VENTA DE LIBROS INGENIERIA - DISTRITO FEDERAL

Vendo los siguientes libros, si viven en México D.F., escríbanme un comment y nos ponemos de acuerdo. Saludos!

Para exámenes en universidades extranjeras (Licenciatura y Posgrado)
* The Official Guide to the GRE – 2a ed – ETS (Copias)- $200
* GRE Premier 2013. Kaplan. - $350
* SAT 2006 Edition. Kaplan. Premier Program. - $150
* The official study guide for all SAT subject tests - CollegeBoard - $150
* The official SAT subject tests in Mathematics Levels 1 & 2 Study Guide - CollegeBoard - $150
* SAT Subject Test Physics (2007) - Barron's - $150

Programación:
* Matlab para ingenieros – 3a ed - Holly Moore (Copias) - $150
* Java, Cómo programar – 7ª ed - Deitel - $280.
* C# cómo programar – 2ª ed - Deitel - $280

Otros ingeniería:
* Inteligencia artificial con aplicaciones en ingeniería – 1ª ed - Pedro Ponce Cruz - $150
* Tratamiento digital de señales – 4a ed - Proakis - $300
* Estática, Las leyes del equilibrio – 1a ed - Gánem - $180

Matemáticas:
* Matemáticas avanzadas para ingeniería, Vol. 1: Ecuaciones diferenciales - Dennis G. Zill,
Michael R. CUllen. - $200
* Estadística y Probabilidad - Piotr W. - $100
* Matemáticas avanzadas para ingeniería - Peter O'Neil - $200
* Cálculo con trascendentes tempranas - Edwards Penney - $250
* Precálculo - Stewart - 3a ed. - $200
* An Introduction to the Theory of Numbers - 5a ed - Hardy, Wright - $250

Física:
* Física Universitaria Volumen 1 - 11a ed - Young et al - $280
* Física Conceptual - 9a ed - Hewitt - $180
* Física - 5a ed - Wilson Buffa - $180
* Physics for the IB Diploma - 2003 - Tim Kirk - $200
* Exámenes muestra de Física Standard Level para IB Diploma (Paper1, Paper2, Paper3) - $200 c/u

Otros:
* Marketing - 8a ed - Kotler, Amstrong - $200
* Biology, Life on Earth - 7a ed - Auderisk Teresa - $300
* Química, Conceptos y aplicaciones - 1a ed - Philips, Strozak, Wistrom - $180

Obstacle avoidance and path planning using Rapidly Random Trees

Hola, espero estén bien.

Aquí les muestro un video explicativo sobre el procesamiento de imágenes, representación de obstáculos y planificación de obstáculos para robots domésticos (indoors) utilizando una cámara web en el techo de la casa. Utilizé un robot Roomba y Matlab para probar los algoritmos.

El sistema es el siguiente... La cámara web manda la imágenes a la computadora central y esta las procesa para asignarle alguna actividad al roomba y decirle como evadir los obstáculos.

Y el video es el siguiente:

Marble RollerCoaster

In this post I’ll describe what I think was my first college project: a rollercoaster. My team and I finished it the night before the deadline and we had to work in the school’s common areas because we get kicked off the lab hahaha. Here is a video showing our work late at night and the final result.

                                               

Link to the youtube video.

Tips

From what I can remember, my general tips for building a rollercoaster in a cheap and easy way:

• Build the supports for your rails from wood, it is easy to cut and glue to fixed base. In this way you will not have to do extra soldering.
• If you decide to choose cooper wire to build your railways maybe you will find difficult in bending and keeping them in the form/shape you want. If this is case, fix one end to a press and stick the other end into a drill and set the RPMs to a low level to make the copper wire more malleable/ductile. You will notice that the longer you keep the wire turning it will turn easier to shape.
• From the materials I tried and the ones I saw my classmates using, I think an aluminum angle profile is the best way to go. You can bend them to make the shapes you want by making little straight cuts with a hacksaw in the angle corner of the aluminum, more or less as the red lines shown in the next picture.

                                                                   

• I ended up collecting some unused pipes from a hardware store, then cutting them in half with an electric chainsaw to make the rails. It is an easy way too, but the pipes are more difficult to bend to the shape you want. I used wood to make the base and the supports.

Interesting calculations on some components of a roller coaster

Ascendant and descendant slopes

A common force analysis is made in this type of railway as show in the next image.

This equation shows that the acceleration is proportional to the sine of the slope’s angle, so as the rollercoaster’s car goes down, the higher the slope the greater the acceleration. Same for when  it goes up hill, but since this acceleration is opposite to the direction of movement, it slows the car down.

Vertical loop

Vertical loops are very popular in rollercoasters. To make the car stay in the railway at the loop’s zenith, the centripetal acceleration has to be greater or equal to the acceleration due to gravity as the next diagram show. 

Based upon the free force diagram in Point C, the zenith, we compute the summatory of the forces. By convention, we consider the axis parallel to the acceleration to always positive.

