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Videos search results: "surface"
 
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Title          
Physics of Fluids - Waves in a large free sph... 
   
 
Abstract    
In physics a free surface is the surface of a body that is subject to neither perpendicular normal stress nor parallel shear stress, such as the boundary between two homogenous fluids, for example liquid water and the air in the Earth's atmosphere. Unlike liquids, gases cannot form a free surface on their own. A liquid in a gravitational field will form a free surface if unconfined from above. Under mechanical equilibrium this free surface must be perpendicular to the forces acting on the liquid; if not there would be a force along the surface, and the liquid would flow in that direction. Thus, on the surface of the Earth, all free surfaces of liquids are horizontal unless disturbed (except near solids dipping into them, where surface tension distorts the surface locally). If the free surface of a liquid is disturbed, waves are produced on the surface. These waves are not elastic waves due to any elastic force; they are gravity waves caused by the force of gravity tending to bring the surface of the disturbed liquid back to its horizontal level, but due to momentum, it overshoots. Thus it oscillates and spreads the disturbance to the neighboring portions of the surface. The velocity of the surface waves varies as the square ...
 
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Added By - sidpatel
Subject - Mechanical Engineering
Document Type -
Video Duration - 00:02:52
 
 
 

 

Title          
Greedy Computation of a Homotopy Basis for a ... 
   
 
Abstract    

I found this video on the web and it does not belong to me. However i thought this will be of interets to the community. Thanks Keenan for this wonderful work. Following is quoted from Keenan. "Several tools from topology are useful for mesh processing and computer graphics. These tools often operate on the 1-skeleton of a surface, i.e., the graph of edges embedded in the surface. A common task is to find a collection of edges called a cut graph - cutting along these paths turns the surface into a shape which can be flattened into the plane. This kind of flattening is necessary for texture mapping, remeshing, etc. One way to find a cut graph is to find a set of loops, no two of which are homologous, which cut the surface into a disk when removed. Intuitively, two loops on a surface are homologous if one can be deformed into the other while always keeping it entirely on the surface. For a closed orientable surface with genus g (i.e., a torus with g handles), there are 2g classes of homologically independent loops. A homology basis consists of one loop from each class. Not every homology basis is a cut graph: some homology bases either disconnect the surface or cut it into a punctured sphere. However, a homot...

 
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Added By - appliedmath
Subject - Mathematics
Document Type - Computer Simulations
Video Duration - 00:00:39
 
 
 

 

Title          
Experiments with the Mobius Strip 
   
 
Abstract    
The Möbius strip or Möbius band (pronounced /moʊbiːəs, mei-/ i.e. beginning with "Moe" or "may"; German /ˈmøbiʊs/) is a surface with only one side and only one boundary component. It has the mathematical property of being non-orientable. It is also a ruled surface. It was discovered independently by the German mathematicians August Ferdinand Möbius and Johann Benedict Listing in 1858 [1] [2] [3].

A model can easily be created by taking a paper strip and giving it a half-twist, and then joining the ends of the strip together to form a single strip. In Euclidean space there are in fact two types of Möbius strips depending on the direction of the half-twist: clockwise and counterclockwise. The Möbius strip is therefore chiral, which is to say that it is "handed".

It is straightforward to find algebraic equations the solutions of which have the topology of a Möbius strip, but in general these equations do not describe the same geometric shape that one gets from the twisted paper model described above. In particular, the twisted paper model is a developable surface (it has zero Gaussian curvature). A system of differential-algebraic equations that describes models of this type was ...
 
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Added By - 123
Subject - Mathematics
Document Type - Experiments
Video Duration - 00:00:02
 
 
 

 

Title          
Superhydrophobic Surface Technology 
   
 
Abstract    
This technology can be used to create icing resistant surfaces on airplane wings, toilets that stay clean by themselves, zero rust surfaces and many more. It is a superhydrophobic material developed by Prof Chunlei Guo, professor of optics at University of Rochester and his team. Using laser to etch an unique pattern of surface structures at micro and nano scales the surface of materials is rendered hydrophobic. Unlike the conventional approach of chemical coating to make surfaces hydrophobic this approach gives much stronger hydrophobia and doesn\'t come with the risk of peeling off. The materials Guo has created are much more slippery than Teflon. The article, “Multifunctional surfaces produced by femtosecond laser pulses,” was published in the Journal of Applied Physics on January 20, 2015 (DOI: 10.1063/1.4905616). It can be accessed at: http://scitation.aip.org/content/aip/journal/jap/117/3/10.1063/1.4905616
 
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Added By - A Ghosh
Subject - Material Science and Engineering
Document Type - Demonstration
Video Duration - moderate
 
 
 

 

Title          
Underwater Explosion Phenomena 
   
 
Abstract    
An underwater explosion (also known as an UNDEX) is a chemical or nuclear explosion that occurs under the surface of a body of water.The effects of an underwater explosion depend on several things, including distance from the explosion, the energy of the explosion, the depth of the explosion, and the depth of the water. Underwater explosions are categorized by the depth of the explosion. Shallow underwater explosions are those where a crater formed at the water's surface is large in comparison with the depth of the explosion. Deep underwater explosions are those where the crater is small in comparison with the depth of the explosion, or nonexistent. The overall effect of an underwater explosion depends on depth, the size and nature of the explosive charge, and the presence, composition and distance of reflecting surfaces such as the seabed, surface, thermoclines, etc. This phenomenon has been extensively used in antiship warhead design since an underwater explosion (particularly one underneath a hull) can produce greater damage than an above-surface one of the same explosive size. Initial damage to a target will be caused by the first shockwave; this damage will be amplified by the subsequent physical movement of water and by the ...
 
