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Bichromophoric pyrazoline derivative with solvent-selective photoluminescence quenching
摘要： The quenching of fluorescence in the presence of chloromethanes, which is an unprecedented effect for pyrazolines, has been evidenced for the first time in the case of 1,3-diphenyl-5-{4-[(4-vinylbenzyl)oxy]phenyl}-4,5-dihydropyrazole. The detailed synthesis of this aryl trisubstituted pyrazoline that combines two chromophoric units in a non-conjugated manner is presented. The compound has been extensively characterized from a structural point of view, and its crystal structure has been determined by single crystal X-ray crystallography. The fluorescence study has evidenced the particular behavior of this pyrazoline derivative in solutions of chloromethanes, and the insight gained from the experimental data has been useful in elaborating a plausible fluorescence quenching mechanism. The investigated compound was modeled by Density Functional Theory (DFT) to point out the particularities of the electron transitions in gas phase as well as in the implicit solvents. Also, the HOMO-LUMO energy gap, mapped electrostatic potential, electronic density, dipole moment and polarizability have been reported for the pyrazoline derivative.
关键词： Fluorescence,Synthesis,Quenching,Molecular modelling,Bichromophore,Pyrazoline
更新于2025-09-23 15:22:29
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Molecular and excited state properties of photostable anthraquinone blue dyes for hydrophobic fibers
摘要： Synthetic dyes having high photostability on hydrophobic fibers such as poly(ethylene terephthalate) (PET) are of interest for use on textile substrates for outdoor applications. While much is known about photostable dyes developed for PET in the 1980s, owing to their viability for use in automobile interiors, little has been published on currently viable photostable disperse dyes. As part of an effort to help fill this void and to facilitate future photostable disperse dye design, the present study involved the use of experimental measurements and modelling studies to help characterize the molecular structures of commercially viable dyes for producing photostable colors on PET fibers, beginning with a pair of blue dyes. With the aid of HR-MS, 500 MHz 1H NMR, and X-ray crystallography, it was established that the two dyes are structural isomers having 1,5-(OH)2-anthraquinone (AQ) and 1,8-(OH)2-AQ base structures. It is proposed that the photostability of these dyes arises from the presence of multiple OH/NH groups ortho to the AQ C]O groups which enables them to dissipate excited state energy through intramolecular proton transfer. Further, using DFT-based molecular modelling studies, it was shown that the dye having the 1,5-(OH)2-AQ base structure has a lower ESOP than the isomeric dye having the 1,8-(OH)2-AQ base structure. Similarly, results from calculating Frontier HOMO and LUMO isosurfaces indicated that the LUMO lobes of the latter dye are larger, suggesting that this dye undergoes excitation faster than the 1,5-(OH)2-AQ isomer.
关键词： Molecular modelling,Anthraquinone disperse dyes,X-ray crystallography,Intramolecular H-bonding,Structural analysis
更新于2025-09-23 15:22:29
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Feasibility of 4H-SiC p-i-n Diode for Sensitive Temperature Measurements between 20.5 K and 802 K
摘要： For the first time, we report on the performances of 4H-SiC pin-diode temperature sensors for operating temperatures between 20.5 K and 802 K. In this huge temperature range three ranges of performance were identified with the limit temperatures at 78.2 K and 176.3 K. In each of these ranges a different dominant current transport mechanism is shown and in the manuscript a detailed analysis and discussion is reported. The sensor performances were extracted from VD-T characteristics at different fixed ID values. In particular, at ID=1 μA and in the temperature range between 78.2 K and 802 K, we found a sensor sensitivity of 2.3 mV/K up to 3.4 mV/K with a rms temperature error, eT, of less than 4.2 K and the sensor shows an excellent linearity – quantified by the coefficient of determination R2 higher than 0.9993. For even lower temperatures (below 78.2 K), low measurement currents like 10 nA are required leading to a sensitivity of 5.8 mV/K, but a lower linearity (R2=0.9095) and a rms temperature error of 9.7 K which makes the sensor only partially usable in the temperature range between 20.5 K and 78.2 K. Finally, the sensor performances are compared to other state-of-the-art solutions.
