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    Augmenting wire arc additive manufacturing with laser forming for generative realization of complex geometries

    Gudur S.Simhambhatla S.
    5页
    查看更多>>摘要：© 2022 Elsevier GmbHDue to its advantages like higher deposition rates and lower costs, Wire Arc Additive Manufacturing (WAAM) is increasingly used to fabricate metal AM parts, particularly big-sized components. However, realization of complex geometrical features, like overhangs, remains one of the major challenges. The present work describes a hybrid approach of intervention of fiber laser intermittently during part fabrication to enhance the geometrical complexity possible. In this two-step process, a component deposited in first stage is subjected to multiple laser passes in second stage to obtain a desired angle/shape. This cycle of deposition and laser forming continues till the final desired geometry is realized. The study includes preliminary trials on deposited specimens to understand dominant laser bending mechanism and decide optimum laser process parameters. Subsequently, a few illustrative components are manufactured using current hybrid process, establishing the effectiveness of this approach in realizing complex shapes, thus laying a foundation for a potential metal 4D printing technology.
      原文链接:
    • NSTL

    Optical properties of Sm3+ doped in CaO-Al2O3-Na2O-BaO-B2O3 glasses for under-sea optical device applications

    GarimaHebbar V D.Rajaramakrishna R.Gurav B....
    5页
    查看更多>>摘要：© 2022 Elsevier GmbH23CaO-10Al2O3-10Na2O-6BaO-(51-X)B2O3-XSm2O3 where, X = 0.0 (S0), 0.1(S1), 0.3(S2), 0.5(S3), 1.0(S4) glasses was fabricated by melt-quench technique. The characterization for the glass was performed by the standard techniques of XRD, FTIR, optical absorption, and fluorescence spectra. Physical properties such as dielectric constant, rare earth ion (Sm3+) concentration, polaron radius, interionic distance, field strength, average boron-boron interaction, molar refractivity, molar polarizability, metallization criteria, molar cation polarizability, electronic oxide ion polarizability, optical basicity, theoretical optical basicity, interaction parameter was determined. FTIR spectra confirm the signature borate vibrations. Judd-Ofelt (JO) analysis was evaluated and JO parameters show Ω2 > Ω4 > Ω6 trend. Glasses with 0.1 and 0.3 mol% Sm2O3 had the greatest value of Ω2, due to ligand field asymmetry and rare earth oxygen (Sm-O) covalent bonds at rare-earth ion sites. Photoluminescence spectra reveal three emission peaks originating from 565, 602, and 649 nm corresponding to 4G5/2→6H5/2, 6H7/2, and 6H9/2 respectively. Radiative properties such as stimulated emission cross-sections (σ) and branching ratios (β) was calculated and show higher value for 0.3 mol% Sm2O3 sample which is compared with other glasses. At 0.3 mol% of Sm2O3 content, concentration quenching was observed and attributed to transfer of energy via cross-relaxation channels within Sm3+ ions. The observed radiative properties for the prepared glass system show that they are efficient for developing under-sea optical device applications in the reddish-orange spectral region. The chromaticity coordinates were evaluated for the glasses. The evaluated (x,y) coordinates are observed to be found in the orange-red region of the CIE 1931 chromaticity diagram. The CCT values were obtained from CIE (x,y) coordinates.
      原文链接:
    • NSTL

    Structural, optical and Judd-Offelt intensity parameters of samarium doped with zinc tellurite glasses

    Lakin I.I.Tafida R.A.Halimah M.K.Azlan M.N....
    5页
    查看更多>>摘要：© 2022 Elsevier GmbHObjective: The current challenges in materials science and technology is to modify the optical response of rare-earth-doped inorganic glasses for optical applications. The main objectives of the present study are to identify the effect of samarium oxide concentration on the linear optical properties of the zinc tellurite glass system and to use the Judd–Ofelt analysis to study the compositional dependence of the optical properties of the synthesized glasses. Mehodology: Zinc tellurite glasses [(TeO2)0.7 (ZnO) 0.3]1−x [Sm2O3NPs] x, with x = 0.01, 0.02, 0.03, 0.04 and 0.05 molar fraction are prepared by melt quenching technique. The glass samples were produced by employing high-purity analytical chemicals of TeO2 (Alfa Aesar 99.99 per cent), ZnO (Alfa Aesar 99.99 per cent) and Sm2O3 NPs (Alfa Aesar 99.99 per cent). The density of the glass samples was determined based on Archimedes principles with distilled water as an immersed liquid. The density measurement was taken at 10 different times and the average value was recorded. Results: Densimeter, Fourier transform infrared (FTIR) and X-ray diffraction (XRD) were used to study the physical and structural properties. The density and molar volume increases from 5.10 to 5.32 g/cm3 and 27.06–27.54 cm3/mol with an increase in Sm2O3 NPs concentrations. The XRD revealed that the glasses are amorphous. FTIR spectrum reflects the TeO4 structural unit stretching mode. The UV-Vis absorption spectra have seven absorption peaks from the ground state 6H5/2 to 4F7/2, 4I9/2, 6F11/2, 6F9/2, 6F7/2,6F5/2, and 6F3/2 excited energy levels of Sm3+ NPs. The emission spectra under 404 nm wavelength comprised of four bands at 566 nm, 604 nm, 647 nm, and 710 nm represented as 4G5/2→ 6H5/2, 6H7/2, 6H9/2, and 6H11/2 transitions. The presence of Sm2O3 NPs was confirmed by high-resolution electron microscopy transmission (HR-TEM) with a particle size of 72.43 nm. Judd-Offelt parameters (Ω2= 4.94, Ω4=4.38 and Ω6=3.38) were obtained from the least square fitting and the results revealed that the glasses have potential for laser application.
      原文链接:
    • NSTL

