1. A new sustainable warehouse management approach for workforce and activities schedulingVlado Popović, Milorad J. Kilibarda, Milan Andrejić, Borut Jereb, Dejan Dragan, 2021, original scientific article Abstract: Sustainable engineering is very important for logistics systems. Nowadays, sustainable warehouse management is a key factor in market success. Workforce fluctuation and inverting the number of customers' demands make a lot of problems in distribution warehouses. This study addresses a sustainable approach for the workforce scheduling problem recognized in a real distribution warehouse. The problem arises from the high variability of demand for workers over oneworkday, which causes workforce surplus in some periods of the workday and shortages in others. Engineering managers of the distribution warehouse already use different full-time and part-timeshifts, and schedule workers on different activities, but they still have significant workforce surplusesor shortages in some periods. This study proposes the scheduling of activities' execution together with workers to face that variability and decrease the cost of the workforce. This idea comes from the fact that some activities in a distribution warehouse can be done in a specific time period after the need for them occurs. In this way, the variability of demand for workers can be decreased, and alower workforce cost may be ensured. Based on this idea, the entire problem is modeled as integer linear programming. The real example of the problem is solved, and the proposed model is tested on randomly generated instances of the problem in Python by means of the PuLP linear programming package. The results indicate different positive effects in the manner of sustainable warehouse management: lower workforce costs, time savings, better utilization of all types of resources andequipment, increased employee satisfaction, and so on. For even 61% of instances of the introduced problem, the obtained cost of the workforce is lower by more than 20% if activities' executions arescheduled together with employees.
Keywords: workforce, activities planning, schedule, optimization, warehouses, sustainable warehouse management, logistics
Published in DKUM: 11.10.2024; Views: 0; Downloads: 0
 Full text (1,28 MB)
This document has many files! More... |
2. Methods and models for electric load forecasting : a comprehensive reviewMahmoud A. Hammad, Borut Jereb, Bojan Rosi, Dejan Dragan, 2020, original scientific article Abstract: Electric load forecasting (ELF) is a vital process in the planning of the electricity industry and plays a crucial role in electric capacity scheduling and power systems management and, therefore, it has attracted increasing academic interest. Hence, the accuracy of electric load forecasting has great importance for energy generating capacity scheduling and power system management. This paper presents a review of forecasting methods and models for electricity load. About 45 academic papers have been used for the comparison based on specified criteria such as time frame, inputs, outputs, the scale of the project, and value. The review reveals that despite the relative simplicity of all reviewed models, the regression analysis is still widely used and efficient for long-term forecasting. As for short-term predictions, machine learning or artificial intelligence-based models such as Artificial Neural Networks (ANN), Support Vector Machines (SVM), and Fuzzy logic are favored.
Keywords: methods, models, electric load forecasting, modeling electricity loads, electricity industry, power management, logistics
Published in DKUM: 22.08.2024; Views: 95; Downloads: 8
Full text (1,23 MB)
This document has many files! More... |
3. Forecasting US tourists' inflow to Slovenia by modified holt-winters damped model : a case in the tourism industry logistics and supply chainsDejan Dragan, Abolfazl Keshavarzsaleh, Tomaž Kramberger, Borut Jereb, Maja Rosi, 2019, original scientific article Abstract: Forecasting is important in many branches of logistics, including the logistics related to Tourism supply chains. With an increasing inflow of American tourists, planning and forecasting the US tourists' inflow to Slovenia have gained far more importance attention amongst scholars and practitioners. This study, therefore, was conducted to forecast the American tourists' inflow to Slovenia using one of the predictive models based on the exponential smoothing approach, namely Holt-Winters damped additive (HWDA) exponential smoothing method. The model was modified by several improvements, while the obtained results were generalized to other supply chain components. The results show that the forecasting system can predict well the observed inflow, while the methodology used to derive the model might have enriched the plethora of existing practical forecasting approaches in the tourism domain. Benchmarking demonstrates that the proposed model outperforms a competitive ARIMA model and official forecasts. The practical implications are also discussed in this paper.
Keywords: tourism, forecasting, Holt-Winters model, US tourists, supply chains, logistics
Published in DKUM: 22.08.2024; Views: 42; Downloads: 8
Full text (1,36 MB)
This document has many files! More... |
4. Electric vehicles as electricity storages in electric power systemsVlado Popović, Borut Jereb, Milorad J. Kilibarda, Milan Andrejić, Abolfazl Keshavarzsaleh, Dejan Dragan, 2018, original scientific article Abstract: Improvements in battery technology make electric vehicles more and more suitable for the use as electricity storages. Many benefits could be achieved by using electric vehicles for storing electricity in their batteries. This paper talks about the idea of electric vehicles as electricity storages in electric power systems. The idea has a great number of supporters, but also a significant part of the professional community believes that is unfeasible. This paper is not classified in either side and strives to give a realistic picture of this idea. For this purpose, findings from papers published in scientific journals are mainly used. There is also some information from websites, mainly for some technical issues. Partly, the opinions of the authors are present. Specificities of EVs and EPSs that enabled the birth of this idea are explained along with proposed concepts through which the idea can be implemented. Keeping with the vehicle to grid concept, issues about the implementation of the idea are considered. Achievements in the practical realization of the idea are also presented.
