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Volume 12 (2021): Edizione 1 (May 2021)

Volume 11 (2020): Edizione 3 (November 2020)

Volume 11 (2020): Edizione 2 (October 2020)

Volume 11 (2020): Edizione 1 (March 2020)

Volume 10 (2019): Edizione 2 (September 2019)

Volume 10 (2019): Edizione 1 (April 2019)

Volume 9 (2018): Edizione 2 (July 2018)

Volume 9 (2018): Edizione 1 (March 2018)

Volume 8 (2017): Edizione 2 (September 2017)

Volume 8 (2017): Edizione 1 (March 2017)

Volume 7 (2016): Edizione 2 (September 2016)

Volume 7 (2016): Edizione 1 (March 2016)

Volume 6 (2015): Edizione 2 (September 2015)

Volume 6 (2015): Edizione 1 (March 2015)

Volume 5 (2014): Edizione 3 (September 2014)
“Novel solutions or novel approaches in Operational Research” co-published with the Slovenian Society INFORMATIKA – Section for Operational Research (SDI-SOR), Edizione Editors: Ksenija Dumičić (University of Zagreb), Lidija Zadnik Stirn (University of Ljubljana), and Janez Žerovnik (University of Ljubljana)

Volume 5 (2014): Edizione 2 (June 2014)

Volume 5 (2014): Edizione 1 (March 2014)
Special Edizione: Embedded Systems Applications: Future Society Applications

Volume 4 (2013): Edizione 2 (December 2013)

Volume 4 (2013): Edizione 1 (March 2013)

Volume 3 (2012): Edizione 2 (September 2012)
"Innovative Approaches to Operations Research Methodology and Its Applications in Business, Economics, Management and Social Sciences" co-published with the Slovenian Society INFORMATIKA - Section for Operational Research (SDI-SOR)

Volume 3 (2012): Edizione 1 (June 2012)

Volume 2 (2011): Edizione 2 (June 2011)

Volume 2 (2011): Edizione 1 (January 2011)

Volume 1 (2010): Edizione 1-2 (January 2010)

Dettagli della rivista
Formato
Rivista
eISSN
1847-9375
Pubblicato per la prima volta
19 Sep 2012
Periodo di pubblicazione
2 volte all'anno
Lingue
Inglese

Cerca

Volume 5 (2014): Edizione 3 (September 2014)
“Novel solutions or novel approaches in Operational Research” co-published with the Slovenian Society INFORMATIKA – Section for Operational Research (SDI-SOR), Edizione Editors: Ksenija Dumičić (University of Zagreb), Lidija Zadnik Stirn (University of Ljubljana), and Janez Žerovnik (University of Ljubljana)

Dettagli della rivista
Formato
Rivista
eISSN
1847-9375
Pubblicato per la prima volta
19 Sep 2012
Periodo di pubblicazione
2 volte all'anno
Lingue
Inglese

Cerca

6 Articoli
access type Accesso libero

Optimization of a Call Centre Performance Using the Stochastic Queueing Models

Pubblicato online: 25 Sep 2014
Pagine: 6 - 18

Astratto

Abstract

Background A call centre usually represents the first contact of a customer with a given company. Therefore, the quality of its service is of key importance. An essential factor of the call centre optimization is the determination of the proper number of operators considering the selected performance measure. Results of previous research show that this can be done using the queueing theory approach. Objectives: The paper presents the practical application of the stochastic queueing models aimed at optimizing a Slovenian telecommunication provider’s call centre.

Methods/Approach: The arrival and the service patterns were analysed, and it was concluded that the call centre under consideration can be described using the M/M/r {infinity/infinity/FIFO} queueing model.

Results: An appropriate number of operators were determined for different peak periods of the working day, taking into consideration the following four performance measures: the expected waiting time, the expected number of waiting customers, the probability that a calling customer will have to wait, and the call centre service level.

Conclusions: The obtained results prove the usefulness and applicability of the queueing models as a tool for a call centre performance optimization. In practice, all the data needed for such a mathematical analysis are usually provided. This paper is aimed at illustrating how such data can be efficiently exploited.

Keywords

  • call centre
  • service quality
  • performance measure
  • optimization
  • stochastic queueing models
access type Accesso libero

Regions for Servicing Old People: Case study of Slovenia

Pubblicato online: 25 Sep 2014
Pagine: 19 - 36

Astratto

Abstract

Background: Aging is one of the most serious problems that most developed countries are facing in the 21st century. In the European Union, Member States are responsible for the planning, funding and administration of health care and social protection systems. Local authorities and state governments should undertake research toward developing an appropriate array of community-based care services for old people. Objectives: This study analyses the regions of Slovenia for servicing old people in the 2000-2010 time horizon. Methods/Approach: Sets of functional regions were modelled for each year in the analysed period using the Intramax method. Functional regions were evaluated based on the attractiveness of central places for labour commuters and the propensity to commute between regions. Results: The results show that in addition to the nominally declared regional centres of Slovenia, there are also some other local centres that should be potentially included in the functional areas for servicing old people. Conclusions: The results suggest that the regionalization into seven functional regions is the most convenient for servicing old people in the region. Furthermore, some additional functional regions at a lower level are suggested.