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Added By - A Ghosh
Subject - Physics
Document Type - Demonstration
Video Duration - moderate
 
 
 

 

Title          
Sound Reflection from Concave Surfaces 
   
 
Abstract    

Reflection is the change in direction of a wavefront at an interface between two different media so that the wavefront returns into the medium from which it originated. Common examples include the reflection of light, sound and water waves. The law of reflection says that for specular reflection the angle at which the wave is incident on the surface equals the angle at which it is reflected. Mirrors exhibit specular reflection. In acoustics, reflection causes echoes and is...

 
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Added By - reberg
Subject - Physics
Document Type - Demonstration
Video Duration - 00:04:44
 
 
 

 

Title          
CO2 emissions and climate change 
   
 
Abstract    
Global warming is the increase in the average temperature of the Earth's near-surface air and oceans in recent decades and its projected continuation. The global average air temperature near the Earth's surface rose 0.74 ± 0.18 °C (1.33 ± 0.32 °F) during the 100 year period ending in 2005.[1] The Intergovernmental Panel on Climate Change (IPCC) concludes "most of the observed increase in globally averaged temperatures since the mid-20th century is very likely due to the observed increase in anthropogenic greenhouse gas concentrations"[1] via the greenhouse effect. Natural phenomena such as solar variation combined with volcanoes probably had a small warming effect from pre-industrial times to 1950 and a small cooling effect from 1950 onward.[2][3] These basic conclusions have been endorsed by at least 30 scientific societies and academies of science,[4] including all of the national academies of science of the major industrialized countries.[5][6][7] While individual scientists have voiced disagreement with the conclusions of the IPCC[8], the overwhelming majority of scientists working on climate change are in agreement with the conclusions.
 
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Added By - publichealth
Subject - Public Health
Document Type - Discussion
Video Duration - 00:01:55
 
 
 

 

Title          
Reflection of Pulses 
   
 
Abstract    

Reflection is the change in direction of a wavefront at an interface between two different media so that the wavefront returns into the medium from which it originated. Common examples include the reflection of light, sound and water waves. The law of reflection says that for specular reflection the angle at which the wave is incident on the surface equals the angle at which it is reflected. Mirrors exhibit specular reflection. In acoustics, reflection causes echoes and is...

 
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Added By - reberg
Subject - Physics
Document Type - Demonstration
Video Duration - 00:09:53
 
 
 

 

Title          
SEM Stage U2B 
   
 
Abstract    
SEM stage adjustments, movements and sample loading.A demonstration video with instructions on the basic operation of an electron scanning microscope. The scanning electron microscope (SEM) is a type of electron microscope that images the sample surface by scanning it with a high-energy beam of electrons in a raster scan pattern. The electrons interact with the atoms that make up the sample producing signals that contain information about the sample's surface topography, composition and other properties such as electrical conductivity.The types of signals produced by an SEM include secondary electrons, back scattered electrons (BSE), characteristic x-rays, light (cathodoluminescence), specimen current and transmitted electrons. These types of signal all require specialized detectors for their detection that are not usually all present on a single machine. The signals result from interactions of the electron beam with atoms at or near the surface of the sample. In the most common or standard detection mode, secondary electron imaging or SEI, the SEM can produce very high-resolution images of a sample surface, revealing details about 1 to 5 nm in size. Due to the way these images are created, SEM micrographs have a very large depth ...
 
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Added By - quantum
Subject - Physics
Document Type - Demonstration
Video Duration - 00:05:45
 
 
 

 

Title          
The Lunar Orbiter: A Spacecraft to Advance Lu... 
   
 
Abstract    
1966. The film describes the Lunar Orbiter's mission to photograph landing areas on the Moon. The Orbiter will be launched from Cape Kennedy using an Atlas Agena booster rocket. Once it is boosted in a trajectory toward the Moon, the Orbiter will deploy two-way earth communication antennas and solar panels for electricity. Attitude control jets will position the solar panels toward the sun and a tracker for a fix on its navigational star. The Orbiter will be put in an off-center orbit around the Moon where it will circle from four to six days. Scientists on Earth will study the effects of the Moon's gravitational field on the spacecraft, then the orbit will be lowered to 28 miles above the Moon's surface. Engineers will control the Orbiter manually or by computer to activate two camera lenses. The cameras will capture pictures of 12,000 square miles of lunar surface in 25 and 400 square mile increments. Pictures will be sent back to Earth using solar power to transmit electrical signals. The signals will be received by antennas at Goldstone, CA, and in Australia and Spain. Incoming photographic data will be electronically converted and processed to produce large-scale photographic images. The mission will be directed from the Spac...
 
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Added By - A Ghosh
Subject - Aeronautics and Astronautics
Document Type - Demonstration
Video Duration - 00:07:38
 
 
 

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