Journal articles on the topic 'Equivalent-layer technique'
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Oliveira Jr., Vanderlei C., Valéria C. F. Barbosa, and Leonardo Uieda. "Polynomial equivalent layer." GEOPHYSICS 78, no. 1 (January 1, 2013): G1—G13. http://dx.doi.org/10.1190/geo2012-0196.1.
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We have developed a new cost-effective method for processing large-potential-field data sets via the equivalent-layer technique. In this approach, the equivalent layer is divided into a regular grid of equivalent-source windows. Inside each window, the physical-property distribution is described by a bivariate polynomial. Hence, the physical-property distribution within the equivalent layer is assumed to be a piecewise polynomial function defined on a set of equivalent-source windows. We perform any linear transformation of a large set of data as follows. First, we estimate the polynomial coefficients of all equivalent-source windows by using a linear regularized inversion. Second, we transform the estimated polynomial coefficients of all windows into the physical-property distribution within the whole equivalent layer. Finally, we premultiply this distribution by the matrix of Green’s functions associated with the desired transformation to obtain the transformed data. The regularized inversion deals with a linear system of equations with dimensions based on the total number of polynomial coefficients within all equivalent-source windows. This contrasts with the classical approach of directly estimating the physical-property distribution within the equivalent layer, which leads to a system based on the number of data. Because the number of data is much larger than the number of polynomial coefficients, the proposed polynomial representation of the physical-property distribution within an equivalent layer drastically reduces the number of parameters to be estimated. By comparing the total number of floating-point operations required to estimate an equivalent layer via our method with the classical approach, both formulated with Cholesky’s decomposition, we can verify that the computation time required for building the linear system and for solving the linear inverse problem can be reduced by as many as three and four orders of magnitude, respectively. Applications to synthetic and real data show that our method performs the standard linear transformations of potential-field data accurately.
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Takahashi, Diego, Vanderlei C. Oliveira Jr., and Valéria C. F. Barbosa. "Convolutional equivalent layer for gravity data processing." GEOPHYSICS 85, no. 6 (November 1, 2020): G129—G141. http://dx.doi.org/10.1190/geo2019-0826.1.
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We have developed an efficient and very fast equivalent-layer technique for gravity data processing by modifying an iterative method grounded on an excess mass constraint that does not require the solution of linear systems. Taking advantage of the symmetric block-Toeplitz Toeplitz-block (BTTB) structure of the sensitivity matrix that arises when regular grids of observation points and equivalent sources (point masses) are used to set up a fictitious equivalent layer, we develop an algorithm that greatly reduces the computational complexity and RAM memory necessary to estimate a 2D mass distribution over the equivalent layer. The structure of symmetric BTTB matrix consists of the elements of the first column of the sensitivity matrix, which, in turn, can be embedded into a symmetric block-circulant with circulant-block (BCCB) matrix. Likewise, only the first column of the BCCB matrix is needed to reconstruct the full sensitivity matrix completely. From the first column of the BCCB matrix, its eigenvalues can be calculated using the 2D fast Fourier transform (2D FFT), which can be used to readily compute the matrix-vector product of the forward modeling in the fast equivalent-layer technique. As a result, our method is efficient for processing very large data sets. Tests with synthetic data demonstrate the ability of our method to satisfactorily upward- and downward-continue gravity data. Our results show very small border effects and noise amplification compared to those produced by the classic approach in the Fourier domain. In addition, they show that, whereas the running time of our method is [Formula: see text] s for processing [Formula: see text] observations, the fast equivalent-layer technique used [Formula: see text] s with [Formula: see text]. A test with field data from the Carajás Province, Brazil, illustrates the low computational cost of our method to process a large data set composed of [Formula: see text] observations.
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Mendonça, Carlos Alberto, and João B. C. Silva. "The equivalent data concept applied to the interpolation of potential field data." GEOPHYSICS 59, no. 5 (May 1994): 722–32. http://dx.doi.org/10.1190/1.1443630.
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The equivalent layer calculation becomes more efficient by first converting the observed potential data set to a much smaller equivalent data set, thus saving considerable CPU time. This makes the equivalent‐source method of data interpolation very competitive with other traditional gridding techniques that ignore the fact that potential anomalies are harmonic functions. The equivalent data set is obtained by using a least‐squares iterative algorithm at each iteration that solves an underdetermined system fitting all observations selected from previous iterations and the observation with the greatest residual in the preceding iteration. The residuals are obtained by computing a set of “predicted observations” using the estimated parameters at the current iteration and subtracting them from the observations. The use of Cholesky’s decomposition to implement the algorithm leads to an efficient solution update everytime a new datum is processed. In addition, when applied to interpolation problems using equivalent layers, the method is optimized by approximating dot products by the discrete form of an analytic integration that can be evaluated with much less computational effort. Finally, the technique is applied to gravity data in a 2 × 2 degrees area containing 3137 observations, from Equant‐2 marine gravity survey offshore northern Brazil. Only 294 equivalent data are selected and used to interpolate the anomalies, creating a regular grid by using the equivalent‐layer technique. For comparison, the interpolation using the minimum‐curvature method was also obtained, producing equivalent results. The number of equivalent observations is usually one order of magnitude smaller than the total number of observations. As a result, the saving in computer time and memory is at least two orders of magnitude as compared to interpolation by equivalent layer using all observations.
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Tang, Wenwu, Yaoguo Li, Douglas W. Oldenburg, and Jianxin Liu. "Removal of galvanic distortion effects in 3D magnetotelluric data by an equivalent source technique." GEOPHYSICS 83, no. 2 (March 1, 2018): E95—E110. http://dx.doi.org/10.1190/geo2016-0668.1.
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The galvanic distortion induced by the electric charge buildup across near-surface inhomogeneities can severely affect the interpretation of magnetotelluric (MT) data for deeper structures. In addition to the methods already available, we have developed an alternative approach for processing MT impedance data with such distortions using an equivalent source technique. One prerequisite for the method is that all data are acquired on the surface, which is nearly always the case in land-based MT surveys. The method works with the electric field scaled from the impedance data and constructs an equivalent electrical polarization layer that attempts to reproduce the signal in the data while misfitting the galvanic distortion. Because of the uncorrelated characteristics of galvanic distortions across multiple stations at the same frequency, they can be distinguished and removed by constructing an equivalent source layer of electrical polarization using a regularized inverse formulation. The tradeoff between the signal and distortion is achieved through the use of generalized cross-validation method during the equivalent source construction, whereas the choice of equivalent source parameters also affects the separation. Numerical tests indicate that good results are obtained when the depth of the equivalent source layer is slightly greater than 10 times the nominal data spacing, and the lateral extent is twice that of the data area. The simultaneous processing with multiple frequencies yields more stable apparent resistivity curves than the separate single-frequency processing. The method has performed well in removing the galvanic distortions in the synthetic- and field-data examples.
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Siqueira, Fillipe C. L., Vanderlei C. Oliveira Jr., and Valéria C. F. Barbosa. "Fast iterative equivalent-layer technique for gravity data processing: A method grounded on excess mass constraint." GEOPHYSICS 82, no. 4 (July 1, 2017): G57—G69. http://dx.doi.org/10.1190/geo2016-0332.1.
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We have developed a new iterative scheme for processing gravity data using a fast equivalent-layer technique. This scheme estimates a 2D mass distribution on a fictitious layer located below the observation surface and with finite horizontal dimensions composed by a set of point masses, one directly beneath each gravity station. Our method starts from an initial mass distribution that is proportional to the observed gravity data. Iteratively, our approach updates the mass distribution by adding mass corrections that are proportional to the gravity residuals. At each iteration, the computation of the residual is accomplished by the forward modeling of the vertical component of the gravitational attraction produced by all point masses setting up the equivalent layer. Our method is grounded on the excess of mass and on the positive correlation between the observed gravity data and the masses on the equivalent layer. Mathematically, the algorithm is formulated as an iterative least-squares method that requires neither matrix multiplications nor the solution of linear systems, leading to the processing of large data sets. The time spent on the forward modeling accounts for much of the total computation time, but this modeling demands a small computational effort. We numerically prove the stability of our method by comparing our solution with the one obtained via the classic equivalent-layer technique with the zeroth-order Tikhonov regularization. After estimating the mass distribution, we obtain a desired processed data by multiplying the matrix of the Green’s functions associated with the desired processing by the estimated mass distribution. We have applied the proposed method to interpolate, calculate the horizontal components, and continue gravity data upward (or downward). Testing on field data from the Vinton salt dome, Louisiana, USA, confirms the potential of our approach in processing large gravity data set over on undulating surface.
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Mendonça, Carlos A. "Subspace method for solving large-scale equivalent layer and density mapping problems." GEOPHYSICS 85, no. 3 (May 1, 2020): G57—G68. http://dx.doi.org/10.1190/geo2019-0302.1.
