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Search Results: 1 - 10 of 130475 matches for " Baki? Vukman V. "
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NUMERICAL SIMULATION OF THE AIR FLOW AROUND THE ARRAYS OF SOLAR COLLECTORS
Vukman V Baki,Goran S ?ivkovi?,Milada Pezo
Thermal Science , 2011, DOI: tsci110222051b
Abstract: This paper deals with the numerical simulation of air around the arrays of flat plate collectors and determination of the flow field, which should provide a basis for estimating a convective heat losses, a parameter which influences their working characteristics. Heat losses are the result of the reflection on the glass, conductive losses at the collector's absorber plate, radiation of the absorber plate and convective losses on the glass. Wind velocity in the vicinity of the absorber plate depends on its position in the arrays of collectors. Results obtained in the numerical simulation of flow around collectors were used as boundary conditions in modeling of thermal-hydraulic processes inside the solar collector. A method for coupling thermal-hydraulic processes inside the collector with heat transfer from plate to tube bundle was developed, in order to find out the distribution of the temperature of the absorber plate and the efficiency of the flat plate collectors. Analyses of flow around arrays of collectors are preformed with RNG k - ε model. Three values for free-stream velocity were analysed, i.e. 1 m/s, 5 m/s and 10 m/s, as well as two values for the angle between the ground and the collector (20° and 40°). Heat transfer coefficient was determined from the theory of boundary layer. Heat transfer inside the plate cavity was analyzed assuming constant intensity of radiation.
Evaluation of Kolubara lignite carbon emission characteristics
Stefanovi? Predrag Lj.,Markovi? Zoran J.,BakiVukman V.,Cvetinovi? Dejan B.
Thermal Science , 2012, DOI: 10.2298/tsci120215130s
Abstract: The revised Intergovernmental Panel on Climate Change (IPCC) guidelines for national greenhouse gas (GHG) inventories recommends that more comprehensive and thus more reliable characteristics of the local fossil fuels should be used for the national GHG inventory calculations. This paper deal with the carbon emission characteristics of low-calorific lignite recovered from the Kolubara open-pit mine. The samples of coal were carefully selected in order to cover the net calorific value, ash and water content of the broad spectrum of the quality of the raw lignite supplied to the Serbian thermal power plants. Correlation analysis of the laboratory analysis data gave a linear dependency of the net calorific value on the combustible content in the coal samples. Also, linear correlation between the carbon content and the net calorific value was found. The regression analysis of experimentally determined coal characteristics implies that the carbon emission factor is dependent on the net calorific value. For the subset of raw lignite samples with the net calorific value Qdr = 6 ÷ 10 MJ/kg, that is most representative for current and near future use for power generation in Serbian thermal power plants, the linear dependency CEFr (tC/TJ) = 34.407 - 0.5891×Qdr (MJ/kg) was proposed. Regarding the net calorific ranges of samples examined, the raw Kolubara lignite carbon emission factor is considerably higher than those recommended by IPCC Tier 1 method of 27.6 tC/TJ.
Technical analysis of photovoltaic/wind systems with hydrogen storage
BakiVukman V.,Pezo Milada L.,Jovanovi? Marina P.,Turanjanin Valentina M.
Thermal Science , 2012, DOI: 10.2298/tsci120306132b
Abstract: The technical analysis of a hybrid wind-photovoltaic energy system with hydrogen gas storage was studied. The market for the distributed power generation based on renewable energy is increasing, particularly for the standalone mini-grid applications. The main design components of PV/Wind hybrid system are the PV panels, the wind turbine and an alkaline electrolyzer with tank. The technical analysis is based on the transient system simulation program TRNSYS 16. The study is realized using the meteorological data for a Typical Metrological Year (TMY) for region of Novi Sad, Belgrade cities and Kopaonik national park in Serbia. The purpose of the study is to design a realistic energy system that maximizes the use of renewable energy and minimizes the use of fossil fuels. The reduction in the CO2 emissions is also analyzed in the paper. [Acknowledgment. This paper is the result of the investigations carried out within the scientific project TR33036 supported by the Ministry of Science of the Republic of Serbia.]
