Commenced in January 2007
Frequency: Monthly
Edition: International
Paper Count: 15

Search results for: Josip Vasilj

15 Wind Power Forecast Error Simulation Model

Authors: Josip Vasilj, Petar Sarajcev, Damir Jakus

Abstract:

One of the major difficulties introduced with wind power penetration is the inherent uncertainty in production originating from uncertain wind conditions. This uncertainty impacts many different aspects of power system operation, especially the balancing power requirements. For this reason, in power system development planing, it is necessary to evaluate the potential uncertainty in future wind power generation. For this purpose, simulation models are required, reproducing the performance of wind power forecasts. This paper presents a wind power forecast error simulation models which are based on the stochastic process simulation. Proposed models capture the most important statistical parameters recognized in wind power forecast error time series. Furthermore, two distinct models are presented based on data availability. First model uses wind speed measurements on potential or existing wind power plant locations, while the seconds model uses statistical distribution of wind speeds.

Keywords: wind power, uncertainty, stochastic process, Monte Carlo simulation

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14 Statistical Description of Counterpoise Effective Length Based on Regressive Formulas

Authors: Petar Sarajcev, Josip Vasilj, Damir Jakus

Abstract:

This paper presents a novel statistical description of the counterpoise effective length due to lightning surges, where the (impulse) effective length had been obtained by means of regressive formulas applied to the transient simulation results. The effective length is described in terms of a statistical distribution function, from which median, mean, variance, and other parameters of interest could be readily obtained. The influence of lightning current amplitude, lightning front duration, and soil resistivity on the effective length has been accounted for, assuming statistical nature of these parameters. A method for determining the optimal counterpoise length, in terms of the statistical impulse effective length, is also presented. It is based on estimating the number of dangerous events associated with lightning strikes. Proposed statistical description and the associated method provide valuable information which could aid the design engineer in optimising physical lengths of counterpoises in different grounding arrangements and soil resistivity situations.

Keywords: counterpoise, grounding conductor, effective length, lightning, Monte Carlo method, statistical distribution

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13 Volatility Switching between Two Regimes

Authors: Josip Visković, Josip Arnerić, Ante Rozga

Abstract:

Based on the fact that volatility is time varying in high frequency data and that periods of high volatility tend to cluster, the most successful and popular models in modelling time varying volatility are GARCH type models. When financial returns exhibit sudden jumps that are due to structural breaks, standard GARCH models show high volatility persistence, i.e. integrated behaviour of the conditional variance. In such situations models in which the parameters are allowed to change over time are more appropriate. This paper compares different GARCH models in terms of their ability to describe structural changes in returns caused by financial crisis at stock markets of six selected central and east European countries. The empirical analysis demonstrates that Markov regime switching GARCH model resolves the problem of excessive persistence and outperforms uni-regime GARCH models in forecasting volatility when sudden switching occurs in response to financial crisis.

Keywords: central and east European countries, financial crisis, Markov switching GARCH model, transition probabilities

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12 Multidimensional Integral and Discrete Opial–Type Inequalities

Authors: Maja Andrić, Josip Pečarić

Abstract:

Over the last five decades, an enormous amount of work has been done on Opial’s integral inequality, dealing with new proofs, various generalizations, extensions and discrete analogs. The Opial inequality is recognized as a fundamental result in the analysis of qualitative properties of solution of differential equations. We use submultiplicative convex functions, appropriate representations of functions and inequalities involving means to obtain generalizations and extensions of certain known multidimensional integral and discrete Opial-type inequalities.

Keywords: Opial's inequality, Jensen's inequality, integral inequality, discrete inequality

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11 Tourism Development Analysis According to Offer Improvements: Case of Crikvenica

Authors: Josip Arneric, Antonio Sostaric

Abstract:

Crikvenica is one of the favourite tourist destinations at the Adriatic Sea in Croatia which attracts guests with its natural beauties and is one of the top destinations with the highest number of overnights stays. The main purpose of this research is to determine which elements of tourist offer should be improved to achieve sustainable development of the town of Crikvenica. Namely, the survey results from a random sample have shown that the most common reason of the visits is relaxation and vacation, and that more attention should be given to the following categories: restaurants and the working hours of stores and banks. We have also examined whether or not there is a correlation between an average daily expenditure and the overnight stay. The paper ends with the conclusion and the recommendations on how to improve the tourist offer of Crikvenica in order to increase guest satisfaction and to keep its reputation at a high level.

