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  1. 3 Polish Journal of Management Studies
  2. 2 Diagnostyka
  3. 2 International Journal of Electronics and Telecommunications
  4. 2 Journal of Sustainable Development of Transport and Logistics
  5. 2 Management and Production Engineering Review
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  1. 4 Szarata A.
  2. 4 Wiśniewski T.
  3. 2 Biruk S.
  4. 2 Gubarevych Oleg
  5. 2 Korytkowski P.
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  1. 1 2024
  2. 5 2023
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1
Content available remote Solving technological problems of flight services at airport involving composite materials
Romele Marina, Zabirov Anwar, Chatys Rafał, Shestakov Vladimir
Composites Theory and Practice
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2024
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R. 24, nr 2
123--129
EN
Inadequate information support and dispatch of the execution of individual operations of the technological process (especially the repair of composite structures) of aircraft preparation for a flight is one of the reasons for delays. In this regard, there is a need to study the management processes of airport services that ensure the performance of individual technological operations in the preparation of aircraft for departure. This problem belongs to the class of multi-criteria problems, which is solved using simulation modelling. The model is represented by an interconnected set of modules, each of which is associated with a separate technological operation of the general technological process, i.e. the technological process is divided into separate technological operations. The links of individual blocks of the model reflect the information and technological links of a real set of technological operations of flight preparation for departure and are represented by the synthesising algorithm of the simulation model.
2
Content available Management system structure vs. Behavior - a supply chain simulation analysis
Pietroń Roman
Zeszyty Naukowe. Organizacja i Zarządzanie / Politechnika Śląska
|
2023
|
z. 169
575--597
EN
Purpose: The purpose of this article is to present a research report on a system dynamics simulation modeling and experimenting of bullwhip effect (BWE) to examine effectiveness of some selected inventory control policies with down- and upstream information flow in a Beer Distribution Game (BDG) of a supply chain structure. Design/methodology/approach: The impact of systems’ structures and decision making policies in supply chains or logistics systems are measured and analyzed by an application of systems thinking paradigms and approaches. Particularly, the continuous simulation modeling approach with systems thinking Iceberg model metaphor, allowing to focus on strategic aspects of management with some recommendation to design better structures and decision making policies are taken. For the bullwhip effect analysis of a supply chain example (based on BDG model), a System Dynamics (SD) continuous simulation modeling method with some proposals in order to analyze feedback loop dominance are undertaken to explain supply chain behaviors and to make some sensitivity analysis for decision making (inventory control) policies. Findings: The research findings outline the impact of cause - effect relations, feedback loops polarities, and decision making policies to particular behaviors of the BDG supply chain. Research limitations/implications: Because of complexity of heuristic methods for feedback loop dominance analysis only simple approach was applied (LPD), and some selected scenario for simulation experiments were undertaken resulting in limited conclusions. Practical implications: The conclusions of the research draw some practical recommendations for a design of information sharing system and an effectiveness of some inventory control policies to be applied in supply chains. Social implications: One of the systems thinking elements in practical management is an influence to mental models of managers and decision makers. Managers in supply chain systems particularly need some recommendations to avoid bullwhip effect negative impacts. Additionally, managers and also scholars still call for more research to investigate the design and decision making in supply chains, therefore systems thinking simulation research can bridge the gap between traditional operations research and management with other approaches to provide insight into supply-chain dynamics and deliver impactful suggestions to managers. Originality/value: The paper gives a concept of supply chain dynamic analysis by an application of Iceberg model systems thinking metaphor, feedback loop dominance analysis, and a measurement of some selected inventory control policies effectiveness.
