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Geometrical heterogeneity of the joint roughness coefficient revealed by 3D laser scanning
摘要： The joint roughness coefficient (JRC) is an important indicator that characterizes the physical and mechanical behaviors of a jointed rock mass. To investigate the distribution characteristics of the JRC, 31 joint samples belonging to the same joint group with dominant attitude of 209°∠71° were collected from the Guanshan railway tunnel, and the morphologies of the joint samples were digitized using 3D laser scanning. The JRC values in different directions were obtained based on the fractal theory, and the effects of sampling interval on JRC were assessed during the JRC calculation process. The results show that the sampling intervals of profile line and digital point both affect the calculated JRC values. With sampling interval increasing, there exists an obvious threshold above which the JRC value changes from constant to variable. It is found that, the JRC value keeps constant if the profile line sampling interval is smaller than the threshold value (4 mm), which is independent of the roughness degree of the joint. However, the threshold of digital point sampling interval is influenced by joint roughness and has a negative exponential relationship with the JRC value. According to the calculated results of JRC in different directions of the 31 joint samples, it is clear that the JRC values present significant anisotropy and large variation in certain directions. Meanwhile, it is verified that the JRC values in the same direction follow a log-normal distribution. The expected JRC values calculated depend on the probability density function are generally larger than the arithmetic mean values, with a maximum difference up to 23.1%. In consideration of natural distribution, the expected JRC values calculated from probability density function should be more reliable than the arithmetic mean values. Therefore, as a natural property of joint roughness, accurate understanding on the geometrical heterogeneity of JRC will have significant effects on the evaluation of mechanical effects of rock mass structure.
关键词： log-normal distribution,sampling effect,anisotropy,joint roughness coefficient
更新于2025-09-11 14:15:04
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Transparent Collision Visualization of Point Clouds Acquired by Laser Scanning
摘要： Exploring two-dimensional (2D) materials with room-temperature ferromagnetism and large perpendicular magnetic anisotropy is highly desirable but challenging. Here, through first-principles calculations, we propose a viable strategy to achieve such materials based on transition metal (TM) embedded borophene nanosheets. Due to electron deficiency, the commonly existent hexagon boron vacancies in various borophene phases serve as intrinsic anchor points for electron-rich transition metals, which not only adsorb strongly upon the vacancies but also favor to be embedded into the vacancies, forming 2D planar hybrid nanosheets. The adsorption-to-embedding transition is feasible thermodynamically and kinetically, owing to its exothermic nature and relatively small kinetic barriers. After embedding, phase transition is further proposed to obtain diverse structures of TM embedded borophenes with versatile magnetic properties. Based on the example of χ3 phase borophene, several ferromagnetic TM embedded borophene nanosheets with high Curie temperature and large perpendicular magnetic anisotropy have been predicted.
关键词： transition metal embedded borophene nanosheets,first-principles calculations,perpendicular magnetic anisotropy,room-temperature ferromagnetism,two-dimensional materials
更新于2025-09-11 14:15:04
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Bound-to-continuum intraband transition properties in InAs/GaAs quantum dot superlattice solar cells
摘要： We studied the interband and intraband excitation densities and the polarization dependent photocurrent in InAs/GaAs quantum dot superlattice (QDSL) solar cells with a built-in electric field of 5 kV cm?1. An almost polarization-insensitive intraband transition was observed for normal incident light, whereas slight anisotropy in the intraband transition resulted from the mixing between the conduction and valence bands. Furthermore, saturable two-color photocurrent was observed in the p–i–n solar-cell device because of electron transport in the QDSL miniband.
关键词： intraband transition,polarization anisotropy,quantum dot superlattice,solar cells,InAs/GaAs
更新于2025-09-11 14:15:04
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Anisotropic lateral oxidation of Al-III-V semiconductors: inverse problem and circular aperture fabrication
摘要： The lateral wet oxidation of aluminum-containing III-V-semiconductors is a technological process which converts a buried (thin) cristalline material into an amorphous insulator and, as such, tends to exhibit an anisotropic behavior. As a result, the shape of the interface between the semiconductor and the insulator, often referred as the oxide aperture, differs from the etched mesa contour from which the oxidation proceeds. This, in turn, complicates the design of the devices relying on this process especially when specific oxide patterns are needed. In this paper, we introduce a method based on a morphological dilatation to determine the shape of the mesas which will lead to a specific targetted contour upon an anisotropic oxidation over a modest extent. The approach is experimentally validated by demonstrating the fabrication of circular oxide apertures which are inherently difficult to make because of their high degree of symmetry but which also turn out to be of critical importance in obtaining efficient single-mode vertical-cavity surface-emittting lasers.
