Appearance Of Self-oscillations Research Articles

Oscillatory processes in a nonlinear system of an individual traction electric drive

When the tires interact with the road in contact, self-oscillations occur. The appearance of self-oscillations in the interaction zone can serve as a useful diagnostic sign of the development of the process of loss of adhesion in the work, cases of self-oscillations for an individual electric drive are investigated. In traction and driven modes, a "soft" mode of occurrence of self-oscillation of wheel rotation is possible. When braking, there is a "soft" mode of excitation of self-oscillations, and when the wheels are locked, a "hard" mode of self-oscillations of the translational movement of the wheel center. Keywords: self-oscillation; frictional interaction of the wheel with the base; "soft mode" of self-oscillation; "hard mode" of self-oscillation; Bendixon criterion; friction force; individual electric wheel drive

ОЦІНЮВАННЯ ВПЛИВУ «КОНСТРУКЦІЙНОГО» ТЕРТЯ В ПІДВІСЦІ НА ПРОСТОРОВІ КОЛИВАННЯ ТРАНСПОРТНОГО ЗАСОБУ

In the process of creating and modernizing ground vehicles for various purposes, in particular armored vehicles, there is a problem of assessing the influence of design features on working processes in operating conditions. These features include the presence of "structural" friction, in its manifestations and the effect similar to "dry" friction. In some cases, this leads to the appearance of self-oscillations, which is undesirable. Therefore, the development of the theory and practice of numerical assessment of vehicle performance with the possibility of manifestation of self-oscillating properties is an urgent task. Obviously, in the framework of the methodology of applied optimal design of complex technical systems, it is necessary to have an adequate mathematical model of the object of study. An original mathematical model of free spatial vibrations of the sprung part of the transport machine (body) is proposed, which allows one to evaluate the influence of the features of the new vehicle suspension design. The new suspension is hydropneumatic, with a helical gear, with the presence of "structural" friction. Calculations carried out numerically using the original program confirmed the correspondence of the mathematical model to modern ideas about the theory and practice of work processes with free vibrations of complex technical systems. The motion parameters during the manifestation of self-oscillating properties and parametric vibrations of an object close in weight and size to the BTR70 and BTR80 are numerically estimated.

First Order Phase Transition in Ferromagnetic Semiconductors in External Electric and Magnetic Fields (by the example of La-=SUB=-1-x-=/SUB=-Ca-=SUB=-x-=/SUB=-MnO-=SUB=-3-=/SUB=-) (on the example of La-=SUB=-1-x-=/SUB=-Ca-=SUB=-x-=/SUB=-MnO-=SUB=-3-=/SUB=-)

It is shown that during a first-order phase transition in ferromagnetic semiconductors based on lanthanum manganites, along with the semiconductor phase of s-electrons, a phase arises with fluctuation short-range order associated with a change in the sign of the intermode interaction parameter in the system of d-electrons. The phase separation region is characterized by fluctuations of local magnetization depending on temperature and external magnetic field. In this case, the temperature of the first order phase transition, above which phase separation arises, is appreciably affected by double exchange. Due to self-heating, the phase separation is significantly affected by the electric field, which leads to N-shaped current-voltage characteristics. Using La1-xCaxMnO3 as an example, it is shown that the switching on of electric and magnetic fields during a first-order phase transition in ferromagnetic semiconductors is accompanied by the appearance of self-oscillations of the electric current and magnetization. Keywords: double exchange, electron fluctuations of spin and charge density, Anderson localization, self-oscillations.

