### Understanding Carcinogenic Communications Devices

People are usually afraid to place cellphone gadgets close to them because of the risk that it would
“mutate their cells into unstoppable reproduction” and thus end up getting cancer. Well, there is
some truth behind this, but the claim is valid only if it meets special conditions and probability is
accounted for. No matter what we do, as long as we are breathing, we are exposed to the risk of
cancer. We are always exposed to radiation caused by nature and there is nothing we can do about
it, unless you want to spend the rest of your life covered in lead coating. But it alsodoesn't mean we
should all turn carefree and ignore every risk that can lead to cancer. The thing is, we are living in a
world governed by entropy (putting religion aside for the moment). Everything that occurs is
probabilistic, existence is a game of chance. We may be powerless against this unforeseen trick of
reality, but we can make the odds turn in our favor in as much as the probability of the other event
happening becomes infinitesimal. This is what certain regulations specified by the international
telecommunications union, the federal communications commission, and other governing
telecommunications entities are for. (For example, only phones with maximum Specific Absorption
Rate SAR levels of 1.6 watts per kilogram can be sold in the United States)

Before anything else, we should understand fundamentally what is actually being emitted by our
cellphones and routers. Analog modulated digital signals in the form of electromagnetic waves are
propagated by 2 antennas (for mobile communications devices employing space diversity). These
electromagnetic waves are the same waves that define light, infrared, x-rays, and cosmic rays; the
only primary difference of each from each other being frequency. The frequency used by our
devices is commonly at the Gigahertz range (10^9 Hertz), all lower frequencies being utilized by all
other communications applications. Above the Gigahertz frequencies (in ascending order) are the
frequencies of infrared, light, x-rays, and cosmic rays respectively. Now the energy is described by
E=hf, where h is Planck's constant and f is the frequency of the radiating particle (photon for light).
We observe that energy increases as it goes up the frequency spectrum, indicating that x-rays and
cosmic rays are the electromagnetic waves with the highest energy density making them dangerous
and carcinogenic. Now, because of Einstein's theory on the photoelectric effect, where it was
observed that increasing the magnitude of electromagnetic waves does not increase its effectiveness
in releasing free electrons from metals,we consequently then are not necessarily at risk when we
expose ourselves to very high power radio waves. The story changes however, when we put into
account the footprint of the antenna and the duration of exposure. The near field has an energy
density much much higher than the far field, thus we would want to avoid sticking electronics
devices that are incessantly transmitting electromagnetic signals too close to ourselves. The range of
this near field we would want to avoid is very short, like some 2 inches with a broadband USB
stick. As for exposure, it is common knowledge that longer exposure leads to higher chances of
developing cancer.

There is a probability that we can get cancer from radiation from our cellular phones, there is, but
very small. So small that the probability is the same as that of getting cancer from natural occurring
sources. This probability can increase or decrease based on the way we handle our mobile handsets.
It is up to us to take care and take responsibility in minimizing such chances.

### 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