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Contemporary Mathematics and Applications (ConMathA)
Published by Universitas Airlangga
ISSN : -     EISSN : 26865564     DOI : https://doi.org/10.20473/conmatha
Core Subject : Science, Education,
Materials Science & Nanotechnology Mathematics
Contemporary Mathematics and Applications welcome research articles in the area of mathematical analysis, algebra, optimization, mathematical modeling and its applications include but are not limited to the following topics: general mathematics, mathematical physics, numerical analysis, combinatorics, optimization and control, operation research, statistical modeling, mathematical finance and computational mathematics.
Arjuna Subject : Matematika - Matematika (Lain-Lain)
Articles 6 Documents
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Search results for , issue "vol. 8 no. 2 (2026)" : 6 Documents clear
Modelling the Effect of Toxicants in Water and Sediments on Aquatic Population Kenneth Ojotogba Achema; Danjuma Jibrin Yahaya; Charity Jumai Alhassan
Contemporary Mathematics and Applications (ConMathA) Vol. 8 No. 2 (2026)
Publisher : Universitas Airlangga

Show Abstract | Download Original | Original Source | Check in Google Scholar | DOI: 10.20473/conmatha.v8i2.81566

Abstract

A mathematical model to study the effect of toxicants in water and sediments on aquatic population is proposed and analyzed. The model has six possible equlibria. By applying stability theory, it was demonstrated that the overall species population stabilizes at an equilibrium level. However, it was found that as the toxicant emission rates increases, the aquatic population density was severely affected and the aquatic population decreased significantly.
The Impact of Investment Value and Number of Projects on Employment in Surabaya’s Leading Economic Sectors Karisma Indra Pitaloka; Dian Yuliati; Hani Khaulasari
Contemporary Mathematics and Applications (ConMathA) Vol. 8 No. 2 (2026)
Publisher : Universitas Airlangga

Show Abstract | Download Original | Original Source | Check in Google Scholar | DOI: 10.20473/conmatha.v8i2.85955

Abstract

This study aims to analyze the impact of investment value and the number of projects on employment in Surabaya’s leading economic sectors during the 2020–2024 period, motivated by fluctuations in investment realization and labor absorption. The data used are sectoral panel data obtained from the Surabaya City Investment and One-Stop Integrated Service Office (DPMPTSP). The analytical method applied is panel data regression, with model selection conducted using the Chow Test and Lagrange Multiplier Test. The results indicate that the Common Effect Model (CEM) is the most appropriate model. The estimation results show that both the number of projects and investment value have a positive and statistically significant effect on employment, as indicated by t-statistics of 24.85441 (p-value = 0.00) and 2.220927 (p-value = 0.037), respectively. Simultaneously, the model is significant based on the F-test (F = 381.9359; p-value = 0.00). The model demonstrates strong explanatory power, with an R-squared value of 0.972006 (97.20%) and an adjusted R-squared of 0.969461, indicating that most of the variation in employment can be explained by the independent variables. Furthermore, classical assumption tests confirm that the model satisfies normality (Jarque-Bera p-value = 0.1064), shows no multicollinearity (VIF < 10), no autocorrelation (Breusch–Godfrey p-value = 0.8476), and no heteroscedasticity (Goldfeld–Quandt p-value = 0.9684). These findings suggest that increasing the number of projects has a more substantial effect on employment compared to increasing investment value, highlighting the importance of expanding labor-intensive projects to enhance job creation.
Predicting Customer Numbers at PT PLN (Persero) West Nusa Tenggara Regional Main Unit Using the Prophet Time Series Model Rida Alkausar Hardi; Rio Satriyantara; Yunita Septriana Anwar; I Gede Adhitya Wisnu Wardhana
Contemporary Mathematics and Applications (ConMathA) Vol. 8 No. 2 (2026)
Publisher : Universitas Airlangga

Show Abstract | Download Original | Original Source | Check in Google Scholar | DOI: 10.20473/conmatha.v8i2.88166

Abstract

Electricity is a fundamental need for modern society, and in developing regions such as West Nusa Tenggara, the continuous growth in the number of customers requires PT PLN (Persero) to conduct effective resource planning to prevent potential energy crises. This study aims to predict the growth of PLN’s customer numbers using the Facebook Prophet time series model. A quantitative approach was applied using monthly customer data from PT PLN (Persero) covering the period from January 2019 to December 2024. The model was optimized through a hyperparameter tuning process, and its performance was evaluated using the Mean Absolute Percentage Error (MAPE) metric. The results demonstrate that the optimized model achieved a MAPE of 0.27% during cross-validation. Analysis of the results indicates that the model effectively captured long-term growth trends and seasonal fluctuations. These findings suggest that the Prophet model can serve as a technical reference for forecasting customer numbers, potentially supporting strategic decision-making and resource allocation at PT PLN (Persero).
Spectral Properties and Determinant Formulas for a Two-Parameter Family of Symmetric Circulant Matrices Eric Machisi; Anas Mahmoud Ahmad Alrababah; Abdullah Kurudirek
Contemporary Mathematics and Applications (ConMathA) Vol. 8 No. 2 (2026)
Publisher : Universitas Airlangga

