Journal articles on the topic 'Electrical anisotropy'
To see the other types of publications on this topic, follow the link: Electrical anisotropy.
Create a spot-on reference in APA, MLA, Chicago, Harvard, and other styles
Consult the top 50 journal articles for your research on the topic 'Electrical anisotropy.'
Next to every source in the list of references, there is an 'Add to bibliography' button. Press on it, and we will generate automatically the bibliographic reference to the chosen work in the citation style you need: APA, MLA, Harvard, Chicago, Vancouver, etc.
You can also download the full text of the academic publication as pdf and read online its abstract whenever available in the metadata.
Browse journal articles on a wide variety of disciplines and organise your bibliography correctly.
1
Liu, Yajun, Pritam Yogeshwar, Xiangyun Hu, Ronghua Peng, Bülent Tezkan, Wiebke Mörbe, and Jianhui Li. "Effects of electrical anisotropy on long-offset transient electromagnetic data." Geophysical Journal International 222, no. 2 (May 2, 2020): 1074–89. http://dx.doi.org/10.1093/gji/ggaa213.
Full textAbstract:
SUMMARY Electrical anisotropy of formations has been long recognized by field and laboratory evidence. However, most interpretations of long-offset transient electromagnetic (LOTEM) data are based on the assumption of an electrical isotropic earth. Neglecting electrical anisotropy of formations may cause severe misleading interpretations in regions with strong electrical anisotropy. During a large scale LOTEM survey in a former mining area in Eastern Germany, data was acquired over black shale formations. These black shales are expected to produce a pronounced bulk anisotropy. Here, we investigate the effects of electrical anisotropy on LOTEM responses through numerical simulation using a finite-volume time-domain (FVTD) algorithm. On the basis of isotropic models obtained from LOTEM field data, various anisotropic models are developed and analysed. Numerical results demonstrate that the presence of electrical anisotropy has a significant influence on LOTEM responses. Based on the numerical modelling results, an isolated deep conductive anomaly presented in the 2-D isotropic LOTEM electric field data inversion result is identified as a possible artifact introduced by using an isotropic inversion scheme. Trial-and-error forward modelling of the LOTEM electric field data using an anisotropic conductivity model can explain the data and results in a reasonable quantitative data fit. The derived anisotropic 2-D model is consistent with the prior geological information.
2
Luo, Tianya, Xiangyun Hu, Longwei Chen, and Guilin Xu. "Investigating the Magnetotelluric Responses in Electrical Anisotropic Media." Remote Sensing 14, no. 10 (May 11, 2022): 2328. http://dx.doi.org/10.3390/rs14102328.
Full textAbstract:
When interpreting magnetotelluric (MT) data, because of the inherent anisotropy of the earth, considering electrical anisotropy is crucial. Accordingly, using the edge-based finite element method, we calculated the responses of MT data for electrical isotropic and anisotropic models, and subsequently used the anisotropy index and polar plot to depict MT responses. High values of the anisotropy index were mainly yielded at the boundary domains of anomalous bodies for isotropy cases because the conductive differences among isotropic anomalous bodies or among anomalous bodies and background earth can be regarded as macro-anisotropy. However, they only appeared across anomalous bodies in the anisotropy cases. The anisotropy index can directly differentiate isotropy from anisotropy but exhibits difficulty in reflecting the azimuth of the principal conductivities. For the isotropy cases, polar plots are approximately circular and become curves with a big ratio of the major axis to minor axis, such as an 8-shaped curve for the anisotropic earth. Furthermore, the polar plot can reveal the directions of principal conductivities. However, distorted by anomalous bodies, polar plots with a large ratio of the major axis to minor axis occur in isotropic domains around the anomalous bodies, which may lead to the misinterpretation of these domains as anisotropic earth. Therefore, combining the anisotropy index with a polar plot facilitates the identification of the electrical anisotropy.
3
Pillai, Pramod P., Krzysztof Pacławski, Jiwon Kim, and Bartosz A. Grzybowski. "Nanostructural Anisotropy Underlies Anisotropic Electrical Bistability." Advanced Materials 25, no. 11 (January 20, 2013): 1623–28. http://dx.doi.org/10.1002/adma.201202915.
Full text
4
Lee, Joonsung, Yizhuang Song, Narae Choi, Sungmin Cho, Jin Keun Seo, and Dong-Hyun Kim. "Noninvasive Measurement of Conductivity Anisotropy at Larmor Frequency Using MRI." Computational and Mathematical Methods in Medicine 2013 (2013): 1–12. http://dx.doi.org/10.1155/2013/421619.
Full textAbstract:
Anisotropic electrical properties can be found in biological tissues such as muscles and nerves. Conductivity tensor is a simplified model to express the effective electrical anisotropic information and depends on the imaging resolution. The determination of the conductivity tensor should be based on Ohm's law. In other words, the measurement of partial information of current density and the electric fields should be made. Since the direct measurements of the electric field and the current density are difficult, we use MRI to measure their partial information such as B1 map; it measures circulating current density and circulating electric field. In this work, the ratio of the two circulating fields, termed circulating admittivity, is proposed as measures of the conductivity anisotropy at Larmor frequency. Given eigenvectors of the conductivity tensor, quantitative measurement of the eigenvalues can be achieved from circulating admittivity for special tissue models. Without eigenvectors, qualitative information of anisotropy still can be acquired from circulating admittivity. The limitation of the circulating admittivity is that at least two components of the magnetic fields should be measured to capture anisotropic information.
5
Jakučionis, L., and V. Kleiza. "Electrical Anisotropy of Thin Metal Films Growing on Dielectric Substrates." Nonlinear Analysis: Modelling and Control 7, no. 2 (December 5, 2002): 45–52. http://dx.doi.org/10.15388/na.2002.7.2.15193.
Full textAbstract:
Electrical properties of conductive thin films, that are produced by vacuum evaporation on the dielectric substrates, and which properties depend on their thickness, usually are anisotropic i.e. they have uniaxial anisotropy. If the condensate grow on dielectric substrates on which plane electrical field E is created the transverse voltage U⊥ appears on the boundary of the film in the direction perpendicular to E. Transverse voltage U⊥ depends on the angle γ between the applied magnetic field H and axis of light magnetisation. When electric field E is applied to continuous or grid layers, U⊥ and resistance R of layers are changed by changing γ. It means that value of U⊥ is the measure of anisotropy magnitude. Increasing voltage U0 , which is created by E, U⊥ increases to certain magnitude and later decreases. The anisotropy of continuous thin layers is excited by inequality of conductivity tensor components σ0 ≠ σ⊥. The reason of anisotropy is explained by the model which shows that properties of grain boundaries are defined by unequal probability of transient of charge carrier.
6
Krizsky, Vladimir N., Pavel N. Aleksandrov, Alexey A. Kovalskii, and Sergey V. Viktorov. "Mathematical modeling of cathodic protection of electric fields for major pipelines in anisotropic terrains." SCIENCE & TECHNOLOGIES OIL AND OIL PRODUCTS PIPELINE TRANSPORTATION 10, no. 1 (February 29, 2020): 52–63. http://dx.doi.org/10.28999/2541-9595-2020-10-1-52-63.
Full textAbstract:
The authors consider the problem of the computational investigation of cathodic protection electric fields measured for an underground pipeline taking into account the anisotropic nature of soil specific electrical conductivity. A computational experimental method was used to compare the figures for anisotropic soils against the current distribution for a homogeneous half-space; the influence of anisotropy factors and the azimuth conductivity tensor rotation angle for pipeline-enclosing soil on the electrical parameters of cathodic protection of the pipeline were investigated. It was demonstrated that protective capacity can vary significantly for areas close to the drainage points of cathode stations and for defective segments. It was concluded that there is a need to take into account terrain structure (its electrical anisotropy) when there are prerequisites of soil lamination/fracturing, or if its specific electrical conductivity contrast in the lateral direction is in excess of 2–2.5 times.
7
Pillai, Pramod P., Krzysztof Pacławski, Jiwon Kim, and Bartosz A. Grzybowski. "Correction: Nanostructural Anisotropy Underlies Anisotropic Electrical Bistability." Advanced Materials 25, no. 16 (April 18, 2013): 2257. http://dx.doi.org/10.1002/adma.201390003.
Full text
8
Linde, Niklas, and Laust B. Pedersen. "Evidence of electrical anisotropy in limestone formations using the RMT technique." GEOPHYSICS 69, no. 4 (July 2004): 909–16. http://dx.doi.org/10.1190/1.1778234.
