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Abstract: Purpose: Double flow-focusing nozzles (DFFNs) form a coaxial flow of primary liquid with microcrystalline samples, surrounded by secondary liquid and focusing gas. This paper aims to develop an experimentally validated numerical model and assess the performance of micro-jets from a DFFN as a function of various operating parameters for the water–ethanol–helium system, revealing the jet's stability, diameter, length and velocity. Design/methodology/approach: The physical model is formulated in the mixture-continuum formulation, which includes coupled mass, momentum and species transport equations. The model is numerically formulated within the finite volume method–volume of fluid approach and implemented in OpenFOAM to allow for a non-linear variation of the fluid's material properties as a function of the mixture concentration. The numerical results are compared with the experimental data. Findings: A sensitivity study of jets with Reynolds numbers between 12 and 60, Weber numbers between 4 and 120 and capillary numbers between 0.2 and 2.0 was performed. It was observed that jet diameters and lengths get larger with increased primary and secondary fluid flow rates. Increasing gas flow rates produces thinner, shorter and faster jets. Previously considered pre-mixed and linear mixing models substantially differ from the accurate representation of the water–ethanol mixing dynamics in DFFNs. The authors demonstrated that Jouyban–Acree mixing model fits the experimental data much better. Originality/value: The mixing of primary and secondary liquids in the jet produced by DFFN is numerically modelled for the first time. This study provides novel insights into mixing dynamics in such micro-jets, which can be used to improve the design of DFFNs.
Keywords: serial femtosecond crystallography, sample delivery, double flow focusing, water–ethanol mixing, jet properties, finite volume method, volume of fluid
Published in DiRROS: 05.08.2025; Views: 351; Downloads: 246
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Abstract: The aim of the study was to examine the effects of eccentric- and concentric-based plyometric programmes on the strength, speed, and tensiomyography (TMG) parameters of female athletes. The study included twenty junior female participants from three different sports equally divided into two experimental groups of n = 10. Two plyometric programmes with contrasting designs were conducted for a period of six weeks, with sessions held twice per week. The first plyometric programme (ECC-CON-G) was based on exercises with eccentric, and the second (CONC-CON-G) with concentric contractions. TMG was used to evaluate neuromuscular performances of six muscles of both legs – vastus lateralis (VL), vastus medialis (VM), biceps femoris (BF), semitendinosus (SM), gastrocnemius lateralis (GL), and gastrocnemius medialis (GM)) – and two strength and speed tests: countermovement jump (CMJ), and sprint test at 10 m and 20 m. The results show that both groups had significant effects between pre-post measurements in CMJ (Diff, ECC-CON-G = 9.02%, and CONC-CON-G = 5.59%, p < 0.05), at 10 m (Diff, ECC-CON-G = 9.23%, and CONC-CON-G = 9.35%, p < 0.001), and 20 m (Diff, ECC-CON-G = 6.16%, and CONC-CON-G = 5.35%, p < 0.001), and TMG parameters in ECC-CON-G (all 6 left leg muscles, and right leg-VL, BF, GL, GM, p < 0.05), in CONC-CON-G (left leg-BF, SM, GL, GM, and right leg-VL, BF, GL, GM, p < 0.05). There were significantly better effects in ECC-CON-G compared to CONC-CON-G for CMJ height and time, for only time in 20 m sprint, and TMG parameters for left leg VL and VM, and right leg BF and GM. A plyometric programme based on exercises with eccentric contractions proved more beneficial for strength, speed, and TMG parameters in young female athletes compared to a programme based on concentric contractions.
