Value Of αE Research Articles

Comparação entre valores de ensaios experimentais e calculados da resistência ao embutimento da madeira de Pinus taeda L.

Para dimensionar ligações entre membros estruturais de madeira com pinos metálicos (pregos ou parafusos), dois fenômenos devem ser levados em consideração: a flexão do pino metálico e a resistência da madeira ao embutimento. A norma brasileira ABNT NBR 7190:1997 preconiza a metodologia empregada em ensaios laboratoriais para determinação da resistência da madeira ao embutimento com pino metálico e, na ausência dos ensaios, especifica relações para estimar a resistência da madeira ao embutimento a partir da resistência na compressão. O objetivo desta pesquisa consistiu na comparação entre valores de resistência ao embutimento da madeira determinados experimentalmente e calculados utilizando parâmetros recomendados pela ABNT NBR 7190:1997. Pelos resultados dos testes de hipótese, pode-se concluir que a estimativa da resistência ao embutimento paralelo às fibras proposta pela ABNT NBR 7190:1997, que estabelece equivalência com os resultados de compressão na mesma direção, mostrou-se precisa para as madeiras de Pinus taeda L.. Entretanto, o mesmo não foi observado na direção normal em relação às fibras, possivelmente explicada pelo valor do coeficiente áe presente na equação para o cálculo de fe90.

Thickness and frequency dependence of magnetoelectric effect for epitaxial La0.7Sr0.3MnO3/BaTiO3 bilayer

The epitaxial La0.7Sr0.3MnO3/BaTiO3 (LSMO/BTO) bilayer films were grown on (001) oriented (LaAlO3)0.3(SrAl0.5Ta0.5O3)0.7 (LSAT) substrate by pulsed laser deposition technique. The effect of film thickness on its ferromagnetic properties, ferroelectric properties and magnetoelectric (ME) effect was investigated. Measurements of thickness and frequency dependence (0.1—100KHz) of the ME voltage coefficient (αE) and phase angle (Δθ) demonstrated a strong ME coupling at room temperature for all bilayer films. The value of αE approached the maximum (140mV/cm Oe) when the thickness of LSMO and BTO films was all equal to 100nm, which was at least one order of magnitude higher than previous reported similar structure due to a rather low dielectric constant of BTO film. The value of αE decreased with the increasing bilayer film thickness when both the LSMO and BTO film thickness were higher than 100nm. It was a combined effect of the thickness dependence for the magnetic and electric properties.

Magnetoelectric, Raman, and XPS Properties of Pb0.7Sr0.3[(Fe2/3Ce1/3)0.012Ti0.988]O3 and Pb0.7Sr0.3[(Fe2/3La1/3)0.012Ti0.988]O3 Nanoparticles

The Pb0.7Sr0.3[(Fe2/3Ce1/3)0.012Ti0.988]O3 (PSFCT) and Pb0.7Sr0.3[(Fe2/3La1/3)0.012Ti0.988]O3 nanoparticles were prepared by chemical synthesis route using polyvinyl alcohol as surfactant. X-ray diffraction pattern has been used to analyze the phase structure and average particles size. The phase structure is also confirmed by Raman spectra. The chemical states of Pb2+, Sr2+, Fe3+; Ti4+, Ce3+, La3+, and oxygen ions have been analyzed by X-ray photoelectron spectroscopy. The magnetoelectric coupling effect is confirmed by magnetic phase transition near ferroelectric phase-transition temperature. The magnetoelectric effect is also confirmed by measuring the value of magnetoelectric coefficient (αE) as the function of applied dc magnetizing field under the influence of ac magnetic field of 10 Oe and frequencies of 847 and 997 Hz. The higher value of αE is observed in PSFCT sample.

