bluuebunny/crossref_metadata_2025_split huggingface dataset:
Applying text mining methods to extracting information from news articles
Authors: Georgieva-Trifonova Tsvetanka , Dechev Miroslav 
Published: February 2021

Abstract
In the present paper, the text mining methods from the point of view of their application for extracting information from news articles, are discussed. For this purpose, research questions are formulated and opportunities to assist in obtaining their respective answers are presented, as they are illustrated by the application of text mining methods on a created dataset with articles in Bulgarian. The extracted information could be useful for research of the topics covered in the articles, exploration of customer interests, etc.
Attributes selection using machine learning for analysing students’ dropping out of university: a case study
Authors: Pehlivanova T I , Nedeva V I 
Published: February 2021

Abstract
Many students in Bulgarian universities drop out of the university before completing their studies. Identifying students at risk of dropping out allows timely taking measures for their retention. The paper presents the results of a study conducted among students of engineering programs at Trakia University - Stara Zagora. The collected data are subjected to processing, which aims to find the most important attributes that determine the risk of dropping out of university. The processing is done with Weka open source software. Different algorithms for selecting attributes with different search methods are applied. The most appropriate attribute selection algorithm was selected after applying the BayesNet classifier to the results obtained. The indicators TP rate, Precision and F-measure were compared. When applying InfoGainAttributeEval, the highest results are obtained for the accuracy of the classification. At the next stage, it is planned to expand the study among a larger number of students from different programs and create an effective forecasting model.
Students’ Performance Analyses Using Machine Learning Algorithms in WEKA
Authors: Nedeva Veselina , Pehlivanova Tanya 
Published: February 2021

Abstract
Predicting student performance is important for universities. Thus, they can identify students who need support and take measures to improve educational outcomes.
The paper presents analyze of the results of a study conducted at the Trakia University of Stara Zagora. The study aims to identify the most significant features that affect student performance and to select the most efficient machine-learning algorithm to predict their performance.
The efficiency of four classification algorithms was compared-BayesNet (BN), Multilayer Perceptron (MLP), Sequential minimal optimization (SMO) and Decision tree (J48). For comparison, the indicators TP Rate, Precision, F-Measure, Accuracy and error measures-MAE, RMSE, RAE, and RRSE were used. The processing is done with Weka open-source software. The obtained results show that the MLP algorithm is the best for the used data. The obtained accuracy is sufficient to create an effective forecast model. 12 attributes have been identified that have the greatest impact on student performance.
E-assessment-beyond the traditional assessment in digital environment
Authors: Kiryakova Gabriela 
Published: February 2021

Abstract
An assessment is an integral part of the learning process, which determines whether and to what extent the learning objectives have been achieved. It indicates whether the used tools, technologies and pedagogical approaches have produced positive results. Today technologies are implemented in all stages and activities in the learning process. They allow teachers to diverse, enrich and develop traditional assessment methods. E-assessment guarantees rapid, instant, automated results and feedback and the implementation of new approaches for assessing learners’ knowledge. Learning Management Systems offer a variety of tools for e-assessment and provide the opportunities to integrate assessment exercises into other learning activities. The aim of the current work is to present some of the innovative assessment tools in Learning Management Systems illustrated by LMS Moodle. They allow the implementation of new assessment approaches that differ from traditional ones. They prove the thesis that e-assessment is not equivalent to traditional assessment carried out in a digital environment and provides new attractive opportunities and techniques for evaluating various aspects and levels of knowledge, skills and competencies.
Hybrid model for quality evaluation in secondary education
Authors: Docheva M , Totkov G , Gaftandzhieva S , Doneva R 
Published: February 2021