    Designing digital circuits based on quantum-dots cellular automata using nature-inspired metaheuristic algorithms: A systematic literature review

    Wang X.
    5页
    查看更多>>摘要：© 2022 Elsevier GmbHQuantum-dot Cellular Automata (QCA) is prospective nanotechnology that has been named one of the top six upcoming computer technologies. QCA is a method for building computational systems that encode binary logics via the arrangement of charges among quantum dots. It is highly fast, has low power usage, and is extremely dense. QCA technology, in particular, brings up new possibilities for power savings and high-performance clock rates. Because of the appropriate properties, the execution of logic circuits utilizing QCA technology is a hotly debated topic. Design tools must handle many problems posed by QCA technology circuit design. Nature-inspired meta-heuristic algorithms play a vital role in computer processing, and algorithms with faster performance rates are more valuable. However, so far, there is no systematic study that regularly examines the role of nature-inspired met heuristic algorithms in QCA. Hence, the present investigation examines the applications of nature-inspired met heuristic algorithms in QCA. The articles on QCA optimization algorithms are selected and analyzed using the systematic literature review method. Also, important challenges and suggestions for future work are highlighted. The results showed that QCA-based digital logic circuits could be optimized using nature-inspired algorithms by reducing the number of gates.
      原文链接:
    • NSTL

    Perovskite-based multi-dimension THz modulation of EIT-like metamaterials

    Zhang Y.G.Liu W.J.Qiu F.Liang L.J....
    5页
    查看更多>>摘要：© 2022 Elsevier GmbHThis letter presents a form of fabricated perovskite-based multi-dimension THz modulator. With such a device, both the depth and the phase of the THz waves can be modulated by a tuning of the continuous luminous flux. The measurements show that the modulation depth can reach 45.4% at a frequency of 1.17 THz, when the pump power is set at 78.7 mW/cm2. Moreover, a phase difference of 168° is reached at 1.17 THz, when the optical power is 109.1 mW/cm2. The determined results verify the quantitative controllability of the perovskite in THz modulating, and the study proves that perovskites have excellent potential for application in THz modulation.
      原文链接:
    • NSTL

    Photoluminescence characteristics of Sm3+ doped Na13Sr2Ta2(PO4)9 as new orange-red emitting phosphors

    Xue Y.-L.Zhao D.Zhang S.-R.Li R....
    5页
    查看更多>>摘要：© 2022This paper describes the synthesis and properties of a new Sm3+-activated phosphor Na13Sr2(1-x)Ta2(PO4)9:2xSm3+ (x = 0.01–0.12). The crystal structure and the phase purities were characterized, and using scanning electron microscopy (SEM), the morphology was investigated. The emission spectra of as prepared phosphors contain some emitting peaks at 560, 595, 650, and 710 nm. The strongest one is 595 nm, resulting from the Sm3+ 4G5/2→6H7/2 transition. In addition, the optimal Sm3+ concentration was determined to be 9 mol%, and we determined that the critical energy transition distance at which concentration quenching occurs is 2.05 nm, suggesting that it is primarily caused by electric multipole interaction. The achievement of this work is to provide a new orange-red phosphor based on a phosphate host lattice.
      原文链接:
    • NSTL

    Performance and efficiency control method of in-situ TiC generated by laser cladding

    Lian G.Zeng J.Chen C.Huang X....
    5页
    查看更多>>摘要：© 2022 Elsevier GmbHThe work studied the effects of differences in the molar ratios of carbon to titanium on the performance and forming efficiency of in-situ TiC materials generated by laser cladding. The full factor test method was used to explore the coupling effect of process parameters on the hardness of the cladding layer and the formation efficiency of TiC. The combined-parameter method was used to establish the mathematical models of laser power, scanning speed, powder ratio versus hardness, hard-phase production, and cladding efficiency. The results showed that the hardness and hard-phase formation increased with increased laser power and powder ratio and decreased with the increased scanning speed. The cladding efficiency increased with increased laser power and decreased with the increased scanning speed and powder ratio. With the low molar ratio of carbon to titanium, TiC in the form of dendrites was found in the cladding layer. When the carbon-titanium ratios were close and carbon was surplus, the morphology of the generated TiC particles was petal-like and spherical. Besides, the production increased and grain had finer sizes. Sensitivity analysis showed that fine adjustment of the powder ratio significantly affected the three models with the laser power of 1800 W, a scanning speed of 4 mm·s−1, and a powder ratio of 0.7, and the accuracy of the sensitivity analysis was proved through experiments.
      原文链接:
    • NSTL

