У цій роботі ми досліджуємо принцип роботи голографічних дисплеїв (моніторів), їхні технічні характеристики та потенційні переваги порівняно з традиційними дисплеями. Також розглядаються перспективи використання голографічних дисплеїв у різних галузях, включаючи медицину, освіту, розваги, телекомунікації та виробництво. Розуміння принципів функціонування цих пристроїв та їхніх потенційних можливостей може привести до нових можливостей для візуалізації даних та створення іммерсивних візуальних досвідів

This article examines the correlation between the pyroelectric response in typical films of ferroelectric polymers and the value of the residual ferroelectric polarization. The pyroelectric response was obtained by the thermal pulse method proposed by Collins. The magnitude of the residual polarization was measured depending on the magnitude of the applied electric field during primary electrification (poling) and during its switching. It is shown that the used method has the high sensitivity. It was found that the magnitude of the pyroelectric response depends significantly on the polarized state, which is determined by the values of the electric field during electrification and polarization switching and on the duration of exposure to this field. The identity of the graphs of the dependence of the residual polarization on the field and time and the corresponding graphs of the magnitude of the pyroelectric response led to the final conclusion about the proportionality of the magnitude of the response to the residual polarization. Thus, it is concluded that the pyroelectric response method can be used to estimate the magnitude of polarization in ferroelectric polymers

The vinylidene fluoride copolymer with tetrafluoroethylene P(VDF-TFE) is a typical ferroelectric polymer that has not been sufficiently studied so far in comparison with pure polyvinylidene fluoride (PVDF) and its copolymer with trifluoroethylene. The purpose of this work was to reveal the features of forming ferroelectric polarization and its switching in thin films of P(VDF-TFE) under various conditions, such as the level of the applied electric field and the duration of its action within 8 orders of magnitude from 10 μs to 100 s. The sequence of voltage pulses applied during poling and polarization reversal allowed to reveal the characteristics of the polarization switching dynamics. To increase the resolution of the measurements, two complementary methods of recording electrical induction were used. The features of polarization and space charge relaxation over time have been studied by thermally stimulated depolarization method. A new phenomenon of gradual separation of the relaxation processes associated with polarization and space charge was observed. Both components were accompanied by trapped charges that compensated the depolarizing field. Several practical recommendations have been formulated regarding the desirable values of poling parameters and additional processing to increase the ferroelectric polarization stability.

The present study is focused on tubular multi-channel arrays composed of commercial fluoropolymer (FEP) tubes with different wall thickness. After proper charging in a high electric field, such tubular structures exhibit a large piezoelectric d_33 coefficient significantly exceeding the values of classical polymer ferroelectrics and being even comparable to conventional lead-free piezoceramics. The quasistatic piezoelectric d_33 coefficient was theoretically derived and its upper limits were evaluated considering charging and mechanical properties of the arrays. In order to optimize the d_33 coefficient the remanent polarization and the mechanical properties were taken into account, both being strongly dependent on the air channel geometry as well as on the wall thickness of the FEP tubes. The model predictions are compared with experimental d 33 coefficients for two particular arrays with equal air gaps of 250 μm, but with different wall thickness of utilized FEP tubes of 50 μm and 120 μm, respectively. Analytical modeling allows for the prediction that arrays made of FEP tubes with a wall thickness of 10 μm are foreseen to exhibit a superb piezoelectric response of up to 600 pC/N if the height of stadium-like shaped air channels is reduced down to 50 μm, making them potentially interesting for application as highly sensitive sensors and energy harvesting.

Polymers with electrically charged internal air cavities called ferroelectrets exhibit a pronounced piezoelectric effect and are regarded as soft functional materials suitable for sensor and actuator applications. In this work, a simple method for fabricating piezoelectret arrays with open-tubular channels is introduced. A set of individual fluoroethylenepropylene (FEP) tubes is compressed between two heated metal plates. The squeezed FEP tubes are melted together at + 270 degrees C. The resulting structure is a uniform, multi-tubular, flat array that reveals a strong piezoelectric response after a poling step. The fabricated arrays have a high ratio between piezoelectrically active and non-active areas. The optimal charging voltage and stability of the piezoelectric coefficients with pressures and frequency were experimentally investigated for two specific array structures with wall thickness of 50 and 120 mu m. The array fabricated from 50 mu m thick FEP tubes reveals a stable and high piezoelectric coefficient of d(33) = 120-160 pC N-1 with a flat frequency response between 0.1 Hz and 10 kHz for pressures between 1 and 100 kPa. An increase of wall thickness to 120 mu m is accompanied by a more than twofold decrease in the piezoelectric coefficient as a result of a simultaneously higher effective array stiffness and lower remanent polarization. The obtained experimental results can be used to optimize the array design with regard to the electromechanical performance.

