Search

Copyright of Hydrogeology Journal is the property of Springer Nature and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

The structure of sub-wavelength array (SWA) oriented along the low-symmetric atomic direction could enhance the polarization ratio (PR) of in-plane anisotropic 2D materials. By applying the SWA strategy to the stable anisotropic 2D GeSe, the PR increases from 1.6 (pristine GeSe flake) to 18 (GeSe SWA) with the array width of 200 nm and proportion of 25%. For the SWA strategy, it shows the ability of PR enhancement in full detection wavelength especially in the wavelength corresponding to the band gap. [Display omitted] Polarization-sensitive photodetectors, with the ability of identifying the texture-, stress-, and roughness-induced light polarization state variation, displace unique advantages in the fields of national security, medical diagnosis, and aerospace. The utilization of in-plane anisotropic two-dimensional (2D) materials has led the polarization photodetector into a polarizer-free regime, and facilitated the miniaturization of optoelectronic device integration. However, the insufficient polarization ratio (usually less than 10) restricts the detection resolution of polarized signals. Here, we designed a sub-wavelength array (SWA) structure of 2D germanium selenium (GeSe) to further improve its anisotropic sensitivity, which boosts the polarized photocurrent ratio from 1.6 to 18. This enhancement comes from the combination of nano-scale arrays with atomic-scale lattice arrangement at the low-symmetric direction, while the polarization-sensitive photoresponse along the high-symmetric direction is strongly suppressed due to the SWA-caused depolarization effect. Our mechanism study revealed that the SWA can improve the asymmetry of charge distribution, attenuate the matrix element in zigzag direction, and the localized surface plasma, which elevates the photo absorption and photoelectric transition probability along the armchair direction, therefore accounts for the enhanced polarization sensitivity. In addition, the photodetector based on GeSe SWA exhibited a broad power range of 40 dB at a near-infrared wavelength of 808 nm and the ability of weak-light detection under 0.1 LUX of white light (two orders of magnitude smaller than pristine 2D GeSe). This work provides a feasible guideline to improve the polarization sensitivity of 2D materials, and will greatly benefit the development of polarized imaging sensors. [ABSTRACT FROM AUTHOR]

Copyright of China Rural Water & Hydropower is the property of China Rural Water & Hydropower Editorial Office and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

The bidirectional 3ω method was used to measure the thermal conductivity of a mixture of polydimethylsiloxane (PDMS) and carbon fiber. A PDMS and carbon fiber mixture was printed using fused filament fabrication (FFF) with and without an orifice channel in the extrusion nozzle. Through-plane alignment of carbon fibers inside the PDMS medium can be promoted by embedding an orifice channel in the nozzle during FFE Thermal conductivity measurement of samples with carbon fiber content varying from 0 to 20 wt. % was performed. Compared with a pristine PDMS. the composite's thermal conductivity increased up to 50%. Additionally. through- and in-plane thermal conductivities were analyzed through the calculation of the anisotropy ratio. The sample fabricated with the orifice channel embedded nozzle showed up to a 12% higher anisotropy ratio compared to the non-orifice nozzle fabricated sample. In the FFF process, an orifice-embedded nozzle is found to enhance through-plane thermal conductivity by promoting the perpendicular alignment of carbon fibers. [ABSTRACT FROM AUTHOR]

Geomaterials tend to be stratified due to the geological process, and their properties are often anisotropic. In this study, the quartet structure generation set (QSGS) method is adopted to reconstruct the mesoscale internal structure of anisotropic geomaterials. In addition, the fractal theory and several morphological parameters are employed to describe the structural features of anisotropic geomaterials. The effective thermal properties parallel and perpendicular to the layered structure are evaluated via the finite element method coupled with Monte Carlo simulations. A representative volume element of anisotropic geomaterials is determined by the homogenization method. The importance of morphological parameters is ranked by Pearson correlation coefficient. Results indicate that the porosity and arrangements of solid fabric have significant influences on thermal conductivity and its anisotropy. Prediction models for assessing the orthogonal thermal conductivities and anisotropic ratio are established, and their performances are benchmarked against the finite element analysis results. The results obtained from this work can provide a reference for the investigation of anisotropy of geomaterials properties and a link between effective thermal properties and features of the internal structure. [ABSTRACT FROM AUTHOR]

In this study, the effect of orientation of mineralized collagen fibrils on bone mechanical properties relating to bone anisotropy was studied using data obtained from rehydrated lamellar bone samples. The dehydration-rehydration based and experimentally determined contraction, observed in orientations parallel and perpendicular to the osteonal axis was used to calculate bone anisotropy. The sublamellar bone model, with the layered mineralized collagen fibrils rotating at 5° was used. Following this model, the mineralized collagen layers were transformed at 5° relative to the orthogonal axes using a transform matrix. With dehydration, fibril diameter was reduced towards the mineral, forming contraction vectors. The x, y and z intercepts for these vectors were then calculated to give the u, v and w displacements, which gave anisotropy ratios ranging from 0.15266 to 6.55054. Compared with the experimental nanoindentation findings in the literature, there may be an indication of a correlation with the results of sublamellar arrangement at 20° angles. As the lateral indentation used in the anisotropy experiments may involve varying amounts of u and v displacements, the aspect angle of lateral indentation was evaluated in relation to the structural features of the model. This evaluation indicated the larger contribution of v displacement and thus relatively much smaller contribution of u displacement to lateral contraction. These findings indicate the significant effect of the mineralized collagen fibril arrangement on bone anisotropy.

