Sodium alginate (NaAlg) is widely used as a food additive. To study the effect of irradiation with X-ray quanta with energies of 1253.6 eV and 1486.6 eV on the composition of NaAlg, thick films with ...a smooth surface were prepared, which did not differ in IR spectra from the original powders. The films were irradiated in a high vacuum (3 × 10−10 mbar) in the chamber of a Specs PHOIBOS 150 MCD9 XPS spectrometer with an X-ray source power of 150 W and an irradiation duration of up to 300 min, which significantly exceeded the time required to obtain an XPS spectrum. This made it possible to use XPS to monitor changes in the composition of the NaAlg surface directly during irradiation. As a result of the research, it has been established that NaAlg degrades with prolonged irradiation, which is accompanied by a significant decrease in the O/C ratio. When analyzing the dependence of the intensities of individual peaks in the C1s spectrum on the irradiation time, it was found that after 100 min of irradiation, a peak due to the carbonate group appears in the spectrum. The decomposition was also accompanied by a change in the color of NaAlg from white to yellow-brown. In the IR spectrum of the NaAlg film irradiated for 300 min, an absorption band was detected at 1910 cm−1, which is usually associated with the presence of allene groups.
Many properties of solutions to linear differential equations with unbounded operator coefficients (their boundedness, almost periodicity, stability) are closely connected with the corresponding ...properties of the differential operator defining the equation and acting in an appropriate function space. The structure of the spectrum of this operator and whether it is invertible, correct, and Fredholm depend on the dimension of the kernel of the operator, the codimension of its range, and the existence of complemented subspaces. The notion of a state of a linear relation (multivalued linear operator) is introduced, and is associated with some properties of the kernel and range. A linear difference operator (difference relation) is assigned to the differential operator under consideration (or the corresponding equation), the sets of their states are proved to be the same, and necessary and sufficient conditions for them to have the Fredholm property are found. Criteria for the almost periodicity at infinity of solutions of differential equations are derived. In the proof of the main results, the property of exponential dichotomy of a family of evolution operators and the spectral theory of linear relations are heavily used. Bibliography: 98 titles.
The electrochemical properties of the highly porous reduced graphene oxide/titanium dioxide (rGO/TiO2) nanocomposite were studied to estimate the possibility of using it as a supercapacitor ...electrode. Granular aerogel rGO/TiO2 was used as an initial material for the first time of manufacturing the electrode. For the aerogel synthesis, industrial TiO2 Hombikat UV100 with a high specific surface area and anatase structure was used, and the aerogel was carried out with hydrazine vapor. Porous structure and hydrophilic–hydrophobic properties of the nanocomposite were studied with a method of standard contact porosimetry. This is important for a supercapacitor containing an aqueous electrolyte. It was found that the hydrophilic specific surface area of the nanocomposite was approximately half of the total surface area. As a result of electrochemical hydrogenation in the region of zero potential according to the scale of a standard hydrogen electrode, a reversible Faraday reaction with high recharge rate (exchange currents) was observed. The characteristic charging time of the indicated Faraday reaction does not exceed several tens of seconds, which makes it possible to consider the use of this pseudocapacitance in the systems of fast energy storage such as hybrid supercapacitors. Sufficiently high limiting pseudo-capacitance (about 1200 C/g TiO2) of the reaction was obtained.
Introduction.
To develop new system modules of software to help employees with disabilities, it is required to work out an architectural solution for the interaction of all parts of the system. ...As a result of the analysis and design, it is necessary to obtain a software architecture that must meet a number of standard requirements. First of all, it should be safe. To do this, you should take into account the error logging system, event auditing, the possibility of disabling the functionality immediately after putting it into commercial operation, internal mechanisms for validating client input requests and server responses. This study is aimed at the development of basic system maintenance options, the analysis of exception cases under interacting with the user for further evaluation of the architecture efficiency, and the direct project development.
Materials and Methods.
The architectural decision was carried out using the Unified Modeling Language (UML), which helps to build visual images of the life cycle and interaction of all components of the system. The syntax of the UML deployment diagram was used to study the interaction of the main modules of the future system, and the syntax of the UML sequence diagram was used to process the lifecycle. A use case diagram was also applied to describe the main use cases. To study the interaction of the main modules of the future system, the UML deployment diagram syntax was used. For life cycle processing, the UML sequence diagram syntax was applied. In addition, a use case diagram was applied to describe the base use cases.
