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1
Weigand, M., and A. Kemna. "Debye decomposition of time-lapse spectral induced polarisation data." Computers & Geosciences 86 (January 2016): 34–45. http://dx.doi.org/10.1016/j.cageo.2015.09.021.
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Ustra, Andrea, Carlos Alberto Mendonça, Dimitrios Ntarlagiannis, and Lee D. Slater. "Relaxation time distribution obtained from a Debye decomposition of spectral induced polarization data." GEOPHYSICS 81, no. 2 (March 1, 2016): E129—E138. http://dx.doi.org/10.1190/geo2015-0095.1.
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We have developed an alternative formulation for Debye decomposition of complex electric conductivity spectra, by recasting it into a new set of parameters with a close relationship to the continuous formulation for the complex conductivity method. The procedure determines a relaxation time distribution (RTD) and two frequency-independent parameters that modulate the complex conductivity spectra. These two parameters represent (1) the direct current contribution and (2) the conductivity range spanned by the low- and high-frequency limits. The distribution of relaxation times quantifies the contribution of each distinct relaxation process. Assuming that characteristic times with insignificant contributions can be ignored, a minimum set of characteristic relaxation times is determined. Each contribution can then be associated with specific polarization processes that can be interpreted in terms of electrochemical or interfacial parameters of mechanistic models derived from inverted parameters obtained from the proposed approach. Synthetic tests show that the procedure can fit spectral induced polarization (SIP) data and successfully retrieve the RTD. We have applied the procedure to laboratory SIP data from experiments with sand and oil mixtures undergoing microbial degradation of hydrocarbons. The RTD reveals evidence of a length scale at which a new polarization process takes place as a result of the biodegradation process.
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Wolpmann, Marius, Lars Robben, and Thorsten M. Gesing. "Halide-sodalites: thermal expansion, decomposition and the Lindemann criterion." Zeitschrift für Kristallographie - Crystalline Materials 237, no. 1-3 (February 7, 2022): 39–50. http://dx.doi.org/10.1515/zkri-2022-0004.
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Abstract Twelve cubic sodalites |Na8X2|[T1T2O4]6 (T1 = Al3+, Ga3+; T2 = Si4+, Ge4+; X = Cl−, Br−, I−) were examined using high-temperature (HT) X-ray diffraction experiments and TGA-DSC measurements. Temperature-dependent structure data was obtained by Rietveld refinements. Decomposition temperatures were determined using TGA-DSC data for all compounds. The temperature-dependent volume expansion was used to determine Debye and Einstein temperatures using DEA fits. Distinct relations between thermal expansion, bond lengths and the decomposition temperature could not be found. Determination of Lindemann constants of all compounds enables a classification of the sodalites in three groups.
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Grosse, C., R. Barchini, C. Halloy, and R. Pottel. "On the decomposition of the Maxwell mixture formula into a sum of Debye type contributions." Journal of Physics D: Applied Physics 19, no. 10 (October 1, 1986): 1957–64. http://dx.doi.org/10.1088/0022-3727/19/10/021.
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Černý, R. "Powder Pattern Decomposition with the Aid of Preferred Orientation - Use of the Whole Debye-Scherrer Ring." Materials Science Forum 378-381 (October 2001): 24–29. http://dx.doi.org/10.4028/www.scientific.net/msf.378-381.24.
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Gurin, Grigory, Andrey Tarasov, Yuri Ilyin, and Konstantin Titov. "Time domain spectral induced polarization of disseminated electronic conductors: Laboratory data analysis through the Debye decomposition approach." Journal of Applied Geophysics 98 (November 2013): 44–53. http://dx.doi.org/10.1016/j.jappgeo.2013.07.008.
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Goel, S. P., and P. N. Mehrotra. "A new Debye-Scherrer pattern of caesium molybdate prepared by the thermal decomposition of caesium oxomolybdenum(VI) oxalate." Journal of the Less Common Metals 106, no. 1 (March 1985): 27–33. http://dx.doi.org/10.1016/0022-5088(85)90362-5.
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Gurin, G. V., A. V. Tarasov, Yu T. Il’in, and K. V. Titov. "Application of the Debye decomposition approach to analysis of induced-polarization profiling data (Julietta gold-silver deposit, Magadan Region)." Russian Geology and Geophysics 56, no. 12 (December 2015): 1757–71. http://dx.doi.org/10.1016/j.rgg.2015.11.008.
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Georgescu, Vasile, Gabriel Vasilievici, Mihaela Bombos, and Casen Panaitescu. "Study of Co-Cr Mixed Oxides for Different Applications." Revista de Chimie 68, no. 9 (October 15, 2017): 2039–42. http://dx.doi.org/10.37358/rc.17.9.5817.
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Mixture metal oxide system Co-Cr were prepared by decomposition of the precursor complexes obtained from a mixture Co-Cr nitrates with tartaric acid. The samples were subsequently submitted to chemical analysis, magnetic measurements, IR spectrometry, UV-Vis, thermal analysis, XRD, EXAFS and TPR. At 600oC was identificated a solid solution of CoCr2O4 with Co3O4. With Cu-CrK-edge EXAFS the local structure of samples calcinated of 420oC and 600oC was obtained. By theirs analysis was calculated: the lengths of M-O bounds, number of coordination (N), Debye-Waller factor (A1) and x metallic cations fraction in tetrahedral structures (spinelic centers). The TPR measurements were emphasized the existence of two reduction cycles.
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BAZAVOV, ALEXEI, BERND A. BERG, and ALEXANDER VELYTSKY. "EVOLUTION OF THE STRUCTURE FACTORS IN PURE SU(N) LATTICE GAUGE THEORY AND EFFECTIVE SPIN MODELS." International Journal of Modern Physics A 20, no. 15 (June 20, 2005): 3459–68. http://dx.doi.org/10.1142/s0217751x05026777.
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We consider model A dynamics for a quench from the disordered into the ordered phase of SU (3) lattice gauge theory and the analogue 3d 3-state Potts model. For the gauge model this corresponds to a rapid heating from the confined to the deconfined phase. The exponential growth factors of low-lying structure function modes are numerically calculated. The linear theory of spinodal decomposition is used to determine the critical modes. This allows for the Debye screening mass estimation in an effective phenomeno-logical model. The quench leads to competing vacuum domains, which make the equilibration of the QCD vacuum after the heating non-trivial. The influence of such domains on the gluonic energy density is studied.
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Hansen, Anna-Lena, Bastian Dietl, Martin Etter, Reinhard K. Kremer, David C. Johnson, and Wolfgang Bensch. "Temperature-dependent synchrotron X-ray diffraction, pair distribution function and susceptibility study on the layered compound CrTe3." Zeitschrift für Kristallographie - Crystalline Materials 233, no. 6 (June 27, 2018): 361–70. http://dx.doi.org/10.1515/zkri-2017-2100.
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Abstract Results of combined synchrotron X-ray diffraction and pair distribution function experiments performed on the layered compound CrTe3 provide evidence for a short range structural distortion of one of the two crystallographically independent CrTe6 octahedra. The distortion is caused by higher mobility of one crystallographically distinct Te ion, leading to an unusual large Debye Waller factor. In situ high temperature X-ray diffraction investigations show an initial crystallization of a minor amount of elemental Te followed by decomposition of CrTe3 into Cr5Te8 and Te. Additional experiments provide evidence that the Te impurity (<1%) cannot be avoided. Analyses of structural changes in the temperature range 100–754 K show a pronounced anisotropic expansion of the lattice parameters. The differing behavior of the crystal axes is explained on the basis of structural distortions of the Cr4Te16 structural building units. An abrupt distortion of the structure occurs at T≈250 K, which then remains nearly constant down to 100 K. The structural distortion affects the spin exchange interactions between Cr3+ cations. A significant splitting between field-cooled (fc) and zero-field-cooled (zfc) magnetic susceptibility is observed below about 200 K. Applying a small external magnetic field results in a substantial spontaneous magnetization, reminiscent of ferro- or ferrimagnet exchange interactions below ~240 K. A Debye temperature of ~150 K was extracted from heat capacity measurements.
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Yin, Ming, and Stephen O’Brien. "Synthesis and Characterization of Nanostructured Nickel Diselenide NiSe2from the Decomposition of Nickel Acetate, (CH3CO2)2Ni." Journal of Nanomaterials 2014 (2014): 1–7. http://dx.doi.org/10.1155/2014/503676.
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Solution processed NiSe2nanorods were synthesized by a modified colloidal synthesis technique, by chemical reaction of TOPSe and nickel acetate at150°C. The rods exist as an oleic acid ligand stabilized solution, with oleic acid acting as a capping group. Structural characterization by X-ray diffraction and transmission electron microscopy indicates that the particles are rod-like shaped crystals with a high and relatively constant aspect ratio (30 : 1). TEM shows that the width and the length of the nanorods are in the range 10–20 nm and 300–350 nm, respectively. XRD indicates that the nanorods are pure and well crystallized. The size of nanorods based on the Debye-Scherrer effect, was 150 nm, the average value of length and width. They display thermal stability over prolonged heating times (<100 hours) at150°C, for which the average particle size is roughly constant. After about 100 hours of heating time there is an onset and growth of micron sized cubes and concurrent decomposition of NiSe2to Ni and NiSe at150°C.
