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История развития двигателей внутреннего сгорания
История развития двигателей внутреннего сгорания
ДВС Двигатель внутреннего сгорания (ДВС) – тепловой двигатель, в котором химическая энергия топлива, сгорающего в рабочей полости, преобразуется в механическую работу. Внутренней энергией обладают все тела – земля, камни, облака. Однако извлечь их внутреннюю энергию довольно трудно, а порой и невозможно. Наиболее легко на нужды человека может быть использована внутренняя энергия лишь некоторых, образно говоря, "горючих" и "горячих" тел. К ним относятся: нефть, уголь, горячие источники вблизи вулканов, теплые морские течения и т.п. Применение двигателей внутреннего сгорания чрезвычайно разнообразно: они приводят в движение самолеты, теплоходы, автомобили, тракторы, тепловозы. Мощные двигатели внутреннего сгорания устанавливают на речных и морских судах.
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Higher education traditions in the USA
Higher education traditions in the USA
Higher education in the United States includes a variety of institutions of higher education. Strong research and funding have helped make United States colleges and universities among the world's most prestigious, making them particularly attractive to international students, professors and researchers in the pursuit of academic excellence. According to the Shanghai Jiao Tong University's Academic Ranking of World Universities, more than 30 of the highest-ranked 45 institutions are in the United States. Public universities, private universities, liberal arts colleges, and community colleges all have a significant role in higher education in the United States. Higher education in the United States includes a variety of institutions of higher education. Strong research and funding have helped make United States colleges and universities among the world's most prestigious, making them particularly attractive to international students, professors and researchers in the pursuit of academic excellence. According to the Shanghai Jiao Tong University's Academic Ranking of World Universities, more than 30 of the highest-ranked 45 institutions are in the United States. Public universities, private universities, liberal arts colleges, and community colleges all have a significant role in higher education in the United States. Colleges and universities in the U.S. vary in terms of goals: some may emphasize a vocational, business, engineering, or technical curriculum while others may emphasize a liberal arts curriculum. Many combine some or all of the above. Colleges and universities in the U.S. vary in terms of goals: some may emphasize a vocational, business, engineering, or technical curriculum while others may emphasize a liberal arts curriculum. Many combine some or all of the above.
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Gas compressor
Gas compressor
A gas compressor is a mechanical device that increases the pressure is a mechanical device that increases the pressure of a gas is a mechanical device that increases the pressure of a gas by reducing its volume is a mechanical device that increases the pressure of a gas by reducing its volume. An air compressor is a specific type of gas compressor. An air compressor is a device that converts power (usually from an electric motor, a diesel engine or a gasoline engine) into potential energy by forcing air into a smaller volume and thus increasing its pressure. The energy in the compressed air can be stored while the air remains pressurized. The energy can be used for a variety of applications, usually by utilizing the kinetic energy of the air as it is depressurized. Compressors are similar to pumpsCompressors are similar to pumps: both increase the pressure on a fluidCompressors are similar to pumps: both increase the pressure on a fluid and both can transport the fluid through a pipe. As gases are compressible, the compressor also reduces the volume of a gas. Liquids are relatively incompressible; while some can be compressed, the main action of a pump is to pressurize and transport liquids. Centrifugal compressors Centrifugal compressors use a rotating disk or impeller in a shaped housing to force the gas to the rim of the impeller, increasing the velocity of the gas. They are primarily used for continuous, stationary service in industries such as oil refineriesThey are primarily used for continuous, stationary service in industries such as oil refineries, chemicalThey are primarily used for continuous, stationary service in industries such as oil refineries, chemical and petrochemicalThey are primarily used for continuous, stationary service in industries such as oil refineries, chemical and petrochemical plants and natural gas processing plants
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The second law of thermodynamics
The second law of thermodynamics
