- 标题
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Model Calculation of the Piezoelectric Coefficient of Hexagonal 2D Materials
摘要： A quantum-mechanical microscopic model of the piezoelectric e?ect in 2D materials is developed. The piezoelectric coe?cient requires the calculation of an internal atomic displacement and an e?ective piezoelectric charge. The internal displacement is obtained from minimizing the strain energy given by a Keating-like model, while the e?ective charge takes into account the atomic displacements and also a redistribution of the electronic charge; a bond-orbital model is used to compute the latter. The ?nal theory only requires atomic energies and the elasticity constants of the materials as input parameters. The piezoelectric coe?cients of a number of II-VI, III-V and IV-IV materials that could stably form in the planar hexagonal structure are computed; results for the IV-IV materials are obtained for the ?rst time.
关键词： piezoelectric coefficient,electronic structure,2D materials,bond-orbital model
更新于2025-09-04 15:30:14
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Intrinsic correlation between electronic structure and degradation: from few layers to bulk black phosphorus
摘要： Black phosphorus (BP) has received much attention due to its fascinating properties, such as a high mobility and tunable band gap which covers the band gap lacuna between graphene and transition metal dichalcogenides. However, these advantages have been overshadowed due to the fast degradation of BP in ambient conditions. To overcome this obstacle, the degradation mechanisms should be unveiled with direct observation followed by a thorough analysis. Here, we reveal two sequential degradation processes and layer-dependent degradation rates of BP under dark conditions by scanning Kelvin probe microscopy (SKPM) measurements and theoretical modeling. The layer-dependent degradation is successfully interpreted with the oxidation model based on the Marcus-Gerischer theory (MGT). Under dark conditions, the electron transfer rate from BP to oxygen molecule depends on the number of layers that give different carrier concentrations. The oxidation rate is strongly dependent on the number of layers, and thus carrier concentrations. This suggests the possibility of stability improvement by carrier modulation. This work not only provides a deeper understanding of the degradation mechanism itself but also suggest new strategies for stable BP-based electronics design.
关键词： oxidation model,degradation,work function,Marcus-Gerischer theory,black phosphorus
更新于2025-09-04 15:30:14
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Wavelength selection of the multispectral lidar system for estimating leaf chlorophyll and water contents through the PROSPECT model
摘要： The estimation of leaf biochemical constituents is of high interest for the physiological and ecological applications of remote sensing. The multispectral lidar (MSL) system emerges as a promising active remote sensing technology with the ability to acquire both three-dimensional and spectral characteristics of targets. The detection wavelengths of the MSL system can be geared toward the specific application purposes. Therefore, it’s important to conduct the wavelength selection work to maximize the potential of the MSL system in vegetation monitoring. Traditional strategies of wavelength selection attempt to establish an empirical relationship between large quantities of observed reflectance and foliar biochemical constituents. By contrast, this study proposed to select wavelengths through the radiative transfer model PROSPECT. A five-wavelength combination was established to estimate leaf chlorophyll and water contents: 680, 716, 1104, 1882 and 1920 nm. The consistency of the wavelengths selected were tested by running different versions of PROSPECT model. Model inversion using simulated and experimental datasets showed that the selected wavelengths have the ability to retrieve leaf chlorophyll and water contents accurately. Overall, this study demonstrated the potential of the MSL system in vegetation monitoring and can serve as a guide in the design of new MSL systems for the application community.
关键词： Multispectral lidar,Wavelength selection,Leaf water content,Leaf chlorophyll content,PROSPECT model
更新于2025-09-04 15:30:14
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[Micro/Nano Technologies] Micro and Nano Fabrication Technology Volume 1 || Micro Milling for Functional Surface
摘要： Micro manufacturing has recently increased in the several ?elds that include optics, electronics, medicine, biotechnology, and communications. Then, drastic progresses have been seen in the micro milling with the technologies in micro/nano-scale measurement, control, and tooling. This chapter describes the micro milling for manufacturing of the functional surfaces, which control material behavior with the surface topography. In the introduction, the current technical status in the functional surfaces is reviewed with the micro fabrication processes, and some issues in the micro milling are described to achieve high qualities of the micro elements and structures on the surfaces. Then, the typical micro milling process is discussed in terms of the operations and the removal process. Regarding material behavior, the effect of crystal grain size and orientation on the removal process becomes relatively large. When the grain size reduces, the dynamic components in the cutting force, burr formation, and affected layer can be controlled in micro cutting. Micro milling is applied to manufacture the functional surfaces with the micro dimples at high machining rates. The micro dimples are machined in milling with the inclined spindle at 45(cid:1). The milling with the cutter axis inclination is also applied to machine the micro dimples on the cylinder surfaces. A mechanistic model is applied to control the dimple shape for the cutting parameters, the feed direction, and the tool geometry. The surfaces with the micro dimples are applied to control the surface functions such as optical re?ection and wettability.
关键词： Surface function,Micro milling,Micro dimple,Wettability,Mechanistic model,Fine grained steel,Optical control
更新于2025-09-04 15:30:14
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Comments on “Dynamics of optical solitons with Radhakrishnan–Kundu–Lakshmanan model via two reliable integration schemes, Optik 178 (2019) 557–566”
摘要： In this comment, we looked into solutions drawn by authors in the paper [1] and pointed out that many of them are incorrect. We showed that the conditions obtained by the authors [1] did not satisfy the solutions. Therefore, many of the results in [1] are not true.