Identities with derivations and automorphisms on semiprime rings
Joso Vukman
International Journal of Mathematics and Mathematical Sciences , 2005, DOI: 10.1155/ijmms.2005.1031
Abstract: The purpose of this paper is to investigate identities with derivations and automorphisms on semiprime rings. A classical result of Posner states that the existence of a nonzero centralizing derivation on a prime ring forces the ring to be commutative. Mayne proved that in case there exists a nontrivial centralizing automorphism on a prime ring, then the ring is commutative. In this paper, some results related to Posner's theorem as well as to Mayne's theorem are proved.
Amphiphilic Poly (3-Hydroxy Alkanoate)s: Potential Candidates for Medical Applications  [PDF]
Baki HAZER
Energy and Power Engineering (EPE) , 2010, DOI: 10.4236/epe.2010.21006
Abstract: Poly (3-hydroxy alkanoate)s, PHAs, have been very attractive as biomaterials due to their biodegradability and biocompatibility. These hydrophobic natural polyesters, PHAs, need to have hydrophilic character particularly for drug delivery systems. In this manner, poly (ethylene glycol) (PEG) and hydrophilic functional groups such as amine, hydroxyl, carboxyl and sulfonic acid have been introduced into the PHAs in order to obtain amphiphilic polymers. This review involves in the synthesis and characterization of the amphiphilic PHAs.
On the instability of equilibrium of a mechanical system with nonconservative forces
Veskovi? Miroslav,?ovi? Vukman
Theoretical and Applied Mechanics , 2004, DOI: 10.2298/tam0404411v
Abstract: In this paper the stability of equilibrium of nonholonomic systems, on which dissipative and nonconservative positional forces act, is considered. We have proved the theorems on the instability of equilibrium under the assumptions that: the kinetic energy, the Rayleigh’s dissipation function and the positional forces are infinitely differentiable functions; the projection of the positional force component which represents the first nontrivial form of Maclaurin’s series of that positional force to the plane, which is normal to the vectors of nonholonomic constraints in the equilibrium position, is central and repulsive (with its centre of action in the equilibrium position). The suggested theorems are generalization of the results from [V.V. Kozlov, Prikl. Math. Mekh. (PMM), T58, V5, (1994), 31-36] and [M.M. Veskovic, Theoretical and Applied Mechanics, 24, (1998), 139-154]. The result obtained is analogous to the result from [D.R. Merkin, Introduction to theory of the stability of motion, Nauka, Moscow (1987)], which refers to the impossibility of equilibrium stabilization in a holonomic conservative system by dissipative and nonconservative positional forces in case when the potential energy in the equilibrium position has the maximum. The proving technique will be similar to that used in the paper [V.V. Kozlov, Prikl. Math. Mekh. (PMM), T58, V5, (1994), 31-36]. .
An Application of Kalman Filtering and Artificial Neural Network with K-NN Position Detection Technique  [PDF]
Hakan Koyuncu, Baki Koyuncu
Wireless Sensor Network (WSN) , 2017, DOI: 10.4236/wsn.2017.98013
Abstract: RFID technology is one of the important technologies to determine the object locations. Distances are calculated with respect to calibration curves of RSSI amplitudes. The aim of this study is to determine the 2D position of mobile objects in the indoor environment. The importance of the work is to show that localization by using Artificial Neural Network plus Kalman Filtering is more accurate than using classical KNN method. An indoor wireless sensing network is established with strategically stationed RFID transmitter nodes and a mobile object with a RFID receiver node. A fingerprint map is generated and K-Nearest Neighbourhood algorithm (KNN) is deployed to calculate the object locations. Fingerprint coordinates and RSS values received at these coordinates are deployed to set up an Artificial Neural Network (ANN). This network is used to determine the unknown object locations by using RSS values received at these locations. The accuracy of object localization is found to be better with ANN technique than KNN technique. Object coordinates, determined with ANN technique, are subjected to Kalman filtering. The results show that localization accuracies are improved and localization error distances are reduced by 46% with the deployment of ANN + Kalman Filtering.
Laparoscopic cholecystectomy in elderly patients
Stani?i? V.,Baki? M.,Magdelini? M.,Kola?inac H.
