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81.
A multiscale approach to deformation and fracture of heat-resistant steel under static and cyclic loading
P. O. Maruščak, Denys Baran, Vladimir Gliha, 2013, izvirni znanstveni članek

Opis: Regularities of static and cyclic deformation, damage and fracture of heat-resistant steel 25Kh1M1F, based on the approaches of physical mesomechanics and 3D interferometry method, are presented in this paper. The applicability of these techniques for different hierarchy levels of deformation was studied. The investigation of scanning microscope photos was conducted for several dissipative structures, fragmentation of the material, localisation of macrodeformation and subsequent failure on macro- and mesolevel. It is shown that the used modern techniques of experimental analysis are very efficient in understanding deformation and damage evolution in materials.
Ključne besede: fracture, heat-resistant steel, cyclic loading, fatigue, plastic deformation
Objavljeno: 18.08.2017; Ogledov: 182; Prenosov: 44
.pdf Celotno besedilo (2,42 MB)
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82.
Altered Wiener indices
Damir Vukičević, Janez Žerovnik, 2005, izvirni znanstveni članek

Opis: Recently Nikolić, Trinajstić and Randić put forward a novel modification ▫$^mW(G)$▫ of the Wiener number ▫$W(G)$▫, called modified Wiener index, which definition was generalized later by Gutman and the present authors. Here we study another class of modified indices defined as ▫$W_{min,λ}(G) = ∑(V(G)^λm_G(u,ν)^λ−m_G(u,ν)^{2λ})$▫ and show that some of the important properties of ▫$W(G)$▫, ▫$^mW(G)$▫ and ▫$^λW(G)$▫ are also properties of ▫$W_{min,λ}(G)$▫, valid for most values of the parameter λ. In particular, if ▫$T_n$▫ is any n-vertex tree, different from the n-vertex path ▫$P_n$▫ and the n-vertex star ▫$S_n$▫, then for any λ ≥ 1 or λ < 0, ▫$^W_{min,λ}(P_n) > W_{min,λ}(T_n)>W_{min,λ}(S_n)$▫. Thus for these values of the parameter λ, ▫$W_{min,λ}(G)$▫ provides a novel class of structure-descriptors, suitable for modeling branching-dependent properties of organic compounds, applicable in QSPR and QSAR studies. We also demonstrate that if trees are ordered with regard to ▫$W_{min,λ}(G)$▫ then, in the general case, this ordering is different for different λ.
Ključne besede: mathematics, chemical graph theory, Wiener index, modified Wiener index
Objavljeno: 17.08.2017; Ogledov: 151; Prenosov: 33
.pdf Celotno besedilo (991,46 KB)
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83.
A novel approach to N,N'-dimethyl and N,N'-ethylene bridged dibenzodithiadiazafulvalane
Zdenko Časar, Dominique Lorcy, Ivan Leban, Alenka Majcen Le Marechal, 2002, izvirni znanstveni članek

Opis: A novel approach to electron rich olefins, such as dibenzodithiadiazafulvalenes (DTDAFs) is reported. These compounds have been prepared by alkalination of the benzothiazole-2-thione ring. The first crystal structure of the N,N'-dimethyl dibenzoDTDAF dicationis also reported.
Ključne besede: organic chemistry, benzothiazole, thermal rearrangement, dithiadiazafulvalene, dication
Objavljeno: 17.08.2017; Ogledov: 161; Prenosov: 44
.pdf Celotno besedilo (365,86 KB)
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84.
Structural properties and thermal stability of cobalt- and chromium-doped $α-MnO_2$ nanorods
Romana Cerc Korošec, Polona Umek, Alexandre Gloter, Jana Padežnik Gomilšek, Peter Bukovec, 2017, izvirni znanstveni članek

