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1
Hou, Yusong, Jianguo Jiang, and J. Wu. "The Form of Waiting Time Distributions of Continuous Time Random Walk in Dead-End Pores." Geofluids 2018 (2018): 1–6. http://dx.doi.org/10.1155/2018/8329406.
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Anomalous dispersion of solute in porous media can be explained by the power-law distribution of waiting time of solute particles. In this paper, we simulate the diffusion of nonreactive tracer in dead-end pores to explore the waiting time distributions. The distributions of waiting time in different dead-end pores show similar power-law decline at early time and transit to an exponential decline in the end. The transition time between these two decline modes increases with the lengths of dead-end pores. It is well known that power-law distributions of waiting time may lead to anomalous (non-Fickian) dispersion. Therefore, anomalous dispersion is highly dependent on the sizes of immobile zones. According to the power-law decline, we can directly get the power index from the structure of dead-end pores, which can be used to judge the anomalous degree of solute transport in advance.
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Battat, Sarah, Jesse T. Ault, Sangwoo Shin, Sepideh Khodaparast, and Howard A. Stone. "Particle entrainment in dead-end pores by diffusiophoresis." Soft Matter 15, no. 19 (2019): 3879–85. http://dx.doi.org/10.1039/c9sm00427k.
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Kahler, David. "Rapidly Pulsed Pumping Accelerates Remediation in A Vertical Circulation Well Model." Water 10, no. 10 (2018): 1423. http://dx.doi.org/10.3390/w10101423.
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One factor that slows groundwater remediation is the sequestration of contaminant in dead-end pores, that is, pores that are not flushed through by flow through the aquifer. Furthermore, rebound of apparently remediated aquifers can occur as a result of the eventual release of the contaminant trapped in these dead-end pores. Since the operational costs generally outweigh the capital costs of a remediation project, reduction of the duration of treatment should reduce the overall cost of the average remediation. It has been shown that a rapidly pulsed flow can increase the mixing between dead-end and well-connected pores through computational fluid dynamics models with idealized pore geometry and column tests. A rapidly pulsed flow induces a deep sweep upon a sudden increase in velocity and a vortex ejection upon a sudden decrease in velocity that substantially accelerates the remediation of contaminant from these dead-end pores. To examine rapidly pulsed pumping in a more realistic configuration, a model vertical circulation well was constructed. The porous medium was well-sorted crushed glass to minimize sorption. Removal of a fluorescent dye, which represents a dissolved contaminant, under a rapidly pulsed flow was compared to a steady flow. The modeled well revealed accelerated removal of dissolved contaminants under a rapidly pulsed flow.
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Kar, Abhishek, Tso-Yi Chiang, Isamar Ortiz Rivera, Ayusman Sen, and Darrell Velegol. "Enhanced Transport into and out of Dead-End Pores." ACS Nano 9, no. 1 (2015): 746–53. http://dx.doi.org/10.1021/nn506216b.
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Ji, Zeming, Chang He, Yingying Sun, et al. "Molecular Dynamics Simulation of CO2 Storage in Reservoir Pores with a Dead-End." Energies 16, no. 21 (2023): 7341. http://dx.doi.org/10.3390/en16217341.
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The carbon capture, utilization and storage (CCUS) technique is widely applied in order to solve energy shortages and global warming, in which CO2 storage plays an important part. Herein, the CO2 storage in reservoir pores with a dead-end is investigated using a molecular dynamics simulation. The results indicate that, when a CO2 molecule flows through a reservoir pore towards its dead-end, it is readily captured inside said dead-end. When the pressure difference of the CO2 injection increases, the transport speed of the CO2 becomes faster, and the storage efficiency increases. The rate constants for the absorption of the carbon dioxide at 5 MPa, 10 MPa, and 15 MPa are 0.47 m/s, 2.1 m/s, and 3.1 m/s. With the same main channel, a narrower dead-end with less oil molecules would cause a smaller spatial potential resistance, which would lead to a faster CO2 replacement and storage process. The 3 nm main channel with a 1.5 nm dead-end model had the highest absorption rate of 5.3 m/s out of the three sets of models with different dead-ends. When the dead-end’s width was constant, the rate constants for the absorption of carbon dioxide in the 6 nm main channel with a 1.5 nm dead-end model was 1.8 m/s, which was higher than that of the 3 nm–1.5 nm model. This study investigates the mechanism of CO2 storage in reservoir pores with a dead-end at the molecular level and provides a scientific basis for the practical application of CO2 storage.
