scholarly journals Impact Fracture of Composite and Homogeneous Nanoagglomerates

2008 ◽  
Vol 2008 ◽  
pp. 1-7 ◽  
Author(s):  
S. J. Antony ◽  
R. Moreno-Atanasio ◽  
J. Musadaidzwa ◽  
R. A. Williams
Keyword(s):  
Kinetic Energy ◽  
Impact Loading ◽  
Fracture Behaviour ◽  
Time Lag ◽  
Impact Fracture ◽  
Initial Kinetic Energy ◽  
Normal Impact ◽  
Fracture Characteristics ◽  
Hard Shell ◽  
The Moment

It is not yet clear on whether the fracture characteristics of structured composite capsules and homogeneous nanoagglomerates differ significantly under impact loading conditions. Experimental measurement of impact fracture properties of such small agglomerates is difficult, due to the length and time scales associated with this problem. Using computer simulations, here we show that nanoagglomerates are subjected to normal impact loading fracture within a few nanoseconds in a brittle manner. The restitution coefficient of the nanoagglomerates varies nonlinearly with initial kinetic energy. The fracture of nanoagglomerates does not always happen at the moment when they experience the maximum wall force, but occurs after a time lag of a few nanoseconds as characterised by impact survival time (IST) and IST index. IST is dependant on the initial kinetic energy, mechanical and geometric properties of the nanoagglomerates. For identical geometries of the capsules, IST index is higher for capsules with a soft shell than for these with a hard shell, an indication of the enhanced ability of the soft nanocapsules to dissipate impact energy. The DEM simulations reported here based on theories of contact mechanics provide fundamental insights on the fracture behaviour of agglomerates—at nanoscale, the structure of the agglomerates significantly influences their breakage behaviour.

Ranges of projectiles in amorphous materials

1968 ◽  
Vol 46 (6) ◽  
pp. 455-465 ◽  
Author(s):  
J. B. Sanders
Keyword(s):  
Distribution Function ◽  
Kinetic Energy ◽  
Power Law ◽  
Interaction Potential ◽  
Amorphous Materials ◽  
Initial Kinetic Energy ◽  
Initial Direction ◽  
Average Value ◽  
Inverse Power Law ◽  
The Moment

By using an inverse power-law approximation for the interaction potential between a fast-moving projectile and the atoms of an amorphous target into which it penetrates, it is possible to calculate moments of any order of different combinations of range quantities as functions of the initial kinetic energy of the projectile. By the moment of order n of a statistically distributed quantity X we mean the average value of Xn. The quantities concerned are the projection of the total distance from its point of entrance, reached by the projectile on its initial direction of motion, and the projection on the plane, perpendicular to this direction. From these moments, a distribution function of the penetration depth can be constructed. This calculation has been performed for 85Kr ions entering amorphous Al2O3 with different energies. The result is compared with measurements made by Domeij et al.

OBOLESCENCE AND THE DIFFUSION OF INNOVATIONS

2020 ◽  
pp. 113-130
Author(s):  
A.V. GOLUBEV ◽  
Keyword(s):  
Diffusion Of Innovations ◽  
Time Lag ◽  
Practical Implementation ◽  
Primary Role ◽  
Innovation Development ◽  
Scientific Hypothesis ◽  
Scientific Papers ◽  
The Moment ◽  
Sociological Studies

The diffusion of innovations is described as a process in a number of scientific papers. At the same time, the causes of this process have not been sufficiently studied. The author’s goal is to consider the main regularities, under which the life cycle of innovations begins, and propose measures to enhance diffusion in modern conditions. As a scientific hypothesis, the author accepts the postulate about the primary role of the obolescence of attracted innovations in this process. The analysis revealed not only the economic proportions that initiate the start of innovation promotion, but also the influence on the diffusion rate of the obsolescence degree of innovations and the market share occupied by the new product. Methodological approaches have been developed to determine economic efficiency depending on the moment of technological change-over, as well as to determine the absolute and relative speed of innovation diffusion. Sociological studies were conducted to determine the state of innovation development and the time lag between obtaining information about an innovation and its practical implementation. The author presents his “Agroopyt” information system developed to disseminate knowledge in the agricultural sphere and ensure technology transfer in agriculture. Digital methods provide for significant accelerateion of the diffusion of innovations and expand its scope.