Full textAbstract:
Azimuthal resistivity surveys are often applied to complement hydrological information or to improve the location of observation boreholes in pump tests. Symmetric electrode configurations cannot distinguish anisotropy from lateral changes or dipping layers, but asymmetric arrays (e.g., the offset Wenner array) can. Tensor radiomagnetotellurics (RMT) is presented as an alternative method in studies of electrical anisotropy in the shallow subsurface. The electromagnetic and geomagnetic transfer functions provide information about the dimensionality of the data. These transfer functions can also be used to find the directions of anisotropy. Data with an anisotropic signature can be inverted for a one‐dimensional (1D) azimuthal anisotropy model. The method is faster than the azimuthal resistivity method. A 380‐m‐long profile of tensor RMT data (12.7–243 kHz) from limestones that overlie shale on the island of Gotland, Sweden, is used to show the merits of the method. The data have a clear anisotropic signature. The data are inverted for a three‐layer 1D model with azimuthal anisotropy using two different approaches: (1) a moving median filter of five neighboring stations and neglecting static shift parameters; and (2) treating each station separately and including static shifts of the electric field in the inversion. Both inversions show models having a marked anisotropy with anisotropy factors of 3.7 and 4.5, respectively, in the limestones. The second approach has a significantly better data fit. However, the first approach is preferred because the models are smoother from station to station.
9
Bachrach, Ran. "Elastic and resistivity anisotropy of shale during compaction and diagenesis: Joint effective medium modeling and field observations." GEOPHYSICS 76, no. 6 (November 1, 2011): E175—E186. http://dx.doi.org/10.1190/geo2010-0381.1.
Full textAbstract:
Shales are anisotropic materials which have been observed to have both electrical and elastic anisotropy. Shales also comprise most of the sedimentary column in clastic basins, and thus, the ability to model shale response to electrical and seismic fields may improve our ability to better resolve anisotropy by using different measurements. Compacting shale-effective media modeling, which captures the geological process of porosity reduction and geochemical compaction, was formulated in this research in microstructural parameters associated with particle alignment and pore-shape deformation. The state of compaction, captured by the porosity of the soft sediment, governs the pore aspect ratio and the amount of particle alignment. Diagenetic processes are captured using temperature-dependent mineral elasticity and conductivity. The model uses the same microstructural parameters and equivalent effective medium approximation scheme to predict electrical and elastic anisotropy. In situ measurements of electrical anisotropy and seismic based estimates of elastic anisotropy in shales in the same basin compare favorably with modeling results. The joint-modeling formulation provides ways to study electrical resistivity and elastic-anisotropy jointly and explore the use of electrical resistivity anisotropy measurements to constrain elastic anisotropy, and vice versa.
10
Kong, Wenxin, Changhong Lin, Handong Tan, Miao Peng, Tuo Tong, and Mao Wang. "The Effects of 3D Electrical Anisotropy on Magnetotelluric Responses: Synthetic Case Studies." Journal of Environmental and Engineering Geophysics 23, no. 1 (March 2018): 61–75. http://dx.doi.org/10.2113/jeeg23.1.61.
Full textAbstract:
Using the staggered-grid finite difference method, a numerical modeling algorithm for a 3D arbitrary anisotropic Earth is implemented based on magnetotelluric (MT) theory. After the validation of this algorithm and comparison with predecessors, it was applied to several qualitative and quantitative analyses containing electrical anisotropy and a simple 3D prism model. It was found that anisotropic parameters for ρ 1 , ρ 2 , and ρ 3 play almost the same role in affecting 3D MT responses as in 1D and 2D without considering three Euler's angles α S , α D , and α L . Significant differences appear between the off-diagonal components of the apparent resistivity tensor and also between the diagonal components in their values and distributing features under the influence of 3D anisotropy, which in turn help to identify whether the MT data are generated from 3D anisotropic earth. Considering the deflecting effects arising from the inconsistency between the anisotropy axes and the measuring axes, some strategies are also provided to estimate the deflecting angles associated with anisotropy strike α S or dip α D , which may be used as initial values for the 3D anisotropy inversion. [Figure: see text]
11
Wang, Ting-Ting, Sining Dong, Chong Li, Wen-Cheng Yue, Yang-Yang Lyu, Chen-Guang Wang, Chang-Kun Zeng, et al. "In situ tunable giant electrical anisotropy in a grating gated AlGaN/GaN two-dimensional electron gas." Applied Physics Letters 121, no. 9 (August 29, 2022): 092101. http://dx.doi.org/10.1063/5.0097518.
Full textAbstract:
Materials with in-plane electrical anisotropy have great potential for designing artificial synaptic devices. However, natural materials with strong intrinsic in-plane electrical anisotropy are rare. We introduce a simple strategy to produce extremely large electrical anisotropy via grating gating of a semiconductor two-dimensional electron gas (2DEG) of AlGaN/GaN. We show that periodically modulated electric potential in the 2DEG induces in-plane electrical anisotropy, which is significantly enhanced in a magnetic field, leading to an ultra large electrical anisotropy. This is induced by a giant positive magnetoresistance and a giant negative magnetoresistance under two orthogonally oriented in-plane current flows, respectively. This giant electrical anisotropy is in situ tunable by tailoring both the grating gate voltage and the magnetic field. Our semiconductor device with controllable giant electrical anisotropy will stimulate new device applications, such as multi-terminal memtransistors and bionic synapses.
12
Secco, R. A., and P. S. Balog. "On the possibility of anisotropic heat flow in the inner core." Canadian Journal of Earth Sciences 38, no. 6 (June 1, 2001): 975–82. http://dx.doi.org/10.1139/e00-116.
Full textAbstract:
We consider the possibility of anisotropic heat flow in the inner core by examining the potential for anisotropic thermal conductivity of hexagonal close-packed (hcp-)Fe. Because hcp-Fe exists only at pressures above 13 GPa at room temperature, we investigate thermal conductivity anisotropy in analog material Gd by measuring the electrical conductivity and applying the WiedemannFranz Law to determine thermal conductivity (k). The electrical conductivity anisotropy of Gd was measured at pressures up to 1.4 GPa and temperatures up to 873 K in the hcp phase range. At elevated pressure, the variation with temperature of anisotropic thermal conductivity of Gd single crystal resembles the anisotropic behavior at high temperature and 1 atm observed in earlier work. The temperature range of anisotropy of thermal conductivity of Gd, where kc > ka, is extended by pressure, but the anisotropy disappears before the high temperature hcp[Formula: see text]bcc (body-centered cubic) transformation. Our results on hcp-Gd lead us to raise the question of the possibility of hcp-Fe exhibiting anisotropy of thermal conductivity. Together with the known seismic anisotropy of the inner core, and the inferred textural alignment of hcp crystals causing it, we suggest some implications that an anisotropy of thermal conductivity of hcp-Fe, and a concomitant anisotropy of inner core heat flow, could have on thermally driven core processes.
13
Wang, Feiyan, Zhengyong Ren, and Lihong Zhao. "A goal-oriented adaptive finite-element approach for 3-D marine controlled-source electromagnetic problems with general electrical anisotropy." Geophysical Journal International 229, no. 1 (November 30, 2021): 439–58. http://dx.doi.org/10.1093/gji/ggab485.
Full textAbstract:
SUMMARY We present a goal-oriented adaptive finite-element algorithm for accurately modelling marine controlled-source electromagnetic responses in 3-D media with general electrical anisotropy. We formulate the primal boundary value problem in terms of the total electric field for general applications. Following the goal-oriented adaptivity concept, the dual problem is derived from a functional designed to measure the data errors of interest in light of the data quality. We approximate the solutions to the primal and dual formulations using the edge finite-element method on tetrahedral grids for a flexible treatment of complex geological settings and survey geometries. To control the mesh adaptation, we develop a reliable residual-type a posteriori error estimation that takes account of the volumetric residual and the numerical discontinuity of the normal component of the electrical current density and that of the tangential component of the magnetic field with respect to non-smooth and anisotropic coefficients. We demonstrate the proposed modelling solver on 1-D MCSEM scenarios with varying degrees of electrical anisotropy. The comparison with goal-oriented adaptivity results obtained from other three commonly used error indicators shows that our approach is robust in dealing with both moderate and strong electrical anisotropy. After that, we constructed a 3-D hydrocarbon-bearing reservoir model with slope seafloor topography and tilted transverse isotropy in the background to examine our algorithm for the case of multiple sources. Finally, we implement a sensitivity analysis procedure to evaluate the resolution of the electrical anisotropy. The quantitative results indicate limitations and preferences of conventional MCSEM data in resolving anisotropic models, providing fundamental insights for inversion based data interpretation.
14
Zhang, Qiankun, Rongjie Zhang, Jiancui Chen, Wanfu Shen, Chunhua An, Xiaodong Hu, Mingli Dong, Jing Liu, and Lianqing Zhu. "Remarkable electronic and optical anisotropy of layered 1T’-WTe2 2D materials." Beilstein Journal of Nanotechnology 10 (August 20, 2019): 1745–53. http://dx.doi.org/10.3762/bjnano.10.170.