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Broens, M., and E. Unsal. "Emulsification kinetics during quasi-miscible flow in dead-end pores." Advances in Water Resources 113 (March 2018): 13–22. http://dx.doi.org/10.1016/j.advwatres.2018.01.001.
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Kar, Abhishek, Tso-Yi Chiang, Isamar Ortiz Rivera, Ayusman Sen, and Darrell Velegol. "Correction to Enhanced Transport into and out of Dead-End Pores." ACS Nano 10, no. 3 (2016): 3871. http://dx.doi.org/10.1021/acsnano.6b00965.
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Amarasinghe, Widuramina, Seyed Farzaneh, Ingebret Fjelde, Mehran Sohrabi, and Ying Guo. "A Visual Investigation of CO2 Convective Mixing in Water and Oil at the Pore Scale Using a Micromodel Apparatus at Reservoir Conditions." Gases 1, no. 1 (2021): 53–67. http://dx.doi.org/10.3390/gases1010005.
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CO2 convective mixing in water has been visualized in Hele-Shaw and PVT cell experiments but not at the pore scale. Furthermore, CO2 convective mixing in a three-phase system (i.e., CO2 in the presence of both water and oil) has not been visually investigated. A vertically placed micromodel setup was used to visualize CO2 convective mixing at 100 bar and 50 °C, representative of reservoir conditions. To the best of our knowledge, for the first time, we have visually investigated CO2 convective mixing in water at the pore scale and also CO2 convective mixing in a multiphase system (water and oil). CO2 mixing in water governed by both diffusion and convection mechanisms was observed. The vertical CO2 transport velocity was calculated to be 0.3 mm/min in both a 100% water saturation system and a residual oil-saturated system. First, CO2 always found the easiest path through the connected pores, and then CO2 was transported into less connected pores and dead-end pores. CO2 transport into dead-end pores was slower than through the preferential path. CO2 transport into water-filled ganglia with trapped oil was observed and was slower than in water.
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Verbeck, J. Q. J. C., G. I. M. Worm, H. Futselaar, and J. C. van Dijk. "Combined air-water flush in dead-end ultrafiltration." Water Supply 1, no. 5-6 (2001): 393–402. http://dx.doi.org/10.2166/ws.2001.0139.
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Dead-end ultrafiltration has proven itself as a technique for reclamation of backwash water of sand filters and as a pre-treatment step for spiral wound reverse osmosis. A direct result of dead-end filtration is a decreased flux caused by the accumulation of material in the membrane pores and on the membrane surface. Different cleaning techniques are used to remove this accumulated material. Recently a new technique has been introduced, the AirFlush. This technique makes use of air to create higher turbulence as compared to a water flush. At Delft University of Technology research has started into the fundamentals of the combined air- and water-flush. First a series of experiments has been carried out to determine the different flow patterns, followed by experiments to determine which air- and water-velocities give the best cleaning. Finally head loss experiments have been done to get information about the energy dissipated in the system. The results of the head loss experiments have been compared to the theoretical head loss calculated with the theory of heterogeneous two-phase flow.
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Köry, J., A. Krupp, C. Please, and I. Griffiths. "Optimising Dead-End Cake Filtration Using Poroelasticity Theory." Modelling 2, no. 1 (2021): 18–42. http://dx.doi.org/10.3390/modelling2010002.
