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Open access

Tamás Ruppert and János Abonyi

Abstract

Human resources are still utilized in many manufacturing systems, so the development of these processes should also focus on the performance of the operators. The optimization of production systems requires accurate and reliable models. Due to the complexity and uncertainty of the human behavior, the modeling of the operators is a challenging task. Our goal is to develop a worker movement diagram based model that considers the stochastic nature of paced open conveyors. The problem is challenging as the simulator has to handle the open nature of the workstations, which means that the operators can work ahead or try to work off their backlog, and due to the increased flexibility of the moving patterns the possible crossings which could lead to the stopping of the conveyor should also be modeled. The risk of such micro-stoppings is calculated by Monte-Carlo simulation. The applicability of the simulator is demonstrated by a well-documented benchmark problem of a wire-harness production process.

Open access

Hayder Al-Maliki and Gábor Kalácska

Abstract

A review to enrich the literature concerning the effect of various plasmas on the tribological behaviour of polymers and monitor the developments of plasma for the modification of polymer surfaces over recent decades using up-to-date data. A comparative study of plasmas was conducted to identify the most useful and efficient ones which facilitate optimal improvements with regard to the characterizations of polymer surfaces and tribological properties. The studies included in this review strongly suggest that (besides Plasma-Immersion Ion Implantation, PIII) atmospheric plasmas (dielectric barrier discharges, DBD) are an effective technique in terms of modifying the characterizations of polymer surfaces thereby enhancing the tribological behaviour of polymers under different operating conditions that extends the operating life of elements within the machine.

Open access

Eszter Virágh and Bálint Kiss

Abstract

The controllability of reactions is an important issue in the chemical industry. The control of reactions is of great practical interest in order to ensure the energy- and time-efficient production of compounds. This paper studies the dynamical models of some chemical reactions in order to verify their controllability with regard to a candidate input signal, namely the change in the ambient temperature of a reaction.

Open access

Veronika Varga, Katalin Bélafi-Bakó, Dávid Vozik and Nándor Nemestóthy

Abstract

Itaconic acid is an organic acid produced mainly for non-food purposes. It can be manufactured by biotechnological synthesis using various strains which results in the salt form of the acid. In this work, the separation of sodium itaconate by electrodialysis was studied. Homopolar cation- and anion-selective membranes were applied and the module was operated under a constant voltage. The transport of the acid was followed by on-line ultraviolet and visible absorption spectroscopy, where the detector was installed in the system. The experiments with models of aqueous solutions confirmed that the technique is suitable for the effective recovery of itaconic acid.

Open access

Zsófia Bedő, Katalin Bélafi-Bakó, Nándor Nemestóthy and László Gubicza

Abstract

The possible replacement of lubricants with fossil-fuel sources and the manufacture of biolubricants with more beneficial features were studied. Oleic acid and isoamyl alcohol were reacted with an enzyme in an ionic liquid. During the reaction conventional as well as microwave heating was applied. After the experimental determination of the optimal reaction parameters, it was unexpectedly found that a synergistic effect occurred by applying ionic-liquid and microwave-heat treatment simultaneously. The enzyme exhibited a much higher level of activity than the value expected based on the measurements carried out separately by using an ionic liquid instead of an organic solvent and microwave-heat treatment or a conventional method. In the experiments with recycled enzyme it was found that ionic liquid maintained the enzyme more effectively, as if it was immobilized by it: the enzyme managed to maintain its activity and recycling ability.

Open access

Bálint Levente Tarcsay, Éva Mihálykó-Orbán and Csaba Mihálykó

Abstract

Safety regulations demand the elimination of random mistakes and the reliable operation of production units. However, the control and maintenance of batch and semi-continuous processes haalways been difficult. In this paper, a way of preventing malfunctions in batch and semi-continuous processes is presented by using appropriately designed buffer tanks. A stochastic model was investigated in which batch and continuous subsystems were linked by an intermediate storage tank. The main concern was the reliability of the system. Reliable operation was defined as neither the exhaustion of raw materials nor the excessive accumulation of them. The counting processes that describe the random batch-input and random batch-output processes are supposed to be independent homogeneous Poisson processes with different rates. By introducing a function that describes the material in storage, reliable operation is defined as when this function satisfies two inequalities for a time interval of any duration. By applying probabilistic methods, an integral equation is set up for the the reliability. Nevertheless, its analytical solution cannot be determined, hence the values according to a Monte Carlo simulation are approximated. By applying this method, a link could be identified between the necessary initial buffer and tank capacities that belong to a reliability level. Economic investigations were conducted to help determine the optimal initial buffer and tank capacities that satisfy the appointed reliability level.

