Analiza kvaliteta vode reke Mlave na osnovu vodenih makroinvertebrata

Cilj rada je da se predstave rezultati ispitivanja kvaliteta vode reke Mlave, zasnovani na prisutnoj zajednici vodenih makroinvertebrata. Mlava, sa dužinom toka od 78 km i površinom sliva od 1885 km², jedna je od značajnijih pritoka Dunava u Srbiji. Kao najvažniji izvori komunalnog i industrijskog zagađenja mogu se izdvojiti gradovi Požarevac (70000 stanovnika; u donjem toku) i Petrovac na Mlavi (8000 stanovnika; srednji tok), kao i Žagubica (2600 stanovnika; gornji tok). Slivno područje, naročito u srednjem delu toka, je i pod uticajem spiranja sa poljoprivrednih površina, kao i komunalnih otpadnih voda iz brojnih manjih naselja. Negativni efekti, ovih antropogenih uticaja mogu biti još izraženiji, zbog specifične hidrologije, odnosno preovlađivanja stanja niskih voda u slivu ove reke. Uzorkovanje je izvršeno u julu 2013. godine. Kao parametri za ocenu kvaliteta vode, korišćeni su sledeći pokazatelji: Saprobni indeks (SI; Zelinka & Marvan), BMWP i ASPT skorovi, broj taksona grupa Ephemeroptera, Plecoptera and Trichoptera (EPT) i indeks diverziteta (SWI; Shannon-Wiener’s indeks). Ukupno 72 taksona makroinvertebrata su identifikovana. Insekti su bili najraznovrsnija komponenta, a u okviru njih najbrojnije su bile grupe Ephemeroptera (13 taksona) i Trichoptera (11 taksona). Najveća raznovrsnost zabeležena je na lokalitetu Leskovac (33 taksona). Većina taksona je tolerantna na određeni stepen organskog zagađenja (β –mezosaprobni i α–mezosaprobni organizmi), naročito u donjem delu toka (Rašanac i Požarevac). Vrednosti SI na svim lokalitetima upućuju na veoma dobar i dobar kvalitet vode (klase I i II). Vrednosti BMWP i ASPT ukazuju na veoma dobar kvalitet vode samo na lokalitetima u srednjem i donjem delu toka (Leskovac i Požarevac), dok je u gornjem delu toka, kvalitet vode, ili loš (BMWP), ili umeren do dobar (ASPT). I preostali pokazatelj (EPT), takođe, ukazuje na bolji kvalitet vode u donjem delu toka. Na osnovu svih korišćenih pokazatelja, kvalitet vode reke Mlave u julu 2013. godine se može oceniti kao dobar (klasa II)

Collaborative Localization in Wireless Sensor Networks via Pattern Recognition in Radio Irregularity Using Omnidirectional Antennas

In recent years, various received signal strength (RSS)-based localization estimation approaches for wireless sensor networks (WSNs) have been proposed. RSS-based localization is regarded as a low-cost solution for many location-aware applications in WSNs. In previous studies, the radiation patterns of all sensor nodes are assumed to be spherical, which is an oversimplification of the radio propagation model in practical applications. In this study, we present an RSS-based cooperative localization method that estimates unknown coordinates of sensor nodes in a network. Arrangement of two external low-cost omnidirectional dipole antennas is developed by using the distance-power gradient model. A modified robust regression is also proposed to determine the relative azimuth and distance between a sensor node and a fixed reference node. In addition, a cooperative localization scheme that incorporates estimations from multiple fixed reference nodes is presented to improve the accuracy of the localization. The proposed method is tested via computer-based analysis and field test. Experimental results demonstrate that the proposed low-cost method is a useful solution for localizing sensor nodes in unknown or changing environments

Angle and Time of Arrival Characteristics of 3D Air-to-Ground Radio Propagation Environments

A three dimensional (3D) geometric channel model is proposed for ground-to-air (G2A) and air-toground (A2G) communication links. A low-elevated ground station (GS) and a high-elevated air station (AS) are taken at foci points of a virtual bounding ellipsoid corresponded from known knowledge of delay of longest propagation path. The effective region of scatterers around the GS is designed on the basis of this ellipsoid truncated by the average rooftop level (or average height of sea waves) and ground plane. Closedform expressions for joint and marginal probability density functions (PDFs) of angle of arrival (AoA) observed at AS and GS in correspondence with azimuth and elevation angles are derived. Furthermore, closed-form expressions for density of energy with respect to the delay of arriving multipath waves corresponded from both the elevation and azimuth AoA are derived independently when observed from either end of the communication link. Moreover, effect of different physical parameters of the channel on distribution of energy in angular and temporal domains is presented. The comparison of analytical results with results of a notable model is also presented. In order to verify the derived analytical expressions, a comparison of analytical results with the performed simulation results is presented, which shows a good match