Wse
From MariachiWiki
Responses for Questions
Class 1 (02/22/2007)
What are Cosmic Rays?
Cosmic rays are high energy charged particles. Above 1014 eV, high energy cosmic ray (CR) particles are blocked by Earth's atmosphere and reveal their existence on the ground only through indirect effects such as ionization and showers of secondary charged particles. This kind of secondary particles cascade is usually called an extensive air shower (EAS) Paper by J.A. Goodman. By measuring the features of EAS, the incident particle type, energy and arrival direction can be estimated.
What kind of Cosmic Rays are we looking for?
We want to find out the nature and origin of CRs above 1018 eV, which we call UltraHigh Energy Cosmic Rays (UHECRs). And we are extremely interested in CRs above 1020 eV.
Where do Cosmic Rays come from?
[[The origin of UHECRs is still mysterious. There is no single convincing theoretical model for the UHECRs' origin yet, and thus the solution to this problem will depend on detailed measurements of energy distributions, arrival directions, and compositions.
More References about Cosmic Rays
Paper in Science magazine about Cosmic Ray
Will a Stealth Bomber reflect Radio Waves?
In general, the answer is Yes. Modern stealth technology is designed to absorb and deflect radio waves transmitted from Radars. Stealth bombers use Radar absorbent material (RAM) to absorb certain frequency radio waves, but no one RAM that is suited to absorption of all radar frequencies waves. And also the shape of the stealth bombers is carefully designed to deflect radio wave. Because most modern Radar systems use monostatic settings, which transmitter and receiver are collocated, stealth bombers will be "invisible" to radar if no wave is reflected back to the same direction as the radar transmitter. The concept behind this is that of reflecting a light beam from a torch with a mirror. But remember, nothing is completely "invisible" to radar, the stealth technology can only make radar detection difficult. And radio waves will be reflected by stealth bombers, only the angle and power of reflected waves will be different.
What is GNU?
GNU is a recursive acronym for GNU's Not Unix. For more information, see Wiki page GNU WIKI
Class 2 (02/27/2007)
Is there any Omni-directional antennas in the lab?
No, we do not have any Omni-directional antennas in the lab. The antenna we are using for data collecting is a directional one. The main problem in our radio detecting process is from local interferences. One way to minimize this kind of interference is to adopt a directional antenna, since most likely the local TV stations and distance TV stations are not in the same direction.
How to measure the radiation pattern of an antenna?
There are usually two ways. One is to do an experiment, which requires expensive facilities and equipments. The other way is to do the simulations with softwares. Because we know in theory how the basic elements work, we could be able to calculate the radiation pattern of some kind of antennas which are combinations of basic elements. For example, Yagi antennas are built with dipole arrays.
What is a Mixer inside a receiver?
A mixer inside receiver is also called a frequency mixer, which is a nonlinear circuit or device that accepts as its input two different frequencies and presents at its output a mixture of signals at several frequencies. Basic introductions and formulas
Class 3 (03/01/2007)
How to multiple each number in the matrix?
If the input is [1 2 3], and the desired out put is [1 4 9]. One possible way to do it is using Array multiply operator .*. For previous situation, we could input [1 2 3].*[1 2 3], the answer should be [1 4 9].
Class 8 (03/20/2007)
Several questions from Survey
A. Radio signals are captured by Antennas and processed by Radio receivers.
B. The radio signals we are interested in are transmitted from Distant TV transmitters, and reflected or scattered by ionization trails produced by Cosmic rays.
C. Radio waves travel at The speed of light.