Keywords: electricity, electric vehicles, storages, V2G
Published in DKUM: 22.08.2024; Views: 66; Downloads: 4
Full text (298,24 KB)
This document has many files! More... |
5. Optimal bus stops' allocation : a school bus routing problem with respect to terrain elevationKlemen Prah, Abolfazl Keshavarzsaleh, Tomaž Kramberger, Borut Jereb, Dejan Dragan, 2018, original scientific article Abstract: The paper addresses the optimal bus stops allocation in the Laško municipality. The goal is to achieve a cost reduction by proper re-designing of a mandatory pupils' transportation to their schools. The proposed heuristic optimization algorithm relies on data clustering and Monte Carlo simulation. The number of bus stops should be minimal possible that still assure a maximal service area, while keeping the minimal walking distances children have to go from their homes to the nearest bus stop. The working mechanism of the proposed algorithm is explained. The latter is driven by three-dimensional GIS data to take into account as much realistic dynamic properties of terrain as possible. The results show that the proposed algorithm achieves an optimal solution with only 37 optimal bus stops covering 94.6 % of all treated pupils despite the diversity and wideness of municipality, as well as the problematic characteristics of terrains' elevation. The calculated bus stops will represent important guidelines to their actual physical implementation.
Keywords: logistics, maximal covering problems, optimization, data clustering, Monte Carlo simulation, geographic information system (GIS), reduction of transportation costs, Laško, Slovenia
Published in DKUM: 22.08.2024; Views: 35; Downloads: 9
Full text (2,40 MB)
This document has many files! More... |
6. Road freight transport forecasting : a fuzzy Monte-Carlo simulation-based model selection approachDejan Dragan, Simona Šinko, Abolfazl Keshavarzsaleh, Maja Rosi, 2022, original scientific article Abstract: As important as the classical approaches such as Akaike's AIC information and Bayesian BIC criterion in model-selection mechanism are, they have limitations. As an alternative, a novel modeling design encompasses a two-stage approach that integrates Fuzzy logic and Monte Carlo simulations (MCSs). In the first stage, an entire family of ARIMA model candidates with the corresponding information-based, residual-based, and statistical criteria is identified. In the second stage, the Mamdani fuzzy model (MFM) is used to uncover interrelationships hidden among previously obtained models criteria. To access the best forecasting model, the MCSs are also used for different settings of weights loaded on the fuzzy rules. The obtained model is developed to predict the road freight transport in Slovenia in the context of choosing the most appropriate electronic toll system. Results show that the mechanism works well when searching for the best model that provides a well-fit to the real data.
Keywords: forecasting road transport, electronic toll system, Monte Carlo simulation, ARIMA models, logistics
Published in DKUM: 11.06.2024; Views: 135; Downloads: 6
Full text (2,36 MB)
This document has many files! More... |
7. |
8. |
9. Repositioning and optimal re-allocation of empty containers : a review of methods, models, and applicationsAlaa Abdelshafie, May Salah, Tomaž Kramberger, Dejan Dragan, 2022, original scientific article Abstract: Managing empty-container movements is one of the most challenging logistics problems in the shipping field. With the growth of global trade imbalance, the repositioning process has become necessary, immediately after emptying a container. The main contribution of this research paper is to enrich the most frequently used methods, models, and applications in the literature, for relaxing the empty-container-repositioning problem. The article presents practices that vary between organizational policies, technical solutions, and modelling applications. A review of optimization models has been used for comparisons, based on specified criteria, such as the time frame, inputs, outputs, scale of the project, and value. Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) was applied through the online database Web of Science (WOS). It gives a comprehensive description of all the relevant published documents. On the basis of conducting a brief systematic review, future research opportunities have been determined, considering the emerging phenomena in container transport chains.
Keywords: shipping industry, container-transportation management, empty-container repositioning, optimization methods
Published in DKUM: 08.08.2023; Views: 444; Downloads: 48
Full text (886,56 KB)
This document has many files! More... |
10. Celovitejši pristop k planiranju urbanega mobilnostnega sistema na osnovi mehkega večkriterijskega odločitvenega modela : doktorska disertacijaUroš Kramar, 2019, doctoral dissertation Abstract: Urbani mobilnostni sistem (UMS) predstavlja pomemben element družbenega razvoja. Prihodnjega razvoja urbane mobilnosti se je tako potrebno lotiti na način, ki bo omogočal uravnotežen trajnostni razvoj. V doktorski disertaciji je prikazan nov in celovitejši pristop k planiranju UMS, ki ob široki vključenosti različnih deležnikov omogoča sprejemanje strateških odločitev. Na osnovi izbrane metodologije smo razvili novi model, ki je sestavljeni iz treh faz: po zbranih vhodnih podatkih se preko modificirane metode ciljnih skupin s tehniko nominalnih skupin izvede SWOT analiza in v zadnji fazi nadgradi z metodo mehki analitični hierarhični proces (FAHP). S tem se pridobijo rangirana prioritetna področja, ki posledično omogočajo razvoj scenarijev. Predlagani izvirni model tako omogoča celovitejše in poglobljeno razumevanje iskanja kompromisov, s katerimi se soočamo pri večkriterijskem odločanju in usklajevanju pogosto nasprotujočih si ciljev. Novi model planiranja UMS je bil uspešno testiran na primeru realnega urbanega okolja, kar potrjuje njegovo sposobnost zagotavljanja celovitejšega pristopa k planiranju UMS.
Keywords: mobilnost, urbani mobilnostni sistem, celovitejši pristop, strateško planiranje, AHP, mehka logika, FAHP, ciljne skupine, SWOT analiza
Published in DKUM: 10.03.2020; Views: 1966; Downloads: 257
Full text (4,29 MB) |
