Matic P.,Herzegovina University |
Vukosavic S.N.,University of Belgrade
Advances in Electrical and Computer Engineering | Year: 2011
The paper describes sensorless speed controlled continuous Direct Torque Control (DTC) Induction Motor (IM) drive in the field weakening regime. Drive comprises an inner torque loop and an outer speed loop. Torque control is based on Proportional - Integral (PI) controller with adaptive Gain Scheduling (GS) parameters. The GS PI control provides full DC link voltage utilization and a robust disturbance rejection along with a fast torque response. Outer speed loop has a PI regulator with the gains selected so as to obtain a fast and strictly aperiodic response. Proposed drive fully utilizes the available DC bus voltage. The paper comprises analytical considerations, simulation results, and detailed description of the implementation steps. Experimental verification of the proposed solution is conducted on a fixed point Digital Signal Processor (DSP) platform. © 2011 AECE.
Zubic S.J.,Herzegovina University |
Djuric M.B.,University of Belgrade
Electric Power Systems Research | Year: 2012
In this paper we propose a distance relay algorithm based on a time-domain phase comparator with a smaller computational burden than the traditional phasor-domain based algorithms. The phase comparator used in the time-domain algorithm is based on the average power on a half and full-cycle data window. The algorithm includes a filter which mitigates decaying DC-offset in the current as well as the capacitive coupled voltage transformer transients. The algorithm is compared to an algorithm based on the phasor-domain approach with full-cycle DFT. Both algorithms are tested on various fault locations, fault resistances, load directions, inception angles and SIR. This paper also includes analysis of the complex frequency response of the complete time-domain algorithm, and how the protected zone for a chosen operating characteristic depends on the line load and SIR. © 2012 Elsevier B.V. All rights reserved.
Filipovic V.,University of Belgrade |
Kartelj A.,University of Belgrade |
Matic D.,Herzegovina University
Applied Soft Computing Journal | Year: 2013
In this paper we present an electromagnetism (EM) metaheuristic for solving NP hard Maximum Betweenness Problem (MBP). A new encoding scheme with appropriate objective functions is implemented. Specific representation of the individuals enables the EM operators to explore the searching space in a way that achieves high quality solutions. An effective 1-swap based local search procedure improved by the specific caching technique is performed on each EM point. The algorithm is tested both on real and artificial instances from the literature. Experimental results show that the proposed EM approach achieves all previously known optimal solutions, except one, and achieves the best-known solutions or outperforms other approaches on all large-scale instances, except two. Provided statistical analysis indicates that the EM approach is significantly better than other approaches. © 2012 Elsevier B.V. All rights reserved.
Duric Z.,Herzegovina University |
Gasevic D.,Athabasca University
Computer Journal | Year: 2013
Source code plagiarism is an easy to do task, but very difficult to detect without proper tool support. Various source code similarity detection systems have been developed to help detect source code plagiarism. Those systems need to recognize a number of lexical and structural source code modifications. For example, by some structural modifications (e.g. modification of control structures, modification of data structures or structural redesign of source code) the source code can be changed in such a way that it almost looks genuine. Most of the existing source code similarity detection systems can be confused when these structural modifications have been applied to the original source code. To be considered effective, a source code similarity detection system must address these issues. To address them, we designed and developed the source code similarity system for plagiarism detection. To demonstrate that the proposed system has the desired effectiveness, we performed a well-known conformism test. The proposed system showed promising results as compared with the JPlag system in detecting source code similarity when various lexical or structural modifications are applied to plagiarized code. As a confirmation of these results, an independent samples t-test revealed that there was a statistically significant difference between average values of F-measures for the test sets that we used and for the experiments that we have done in the practically usable range of cut-off threshold values of 35-70%. © 2012 The Author. Published by Oxford University Press on behalf of The British Computer Society. All rights reserved.
