# Recent content by pj33

1. ### Anisotropic Etching in Semiconductor Fabrication

I am learning about designing semiconductors but I had some issues understanding some things about the structure of Si. About lattice structure: 1) Why does an FCC has 8 atoms per cell? Doesnt has 14? About wafers 1) I know you can have wafers along different surfaces. What information can I...
2. ### Lagrangian mechanics - rotating rod

I was just thinking of a simple beam attached at one end at a stationary point. If I understand this, it helps to tackle harder problems. Thank you!
3. ### Lagrangian mechanics - rotating rod

Hello, It might sound silly, but when I try to calculate the kinetic energy of a rotating rod to form the Langrangian (and in general), why it has both translational and rotational kinetic energy? Is it because when I consider the moment of Inertia about the centre I need to include the...
4. ### Silicon FCC -- Why are so many atoms shown in the lattice?

Can you explain this in a bit more detail please. I though this correspond to the configuration of the minimum number of atoms thus all of the to have a complete outer layer. Correct me if I am wrong, but since the Si atom has 4valence electrons and it needs 4 more to be complete, doesnt this...
5. ### Silicon FCC -- Why are so many atoms shown in the lattice?

I see, I got it wrong, by "electrons shwon as nodes" I meant the spheres that form the cube, so those are the Si atoms.
6. ### Silicon FCC -- Why are so many atoms shown in the lattice?

here the fcc silicon lattice is shown. My question is: Since the silicon atom has 4 valence electrons and requires 4 more to be completed, why are so many atoms shown in the lattice. There are 8 electrons shown as nodes and each of it, is connected to a neighbouring node, thus each silison...
7. ### Can someone give me a better intuition of bandwidth?

Yes, I know how each work. What I meant is that, if someone uses full bandwidth for certain amount of time (TDMA) is it equivalent for someone to use part of the bandwidth for more time (FDMA).
8. ### Can someone give me a better intuition of bandwidth?

Can someone give me a better intuition of bandwidth. The way I see it, is that the bandwidth is the range of frequencies which a signal/wave is allowed to have. This doesnt feel complete though. For example, how can I explain that TDMA, FDMA and CDMA are similar in this sense. As far as I know...
9. ### Semiconductor -- Conduction and Valence bands

I am a new to this and I try to understand the basics. So initially once the atoms of silicon come together to form a solid, due to Pauli law no electrons can exist in the same energy state,thus many energy states are formed which together make the bands. My problem starts at this stage where I...
10. ### Calculate the maximum vertical point force P that this beam can sustain

A simply-supported steel beam with a vertical point force P is shown in Fig. 2(a). A cross-section of the beam, which is composed of two identical C-shaped members bolted back-to-back, is shown in Fig. 2(b). Both C-shaped members have a uniform thickness of 1 cm. Pairs of bolts are located at a...
11. ### Reinforced concrete beams

It is a rectangular shaped concrete which has 3 beams of steal in order to reinforce it. When I transforme the 3 beams, I have converted all 3 of them to a single piece of concrete with area mA. A is the total area of the 3 beams of steal and m is the ratio of the steal's Young's Modulus to the...
12. ### Reinforced concrete beams

In a simple case like this.
13. ### Reinforced concrete beams

When I convert the steel beams to concrete, do I transform the several different beams into a single piece of concrete in order to do the calculations to find the second moment of area of the beam or do I transform each beam seperately into a concrete piece? Intuitively, t seems reasonable to...
14. ### Beams-Bending stress exercise

Thanks a lot, that answers a lot! No I have solved the question.
15. ### Beams-Bending stress exercise

A chimney has a rectangular cross-section with external dimensions 800 × 600 mm and wall thickness 150 mm. It is 5 m high. The density of the material is 2000 kg/m3. Assuming that the material is elastic, calculate the maximum uniform wind-pressure loading (N/m2) that...