Level Crossing Rate of Macrodiversity System in the Presence of Multipath Fading and Shadowing

Macrodiversity system including macrodiversity SC receiver and two microdiversity SC receivers is considered in this paper. Received signal experiences, simultaneously, both, long term fading and short term fading. Microdiversity SC receivers reduces Rayleigh fading effects on system performance and macrodiversity SC receiver mitigate Gamma shadowing effects on system performance. Closed form expressions for level crossing rate of microdiversity SC receivers output signals envelopes are calculated. This expression is used for evaluation of level crossing rate of macrodiversity SC receiver output signal envelope. Numerical expressions are illustrated to show the influence of Gamma shadowing severity on level crossing rate

On the Transmission of Colour Image Over Double Generalized Gamma FSO Channel

In this paper performance analysis of colour image Free Space Optics (FSO) transmission over Double Generalized Gamma (DGG) turbulence communication channel is carried out. At the reception side, we have used an average bit error rate (ABER) for reconstructed image performance measure, as the function of FSO link transmission parameters, such as propagation distance, Rytov variance and turbulence shaping and severity parameters (γ1, γ2, m1, m2). Obtained results cover a large number of colour image FSO transmission scenarios, for Gamma-Gamma, Double-Weibull and K turbulence models channels considered as special cases

Performance Analysis of Selection Combining Over Correlated Nakagami-m Fading Channels with Constant Correlation Model for Desired Signal and Cochannel Interference

A very efficient technique that reduces fading and channel interference influence is selection diversity based on the signal to interference ratio (SIR). In this pa¬per, system performances of selection combiner (SC) over correlated Nakagami-m channels with constant correlation model are analyzed. Closed-form expressions are obtained for the output SIR probability density function (PDF) and cumulative distribution function (CDF) which is main contribution of this paper. Outage probability and the average error probability for coherent, noncoherent modulation are derived. Numerical results presented in this paper point out the effects of fading severity and cor¬relation on the system performances. The main contribu¬tion of this analysis for multibranch signal combiner is that it has been done for general case of correlated co-channel interference (CCI)

Calculation of runoff and soil erosion on the Tifran watershed, Polimlje, North-East of Montenegro

Soil erosion is a growing problem in South East Europe and is creating a hazard to soil quality, environment and biodiversity. It is well-known fact that runoff, soil erosion and as consequence sedimentation, are decreasing a reservoirs capacity and that is noticeable in the region of Polimlje, where the studied watershed belongs. This is causing the new expenses to the weak economies of the Countries of this underdeveloped area. Ecological factors, which are the basis for the calculation of soil erosion intensity, we included in the simulation model. At the level of the watershed, the use of computer-graphic methods allowed the quantification of the environmental effects of runoff and soil erosion. Maximal outflow (incidence of 100 years) from the studied watershed, Qmax, was predicted on 31 m3/s. The value of the Z coefficient was calculated on 0.271 and according to the result the watershed belongs in the destruction category IV. The strength of the erosion process is low, and mixed erosion dominates in the studied area. The calculated soil losses were 277 m³ per year for the watershed, specific 115.5 m³/km2 per year. We have not evaluated proposed anti-erosion measures in the area because they have not been put into practice. This study shown that IntErO model is a useful tool for researchers in calculation of runoff and sediment yield at the level of the river basins in the South East European region

Soil erosion in the Zim Potok watershed, Polimlje river basin, Montenegro

The negative impact of sediments on the environment and water resources is widely acknowledged with many watercourses in Montenegro and in the South Eastern European Region. To reduce sediment exports from the big river basins discharging to the accumulations, it is essential to identify the sources: critical sub basins and the quantity of its sediment yield and runoff. The off-site impacts of runoff and eroded soil, eutrophication of water bodies, loss of reservoir capacity, muddy flooding of roads and communities, are increasingly recognised. Establishing the correlation between on-site erosion rates with off-site impacts is complicated because of the limited data on soil erosion processes in Montenegro and the dynamic nature of this process over space and time. The use of computer-graphic methods allowed the quantification of the environmental effects of soil erosion. We used modelling of sediment yield and runoff for calculation of soil erosion intensity for a Zim Potok watershed of Polimlje, Montenegro. Ecological factors, which are the basis for the calculation of soil erosion intensity, are included in the IntErO simulation model, with the Erosion potential analytical method of Gavrilovic embedded in the algorithm of this computer-graphic method. Our results shown that the calculated maximal outflow from the river basin may be 144 m3s-1 for the 100 years return time flood. The sediment yield was calculated as 689 m³yr-1, specific 155 m³km-2yr-1. The important results of this study are the determination of erosion processes in the study watershed and new particular information about the recent state of runoff and sediment yield in formats that can facilitate its efficient management and protection, illustrating the possibility of sediment yield modelling with such approach

Sustainable Heat Transfer Management: Modeling of Entropy Generation Minimization and Nusselt Number Development in Internal Flows with Various Shapes of Cross-Sections Using Water and Al₂O₃/Water Nanofluid

In order to achieve the best performance of a thermal system, two major analyses must be carried out on the system: energy and entropy generation. The best scenario is a mechanism in which the system has minimum entropy generation and the highest Nu number. In this regard, we investigated entropy generation and Nu number of fluid flow through tubes of various cross-sections, namely circular tubes, square channels, and rectangular ducts. Additionally, the addition of nanoparticles was tested, and both analyses were carried out. The results reveal that using nanoparticles could significantly increase Nu number and, at the same time, decrease entropy generation. The results showed that the circular cross-section performs better in Nu number and entropy generation. In most cases, the rectangular cross-section performed better than the square one in terms of energy and entropy. In the best case, the average Nu for the circular cross-section was 26% greater than that of the square. The average Nu of the rectangular cross-section showed that this value is 5% greater than that of the square cross-section. Additionally, the total entropy generation of circular cross-sections, which is the minimum, was 44% and 38% lower than rectangular and square cross-sections, respectively

Structural and ecological characteristics of mixed broadleaved old-growth forest (Biogradska gora-montenegro)

Biogradska Gora National Park in Montenegro is part of the Dinaric Mountains mixed forest, which belongs to the montane region of the Dinaric Alps. This paper presents some of the main structural and ecological characteristics of the mixed broadleaved old-growth forest with beech [Fagus moesiaca (Domin, Maly) Czecz.], sycamore maple (Acer pseudoplatanus L.) and European ash (Fraxinus excelsior L.) from the preserve area of the Biogradska Gora. These forest ecosystems are characterized by the high species richness and potential productivity. In the study area, 58 vascular plant species were recorded in 4 sample plots of 0.25 ha each. The average timber volume found in the sample plots was 814 m3/ha. This value is twice as high as that of similar pure beech forests in the same preserve area. The results are confirmed the biodiversity and production potential of mixed broadleaved forests, which rarely occur spontaneously. A better understanding of the processes of the pristine forest ecosystems could form a realistic basis for close-tonature management of similar stands. The obtained data provides overview of the structural characteristics of these forests, which have developed without anthropogenic influence. Exploring the structure of forests in permanent preservation areas could be an excellent basis for close-to-nature forest management