Impact Of Permeation Research Articles

Impact of Helium Permeability on Endurance and Altitutde Control of Geostationary Stratospheric Airship - A Mathematical Model

A geostationary stratospheric airship is lighter than air platform to be used for several civil and military purposes. In this study, the impact of Helium permeation through the hull and ballonet skin is considered. Mathematical modeling of the system is being done to estimate the amount of Helium and air transmission through the hull and the ballonet skin for a general airship system. Impact of permeation mainly affecting its ability to maintain constant altitude and a minimum level of differential pressure is shown in this study. A method is also devised so as to develop an open loop control system to maintain the altitude of the airship by maintaining the net vertical force due to buoyancy and weight on the airship as zero. Both the cases with and without the altitude control are simulated by numerically solving the model using RK4 algorithm. The results obtained are discussed and appropriate conclusions are drawn from the analysis.

Permeation Increases Biofilm Development in Nanofiltration Membranes Operated with Varying Feed Water Phosphorous Concentrations.

Nutrient limitation has been proposed as a biofouling control strategy for membrane systems. However, the impact of permeation on biofilm development under phosphorus-limited and enriched conditions is poorly understood. This study analyzed biofilm development in membrane fouling simulators (MFSs) with and without permeation supplied with water varying dosed phosphorus concentrations (0 and 25 μg P·L−1). The MFSs operated under permeation conditions were run at a constant flux of 15.6 L·m2·h−1 for 4.7 days. Feed channel pressure drop, transmembrane pressure, and flux were used as performance indicators. Optical coherence tomography (OCT) images and biomass quantification were used to analyze the developed biofilms. The total phosphorus concentration that accumulated on the membrane and spacer was quantified by using microwave digestion and inductively coupled plasma atomic emission spectroscopy (ICP-OES). Results show that permeation impacts biofilm development depending on nutrient condition with a stronger impact at low P concentration (pressure drop increase: 282%; flux decline: 11%) compared to a higher P condition (pressure drop increase: 206%; flux decline: 2%). The biofilm that developed at 0 μg P·L−1 under permeation conditions resulted in a higher performance decline due to biofilm localization and spread in the MFS. A thicker biofilm developed on the membrane for biofilms grown at 0 μg P·L−1 under permeation conditions, causing a stronger effect on flux decline (11%) compared to non-permeation conditions (5%). The difference in the biofilm thickness on the membrane was attributed to a higher phosphorus concentration in the membrane biofilm under permeation conditions. Permeation has an impact on biofilm development and, therefore, should not be excluded in biofouling studies.

Geomechanics Study on the Influence of Water Level Variation on Landslide Safety in Three Gorges Reservoir Region

Up concave and linear slices are two basic geometric shapes of the landslides. In this paper, the unsaturated seepage fields of landslides are described by Richards’s equation and the safety of landslides are calculated by the Morgenstern-Prince method. The Influences of water level variation on landslide safety in Three Gorges reservoir region are discussed through two landslides. It indicates that,the impact of buoyancy is significant and related closely to water level change, and the most dangerous condition is stable high water level. To the slide which slice is line, the impact of permeation is significant and related closely to water change too, and the most dangerous condition is at the beginning of reaching the low water level.