Papers by Monika Lutovska
In this paper, risk assessment for the activities associated with construction of bridge as part ... more In this paper, risk assessment for the activities associated with construction of bridge as part of the risk assessment for the project comprising building of new motorway section from Demir Kapija to the village of Smokvica, Republic of Macedonia is presented. After identified risks and hazards, during activities related with bridge works and after performed risk assessment, control measures are proposed.
In this paper, the results of comparative analysis between transcendental and cyclometric sorptio... more In this paper, the results of comparative analysis between transcendental and cyclometric sorption isotherm models are presented. In order to find which model gives the best results, some numerical experiments were made. The experimental data set for equilibrium moisture content and the water activity for apple, pear, kiwi and banana at two different temperatures were used from the scientific literature. For each model and data set, several statistical parameters were calculated and models were ranked afterwards. The performed comparative analysis shows that the cyclometric models in many cases have higher values of the coefficient of determination, and lower values of the root mean squared error and the mean relative deviation than transcendental the isotherm models. All these results show that the cyclometric sorption isotherm models give the best overall fit to experimental data. After choosing the best transcendental and cyclometric model with the high value of statistical perfo...
In this paper, a new approach for selection of a thin-layer drying model based on serial statisti... more In this paper, a new approach for selection of a thin-layer drying model based on serial statistical criteria was proposed. The experimental data set of thin-layer drying kinetics of apple slices at five different drying air temperatures (40, 60, 80, 100 and 120 C) and three drying air velocities (1, 2 and 3 ms-1) were obtained on the experimental setup, designed to imitate an industrial convective dryer. The drying data were fitted with twenty-three published thin-layer drying models (Lewis, Page, Modified Page, Henderson and Pabis, Modified Henderson and Pabis, Logarithmic(Asymptotic), Two term, Two term exponential, Midilli, Diffusion approach, Wang and Singh, Weibull, Aghbashlo, Verma., Grigorias, Parabolic, Hll, Demir, Logarithmic,Logistic, Vega-Lemus, Jena-Das and Alibas). In order to find which model gives the best results, some numerical experiments were made. For each model and data set, the performance index was calculated and models were ranked afterwards. After that, sev...
This paper describes the experimental results on the drying of the potato slices by infrared radi... more This paper describes the experimental results on the drying of the potato slices by infrared radiation under vacuum condition. The investigation of vacuum far-infrared drying processes was conducted on the experimental set-up that is designed to imitate industrial batch dryer. The experimental conditions have been chosen such that heaters’ temperature and vacuum chambers’ pressure have been in the range used on the industrial dryer. Potato slices were dried at various vacuum pressures (20, 40, 60 and 80 kPa) and temperatures (120, 140, 160, 180 and 200 C) which were kept constant during the single experiments. Based on experimental drying data, it was found that the drying time decreased with an increase of temperature of heaters and the decrease in the chamber pressure. It was also concluded that the influence of the temperature in vacuum chamber has more significant effect on reducing of the drying time than the vacuum pressure. Ten well known thin layer drying models from scienti...
Journal of Hygienic Engineering and Design, 2014
Drying of food materials is a complex process of simultaneous heat and mass transfer within dried... more Drying of food materials is a complex process of simultaneous heat and mass transfer within dried material and from its surface to the surroundings, caused by a number of transport mechanisms. There are several different methods of describing the complex simultaneous heat and moisture transport processes within drying material. Thin-layer drying models are important tools in mathematical modeling of drying processes. In scientific literature generally for evaluation of thin-layer models, that use approximation of experimental drying data, the values of the coefficient of determination (R2), correlation coefficient (r), reduced chi-square, root mean square error (RMSE), and mean bias error (MBE) are the most common criteria to select the best model. In this paper one approach for selection of a thin-layer drying model based on serial statistical criteria was proposed. Fresh banana were used in this study. The experimental data set of thin-layer drying kinetics of banana slices at fou...
2020 55th International Scientific Conference on Information, Communication and Energy Systems and Technologies (ICEST), 2020
Brief review of few major air pollutants of Skopje is presented in this article. State automatic ... more Brief review of few major air pollutants of Skopje is presented in this article. State automatic monitoring system for ambient air quality measures up to 7 air pollutants is presented. It consists of network of 17 fixed and 1 mobile monitoring stations installed throughout the country. Performed analysis of pollutants’ inventory reveals that suspended particles (PM10 and PM2.5) are the most critical air pollutants in Skopje in the last couple of years.
