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Prof. Camelia Delcea
Bucharest University of Economic Studies

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1 Agent-based Modeling
0 Airplane
0 Cybernetics
0 Evacuation
0 Hospital Operations

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Agent-based Modeling
Evacuation
Grey System Theory
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Journal article
Published: 21 May 2021 in Mathematics
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The purpose of this paper was to model, with the help of neutrosophic fuzzy numbers, the optimal financial asset portfolios, offering additional information to those investing in the capital market. The optimal neutrosophic portfolios are those categories of portfolios consisting of two or more financial assets, modeled using neutrosophic triangular numbers, that allow for the determination of financial performance indicators, respectively the neutrosophic average, the neutrosophic risk, for each financial asset, and the neutrosophic covariance as well as the determination of the portfolio return, respectively of the portfolio risk. There are two essential conditions established by rational investors on the capital market to obtain an optimal financial assets portfolio, respectively by fixing the financial return at the estimated level as well as minimizing the risk of the financial assets neutrosophic portfolio. These conditions allowed us to compute the financial assets’ share in the total value of the neutrosophic portfolios, for which the financial return reaches the level set by investors and the financial risk has the minimum value. In financial terms, the financial assets’ share answers the legitimate question of rational investors in the capital market regarding the amount of money they must invest in compliance with the optimal conditions regarding the neutrosophic return and risk.

ACS Style

Marcel-Ioan Boloș; Ioana-Alexandra Bradea; Camelia Delcea. Optimization of Financial Asset Neutrosophic Portfolios. Mathematics 2021, 9, 1162 .

AMA Style

Marcel-Ioan Boloș, Ioana-Alexandra Bradea, Camelia Delcea. Optimization of Financial Asset Neutrosophic Portfolios. Mathematics. 2021; 9 (11):1162.

Chicago/Turabian Style

Marcel-Ioan Boloș; Ioana-Alexandra Bradea; Camelia Delcea. 2021. "Optimization of Financial Asset Neutrosophic Portfolios." Mathematics 9, no. 11: 1162.

Journal article
Published: 26 March 2021 in Symmetry
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The social distancing imposed by the novel coronavirus, SARS-CoV-2, has affected people’s everyday lives and has resulted in companies changing the way they conduct business. The airline industry has been continually adapting since the novel coronavirus appeared. A series of airlines have changed their airplane boarding and passenger seat allocation process to increase their passengers’ safety. Many suggest a minimum social distance among passengers in the aisle while boarding. Some airlines have reduced their airplanes’ capacities by keeping the middle seats empty. Recent literature indicates that the Reverse Pyramid boarding method provides favorable values for boarding time and passenger health metrics when compared to other boarding methods. This paper analyses the extent to which aisle social distancing, the quantity of carry-on luggage, and an airline’s relative preferences for different performance metrics influence the optimal number of passengers to board the airplane in each of three boarding groups when the Reverse Pyramid method is used and the middle seats are empty. We also investigate the resulting impact on the average boarding time and health risks to boarding passengers. We use an agent-based model and stochastic simulation approach to evaluate various levels of aisle social distancing among passengers and the quantity of luggage carried aboard the airplane. When minimizing boarding time is the primary objective of an airline, for a given value of aisle social distance, decreasing the carry-on luggage volumes increases the optimal number of boarding group 1 passengers and decreases the optimal number of group 2 passengers with aisle seats; for a given volume of luggage, an increase in aisle social distance is associated with more passengers in group 1 and more aisle seat passengers in group 2. When minimizing the health risk to aisle seat passengers or to window seat passengers, the optimal solution results from assigning an equal number of window seat passengers to groups 1 and 2 and an equal number of aisle seat passengers to groups 2 and 3. This solution is robust to changes in luggage volume and the magnitude of aisle social distance. Furthermore, across all luggage and aisle social distancing scenarios, the solution reduces the health risk to aisle seat passengers between 22.76% and 35.31% while increasing average boarding time by less than 3% in each scenario.

ACS Style

Liviu-Adrian Cotfas; R. Milne; Camelia Delcea; Corina Ioanăș. An Investigation of Social Distancing and Quantity of Luggage Impacts on the Three Groups Reverse Pyramid Boarding Method. Symmetry 2021, 13, 544 .

AMA Style

Liviu-Adrian Cotfas, R. Milne, Camelia Delcea, Corina Ioanăș. An Investigation of Social Distancing and Quantity of Luggage Impacts on the Three Groups Reverse Pyramid Boarding Method. Symmetry. 2021; 13 (4):544.

Chicago/Turabian Style

Liviu-Adrian Cotfas; R. Milne; Camelia Delcea; Corina Ioanăș. 2021. "An Investigation of Social Distancing and Quantity of Luggage Impacts on the Three Groups Reverse Pyramid Boarding Method." Symmetry 13, no. 4: 544.

