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1.
The complex impedance of the Ag 2ZnP 2O 7 compound has been investigated in the temperature range 419–557 K and in the frequency range 200 Hz–5 MHz. The Z′ and Z′ versus frequency plots are well fitted to an equivalent circuit model. Dielectric data were analyzed using complex electrical
modulus M* for the sample at various temperatures. The modulus plot can be characterized by full width at half-height or in terms of
a non-exponential decay function
f( \text t ) = exp( - \text t/t ) b \phi \left( {\text{t}} \right) = \exp {\left( { - {\text{t}}/\tau } \right)^\beta } . The frequency dependence of the conductivity is interpreted in terms of Jonscher’s law:
s( w) = s \textdc + \text Aw n \sigma \left( \omega \right) = {\sigma_{\text{dc}}} + {\text{A}}{\omega^n} . The conductivity σ
dc follows the Arrhenius relation. The near value of activation energies obtained from the analysis of M″, conductivity data, and equivalent circuit confirms that the transport is through ion hopping mechanism dominated by the
motion of the Ag + ions in the structure of the investigated material. 相似文献
2.
The Ac electrical conductivity and the dielectric relaxation properties of the [(C 3H 7) 4N] 2Cd 2Cl 6 polycrystalline sample have been investigated by means of impedance spectroscopy measurements over a wide range of frequencies
and temperatures, 209 Hz–5 MHz and 361–418 K, respectively. The purpose is to make a difference between the electrical and
dielectric properties of the polycrystalline sample and single crystal. Besides, a detailed analysis of the impedance spectrum
suggests that the electrical properties of the material are strongly temperature-dependent. Plots of (Z" versus Z') are well
fitted to an equivalent circuit model consisting of a series combination of grains and grains boundary elements. Moreover,
the temperature dependence of the electrical conductivity in the different phases follows the Arrhenius law and the frequency
dependence of σ (ω) follows the Jonscher’s universal dynamic law. Furthermore, the modulus plots can be characterized by full
width at half height or in terms of a nonexperiential decay function φ( t) = exp( t/ t) β. Finally, the imaginary part of the permittivity constant is analyzed with the Cole–Cole formalism. 相似文献
3.
The [N(CH 3) 4][N(C 2H 5) 4]ZnCl 4 compound has been synthesized by a solution-based chemical method. The X-ray diffraction study at room temperature revealed
an orthorhombic system with P2 12 12 space group. The complex impedance has been investigated in the temperature and frequency ranges 420–520 K and 200 Hz–5 MHz,
respectively. The grain interior and grain boundary contribution to the electrical response in the material have been identified.
Dielectric data were analyzed using the complex electrical modulus M
* for the sample at various temperature. The modulus plots can be characterized by full width at half height or in terms of
a non-exponential decay function ϕ( t) = exp[( −t/τ)
β
]. The detailed conductivity study indicated that the electrical conduction in the material is a thermally activated process.
The variation of the AC conductivity with frequency at different temperatures obeys the Almond and West universal law. 相似文献
4.
In this paper we compute some of the higher order terms in the asymptotic behavior of the two point function
\mathbb P( A2(0) £ s1, A2( t) £ s2)\mathbb{P}(\mathcal {A}_{2}(0)\leq s_{1},\mathcal{A}_{2}(t)\leq s_{2}), extending the previous work of Adler and van Moerbeke (; Ann. Probab. 33, 1326–1361, 2005) and Widom (J. Stat. Phys. 115, 1129–1134, 2004). We prove that it is possible to represent any order asymptotic approximation as a polynomial and integrals of the Painlevé
II function q and its derivative q′. Further, for up to tenth order we give this asymptotic approximation as a linear combination of the Tracy-Widom GUE density
function f
2 and its derivatives. As a corollary to this, the asymptotic covariance is expressed up to tenth order in terms of the moments
of the Tracy-Widom GUE distribution. 相似文献
5.
