Lubos Buzna

• Professor
• Professor at University of Žilina

This contribution is focused on an acceleration of branch and bound algorithms for the uncapacitated facility location problem. Our approach is based on the well-known Erlenkotters’ procedures and Körkels’ multi-ascent and multi-adjustment algorithms, which have proved to be the efficient tools for solving the large-sized instances of the uncapacit...

We propose a versatile concept of the adaptive aggregation framework for the facility location problems that keeps the problem size in reasonable limits. Most location-allocation problems are known to be NP-hard. Thus, if a problem reaches the critical size, the computation exceeds reasonable time limits, or all computer memory is consumed. Aggrega...

Vehicle-to-infrastructure communications can inform an intersection controller about the location and speed of connected vehicles. Recently, the design of adaptive intersection control algorithms that utilize this information received substantial research attention. These studies typically assume perfect communications. This study explores the poss...

Climate change prompts humanity to look for decarbonisation opportunities, and a viable option is to supply electric vehicles with renewable energy. The stochastic nature of charging demand and renewable generation requires intelligent charging driven by predictions of charging behaviour. The conventional prediction models of charging behaviour usu...

Connected and automated vehicles bring the capability to generate traffic data for intersection control applications. Unfortunately, for various reasons, such as signal blocking and interference, vehicles may experience communication failures leading to inefficiencies, e.g., unnecessarily long waiting queues, increased noise and greenhouse gas emis...

The rapid adoption of electric vehicles (EVs) has catalyzed the urgency of a resilient and sustainable charging infrastructure. This study addresses this issue by harnessing offshore wind energy resources to meet the charging demands, particularly in remote coastal regions. The primary challenge tackled in this research involves the complex managem...

Electric vehicles (EVs) offer a promising solution to achieve zero tailpipe emissions in urban areas. Effective deployment of EVs requires a robust energy-management-based charging infrastructure. Bipolar DC-bus-fed charging stations are popular due to their efficient connection to distributed generation and reduced conversion steps. However, volta...

The increase in greenhouse gas emissions (GHG) from the transportation sector, along with the ongoing depletion of fossil fuels, emphasizes the necessity for increased focus on energy storage systems (ESSs) and renewable energy sources (RESs) in seaports and on short-distance vessels such as ferries. This paper investigates the development of next-...

Residential chargers are going to become the standard in the near future. Their operational cycles are closely tied to users’ daily routines, and the power consumption fluctuates between zero and peak levels. These types of installations are particularly challenging for the grid, especially concerning the balance of electricity production and consu...

Developing an efficient and economical journey plan in multimodal transportation networks is of significant and fast-growing importance, but it is still an annoying experience for a traveler. This paper aims to find the journey plan at a combined cross-border and inter-regional level when visiting a sequence of cities while utilizing several transp...

Nowadays, efforts to encourage changes in travel behaviour towards eco-friendly and active modes of transport are intensifying. A promising solution is to increase the use of sustainable public transport modes. Currently, a significant challenge related to this solution is the implementation of journey planners that will inform travellers about ava...

Zero-emission transportation is currently a public priority, especially in big cities. For this reason, the use of electric vehicles (EVs) is receiving much attention. To facilitate the adoption of EVs, a proper charging infrastructure together with energy management is essential. This article proposes a design guideline for a direct current (DC) c...

The power system is undergoing significant changes so as to accommodate an increasing amount of renewably generated electricity. In order to facilitate these changes, a shift from the currently employed zonal pricing to nodal pricing is a topic that is receiving increasing interest. To explore alternative pricing mechanisms for the European electri...

A vehicle-to-infrastructure communication can inform an intersection controller about the location and speed of connected vehicles. Recently, the design of adaptive intersection control algorithms that take advantage of this information evoked a lot of research, typically assuming a perfect communication. In this study, we explore possible effects...