Peculiarities of the polarization build-up and its relaxation in corona poled PVDF films meant for manufacturing of pyro- and piezoelectric sensors have been revealed from the complex experimental investigation of the polymer. It has been found that the polarization and the space charge are interrelated forming a self-balanced system. Its stability depends mainly on charges trapped in the volume. It has been shown that the charge trapping occurs in macroscopic zones positioned at the borders of completely polarized parts of the volume. The trapped charges play an important role in stability of the ferroelectric polarization, since they neutralize the depolarizing field.

BACKGROUND:Bran, being a by-product of grain grinding, is characterised by a high biological value and is thus widely used in food production. In this study, different streams of bran and shorts from the wheat graded milling process were incorporated into wheat flour at levels of 5, 11, 17 and 23% (w/w) to investigate their influence on the nutritional and baking properties of flour.RESULTS:Bran and shorts streams improved the baking properties of flour blends. The best result in the case of graded flour blends with different bran products was obtained at the 95:5 ratio. The products containing peripheral parts of grain had higher proteolytic enzyme and superoxide dismutase activities and lower trypsin inhibitor content and β-amylase activity compared with graded flour.CONCLUSION:Streams of wheat milled fractions including peripheral parts of grain increase the content of bioactive substances and dietary fibre in blends with wheat graded flour.

BACKGROUND Nutrition and health claims are permitted in foods marketed in the European Union under Regulation 1924/2006. Quality products such as traditional foods might benefit from this act, as it can highlight their nutritional richness. In this study the nutritional content of 33 traditional foods from the Black Sea Area Countries was evaluated against the thresholds of the Regulation for nutrition claims. RESULTS Most of the foods were eligible to bear several nutrition claims, mostly related to their fat, sugar, fiber and sodium content. The average number of claims per traditional food was two, with a range between zero and nine. Overall, about 72 nutrition claims were potentially relevant for the 33 traditional foods studied. Foods linked with the most claims were nuts and seeds. CONCLUSION The inclusion of traditional foods under this standardized European scheme could be an efficient way to highlight their possible beneficial nutritional properties. The production and marketing of traditional foods could be of benefit to both the health of consumers and the economic viability of producers, especially small- and medium-size enterprises.

Experimentally obtained data on the polarization dynamics in polyvinylidene fluoride, a typical ferroelectric polymer, are analyzed during initial poling, short circuiting and polarization switching. Considering a two-component structure of the samples, namely, presence of ferroelectric and non-ferroelectric phases, it is shown that value and stability of the ferroelectric polarization significantly depend on conductivity and space charges. Application of a simple two-layer theoretical model with an explicit conductivity allowed explaining such important features, as slow development and switching of the ferroelectric polarization and a partial back-switching of the already formed polarization after short-circuiting of the sample.

During the last years piezoelectrets having a voided or foamed structure possess high piezoelectric d33 coefficients after proper poling and have attracted considerable attention. Since very promising cellular polypropylene (PP) films turned out to be not sufficiently stable at temperatures above 60°C, new and hybrid materials still are explored including sandwich structures which consist of solid polyfluoroethylene propylene (Teflon FEP) blocking layers enveloping a layer of porous polytetrafluoroethylene (ePTFE). Figure 1 displays a schematic drawing of such a 3-layer sandwich. The respective notations for the thicknesses (dF, dρ) and dielectric constants (εF, ερ) are included in Fig. 1. The open-porous morphology of the ePTFE films consists of solid nodes and connecting fibres.