3
Content available Navigating the future: Evaluating two-level transport solutions for sustainable urban development
Stashkiv Mykola, Tson Oleg, Łakomy-Zinowik Marta, Basta Michał
Journal of Sustainable Development of Transport and Logistics
|
2023
|
Vol. 8, No. 2
91--112
EN
Purpose: The purpose of this paper is to propose and evaluate two options for two-level transport solutions at the intersection of the bypass road and the Pidvolochyske Highway in Ternopil, Ukraine. The aim is to address the issues associated with the current road network passing through residential zones and present an optimal resolution for the intersection. Methodology: The methodology involves using the PTV Vissim software to conduct simulation modelling. The transport and operational indicators of the two options for two-level transport solutions, an elongated loop and two interconnected rings, are compared across different traffic intensities. Results: The results show that the transport solution with two roundabouts exhibits superior characteristics, particularly under high traffic flow conditions. The strengths and limitations of each solution are comprehensively delineated, encompassing factors like efficiency, cost-effectiveness, safety measures, and ecological impacts. Theoretical contribution: The paper contributes to advancing knowledge and practice in two-level transport solutions. It provides valuable insights for developing the transportation system in Ternopil and other post-conflict cities. The advantages and disadvantages of public-private partnerships (PPP) as a tool for attracting investments and innovations in transportation infrastructure are also discussed. Practical implications: The findings of this research can be used by professionals in transportation, urban planning, and ecology for infrastructure development. It also serves as a valuable resource for residents of Ternopil interested in fostering improvements to their city’s quality of life.
4
Content available Preventing the development of emergency modes of interlocked electric drives of a rolling mill under the impact loads
Druzhinin Valeriy, Sivyakova Galina, Kalinin Alexey, Tytiuk Valerii, Nikolenko Anatolii, Kuznetsov Vitaliy Vadimovich, Kuzmenko Mykhailo
Diagnostyka
|
2023
|
Vol. 24, No. 1
art. no. 2023105
EN
In recent years, due to the tightening of competition in the global market of steel producers, the requirements for the quality of hot-rolled steel have increased. The finishing group of the rolling mill is characterized by a complex structure of mechanical and electrical parts. The operation of electric drive systems of such units is characterized by the interrelation of electromagnetic processes, mechanical phenomena and technological factors. As experimental studies have shown, the quality of the supply voltage is inextricably linked with the impact nature of the loads in the rolling stands of the roughing and finishing groups of the hot rolling mill. A decrease in the supply voltage may be accompanied by the development of emergency modes of synchronous electric drives, leading to a decrease in the quality of the finished product.The paper developed a mathematical model of the power supply system of the rolling mill JSC "ArcelorMittal Temirtau". It is shown that this can lead to loss of synchronism of the synchronous motor. Such a voltage drop has a significant impact on the operation of DC electric drives of the finishing group. Various strategies are proposed to counter the development of emergency situations.
5
Content available Analysis of the features of application of vibration diagnostic methods of induction motors of transportation infrastructure using mathematical modeling
Gubarevych Oleg, Gerlici Juraj, Gorobchenko Oleksandr, Kravchenko Kateryna, Zaika Denys
Diagnostyka
|
2023
|
Vol. 24, No. 1
art. no. 2023111
EN
In the work, studies were carried out on the use of vibration diagnostic methods for monitoring the state of induction motors with a squirrel-cage rotor, operated in electric drives of transport equipment. The most common and difficult-todiagnose damage to an induction motor is turn-to-turn short circuits in the stator winding, which require timely determination and establishment of the degree of damage to prevent an emergency shutdown of the equipment. The main purpose of the study is to establish the most effective areas of application of vibration diagnostic methods in determining the technical condition of the stator of induction motors under load. The experiments were carried out using simulation modeling for cases of turn-to-turn short circuits in one and two phases simultaneously, as well as with the influence of a low-quality supply voltage system on vibration parameters. The results of the work are relevant for further improvement of systems for diagnostic control of drives of transport equipment to increase the efficiency and reliability of their work.
