A
bstract
We study a relation between the thermal diffusivity (
D
T
) and two quantum chaotic properties, Lyapunov time (τ
L
) and butterfly velocity (
v
B
) in strongly correlated systems by using a ...holographic method. Recently, it was shown that
E
i
:
=
D
T
,
i
/
v
B
,
i
2
τ
L
i
=
x
,
y
is universal in the sense that it is determined only by some scaling exponents of the IR metric in the low temperature limit regardless of the matter fields and ultraviolet data. Inspired by this observation, by analyzing the anisotropic IR scaling geometry carefully, we find the concrete expressions for
E
i
in terms of the critical dynamical exponents
z
i
in each direction,
E
i
=
z
i
/
2
z
i
−
1
. Furthermore, we find the lower bound of
E
i
is always 1
/
2, which is not affected by anisotropy, contrary to the
η/s
case. However, there may be an upper bound determined by given fixed anisotropy.
A
bstract
We investigate the upper bound of charge diffusion constant in holography. For this purpose, we apply the conjectured upper bound proposal related to the equilibration scales (
ω
eq
,
k
eq
...) to the Einstein-Maxwell-Axion model. (
ω
eq
,
k
eq
) is defined as the collision point between the diffusive hydrodynamic mode and the first non-hydrodynamic mode, giving rise to the upper bound of the diffusion constant
D
at low temperature
T
as
D
=
ω
eq
/
k
eq
2
. We show that the upper bound proposal also works for the charge diffusion and (
ω
eq
,
k
eq
), at low
T
, is determined by
D
and the scaling dimension ∆(0) of an infra-red operator as
ω
eq
k
eq
2
=
2
πT
Δ
0
ω
eq
/
D
, as for other diffusion constants. However, for the charge diffusion, we find that the collision occurs at real
k
eq
, while it is complex for other diffusions. In order to examine the universality of the conjectured upper bound, we also introduce a higher derivative coupling to the Einstein-Maxwell-Axion model. This coupling is particularly interesting since it leads to the violation of the
lower
bound of the charge diffusion constant so the correction may also have effects on the
upper
bound of the charge diffusion. We find that the higher derivative coupling does not affect the upper bound so that the conjectured upper bound would not be easily violated.
Bi-Te based materials have been used for near-room-temperature thermoelectric applications. However, their properties dramatically decrease at high temperatures (over 100 °C), limiting their use in ...power generation. In this study, we investigated the enhanced thermoelectric properties of Bi-Te based materials by Cu doping and employing the melt-spinning (MS) process that can be utilized especially at elevated temperatures. By changing the doping amount, we could modulate the temperature dependence of thermoelectric properties, where the maximum ZT temperature could be shifted from room temperature to 450 K. The highest ZT value, 1.34, was achieved at 400 K for 2% Cu-doped Bi0.5Sb1.5Te3, which is due to the enhancement in power factor and reduction in lattice thermal conductivity. The average ZT value between room temperature and 530 K was 1.17 for 2% Cu-doped Bi0.5Sb1.5Te3, which is 46% higher than that of pristine Bi0.5Sb1.5Te3. Consequently, the synergetic effect of MS process and Cu incorporation can be a promising method to widen the application of Bi-Te based thermoelectric materials for mid-temperature power generation.
The combined effect of melt-spinning process and Cu incorporation gives to widen Bi-Te-based thermoelectric materials for mid-temperature power generation. Display omitted
PurposeThe current study aims to explore the relationships between three kinds of customer-to-customer (C2C) interaction quality and brand loyalty via customer promotion and prevention ...emotions.Design/methodology/approachIn order to test the model, we gathered self-administered data through an online survey. The relationships were examined using structural equation modelling (SEM).FindingsThe findings show that the influence of customer-to-customer interaction quality on promotion/prevention emotion varies: friend-interaction quality evokes both promotion emotion (high-arousal feelings) and prevention emotion (low-arousal feelings), whereas neighbouring customer-interaction quality elicits promotion emotion, and audience-interaction quality elicits prevention emotion. Moreover, the findings show that enhancing both promotion and prevention emotions is crucial to improve customer attitudinal loyalty in mass service settings, and the strength of the link from promotion emotion to attitudinal loyalty is stronger than that from prevention emotion.Practical implicationsThe authors suggest that marketers should focus on facilitating effective friend- and neighbouring customer-interaction to enhance promotion emotion.Originality/valueThe paper contributes to a stream of research on customer-to-customer interaction by exploring the relative influences of three kinds of customer-to-customer interaction quality on customer attitudinal loyalty via post-consumption emotions.