In this paper, a new approach for selection of a thin-layer drying model based on serial statisti... more In this paper, a new approach for selection of a thin-layer drying model based on serial statistical criteria was proposed. The experimental data set of thin-layer drying kinetics of apple slices at five different drying air temperatures (40, 60, 80, 100 and 120 o C) and three drying air velocities (1, 2 and 3 ms -1 ) were obtained on the experimental setup, designed to imitate an industrial convective dryer. The drying data were fitted with twenty-three published thin-layer drying models (Lewis, Page, Modified Page, Henderson and Pabis, Modified Henderson and Pabis, Logarithmic(Asymptotic), Two term, Two term exponential, Midilli, Diffusion approach, Wang and Singh, Weibull, Aghbashlo, Verma., Grigorias, Parabolic, Hll, Demir, Logarithmic,Logistic, Vega-Lemus, Jena-Das and Alibas). In order to find which model gives the best results, some numerical experiments were made. For each model and data set, the performance index was calculated and models were ranked afterwards. After that,...
a free-access multidisciplinary publication of the Faculty of Engineering Hunedoara 1. Abstract: ... more a free-access multidisciplinary publication of the Faculty of Engineering Hunedoara 1. Abstract: In this paper, some of the statistical indicators which refer to serious and fatal accidents at work in the European Union (EU-28) and in the Republic Macedonia are presented. The performed statistical analysis shows that the number of serious and fatal accidents at work in EU-28 and in the Republic Macedonia, in 2012 was decreased in comparison with 2008. Nevertheless, the Republic of Macedonia has high incidence rate for fatal accidents at work compared to highly develop European countries. The activities of public administration and defense, construction, manufacturing, transportation and storage sector and the activities of households as employers are the economic sectors in which it is possible to prevent injuries caused by serious accidents at work. Тhe activities of households as employers, construction sector, transportation and storage sector and agriculture, forestry and fishin...
Journal on Processing and Energy in Agriculture
The hot air convective drying of blueberries (Vaccinium corymbosum) in a thin layer was performed... more The hot air convective drying of blueberries (Vaccinium corymbosum) in a thin layer was performed using a laboratory-scale dryer. The experiments were carried out at drying air temperatures of 60, 70 and 80 o C, and drying air velocities of 0.5 and 1.5 m/s. At higher values of the drying air temperature and the drying air velocity, less time was required for the convective drying of blueberries, i.e. the drying time of blueberries decreased with increasing drying air temperatures and velocities. The experimental data obtained during the drying process were fitted to ten different mathematical models. The Midilli et al. model was found to be the most appropriate model for explaining the drying behavior of blueberries during convective drying. Effective moisture diffusion coefficients were calculated using the Fick's diffusion model, ranging from 9.66 x 10-12 m 2 /s to 9.67 x 10-11 m 2 /s. These values were found to increase proportionally with the increase in drying air temperatures and velocities. The lowest total color change and shrinkage of dried blueberries were recorded during freeze drying. A water activity less than 0.6 was measured at a blueberry moisture content of 0.235 kg w /kg d.m , a drying air temperature of 26 o C and a relative air humidity of 60 %.
Journal on Processing and Energy in Agriculture
Journal on Processing and Energy in Agriculture
In this paper, a faster and easier way, in comparison with classical methods, to determine the eq... more In this paper, a faster and easier way, in comparison with classical methods, to determine the equilibrium moisture content in food materials is shown. The equilibrium moisture content is determined only experimentally, with determination of sorption isotherms. However, the key issue that is a condition for application of certain experimental method for determining of sorption isotherms is the reliability of experimental data obtained for equilibrium moisture content, as well as the time required to determine specific sorption isotherm. Despite numerous advantages of the static gravimetric method, the long time to achieve equilibrium moisture content of the sample is its main drawback and reason why the researchers use other techniques and methods. Out of these reasons came the idea to apply relatively fast and simple method to determine equilibrium moisture content in food materials, based on the values of average material temperature change obtained from experiments including convective drying kinetics. Furthermore, the resulting temperature response from the conducted experiments can be successfully used to determine unknown parameters in the models for calculation of equilibrium moisture content, by applying of inverse approach method that is an essential tool in modeling of heat and mass transfer processes for different food materials.
