Vibrational resonance in a driven two-level quantum system, linear and nonlinear response

We consider a two-level quantum system interacting with two classical time-periodic electromagnetic fields. The frequency of one of the fields far exceeds that of the other. The effect of the high-frequency field can be averaged out of the dynamics to realize an effective transition frequency of the field-dressed two-level system. We examine the linear response, second harmonic response and Stokes and anti-Stokes Raman response of the dressed two-level system, to the weak frequency field. The vibrational resonance enhancement in each case is demonstrated for optimal strength of the high-frequency field. Our theoretical scheme is corroborated by full numerical simulation of the two-level, two-field dynamics governed by loss-free Bloch equations. We suggest that quantum optics can offer an interesting arena for the study of the vibrational resonance. This article is part of the theme issue ‘Vibrational and stochastic resonance in driven nonlinear systems (part 1)’.

Прототип протонного ондуляторного линейного ускорителя

One of the ways to realize undulator acceleration is to ensure particles motion in a magnetostatic undulator, where spatial oscillations of particles in the transverse direction are synchronized with temporal oscillations of transverse high-frequency field, which allows its energy transfer to the accelerated particles. The resonators, tcapable to provide a uniform transverse field, are structurally simpler than resonators with a periodically variable longitudinal field, which makes undulator accelerators an attractive alternative to coventional accelerators.Although the physics of such accelerators was previously descussed in the literature, the task of creating a physical prototype of undulator linac is still not realized. In this paper, we privde a practical description of the project of a proton undulator linear accelerator based on based on this principle, developed by RadiaBeam (USA).

RESEARCH ON THE EFFECT OF SUPER HIGH FREQUENCY FIELD ON GREEN TEA EXTRACTION AND EXTRACT QUALITY

The article characterises non-brick green tea as a product of mass consumption. It has been described how practical it is to produce liquid extracts based on it and use them further in the non- alcoholic drinks technology. Achieving high yields of extractives from tea requires intensification of the mass transfer process. The analysis of scientific sources has shown that pre-treatment of raw materials is one of the most promising methods for this purpose. The article presents comparative characteristics of green tea extracts obtained using pre- treatment in the super high frequency field and of ones produced without it. The optimal power of the super high frequency field for extracts heated up to 60°С has been selected and analysed. If the energy of super high frequency is applied to a fresh mixture of tea and an extractant, with its further extraction in a rotary extractor IKA-RV-10 at the dilution 280 mBr, the yield of extractives doubles. The action of the microwave field leads to a 40% increase in the content of extractives in the resulting extract: the yield of phenolic substances increases by 44%, of caffeine by 45%, of substances with vitamin P activity by 23%, compared with the extracts produced without additional treatment. However, the chlorophyll and aldehyde content decreases. Pre-treatment with super high frequency energy in the course of green tea extraction helps effectively extract phenolic compounds like catechins that affect the taste of final beverages. This technique allows doubling the yield of catechins. Besides, it has been confirmed that the chemical composition (namely the quantity of hydroxyl groups in the catechin structure) determines the intensity of the transition of catechins into the composition of the extract. The findings on the safety of the extracts obtained have allowed establishing that though the contents of mercury, arsenic, lead, copper, and iron increase, they do not exceed the maximum permissible concentrations. This proves the safety of the extracts produced. The research results obtained make it possible to intensify the plant extract production technology without using any special extractors.

The Results of Studying the Energy Efficient Modes of Grain Drying Using Microwave Radiation

Classical thermal methods of grain drying are characterized by high energy intensity. The study of grain processing modes using electrical technologies allows to reduce the cost of drying. When studying, it is necessary to take into account the technological requirements for the processed material, types of electrical technologies, and the operating mode of the intensifying equipment (constant, pulse, and others). (Research purpose) The research purpose is obtaining dependences of the energy efficiency of drying wheat grain using the energy of the microwave field for different states of the layer. (Materials and methods) A diagram of a laboratory installation has been used. Experimental studies were performed to determine the drying curves and the energy intensity of drying the layer of wheat grain. (Results and discussion) The two-factor experiment was conducted to determine the effect of the power of the field and the density of the grain mound on the energy intensity of the grain drying process. Article presents the required dependencies. (Conclusions) Data has been obtained as a result of an experiment on drying a grain layer located in a dense, fluidized and suspended layer under the influence of a microwave field at an initial grain humidity of 17 percent. It was found that the use of an ultra-high-frequency field in the process of drying grain crops is advisable when the humidity of the processed material is close to the standard one (17-18 percent for wheat). It was found that the use of an ultra-high-frequency field makes it possible to intensify the drying process when humidity is close to the standard by 3-4 times and reduce the overall energy consumption of the drying process in areas of humidity close to the standard by 20-40 percent. It was found that in order to increase the reliability of data, it is necessary to increase experiments on large-scale models that allow predicting the energy intensity of drying in industrial plants.

The Use of a Magnetic Suspension for the Crucibleless Metal Melting

Nowadays, the magnetic suspension is widely used in metallurgy for crucibleless melting of metals. We carry out the contactless suspension of metal under the inductor (a source of the high-frequency field), using the forces of interaction of the eddy currents, which are induced in the metal with a high-frequency magnetic field causing them. Besides, such a method of the suspension of metals allows to carry out simultaneously its heating and melting at the expense of the energy of the electromagnetic field of suspension

Electric discharge as technological factor of intensification of chemical-thermal treatment of engineering products

The advantages of nitriding in an electrostatic and high-frequency field connected with the possibility of carrying out processes at normal pressure are shown. The acceleration of the process of diffusion saturation with nitrogen in an electric field with the formation of a spark discharge as compared with gas nitriding is confirmed experimentally. This method of steel nitriding allows forming layers of different structure and thickness with the specified gradient of hardness.