Optics and Spectroscopy最新文献

The possibility of combining solid-phase extraction of natural catecholamines (adrenaline, norepinephrine, and dopamine) on a microcolumn filled with hypercrosslinked polystyrene with their subsequent spectrophotometric or solid-phase spectroscopic determination in an eluate using gold nanorods or their nanocomposites with polyurethane foam has been investigated. The desorption of catecholamines from hypercrosslinked polystyrene by various eluents has been studied. It has been shown that the quantitative elution of all three catecholamines is achieved using 6 M acetic acid, which as an eluent is well combined with the proposed determination options. The features of a dynamic sorption extraction of catecholamines from urine and blood serum have been described. It allows you to reduce the influence of the matrix components and increase the analysis sensitivity by concentrating. The average concentration coefficient is 10–56 with sample volumes of 10–300 mL. The developed methods make it possible to determine catecholamines in urine at the level of their normal content.

The article has considered the possibility of using the developed original method for estimating the parameters of photovoltaic converters (PVCs) both during the output control at the production site and during the input control carried out before the assembly and installation of solar panels. A comparison of products from different manufacturers has been performed. It has been shown that the proposed method is effective and can be recommended for use by specialized enterprises.

The dependence of energy transferred to a damped harmonic oscillator by a pulse of periodic force on pulse duration, carrier frequency, and shape of the pulse envelope is investugated. The cases of pulses with an exponential and Gaussian shape of the envelope are analyzed. Analytical expressions describing the process are obtained. It is established that the dependence of energy transferred to the oscillator on pulse duration in the case of an exponential pulse can have an inflection point, while extrema appear in the discussed dependence at sufficiently large offset of the pulse carrier frequency from the oscillator natural frequency in the case of a Gaussian pulse. It is demonstrated that the number of quanta and the amplitude of the average value of the coordinate operator upon excitation of a quantum oscillator are determined by the same dependences on the driving-pulse parameters as in the case of the classical oscillator.

This work is devoted to problems arising in calculation of parameters of surface acoustic waves (SAWs) of the main and multiple frequency harmonics using the finite element method. The technique and main features of the SAW analysis by a numerical method are considered. Simple one-wavelength test cells were chosen as the main mode of the study. It is shown that, using these SAW parameters in the analytical modified coupling-of-modes model, one can preliminarily calculate amplitude–frequency responses of SAW devices using higher-order frequency harmonics. The calculation results are compared with experimental measurements of the transfer coefficients of SAW filter and SAW delay line.

The replicated aluminum foam technology implies impregnation of the water-soluble filler (NaCl) with a melt. Products made of replicated aluminum foam have a porosity range of 40–70% and a rather high prime cost; hence, they cannot be commercially competitive as a structural material with an aluminum foam with its porosity of 80–95% and low prime cost. Still, replicated aluminum foam is recognized as an excellent functional material for transferring liquids and gases, and products from it are used as filters. The operational life before cleaning is an important operation parameter of a filtering element. It is determined by porosity, which can be increased using filler multifraction beds. However, to predict the filtering element characteristics, the number of fractions was limited to two, which makes it possible to increase porosity by 10–15%. The size of fine filler fractions was 200–400, 400–630, and 1000–1600 μm in the proportion 30, 50, and 70%, and the coarse fraction was 2500–4000 μm in size. Preparing the filler bed consists in mixing two fractions in a certain proportion and heating up the filler bed in a box resistance furnace with subsequent filling it into a metal mold and pouring with AlSi melt. Impregnation of the filler with the melt was ensured by vacuuming the mold. After crystallization of the casting, it was machined by cutting out a cylindrical sample from the bottom of the composite casting, and then the filler was dissolved in water. The coefficient of permeability of dual-sized replicated aluminum foam was experimentally studied by the nonstationary method. The additive dependence of the permeability coefficient on the proportions and permeability coefficients of monofractions is shown. Permeability coefficients of monofractions are calculated using the model of concentration of single resistances. A review of dual-sized bed permeability models is performed, and it is shown that the Kazemi model is most consistent with the experimental data obtained. A discrepancy with the experiment is evident only at a significant difference of fraction sizes, with a small size of the fine fraction, which is caused by the loosening effect. The obtained results make it possible to design filtering elements with a higher porosity.

A mathematical model of microwave heating of the deformation joint of a rigid airfield coating has been presented. The development of the temperature field has been studied numerically on the basis of calculations of the distribution of the electric field intensity generated by the radiation source. The simulation results have been compared and confirmed by experimental data obtained by direct measurements in a specially designed model microwave heating system.

It is assumed that an electric charge moving along a circular path, i.e., with centripetal acceleration, necessarily emits photons. The purpose of this work is to establish the conditions for the radiation of an electric charge proceeding from significant differences between its tangential and centripetal accelerations. Materials and methods. The starting point is a credible statement. A number of mathematically correct transformations are performed with it. Therefore, the result is necessarily reliable. Since electromagnetic radiation carries away energy, the energy of the radiating system changes during radiation. Associated with this is the following well-known rule: change in energy is equal to the work performed. The research results can be used in the construction of theoretical models of phenomena and processes, as well as considered in technical applications.

The Young’s single- and double-slit experiments are explained using six-component quantum and one-component quasi-classical photon wave functions in the coordinate representation, which are modeled by different mechanisms of photon diffraction on slits or simultaneous emission of two photons by (two) independent sources. This explanation is compared with the well-known statement about the interference of a particle with itself when passing through both slits simultaneously in the Young’s experiment on the basis of the postulated Feynman amplitudes. It is argued that these amplitudes cannot be wave functions, in the literal sense, describing some states of quantum particles. In all cases, under the assumption of the linear polarization of photons, a pronounced interference pattern has been obtained, which suggests that the coordinate wave function of a photon can explain the phenomena of the one- and two-photon interference. This conclusion, in turn, makes it possible to associate the coordinate wave function of a photon (two photons, in the entangled state) measured in some recent experiments with the quasi-classical wave function of a photon (two photons), although it does not take into account its (their) polarization properties.

Based on the known differential and integral equations of the balance of forces acting on a spring pendulum, an algorithm for calculating the amplitude of its vibrations is considered when the natural vibration frequency coincides or is close to the vibration frequency of the coerced force of a vibrating centrifugal separator. An example is given how to calculate the vibration amplitude of a vibrating centrifugal separator depending on the spring elasticity coefficient, the vibrating mass, and the resistance of the medium in which the vibrating mass is suspended.

The problem about heat propagation from a transient point heat source located inside or outside a plane layered heat-conducting medium is studied. The transient problem is reduced to the harmonic point heat source problem for which the reflection method is generalized. The developed reflection method for a point harmonic source is generalized to the case of an arbitrary system of sources and applied to solving problems of transient heat conduction of plane layered media with axially symmetric heat sources with a complex shape.