BOOST CONVERTER STEADY-STATE DEPENDANCE ON SWITCHING FREQUENCY

Na fizički izvedenom uzlaznom pretvaraču identificirana su ustaljena stanja za nekoliko različitih sklopnih frekvencija mijenjanjem ulaznog napona u punom opsegu njegovih vrijednosti. Izmjereni su valni oblici struje prigušnice, pilastog napona i napona povratne veze. Temeljem tih valnih oblika identificirana su ustaljena stanja, bifurkacije udvostručenjem periode i srazom granica, te put u kaos udvostručenjem periode. Dvoparametarskim bifurkacijskim dijagramom po sklopnoj frekvenciji i ulaznom naponu prikazana su područja identificiranih ustaljenih stanja. Smanjenjem sklopne frekvencije područja vrijednosti ulaznog napona za koja se postiže rad u ustaljenom stanju osnovne periode sve su uža, a područja subharmoničkih ustaljenih stanja i kaotičnog ustaljenog stanja sve su brojnija i šira. Pritom, bifurkacije nastaju na sve nižem ulaznom naponu. Temeljem identificiranih ustaljenih stanja moguće je odrediti prihvatljiv raspon vrijednosti sklopne frekvencije uzlaznog pretvarača.The boost converter is realized. By changing input voltage in its full range the steady-states of boost converter for a few switching frequencies are indentified. The waveforms of inductor current, ramp voltage and feedback voltage are taken. Based on those waveforms steady-states, period doubling bifurcations, border collision bifurcations and period doubling route to chaos are identified. The ranges of identified steady states are shown in twoparameter bifurcation diagram with switching frequency and input voltage. By decreasing switching frequency ranges of input voltage which set fundamental period operation are getting narrower and ranges of input voltage which set subharmonic and chaotic steady-states are getting more numerous and broader. At the same time, input voltage causing bifurcations is lowering. On the basis of identified steady-states one can determine acceptable range of converter\u27s switching frequency

DOPRINOS RAZVIJENOSTI MOTORIČKIH SPOSOBNOSTI KOD SAVLADAVANJA SKIJAŠKE TEHNIKE

Ovim istraživanjem utvrđen je uticaj motoričkih sposobnosti na proces učenja alpskog skijanja. Takođe, cilj ovog istraživanja bio je utvrditi uticaj određenih morfoloških karakteristika na savladavanje skijaških znanja. Na početku istraživanja ispitanici su bili testirani pomoću testova za procjenu: ravnoteže, agilnosti, eksplozivne i statičke snage, frekvencije pokreta, te fleksibilnosti. Nakon procjene motoričkih sposobnosti, ispitanicima su utvrđene osnovne morfološke karateristike, te su pristupili školi alpskog skijanja u trajanju od sedam dana. Po završetku učenja alpskog skijanja svi ispitanici demonstrirali su sedam elemenata skijaške tehnike ispred pet nezavisnih ispitivača. Analiza rezultata pokazala je kako agilnost pozitivno utiče pri učenju svih ispitanih elemenata skijaške tehnike (kosi spust, β = 0,38; β = 0,26; zavoj ka padini, β = 0,33; β = 0,23; osnovni zavoj, β = 0,18; paralelni zavoj, β = 0,32; vijuganje, β = 0,34). Rezultati ispitanika u testu izdržaj u čučnju kojim se procjenjuje statička snaga nogu pozitivno utiče kod učenja zavoja ka padini (β = 0,19), osnovnog zavoja (β = 0,35), te paralelnog zavoja (β = 0,27). Test za procjenu ravnoteže (ravnotežni položaj lijeve noge uzdužno) značajno utiče pri učenju osnovnih elemenata skijaške tehnike (kosi spust u desnu stranu, β = 0,23; kosi spust u lijevu stranu, β = 0,28; zavoj ka padini u lijevu stranu, β = 0,24). Tjelesna visina skijaša početnika negativno utiče na efikasnost usvajanja skijaških znanja (β = -0,5), što znači da će višim skijašima biti teže usvajati skijaška znanja u odnosu na niže skijaše. S obzirom na rezultate ovog istraživanja moguće je istaknuti agilnost, statičku snagu, te ravnotežu kao one motoričke sposobnosti koje najviše doprinose skijaškim početnicima prilikom učenja skijaške tehnike

Kemijski i masnokiselinski sastav najduljeg leđnog mišića mlade simentalske junadi.

