윤후 교수

Abstract In this decade, the demands of energy saving and diverse personal thermoregulation requirements along with the emergence of wearable electronics and smart textiles give rise to the resurgence of personal thermal management (PTM) technologies. PTM, including personal cooling, heating, insulation, and thermoregulation, are far more flexible and extensive than the traditional air/liquid cooling garments for the human body. Concomitantly, many new advanced materials and strategies have emer

"Fata Morgana" or "Mirage" phenomena have long been captivated as optical illusions, which actually relies on gradient-density air or vapor. Man-made optical illusions have witnessed significant progress by resorting to artificially structured metamaterials. Nevertheless, two long-standing challenges remain formidable: first, exotic parameters (negative or less than unity) become inevitable; second, the signature of original object is altered to that of a virtual counterpart. It is thus not able

Lattice heat conduction can be modulated via nanostructure interfaces. Although advances have been made by viewing phonons as particles, the controllability should be enhanced by fully utilizing their wave nature. By considering phonons as coherent waves, herein we design an optimized aperiodic superlattice that minimizes the coherent phonon heat conduction by alternatingly coupling coherent phonon transport calculations and machine learning. The thermal conductivity of the fabricated aperiodic

Low-grade heat exists ubiquitously in the environment. Thermogalvanic cells (TGCs) are promising for converting the widespread low-grade heat directly into electricity owing to relatively high thermopowers of redox reactions. This work reports polarized electrolytes with ultrahigh thermopowers of -8.18 mV K^-1 for n-type and 9.62 mV K^-1 for p-type. The electrolyte consists of I^-/I₃^- redox couple, methylcellulose, and KCl. Thermoresponsive met

A conformal phosphor coating can realize a phosphor layer with uniform thickness, which could enhance the angular color uniformity (ACU) of light-emitting diode (LED) packaging. In this study, a novel freeform lens was designed for simultaneous realization of LED uniform illumination and conformal phosphor coating. The detailed algorithm of the design method, which involves an extended light source and double refractions, was presented. The packaging configuration of the LED modules and the mode

Abstract Thermal camouflage, which is used to conceal objects in the infrared vision for confrontation with infrared detection in civilian or military applications, has garnered increasing attraction and interest recently. Compared with conductive thermal camouflage, that is to tune heat conduction to achieve equivalent temperature fields, radiative thermal camouflage, based on emissivity engineering, is more promising and shows much superiority in the pursuit of dynamic camouflage technology wh

Transformation thermodynamics, as one of the important branches among the extensions of transformation optics, has attracted plentiful attentions and interests recently. The result of transformation thermodynamics, or called as "thermal cloak", can realize isothermal region and hide objects from heat. In this paper, we presented the concept of "reverse thermal cloak" to correspond to the thermal cloak and made a simple engineering definition to identify them. By full-wave simulations, we verifie

The light extraction efficiency (LEE), correlated color temperature (CCT), and angular color uniformity (ACU) of the conformal coating phosphor silicone gel were investigated by Monte Carlo ray-tracing simulations. Relative to the conventional dispensing method, the conformal coating method can make the light-emitting diode (LED) module obtain better optical properties. It was found that the thickness of the phosphor layer in conformal coating was a key factor determining the optical performance