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After a brief overview of most important general features of the nonclassical diffusion on the base of the extended irreversible thermodynamics, the relevant mathematical formulae are incorporated into general formalism of the simultaneous convection–diffusion processes taking place in porous media. Then, using the simplest variant of the convection–diffusion equation, novel-type analytic solutions are derived for transport processes with both subdiffusion and superdiffusion characters in Lagrangian representation. [ABSTRACT FROM AUTHOR]

Various factors such as energy efficiency, the quality of end-products, and environmental aspects have to be taken into account during the drying of agricultural produce. During the recent past, several new approaches for the application of solar dryers to drying various biological materials were developed. In this paper, the background of solar drying, current solar drying practices, and drying of biological products such as grain, fruit, vegetables, hay, etc., are discussed. Additionally, an integrated energy/technology approach in order to maximize solar energy usage and thereby meet the drying requirements has been introduced. This will aid in achieving a sophisticated solution for drying process control, as well. [ABSTRACT FROM PUBLISHER]

This paper discusses the opportunities for the use of artificial intelligence methods for the modelling of drying processes. The main emphasis is given to the artificial neural network (ANN) modelling of heat and mass transfer in the course of grain and hay drying. The main conclusion is that a properly selected structure of neural network model can be used to determine the moisture distribution in a fixed-bed dryer. It is important to mention that, in addition to other factors, the selection of training and validation input data for the ANN model has a strong influence on the applicability. [ABSTRACT FROM PUBLISHER]

Abstract: One possibility to exploit solar energy better is the efficiency enhancement of the control of solar thermal heating systems. In this paper an improved differential control and the generally used ordinary differential control operating with fixed switch-on and switch-off temperature differences are compared in different efficiency viewpoints. The comparison is based on measured data of a particular system at the Szent István University, Gödöllő and on a TRNSYS model developed for solar heating systems. According to the results the improved control provides a higher value of utilizability and brings forth fewer switch-ons and switch-offs for the pumps. These advantages nevertheless result in extended operation time and thus extended parasitic consumption of the pumps. This drawback can, however, be moderated or even extinguished by modern pumps with low energy consumption or if supplied by renewable energy source. Comparing the amount of utilized solar energy and consumed parasitic energy increments, the improved control can be generally recommended. [Copyright &y& Elsevier]

Abstract: In this study an artificial neural network (ANN) model is introduced for modelling the layer temperatures in a storage tank of a solar thermal system. The model is based on the measured data of a domestic hot water system. The temperatures distribution in the storage tank divided in 8 equal parts in vertical direction were calculated every 5min using the average 5min data of solar radiation, ambient temperature, mass flow rate of collector loop, load and the temperature of the layers in previous time steps. The introduced ANN model consists of two parts describing the load periods and the periods between the loads. The identified model gives acceptable results inside the training interval as the average deviation was 0.22°C during the training and 0.24°C during the validation. [Copyright &y& Elsevier]

The solar drying is an attractive drying method in a sense of low temperature dehydration process which is useful for the dry product quality and energy saving including the environmental issues. Moreover, it can be applied in small scale (family size farms) which is in accordance with the distributed resource approach of the sustainable development. In the course of the recent research numerous drying experiments were elaborated with the solar drying of biomaterials, mainly with fruits. Beside the measurements, the modelling of the drying process was also investigated. Special attempt was carried out developing a low range air speed sensor (for measuring natural ventilation during the solar drying process) which can be used with a usual data logging system. After choosing the working principle a one dimensional prototype of the sensor was developed and constructed. Based on the measurements the optimal setting of the sensor was determined. Additionally, the set-up of a two-dimensional sensor prototype is also presented, along with its first measurement results. [ABSTRACT FROM AUTHOR]

Abstract: In this study, different model-based controllers designed for the operation of a solar power plant are discussed and tested. A simplified physically based model of the plant was developed on the basis of energy balances, including solar radiation as an input, heat transferred by the flow of the oil used as a working medium and overall heat loss from the plant. Average outlet temperature of the collector field is the reference/set-point value, while volumetric flow rate of oil is the manipulation variable to the controller. Solar radiation, ambient temperature and temperature of the inlet oil to the collector field are assumed as disturbances. The model developed and identified is an internal part of the robust controller. The modelling and experimental results are presented, pointing out the applicability of robust internal model-based control. [Copyright &y& Elsevier]