Knor T.,Herzegovina University |
Meholji-Fetahovi A.,University of Sarajevo |
Mehmedagi A.,University of Sarajevo
Acta Dermatovenerologica Croatica | Year: 2011
Atopic dermatitis (AD) is a chronically relapsing skin disease with genetic predisposition, which occurs most frequently in preschool children. It is considered that dryness and pruritus, which are always present in AD, are in correlation with degradation of the skin barrier function. Measurement of hydration and pH value of the stratum corneum is one of the noninvasive methods for evaluation of skin barrier function. The aim of the study was to assess skin barrier function by measuring stratum corneum hydration and skin surface pH of the skin with lesions, perilesional skin and uninvolved skin in AD patients, and skin in a healthy control group. Forty-two patients were included in the study: 21 young and adult AD patients and 21 age-matched healthy controls. Capacitance, which is correlated with hydration of stratum corneum and skin surface pH were measured on the forearm in the above areas by SM810/CM820/pH900 combined units (Courage & Khazaka, Germany). The mean value of water capacitance measured in AD patients was 44.1±11.6 AU (arbitrary units) on the lesions, 60.2±12.4 AU on perilesional skin and 67.2± 8.8 AU on uninvolved skin. In healthy controls, the mean value was 74.1±9.2 AU. The mean pH value measured in AD patients was 6.13±0.52 on the lesions, 5.80±0.41 on perilesional skin, and 5.54±0.49 on uninvolved skin. In control group, the mean pH of the skin surface was 5.24±0.40. The values of both parameters measured on lesional skin were significantly different (capacitance decreased and pH increased) from the values recorded on perilesional skin and uninvolved skin. The same held for the relation between perilesional and uninvolved skin. According to study results, the uninvolved skin of AD patients had significantly worse values of the measured parameters as compared with control group. The results of this study suggested the skin barrier function to be degraded in AD patients, which is specifically expressed in lesional skin.
Alajbegovic A.,Herzegovina University
Medicinski arhiv | Year: 2011
Multiple sclerosis (MS) manifests also with the symptoms of affective disorders. Depression is the most common mental disorder among patients with MS and it has negative impact on their working ability, social relations and quality of life. The aim of this study is to investigate gender, age, marital status, education level and employment related to patients with depressive symptoms in population of MS, treated at the Department of Neurology, Clinical Center University of Sarajevo. In the study it was analyzed 50 randomly selected patients with various types of multiple sclerosis. Severity of depression was evaluated using the Beck Depression Inventory (BDI). The study included 33 female and 17 male patients aged 21 to 60 years. In the sample of MS patients there were 56% with depressive disorder. There is no statistically significant difference between patients gender. Depression is more frequent among younger and middle age patients, while all the patients older than 51 years are in a normal mood (total 31.9%). Significantly higher percentage of non-depressive patients (72.2%) are married, while depression is present among all divorced patients (10.7%), majority of single (35.8%) and widowers (21.4%). Taking into consideration level of education, there is a statistically significant difference as follows: depression is more frequent among patients who graduated university (46.4%) and secondary school (50%) compared to ones who finished only primary school (3.6%). There is significantly higher number of unemployed and retired patients with depressive symptoms (75%) in comparison to the employed ones. Depression occurs more frequently among MS patients who are younger, unemployed, highly educated and without spouse. There is no statistically significant difference between male and female patients.
Milicevic S.,Herzegovina University
Medicinski arhiv | Year: 2011
Benign prostatic hyperplasia is one of the most common diseases in older men. The objective of this study was to evaluate the impact of the surgical treatment of the benign prostatic hyperplasia (BPH) with the methods of open prostatectomy (OP) and transurethral resection of the prostate (TURP) on the quality of life. The research material was based on 80 patients, out of whom 40 patients were treated with the method of open prostatectomy (Group A), and the other 40 patients with the method of transurethral resection of prostate gland (Group B) due to benign prostatic hyperplasia. All patients were under the age of 80 years old (approximate age in Group A 70.23 with variation interval of 21 years old, and in Group B 69.37 with variation interval of 22 years old), with the International Prostate Symptom Score (IPSS) value >19 points, postvoid residual urine higher than 150 ml, the weight of benign prostatic gland hyperplasia tissue over 30 grams for method of prostate transurethral resection, and over 80 grams for the method of open prostatectomy. The quantification of the quality of life, as a consequence of urinary symptoms, was done by the Quality of Life Index (QLI) which is question No 8 in IPSS. All patients were determined the value of this score before the operation, and then in postoperative period in time intervals of 4.8 and 12 weeks. The QLI arithmetic mean, before the operation, was 5.55 points in Group A, and 5.45 points in Group B. During postoperative checkups in time intervals of 4.8 and 12 weeks, the arithmetic means in Group A were 0.975, 0.450 and 0.100 points, and in Group B 1.850, 1.700 and 1.575 points. By analyzing the obtained results, there was a highly statistically significant difference between preoperative test results and the results during all the postoperative checkups in both groups, A and B. By testing the difference of the QLI arithmetic mean between the patients in both groups, preoperatively there was no statistically significant difference, but during all postoperative checkups, there was a highly statistically significant difference between the test values. The surgical treatment of BPH leads to significant improvement of the quality of life, as a consequence of urinary symptoms. The improvement of the quality of life was more evident in patients whose BPH was treated with the OP method.
