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Open AccessArticle

An Exploration and Exploitation-Based Metaheuristic Approach for University Course Timetabling Problems

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Predrag S. Stanimirović

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Lev A. Kazakovtsev

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Darjan Karabašević

Axioms 2023, 12(8), 720; https://doi.org/10.3390/axioms12080720 - 25 Jul 2023

Viewed by 547

Abstract

The university course timetable problem (UCTP) is known to be NP-hard, with solution complexity growing exponentially with the problem size. This paper introduces an algorithm that effectively tackles UCTPs by employing a combination of exploration and exploitation strategies. The algorithm comprises two main [...] Read more.

The university course timetable problem (UCTP) is known to be NP-hard, with solution complexity growing exponentially with the problem size. This paper introduces an algorithm that effectively tackles UCTPs by employing a combination of exploration and exploitation strategies. The algorithm comprises two main components. Firstly, it utilizes a genetic algorithm (GA) to explore the search space and discover a solution within the global optimum region. Secondly, it enhances the solution by exploiting the region using an iterated local search (ILS) algorithm. The algorithm is tested on two common variants of UCTP: the post-enrollment-based course timetable problem (PE-CTP) and the curriculum-based course timetable problem (CB-CTP). The computational results demonstrate that the proposed algorithm yields competitive outcomes when compared empirically against other existing algorithms. Furthermore, a t-test comparison with state-of-the-art algorithms is conducted. The experimental findings also highlight that the hybrid approach effectively overcomes the limitation of local optima, which is encountered when solely employing GA in conjunction with local search. Full article

(This article belongs to the Special Issue Applied Mathematics and Information Sciences)

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Open AccessArticle

Proposed Shaft Coupling Based on RPRRR Mechanism: Positional Analysis and Consequences

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Stelian Alaci

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Ioan Doroftei

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Florina-Carmen Ciornei

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Ionut-Cristian Romanu

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Toma-Marian Ciocirlan

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Mariana-Catalina Ciornei

Axioms 2023, 12(7), 707; https://doi.org/10.3390/axioms12070707 - 20 Jul 2023

Viewed by 348

Abstract

This study proposes a solution for the transmission of rotation motion between two shafts with crossed directions. For constructive simplicity, the solutions including the planar pair were preferred and, from the two variants, namely structurally symmetric, revolute–planar–revolute (RPR), or asymmetric RRP, the last [...] Read more.

This study proposes a solution for the transmission of rotation motion between two shafts with crossed directions. For constructive simplicity, the solutions including the planar pair were preferred and, from the two variants, namely structurally symmetric, revolute–planar–revolute (RPR), or asymmetric RRP, the last was selected. The resulting solution, RPRRR, is a non-Denavit–Hartenberg (non-D–H) mechanism. The D–H methodology is laborious since the structure of the equivalent mechanism is more complex than the actual one. For this reason, in the present paper, the kinematic analysis of the mechanism uses geometrical conditions of existence of the planar pair. The system is solved analytically and two main conclusions result: for a set of constructive data and a stipulated position of the driving element, two different assembling positions exist and a rotation motion occurs in the final revolute joint, but in the internal revolute pairs, the motion is oscillatory. The correctness of the theoretical results was corroborated by a CATIA model. The mechanism was also constructed and smooth running was noticed. Two main concerns were considered for the design of the mechanism: avoiding mechanical interference between the elements and estimating the stresses and deformations. Full article

(This article belongs to the Special Issue Applied Mathematics and Information Sciences)

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Open AccessArticle

A Multiple Linear Regression Analysis to Measure the Journal Contribution to the Social Attention of Research

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Pablo Dorta-González

Axioms 2023, 12(4), 337; https://doi.org/10.3390/axioms12040337 - 30 Mar 2023

Viewed by 930

Abstract

This paper proposes a three-year average of social attention as a more reliable measure of the social impact of journals since the social attention of research can vary widely among scientific articles, even within the same journal. The proposed measure is used to [...] Read more.

This paper proposes a three-year average of social attention as a more reliable measure of the social impact of journals since the social attention of research can vary widely among scientific articles, even within the same journal. The proposed measure is used to evaluate a journal’s contribution to social attention in comparison to other bibliometric indicators. This study uses Dimensions as a data source and examines research articles from 76 disciplinary libraries and information science journals through multiple linear regression analysis. This study identifies socially influential journals whose contribution to social attention is twice that of scholarly impact, as measured by citations. In addition, this study finds that the number of authors and open access have a moderate effect on social attention, while the journal impact factor has a negative effect and funding has a small effect. Full article

(This article belongs to the Special Issue Applied Mathematics and Information Sciences)

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Open AccessArticle

Probabilistic Coarsening for Knowledge Graph Embeddings

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Marcin Pietrasik

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Marek Z. Reformat

Axioms 2023, 12(3), 275; https://doi.org/10.3390/axioms12030275 - 06 Mar 2023

Cited by 1 | Viewed by 930

Abstract

Knowledge graphs have risen in popularity in recent years, demonstrating their utility in applications across the spectrum of computer science. Finding their embedded representations is thus highly desirable as it makes them easily operated on and reasoned with by machines. With this in [...] Read more.

