scholarly journals Pulse-driven robot: Motion via solitary waves

2020 ◽  
Vol 6 (18) ◽  
pp. eaaz1166
Author(s):  
Bolei Deng ◽  
Liyuan Chen ◽  
Donglai Wei ◽  
Vincent Tournat ◽  
Katia Bertoldi

The unique properties of nonlinear waves have been recently exploited to enable a wide range of applications, including impact mitigation, asymmetric transmission, switching, and focusing. Here, we demonstrate that the propagation of nonlinear waves can be as well harnessed to make flexible structures crawl. By combining experimental and theoretical methods, we show that such pulse-driven locomotion reaches a maximum efficiency when the initiated pulses are solitons and that our simple machine can move on a wide range of surfaces and even steer. Our study expands the range of possible applications of nonlinear waves and demonstrates that they offer a new platform to make flexible machines to move.

Author(s):  
A. M. Oleynikov ◽  
L. N. Kanov

The paper gives the description of the original wind electrical installation with mechanical reduction in which the output of vertical axis wind turbine with rather low rotation speed over multiplicator is distributed to a certain number of generators. The number of acting generators is determined by the output of actual operating wind stream at each moment. According to this constructive scheme, it is possible to provide effective and with maximum efficiency installation work in a wide range of wind speeds and under any schedule issued to the consumer of electricity. As there are no any experience in using such complexes, mathematical description of its main elements is given, namely windwheels, generators with electromagnetic excitation of magnetic electrical type, then their interaction with windwheel, and also the results of mathematical modeling of work system regimes under using the offered system of equations. The basis for the mathematical description of the main elements of the installation – synchronous generators – are the system of equations of electrical and mechanical equilibrium in relative units in rotating coordinates without considering saturation of the magnetic circuit. The equation of mechanical equilibrium systems includes torque and brake windwheel electromagnetic moments of generators with taking into account the reduction coefficients and friction. In addition, we specify the alternator rotor dynamics resulting from continuous torque of windwheel fluctuations under the influence of unsteady wind flow and wind speed serving as the original variable is modeled by a set of sinusoids. Model simplification is achieved by equivalization of similar generators and by disregarding these transitions with a small time constant. Calculation the installation with synchronous generators of two types of small and medium capacity taking into account the operational factors allowed us to demonstrate the logic of interactions in the main elements of the reported complex in the process of converting wind flow into the generated active and reactive power. We have shown the possibility of stable system work under changeable wind stream condition by regulating of the plant blade angle and with simultaneous varying of generator number of different types. All these are in great interest for project organizations and power producers.


Applied Nano ◽  
2021 ◽  
Vol 2 (3) ◽  
pp. 148-161
Author(s):  
Katerina Govatsi ◽  
Aspasia Antonelou ◽  
Labrini Sygellou ◽  
Stylianos G. Neophytides ◽  
Spyros N. Yannopoulos

The rational synthesis of semiconducting materials with enhanced photoelectrocatalytic efficiency under visible light illumination is a long-standing issue. ZnO has been systematically explored in this field, as it offers the feasibility to grow a wide range of nanocrystal morphology; however, its wide band gap precludes visible light absorption. We report on a novel method for the controlled growth of semiconductor heterostructures and, in particular, core/sheath ZnO/MoS2 nanowire arrays and the evaluation of their photoelectrochemical efficiency in oxygen evolution reaction. ZnO nanowire arrays, with a narrow distribution of nanowire diameters, were grown on FTO substrates by chemical bath deposition. Layers of Mo metal at various thicknesses were sputtered on the nanowire surface, and the Mo layers were sulfurized at low temperature, providing in a controlled way few layers of MoS2, in the range from one to three monolayers. The heterostructures were characterized by electron microscopy (SEM, TEM) and spectroscopy (XPS, Raman, PL). The photoelectrochemical properties of the heterostructures were found to depend on the thickness of the pre-deposited Mo film, exhibiting maximum efficiency for moderate values of Mo film thickness. Long-term stability, in relation to similar heterostructures in the literature, has been observed.


2013 ◽  
Vol 2013 ◽  
pp. 1-14
Author(s):  
Yun Wu ◽  
Zhengrong Liu

We study the bifurcation phenomena of nonlinear waves described by a generalized Zakharov-Kuznetsov equationut+au2+bu4ux+γuxxx+δuxyy=0. We reveal four kinds of interesting bifurcation phenomena. The first kind is that the low-kink waves can be bifurcated from the symmetric solitary waves, the 1-blow-up waves, the tall-kink waves, and the antisymmetric solitary waves. The second kind is that the 1-blow-up waves can be bifurcated from the periodic-blow-up waves, the symmetric solitary waves, and the 2-blow-up waves. The third kind is that the periodic-blow-up waves can be bifurcated from the symmetric periodic waves. The fourth kind is that the tall-kink waves can be bifurcated from the symmetric periodic waves.