Keywords: tourism development, survey, Crikvenica, management sciences

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10 Monotonicity of the Jensen Functional for f-Divergences via the Zipf-Mandelbrot Law

Authors: Neda Lovričević, Đilda Pečarić, Josip Pečarić

Abstract:

The Jensen functional in its discrete form is brought in relation to the Csiszar divergence functional, this time via its monotonicity property. This approach presents a generalization of the previously obtained results that made use of interpolating Jensen-type inequalities. Thus the monotonicity property is integrated with the Zipf-Mandelbrot law and applied to f-divergences for probability distributions that originate from the Csiszar divergence functional: Kullback-Leibler divergence, Hellinger distance, Bhattacharyya distance, chi-square divergence, total variation distance. The Zipf-Mandelbrot and the Zipf law are widely used in various scientific fields and interdisciplinary and here the focus is on the aspect of the mathematical inequalities.

Keywords: Jensen functional, monotonicity, Csiszar divergence functional, f-divergences, Zipf-Mandelbrot law

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9 Housing Loans Determinants before and during Financial Crisis

Authors: Josip Visković, Ana Rimac Smiljanić, Ines Ivić

Abstract:

Housing loans play an important role in CEE countries’ economies. This fact is based on their share in total loans to households and their importance for economic activity and growth in CEE countries. Therefore, it is important to find out key determinants of housing loans demand in these countries. The aim of this study is to research and analyze the determinants of the demand for housing loans in Croatia. In this regard, the effect of economic activity, loan terms and real estate prices were analyzed. Also, the aim of this study is to find out what motivates people to take housing loans. Therefore, primarily empirical study was conducted among the Croatian residents. The results show that demand for housing loans is positively affected by economic growth, higher personal income and flexible loan terms, while it is negatively affected by interest rate rise.

Keywords: CEE countries, Croatia, demand determinants, housing loans

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8 Political Determinants of Sovereign Spread: The Great East-West Divide

Authors: Maruska Vizek, Josip Glaurdic, Marina Tkalec, Goran Vuksic

Abstract:

We empirically explore whether and how taxation affects bilateral real exchange rates in the euro area – relative unit labor costs and relative consumer price indices. We find that employers’ social security contributions and the value added tax changes have the expected effects put forward in the fiscal devaluation literature and simulations. Increases in employers’ contributions appreciate the relative unit labor costs in the short- and the long-run, while value added tax hike appreciates the relative consumer prices. Somewhat surprisingly, for personal income tax increases, we find a short-run depreciating impact on the relative unit labor costs, while increases in employees’ contributions depreciate both measures of real exchange rates in the short-run.

Keywords: sovereign bonds, European Union, developing countries, political determinants

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7 Markov Switching of Conditional Variance

Authors: Josip Arneric, Blanka Skrabic Peric

Abstract:

Forecasting of volatility, i.e. returns fluctuations, has been a topic of interest to portfolio managers, option traders and market makers in order to get higher profits or less risky positions. Based on the fact that volatility is time varying in high frequency data and that periods of high volatility tend to cluster, the most common used models are GARCH type models. As standard GARCH models show high volatility persistence, i.e. integrated behaviour of the conditional variance, it is difficult the predict volatility using standard GARCH models. Due to practical limitations of these models different approaches have been proposed in the literature, based on Markov switching models. In such situations models in which the parameters are allowed to change over time are more appropriate because they allow some part of the model to depend on the state of the economy. The empirical analysis demonstrates that Markov switching GARCH model resolves the problem of excessive persistence and outperforms uni-regime GARCH models in forecasting volatility for selected emerging markets.

Keywords: emerging markets, Markov switching, GARCH model, transition probabilities

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6 Sustainability in Maritime Transport: Impact of Cruise Ships Routing in Coastal Navigation

Authors: Josip Dorigatti, Tina Perić, Gorana Jelić Mrčelić

Abstract:

This paper makes a review of present researches on sustainable development, sustainable maritime transport and presents the problem of sustainability in the cruise ships industry. It deals with cruise ships' routing in coastal navigation and its impact on sustainability from environmental, economical, and social aspects. A review of researches available on maritime sustainability brings to the attention how sustainability from a maritime transport perspective is still not enough analysed and researched as it is the case in other industries. The paper emphasises how the operational part of the cruising industry, in particular cruise ships routing in coastal navigation, is not yet researched nor analysed from the aspect of sustainability. The author, based on his extensive senior officer experience in the cruising industry, makes an overview of cruise ship routing practice. Accordingly, based on present cruise industry trends, challenges are highlighted from the aspect of sustainable cruise ships routing in coastal navigation.