Full textAbstract:
Anisotropic 2D materials exhibit novel optical, electrical and thermoelectric properties that open possibilities for a great variety of angle-dependent devices. Recently, quantitative research on 1T’-WTe2 has been reported, revealing its fascinating physical properties such as non-saturating magnetoresistance, highly anisotropic crystalline structure and anisotropic optical/electrical response. Especially for its anisotropic properties, surging research interest devoted solely to understanding its structural and optical properties has been undertaken. Here we report quantitative, comprehensive work on the highly anisotropic, optical, electrical and optoelectronic properties of few-layer 1T’-WTe2 by azimuth-dependent reflectance difference microscopy, DC conductance measurements, as well as polarization-resolved and wavelength-dependent optoelectrical measurements. The electrical conductance anisotropic ratio is found to ≈103 for a thin 1T’-WTe2 film, while the optoelectronic anisotropic ratio is around 300 for this material. The polarization dependence of the photo-response is ascribed to the unique anisotropic in-plane crystal structure, consistent with the optical absorption anisotropy results. In general, 1T’-WTe2, with its highly anisotropic electrical and photoresponsivity reported here, demonstrates a route to exploit the intrinsic anisotropy of 2D materials and the possibility to open up new ways for applications of 2D materials for light polarization detection.
15
Yin, Changchun. "MMT forward modeling for a layered earth with arbitrary anisotropy." GEOPHYSICS 71, no. 3 (May 2006): G115—G128. http://dx.doi.org/10.1190/1.2197492.
Full textAbstract:
The standard model of a layered isotropic earth is a good approximation to geophysical reality in geoelectromagnetic mapping. In regions with distinct dipping stratification, however, it is difficult to model these fine structures because of large storage and time requirements. In this case, we may approximately replace the isotropic conductors with a preferential electrical direction by macro-scale anisotropy. The marine-magnetotelluric (MMT) forward problem is formulated for a layered earth with arbitrary anisotropy. For a given layer beneath the ocean, the two horizontal components of the electric field are projected onto the principal anisotropic directions and continued from layer to layer using continuity conditions. The formulation is used to derive the impedance tensor and apparent resistivities for a uniform anisotropic half-space, which clearly distinguish the effect of electrical anisotropy on MMT responses. The principal anisotropic orientations are clearly identified in the polar plots, which show the azimuthal variation of the apparent resistivity. The resolvability analysis of a resistive intermediate layer indicates that the depth of exploration for the MMT method depends strongly on the anomaly threshold associated with system sensitivity and environmental noise level but less on the resistivity contrast between the target and surrounding media. For an anisotropic target, to obtain a larger depth of exploration the electric field should be measured in the direction of higher target-host resistivity contrast. The simulation of reservoir characterization using marine MT shows that the current MMT technique cannot be an effective tool yet for direct offshore reservoir characterization, but it can be a good complementary tool for controlled-source electromagnetic (EM) technologies emerging for offshore hydrocarbon exploration.
16
Matsuno, Tetsuo, Kiyoshi Baba, and Hisashi Utada. "Probing 1-D electrical anisotropy in the oceanic upper mantle from seafloor magnetotelluric array data." Geophysical Journal International 222, no. 3 (May 6, 2020): 1502–25. http://dx.doi.org/10.1093/gji/ggaa221.
Full textAbstract:
SUMMARY Electrical anisotropy in the oceanic upper mantle can only be imaged by seafloor magnetotelluric (MT) data, and arguably provides important clues regarding the mantle structure and dynamics by observational determinations. Here, we attempt to probe the electrical (azimuthal) anisotropy in the oceanic mantle by analysing recent seafloor MT array data from the northwestern Pacific acquired atop 125–145 Ma seafloor. We propose a method in which an isotropic 1-D model is first obtained from seafloor MT data through an iterative correction for topographic distortions; then, the anisotropic properties are inferred as deviations from the isotropic 1-D model. We investigate the performance of this method through synthetic forward modelling and inversion using plausible anisotropic 1-D models and the actual 3-D bathymetry and topography of the target region. Synthetic tests reveal that the proposed method will detect electrical anisotropy in the conductive upper mantle or electrical asthenosphere. We also compare the performance of the proposed scheme by using two rotational invariant impedances and two topographic correction equations. The comparison reveals that using different rotational invariants and correction equations provides relatively consistent results, but among the rotational invariants, the sum of squared elements (ssq) impedance yields better recovered results for topographically distorted data than the determinant impedance. An application of the method to seafloor MT array data sets from two areas in the northwestern Pacific reveals the possible presence of two layers of electrical anisotropy in the conductive mantle (<100 Ω-m) at depths of ∼60–200 km. The anisotropy is estimated to be more intense in the shallower layer for both areas. On the other hand, the estimated anisotropic azimuth (defined as the most conductive direction) and the depth to the interface between the two layers are different between the two array areas separated by a small horizontal distance of ∼1000 km in spite of their similar seafloor ages. The most conductive directions are aligned neither with the current absolute plate motion direction nor with the fastest direction of seismic azimuthal anisotropy. The inferred electrical anisotropy features may result from array-scale (∼1000 km) mantle dynamics, such as small-scale convection, which might affect the electrical and seismic properties differently, although there remains the possibility that some portions of these features are explained by laterally heterogeneous mantle structures.
17
Bang, Jon, Arne Solstad, and Svein Mjaaland. "Formation Electrical Anisotropy Derived From Induction-Log Measurements in a Horizontal Well." SPE Reservoir Evaluation & Engineering 4, no. 06 (December 1, 2001): 483–88. http://dx.doi.org/10.2118/75115-pa.
Full textAbstract:
Summary An existing theory describes how electrical anisotropy in the formationaffects the response of resistivity logging tools. We have related this theory to the processing of logging while drilling (LWD) induction logs and are thus able to calculate the anisotropic resistivities directly from the logs. The method has been demonstrated by application to logs from a horizontal well section. Anisotropy ratios of 2 to 5, and occasionally higher values, were obtained for this formation. We also addressed the accuracy of these numbers by using independent sets of input logs. The results indicate that the logs are influenced by factors like invasion, in addition to the anisotropy. Our approach provides a fast and efficient computer algorithm. The output is calculated at the depths of the input logs; hence, the resulting anisotropy becomes a depth-dependent formation property. Introduction Electrical anisotropy has gained considerable attention in recent years. If present in the formation, neglection of this property when interpreting resistivity logs may lead to erroneous saturation estimates and may thus have great consequences upon development and production strategies and the overall economic situation. Electrical anisotropy denotes that the resistivity shows directional dependence. In sedimentary formations, it is commonly assumed that the anisotropy is caused by the deposition process, which yields different small-scale (grain and pore-size scale) structural properties in the vertical and horizontal directions. Anisotropy may also occur on a lithology scale[i.e., as a result of thin layers (compared to the extension of the electricfield) having individual isotropic properties]. Because the effect is determined by the sedimentary structure, a formation can be expected to show anisotropy in several properties, such as electric, acoustic, and fluid-flow resistance (permeability) properties, simultaneously. A common way of describing anisotropy is to distinguish between the vertical direction and directions in the horizontal plane. In this paper, we shall denote the resistivities in these directions by RV andRH, respectively. However, the terms "vertical" and"horizontal" refer to the original deposition process and may no longer correspond to the actual orientation of the formation owing to small- or large-scale geological activity. For dipping beds, it is common practice to assume one resistivity (R H) in the bedding plane and one (RV) in the direction normal to the bed, unless evidence of intrabed disturbances suggests other orientations of the anisotropy. Numerous publications have addressed the influence of electrical anisotropy on resistivity logs. Among the effects that have been studied are anisotropy in dipping and thinly laminated formations1–3 and in crossbedded formations.4 Effort has been put on theoretical tool response modeling and simulation 5–7 and on anisotropy corrections to logs.8,9 From field cases, anisotropy ratios(RV/R H) up to the order of 5 to 10 have been reported.7,8,10 In this paper, we demonstrate a method for calculating the electrical anisotropy directly from well logs, based on the theory developed by Hagiwara.6 The method has been implemented and applied to log data from a horizontal North Sea well. Theory Hagiwara6 has analyzed the resistivity log's response in anisotropic formations. According to this reference, two different measurements are sufficient to determine the anisotropy unambiguously, as long as the anisotropy orientation is known. The measurements may differ with respect to one or more of the following:antenna spacing (which is a prerequisite for phase- and attenuation-derived resistivity),frequency, ordeviation angle between tool axis and anisotropy orientation. In our work, we consider the LWD induction response. For this instrument class, Hagiwara shows that the complex voltage V recorded by one transmitter-receiver pair of electrodes isEquation 1 where i=the imaginary unit (i=-11/2) and L=the antenna spacing. Further,Equation 2 where a2= RH/RV is the anisotropy ratio between horizontal and vertical resistivitiesRH and RV, and ?=the deviation of tool direction from the R V direction. Notice the interpretation of the terms "vertical" and "horizontal," as discussed in the introduction. The wave number k is defined byEquation 3 where ?=the measurement angular frequency, µ=the magnetic permeability, andeH=the horizontal dielectric constant. In this study, we used the free space magnetic permeability µ=µ0=4p×10–7 N/A, and approximated eH from the logged resistivity through an empirical relation. Both these approximations are considered to have negligible influence on the results.
