Browsing by Subject "hardness"

Now showing 1 - 8 of 8

Access status: Open Access ,
A note on hardness of multiprocessor scheduling with scheduling solution space tree
(Wydawnictwa AGH, 2023) Dwibedy, Debasis; Mohanty, Rakesh
We study the hardness of the non-preemptive scheduling problem of a list of independent jobs on a set of identical parallel processors with a makespan minimization objective. We make a maiden attempt to explore the combinatorial structure of the problem by introducing a scheduling solution space tree (SSST) as a novel data structure. We formally define and characterize the properties of SSST through our analytical results. We show that the multiprocessor scheduling problem is $\cal {NP}$-complete with an alternative technique using SSST and weighted scheduling solution space tree (WSSST) data structures. We propose a non-deterministic polynomial-time algorithm called magic scheduling (MS) based on the reduction framework. We also define a new variant of multiprocessor scheduling by including the user as an additional input parameter, which we called the multiuser multiprocessor scheduling problem (MUMPSP). We also show that MUMPSP is $\cal {NP}$-complete. We conclude the article by exploring several non-trivial research challenges for future research investigations.
Access status: Open Access ,
Characterization of microstructure and mechanical properties of laser-welded stainless steels
(Wydawnictwa AGH, 2016) Koclęga, Damian; Radziszewska, Agnieszka; Kąc, Sławomir; Zowczak, Włodzimierz; Dębowska, Aleksandra; Jędrusik, Mateusz; Petrzak, Paweł
This work presents the laser welding of dissimilar X12CrCoWVNbN12-2-2 and X10CrNi18-10 steels. This system is of interest, as laser welding offers new flexibility in the joining of metals and laser welds (LWs) and are usually of high quality, they are obtained only after the optimization of process parameters. The aim of the work was to investigate the microstructure, chemical composition, and hardness changes of laser-welded steels. After laser welding, two zones were generated in the processed materials: a fusion zone and a heat-affected zone. Due to solidification, a refinement of the microstructure occurred in the fusion zone. Examinations of the chemical composition of particular melted areas showed the occurrence of Nb-rich precipitations. The laser welding of steels led to increased hardness in the fusion zone (about 240–530 HV0.3).
Access status: Open Access ,
Microstructure of magnesium alloy AZ31 after low-speed extrusion
(2007) Skubisz, Piotr; Skowronek, Tadeusz; Sińczak, Jan
Direct extrusion of magnesium alloy AZ31 and changes in microstructure resultant from low-speed small-reduction extrusion are presented. The results show possibilities of grain refinement and improvement of mechanical properties associated with limited amount of generated deformation heat in aspect of using as-extruded material as a forging stock.
Access status: Restricted ,
Mikrostruktura i właściwości tribologiczne lokalnych wzmocnień kompozytowych typu TiC Fe/L35GSM
(Data obrony: 2015-07-23) Batóg, Paweł
Wydział Odlewnictwa
Access status: Restricted ,
Odporność kompozytów ceramicznych na zużycie ścierne w różnych warunkach pracy
(Data obrony: 2014-07-03) Saferna, Izabela
Wydział Inżynierii Materiałowej i Ceramiki
Access status: Open Access ,
Plastic deformation mechanisms in BCC single crystals and equiatomic alloys: Insights from nanoindentation
(Wydawnictwa AGH, 2024) Dominguez-Gutierrez, Francisco Javier; Papanikolaou, Stefanos; Bonfanti, Silvia; Alava, Mikko
Deformation plasticity mechanisms in alloys and compounds may reveal the material’s capacity towards optimal mechanical properties. We conducted a series of molecular dynamics (MD) simulations to investigate plasticity mechanisms due to nanoindentation in pure tungsten, molybdenum, and vanadium body-centered cubic single crystals, as well as the body-centered cubic, equiatomic, random solid solutions (RSS) of tungsten–molybdenum and tungsten–vanadium alloys. Our analysis focuses on a thorough, side-by-side comparison of dynamic deformation processes, defect nucleation, and evolution, along with corresponding stress–strain curves. We also checked the surface morphology of indented samples through atomic shear strain mapping. As expected, the presence of Mo and V atoms in W matrices introduces lattice strain and distortion, increasing material resistance to deformation and slowing down dislocation mobility of dislocation loops with a Burgers vector of 1/2 ?111?. Our side-by-side comparison displays a remarkable suppression of the plastic zone size in equiatomic W–V RSS, but not in equiatomic W–Mo RSS alloys, displaying a clear prediction for optimal hardening response of equiatomic W–V RSS alloys. If the small-depth nanoindentation plastic response is indicative of overall mechanical performance, it is possible to conceive a novel MD-based pathway towards material design for mechanical applications in complex, multi-component alloys.
Access status: Restricted ,
Polikrystaliczny $Al_{2}O_{3}$ o podwyższonej odporności na kruche pękanie
(Data obrony: 2010-07-09) Nowak, Wojciech
Wydział Inżynierii Materiałowej i Ceramiki
Access status: Open Access ,
The hardness of the independence and matching clutter of a graph
(2016) Ambarcumân, Sasun; Mkrtčân, Vahan V.; Musoân, Vahe L.; Sargsân, Hovhannes
A clutter (or antichain or Sperner family) $L$ is a pair $(V,E)$, where $V$ is a finite set and $E$ is a family of subsets of $V$ none of which is a subset of another. Usually, the elements of $V$ are called vertices of $L$, and the elements of $E$ are called edges of $L$. A subset se of an edge e of a clutter is called recognizing for e, if $s_e$ is not a subset of another edge. The hardness of an edge $e$ of a clutter is the ratio of the size of $e$'s smallest recognizing subset to the size of $e$. The hardness of a clutter is the maximum hardness of its edges. We study the hardness of clutters arising from independent sets and matchings of graphs.