AbstractThe paper introduces a hybrid model for quality evaluation of the educational process in high school, based on a set of qualitative and quantitative indicators. The model overcomes the subjectivity of external evaluation by using a relatively small number, clear and objectively measurable criteria for different types of indicators, divided into 12 groups. All 132 indicators (75 qualitative and 57 quantitative) are measures of the educational process from different points of view -to measure compliance of essential quality criteria with European and national best practices, to objectively compare specific numerical indicators, etc. Quality indicators are evaluating by using two types of measuring scales. The first type is suitable for such indicators which are used mainly to classify the assessed objects according to a specific characteristic. The second type of measuring scales are suitable for indicators, the values of which are used to compare the qualities of objects. The proposed hybrid model for quality evaluation of high schools uses 4 measurement scales, based on relative measurements of 57 quantitative indicators.
Fuzzy U-Net Neural Network Architecture Optimization for Image Segmentation
Authors: Kirichev M M , Slavov T S , Momcheva G D 
Published: February 2021

Abstract
In this article, the optimization of the modified U-Net neural network model extended with fuzzy layers has been studied with the usage of Grid search and Keras tuner. The article is a continuation of previous work where the model is suggested and explored. From one point of view, the research is focused on the optimization of Fuzzy Layers embedded in the U-Net model in order to find the better neural network architecture for nuclei segmentation in the research work in BioMed Varna R&D ecosystem for the segmentation of cellular nuclei. At the same time from a global perspective, this experiment is a part of the bigger one for the searching of new neural network architecture design techniques.
Generation of phase trajectories of experimental data
Authors: Yankov K B 
Published: February 2021

Abstract
The phase plane method (PPM) is a graph-analytical approach for studying the stability and long-time behavior of systems described by differential equations. In order to apply the PPM to experimental data, it is necessary to identify these data with a first-or second-order differential equation. This work presents a numerical-analytical algorithm for obtaining phase trajectories from experimental data avoiding identification with a differential equation. For this purpose, the data are interpolated with a cubic spline. The first derivative was obtained analytically from the spline. The abscissa coordinates are the values of the spline at a given point, and the ordinate is the analytical representation of the first derivative. As an example, the phase trajectory of the dose-dependent curve of the drug tubazid is constructed by two methods-with identification of the differential equation describing the process and with the algorithm proposed in the article. The approach is implemented with Korelia software.
Risk analysis in terms of implementation of large scale cogeneration power plant
Authors: Terziev A K , Beloev H I , Iliev I K 
Published: February 2021

Abstract
The introduction of large-scale technology carries a number of risks. This paper presents the risks associated with the introduction of a system for combined production of electricity and thermal energy (CHP) through direct combustion of biomass. It is envisaged that the residual amount of heat energy will be converted into electricity through the use of an ORC module. All possible risks have been identified based on the technology specifics, and the possible consequences of the risk have been indicated. A risk matrix has been prepared for both site and technology specifics in order to identify the type of risk. Based on the outputs, a proposal for reducing the risk has been made.
Technology of butter fortified with phytosterols
Authors: Ivanova M G , Dobrev G T 
Published: February 2021

Abstract
The aim of the resent study was to determine the appropriate moment to enrich the butter with phytosterols. The butter was enriched in phytosterols at three different stages of the technological process – before cream pasteurisation (batch B), before cream ripening (batch C) and before working the butter into a continuous fat phase (batch D). A control sample with no added phytosterols was prepared (batch A). The titratable acidity of cream before and after biological ripening and of the resulting butter was determined. No significant differences between samples were found (p>0.05). The fat, moisture and phytosterol content of butters, produced from different batches, were evaluated. Any significant differences between samples were found (p>0.05). The number of lactic acid microorganisms in the final product was similar in all analysed samples (p>0.05). The butters enriched with phytosterols were characterized by high sensory scores comparable with those of the control sample (p>0.05). This study suggested that the addition of phytosterols in butter could be performed at different stages of the technological process with no reflect on the phytosterol content in the final product. From a safety point of view, it is appropriate to add the phytosterols before pasteurisation process. The obtained butter is considered as functional product with potential health effects.
Volatile compounds in flowers, samaras, leaves and stem bark of Ailanthus altissima (Mill.) Swingle, growing in Bulgaria
Authors: Andonova Ts G , Dimitrova-Dyulgerova I Zh , Slavov Zh , Dincheva I N , Stoyanova A S 
Published: February 2021

