Repository of University of Nova Gorica

Search the repository
A+ | A- | Help | SLO | ENG

Query: search in
search in
search in
search in
* old and bolonia study programme

Options:
  Reset


1 - 9 / 9
First pagePrevious page1Next pageLast page
1.
Photoactivated processes in optical fibers: generation and conversion mechanisms of twofold coordinated Si and Ge atoms
Nicolas Richard, Stefano De Gironcoli, Antonino Alessi, Sylvain Girard, A. Boukenter, Youcef Ouerdane, Layla Martin-Samos, Luigi Giacomazzi, 2017, original scientific article

Found in: ključnih besedah
Summary of found: ...ODC(II), silica, color centers, first-principles, twofold Si, GLPC...
Keywords: ODC(II), silica, color centers, first-principles, twofold Si, GLPC
Published: 15.10.2018; Views: 2299; Downloads: 0
.pdf Fulltext (1,39 MB)

2.
Radiation induced color centers in Silica: a first-principles investigation.
Nicolas Richard, Layla Martin-Samos, Luigi Giacomazzi, 2013, published scientific conference contribution

Found in: ključnih besedah
Keywords: Silica, EPR, E' centers, ODC
Published: 22.10.2018; Views: 2453; Downloads: 0
.pdf Fulltext (130,79 KB)

3.
Paramagnetic centers in amorphous GeO2
Luigi Giacomazzi, Layla Martin-Samos, Nicolas Richard, 2015, published scientific conference contribution abstract

Found in: ključnih besedah
Keywords: Ge-E' centers, first-principles, EPR, GeO2
Published: 25.10.2018; Views: 2130; Downloads: 0
.pdf Fulltext (214,90 KB)

4.
OXYGEN-EXCESS RELATED DEFECTS IN SiO2-BASED MATERIALS: COUPLING THEORY AND EXPERIMENTS
Blaž Winkler, 2019, doctoral dissertation

Abstract: This work is primarily focused on application of standard first-principle computational approaches to model oxygen excess related point defects in amorphous silica. Atomic models with their respective electronic and optical properties are explored together with some conversion mechanisms between defect models. The first chapter overviews extensive literature about the already known properties of oxygen related defects. Second chapter briefly introduces main methods that have been used in this research, in particular Density Functional Theory (DFT) as energy and force engine with short description of minimal energy path (MEP) algorithm used for modeling chemical/migration reactions, GW approximation for charged electronic excitations (band structure) and Bethe-Salpeter Equation (BSE) for neutral excitations (optical absorption and excitonic structure including electron hole interaction). The third chapter is devoted to the presentation of results. Thanks to the calculation of optical properties of peroxy bridge (POL), a correlation has been found between structural disorder, specifically dihedral angle dispersion, and low coupling with light, which has been identified as main reason why no clear absorption bands have been assigned to the POL. Structure and stability of some other defects, like interstitial ozone molecule (ozonyl) and dioxasilirane (silicon analogy of dioxirane), have been studied. These defects are usually not considered as most important species, however their calculated formation energies are lower compared to some known defects, which indicates they might be present in silica. From a detailed study on possible reaction mechanisms, it has been found that ozonyl might be one of the most important intermediate steps for oxygen exchange reactions. Results also show that dioxasilirane can be spontaneously created during the interaction of oxygen with lone pair defects. By exploring different reactions between oxygen and pre-existing oxygen deficiency centers (ODCs), calculations predict two kinds of passivation behaviors: single-barrier reversible mechanisms with the formation of dioxasilirane-like groups, for which the network keeps the memory of the precursory lone pair defects, and single or multiple-barrier mechanisms, for which the network loses its memory, either because of the high reverse barrier or because of a reconstruction. Final part of this research has been devoted to experimental characterization of the response and tolerance of optical fibers loaded with oxygen under irradiation. These include experiments on commercial fiber along with canonical samples (Optical fibers developed with the intention of studying correlations between different fabrication parameters, dopant/impurity concentration and doping concentrations). Studied fibers also include rare-earth doped fibers.
Found in: ključnih besedah
Summary of found: ...reactions between oxygen and pre-existing oxygen deficiency centers (ODCs), calculations predict two kinds of passivation...
Keywords: Silica, DFT, GW-approximation, Bethe-Salpeter equation, NEB, defect, oxygen, oxygen excess centers, oxygen deficiency centers, optical absorption, optical fibers, radiation induced attenuation.
Published: 07.05.2019; Views: 2542; Downloads: 131
.pdf Fulltext (13,18 MB)

5.
First-principles investigation of paramagnetic centers in P2O5 based glasses
Matjaz Valant, Luigi Giacomazzi, 2019, published scientific conference contribution

Found in: ključnih besedah
Keywords: glasses, phosphates, paramagnetic centers
Published: 30.10.2019; Views: 1747; Downloads: 0
.pdf Fulltext (915,51 KB)