Keywords

  • population aging
  • servicing old people
  • functional region
  • commuting
  • SIM
  • Slovenia
access type Accesso libero

Statistical Methods Use in Small Enterprises: Relation to Performance

Pubblicato online: 25 Sep 2014
Pagine: 37 - 48

Astratto

Abstract

Background: There are several factors that lead to an improved level of competitiveness and increased net income of enterprises. Previous studies have shown that an appropriate use of statistical methods has positive effects on the level of competitiveness and on enterprises’ net income in general. Objectives: This study analyses the statistical methods use in Croatian small enterprises. The goal of this research is to establish whether most Croatian small enterprises use statistical methods and whether the enterprises that use statistical methods on average have greater net income than the enterprises that do not use statistical methods.

Methods/Approach: A web survey was conducted on the sample of 631 small enterprises in Croatia in 2012. In the analysis a complex survey design was taken into account. Results: The results have shown that in most Croatian small enterprises statistical methods are not used. The enterprises that use statistical methods on average have greater net income than the enterprises that do not use them.

Conclusions: The results suggest that even though the use of statistical methods in small enterprises leads to higher net income, they are not used in the majority of Croatian small enterprises. If Croatian small enterprises want to succeed on the demanding European Union’s market they should consider using statistical methods in their business.

Keywords

  • small enterprises
  • statistical methods use
  • logistic regression
  • complex survey design
  • net income
  • Croatia
access type Accesso libero

How to Use Linear Programming for Information System Performances Optimization

Pubblicato online: 25 Sep 2014
Pagine: 49 - 66

Astratto

Abstract

Background: Organisations nowadays operate in a very dynamic environment, and therefore, their ability of continuously adjusting the strategic plan to the new conditions is a must for achieving their strategic objectives. BSC is a well-known methodology for measuring performances enabling organizations to learn how well they are doing. In this paper, “BSC for IS” will be proposed in order to measure the IS impact on the achievement of organizations’ business goals. Objectives: The objective of this paper is to present the original procedure which is used to enhance the BSC methodology in planning the optimal targets of IS performances value in order to maximize the organization's effectiveness. Methods/Approach: The method used in this paper is the quantitative methodology - linear programming. In the case study, linear programming is used for optimizing organization’s strategic performance. Results: Results are shown on the example of a case study national park. An optimal performance value for the strategic objective has been calculated, as well as an optimal performance value for each DO (derived objective). Results are calculated in Excel, using Solver Add-in. Conclusions: The presentation of methodology through the case study of a national park shows that this methodology, though it requires a high level of formalisation, provides a very transparent performance calculation.

Keywords

  • linear optimization
  • information systems
  • performance management
  • balanced scorecard
access type Accesso libero

How to Measure Illiquidity on European Emerging Stock Markets?

Pubblicato online: 25 Sep 2014
Pagine: 67 - 81

Astratto

Abstract

Background: Liquidity is, in practice of portfolio investment, an important attribute of stocks and measuring illiquidity presents a real challenge for researchers, primarily on developed stock markets. Moreover, there is a lack of research dealing with (il)liquidity on emerging markets. In the paper, the problem of applicability and validity of two well-known illiquidity measures, ILLIQ and TURN, on European emerging markets is observed. Objectives: The paper has two main purposes. The first is to test the relative performance of the two selected illiquidity measures in terms of their validity on European emerging stock markets. The second is to propose a new and improved illiquidity measure named Relative Change in Volume (RCV).

Methods/Approach: Using daily returns and traded volumes for 12 stocks which are constituents of stock indices on seven observed markets, ILLIQ and TURN along with the new proposed measure are calculated and tested based on correlation with return. All measures are tested and proposed using the single stock approach.

Results: It is shown that ILLIQ and TURN are not appropriate for seven observed markets. The measures do not follow the obligatory request that returns increase in illiquidity while RCV has the ability of taking into account the pressure of big differences in volume on return. RCV gives satisfactory results, making clear the distinction between liquid and illiquid stocks and between liquid and illiquid markets.

Conclusions: The proposed measure potentially has important implications in illiquidity measurement in general, and not only for investors on emerging stock markets.

