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Excitonic complexes in anisotropic atomically thin two-dimensional materials: Black phosphorus and
摘要： The effect of anisotropy in the energy spectrum on the binding energy and structural properties of excitons, trions, and biexcitons is investigated. To this end we employ the stochastic variational method with a correlated Gaussian basis. We present results for the binding energy of different excitonic complexes in black phosphorus (bP) and TiS3 and compare them with recent results in the literature when available, for which we find good agreement. The binding energies of excitonic complexes in bP are larger than those in TiS3. We calculate the different average interparticle distances in bP and TiS3 and show that excitonic complexes in bP are strongly anisotropic whereas in TiS3 they are almost isotropic, even though the constituent particles have an anisotropic energy spectrum. This is also confirmed by the correlation functions.
关键词： biexciton,TiS3,binding energy,black phosphorus,trion,anisotropy,stochastic variational method,exciton
更新于2025-09-09 09:28:46
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Uncertainty Quantification of Microstructure—Governed Properties of Polysilicon MEMS
摘要： In this paper, we investigate the stochastic effects of the microstructure of polysilicon films on the overall response of microelectromechanical systems (MEMS). A device for on-chip testing has been purposely designed so as to maximize, in compliance with the production process, its sensitivity to fluctuations of the microstructural properties; as a side effect, its sensitivity to geometrical imperfections linked to the etching process has also been enhanced. A reduced-order, coupled electromechanical model of the device is developed and an identification procedure, based on a genetic algorithm, is finally adopted to tune the parameters ruling microstructural and geometrical uncertainties. Besides an initial geometrical imperfection that can be considered specimen-dependent due to its scattering, the proposed procedure has allowed identifying an average value of the effective polysilicon Young’s modulus amounting to 140 GPa, and of the over-etch depth with respect to the target geometry layout amounting to O = ?0.09 μm. The procedure has been therefore shown to be able to assess how the studied stochastic effects are linked to the scattering of the measured input–output transfer function of the device under standard working conditions. With a continuous trend in miniaturization induced by the mass production of MEMS, this study can provide information on how to handle the foreseen growth of such scattering.
关键词： microelectromechanical systems (MEMS),stochastic effects,parameter identification,coupled electromechanical analysis,polysilicon
更新于2025-09-09 09:28:46
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Stochastic Resonance in Bioinspired Electronic Device Using Polymer Field Effect Transistors
摘要： Stochastic resonance (SR) phenomenon is emerged in organic field effect transistors (OFETs) using π-conjugated polymer, where application of external noise to the OFET system enhances signal/information processing performance which is often found in biological systems. The channel conductivity of the OFET is slightly increased by spin-coating using heated semiconductor polymer solution with heated glass substrate. In order to improve frequency responses of OFET, optimal width of the gate electrode is explored. Furthermore, it turns out that scratching and removing semiconductor film outside the source-drain electrodes and the channel enhances the On-Off current ratio of the device. These fabrication processes lead to steeper nonlinearity on the IDS vs. VGS curve, resulting in emergence of SR, which is fingerprinted in increase of correlation value between input and output signals with increase of intensity of external noise.
关键词： Stochastic resonance,Polymer thin films,Organic semiconductors,Bioinspiration,Field effect transistors
更新于2025-09-09 09:28:46
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A Gaussian Filter for Plate Flatness Evaluation System with 3-D Scanner
摘要： A LIDAR (light detection and ranging) system was applied to a plate flatness evaluation system. Plate flatness surfaces are reconstructed from many points generated by LIDAR by a smoothing spline method. We defined a smoothing spline functional with sampling measure weights. The equivalent number of parameters defined on this functional does not depend on the distributions of samples. The approximation of the equivalent number of parameters is derived when the number of samples becomes infinity. This approximation greatly reduced the calculation time needed to estimate the optimal smoothing. The smoothing spline calculation cost was so high that new algorithms (FMM: fast multi-pole method) were introduced and we developed a smoothing engine which was applied to practical problems. The engine generated clear surfaces and was robust against various dirty point clouds.
关键词： smoothing spline,FMM,surfaces,stochastic process,information criteria
更新于2025-09-09 09:28:46
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[IEEE 2018 IEEE Conference on Antenna Measurements & Applications (CAMA) - V?ster?s, Sweden (2018.9.3-2018.9.6)] 2018 IEEE Conference on Antenna Measurements & Applications (CAMA) - Toward Standard Near-Field Measurement Solutions for Stochastic Electromagnetic Fields
摘要： This paper investigates directions towards standardization of Near-Field measurement solutions for stochastic electromagnetic fields. An overview of Single-Probe, Dual-probe and Multi-Probe Array based measurements for deterministic fields is given and their capabilities and performances including test-time for industrial deployment are discussed. Importance of Field-Field correlation based analysis is underlined both from an experimental and modeling stand points and finally for combination of measurements and full-wave EM modeling.
关键词： Correlation,Field-Field Correlation,Stochastic Electromagnetic Field,Spintronic,Near Field imaging
更新于2025-09-09 09:28:46
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Weak convergence rates for stochastic evolution equations and applications to nonlinear stochastic wave, HJMM, stochastic Schr?dinger and linearized stochastic Korteweg–de Vries equations
摘要： We establish weak convergence rates for noise discretizations of a wide class of stochastic evolution equations with non-regularizing semigroups and additive or multiplicative noise. This class covers the nonlinear stochastic wave, HJMM, stochastic Schr¨odinger and linearized stochastic Korteweg–de Vries equation. For several important equations, including the stochastic wave equation, previous methods give only suboptimal rates, whereas our rates are essentially sharp.