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Understanding the operation of filters used to remove particulates from fluids is important in many practical industries. Typically the particles are larger than the pores in the filter so a cake layer of particles forms on the filter surface. Here we extend existing models for filter blocking to account for deformation of the filter material and the cake layer due to the applied pressure that drives the fluid. These deformations change the permeability of the filter and the cake and hence the flow. We develop a new theory of compressible-cake filtration based on a simple poroelastic model in which we assume that the permeability depends linearly on local deformation. This assumption allows us to derive an explicit filtration law. The model predicts the possible shutdown of the filter when the imposed pressure difference is sufficiently large to reduce the permeability at some point to zero. The theory is applied to industrially relevant operating conditions, namely constant flux, maximising flux and constant pressure drop. Under these conditions, further analytical results are obtained, which yield predictions for optimal filter design with respect to given properties of the filter materials and the particles.
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Köry, J., A. Krupp, C. Please, and I. Griffiths. "Optimising Dead-End Cake Filtration Using Poroelasticity Theory." Modelling 2, no. 1 (2021): 18–42. http://dx.doi.org/10.3390/modelling2010002.
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Understanding the operation of filters used to remove particulates from fluids is important in many practical industries. Typically the particles are larger than the pores in the filter so a cake layer of particles forms on the filter surface. Here we extend existing models for filter blocking to account for deformation of the filter material and the cake layer due to the applied pressure that drives the fluid. These deformations change the permeability of the filter and the cake and hence the flow. We develop a new theory of compressible-cake filtration based on a simple poroelastic model in which we assume that the permeability depends linearly on local deformation. This assumption allows us to derive an explicit filtration law. The model predicts the possible shutdown of the filter when the imposed pressure difference is sufficiently large to reduce the permeability at some point to zero. The theory is applied to industrially relevant operating conditions, namely constant flux, maximising flux and constant pressure drop. Under these conditions, further analytical results are obtained, which yield predictions for optimal filter design with respect to given properties of the filter materials and the particles.
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Leclaire, P., O. Umnova, T. Dupont, and R. Panneton. "Acoustical properties of air-saturated porous material with periodically distributed dead-end pores." Journal of the Acoustical Society of America 137, no. 4 (2015): 1772–82. http://dx.doi.org/10.1121/1.4916712.
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Dupont, Thomas, Philippe Leclaire, and Raymond Panneton. "Acoustic methods for measuring the porosities of porous materials incorporating dead-end pores." Journal of the Acoustical Society of America 133, no. 4 (2013): 2136–45. http://dx.doi.org/10.1121/1.4792484.
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Yusupov, Mazhid, Raikhan Tazhibayeva, Sholpan Ziyaeva, and Kurash Kubyashev. "Numerical modeling of the salt-transfer problem in soils." E3S Web of Conferences 264 (2021): 01005. http://dx.doi.org/10.1051/e3sconf/202126401005.
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The article discusses the urgent problem associated with solving the problems of salt transfer in soils and is devoted to numerical modelling of the transference and diffusion of salts in soils, in which the total porosity of the soil is divided by the fraction of “through” and “dead-end” pores with the corresponding concentration of the solution. A brief review of scientific publications devoted to this problem is given. To study and predict the process of the spread of harmful substances, a mathematical model and a numerical algorithm for computer experimentation have been developed. The solution was obtained using a method based on the use of quadrature formulas in combination with the differential sweep method for a system of ordinary second-order differential equations with arbitrary linear boundary conditions. The concentrations of salts in the “through” and “dead-end” pores, respectively, were studied at various values of the filtration process. The results are shown in the graphs.
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Roorda, J. H., S. te Poele, and J. H. J. M. van der Graaf. "The role of microparticles in dead-end ultrafiltration of wwtp-effluent." Water Science and Technology 50, no. 12 (2004): 87–94. http://dx.doi.org/10.2166/wst.2004.0699.
