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Energy Density
In physics, energy density is the amount of energy stored in a given system or region of space per unit volume. It is sometimes confused with energy per unit mass which is properly called specific energy or . Often only the ''useful'' or extractable energy is measured, which is to say that inaccessible energy (such as rest mass energy) is ignored. In cosmological and other general relativistic contexts, however, the energy densities considered are those that correspond to the elements of the stress–energy tensor and therefore do include mass energy as well as energy densities associated with pressure. Energy per unit volume has the same physical units as pressure and in many situations is synonymous. For example, the energy density of a magnetic field may be expressed as and behaves like a physical pressure. Likewise, the energy required to compress a gas to a certain volume may be determined by multiplying the difference between the gas pressure and the external pressure by ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Specific Orbital Energy
In the gravitational two-body problem, the specific orbital energy \varepsilon (or vis-viva energy) of two orbiting bodies is the constant sum of their mutual potential energy (\varepsilon_p) and their total kinetic energy (\varepsilon_k), divided by the reduced mass. According to the orbital energy conservation equation (also referred to as vis-viva equation), it does not vary with time: \begin \varepsilon &= \varepsilon_k + \varepsilon_p \\ &= \frac - \frac = -\frac \frac \left(1 - e^2\right) = -\frac \end where *v is the relative orbital speed; *r is the orbital distance between the bodies; *\mu = (m_1 + m_2) is the sum of the standard gravitational parameters of the bodies; *h is the specific relative angular momentum in the sense of relative angular momentum divided by the reduced mass; *e is the orbital eccentricity; *a is the semi-major axis. It is expressed in MJ/kg or \frac. For an elliptic orbit the specific orbital energy is the neg ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Heptanitrocubane
Heptanitrocubane is an experimental high explosive based on the cubic eight-carbon cubane molecule and closely related to octanitrocubane. Seven of the eight hydrogen atoms at the corners of the cubane molecule are replaced by nitro groups, giving the final molecular formula . As with octanitrocubane, not enough heptanitrocubane has been synthesized to perform detailed tests on its stability and energy. It is hypothesized to have slightly better performance than explosives such as HMX, the current high-energy standard explosive, based on chemical energy analysis. While in theory not as energetic as octanitrocubane's theoretical maximum density, the HNC that has been synthesized so far is a more effective explosive than any ONC that has been produced, due to more efficient crystal packing and hence higher density. Heptanitrocubane was first synthesized by the same team who synthesized octanitrocubane, Philip Eaton and Mao-Xi Zhang at the University of Chicago The Univers ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Octanitrocubane
Octanitrocubane (molecular formula: C8(NO2)8) is a high explosive that, like Trinitrotoluene, TNT, is shock-insensitive (not readily detonated by shock). The octanitrocubane molecule has the same chemical structure as cubane (C8H8) except that each of the eight hydrogen atoms is replaced by a nitro compound, nitro group (NO2). It is however not as powerful an explosive as once thought, as the high-density theoretical crystal structure has not been achieved. For this reason heptanitrocubane, the slightly less nitrated form is believed to have marginally better performance, despite having a worse oxygen balance. Octanitrocubane is thought to have 20–25% greater performance than HMX (octogen). This increase in power is due to its highly expansive breakdown into CO2 and N2, as well as to the presence of strained chemical bonds in the molecule which have stored potential energy. In addition, it produces no water vapor upon combustion, making it less visible, and both the chemical i ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Gasoline
Gasoline (; ) or petrol (; ) (see ) is a transparent, petroleum-derived flammable liquid that is used primarily as a fuel in most spark-ignited internal combustion engines (also known as petrol engines). It consists mostly of organic compounds obtained by the fractional distillation of petroleum, enhanced with a variety of additives. On average, U.S. refineries produce, from a barrel of crude oil, about 19 to 20 gallons of gasoline; 11 to 13 gallons of distillate fuel (most of which is sold as diesel fuel); and 3 to 4 gallons of jet fuel. The product ratio depends on the processing in an oil refinery and the crude oil assay. A barrel of oil is defined as holding 42 US gallons, which is about 159 liters or 35 imperial gallons. The characteristic of a particular gasoline blend to resist igniting too early (which causes knocking and reduces efficiency in reciprocating engines) is measured by its octane rating, which is produced in several grades. Tetraethyl lead and o ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Hydrogen
