The aim of this paper is to give a review of the main models of thermoluminescence, from the most simple postulated by Randal and Wilkins in 1945. After that, a computer simulation emphasizes some problems relative to the use of the models to describe the behaviour of the thermoluminescent glow curve. Some suggestions are also given for obtaining a correct interpretation from the experimental data. 相似文献
Home storage is the final step of the frozen foods distribution chain, and little is known on how it affects the products quality. The present research describes frozen green beans (Phaseolus vulgaris, L.) quality retention profile during the recommended ‘star marking’ system dates, at the storage temperatures of +5, −6, −12 and −18 °C (along 1, 4, 14 and 60 days, respectively).
The quality profile was assessed by a simulation system. Simulations were set by a response surface methodology to access the effect of different packaging materials (thermal conductivities and thickness), surface heat transfer coefficient, and refrigerator dynamics (effect of refrigeration cycles at the different storage temperatures) on the average retentions of Ascorbic Acid, total vitamin C, colour and flavour.
Green beans quality losses along frozen storage are significantly influenced by temperature, refrigerator dynamics and kinetic properties. Quality is also highly dependent on packaging materials thermal insulation (e.g. at temperatures above the melting point). Temperature cycles inside frozen chambers have a long term effect, and at the higher storage temperatures (e.g. T>−6 °C) are detrimental to frozen green beans quality after shorter periods. 相似文献
This paper investigates three kinds of permanent-magnet arrays used in planar motors with polarity centers distributed in the lattices of a matrix. The magnetic field of every kind of magnet array is analyzed by analytical methods. First, we give a Laplace equation of magnetic scalar potential and a series of boundary conditions. Then, we derive the analytical expressions of magnet field strength and magnet flux density in the air gap of each kind of magnet array by the method of separation of variables. Finally, we compare the three types of magnet arrays on the basis of the analytical solutions. 相似文献
A physically based hysteresis theory incorporating a domain size that depends on the Weiss effective field explains the observed ranges of reversible and irreversible magnetization in the initial-magnetization curve and exterior loop of ferromagnetic materials. The theory applies to materials exhibiting both normal and wasp-waisted exterior loops and agrees well with measured data. It also provides close linkages between magnetization at the quantum scale, domain properties at the mesoscopic scale, and measurements at the macroscopic scale. 相似文献
We present here the results of a study of the separation process in the extraction matrix of a novel high-intensity magnetic separator (HIMS). The matrix uses an ordered array of grooved plates (replacing conventional collectors, which are generally made of wires). Only experimental results are available for grooved plates in the literature, but here we propose a new theoretical approach. We report on the particles' behavior, the existence of a percolation phenomenon, and the filtration efficiency, in order to analyze and compare the performance of matrix structures (Lenoir's and Jones'). We discuss the causes of the percolation phenomenon and its effect on filtration efficiency. Correspondence between the theory and the experiments is good. We suggest appropriate uses of each matrix structure according to the property of the processed particles. 相似文献
The conditions of Bi2Ti4O11 formation are studied. It is shown that the process is diffusion-controlled and depends significantly on the heating rate. The optimal conditions for producing Bi2Ti4O11 ceramics are determined. Cold pressing of Bi2Ti4O11 ceramic powder at high pressures is shown to influence the unit-cell parameters and volume, positional parameters of Bi and Ti, and bond distances in the ferroelectric ceramics produced by subsequent sintering. The ferroelectric transition temperature decreases steadily with increasing densification pressure. 相似文献