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The equivalent layer technique explores an intrinsic property of potential fields that any observed field at the ground surface can be reconstituted from a fictitious continuous distribution at an arbitrary flat surface that is indistinguishable from the field of the true sources. This continuous distribution can be represented by a set of discrete cells of known position and size but unknown physical property by solving a linear system, with size proportional to the number of data points measured. The density distribution at the equivalent layer carries information about the true sources because it is a scaled and downward-continued version of the field generated by the true sources at the level that the geophysical survey was undertaken. The computation of this downward-continued field is unstable, and an equivalent source evaluation is constrained by the intense computational demand required to solve the associated large linear system. A new formulation is developed to directly solve large-scale gravity equivalent layer problems using a subspace representation for the unknown density distribution. This subspace basis is constructed by applying the singular value decomposition to the matrix containing the gridded data set. A procedure to diminish (by two orders of magnitude) the number of forward model evaluations is introduced by exploring the symmetry of the gravity kernel and its evaluation on a regular mesh. The density distribution at the equivalent layer is used to outline the spatial distribution of contrasting underlying sources, to discriminate regions with predominant positive or negative density contrast, and to estimate the mass excess or deficiency for sources with positive or negative density contrast. This technique is applied to determine density models for the Carajás airborne gravity survey and to analyze density distributions associated with banded iron formations and structures of the Carajás Mineral Province, Brazil, providing mass estimates for specific geologic unities.
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Bi Chuan-Xing, Hu Ding-Yu, Zhang Yong-Bin, and Xu Liang. "Sound field separation technique based on equivalent source method and double-layer particle velocity measurements." Acta Physica Sinica 62, no. 8 (2013): 084301. http://dx.doi.org/10.7498/aps.62.084301.
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Михеевская, Marina Mikheevskaya, Сушков, Sergey Sushkov, Бурмистрова, and Olga Burmistrova. "Dynamic analysis technique for bodies of forest motor roads." Forestry Engineering Journal 3, no. 4 (January 21, 2014): 89–93. http://dx.doi.org/10.12737/2185.
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The article describes a method of dynamic analysis of pavement bodies of timber road Ukhta – Troitsky-Pechorsk, a forecast of full sinkage and consolidation time of the subsoil. Reinforcing gravel with geogrids increases the overall (equivalent) elastic modulus of structure for 6…15 %, reduces the magnitude of the tangential stress in the layer, underlying the geogrid by 25…80 %, increases the modulus of defor-mation with significant precipitation more than in 2 times.
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Reis, André L. A., Vanderlei C. Oliveira Jr., and Valéria C. F. Barbosa. "Generalized positivity constraint on magnetic equivalent layers." GEOPHYSICS 85, no. 6 (November 1, 2020): J99—J110. http://dx.doi.org/10.1190/geo2019-0706.1.
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It is known from the potential theory that a continuous and planar layer of dipoles can exactly reproduce the total-field anomaly produced by arbitrary 3D sources. We have proven the existence of an equivalent layer having an all-positive magnetic-moment distribution for the case in which the magnetization direction of this layer is the same as that of the true sources, regardless of whether the magnetization of the true sources is purely induced or not. By using this generalized positivity constraint, we have developed a new iterative method for estimating the total magnetization direction of 3D magnetic sources based on the equivalent-layer technique. Our method does not impose a priori information about the shape or the depth of the sources, does not require regularly spaced data, and presumes that the sources have a uniform magnetization direction. At each iteration, our method performs two steps. The first step solves a constrained linear inverse problem to estimate a positive magnetic-moment distribution over a discrete equivalent layer of dipoles. We consider that the equivalent sources are located on a plane and have a uniform and fixed magnetization direction. In the second step, we use the estimated magnetic-moment distribution and solve a nonlinear inverse problem for estimating a new magnetization direction for the dipoles. The algorithm stops when the equivalent layer yields a total-field anomaly that fits the observed data. Tests with synthetic data simulating different geologic scenarios show that the final estimated magnetization direction is close to the true one. We apply our method to field data from the Goiás alkaline province, over the Montes Claros complex, in the center of Brazil. The results suggest the presence of intrusions with remarkable remanent magnetization, in agreement with the current literature for this region.
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Melnyk, V. G., P. I. Borshchov, O. D. Vasylenko, O. L. Lameko, and S. V. Dzyadevyc. "DETERMINATION OF FARADAY IMPEDANCE PARAMETERS TO INCREASE ACCURACY IN CONDUCTOMETRY AND OBTAIN ADDITIONAL DATA." Sensor Electronics and Microsystem Technologies 19, no. 3 (October 18, 2022): 38–52. http://dx.doi.org/10.18524/1815-7459.2022.3.265297.
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A simple algorithm for determining the set of parameters of the equivalent circuits of the impedance of a planar conductometric transducer with an interdigital comb topology, consisting of interelectrode and Faraday impedances is proposed. The frequency characteristics of the impedance parameters of the transducer samples and the electrical equivalent with averaged values of the parameters have been studied. A technique for determining the parameters of a three-element equivalent circuit, including solution resistance, double layer capacitance, and charge transfer resistance, has been developed and tested on a series of transducer samples. The optimal operating frequencies of the impedance-measuring channel are determined, and its schemes are developed. A technique for estimating the parameters of the Warburg impedance of transducer samples is demonstrated. The results obtained in the work make it possible to determine the optimal operating frequency range of biosensor systems and reduce errors from the influence of the Faraday impedance. The possibility of extending the functions of such transducers by using the near-electrode layer impedance parameters as informative ones is shown.
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Costa e Silva, Mercia Betania, and Alexey Stovas. "Correspondence between the low- and high-frequency limits for anisotropic parameters in a layered medium." GEOPHYSICS 74, no. 2 (March 2009): WA25—WA33. http://dx.doi.org/10.1190/1.3075143.
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Wave propagation in a layered medium when the wavelength is much greater than each layer thickness (low frequency) produces a response equivalent to that of wave propagation in an equivalent single-layer medium. This equivalent medium is transversely isotropic with symmetry about a vertical axis (VTI), and the elastic parameters are computed with the Backus averaging technique. Conversely, when the wavelength is comparable to each layer thickness (high frequency), the directional dependence of the phase velocity in the transmission response also can be simulated by replacing the layered medium with a single homogeneous medium with properties derived from a time average. It then can be treated approximately as a VTI medium. To compute the medium parameters, a method based on fitting the traveltime parameters is used. We investigated the relationship between Thomsen’s anisotropic parameters [Formula: see text] and [Formula: see text] computed for the equivalent medium in the low-frequency limit and for the homogenized medium in the high-frequency limit. In our experiments, we used a medium in which layers of only two isotropic materials alternate repeatedly. For the high-frequency limit, we obtained solutions for PP- and SS-wave propagation.
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Klemp, J. B., J. Dudhia, and A. D. Hassiotis. "An Upper Gravity-Wave Absorbing Layer for NWP Applications." Monthly Weather Review 136, no. 10 (October 2008): 3987–4004. http://dx.doi.org/10.1175/2008mwr2596.1.
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Although the use of a damping layer near the top of a computational model domain has proven effective in absorbing upward-propagating gravity-wave energy in idealized simulations, this technique has been less successful in real atmospheric applications. Here, a new technique is proposed for nonhydrostatic model equations that are solved using split-explicit time-integration techniques. In this method, an implicit Rayleigh damping term is applied only to the vertical velocity, as a final adjustment at the end of each small (acoustic) time step. The adjustment is equivalent to including an implicit Rayleigh damping term in the vertical momentum equation together with an implicit vertical diffusion of w, and could be applied in this manner in other time-integration schemes. This implicit damping for the vertical velocity is unconditionally stable and remains effective even for hydrostatic gravity waves. The good absorption characteristics of this layer across a wide range of horizontal scales are confirmed through analysis of the linear wave equation and numerical mountain-wave simulations, and through simulations of an idealized squall line and of mountain waves over the Colorado Rocky Mountains.
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Liu, Qi Qiang, Mingwei Zhuang, Weichen Zhan, Na Liu, and Qing Huo Liu. "An efficient thin layer equivalent technique of SETD method for thermo-mechanical multi-physics analysis of electronic devices." International Journal of Heat and Mass Transfer 192 (August 2022): 122816. http://dx.doi.org/10.1016/j.ijheatmasstransfer.2022.122816.
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Vicentini, Rafael, Leonardo Morais Da Silva, Edson Pedro Cecilio Junior, Thayane Almeida Alves, Willian Gonçalves Nunes, and Hudson Zanin. "How to Measure and Calculate Equivalent Series Resistance of Electric Double-Layer Capacitors." Molecules 24, no. 8 (April 12, 2019): 1452. http://dx.doi.org/10.3390/molecules24081452.
