Part Of Constant Research Articles

Электрофизические свойства композитов на основе полиэтилена низкой плотности и цеолитового менерала, модифицированных гамма-излучением

Dielectric parameters (ε′, tgδ) and electrical conductivity (σ) of composite samples of LDPE 60 vol. %/Zeolite 40 vol.% and LDPE 40 vol. %/Zeolite 60 vol. % γ-irradiation dose of 50 – 300 kGy in air, was measured in the temperature range 293 – 403 K and at frequencies 25 – 106 Hz. Composites based on a homogeneous mixture of LDPE with powdered natural zeolite (clinoptilolite and heulandite — Agdag deposits, Azerbaijan) were obtained in the form of film samples 140 – 200 μm thick and 20 mm in diameter by hot pressing at a temperature of 403 – 413 K and a pressure of 15 MPa, followed by quenching them in an ice-water mixture. The temperature dependence of the electrophysica parameters of the composite samples made it possible to reveal that the real part of the dielectric constant (ε’), dielectric losses tgδ and electrical conductivity с decrease with an increase in the filler content, and this is associated with an increase in the concentration of charge carriers and their mobility after exposure to γ-irradiation with a dose 50 – 300 kGy. The study of the frequency dependences ε′ = ƒ(lgν), tgδ = ƒ(lgν) and lgσ = ƒ(lgν) of the samples modified by γ-irradiation showed the presence of two linear regions of the frequency dependences of the electrical conductivity, observed as in unirradiated samples, which have lower values ​​and change according to the law σac(ν) ~ ν0.73, and this is more consistent with the hopping mechanism of electrical conductivity of LDPE / zeolite composites.

Soil Moisture Retrieval Over Bare Soil Surface From Single-Polarization SAR Data by Combining Neighborhood Pixels

The objective of this letter is to extend a method proposed by Kweon et al. to retrieve soil moisture (m_v) over bare soil surface by combining neighborhood pixels of single-polarization synthetic aperture radar (SAR) data. This letter uses single-polarization (HH, VV) SAR data to simultaneously retrieve the root-mean-square (rms) height (h_rms) and the real part of the relative dielectric constant (ε_s) which can be converted to soil moisture content. For the copolarization SAR data, the letter first uses the Integral Equation Model (IEM) and the semiempirical calibration of the correlation length (L) to obtain the probability distribution curve of rms height and the real part of the relative dielectric constant for each neighborhood pixel. Then, these probability distribution curves are placed on the ε_s-h_rms plane, and the juxtaposition model is applied to obtain the average value of estimations of neighborhood pixels. The average soil moisture estimations of neighborhood pixels in farmlands are compared with the in-situ measurements with the RMSE equal to 0.036 cm³/cm³ and the correlation coefficient equal to 0.84 at VV polarization in the L band, which demonstrates that the proposed method is suitable to invert soil moisture with acceptable accuracy and high resolution. However, volume scattering contribution from crops can decrease the performance of the proposed method.

Durability and strength properties of concrete by using egg shell powder and copper slag

Natural resources of construction materials decreasing rapidly due to rise in demand in the construction field. In order to overcome this issue in an economical manner, utilization of alternative eco- friendly materials could be better choice to minimize the demand to some extent. Copper Slag is a consequence material originated from copper manufacturing progression and Egg Shells grounded to fine powder. This paper reports on mechanical and durability properties of M25 grade concrete to ascertain strength parameters trials were exhibited on account of Compression, split tensile under stipulated loading, Egg shell powder (ESP) as partial replacement to cement by equal interval 0–20% with an off set of 5% and also copper slag as partial replacement to fine aggregate by equal interval 5–25%. Concretesamples were inspected at 7, 14, and 28 days after curing, and acid attack trial accomplished under durability trial led on changing the extents of Copper Slag (CS) with fine aggregates up to 25%. A blend of 10% Egg Shell Powder (ESP) and 90% cement resulted with higher value under compression with that proportion kept constant fine aggregate part substituted by Copper Slag (CS), rise in strength was noted, optimal value attained at 15% Copper Slag (CS) and 85% sand.

