1. Solar irradiance stability factorsBorut Jereb, 2024, izvirni znanstveni članek Opis: In the field of renewable energies, the logistical intricacies of production, as well as the use
and storage of photovoltaic energy, have become critical issues. In addition to sheer quantity, the
stability of this type of energy is a crucial factor in ensuring the reliability and consistency of power
generation. This paper defines Solar Irradiance Stability Factors (SISFs) as indicators complementing
electricity production. When planning solar energy production in each geographical area, both the
quantity and stability of solar irradiance are necessary for exploitation and determining the quality of
solar irradiance. While the average production of solar energy per unit area in each time interval is a
widely used parameter in daily practice, the observation of the amplitude of solar irradiance and its
influence on energy production in the observed time interval is currently still rare. The SISFs defined
in this article are new metrics that mainly depend on the meteorological variability in an area, and
the observed time intervals should be in the range of seconds, minutes, or even hours. Larger time
intervals are not helpful for the stability of solar irradiance in energy production and logistics from
the source to the destination. They provide a complementary and more accurate measure of how
suitable a particular geographical area is for producing solar energy.
Ključne besede: solar irradiance, stability metrics, photovoltaic energy, meteorological variability, geographical area
Objavljeno v DKUM: 23.09.2024; Ogledov: 0; Prenosov: 2
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2. Green sourcing: effects on supplier performance metrics in fast food restaurants in frontier marketsPaul Mukucha, Bongani E. Mushanyuri, Divaries Cosmas Jaravaza, 2021, izvirni znanstveni članek Opis: Following the banning of expanded polystyrene packaging material, the fast food restaurant industry was serendipitously plunged into green sourcing initiatives for its packaging materials leading to heightened efforts on evaluating the suitability of various suppliers of green packaging material. This study therefore sought to assess the performance of selected suppliers on supplier performance metrics of total cost of ownership, quality of sourced material and delivery performance, in Zimbabwe’s restaurant industry. Methodology: Data was collected from senior procurement officers of 30 officially registered fast food restaurants in Zimbabwe. Each restaurant randomly selected 5 suppliers from their supplier lists. Each unit was asked to rate their 5 major suppliers of packaging material leading to an effective sample size of 150 suppliers. Structural Equation Modeling (SEM) was used to analyse data in AMOS. The five steps in SEM, that is: model specification, model identification, parameter estimation, model evaluation and modification were done. Findings: The findings in this study revealed that green sourcing leads to improved procurement performance in terms of total cost of ownership, quality of the materials sourced, and delivery performance. Implications for theory and practice: It was therefore recommended that practically the restaurant industry should explore various options of green packaging material ranging from recyclable and reusable plastic, paper, aluminium and steel material. Originality and value: Although the study was done in a single market, there is dearth in literature on green sourcing in frontier markets, of which the study provides empirical evidence from the restaurant industry in SubSaharan Africa.
Ključne besede: green sourcing, supplier evaluation, fast food restaurant, frontier markets, supplier performance metrics, green packaging material, total cost of ownership, quality of sourced material, delivery performance
Objavljeno v DKUM: 23.08.2024; Ogledov: 80; Prenosov: 7
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3. Presence of alien Prunus serotina and Impatiens parviflora in lowland forest fragments in NE SloveniaMirjana Šipek, Eva Horvat, Ivana Vitasović Kosić, Nina Šajna, 2022, izvirni znanstveni članek Opis: Temperate alluvial, riparian and lowland forests are the European forests with the greatest presence of invasive alien plants. Consequently, identifying the environmental conditions for and other drivers behind the establishment of invasive species in natural forest communities is crucial for understanding the invasibility of these habitats. We focused on fragments (patches) of Illyrian oak-hornbeam forest in NE Slovenia, which are the least studied in this regard. Because alien phanerophytes and therophytes are significantly over-represented compared to native plantsin lowland forests, we selected two representative invasives: the phanerophyte Prunus serotina and the therophyte Impatiens parviflora. By using logistic regression models on vegetation surveys, environmental data based on Ellenberg´s indicator values, and patch metrics, we identified patch characteristics explaining the presence of each species. Moreover, we included human impact in the models. We reveal significant characteristics differentiating P. serotina from I. parviflora. We also show that the perimeterarea ratio and soil nutrients of the forest patches correlate significantly with the presence of P. serotina, while human disturbance correlates significantly with the presence of I. parviflora. Our results and a similar approach for other invasive plant species can be applied to assess habitat invasibility on potential and species’ current geographic distribution, as well as to develop management plans.
Ključne besede: biological invasions, forest fragmentation, landscape metrics, habitat characteristics, human presence, anthropogenic factors, neophytes, Slovenia
Objavljeno v DKUM: 12.07.2024; Ogledov: 136; Prenosov: 11
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5. Gaussian null coordinates for rotating charged black holes and conserved chargesMirjam Cvetič, Christopher N. Pope, Aritra Saha, Alejandro Satz, 2020, izvirni znanstveni članek Opis: Motivated by the study of conserved Aretakis charges for a scalar field on the horizon of an extremal black hole, we construct the metrics for certain classes of four-dimensional and five-dimensional extremal rotating black holes in Gaussian null coordinates. We obtain these as expansions in powers of the radial coordinate, up to sufficient order to be able to compute the Aretakis charges. The metrics we consider are for 4-charge black holes in four-dimensional STU supergravity (N = 2 supergravity coupled to three vector multiplets) (including the Kerr-Newman black hole in the equal-charge case) and the general 3-charge black holes in five-dimensional STU supergravity. We also investigate the circumstances under which the Aretakis charges of an extremal black hole can be mapped by conformal inversion of the metric into Newman-Penrose charges at null infinity. We show that while this works for four-dimensional static black holes, a simple radial inversion fails in rotating cases because a necessary conformal symmetry of the massless scalar equation breaks down. We also discuss that a massless scalar field in dimensions higher than four does not have any conserved Newman-Penrose charge, even in a static asymptotically flat spacetime.
