scholarly journals Chemomechanical origin of directed locomotion driven by internal chemical signals

2020 ◽  
Vol 6 (18) ◽  
pp. eaaz9125
Author(s):  
Lin Ren ◽  
Ling Yuan ◽  
Qingyu Gao ◽  
Rui Teng ◽  
Jing Wang ◽  
...  
Keyword(s):  
Internal Wave ◽  
Mechanical System ◽  
Chemical Dynamics ◽  
Biomimetic Materials ◽  
Soft Robots ◽  
Wave Dynamics ◽  
System Parameters ◽  
Structural Modulation ◽  
Active Locomotion ◽  
Homogeneous Environment

Asymmetry in the interaction between an individual and its environment is generally considered essential for the directional properties of active matter, but can directional locomotions and their transitions be generated only from intrinsic chemical dynamics and its modulation? Here, we examine this question by simulating the locomotion of a bioinspired active gel in a homogeneous environment. We find that autonomous directional locomotion emerges in the absence of asymmetric interaction with the environment and that a transition between modes of gel locomotion can be induced by adjusting the spatially uniform intensity of illumination or certain kinetic and mechanical system parameters. The internal wave dynamics and its structural modulation act as the impetus for signal-driven active locomotion in a manner similar to the way in which an animal’s locomotion is generated via driving by nerve pulses. Our results may have implications for the development of soft robots and biomimetic materials.

Numerical Studies of Internal Wave Dynamics

1997 ◽  
Author(s):  
George F. Carnevale ◽  
M. C. Hendershott
Keyword(s):  
Internal Wave ◽  
Wave Dynamics ◽  
Numerical Studies

On the irreversibility of internal-wave dynamics due to wave trapping by mean flow inhomogeneities. Part 1. Local analysis

1993 ◽  
Vol 251 ◽  
pp. 21-53 ◽  
Author(s):  
Sergei I. Badulin ◽  
Victor I. Shrira
Keyword(s):  
Shear Flow ◽  
Internal Wave ◽  
Wave Field ◽  
Large Scale ◽  
Spatial Scales ◽  
Energy Concentration ◽  
Local Analysis ◽  
Mean Flow ◽  
Wave Trapping ◽  
Wave Dynamics

The propagation of guided internal waves on non-uniform large-scale flows of arbitrary geometry is studied within the framework of linear inviscid theory in the WKB-approximation. Our study is based on a set of Hamiltonian ray equations, with the Hamiltonian being determined from the Taylor-Goldstein boundary-value problem for a stratified shear flow. Attention is focused on the fundamental fact that the generic smooth non-uniformities of the large-scale flow result in specific singularities of the Hamiltonian. Interpreting wave packets as particles with momenta equal to their wave vectors moving in a certain force field, one can consider these singularities as infinitely deep potential holes acting quite similarly to the ‘black holes’ of astrophysics. It is shown that the particles fall for infinitely long time, each into its own ‘black hole‘. In terms of a particular wave packet this falling implies infinite growth with time of the wavenumber and the amplitude, as well as wave motion focusing at a certain depth. For internal-wave-field dynamics this provides a robust mechanism of a very specific conservative and moreover Hamiltonian irreversibility.This phenomenon was previously studied for the simplest model of the flow non-uniformity, parallel shear flow (Badulin, Shrira & Tsimring 1985), where the term ‘trapping’ for it was introduced and the basic features were established. In the present paper we study the case of arbitrary flow geometry. Our main conclusion is that although the wave dynamics in the general case is incomparably more complicated, the phenomenon persists and retains its most fundamental features. Qualitatively new features appear as well, namely, the possibility of three-dimensional wave focusing and of ‘non-dispersive’ focusing. In terms of the particle analogy, the latter means that a certain group of particles fall into the same hole.These results indicate a robust tendency of the wave field towards an irreversible transformation into small spatial scales, due to the presence of large-scale flows and towards considerable wave energy concentration in narrow spatial zones.

scholarly journals Assessment of vibration isolation in «Flexible connector–pipeline–vibration isolators Pendants» mechanical system

2020 ◽  
pp. 9-14
Author(s):  
Yu. A. Burian ◽  
◽  
A. V. Zubarev ◽  
S. N. Polyakov ◽  
◽  
...  
Keyword(s):  
Mechanical System ◽  
Vibration Isolation ◽  
Mechanical Resistance ◽  
Vibration Source ◽  
Vibration Isolators ◽  
Vibration Load ◽  
System Parameters ◽  
Radiated Power ◽  
Pipeline Vibration ◽  
Pumping Units

When designing pipeline systems, the question of reducing the vibration load transmitted from vibroactive elements (pumping units, compressors, etc.) through the pipelines to the base almost always arises. In this case, as a rule, when laying pipes, one end is connected to a vibration source through flexible elements (bellows, elastic compensators, pipes). The pipeline is installed on hangers with vibration dampers. The paper considers the issues of calculating the mechanical resistance of flexible connectors, pipelines and vibration isolators of suspensions, as well as analytical dependences and the results of numerical calculation of the forces transmitted to the base and the radiated power depending on the frequency. The graphic materials show the frequency characteristics of the forces on the base and vibration power, depending on the considered mechanical system parameters

scholarly journals A Combined H2/Sliding Mode Controller Design for a TORA System

2018 ◽  
Vol 21 (4) ◽  
pp. 501-507
Author(s):  
Hazem I. Ali ◽  
Mustafa J. Kadhim
Keyword(s):  
Sliding Mode Control ◽  
Mechanical System ◽  
Controller Design ◽  
Sliding Mode ◽  
Translational Motion ◽  
Sliding Mode Controller ◽  
Nonlinear Coupling ◽  
Underactuated Mechanical System ◽  
System Parameters ◽  
Rotational Actuator

In this work, the control of Translational Oscillations with a Rotational Actuator (TORA) system is presented in this paper. The optimal sliding mode controller is proposed to control the two DOF underactuated mechanical system. The nonlinear coupling from the rotational to the translational motion is the main problem that faces the controller design. The H2 sliding mode controller is designed to give a better performance if only sliding mode control is used. The results illustrate that the proposed H2 sliding mode controller can achieve the stabilization of the system with the variation in system parameters and disturbance.

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