Buzna Ľ, Czimmermann P. On the Modelling of Emergency Ambulance Trips: The Case of the Žilina Region in Slovakia. Mathematics. 2021; 9(17):2165. https://doi.org/10.3390/math9172165 The efficient operation of emergency medical services is critical for any society. Typically, optimisation and simulation models support decisions on emergency ambulan...

Here, we develop a data-centric approach to analyse which activities, functions, and characteristics of the environment surrounding the slow charging infrastructure impact the distribution of the electricity consumed at slow charging infrastructure. We analysed the probability distribution of energy consumption and its relation to indicators charac...

With the spread of connected vehicles (CVs), a growth of novel information services exploiting data transmitted by CVs is expected. Wireless communication systems, in particular in vehicular applications, operate with a varying level of transmission reliability, which may affect the quality of V2X-data-driven intelligent transport systems (ITS). Th...

In this paper, we apply a data-driven approach to analyse the temporal characteristics of charging sessions performed at a slow charging infrastructure. By using the variable selection ability of the Lasso method, combined with the bootstrap driven post-selection inference, we evaluate measures quantifying the potential impacts of charging infrastr...

Based on the electric vehicle (EV) arrival times and the duration of EV connection to the charging station, we identify charging patterns and derive groups of charging stations with similar charging patterns applying two approaches. The ruled based approach derives the charging patterns by specifying a set of time intervals and a threshold value. I...

Based on the electric vehicle (EV) arrival times and the duration of EV connection to the charging station, we identify charging patterns and derive groups of charging stations with similar charging patterns applying two approaches. The ruled based approach derives the charging patterns by specifying a set of time intervals and a threshold value. I...

Transportation electrification is a valid option for supporting decarbonization efforts but, at the same time, the growing number of electric vehicles will produce new and unpredictable load conditions for the electrical networks. Accurate electric vehicle load forecasting becomes essential to reduce adverse effects of electric vehicle integration...

(https://arxiv.org/abs/2006.01672) Here, we develop a data-centric approach enabling to analyse which activities, function, and characteristics of the environment surrounding the slow charging infrastructure impact the distribution of the electricity consumed at slow charging infrastructure. To gain a basic insight, we analysed the probabilistic di...

The availability of charging infrastructure is essential for large-scale adoption of electric vehicles (EV). Charging patterns and the utilization of infrastructure have consequences not only for the energy demand by loading local power grids, but influence the economic returns, parking policies and further adoption of EVs. We develop a data-driven...

With the deployment of Vehicular Ad hoc Networks (VANETs), new transport safety and efficiency applications are emerging. One of the fields where the adoption of information and communication technologies (ICT) is expected to bring great benefits, is emergency systems. A properly designed emergency vehicle warning system should provide car drivers...

(https://ieeexplore.ieee.org/abstract/document/8955852) The availability of charging infrastructure is essential for large-scale adoption of electric vehicles (EV). Charging patterns and the utilization of infrastructure have consequences not only for the energy demand, loading local power grids but influence the economic returns, parking policies...

Women and men often do not experience equal mobility opportunities. Increasingly, gender is being recognized to play a significant role in transport planning, particularly for addressing individual mobility needs in urban and rural areas. Previous studies have shown that transport policy and mobility planning are better suited to men’s activities a...

The recent rise of electric vehicles (EV) brings social and technological changes in the transportation and energy sectors, including the massive deployment of charging stations. To provide effective decision support for the operators of charging stations, we are exploring possibilities for exploiting the available dataset and present results of pr...

When a government or a municipality intends to incentivize electromobility a chicken-egg problem arises: shall citizens first buy electric vehicles or should the charging stations be installed first? Often, a charging infrastructure is deployed, even if the number of electric vehicles is small, in the hope to stimulate a larger interest in electric...

Here, a data set collected within the large network of charging stations located in one of the electromobility leading countries the Netherlands, is analysed. The data set consists of more than one million charging transactions that took place in more than 1700 charging stations in the time period of four years. Clustering algorithms such as k-mean...