关键词： Semiconductor device modelling,Cryogenic temperatures,Temperature sensors,4H-Silicon Carbide device,High temperatures,Semiconductor p-i-n diodes
更新于2025-09-23 15:22:29
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A Complete System Modelling of Piezoelectric Energy Harvester (PEH) with Silicon Carbide (SiC) Used as Cantilever Base
摘要： Silicon carbide (SiC) is a material that possesses hardness and robustness to operate under high temperature condition. This work is a pilot in exploring the feasibility of cubic piezo element on the SiC wafer with integrated proof mass as horizontal cantilever with perpendicular displacement with respect to the normal plane. With the advance of electronic circuitry, the power consumption is reduced to nano-watts. Therefore, harvesting ambient energy and converting into electrical energy through piezoelectric material will be useful for powering low power devices. Resonance is a property which able to optimize the generated output power by tuning the proof masses. The damping ratio is a considerable parameter for optimization. From analytical study, small damping ratio will enhance the output power of the piezoelectric energy harvester (PEH). This paper will present mathematical modelling approach, simulation verification and the conditional circuit named versatile precision full wave rectifier.
关键词： Silicon carbide,optimization,analytical modelling,cantilever beam,piezoelectric
更新于2025-09-23 15:22:29
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Experimental and numerical investigation to rationalize both near-infrared and mid-infrared spontaneous emission in?Pr3+ doped selenide-chalcogenide fiber
摘要： This contribution reports on detailed experimental and numerical investigations of both near-infrared (NIR) and mid-infrared (MIR) photoluminescence obtained in praseodymium trivalent ion doped chalcogenide-selenide glass fiber. The experimental analysis allows for the identification of the radiative transitions within the praseodymium ion energy level structure to account for the photoluminescent behavior. Numerical analysis is carried out using the rate equations' approach to calculate the level populations. The numerical analysis provides further insight into the nature of the radiative transitions in the Pr3+ ion doped chalcogenide-selenide glass and allows for the identification of the electronic transitions, which contribute to the observed photoluminescence. The numerical results agree well with the experimental results.
关键词： chalcogenide glass fibers,optical fiber modelling,lanthanide doped fibers
更新于2025-09-23 15:22:29
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Label-free nanoparticle sensors based on a triple-layer-coated microsphere structure
摘要： We present a design for a sensitive, label-free nanoparticle sensor based on triple-layer-coated microsphere resonators. The surfaces of the microsphere structure are coated with three layers that have high, low, and high refractive indexes from inside to outside, respectively. We theoretically and numerically investigate two cladding modes, we call the inner mode and outer mode. The resonance wavelengths of the two modes are used to detect the resonance wavelength shift caused by a single-nanoparticle. Numerical calculation suggests that if we change the thickness of the middle layer, the device offers another degree of freedom to obtain higher detection sensitivity. We build a model to accurately describe a nanoparticle close to the microsphere. The method for the sensors may promote the design of biosensing applications.
关键词： Optical materials and properties,Sensors,Simulation and modelling,Microstructure
更新于2025-09-23 15:22:29
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Driving force of crystallisation based on diffusion in the boundary and the integration layers
摘要： Crystal growth rates are notoriously difficult to predict and even experimental data are often inconsistent. By allowing for mass and energy diffusion through the molecular and thermal layers surrounding a growing crystal and for the heat effect of crystallization, a new model of crystal growth from solution is proposed and applied to crystallization of potassium chloride from aqueous solution. The driving force for crystal growth was calculated using the solubility at the interface temperature in contrast to the conventional one based on bulk temperature. A positive heat effect at the crystal interface as well as the resistances to the mass and energy transfer processes to and from the crystal surface can reduce the conventional driving force for crystal growth by more than 20%.