Earlycite article
Published: 11 March 2021 in Grey Systems: Theory and Application
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Purpose The airline industry has been significantly hit by the occurrence of the new coronavirus SARS-CoV-2, facing one of its worst crises in history. In this context, the present paper analyses one of the well-known boarding methods used in practice by the airlines before and during the coronavirus outbreak, namely back-to-front and suggests which variations of this method to use when three passenger boarding groups are considered and a jet bridge connects the airport terminal with the airplane. Design/methodology/approach Based on the importance accorded by the airlines to operational performance, health risks, and passengers' comfort, the variations in three passenger groups back-to-front boarding are divided into three clusters using the grey clustering approach offered by the grey systems theory. Findings Having the clusters based on the selected metrics and considering the social distance among the passengers, airlines can better understand how the variations in back-to-front perform in the new conditions imposed by the novel coronavirus and choose the boarding approach that better fits its policy and goals. Originality/value The paper combines the advantages offered by grey clustering and agent-based modelling for offering to determine which are the best configurations that offer a reduced boarding time, while accounting for reduced passengers' health risk, measured through three indicators: aisle risk, seat risk and type-3 seat interferences and for an increased comfort for the passengers manifested through a continuous walking flow while boarding.

ACS Style

Camelia Delcea; Liviu-Adrian Cotfas; R. John Milne; Naiming Xie; Rafał Mierzwiak. Grey clustering of the variations in the back-to-front airplane boarding method considering COVID-19 flying restrictions. Grey Systems: Theory and Application 2021, ahead-of-p, 1 .

AMA Style

Camelia Delcea, Liviu-Adrian Cotfas, R. John Milne, Naiming Xie, Rafał Mierzwiak. Grey clustering of the variations in the back-to-front airplane boarding method considering COVID-19 flying restrictions. Grey Systems: Theory and Application. 2021; ahead-of-p (ahead-of-p):1.

Chicago/Turabian Style

Camelia Delcea; Liviu-Adrian Cotfas; R. John Milne; Naiming Xie; Rafał Mierzwiak. 2021. "Grey clustering of the variations in the back-to-front airplane boarding method considering COVID-19 flying restrictions." Grey Systems: Theory and Application ahead-of-p, no. ahead-of-p: 1.

Conference paper
Published: 02 March 2021 in Financial Environment and Business Development
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The rapid growth and use of the online social networks have generated an increasing interest in different research areas, while a series of studies have shown the importance of the consumers’ influence in these networks on other users’ decisions and attitudes. In this context, the current research focuses on the recycling habits’ influences that might be exerted on the online social networks. As a starting point, based on the current researches, a questionnaire has been created and validated. During the validation process, the questionnaire has passed the unidimensionality, feasibility, convergent, and similarity validity. Three hundred seventeen respondents have taken part in this study. The questions have tried to extract the respondents’ attitude toward recycling and the online media exposure in relation to the recycling habits. Most of the questions have been evaluated using a 5-point Likert scale. Among the results, the potential frequency for the recycling process based on the users’ activity in online social networks has been determined. Knowing this frequency and the type of online social networks interactions related to the recycling habits, the interested organizations can conduct a series of campaigns in online environments in order to reduce the duration needed for a full adoption rate of the recycling attitude.

ACS Style

Camelia Delcea; Liviu-Adrian Cotfas; Rafal Mierzwiak; Mihai Orzan. Consumers’ Influence in Online Social Networks Regarding Recycling Habits. Financial Environment and Business Development 2021, 295 -305.

AMA Style

Camelia Delcea, Liviu-Adrian Cotfas, Rafal Mierzwiak, Mihai Orzan. Consumers’ Influence in Online Social Networks Regarding Recycling Habits. Financial Environment and Business Development. 2021; ():295-305.

Chicago/Turabian Style

Camelia Delcea; Liviu-Adrian Cotfas; Rafal Mierzwiak; Mihai Orzan. 2021. "Consumers’ Influence in Online Social Networks Regarding Recycling Habits." Financial Environment and Business Development , no. : 295-305.

Journal article
Published: 16 February 2021 in IEEE Access
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The coronavirus outbreak has brought unprecedented measures, which forced the authorities to make decisions related to the instauration of lockdowns in the areas most hit by the pandemic. Social media has been an important support for people while passing through this difficult period. On November 9, 2020, when the first vaccine with more than 90% effective rate has been announced, the social media has reacted and people worldwide have started to express their feelings related to the vaccination, which was no longer a hypothesis but closer, each day, to become a reality. The present paper aims to analyze the dynamics of the opinions regarding COVID-19 vaccination by considering the one-month period following the first vaccine announcement, until the first vaccination took place in UK, in which the civil society has manifested a higher interest regarding the vaccination process. Classical machine learning and deep learning algorithms have been compared to select the best performing classifier. 2 349 659 tweets have been collected, analyzed, and put in connection with the events reported by the media. Based on the analysis, it can be observed that most of the tweets have a neutral stance, while the number of in favor tweets overpasses the number of against tweets. As for the news, it has been observed that the occurrence of tweets follows the trend of the events. Even more, the proposed approach can be used for a longer monitoring campaign that can help the governments to create appropriate means of communication and to evaluate them in order to provide clear and adequate information to the general public, which could increase the public trust in a vaccination campaign.