In this article, we assume that there exist scalar D*[`( D)] *{D}^{\ast}{\bar {D}}^{\ast}, Ds*[`( D)] s*{D}_{s}^{\ast}{\bar{D}}_{s}^{\ast}, B*[`( B)] *{B}^{\ast}{\bar {B}}^{\ast} and Bs*[`( B)] s*{B}_{s}^{\ast}{\bar{B}}_{s}^{\ast} molecular states, and study their masses using the QCD sum rules. The numerical results indicate that the masses are about
(250–500) MeV above the corresponding D
*–[`( D)] *{\bar{D}}^{\ast}, D
s
*–[`( D)] s*{\bar {D}}_{s}^{\ast}, B
*–[`( B)] *{\bar{B}}^{\ast} and B
s
*–[`( B)] s*{\bar {B}}_{s}^{\ast} thresholds, the Y(4140) is unlikely a scalar Ds*[`( D)] s*{D}_{s}^{\ast}{\bar{D}}_{s}^{\ast} molecular state. The scalar D*[`( D)] *D^{\ast}{\bar{D}}^{\ast}, Ds*[`( D)] s*D_{s}^{\ast}{\bar{D}}_{s}^{\ast}, B*[`( B)] *B^{\ast}{\bar{B}}^{\ast} and Bs*[`( B)] s*B_{s}^{\ast}{\bar{B}}_{s}^{\ast} molecular states maybe not exist, while the scalar D¢ *[`( D)] ¢*{D'}^{\ast}{\bar{D}}^{\prime\ast}, Ds¢*[`( D)] s¢*{D}_{s}^{\prime\ast}{\bar{D}}_{s}^{\prime\ast}, B¢*[`( B)] ¢*{B}^{\prime\ast}{\bar{B}}^{\prime\ast} and Bs¢*[`( B)] s¢*{B}_{s}^{\prime\ast}{\bar{B}}_{s}^{\prime\ast} molecular states maybe exist. 相似文献
6.
The AC conductivity of the LiCaPO 4 compound has been measured in the temperature range 634–755 K and the frequency range 300 Hz–5 MHz. The impedance data were
fitted to an equivalent circuit consisting of series combination of grains, grains boundary, and electrode elements. Dielectric
data were analyzed using complex electrical modulus M* at various temperatures. The modulus plots are characterized by the presence of two relaxation peaks thermally activated.
The activation energies obtained from the analysis of M″ (0.90 eV) and conductivity data (0.94 eV) are very close, revealing an ionic hopping mechanism. 相似文献
7.
Rutile filled PTFE composites have been fabricated through Sigma Mixing, Extrusion, Calendering and Hot pressing (SMECH) process.
Dielectric constant (e r¢\varepsilon_{r}') and loss tangent (tan δ) of filled composites at microwave frequency region were measured by waveguide cavity perturbation technique using a Vector
Network Analyzer. The temperature coefficient of dielectric constant (t er¢\tau_{\varepsilon_{r}'}) was measured in the 0–100°C temperature range. In order to tailor the temperature coefficient of dielectric constant of
the composite, thermoplastic Poly (ether ether ketone) (PEEK) has been used as a secondary polymer. Flexible laminate having
a dielectric constant, e r¢ ~ 10.4\varepsilon_{r}'\sim10.4, loss tangent tan δ∼0.0045 and t er¢ ~ -40 ppm/K\tau_{\varepsilon_{r}'}\sim-40\mbox{ ppm}/\mbox{K} was realized in Polytetrafluroethylene (PTFE)/rutile composites with the addition of 8 wt% PEEK. The reduction in t er¢\tau_{\varepsilon_{r}'} is mainly attributed to the positive t er¢\tau_{\varepsilon_{r}'} of PEEK and increased interface region in the composites as a result of the PEEK addition. 相似文献
8.
To date, the fastest lithium ion-conducting solid electrolytes known are the perovskite-type ABO3 oxide, with A = Li, La and B = Ti, lithium lanthanum titanate (LLTO)
Li3x La( 2 \mathord | / |
\vphantom 2 3 3 ) - x [¯]( 1 \mathord | / |
\vphantom 1 3 3 ) - x TiO3 {\rm Li}_{3x} {\rm La}_{\left( {{2 \mathord{\left/ {\vphantom {2 3}} \right. \kern-\nulldelimiterspace} 3}} \right) - x} \Box_{\left( {{1 \mathord{\left/ {\vphantom {1 3}} \right. \kern-\nulldelimiterspace} 3}} \right) - x} {\rm TiO}_3 and its structurally related materials. In this formula, [¯]\Box represents the vacancy. These materials have attracted much attention due to their application in lithium ion batteries used
as energy sources in microelectronic and information technologies. In addition to the well-established simple cubic, tetragonal
and orthorhombic perovskite type distorted cell structures, the hexagonal unit cell was reported in a recent study for Li0.5 La0.5 TiO3 − δ
, ( 0 £ d £ 0.06 )\left( {0 \le \delta \le 0.06} \right). We investigated the ionic conductivity in hexagonal La0.5 Li0.5 TiO3{\rm La}_{0.5} {\rm Li}_{0.5}\- {\rm TiO}_3 by molecular dynamics. We confirmed that ionic conductivity in this compound is due to the motion of lithium ions. We show
that both Arrhenius and Vogel–Tamman–Fulcher-type relationships could be used to express the high-temperature conductivity
of this compound. From our results, hexagonal LLTO exhibits almost 1.7–1.9 ×10 − 3 S cm − 1 at room temperature. Thus, due to its high ionic conductivity, this compound is expected to show some advantages in comparison
with the best conductors of this family, for usual applications of ionic conductors. 相似文献
9.