Battery-Ultracapacitor Hybrid Energy Storage System to Increase Battery Life Under Pulse Loads

This work presents a battery-ultracapacitor hybrid energy storage system (HESS) for pulsed loads (PL) in which ultracapacitors (UCs) run the pulse portion of the load while the battery powers the constant part of the load. Energy stored in UC depends upon the square of its voltage that’s why an active parallel hybrid topology with two bidirectional converters (BDC) is employed here that assigns UC a separate BDC to control its voltage between an upper and lower limit as per-requisite. The other converter is connected between the battery and DC-link to provide a distinct control of the battery. A MATLAB/Simulink model is developed to minimize the factors affecting the battery life such as capacity rate (C-rate), depth of discharge (DoD), and temperature rise due to PL by controlling the operating modes of the BDCs in which voltage of the UC and state of charge (SoC) of the battery are control variables. A constant output voltage across the load is maintained through feedback control. A detailed comparative analysis, among battery-alone, UC-alone, and battery-UC hybrid modes is performed which signifies that the proposed system is 55% lower in cost than its counterparts. The analysis shows that the proposed HESS reduces 50% capacity of a lead-acid battery, which is otherwise necessary to withstand the pulsating loads. Moreover, the performance of the HESS is also tested for electric vehicle (EV) load by hybridizing a high-voltage lithium-ion battery pack with a UC bank which confirms its suitability for EV applications.

Paramedics’ educational needs regarding cultural competence: cross-sectional study of selected two regions of Poland

INTRODUCTION: Approximately 743 700 foreigners reside permanently in Poland, and 180.2 million visit Poland every year. Paramedics should be prepared to assist foreigners whose expectations and needs related to their culture may be different than those typical of Poles. Education on cultural competence should therefore be a part of both undergraduate education and professional development. The aim of the study was to assess the educational needs of paramedics working in the National Medical Emergency System in terms of cultural competence. MATERIAL AND METHODS: The study group consisted of all paramedics working in National Medical Emergency System in the Subcarpathian and West Pomeranian provinces. Responses were obtained from 563 out of the total of 2229 participants invited to participate in the study. The questionnaire used to study the educational needs of paramedics was created by a team of executors of the international project Multicultural Care in European Intensive Care Units (MICE-ICU) and adapted to study paramedics. RESULTS: Paramedics from the Subcarpathian province (M = 3.56; SD = 0.67) reported greater educational needs in terms of cultural competence than their colleagues from the West Pomeranian province (M = 2.84; SD = 0.82, p < 0.001). In the Subcarpathian province, 80.4% of paramedics declared willingness to improve their knowledge of foreign languages, while in the West Pomeranian province this number amounted to 45.9%. In both provinces, paramedics with MSc in another field of study and BSc in emergency medical services reported greater educational needs compared to paramedics with lower education. In the Subcarpathian province, the preferred form of education was a conference (60.8% of respondents), while in the West Pomeranian province the respondents opted for workshops with experts representing various ethnic and religious groups (39.4%). The percentage of paramedics interested in online courses on multicultural emergency medicine was 41.74%. CONCLUSIONS: The study demonstrated that paramedics from provinces located on opposite ends of the country who had contact with different groups of foreigners have great educational needs in the field of cultural competence and education in this area should be a constant part of professional development. Conferences and workshops are the preferred form of education.

Shielding performance of MnxNi0.8–xZn0.2Fe2O4 (0.1≤x≤0.7) for electromagnetic interference (EMI) in X-band frequency

