Experimental and numerical investigations on spatial and temporal heat transfer characteristics of a thermal convection domain due to the presence of a centrally placed heated cylinder are presented. Modification of thermal convection currents are ubiquitous in various immersion cooling applications in which the presence of a secondary heat transferring surface plays a significant role. A comprehensive assessment of the dynamic evolution of plumes, its reorganization due to the presence of fully or partially heated cylinder, and resulting surface heat transfer augmentations are presented. Extensive experimental and numerical trials have been performed to figure out the effect of extent of occupancy of the cylinder in terms of area ratio (0.006419 ≤ AR ≤ 0.2563), Rayleigh number of the thermal convection domain (4.35 × 107 ≤ Ra ≤ 2.9 × 108), amount of heat generation from the cylinder and its location. Shadowgraph and temperature measurements at various locations inside the convection domain are used to characterize the thermal plumes experimentally. A finite-volume solver based on SIMPLE algorithm is used for numerical simulations and is validated using the experimental transient temperature data at different locations inside the enclosure. A generalized correlation of the form Nu=CRam for the time averaged Nusselt number as a function of the Rayleigh number are developed for thermal convection in presence of a partially heated cylinder for various geometric configurations and thermal conditions of the central cylinder.
The exponential growth of electronic devices, satellite technology, and wireless communication has significantly increased electromagnetic (EM) pollution, leading to widespread electromagnetic interference (EMI). Therefore, there is an urgent need for high-performance, environmentally friendly EMI shielding materials to protect both electronic systems and human well-being. This article highlights the importance of developing high-performance EMI shielding materials through intelligent micro- and nano-structural engineering and careful compositional tuning, with a focus on the innovative strategies enabled by carbon composites. It provides an in-depth discussion of the preparation methods for carbon foams and carbon fiber composites aiming to achieve high EMI shielding performance. This article aims to provide valuable insights and inspiration to researchers in related fields, promoting the collective advancement of research and practical applications of carbon composites for EMI shielding across a broad frequency range. The multifunctionality of carbon composites such as carbon foams and carbon fiber composites has strong potential in the field of aerospace, electronics, defense, and stealth technologies due to their high electrical conductivity, lightweight nature, heat dissipation ability, fire resistance, moisture insensitivity, and tunable mechanical properties.
Despite decades of research on CO 2 capture and conversion, translating laboratory advances into products for widespread public use remains elusive.
In this paper, a new similarity measure for comparing two Gaussian Mixture Models (GMMs) is obtained. This is based on an embedding of the manifold of K-component GMMs into the manifold of the symmetric positive definite matrices (SPD). The GMM manifold with the pullback of the induced metric is shown to be isometric to the submanifold with the metric induced by the affine-invariant Riemannian metric (AIRM) on the SPD manifold. We also prove that on the GMM manifold the AIRM is a lower bound for the pullback of the induced metric. This enables to use the AIRM as a similarity measure of GMMs. The effectiveness of this framework is demonstrated through texture recognition experiments on standard machine learning benchmarks.
Luminous Red Novae (LRNe) have been argued to be related to the ejection of common envelopes (CEs) in binary star systems. Ejection of CEs leads to tightened stellar orbits capable of forming compact binaries that merge in Hubble time. As these mergers are seen by gravitational-wave (GW) detectors such as LIGO, Virgo and KAGRA (LVK), we ask what the merger rates of compact binaries in LVK tell us about the fraction of LRNe that lead to the formation of compact binaries that merge in Hubble time. Using the observed volumetric rates of LRNe from the Zwicky Transient Facility (ZTF) and of compact binary mergers from LVK observations, we derive limits on the fraction of LRNe that produce compact binaries that merge in Hubble time. Assuming the LRNe rate closely follows the star formation rate at any redshift, we use the delay time distribution models for compact binaries to compute the compact binary merger rate. A comparison of this merger rate with the latest volumetric rates of compact binary mergers from the fourth GW transient catalog (GWTC-4) at the present epoch of LVK allows us to constrain the above fraction. We find that only a fraction as small as ∼ 10^-3 (median) of the LRNe correspond to the GW-observed binary neutron star (BNS) and neutron star-black hole (NSBH) mergers. This potentially implies that the majority of the LRNe population will not lead to mergers of compact objects, but other end products, such as stellar mergers.
