Today I Learn

2021-03-04 18:57:37 Thermal Expansion

Thermal expansion is the tendency of matter to change in shape, volume, and area in response to a change in temperature.

Temperature is a monotonic function of the average molecular kinetic energy of a substance. Monotonic function is a function which is either entirely nonincreasing or nondecreasing.

The degree of expansion divided by the change in temperature is called the material's coefficient of thermal expansion. It is found to generally vary with temperature.

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2021-03-03 07:28:39 ​​What are Railway Sleepers and What is their purpose?

Railway sleepers, also called railroad ties, railway ties or crossties, are an important railway component. Generally, the rail sleeper is always laying between two rail tracks to keep the correct space of gauge. In the recent time, concrete sleepers are widely used, especially in Europe and Asia. And in UK, steel ties are common. Besides, plastic composite ties are also employed in the rail track transportation.

The functions of sleepers in railway works are as follows:

(i) The primary function of a sleeper is to grip the rail to gauge and to distribute the rail loads to ballast with acceptable induced pressure.
(ii) The side functions of a sleeper include the avoidance of both longitudinal and lateral track movement.
(iii) It also helps to enhance correct line and level of the rails.

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2021-02-27 06:24:27 ​​What is Pontoon Bridge?

A pontoon bridge, also known as a floating bridge, uses floats or shallow-draft boats to support a continuous deck for pedestrian and vehicle travel. The buoyancy of the supports limits the maximum load they can carry. Most pontoon bridges are temporary, used in wartime and civil emergencies.

Floating bridges are made of large water-tight concrete pontoons connected rigidly end-to-end, upon which the roadway is built. Despite their heavy concrete composition, the weight of the water displaced by the pontoons is equal to the weight of the structure (including all traffic), which allows the bridge to float.

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2021-02-20 15:52:39 ​​What is Bio-Electrical Impedance Analysis (BIA)?

Bio-electrical Impedance Analysis or Bioimpedance Analysis (BIA) is a method of assessing your body composition: the measurement of body fat in relation to lean body mass. It is an integral part of a health and nutrition assessment.

BIA allows for early detection of an improper balance in your body composition, which fosters earlier intervention and prevention. BIA also provides a measurement of fluid and body mass that can be a critical assessment tool for your current state of health. This non-invasive test simply involves the placement of two electrodes on the person's right hand and foot. A low level, imperceptible electrical current is sent through the body. The flow of the current is affected by the amount of water in the body. The device measures how this signal is impeded through different types of tissue. Tissues that contain large amounts of fluid and electrolytes, such as blood, have high conductivity, but fat and bone slow the signal down. As BIA determines the resistance to flow of the current as it passes through the body, it provides estimates of body water from which body fat is calculated using selected equations.

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2021-02-20 15:52:25 Open / Comment

2021-02-15 10:58:48 Auxanometer

An auxanometer is an apparatus for measuring increase of growth in plants. In case of an arc-auxanometer, there is a thin cord fixed to the plant apex on one end and a dead-weight on the other with a pointer indicating against an arc scale. In some forms it passes over a pulley which has a pointer attached to it.

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2021-02-15 10:20:15 ​​How do Fighter Pilots use Washroom while flying?

As a fighter pilot, one of the most common questions they get is: How do you go to the bathroom in an F-16 or F-35? Let me start off by describing the cockpit.

Now, typically in training, flights are less than an hour and a half. As long as you don’t drink too much coffee before a flight, it’s generally not a problem. However, in combat, flown missions as long as 8 hours; crossing the Atlantic, for over 10 hours. For these missions, They use what affectionately call, piddle-packs.
Piddle-packs are the ultimate long road trip solution. They are specially shaped bags with absorbent beads in them. If they have to relieve themselves, they’ll unzip the flight suit which is designed to unzip from the top as well as the bottom unroll the piddle pack, and then pee into it. Once done, they’ll seal the top, while the absorbent beads turn it into a gel that won’t leak during hard maneuvering.
While the concept is simple, it takes time to become proficient at it. In the Air Force, a number of devices have been developed to make the process easier particularly for women.

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2021-02-15 10:20:05 Open / Comment

2021-02-13 19:17:31 ​​What is Contact Torpedo and How do it work under Water?

Simply put, a torpedo is a self propelled underwater missile that carries an explosive warhead to a target. Early torpedoes damaged their target by exploding as soon as it made contact. These torpedoes were called contact torpedoes. Newer torpedoes can detonate once in close proximity to a target. These proximity torpedoes do not even have to touch the ship to inflict damage upon it. A contact torpedo is one that has to physically hit the target to detonate. It accomplishes this through a contact fuse housed in the torpedo’s nose.
The method in which a contact torpedo causes damage is actually a two step process.

The initial explosion of the torpedo’s warhead causes a large gas bubble to form. Because this bubble expands so quickly, it forms a shockwave. Once this bubble/shock wave strikes the ship’s hull, it punches the hull plates in, rupturing the hull. The energy radiating out from the point of contact is enough to tear surrounding plates off of the hull. This forms a large hole in the ship’s hull.
Following the creation of the bubble, the displaced water around it rapidly begins pushing back. Once the bubble finally collapses, the water rushes back in to fill the void. Because contact torpedoes cause the bubble to form against the ship’s hull, the returning water collects right at the rupture formed by the initial explosion. With so much water rushing into this point, it forces a very strong jet of water to enter the rupture. This water jet can be powerful enough to punch through bulkheads or plating already weakened by the initial blast.

In addition to the blast wave itself, shrapnel is created from the pieces of the ship torn away in the explosion. Traveling at extremely high speeds, these projectiles can perforate the insides of the ship, causing extensive damage and further compromising watertight integrity.

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2021-02-13 19:17:21 Open / Comment