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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

Hana Yasin, Zerihun Kebebew and Kitessa Hundera

Abstract

The southwest Ethiopian Afromontane moist forests are recognized as one of the biodiversity hotspots as they are the centres of origin and domestication of Arabica coffee. But they are under threat due to deforestation and conversion to coffee farms. Coffee agroforests are believed to buffer the natural forest from these threats. The study was conducted to investigate the importance of coffee agroforest adjacent to Belete forest southwest Ethiopia. Vegetation data were collected from 68 plots (34 each) and socioeconomic data were collected from 136 households (68 each). The results showed that statistically, there were no significant differences between the natural forest and adjacent coffee agroforests in the species composition, species richness and Shannon diversity index of the woody species(P > 0.05). The socioeconomic benefit result showed a number of forest products that are collected from the coffee agroforest. There were statistically significant differences between the natural forest and coffee agroforest in the forest income and the Simpson Diversification Index of the households (p < 0.05). Coffee agroforests contribute to the conservation of woody species through the retention of woody species and reducing pressure on the natural forest. Therefore, the socioeconomic benefits of coffee agroforests must take into account the conservation of woody species in linking the conservation and development arena.

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

Olexander Zhukov, Olga Kunah, Yulia Dubinina and Victoria Novikova

Abstract

The article presents the results of evaluation of the role of edaphic and vegetation factors on beta diversity of soil macrofauna by means of the MDM-approach. The multinomial diversity model (MDM) is a method for relating the Shannon diversity to ecological factors. The research was conducted in the ‘Dnipro-Orils’kiy’ Nature Reserve (Ukraine). The research polygon was laid in the forest within the Orlova ravine (48º31’13 “N, 34º48”15 “E). The study site comprises 1.0 ha of deciduous woodland bordered by an area of herbaceous cover within the ravine. In the soil of the studied polygon, 38 species of soil invertebrates were identified, which characterizes the gamma diversity. Alpha diversity, or the number of species on average at each sample point is 4.3. Beta diversity is 8.8. The principal component analysis of the edaphic parameters revealed four statistically significant principal components. For vegetation characteristics, six statistically significant principal components were identified. The sequential analysis of the effects shows that edaphic factors accounted for 20.9% (0.81 bit) of the available entropy (1.71–0.91). The largest decrease in the community entropy takes place under the action of the principal components 2 and 3 (0.06 bit and 0.05, respectively). A permutation test showed that these effects are statistically significant. In turn, 28.4% of the community β-diversity is attributable to vegetation factors. The greatest decrease in community entropy is related to the principal vegetation components 1, 3 and 4 (0.07, 0.05 and 0.04 bits, respectively). A permutation test indicated that this effect is statistically reliable. Geostatistical models substantially describe the varying effects on the beta-diversity of edaphic principal components 1 and 2, and the vegetation principal components 1 and 3. It was found that edaphic and plant factors play an important role in structuring the communities of soil macrofauna on the level of beta diversity. Community sensitivity to environmental factors varies in space and is spatially structured. For different environmental factors, specific spatial patterns of community sensitivity are allocated. Beta diversity may be due to the fact that the species of soil macrofauna communities also vary in the degree of sensitivity to various environmental factors. The species of soil microfauna are also divided according to their extent of sensitivity to different ecological factors.

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

Zuzana Krumpálová and Barbora Holienková

Abstract

In last decades, the number of non-native land snails increased up to 15 percentages; they create more than eight percent of all the Slovakian species. Trend of newly established snail species corresponds with increases in the average temperatures as well as the intensity of foreign trade, suggesting a synergistic effect of both climatic conditions and socioeconomic factors. The research of the open-air garden centres in Slovakia confirmed both factors. We report here some of the newly established populations of sixteen mollusc species. In the old garden centres, the number of species as well as the number of individuals decreased slightly. Area of the garden centre has a very high impact on both abundance and species diversity. The size and age of garden centre proportionally influences the composition of mollusc assemblages. Two new species Cornu aspersum and Cepaea nemoralis were noticed for the first time in Slovakia. The recent findings of the introduced populations demonstrate the potential of this snail to colonise new areas.