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Dense restructuring of amorphous silicon network induced by non-bonded hydrogen
摘要： We con?rmed the presence of non-bonded hydrogens (NBHs) in hydrogenated amorphous silicon (a-Si:H) ?lms, using a combination of multiple techniques (Rutherford backscattering spectrometry/hydrogen forward scattering, Fourier-transform infrared spectroscopy-attenuated total re?ection, and thermal desorption spectrometry). The hydrogen e?usion pro?le of an a-Si:H ?lm with large amounts of NBHs was analyzed in detail. We report the e?ect of NBHs on band structure and electrical conductivity, and we present additional considerations for previous data on number density of silicon, optical bandgap, and vacancy size distribution [J. Non-Cryst. Solids 447, 207 (2016)]. The e?ect of NBHs on the a-Si network is explained by the “dense restructuring model”.
关键词： thermal desorption spectrometry,Rutherford backscattering spectrometry,hydrogenated amorphous silicon,non-bonded hydrogens,dense restructuring model,Fourier-transform infrared spectroscopy
更新于2025-09-09 09:28:46
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Optimized Electrolyte Loading and Active Film Thickness for Sandwich Polymer Light-Emitting Electrochemical Cells
摘要： Effects of ion concentration and active layer thickness play a critical role on the performance of light-emitting electrochemical cells. Expanding on a pioneering materials system comprising the super yellow (SY) polymer, and the electrolyte trimethylolpropane ethoxylate (TMPE)/Li+CF3SO3?, it is reported that a slightly lowered salt concentration and layer thickness result in a substantial efficiency increase, and that this increase is confined to a narrow concentration and thickness range. For a film thickness of 70 nm, a blend ratio SY:TMPE:Li+CF3SO3? = 1:0.075:0.0225, and a current of 7.7 mA cm?2 the current efficacy is 11.6 cd A?1, on a par with SY light-emitting diodes. The optimized salt content can be explained by increased exciton quenching at higher concentrations and hindered carrier injection and conduction at lower concentrations, while the optical dependence on the layer thickness is due to weak microcavity effects. A comprehensive optical modeling study is presented, which includes the doping-induced changes of the refractive indices and self-absorption losses due the emission–absorption overlap of intrinsic and doped SY. The analysis indicates either a thickness-independent emitter position (EP) close to the anode or a thickness-dependent EP, shifted to the cathode for increased thicknesses.
关键词： electrolyte,super yellow,light-emitting electrochemical cell,LEC,optical model
更新于2025-09-09 09:28:46
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Relaxed micromorphic model of transient wave propagation in anisotropic band-gap metastructures
摘要： In this paper, we show that the transient waveforms arising from several localised pulses in a micro-structured material can be reproduced by a corresponding generalised continuum of the relaxed micromorphic type. Specifically, we compare the dynamic response of a bounded micro-structured material to that of bounded continua with special kinematic properties: (i) the relaxed micromorphic continuum and (ii) an equivalent Cauchy linear elastic continuum. We show that, while the Cauchy theory is able to describe the overall behaviour of the metastructure only at low frequencies, the relaxed micromorphic model goes far beyond by giving a correct description of the pulse propagation in the frequency band-gap and at frequencies intersecting the optical branches. In addition, we observe a computational time reduction associated with the use of the relaxed micromorphic continuum, compared to the sensible computational time needed to perform a transient computation in a micro-structured domain.
关键词： anisotropy,transient dynamic response,elastic metamaterials,relaxed micromorphic model
更新于2025-09-09 09:28:46
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Variational Bayesian image restoration with multi-structured model of wavelet transform coefficients
摘要： Recent works have demonstrated that using a properly structured prior for model-based compressive sensing (CS), can improve the recovery performance. However, there exists the low prior utilization in previous works. Therefore, in this study, we introduce a multi-structured-wavelet Bayesian CS framework (MSW-BCS) that works for image compression with fully employing the prior knowledge. Our work can be briefly summarised by the following three aspects. Firstly, we explore the multi-structured prior knowledge, including the cluster structure and tree structure in the wavelet transform coefficients of images via statistical analyses. Secondly, a multi-variable joint recovery model is designed to describe this multi-structured prior. Finally, the detailed learning algorithm of model parameters based on variational Bayesian inference is given. The simulation experiments show that the proposed recovery model can effectively merge the different priors and achieve the superior performance compared with that of the other well-known CS algorithms under both noise-free and noisy measurement environments.
关键词： variational Bayes inference,multi-structure model,Bayesian compressive sensing,wavelet-tree structure
更新于2025-09-09 09:28:46
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Extending the SCOPE model to combine optical reflectance and soil moisture observations for remote sensing of ecosystem functioning under water stress conditions
摘要： A radiative transfer and process-based model, called Soil-Canopy-Observation of Photosynthesis and Energy fluxes (SCOPE), relates remote sensing signals with plant functioning (i.e., photosynthesis and evapotranspiration). Relying on optical remote sensing data, the SCOPE model estimates photosynthesis and evapotranspiration, but these ecosystem-level fluxes may be significantly overestimated if water availability is the primary limiting factor for vegetation. Remedying this shortcoming, additional information from extra sources is needed. In this study, we propose considering water stress in SCOPE by incorporating soil moisture data in the model, besides using satellite optical reflectance observations. A functional link between soil moisture, soil surface resistance, leaf water potential and carboxylation capacity is introduced as an extra element in SCOPE, resulting in a soil moisture integrated version of the model, SCOPE-SM. The modified model simulates additional state variables: (i) vapor pressure (ei), both in the soil pore space and leaf stomata in equilibrium with liquid water potential; (ii) the maximum carboxylation capacity (Vcmax) by a soil moisture dependent stress factor; and (iii) the soil surface resistance (rss) through approximation by a soil moisture dependent hydraulic conductivity. The new approach was evaluated at a Fluxnet site (US-Var) with dominant C3 grasses and covering a wet-to-dry episode from January to August 2004. By using the original SCOPE (version 1.61), we simulated half-hourly time steps of plant functioning via locally measured weather data and time series of Landsat (TM and ETM) imagery. Then, SCOPE-SM was similarly applied to simulate plant functioning for three cases using Landsat imagery: (i) with modeled ei; (ii) with modeled ei and Vcmax; and (iii) with modeled ei, Vcmax, and rss. The outputs of all four simulations were compared to flux tower plant functioning measurements. The results indicate a significant improvement proceeding from the first to the fourth case in which we used both Landsat optical imagery and soil moisture data through SCOPE-SM. Our results show that the combined use of optical reflectance and soil moisture observations has great potential to capture variations of photosynthesis and evapotranspiration during drought episodes. Further, we found that the information contained in soil moisture observations can describe more variations of measured evapotranspiration compared to the information contained in thermal observations.