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Ducasse, Eric, and Marc Deschamps. "A nonstandard wave decomposition to ensure the convergence of Debye series for modeling wave propagation in an immersed anisotropic elastic plate." Wave Motion 49, no. 8 (December 2012): 745–64. http://dx.doi.org/10.1016/j.wavemoti.2012.05.001.
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Cercignani, Carlo, Irene M. Gamba, Joseph W. Jerome, and Chi-Wang Shu. "Applicability of the High Field Model: An Analytical Study Via Asymptotic Parameters Defining Domain Decomposition." VLSI Design 8, no. 1-4 (January 1, 1998): 135–41. http://dx.doi.org/10.1155/1998/54618.
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In this paper, we present a mesoscopic-macroscopic model of self-consistent charge transport. It is based upon an asymptotic expansion of solutions of the Boltzmann Transport Equation (BTE). We identify three dimensionless parameters from the BTE. These parameters are, respectively, the quotient of reference scales for drift and thermal velocities, the scaled mean free path, and the scaled Debye length. Such parameters induce domain dependent macroscopic approximations. Particular focus is placed upon the so-called high field model, defined by the regime where drift velocity dominates thermal velocity. This model incorporates kinetic transition layers, linking mesoscopic to macroscopic states. Reference scalings are defined by the background doping levels and distinct, experimentally measured mobility expressions, as well as locally determined ranges for the electric fields. The mobilities reflect a coarse substitute for reference scales of scattering mechanisms. See [9] for elaboration.The high field approximation is a formally derived modification of the augmented drift-diffusion model originally introduced by Thornber some fifteen years ago [25]. We are able to compare our approach with the earlier kinetic approach of Baranger and Wilkins [5] and the macroscopic approach of Kan, Ravaioli and Kerkhoven [20].
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Onderka, B., J. Unland, and R. Schmid-Fetzer. "Thermodynamics and phase stability in the In–N system." Journal of Materials Research 17, no. 12 (December 2002): 3065–83. http://dx.doi.org/10.1557/jmr.2002.0445.
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Results of a chemical vapor deposition crystal growth method intended to produce large amounts of InN needed for thermodynamic experiments are reported. Polycrystalline films of InN were grown by reaction of InCl3 and NH3 in a hot-wall silica reactor under nearly atmospheric pressure. Samples were analyzed using x-ray diffraction and chemical analysis. The decomposition of InN was studied in both thin film and powder form. InN films were investigated by isothermal heating under nitrogen and subsequent microscopic inspection. The removal of the nucleation barrier of forming the first liquid phase was emphasized. InN powder decomposition experiments involved two different customized thermogravimetric methods: (i) dynamic oscillation thermogravimetric analysis (TGA), and (ii) isothermal stepping TGA for a higher resolution of the decomposition start. The decomposition start was found consistently at (773 ±5) K under 1 bar of nitrogen. Nevertheless, it is suggested that InN may be metastable even below room temperature based on Computer Coupling of Phase Diagrams and Thermo chemistry-type thermodynamic analysis of all available phase equilibrium and thermodynamic data. This included the determination of the absolute entropy of InN, 31.6 ±3 J/mol-formula K, based on a Debye and Einstein analysis of the experimental data on the heat capacity. All calculations of pressure are corrected for the fugacity of nitrogen, which becomes crucial above 1000 bar. The contradictory literature data in the In–N system are discussed based on three different internally consistent thermodynamic analyses of the system that highlight the consequences of different choices made on the decomposition temperature of InN. Widely reproduced data in the literature are shown to produce thermodynamically impossible negative absolute entropy of InN. Complete P-T-x phase diagrams are given, which strongly suggest that solid InN is metastable under ambient conditions. To find out that InN crystals could be reproducibly superheated more than 500 K before they actually decompose comes as a surprise compared to other III-V systems, especially Ga–N.
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Pickles, C. A., J. Mouris, and R. M. Hutcheon. "High-Temperature Dielectric Properties of Goethite From 400 to 3000 MHz." Journal of Materials Research 20, no. 1 (January 2005): 18–29. http://dx.doi.org/10.1557/jmr.2005.0012.
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The dielectric properties of goethite and, in particular, the changes during the topotactic conversion of goethite to hematite were studied from room temperature to about 800 °C in the frequency range of 400 to 3000 MHz using the cavity perturbation technique. The complex permittivity, that is, both the real and the imaginary or absorptive parts (έ and ἕ), were measured under various heating regimens. In addition, thermogravimetric analysis (TGA) was performed to characterize the transformation of goethite to hematite. The Debye relaxation formalism was applied to the processes occurring both during and after the main dehydroxylation reaction to calculate the relaxation times. The Arrhenius equation for thermally activated relaxation times was used to determine the activation energies. Both the real and the absorptive parts of the permittivity exhibited a significant peak during the main part of the goethite to hematite decomposition reaction. Above the transformation, there was another, less dramatic, thermally activated increase in the permittivity values. The increase in the permittivities during the goethite to hematite transformation was attributed to the formation of quasi-free migrating radicals, for example, hydroxyl ions, oxygen ions, or hydrogen atoms, during the dehydroxylation of goethite. The derivative thermogravimetric analysis (DTGA) curve was found to be directly related to the transient values of the real and the imaginary permittivities. Higher heating rates resulted in an accelerated rate of dehydroxylation and therefore higher values of the transient permittivities. In the temperature range of 400 °C to 500 °C (i.e., just above the dehydroxylation peak), the real permittivity exhibited a varying frequency dependence, which suggested that changes were occurring in the newly formed, highly defected hematite structure, which is referred to as hydrohematite. During the reaction there were multiple relaxation processes and thus the Debye relationship could not be applied. However, at temperatures above about 500 °C, the structure stabilized, the Debye relationship was more closely followed, and the relaxation times could be determined as a function of temperature. The activation energy for the relaxation process above 500 °C was determined to be 0.47 kJ/mol.
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de Lima Batista, Anderson Márcio, Marcus Aurélio Ribeiro Miranda, Fátima Itana Chaves Custódio Martins, Cássio Morilla Santos, and José Marcos Sasaki. "Synthesis of cerium oxide (CeO2) by co-precipitation for application as a reference material for X-ray powder diffraction peak widths." Powder Diffraction 33, no. 1 (January 21, 2018): 21–25. http://dx.doi.org/10.1017/s0885715617001208.
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Several methods can be used to obtain, from powder diffraction patterns, crystallite size and lattice strain of polycrystalline samples. Some examples are the Scherrer equation, Williamson–Hall plots, Warren/Averbach Fourier decomposition, Whole Powder Pattern Modeling, and Debye function analysis. To apply some of these methods, it is necessary to remove the contribution of the instrument to the widths of the diffraction peaks. Nowadays, one of the main samples used for this purpose is the LaB6 SRM660b commercialized by the National Institute of Standard Technology; the width of the diffraction peak of this sample is caused only by the instrumental apparatus. However, this sample can be expensive for researchers in developing countries. In this work, the authors present a simple route to obtain micron-sized polycrystalline CeO2 that have a full width at half maximum comparable with the SRM660b and therefore it can be used to remove instrumental broadening.
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Peschke, Irma, Lars Robben, Christof Köhler, Thomas Frauenheim, Josef-Christian Buhl, and Thorsten M. Gesing. "Crystal structure and temperature-dependent properties of Na2H4Ga2GeO8 – a novel gallogermanate." Zeitschrift für Naturforschung B 75, no. 9-10 (November 26, 2020): 805–13. http://dx.doi.org/10.1515/znb-2020-0159.
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AbstractSynthesis, crystal structure and temperature-dependent behavior of Na2H4Ga2GeO8 are reported. This novel gallogermanate crystallizes in space group I41/acd with room-temperature powder diffraction lattice parameters of a = 1298.05(1) pm and c = 870.66(1) pm. The structure consists of MO4 (M = Ga, Ge) tetrahedra in four-ring chains, which are connected by two different (left- and right-handed) helical chains of NaO6 octahedra. Protons coordinating the oxygen atoms of the GaO4 tetrahedra not linked to germanium atoms ensure the charge balance. Structure solution and refinement are based on single crystal X-ray diffraction measurements. Proton positions are estimated using a combined approach of DFT calculations and NMR, FTIR and Raman spectroscopic techniques. The thermal expansion was examined in the range between T = 20(2) K and the compound’s decomposition temperature at 568(5) K, in which no phase transition could be observed, and Debye temperatures of 266(11) and 1566(65) K were determined for the volume expansion.
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Etape, Ekane Peter, Josepha Foba-Tendo, Lambi John Ngolui, Beckley Victorine Namondo, Fomogne Cyrille Yollande, and Marius Borel Nguefack Nguimezong. "Structural Characterization and Magnetic Properties of Undoped and Ti-Doped ZnO Nanoparticles Prepared by Modified Oxalate Route." Journal of Nanomaterials 2018 (2018): 1–9. http://dx.doi.org/10.1155/2018/9072325.