Acta Chirurgica Iugoslavica , 2009, DOI: 10.2298/aci0902087s
Abstract: Laparoscopic cholecystectomy (LC ) is the method of choice of surgical treatment of gallbladder diseases. Operations in elderly people over 65 years because of chronic diseases, are often associated with high operative and postoperative morbidity and mortality. The aim of this study was to analyze the outcome of LC in the treatment of cholelithiasis in patients older than 65 years. For evaluation of LC effectiveness and security in old patients, we did this prospective analysis of 81 patients surgically treated because of symptomatic cholelithiasis . We had analyzed associated diseases, operative and postoperative complications, the reasons of conversion to open cholecystectomy. The research points to the small percentage of operative and postoperative complications, short hospital stay, less postoperative pain, quick recovery and savings in treatment. The age can not be contraindication for LC in older patients. In uncomplicated symptomatic cholelithiasis in elderly people, LC is a successful and safe procedure. Complicated symptomatic cholelithiasis, because of longer duration of operations is looking for a good assessment of general condition and associated diseases for LC.
Amphiphilic Poly(3-hydroxy alkanoate)s: Potential Candidates for Medical Applications
Baki Hazer
International Journal of Polymer Science , 2010, DOI: 10.1155/2010/423460
Abstract: Poly(3-hydroxy alkanoate)s, PHAs, have been very attractive as biomaterials due to their biodegradability and biocompatibility. These hydrophobic natural polyesters, PHAs, need to have hydrophilic character particularly for drug delivery systems. In this manner, poly(ethylene glycol) (PEG) and hydrophilic functional groups such as amine, hydroxyl, carboxyl, and sulfonic acid have been introduced into the PHAs in order to obtain amphiphilic polymers. This review involves in the synthesis and characterization of the amphiphilic PHAs. 1. Introduction Biomaterials have been widely used in medical applications, such as drug delivery, tissue engineering, device-based therapies, and medical imaging [1, 2]. Synthetic and naturally occurring polymers have played important role in the treatment of disease and the improvement of health care. Among them, PHAs are promising materials for biomedical applications in tissue engineering and drug delivery system because they are natural, renewable, biodegradable, and biocompatible thermoplastics. PHAs have been used to develop devices, including sutures, nerve repair devices, repair patches, slings, cardiovascular patches, orthopedic pins, adhesion barriers, stents, guided tissue repair/regeneration devices, articular cartilage repair devices, nerve guides, tendon repair devices, bone-marrow scaffolds, tissue engineered cardiovascular devices, and wound dressing. However the direct use of these polyesters has been hampered by their hydrophobic character and some physical shortcomings [3]. The key to biocompatibility of biomedical implantable materials is to render their surface in a way that minimizes hydrophobic interaction with the surrounding tissue. Therefore, hydrophilic groups have been introduced into the PHAs in order to obtain amphiphilic polymer. This review has been focused on the chemically modified PHAs with enhanced hydrophilic character as biomaterials for medical applications. 2. PHAs PHAs are accumulated as intracellular granules as a result of a metabolic stress upon imbalanced growth due to a limited supply of an essential nutrient and the presence of an excess of a carbon source. These novel biopolymers have material properties ranging from rigid and highly crystalline to flexible, rather amorphous and elastomeric. There have been many studies reported on the modification reactions to enhance mechanical and thermal properties to prepare new biomaterials for the medical applications [4–13]. PHAs can be classified into three groups based on the number of carbon atoms in the monomer units:
Theoretical approaches to ethnicity, nationalism and nation
Baki? Jovo
Sociologija , 2006, DOI: 10.2298/soc0603231b
Abstract: The author takes into consideration main theory of ethnicity and nationalism: primordialism, perennialism, modernism, ethno-symbolism, post-modernism, and interactionism. He pays his attention on both good and bad features of the different theoretical approaches in order to formulate his own approach. In addition, he offers several the most famous and convincing definitions and typologies of the nations and nationalism. At the end, he tries to make definitions of the ethnicity (ethnical connectedness), ethnical resource, e. g. language, religion, "race", ethnic myths etc, ethnic category, and ethnic as well as to briefly outline his own approach that is basically interactionist with some additions of ethno-symbolism.
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