Sanja Lazarova-Molnar

Karlsruhe Institute of Technology | KIT · Institute of Applied Informatics and Formal Description Methods

The proxel-based method is an intuitive approach to analysing discrete stochastic models, such as are described by stochastic Petri nets or queuing systems for example. The approach analyses models in a deterministic manner, avoiding the typical problems of discrete-event simulation (e.g. finding good-quality pseudo-random-number generator) and par...

Project schedules are typically defined in relatively strict terms and often rely on well-defined task ordering. Commonly, each task has either a pre-determined duration, or, a minimum, a maximum and a most-likely duration length. In real-life, however, projects are subject to numerous uncertainties. They often impact durations of tasks and may lea...

Existing commercial buildings represent a challenge in the energy efficiency domain. Energy efficiency of a building, very often equalized to a building’s performance should not be observed as a standalone issue. For commercial buildings, energy efficiency needs to be observed and assessed within the context of performance of resident businesses. W...

Within the emerging discipline of Energy Informatics people are researching, developing and applying information and communication technologies, energy engineering and computer science to address energy challenges. In this paper we discuss the challenge of advancing energy informatics to enable assessable improvements of energy performance in build...

KEYWORDS Proxel, supplementary variables, stochastic Petri net, state space-based simulation. ABSTRACT The Proxel method is a state space-based approach to the simulation of discrete stochastic models. It implements the method of supplementary variables in an algorithmic, rather than mathematical way, without using partial differential equations an...

Stochastic Petri Nets (SPNs) are a powerful formalism, widely used for modeling complex systems in various domains, ranging from manufacturing and logistics to healthcare and computer networks. In this paper, we introduce PySPN, a flexible and easily extendable Python library for Modeling & Simulation (M&S) of SPNs. PySPN aims to provide researcher...

Classical fault tree analysis (FTA) can be used to analyze and assess combinations of failures of basic components that lead to system failures within a given system. Classical FTA is however unable to handle how temporal sequences of faults lead to system failures. This is an important issue in complex dynamic systems. To model complex systems whe...

In the field of simulation, the key objective of a system designer is to develop a model that performs a specific task and accurately represents real-world systems or processes. A valid simulation model allows for a better understanding of the system’s behavior and improved decision-making in the real world. Face validity is a subjective measure th...

When designing simulations, the objective is to create a representation of a real-world system or process to understand, analyze, predict, or improve its behavior. Typically, the first step in assessing the credibility of a simulation model for its intended purpose involves conducting a face validity check. This entails a subjective assessment by i...

The livestock sector has complex relationships with the three fundamental pillars of sustainability, i.e., environmental, economic, and social. Devising a livestock farming strategy by considering the different sustainability pillars is essential. Although several decision support systems (DSSs) are available for the livestock sector, these DSSs di...

The European pharmaceutical parallel trade refers to the practice of purchasing pharmaceutical products in one European Union (EU) member state at a lower price and reselling the products in another EU member state at a higher price. In the pharmaceutical market, pricing strategies are of utmost importance as the market structure and regulations al...

Agent-based models are often used to explore the potentialconsequences of different assumptions or scenarios and support decision-making in complex systems. One challenge in employing agent-basedmodels for decision-making is identifying the appropriate level of detailand granularity of the models in relation to the decision-relevant ques-tions. On...

The rapid growth in industrialization and the increasing demand for energy have brought about a critical need for energy efficiency in various industries. Adopting intelligent manufacturing techniques is imperative to optimize energy consumption and reduce environmental impacts caused by traditional manufacturing processes. Enhancing energy efficie...

In today's industrial landscape, manufacturing systems face challenges that have significant implications for productivity, efficiency, and overall performance. The growing complexity of these systems and the need for optimization, efficient resource allocation, and adaptability demand innovative approaches. One solution that has gained prominence...

In recent years, there has been a significant increase in the deployment of Cyber-physical Production Systems (CPPS) across various industries. CPPS consist of interconnected devices and systems that combine physical and digital elements to enhance the efficiency, productivity, and reliability of manufacturing processes. Due to the continuous and f...