The second law of thermodynamics asserts the irreversibility of natural processes, and the tendency of natural processes to lead towards spatial homogeneity of matter and energy, and especially of temperature. It can be formulated in a variety of interesting and important ways. It implies the existence of a quantity called the entropy It implies the existence of a quantity called the entropy of a thermodynamic system. When two initially isolated systems It implies the existence of a quantity called the entropy of a thermodynamic system. When two initially isolated systems in separate but nearby regions of space, each in thermodynamic equilibrium It implies the existence of a quantity called the entropy of a thermodynamic system. When two initially isolated systems in separate but nearby regions of space, each in thermodynamic equilibrium with itself but not necessarily with each other, are then allowed to interact, they will eventually reach a mutual thermodynamic equilibrium. The sum of the entropies of the initially isolated systems is less than or equal to the total entropy of the final combination. This statement of the law recognizes that in classical thermodynamics, the entropy of a system is defined only when it has reached its own internal thermodynamic equilibrium. The second law refers to a wide variety of processes, reversible and irreversible. All natural processes are irreversible. Reversible processes are a convenient theoretical fiction and do not occur in nature. A prime example of irreversibility is in the transfer of heat by conduction or radiation. It was known long before the discovery of the notion of entropy that when two bodies initially of different temperatures come into thermal connection, then heat always flows from the hotter body to the colder one. According to the second law of thermodynamics an element of heat transferred, δQ, is the product of the temperature (T) with the increment (dS) of the system's conjugate variable, its entropy (S).
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Ideal gas law Equation of state
Ideal gas law Equation of state
In physicsIn physics and thermodynamics, an equation of state is a relation between state variables is a relation between state variables. More specifically, an equation of state is a thermodynamic equation is a relation between state variables. More specifically, an equation of state is a thermodynamic equation describing the state of matter under a given set of physical conditions. It is a constitutive equation is a relation between state variables. More specifically, an equation of state is a thermodynamic equation describing the state of matter under a given set of physical conditions. It is a constitutive equation which provides a mathematical relationship between two or more state functions is a relation between state variables. More specifically, an equation of state is a thermodynamic equation describing the state of matter under a given set of physical conditions. It is a constitutive equation which provides a mathematical relationship between two or more state functions associated with the matter, such as its temperature is a relation between state variables. More specifically, an equation of state is a thermodynamic equation describing the state of matter under a given set of physical conditions. It is a constitutive equation which provides a mathematical relationship between two or more state functions associated with the matter, such as its temperature, pressure is a relation between state variables. More specifically, an equation of state is a thermodynamic equation describing the state of matter under a given set of physical conditions. It is a constitutive equation which provides a mathematical relationship between two or more state functions associated with the matter, such as its temperature, pressure,volume is a relation between state variables. More specifically, an equation of state is a thermodynamic equation describing the state of matter under a given set of physical conditions. It is a constitutive equation which provides a mathematical relationship between two or more state functions associated with the matter, such as its temperature, pressure,volume, or internal energy is a relation between state variables. More specifically, an equation of state is a thermodynamic equation describing the state of matter under a given set of physical conditions. It is a constitutive equation which provides a mathematical relationship between two or more state functions associated with the matter, such as its temperature, pressure,volume, or internal energy. Equations of state are useful in describing the properties of fluids is a relation between state variables. More specifically, an equation of state is a thermodynamic equation describing the state of matter under a given set of physical conditions. It is a constitutive equation which provides a mathematical relationship between two or more state functions associated with the matter, such as its temperature, pressure,volume, or internal energy. Equations of state are useful in describing the properties of fluids, mixtures of fluids, solids is a relation between state variables. More specifically, an equation of state is a thermodynamic equation describing the state of matter under a given set of physical conditions. It is a constitutive equation which provides a mathematical relationship between two or more state functions associated with the matter, such