We combine the power flow model with the proportionally fair optimization criterion to study the control of congestion within a distribution electric grid network. The form of the mathematical optimization problem is a convex second order cone that can be solved by modern non-linear interior point methods and constitutes the core of a dynamic simul...

We combine the power flow model with the proportionally fair optimization criterion to study the control of congestion within a distribution electric grid network. The form of the mathematical optimization problem is a convex second order cone that can be solved by modern non-linear interior point methods and constitutes the core of a dynamic simul...

We propose optimization model to design a charging infrastructure for a fleet of electric vehicles. Applicable examples include a fleet of vans used in the city logistics, a fleet of taxicabs or a fleet of shared vehicles operating in urban areas. Fleet operator is wishing to replace vehicles equipped with an internal combustion engine with fully e...

Designers of location algorithms share test data sets (benchmarks) to be able to compare performance of newly developed algorithms. In previous decades, the availability of locational data was limited. Big data has revolutionised the amount and detail of information available about human activities and the environment. It is expected that integrati...

This book constitutes the proceedings of the First International Conference on Intelligent Transport Systems, INTSYS 2107, which was held in Helsinki, Finland, in November 2017. The 30 revised full papers were selected from 47 submissions and are organized in 6 thematic sessions on planning and sustainable transport and smart cities, intelligent ra...

We consider two elementary (max-flow and uniform-flow) and two realistic (max-min fairness and proportional fairness) congestion control schemes, and analyse how the algorithms and network structure affect throughput, the fairness of flow allocation, and the location of bottleneck edges. The more realistic proportional fairness and max-min fairness...

With the expected uptake of electric vehicles in the near future, we are likely to observe overloading in the local distribution networks more frequently. Such development suggests that a congestion management protocol will be a crucial component of future technological innovations in low voltage networks. An important property of a suitable networ...

We show that real multiplex networks are unexpectedly robust against targeted attacks on high degree nodes, and that hidden interlayer geometric correlations predict this robustness. Without geometric correlations, multiplexes exhibit an abrupt breakdown of mutual connectivity, even with interlayer degree correlations. With geometric correlations,...

We show that real multiplex networks are unexpectedly robust against targeted attacks on high degree nodes, and that hidden interlayer geometric correlations predict this robustness. Without geometric correlations, multiplexes exhibit an abrupt breakdown of mutual connectivity, even with interlayer degree correlations. With geometric correlations,...

Here, we propose a method to design a charging infrastructure for a fleet of electric vehicles such as a fleet of taxicabs, fleet of vans used in the city logistics or a fleet of shared vehicles, operating in large urban areas. Design of a charging infrastructure includes decisions about charging stations location and number of charging points at e...

We propose a new approximative approach to the discrete facility location problem that provides solutions close to the lexicographic minimax optimum. The lexicographic minimax optimum is concept that allows to find equitable location of facilities. Our main contribution is the approximation approach, which is based on the rules allowing: (i) to tak...

From the Internet to road networks and the power grid, modern life depends on controlling flows on critical infrastructure networks that often operate in a congested state. Yet, we have a limited understanding of the relative performance of the control mechanisms available to manage congestion and of the interplay between network topology, path lay...

Public service systems, such as emergency health care, police or fire brigades, are critical for day-to-day functioning of the society. To design and operate these systems efficiently much data needs to be collected and properly utilised. Here, we use the OpenStreetMap (OSM) data to model the demand points (DPs), which approximate the geographical...

The increasing penetration of electric vehicles over the coming decades, taken together with the high cost to upgrade local distribution networks and consumer demand for home charging, suggest that managing congestion on low voltage networks will be a crucial component of the electric vehicle revolution and the move away from fossil fuels in transp...

We propose a new heuristic algorithm that provides solutions to the discrete lexicographic minimax location problem. The algorithm is applicable to large instances of the problem. The lexicographic minimax location problem is known to be NP-hard. Therefore, the large instances of the problem are not computable in reasonable time. An aggregation is...