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Ultrafiltration is considered as an interesting polishing technique for effluent of wastewater treatment plants (wwtp-effluent). Results in pilot-scale experiments indicated that microparticles might dominate the filtration characteristics. In this article the results of investigations on the role of microparticles on the filterability of effluent is described. Calculation effects on particle size distributions of effluent showed that particles smaller than 2.0 μm predominantly influence the filterability of the wwtp-effluent. Additionally, experiments were performed on the filterability of size fractions of effluent. Effluent was fractionated with laboratory filters (pore diameter 5.0, 1.2, 0.45, 0.2 and 0.1 μm). The filterability of this pre-filtered effluent in applying ultrafiltration was evaluated by measurement of the SUR, a new parameter for measurement of the filterability of effluent. The results showed that filterability of the effluent was mainly influenced by 40% to 57% by the fraction larger than 0.1 μm and smaller than 0.2 μm, which is five to twenty times larger than the ultrafiltration membrane pores. Pre-treatment of the effluent by coagulation or sand filtration showed only minor influence on these results.
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Kennedy, M., L. Zhizhong, E. Febrina, S. Van Hoof, and J. Shippers. "Effects of coagulation on filtration mechanisms in dead-end ultrafiltration." Water Supply 3, no. 5-6 (2003): 109–16. http://dx.doi.org/10.2166/ws.2003.0156.
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Filtration mechanisms occurring during ultrafiltration of coagulated and non-coagulated surface water were investigated using the general blocking filtration laws. The sharp decline in permeate flux in the first 10-20 minutes of filtration was largely due to a combination of the blocking filtration mechanisms. However, a distinction between “complete”, “standard” and “intermediate blocking” mechanisms was not possible as a large degree of overlap existed between the mechanisms and the transition from one type of blocking to another was very smooth. Coagulation appeared to retard blocking and consequently, the duration of the “blocking phase” was twice as long for coagulated water compared with non-coagulated water. The “transition phase”, where both blocking and cake filtration occurred simultaneously, was also extended in the case of coagulated water as continuous blocking of the membrane through the pores of the cake was observed. The modified fouling index-ultrafiltration (MFI-UF) was employed to examine the impact of coagulation on filter cake properties. Coagulation reduced the specific resistance of the filter cake by 50% at a TMP of 1.5 bar, and 35% at a TMP of 0.5 bar. Depth filtration was hardly evident at a TMP of 0.5 bar, but was very pronounced at a TMP of 1.5 bar as the specific resistance of the filter cake increased continuously, particularly in the absence of coagulant. The filter cake was sensitive to the applied TMP and the MFI-UF value increased by 130% for non-coagulated surface water and 55% for coagulated water due to compression of the cake, when the TMP increased from 0.5 to 1.5 bar.
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Nikonov, Eduard G., Miron Pavluš, and Mária Popovičová. "Molecular Dynamic Simulation of Water Vapor and Determination of Diffusion Characteristics in the Pore." EPJ Web of Conferences 173 (2018): 06009. http://dx.doi.org/10.1051/epjconf/201817306009.
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One of the varieties of pores, often found in natural or artificial building materials, are the so-called blind pores of dead-end or saccate type. Three-dimensional model of such kind of pore has been developed in this work. This model has been used for simulation of water vapor interaction with individual pore by molecular dynamics in combination with the diffusion equation method. Special investigations have been done to find dependencies between thermostats implementations and conservation of thermodynamic and statistical values of water vapor – pore system. The two types of evolution of water – pore system have been investigated: drying and wetting of the pore. Full research of diffusion coefficient, diffusion velocity and other diffusion parameters has been made.
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Noyan, A. A., I. V. Kolesnik, A. P. Leont’ev, and K. S. Napol’skii. "Electrocrystallization of Metals in Channels of Porous Films of Anodic Aluminum Oxide: The Real Template Structure and the Quantitative Model of Electrodeposition." Электрохимия 59, no. 7 (2023): 378–90. http://dx.doi.org/10.31857/s0424857023070083.
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A method is proposed for analytical description of current transients at the template-assisted electrodeposition of metal into porous films in anodic aluminum oxide (AAO). The template-assisted electrodeposition of copper and gold is accomplished. For the copper electrodeposition, it is shown that the experimental data are in quantitative agreement with the calculated values of current without any fitting parameters. The parameters of the AAO film structure including the conicity of pores and the number of dead-end channels are measured and their effect on the process of template-assisted electrodeposition is studied .
