First-principles calculations based on density functional theory (DFT) are used to calculate the structural, elastic and thermodynamic properties of the supersaturated solid-solution AgNi10 alloy, ...applied mainly to electrical contact materials. In this work, for the exchange-correlation energy, the generalized gradient approximation (GGA) functional is used. The calculated structural and electronic properties of supersaturated solid-solution AgNi10 alloys show that the occupation of Ni in the Ag lattice is ordered. All single-crystal elastic stiffness constants of the energetically and mechanically optimized stable AgNi10 model are calculated using the finite strain method and using the Voigt-Reuss-Hill approximation. Various anisotropic indices like the universal anisotropic index, shear anisotropic index, directional dependence of Young’s modulus, bulk modulus and others are calculated to study the elastic anisotropy. The strong anisotropy in the elastic properties of AgNi10 was confirmed. Phonon dispersions were carried out, showing that the AgNi10 crystal has dynamic stability. The Debye temperature is calculated from the elastic data by estimating the average sound velocity in the AgNi10. Furthermore, the vibrational thermodynamic properties (free energy, enthalpy, entropy and heat capacity) of AgNi10 are obtained successfully.
A new refractory alloy, HfMoNbTiCr, was obtained by replacing Zr with Cr or Mo in the HfMoNbTiZr or HfNbTiCrZr alloys using vacuum arc melting. The phase components, microstructures and compressive ...properties of the alloy in the as-cast and annealed states were investigated. The results showed that the phase components changed from a single BCC phase in HfMoNbTiZr and BCC+Laves phases in HfNbTiCrZr to multiple phases – primarily two BCC phases and two cubic Laves phases – in HfMoNbTiCr. Notably, the yield and ultimate compressive strength of the as-cast alloy significantly increased from 1719 and 1803 MPa to 1851 and 2489 MPa, without a decrease in the ductility. The stress fields induced by Mo and the Cr-containing Laves phases were responsible for the enhanced strength, while the stiff network-like framework composed of intrinsically-strong Cr-containing Laves phases may have played a vital role in retaining the ductility.
One of the friction-stir welding (FSW) limitations is joining thin sheets in sheet-metal manufacturing. To solve this limitation, thicker sheets can be welded with FSW and then rolled to a thinner ...thickness. This can improve the mechanical properties and save the weld zone soundly. In this work, 3-mm aluminum sheets were joined with FSW. The microstructure and mechanical properties of the samples were assessed at various rotational speeds (w) and travel speeds (v). Then, the welded samples were cold worked (CW) by rolling them at different percentages so that the samples were 2 mm and 1 mm thick. The effects of welding and post rolling on the mechanical properties and a failure analysis were deliberated. It was shown that welding reduces the transverse ultimate tensile strength (UTS) of FSWed samples by up to 29 % compared to the UTS of the base metal (BM), while rolling FSWed samples increased the UTS of the cold-worked FSWed samples by up to 94.7 % in comparison to the UTS of FSWed samples. Also, during the tensile test of the specimens FSWed at a lower travel speed, a fracture occurred at the stir zone (SZ)/thermo-mechanically affected zone (TMAZ) interface, on the advancing part; however, at a higher travel speed, it occurred at the interface of the heat-affected zone (HAZ) and TMAZ, on the retreating part. Moreover, during the tensile test of the cold-worked FSWed samples, the failure took place at the HAZ and the interface of the SZ and TMAZ, respectively. The UTS was risen by increasing the cold work. The UTS of a specimen FSWed at 50 mm/min and 1200 min–1 went up from 76 MPa to 124 MPa due to 33-% cold work and to 148 MPa due to 66-% cold work; meanwhile, the fracture occurred at the SZ/TMAZ interface or TMAZ of most of the post-rolled FSWed samples.
V članku avtorica analizira in ovrednoti dva zgleda razčlenjevalnih meril za ocenjevanje razlagalnih/utemeljevalnih sestavkov, in sicer Meril Holly L. Jacobs et al. (1981) in Navodil za ocenjevanje ...Vicki Spandlove et al. (1990). Avtorica prispevka je obravnavana merila izbrala zato, ker so med učitelji in učiteljicami še vedno zelo priljubljena. Pri pretresanju dobrih in slabih plati meril se osredotoča na lastnosti opisnikov. V skladu s priporočili Splošnega evropskega jezikovnega okvira/SEJO (2001: 205–207) ugotavlja, do kakšne mere so dorečeni, jasni, kratki in neodvisni. Analiza razkriva, koliko sta si zgleda meril podobna in v čem se razlikujeta, obravnava njune dobre in šibke plati in pripelje do zaključka, da bi učitelji in učiteljice morali navodila za ocenjevanje kritično ovrednotiti, po potrebi izboljšati in prilagoditi izobraževalnemu kontekstu, v katerem delujejo, preden jih začnejo uporabljati.
The objective of this work was to study the suitability of three types of cast iron for the manufacture of a ship engine: EN-GJS-500-7U for the manufacture of the engine block, EN-GJS-400-15U for the ...cylinder head and EN-GJL-200 for the liner. Tensile tests were carried out to obtain the ultimate tensile strength (UTS) of each material. The results for the UTS were: 460 MPa for EN-GJS-500-7U, 390 MPa for EN-GJS-400-15U and 170 MPa for EN-GJL-200. Likewise, Brinell-hardness measurements were carried out and the elements present in the materials were determined with spectrometry. Finally, the size of graphite particles in each sample was determined.
Translations of instruments for measuring quality of life developed in certain, mostly more developed, parts of the world usually do not cover regionally specific aspects of health-related quality of ...life, even after transcultural validation. The aim of this study was to develop and validate a reliable questionnaire in Serbian, Croatian, Bosnian, and Montenegrin languages suitable for measuring health-related quality of life in adults.
The study was of a cross-sectional type, assessing the reliability and validity of a newly developed questionnaire for measuring health-related quality of life (HRQoL) in adults residing in western Balkan states (WB-HRQoL). It was conducted on a sample of 489 adults from Serbia, Croatia, Bosnia & Herzegovina, and Montenegro, with a mean age of 52.2±14.4 years and a male/female ratio of 195/294 (39.9%/60.1%).
The definitive version of the WB-HRQoL scale with 19 items showed very good reliability, with Cronbach's alpha 0.905. The scale was temporally stable, and satisfactory results were obtained for divergent and convergent validity tests. Exploratory factorial analysis brought to the surface four domains of health-related quality of life, namely the physical, psychical, social, and environmental.
The WB-HRQoL scale is a reliable and valid generic instrument for measuring HRQoL that takes into account the cultural specifics of the western Balkan region.
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