Predicting remaining cycle times of products in manufacturing systems is critical to ensure on-time deliveries to customers, schedule resources and actions for expected order completions, and address excessive production stops proactively rather than retroactively. Recent advances in Predictive Process Monitoring (PPM), a sub-discipline of Process...

Complex manufacturing systems produce highly engineered products with long product cycle times and are characterized by complex production process behaviors. Ensuring the reliability of these systems is critical to meet customer demands, improve product quality and minimize production losses. The collection and storage of data by sensors and inform...

Reliability modeling enables deriving reliability measurements and illustrating relevant fault-dependencies in manufacturing systems. Data-driven reliability modeling uses data generated in systems to either automate or at least support extraction of reliability models. To use these extracted models for decision support, we need to ensure models' v...

Pharmaceutical parallel trade is a legal trade in European countries, where traders can buy medicinal products in one country and sell them in other countries to make a profit. In the pharmaceutical parallel trade market, players such as manufacturers, wholesalers, parallel traders, pharmacies, and hospitals are involved. Studying and analyzing thi...

Simulation is an advantageous solution to calculate reliability of complex systems when analytical methods are not able to deliver results in time or when we do not have the resources to apply analytical methods. Proxel-based simulation has shown to be very efficient in reliability analysis of complex systems. In this paper, we present a package ca...

Digital twins enjoy increasing interest in a diverse array of industrial sectors, such as manufacturing, healthcare, urban planning, etc. Their usefulness depends on the robustness of the corresponding digital twin models; however, validation of the model, as a mean to ensure models' robustness, is a difficult problem. Moreover, traditional validat...

Accurate reliability modeling and assessment of manufacturing systems leads to lower maintenance costs and higher profits. However, the complexity of modern Smart Manufacturing Systems poses a challenge to traditional expert-driven reliability modeling techniques. The growing research field of data-driven reliability modeling seeks to harness the a...

Agent-based modeling is widely used for modeling and simulation of self-organizing sociotechnical systems that are composed of distributed autonomous agents. In these systems, macro level behaviors emerge from local micro level behaviors of agents that follow rules and interact with each other and the environment. Although the individual agents' be...

Analytical methods for calculating unavailability of complex systems are not always able to deliver results. Proxel-based simulation has shown to be very efficient in reliability analysis of complex systems. In this paper, we apply ftaproxim an R package for proxel-based simulation of fault trees to estimate unavailability of a complex system. ftap...

Fault tree analysis is a probability-based technique for estimating the risk of an undesired top event, typically a system failure. Traditionally, building a fault tree requires involvement of knowledgeable experts from different fields, relevant for the system under study. Nowadays’ systems, however, integrate numerous Internet of Things (IoT) dev...

Pharmaceutical parallel trade emerged due to the European Union's single market for medicines. While many players, such as manufacturers, wholesalers, parallel traders, pharmacies, regulatory authorities, and hospitals, are involved in this market, having a model that accurately reflects the parallel trade market could be a considerable advantage f...

Quantifying and mitigating the environmental impact of livestock sector is of global interest as it has an important role in the global climate change. Although accurate estimation of greenhouse gas (GHG) emissions from livestock production systems is complex, there are several available tools to assist with the emissions estimation. These tools di...

Modern manufacturing systems can benefit from the use of digital tools to support both short- and long-term decisions. Meanwhile, such systems reached a high level of complexity and are frequently subject to modifications that can quickly make the digital tools obsolete. In this context, the ability to dynamically generate models of production syst...

Adoption of digital twins in smart factories, that model real statuses of manufacturing systems through simulation with real time actualization, are manifested in the form of increased productivity, as well as reduction in costs and energy consumption. The sharp increase in changing customer demands has resulted in factories transitioning rapidly a...

Simulation is a growing and very relevant field today. With many application domains and increasing computational power, simulations are solving an increasing number of real-world problems in a safe and efficient manner. The aim of this study is to make an experimental comparison among popular open-source discrete-event simulation frameworks, selec...

