The paper is aimed to investigate the reliability metrics of a multi-unit fault-tolerant control (FTC) system wherein the units are subject to failure and those are repairable by two heterogeneous servers. Server 1 remains permanently available for essential service of failed units, whereas server 2 goes on vacation and renders service based on the N-policy threshold, which may also provide optional and essential services. Server 1 may break down at a steady rate during its servicing period but immediately gets repaired and resume servicing the failed units. When the working unit fails, the available warm standby unit holds responsibility for the smooth operation of the system. The transition of standby units to operational mode may be unsuccessful with switching failure probability. We develop a Markovian model to obtain the steady-state probabilities. We explore computational and sensitivity analysis of different performance measures for various variability of the parameters
{"title":"Reliability analysis of N-policy vacation based FTC system subject to standby switching failures","authors":"Sudeep Kumar, Ritu Gupta","doi":"10.37190/ord230204","DOIUrl":"https://doi.org/10.37190/ord230204","url":null,"abstract":"The paper is aimed to investigate the reliability metrics of a multi-unit fault-tolerant control (FTC) system wherein the units are subject to failure and those are repairable by two heterogeneous servers. Server 1 remains permanently available for essential service of failed units, whereas server 2 goes on vacation and renders service based on the N-policy threshold, which may also provide optional and essential services. Server 1 may break down at a steady rate during its servicing period but immediately gets repaired and resume servicing the failed units. When the working unit fails, the available warm standby unit holds responsibility for the smooth operation of the system. The transition of standby units to operational mode may be unsuccessful with switching failure probability. We develop a Markovian model to obtain the steady-state probabilities. We explore computational and sensitivity analysis of different performance measures for various variability of the parameters","PeriodicalId":43244,"journal":{"name":"Operations Research and Decisions","volume":"62 1","pages":""},"PeriodicalIF":0.4,"publicationDate":"2023-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"84054394","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
The article presents proposals for a university management model supporting the process of strategic management at a university. The proposed model is based on the use of multi-criteria methods such as the 0–10 technique, object ranking, and optimisation methods – linear programming. The proposed solution integrates ranking and optimisation methods, the use of which may be helpful in the hands of managers in making management decisions. The proposed approach may also be helpful in developing a strategic scorecard, especially in the stage of formulating goals. It also enables the optimal selection of goals with the existing time constraints for the implementation of the strategy. The article presents a proposal for the use of the strategy implementation model and an example of its use. The strengths and weaknesses of the model were also indicated.
{"title":"The use of rank and optimisation methods in strategic management in higher education","authors":"R. Ryńca, Natalia Piórkowska","doi":"10.37190/ord230107","DOIUrl":"https://doi.org/10.37190/ord230107","url":null,"abstract":"The article presents proposals for a university management model supporting the process of strategic management at a university. The proposed model is based on the use of multi-criteria methods such as the 0–10 technique, object ranking, and optimisation methods – linear programming. The proposed solution integrates ranking and optimisation methods, the use of which may be helpful in the hands of managers in making management decisions. The proposed approach may also be helpful in developing a strategic scorecard, especially in the stage of formulating goals. It also enables the optimal selection of goals with the existing time constraints for the implementation of the strategy. The article presents a proposal for the use of the strategy implementation model and an example of its use. The strengths and weaknesses of the model were also indicated.","PeriodicalId":43244,"journal":{"name":"Operations Research and Decisions","volume":"10 1","pages":""},"PeriodicalIF":0.4,"publicationDate":"2023-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"72900463","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
The occurrence of a disaster and the appearance of a new product are items of news that can reach many people rapidly. Decision-makers would like to know how many individuals will obtain such information. In this paper, we study the case in which there are spreaders who think that the news is true and others that claim it is false. We simulate the propagation of a rumour and propose an algorithm for estimating the parameters of the resulting dynamical system. The relation between the parameters defining the simulation and the dynamical system is also studied. We conclude that the simulation describes the phenomenon well, in particular when the method proposed in this paper is used to estimate the parameters.
