Concrete and cement are (mostly) two different materials. Why mostly? Because concrete is made using cement. Though cement can (technically) be used on its own, concrete cannot be made without first making cement.
Classified as a ceramic, cement starts as a powder, a mixture of limestone and other minerals, which is heated and mixed with gypsum to form what we know of as cement. Still a powder in this form, once water is added and mixed the cement then hardens.
Portland cement, probably the most well known and commonly used cement, is classified as a hydraulic cement. This essentially means that once water has been added the chemical reaction, called hydration, that hardens the cement is not dependent on how much water is added. Hydraulic cements can harden underwater and remain strong even in wet conditions. As a side note, Portland cement is not a brand name, but a particular type of cement.
On the other hand, concrete is composed of cement, aggregate, and water, and is thus classified as a composite. Composites are defined as consisting of a matrix or binder that has a reinforcement within it. In the case of concrete, the cement water mixture is the matrix in which the reinforcement, or aggregate exists.
The aggregate is typically comprised of stones, rocks, and sand and its addition increases the durability of the concrete. The amount of the aggregate or the size of the aggregate added can also effect the water-to-cement ratio required to harden the material, strengthening the final product. The hardening process continues for years, meaning that concrete only gets stronger with age.
Though most concretes are lime-based, asphalt concrete uses asphalt as the cement material and polymer concretes also exist. Another common type of concrete is reinforced concrete, in which rebar, or reinforcing bars, are embedded within to add to the strength of the concrete.
Sources: ( 1 ) ( 2 ) ( 3 ) ( 4 ) ( 5 )
“Can you please make it stop, even for a moment? We were biologically determined for one purpose and one purpose alone: to sense the coming of death. I sense it coming now. We have come to Pahvo for your help. We have come to end this war. I am so afraid. So. Afraid.”
You’re in a time of war, and your enemy has a technological advantage that makes you unable to fight them on equal footing. This has happened so often throughout history: with iron vs. bronze weapons; with the invention and application of gunpowder; with the rise of nuclear capabilities. In space, the augmentation of a cloaking device makes the Klingons virtually invincible, and the Federation is losing this war, badly. What are they to do? What comes next? The ability to see an invisible ship is what’s needed, and this latest episode highlights an attempt to do so, by exploiting an uncontacted alien world. The aliens there are sentient, however, so using this technology would be a violation of both the Prime Directive and First Contact protocols. But what’s the ethical thing to do? Is it better to not interfere and face certain defeat? Or to exploit their technology, violate your principles, and gain the advantage?
Star Trek: Discovery is a show where right-and-wrong isn’t so cut-and-dry. Despite its flaws, it’s an interesting development that makes you think, without providing easy answers. Those, fortunately, will come next episode!
It’s easy: Form a triangle, then a hexagon, then a bicycle wheel
This is the general mechanism on how a spider spins its web (talk about engineering, right?). When an insect gets caught in its web, the vibrations caused by the insect is felt by the spider which then rushes to engulf its prey.
Now here is the trippy part ; This is the effect of drugs on the pattern of the web.
Hope you are having a great week. Have a good one!
* Spider spinning a web (video) (if you find a better full video let us know)
** Spiders on drugs - NASA article ; Video
It’s a technicolour dreamcoat for your crisp packet – a strong, flame-retardant and airtight new material that mimics mother of pearl.
The natural version, also called nacre, is found on the inner shell of some molluscs, where it is built up of layers of the mineral aragonite separated by organic polymers such as chitin. It is remarkably strong, without being brittle or dense.
We would like to use nacre and similar materials as a protective coating in many situations. However, making them is a slow and delicate process that is difficult to recreate at any useful scale. Artificial nacre-like materials are usually painstakingly built up layer by layer, but Luyi Sun at the University of Connecticut in Storrs and his colleagues found a way to do it all in one go.
Continue Reading.
If i could catch a rainbow,
I would just do it for you
And share with you it’s beauty,
On the days you are feeling Blue.
Rainbows are nature’s optical illusion.
It’s not possible unfortunately to catch a rainbow. They are not objects and are not located at specific distance from the observer that one can physically approach.
Rainbows stems from an optical illusion caused by any water droplets viewed from a certain angle relative to a light source.
They are user-specific and everyone sees a different rainbow.