18
Selvakumaran, Lakshmi, and Gilles Lubineau. "Validation of Micro-Meso Electrical Relations for Laminates with Varying Anisotropy." Applied Mechanics and Materials 784 (August 2015): 435–42. http://dx.doi.org/10.4028/www.scientific.net/amm.784.435.
Full textAbstract:
For electrical impedance tomography (EIT) to be useful in monitoring transverse cracks in composites, it is imperative to establish the relation between conductivity and cracking density. Micro to meso scale homogenization has been developed for classical carbon fiber reinforced polymer (CFRP) laminate which provides such a relationship. However, we have shown in previous studies that the detectability of transverse cracks in such CFRP, which are characterized by very anisotropic electrical properties, is poor. Then, it is better to lower the electrical anisotropy, which can be achieved by various technologies including doping the polymeric resin by conductive nanoparticles. However, the validity of mesoscale homogenization for laminates with such low anisotropy has not been tested before. Here, we show that the mesoscale damage indicator is intrinsic for composites with varying anisotropy.
19
Shalaginov, Aleksandr, Nina Nevedrova, Aidisa Sanchaa, Ilya Shaparenko, and Petr Ponomarev. "ELECTRICAL ANISOTROPY ACCORDING TO DC METHODS IN THE BYSTROVKA FIELD AREA (SHORE RESERVOIR IN THE NOVOSIBIRSK REGION)." Interexpo GEO-Siberia 2, no. 2 (2019): 158–64. http://dx.doi.org/10.33764/2618-981x-2019-2-2-158-164.
Full textAbstract:
The article presents the results of the study of electrical anisotropy by two methods of DC (vertical electrical sounding and electrical tomography) in the area of the Bystrovka field area, on the shore of the Novosibirsk reservoir. Taking into account a priori well data, the parameters of the geoelectric model and the anisotropic characteristics of the section are determined. On the site of the study, according to the data of two methods, electrical anisotropy observed in the reference geoelectric horizon, represented by shale. In addition, the main direction of crack propagation is determined.
20
Newman, Gregory A., Michael Commer, and James J. Carazzone. "Imaging CSEM data in the presence of electrical anisotropy." GEOPHYSICS 75, no. 2 (March 2010): F51—F61. http://dx.doi.org/10.1190/1.3295883.
Full textAbstract:
Formation anisotropy should be incorporated into the analysis of controlled-source electromagnetic (CSEM) data because failure to do so can produce serious artifacts in the resulting resistivity images for certain data configurations of interest. This finding is demonstrated in model and case studies. Sensitivity to horizontal resistivity will be strongest in the broadside electric field data where detectors are offset from the tow line. Sensitivity to vertical resistivity is strongest for overflight data where the transmitting antenna passes directly over the detecting antenna. Consequently, consistent treatment of overflight and broadside electric field measurements requires an anisotropic modeling assumption. To produce a consistent resistivity model for such data, we develop and use a 3D CSEM imaging algorithm that treats transverse anisotropy. The algorithm is based on nonlinear conjugate gradients and full wave-equation modeling. It exploits parallel computing systems to effectively treat 3D imaging problems and CSEM data volumes of industrial size. We use it to demonstrate the anisotropic imaging process on model and field data sets from the North Sea and offshore Brazil. We also verify that isotropic imaging of overflight data alone produces an image generally consistent with vertical resistivity. However, superior data fits are obtained when the same overflight data are analyzed assuming an anisotropic resistivity model.
21
Brown, Vanessa, Mike Hoversten, Kerry Key, and Jinsong Chen. "Resolution of reservoir scale electrical anisotropy from marine CSEM data." GEOPHYSICS 77, no. 2 (March 2012): E147—E158. http://dx.doi.org/10.1190/geo2011-0159.1.
Full textAbstract:
A combination of 1D and 3D forward and inverse solutions is used to quantify the sensitivity and resolution of conventional controlled source electromagnetic (CSEM) data collected using a horizontal electric dipole source to transverse electric anisotropy located in a deep-water exploration reservoir target. Because strongly anisotropic shale layers have a vertical resistivity that can be comparable to many reservoirs, we examined how CSEM can discriminate confounding shale layers through their characteristically lower horizontal resistivity. Forward modeling indicated that the sensitivity to reservoir level anisotropy is very low compared with the sensitivity to isotropic reservoirs, especially when the reservoir is deeper than about 2 km below the seabed. However, for 1D models where the number of inversion parameters can be fixed to be only a few layers, both vertical and horizontal resistivity of the reservoir can be well resolved using a stochastic inversion. We found that the resolution of horizontal resistivity increases as the horizontal resistivity decreases. This effect is explained by the presence of strong horizontal current density in anisotropic layers with low horizontal resistivity. Conversely, when the reservoir has a vertical to horizontal resistivity ratio of about 10 or less, the current density is vertically polarized and hence has little sensitivity to the horizontal resistivity. Resistivity anisotropy estimates from 3D inversion for 3D targets suggest that resolution of reservoir level anisotropy for 3D targets will require good a priori knowledge of the background sediment conductivity and structural boundaries.
22
Greve, Anna K., R. Ian Acworth, and Bryce F. Kelly. "Detection of subsurface soil cracks by vertical anisotropy profiles of apparent electrical resistivity." GEOPHYSICS 75, no. 4 (July 2010): WA85—WA93. http://dx.doi.org/10.1190/1.3474590.
Full textAbstract:
To date, an understanding of crack dynamics has been fundamentally hampered by the lack of available techniques to observe or monitor crack dynamics below the soil surface. A new technique relates the growth of soil cracks to a progressive increase in the electrical anisotropy of the soil. Although a single measurement of anisotropy is possible using a surface array of electrodes, the use of four strings of electrodes installed vertically at the corners of a square provides a valuable picture of the crack pattern at depth. In addition, time-lapse electrical surveys allow the growth of cracks to be clearly monitored. The electrical anisotropy is defined as the ratio of the [Formula: see text]-to-[Formula: see text] apparent resistivity for the square array and is determined for each coplanar set of four electrodesusing one electrode from each of the four vertical strings. In a laboratory, we measured the electrical anisotropy in a sand-filled lysimeter with a plastic sheet, introduced to represent an electrically insulating crack. Measurements were then repeated in a cracking-soil-filled lysimeter. Finally, measurements were made in a field where a flood-irrigated sorghum crop was grown on cracking soil. Measurements under all three conditions demonstrate that the lateral and vertical extents of cracking in a soil profile strongly influence the electrical anisotropy. The larger the cumulative cracking volume, the higher the electrical anisotropy. Soil-moisture changes after crack closure have a minor influence on the measured anisotropy, as have sorghum roots. These experiments demonstrate that electrical-anisotropy profiles are a valuable tool for monitoring crack dynamics within a soil profile.
23
Upadhaya, Brijesh, Floran Martin, Paavo Rasilo, Paul Handgruber, Anouar Belahcen, and Antero Arkkio. "Modelling anisotropy in non-oriented electrical steel sheet using vector Jiles–Atherton model." COMPEL - The international journal for computation and mathematics in electrical and electronic engineering 36, no. 3 (May 2, 2017): 764–73. http://dx.doi.org/10.1108/compel-09-2016-0399.
Full textAbstract:
Purpose Non-oriented electrical steel presents anisotropic behaviour. Modelling such anisotropic behaviour has become a necessity for accurate design of electrical machines. The main aim of this study is to model the magnetic anisotropy in the non-oriented electrical steel sheet of grade M400-50A using a phenomenological hysteresis model. Design/methodology/approach The well-known phenomenological vector Jiles–Atherton hysteresis model is modified to correctly model the typical anisotropic behaviour of the non-oriented electrical steel sheet, which is not described correctly by the original vector Jiles–Atherton model. The modification to the vector model is implemented through the anhysteretic magnetization. Instead of the commonly used classical Langevin function, the authors introduced 2D bi-cubic spline to represent the anhysteretic magnetization for modelling the magnetic anisotropy. Findings The proposed model is found to yield good agreement with the measurement data. Comparisons are done between the original vector model and the proposed model. Another comparison is also made between the results obtained considering two different modifications to the anhysteretic magnetization. Originality/value The paper presents an original method to model the anhysteretic magnetization based on projections of the anhysteretic magnetization in the principal axis, and apply such modification to the vector Jiles–Atherton model to account for the magnetic anisotropy. The replacement of the classical Langevin function with the spline resulted in better fitting. The proposed model could be used in the numerical analysis of magnetic field in an electrical application.