Фазовый переход первого рода в ферромагнитных полупроводниках во внешних электрическом и магнитном полях (на примере La-=SUB=-1-x-=/SUB=-Ca-=SUB=-x-=/SUB=-MnO-=SUB=-3-=/SUB=-)

It is shown that during a first-order phase transition in ferromagnetic semiconductors based on lanthanum manganites, along with the semiconductor phase of s-electrons, a phase arises with fluctuation short-range order associated with a change in the sign of the intermode interaction parameter in the system of d-electrons. The phase separation region is characterized by fluctuations of local magnetization depending on temperature and external magnetic field. In this case, the temperature of the first order phase transition, above which phase separation arises, is appreciably affected by double exchange. Due to self-heating, the phase separation is significantly affected by the electric field, which leads to N-shaped current-voltage characteristics. Using La1–xCaxMnO3 as an example, it is shown that the switching on of electric and magnetic fields during a first-order phase transition in ferromagnetic semiconductors is accompanied by the appearance of self-oscillations of the electric current and magnetization.

ВЛИЯНИЕ КРУТИЛЬНЫХ И ПРОДОЛЬНЫХ КОЛЕБАНИЙ НА СКОРОСТЬ БУРЕНИЯ И ОБРАЗОВАНИЕ ПОЛОМОК РЕЖУЩИХ ЭЛЕМЕНТОВ БУРОВЫХ ДОЛОТ, АРМИРОВАННЫХ PDC

Актуальность. В настоящее время для сооружения скважин на нефть и газ наиболее эффективным инструментом являются долота, армированные пластинами PDC (polycrystalline diamond cutters). Такие долота работают по принципу резания–скалывания, так как из всех механизмов разрушения породы резание является наиболее эффективным по причине того, что прочность породы на растяжение и скол значительно меньше её прочности на сжатие. Анализ состояния отработанных буровых долот, армированных пластинами PDC, показывает, что они отрабатывают свой ресурс не полностью, так как часть режущих PDC элементов выходит из строя по причине скола. Многообразие форм сколов по форме и размерам требует провести классификацию, выявить причину появления и определить нагрузки, приводящие к их возникновению. Кроме того, слом пластин или их потеря в значительной степени сказываются на конечных технико-экономических показателях бурения разведочных и эксплуатационных скважин. Решение вопросов повышения качества долот путем уменьшения числа поломок будет способствовать повышению экономической эффективности работ при добыче и разведке полезных ископаемых. Целью исследования является определение размеров площадок скола пластин PDC для дальнейшей классификации в зависимости от толщины срезаемого слоя породы, причин возникновения крутильных и продольных колебаний в бурильной колонне, вызывающих поломки PDC, а также разработка конструкции бурового долота, армированного пластинами PDC, предупреждающего появление автоколебаний в бурильной колонне. Объекты: режущие элементы буровых долот, армированных пластинами PDC с плоской передней гранью и PDC с выпуклой передней гранью, сколы пластин PDC на буровых долотах, возникающие в процессе бурения скважин. Методы: экспериментально-аналитический метод исследования на лабораторных образцах и на отработанных буровых долотах, армированных пластинами PDC. Результаты. На основании анализа и обобщения результатов выполненных лабораторных исследований причин возникновения поломок пластин PDC и их характера разработан ряд технических и технологических решений, предупреждающих возникновение крутильных и продольных автоколебаний в бурильной колонне и повышающих эффективность породоразрушающего инструмента, армированного пластинами PDC.

Method of Phase Diagrams for the Analysis of Seism-Acoustical Spatial-Time Monitoring Data in Oil Wells

Experimental and theoretical studies of the mechanisms of vibration stimulation of oil recovery in watered fields lead to the conclusion that resonance oscillations develop in fractured-block formations. These oscillations, caused by weak but long-lasting and frequency-stable influences, create the conditions for ultrasonic wave’s generation in the layers, which are capable of destroying thickened oil membranes in reservoir cracks. For fractured-porous reservoirs in the process of exploitation by the method of water high-pressure oil displacement, the possibility of intensifying ultrasonic vibrations can have an important technological significance. Even a very weak ultrasound can destroy, over a long period of time, the viscous oil membranes formed in the cracks between the blocks, which can be the reason for lowering the permeability of the layers and increasing the oil recovery. To describe these effects, it is necessary to consider the wave process in a hierarchically blocky environment and theoretically simulate the mechanism of the appearance of self-oscillations under the action of relaxation shear stresses. For the analysis of seism acoustic response in time on fixed intervals along the borehole an algorithm of phase diagrams of the state of many-phase medium is suggested.

