SPI module 1 정리 - ①

* unit

Prefix	Meaning	Factor	Power of 10 prefix	Symbol
giga	billion	1,000,000,000	10^9	G
mega	million	1,000,000	10^6	M
kilo	thousand	1,000	10^3	k
centi	hundredth	0.01	10^(-2)	c
milli	thousandth	0.001	10^(-3)	m
micro	milionth	0.000001	10^(-6)	μ
nano	billionth	0.000000001	10^(-9)	n

 

* scientific notation (과학적 표기)

 

ex) 1540 m/s → 1.54 * 10^3 m/s

 

---

* Sound wave

 - Sound is a mechanical process = mechanical energy

 - Mechanical vibration propagates through the medium

 - Sound energy moves thtough the medium not molecule

 - Sound cannot travel though a vacuum.

 

 - Sound is mechanical longitudinal wave.

 - Wave carry energy, not matter

 

 

* Acoustic variables = PPDT

 - Pressure

 - Particle motion

 - Density

 - Tenperature

 

* Compression = condensation : high pressure, high density

   Rarefaction = relaxation : low pressure, low density

 

---

 

*Sound range

 - acuostic wave : 20 Hz ~ 20 kHz = 20~20,000Hz

 - Ultrasonic(US) : 20kHz ~

 

 - medical use... = therapeutic, diagnostic, surgical US : 1-10MHz 

 - endoluminal probe(GI, ureter, vessel) : 20MHz