Narrow Results

The thermal performance of two-dimensional (2D) field-effect transistors (FET) is investigated frequently by solving the Fourier heat diffusion law and the Boltzmann transport equation (BTE). With the introduction of the new generation of 3D FETs in which their thickness is less than the phonon mean-free-path it is necessary to carefully simulate the thermal performance of such devices. This paper numerically integrates the BTE in common 2D transistors including planar single layer and Silicon-On-Insulator (SOI) transistor, and the new generation of 3D transistors including FinFET and Tri-Gate devices. In order to decrease the directional dependency of results in 3D simulations; the Legendre equal-weight (P_N-EW) quadrature set has been employed. It is found that if similar switching time is assumed for 3D and 2D FETs while the new generation of 3D FETs has less net energy consumption, they have higher hot-spot temperature. The results show continuous heat flux distribution normal to the silicon/oxide interface while the temperature jump is seen at the interface in double layer transistors.

This paper uses the finite volume lattice Boltzmann method (FVLBM) to simulate the transient heat conduction from macro- to nano-scales corresponding to Kn = 0.01–10. This model is used for two dimensional (2D) transient hotspot modeling. The results of the diffusive regime are compared with those of the Fourier law as a model of continuum mechanics and an excellent agreement is found in this regime. After the validation of model for the case of Kn = 0.01, it has been used for high-Knudsen number simulations and a test case with Kn = 10 is studied. By increasing the Knudsen number from 0.01 up to 10, the transition from totally diffusive to totally ballistic behavior has been discussed and the wave-feature of heat transport through the solid material has been investigated.

Therapy using the acupuncture meridian system is an important part of traditional Chinese medicine. The purpose of this study was to investigate the electrical conduction properties of the meridians. The current conduction and potential profiles were compared after switching the current direction in the Hegu (LI-4) and Quchi (LI-11) meridians and over a non-acupuncture point 1 cm from Quchi (LI-11) in 20 healthy subjects. Both meridians demonstrated significantly higher conductivity between Hegu (LI-4) and Quchi (LI-11) than between Hegu (LI-4) and the non-acupuncture point. The direction of current, peak frequency and absolute potential values in the direction Hegu (LI-4) to Quchi (LI-11) differed significantly from those in the direction Quchi (LI-11) to Hegu (LI-4). These results suggest that the conducting pathways are stronger in the meridians than in the non-meridians and that preferential conduction directions exist between two acupuncture points. These results are consistent with the theories of Qi-circulation and traditional Chinese medicine.

Nonlocal f(R) gravity was proposed as a powerful alternative to general relativity (GR). This theory has potentially adverse implications for infrared (IR) regime as well as ultraviolet (UV) early epochs. However, there are a lot of powerful features, making it really user-friendly. A scalar–tensor frame comprising two auxiliary scalar fields is used to reduce complex action. However, this is not the case for the modification complex which plays a distinct role in modified theories for gravity. In this work, we study the dynamics of a static, spherically symmetric object. The interior region of space–time had rapidly filled the perfect fluid. However, it is possible to derive a physically based model which relates interior metric to nonlocal f(R). The Tolman–Oppenheimer–Volkoff (TOV) equations would be a set of first-order differential equations from which we can deduce all mathematical (physical) truths and derive all dynamical objects. This set of dynamical equations govern pressure p, density ρ, mass m and auxiliary fields {ψ, ξ}. The full conditional solutions are evaluated and inverted numerically to obtain exact forms of the compact stars Her X-1, SAX J 1808.4-3658 and 4U 1820-30 for nonlocal Starobinsky model of f(◻^-1 R) = ◻^-1 R+α(◻^-1 R)². The program solves the differential equations numerically using adaptive Gaussian quadrature. An ascription of correctness is supposed to be an empirical equation of state for star which is informative in so far as it excludes an alternative nonlocal approach to compact star formation. This model is most suited for astrophysical observation.