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Ti-doped zinc oxide and pure zinc oxide nanoparticles were synthesized by a modified oxalate route using Averrhoa carambola fruit juice as a natural source of oxalate. The characteristics of the precursors have been investigated by FTIR, TGA, and XRD. The results from the investigation revealed that the precursors are zinc oxalate and Ti-doped zinc oxalate which readily decompose at 450°C. The as-prepared precursors were calcined at 450°C for 4 hours, and the decomposition products have been characterized by XRD, SEM, EDX, and VSM. XRD results revealed crystallinity with hexagonal wurtzite structure, while the average grain size was found to be 26 nm for Ti-doped ZnO and 29 nm for ZnO, using calculations based on Debye-Scherrer equation. Furthermore, the morphological studies by SEM showed particle agglomeration, while the presence of Ti3+ in the zinc oxide lattice is indicated by EDS analysis. Finally the hysteresis loop from VSM results shows that Ti-doped ZnO exhibits ferromagnetism.
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Razmara, M. F., C. M. B. Henderson, R. A. D. Pattrick, A. M. T. Bell, and J. M. Charnock. "The crystal chemistry of the solid solution series between chalcostibite (CuSbS2) and emplectite (CuBiS2)." Mineralogical Magazine 61, no. 404 (February 1997): 79–88. http://dx.doi.org/10.1180/minmag.1997.061.404.08.
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AbstractSulphosalts in the system CuSbS2-CuBiS2 (chalcostibite-emplectite) form a complete solid solution series. Seven compositions with the general formula Cu(SbxBi1–x)S2 have been synthesized using dry methods at 310°C. All members of the series are orthorhombic (space group Pnma) and show smoothly increasing a and b cell parameters with substitution of Bi for Sb; the c cell parameter increases up to 50% CuBiS2 substitution and then becomes constant. DSC experiments on CuBiS2 show an endothermic heat effect (2.45 kJ/mol.) at 472°C due to the breakdown reaction to Cu3BiS3 (wittichenite) plus Bi2S3 (bismuthinite). With the addition of 10% CuSbS2 to CuBiS2, the decomposition temperature increases and the endothermic peak is broadened but the energy remains essentially the same (2.53 kJ/mol.). No evidence of this decomposition was observed when the amount of the CuSbS2 component was >30%. The local structure and co-ordination of Cu in the samples were studied by EXAFS analysis of the Cu-K edge but no significant variation occurs in the local Cu environment. The Debye-Waller factor for the first shell of S atoms surrounding Cu in end member CuSbS2 tends to be slightly smaller than for the intermediate solid solutions, suggesting that the tetrahedral Cu environments in the intermediate composition samples is somewhat more disordered than in the end-member. The low expansion characteristics along c appear to be controlled by the linkages between the (CuS3 + BiS2) sheets perpendicular to c being relatively inflexible.
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Honkimäki, V., and P. Suortti. "Whole-pattern fitting in energy-dispersive powder diffraction." Journal of Applied Crystallography 25, no. 2 (April 1, 1992): 97–104. http://dx.doi.org/10.1107/s0021889891010786.
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A new procedure of pattern decomposition in energy-dispersive powder diffraction is presented. The total observed pattern is taken as a sum of incoherent and coherent scattering. The incoherent part is calculated from theoretical cross sections for individual atoms, the coherent part is described as a sum of discrete Bragg peaks and acoustic and optic phonon thermal diffuse scattering (TDS) is calculated from the Debye and Einstein models, respectively. The total TDS is scaled to be the scattering missing from the Bragg reflections due to thermal motion. The model pattern is convoluted by the instrument function calculated from the diffraction geometry, and the pattern is fitted to the observed one by varying the integrated Bragg intensities and thermal motion parameters. The method is applied to patterns of Mg, Al and Ti powders, leading to an unambiguous and self-consistent division to the background and the pattern of Bragg reflections. As an application, the flux of continuous radiation from a W-anode X-ray tube is determined using theoretical integrated Bragg intensities.
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Sun, Jianguo. "3-D crosswell transmissions: Paraxial ray solutions and reciprocity paradox." GEOPHYSICS 60, no. 3 (May 1995): 810–20. http://dx.doi.org/10.1190/1.1443819.
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Transmission of seismic waves through a 3-D earth model is of fundamental importance in seismology. If the model consists of many layers separated by curved interfaces, the only feasible solution to the transmitted waves is the one given by the geometrical optics approximation. Transmitted rays, transmitted wavefield, and the first Fresnel zone associated with a transmission point can be expressed by four 2 × 2 constant matrices constituting the 4 × 4 linearized ray transformation matrix. Generally, the ray transformation matrix can be constructed by dynamic ray tracing. However, if the layers are homogeneous, it can be formulated in closed form by using elementary vector calculus and coordinate transformations. Using the symplecticity of the ray transformation matrix, transmissions in opposite directions can be formulated by the ray transformation matrix for only one direction, and a reciprocity relation can be established. After the decomposition theorem for the ray transformation matrix, the transmitted wavefield in a model with many curved interfaces can be computed in a cascaded way. Using the [Formula: see text]‐matrix decomposition theorem, the normalized geometrical spreading factor can be expressed by means of the area of the first Fresnel zone of a transmission point. If seismic waves propagate through a locally spherical interface, the reciprocity relation may not hold. Using ray theory, this fact is shown by formulating the transmitted wavefield with the two principal radii of curvature of the transmitted wavefront at the transmission point under consideration. Using wave theory, this fact is shown by analyzing the Debye integral with the method of stationary phase.
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TAN, XUE-RONG, XIAO-HUI DUAN, CHONG-HUA PEI, and HONG-LIN XU. "PREPARATION OF NANO-TATB BY SEMIBATCH REACTION CRYSTALLIZATION." Nano 08, no. 05 (August 18, 2013): 1350055. http://dx.doi.org/10.1142/s1793292013500550.
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The 1,3,5-triamino-2,4,6-trinitrobenzene (TATB) nanoparticles were prepared by using semibatch reaction crystallization method, and the influencing factors in close relationship with the grain size and crystal morphology control, such as the concentration of reaction system and categories of surfactants, were studied in this paper. The synthesized nano-TATB particles had been characterized by SEM, XRD, thermo gravimetric/differential scanning calorimetric (TG/DSC) and N 2 physisorption. The grain size of TATB particles using nonionic surfactant as the additive ranged from 30 nm to 65 nm with a shape of spheres or ellipsoids. The broadening of the peaks and the weakening of the strength for nano-TATB were observed by XRD analysis. The corrected average particle size of nano-TATB was calculated using the Debye–Scherrer equation and the range was from 18 nm to 50 nm. TG and DSC curves revealed that thermal decomposition of nano-TATB occurred in the range of 361.5°C–385.0°C and its peak temperature was 373.7°C with a decrease of approximately 7°C compared with original TATB. Furthermore, the specific surface area (21.54 m2/g) of nano-TATB was calculated by BET method using N 2 physisorption (at 77°C).
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Mandal, T. K. "Rietveld refinement on XRD and TEM study of nanocrystalline PbZr0:5Ti0:5O3 ceramics prepared with a soft chemistry route." Materials Science-Poland 33, no. 1 (March 1, 2015): 18–24. http://dx.doi.org/10.1515/msp-2015-0040.
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AbstractPbZr0:5Ti0:5O3 nanopowders (~27 nm) have been prepared by a controlled reconstructive thermal decomposition and crystallization from an amorphous polymeric precursor with polyvinyl alcohol (PVA) and sucrose at 400 to 700 °C in air. The Rietveld refinement of the XRD profiles which were recorded at room temperature for the PbZr0:5Ti0:5O3 powder prepared by a thermal treatment at 700 °C for 2 h, confirmed the P4mm tetragonal crystal structure of the as prepared PbZr0:5Ti0:5O3 nanopowders, with a = 0.4036 nm and c = 0.4147 nm. A hexagonal symmetry (R3c), with a = 0.5774 nm and c = 1.4212 nm, was also detected from Rietveld refinement analysis. Thus, tetragonal and hexagonal phases were found to coexist with the as prepared PbZr0:5Ti0:5O3 nanopowders. The average particle size (D) of the PbZr0:5Ti0:5O3 powders, estimated with the help of the specific surface area, measured by BET method, was 26.1 nm. Average D value, calculated by D2θ1/2 in the XRD peaks with the Debye-Scherrer relation was ~24 nm. TEM study made it possible to measure the particle size of PbZr0:5Ti0:5O3 powders with an average diameter of 27 nm.
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Heenan, Jeffrey, Abigail Porter, Dimitrios Ntarlagiannis, Lily Y. Young, Dale D. Werkema, and Lee D. Slater. "Sensitivity of the spectral induced polarization method to microbial enhanced oil recovery processes." GEOPHYSICS 78, no. 5 (September 1, 2013): E261—E269. http://dx.doi.org/10.1190/geo2013-0085.1.
