SCIDAR - Дигитална архива Универзитета у Крагујевцу
Not a member yet
9015 research outputs found
Sort by
On Bishop frame of a partially null curve in Minkowski space-time E^4_1
Full text linkIn this paper, we introduce Bishop frame of a partially null curve α in Minkowski space-time E41. We prove that such curve has three Bishop frames determined by the particular solutions of the third order non-linear differential equation. We show that the Frenet frame of α can be obtained by rotating the Bishop
frame that corresponds to the particular solution θ(s) =R
κ1(s) ds of the mentioned differential equation. As an application, we obtain the parametrization of a lightlike hypersurface and focal surface with base
curve α in terms of its Bishop frame. Finally, we prove that a lightlike focal surface along a partially null helix has no critical value set.https://journal.pmf.ni.ac.rs/filomat/index.php/filomatPublishe
Phase-field damage simulation of subloop loading in TiNi SMA
Full text linkIn practical applications, TiNi shape memory alloys (SMAs) exhibit behavior that can pose a challenge
with current constitutive models and their implementations in finite element method (FEM) software.
TiNi SMA devices typically operate in the forward or reverse martensitic transformation regime, which
is known as subloop loading. During such cyclic loading–unloading, the hysteresis stress–strain loop
changes because of material damage, which can be considered the fatigue of TiNi SMAs. During both
the loading and unloading processes, the stress plateau decreases. At the same time, the accumulated
(residual) martensitic transformation strain increases. In this study, the experimental investigation
results and observations of the aforementioned phenomena are presented. Next, the phase-field damage
model is employed, along with a modified Lagoudas constitutive model, to simulate the change in
stress–strain hysteresis. Furthermore, a fatigue function is used to simulate the accumulation of
martensitic transformation strain. The experimental stress–strain response is compared with the
simulation results, and good quantitative and qualitative agreement is obtained. The damage and
martensitic volume fraction with respect to strain are discussed for full-loop and subloop loading. The
observations and conclusions, as well as open questions, are presented. Possible directions for future
research are provided.Publishe
EFFECTS OF LIME ON ALFALFA CULTIVARS YIELD ON ACIDIC SOIL
Full text linkSoil acidity limits the cultivation of alfalfa and the effecting of high yields. The experiment was set up on acidic soil to determine the effect of lime (0, 1 t ha-1, 2.5 t ha-1) on forage yield of alfalfa cultivars (K-28, Zuzana, NS-Nijagara) in the year of establishment. The yield of the liming variants was higher in all three cut and total yield, compared to the control. The significant differences in yield were only in the third cut, where the K-28 (4.76 t ha-1) and NS-Nijagara (4.46 t ha-1) had a higher yield compared to the Zuzana (3.65 t ha-1 Alfalfa (Medicago sativa L.) is one of the most important forage crops, cultivated on over 33 million hectares worldwide, due to its high nutritional value and high yield (Radović et al., 2009). In the Republic of Serbia, the total growing area in 2021 was 106.340 ha, with an average hay yield of 5.1 t ha). Interaction cultivar/lime was significant only in the first cut, while in the other two cuts and in the total yield it wasn’t.Publishe
DETERMINATION OF THE CONTENT OF BIOACTIVE COMPONENTS IN DIFFERENT EXTRACTS OF CELERY LEAVES (Apium graveolens L.)
Full text linkPlants with active compounds, i.e. those that have medicinal properties have been used since ancient times both for medicinal purposes and for preserving food. The aim of the work is to determine the most optimal extraction method for obtaining the highest yield of vitamin C and organic acids from celery leaves, which could have potential application in the food industry. Three extraction methods were combined, the density of the obtained extracts, the content of vitamin C and the content of organic acids were measured. The correlation of the content of bioactive components and the density of the obtained extracts was monitored.Publishe
The Influence of Friction and Twisting Angle on the Tensile Strength of Polypropylene Baling Twine
Full text linkPolypropylene is a widely used linear hydrocarbon polymer with diverse applications due to its exceptional physicochemical characteristics and minimal changes during the recycling process. Numerous studies have focused on factors influencing the mechanical properties of polypropylene and its application in composites. However, despite their significance in the agricultural industry, there is limited research on polypropylene baling twines. This study analyses the behaviour of polypropylene baling twine under tensile loading, exploring the influence of fibre friction and twisting angle on the material’s tensile strength. Experimental investigation indicated that tensile strength increases with twisting angle, but only until the angle reaches a critical value. Further increase in the twist angle led to a decrease in tensile strength. The increase in tensile strength is attributed to the rise in the coefficient of friction between fibres in the twine. An experimental approach was employed to evaluate the mechanical characteristics of the twine, including the effect of prestressing by twisting. Understanding these characteristics is crucial for enhancing the quality of polypropylene baling twines and optimising their application in the agricultural industry.Publishe
