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Nano-scale wave dispersion beyond the First Brillouin Zone simulated with inertia gradient continua
摘要： Nano-scale wave dispersion beyond the First Brillouin Zone is often observed as descending branches and inflection points when plotting frequency or phase velocity against the wave number. Modeling this with discrete chain models is hampered by their restricted resolution. A continuum model equipped with higher-order inertia gradients is here developed as a suitable and versatile alternative. This model can be derived from discrete chain models, thereby providing a lower-scale motivation for the higher-order gradient terms. The derived gradient model is without free parameters, as the material constants are calculated a priori by minimising the error with respect to the discrete chain response. Unlike asymptotic approximations that provide a best fit for vanishing wave numbers, the error is here minimised over the entire range of reduced wave numbers 0 to 1, which leads to a much improved accuracy beyond the First Brillouin Zone. The new gradient model has been validated against (i) phonon dispersion curves measured through neutron scattering experiments in bismuth, aluminum, and nickel and (ii) Molecular Dynamics (MD) flexural wave propagation simulations of carbon nanotubes. The model captures all qualitative aspects of the experimental and MD dispersion curves without requiring a bespoke curve fitting procedure. With the exception of one set of MD results, the accuracy of the gradient model is very good.
关键词： Nano-scale wave dispersion,Molecular Dynamics,First Brillouin Zone,inertia gradient continua,carbon nanotubes,phonon dispersion curves
更新于2025-09-10 09:29:36
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Magnetoelectric effect in self-bias gradient structure CoFe <sub/>2</sub> O <sub/>4</sub> /Ni/BaTiO <sub/>3</sub> with 0-3 connectivity
摘要： The paper is devoted to the study of mechanism of internal magnetic fields occurrence in the magnetostrictive-piezoelectric gradient structure CoFe2O4/Ni/BaTiO3. The insertions of CoFe2O4 and Ni in this gradient structure in the matrix BaTiO3 is located. The connectivity type of this composite is 0-3 and a modified model of the cell in the form of a parallelepiped is used. This parallelepiped consists of two cubic cells of BaTiO3 matrix. One cubic cell contains of CoFe2O4 insertion and another cell contains of Ni one. The corresponding magnetic circuit by using the magnetostatics equations was considered. Internal magnetic fields which arise in sublattices of CoFe2O4 and Ni, taking into account the known parameters of their magnetization curves were found and equal of 860 Oe and of 50 Oe for CoFe2O4 and Ni, respectively. Further, the pseudo-piezomagnetic constants that correspond to the resulting internal magnetic fields were found by using of the existing dependencies of the pseudo-piezomagnetic coefficients of CoFe2O4 and Ni on the bias magnetic field. The effective parameters of the structure in the form of a parallelepiped was found.
关键词： internal magnetic fields,CoFe2O4/Ni/BaTiO3,magnetoelectric effect,gradient structure,0-3 connectivity
更新于2025-09-09 09:28:46
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THERMOLUMINESCENCE OF NEWLY DEVELOPED HIGHLY SENSITIVE α-Al2O3:C BY THE VERTICAL GRADIENT FREEZING METHOD
摘要： A highly sensitive α-Al2O3:C crystal was directly grown by the vertical gradient freezing (VGF) method using Al2O3 and graphite powder as the raw materials. The main thermoluminescence (TL) characteristics of α-Al2O3:C detectors grown by the VGF method and TLD-500K detectors were compared. The α-Al2O3:C grown by the VGF method shows good dosimetric properties, such as high TL sensitivity (152 times higher than that of the TLD-100 at heating rate of 1°C/s), an extremely low residual signal of 0.03%, a minimum measurable dose of 0.12 μGy and an excellent linear response within the dose range studied from 1 μGy to 10 Gy. The α-Al2O3:C detectors grown by the VGF method have a higher sensitivity and a better linear response compared to the TLD-500K detectors. Both kinds of α-Al2O3:C can be used in an unannealed form and to measure the very low dose in environmental monitoring and personnel dosimetry.
关键词： α-Al2O3:C,personnel dosimetry,dosimetric properties,vertical gradient freezing method,thermoluminescence,environmental monitoring
更新于2025-09-09 09:28:46
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Robust Optimization of Nanoslit Array Sensor Based on Extraordinary Optical Transmission
摘要： A robust optimization approach for plasmonic periodic array sensor based on extraordinary optical transmission is proposed using Kriging surrogate models to reduce the effects of uncertainty in various manufacturing processes while maintaining sensor performance. For systematic design with reasonable computation cost, the author adopt the universal Kriging models whose regression function is a polynomial. The gradient index and the multiobjective genetic algorithm are chosen as a robustness measure and a global optimization tool, respectively. The figure of merit and the gradient index are set as two objective functions, and the design variables are the slit width and height, respectively. The optical properties of interest are investigated using the finite-element method. The numerical optimization results show the proposed scheme to be powerful and efficient in designing nanoslity array sensors based on extraordinary optical transmission with fabrication uncertainty.
