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Finite-Difference Time-Domain Analysis of Tapered Photonic Crystal Fiber
摘要： This paper brief about the simulation of tapered photonic crystal fiber (PCF) LMA-8 single-mode type based on correlation of scattering pattern at wavelength of 1.55 μm, analyzation of transmission spectrum at wavelength over the range of 1.0 until 2.5 μm and correlation of transmission spectrum with the refractive index change in photonic crystal holes with respect to taper size of 0.1 until 1.0 using Optiwave simulation software. The main objective is to simulate using Finite-Difference Time-Domain (FDTD) technique of tapered LMA-8 PCF and for sensing application by improving the capabilities of PCF without collapsing the crystal holes. The types of FDTD techniques used are scattering pattern and transverse transmission and principal component analysis (PCA) used as a mathematical tool to model the data obtained by MathCad software. The simulation results showed that there is no obvious correlation of scattering pattern at a wavelength of 1.55 μm, a correlation obtained between taper sizes with a transverse transmission and there is a parabolic relationship between the refractive index changes inside the crystal structure.
关键词： scattering pattern,photonic crystal fiber,optiwave,transmission spectrum,tapered
更新于2025-09-10 09:29:36
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Simulating terahertz absorption of fluorinated phenylacetylene biphenyl liquid crystal molecules
摘要： Based on the density functional theory, ten kinds of fluoro-substituted liquid crystal derivative molecules, 4-butyl-4’-[(4-butylphenyl)acetylene]biphenyl, are simulated using Gaussian09 package with Opt+Freq optimization type and B3LYP/6-311g basis set. Comparing the substituted position and number of fluorine atoms, the absorption in terahertz region is discussed. Because measurement data of liquid crystal material absorption is lacking, we can only compare in the range of 0.3?3 THz. The results show that the calculation results have the same trend as the experimental measurement absorption curve of related literature. As a conclusion, our calculations can better reflect the absorption of molecular materials and provide effective suggestions for the design and synthesis of related molecules.
关键词： Gaussian simulation,absorption,fluorine liquid crystal,spectrum,terahertz
更新于2025-09-10 09:29:36
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Evaluation of a spectral line width for the Phillips spectrum by means of numerical simulation
摘要： The work aims to check one of the assumptions under which the kinetic equation for water waves was derived in order to understand whether it can be applied to the situations described by the Phillips spectrum. We evaluate a spectral line width of the spectrum from the simulations in the framework of primordial dynamical equations at different levels of nonlinearity in the system, corresponding to the weakly turbulent Kolmogorov–Zakharov spectra ω?4, Phillips spectra ω?5, and intermediate cases. The original motivation of the work was to check one of the assumptions under which the kinetic equation for water waves was derived in order to understand whether it can be applied to the Phillips spectrum. It is shown that, even in the case of relatively high average steepness, when the Phillips spectrum is present in the system, the spectral lines are still very narrow, at least in the region of the direct cascade spectrum. It allows us to state that, even in the case of the Phillips spectrum, one of the assumptions used for the derivation of the Hasselmann kinetic equation is still valid, at least in the case of moderate whitecapping.
关键词： numerical simulation,water waves,Phillips spectrum,spectral line width,kinetic equation
更新于2025-09-10 09:29:36
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[IEEE 2018 Conference on Precision Electromagnetic Measurements (CPEM 2018) - Paris, France (2018.7.8-2018.7.13)] 2018 Conference on Precision Electromagnetic Measurements (CPEM 2018) - Josephson Arbitrary Waveform Synthesizer as a Reference Standard for the Measurement of the Phase of Harmonics in Distorted Signals
摘要： We use the Josephson arbitrary waveform synthesizer to provide traceability for the phase of the harmonics, relative to its fundamental, of a distorted waveform. For distorted waveforms with rms values in the range from 0.154 V to 0.2 V and harmonic magnitudes from 5% to 40 % of the fundamental, our system can generate odd harmonics up to the 39th with phase uncertainties from 0.002° to 0.010° (k=2.0), depending on the harmonic number and harmonic magnitude.
