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EN
Purpose: The purpose of this article is to identify scheduling problems in Polish local government units, examine the standards that are already used and identify the possibilities of improvement. For these reasons, three research questions are stated and then answered. Design/methodology/approach: A questionnaire method is used. The answers are collected from Polish local government units. A quantitative data analysis is performed, supplemented by an in-depth analysis of the open question answers. Findings: The results reveal that public projects do not always end on time and that standard scheduling and estimation are not always used. We provide recommendations for scheduling improvements. Research limitations/implications: The scheduling procedure is subject to further research, as it has not been verified and adjusted. Other countries’ insight is also needed. Practical implications: We believe that our work has a practical aspect for many Polish local government units and helps them in standardizing project scheduling supported by IT tools. Social implications: Infrastructure projects include the interests of local businesses and communities. Scheduling is a crucial element of providing project transparency and accountability, as well as enables communication with the stakeholders and the general public. Originality/value: The work tries to fill in the gap in standardizing scheduling practices in Polish local government units. The questionnaire data collected can also be used for further research.
EN
The importance of compliance with the schedule of work of road trains on the highway transport network of the European Union is shown. The possible options for work and rest modes for truck drivers on international routes have been analyzed. A model for optimizing the truck fleet operation plan has been developed. This model has two levels, that is, the general graph contains subgraphs designed with incompatible vertices to determine the active and shortest schedule. Each of the subgraphs reflects alternative routes and schedules of a truck. The model also includes restrictions on the total cycle time and active period duration of available unloading points. To find the shortest schedule, integer programming with a guaranteed optimal solution was applied. Testing of the proposed algorithm was performed for the example of serving orders for international freight transportation between the cities of Ukraine, Poland, and the Czech Republic. The active schedule is based on the criterion of the minimum of the total duration of drivers’ work. The results obtained are valid, consistent with the rules of the European Agreement. They indicate that the choice of the best schedule for a single car on a unitary route is not the best solution for the entire truck fleet and the entire flow of orders.
3
Content available remote Hierarchical method of rescheduling for assembly lines with intermediate buffers
EN
A method of scheduling assembly in flexible assembly lines without parallel machines is presented. The method applies to lines fitted with intermediate buffers with limited capacities. The developed method is distinguished by the possibility of rescheduling. This is very significant in the case of a need to provide for new, urgent orders, as well as machine failures. The first level of the method concerns balancing the load of the assembly machines. Starting times of individual operations are determined at the second level of the method. Integer programming was used to solve the tasks allocated to both levels of the method. The results of computational experiments regarding the method are described.
PL
Zaprezentowano metodę budowy harmonogramów montażu w elastycznych liniach montażowych bez maszyn równoległych. Metoda dotyczy linii wyposażonych w bufory międzyoperacyjne o ograniczonych pojemnościach. Opracowaną metodę wyróżnia możliwość reharmonogramowania. Ma to duże znaczenie w przypadku konieczności uwzględnienia nowych, pilnych zleceń, a także awarii maszyn. Pierwszy poziom metody dotyczy równoważenia obciążeń maszyn montażowych. Wyznaczenie czasów rozpoczęcia wykonywania poszczególnych operacji dokonywane jest na poziomie drugim metody. Do rozwiązania zadań przyporządkowanych obu poziomom metody zastosowano programowanie całko-witoliczbowe. Zamieszczono wyniki eksperymentów obliczeniowych dotyczących metody.
EN
Packet scheduling in 5G networks is extremely important because it is responsible for resource allocation and allows for increasing the efficiency of these networks. However, thanks to the scheduling algorithms used, data traffics are obtained with the required priorities and meeting the time limits. The paper presents an algorithm for download traffic scheduling in 5G networks, which takes priorities and deadlines into account. Simulation results show that the proposed scheduler provides robust latency performance with satisfied customer satisfaction.
PL
Szeregowanie pakietów w sieciach 5G jest niezwykle ważne, ponieważ odpowiada za alokację zasobów i pozwala na zwiększenie wydajności tych sieci. Jednak dzięki zastosowanym algorytmom szeregowania, ruch danych jest uzyskiwany z wymaganymi priorytetami i dotrzymaniem terminów. Artykuł przedstawia algorytm do szeregowania pakietów w sieciach 5G, który uwzględnia priorytety i czasy krytyczne. Wyniki symulacji pokazują, że proponowany program szeregujący zapewnia wymagane opóźnienie przy zadowoleniu klienta.
