### Microwave-Generated Tropical Typhoons Unraveled

So, after a bunch of typhoons have struck the Philippines over the years, typhoon Maiyan being the latest and strongest, I've been hearing and seeing over some news media talks about a secret microwave weapon for generating tropical cyclones used by a rival neighboring country to wreak havoc on the Philippines. Well, it does seem logical. If microwaves can heat food, then it can be used to accelerate the heating of Pacific Ocean waters. Now let us not jump to that conclusion too fast. Before we make such a conclusion, let us first analyze the requirements and conditions for such a mechanism to work.

Microwave, as any electronics engineer would know, is an electromagnetic wave with a frequency ranging from 1 Ghz to around 110 Ghz (L, S, C, X, K, Ku, Ka, V, W bands) that is typically propagated directionally if it were to reach a significant distance (noting that the free space loss = (4*pi*f*D/c)^2 -- the square relationship making its value very high at high frequencies). The radiated power of
a typical directional parabolic antenna would be the input transmit power multiplied by the gain n(pi*D/lambda)^2 minus the free space loss and the fade margin.

Let us assume, under a worst case scenario, that a parabolic antenna with efficiency of 60% (typical value), diameter of 300 meters (extreme case) at 2.45 Ghz fed with 20kW (extreme case) tries to accelerate the heating of a part of the Pacific Ocean.
At the output of the parabolic antenna, the signal power will be .6*(pi*300/(299792458/2.45*10^9))=35.6MW.
Assuming a distance of 1 kilometer (extreme case), the FSL=50.11dB.  The signal will be reduced to 347W.
Fade Margin = Multipath effect + Terrain Sensitivity - Reliability Objectives - Constant
FM = 30 log (1) + 10 log (6*4(over water)*0.5(hot humid areas-tropics)*2.45) -  - 70
FM = -55 dB
But, since we are expecting the worst, let us forget about the fade margin.
So, 347 W of power is delivered on a pi*300^2 m^2 area of the Pacific ocean.
m=(1000kg/m^3)*(pi*300^2 m^2*0.5 m.) assuming the conduction of heat penetrates up to 0.5 meters deep. Thus, the mass affected is 141,371 kg.
Q=mc*(change in T)
Q=(141,371 kg.)*(4.186 J/(cal*g))*(change in T)
We need to a sample value for Q, say for 5 seconds.
P=Q/t, 347 W = Q/5 sec.
Q= 1735 Joules
Therefore, change in temperature is 2.93*10^(-6) degrees Celsius for a period of 5
seconds.

Wow, the factor 10^-6 is so insignificant its like comparing the length of a meterstick to the diameter of a strand of your hair. And we have done this calculation over an extreme case (not to mention neglecting the fade margin). And
the affected area is only 300 m. of the Pacific Ocean. And we treated the system as an isolated system (which in reality isn't).

Therefore, we conclude based on the immediate calculations that it is nearly impossible to accelerate the heating of a part of the Pacific Ocean. (If you also think about it intuitively, the law of energy and thermodynamics would be violated if this were to be possible.)

Of course, the calculations above were very rough, so the result is just a very rough estimate.

### Calculator Techniques for the Casio FX-991ES and FX-991EX Unraveled

In solving engineering problems, one may not have the luxury of time. Most situations demand immediate results. The price of falling behind schedule is costly and demeaning to one's reputation. Therefore, every bit of precaution must be taken to expedite calculations. The following introduces methods to tackle these problems speedily using a Casio calculator FX-991ES and FX-991EX.

►For algebraic problems where you need to find the exact value of a dependent or independent variable, just use the CALC or [ES] Mode 5 functions or [EX] MENU A functions.

►For definite differentiation and integration problems, simply use the d/dx and integral operators in the COMP mode.

►For models that follow the differential equation: dP/dx=kt and models that follow a geometric function(i.e. A*B^x).

[ES]
-Simply go to Mode 3 (STAT) (5)      e^x
-For geometric functions Mode 3 (STAT) 6 A*B^x
-(Why? Because the solution to the D.E. dP/dx=kt is an exponential function e^x.
When we know the boundary con…

### Common Difficulties and Mishaps in 6.004 Computation Structures (by MITx)

Updated:
May 6, 2018
VLSI Project: The Beta Layout [help needed]Current Tasks: ►Complete 32-bit ALU layout [unpipelined] in a 3-metal-layer C5 process. ►Extend Excel VBA macro to generate code for sequential instructions (machine language to actual electrical signals).
Current Obstacles/Unresolved Decisions:
►Use of complementary CMOS or pass transistor logic (do both? time expensive, will depend on sched.
►Adder selection: Brent-Kung; Kogge Stone; Ladner Fischer (brent takes up most space but seems to be fastest, consider fan-out) [do all? time expensive, will depend on sched.)
►layout requirements and DRC errors