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Electric double-layer capacitors (EDLCs) are energy storage devices that have attracted attention from the scientific community due to their high specific power storage capabilities. The standard method for determining the maximum power (Pmax) of these devices uses the relation Pmax = U2/4RESR, where U stands for the cell voltage and RESR for the equivalent series resistance. Despite the relevance of RESR, one can observe a lack of consensus in the literature regarding the determination of this parameter from the galvanostatic charge-discharge findings. In addition, a literature survey revealed that roughly half of the scientific papers have calculated the RESR values using the electrochemical impedance spectroscopy (EIS) technique, while the other half used the galvanostatic charge discharge (GCD) method. RESR values extracted from EIS at high frequencies (>10 kHz) do not depend on the particular equivalent circuit model. However, the conventional GCD method better resembles the real situation of the device operation, and thus its use is of paramount importance for practical purposes. In the latter case, the voltage drop (ΔU) verified at the charge-discharge transition for a given applied current (I) is used in conjunction with Ohm’s law to obtain the RESR (e.g., RESR = ΔU/ΔI). However, several papers have caused a great confusion in the literature considering only applied current (I). In order to shed light on this important subject, we report in this work a rational analysis regarding the GCD method in order to prove that to obtain reliable RESR values the voltage drop must be normalized by a factor of two (e.g., RESR = ΔU/2I).
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Murakami, Masato, Takami Akagi, Yumi Sasano, and Mitsuru Akashi. "Effect of 3D-Fibroblast Dermis Constructed by Layer-by-Layer Cell Coating Technique on Tight Junction Formation and Function in Full-Thickness Skin Equivalent." ACS Biomaterials Science & Engineering 7, no. 8 (July 21, 2021): 3835–44. http://dx.doi.org/10.1021/acsbiomaterials.1c00375.
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Desai, Siddesh, Vinayak Kulkarni, and Hrishikesh Gadgil. "Separation mitigation using pressure feedback technique for hypersonic shock wave boundary layer interaction." Proceedings of the Institution of Mechanical Engineers, Part G: Journal of Aerospace Engineering 233, no. 10 (October 14, 2018): 3519–33. http://dx.doi.org/10.1177/0954410018802959.
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Present studies are focused on the use of pressure feedback technique as a separation control technique for ramp induced flow separation at hypersonic speed. Numerical simulations portrayed that though pressure feedback technique can reduce the flow separation, further cooling of the feedback channel enhances its potential for separation control. Marginal cooling of channel walls to 175 K has reduced separation bubble size by 18.18% while strong cooling of those walls to 50 K reduced the separation by 30%. Such low enthalpy perfect gas simulations also showed the lower effectiveness of pressure feedback technique with increased ramp angle. Further, it has been noticed from the perfect and nonequilibrium gas flow simulations that the cooling of pressure feedback channel introduces differential separation size for the same wall-to-total temperature ratio cases. Integration of cooled pressure feedback channel with blunt leading edge configuration showed reduced separation size for any bluntness radius. Effectiveness of this integration is seen in lowering the values of inversion and equivalent radii. Thus, use of cooled pressure feedback technique in conjunction with leading edge bluntness is not only seen to have reduced the intensity of shock wave boundary layer interaction but also has enhanced the controllability of blunted leading edge without altering the entropy layer–boundary layer interaction.
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Kajánek, D., B. Hadzima, F. Pastorek, and M. Neslušan Jacková. "Evolution of the dicalcium phosphate-dihydrate (DCPD) coating created by large amplitude sinusoidal voltammetry (LASV) on corrosion resistance of the ZW3 magnesium alloy in chloride containing environment." Koroze a ochrana materialu 62, no. 1 (February 1, 2018): 14–18. http://dx.doi.org/10.2478/kom-2018-0003.
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Abstract The contribution is focused on the preparation of coating based on the dicalcium phosphate-dihydrate (DCPD) on the surface of ZW3 magnesium alloy. For the preparation of the coating a cathodic electrodeposition technique called Large Amplitude Sinusoidal Voltammetry (LASV) was used. The DCPD layer was prepared at the temperature of 22 ± 2 °C in electrolyte composed of 0.1M Ca(NO3).4H2O, 0.06 M NH4H2PO4 and H2O2. Electrochemical characteristics were evaluated by electrochemical impedance spectroscopy (EIS) in 0.1M NaCl solution. The obtained data in form of Nyquist plots were analysed by the equivalent circuit method. It is clear from the measured values of polarization resistance Rp that dicalcium phosphate-dihydrate (DCPD) layer prepared by LASV electro-deposition technique improved corrosion resistance of ZW3 alloy in the chosen environment.
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Chen, Shen Li, and Yet Fan Chang. "Lateral Non-Uniformity Charges Influence on Interface Trap Density (Dit) by Terman Method in the nMOS Fabrication." Advanced Materials Research 690-693 (May 2013): 1846–50. http://dx.doi.org/10.4028/www.scientific.net/amr.690-693.1846.
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Generally speaking, the oxide interface quality can be determined by the interface trap density (Dit) distribution. In this paper, the Dit quantity obtained from the Terman method, which it is assumed that the Dit is equal to zero at the beginning for simulating the Dit effect in ultra-thin oxide. However, the lateral non-uniformity charges have existed in the oxide layer, which maybe obtained an equivalent Dit density not equal to zero also producing an equivalent Dit value. And, such faked Dit will be resulted in an error in high frequency measurement. Fortunately, it can be solved by differentiating technique to obtain an accuracy Dit quantity.
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Fernández Álvarez, Humberto, María Elena de Cos Gómez, and Fernando Las-Heras Andrés. "On the Broadening of Single-Layer Metasurface Bandwidth by Coupling Resonances." Materials 13, no. 9 (April 29, 2020): 2063. http://dx.doi.org/10.3390/ma13092063.
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In this contribution a new technique to increase the bandwidth of metasurfaces without increasing their profile is presented. This work takes advantage of the potential multiresonant behavior of a metamaterial whose unit cells comprise nested metallization geometries in the same layer. The novelty stems from the possibility of overlapping these resonances for increasing the bandwidth (instead of obtaining a multiresonant metasurface). Several guidelines to achieve the aforementioned bandwidth broadening, which are applicable to all metasurface designs, will be provided. An equivalent circuit model will be used to better explain the presented technique; then, it will be applied to several metasurface absorbers (MTAs), showing not only a bandwidth broadening but also an absorption reinforcement. Measurements will be also presented to corroborate the simulation results.
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Dingenen, Fons, Natan Blommaerts, Myrthe Van Hal, Rituraj Borah, Daniel Arenas-Esteban, Silvia Lenaerts, Sara Bals, and Sammy W. Verbruggen. "Layer-by-Layer-Stabilized Plasmonic Gold-Silver Nanoparticles on TiO2: Towards Stable Solar Active Photocatalysts." Nanomaterials 11, no. 10 (October 6, 2021): 2624. http://dx.doi.org/10.3390/nano11102624.
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To broaden the activity window of TiO2, a broadband plasmonic photocatalyst has been designed and optimized. This plasmonic ‘rainbow’ photocatalyst consists of TiO2 modified with gold–silver composite nanoparticles of various sizes and compositions, thus inducing a broadband interaction with polychromatic solar light. However, these nanoparticles are inherently unstable, especially due to the use of silver. Hence, in this study the application of the layer-by-layer technique is introduced to create a protective polymer shell around the metal cores with a very high degree of control. Various TiO2 species (pure anatase, PC500, and P25) were loaded with different plasmonic metal loadings (0–2 wt %) in order to identify the most solar active composite materials. The prepared plasmonic photocatalysts were tested towards stearic acid degradation under simulated sunlight. From all materials tested, P25 + 2 wt % of plasmonic ‘rainbow’ nanoparticles proved to be the most promising (56% more efficient compared to pristine P25) and was also identified as the most cost-effective. Further, 2 wt % of layer-by-layer-stabilized ‘rainbow’ nanoparticles were loaded on P25. These layer-by-layer-stabilized metals showed superior stability under a heated oxidative atmosphere, as well as in a salt solution. Finally, the activity of the composite was almost completely retained after 1 month of aging, while the nonstabilized equivalent lost 34% of its initial activity. This work shows for the first time the synergetic application of a plasmonic ‘rainbow’ concept and the layer-by-layer stabilization technique, resulting in a promising solar active, and long-term stable photocatalyst.
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VANDENBERG, AILEEN, and KENNETH J. LOH. "EVALUATING THE PH SENSITIVITY OF CARBON NANOTUBE-POLYANILINE THIN FILMS WITH DIFFERENT DOPANTS." Nano LIFE 02, no. 04 (December 2012): 1242001. http://dx.doi.org/10.1142/s1793984412420019.