Abstract
The aim of the present study was to determine the composition of essential oils (EOs) of different plant parts of A. altissima, growing in Bulgaria. Four samples (flowers, immature samaras, leaves, stem bark) of A. altissima were collected in the period June-July of the 2019 growing season, from Plovdiv, Bulgaria. The EOs were obtained by hydrodistillation with a Clevinger-type apparatus. Gas Chromatography/Mass Spectrometry analysis was applied to determine the volatile compounds. The yield (in fresh material) was 0.5 ml/kg (samaras), 0.27 ml/kg (flowers), 0.23 ml/kg (leaves), and 0.18 ml/kg (bark). There were identified 75 volatiles from the different plant parts. Oxygenated hydrocarbons (mainly fatty acids, their esters) were the best-represented group in samaras, leaves, bark (65.87%; 47.53%; 49.41% respectively). Oleic acid was the major constituent in the three EOs (samaras -34.26%; stem bark -30.21%; leaves -22.94%). In the flower EO, the dominant group was sesquiterpene hydrocarbons (46.48%) with main compounds β-caryophyllene (16.98%) and germacrene D (16.24%). The volatile components in Ailanthus altissima, growing in Bulgaria, have been determined for the first time. Differences in the composition of EOs were found.
Investigation and characterization of O/W emulsions on stability with different methods
Authors: Gandova V D , Tasheva STz , Petrova I G , Dobreva K Z 
Published: February 2021

Abstract
The properties and efficiency of O/W emulsions were investigated. Influence by oil phase in the emulsification processes was determined. After centrifugation measurements in emulsions with high percent oil four phases were observed. pH values in all emulsions was measured and found from 5.8 to 6.3 in connection with application of foods. During the storage period of fourteen days the spectroscopic measurements were perform in continuous phase and middle radius of particle sizes were calculated.
Technological aspects of obtaining ethanol extracts from Physalis alkekengi L. leaves
Authors: Ivanova T A , Popova V T , Tasheva S T , Mazova N N , Stoyanova A S 
Published: February 2021

Abstract
The aim of the study was the provision of a technological background for obtaining ethanol extracts with prospective cosmetic application from the leaves of P. alkekengi L. Extraction was carried out in laboratory conditions, as a batch static mode process, with four solvents, 95%, 70%, 50%, and 30% ethanol, respectively. The influence of the main technological factors, temperature (20°C, 40°C, and 60°C) and duration (1 h, 3 h, 5 h and 7 h), upon the content of tannins in the extracts was studied by mathematical modelling of the experiment. The equations of extraction, based on the concentration of extracted tannins were derived. The optimal conditions for the extraction procedure of P. alkekengi leaves were determined (70% ethanol, 5 h, 60°C). The results from the study, i.e. the dynamics of tannin extraction, the equations of extraction and the technological factors’ combination, could be applied in the obtaining of P. alkekengi leaf extraction products intended for use in different personal care products; of course, additional investigations on the subject are necessary, especially in terms of extracts’ individual composition and biological activities.
The leaves and stems of Cape gooseberry (Physalis peruviana L.) as an alternative source of bioactive substances
Authors: Popova V T , Ivanova T A , Stoyanova M A , Mazova N N , Panayotov N D , Stoyanova A S 
Published: February 2021