Ključne besede: supergravitiy, flat spacetime, black hole, four-dimensional rotating, metrics
Objavljeno v DKUM: 16.10.2023; Ogledov: 342; Prenosov: 18
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6. T-branes and G(2) backgroundsRodrigo Barbosa, Mirjam Cvetič, Jonathan J. Heckman, Craig Lawrie, Ethan Torres, Gianluca Zoccarato, 2020, izvirni znanstveni članek Opis: Compactification of M-string theory on manifolds with G(2) structure yields a wide variety of 4D and 3D physical theories. We analyze the local geometry of such compactifications as captured by a gauge theory obtained from a three-manifold of ADE singularities. Generic gauge theory solutions include a nontrivial gauge field flux as well as normal deformations to the three-manifold captured by noncommuting matrix coordinates, a signal of T-brane phenomena. Solutions of the 3D gauge theory on a three-manifold are given by a deformation of the Hitchin system on a marked Riemann surface which is fibered over an interval. We present explicit examples of such backgrounds as well as the profile of the corresponding zero modes for localized chiral matter. We also provide a purely algebraic prescription for characterizing localized matter for such T-brane configurations. The geometric interpretation of this gauge theory description provides a generalization of twisted connected sums with codimension seven singularities at localized regions of the geometry. It also indicates that geometric codimension six singularities can sometimes support 4D chiral matter due to physical structure "hidden" in T-branes.
Ključne besede: Yang-Mills connections, spin(7), holonomy, bundles, metrics
Objavljeno v DKUM: 16.10.2023; Ogledov: 240; Prenosov: 17
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7. Effects of differential time and difficulty weighting on the improvement of OSCE quality metricsMatic Mihevc, Klara Masnik, Tadej Petreski, Nejc Pulko, Sebastjan Bevc, 2022, izvirni znanstveni članek Ključne besede: OSCE, clinical skills, peer assessment, quality metrics, weighting, outliers
Objavljeno v DKUM: 17.01.2023; Ogledov: 487; Prenosov: 54
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8. Quantitative model for economic analyses of information security investment in an enterprise information systemRok Bojanc, Borka Jerman-Blažič, 2012, izvirni znanstveni članek Opis: The paper presents a mathematical model for the optimal security-technology investment evaluation and decision-making processes based on the quantitative analysis of security risks and digital asset assessments in an enterprise. The model makes use of the quantitative analysis of different security measures that counteract individual risks by identifying the information system processes in an enterprise and the potential threats. The model comprises the target security levels for all identified business processes and the probability of a security accident together with the possible loss the enterprise may suffer. The selection of security technology is based on the efficiency of selected security measures. Economic metrics are applied for the efficiency assessment and comparative analysis of different protection technologies. Unlike the existing models for evaluation of the security investment, the proposed model allows direct comparison and quantitative assessment of different security measures. The model allows deep analyses and computations providing quantitative assessments of different options for investments, which translate into recommendations facilitating the selection of the best solution and the decision-making thereof. The model was tested using empirical examples with data from real business environment.
Ključne besede: modelling, security technology, economic metrics, investment, enterprise information system
Objavljeno v DKUM: 22.01.2018; Ogledov: 1235; Prenosov: 405
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9. Usage, Potentials and Challenges of Building Information Modelling (BIM) in Slovenia, Austria, Germany and SwitzerlandAmanda Jus, 2017, magistrsko delo Opis: In the master’s thesis, the main potentials, challenges and usage of Information Building Modelling (BIM) in Slovenia, Austria, Germany and Switzerland are presented, including its, because BIM is currently the most widely discussed topic in civil engineering.
The study was based on a questionnaire that was carefully created at the HSLU (Hochschule Luzern) in Switzerland. We participated in the last phases of its development. With the help of the results of the questionnaire, we evaluated the current usage and acceptance of BIM among all participants in the building process.
Ključne besede: civil engineering, BIM, Building Information Modelling, BIM metrics
Objavljeno v DKUM: 25.09.2017; Ogledov: 2247; Prenosov: 246
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10. XML Schema metrics for quality evaluationMaja Pušnik, Marjan Heričko, Zoran Budimac, Boštjan Šumak, 2014, izvirni znanstveni članek Opis: In XML Schema development, the quality of XML Schemas is a crucial issue for further steps in the life cycle of an application, closely correlated with the structure of XML Schemas and different building blocks. Current research focuses on measuring complexity of XML Schemas and mainly do not consider other quality aspects. This paper proposes a novel quality measuring approach, based on existing software engineering metrics, additionally defining the quality aspects of XML Schemas using the following steps: (1) definition of six schema quality aspects, (2) adoption of 25 directly measurable XML Schema variables, (3) proposition of six composite metrics, applying 25 measured variables and (4) composite metrics validation. An experiment was conducted using 250 standard XML Schemas collected from available e-business information systems. The results illustrate the influence of XML Schemaʼs characteristics on its quality and evaluate the applicability of metrics in the measurement process, a useful tool for software developers while building or adopting XML Schemas.
Ključne besede: XML, metrics, quality variables, quality index, evaluation, validation
Objavljeno v DKUM: 06.07.2017; Ogledov: 1432; Prenosov: 413
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