Opis: $α-MnO_2$ nanorods were synthesized via the hydrothermal decomposition of $KMnO_4$ in an acidic environment in the presence of $Co^{2+}$ and $Cr^{3+}$ ions. Reactions were carried out at three different temperatures: 90, 130 and 170 °C. All prepared samples exhibit a tetragonal $MnO_2$ crystalline phase. SEM–EDS analysis shows that cobalt cations are incorporated to a higher degree into the $MnO_2$ framework than chromium ions, and that the content of the dopant ions decreases with increasing reaction temperature. The oxidation of $Co^{2+}$ to $Co^{3+}$ during the reaction was proved by an XANES study, while EXAFS results confirm that both dopant ions substitute $Mn^{4+}$ in the center of an octahedron. The K/Mn ratio in the doped samples synthesized at 170 °C is significantly lower than in the undoped samples. Analysis of an individual cobalt-doped $α-MnO_2$ nanorod with HAADF-STEM reveals that the distribution of cobalt through the cross-section of the nanorod is uniform. The course of thermal decomposition of the doped nanorods is similar to that of the undoped ones. Dopant ions do not preserve the $MnO_2$ phase at higher temperatures nor do they destabilize the cryptomelane structure.
Ključne besede: $α-MnO_2$, manganese dioxide, doping, EXAFS, nanorods, XANES
Objavljeno: 10.08.2017; Ogledov: 303; Prenosov: 53
.pdf Celotno besedilo (8,24 MB)
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85.
Effects of ultrasound irradiation on the preparation of ethyl cellulose nanocapsules containing spirooxazine dye
Julija Volmajer Valh, Simona Vajnhandl, Lidija Škodič, Aleksandra Lobnik, Matejka Turel, Bojana Vončina, 2017, izvirni znanstveni članek

Opis: This article presents the influence of low frequency, high intensity ultrasonic irradiation on the characteristics (average size, polydispersity index) of ethyl cellulose nanocapsules encapsulating a photochromic dye. Photochromic nanocapsules were prepared by the emulsion-solvent evaporation method. The acoustic densities entering the system were systematically studied with respect to their abilities to modify and reduce the average sizes and polydispersity indexes of the nanocapsules. Scanning electron microscope, confocal laser microscope, and dynamic light scattering were utilised to characterise the structure, shape, size, and polydispersity of ethyl cellulose photochromic nanocapsules. We were able to tailor the size of the photochromic nanocapsules simply by varying the acoustic densities entering the system. At an acoustic density of 1.5 W/mL and 60 s of continuous irradiation, we were able to prepare an almost monodispersed population of the nanocapsules with an average size of 193 nm.
Ključne besede: encapsulation, ethyl cellulose microcapsules, nanocapsules
Objavljeno: 09.08.2017; Ogledov: 376; Prenosov: 53
.pdf Celotno besedilo (3,31 MB)
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86.
Dependence of warm or cold feeling and heat retention ability of knitwear from digital print parameters
Mladen Stančić, Dragana Grujić, Dragoljub Novaković, Nemanja Kašiković, Branka Ružičić, Jelka Geršak, 2014, izvirni znanstveni članek

Opis: Textile materials are increasingly being subjected to the process of printing. The printing process with its parameters significantly affects the properties of textile materials and clothes made from these materials. This paper examines the effect of the parameters of digital printing on thermo-physiological characteristics of printed textile materials. As the essential print parameters were selected tone value and a different number of passes. In this research were used knitted fabric materials of 100% cotton fibers (100% CO), 100% polyester fibers (100% PES) and their mixture (50%CO/50% PES). The influence of print parameters to thermo-physiological properties of the material is evaluated through a warm or cold feeling and heat retention ability. Results of the research demonstrated that, in addition to material composition, the printing process with its parameters have a significant influence on the thermo-physiological characteristics of textile materials.
Ključne besede: digital printing, textile materials, thermo-physiological comfort, warm of cold feeling, heat retention ability
Objavljeno: 09.08.2017; Ogledov: 194; Prenosov: 32
.pdf Celotno besedilo (934,30 KB)
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87.
Force measurements on teeth using fixed orthodontic systems
Rebeka Rudolf, Janko Ferčec, 2013, pregledni znanstveni članek

Opis: The fixed orthodontic appliance consists of brackets that are bonded to the teeth. When the wire is engaged in the slot of the brackets, it generates forces for orthodontic tooth movement. The change in periodontal blood supply provides a biological response which leads to remodelling of the alveolar bone and the orthodontic tooth movement. Many variables influencing orthodontic treatment cannot be controlled fully, such as growth and tissue response to appliances. However, the force placed on the tooth should be a controllable variable, and a careful study of the physics underlying clinical applications can help in reducing undesirable side effects. The properties of orthodontic wires such as: strength, stiffness, elasticity and spring-back define their clinical usefulness. The ideal orthodontic wire should exhibit the following properties: large spring-back, low stiffness, good formability, high stored energy, biocompatibility and environmental stability, low surface friction, and the capability of being welded or soldered to auxiliaries. The ideal arch wire has not been introduced yet. Once the wire is activated or bent, it is the unloading or deactivating forces that produce the orthodontic tooth movement. For these reasons, it is necessary to know the force level caused by each individual wire used in orthodontic treatment. Finally, the purpose of this paper is a presentation of force measurements which are generated by different super-elasticity NiTi wires.
Ključne besede: force measurements, orhodontic system, teeth, NiTi alloys
Objavljeno: 09.08.2017; Ogledov: 185; Prenosov: 36
.pdf Celotno besedilo (1,33 MB)
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88.
Determination of microstructural changes by severely plastically deformed copper-aluminum alloy
Nebojša Romčević, M. Gilić, Ivan Anžel, Rebeka Rudolf, Miodrag Mitrić, M. Romčević, B. Hadžić, D. Joksimović, Milica Petrović Damjanović, Matija Kos, 2014, izvirni znanstveni članek

