Performanse bežičnog telekomunikacionog sistema u prisustvu n-m fedinga

In this thesis characteristics of wireless communication system operating over η-μ fading channel are considered together with diversity reception techniques which reduce the influence of η-μ fading on the system’s outage probability, average bit error rate, channel capacity, level crossing rate and average fade duration. Performance improvement is very significant within radio systems operating into cell network configuration. Cell network configuration realization could be used for increasing capacity of wireless communication system. With the increase of number of cells, i.e. with reducing the surface area of each cell, channel capacity increases. With the increase of number of cells, co-channel interference level increase, which degrades system performance values. In this work the compromise between the system capacity and reception quality is inquired. By applying diversity reception techniques, system performance values, degraded by the influences of slow fading, multipath fading and co-channel interference, are improved, so it is possible to reduce the cell area and to increase system capacity. In the second part of Phd thesis, various distributions for modeling the envelope variations in fading channels have been presented, cases in which these models are used have been pointed out, and advantages and imperfections of corresponding models for corresponding propagation scenarios have been presented. In third chapter, statistical characteristics of the first order of η-μ random variable, α-η-μ random variable and squared η-μ random variable are considered. For each mentioned variables, expressions for probability density function, cumulative distributive function, characteristic function and moments have been derived. Also for each observed case sum of two random variables, product of two random variables, ratio of two random variables, maximal value of two random variables and minimum value of two random variables have been determined. Obtained results are used for determining performances of wirelles reception with applied diversity technique for mitigation fading influence on system performances. Based on obtained expressions, graphs are depicted for probability density functions and cumulative distribution functions for the various values of propagation environment parameters. Probability density function and cumulative distribution function values are also graphically presented for α-η-μ random variable in the function of α and μ parameter change. For the purpose of performance analysis in η-μ fading environment, in the fourth chapter have been considered transformations of three η-μ random variables. Based on presented transformations of η-μ random variables, transmission performances estimation has been conducted, for the η-μ fading channel. Estimation of signal performances for the cases when diversity techniques are applied are carried out based on standard signal performance measures, i.e. outage probability (OP), average bit error probability (ABER), for observed modulation format and channel capacity. Graphically are presented ABER values for various values of system parameters when transmission is carried out with different modulation formats. By comparing obtained values it can be seen received signal performance improvement for the cases when diversity techniques are apliied over the reception case when there is no diversity technique applied. In the fifth chapter statistical characteristics of the second order of η-μ radnom proccess, and random proccesses which represent various variations of η-μ radnom proccess, are considered. Brand new random proccesses, for describing fading in special channel conditions are fromed. For all this cases level crossing rates are determined. In the sixth chapter of this Phd thesis are considered wireless communication systems with reception with applied diversity techniques for mitigating the influence of η-μ fading on system performances. Space diveristy technique has been used. Useful signals are accepted at the antennas, envelopes of these signals are combined and decision is made based on the signal values at the combiner outputs. System performances are determined for the cases of SC and MRC combining. For bouth cases probability density function and cumulative distribution function of the signal at the combiners outouts are derived, as well as the average bit error rate for the various used modualtion formats and level crossing rate. Results for ABER for various modulation formats are graphically presented as well as the improvement of the outage probability at the reception obtained by applying SC with two reception branches. In this part it has also been considered the case when bouth desired and interferring signal are described with η-μ distribution, as well as the case when desired signal has been described with η-μ distribution while interference has been described with κ-μ distribution. In the seventh chapter macrodiversity sistem with SC reception and two MRC microdiversity combiners has been considered. At the inputs at the microdiversity combiners η-μ fading is present, while at the inputs as macrodiversity combiners slow Gamma fading is present. For this model of system it has been calculated probability density function, cumulative distribution function, characteristic function, moments, variance, outage probability and level crossing rate for the signal at the macrodiversity combiner output. Results obtained for level croosing rate at the macrodiversity combiner output are graphically presented

Potential drug-drug interactions among patients with spontaneous intracerebral hemorrhage treated at the Neurological Intensive Care Unit: a single-center experience

Our aim was to determine the prevalence of potential drug-drug interactions (pDDIs) and to identify relevant factors associated with the occurrence of the most dangerous or contraindicated pDDIs (pCDDIs) in hospitalized patients with spontaneous intracerebral hemorrhage (sICH). A retrospective cross-sectional study was performed enrolling all consecutive patients with sICH treated at the Neurological Intensive Care Unit, Clinical Center in Kragujevac, Serbia, during the three-year period (2012-2014). The inclusion criteria encompassed patients aged 18 years and over, those diagnosed with ICH, and those prescribed at least two drugs during hospitalization, while we did not include patients whose hospitalization lasted less than 7 days, those who were diagnosed with other neurological diseases and patients with incomplete medical files. For each day of hospitalization, the online checker Micromedex® software was used to identify pDDIs and classify them according to severity. A total of 110 participants were analysed. A high prevalence of pDDIs (98.2%) was observed. The median number of pDDIs regardless of severity, was 8.00 (IQR 4.75-13.00;1-30). The pairs of drugs involving cardiovascular medicines were the most commonly identified pDDIs. Twenty percent of the total number of participants was exposed to pCDDIs. The use of multiple drugs from different pharmacological-chemical subgroups and the prescribing of anticoagulant therapy significantly increase the chance of pCDDI (aOR with 95% CI 1.19 (1.05-1.35) and 7.40 (1.13-48.96), respectively). This study indicates a high prevalence of pDDIs and pCDDIs in patients with sICH. The use of anticoagulant therapy appears to be the only modifiable clinically relevant predictor of pCDDIs

Translation to Serbian, cultural adaptation, reliability testing and validation of the questionnaire estimating the fear of injections

Background/Aim. The two-part questionnaire called Injection Phobia Scale (IPS)-Anxiety and IPS-Avoidance represents one of the most commonly used questionnaires for assessing the fear of injections. The aim of the present study was to translate and culturally adapt this questionnaire from English into Serbian as well as to assess reliability and validity of the translation. Methods. The translation and cultural adaptation of the IPS–Anxiety and IPS–Avoidance was performed in accordance with the International Society for Pharmacoeconomics and Outcomes Research (ISPOR) guidelines. Reliability testing, factor analysis and validation of Serbian translation of IPS-Anxiety and IPS-Avoidance were carried out on a sample of 485 students of pharmacy, or medicine at the University of Kragujevac, Serbia. Results. Serbian translation of IPS-Anxiety and IPSAvoidance demonstrated high internal consistency with Cronbach’s alpha of 0.934 for IPS-Anxiety and 0.911 for IPS-Avoidance. Factor analysis of IPS-Anxiety showed that there are two domains, which we have called as Direct Experience (9 items) and Indirect Experience (9 items); factor analysis of IPS-Avoidance also pointed out on two domains referring to direct and indirect fear of injections. Female students scored higher on the scale showing more extensive injection phobia than male students. It is also interesting that students of pharmacy have higher level of injection phobia than students of medicine, and those students of the fifth year of study feel more fear of injections than students from the first four years. Conclusion. Serbian translation of IPS-Anxiety and IPS-Avoidance showed good psychometric properties on population consisted of students medicine and pharmacy. [Project of the Serbian Ministry of Education, Science and Technological Development, Grant no. 175007