The application domains of biological and ecological systems provide many opportunities and challenges for the technologies of modelling and control. These domains feature prominently amongst the activities of the IFAC community. This paper, written by authors who have had close connections with IFAC activities in these domains, provides insights as to achievements that have been made and challenges which need to be addressed during this first decade of the 21st century. Applications focus on agricultural systems, the biomedical domain and on environmental systems. [Copyright &y& Elsevier]

A new method is given for mathematical modeling of the coupled heat and mass transfer through porous media. The behavior of the moisture level function in the vicinity of the critical value of the conductivity probability is discussed, at general initial-, and boundary conditions. Instead of the usually applied two coupled partial differential equations of parabolic type, a coupled system of hyperbolic partial differential equations containing also explicitly the relaxation time constants is used. A general solution is presented for the moisture level function, when the relaxation time constant relevant for temperature changes tends to value zero. This description is combined with scaling relations following from the contemporary statistical physical theory of percolation phenomena. [ABSTRACT FROM AUTHOR]

Mexican wave first widely broadcasted during the 1986 World Cup held in Mexico, is a human wave moving along the stands of stadiums as one section of spectators stands up, arms lifting, then sits down as the next section does the same. Here we use variants of models originally developed for the description of excitable media to demonstrate that this collective human behaviour can be quantitatively interpreted by methods of statistical physics. Adequate modelling of reactions to triggering attempts provides a deeper insight into the mechanisms by which a crowd can be stimulated to execute a particular pattern of behaviour and represents a possible tool of control during events involving excited groups of people.Interactive simulations, video recordings and further images are available at the webpage dedicated to this work: http://angel.elte.hu/wave. [Copyright &y& Elsevier]

In this study, different approaches to the modelling of flat-plate solar collectors are introduced and analysed. Among the physically based models, the heat network model and Hottel–Vhillier (H–V) models are discussed. The parameters of the latter model are identified for three different types of these solar collectors. The identification exhibited good agreement with the measured values. Finally, modelling simulations with an artificial neural network (ANN) technique were carried out. A sensitivity study was performed on the parameters of the neural network. The possible ANN structures, the size of training data set, the number of hidden neurons, and the type of training algorithm were analysed in order to identify the most appropriate model. The same ANN structures were trained and validated for the three solar collectors, using data generated from the H–V model and long-term (17 days) measurements. [Copyright &y& Elsevier]

In this paper, numerical analyses have been carried out to describe the velocity and temperature fields inside a storage tank to be used in a solar system under various boundary conditions with upper and lower inlet flows. The aim of the study was to evaluate the effect of different plate sizes situated opposite the inlet in order to increase the thermal stratification. A numerical model was developed, and validated using experimental results. Two different initial temperature assumptions were taken into account along with a two-layer configuration. Two cases were analysed, the thermocline in the vicinity of the plate and the thermocline in the middle of the tank. In the latter case, the plate diameter had little impact, but moving the thermocline closer to the plates resulted in the diameter having a greater influence. It was also found that larger plates made it possible to preserve stratification with at larger inlet flow rates than the flow rates of the conventional low flow systems. Cold water inflow into the top of the tank was also studied. The influence of the plate diameter for the colder inflow was examined along with two temperature differences between the inlet and the tank. It was found that the diameter of the plate and the distance between the plate and the top of the tank have a significant effect on the temperature stratification within the tank when cold water enters at the top of the tank. [Copyright &y& Elsevier]