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The objective of this study is to characterize the pH sensing performance of carbon nanotube-based thin films and compare them to their non-carbon nanotube-based counterparts. A layer-by-layer technique is employed for fabricating the nanocomposites, and pH sensitivity is encoded by incorporating polyaniline (PANI) by itself or with single-walled carbon nanotubes during film fabrication. In particular, polyaniline is doped with different counter ions such as hydrochloric acid (HCl) and methane sulfonic acid (MeSA) for fabricating four different thin film sample sets. The as fabricated films are subjected to various pH buffer solutions ranging from pH 1 to 13 while their electrical properties are simultaneously measured using two different techniques. First, time-domain bulk film resistance measurements have been conducted, and the findings show that all four types of films exhibit pH sensitivity. Their bulk film resistances increase in tandem with increasing pH. Second, frequency-domain electrical impedance spectroscopy (EIS) has also been conducted when the films are exposed to different pH buffers. The recorded EIS spectra have been fit to a proposed equivalent circuit model consisting of resistors, capacitors and a constant-phase element. The results suggest that the MeSA-based films exhibit linear sensitivity, whereas the HCl-based films exhibit a bilinear sensitivity in the time-domain case. Both HCl- and MeSA-based films exhibit a bilinear pH response in the frequency domain. The equivalent circuit has also revealed that the equivalent parallel capacitor and the constant-phase element of the HCl-and MeSA-doped films also exhibit an inverse bilinear sensitivity to pH buffer solutions.
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Kuznetsov, P. L., V. A. Kuznetsova, and V. V. Muravyev. "Investigation of Tantalum Capacitors Using the Accelerated Quality Assessment Technique STRESS TEST." Intellekt. Sist. Proizv. 19, no. 4 (2021): 49–54. http://dx.doi.org/10.22213/2410-9304-2021-4-49-54.
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The paper discusses the possibility of conducting accelerated tests to assess the quality of tantalum bulk-porous capacitors according to the developed STRESS TEST technique instead of outdated methods that require costly resources for testing and do not provide proper rejection of capacitors (detection of defects in the oxide layer). It is known that the grown amorphous pentoxide is able to form a uniform layer on the surface of tantalum, but due to various factors (due to surface roughness, porosity, uneven distribution of the electrolyte during the oxidation process and the electric contact of the carrier-anode), a surface is created with "problem areas", "incomplete formation", or, in other words, a "weak spot", the rejection of which is most important for modern tantalum capacitors. A comparative analysis of the application of the standard method and the STRESS TEST technique for accelerated evaluation of the quality of tantalum bulk-porous capacitors will prove the effectiveness of the developed technique. The developed STRESS TEST technique is based on cyclic (10 cycles) application of an increased voltage to the capacitor (corresponding to the voltage during the formation of an oxide layer on a tantalum anode) for the duration of each cycle for 5 minutes, which is proved by calculating this process based on the Zhurkov reliability acceleration model. The technique makes it possible to identify low-quality capacitors in advance with defects in the structure of the oxide layer. The technique makes it possible to evaluate the quality of capacitors in an accelerated time, which is confirmed by the obtained regression model of equivalent series resistance in comparison with the regression model of the standard type of tests for long-term reliability for 24,000 hours. The application of the STRESS TEST technique for tantalum volumetrically porous capacitors will reduce the testing time by approximately two and a half years.
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Ghasemi Nejhad, Mehrdad N., Chiling Pan, and Hongwei Feng. "Intrinsic Strain Modeling and Residual Stress Analysis for Thin-Film Processing of Layered Structures." Journal of Electronic Packaging 125, no. 1 (March 1, 2003): 4–17. http://dx.doi.org/10.1115/1.1512295.
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Residual stresses develop due to intrinsic and extrinsic strains that form during the processing. Extrinsic strains can be determined using coefficient of thermal expansion, material properties, and processing conditions. An “Equivalent Reference Temperature (ERT)” technique is described and used to model and evaluate the intrinsic strains. piezoelectric microelectromechanical systems (P-MEMS) are considered in this work. Laminate theory with three-dimensional state of stress and strain is used to evaluate residual stresses using the ERT model. In finite element analysis (FEA), the residual stresses and strains of multi-layer P-MEMS structures deposited layer-by-layer during processing, are simulated using the “element birth-and-death” approach. The evaluated residual stresses for a simplified geometry using ANSYS three-dimensional FEA and analytical analysis employing three-dimensional laminate theory are presented along with their corresponding experimental results. A user-friendly software based on the 3-D laminate theory is developed and installed on the Internet. The “equivalent reference temperature” as well as residual stresses and strains can be determined using this software. The level of residual stresses and strains of P-MEMS depend upon various factors such as geometrical design, material selection, and process conditions.
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Happ, Fabian, Heinz-D. Brüns, Gazmend Mavraj, and Frank Gronwald. "Numerical computation of lightning transfer functions for layered, anisotropically conducting shielding structures by the method of moments." Advances in Radio Science 14 (September 28, 2016): 107–14. http://dx.doi.org/10.5194/ars-14-107-2016.
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Abstract. A formalism for the computation of lightning transfer functions by the method of moments, which involves shielding structures that may consist of layered, anisotropically conducting composite materials, is presented in this contribution. The composite materials, being of a type that is widely used in space- and aircraft design, are electrically characterized by an equivalent conductivity. As basis for the quantitative analysis the method of moments is used where shielding surfaces can be treated by a thin layer technique which utilizes analytical solutions inside the layer. Also the effect of an extended lightning channel can be taken into account. The method is applied to geometries that resemble an actual airplane fuselage.
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Li, Lianchun, Yifan Diao, Haijun Wu, and Weikang Jiang. "The study of ultrasonic layer-matched to penetrate bone." INTER-NOISE and NOISE-CON Congress and Conference Proceedings 263, no. 3 (August 1, 2021): 3691–98. http://dx.doi.org/10.3397/in-2021-2491.
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Acoustic metamaterial layer-matched was designed to enhance ultrasound penetration through bones. The conventional ultrasound layer-matched, known as coupling agent, can only enhance the transmittance of ultrasound to soft biological media, such as cartilage and muscle, but cannot penetrate hard media, i.e. bone. An ultrasound layer-matched based on the impedance matching principle is presented to make ultrasound penetrate bone, which parameters are designed by acoustic metamaterial equivalent parameter technique. The ultrasound layer-matched is fabricated by 3D printing which can correct the aberrations of the bone. Some configurations are investigated by numerical simulation as well as experiments in the anechoic chamber. In particular, a bone matching layer can be designed optimally for the definite thickness of the bone and the definite operating frequency of the ultrasound probe, which enhanced ultrasound to penetrate both of the layer-matched and the bone with no echo. The results of experiments and simulations show that the proposed ultrasound layer-matched metamaterial can enhance the transmission efficiency of ultrasound to penetrate some hard biological media bones.
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Men, Yu-tao, Xiao-ming Li, Ling Chen, and Hu Fu. "Experimental Study on the Mechanical Properties of Porcine Cartilage with Microdefect under Rolling Load." Journal of Healthcare Engineering 2017 (2017): 1–9. http://dx.doi.org/10.1155/2017/2306160.
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Objectives. To investigate the mechanical responses of microdefect articular cartilage under rolling load and find out the failure rule. Methods. Rolling load was applied to the porcine articular cartilage samples with rectangular notches of different depths. The displacement and strain near the notches were obtained by the noncontact digital image correlation technique. Results. The strain value and peak frequency around the notch increased; the maximum equivalent strain value could be observed at both bottom corners of the notch; the equivalent strain value first increased and then decreased at the points in the superficial and middle layers with the increase of rolling velocity; the points in the deep layer were less affected by rolling velocity; the equivalent strain value of the points in the superficial layer declined after rising with the increase of defect depth, while a decreased trend could be found for the points in the middle and deep layers. Conclusions. The shear strain, which rose with the increase in defect depth, was the main factor in cartilage destruction. The cartilage tended to be destructed firstly at the bottom corner of the defect. Rolling velocity showed significant effects on superficial and middle layers. Cartilage had the ability to resist destruction.
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Yang, Shu Yong, Li Sheng Liu, and Qing Jie Zhang. "Fracture Analysis of Functionally Graded Thermal Barrier Coating with Interface Crack by Computational Micromechanics Method." Materials Science Forum 492-493 (August 2005): 385–90. http://dx.doi.org/10.4028/www.scientific.net/msf.492-493.385.