Open access

Ildikó Szedljak, Anikó Kovács, Gabriella Kun-Farkas, Botond Bernhardt, Szabina Králik and Katalin Szántai-Kőhegyi

Abstract

Red lentils are a very important raw material in the food industry due to their high protein content and high level of health-promoting components. The nutritive value of red lentils is the most important attribute from a research point of view; it can be increased by germination, soaking as well as physical and biochemical processes. The antinutritive materials are reduced or denatured by the germination process and indigestible components become available to the human body. Heat treatment was applied to achieve different temperatures and increase the microbiological stability of germinating samples. The effect of heat treatment on the amounts of certain components and the activity of oxidative enzymes was tested during our experiments; the nutritional characteristics (water-soluble total polyphenol content (WSTPC), water-soluble protein content (WSPC), water-soluble antioxidant capacity, in addition to peroxidase and polyphenol oxidase enzyme activities) of different treatments in red lentil samples were monitored. The WSTPC in our samples ranged from 0.726 mg Gallic Acid Equivalent GAE/g DW (DW being dry weight) to 1.089 mg GAE/g DW, and the WSPC varied from 19.078 g / 100g DW to 29.692 g / 100 g DW. Results showed that germination led to an increase in the WSTPC and WSPC. The peroxidase enzyme activity also exhibited an increase during germination which could result in deepening of the colour of the finished products. Germination resulted in the water-soluble antioxidant capacity of red lentil samples decreasing.

Open access

Katalin Kóczán-Manninger and Katalin Badak-Kerti

Abstract

Bread samples were made using flour mixes of Triticum monococcum (Tr. monococcum) and Triticum spelta (Tr. spelta). They were tested for their rheological behaviour over the first 3 days of storage at room temperature, and for their characteristics based on a Hungarian Standard. Parameters were set such as the volume of the baked product, baking loss, crumb characteristics and elasticity of crumbs. The behaviour of flour from einkorn wheat is different to that of Tr. spelta. The properties of the tested flour mixes measured by a farinograph show that Tr. spelta produces an acceptable dough, on the other hand, the dough of Tr. monococcum develops quickly but is very unstable so weakens within minutes of being kneaded. This also suggests that doughs composed of einkorn wheat flour require a different type of kneading than those of Tr. spelta (or Tr. aestivum, also referred to as common wheat) flours. Breads composed of Tr. spelta were comparable with those made with Tr. aestivum, the crumb elasticity was above 90 % on the day of baking, which indicates high quality. The Tr. monococcum breads, however, were of low grade: the volume of the breads decreased by increasing the ratio of Tr. monococcum to Tr. spelta and the elasticity reduced to unacceptable levels (less than 60 %). It should be mentioned that the grading was based on breads made purely from Tr. aestivum flours.

Open access

Sándor Nagy

Abstract

To correlate the dipole moment and density dependence of the initial magnetic susceptibility on the basis of the former related theories and the probability analysis of chain formation, physically based analytical correlation equation was derived. After the local magnetic field strength and the chaining probability between two particle have been determined the chain and particle distributions came from the geometric distribution. The initial magnetic susceptibility was resulted from the summation of Langevin initial susceptibility of k-length chains. Two particles were considered in a chain if the interaction energy between them was below a certain limit. By varying slightly this energy limit around 70–75 % good agreement has been obtained between the simulation and theoretical data. Monte Carlo simulations were used to calculate the initial magnetic susceptibility of dipolar hard sphere system at different dipole moments and densities.

Open access

Erzsébet Bognár, Gabriella Hellner, Andrea Radnóti, László Somogyi and Zsolt Kemény

Abstract

Glycidyl esters are foodborne contaminants formed during the production of fats and oils, especially during the deodorization of palm oil. The hydrolyzed free form of glycidol has been categorized as probably carcinogenic to humans by the World Health Organization’s International Agency for Research on Cancer. The aim of this research was to study the formation of glycidyl esters during the lab-scale deodorization of the three most widely produced seed oils in the world (sunflower, rapeseed and soybean). The effects of two independent factors – temperature and residence time – were analyzed by a 32 full factorial experimental design and evaluated by response surface methodology. In accordance with findings in the literature, the greatest amount of glycidyl esters was formed in the soybean oil matrix. For all three oils, the effects of both residence time and temperature were significant, while the latter was more so. To reduce the formation of glycidyl esters, milder deodorization is required, which is limited because of the purposes sought by the thermal operation and removal of volatile minor components and contaminants.