A series of MnxNi0.8–xZn0.2Fe2O4 (0.1≤x≤0.7) nanoferrites were prepared by sol-gel auto combustion method. The TGA-DSC studies revealed the weight loss up to 700 °C and after no weight loss was found confirming the complete ferrite phase. Therefore, the as-burnt samples subjected to conventional sintering at 900 °C for 2h. The traces of XRD patterns revealed that formation of ferrite phase co-existed with secondary phases. The complex permittivity and permeability of present ferrite systems are found to be dependent of Mn2+ ion concentration. The real part of dielectric constant (ε′) for the all compositions are in the range of 5.184–6.951 at 8.2 GHz while it is 5.269–7.663 at 12.4 GHz. The values of ε′ at 8.2 GHz are slightly lower than the values at 12.4 GHz. The imaginary part of dielectric constant (ε″) was found to be in the range of 0.046–0.315 for all compositions over the entire range of X-band frequency (8.2–12.4 GHz). Compared to the variation of ε′, the variation of ε″ is more disorder. The number of semicircles in Cole-Cole plots is a witness of multiple di-electric relaxations of EM energy dissipation. The real part of magnetic permeability (μ′) is increasing, while imaginary part of magnetic permeability (μ″ ) is decreasing for all compositions as frequency is increasing from 8.2 to 12.4 GHz. Compared to the other ferrite compositions, the ferrite with low content of Mn2+ i.e. Mn0.1Ni0.7Zn0.2Fe2O4 ferrite system has higher value of μ″ and seems to be invariant over the entire X-band frequency range. The total effective shielding (SET) for all compositions is found to be in the range 37–12 dB. The highest values of SET 37 dB at 8.2 GHz and 28 dB at 12.4 GHz were reported for the ferrite composition Mn0.1Ni0.7Zn0.2Fe2O4. The shielding studies revealed that Mn–Ni–Zn ferrite systems are effectively suppressing electromagnetic interference (EMI) in X-band frequency. Comparatively, the ferrite system Mn0.1Ni0.7Zn0.2Fe2O4 is useful for the fabrication of EMI suppressor.

Ecotoxicological parameters of safe application and adaptation of chemical protection systems against harmful organisms in apple orchards to the soil and climatic conditions of the Precarpathian province of Carpathian mountain zone of Ukraine

Goal. Ecotoxicological and economic substantiation of chemical systems of apple protection against harmful organisms, their optimization and adaptation to weather and phytosanitary conditions of apple agrocenosis in the Precarpathian province of the Carpathian mountain zone of Ukraine.
 Methods. Phytosanitary monitoring was performed visually and using pheromone traps. Classification of pesticides by polarity, determination of residues, study of pesticide detoxification processes in the apple agrocenosis were performed using physico-chemical methods of analysis according to officially approved methods. The degree of hazard of pesticides was assessed by an integrated 7-point scale, the risk — by agroecotoxicological index (AETI).
 Results. The ecotoxicological characteristics of pesticides of modern assortment used to protect apple trees from pests and diseases were determined: the value of the dipole moment (µ), the detoxication rate constant (parts per day), the period of semi- and complete decomposition (T50 and T95, days) in the apple agrocenosis, the classification according to the degree of hazard of their use was carried out. The most dangerous are non-polar compounds of 1—3 degrees of hazard and partially low-polar of 4 degree, which belong to the I and II class of danger in terms of toxicity (LD50 ) or persistence (k). According to the monitoring of phytosanitary conditions and pesticides in the apple agrocenosis in 2015—2020, scientific and methodological parameters of ecologically safe (AETI <1) and cost-effective systems of chemical protection of apple adapted to soil and climatic conditions of the Precarpathian province of the Carpathian mountain zone of Ukraine were developed: chemical, advanced chemical.
 Conclusions. Based on the co-measurement of pesticide load with the ability of agrocenosis to self-cleaning, a model of ecologically safe protection of apple orchard from a complex of pests which is adapted to soil and climatic conditions and phytosanitary conditions of Precarpathian province of Carpathian mountain zone of Ukraine was developed. According to research, the rate of detoxification of pesticides in the leaves and fruits of apple depends on their physicochemical properties and correlates with the polarity of the compounds. The classification of pesticides used to control the complex of pests and diseases in the apple agrocenosis was shown. It was shown that modern assortment of pesticides allows to develop protection systems with weighted average degree of hazard at the level Q=5. A model of the maximum pesticide load on the apple agrocenosis, in which the AETI does not exceed 1, has been developed. Investigations and calculations showed that the chemical protection of apple is ecologically and economically viable. In the conditions of 2018—2020, the profit was at the level from forty thousands to ten thousands UAH/ha, with a profitability of 32.4—76.5%.

