The influence of the relative position of a magnetron and substrate on the electrical and optical properties of a forming indium–tin oxide (ITO) layer is shown. The reasons for this behavior are ...considered and the role of oxygen in the occurrence of inhomogeneities in the properties of ITO films is shown. It is shown that in the growth mode without the supplementary addition of oxygen, the resistivity of ITO films differs by an order of magnitude ((2–14) × 10
–2
Ω cm) for different positions of the substrate on the substrate holder along the radius in the range of 0–14 cm. In this case, differences in the shape of the short-wavelength spectral region are observed in the absorption spectra. The addition of a small (0.1 sccm) amount of oxygen to the working chamber during oxide growth leads to a significant increase in the uniformity of the electrical and optical properties of ITO films.
Adsorption heat pumps are an alternative way of heat and cold generation. Due to the high adsorption capacity and high specific energy storage capacity, the SWS-1L adsorbent can be efficient in ...adsorption heat pumps. The physicochemical properties of various adsorbents and kinetics of adsorption and desorption of vapors of working fluids based on them have been studied quite well, and methods have been developed to optimize the efficiency of cycles with consideration of a large number of determining parameters: properties of adsorbent, temperature, pressure, and geometric parameters of the adsorbing heat exchanger. However, there is little experimental data on the change with time in the temperature of the free surface of a layer of adsorbent granules. It is important to know how this temperature varies for accurate calculation of the heat transfer parameters. The work shows that at the beginning of heating, the surface temperature of the heat exchanger (metal) without an adsorbent increases to a quasi-stable value within 40–45 s. In the presence of the adsorbent, this time almost doubles and corresponds to 70–75 s. Increase in the thermal fluid flow from 0.65 l/min to 2.7 l/min (4.1 times) leads to a 3.8-fold decrease in the heating time of the heat exchanger with the adsorbent (also approximately 4 times). The characteristic time of thermal inertia (along the thickness of the heat exchanger wall and along the height of the adsorbent layer) without and with the adsorbent is 0.5–1 s and 4–6 s, respectively. The growth of the thermal fluid velocity leads to a significant reduction in the heating time of the heat exchanger and adsorbent and can also reduce the desorption time in a heat pump.
Abstract
In this work last results on optimization of (p)a-Si:H/p-Si ohmic contact made by PECVD method are presented. A strong effect of growth temperature and trimethylboron flow on charge carriers ...transport was demonstrated. An optimized (p)a-Si:H layer also was successfully applied as an emitter layer to a heterojunction solar cell fabrication where a measured open circuit voltage of 0.65 V was obtained.
The effect of structure of 25 aromatic compounds on the morphology of carbon formed from them during heating to a temperature of 970°C in an inert atmosphere is studied. The specific surface area is ...determined for a number of products via nitrogen adsorption (28–48 m
2
/g). Several aromatic compounds are shown to form carbon without melting stage. X-ray phase analysis nevertheless confirms the formation of just amorphous carbon in all cases, and a negligible amount of graphite in amorphous carbon in only two cases. The thermolysis of a number of compounds is studied via synchronous thermal analysis. It is shown that slow heating during thermolysis can reduce the temperatures of transformation by tens of degrees and even alter the nature of thermolysis.
Abstract
We propose a simple integrated resonant structure for the Bloch surface wave platform, which consists of two subwavelength grooves patterned on the surface of a one-dimensional dielectric ...photonic crystal. We demonstrate that the investigated structure can operate in a parasitic-scattering-free regime and, in this case, provide unity transmittance and zero reflectance at resonance conditions associated with the excitation of a leaky mode of the structure localized at the central ridge formed by the grooves. The proposed structure may find application in integrated photonic devices for optical filtering and analog optical computing.
We demonstrate synthesis and theoretical study of the optical properties of Au:SiO2 nanocomposite thin films. Localized surface plasmon resonance peak induced by Au NPs was clearly observed in ...optical spectra at wavelength range between 500 and 600 nm. Intensity and position of PL peak are demonstrated to depend on the Au NPs embedding depth.
