Search results - CEJSH

1

An analysis of maintenance schedules for public facilities

100%

HOPLAND A. O., KVAMSDAL S. F., SANDAL L. K.

Operations Research and Decisions

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2019

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vol. 29

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issue 1

17-35

EN

We present a flexible, formal framework for maintenance scheduling for public facilities. Key features of the model include an accelerating deterioration scheme, a general utility measure, and real estate market effects in the salvage function. The model is rich enough to capture a range of stylistic scenarios pertaining to public facilities while remaining simple enough to allow formal analysis of the optimal maintenance schedule. Based on our analysis, we draw a phase diagram that classifies the generic behavior of the optimal solution. We illustrate our analysis in numerical examples that highlight essential trade-offs and the time dependence of the facility maintenance problem. Under simplifying assumptions, we also derive the basics of an exact solution.

2

An intelligent modeling method based on genetic algorithm for partner selection in virtual organizations

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Simona D., Raluca P.

Business and Economic Horizons

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2011

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vol. 5

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issue 2

23-34

EN

The goal of a Virtual Organization is to find the most appropriate partners in terms of expertise, cost wise, quick response, and environment. In this study we propose a model and a solution approach to a partner selection problem considering three main evaluation criteria: cost, time and risk. This multiobjective problem is solved by an improved genetic algorithm (GA) that includes meiosis specific characteristics and step-size adaptation for the mutation operator. The algorithm performs strong exploration initially and exploitation in later generations. It has a high global search ability and a fast convergence rate and also avoids premature convergence. On the basis of the numerical investigations, the incorporation of the proposed enhancements has been successfully proved.

3

The allocation of seats in the European Parliament and the principle of degressive proportionality

100%

Peternek P., Kośny M.

Mathematical Economics

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2015

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issue 11(18)

99-113

EN

One of the key issues in the process of preparing for an election to the European Parliament is to determine the number of seats for each country. The Treaty of Lisbon, signed by Member States of the European Union, has obliged the European Parliament to establish rules guaranteeing that the distribution of seats should be done according to, inter alia, the principle of degressive proportionality. The purpose of this paper is to explore how the principle of degressive proportionality is actually implemented, and to propose a compromise – a mathematical solution, guaranteeing that the distribution of seats is consistent with the requirements of the Lisbon Treaty.

4

Maintenance Optimization for Transport Vehicles in a Supply Chain

100%

Rezg N., Sofiene D., Zied H.

Logistics and Transport

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2014

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vol. 24

7-14

EN

In this paper, we are interested in determining a maintenance policy with an optimal cost to enable the company to generate significant profits, often the means of transport travelled different paths, they are characterized by the distance they covered; however each distance has an effect on the operating characteristics of means of delivery. The objective of this paper is twofold: It aims both to introduce the model of supply chain and specify distances, and codify the use of it in the proportional hazard model, later a maintenance policy was presented which takes into consideration the types of paths travelled by the means of delivery.

5

Chosen Operational and Logistic Aspects Determining the Optimizing Space of the Polish Armed Forces Logistic System

100%

Kowalski K., Hajt S., Stankiewicz G.

Logistics and Transport

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2010

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vol. 11

103-110

EN

New organizational and technical solutions aimed at optimizing the Polish Armed Forces Logistic System (PAFLS) and national task contingents are due to modern conditions under which military operations, mainly of expeditionary character, are conducted in the allied and international environment. The PAFLS and the Polish Military Contingent's organizational and technical structure is still (notwithstanding the numerous efforts that were made) the vast optimizing space which can be filled when the possibilities created by civil logistics experience are taken into account.

6

Effectiveness of hybrid optimization methods in solving test problems and practical issues

100%

Twardochleb M., Król T., Włoch P., Kuka B.

Informatyka Ekonomiczna

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2013

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issue 4(30)

279-289

EN

This paper shows the results of analyzing the effectiveness and efficiency of a hybrid approach against a variety of optimization problems. An application with a serial-optimization structure, consisting of several methods with different characteristics, is presented. In order to evaluate the initial effectiveness of the hybrid optimization method, a number of test tasks, represented by complex functions with many variables, were examined. Additionally, a real-life case, determining an optimal product variety in a supermarket environment, regarding the highest rate of return for given conditions and limitations, is presented as an instance of the practical use of a hybrid algorithm. The research shows that the results achieved by the hybrid- -optimization method are highly satisfactory, both in terms of efficiency as well as effectiveness.

