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The photoacoustic effect was explained more than half a century ago and has since been used to develop non-destructive and non-contact techniques for testing materials. Most existing experimental setups are time-consuming. In this paper, we deal with the development of time-resolved photoacoustics to use all the advantages of photoacoustic techniques in the development of real-time characterization of various samples. We propose a model for a time-resolved photoacoustic signal of thin samples measured in a gas-microphone setup with a minimal volume cell, assuming that the gas column in the cell can be shorter than the thermal diffusion length in air. The derived model additionally includes the influence of thermal relaxations and detector transfer function. We also suggest a methodology for inverse problem solving, i.e., to determine the sample properties from measured signals using the presented model. The model has been validated by comparing the model predictions with an experimentally measured signal for a thin metallic sample excited by an optical pulse train of a repetition rate of 12 Hz. The results obtained by the suggested inverse-problem solving methodology are in accordance with the literature, thus confirming the validity of the proposed methodology. We have shown that the proposed model and the methodology of inverse time-resolved photoacoustic problems give the same results as the widespread time-consuming frequency photoacoustic measurements. This means that the presented model and methodology enable the employment of low-frequency time-resolved gas-microphone photoacoustics in the real-time characterization of thin solids.

In this paper, the influence of the measurement range on the prediction of thermoelastic and geometric properties of a thin aluminum sample obtained by solving the inverse photoacoustic problem using neural networks was analyzed. Tests of neural networks on theoretical photoacoustic signals showed that the accuracy of solving the inverse problem increases with the increase of the measurement range, which is in accordance with the theory of solving inverse problems. Tests on experimentally measured signals in a transmission experimental setup with an open photoacoustic cell, from which the influence of the transmission characteristic of the detector was removed, show the advantages of using narrow frequency bands. This result indicates the need for further investigations of both: the influence of the measuring chain on the recorded signal and the influence of additional processes and sample properties on the thermoelastic behavior of thin metal films.

Irrational and transcendental functions can often be seen in signal processing or physical phenomena analysis as consequences of fractional-order and distributed-order models that result in fractional or partial differential equations. In cases when finding solution in analytical form tends to be difficult or impossible, numerical calculations such as Haar wavelet operational matrix method can be used. In order to evaluate accuracy of the numerical inversion of irrational and transcendental Laplace transform using Haar wavelet operational matrix, a number inverse Laplace transforms are numerically solved and compared with the analytical solutions and solutions provided by Invlap and NILT algorithms.

Current trends such as digitalization, digital transformation, Industry 4.0 and the like, which are characteristic of modern society as a whole, have imposed the world of data as an imperative of all spheres of human activity. In a very short period of time, all previously assumed barriers in the current amount of data in circulation at the global level, which is currently measured in tens of zettabytes with a tendency to continuously increase in the years to come, have been exceeded. Even if we reduce the level of observation to a single instance, there is almost no case in which we cannot identify any increase in the amount of data. In proportion to the increase in the amount of data, the required energy that needs to be provided at different levels for any action taken on this data has increased, whether it is the creation of this data, its storage, some processing, replication or some other adequate type of action. It is estimated that already few percents of the entire world production of electricity go to the segment of providing the necessary conditions for the performance of some of the work on data. Accordingly, many large data centers are partially or completely switching to systems based on the use of renewable energy sources. Although this transfer has brought a number of advantages, there is still the problem of data expansion in a long-term plan that new energy solutions need to follow. The paper will show how a more rational data handling at different levels of use can create a far more favorable energy environment at the global level and how this environment can contribute to the sustainability of currently applied solutions for renewable energy in different segments of use and work with data in a modern environment., Trenutni trendovi poput digitalizacije, digitalne transformacije, industrije 4.0 i sličnog, koji su karakteristika savremenog društva u celini, nametnuli su svet podataka kao imperativ svih sfera ljudskog delovanja. U vrlo kratkom vremenskom roku probijene su sve ranije pretpostavljane barijere u trenutnoj količini podataka koja je u opticaju na globalnom nivou i koja se trenutno meri u desetinama zetabajta sa tendencijom kontinuiranog uvećanja u godinama koje slede. Trend povećanja količine podataka može se zabeležiti na svim nivoima, bez obzira da li posmatramo neki manji, lokalizovani uzorak, regionalni uzorak, ili, kao što je već navedeno, posmatramo globalni digitalni svet. Čak i ako nivo posmatranja svedemo na pojedinačnu instancu, gotovo da nema slučaja u kome ne možemo identifikovati neko povećanje količine podataka. Proporcionalno povećanju količine podataka, uvećala se i potrebna energija koju na različitim nivoima treba obezbediti za neku preduzetu radnju nad tim podacima, bilo da se radi o samom kreiranju tih podataka, skladištenju istih, nekoj vrsti obrade, umnožavanju ili nekoj drugoj adekvatnoj vrsti radnje nad tim podacima. Procenjuje se da već nekoliko procenata celokupne svetske proizvodnje električne energije odlazi na segment obezbeđenja neophodnih uslova za izvršenje neke od radnji nad podacima. U skladu sa tim, mnogi veliki centri za rukovanje podacima parcijalno ili u celosti prelaze na sisteme zasnovane na upotrebi obnovljivih izvora električne energije. Iako je taj transfer doneo niz prednosti i dalje postoji problem ekspanzije podataka na jednom dugoročnijem planu koji nova energetska rešenja treba da isprate. U radu će se pokazati kako se jednim racionalnijim rukovanjem podacima na različitim nivoima upotrebe može stvoriti daleko povoljnije energetsko okruženje na globalnom nivou i kako to okruženje može doprineti jednoj održivosti trenutno primenjenih rešenja koji se tiču upotrebe obnovljivih izvora električne energije u različitim segmen