In this article, the value of anisotropy ratio $\kappa / \mu $ for ideal symmetric three-port circulator is derived by using the transmission line equivalent model. This value plays a vital role in the design of circulator. In order to obtain the value of $\kappa / \mu $ , eigenvectors of the scattering matrix S for the circulator are given first. Then, one-port transmission line equivalent models for ideal circulator are presented. Finally, the value of $\kappa / \mu $ is derived in terms of the relationships between reflection coefficients of three one-port transmission line equivalent models. Furthermore, a three-port waveguide circulator is designed in order to verify the theoretical value of $\kappa / \mu $. And the experimental value of $\kappa / \mu $ is approximately equal to the theoretical result. Also, this value derived in this article is in good agreement with the one obtained by field method and circuit method in published literatures. [ABSTRACT FROM AUTHOR]

Paper deals with statistical classification of spatial data as a part of widely applicable statistical approach to pattern recognition. Error rates in supervised classification of Gaussian random field observation into one of two populations specified by different constant means and common stationary geometric anisotropic covariance are considered. Formula for the exact Bayesian error rate is derived. The influence of the ratio of anisotropy to the error rates is evaluated numerically for the case of complete parametric certainty.

The displacement field in a circular disc made of a transversely isotropic material is explored in a parametric manner. The disc is assumed to be loaded by a parabolic distribution of compressive radial stresses along two finite arcs of its periphery in the absence of any tangential (frictional) stresses. Advantage is here taken of a recently introduced closed-form analytic solution for the displacement field developed in an orthotropic disc under diametral compression which was achieved adopting the complex potentials technique for rectilinear anisotropic materials as it was formulated in the pioneering work of S.G. Lekhnitskii. The analytic nature of this solution permits thorough, indepth exploration of the influence of some crucial parameters on the qualitative and quantitative characteristics of the deformation of transversely isotropic circular discs compressed between the jaws of the devise suggested by the International Society for Rock Mechanics for the standardized implementation of the Brazilian-disc test. The parameters considered include the anisotropy ratio (i.e., the ratio of the two elastic moduli characterizing the disc material), the angle between the loading axis and the planes of transverse isotropy and the length of the loaded arcs. Strongly non-linear relationships between these parameters and the components of the displacement field are revealed.

A linked Simulation-Optimization (S-O) model was developed to find the optimum design of Hydraulic Water Retaining Structure (HWRS) constructed on permeable soils. The nonlinear relationship between seepage design variables can accurately and solely simulated by numerical methods. To increase the computational efficiency of the S-O model, the seepage numerical model was replaced by approximation simulator based on the Support Vector Machine (SVM) surrogate models. The surrogate models incorporated and highlighted the effects of hydraulic conductivity (k) and anisotropy ratio (ky/kx) on the optimum design of HWRS. The results revealed that reducing k and (ky/kx) values augments the optimum cost. The most effective seepage controller variables were the depth and inclination angle of the last cut-off. Increasing these variables effectively reduced the exit gradient value to the allowable limits. Also, the first and second last aprons (b9, b10) were important to provide a sufficient cross section for HWRS to increase the stability of the HWRS against the overturning, flotation, sliding, etc. The evaluation of S-O technique demonstrated a good agreement between the predicted and simulated seepage characteristics of the optimum HWRS design. Hence, the S-O methodology is applicable to obtain an optimal and minimum cost HWRS design. [ABSTRACT FROM AUTHOR]

The strength and hydraulic conductivity anisotropy of rock slopes have a great impact on the slope stability. This study took a layered rock slope in Pulang, Southwestern China as a case study. The strength conversion equations of the seriously weathered rock mass were proposed. Then, considering the anisotropy ratio and anisotropy angle (dip angle of bedding plane) of strength and hydraulic conductivity, the deformation and stability characteristics of rock slope were calculated and compared with field monitoring data. The results showed that the sensitivity analysis of strength and hydraulic conductivity anisotropy could successfully predict the occurrence time, horizontal displacement (HD), and the scope of the rock landslide. When the anisotropy ratio was 0.01 and the dip angle was 30°, the calculated HD and scope of the landslide were consistent with the field monitoring data, which verified the feasibility of the strength conversion equations. The maximum horizontal displacement (MHD) reached the maximum value at the dip angle of 30°, and the MHD reached the minimum value at the dip angle of 60°. When the dip angle was 30°, the overall factor of safety (FS) and the minimum factor of safety (MFS) of the rock slope were the smallest. By assuming that the layered rock slope was homogeneous, the HD and MHD would be underestimated and FS and MFS would be overestimated. The obtained results are likely to provide a theoretical basis for the prediction and monitoring of layered rock landslides.

