Posted in Uncategorized

periphery of a tubular

Since previously I have been dealing with lot of calculation of a tubular member, there is an interesting yet fun discovery (which I believe some people may have found it too) where you can find more than one way to calculate the cross-section area of the tubular member.

You see when you have a tubular member or a pipe, the area of the cross-sectional circle can be measured by using the equation

A = π r^2…..(1)

This is a common equation for calculating the area considering the tubular member is rigid.

The circumference of the circle (C) can be calculated as

C = 2 π r…..(2)

In a real application, we deal with a lot of tubular member which has an inner diameter (id) and outer diameter (od).

When we calculate the cross-section area of this tubular, the equation (1) becomes

A = π r.outer^2 – π r.inner^2

where r is the radius of the tubular member


A = (π/4) (od^2 – id^2)

For example,

with od = 6 mm,

id = 5 mm

The cross-section area will be

A = (π/4) (6^2 – 5^2) = 8.639 mm^2

In other analysis, we can calculate the cross-section area by breaking off the tubular such that

A = (thickness of tubular) * (the circumference of outer tubular member)


t = thickness of tubular

Substituting parameter provided from the example, we can get

A = (0.5 ((od) – (id))) * (2 π r.outer)

A = (0.5 (6 – 5)) * (2 π (6/2)) = 9.425 mm^2

In logical thinking, both ways of calculating the cross-section area should have been resulting the same.

There is a deviation around,

δ = (9.425 – 8.639) / 8.639 = 9.09 %

Quite interesting, isn’t it ?

Posted in daily life, Uncategorized

best way to operate windows 7

Windows 7 has been the best operating system since its popularity for the amount of users all around the world among all other system. From March 2014 until January 2015, statistics show about half of overall windows users use windows 7.

Windows Statisctic Users

For all people who like to use windows 7, I have experienced some best way to operate it. Sometimes you need this so that you do not have to move your hands to use your mouse. These all some of the useful shortcuts if you want to use your computer effectively using  windows 7 :

1. If you want to leave your desk for awhile, you can press Windows button + L. It will put your laptop on the ‘locked mode’ suddenly. You save your time without using mouse pad.

2. When you want to find some documents or see other things in your laptop, you will firstly open the explorer, and open ‘My Computer’. To get a shortcut, just press Windows + E.

3. Your boss is coming when you are playing games in your pc. Don’t worry, just press Windows+D, Desktop screen will save you 😀

4. If you want to find a recorder application in windows, you can do it in shortcut by pressing Windows+R, then type psr.exe. Enter. Tadaaa… Start recording !

5. You can see a cool stuff when you press Windows +R and type osk. Enter. and yess. Virtual keyboard !

6. If you find your object in the screen (either a picture or sentences) very small to you, you can adjust it by pressing Windows + ‘+’ or ‘-‘ (zoom in or zoom out).

7. During surfing on the internet, you can switch your tab by pressing Ctrl + Tab. This will be useful if you have a lot of things to do (googling, literature research, downloading, etc.)

8. I know you can press Windows button to open ‘Start’ program. Other way to do it is by pressing Ctrl+Esc.

So there are some of the ways the best and the effective one to operate windows 7 that I have found. Hopefully it will be useful for you.