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Showing posts from 2013

### 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 frequencie…

### Numerical Methods for Partial Differential Equations: A Simplified Unravelling

Liebmann Method

This is simply the Gauss-Seidel method applied for elliptic PDEs (i.e. B^2-4*A*C<0, usually steady-state).

A good example would be applications of the Laplace PDE to heat conduction.
(Working with Maths symbols is hard with a keyboard so I'll just do it on paper)

General steps in using numerical methods for solving PDEs:

Step 1: Transform the continuous PDE into a discrete representation.

Step 2: Isolate the present state variable (or the variable asked by the problem).

Step 3: Use overrelaxation if necessary to fasten convergence.

Explicit Method

This method is used for parabolic PDEs with a little problem in stability. (i.e. B^2-4*A*C=0).

A good example would be applications of the Fourier's Law of Heat Conduction.

The problem above differs from the plate problem due to the fact that we are dealing with unbounded sides. Also, the explicit method is only stable when the "constant" (that is, 0.02087 we've used in the problem) is less …

### The Misconception of Heat Unravelled

Most books define heat as if it were a form of energy. Heat transfer is dealt as the transfer of heat from one control volume to another control volume. Nothing can be farther from the truth. Not only does this kind of definition or representation give a false intuitive idea to the newbie, but it also causes confusion since the person would notice that something doesn't seem to fit in when he/she looks at the thermodynamic equations.

Before I had my College Physics classes, I was a victim to this admittedly. I thought heat was transferred from one point to another and whose abundance was dependent on temperature. The first time I've read of a warning that this perspective was wrong was when I was doing advanced readings a few months before the start of classes (that is, the classes which include College Physics - somehow, reading the materials over the summer seems to help make things easier to understand). It said that a popular convention, and an extremely erroneous…

### 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…

### How to Fix "Virtual Router" 0.9 and Above - "Virtual Router Can't Be Started"

Aside from electronics and communications (physical layer), we've also had network fundamentals taught in our curriculum (through advanced). I've heard of this free software called Virtual Router that allows you to turn your computer into a router per se. Strictly speaking, by definition of a router, it doesn't. But it looks like it serves the purpose of a wireless router configured for 802.11 services, so that will suffice. And its free, so I gave it a shot. I've managed to turn a broadband connection from a USB connector (SMART, that is) into a wi-fi hotspot. It offers WPA2-PSK encryption and a view-able list of devices connected. However, a problem occured after some time using it. That is, when I click on the Start Virtual Router button, a window would appear saying that "Virtual Router Can't Be Started". Some suggest to simply restart the program, or wait some time. Sometimes this won't work, and not for everyone. Why? Sometimes, the targets…

### Proposed Solutions to Doomsday Asteroids

The risk of a collision course with asteroids has fueled the imagination of countless writers and movie producers. One lump of rock (ice or something) more than 1 kilometer in size strays away from the asteroid belt or outer solar system and goes on a collision course with Earth. The asteroid upon entry will heat up the Earth's atmosphere and end all life, sharing the same fate as the dinosaurs. Fortunately, we now have enough knowhow to meddle with cosmic affairs, such as landing probes and rovers on extraterrestrial territories. But is it enough to stop a 1-kilometer-big bullet from hitting its 6400-kilometer-big target? I don't know. Watch National Geographic, they have a program specifically tailored to this. But that doesn't mean you shouldn't read on.

Below are some solutions given by external sources with the details explained from my perspective:

A.) Shooting Lasers from the Moon

Effectiveness: 1/10

Simplicity: 2/10

Feasibility: 0/10

Le…

### Fast Facts: Current Mirrors

The current mirror is very popular in IC design. But what does it do? As the name implies, it simply tries to provide a stable current source by "mirroring" the current of a reference branch. (Remember that current sources when loaded still provide the same amount of current, the voltage varying consequently). The current mirror is constructed by shorting a collector and 2 bases of 2 BJTs and a drain and 2 gates of 2 MOS.

Below is a futile attempt in simulation [back when I was still a college amateur].

In order to understand how the transistors provide equal constant currents, let us take the example below.