Keywords: tensiomyography, plyometric, countermovement jump, strength, speed, eccentric-concentric contraction
Published in DiRROS: 04.08.2025; Views: 387; Downloads: 197
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Abstract: V strokovni literaturi se pogosto poudarja, da urbanistična kompleksnost temelji na soobstoju naslednjih treh prvin: regulativnega okvira, ravni urbanističnega oblikovanja in pogajanj med akterji. Avtorji se v članku z navedenim strinjajo, hkrati pa zavračajo zamisel, da so lahko te prvine v idealnem ravnovesju, brez negativnih medsebojnih vplivov. Proučevali so, kje so meje njihovega soobstajanja, in postavili hipotezo, da idealen in uravnotežen soobstoj teh prvin ni mogoč. Njihova raziskava je temeljila na naslednjih štirih glavnih in zaporednih aktivnostih: 1. pregledu literature o temeljih sodobnega urbanističnega načrtovanja, 2. kritični kvalitativni analizi glavnih dokumentov, ki vsebujejo urbanistične direktive in se uporabljajo v treh največjih mestih Latinske Amerike: Buenos Airesu, Ciudadu de Méxicu in São Paulu (s poudarkom na smernicah v teh dokumentih in kako obravnavajo vse tri omenjene prvine), 3. analizi součinkovanja navedenih treh prvin in 4. oblikovanju končnih ugotovitev.
Keywords: participativni urbanizem, urbanistični instrumenti, urbanistični pojmi, urbanistične teorije
Published in DiRROS: 04.08.2025; Views: 379; Downloads: 197
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Abstract: Avtorici v članku proučujeta ukrajinski art nouveau v okviru njegovega vseevropskega razvoja v arhitekturi poznega 19. in zgodnjega 20. stoletja. Z navedenim slogom so posamezni narodi izražali identiteto. Avtorici sta postavili hipotezo, da razvoj tega sloga v arhitekturi Poltave na začetku 20. stoletja izraža identiteto mesta in narodno identiteto prebivalcev ter ponazarja način izražanja narodne zavesti z arhitekturo. Opredelili sta in ponazorili posebnosti tega sloga kot izraza narodnih prvin v arhitekturi Poltave na začetku 20. stoletja. Njuna raziskava je temeljila na metodah kulturološkega pristopa v okviru splošnega kulturnega razvoja mesta. Avtorici sta predstavili tudi splošne značilnosti razvoja arhitekturnega sloga v Poltavi na začetku 20. stoletja in položaj ukrajinskega art nouveauja v polistilizmu proučevanega obdobja. Na koncu sta analizirali vpliv ukrajinskega art nouveauja zgodnjega 20. stoletja na nadaljnji razvoj arhitekture v Poltavi.
Keywords: ljudska arhitektura, urbanistična politika, polistilizem, ukrajinski art nouveau, identiteta kraja
Published in DiRROS: 04.08.2025; Views: 371; Downloads: 217
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Abstract: Avtorici sta se v članku osredotočili na starostnike, ki so zaradi svojega zdravstvenega stanja ter fizičnih in družbenoekonomskih značilnosti bolj ranljivi z vidika posledic podnebnih sprememb kot druge skupine prebivalstva. V svetu sta opazna dva trenda: naraščanje podnebnih sprememb in staranje prebivalstva, zlasti v mestih. Povezave med navedenima skrb vzbujajočima trendoma v teoriji in praksi niso jasne, zato so nujne splošne smernice, ki so preproste za uporabo ter bi vladam, ustanovam in skupnostim omogočile zadevne rešitve. Avtorici sta zato na podlagi kritičnega pregleda literature predstavili sedem tematskih področij na različnih ravneh, ki so poglavitna za načrtovanje starosti prijaznih mestnih območij, odpornih proti podnebnim spremembam: okoljsko varnost, obveščanje in družbeno angažiranost ter zdravstvene in socialne službe na ravni mesta, okolico in prevoz na ravni sosesk ter javne površine in toplotno udobje in stanovanjske objekte na ravni skupin stanovanjskih zgradb. Predstavitev povezav med omenjenima trendoma v okviru, predstavljenem v tem članku, prispeva h globalnemu ozaveščanju, oblikovanju ukrepov in usmerjanju politik.
Keywords: podnebne spremembe, urbanistična politika, trajnostni razvoj, staranje prebivalstva, starosti prijazno mesto
Published in DiRROS: 04.08.2025; Views: 460; Downloads: 232
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