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The fracture of the functionally graded thermal barrier coating (TBC) under the thermal loads is a key for the engineering application of this kind of materials. In the previous studies, the functionally graded TBC is usually simplified into a laminate by homogenizing the material of each interlayer as an isotropic layer. Nevertheless, this method is a macro equivalent method, which neglected the microstructure characteristics of materials. In this paper, the computational micromechanics method (CMM) is employed to study the fracture problem of the functionally graded TBC with the interface crack. Essentially, CMM is a finite element analytical method based on the real microstructure of materials, which combines the digital image processing technique, the auto mesh generation technique with the finite element method. Firstly, the microstructure photos of the functionally graded TBC are required. Secondly, the digital image processing technique and the auto mesh generation technique are used to construct the finite element model. Finally, the finite element method is utilized for the fracture analysis of the functionally graded TBC under the thermal shock loads. Moreover, the problem is also analyzed using the macro equivalent method and the results from the two methods are compared. The temperature field obtained using CMM is basically consistent with the one obtained from the macro equivalent method and the influences of the interface crack on the temperature fields are limited in a local region. But results of the driving forces for the crack propagation, J-integrals, from the two methods are quite different. Comparing with the CMM results, J-integrals from the macro equivalent method are smaller. It means that the macro equivalent method tends to underestimate the driving force of the interface crack. On the other hand, the prediction of the critical location of the interface crack from the two methods is also different. Since the influence of the microstructure is taken into account by CMM, results of the present work may suggest that CMM is a more useful and accuracy method for the fracture analysis of the functionally graded TBC.
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Shaharukh, Sk, and Achintya Dhar. "UV/Ozone Based Facile Surface Modulation Technique for Efficient Organic Thin Film Transistor." ECS Meeting Abstracts MA2022-02, no. 35 (October 9, 2022): 1270. http://dx.doi.org/10.1149/ma2022-02351270mtgabs.
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The capacity to actualize a comprehensive range of electronic functions based on organic devices is important to the development of fully functional organic electronic circuits. Specifically low voltage, quick switching transistors, in particular, have previously been demonstrated but a critical function, i.e. dependable data storage, is currently lacking. Organic thin-film transistors (OTFTs) have received a lot of interest for possible use in memory, flexible electronics such as sensors, and light-emitting diodes because of their inexpensive production costs, lightweight, mechanical flexibility, and other advantages. The most often utilised active ingredient in organic TFTs is pentacene (C22H14). The electrical properties of organic TFTs based upon pentacene, such as field-effect mobility, are equivalent to those of amorphous silicon thin film transistors (a-Si TFTs), which are typically employed for the backplane of liquid crystal displays (LCDs), but far inferior to those of generic inorganic TFTs. As a result, electrical properties for high-performance flexible electronics must be improved. The interfacial properties of active layer and gate insulator layer plays a very crucial role in determining the electrical properties of organic TFTs. Therefore in this work we report an UV/ozone treatment on the surface of gate dielectric layer so as to improve the interfacial properties. At first the glass substrate was cleaned in an ultrasonic cleaner with acetone, ethanol, isopropyl alcohol and DI water. Then by using thermal evaporation technique a gate electrode with thickness of approximately 80 nm was deposited on the substrate. Later a solution of Poly 4-vinylphenol (PVP) was spin coated with a thickness of 140 nm, this organic layer was deposited as the bottom insulator layer. Now an ozone treatment (wavelength = 253nm) for 5,10 and 20 min was done over the PVP layer. Subsequently a layer of PMMA was coated over the UV treated layer. Finally with a coating of 70nm thick pentacene active layer 100 nm thick silver drain/source electrodes with channel length of 50µm were also deposited using thermal deposition. Further the morphology and topography was studied using AFM images and element analysis was done from XPS spectra. The device performance (output and transfer characteristics) was characterized using Kiethley 4200 SCS semiconductor parameter analyser. The changes in performance of transistor devices before and after UV/ozone treatment could be explained using XPS spectra, AFM images and water contact angle measurement. It is evident from the AFM images that the grain size of pentacene on UV/Ozone treated dielectric surface are larger than the untreated surface, thus reducing the boundary scattering and enhancing the field effect mobility. Thus surface treatment with UV/Ozone could acts as simple, low cost method to enhance the performance of a organic thin film transistors.
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Gumble, Jason E., and James E. Gaiser. "Characterization of layered anisotropic media from prestack PS-wave-reflection data." GEOPHYSICS 71, no. 5 (September 2006): D171—D182. http://dx.doi.org/10.1190/1.2335419.
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Anisotropy and fracture characterization in individual layers is realized through iterative layer stripping corrections of four, converted-wave (PS-wave) synthetic reflection seismic data sets, generated from azimuthally anisotropic (HTI and TTI) models, and a four component (4-C) data set from the Teal South, Gulf of Mexico. The corrections were applied on a layer-by-layer basis to evaluate the efficacy of constant polarization rotation and time-shift operators. Equivalent isotropic models were compared to anisotropic models after layer-stripping corrections using rms amplitude and shear-wave-splitting time-difference maps to quantify and identify inherent errors in estimating seismic polarization parameters. For HTI media radial and transverse components of PS data that have had layer-stripping corrections applied, exhibit incorrect symmetry and orientations. This may adversely affect inversion and/or amplitude-variation with angle offset (AVO) and amplitude versus azimuth (AVA)analysis. Layer-stripping corrections applied to fast and slow ([Formula: see text] and [Formula: see text], respectively) components exhibit the correct symmetry and orientation. Time differences between PS1 and PS2 are computed using crosscorrelation. Previous studies have addressed some of the problems associated with layer-stripping corrections for the case of vertical fractures (HTI media) and poststack layer-stripping analyses. This study includes an equivalent model with dipping fractures (TTI media) and extends the scope to encompass the effects of anisotropy on prestack data. The results from an application of the same technique are also applied to a limited set of 4-C data from the Teal South project in the Gulf of Mexico. Results are consistent with those of previous studies involving solely poststack 4-C rotation analysis in terms of average, or zero offset, time differences and symmetry orientation. Offset and azimuth amplitude/traveltime variations, however, indicate that there is more information contained in prestack seismic data than 4-C rotation can comprehend.
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Fekete, Z., P. Fürjes, T. Kárpáti, G. A. B. Gál, and I. Rajta. "MEMS-Compatible Hard Coating Technique of Moveable 3D Silicon Microstructures." Materials Science Forum 659 (September 2010): 147–52. http://dx.doi.org/10.4028/www.scientific.net/msf.659.147.
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Mechanical degradation of mobile silicon components of complex MEMS reduces device reliability and operation time. Although the considerable wear of the surface micromachined poly-crystalline elements can be decreased by substitution of crystalline-silicon-based equivalent, there is still room for further improvement in device durability. The demonstration device is the recently presented 3D crystalline silicon micro-turbine formed by the combination of proton beam writing (PBW) and subsequent selective porous silicon (PorSi) etching. Similarly to the DRIE (deep reactive ion etching) process the novel technique is capable to provide elements of vertical walls of high aspect ratio. The 3D silicon components were uniformly covered with LPCVD Si3N4 protective layer. The Si3N4 coating improves the chemical and mechanical properties; strength, hardness and chemical resistance. The elaborated processing technology can easily be adapted for deposition of protective materials of superior properties, e.g. TiN and DLC (diamond like carbon). Present work describes alternative hard coating technique integrated in the MEMS processing sequence. The feasibility of the proposed technique is demonstrated by preliminary qualitative wear tests.
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Ungureanu, Dragoş, Nicolae Ţăranu, Iuliana Dupir, Ion Florenţa, and Vlad Lupăşteanu. "Shear Structural Response of Adhesive Joints for FRP Composites." Advanced Engineering Forum 21 (March 2017): 280–85. http://dx.doi.org/10.4028/www.scientific.net/aef.21.280.
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Adhesive bonding is a suitable joining technique for composite materials. The thick adherents shear’ tests (TASTs) are common joint-specimen tests performed to determine the adhesive shear properties. This paper presents the results of numerical modelling of several TAST specimen configurations. The numerical models were conceived considering the adherents made of fiber reinforced polymer (FRP) strips and bonded with an epoxy type adhesive. The adhesive layer thickness has varied as 1 mm, 2 mm and 3 mm, while the overlap length has been increased from 50 mm to 70 mm and 100 mm, respectively. Unidirectional tensile load of 500 N, 1000 N and 2000 N are applied and the stress-strain distributions are investigated. The results are presented in terms of total deformation, equivalent stress (von-Mises) and equivalent strain (von-Mises).
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Aguilar Cruz, Karen Alicia, José de Jesús Medel Juárez, José Luis Fernández Muñoz, and Midory Esmeralda Vigueras Velázquez. "Neural Net Gains Estimation Based on an Equivalent Model." Computational Intelligence and Neuroscience 2016 (2016): 1–10. http://dx.doi.org/10.1155/2016/1690924.
