ISTRAŽIVANJE UTJECAJA USPJEHA NA STUDIJU NA ODABIR STRUČNE SPECIJALIZACIJE

The aim of the research presented in this paper was to identify the relation of mechanical engineering students’ individual motives and their choice of specialty to success in their studies. The research includes consideration of motivational factors from a number of aspects. The results suggest a connection between academic success and the motives of professional advancement, success in the profession, achieving perceptible success at work, opportunities for hierarchical advancement in a company and others. In accordance with the expressed motives, the results highlight the importance of individual specialties for students depending on the success achieved in the course of their studies.Cilj je istraživanja prikazanog u ovom radu utvrditi povezanost između pojedinačnih motiva studenata strojarstva i njihovog odabira specijalizacije s obzirom na uspjeh u tijeku studija. Istraživanje uključuje razmatranje motivacijskih čimbenika s različitih gledišta. Rezultati upućuju na povezanost između uspjeha na studiju i motiva profesionalnog napredovanja, uspjeha u struci, postignuća vidljivog uspjeha na poslu, mogućnosti hijerarhijskog napredovanja u tvrtki i drugih. U skladu s izraženim motivima, rezultati upućuju na važnost pojedine specijalizacije za studente ovisno o postignutom uspjehu u tijeku studij

Solar Spectral Lines (»Solar Halo«) – Healing or Harmful for The Retina?

The sungazing method has been known for thousands of years as healing method based on chromotherapeutic principle. Our examinations on the island of Rab show that it is acceptable only if applied 10 min before the sunset. Gazing has to be directed towards the green-yellow part of the spectrum, since the remaining part of the sun halo contains harmful energy. However, authors suggest that it would be preferable to use spectacles with medical filters transmitting wavelight of green-yellow colour, especially for treatment of macular degeneration

Primjena automatskog rafiniranja računalne mreže u Numeričkoj mehanici fluida na problemima turbulentnog toka i izmjene topline

Most processes occurring in devices in air-conditioning systems require fluid flow and heat exchange, and the functioning of these devices is crucially dependent on their understanding. Computational Fluid Dynamics is a modern tool which enables development engineers to simulate the physics of processes on a computer. Such simulations may contain errors because the original problem has been replaced by a simplified discrete problem, solved on a mesh of non-overlapping control volumes and assuming certain solution behaviour in every control volume of the modelled domain. This paper presents the advantages of adaptive-mesh refinement which helps engineers get accurate solutions without their intervention by modifying the mesh where higher accuracy is needed. The potential of the method is shown on some examples often found in engineering practice.Strujanje fluida i izmjena topline su važni procesi u klimatizacijskim uređajima, stoga je njihovo funkcioniranje vrlo vezano uz razumijevanje procesa strujanja i izmjene topline. Numerička mehanika fluida (CFD) je moderni alat koji inženjerima omogućuje simuliranje fizike procesa na računalu. No, takve simulacije mogu sadržavati grješke zato jer se sustav parcijalnih diferencijalnih jednadžbi zamjenjuje s pojednostavljenim diskretnim problemom, koji se rješava na mreži ne-preklapajućih kontrolnih volumena, uz pretpostavku ponašanja rješenja u kontrolnom volumenu domene. U ovom članku iznesene su prednosti lokalnog rafiniranja računalne mreže koji omogućava inženjerima dobivanje točnih rješenja matematičkog modela automatski i bez njihove intervencije kroz automatsku modifikaciju računalne mreže na mjestima gdje je potrebna veća točnost. Mogućnosti metode su prikazane na primjerima prisutnima u inženjerskoj praksi

