On the effective temperature of an aging powder
نویسنده
چکیده
– The aging dynamics and the fluctuation-dissipation relation between the spontaneous diffusion induced by a random noise and the drift motion induced by a small stirring force are numerically investigated in a 3D schematic model of compacting powder: a gravity-driven lattice-gas with purely kinetic constraints. The compaction dynamics is characterized by a super-aging behaviour and, in analogy with glasses, exhibits a purely dynamical time-scale dependent effective temperature. A simple experiment to measure this quantity is suggested. Introduction. – Slow relaxation phenomena are ubiquitous in nature. When one deals with glassy dynamics the challenge is the identification of the relevant degrees of freedom which makes a thermodynamic description still possible. In the attempt to provide a unifying framework to the behaviour of aging and non-relaxational systems a microscopic definition of effective temperature was introduced through a generalized fluctuation-dissipation relation [4]. This quantity turns out to coincide, at least in mean-field glasses, with the Edwards’ compactivity [6, 7, 8, 5], previously introduced in a granular matter context [1, 2]. For a class of finite-dimensional and zero-gravity compacting systems, recent numerical results have come to support this correspondence [9]. However, in contrast to the case of strong [10], or moderately strong [11] vibration regime, the absence of a temperature-like quantity in a gently shaken granular material is a rather problematic issue [12, 13, 14]. In this paper we investigate the nature of the aging dynamics and the effective temperature in a simple 3D gravity driven lattice-gas model of compacting powder [16]. We show that the non-equilibrium dynamics is characterized by a three-steps relaxation mechanism and ‘super-aging’ in the mean-square displacement. We then find that during the compaction the response to a random perturbation is positive and observe a violation of the fluctuation-dissipation relation similar to glasses. Such features show that it is possible to describe the compaction dynamics in terms of a purely dynamical time-scale dependent effective temperature. The model. – The model we consider was introduced in [16] as a simple generalization of the Kob-Andersen model [15]. The system consists of N particles on a body centred cubic lattice where there can be at most one particle per site. There is no cohesion energy among Typeset using EURO-LTEX 2 EUROPHYSICS LETTERS particles and the Hamiltonian is simply
منابع مشابه
بررسی عوامل مؤثر بر رسوب پودر آب پرتقال بر دیواره خشککن پاششی
The difficulties in the storage of fruit juice and the use of juice powder in various food processing industries has made the juice powder attractive to consumers and producers. Making powder from fruit juice is one of the most complex methods of fruit processing.The hygroscopic nature of fruit juice component and its thermoplastic properties has caused the drying time control and the transport...
متن کاملبررسی عوامل مؤثر بر رسوب پودر آب پرتقال بر دیواره خشککن پاششی
The difficulties in the storage of fruit juice and the use of juice powder in various food processing industries has made the juice powder attractive to consumers and producers. Making powder from fruit juice is one of the most complex methods of fruit processing.The hygroscopic nature of fruit juice component and its thermoplastic properties has caused the drying time control and the transport...
متن کاملCharacterization of Copper-Manganese Oxide Catalysts and Their Precursors: Effect of Precipitate Aging upon the Structure and Morphology of Precursors and Catalysts
Copper-manganese oxide catalysts are prepared with an atomic ratio of Cu/Mn=2/1 using a coprecipitation procedure under air atmosphere. The time of aging, i.e., the time that precipitate remains in contact with the precipitating medium, has been varied from 0 (for unaged precursor) to 300 minutes and the effect of precipitate aging time in each atmosphere upon the structure and morphology of di...
متن کاملTHE EFFECT OF PROCESSING PARAMETERS ON SOL GEL SYNTHESIS OF β-SiC NANO POWDER
Mono dispersed nano SiC particles with spherical morphology were synthesized in this project by hydrolysis and condensation mechanism during sol gel processing. pH, temperature and precursor’s ratio considered as the main parameters which could influence particles size. According to DLS test results, the smallest size of particles in the sol (<5nm) was obtained at pH<4. It can be observed from ...
متن کاملOptimization of Preparation Factors for Cerium Oxide Synthesis as a Support for CO PrOx Catalyst
Nanocrystalline ceria has been considered as support for carbon monoxide preferentially oxidation. In this study ceria was prepared by precipitation method and the effects of preparation conditions, such as pH of solution (8-10), aging time (1-12 hr), drying temperature (80-120 °C), calcination time (2-6 hr) and temperature (400-600 °C) were investigated on ceria synthesized powders properties....
متن کاملذخیره در منابع من
با ذخیره ی این منبع در منابع من، دسترسی به آن را برای استفاده های بعدی آسان تر کنید
عنوان ژورنال:
دوره شماره
صفحات -
تاریخ انتشار 2009