Knowledge graphs have risen in popularity in recent years, demonstrating their utility in applications across the spectrum of computer science. Finding their embedded representations is thus highly desirable as it makes them easily operated on and reasoned with by machines. With this in mind, we propose a simple meta-strategy for embedding knowledge graphs using probabilistic coarsening. In this approach, a knowledge graph is first coarsened before being embedded by an arbitrary embedding method. The resulting coarse embeddings are then extended down as those of the initial knowledge graph. Although straightforward, this allows for faster training by reducing knowledge graph complexity while revealing its higher-order structures. We demonstrate this empirically on four real-world datasets, which show that coarse embeddings are learned faster and are often of higher quality. We conclude that coarsening is a recommended prepossessing step regardless of the underlying embedding method used. Full article

(This article belongs to the Special Issue Applied Mathematics and Information Sciences)

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Open AccessArticle

Proposal for Mathematical and Parallel Computing Modeling as a Decision Support System for Actuarial Sciences

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Marcos dos Santos

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Carlos Francisco Simões Gomes

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Enderson Luiz Pereira Júnior

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Miguel Ângelo Lellis Moreira

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Igor Pinheiro de Araújo Costa

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Luiz Paulo Fávero

Axioms 2023, 12(3), 251; https://doi.org/10.3390/axioms12030251 - 01 Mar 2023

Viewed by 850

Abstract

This paper aims to find the actuarial tables that best represent the occurrences of mortality and disability in the Brazilian Armed Forces, thus providing a better dimensioning of the costs of military pensions to be paid by the pension system. To achieve this [...] Read more.

This paper aims to find the actuarial tables that best represent the occurrences of mortality and disability in the Brazilian Armed Forces, thus providing a better dimensioning of the costs of military pensions to be paid by the pension system. To achieve this goal, an optimization software was developed that tests 53 actuarial tables for the death of valid military personnel, 21 boards for entry into the disability of assets, and 21 boards for mortality of invalids. The software performs 199 distinct adherence tests for each table analyzed through linear aggravations and de-escalations in the probabilities of death and disability. The statistical–mathematical method used was the chi-square adherence test in which the selected table is the one with the null hypothesis “observed data” equal to the “expected data” with the highest degree of accuracy. It is expected to bring a significant contribution to society, as a model of greater accuracy reduces the risk of a large difference between the projected cost and the cost observed on the date of the year, thus contributing to the maintenance of public governance. Additionally, the unprecedented and dual nature of the methodology presented here stands out. As a practical contribution, we emphasize that the results presented streamline the calculation of actuarial projections, reducing by more than 90% the processing times of calculations referring to actuarial projections of retirees from the armed forces. As a limitation of the study, we emphasize that, although possibly replicable, the database was restricted only to the Brazilian Armed Forces. Full article

(This article belongs to the Special Issue Applied Mathematics and Information Sciences)

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Open AccessArticle

Applying the Fuzzy BWM to Determine the Cryptocurrency Trading System under Uncertain Decision Process

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Yeh-Cheng Yang

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Wen-Sheng Shieh

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Chun-Yueh Lin

Axioms 2023, 12(2), 209; https://doi.org/10.3390/axioms12020209 - 16 Feb 2023

Cited by 1 | Viewed by 907

Abstract

The crypto and digital assets ecosystems have attracted investment, regulators, and speculators to their environment. As the blockchain-based framework can reduce transaction costs, generate distributed trust, and enable decentralized platforms, it has become a potential new base for decentralized business models. Previous studies [...] Read more.

