anglopwr's New Writeups

neutron source (thing)

2003-07-15T00:39:35Z

A neutron source is some material or device that emits a steady stream of neutrons for research or transmutation. There are five primary types of neutron sources, which are detailed below:

Spallation Sources

These sources utilize nuclear spallation, a reaction in which heavy nuclei such as tungsten, lead, or uranium are blown apart by protons accelerated to energies about 1 billion electron volts. About 25-40 neutrons are released for every high energy proton. Spallation is an easy, energy efficient, and effective source with a high neutron flux (amount of neutrons emitted per unit area per unit time). However, it requires a quite large particle accelerator to accelerate the protons.

Alpha emitter + Beryllium Source

In this scheme, a radioactive isotope that emits alpha particles is coated with beryllium. The beryllium absorbs the alpha particles, and emits a small amount of neutrons. Such a device can be very compact, and requires no…

Nuclear Power (idea)

2003-07-14T20:41:33Z

Nuclear fission power is one of the cleanest, safest, and most abundant sources of non-renewable power that can be used with today's technology. However, its use has been limited in the United States, only about one-fifth of all power plants in the US are nuclear. The vast majority of plants in the US are coal-fired. The reason for this is primarily political, not technological, because nuclear power has distinct advantages over coal.

Coal plants emit thick clouds of noxious smoke containing black soot, carbon dioxide, carbon monoxide, sulfur dioxide, and nitrogen oxides. All of these components have adverse effects on the environment. Coal mining is also dangerous business, with many people dying or getting injured each year because of mining-related accidents.

Nuclear plants, on the other hand, emit no polluting gases whatsoever. The only thing that comes out of those big cooling towers is steam. Because so little uranium has to be mined to make the same…

bandwidth (thing)

2003-07-09T03:05:37Z

The following are some formulae to calculate the required bandwidth for many kinds of common modulation techniques:

Amplitude Modulation: 2 * Signal Frequency

Single Sideband Modulation: 1 * Signal Frequency

Vestigial Sideband Modulation: 1.20 to 1.30 * Signal Frequency

Narrowband Frequency Modulation: 2 * Signal Frequency

Wideband Frequency Modulation: 2 * Modulation Ratio * Signal Frequency

Pulse Amplitude Modulation: 0.5 * Pulse Frequency

From this, it can be seen that pulse amplitude modulation is the most bandwidth efficient. However, it cannot carry analog data. Single sideband modulation is the most bandwidth efficient for analog data, and wideband frequency modulation is the least. Even though it uses a lot of bandwidth, wideband frequency modulation has superior noise resistance, making it a good choice for some applications.

recovery rate (thing)

2003-07-09T00:30:23Z

A specification of semiconductor diodes. Recovery rate (t_rr) is the amount of time needed for a diode to switch from on (forward bias) to off (reverse bias), or vice versa after the voltage has switched direction. General purpose diodes have a recovery rate of about a microsecond, while Schottky diodes usually have recovery rates of around a nanosecond.

The faster the recovery rate, the higher a frequency the diode can effectively handle. Recovery rate is not a concern below the radio frequencies, because even the lowest quality diodes have a recovery rate no more than a few microseconds.

Resonance (thing)

2003-07-08T20:26:54Z

In the realm of electricity, a circuit is said to be in resonance if the inductive and capacitive reactances of the circuit cancel out, leaving only the resistance. This state only occurs at one frequency called the resonant frequency. This frequency can be determined by using the following formula:

Frequency = 1 / 2pi * sqrt (capacitance * inductance)

If the capacitance is given in farads, and the inductance in henrys, the frequency will come out as hertz. This frequency not only is the frequency that the circuit will pass with the least impedance, it is also the fundmental frequency the circuit will assume if the circuit is charged, then allowed to discharge through itself.

superconductivity (thing)

2003-07-08T20:11:32Z

There are two types of superconductivity: type 1 and type 2. Type 1 is generally seen in pure elements, while type 2 is usually seen in specially prepared superconducing alloys.

Type 1 superconductivity is much less resistant to magnetic fields and "high" temperatures. In a type 1 material, it is either fully superconducting or not superconducting at all (i.e. there is only one transistion point)

Type 2 superconductivity acts like type 1 until a certain transition point. Once past that first transition point, some atoms of the material is superconducting while others are not. The material still acts like a superconductor in this state. It is not until the second transition point that the material loses all its superconductivity. The second transition point is usually much higher than the transition point of type 1, so type 2 materials keep their superconductivity under much higher magnetic field intensities and temperatures.

Type 1 materials usually can only be superconducting…