Solar energy application in houses heating systems in Russia

The solar energy is widely used around the world for electricity generation and heating systems in municipal services. But its use is complicated in the number of territories with uneven receipts of solar radiation on the earth’s surface and large number of cloudy days during a year. A hypothesis on the possibility of application of individual solar collectors for heating of houses in the number of cities of Russia has been tested. The existing designs of solar collectors and checking the possibility of their application in northern territories of Russia are investigated. The analysis was carried out taking into account features of relief and other climatic conditions of the Perm and Sverdlovsk regions. As the result of research, the basic recommended conditions for application of solar batteries in houses of the northern Russian cities have been resumed

2D Hybrid method:Case of VLF signal amplitude variations in the time vicinity of an earthquake

Extraction of information in the form of oscillations from noisy data of natural phenomena such as sounds, earthquakes, ionospheric and brain activity, and various emissions from cosmic objects is extremely difficult. As a method for finding periodicity in such challenging data sets, the 2D Hybrid approach, which employs wavelets, is presented. Our technique produces a wavelet transform correlation intensity contour map for two (or one) time series on a period plane defined by two independent period axes. Notably, by spreading peaks across the second dimension, our method improves apparent resolution of detected oscillations in the period plane and identifies the direction of signal changes using correlation coefficients. We demonstrate the performance of the 2D Hybrid technique on a very low frequency (VLF) signal emitted in Italy and recorded in Serbia in time vicinity of the occurrence of an earthquake on November 3, 2010, near Kraljevo, Serbia. We identified a distinct signal in the range 120-130 s that appears only in association with the considered earthquake. Other wavelets, such as Superlets, which may detect fast transient oscillations, will be employed in the future analysis.Comment: published in Mathematics MDP

Modeling of thermoelectric module operation in inhomogeneous transient temperature field using finite element method

This paper is the result of research and operation modeling of the new systems for cooling of cutting tools based on thermoelectric module. A copper inlay with thermoelectric module on the back side was added to a standard turning tool for metal processing. For modeling and simulating the operation of thermoelectric module, finite element method was used as a method for successful solving the problems of inhomogeneous transient temperature field on the cutting tip of lathe knives. Developed mathematical model is implemented in the software package PAK-T through which numerical results are obtained. Experimental research was done in different conditions of thermoelectric module operation. Cooling of the hot module side was done by a heat exchanger based on fluid using automatic temperature regulator. After the calculation is done, numerical results are in good agreement with experimental. It can be concluded that developed mathe-matical model can be used successfully for modeling of cooling of cutting tools

Phenolic compounds and biological activity of Capsicum annuum L.

The objective of this study was to evaluate antifungal and antioxidant activities of vegetable extracts (Capsicum annuum L. cv. Dora, cv. Strizanka, cv. Morava), grown in Serbia. Different experimental models have included the determination content of total phenolics, total flavonoids, antioxidant capacity and minimum inhibitory concentration of the extract. The phenolic composition of different extracts was determined by the high-performance liquid chromatography (HPLC) method. The highest amounts of phenols and highest antioxidant capacity were found in the cultivar Dora extracts. The highest phenolic content has been shown in cultivar Strizanka ethanol extract. All of the extracts showed strong antimicrobial activity. On the basis of the results obtained, the extracts were found to serve as a potential source of natural antioxidants and antimicrobial due to their marked activity. The obtained results may be useful in the evaluation of new dietary and food products.Key words: High-performance liquid chromatography (HPLC), phenolic components, antimicrobial activity, antioxidant activity

A Wireless LC Sensor Coated with Ba0.9Bi0.066TiO3 for Measuring Temperature

This paper presents a passive LC wireless sensor for measuring temperature. The sensor is designed as a parallel connection of a spiral inductor and an interdigitated capacitor and it was fabricated in a conductive layer using LTCC (Low Temperature Co-fired Ceramic) technology. The inderdigitated capacitor electrodes were coated with a thin film of bismuth doped barium titanate (Ba0.9Bi0.066TiO3), whose permittivity changes with temperature, which directly induces changes in the capacitance of the interdigitated capacitor and consequently changes the resonant frequency of the sensor. The measurements of S-parameter of the sensor were performed using a Vector Network Analyzer (E5071B, Agilent Technologies, Santa Clara, CA, USA), whose port was connected to the antenna coil that was placed around the sensor in order to be able to wirelessly detect temperature, in the temperature range from 25 degrees C to 165 degrees C