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The demand for more efficient and economic oil recovery techniques has driven research into novel extraction approaches, including microbial enhanced methods. Microbial enhanced oil recovery (MEOR) is an underutilized technology that could significantly enhance tertiary oil recovery. Previous research has shown the spectral induced polarization (SIP) method to be sensitive to microbial degradation of hydrocarbons, so the method should therefore be sensitive to MEOR treatments. To test this hypothesis, heavy-oil-containing sands were monitored for a period of approximately six months while undergoing MEOR treatment. SIP monitoring showed significant sensitivity to biodegradation induced changes. Increases in phase and imaginary conductivity, with a polarization peak centered on approximately 3–8 Hz, were observed for the two MEOR active columns. Similarly, the normalized chargeability, an integrated parameter of a Debye decomposition analysis of the spectra, showed a linear increase in time. Chromatographic methods confirmed oil biodegradation in the active columns. The SIP responses are likely the result of microbial processes and the changes they promote to oil properties, such as altering wettability, or possibly the effect of organic acid production. The results of this experiment indicate that SIP may be a viable method of monitoring MEOR processes.
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Chariton, Stella, Catherine McCammon, Denis M. Vasiukov, Michal Stekiel, Anastasia Kantor, Valerio Cerantola, Ilya Kupenko, et al. "Seismic detectability of carbonates in the deep Earth: A nuclear inelastic scattering study." American Mineralogist 105, no. 3 (March 1, 2020): 325–32. http://dx.doi.org/10.2138/am-2020-6901.
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Abstract Carbonates play an important role in the transport and storage of carbon in the Earth’s mantle. However, the abundance of carbon and carbonates in subduction zones is still an unknown quantity. To determine the most abundant accessory phases and how they influence the dynamical processes that operate within the Earth, investigations on the vibrational, elastic, and thermodynamic properties of these phases are crucial for interpreting seismological observations. Recently, the nuclear inelastic scattering (NIS) method has proved to be a useful tool to access information on the lattice dynamics, as well as to determine Debye sound velocities of Fe-bearing materials. Here we derive the acoustic velocities from two carbonate compositions in the FeCO3-MgCO3 binary system up to ~70 GPa using the NIS method. We conclude that more Mg-rich samples, in this case (Fe0.26Mg0.74)CO3, have ~19% higher sound velocities than the pure end-member Fe composition. In addition, we observed a significant velocity increase after the Fe2+ spin transition was complete. After laser heating of FeCO3 at lower mantle conditions, we observed a dramatic velocity drop, which is probably associated with thermal decomposition to another phase. Parallel to our NIS experiments, we conducted a single-crystal X-ray diffraction (SCXRD) study to derive the equation of states of FeCO3 and (Fe0.26Mg0.74)CO3. The combined information from NIS (i.e., Debye velocities) and SCXRD (i.e., densities and bulk moduli) experiments enabled us to derive the primary and shear wave velocities of our samples. Our results are consistent with results obtained by other methods in previous studies, including Brillouin spectroscopy, inelastic X-ray scattering, and DFT calculations, supporting NIS as a reliable alternative method for studying the elastic properties of Fe-bearing systems at high pressures and temperatures. Finally, we discuss the seismic detectability of carbonates. We determine that nearly 22 wt% CO2 must be present in the subduction slab to detect a 1% shear wave velocity decrease compared to non-carbonated lithologies at the transition zone to lower mantle boundary depths.
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Zisser, Norbert, Andreas Kemna, and Georg Nover. "Relationship between low-frequency electrical properties and hydraulic permeability of low-permeability sandstones." GEOPHYSICS 75, no. 3 (May 2010): E131—E141. http://dx.doi.org/10.1190/1.3413260.
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The relationship between low-frequency electrical properties and hydraulic permeability of rocks has been the focus of geophysical investigations for a long time because it offers a possibility for an in situ and noninvasive permeability estimation of rocks. We examined the hydraulic and low-frequency [Formula: see text] electrical properties as well as the anisotropic properties of low-permeability sandstones from a tight gas reservoir. Single-frequency electrical properties were found to be of low value for the determination of permeability for the studied samples, whereas a strong link between the spectral-induced polarization (SIP) response and permeability was found. The SIP response was transformed into a relaxation-time distribution using a Debye decomposition procedure. We observed a strong positive correlation in form of a power law between median relaxation time of the distribution and permeability, suggesting that relaxation time is a good measure of the effective hydraulic length scale. From a comparison of our results with published relationships between relaxation time and permeability, it becomes evident that the corresponding function is formation specific, requiring a separate calibration for each formation. Nevertheless, SIP offers a high potential for in situ permeability determination because estimation of permeability from relaxation time seems to be applicable for very different lithologies.
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Attwa, M., and T. Günther. "Spectral induced polarization measurements for predicting the hydraulic conductivity in sandy aquifers." Hydrology and Earth System Sciences 17, no. 10 (October 22, 2013): 4079–94. http://dx.doi.org/10.5194/hess-17-4079-2013.
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Abstract. Field and laboratory spectral induced polarization (SIP) measurements are integrated to characterize the hydrogeological conditions at the Schillerslage test site in Germany. The phase images are capable of monitoring thin peat layers within the sandy aquifers. However, the field results show limitations of decreasing resolution with depth. In comparison with the field inversion results, the SIP laboratory measurements show a certain shift in SIP response due to different compaction and sorting of the samples. The SIP data are analyzed to derive an empirical relationship for predicting the hydraulic conductivity (K). In particular, two significant but weak correlations between individual real resistivities (ρ') and relaxation times (τ), based on a Debye decomposition (DD) model, with measured K are found for the upper groundwater aquifer. The maximum relaxation time (τmax) and logarithmically weighted average relaxation time (τlw) show a better relation with K values than the median value τ50. A combined power law relation between individual ρ' and τ with K is developed with an expression of A · (ρ')B · (τlw)C, where A, B and C are determined using a least-squares fit between the measured and predicted K. The suggested approach with the calculated coefficients of the first aquifer is applied for the second. Results show good correlation with the measured K indicating that the derived relationship is superior to single phase angle models as Börner or Slater models.
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Iram, Sadia, Azhar Mahmood, Muhammad Fahad Ehsan, Asad Mumtaz, Manzar Sohail, Effat Sitara, Shehla Mushtaq, et al. "Impedance Spectroscopy Analysis of PbSe Nanostructures Deposited by Aerosol Assisted Chemical Vapor Deposition Approach." Nanomaterials 11, no. 11 (October 23, 2021): 2817. http://dx.doi.org/10.3390/nano11112817.
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This research endeavor aimed to synthesize the lead (II) diphenyldiselenophosphinate complex and its use to obtain lead selenide nanostructured depositions and further the impedance spectroscopic analysis of these obtained PbSe nanostructures, to determine their roles in the electronics industry. The aerosol-assisted chemical vapor deposition technique was used to provide lead selenide deposition by decomposition of the complex at different temperatures using the glass substrates. The obtained films were revealed to be a pure cubic phase PbSe, as confirmed by X-ray diffraction analysis. SEM and TEM micrographs demonstrated three-dimensionally grown interlocked or aggregated nanocubes of the obtained PbSe. Characteristic dielectric measurements and the impedance spectroscopy analysis at room temperature were executed to evaluate PbSe properties over the frequency range of 100 Hz–5 MHz. The dielectric constant and dielectric loss gave similar trends, along with altering frequency, which was well explained by the Koops theory and Maxwell–Wagner theory. The effective short-range translational carrier hopping gave rise to an overdue remarkable increase in ac conductivity (σac) on the frequency increase. Fitting of a complex impedance plot was carried out with an equivalent circuit model (Rg Cg) (Rgb Qgb Cgb), which proved that grains, as well as grain boundaries, are responsible for the relaxation processes. The asymmetric depressed semicircle with the center lower to the impedance real axis provided a clear explanation of non-Debye dielectric behavior.
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Bérubé, Charles L., and Pierre Bérubé. "Data-driven modeling of time-domain induced polarization." GEOPHYSICS 87, no. 3 (April 1, 2022): E135—E146. http://dx.doi.org/10.1190/geo2021-0497.1.
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Induced polarization (IP) measurements are affected by various types of noise, which should be removed prior to data interpretation. However, existing data processing methods often rely on empirical assumptions about the standard shape of IP decay curves. Our goal is to introduce a data-driven approach for modeling and processing time-domain IP measurements. To reach this goal, we train a variational autoencoder (VAE) on 1,600,319 IP decays collected in Canada, the United States, and Kazakhstan. The proposed deep learning approach is unsupervised and avoids the pitfalls of IP parameterization with empirical Cole-Cole and Debye decomposition models, simple power-law models, or mechanistic models. Four applications of VAEs are key to modeling and processing IP data: (1) synthetic data generation, (2) Bayesian denoising, (3) evaluation of signal-to-noise ratio, and (4) outlier detection. Furthermore, we interpret the IP data compilation’s latent representation and reveal a correlation between its first dimension and the average chargeability. Finally, we determine that a single real-valued scalar parameter contains sufficient information to encode IP data. This new finding suggests that modeling time-domain IP data using mathematical models governed by more than one free parameter is ambiguous, whereas modeling only the average chargeability is justified. A pretrained implementation of the VAE model is available as open-source Python code.
