Technical College Požarevac
  • Požarevac, Serbia, Serbia
Recent publications
The evaluation of the embryonic root and stem of bread wheat (Triticum aestivum L.) in the early stage of development (seedling stage) can be a powerful tool in wheat breeding aimed at obtaining progenies with a greater early vigour. It is revealed that genotypes with faster early vigour have produced higher biomass and grain yield. In this study, the evaluation of traits of the embryonic root and the embryonic stem of 101 bread wheat genotypes was preformed at the 10-day old seedlings. The following eight morphological traits of roots and stems were analysed: primary root length, branching interval, the number of roots, total length of lateral roots, angle of seminal roots, stem length, root dry weight and the stem dry weight. Analysed lateral roots included seminal roots. The greatest, i.e. the smallest variability of observed traits was detected in the branching interval, i.e. the stem length, respectively. The highest positive correlation was determined between the primary root length and the total length of lateral roots. The cluster analysis, based on observed traits, shows that genotypes were clearly divided into two main clusters, A and B. The two clusters essentially differed from each other in the values of the following traits: primary root length, total length of lateral roots, root dry weight, stem dry weight and the stem length. Genotypes with shorter primary and lateral roots, lower root and stem dry weight and a shorter stem were grouped in the cluster B. On the other hand, the cluster A encompassed genotypes with values of these traits above or around the average. The values of the remaining analysed traits: the angle of seminal roots, the number of lateral roots and the branching interval varied greatly between obtained clusters. The cluster analysis showed the homogeneity of genotypes originating from Serbia and the region; their values of the root and stem length and weight were mostly around and below the average. However, the values of the angle of seminal roots, number of lateral roots and the branching interval were above average.
The fractal family $\left\{p\left(n,k\right), 1\le k\le n\right\}$, describe a rule to calculate the number of partitions obtained by decomposing $n\in \mathbb{N}$, into exactly $k$ parts. In this paper, we will present a novel method for proving that polynomials $\left\{p\left(n,k\right), 1<k<n\right\}$ have fractal form. For each class $k$, up to the $LCM\left(1,2,3,\dots,k\right)$, different polynomials of degree $k-1$ are needed to form a single quasi-polynomial $p\left(n,k\right)$. All the polynomials (needed for the same class $k$) have all coefficients of the higher degrees ending with the $ \left[\frac{k}{2}\right] $ degree in common. Moreover, we will prove that, for a fixed value of $k$, all the first, second, etc. coefficients of the common part of the fractal family have a general form, showing the vertical connection between the corresponding coefficients of all fractal family $\left\{ p\left(n,k\right)\right\} $. Furthermore, for a fixed value of $n$, all the coefficients within the same fractal polynomial have a unique general form, showing the horizontal connection of the coefficients of the polynomial $p\left(n,k\right)$. The partition function is not real a polynomial, but it can be written as a fractal polynomial which can be obtained from the general form of the partition class functions $\left\{p\left(n, k\right)\right\}$. In that case, the partition function for each $n$ uses a different polynomial. We show that all these polynomials can be combined with one single in which each member can be a formula for calculating the total number of partitions of all natural numbers.
The aim of the study was to evaluate our practice of self-directed learning (SDL) among pre-university students in Malaysia. Respondents provided data on their previous school learning experiences besides present SDL experiences in college. We carried out exploratory factor analysis based on the school data. We did a confirmatory factor analysis using College SDL experiences of students. Given high similarities between the measurement models, we decided to use the original structure of the instrument. Students provided feedback using a questionnaire based on Prociuk’s. A large majority declared that they needed SDL experiences which they lacked while at school. The study also showed that students had rated their SDL experiences in college more positively than in school, on four factors of SDL experiences. Pearson correlations showed that “knowledgeable and organised teachers” and “promotion of active learning” correlated significantly with students’ current satisfaction with SDL in college.
This article shows the overview of renewable energy resources in Serbia, since many reseach shows that Serbia has great potential of RES (renewable energy source). It also has good conditions for electricity production and heat energy from renewable resources. The aim is to research and represent the development possibility of a country in a sector of a RES, uncovering proven potential of renewable energy, emphasizing that unused potential of RES, together with energy sector, will create great opportunities and conditions for new market. The scope of this study was to research the potential of RES which exists in Serbia, to identify those which are most promising for implementation and integration into country energy sector and substitution of fosil fuels.
Unstable intertrochanteric (IT) fractures, especially fractures with a reverse or transverse fracture line, have tendencies to make significant impaction on shortening of the femoral neck and lower extremity. The biomechanical complexity of the fracture, the type and the position of the implant are known to influence postoperative outcome. The aim of this study was to compare characteristics of two versions of dynamic hip implants in controlling the dynamization of unstable IT fractures of the femur. In the prospective study that included 1,115 patients with fractures of the proximal femur, 61 patients had IT fractures with a reverse or transverse fracture line. All the patients were treated surgically with the same implant in two versions: Dynamic Hip Screw - DHS-MB-S implant with a rigid part of standard length (40 mm) and DHS-MB-I implant, with a rigid part of the implant individualized for each patient depending on the transverse diameter of the proximal femur. The patients were under gradual radiographic and clinical control. Six months postoperatively we measured the length of the extremity and the degree of the medialization of the distal part of the femur. All the fractures healed six months after the operation. Medialization and shortening of the extremity were significantly less in the group with fractures fixed by the DHS-MB-I implant, in which length of the rigid part of the implant was preoperatively measured individually for each patient. In order to achieve a desired functional result, the control of dynamisation in unstable IT fractures is significant in the fixation of these fractures of the femur. We presented possible methods to realize it by the contact of the rigid part of our implant with medial cortex of the proximal fragment of the femur.
The biomass supply chain constitutes a system that is highly dynamic. The developed and proposed systems architectures for the management of the supply chains of typical industrial products do not directly apply to the case of the biomass supply chain. Nevertheless, it is imperative that a dedicated framework is needed according to the industrial standards. In this paper, a framework for the biomass Concept Model and the System of Supply and Management of Biomass (CMSB) supporting the efficient management of organizational events within the examined supply chain is proposed and analyzed. The conceptual model includes the identification and specification of events and the preparation of necessary notification based on information needs. On this basis, the paper presents the following relevant elements: Overview of existing literature on the system CMSB, supply chain networks and biomass, the concept of supply chain management system, the types of events that occur in the supply chain of biomass, the concept of supply and management of biomass.
This paper gives sufficient conditions for the stability of linear descriptor discrete delay systems of the particular form. These new, delay-independent sufficient conditions are derived using approach based on Lyapunov's direct method. This paper, for the first time, offers a general case in the sense that necessity for regularity of system basic matrix A<sub>0</sub> is not any more required what was a general assumption in already existing results in literature. The presented method is a typical geometric approach to the problem exposed and avoids needs to transform then system under consideration into the classical discrete descriptor system. In that sense one is capable to see how much should be matrix A<sub>0</sub> stable to overcome instability caused by the time delay matrix A<sub>1</sub>. Numerical example has been working out to show the applicability of results derived.
Paper extends some basic results from the area of finite time and practical stability to linear, continuous, time invariant nonautonomous time-delay systems. Sufficient conditions of this kind of stability, for particular class of time-delay systems are derived.
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10 members
Ljubomir Jacić
  • Automation and Control engineering
Tatjana Sekulić
  • Poljoprivreda i Zaštita životne sredine
Nemanjina 2, 12000, Požarevac, Serbia, Serbia
Head of institution
Dr Djulakovic Vladan