Above are 2 2N2222 NPN transistors functioning as a current mirror. Q2 has its collector shorted with the base. The 2 resistors are ohmic, so we can assume Ohm's law to be valid over that branch. The current supplied is 5 mA and 6.667 mA(initially) to Q2 and Q1 respectively. The bipolar junction transistor is a current controlled device. Thus, if the col…

### Opinions or Onions: The Convention of Academic Presentation

Because both may make you cry, but when cooked and digested, are delicious and nutritious.

I always get extremely vexed when a lot of textbooks and lectures introduce concepts for the first time so formally that they end up as mere functions to the listener, (maybe an attempt to make the science appear like a very difficult subject matter or a faithful following of convention), so much so that the soul or true usefulness of the concept is lost. Take for example a lecture in industrial electronics. The students become familiar with the industrial electronic components such as the SCRs, UJTs, thyristors, diacs, triacs, you name it. And, of course, they'll learn how they function as manipulators of power delivery and how to design the triggering circuits and resistors (like for the misleadingly named Programmable Unijunction Transistor or PUT). Fast forward a couple years to the future when they are now working in the industry. Say, that there is a series of loads supplied…

### Flip-Flops Unraveled

No, these flip-flops aren't the ones you wear on the beach. These flip-flops are sequential circuits (circuits whose outputs are dependent on the previous values, like a sequence - hence the name). They're made up of combinational circuits strategically pieced together so that as long as there is a power supply, their outputs follow a sequence based on past inputs. Why would we need such a circuit? Why can't we just directly feed the values we desire by using the combinational circuits that we know? Well, there are instances that we don't want immediately fed values to affect the overall output.

Take for example a security system. There are pressure transducers randomly placed all over the floor of a vault. When pressure is applied on the floor, like the weight of an adult, a voltage results and that voltage triggers a red light at a remote security facility. Now, let us say George Clooney and Brad Pitt manages to get inside the vault. While they walk acros…

### Basic Statistics Unraveled

Measures of Central Tendency

You are gathering information on the number of customers you entertain everyday in a fast food chain. You decide to sample for a period of 1 week, and you decide to assume that the number of customers you get daily is completely uncorrelated with time. You're census yields the results below:

Sunday - 1430

Monday - 950

Tuesday - 870

Wednesday - 1100

Thursday - 950

Friday - 950

Saturday - 1600

Now, you want to process the data so that you arrive with a singular value that can best represent the entirety of the data. The best and simplest processes to use are called measures of central tendency, and the 3 mostly used are the mean, median and mode.

The mean is simply the average of the data. The median is the center of the data set regardless of the value of the data. The mode is the data that has possesses the highest number of occurences.

To get the mean, simply sum the entire data set and divide by the number of data elements. (14…

### Fast Fact: Root Mean Squared Unraveled

RMS or Root Mean Squared is defined as the Root of the Mean of the Square of each sampled value of a signal (for discrete values) or the Root of the Definite Integral of the Square of each bounded function (for continuous values). But what exactly does it mean? It is actually like a means of central tendency (I use the word "like" because it doesn't exactly function the same way as an average) only that negative integers are treated as positive values by squaring them in the first place. After squaring, you take the "mean" then take the square root again to reverse the effects of squaring. Thus, the entire signal is sufficiently represented by one constant value. This constant value can be taken as DC (direct current) since DC is a constant unchanging voltage. Hence, when we take an RMS measurement of an AC signal, we are actually getting an equivalent DC signal that can replace that AC signal in terms of power delivery.

But why not use Cube-Root Mean Cube…

### Some Common Mobile Electronic Devices Usage and Maintenance Unraveled

The Cellphone

A cellular phone is basically composed of solid-state electronics. It can suffer less damage when dropped compared to a laptop under operation assuming they both experience the same amount of force when they hit the ground. It also gets damaged when soaked with water (specially saltwater, being conductive) wherein shorts can occur. Ionized water can also harm electronic components in your cellphone sensitive to static charge. I've heard of water-resistant phones, yet its still safe to take extra measures because you'll never know if there is a fault in the insulation. Its life expectancy greatly decreases when operated at higher temperatures, so exposing the mobile unit to high temperatures is a no-no. When the LCD breaks, the phone is as good as scrap unless you solder a new one on. As for viruses, the smarter the phone, the more vulnerable. Why? Because smarter phones acquire data in more ways, and the more the ways available - the higher are the chances o…

