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MINLP synthesis of reactor networks in overall process schemes based on a concept of time-dependent economic regions
Nataša Iršič Bedenik, Marcel Ropotar, Zdravko Kravanja, 2007, izvirni znanstveni članek

Opis: The design and optimization of reactor networks using the conventional conceptof attainable region is based on technological (conversion, selectivity, etc.), rather than, economical criteria (cost, profit, etc.). The solution from the economical point of view when the operating and investment costs cannot be neglected may not be optimal, not even in regard to the structure. In order to circumvent this deficiency, the conventional Concentration Attainable Region (CAR) is transformed into an Economic Region (ER) using economic optimization criteria. A novel concept for ER constructionis proposed for multi-D problems. One-parametric NLP or MINLP optimizations with reactor volume as a varying parameter are performed to construct trajectories in the ER. In this way the ER is aided by mathematical programming for 3D or more D problems in order to handle dimensions higher than 2 as degrees of freedom for the economic objective function. ER is attainable (EAR) only when the economic objective function is linear. The more the objective function is discontinuous, discrete, nonlinear and non-convex and the more its cost coefficients vary with time, the less the principles of AR can be applied to ER. However, economically optimal reactor systems always lie at the borders of ERs. Two important insights have been gained during the construction of different time-dependent ERs, which have been used in upgrading the MINLP approach to the synthesis of reactor networks in overall process schemes: (i) A reactor network superstructure has been reestablished based on economical optimization criteria and the principles of ER. (ii) Over a longer period, the performing of a stochastic multi-period MINLP synthesis is recommended, in order to consider the time variability and uncertainties of economic parameters. A special multi-period strategy is proposed to upgrade the efficiency of the MINLP synthesis.
Ključne besede: concentration attainable region, economic attainable region, discrete nonlinear region, MINLP
Objavljeno: 01.06.2012; Ogledov: 1297; Prenosov: 79
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An integrated strategy for the hierarchical multilevel MINLP synthesis of overall process flowsheets using the combined synthesis/analysis approach
Nataša Iršič Bedenik, Bojan Pahor, Zdravko Kravanja, 2004, izvirni znanstveni članek

Opis: This paper describes an integrated strategy for a hierarchical multilevel mixed-integer nonlinear programming (MINLP) synthesis of overall process schemes using a combined synthesis/analysis approach. The synthesis is carried out by multilevel-hierarchical MINLP optimization of the flexible superstructure, whilst the analysis is performed in the economic attainable region (EAR). The role of the MINLP synthesis step is to obtain a feasible and optimal solution of the multi-D process problem, and the role of the subsequent EAR analysis step is to verify the MINLP solution and in the feedback loop to propose any profitable superstructure modifications for the next MINLP. The main objective of the integrated synthesis is to exploit the interactions between the reactor network, separator network and the remaining part of the heat/energy integrated process scheme.
Ključne besede: multilevel MINLP, MINLP synthesis, attainable region, economic attainable region, concentration attainable region, continous stirred tank reactor, plug flow reactor, recycle reactor, nonlinear programming, mixed integer nonlinear programme
Objavljeno: 01.06.2012; Ogledov: 1752; Prenosov: 67
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Estimation of solid solubilities in supercritical carbon dioxide: Peng-Robinson adjustable binary parameters in the near critical region
Mojca Škerget, Zorka Novak-Pintarič, Željko Knez, Zdravko Kravanja, 2002, izvirni znanstveni članek

Opis: The density dependence of the binary parameters of the Peng-Robinson equation of state in near the critical region was examined. Published solubility data of eight compounds in pure CO2 have been fitted to the Peng-Robinson equation in combination with one and two parameters van der Waals mixing rules and in combination with the three parameter density dependent mixing rule of Mohamed and Holder. A systematic study has been done to determine the influence of different terms in the mixing rules. In order to obtain density dependence, binary parameters were calculated for each isotherm at particular experimental point separately in the way to equalise experimental and calculated solubility data. The system was formulated as an equation-oriented model and solved by means of a nonlinear programming optimisation algorithm. For all compounds the binary interaction parameters thus obtained were found to vary strongly with pressure in the range from 75 bar to approximately 150 bar, i.e. near the critical end point (CEP) of the low temperature branch of the three phase solid-liquid-gas (SLG) curve. At higher pressures, the parameter is practically independent on pressure. In general, for the systems investigated, kij increases linearly with increasing density and reaches a constant value at higher densities in the range from 700 to 800 kg/m3, depending on the system under investigation.
Ključne besede: solid liquid equilibria, equation of state, mixing rules, binary parameters, near critical region, nonlinear programming, thermodynamic model, supercritical fluids, CO2, solubility
Objavljeno: 01.06.2012; Ogledov: 1372; Prenosov: 68
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Danube Region Entrepreneurship Observatory
Polona Tominc, Miroslav Rebernik, Barbara Bradač Hojnik, Karin Širec, znanstvena monografija