{"title":"Simulating the propagation of rumours with spreaders of distinct characters","authors":"Daniel Menció-Padrón, Gemayqzel Bouza-Allende","doi":"10.37190/ord230305","DOIUrl":"https://doi.org/10.37190/ord230305","url":null,"abstract":"The occurrence of a disaster and the appearance of a new product are items of news that can reach many people rapidly. Decision-makers would like to know how many individuals will obtain such information. In this paper, we study the case in which there are spreaders who think that the news is true and others that claim it is false. We simulate the propagation of a rumour and propose an algorithm for estimating the parameters of the resulting dynamical system. The relation between the parameters defining the simulation and the dynamical system is also studied. We conclude that the simulation describes the phenomenon well, in particular when the method proposed in this paper is used to estimate the parameters.","PeriodicalId":43244,"journal":{"name":"Operations Research and Decisions","volume":"31 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2023-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"135599675","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
The authors develop an agent-based model of the market where firms and consumers exchange products. Consumers in the model are heterogeneous in terms of features, such as risk-aversion or owned assets, which impact their individual decisions. Consumers constantly learn about products’ features through personal experience, word-of-mouth, or advertising, update their expectations and share their opinions with others. From the supply-side of the model, firms can influence consumers with two marketing tools: advertising and pricing policy. Series of experiments have been conducted with the model to investigate the relationship between advertising and pricing and to understand the underlying mechanism. Marketing strategies have been evaluated in terms of generated profit and recommendations have been formulated.
{"title":"An agent-based model of consumer choice. An evaluation of the strategy of pricing and advertising","authors":"M. Kot","doi":"10.37190/ord220104","DOIUrl":"https://doi.org/10.37190/ord220104","url":null,"abstract":"The authors develop an agent-based model of the market where firms and consumers exchange products. Consumers in the model are heterogeneous in terms of features, such as risk-aversion or owned assets, which impact their individual decisions. Consumers constantly learn about products’ features through personal experience, word-of-mouth, or advertising, update their expectations and share their opinions with others. From the supply-side of the model, firms can influence consumers with two marketing tools: advertising and pricing policy. Series of experiments have been conducted with the model to investigate the relationship between advertising and pricing and to understand the underlying mechanism. Marketing strategies have been evaluated in terms of generated profit and recommendations have been formulated.","PeriodicalId":43244,"journal":{"name":"Operations Research and Decisions","volume":"35 1","pages":""},"PeriodicalIF":0.4,"publicationDate":"2022-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"77523898","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
The main objective of this paper is to present an example of the IT system implementation with advanced mathematical optimisation for job scheduling. The proposed genetic procedure leads to the Pareto front, and the application of the multiple criteria decision aiding (MCDA) approach allows extraction of the final solution. Definition of the key performance indicator (KPI) reflecting relevant features of the solutions, and the efficiency of the genetic procedure provide the Pareto front comprising the representative set of feasible solutions. The application of chosen MCDA, namely elimination et choix traduisant la réalité (ELECTRE) method, allows for the elicitation of the decision maker (DM) preferences and subsequently leads to the final solution. This solution fulfils all of the DM expectations and constitutes the best trade-off between considered KPIs. The proposed method is an efficient combination of genetic optimisation and the MCDA method.
{"title":"Multi-criteria human resources planning optimisation using genetic algorithms enhanced with MCDA","authors":"M. Jurczak, Grzegorz Miebs, R. Bachorz","doi":"10.37190/ord220404","DOIUrl":"https://doi.org/10.37190/ord220404","url":null,"abstract":"The main objective of this paper is to present an example of the IT system implementation with advanced mathematical optimisation for job scheduling. The proposed genetic procedure leads to the Pareto front, and the application of the multiple criteria decision aiding (MCDA) approach allows extraction of the final solution. Definition of the key performance indicator (KPI) reflecting relevant features of the solutions, and the efficiency of the genetic procedure provide the Pareto front comprising the representative set of feasible solutions. The application of chosen MCDA, namely elimination et choix traduisant la réalité (ELECTRE) method, allows for the elicitation of the decision maker (DM) preferences and subsequently leads to the final solution. This solution fulfils all of the DM expectations and constitutes the best trade-off between considered KPIs. The proposed method is an efficient combination of genetic optimisation and the MCDA method.","PeriodicalId":43244,"journal":{"name":"Operations Research and Decisions","volume":"22 1","pages":""},"PeriodicalIF":0.4,"publicationDate":"2022-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"83566503","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
In a complex supply chain network, the production nodes, seller nodes, and buyers are connected randomly. We assume a process of joining two random nodes leading to the bivariate Poisson probability mass function. There exist two types of links- one is horizontal (H) and the other is vertical (V), which support the continuous flow of commodities through the supply chain. This induces competition among workers at a node to manage these two types of links within fixed constraints and creates bargaining to decide the optimal degree of both types of links at a node. We use the Nash security point to obtain the bargaining solution describing the optimal links. We reduce the carrying cost and ordering cost of inventory, which are contrary in their nature by introducing horizontal and vertical links, respectively. We modify the total cost function and establish a new economic order quantity (EOQ), optimal shortage quantity, and total optimal cost in terms of the optimal degree of H and V cooperation.