24
Li, Qi, Feng Yan, and John Texter. "Electrospinning Graphene – Retention of Anisotropy." MRS Advances 5, no. 40-41 (2020): 2101–10. http://dx.doi.org/10.1557/adv.2020.263.
Full textAbstract:
AbstractRealization of the full potential of 2D nanosheet materials in energy storage and conversion devices requires heterogeneously structured electrodes having good electrical conductivity and large mean free paths for ion diffusion. Electrospinning of anisotropic objects usually obscures this anisotropy because of a large amount of carrier polymer typically required to form fibers. We demonstrate electrospinning of graphene with nearly quantitative retention of flake anisotropy to provide low to moderate density coatings of randomly oriented flakes having very large inter-flake mean free paths for ionic diffusion. Polyvinyl alcohol (PVA) is used as a carrier polymer and yields graphene anisotropy retention over an instability domain wherein electrospinning transitions to electrospraying. Graphene is deposited in polymer-encapsulated films at weight concentrations up to 50%, almost an order of magnitude higher than previously reported. Electrode applications will require at least partial replacement of PVA by electrically conducting polymers, and such polyelectrolytes should also suppress this electrospraying instability. We believe that large-scale electrospinning of graphene nanosheets will accelerate development of 2D materials in the fields of energy storage and conversion, catalysis, and tissue engineering.
25
Peng, Ronghua, Bo Han, Xiangyun Hu, Jianhui Li, and Yajun Liu. "Transdimensional Bayesian inversion of magnetotelluric data in anisotropic layered media with galvanic distortion correction." Geophysical Journal International 228, no. 3 (October 11, 2021): 1494–511. http://dx.doi.org/10.1093/gji/ggab413.
Full textAbstract:
SUMMARY Presence of electrical anisotropy in the lithosphere can provide useful constraints on regional structure patterns and dynamics of tectonic processes, and they can be imaged by magnetotelluric (MT) data. However, Inversion of MT data for anisotropic structures using standard gradient-based approaches requires subjective choices of model regularization for constraining structure and anisotropy complexity. Furthermore, the ubiquitous presence of galvanic distortion due to small-scale near-surface conductivity inhomogeneities prevents accurate imaging of subsurface structures if ignored or not properly removed. Here, we present a transdimensional Bayesian approach for inverting MT data in layered anisotropic media. The algorithm allows flexible model parametrization, in which both the number of layers and model parameters of each layer are treated as unknowns. In this manner, the presence or absence of anisotropy within the layers, as well as the level of model complexity, is determined adaptively by the data. In addition, to account for the effects of galvanic distortion, three frequency-independent distortion parameters resulting from the distortion decomposition are treated as additional variables during the inversion. We demonstrate the efficiency of the algorithm to resolve both isotropic and anisotropic structures with synthetic and field MT data sets affected by galvanic distortion effects. The transdimensional inversion results for the field data are compatible with results from previous studies, and our results improve the constraints on the magnitude and the azimuth (i.e. most conductive direction) of electrically anisotropic structures. For practical applications, the validity of 1-D anisotropic approximation should be first tested prior to the use of our approach. Otherwise it may produce spurious anisotropic structures due to the inapplicability of the anisotropic 1-D inversion for MT data affected by 2-D or 3-D electrical resistivity structures.
26
Suhorukova, K. V., and A. M. Petrov. "Electrical anisotropy of terrigenous deposits: a brief overview of approaches to its determination from electrical logging data in vertical wells." Russian Journal of Geophysical Technologies, no. 3 (January 28, 2022): 41–66. http://dx.doi.org/10.18303/10.18303/2619-1563-2021-3-41.
Full textAbstract:
The article briefly reviews a number of publications on the problem of determining rocks electrical resistivity anisotropy (primarily of sedimentary genesis) using downhole resistivity logs. We provide the information on the main causes of sandy-clay sediments micro- and macroanisotropy according to Russian papers and the history of the model-based approaches to the resistivity anisotropy description according to Russian and foreign articles. We analyze the main approaches to the vertical resistivity estimation. Both new hardware solutions aimed at direct measurement of electromagnetic field components sensitive to anisotropy and methodological techniques for extracting this information from the signals of "conventional" resistivity logging tools are considered according to published studies. The hardware solutions are multicomponent measurements with inclined and perpendicular (to the tool axis) coils, as well as with coaxial toroidal coils. Methodological techniques include combining data measured by tools with different types of medium excitation, for example, induction and galvanic. A number of papers suggest a two-step scheme: the first step is to determine the horizontal resistivity using induction arrays data, and the second step is to determine the vertical resistivity using focused lateral logs. Such schemes are implemented using numerical inversion algorithms and in some cases by inventing transformations of measured signals. Adding anisotropy to the interpretational model is based on a priori data (core studies, microresistivity logs). In the absence of a priori data, anisotropy is added when it is impossible to reconcile the parameters of isotropic models built independently based on logs with different type of excitation. A special focus of the review is on the development of the theory of unfocused lateral logging (BKZ) method by Soviet and Russian scientists and on the history of research on the electrical anisotropy influence on the signals of gradient probes. Due to the widespread use of the method in the USSR, this topic is presented in a number of papers revealing the results of anisotropic geoelectric models theoretical studies, numerical and physical modeling of BKZ logs and methodological developments for their interpretation.
27
Solanki, G. K., Mohit Tannarana, Pratik Pataniya, and K. D. Patel. "Growth and Electrical Characterizations of Sn0.3Se0.7 Crystals Grown by Direct Vapour Transport Technique." Advanced Materials Research 1141 (August 2016): 103–6. http://dx.doi.org/10.4028/www.scientific.net/amr.1141.103.
Full textAbstract:
Tin monoselenide (Sn0.3Se0.7) crystals have been grown by direct vapour transport technique. These crystals were found exhibit orthorhombic structure with space group D2h16 (Pcmn). The electrical measurements such as thermoelectric power and resistivity were carried out at high temperature on these as-grown crystals. The parameters like See back co-efficient, Fermi energy and scattering co-efficient were calculated from experimental data of TEP. The primary studies show the semiconducting behaviour of these crystals. Activation energy was also calculated by employing Arrhenius equation for grown samples. These layered materials, due to different kinds of interactions exhibits anisotropic crystalline structure and this lead to an anisotropy in electrical transport. Anisotropy seems to be decrease with temperature for all grown crystals. A detailed study about electrical transport and anisotropy in all such crystals will be presented at the time of presentation.
28
Soiński, Marian. "Anisotropy of electrical resistivities in electrical sheets." Journal of Magnetism and Magnetic Materials 53, no. 1-2 (November 1985): 54–62. http://dx.doi.org/10.1016/0304-8853(85)90129-5.
Full text
29
Аshcheulov, А. А., M. Ya Derevianchuk, D. А. Lavreniuk, and I. S. Romaniuk. "Electric current transformation by anisotropic electrically conductive medium." Технология и конструирование в электронной аппаратуре, no. 5-6 (2020): 28–32. http://dx.doi.org/10.15222/tkea2020.5-6.28.
Full textAbstract:
The authors consider the aspects of electric current distribution in electrically conductive anisotropic medium and establish how geometrical factors affect its longitudinal and transverse components. In the case of an a×b×с rectangular plate, its selected crystallographic axes are located on the plane of the side face a×b, whereas one of these axes is oriented at an angle α to the edge a. Applying a certain potential difference to the upper and lower end faces of the plate causes the appearance of longitudinal and transverse components of the internal electric current. The paper demonstrates the possibility of transforming the magnitude of the electric current and a way to optimize this magnitude. The transformation coefficient of such a device is determined by the anisotropy of the electrical conductivity of the plate and the coefficient of its shape k = a/b. The authors consider a few versions of anisotropic dielectric transformer design and offer their equivalent electric circuits. Another suggested transformer design is spiral in shape, compact and is characterized by high transformation coefficient value n. For example, at external radius r1 = 12,5 mm, internal radius r2 = 2 mm, height b = 2 mm and plate thickness c = 2,0 mm, its transformation coefficient n = 103. The information is given on existing monocrystalline and artificial anisotropic materials that can be used for the proposed device. High-temperature superconducting materials characterized by a high value of residual resistance anisotropy hold special promise in this case. Using the described transformation effect will significantly expand the possibilities of practical application of the considered electroohmic phenomenon. This will lead to the emergence of a new generation of devices for microwave technology, electronics and power engineering.