Mathematical simulation of self-oscillations in methane oxidation on nickel: An isothermal model

The dynamics of methane oxidation on nickel was studied by mathematical modeling within the framework of an 18-step microkinetic scheme. The model examined predicts the appearance of self-oscillations caused by the periodic oxidation-reduction of nickel in the reaction proceeding under isothermal conditions.

Propane oxidation on nickel in a self-oscillation mode

The kinetics of the catalytic oxidation of propane with oxygen on nickel in a self-oscillation mode was studied. A comparative analysis of changes in reaction rate oscillations with time in the presence of nickel wire and foil was performed. It was found that the reaction medium influenced the morphology of the catalyst surface. With the use of X-ray photoelectron spectroscopy, it was demonstrated that a NiO layer no less than 100 nm in thickness was formed on the catalyst surface in the course of the reaction of propane oxidation. The mechanism of the appearance of self-oscillations in the test system is discussed.

Palladium(II, I, 0) Complexes in Catalytic Reactions of Oxidative Carbonylation

The mechanisms of carbonylation of alkenes, alkynes, and alcohols, including the mechanism of oxidative carbonylation of alkynes in the regime of self-oscillations catalyzed by Pd(II), Pd(I), or Pd(0) complexes, are analyzed. It is shown that the main reasons for the appearance of self-oscillations in the oxidation reactions are nonlinear and autocatalytic steps of generation and termination of active centers. The results of studying the functions of para-benzoquinone as an oxidant, ligand, and catalyst in the oxidative reactions are generalized. It is found that Pd(0) complexes with para-benzoquinone can catalyze oxidation reactions.

Time and Space Instabilities in Binary Alloys at Phase Transitions Under Irradiation

AbstractA manifestation of antisite defects created by nuclear irradiation in binary ordered alloys is investigated. Calculations show that the concentration of such defects can be large at typical values of intensity of irradiation and temperature. The appearance of structural defects can cause the time and space instabilities in crystal during irradiation. Time instabilities are connected with the acceleration of antisite defect relaxation due to the heat that is released during this relaxation. The instability leads to appearance of self-oscillations of defect density and temperature of crystal. Space instability arises due to interaction between defects created by irradiation. It leads to spatial periodical modulation of antisite defect density.

Self-oscillations in the rate of CO oxidation on Pt(110)

The surface of Pt(110) was found to be metastable under the reaction conditions. The necessary condition for the appearance of self-oscillations in the system is the change of platinum surface properties under the action of reaction medium. Self-oscillations in the rate are maintained due to reversibility of these changes.

Adsorption of carbon monoxide and oxygen on Pt(110)

Adsorption of CO and O2 on Pt(110) was studied by XPS, LEED and TDS methods to elucidate the role of Oads states and structural rearrangements of the surface under the action of COads in the appearance of self-oscillations in the rate of CO oxidation on Pt(110).

The simplest possibility for the appearance of self-oscillations in pacemaker cells

This paper considers the simplest case of the appearance of membrane potential self-oscillations, the one which is connected only with the circulation of sodium ions between the cell and the medium. It is shown that the presence of a potential-dependent Na + channel and a Na +-K + pump in the membrane is sufficient for the appearance of a wide spectrum of oscillatory processes.

Relaxation self-oscillations in chemical kinetics: A model, conditions for realization

Nonlinearity + reversibility = feedback for self-oscillations. This qualitative conclusion was obtained after a detailed analysis of the simplest model describing relaxation self-oscillations, which were experimentally found in some chemical systems. The reversibility of some steps is shown to be responsible to a great extent for the appearance of relaxation self-oscillations. It is just the combination of reversibility with specific nonlinearity that forms the feedback necessary for the appearance of self-oscillations.