There are two primary ways to save energy within a building: (1) through improving building engineering structures and adopting efficient appliance ownership, and (2) through changing occupants’ energy-consuming behaviors. Unfortunately the second way suffers from many challenges and limitations. Occupant behavior is, indeed, a complex and multi-di...

The sharing economy is a peer-to-peer economic model characterized by people and organizations sharing resources. With the emergence of such economies, an increasing number of logistics providers seek to collaborate and derive benefit from the resultant economic efficiencies, sustainable operations, and network resilience. This study investigates t...

Fault tree modelling and failure analysis of systems that are equipped with sensors and meters are becoming more automated and less human-dependent. For a single system to benefit from its own collected data, it will need to wait for a long time to collect sufficient data to build representative models to increase its reliability. Therefore, if mul...

Modern manufacturing systems can benefit from the use of digital tools to support both short- and long-term decisions. Meanwhile, such systems reached a high level of complexity and are frequently subject to modifications that can quickly make the digital tools obsolete. In this context, the ability to dynamically generate models of production syst...

Planning and deploying reliable Smart Manufacturing Systems (SMSs) is of increasing interest to both scholars and practitioners. High system reliability goes hand in hand with reduced maintenance costs and enables optimized repairs and replacements. To leverage the full potential of SMSs and enable data-driven reliability assessment, data needs sho...

Planning and deploying reliable Smart Manufacturing Systems (SMSs) is of increasing interest to both scholars and practitioners. High system reliability goes hand in hand with reduced maintenance costs and enables optimized repairs and replacements. To leverage the full potential of SMSs and enable data-driven reliability assessment, data needs sho...

Several cities have recently moved towards becoming smart cities for better services and quality of life for residents and visitors, with: optimized resource utilization; increased environmental protection; enhanced infrastructure operations and maintenance; and strong safety and security measures. Smart cities depend on deploying current and new t...

Reliability analysis of cyber-physical systems have benefitted substantially from the introduction of a range of technology enablers. Internet of things (IoT), advanced computing architectures and digital platforms are among the new technologies that are enhancing the data collection and analytics perceptions in the era of Industry 4.0. Fault tree...

The rapid increase in livestock production poses an alarming threat to environmental sustainability. With appropriate mitigation strategies and technical interventions, the livestock sector can achieve a substantial level of Greenhouse Gas (GHG) emissions reduction. There are several tools and techniques available to quantify the GHG emissions from...

Precision Livestock Farming (PLF) is a concept that allows real-time monitoring of animals, by equipping them with sensors that surge livestock-related data to be further utilized by farmers. PLF comes with many benefits and ensures maximum use of farm resources, thus, enabling control of health status of animals, while potentially mitigating Green...

Complex manufacturing systems require digital tools for online production planning and control, and simulation models generated from data can guarantee the ability to take prompt decisions at any time. In this context, reliability is a key performance measure that has to be correctly represented in the digital instances of smart manufacturing syste...

Reliability is one of the most important performance indicators in contemporary production facilities. Increasing reliability of manufacturing systems results in their prolonged lifetimes, and reduced maintenance and repair costs. Reliability modeling is a common technique for deriving reliability measurements and illustrating relevant fault-depend...

The adoption of a digital twin for a smart factory offers several advantages, such as improved production and reduced costs, and energy consumption. Due to the growing demands of the market, factories have adopted the reconfigurable manufacturing paradigm, wherein the structure of the factory is constantly changing. This situation presents a unique...

Digital innovation is leading to a greater uptake of smart technologies in the building industry. Smart systems can reduce the built environment carbon footprint, improve occupant productivity and enable buildings to participate in managing the electricity network. However, their deployment poses significant challenges, given the heterogeneity of h...

Livestock sector is known for its contribution to environmental pollution. A large portion of anthropogenic emissions is from livestock-related activities, such as animal feeding and manure management. According to the Food and Agriculture Organization of the United Nations, by 2050, 73% increase in livestock product consumption is anticipated. Thi...

Cyber-Physical Systems (CPS) are marking our time and they are characterized by the smooth integration of cyber and physical parts. This integration carries along both challenges and new opportunities. The combination of software and hardware elements implies more complex systems that are prone to intricate interdependencies that affect the overall...