Preparation and magnetoelectric characteristics of K0.5Na0.5NbO3-LiSbO3-BiFeO3/CuFe2O4 composite ceramics

The (1-x)(K0.5Na0.5NbO3-LiSbO3-BiFeO3)-xCuFe2O4 (x=0.1, 0.2, 0.3 and 0.4) magnetoelectric composite ceramics are prepared by the conventional solid-state reaction method. The microstructures and properties of the composite ceramics are characterized by X-ray diffractometer, scanning electron microscope and magnetoelectric coupling coefficient meter. The weak ionic interdiffusions between the phases K0.5Na0.5NbO3-LiSbO3-BiFeO3 and CuFe2O4 are observed and their particle sizes are well matched between each other. With the increase of CuFe2O4 content, the piezoelectric coefficient (d33) of the composite ceramics decreases from 130 pC/N to 30 pC/N and the magnetostriction coefficient (-λ) increases from 4.5×10-6 to 12.4×10-6. The magnetoelectric coupling coefficient (αE) of the composite ceramics first increases and then decreases with the CuFe2O4 content increasing. When the composition x=0.3, a maximum value of αE=9.4 mV·cm-1·Oe-1 is achieved.

Dielectric and magnetoelectric properties of BaTiO3–Co0.6Zn0.4Fe1.7Mn0.3O4 composite

Abstract In this paper we studied the structural, dielectric, magnetic and magnetoelectric properties of (x)BaTiO3–(1 − x)Co0.6Zn0.4Fe1.7Mn0.3O4 particulate composite series where x = 0.50, 0.60 and 0.70. BaTiO3–Co0.6Zn0.4Fe1.7Mn0.3O4 composite has the advantage of being non-toxic and environmental friendly from the point of view of device fabrication. High ME voltage coefficients were obtained in the whole series with the highest value of αE ∼ 73 mV/cm Oe achieved in sample x = 0.50 containing equal mole fractions of both the component phases. This value of αE is an order of magnitude higher than that of particulate sintered BaTiO3–CoFe2O4 composites (∼2–4 mV/cm Oe). Dielectric characteristics for these samples indicated two anomalies: (i) one at low temperature close to ferroelectric to paraelectric transition temperature of pure BaTiO3 and (ii) another at higher temperature related to the magnetic transition in ferrite, a characteristic dielectric feature of composite sample.

Excess thermodynamic parameters for binary and ternary mixtures of {1-butanol (1) + cyclohexylamine (2) + n-heptane (3)} at different temperatures: A theoretical study

In this work, we used the experimental data of Kijevcanin et al. for determining the excess thermodynamic parameters such as excess thermal expansion coefficients αE, isothermal coefficient of pressure excess molar enthalpy (∂HmE/∂P)T and excess partial molar volumes V¯m,iE for the binary and ternary mixtures formed by {1-butanol+cyclohexylamine+n-heptanes} at (288.15–323.15) K. The αE values, for 1-butanol+cyclohexylamine are S-shaped and for 1-butanol+n-heptane are positive and for cyclohexylamine+n-heptane are negative over the mole fraction range. The (∂HmE/∂P)T values, for 1-butanol+cyclohexylamine are S-shaped and for binary mixture of 1-butanol+n-heptane are negative and for binary mixture of cyclohexylamine+n-heptane are positive over the mole fraction. The values of αE and (∂HmE/∂P)T are calculated by using the Flory theory, the results show a good agreement with experimental data. The values of αE and (∂HmE/∂P)T for ternary mixture {1-butanol+cyclohexylamine+n-heptanes} are determined and the experimental data are correlated as a function of the mole fraction by using the equations of Cibulka, Jasinski and Malanowski, Singe et al., Pintos et al., Calvo et al., Kohler, and Jacob–Fitzner. The results show that the Calvo et al. equation is better than others.

Effect of misfit strain on multiferroic and magnetoelectric properties of epitaxial La0.7Sr0.3MnO3/BaTiO3 bilayer

La0.7Sr0.3MnO3/BaTiO3 (LSMO/BTO) bilayer films were grown on (0 0 1) oriented SrTiO3 (STO), LaAlO3 (LAO) and (LaAlO3)0.3(SrAl0.5Ta0.5O3)0.7 (LSAT) substrates by pulsed laser deposition. The bilayer deposited on the LSAT substrate presented the best ferromagnetic properties due to the smallest lattice mismatch between LSAT and LSMO. However, the best ferroelectric properties and strongest magnetoelectric (ME) effect existed in the bilayer on the STO substrate due to the minimal compressive strain in the BTO film. All these showed similar frequency-dependent ME behaviour from 0.1 to 100 kHz, and the largest value of ME voltage coefficient (αE) was obtained on the STO substrate. The values of αE were around 263 mV cm−1 Oe−1, 202 mV cm−1 Oe−1 and 169 mV cm−1 Oe−1 at 1 kHz on STO, LSAT and LAO substrates, respectively, which were at least one order of magnitude higher than previously reported values for similar composites and were ascribed mainly to the rather low dielectric constant of the BTO film.