Síntesis e investigación del mono cristal BiSBTeSe dopado con Zr obtenido mediante el método de Bridgman

Single crystal ingot of BiSbTeSe doped with Zr was synthesized using Bridgman method. Energy dispersive spectrometry (EDS) analysis was used to determine chemical composition of studied samples as well as to check and confirm samples homogeneity. X-ray diffraction (XRD) measurements proved that obtained crystal ingot is a single cristal and confirms Bi2Te3-type compound with orientation (00l) of single crystal. Melting point was determined by dilatometrically measured shrinkage during heating. Mobility, concentration, resistivity/conductivity and Hall coefficient of BiSbTeSe doped with Zr samples were determined using a Hall Effect measurement system based on the Van der Pauw method. The Hall Effect was measured at room tem-perature with an applied magnetic field strength of 0.37 T at different current intensities. The measured ingot samples were cut and cleaved from different regions. Calculated results obtained using a Hall Effect measurement system (Ecopia, HMS-3000) were mutually compared for cleaved and cut samples. Changing of transport and electrical parameters with the increase of the current intensity was also monitored.The results confirmed that electrical and transport properties of single crystal depend on crystal growth direction and mobility was also significantly improved in comparison with theoretical value of Bi2Te3 and available literature data.El lingote del mono cristal de BiSbTeSe dopado con Zr se sintetizó utilizando el método de Bridgman. La composición química se determinó mediante análisis con espectroscopía de dispersión de energía (EDS). Mediante difracción de rayos X (DRX) se demostró que el lingote de cristal obtenido es un mono cristal y confirmó que se trata de un compuesto del tipo Bi2Te3, con orientación del mono cristal (001). El punto de fusión se determinó por medidas dilatométricas. La movilidad, concentración, resistividad/conductividad, y el coeficiente de Hall del BiSbTeSe dopado con Zr, se determinaron utilizando un sistema de medición de efecto Hall basado en el método de Van der Pauw. El efecto Hall se midió a temperatura ambiente con una intensidad de campo magnético aplicada de 0,37 T a diferentes intensidades de corriente. Las muestras de lingotes medidos se cortaron y se rompieron de diferentes regiones. Las muestras de lingotes utilizadas en las medidas fueron obtenbidas mediante corte y escisión en distintas zonas. Los resultados obtenidos utilizando un sistema de medición de efecto Hall (Ecopia, HMS-3000) en las distintas muestras, se compararon entre sí. Los resultados confirmaron que las propiedades eléctricas y de transporte del mono cristal dependen de la dirección del crecimiento del cristal. La movilidad se mejoró significativamente en comparación no solo con el valor teórico de Bi2Te3 sino también con los datos existentes en la literatura

Reconstruction of the erythemal UV radiation data in Novi Sad (Serbia) using the NEOPLANTA parametric model

This paper focuses on the development and application of a technique for filling the daily erythemal UV dose data gaps and the reconstruction of the past daily erythemal UV doses in Novi Sad, Serbia. The technique implies developing the empirical equation for estimation of daily erythemal UV doses by means of relative daily sunshine duration under all sky conditions. A good agreement was found between modeled and measured values of erythemal UV doses. This technique was used for filling the short gaps in the erythemal UV dose measurement series (2003–2009) as well as for the reconstruction of the past time-series values (1981–2002). Statistically significant positive erythemal UV dose trend of 6.9 J m−2 per year was found during the period 1981–2009. In relation to the reference period 1981–1989, an increase in the erythemal UV dose of 6.92 % is visible in the period 1990– 1999 and the increase of 9.67 % can be seen in the period 2000–2009. The strongest increase in erythemal UV doses has been found for winter and spring seasons