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Weller, Andreas, Sven Nordsiek, and Wolfgang Debschütz. "Estimating permeability of sandstone samples by nuclear magnetic resonance and spectral-induced polarization." GEOPHYSICS 75, no. 6 (November 2010): E215—E226. http://dx.doi.org/10.1190/1.3507304.
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Two techniques to estimate permeability are compared in this paper: nuclear magnetic resonance (NMR) and spectral-induced polarization (SIP). Both methods are based on relaxation processes. NMR records the relaxation of hydrogen nuclei after excitation in an external magnetic field. The phenomenon of induced polarization can be characterized by a relaxation of ions after excitation by an electric field. Hydrogen nuclei are concentrated in the pore water, the current flow is restricted to the pore space for most reservoir rocks, and permeability is related to the pore space geometry. Based on the similarity between fluid movement and current flow in the pore space, different relations have been published linking parameters derived from NMRand SIP data to predict permeability. NMR, SIP and permeability data have been acquired on 53 sandstone samples of the cretaceous Bahariya Formation (Western Desert, Egypt) including 27 samples showing a lamination that causes anisotropy. We compare the applicability of known and generalized relations for permeability prediction including isotropic and anisotropic samples. Because NMR relaxation ignores directionality of pore space geometry, the known relations provide only a weak accuracy in permeability estimation. The integrating parameters derived from a Debye decomposition of SIP data are partly sensitive to anisotropy. A generalized power-law relation using resistivity, chargeability, and mean relaxation time provide a reliable permeability prediction for isotropic and anisotropic samples.
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Williams, Celia K., William C. Galley, and G. Ronald Brown. "The influence of competing factors on the endothermic nature of bile salt binding by cationic adsorbent." Canadian Journal of Chemistry 81, no. 2 (February 1, 2003): 133–40. http://dx.doi.org/10.1139/v03-003.
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The binding of sodium chenodeoxycholate, a hydrophobic bile salt, by a polyacrylamide resin with N,N,N-trimethylammonium dodecyl chloride (QPDA12) pendant groups was studied in the presence of elevated concentrations of competing anions. The equilibrium bile salt concentration was determined from HPLC data for a range of initial bile salt concentrations. Binding constants extracted from the fit of the isotherms to the Langmuir equation were obtained for data for temperatures from 24 to 60°C. A reduction in chenodeoxycholate binding affinity was observed in comparison with that reported previously at lower overall anion concentrations. A van't Hoff analysis of the data revealed that a decrease in the favourable entropy of binding was responsible for this reduced affinity. Decomposition of the binding constants into specific contributions for the competing buffer anions and the chenodeoxycholate anion returned positive values of ΔH° and ΔS° for the binding of both the competing ions and bile salt. These findings reveal that the weakening of the bile salt binding that occurs with added salt is not due to Debye screening of an attraction between ions of opposite charge. A binding mechanism consistent with the thermodynamics observed was proposed in which the dominant role of hydration changes that occur on binding provides the principal driving force for the process.Key words: bile salts, endothermic binding, polymer sorbents, solvent randomization.
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Pratt, Dyan L., and Terrance A. Fonstad. "Speciation and Geochemical Implications of Carcass Burial Leachate." Transactions of the ASABE 61, no. 2 (2018): 559–70. http://dx.doi.org/10.13031/trans.12447.
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Abstract. In the event of a mass livestock mortality situation, disposal routes such as burial are commonly chosen. The impact of burial on the environment could be substantial, but the composition of the leachate arising from a burial site has not been well documented. This study was performed to determine the chemical composition of leachate arising from animal mortalities in a burial setting. Three species of livestock were used: bovine, swine, and poultry. Leachate collected from lined burial pits over two years of decomposition was analyzed for major and minor ions. Analysis indicated that livestock mortality leachate contains, on average, concentrations of 46,000 mg L-1 of alkalinity (as bicarbonate), 12,600 mg L-1 of ammonium-N, 2600 mg L-1 of chloride, 3600 mg L-1 of sulfate, 2300 mg L-1 of potassium, 1800 mg L-1 of sodium, and 1500 mg L-1 of phosphorus, along with lesser amounts of iron, calcium, and magnesium. Select samples had maximum concentrations of ammonium-N and bicarbonate up to 50% higher than these average values. In comparison to earthen swine manure storages and landfills, the ionic strength of the leachate was 2 to 4 times higher, and therefore its impact on water resources could be greater. Following the study of the chemical composition of livestock mortality leachate, the potential impacts of this leachate on the soil/water systems below a burial site were investigated. The ionic strength of the leachate presents its own set of challenges. Basic modeling of ion activity using the five most common activity coefficient equations (Debye-Hückel, extended Debye-Hückel, Truesdell-Jones, Davies, and Pitzer) were considered to assess the sensitivity of these methods for calculated ion activity as impacted by the ionic strength of the leachate. This was completed to further enhance the modeling and speciation efforts. Based on the results and the applicability of the Truesdell-Jones equation, PHREEQC was used to assess the chemical speciation of the leachate. The speciation of this leachate provides evidence of phosphate and sulfate compounds available for potential unattenuated transport. Understanding the geochemical implications of livestock mortality burial will give scientists and regulators more information for performing future risk analyses when considering mortality burial as a management option, either routinely or during a mass mortality event. Keywords: Ion activity coefficient, Ionic strength, Leachate chemical composition, Livestock burial leachate, Speciation.
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Iram, Sadia, Azhar Mahmood, Muhammad Fahad Ehsan, Asad Mumtaz, Manzar Sohail, Effat Sitara, Syeda Aqsa Batool Bukhari, et al. "Impedance Spectroscopic Study of Nickel Sulfide Nanostructures Deposited by Aerosol Assisted Chemical Vapor Deposition Technique." Nanomaterials 11, no. 5 (April 24, 2021): 1105. http://dx.doi.org/10.3390/nano11051105.
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This research aims to synthesize the Bis(di-isobutyldithiophosphinato) nickel (II) complex [Ni(iBu2PS2)] to be employed as a substrate for the deposition of nickel sulfide nanostructures, and to investigate its dielectric and impedance characteristics for applications in the electronic industry. Various analytical tools including elemental analysis, mass spectrometry, IR, and TGA were also used to further confirm the successful synthesis of the precursor. NiS nanostructures were grown on the glass substrates by employing an aerosol assisted chemical vapor deposition (AACVD) technique via successful decomposition of the synthesized complex under variable temperature conditions. XRD, SEM, TEM, and EDX methods were well applied to examine resultant nanostructures. Dielectric studies of NiS were carried out at room temperature within the 100 Hz to 5 MHz frequency range. Maxwell-Wagner model gave a complete explanation of the variation of dielectric properties along with frequency. The reason behind high dielectric constant values at low frequency was further endorsed by Koops phenomenological model. The efficient translational hopping and futile reorientation vibration caused the overdue exceptional drift of ac conductivity (σac) along with the rise in frequency. Two relaxation processes caused by grains and grain boundaries were identified from the fitting of a complex impedance plot with an equivalent circuit model (Rg Cg) (Rgb Qgb Cgb). Asymmetry and depression in the semicircle having center present lower than the impedance real axis gave solid justification of dielectric behavior that is non-Debye in nature.
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Weller, Andreas, Lee Slater, Sven Nordsiek, and Dimitrios Ntarlagiannis. "On the estimation of specific surface per unit pore volume from induced polarization: A robust empirical relation fits multiple data sets." GEOPHYSICS 75, no. 4 (July 2010): WA105—WA112. http://dx.doi.org/10.1190/1.3471577.
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We analyze the relationship between induced polarization (IP) parameters and the specific surface area normalized to the pore volume [Formula: see text] for an extensive sample database. We find that a single linear imaginary conductivity-[Formula: see text] relation holds across a range of single-frequency IP data sets composed of sandstones and unconsolidated sediments that lack an appreciable metallic mineral content. We also apply a recent approach defined as Debye decomposition (DD) to determine normalized chargeability [Formula: see text], a global estimate of polarization magnitude from available spectral IP (SIP) data sets. A strong linear relationship between [Formula: see text] and [Formula: see text] is also found across multiple data sets. However, SIP model parameters determined for samples containing metallic minerals are approximately two orders of magnitude greater than for the model parameters estimated for the nonmetallic sample database. We propose a concept of “polarizability of the mineral-fluid interface per unit [Formula: see text]” to explain this difference, which is supported by the observed dependence of IP parameters on fluid conductivity between sample types. We suggest that this linear IP-[Formula: see text] relation can be considered the IP equivalent of the classical Archie empirical relation. Whereas the Archie relation describes a power-law relation between electrical conductivity due to electrolytic conduction through the available interconnected pore volume, the IP-[Formula: see text] relation is an equivalent relation between mineral-fluid interfacial polarization and available pore surface area.