6
Content available Proactive-reactive repetitive project scheduling method - the concept of risk consideration at the project planning and execution stage
Jaśkowski Piotr, Biruk Sławomir, Krzemiński Michał
Archives of Civil Engineering
|
2023
|
Vol. 69, nr 4
89--104
EN
The construction contractor is concerned with reducing the cost of the project, including reducing unnecessary downtime. This is achieved when resources are fully utilized; this means the crews work continuously moving without interruption from one location to the other. However, any disturbance in the optimally scheduled workflow caused by random events is likely to result in delays, interruptions in the crews work, and productivity losses. There is therefore a need for scheduling methods that allow plans to be more resilient to disruptions and ensure a reduction in downtime and implementation costs. The authors put forward a proactive-reactive approach to the schedule risk management. Proposed method makes it possible to protect schedule deadlines from the impact of risk factors by allocating time buffers (proactive approach). It also takes into account the measures that managers take during execution in response to delays that occur, such as changing construction methods, employing extra resources, or working overtime (reactive approach). It combines both ideas and is based on project simulation technique. The merits of the proposed approach are illustrated by a case of a repetitive project to erect a number of buildings. The presented example proves that the proposed method enables the planner to estimate the scale of delays of processes’ start and consider the impact of measures to reduce duration of processes in particular locations taken in reaction to delays. Thus, it is possible to determine the optimal schedule, at which the costs of losses associated with delays and downtime are minimal.
PL
Najlepsze rezultaty realizacji przedsięwzięć budowlanych są osiągane wówczas, gdy brygady pracują bez przerw i po zakończeniu procesu na jednej części obiektu (działce roboczej) mogą rozpocząć pracę na działce kolejnej, na której zakończono wykonanie procesów poprzedzających. Dzięki ciągłości pracy brygad i powtarzalności realizacji tych samych zadań na poszczególnych działkach roboczych może wystąpić efekt uczenia się i redukcji czasu wykonania zadań. Zakłócenia w realizacji robót, na skutek oddziaływania czynników ryzyka o charakterze losowym, mogą prowadzić do opóźnień w wykonaniu procesów poprzedzających i w efekcie do przestojów w pracy brygad oraz wydłużenia czasu realizacji całego przedsięwzięcia. W związku z tym istotne jest rozwijanie metod harmonogramowania uwzględniających dynamikę rzeczywistego przebiegu wykonania procesów w zmiennych warunkach realizacyjnych. Redukcja odchyleń terminów zaplanowanych od rzeczywistych umożliwia zmniejszenie kosztów związanych z ich przekroczeniem, m.in. zamrożenia środków obrotowych w zapasach, przestojów w pracy brygad roboczych, kar umownych za niedotrzymanie terminów kontraktowych itp. Zdeterminowane terminy realizacji procesów w harmonogramie pozwalają na tworzenie planów produkcji pomocniczej, optymalizację zaopatrzenia budowy w materiały i sprzęt, pozyskiwanie zasobów ludzkich i zawieranie kontraktów z podwykonawcami. Ryzyko wystąpienia opóźnień może być uwzględnione już na etapie harmonogramowania poprzez określenie wielkości buforów czasu i ich alokację w harmonogramie. Takie podejście jest określane mianem harmonogramowania proaktywnego. Nawet mimo uodpornienia harmonogramu przy zastosowaniu metod proaktywnych, w trakcie realizacji mogą pojawić się nieprzewidziane zdarzenia, które powodują, że ochrona taka jest niewystarczająca i rozpoczęcie kolejnych zadań w zaplanowanych terminach jest niemożliwe ze względu na opóźnienia procesów poprzedzających lub niezwolnienie niezbędnych zasobów. Zachodzi wówczas konieczność reakcji - podjęcia działań redukujących odchylenia od planu lub aktualizacji planu. W reakcji na zakłócenia są podejmowane działania zmierzające do skrócenia czasu procesów jeszcze niewykonanych (zmiana wariantu technologicznego wykonania procesu, zatrudnienie dodatkowych zasobów, praca w nadgodzinach lub wydłużony tydzień pracy). W artykule zaproponowano podejście do uwzględnienia ryzyka o charakterze proaktywno-reaktywnym, wykorzystujące metodę symulacji cyfrowej w celu oszacowania wielkości opóźnień terminów rozpoczynania kolejnych procesów z uwzględnieniem reaktywnych działań redukujących czas ich wykonania na działkach roboczych, podejmowanych już w fazie realizacji. W proponowanej metodzie proaktywno-reaktywnego harmonogramowania przedsięwzięć powtarzalnych zakłada się, że czasy realizacji procesów są zmiennymi losowymi o znanej funkcji gęstości i parametrach rozkładu.