关键词： stochastic evolution equations,multiplicative noise,additive noise,linearized stochastic Korteweg–de Vries equation,stochastic Schr¨odinger,non-regularizing semigroups,weak convergence rates,HJMM,stochastic wave equation
更新于2025-09-04 15:30:14
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Non-blind Image Deconvolution using Sampling without Replacement
摘要： Image degradations can be modeled as a process of linear systems which are usually denoted by convolution. Deconvolution refers to a reverse operation of the linear system in which an original image is convolved with a blur kernel, which is also known as a point spread function (PSF) of the linear system. If the blur kernel, which can represent linear degradations such as an out-of-focus blur or motion blurs due to the shake of a camera, is known, we call this ill-posed problem the non-blind deconvolution problem. In this paper, we propose a non-blind deconvolution method using a convex optimization method in which a non-derivative approach is used to solve the ill-posed problem. The proposed method minimizes the objective function using the stochastic process in which the random variable selects the coordinate. The objective function is minimized along the selected coordinate direction at each iteration. If several coordinate directions are picked simultaneously, the cost can be decreased independently along each coordinate direction.
关键词： convex optimization,Non-blind deconvolution,stochastic process,image restoration
更新于2025-09-04 15:30:14
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A Non-Stationary 3-D Wideband GBSM for HAP-MIMO Communication Systems
摘要： The measurement results in land mobile satellite (LMS) communication scenario have shown that the propagation characteristic of LMS channel is a non-stationary process. In this paper, a non-stationary three-dimensional (3-D) wideband geometry-based stochastic model (GBSM) and the corresponding simulation model are proposed for high altitude platform (HAP) multiple-input multiple-output (MIMO) communication system. The proposed GBSM uses two-dimensional (2-D) one-ring and 3-D multi-cylinders to model moving scatterers and near and far stationary scatterers, respectively. In the proposed GBSM, we assume that the multipath components (MPCs) scattering from the far stationary scatterers could appear again after their disappearance, and a two-state continuous-time Markov process is used to model the dynamic properties of MPCs such as MPCs appearance and disappearance, and the closed-form expressions of the survival probabilities of MPCs are derived. In the proposed GBSM, the long distance and small-scale time-variant parameters are also used to investigate the non-stationarities of HAP-MIMO channel. Using the survival probabilities of MPCs, the statistical properties of the proposed 3-D GBSM are derived. The numerical the proposed 3-D GBSM is more results demonstrate that practical to characterize the HAP-MIMO channel.
关键词： High Altitude Platform (HAP),wideband channel,two-state continuous-time Markov process,geometry-based stochastic model (GBSM),non-stationarities
更新于2025-09-04 15:30:14
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Two-timescale stochastic Langevin propagation for classical and quantum optomechanics
摘要： Interesting experimental signatures of quantum cavity optomechanics arise because the quantum back-action induces correlations between incident quantum shot noise and the cavity field. While the quantum linear theory of optomechanics (QLT) has provided vital understanding across many experimental platforms, in certain new setups it may be insufficient: analysis in the time domain may be needed, but QLT obtains only spectra in frequency space; and nonlinear behavior may be present. Direct solution of the stochastic equations of motion in time is an alternative, but unfortunately standard methods do not preserve the important optomechanical correlations. We introduce two-timescale stochastic Langevin (T2SL) propagation as an efficient and straightforward method to obtain time traces with the correct correlations. We show that T2SL, in contrast to standard stochastic simulations, can efficiently simulate correlation phenomena such as ponderomotive squeezing and reproduces accurately cavity sideband structures on the scale of the applied quantum noise and even complex features entirely submerged below the quantum shot noise imprecision floor. We investigate nonlinear regimes and find that, where comparison is possible, the method agrees with analytical results obtained with master equations at low temperatures and in perturbative regimes.
关键词： quantum back-action,nonlinear regimes,ponderomotive squeezing,quantum cavity optomechanics,stochastic Langevin propagation
更新于2025-09-04 15:30:14
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Stochastic stimulated electronic x-ray Raman spectroscopy
摘要： Resonant inelastic x-ray scattering (RIXS) is a well-established tool for studying electronic, nuclear, and collective dynamics of excited atoms, molecules, and solids. An extension of this powerful method to a time-resolved probe technique at x-ray free electron lasers (XFELs) to ultimately unravel ultrafast chemical and structural changes on a femtosecond time scale is often challenging, due to the small signal rate in conventional implementations at XFELs that rely on the usage of a monochromator setup to select a small frequency band of the broadband, spectrally incoherent XFEL radiation. Here, we suggest an alternative approach, based on stochastic spectroscopy, which uses the full bandwidth of the incoming XFEL pulses. Our proposed method is relying on stimulated resonant inelastic x-ray scattering, where in addition to a pump pulse that resonantly excites the system a probe pulse on a specific electronic inelastic transition is provided, which serves as a seed in the stimulated scattering process. The limited spectral coherence of the XFEL radiation defines the energy resolution in this process and stimulated RIXS spectra of high resolution can be obtained by covariance analysis of the transmitted spectra. We present a detailed feasibility study and predict signal strengths for realistic XFEL parameters for the CO molecule resonantly pumped at the O1s ! p(cid:2) transition. Our theoretical model describes the evolution of the spectral and temporal characteristics of the transmitted x-ray radiation, by solving the equation of motion for the electronic and vibrational degrees of freedom of the system self consistently with the propagation by Maxwell equations.
关键词： CO molecule,covariance analysis,Stochastic stimulated electronic x-ray Raman spectroscopy,resonant inelastic x-ray scattering,XFEL
更新于2025-09-04 15:30:14