Keywords

  • illiquidity measures
  • emerging markets
  • Relative Change in Volume-RCV
access type Accesso libero

A Comparison of Machine Learning Methods in a High-Dimensional Classification Problem

Pubblicato online: 25 Sep 2014
Pagine: 82 - 96

Astratto

Abstract

Background: Large-dimensional data modelling often relies on variable reduction methods in the pre-processing and in the post-processing stage. However, such a reduction usually provides less information and yields a lower accuracy of the model. Objectives: The aim of this paper is to assess the high-dimensional classification problem of recognizing entrepreneurial intentions of students by machine learning methods. Methods/Approach: Four methods were tested: artificial neural networks, CART classification trees, support vector machines, and k-nearest neighbour on the same dataset in order to compare their efficiency in the sense of classification accuracy. The performance of each method was compared on ten subsamples in a 10-fold cross-validation procedure in order to assess computing sensitivity and specificity of each model. Results: The artificial neural network model based on multilayer perceptron yielded a higher classification rate than the models produced by other methods. The pairwise t-test showed a statistical significance between the artificial neural network and the k-nearest neighbour model, while the difference among other methods was not statistically significant. Conclusions: Tested machine learning methods are able to learn fast and achieve high classification accuracy. However, further advancement can be assured by testing a few additional methodological refinements in machine learning methods.

Keywords

  • machine learning
  • support vector machines
  • artificial neural networks
  • CART classification trees
  • k-nearest neighbour
  • large-dimensional data
  • crossvalidation
6 Articoli
access type Accesso libero

Optimization of a Call Centre Performance Using the Stochastic Queueing Models

Pubblicato online: 25 Sep 2014
Pagine: 6 - 18

Astratto

Abstract

Background A call centre usually represents the first contact of a customer with a given company. Therefore, the quality of its service is of key importance. An essential factor of the call centre optimization is the determination of the proper number of operators considering the selected performance measure. Results of previous research show that this can be done using the queueing theory approach. Objectives: The paper presents the practical application of the stochastic queueing models aimed at optimizing a Slovenian telecommunication provider’s call centre.

Methods/Approach: The arrival and the service patterns were analysed, and it was concluded that the call centre under consideration can be described using the M/M/r {infinity/infinity/FIFO} queueing model.

Results: An appropriate number of operators were determined for different peak periods of the working day, taking into consideration the following four performance measures: the expected waiting time, the expected number of waiting customers, the probability that a calling customer will have to wait, and the call centre service level.

Conclusions: The obtained results prove the usefulness and applicability of the queueing models as a tool for a call centre performance optimization. In practice, all the data needed for such a mathematical analysis are usually provided. This paper is aimed at illustrating how such data can be efficiently exploited.

Keywords

  • call centre
  • service quality
  • performance measure
  • optimization
  • stochastic queueing models
access type Accesso libero

Regions for Servicing Old People: Case study of Slovenia

Pubblicato online: 25 Sep 2014
Pagine: 19 - 36

Astratto

Abstract

Background: Aging is one of the most serious problems that most developed countries are facing in the 21st century. In the European Union, Member States are responsible for the planning, funding and administration of health care and social protection systems. Local authorities and state governments should undertake research toward developing an appropriate array of community-based care services for old people. Objectives: This study analyses the regions of Slovenia for servicing old people in the 2000-2010 time horizon. Methods/Approach: Sets of functional regions were modelled for each year in the analysed period using the Intramax method. Functional regions were evaluated based on the attractiveness of central places for labour commuters and the propensity to commute between regions. Results: The results show that in addition to the nominally declared regional centres of Slovenia, there are also some other local centres that should be potentially included in the functional areas for servicing old people. Conclusions: The results suggest that the regionalization into seven functional regions is the most convenient for servicing old people in the region. Furthermore, some additional functional regions at a lower level are suggested.

Keywords

  • population aging
  • servicing old people
  • functional region
  • commuting
  • SIM
  • Slovenia
access type Accesso libero

Statistical Methods Use in Small Enterprises: Relation to Performance

Pubblicato online: 25 Sep 2014
Pagine: 37 - 48

Astratto

Abstract

Background: There are several factors that lead to an improved level of competitiveness and increased net income of enterprises. Previous studies have shown that an appropriate use of statistical methods has positive effects on the level of competitiveness and on enterprises’ net income in general. Objectives: This study analyses the statistical methods use in Croatian small enterprises. The goal of this research is to establish whether most Croatian small enterprises use statistical methods and whether the enterprises that use statistical methods on average have greater net income than the enterprises that do not use statistical methods.

Methods/Approach: A web survey was conducted on the sample of 631 small enterprises in Croatia in 2012. In the analysis a complex survey design was taken into account. Results: The results have shown that in most Croatian small enterprises statistical methods are not used. The enterprises that use statistical methods on average have greater net income than the enterprises that do not use them.