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A model of an Equivalent Artificial Neural Net (EANN) describes the gains set, viewed as parameters in a layer, and this consideration is a reproducible process, applicable to a neuron in a neural net (NN). The EANN helps to estimate the NN gains or parameters, so we propose two methods to determine them. The first considers a fuzzy inference combined with the traditional Kalman filter, obtaining the equivalent model and estimating in a fuzzy sense the gains matrixAand the proper gainKinto the traditional filter identification. The second develops a direct estimation in state space, describing an EANN using the expected value and the recursive description of the gains estimation. Finally, a comparison of both descriptions is performed; highlighting the analytical method describes the neural net coefficients in a direct form, whereas the other technique requires selecting into the Knowledge Base (KB) the factors based on the functional error and the reference signal built with the past information of the system.
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Pan, Tongyan, and Qifeng Yu. "Comprehensive evaluation of anti-corrosion capacity of electroactive polyaniline for steels." Anti-Corrosion Methods and Materials 63, no. 5 (2016): 360–68. http://dx.doi.org/10.1108/acmm-10-2014-1452.
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Purpose This study aims to present the fabrication of the two-layer system, coating it on steel surface and evaluating the system’s anti-corrosion performance using the ASTM Standard Salt-Spray Test: B117 and the technique of Electrochemical Impedance Spectroscopy (EIS). Design/methodology/approach A synthesized electroactive polyaniline (PANi) was utilized in this study to make a PANi-based primer, with which a two-layer coating system was fabricated by overlaying the primer with a polyurethane top-coat. Findings In the Salt-Spray test, the two-layer PANi/polyurethane system exhibited higher corrosion resistance than the two-layer control epoxy/polyurethane system. In particular, the PANi/polyurethane system tended to mitigate the production of rust on substrate surface and demonstrated higher delamination resistance. The EIS analysis confirmed the high corrosion resistance and delamination resistance of the two-layer PANi/polyurethane system based on parameters obtained using the best-fit equivalent circuits. Practical implications The demonstrated anti-corrosion capacity of this new PANi/polyurethane system laid a solid base for industrial applications. Originality/value This novel coating system is expected to achieve improved corrosion protection for steels than the conventional zinc-rich three-layer coatings.
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Tawfeic, S. R., A. Baz, A. A. Ismail, O. A. Azim, and S. S. Karar. "Vibration Control of a Flexible Arm with Active Constrained Layer Damping." Journal of Low Frequency Noise, Vibration and Active Control 16, no. 4 (December 1997): 271–87. http://dx.doi.org/10.1177/026309239701600405.
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The vibration of a single link flexible manipulator is attenuated using the Active Constrained layer damping (ACLD) treatment. The ACLD treatment consists of a viscoelastic layer sandwiched between two piezo-electric layers acting as constraining layers with sensing and actuation capabilities. The shear deformation of the visco-elastic layer is controlled to enhance the energy dissipation mechanism and attenuate the vibration of the flexible manipulator. A finite element model is used to describe the dynamics of the system. A third order polynomial is used to describe the lateral displacement of the manipulator and a second order polynomial is used to describe the longitudinal displacements of the different layers of the manipulator. An appropriate control law is used to control the system. The Coupled Modal Strain energy technique is used to compute the equivalent viscous damping ratios for the elastic layer using the loss factor data of the material. The theoretical predictions of the model are compared with the experimental performance of a manipulator fully treated with a Dyad 606 visco-elastic layer sandwiched between two layers of polyvinylidene fluoride (PVDF) piezo-electric films. The results obtained clearly demonstrate the attenuation capabilities of the Actively-Controlled Constrained Layer Damping.
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Mao, Yong Jian, Hong Jian Deng, Yu Long Li, Rong Jian He, Hong Wei Xiao, Xiao Hong Yue, Hai Ying Huang, and Qing Zhou. "A Rod-Explosive Technique for Testing Structural Responses Induced by X-Ray Blow-Off Impulses." Applied Mechanics and Materials 29-32 (August 2010): 72–77. http://dx.doi.org/10.4028/www.scientific.net/amm.29-32.72.
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When a structure is irradiated by a pulsed cold X-ray with high energy density, the instantaneous deposition of energy will induce melting, vaporization, and sublimation of the outer layer of material(s). As a result, the material(s) will blow off and hence lead to a so-called blow-off impulse. This kind of impulsive load will cause high-level structural responses. In order to investigate the effects, various test simulation techniques, such as the light-initiated high explosive (LIHE) technique, the spray lead at target (SPLAT) technique and the sheet-explosive technique, were developed due to the lack of proper X-ray sources. This paper presents a rod-explosive technique developed from the sheet-explosive technique. In this technique, the main property of the explosive, i.e. the specific impulse, is determined by using a pendulum test facility. The simulation load (equivalent to the cosine-distributed specific impulse on a conical shell induced by X-ray) is designed by load discretization and impulse equivalence. Numerical simulations of structural responses to both X-ray loads and rod-explosive loads were performed for validating the test simulation technique. An application example of testing a complex structure is briefly given in the end. The rod-explosive technique has the features of low costs and rather high fidelities. It provides a new approach for testing the structural responses induced by X-ray blow-off impulses.
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Sellitto, Andrea, R. Borrelli, Francesco Caputo, Aniello Riccio, and Francesco Scaramuzzino. "Application of the Mesh Superposition Technique to the Study of Delaminations in Composites Thin Plates." Key Engineering Materials 525-526 (November 2012): 533–36. http://dx.doi.org/10.4028/www.scientific.net/kem.525-526.533.
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Laminated composite structures are increasingly finding more applications in various fields thanks to their lower weight if compared with other materials of the same strength. Nevertheless, composites thin plates show a critical behavior in terms of damage propagation mechanisms when subjected to (low velocity) impact. Indeed they tend to produce delaminations which can be hardly detected by optical inspections and can affect the global load carrying capability, leading to a premature structural collapse. The aim of this paper is to assess the capabilities of the Davies-Zhang approach (introduced in 1994 and aimed to the estimation of both the delamination initiation impact load and the size of the impact induced delaminations) by using a multiscale FE model based on the mesh superposition technique. Indeed the impact area has been modeled layer-wise with an element per layer while the rest of the structure has been modeled at laminate level by layered elements by means of a homogenization approach for the determination of the equivalent laminate material properties. The impact induced delamination area has been determined by adopting stress-based criteria. The results (in terms of delamination initiation impact force and delamination size) have been compared to the ones obtained by adopting the Davies-Zhang approach.
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Salazar Betancourt, Luis Fernando, Patrice Laure, Luisa Silva, and Mustafa Sager. "Numerical Implementation of a Rheology Model for Fiber-Reinforced Composite and Viscous Layer Approach for Friction Study." Key Engineering Materials 651-653 (July 2015): 848–54. http://dx.doi.org/10.4028/www.scientific.net/kem.651-653.848.
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A transverse isotropic viscous model accounting for the anisotropy exhibited in fiber-reinforced composite is integrated in the numerical platform of the software Rem3D®. Simulations under various mechanical loading are tested for volume fiber concentrations of 3.5% and 14.7%. Equivalent stresses and equivalent strain rate deformations given by the software were compared to the ones predicted by the model, finding very good agreements. As a second point developed on this paper, we comment on the slip condition between Die/Punch tool with the composite under compression. We noticed that the variation of the viscosity value on a small layer between the Die/Punch tooland the composite affects the nature of the contact. A viscous friction is then formulated as a technique to set slip/no-slip contact condition. We found that the slip condition is recovered at lower values of the viscosity in the interface Die/Punch with the reinforced composite, whereas the no slip condition stated for higher viscosity values.
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Kemelbay, Tikhonov, Aloni, and Kuykendall. "Conformal High-K Dielectric Coating of Suspended Single-Walled Carbon Nanotubes by Atomic Layer Deposition." Nanomaterials 9, no. 8 (July 28, 2019): 1085. http://dx.doi.org/10.3390/nano9081085.
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As one of the highest mobility semiconductor materials, carbon nanotubes (CNTs) have been extensively studied for use in field effect transistors (FETs). To fabricate surround-gate FETs— which offer the best switching performance—deposition of conformal, weakly-interacting dielectric layers is necessary. This is challenging due to the chemically inert surface of CNTs and a lack of nucleation sites—especially for defect-free CNTs. As a result, a technique that enables integration of uniform high-k dielectrics, while preserving the CNT’s exceptional properties is required. In this work, we show a method that enables conformal atomic layer deposition (ALD) of high-k dielectrics on defect-free CNTs. By depositing a thin Ti metal film, followed by oxidation to TiO2 under ambient conditions, a nucleation layer is formed for subsequent ALD deposition of Al2O3. The technique is easy to implement and is VLSI-compatible. We show that the ALD coatings are uniform, continuous and conformal, and Raman spectroscopy reveals that the technique does not induce defects in the CNT. The resulting bilayer TiO2/Al2O3 thin-film shows an improved dielectric constant of 21.7 and an equivalent oxide thickness of 2.7 nm. The electrical properties of back-gated and top-gated devices fabricated using this method are presented.