Not all rainbows that occur in nature are multicolored. Under specific atmospheric conditions, one can spot the Mono-chrome rainbow i.e It has only one color.
PC : rodjonesphotography
A Moonbow / Lunar rainbow /White rainbow is a rainbow produced by light reflected off the surface of the moon (as opposed to direct sunlight) refracting off of moisture-laden clouds in the atmosphere / from waterfalls.
PC: GanMed64
Just as no two people see exactly the same rainbow, even if they’re standing next to each other, the few inches between your eyes make a difference in what you are viewing.
One can distinguish almost all colors in a rainbow but Indigo.
Legend has it that Newton included indigo because he felt that there should be seven rather than six colors in a rainbow due to his strong religious beliefs.
The Greeks and Romans thought a rainbow was the path made by Iris, the goddess of the rainbow, between heaven and earth, linking gods with humans. “Rainbow” in Latin is arcus iris or arcus pluvius, a “rainy arch”.
The iris of the eye is named after her, because of its colour.
The Greeks used the word “iris” to describe any coloured circle, such as the “eye” of a peacock’s tail. The flower called iris gets its name from the Greek, as does the chemical iridium (Ir), compounds of which are highly coloured. Iris is also the root of “iridescent”.
Place a linear polarizer over the camera whilst capturing a rainbow and you get pulsating rainbows.
Source
A double rainbow is a phenomenon in which two rainbows appear. They are caused by a double reflection of sunlight inside the raindrops. Similarly multiple rainbows are a possibility as well.
Observe that the colors in the second rainbow are inverted because the light is reflected twice inside the water droplet
PC: Janbazian
This video of a man witnessing a double rainbow for the first time went viral, featuring on numerous popular talk shows. Pure ecstasy!
Whilst standing on earth, we see rainbows as magical arcs across the sky, but rainbows are full circles. The bottom part of the full circle is usually blocked by the horizon.
Pilots however do not face this difficulty. Under the right sky conditions, pilots are spectators to one of nature’s most beautiful spectacles - The full rainbow.
PC : Steve Kaufman
Everything has beauty, but not everyone sees it.
Have a great day!
Fallstreak holes are natural phenomena that often get mistaken for UFOs. These ‘hole punch clouds’ occur when water droplets inside a cloud freeze and fall beneath it, creating a large gap that looks like a perfect hiding place for a flying saucer.
Aliens, obvi.
The rarity of fallstreak holes is what tends to throw people.
That paired with the tendency to look at anything in the sky and cry ‘UFO!’ is the perfect makings of a false alien alarm.
Sometimes these clouds have little rainbows inside.
They aren’t always circular, though…
They make all kinds of crazy shapes.
Including airplane/sword/cross/wieners.
Photos via: Rantplaces
Source
You might be an engineer if you know how long a zeptosecond is. (It's a trillionth of a billionth of a second!) http://ow.ly/uUUb30caXrH
According to Dictionary.com, steel is “any of various modified forms of iron, artificially produced, having a carbon content less than that of pig iron and more than that of wrought iron, and having qualities of hardness, elasticity, and strength varying according to composition and heat treatment: generally categorized as having a high, medium, or low-carbon content”.
Perhaps the most well known alloy around, as well as one of the most common materials in the world, steel is essentially iron with a small percentage of carbon (and, on occasion, one or more other elements). Not enough carbon and you’re stuck with wrought iron, too much carbon and you get cast iron. The graph above is a binary iron-carbon phase diagram that goes from zero percent carbon to about 6.5 percent, illustrating the various phases that can form.
Steel has been known about since ancient times, some pieces dating back to 1800 BC, but it was the invention of the Bessemer process during the industrial revolution that really popularized the alloy. (Technically, similar methods had been used before, particularly in China and Japan, but Henry Bessemer invented the modern method, industrializing it and obtaining a patent in 1856.)
Mainly used in construction, the alloy has been used for almost every possible application: from office furniture to steel wool, from bulldozers to washing machines, and from wires to watches, the possibilities are pretty much endless. Steel is also one of the world’s most-recycled materials, able to be used more than once, with a recycling rate of over 60% globally.
The addition of carbon allows the steel to be stronger than the iron it’s made from. Adding nickel and manganese increases its tensile strength, chromium increases hardness and melting temperature, and vanadium also increases hardness while making it less prone to metal fatigue. Stainless steel has at least eleven percent chromium, whereas Hadfield steel (which resists wearing) contains twelve to fourteen percent manganese. Check out these links for more information on the effects of adding certain elements.