Impact of carbon dioxide on Ivanić oilfield in tertiary oil recovery phase

Godišnja proizvodnja nafte u Hrvatskoj s više od 30 naftnih polja je nešto veća od 500 000 tona. Tijekom proteklih 50 godina iz naftnih ležišta u Hrvatskoj ostvaren je prosječan iscrpak nafte od 32,6% utvrđenih rezervi nafte. Sadašnja cijena nafte na svjetskom tržištu potencira primjenu tercijarnih metoda povećanja iscrpka nafte. Ukoliko se iz postojećih ležišta nafte u Hrvatskoj uz te metode poveća iscrpak nafte za 3%, to dovodi do povećanja godišnje proizvodnje od 15 000 tona nafte. U svjetskoj praksi sve zastupljenija je proizvodnja nafte tercijarnim metodama pri čemu utiskivanje ugljičnog dioksida u naftna ležišta ima najveću primjenu. Na temelju laboratorijskih ispitivanja primjene tercijarnih metoda povećanja iscrpka iz naftnih ležišta u Hrvatskoj utiskivanje ugljičnog dioksida je odabrano kao najpovoljnija metoda povećanja iscrpka nafte iz ležišta naftnog polja Ivanić. Tijekom utiskivanja ugljičnog dioksida u naftno ležište mijenja se njegovo agregatno stanje iz kapljevitog u plinsko ili pregrijano stanje. Mjereni podaci o ugljičnom dioksidu u laboratorijskim uvjetima i uvjetima utiskivanja u ležište nažalost odstupaju. S obzirom na to da su mjerenja u bušotinskim uvjetima skupa, a neki puta i tehnološki neizvediva, za poznavanje stanja ugljičnog dioksida u bušotinskim uvjetima uzimaju se različite aproksimacije uz upotrebu raznovrsnih jednadžbi stanja. Izmjereni podaci o faznom stanju ugljičnog dioksida u širokom rasponu p,T uvjeta tijekom njegova utiskivanja u ležišta naftnog polja Ivanić tijekom pilot projekta željeli su se aproksimirati nekom od brojnih jednadžbi stanja i ne mogu se na nekom drugom ležištu koristiti. Od brojnih kubičnih jednadžbi stanja odabrane su van der Waalsova, Redlich-Kwongova, Soave-Redlich-Kwongova, Peng-Robinsonova, Valderrama-Cisternasova, Patel-Tejina, Lawal-Lake- Silberbergova i Martin-Houova jednadžba. Nakon sveobuhvatne analize mjerenih i računatih vrijednosti u širokom rasponu p,T uvjeta preporučene su jednadžbe stanja za proračunavanje faznih stanja ugljičnog dioksida kod njegova utiskivanja u ležišta naftnog polja Ivanić.Current annual oil production in Croatia on more than 30 oilfields, amounts to a little more than 0.5 million t per year. In the last 50 years, the realized oil recovery factor from the oil reservoirs has on average amounted to 32.6% of original oil in place. The currently favourable oil price increases the need for higher oil recovery from existing oilfields through the implementation of tertiary oil recovery methods. As for Croatia, a 3% increase in the oil recovery factor from current oil reservoirs, obtained due to the implementation of tertiary oil recovery methods, increases annual oil production by 15 000 t. Although tertiary oil recovery methods (EOR methods) are becoming more common worldwide, carbon dioxide injection in oil reservoirs is the most implemented EOR method. Based on the laboratory test results of the applications of tertiary oil recovery methods on oil reservoirs in Croatia, the carbon dioxide injection process was chosen as an appropriate method for increasing oil production on the Ivanić oil field. During the injection stage, carbon dioxide changes the state of the matter from liquid to gaseous or supercritical state. Unfortunately, the measured carbon dioxide injection results and laboratory test results differ. In situ measurements are very expensive and sometimes impractical; therefore, various approximations are taken into account with numerous equations of state. The aim was to approximate an equation of state on the measured data, for a wide range of p,T conditions, during a pilot project of carbon dioxide injection on the Ivanić oilfield reservoir. Among numerous cubic equations of state, van der Waals, Redlich-Kwong, Soave-Redlich-Kwong, Peng-Robinson, Valderrama-Cisternas, Patel-Teja, Lawal-Lake- Silberberg and Matin and Hou equation of state. After comprehensive comparisons and analysis of the values measured and calculated for a wide range of p,T conditions during carbon dioxide injection on the Ivanić oilfield, some of equations of state were recommended for determinations carbon dioxide changes of state

WIND PERSISTENCE AT THE ADRIATIC

Using anemograph data from 8 stations in the Adriatic area and two stations in the interior of Croatia the main characteristics of wind persistence were delineated. For several thresholds of wind speeds the mean duration of continuous wind blowing and values of 90%, 99% and maximal duration of all cases are presented. For all duration of wind runs the simple function y = A + B/x could be used which connects the probability of occurrence y with the chosen duration of wind run x in hours, and coefficients A and B may be determined by several nomograms and by the annual wind speed. ln the last chapter of the work results on wind direction persistence are also presented

