Investigation of the confinement of high energy non-neutral proton beam in a bent magnetic mirror

By using the Particle-In-Cell(PIC) simulation method, we study how the proton beam is confined in a bent magnetic mirror. It is found that the loss rate of the charged particles in a bent mirror is less than that in the axi-symmetric mirror. For a special bent mirror with the deflection angle of the coils $\alpha=45^{\circ}$, it is found that the loss rate reaches maximum value at certain ion number density where the ion electrostatic oscillation frequency is equal to the ion cyclotron frequency. In addition, the loss rate is irrelevant to the direction of the proton beam. Our results may be helpful to devise a mirror. In order to obtain the least loss rate, we may choose a appropriate deflection angle, and have to avoid a certain ion number density at which the ion electrostatic oscillation frequency is equal to the ion cyclotron frequency.

Non-adiabatic modulation of premixed-flame thermoacoustic frequencies in slender tubes

This paper presents an experimental study of the influence of heat losses on the onset of thermoacoustic instabilities in methane–air premixed flames propagating in a horizontal tube of diameter, $D = 10$ mm. Flames are ignited at the open end of the tube and propagate towards the closed end undergoing strong oscillations of different features owing to the interaction with acoustic waves. The frequency of oscillation and its axial location are controlled through the tube length $L$ and the intensity of heat losses. These parameters are respectively modified in the experiments by a moveable piston and a circulating thermal bath of water prescribing temperature conditions. Main experimental observations show that classical one-dimensional predictions of the oscillation frequency do not accurately describe the phenomena under non-adiabatic real scenarios. In addition to the experimental measurements, a quasi-one-dimensional analysis of the burnt gases is provided, which introduces the effect of heat losses at the wall of the tube on the interplay between the acoustic field and the reaction sheet. As a result, this analysis provides an improved description of the interaction and accurately predicts the excited flame-oscillation harmonics through the eigenvalues of the non-adiabatic acoustics model. Unlike the original one-dimensional analysis, the comparison between the flame oscillation frequency provided by the non-adiabatic extended theory and the frequencies measured in our experiments is in excellent agreement in the whole range of temperatures considered. This confirms the importance of heat losses in the modulation of the instabilities and the transition between different flame oscillation regimes.

Precise determination of the $$B_{\mathrm{s}}^0$$–$$\overline B_{\mathrm{s}}^0$$ oscillation frequency

Mesons comprising a beauty quark and strange quark can oscillate between particle ($${B}_{\mathrm{s}}^{0}$$ B s 0 ) and antiparticle ($${\overline{B}}_{\mathrm{s}}^{0}$$ B ¯ s 0 ) flavour eigenstates, with a frequency given by the mass difference between heavy and light mass eigenstates, Δms. Here we present a measurement of Δms using $${B}_{\mathrm{s}}^{0}\to {D}_{\mathrm{s}}^{-}$$ B s 0 → D s − π+ decays produced in proton–proton collisions collected with the LHCb detector at the Large Hadron Collider. The oscillation frequency is found to be Δms = 17.7683 ± 0.0051 ± 0.0032 ps−1, where the first uncertainty is statistical and the second is systematic. This measurement improves on the current Δms precision by a factor of two. We combine this result with previous LHCb measurements to determine Δms = 17.7656 ± 0.0057 ps−1, which is the legacy measurement of the original LHCb detector.

Oblique instability of a stratified oscillatory boundary layer

The instability and dynamics of a vertical oscillatory boundary layer in a container filled with a stratified fluid are addressed. Past experiments have shown that when the boundary oscillation frequency is of the same order as the buoyancy frequency, the system is unstable to a herringbone pattern of oblique waves. Prior studies assuming the basic state to be a unidirectional oscillatory shear flow were unable to account for the oblique waves. By accounting for confinement effects present in the experiments, and the ensuing three-dimensional structure of the basic state, we are able to numerically reproduce the experimental observations, opening the door to fully analysing the impacts of stratification on such boundary layers.