关键词： Crystal growth rate,Boundary layer,Driving force,Mathematical modelling,Integration (Desolvation) layer
更新于2025-09-23 15:22:29
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A Luneburg lens for spin waves
摘要： We report on the theory of a Luneburg lens for forward-volume magnetostatic spin waves and verify its operation via micromagnetic modelling. The lens converts a plane wave to a point source, and vice versa, by a designed graded refractive index, realized by modulating either the thickness or the saturation magnetization in a circular region. We ?nd that the lens enhances the wave amplitude by about 5 times at the lens focus, and 47% of the incident energy arrives in the focal region. A lens with small deviations from the optimal pro?le can still result in good focusing if the index is graded smoothly.
关键词： graded refractive index,Luneburg lens,micromagnetic modelling,spin waves
更新于2025-09-23 15:21:21
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Improving satellite-based modelling of gross primary production in deciduous broadleaf forests by accounting for seasonality in light use efficiency
摘要： Vegetation gross primary production (GPP), the photosynthetic yields by green plants per unit area per unit time, is a key metric of carbon flux in understanding the land–atmosphere interactions and terrestrial carbon cycles. Satellite-based light use efficiency (LUE) models are valuable methods to retrieve large-scale terrestrial GPP using remote sensing data. As studies have reported that maximum light use efficiency, a key parameter that is often assumed to be constant in the LUE models, there is a need to explore the effects of LUE seasonality on GPP simulation and ways for correction. This study proposes a method based on leaf area index to account for LUE seasonality and applies it to four different light use efficiency models (i.e., the MOD17 algorithm, the vegetation photosynthesis model, the radiation partitioning model, and the vegetation index model) for comparisons. Based on 59 site-years flux tower data from deciduous broadleaf forest sites in the United States, the results show that all models could simulate daily GPP time series well and explain more than 85.0% variance of tower-based GPP. There is, however, a tendency to overestimate GPP during the non-growing season but underestimate GPP during the growing season. By applying the correction function, GPP simulation using the LUE models improved in all experiments as indicated by increased correlation coefficients, the index of agreement and decreased root-mean-square errors. Among all models, the radiation partitioning model achieves the highest correlation coefficients between modelled and observed daily GPP likely because it considers the influences of direct and diffuse radiation partitioning on daily canopy photosynthesis. Our study indicates that satellite-based light use efficiency models could be successfully applied for deriving daily vegetation GPP and potentially producing daily routine satellite products, while considering the effects of LUE seasonality on canopy could help improve significantly the simulation accuracy of daily GPP in phenology.
关键词： seasonality,light use efficiency,satellite-based modelling,gross primary production,deciduous broadleaf forests
更新于2025-09-23 15:21:21
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[IEEE IGARSS 2018 - 2018 IEEE International Geoscience and Remote Sensing Symposium - Valencia, Spain (2018.7.22-2018.7.27)] IGARSS 2018 - 2018 IEEE International Geoscience and Remote Sensing Symposium - Developing a Sandbox Environment for Prosail, Suitable for Education and Research
摘要： We introduce the Interactive Visualization of Vegetation Reflectance Models (IVVRM) tool as a sandbox environment for the PROSAIL family of radiative transfer models. Every interaction with the Graphical User Interface (GUI) invokes a new model run of the updated parameter set and the results are instantly plotted on the screen. The quasi-simultaneous response allows easy hands-on practice with PROSAIL for education and training as well as straightforward inversions of biophysical variables from spectra by manual curve fitting. It is shown that expert knowledge can improve the quality of parameter retrieval and reveal sources of uncertainties in the field data and the models. IVVRM is free of charge and available as an application through the EnMAP-Box 3.0.
关键词： reflectance modelling,model environment,PROSAIL,radiative transfer,EnMAP-Box
更新于2025-09-23 15:21:21