Božidar Radenković

Supply network modelling and simulation methodology

Abstract Supply network management in today’s business climate characterized by high uncertainty, globalization of business, outsourcing, shorter product life-cycles, and high customer expectations is extremely challenging. Simulation can be a valuable tool for supply network analysis, planning, optimization, evaluation, and risk management. This paper presents a methodology for modelling both structure and dynamics of complex supply networks based on process approach. It also describes the model-driven simulation methodology and the main components of the simulation software solution: model database, process library, knowledge base, and execution engine. Finally, simulation results of the case supply network are presented.

Study of the high pressure effect on nanoparticles GdVO4: Eu3+ optical properties

This study considers the effects of hydrostatic pressure on the line position and fluorescence lifetime τ for 5D0 → 7F2 transitions in GdVO4: Eu3+ nanocrystals. The results indicate that the pressure induced the red shift toward longer wavelengths for all the considered lines with different rate. The fluorescence lifetime τ nonlinearly decreases with pressure in the considered pressure range. High pressure induced the fluorescence lifetime τ that can be explained with a simple theoretical model. The measured line position and τ are in a satisfactory agreement with the theoretical calculations.

High-pressure and optical properties of LaMgAl11O19:Sm3+ laser material

Emission spectra and decay properties of the 4G 5/2 level of Sm3+ ions in LaMgAl11O19:Sm3+ (LMA:Sm3+) have been measured as functions of pressure up to 100 kbar at room temperature. Changes of the positions of three considered fluorescence lines (560, 606, and 643 nm) under pressure are very small. The fourth one (594 nm) is practically insensitive upon pressure and has a red shift rate (RSR) close to zero. Fluorescence lifetime τ for the 594 nm line decreases non-linearly with pressure in the considered pressure range. Effect of the pressure on τ was described using a model which considered the change of the inter-ionic distance (r), ionic polarizability (α), and material refractive index (n) with pressure. Calculated pressure-induced change of the lifetime τ is in good agreement with the experimental data. Insensitivity of the lines position upon the pressure, and small RSR, leads to conclusion that LMA:Sm3+ can be the base for a new generation of solid state lasers with numerous applications.

Web portal for adaptive e-learning

In this paper we present an approach to developing web portal for adaptive e-learning. Educational web portal is single access point to all relevant information, resources and applications in the education process. Web portal integrates different functionalities and services for adaptation of e-learning courses with existing learning management system Moodle. Integration includes: educational web portal users, information, processes and software platforms used in e-learning system. We describe architecture of the portal for adaptive e-learning, technologies, design and techniques applied in implementation of portals key components.

Integration of web based environment for learning discrete simulation in e-learning system

Abstract This paper proposes a new web-based environment for learning discrete simulation. FONWebGPSS is an application that provides a web-based interface for creating, storing and executing discrete system simulation models in the GPSS language. The primary goal of the paper is to improve the process of learning simulation by integration of the FONWebGPSS in the existing e-learning system, Moodle. Evaluation of the developed integrated solution for learning simulation has been performed within an undergraduate course, Simulation and simulation languages, at the Faculty of Organizational Sciences, University of Belgrade on a testing sample of 208 students divided into an experimental and a control groups. The research results show that students achieve better results on the final test when using the FONWebGPSS application integrated into the e-learning system in comparison with the standard desktop version of the GPSS.

GPSS for e-learning environment

The main issue in this paper is an implementation of GPSS (general purpose simulation system) for learning discrete event simulation in e-learning environment. Primary goal of the research is to develop interactive and user-friendly for creating, testing and analyzing discrete event system models and integrate it in existing e-learning system. We propose a new solution for learning simulation via Web - FONWebGPSS. Architecture and key concepts of FONWebGPSS application are described in the paper. In addition, we present an example of applying FONWebGPSS in solving a typical problem of discrete event simulation.

High-pressure optical studies on R-line fluorescence lifetime in Al2O3:V2+

ABSTRACT The effect of high hydrostatic pressure (up to 10.3 GPa) at room temperature on fluorescence lifetime τ for R line (2E→4A2 transition) in ruby Al2O3:V2+ was studied. The performed studies show the linear increase of τ with increasing pressure. At 10.3 GPa, τ is about 1.36 times higher than at ambient pressure. The obtained trend was explained by a model which considered the effect of pressure on τ through an induced change of line position, inter-ionic distance, compressibility, and molecular polarizability. A good agreement between the calculated and experimental values for τ was obtained.

High pressure effect on photosynthetic properties of green plant leaves

We investigated the effects of high pressure treatment on green plant leaves of two species, red rose (Rosa rubiginosa L.) and silver birch male (Betula pendula Roth). Both species were treated with pressure up to 100 bar in order to explore stress reactions, including desirable or undesirable metabolites in plant. When increasing the pressure, chlorophyll (Chl) fluorescence maximum shifts to the wavelength of about 680 nm for both red rose and silver birch, with shift rates–0.062 nm/bar and–0.082 nm/bar, respectively. High pressure induces the changes of the position for the second fluorescence maximum at approximately 730 nm in both species with the same shift rate–0.083 nm/bar. When increasing pressure the change of the photosynthetic apparatus efficiency decreases for both plant species slowly and nonlinearly. High-pressure treatments irreversibly damaged the leaf tissue and at this way induced changes of Chl fluorescence and photosynthetic efficiency.