How much blessed we are ?!!

One week ago, I was travelling by bus. 10 minutes travel. There is a reason for sharing my experience with you right now. There would be almost 35+ passengers in that bus. Some of them were talking each other, some of them were doing nothing and some of them were dreaming. ;).

At that time, a new passenger came. The conductor who gives bus tickets helped him to climb foot path and ensured that he got his seat. I thought why he helped the new one. Then I realized that he was blind! Yes, can you imagine that what would be your life if you were blind?! Can you imagine?  You don't like that life, right? No sun, no moon, no sky, no birds, nothing...totally darkness..! Even you can't see your mother, father!!! Also you will be unable to see yourself..! What would be that life? Yes, such a life is lead by them, Blinds. So think how much blessed we are. We can see ourselves; we can see our mother, father, relatives, trees, sun, moon, sky etc. Thank your Lord who has created you. Then, we can return to my travel.

Bus is started. After 5 minutes, one person has entered the bus. Remember that, that bus was local bus. The new one's height was too low. Even he couldn't balance his own body! Again, the conductor helped him to be seated. I have seen many persons before who has no sufficient height but a man who can't balance his own body...?! It was the 1st time in my life. Again we want to think about our life, our height, our skills, our talents, our abilities. Yes, we are so blessed!

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Again after 3 minutes, one person left the bus. He had a problem with his legs. His right leg was not good. But he was one of the people who continuously spoke during travel. Said jokes. But he has too a big problem. We want to think about our legs. So good! right?  Then thank your Lord.

Realize that there are so many people like this around you. They don't want Lamborghini car! They don't want royal Enfield bullet bikes. They don't want 10kg gold. Also they don't need those things. There is one thing above them all. What is that?  Love, compassion and unconditional love for the sake of our Lord. Love them. Mind them. Honor them. Don't ignore them.

What is Pre Ignition in SI engine ?

Do you know, some parts of engine like spark plugs, exhaust valves etc. have very high temperature, around 973 K before the end of compression stroke. Further, carbon particles will be deposited in various parts of engine due to incomplete combustion. These carbon particles also have very high temperature. These overheated things will cause a pre-mature combustion even before spark application. This pre-mature combustion before the application of spark is generally called pre ignition.

Then what will happen when spark is applied after pre ignition ?

When spark is applied, then there will be multiple flame fronts and it will increase the rate of pressure and decrease power output.

Due to pre ignition, more work is needed for compression so that there is a tendency for mechanical damages such as crank failure. Also it increases the chance of detonation and knocking. Then we can conclude that this is a serious problem and major type of abnormal combustion. 

Remember that "you will DIE at any time" !

"Every soul will taste death,

and you will only be given your [full] compensation on the Day of Resurrection. So he who is drawn away from the Fire and admitted to Paradise has attained [his desire].

And what is the life of this world except the enjoyment of delusion."

[Al - Qur’an 03:185]

"Every soul will taste death.

And We test you with evil and with good as trial;

and to Us you will be returned."

[Al - Qur’an 21:35]

"Every soul will taste death. Then to Us will you be returned"

[Al - Qur’an 29:57]

Velocity potential function and stream function

What is potential function in fluid mechanics? 

It's a scalar function of space and time. Its negative partial derivative with respect to any direction will give the fluid velocity in that direction. 

Note that if velocity potential function exists, then the flow will be irrotational and if it satisfies laplace equation, then it represents a possible case of steady - incompressible - irrotational fluid flow. 

What is stream function in fluid mechanics? 

It's also a scalar function of space and time. Its partial derivative with respect to any direction will give the fluid velocity in the direction of right angle to it. It's applicable only for 2D flow. 

Note that if stream function exists, it represents a possible case of fluid flow and it may be rotational or irrotational and if it satisfies laplace equation, then the flow will be irrotational. 

If you don't know what laplace equation is, then Click here