Frequency dependence of magnetoelectric effect in epitaxial La0.7Sr0.3MnO3/BaTiO3 bilayer film

The epitaxial La0.7Sr0.3MnO3/BaTiO3 bilayer film was deposited on (001) oriented SrTiO3 single-crystal substrate by pulsed laser deposition. The bilayer film possessed inherent ferromagnetic, ferroelectric properties. The frequency dependence of magnetoelectric (ME) voltage coefficient revealed a strong ME coupling from 0.1kHz to 100kHz. The value of ME voltage coefficient (αE) was around 213mV/cmOe at 1kHz, which was at least one order of magnitude higher than other reports in the similar structure due to the rather low dielectric constant of BTO film. The measured value of αE corresponded to the theoretical expectation when interface coupling coefficient was 0.88.

Magnetoelectric effect of (100−x)BaTiO3–(x)NiFe1.98O4 (x=20–80 wt %) particulate nanocomposites

The magnetoelectric (100−x)BaTiO3–(x)NiFe1.98O4 (x=20, 40, 60, and 80 wt %) particulate composites have been prepared and the effects of size and interface are studied through microscopy measurements. Large magnetoelectric voltage coefficient (αE) values accompanied by large piezoelastic coefficient, large magnetostrictive strain coefficient, and an adequate interface contact between the magnetic and electric phases were observed in these nanocomposites. The nanocomposite with x=40 has an αE value of 252 mV cm−1 Oe−1, which is the largest value for any particulate magnetoelectric composite, based on the available open literature.

Magnetoelectric effect in magnetostrictive/piezoelectric laminate composite Terfenol-D∕LiNbO3 [(zxtw)−129°∕30°

A magnetoelectric (ME) laminate composite consisting of a new cut type [(zxtw)−129°∕30°] piezoelectric LiNbO3 single crystal and the magnetostrictive Tb1−xDyxFe2−y has been developed and its ME effect has been studied. Our small laminate shows a superior ME voltage coefficient (αE). A wide bandwidth of the frequency peak under a fixed magnetic bias field and a wide bandwidth of optimized magnetic bias field under a high fixed frequency were also observed. The largest value of αE is 2.31V∕cmOe at 160kHz when the magnetic bias field reaches 1.76kOe.

Magnetoelectric effect of the TbDyFe/PZT laminated composite

The great magnetoelectric(ME) effect is a product property of the composite consisting of individual piezoelectric and magnetostrictive phases. The TbDyFe/PZT laminate composites were prepared by magnetron sputtering, and the ME coefficients αE were examined experimentally and calculated by using a finite e lement analysis software. Results showed that the experimental data were in agreement with the calculated results and the value of αE reached the maxim um at the resonance frequency, and αE increased with the increase of the magnetostricive thickness.

Geometric Effects in Avalanche Models of Solar Flares: Implications for Coronal Heating

Observational inferences of the power-law frequency distribution of energy release by solar flares, and in particular its logarithmic slope αE, depend critically on the geometric relationship assumed to relate the observed emitting area A and the underlying emitting volume V. Recent results on the fractal nature of avalanches in self-organized critical models for solar flares indicate that this relationship is a power law V ∝ Aγ with index γ = 1.41(±0.04). We show that when proper account is made for the fractal geometry of the flaring volume, hitherto discrepant observational inferences of αE are brought in much closer agreement. The resulting values of αE lie tantalizingly close, but still below the critical value αE = 2.0, beyond which Parker's conjecture of coronal heating by nanoflares is tenable.

