Nikos Themelis

Prof. Nikos Themelis

Assistant Professor, School of Naval Architecture & Marine Engineering, National Technical University of Athens
orcid

Research Focus & Metrics

Academic Career Length

20Years (2007-Present)

(Calculated once Scilit publication data is synced: current year − year of first publication + 1)

Representative Publications

View All Publications
Verified
Journal Article
Open access
PDF file
CSChristos Spandonidis
Christos Spandonidis
CSChristos Spandonidis
Christos Spandonidis
Nikos ThemelisNikos Themelis
Nikos Themelis
CGChristos Giordamlis
Christos Giordamlis
Spilios D FassoisSpilios D Fassois
Spilios D Fassois
Adverse conditions within specific offshore environments magnify the challenges faced by a vessel’s energy-efficiency optimization in the Industry 4.0 era. As the data rate and volume increase, the analysis of big data using analytical techniques might not be efficient, or might even be infeasible in some cases. The purpose of this study is the development of deep-learning models that can be utilized to predict the propulsion power of a vessel. Two models are discriminated: (1) a feed-forward neural network (FFNN) and (2) a recurrent neural network (RNN). Predictions provided by these models were compared with values measured onboard. Comparisons between the two types of networks were also performed. Emphasis was placed on the different data pre-processing phases, as well as on the optimal configuration decision process for each of the developed deep-learning models. Factors and parameters that played a significant role in the outcome, such as the number of layers in the neural network, were also evaluated.

1 November 2022 in Journal of Navigation
Verified
Journal Article
Open access
PDF file
AKAgeliki Kytariolou
Ageliki Kytariolou
Nikos ThemelisNikos Themelis
Nikos Themelis
A weather routing tool is presented based on forecasted weather data along the route and considering safety aspects. The tool aims to determine the optimal path for the minimisation of the fuel oil consumption, ensuring a safe passage. It is developed in MATLAB and considers detailed ship characteristics. Specifically, ship's motions and fuel oil consumption of the main engine during a potential path are estimated. For the latter, a physics-based model for a specific vessel is developed where tools of different level of detail are utilised to calculate the various resistance components. A speed management strategy along the route is specified as well as safety criteria representing acceptable limits of ship's responses. When the set criteria and constraints have been set, a genetic algorithm is used to find the optimal route by means of ship's heading or by considering both heading and ship's power settings as variables to minimise the fuel oil consumption. The search space of the algorithm lies within a predefined envelop, but still the evolutionary optimisation approach used has no pre-assigned values to any possible candidate waypoint.

1 August 2019 in Ocean Engineering
Verified
Journal Article
Closed access
TMTeemu Manderbacka
Teemu Manderbacka
Nikos ThemelisNikos Themelis
Nikos Themelis
IBIgor Bačkalov
Igor Bačkalov
Evangelos BoulougourisEvangelos Boulougouris
Evangelos Boulougouris
EEEleftheria Eliopoulou
Eleftheria Eliopoulou
DTDaisuke Terada
Daisuke Terada

13 June 2014 in Nonlinear Dynamics
Verified
Journal Article
Closed access
PDF file
Kostas J. SpyrouKostas J. Spyrou
Kostas J. Spyrou
VBV. Belenky
V. Belenky
Nikos ThemelisNikos Themelis
Nikos Themelis
KWK. Weems
K. Weems

1 August 2008 in Ocean Engineering
Verified
Journal Article
Closed access
KSK.J. Spyrou
K.J. Spyrou
ITI. Tigkas
I. Tigkas
GSG. Scanferla
G. Scanferla
NPN. Pallikaropoulos
N. Pallikaropoulos
Nikos ThemelisNikos Themelis
Nikos Themelis

1 July 2016 in Ocean Engineering
Verified
Journal Article
Closed access
Nikos ThemelisNikos Themelis
Nikos Themelis
Kostas J. SpyrouKostas J. Spyrou
Kostas J. Spyrou
VBVadim Belenky
Vadim Belenky