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Transient circuit simulation of arc-free current breaking by resistance rise
Dareer Bin Khalid, Michael Rock, Luigi Piegari, 2021, izvirni znanstveni članek

Opis: There has been intensive research and development in the field of Circuit breakers, whether DC and AC, or low voltage and high voltage. The result of this has led to the production of highly reliable circuit breakers that accompany a built-in arc extinguishing system. However, the purpose of this study is to give the basics for arc-free current breaking with fast interruption of fault currents, e.g., in surge protective devices (SPD) for AC and DC systems, by means of a time-dependent resistor with fast rising resistance. This investigation shall illustrate how the current can be driven almost to zero with a steadily time increasing resistance, and interrupted completely without an electric arc. The basic aim of the conducted transient circuit simulations is to determine suitable time functions for the current or resistance and necessary initial and final resistances. This paper will discuss the "optimisation conditions", a switching time as short as possible, small switch-off overvoltage, and possibly an energy conversion in the resistor as low as possible is set using ATP-EMTP and analytical calculations.
Ključne besede: current breaking, ATP-EMTP, time-dependent resistance, optimisation, concave functions, convex functions
Objavljeno v DKUM: 13.11.2023; Ogledov: 97; Prenosov: 2
.pdf Celotno besedilo (1,04 MB)
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Time pressure, work-related spousal support seeking, and relationship satisfaction : spillover and crossover effects among dual-earner couples
Sara Tement, Katarina Katja Mihelič, Bettina Kubicek, 2023, izvirni znanstveni članek

Opis: The present study examined how time pressure at work is transmitted to the home domain and how it affects individuals’ (spillover) as well as their partners’ relationship satisfaction (crossover). We examined the role of work-related spousal support seeking and proposed that it serves as a mediator of the spillover as well as the crossover process. We further explored whether the proposed spillover-crossover process is gender-contingent. Using a sample of 308 dual-earner couples, we found support for a positive link between time pressure at work and spousal support seeking. As hypothesized, spousal support seeking served also as a crossover mechanism. However, distinct spillover and crossover processes were found for men and women. These findings not only point to a new spillover and crossover mechanism but also highlight gender-specific patterns in the role of support seeking. As this coping strategy is feasible when job stressors are high, it should be considered a part of stress management trainings and organizational practices.
Ključne besede: spillover, crossover, time pressure, dual-earner couples, work-related spousal support, relationship satisfaction, gender differences
Objavljeno v DKUM: 13.07.2023; Ogledov: 163; Prenosov: 15
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Assembly line optimization using MTM time standard and simulation modeling—A case study
Matic Breznik, Borut Buchmeister, Nataša Vujica-Herzog, 2023, izvirni znanstveni članek

Opis: This study presents an approach to solving the assembly line balancing problem (ALBP) using the Methods-Time Measurement (MTM) time standard and simulation software. ALBP is a common problem in manufacturing where a set of tasks with fixed times must be assigned to a series of sequential workstations in order to minimize the total idle time and reduce the assembly cost per product. This study uses MTM, a widely used production process scheduling method, to create a new time analysis of an assembly process that was previously balanced using the Work-Factor method and time study. This literature review shows that there are a lack of combinations of updated time analyses with newer simulation approaches in the current literature, and this was the motivation for the present work. An assembly line simulation was performed using Simio software to evaluate different design options and operating scenarios. The results show that the use of MTM and simulation can help minimize idle time and improve assembly line performance, thereby reducing costs and increasing efficiency. This study shows that the approach of using MTM and simulation is effective in solving ALBP and is a useful tool for manufacturing companies to improve the performance of their assembly lines and reduce costs.
Ključne besede: optimization, production planning, assembly line, MTM time standard, simulation, industry 4.0
Objavljeno v DKUM: 23.05.2023; Ogledov: 229; Prenosov: 27
.pdf Celotno besedilo (3,25 MB)

Development of a methodology to calibrate a pedestrian microsimulation model : doctoral dissertation
Chiara Gruden, 2022, doktorska disertacija