EN
Cross-docking is the practice of unloading goods from inbound delivery vehicles and loading them directly onto outbound vehicles. Cross-docking can streamline supply chains and help them move goods to markets faster and more efficiently by eliminating or minimizing warehouse storage costs, space requirements, and inventory handling. Regarding their short shelf-life, the movement of perishable commodities to cross-dock and their freight scheduling is of great importance. Accordingly, the present study developed a Mixed-Integer linear Programming (MILP) model for routing and scheduling, cross-docking, and transportation in a reverse logistics network. The model was multi-product and multi-level and focused on minimizing the logistics network costs to increase efficiency and maximizing the consumption value of delivered products. Considering cost minimization (i.e., earliness and tardiness penalty costs of customer order delivery, the inventory holding costs at the temporary storage area of the cross-dock and costs of crossover and use of outbound vehicles) as well as uncertainty in customer demand for perishable products, the model was an NP-hard problem. In this model, the problem-solving time increased exponentially according to the problem dimensions; hence, this study proposed an efficient method using the NSGA II algorithm.
PL
Cross-docking to praktyka polegająca na rozładowywaniu towarów z przychodzących samochodów dostawczych i ładowaniu ich bezpośrednio na pojazdy wyjeżdżające. Cross-docking może usprawnić łańcuchy dostaw i pomóc im szybciej i wydajniej przemieszczać towary na rynki, eliminując lub minimalizując koszty magazynowania, wymagania przestrzenne i obsługę zapasów. Ze względu na ich krótki okres przydatności do spożycia ogromne znaczenie ma przemieszczanie łatwo psujących się towarów do cross-dockingu i planowanie ich przewozu. W związku z tym w niniejszym badaniu opracowano model programowania liniowego (MILP) z mieszaną liczbą całkowitą do wyznaczania tras i harmonogramów, przeładunku towarów i transportu w sieci logistyki zwrotów. Model był wieloproduktowy i wielopoziomowy oraz koncentrował się na minimalizacji kosztów sieci logistycznej w celu zwiększenia wydajności i maksymalizacji wartości konsumpcyjnej dostarczanych produktów. Uwzględniając minimalizację kosztów (tj. Koszty karne za wczesne i spóźnione dostawy zamówień do klienta, koszty magazynowania w tymczasowej strefie składowania cross-docku oraz koszty crossovera i wykorzystania pojazdów wychodzących), a także niepewność dotyczącą zapotrzebowania klientów na łatwo psujące się produkty model był problemem NP-trudnym. W tym modelu czas rozwiązywania problemów wzrastał wykładniczo zgodnie z wymiarami problemu; stąd w badaniu zaproponowano skuteczną metodę wykorzystującą algorytm NSGA II.
6
Content available remote BIM na budowie
EN
The rapid global economic development of the world economy depends on the availability of substantial energy and resources, which is why in recent years a large share of non-renewable energy resources has attracted interest in energy control. In addition, inappropriate use of energy resources raises the serious problem of inadequate emissions of greenhouse effect gases, with major impact on the environment and climate. On the other hand, it is important to ensure efficient energy consumption in order to stimulate economic development and preserve the environment. As scheduling conflicts in the different workshops are closely associated with energy consumption. However, we find in the literature only a brief work strictly focused on two directions of research: the scheduling with PM and the scheduling with energy. Moreover, our objective is to combine both aspects and directions of in-depth research in a single machine. In this context, this article addresses the problem of integrated scheduling of production, preventive maintenance (PM) and corrective maintenance (CM) jobs in a single machine. The objective of this article is to minimize total energy consumption under the constraints of system robustness and stability. A common model for the integration of preventive maintenance (PM) in production scheduling is proposed, where the sequence of production tasks, as well as the preventive maintenance (PM) periods and the expected times for completion of the tasks are established simultaneously; this makes the theory put into practice more efficient. On the basis of the exact Branch and Bound method integrated on the CPLEX solver and the genetic algorithm (GA) solved in the Python software, the performance of the proposed integer binary mixed programming model is tested and evaluated. Indeed, after numerically experimenting with various parameters of the problem, the B&B algorithm works relatively satisfactorily and provides accurate results compared to the GA algorithm. A comparative study of the results proved that the model developed was sufficiently efficient.