Opis: Our work deals with the problem of producing a complex metal-ceramic composite using the processes of internal oxidation (IO) and severe plastic deformation. For this purpose, Cu-Al alloy with 0.4wt.% of Al was used. IO of sample serves in the first step of the processing as a means for attaining a fine dispersion of nanosized oxide particles in the metal matrix. Production technology continues with repeated application of severe plastic deformation (SPD) of the resulting metal matrix composite to produce the bulk nanoscaled structural material. SPD was carried out with equal channel angular pressing (ECAP), which allowed that the material could be subjected to an intense plastic strain through simple shear. Microstructural characteristics of one phase and multiphase material was studied on internally oxidized Cu with 0.4wt.% of Al sample composed of one phase copper-aluminum solid solution in the core and fine dispersed oxide particles in the same matrix in the mantle region. In this manner AFM, X-ray diffraction and Raman spectroscopy were used. Local structures in plastically deformed samples reflect presence of $Cu$, $CuO$, $Cu_2O$, $Cu_4O_3$ or $Al_2O_3$ structural characteristics, depending on type of sample.
Ključne besede: metals, oxides, atomic force microscopy, Raman spectroscopy, microstructure
Objavljeno: 08.08.2017; Ogledov: 224; Prenosov: 44
.pdf Celotno besedilo (596,63 KB)
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89.
Deformation and energy parameters of fracture of steel of the main gas pipeline
P. O. Maruščak, Sergey Panin, Ulyana Polyvana, Tomaž Vuherer, Anna Guzanová, Janette Brezinová, 2015, izvirni znanstveni članek

Opis: By example of steel 17G1S, the regularities in the impact fracture of Charpy specimens at normal and low temperatures are described. The relationship between the energy parameters of fracture (impact toughness) and the deformation response of the material (the height of shear lips) of the specimens from the pipe steel is established. The micromechanisms of impact fracture of the material are described. At 20 °C and –30 °C, focal splitting of the material was observed on the fracture surface of specimens; at –60 °C, the material failed in a brittle manner by the mechanism of cleavage.
Ključne besede: impact toughness, main gas pipeline, failure analysis
Objavljeno: 08.08.2017; Ogledov: 221; Prenosov: 65
.pdf Celotno besedilo (2,03 MB)
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90.
The correlation between pain perception among patients with six different orthodontic archwires and the degree of dental crowding
Evgenija Marković, Janko Ferčec, Ivana Ščepan, Branislav Glišič, Nenad Nedeljković, Jovana Juloski, Rebeka Rudolf, 2015, izvirni znanstveni članek

Opis: Introduction: Forces generated in orthodontic treatment with fixed appliances create tension and compression zones in the periodontal ligament resulting in a painful experience for patients. In the first phase of orthodontic treatment, when leveling of teeth is needed, nickel-titanium (NiTi) archwires can be completely engaged in brackets, even in the cases of extreme crowding, exerting small forces. There is a great individual variation in the pain perception related to the application of orthodontic forces. Objective: The aim of this study was to investigate the pain perception among patients with dental crowding after insertion of six different NiTi orthodontic archwires as a part of fixed appliances in the first stage of orthodontic treatment. Methods: The study was conducted on a sample of 189 orthodontic patients receiving one of six different either superelastic or heat activated NiTi archwires, in the first phase of orthodontic treatment. Pain perception was evaluated in groups of patients with different degree of crowding. The modified McGill Pain Questionnaire with Visual Analogue Scale was used to evaluate the quality and intensity of pain. Statistical analysis was performed using simple descriptive statistics, and Pearson`s chi-square test with statistical significance of p<0.05. Results: Majority of patients reported pain as discomfort or pressure of moderate intensity caused by chewing or biting, started within 12 hours, carried on for 3-4 days, and decreased over time without self-medication. Conclusion: No correlation was found between pain perception among patients with different types of NiTi archwires and the degree of crowding.
Ključne besede: nickel-titanium archwires, pain, dental crowding, orthodontics
Objavljeno: 04.08.2017; Ogledov: 227; Prenosov: 45
.pdf Celotno besedilo (258,88 KB)
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