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Zhang, Zeyu, Andreas Weller, Sabine Kruschwitz, and Sven Nordsiek. "Effect of evaporative drying on complex conductivity spectra of sandstones." GEOPHYSICS 84, no. 1 (January 1, 2019): MR61—MR72. http://dx.doi.org/10.1190/geo2018-0054.1.
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Dehydration is a common process occurring in natural environments, rocks, and building materials. Suitable methods for monitoring the changing moisture content should be identified. We have investigated the impact of dehydration of sandstones on complex conductivity spectra. Spectral induced polarization measurements were performed on five sandstone samples during evaporative drying. The complex conductivity spectra indicate considerable changes with decreasing saturation. The relationship between conductivity and saturation can be described by a power law known as the second empirical Archie equation. Separate saturation exponents have been determined for the real and imaginary parts of conductivity. The imaginary part of conductivity indicates higher saturation exponents for the investigated sandstones compared to the real part. Obviously, the saturation exponents depend on the method used for changing water saturation. Evaporative drying, which is used in our experiments, causes an increase of pore-water salinity and results in lower saturation exponents for the real part of conductivity but higher exponents for the imaginary part in comparison with the classical imbibition/drainage technique. We evaluate a theoretical approach that considers the influence of pore water salinity on the saturation exponents of the real and imaginary parts of conductivity. The complex conductivity spectra are processed by a Debye decomposition procedure. The resulting integrating parameters such as direct current resistivity, total chargeability, normalized chargeability, and mean relaxation time indicate a power law dependence on saturation. Our experiments indicate that the imaginary part of conductivity and normalized chargeability have a high sensitivity related to the drying process of rocks and might be suitable indicators to monitor the changes of moisture content in sandstones.
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Kruschwitz, Sabine, Matthias Halisch, Raphael Dlugosch, and Carsten Prinz. "Toward a better understanding of low-frequency electrical relaxation — An enhanced pore space characterization." GEOPHYSICS 85, no. 4 (June 19, 2020): MR257—MR270. http://dx.doi.org/10.1190/geo2019-0074.1.
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The relaxation phenomena observed in the electrical low-frequency range (approximately 1 MHz–10 kHz) of natural porous media such as sandstones are often assumed to be directly related to the dominant (modal) pore throat sizes measured, for instance, with mercury intrusion porosimetry. Attempts to establish a universally valid relationship between pore size and peak spectral induced polarization (SIP) relaxation time have failed, considering sandstones from very different origins and featuring great variations in textural and chemical compositions as well as in geometric pore space properties. In addition working with characteristic relaxation times determined in Cole-Cole or Debye decomposition fits to build the relationship have not been successful. In particular, samples with narrow pore throats are often characterized by long SIP relaxation times corresponding to long “characteristic length scales” in these media, assuming that the diffusion coefficients along the electrical double layer were constant. Based on these observations, three different types of SIP relaxation can be distinguished. We have developed a new way of assessing complex pore spaces of very different sandstones in a multimethodical approach to combine the benefits of mercury intrusion porosimetry, micro-computed tomography, and nuclear magnetic resonance. In this way, we achieve much deeper insight into the pore space due to the different resolutions and sensitivities of the applied methods to pore constrictions (throats) and wide pores (pore bodies). We experimentally quantify pore aspect ratios and volume distributions within the two pore regions. We clearly observe systematic differences between three SIP relaxation types identified previously, and we can attribute the SIP peak relaxation times to measured characteristic length scales within our materials. We highlight selected results for a total of nine sandstones. It seems that SIP relaxation behavior depends on the size difference of the narrow pore throats to the wide pore bodies, which increases from SIP type 1 to type 3.
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Nordsiek, Sven, and Andreas Weller. "A new approach to fitting induced-polarization spectra." GEOPHYSICS 73, no. 6 (November 2008): F235—F245. http://dx.doi.org/10.1190/1.2987412.
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Best fitting of induced-polarization (IP) spectra by different models of Cole-Cole type evidences discrepancies in the resulting model parameters. The time constant determined from the same data could vary in magnitude over several decades. This effect, which makes an evaluation of the results of different models nearly impossible, is demonstrated by induced polarization measurements in the frequency range between [Formula: see text] and [Formula: see text] on thirteen mixtures of quartz sand and slag grains. The samples differ in size and the amount of the slag grains. Parameters describing the IP spectra are derived by fitting models of the Cole-Cole type to the measured data. The fitting quality of the generalized Cole-Cole model, the standard Cole-Cole model, and the Cole-Davidson model is investigated. The parameters derived from these models are compared and correlated with mass percentage and grain size of the slag particles. An alternative fittingapproach is introduced, using the decomposition of observed IP spectra into a variety of Debye spectra. Four integrating parameters are derived and correlated with parameters of the slag-sand mixtures and Cole-Cole parameters, respectively. The alternative approach generally enables a better fitting of measured spectra compared with Cole-Cole type models. It proves to be more flexible and stable, even for complicated phase spectra that cannot be fitted by single Cole-Cole type models. The integrating parameters are well correlated with characterizing parameters of the slag-sand mixtures. The total chargeability well indicates the mass percentage of slag grains, and the mean relaxation time is related to the grain size. The relaxation time distribution can be displayed by cumulative normalized chargeability versus relaxation time, similar to granulation curves. Anologous to the latter, a nonuniformity parameter characterizes the width of the relaxation time distribution.
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Weller, Andreas, Katrin Breede, Lee Slater, and Sven Nordsiek. "Effect of changing water salinity on complex conductivity spectra of sandstones." GEOPHYSICS 76, no. 5 (September 2011): F315—F327. http://dx.doi.org/10.1190/geo2011-0072.1.
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We analyzed the influence of pore fluid composition on the complex electrical conductivity of three sandstones with differing porosity and permeability. The fluid electrical conductivity ([Formula: see text]) of sodium and calcium chloride solutions was gradually increased from 25 mS/m to 2300 mS/m. The expected linear relation between [Formula: see text] and the real component of electrical conductivity ([Formula: see text]) of the saturated samples was observed. The imaginary component ([Formula: see text]) exhibits a steeper increase at lower salinities that flattens at higher salinities. For a glauconitic sandstone and a high porosity Bunter sandstone, [Formula: see text] approaches an asymptotic value at high salinities. Sodium cations result in larger values of [Formula: see text] than calcium cations in solutions of equal concentration. Debye decomposition was used to determine normalized chargeability ([Formula: see text]) and average relaxation time ([Formula: see text]) from spectral data. The behavior of [Formula: see text] is comparable to [Formula: see text] as both parameters measure the polarizability. At lower salinity, the relation between [Formula: see text] and [Formula: see text] approximates a power law with an exponent of [Formula: see text]. The average relaxation time shows only a weak dependence on [Formula: see text]. The normalized chargeability of sandstone samples can be described by the product of the pore space related internal surface and a quantity characterizing the polarizability of the mineral-fluid interface that depends on fluid chemistry. We introduce a new parameter, the specific polarizability, describing this dependence. We propose relations between polarizability and fluid chemistry that could be used to estimate pore space internal surface across samples of varying [Formula: see text]. We observe a consistent maximum polarizability for quartz dominated siliceous material.
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Attwa, M., and T. Günther. "Spectral induced polarization measurements for environmental purposes and predicting the hydraulic conductivity in sandy aquifers." Hydrology and Earth System Sciences Discussions 10, no. 4 (April 29, 2013): 5315–54. http://dx.doi.org/10.5194/hessd-10-5315-2013.
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Abstract. Low-frequency field and laboratory induced polarization measurements are carried out to characterize the hydrogeological conditions at Schillerslage test site in Germany. The laboratory spectral induced polarization (SIP) data are analyzed to derive an empirical relationship for predicting the hydraulic conductivity (K) in the field scale. On the other hand, the results from SIP sounding and profiling field data indicate that the method identifies the lithological layers with sufficient resolution to achieve our objectives. Two main Quaternary groundwater aquifers separated by a till layer can be well differentiated. Furthermore, the phase images are also capable of monitoring thin peat layers within the sandy groundwater aquifer. However, the field results show limitations of decreasing resolution with depth and/or low data coverage. Similarly, the SIP laboratory results show a certain shift in SIP response due to different compaction and sorting of the samples. The overall results obtained show that the integration of field and laboratory SIP measurements is an efficient tool to avoid a hydrogeological misinterpretation. In particular, two significant but weak correlations between individual real resistivities (ρ') and relaxation times (τ), based on a Debye decomposition (DD) model, with measured K are found for the upper groundwater aquifer. While the maximum relaxation time (τmax) and logarithmically weighted average relaxation time (τlw) show a better relation with K values than the median value τ50, however, the single relationships are weak. A combined power law relation between individual ρ' and/or τ with K is developed with an expression of A · (ρ')B · (τlw)C, where A, B and C are determined using a least-squares fit between the measured and predicted K. The suggested approach with the calculated coefficients of the first aquifer is applied for the second one. The results indicate a good correlation with the measured K and prove to be superior to single phase angle models as the Börner or Slater models.