Optimization of road design via the use of a queueing model with transit and local users and processor sharing discipline

A problem of the optimal choice of the number of lanes and admission control in the road that is shared by the local and transit vehicles is considered. The operation of a road is modelled by the type queue with two types of customers. The service of type-2 (local) customers is mandatory. Type-1 (transit) customers can use alternative routes and, therefore, abandon or interrupt service in the considered system. All admitted customers are serviced simultaneously. A customer receives a constant part of a server bandwidth if the number of customers does not exceed a predefined in advance threshold and the reduced part, otherwise. The stability condition is derive and the stationary distribution of the system states is computed. A potential application for optimizing the number of lanes in the road is numerically illustrated.

Dielectric relaxation and optical propeties in ferroelectric bis(methylammonium) tetrachloro zincate single crystal

Bis (Methylammonium) tetrachlorozincate [MAC-Zn] is a well-known ferroelectric crystal. The crystal was synthesized by slow evaporation technique at room temperature. The grown crystal when subjected to single crystal X – Ray diffraction reveals that it belongs to monoclinic system. Dielectric properties, impedance spectroscopy and optical properties were analyzed. The variation of dielectric constant, dielectric loss, real and imaginary part of dielectric modulus were explored at different temperatures and frequencies. The yielded crystal exhibits Debye – type relaxation behavior and Correlation Barrier Hopping (CBH) conduction mechanism. The Debye phonon frequency and Debye temperature were calculated using dielectric studies. The resistance of the MAC-Zn crystal was determined using impedance spectroscopy. The theoretical calculation of optical transmittance, reflectance, refractive index, electrical conductivity, optical conductivity, electrical susceptibility and optical polarizability were calculated using optical studies and the results were discussed elaborately.

Structural and optical characterization of Mg2SiO4 and Mg2SiO4-Pr6O11 nanocomposite for optical devices

The knowledge on optical properties of magnesium orthosilicate (Mg2SiO4) and its composite materials are very important as these silicate-based materials play a significant role in the field of optics and electronics. Mg2SiO4 nanomaterial and Mg2SiO4-Pr6O11 nanocomposite materials were therefore chosen in the present study, and they were synthesized in the present work, by simple sol-gel route. Powder x-ray diffraction (PXRD) pattern, Fourier-transform infrared (FT-IR) spectroscopy and ultraviolet–visible (UV–vis) spectroscopy techniques were adopted to understand the structural and optical properties of the prepared samples. The crystalline size of the two samples were estimated using Debye–Scherrer's equation and they are found to be 43 nm (Mg2SiO4) and 52 nm (Mg2SiO4-Pr6O11). The FT-IR results of Mg2SiO4-Pr6O11 revealed the SiO4 stretching and PrO vibrations clearly. The optical absorbances were used to determine the absorption coefficient α and hence the optical band gap energies Eg whose values are 5.60 eV and 5.17 eV for the samples Mg2SiO4 and Mg2SiO4-Pr6O11 respectively. Further with the help of UV–Vis spectra, the refractive index (n), extinction coefficient (k), optical conductivity (σ), real and imaginary part of dielectric constant (ε′ and ε''), volume energy loss function (VELF), surface energy loss function (SELF), linear susceptibility and non-linear susceptibility were investigated with respect to the incident photon energy. The Urbach energy was calculated using ln α vs graph and they are found to be 21 meV and 265 meV for Mg2SiO4 and Mg2SiO4-Pr6O11. The non-linear optical properties of the samples were also discussed by deriving the linear and non-linear optical susceptibilities and by exploring the possibilities of usage of this composite in optical devices.