Electrical properties of intestinal muscle as measured intracellularly and extracellularly

ARTICLESElectrical properties of intestinal muscle as measured intracellularly and extracellularlyM Kobayashi, CL Prosser, and T NagaiM Kobayashi, CL Prosser, and T NagaiPublished Online:01 Jul 1967https://doi.org/10.1152/ajplegacy.1967.213.1.275MoreSectionsPDF (2 MB)Download PDF ToolsExport citationAdd to favoritesGet permissionsTrack citations ShareShare onFacebookTwitterLinkedInWeChat Previous Back to Top Next Download PDF FiguresReferencesRelatedInformation Cited ByMovement based artifacts may contaminate extracellular electrical recordings from GI muscles25 September 2011 | Neurogastroenterology & Motility, Vol. 23, No. 11Enteric nervous system: reflexes, pattern generators and motilityCurrent Opinion in Gastroenterology, Vol. 24, No. 2Is colonic electrical activity a similar phenomena to small-bowel electrical activity?Diseases of the Colon & Rectum, Vol. 40, No. 1Mathematical modeling of the peristaltic reflex: A numerical experimentJournal of Mathematical Sciences, Vol. 71, No. 6Biomechanics of small bowel motilityMedical Engineering & Physics, Vol. 16, No. 5System identification of electrically coupled smooth muscle cells: the passive electrical propertiesIEEE Transactions on Biomedical Engineering, Vol. 38, No. 11Impedance analysis applicable to cardiac muscle and smooth muscle bundlesIEEE Transactions on Biomedical Engineering, Vol. 38, No. 10Gastrointestinal Physiology, 1895–1975: Motility1 January 2011Electrophysiology of the intestinal musculature1 January 2011Interstitial cells of Cajal1 January 2011In vivo myoelectric activity: methods, analysis, and interpretation1 January 2011The simplest possibility for the appearance of self-oscillations in pacemaker cellsBioelectrochemistry and Bioenergetics, Vol. 17, No. 3Gap Junctions in Smooth MuscleSummation and gradient characteristics of local electroantennogram response of the European corn borer, Ostrinia nubilalisPesticide Biochemistry and Physiology, Vol. 24, No. 1Interstitial Cells of Cajal: Selective Uptake of Methylene Blue Inhibits Slow Wave ActivityElectrophysiology of Intestinal Smooth MuscleOn Exploring The Basis For Slow Potential Oscillations in the Mammalian Stomach and IntestineJournal of Experimental Biology, Vol. 81, No. 1An Atlas of Cellular Oscillators1 August 1979 | Journal of Experimental Biology, Vol. 81, No. 1Electrophysiological properties of human oviduct smooth muscle cells in dissociated cell cultureJournal of Cellular Physiology, Vol. 98, No. 2Junctional Transmission in Smooth Muscle and the Autonomic Nervous System1 January 2011Evaluation of electric field changes in the cleft between excitable cellsJournal of Theoretical Biology, Vol. 64, No. 1Models of Smooth Muscle Electrical ActivityReferencesRatio of transverse to longitudinal resistivities of isolated cardiac muscle fiber bundlesJournal of Electrocardiology, Vol. 7, No. 4Shunting effect on resistance measurements in visceral smooth muscle tissueJournal of Theoretical Biology, Vol. 46, No. 2The Permeability Change Produced by Acetylcholine in Smooth MuscleThe electrical activity of single isolated smooth muscle cellsPfl�gers Archiv European Journal of Physiology, Vol. 341, No. 4Physiological and morphological correlation of the functional syncytium in the bivalve myocardiumComparative Biochemistry and Physiology Part A: Physiology, Vol. 44, No. 1Propagation and electrical entrainment of intestinal slow wavesThe American Journal of Digestive Diseases, Vol. 17, No. 4Electrical activity of the stomach and upper intestineThe American Journal of Digestive Diseases, Vol. 16, No. 7The possible role of close contacts (nexuses) in the propagation of control electrical activity in the stomach and small intestineThe American Journal of Digestive Diseases, Vol. 16, No. 7Studies of intestinal slow wave activity with a double sucrose gap apparatusLife Sciences, Vol. 10, No. 6Insect visceral muscle. 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