A central goal of postgenomic biology is the elucidation of the regulatory relationships among all cellular constituents that together comprise the ‘genetic network’ of a cell or microorganism. Experimental manipulation of gene activity coupled with the assessment of perturbed transcriptome (i.e., global mRNA expression) patterns represents one approach toward this goal, and may provide a backbone into which other measurements can be later integrated.We use microarray data on 287 single gene deletion Saccharomyces cerevisiae mutant strains to elucidate generic relationships among perturbed transcriptomes. Their comparison with a method that preferentially recognizes distinct expression subpatterns allows us to pair those transcriptomes that share localized similarities. Analyses of the resulting transcriptome similarity network identify a continuum hierarchy among the deleted genes, and in the frequency of local similarities that establishes the links among their reorganized transcriptomes. We also find a combinatorial utilization of shared expression subpatterns within individual links, with increasing quantitative similarity among those that connect transcriptome states induced by the deletion of functionally related gene products. This suggests a distinct hierarchical and combinatorial organization of the S. cerevisiae transcriptional activity, and may represent a pattern that is generic to the transcriptional organization of all eukaryotic organisms.Color versions of both the Supplementary Material and the article are available at http://angel.elte.hu/bioinf. [Copyright &y& Elsevier]

We analyze growing networks ranging from collaboration graphs of scientists to the network of similarities defined among the various transcriptional profiles of living cells. For the explicit demonstration of the scale-free nature and hierarchical organization of these graphs, a deterministic construction is also used. We demonstrate the use of determining the eigenvalue spectra of sparse random graph models for the categorization of small measured networks. [Copyright &y& Elsevier]

Focuses on the interpretation and quantification of the collective human behavior of the Mexican 'wave', using a variant of models that were originally developed to describe excitable media such as cardiac tissue. Rolling of the wave in a clockwise direction; Typical speed; Generation of a wave by no more than a few dozen people standing up simultaneously.

Information about several papers discusses at the 6th Hungarian Drying Symposium in Hungary on the advances in drying technologies and equipment is presented. There were 21 presentations connected to the agricultural, chemical and food drying industries in the symposium program. Topics include "Analysis of Grain Mass Flow in Mixed-Flow Dryers" and "Future Trends in Drying Technologies."

We report on the fabrication of n+3C/n-4H SiC heterojunction diodes (HJDs) potentially promising the ultimate thermal stability of the junction. The diodes were systematically analyzed by TEM, X-ray diffraction, AFM, and secondary ion mass spectroscopy, indicating the formation of epitaxial 3C-SiC crystal on top of 4H-SiC substrate with continuous interface, low surface roughness, and up to ~7×1017cm–3 dopant impurity concentration. The conduction band off-set is about 1V as extracted from CV measurements, while the valence bands of both SiC polytypes are aligned. The HJDs feature opening voltage of 1.65 V, consistent with the barrier height of about 1.5 eV extracted from CV measurement. We finally compare the electrical results of the n+3C/n-4H SiC heterojunction diodes with those featuring Si and Ge doped anodes in order to evaluate current challenges involved in the fabrication of such devices. [ABSTRACT FROM AUTHOR]

A modular solar cabinet dryer equipped with an air collector including a drying chamber with different tray arrangements was developed to determine moisture changes in different sizes and forms (slices and cubes) of apple and carrot pieces and to carry out serial measurements of temperatures, solar radiation, and air humidity distributions during the drying process. The initial and final moisture contents (w.b.) of fresh products were 88 and 26% for apple and 71 and 13% for carrot with initial weights of 1.56 and 3 kg, respectively. The results revealed that the temperature inside the chamber was strongly negatively correlated with air humidity (R2 = 0.91) and that the length of the drying period was influenced by the weather conditions, as the cloudy weather retarded drying of carrots. It was possible to reach an air drying temperature over 41°C with a daily total solar energy incident on the collector's surface of 857.2 kJ/(m2 day) for apples and 753.20 kJ/(m2 day) for carrots. The analysis of energy requirements to remove moisture from apples and carrots during the total drying period showed values of 3300.19 and 7428.28 kJ/kg, respectively. The amount of air to remove water from the samples was also determined as 126.93 m3 for apples and 928.56 m3 for carrots. [ABSTRACT FROM AUTHOR]

A novel evaluation method was developed for Raman microscopic quantitative characterization of polymer waste. Car shredder polymer waste was divided into different density fractions by magnetic density separation (MDS) technique, and each fraction was investigated by Raman mapping, which is capable of detecting the components being present even in low concentration. The only method available for evaluation of the mapping results was earlier to assign each pixel to a component visually and to count the number of different polymers on the Raman map. An automated method is proposed here for pixel classification, which helps to detect the different polymers present and enables rapid assignment of each pixel to the appropriate polymer. Six chemometric methods were tested to provide a basis for the pixel classification, among which multivariate curve resolution-alternating least squares (MCR-ALS) provided the best results. The MCR-ALS based pixel identification method was then used for the quantitative characterization of each waste density fraction, where it was found that the automated method yields accurate results in a very short time, as opposed to manual pixel counting method which may take hours of human work per dataset. [ABSTRACT FROM AUTHOR]

