Prenex normal form - Revision history

en>BD2412: minor fixes, mostly disambig links using AWB

2014-08-20T21:50:42Z

minor fixes, mostly disambig links using AWB

← Older revision		Revision as of 23:50, 20 August 2014
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	~~{{Unreferenced\|date=December 2009}}~~		Adrianne Le is the brand my parents gave but you can call me anything you really like. My house is now for South Carolina. Filing happens to be my day job well but soon I'll getting on my own. What me and my family genuinely like is acting but I've can't make it all of my profession really. See what's new on excellent website here: http://prometeu.net<br><br>my website; [http://prometeu.net clash of clans hack android]
	~~The '''Coulomb barrier''', named after [[Coulomb's law]], which is named after physicist [[Charles-Augustin de Coulomb]] (1736–1806),~~ is the ~~energy barrier due to [[electrostatic]] interaction that two nuclei need to overcome so they~~ can ~~get close enough to undergo a [[nuclear reaction]]~~. ~~This energy barrier~~ is ~~given by the [[electrostatic potential energy]]:~~

	~~:<math>U_{coul} = k {{q_1\,q_2} \over r}={1 \over {4 \pi \epsilon_0}}{{q_1 \, q_2} \over r}</math>~~
	~~where~~
	~~:''k'' is the Coulomb~~'~~s constant = 8~~.~~9876×10<sup>9</sup> N m² C<sup>−2</sup>;~~
	~~:''ε''<sub>0</sub>~~ is ~~the [[Vacuum permittivity\|permittivity of free space]];~~
	:''~~q<sub>1</sub>'', ''q<sub>2</sub>'' are the charges of the interacting particles;~~
	~~:''r'' is the interaction radius.~~

	~~A positive value~~ of ~~U is due to a repulsive force, so interacting particles are at higher energy levels as they get closer~~. ~~A negative potential energy indicates a bound state (due to an attractive force).~~

	~~Coulomb~~'s ~~barrier increases with the [[atomic number]]s (i.e. the number of protons) of the colliding nuclei~~:
	:<~~math~~>~~U_{coul}={{k \, Z_1 \, Z_2 \, e^2} \over r}~~<~~/math~~>
	~~where ''e'' is the~~ [~~[elementary charge]], 1.602 176 53×10<sup>−19<~~/~~sup> C, and ''Z<sub>i<~~/~~sub>'' the corresponding atomic numbers.~~

	~~To overcome this barrier, nuclei have to collide at high velocities, so their kinetic energies drive them close enough for the [[strong interaction]] to take place and bind them together~~.

	~~According to the [[kinetic theory of gases]], the temperature of a gas is just a measure of the average kinetic energy~~ of the particles in that gas. For normal gases,{{Clarify\|reason = "normal" in what sense?\|date=January 2012}} the [[Maxwell-Boltzmann distribution]] gives the fraction of particles moving at a given velocity as a function of gas temperature, and thus the fraction of particles moving at velocities high enough to overcome the Coulomb's barrier can be derived.

	In practice, temperatures needed to overcome Coulomb's barrier turn out to be smaller than expected due to quantum-mechanical [[quantum tunnelling\|tunnelling]], as established by [[George Gamow\|Gamow]]. The consideration of barrier-penetration through tunnelling and the speed distribution gives rise to a limited range of conditions where the fusion can take place, known as the [[Gamow window]].

	~~It was the absence of a Coulomb barrier for the neutron that enabled [[James Chadwick]] to discover the neutron.~~

	~~== See also ==~~
	* [[Quantum tunnelling]]

	~~{{DEFAULTSORT:Coulomb Barrier}}~~
	~~[[Category:Nuclear physics]]~~
	~~[[Category:Nuclear fusion]]~~
	~~[[Category:Nuclear chemistry]~~]

en>AnomieBOT: Dating maintenance tags: {{Dn}}

2013-12-27T23:13:03Z

Dating maintenance tags: {{Dn}}

← Older revision		Revision as of 01:13, 28 December 2013
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	~~Gabrielle Straub is what you can call me although it~~'s ~~not~~ the ~~numerous feminine of names~~. ~~Fish keeping~~ is ~~what I provide every week. Managing people~~ is ~~my working day job now~~. ~~My house~~ is ~~now inside~~ of ~~South Carolina~~. Go to ~~my web site~~ to ~~find out more~~: ~~http~~://~~circuspartypanama.com~~<br><br>~~My site;~~ [~~http://circuspartypanama~~.~~com Clash~~ of ~~Clans hack no survey~~]		{{Unreferenced\|date=December 2009}}
			The '''Coulomb barrier''', named after [[Coulomb's law]], which is named after physicist [[Charles-Augustin de Coulomb]] (1736–1806), is the energy barrier due to [[electrostatic]] interaction that two nuclei need to overcome so they can get close enough to undergo a [[nuclear reaction]]. This energy barrier is given by the [[electrostatic potential energy]]:

			:<math>U_{coul} = k {{q_1\,q_2} \over r}={1 \over {4 \pi \epsilon_0}}{{q_1 \, q_2} \over r}</math>
			where
			:''k'' is the Coulomb's constant = 8.9876×10<sup>9</sup> N m² C<sup>−2</sup>;
			:''ε''<sub>0</sub> is the [[Vacuum permittivity\|permittivity of free space]];
			:''q<sub>1</sub>'', ''q<sub>2</sub>'' are the charges of the interacting particles;
			:''r'' is the interaction radius.

			A positive value of U is due to a repulsive force, so interacting particles are at higher energy levels as they get closer. A negative potential energy indicates a bound state (due to an attractive force).

			Coulomb's barrier increases with the [[atomic number]]s (i.e. the number of protons) of the colliding nuclei:
			:<math>U_{coul}={{k \, Z_1 \, Z_2 \, e^2} \over r}</math>
			where ''e'' is the [[elementary charge]], 1.602 176 53×10<sup>−19</sup> C, and ''Z<sub>i</sub>'' the corresponding atomic numbers.

			To overcome this barrier, nuclei have to collide at high velocities, so their kinetic energies drive them close enough for the [[strong interaction]] to take place and bind them together.

			According to the [[kinetic theory of gases]], the temperature of a gas is just a measure of the average kinetic energy of the particles in that gas. For normal gases,{{Clarify\|reason = "normal" in what sense?\|date=January 2012}} the [[Maxwell-Boltzmann distribution]] gives the fraction of particles moving at a given velocity as a function of gas temperature, and thus the fraction of particles moving at velocities high enough to overcome the Coulomb's barrier can be derived.

			In practice, temperatures needed to overcome Coulomb's barrier turn out to be smaller than expected due to quantum-mechanical [[quantum tunnelling\|tunnelling]], as established by [[George Gamow\|Gamow]]. The consideration of barrier-penetration through tunnelling and the speed distribution gives rise to a limited range of conditions where the fusion can take place, known as the [[Gamow window]].

			It was the absence of a Coulomb barrier for the neutron that enabled [[James Chadwick]] to discover the neutron.

			== See also ==
			* [[Quantum tunnelling]]

			{{DEFAULTSORT:Coulomb Barrier}}
			[[Category:Nuclear physics]]
			[[Category:Nuclear fusion]]
			[[Category:Nuclear chemistry]]

115.254.112.4 at 02:34, 22 August 2012

2012-08-22T02:34:47Z

New page

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