ACS Style

Liviu-Adrian Cotfas; Camelia Delcea; Ioan Roxin; Corina Ioanas; Dana Simona Gherai; Federico Tajariol. The Longest Month: Analyzing COVID-19 Vaccination Opinions Dynamics From Tweets in the Month Following the First Vaccine Announcement. IEEE Access 2021, 9, 33203 -33223.

AMA Style

Liviu-Adrian Cotfas, Camelia Delcea, Ioan Roxin, Corina Ioanas, Dana Simona Gherai, Federico Tajariol. The Longest Month: Analyzing COVID-19 Vaccination Opinions Dynamics From Tweets in the Month Following the First Vaccine Announcement. IEEE Access. 2021; 9 (99):33203-33223.

Chicago/Turabian Style

Liviu-Adrian Cotfas; Camelia Delcea; Ioan Roxin; Corina Ioanas; Dana Simona Gherai; Federico Tajariol. 2021. "The Longest Month: Analyzing COVID-19 Vaccination Opinions Dynamics From Tweets in the Month Following the First Vaccine Announcement." IEEE Access 9, no. 99: 33203-33223.

Journal article
Published: 09 December 2020 in Symmetry
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The onset of the novel coronavirus SARS-CoV2 has changed many aspects of people’s economic and social activities. For many airlines, social distancing has reduced airplane capacity by one third as a result of keeping the middle seats empty. Additionally, social distancing between passengers traversing the aisle slows the boarding process. Recent literature has suggested that the reverse pyramid boarding method provides favorable values for boarding time and passenger health metrics when compared to other boarding methods with social distancing. Assuming reverse pyramid boarding with the middle seats unoccupied, we determined the number of passengers to include in each of three boarding groups. We assumed that passengers use a jet-bridge that connects the airport terminal to the airplane’s front door. We used agent-based modeling and a stochastic simulation to evaluate solutions. A full grid search found an initial good solution, and then local search optimization determined the best solution based upon the airline’s relative preference for minimizing average boarding time and minimizing risks to previously seated passengers from later-boarding, potentially contagious passengers breathing near them. The resulting solution contained the number of passengers to place into each of the three boarding groups. If an airline is most concerned about the health risk to seated passengers from later boarding passengers walking near them, the best three-group reverse pyramid method adapted for social distancing will first board passengers with window seats in the rear half of the airplane, then will board passengers with window seats in the front half of the airplane and those with aisle seats in the rear half of the airplane, and finally will board the passengers with aisle seats in the front half of the airplane. The resulting solution takes about 2% longer to board than the three-group solution that minimizes boarding time while providing a 25% decrease in health risk to aisle seat passengers from later boarding passengers.

ACS Style

Camelia Delcea; R. John Milne; Liviu-Adrian Cotfas. Determining the Number of Passengers for Each of Three Reverse Pyramid Boarding Groups with COVID-19 Flying Restrictions. Symmetry 2020, 12, 2038 .

AMA Style

Camelia Delcea, R. John Milne, Liviu-Adrian Cotfas. Determining the Number of Passengers for Each of Three Reverse Pyramid Boarding Groups with COVID-19 Flying Restrictions. Symmetry. 2020; 12 (12):2038.

Chicago/Turabian Style

Camelia Delcea; R. John Milne; Liviu-Adrian Cotfas. 2020. "Determining the Number of Passengers for Each of Three Reverse Pyramid Boarding Groups with COVID-19 Flying Restrictions." Symmetry 12, no. 12: 2038.

Research article
Published: 04 November 2020 in PLoS ONE
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Social distancing resulting from the new coronavirus (SARS-CoV2) has disrupted the airplane boarding process. Social distancing norms reduce airplane capacity by keeping the middle seats unoccupied, while an imposed aisle social distance between boarding passengers slows the boarding. Recent literature suggests the Reverse Pyramid boarding method is a promising way to reduce health risk and keep boarding times low when 10 apron buses (essentially 10 boarding groups) are used to transport passengers from the airport terminal to a two-door airplane. We adapt the Reverse Pyramid method for social distancing when an airplane is boarded using a jet bridge that connects the terminal the airplane’s front door. We vary the number of boarding groups from two to six and use stochastic simulation and agent-based modelling to show the resulting impact on four performance evaluation metrics. Increasing the number of boarding groups from two to six reduces boarding time only up to four groups but continues to reduce infection risk up to six groups. If the passengers carry fewer luggage aboard the airplane, health risks (as well as boarding times) decrease. One adaptation of the Reverse Pyramid (RP) method (RP-Spread) provides slightly faster boarding times than the other (RP-Steep), when luggage volumes are high, while RP-Steep results in less risk to window seat passengers from later-boarding passengers walking by their row. Increasing the minimum aisle social distance from 1 m to 2 m increases boarding times but results in lower health risks to passengers walking down the aisle and to the previously seated passengers they pass.

ACS Style

R. John Milne; Liviu-Adrian Cotfas; Camelia Delcea; Liliana Crăciun; Anca-Gabriela Molănescu. Adapting the reverse pyramid airplane boarding method for social distancing in times of COVID-19. PLoS ONE 2020, 15, e0242131 .

