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Population-based improvement heuristic with local search for single-row facility layout problem
Soumen Atta, Priya Ranjan Sinha Mahapatra, 2019, original scientific article

Abstract: The Single-Row Facility Layout Problem (SRFLP) is a well-known combinatorial optimization problem. The objective of SRFLP is to find out the arrangement of facilities with given lengths on a line so that the weighted sum of the distances between all pairs of facilities is minimized. This problem is known to be NP-hard. Hence, a population-based improvement heuristic algorithm with local search is presented in this article to solve SRFLP. The proposed algorithm works well also for the Single-Row Equidistant Facility Layout Problem (SREFLP), where the length of each facility is equal. The computational efficiency of the proposed algorithm is checked with the instances of sizes ranging from 5 to 300 available in the literature for SRFLP and SREFLP. The obtained results are compared to those from different state-of-the-art algorithms. The proposed algorithm achieves best known solutions to date for every instance considered in this article in reasonable computational time.
Keywords: Single-row facility layout problem (SRFLP), single-row equidistant facility layout problem (SREFLP), population-based heuristic, improvement heuristic, local search
Published in RUNG: 17.04.2023; Views: 891; Downloads: 0
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Solving maximal covering location problem using genetic algorithm with local refinement
Soumen Atta, Priya Ranjan Sinha Mahapatra, Anirban Mukhopadhyay, 2018, original scientific article

Abstract: The maximal covering location problem (MCLP) deals with the problem of finding an optimal placement of a given number of facilities within a set of customers. Each customer has a specific demand and the facilities are to be placed in such a way that the total demand of the customers served by the facilities is maximized. In this article an improved genetic algorithm (GA)-based approach, which utilizes a local refinement strategy for faster convergence, is proposed to solve MCLP. The proposed algorithm is applied on several MCLP instances from literature and it is demonstrated that the proposed GA with local refinement gives better results in terms of percentage of coverage and computation time to find the solutions in almost all the cases. The proposed GA-based approach with local refinement is also found to outperform the other existing methods for most of the small as well as large instances of MCLP.
Keywords: Facility location problem, Covering location problem, Maximal covering location problem (MCLP), Genetic algorithm (GA), Local refinement
Published in RUNG: 17.04.2023; Views: 923; Downloads: 0
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Spectroscopic investigation of oxygen vacancies in CeO[sub]2 : dissertation
Thanveer Thajudheen, 2021, doctoral dissertation

Abstract: A unique material, ceria (CeO2), which is widely applied in automobile exhaust catalysts, is functional due to presence of defects in its crystal structure. Furthermore, the structural defects dictate electrical and chemical properties of ceria. The creation of intrinsic oxygen vacancies in ceria is responsible for oxygen-ion conductivity in solid oxide fuel cells. This unfolds the keen interest in ceria defects. Using the analytical technique cathodoluminescence spectroscopy (CLS) we can characterize ceria for its band gap and the defect states within the band gap. Since CLS has a high spatial resolution, high sensitivity to low concentration of defects and ability to obtain depth resolved information it is an obvious technique of choice. The first part of the thesis is an introduction to the topic and description of the experimental techniques. Importance of ceria as a multifaceted material finding applications in areas spanning from energy production and conversion to biomedical applications is detailed. CLS as a tool to understand defect-related optical properties and advancement in the CL detection systems are discussed. To study the relationship between local structure and its impact on CL emission spectra, an X-ray absorption spectroscopy techniques were used. The X-ray absorption near edge structure (XANES) and the Extended x-ray absorption fine structure (EXAFS) techniques are summarized. The second part discusses CL emission from ceria. Initially, CL emission from reduced ceria and its dependence on oxygen vacancy concentration are presented. The origin of emission was attributed to different configurations of the oxygen vacancies and polarons. The recent F center description in ceria was adopted here. The intriguing observation of CL emission quenching as a function of oxygen vacancy concentration was explained on the basis of a relative change in population of F centers in ceria. This demonstrated the relevance of local structure for the CL emission in ceria. In order to have a better understanding of the system, La-doped ceria was proposed as a model system. A precise control over the stoichiometry helped to achieve a desired oxygen vacancy concentration. The CL emission behavior, as observed in reduced ceria, was replicated in the case of La-doped ceria and the analysis revealed that F+ centers favor CL emission whereas F0 centers are disadvantageous. The local structure investigation using EXAFS analysis of both cations Ce and La (K-Edge) showed distortion from the fluorite symmetry and corroborated the F center description of oxygen vacancies in ceria. Our results provide an experimental evidence for F center description involving oxygen vacancies and polarons.
Keywords: ceria, cathodoluminescence spectroscopy, local structure distortion, EXAFS analysis, La doped ceria, luminescence quenching, F centers, dissertations
Published in RUNG: 25.11.2021; Views: 2562; Downloads: 104
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In-situ Fe K-edge XAS analysis of ionic species in the highly-concentrated FeCl2 aqueous solutions for Power-to-Solid energy storage technology
Uroš Luin, Iztok Arčon, Matjaž Valant, unpublished conference contribution