Biofuels - Top Subject

Velik broj predavanja u sekciji B Primjena goriva i zahtjevi kvalitete i zaštite okoliša na prošlogodišnjem 39. stručno-znanstvenom simpoziju GORIVA 2006 obrađivao je teme o biogorivima. Autori su se u radovima bavili aktualnom temom uvođenja biogoriva kao zamjene ili komponente u mineralnim gorivima u uporabi u prometu. O biogorivima su govorili i proizvođači goriva i proizvođači aditiva i kolege s fakulteta baveći se tim gorivima sa strane primjene u vozilima. Tema je aktualna u svijetu, Europi, a postaje i kod nas u Hrvatskoj. Europska komisija je 2003. godine donijela uredbu 2003/30/EC o promociji uporabe biogoriva u prijevozu. Rastom životnog standarda upravo sektor prometa bilježi neprestani porast motornih vozila i potrošnje motornih goriva. Ključni pokretači europskih političara kod donošenja ove uredbe su bili: 1. traženje veće sigurnosti opskrbe energijom u Europi - oslobađanje od dijela uvoza energije iz naftom bogatih zemalja zahvaćenih stalnim ratnim prijetnjama, 2. briga za razvoj poljoprivrede i zbrinjavanje viškova poljoprivrednih proizvoda, kako bi se sačuvala radna mjesta u poljoprivrednom sektoru, te 3. nadasve briga za smanjenje emisije stakleničkih plinova, kako bi se ublažio intenzitet klimatskih promjena.A number of lectures in section B Fuel application, quality and environmental protection requirements on last year’s 39th scientific symposium FUELS 2006 has treated the subject of biofuels. The authors have in their papers treated the topical subject of introducing biofuels as replacement or component in mineral fuels used in traffic and transportation. Biofuels were the topic of both fuel and additive producers, as well as colleagues from the faculty, approaching the subject from the aspect of application in vehicles. The subject has been topical globally, in Europe, and has been becoming so also in Croatia. European Comission has in 2003 passed the regulation 2003/30/EC on promoting biofuel use in transportation. Owing to the growth of the living standard, it is the traffic sector that records a constant increase of motor vehicles and motor fuels consumption. Key motivators of the European politicians in passing the regulation were: 1. seeking greater energy supply safety in Europe – freeing it in part from importing energy from oil-rich countries involved in constant war threats, 2. concern for agricultural development and management of excess agricultural products, in order to preserve workplaces in the agricultural sector, and 3. most of all concern for reducing the emission of greenhouse gases, in order to bring down the intensity of climatic changes

Application of Natural Resources Indicators to Agricultural Land Management in Slovenia

Th e group of indicators to establish the impact of land management measures on natural resources in the agricultural landscapes in Slovenia is discussed and identifi ed. Each chosen natural resource indicator is defi ned regarding indicator status, quality parameters of an indicator and indicator costs. The indicators are divided into two subgroups: abiotic indicators and biodiversity indicators, whereby biodiversity indicators are threatened on tree levels: genetic, species and ecosystem level. Th e result is the synthesis of natural resources indicators with the tabular review of their main characteristics, named indicators personal data. With selected indicator group the evaluation and monitoring of management measures regarding sustainability is possible. The weaknesses of some selected natural resources indicators are discussed and the fact that the indicators characteristics are not stable, but are time and space dependable is taken into consideration

Effectiveness in Prosthodontics with Mechanically Strong, Paltform Switched Implant Systems

Presudno obilježje današnjeg dvodijelnog implantacijskog sustava je mehanički čvrsta, pouzdana površina usatka koja će biti u dodiru s kosti. Tom se zahtjevu može na optimalan način udovoljiti precizno izrađenim spojem s nosačem konusnog oblika (Morseov konus). Taj je spoj s nosačem konusnog oblika vrlo otporan na savijanje i torziju pri obavljanju kliničke funkcije, čime se znatno smanjuje mogućnost kidanja vijaka ili njihova labavljenja. Uz to, spoj s nosačem konusnog oblika omogućava i izradu oblika platforme na koronalnom dijelu usatka. Time se omogućava stvaranje debelog sloja gustog, mekog tkiva oko vrata nosača i prekrivanje preostalog, horizontalnog dijela platforme. Tim se debelim slojem tkiva prikriva boja titana na cervikalnom dijelu fiksne proteze i omogućava da taj dio poprimi boju normalnog tkiva. Takav oblik usatka s platformom također omogućava da se mjesto kontakta implantat-nosač s vanjskog gornjeg ruba pomakne prema središtu ramena implantata, čime se dobiva biološka širina u smjeru okomitom na uzdužnu os implantata. Tako se održava visina rubnog koštanog grebena (grebenska kost) na koronalnom vrhu ramena implantata - što ima presudnu ulogu u stvaranju i dugoročnom održavanju papila. Uz to, oblik implantata s platformom olakšava postavljanje nosača u submukozu i sprječava utiskivanje mekog tkiva u područje kontakta između usatka i nosača. Velika čvrstoća i inicijalno mali promjer nosača omogućavaju postizanje: (1) izvrsne estetike i (2) suprastruktura koje su klinički vrlo slične zubu koji je u mostu.A decisive feature of the two-piece implant system of today is a mechanically strong, reliable implant abutment interface. This demand can be optimally achived by a precisely machined, tapered cone abutment (Morse taper) connection. This tapered abutment connection provides high resistance to bending and rotational torque during clinical function which significantly reduces the possibilities of screw fracture of loosening. Additionally, tapered abutement connection causes a platform switched design at the coronal portion of the implant. It enables a thick layer of dense soft tissue to form around the neck of the abutment an dcover the remaining horizontal area of the platform. This thick tissue masks the colour of the titanium that is cervical to the fixed prosthesis and is responsible for normal tissue colour. This platform switched implant design also moves the site of the implant-abutment interface from the outer top margin to the center of the implant shoulder, enabling the establishment of a bilogical width that is perpendicular to the long axis of the implant. The height of the marginal osseous crest (crestal bone) is maintained at the coronal top of the implant shoulder- it plays a decisive role in the formation and long term maintenance of papillas. Additionally, the platform switched design facilitates the mounting of submucosal placed abutments, preventing imapction of soft tissue between the implant-abutment interface. Both the high strength and initial small diameter of the abutment make it possible to obtain: (1) excellent aesthetics and (2) suprastructures that are clinically very similar to tooth borne prostheses