Sources: 1 (top images), 2 (bottom images)
It has been a blissful month in physics with the nobel prize for the work on gravitational waves and LIGO swiftly striking back with the detection of a neutron star merger.
At FYP! we have started to dwell a little bit into the essence of condensed matter physics while exploring some really cool science and engineering along the way.
Here’s what went down on FYP! this month:
Nobel prize in physics article on Gravitational waves
Gravitational waves, Light and Merging neutron stars
Paramagnets and Combinatorics
Diamagnetic levitation - Ig Nobel prize(2000)
Levitating frogs and superconductivity
Revisiting rolling shutter
Cooking with a computer (the importance of a heat sink on a computer)
Cartoon laws of physics
Beautiful proofs (#3) - Euler’s sum
Have a great day!
Two years ago today (July 14), our New Horizons spacecraft made its closest flyby of Pluto…collecting images and science that revealed a geologically complex world. Data from this mission are helping us understand worlds at the edge of our solar system.
The spacecraft is now venturing deeper into the distant, mysterious Kuiper Belt…a relic of solar system formation…to reach its next target. On New Year’s Day 2019, New Horizons will zoom past a Kuiper Belt object known as 2014 MU69.
The Kuiper Belt is a disc-shaped region of icy bodies – including dwarf planets such as Pluto – and comets beyond the orbit of Neptune. It extends from about 30 to 55 Astronomical Units (an AU is the distance from the sun to Earth) and is probably populated with hundreds of thousands of icy bodies larger than 62 miles across, and an estimated trillion or more comets.
Nearly a billion miles beyond Pluto, you may be asking how the spacecraft will function for the 2014 MU69 flyby. Well, New Horizons was originally designed to fly far beyond the Pluto system and explore deeper into the Kuiper Belt.
The spacecraft carries extra hydrazine fuel for the flyby; its communications system is designed to work from beyond Pluto; its power system is designed to operate for many more years; and its scientific instruments were designed to operate in light levels much lower than it will experience during the 2014 MU69 flyby.
During its encounter, the New Horizons spacecraft collected more than 1,200 images of Pluto and tens of gigabits of data. The intensive downlinking of information took about a year to return to Earth! Here are a few things we’ve discovered:
Pluto Has a Heart
This image captured by New Horizons around 16 hours before its closest approach shows Pluto’s “heart.” This stunning image of one of its most dominant features shows us that the heart’s diameter is about the same distance as from Denver to Chicago. This image also showed us that Pluto is a complex world with incredible geological diversity.
Icy Plains
Pluto’s vast icy plain, informally called Sputnik Planitia, resembles frozen mud cracks on Earth. It has a broken surface of irregularly-shaped segments, bordered by what appear to be shallow troughs.
Majestic Mountains
Images from the spacecraft display chaotically jumbled mountains that only add to the complexity of Pluto’s geography. The rugged, icy mountains are as tall as 11,000 feet high.
Color Variations
This high-resolution enhanced color view of Pluto combines blue, red and infrared images taken by the New Horizons spacecraft. The surface of tPluto has a remarkable range of subtle color variations. Many landforms have their own distinct colors, telling a complex geological and climatological story.
Foggy Haze and Blue Atmosphere
Images returned from the New Horizons spacecraft have also revealed that Pluto’s global atmospheric haze has many more layers than scientists realized. The haze even creates a twilight effect that softly illuminates nightside terrain near sunset, which makes them visible to the cameras aboard the spacecraft.
Water Ice
New Horizons detected numerous small, exposed regions of water ice on Pluto. Scientists are eager to understand why water appears exactly where it does, and not in other places.
Stay updated on New Horizons findings by visiting the New Horizons page. You can also keep track of Pluto News on Twitter via @NASANewHorizons.
Make sure to follow us on Tumblr for your regular dose of space: http://nasa.tumblr.com
Does one of these LEGO men look bigger than the other? They’re actually the exact same size, but are in an Ames room - a false-perspective illusion room that tricks your brain into thinking things are smaller, or larger, than they really are.
You can make one of these models to try this for yourself. Download our free template from here. And it even works in full size, if you can make one large enough!