2007 ◽  
Vol 62 (1-2) ◽  
pp. 21-28
Author(s):  
Hilmi Demiray

In this work, treating an artery as a prestressed thin-walled elastic tube and the blood as an inviscid fluid, the interactions of two nonlinear waves propagating in opposite directions are studied in the longwave approximation by use of the extended PLK (Poincaré-Lighthill-Kuo) perturbation method. The results show that up to O(k3), where k is the wave number, the head-on collision of two solitary waves is elastic and the solitary waves preserve their original properties after the interaction. The leading-order analytical phase shifts and the trajectories of two solitons after the collision are derived explicitly.


Author(s):  
Fábio Orssatto ◽  
Maria Hermínia Ferreira Tavares ◽  
Flávia Manente da Silva ◽  
Eduardo Eyng ◽  
Leandro Fleck

This work evaluated the removal of total Kjeldahl nitrogen (TKN) and total phosphorus (P) through electrocoagulation and used aluminum electrodes to optimize the potential differential (pd) and hydraulic retention time (HRT) variables in a batch reactor. The experimental design used was Rotatable Central Composite Design (RCCD). The application of the electrocoagulation in the treatment of effluents from pig slaughterhouses and packing plants proved to be efficient in relation to the removal of TKN and total phosphorus, obtaining maximum efficiency equal to 67.15% and 99%, respectively. The maximum TKN removal value was found in Test 12, where treatment conditions were 30 minutes for HRT and 20 volts for pd, which corresponds to 0.86 A of electric current and a current density of 17.2 mA cm-2. For P, the only test that removed below 99% was the first. Through statistical analyses, it was only possible to obtain a mathematical model for TKN removal. While the response surface graph did not present a defined range of the best conditions for the independent variables, it was possible to observe the tendency for better removal, a wide range of pd and values over 30 minutes for retention time.


1970 ◽  
Author(s):  
R. R. Oliver ◽  
F. Fraschetti

This paper describes the performance and mechanical design of a 4500-hp, two shaft heavy duty simple or regenerative cycle gas turbine. This machine resulted from an international cooperative effort of the joint authors’ respective companies. Initially planned for gas pipelines and process applications, a line of load compressors has been integrated into the single package design. Options include indoor or outdoor models and geared or direct mechanical output for applications not served by the integral compressor models. A variable area load turbine nozzle assures maximum efficiency over a wide range of load, speed, and amibient conditions.


2021 ◽  
Vol ahead-of-print (ahead-of-print) ◽  
Author(s):  
Ahmed Ketata ◽  
Zied Driss

PurposeVariable geometry turbine (VGT), a key component of modern internal combustion engines (ICE) turbochargers, is increasingly used for better efficiency and reduced exhaust gas emissions. The aim of this study is the development of a new meanline FORTRAN code for accurate performance and loss assessment of VGTs under a wider operating range. This code is a useful alternative tool for engineers for fast design of VGT systems where higher efficiency and minimum loss are being required.Design/methodology/approachThe proposed meanline code was applied to a variable geometry mixed flow turbine at different nozzle vane angles and under a wide range of rotational speed and the expansion ratio. The numerical methodology was validated through a comparison of the predicted performance to test data. The maps of the mass flow rate as well as the efficiency of the VGT system are discussed for different nozzle vane angles under a wide range of rotational speed. Based on the developed model, a breakdown loss analysis was carried out showing a significant effect of the nozzle vane angle on the loss distribution.FindingsResults indicated that the nozzle angle of 70° has led to the maximum efficiency compared to the other investigated nozzle vane angles ranging from 30° up to 80°. The results showed that the passage loss was significantly reduced as the nozzle vane angle increases from 30° up to 70°.Originality/valueThis paper outlines a new meanline approach for variable geometry turbocharger turbines. The developed code presents the novelty of including the effect of the vane radii variation, due to the pivoting mechanism of the nozzle ring. The developed code can be generalized to either radial or mixed flow turbines with or without a VGT system.


