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An Experimental and Simulation Study of Ultrasonic-Assisted MIG Welding Power Supply
No full textThis paper presents the design and control of a digitally regulated MIG welding power supply capable of superimposing ultrasonic-frequency current (20-100 kHz) onto a low-frequency pulsed current (0-500 A, 10 ms period). The proposed topology employs a full-bridge inverter at the primary stage and three Buck converters at the secondary stage, with IGBT modules as switching devices. To ensure stable high-frequency operation, an active snubber and energy feedback circuit are integrated. The control system, implemented on an STM32 microcontroller with PI-based closed-loop regulation, enables flexible waveform modulation and precise current control. System parameters were optimized in MATLAB/Simulink and validated experimentally. Results demonstrate accurate generation of complex current waveforms and improved stability of droplet transfer compared with conventional power supplies. The developed system provides a viable solution for next-generation MIG welding applications requiring high efficiency, reduced spatter, and controllable heat input
Paragenetic interpretation of Ti-clinohumite-bearing marble from Zorovac Creek, Mt. Moslavačka Gora (Croatia) and its petrogenesis
No full textThis study examines impure grey marble occurring as interlayers in amphibolite and diop-side-amphibole schists which belong to the magmatic-metamorphic complex of Mt. Moslavačka Gora in Croatia. The marble is composed mainly of calcite with abundant accessory minerals: dolomite, forsterite, spinel, pargasite, phlogopite, ilmenite, apatite, Ti-clinohumite, tremolite, chlorite, serpentine and talc. Detailed descriptions of mineral assemblages, their textural relationships and mineral chemistry analyses in situ, as well as compositional maps of characteristic mineral assemblages, revealed that the marble experienced at least three different metamorphic stages. These can be summarized as follows: a) the regional metamorphic stage characterised by peak metamorphic stage in granulite facies and a mineral assemblage consisting of calcite + dolomite + forsterite + spinel + pargasite + phlogopite + ilmenite + apatite; b) the stage of subsequent infiltration of an external Ti-rich, fluorinated fluid into the marble giving rise to the origin of Ti-clinohumite, the Ti content of which varies from 0.070 to 0.325 pfu and its XF value, defined as F/(F + OH), is in the range of 0.32 to 0.57; c) the stage of uplift and exhumation of the terrain causing diverse retrograde metamorphic reactions such as the replacement of Ti-clinohumite, spinel and pargasite by chlorite, formation of tremolite on the rims of pargasite and forsterite, as well as the replacement of forsterite by serpentine and talc. Due to the differences in the age determinations of both metamorphisms and magmatic intrusions, good correlation between the occurrence of the Ti-clinohumite bearing marbles of Mt. Moslavačka Gora with those found in surrounding terrains, for instance in Alps (Switzerland/Italy, Austria, Czech Republic) and Rhodope massif (Greece), could not be established at this stage of the investigation
Adhezivno cementiranje cirkonij-oksidnih keramičkih nadomjestaka
No full textCirkonij-oksidna keramika zauzima ključno mjesto u suvremenoj fiksnoj protetici zahvaljujući iznimnim mehaničkim, estetskim i biološkim svojstvima. U svakodnevnom kliničkom radu primjenjuju se različiti protokoli cementiranja ovisno o vrsti nadomjestka, morfologiji preparacije i individualnim zahtjevima slučaja. S obzirom na kemijsku inertnost cirkonijeva dioksida i njegovu polikristaliničnu strukturu za uspješno povezivanje sa zubnim tkivima nužno je poštivanje specifičnih kliničkih postupaka. Najčešće je preporučena tehnika adhezivnog cementiranja, no njegova učinkovitost uvelike ovisi o pravilnoj provedbi svakog koraka protokola. U članku su opisana svojstva cirkonij-oksidne keramike, osnovna načela adhezivnog cementiranja te razlike u odnosu na konvencionalne tehnike. Opisane su indikacije primjene materijala te klinički pro- tokoli cementiranja, uključujući površinsku obradu, vrste cementa i najčešće pogreške koje mogu utjecati na ishod. Posebno je prikazan APC protokol (engl. Airborne-particle abrasion – Primer – Composite resin cement), koji se smatra standardom u adhezivnom cementiranju cirkonij-oksidnih radova. Cilj je članka pružiti pregled znanstveno utemeljenih preporuka i aktualnih kliničkih smjernica koje omogućuju bolju kliničku predvidivost i dugoročan uspjeh terapije
Patogeneza periimplantitisa – kada, kako i zašto?
No full textPeriimplantitis predstavlja jedan od najvećih izazova suvremene stomatologije zbog sve veće upotrebe dentalnih implantata kao rješenja za nadomještanje izgubljenih zuba. Ova bolest upalnog karaktera zahvaća tkiva oko implantata, dovodeći do progresivnog gubitka potpornog koštanog tkiva, što može rezultirati destabilizacijom i gubitkom implantata. Periimplantitis značajno utječe na kvalitetu života pacijenata i predstavlja izazov za stomatološke stručnjake u pogledu dijagnostike, prevencije i liječenja.
Uzročnici periimplantitisa su prvenstveno bakterijski mikroorganizmi koji stvaraju biofilm na površini implantata. Međutim, razvoj bolesti nije uzrokovan isključivo prisutnošću bakterija, već i složenim interakcijama između patogena i imunološkog sustava domaćina. Osim bakterijske infekcije, značajnu ulogu u na- stanku periimplantitisa imaju različiti lokalni i sistemski čimbenici rizika, poput loše oralne higijene, pušenja, metaboličkih bolesti poput dijabetesa, te genetske predispozicije.
