scholarly journals Using Amorphous CoB Alloy as Transducer to Detect Acoustic Propagation and Heat Transport at Interface

2021 ◽  
Vol 11 (11) ◽  
pp. 5155
Author(s):  
Liu Jian ◽  
Gyung-Min Choi
Keyword(s):  
Heat Transport ◽  
Sapphire Substrate ◽  
Intermediate Layer ◽  
Thermal Conductance ◽  
Acoustic Oscillation ◽  
Acoustic Propagation ◽  
Acoustic Oscillations ◽  
Interfacial Coupling ◽  
Soft Layer ◽  
Substrate Interface

Acoustic oscillation provides useful information regarding the interfacial coupling between metal transducer layers and substrate materials. The interfacial coupling can be significantly reduced by a mechanically soft layer between the transducer and substrate. However, preserving a thin, soft layer at the interface during fabrication is often challenging. In this study, we demonstrate that an amorphous CoB alloy on top of a sapphire substrate can substantially amplify acoustic oscillations. By analyzing the attenuation of acoustic oscillations, we show that a thin, soft layer with a thickness of >2 ± 1 Å exists at the interface. The intermediate layer at the interface is further verified by investigating heat transport. By analyzing the slow decrease of the temperature of the transducer layer, we determine a thermal conductance of 35 ± 5 MW m−2 K−1 at the transducer/substrate interface. This low value supports the existence of a thin, soft layer at the interface. Our results demonstrate that an amorphous metal with B alloying effectively preserves the soft nature at the interface and detects the acoustic propagation and heat transport across it.

scholarly journals Baryon acoustic oscillations signature in the three-point angular correlation function from the SDSS-DR12 quasar survey

2020 ◽  
Vol 492 (3) ◽  
pp. 4469-4476 ◽  
Author(s):  
E de Carvalho ◽  
A Bernui ◽  
H S Xavier ◽  
C P Novaes
Keyword(s):  
Correlation Function ◽  
Angular Correlation ◽  
Statistical Significance ◽  
Acoustic Oscillation ◽  
Sloan Digital Sky Survey ◽  
Similar Data ◽  
Acoustic Oscillations ◽  
Data Set ◽  
A Value ◽  
Angular Correlation Function

ABSTRACT The clustering properties of the Universe at large scales are currently being probed at various redshifts through several cosmological tracers and with diverse statistical estimators. Here we use the three-point angular correlation function (3PACF) to probe the baryon acoustic oscillation (BAO) features in the quasars catalogue from the Sloan Digital Sky Survey Data Release 12, with mean redshift $\overline{z} = 2.225$, detecting the BAO imprint with a statistical significance of $2.9 \sigma$, obtained using lognormal mocks. Following a quasi-model-independent approach for the 3PACF, we find the BAO transversal signature for triangles with sides θ1 = $1{^{\circ}_{.}}0$ and θ2 = $1{^{\circ}_{.}}5$ and the angle between them of α = 1.59 ± 0.17 rad, a value that corresponds to the angular BAO scale $\theta_{\rm BAO}=1{^{\circ}_{.}}82 \pm 0{^{\circ}_{.}}21$, in excellent agreement with the value found in a recent work ($\theta_{\rm BAO}=1{^{\circ}_{.}}77 \pm 0{^{\circ}_{.}}31$) applying the two-point angular correlation function (2PACF) to similar data. Moreover, we performed two types of test: one to confirm the robustness of the BAO signal in the 3PACF through random displacements in the data set, and the other to verify the suitability of our random samples, a null test that in fact does not show any signature that could bias our results.

scholarly journals Baryon acoustic oscillations from the cross-correlation of Lyα absorption and quasars in eBOSS DR14

2019 ◽  
Vol 629 ◽  
pp. A86 ◽  
Author(s):  
Michael Blomqvist ◽  
Hélion du Mas des Bourboux ◽  
Nicolás G. Busca ◽  
Victoria de Sainte Agathe ◽  
James Rich ◽  
...  
Keyword(s):  
Three Dimensional ◽  
Acoustic Oscillation ◽  
Companion Paper ◽  
Peak Position ◽  
Sloan Digital Sky Survey ◽  
Acoustic Oscillations ◽  
Microwave Background ◽  
Angular Diameter Distance ◽  
Statistical Precision ◽  
Sky Survey

We present a measurement of the baryon acoustic oscillation (BAO) scale at redshift z = 2.35 from the three-dimensional correlation of Lyman-α (Lyα) forest absorption and quasars. The study uses 266 590 quasars in the redshift range 1.77 <  z <  3.5 from the Sloan Digital Sky Survey (SDSS) Data Release 14 (DR14). The sample includes the first two years of observations by the SDSS-IV extended Baryon Oscillation Spectroscopic Survey (eBOSS), providing new quasars and re-observations of BOSS quasars for improved statistical precision. Statistics are further improved by including Lyα absorption occurring in the Lyβ wavelength band of the spectra. From the measured BAO peak position along and across the line of sight, we determined the Hubble distance DH and the comoving angular diameter distance DM relative to the sound horizon at the drag epoch rd: DH(z = 2.35)/rd = 9.20 ± 0.36 and DM(z = 2.35)/rd = 36.3 ± 1.8. These results are consistent at 1.5σ with the prediction of the best-fit spatially-flat cosmological model with the cosmological constant reported for the Planck (2016) analysis of cosmic microwave background anisotropies. Combined with the Lyα auto-correlation measurement presented in a companion paper, the BAO measurements at z = 2.34 are within 1.7σ of the predictions of this model.