Abstract
The objective of this work was the investigation of the chemical composition of the leaves and stems of two Cape gooseberry (Physalis peruviana L.) genotypes from Bulgaria (CG-SB and CG-NB), with the view of establishing the presence of certain bioactive substances and the prospects for their use as livestock feed or cosmetic ingredients. The leaves and stems of CG-SB genotype contained 18.63% and 40.26% cellulose, respectively, and 24.83% and 13.73% protein; the respective contents in the leaves and stems of CG-NB genotype were 27.63% and 47.63% cellulose, and 9.36% and 8.07% protein. The dominant amino acids in CG-SB leaves were aspartic acid (32.04 mg.g-1) and lysine (30.54 mg.g-1), and in the stems – proline (46.90 mg.g-1) and phenylalanine (15.42 mg.g-1). The amino acid composition of the leaves of CG-NB genotype was dominated by histidine (24.88 mg.g-1) and proline (21.25 mg.g-1), and that of the stems – by proline (13.38 mg.g-1). The main macro and micro minerals in the leaves and stems of both genotypes were K, Mg and Fe, respectively, but numerical differences were observed on a genotype and plant part basis. The leaves were processed by extraction with n-hexane and the content of volatiles was determined (by GC-MS). A total of 32 components was identified in each of the genotypes. The major volatile in both genotypes was n-pentacosanol, 17.07% in CG-SB and 12.39% in CG-NB; the dominant group of chemicals was that of oxygenated aliphatics, followed by diterpenes. The results from the study provide arguments that the leaves and stems of Cape gooseberry, currently discarded byproducts, could be regarded as alternative sources of bioactive substances.
Effect of hop extracts on rheological properties of wheat dough
Authors: Sokolova N 
Published: February 2021

Abstract
The choice of technological equipment and the mode selection in bakery industry is determined by the rheological properties of the processed or transported food masses, pre-ferments, and products. In this aspect, the effect of new ingredients in bakery production such as two types of hop extracts (the hop-water and hop-milk whey systems) and their percentage in the formula on the rheological properties of wheat dough during kneading and fermentation has been investigated. The effect of extracts and their percentage in dough formula on time development and strength of the dough has been studied. It was found, using the Brabender Farinograph, that hop extracts lead to decreasing of the elasticity and degree of softening of wheat dough with hop-water extract by 9—27% compared to the control, and hop-milk whey-by 33—41%. Brabender Extensograph carried out the assessment of changes in physical properties of the dough with hop extracts during fermentation after 45, 90 and 135 min. It was found that hop extracts increase the strength of the dough and resistance to extension, which also indicates strengthening effect of hop extracts on wheat gluten. The changes in the quality characteristics of wheat bread with different dosage of hop extracts have been investigated. It was found that the addition of the extract based on water increases the ability to hold the shape of baked bread, on average, by 2—17% whereas extract based on whey increase this index by 8—25%.
Mid-season peach varieties – physicochemical and sensory profile
Authors: Mihaylova Sp D , Popova A T , Dessev Tz T , Petkova N T 
Published: February 2021

Abstract
Prunus varieties are a major contributor to bioactive compounds in the daily diet in the spring and summer. There is a need to disseminate knowledge about the benefits of consuming fruits and their products to the public and to expand research into the potential for harnessing their health potential. The study aims at evaluating target physicochemical and composition attributes of two mid-season ripening dessert peach varieties: “July Lady” (freestone) and “Laskava” (freestone). Fruit weight, shape and size, as well as colour and firmness were evaluated. Image analysis was used to describe properties such as length, width, thickness, etc. Dry matter (%), ash content (%), total soluble solids, pH, titratable acidity, total sugar content, and protein content were employed to characterize the studied varieties. Total soluble solids varied from 12.52 to 13.52 and dry content-from 14.98 to 16.16%. A descriptive sensory method characterised the studied varieties, and the panellists detected differences in each of the categories (aroma, taste, texture and appearance). These results highlight new data about peach varieties and help to better feature their unique characteristics.
Biologically active compounds from Tussilago farfara L
Authors: Stoyanova M A , Perifanova-Nemska M N 
Published: February 2021