AMA Style

R. John Milne, Liviu-Adrian Cotfas, Camelia Delcea, Liliana Crăciun, Anca-Gabriela Molănescu. Adapting the reverse pyramid airplane boarding method for social distancing in times of COVID-19. PLoS ONE. 2020; 15 (11):e0242131.

Chicago/Turabian Style

R. John Milne; Liviu-Adrian Cotfas; Camelia Delcea; Liliana Crăciun; Anca-Gabriela Molănescu. 2020. "Adapting the reverse pyramid airplane boarding method for social distancing in times of COVID-19." PLoS ONE 15, no. 11: e0242131.

Journal article
Published: 26 October 2020 in Safety Science
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Airlines have recently instituted practices to reduce the risk of their passengers becoming infected with the novel coronavirus (SARS-CoV-2). Some airlines block their airplanes’ middle seats to preserve social distancing among seated passengers. In this context, we present six new boarding methods and compare their performance with that of the two best boarding methods used to date with social distancing. We evaluate the eight boarding methods using three performance metrics related to passenger health and one operational metric (airplane boarding time) for a one-door airplane. The three health metrics reflect the risks of virus spread by passengers through the air and surfaces (e.g. headrests and seat arms) and consider the amount of aisle social distancing between adjacent boarding passengers walking towards their seats. For an airline that highly values the avoidance of window seat risk, the best method to use is one of the new methods: back-to-front by row – WilMA, though it will result in a longer time to complete boarding of the airplane. Airlines placing greater emphasis on fast boarding times— while still providing favorable values for the health metrics—will be best served by using new methods back-to-front by row – WilMA – offset 2 and – offset 3 when aisle social distancing is 1 m and 2 m respectively.

ACS Style

R. John Milne; Camelia Delcea; Liviu-Adrian Cotfas. Airplane boarding methods that reduce risk from COVID-19. Safety Science 2020, 134, 105061 .

AMA Style

R. John Milne, Camelia Delcea, Liviu-Adrian Cotfas. Airplane boarding methods that reduce risk from COVID-19. Safety Science. 2020; 134 ():105061.

Chicago/Turabian Style

R. John Milne; Camelia Delcea; Liviu-Adrian Cotfas. 2020. "Airplane boarding methods that reduce risk from COVID-19." Safety Science 134, no. : 105061.

Journal article
Published: 11 September 2020 in Journal of Air Transport Management
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This paper addresses the airplane passengers’ seat assignment problem while practicing social distancing among passengers. We proposed a mixed integer programming model to assign passengers to seats on an airplane in a manner that will respect two types of social distancing. One type of social distancing refers to passengers being seated far enough away from each other. The metric for this type of social distancing is how many passengers are seated so close to each other as to increase the risk of infection. The other type of social distancing refers to the distance between seat assignments and the aisle. That distance influences the health risk involved in passengers and crew members walking down the aisle. Corresponding metrics for both health risks are included in the objective function. To conduct simulation experiments, we define different scenarios distinguishing between the relative level of significance of each type of social distancing. The results suggest the seating assignments that best serve the intention of the scenarios. We also reformulate the initial model to determine seat assignments that maximize the number of passengers boarding an airplane while practicing social distancing among passengers. In the last part of this study, we compare the proposed scenarios with the recommended middle-seat blocking policy presently used by some airlines to keep social distancing among passengers. The results show that the proposed scenarios can provide social distancing among seated passengers similar to the middle-seat blocking policy, while reducing the number of passengers seated close to the aisle of an airplane.

ACS Style

Mostafa Salari; R. John Milne; Camelia Delcea; Lina Kattan; Liviu-Adrian Cotfas. Social distancing in airplane seat assignments. Journal of Air Transport Management 2020, 89, 101915 -101915.

AMA Style

Mostafa Salari, R. John Milne, Camelia Delcea, Lina Kattan, Liviu-Adrian Cotfas. Social distancing in airplane seat assignments. Journal of Air Transport Management. 2020; 89 ():101915-101915.

Chicago/Turabian Style

Mostafa Salari; R. John Milne; Camelia Delcea; Lina Kattan; Liviu-Adrian Cotfas. 2020. "Social distancing in airplane seat assignments." Journal of Air Transport Management 89, no. : 101915-101915.

Journal article
Published: 12 August 2020 in Sustainability
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The increase in consumerism due to population growth, excessive advertising and the constant encouragement of buying behavior by advertising media and opinion formers comes with side effects for the environment and public health if it is not properly supported by a sustainable selective waste collection process. In this context, the paper aims at determining the impact of different elements on people’s intention to participate in selective waste collection and on their behavior related to the collection process. Based on the literature, a series of variables were considered and a questionnaire was created in order to extract people’s opinions related to the selective waste collection process. As discrepancies in findings might appear due to culture in various countries, the analysis has been conducted with reference to Romania’s case. The waste collection situation in Romania is similar in some ways to other countries in the world, with some differences related to a small recycling rate compared to other countries in the European Union. In this context, it is important to identify the determinants of the consumers’ behavior in selective waste collection and to act based on these findings. Creating better policies that can support the selective waste collection process will have results in increasing the waste collection rate, offering a clear and safer environment to all the citizens.