{"title":"Determination of EOQ in terms of optimum degrees of horizontal and vertical cooperation at a node of supply chain","authors":"P. P. Mishra, Chipem Zimik, S. Borkotokey","doi":"10.37190/ord220206","DOIUrl":"https://doi.org/10.37190/ord220206","url":null,"abstract":"In a complex supply chain network, the production nodes, seller nodes, and buyers are connected randomly. We assume a process of joining two random nodes leading to the bivariate Poisson probability mass function. There exist two types of links- one is horizontal (H) and the other is vertical (V), which support the continuous flow of commodities through the supply chain. This induces competition among workers at a node to manage these two types of links within fixed constraints and creates bargaining to decide the optimal degree of both types of links at a node. We use the Nash security point to obtain the bargaining solution describing the optimal links. We reduce the carrying cost and ordering cost of inventory, which are contrary in their nature by introducing horizontal and vertical links, respectively. We modify the total cost function and establish a new economic order quantity (EOQ), optimal shortage quantity, and total optimal cost in terms of the optimal degree of H and V cooperation.","PeriodicalId":43244,"journal":{"name":"Operations Research and Decisions","volume":"62 1","pages":""},"PeriodicalIF":0.4,"publicationDate":"2022-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"84025194","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Credit scores are critical for financial sector investors and government officials, so it is important to develop reliable, transparent and appropriate tools for obtaining ratings. This study aims to predict company credit scores with machine learning and modern statistical methods, both in sectoral and aggregated data. Analyses are made on 1881 companies operating in three different sectors that applied for loans from Turkey’s largest public bank. The results of the experiment are compared in terms of classification accuracy, sensitivity, specificity, precision and Mathews correlation coefficient. When the credit ratings are estimated on a sectoral basis, it is observed that the classification rate considerably changes. Considering the analysis results, it is seen that logistic regression analysis, support vector machines, random forest and XGBoost have better performance than decision tree and k-nearest neighbour for all data sets.
{"title":"A comparative study of corporate credit ratings prediction with machine learning","authors":"Seyyide Doğan, Yasin Büyükkör, Murat Atan","doi":"10.37190/ord220102","DOIUrl":"https://doi.org/10.37190/ord220102","url":null,"abstract":"Credit scores are critical for financial sector investors and government officials, so it is important to develop reliable, transparent and appropriate tools for obtaining ratings. This study aims to predict company credit scores with machine learning and modern statistical methods, both in sectoral and aggregated data. Analyses are made on 1881 companies operating in three different sectors that applied for loans from Turkey’s largest public bank. The results of the experiment are compared in terms of classification accuracy, sensitivity, specificity, precision and Mathews correlation coefficient. When the credit ratings are estimated on a sectoral basis, it is observed that the classification rate considerably changes. Considering the analysis results, it is seen that logistic regression analysis, support vector machines, random forest and XGBoost have better performance than decision tree and k-nearest neighbour for all data sets.","PeriodicalId":43244,"journal":{"name":"Operations Research and Decisions","volume":"391 1","pages":""},"PeriodicalIF":0.4,"publicationDate":"2022-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"78067152","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
In this study, panel regression models for 21 European countries and data covering the period between 2008 and 2014 were used to demonstrate that the distribution of working population across different occupational groups explains cross-country differences in terms of the average effective retirement age. Thus, while the great majority of previous studies verified the causal trade-off investigated on the basis of single-country micro data with reference to one economy, this study takes perspective of cross-country diversity in terms of the investigated relationship. The confirmed link holds even when controlling inter alia for health status, education, unemployment, old-dependency ratio, interest rate, GDP per capita, or the share of salaries and wages in GDP. An important practical implication for the policy-makers is that decisions limited only to the increase in the universal pensionable age cannot be effective, since the occupational composition of an economy is very relevant.