7
Content available Simulation modeling for evaluation of efficiency of observed ship coordinates
Vorokhobin I., Burmaka I., Fusar I., Burmaka O.
TransNav : International Journal on Marine Navigation and Safety of Sea Transportation
|
2022
|
Vol. 16 No. 1
137--141
EN
Simulation computer modeling was used to evaluate the efficiency of the vessel’s observed coordinates using the mixed laws of distribution errors of the first and second type for lines of position (LOP). Simulation modeling showed good convergence of evaluation of efficiency calculated by analytical expressions and obtained by simulation. A graphical depiction of the observed points’ deviation relative to the mathematical expectation in the case of distribution of LOP errors of both types according to mixed laws is obtained by the method of least squares and the method of maximum likelihood estimation.
8
Content available Comparison of the results of simulation modeling of an asynchronous electric motor with the calculated electrodynamic and energy characteristics
Gubarevych Oleg, Golubieva Svitlana, Melkonova Inna
Przegląd Elektrotechniczny
|
2022
|
R. 98, nr 10
61--66
EN
The paper presents the results of a comparison of the electrodynamic and energy characteristics and parameters of an asynchronous motor, obtained by simulation and calculated by the classical method. The mathematical model in the MATLab software environment is used for research. The research results are relevant when choosing and using the proposed simulation model of three-phase squirrel-cage asynchronous motors for further research, including the effect of various engine defects on its performance.
XX
W artykule przedstawiono wyniki porównania charakterystyk i parametrów elektrodynamicznych i energetycznych silnika asynchronicznego, uzyskanych metodą symulacji i obliczonych metodą klasyczną. Do badań wykorzystano model matematyczny wykonany w środowisku oprogramowania MATLab. Wyniki prac mają istotne znaczenie dla wyboru i wykorzystania zaproponowanego modelu symulacyjnego asynchronicznego silnika elektrycznego z wirnikiem klatkowym do dalszych badań, w tym wpływu różnego rodzaju uszkodzeń silnika na jego pracę.
9
Content available Research on the risk classification of cruise ship fires based on an attention-BP neural network
Xiong Zhenghua, Xiang Bo, Chen Ye, Chen Bin
Polish Maritime Research
|
2022
|
nr 3
61--68
EN
Due to the relatively closed environment, complex internal structure, and difficult evacuation of personnel, it is more difficult to prevent ship fires than land fires. In this paper, taking the large cruise ship as the research object, the physical model of a cruise cabin fire is established through PyroSim software, and the safety indexes such as smoke temperature, CO concentration, and visibility are numerically simulated. An Attention-BP neural network model is designed for realizing the intelligent identification of a cabin fire and dividing the risk level, which integrates the diagnosis results of multiple neural network models through the self-Attention mechanism and adaptively distributes the weight of each BP neural network model. The proposed model can provide decision-making reference for subsequent fire-fighting measures and personnel evacuation. Experimental results show that the proposed Attention-BP neural network model can effectively realize the early warning of the fire risk level. Compared with other machine learning algorithms, it has the highest stability and accuracy and reduces the uncertainty of early cabin fire warning.