关键词： Josephson junction array,measurement techniques,measurement quantum voltage standards,standards,phase measurement,spectrum analysis
更新于2025-09-10 09:29:36
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Structural, optical and nonlinear optical properties and TD-DFT analysis of heteroleptic bis-cyclometalated iridium(III) complex containing 2-phenylpyridine and picolinate ligands
摘要： In this work, we studied the structural, optical and nonlinear optical properties and UV–visible absorption spectrum of the heteroleptic bis-cyclometalated iridium(III) complex (tfmppy)2Ir(pic) recently synthesized with tfmppy = 5-trifluoromethyl-2-phenylpyridine and pic = picolinate. The calculations were performed by means of density functional theory (DFT) and time-dependent density functional (TD-DFT) methods using four functionals B3LYP, PBE0, CAM-B3LYP and M06-2X. Calculated geometric parameters agree with the experimental data. CAM-B3LYP and M06-2X lower the HOMO energy level and give a large energy gaps compared with B3LYP and PBE0. The four functionals show that LUMO is delocalized over ??? ppy and dIr orbitals. The studied complex gets a remarkably large first-order NLO response. B3LYP would provide good estimates of the energy gap and shows the strongest values of the first hyperpolarizabilities βHRS; M06-2X and CAM-B3LYP functionals overestimate the gaps and lower βHRS values. PBE0 and B3LYP spectra agree better with the experimental spectrum in the visible region, while CAM-B3LYP and M06-2X are more accurate in UV-C region. Natural transition orbital analysis shows that the weak band observed at 468 nm corresponds to MLCT/LLCT charge transfer transitions and the intense band observed at 270 nm is mainly assigned to intra-ligand state.
关键词： Excited states,Wiberg indices,Absorption spectrum,Hyperpolarizability,Complexes,Iridium,NTO,TD-DFT,Optical, nonlinear optical,Picolinate
更新于2025-09-10 09:29:36
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Molecularly imprinted photonic hydrogel sensor for optical detection of L-histidine
摘要： A molecularly imprinted photonic hydrogel (MIPH) is described for the optical determination of L-histidine (L-His). The inverse opal structure of MIPH was obtained by placing silica particles (230 nm) in molecularly imprinted polymer on a glass slide. After being fully etched by hydrofluoric acid, this inverse opal structure brings about a high specific surface and plentiful binding sites for L-His. If L-His is absorbed by the modified MIPH, its average effective refraction coefficient is increased. This causes the Bragg diffraction peak to be red-shifted by about 34 nm as the concentration of L-His increases from 0 to 100 nM. Much smaller diffraction peak shifts are obtained for other amino acids. The detection limit of this method is 10 pM. The response time towards L-His is as short as 60 s. In addition, the sensor can be recovered by treatment with 0.1 M acetic acid/methanol. It was applied to the determination of L-His in drinks sample.
关键词： Inverse opal structure,St?ber method,Nanoporous materials,Photonic crystal array,UV curing,Bragg diffraction peak,Hydrogen bonding,Reflection spectrum
更新于2025-09-10 09:29:36
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?Lab on a Chip“; Lab on a Chip;
摘要： Background. Miniaturization has not only driven microelectronics and generated new unforeseen options but has also dramatically changed sensors and analytics. Developments. The Lab on a Chip (LOC) technology enables laboratory processes to run fully automated in canals in the micrometre range. The biggest challenge for LOC is to keep production costs low despite miniaturization and application-specific design. If this is achieved medical laboratory analyses can usually be carried out faster and with less hands on time. This explains why LOCs are already integrated into many laboratory instruments and why point-of-care testing (POCT) can no longer be imagined without it. New markers, such as in liquid biopsies and measurement techniques, such as Raman spectroscopy and mass spectroscopy, create further potentials that will enable faster and more specific laboratory analyses to be made using LOC technology. Conclusion. The LOC technology has the potential of changing the medical practice especially in cases when the central laboratory is not available or is unable to provide results fast enough.
