Units of pressure or stress

PASCAL (Pa). A unit of pressure or stress. One pascal equals 1 newton per square meter. 

Pascal, SI unit of pressure or stress (= N/m ) vapor pressure of pure solvent at given temperature magnitude of a colligative property of a polymer solution (Section 2.9)... 

Equations (7.83) and (7.84) describe two important relations in sintering. Since the terms containing Q and are normally very small, they show that Pa and Pv depend primarily on the hydrostatic pressure in the solid and on the curvature of the surface. The curvature term ysvK has the units of pressure or stress, so that curvature and applied pressure effects can tha-efore be treated by the same formulation. This concept will be used in the next chapter when the sintering models are considered. 

Newton per square meter N/m SI unit of pressure or stress see pascal. 

Pico P SI unit of pressure or stress. This name accepted by the 14th Conference Generate des Poids et Mesures. SI prefix for 10 2. 

Exact conversions are shown in boldface type. Repeating decimals are underlined. The SI unit of pressure or stress is the Pascal (Pa). 

In Eqs. (5.84) and (5.85), because Ca and Cy are generally very low, the last terms can be neglected. Therefore, //a and py are determined essentially by the hydrostatic pressure in the solid and the curvature of the surface. Since the curvature term ysv has the same units as pressure or stress, the curvature, and applied pressure effects can be treated with same formulation for the analysis of sintering. 

Frequency-Magnitude Distribution of Seismicity in Volcanic Regions, Table 1 Main features of -value anomalies and data on mineral stabilization and gas processes at volcanoes around the world. Reported and calculated stabilization pressure values from various authors are converted to pascals (Pa, N/m = m kg s ) or megapascals (MPa = 10 Pa) as this is the SI derived unit for pressure or stress... 

These two examples illustrate that 7) is, in general, an excess quantity for a given D-face. As a consequence of this result, there is no physical difference between interfacial and surface tension in thermodynamic equilibrium. In the literature, the term surface tension is attributed to the D-face, or interface, between a condensed phase and the corresponding vapor phase. Some authors define the surface tension as the interfacial tension of a condensed phase in contact with vacuum. This is incorrect in the framework of equilibrium thermodynamics. A condensed phase will fill a vacuum with its vapor phase to be at thermodynamic equilibrium. Hence, any interfacial tension results from a defined pair of phases, never fi om a single phase, and they need to be marked by the subscript AB or similar. Otherwise, the interfacial tension would be ill-defined. 7 5 accounts for the real distribution of pressure or stress inside the phase boundary. It is called a tension because it possesses the dimension of a force per unit length [N m ] in the 2D space of the D-face, and indeed acts somewhat like a tension in a membrane (except there is no elastic proportionality between the tension and extension). Moreover, (O 4.15b) reveals that the value for 7 5 usually depends on the position, here rjy, chosen for that D-face. is always positive. This is a condition of stability for the interphase and hence for the phase itself, and it is proven by experiment and by statistical mechanics calculations as well. The value remains almost constant when p decreases. Therefore, py-must he negative, at least inside the dominant part of the interphase, and as a consequence, the interphase and the corresponding D-face will adopt the minimum volume and area, respectively. 

Besides being desiccated and irradiated, microorganisms traveling in space will be exposed to space vacuum that can reach 10-14 pascal (a unit of pressure—100 Pa = 1 mbar).57 The result is extreme dehydration, and naked spores can survive for only days if exposed to space vacuum. Survival of spores is increased if they are associated with various chemicals such as sugars, or are embedded in salt crystals. Nicholson et al. (2000) discuss the various stresses that a microbial cell or spore would have to endure to survive interplanetary travel.58 They include the process that transports them out of Earth s atmosphere, such as volcanic eruptions and bolide impacts, long periods of transit in the cold of space, and atmospheric entry into a new planetary home. Spores have been shown to survive the shock conditions of a meteorite impact and the ultraviolet radiation and low temperature of space.59 It is clear that panspermia is possible and even probable if bacterial spores become embedded in rocks that are ejected from one planet and eventually enter the atmosphere of another. Bacterial... 

PASCAL - The accepted metric unit of measurement or pressure and stress component in the measurement of viscosity. A Pascal is equal to a force of 1 Newton acting an area of 1 square meter. The symbol is Pa. 