Effect of the cobalt ferrite and carbon fiber powder doping ratio on the electromagnetic properties of coated polyaniline-based polyester–cotton fabric

In this project, firstly, polyaniline-based polyester–cotton fabric was prepared by in situ polymerization using polyester–cotton fabric as the base fabric, aniline as the monomer, ammonium persulfate as the oxidizer, and camphor sulfonic acid as the dopant. Secondly, cobalt ferrite/carbon fiber powder-coated polyaniline-based polyester–cotton fabric was prepared by the textile coating process using polyaniline-based polyester–cotton fabric as the base fabric, PU2540-type polyurethane as the adhesive, and cobalt ferrite and carbon fiber powder as functional particles. Finally, the effect of the cobalt ferrite and carbon fiber powder doping ratio on the shielding effectiveness, reflection loss, dielectric constant real part, imaginary part, and loss angle tangent of cobalt ferrite/carbon fiber powder-coated polyaniline-based polyester–cotton fabric was studied by using the controlled variable method with emphasis on the cobalt ferrite/carbon fiber powder doping ratio. The results show that in the frequency range of 0.01–3.0 GHz, when the doping ratio of cobalt ferrite to carbon fiber powder is 0:3, the reflection loss of cobalt ferrite/carbon fiber powder-coated polyaniline-based polyester–cotton fabric reaches the minimum value at 1.49 GHz, the minimum reflection loss is –21.4 dB, and the effective absorption band is 1.25–1.94 GHz. In the test band, the shielding efficiency, reflection loss, the real part and imaginary part of the dielectric constant, and the loss angle tangent of the carbon fiber powder-coated polyaniline-based polyester–cotton fabric are larger than those of cobalt ferrite-coated polyaniline-based polyester–cotton fabric. The smaller the doping ratio of cobalt ferrite to carbon fiber powder, the larger value of the shielding efficiency, reflection loss, the real part and imaginary part of the dielectric constant, and loss angle tangent of the cobalt ferrite/carbon fiber powder-coated polyaniline-based polyester–cotton fabric.

Phase transition impact on electronic and optical properties of Fe-doped MoSe2 monolayer via N2O adsorption

Electronic and optical properties of Fe-doped MoSe 2 monolayer with (without) N 2 O gas adsorption are reported in this paper. The impact of N 2 O gas adsorption on both the properties (electronic, optical) is significantly observed as compared to their pristine MoSe2 monolayer (ML) counterpart. The adsorption energy (Eads) is −0.40 eV for N 2 O/Fe-doped MoSe 2 ML followed by charge transfer of 8.00e for the electronic property. Similarly, for Fe-doping on MoSe 2 ML a phase transition from semiconducting to metallic (2H →1T) behavior, is displayed from the band structure analysis. Later, after N 2 O gas adsorption, semiconducting (2H) behavior is regained due to high electron affinity of Fe-atom, as analyzed from its band structure. Moreover, the work function is modulated from 5.73 eV for pristine MoSe 2 ML, to 4.12 eV for Fe–MoSe 2 ML and 4.06 eV for N 2 O/Fe-doped MoSe 2 ML post gas adsorption respectively. Further, the imaginary part (ε 2 ) of dielectric constant is shifted from 2.38 to 6.83 arbitrary unit (a.u.) from pristine to N 2 O/Fe-doped MoSe 2 ML, respectively. Noticeably, the refractive index is altered from 1.54 to 6.6 a.u. while absorption index is varied from 1.07 to 0.00 a.u. showing its potential ability to absorb light in the visible region. Lastly, this nature is again confirmed from orbital and molecular level interaction in total density of states plots. This increases its utility to be used for different photovoltaic applications such as photo detectors and display devices. • A novel N 2 O gas was chosen for study, that has not been reported on either MoSe 2 or MoS 2 monolayers. • Doping of Fe-atom remarkably improves the electronic and optical properties than the other reported doped (Pd, Ag, Co) systems on MoSe 2 monolayer for gas sensing. • There is phase transition observed and analyzed for both Fe-doped MoSe 2 monolayer and N 2 O/Fe–MoSe 2 ML.

