Diffusion characteristics

Vapor permeability parameters of films from linear polymers are given in Table 3.1 

There are examples supporting the effect of the named factors on the diffusion characteristics of the coatings. 

The scheme of the experimental setup is presented in Fig. 3.7. The junction under study consists of discs 1 and the polymer coating 2 formed on the substrate 3. The substrate is made as a ring plate with a coating having a capillary puncture 4 in the center of its plane surface, which communicates with orifice 5 and clearance 6 of the junction. Orifice 5 is connected through tube 7 with the glass capillary 8 containing water (bidistillate). 

The initial water level ho in the capillary is set so as to form a convex meniscus in puncture 4 when disc 1 is offloaded. Once disc 1 is installed on the meniscus, water from capillary 8 flows to the junction under study and spreads under the capillary pressure effect over the surface under consideration. The new level hi of water in capillary 8 and the height decrease A/i = ho — hi of the water column are recorded. The kinetic dependence A/i has the form of an exponent. The installation time of disc 1 before hi measurement is taken is 5 min, corresponding to the exponent approach to a constant value. 

The experimental results presented in Fig. 3.8 show that the substrate significantly affects the coating surface properties. The dependence Ah 5) is distinguished by a high conjugation degree. Its correlation coefficient values are within 0.755 0.102 at a significance level of 0.01. 

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The antiozonant should possess adequate solubiUty and diffusivity characteristics (19). Siace ozone attack is a surface phenomenon, the antiozonant must migrate to the surface of the mbber to provide protection. The antiozonant should have no adverse effects on the mbber processiag characteristics, eg, mixing, fabrication, vulcanization, or physical properties. 

Rodgers, C., Influence of Impeller and Diffuser Characteristic and Matching on Radial Compressor Performance, SAE Preprint 268B, January 1961. 

Air supplied in confined space by downward vertical jets creates a similar flow pattern as in the case of air supply by horizontal nonattached jets. With vertical air supply, the occupied zone is ventilated directly by air jets. Grimitlyn suggests that the area of occupied zone ventilated by one jet be sized based on the jet s cross-sectional area at the point it enters the occupied zone. The jet cross-sectional area and configuration depend upon the height of the air supply, the type of air jet, and diffuser characteristics ( K, and K, ). 

S. Murakami, S. Kato, S. Nagano, Y. Tanaka. Diffusion characteristics of airborne particles with gravitational settling in a convective-dominant indoor flow field. ASHRAE Transactions. 98(1), 1992, 82-97. 

The progress of this category of reactions is expected to depend on the composition of the materials within the phase as well as the temperature and pressure of the system. The rate of homogeneous reaction should not be affected by the shape of the container, the surface properties of the solid materials in contact with the phase, and the diffusion characteristics of the fluid. Thus the rate of reaction of component i may be expressed as... 

JH Kou, GL Amidon, PI Lee. pH dependent swelling and solute diffusion characteristics of poly(hydroxyethyl methacrylate-co-methacrylic acid) hydrogels. Pharm Res 5 592-597, 1988. 

The effective diffusivities determined from limiting-current measurements appear at first applicable only to the particular flow cell in which they were measured. However, it can be argued plausibly that, for example, rotating-disk effective diffusivities are also applicable to laminar forced-convection mass transfer in general, provided the same bulk electrolyte composition is used (H8). Furthermore, the effective diffusivities characteristic for laminar free convection at vertical or inclined electrodes are presumably not significantly different from the forced-convection diffusivities. 

The methods outlined in Reid and Sherwood (87) have been used to estimate the diffusivities characteristic of binary mixtures of the various components of the fluid in the reactor. 

The above diffusion characteristics of deuterium in p-type GaAs and InP are very close to those found in deuterated boron doped silicon (Johnson,... 

To obtain an expression for tj, we first derive the continuity equation governing steady-state diffusion of A through the pores of the particle. This is based on a material balance for A across the control volume consisting of the thin strip of width dx shown in Figure 8.10(a). We then solve the resulting differential equation to obtain the concentration profile for A through the particle (shown in Figure 8.10(b)), and, finally, use this result to obtain an expression for tj in terms of particle, reaction, and diffusion characteristics. 

Characteristics of a catalyst particle include its chemical composition, which primarily determines its catalytic activity, and its physical properties, such as size, shape, density, and porosity or voidage, which determine its diffusion characteristics. We do not consider in this book the design of catalyst particles as such, but we need to know these characteristics to establish rate of reaction at the surface and particle levels (corresponding to levels (1) and (2) in Section 1.3). This is treated in Section 8.5 for catalyst particles. Equations 8.5-1 to -3 relate particle density pp and intraparticle voidage or porosity p. 

We find that the degree of para-selectivity obtainable depends uniquely on the activity and diffusion characteristics of the catalyst, independent of how these properties are obtained. While we will discuss these relationships with regard to STDP, the principles involved are generally applicable to those reactions over ZSM-5 where dialkylaromatic products are formed. 

At the external boundary of the constrained diffusion layer, application of the linear diffusion characteristic equations leads to... 

In a subsequent study, NoorBatcha et al. varied the valence-force parameters used for the lattice interactions to evaluate the effect of the vibrational properties of the crystal on diffusion characteristics. Using three sets of lattice potential parameters, they determined a range of effective activation barriers for diffusion of 3.63 kcal/mole to 7.47 kcal/mole on the Si(001) surface. This range encompasses the experimental estimate of 4.6 kcal/mole for the Si(lll) surface, and further suggests this value as the more accurate experimental estimate. 

Assessment of Relaxation Times, MT Effects and Diffusion Characteristics 35... 

ASSESSMENT OF RELAXATION TIMES, MT EFFECTS AND DIFFUSION CHARACTERISTICS... 

Fatty acids are clearly larger in size and show markedly slower diffusion velocity than the small water (or creatine) molecules which have been examined so far by diffusion weighted NMR spectroscopy. However, assessment of diffusion properties of lipids could be a key step for further experimental studies of skeletal muscle lipid metabolism. Diffusion properties of FFA and triglycerides are likely different due to differences in molecular weight. In addition, effects of temperature, chemical surroundings, and the mobility of small lipid droplets in the cytosol may also lead to measurable differences in the diffusion characteristics. 

Fig. 23. Diffusion weighted spectral series of tibial bone marrow (a) and TA (b) of a 27-year-old healthy female subject for determination of ADC in lipids. Spectra were recorded using sequence S2 with TE=154 ms, TM=149 ms,. 5 = 69 ms, 6 = 0, 2500, 5000, 10,000 and 20,000 s/mm. Similar diffusion characteristics are visible for marrow fat and EMCL, whereas IMCL shows more pronounced diffusion related signal loss.

Kanezashi, M. and lin, Y.S. (2009) Gas permeation and diffusion characteristics of MFI-type zeolite membranes at high temperatures. J. Chem. Phys. C, 113, 3767-3774. 

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