关键词： Laboratory diagnostics,Mass spectrometry,Point-of-care testing,Spectrum analysis, Raman,Microfluidics
更新于2025-09-10 09:29:36
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Mapping the Leaf Economic Spectrum across West African Tropical Forests Using UAV-Acquired Hyperspectral Imagery
摘要： The leaf economic spectrum (LES) describes a set of universal trade-offs between leaf mass per area (LMA), leaf nitrogen (N), leaf phosphorus (P) and leaf photosynthesis that influence patterns of primary productivity and nutrient cycling. Many questions regarding vegetation-climate feedbacks can be addressed with a better understanding of LES traits and their controls. Remote sensing offers enormous potential for generating large-scale LES trait data. Yet so far, canopy studies have been limited to imaging spectrometers onboard aircraft, which are rare, expensive to deploy and lack fine-scale resolution. In this study, we measured VNIR (visible-near infrared (400–1050 nm)) reflectance of individual sun and shade leaves in 7 one-ha tropical forest plots located along a 1200–2000 mm precipitation gradient in West Africa. We collected hyperspectral imaging data from 3 of the 7 plots, using an octocopter-based unmanned aerial vehicle (UAV), mounted with a hyperspectral mapping system (450–950 nm, 9 nm FWHM). Using partial least squares regression (PLSR), we found that the spectra of individual sun leaves demonstrated significant (p < 0.01) correlations with LMA and leaf chemical traits: r2 = 0.42 (LMA), r2 = 0.43 (N), r2 = 0.21 (P), r2 = 0.20 (leaf potassium (K)), r2 = 0.23 (leaf calcium (Ca)) and r2 = 0.14 (leaf magnesium (Mg)). Shade leaf spectra displayed stronger relationships with all leaf traits. At the airborne level, four of the six leaf traits demonstrated weak (p < 0.10) correlations with the UAV-collected spectra of 58 tree crowns: r2 = 0.25 (LMA), r2 = 0.22 (N), r2 = 0.22 (P), and r2 = 0.25 (Ca). From the airborne imaging data, we used LMA, N and P values to map the LES across the three plots, revealing precipitation and substrate as co-dominant drivers of trait distributions and relationships. Positive N-P correlations and LMA-P anticorrelations followed typical LES theory, but we found no classic trade-offs between LMA and N. Overall, this study demonstrates the application of UAVs to generating LES information and advancing the study and monitoring tropical forest functional diversity.
关键词： hyperspectral,spectroscopy,West Africa,tropical forest,UAV,Ghana,leaf traits,PLSR,leaf economic spectrum
更新于2025-09-10 09:29:36
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Disorder Engineering in Monolayer Nanosheets Enabling Photothermic Catalysis for Full Solar Spectrum (250 <b>-</b> 2500?nm) Harvesting
摘要： A persistent challenge in classical photocatalyst systems with extended light absorption is the unavoidable trade-off between maximizing light harvesting and sustaining high photoredox capability. Alternatively, cooperative energy conversion through photothermic activation and photocatalytic redox is a promising yet unmet scientific proposition that critically demands a spectrum-tailored catalyst system. Here, we construct a solar thermal-promoted photocatalyst, an ultrathin “biphasic” ordered–disordered D-HNb3O8 junction, which performs two disparate spectral selective functions of photoexcitation by ordered structure and thermal activated conversion via disordered lattice for combinatorial photothermal mediated catalysis. This in situ synthetically immobilized lattice distortion, constrained to a single-entity monolayer structure not only circumvents interfacial incompatibility but also triggers near-field temperature rise at the catalyst–reactant complexes’ proximity to promote photoreaction. Ultimately, a generic full solar conversion improvement for H2 fuel production, organic transformation and water purification is realized.
关键词： redox reaction,photothermic catalysis,defect engineering,order–disorder,full solar spectrum
更新于2025-09-10 09:29:36
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Enhanced sensitivity of hemoglobin sensor using dual-core photonic crystal fiber
摘要： A Hemoglobin (Hb) biosensor based on dual-core photonic crystal fiber is proposed and analyzed. In this paper, the effective refractive index dependency on the Hb concentration within a blood sample is utilized in obtaining the transmission spectrum variation. The results are calculated using full vectorial finite element method. Through this study, the effect of the structure geometrical parameters on the sensor performance is optimized to maximize the sensor sensitivity. The numerical results show a sensitivity of 8.013 nm/g/dL for the X-polarized mode at 3.7 cm fiber length and 7.68 nm/g/dL for the Y-polarized mode at 3.2 cm fiber length of the proposed sensor.
关键词： Coupling length,Finite element method,Transmission spectrum,Dual-core photonic crystal fiber,Hemoglobin concentration
更新于2025-09-10 09:29:36