Dielectric and microwave absorption properties of polymer‐derived TiC/SiC/SiOC multiphase ceramics in X band

AbstractPolymer‐derived TiC/SiC/SiOC ceramics were prepared using tetrabutyl titanate (TBT)‐modified polysiloxane (PSO) as precursor. The effects of heat treatment temperature and TBT content in precursor on the microstructure, phase composition, and microwave absorbing properties of TiC/SiC/SiOC ceramics were investigated. The crystallinity of the ceramics increases with the increase of heat treatment temperature. With the increase of TBT content, the TiC content of the ceramics increases and the SiC content decreases. When the TBT content ranges from 1 to 5 wt.%, the increase of TBT content has little effect on the real part of the dielectric constant of TiC/SiC/SiOC ceramics. When the TBT content is 7 wt.%, the imaginary part of the dielectric constant of the ceramics changes. For TiC/SiC/SiOC ceramic obtained from the pyrolysis of PSO‐TBT precursor with 7 wt.% TBT, the dielectric constant is within the target electromagnetic parameters. Therefore, it has an effective absorption bandwidth of 4.2 GHz, covering the entire X band, showing an excellent microwave absorbing performance.

Elements of Precarious Employment in the Work of Scientifc and Pedagogical Workers

The paper highlights the problem of the growth of the segment of precarious employment in the work of researchers and the faculty, who work mainly in scientific and educational institutions (scientific and pedagogical workers). Besides the elements of precarious employment characteristic of the category of workers under consideration, the author considers the fixed-term nature of labor relations and the low level of the conditionally constant part of wages in the general structure of wages of scientific and pedagogical workers, which can be attributed to the legal prerequisites for the deterioration (precarization) of their labour regulation. In addition to the acts of federal legislation regulating the labor of scientific and pedagogical workers, the author analyzes the provisions of the relevant acts of social partnership for the period from 2015 untill 2023. The author highlights the problem of increasing the types of work included by the employer in the employment of the “second half of the day” of scientific and pedagogical workers without paying additional wages. The lack of legal regulation of the distribution of types of work performed by a scientific and pedagogical worker within a 36-hour working week is also noted by the author among the legal preconditions that, with appropriate law enforcement, worsen the conditions of employment of such workers due to the significantly increasing proportion of time that workers spend on achieving performance indicators and efficiency determined by the employer. In the conclusion of the paper, the author justifies amendments to the legislation in terms of regulating a fixed-term employment contract, establishing the share of guaranteed wages in the overall structure of wages, regulating the types of work included in the working hours of scientific and pedagogical workers at the level of a by-law, which cumulatively will promote sustainability of employment conditions for employees and improve their legal status.

Giant Goos-Hänchen shifts controlled by exceptional points in a PT-symmetric periodic multilayered structure coated with graphene

We theoretically study the Goos-Hänchen (GH) shifts of Gaussian beams reflected in parity-time (PT) symmetric multilayered structure coating graphene structures. And there are the exceptional points (EPs) in this structure, whose position can be adjusted by the real part of the dielectric constant and the incident angle. Moreover, we find that the value and direction of the GH shifts change significantly under different EPs, so we could control the GH shifts by the position of the EPs. When the dielectric constant is fixed, the GH shifts can also be adjusted by the Fermi energy of graphene and the period number of the PT-symmetric structure. With the increase of the period number of the PT system, the system will produce the Bragg resonance, which refers to the phenomenon of total reflection caused by the interaction between the wave and the periodic structure with a specific frequency. And at the Bragg resonance, the special GH shifts independent of the incident direction can be obtained with large reflectivity. In addition, the incident direction of the beam can also affect the GH shifts in this asymmetric structure. Our results may find great applications in highly sensitive sensors, optoelectronic switches, and all-optical devices.

Integrable cosmological models with an additional scalar field

We consider modified gravity cosmological models that can be transformed into two-field chiral cosmological models by the conformal metric transformation. For the R^2 gravity model with an additional scalar field and the corresponding two-field model with the cosmological constant and nonstandard kinetic part of the action, the general solutions have been obtained in the spatially flat FLRW metric. We analyze the correspondence of the cosmic time solutions obtained and different possible evolutions of the Hubble parameters in the Einstein and Jordan frames.

