GYROSURFING ACCELERATION OF IONS IN FRONT OF EARTH's QUASI-PARALLEL BOW SHOCK

International audienceIt is well known that shocks in space plasmas can accelerate particles to high energies. However, many details of the shock acceleration mechanism are still unknown. A critical element of shock acceleration is the injection problem; i.e., the presence of the so called seed particle population that is needed for the acceleration to work efficiently. In our case study, we present for the first time observational evidence of gyroresonant surfing acceleration in front of Earth's quasi-parallel bow shock resulting in the appearance of the long-suspected seed particle population. For our analysis, we use simultaneous multi-spacecraft measurements provided by the Cluster spacecraft ion (CIS), magnetic (FGM), and electric field and wave instrument (EFW) during a time period of large inter-spacecraft separation distance. The spacecraft were moving toward the bow shock and were situated in the foreshock region. The results show that the gyroresonance surfing acceleration takes place as a consequence of interaction between circularly polarized monochromatic (or quasi-monochromatic) transversal electromagnetic plasma waves and short large amplitude magnetic structures (SLAMSs). The magnetic mirror force of the SLAMS provides the resonant conditions for the ions trapped by the waves and results in the acceleration of ions. Since wave packets with circular polarization and different kinds of magnetic structures are very commonly observed in front of Earth's quasi-parallel bow shock, the gyroresonant surfing acceleration proves to be an important particle injection mechanism. We also show that seed ions are accelerated directly from the solar wind ion population. Key words: acceleration of particles – plasmas – shock waves – supernovae: general – waves Online-only material: color figure

Estimating the Dynamics of A Machine-tractor Assembly Considering the Effect of the Supporting Surface Profile

Results of theoretical studies of dynamics of the machine-tractor assembly taking into account the influence of a bearing surface profile were presented. It was established that in the course of operation, the machine-tractor assembly is exposed to a number of external factors leading to a change of vertical loads on the chassis and the engine. Mathematical models of dynamics of a tractor and a machine and a tractor unit consisting of a tractor of pivotally connected arrangement and a trailed sower were constructed. Such models make it possible to study dynamics and oscillatory processes of multi-element units. A mathematical model of tractor wheel dynamics was formed. Speeds and angles of orientation of elements of the machine-tractor assembly in space were determined. Influence of profile of the bearing surface on the unit elements when moving in the field prepared for sowing and the field after plowing was calculated. Theoretical studies of the influence of the bearing surface profile on dynamics of the machine-tractor assembly were performed on the example of KhTZ-242K tractor and Vega-8 Profi sower (Ukraine). When moving, the sower frame has a smaller amplitude of vibration accelerations than that of the tractor. Accordingly, the tractor has higher oscillation energy because it rests on the ground through its wheels having appropriate stiffness. The sower moves with its working bodies immersed into the soil which leads to a decrease in the amplitude of oscillations. The highest energy of amplitude of oscillation accelerations of the sower frame in the vertical direction was observed at frequencies of 15.9; 23.44; 35.3 and 42.87 Hz. It was found that the increase in working speeds of agricultural units leads to the fact that oscillations of all components reach significant values. This entails an increase in dynamic loads on soil and, as a consequence, its compactio

Estimating the Dynamics of A Machine-tractor Assembly Considering the Effect of the Supporting Surface Profile

Results of theoretical studies of dynamics of the machine-tractor assembly taking into account the influence of a bearing surface profile were presented. It was established that in the course of operation, the machine-tractor assembly is exposed to a number of external factors leading to a change of vertical loads on the chassis and the engine. Mathematical models of dynamics of a tractor and a machine and a tractor unit consisting of a tractor of pivotally connected arrangement and a trailed sower were constructed. Such models make it possible to study dynamics and oscillatory processes of multi-element units. A mathematical model of tractor wheel dynamics was formed. Speeds and angles of orientation of elements of the machine-tractor assembly in space were determined. Influence of profile of the bearing surface on the unit elements when moving in the field prepared for sowing and the field after plowing was calculated. Theoretical studies of the influence of the bearing surface profile on dynamics of the machine-tractor assembly were performed on the example of KhTZ-242K tractor and Vega-8 Profi sower (Ukraine). When moving, the sower frame has a smaller amplitude of vibration accelerations than that of the tractor. Accordingly, the tractor has higher oscillation energy because it rests on the ground through its wheels having appropriate stiffness. The sower moves with its working bodies immersed into the soil which leads to a decrease in the amplitude of oscillations. The highest energy of amplitude of oscillation accelerations of the sower frame in the vertical direction was observed at frequencies of 15.9; 23.44; 35.3 and 42.87 Hz. It was found that the increase in working speeds of agricultural units leads to the fact that oscillations of all components reach significant values. This entails an increase in dynamic loads on soil and, as a consequence, its compactio

Establishing the Influence of Technical and Technological Parameters of Milking Equipment on the Efficiency of Machine Milking

