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Magnetic Parameters (magnetic + parameter)
Selected AbstractsEffect of a Magnetic Field on a Micropolar Fluid Flow in the Vicinity of an Axisymmetric Stagnation Point on a Circular CylinderCHEMICAL ENGINEERING & TECHNOLOGY (CET), Issue 8 2009G. M. Abdel-Rahman Abstract The effect of a magnetic field on a micropolar fluid flow in the vicinity of an axisymmetric stagnation point on a circular cylinder is studied numerically. The governing conservation equations of continuity, momentum and angular momentum are partial differential equations which are transformed into a system of ordinary differential equations by using the usual similarity transformations. The resulting system of coupled non-linear ordinary differential equations is solved numerically by using the shooting method. The numerical results indicate the velocity, angular velocity and pressure distributions for different parameters of the problem including Reynolds number, magnetic parameter and dimensionless material properties, etc. In addition, the effect of the pertinent parameters on the local skin friction coefficient and the couple stress are discussed numerically and illustrated graphically. [source] Using analytic signal to determine magnetization/density ratios of geological structuresGEOPHYSICAL JOURNAL INTERNATIONAL, Issue 1 2009Wen-Bin Doo SUMMARY The Poisson theorem provides a simple relationship between the gravity and magnetic potentials, which is useful in interpreting joint data sets of gravity and magnetic data. Based on the simple Poisson theorem, magnetization/density ratio (MDR) can be estimated. However, potential field data is often ambiguous in datum level and multisources interference that may cause bias in interpretation. Here, we propose an improved Poisson theorem to estimate MDR by using analytic signals of gravity and magnetic data. The major advantage of using the analytic signal is that we can also determine the sources locations and boundaries supposing that we know the ambient magnetic parameters. Besides, we can also avoid the determination error from uncertain datum levels. We demonstrate the feasibility of the proposed method in 2-D and 3-D synthetic models. The proposed method is also applied to a profile across the offshore area of northern Taiwan. Comparing with the reflection seismic profile, our result can help identify the existence of a deep-seated igneous body beneath the area of Mienhuayu and Pengchiagu islands off northern Taiwan. [source] Magnetic investigation of heavy metals contamination in urban topsoils around the East Lake, Wuhan, ChinaGEOPHYSICAL JOURNAL INTERNATIONAL, Issue 2 2007Tao Yang SUMMARY Magnetic measurements and heavy metal analyses were performed on 133 samples from the urban soils around the East Lake in Wuhan, China. Samples were collected from four areas with different environmental settings: a heavy industrial area well known for thermal power generation and steel works; villages located in the downwind area of the industrial area; a main road with heavy traffic and roads around the East Lake. Results show that concentrations of magnetic particle and heavy metals in urban topsoils are significantly elevated due to the input of coarser-grained magnetite from industrial (e.g. power generation and steel production) and other anthropogenic activities (e.g. vehicle emissions). Concentration-related magnetic parameters, for example, magnetic susceptibility, saturation isothermal remanent magnetization and anhysteretic remanent magnetization, significantly correlate with the concentration of heavy metals. Moreover, in terms of grain sizes, the magnetic particles of different origins can be efficiently discriminated at the studied region. Therefore, magnetic measurements provide a basis for discrimination and identification of different contamination sources, and can be used as an economic alternative to chemical analysis when mapping heavy metal contamination in urban soil around the East Lake region, Wuhan, China. [source] Theory of chemical bonds in metalloenzymes III: Full geometry optimization and vibration analysis of ferredoxin-type [2Fe,2S] clusterINTERNATIONAL JOURNAL OF QUANTUM CHEMISTRY, Issue 1 2007Mitsuo Shoji Abstract The nature of chemical bonds in a ferredoxin-type [2Fe,2S] cluster has been investigated on the basis of natural orbitals and several bond indices developed in Parts I and II of this study. The broken-symmetry hybrid density functional theory (BS-HDFT) with spin projection approach has been applied to elucidate the natural orbitals and occupation numbers for a model compound [Fe2S2(SCH3)4] (1), which is used to calculate the indices. The molecular structure, vibration frequencies, electronic structures, and magnetic properties in both oxidized and reduced forms of 1 have been calculated and compared with the experimental values. The optimized molecular structures after approximate spin projection have been in good agreement with experimental data. The structure changes upon one-electron reduction have been slight (<0.1 Å) and only limited around one side of the Fe atom. Raman and infrared (IR) spectra have been calculated, and their vibration modes have been assigned using the bridging 34S isotope substitution. Their magnetic properties have been examined in terms of spin Hamiltonians that contain exchange interactions and double exchange interactions. The BS-HDFT methods have provided the magnetic parameters; i.e., effective exchange integral (J) values and valence delocalization (B) values, which agree with the experimental results. It is found that large charge transfer (CT) from the bridging sulfur to the iron atoms has led to the strong antiferromagnetic interactions between iron atoms. © 2006 Wiley Periodicals, Inc. Int J Quantum Chem, 2007 [source] Matrix isolation and magnetic parameters of septet 3,5-dicyanopyridyl-2,4,6-trinitreneJOURNAL OF PHYSICAL ORGANIC CHEMISTRY, Issue 4 2010Sergei V. Chapyshev Abstract Septet 