Introduction of nanophases is known to be effective in improving thermoelectric performance as it allows the simultaneous engineering of electronic and thermal transports. In this study, we ...synthesized Fe and Co nanoparticle-embedded MnSi1.787Al0.01 nanocomposites through a simple nanometal-decoration technique and spark plasma sintering. The nanoparticles introduced in the matrix caused energy band bending at the matrix–nanoparticle interface, which induced charge transfer and energy filtering effects. These two seemingly opposing effects were combined so as to increase the power factor of the nanocomposites by enhancing the electronic transport. Moreover, we found that the lattice thermal conductivity decreased owing to intensified phonon scattering. Hence, a maximum ZT of 0.53 (at 773 K) was achieved in 0.6 vol% Fe nanoparticle-embedded nanocomposites, which is 25% higher than that of the pristine sample.
Display omitted
•We synthesized Fe and Co nanoparticles-embedded nanocomposites.•Enhanced electronic transport properties by a well-controlled band alignment.•Improved power factor by the optimized charge transfer and energy filtering effect.•Suppressed lattice thermal conductivity due to the intensified phonon scattering.•Increased thermoelectric performance by 25% achieved.
Numerous studies have demonstrated the negative influence of sexual debut during adolescence on mental health outcomes. This article contributes to this literature by investigating whether sexual ...debut has negative effects on mental health among South Korean adolescents and whether the timing of adolescent sexual debut matters. Drawing on longitudinal data from a nationally representative survey, we first predicted mental health outcomes at one year after high school graduation using first sexual intercourse that had occurred before the outcomes were measured. In a second statistical model, adolescent sexual debut was defined as first coitus that had occurred before high school graduation. Sexual debut was associated with an increase in problematic aggressive behaviors for both genders. In contrast, only girls experienced a rise in depressive symptoms after becoming sexually active. For girls, having sex before high school graduation was correlated with worse mental health outcomes to the extent that sexual debut even enhanced the risk of suicidal ideation. We concluded that the negative effects of sexual activity among South Korean adolescents are attributable mainly to the sexually conservative atmosphere and gendered sexuality in that country.
Four types of undulated cylinders with streamwise undulation, transverse undulation, in-phase undulation and antiphase undulation are employed to investigate the undulation-axis effect on the ...structure of heat transfer around wavy cylinders. The flows around these undulated cylinders are numerically simulated by large eddy simulation at Re = 3000. The force coefficients and Nusselt numbers of the cylinders with transverse undulation and in-phase undulation are significantly influenced by wavelength and wave amplitude. On the other hand, the cylinders with streamwise undulation and antiphase undulation show a very weak dependence of the force coefficients and Nusselt numbers on the combinations of wavelength and wave amplitude. It is noted that the cylinder with antiphase undulation, under certain wavy conditions, provides about the same Nusselt number as the smooth cylinder, even though the force coefficients are considerably decreased. The thermal characteristics, according to the combination of wavy geometric parameters, are supported by the surface distribution of the Nusselt numbers. In addition, the isothermal distribution, which depends on the wake flow, explains the variation in the Nusselt numbers. The present results suggest that a proper modification of geometry can improve both heat transfer and aerodynamic performances.
s
Noting the source-dependent properties of dissolved organic matter (DOM), this study explored the recoverable compounds by solid phase extraction (SPE) of two common sorbents (C18 and PPL) eluted ...with methanol solvent for contrasting DOM sources via fluorescence excitation-emission matrix coupled with parallel factor analysis (EEM-PARAFAC) and Fourier transform ion cyclotron resonance mass spectrometry (FT-ICR-MS). Fresh algae and leaf litter extracts DOM, one riverine DOM, and one upstream lacustrine DOM were selected for the comparison. C18 sorbent was generally found to extract more diverse molecular formula, relatively higher molecular weight, and more heteroatomic DOM compounds within the studied mass range than PPL sorbent except for the leaf litter extract. Even with the same sorbent, the main molecular features of the two end member DOM were distributed on different sides of the axes of a multivariate ordination, indicating the source-dependent characteristics of the recoverable compounds by the sorbents. In addition, further examination of the molecular formula uniquely present in the two end members and the upstream lake DOM suggested that proteinaceous, tannin-like, and heteroatomic DOM constituents might be potential compound groups which are labile and easily degraded during their mobilization into downstream watershed. This study provides new insights into the sorbent selectivity of DOM from diverse sources and potential lability of various compound groups.
Virtual screening is becoming a ground-breaking tool for molecular discovery due to the exponential growth of available computer time and constant improvement of simulation and machine learning ...techniques. We report an integrated organic functional material design process that incorporates theoretical insight, quantum chemistry, cheminformatics, machine learning, industrial expertise, organic synthesis, molecular characterization, device fabrication and optoelectronic testing. After exploring a search space of 1.6 million molecules and screening over 400,000 of them using time-dependent density functional theory, we identified thousands of promising novel organic light-emitting diode molecules across the visible spectrum. Our team collaboratively selected the best candidates from this set. The experimentally determined external quantum efficiencies for these synthesized candidates were as large as 22%.
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