Keywords: In situ Fe K-edge XAS, highly-concentrated FeCl2 aqueous solutions, local structure, coordination number, Power-to-Solid, energy storage technology
Published in RUNG: 28.01.2021; Views: 2885; Downloads: 66  (1 vote)
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Renewables in buildings and local communities : Buildings Energy Efficiency
Henrik Gjerkeš, invited lecture at foreign university

Keywords: Renewable energy sources, sustainable development, buildings, local communities
Published in RUNG: 03.12.2020; Views: 2283; Downloads: 0
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Comparison and complementary use of in situ and remote sensing aerosol measurements in the Athens Metropolitan Area
S. Vratolis, Griša Močnik, Konstantinos Eleftheriadis, 2020, original scientific article

Abstract: In the summer of 2014 in situ and remote sensing instruments were deployed in Athens, in order to study the concentration, physical properties, and chemical composition of aerosols. In this manuscript we aim to combine the measurements of collocated in situ and remote sensing instruments by comparison and complementary use, in order to increase the accuracy of predictions concerning climate change and human health. We also develop a new method in order to select days when a direct comparison on in situ and remote sensing instruments is possible. On selected days that displayed significant turbulence up to approximately 1000 m above ground level (agl), we acquired the aerosol extinction or scattering coefficient by in situ instruments using three approaches. In the first approach the aerosol extinction coefficient was acquired by adding a Nephelometer scattering coefficient in ambient conditions and an Aethalometer absorption coefficient. The correlation between the in situ and remote sensing instruments was good (coefficient of determination equal to 0.69). In the second approach we acquired the aerosol refractive index by fitting dry Nephelometer and Aethalometer measurements with Mie algorithm calculations of the scattering and absorption coefficients for the size distribution up to a maximum diameter of 1000 nm obtained by in situ instruments. The correlation in this case was relatively good ( equal to 0.56). Our next step was to compare the extinction coefficient acquired by remote sensing instruments to the scattering coefficient calculated by Mie algorithm using the size distribution up to a maximum diameter of 1000 nm and the equivalent refractive index (), which is acquired by the comparison of the size distributions obtained by a Scanning Mobility Particle Sizer (SMPS) and an Optical Particle Counter (OPC). The agreement between the in situ and remote sensing instruments in this case was not satisfactory ( equal to 0.35). The last comparison for the selected days was between the aerosol extinction Ångström exponent acquired by in situ and remote sensing instruments. The correlation was not satisfactory ( equal to 0.4), probably due to differences in the number size distributions present in the air volumes measured by in situ and remote sensing instruments. We also present a day that a Saharan dust event occurred in Athens in order to demonstrate the information we obtain through the synergy of in situ and remote sensing instruments on how regional aerosol is added to local aerosol, especially during pollution events due to long range transport.
Keywords: Aerosol mixing in the vertical, In situ — Remote sensing comparison, Regional aerosol addition to local aerosol
Published in RUNG: 09.04.2020; Views: 2980; Downloads: 0
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Drifting through Cityscapes : Mapping the Local
Szabolcz Kisspal, Allan Siegel, Eszter Lazar, Olivera Batajić Sretenović, Danica Bojić, 2018, professional monograph

Keywords: local, city, urban, mapping, intermedia
Published in RUNG: 06.06.2018; Views: 3704; Downloads: 34
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