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Sedaghat, Mohammad Hossein, Amir Hatampour, and Rasool Razmi. "Investigating the role of polymer type and dead end pores’ distribution on oil recovery efficiency during ASP flooding." Egyptian Journal of Petroleum 22, no. 2 (2013): 241–47. http://dx.doi.org/10.1016/j.ejpe.2013.06.003.
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Wiklund, Hanna, and Tetsu Uesaka. "Edge-wicking: Micro-fluidics of two-dimensional liquid penetration into porous structures." Nordic Pulp & Paper Research Journal 27, no. 2 (2012): 403–8. http://dx.doi.org/10.3183/npprj-2012-27-02-p403-408.
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Abstract We have performed free-energy-based two-dimensional lattice Boltzmann simulations of the penetration of liquid into the edge of a porous material. The purpose was to gain further insight into possible mechanisms involved in the penetration of liquid into the unsealed edges of paper and paper board. In order to identify the fundamental mechanisms we have focused on a model structure that consists of a network of interconnected capillaries. Two different mechanisms were identified: pinning at corners of solid surfaces and increased pressure in dead-end pores. These mechanisms significantly decelerate or even stop the liquid penetration into the porous structures.
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Ibadat, Nur Faezah, Suryani Saallah, Clarence M. Ongkudon, and Mailin Misson. "Preparation of Polystyrene Microsphere-Templated Porous Monolith for Wastewater Filtration." Materials 14, no. 23 (2021): 7165. http://dx.doi.org/10.3390/ma14237165.
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Porous monoliths prepared using templates are highly sought after for filtration applications due to their good mass transport properties and high permeability. Current templates, however, often lead to the formation of dead-end pores and irregular pore distributions, which reduce the efficiency of the substrate flow across the monolith column. This study focused on the preparation of a microsphere-templated porous monolith for wastewater filtration. The optimal template/monomer ratio (50:50, 60:40, 70:30) was determined, and appropriate template removal techniques were assessed for the formation of homogenous pores. The physicochemical characteristics and pore homogeneity of the monoliths were examined. The 60:40 ratio was determined to result in monoliths with homogeneous pore distributions ranging from 1.9 μm to 2.3 μm. SEM and FTIR investigations revealed that solvent treatment was effective for removing templates from the resulting solid monolith. The water quality assessments revealed reductions in the turbidity and the total number of suspended particles in the tested wastewater of up to 96–99%. The findings of this study provide insightful knowledge regarding the fabrication of monoliths with homogenous pores that are beneficial for wastewater treatment.
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Sanaei, P., G. W. Richardson, T. Witelski, and L. J. Cummings. "Flow and fouling in a pleated membrane filter." Journal of Fluid Mechanics 795 (April 13, 2016): 36–59. http://dx.doi.org/10.1017/jfm.2016.194.
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Pleated membrane filters are widely used in many applications, and offer significantly better surface area to volume ratios than equal-area unpleated membrane filters. However, their filtration characteristics are markedly inferior to those of equivalent unpleated membrane filters in dead-end filtration. While several hypotheses have been advanced for this, one possibility is that the flow field induced by the pleating leads to spatially non-uniform fouling of the filter, which in turn degrades performance. In this paper we investigate this hypothesis by developing a simplified model for the flow and fouling within a pleated membrane filter. Our model accounts for the pleated membrane geometry (which affects the flow), for porous support layers surrounding the membrane, and for two membrane fouling mechanisms: (i) adsorption of very small particles within membrane pores; and (ii) blocking of entire pores by large particles. We use asymptotic techniques based on the small pleat aspect ratio to solve the model, and we compare solutions to those for the closest-equivalent unpleated filter.
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Li, Chi-Wang, Chun-Hao Chiu, Yu-Cheng Lee, Chia-Hao Chang, Yu-Hsun Lee, and Yi-Ming Chen. "Integration of ceramic membrane and compressed air-assisted solvent extraction (CASX) for metal recovery." Water Science and Technology 62, no. 6 (2010): 1274–80. http://dx.doi.org/10.2166/wst.2010.851.