Effect of Interfacial Thermal Conductance Between the Nanoparticles

2018 ◽  
Author(s):  
Anil Yuksel ◽  
Edward T. Yu ◽  
Michael Cullinan ◽  
Jayathi Murthy
Keyword(s):  
Heat Transfer ◽  
Heat Transport ◽  
Thermal Management ◽  
Contact Point ◽  
Radiation Heat Transfer ◽  
Thermal Conductance ◽  
Radiation Heat ◽  
Interfacial Thermal Conductance ◽  
Nanostructured Interfaces

Heat transport across nanostructured interfaces, such as between nanoparticles, has been of great interest for advanced thermal management. Interfacial thermal conductance, G, is central to understanding thermal heat transport between nanoparticles that have a contact point between each other as well as the surrounded medium. In this study, we show that G dominates the heat transport compared to the conduction and radiation heat transfer modes between the nanoparticles for values higher than ∼20 (MW/m2K). We also investigate the effect of radius of contact between the nanoparticles on the overall modes of heat transfer.

scholarly journals How accurately can we measure the baryon acoustic oscillation feature?

2020 ◽  
Vol 498 (3) ◽  
pp. 3744-3757
Author(s):  
Rossana Ruggeri ◽  
Chris Blake
Keyword(s):  
Asymptotic Variance ◽  
Confidence Region ◽  
Acoustic Oscillation ◽  
Acoustic Oscillations ◽  
Noise Component ◽  
Posterior Probability Distribution ◽  
The Difference ◽  
Definition Of ◽  
The Individual ◽  
The Impact

ABSTRACT Baryon acoustic oscillations (BAOs) represent one of the cleanest probes of dark energy, allowing for tests of the cosmological model through the measurement of distance and expansion rate from a 3D galaxy distribution. The signal appears at large scales in the correlation function where linear theory applies, allowing for the construction of accurate models. However, due to the lower number of modes available at these scales, sample variance has a significant impact on the signal, and may sharpen or widen the underlying peak. Therefore, equivalent mock realizations of a galaxy survey present different errors in the position of the peak when uncertainties are estimated from the posterior probability distribution corresponding to the individual mocks. Hence, the posterior width, often quoted as the error in BAO survey measurements, is subject to sample noise. A different definition of the error is provided by the asymptotic variance of the maximum likelihood estimator, which involves the average over multiple realizations, and is not subject to sample noise. In this work, we reanalyse the main galaxy survey data available for BAO measurements and quantify the impact of the noise component on the error quoted for BAO measurements. We quantify the difference between three definitions of the error: the confidence region computed from a single posterior, the average of the variances of many realizations, and the Fisher matrix prediction assuming a Gaussian likelihood. We also explore the impact of a ‘detectability prior’ based on the significance of the BAO detection.

Thermal conductance attributed to phonon and electron in graphene nanoribbon

2014 ◽  
Vol 28 (18) ◽  
pp. 1450116 ◽  
Author(s):  
En-Jia Ye ◽  
Yi-Jian Shi ◽  
Lihong Shi ◽  
Xuean Zhao
Keyword(s):  
Low Temperature ◽  
Heat Transport ◽  
Energy Band ◽  
Function Method ◽  
Energy Transport ◽  
Graphene Nanoribbons ◽  
Thermal Conductance ◽  
Square Lattice ◽  
Heat Current ◽  
Electron Contribution

In this work, the energy transport of phonon and electron in graphene nanoribbons (GNRs) are investigated by the nonequilibrium Green's function method without considering the interaction of phonon and electron. The heat current of phonon contribution comes from the gradient of temperature. While for the electron contribution, it stems from the gradient of both temperature and electrochemical potential. The corresponding intermediate functions satisfy the Onsager relationship. Thermal conductances are calculated in GNR and compared to those in square lattice ribbon model respectively. It is found that both the phonon and electron thermal conductances in square lattice ribbon are smaller than those in GNRs at low temperature and surpass those in armchair and zigzag GNRs respectively, as the temperature increases. Meanwhile, the heat transport is related to the edges of GNRs. These phenomena depend on their dispersion relations and energy band structures.

Silicon Nanowire Conductance in the Ballistic Regime: Models and Simulations

2012 ◽  
Vol 134 (5) ◽  
Author(s):  
David Lacroix ◽  
Karl Joulain ◽  
Jerome Muller ◽  
Gilles Parent
Keyword(s):  
Elastic Wave ◽  
Heat Transport ◽  
Silicon Nanowires ◽  
Silicon Nanowire ◽  
Normal Modes ◽  
Thermal Conductance ◽  
Wave Theory ◽  
Ballistic Regime ◽  
Thin Wires ◽  
Transmission And Reflection

This study deals with phonon heat transport in silicon nanowires. A review of various methods that can be used to assess thermal conductance of such nanodevices is presented. Here, a specific attention is paid to the case of the Landauer Formalism, which can describe extremely thin wires conductance. In order to use this technique, the calculation of propagating modes in a silicon nanowire is necessary. Among the several existing models allowing such calculation, the elastic wave theory has been used to obtain the normal mode number. Besides, in this study, the transmission and reflection of phonon at the interface between two nanostructures are discussed. Using the diffuse mismatch model (DMM), the global transmissivity of the system made of a nanowire suspended between two thermal reservoirs is addressed. Then, the calculations of normal modes’ numbers and thermal conductances of several silicon nanowires, with various diameters set between bulk thermal reservoirs, are presented and compared to other models and available experiments.

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