2013 ◽  
Vol 135 (10) ◽  
Author(s):  
Hongyi Yu ◽  
Tatiana Gambaryan-Roisman ◽  
Peter Stephan

The flow of thin falling liquid films is unstable to long-wave disturbances. The flow instability leads to development of waves at the liquid–gas interface. The effect of the waves on heat and mass transfer in falling liquid films is a subject of ongoing scientific discussion. In this work, numerical investigation of the wave dynamics has been performed using a modified volume-of-fluid (VOF) method for tracking the free surface. The surface tension is described using the continuum surface force (CSF) model. With low disturbance frequency, solitary waves of large amplitude are developed, which are preceded by low-amplitude capillary waves. With high disturbance frequency, low amplitude sinusoidal waves are developed. The waveforms dependent on the Reynolds number and disturbance frequency are summarized in a form of a regime map. A correlation describing the separation curve between the sinusoidal waves regime and solitary waves regime is proposed. The wave parameters (peak height, length, and propagation speed) are computed from the simulation results and compared with available experimental correlations in a wide range of parameters. The effects of the disturbance frequency and the plane inclination angle on the wave dynamics have been studied. The interaction of waves initiated by simultaneous disturbances of two different frequencies has been investigated. The heat transfer in the wavy film has been simulated for the constant wall temperature boundary condition. The effects of Prandtl number and disturbance frequency on local and global heat transfer parameters have been investigated. It has been shown that the influence of waves on heat transfer is significant for large Prandtl numbers in a specific range of disturbance frequencies.


Sensors ◽  
2020 ◽  
Vol 20 (18) ◽  
pp. 5378 ◽  
Author(s):  
Szymon Borys ◽  
Wojciech Kaczmarek ◽  
Dariusz Laskowski

The article presents the results of computer simulations related to the selection and optimization of the parameters of robotic packing process of one type of product. Taking the required performance of the robotic production line as a basis, we proposed its configuration using the RobotStudio environment for offline robot programming and virtual controller technology. Next, a methodology for the validation of the adopted assumptions was developed, based on a wide range of input data and a precise representation of the applicable conditions in the packaging process of one type of product. This methodology included test scenarios repeated an appropriate number of times in order to obtain the result data with the desired reliability and repeatability. The main element of the research was a computer simulation of the station based on the Picking PowerPac package. It was assumed that the products on the technological line are generated pseudo-randomly, thus reflecting the real working conditions. The result of the conducted works is the optimal operating speed of industrial robots and conveyors. The developed methodology allows for multifaceted analyses of the key parameters of the technological process (e.g., the number of active robots and their load, speed of conveyors, and station efficiency). We paid special attention to the occurrence of anomalies, i.e., emergency situations in the form of “halting” the operation of chosen robots and their impact on the obtained quality of the industrial process. As a result of the simulations, numerical values were obtained, maximum efficiency, with regard to maximum overflow of items of 5%, for LB algorithm was equal to 1188 completed containers per hour, with conveyors speeds of 270 mm/s and 165 mm/s. This efficiency was possible at robot speeds R1 = 6450 mm/s, R2 = 7500 mm/s, R3 = 6500 mm/s, R4 = 6375 mm/s, R5 = 5500 mm/s, R6 = 7200 mm/s. The ATC algorithm reached efficiency of 1332 containers per hour with less than 5% overflown items, with conveyor speeds of 310 mm/s and 185 mm/s. This efficiency was possible at robot speeds R1 = 7500 mm/s, R2 = 7500 mm/s, R3 = 7200 mm/s, R4 = 7000 mm/s, R5 = 6450 mm/s, R6 = 6300 mm/s. Tests carried out for emergency situations showed that the LB algorithm does not allow for automatic continuation of the process, while the ATC algorithm assured production efficiency of 94% to 98% of the maximum station efficiency.


Nanophotonics ◽  
2020 ◽  
Vol 9 (10) ◽  
pp. 3235-3242 ◽  
Author(s):  
Tingting Lv ◽  
Xieyu Chen ◽  
Guohua Dong ◽  
Meng Liu ◽  
Dongming Liu ◽  
...  

AbstractPolarization conversion dichroism is of particular interest in manipulating the polarization state of light, whereas high-performance asymmetric transmission (AT) of linearly polarized waves is still inaccessible in the terahertz range. Here, a bilayer chiral metamaterial consisting of orthogonally chained S-shaped patterns with broken symmetry along the light propagation direction is proposed and demonstrated experimentally to realize a dual-band dichroic AT effect for linearly polarized terahertz waves. The AT effects are robust across a wide range of incident angles. The observed strong AT can be theoretically explained by a multiple reflection and transmission interference model and the transfer matrix method. The proposed bilayer chiral metamaterial may have broad applications in polarization manipulation, chiral biosensing and direction-dependent information processing.


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