关键词： AlOx,oxidation,anisotropy,VCSEL
更新于2025-09-11 14:15:04
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Optical and neural anisotropy in peripheral vision
摘要： Optical blur in the peripheral retina is known to be highly anisotropic due to nonrotationally symmetric wavefront aberrations such as astigmatism and coma. At the neural level, the visual system exhibits anisotropies in orientation sensitivity across the visual field. In the fovea, the visual system shows higher sensitivity for cardinal over diagonal orientations, which is referred to as the oblique effect. However, in the peripheral retina, the neural visual system becomes more sensitive to radially-oriented signals, a phenomenon known as the meridional effect. Here, we examined the relative contributions of optics and neural processing to the meridional effect in 10 participants at 08, 108, and 208 in the temporal retina. Optical anisotropy was quantified by measuring the eye’s habitual wavefront aberrations. Alternatively, neural anisotropy was evaluated by measuring contrast sensitivity (at 2 and 4 cyc/deg) while correcting the eye’s aberrations with an adaptive optics vision simulator, thus bypassing any optical factors. As eccentricity increased, optical and neural anisotropy increased in magnitude. The average ratio of horizontal to vertical optical MTF (at 2 and 4 cyc/deg) at 08, 108, and 208 was 0.96 6 0.14, 1.41 6 0.54 and 2.15 6 1.38, respectively. Similarly, the average ratio of horizontal to vertical contrast sensitivity with full optical correction at 08, 108, and 208 was 0.99 6 0.15, 1.28 6 0.28 and 1.75 6 0.80, respectively. These results indicate that the neural system’s orientation sensitivity coincides with habitual blur orientation. These findings support the neural origin of the meridional effect and raise important questions regarding the role of peripheral anisotropic optical quality in developing the meridional effect and emmetropization.
关键词： peripheral retina,anisotropy,wavefront aberrations,neural adaptation,adaptive optics
更新于2025-09-11 14:15:04
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Reduction in crystalline quality anisotropy for non-polar a-plane GaN directly grown on titanium patterned sapphire substrate
摘要： Nonpolar a-plane GaN films were directly grown on titanium patterned sapphire substrates (Ti-PSS) by metalorganic chemical vapor deposition (MOCVD). It is demonstrated that the GaN film grown on Ti-PSS has superior surface quality and less surface pits than that on flat sapphire substrate. More importantly, the anisotropic behavior of the X-ray rocking curve-full width at half maximum values for the on-axis reflections were significantly improved. It is found that, the increased mosaic block size along m-direction could be the main reason for the reduction in the crystalline quality anisotropy. This work provides a simple and effective method to improve the crystal quality of non-polar GaN films.
关键词： X-ray rocking curve,crystalline quality anisotropy,MOCVD,titanium patterned sapphire substrates,Nonpolar a-plane GaN
更新于2025-09-10 09:29:36
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[IEEE 2018 12th International Congress on Artificial Materials for Novel Wave Phenomena (Metamaterials) - Espoo, Finland (2018.8.27-2018.9.1)] 2018 12th International Congress on Artificial Materials for Novel Wave Phenomena (Metamaterials) - Practical Isotropy and Anisotropy of 3-D Printed Artificial Foam-Like Dielectrics with Antenna Applications
摘要： The models, limitations and realization of homogenized foam-like 3-D printed dielectrics have been presented applying different fully symmetrical unit cells. The strategy for control of the absolute values of the resultant isotropic equivalent dielectric constant of these artificial dielectrics has been presented and verified and a possible anisotropy has been minimized.