7

Quantitative approach to project portfolio management: proposal for Slovak companies

100%

Kral P., Valjaskova V., Janoskova K.

Oeconomia Copernicana

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2019

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vol. 10

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issue 4

797-814

EN

Research background: Project portfolio optimization isa demanding process in the case of considering a large number of project intentions and has so far been the subject of research by many authors, especially foreign authors. However, the issue of project portfolio optimization is an area that is not sufficiently addressed by Slovak authors. This was the main impulse to create a specific mathematical model of integer programming with bivalent variables to optimize the company's project portfolio with the intention to reflect the specific requirements of Slovak companies. Purpose of the article: The aim of the article is to propose a mathematical model of integer programming with bivalent variables to optimize the project portfolio with a focus on Slovak companies. Methods: In accordance with the aim of the article, a questionnaire survey was carried out with the intention of identifying the criteria that are perceived by the managers of Slovak companies as important in the optimization of the project portfolio. These criteria were subsequently reflected in the mathematical model design using the mathematical programming method. Findings & Value added: Based on a literature review aimed at the project portfolio optimization, we have found a gap in considering the compliance of project intentions and strategic objectives of the company within the optimization of the project portfolio. Based on the results of the questionnaire survey, the significance of the mutual compliance of project intentions with the strategic objectives of the company was confirmed from the point of view of Slovak companies. Given the fact that our aim was to create an innovative integer programming model with bivalent variables orientated to the conditions of Slovak companies, we included in the resulting model the criteria that were not considered within the scope of existing research in this area, and which are perceived as important by the Slovak companies.

8

Dynamic vehicle parking pricing. A review

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BAYIH S. H., TILAHUN S. L.

Operations Research and Decisions

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2024

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vol. 34

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issue 1

35-59

EN

Dynamic parking pricing refers to the adjustment of the price of parking to achieve the required occupancy rates. It plays a significant role in parking management systems to minimize traffic congestion and cruising time, as well as to maximize revenue. The optimization of parking pricing and supply through a time-varying pricing strategy is a crucial issue. This paper reviews academic work on approaches to parking pricing, giving emphasis to time-varying pricing strategies. Approaches based on game theory, dynamic and stochastic control, multiobjective and multilevel programming, queuing theory, artificial intelligence, statistics, among others, are reviewed. We categorize these techniques to examine various issues of dynamic parking pricing. The main contributions and methods used are summarized. Furthermore, a brief discussion of the strengths, limitations, and possible future work is given.

9

Sensitivity Analysis and Optimization for Selected Supply Chain Management Issues in the Company – Using System Dynamics and Vensim

100%

Kasperska E., Mateja-Losa E., Marjasz R.

Journal of Entrepreneurship, Management and Innovation

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2013

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vol. 9

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issue 2

29-44

EN

The aim of our paper is to present the new results of research work on optimization and simulation for some logistic problems in the company. The System Dynamics (SD) method and the Vensim simulation language are applied in order to solve specific managerial problems described by Forrester in the model of supply chain. The historical model of Customer-Producer-Employment System by Forrester (Forrester, 1961) has not been examined with the sensitivity analysis, from the “automatic” testing perspective. Optimization experiments have not been conducted, either. It is surprising, since the model is old and widely known. The opportunities offered by the Vensim language allow us to perform such analysis. The visualization called “confidence bounds“ is used, to show the behaviour of chosen variables over a period of time. The Monte-Carlo method is applied for sampling a set of numbers from within bounded domains (distribution for each searching parameters is specified). The authors of this paper conducted numerous experiments in this scope. This paper presents their results and offers some conclusions formulated at the end.

10

Intermodal Transport and Road Transport in Poland – Results of the Study

100%

Walasek R., Grodzki A.