The crypto and digital assets ecosystems have attracted investment, regulators, and speculators to their environment. As the blockchain-based framework can reduce transaction costs, generate distributed trust, and enable decentralized platforms, it has become a potential new base for decentralized business models. Previous studies have highlighted the advantages and drawbacks of each platform, such as interest rates, cost concerns, transparency issues, hacking issues, and hazards. Consequently, it is challenging for investors to evaluate the cryptocurrency trading system which determines the optimum exchanges and crucial aspects. Therefore, in order to rank the optimal digital token trading system, this paper develops an evaluation architecture to determine the various token trading systems. The developed architecture integrates fuzzy theory and the best-worst method (BWM) into the decision-making process to assess decision behaviors regarding preference for digital token trading systems in investors in Taiwan. First, this work establishes the views and parameters by modifying the Delphi method based on a literature review and survey. Second, the fuzzy-BWM is applied to obtain the fuzzy weights of the views and parameters. Then, defuzzification and BWM are used to rank the optimal alternatives of the digital token trading systems for investors. The results indicate that the optimal digital token trading system is the decentralized platform, and the critical parameters are gas fees, interest rates, and the mechanism of savings under fuzzy uncertain scenarios. This means that when considering the uncertain and ambiguous characteristics of the expert decision process in digital token trading systems, the evaluation is decentralized and the gas fees are the most important parameter in the digital token investment platform. Academically, the fuzzy BWM-based decision-making architecture can provide corporations and investors with valuable guidance to rank the optimal digital token trading systems based on fuzzy uncertain scenarios. Commercially, the proposed architecture could provide corporations and investors with a useful model to measure the optimal digital token trading system. Full article

(This article belongs to the Special Issue Applied Mathematics and Information Sciences)

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Open AccessArticle

Mathematical Model Investigation of a Technological Structure for Personal Data Protection

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Radi Romansky

Axioms 2023, 12(2), 102; https://doi.org/10.3390/axioms12020102 - 18 Jan 2023

Cited by 1 | Viewed by 987

Abstract

The contemporary digital age is characterized by the massive use of different information technologies and services in the cloud. This raises the following question: “Are personal data processed correctly in global environments?” It is known that there are many requirements that the Data [...] Read more.

The contemporary digital age is characterized by the massive use of different information technologies and services in the cloud. This raises the following question: “Are personal data processed correctly in global environments?” It is known that there are many requirements that the Data Controller must perform. For this reason, this article presents a point of view for transferring some activities for personal data processing from a traditional system to a cloud environment. The main goal is to investigate the differences between the two versions of data processing. To achieve this goal, a preliminary deterministic formalization of the two cases using a Data Flow Diagram is made. The second phase is the organization of a mathematical (stochastic) model investigation on the basis of a Markov chain apparatus. Analytical models are designed, and their solutions are determined. The final probabilities for important states are determined based on an analytical calculation, and the higher values for the traditional version are defined for data processing in registers (“2”: access for write/read −0.353; “3”: personal data updating −0.212). The investigation of the situations based on cloud computing determines the increasing probability to be “2”. Discussion of the obtained assessment based on a graphical presentation of the analytical results is presented, which permits us to show the differences between the final probabilities for the states in the two versions of personal data processing. Full article

(This article belongs to the Special Issue Applied Mathematics and Information Sciences)

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Open AccessArticle

The Influence of Hedge, Arbitrage, and After-Hours Trading on the Holding Returns of TAIEX Futures

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Axioms 2023, 12(1), 71; https://doi.org/10.3390/axioms12010071 - 10 Jan 2023

Viewed by 1078

Abstract

This study points out a new explanation of the non-trading effect of financial derivatives from the perspective of hedging demand. We examine the influence of hedging demand on the non-trading effect of TAIEX (Taiwan Stock Exchange Capitalization Weighted Stock Index) Futures. By dividing [...] Read more.

This study points out a new explanation of the non-trading effect of financial derivatives from the perspective of hedging demand. We examine the influence of hedging demand on the non-trading effect of TAIEX (Taiwan Stock Exchange Capitalization Weighted Stock Index) Futures. By dividing the sample period into trading period and non-trading period and testing the difference between the risk premiums in these two intervals, we find that there is a non-trading effect in TAIEX Futures, which means that the holding returns of TAIEX Futures in the non-trading period are higher than those in the trading period. By estimating a dummy-regression model, the evidence shows that when the VIX (Taiwan Index Option Volatility Index) indicator is relatively high, the non-trading effect will be more significant, indicating that the non-trading effect may come from investors’ hedging needs. In addition, it is found that when the futures index is higher than the spot index, the non-trading effect becomes less obvious. The possible reason is that when there is a positive spread in index futures, investors will expect a bull market, thus reducing the hedging demand of index futures. In the end, we find that the liquidity in the after-hours trading session is poor, resulting in high hedging costs, and forcing investors to hedge during the regular trading period. Therefore, the after-hours trading of TAIEX Futures fails to reduce the non-trading effect. Full article

(This article belongs to the Special Issue Applied Mathematics and Information Sciences)

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