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In our previous publications, compressed air-assisted solvent extraction process (CASX) was developed and proved to be kinetically efficient process for metal removal. In the current study, CASX with a ceramic MF membrane integrated for separation of spent solvent was employed to remove and recover metal from wastewater. MF was operated either in crossflow mode or dead-end with intermittent flushing mode. Under crossflow mode, three distinct stages of flux vs. TMP (trans-membrane pressure) relationship were observed. In the first stage, flux increases with increasing TMP which is followed by the stage of stable flux with increasing TMP. After reaching a threshold TMP which is dependent of crossflow velocity, flux increases again with increasing TMP. At the last stage, solvent was pushed through membrane pores as indicated by increasing permeate COD. In dead-end with intermittent flushing mode, an intermittent flushing flow (2 min after a 10-min or a 30-min dead-end filtration) was incorporated to reduce membrane fouling by flush out MSAB accumulated on membrane surface. Effects of solvent concentration and composition were also investigated. Solvent concentrations ranging from 0.1 to 1% (w/w) have no adverse effect in terms of membrane fouling. However, solvent composition, i.e. D2EHPA/kerosene ratio, shows impact on membrane fouling. The type of metal extractants employed in CASX has significant impact on both membrane fouling and the quality of filtrate due to the differences in their viscosity and water solubility. Separation of MSAB was the limiting process controlling metal removal efficiency, and the removal efficiency of Cd(II) and Cr(VI) followed the same trend as that for COD.
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Chen, Ziqiu, and Baron Peters. "Mason–Weaver theory: Revised and extended for a semi-infinite domain." AIP Advances 12, no. 7 (2022): 075215. http://dx.doi.org/10.1063/5.0100060.
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Mason and Weaver developed equations to describe small particles settling under the influence of gravity and Brownian motion, including the limiting case for an infinitely deep suspension. We encountered this common convection–diffusion equation and no-flux boundary conditions in a model for dynamics of adsorbed polymers in dead end pores of a depolymerization catalyst. Close examination reveals that the Mason–Weaver solution is not correct for the infinite domain with a non-uniform initial condition. In this paper, we obtain the time dependent Green’s function for the no flux boundary condition and also for a more general reactive boundary condition. We demonstrate how the results provide solutions, via superposition, which provide solutions for several boundary conditions and all initial conditions.
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Dünn-Kittenplon, Daniela, Asaf Ashkenazy-Titelman, Inna Kalt, Jean-Paul Lellouche, Yaron Shav-Tal, and Ronit Sarid. "The Portal Vertex of KSHV Promotes Docking of Capsids at the Nuclear Pores." Viruses 13, no. 4 (2021): 597. http://dx.doi.org/10.3390/v13040597.
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Kaposi’s sarcoma-associated herpesvirus (KSHV) is a cancer-related herpesvirus. Like other herpesviruses, the KSHV icosahedral capsid includes a portal vertex, composed of 12 protein subunits encoded by open reading frame (ORF) 43, which enables packaging and release of the viral genome into the nucleus through the nuclear pore complex (NPC). Capsid vertex-specific component (CVSC) tegument proteins, which directly mediate docking at the NPCs, are organized on the capsid vertices and are enriched on the portal vertex. Whether and how the portal vertex is selected for docking at the NPC is unknown. Here, we investigated the docking of incoming ORF43-null KSHV capsids at the NPCs, and describe a significantly lower fraction of capsids attached to the nuclear envelope compared to wild-type (WT) capsids. Like WT capsids, nuclear envelope-associated ORF43-null capsids co-localized with different nucleoporins (Nups) and did not detach upon salt treatment. Inhibition of nuclear export did not alter WT capsid docking. As ORF43-null capsids exhibit lower extent of association with the NPCs, we conclude that although not essential, the portal has a role in mediating the interaction of the CVSC proteins with Nups, and suggest a model whereby WT capsids can dock at the nuclear envelope through a non-portal penton vertex, resulting in an infection ‘dead end’.