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Al-Zoubi, Omar H., and Hameed Naseem. "Enhancing the Performance of the Microwave Absorbing Materials by Using Dielectric Resonator Arrays." Modelling and Simulation in Engineering 2017 (2017): 1–8. http://dx.doi.org/10.1155/2017/3658247.
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We present a technique for enhancing the performance of microwave absorbing materials in terms of weight, thickness, and bandwidth. The introduced technique is based on fabricating the microwave absorbing (MA) material in a structure comprised of an array of circular cylinder dielectric resonators (CDR) backed by a perfect electric conductor (PEC) ground plane. Numerical electromagnetic methods are employed to study the properties of the proposed MA array structures, where 3D full wave simulation using finite-element method is implemented. The obtained results show that the performance of the MA-CDR arrays significantly outperforms that of a flat layer composed of the same material and having equivalent thickness. A flat layer of MA material with thickness of 5 mm backed by perfect electric conductor (PEC) shows as low as -50 dB reflection loss (RL) peak and ~3 GHz 10-dB bandwidth, whereas an MA-CDR array, composed of the same MA material, of height of 4 mm can achieve as low as ~−50 dB RL peak and ~12 GHz 10-dB RL bandwidth.
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Ali, Aidy, Wei Kuan Ng, Faiz Arifin, Kannan Rassiah, Faiz Othman, Shauqi Hazin, and Megat Hamdan Megat Ahmad. "Fracture properties of hybrid woven bamboo/woven e-glass fiber composites." International Journal of Structural Integrity 9, no. 4 (August 13, 2018): 491–519. http://dx.doi.org/10.1108/ijsi-09-2017-0051.
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Purpose The purpose of this paper is to investigate the fracture properties of hybrid woven bamboo (WB)/woven e-glass (EG) fiber composites with various layer arrangements. This paper utilized a specific type of bamboo species named Gigantochloa Scortechinii (Buluh Semantan). Design/methodology/approach In these experiments, unsaturated polyester, woven EG and WB fibers were prepared through the hand lay-up technique. The composite bamboo strips were prepared in 1.5 mm thickness. The strips are woven to make a single layer. The layer was then laminated into several thicknesses. The specimens were then characterized using compact tension fracture tests. Findings The fracture toughness of 12–14 MPa was obtained. These findings suggest that this hybrid bamboo composite provides superior fracture strength that is equivalent with steel alloy and is extremely a good alternative for reinforcing fibers to combat fracture failures of materials and structures. Originality/value In this paper, experimental determination of newly developed composite made of WB and woven EG is presented.
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Goykhman, Yuriy, and Mahta Moghaddam. "Retrieval of Parameters for Three-Layer Media with Nonsmooth Interfaces for Subsurface Remote Sensing." International Journal of Antennas and Propagation 2012 (2012): 1–12. http://dx.doi.org/10.1155/2012/563730.
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A solution to the inverse problem for a three-layer medium with nonsmooth boundaries, representing a large class of natural subsurface structures, is developed in this paper using simulated radar data. The retrieval of the layered medium parameters is accomplished as a sequential nonlinear optimization starting from the top layer and progressively characterizing the layers below. The optimization process is achieved by an iterative technique built around the solution of the forward scattering problem. The forward scattering process is formulated by using the extended boundary condition method (EBCM) and constructing reflection and transmission matrices for each interface. These matrices are then combined into the generalized scattering matrix for the entire system, from which radar scattering coefficients are then computed. To be efficiently utilized in the inverse problem, the forward scattering model is simulated over a wide range of unknowns to obtain a complete set of subspace-based equivalent closed-form models that relate radar backscattering coefficients to the sought-for parameters including dielectric constants of each layer and separation of the layers. The inversion algorithm is implemented as a modified conjugate-gradient-based nonlinear optimization. It is shown that this technique results in accurate retrieval of surface and subsurface parameters, even in the presence of noise.
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Yasin, Abdul, Muhammad Ashraf, and Aamer Bhatti. "A Novel Filter Extracted Equivalent Control Based Fixed Frequency Sliding Mode Approach for Power Electronic Converters." Energies 12, no. 5 (March 5, 2019): 853. http://dx.doi.org/10.3390/en12050853.
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The key issue in the implementation of the Sliding Mode Control (SMC) in analogue circuits and power electronic converters is its variable switching frequency. The drifting frequency causes electromagnetic compatibility issues and also adversely affect the efficiency of the converter, because the proper size of the inductor and the capacitor depends upon the switching frequency. Pulse Width Modulation based SMC (PWM-SMC) offers the solution, however, it uses either boundary layer approach or employs pulse width modulation of the ideal equivalent control signal. The first technique compromises the performance within the boundary layer, while the latter may not possess properties like robustness and order reduction due to the absence of the discontinuous function. In this research, a novel approach to fix the switching frequency in SMC is proposed, that employs a low pass filter to extract the equivalent control from the discontinuous function, such that the performance and robustness remains intact. To benchmark the experimental observations, a comparison with existing double integral type PWM-SMC is also presented. The results confirm that an improvement of 20% in the rise time and 25.3% in the settling time is obtained. The voltage sag during step change in load is reduced to 42.86%, indicating the increase in the robustness. The experiments prove the hypothesis that a discontinuous function based fixed frequency SMC performs better in terms of disturbances rejection as compared to its counterpart based solely on ideal equivalent control.
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Щербинский and Viktor Shcherbinskii. "Effective Method of Correction of Acoustic Losses in a Contact Layer at Ultrasonic Flaw Detection." NDT World 18, no. 3 (September 1, 2015): 45–46. http://dx.doi.org/10.12737/12570.
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At ultrasonic flaw detection it is necessary to take into account an acoustic loss in a contact layer, especially for products with a statistically rough surface (roughness, waviness). Using samples with the surface identical to the product’s one is the most desirable variant, it is regulated in many techniques, but in practice in vast majority of cases this is not so. Measurements with profilographs or profilometers are taken on a very small area (less than the piezoelectric transducer size) and cannot give an estimation of a real contact layer condition under the whole transducer area. For integral roughness estimation in “CNIITMASH” the capacitance-type sensor DShV has been developed. The sensor is compatible with flaw detectors of any type; it forms a service signal with amplitude that is inversely proportional to a roughness height.
Within a frequency rate of 1.8–5 MHz and an incident angle rate of 35–70° the correlation between sensor readings and acoustic losses in a contact layer has been ascertained; a general dependence for them has been obtained, a heuristic equation has been derived and nomograms for piezoelectric transducers of different manufacturers on the sample basis of 123 measurements have been plotted.
As a result the new technique of ultrasonic flaw detection has been developed that includes: estimation of tested object real surface roughness with the DShV sensor, flaw detector sensitivity adjustment using a sample with a smooth surface, a gain factor correction by the value taken from a nomogram or calculated on the formula basis. Equivalent defect area should also be measured according to the algorithm described. This technique on principle increases repeatability and reliability of flaw detection results.
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Lynn, Walt, Scott MacKay, and Craig J. Beasley. "Efficient migration through complex water‐bottom topography." GEOPHYSICS 58, no. 3 (March 1993): 393–98. http://dx.doi.org/10.1190/1.1443422.
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An efficient means of imaging structures beneath complex water‐bottom topography is obtained using a conventional time‐migration algorithm with a simple modification to the migration‐velocity field. The process consists of two migration steps: one with the migration velocity set to zero below the water bottom and the other with the migration velocity set to zero above the water bottom. Between the two steps the data are vertically time shifted to account for the lateral velocity variations between the water‐sediment interface. The time shifts used are equivalent to the so‐called “thin‐lens” term used in depth‐migration algorithms. Efficiency is obtained by applying the thin‐lens term only once and by using computationally optimized time‐migration algorithms. Results obtained from this technique are nearly identical to more costly wave‐equation, layer‐replacement, and depth‐migration techniques.
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Rahmawati, E., D. R. Santoso, J. A. F. Noor, and A. Nadhir. "Electrical impedance analysis of NaCl and CaCl2 solutions based on equivalent electric circuit." Journal of Physics: Conference Series 2165, no. 1 (January 1, 2022): 012025. http://dx.doi.org/10.1088/1742-6596/2165/1/012025.
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Abstract In this paper, we report the behaviour of electrical impedance of sodium chloride (NaCl) and Calcium chloride (CaCl2) with the concentration of 1.25 to 100 mM/L in frequencies ranging from 10 mHz to 1 MHz. The complex electrical impedance (real and imaginary parts) is obtained using the electrical impedance spectroscopy (EIS) technique. The experimental data had been fitted with three models of equivalent electrical circuit (EEC), model-a is Randles circuit, model-b consist of R solution (Rs) in series with constant phase element (CPE) and model-c consist of Randles circuit in series with CPE. Best fit data is obtained from model-c with goodness of fit less than 0.005. The CPE in this circuit associated with the electric double-layer. As expected from the experimental and fitting spectra, even for a low concentration for both salts, an inverse relationship was observed between impedance and salt concentration. The number of ions contains in CaCl2, which are more than NaCl is estimated to be the cause that CaCl2 impedance is lower than NaCl. The total impedance influenced by the CPE component increased significantly at frequencies about 100 Hz, indicating that the equivalent electric circuit used can estimate the effect of double-layer on the measurement.