{"title":"Occupational composition of an economy and effective retirement age across European countries: an econometric analysis","authors":"F. Chybalski","doi":"10.37190/ord220305","DOIUrl":"https://doi.org/10.37190/ord220305","url":null,"abstract":"In this study, panel regression models for 21 European countries and data covering the period between 2008 and 2014 were used to demonstrate that the distribution of working population across different occupational groups explains cross-country differences in terms of the average effective retirement age. Thus, while the great majority of previous studies verified the causal trade-off investigated on the basis of single-country micro data with reference to one economy, this study takes perspective of cross-country diversity in terms of the investigated relationship. The confirmed link holds even when controlling inter alia for health status, education, unemployment, old-dependency ratio, interest rate, GDP per capita, or the share of salaries and wages in GDP. An important practical implication for the policy-makers is that decisions limited only to the increase in the universal pensionable age cannot be effective, since the occupational composition of an economy is very relevant.","PeriodicalId":43244,"journal":{"name":"Operations Research and Decisions","volume":"26 1","pages":""},"PeriodicalIF":0.4,"publicationDate":"2022-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"74894163","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
A. Bouchentouf, Abdelhak Guendouzi, Meriem Houalef, Shakir Majid
In this paper, we analyze an M/M/1 queueing system under both single and multiple working vacation policies, multiphase random environment, waiting server, balking and reneging. When the system is in operative phase j = 1,2,...,K, customers are served one by one. Whenever the system becomes empty, the server waits a random amount of time before taking a vacation, causing the system to move to working vacation phase 0 at which new arrivals are served at a lower rate. Using the probability generating function method, we obtain the distribution for the steady-state probabilities of the system. Then, we derive important performance measures of the queueing system. Finally, some numerical examples are illustrated to show the impact of system parameters on performance measures of the queueing system.
{"title":"Analysis of a single server queue in a multi-phase random environment with working vacations and customers’ impatience","authors":"A. Bouchentouf, Abdelhak Guendouzi, Meriem Houalef, Shakir Majid","doi":"10.37190/ord220202","DOIUrl":"https://doi.org/10.37190/ord220202","url":null,"abstract":"In this paper, we analyze an M/M/1 queueing system under both single and multiple working vacation policies, multiphase random environment, waiting server, balking and reneging. When the system is in operative phase j = 1,2,...,K, customers are served one by one. Whenever the system becomes empty, the server waits a random amount of time before taking a vacation, causing the system to move to working vacation phase 0 at which new arrivals are served at a lower rate. Using the probability generating function method, we obtain the distribution for the steady-state probabilities of the system. Then, we derive important performance measures of the queueing system. Finally, some numerical examples are illustrated to show the impact of system parameters on performance measures of the queueing system.","PeriodicalId":43244,"journal":{"name":"Operations Research and Decisions","volume":"56 1","pages":""},"PeriodicalIF":0.4,"publicationDate":"2022-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"78427822","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
This study proposes a methodology to obtain an efficient solution for a programming model which is multi-objective quadratic fractional with pentagonal fuzzy numbers as coefficients in all the objective functions and constraints. The proposed approach consists of three stages. In the first stage, defuzzification of the coefficients is carried out using the mean method of α-cut. Then, in the second stage, a crisp multi-objective quadratic fractional programming model (MOQFP) is constructed to obtain a non-fractional model based on an iterative parametric approach. In the final stage, this multiobjective non-fractional model is transformed to obtain a model with a single objective by applying the ε-constraint method. This final model is then solved to get desired solution. Also, an algorithm and flowchart expressing the methodology are given to present a clear picture of the approach. Finally, a numerical example illustrating the complete approach is given.
{"title":"An algorithm for quadratically constrained multi-objective quadratic fractional programming with pentagonal fuzzy numbers","authors":"V. Goyal, N. Rani, D. Gupta","doi":"10.37190/ord220103","DOIUrl":"https://doi.org/10.37190/ord220103","url":null,"abstract":"This study proposes a methodology to obtain an efficient solution for a programming model which is multi-objective quadratic fractional with pentagonal fuzzy numbers as coefficients in all the objective functions and constraints. The proposed approach consists of three stages. In the first stage, defuzzification of the coefficients is carried out using the mean method of α-cut. Then, in the second stage, a crisp multi-objective quadratic fractional programming model (MOQFP) is constructed to obtain a non-fractional model based on an iterative parametric approach. In the final stage, this multiobjective non-fractional model is transformed to obtain a model with a single objective by applying the ε-constraint method. This final model is then solved to get desired solution. Also, an algorithm and flowchart expressing the methodology are given to present a clear picture of the approach. Finally, a numerical example illustrating the complete approach is given.","PeriodicalId":43244,"journal":{"name":"Operations Research and Decisions","volume":"45 1","pages":""},"PeriodicalIF":0.4,"publicationDate":"2022-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"86700728","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
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