ACS Style

Adina-Iuliana Jigani; Camelia Delcea; Corina Ioanăș. Consumers’ Behavior in Selective Waste Collection: A Case Study Regarding the Determinants from Romania. Sustainability 2020, 12, 6527 .

AMA Style

Adina-Iuliana Jigani, Camelia Delcea, Corina Ioanăș. Consumers’ Behavior in Selective Waste Collection: A Case Study Regarding the Determinants from Romania. Sustainability. 2020; 12 (16):6527.

Chicago/Turabian Style

Adina-Iuliana Jigani; Camelia Delcea; Corina Ioanăș. 2020. "Consumers’ Behavior in Selective Waste Collection: A Case Study Regarding the Determinants from Romania." Sustainability 12, no. 16: 6527.

Journal article
Published: 11 August 2020 in IEEE Access
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Social distancing reduces the risk of people becoming infected with the novel coronavirus (SARS-CoV-2). When passengers are transported from an airport terminal to an airplane using apron buses, safe social distancing during pandemic times reduces the capacity of the apron buses and has led to the practice of airlines keeping the middle seats of the airplanes unoccupied. This paper adapts classical boarding methods so that they may be used with social distancing and apron buses. We conduct stochastic simulation experiments to assess nine adaptations of boarding methods according to four performance metrics. Three of the metrics are related to the risk of the virus spreading to passengers during boarding. The fourth metric is the time to complete boarding of the two-door airplane when apron bus transport passengers to the airplane. Our experiments assume that passengers advancing to their airplane seats are separated by an aisle social distance of 1 m or 2 m. Numerical results indicate that the three variations (adaptations) of the Reverse pyramid method are the best candidates for airlines to consider in this socially distanced context. The particular adaptation to use depends on an airline’s relative preference for having short boarding times versus a reduced risk of later boarding passengers passing (and thereby possibly infecting) previously seated window seat passengers. If an airline considers the latter risk to be unimportant, then the Reverse pyramid – Spread method would be the best choice because it provides the fastest time to board the airplane and is tied for the best values for the other two health risk measures.

ACS Style

R. John Milne; Camelia Delcea; Liviu-Adrian Cotfas; Corina Ioanas. Evaluation of Boarding Methods Adapted for Social Distancing When Using Apron Buses. IEEE Access 2020, 8, 151650 -151667.

AMA Style

R. John Milne, Camelia Delcea, Liviu-Adrian Cotfas, Corina Ioanas. Evaluation of Boarding Methods Adapted for Social Distancing When Using Apron Buses. IEEE Access. 2020; 8 (99):151650-151667.

Chicago/Turabian Style

R. John Milne; Camelia Delcea; Liviu-Adrian Cotfas; Corina Ioanas. 2020. "Evaluation of Boarding Methods Adapted for Social Distancing When Using Apron Buses." IEEE Access 8, no. 99: 151650-151667.

Journal article
Published: 01 July 2020 in Symmetry
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As it is well acknowledged that the electoral system is one of the fundamental rocks of our modern society, the behavior of electors engaged in a voting system is of the utmost importance. In this context, the goal of the study is to model the behavior of voters in a first-past-the-post system and to analyze its consequences on a party system. Among the assumptions of this study is Duverger’s law, which states that first-past-the-post systems favor a two-party system as the voters engage in tactical voting, choosing to vote in favor of a less preferred candidate who has better odds of winning. In order to test this assumption and to better analyze the occurrence of the strategic behavior, a laboratory experiment was created. A total of 120 persons participated in the study. An asymmetrical payoff function was created to value the voters’ preference intensity. As a result, it was observed that as voters got used to the voting system, they engaged in more tactical voting behavior in order to either maximize the gain or minimize the loss of their choice. Moreover, the iterations where voters started displaying tactical behavior featured a clustering around two main choices. The obtained results are consistent with both the empirical results of real-life elections and Duverger’s law. A further discussion regarding the change in voters’ choice completes the analysis on the strategic behavior.

ACS Style

Andrei Chiriță; Camelia Delcea. A Laboratory Experiment for Analyzing Electors’ Strategic Behavior in a First-Past-the-Post System. Symmetry 2020, 12, 1081 .

AMA Style

Andrei Chiriță, Camelia Delcea. A Laboratory Experiment for Analyzing Electors’ Strategic Behavior in a First-Past-the-Post System. Symmetry. 2020; 12 (7):1081.

Chicago/Turabian Style

Andrei Chiriță; Camelia Delcea. 2020. "A Laboratory Experiment for Analyzing Electors’ Strategic Behavior in a First-Past-the-Post System." Symmetry 12, no. 7: 1081.

