An adaptive differentiation filter for tracking instantaneous frequency in power systems

Copyright © 2007 IEEEThis paper presents an application of adaptive differentiation filter in tracking instantaneous frequency in electrical power systems. For each new sample, the filter automatically selects an optimal window length that maximizes measurement accuracy. Large window length is selected if the frequency is slow varying or steady state, to increase efficiency in filtering noise and harmonics. For fast-varying frequency, the window length is automatically reduced in order to make frequency tracking more accurate, sacrificing filtering efficiency. Automatic selection of the optimal window length that balances between tracking and filtering performance is the unique feature of this technique. This paper concludes with the presentation of the representative results obtained in the simulation study as well as in some practical applications. The results show the adaptive differentiation filter gives accurate frequency measurement under both steady-state and dynamic conditions.Rastko Zivanovi

Estimate level of contamination of ecosystems by means of the distribution of some heavy metals in substrates

During the year 2000 we have researched the terrain around the river basin of the river Bregalnica. This paper contains the results of this research from four measuring points, one of which is the control measuring point Blatec on the river Osojnica. The content of some heavy metals (Pb, Cd, Zn, and Mn) has been analyzed in ambiental water (filterable heavy metals), sediment, plant material (Capsicum annuum) and animal material (bone of frog Rana ridibunda). The highest contents of heavy metals were measured at the measuring points above Makedonska Kamenica on the rivers Kamenicka and Kiselica. This is a direct consequence of the discharge of waste waters from the mines Sasa and Zletovo

The role of the GPS-system in integrated control system skylines in mine for copper Bucim

With the hastily ascent of the techniques at the end of 20th century, the role of the GPS systems rapidly increases in all fields of technologies prevalent on the surface layer and hence in open-cut mining. All tippers and dredgers are equipped with GPS receiver, so both the dispatcher and employer can have information about the current position of the machines. In this article are described part of the GPS receiver, the integration in the Skylines and part of the reports

Inbreeding and thermal adaptation in Drosophila subobscura

Using a well-adapted Drosophila subobscura population (Avala, Serbia), a drastic experiment of inbreeding was carried out to assess whether the expected level of homozygosity could be reached or if other evolutionary forces affected the process. In general, no significant changes of inversion (or arrangement) frequencies were detected after 12 brother sister mating generations. Furthermore, no significant differences were obtained between observed and expected (under the inbreeding model) karyotypic frequencies. Thus, these results seemed to indicate that the main evolutionary factor in the experiment was inbreeding. However, in the G12 generation, complete chromosomal fixation was reached only in two out of the eight final inbred lines. In these lines, the chromosomal compositions were difficult to interpret, but they could be likely a consequence of adaptation to particular laboratory conditions (constant 18 °C, food, light period, etc.). Finally, in a second experiment, the inbred lines presented higher fertility at 18 °C than at 13 °C. Also, there was a significant line effect on fertility: inbred line number 6 (A1, J1, U1+2; U1+2+6, E8, and O3+4+7) presented the highest values, which maybe the result of an adaptation to laboratory conditions. Thus, the results obtained in our experiments reflect the adaptive potential of D. subobscura inversions

Identification of the resonant-grounded system parameters by evaluating fault measurement records

Copyright © 2004 IEEEThe operation of a resonant-grounded network during an earth-fault condition depends on the three basic parameters: damping, detuning, and unbalance factor. These parameters are influenced by the environmental conditions (e.g. humidity, temperature, and pollution), and the network topology. Accurate values of these parameters during an earth-fault condition are required to examine the operation of the compensation system. The fault records could be used for that purpose. The recorded neutral-to-ground voltage signals have been parameterized (using damping and detuning as parameters) according to the mathematical model of the transient process. Iteratively reweighted least squares algorithm has been used to fit the model. This algorithm is the major improvement over the classical least squares approach. It is able to filter out noise more efficiently. As a direct result, very accurate parameter identification has been achieved. This paper concludes with the practical examples.Rastko Zivanovic´, Peter Schegner, Olaf Seifert, and Georg Pil

Com s'adapten els organismes al canvi climàtic? Les inversions cromosòmiques de Drosophila subobscura: el cas de les poblacions de Sèrbia

És conegut el fet que les inversions cromosòmiques de les poblacions naturals de l'espècie Drosophila subobscura són adaptatives respecte a les variacions de l'ambient. S'ha observat que les inversions canvien en freqüència al llarg del temps segons la predicció de l'escalfament global del nostre planeta. Aquests resultats es posen de manifest en els nostres estudis realitzats a poblacions sèrbies de D. subobscura. Així, el polimorfisme cromosòmic per inversions canvia segons les estacions de l'any i també a llarg termini (períodes de 10-15 anys) d'acord amb el que s'esperaria segons l'escalfament global. Per tant, les inversions cromosòmiques d'aquesta espècie són uns bons indicadors del canvi climàtic i també són útils per estudiar com els organismes s'hi poden adaptar

Medium-term changes in Drosophila subobscura chromosomal inversion polymorphism: a possible relation with global warming?

Drosophila subobscura is a species with a rich chromosomal polymorphism for inversions. Evidence demonstrates that it is adaptive. In the present research, we studied whether it is possible to detect changes in the inversion chromosomal polymorphism of D. subobscura in a medium-term period of time. The Serbian population of Avala was selected and its inversion composition in 2004 and 2011 (a seven year period) was compared. Significant variation was found in the U chromosome. This result was due to a significant increase of U1+2 (warm) and a decrease of Ust (cold) and U1+2+6. Further, minimum, maximum and mean temperatures increased (although not significantly). Thus, U chromosome seems to be able to react in a medium-term to temperature changes in the way expected by the global warming

How do organisms adapt to climate change?

It is well known that chromosomal inversions in natural populations of the species Drosophila subobscura are adaptations to changes in the environment. It has been observed that inversions change in frequency over time and that they are so far following the pattern expected given the global warming of our planet. These results have been brought to light by our research on Serbian populations of D. subobscura. We found that inversion-related changes in chromosomal polymorphisms depended on the season of the year and in the long term (10-15 year periods) they followed what we would expect given global warming. Therefore, chromosomal inversions in this species are good indicators of climate change and can help us to study how organisms adapt to it