On graphs whose second largest eigenvalue equals 1 – the star complement technique

AbstractThe star complement technique is a spectral tool recently developed for constructing some bigger graphs from their smaller parts, called star complements. Here we first identify among trees and complete graphs those graphs which can be star complements for 1 as the second largest eigenvalue. Using the graphs just obtained, we next search for their maximal extensions, either by theoretical means, or by computer aided search

Second harmonic generation in nonlinear transformation of electromagnetic waves in suddenly created cold magnetized plasma: Transversal propagation

U radu je analizirana transformacija izvornog linearno polarizovanog elektromagnetskog talasa, usled slabih nelinearnosti, u elektronske i elektromagnetske oscilacije, stacionarne (prostorno promenljive i jednosmerne) i talasne elektromagnetske i elektronske modove u plazmi primenom perturbacione teorije drugog reda. Efikasnost eksitacije transverzalnih električnih modova, dvostruko veće frekvencije i dvostruko većeg talasnog broja od modova dobijenih u linearnoj teoriji, analizirana je za različite vrednosti ugaone frekvencije izvornog talasa i za vrednost ugaone elektronske žiro-frekvencije koja odgovara vrednosti ugaone elektronske razmene frekvencije.The nonlinear transformation of linearly polarized source electromagnetic wave in electron and electromagnetic plasma oscillations, stationary (rectification and space-varying) modes and travelling electron and electromagnetic plasma waves, due to a weak nonlinearity, has been analyzed by using the second order perturbation theory in radio approximation. The efficiency of excitation of the transversal secondharmonic electric wave modes with double wave number with respect to the wave number modes in the linear transformation has been studied for different values of source wave frequency, taking the electron cyclotron frequency as a parameter)

Second harmonic generation in nonlinear transformation of electromagnetic waves in suddenly created cold magnetized plasma: Transversal propagation

U radu je analizirana transformacija izvornog linearno polarizovanog elektromagnetskog talasa, usled slabih nelinearnosti, u elektronske i elektromagnetske oscilacije, stacionarne (prostorno promenljive i jednosmerne) i talasne elektromagnetske i elektronske modove u plazmi primenom perturbacione teorije drugog reda. Efikasnost eksitacije transverzalnih električnih modova, dvostruko veće frekvencije i dvostruko većeg talasnog broja od modova dobijenih u linearnoj teoriji, analizirana je za različite vrednosti ugaone frekvencije izvornog talasa i za vrednost ugaone elektronske žiro-frekvencije koja odgovara vrednosti ugaone elektronske razmene frekvencije.The nonlinear transformation of linearly polarized source electromagnetic wave in electron and electromagnetic plasma oscillations, stationary (rectification and space-varying) modes and travelling electron and electromagnetic plasma waves, due to a weak nonlinearity, has been analyzed by using the second order perturbation theory in radio approximation. The efficiency of excitation of the transversal secondharmonic electric wave modes with double wave number with respect to the wave number modes in the linear transformation has been studied for different values of source wave frequency, taking the electron cyclotron frequency as a parameter)

PRIVATIZATION OF THE POWER SECTOR IN CROATIA - DEVELOPMENTAL BREAKTHROUGH OR FALLACY OF THE NEOLIBERAL IDEOLOGY?

Autori analiziraju različite dimenzije elektroenergetskog sustava -tehnološku, organizacionu, ekonomsku, ekološku i stratešku - iz kojih se vidi da je električna energija roba sui generis, pri čemu tržište i njegova uloga u alokaciji resursa imaju sasvim osebujan karakter. Prema tome i privatizacija elektroenergetskog sustava ima na društvo i ekonomiju drugačije odraze od privatizacije u nekim drugim ekonomskim sektorima. Između ostaloga, pojavljuje se problem određivanja granice gdje prestaje odgovornost privatnog, a počinje odgovornost državnog sektora u osiguranju društveno potrebnih količina energije. Autori daju kritički prikaz nekih međunarodnih iskustva u privatizacijii tehnološkom razdvajanju energetskog sustava. Na osnovi toga i na osnovi općenitih i nacionalnih specifičnosti elektroenergetskog sustava zaključuju dane postoji opravdani razloga za potpunu privatizaciju i razdvajanje HEP jednako kao ni za otvaranja hrvatskoga energetskog tržišta globalnoj konkurenciji. Sa druge strane, postoji prostor za parcijalnu privatizaciju HEP i otvaranje tržišta za proizvodnju električne energije iz aditivnih (zelenih) izvora. Napomena: stavovi autora izneseni u ovome radu nisu stavovi institucija u kojima su oni zaposleni.Authors analyze different dimensions of power sector – technological, organizational, economic, environmental and strategic – which show the su i generis character of electrical energy regarded as commodity. This implies also the peculiar functioning of themarket in the power sector. Consequently, privatization in the power sector has muchwider implications on the society and economy then privatization in any other economic sector. Among other things, we emphasize the problem of demarcation line between the risk and responsibility taken by the private sector and that endorsed by the state in securing necessary supply of energy for the normal functioning of society. Authors discusssome of the international experiences in the privatization and deregulation of the power sector. Based on these experiences and generic and national peculiarities of the power sector, we conclude that there are no reasonable grounds for full privatization and deregulation of the Croatian power sector or for its opening to global competition. On the otherhand, there is a room for partial privatization and opening of market for production of green energy

DEM-based GIS algorithms for automatic creation of hydrological models data

In this paper the authors discuss the Digital Elevation Model (DEM) based GIS algorithms, applicable for automatic creation of input data needed by hydrological models. The expected source of DEM data are standard digital data sets that a modeler can purchase from the official data sources. The DEM has to be cleared from errors and prepared for standard hydrology usage as the depression less version, or a version of DEM where only small depressions are filled-in, while larger depressions are extracted as separate objects. The slopes and aspects are calculated from such DEM. The flow accumulation image is created using slopes and aspects and using information about large ponds. From flow accumulation image the surface drainage network is extracted with user-specified density. Based on slopes and aspects, the catchment is delineated into subcatchments, the areas drained by each river segment. Finally, the model-specific parameters like length of flow segment along the terrain and along the river to the subcatchment outlet, slope of those segments, subcatchment shape factor, or subcatchments mean or weighted slope are calculated. Paper explains the used algorithms and emphasizes the problems one can encounter during the usage of DEM data using examples from River Drina catchment. Finally, the authors comment on overall usability of presented GIS algorithms, especially if purchased data are of low quality.

Influence of fused deposition modelling printing parameters on tablet disintegration times: a design of experiments study

Despite the importance of process parameters in the printing of solid dosage forms using fused deposition modelling (FDM) technology, the field is still poorly explored. A design of experiment study was conducted to understand the complete set of process parameters of a custom developed FDM 3D printer and their influence on tablet disintegration time. Nine settings in the Simplify 3D printing process design software were evaluated with further experimental investigation conducted on the influence of infill percentage, infill pattern, nozzle diameter, and layer height. The percentage of infill was identified as the most impactful parameter, as increasing it parabolically affected the increase of disintegration time. Furthermore, a larger nozzle diameter prolonged tablet disintegration, since thicker extruded strands are generated through wider nozzles during the printing process. Three infill patterns were selected for in-depth analysis, demonstrating the clear importance of the geometry of the internal structure to resist mechanical stress during the disintegration test. Lastly, layer height did not influence the disintegration time. A statistical model with accurate fit (R2 = 0.928) and predictability (Q2 = 0.847) was created. In addition, only the infill pattern and layer height influenced both the uniformity of mass and uniformity of the disintegration time, which demonstrates the robustness of the printing process