Unapređenje metoda merenja fedinga u RF telemetrijskim sistemima srednje naponskih distributivnih mreža

In this paper, the estimation of Nakagami-m short term fading severity parameter and signal envelope average power are considered. Two methods enabling calculation severity parameter of Nakagami-m fading and are average power of signal envelope propagation in Nakagami-m fading channel by using measured values samples of Nakagami-m random process is considered in this work. By using measured values moments of Nakagami-m random process can be calculated. Nakagami-m fading parameters can be evaluated from moments. In this paper is considered the case when fading parameters are calculated from the second moment and the forth moment. Also, the case when Nakagami-m parameters are calculated by using the first, the second and the three moment is studied. In this paper diversity technique is applied for evaluation Nakagami-m fading parameters by using method of moments. Used diversity technique has MRC (maximal ratio combining) receiver with two and three inputs operating over independent and identical multipath fading channel. Moments of MRC receiver output signal enable Nakagami-m fading parameters evaluation. The accuracy of obtained results increases as the number of samples increases, the order of diversity increases and when the number of realizations increases. The second method studied in this paper, for estimating the Nakagami-m fading severity parameter and average power of Nakagami-m fading signal envelope is level crossing method. Level crossing rate is calculated for three values of signal envelope and from these three equations evaluated Nakagami-m parameters. Obtained expressions for level crossing rate are simple and Nakagami-m parameters can be determined. MRC diversity technique is applied for the estimation of Nakagami-m fading severity parameter and Nakagami-m signal envelope average power. The accurately of calculated values for Nakagami-m parameters increases as the number of samples increases, the number of realization increases and MRC diversity order increases. Also the accurately of obtained reports is higher for lower values of Nakagami-m fading severity parameter. *Application diversity technique for estimation of Nakagami-m fading parameters by using the method moments is not considered in open technical literature. *Level crossing rate method for estimation of Nakagami-m fading parameters is not considered in open technical literature

INCREASED ACCURACY OF THE NAKAGAMI M PARAMETER MEASUREMENT METHOD BASED ON SPACE DIVERSITY RECEPTION

In this paper we will present increased accuracy measurement method for the Nakagami-m m parameter estimation, based on implementation of space diversity reception. Parameter m will be estimated in real time, based on the obtained values of first, second and third order moments of signal, measured by a proposed system. The obtained results will show an increase of accuracy obtained by using this method over the results obtained by using a standard measurement procedure, so it creates a potential to apply this measurement method for estimation of fading parameters in various propagation environments

Level crossing rate of SC receiver over gamma shadowed Weibull multipath fading channel

U ovom radu je razmotren bežični telekomunikacijski sustav sa SC prijemnikom koji radi u prisustvu Weibull-ovog fedinga i Gamma sjenke. Utjecaj Weibull-ovog fedinga na primljeni signal se ogleda u promjeni anvelope signala, a utjecaj Gamma sjenke u promjeni snage izlaznog signala. SC prijemnik se koristi za smanjenje utjecaja fedinga i sjenke na karakteristike sustava. Izraz za srednji broj osnih presjeka izlaznog signala iz SC prijemnika je izveden u zatvorenom obliku. Dobiveni rezultati se mogu koristiti za izračunavanje prosječnog trajanja otkaza bežičnog sustava. Numerički rezultati su predstavljeni grafički, kako bi se prikazao utjecaj parametara fedinga i sjenke na karakteristike sustava.The wireless telecommunication system consisting of selection combining (SC) receiver which works in Gamma shadowed Weibull multiple-faded channel is discussed in this work. The received signal suffers Weibull small scale fading which leads in variation of the signal envelope and Gamma large scale fading which results in variation of the SC receiver output signal envelope power. SC receiver is utilized to abate the impact of Gamma large scale fading effects and Weibull small scale fading effects on system characteristics. The formula for average level crossing rate (LCR) of signal envelope at SC combiner output is performed in the closed shape. The result we get can be applied to calculate the average fade duration (AFD) of such wireless systems. The obtained solutions are plotted in a few graphs to point out the impact of Weibull fading envelope severity parameter and Gamma shadowing severity parameter on system features

Desiccation, postharvest maturity and seed aging of tall oat-grass

The objectives of this work were to determine whether and at which seed physiological maturity stage the diquat desiccant affects the tall oat-grass (Arrhenatherum elatius) seed quality and yield, as well as the proper storage period between harvest and sowing. Diquat desiccation was evaluated in applications during milk or dough seed maturation stages. Seeds conventionally produced and stored under traditional storage conditions were used for the analyses. Seed samples were drawn every 30(th) day after harvest (DAH). After the 240(th) DAH, samples were drawn every 90(th) day up the to 690(th) DAH. The highest yield were obtained by desiccation applied at the beginning of the seed dough stage, with a satisfactory seed quality. Both final germination and seedling growth parameters achieved their maximum values between 180(th) and 240(th) DAH. Oat-grass seeds preserved satisfactory level of final germination (75%) up to 420(th) DAH. The application of diquat desiccant at the beginning of seed dough maturity stage can be a good solution for seed production of tall oat-grass. Early spring is the best sowing period for freshly harvested seeds of tall oat-grass regarding germination and seedling growth

Drying of forage grass seed harvested at different maturity and its utility value in autumn and spring sowing time

