping images demonstrate the homogeneous distribution of the elements and their chemical composition. The powder XRD pattern confirms the formation of highly crystalline composite Ag@Au core–shell NPs. The UV–Vis absorption spectrum shows contribution of Ag and Au characteristic absorption bands and the slight red shift provides the strong evidence for coating of Au shell over the Ag core. Moreover, the linear optical parameters such as the extinction coefficient, reflectance, refractive index, conductivity, susceptibility and polarizability are studied. z-scan analysis reveals the enhanced nonlinear optical properties of the composite Ag@Au core–shell NPs with nonlinear refraction coefficient (n2) being ten times higher than that of Ag NPs and eight times increase in comparison with that of Au NPs.
关键词： Nonlinear optical properties,Ag@Au core–shell nanoparticles,z-scan technique,Galvanic replacement reaction,Linear optical properties
更新于2025-09-23 15:21:21
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Transient photoinduced phenomena in graphitic carbon nitride as measured at nanoseconds resolution by step-scan FTIR
摘要： Transient FTIR measurements were performed on graphitic carbon nitride using a step-scan method, facilitating temporal resolution of a few nanoseconds. Variations in the location and the intensity of specific peaks and emerging of new peaks were observed during the first 170 nanoseconds after excitation. A comparison was made between graphitic carbon nitride prepared at two temperatures: 510 °C and 650 °C. The material prepared at 650 °C revealed very strong non-specific absorption beginning 35 nanoseconds after excitation and lasting for 20 nanoseconds. This phenomenon, termed “IR-blackening” was observed neither in g-C3N4 prepared at 510 °C nor in g-C3N4 prepared at 650 °C that was exposed to hole scavengers (ethanol and benzyl alcohol). In contrast, exposure of material prepared at 650 °C to an electron scavenger (methyl viologen) hardly alter the “IR-blackening” phenomenon. The results were explained by a mechanism, predicting higher reductive activity for materials having imperfect heptazine polymerization, as indeed was found in the photocatalytic degradation of 4-nitrophenol.
关键词： Photocatalysis,IR- blackening,Step-scan,graphitic carbon nitride,Transient FTIR
更新于2025-09-23 15:21:21
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SLAM-aided forest plot mapping combining terrestrial and mobile laser scanning
摘要： Precise structural information collected from plots is significant in the management of and decision-making regarding forest resources. Currently, laser scanning is widely used in forestry inventories to acquire three-dimensional (3D) structural information. There are three main data-acquisition modes in ground-based forest measurements: single-scan terrestrial laser scanning (TLS), multi-scan TLS and multi-single-scan TLS. Nevertheless, each of these modes causes specific difficulties for forest measurements. Due to occlusion effects, the single-scan TLS mode provides scans for only one side of the tree. The multi-scan TLS mode overcomes occlusion problems, however, at the cost of longer acquisition times, more human labor and more effort in data preprocessing. The multi-single-scan TLS mode decreases the workload and occlusion effects but lacks the complete 3D reconstruction of forests. These problems in TLS methods are largely avoided with mobile laser scanning (MLS); however, the geometrical peculiarity of forests (e.g., similarity between tree shapes, placements, and occlusion) complicates the motion estimation and reduces mapping accuracy. Therefore, this paper proposes a novel method combining single-scan TLS and MLS for forest 3D data acquisition. We use single-scan TLS data as a reference, onto which we register MLS point clouds, so they fill in the omission of the single-scan TLS data. To register MLS point clouds on the reference, we extract virtual feature points that are sampling the centerlines of tree stems and propose a new optimization-based registration framework. In contrast to previous MLS-based studies, the proposed method sufficiently exploits the natural geometric characteristics of trees. We demonstrate the effectiveness, robustness, and accuracy of the proposed method on three datasets, from which we extract structural information. The experimental results show that the omission of tree stem data caused by one scan can be compensated for by the MLS data, and the time of the field measurement is much less than that of the multi-scan TLS mode. In addition, single-scan TLS data provide strong global constraints for MLS-based forest mapping, which allows low mapping errors to be achieved, e.g., less than 2.0 cm mean errors in both the horizontal and vertical directions.
关键词： MLS,Single-scan TLS,Forest mapping,SLAM,LiDAR
更新于2025-09-23 15:21:01