关键词： SCOPE-SM model,Landsat,Evapotranspiration,Vegetation properties,Water stress,Remote sensing,Soil moisture,Vegetation functioning,Vapor pressure,Photosynthesis,Maximum carboxylation capacity,Soil surface resistance,Reflectance
更新于2025-09-09 09:28:46
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Effects of intergranular barrier fluctuations on the electrical conductivity of polycrystalline semiconductors
摘要： We studied the in?uence of intergranular barrier ?uctuations on the electrical response of 3D semiconductor polycrystals. We ?rst computed with a numerical simulation model the dispersion in the intergranular barrier height on polycrystalline tin oxide due to the punctual character of the donors. Then, in order to quantify the e?ects of the barrier ?uctuation in the overall conductivity of the semiconductor, we added the dispersion to the well known brick-layer model and determined the connection between impedance measurements and grain boundary resistivity. We found that, the brick-layer model gives lower values for the real intergrain resistivity. However, the error can be quanti?ed indicating that the brick-layer model is not a bad approximation to determine electrical properties of intergrains of a polycrystal, specially for relatively large grains.
关键词： Electrical conduction,Bricklayer model,Intergranular barriers,Polycrystals
更新于2025-09-09 09:28:46
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Dynamical modeling of manipulation process in Trolling-Mode AFM
摘要： Dynamical lumped modeling of Trolling-mode AFM in manipulation of bio-samples is presented. The combination of high accuracy and compatibility with physiological conditions makes AFM a unique tool for studying biological materials in liquid medium. However, AFM microcantilever suffers from severe sensitivity degradation and noise intensification while operating in liquid; the large hydrodynamic drag between the cantilever and the surrounding liquid overwhelms the tip-sample interaction forces that are important in controlling the process. Therefore, an appropriate nanoneedle should be long enough to keep the cantilever out of liquid medium and short enough to be able to transmit the required force to push nanoparticle. Nonetheless, a long nanoneedle may deflect under the pushing force; therefore, its bending deflection should be accounted for in governing equations. Moreover, analytical and finite element stress analysis of nanoneedle and cantilever is performed to assure about their selected material and geometry. JKR theory is utilized to model contact mechanics between the needle/surface and the particle. Drag and meniscus forces are used to model the liquid media. Governing equations are solved using ODE45 and the system behavior is simulated. Critical conditions of sliding including critical time and force are obtained and changes of pushing force, needle deflection and indentation depths are illustrated. Also, effects of velocity variations are observed. Then, different heights for nanoneedle are tested and an appropriate one is selected for our purpose (to keep the needle out of liquid and transmit the force appropriately). The simulation is repeated for various biological particles and their behaviors are studied. At the end, the present simulation is validated through comparing the results with a previous work. This comparison shows that the simulation is reliable for the intended purpose.
关键词： Trolling-Mode AFM,Lumped model,Liquid environment,Manipulation
更新于2025-09-09 09:28:46
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Accurate Formula for the Macroscopic Polarization of Strongly Correlated Materials
摘要： The many-body Berry phase formula for macroscopic polarization is approximated by a sum of natural orbital geometric phases with fractional occupation numbers accounting for the dominant correlation effects. This formula accurately reproduces the exact polarization in the Rice?Mele?Hubbard model across the band insulator?Mott insulator transition. A similar formula based on a reduced Berry curvature accurately predicts the interaction-induced quenching of Thouless topological charge pumping.
关键词： natural orbital geometric phases,Rice?Mele?Hubbard model,Berry phase,macroscopic polarization,band insulator?Mott insulator transition,Thouless topological charge pumping
更新于2025-09-09 09:28:46
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First application of the optimal estimation method to retrieve temperature from pure rotational raman scatter lidar measurements
摘要： We present the application of the Optimal Estimation Method (OEM) to retrieve atmospheric temperatures from pure rotational Raman (PRR) backscatter lidar measurements. A forward model (FM) is developed to retrieve temperature and tested using synthetic measurements. The OEM offers many advantages for this analysis, including eliminating the need to determine temperature calibration coefficients.
关键词： forward model,pure rotational Raman,Optimal Estimation Method,Raman lidar,temperature retrieval
更新于2025-09-09 09:28:46
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Diffractive scattering: problems in theory and practice
摘要： We give a retrospective overview of the conceptual content of the strong interaction scattering at high energies with account of the latest experimental findings made at the LHC.
关键词： high energies,strong interaction,Standard Model,diffractive scattering,LHC
更新于2025-09-09 09:28:46