Heat Transfer Model for Regenerative Beds

Regenerative catalytic oxidizers (RCO) are an economic and effective means of controlling volatile organic compounds with concentrations exceeding 1,200 mg/m3 in a gas stream. However, factors influencing the performance of RCO when treating volatile organic compounds in gas streams have seldom been addressed. Therefore, this study presents a convection-dispersion model with an effective thermal diffusivity αe as a parameter to simulate the performance of RCO. To verify the effectiveness of the proposed model, a pilot-scale RCO was constructed with two 20 × 200 cm (inside diameter × height) regenerative beds. Gravel was used as the thermal regenerative solid material. Experimental results indicated that the model with an αe of 2.0–3.8 × 10−6 m2/s can be used to describe the time variation of solids temperature with the packing height at superficial gas velocities Ug of 0.080–0.382 m/s. Values of αe for the bed are closer to those for the gravel solids (αs = 1.0 × 10−6 m2/s) than for air (αg = 54 × 10−6 m2...

Oscillations of the magnetoresistance in an inclined magnetic field for MIS structures on (100) silicon with a high electron density

At electron densities NS>6×10−2 cm−22 a second series of oscillations, which are tentatively attributed to population of the second energy subband, is observed in addition to the main series of Shubnikov-de Haas oscillations. A change in phase of the oscillations of the second series is observed at some angle of inclination αe of the field. The measured value of αe is used to calculate the ratio of the cyclotron mass to the effective g factor. The maximum possible cyclotron mass is also determined as mH< 0.32me. On this basis it is concluded that the second series of oscillations is due to electrons which have an in-plane effective mass m*≈0.2me and which belong to the same valleys of the Fermi surface as in the case of the main oscillations.

Effect of Charge Density on the Dynamic Behavior of Polyelectrolytes in Aqueous Solution

Dynamic light scattering experiments and measurements of surface tension and viscosity of aqueous solutions of poly(2-vinylpyridine) quaternized with ethyl bromide are carried out as function of the charge density and polyelectrolyte concentration (Mw = 2.9 × 105, Mw/Mn = 1.11; αe, degree of quaternization, 0.09 ≤ αe ≤ 0.46). The polyelectrolytes are dissolved in an aqueous solution of potassium bromide (cs = 1 × 10-2c+, c+ = 1 mol dm-3). Their concentrations c̄p are in the range 0.1c̄+ ≤ c̄p ≤ 27c̄+ (c̄+ = 1 g dm-3). The reduced variable Λ (=αecm/cs) is used to characterize the composition of the solutions (cm, molar volume concentration of the repeat unit of the polymer backbone). Monomodal and bimodal dynamic modes characterized by the apparent diffusion coefficients Ds and Df (index s, slow; index f, fast) are found under the following conditions: monomodal, 0.03 ≤ Λ ≤ 0.1; bimodal, 0.1 ≤ Λ ≤ 8. A third dynamic mode characterized by the apparent diffusion coefficient Dint (index int, intermediate) appears at Λ ≳ 1 with small values of αe in the range 0.09 ≤ αe ≤ 0.15 (Ds < Dint < Df). It is assumed that the third mode reflects dynamic properties of hydrophobic domains formed by uncharged segments of the polymer backbone at low values of αe. Hydrophobic interactions show up also in surface tension and viscosity measurements. A model proposed by Lee and Schurr (J. Polym. Sci. 1975, 13, 873) describes the experimental Df data of the fast diffusive mode with two fit parameters (Zeff, effective number of charges of a polyion; Dp, diffusion coefficient of a polyion). Zeff is smaller by a factor of 5−7 than the value calculated on the basis of αe.