Opis: Walking, as a mode of transport, is becoming widespread, in a world, where urban conglomerates are broadening and becoming denser. Modern lifestyle trends on a side, and eco-friendly policies on the other, push people into walking habits, increasing the need for a suitable, attractive, accessible, connected and safe walking infrastructure. To reach such a result, it is necessary to understand, what are the needs of the users of this infrastructure, taking into consideration the behavioral specificities and the safety needs of pedestrians. In this process pedestrian microsimulation models, surrogate safety techniques, and technologies able to measure specific traits of pedestrian dynamics play a central role. The firsts allow to reproduce repeatedly in a virtual environment a specific infrastructure and to study the response of pedestrians. Nevertheless, to be accurate and efficient, they need to go through long and tedious calibration and validation processes, that are often seen as an important limitation by technicians. Surrogate safety techniques are methods, that are based on the concept, that it is possible to predict the safety level of a location, using near accidents. The main advantage of such techniques is that they are proactive. Till this moment, these techniques have been mainly applied to on-field measurements and are primarily centered on motorized road users. Less interest has been shown for vulnerable road users, especially for pedestrians, who have been less extensively studied. Finally, an element that could highly affect pedestrian safety is their reaction time. Nevertheless, its measurement has long been a big issue. Eye-tracking technology could be one of the solutions, allowing to analyze the directions and objects fixated by pedestrians. These listed issues are also the topics that are addressed by this research work. Focusing on the study of the action of pedestrians while crossing the road on an unsignalized crosswalk set on a roundabout entry leg, the dissertation thesis aims at studying the crossing time, reaction time and surrogate safety aspects typical of pedestrians at the recalled location. The main purpose of the research work is to develop a methodology to calibrate pedestrian Social Force Model at a selected location, using a specifically formulated neural network as a tool to fine-tune model's behavioral parameters. Eight parameters have been chosen to be fine-tuned, five of those are related to pedestrian behavior and three of them are related to car-following behavior. After the selection of input parameters, a feedforward network has been formulated. Its application in the framework of the whole calibration process has brought to considerably positive results, finding a combination of input parameters that improved the performance of the microsimulation model of 37 % in comparison to the default one. The outputs of the calibrated model have been used to calculate three measures of surrogate safety, and also in this case results demonstrated an improvement in the calculation of surrogate safety measures when using the calibrated outcomes in comparison to their calculation on the “default” model outputs. Finally, reaction time measurement and prediction have been addressed by the thesis, in order to be able to describe pedestrian crossing action in its completeness. Quantitative eye-tracking outputs have been the starting point for the calculation of pedestrian reaction time at different locations, and they allowed to create a database of behavioral, geometric, regulatory and flow characteristics, which was the foundation for the formulation of a new prediction model for pedestrian reaction time. The prediction model, which consists of a cascade-correlation neural network, gave a good response to the learning and generalization steps, turning a 74 % correlation between the measured reaction time values and the predicted ones, and being able to follow the variability of these values.
Ključne besede: pedestrian, microsimulation model, calibration, neural network, surrogate safety indicators, reaction time.
Objavljeno v DKUM: 03.10.2022; Ogledov: 539; Prenosov: 71
.pdf Celotno besedilo (5,93 MB)

Postavitev kanban sistema na oddelku predmontaže gonil v podjetju sip strojna industrija
Gregor Kolenc, 2022, diplomsko delo

Opis: V diplomskem delu so predstavljene osnove vitke linije, bolj podrobno pa je razdelanih nekaj njenih gradnikov, kot so metoda 5S, metoda 5x ZAKAJ, 7 vrst izgub, poka-yoke, TPM – Total productive maintenance in SMED – Single minute exchange of dies. Opisana je tudi proizvodnja just-in-time. V nadaljevanju je opisan glavni pojem diplomskega dela – kanban. Omenjene so tudi zaloge, ki so v sodobni proizvodnji ključnega pomena. V praktičnem delu, izvedenem v podjetju SIP, sem se osredotočil na postavitev kanban regala na oddelku predmontaže gonil. Izvedena naloga je predstavljena od zasnove ideje do končne postavitve regala. Opisan je celoten postopek lotevanja naloge in načini reševanja težav, ki so se spotoma pojavljale.
Ključne besede: kanban, vitka proizvodnja, just-in-time, zaloge
Objavljeno v DKUM: 23.09.2022; Ogledov: 383; Prenosov: 77
.pdf Celotno besedilo (2,70 MB)

Optimizacija proizvodnega procesa naročniške proizvodnje v podjetju SMM – Maribor : diplomsko delo
Semir Kadirić, 2021, diplomsko delo