Solarni sistemi u poslednje vreme beleže esponencijalni rast instalisane snage. Ostvareni ekonomski efekti podstiču dalji razvoj tehnologije, tako da se postiže sve veća energetska efikasnost uz sve niža investiciona ulaganja. Države dodatno pomažu merama podsticaja, posebno u uslovima krize drugih energenata, tako da se očekuje još veći rast u budućnosti. U radu je dat pregled stanja tehnologije i regulative, kao i projekcije za budućnost u Evropi i Srbiji., owadays, solar systems have recorded in an exponential increase in installed power. The achieved economic effects encourage further development of technology, so that increasing energy efficiency have been achieved with lower investments. Countries additionally help with incentive measures, especially in the states of the crisis of other energy sources, thus the greater growth is expected in the future. The paper provides an overview of the state of technology and legal regula-tions, as well as projections for the future in Europe and Serbia.

By returning to the classical forms of teaching and attendance of classes in the faculty facilities, appropriate anti-covid measures have been introduced. One of those measures is the regular check of the students' temperature before accessing any form of teaching in the faculty classrooms. However, serious issues soon are manifested by measuring temperature with conventional non-contact thermometers. The paper shows how some of these issues and limitations can be overcome by using thermal imaging when controlling the temperature within anti-covid measures.

Trenutni trendovi poput digitalizacije, digitalne transformacije, industrije 4.0 i sličnog, koji su karakteristika savremenog društva u celini, nametnuli su svet podataka kao imperativ svih sfera ljudskog delovanja. U vrlo kratkom vremenskom roku probijene su sve ranije pretpostavljane barijere u trenutnoj količini podataka koja je u opticaju na globalnom nivou i koja se trenutno meri u desetinama zetabajta sa tendencijom kontinuiranog uvećanja u godinama koje slede. Trend povećanja količine podataka može se zabeležiti na svim nivoima, bez obzira da li posmatramo neki manji, lokalizovani uzorak, regionalni uzorak, ili, kao što je već navedeno, posmatramo globalni digitalni svet. Čak i ako nivo posmatranja svedemo na pojedinačnu instancu, gotovo da nema slučaja u kome ne možemo identifikovati neko povećanje količine podataka. Proporcionalno povećanju količine podataka, uvećala se i potrebna energija koju na različitim nivoima treba obezbediti za neku preduzetu radnju nad tim podacima, bilo da se radi o samom kreiranju tih podataka, skladištenju istih, nekoj vrsti obrade, umnožavanju ili nekoj drugoj adekvatnoj vrsti radnje nad tim podacima. Procenjuje se da već nekoliko procenata celokupne svetske proizvodnje električne energije odlazi na segment obezbeđenja neophodnih uslova za izvršenje neke od radnji nad podacima. U skladu sa tim, mnogi veliki centri za rukovanje podacima parcijalno ili u celosti prelaze na sisteme zasnovane na upotrebi obnovljivih izvora električne energije. Iako je taj transfer doneo niz prednosti i dalje postoji problem ekspanzije podataka na jednom dugoročnijem planu koji nova energetska rešenja treba da isprate. U radu će se pokazati kako se jednim racionalnijim rukovanjem podacima na različitim nivoima upotrebe može stvoriti daleko povoljnije energetsko okruženje na globalnom nivou i kako to okruženje može doprineti jednoj održivosti trenutno primenjenih rešenja koji se tiču upotrebe obnovljivih izvora električne energije u različitim segmen, Current trends such as digitalization, digital transformation, Industry 4.0 and the like, which are characteristic of modern society as a whole, have imposed the world of data as an imperative of all spheres of human activity. In a very short period of time, all previously assumed barriers in the current amount of data in circulation at the global level, which is currently measured in tens of zettabytes with a tendency to continuously increase in the years to come, have been exceeded. Even if we reduce the level of observation to a single instance, there is almost no case in which we cannot identify any increase in the amount of data. In proportion to the increase in the amount of data, the required energy that needs to be provided at different levels for any action taken on this data has increased, whether it is the creation of this data, its storage, some processing, replication or some other adequate type of action. It is estimated that already few percents of the entire world production of electricity go to the segment of providing the necessary conditions for the performance of some of the work on data. Accordingly, many large data centers are partially or completely switching to systems based on the use of renewable energy sources. Although this transfer has brought a number of advantages, there is still the problem of data expansion in a long-term plan that new energy solutions need to follow. The paper will show how a more rational data handling at different levels of use can create a far more favorable energy environment at the global level and how this environment can contribute to the sustainability of currently applied solutions for renewable energy in different segments of use and work with data in a modern environment.