10
Content available Simulation of the influence of wind power plants on the compartments of the complex landscape system
Ruda Mariia, Boyko Taras, Chayka Oksana, Mikhalieva Maryna, Holodovska Olena
Journal of Water and Land Development
|
2022
|
no. 52
156--165
EN
The impact of wind power plants on the environmental components is assessed taking into account a number of their parameters, in particular the technical characteristics of wind turbines, the characteristics of networks, engineering and other structures. To do this the life cycle of the wind power plants is described taking into account (by way of inventory) all the necessary materials and resources. Waste management scenarios have been developed, the use of which will make it possible to reduce the harmful impact on the environment. Based on the inventory and input data on the wind farm under study, a diagram is generated - a tree of life cycle processes of the wind power plant - to determine the potential environmental impacts. A list of impact categories that represent the load on the environment caused by the wind power plant is defined; also, the relative contribution of harmful factors is determined for each category, taking into account possible scenarios of waste management. Ecological profiles have been built for all potential impacts on the environment. After normalisation and determination of significance, individual estimates of all indicators and their distribution in three categories of lesions were obtained: human health, ecosystem quality and resources, as well as four stages of the wind farm life cycle: production, dismantling and disposal, operation, transportation and installation. The obtained profiles made it possible to determine individual indicators and eco-indicators, expressed in eco-points that characterise the wind farm under study.
11
Content available Elaborationand research of a model of optimal production and development of industrial systems taking into accountthe use of the external resources
Hryshyn Dmytro, Borovska Taisa, Kalizhanova Aliya
Informatyka, Automatyka, Pomiary w Gospodarce i Ochronie Środowiska
|
2022
|
T. 12, nr 4
60--66
EN
The problem of optimization of investment projects related to the development of modern production systems is considered. The tasks of managing of operation and development of production systems considering external resources – the synthesis and analysis of optimal credit strategies – are posed and solved. An analysis of analogs – solutions of the variational problem of optimal development, the disadvantage of which is the difficulty of obtaining information about the state of production and the external environment, was carried out. The new solution is based on the resource approach, when external resources are taken into account in the cost of production resources. A generalized model of optimal development is used, in which the planned period of the investment project is divided into intervals. At the beginning of each interval, the optimal development strategy is adjusted taking into account the clarification of information about the future state of the active environment: actions of competitors, consumers, world markets. To determine the optimal amount and optimal distribution of credits between subsystems, the maxima of the criterion – the parameterized function of the system's efficiency – are determined at each interval. A new model has been developed based on the model of optimal development, which takes into account the use of external resources, such as loans. The method of including an external resource in the development function and the production function is considered. Examples of modeling are given.
PL
Rozpatrywany jest problem optymalizacji przedsięwzięć inwestycyjnych związanych z rozwojem nowoczesnych systemów produkcyjnych. Postawiono i rozwiązano zadania zarządzania funkcjonowaniem i rozwojem systemów produkcyjnych z uwzględnieniem zasobów zewnętrznych – synteza i analiza optymalnych strategii kredytowych. Przeprowadzono analizę analogów – rozwiązań wariacyjnego problemu optymalnego rozwoju, którego wadą jest trudność uzyskania informacji o stanie produkcji i otoczeniu zewnętrznym. Nowe rozwiązanie oparte jest na podejściu zasobowym, kiedy to zasoby zewnętrzne są uwzględniane w kosztach zasobów produkcyjnych. Wykorzystano uogólniony model optymalnego rozwoju, w którym planowany okres realizacji projektu inwestycyjnego podzielono na przedziały. Na początku każdego interwału optymalna strategia rozwoju jest korygowana z uwzględnieniem doprecyzowania informacji o przyszłym stanie otoczenia aktywnego: działań konkurentów, konsumentów, rynków światowych. W celu określenia optymalnej ilości i optymalnej dystrybucji kredytów pomiędzy podsystemami, w każdym interwale wyznaczane są maksima kryterium – sparametryzowanej funkcji efektywności systemu. Na podstawie modelu optymalnego rozwoju opracowano nowy model, który uwzględnia wykorzystanie zasobów zewnętrznych, takich jak kredyty. Rozpatrzono metodę uwzględniania zasobu zewnętrznego w funkcji rozwoju i funkcji produkcji. Podano przykłady modelowania.
