Acta Polytechnica. 2021, vol. 61, no.6
http://hdl.handle.net/10467/100595
2024-03-28T21:08:46ZDirac oscillator in dynamical noncommutative space
http://hdl.handle.net/10467/100616
Dirac oscillator in dynamical noncommutative space
Haouam, Ilyas
In this paper, we address the energy eigenvalues of two-dimensional Dirac oscillator perturbed by a dynamical noncommutative space. We derived the relativistic Hamiltonian of Dirac oscillator in the dynamical noncommutative space, in which the space-space Heisenberg-like commutation relations and noncommutative parameter are position-dependent. Then, we used this Hamiltonian to calculate the first-order correction to the eigenvalues and eigenvectors, based on the language of creation and annihilation operators and using the perturbation theory. It is shown that the energy shift depends on the dynamical noncommutative parameter τ . Knowing that, with a set of two-dimensional Bopp-shift transformation, we mapped the noncommutative problem to the standard commutative one.
2021-01-01T00:00:00ZCavitation wear of Eurofer 97, Cr18Ni10Ti and 42HNM alloys
http://hdl.handle.net/10467/100615
Cavitation wear of Eurofer 97, Cr18Ni10Ti and 42HNM alloys
Rostova, Hanna; Voyevodin, Victor; Vasilenko, Ruslan; Kolodiy, Igor; Kovalenko, Vladimir; Marinin, Vladimir; Zuyok, Valeriy; Kuprin, Alexander
The microstructure, hardness and cavitation wear of Eurofer 97, Cr18Ni10Ti and 42HNM have been investigated. It was revealed that the cavitation resistance of the 42HNM alloy is by an order of magnitude higher than that of the Cr18Ni10Ti steel and 16 times higher than that of the Eurofer 97 steel. Alloy 42HNM has the highest microhardness (249 kg/mm2) of all the investigated materials, which explains its high cavitation resistance. The microhardness values of the Cr18Ni10Ti steel and the Eurofer 97 were 196.2 kg/mm2 and 207.2 kg/mm2, respectively. The rate of cavitation wear of the austenitic steel Cr18Ni10Ti is 2.6 times lower than that of the martensitic Eurofer 97.
2021-01-01T00:00:00ZComparision of the walk techniques for fitness state space analysis in vehicle routing problem
http://hdl.handle.net/10467/100614
Comparision of the walk techniques for fitness state space analysis in vehicle routing problem
Agárdi, Anita; Kovács, László; Bányai, Tamás
The Vehicle Routing Problem (VRP) is a highly researched discrete optimization task. The first article dealing with this problem was published by Dantzig and Ramster in 1959 under the name Truck Dispatching Problem. Since then, several versions of VRP have been developed. The task is NP difficult, it can be solved only in the foreseeable future, relying on different heuristic algorithms. The geometrical property of the state space influences the efficiency of the optimization method. In this paper, we present an analysis of the following state space methods: adaptive, reverse adaptive and uphill-downhill walk. In our paper, the efficiency of four operators are analysed on a complex Vehicle Routing Problem. These operators are the 2-opt, Partially Matched Crossover, Cycle Crossover and Order Crossover. Based on the test results, the 2-opt and Partially Matched Crossover are superior to the other two methods.
2021-01-01T00:00:00ZHydrothermally-calcined waste paper ash nanomaterial as an alternative to cement for clay soil modification for building purposes
http://hdl.handle.net/10467/100593
Hydrothermally-calcined waste paper ash nanomaterial as an alternative to cement for clay soil modification for building purposes
Robert, Ubong Williams; Etuk, Sunday Edet; Agbasi, Okechukwu Ebuka; Umoren, Grace Peter; Akpan, Samuel Sunday; Nnanna, Lebe Agwu
It has been observed that clay soil cannot be used for building design, unless it is modified by firing or with cement. Either method of stabilization can adversely affect the environment and public health just like indiscriminate dumping or open burning adopted in developing countries as the prevalent disposal technique for waste papers. This paper sought to examine the feasibility of using assorted waste papers to derive an alternative stabilizer to Portland Limestone Cement for modification of clay soil into composite materials suitable for building design. Specifically, clay-based composites were fabricated at 0 %, 5 %, 10 %, 15 %, and 20% replacement levels by weight with cement, and then hydrothermally-calcined waste paper ash nanomaterial (HCWPAN). Water absorption, sorptivity, bulk density, thermal conductivity, specific heat capacity, thermal diffusivity, flaking concentration, flexural strength, and compressive strength were investigated for each of the fabricated samples. Irrespective of the stabilizing agent utilized, 10% loading level was found to be the optimum for possession of maximum mechanical strength by the samples. Only samples with the HCWPAN content were found to be capable of reducing building dead loads and improving thermal insulation efficiency over un-stabilized clay material, if applied as walling elements in buildings. Generally, it was revealed that the cement and HCWPAN have comparable influences on the properties of clay soil, thus indicating that HCWPAN could be utilized as an alternative stabilizer to cement. In addition, the preparation of HCWPAN was found to be more energy-saving than that of the cement.
2021-01-01T00:00:00Z