An analytical solution is presented to the heat equation in the vicinity of a surface fluid, heated by a modulated Gaussian Laser beam and taking into account three heat transfer modes: conduction, radiation and convection. A new calculation method is performed for profiling temperature inside a surface fluid. Comparison with several experimental profiles explains some unexpected temperature profile results as non-Gaussian behaviour.

In this study, ZnO nanoparticles and MnO-doped SnO₂-based thick film varistors (TFVs) were fabricated using screen printing technique. The sintering temperature had significant impact on the SZM-based TFVs, especially in terms of grain growth, even at a low sintering temperature of 1100${}^{\circ }$C. The strong solid-state reaction during sintering may be attributed to the large surface area of the 20 nm ZnO nanoparticles that promoted strong surface reaction even at low sintering temperatures. Moreover, the X-ray diffraction lattice constant and full wave at half maximum data indicated that the sintering process also improved the grain crystallinity with the decrease in intrinsic compressive stress. The sintering temperatures also significantly influenced the electrical properties of the SZM-based TFVs with a significant decrease in the breakdown field from 360 V/mm (sample at 1100${}^{\circ }$C) to 158 V/mm (sample at 1250${}^{\circ }$C). The grain boundary resistance ($R_{\mathrm{\text{GB}}})$ also experienced a dramatic drop from 266.4 k$\mathrm{\Omega }$ (sample at 1100${}^{\circ }$C) to 89.46 k$\mathrm{\Omega }$ (sample at 1250${}^{\circ }$C). The sample sintered at 1200${}^{\circ }$C exhibited superior electrical behaviors with a nonlinear exponent of 61 and leakage current of 115 $\mu$A. Furthermore, it achieved high permittivity and low dissipation factor at the low frequency range. The conduction behaviors of ${\mathrm{\text{O}}}^{\prime }$ ions with activation energy of approximately 0.6 eV was dominated by decreasing ${\mathrm{\text{Zn}}}_{\mathrm{\text{Sn}}}^{\prime \prime }$ and ${\mathrm{\text{Mn}}}_{\mathrm{\text{Sn}}}^{\prime \prime }$ defects (around 0.4 eV) with increasing sintering temperature. Therefore, the sintering process can be applied to control the conduction behaviors of SZM-based TFVs doped with ZnO nanoparticle powder and achieve improved structural and electrical properties with good nonlinear behaviors.

The anatomy of the atrioventricular conduction system was first described nearly a hundred years ago. Since then, it has been an occasional subject of controversy mainly through a lack of adherence to the original definitions based on histology. The gross landmarks for locating the atrial component of the conduction system are found in the right atrium. The components and structure of the system in human are comparable to that found in commonly used laboratory animals. The conduction system is composed of specialized myocytes. Its atrial component, the atrioventricular node, is in contact with atrial myocardium. Having penetrated the atrioventricular insulating plane, the major ventricular bundles are encased in fibrous sheaths that separate the specialized myocytes from the ordinary myocardium. Only at the distal ramifications of the bundle branches do the fibrous sheaths disappear, allowing continuity with ventricular myocardium. Being the only muscular pathway connecting atrial with ventricular myocardium, knowledge of its structure can help in developing potential therapies for some forms of cardiac arrhythmias.

The components of the diffusive thermal conductivity tensor of superfluid neutron stars are calculated by using anisotropic energy gap for ³p₂ pairing and approximation collision integrals at temperatures where . The contribution from neutron–neutron collisions is taken into account. Nonrelativistic effects for pairing will be studied. A comparison with the corresponding relativistic case is also made.

