Pleasure of knowing-Container shape

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bprasad2005
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Pleasure of knowing-Container shape

Post by bprasad2005 » Fri Jun 20, 2014 6:05 am

Many of the water and liquid fuel tankers have the container in an elliptical cross section. But for the same surface area a perfect cylindrical cross section container would have more volume. Then why is the elliptical cross section preferred?
There are a number of factors which affect the shape of a liquid carrying tank. Most important one is the stability of the vehicle on the move while taking a turn on the road. To have maximum safety factor, the centre of gravity of the loaded vehicle has to be as close as possible to the ground.

This is achieved by adopting an elliptical shape of cross section of the tank. In fact the height of the centre of gravity will be least for a rectangular cross section.

But then there are other problems with a rectangular section like presence of corners (leading to cleaning problems), large number of joints and larger area of metal sheet for the same volume of the tank.

An elliptical section also provides maximum stability against liquid movement inside the tank on account of lateral acceleration.

Then the question is why there are some tanks which have circular section. In fact for vessels which contain pressurized liquids or gases like LPG or PNG, the circular section is the most efficient section which gives maximum strength against internal pressure.

In such cases the strength of the tank may be the governing factor to decide the shape of the tank. That is why we find circular section tanks for carrying LPG or similar contents.

S.P.S. JAIN

Former Member, Engineering, Indian Railways

Greater Noida, Uttar Pradesh
Ref:http://www.thehindu.com/todays-paper/tp ... 128312.ece

bprasad2005
Posts: 35
Joined: Tue Apr 08, 2014 5:13 pm
Location: kurukshetra
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Re: Pleasure of knowing-AIDS & mosquitoes

Post by bprasad2005 » Mon Jul 07, 2014 7:48 am

AIDS is spread through blood transmission from infected persons. Though mosquitoes suck blood from the infected person, why is it not possible for mosquitoes to spread this disease?
HIV does not survive outside the body for very long, and it does not replicate in insects. In addition, mosquitoes transmit malaria and other infections when they inject saliva into the victim.

HIV does not get into the insect's saliva much at all, and mosquitoes do not inject blood into the victim. Furthermore, blood that remains on the bug's mouth or other body parts after it bites an AIDS victim also does not pose much risk, because the amount of blood present is very small, and the insect usually does not go directly from one feeding to another.

Many people think of mosquitoes as tiny, flying hypodermic syringes, and if hypodermic needles can successfully transmit HIV from one individual to another then mosquitoes ought to be able to do the same.

However, even if HIV-positive individuals did circulate high levels of virus, mosquitoes could not transmit the virus by the methods that are employed in used syringes.

Most people have heard that mosquitoes regurgitate saliva before they feed, but are unaware that the food canal and salivary canal are separate passageways in the mosquito. The mosquito's feeding apparatus is an extremely complicated structure that is totally unlike the crude single-bore syringe. Unlike a syringe, the mosquito delivers salivary fluid through one passage and draws blood up another. As a result, the food canal is not flushed out like a used needle, and blood flow is always unidirectional.

The mechanics involved in mosquito feeding are totally unlike the mechanisms employed by the drug user's needles. In short, mosquitoes are not flying hypodermic needles and a mosquito that disgorges saliva into your body is not flushing out the remnants of its last blood meal.

K. AGILANDESWARI

Research Scholar

VIT University
Vellore, Tamil Nadu
http://www.thehindu.com/todays-paper/tp ... 083801.ece

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