We deduce and discuss the implications of self-similarity for the stability in terms of robustness to failure of multiplexes, depending on interlayer degree correlations. First, we define self-similarity of multiplexes and we illustrate the concept in practice using the configuration model ensemble. Circumscribing robustness to survival of the mutu...

The increasing penetration of electric vehicles over the coming decades, taken together with the high cost to upgrade local distribution networks, and consumer demand for home charging, suggest that managing congestion on low voltage networks will be a crucial com-ponent of the electric vehicle revolution and the move away from fossil fuels in tran...

The increasing penetration of electric vehicles over the coming decades, taken together with the high cost to upgrade local distribution networks, and consumer demand for home charging, suggest that managing congestion on low voltage networks will be a crucial component of the electric vehicle revolution and the move away from fossil fuels in trans...

When a location problem is too large to be computed in a reasonable time or if it is impossible to store it in the computer memory, an aggregation is commonly used tool that allows for transforming it to smaller size. Typically, an aggregation method is used only once, in the initial phase, before the solving process. An unavoidable consequence of...

We present a new approximation algorithm to the discrete facility location problem providing solutions that are close to the lexicographic minimax optimum. The lexicographic minimax optimum is a concept that allows to find equitable location of facilities serving a large number of customers. The algorithm is independent of general purpose solvers a...

Conflicts, geo-political crises, terrorist attacks, or natural disasters can turn large parts of energy distribution networks off-line, creating unexpected congestion in the remaining infrastructure. Given the importance of the security of natural gas supply, we need models that enable the management of network congestion, especially during crises....

Human conflict, geopolitical crises, terrorist attacks, and natural disasters can turn large parts of energy distribution networks offline. Europe's current gas supply network is largely dependent on deliveries from Russia and North Africa, creating vulnerabililties to social and political instabilities. During crises, less delivery may mean greate...

The reliable functioning of an electrical power grid is dependent on the proper interaction between many of its elements. What is critically important is its ability to keep the frequency across the entire system stable. Considering a simple mathematical model, representing the network of coupled oscillators, we study the stability of frequency syn...

Traditional approaches to the public service system design can be seen as a resource allocation problem with a central planner, where social costs are minimized. Even though all tax payers share the costs of the system construction and its operation, not all citizens have the same access to the service. There are two different ways of evaluating th...

This paper focuses on the utilitarian solution of public service system design problem, obtained when maximising the sum of all utilities and proportionally fair-like solution, taking into account proportional changes in individual utilities. As an archetypal example of the optimization problem, we are examining the weighted p-median problem, which...

Our contemporary societies are supported by several systems of high importance providing large-scale services substantial for citizens everyday life. Typically, these systems are built or rely on various types of complex networks such as road networks, railway networks, electricity networks, communication networks etc. Examples of such systems are...

We study synchronization dynamics in networks of coupled oscillators with bimodal distribution of natural frequencies. This setup can be interpreted as a simple model of frequency synchronization dynamics among generators and loads working in a power network. We derive the minimum coupling strength required to ensure global frequency synchronizatio...

This paper investigates the effect of network topology on the fair allocation of network resources among a set of agents, an all-important issue for the efficiency of transportation networks all around us. We analyze a generic mechanism that distributes network capacity fairly among existing flow demands. The problem can be solved by semianalytical...

While degree correlations are known to play a crucial role for spreading phenomena in networks, their impact on the propagation speed has hardly been understood. Here we investigate a tunable spreading model on scale-free networks and show that the propagation becomes slow in positively (negatively) correlated networks if nodes with a high connecti...

We analyze populations of Kuramoto oscillators with a particular distribution of natural frequencies. Inspired by networks where there are two groups of nodes with opposite behaviors, as for instance, in power-grids where energy is either generated or consumed at different locations, we assume that the frequencies can take only two different values...

An approach to Quantitative Interdependency Analysis, in the context of Large Complex Critical Infrastructures, is presented in this paper. A Discrete state–space, Continuous–time, Stochastic Process models the operation of critical infrastructure, taking interdependencies into account. Of primary interest are the implications of both model detail...