Tall fescue (Festuca arundinacea Schreb.), red fescue (Festuca rubra L.) and cocksfoot (Dactylis glomerata L.) are important fodder grasses, but in seed production, they are prone to seed shedding and certain yield losses. In practice, seeds are usually harvested at approximately 20-35% moisture content and then are additionally dried to the moisture content of 12% or lower. However, to prevent shedding, seed was harvested at 45% moisture content. The effects of drying temperatures of 70, 60, 50, 40, 30 and 22 degrees C on germination and dormancy of tall fescue, red fescue, cocksfoot seeds, harvested at moisture contents of 45, 35 and 25 %, were observed in the present study. The analysis was done immediately upon seed drying, then three, eight and fourteen months later, which corresponds to the autumn and spring sowing time in the continental part of central and south-eastern Europe. In all the three species, drying temperature of 70 degrees C, regardless of the moisture content, and 60 degrees C in the combination with a seed moisture content of 45%, reduced germination. After three months, the highest germination was detected in tall fescue harvested at seed moisture of 25% and dried at 50 degrees C. Furthermore, the greatest germination in red fescue and cocksfoot was determined in seeds harvested with the moisture content of 35% and dried at 50 degrees C. After eight months, the highest germination in tall and red fescue were determined in seeds harvested with the moisture content of 25% and dried at 40-50 degrees C, while corresponding values in cocksfoot amounted to 25% and 22-30 degrees C, respectively. A positive and significant correlation was established between seed germination and seedling vigour

Seed germination and seedling vigour of Italian ryegrass, cocksfoot and timothy following harvest and storage

During post-harvest maturation, different species vary in the length of dormancy breaking or germination increases. Seed dormancy and slow seedling development often limit establishment of forage grass stands. Seed germination and seedling vigour of Italian ryegrass (Lolium italicum A. Braun, Synonym Lolium multiflorum L.), cocksfoot (Dactylis glomerata L.) and timothy (Phleum pretense L.) were observed after harvest and storage. After harvest in June, seeds were stored under standard storage conditions and sampled every 30 days after harvest (DAH), up to 270 DAH, and then every 60 days up to 990 DAH. At each date, seeds were tested for final germination percentage and for seedling vigour traits. Timothy seeds had a maximum germination (88%) and the best seedlings vigour at 90 DAH, which implies that early autumn (September-October) is the best sowing period for freshly harvested seeds of timothy. Timothy seed germination was poor from 270 DAH (73%). The best germination and vigour of Italian ryegrass and cocksfoot seedlings were between 270 and 330 DAH, which equates to spring sowing time (March-April) in the succeeding year. Cocksfoot and Italian ryegrass seeds maintained satisfactory germination levels up to 630 DAH (81%) and 810 DAH (81%), respectively. The data can serve for the determination of a proper storage duration management between harvest and sowing of the tested species under ambient conditions of south-eastern Europe

Dessecação, maturidade pós-colheita e deterioração de sementes de aveia-perene

The objectives of this work were to determine whether and at which seed physiological maturity stage the diquat desiccant affects the tall oat-grass (Arrhenatherum elatius) seed quality and yield, as well as the proper storage period between harvest and sowing. Diquat desiccation was evaluated in applications during milk or dough seed maturation stages. Seeds conventionally produced and stored under traditional storage conditions were used for the analyses. Seed samples were drawn every 30th day after harvest (DAH). After the 240th DAH, samples were drawn every 90th day up the to 690th DAH. The highest yield were obtained by desiccation applied at the beginning of the seed dough stage, with a satisfactory seed quality. Both final germination and seedling growth parameters achieved their maximum values between 180th and 240th DAH. Oat-grass seeds preserved satisfactory level of final germination (75%) up to 420th DAH. The application of diquat desiccant at the beginning of seed dough maturity stage can be a good solution for seed production of tall oat-grass. Early spring is the best sowing period for freshly harvested seeds of tall oat-grass regarding germination and seedling growth.O objetivo deste trabalho foi determinar se e em qual estágio de maturidade fisiológica das sementes o dessecante diquat afeta a produtividade e a qualidade de sementes de aveia-perene (Arrhenatherum elatius), bem como o período de armazenamento adequado entre colheita e semeadura. O dessecante diquat foi avaliado em aplicações nos estágios de leite ou de cera do amadurecimento de sementes. Sementes produzidas convencionalmente e armazenadas em condições tradicionais foram utilizadas para as análises. Amostras de sementes foram coletadas a cada 30 dias após a colheita (DAC). Após o 240º DAC, as amostras foram retiradas a cada 90 dias até o 690º DAC. A maior produtividade, com qualidade satisfatória da semente, foi obtida pela dessecação aplicada no início da fase de cera. A germinação final e os parâmetros de crescimento das plântulas alcançaram valores máximos entre 180 e 240 dias após a colheita. As sementes de aveia-perene mantiveram germinação final satisfatória (75%) até 420 dias após a colheita. A dessecação com diquat, na fase inicial do estágio de cera do amadurecimento das sementes, pode ser uma boa solução para a produção de sementes de aveia perene. O início da primavera é o melhor período para plantio de sementes recém-colhidas de aveia-perene, em termos de germinação e crescimento de plântulas