Show Abstract | Download Original | Original Source | Check in Google Scholar | DOI: 10.20473/conmatha.v8i2.89073

Abstract

This paper investigates the spectral properties of the symmetric circulant matrix ??(?,?)=circ (?,?,0,…,0,?), where ?,?∈ℝ and ?≥3. While the eigenvalue structure of general circulant matrices is well understood, explicit and unified characterizations for specific structured subclasses remain of interest. In this work, we derive closed-form expressions for the eigenvalues and provide a complete characterization of the positive definiteness of this matrix family, explicitly highlighting the role of the parity of ?. In addition, we obtain a compact determinant formula using Chebyshev polynomials, yielding an analytically tractable condition for singularity. The results establish a direct connection between circulant matrix theory and classical trigonometric polynomial identities, providing a unified framework that links spectral properties, determinant structure, and parity effects. These findings extend existing formulations by providing explicit, structurally transparent results for this class of symmetric circulant matrices.
The Illusion of Permanence: A Superposition Model of Technology Adoption and Displacement with Closed-Form Conditions for Peak Deception Farai Nyabadza
Contemporary Mathematics and Applications (ConMathA) Vol. 8 No. 2 (2026)
Publisher : Universitas Airlangga

Show Abstract | Download Original | Original Source | Check in Google Scholar | DOI: 10.20473/conmatha.v8i2.89507

Abstract

Technologies that attain high adoption on a given value axis, the dimension of human need they address, frequently exhibit what we term the ‘illusion of permanence’: a local adoption maximum that observers systematically misinterpret as a stable equilibrium. We formalise this phenomenon through the Adoption-Decay Superposition Model (ADSM), in which each technology’s market share is expressed as the product of a logistic growth term and an exponential decay envelope activated by the emergence of a superior competitor. We derive the Illusion Point, the exact moment at which adoption is maximised and the impending decline is least visible. From this we introduce two derived indices; the Illusion Strength Index (ISI) and the Displacement Susceptibility (DS). Formal theorems establish that every technology with a positive decay parameter must eventually relinquish dominance, and that switching costs prolong the illusion without averting it. Four empirical cases, SMS, the ‘Please Call Me’ callback feature, BlackBerry Messenger, and the fax machine, are parametrised and simulated in MATLAB. A Conservation Principle is stated, linking individual technology decline to the bounded capacity of any shared value axis. The model provides a foundation for anticipating displacement, evaluating technological lock-in, and understanding why dominant technologies consistently fail to foresee their own decline.
Analysis of Music Genre Trends on Spotify Indonesia Using the Louvain Algorithm (Top 100 Songs, May 2025) Silfiatis Sabila Azra Shofa; Siti Amiroch
Contemporary Mathematics and Applications (ConMathA) Vol. 8 No. 2 (2026)
Publisher : Universitas Airlangga

Show Abstract | Download Original | Original Source | Check in Google Scholar | DOI: 10.20473/conmatha.v8i2.92131

Abstract

Digital music streaming platforms have transformed the way audiences consume music, making Spotify one of the leading sources for analyzing music popularity and listening trends. This study investigates music genre trends in the Spotify Indonesia Top 100 dataset for May 2025 using a graph-based community detection approach. Songs were represented as nodes connected through genre similarity and normalized popularity attributes, including Streams, Total Streams, and Days on Chart. A weighted graph was constructed using Euclidean distance and inverse-distance similarity, after which communities were detected using the Louvain algorithm. The detected communities were further analyzed according to genre composition and streaming performance, while community quality was evaluated using modularity. The results identified 15 communities with a modularity value of 0.776, indicating a well-defined community structure. Although genre information was incorporated during graph construction, the detected communities were also influenced by similarities in popularity characteristics, revealing structural relationships beyond simple genre classification. Based on accumulated Total Streams, Indie Pop, Pop, and Pop Rock emerged as the dominant genres in the analyzed dataset. These findings demonstrate that graph-based community detection provides additional insights into song connectivity and genre organization that cannot be obtained through conventional descriptive aggregation alone.

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