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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

Joanna Gocłowska-Bolek

Abstract

In the article, a phenomenon of urbanization of Latin America was analysed in terms of its impact on the level of competitiveness of the cities. A role that cities play in Latin America’s economy was emphasized. The author has examined a number of reliable reports on competitiveness of the cities and on this basis formulated its assessment of the level of competitiveness on a global basis, including identifying strengths and weaknesses of the cities, key areas for strong economic development and proposes recommendations. Based on the analysis of available data and source reports, the main trends in urbanization have been identified that may affect the dynamics of the Latin American city's competitiveness.

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

Babulia Mghebrishvili

Abstract

The article emphasizes significance of the laws within the legal framework for performing marketing activities, timely solution of the problems and protection of the consumers’ interests. The author describes the process of development of the legal framework for business in Georgia and pays particular attention to the activities performed after signing and effectiveness of the Association Agreement with the European Union. With respect of protection of the consumers’ rights, the article provides analysis of Georgian laws: Code of Food Safety and Free Circulation, Code of Food/Animal Fodder Safety, Veterinary and Plants Protection, Georgian Law on Advertising, Technical Regulation on Additional Requirements to Labeling of Food Products, Technical Regulations on Providing Information on the Products to the Consumers. In the author’s opinion, significant weakness of the legislation affecting marketing is the fact that Georgian Law on Protection of Consumers’ Rights suspended in 2012 has not been enacted yet while the draft law is ready and published. On the basis of analysis of legal framework the author concludes that the consumers’ rights, in general, are protected in the country by the effective legislation but the main thing is not only existence of the laws but rather their enforcement. For this purpose, states the article, Georgian government has adopted the resolution (2015) Food/Animal Fodder Safety State Control Rule, according to which the relevant state structures control the respective businesses and protect the consumers’ rights in this way. The process of improvement of the legal basis affecting marketing in Georgia is still in progress.

Open access

Georgios Chatzinas, Maria Markopoulou and Simeon Papadopoulos

Abstract

The financial assistance provided by European Stability Mechanism during the recent European crisis was accompanied with severe austerity measures and strict reforms that changed significantly the economic environment in the countries that accepted it. The present study examines whether these changes affected the capital structure of the European firms in these countries. Using accounting data for firms in Cyprus, Greece, Ireland and Portugal, the researchers created a balanced panel database and applied the Shyam-Sunders and Myers (1999) methodology to investigate whether pecking order or trade-off hypotheses can better explain the financing decision of the firms in these countries during the period before and after the outset of the ESM financial assistance. The results indicate that the firms’ capital structure decisions are explained by both theories in Greece, Cyprus and Portugal before the beginning of the EMS program, while only by trade-off in Ireland. On the other hand, after the beginning of the ESM program the firms’ capital structures are better explained by trade-off hypothesis in Greece and Cyprus, while nothing changed in cases of Ireland and Portugal. The fact that Greek and Cypriot tax rates increased the most among the four examined countries may explain at least partially the above differentiations. So, the economic environment is a primary factor that affects the explanatory power of each capital structure theory. Moreover, a change in economic environment may lead to a change in the dominant capital structure theory.

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.