30
Bouknia, Mohamed Lamine, Chemseddine Zebiri, Djamel Sayad, Issa Elfergani, Jonathan Rodriguez, Mohammad Alibakhshikenari, Raed A. Abd-Alhameed, Francisco Falcone, and Ernesto Limiti. "Theoretical Study of the Input Impedance and Electromagnetic Field Distribution of a Dipole Antenna Printed on an Electrical/Magnetic Uniaxial Anisotropic Substrate." Electronics 10, no. 9 (April 29, 2021): 1050. http://dx.doi.org/10.3390/electronics10091050.
Full textAbstract:
The present work considers the investigation of the effects of both electrical and magnetic uniaxial anisotropies on the input impedance, resonant length, and fields distribution of a dipole printed on an anisotropic grounded substrate. In this study, the associated integral equation, based on the derivation of the Green’s functions in the spectral domain, is numerically solved employing the method of moments. In order to validate the computing method and the evaluated calculation code, numerical results are compared with available data in the literature treating particular cases of electrical uniaxial anisotropy; reasonable agreements are reported. Novel results of the magnetic uniaxial anisotropy effects on the input impedance and the evaluated electromagnetic field are presented and discussed. This work will serve as a stepping stone for further works for a better understanding of the electromagnetic field behavior in complex anisotropic and bi-anisotropic media.
31
Derevianchuk, M. Y., A. A. Аshcheulov, and D. A. Lavreniuk. "The Phenomenon of Electroohmic Transformation." Physics and Chemistry of Solid State 21, no. 4 (December 31, 2020): 743–48. http://dx.doi.org/10.15330/pcss.21.4.743-748.
Full textAbstract:
Peculiarities of electric current distribution in an anisotropic electrically conductive medium are considered and dependences of its longitudinal and transverse components on geometrical factors are established. In the case of a rectangular plate of length a, height b, and width c, the selected crystallographic axes are located in the plane of the side face (a × b), and one of these axes is oriented at an angle α to the edge α. Application to the upper and lower end faces of the plate of some potential difference leads to the appearance of longitudinal and transverse components of the flowing electric current. This leads to the possibility of transforming the electric current magnitude. The methods of optimizing the transformation coefficient magnitude which is determined by both the magnitude of the anisotropy of the electrical conductivity of the plate material and the coefficient of its shape k = a/b. The design variants of anisotropic electrically conductive transformers are proposed. The use of this transformation effect makes it possible to expand the practical use of electroohmic phenomena. This principle of transformation will expand the areas of its use in metrology and measurement technology.
32
Xiong, Zonghou. "Electromagnetic fields of electric dipoles embedded in a stratified anisotropic earth." GEOPHYSICS 54, no. 12 (December 1989): 1643–46. http://dx.doi.org/10.1190/1.1442633.
Full textAbstract:
The anisotropy of electrical conductivity in earth formations may be caused by crystal anisotropies of minerals, as well as by minilayers which occur frequently in sedimentary environments. The effects of anisotropy on the propagation of electromagnetic (EM) fields have been studied by many geophysicists. For instance, Kong (1972) and Wait (1981) solved the EM propagation problem for vertically anisotropic layered earths; O’Brien and Morrison (1967), for a horizontally anisotropic multilayer half‐space; Chetayev (1960), as well as Reddy and Rankin (1971), for media of dipping anisotropies; and Al’tgauzen (1969), for more complicated anisotropic media with a tensor dielectric constant of five components.
33
Tokarska, Magdalena, and Maciej Orpel. "Study of anisotropic electrical resistance of knitted fabrics." Textile Research Journal 89, no. 6 (March 15, 2018): 1073–83. http://dx.doi.org/10.1177/0040517518763978.
Full textAbstract:
Knitted fabrics, due to their multifunctional characteristics in terms of flexibility, elasticity and pliancy, are suitable to be used in electro-thermal garments as monitoring sensors for body movement. The arrangement of fibers and yarns in textiles makes them, in the majority of cases, inhomogeneous and anisotropic materials. Five highly conductive plain weft knitted fabrics in which anisotropy of electro-conductive properties occurred were chosen. In order to assess the global degree of planar anisotropy of the knitted fabrics, a new measurement procedure was designed. The Van der Pauw electrode configuration was used. The determination of resistance at selected points on the sample surface allowed us to find the surface response for each sample. Based on the results, the assessment of the global degree of planar anisotropy of electro-conductive properties of knitted fabrics was possible. Moreover, the experiment was designed to simultaneously solve the problem of measuring the resistance at the sample edge. The quotients ratio used as a measure representing the degree of global anisotropy was found to range from 2.5 to 11.1. This quotient was higher compared to that determined on the basis of measurements conducted in multi-directions lying in the sample plane and at a constant distance from the electrodes and from the sample edge. The relatively wide range of resistance values obtained for three samples makes it possible to use them as strain sensors, for example. The narrow resistance range observed in two samples is suited for the development of medical sensors, such as electrocardiogram electrodes.
34
Аshcheulov, А. А., D. А. Lavreniuk, and M. Ya Derevianchuk. "Electric field transformation effect in anisotropic dielectric medium." Технология и конструирование в электронной аппаратуре, no. 3-4 (2020): 24–27. http://dx.doi.org/10.15222/tkea2020.3-4.24.
Full textAbstract:
The authors consider the aspects of the electric field distribution in an anisotropic medium and establish how its longitudinal and transverse components depend on the geometric factors. A rectangular plate of dimensions a×b×c is studied, its selected crystallographic axes located in the plane of the side face (a×b), while one of the axes is oriented at a certain angle α to the edge a. It is shown that applying a certain potential difference to the upper and lower faces electrically polarizes the volume of the plate and causes the appearance of the longitudinal and transverse components of the internal electric field. The authors investigate the possibility of transforming the magnitude of the electric field and methods for its optimization. The transformation coefficient of such a device is determined by the anisotropy of the dielectric permeability of the plate material and its shape coefficient k = a/b. The paper considers one of the design options for an anisotropic dielectric transformer and proposes its equivalent electrical circuit. Structural elements based on anisotropic dielectric transformers may be widely used both in power supplies of various electronic devices and for coordination of radar transceiver systems with antenna arrays of centimeter, millimeter and submillimeter wavelength ranges. The possibility of simultaneous transformation of constant and alternating electric fields allows them to be used in devices of simultaneous comparison, enabling to determine the current values of voltage, as well as the power of electromagnetic radiation in a wide range of wavelengths. The vortex nature of the electric field in the plate’s volume caused by the coefficient anisotropy of the dielectric permeability also creates the preconditions for the emergence of new principles for generating high-power electromagnetic radiation in a wide spectral range. The generation frequency of such devices is determined by the geometric dimensions of the anisotropic plate. The use of the described transformation effect will significantly expand the possibilities of practical application of the considered electrostatic phenomena, which will lead to the emergence of a new generation of devices for microwave technology, electronics and electric power.
35
Nam, Myung Jin, David Pardo, and Carlos Torres-Verdín. "Simulation of DC dual-laterolog measurements in complex formations: A Fourier-series approach with nonorthogonal coordinates and self-adapting finite elements." GEOPHYSICS 74, no. 1 (January 2009): E31—E43. http://dx.doi.org/10.1190/1.3000681.
Full textAbstract:
Dual laterolog (DLL) makes use of a galvanic conduction principle to focus electrical currents into rock formations, thereby minimizing shoulder and borehole effects in the measurement of formation resistivity. The tool includes two separate focusing systems: deep-sensing (LLd) and shallow-sensing modes (LLs). Laterolog current-focusing systems were designed for operation primarily in vertical boreholes penetrating horizontal layers; only recently their design has been revised for operation in deviated wells in the presence of electrical anisotropy. We simulated three-dimensional (3D) DLL measurements in dipping, invaded, and electrically anisotropic formations and appraised the corresponding effects on apparent resistivity logs. Simulations were performed by combining the use of a Fourier-series expansion in a nonorthogonal system of coordinates with an existing 2D goal-oriented, higher-order, and self-adaptive finite-element method. This numerical algorithm yields accurate solutions in limited CPU time because only a few Fourier modes are needed to simulate practical applications. For the calculation of focused currents, we introduced an embedded postprocessing method that incorporates a synthetic focusing principle to compute current intensities at each iterative step of optimal mesh refinements. Our numerical method accurately simulates 3D DLL measurements in rock formations that exhibit extreme contrasts of electrical resistivity. Simulations indicate that LLs resistivity logs are more sensitive to both invaded and anisotropic layers than LLd resistivity logs. In deviated wells, shoulder-bed effects on apparent resistivity logs increase with an increase of dip angle, and are emphasized across thin conductive layers. Electrical anisotropy effects on apparent resistivity logs increase substantially with dip angle.
