Transient processes generally constitute part of energy-system cycles. If skillfully manipulated, they actually are capable of assisting systems to behave beneficially to suit designers needs. In the present study, behaviors related to both thermal c
onductivities ($kappa$) and heat capacities ($c_{v}$) are analyzed. Along with solutions of the temperature and the flow velocity obtained by means of theories and simulations, three findings are reported herein: $(1)$ effective $kappa$ and effective $c_{v}$ can be controlled to vary from their intrinsic material-property values to a few orders of magnitude larger; $(2)$ a parameter, tentatively named as nonlinear thermal bias, is identified and can be used as a criterion in estimating energies transferred into the system during heating processes and effective operating ranges of system temperatures; $(3)$ When a body of water, such as the immense ocean, is subject to the boundary condition of cold bottom and hot top, it may be feasible to manipulate transient behaviors of a solid propeller-like system such that the system can be turned by a weak buoyancy force, induced by the top-to-bottom heat conduction through the propeller, provided that the density of the propeller is selected to be close to that of the water. Such a turning motion serves both purposes of performing the hydraulic work and increasing the effective thermal conductivity of the system.
We demonstrate experimentally an air-slot mode-gap photonic crystal cavity with quality factor of 15,000 and modal volume of 0.02 cubic wavelengths, based on the design of an air-slot in a width-modulated line-defect in a photonic crystal slab. The o
rigin of the high Q air-slot cavity mode is the mode-gap effect from the slotted photonic crystal waveguide mode with negative dispersion. The high Q cavities with ultrasmall mode volume are important for applications such as cavity quantum electrodynamics, nonlinear optics and optical sensing.