Insufficient sleep could severely impair both cognitive and learning skills. More prominent changes are found in children and adolescents. Tools used to estimate sleepiness in the adult population ...are commonly inappropriate for children. The objective of our study was to provide a reliable instrument to measure excessive sleepiness for upcoming studies in Russian-speaking children, applying the Russian version of Pediatric Daytime Sleepiness Scale (PDSS). The following tasks were resolved in our study: translation, validation, and analysis of psychometric properties of the Russian adaptation of the PDSS by standard tests. After the semantic validation of the instrument through a multi-stage translation process we checked its psychometric validation. A total of 552 students, consisting of N = 285 for the exploratory factor analysis (EFA), N = 267 for the confirmatory factor analysis (CFA) and N = 204 for test-retest analysis of public elementary schools located in Northern Russia completed the PDSS and Munich Chronotype Questionnaire to estimate sleep parameters in the classroom during the lessons. Response rate was 90%; excluded cases contained no data. Further, 204 of our participants completed the PDSS in a 3 months interval to check the test-retest reliability. Internal consistency was measured by Cronbach's alpha coefficients and CFA was used to test factorial validity of the tool. Concurrent validity and test-retest reliability were assessed via intra-class coefficient. Internal consistency of the PDSS scale was high (Cronbach's α = 0.8). The construct validity of the PDSS was supported by CFA (factor loadings were from 0.438 to 0.727) and the test-retest reliability demonstrated by the intra-class coefficient was 0.70. The total PDSS score was independent of sex. The mean total value of PDSS was 11.95 ± 6.24. Higher scores on PDSS were negatively correlated with sleep duration. Thus, the construct validity of the instrument remains valid and could be used for Russian-speaking youth samples in the evaluation of daytime sleepiness. It could be useful in future applications by sleep scientists and health practitioners.
Currently semiconductor lasers in the wavelength range from 20 to 60 μm are scarce. HgTe/CdHgTe heterostructures is a potential basis for alternative sources of coherent radiation in this range. We ...propose that in such structures carrier heating is the main mechanism, which quenches stimulated emission under high excitation intensity. Lower-energy optical excitation is one way to reduce this negative effect. We compare output power vs excitation intensity at pumping wavelengths of 2.3 and 10.6 μm. Comparison shows that longer wavelength leads up to 3 order of magnitude higher total output power at the same number of photons in pulse. At the same time, for structures designed for the wavelengths above 20 μm, the heating is observed even under 10.6 μm pumping. We debate excitation by quantum cascade lasers with low energy of photons to be the main route for further development of HgTe/CdHgTe sources for 20–60 μm wavelength range.
Highly stable trityl-nitroxide biradicals were synthesized, which are promising for the use as polarizing agents for dynamic nuclear polarization (DNP) in reducing environments, such as living cells. ...The EPR spectra of the biradicals were studied, parameters of hyperfine and exchange interactions were obtained, and the dipole—dipole interaction values were estimated using the results of conformational analysis. The reduction kinetics of the synthesized biradicals by ascorbic acid in a model medium were measured. Prospects for application of the biradicals for DNP in various magnetic fields based on the ratio of the exchange and dipole—dipole interactions are discussed.
On the basis of a geometrically nonlinear model of a Bernoulli-Euler beam, the influence of the amplitude and shape of the initial curvature on the nature and stability of the static equilibrium ...positions of the system under conditions of electrostatic and thermal effects has been studied. With the help of numerical methods of the theory of bifurcations, a complete parametric analysis of the diagrams of evolution of the equilibrium positions for beams with initial curvature in terms of symmetric and asymmetric lower modes of free vibrations is conducted. The regions in the parameter space of the values of the axial force of a mechanical or temperature nature and the strength of the electrostatic field, in which the elastic system has the property of bistability, are determined. The prospect of using the considered class of structures with projected geometry perturbations as sensitive elements of high-precision microelectromechanical sensors of various physical quantities is noted.
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