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Gilmanova, N. V., R. Z. Livaev, and E. S. Bazhenova. "ANALYSIS OF THE CORE GLOW INTENSITY AND TEST RESULTSOF PRODUCTIVE ZEOLITE-CONTAINING ROCKS OF SORTYM FORMATION." Oil and Gas Studies, no. 5 (October 30, 2018): 41–45. http://dx.doi.org/10.31660/0445-0108-2018-5-41-45.
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The article deals with the results of studied structure features of reservoirs in productive zeolite-containing rocks. We have established that the content of pelite fraction and carbonate content have impact on the deterioration of reservoir properties, and the development of zeolitization is characteristic for zones of improved reservoir properties.It is shown that the presence of the core glow in the ultraviolet light for zeolite-containing rocks doesn’t guarantee the receipt of the product during testing and will depend on the thickness ratio with different intensity of luminescence. The change in wettability of the rock in the reservoir conditions, an increase in the share of residual oil, and the presence of oil in the dead-end pores are the most likely explanation for the described situation. If the core luminescence is «weak», the product from the reservoir can only be obtained by applying special impact methods.
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Sadare, Olawumi O., Rivoningo Ngobeni, and Michael O. Daramola. "Effect of Silica Sodalite Loading on SOD/PSF Membranes during Treatment of Phenol-Containing Wastewater." Membranes 12, no. 8 (2022): 800. http://dx.doi.org/10.3390/membranes12080800.
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In this study, silica sodalite (SSOD) was prepared via topotactic conversion and different silica sodalite loadings were infused into the polysulfone (PSF) for application in phenol-containing water treatment. The composite membranes were fabricated through the phase inversion technique. Physicochemical characteristics of the nanoparticles and membranes were checked using a Scanning Electron Microscope (SEM), Brunauer Emmett–Teller (BET), and Fourier Transform Infrared (FTIR) for surface morphology, textural properties, and surface chemistry, respectively. A nanotensile test, Atomic Force Microscopy (AFM), and contact angle measurement were used to check the mechanical properties, surface roughness, and hydrophilicity of the membranes, respectively. SEM results revealed that the pure polysulfone surface is highly porous with large evident pores. However, the pores decreased with increasing SSOD loading. The performance of the fabricated membranes was evaluated using a dead-end filtration device at varying feed pressure during phenol-containing water treatment. The concentration of phenol in water used in this study was 20 mg/L. The pure PSF displayed the maximum phenol rejection of 95 55% at 4 bar, compared to the composite membranes having 61.35% and 64.75% phenol rejection for 5 wt.% SSOD loading and 10 wt.% SSOD loading, respectively. In this study, a novel Psf-infused SSOD membrane was successfully fabricated for the treatment of synthetic phenol-containing water to alleviate the challenges associated with it.
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Herath, Gemunu, Kazuo Yamamoto, and Taro Urase. "Mechanism of bacterial and viral transport through microfiltration membranes." Water Science and Technology 38, no. 4-5 (1998): 489–96. http://dx.doi.org/10.2166/wst.1998.0703.
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Microorganisms such as Qβ, MS2, T4 virus and several bacteria strains in Pseudomonas, Alcaligenes and E-coli groups were filtered with different pore size nuclepore and anopore flat sheet membranes in dead end mode. The obtained rejection results were analyzed with existing pore models in which the rejection is related to the ratio of solute size to pore size. The existing pore models (transport equations) were adjusted to accommodate the microfiltration range particles. The adjusted pore models showed good agreement with the obtained experimental rejection results for virus while the bacteria rejection results showed a deviation. This deviation is partially explained with the wide size distribution of bacteria. The equivalent spherical diameter can be used to represent the virus size while the oval diameter of the cells may be the best possible dimension for bacteria size in membrane filtration. This determination showed the possibility of bacteria cells approaching the membrane pores in their longitudinal direction.
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Manga, Michael. "Dynamics of drops in branched tubes." Journal of Fluid Mechanics 315 (May 25, 1996): 105–17. http://dx.doi.org/10.1017/s0022112096002352.
