Teaching Areas

•  Engineering Mathematics
•  Operational Research
•  Statistics

Research Interests

•  Applied Mathematics
•  Numerical Methods
•  Data Mining Algorithm
•  Computational Fluid Dynamics

Publications

• N.S. Rathnayaka, J. K. Wijerathna, B.G.S.A. Pradeep, Stability Properties and Hopf Bifurcation of a Delayed HIV Dynamics Model with Saturation Functional Response, Absorption Effect and Cure Rate, Int. J. Anal. Appl., 23 (2025), 92.
• N.S. Rathnayaka, J.K. Wijerathna, B.G.S.A. Pradeep, Global stability of a delayed HIV-1 dynamics model with saturation response with cure rate, absorption effect and two time delays, Journal of Commun. Math. Biol. Neurosci., 2023 (2023), Article ID 16. 
• Silva, P.D.N., Pradeep, B.G.S.A.,Guo, S.; Rathnayaka, N.S., Stability properties of a delayed HIV infection model with absorption and apoptosis, Proceedings of 10th Ruhuna International Science & Technology Conference University of Ruhuna, Matara, Sri Lanka, January 18, 2023, ISSN: 1391-8796. 
• Rathnayaka, Nimal & Wijerathna, Jagath & Pradeep, B.G. Sampath & Silva, P. Damith Nilanga. (2022). Stability of a delayed HIV-1 dynamics model with Beddington-DeAngelis functional response and absorption effect with two delays. Journal of Communications in Mathematical Biology and Neuroscience. 2022. 1-24. 10.28919/cmbn/7702.
• B.G.S.A Pradeep, N.S Rathnayaka, and M.P.A Wijayasiri, “Local Stability Properties of a Delayed HIV-1 Dynamics Model with Beddington- DeAngelis Functional Response”, 17th Academic Sessions at the University of Ruhuna,Sri Lanka, 04th March 2020.
• MKS Mendis and NS Rathnayake, “Comparison on virus dynamics models with different functional responses including time delays”, Proceedings of the 11th International Research Conference on Engineering Excellence through Collaborative Research and Innovation, General Sir John Kotelawala Defence University, Sri Lanka, September 14, 2018, ISBN: 978-955-0301-42-3, pp 73-77.
• Mendis M.K.S, Predeep B.G.S.A, Rathnayaka N.S. “Stability analysis of a double delayed HIV-I Dynamics model with nonlinear functional response and absorption effect”, Proceeding of 5th Ruhuna intenational Science and Technology Conference, University of Ruhuna, Sri Lanka, February 15, 2018, ISSN: 1391-8796. pp 63.
• S.D. Pavithra Jayasundara, S.S.N. Perera, N. S. Rathnayaka, “Developing a Decision Support Testing Algorithm to Detect Severity Level of Dengue”, European Scientific Journal March 2017 edition vol.13, No.9 ISSN: 1857 - 7881 (Print) e - ISSN 1857- 7431
• N.S. Rathnayaka, J.K.Wijerathna, “Modification of information gain measure to select the best group of attributes in a data set for a binary decision tree inducer”, Proceedings of the Research Symposium on Value Addition for Sustainable Development, Uva Wellassa University, Sri Lanka, January 29-30,2015, ISBN 978-955-0481-08-8. pp 14-16.
• N.S. Rathnayaka, J.K.Wijerathna, “Modification of ID3 Algorithm to explore student performance with their attributes”, Proceedings of the International Research Conference on Expanding Developmental Horizons through Education, Research and Innovation, General Sir John Kotelawala Defence University, Sri Lanka, December-22, 2014, ISBN 978-955-0301-14-0, pp 136-142.
• Bandara R M P S & Rathnayaka N S, “Modelling of Conventional Swing of the Cricket Ball using Computational Fluid Dynamics”, Outcomes of the International Symposium on Ensuring National Security Through Reconciliation & Sustainable Development, General Sir John Kotelawala Defence University, Sri Lanka, 22nd-23rd August, 2012, ISBN 978-955-0301-05-8, pp. 447-457.
• N.S. Rathnayaka,  “A Survey of Numerical Solutions of Linear Equations Systems”, Unpublished Thesis, Department of Mathematics, University of Ruhuna, Sri Lanka, 2003.

Workshops/Seminars

• Workshop on Financial Risk Management in Research and development Center for mathematical Modeling, Department of mathematics, University of Colombo, Sri Lanka, 11th January 2014.
•  Participation/Present in DAAD partnership workshop organized by Department of Natural Sciences, School of Science, Kathmandu University,  on “Numerical Methods for Ordinary and Partial Differential Equations” held during  September 2 - 13, 2013 at Kathmandu University, Dhulikhel, Nepal.
•  Workshop on “Open Source in Education” Organized by Department of Computer Science, Faculty of Science, University of Ruhuna on 11th Oct. 2006, at the University of Ruhuna.
•  Ruhuna International School Computational and Mathematical Physics (RISCMAP) in Sri Lanka from 20 December-25 December, 2004.

Working Experience

UNDERGRADUATE TEACHING EXPERIENCES

• Senior Lecture Gr I, Faculty of Engineering, General Sir John Kotelawala, Defence University, Sri Lanka (2022 onwards)
• Senior Lecture Gr II, Faculty of Engineering, General Sir John Kotelawala, Defence University, Sri Lanka (2016 - 2022)
•  Lecturer (probationary), Faculty of Engineering, General Sir John Kotelawala, Defence University, Sri Lanka (2009 - 2016).
•  Assistant Lecturer , Department of Mathematics, University of Ruhuna, Sri Lanka (Nov 2004-Nov 2007)
•  Tutor in Mathematics, Department of Mathematics, University of Ruhuna, Sri Lanka (Nov.2003-Nov 2004).

VISITING APPOINTMENTS

•  Visiting Lecturer, Department of Tech./B.Tech for MPZ 3230/ MPZ 5230 in the Open University of Sri Lanka - (July 2007 to July 2008).

Positions Held

• Head of the Department, Department of Mathematics, General Sir John Kotelawala Defence University (from September 2018 to September 2021)
• Chairperson, Engineering Faculty, IT Cell (EF), KDU (from February 2018 to February 2019)
• Coordinator of Department of Mathematics, General Sir John Kotelawala Defence University (from August 2016 to February 2017)