关键词： gradient index,robust optimization,Plasmonics,surface plasmon polariton,multiobjective optimization,Kriging model
更新于2025-09-09 09:28:46
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Fusion of Polarimetric Features and Structural Gradient Tensors for VHR PolSAR Image Classification
摘要： This paper proposes a fast texture based supervised classification framework for fully polarimetric synthetic aperture radar (PolSAR) images with very high spatial resolution (VHR). With the development of recent polarimetric radar remote sensing technologies, the acquired images contain not only rich polarimetric characteristics but also high spatial content. Thus, the notion of geometrical structures and heterogeneous textures within VHR PolSAR data becomes more and more significant. Moreover, when the spatial resolution is increased, we need to deal with large-size image data. In this paper, our motivation is to characterize textures by incorporating (fusing) both polarimetric and structural features, and then use them for classification purpose. First, polarimetric features from the weighted coherency matrix and local geometric information based on the Di Zenzo structural tensors are extracted and fused using the covariance approach. Then, supervised classification task is performed by using Riemannian distance measure relevant for covariance-based descriptors. In order to accelerate the computational time, we propose to perform texture description and classification only on characteristic points, not all pixels from the image. Experiments conducted on the VHR F-SAR data as well as the AIRSAR Flevoland image using the proposed framework provide very promising and competitive results in terms of terrain classification and discrimination.
关键词： polarimetric synthetic aperture radar (PolSAR),gradient tensors,Covariance descriptor,textures,Riemannian distance,supervised classification
更新于2025-09-09 09:28:46
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Facile Preparation of Functional Group Gradient Surfaces by Desorption and <i>Re</i> -Adsorption of Alkanethiols on Gold
摘要： Many organisms live in various stimuli-responsive milieus of signaling components in gradient forms which are known to be closely related to biological phenomena including embryonic development, wound repair, and tumor metastasis. In addition, the physicochemical properties of gradient surfaces, i.e., a continuous spatial variation of gradient components, enable various types of biological/biochemical research such as cell proliferation/migration and tissue engineering. Various techniques have been reported for the preparation of gradient surfaces, including laminar flow mixing in microfluidic channels, cross-diffusion of alkanethiols, microfluidic permeation printing, oblique deposition and template coating, controlled polymerization on substrates, and controlled UV irradiation on photo-responsive substrates. Previously, we reported a simple method for the generation of multi-component gradient surfaces on self-assembled monolayers (SAMs) on gold. The monolayers consisted of quinone derivatives which reacted with reducing agents in a predictable manner to produce amine gradient surfaces. Recently, desorption and re-adsorption-based methods on SAMs have gained attention, in which alkanethiolates on gold surfaces were desorbed in order to provide an empty space gradient, following which other types of alkanethiols filled up the empty space, leading to an end group gradient of alkanethiolates. For example, Kim et al. reported a simple and flexible method for preparing cell adhesion ligand patterns on SAMs by using a laser beam equipped in a matrix-assisted laser desorption/ionization time-of-flight (MALDI-TOF) mass spectrometer. Similarly, Meyyappan et al. demonstrated that a surface gradient can be achieved by irradiating a focused laser beam on SAMs with subsequent re-adsorption of a second alkanethiol. Fioravanti et al. reported on a new method to fabricate surface chemical gradients of alkanethiols through combining reductive electrochemical desorption and partial re-adsorption of alkanethiolates. Recently, we found that tetrahydrofuran (THF) highly compromises the stability of SAMs on gold, and thus induces unusually fast exchange of alkanethiolates of SAMs with other alkanethiols in the solution. In this study, we harnessed this desorption capability of THF for the preparation of functional group gradient surfaces. In our strategy, a monolayer of alkanethiolates was exposed to THF in a time-dependent manner followed by immersion in a solution of other functional group-terminated alkanethiols, leading to functional group gradient surfaces. The functional group then played a role of a chemical handle to conjugate various functional molecules for the formation of gradients of those components.