12
Content available The stack control strategy based on the concept of operational temperature
Kuznetsov Alexander L., Semenov Anton D., Oja Hannu
Scientific Journal of Gdynia Maritime University
|
2021
|
nr 120
22--32
EN
The paper studies two different types of container strategy: the traditional one, which involves container allocation into positions with a minimum stack height; and the “temperature” one, which considers the positions with a minimum “temperature” for the containers in the stack below. The “temperature” in this case means a metric which is connected to the storage (dwell) time of the containers. Particularly, this value can be represented by container selection probability or number of days stored in the container yard. Utilization of different metrics results in significantly different numbers of moves. Therefore, the authors compare two container stacking strategies: the traditional one and the temperature strategy with different metrics. It is stated that these strategies can be compared only by simulation modelling. The paper describes the main algorithms used to provide simulation modelling. The results of the research show that the temperature strategy with container dwell time as temperature metrics can save 6% of the total moves necessary to maintain the container flow.
13
Content available Intelligent System in the Context of Business Process Modelling
Yaremko Svetlana A., Kuzmina Elena M., Savina Nataliia B., Gromaszek Konrad, Yeraliyeva Bakhyt, Borankulova Gauhar
International Journal of Electronics and Telecommunications
|
2021
|
Vol. 67, No. 2
163--168
EN
The article deals with the features and characteristics of intelligent systems for modelling business processes. Their classification was made and criteria for comparison were developed. According to the comparative analysis of existing expert systems for intelligent analysis, a reasonable choice of system for modelling business processes of a particular enterprise has been carried out. In general, it was found that the introduction of intelligent systems for modelling business processes of the enterprise and forecasting its activities for future allows management of the company to obtain relevant and necessary information for the adoption of effective management decisions and the development of a strategic plan.
14
Content available Robotic automation of inland container terminals
Malyshev Nikolay V., Koroviakovskii Evgenii K., Rostovceva Svetlana A.
Zeszyty Naukowe Akademii Morskiej w Szczecinie
|
2020
|
nr 63 (135)
69--76
EN
The article presents the analysis of options for a transshipment terminal system with consideration of Russian transport system development. The aim is to determine the premises and possible problems, considering human absence, in the technological process at an inland container terminal. Statistical methods are used to analyze the market of robotic automation and the perspective for unmanned technology introduction. Simulation modeling of inland container terminal operation with various types of equipment, to study the applicability of robotic automation. The choice of modeling equipment results from the impossibility of completing an experiment on the real object, difficulties of analytical modeling (the system contains casual relations, nonlinear logic, stochastic variables), and the necessity to analyze the system’s time behavior. Consideration of robotic automation in a terminal warehouse complex is of particular importance due to technological progress followed by the freight terminal to be an area with highly organized technological processes and the need for highly paid specialists.
15
Content available Evaluation of ships turnaround time in port with approach channel
Kuznetsov Alexander L., Kirichenko Alexander V., Semenov Anton D.
Scientific Journal of Gdynia Maritime University
|
2020
|
nr 115
31--41
EN
The operation efficiency of a port with an approach channel to a great extent depends on decisions made by the port authority and harbor master over the channel scheduling. Currently there are no formal methods which allow to evaluate the influence of the channel schedule on the ship turnaround time, especially when the throughput capacity is restricted. The relevant system has a complex structure that rules out common mathematical methods. The paper studies some typical structures of these systems and offers an approach for developing adequate simulation models. These models enable the conduct of comparative studies of different variants of approach channel scheduling and serve as a toolkit to support the decision-making procedure for harbor master and port operators.