Electron Trajectories Calculations of an Energy - Filtering Field-Emission Gun

In many cases, the contribution of beam energy spread to the limitation of the performances of an electron microscope is strong. In the case of the field emission gun (FEG) , Troyon has experimentally shown it is possible to reduce considerably the energy spread by energy filtering at the gun level. The system developed consists basically of a magnetic FEG with a retarding electrode working as the retarding electrode of an energy filter. The principle is recalled in Fig. 1 and the cross section of the accelerator is given in Fig. 2. In this paper, the results of electron trajectories calculations inside the energy filtering field emission gun (EFFEG) are given.Fig. 3 shows that electrons of same energy, but entering the retarding field with different angles, can have exit angles very different. Due to the work function of approximately 4.5 eV the electrons, for an extracting potential Vo = 2 kV, enter in the field of the retarding electrode with an energy smaller than 2 keV. In Fig. 3 trajectories are computed for an electron of 1996 eV. Electrons passing by the nodal points have the same entering and exit angles. Trajectory 1 in Fig. 3 corresponds to an entering radius re = 17.5 μm and an entering semi angle αe = 1.2 mrad. For these re and αe values, at Vr =6 V, the exit semi angle αs = αe . Fig. 3 shows that an electron entering parallely to the axis, even very close to the axis (re = 10 μm) has a larger exit angle than electrons passing by the nodal points.

Magneto-optical rotation studies of liquid mixtures. Part 7.—Further studies with mixtures involving methanol, acetone and ether, and the calculation of the equilibrium constant of interaction

In this final paper of a series concerned with the magneto-optical rotations of binary liquid mixtures the results are presented of a study (at 436 nm) of mixtures of a second component with (a) methanol, (b) acetone and (c) diethyl ether. As in previous work, the departures from ideality were treated in terms of an excess magnetic rotation, αE, and this function was correlated with interactions between the components of the mixtures. Some determinations of αE were also made at 366 nm for systems in which complexes of the charge-transfer type are thought to be present and the results are compared with previous work at 436 nm. Using the αE–composition results for various systems, an attempt has been made to calculate the interaction equilibrium constant, K, between the components in an equimolar mixture and also the magnetic rotation of the resultant complex. It is likely that the K values are more appropriate than the αE values in comparing the interactions between the components in mixtures of widely differing character.

Magneto-optical rotation studies of liquid mixtures. Part 5.—Binary mixtures of water with dimethylsulphoxide, formamide, methyl formamide, dimethyl formamide and acetonitrile

Measurements have been made of the magneto-optical rotations at 435.8 nm of binary liquid mixtures of water with dimethylsulphoxide, formamide, methyl formamide, dimethyl formamide and acetonitrile as part of a study to investigate the applicability of the magneto-optical method in detecting weak molecular interactions in liquid mixtures. The departure from ideality of the mixtures was treated in terms of an excess magnetic rotation, αE. For mixtures of water with dimethylsulphoxide, formamide, methyl formamide and dimethyl formamide the values of αE indicated interaction between the components, whereas with acetonitrile the αE values were compatible with a breakdown of the water structure in the mixtures.

New Potential Function for Alkali Halide Molecules

A new potential-energy function has been suggested for the alkali halide molecules, U=(−e2/r)+Pexp(−kr2),where P and k are constants. Values of αe, ωeχe, and the ionic binding energy Di have been derived for the following three functions: (1) simple Born-Mayer potential, (2) Rittner potential, and (3) the above suggested potential. The results obtained with the new function are much better than those obtained with the Born-Mayer potential, but slightly inferior to those obtained with the Rittner potential.

Road bridge over Lansdowne Valley, Fairmount Park, Philadelphia

In this study, a new kind of magnetoelectric (ME) structure is designed with Terfenol-D, PZT-5A and nonmagnetic and nonelectric trestle. The configuration of this ME structure presents “A-line” type, PZT-5A and Terfenol-D are respectively bonded with the trestles, which adopt the knuckle joint assembly. Differently from the conventional ME layered structure, in the new structure, the deformation of the PZT-5A of larger size is driven by a Terfenol-D layer of smaller size at an external magnetic field. Since the driven force is applied at the ends of piezoelectric layer through the trestles, the whole piezoelectric layer can be completely stretched or compressed, and the larger voltage should be induced. For the new ME structure with mica trestle, the maximum value of αE is twice higher than that for the conventional laminated ME structure. Furthermore, a wider range of response frequency is also observed in this structure. For the new ME structure with ABS trestle, the experimental results indicate that the maximum ME voltage coefficient is measured as high as 31.85 V/cm Oe at 405 Oe.