The objective of this paper was to analyse the carcass characteristics (live weight at slaughter, hot and cold carcass weight, fat weight and fat ratio in cold carcass weight), chemical composition and fatty acid profile of the Simmental cattle longissimus dorsi muscle (MLD). The experiment was carried out on 20 young bulls (sons of sires in progeny testing for meat quality). The average live weight at slaughter (LWS) was 555 ± 12.47 kg, hot carcass weight (HCW) 332.6 ± 7.88 kg, cold carcass weight (CCW) 331.3 ± 8.43 kg, fat weight 15.9 ± 0.81 kg, fat ratio in CCW was 4.89 ± 0.23%. The average chemical composition of MLD was as follows: dry matter 24.84 ± 0.17%, water 75.16 ± 0.17%, protein 20.46 ± 0.26%, intramuscular fat 3.28 ± 0.06% and ash 1.11 ± 0.01%. Linear correlation was calculated for all parameters and high correlations were found between LWS, HCW and CCW, as expected, but there was no significant effect of LWS on the chemical composition of the longissimus dorsi muscle. Intramuscular fat (IMF) consisted on average of 48.04 ± 0.59%, 47.58 ± 0.71% and 4.16 ± 0.25% of total fatty acids (FA) as saturated fatty acids (SFA), mono unsaturated fatty acids (MUFA) and poly unsaturated fatty acids (PUFA), respectively. The PUFA/SFA ratio for beef was low, at around 0.1, similar to that reported by other authors. As expected, the level of MUFA correlated highly with the Δ9-desaturase (18) index (r = 0.84) and elongation index (r = 0.54). Statistically significant correlations between specific fatty acids, LWS, fat and IMF were generally weak. The percentages found of SFA and PUFA, as well as the PUFA/SFA ratio, were in accordance with results reported by other authors but still unfavourable for human health. To improve the unfavourable characteristics of beef, further study should include genetic parameters that affect the FA composition of beef beside the other factors mentioned above.Istraživanjem smo htjeli utvrditi osobine trupova te kemijski i masnokiselinski sastav najduljega leđnog mišića simentalske junadi. U istraživanje je bilo uključeno 20 junadi. Utvrđena je prosječna masa živih životinja 555 ± 12,47 kg, masa toplih polovica 332,6 ± 7,88 kg, masa hladnih polovica 331,3 ± 8,43 kg, masa masti 15,9 ± 0,81 kg, omjer masti i mase hladnih polovica 4,89 ± 0,23%. Prosječan kemijski sastav MLD bio je: suha tvar 24,84 ± 0,17%, voda 75,16 ± 0,17%, protein 20,46 ± 0,26%, intramuskularna mast 3,28 ± 0,06% i pepeo 1,11 ± 0,01%. Izračunali smo linearne korelacije između promatranih obilježja te su pronađene visoke korelacije između mase živih životinja, mase toplih i hladnih polovica. No nije utvrđena značajna korelacija između mase živih životinja i kemijskog sastava MLD. U intramuskularnom masnom tkivu utvrđeno je 48,04 ± 0,59%, 47,58 ± 0,71% i 4,16 ± 0,25% zasićenih (SFA), mononezasićenih (MUFA) i polinezasićenih (PUFA) masnih kiselina. Omjer PUFA/SFA je nizak i iznosi oko 0,1 što je slično istraživanjima drugih autora. Očekivano je ukupna količina MUFA u visokoj korelaciji s indeksom Δ9-desaturaze (18) (r = 0,84) i indeksom elongacije (r = 0,54). Utvrđene su slabe, iako statistički značajne korelacije između pojedinih masnih kiselina, mase živih životinja, ukupne i intramuskularne masti. Utvrđeni rezultati za SFA i PUFA, kao i P/S omjer u skladu su s rezultatima drugih autora no i dalje nepovoljni za ljudsko zdravlje

