Search

This paper demonstrates the benefits that high-frequency surface wave radars (HFSWR) are bringing to maritime safety and security in off-shore activities at over the horizon distances. As a primary means for remote sensing of marine and maritime environment, a network of HFSWRs is deployed in the western part of the Gulf of Guinea and covers an area of over 100 km2. Alongside HFSWRs, usual maritime sensors are utilized for vessel tracking as well, however, only satellite automatic identification systems (SAIS) and land automatic identification systems (LAIS) are capable of covering over the horizon distances. Unfortunately, both LAIS and SAIS require vessel cooperation in order to provide any data, which is often abused by vessels conducting illegal activities. Here, analysis is done in which AIS and HFSWR data are compared in order to identify a pattern of behavior of non–cooperative vessels (vessels with onboard AIS devices turned off) so a proper risk assessment may be achieved. It is shown that typical patterns can be easily recognized for two illegal activities which plague the waters where this study is conducted. Those illegal activities are oil bunkering and piracy, both conducted off-shore and out of the reach of the usual coastal sensors such as X or S band radars. Furthermore, tracks created whilst conducting illegal activities are easily distinguishable from others in the overall operational picture. Additionally, it should be pointed out that numerous vessels are switching off their AIS devices when they leave the coastal regions in order to avoid detection by pirate vessels. This behavior can also be easily recognized and must not be mixed with the illegal activities mentioned above.

In order to efficiently cover maritime areas at over the horizon (OTH) distances and thus increase marine safety in a nation’s exclusive economic zone (EEZ), a network of maritime sensors built around High Frequency Surface Wave Radars (HFSWR) can be an excellent choice. The critical parameter for success of the deployed sensor network is a real time tracking of all detected vessels. During the tracking process, data association (DA) is the first step and it defines the complexity and thus the speed of the whole tracking process. This paper presents a density based clustering DA procedure where the cluster complexity determines the applied DA procedure within the cluster itself. It is demonstrated that the great majority of clusters (over 98 % of all clusters in the worst case) may be processed in a timely manner with an optimal DA procedure, or more precisely, a Joint Probability Data Association (JPDA). However, a small number of unusually large clusters (less than 2 % of all clusters) requires the application of a sub–optimal DA procedure, more accurately, the Roecker’s suboptimal JPDA algorithm, in order to maintain real time performance of the whole tracking process. Moreover, unlike standard JPDA procedure which tends to be inapplicable for real time tracking in heavily cluttered environment, the density based clustering DA procedure presented here provides real time performances in the very same environment. The whole analysis is done on real HFSWR data obtained from two HFSWR, located in the Gulf of Guinea. The data set used for the experiments includes data obtained during a month and a half of constant HFSWR operation.

With maximum range of about 200 nautical miles (approx. 370 km) High Frequency Surface Wave Radars (HFSWR) provide unique capability for vessel detection far beyond the horizon without utilization of any moving platforms. Such uniqueness requires design principles unlike those usually used in microwave radar. In this paper the key concepts of HFSWR based on Frequency Modulated Continuous (FMCW) principles are presented. The paper further describes operating principles with focus on signal processing techniques used to extract desired data. The signal processing describes range and Doppler processing but focus is given to the Digital Beamforming (DBF) and Constant False Alarm Rate (CFAR) models. In order to better present the design process, data obtained from the HFSWR sites operating in the Gulf of Guinea are used.

Titania based catalyst and TiO2 doped with zirconia were prepared by modified sol–gel method. The synthesized catalysts samples were characterized by BET, XRD, SEM and FTIR techniques. Photocatalytic activity was tested in the reaction of crystal violet (CV) dye decolorization/decomposition under UV light irradiation. The effect of several operational parameters, such as catalyst dosage, initial dye concentrations, duration of UV irradiation treatment and number of reaction cycles were also considered. The obtained results indicated faster dye decolorization with the increase of the catalyst amount and a decrease of initial CV concentrations. An influence of doping with zirconia on the physico-chemical properties of bare titania was studied. The doping procedure had affected photocatalytic properties of the final catalytic material, and had improved photocatalytic performances of doped catalyst on crystal violet decolorization/degradation in comparison to bare titania. [Project of the Serbian Ministry of Education, Science and Technological Development, Grant no. 1612008, Grant no. 45012 and Grant no. 172061]

Heterogeneous catalysis is in recent focus of research for biodiesel production from vegetable oils because of advantages such as easy separation and reuse of catalysts, although homogeneous catalysis is most commonly used method. The aim of this study was preparation of γ-Al2O3 support by modified sol-gel procedure, synthesis of the KI/Al2O3 catalyst and testing its activity in the transesterification of sunflower oil with methanol. Influences of different process parameters on conversion of sunflower oil to methyl esters were examined. The gained results implicate that the potassium iodide incorporation into/onto the structure of γ-Al2O3 significantly influences textural and structural properties of the catalyst. Additionally, the catalyst basic strength is increased and all together those properties are positively affecting the activity of the catalyst in the reaction of transesterification of sunflower oil with methanol. The impregnation of alumina with potassium iodide resulted in the additional formation of basic catalytically active sites. The surface properties of the catalyst have an essential impact on its catalytic performance. Under relatively mild process conditions and relatively short reaction time, the usage of the KI/Al2O3 catalyst resulted in very high conversion to fatty acids methyl esters (i.e. 99.99 %). [Projekat Ministarstva nauke Republike Srbije, br. 172061 i br. TR 34008]

The aim of this paper is to present a development and an implementation of a tracking algorithm for Over-The-Horizon Radar (OTHR) with surface wave propagation. Proposed implementation utilizes standard tracking algorithm design for OTHR and introduces modifications of Joint Probability Data Association (JPDA) algorithm in order to simplify processing. To justify chosen approach, a simulated environment consisting of one OTHR and its corresponding targets is created and proposed implementation is tested.

