Ispitivanje energetske efikasnosti solarnih modula u zavisnosti od njihove zaprljanosti u realnim klimatskim uslovima u Nišu

The doctoral dissertation provides basic information on solar radiation, photovoltaic conversion of solar radiation, solar cells and solar modules and their output parameters, and a literature review of the current research in the world about dust and solar modules soiling. In addition, the results of the measurement of electrical parameters of clean and solar modules soiled with carbon, calcium carbonate and soil are given. Furthermore, a comparative overview of the results of the energy efficiency tests of the clean and solar modules soiled with carbon, calcium carbonate and soil is given. In the end, the results of the measurement of the electrical parameters of the clean and solar modules soiled with accumulated soot from the chimney of the boiler room, located in the basement of the Faculty of Sciences and Mathematics in Niš, are presented

Sioranove vježbe nepokornosti

Osnovni cilj prispevka je iskanje sistema v Sioranovem filozofskem nesistemu. Opus tega filozofa ponuja obilo prodornih in nevsakdanjih razmišljanj o fenomenu Boga, umetnosti (v prvi vrsti glasbe in poezije) ter o smislu obstoja. V središču njegovih obsesij se nahaja prepričanje o nesposobnosti človeštva (obsojenega na neskončno ponavljanje trpljenja in revščine), da bi bistveno spremenilo svoj položaj. Pri tem sta imela po njegovem videnju pomembno vlogo prav religija in Bog, ki si ju je človek izmislil zato, da bi pojasnil svojo bolečino, nesrečo in notranje skušnjave. Čeprav kaotična in kontradiktorna, je Sioranova filozofska misel predvsem antidogmatska, takšen pa je tudi njen jezikovni izraz, zato jo karakterizira izrazita poetska zgoščenost. Ta izhaja iz globokega občutka tragičnega obstoja in je usmerjena na življenje samo – kot takšna se upira vsakršni sistematizaciji. The fundamental objective of this paper is to determine the system of Cioran’s philosophical non-system. The entire opus of this philosopher offers an abundance of lucid and extraordinary analyses of the phenomenon of God, art (mostly music and poetry), and the meaning of life. At the center of his obsessions is the standpoint about the impotence of mankind, destined to endless recurrences of trouble and misery, to fundamentally change its position, which, in his opinion, was largely contributed by religion and God, which man created to explain his pain, misery and inner temptations. Although seemingly chaotic and contradictory, Cioran’s philosophical thought is primarily anti-dogmatic, as well as its literary expression, and it is characterized by great poetic “density.” Deriving from the profound personal feeling of tragedy of existence, it is oriented at life itself, and, as such, refuses to be systematized

Emergence of classical behavior from the quantum spin

Classical Hamiltonian system of a point moving on a sphere of fixed radius is shown to emerge from the constrained evolution of quantum spin. The constrained quantum evolution corresponds to an appropriate coarse-graining of the quantum states into equivalence classes, and forces the equivalence classes to evolve as single units representing the classical states. The coarse-grained quantum spin with the constrained evolution in the limit of the large spin becomes indistinguishable from the classical system

EFFECTS OF TEMPERATURE ON ACYRTHOSIPHON PISUM AND THERIOAPHIS TRIFOLII (HEMIPTERA: APHIDIDAE) ABUNDANCE IN ALFALFA CROPS: A CASE STUDY IN NORTHERN SERBIA

Populations of the most abundant alfalfa aphids, Acyrthosiphon pisum and Therioaphis trifolii, have periodic fluctuations, and many factors affect their dynamics. In the present study, we examined the impact of daily air temperatures on the abundance of two alfalfa aphids in field conditions. The numbers of these two aphids on alfalfa were documented at two locations in a representative alfalfa growing area in Serbia during a three-year field study. Based on the records of aphid abundance and daily air temperatures during the whole study, it was found that a correlation between the sum of optimal daily air temperatures for aphid development, the sum of maximum daily air temperatures and the number of recorded aphid peaks was significant and can therefore be considered for the detection of suitable temperature conditions to increase aphid abundance. The study shows that the highest correlations were between a high density of A. pisum and the sum of optimal daily air temperatures for its development (Ck=0.569) and between a high density of T. trifolii and the sum of maximum daily air temperatures (Ck=0.595). The length of time required for the growth of populations of the two alfalfa aphids differed: 30 days for A. pisum and 5 days for T. trifolii. The association of temperature data to alfalfa aphid abundance enables a projection of their population behavior in changed future climate conditions. This study suggests increased population sizes of T. trifolii and decreased population sizes of A. pisum on alfalfa under the warmer conditions that are expected to prevail in the future. © 2022 Journal of Agricultural Sciences (Belgrade). All rights reserved

Digitization of the Belgrade Astronomical Observatory's vertical circle observational heritage

The aim of the paper is to present the digitization of the results of last observations of bright stars made by the Belgrade vertical circle ASKANIA N±80118 (D = 190 mm, f = 2578 mm) at the Astronomical Observatory of Belgrade. The observations are mainly made by Djuro Bozhichkovich in the period between 1982 and 1985. All of the found observational data and intermediary results are referenced and presented and some research possibilities are suggested. [Project of the Serbian Ministry of Education, Science and Technological Development, Grant no. III044006

Overview of fruit flies important for fruit production on the Montenegro seacoast

Description of the subject. Fruit flies are a large group of pests belonging to the order Diptera. The family Tephritidae is one of two fly families referred to as "fruit flies". Tephritidae (true fruit flies) represent one of the largest families of flies and are part of a group of the most destructive agricultural pests in the world, attacking a wide range of fruits and fleshy vegetables. The other fruit fly family is the Drosophilidae, often called "vinegar flies". There are also fly species from other Diptera families that attack the fruits of agricultural crops. Objectives. Due to its favorable geographic position and Mediterranean climate, the Montenegro seacoast is suited to fruit and vegetable production. The aim of this study was to make an inventory of the fruit fly species affecting fruit crops on the Montenegro seacoast. Method. The study area was 300 km along the Montenegro coast. Different types of traps (lure attractants, pheromone, and yellow sticky traps) were used for the monitoring, detection and recording of the spread of fruit flies in the area. Results. From an economic point of view, the most important species of fruit flies recorded were the Bactrocera oleae Gmel. and Ceratitis capitata Wiedem. Rhagoletis cerasi L. and Carpomya vesuviana Costa were also found to be present. Although several specimens of Rhagoletis cingulata Loew were detected in 2013-2014, this species has not, to date, been considered as established in the area of study. After the first detection of Drosophila suzukii Matsumura in 2013, this fruit fly was found to spread rapidly, and its presence is now observed along the whole Montenegro seacoast. One of the fruit fly species recorded, Silba adipata McAlpine, is considered to be one of the most destructive pests for fig production in Montenegro. Conclusions. Of seven species recorded in the study, five belonged to the family Tephritidae, and one each to Drosophilidae and Lonchaeidae