Performance of wireless optical telecommunication systems in the presence of fading and interference

Postojeći komunikacioni sistem u domenu RF elektromagnetnog spektra nije u mogućnosti da zadovolji sve potrebe brzog i obimnog prenosa podataka, koje se javljaju usled ekspanzije i sve veće upotrebe IoT uređaja, 5G i B5G mreža, kao i raznovrsnih aplikacija i multimedijalnog sadržaja. Optička bežična komunikacija (OWC), koja koristi veliki opseg nelicenciranog dela spektra, se pokazala kao dobra alternativa za ublažavanje nedostataka konvencionalnog sistema za prenos podataka koji radi u RF domenu. FSO (Free Space Optics) tehnologija predstavlja jednu od vrsta optičkih bežičnih komunikacija, ima veliku upotrebu u LAN i MAN mrežama , bežičnom video nadzoru, koristi se u medicinske svrhe, u svemirskoj komunikaciji, za rešavanje problema poslednje milje itd. Primena bežičnih komunikacija, znatno može da doprinese performansama sistema, i to u smislu spektralne i energetske efikasnosti kao i u smislu pouzdanosti. U disertaciji je u cilju utvrđivanja optimalnog scenarija prijema signala, kao i određivanja optimalnih vrednosti parametara takvog prenosa, izvršena analiza karakteristika bežičnog optičkog prenosa signala u prisustvu turbulencije i efekta greške pozicioniranja, koji se odvija pod kompozitnim uticajem navedenih smetnji. Za posmatrane scenarije prenosa razmatrane su standardne mere performansi sistema, kao što su srednja verovatnoća greške po bitu, posmatrana za odgovarajuće modulacione formate, kao i verovatnoća otkaza. Predstavljena su analitička i numerička rešenja problema, a uticaji pojedinih parametara sistema na performanse bežičnog optičkog prenosa prikazani su i grafički

Situational and Trait Self-Handicapping among Grandiose and Vulnerable Narcissists

Self-handicapping is an effective strategy for self-enhancement and self-protection in situations in which one’s self-image is evaluated. Previous studies have shown that grandiose narcissists use self-handicapping for self-enhancement, while research on vulnerable narcissists’ use of self-handicapping is still scarce. In this study, we examined trait, behavioural, and proclaimed self-handicapping among the two forms of narcissism. After questionnaire measures were collected, a total of 105 individuals participated in the experimental study, in which they were led to believe they would be doing a hard or an easy ability test. The results showed that grandiose narcissism was only related to trait self-handicapping in achievement situations, while vulnerable narcissism was related to self-handicapping in interpersonal and achievement situations. Experimental results showed that participants did not seize the opportunity for behavioural or proclaimed self-handicapping. Moreover, the use of these strategies was not related to vulnerable or grandiose narcissism. The results are here discussed in the context of self-image maintenance dynamics of individuals with different levels of vulnerable and grandiose narcissism as well as methodological aspects of the study, and the validity of the concept of self-handicapping

LEVEL CROSSING RATE OF MACRODIVERSITY OUTPUT PROCESS IN THE PRESENCE OF η-μ SHORT TERM FADING AND GAMMA LONG TERM FADING

In this paper macrodiversity reception with macrodiversity selection combining (SC) receiver and two microdiversity MRC receivers operating over shadowed multipath fading channel is studied. Received signal experiences  short term fading and correlated Gamma long term fading resulting in system performance degradation. Level crossing rate (LCR) of η-μ random process and level crossing rate of signals at outputs of microdiversity MRC receivers are efficiently calculated. By using these derived formulas, level crossing rate of macrodiversity SC receiver output signal process is calculated. By using this result, average fade duration (AFD) of the proposed wireless communication system can be calculated. The influence of  η-μ  short term fading severity parameter, Gamma long term fading severity parameter and Gamma long term correlation coefficient on level crossing rate is analysed and studied

Coronaphobia – What Do Coronaphobia Scales Measure? An Analysis of 12 Open Instruments and their Correlates

Previous studies confirmed the psychological, psychosomatic, and economic consequences of the COVID-19 outbreak, which lead to the introduction of a new concept of coronaphobia as a persistent and excessive fear of the novel coronavirus. With the beginning of the pandemic, the interest in coronaphobia-related measurement began and until 2021, 12 instruments were created, with a total of 28 (sub)scales. The first aim of this study was to explore the joined factor structure of these measurements. The second aim was to explore a wide range of correlates of coronaphobia (sociodemographic characteristics, general anxiety disorder, Big Five traits, knowledge about coronavirus, and political orientation). The sample included 347 participants (42.1% male) from the general population of Serbia and data were collected in April 2021. Results showed that only one component could be extracted based on 28 (sub)scales of coronaphobia, meaning that physiological, cognitive, emotional, and behavioral aspects of coronaphobia are rather intercorrelated. Furthermore, among explored correlates, general anxiety disorder had the highest contribution to the explanation of coronaphobia. Additionally, Openness showed a negative, and age showed a positive contribution to the explanation of coronaphobia. Our results suggest that coronaphobia should be understood as a syndrome that captures physiological, cognitive, behavioral, and emotional aspects, and that individuals who are already prone to anxiety disorders are more prone to coronaphobia as well

Theta burst stimulation influence the expression of BDNF in the spinal cord on the experimental autoimmune encephalomyelitis.

