Dr. Sergey Melnik
Department of Mathematics and Statistics, University of Limerick, Ireland Telephone: +353 61 233264 Office: A2015f, Main building, UL. Email: sergeydotmelnikatuldotie
I am a postdoctoral research fellow at the University of Limerick and a member of the group of Prof. J.P. Gleeson and MACSI. I have previously held an IRCSETMarie Curie Research Fellowship
at the University of Oxford. Prior to that I have held a postdoctoral
position at the University of Limerick. I received PhD in Physics
(2008, University College Cork, Ireland) and the joint MSc/BSc in Computer Science & Mathematics (2003, Nayanova University, Samara, Russia).
My Google Scholar, ResearcherID and LinkedIn profiles.
News
 [Sept.
2016] I won 1st prize in the HackOn(Data) Data Science / Machine
Learning workshop exercises and challenges, competing with over 200
participants. http://hackondata.com/#participants
 [July 2016] Our paper "Double cascade model of financial crises" has just been published in Int. J. Theor. Appl. Fin. 19,1650041 (2016). In
this paper, we introduce a financial network model that combines the default and liquidity stress mechanisms and demonstrates that the level of defaults in a financial network is negatively related to the strength of bank liquidity hoarding.
 [June 2016] Our paper "Emergence of coexisting percolating clusters in networks" has just been published in Phys. Rev. E 93, 062308 (2016). In
this paper, we show that multiple coexisting percolating clusters can
emerge in networks, contrary to the common assumption that at most one
percolating cluster can exist.
 [Apr. 2016] Our new paper "Simple and accurate analytical calculation of shortest path lengths" has just appeared on arXiv:1604.05521. In
this paper, we propose a simple method that allows one to accurately predict the distribution of shortest path lengths on synthetic or realworld networks using their degree distribution, or joint degreedegree distribution. Compared to some other analytical methods, our approach is simpler and yields more accurate results.
 [March 2016] Our new paper "The limitations of discretetime approaches to continuoustime contagion dynamics" has just appeared on arXiv:1603.01132. In
this paper, we show that discretetime approaches should be used with
care when analysing continuoustime systems as they can lead, for
example, to incorrect prediction of epidemic threshold. Simulation code
written in C++ is available online.
 [Nov. 2013] Octave/MATLAB code for generating
modular networks with heterogeneous correlations (the socalled
Piikknetworks introduced in Melnik et al., Chaos 24, 023106 (2014) [see also arXiv:1207.1809v2]) is now available for download from here.
Papers
 [Get PDF] [Get CODE] E. Laurence, J.G. Young, S. Melnik and L. J. Dubé, "Exact analytical solution of irreversible binary dynamics on networks", [arXiv:1711.02721] (2017).
 [Get PDF] S. Melnik and J. P. Gleeson, "Simple and accurate analytical calculation of shortest path lengths", [arXiv:1604.05521] (2016).
 [Get PDF] A. Faqeeh, S. Melnik,
P. ColomerdeSimón, and J. P. Gleeson, "Emergence of coexisting percolating clusters in networks", [arXiv:1508.05590] (2016).
 [Get PDF] T. R. Hurd, D. Cellai, H. Cheng, S. Melnik, and Q. Shao, "Illiquidity and Insolvency: a Double Cascade Model of Financial Crises" [arXiv:1310.6873] (2016).
 [Get PDF] P. G. Fennell, S. Melnik, and J. P. Gleeson, "The limitations of discretetime approaches to continuoustime contagion dynamics", [arXiv:1603.01132] (2016).
 [Get PDF] A. Faqeeh, S. Melnik, and J. P. Gleeson, "Network cloning unfolds the effect of clustering on dynamical processes", Phys. Rev. E 91, 052807 (2015). [arXiv:1408.1294] MATLAB code for Lcloning is here.
 [Get PDF] P. Krejčí, H. Lamba, S. Melnik, and D. Rachinskii, "Kurzweil integral representation of interacting PrandtlIshlinskii operators", Discrete. Contin. Dyn. Syst. B 20, 2949 (2015).
 [Get PDF] S. Melnik, M. A. Porter, P. J. Mucha, and J. P. Gleeson, "Dynamics on modular networks with heterogeneous correlations", Chaos 24, 023106 (2014). [arXiv:1207.1809v2] MATLAB code and examples are here.
 [Get PDF] P. Krejčí, H. Lamba, S. Melnik, and D. Rachinskii, "Analytical solution for a class of network dynamics with mechanical and financial applications", Phys. Rev. E 90, 032822 (2014). [arXiv:1309.4050]
 [Get PDF] S. Melnik, J. A. Ward, J. P. Gleeson, and M. A. Porter, "Multistage complex contagions", Chaos 23, 013124 (2013). [arXiv:1111.1596v2]
 [Get PDF] J. P. Gleeson, S. Melnik, J. A. Ward, M. A. Porter, and P. J. Mucha, "Accuracy of meanfield theory for dynamics on realworld networks", Phys. Rev. E 85, 026106, (2012). [arXiv:1011.3710v3]
 [Get PDF] A. Hackett, S. Melnik, and J. P. Gleeson, "Cascades on a class of clustered random networks", Phys. Rev. E 83, 056107, (2011). [arXiv:1012.3651v2]
 [Get PDF] A. Hackett, J. P. Gleeson, and S. Melnik, "Site percolation in clustered random networks", Int. J. Comp. Syst. Sci. 1, 2530 (2011).