The three- and multi-layered sandwiched structures of polyfluoroethylene propylene (FEP) and porous polytetrafluoroethylene (ePTFE) have gained considerable interest as ferroelectrets [1-6]. Being initially completely non-polar, after proper poling in a high electric field they reveal a large piezoelectric d33 coefficient comparable to conventional ferroelectric Pb(Zr,Ti)O3 (PZT) ceramics. It has been recognized that a unique combination of charge storage ability together with a low elastic modulus typical for foams is responsible for high piezoelectric response of such hybrid structures. The ePTFE films are commercially produced by many companies such as Gore Ltd., DuPont Ltd., DeWal Industries Ltd. and Tetratex Ltd. The open-porous morphology of the ePTFE films strongly depends on preparation, stretching and expansion processes and usually consists of separated phases with solid nodes and fibres. Fig. 1 displays the scanning electron micrographs of the 91% porous ePTFE film from GoodFellow. Moreover, the possible high thermal piezoelectric stability of sandwiched arrangements has also been demonstrated [1-3,5]. All this makes the polymer porous structures a very promising object for applications in electromechanically active devices. Several ways to realize a full potential of such hybrid structures will be considered in the current contribution. To this end the charging and mechanical properties of different sandwich arrangements will be analysed.

Sandwiched structures of open-porous and solid polymer dielectrics reveal a strong piezoelectric response after proper charging by high electric fields. Here, the electrical properties of corona-poled three-layer FEP/ePTFE/FEP sandwiches are studied theoretically and experimentally with the objective of its possible optimization for the highest piezoelectric activity. Modelling of the charging properties is performed for different sandwich geometries. It is shown that the maximum value of the remanent interface charge density accumulated during poling depends mainly on the ratio of the solid and porous layers thicknesses and on parameter E(B), which characterizes the electric breakdown strength of air in the porous layer. E(B) exhibits specific dependences on porosity and thickness of the porous layer. For a given porous layer E(B) is independent of the solid film thickness. The obtained results can be utilized to further optimize the sandwich structure as an electromechanically active device.

Electrical and mechanical properties of corona poled three layer FEP/ePTFE/FEP sandwiches were studied theoretically and experimentally. Modeling of the properties has been performed, as well as their experimental verification. The piezoelectric d(33) coefficient has been studied with the objective of its possible optimization. It has been shown that the maximum value of the d(33) piezocoefficient depends on interrelation between solid and porous layers thicknesses, the intrinsic Young modulus of the porous layer and dependence of the breakdown field on the thickness of the porous layer. The best geometry of the sample can be designed considering the obtained results.

It is established that for obtaining the prolonged stability at elevated temperatures it is necessary to perform preliminary annealing; moreover the temperature of annealing must be somewhat higher than the assumed temperature of operation. Properties of the sensor remain constant for the duration of prolonged time. It is revealed that the maximum temperature of the operation of the developed pyroelectric and piezoelectric sensors should not exceed 80 °C. It is advisable toestablish the lower boundary of the range of operating temperatures at the level of -20…-25 °C taking into account that the glass transition temperature of the PVDF amorphous phase is in the range of -40…-50 °C.

It has been found that the piezoelectric sensors produced on the basis of electrified films of polyvinylidene fluoride (PVDF) work reliably in the temperature range from –20°C to +80°C. At the operating temperature of 80°C d33 piezocoefficient decreases by 2% during two years that is permissible. At higher temperatures irreversible reduction of the piezocoefficient was observed. The lowest temperature of the working range is close to the glass transition temperature of the amorphous phase of PVDF. Annealing of the films at 80°C ensures stabile characteristics of the sensors within a few years.

From comparison of experimental results on polarization switching in fresh and electrically fatigued lead-zirconate-titanate (PZT) over a wide range of applied fields and switching times it is concluded that fatigue alters the local field distribution inside the sample due to the generation of discrete defects, such as voids and cracks. Such defects have a strong influence on the overall electric field distribution by their shape and dielectric permittivity. On this hypothesis, a new phenomenological model of polarization switching in fatigued PZT is proposed. The model assumes that the fatigued sample can be composed of different local regions which exhibit different field strengths but otherwise can be considered as unfatigued. Consequently the temporal response of a fatigued sample is assumed to be the superposition of the field-dependent temporal responses of unfatigued samples weighted by their respective volume fraction. A certain part of the volume is excluded from the overall switching process due to the domain pinning even at earlier stages of fatigue, which can be recovered by annealing. Suitability of the proposed model is demonstrated by a good correlation between experimental and calculated data for differently fatigued samples. Plausible cause of the formation of such regions is the generation of defects such as microcracks and the change in electrical properties at imperfections such as pores or voids.