Keywords: sustainable development, maritime transport, cruise shipping, cruise ship routes, coastal navigation

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5 Chemical and Sensory Properties of Chardonnay Wines Produced in Different Oak Barrels

Authors: Valentina Obradović, Josip Mesić, Maja Ergović Ravančić, Kamila Mijowska, Brankica Svitlica

Abstract:

French oak and American oak barrels are most famous all over the world, but barrels of different origin can also be used for obtaining high quality wines. The aim of this research was to compare the influence of different Slavonian (Croatian) and French oak barrels on the quality of Chardonnay wine. Grapes were grown in Croatian wine growing region of Kutjevo in 2015. Chardonnay wines were tested for basic oenological parameters (alcohol, extract, reducing sugar, SO2, acidity), total polyphenols content (Folin-Ciocalteu method), antioxidant activity (ABTS and DPPH method) and color density. Sensory evaluation was performed by students of viticulture/oenology. Samples produced by classical fermentation and ageing in French oak barrels, had better results for polyphenols and sensory evaluation (especially low toasting level) than samples in Slavonian barrels. All tested samples were scored as a “quality” or “premium quality” wines. Sur lie method of fermentation and ageing in Slavonian oak barrel had very good extraction of polyphenols and high antioxidant activity with the usage of authentic yeasts, while commercial yeast strain resulted in worse chemical and sensory parameters.

Keywords: chardonnay, French oak, Slavonian oak, sur lie

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4 Accuracy of VCCT for Calculating Stress Intensity Factor in Metal Specimens Subjected to Bending Load

Authors: Sanjin Kršćanski, Josip Brnić

Abstract:

Virtual Crack Closure Technique (VCCT) is a method used for calculating stress intensity factor (SIF) of a cracked body that is easily implemented on top of basic finite element (FE) codes and as such can be applied on the various component geometries. It is a relatively simple method that does not require any special finite elements to be used and is usually used for calculating stress intensity factors at the crack tip for components made of brittle materials. This paper studies applicability and accuracy of VCCT applied on standard metal specimens containing trough thickness crack, subjected to an in-plane bending load. Finite element analyses were performed using regular 4-node, regular 8-node and a modified quarter-point 8-node 2D elements. Stress intensity factor was calculated from the FE model results for a given crack length, using data available from FE analysis and a custom programmed algorithm based on virtual crack closure technique. Influence of the finite element size on the accuracy of calculated SIF was also studied. The final part of this paper includes a comparison of calculated stress intensity factors with results obtained from analytical expressions found in available literature and in ASTM standard. Results calculated by this algorithm based on VCCT were found to be in good correlation with results obtained with mentioned analytical expressions.

Keywords: VCCT, stress intensity factor, finite element analysis, 2D finite elements, bending

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3 Relationship between Physical Activity Level and Functional Movement in 16-years old Schoolchildren: A Multilevel Modelling Approach

Authors: Josip Karuc, Marjeta Mišigoj-Duraković, Goran Marković, Vedran Hadžić, Michael J. Duncan, Hrvoje Podnar, Maroje Sorić

Abstract:

As a part of the CRO-PALS longitudinal study, this investigation aimed to examine the association between different levels of physical activity (PA) and movement quality in 16-years old school children. The total number of participants in this research was 725. Movement quality was assessed via the Functional Movement Screen (FMSTM), and the PA level was estimated using the School Health Action, Planning, and Evaluation System (SHAPES) questionnaire. In addition, body fat and socioeconomic status (SES) were assessed. In order to investigate the association between total FMS score and different levels of PA, multilevel modeling was employed for boys (n=359) and girls (n=366) separately. All models were adjusted for age, body fat, and SES. Among boys, MVPA, MPA, and VPA were not significant predictors of the total FMS score (β=0.000, p=0.78; β=-0.002, p=0.455; β=0.004, p=0.158, respectively). On the contrary, among girls, VPA and MVPA showed significant effects on the total FMS score (β=0.011, p=0.001, β=0.005, p=0.006, respectively). The findings of this research provide evidence that the intensity of PA is a minor but relevant factor in describing the association between PA and movement quality in adolescent girls but not in boys. This means that the PA level does not guarantee optimal functional movement patterns. Therefore, practicing functional movement patterns in an isolated manner and at moderate to vigorous intensity could be beneficial in order to reduce the risk of injury incidence and potential orthopedic abnormalities in later life. This work was supported by the Croatian Science Foundation, grant no: IP-2016-06-9926 and grant no: DOK-2018-01-2328.