关键词： Gradient surfaces,Alkanethiols,Desorption,Self-assembled monolayers,Tetrahydrofuran
更新于2025-09-09 09:28:46
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[Advances in Intelligent Systems and Computing] Soft Computing for Problem Solving Volume 817 (SocProS 2017, Volume 2) || Image Compression Using Neural Network for Biomedical Applications
摘要： As images are of large size and require huge bandwidth and large storage space, an effective compression algorithm is essential. Hence in this paper, feedforward backpropagation neural network with the multilayer perception using resilient backpropagation (RP) algorithm is used with the objective to develop an image compression in the field of biomedical sciences. With the concept of neural network, data compression can be achieved by producing an internal data representation. This network is an application of backpropagation that takes huge content of data as input, compresses it while storing or transmitting, and decompresses the compressed data whenever required. The training algorithm and development architecture give less distortion and considerable compression ratio and also keep up the capability of hypothesizing and are becoming important. The efficiency of the RP is evaluated on x-ray image of rib cage and has given better results of the various performance metrics when compared to the other algorithms.
关键词： Artificial neural network,Backpropagation neural network,Gradient descent algorithm (GD),Resilient backpropagation algorithm (RP),Image compression
更新于2025-09-09 09:28:46
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GCforce: Decomposition of optical force into gradient and scattering parts
摘要： A MATLAB function GCforce is presented for the calculation of gradient and scattering parts of optical force (OF). The decomposition of OF into the gradient and scattering parts, or, equivalently, the conservative and nonconservative components, is of great importance to the physical understanding of optical micromanipulation. In this paper, we propose a formulation to decompose the OF acting on a spherical particle immersed in an arbitrary monochromatic optical field, based on the generalized Lorenz-Mie theory and the Cartesian multipole expansion approach. The expressions for the gradient and scattering forces are given explicitly in terms of the partial wave expansion coefficients of the optical field shining on the particle and the Mie coefficients of the particle. A MATLAB function GCforce.m is also presented for the calculation. The explicit and rigorous decomposition of the OF into conservative and non-conservative forces shed light on the understanding of light-matter interaction as well as contributes significantly to the designing of optical fields to achieve various optical micromanipulation.
关键词： Scattering force,Gradient force,Multipole expansion theory,Generalized Lorenz-Mie theory
更新于2025-09-09 09:28:46
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Propagation of Electromagnetic Waves through an Invisible Gradient-Index Lens with Negative Refractive Index
摘要： A radially inhomogeneous (gradient-index) lens made of material with a negative refractive index, invisible from the viewpoint of geometrical optics, is proposed and designed. The design includes derivation and solution of an equation for determining the refractive index profile, as well as derivation of an expression allowing calculation of the ray trajectories in the lens. Propagation of a plane wave through a cylindrical modification of the proposed lens both for the case of E-polarization and for the case of H-polarization is analyzed numerically using the hybrid projection method. The results obtained for the RCS of the lens are compared to the similar performance of a positive-index lens described in the previous publications.
关键词： numerical methods,RCS,geometrical optics,invisible lens,Electromagnetic wave propagation,negative refractive index,gradient-index lens
更新于2025-09-09 09:28:46
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Fast Solution of Electromagnetic Scattering for 3D Inhomogeneous Anisotropic Objects Embedded in Layered Uniaxial Media by the BCGS-FFT Method
摘要： In this paper, the stabilized biconjugate gradient fast Fourier transform (BCGS-FFT) method is used to solve the electromagnetic scattering problem for three-dimensional (3D) inhomogeneous uniaxial anisotropic objects embedded in a layered uniaxial medium. The optical axis of the background medium is perpendicular to the layer boundaries. However, the optical axis of the scatterer can be rotated through any angles. The electric field integral equation (EFIE) is formulated in the layered uniaxial anisotropic background medium. The volumetric roof-top function is used for the basis function as well as the testing function. The dyadic Green’s functions (DGFs) for both the electric field and the magnetic vector potential are used to solve the EFIE, and the results as well as the performance are compared. Several numerical simulations are carried out to validate the accuracy and efficiency of the proposed method. The major new contribution of this work is to extend the BCGS-FFT method to accommodate the uniaxial anisotropy of the layered background medium. Therefore, the DGFs for the layered uniaxial medium are evaluated before solving the EFIE. In addition, the DGF for the electric field is also used to solve the 3D scattering problem through BCGS-FFT iterations, which is different from the previous work.
关键词： electric field integral equation (EFIE),layered media,uniaxial anisotropic,stabilized biconjugate gradient (BCGS),Dyadic Green’s functions
更新于2025-09-09 09:28:46