Opis: Namen diplomskega dela je bil predstaviti način in metode dela v podjetju SMM proizvodni sistemi d. o. o. – Maribor in poskušati narediti oz. predlagati optimizacijo postopka operacij izdelka v podjetju na konkretnem primeru. Predstavil in opisal sem podjetje ter prikazal prednosti in težave, s katerimi se podjetje srečuje pri pripravi proizvodnje, poteku izdelave, kontroli, montaži … Potek izvajanja projekta po naročnikovi dokumentaciji (tuji dokumentaciji) je osrednja tema dela, opredelil pa sem tudi prednosti in slabosti.
Ključne besede: proizvodni proces, just in time (JIT), optimizacija, kvaliteta, izdelava, vrstni red operacij, čas, kontrola, montaža, transport.
Objavljeno v DKUM: 01.07.2021; Ogledov: 770; Prenosov: 67
.pdf Celotno besedilo (3,01 MB)

Supplementary material for paper Comparison of the evolution of the COVID-19 disease between Romania and Italy
Ciprian Chiruţa, Emilian Bulgariu, Jurij Avsec, Brigita Ferčec, Matej Mencinger, 2020, zaključena znanstvena zbirka raziskovalnih podatkov

Ključne besede: COVID-19 pandemic evolution, time dependent SIR model, coronavirus
Objavljeno v DKUM: 23.12.2020; Ogledov: 4030; Prenosov: 1424
.png Raziskovalni podatki (348,32 KB)
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Comparison of the evolution of the COVID-19 disease between Romania and Italy
Ciprian Chiruţa, Emilian Bulgariu, Jurij Avsec, Brigita Ferčec, Matej Mencinger, 2020, izvirni znanstveni članek

Opis: After the outbreak of COVID-19 in Italy, thousands of Romanian citizens who worked in Northern Italy, Spain or Germany returned to Romania. Based on the time-dependent susceptible–infected–recovered—SIR model, this paper compares the evolution of the COVID-19 disease between Romania and Italy, assuming that the parameter value of R0 in the time-dependent SIR model decreases to R1 < R0 after publicly announced restrictions by the government, and increases to a value of R2 < R1 when the restrictions are lifted. Among other things, we answer the questions about the date and extent of the second peak in Italy and Romania with respect to different values of R2 and the duration of the restrictions.
Ključne besede: COVID-19 pandemic evolution, time dependent SIR model, coronavirus
Objavljeno v DKUM: 22.12.2020; Ogledov: 869; Prenosov: 187
.pdf Celotno besedilo (8,75 MB)
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Oblikovanje pripravljalnega mesta za montažo v Ledinek engineering d.o.o. : diplomsko delo
Aleš Ačko, 2019, diplomsko delo

Opis: Podjetje Ledinek Engineering d.o.o. izvaja poleg ostalih dejavnosti tudi montažo strojev in naprav. Montaža poteka po sistemu, ki se je razvil skozi leta in je prinašal dobre rezultate, vendar se je ob porastu naročil ter širitvijo podjetja v nove proizvodne prostore pokazalo nekaj pomanjkljivosti v zdajšnjih metodah montaže. Področje, kjer bi se izboljšave najbolj občutile, je na nivoju organizacije montažnih komponent. Tukaj se v sedanjem sistemu izgubi ogromna količina časa, ki ga monterji porabijo za iskanje komponent, potrebnih za sestavo in montažo sklopa, ki ga v danem trenutku montirajo. V prenovljenem sistemu igra ključno vlogo pripravljalno mesto. Na tem pripravljalnem mestu je definiran potek dela, potrebna oprema in znanja delavca. Pripravljalno mesto je namenska lokacija znotraj podjetja, kjer delavec, usposobljen za to delo, zbere vse komponente, potrebne za montažo nekega sklopa stroja, ki se nato zabeležijo in odpišejo. Nato se dajo v transportne enote in oddajo v čakalno vrsto ali pa naravnost v montažo. S tem se občutno zmanjša izguba časa na montažnem mestu, s čimer se močno izboljša sledljivost komponent.
Ključne besede: pripravljalno mesto, organizacija dela, montaža, kanban, just in time
Objavljeno v DKUM: 10.09.2019; Ogledov: 1164; Prenosov: 109
.pdf Celotno besedilo (2,28 MB)

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