Journal of Food Process Engineering, 2015
ABSTRACT In this study, a power series which can generate different families of new water sorptio... more ABSTRACT In this study, a power series which can generate different families of new water sorption isotherm models were presented. Experimentally obtained values for equilibrium moisture content of pear for three different temperatures, 15, 30 and 45C, and water activities, from 0.112 to 0.920, as well as literature experimental values for equilibrium moisture content of potato for three different temperatures, 30, 45 and 60C, and water activities, from 0.112 to 0.900, were fitted with the newly generated sorption isotherm models plus the referent Anderson model known in the literature as Guggenheim-Anderson-de Boer (GAB) model. In order to find which model gives the best results for approximation of experimental sorption data, several statistical criteria proposed in scientific literature were used. For each model and experimental data set, the average performance index was calculated and models were ranked afterwards. After that, some statistical rejection criteria were checked (D’Agostino-Pearson test of normality, single-sample run test, confidence intervals of estimated parameters, significance and precision of the model parameters). The performed statistical analysis shows that the two newly generated three-parameter models, M32 and M34, give the better fit to the sorption data of pear than the referent three-parameter Anderson model, while M32 gives the best fit to the sorption data of potato.Practical ApplicationsThe sorption isotherms of food materials are of great importance in the food industry and technology, especially for the design and optimization of the drying equipment and in the approach to the prediction of shelf life stability of material. The new generated three-parameter models, M32 and M34, can be successfully used in practical calculations of the equilibrium moisture content, which is an important parameter in storage conditions of dry food materials. With the incorporation of M32 or M34 in the drying model, more accurate values of transient moisture and temperature profiles on the dried materials will be obtained.
Wind energy as renewable energy source with the highest growth rate in the last two decades, is c... more Wind energy as renewable energy source with the highest growth rate in the last two decades, is considered as a very important source of electricity for the future. According to the study WIND FORCE which is funded and conducted by the EU, the share of wind energy in the global world electricity generation in 2020 is estimated at 12%. So far, several studies for determination of most suitable locations for construction of wind farms have been made in Macedonia. According to a study prepared by AWS Truewind, atlas of wind energy potential of Macedonia is made. 15 most suitable locations for building of wind farms determined out of this study. According to the wind map and according to conducted measurements at 4 locations, projected installed capacity by location varies from 20 MW to 30 MW. State owned electricity producing company (JSC Macedonian Power Plant - ELEM), earlier this year, on a location near Bogdanci, started with construction of first wind farm in the country.
Thermal Science
Wind energy as a renewable energy source with the highest growth rate in the last two decades, is... more Wind energy as a renewable energy source with the highest growth rate in the last two decades, is considered as a very important source of electricity for the future. The forecasts for development of wind energy are highly optimistic and state that this type of energy will be really important in the future. Following recent data and analysis from certain studies, the share of wind energy in the global world electricity generation in 2020 is estimated to reach 12%. In the same context, and in order to reduce high dependence on fossil fuels, Macedonian government took some steps to introduce and enforce utilization of renewable energy sources. First wind park with capacity of 36.8 MW, installed and operated by the state-owned electricity producing company (JSC Macedonian Power Plants - ELEM), started with operation in April 2014, on a location near Bogdanci. The techno-economic analysis regarding its performance in terms of investment costs, operation and maintenance costs, electricit...
Thе renewable energy is very important segment of human life in modern world, which provides ener... more Thе renewable energy is very important segment of human life in modern world, which provides energy for electricity generation, that is collected from renewable resources which are naturally replenished on a human timescale such as sunlight, wind, rain and others. The renewable energy resources, that are easily accessible in rural areas are mostly unused. Renewable energy has less negative impacts on environment than fossil fuels. Site selection is a crucially important step for utilizing large investments like small hydropower plants, solar farms and wind turbines. Multi-criteria evaluation methods are commonly used for site selection. The main goal of this paper is to show the contemporary GIS-based approach for for geospatial analyses of suitable locations for exploatation of renewable energy resources no matter of whether it is going for hydro power of small streams, wind or solar power. The focus of analysis is set to some of the most important topographic land surface parameters such as: slope (gradient of surface), aspect of slope, as well as the other land surface parameters that have impact and are important for optimal decision making concerning the site suitability for renewable energy expoatation. The methodology and analysis is performed on a study area which encompasses a part of the northeastern watershed of Prespa lake for small hydropower and solar farms, while the analyses for wind energy have been performed for entire area of the country. Throughout the researches it is showed, that the DEM (Digital Elevation Model) is one of primary driving force for analyzing of physical processes of surface resources. In the paper is proposed a methodology for assessment of hydropower potential of small streams as one of the oldest renewable energy resources, solar power plants and wind farms. The obtained results of performed analyses show, that the analyzed areas have considerable potential for use of renewable energy resources. The proposed GIS based multicriteria spatial analysis of suitable sites can be modifyed and efficiently applied to any other spatial location.
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Papers by Monika Lutovska