TiO2/PPy nanocomposites for photocatalytic application

Titan(IV)-oksid je jedan od najčešće korišćenih fotokatalizatora, dok za polipirol (PPy) postoje potvrde da je pogodan za ovu primenu. Cilj ovog rada bio je dobijanje kompozita TiO2/PPy sa boljom fotokatalitičkom aktivnosti u odnosu na TiO2. Kako bi se optimizovao sadržaj PPy u kompozitu, sintetisani su uzorci TiO2/x%PPy (x = 0, 0,5, 1, 1,5, 3, 5 mas.%), koji su okarakterisani TG/DTA, XRD, FTIR, FESEM i UV-Vis metodama, dok su njihova fotokatalitička svojstva ispitana kroz razgradnju tekstilne boje RO16. Nanokristalni TiO2 je dobijen u obliku anatasa veličine kristalita oko 2 nm, dok su izračunati parametri jedinične ćelije potvrdili da je kristalna struktura anatasa ostala nepromenjena nakon dodatka PPy. Gotovo svi uzorci (izuzev TiO2/3%PPy) su fotokatalitički aktivniji od TiO2, dok je TiO2/1%PPy pokazao najizraženiju fotokatalitičku aktivnost razgradivši 9 % boje nakon 75 min.Titanium(IV) oxide is one of the most used photocatalysts while polypyrrole (PPy) is a promising material for photocatalytic application. The aim of this work was to obtain TiO2/PPy composites exhibiting higher photocatalytic activity than TiO2. In order to determine the optimal PPy content in a composite, TiO2/x%PPy (x = 0, 0.5, 1, 1.5, 3, 5 wt.%) samples were synthesized and characterized by TG/DTA, XRD, FTIR, FESEM and UV-Vis methods, while the photocatalytic behavior was examined towards the degradation of the textile dye RO16. Nanocrystalline TiO2 was obtained in anatase form with crystallite size around 26 nm and preserved anatase crystal structure despite the addition of PPy according to the calculated unit cell parameters. Almost all samples (except TiO2/3%PPy) showed better photocatalytic activity than TiO2 while the best photocatalytic activity was demonstrated by TiO2/1%PPy which degraded 98 % of the dye after 75 min

Photocatalytic degradation of Reactive Orange 16 dye using TiO2/PPy nanocomposites under simulated solar light

It is well known that titanium dioxide is usually used as a photocatalyst due to its nontoxicity, low cost, and stability. Conductive polymer, polypyrrole (PPy) is also appropriate for photocatalytic application being stable and easy to synthesize. The aim of this study was to obtain TiO2/PPy composites reaching higher photocatalytic efficiency compared to pure TiO2. Therefore, TiO2 was synthesized by the hydrothermal route, while PPy was obtained by the chemical oxidative polymerization method. TiO2/x% PPy nanocomposites (x = 0, 0.5, 1, 1.5, 3, 5 wt.%) were prepared by hand-mixing of powders in agate mortar for 30 min in order to find the optimal PPy content. Obtained materials were characterized by XRD, FTIR, TG/DSC, FESEM, and UV-Vis methods while their photocatalytic activity was estimated towards degradation of Reactive Orange 16 dye (RO16). A kinetic study was performed and a detailed mechanism of RO16 photocatalytic degradation in the presence of TiO2/PPy composites was proposed based on scavenger tests. The results showed that, despite PPy addition, TiO2 was present in anatase form in all samples with sufficiently small crystallites (around 26 nm) and preserved structure with no significant deviations in unit cell parameters. The band gap energy decreased with increasing of PPy content, from 3.14 eV for pure TiO2 to 2.94 eV for TiO2/5% PPy. All the obtained nanocomposites demonstrated higher photocatalytic activity than pure TiO2, whereby TiO2/1% PPy nanocomposite was the most efficient by degrading 99.6% of the dye for 105 min under simulated solar light. Therefore, the amount of 1 wt.% should be consider as optimal amount of PPy in a composite. It is established that the photodegradation of RO16 using TiO2/PPy nanocomposites follows pseudo-first kinetic order. RO16 photocatalytic degradation mechanism in the presence of TiO2/PPy nanocomposites can be well described by direct Z-scheme heterojunction which has never been reported for TiO2/PPy system