POSITIVE EVALUATION IN NEGATIVE CRITICISM: TYPES AND FUNCTIONS (IN THE REVIEWS FROM THE INTERWAR VOLUMES OF SOUTH SLAVIC PHILOLOGIST)
No full textThe paper examines positive commentaries in academic reviews that convey predominantly negative evaluation of either the reviewed material or its authors. The corpus consists of thirty-six reviews published in South Slavic Philologist throughout the 1920s and 1930s. Formal, semantic analysis showed that positive and negative assessments stand in two types of relations: adversative and concessive. Further, functional analysis showed that the function of positive assessment and its position in reviews correlate. While a number of positive remarks per review have been observed, in the majority of excerpted examples positive evaluation does not actually communicate positive meaning. Instead, it either introduces or emphasises negative comments. Much rarer instances of genuinely positive opinion were found in concluding and, to an extent, introductory segments.Publishe
Advanced Diagnostics of Respiratory Distress Syndrome in Premature Infants Treated with Surfactant and Budesonide through Computer-Assisted Chest X-ray Analysis
Full text linkThis research addresses the respiratory distress syndrome (RDS) in preterm newborns caused by insufficient surfactant synthesis, which can lead to serious complications, including pneumothorax, pulmonary hypertension, and pulmonary hemorrhage, increasing the risk of a fatal outcome. By analyzing chest radiographs and blood gases, we specifically focus on the significant contributions of these parameters to the diagnosis and analysis of the recovery of patients with RDS. The study involved 32 preterm newborns, and the analysis of gas parameters before and after the administration of surfactants and inhalation corticosteroid therapy revealed statistically significant changes in values of parameters such as FiO2, pH, pCO2, HCO3, and BE (Sig. < 0.05), while the pO2 parameter showed a potential change (Sig. = 0.061). Parallel to this, the research emphasizes the development of a lung segmentation algorithm implemented in the MATLAB programming environment. The key steps of the algorithm include preprocessing, segmentation, and visualization for a more detailed understanding of the recovery dynamics after RDS. These algorithms have achieved promising results, with a global accuracy of 0.93 ± 0.06, precision of 0.81 ± 0.16, and an F-score of 0.82 ± 0.14. These results highlight the potential application of algorithms in the analysis and monitoring of recovery in newborns with RDS, also underscoring the need for further development of software solutions in medicine, particularly in neonatology, to enhance the diagnosis and treatment of preterm newborns with respiratory distress syndrome.This research received financial support from the Faculty of Medical Sciences at the University of Kragujevac, Serbia, via grants JP 18/22. Additional backing was provided by the Ministry of Science, Technological Development, and Innovation of the Republic of Serbia, under contract number 451-03-47/2023-01/200111.Publishe
The effect of protease enzyme on the meat classes of two broiler chicken hybrids
No full textThe aim of the study was to evaluate the effect of three protein
levels (with or without protease enzymes) on the weight and percentage yield of
each meat class in two genotypes of broiler chickens (fast-growing hybrid Cobb
500 and medium-growing hybrid Master Gris). Each genotype was divided into a
control group (C group) fed with a commercial feed mixture and an experimental
group fed with a low protein diet of 4% (E-I group) or 6% (E-II group) in relation
to the control group, with the addition of 200 mg/kg Ronozyme ProAct (E-I
group) or 300mg/kg Ronozyme ProAct (E-II group).
Weight and percentage yield of the meat classes were influenced by the
genotype. The fast-growing hybrid Cobb 500 had higher masses of all meat
classes and a higher percentage of class I meat, while the percentage of class II
and III meat was lower than in the medium-growing hybrid Master Gris (P<0.05).
Feeding had no effect on the weight and percentage yield of the individual meat
classes in either hybrid (P>0.05).Publishe
EXPERTISE JUSTIFICATION AND PROPOSAL OF INTRODUCING ARTIFICIAL INTELLIGENCE INTO MEDICATION PROCUREMENT SYSTEMS
Full text linkAbstractThis paper explores the justification and proposes a model for the introduction of artificial intelligence (AI) into medication procurement systems. By analyzing the current state of medication procurement, we identify key areas where AI could enhance efficiency, accuracy, and reliability of the process. The implementation of
AI is suggested for automating ordering, predicting demands, optimizing inventory, and analyzing supply chain risks. Through testing and evaluating selected AI models, their ability to enhance medication procurement processes can be revealed. Implementation of these models, along with continuous monitoring and optimization, enables medication procurement systems to more efficiently manage inventory, reduce the risk of shortages, and achieve long-term financial savings. This study provides a framework for a systematic approach to introducing AI into medication procurement systems to improve performance and process optimization.Publishe