When Nr=0,  as the railway does not exert any force on the car, the rollercoaster’s van attains the minimum velocity needed to reach the loop’s zenith. If the car had a speed lower than this, it could not make a complete loop. Thus, we compute this minimum velocity:

This relation can help us establish or adjust the radius of our loops in order for our marble, or whatever stuff you are using to simulate a rollercoaster, to complete the entire trajectory.  We just have to compute the velocity with which the marble enters the loop, and then solve for the radius in the previous equation. This velocity can be obtained using the conservation of energy law.

In actual rollercoasters, engineers do not make circular loops but clothoid loops in order to reduce the acceleration to which the riders are subjected to. 

LEGO NXT SEGWAY (LONE RIDER)

Here is the youtube link.

This time I re-built a LEGO NXT in the form of a Segway (or an inverted pendulum) and tried to balance it using a light sensor. It is clear that with a gyroscope it will be much easier and precise; but this sensor is not included in the regular LEGO NXT, you have to buy it separetely.

I found the building instructions here. I think there are much more stable designs in the web that are more stable than this one: but this one seems so funny and remembers me of the security men at my college (which are useless and have the brain the size of a penny. Actually I always have the urge to make them fall when I see them).

See??

My next blog will talk about programming the control law using the LEGO NXT ROBOTICS toolkit from Labview.

Integral Formula Table For Math Contests

For this post I made a table of formulas for you to solve integrals, especially if you are going to compete or train for a math contest, like the so called "Integration Bee" contests or "Integration Marathons." I competed in some of them at my home college, and based on my experience and the studying I did during those times I made this table of formulas. 

The table contains the basic integration rules, but I compiled this list for the ones that have already studied or seen at least once the basic methods of integration. Thus, this table of integrals has the purpose to improve your speed at solving some integrals by recommending some tricks or methods. I also suggest to memorize some formulas, they are the ones I consider more useful due to their frequent repetition in the integrals I have solved during the contests and training. Also, the ratio of time and paper-work to memorization make them advantageous to learn. 

So, the first document is just a list of the integration formulas, tricks and methods divided into groups according to the type of functions we are dealing with. The second document contains the same formulas but they are explained in more detail and have some few examples.

Of course you can derive more general formulas for some type of integrals, but you have to choose how many to memorize and which ones you can derive in the exam quickly.

If you discover/know some cool integration tricks I invite you to share them in this post. Inquiries and corrections are also welcome. Likewise, I promise some other integration suggestions for definite and improper integrals in the next couple of weeks. 

* Integral-Table , Integral-Formulas explained and with examples

CHAOS GENERATOR - Electronic Circuit

Well, this time I’ll show you an electronic circuit that I thought was cool. It is called the CHAOS GENERATOR, why? Because when you see its output in the oscilloscope in the XY mode you get something like this:

So, it looks like an electromagnetic field attractor (if you remember some of you physics classes). And it is said to generate chaos because the circuit does not seem to set to into a stable mode for a reasonable period of time, that’s why the XY view looks like the signal moves without control.

The circuit that I show you here is a variation of the classic phase shift oscillator. And it is cheap and entertaining for a nothing-to-do afternoon.

Without the components inside the blue line, the circuit oscillates in a stable way, and there is a deformed sine wave at the T1 transistor collector. As show in the Bode diagrams of the classic phase shift oscillator below, the three stages of the RC ladder shift the phase 180 degrees.  So only at the frequency that produces this phase shift the circuit will oscillate, in this way the total shift around the loop will be o or 360 degrees (T1 also produces a 180° phase displacement).

For oscillations to be sustained, the gain K produced by the transistor should be inverse to the magnitude of the RC network transfer function at the frequency of oscillation.  This is to satisfy the unity-gain loop condition for oscillators.

Nevertheless, with the addition of the extra components in the blue line the output is completely different. When the amplitude increases during the booting of the oscillator, the transistor T2 will start to conduct at a certain point. This makes the resistor R5 to join the feedback loop and change the phase relation, which will force the circuit to find a new point of equilibrium.

To achieve CHAOS, the circuit should not find a stable situation, but a series of instable situations very close to each other. These situations are represented by “orbits” in the oscilloscope forming the so called “attractor.” Playing with the potentiometer P and the input voltage you can force the circuit to pass from one stable oscillation to chaos to another stable condition. Also, changing P1, R5 and C5 influence in the attractor’s shape.

The circuit contains 4 elements that store energy, for this reason the phase space has 4 dimensions. What we see in the oscilloscope is actually a 2D projection of an attractor in 4D. We can see other projections connecting the Y and Z instead of the X and Y points.

Here is a video compilation of the images I got. You can also see the video in my youtube account: http://www.youtube.com/watch?v=EvB6w3WwP_0&feature=youtu.be

Video explicativo sobre Polarización de Ondas Electromagnéticas

Ver en youtube:  http://www.youtube.com/watch?v=erVshbIRpPo