Modeling, Mathematical and Numerical Studies of a New Biventricular Model for Artificial Heart Powered by an Electromagnet Subjected to Sinusoidal and Square Voltages

2018 ◽  
pp. 172-198
Author(s):  
Paul Woafo ◽  
Abobda Theodore Lejuste

This paper describes and investigates the dynamics of a new model of biventricular model for artificial heart which consists of two ferromagnetic masses fixed on springs and subjected to a common electromagnet powered by sinusoidal and square wave voltage sources. The effects of the following control parameters are considered: the external voltage source frequency and amplitude, the ratio between the stiffness coefficients, and the one between the masses. As results in both cases of external excitations, subharmonic oscillations, hysteresis, coexistence of limit cycle and point attractor, permanent bounding are found. The optimal voltage and the ratio between the stiffness coefficients are obtained. Bursting oscillations usable for pulsatile pumping are observed for low frequencies under square wave voltage.

2015 ◽  
Vol 5 (1) ◽  
pp. 1-26
Author(s):  
Paul Woafo ◽  
Abobda Theodore Lejuste

This paper describes and investigates the dynamics of a new model of biventricular model for artificial heart which consists of two ferromagnetic masses fixed on springs and subjected to a common electromagnet powered by sinusoidal and square wave voltage sources. The effects of the following control parameters are considered: the external voltage source frequency and amplitude, the ratio between the stiffness coefficients, and the one between the masses. As results in both cases of external excitations, subharmonic oscillations, hysteresis, coexistence of limit cycle and point attractor, permanent bounding are found. The optimal voltage and the ratio between the stiffness coefficients are obtained. Bursting oscillations usable for pulsatile pumping are observed for low frequencies under square wave voltage.


2020 ◽  
Vol 20 (2) ◽  
pp. 437-458 ◽  
Author(s):  
Félix del Teso ◽  
Jørgen Endal ◽  
Juan Luis Vázquez

AbstractThe classical Stefan problem is one of the most studied free boundary problems of evolution type. Recently, there has been interest in treating the corresponding free boundary problem with nonlocal diffusion. We start the paper by reviewing the main properties of the classical problem that are of interest to us. Then we introduce the fractional Stefan problem and develop the basic theory. After that we center our attention on selfsimilar solutions, their properties and consequences. We first discuss the results of the one-phase fractional Stefan problem, which have recently been studied by the authors. Finally, we address the theory of the two-phase fractional Stefan problem, which contains the main original contributions of this paper. Rigorous numerical studies support our results and claims.


2016 ◽  
Vol 684 ◽  
pp. 111-119 ◽  
Author(s):  
Stanislav Rafaelevich Abulkhanov ◽  
Dmitrii Sergeevich Goryainov

Natural frequencies of the four upgraded front searchlight designs were received in ANSYS software environment. In the first case serial front searchlight incandescent electric lamp was replaced by a LED group which was mounted on the one-piece cylinder backing. The second front searchlight design had the backing which was upgraded by a radial ribs and concentric rigidity ferrules. Analyze of the backing deformation character by vibrations with the natural frequencies established a number of design solutions which make it possible to raise front searchlight vibration resistance. By the front searchlight model were established that the natural frequencies of the searchlight with the one-piece backing appertain to the whole range of the train vibrations. Natural frequencies of the backing with perforation, rigidity ferrules, and radial ribs appertain to the low frequencies of the railway locomotive vibrations spectrum. On basis of devised methodology of analyze of the deformation and natural frequencies of the surface carrying a LED group the vibration-proof searchlight design was introduced and researched.


2011 ◽  
Vol 133 (6) ◽  
Author(s):  
A. Wagner ◽  
M. E. Johnson ◽  
K. Idrisi ◽  
D. P. Bartylla

The heterogeneous (HG) blanket is a passive treatment used to reduce the low frequency transmission of sound through partitions. HG blankets, glued onto a structure, consist of an elastic medium with embedded mass inhomogeneities that mechanically replicate a mass-spring-damper system to reduce efficient radiating structural modes at low frequencies. The elastic layer typically used has sound absorption properties to create a noise control device with a wide bandwidth of performance. The natural frequency of an embedded dynamic vibration absorber is determined by the mass of the inhomogeneity as well as by its effective stiffness due to the interaction of the mass inclusion with the elastic layer. A novel analytical approach has been developed to describe in detail the interaction of the mass inclusions with the elastic layer and the interaction between the masses by evaluating special elastomechanical concepts. The effective stiffness is predicted by the analytical approach based on the shape of the mass inclusions as well as on the thickness and material properties of the layer. The experimental validation is included and a simplified direct equation to calculate the effective stiffness of a HG blanket is proposed. Furthermore, the stress field inside the elastic material will be evaluated with focus on the stresses at the base to assess the modeling of one or more masses placed on top of the elastic layer as dynamic vibration absorbers. Finally, the interaction between two (or more) masses placed onto the same layer is studied with special focus on the coupling of the masses at low distances between them.


