Porosity redistribution

COMETHE II Belgonucleaire Temperature, porosity redistribution and swelling. Future version may be linked to CRASH 7,8... 

SATURN GfK, Karlsruhe Temperature, porosity redistribution, swelling, and estimates clad restraint 5,6... 

Some of the complications involved in multi-scale porosities and evolutionary paths within fractured rock systems have been explored. For example, in the Palmottu site of gneisses in Finland U, as well as Th, was found to be redistributed into fracture coatings of carbonates and Fe oxides (Suksi et al. 1991). Suksi and Rasilainen (1996) have demonstrated how U concentrated in these fracture fillings can implant daughters in the surrounding phases, generating large fractionations between and Th/ U. 

In aerobic composting, an air blower distributes air under the pile and maintains most of the pile in aerobic conditions for faster degradation. The piles are turned daily to redistribute material and moisture and to maintain porosity of the pile. The mechanical stress imposed by turning the compost piles facilitates... 

Contaminants may reach the subsurface in a gaseous phase, dissolved in water, as an immiscible hquid, or as suspended particles. Contaminant partitioning in the subsurface is controlled by the physicochemical properties and the porosity of the earth materials, the composition of the subsurface water, as well as the properties of the contaminants themselves. While the physicochemical and mineralogical characteristics of the subsurface sohd phase define the retention capacity of contaminants, the porosity and aggregation stams determine the potential volume of liquid and air that are accessible for contaminant redistribution among the subsurface phases. Enviromnental factors, such as temperature and water content in the subsurface prior to contamination, also affect the pollution pattern. 

The redistribution of DDT with depth also was tested, in the presenee of organic suspended solids from sewage effluents. Figure 12.18B shows a range of behaviors of " C-labeled DDT observed in three soils with different properties. In the low-porosity Gilat soil (silt loam), the flow rate was slow and little DDT transport occurred only 3% of the amount applied reaehed a depth of 5.4em. In the sandy loam Bet-Dagan soil, considerable DDT transport was observed. In this... 

Giles M. R. and De Boer R. B. (1990) Origin and significance of redistributional secondary porosity. Mar. Petrol. Geol. 7, 378-397. 

He used three length scales derived from mercurj -injection data to characterize a porous medium. He defined thresholds pressure as the pressure at which mercury forms a connected pathway across the sample and indicated that the measured threshold pressure corresponded graphically to the inflection point on a mercury injection plot. This protocole is often insufficient to characterize the porous space and to describe completly the phenomena in mercury injection. Experiments often show that between two successive experiments points the decrease of capillary pressure can be important and during this time the volume of injected mercury can be 50% of the total volume. Indeed, it observed sudden falls of pressure eorresponding to the spontaneous redistribution of mercury in porous network. For similar porosity of samples we have unexplained different mercury saturation time of pore network. 

The scales of carbonate redistribution, and thus reservoir quality enhancement, are difficult to constrain. Several workers have argued that the reservoir properties of sandstones are greatly enhanced due to large-scale carbonate dissolution (Lonoy et al., 1986 Schmidt McDonald, 1979). As the undersaturated waters have to circulate through large volumes of permeable sediment to cause economically important carbonate cement dissolution, it is expected that such secondary porosity develops in partially rather than pervasively cemented sand-... 

Cake compressibility is the ability of a cake to reduce its volume, i.e., porosity, when stress is applied. The resulting cake will display an increase in hydraulic resistance. This is not necessarily caused by an average change in porosity, as a porosity gradient can occur by the redistribution of the solid material. Rigid granular particles tend to be incompressible and filter well even with thick cakes. Materials that are easily deformed such as amorphous or thixotropic materials will respond well to mechanical pressure or operation with thin cakes. (See Ch. 6 on Cake Compressibility.)... 

Neutron radiography of the pins was carried out for the first time and the results were comparable with X-radiography results. There was no evidence of any abnormality or redistribution of actinides in neutron radiography. The fission gases were extracted and analyzed. The total gas release into the plenum (Xe+Kr) was found to be varying from 6 to 22% for 50 000 MWd/T fuel compared to 1 to 3% for 25 000 MWd/T fuel. Metallography of cut -cross section revealed that no restmcturing of fuel had taken place. However reduction in porosity was noticed for 50 000 MWd/T fuel compared to 25 000 MWd/T fuel. 

Pressure sintering can also be useful to further density sintered ceramics. The density of liquid-phase sintered PZT was improved from —97% to -98% of theoretical density by HIPing for 7.5—60 min at 1300 °C and 7—21 MPa. Consistent with the microstructural evidence of liquid formation and redistribution (Figure 5.7), and the preferential annihilation of the fine, submicrometer porosity within the micro-structure, the majority of densification occurs rapidly, within the first few minutes of HIPing. 

The bonded joints between typical thin structural elements have an extensive capability to tolerate the load redistribution that is caused by local flaws and porosity with no loss whatever in strength or durability. This derives from the same minimum overlaps needed to provide resistance to creep rupture that were discussed earlier. Figs. 26-29, taken from ref. [19], address this issue in the context of the longitudinal skin splices in the PABST forward fuselage, where the thickness was 0.050 inch of 2024-T3 aluminum alloy. Fig. 27 shows the adhesive stress distribution at room temperature for a load of 1000 Ibs./in., which corresponds with a 1.3 x P proof pressure load. Significantly, this load does not even exceed the elastic capability of the adhesive for this environment. 

MPL is to improve water management [20,21] and redistribute the reactants, as (1) it can wick liquid water away from the CL to the GDL and thus facilitate gas transportation in the opposite direction [19] (2) it changes the porosity of the GDM, preventing the catalyst ink from penetrating the GDM and (3) it reduces the contact resistance between the GDL and the adjacent CL and thus decreases the internal resistance of a PEM fuel cell. 

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