Numerical modeling of nonisothermal moisture transfer in biological colloidal porous materials

The authors derive and substantiate a system of equations of heat and moisture transfer in colloidal capillary-porous undersaturated media with account for the mutual effect of the vapor and liquid pressure, determined by the contribution of surface forces, and the temperature on the rate of interphase mass transfer and the thermocapillary flows. Examples are given of the numerical calculation of evolution of the moisture content and temperature fields and the kinetic dependences in a wide moisture content range for materials of biological origin, namely, yeast, soil. A comparison is made with experimental data.The work was carried out in 1992/93 on the basis of grant No. 1392/3-91, sponsored by the Science Committee of Poland.Academic Scientific Complex A. V. Luikov Heat and Mass Transfer Institute, Academy of Sciences of Belarus, Minsk, Belarus. Technical University of Lodz', Poland. Translated from Inzhenerno-Fizicheskii Zhurnal, Vol. 66, No. 2, pp. 202–212, February, 1994.     

Kernel orthonormalization in radial basis function neural networks

This paper deals with optimization of the computations involved in training radial basis function (RBF) neural networks. The main contribution of the reported work is the method for network weights calculation, in which the key idea is to transform the RBF kernels into an orthonormal set of functions (using the standard Gram-Schmidt orthogonalization). This significantly reduces the computing time if the RBF training scheme, which relies on adding one kernel hidden node at a time to improve network performance, is adopted. Another property of the method is that, after the RBF network weights are computed, the original network structure can be restored back. An additional strength of the method is the possibility to decompose the proposed computing task into a number of parallel subtasks so gaining further savings on computing time. Also, the proposed weight calculation technique has low storage requirements. These features make the method very attractive for hardware implementation. The paper presents a detailed derivation of the proposed network weights calculation procedure and demonstrates its validity for RBF network training on a number of data classification and function approximation problems.     

Refinement of depth from stereo camera ego-motion parameters

An algorithm for refinement of depth (disparity) map from stereoscopic sequences is proposed. the method is based on estimation of ego-motion parameters of the camera system and frame-by-frame prediction of 3d scene feature point co-ordinates. disparity maps with sub-pixel accuracy were obtained without the need for disparity computations in each single frame.     

Nested median filtering for detecting T-wave offset in ECGs

The capabilities of a nonlinear signal decomposition method based on nested median filters for electrocardiogram (ECG) analysis are demonstrated. This method is comparable to linear scale-space filtering in terms of computation cost but outperforms it with regard to detection accuracy of characteristic points of ECGs (e.g. the T-wave offset). Obtained results are validated on the CSE database of ECGs     

Effect of Particle Structure on Quality Retention of Bio-Products During Thermal Drying

To study the influence of particle structure on quality retention of hioproducts during thermal drying, the porous particles formed of albumin and solid carriers were dried in a vibm-fluidized bed dryn at different inlet air temperatures and different initial bulk porosities. Equations to predict temperature and moishrre content of panicles as well as the kinetics of biomass degradation were developed. The particle bulk porosity was incorporated into concentration-dependent moisture diffusivity model to estimate the erect of particle structure on product quality. The analysis of both calculated and experimental results indicates that the more porous structure promotes moisture diffusion, increases drying rate and finally improves the quality retention of bio-products. An extensive literature survey on quality retention issues during thermal drylng has been done.     

THE INFLUENCE OF TEMPERATURE ON SORPTION ISOTHERMS OF PROTEIN-CONTAINING MIXTURES

This paper presents a method for calculation of water sorption isotherms for multicomponent mixtures at different temperatures from mass fractions and sorption isotherms of components at a reference temperature. Additionally, Krischer's coefficients are required for the components. To compare experimental and calculated data, investigations on whey protein concentrates were carried out.     

An analysis of a pulse combustion drying system

The paper presents a theoretical and experimental analysis of a pulse combustion spray drying system. Measurements of the velocity flow field inside the drying chamber and extensive tests on drying and water evaporation were carried out for various feed rates and operating parameters of the pulse combustor. Each test included the analysis of temperature distribution in the dryer, evaporation level and sprayed material structure. LDA and PDA techniques were employed to determine the character of pulsating flow in the chamber, amount of water evaporated and to perform a profound analysis of spray structure. Experimental results show an intensive and efficient drying process. An attempt was made to perform theoretical predictions of velocity and temperature distribution in the drying chamber. The CFD technique was used to calculate time-dependent flow in the chamber. Results show vanishing velocity, pressure and temperature oscillations along the length of the drying chamber. Temperature oscillations decline faster than oscillations of pressure and velocity. Satisfactory agreement between calculations and experimental results was found in certain regions of the drying chamber. Discrepancies might be caused by simplification of the system geometry and flow pattern which were assumed to perform calculations in reasonable time.     

Hygroscopic properties of biological materials and the binding energy of moisture

The binding energy of moisture with biological materials is determined from sorption isotherms for yeast at different temperatures.The work was done in 1992–1993 as a part of a research plan under Grant No. 1392/3-91, financed through the Science Committee of Poland.Translated from Inzhenerno-Fizicheskii Zhurnal, Vol. 67, Nos. 5–6, pp. 461–466, November–December, 1994.     

Effect of Turbulence on Heat and Mass Transfer in the Atomization Zone

One of possibilities to extend operating efficiency of spray dryers is to increase turbulence of the drying agent flow. In the literature no quantitative data describing this phenomenon are available.

In the paper results of experimental investigations on the effect of turbulence on heat and mass transfer during atomization are discussed. The scope of experiments covered the analysis of changing evaporation capacity. temperature of gas and atomized material and particle size distribution as a function of distance to the atomizer. It was proven that an increase of air flow turbulence could cause 20-25% increase of evaporation capacity.     

Poincare mapping for detecting abnormal dynamics of cardiacrepolarization

This article concentrates on analysis of subtle ECG signal features associated with characteristic temporal variations in the repolarization phase of cardiac electrical activation (i.e., variations that are embedded within the T-wave). These variations are termed T-wave alternans (TWA) to connote larger similarity between T-wave shapes in every other beat than that in the adjacent beats that occur during regular heart rhythm of an increased rate. In an early work the concept of associating TWA with period-doubling bifurcation of the cardiac oscillator has been put forward and demonstrated on canine ECG traces. In this article we extend this idea and use it for quantification of TWA in human ECGs recorded from postinfarction patients. The purpose of this work is to show that: a statistically significant correlation exists for the analyzed ECGs between the TWA level computed by means of an inter-cycle synchronized sampling technique known as Poincare mapping (PM) and a widely used Fourier spectrum (FS) method, and that the PM method outperforms the widely used FS method for TWA analysis in a number of ways