36
Winchen, Tobias, Andreas Kemna, Harry Vereecken, and Johan A. Huisman. "Characterization of bimodal facies distributions using effective anisotropic complex resistivity: A 2D numerical study based on Cole-Cole models." GEOPHYSICS 74, no. 3 (May 2009): A19—A22. http://dx.doi.org/10.1190/1.3113986.
Full textAbstract:
Subsurface heterogeneity characteristics are of major importance in hydrologic modeling, and likely result in anisotropic electrical properties. We computed the anisotropic effective complex resistivity of 2D bimodal facies distributions numerically. Complex resistivities of individual facies are described in terms of the Cole-Cole relaxation model. First, we determined that effective DC resistivities of the distributions can be reasonably well described by power averaging the properties of individual facies. We found a clear relationship between the mixing parameter and correlation lengths of the facies distributions with respect to horizontal and vertical directions. Then, we used the power-law mixing model to invert for individual Cole-Cole model parameters by fitting predicted electrical responses to simulated spectral effective complex-resistivity data for the two perpendicular directions. Thus, it is possible to derive the electrical properties of individual facies as well as structural parameters describing bimodal facies distribution by means of a noninvasive measurement approach. In particular, anisotropy of the spectral complex-resistivity response provides information on correlation lengths of the distribution. This finding is relevant for all applications of electrical-impedance spectroscopy where anisotropy might be encountered.
37
Macfarlane, Jake, Stephan Thiel, Jared Peacock, Josef Pek, and Graham Heinson. "Anisotropic forward modelling of geothermal fluid using 2-dimensional electrical anisotropy." ASEG Extended Abstracts 2013, no. 1 (December 2013): 1–3. http://dx.doi.org/10.1071/aseg2013ab155.
Full text
38
Halauchuk V. I., Bumai Y. A., Lukashevich M. G., Lyadov N. M., Faizrakhmanov I. A., and Khaibullin R.I. "Correlation between electrical, galvanomagnetic and magnetic properties of nanocrystalline iron films obtained by ion assisted deposition." Physics of the Solid State 64, no. 14 (2022): 2366. http://dx.doi.org/10.21883/pss.2022.14.54335.163.
Full textAbstract:
Here we present the measurements of the temperature dependence of resistance, transverse and longitudinal magnetoresistance (MR) in nanocrystalline iron films in the temperature range 2-300 K and the sweep of the magnetic field up to 8 T. Thin nanocrystalline films of α-iron phase with 80 nm thickness were obtained by ion-beam assisted deposition on a silicon substrate. In addition to the shape anisotropy, the obtained iron films exhibited perpendicular magnetic anisotropy (PMA), which disappeared after annealing the films at a temperature of 450oC in a vacuum. The effect of PMA on the sign and magnitude of the MR of iron films, as well as on the magnetic field dependences of the magnetoresistive effect, recorded at different orientations of the external magnetic field with respect to the film plane and current direction, is experimentally shown. The results obtained are discussed in the framework of modern views on the processes of charge transfer in a weakly disordered ferromagnetic films with different magnetic anisotropy and domain structure when a weak (less than the saturation field of magnetization) or strong (higher than the saturation field) external magnetic field is applied. Keywords: nanocrystalline iron films, perpendicular magnetic anisotropy, magnetoresistance, anisotropic magnetoresistance, magnon magnetoresistance, percolation, weak localization.
39
Yuan, Ning, Xiao Chun Nie, Richard Liu, and Cheng Wei Qiu. "Simulation of full responses of a triaxial induction tool in a homogeneous biaxial anisotropic formation." GEOPHYSICS 75, no. 2 (March 2010): E101—E114. http://dx.doi.org/10.1190/1.3336959.
Full textAbstract:
Triaxial induction tools are used to evaluate fractured and low-resistivity reservoirs composed of thinly laminated sand-shale sequences. Thinly laminated and fractured reservoirs demonstrate transversely isotropic or fully anisotropic (biaxial anisotropic) electrical properties. Compared to the number of studies on transverse isotropy, relatively little work covers biaxial anisotropy because of the mathematical complexity. We have developed a theoretical analysis for the full response of a triaxial induction tool in a homogeneous biaxial anisotropic formation. The triaxial tool is composed of three mutually orthogonal transmitters and three mutually orthogonal receivers. The bucking coils are also oriented at three mutually orthogonal directions to remove direct coupling. Starting from the space-domain Maxwell’s equations, which the electromagnetic (EM) fields satisfied, we obtain the spectral-domain Maxwell’s equations by defining a Fourier transform pair. Solving the resultant spectral-domain vector equation, we can find the spectral-domain solution for the electric field. Then, the magnetic fields can be determined from a homogeneous form of Maxwell’s equations. The solution for the EM fields in the space domain can be expressed in terms of inverse Fourier transforms of their spectral-domain counterparts. We use modified Gauss-Laguerre quadrature and contour integration methods to evaluate the inverse Fourier transform efficiently. Our formulations are based on arbitrary relative dipping and azimuthal and tool angles; thus, we obtain the full coupling matrix connecting source excitations to magnetic field response. We have validated our formulas and investigated the effects of logging responses on factors such as relative dipping, azimuthal and tool angles, and frequency using our code. We only consider conductivity anisotropy, not anisotropy in dielectric permittivity and magnetic permeability. However, our method and formulas are straightforward enough to consider anisotropy in dielectric permittivity.
40
TSYBRIY, I. K., V. I. IGNATENKO, I. L. VYALIKOV, and A. Y. RODICHEV. "APPLICATION OF THE BARKHAUSEN EFFECT IN MECHATRONIC QUALITY CONTROL SYSTEMS OF ELECTRICAL STEEL." Fundamental and Applied Problems of Engineering and Technology, no. 6 (2021): 83–88. http://dx.doi.org/10.33979/2073-7408-2021-350-6-83-88.
Full textAbstract:
Residual magnetic anisotropy of isotropic electrical steel adversely affects the performance of electrical machines. Mechanical stresses and deformations arising during the manufacture of parts lead to an increase in the anisotropy of the magnetic properties. The aim of this work is to develop a method that makes it possible to assess the degree of residual magnetic anisotropy in finished products. For this, the paper considers the possibility of using the parameters of the Barkhausen effect (EB), reflecting the dynamics of the magnetic structure of the material in alternating magnetic fields. As samples for the study, a set of ready–made stamped plates of the core of a toothed rotor of an electric machine was used. The microstructure of the samples was investigated using a Neopfot–21 metallographic microscope. The studies of the magnetic structure were carried out using the original Barkhausen device for recording magnetic noise, which includes a magnetic noise sensor, a system of amplifying–converting units, and a digital processing unit for measuring information. The results of measurements of the area of the envelope around the circumference of the average diameter and along the teeth of the rotor plate are given, which make it possible to estimate the level of residual anisotropy of isotropic steel by scanning the surface of the tooth rotor plates with a magnetic noise sensor. The data obtained can serve as the basis for the development of a method for controlling the level of magnetic anisotropy of isotropic electrical steels induced in finished products as a result of mechanical processing.
41
KIM, Sei-Ki, Masaru MIYAYAMA, and Hiroaki YANAGIDA. "Electrical Anisotropy of BaBi4Ti4O15 Single Crystal." Journal of the Ceramic Society of Japan 102, no. 1188 (1994): 722–26. http://dx.doi.org/10.2109/jcersj.102.722.
Full text
42
Volkov, Alexander G., Justin C. Foster, Kara D. Baker, and Vladislav S. Markin. "Mechanical and electrical anisotropy inMimosa pudicapulvini." Plant Signaling & Behavior 5, no. 10 (October 2010): 1211–21. http://dx.doi.org/10.4161/psb.5.10.12658.
Full text
43
Taccardi, B., B. B. Punske, R. S. MacLeod, and Q. Ni. "Extracardiac effects of myocardial electrical anisotropy." Biomedizinische Technik/Biomedical Engineering 46, s2 (2001): 216–18. http://dx.doi.org/10.1515/bmte.2001.46.s2.216.
Full text
44
Adams, Amy L., Taylor J. Nordquist, John T. Germaine, and Peter B. Flemings. "Permeability anisotropy and resistivity anisotropy of mechanically compressed mudrocks." Canadian Geotechnical Journal 53, no. 9 (September 2016): 1474–82. http://dx.doi.org/10.1139/cgj-2015-0596.