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Aleksandrov, Samuil R., Timo T. Overboom, and Elena A. Lomonova. "2D Hybrid Steady-State Magnetic Field Model for Linear Induction Motors." Mathematical and Computational Applications 24, no. 3 (July 25, 2019): 74. http://dx.doi.org/10.3390/mca24030074.
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This paper presents a 2D hybrid steady-state magnetic field model, capable of accurately modeling the electromagnetic behavior in a linear induction motor, including primary slotting, finite yoke length, and longitudinal end-effects by primary motion. This model integrates a complex harmonic modeling technique with a discretized magnetic equivalent circuit model. The Fourier model is applied to regions with homogeneous material properties, e.g., air regions and the track of the motor, while the magnetic equivalent circuit (MEC) approach is used for the regions containing non-homogeneous material properties, e.g., the primary of the linear induction motor (LIM). By only meshing the domains containing highly-permeable materials, the computational effort is reduced in comparison with the finite element method (FEM). The model is applied to a double-layer single-sided LIM, and the resulting thrust and normal forces show an excellent agreement with respect to finite element analysis and measurement data.
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Habib, Khaled, K. Al-Muhanna, F. Al-Sabti, and A. Al-Arbeed. "Measurement of Aluminium Oxide-Film Thickness: Barrier Oxide Film and Oxide Porous Layer." Defect and Diffusion Forum 273-276 (February 2008): 283–93. http://dx.doi.org/10.4028/www.scientific.net/ddf.273-276.283.
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In the present investigation, holographic interferometry was utilized for the first time to measure in situ the thickness of the oxide film, alternating current (A.C.) impedance, and double layer capacitance of aluminium samples during anodization processes in aqueous solution without any physical contact. The anodization process (oxidation) of the aluminium samples was carried out by the electrochemical impedance spectroscopy (EIS), in different concentrations of sulphuric acid (0.5-2.5 % H2SO4) at room temperature. In the mean time, the real-time holographic interferometric was used to measure the thickness of anodized (oxide) film of the aluminium samples in aqueous solutions. Also, mathematical models were applied to measure the alternating current (A.C.) impedance, and double layer capacitance of aluminium samples by holographic interferometry, during anodization processes in aqueous solution. Consequently, holographic interferometric is found very useful for surface finish industries especially for monitoring the early stage of anodization processes of metals, in which the thickness of the anodized film, the A.C. impedance, and the double layer capacitance of the aluminium samples in sulphuric acid (0.5-2.5 % H2SO4) can be determined in situ. Futhermore, a comparison was made between the electrochemical values obtained from the holographic interferometry measurements and from measurements of electrochemical impedance spectroscopy(EIS) on aluminium samples in sulphuric acid (0.5-2.5 % H2SO4). The comparison indicates that there is good agreement between the obtained electrochemical data from both techniques. However, there is a drastic difference between the measurement of the oxide film thickness by both techniques. The oxide film thickness of the aluminium samples in 0, 0.5, 1.0, 1.5, 2.0, 2.5% H2SO4 by the optical interferometry is in a micrometer scale. However, the oxide film thickness of the aluminium samples in 0, 0.5, 1.0, 1.5, 2.0, 2.5% H2SO4 by the E.I.Spectroscopy in a nanometer scale. This can be explained due to the fact that the E.I.Spectroscopy is useful technique to measure the electrochemical parameters and the thickness of the barrier (compact) oxide films. In contrast, the optical interferometry is found useful technique to characterize and measure the thickness of the porous oxide layer. Also, the optimum thickness of the oxide barrier film was detected to be equivalent to 0.612nm in sulphuric acid concentration of 2.5% H2SO4 by E.I. spectroscopy.
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Kamm, Jochen, Michael Becken, and Rafael Abreu. "Electromagnetic modelling with topography on regular grids with equivalent materials." Geophysical Journal International 220, no. 3 (December 13, 2019): 2021–38. http://dx.doi.org/10.1093/gji/ggz563.
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SUMMARY Maxwell’s equations are valid regardless of the choice of the coordinate system. By this property a change of coordinates can be equivalently expressed as a change of the material parameters. This idea opens a new approach to the problem of accurate electromagnetic modelling in the vicinity of steep topography or bathymetry. Via a change of coordinates, any earth model with complicated layer interfaces can be represented by an equivalent model where those interfaces are flat, but with its materials correspondingly altered. This new model could then be discretized on a regular mesh and fields could be computed by an appropriate finite difference or integral equation code. Unfortunately, this is not straightforward because both the new electric and magnetic materials are fully anisotropic. By instead applying a finite element secondary field approach to the equivalent model, we can completely account for the topography interface in the planar layered background model. The only modification required to existing finite element formulations is a slightly more complicated right-hand side of the linear system of equations, whereas the system matrix is unchanged in any coordinate system. In a numerical modelling experiment we confirm that our technique gives increased accuracy when compared with a recently published technique for dealing with topography in a secondary field formulation for the case of a magnetotelluric source field. In turn, in the vicinity of conductivity anomalies, accuracy can also be negatively affected.
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Acuña, T. L. Botwright, and L. J. Wade. "Root penetration ability of wheat through thin wax-layers under drought and well-watered conditions." Australian Journal of Agricultural Research 56, no. 11 (2005): 1235. http://dx.doi.org/10.1071/ar05067.
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Sand over clay duplex soils and those compacted by heavy farm machinery restrict water infiltration and root growth because roots cannot penetrate hard soil. Under drought, restriction of roots to soil above the hard layer results in the early onset of plant water-deficit, unless roots can penetrate the hard layer to reach soil water and nutrients at depth. There is little to no information on the ability of roots of bread wheat (Triticum aestivum L.) to penetrate hardpans. Here we report on 3 experiments undertaken in a controlled environment in pots that validate and explore the use of thin Paraffin wax–Vaseline (WV) layers of different strengths to simulate a hardpan under contrasting water regimes. Seeds produced an average of 5 seminal roots, which all penetrated the low-impedance wax-layer (0.03WV), in such a way that seminal root dry matter (DM) was evenly distributed throughout the soil profile. The number and depth of penetrating seminal root axes declined as wax-layer strength increased, and a significant proportion of total length and DM of main seminal root axes was instead restricted to the 0–0.12-m soil layer above the wax layer. No roots penetrated the 0.60WV, which was equivalent to ~1.50 MPa penetrometer resistance. The distribution of seminal roots was less affected by water regime than nodal roots, which were severely reduced in number when drought was imposed at 14 days after sowing (DAS), compared with well-watered conditions. Growth of the seminal roots into soil beneath the wax-layer determined the pattern of stomatal conductance and volumetric soil water content (Jv) over the period of drought stress, as few nodal roots reached and penetrated the wax layer. Stomatal conductance declined suddenly at 19 days after the last irrigation, and partially recovered as water extraction increased in the 0.40–0.60-m soil depth. Reasons for this are discussed. The wax-layer technique requires validation for wheat in the field, but the technique offers promise for screening breeding lines for the ability to penetrate a hardpan.
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Araujo, Jefferson F. D. F., Andre L. A. Reis, Angela A. P. Correa, Elder Yokoyama, Vanderlei C. Oliveira, Leonardo A. F. Mendoza, Marcos A. C. Pacheco, et al. "Scanning Magnetic Microscope Using a Gradiometric Configuration for Characterization of Rock Samples." Materials 12, no. 24 (December 11, 2019): 4154. http://dx.doi.org/10.3390/ma12244154.
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Scanning magnetic microscopy is a tool that has been used to map magnetic fields with good spatial resolution and field sensitivity. This technology has great advantages over other instruments; for example, its operation does not require cryogenic technology, which reduces its operational cost and complexity. Here, we presented a spatial domain technique based on an equivalent layer approach for processing the data set produced by magnetic microscopy. This approach estimated a magnetic moment distribution over a fictitious layer composed by a set of dipoles located below the observation plane. For this purpose, we formulated a linear inverse problem for calculating the magnetic vector and its amplitude. Vector field maps are valuable tools for the magnetic interpretation of samples with a high spatial variability of magnetization. These maps could provide comprehensive information regarding the spatial distribution of magnetic carriers. In addition, this approach might be useful for characterizing isolated areas over samples or investigating the spatial magnetization distribution of bulk samples at the micro and millimeter scales. This technique could be useful for many applications that require samples that need to be mapped without a magnetic field at room temperature, including rock magnetism.