    Verifiable visually meaningful image encryption based on compressed sensing (CS) and improved game of life (IGOL)

    Chai X.Fu Z.Ma Y.Gan Z....
    5页
    查看更多>>摘要：© 2022 Elsevier GmbH(objective) Image encryption converts the plain image into a noise-like one to protect information security. However, the obtained cipher images are easy to attract the attention of third parties during transmission and storage, and it is vulnerable to information damage and tampering caused by hacking or noise pollution, which in turn makes the receiver unable to obtain the correct decrypted image even spending many resources. To address these issues, this paper proposed a verifiable visually meaningful image encryption based on compressed sensing (CS) and improved game of life (IGOL). (methods) Specifically, the plain image is preprocessed and compressed to obtain compressed image via CS, achieving the purpose of reducing the image size. Subsequently, to improve the encryption effect, dynamic cyclic shift confusion method (DCSCM) and diffusion method based on improved game of life (DMIGOL) are presented and performed on the compressed image to obtain the secret image. Next, multiple shadow images are obtained using the secret image sharing based on the Chinese remainder theorem (CRT-SIS) on the secret image, which improves the robustness of this scheme and achieves multi-party data transfer of image. Finally, the shadow images are embedded into the carrier images respectively to obtain visually meaningful cipher images, reducing the attacker's attention to the cipher images during transmission. Additionally, the Hamming distance authentication method relying on plain image and carrier image is applied, and users can perform identity authentication and integrity check on cipher image. (result) Experimental results demonstrate the security and effectiveness of the proposed scheme.
      原文链接:
    • NSTL

    Impact of L-Leucine on the structural and optical properties of potassium dihydrogen phosphate (KDP) crystals

    Mahadik A.Soni P.H.Mithani A.Chaudhari K....
    5页
    查看更多>>摘要：© 2022 Elsevier GmbHIntroduction: Potassium Dihydrogen Phosphate (KDP) is an exceptionally good non-linear optical (NLO) material used for optoelectronics, electro-optics, etc. The inclusion of amino acids enhances the properties of KDP because amino acids have properties like molecular chirality and zwitterionic nature. Objective: In this study, our primary goal was to describe the effects of L-Leucine doping on KDP and to study the changes in its optical and structural properties for different applications related to non-linear optics. Methods: Pure KDP and L-Leucine doped KDP (1 mol% and 2 mol%) crystals were grown using the slow evaporation method at room temperature. The crystals have been characterized using Powder X-ray Diffraction (XRD), Fourier Transform Infrared (FT-IR) Spectroscopy, Ultraviolet-Visible (UV-Vis) Spectroscopy, Photoluminescence (PL) Spectroscopy and Relative Second Harmonic Generation (SHG) measurement. Result: The FTIR spectroscopy confirms the presence of amino acid, L-Leucine in KDP as implied by functional groups. The UV-Vis spectroscopy helps with the optical transparency of crystals and the bandgap of pure KDP was observed to be enhanced with the addition of L-Leucine. The PL spectra confirm the existence of point defects in the grown crystals. Furthermore, L-Leucine doping in KDP improves its relative SHG efficiency. Conclusion: It has been seen those optical properties of pure KDP is immensely improved with the addition of L-Leucine without altering the KDP lattice.
      原文链接:
    • NSTL

    Evolving electromagnetic chirality of a focused field from the Poincaré sphere perspective

    Zhu M.Fu S.Man Z.
    5页
    查看更多>>摘要：© 2022 Elsevier GmbHChirality, which describes not only the three-dimensional mirror-symmetry violation of objects but also the local handedness and spatial geometrical structure of electromagnetic fields, has gained enormous interest recently because of its fundamental features as well as practical and potential applications in chiral light–matter interactions. Analytical forms of the electric and magnetic field strength vectors as well as optical chirality density and flow of strongly focused full Poincaré sphere beams are presented. The evolution of nonparaxial electromagnetic chirality of input fields from the Poincaré sphere view is explored; in addition its roles in relation to ellipticity, handedness, and orientation are revealed based on the analytical model. Ellipticity affects the localization and magnitude of both chirality density and flow. In contrast, handedness mainly affects the magnitude of the optical chirality density and longitudinal component of flow, whereas both density and flow are independent of the input orientation. Moreover, the structure and appearance of the optical chirality density are dominated by the longitudinal component of its flow. These findings may be of help in chiral particle trapping, nanoscale chiral detection, and sensing.
      原文链接:
    • NSTL