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181.
G. Litsardakis A.C. Stergiou J. Georgiou S. Sklavounos D. Samaras M. Pernet P. Germi 《Journal of magnetism and magnetic materials》1993,120(1-3):58-60
The organometallic precursor method was employed for the synthesis of β” ferrites, from which non-stoichiometric Ba ferrite particles have been prepared by ionic exchange. The magnetic grains are hexagonal platelets with diameters as low as 50 nm and aspect ratio of 1.5. After annealing, the sample diameter increases to 200 nm while the grains remain single-domain. The Curie temperature is 455°C. Annealed samples show specific magnetization up to 62 emu/g, coercive fields jHc close to 2 kOe, and an SFD factor 1−S* of 0.55 相似文献
182.
An analysis of the thermal performance for convective annular fins, having a general trapezoidal profile and internal heat generation, is presented. The solution of the optimal problem is also given when either the heat dissipation rate or the volume of the fin is specified. The results are expressed in suitable nondimensional variables that are specified by the problem, and presented graphically. The effect of the fin's profile and thermal conductivity upon the optimum dimensions is discussed. It is shown that the presence of heat generation reduces the ability of the fin to convect heat. Furthermore, certain limiting values of the heat generation that may be imposed on the fin for a feasible optimization are also derived. 相似文献
183.
Prof. Georgios C. Georgiou 《Rheologica Acta》1996,35(1):39-47
In this paper we solve the time-dependent shear flow of an Oldroyd-B fluid with slip along the fixed wall. We use a non-linear slip model relating the shear stress to the velocity at the wall and exhibiting a maximum and a minimum. We assume that the material parameters in the slip equation are such that multiple steady-state solutions do not exist. The stability of the steady-state solutions is investigated by means of a one-dimensional linear stability analysis and by numerical calculations. The instability regimes are always within or coincide with the negative-slope regime of the slip equation. As expected, the numerical results show that the instability regimes are much broader than those predicted by the linear stability analysis. Under our assumptions for the slip equation, the Newtonian solutions are stable everywhere. The interval of instability grows as one moves from the Newtonian to the upper-convected Maxwell model. Perturbing an unstable steady-state solution leads to periodic solutions. The amplitude and the period of the oscillations increase with elasticity. 相似文献
184.
Ioannis Georgiou 《Nonlinear dynamics》2005,41(1-3):69-110
Reduced order models for the dynamics of geometrically exact planar rods are derived by projecting the nonlinear equations of motion onto a subspace spanned by a set of proper orthogonal modes. These optimal modes are identified by a proper orthogonal decomposition processing of high-resolution finite element dynamics. A three-degree-of-freedom reduced system is derived to study distinct categories of motions dominated by a single POD mode. The modal analysis of the reduced system characterizes in a unique fashion for these motions, since its linear natural frequencies are near to the natural frequencies of the full-order system. For free motions characterized by a single POD mode, the eigen-vector matrix of the derived reduced system coincides with the principal POD-directions. This property reflects the existence of a normal mode of vibration, which appears to be close to a slow invariant manifold. Its shape is captured by that of the dominant POD mode. The modal analysis of the POD-based reduced order system provides a potentially valuable tool to characterize the spatio-temporal complexity of the dynamics in order to elucidate connections between proper orthogonal modes and nonlinear normal modes of vibration. 相似文献
185.
Georgios C. Florides Andreas N. Alexandrou Georgios C. Georgiou 《ournal of non Newtonian Fluid Mechanics》2007
The flow and shape evolution during the compression of a finite amount of a Bingham plastic is investigated by means of numerical simulations. The problem relates to the popular compression test used for the rheological characterization of non-Newtonian fluids. The flow is modelled in Lagrangian coordinates using the Papanastasiou regularization for the Bingham plastic and a mixed-Galerkin finite element method. Simulations have been performed for compression under both constant load and constant velocity. Results for various Reynolds and Bingham numbers are presented and discussed. 相似文献
186.
Gul Melek Elemes Yiannis Pelit Emel Dernektsi Eleni Georgiou Dimitra Oikonomou Kosmas Lis Tadeusz Szafert Sławomir 《Research on Chemical Intermediates》2017,43(2):1031-1045
Research on Chemical Intermediates - Stereospecific α-amination has been accomplished via addition of N-phenyltriazolinedione (PhTAD) to the allylic position of dihydropyrroles. The aim of... 相似文献
187.
