Laser Application in Procesing, Technology, Conservation and Experience of Artwork based on light Metals

Application of lasers in fine arts, in connection even with light metals, exists almost half a century. Due to multifold role of lasers, only few approaches, showing either potential applications or applications already implemented on this type of materials, is shown in this work

Analysis of the heat affected zone in CO2 laser cutting of stainless steel

This paper presents an investigation into the effect of the laser cutting parameters on the heat affected zone in CO2 laser cutting of AISI 304 stainless steel. The mathematical model for the heat affected zone was expressed as a function of the laser cutting parameters such as the laser power, cutting speed, assist gas pressure and focus position using the artificial neural network. To obtain experimental database for the artificial neural network training, laser cutting experiment was planned as per Taguchi’s L27 orthogonal array with three levels for each of the cutting parameter. Using the 27 experimental data sets, the artificial neural network was trained with gradient descent with momentum algorithm and the average absolute percentage error was 2.33%. The testing accuracy was then verified with 6 extra experimental data sets and the average predicting error was 6.46%. Statistically assessed as adequate, the artificial neural network model was then used to investigate the effect of the laser cutting parameters on the heat affected zone. To analyze the main and interaction effect of the laser cutting parameters on the heat affected zone, 2-D and 3-D plots were generated. The analysis revealed that the cutting speed had maximum influence on the heat affected zone followed by the laser power, focus position and assist gas pressure. Finally, using the Monte Carlo method the optimal laser cutting parameter values that minimize the heat affected zone were identified

The role of microscopy in the evaluation of the autenticity of the material of cultural heritage

In determining the autenticity of materials and technological processes in the creation of objects of art, comparative analysis provides information necessary for conservation planning. This is of particular importance for rare preserved artifacts that belong to the same school of art, or author. Here, we present the first experimental data concerning the identification of the authentification characteristics, being part of a large project that has as its finala im the evaluation of the effectiveness and effects of the cleaning agent on the paint layers material from the icon of the Virgin Mary with Christ, the Monastery St. Prohor Pčinjski, Serbia

Analysis and modeling of the effects of process parameters on specific cutting energy in abrasive water jet cutting

The problem of cutting difficult-to-machine materials used in the aerospace industry, aircraft industry, and automobile industry, led to the development and application one of today’s most attractive technology for contour cutting - abrasive water jet cutting. For the efficient use of abrasive water jet cutting, it is of great importance to analyze the impact of process parameters on performance indicators, such as cutting quality, productivity, and costs. But also, from the energy utilization point of view, it is very important to analyze the impact of these parameters on the specific cutting energy which represents the amount of energy spent on the removal of material in the unit time. Having this in mind, this study presents the experimental results of abrasive water jet cutting of aluminum alloy with the aim of creating a mathematical model for estimating specific cutting energy as an important indicator of the degree of utilization of the available energy in the cutting process. The mathematical model of the specific cutting energy is explicitly represented as a non-linear function of the process parameters, obtained by the artificial neural network. [Project of the Serbian Ministry of Education, Science and Technological Development, Grant no. TR 35034

Investigations of combustion process in stove fired on biomass

The aim of the investigation was to make some reconstructions on the existing stove used for cooking and baking and to obtain the combined cooker-boiler which will fulfill the demands of European standard EN 12815. Implementation of modem scientific achievements in the field of combustion on stoves and furnaces fired on biomass was used. During the investigations four various constructions were made with different fresh air inlet and secondary air supply with the intention to obtain more complete combustion with increased efficiency and reduced CO emission. Three different fuels were used: firewood, coal, and wood briquette. A numerous parameters were measured: fuel weight changes during the combustion process, temperature of inlet and outlet water, flue gas composition (O-2, CO, SO2, CO2, NOx), flue gas temperature, ash quantity ect. The result of the investigations is the stove with the efficiency of more than 75% - boiler Class 1 (according EN 12815) and CO emission of about 1 %v/v. The results obtained during the measurements were used as parameters for modeling of combustion process