To move a broken-down motor car I might exert a force on the back of the car to propel it forward. My hands would apply a pressure on the body panel at the point of contact with the car. Pressure or stress is a measure of the force per unit area. 

Pressure or stress is a measure of the force per unit area. 

As has already been stated, the elastic modulus has the units of pressure. Pa, or N/m, which is also equivalent to J/m. The latter means that, in agreanent with Equation 3.1, it is possible to formally view the elasticity modulus as twice the elastic energy stored by the unit volume subjected to the unit strain. At a given shear stress, in agreement with Eqnation 3.1, the smaller the modnlns G, the higher the elastic energy density stored by the body. 

Another property that determines a plastic s usefulness is its modulus. Modulus is related to stiffness high stiffness corresponds to high modulus. Modulus is defined as the ratio of stress (deforming force per unit cross-sectional area) to strain (increment of deformation) for elastic deformation (Fig. 19.7). Its dimensions are the same as those of pressure or tensile strength. 

Of particular interest in fluid flow is the distinction between shear stress and pressure (or pressure difference), both of which are defined as force per unit area. For steady-state... 

These reflection and transmission coefficients relate the pressure amplitude in the reflected wave, and the amplitude of the appropriate stress component in each transmitted wave, to the pressure amplitude in the incident wave. The pressure amplitude in the incident wave is a natural parameter to work with, because it is a scalar quantity, whereas the displacement amplitude is a vector. The displacement amplitude reflection coefficient has the opposite sign to (6.90) or (6.94) the displacement amplitude transmission coefficients can be obtained from (6.91) and (6.92) by dividing by the appropriate longitudinal or shear impedance in the solid and multiplying by the impedance in the fluid. The impedances actually relate force per unit area to displacement velocity, but displacement velocity is related to displacement by a factor to which is the same for each of the incident, reflected, and transmitted waves, and so it all comes to the same thing in the end. In some mathematical texts the reflection... 

Elasticity is the inherent property in bodies by which they recover their former figure or state after the force (stress) of external pressure, tension, or distortion have been removed (as for instance elasticity of gases, rubber, etc). Any force or distribution of forces which acts upon a body and is balanced by equal and opposite forces in the body is, in general, termed as a stress, although.the term is more particularly applied to the force per unit area acting upon the body. The change in size per unit size, or the change in some dimension per its unit, produced by the stress is called a strain. For each substance and for each kind of strain there is some limit beyond which Hooke s Law does not apply. 

PRESSURE. If a body of fluid is at rest, the forces are in equilibrium or the fluid is in static equilibrium. The types of force that may aci on a body are shear or tangential force, tensile force, and compressive force. Fluids move continuously under the action of shear or tangential forces. Thus, a fluid at rest is free in each part from shear forces one fluid layer does not slide relative to an adjacent layer. Fluids can be subjected to a compressive stress, which is commonly called pressure. The term may be defined as force per unit area. The pressure units may be dynes per square centimeter, pounds per square foot, torr. mega-Pascals, etc. Atmospheric pressure is the force acting upon a unit area due to the weight of the atmosphere. Gage pressure is the difference between the pressure of the fluid measured (at some point) and atmospheric pressure. Absolute pressure, which can be measured by a mercury barometer, is the sum of gage pressure plus atmospheric pressure. 

The word viscosity comes from the Latin word for mistletoe, viscum. Anyone familiar with this plant is aware that it exudes a viscous sticky sap when harvested. Viscosity is defined after Isaac Newton in his Principia as the ratio of stress to shear rate and is given the symbol T. Stress (a) in a fluid is simply force/area, like pressure, and has the units of pascals (Pa S.I. units) or dynes/cm2 (c.g.s.). Shear rate or strain rate (y or dyldt) is the differential of strain (y) with respect to time. Strain is simply the change in shape of a volume of fluid as a result of an applied stress and has no units. The shear rate is in fact a velocity gradient, not a flow rate. It has the bizarre units of 1/time (sec-1) and is the velocity at a given point in the fluid divided by the distance of that point from the stationary plane. 

For the momentum conservation of a single-phase fluid, the momentum per unit volume / is equal to the mass flux pU. The momentum flux is thus expressed by the stress tensor i/r = (pi — t). Here p is the static pressure or equilibrium pressure / is a unit tensor and r is the shear stress tensor. Since <1> = —pf where / is the field force per unit mass, Eq. (5.12) gives rise to the momentum equation as... 

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