Logistics and Transport

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2016

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vol. 31

27-36

EN

The main objective of the text is to try to carry out the analysis with the predominant objective to try and present in realistic way the factors influencing the choice between a service realised only with the use of a road transport and intermodal transport. The author of the analysis put particular stress on the costs of the carriage service, time of its realisation and CO2 emission. The analysis also aimed at showing which of the presented technologies of service providing is more friendly to natural environment. This is due to the fact that the market for intermodal transport and road transport in Poland, knowledge of the mechanisms of price formation and the costs are still low. It is often difficult to determine the unit price of transport modes or mechanisms of shaping them. This results primarily from difficulties with the calculation of the actual cost of transport, terminal operations, management and other issues occurring in road transport and intermodal logistics functions.

11

A concept of using a dynamic programming method to optimize an investment portfolio allowing for asymmetric rates of return and a minimum risk portfol

100%

Tymiński J.

Nauki o Finansach

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2014

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issue 4(21)

52-61

EN

Investment management on the capital market is a complex and multifarious process and the accuracy of decisions is an indispensable condition that an investor needs to fulfill if the expected economic results are to be achieved. The paper presents the concept of the optimization of investment portfolio on the capital market of shares. The maximum value of portfolio quality measure was used as an optimization criterion. It is expressed by the index of variability R/σ of the rate of return for each share in the portfolio. The cumulation of values of R/σ index in the successive years of the investigated period allowed for an econometric estimation of the continuous functions and their maximum. The indexes of asymmetry of rate of return for particular shares in the portfolio were introduced into the functions, which enabled to increase the efficiency of the selection of shares for the portfolio. This, in turn, allowed to achieve the optimum structure of shares in the portfolio.

12

Pricing-inventory model with discrete demand and delivery orders

100%

SADEGHI H., GOLPÎRA H., HNAIEN F., MAGAZZINO C.

Operations Research and Decisions

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2023

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vol. 33

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issue 3

119-139

EN

This paper aims to develop an inventory model considering discrete demand, coordinated pricing, and multiple delivery policy in a single-buyer single-supplier production-inventory system. The shortage is not allowed and the planning horizon is considered to be infinite. The main objective of the framework is to equip the decision-maker with optimal order, pricing, and shipment quantities to maximize the total profit of the system. The results obtained from the numerical example reveal that the proposed approach with an average selling price equal to about 94% of the classical model, has resulted in an average profit increase of about 16% and an average order increase of about 34% compared to the classical approach.

13

Optimization of an M/M/1/N feedback queue with retention of reneged customers

100%

KUMAR R., JAIN N. K., SOM B. K.

Operations Research and Decisions

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2014

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vol. 24

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issue 3

45-58

EN

Customer impatience has become a threat to the business world. Firms employ various customer retention strategies to retain their impatient (or reneged) customers. Customer retention mechanisms may help to retain some or all impatient customers. Further, due to unsatisfactory service, customers may rejoin a queue immediately after departure. Such cases are referred to as feedback customers. Kumar and Sharma take this situation into account and study an M/M/1/N feedback queuing system with retention of reneged customers. They obtain only a steady-state solution for this model. In this paper, we extend the work of Kumar and Sharma by performing an economic analysis of the model. We develop a model for the costs incurred and perform the appropriate optimization. The optimum system capacity and optimum service rate are obtained.

14

Solving Delivery Problems in Distribution Systems

100%

Michlowicz E.

Logistics and Transport

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2013

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vol. 18

33-40

EN

The subject matter of this article is the optimization of delivery problems (Vehicle Routing Problems – VRP) with regard to distribution systems. These issues belong to the class of NP-hard problems. Current solutions to various delivery problems (VRP, TSP, MTSP, VRPTW, RDPTW) were analysed. Two examples were presented. In a transport and production task, a marginal cost equalling (MCE) algorithm was used. In the case of a Multi Depot Vehicle Routing Problem (MDVRP), an evolutionary algorithm was used.

15

Modified optimization model for selecting project risk response strategies

100%

MARCHWICKA E., KUCHTA D.

Operations Research and Decisions

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2017

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vol. 27

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issue 2

77-90

EN

The authors present modifications of the optimization model for selecting project risk response strategies proposed by Zhang and Fan. The weaknesses of the original model has been identified and an improved model with the main suggestions has been proposed. The main improvement concerned the objective function. The modified model was tested using a real project in the electrical industry – engineering and construction of the main low voltage switchboard for a live fish carrier (Helix Q7000) in Norway. Project team members report that the analysis is time consuming but results are satisfying – the model allows more systematic and efficient risk management.