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Weller, Andreas, Lee Slater, and Sven Nordsiek. "On the relationship between induced polarization and surface conductivity: Implications for petrophysical interpretation of electrical measurements." GEOPHYSICS 78, no. 5 (September 1, 2013): D315—D325. http://dx.doi.org/10.1190/geo2013-0076.1.
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Petrophysical interpretation of resistivity measurements is often hindered by the dependence of resistivity on the interconnected pore fluids and the interconnected pore surfaces. Induced polarization (IP) measurements yield parameters that are only controlled by the interconnected pore surfaces, thereby offering the opportunity to constrain interpretation of resistivity measurements. Using a database composed of 63 sandstone and unconsolidated sediment samples covering nine independent investigations, we identified a strong linear relationship between the real part of surface conductivity ([Formula: see text]) determined from multisalinity ([Formula: see text]) resistivity measurements and the imaginary conductivity ([Formula: see text]) measured with IP at a frequency of about 1 Hz. We found [Formula: see text] with a coefficient of determination ([Formula: see text]) of 0.911 and a standard deviation of [Formula: see text] of 0.022. We found a similar relation when the normalized chargeability (from Debye decomposition) of the frequency dependence of the IP response is used instead of [Formula: see text]. By estimating the true formation factor ([Formula: see text]) recorded at high salinity, we solved for [Formula: see text] and found that it parallels the salinity dependency of the imaginary conductivity, [Formula: see text], as reported in recent studies. We also found that the value of the [Formula: see text] determined from this experimental study was generally consistent with predictions of the POLARIS model when the mobility of the ions in the Stern layer was assumed to be [Formula: see text] of the mobility of the ions in the diffuse layer (considered equal to the mobility of the ions in the bulk solution). We discovered how the identified relationship can be used to significantly improve (1) the estimation of the true formation factor and (2) the groundwater conductivity, from a single salinity resistivity measurement when an IP measurement is also made. The approach offers an opportunity to improve estimation of porosity, formation factor, and salinity in well logging and hydrogeophysical investigations.
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Martin, Tina, Andreas Weller, and Laura Behling. "Desaturation effects of pyrite–sand mixtures on induced polarization signals." Geophysical Journal International 228, no. 1 (August 27, 2021): 275–90. http://dx.doi.org/10.1093/gji/ggab333.
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SUMMARY Induced polarization (IP) is an acknowledged method in ore exploration and can be applied to evaluate the metal content in dumps containing the residues of ore processing facilities. Existing models explain the relationships between ore content and grain size of the ore particles with IP parameters. However, the models assume full water saturation of the ore containing samples, which is often not the case in field conditions at dump sites. Hence, our study investigates the effect of desaturation on the resulting IP signal. We used six different sand–pyrite mixtures with varying amount and grain sizes of the pyrite particles. Evaporative drying desaturated the samples. Complex conductivity spectra were recorded in the frequency range between 0.02 and 1000 Hz at certain saturation levels. The resulting spectra indicate an decrease of the conductivity amplitude with progressing desaturation. This effect agrees with the second empirical Archie equation. The saturation exponent of the conductivity amplitude shows values slightly larger than one. The measured spectra were processed by a Debye decomposition. We observe a nearly constant total chargeability during desaturation. This finding is in agreement with existing models that relate the total chargeability to the metal content in the sample. However, the mean relaxation time decreases remarkably during the drying process, whereas the normalized relaxation time, which considers the ratio between the mean relaxation time and the resistivity of the embedding material, does not indicate any dependence on water saturation. This behaviour contradicts existing models that predict a decreasing relaxation time with increasing water salinity, which results from evaporative drying. In order to explain the observed effects, we propose a conceptional model that compares a mixture of pyrite particles in an embedding material (sand, water and air) with an electrical RC circuit. The pyrite grains behave as small condensers that are charged and discharged via the conductive background material. According to this simple physical model, the relaxation time is proportional to the resistivity of the embedding material. A resistivity increase while desaturation causes an increase of relaxation time as observed in our experiments. This conceptional model is in good agreement with other experiments that change the resistivity in the background material by varying water salinity or clay content. The capacitive behaviour of the dispersed particles is characterized by the normalized relaxation time that depends on the grain size and the volume content of the pyrite particles.
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Weigand, Maximilian, and Andreas Kemna. "Multi-frequency electrical impedance tomography as a non-invasive tool to characterize and monitor crop root systems." Biogeosciences 14, no. 4 (February 28, 2017): 921–39. http://dx.doi.org/10.5194/bg-14-921-2017.
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Abstract. A better understanding of root–soil interactions and associated processes is essential in achieving progress in crop breeding and management, prompting the need for high-resolution and non-destructive characterization methods. To date, such methods are still lacking or restricted by technical constraints, in particular the charactization and monitoring of root growth and function in the field. A promising technique in this respect is electrical impedance tomography (EIT), which utilizes low-frequency (< 1 kHz)- electrical conduction- and polarization properties in an imaging framework. It is well established that cells and cell clusters exhibit an electrical polarization response in alternating electric-current fields due to electrical double layers which form at cell membranes. This double layer is directly related to the electrical surface properties of the membrane, which in turn are influenced by nutrient dynamics (fluxes and concentrations on both sides of the membranes). Therefore, it can be assumed that the electrical polarization properties of roots are inherently related to ion uptake and translocation processes in the root systems. We hereby propose broadband (mHz to hundreds of Hz) multi-frequency EIT as a non-invasive methodological approach for the monitoring and physiological, i.e., functional, characterization of crop root systems. The approach combines the spatial-resolution capability of an imaging method with the diagnostic potential of electrical-impedance spectroscopy. The capability of multi-frequency EIT to characterize and monitor crop root systems was investigated in a rhizotron laboratory experiment, in which the root system of oilseed plants was monitored in a water–filled rhizotron, that is, in a nutrient-deprived environment. We found a low-frequency polarization response of the root system, which enabled the successful delineation of its spatial extension. The magnitude of the overall polarization response decreased along with the physiological decay of the root system due to the stress situation. Spectral polarization parameters, as derived from a pixel-based Debye decomposition analysis of the multi-frequency imaging results, reveal systematic changes in the spatial and spectral electrical response of the root system. In particular, quantified mean relaxation times (of the order of 10 ms) indicate changes in the length scales on which the polarization processes took place in the root system, as a response to the prolonged induced stress situation. Our results demonstrate that broadband EIT is a capable, non-invasive method to image root system extension as well as to monitor changes associated with the root physiological processes. Given its applicability on both laboratory and field scales, our results suggest an enormous potential of the method for the structural and functional imaging of root systems for various applications. This particularly holds for the field scale, where corresponding methods are highly desired but to date are lacking.
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Faus-Bertomeu, Aina, Ramón Domènech Giménez, Svitlana Poniakina, Noelia Cámara-Izquierdo, and Rosa Gómez-Redondo. "Main components of life expectancy increase during the cardiovascular revolution in spain." Empiria. Revista de metodología de ciencias sociales, no. 48 (September 10, 2020): 167. http://dx.doi.org/10.5944/empiria.48.2020.28075.
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The circulatory system diseases have contributed decisively to an increase in life expectancy (LE) in Spain. The contribution to LE is calculated through a decomposition analysis by sex and five-year age groups. We divide the years studied into two periods, 1980–1996 and 1996–2012. Using the Human Cause-of-Death Database (HCD), we examine specific subcauses at a 4-digit ICD-10 level and how they contribute to the change in LE among men and among women. The analysis shows that cerebrovascular diseases (CBVDs) contribute most to years gained until 1996, while ischemic heart diseases (IHDs) contribute most thereafter. Among women, the largest increase is due to specific CBVDs subcauses; among men IHD subcauses also have an important role. Regarding contribution by age, gains by CVDs are particularly significant at older ages, while contributions by IHDs are more relevant from the age of 50 onwards, especially among men. Furthermore, the gender gap in LE is influenced by the different evolution of various circulatory diseases during the period of study, but the evolution of these diseases is not always reflected equally in both sexes. The study evidences the need for greater precision in the registers in order to take advantage of the potentialities of the 4-digit classification of the ICD, thus leading to a better in depth knowledge in health trends. Finally, it shows the mortality due to modifiable factors mainly classified in IHDs, and the consequent need for the Spanish health system to act on them.Las enfermedades del sistema circulatorio, han contribuido de manera decisiva al aumento de la esperanza de vida (LE) en España. Las contribuciones a la LE se calculan a través de un análisis de descomposición por sexo y grupos de edad quinquenales. Dividimos los años estudiados en dos períodos, 1980–1996 y 1996–2012. Utilizando la Human Cause-of-Death Database (HCD), examinamos subcausas específicas a un nivel de 4 dígitos de ICD-10 y cómo contribuyen al aumento o disminución de LE tanto en hombres como en mujeres. El análisis muestra que las enfermedades cerebrovasculares (CBVD) son las que más contribuyen a los años ganados hasta 1996, mientras que las enfermedades isquémicas (IHD) son las que más contribuyen posteriormente. Entre las mujeres, el mayor aumento se debe a subcausas específicas de las CBVD; en los hombres, las subcausas de IHD también tienen un papel importante. En lo que respecta a la contribución por edad, las ganancias por CBVDs son particularmente significativas en las edades mayores, mientras que las contribuciones por las IHD son más relevantes a partir de los 50 años, especialmente entre los hombres. La brecha entre hombres y mujeres en la LE está influenciada por la evolución diferente de varias enfermedades circulatorias durante el período de estudio, pero la evolución de estas enfermedades no siempre se refleja por igual en ambos sexos. Además, se pone en evidencia la necesidad de una mayor precisión en los registros para aprovechar las potencialidades de la clasificación a 4 dígitos de la CIE, alcanzando de este modo un conocimiento más profundo de las tendencias de salud. Finalmente, el estudio muestra la mortalidad debida a factores modificables que se clasifican principalmente en las IHD, y la consiguiente necesidad de que el sistema de salud español actúe sobre ellas.