as its temperature, pressure,volume, or internal energy. Equations of state are useful in describing the properties of fluids, mixtures of fluids, solids, and even the interior of stars. An ideal gas is a theoretical is a theoretical gas is a theoretical gas composed of many randomly moving point particles is a theoretical gas composed of many randomly moving point particles that do not interact except when they collide elastically. The ideal gas concept is useful because it obeys the ideal gas law is a theoretical gas composed of many randomly moving point particles that do not interact except when they collide elastically. The ideal gas concept is useful because it obeys the ideal gas law, a simplified equation of state is a theoretical gas composed of many randomly moving point particles that do not interact except when they collide elastically. The ideal gas concept is useful because it obeys the ideal gas law, a simplified equation of state, and is amenable to analysis under statistical mechanics is a theoretical gas composed of many randomly moving point particles that do not interact except when they collide elastically. The ideal gas concept is useful because it obeys the ideal gas law, a simplified equation of state, and is amenable to analysis under statistical mechanics. One mole of an ideal gas has a volume of 22.7 L at STP. At normal conditions such as standard temperature and pressureAt normal conditions such as standard temperature and pressure, most real gasesAt normal conditions such as standard temperature and pressure, most real gases behave qualitatively like an ideal gas. Many such as nitrogenAt normal conditions such as standard temperature and pressure, most real gases behave qualitatively like an ideal gas. Many such as nitrogen, oxygenAt normal conditions such as standard temperature and pressure, most real gases behave qualitatively like an ideal gas. Many such as nitrogen, oxygen, hydrogenAt normal conditions such as standard temperature and pressure, most real gases behave qualitatively like an ideal gas. Many such as nitrogen, oxygen, hydrogen, noble gasesAt normal conditions such as standard temperature and pressure, most real gases behave qualitatively like an ideal gas. Many such as nitrogen, oxygen, hydrogen, noble gases, and some heavier gases like carbon dioxideAt normal conditions such as standard temperature and pressure, most real gases behave qualitatively like an ideal gas. Many such as nitrogen, oxygen, hydrogen, noble gases, and some heavier gases like carbon dioxide can be treated like ideal gases within reasonable tolerances. Generally, a gas behaves more like an ideal gas at higher temperatureAt normal conditions such as standard temperature and pressure, most real gases behave qualitatively like an ideal gas. Many such as nitrogen, oxygen, hydrogen, noble gases, and some heavier gases like carbon dioxide can be treated like ideal gases within reasonable tolerances. Generally, a gas behaves more like an ideal gas at higher temperature and lower pressureAt normal conditions such as standard temperature and pressure, most real gases behave qualitatively like an ideal gas. Many such as nitrogen, oxygen, hydrogen, noble gases, and some heavier gases like carbon dioxide can be treated like ideal gases within reasonable tolerances. Generally, a gas behaves more like an ideal gas at higher temperature and lower pressure, as the workAt normal conditions such as standard temperature and pressure, most real gases behave qualitatively like an ideal gas. Many such as nitrogen, oxygen, hydrogen, noble gases, and some heavier gases like carbon dioxide can be treated like ideal gases within reasonable tolerances. Generally, a gas behaves more like an ideal gas at higher temperature and lower pressure, as the work which is against intermolecular forces becomes less significant compared with the particles' kinetic energy, and the size of the molecules becomes less significant compared to the empty space between them. The ideal gas model tends to fail at lower temperatures or higher pressures, when intermolecular forces and molecular size become important. At some point of low temperature and high pressure, real gases undergo a phase transitionThe ideal gas model tends to fail at lower temperatures or higher pressures, when intermolecular forces and molecular size become important. At some point of low temperature and high pressure, real gases undergo a phase transition, such as to a liquidThe ideal gas model tends to fail at lower temperatures or higher pressures, when intermolecular forces and molecular size become important. At some point of low temperature and high pressure, real gases undergo a phase transition, such as to a liquid or a solidThe ideal gas model tends to fail at lower temperatures or higher pressures, when intermolecular forces and molecular size become important. At some point of low temperature and high pressure, real gases undergo a phase transition, such as to a liquid or a solid. The model of an ideal gas, however, does not describe or allow phase transitions. These must be modeled by more complex equations of state.
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