DIE LEDENA JAMA (EISGRUBE) IN DER LOMSKA DULIBA

Tijekom speleoloških istraživanja Ledene jame u Lomskoj dulibi na sjevernom Velebitu, koja su trajala od 1962. do 1968., izmjerena je dubina jame od 536 m. Iako jama morfološkii zgleda jednostavna, istraživanja je otežavao snijeg i led na ulaznom dijelu jame, koji se u vrijeme istraživanja topio i odjepljivao od stijena pa je bio stalna prijetnja istraživačima. Kako debljina ledenog čepa iznosi oko 40 m, a kroz Lomsku dulibu nekada je tekao ledenjak, speleologe je to navelo na misao da taj led možda potječe još iz Ledenog doba. Zbog toga su uzeti uzorci leda, grana u ledu i sige sa stijene jame, radi određivanja njihove starosti. Rezultati mjerenja pokazali su da je led u jami star samo oko 450 godina, a da je siga stara čak oko 300000 godina. Ti iznenađujući rezultati upućuju na potrebu novih mjerenja u ovoj jami, ali radi usporedbe i u drugim špiljama i jamama u Hrvatskoj.Lomska duliba is a glacier valley with WNW-ESE strike and is located between Veliki Rajinac to the north and Hajdučki kukovi to the south of Mt. Velebit. The entrance to Ledena jama Ice Pit) is situated on the most eastern part of this one kilometre long valley at the level of 1235 above the sea. Ledena jama, just as most pits located on the northern part of Velebit, has a rather simple morphology. Nevertheless, its simplicity is in inverse proportion with the speed and simplicity of exploration, which makes it very different in comparison with other deep pits in this part of Velebit. consider today, it takes three hours for a coordinated team of three speleologists to reach the bottom, the complexity and duration of its investigation in the past is surprising. The complexity the performed investigation makes the story of Ledena jama in Lomska duliba much more interesting. The initial investigations were performed by the members of the Croatian speleological society in 1962. Further investigations were continued in 1977, when a team of speleologists from Željezničar" mapped the pit to the depth of-50 m. The floor of the pit was covered by a thick Since the Croatian speleologists considered they had definitely reached pit\u27s bottom, no further investigations were performed. During the summer of 1992, a team of Slovakian speleogists visited the pit, found a hole in ice and descended through it to the depth of-90 m. Since the pit extended further, the following the investigations continued with the participation of both Slovak and Croatian speleologists. During 1993 and 1994 investigations were performed in combination with the investigators of Lukina jama (-1392 m). In the period between 1995 and 1997 further investigations were undertaken the pit by widening the passage at 473 m and by reaching the bottom of the pit at the depth of-536 m. On the 29th June 1997 during a sport tour of the pit occurred one of the most serious accidents in the Craotian speleology. At the depth of 160 m a landslide of rock and ice caused severe injuries (multiple fracture of various limbs and bones and also muscle ruptures) to B. Bukovčak, who was hanging on the rope. The rescue of the injured speleologists was performed by members of his team and by the Mountain Rescue Service from Karlovac. After a long-lasting recovery, B. Bukovčak is an active speleologist again. In the summer of 1993 it was determined that there was a passage between the ice and the north wall of the pit wide enough for a person to pass. This led to a discovery of an ice plug twenty meters in diameter, well bedded and 40 m thick. Several branches were found to be peeking out of the ice. There was a possibility that the ice originated from the Ice Age, since the Lomska duliba was formed by a glacier. So, speleologists in agreement with the scientists from the Institute Ruder Bošković in Zagreb collected some samples of ice, branches and speleothems for dating. The results of analysis were surpassing. Dating with radioactive isotopes tritium (3H), carbon (14C) and thorium and uranium (230Th/234U) gave an approximate age of ice of 500 years. Said age indicated that the samplings of ice were badly performed (contaminated by more recent waters) or that larger temperature variations existed on Velebit, which should be confirmed by other methods. The branches were younger, which means that they fell into the crack and froze. The most surprising was the age of the speleothem from the depth of 60 m, which was estimated at 300.000 years. This is the oldest registered age of Speleothems measured in Croatia so far although by method not used before on speleothems from other caves and pits. In order to determine the age of this largest piece of old ice in Croatia and speleothems from this pit and other caves and pits, further investigations with modern methods would be required in the future.Im Laufe späleologischer Untersuchungen in der Ledena Jama in der Lomska Duliba am nördlichen Velebit-Gebirge vom 1962 bis zum 1998 wurde die Tiefe der Grube ausgemessen, und man stellte fest, dass sie 536 m beträgt. Obwohl die Grube morphologisch sehr einfach aussieht, war es sehr schwer die Untersungen durchzufuhren, da an dem Eintrittsteil der Grube viel Schnee und Eis gefunden wurde, die sich zur Zeit der Untersuchungen schmelzten und ablosten und waren fur die Erforscher eine dauernde Gefahr. Da die Dicke des Eispropfens ungefahr 40 m beträgt und durch die Lomska Duliba einst ein Eisblock lief, kamen die Erforscher auf den Gedanken, dass dieses Eis vielleicht aus der Glazialzeit stammen wiirde. Darum wurden Muster des Eises, der Äste im Eis und der Tropfsteine genommen um ihr Alter zu bestimmen. Die Resultate der Abmessungen zeigten, dass das Eis in der Grube nur 450 Jahre alt sei und dass der Tropfstein weithin 300.000 Jahre alt sei. Diese iiberraschenden Resultate weisen auf die Notwendigkeit hin neue Abmessungen in dieser Grube durchzufuhren, aber - um des Vergleichens willen - auch in anderen Gruben und Höhlen Kroatiens

