Luka Borozan

 

Teaching Assistant
Department of Mathematics
Josip Juraj Strossmayer University of Osijek
Trg Ljudevita Gaja 6
Osijek, HR-31000, Croatia¸
phone: +385-31-224-xxx
fax: +385-31-224-801
email:  lborozan @ mathos.hr
office:  8 (ground floor)

 


Research Interests

Convex optimization
Linear programming
Parallel computing

Degrees

MSc in Mathematics and Computer Science, Department of Mathematics, University of Osijek, Croatia, 2015.
BSc in Mathematics, Department of Mathematics, University of Osijek, Croatia, 2013.
 

Publications

 
Journal Publications

  1. Đ. Borozan, L. Borozan, Analyzing total-factor energy efficiency in Croatian counties: evidence from a non-parametric approach, Central European Journal of Operations Research 26/3 (2018), 673-694
    Using energy efficiently has become top priority concern which requires an adequate policy reaction bearing in mind both energy conservation and efforts to combat adverse climate changes. The paper explored the total-factor energy efficiency and change trends in technical efficiency in the Croatian counties during the period 2001–2013. Employing data envelopment analysis, the overall technical, pure technical and scale efficiency are assessed. Considering the empirical results, we have concluded the following. Technical inefficiency is generated almost equally by the pure technical effect and an incorrect production scale. The overall geographical distribution of the technical efficiency scores points to the presence of spatial concentration, i.e., a dualistic pattern (centre vs. periphery) in the production process. The differences between the best practice and the worst technical efficiency scores indicate the presence of significant disparities among Croatian counties. The years with deteriorating electricity efficiency seem to coincide with the important economic/energy changes that happened in Croatia. Finally, subnational governments may play an important role in energy efficiency policies.
  2. D. Marković, L. Borozan, On Parameter Estimation by Nonlinear Least Squares in Some Special Two-Parameter Exponential Type Models, Applied Mathematics & Information Sciences 9/6 (2015), 2925-2931
    Two-parameter growth models of exponential type f(t;a,b) = g(t)exp(a+bh(t)), where a and b are unknown parameters and g and h are some known functions, are frequently employed in many different areas such as biology, finance, statistic, medicine, ect. The unknown parameters must be estimated from the data (w_i, t_i, y_i), i = 1,...,n, where t_i denote the values of the independent variable, y_i are respective estimates of regression function f and w_i > 0 are some data weights. A very popular and widely used method for parameter estimation is the method of least squares. In practice, to avoid using nonlinear regression, this kind of problems are commonly transformed to linear, which is not statistically justified. In this paper we show that for strictly positive g and strictly monotone h original nonlinear problem has a solution. Generalization in the lp norm (1 ≤ p < ∞) and some illustrative examples are also given.


Refereed Proceedings

  1. V. Hoan Do, M. Blažević, P. Monteagudo, L. Borozan, K. Elbassioni, S. Laue, F. Rojas Ringeling, D. Matijević, S. Canzar, Dynamic pseudo-time warping of complex single-cell trajectories, 23nd Annual International Conference on Research in Computational Molecular Biology, The George Washington University, 2019, 294-297
    Single-cell RNA sequencing enables the construction of trajectories describing the dynamic changes in gene expression underlying biological processes such as cell differentiation and development. The comparison of single-cell trajectories under two distinct conditions can illuminate the differences and similarities between the two and can thus be a powerful tool. Recently developed methods for the comparison of trajectories rely on the concept of dynamic time warping (dtw), which was originally proposed for the comparison of two time series. Consequently, these methods are restricted to simple, linear trajectories. Here, we adopt and theoretically link arboreal matchings to dtw and propose an algorithm to compare complex trajectories that more realistically contain branching points that divert cells into different fates. We implement a suite of exact and heuristic algorithms suitable for the comparison of trajectories of different characteristics in our tool Trajan. Trajan automatically pairs similar biological processes between conditions and aligns them in a globally consistent manner. In an alignment of singlecell trajectories describing human muscle differentiation and myogenic reprogramming, Trajan identifies and aligns the core paths without prior information. From Trajan’s alignment, we are able to reproduce recently reported barriers to reprogramming. In a perturbation experiment, we demonstrate the benefits in terms of robustness and accuracy of our model which compares entire trajectories at once, as opposed to a pairwise application of dtw. Trajan is available at https://github.com/canzarlab/Trajan.
  2. Đ. Borozan, L. Borozan, The stationarity of per capita electricity consumption in Croatia allowing for structural break(s), 13th International Symposium on Operational Research, Bled, Slovenia, 2015, 337-342
    Understanding the stationarity properties of electricity consumption provides valuable insights for energy policy-makers and practitioners. The paper examines the unit root properties of per capita electricity consumption for Croatian counties using the panel unit root tests with structural break(s) during the period 2001-2013. The results indicate that the series of most counties are non-stationary processes, and that statistically significant structural break(s) happened only in a few of them. Hence, the impacts of shocks on per capita electricity consumption are permanent and have a long memory for a majority of them. Moreover, their behaviors are path-dependent.


Others

  1. D. Matijević, D. Ševerdija, S. Jelić, L. Borozan, Uparena optimizacijska metoda, Math.e : hrvatski matematički elektronski časopis 30 (2016)
    U ovom članku analiziramo metode gradijentnog i zrcalnog spusta u području konveksne optimizacije s danim naglaskom na njihove brzine konvergencije. Nadalje, uparujući dvije spomenute metode dobivamo takozvanu uparenu metodu čija analiza konvergencije pokazuje ubrzanje u odnosu na gradijentnu i zrcalnu metodu, te bilo koju drugu nama poznatu metodu prvoga reda.



Projects

  • Problem procjene parametara u nekim dvoparametarskim monotonim matematičkim modelima (Odjel za matematiku, Sveučilište u Osijeku - Sveučilište u Osijeku), voditelj projekta: Darija Marković, 25.9.2013. - 24.9.2014.


Professional Activities

Editorial Boards

 


 

Committee Memberships

 


 

Refereeing/Reviewing

 


 

Service Activities

 


Teaching

Uvod u teoriju mjere

Uvod u teoriju integracije

Funkcijsko programiranje

Vektorski prostori

Elementarna matematika

Uvod u strukture podataka i algoritme

Prethodne godine:

Linearna Algebra II

Matematika (PFOS)

Integralni račun

Matematika I (GFOS)

Primjene diferencijalnog i integralnog računa II

 

Konzultacije (Office Hours): Po dogovoru putem e-maila.

 


Personal

Here goes the private stuff.