Analysis of failure modes in a system is essential in increasing the reliability of the system. Fault trees model probabilistic causal chains of events that lead to a global system failure. With the emerging availability of data, deriving fault trees from observational data, rather than expert knowledge, would more accurately reflect the true behav...

Industry 4.0 is a promising vision for advancing the manufacturing sector through the recent innovations in information and Communication Technologies that enable collecting, storing, and processing detailed and accurate data about industry processes. This data enables manufacturers for data‐driven decision making to significantly improve their ope...

Performance testing of components and subsystems of buildings is a promising practice for increasing energy efficiency and closing gaps between intended and actual performance of buildings. A typical shortcoming of performance testing is the difficulty of linking a failing test to a faulty or underperforming component. Furthermore, a failing test c...

Sanja Lazarova-Molnar, with an introduction by Lucinda Periac-Arnold, Senior Publishing Editor, SAGE Publishing - As we approach the 2019 International Women in Engineering Day, this 23rd June, at SAGE we are excited to highlight the work of our talented women partners. With over 80 journals in the Engineering and Materials Science disciplines we...

Factories use many manufacturing processes that consume a lot of energy and highly contribute in greenhouse gas emissions. The introduction of the concept of Industrial Internet in USA and Industry 4.0 in Europe offers many opportunities to reduce energy consumption in these factories. Introducing and utilizing smart techniques for the applications...

Smart buildings equipped with state-of-the-art sensors and meters are becoming more common. Large quantities of data are being collected by these devices. For a single building to benefit from its own collected data, it will need to wait for a long time to collect sufficient data to build accurate models to help improve the smart buildings systems....

A significant proportion of energy consumption by buildings worldwide, estimated to ca. 40%, has yielded a high importance to studying buildings’ performance. Performance Testing is a mean by which buildings can be continuously commissioned to ensure that they operate as designed. Historically, setup of Performance Tests has been manual and labor-i...

Reliability is the measure of the likelihood that a product, system or service will perform its intended function adequately for a specified period of time. Low reliability of a manufacturing system, besides the costly repairs and replacements, also implies reduced production, and consequently, significantly reduced profits. Therefore, it is very i...

Energy consumption in buildings is responsible for a significant portion of the total energy use and carbon emissions in large cities. One of the main approaches to reduce energy consumption and its environmental impact is to convert buildings into smart buildings using computer, software, sensor, and network technologies. Using smart building ener...

Cyber-Physical Systems (CPS) are being developed to provide useful interactions between physical systems and environments and cyber world for a variety of applications. CPS are designed with a set of software and interconnected distributed hardware components that are linked with physical elements to provide advanced monitoring and control mechanis...

Smart buildings are run by Cyber-Physical Systems (CPS), termed as Building Management Systems (BMS). Typical goals for the operation of BMS are increasing occupant comfort and decreasing buildings energy consumption. The central and critical figure, however, for achieving both goals are buildings' occupants. In some BMS, occupants have a high leve...

Smart cities are becoming a reality. Various aspects of modern cities are being automated and integrated with information and communication technologies (ICT) to achieve higher functionality, optimized resources utilization and management and improved quality of life for the residents. Smart cities rely heavily on utilizing various software, hardwa...

Energy consumption of buildings represents roughly 40% of the overall energy consumption. Most of the national agendas include rigorous measures aimed at reducing the energy consumption and, thereby, the carbon footprint. Timely and accurate Fault Detection and Diagnosis (FDD) in Building Management Systems (BMS) have the potential to reduce energy...

Smart buildings are run by Building Management Systems (BMS) that are cyber-physical systems that control and monitor a number of buildings' subsystems. BMS have not been sufficiently prioritized on their reliability measures. Reliability, however, along with security, safety, energy performance and occupant comfort, are very important for certain...

In software engineering, project scheduling is an essential factor that determines success of projects. Success is influenced by various project scheduling estimates, such as accurate estimates of project's duration and budget. These estimates highly depend on un