Abstract
The modern interest in the chemical component of the coltsfoot is due to the fact that many of the ingredients in the tea have physiological activity and can be used in the treatment and prevention of many diseases. The results from this study showed, that the main phenolic acids was caffeic acid (1867.34±3.12 μg/g), ferulic acid was in approximately lower concentration, triple lower than caffeic acid (545.23±4.36 μg/g), while chlorogenic acid was not detected. Ascorbic, malic and citric acids were determined by HPLC analysis as the main organic compounds in the leaves of coltsfoot. The most abundant organic acids were ascorbic acid (67.43±0.95 mg/g) and malic acid (45.25±1.15 mg/g). The 17 amino acids were determined in our study. The highest quantities of essential amino acids were phenylalanine (6.23 g/100 g protein) and valine (5.56 g/100 g protein). Other essential amino acid such as threonine, leucine, isoleucine and lysine were found at 4.90 g/100 g protein, 4.64 g/100 g protein, 3.76 g/100 g protein, and 2.45 g/100 g protein respectively.
Influence of sucrose and barley flour on some physical, texture and sensory characteristics of cookies
Authors: Nakov Gjore , Dimov Ivan , Taneva Ira , Stamatovska Viktorija 
Published: February 2021

Abstract
The aim of the present paper is to establish the influence of sucrose on the basic properties of the cookies – losses during baking, thickness, volume, specific volume, colour, as well as on their texture and sensory characteristics.
A total of six kinds of cookies were prepared from wheat four, barley flour and mixture of them in ratio 50:50, in two groups according to the sweetener used – with and without sucrose. The results obtained indicated that sucrose and the barley flour exert certain effect on the basic physical properties of the cookies, as well as on their texture and sensory characteristics.
When sucrose is used for preparation of cookies, beside that it imparts sweet taste, the baking losses decreases (13.64 %), thicker cookies are produced (15.95 mm), diameter (68.90 mm), expansion factor (44.43), volume (40 cm3) and specific volume (1.65 cm3/g) compared to the cookies prepared without sucrose. The sucrose containing cookies are harder, darker and have more intense red and yellow colour. It was found from the sensory analysis carried out that these cookies are preferred by the consumers.
The addition of barley flour to the cookies composition results in higher loss during the baking but the cookies obtained have bigger diameter compared to these which do not contain barley flour. The cookies prepared from mixture of wheat and barley flour in ratio had the best sensory properties.
Synthesis, characterization, and activity of 6-(10H-phenothiazine-10-yl)-1H,3H-benzo[de]-isochromen-1,3-dione derivative of 4-aminophenylacetic acid
Authors: Haralanova T , Marinov M , Kostova I , Nikolova I , Damyanova S , Stoyanov N 
Published: February 2021

Abstract
The objective of the present paper was to study the synthesis of a new compound 6-(10H-phenothiazme-10-yl)-1H,3H-benzo[de]-isochromen-1,3-dione derivative of 4-aminophenylacetic acid (PTZD). Its physicochemical characteristics and spectral data were presented. PTZD was found to have good inhibitory activity. The phenothiazine derivative showed good fungicidal activity against the studied yeast (S. cerevisiae and C. albicans) and mold species (A. brasiliensis and F. moniliforme), weak bactericidal activity against the Gram-positive bacteria S. aureus and B. subtilis and did not affect the growth of Gram-negative bacteria E. coli, P. aeruginosa and S. abony.
Synthesis, complexation properties, antimicrobial and anticoagulant activity of 2-{3-[4-(dimethylamino)phenyl]-1-hydroxyprop-2-en-1-ylidene}-4-nitro-1H-indene-1,3(2H)-dione
Authors: Nikolova I , Kostova I , Staneva M , Marinov M 
Published: February 2021

Abstract
This article presents the synthesis of a new 4-nitro-cinnamoyl derivative of 2-acyl-1,3-indandione. The resulting compound was subjected to interaction with ErCl3x6H2O, which was obtained from Er2O3 and HCl. The synthesized compounds were proven by IR and NMR spectroscopy. The spectral data clearly proves the formation of a chelate complex. A probable structural formula of the coordination compound is also proposed. The obtained compounds were used for analysis of their antimicrobial and anticoagulant activity.