We derive and validate a technique for predicting phonon dispersion relations lifetimes from the atomic velocities in crystal using spectral energy density. This procedure, applied here to carbon nanotubes, incorporates full anharmonicity of interactions into lifetime frequency predictions. It can also account nonperiodic between phonons nonbonded molecules near solid surface. properties obtained anharmonic lattice dynamics calculations thermal conductivities nonequilibrium...

Two methods for predicting phonon frequencies and relaxation times are presented. The first is based on quasiharmonic anharmonic lattice dynamics calculations, the second a combination of calculations molecular simulations. These properties then used with Boltzmann transport equation under relaxation-time approximation to predict thermal conductivity. validity low-temperature assumptions made in framework assessed by comparing conductivities predicted Green-Kubo direct test system...

The validity of the commonly used quantum corrections for mapping a classically predicted thermal conductivity onto corresponding value are assessed by self-consistently predicting classical and conductivities crystalline silicon system via lattice-dynamics calculations. Applying to predictions, with or without zero-point energy, does not bring them into better agreement predictions compared uncorrected values above temperatures 200 K. By examining mode dependence phonon properties, we...

In recent years, the Boltzmann transport equation (BTE) has begun to be used for predicting thermal in dielectrics and semiconductors at submicron scale. However, most published studies make a gray assumption do not account either dispersion or polarization. this study, we propose model based on BTE, accounting transverse acoustic longitudinal phonons as well optical phonons. This incorporates realistic phonon curves silicon. The interactions among different branches frequencies are...

This letter proposes a method for fabricating suspended micro-/nanoscale polymer fibers continuously, in which polymeric micro-/nanofibers are formed by drawing and solidification of viscous liquid solution is pumped through glass micropipette. By controlling the parameters, this demonstrated to form networks having amorphous internal structure uniform diameters from micrometers down sub-50-nm different molecular weights polystyrene dissolved xylene.

We present an analytical model for the size-dependence of thin film and nanowire thermal conductivity compare predictions to experimental measurements on silicon nanostructures. The contains no fitting parameters only requires bulk lattice constant, conductivity, acoustic phonon speed as inputs. By including mode-dependence lifetimes resulting from phonon-phonon phonon-boundary scattering, captures approach data better than gray models based a single lifetime.

The in-plane phonon thermal conductivities of argon and silicon thin films are predicted from the Boltzmann transport equation under relaxation time approximation. We model using bulk properties obtained harmonic anharmonic lattice dynamics calculations. input required for calculations is interatomic potentials: Lennard-Jones Stillinger–Weber silicon. effect boundaries included by considering only phonons with wavelengths that fit within film adjusting times to account mode-dependent,...

We predict the cross-plane phonon thermal conductivity of Stillinger-Weber silicon thin films as 17.4 nm using lattice Boltzmann method. The are modeled bulk properties obtained from harmonic and anharmonic dynamics calculations. use this approach, which considers all phonons in first Brillouin-zone, to assess suitability common assumptions. Specifically, we validity of: (i) neglecting contributions optical modes, (ii) isotropic approximation, (iii) assuming an averaged mean-free path, (iv)...

This paper investigates the effectiveness of a thermal control unit (TCU) for portable electronic devices by performing experimental and numerical analyses. The TCU objective is to improve management when their operating time limited few hours. It composed an organic phase change material (PCM) conductivity enhancer (TCE). To overcome relatively low PCM, TCE incorporated into PCM boost its conductivity. structure complex, modeling device with it requires effort. Hence, this research develops...

Numerical predictions of blood flow patterns and hemodynamic stresses in Abdominal Aortic Aneurysms (AAAs) are performed a two-aneurysm, axisymmetric, rigid wall model using the spectral element method. Physiologically realistic aortic is simulated under pulsatile conditions for range time-averaged Reynolds numbers 50⩽Rem⩽300, corresponding to peak 262.5⩽Repeak⩽1575. The vortex dynamics induced by AAAs characterized sequence five different phases one period cycle. Hemodynamic disturbance...

In the abdominal segment of human aorta under a patient's average resting conditions, pulsatile blood flow exhibits complex laminar patterns with secondary flows induced by adjacent branches and irregular vessel geometries. The dynamics becomes more when there is pathological condition that causes changes in normal structural composition wall, for example, presence an aneurysm. This work examines hemodynamics hypothetical three-dimensional models aortic aneurysms (AAAs). Numerical...

The clinical assessment of abdominal aortic aneurysm (AAA) rupture risk is based on the quantification AAA size by measuring its maximum diameter from computed tomography (CT) images and estimating expansion rate sac over time. Recent findings have shown that geometrical shape size, as well local wall thickness may be related to this risk; thus, reliable noninvasive image-based methods evaluate geometry a potential become valuable tools. Utilizing existing CT data, three-dimensional nine...

Polymeric nanofibers are finding increasing number of applications and hold the potential to revolutionize diverse fields such as tissue engineering, smart textiles, sensors, actuators. Aligning producing high aspect ratio fiber arrays (length/diameter > 2 000) in sub-micron nanoscale diameters has been challenging due fragility polymeric materials, thus making it difficult deposit them one dimensional structures functionally interfaced with other systems. Here, we present a pseudo dry...