EN
The purpose of this research is to effectively schedule jobs in a production company using heuristic Johnson’s algorithm. A popular pure water production factory, Iterlene industrial services limited (IISL) located at Effurun, Nigeria was investigated and it was noticed that different sizes of jobs (bottled water) are produced ranging from 25 cl, 50 cl, 60 cl, 75 cl, and 150 cl respectively, which are processed through the filling machine (FM1) and capping machine (CM2). In the order FM1CM2. Each job has to pass through the same sequence of operations. Jobs are assigned in such a way that a job is assigned on FM1 first and once processing is completed on FM1, it is assigned to CM2 and passing is not allowed. The idle time for the production of 500 bottles of water was estimated to be 1020 seconds (17.00 mins.). Johnson’s algorithm was applied to minimize the idle time for both FM1 and CM2 by determining the optimal sequence of the processed jobs. This was achieved within 780 seconds (13.00 mins.). Conclusively, the minimization of total elapsed time between the completion of first and last job was achieved. This would greatly improve productivity, effectiveness, and profitability at iterlene factory.
EN
In this work we investigate the performance of greedy randomised search (GRS) techniques to the problem of compiling quantum circuits to emerging quantum hardware. Quantum computing (QC) represents the next big step towards power consumption minimisation and CPU speed boost in the future of computing machines. Quantum computing uses quantum gates that manipulate multi-valued bits (qubits ). A quantum circuit is composed of a number of qubits and a series of quantum gates that operate on those qubits, and whose execution realises a specific quantum algorithm. Current quantum computing technologies limit the qubit interaction distance allowing the execution of gates between adjacent qubits only. This has opened the way to the exploration of possible techniques aimed at guaranteeing nearest-neighbor (NN) compliance in any quantum circuit through the addition of a number of so-called swap gates between adjacent qubits. In addition, technological limitations (decoherence effect) impose that the overall duration (makespan) of the quantum circuit realization be minimized. One core contribution of the paper is the definition of two lexicographic ranking functions for quantum gate selection, using two keys: one key acts as a global closure metric to minimise the solution makespan; the second one is a local metric, which favours the mutual approach of the closest qstates pairs. We present a GRS procedure that synthesises NN-compliant quantum circuits realizations, starting from a set of benchmark instances of different size belonging to the Quantum Approximate Optimization Algorithm (QAOA) class tailored for the MaxCut problem. We propose a comparison between the presented meta-heuristics and the approaches used in the recent literature against the same benchmarks, both from the CPU efficiency and from the solution quality standpoint. In particular, we compare our approach against a reference benchmark initially proposed and subsequently expanded in [1] by considering: (i) variable qubit state initialisation and (ii) crosstalk constraints that further restrict parallel gate execution.
EN
In this work we consider a problem from the field of power- and energy-aware scheduling, in which a set of batteries have to be charged in a minimum time. The formulated problem is to schedule independent and nonpreemptable jobs to minimize the schedule length, where each job requires some amount of power and consumes a certain amount of energy during its processing. We assume that the power demand of each job linearly decreases with time, as it is the case when Li-ion batteries are being charged. For the assumed job model we prove that each next job should be started as soon as the required amount of power is available. Basing on the proven theorem we formulate a procedure generating a minimum-length schedule for an assumed order of jobs. We also analyze the case of identical jobs, and show some interesting properties of this case.
EN
The paper presents a production scheduling problem in a foundry equipped with two furnaces and one casting line, where the line is a bottleneck and furnaces, of the same capacity, work in parallel. The amount of produced castings may not exceed the capacity of the line and the furnaces, and their loads determine metal type from which the products are manufactured on the casting line. The purpose of planning is to create the processing order of metal production to prevent delays in the delivery of the ordered products to the customers. The problem is a mix of a lot-sizing and scheduling problems on two machines (the furnaces) run in parallel. The article gives a mathematical model that defines the optimization problem, and its relaxed version based on the concept of a rolling-horizon planning. The proposed approaches, i.e. commercial solver and Iterated Local Search (ILS) heuristic, were tested on a sample data and different problem sizes. The tests have shown that rolling horizon approach gives the best results for most problems, however, developed ILS algorithm gives better results for the largest problem instances with tight furnace capacity.
