Dr Diego Ruiz-Hernandez

Senior Lecturer in Management Science

Room: B064
Phone: +44 (0)114 222 3211
Email: d.ruiz-hernandez@sheffield.ac.uk

"The great delusion of modernity is that the laws of nature explain the universe for us. The laws of nature describe the universe, they describe the regularities. But they explain nothing." L. Wittgenstein
" 'anything goes' is not a 'principle', I hold... but the terrified exclamation of a rationalist who takes a closer look at history." P. Feyerabend


Diego Ruiz-Hernández holds a PhD in Operational Research from the Universitat Pompeu Fabra in Catalonia. He is currently Senior Lecturer in Management Science at Sheffield University Management School and Programme Director of MSc Management. He developed his academic career at the following institutions: Universitat Pompeu Fabra (1998-2009), Universidad de Navarra (2006-2009), and the University College for Financial Studies (2009 to 2018). He has been visiting scholar at the universities of Edinburgh, Strathclyde and Lancaster in the United Kingdom. He has been visiting lecturer at Kedge Business School in Bordeaux for several years. His research covers, but is not limited to, fields in the areas of mathematical programming, combinatorial optimisation, discrete and network location, stochastic scheduling and dynamic resource allocation. He has published scientific articles in international journals as Advances in Applied Probability, Computers and Operations Research, European Journal of Operational Research, Expert Systems with Applications and Transportation Research B, among others. Diego is member of the Catalan Statistics Society (SCE); the Operational Research Society of the United Kingdom (OR); the Institute for Operations Research and the Management Sciences (INFORMS); the Spanish Association of

Statistics and Operational Research (SEIO); the European Working Group on Locational Analysis (EWGLA); and the Spanish Network on Locational Analysis and Related Problems (RedLoca). He currently leads a research project on bank network restructuring in collaboration with the Spanish bank BBVA.

Teaching Interests

Diego Ruiz-Hernandez is module leader of MGT253 Principles of Operations Management and MGT6122 Company Project.

Research Interests

Over the last few years Diego's research has focused on the wide area of facility location and related problems. In particular, inspired by the current trend in banking services, he and his coauthors have addressed the problem of restructuring branch networks, where the most important decision is how many and which branches should be closed and/or resized in order to better service their customers while reducing the size of a, typically, oversized network. This has been referred to in location literature as the "delocation" problem.

In a different vein, Diego has recently approached a new and challenging topic: the problem of numerousness or proliferation in the supply chain. Over the last couple of decades, in the quest for growth in highly competitive and slow-growing markets, firms have proliferated almost everything: products, channels, and markets. Notwithstanding this proliferation has pushed their revenues up, the problem is that this growth is not reflected in the bottom line. The monster eating the businesses profits is commonly referred to as "complexity". Diego and his co-authors have proposed an entropy-based measure for complexity that satisfies the double logical-consistency requirement for any model of the real world: internal (i.e. has no paradoxes or contradictions) and external consistency (is an adequate representation of the world it aims at representing). Moreover, they have established its empirical relevance in collaborations with three renowned forms of global presence. Their work is now is heading towards the identification of mechanisms for controlling complexity and lessening its impact on the firm's finances.

Finally, Diego continues his work on stochastic scheduling and dynamic resource allocation. In this regard, he is currently working on the problem of scheduling preventative maintenance interventions for systems consisting in a large number of independently deteriorating equipment. The main research question is the design of efficient scheduling rules that are robust to errors or imperfections incurred during the execution of the maintenance tasks.

PhD Supervision

I am looking forward to interacting with potential students that may share my interest in the problem of supply chain complexity, its measure, and the mechanisms for mitigating it.

I would also like to attract students interested on facility location and delocation problems, network restructuring problems or any other problem that can be addressed using facility location models or techniques (median, centre or covering models, etc.) are more than welcome to talk with me.

Finally, I will be happy to talk to students with a strong mathematical background (dynamic programming, Markov decision processes) which may be interested in dynamic resource allocation or stochastic scheduling problems (with particular focus on -but not limited to- machine maintenance problems) will also get my attention.

Recent Publications

Ruiz-Hernandez, D., Delgado-Gómez, D., and Lopez-Pascual, J. (2015) Restructuring bank networks after mergers and acquisitions: A capacitated delocation model for closing and resizing branches. Computers & Operations Research, 62:316-324

Ruiz-Hernandez, D. and Delgado-Gómez, D. (2016) The Stochastic Capacitated Branch Restructuring Problem. Annals of Operations Research, 246 (1): 1-24

Ruiz-Hernández, D., Elizalde, J. and Delgado, D. (2016) Cournot-Stackelberg Games in Competitive Delocation. Annals of Operations Research, 256 (1): 149-170

Menezes, M., Ruiz-Hernandez, D. and Guimaraes, R. (2016) The Component Commonality Problem in a Real Multidimensional Space: An Algorithmic Approach. European Journal of Operational Research, 249(1):105-116

Menezes, M., Ruiz-Hernandez, D. and Verter, V. A (2016) Rough-cut Approach for Evaluating Location-Routing Decisions via Approximation Algorithms. Transportation Research Part B: Methodological, 87(1):89-106

Delgado-Gomez, D. and Ruiz-Hernandez, D. (2017) A One-Sample per Individual Face Recognition Algorithm Based on Multiple One-Dimensional Projection Lines. International Journal of Pattern Recognition and Artificial Intelligence, 31(7): 1756012 (15 pages)

Ruiz-Hernandez, D. and Pinar-Perez, J.M. (2018) Cost/Efficiency Assessment of Alternative Maintenance Management Policies. In Xu, J., Gen, M., Hajiyev, A. and Cooke, F. Eds. Proceedings of the Eleventh International Conference on Management Science and Engineering Management (pp. 1395-1406). Springer, Cham.

Pliego-Marugan, A., García-Marquez, F.P., Pinar-Pérez, J.M., and Ruiz-Hernandez, D. (2018) A Survey of Artificial Neural Networks in Wind Energy Systems. Applied Energy, 228: 1822-1836

Ruiz-Hernandez, D., Menezes, M.B.C. and Amrani, A. (2019) An Information-Content Based Measure of Proliferation as a Proxi for Structural Complexity. International Journal of Production Economics, 212:79-81

Delgado-Gómez, D., Laria, J.C., and Ruiz-Hernández, D. (2019) Computerised adaptive tests and decision trees: a unifying approach. Expert Systems with Applications, 117: 358-366.

Ruiz-Hernandez, D., García-Heredia, D., Delgado-Gómez, D. and Baca-García, E. (2019) A probabilistic patient scheduling model for reducing the number of no-shows, Journal of the Operational Research Society, DOI: 10.1080/01605682.2019.1658552

Ruiz-Hernández, D., Pinar-Pérez, J.M., and Delgado-Gómez, D. (2020) Multi-machine preventive maintenance scheduling with imperfect interventions: a restless bandit approach. Computers and Operations Research. Forthcoming.