If X = X( t, ξ) is the solution to the stochastic porous media equation in O ì Rd, 1 £ d £ 3,{\mathcal{O}\subset \mathbf{R}^d, 1\le d\le 3,} modelling the self-organized criticality (Barbu et al. in Commun Math Phys 285:901–923, 2009) and X
c
is the critical state, then it is proved that
ò ¥0m( O\ Ot0) dt < ¥,\mathbb P-a.s.{\int^{\infty}_0m(\mathcal{O}{\setminus}\mathcal{O}^t_0)dt<{\infty},\mathbb{P}\hbox{-a.s.}} and
lim t?¥ ò O| X( t)- Xc| dx = l < ¥, \mathbb P-a.s.{\lim_{t\to{\infty}} \int_\mathcal{O}|X(t)-X_c|d\xi=\ell<{\infty},\ \mathbb{P}\hbox{-a.s.}} Here, m is the Lebesgue measure and Otc{\mathcal{O}^t_c} is the critical region {x ? O; X( t,x)= Xc(x)}{\{\xi\in\mathcal{O}; X(t,\xi)=X_c(\xi)\}} and X
c
( ξ) ≤ X(0, ξ) a.e. x ? O{\xi\in\mathcal{O}}. If the stochastic Gaussian perturbation has only finitely many modes (but is still function-valued), lim t ? ¥ ò K| X( t)- Xc| dx = 0{\lim_{t \to {\infty}} \int_K|X(t)-X_c|d\xi=0} exponentially fast for all compact K ì O{K\subset\mathcal{O}} with probability one, if the noise is sufficiently strong. We also recover that in the deterministic case ℓ = 0. 相似文献
10.
The massive wave equation ${\square_{g}\psi - \alpha \frac{\Lambda}{3}\psi = 0}The massive wave equation
\squaregy- a\fracL3y = 0{\square_{g}\psi - \alpha \frac{\Lambda}{3}\psi = 0} is studied on a fixed Kerr-anti de Sitter background (M,gM,a,L){\left(\mathcal{M},g_{M,a,\Lambda}\right)}. We first prove that in the Schwarzschild case (a = 0), ψ remains uniformly bounded on the black hole exterior provided that
a < \frac94{\alpha < \frac{9}{4}}, i.e. the Breitenlohner-Freedman bound holds. Our proof is based on vectorfield multipliers and commutators: The total flux
of the usual energy current arising from the timelike Killing vector field T (which fails to be non-negative pointwise) is shown to be non-negative with the help of a Hardy inequality after integration
over a spacelike slice. In addition to T, we construct a vectorfield whose energy identity captures the redshift producing good estimates close to the horizon. The
argument is finally generalized to slowly rotating Kerr-AdS backgrounds. This is achieved by replacing the Killing vectorfield
T = ∂
t
with K=?t + l?f{K=\partial_t + \lambda \partial_\phi} for an appropriate λ ~ a, which is also Killing and–in contrast to the asymptotically flat case–everywhere causal on the black hole exterior. The
separability properties of the wave equation on Kerr-AdS are not used. As a consequence, the theorem also applies to spacetimes
sufficiently close to the Kerr-AdS spacetime, as long as they admit a causal Killing field K which is null on the horizon. 相似文献
11.
The following hydrogen and oxygen concentration cells using the oxide protonic conductors,
\text CaZ\text r0.98\text I\text n0.02\text O3 - d {\text{CaZ}}{{\text{r}}_{0.98}}{\text{I}}{{\text{n}}_{0.02}}{{\text{O}}_{3 - \delta }} and
\text CaZ\text r0.9\text I\text n0.1\text O3 - d {\text{CaZ}}{{\text{r}}_{0.{9}}}{\text{I}}{{\text{n}}_{0.{1}}}{{\text{O}}_{{3} - \delta }} , as the solid electrolyte were constructed, and their polarization behavior was studied,
( \textreversible: - )\text Pt,\textH2 + \textH2\textO/\textCaZ\textr1 - y\textI\textny\textO3 - d( y = 0.02\text or 0.1 )/\textAr( + \textH2 + \textO2 ),\text Pt( + :\textirreversible ) \left( {{\text{reversible}}: - } \right){\text{ Pt}},{{\text{H}}_2}{ + }{{\text{H}}_2}{\text{O}}/{\text{CaZ}}{{\text{r}}_{1 - y}}{\text{I}}{{\text{n}}_y}{{\text{O}}_{3 - \delta }}\left( {y = 0.02{\text{ or }}0.1} \right)/{\text{Ar}}\left( { + {{\text{H}}_2} + {{\text{O}}_2}} \right),{\text{ Pt}}\left( { + :{\text{irreversible}}} \right) 相似文献
12.
