Journal of Contemporary Mathematical Analysis
(Armenian Academy of Sciences)
• 21 Nov 2021
Valjarević, Dragana • Petrović, Ljiljana
In this paper we consider the concept of statistical causality in continuous time between
filtrations associated with stopping times, which is based on Granger’s definition of causality.
Especially, we consider a generalization of a causality relationship “His a cause of E within F” from
fixed to stopping time. Then we apply the given concept of causality to strongly orthogonal stopped
martingales. We show the equivalence between the given concept of causality and orthogonality of
stopped l ...
Land Use Policy
(Elsevier Ltd.)
• 21 Sep 2019
Ristić, Dušan • Vukoičić, Danijela • Milinčić, Miroljub
With the formulation of tourism development strategies for the social and economic development of an area, rural tourism moved to a more complex phase of development. Numerous empirical studies have shown that different forms of rural tourism can have positive and negative effects on the natural and socio-economic context in the area where they are present. There are several methodologies for assessing the development of tourism in rural areas. One of the efficient and commonly used tools in pre ...
Optics Express
(Optica Publishing Group (Formerly OSA))
• 23 Jun 2022
Drljača, Branko • Savović, Svetislav • Kovačević, Milan • Simović, Ana • Kuzmanović, Ljubica • Djordjevich, Alexandar • Min, Rui
By solving the time-independent power flow equation (TI PFE), we study mode coupling in a multimode W-type microstructured polymer optical fiber (mPOF) with a solid-core. The multimode W-type mPOF is created by modifying the cladding layer and reducing the core of a multimode singly clad (SC) mPOF. For such optical fiber, the angular power distributions, the length Lc at which an equilibrium mode distribution (EMD) is achieved, and the length zs for establishing a steady state distribution (SSD) ...
Frontiers in Physics
(Frontiers)
• 25 May 2022
Savović, Svetislav • Djordjevich, Alexandar • Drljača, Branko • Simović, Ana • Min, Rui
Using the power flow equation (PFE), this article investigates mode coupling in step-index
(SI) multimode (MM) polymer optical fiber (POF). This equation’s coupling coefficient was
initially fine-tuned so that it could appropriately reconstruct previously recorded far-field
(FF) power distributions. The equilibrium mode distribution (EMD) and steady-state
distribution (SSD) in the SI MM POF were found to be obtained at lengths Lc = 15 m
and zs = 41 m, respectively. These lengths are substan ...
Polymers
(MDPI)
• 01 Dec 2021
Drljača, Branko • Savović, Svetislav • Kovačević, Milan • Simović, Ana • Kuzmanović, Ljubica • Djordjevich, Alexandar • Min, Rui
By solving the time-dependent power flow equation, we present a novel approach for evaluating the bandwidth in a multimode step-index polymer photonic crystal fiber (SI PPCF) with a solid core. The bandwidth of such fiber is determined for various layouts of air holes and widths of Gaussian launch beam distribution. We found that the lower the NA of SI PPCF, the larger the bandwidth. The smaller launch beam leads to a higher bandwidth for short fibers. The influence of the width of the launch be ...
Polymers
(MDPI)
• 17 Nov 2021
Simović, Ana • Savović, Svetislav • Drljača, Branko • Alexandar, Djordjevich • Min, Rui
The bandwidth of multimode W-type plastic optical fibers (POFs) with graded-index (GI) core distribution is investigated by solving the time-dependent power flow equation. The multimode W-type GI POF is designed from a multimode single-clad (SC) GI POF fiber upon modification of the cladding layer of the latter. Results show how the bandwidth in W-type GI POFs can be enhanced by increasing the wavelength for different widths of the intermediate layer and refractive indices of the outer cladding. ...
Optics Express
(Optica Publishing Group)
• 13 Sep 2021
Simović, Ana • Drljača, Branko • Savović, Svetislav • Djordjevich, Alexandar • Min, Rui
A new method is proposed for investigating the bandwidth in multimode graded-index
plastic optical fibers (GI POFs). By numerically solving the time-dependent power flow equation,
bandwidth is reported for a varied launch conditions (radial offsets) of multimode GI POF. Our
theoretical results are supported by the experimental results which show that bandwidth decreases
with increasing radial offset. This decrease is more pronounced at short fiber lengths. At fiber
length close to the coupl ...
Optics and Laser Technology
(Elsevier)
• 11 Jun 2021
Simović, Ana • Djordjevich, Alexandar • Drljača, Branko • Savović, Svetislav
A method is proposed for investigation of transmission along a multimode W-type (doubly clad) plastic optical fiber (POF) with graded index (GI) distribution of the core. The multimode W-type GI POF is designed from a multimode singly clad (SC) GI POF fiber upon modification of the cladding layer of the latter. The transmission characteristics of such proposed W-type GI POF are determined from the numerical solution of the power flow equation. We have shown that coupling length Lc at which an eq ...
Numerical Algorithms
(Springer)
• 03 Dec 2019
Petrović, Milena • Rakočević, Vladimir • Valjarević, Dragana • Ilić, Dejan
We introduce a hybrid gradient model for solving unconstrained optimization problems based on one specific accelerated gradient iteration. Having applied a three term hybridization relation on transformed accelerated double step size model, we develop an efficient hybrid accelerated scheme. We determine an iterative step size variable using Backtracking line search technique in which we take an optimally calculated starting value for the posed method. In convergence analysis, we show that the pr ...
Filomat
• 15 Jun 2018
Petrović, Ljiljana • Valjarević, Dragana
In this paper we consider the concept of statistical causality between filtrations associated with
stopping times, which is based on Granger’s definition of causality. Especially, we consider a generalization
of a causality relationship ”G is a cause of E within H” from fixed to stopping time. Then we apply the
given causality concept to local uniqueness for the solution of the martingale problem. Also, we give some
applications in finance.