EN
A method of creating production schedules regarding production lines with parallel machines is presented. The production line setup provides for intermediate buffers located between individual stages. The method mostly concerns situations when part of the production machines is unavailable for performance of operations and it becomes necessary to modify the original schedule, the consequence of which is the need to build a new schedule. The cost criterion was taken into account, as the schedule is created with the lowest possible costs regarding untimely completion of products (e.g. fines for delayed product completion). The proposed method is relaxing heuristics, thanks to which scheduling is performed in a relatively short time. This was confirmed by the presented results of computational experiments. These experiments were carried out for the rescheduling of machine parts production.
13
Content available Problem marszrutyzacji floty dronów
PL
W artykule rozważany jest problem dostarczania towarów w sieci dystrybucyjnej, w której operacje transportu realizowane są przez flotę bezzałogowych statków powietrznych (BSP). Szczególny nacisk położony jest na możliwość uwzględniania warunków pogodowych, w których odbywa się transport. Rozważany problem sprowadza się do wyznaczenia marszruty gwarantującej bezkolizyjne dostarczenie towaru do węzła, przy uwzględnieniu warunków pogodowych oraz poziomu baterii dronów. Zaproponowany został deklaratywny model, którego implementacja w środowisku programowania IBM ILOG pozwala na rozwiązywanie tego typu problemów w trybie on-line. Przedstawione eksperymenty obliczeniowe, potwierdzają poprawność opracowanego modelu.
EN
A problem of delivering goods in a distribution network is considered in which, transport operations are carried out by a fleet of unmanned aerial vehicles (UAV). The weather conditions in which a transport operations take place and a UAV battery level are taken into account. The above-mentioned weather conditions and the battery level affect the determination of the route guaranteeing collision-free delivery. The goods must be delivered to a specific node in a given time window. Specifying the route is the focus of this study. Solutions maximizing the level of customer satisfaction are sought. Computational experiments which show impact of the weather conditions to on route determination are presented.
14
EN
Programs are collections of projects related to a common goal. Scheduling programs follow other rules than scheduling projects. Even when projects in programs are connected logically, simple methods as the critical path method (CPM) cannot always be used. This paper has the following objectives: to describe the problem of scheduling programs and use the multi-criteria approach to scheduling projects in it. Using a system approach, after analyzing project-scheduling solutions in literature, we applied them appropriately to determine the schedule of the project. The approach was verified using an example taken from the literature on the subject.
EN
The method intended to build the possibly shortest assembly schedules is presented in the paper. The method is constructed for assembly lines without parallel machines. The intermediate buffers are located between the assembly machines. A flow of products of different types is unidirectional in the assembly line. The proposed method is a heuristic because the fixed tasks are characterized by a large size and considerable computational complexity. It is a relaxation heuristic. The linear mathematical model is used in the mentioned heuristic method. The method is constructed for assembly scheduling for multioption products. Assembly of various types of products in different variants is the reply to the contemporary challenges faced by the manufacturers, who try to satisfy the demands of individual customers. The planned downtimes of machines are regarded in the method, for example downtime of machines connected with maintenance. The results of computational experiments with proposed heuristic method are presented. The described heuristic method is compared with optimal method based on the integer programming. The fixed makespans and computational fixed times using heuristic method and optimal method are compared.
PL
Przedstawiono metodę przeznaczoną do budowy najkrótszych harmonogramów montażu produktów w liniach montażowych bez maszyn równoległych. Konfiguracja linii montażowej uwzględnia obecność buforów międzyoperacyjnych pomiędzy maszynami. Przepływ równocześnie montowanych produktów różnych typów jest jednokierunkowy. Ze względu na rozmiary rozwiązywanych problemów i związaną z tym złożoność obliczeniową metoda jest heurystyką. Jest to heurystyka relaksacyjna, w której wykorzystano model zadania programowania liniowego. Metoda dotyczy produktów wielowariantowych. Produkty danego typu mogą różnić się wariantami wykonania - specyficznymi cechami, uwzględniającymi wymagania odbiorców. Metodę wyróżnia także uwzględnienie planowanych przestojów maszyn, np. przeznaczonych na konserwację. Zaprezentowano wyniki eksperymentów obliczeniowych, za pomocą których oceniono jakość opracowanej metody. Długości harmonogramów wyznaczanych za pomocą przedstawionej metody porównano z długościami harmonogramów optymalnych, znanymi dzięki zastosowaniu modelu zadania programowania całkowitoliczbowego. Porównano także czasochłonność obliczeń.