Hydrogen is the chemical element with the symbol H and atomic number 1. Hydrogen is the lightest element. At standard conditions hydrogen is a gas of diatomic molecules having the formula . It is colorless, odorless, tasteless, non-toxic, and highly combustible. Hydrogen is the most abundant chemical substance in the universe, constituting roughly 75% of all normal matter.However, most of the universe's mass is not in the form of baryons or chemical elements. See dark matter and dark energy. Stars such as the Sun are mainly composed of hydrogen in the plasma state. Most of the hydrogen on Earth exists in molecular forms such as water and organic compounds. For the most common isotope of hydrogen (symbol 1H) each atom has one proton, one electron, and no neutrons. In the early universe, the formation of protons, the nuclei of hydrogen, occurred during the first second after the Big Bang. The emergence of neutral hydrogen atoms throughout the universe occurred about 370,000 ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Ammonia
Ammonia is an inorganic compound of nitrogen and hydrogen with the formula . A stable binary hydride, and the simplest pnictogen hydride, ammonia is a colourless gas with a distinct pungent smell. Biologically, it is a common nitrogenous waste, particularly among aquatic organisms, and it contributes significantly to the nutritional needs of terrestrial organisms by serving as a precursor to 45% of the world's food and fertilizers. Around 70% of ammonia is used to make fertilisers in various forms and composition, such as urea and Diammonium phosphate. Ammonia in pure form is also applied directly into the soil. Ammonia, either directly or indirectly, is also a building block for the synthesis of many pharmaceutical products and is used in many commercial cleaning products. It is mainly collected by downward displacement of both air and water. Although common in nature—both terrestrially and in the outer planets of the Solar System—and in wide use, ammonia is both caust ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Octaazacubane
Octaazacubane is a hypothetical explosive allotrope of nitrogen with formula N8, whose molecules have eight atoms arranged into a cube. (By comparison, nitrogen usually occurs as the diatomic molecule N2.) It can be regarded as a cubane-type cluster, where all eight corners are nitrogen atoms bonded along the edges. It is predicted to be a metastable molecule, in which despite the thermodynamic instability caused by bond strain, and the high energy of the N–N single bonds, the molecule remains kinetically stable for reasons of orbital symmetry. Explosive and fuel Octaazacubane is predicted to have an energy density (assuming decomposition into N2) of 22.9 MJ/ kg, which is over 5 times the standard value of TNT. It has therefore been proposed (along with other exotic nitrogen allotropes) as an explosive, and as a component of high performance rocket fuel. Its velocity of detonation is predicted to be 15,000 m/s, much (48.5%) more than octanitrocubane, the faste ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Fluorine
Fluorine is a chemical element with the symbol F and atomic number 9. It is the lightest halogen and exists at standard conditions as a highly toxic, pale yellow diatomic gas. As the most electronegative reactive element, it is extremely reactive, as it reacts with all other elements except for the light inert gases. Among the elements, fluorine ranks 24th in universal abundance and 13th in terrestrial abundance. Fluorite, the primary mineral source of fluorine which gave the element its name, was first described in 1529; as it was added to metal ores to lower their melting points for smelting, the Latin verb meaning 'flow' gave the mineral its name. Proposed as an element in 1810, fluorine proved difficult and dangerous to separate from its compounds, and several early experimenters died or sustained injuries from their attempts. Only in 1886 did French chemist Henri Moissan isolate elemental fluorine using low-temperature electrolysis, a process still employed for modern pr ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Lithium
Lithium (from el, λίθος, lithos, lit=stone) is a chemical element with the symbol Li and atomic number 3. It is a soft, silvery-white alkali metal. Under standard conditions, it is the least dense metal and the least dense solid element. Like all alkali metals, lithium is highly reactive and flammable, and must be stored in vacuum, inert atmosphere, or inert liquid such as purified kerosene or mineral oil. When cut, it exhibits a metallic luster, but moist air corrodes it quickly to a dull silvery gray, then black tarnish. It never occurs freely in nature, but only in (usually ionic) compounds, such as pegmatitic minerals, which were once the main source of lithium. Due to its solubility as an ion, it is present in ocean water and is commonly obtained from brines. Lithium metal is isolated electrolytically from a mixture of lithium chloride and potassium chloride. The nucleus of the lithium atom verges on instability, since the two stable lithium isotopes foun ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
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