3,5-dicyanopyridyl-2,4,6-trinitrene was synthesized together with quintet 2-azido-3,5-dicyanopyridyl-4,6-dinitrene, quintet 4-azido-3,5-dicyanopyridyl-2,6-dinitrene, triplet 2,6-diazido-3,5-dicyanopyridyl-4-nitrene, and triplet 2,4-diazido-3,5-dicyanopyridyl-6-nitrene by photolysis of 2,4,6-triazido-3,5-dicyanopyridine in solid argon at 4,K. The electronic and magnetic properties of the matrix-isolated nitrenes were studied using electron paramagnetic resonance (EPR) spectroscopy in combination with density functional theory (DFT) calculations. The fine-structure parameters of the nitrenes were determined with high accuracy from spectral simulations. All signals in the EPR spectra of the nitrenes, randomly oriented in the solid phase, were unambiguously assigned based on eigenfield calculations of the Zeeman energy levels and angular dependences of resonance fields. Copyright © 2009 John Wiley & Sons, Ltd. [source] Magnetic study of Hitperm alloys (Fe0.5Co0.5)1,x ,y ,zMxByCuz (M = Hf, Zr, Nb)PHYSICA STATUS SOLIDI (A) APPLICATIONS AND MATERIALS SCIENCE, Issue 7 2006Abstract A family of the Hitperm alloys (Fe0.5Co0.5)1,x ,y ,zMxByCuz (M = Hf, Zr, Nb) produced in an argon atmosphere as amorphous ribbons with 0.025 mm thickness are investigated up to 1200 K. The partial replacement of Fe by Co with optimal Fe0.5Co0.5 ratio increases the Curie temperature of the amorphous phase and the magnetic moment per formula unit. The early stages of crystallization can be observed by magnetization measurements. Alloys subjected to the first controlled crystallization stage are built of bcc-(Fe,Co) nanocrystals that are homegeneously embedded in the amorphous matrix. Mean grain sizes are about 11 nm. These two-phase alloys exhibit good soft magnetic properties with the relatively low coercive fields up to 50 A/m. Hafnium and hafnium/zirconium mixture are found to be the best inhibitors of the nanograin growth resulting in the best soft magnetic parameters. Alloys with niobium exhibit lower thermal stability and higher coercive fields. The correlation between the structure evolution and the magnetic properties is analysed and discussed. Conditions for optimum heat treatment are also determined. (© 2006 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Synthesis of MnGeO3 polycrystalline and single-crystal samples and comparative analysis of their magnetic propertiesPHYSICA STATUS SOLIDI (B) BASIC SOLID STATE PHYSICS, Issue 1 2009N. V. Sapronova Abstract MnGeO3 single crystals have been grown by a flux method. The obtained MnGeO3 is orthorhombic; a Pbca space group does not undergo any structural phase transitions in the range from room temperature to 900 °C. Magnetic measurements carried out for the first time on the MnGeO3 single crystal have revealed higher values (TN = 38 K and , = ,100 K) as compared to the data for polycrystalline samples reported in the literature (TN = 10 K and 14 K, , = ,54 K and ,46 K). These magnetic parameters for polycrystalline samples synthesized by us are close to the literature data. A Mössbauer spectrum taken at T = 300 K for a sample containing 5% Fe257O3 shows that manganese ions, Mn2+, occupy two nonequivalent positions and iron is included in a sublattice as Fe2+ and distributed among two positions substituting Mn2+. In this study, the magnetic characteristics are shown to be sensitive even to minor impurity amounts. The MnGeO3 magnetic structure and one of possible reasons causing the effect of impurities on the MnGeO3 magnetic properties are considered in the framework of a simple indirect coupling model. (© 2009 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Magnon energy gap and the magnetically structural symmetry in a three-layer ferrimagnetic superlatticePHYSICA STATUS SOLIDI (B) BASIC SOLID STATE PHYSICS, Issue 8 2006Rong-ke Qiu Abstract The magnon energy band in a ferrimagnetic superlattice with three layers in a unit cell is studied by employing retarded Green's functions and the spin-wave method. Two modulated energy gaps ,,13 and ,,23 are evaluated systematically, which exist in the magnon energy band along the Kx -direction perpendicular to the plane of the superlattice. It is revealed that the energy gap ,,13 has a direct relation with the symmetry among the spin quantum numbers and the interlayer exchange couplings, while the energy gap ,,23 relates to the symmetry among these spin quantum numbers only. These symmetries differ from the symmetry of crystallographic point groups. We define the magnetically structural symmetry that is dominated mainly by the magnetic parameters. The absence of the energy gap at a certain condition means that the system has a high magnetically structural symmetry. The magnetically structural symmetry of the superlattice, which is an intrinsic property, strongly affects the magnon energy band structure and thus the magnetic behaviors of the system. Furthermore, two complete bandgaps are observed to extend through the Brillouin zone (referred to as "magnonic crystal") in this superlattice system. (© 2006 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Temperature-induced changes of domain structures in ultrathin magnetic filmsPHYSICA STATUS SOLIDI (C) - CURRENT TOPICS IN SOLID STATE PHYSICS, Issue 5 2006T. Polyakova Abstract We describe the thermal-driven evolution of stripe domain structures in ultrathin magnetic films with perpendicular anisotropy. Taking into account temperature dependencies of the film magnetic parameters we analyze possible temperature dependencies of the domain period. It is shown that the film heating leads to a decrease in the domain period. In soft films thermally assisted domain nucleation could provide a continuous decrease of the domain period while the domain structure passes through equilibrium states. On increasing the temperature of a hard film, the domain structure exists as metastable one adjusting its period by a sequence of jumps towards to equilibrium. (© 2006 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] | |||||||||||||