 [Get PDF] S. Melnik, A. Hackett, M. A. Porter, P. J. Mucha, and J. P. Gleeson, "The unreasonable effectiveness of treebased theory for networks with clustering", Phys. Rev. E 83, 036112 (2011).
 [Get PDF] J. P. Gleeson, S. Melnik, and A. Hackett, "How clustering affects the bond percolation threshold in complex networks", Phys. Rev. E 81, 066114 (2010).
 [Get PDF] J. P. Gleeson and S. Melnik, "Analytical results for bond percolation and kcore sizes on clustered networks", Phys. Rev. E 80, 046121 (2009). [arXiv:0811.4511v2]
 [Get PDF] S. Melnik, O. Rasskazov, and G. Huyet, "A Route to Robust Double Pulse Excitability in Optically Injected Semiconductor Lasers", J. Phys. Conf. Ser. 138, 012014 (2008).
 [Get PDF] D. Goulding, S. Melnik, D. Curtin, T. Piwonski, J. Houlihan, J. P. Gleeson and G. Huyet, "Kramers' Law for a Bistable System with TimeDelayed Noise", Phys. Rev. E. 76, 031128 (2007).
 [Get PDF] D. Goulding, S. P. Hegarty, O. Rasskazov, S. Melnik, M. Hartnett, G. Greene, J. G. McInerney, D. Rachinskii, and G. Huyet, "Excitability in a Quantum Dot Semiconductor Laser with Optical Injection", Phys. Rev. Lett. 98, 153903 (2007).
 [Get PDF] S. Melnik, G. Huyet, A.V. Uskov, "The Linewidth Enhancement Factor Alpha of Quantum Dot Semiconductor Lasers", Opt. Express 14, 29502955 (2006).
Research Interests
 Machine Learning
 Data Science
 Social network analysis
 Dynamics on networks
 Parallel computations
 Bifurcation analysis
Education
 20032008: PhD in Physics, University College Cork, Ireland. Thesis
title: "Nonlinear and stochastic dynamics of semiconductor laser
systems"
 19992003: BSc & MSc (with 1st honours) in Computer Science and
Mathematics, Nayanova University, Samara, Russia.
Awards & Funding
 2016 $500: 1st prize at HackOnData.com Data Science exercises and challenges competition.
 2015 €6,000: New Foundations award from the Irish Research Council.
 2014 €6,000: New Foundations award from the Irish Research Council.
 2010 €220,000: INSPIRE: IRCSETMarie Curie Postdoctoral Fellowship. Awarded to two mathematicians in Ireland.
 2010 €200: Prize in the Best Paper Awards at ECCS'10: European Conference on Complex Systems, September 1317, 2010, Lisbon, Portugal.
 2010 €800: The only Irishbased researcher selected to attend the competitive 3week long Santa Fe Insititute's Complex Systems Summer School in NM, USA. Received financial support from ERAComplexity, Ireland.
 2009 €8,000: Short Term Travel Fellowship from Science Foundation Ireland to support a 3month research visit to the group of Prof. Mason A. Porter at the University of Oxford, UK.
Teaching
 Spring 2014: Science Mathematics II (MA4602), Lecturer. Department of Mathematics & Statistics, University of Limerick, Ireland.
 Fall 2011: Mathematical Biology and Ecology (B8a), Class Tutor, managed two teaching assistants. Mathematical Institute, University of Oxford, UK.
 Spring 2006: Numerical Methods and Programming (AM2032), Tutor. Department of Applied Mathematics, University College Cork, Ireland.
 Fall 2004  Spring 2006: Introductory Physics I (PY1052) & II (PY1053), Practical demonstrator. Physics Department, University College Cork, Ireland.
 Fall 2003  Spring 2004: Manager of Physics Helpdesk, Physics Department, University College Cork, Ireland.
Work Experience
 01/2012  present: Research Fellow, Department of Mathematics & Statistics, University of Limerick.
 09/2010  01/2012: IRCSETMarie Curie Research Fellow, OCIAM, Mathematical Institute, University of
Oxford.
 03/2008  09/2010: Postdoctoral researcher, Department of Mathematics and Statistics, University of Limerick, Ireland.
 10/2003  03/2008: PhD Studies
 06/2002  07/2003: Software Engineer, Institute of Industrial Automation, Samara, Russia.
 01/1998  07/2003: Computer System Administrator, Audit Company "KornaudS", Samara, Russia
Computer Skills
 MATLAB, Python, R, C/C++, Java, Distributed computations, Spark, Scala, Map/Reduce, Bash, Perl, Mathematica, AUTO, XPPAUT, Mathcad, Pascal, Assembler.
 Linux and Windowsbased computer systems administration.