Distributed Phase Oscillatory Excitation Efficiently Produces Attractors Using Spike-Timing-Dependent Plasticity

The brain is thought to represent information in the form of activity in distributed groups of neurons known as attractors. We show here that in a randomly connected network of simulated spiking neurons, periodic stimulation of neurons with distributed phase offsets, along with standard spike-timing-dependent plasticity (STDP), efficiently creates distributed attractors. These attractors may have a consistent ordered firing pattern or become irregular, depending on the conditions. We also show that when two such attractors are stimulated in sequence, the same STDP mechanism can create a directed association between them, forming the basis of an associative network. We find that for an STDP time constant of 20 ms, the dependence of the efficiency of attractor creation on the driving frequency has a broad peak centered around 8 Hz. Upon restimulation, the attractors self-oscillate, but with an oscillation frequency that is higher than the driving frequency, ranging from 10 to 100 Hz.

Estimating the oscillation frequency of a payload mass on quadcopter in non-autonomous flight

Unmanned aerial vehicles (UAVs) have been employed in several engineering applications, such as aerial photography, environmental surveillance, delivery tasks, and others. Most of these applications have attracted increasing attention due to their ability to carry different payloads, which can change the dynamic of flight. The present article investigates the dynamics of a quadcopter with a payload mass including the stiffness of the attachment to the aerial vehicle. An approach to obtain non-dimensional equations of motion is introduced, and as a consequence, it is possible to determine the frequency of vibration of the payload mass during the flight. The results are presented for non-autonomous flight, and they establish a simple equation to estimate the oscillation frequency depending on the relation between the quadcopter and the payload masses, also considering the stiffness of attachment, without requiring a solution to the equation of motion in the time domain.

Cleaning of vegetable seeds on a pneumatic sorting table

Семенной ворох с поля никогда не бывает чистым. В процессе уборки семян в семенной ворох попадают различные примеси – семена сорняков, различные обломки частей растений, минеральные частицы: комочки земли, камешки и др. Очистка семенного вороха до регламентированных показателей, предусмотренных в нормативном документе, – основная задача послеуборочной доработки семян. Примеси, которые отличаются размером от семян основной культуры, легко удаляются на ветрорешетных машинах. Полностью удалить все примеси на ветрорешетных машинах невозможно. Поэтому существует необходимость во вторичной, более качественной очистке семенного вороха. Пневмосортировальные столы способны разделить семенной ворох по плотности семян. В результате дополнительной вторичной очистки семян можно повысить чистоту семян, которая необходима для безотказной работы современных высевающих аппаратов. Пневмосортировальный стол ПСС-1 имеет ряд настроек, которые меняются оператором в зависимости от культуры. Основные настройки: подача семян, регулировка заслонки вентилятора, изменение продольного и поперечного угла наклона рабочей деки, частота колебания рабочей деки, регулируемые заслонки приемника семян. Все настройки могут быть оперативно изменены оператором технологического процесса очистки. Использование пневмосортировального стола во вторичной очистке семенного вороха возможно на различных овощных культурах. В процессе очистки семян на пневмосортировальном столе из семенного вороха удаляются вместе с легковесными примесями, обломками стебельков, листьев, стручков и прочими, удаляются и легковесные невызревшие семена, что способствует повышению всхожести получаемых после очистки семян. The resulting seed heap from the field is never clean. In the process of harvesting seeds, various impurities are found in the seed pile. As impurities in the seed heap, there may be weed seeds, various fragments of plant parts, mineral particles: lumps of earth, pebbles and others. Cleaning the seed pile to the regulated indicators provided for in the regulatory document is the main task of post-harvest seed refinement. Impurities that differ in size from the seeds of the main crop are easily removed by wind-screen machines. It is impossible to completely remove all impurities on windscreen machines. Therefore, there is a need for a secondary, better cleaning of the seed pile. Pneumatic sorting tables are able to divide the seed pile according to the density of seeds. Because of additional secondary cleaning of seeds, it is possible to increase the purity of seeds, which is necessary for the trouble-free operation of modern sowing machines. The PSS-1 pneumatic sorting table has a number of settings that are changed by the operator depending on the culture. Basic settings: seed feeding, fan flap adjustment, changing the longitudinal and transverse angle of inclination of the working deck, the oscillation frequency of the working deck, adjustable shutters of the seed receiver. The operator of the cleaning process can quickly change all settings. The use of a pneumatic sorting table in the secondary cleaning of the seed pile is possible on various vegetable crops. In the process of cleaning seeds on a pneumatic sorting table, fragments of stems, leaves, pods and others are removed from the seed pile together with lightweight impurities, and lightweight unripe seeds are also removed, which helps to increase the germination of seeds obtained after cleaning.