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"APPLICATION OF THE DEBYE DECOMPOSITION TO ANALYSIS OF INDUCED-POLARIZATION PROFILING DATA (Julietta gold-silver deposit, Magadan Region)." Геология и геофизика 56, no. 12 (2015). http://dx.doi.org/10.15372/gig20151208.
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GOEL, S. P., and P. N. MEHROTRA. "ChemInform Abstract: A NEW DEBYE-SCHERRER PATTERN OF CESIUM MOLYBDATE PREPARED BY THE THERMAL DECOMPOSITION OF CESIUM OXOMOLYBDENUM(VI) OXALATE." Chemischer Informationsdienst 16, no. 24 (June 18, 1985). http://dx.doi.org/10.1002/chin.198524036.
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Lim, B. S., and A. S. Nowick. "Decomposition of Universal AC Ionic Conductivity Response into Two Ranges with Constant Exponents." MRS Proceedings 293 (1992). http://dx.doi.org/10.1557/proc-293-219.
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AbstractMany disordered materials both crystalline and glasses show universal dynamic response [1], which is characterized by appropriate power-laws. The ac-conductivity as a function of frequency, is given by: σ(ω)=σ(0)+ Aωs where σ(0) is the dc-conductivity and the exponent s (≤1) generally decreases with increasing temperature. In previous work on ionically conducting crystals and glasses, we have observed two ranges in which s = constant, independent of temperature: at high temperatures, s=so (a value between 0.5 and 0.6) and, at low temperatures, s = 1. Further for the s = so region, the parameter A is activated with activation energy related to that of σ(0), while for the s = 1 region, A varies only slowly with temperature. For the cases of borate and silicate glasses as well as for crystalline CaTiO3 doped with 30% A13+, careful analysis was carried out over the region in which the effective s falls from 1.0 to so. The results show that this region can be described by the relation: σ(ω)= σ(0) + Aωs0 + A'ωl.0 with parameters A and A’ consistent with those obtained from the high and low- temperature regions, respectively. Thus, we conclude that two separate types of universal behavior are superimposed throughout the entire temperature region; each is described by a constant value of s, and is due to an independent mechanism of non-Debye relaxational behavior.
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Tsu, Robert, Hung-Yu Liu, Wei-Yung Hsu, Scott Summerfelt, Katsuhiro Aoki, and Bruce Gnade. "Correlations of Ba1−xSrxTiO3 Materials and Dielectric Properties." MRS Proceedings 361 (1994). http://dx.doi.org/10.1557/proc-361-275.
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ABSTRACTThin film barium strontium titanate, Ba1−xSrxTiO3 (BST), has been deposited on Pt bottom electrodes using metal-organic decomposition (MOD). Optimization of BST electric properties, including capacitance density and leakage current, can be achieved by altering the chemical and microstructural attribute of the films. Dielectric properties of BST are strongly dependent on processing temperature, film thickness, composition, and microstructure, which are closely correlated with each other. Nucleation temperatures of BST range from 580°C – 650°C depending on film thicknesses. The chemical composition giving the highest dielectric constant is explained in terms of microstructure; capacitance increases with increasing grain size for the BST films in this study. Capacitance density of 50 fF/μ m2 and leakage current density < 100 nA/cm2 at 1.6 V can be achieved by optimizing BST materials properties. In addition, leakage conduction through the Pt/BST/Pt capacitor is shown to consist of polarization current resulting from Debye relaxation and true leakage current attributed to Schottky electron emission.
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Elaprolu, NARSIMHA RAO, and Vepa Kameswara Rao. "Pressure, Directional Dependent Mechanical Anisotropies and Phase Transition Studies ofβ-5-nitro-2,4-dihydro-3H-1,2,4-triazol-3-one (NTO) and 2,4,6-triamino-1,3,5-trinitrobenzene (TATB)." Journal of Physics: Condensed Matter, November 9, 2022. http://dx.doi.org/10.1088/1361-648x/aca199.
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Abstract This work highlights the effect of pressure ranging from 0-9GPa on structural, directional dependent mechanical properties and unravel the previously unknown phase transitions of two important high energy molecular solids namely monoclinic-β-NTO (Nitrotriazole) and TATB (2,4,6-triamino-1,3,5- trinitrobenzene). The projected augmented plane wave method with generalized gradient approximation (GGA) Perdew-Burke-Ernzerhof(PBE) functional with the D2 van der Waals (vdW) corrections method of Grimme is used to reproduce the experimental data within ∼ 1% error. The structural optimization results reveal that β-NTO undergoes a previously unknown structural phase transition at 9GPa which is evident from the abrupt change of calculated lattice vectors, volume (V), lattice angle β at 9GPa. The single crystal elastic properties analysis also supports these findings and NTO voilate the Born’s mechanical stability criteria at 9GPa. Besides to it, all the calculated volumetric and directional dependent shear modulus (G), bulk modulus (B), compressibility results of β-NTO in (100), (010), (001) planes also suggest a possible phase transition around 9GPa. The directional dependent polycrystalline compressibility anisotropy analysis of TATB with pressure in (100), (010), (001) planes unreveal the origin of experimentally reported new phase transition around 4GPa. The calculated Pugh B/G ratio suggests that, both the materials found to be brittle in the studied pressure range except NTO at 9GPa. The degree of mechanical anisotropy of β-NTO found to increase with increasing pressure from (100)–>(010)–>(001) planes, while the TATB anisotropy results were found to be relatively small and stable. The Young’s modulus (E), Poisson’s ratio (σ), P-wave modulus, Universal elastic anisotropy (AU ), Chung-Buessen anisotropy (Ac ), Vickers hardness coefficient (Hv ), sound velocities ((Vm ) average, (Vl ) longitudinal, (Vt ) transverse) and (θD ) Debye temperature are also predicted. The calculated intermolecular interaction strength contribution to the total Hirsh Field Surface at different pressures confirms the initial decomposition mechanism of NTO, TATB and the results are good in agreement with previous observations. Thus our work has accentuated the reasons behind the impact and friction sensitivity differences of β-NTO, TATB through the two new phase transitions.
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Martin, Tina, and Andreas Weller. "Superposition of Induced Polarization signals measured on pyrite-sand mixtures." Geophysical Journal International, March 2, 2023. http://dx.doi.org/10.1093/gji/ggad091.
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Summary Induced polarization (IP) is a common method in ore exploration. IP spectra measured over a wide frequency range can be used to characterize material properties of ores, slags and other residual material from mines and processing facilities. Previous studies have shown that IP parameters are sensitive to type, content or grain size of electronically conductive or semi-conductive minerals. Up to now, a variety of experiments has been performed on sand mixtures with fractions of ore minerals. Most experiments consider only a single fraction with a fixed grain size. We continue a series of experiments that have been done with sand-pyrite mixtures. The presented study compares IP spectra recorded for samples either with a single grain radius fraction (E-samples) or with two different grain radii fractions (Z-samples). The spectra are fitted to Pelton models. A Debye decomposition that provides a relaxation time distribution (RTD) is applied to the complex conductivity spectra. The RTD indicates separated maxima only if the ratio of mean grain radii is larger than a factor five. The resolution of the phase spectra and the spectra of imaginary part of conductivity is lower. Even though the volumetric pyrite content is equal in each fraction, the phase spectra and RTD of the Z-samples indicate much higher signals for the pyrite fraction with smaller grain radius. The same observation is made for the chargeability that shows larger values for decreasing grain radii. This finding contradicts existing theories that consider the chargeability as a suitable proxy of the volumetric content of ore minerals. We explain the observed effect by an interaction between neighboring pyrite particles. The conductivity of the mixtures of the E-samples increases with decreasing grain radius of the pyrite fraction. This effect is attributed to dissolution effects on the surface of the pyrite particles during the sample preparation. We find that the additive superposition of the phase spectra of two E-samples is in good agreement with the measured phase spectra of the Z-samples (measured superposition) containing the two corresponding pyrite fractions. The agreement is slightly worse for the spectra of imaginary part of conductivity, where the measured superposition overestimates the mathematical superposition. The experimental results of our study motivate a further improvement of existing mechanistic models.