Here, we uncover the load and fault-tolerant backbones of the trans-European gas pipeline network. Combining topological data with information on intercountry flows, we estimate the global load of the network and its tolerance to failures. To do this, we apply two complementary methods generalized from the betweenness centrality and the maximum flo...

We analyze populations of Kuramoto oscillators with a particular distribution of natural frequencies. Inspired by networks where there are two groups of nodes with opposite behaviors, as for instance in power-grids where energy is either generated or consumed at different locations, we assume that the frequencies can take only two different values....

Here we uncover the load and fault-tolerant backbones of the trans-European gas pipeline network. Combining topological data with information on inter-country flows, we estimate the global load of the network and its tolerance to failures. To do this, we apply two complementary methods generalized from the betweenness centrality and the maximum flo...

The electricity network represents an example of an evolving complex system. The first local networks contained only a few nodes, but within several decades, they have evolved into a highly connected continental system. The growth of these networks was influenced by various factors such as economic, demographic, political and technological developm...

We demonstrate that a broad spectrum of spreading processes taking place on complex networks can be categorized into two fundamentally different regimes, in which either positive or negative degree-degree correlation decelerates their propagation. This result can be explained by the role of the nodes with a high connectivity and their distribution...

We study cascading failures in networks using a dynamical flow model based on simple conservation and distribution laws. It is found that considering the flow dynamics may imply reduced network robustness compared to previous static overload failure models. This is due to the transient oscillations or overshooting in the loads, when the flow dynami...

In order to assess cascading effects in directed networks, we present a model for the dynamics of failure spreading. The model combines network nodes as active, bistable elements and delayed interactions along directed links. Through simulations, we study the dynamics behaviour of generic sample networks. Besides evaluating the failure cascades, fo...

We study the effectiveness of recovery strategies for a dynamic model of failure spreading in networks. These strategies control the distribution of resources based on information about the current network state and network topology. In order to assess their success, we have performed a series of simulation experiments. The considered parameters of...

Most infrastructures, organisations and communication systems in modern societies are based on large complex networks. The possibility of cascading failures is an "Achille's heel" of these complex systems and reflects their vulnerability (Helbing & Kühnert 2003). If an initial failure affects other elements of the network, it may multiply its impac...

We study the effectiveness of recovery strategies for a dynamic model of failure spreading in networks. These strategies control the distribution of resources based on information about the current network state and network topology. In order to assess their success, we have performed a series of simulation experiments. The considered parameters of...

We present a model for the dynamic spreading of failures in networked systems. The model combines network nodes as active, bistable elements and delayed interactions along directed links. By means of simulations, we explore the time-dependent spreading and cascade failures in different network topologies.The results of these simulations point towar...

This paper is dedicated to the recent unprecedented boom of new supermarkets and hypermarkets in middle Europe. The motivation is to provide for the newcomers the tool for decision support, and to help answer the questions: "Is still economically advantageous to build new shopping malls and where to locate them?" We introduce the four versions of d...

To test simulation models of pedestrian flows, we have performed experiments for corridors, bottleneck areas, and intersections. Our evaluations of video recordings show that the geometric boundary conditions are not only relevant for the capacity of the elements of pedestrian facilities, they also influence the time gap distribution of pedestrians...

Distribution system designers often need to answer the question: “How many terminals should be established, when a distribution system with transhipments is designed?” There are two extremally different ways, how to estimate the economical-optimal number of the terminals. The first approach makes use of mathematical programming and solves the discr...

The design of optimal transportation system structure is described. The decision support tool development, which should be able to find optimal decision for the system structure in the case when an objective function and associated constraints are given is also focused. The support tool should offer the solution to a decision marker and enable to r...

The complicated way of obtaining true values of entry parameters is a weaker part of distribution system design problem. This paper uses a continuous approximation approach to identify an optimal number of terminals. It is focused on applying real settlement data obtained from close surroundings of towns that are suitable for placing terminals. Thi...