TiO 2 nanoparticles with enhanced solid solution of Cr up to 16 wt% in polymorphs of rutile, anatase, brookite, α-PbO 2-type, and occasionally baddeleyite-type were synthesized via pulse laser ablation on ceramic TiO 2 target dissolved with Cr 2O 3 or clamped Cr/Ti plates in air. Analytical electron microscopic observations indicated these nanocondensates have prevalent
crystallographic shear (CS) along specific planes to form superstructures. The rutile type typically shows (100) and (010)
CS besides the conventional ones rotating about the [111] zone axis as reported for ambient samples. The CS planes are parallel
to (001) for anatase, (001) and ([`1] \overline{1} 10) for brookite, whereas (001) and {1[`3] \overline{3} 1} for the α-PbO 2-type TiO 2 with varied extent of Cr dissolution. Surface modification, as a result of Cr dissolution and/or internal stress, was observed
for all the polymorphs. 相似文献
13.
Li reactivity of the monoclinic NiP 2 electrode is investigated through first-principles density functional theory calculations and local chemical bond analysis.
The stability of various Li
x
NiP 2 is studied with respect to the conversion reaction . The T = 0K Li
x
NiP 2 phase stability diagram, as obtained, reveals that several ternary phases of lithium composition Li 2NiP 2 can be electrochemically achieved upon reduction. They correspond to monoclinic or tetragonal structures in which Ni adopts
a square-planar (D 4h-Li 2NiP 2) or a pseudo-tetrahedral (Td-Li 2NiP 2) environment. A local chemical bond analysis suggests that D 4h–Li 2NiP 2 would result from an interlayer P–P bond breaking induced by a two-phase (P redox) process, while Td-Li 2NiP 2 would result from a Jahn–Teller distortion associated with a single-phase (Ni–P redox) process.
Electronic supplementary material The online version of this article (doi:) contains supplementary material, which is available to authorized users.
This paper was presented at the 11th EuroConference on the Science and Technology of Ionics, Batz-sur-Mer, Sept. 9–15, 2007. 相似文献
14.
Solid polymer electrolytes (SPE) based on poly-(vinyl alcohol) (PVA) 0.7 and sodium iodide (NaI) 0.3 complexed with sulfuric acid (SA) at different concentrations were prepared using solution casting technique. The structural
properties of these electrolyte films were examined by X-ray diffraction (XRD) studies. The XRD data revealed that sulfuric
acid disrupt the semi-crystalline nature of (PVA) 0.7(NaI) 0.3 and convert it into an amorphous phase. The proton conductivity and impedance of the electrolyte were studied with changing
sulfuric acid concentration from 0 to 5.1 mol/liter (M). The highest conductivity of (PVA) 0.7(NaI) 0.3 matrix at room temperature was 10 −5 S cm −1 and this increased to 10 −3 S cm −1 with doping by 5.1 M sulfuric acid. The electrical conductivity (σ) and dielectric permittivity ( ε′) of the solid polymer electrolyte in frequency range (500 Hz–1 MHz) and temperature range (300–400) K were carried out.
The electrolyte with the highest electrical conductivity was used in the fabrication of a sodium battery with the configuration
Na/SPE/MnO 2. The fabricated cells give open circuit voltage of 3.34 V and have an internal resistance of 4.5 kΩ. 相似文献
15.
The lead pyrophosphate, Pb 2P 2O 7, compound was prepared by conventional solid-state reaction and identified by X-ray powder diffractometer. Pb 2P 2O 7 has a triclinic structure whose electrical properties were studied using impedance spectroscopy technique. Both impedance
and modulus analysis exhibit the grain and grain boundary contribution to the electrical response of the sample. The temperature
dependence of the bulk and grain boundary conductivity were found to obey the Arrhenius law with activation energies E
g = 0.66 eV and E
gb = 0.67 eV, respectively. The scaling behavior of the imaginary part of the complex impedance suggests that the relaxation
describes the same mechanism at various temperatures. 相似文献
16.