Journal article
Published: 01 July 2020 in Symmetry
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The novel coronavirus (SARS-CoV-2) has imposed the need for a series of social distancing restrictions worldwide to mitigate the scourge of the COVID-19 pandemic. This applies to many domains, including airplane boarding and seat assignments. As airlines are considering their passengers’ safety during the pandemic, boarding methods should be evaluated both in terms of social distancing norms and the resulting efficiency for the airlines. The present paper analyzes the impact of a series of restrictions that have been imposed or mooted worldwide on the boarding methods used by the airlines, featuring the use of jet-bridges and one-door boarding. To compare the efficacy of classical airplane boarding methods with respect to new social distancing norms, five metrics were used to evaluate their performance. One metric is the time to complete the boarding of the airplane. The other four metrics concern passenger health and reflect the potential exposure to the virus from other passengers through the air and surfaces (e.g., headrests and luggage) touched by passengers. We use the simulation platform in NetLogo to test six common boarding methods under various conditions. The back-to-front by row boarding method results in the longest time to complete boarding but has the advantage of providing the lowest health risk for two metrics. Those two metrics are based on passengers potentially infecting those passengers previously seated in the rows they traverse. Interestingly, those two risks are reduced for most boarding methods when the social distance between adjacent passengers advancing down the aisle is increased, thus indicating an unanticipated benefit stemming from this form of social distancing. The modified reverse pyramid by half zone method provides the shortest time to the completing boarding of the airplane and—along with the WilMA boarding method—provides the lowest health risk stemming from potential infection resulting from seat interferences. Airlines have the difficult task of making tradeoffs between economic productivity and the resulting impact on various health risks.

ACS Style

Liviu-Adrian Cotfas; Camelia Delcea; R. John Milne; Mostafa Salari. Evaluating Classical Airplane Boarding Methods Considering COVID-19 Flying Restrictions. Symmetry 2020, 12, 1087 .

AMA Style

Liviu-Adrian Cotfas, Camelia Delcea, R. John Milne, Mostafa Salari. Evaluating Classical Airplane Boarding Methods Considering COVID-19 Flying Restrictions. Symmetry. 2020; 12 (7):1087.

Chicago/Turabian Style

Liviu-Adrian Cotfas; Camelia Delcea; R. John Milne; Mostafa Salari. 2020. "Evaluating Classical Airplane Boarding Methods Considering COVID-19 Flying Restrictions." Symmetry 12, no. 7: 1087.

Journal article
Published: 15 April 2020 in Symmetry
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As the evacuation problem has attracted and continues to attract a series of researchers due to its high importance both for saving human lives and for reducing the material losses in such situations, the present paper analyses whether the evacuation doors configuration in the case of classrooms and lecture halls matters in reducing the evacuation time. For this aim, eighteen possible doors configurations have been considered along with five possible placements of desks and chairs. The doors configurations have been divided into symmetrical and asymmetrical clusters based on the two doors positions within the room. An agent-based model has been created in NetLogo which allows a fast configuration of the classrooms and lecture halls in terms of size, number of desks and chairs, desks and chair configuration, exits’ size, the presence of fallen objects, type of evacuees and their speed. The model has been used for performing and analyzing various scenarios. Based on these results, it has been observed that, in most cases, the symmetrical doors configurations provide good/optimal results, while only some of the asymmetrical doors configurations provide comparable/better results. The model is configurable and can be used in various scenarios.

ACS Style

Camelia Delcea; Liviu-Adrian Cotfas; Ioana-Alexandra Bradea; Marcel-Ioan Boloș; Gabriella Ferruzzi. Investigating the Exits’ Symmetry Impact on the Evacuation Process of Classrooms and Lecture Halls: An Agent-Based Modeling Approach. Symmetry 2020, 12, 627 .

AMA Style

Camelia Delcea, Liviu-Adrian Cotfas, Ioana-Alexandra Bradea, Marcel-Ioan Boloș, Gabriella Ferruzzi. Investigating the Exits’ Symmetry Impact on the Evacuation Process of Classrooms and Lecture Halls: An Agent-Based Modeling Approach. Symmetry. 2020; 12 (4):627.

Chicago/Turabian Style

Camelia Delcea; Liviu-Adrian Cotfas; Ioana-Alexandra Bradea; Marcel-Ioan Boloș; Gabriella Ferruzzi. 2020. "Investigating the Exits’ Symmetry Impact on the Evacuation Process of Classrooms and Lecture Halls: An Agent-Based Modeling Approach." Symmetry 12, no. 4: 627.

Journal article
Published: 01 April 2020 in Sustainability
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Due to the increase of the amount of electrical and electronical equipment waste (e-waste), the understanding of individual consumers’ main decision triggers represents a key point in increasing the quantity of recycled e-waste. A series of studies from the literature have shown a positive relationship between the consumers’ attitude, awareness, self-efficacy, social norms, and their e-waste recycling intention, as well as the positive influence between the intention and the manifested behavior. Additional to these determinants, in the present study, the influence of social media was analyzed along with the actions taken by the government and nongovernmental organizations, with the purpose to include and to capture, as much as possible, a high amount of determinants in the e-waste recycling process. Nevertheless, the demographic or socio-economic variables, such as age, gender, income, education, number of family members, etc., have shown over time to have a contribution to predicting the consumers’ pro-recycling behavior. As on one side, in the research literature, the opinions related to which of the demographic or socio-economic factors can have an impact on the recycling behavior have been divided and, on another side, a series of researchers believe that the discrepancies in the findings of different studies can be due to culture in various countries, in this paper we conducted such an analysis with reference to the Romania’s case. The results have shown that the demographic variables, such as age and gender, can have a contribution to predicting residents’ pro-e-waste recycling behavior. Based on these findings, the policymakers can gain a better understanding of the e-waste recycling phenomenon and on its main triggers, with results in creating better policies for sustaining a proper e-waste managing system.