In general, the transport of thermal energy in living tissue is a complex process. The analysis of the heat conduction of skin tissue is helpful for understanding of the bio-thermo-mechanical behavior of skin tissue. So far, three kinds of conduction law — (1) the Fourier model, (2) the C-V model and (3) dual-phase-lag (DPL) model — are often investigated in bio-thermal transfer process. In this study, the mathematical model of heat conduction of the skin tissue subjected to a general transient heating at the skin surface was established. The analytical solutions of these three conduction models are presented. In addition, the measure of thermal injury of the skin tissue subjected to a harmonic heating was investigated. It was found that the phenomenon of Fourier model is greatly different to those of the C-V and DPL models. Moreover, the effects of the phase lags, the heating frequency, and the heat quantity on the temperature variation and the index of thermal injury were significant. In sum, the analytical method can be used to solve the conduction problem of any one-layer tissue.

This work is about a heat transfer phenomenon in relation to the periodically laminated composite. The specific type of thermal loading, analyzed in this paper, require formulation of Robin boundary conditions. To consider a layered structure of analyzed composite, the tolerance averaging technique is used. This method allows to take into account a thickness of the layers and obtain the equations with continuous coefficients. To solve these equations, the finite difference method is used, because an analytical solution is not available in this case (in contrast to the analogous issue in relation to a homogeneous layer).

Flexible dielectric polymers that can withstand high electric field and simultaneously have high dielectric constant are desired for high-density energy storage. Here, we systematically investigated the impact of oxygen-containing ether and carbonyl groups in the backbone structure on dielectric properties of a series of cyclic olefin. In comparison to the influence of the –CF₃ pendant groups that had more impact on the dielectric constant rather than the band gap, the change of the backbone structure affected both the dielectric constant and band gaps. The one polymer with ether and carbonyl groups in the backbone has the largest band gap and highest discharge efficiency, while it has the lowest dielectric constant. The polymer without any ether groups in the backbone has the smallest band gap and lowest discharge efficiency, but it has the highest dielectric constant. Polymers that have no dipolar relaxation exhibit an inversely correlated dielectric constant and band gap. Enhancing the dipolar relaxation through rational molecular structure design can be a novel way to break through the exclusive constraint of dielectric constant and band gap for high-density energy storage.

The effect of local thermal nonequilibrium on the steady state heat conduction in metal foam tube heat exchanger as a porous layer in the presence of internal heat generated by considering the thermal conductivity coefficient as a function of temperature was investigated. A two temperature model is investigated by using reconstruction of variational iteration method (RVIM). The obtained results from RVIM are compared with the numerical results of Maple. These comparisons reveal that RVIM is a very powerful and precise approach to solve nonlinear ordinary differential equations and there is a good agreement between them. In this study, the effects of porosity and internal heat generation on the temperature distribution in the solid and liquid phases are presented.

Over the last decade or so, we have been developing the possible existence of highly magnetized white dwarfs with analytical stellar structure models. While the primary aim was to explain the nature of the peculiar overluminous type Ia supernovae, later on, these magnetized stars were found to have even wider ranging implications including those for white dwarf pulsars, soft gamma-ray repeaters and anomalous X-ray pulsars, as well as gravitational radiation. In particular, we have explored in detail the mass-radius relations for these magnetized stars and showed that they can be significantly different from the Chandrasekhar predictions which essentially leads to a new super-Chandrasekhar mass-limit. Recently, using the stellar evolution code STARS, we have successfully modelled their formation and cooling evolution directly from the magnetized main sequence progenitor stars. Here we briefly discuss all these findings and conclude with their current status in the scientific community.

Philosophically, embedded-cooling strategies seek to remove as many barriers as possible between the primary thermal management solution and the component(s) of interest. However, in many cases, such as three-dimensional chip stacks and flexible electronics, conduction processes can still limit primary or secondary heat transfer pathways. Thus, materials development and an enhanced understanding of conduction physics represent opportunities for improving the cooling performance of the overall solution. Here, recent advances in bulk cubic crystals, two-dimensional layered materials, and advances in understanding conduction physics are briefly discussed, with a critical outlook on their potential for improving embedded cooling of electronic devices.