关键词： antenna applications,3-D printed dielectrics,dielectric anisotropy,isotropic equivalent dielectric constant
更新于2025-09-10 09:29:36
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[IEEE 2018 12th International Congress on Artificial Materials for Novel Wave Phenomena (Metamaterials) - Espoo, Finland (2018.8.27-2018.9.1)] 2018 12th International Congress on Artificial Materials for Novel Wave Phenomena (Metamaterials) - Modular approach to understanding and synthesis of metamaterials and metasurfaces
摘要： The vast majority of previously proposed metamaterials and metasurfaces are anisotropic or bianisotropic (exhibiting magnetoelectric coupling). Nevertheless, their anisotropy was not fully exploited as they were designed only for one or several specific illumination directions. In this talk, we propose a simple analytical approach to characterize properties of general bianisotropic meta-atoms for an arbitrary illumination. The approach is based on the qualitative decomposition of an arbitrary meta-atom into separate basic “modules” with elementary polarization properties. Such decomposition can be used for comprehensive characterization of previously designed structures as well as for synthesizing novel bianisotropic inclusions of arbitrary complexity and with desired response.
关键词： polarization properties,anisotropy,metamaterials,bianisotropic,metasurfaces,magnetoelectric coupling
更新于2025-09-10 09:29:36
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Strength and toughness anisotropy in hexagonal boron nitride: An atomistic picture
摘要： Strength and toughness are two crucial mechanical properties of a solid that determine its ability to function reliably without undergoing failure in extreme conditions. While hexagonal boron nitride (hBN) is known to be elastically isotropic in the linear regime of mechanical deformation, its directional response to extreme mechanical loading remains less understood. Here, using a combination of density functional theory calculations and molecular dynamics simulations, we show that strength and crack nucleation toughness of pristine hBN are strongly anisotropic and chirality dependent. They vary nonlinearly with the chirality of the lattice under symmetry breaking deformation, and the anisotropic behavior is retained over a large temperature range with a decreasing trend at higher temperatures. An atomistic analysis reveals that bond deformation and associated distortion of electron density are nonuniform in the nonlinear regime of mechanical deformation, irrespective of the loading direction. This nonuniformity forms the physical basis for the observed anisotropy under static conditions, whereas reduction in nonuniformity and thermal softening reduce anisotropy at higher temperatures. The chirality-dependent anisotropic effects are well predicted by inverse cubic polynomials.
关键词： chirality,anisotropy,hexagonal boron nitride,molecular dynamics simulations,density functional theory,strength,toughness
更新于2025-09-10 09:29:36
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Localized surface plasmon resonance on two-dimensional HfSe <sub/>2</sub> and ZrSe <sub/>2</sub>
摘要： HfSe2 and ZrSe2 are newly discovered two-dimensional (2D) semiconducting transition metal dichalcogenides with promising properties for future nanoelectronics and optoelectronics. We theoretically revealed the electronic and optical properties of these two emerging 2D semiconductors, and evaluated their performance for the application of localized surface plasmon resonance (LSPR) at extreme conditions — in-plane direction versus out-of-plane direction and monolayer versus multilayer. First, the energy band structure and dielectric constants were calculated for both the monolayer and multilayer structures using Kohn-Sham density functional theory with van der Waals corrections. A parallel-band effect observed in the monolayer band structure indicates a strong light-matter interaction. Then, based on the calculated dielectric constants, the performance of the LSPR excited by Au sphere nanoparticles was quantitatively characterized, including polarizability, scattering and absorption cross-sections, and radiative ef?ciency using Mie theory. For the multilayer HfSe2 and ZrSe2, the LSPR showed very comparable intensities in both the in-plane and out-of-plane directions, suggesting an isotropy-like light-matter interaction. In a comparison, the LSPR excited on the monolayer HfSe2 and ZrSe2 was clearly observed in the in-plane direction but effectively suppressed in the out-of-plane direction due to the unique anisotropic nature. In addition to this extraordinary anisotropy-to-isotropy transition as the layer number increases, a red-shift of the LSPR wavelength was also found. Our work has predicated the thickness-dependent anisotropic light-matter interaction on the emerging 2D semiconducting HfSe2 and ZrSe2, which holds great potential for broad optoelectronic applications such as sensing and energy conversion.
关键词： ZrSe2,anisotropy,plasmon,2D materials,HfSe2
更新于2025-09-10 09:29:36