Conclusions: The results suggest that even though the use of statistical methods in small enterprises leads to higher net income, they are not used in the majority of Croatian small enterprises. If Croatian small enterprises want to succeed on the demanding European Union’s market they should consider using statistical methods in their business.

Keywords

  • small enterprises
  • statistical methods use
  • logistic regression
  • complex survey design
  • net income
  • Croatia
access type Accesso libero

How to Use Linear Programming for Information System Performances Optimization

Pubblicato online: 25 Sep 2014
Pagine: 49 - 66

Astratto

Abstract

Background: Organisations nowadays operate in a very dynamic environment, and therefore, their ability of continuously adjusting the strategic plan to the new conditions is a must for achieving their strategic objectives. BSC is a well-known methodology for measuring performances enabling organizations to learn how well they are doing. In this paper, “BSC for IS” will be proposed in order to measure the IS impact on the achievement of organizations’ business goals. Objectives: The objective of this paper is to present the original procedure which is used to enhance the BSC methodology in planning the optimal targets of IS performances value in order to maximize the organization's effectiveness. Methods/Approach: The method used in this paper is the quantitative methodology - linear programming. In the case study, linear programming is used for optimizing organization’s strategic performance. Results: Results are shown on the example of a case study national park. An optimal performance value for the strategic objective has been calculated, as well as an optimal performance value for each DO (derived objective). Results are calculated in Excel, using Solver Add-in. Conclusions: The presentation of methodology through the case study of a national park shows that this methodology, though it requires a high level of formalisation, provides a very transparent performance calculation.

Keywords

  • linear optimization
  • information systems
  • performance management
  • balanced scorecard
access type Accesso libero

How to Measure Illiquidity on European Emerging Stock Markets?

Pubblicato online: 25 Sep 2014
Pagine: 67 - 81

Astratto

Abstract

Background: Liquidity is, in practice of portfolio investment, an important attribute of stocks and measuring illiquidity presents a real challenge for researchers, primarily on developed stock markets. Moreover, there is a lack of research dealing with (il)liquidity on emerging markets. In the paper, the problem of applicability and validity of two well-known illiquidity measures, ILLIQ and TURN, on European emerging markets is observed. Objectives: The paper has two main purposes. The first is to test the relative performance of the two selected illiquidity measures in terms of their validity on European emerging stock markets. The second is to propose a new and improved illiquidity measure named Relative Change in Volume (RCV).

Methods/Approach: Using daily returns and traded volumes for 12 stocks which are constituents of stock indices on seven observed markets, ILLIQ and TURN along with the new proposed measure are calculated and tested based on correlation with return. All measures are tested and proposed using the single stock approach.

Results: It is shown that ILLIQ and TURN are not appropriate for seven observed markets. The measures do not follow the obligatory request that returns increase in illiquidity while RCV has the ability of taking into account the pressure of big differences in volume on return. RCV gives satisfactory results, making clear the distinction between liquid and illiquid stocks and between liquid and illiquid markets.

Conclusions: The proposed measure potentially has important implications in illiquidity measurement in general, and not only for investors on emerging stock markets.

Keywords

  • illiquidity measures
  • emerging markets
  • Relative Change in Volume-RCV
access type Accesso libero

A Comparison of Machine Learning Methods in a High-Dimensional Classification Problem

Pubblicato online: 25 Sep 2014
Pagine: 82 - 96

Astratto

Abstract

Background: Large-dimensional data modelling often relies on variable reduction methods in the pre-processing and in the post-processing stage. However, such a reduction usually provides less information and yields a lower accuracy of the model. Objectives: The aim of this paper is to assess the high-dimensional classification problem of recognizing entrepreneurial intentions of students by machine learning methods. Methods/Approach: Four methods were tested: artificial neural networks, CART classification trees, support vector machines, and k-nearest neighbour on the same dataset in order to compare their efficiency in the sense of classification accuracy. The performance of each method was compared on ten subsamples in a 10-fold cross-validation procedure in order to assess computing sensitivity and specificity of each model. Results: The artificial neural network model based on multilayer perceptron yielded a higher classification rate than the models produced by other methods. The pairwise t-test showed a statistical significance between the artificial neural network and the k-nearest neighbour model, while the difference among other methods was not statistically significant. Conclusions: Tested machine learning methods are able to learn fast and achieve high classification accuracy. However, further advancement can be assured by testing a few additional methodological refinements in machine learning methods.

Keywords

  • machine learning
  • support vector machines
  • artificial neural networks
  • CART classification trees
  • k-nearest neighbour
  • large-dimensional data
  • crossvalidation

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