16

Optimization Criteria in End-of-Life Products Reverse Logistics Network Organisation

100%

Merkisz-Guranowska A., Maciejewski M.

Logistics and Transport

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2013

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vol. 17

25-32

EN

The paper discusses the problem of selection of objective function in modelling of the reverse logistics network entity location. A growing ecological awareness of societies as well as implementing concepts of manufacturer responsibility for their products result in a creation of systems of collecting and treatment of end-of-life products. Rather than being a random process a reverse logistics network should be designed as an effect of informed decisions taking into account all aspects and points of view of the stakeholders. A key issue in network design related to the use of decision support tools based on mathematical optimization is the appropriate selection of the objective function for evaluation of the potential solutions.

17

Balance sheet shaping through a decision model and funds transfer pricing

100%

Lubińska B.

Prace Naukowe Uniwersytetu Ekonomicznego we Wrocławiu

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2017

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issue 482

140-157

XX

The banking industry is currently facing a number of challenges driven by the regulatory requirements, low or even negative interest rates and margin compression. As a result, active and conscious balance sheet management has increased in importance and banks are required to optimize and allocate resources very precisely to their businesses. There is a clear need for maximization of the assets income, redesign of the funding mix to achieve the lower funding costs and, at the same time, to respect regulatory requirements. This article verifies the hypotheses that the application of the optimization technique improves the management of the banking book in terms of quantifiable impact on a bank’s P&L and that the funds transfer pricing (FTP) process could be used as a mean to achieve the target position of a bank. It proposes a two-step approach to prove the above hypotheses, i.e. the application of the decision model and the FTP process. In addition, the article provides the reader with the main concepts of the FTP process, FTP landscape and details regarding the Balance Sheet shaping.

18

Some Aspects of the Application of Genetic Algorithm for Solving the Assignment Problem of Tasks to Resources in a Transport Company

100%

Izdebski M., Jacyna M.

Logistics and Transport

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2014

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vol. 21

13-20

EN

The article defines the assignment problem of tasks to resources in a transport company. The paper describes mathematical model of a transport system taking into account the assignment of vehicles to the tasks. It also provides stages of creation of the genetic algorithm for solving the assignment problem in the transport company.

19

An empirical comparison of different risk measures in portfolio optimization

100%

Hoe L. W., Hafizah J. S., Zaidi I.

Business and Economic Horizons

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2010

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vol. 1

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issue 1

39-45

EN

Risk is one of the important parameters in portfolio optimization problem. Since the introduction of the mean-variance model, variance has become the most common risk measure used by practitioners and researchers in portfolio optimization. However, the mean-variance model relies strictly on the assumptions that assets returns are multivariate normally distributed or investors have a quadratic utility function. Many studies have proposed different risk measures to overcome the drawbacks of variance. The purpose of this paper is to discuss and compare the portfolio compositions and performances of four different portfolio optimization models employing different risk measures, specifically the variance, absolute deviation, minimax and semi-variance. Results of this study show that the minimax model outperforms the other models. The minimax model is appropriate for investors who have a strong downside risk aversion.

20

The reloading of a ship in a maritime container terminal as a queuing problem of interacting processes

100%

BARTOSIEWICZ A., KUCHARSKI A.

Operations Research and Decisions

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2024

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vol. 34

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issue 1

17-33

EN

In this work, we propose a multi-server queuing system for modeling the processes that occur in a maritime container terminal. In our study, the main operations that take place at the quay and in the yard are first disaggregated into several elementary activities. Then we propose the step-by-step calculation of the times of each operation that influences both the unloading and the loading of a container. Next, we analyze the vessel cycle time while separately investigating the STS (ship to shore) crane cycle time, the RTG (rubber tyred gantry) cycle time, as well as the IMV (internal movement vehicle) transfer time. Finally, we apply two process-driven simulation experiments to the system analysis. The paper demonstrates the proposed model’s effectiveness with data from the BCT Gdynia container terminal. We show that, among others, even with properly planned work of STS cranes and RTGs, there is still a high probability that the quay will become a bottleneck of the described processes.

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