6.
Fuzzy C-means clustering and particle swarm optimization based scheme for common service center location allocation
Rajan Gupta, Sunil K. Muttoo, Saibal K. Pal, 2017, original scientific article

Abstract: Common Service Centers (CSCs), which are also known as Tele-centers and Rural Kiosks, are important infrastructural options for any country aiming to provide E-Governance services in rural regions. Their main objective is to provide adequate information and services to a country’s rural areas, thereby increasing government-citizen connectivity. Within developing nations, such as India, many CSC allocations are being planned. This study proposes a solution for allocating a CSC for villages in a country according to their E-Governance plan. The Fuzzy C-Means (FCM) algorithm was used for clustering the village dataset and finding a cluster center for CSC allocation, and the Particle Swarm Optimization (PSO) algorithm was used for further optimizing the results obtained from the FCM algorithm based on population. In the context of other studies addressing similar issues, this study highlights the practical implementation of location modeling and analysis. An extensive analysis of the results obtained using a village dataset from India including four prominent states shows that the proposed solution reduces the average traveling costs of villagers by an average of 33 % compared with those of allocating these CSCs randomly in a sorted order and by an average of 11 % relative to centroid allocation using the FCM-based approach only. As compared to traditional approaches like P-Center and P-Median, the proposed scheme is better by 31 % and 14 %, respectively. Therefore, the proposed algorithm yields better results than classical FCM and other types of computing techniques, such as random search & linear programming. This scheme could be useful for government departments managing the allocation of CSCs in various regions. This work should also be useful for researchers optimizing the location allocation schemes used for various applications worldwide.
Found in: ključnih besedah
Summary of found: ...Common Service Centers (CSCs), which are also known as Tele-centers...
Keywords: common service centers, tele-centers, e-governance, location allocation, fuzzy C-means clustering, particle swarm optimization
Published: 17.02.2021; Views: 1065; Downloads: 0
.pdf Fulltext (2,67 MB)

7.
BAT algorithm for improving fuzzy C-means clustering for location allocation of rural kiosks in developing countries under e-governance
Saibal K. Pal, Rajan Gupta, Sunil K. Muttoo, 2016, original scientific article

Abstract: Rural Kiosks are important infrastructural pillar in rural regions for internet and basic technology facility all around the world. They are also known as Tele-centers or Common Service Centers and are majorly used by government to promote Electronic Governance. The major characteristic of setting up of Rural Kiosk is their appropriate location so that people from rural region can avail the services at minimum travel cost and time. There are lot of traditional schemes used by researchers in past for location allocation but this paper proposes the usage of Fuzzy C-Means clustering and BAT algorithm to optimize the location of Rural Kiosk. The meta-heuristic approach has produced better results as compared to normal graph theories in past. The experiment has been conducted on a random data set of 72 village locations from India and their clusters are formed. It is found that using only Fuzzy C-Means clustering to allocate the center and by using it in combination with BAT algorithm produced up to 25% of efficient results. This can drastically help the key stakeholders in allocation of these Rural Kiosks at right places so as to maximize their utility.
Found in: ključnih besedah
Summary of found: ...the world. They are also known as Tele- centers or Common Service Centers and are majorly...
Keywords: BAT algorithm, location allocation, rural kiosks, fuzzy C-means, e-governance, tele-centers, common service centers
Published: 01.04.2021; Views: 780; Downloads: 0
.pdf Fulltext (517,82 KB)

8.
Development of e-governance in an emerging economy like India
Saibal K. Pal, Rajan Gupta, Sunil K. Muttoo, 2017, published scientific conference contribution

Abstract: In this paper, we describe the key research questions handled during the doctoral work done in the area of E-Governance. The five research questions in the study are related to the concepts like Development of E-Governance & its assessment, Infrastructure management to reach out to maximum citizens, Various types of Security concerns faced during the E-Governance Development, Analyzing the E-Governance transaction pattern to capture citizen's interest, and finally the way ahead for the E-Governance development through the route of efficiency and optimization in the service designing. The methodology adopted and results obtained for various research questions are discussed at high level. Some portion of the current work is still in progress.
Found in: ključnih besedah
Summary of found: ...e-governance, location allocation, common service centers, intrusion detection system, security, analytics...
Keywords: e-governance, location allocation, common service centers, intrusion detection system, security, analytics
Published: 02.04.2021; Views: 747; Downloads: 28
URL Fulltext (0,00 KB)
This document has many files! More...

9.
Spectroscopic investigation of oxygen vacancies in CeO[sub]2
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.
Found in: ključnih besedah
Summary of found: ...a relative change in population of F centers in ceria. This demonstrated the relevance of...
Keywords: ceria, cathodoluminescence spectroscopy, local structure distortion, EXAFS analysis, La doped ceria, luminescence quenching, F centers, dissertations
Published: 25.11.2021; Views: 664; Downloads: 27
URL Fulltext (0,00 KB)
This document has many files! More...

Search done in 0 sec.
Back to top