Pronounced asymmetry in the crystallization behavior during constant heating and cooling of a bulk metallic glass-forming liquid

The crystallization behavior of the supercooled bulk metallic glass-forming Zr41Ti14Cu12Ni10Be23 liquid was studied with different heating and cooling rates. A rate of about 1 K/s is sufficient to suppress crystallization of the melt upon cooling from the equilibrium liquid. Upon heating, in contrast, a rate of about 200 K/s is necessary to avoid crystallization. The difference between the critical heating and cooling rate is discussed with respect to diffusion-limited growth taking classical nucleation into account. The calculated asymmetry of the critical heating and cooling rate can be explained by the fact that nuclei formed during cooling and heating are exposed to different growth rates

Cooling rate, heating rate and aging effects in glassy water

We report a molecular dynamics simulation study of the properties of the potential energy landscape sampled by a system of water molecules during the process of generating a glass by cooling, and during the process of regenerating the equilibrium liquid by heating the glass. We study the dependence of these processes on the cooling/heating rates as well as on the role of aging (the time elapsed in the glass state). We compare the properties of the potential energy landscape sampled during these processes with the corresponding properties sampled in the liquid equilibrium state to elucidate under which conditions glass configurations can be associated with equilibrium liquid configurations.Comment: to be published in Phys. Rev. E (rapid comunication

A comparison of recently introduced instruments for measuring rice flour viscosity

The Rapid Visco-Analyser (RVA) and the Micro Visco-Amylograph (MVA) were compared in measuring the viscosity properties of rice flours. A total of 72 rice samples were procured from three cultivars harvested at two locations and three moisture contents and separated into thin, medium, and thick kernel-thickness fractions. A fast and a slow heating rate was used in the procedure for both instruments. Cultivar, kernel thickness, and harvest location affected rice viscosity. The RVA viscosity profiles using a fast heating rate were best correlated with those of the MVA using a slow heating rate. The RVA slow heating rate resulted in lower final viscosities than those using the MVA because of the spindle structure of the RVA. For both the RVA and the MVA, greater rice flour peak viscosities and less trough and final viscosities were obtained with a slow rather than a fast heating rat

Thermal electron heating rate: A derivation

The thermal electron heating rate is an important heat source term in the ionospheric electron energy balance equation, representing heating by photoelectrons or by precipitating higher energy electrons. A formula for the thermal electron heating rate is derived from the kinetic equation using the electron-electron collision operator as given by the unified theory of Kihara and Aono. This collision operator includes collective interactions to produce a finite collision operator with an exact Coulomb logarithm term. The derived heating rate O(e) is the sum of three terms, O(e) = O(p) + S + O(int), which are respectively: (1) primary electron production term giving the heating from newly created electrons that have not yet suffered collisions with the ambient electrons; (2) a heating term evaluated on the energy surface m(e)/2 = E(T) at the transition between Maxwellian and tail electrons at E(T); and (3) the integral term representing heating of Maxwellian electrons by energetic tail electrons at energies ET. Published ionospheric electron temperature studies used only the integral term O(int) with differing lower integration limits. Use of the incomplete heating rate could lead to erroneous conclusions regarding electron heat balance, since O(e) is greater than O(int) by as much as a factor of two

Regimes of heating and dynamical response in driven many-body localized systems

We explore the response of many-body localized (MBL) systems to periodic driving of arbitrary amplitude, focusing on the rate at which they exchange energy with the drive. To this end, we introduce an infinite-temperature generalization of the effective "heating rate" in terms of the spread of a random walk in energy space. We compute this heating rate numerically and estimate it analytically in various regimes. When the drive amplitude is much smaller than the frequency, this effective heating rate is given by linear response theory with a coefficient that is proportional to the optical conductivity; in the opposite limit, the response is nonlinear and the heating rate is a nontrivial power-law of time. We discuss the mechanisms underlying this crossover in the MBL phase, and comment on its implications for the subdiffusive thermal phase near the MBL transition.Comment: 17 pages, 9 figure

Occurrence of Hysteresis like behavior of resistance of Sb2Te3Sb_2 Te_3 film in heating-cooling cycle

Experimental observations of a peculiar behavior observed on heating and cooling ${\rm Sb_2Te_3}$ films at different heating and cooling rate are detailed. The film regained its original resistance, forming a closed loop, on the completion of the heating-cooling cycle which was reproducible for identical conditions of heating and cooling. The area enclosed by the loop was found to depend on (i) the thickness of the film, (ii) the heating rate, (iii) the maximum temperature to which film was heated and (iv) the cooling rate. The observations are explained on basis of model which considers the film to be a resultant of parallel resistances. The film's finite thermal conductivity gives rise to a temperature gradient along the thickness of the film, due to this and the temperature coefficient of resistance, the parallel combination of resistance changes with temperature. Difference in heating and cooling rates give different temperature gradient, which explains the observed hysteresis.Comment: 21 pages and 10 figure