Borkovic A.,Herzegovina University
Civil-Comp Proceedings | Year: 2013
This paper presents buckling analysis of stiffened thin-walled sections due to arbitrary loading. One variation of the well-established finite strip method, namely the compound strip method, is used for the analysis. This method is a semi-analytical procedure which enables modelling of longitudinal and transverse stiffeners, as well as columns, within the flat shell finite strip. Influence of stiffeners is introduced through their interface lines using appropriately calculated rigidities. The main contribution of this method is its elegant and efficient approach for modelling of transverse stiffener within the harmonic finite strip method. In order to address the problem of buckling an arbitrary loading strip is longitudinally divided into cells, where the three stress components obtained from linear static analysis are recorded. Next the integration over these sub-domains is performed, results are summed and the geometric stiffness matrix is formed. Extensive numerical analysis is carried out with three examples. The results obtained are in excellent agreement with the ones from the finite element method. For prismatic structures, the procedure presented can provide better insight into the problems analysed than other purely numerical methods. © Civil-Comp Press, 2013.
Borkovic A.,Herzegovina University
Civil-Comp Proceedings | Year: 2013
This paper shows that geometric nonlinear behaviour of stiffened prismatic shells can be successfully modelled with the compound strip method. Longitudinal and transverse beams are introduced into the finite strip method using strain energy through their interface lines. Advantages of the presented method are the low number of employed degrees of freedom and the semi-analytical approximation of the displacement field. This method also addresses one of the main drawbacks of the finite strip method, which is the inclusion of intermediate supports. All matrices are derived in a closed form and analytical solutions of five characteristic integrals are given. Numerical analysis shows that the compound strip method gives reasonably accurate results for complex equilibrium paths when compared with the finite element method. This method gives stiffer solutions for softening branch and more flexible results for hardening branch of the equilibrium path. Convergence of all variables is very fast except the longitudinal stresses in the shell above the transverse beam. Simple parallelization is applied and the computation time is significantly reduced. © Civil-Comp Press, 2013.
Prohic A.,Herzegovina University
Mycoses | Year: 2010
Summary Malassezia species are implicated in the pathogenesis of seborrhoeic dermatitis (SD), but the relationship between each species and the disorder remains unclear. It is hypothesised that the pathogenesis of SD has an immune component, which is supported by the increased incidence in patients with immunosuppressive disorders. The purpose of our study was to analyse the prevalence of Malassezia species in lesional skin of SD, and to assess the distribution of the species according to severity of the disease and cellular immune status of the patients. Forty SD patients with scalp involvement were included in the study. The samples were obtained by scraping the skin surface of the scalp and then incubated on Sabouraud dextrose agar and modified Dixon agar. The yeasts isolated were identified by their morphological and physiological properties according to the method of Guillot et al. In addition, we performed two-colour flow cytometry analysis to investigate the lymphocyte subpopulations in the peripheral blood. The most commonly isolated species was Malassezia restricta (27.5%), followed by Malassezia globosa (17.5%) and Malassezia slooffiae (15%). We demonstrated low helper/suppressor ratios in 70% patients, because of an increase in the suppressor T-cell population, suggesting an impaired cellular immunity. However, we found no significant difference in the distribution of isolated Malassezia species according to the severity of the scalp involvement and changes in the peripheral blood lymphocyte subpopulations. © 2009 Blackwell Verlag GmbH.