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21.
We consider the effect of a variable representing the competition between the frequency of the field and the frequency of the spin flipping (Ω) on the dynamics of the metamagnetic Ising model in a cubic lattice under the presence of a time varying (oscillating) external magnetic field. The system is modelled with a formalism of master equation at a mean-field level. The time averaged staggered magnetization (Ms) acts as the order parameter and divides temperature field plane into three regions: anti-ferromagnetic, paramagnetic and coexistence of anti-ferromagnetic and paramagnetic phases. It is observed that the topology of the dynamical phase diagram depends strongly on Ω as well as the ratio between interlayer and intralayer couplings. 相似文献
22.
Yavuz Surme Ibrahim Narin Mustafa Soylak Huseyin Yuruk Mehmet Dogan 《Mikrochimica acta》2007,157(3-4):193-199
The conditions for cloud point extraction of lead(II) from aqueous solutions were investigated and optimized. The procedure
is based on the separation of Pb(II) – brillant cresyl blue (BCB) complexes into the micellar media by adding the surfactant
Triton X-114. After phase separation, the surfactant-rich phase was dissolved with 1 mol L−1 HNO3 in ethanol and diluted with 1 mol L−1 HNO3 solution before lead was determined by flame atomic absorption spectrometry. Optimization of the pH, ligand and surfactant
quantities, incubation time, temperature, viscosity, sample volume, and interfering ions was performed. The effects of the
matrix ions were also examined. The detection limits for three times the standard deviations of the blank for lead were 7.5 μg L−1 for water samples and 0.33 μg g−1 for sediment samples. The validity of cloud point extraction was checked by employing certified reference samples of Lake
Sediment IAEA-SL-1 and Sewage Sludge BCR-CRM 144R. The procedure was applied to natural waters and sediment samples with satisfactory
results (recoveries >95%, relative standard deviations <6.4%). 相似文献
23.
24.
Nonuniform line broadening in quadrupole spin systems is analyzed. It is shown theoretically that this broadening is of the
tensor type. This forms the basis of the method for analyzing the distribution of local inhomogeneities in the crystal lattice,
which is verified experimentally on a sodium nitride sample. 相似文献
25.
Neutron scattering has been used to measure the charge and spin structure in the YBa2Cu3O6+x superconductors. Incommensurate static charge ordering is found at low doping levels while only charge fluctuations are found at higher doping. The spin structure is complex with both a commensurate resonance and incommensurate structure observed at low temperatures. The scattering results are used to construct a phase diagram for stripes in the YBa2Cu3O6+x system. 相似文献
26.
Nihan Nugay Gabor Erdodi J. P. Kennedy 《Journal of polymer science. Part A, Polymer chemistry》2005,43(3):630-637
This article mainly concerns the synthesis of novel PD5/PDMS conetworks by the copolymerization of cyclic D5H and linear HO? PDMS? OH units, and the characterization of the product by DMTA, DSC, and TGA. The ultimate properties of the conetworks may be controlled by varying the relative composition of D5H and PDMS components. DMTA and DSC thermograms indicate compatibility between the PD5 and PDMS domains. Understanding of the polymer chemical transformations involved in conetwork formation combined with an analysis of DMTA and DSC thermograms led to a proposition of the microarchitecture of PD5/PDMS conetworks. © 2004 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 43: 630–637, 2005 相似文献
27.
28.
Investigation of heat transfer by means of pool film boiling on vertical cylinders in gravity 总被引:1,自引:0,他引:1
In this study, the heat transfer by means of pool film boiling on immersed vertical cylindrical rods was investigated. For
this purpose, the rods with various dimensions, which have been heated up to 600°C, were immersed in a pure water pool in
the different temperatures. The centre temperature and water temperature versus operation time were measured by K type thermocouples
at the atmospheric pressure. After experimental studies, the surface temperatures of rods and heat transfer coefficients were
calculated by means of Lumped method from the measured temperatures. Consequently, an empirical equation was developed between
the Nusselt, Grashof, Prandtl and Jakob numbers. The experimental results showed that the specimens having the same characteristic
lengths exhibited the same heat transfers performance although the specimen’s diameters and lengths differed considerably. 相似文献
29.
In this study, two-dimensional transient dynamic response of orthotropic plane layered media is investigated. The plane multilayered
media consist of N different generally orthotropic, homogeneous and linearly elastic layers with different ply angles. In the generally orthotropic
layer, representing a ply reinforced by unidirectional fibers with an arbitrary orientation angle, the principal material
directions do not coincide with body coordinate axes. The solution is obtained by employing a numerical technique which combines
the use of Fourier transform with the method of characteristics. The numerical results are displayed in curves denoting the
variations of stress and displacement components with time at different locations. These curves clearly reveal, in wave profiles,
the scattering effects caused by the reflections and refractions of waves at the boundaries and at the interfaces of the layers,
and also the effects of anisotropy caused by fiber orientation angle. The curves properly predict the sharp variations in
the response at the neighborhood of the wave fronts, which shows the power of the numerical technique employed in the study.
By suitably adjusting the elastic constants, the results for multilayered media with transversely isotropic layers, or layers
with cubic symmetry, or isotropic layers can easily be obtained from the general formulation. Furthermore, solutions for some
special cases, including Lamb’s problem for an elastic half-space, are obtained and compared with the available solutions
in the literature and very good agreement is found.
Preliminary version presented at the Second International Congress on Mechatronics (MECH2K3), Graz, Austria, July 14-17, 2003. 相似文献
30.
Designing Excited States: Theory‐Guided Access to Efficient Photosensitizers for Photodynamic Action