Dobro odabrana skijaška oprema povezana je s razinom usvojenog skijaškog znanja kod skijaških početnika

Numerous factors influence efficacy of alpine ski learning, among which dominate weather conditions, motivation, and capabilities of ski beginners as well as motivation and knowledge of ski instructors and quality and suitability of ski equipment, which when suitable also prevents injuries. The aim of this research was to determine whether the length of skis and the length of ski boots affect learning of basic elements of alpine skiing technique. We included 178 ski beginners (132 males and 46 females). At the beginning of the research, the subjects’ height and feet length were measured, and based on the measures, they were given adequate ski equipment. Afterwards participants were included in 10 days alpine skiing where they learned according to precisely defined program. Upon completion of the alpine ski program, participants demonstrated skiing skills (snowplough, basic turn, parallel turn, and short turn) in front of five independent judges. Small but statistically significant negative correlation was determined between ski length and average grade for element snowplough (r=-0,19). Statistically significant correlation was determined between feet length and average grade for parallel turn (r=-0,16) and length of ski boots and element parallel turn (r=-0,20). Our results suggest that ski equipment through ski length and ski boots can influence the speed and level of learning basics of alpine skiing.Više čimbenika utječe na učinkovitost procesa usvajanja osnova alpskoga skijanja. Između ostaloga uvjeti u kojima se uči, motiviranost i sposobnosti učenika, stručnost i motiviranost učitelja te prilagođenost skijaške opreme korisnicima, a dobro odabrana skijaška oprema je neophodan čimbenik i u prevenciji ozljeda. Cilj ovog istraživanja je bio utvrditi povezanost između duljine skija i duljine skijaških cipela s razinom usvojenog skijaškog znanja kod skijaških početnika. U istraživanje je bilo uključeno 178 skijaških početnika (132 muškog i 46 ženskog spola), kojima je na početku istraživanja izmjerena tjelesna visina te duljina stopala. Na temelju izmjerene tjelesne visine ispitanicima su iznajmljene adekvatne skije, a na temelju izmjerene duljine stopala skijaške cipele određene veličine. Nakon odabira skijaške opreme ispitanici su bili uključeni u desetodnevnu školu u kojoj su po točno definiranom programu usvajali skijaška znanja. Po završetku škole svi ispitanici su ispred pet nezavisnih ispitivača demonstrirali 4 elementa skijaške tehnike (plužni zavoj, osnovni zavoj, paralelni zavoj i vijuganje). Mala, ali statistički značajna negativna korelacija utvrđena je između duljine skija i prosječne ocjene skijaškog znanja na elementu plužni zavoj (r=-0,19). Između dužine stopala i prosječne ocjene skijaškog znanja na elementu paralelni zavoj utvrđena je mala, ali statistički značajna negativna korelacija (r=-0,16). Također mala ali statistički značajna negativna korelacija (r=-0,20) utvrđena je i između duljine skijaških cipela i ocjena na elementu paralelni zavoj. Ovo istraživanje potvrđuje kako skijaška oprema preko duljine skija i skijaških cipela može utjecati na brzinu i razinu stjecanja osnovnih skijaških znanja