ACS Style

Camelia Delcea; Liliana Crăciun; Corina Ioanăș; Gabriella Ferruzzi; Liviu-Adrian Cotfas. Determinants of Individuals’ E-Waste Recycling Decision: A Case Study from Romania. Sustainability 2020, 12, 2753 .

AMA Style

Camelia Delcea, Liliana Crăciun, Corina Ioanăș, Gabriella Ferruzzi, Liviu-Adrian Cotfas. Determinants of Individuals’ E-Waste Recycling Decision: A Case Study from Romania. Sustainability. 2020; 12 (7):2753.

Chicago/Turabian Style

Camelia Delcea; Liliana Crăciun; Corina Ioanăș; Gabriella Ferruzzi; Liviu-Adrian Cotfas. 2020. "Determinants of Individuals’ E-Waste Recycling Decision: A Case Study from Romania." Sustainability 12, no. 7: 2753.

Journal article
Published: 21 January 2020 in IEEE Access
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R. John Milne; Liviu-Adrian Cotfas; Camelia Delcea; Mostafa Salari; Liliana Craciun; Anca Gabriela Molanescu. Airplane Boarding Method for Passenger Groups When Using Apron Buses. IEEE Access 2020, 8, 18019 -18035.

AMA Style

R. John Milne, Liviu-Adrian Cotfas, Camelia Delcea, Mostafa Salari, Liliana Craciun, Anca Gabriela Molanescu. Airplane Boarding Method for Passenger Groups When Using Apron Buses. IEEE Access. 2020; 8 ():18019-18035.

Chicago/Turabian Style

R. John Milne; Liviu-Adrian Cotfas; Camelia Delcea; Mostafa Salari; Liliana Craciun; Anca Gabriela Molanescu. 2020. "Airplane Boarding Method for Passenger Groups When Using Apron Buses." IEEE Access 8, no. : 18019-18035.

Journal article
Published: 19 January 2020 in Entropy
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This paper studies the problem of tangible assets acquisition within the company by proposing a new hybrid model that uses linear programming and fuzzy numbers. Regarding linear programming, two methods were implemented in the model, namely: the graphical method and the primal simplex algorithm. This hybrid model is proposed for solving investment decision problems, based on decision variables, objective function coefficients, and a matrix of constraints, all of them presented in the form of triangular fuzzy numbers. Solving the primal simplex algorithm using fuzzy numbers and coefficients, allowed the results of the linear programming problem to also be in the form of fuzzy variables. The fuzzy variables compared to the crisp variables allow the determination of optimal intervals for which the objective function has values depending on the fuzzy variables. The major advantage of this model is that the results are presented as value ranges that intervene in the decision-making process. Thus, the company’s decision makers can select any of the result values as they satisfy two basic requirements namely: minimizing/maximizing the objective function and satisfying the basic requirements regarding the constraints resulting from the company’s activity. The paper is accompanied by a practical example.

ACS Style

Marcel-Ioan Boloș; Ioana-Alexandra Bradea; Camelia Delcea. Linear Programming and Fuzzy Optimization to Substantiate Investment Decisions in Tangible Assets. Entropy 2020, 22, 121 .

AMA Style

Marcel-Ioan Boloș, Ioana-Alexandra Bradea, Camelia Delcea. Linear Programming and Fuzzy Optimization to Substantiate Investment Decisions in Tangible Assets. Entropy. 2020; 22 (1):121.

Chicago/Turabian Style

Marcel-Ioan Boloș; Ioana-Alexandra Bradea; Camelia Delcea. 2020. "Linear Programming and Fuzzy Optimization to Substantiate Investment Decisions in Tangible Assets." Entropy 22, no. 1: 121.

Journal article
Published: 05 November 2019 in Journal of Risk and Financial Management
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Bad decisions have harmful effects on the quality of human life and an increase of their duration expands these undesirable effects. Systematic bad decisions related to dividend policy can affect the investors’ quality of life in the long-term. We propose an agent-based model for the estimation of the duration of systematically making bad decisions, with an application on dividend policy. We propose an algorithm that can be used in modelling the interaction between different classes of shareholders and for predicting this duration. We perform numerical simulations based on this model using NetLogo 6.0.4. We prove that, as a result of agents’ interaction, in some conditions, the duration of systematically making bad decisions can be very long: some numerical simulations suggest that, in some circumstances, this duration can significantly exceed the human lifetime. Additionally, in some conditions, the company can fail before the power is switched. This duration can increase dramatically if the shareholders have a great level of trust in the management’s decisions. As an implication, a greater concern for the quality of financial education, and more performant instruments for controlling the power’s decisions are required.

