Radiology - Technology Information Portal
Thursday, 28 March 2024
• Welcome to Radiology-TIP.com!
     • Sign in / Create account
 
 'Frequency' p4
SEARCH   
A B C D E F G H I J K L M N O P Q R S T U V W X Y Z 
Searchterm 'Frequency' found in 3 terms [
] and 21 definitions [
]
Result Pages :
Hertz
(Hz) The standard SI unit of frequency.
Definition: The number of repetitions of a periodic process per unit time. It is equal to the old unit cycles or oscillations each second of a simple harmonic motion. The unit is named for the German physicist Heinrich Rudolf Hertz.
Larger units are:
kilohertz (KHz) = 1 000 Hz = 103 Hertz
megahertz (MHz) = 1 000 KHz = 106 Hertz
gigahertz (GHz) = 1 000 MHz = 109 Hertz
terahertz (THz) = 1 000 GHz = 1012 Hertz
petahertz (PHz) = 1 000 THz = 1015 Hertz
exahertz (EHz) = 1 000 PHz = 1018 Hertz

See also Oscillation, Coherence, Duty Cycle, Cine Mode, and System International.
Ionizing Radiation
Radiation can ionize matter caused by the high energy which displaces electrons during interactions with atoms. In the electromagnetic spectrum higher frequency ultraviolet radiation begins to have enough energy to ionize matter.
Examples of ionizing radiation include alpha particles, beta particles, gamma rays, x-rays, neutrons, high-speed electrons, high-speed protons, and other particles capable of producing ions by direct or secondary processes in passage through tissues.
Damage of living tissue results from the transfer of energy to atoms and molecules in the cellular structure. Ionized cells have to repair themselves to remain alive. Generally, healthy cells have a higher capability to repair themselves than cancer cells.

Biological effects of ionizing radiation exposure:
Generation of free radicals;
break down of chemical bonds;
production of new chemical bonds and cross-linkage between macromolecules;
deregulation of vital cell processes by molecule damage (e.g. DNA, RNA, proteins).

Ionizing radiation are used in a wide range of facilities, including health care, research institutions, nuclear reactors and their support facilities, and other manufacturing settings. These radiation sources can pose a serious hazard to affected people and environment if not properly controlled.

See also Radiation Safety, Controlled Area, Radiotoxicity and As Low As Reasonably Achievable.
Phon
A logarithmic measure of sound loudness closely related to the decibel. The unit decibel is used for objective measurements that mean, they measure the actual pressure of the sound waves as recorded using a microphone. The unit phon is used for subjective measurements, which means, measurements made using the ears of a human listener.
A sound has the loudness 'p' phon if it seems to the listener to be equal in loudness to the sound of a pure tone of the frequency 1 kilohertz and strength 'p' decibel. A measurement in phons will be similar to a measurement in decibels, but not identical, since the perceived loudness of a sound depends on the distribution of frequencies in the sound as well as the pressure of the sound waves. In the U.S., sound loudness is frequently measured in sones rather than phons: a sound of loudness x sones has loudness 10 log2 x + 40 phons.
Quantum
Quantum is a discrete and the smallest natural unit of energy and momentum. Planck makes the assumption that every energy transfer on a sub-atomic level consist of small units, called quanta. The view of electromagnetic energy as photons reflects this quantization.
E = h x v
E = energy
h = Planck quantum of action = 6.6261 x 10-27 erg sec
v = frequency.
Sampling
Conversion of the analog signal to a series of digital values by measurement at a set of particular times; this utilizes the analog to digital converter. If the rate of sampling is less than twice the highest frequency in the signal, aliasing will occur. The duration of sampling determines how small a difference of frequencies can be separated.

See also Algorithm, Trigonometric Functions, Digitization, Exponential Functions, Imaginary Number, Logarithms, Point Spread Function.
Result Pages :
 
Share This Page
Facebook
Twitter
LinkedIn
Look
      Ups
Radiology - Technology Information Portal
Member of SoftWays' Medical Imaging Group - MR-TIP • Radiology-TIP • Medical-Ultrasound-Imaging
Copyright © 2008 - 2024 SoftWays. All rights reserved.
Terms of Use | Privacy Policy | Advertising
 [last update: 2023-11-06 02:01:00]