Mohammadine El Haddad Rajâa Boulahjar Rachid Slimani Marie-Claude Viaud-Massuard Saïd El Antri Saïd Lazar 《Journal of Analytical Chemistry》2011,66(6):586-590
The retention of alkylphosphonic acids (MPA, EPA, PPA, and BPA) and inorganic anions (Cl−, NO3−, and SO42−) were studied on two anion exchangers, e.g., Dionex IonPac AS4A-SC (250 ± 4 mm I.D.) and Satisfaction P 4000-SAX (50 ± 4.6
mm I.D.) under isocratic elution conditions with evaporative light scattering detector. The plots of retention factors, k, of organic anions vs. the reciprocal of eluent ion concentration show good linearity. The major retention mechanisms are
interpreted as ion exchange and some others interactions. The C effect of organic modifier added to the aqueous buffered mobile
phase is also investigated. 相似文献
188.
Larisa Muravleva Ekaterina Muravleva Georgios C. Georgiou Evan Mitsoulis 《ournal of non Newtonian Fluid Mechanics》2010,165(9-10):544-550
The augmented Lagrangian/Uzawa method has been used to study benchmark one-dimensional cessation flow problems of a Bingham fluid, such as the plane Couette flow, and the plane, round, and annular Poiseuille flows. The calculated stopping times agree well with available theoretical upper bounds for the whole range of Bingham numbers and with previous numerical results. The applied method allows for easy determination of the yielded and unyielded regions. The evolution of the rigid zones in these unsteady flows is presented. It is demonstrated that the appearance of an unyielded zone near the wall occurs for any non-zero Bingham number not only in the case of a round tube but also in the case of an annular tube of small radii ratio. The advantages of using the present method instead of regularizing the constitutive equation are also discussed. 相似文献
189.
Marilena Vlachou Angeliki-Sofia Foscolos Angeliki Siamidi Angeliki Syriopoulou Nikitas Georgiou Aikaterini Dedeloudi Antonis D. Tsiailanis Andreas G. Tzakos Thomas Mavromoustakos Ioannis P. Papanastasiou 《Molecules (Basel, Switzerland)》2022,27(1)
The aqueous dissolution profile of the isomeric synthetic adamantane phenylalkylamine hydrochlorides I and II was probed. These adducts have shown significant antiproliferative/anticancer activity associated with an analgesic profile against neuropathic pain. They are both devoid of toxic effects and show appreciable enzymatic human plasma stability. The structures of these two compounds have been elucidated using 2D NMR experiments, which were used to study their predominant conformations. Compound II’s scaffold appeared more flexible, as shown by the NOE spatial interactions between the alkyl bridge chain, the aromatic rings, and the adamantane nucleus. Conversely, compound I appeared very rigid, as it did not share significant NOEs between the aforementioned structural segments. MD simulations confirmed the NOE results. The aqueous dissolution profile of both molecules fits well with their minimum energy conformers’ features, which stem from the NOE data; this was nicely demonstrated, especially in the case of compound II. 相似文献
190.
Synchronous fluorescence spectroscopy for quantitative determination of virgin olive oil adulteration with sunflower oil 总被引:2,自引:0,他引:2
Adulteration of extra virgin olive oil with sunflower oil is a major issue for the olive oil industry. In this paper, the
potential of total synchronous fluorescence (TSyF) spectra to differentiate virgin olive oil from sunflower oil and synchronous
fluorescence (SyF) spectra combined with multivariate analysis to assess the adulteration of virgin olive oil are demonstrated.
TSyF spectra were acquired by varying the excitation wavelength in the region 270–720 nm and the wavelength interval (Δλ) in the region from 20 to 120 nm. TSyF contour plots for sunflower, in contrast to virgin olive oil, show a fluorescence
region in the excitation wavelength range 325–385 nm. Fifteen different virgin olive oil samples were adulterated with sunflower
oil at varying levels (0.5–95%) resulting in one hundred and thirty six mixtures. The partial least-squares regression model
was used for quantification of the adulteration using wavelength intervals of 20 and 80 nm. This technique is useful for detection
of sunflower oil in virgin olive oil at levels down to 3.4% (w/v) in just two and a half minutes using an 80-nm wavelength
interval. 相似文献