2020 ◽  
Vol 19 (3) ◽  
pp. 641-653
Author(s):  
Gennadiy N. Mokshin

This article reconstructs the cultural doctrine of the famous publicist of populism (narodnichestvo), I.I. Kablits (Yuzov). To just equate Kablits views with the slogan of yuzovshchina would be a narrow interpretation of his kul'turnichestvo; the slogan is characteristic for extreme right-wing populism during the upsurge of the revolutionary populist movement (narodovol'cheskoe dvizhenie). In 1880, Kablits was the first of the legal populists to pose the question, What is populism? According to the publicist, true narodnichestvo should be based on the principle that the forms of public life of the people must be in conformity with the development level of their consciousness. The author explains Kablits evolution from Bakunism to a peasant-centered narodnichestvo by his interpretation of the reasons for the split between the intelligentsia and the people. Kablits considered them antagonists, and defined the ultimate goal of the narodniki as the liberation of the people from the power of the intellectualbureaucratic minority, the latter supposedly trying to subjugate the life of the masses to its will. The article analyzes the main provisions of Kablits sociocultural concept of social transformations: apolitism, populism, and the initiative of the masses. The article identifies the differences between his program of developing the cultural identity of the people, on the one hand, and other populists' understanding of the tasks of cultural work, on the other. Particular attention is paid to Kablits-Yuzov's attitude towards the problem of educating the masses. Kablits was one of the few Russian populists who opposed the idea that the foundations of the worldview of the people must be changed, arguing that this would eliminate the traditional moral values of the village, including the sense of collectivism. The author assesses how Kablits, the leading publicist of the newspaper Nedelya, contributed to the establishment of a cultural direction in narodnichestvo at the turn of the 1870s and 1880s. According to the author, Kablits played a leading role in shaping the ideology of the right flank of the cultural direction in narodnichestvo. However, the pure populism of Kablits turned out to be too pseudo-scientific, dogmatic and irrational to attract the democratic intelligentsia for a long time; the latter had already become disillusioned with the idea of the people as the creator of new forms of social life.


2021 ◽  
pp. 136-146
Author(s):  
Elena V. Barysheva ◽  
◽  
Dmitriy V. Morozov ◽  

The authors make an attempt to analyse on the basis of Hayden White’s theory of historical narrative historiosophical prerequisites for the formation of the cult of personality in the soviet biographies of V.I. Lenin published in 1924–1956. The basis of texts is a plot structure, implying, on the one hand, the existence of immutable laws of historical development, which humanity is forced to obey, and, on the other, a person who is able to learn them through the bitterness of defeats and put them at his service. The explanation of the facts of the historical narrative takes place by using two types of formal argument: Mechanism, which emphasizes the laws of historical development and the role of the masses in the historical process, and organicism, which gives high priority to V.I. Lenin himself and the party he created. The authors conclude that the articulation of the plot structure and types of formal argument embodied in the biographies becomes a prerequisite for the formation of the cult of personality. The latter implies the construction of an image of a person capable of transforming the reality, according to the concept of historical development that dominates in the party political historiography


2016 ◽  
Vol 55 (4) ◽  
Author(s):  
Ignas Nevinskas ◽  
Sandra Stanionytė ◽  
Vaidas Pačebutas ◽  
Arūnas Krotkus

Lattice-matched GaInAs p-i-n diodes of different i-region thicknesses have been MBE grown on n-type InP (100) and (111) crystallographic orientation substrates. It has been found that terahertz emission from such structures when illuminated with femtosecond laser pulses can be more efficient than that from the known to date best surface terahertz emitter (111) p-InAs. The explanation of the terahertz generation mechanism from p-i-n diodes is based on ultrafast photocurrent effects. Anisotropic transient photocurrents causing the 3ϕ azimuthal angle dependence are observed in the sample on (111) substrate. These p-i-n structures allow covering a technologically important 1.55 μm range and may provide controllability and compactness of a THzTDS system when biased with an external voltage source.


2020 ◽  
Vol 13 (3) ◽  
pp. 1737-1761
Author(s):  
Ting-Chen Chen ◽  
Man-Kong Yau ◽  
Daniel J. Kirshbaum

Abstract. Budget analysis of a tendency equation is widely utilized in numerical studies to quantify different physical processes in a simulated system. While such analysis is often post-processed when the output is made available, it is well acknowledged that the closure of a budget is difficult to achieve without temporal and/or spatial averaging. Nevertheless, the development of errors in such calculations has not been systematically investigated. In this study, an inline budget retrieval method is first developed in the WRF v3.8.1 model and tested on a 2D idealized slantwise convection case with a focus on the momentum equations. This method extracts all the budget terms following the model solver, which gives a high accuracy, with a residual term always less than 0.1 % of the tendency term. Then, taking the inline values as truth, several offline budget analyses with different commonly used simplifications are performed to investigate how they may affect the accuracy of the estimation of individual terms and the resultant residual. These assumptions include using a lower-order advection operator than the one used in the model, neglecting grid staggering, or following a mathematically equivalent but transformed format of the governing equations. Errors in these post-processed analyses are found mostly over the area where the dynamics are the most active, thus impairing the subsequent physical interpretation. A maximum 99th percentile residual can reach >50 % of the concurrent tendency term, indicating the danger of neglecting the residual term as done in many budget studies. This work provides general guidance not only for budget diagnoses with the WRF model but also for minimizing the errors in post-processed budget calculations.


2020 ◽  
Vol 249 (1) ◽  
pp. 3-52
Author(s):  
Julio Cesar Magalhães de Oliveira

Abstract The objective of this article is to place the study of urban protest and violence in the period from about 300 to about 600 CE in a broader perspective and to subject the investigation of plebeian activism to the basic precepts of analysis of collective action developed by social scientists and historians studying other periods. Its main argument is that, contrary to wide held assumptions in the historiography, what characterized Late Antiquity was not simply the exacerbation of violence or its tighter control, but the crisis of aristocratic hegemony and the expansion of opportunities for popular intervention in city life. What has been perceived as the product fanaticism, irrationality and deprivation of the masses, of the manipulation of bishops and aristocrats or of the failure of the mechanisms of coercion was actually the result of a dramatic social change that, on the one hand, involved a new dynamic of power and, on the other, a shift in the way the people understood their role and power in local communities.


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