Another example is the determination of bentazone in aqueous samples. Bentazone is a common medium-polar pesticide, and is an acidic compound which co-elutes with humic and/or fulvic acids. In this application, two additional boundary conditions are important. Eirst, the pH of the M-1 mobile phase should be as low as possible for processing large sample volumes, with a pH of 2.3 being about the best that one can achieve when working with alkyl-modified silicas. Secondly, modifier gradients should be avoided in order to prevent interferences caused by the continuous release of humic and/or fulvic acids from the column during the gradient (46). [Pg.346]

One additional boundary condition being needed, two cases have been treated in the literature ... [Pg.523]

In terms of modeling, the equations are the same as those in section 4, with perhaps some simplifications. Additional boundary conditions are required due to the higher dimensionality of the equations, but these are relatively straightforward, such as no fluxes of gas species across the external boundary of the gas channels. [Pg.476]

For solid particles a sufficient set of boundary conditions is provided by the no slip condition, the requirement of no flow across the particle surface, and the flow field remote from the particle. For fluid particles, additional boundary conditions are required since Eqs. (1-1) and (1-9) apply simultaneously to both phases. Two additional boundary conditions are provided by Newton s third law which requires that normal and shearing stresses be balanced at the interface separating the two fluids. [Pg.5]

The uncorrelated particle distribution (4.1.12) is used, as standard initial conditions for the correlation dynamics. After the transient period the solution (for the stable regime) becomes independent on the initial conditions. For both the joint correlation functions boundary conditions at large distances X (oo, t) = Y(oo, t) = 1 has to be fulfilled due to the correlation weakening. The black sphere model imposes the additional boundary condition (5.1.39) for the correlation function Y(r,t). [Pg.480]

In order to calculate the potential distribution in the gap we need not only the Poisson-Boltzmann equation, but in addition, boundary conditions must be specified. Two common types of boundary conditions are ... [Pg.100]

The relation between the surface charge density and surface potential, as a function of the distance/,is obtained using the additional boundary condition required by symmetry dip(x)/dx x=i/2 = 0. Consequently, eqs 12 can be integrated numerically to provide the value of the double layer force. [Pg.336]

The symmetry condition provides an additional boundary condition,... [Pg.651]

It was discussed that the structure created by the ternary system oil/water/ nanoparticle follows the laws of spreading thermodynamics, as they hold for ternary immiscible emulsions (oil 1 /oil 2/water) [114,116,117]. The only difference is that the interfacial area and the curvature of the solid nanoparticle has to stay constant, i.e., an additional boundary condition is added. When the inorganic nanoparticles possess, beside charges, also a certain hydrophobic character, they become enriched at the oil-water interface, which is the physical base of the stabilizing power of special inorganic nanostructures, the so-called Picker-... [Pg.112]

The fundamental equations for the flow velocity of the liquid ii(r) at position r and that of the /th ionic species v,(r) are the same as those for the dilute case (Chapter 5) except that Eq. (5.10) applies to the region b

Consider a concentrated suspension of porous spheres of radius a in a liquid of viscosity rj [27]. We adopt a cell model that assumes that each sphere of radius a is surrounded by a virtual shell of outer radius b and the particle volume fraction 4> is given by Eq. (27.2) (Eig. 27.3). The origin of the spherical polar coordinate system (r, 6, cp) is held fixed at the center of one sphere. According to Simha [2], we the following additional boundary condition to be satisfied at the cell surface r = b ... [Pg.527]

The unknown dependent variables of the problem become p, m, Z, T, and Yfc. Equations (86) and (110) provide two algebraic equations relating these variables the other N -f 2 variables are determined by the iV + 1 differential equations given by equations (95) and (105) and by the integro-differential equation given in equation (92). The initial values Po, Zq, Tq, and Yj, o are controlled by the experimenter. Attention will be restricted to lean mixtures, whence Z -> 1 as x -> oo for chemical equilibrium to exist at the hot boundary. Since all the differential equations are of the first order, the additional boundary condition suggests that solutions will exist only for particular values of a parameter, which physically is expected to be the burning velocity Uq. ... [Pg.478]

Equations (10-98) through (10 100) constitute 7+1 governing equations for 7+1 variables Xj (/= ,...-/) andp/. They can be solved numerically, for example, by a discretization technique where a set of coupled differential equations is replaced by a set of NxM finite difference equations on a grid consisting of M mesh points. The necessary boundary conditions can be established by requiring the reaction equilibrium (i.e.. Equation (10 99)) and the sum of the mole fractions equal to one (i.e.. Equation (10 100) at the membrane interface and equality of the pressure at the membrane interface and the pressure in the adjacent gas phase. Additional boundary conditions can be obtained from mass balances coupling the molar fluxes from the gas phase to the membrane interface with those at the interface. Details can be found elsewhere [Sloot et al.. 1990]. [Pg.468]

