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Ključne besede: compounds, 3D electron diffraction
Objavljeno v DiRROS: 17.04.2025; Ogledov: 91; Prenosov: 27
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Povzetek: Aluminium cast alloy AlSi7Mg0.3 is a lightweight metal commonly used in automotive, aeronautical and mechanical applications. It has good corrosion resistance but, under harsh operative conditions, would benefit from additional protection. In this study, a corrosion-protective multilayer coating system for AlSi7Mg0.3 based on hexafluoro-zirconated trivalent chromium coating (Zr-CrCC) and polyacrylic/siloxane-silica (PEHA-SS) coating was developed. The Zr-CrCC was formed by immersion of the substrate in a commercial conversion bath (SurTec® 650). PEHA-SS synthesis was based on organic precursors (2-ethylhexyl acrylate and [3-(methacryloyloxy)propyl]trimethoxysilane) and an inorganic precursor, tetraethyl orthosilicate. After deposition on AlSi7Mg0.3, each coating was first characterised individually, followed by the analysis of the multilayer using scanning electron microscopy and energy-dispersive X-ray spectroscopy. The adhesion of the coatings was evaluated with a cross-hatch cut test. The corrosion studies in sodium chloride solution using electrochemical impedance spectroscopy and salt spray testing showed that the multilayer system is superior to individual Zr-CrCC and PEHA-SS coatings. After 4 months in 0.1 M NaCl, the multilayer-coated samples exhibited the impedance at 10 mHz in the range of GΩ cm2, while scribed samples withstood the corrosion attack in a salt spray chamber for one week. Thus, albeit only about 100 nm thick, the Zr-CrCC deposited between the substrate and a 9-micrometre thick barrier sol-gel PEHA-SS coating acts as an active corrosion protection interlayer and contributes to the overall protectiveness of the multilayer system.
Ključne besede: corrosion-protective, aluminium, material
Objavljeno v DiRROS: 17.04.2025; Ogledov: 65; Prenosov: 31
Celotno besedilo (8,28 MB)
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Povzetek: A 68-year-old man was referred due to bilateral hip pain and gradual deterioration of walking. He had mold arthroplasties on both hips at the age of 7 years and has been functioning well for more than 5 decades. However, the original data on operative report and the prostheses were missing. The radiological examination revealed bilateral broken prosthetic material. Thus, stage bilateral revision total hip arthroplasty was performed. A detailed chemical analysis of retrieved mold arthroplasty implants proved that the acrylic material was noted to be the same composition with the difference in appearance likely being related to different thermal treatments originally applied to the implants. As presented in our clinical case, even obsolete implants may have good survivorship. According to the case presented, total hip arthroplasty could be considered an effective option with the desired functional outcome when conservative and joint-preserving measures are exhausted
Objavljeno v DiRROS: 17.04.2025; Ogledov: 85; Prenosov: 18
Celotno besedilo (1,87 MB)

Povzetek: Molybdate anions are used as an individual inhibitor or in mixed synergistic combinations added directly to the solution, incorporated as fillers, pigments or nanocontainers into various coatings (sol-gel, anodised, plasma electrolytic, organic and layer double hydroxide coatings), as an agent in pre-treatments or post-treatments or as individual conversion coatings prepared to be exposed to aggressive media. The review addresses the action of molybdate on aluminium alloys in each of these applications. The general chemical characteristics of molybdenum are described with a particular emphasis on aqueous chemistry and the formation of monomer and polynuclear species.
Ključne besede: aluminium, molybdate, corrosion inhibition
Objavljeno v DiRROS: 17.04.2025; Ogledov: 76; Prenosov: 26
Celotno besedilo (8,99 MB)
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Povzetek: Let $W(G)$ be the Wiener index of a graph $G$. We say that a vertex $v \in V(G)$ is a Šoltés vertex in $G$ if $W(G - v) = W(G)$, i.e. the Wiener index does not change if the vertex $v$ is removed. In 1991, Šoltés posed the problem of identifying all connected graphs $G$ with the property that all vertices of $G$ are Šoltés vertices. The only such graph known to this day is $C_{11}$. As the original problem appears to be too challenging, several relaxations were studied: one may look for graphs with at least $k$ Šoltés vertices; or one may look for $\alpha$-Šoltés graphs, i.e. graphs where the ratio between the number of Šoltés vertices and the order of the graph is at least $\alpha$. Note that the original problem is, in fact, to find all $1$-Šoltés graphs. We intuitively believe that every $1$-Šoltés graph has to be regular and has to possess a high degree of symmetry. Therefore, we are interested in regular graphs that contain one or more Šoltés vertices. In this paper, we present several partial results. For every $r\ge 1$ we describe a construction of an infinite family of cubic $2$-connected graphs with at least $2^r$ Šoltés vertices. Moreover, we report that a computer search on publicly available collections of vertex-transitive graphs did not reveal any $1$-Šoltés graph. We are only able to provide examples of large $\frac{1}{3}$-Šoltés graphs that are obtained by truncating certain cubic vertex-transitive graphs. This leads us to believe that no $1$-Šoltés graph other than $C_{11}$ exists.
Ključne besede: Šoltés problem, Wiener index, regular graphs, cubic graphs, Cayley graph, Šoltés vertex
Objavljeno v DiRROS: 17.04.2025; Ogledov: 79; Prenosov: 28
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