Results.
An architecture that has a scheme for the interaction of individual modules and systems, as well as options for using the software package for the future implementation of the software product, has been developed. The proposed system architecture meets the requirements of security, reliability (fault tolerance), and performance. The authors have fixed the functional requirements of the system of assistance to employees of enterprises with hearing problems for the possibility of their employment and work on the telecommunication Internet. Basic variations of system maintenance have been developed.
Discussion and Conclusions.
Building a competent architecture provides taking into account cases that go beyond the normal use of the system, and applying a fuzzy model to determine the system efficiency. Further in-depth description of deployment and operation options will enable to implement an efficient and productive system.
We present spectrum localization theorems for Dirac operators and operators with involution in a class of function spaces introduced in
Contemp. Math.,
2018, vol. 706, pp. 93–114.
A special technique has been developed for producing a composite aerogel which consists of graphene oxide and soy wax (GO/wax). The reduction of graphene oxide was carried out by the stepwise heating ...of this aerogel to 250 °C. The aerogel obtained in the process of the stepwise thermal treatment of rGO/wax was studied by IR and Raman spectroscopy, scanning electron microscopy, and thermogravimetry. The heat treatment led to an increase in the wax fraction accompanied by an increase in the contact angle of the rGO/wax aerogel surface from 136.2 °C to 142.4 °C. The SEM analysis has shown that the spatial structure of the aerogel was formed by sheets of graphene oxide, while the wax formed rather large (200–1000 nm) clumps in the folds of graphene oxide sheets and small (several nm) deposits on the flat surface of the sheets. The sorption properties of the rGO/wax aerogel were studied with respect to eight solvent, oil, and petroleum products, and it was found that dichlorobenzene (85.8 g/g) and hexane (41.9 g/g) had the maximum and minimum sorption capacities, respectively. In the case of oil and petroleum products, the indicators were in the range of 52–63 g/g. The rGO/wax aerogel was found to be highly resistant to sorption–desorption cycles. The cyclic tests also revealed a swelling effect that occurred differently for different parts of the aerogel.
Nanocomposites based on waterborne polyurethane (WPU) and graphene oxide (GO) have been synthesized and characterized. It was found that after the incorporation of GO, WPU films became mechanically ...more rigid, and the Young's modulus increased by almost six times. It is shown that the lateral size of GO sheets influences the mechanical properties of WPU/GO composites. In particular, composites with larger lateral size of GO sheets have higher values of Young's modulus. Additionally, if the mechanical properties are improved with the addition of GO additive, then water absorption decreases for WPU modified with small GO sheets whereas it increases for WPU modified with large GO sheets. Possible reasons for this behavior are discussed.
By applying Lyapunov's equation, the method of similar operators, and the methods of harmonic analysis, we obtain estimates for the parameters of exponential dichotomy and for the Green's function ...constructed for a hyperbolic operator semigroup and a hyperbolic linear relation. Estimates are obtained using quantities which are determined by the resolvent of the infinitesimal operator of the operator semigroup and of the linear relation. Bibliography: 51 titles.
Cellulose HogC was produced by the modified traditional method with 35% yield from the stem of Sosnovsky hogweed and was characterized by elemental analysis, infrared (IR) spectroscopy, powder X-ray ...diffractometry, differential scanning calorimetry (DSC) and X-ray photoelectron spectroscopy (XPS). For HogC, the degree of crystallinity (approximately 70%) and the glass transition temperature (105–108 °C) were determined. It was found that the whiteness characteristic in the case of HogC was 92% and this significate was obtained without a bleaching procedure using chlorine-containing reagents. In this paper, the possibility of hydrophobization of HogC films by treatment with radiation-synthesized telomers of tetrafluoroethylene is shown. It was found that the contact angle of the telomer-treated cellulose film surface depended on the properties of the telomers (the chemical nature of the solvent, and the initial concentration of tetrafluoroethylene) and could reach 140 degrees.
In this paper, we consider first-order differential operators with periodic boundary conditions acting in a Hilbert space of square summable functions on the segment 0
, ω
perturbed by Hilbert– ...Schmidt integral operators. A similarity transformation of the original operator to the operator of the block-diagonal structure is performed; this allows one to study spectral properties of the perturbed operator. The research method is the method of similar operators, which also presented in this work.