Influence of Mg doping on the structural, electrical and dielectric properties of Co-Zn nanoferrites

Mg-Co-Zn nanoferrites of composition MgxCo0.5Zn0.5Fe2−xO4 (x = 0.25, 0.5, 0.75 and 1.0) were successfully synthesized by using a citrate precursor method. After synthesis, the samples were examined using different techniques for structural, morphological, electrical and dielectric characterizations. All the samples were found to have single phase spinel cubic structure with Fd-3m space group in the X-ray diffraction spectroscopy (XRD) investigation. The value of average crystallite size ranged from 37 to 47 nm with the increase in Mg ion concentration from x = 0.25 to 1.0. The hopping lengths at tetrahedral and octahedral sites showed an increasing behaviour with increasing magnesium ion concentration. The presence of tensile strain in the samples was confirmed by W-H plots. The dielectric behaviour of the prepared nanoferrites was recorded at room temperature in the frequency range 10 kHz–10 MHz. The real part and imaginary part of the dielectric constant were found to be in the range 3.80–7.93 and 0.0036–0.644 at 1 MHz frequency and the value of loss tangent was 0.00095–0.081 at 1 MHz for the magnesium doped Co-Zn nanoferrites. The value of loss tangent decreased very sharply to remarkably low values at 10 MHz frequency. The dc resistivity value was found very low in the range 3.2 × 108 Ω-cm to 4.0 × 109 Ω-cm for different concentrations of Mg2+ ions in the samples. Due to such low losses at high frequency region and high value of dc resistivity, these materials can be considered as potential candidate for high frequency applications.

Effect of Al doping on morphology and optical properties of spray pyrolized MgO thin films

Thin films of magnesium oxide (MgO) and aluminium (Al) doped MgO were deposited onto glass substrate at 350 °C by spray pyrolysis technique. The microstructure, morphology and optical properties of the MgO films have been investigated and characterized as a function of Al doping concentration (0–2) mol%. X-ray diffraction study confirms the successful fabrication of MgO thin films. The surface morphology of the films reveals that the morphology of the MgO films greatly changes with Al doping concentration. The optical properties like optical transmittance, optical band gap, refractive index, extinction coefficient, real & imaginary part of the dielectric constant, electron energy loss function and optical conductivity have been characterized and discussed. It has been found that the optical properties of MgO films have been changes significantly with Al doping concentration.

Studies on structural and dielectric properties of NbO[formula omitted]-Nb[formula omitted]O[formula omitted] thin-film-based devices

The thin-film composition of NbO2 and Nb2O5 with excellent homogeneity are deposited using reactive sputtering technique by controlling oxygen flow rate in the Ar/O2 plasma ranging between 4 to 8 sccm. All the deposited films have been characterized using x-ray reflectivity (XRR), x-ray photoelectron spectroscopy (XPS) and Field Emission Scanning Electron Microscopy (FE-SEM) technique. Further, cross-sectional transmission electron microscope (TEM) and Energy-dispersive X-ray spectroscopy (EDX) were performed on one sample. Dielectric properties of Niobium oxide thin-film-based metal–oxide–semiconductor (MOS) devices also have been studied at frequencies ranging from 1 to 106Hz. The studies indicate that NbO2 content in the NbO2-Nb2O5 film decreases with the oxygen content in the plasma. The real (ε′) and imaginary (ε′′) part of dielectric constant, dissipation factor (tanδ) and ac conductivity (σac) are found to be dependent on the oxygen content in the film. The distribution parameter (α), mean relaxation time (τ0) and molecular relaxation time (τ), derived from Cole–Cole plot also vary with the oxygen content. In brief, oxygen vacancy and grain boundaries play vital role in exhibiting different electrical properties of the devices.

Machine learning approach to transform scattering parameters to complex permittivities

This study investigates the application of artificial neural networks to determine the complex dielectric material properties derived from experimental VNA scattering parameter measurements. The study utilizes a finite element approach to synthetically generate data to train the neural network. The neural network was trained using a supervised learning approach and validated using experimental measurement data. The frequency range of interest was between 0.1 and 13.5 GHz with the real part of the dielectric constants ranging from 1 − 100 and the imaginary part ranging from 0 − 0.2. This modelling approach decreases the uncertainty when compared to existing inverse approaches. This approach demonstrates a general framework that can be used for converting experimental or computational derived scattering parameters to complex permittivities.