Stylohyoid complex is anatomical structure predisposed to numerous individual variations. These may result in its extreme elongation, medial deviation and finally Eagle’s syndrome occurrence. The aim of this study was to measure the length, angulation, evaluate morphological variations of stylohyoid complex by computed tomography and, subsequently, relate obtained data to the gender and the age of the evaluated cases. The material included CT scans of stylohyoid complexes of 282 individuals. The entire length, maximal thickness, and angulation of the stylohyoid complexes in the coronal, transverse, and sagittal planes were measured. According to their morphology, orientation and length, stylohyoid complexes were classified into six morphological types. Elongated, bent, segmented, and segmented with attached stylohyoid ligament for the lesser horns of the hyoid bone stylohyoid complex types were characterized by significantly greater length, while pseudoarticulated type was characterized by significantly lower length in relation to normal stylohyoid complex type. The elongated type was additionally significantly thicker and with significantly lower value of medial angle in transverse plain than the normal stylohyoid complex type. Elongated, bent, and segmented types were significantly more frequent in males than in females. Furthermore, the frequency of the elongated stylohyoid complex type increased, whereas normal and pseudoarticulated types decreased with age. In conclusion, elongated and more medially deviated stylohyoid complexes are more frequent in males than in females. Their more frequent presence in the older age groups indirectly connects this phenomenon with the aging process.

Due to its biocompatibility, biodegradability, hydrophility, technological properties and vast availability, polysaccharides are widely used as natural non-toxic polymers in different branches of industry (food, cosmetic, textile, construction industries). Exopolysaccharides (as dextran, pullulan) have recently taken up a significant position in pharmaceutical industry. Alginate has an irreplaceable role in biomedicine, since its hydrogel form is successfully applied for immobilization of a wide range of enzymes, therapeutics, biochemical agents and different kinds of microorganisms and cells (herbal, animal or human). Alginate microspheres and microcapsules are used for controlled release of biologically active molecules, as well as cell carriers in tissue engineering. Special benefits are brought by the simplicity of configuration of alginate hydrogel, including the possibility of the controlled production of micro- and nanoparticles. Taking into account a very important role of alginates in the form of hydrogel in biomedicine, in this paper a specific attention is paid on the preparation and application of alginate matrices, microspheres and microcapsules that may have essential and unexchangeable usage/application. This paper therefore displays various possibilities of use of polysaccharide matrices for biomolecules, polysaccharide as excipients of pharmaceutical products for oral or local application, and provides a review of the examples of innovative applications.

Two series of zirconia based catalysts promoted with either sulfates or phosphates were prepared, calcined at different temperatures (600 and 700?C) and evaluated for the n-hexane isomerization reaction. The catalysts with different concentrations of sulfates or phosphates (4 or 10 wt. %) were characterized by BET, XRD, SEM methods, and total acidity was evaluated by using the Hammett indicators. Their final catalytic performances were correlated with their physical-chemical properties (surface, structural, textural and morphological). It was found that sulfated zirconia catalyst calcined at lower temperature showed the highest initial activity of all tested catalysts as the result of favorable total acidity, mesopore texture and structural properties. Somewhat lower activity of the sulfated catalyst calcined at higher temperature is related to the content of acid groups partially removed during thermal treatment, thus, lower total acidity, and also to less favorable textural and structural features. Negligible activity of phosphated zirconia catalysts is connected with low total acidity despite the positive status of particular property showing the complexity of the active phase/site formation in the catalyst.

Wine production generated significant quantities of waste - grape pomace (seeds, skin and stems of grapes). In these vinification by-products a significant amount of bioactive compounds such as phenol compounds can still be found. The phenol composition and radical scavenging activity of grape pomace obtained during winemaking from the red wine grape of Vranac variety (Vitis vinifera L.) were investigated to determine their usable values. Reversephase high performance liquid chromatography (RP-HPLC) assays were used for determination of the phenolic composition of pomace extracts and the DPPH test was done for their radical scavenging activity. The oil obtained from the pomace was subjected to GC/MS analysis in order to establish its fatty acid composition. As correlation calculations showed (R2=0.9732), phenol compounds are responsible for strong radical scavenging activities of the tested extracts (1.160 ± 0.03 mg DM/ml). Grape pomace oil with a high degree of of unsaturation (over 88%) plays an important role for human health. The phenolic rich extract and grape pomace oil can be used as additives in food and pharmacy industries.

In this paper, we proposed experimental space segmentation method for WLAN indoor positioning. Experiments in a real WLAN environment indicate that the proposed method leads to substantial improvements in the localization accuracy in comparison to positioning methods with similar requirements. The approach is conceptually simple, easy to implement, and does not require any additional hardware.