Full textAbstract:
Permeability anisotropy (the ratio of the horizontal to vertical permeability) develops in mudrocks at the macroscale due to heterogeneities such as layering and at the element scale (i.e., within a single homogeneous layer or unit) due to decreasing porosity and increasing platy particle alignment. This work describes new experimental methods and results from a laboratory program using cubic specimens to investigate the evolution of mudrock permeability and resistivity at the element scale. A systematic study analyzes the evolution of the permeability anisotropy and electrical resistivity anisotropy using resedimented Boston blue clay (RBBC) over a stress range of 0.4–40 MPa; additional measurements are presented for three other mudrocks within varying clay fraction and clay mineralogy within the stress range 1.2–10 MPa. The permeability anisotropy and the conductivity anisotropy (inverse of the resistivity anisotropy) of all four mudrocks studied ranges from 1 to 2.2 over the porosity range 0.55–0.30. A nearly 1:1 correlation between the electrical conductivity anisotropy and the permeability anisotropy is observed to be independent of clay fraction or clay mineralogy.
45
Shiozaki, M., and Y. Kurosaki. "Anisotropy of Magnetic Properties in Non-oriented Electrical Steel Sheets." Textures and Microstructures 11, no. 2-4 (January 1, 1989): 159–70. http://dx.doi.org/10.1155/tsm.11.159.
Full textAbstract:
The anisotropy of magnetic properties in non-oriented electrical steel sheets can be evaluated by measuring Epstein specimens in the radial directions. The magnetic properties measured on ring cores are practically equal to the approximate values of magnetic properties determined by Epstein specimens in the radial directions. Non-oriented electrical steel sheets with anisotropy are not desirable for motors but are suitable for transformers and fluorescent lamp ballasts. The core loss and magnetic induction as measured with ring specimens are better with non-oriented electrical steel sheets with anisotropy than with non-oriented electrical steel sheets with random crystallographic orientation. This phenomenon depends on the texture change of the product.
46
Li, Guo, Wang, and Zhang. "Band Tunability of Coupled Elastic Waves along Thickness in Laminated Anisotropic Piezoelectric Phononic Crystals." Crystals 9, no. 8 (August 16, 2019): 426. http://dx.doi.org/10.3390/cryst9080426.
Full textAbstract:
Although the passively adjusting and actively tuning of pure longitudinal (primary (P-)) and pure transverse (secondary or shear (S-)) waves band structures in periodically laminated piezoelectric composites have been studied, the actively tuning of coupled elastic waves (such as P-SV, P-SH, SV-SH, and P-SV-SH waves), particularly as the coupling of wave modes is attributed to the material anisotropy, in these phononic crystals remains an untouched topic. This paper presents the analytical matrix method for solving the dispersion characteristics of coupled elastic waves along the thickness direction in periodically multilayered piezoelectric composites consisting of arbitrarily anisotropic materials and applied by four kinds of electrical boundaries. By switching among these four electrical boundaries—the electric-open, the external capacitance, the electric-short, and the external feedback control—and by altering the capacitance/gain coefficient in cases of the external capacitance/feedback-voltage boundaries, the tunability of the band properties of the coupled elastic waves along layering thickness in the concerned phononic multilayered crystals are investigated. First, the state space formalism is introduced to describe the three-dimensional elastodynamics of arbitrarily anisotropic elastic and piezoelectric layers. Second, based on the traveling wave solutions to the state vectors of all constituent layers in the unit cell, the transfer matrix method is used to derive the dispersion equation of characteristic coupled elastic waves in the whole periodically laminated anisotropic piezoelectric composites. Finally, the numerical examples are provided to demonstrate the dispersion properties of the coupled elastic waves, with their dependence on the anisotropy of piezoelectric constituent layers being emphasized. The influences of the electrical boundaries and the electrode thickness on the band structures of various kinds of coupled elastic waves are also studied through numerical examples. One main finding is that the frequencies corresponding to (with the dimensionless characteristic wavenumber) are not always the demarcation between pass-bands and stop-bands for coupled elastic waves, although they are definitely the demarcation for pure P- and S-waves. The other main finding is that the coupled elastic waves are more sensitive to, if they are affected by, the electrical boundaries than the pure P- and S-wave modes, so that higher tunability efficiency should be achieved if coupled elastic waves instead of pure waves are exploited.
47
Chaudhary, Kundan, Michele Tamagnone, Mehdi Rezaee, D. Kwabena Bediako, Antonio Ambrosio, Philip Kim, and Federico Capasso. "Engineering phonon polaritons in van der Waals heterostructures to enhance in-plane optical anisotropy." Science Advances 5, no. 4 (April 2019): eaau7171. http://dx.doi.org/10.1126/sciadv.aau7171.
Full textAbstract:
Van der Waals (vdW) heterostructures assembled from layers of two-dimensional materials have attracted considerable interest due to their novel optical and electrical properties. Here, we report a scattering-type scanning near-field optical microscopy study of hexagonal boron nitride on black phosphorus (h-BN/BP) heterostructures, demonstrating the first direct observation of in-plane anisotropic phonon polariton modes in vdW heterostructures. Notably, the measured in-plane optical anisotropy along the armchair and zigzag crystal axes exceeds the ratio of refractive indices of BP in the x-y plane. We explain that this enhancement is due to the high confinement of the phonon polaritons in h-BN. We observe a maximum in-plane optical anisotropy of αmax = 1.25 in the frequency spectrum at 1405 to 1440 cm−1. These results provide new insights into the behavior of polaritons in vdW heterostructures, and the observed anisotropy enhancement paves the way to novel nanophotonic devices and to a new way to characterize optical anisotropy in thin films.
48
Nelson, C. B., and T. H. Gilani. "Anisotropic electrical properties of sculptured thin films." Canadian Journal of Physics 91, no. 8 (August 2013): 658–61. http://dx.doi.org/10.1139/cjp-2012-0514.
Full textAbstract:
The anisotropy in DC electrical resistivity of a chromium (Cr) sculptured thin film (STF) prepared on a glass substrate is measured and explained using a simple linear dielectric model for electrical conduction in metallic STFs. The experimental anisotropy as a function of growth angle of Cr columns on a glass substrate is in good agreement with the model.
49
Wei, Qiqi, Hailong Wang, Xupeng Zhao, and Jianhua Zhao. "Electron mobility anisotropy in (Al,Ga)Sb/InAs two-dimensional electron gases epitaxied on GaAs (001) substrates." Journal of Semiconductors 43, no. 7 (July 1, 2022): 072101. http://dx.doi.org/10.1088/1674-4926/43/7/072101.
Full textAbstract:
Abstract The electron mobility anisotropy in (Al,Ga)Sb/InAs two-dimensional electron gases with different surface morphology has been investigated. Large electron mobility anisotropy is found for the sample with anisotropic morphology, which is mainly induced by the threading dislocations in the InAs layer. For the samples with isotropic morphology, the electron mobility is also anisotropic and could be attributed to the piezoelectric scattering. At low temperature (below transition temperature), the piezoelectric scattering is enhanced with the increase of temperature, leading to the increase of electron mobility anisotropy. At high temperature (above transition temperature), the phonon scattering becomes dominant. Because the phonon scattering is isotropic, the electron mobility anisotropy in all the samples would be reduced. Our results provide useful information for the comprehensive understanding of electron mobility anisotropy in the (Al,Ga)Sb/InAs system.
50
Zhang, Chao, Xiangzhuang Kong, Xian Wang, Yanxia Du, and Guangming Xiao. "A Predicting Model for the Effective Thermal Conductivity of Anisotropic Open-Cell Foam." Energies 15, no. 16 (August 22, 2022): 6091. http://dx.doi.org/10.3390/en15166091.
Full textAbstract:
The structural anisotropy of open-cell foam leads to the anisotropy of effective thermal conductivity (ETC). To quantitatively analyze the effect of structural anisotropy on the anisotropy of ETC, a new predicting model for the ETC of anisotropic open-cell foam was proposed based on an anisotropy tetrakaidecahedron cell (ATC). Feret diameters in three orthogonal directions obtained by morphological analysis of real foam structures were used to characterize the anisotropy of ATC. To validate our proposed anisotropic model, the ETCs of real foam structures in three orthogonal directions predicted by it were compared with the numerical results, for which the structures of numerical models are reconstructed by X-ray computed tomography (X-CT). Using the present anisotropic model, the influences of the thermal conductivity ratio (TCR) and porosity of the foams on the anisotropic ratios of ETCs are also investigated. Results show that there is good consistency between the ETCs obtained by the anisotropic model and the numerical method. The maximum relative errors between them are 2.84% and 13.57% when TCRs are 10 and 100, respectively. The present anisotropic model can not only predict the ETCs in different orthogonal directions but also quantitatively predict the anisotropy of ETC. The anisotropies of the ETCs decrease with porosity because the proportion of the foam skeleton decreases. However, the anisotropies of ETCs increase with TCR, and there exist asymptotic values in anisotropic ratios of ETCs as TCR approaches infinity and they are equal to the relative Feret diameters in different orthogonal directions.