Dizajniranje i sinteza novih derivata tiofenkarbohidrazida, tienopirazola i tienopirimidina s antioksidativnim i antitumorskim djelovanjem

2-Amino-5-acetyl-4-methyl-thiophene-3-carboxylic acid ethyl ester (1) and 5-acetyl-2-amino-4-methylthiophene-3-carbohydrazide (2) were synthesized and used as starting materials for the synthesis of new series of 1-(5-amino-4-(3,5-dimethyl-1H-pyrazole-1-carbonyl)-3-methylthiophen-2-yl) ethanone (3a), 1-(5-amino-4-(4-chloro-3,5-dimethyl-1H-pyrazole-1-carbonyl)-3-methylthiophen-2-yl) ethanone (3b), 1-(4-methyl-2-amino-5-acetylthiophene-3-carbonyl) pyrazolidine-3,5-dione (4), (Z)-N\u27-(4-methyl-2-amino-5-acetylthiophene-3-carbonyl) formohydrazonic acid (5a), (Z)-ethyl-N\u27-(4-methyl-2-amino-5-acetylthiophene-3-carbonylformo hydrazonate (5b), 6-acetyl-3-amino-2,5-dimethylthieno2,3-dpyrimidin-4(3H)-one (8), 5-methyl-3-amino-2-mercapto-6-acetylthieno2,3-dpyrimidin-4(3H)-one (10) and 5-methyl-6-acetyl-2-thioxo-2,3-dihydrothieno2,3-dpyrimidin-4(1H)-one (12) as potential antioxidant and antitumor agents. Pharmacological results showed that compounds 6a, 6b, 8, 10 and 12 exhibited promising antitumor and antioxidant activity.Etilni ester 2-amino-5-acetil-4-metil-tiofen-3-karboksilne kiseline (1) i 5-acetil-2-amino-4-metiltiofen-3-karbohidrazid (2) sintetizirani su i upotrebljeni kao reaktanti u sintezi novih spojeva 1-(5-amino-4-(3,5-dimetil-1H-pirazol-1-karbonil)-3-metiltiofen-2-il) etanona (3a), 1-(5-amino-4-(4-klor-3,5-dimetil-1H-pirazol-1-karbonil)-3-metiltiofen-2-il) etanona (3b), 1-(4-metil-2-amino-5-acetiltiofen-3-karbonil) pirazolidin-3,5-diona (4), (Z)-N\u27-(4-metil-2-amino-5-acetiltiofen-3-karbonil) formohidrazonske kiseline (5a), (Z)-etil-N\u27-(4-metil-2-amino-5-acetiltiofen-3-karbonilformo hidrazonata (5b), 6-acetil-3-amino-2,5-dimetiltieno2,3-dpirimidin-4(3H)-one (8), 5-metil-3-amino-2-merkapto-6-acetiltieno2,3-dpirimidin-4(3H)-ona (10) i 5-metil-6-acetil-2-tiokso-2,3-dihidrotieno2,3-dpirimidin-4(1H)-ona (12) kao potencijalnih antioksidansa i citostatika. Farmakološka ispitivanja ukazuju na to da spojevi 6a, 6b, 8, 10 i 12 imaju značajno antitumorsko i antioksidativno djelovanje

The Role of Financial Constraints in Determining Export Status

In spite of the mounting evidence on the advantages of exporters over firms focused solely on their domestic markets, the source of these differences is yet to be explained. The present contribution analyzes the role of financial constraints as one of the key factors determining firm export status. Through a survey of existing literature and an empirical analysis of Slovenian manufacturing firms the role of financial constraints that limit foreign market access to only a subset of the firms is revealed. It is shown that financial constraints, even when other factors are explicitly considered, determine the firms that will be able to enter into foreign markets and financially constrained firms end up exporting less frequently and smaller quantities than could otherwise be expected