Repetitive transcranial magnetic stimulation (rTMS) induces changes in expression of proteins engaged in the activity of excitatory and inhibitory systems, restores these functions and suppresses the progression of disability in experimental autoimmune encephalitis (EAE). The structural type of TMS, the arrangement as theta burst stimulation (TBS) has been applied as intermittent TBS (iTBS) and continuous TBS (cTBS) protocols to female adult DA rats. The animals were randomly divided into experimental groups: control group (C), group treated with complete Freund's adjuvant (CFA), experimental autoimmune encephalomyelitis (EAE) group, group treated with iTBS post EAE immunization (EAE + iTBS), group treated with cTBS post EAE immunization (EAE + cTBS), group of healthy animals treated with iTBS or cTBS. Therapeutic protocols of iTBS or cTBS in all EAE groups of animals were performed starting from 14 days post immunization (dpi), for 10 days with time point decapitation at 24 dpi. After decapitation, spinal cords were analysed for BDNF and Ki67 expression. The results revealed reduced BDNF expression in the rat's spinal cord of EAE animals in the stage of remission, which was associated with increased Ki67 and GFAP expressions. Decreased Iba 1 and BDNF expression, contrary to increased Iba 1 and Ki67 expression, suggests clustered microglia in the resolution phase of EAE. Enhanced GABA expression in spinal cord sections indicates higher GABA metabolic turnover, and also GAD activity in astrocytes, or prominent activity of GABAergic neurons. Both TBS protocols induced advance BDNF expression; amongst iTBS application provoked elevating of BDNF and stabilizing of GFAP and Ki67 expressions

Spatial analysis of air temperature and its impact on the sustainable development of mountain tourism in Central and Western Serbia

Empirical studies of the late twentieth and early twenty-first century indicate the existence of a growth trend in air temperature. This trend is particularly pronounced in the region of Southern Europe, including the Republic of Serbia. Many problems occur in the socio-economic areas due to global warming, which directly influences the development of tourism. In this study, we will deal with the influence of climate change on the sustainable development of mountain tourism in the area of the western and central Serbia tourist zones, which includes Starovlaška and Kopaonik mountain chain. The data on changes in the temperature of air will be gathered at six different altitude meteorological stations, for the period from 1990 to 2014. All weather stations in the studied area were classified into three groups: lowland, middle and high mountain. In order to obtain trends, three sets of data were used: the average monthly temperature, the maximum monthly temperature, and the monthly minimum temperature, recorded in each station. The seasonal classification has been conducted based on four seasons: spring,m summer, autumn, and winter. Three statistical approaches were used to analyze the temperature trends in 15 time series, for each group of stations individually. First, the trend equation was calculated for each time series, then, completely separate from the first approach, all trends were assessed using the Mann-Kendall test, and in the end, in all cases, the trend magnitude was calculated based on the trend equation. The results show that there is a significant positive trend of temperature rise on an annual basis, while the trend is significantly positive during the fall and spring seasons. In winter, the trend is slightly positive or absent, while in the summer trend is moderately positive in all three groups of stations

Forensic DNA databasesin Western Balkan region:retrospectives, perspectives, and initiatives

The European Network of Forensic Science Institutes (ENFSI) recommended the establishment of forensic DNA databases and specific implementation and management legislations for all EU/ENFSI members. Therefore, forensic institutions from Bosnia and Herzegovina, Serbia, Montenegro, and Macedonia launched a wide set of activities to support these recommendations. To assess the current state, a regional expert team completed detailed screening and investigation of the existing forensic DNA data repositories and associated legislation in these countries. The scope also included relevant concurrent projects and a wide spectrum of different activities in relation to forensics DNA use. The state of forensic DNA analysis was also determined in the neighboring Slovenia and Croatia, which already have functional national DNA databases. There is a need for a ‘regional supplement’ to the current documentation and standards pertaining to forensic application of DNA databases, which should include regional-specific preliminary aims and recommendations

Porodično nasilje - karakteristike nasilja nad decom i posledice na razvoj dece

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