16
Content available Integrated Approaches to Determination of CO2 Concentration and Air Rate Exchange in Educational Institution
Deshko Valerii, Bilous Inna, Vynogradov-Saltykov Volodimer, Shovkaliuk Maryna, Hetmanchuk Hanna
Rocznik Ochrona Środowiska
|
2020
|
Tom 22, cz. 1
82--104
EN
Many old public buildings in Central and Eastern Europe are characterized by low energy efficiency and often lack of mechanical ventilation. The general trends are aimed to improve the energy efficiency of the building sector and to provide comfort conditions. The indoor air quality can be determined based on the CO2 concentrations. In the article, a complex approach to the definition and analysis of data on the indoor CO2 concentration and the air exchange rate in educational institutions at natural air exchange and in the absence of mechanical air circulation was implemented. Educational institutions in Kyiv have been considered. The study of the CO2 concentration of indoor and outdoor air of three typical schools of mass development in the 80 s, as well as the training building of Igor Sikorsky KPI, was carried out. Experimental determination of the background CO2 concentration during the day next to the considered objects showed that the background concentration of CO2 is in the range of 400-420 ppm. Measurements of the CO2 concentration distribution were carried out after classes throughout the classroom area, according to which the difference between the values at the level of the working area was 30...180 ppm. It was found that the concentration of CO2 varies during classes between 700-1100 ppm. During the break, the CO2 concentration decreases to 500-1000 ppm, depending on the type of ventilation. Experimental data on the dynamics of changes in the indoor CO2 concentration are used to determine the air exchange rate based on balances of air flows and CO2. It is shown that the number of present persons influences the indoor CO2 concentration more significantly than the air exchange rate. On the example of an experimental study of the CO2 concentration in the classrooms for high school students it was found that the air exchange rate during the classes is in the range of 0.4...0.75 h-1. During breaks the air exchange rate increases to 2.9-3.5 h-1. For the range considered, the weighted average air exchange rate is 0.8 h-1, and even with forced airing, the air exchange rate is insufficient to ensure acceptable CO2 concentration. For the training building of Igor Sikorsky KPI a field experiment was carried out to determine the dynamics of changes in CO2 concentration in time and on the basis of it the air exchange rates for representative classrooms were determined. The concentration of CO2 ranged from 500 to 2000 ppm and increases by 350-850 ppm depending on the use and location of classrooms. Based on experimental data, the air exchange rate for the training building of the education institution is in the range of 0.35-0.7 h-1. During the periods of airing the air exchange may increase by 0.45 h-1, but this does not allow reaching the standard value. When analyzing the obtained results, simulation models of natural air exchange of the examined classrooms were used on the basis of the improved ASHRAE method. The natural air exchange rate based on simulations is in the -0.8…0.5 h-1 range. Negative values are explained by exfiltration, which is typical for the upper floors. Not only the comfort and condition of the building envelope, but also the total energy consumption of the building depend on the actual level of air exchange rate. In the total energy balance the ventilation component is 30-60%. Further use of the obtained results can be connected with monitoring of the actual level of air exchange rate and its consideration during complex modernization or implementation of the ventilation systems with heat recovery in the premises of educational institutions.
17
Content available Simulation modeling for predicting hospital admissions and bed utilisation
Hajłasz Maria, Mielczarek Bożena
Operations Research and Decisions
|
2020
|
Vol. 30, No. 3
5--19
EN
Demographic research of the world population shows that societies are ageing. The ongoing changes in the population structure will require appropriate quantitative and qualitative adjustments in health services to meet the needs of society. Simulation methods turn out to be helpful in these kinds of analyses. In this paper, the authors present a case study on using discrete event simulation (DES) to support decision-making in the field of hospital bed management in the light of demographic changes. The case study was elaborated for one of the Polish district hospitals. A DES model was built to simulate admissions to two hospital wards: paediatric and geriatric. A series of experiments were carried out as based on real data extracted from the hospital database and forecasted demographic trends elaborated by the Central Statistical Office of Poland (CSO). The influence of demographic changes on hospital admissions in the chosen age-gender cohorts was explored, examining different variants of hospital bed availability. The results of the experiments show that demographic trends significantly influence healthcare admission and bed utilisation. The reduction in the number of admissions to the paediatric ward by about 6% results in a change in average bed utilisation from 57.90% to 54.06%. With about 12% more admissions to the geriatric ward, the change is from 68.88% to 75.59%.