Unfavourable designs of mixed-flow grain dryers can cause inappropriate residence time distributions, locally different drying conditions and, hence, inhomogeneous drying. To study the effect of design elements and different air duct arrangements, residence time experiments, grain drying experiments and discrete element simulations were conducted both at pilot and industrial scale. These investigations revealed that present dryer designs give broad distributions of residence time, moisture content, and grain temperature. This is a consequence of different drying histories for individual grains. This variation is mainly influenced by the air duct arrangement applied but is affected by other structural and operating parameters as well. Uneven drying is one of the main reasons for elevated energy demands which are still comparatively high in mixed-flow dryers. A future goal will be to develop improved designs of mixed-flow dryers. [Copyright &y& Elsevier]

Abstract: The EU project FLOMIX-R was aimed at describing the mixing phenomena relevant for both safety analysis, particularly in steam line break and boron dilution scenarios, and mixing phenomena of interest for economical operation and the structural integrity. This report will focus on the computational fluid dynamics (CFD) code validation. Best practice guidelines (BPG) were applied in all CFD work when choosing computational grid, time step, turbulence models, modelling of internal geometry, boundary conditions, numerical schemes and convergence criteria. The strategy of code validation based on the BPG and a matrix of CFD code validation calculations have been elaborated. CFD calculations have been accomplished for selected experiments with two different CFD codes (CFX, FLUENT). The matrix of benchmark cases contains slug mixing tests simulating the start-up of the first main circulation pump which have been performed with three 1:5 scaled facilities: the Rossendorf coolant mixing model ROCOM, the Vattenfall test facility and a metal mock-up of a VVER-1000 type reactor. Before studying mixing in transients, ROCOM test cases with steady-state flow conditions were considered. Considering buoyancy driven mixing, experimental results on mixing of fluids with density differences obtained at ROCOM and the FORTUM PTS test facility were compared with calculations. Methods for a quantitative comparison between the calculated and measured mixing scalar distributions have been elaborated and applied. Based on the “best practice CFD solutions”, conclusions on the applicability of CFD for turbulent mixing problems in PWR were drawn and recommendations on CFD modelling were given. The results of the CFD calculations are mostly in-between the uncertainty bands of the experiments. Although no fully grid-independent numerical solutions could be obtained, it can be concluded about the suitability of applying CFD methods in engineering applications for turbulent mixing in nuclear reactors. [Copyright &y& Elsevier]

Rewarming of fruits and vegetables after cooling is characterized by heat and mass transfer processes, which leads commonly to condensation of water on the produce surface at temperatures below the dew point. This effect may affect the produce quality due to microbial growth at unfavorable environmental conditions. The amount of condensed water is a function of the produce surface temperature and of the surrounding conditions as air temperature, air humidity, and air flow. Under practical conditions, both the warming and the condensation are strongly affected by the packaging system used. Depending on the flow conditions close to the produce surface, parameters of heat and mass transfer under laboratory conditions were measured. A mathematical model was developed for the determination of the amount of condensed water on fruit surfaces, its reevaporation, and its total dwell time dependent on the environment air conditions. The model describes the heat and mass transfer processes on single fruits. The process of diffusion of humidity in air and proceed of surface temperature is the basis for the model. [ABSTRACT FROM AUTHOR]

A twofold refinement of the basic mathematical model for describing a coupled heat and mass transfer taking place in porous media is presented. The common application of irreversible thermodynamics and fluctuation theory of phase transitions is proposed for calculating the moisture level and temperature. Instead of parabolic partial differential equations, hyperbolic type partial differential equations are used. The relaxation time constants, whose percolation state-dependence is also taken into account, are incorporated into this formalism. Some possible new research domains in mathematical and statistical physics are also indicated. [ABSTRACT FROM AUTHOR]