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1.
Accuracy of Rotational Speed and Torque Sensors for Determining the Mechanical Power of Rotating Electrical Machines
Gregor Srpčič, Iztok Brinovar, Bojan Štumberger, Sebastijan Seme, Miralem Hadžiselimović, 2019, published scientific conference contribution

Abstract: This paper deals with determining the accuracy of measuring systems for determining the characteristics of rotating electrical machines. Efficiency classes and experimental methods for determining efficiency, are given in a standard, which has to be strictly respected. For determining the efficiency of an electrical machine, it is necessary to have a modern and accurate measurement system with sensors of high accuracy classes, which enables the user to carry out precise measurements and consequently, to determine all the characteristics of the electrical machine. This paper will be focused on torque and speed measurements.
Keywords: efficiency, measuring system, electric machines, torque and rotational sensors, accuracy
Published in DKUM: 04.12.2023; Views: 286; Downloads: 12
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2.
Estimation of the Solar Irradiance on Tilted Surface for Different Types of Pyranometers
Sebastijan Seme, Klemen Sredenšek, Iztok Brinovar, Gregor Srpčič, Miralem Hadžiselimović, Bojan Štumberger, 2019, published scientific conference contribution

Abstract: Accurate measurements of solar irradiance are important in many applications such as studying the distribution of received radiation or estimating the final yield of photovoltaic systems This paper deals with evaluation of different types of pyranometers. The primary objective of this paper is to compare two types of pyranometers, with the use of mathematical model for predicting solar radiation on incline surface. The mathematical model shows that both types of pyranometers receives the highest annual average solar radiation with a surface facing 189° south and inclination angle of 44°. The results in this paper show that the deviation between silicon photodiode and thermopile pyranometer mostly occur, due to irregular calibration, frequent cleaning and errors of silicon photodiode pyranometer under overcast sky conditions.
Keywords: pyranometer, solar radiation, azimuth angle, inclination angle, accuracy
Published in DKUM: 04.12.2023; Views: 196; Downloads: 8
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3.
Accuracy is not enough: optimizing for a fault detection delay
Matej Šprogar, Domen Verber, 2023, original scientific article

Abstract: This paper assesses the fault-detection capabilities of modern deep-learning models. It highlights that a naive deep-learning approach optimized for accuracy is unsuitable for learning fault-detection models from time-series data. Consequently, out-of-the-box deep-learning strategies may yield impressive accuracy results but are ill-equipped for real-world applications. The paper introduces a methodology for estimating fault-detection delays when no oracle information on fault occurrence time is available. Moreover, the paper presents a straightforward approach to implicitly achieve the objective of minimizing fault-detection delays. This approach involves using pseudo-multi-objective deep optimization with data windowing, which enables the utilization of standard deep-learning methods for fault detection and expanding their applicability. However, it does introduce an additional hyperparameter that needs careful tuning. The paper employs the Tennessee Eastman Process dataset as a case study to demonstrate its findings. The results effectively highlight the limitations of standard loss functions and emphasize the importance of incorporating fault-detection delays in evaluating and reporting performance. In our study, the pseudo-multi-objective optimization could reach a fault-detection accuracy of 95% in just a fifth of the time it takes the best naive approach to do so.
Keywords: artificial neural networks, deep learning, fault detection, accuracy, multi-objective optimization
Published in DKUM: 30.11.2023; Views: 232; Downloads: 10
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4.
Experimental validation of a thermo-electric model of the photovoltaic module under outdoor conditions
Klemen Sredenšek, Bojan Štumberger, Miralem Hadžiselimović, Sebastijan Seme, Klemen Deželak, 2021, original scientific article

Abstract: An operating temperature of the photovoltaic (PV) module greatly affects performance and its lifetime. Therefore, it is essential to evaluate operating temperature of the photovoltaic module in different weather conditions and how it affects its performance. The primary objective of this paper is to present a dynamic thermo-electric model for determining the temperature and output power of the photovoltaic module. The presented model is validated with field measurement at the Institute of Energy Technology, Faculty of Energy Technology, University of Maribor, Slovenia. The presented model was compared with other models in different weather conditions, such as clear, cloudy and overcast. The evaluation was performed for the operating temperature and output power of the photovoltaic module using Root-Mean-Square-Error (RMSE) and Mean-Absolute-Error (MAE). The average RMSE and MAE values are 1.75C and 1.14C for the thermal part and 20.34 W and 10.97 W for the electrical part.
Keywords: dynamic modeling, thermo-electric model, accuracy, measuring device, temperature, output power, PV module
Published in DKUM: 13.11.2023; Views: 231; Downloads: 11
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5.
The 100-digit challenge : algorithm jDE100
Janez Brest, Mirjam Sepesy Maučec, Borko Bošković, published scientific conference contribution