In the present chapter, which deals with theoretical concepts applied to vanadium and molybdenum oxide surfaces, we will restrict the discussion to binary oxide systems. So far, mixed metal oxide systems have not been studied by quantitative theory. Theoretical methods that have been used to study oxide surfaces can be classified according to the approximations made in the system geometry where two different concepts are applied at present, local cluster and repeated slab models. Local cluster models are based on the assumption that the physical/chemical behavior at selected surface sites can be described by finite sections cut out from the oxide surface. These sections (surface clusters) are treated as fictitious molecules with or without additional boundary conditions to take the effect of environmental coupling into account. Therefore, their electro-... [Pg.138]

When the physical geometry of the problem under consideration or the expected flow pattern has a cyclically repeating nature, cyclic or periodic boundary conditions can be used to reduce the size of the solution domain. Two types of cyclic boundary condition can be distinguished. The first is for rotationally periodic flow processes, where all the variables at corresponding periodic locations on the cyclic planes are the same. The second is for translationally periodic flow processes, where all the variables, except pressure, at corresponding periodic locations on the cyclic planes are the same. Examples of these two types are shown in Fig. 2.7. Such cyclic planes are in fact part of the solution domain (by the nature of their definitions) and no additional boundary conditions are required at these planes, except the one-to-one correspondence between the two cyclic planes. [Pg.52]

When the second order approximations to the pressure tensor and the heat flux vector are inserted into the general conservation equation, one obtains the set of PDEs for the density, velocity and temperature which are called the Burnett equations. In principle, these equations are regarded as valid for non-equilibrium flows. However, the use of these equations never led to any noticeable success (e.g., [28], pp. 150-151) [39], p. 464), merely due to the severe problem of providing additional boundary conditions for the higher order derivatives of the gas properties. Thus the second order approximation will not be considered in further details in this book. [Pg.256]

Proper boundary conditions are generally required for the primary variables like the gas and particle velocities, pressures and volume fractions at all the vessel boundaries as these model equations are elliptic. Moreover, boundary conditions for the granular temperature of the particulate phase is required for the PT, PGT and PGTDV models. For the models including gas phase turbulence, i.e., PGT and PGTDV, additional boundary conditions for the turbulent kinetic energy of the gas phase, as well as the dissipation rate of the gas phase and the gas-particle fluctuation covariance are required. The... [Pg.927]

If one of the two materials is a solid on which the temperature is known, 6 = 9som, the condition (2-115) is sufficient to solve the thermal energy equation. If, on the other hand, surface S is an interface, or phase boundary, the condition (2 115) provides only one relationship between two unknown temperature fields, and an additional boundary condition... [Pg.68]

The additional boundary conditions are continuity of the tangential velocity,... [Pg.499]

Hence, with the governing equations (7-211), plus additional boundary conditions (7-277), (7-147) and (7-280), all of which apply directly to and fo, we see that the 0(1) problem... [Pg.505]

The boundary-layer equations are third order with respect to 7 and first order with respect to x [this can be seen clearly if (10-40) and (10 41) are expressed in terms of the streamfunction]. Hence, to specify completely the velocity profiles in the boundary layer, we require one additional boundary condition in 7 and an initial profile at the leading edge of the boundary layer (x is usually defined so that this point corresponds to x = 0). In addition, the potential-flow equations are second order and thus require at least one boundary condition in addition to (10 12). In Section A, it was suggested that an appropriate condition was... [Pg.708]

However, the DE for / is sixth order. Thus we require at least four additional boundary conditions. One physically plausible assumption is that the boundaries at z = 0, 1 are isothermal. In this case,... [Pg.850]

In [242], an additional boundary condition at the upper boundary of the foam column is also discussed for the case of nonstationary syneresis. [Pg.322]

The constants A and l> must be found from the boundary conditions at z = 0 and z = i. These so-called additional boundary conditions (ABC) are determined by the value of the surface energy connected with the excitonic polarization and are strongly dependent on the nature of the contacting layers. If we write this energy in the form... [Pg.236]

In conclusion of this section one may say that the linear optics of superlattices bear rich information on the dynamics of interfaces. Such investigations may give an idea of the nature of the interaction of bulk excitations (excitons) with interfaces which manifests itself in additional boundary conditions (ABC) and determines the value of the constant a. Finally, the study of dispersion laws for polaritons in superlattices with semiconductor layer thicknesses small in comparison with the Bohr radius of exciton permits one to follow variations in the properties of excitons. [Pg.239]

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