scholarly journals High speed galloping in the cheetah (Acinonyx jubatus) and the racing greyhound (Canis familiaris): spatio-temporal and kinetic characteristics

2012 ◽  
Vol 215 (14) ◽  
pp. 2425-2434 ◽  
Author(s):  
P. E. Hudson ◽  
S. A. Corr ◽  
A. M. Wilson
Author(s):  
Xiaodong Lu ◽  
Tao Cui ◽  
Jiayao Gu

A nonlinear time-varied similarity(NTVS) simulation algorithm is proposed to solve the problem that the process of space interception is intractable to simulate with high precision in limited platform under the linear constant similarity(LCS). Firstly, the similarity criterions based on the dimensional analysis are given in the simulation of the interception motion at high-speed, and the disadvantage of LCS is analyzed. Then, the reference motion is introduced to establish a time-varied spatio-temporal transform system which scale factors are self-adaptive with time, and the method is proved to satisfy the similarity consistency. Finally the way that linear separation and independent mapping solve the problem that the large magnitude uniform motion in approaching directions and small magnitude overload motion in lateral directions are simulated in a limited ground platform. The results show that the NTVS can simulate the whole process of interception and perform better in accuracy comparing with that via LCS.


2006 ◽  
Author(s):  
C. J. Weiland ◽  
P. P. Vlachos

Supercavitation inception and formation was studied over blunt projectiles. The projectiles were fired using a gas gun method. In this method, projectiles are launched under the action of expanding detonation gases. Both qualitative and quantitative optical flow diagnostics using high speed digital imaging were used to analyze the spatio-temporal development of the supercavitating flow. For the first time, quantification of the supercavitation was achieved using Time Resolved Digital Particle Image Velocimetry (TRDPIV) detailing the two phase flow field surrounding the translating projectiles and the gas vapor bubble. Experimental results indicate that the supercavity forms at the aft end of the projectile and travels forward along the direction of projectile travel. The impulsive start of the projectile generates two asymmetric vortices which are shed from the blunt nose of the projectile. The vortices interact with the moving cavity and subsequently deform. This interaction is believed to directly contribute to the instabilities in the flight path.


2012 ◽  
Vol 9 (77) ◽  
pp. 3378-3386 ◽  
Author(s):  
Richard J. Bomphrey ◽  
Per Henningsson ◽  
Dirk Michaelis ◽  
David Hollis

Aerodynamic structures generated by animals in flight are unstable and complex. Recent progress in quantitative flow visualization has advanced our understanding of animal aerodynamics, but measurements have hitherto been limited to flow velocities at a plane through the wake. We applied an emergent, high-speed, volumetric fluid imaging technique (tomographic particle image velocimetry) to examine segments of the wake of desert locusts, capturing fully three-dimensional instantaneous flow fields. We used those flow fields to characterize the aerodynamic footprint in unprecedented detail and revealed previously unseen wake elements that would have gone undetected by two-dimensional or stereo-imaging technology. Vortex iso-surface topographies show the spatio-temporal signature of aerodynamic force generation manifest in the wake of locusts, and expose the extent to which animal wakes can deform, potentially leading to unreliable calculations of lift and thrust when using conventional diagnostic methods. We discuss implications for experimental design and analysis as volumetric flow imaging becomes more widespread.


2012 ◽  
Vol 709 ◽  
pp. 408-444 ◽  
Author(s):  
S. Davoust ◽  
L. Jacquin ◽  
B. Leclaire

AbstractThe near field of a Reynolds number $R{e}_{0} = 2. 14\ensuremath{\times} 1{0}^{5} $ and low-Mach-number cylindrical jet has been investigated by means of a high-speed stereo PIV setup that provides the spatio-temporal velocity field in a transverse plane, two diameters downstream of the jet exit. Proper orthogonal decomposition (POD) and spatio-temporal correlations are used to identify some of the main dynamical features of this flow. We show that the flow is dominated by streamwise vortices whose production and spatial organization can be related to $m= 0$ and $m= 1$ perturbations, and to the mean shear of the mixing layer. A dynamical scenario is proposed which describes this interaction, in accordance with our observations.


2011 ◽  
Vol 7 (6) ◽  
pp. 882-884 ◽  
Author(s):  
A. W. Crompton ◽  
Catherine Musinsky

It has recently been suggested that the mechanism for lifting liquid from a bowl into the oral cavity during lapping is fundamentally different in cats and dogs: cats use adhesion of liquid to the tongue tip while dogs ‘scoop’ with their backwardly curled tongue. High-speed light videos and X-ray videos show that on the contrary, both cats and dogs use the mechanism of adhesion. Liquid is transported through the oral cavity to the oesophagus, against gravity, on the surface of the tongue as it is drawn upwards, then a tight contact between the tongue surface and palatal rugae traps liquid and prevents its falling out as the tongue is protruded. At least three cycles are needed for intraoral transport of liquid in the dog.


Author(s):  
C. Gong ◽  
L. Qi ◽  
L. Heming ◽  
H. Karimian ◽  
M. Yuqin

Region is a complicated system, where human, nature and society interact and influence. Quantitative modeling and simulation of ecology in the region are the key to realize the strategy of regional sustainable development. Traditional machine learning methods have made some achievements in the modeling of regional ecosystems, but it is difficult to determine the learning characteristics and to realize spatio-temporal simulation. Deep learning does not need prior identification of training characteristics, have excellent feature learning ability, can improve the accuracy of model prediction, so the use of deep learning model has a significant advantage. Therefore, we use net primary productivity (NPP), atmospheric optical depth (AOD), moderate-resolution imaging spectrometer (MODIS), Normalized Difference Vegetation Index (NDVI), landcover and population data, and use LSTM to do spatio-temporal simulation. We conduct spatial analysis and driving force analysis. The conclusions are as follows: the ecological deficit of northwestern Henan and urban communities such as Zhengzhou is higher. The reason of former lies in the weak land productivity of the Loess Plateau, the irrational crop cultivation mode. The latter lies in the high consumption of resources in the large urban agglomeration; The positive trend of Henan ecological development from 2013 is mainly due to the effective environmental protection policy in the 12th five-year plan; The main driver of the sustained ecological deficit growth of Henan in 2004-2013 is high-speed urbanization, increasing population and goods consumption. This article provides relevant basic scientific support and reference for the regional ecological scientific management and construction.


2020 ◽  
Vol 90 (1) ◽  
pp. 85
Author(s):  
А.А. Шибков ◽  
М.Ф. Гасанов ◽  
А.Е. Золотов ◽  
М.А. Желтов ◽  
А.А. Денисов ◽  
...  

Spatio-temporal structures of Portevin-Le Chatelier deformation bands at the pre-failure stage, necking and destruction of an aluminum-magnesium alloy, deformable in an aqueous medium, were investigated by a complex of in situ methods, including high-speed video of the surface and an electrochemical emission method. The latter is based on measuring and analyzing jumps in the electrode potential of a deformable metal under the conditions of the manifestation of intermittent deformation. It is established that discrete signals of electrochemical emission in the frequency band of 10 Hz - 10 kHz contain information on the number of deformation bands, the moments of nucleation and stages of their growth, the statistical temporal structure of the bands, etc. A characteristic series of signals at the pre-failure stage is revealed − an electrochemical precursor neck formation and specimen fracture. The connection between the generation of electrochemical emission signals and the localization of plastic deformation and the destruction of an oxide film on an aluminum alloy surface in contact with an aqueous medium is discussed.


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