Good-quality hexagonal NbSe 2 single crystals were prepared. In 2H-NbSe 2, superconducting and charge density wave (CDW) transitions were found at T
s = 7.4 K and T
c = 35 K respectively as reported previously. We have noticed that these two transitions are changed to T
c = 42 K and T
s = 6.5 K, in 4H-NbSe 2. Thermopower has shown clear anomaly at CDW transitions. The anisotropic upper critical field was calculated as ~3 and 6.3
for 2H- and 4H-single crystals around t = 0.81, where t = T/ T
s, from resistivity and explained in terms of coherence length. From the relation, Hc2 ( T)= Hc2 (0)[1- t2]H_{\rm c2} (T)=H_{\rm c2} (0)[1-t^2], Hc2l (0)H_{\rm c2}^l (0) was calculated as ~8.15 T and 16.98 T at t = 0.84 in 2H-NbSe 2 and 4H-NbSe 2 respectively. However, Hc2t (0) = 2.68H_{\rm c2}^t (0) = 2.68T for both single crystals. 相似文献
17.
The spectral dependence of Stern–Volmer constants ( KSVlK_{SV}^{\lambda} ) for fluorescence quenching by Cu 2+ ions in a standard sample of humic acid (HA) (IHSS) with monochromatic excitation (λ ex = 337.1 nm) conditions has been studied in the spectral range 400–600 nm. This is interpreted within a concept implying that
HA macromolecules possess the property of polydispersity, which means that fluorophore-containing sites are different in terms
of chemical nature and spatial accessibility. Modeling data show that the minimum number of spectral components required for
the simulated spectral dependence of KSVlK_{SV}^{\lambda} to agree as closely as possible with that observed experimentally is three. 相似文献
18.
This paper considers Hardy–Lieb–Thirring inequalities for higher order differential operators. A result for general fourth-order
operators on the half-line is developed, and the trace inequality
tr( (-D)2 - CHRd,2\frac1|x|4 - V(x) )-g £ Cgò\mathbbRd V(x)+g+ \fracd4 dx, g 3 1 - \frac d 4,\mathrm{tr}\left( (-\Delta)^2 - C^{\mathrm{HR}}_{d,2}\frac{1}{|x|^4} - V(x) \right)_-^{\gamma}\leq C_\gamma\int\limits_{\mathbb{R}^d} V(x)_+^{\gamma + \frac{d}{4}}\,\mathrm{d}x, \quad \gamma \geq 1 - \frac d 4, 相似文献
19.
In this article, we assume that there exists a scalar
Ds*[`( D)] s*D_{s}^{\ast}{\bar{D}}_{s}^{\ast}
molecular state in the J/ ψ
φ invariant mass distribution, and we study its mass using the QCD sum rules. The predictions depend heavily on the two criteria
(pole dominance and convergence of the operator product expansion) of the QCD sum rules. The value of the mass is about
MDs*[`(D)]s*=(4.43±0.16)M_{D_{s}^{\ast}{\bar{D}}_{s}^{\ast}}=(4.43\pm0.16)
GeV, which is inconsistent with the experimental data. The
Ds*[`( D)] s*D_{s}^{\ast}{\bar{D}}_{s}^{\ast}
is probably a virtual state and is not related to the meson Y(4140). Another possibility, such as a hybrid charmonium, is not excluded. 相似文献
20.
Lifetime measurements of excited states in 149Nd have been performed using the advanced time-delayed b \beta
g \gamma
g \gamma( t) method. Half-lives of 14 excited states in 149Nd have been determined for the first time or measured with higher precision. Twelve new g \gamma -lines and 5 new levels have been introduced into the decay scheme of 149Pr based on results of the g \gamma
g \gamma coincidence measurements. Reduced transition probabilities have been determined for 40 g \gamma -transitions in 149Nd . Configuration assignments for 6 rotational bands in 149Nd are proposed. Enhanced E1 transitions indicate that the ground-state band and the band built on the 332.9keV level constitute a pair of the Kp = 5/2 ±\ensuremath K^{\pi} = 5/2^{\pm} parity doublet bands. Potential energy surfaces on the (b 2,b 3)\ensuremath (\beta_{2},\beta_{3}) -plane have been calculated for the lowest single quasi-particle configurations in 149Nd using the Strutinski method and the axially deformed Woods-Saxon potential. The predicted occurrence of the octupole-deformed
K = 5/2 configuration is in agreement with experiment. Unexpectedly low | D0|\ensuremath \vert D_0\vert values obtained for the Kp = 5/2 ±\ensuremath K^{\pi} = 5/2^{\pm} parity doublet bands may result from cancellation between the proton and neutron shell correction contributions to | D0|\ensuremath \vert D_0\vert . 相似文献
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