Abstract: Real parameter optimization problems are often very complex and computationally expensive. We can find such problems in engineering and scientific applications. In this paper, a new algorithm is proposed to tackle the 100-Digit Challenge. There are 10 functions representing 10 optimization problems, and the goal is to compute each function’s minimum value to 10 digits of accuracy. There is no limit on either time or the maximum number of function evaluations. The proposed algorithm is based on the self-adaptive differential evolution algorithm jDE. Our algorithm uses two populations and some other mechanisms when tackling the challenge. We provide the score for each function as required by the organizers of this challenge competition.
Keywords: differential evolution, optimization, global optimum, accuracy
Published in DKUM: 23.01.2023; Views: 403; Downloads: 15
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6.
Metacognitive accuracy and learning to learn : a developmental perspective
Karin Bakračevič, 2012, original scientific article

Abstract: Metacognition belongs to higher-order mental processes and enables us to control, plan and accordingly regulate our own learning and problem solving process. In the present study we researched developmental changes in different reasoning domains and in metacognitive accuracy, which is considered as part of successful metacognitive monitoring/regulation, and as an essential element of self-regulated learning and learning to learn competence. The study involved 282 participants from four different age groups: 13-15-, 23-25-, 33-35- and 43-45- year olds. These participants solved tasks addressed to spatial, verbal-propositional and social reasoning, and evaluated their own performance on these tasks. To specify possible differences in metacognitive accuracy, the metacognitive accuracy index was computed. Results showed that metacognitive evaluations were accurate in spatial domain, less accurate in verbal-propositional and quite inaccurate in the social domain. The accuracy of self-evaluation increased with age and males were more accurate in their self-evaluations than females. Improvement of metacognitive accuracy with age is in tune with findings that metacognition becomes more effective with development and that people with age become more reflective and self-aware.
Keywords: reasoning, metacognition, metacognitive accuracy, self-regulated learning
Published in DKUM: 15.12.2017; Views: 1440; Downloads: 113
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7.
Kalman filter or VAR models to predict unemployment rate in Romania?
Mihaela Simionescu, 2015, original scientific article

Abstract: This paper brings to light an economic problem that frequently appears in practice: For the same variable, more alternative forecasts are proposed, yet the decision-making process requires the use of a single prediction. Therefore, a forecast assessment is necessary to select the best prediction. The aim of this research is to propose some strategies for improving the unemployment rate forecast in Romania by conducting a comparative accuracy analysis of unemployment rate forecasts based on two quantitative methods: Kalman filter and vector-auto-regressive (VAR) models. The first method considers the evolution of unemployment components, while the VAR model takes into account the interdependencies between the unemployment rate and the inflation rate. According to the Granger causality test, the inflation rate in the first difference is a cause of the unemployment rate in the first difference, these data sets being stationary. For the unemployment rate forecasts for 2010-2012 in Romania, the VAR models (in all variants of VAR simulations) determined more accurate predictions than Kalman filter based on two state space models for all accuracy measures. According to mean absolute scaled error, the dynamic-stochastic simulations used in predicting unemployment based on the VAR model are the most accurate. Another strategy for improving the initial forecasts based on the Kalman filter used the adjusted unemployment data transformed by the application of the Hodrick-Prescott filter. However, the use of VAR models rather than different variants of the Kalman filter methods remains the best strategy in improving the quality of the unemployment rate forecast in Romania. The explanation of these results is related to the fact that the interaction of unemployment with inflation provides useful information for predictions of the evolution of unemployment related to its components (i.e., natural unemployment and cyclical component).
Keywords: forecasts, accuracy, Kalman filter, Hodrick-Prescott filter, VAR models, unemployment rate
Published in DKUM: 13.11.2017; Views: 1684; Downloads: 376
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8.
9.
The Analysis of the Berlitz Approach to English Language Teaching
Admira Halvadžić, 2013, undergraduate thesis

Abstract: This paper investigates the role of the Berlitz method of teaching English in today's language education. The Berlitz method has been present in the English language area for a long time and the principal objective of this diploma thesis was to prove that even today, it is a very successful and effective method of teaching English, whose characteristics should be implemented in language classrooms around the world. The first part of my thesis introduces the history of English language teaching and the history of the Berlitz method. Characteristics of the Berlitz method, its development and the role in today's education are presented. The second part, which is also the principal part of the thesis, draws upon lesson observations of three children’s and two adult classes which I did at the Berlitz language centre in Maribor. The data collected here focused on three aspects of the didactical triangle: the teacher, the learner and the content. Important information about each segment is introduced, with the emphasis on the content, the use of teaching aids, the role of fluency and accuracy, the rapport between teachers and learners and about motivation in Berlitz classes. The last part of my thesis involves information about Berlitz kids’ camps and a survey which reveals some significant information about the teachers’ and learners’ experiences and views on the Berlitz method.
Keywords: English language teaching, the Berlitz method, lesson observations, the content, teaching aids, fluency and accuracy, rapport, motivation, Berlitz kids' camps.
Published in DKUM: 08.07.2013; Views: 2750; Downloads: 173
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