Some measurements of the flux of infra-red radiation in the atmosphere

1956 ◽  
Vol 236 (1205) ◽  
pp. 175-186 ◽  
Keyword(s):  
Kinetic Energy ◽  
Lower Stratosphere ◽  
Atmospheric Radiation ◽  
Radiative Cooling ◽  
Classical View ◽  
Upper Troposphere ◽  
Infra Red ◽  
The Moment ◽  
Effective Radiation ◽  
Red Radiation

For the continual development of the kinetic energy of the winds, it is necessary for the upper troposphere to be cooled by radiation. Results are reported of nine aircraft ascents on which the upward and downward flows of infra-red radiation were measured and com­pared with values calculated using the radiation charts of Elsasser and Yamamoto. The divergence of radiative flux deduced from these measurements clearly shows that the cooling in the troposphere is not very different from that calculated from radiation charts. The importance of clouds on the radiative pattern is demonstrated; at the moment, incom­plete knowledge of cloud structure will be the chief factor limiting the value of calculations of atmospheric radiation. The measurements are of very limited value in the stratosphere, since, for the very small quantities of water there, the effective radiation is in the rotation band of water vapour ( λ between 30 and 70 μ ) and the radiometer used was not sensitive to these wavelengths. If the use of radiation charts is extrapolated to these conditions they indicate that the radiative cooling continues in the lower stratosphere. This is in contrast with the ‘classical’ view that the stratosphere is in radiative equilibrium.

scholarly journals Simulation of Bullet Fragmentation and Penetration in Granular Media

Materials ◽  
2020 ◽  
Vol 13 (22) ◽  
pp. 5243
Author(s):  
Froylan Alonso Soriano-Moranchel ◽  
Juan Manuel Sandoval-Pineda ◽  
Guadalupe Juliana Gutiérrez-Paredes ◽  
Usiel Sandino Silva-Rivera ◽  
Luis Armando Flores-Herrera
Keyword(s):  
Kinetic Energy ◽  
Granular Media ◽  
Elastic Collision ◽  
Smooth Particle Hydrodynamics ◽  
X Ray ◽  
Bullet Fragmentation ◽  
Particle Hydrodynamics ◽  
The Moment ◽  
Physical Phenomena ◽  
The Impact

The aim of this work is to simulate the fragmentation of bullets impacted through granular media, in this case, sand. In order to validate the simulation, a group of experiments were conducted with the sand contained in two different box prototypes. The walls of the first box were constructed with fiberglass and the second with plywood. The prototypes were subjected to the impact force of bullets fired 15 m away from the box. After the shots, X-ray photographs were taken to observe the penetration depth. Transient numerical analyses were conducted to simulate these physical phenomena by using the smooth particle hydrodynamics (SPH) module of ANSYS® 2019 AUTODYN software. Advantageously, this module considers the granular media as a group of uniform particles capable of transferring kinetic energy during the elastic collision component of an impact. The experimental results demonstrated a reduction in the maximum bullet kinetic energy of 2750 J to 100 J in 0.8 ms. The numerical results compared with the X-ray photographs showed similar results demonstrating the capability of sand to dissipate kinetic energy and the fragmentation of the bullet caused at the moment of impact.

scholarly journals Magnetic Field Amplification and Polar Jet Formation in Protostars

1987 ◽  
Vol 115 ◽  
pp. 384-384
Author(s):  
S. Hinata
Keyword(s):  
Magnetic Field ◽  
Angular Momentum ◽  
Kinetic Energy ◽  
Accretion Disk ◽  
Outer Edge ◽  
Moment Of Inertia ◽  
Simple Relationship ◽  
Field Amplification ◽  
Background Magnetic Field ◽  
The Moment

There is a simple relationship among moment of inertia I, rotational kinetic energy K, and momentum L given by (David Layzer, private communication), 2IK ≧ L. During the Hayashi phase a rotating protostar will amplify the trapped magnetic field by a dynamo-like process. Since the rotation is expected to be fast, many unstable modes will be excited and will grow exponentially in time until some nonlinear processes saturate the amplitude. However, it may happen that the reduction in rotational kinetic energy becomes so large that without increasing the moment of inertia the inequality given above may not be satisfied. The only way to increase the moment of inertia is to move the mass outward. This can be done by transferring the angular momentum outward through the magnetic field. So we will have a fast rotating mass shell at the outer edge of the star. Further transfer of angular momentum will push the shell against the accretion disk; the moving masses of the disk will divert the mass flow along the background magnetic field which extends perpendicular to the accretion disk. This results in the hollow cone jets from both poles because the outward motion is primarily on the equatorial plane.

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