Opis: There is no doubt about the importance of multi-country studies of entrepreneurial activity in enabling the comparison and replication of research and generating meaningful contributions to scholarship, practice and policy. This international comparison perspective is especially important when processes in each single economy are analysed against the broader global, European or regional environment. Since entrepreneurship is a complex social phenomenon, several dependencies can be understood only with comprehensive research that includes continuous positioning of national entrepreneurship in the European and global perspectives. Within Global Entrepreneurship Monitor (GEM) it is possible to compare data for more than 100 countries not only in the field of early-stage entrepreneurial activity but also in areas such as general attitudes of the adult population towards entrepreneurship, entrepreneurial intentions, etc. In this scientific monograph publication, we analyse the entrepreneurial profiles of Danube region countries, entrepreneurial intentions in the region and investigate the competition and aspirations of early-stage entrepreneurs in these countries.
Ključne besede: enterprises, entrepreneurship, business environment, characteristics, activities, economic development, human capital, competitivity, international comparisons, Global Entrepreneurship Monitor, Danube Region, Entrepreneurial Intentions, Entrepreneurial Growth Aspirations
Objavljeno: 18.01.2017; Ogledov: 609; Prenosov: 56
.pdf Celotno besedilo (2,97 MB)
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Cross-country entrepreneurial intentions study
Urban Šebjan, Polona Tominc, Darja Boršič, 2016, izvirni znanstveni članek

Opis: In this article, we investigate how entrepreneurial intentions of individuals in the eight countries of the Danube region are shaped by different components of individuals’ personal attitudes, the subjective norm and personal behavioral control. We analyze the internal structure of these components as well as some demographic and human capital factors. Cultural and developmental differences influencing variation in causal effects among variables in the model are analyzed. Structural equation modeling is used for data obtained by adult population surveys within the GEM research. Results of our study show that the entrepreneurial intention model is applicable across countries and that the internal effects among components of motivational antecedents exist, although not all hypothesized relationships are confirmed. Our study suggests that the process from perception to intention is similarly shaped across the eight countries of the Danube region, although there are several differences in the magnitude of causal effects as well as differences regarding influential factors.
Ključne besede: entrepreneurial intentions, motivational antecedents, cultural and developmental differences, Danube region, education, education policy, activities
Objavljeno: 08.08.2017; Ogledov: 347; Prenosov: 46
.pdf Celotno besedilo (521,51 KB)
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Identification of Czech metropolitan regions
Viktorie Klímová, Vladimír Žítek, 2016, pregledni znanstveni članek

Opis: Concepts of national and regional innovation systems can serve as an analytical framework forming the empirical base for innovation policy creation. It is possible to distinguish various types of these systems. One of these typologies is based on the assessment of innovation deficiencies. There are three types of regions: metropolitan, peripheral, and old industrial. Metropolitan regions can be characterized by a high level of research, innovation, and patent activity. The aims of this paper are to find relevant indicators that can be used as the basis for defining metropolitan regional innovation systems and using them for the identification of Czech metropolitan regions. The results of the point method combined with the cluster analysis showed that the capital city, Prague, as well as the South Moravian, Pardubice, Central Bohemian, Pilsen, and Liberec Regions can be defined as metropolitan regions.
Ključne besede: regional innovation system, knowledge, innovation, region, Czech Republic, metropolitan region
Objavljeno: 13.11.2017; Ogledov: 391; Prenosov: 40
.pdf Celotno besedilo (952,39 KB)
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Outline of implemented eco-innovation activities
Jana Hojnik, Mitja Ruzzier, Aleš Lipnik, 2014, izvirni znanstveni članek

Opis: Background and Purpose: Providing a win-win situation for enterprises and the environment is raising the importance of eco-innovation. This article sheds light on the eco-innovation activities implemented within the clusters of the South Eastern European region (hereafter the SEE region). The main objective of this paper is to provide an outline of the situation pertaining to the implementation of eco-innovation activities in analyzed clusters. Methodology: Empirical evidence is provided through the performance of survey research with a sample of 52 clusters, encompassing 11 countries of the SEE region. The basic research method used in this research was a questionnaire developed for cluster organizations, with which we gathered the data and afterwards conducted descriptive statistics. Results: The findings demonstrate that the majority of analyzed clusters implement eco-innovation activities. The results indicate that 40 clusters out of 52 in all have set objectives with regard to eco-innovation support in their national or regional programs, followed by 35 clusters, which include objectives related to eco-innovation in their cluster strategies, and lastly, only 15 clusters are primarily focused on eco-innovation. Hence, our study depicting the current situation regarding the implementation of eco-innovation activities in analyzed clusters and clusters' orientation towards eco-innovation leads to us the discussion of why such differences in clusters occur. Conclusion: The huge differences related to the implementation of eco-innovation activities in clusters of the SEE region, can also reflect the level of the national/regional development in terms of economic indicators such as GDP and, at the same time, offer room for a lot of improvement, and an exchange of best practice.
Ključne besede: eco-innovation, clusters, SEE region
Objavljeno: 10.01.2018; Ogledov: 276; Prenosov: 29
.pdf Celotno besedilo (413,80 KB)
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Agricultural-industrial integration and new applications of natural fibres
Ana Maria de Bicalho, 2009, izvirni znanstveni članek

Opis: In recent years natural fibre production has taken on considerable appeal because of new industrial applications in environmental friendly products and growing demand for fibres could contribute to social welfare of poor farmers in developing countries. The new uses of natural fibres are part of highly technical green solutions for problems in the industrial and consumption regions but it may be asked whether this demand really addresses social and ecological issues in regions of primary production. These issues are examined in the Brazilian Amazon where recently a composite fibre sheet factory was opened and fibre cropping is making a comeback after decades of economic stagnation. It is shown here that the expansion of the activity, while significant, has not yet reached the scale of the past, but the market is promising, particularly in the automotive industry, which could further stimulate jute and malva production in the region.
Ključne besede: natural fibres, new industrial applications, agricultural-industrial integration, Amazon region, Brazil
Objavljeno: 19.03.2018; Ogledov: 163; Prenosov: 32
.pdf Celotno besedilo (124,41 KB)
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