Structural health monitoring that gathers information about performance and conditions of civil engineering structures requires implementation of sensor networks that include strain sensing devices. This paper introduces RuO2/Bi2Ru2O7 thick-film strain sensor with low-temperature sensitivity. Under strain, RuO2/Bi2Ru2O7 thick resistive film experiences reversible deformation that can be registered as a change in film resistivity. Based on that effect, a prototype of the strain sensor is being realized and evaluated. Evaluation included measurements of the resistance change under applied strain, determination of the gage factor and investigations of and thermal stability.

Screen-printing process has been known for decades as an integral part of thick-film technology. Lately, it has been recognized as a possible means of pattern formation for stretchable electronic devices commonly used in fitness monitoring, epidermal and wearable healthcare. These devices are formed on thin flexible substrates in combination with nanocomposites based on polymeric binders and conductive fillers. The objective of this paper is to present challenges that screen-printing process for stretchable electronics is facing such as key process requirements and parameters, selection of flexible substrates, properties of conductive nanomaterial inks and strain management near rigid areas.

Screen-printing process has been known for decades as an integral part of thick-film technology. Lately, it has been recognized as a possible means of pattern formation for stretchable electronic devices commonly used in fitness monitoring, epidermal and wearable healthcare. These devices are formed on thin stretchable substrates in combination with nanocomposites based on polymeric binders and conductive fillers. The objective of this paper is to present challenges that screen-printing process for stretchable electronics is facing such as key process requirements and parameters, selection of stretchable substrates, properties of conductive nanomaterial inks and strain management near rigid areas.

In order to provide accurate and semi-real-time information about performances and conditions of various civil engineering structures thick-film resistors are often being used as strain sensors. For that purpose, Ba2Ru2O7 thick resistive films based on compositions with sheet resistivities of 1 kOhm/sq, 10 kOhm/sq and 100 kOhm/sq were evaluated. Resistors were fired at three different peak temperatures (825oC, 850oC and 875oC) and with three different dwelling times (5 min, 10 min and 15 min) in order to correlate influence of firing variables and thick resistive film strain sensitivity by tracking structure-related changes in resistance, gage factor and noise index values. For 10 kOhm/sq composition values of resistance change vs. temperature and temperature coefficient of resistance were measured and calculated.

A heat loss flowmeter for measuring the volume flow rate of water in real time (t) was formed using two thick film segmented thermistors, range constant voltage (RCV) power supply, acquisition card, PC, and software. The input water temperature T-w(t) was measured by a cold thermistor, while the water flow rate Q(t) was determined using the heat loss principle by measuring the self-heated thermistor current I(t). The flowmeter inertia, stability, and accuracy were measured and analyzed on a flowmeter prototype in real-time and real conditions on the water mains. The flowmeter response was measured for different durations of step input water flow-out functions and intervals between steps. An independent ultrasonic flowmeter was connected in series with the thermal flowmeter to measure the ordered input water flow functions. The realized intelligent functions in real time were: measuring the input water temperature T-w(t) and self-heating temperature T-s(t), auto-selection of RCV supply voltage U(Tw), determination and modeling of the water flow rate in real time Q(t), determination of the water volume V(t), and determination of the thermal gradient on the self-heating thermistor as a water flow indicator Delta Rs(t).