### Basic Principles of Engineering Economics Unraveled

Interest

Interest, is formally defined as the price paid for borrowing money or payment received for lending money, usually a percentage of the amount borrowed. My vocabulary defines it as the only reason why a sane person would allow someone else to touch his/her money (expenses for necessities and luxuries aside of course). Without interest, the global economy won't function. Companies won't be able to sell their stocks, no investments will occur, no one would be able to borrow money because no one is INTERESTed to lend their money, etc. In this article, I'll freshen up on the very basic principles that govern interest, and then introduce a conceptual analysis for each.

Before we start with simple interest, let us first discuss an even simpler topic that I believe is taken too much for granted that some errors in academic exams are effectuated by such. Interest is the price paid for borrowing money, but it can be a payment that is paid at a constant value, or a payment tha…

### The Importance of Obsolete Technology Unraveled

Most of the time, when lay men are asked what they think of the latest trends in technology and their opinions on the ones that are about to hit the recycling bin, a typical response would be that the usefulness of the new products far outweigh the former. This view is so common it has become an irreversible stereotype. The effects of course are very visible. We see a huge almost exponential demand on the "new" product and the exact inverse on the demand of the "obsolete" one. Electronics practitioners tend to find it highly unnecessary to study old technologies and instead focus on the new. Anything related to anything outside the new is considered ancient and negligible.

Let us take a closer look at exactly how technology evolved from then and now (I won't be tackling much of the earlier 1800s since I've pretty much covered enough on the topic on one of my previous posts). Perhaps one can remember of the old black and white television set and the vacuum tu…

### The Explosively-Pumped Flux Compression Generator Unraveled

When I was still a 2nd year college student 3 years ago, I came upon an article containing information about the e-bomb as a possible means of achieving the goals of a terrorist. First of all, an e-bomb is, from its name, a bomb. But the first two characters so often used and encountered in our day-to-day routines, such as e-mail, e-book, etc. changes the story. An e-bomb is a bomb on the electronics level, that is, it targets the destruction of electronics equipment, specially those with a low power rating. How does it do it? Simple. It  puts to good use one of Maxwell's equations, that is, a changing magnetic flux induces an electric field. And if this induction is done on a magnitude a hundreds of times greater than the contemporary, the electric field can
impress a potential way above the power rating of ordinary electronics, thus frying them to uselessness.

The e-bomb is essentially an explosively-pumped flux compression generator, typically referenced as an EPFCG or HEMP ge…

### Fourier Transform Unraveled

Jean Baptiste Fourier once had a radical idea. He attempted to explain mathematically that the overshoots and undershoots in an oscillating square wave were the result of missing sine/cosine frequencies. However, it was rejected during his time by another renowned mathematician who argued that it was impossible to create a perfect waveform from such sinusoids(which is definitely true, since an infinite number of sinusoids would have to satisfy such), and thus, his theory that every wave can be decomposed into numerous sine/cosine components has been stored on the shelf for decades until its importance was fully recognized and accepted.

It is hard to imagine how any wave can be interpreted as a sum of many sine and cosine waves at different frequencies. In fact, many other modern studies define any waveform as a sum of any other different waveforms at different frequencies, may it be an exponential waveform or whatever. This concept could perhaps be better understood if we imagine the …

### 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

### ON THE HISTORY AND IMPACT OF ELECTRONICS AND COMMUNICATIONS SYSTEMS

When we look at the Iphones and Ipads around us, we sometimes wonder how we got to this point of evolution of technology. How did we go from humble folk contented with engaging in personal conversation with local neighbors to a global community equipped with the means to be internationally aware of everything around them? The story dates back to 1830, when Joseph Henry first successfully propagated an electric signal. Well, the signal was in its most basic form yet, and was no where close to the information content signals are carrying today. What Joseph Henry first established was a means of creating an electrical disturbance from a significant distance. Not until Samuel Finley Breese Morse invented the telegraph 7 years later did these signals come to mean anything to anyone. Yes, Samuel Morse, by relating a series of disturbances (dits and dahs) to the alphabet, a coding scheme popularly known as the Morse code, managed to make the disturbances understandable to the human mind. If…