ACS Style

Victor Dragotă; Camelia Delcea. How Long Does It Last to Systematically Make Bad Decisions? An Agent-Based Application for Dividend Policy. Journal of Risk and Financial Management 2019, 12, 167 .

AMA Style

Victor Dragotă, Camelia Delcea. How Long Does It Last to Systematically Make Bad Decisions? An Agent-Based Application for Dividend Policy. Journal of Risk and Financial Management. 2019; 12 (4):167.

Chicago/Turabian Style

Victor Dragotă; Camelia Delcea. 2019. "How Long Does It Last to Systematically Make Bad Decisions? An Agent-Based Application for Dividend Policy." Journal of Risk and Financial Management 12, no. 4: 167.

Journal article
Published: 03 November 2019 in Mathematics
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This paper studies the problem of neutrosophic portfolios of financial assets as part of the modern portfolio theory. Neutrosophic portfolios comprise those categories of portfolios made up of financial assets for which the neutrosophic return, risk and covariance can be determined and which provide concomitant information regarding the probability of achieving the neutrosophic return, both at each financial asset and portfolio level and also information on the probability of manifestation of the neutrosophic risk. Neutrosophic portfolios are characterized by two fundamental performance indicators, namely: the neutrosophic portfolio return and the neutrosophic portfolio risk. Neutrosophic portfolio return is dependent on the weight of the financial assets in the total value of the portfolio but also on the specific neutrosophic return of each financial asset category that enters into the portfolio structure. The neutrosophic portfolio risk is dependent on the weight of the financial assets that enter the portfolio structure but also on the individual risk of each financial asset. Within this scientific paper was studied the minimum neutrosophic risk at the portfolio level, respectively, to establish what should be the weight that the financial assets must hold in the total value of the portfolio so that the risk is minimum. These financial assets weights, after calculations, were found to be dependent on the individual risk of each financial asset but also on the covariance between two financial assets that enter into the portfolio structure. The problem of the minimum risk that characterizes the neutrosophic portfolios is of interest for the financial market investors. Thus, the neutrosophic portfolios provide complete information about the probabilities of achieving the neutrosophic portfolio return but also of risk manifestation probability. In this context, the innovative character of the paper is determined by the use of the neutrosophic triangular fuzzy numbers and by the specific concepts of financial assets, in order to substantiating the decisions on the financial markets.

ACS Style

Marcel-Ioan Boloș; Ioana-Alexandra Bradea; Camelia Delcea. Neutrosophic Portfolios of Financial Assets. Minimizing the Risk of Neutrosophic Portfolios. Mathematics 2019, 7, 1046 .

AMA Style

Marcel-Ioan Boloș, Ioana-Alexandra Bradea, Camelia Delcea. Neutrosophic Portfolios of Financial Assets. Minimizing the Risk of Neutrosophic Portfolios. Mathematics. 2019; 7 (11):1046.

Chicago/Turabian Style

Marcel-Ioan Boloș; Ioana-Alexandra Bradea; Camelia Delcea. 2019. "Neutrosophic Portfolios of Financial Assets. Minimizing the Risk of Neutrosophic Portfolios." Mathematics 7, no. 11: 1046.

Journal article
Published: 01 October 2019 in Symmetry
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This paper investigates the time to complete the boarding of a partially occupied two-door airplane when its passengers are transported from the airport terminal to the airplane using two apron buses. We propose a greedy method that assigns each passenger to a particular apron bus based on the passengers’ airplane seat assignments. This greedy approach exploits the airplane’s symmetry by providing essentially the same method for those boarding through the front door of the airplane as those boarding through the rear door of the airplane. The symmetrical properties of window, middle, and aisle seats of each row/side are considered in the proposed method as well. Computer simulation results indicate that, when using the greedy method, the boarding time can be reduced by up to 8.33% compared to the boarding time resulting from the best known practices in the literature, and with up to a 43.72% improvement in boarding time when compared to the boarding method commonly used in many airports. Furthermore, experimental results confirm our hypothesis that when the capacity of the apron buses exceeds the number of passengers to be transported to the airplane, the most time-efficient results of the proposed greedy method occur when an equal number of passengers are assigned to each of the two apron buses.

ACS Style

R. John Milne; Liviu-Adrian Cotfas; Camelia Delcea; Mostafa Salari; Liliana Craciun; Anca Gabriela Molanescu. Greedy Method for Boarding a Partially Occupied Airplane Using Apron Buses. Symmetry 2019, 11, 1221 .

AMA Style

R. John Milne, Liviu-Adrian Cotfas, Camelia Delcea, Mostafa Salari, Liliana Craciun, Anca Gabriela Molanescu. Greedy Method for Boarding a Partially Occupied Airplane Using Apron Buses. Symmetry. 2019; 11 (10):1221.

Chicago/Turabian Style

R. John Milne; Liviu-Adrian Cotfas; Camelia Delcea; Mostafa Salari; Liliana Craciun; Anca Gabriela Molanescu. 2019. "Greedy Method for Boarding a Partially Occupied Airplane Using Apron Buses." Symmetry 11, no. 10: 1221.