Keywords: functional movement screen, fundamental movement patterns, movement quality, pediatric

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2 Factors in a Sustainability Assessment of New Types of Closed Cavity Facades

Authors: Zoran Veršić, Josip Galić, Marin Binički, Lucija Stepinac

Abstract:

With the current increase in CO₂ emissions and global warming, the sustainability of both existing and new solutions must be assessed on a wide scale. As the implementation of closed cavity facades (CCF) is on the rise, a variety of factors must be included in the analysis of new types of CCF. This paper aims to cover the relevant factors included in the sustainability assessment of new types of CCF. Several mathematical models are being used to describe the physical behavior of CCF. Depending on the type of CCF, they cover the main factors which affect the durability of the façade: thermal behavior of various elements in the façade, stress, and deflection of the glass panels, pressure inside a cavity, exchange rate, and the moisture buildup in the cavity. CCF itself represents a complex system in which all mentioned factors must be considered mutually. Still, the façade is only an envelope of a more complex system, the building. Choice of the façade dictates the heat loss and the heat gain, thermal comfort of inner space, natural lighting, and ventilation. Annual consumption of energy for heating, cooling, lighting, and maintenance costs will present the operational advantages or disadvantages of the chosen façade system in both the economic and environmental aspects. Still, the only operational viewpoint is not all-inclusive. As the building codes constantly demand higher energy efficiency as well as transfer to renewable energy sources, the ratio of embodied and lifetime operational energy footprint of buildings is changing. With the drop in operational energy CO₂ emissions, embodied energy emissions present a larger and larger share in the lifecycle emissions of the building. Taken all into account, the sustainability assessment of a façade, as well as other major building elements, should include all mentioned factors during the lifecycle of an element. The challenge of such an approach is a timescale. Depending on the climatic conditions on the building site, the expected lifetime of CCF can exceed 25 years. In such a time span, some of the factors can be estimated more precisely than others. The ones depending on the socio-economic conditions are more likely to be harder to predict than the natural ones like the climatic load. This work recognizes and summarizes the relevant factors needed for the assessment of new types of CCF, considering the entire lifetime of a façade element and economic and environmental aspects.

Keywords: assessment, closed cavity façade, life cycle, sustainability

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1 Drivers of Satisfaction and Dissatisfaction in Camping Tourism: A Case Study from Croatia

Authors: Darko Prebežac, Josip Mikulić, Maja Šerić, Damir Krešić

Abstract:

Camping tourism is recognized as a growing segment of the broader tourism industry, currently evolving from an inexpensive, temporary sojourn in a rural environment into a highly fragmented niche tourism sector. The trends among public-managed campgrounds seem to be moving away from rustic campgrounds that provide only a tent pad and a fire ring to more developed facilities that offer a range of different amenities, where campers still search for unique experiences that go above the opportunity to experience nature and social interaction. In addition, while camping styles and options changed significantly over the last years, coastal camping in particular became valorized as is it regarded with a heightened sense of nostalgia. Alongside this growing interest in the camping tourism, a demand for quality servicing infrastructure emerged in order to satisfy the wide variety of needs, wants, and expectations of an increasingly demanding traveling public. However, camping activity in general and quality of camping experience and campers’ satisfaction in particular remain an under-researched area of the tourism and consumption behavior literature. In this line, very few studies addressed the issue of quality product/service provision in satisfying nature based tourists and in driving their future behavior with respect to potential re-visitation and recommendation intention. The present study thus aims to investigate the drivers of positive and negative campsite experience using the case of Croatia. Due to the well-preserved nature and indented coastline, camping tourism has a long tradition in Croatia and represents one of the most important and most developed tourism products. During the last decade the number of tourist overnights in Croatian camps has increased by 26% amounting to 16.5 million in 2014. Moreover, according to Eurostat the market share of campsites in the EU is around 14%, indicating that the market share of Croatian campsites is almost double large compared to the EU average. Currently, there are a total of 250 camps in Croatia with approximately 75.8 thousands accommodation units. It is further noteworthy that Croatian camps have higher average occupancy rates and a higher average length of stay as compared to the national average of all types of accommodation. In order to explore the main drivers of positive and negative campsite experiences, this study uses principal components analysis (PCA) and an impact-asymmetry analysis (IAA). Using the PCA, first the main dimensions of the campsite experience are extracted in an exploratory manner. Using the IAA, the extracted factors are investigated for their potentials to create customer delight and/or frustration. The results provide valuable insight to both researchers and practitioners regarding the understanding of campsite satisfaction.

Keywords: Camping tourism, campsite, impact-asymmetry analysis, satisfaction

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