EN
In this article we present an industrial application of our mathematical model that integrates planning and scheduling. Our main objective is to concretize our model and compare the reel results with the theoretical ones. Our application is realized on a conditioning line of pharmaceutical products at the ECAM EPMI production laboratory. For this reason and to save time, we used Witness simulation tool. It gives an overall idea of how the line works, the Makespan of each simulation and it highlights areas for improvement. We looked for the best resulting sequence which corresponds to the minest Makespan and total production cost. Then this sequence is applied on the conditioning line of pharmaceutical products for simulation. On the other hand, we program our mathematical model with the parameters of the conditioning line under python in version 3.6 and we adopt a simulation/optimization coupling approach to verify our model.
EN
Time-of-use (TOU) electricity pricing has been applied in many countries around the world to encourage manufacturers to reduce their electricity consumption from peak periods to off-peak periods. This paper investigates a new model of Optimizing Electricity costs during Integrated Scheduling of Jobs and Stochastic Preventive Maintenance under time of-use (TOU) electricity pricing scheme in unrelated parallel machine, in which the electricity price varies throughout a day. The problem lies in assigning a group of jobs, the flexible intervals of preventive maintenance to a set of unrelated parallel machines and then scheduling of jobs and flexible preventive maintenance on each separate machine so as to minimize the total electricity cost. We build an improved continuous-time mixed-integer linear programming (MILP) model for the problem. To the best of our knowledge, no papers considering both production scheduling and Stochastic Preventive Maintenance under time of-use (TOU) electricity pricing scheme with minimization total Electricity costs in unrelated parallel machine. To evaluate the performance of this model, computational experiments are presented, and numerical results are given using the software CPLEX and MATLAB with then discussed.
EN
This paper reports a new multi-item planning and scheduling problem in a job-shop production system with the consideration of energy consumption. A mixed integer linear programming is proposed to integrate planning and scheduling with the consideration of energy aspect. In this study a new operational constraint is considered in the tactical level because of the huge interest given to energy consumption and its strong link existing with production system. To evaluate the performance of this model, computational experiments are presented, and numerical results are given using the software CPLEX and then discussed.
EN
The objective of the milk-run design problem considered in this paper is to minimize transportation and inventory costs by manipulating fleet size and the capacity of vehicles and storage areas. Just as in the case of an inventory routing problem, the goal is to find a periodic distribution policy with a plan on whom to serve, and how much to deliver by what fleet of tugger trains travelling regularly on which routes. This problem boils down to determining the trade-off between fleet size and storage capacity, i.e. the size of replenishment batches that can minimize fleet size and storage capacity. A solution obtained in the declarative model of the milk-run system under discussion allows to determine the routes for each tugger train and the associated delivery times. In this context, the main contribution of the present study is the identification of the relationship between takt time and the size of replenishment batches, which allows to determine the delivery time windows for milkrun delivery and, ultimately, the positioning of trade-off points. The results show that this relationship is non-linear.
20
Content available remote Evaluation of train crews schedule in terms of robustness
EN
The evaluation of team work schedules in complex rail transport conditions is related to the robustness of individual solutions. In rail systems there are many aims that are important for users. One of the most important aims is to find a feasible solution. It is characterized by the non-conflicting schedule with another train, minimizing the travel time of the trainset and taking into account the priority of train. The problem of responding to delays in terms of reorganisation of work, prevention of delay propagation and real-time schedule changes is important. Schedules are built in a way that ensures the best use of work time. This has a negative impact on critical situations. The study analysed the changes of the conductor's team to another train depending on the buffer time provided in work plan, real time needed for change and train delays.
PL
Ocena harmonogramów pracy drużyn w złożonych warunkach transportu kolejowego jest związana z odpornością na zakłócenia poszczególnych rozwiązań. Powinny się one charakteryzować brakiem konfliktu w harmonogramie z innym pociągiem, minimalizowaniem czasu przejazdu składu oraz uwzględnieniem priorytetu przejazdu pociągów. Szczególnie istotny jest problem reagowania na opóźnienia pod kątem reorganizacji pracy, zapobiegania propagacji opóźnień oraz bieżących zmian w harmonogramie. Harmonogramy budowane są w sposób zapewniający najlepsze wykorzystanie czasu przeznaczonego na pracę. Wpływa to negatywnie na występujące sytuacje krytyczne. W pracy przeanalizowano przesiadki drużyny konduktorskiej do innego pociągu w zależności od przewidzianego w planie pracy czasu buforowego oraz zmierzonego czasu potrzebnego na przesiadkę i zbadanych opóźnień pociągów.
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