General platform for hydro-information systems – a review of concept

This paper provides insight into the Institute's long-standing engagement in the design and implementation of hydroinformatics systems in Serbia and the region. The introduction provides a definition of the hydroinformatics system and different areas of application, as well as an overview of the best practices in the world. An overview of the general platform that was created based on experience in the development of different systems has been presented here. We have described the functionalities integrated into a single software platform based on mathematical models and computational services. Various practical examples of application by the Institute are presented with the specifics of implementation in line with the purpose and characteristics of the studied systems. The conclusion highlights the role of applied hydroinformatics systems and the effects of application by users. Possible further development and implementation directions in water management and hydropower systems in Serbia and the region have been also presented.Conference in the honour of 75 years of the Jaroslav Černi Water Institute, held in the Serbian Academy of Sciences and Arts, October 19-20th, 2022

Platinum electrocatalyst supported on glassy carbon: a dynamic response analysis of Pt activity promoted by substrate anodization

In previous investigations the physicochemical state of electrochemically activated glassy carbon (GC) has been found to affect the electrochemical activity of GC-supported Pt particles. It has been assumed that carbon functional groups (CFGs) generated by GC anodization are able to renew the Pt surface through bifunctional catalysis. In order to provide evidence for the intimate electrocatalytic relationship between Pt and anodized GC and reveal the cause of CFG-induced enhancement of Pt activity, the dynamic response of Pt black supported on differently anodized GC is analysed in this paper by cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS) in acidic solution. It was found that the capacitive properties of Pt black are not affected by modest GC anodization, but the pore resistance of the Pt layer is considerably affected. Clear evidence for the promoting influence of activated GC (i.e., CFGs) on the Pt desorption capability toward reverse hydrogen spillover at a Pt/CFGs-decorated GC interface in the Pt double layer region is elucidated by both EIS and CV measurements. The extent of GC anodization influences, in a quite similar way, both reverse hydrogen spillover desorption parameters (gained by EIS and CV) and the methanol oxidation rate as it has influence on the parameters describing the particular state of activated GC itself. Namely, the pore resistance of the Pt layer and GC resistance due to the presence of CFGs the highest when GC was moderately anodized, whereas the charge transfer resistance for hydrogen spillover desorption is the lowest. The CFGs of the anodized GC are able to "permeate" the above-applied Pt layer, thus increasing the Pt/ CFGs-decorated GC interface responsible for the enhancement of Pt electrochemical activity

Form follows fractal: use of fractal geometry for uncovering morphological patterns

Uporaba fraktalne geometrije, alternativnega načina gledanja na prostor, pri oblikovanju nove soseske v Velenju, Slovenija. Velenje je znano po svoji eksperimentalni zgodovini modernizma. Fraktalna geometrija ima pravilo samopodobnosti, lastnost, ki nam pomaga razumeti celoto skozi samo en del predmeta. V besedilu je fraktalna geometrija uporabljena na tri načine, kot navdih za strukturo, koncept gradnje in kasneje za vrednotenje drugih dveh. Uporaba je predstavljena pri gledanju narave z boljšim razumevanjem, kar bo privedlo do večje trajnosti v družbi.Use of fractal geometry, alternative way of looking at space, in creating a new neighbourhood in Velenje, Slovenia. Velenje is known for its experimental history with modernism. Fractal geometry has a rule of self-similarity, trait which helps us to understan whole trough only one part of the object. In the text fractal geometry has been used on three ways, as an inspiraton for the structure, concept of build-up and later for the valuation of the other two. Use is presented in viewing nature with better understanding will lead to more sustainability in the society

Promoting effect of carbon functional groups in methanol oxidation on supported Pt catalyst

The contribution of carbon functional groups (CFG) to methanol oxidation at carbon-supported Pt catalysts is studied in this work. Platinum black, attached in a form of a thin layer to electrochemically treated glassy carbon (GC), is investigated as a model system. Impedance measurements reveal significant changes in capacitive response of GC anodically polarized in H2SO4 solution in comparison to unoxidized state. XPS analyses show the increased fraction of oxygen-containing CFGs upon electrochemical treatment of GC. The activity of Pt black attached to oxidized GC for methanol oxidation is more than two times larger in comparison to the catalyst attached to unoxidized GC. Increased activity is most likely due to the promotion Of COads removal by increased content of CFGs

Relationships between structure and activity of carbon as a multifunctional support for electrocatalysts

We report on new insights into the relationships between structure and activity of glassy carbon (GC), as a model material for electrocatalyst support, during its anodization in acid solution. Our investigation strongly confirms the role of CFGs in promotion of Pt activity by the "spill-over'' effect related to COads for methanol electrooxidation (MEO) on a carbon-supported Pt catalyst. Combined analysis of voltammetric and impedance behaviour as well as changes in GC surface morphology induced by intensification of anodizing conditions reveal an intrinsic influence of the carbon functionalization and the structure of a graphene oxide (GO) layer on the electrical and electrocatalytic properties of activated GC. Although GO continuously grows during anodization, it structurally changes from being a graphite inter-layer within graphite ribbons toward a continuous GO surface layer that deteriorates the native structure of GC. As a consequence of the increased distance between GO-spaced graphite layers, the GC conductivity decreases until the case of profound GO exfoliation under drastic anodizing conditions. This exposes the native, yet abundantly functionalized, GC texture. While GC capacitance continuously increases with intensification of anodizing conditions, the surface nano-roughness and GO resistance reach the highest values at modest anodizing conditions, and then decrease upon drastic anodization due to the onset of GO exfoliation. We found for the first time that the activity of a GC-supported Pt catalyst in MEO, as one of the promising half-reactions in polymer electrolyte fuel cells, strictly follows the changes in GC nano-roughness and GO-induced GC resistance. The highest GC/Pt MEO activity is reached when optimal distance between graphite layers and optimal degree of GC functionalization bring the highest amount of CFGs into intimate contact with the Pt surface. This confirms the promoting role of CFGs in MEO catalysis

Comparison of barium titanate thin films prepared by inkjet printing and spin coating

In this paper, barium titanate films were prepared by different deposition techniques (spin coating, office Epson inkjet printer and commercial Dimatix inkjet printer). As inkjet technique requires special rheological properties of inks the first part of the study deals with the preparation of inks, whereas the second part examines and compares structural characteristics of the deposited films. Inks were synthesized by sol-gel method and parameters such as viscosity, particle size and surface tension were measured. Deposited films were examined by optical and scanning electron microscopy, XRD analysis and Raman spectroscopy. The findings consider advantages and disadvantages of the particular deposition techniques

Structural characterization and dielectric properties of BaTiO3 thin films obtained by spin coating

Barium titanate thin films were prepared by spin coating deposition technique of an acetic precursor sol and sintered at 750, 900 and 1050 °C. Phase composition of the obtained thin films was characterized by X-ray diffraction and Raman spectroscopy. Their morphology was analysed by scanning electron microscopy and atomic force microscopy. Dielectric properties of thin films sintered at 750 and 900 °C were characterized by LCD device, where the influence of sintering temperature on dielectric permittivity and loss tangent was inspected. It was concluded that higher sintering temperature increases grain size and amount of tetragonal phase, hence higher relative permittivity was recorded. The almost constant relative permittivity in the measured frequency (800 Hz–0.5 MHz) and temperature (25–200 °C) ranges as well as low dielectric loss are very important for the application of BaTiO3 films in microelectronic devices