18
Content available Optimal gas transport management taking into account reliability factor
Grudz Volodymyr, Grudz Yaroslav, Zapukhliak Vasyl, Chudyk Ihor, Poberezhny Lubomyr, Slobodyan Nazar, Bodnar Vitaliy
Management Systems in Production Engineering
|
2020
|
nr 3 (28)
202--208
EN
In the period of shortage of gas supply, special attention is given to reducing the supply of gas to its consumers, that is, their complete and uninterrupted gas supply. Increasing gas losses associated with technological transportation costs, in particular caused by gas flow instability and frequent changes in gas transmission network operating modes. Considering losses due to unreliability of gas pumping is one of the important tasks of gas supply optimization. The purpose of the study is to develop an optimization mathematical model that will simultaneously take into account the factors of reliability and minimum lossesIn the general case, the optimization calculations of the modes of operation of the main gas pipelines are intended to solve three main problems: determining the maximum productivity, calculating the optimal mode with a given productivity and choosing the optimal strategy, the development of the pipeline. On the basis of approaches of simulation modeling of complex systems, a multiparameter mathematical model of gas supply process optimization was developed. It is shown that a comparative analysis of the forecast and actual indicators of the operating modes of the plunger gas pumping unit shows their satisfactory convergence. The performance of the compressor operation period in the process of injection according to the forecast deviates from the actual value for the whole period of operation of the plunger gas pumping unit in 2016 by 2.98%. The optimization problem of gas pumping planning is considered, taking into account the expected losses, on the basis of which the transfer of the controlled system from the initial state to the final one is carried out by such a sequence of states that minimizes the total cost of the system evolution.
19
Content available Characteristics and study of make-to-stock and make-to-availability production strategy using simulation modelling
Ciechańska Olga, Szwed Cezary
Management and Production Engineering Review
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2020
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Vol. 11, No. 4
68--80
EN
Make-To-Stock (MTS) and Make-To-Order (MTO) are the two traditional strategies in production management. In the case of the MTS there is a growing demand for a new approach, which is called Make-To-Availability (MTA) strategy. The paper characterizes and compares the MTS and MTA strategies. The comparative analysis based, among others, on computational experiments carried out in a computer program developed in Microsoft Visual Studio 2017 Environment was presented. The models have been prepared for both strategies with the same assumptions: external conditions (market demand) and internal conditions (structure of the production process). The investigation of how the strategies respond to various scenarios of demand intensity was done. The simulation models were prepared and validated for the case of the production line in one of the industrial automation company. The research shows that the use of the MTA strategy in the majority of cases gives much better results than the use of the MTS strategy due to the minimization of storage costs and the costs of non-fulfillment of the customers’ demand. The directions for further research were also presented.
20
Content available A simulation study of Industry 4.0 factories based on the ontology on flexibility with using FlexSim® software
Luściński Sławomir, Ivanov Vitalii
Management and Production Engineering Review
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2020
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Vol. 11, No. 3
74--83
EN
The main aim of the article is to develop a simulation model of flexible manufacturing system with applying the ontology on flexibility. Designing manufacturing systems matching both production and market requirements becomes more and more challenging due to the variability of demand for a large number of products made in many variants and short lead times. Manufacturing flexibility is widely recognised as a proven solution to achieve and maintain both the strategical and operational goals of the companies exposed to global competition. Generic simulation model of flexible manufacturing system was developed using FlexSim® 3D software, then the example data were used to demonstrate the developed model applicability. “The Ontology on Flexibility” was applied for evaluation of achieved flexibility of manufacturing system.
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