关键词： Soliton solutions,Radhakrishnan–Kundu–Lakshmanan model,exp(? ?(ε)) method,Modified simple equation
更新于2025-09-04 15:30:14
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Oxyfluoro-zinc-tellurite glasses – Part I: Predicting the elastic properties and glass transition temperature under the substitution of AlF3 by ZnO
摘要： An extensive study has been carried out to predict the elastic properties and glass transition temperature of oxyfluoro-zinc-tellurite (10-x)AlF3-xZnO-90TeO2 (1 ≤ x ≤ 9), (30-x)AlF3-xZnO-70TeO2 (5 ≤ x ≤ 25), (35-x)AlF3-xZnO-65TeO2 (10 ≤ x ≤ 30) and (40-x)AlF3-xZnO-60TeO2 (15 ≤ x ≤ 35) glass systems, for the first time. Changes in the elastic moduli, Poisson’s ratio and glass transition temperature due to the substitution of AlF3 by ZnO have been discussed in terms of molar volume, fractal bond connectivity, packing density and dissociation energy per unit volume of the glass. The correlation between theoretically calculated and experimentally measured elastic moduli and Poisson's ratio has also been studied on the basis of Makishima-Mackenzie’s theory and Rocherulle et al. model. The composition dependence of fractal bond connectivity suggested that the studied oxyfluoro-zinc-tellurite glasses have an intermediate dimensionality between three- and two-dimensional structures. Both AlF3 and ZnO are incorporated into the tellurite network as network modifiers. This results is the conversion of TeO4 trigonal bipyramids into TeO3+1 polyhedral and then to TeO3 trigonal pyramids through breaking of TeeOeTe linkages and creation of non-bridging oxygen atoms. In addition to this, both Makishima-Mackenzie's theory and Rocherulle et al. model appear to be applicable for all the investigated glass systems. The agreement between theoretical and experimental values of elastic moduli and Poisson's ratio is excellent for majority of the samples.
关键词： Rocherulle et al. model,Elastic properties,Makishima–Mackenzie’s theory,Oxyfluorotellurite glasses
更新于2025-09-04 15:30:14
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Performance evaluation of the SIMBIO-SYS Stereo Imaging Channel on board BepiColombo/ESA spacecraft
摘要： The Stereo Imaging Channel (STC) is one of the channels of the Spectrometer and Imagers for MPO BepiColombo Integrated Observatory SYStem (SIMBIO-SYS) onboard the ESA BepiColombo mission to Mercury. STC is a double wide-angle camera designed to image each portion of the Mercury surface from two different lines of sights, whose main aim is to provide panchromatic stereo-image pairs required to generate the Digital Terrain Model (DTM) reconstruction. In addition, selected surface areas will be acquired in color. This work presents the expected STC on-ground and in-flight performance describing the preliminary evaluation of some key parameters: the optical performance, the on-ground resolution and detector response, the achievable Signal to Noise Ratio (SNR) for different integration times and observation strategies and the global coverage of panchromatic filters during the entire scientific phase. The estimation of the SNR has been made using the STC radiometric model with Hapke reflectance model for Mercury surface and the SPICE toolkit software. The SPICE toolkit software with kernel for BepiColombo mission has been used also for the estimation of the on-ground pixel dimension and the global coverage all over the mission.
关键词： Mercury,Reflectance model,SIMBIO-SYS,STC,SNR,Global coverage
更新于2025-09-04 15:30:14
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Quantum and spectral properties of the Labyrinth model
摘要： We consider the Labyrinth model, which is a two-dimensional quasicrystal model. We show that the spectrum of this model, which is known to be a product of two Cantor sets, is an interval for small values of the coupling constant. We also consider the density of states measure of the Labyrinth model and show that it is absolutely continuous with respect to Lebesgue measure for almost all values of coupling constants in the small coupling regime.
关键词： coupling constant,density of states measure,quasicrystal,Labyrinth model,spectrum
更新于2025-09-04 15:30:14
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Entanglement between artificial atoms and photons of lossless cavities
摘要： We investigated the dynamics of atom-field entanglement for two natural or artificial two-level atoms interacting with a one-mode quantum electromagnetic field by means of multiphoton transitions in a lossless cavity. Tavis-Cummings model is used to describe the interaction of the atoms and real microwave coplanar cavity field. We carried out the mathematical modeling of the dynamics of the system under consideration for various initial states of the atomic subsystem and an intensive coherent field of the cavity. We showed that for small multiplicities, the atoms and the field, which were initially in a pure separable state, can return to this state during the evolution. We also found that for large multiplicities the atoms and the field are in the entangled atom-field state in the process of the system evolution with the exception of the initial time instant. These results can be used in the theory of quantum networks.
关键词： Tavis-Cummings model,multiphoton transitions,atom-field entanglement,quantum networks
更新于2025-09-04 15:30:14
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[IEEE 2018 Iranian Conference on Electrical Engineering (ICEE) - Mashhad (2018.5.8-2018.5.10)] Electrical Engineering (ICEE), Iranian Conference on - Tunable Filter by Using Parity Time (PT) Symmetric Periodic Array Electronic
摘要： A circuit model of a periodic array of PT-symmetric (gain/loss coupled) waveguides is reported for the design of a novel tunable filter. This model consists of a pair of coupled circuits, one with amplification resistance and the other with an equivalent attenuation. By varying the value of the gain/loss, one can control the size of bandgap and hence the allowed frequencies propagating within the structure. For a critical value of gain/loss, the eigenvalues merge and the gap disappears. As a result, all frequencies can pass the structure i.e, an all pass filter. The Q-factor of reflected frequency can be varied such that, tunable Q from 20 to greatest has been successfully realized in the central frequency of 0.283 MHz. The remarkable feature of this design lies with its tunability, high speed, and relative simplicity.
关键词： RLC Circuit Model,Parity-Time (PT) Symmetry,Grating Waveguides,Optical Waveguides,Band Stop Filter (BSF)
更新于2025-09-04 15:30:14