One of the tasks that imply increasing the milk productivity of cows is to create optimal maintenance conditions that ensure the increased use of the genetic potential of cattle based on the implementation of engineering and technological solutions. A mathematical model has been built that links the technical and technological parameters of the vacuum system of milking equipment, namely, the value of the working vacuum P, the pulsation frequency n, the ratio of pulsation cycles, and the tension strength of milking rubber FH to cows' milk yield rate V. The range of milking plant operating parameters for milking in the milk line has been determined, at which the milk yield rate is maximum: P=52 kPa, n=57.6–58.8 min–1, δ=0.59–0.64, FH=59.3–60.4 H. Under these parameters, the milk yield rate is V=1.48–1.53 l/min. The results of the multifactor experiment have helped construct an adequate mathematical model of the second order, which confirms the theoretical dependence of the influence of the technical and technological parameters of the vacuum system of milking equipment on milk yield rate and the air flow of the milking machine. Analysis of the mathematical model has made it possible to establish the rational structural and technological parameters for the vacuum system of a milking machine: the value of the working vacuum, P=50.6 kPa; pulsation frequency, n=55.9 min–1, the ratio of pulsation cycles and the tension force of milking rubber FH=64.8 H. Under these parameters, the milk yield rate is maximum: V=1.47–1.52 l/min; the air flow consumption of the milking machine is Q=2.19 m3/h. The mathematical model built fully reveals the influence of technical and technological parameters of milking equipment on the efficiency of machine milking. Owing to this, the issue related to the rational choice of equipment is resolved

Establishing the Influence of Technical and Technological Parameters of Milking Equipment on the Efficiency of Machine Milking

One of the tasks that imply increasing the milk productivity of cows is to create optimal maintenance conditions that ensure the increased use of the genetic potential of cattle based on the implementation of engineering and technological solutions. A mathematical model has been built that links the technical and technological parameters of the vacuum system of milking equipment, namely, the value of the working vacuum P, the pulsation frequency n, the ratio of pulsation cycles, and the tension strength of milking rubber FH to cows' milk yield rate V. The range of milking plant operating parameters for milking in the milk line has been determined, at which the milk yield rate is maximum: P=52 kPa, n=57.6–58.8 min–1, δ=0.59–0.64, FH=59.3–60.4 H. Under these parameters, the milk yield rate is V=1.48–1.53 l/min. The results of the multifactor experiment have helped construct an adequate mathematical model of the second order, which confirms the theoretical dependence of the influence of the technical and technological parameters of the vacuum system of milking equipment on milk yield rate and the air flow of the milking machine. Analysis of the mathematical model has made it possible to establish the rational structural and technological parameters for the vacuum system of a milking machine: the value of the working vacuum, P=50.6 kPa; pulsation frequency, n=55.9 min–1, the ratio of pulsation cycles and the tension force of milking rubber FH=64.8 H. Under these parameters, the milk yield rate is maximum: V=1.47–1.52 l/min; the air flow consumption of the milking machine is Q=2.19 m3/h. The mathematical model built fully reveals the influence of technical and technological parameters of milking equipment on the efficiency of machine milking. Owing to this, the issue related to the rational choice of equipment is resolved

Determining the Effect of Formulation Components on the Physical-chemical Processes in a Semi-finished Flour Whipped Product Under Programmed Changes in Temperature

The method of a differential thermal analysis has been applied to investigate the physical-chemical and chemical processes that occur in a semi-finished whipped flour product under conditions of a programmed change in temperature. Qualitative assessment of the processes that take place in the examined samples during thermal transformations has been performed.We have explored the influence of formulation components of a semi-finished whipped flour product on mass losses, the rate of transformations, and the dehydration processes occurring under non-isothermal conditions at a constant heating rate of 10±1 °C/min while heating up to a temperature of 300 °C.Synergetic interaction between xanthan and gelatin has been confirmed. It was established that the introduction of a xanthan solution to a gelatin solution, the base of a semi-finished whipped flour product, improves structure and enhances its thermal stability during heating. It is likely that this occurs due to the redistribution of associated and non-associated hydroxyl groups, which contributes to forming a large number of inter-molecular hydrogen bonds.We have proven the catalytic effect of the enzyme transglutaminase in the system gelatin-xanthan on the interaction between the amino groups of lysine and the γ-carboxyamide group of glutamine residues bound by a peptide bond. This effect ensured a higher level of crosslinking the macromolecules of a protein framework and substantially slows down the dehydration process in a semi-finished whipped flour product.Our study has established minimum losses of the adsorption-bound moisture in semi-finished whipped flour product, which is likely due to an increase in the degree of binding the groups of -ОН and flour proteins, which predetermines the formation of intermolecular hydrogen bonds with the proteins of a gluten complex.The influence of xanthan, sugar, transglutaminase enzyme, flour, on the ranges of dehydration has been investigated, which depend on different forms of moisture binding in a semi-finished whipped flour product. We have determined the temperature intervals of moisture loss at different shapes and binding energy in a semi-finished whipped flour product.The results obtained have practical significance for establishing the rational temperature conditions for baking a semi-finished whipped flour product, namely 140±5 °