Iako su u posljednjih nekoliko godina napravljeni značajni pomaci u razumijevanju periimplantitisa, još uvijek je potrebno provesti dodatna znanstvena istraživanja kako bi se dobila točna, detaljna i jasna slika o mehanizmima nastanka i razvoju bolesti. Takva saznanja omogućila bi razvoj učinkovitijih metoda prevencije i terapije te poboljšala dugoročnu uspješnost dentalnih implantata
Evaluation of Bernoulli Production Lines with Product Quality Inspection and Rework Stations: Analytical Solution and the Finite State Method
No full textMathematical modelling of production systems is a central task of production system engineering, especially when considering the competitiveness and effectiveness of production companies aiming at quality management and customer-oriented production. Two different approaches to the modelling of a Bernoulli production line with product quality inspection and rework stations are presented in this study. In the first case, analytical modelling is introduced based on Markov chains and the formulation of constitutive transition matrices. In the second case, an approximative approach is presented by employing the finite state method and formulating new finite state elements. The validation of the approximative approach is performed based on theoretical production lines, and the main findings are employed in a shipyard’s plate prefabrication line. The issues of computing requirements and quality-quantity coupling are also discussed, indicating the need for further research in the context of improvability analyses and the design of production systems
Determinants of spectator consumption and the prominence of event attributes in behavioural intentions: insights from a non-mega sport tourism event
No full textPurpose – Sport events can boost the local economy, both through the direct consumption of
goods/services and by enhancing the destination’s image. The prominent focus of existing
literature on mega-events contrasts with the need to study non-mega events, considering the
economic benefits for the destination especially when the later are annually hosted. This study
aimed to outline the profile of non-resident spectators (NRS) of a non-mega recurring sport
tourism event, and analyse their consumption determinants and behavioural intentions.
Methodology/Design/Approach – At the Millennium Estoril Open event, 175 questionnaires
were applied to the NRS. Determinants of consumption were calculated with multiple linear
regression for total NRS expenditure. The association between destination/event attributes
and behavioural intentions was calculated using Spearman’s Rho coefficient.
Findings – Overall, older spectators with higher income, who travelled with family, stayed
overnight, and arrived early spend more money at the destination. The significant and positive
effect on behavioural intentions of NRS is substantiated by five event attributes but only one
respecting the destination. Event attributes are integrated into all dimensions of event service
quality, i.e., overall event quality, functional quality, and hedonic quality. It is important to
promote the recurring events’ hedonic attributes, which encourage anticipation for entertainment
activities and boost spectators’ intentions to return. The findings are aligned with the economic
assumption supporting the joint analysis of the short- and long-term economic benefits arising
from the direct expenditure at the destination and the intensification of its image.
Originality of the research – This study integrates the determinants of NRS expenditure and
their behavioural intentions, generating knowledge for designing strategies to promote the
tangible and intangible effects of the event on the destination’s economic development
A tokenized framework for enhancing the integrity and authenticity of tourism reviews
No full textPurpose – This study explores the application of blockchain technology in smart tourism and
presents a model for reducing fake reviews.
Methodology – By utilizing the transparency and immutability features of blockchain
technology, this paper illustrates how artificial intelligence (AI) can be employed to
address and mitigate fraudulent practices within the tourism sector. A prevalent issue today,
particularly in the tourism sector, is the proliferation of fake reviews, undermining trust, and
reliability. The proposed model focuses on reducing fake reviews, thereby bolstering trust in
online reviews through blockchain and AI technology.
Findings – To encourage user participation in submitting reviews, the authors suggest the
implementation of a loyalty token system, whereby users are rewarded with tokens for each
review submitted. Furthermore, the study systematically compares the proposed model with
relevant research, highlighting loyalty tokens as a blockchain-derived incentive feature that
enhances the validity of reviews.
Originality of the research – Proposing a loyalty token-based model and utilizing blockchain
technology in order to reduce fraudulent practices in the tourism industry
Aktualnosti iz projekta “Znanje+Kreativnost = STEM Inspiracija”: Od znatiželje do otkrića: projekt “Znanje + Kreativnost = STEM Inspiracija” u popularizaciji STEM-a
No full textProcjena emisija stakleničkih plinova u sustavima proizvodnje mlijeka u Tunisu primjenom alata CLEANED
No full textThis study assessed greenhouse gas (GHG) emissions from different dairy farming systems in Tunisia using the CLEANED tool (Comprehensive Livestock Environmental Assessment for Improved Nutrition, a Secured Environment and Sustainable Development). A typology of 102 dairy farms across 17 governorates identified three main systems: (i) landless or rainfed farms with limited forage, (ii) mixed rainfed–irrigated farms with moderate intensification, and (iii) large irrigated farms with diversified feeding. Emissions per kilogram of milk ranged from 0.83 kg CO₂-eq in Cluster II to 0.91 kg CO2-eq in Cluster III (pU ovom su istraživanju procijenjene emisije stakleničkih plinova (GHG) iz različitih sustava proizvodnje mlijeka u Tunisu primjenom alata CLEANED (Comprehensive Livestock Environmental Assessment for Improved Nutrition, a Secured Environment and Sustainable Development). Na temelju tipologije 102 mliječne farme u 17 guvernerata identificirana su tri glavna sustava: (i) farme bez vlastitih površina ili s proizvodnjom na kišnom režimu uz ograničenu dostupnost krmiva, (ii) mješovite farme s kombinacijom kišnog i navodnjavanog uzgoja uz umjerenu razinu intenzifikacije te (iii) velike navodnjavane farme s diverzificiranom hranidbom. Emisije po kilogramu mlijeka kretale su se od 0,83 kg CO2-ekv. u klasteru II do 0,91 kg CO2-ekv. u klasteru III (