Investigations of combustion process in stove fired on biomass

The aim of the investigation was to make some reconstructions on the existing stove used for cooking and baking and to obtain the combined cooker-boiler which will fulfill the demands of European standard EN 12815. Implementation of modem scientific achievements in the field of combustion on stoves and furnaces fired on biomass was used. During the investigations four various constructions were made with different fresh air inlet and secondary air supply with the intention to obtain more complete combustion with increased efficiency and reduced CO emission. Three different fuels were used: firewood, coal, and wood briquette. A numerous parameters were measured: fuel weight changes during the combustion process, temperature of inlet and outlet water, flue gas composition (O-2, CO, SO2, CO2, NOx), flue gas temperature, ash quantity ect. The result of the investigations is the stove with the efficiency of more than 75% - boiler Class 1 (according EN 12815) and CO emission of about 1 %v/v. The results obtained during the measurements were used as parameters for modeling of combustion process

Modeling of cutting temperature in the biomedical stainless steel turning process

Stainless steel is widely used as material in many industries and medicine. As biomedical material, it has been used for making devices, implants as well as tools and equipment in surgery and dentistry. The most of them is processed by turning. Modeling of temperature in the metal cutting process is very important step in understanding and analysis of the metal cutting process. The objective of this study is to develop an artificial neural network model which can be used successfully for accurate prediction of cutting temperature while performing turning of the biomedical stainless steel. Before the modeling, cutting temperature was measured, as one of the significant parameters in turning process, by using the infrared thermal imaging camera. Finally, based on the mathematical model, the effects of the turning parameters on the cutting temperature were examined

Decomposition mechanism and kinetics of zinc–isophthalate complex with 2,2’-dipyridylamine as a precursor for obtaining nanosized zinc oxide

Studies related to the synthesis of nanosized ZnO as the antibacterial agent have become an interdisciplinary area gathering chemists, physicists, biologists, and medics. The broad scope of materials based on ZnO resulted in the development of various techniques for its preparation. Considering the dependence of particle shape and size onto physical and chemical properties of ZnO, the synthesis procedure is of major importance. In this work, an unconventional methodology of synthesis is proposed for obtaining nanosized ZnO. Polymeric zinc complex containing 2,2’-dipyridylamine (dipya) and dianion of 1,3-benzenedicarboxylic acid (ipht), [Zn(dipya)(ipht)]n, was used as precursor. Besides the crystal structure of [Zn(dipya)(ipht)]n which was already published [1], the luminescent properties are presented in this work. Also, the amazing antibacterial activity of this precursor prompted us to investigate the relationship between the crystal structure and thermal properties, especially if we bear in mind the lack of similar studies in the literature. Therefore, the mechanism and kinetics of its degradation was investigated under nonisothermal conditions in nitrogen and air atmospheres. Degradation enthalpies, thermodynamic activation parameters, pre-exponential factor, A, and the apparent activation energy, Ea, were determined for each step using Kissinger’s and Ozawa’s equations. The complexity of degradation steps has been analyzed using isoconversional methods. TG/DCS data were collected at four different heating rates: 10, 15, 20 and 25 ºC min –1 , while the formation of nanosized ZnO was confirmed using XRPD and FESEM techniques. The influence of precursor on the crystallite size and morphology of the resulting ZnO along with its antibacterial activity was examined. The obtained results will be discussed and compared

Laseri, palimpsest i kulturna baština

Uloga lasera u umetnosti i kulturnoj baštini je odavno uključena u mnoge metode dijagnostike, intervencije i zapisa-opisa-beleženja objekata u raznim dimenzijamai oblicima materijala i prostora za zapis. Neophodni prilazi su preko interakcije laserskim snopovima koje ne dovode do ireverzibilnih promena (povreda) sa holografskih (tomografskih) aspekata, ili sa gledišta malih lokalnih povreda, izbacivanja mase, promena boje i sastava, kojima se vrši željena intervencija ili dijagnostikuje željeni parametar. Mnogi od ovih metoda se paralelno mogu koristiti i u medicini. U radu se, pored analize nekoliko savremenih prilaza ovim problematikama i nekoliko eksperimentalnih činjenica dobijenih sa raznih objekata, dotiče i palimpsestna tačka gledišta, kao i dalji razvoj materijala za zapis u sprezi zamene uloge papira složenim strukturama, u vezi sa holografskim zapisima ili ne. Posebni akcenat je dat u vezi sa ultrabrzim optićkim fenomenima, povredama i njihovim praćenjem