Chemical characterization, antioxidant and antimicrobial properties of goji berries cultivated in serbia

Since the fruits of Lycium L. species (Fructus lycii, goji berries) are promoted as a “superfood” with plenty of health benefits, there is extensive research interest in their nutritional and phytochemical composition. In the present study, the nutritional value, minerals, fatty acid composition, and bioactive compounds of L. barbarum L., red, yellow, and black goji berry (L. ruthenicum Murray.) cultivated in Serbia were investigated. Antioxidant and antimicrobial properties of their methanol extracts were assessed. Red goji berry had the highest content of fats, dietary fiber, iron, total carotenoids, and 2-O- -d-glucopyranosyl-l-ascorbic acid (AA-2 G). The yellow goji berry extract showed the highest level of flavonoids and the most prominent antimicrobial (especially against Gram-negative bacteria) properties. The highest total phenolic content and the most potent antioxidant activity were observed for the extract of black goji berry. Therefore, all goji berries could be a valuable source of bioactive compounds in the food and pharmaceutical industry

Influence of oxygen enriched gases during decompression on bubble formation and endothelial function in self-contained underwater breathing apparatus diving: a randomized controlled study

Aim To assess the effect of air, gas mixture composed of 50% nitrogen and 50% oxygen (nitrox 50), or gas mixture composed of 1% nitrogen and 99% oxygen (nitrox 99) on bubble formation and vascular/endothelial function during decompression after self-contained underwater breathing apparatus diving. Methods This randomized controlled study, conducted in 2014, involved ten divers. Each diver performed three dives in a randomized protocol using three gases: air, nitrox 50, or nitrox 99 during ascent. The dives were performed on three different days limited to 45 m sea water (msw) depth with 20 min bottom time. Nitrogen bubbles formation was assessed by ultrasound detection after dive. Arterial/ endothelial function was evaluated by brachial artery flow mediated dilatation (FMD) before and after dive. Results Nitrox 99 significantly reduced bubble formation after cough compared with air and nitrox 50 (grade 1 vs 3 and vs 3, respectively, P = 0.026). Nitrox 50 significantly decreased post-dive FMD compared with pre-dive FMD (3.62 ± 5.57% vs 12.11 ± 6.82% P = 0.010), while nitrox 99 did not cause any significant change. Conclusion Nitrox 99 reduced bubble formation, did not change post-dive FMD, and decreased total dive duration, indicating that it might better preserve endothelial function compared with air and nitrox 50 dive protocols

Technological Properties of Model System Beef Emulsions with Encapsulated Pumpkin Seed Oil and Shell Powder

The aim of this research was to examine the technological properties of beef emulsions in which fatty tissue was partially substituted with pumpkin seed oil (PSO) encapsulated in alginate or pectin matrix, and where phosphates (F treatments) were simultaneously substituted with shell powder (C treatments). Fat replacement (in the amount of 25%) mostly had no significant influence on pH, cooking loss, purge loss, fluid release under pressure, residual nitrite level, and texture properties. On the other hand, higher yellowness and hue angle were observed when backfat was replaced with encapsulated PSO, but only in treatments with phosphates. The use of shell powder as a phosphate replacer led to significantly higher pH values and thus to significantly higher residual nitrite level: 70.87-74.64 mg/kg (C treatments) is. 56.79-62.16 mg/kg (F treatments). The nitrite depletion rate during the seven-week storage was lower in C treatments. Moreover. higher lightness, yellowness and hue angle could be expected, as well as lower hardness, springiness, cohesiveness and chewiness. For the most part, seven-week storage had no influence on the observed technological properties, except on colour properties in which an opposite trend was observed in terms of yellowness - increase in treatments with phosphates and decrease in treatments with shell powder. Further research, which would include sensory analysis, should be conducted to determine how these altered colour and textural properties will be perceived by consumers