In the study of the seepage characteristics of layered rock slope under rainfall conditions, the majority of previous research has considered the hydraulic conduction to be isotropic, or only considered the anisotropy ratio of the hydraulic conductivity, ignoring the anisotropy angle. In the current study, a layered rock slope in the Pulang region was selected as an example. Then, based on the fitting parameters of the Van Genuchten model, pore water pressure sensitivity analyses of the layered rock slope were carried out. The anisotropy ratio and anisotropy angle were used to analyze the sensitivity of the seepage and stability of the layered rock slopes. The results show that as the anisotropy angle of hydraulic conductivity of layered rock slope decreased, the maximum volume water content of surface (MWCS) of layered rock slope gradually increased. Additionally, as the anisotropy ratio decreased and the anisotropy angle increased, the rising heights of the groundwater (RHG) of layered rock slope gradually increased. When the hydraulic conduction of layered rock slope was considered isotropic, the factor of safety (FS) tended to be overestimated. As the anisotropy ratio decreased and the anisotropy angle increased, the factor of safety (FS) of layered rock slope decreased. Prevention should be the objective for rock slopes with larger dip angles in the bedding plane in the Pulang region. This study provides feasible schemes for the evaluation of the seepage and stability of layered rock slopes in Pulang region of southwestern China.

The displacement field in a circular disc made of a transversely isotropic material is explored in a parametric manner. The disc is assumed to be loaded by a parabolic distribution of compressive radial stresses along two finite arcs of its periphery in the absence of any tangential (frictional) stresses. Advantage is here taken of a recently introduced closed-form analytic solution for the displacement field developed in an orthotropic disc under diametral compression which was achieved adopting the complex potentials technique for rectilinear anisotropic materials as it was formulated in the pioneering work of S.G. Lekhnitskii. The analytic nature of this solution permits thorough, indepth exploration of the influence of some crucial parameters on the qualitative and quantitative characteristics of the deformation of transversely isotropic circular discs compressed between the jaws of the devise suggested by the International Society for Rock Mechanics for the standardized implementation of the Brazilian-disc test. The parameters considered include the anisotropy ratio (i.e., the ratio of the two elastic moduli characterizing the disc material), the angle between the loading axis and the planes of transverse isotropy and the length of the loaded arcs. Strongly non-linear relationships between these parameters and the components of the displacement field are revealed. [ABSTRACT FROM AUTHOR]

An iterative procedure is worked out for estimating solute travel times in a subsurface system by making use of the velocity and streamline distributions pertinent to the system. The developed method is then being applied to study the solute travel times to ditch drains originating from a field being subjected to a uniform (1) recharge and (2) ponding field over the surface of the soil. For case (1), both single and layered soils are being considered to estimate the travel times. The developed mathematical procedure is simple to use, robust, reasonably accurate even if being used with a lesser division of a streamline and completely eliminates the necessity of determination of any integrals for estimating the travel times-integrals which, in the methods generally been employed for estimating the travel times from steady-state analytical groundwater models, would otherwise need be evaluated. The study shows that travel times of water particles traversing through a layered soil being subjected to a uniform recharge at the surface are sensitive to the directional conductivities, anisotropy ratio (defined here as the ratio between horizontal and vertical hydraulic conductivities of soil) and thickness of individual layers of a soil profile as well as to the magnitude of the steady-state recharge on the surface of the soil. For the ponded drainage scenarios also, directional conductivities and thickness of a soil profile, extent of partial penetration and width of the ditch drains, levels of water head at the surface of the soil as well as on the ditches are observed to influence the travel times in a noticeable way. The proposed method is important as it provides simple and accurate estimations of migration times of pollutants to subsurface drains under different drainage situations; it can also be used to assess the time of reclamation of a salt-affected or waterlogged soil being drained by a network of subsurface drains being installed for the purpose from the available hydraulic theory relevant to the concerned drainage situation. [ABSTRACT FROM AUTHOR]

Multi-dimensional finite element modelings of instrumented sharp indentation on materials with cubic symmetry are conducted. A novel reverse analysis algorithm for identifying elastoplastic properties is established for the cubic material, while the anisotropy of the material is determined by indentations on distinct orientations. Influences of elastic anisotropy and anisotropic yielding behavior are considered with the help of three-dimensional computations. Sensitivity analysis confirms the accuracy and robustness of the new method. The obtained results are compared and verified with experimental data of a nickel-base single crystal alloy. • Conducted systematic three-dimensional modeling on Berkovich indentation on cubic materials. • Developed an indentation method to identify the anisotropic mechanical parameters of cubic materials. • Verified the possible solutions due to the non-uniqueness problem of the reverse algorithm gathered within small ranges. • Demonstrated the robustness and accuracy of indentation reverse analysis based on extensive computations for cubic material DD6. [ABSTRACT FROM AUTHOR]