Understanding reference:/view/127109.html?wtp=tt
II. Elemental symbols
Rf (element 104 naming) English name: Rutherford Chinese name: 鈩
Relative atomic mass: 261 Common valence: electronegativity: 0
Exterior electron arrangement: 6d2 7s2 Extranuclear electron arrangement: 2,8,18,32,32,10,2
Isotopes and radiation: Rf-257[4.7s]
Electron affinity and energy: 0 KJ-mol-1
First ionization energy: 0 KJ-mol-1 Second ionization energy: 0 KJ-mol-1 Third ionization energy: 0 KJ-mol-1
Monomer density: 0 g/cm3 Monomer melting point: 0 °C Monomer boiling point: 0 °C
Atomic radius. 0 Angstroms Ionic radius: Angstroms *** Valence radius: 0 Angstroms
Common compounds:
Discovered by: Jock et al. Time: 1968 Location: United States
Name origin:
Named in honor of Ernest Rutherford.
Element Description:
Radioactive man-made metallic element.
Elemental origin:
Bombardment of californium 249 atoms with beams of carbon 12 and carbon 13 particles produces the isotopes of hydrazine with half-lives of 4+ and 3 seconds.
Elemental Uses:
No practical use
Electromagnetic Frequency
Also RF is an acronym for Radio Frequency, denoting the electromagnetic frequency that can be radiated into space, which ranges from 300 KHz to 30 GHz.
Radio Frequency abbreviation RF RF is Radio Frequency current, which is a high-frequency alternating variations of electromagnetic waves. Changes per second less than 1000 times the alternating current is called low-frequency current, more than 10000 times called high-frequency current, and radio frequency is such a high-frequency current. Cable television system is the use of radio frequency transmission
In the theory of electronics, the current flows through the conductor, the conductor around the formation of a magnetic field; alternating current through the conductor, the conductor around the formation of an alternating electromagnetic field, known as electromagnetic waves.
In the electromagnetic wave frequency is lower than 100khz, electromagnetic wave will be absorbed by the ground, can not form an effective transmission, but the electromagnetic wave frequency is higher than 100khz, electromagnetic wave can be propagated in the air, and by the outer edge of the atmosphere of the ionosphere reflection, the formation of the ability to transmit over long distances, we have long-distance transmission of high-frequency electromagnetic waves to become the radio frequency, the acronym: RF
< p>The source of electrical information (analog or digital) with high-frequency current modulation (AM or FM), the formation of radio frequency signals, through the antenna launched into the air; long-distance will be received by the radio frequency signals for the anti-modulation, restore the source of electrical information, the process is called wireless transmission.Wireless transmission has been developed for nearly two hundred years, forming a large number of users and product groups, however, due to climate changes and surface obstacles, can not transmit perfect information.
Modern mankind invented a cheap high-frequency transmission cable (RF cable), in order to pursue the perfect quality of information transmission, taking into account the original wireless equipment, wireless mode wired transmission began to popularize. Produced the concept of radio frequency transmission.
If your information source after the second modulation, cable transmission to the opposite end, the opposite end with the anti-modulation of the information source to restore the source of information and then apply, no matter how low the frequency, but also RF transmission mode, if there is no modulation anti-modulation process, just the information source with the cable to the opposite end of the direct use, no matter how high the frequency is, it is a general wired transmission mode.
Rf in analytical chemistry
Thin-layer chromatography in the origin to the spot center (origin) of the distance to the origin knife solvent front (solvent front) distance ratio
is a method of chromatography to indicate the location of the component movement of a parameter. It is defined as the ratio of solute migration distance to mobile phase migration distance. Under certain chromatographic conditions, the Rf value of a particular compound is a constant, so it is possible to identify a compound based on its Rf value.
Rf=(distance moved from origin by component)÷(distance moved from origin by solvent)
Calculation:
Power Sensitivity (dBm dBmV dBuV) dBm=10log( Pout/1mW), where Pout is the power value in mW
dBmV=20log(Vout /1mV), where Vout is the voltage value in mV
dBuV=20log(Vout /1uV), where Vout is the voltage value in uV
Conversion relation: < /p>
Pout = Vout x Vout/R
dBmV = 10log(R/0.001) + dBm, where R is the load impedance
dBuV = 60 + dBmV Application Example Calculation of Wireless Communication Distance
III. Image License Mode
RF (Royalty-Free) royalty-free use mode, also known as royalty-free use of copyrighted images
Defined as the RF mode of the image, the user to obtain the use of the authorization of the use of the characteristics of non-exclusive license to use. After a user purchases a usage license, his/her use of the image is not limited by the number of times, time, space, or use.The license price of an RF product depends mainly on the size of the image, not on the specific use. Once a user has purchased an RF image product, it can be used for multiple purposes over multiple periods of time without any additional fees (of course, illegal uses are prohibited.) RF image products are for the purchaser's own use only, and are not transferable or re-sellable, nor can they be bought out of exclusive use.
The RF model is standardized in licensing and pricing, and is also popular with many customers because of its "buy once, use many" feature.