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The flow of two-dimensional deformable drops through branching (bifurcating) tubes is studied numerically using a boundary integral formulation. The undeformed drop diameter is assumed to be less than the tube diameter. Capillary numbers between 10−2 and 1 are considered. Flow in the branching tube is characterized by the fraction of fluid which enters each of the two downstream branches. The likelihood of drops entering the high-flow-rate branch increases as (i) the viscosity ratio between the drops and suspending fluid decreases, (ii) the capillary number increases, and (iii) the drop size increases. Hydrodynamic interactions between the suspended drops increase the number of drops which enter the low-flow-rate branch. The implications of these results for dispersion processes and local transport are explored. The disturbance flow created by drops passing over ‘dead-end’ pores or cavities results in fluid transfer between the pore and the free stream; suspensions may then be effective in improving the ‘cleaning’ of porous materials.
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Verberk, J., and H. van Dijk. "Research on AirFlush®: distribution of water and air in tubular and capillary membrane modules." Water Supply 3, no. 5-6 (2003): 409–14. http://dx.doi.org/10.2166/ws.2003.0196.
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Dead-end ultrafiltration has proved itself as a technique for reclamation of backwash water of sand filters and as a pretreatment step before spiral wound reverse osmosis. A direct result of dead-end filtration is a flux decrease in time caused by the accumulation of material in the membrane pores and on the membrane surface. Different cleaning techniques are used to remove this accumulated material. Recently a new technique has been introduced, the AirFlush®. This technique makes use of air to create higher turbulence as compared to a water flush. At Delft University of Technology in co-operation with X-flow and Norit Membrane Technology research has been started into the fundamentals of the combined air and water flush. As in many industrial processes, an equal division of water and air over an installation is very important. To check the distribution of water and air over the cross-sectional area of tubular and capillary membrane modules two different test installations have been built. The results from the experiments show that for tubular membrane modules the water and air distribution over the cross-sectional area of the module is not always equally divided. Improvements have to be obtained by a better air distribution system. For capillary membrane modules the distribution of water and air over the cross-sectional area is more equally divided. The results from the experiments are discussed taking into account the theory of two-phase flow. It is shown that from the theory of two-phase flow the good distribution for the capillary membrane module can be explained by the large frictional pressure drop compared to the hydrostatic pressure drop.
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Shalahuddin, Iqbal, and Yusuf Wibisono. "Mekanisme Fouling pada Membran Mikrofiltrasi Mode Aliran Searah dan Silang." Jurnal Rekayasa Proses 13, no. 1 (2019): 6. http://dx.doi.org/10.22146/jrekpros.40458.
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A B S T R A C TMicrofiltration is a low pressure driven membrane process of about 1 bar trans-membrane pressure which is used frequently for separating dissolved particles within 0.1 to 10 μm size. Microfiltration membranes are utilized in water and wastewater treatment processes either during pretreatment, treatment, or post-treatment steps. Moreover in bioprocessing, microfiltration is used in upstream process for substrate sterilization or in downstream process for microbial suspension separation. Fouling is one major concern of membrane filtration processes, including microfiltration. In this article, the fouling mechanism on microfiltration membrane is explained based on the blocking model refer to cake filtration due to the complexity of fouling phenomena. Fouling mechanism on dead-end and cross-flow modes microfiltration are explained, and basically distinguished into four different mechanisms, i.e. complete blocking, standard blocking, intermediate blocking and cake filtration. The proposed models are based on constant pressure operation on the uniform membrane pores, both for dead-end and cross-flow modes. Cross-flow mode, however, is restricted on the beginning of filtration until critical flux condition is reached.Keywords: bioprocess; blocking model; cake filtration; fouling; microfiltration; wastewater A B S T R A KMembran mikrofiltrasi merupakan salah satu teknologi membran yang menggunakan tekanan rendah sekitar 1 bar sebagai gaya pendorong dan digunakan untuk proses pemisahan partikel terlarut yang berukuran antara 0,1 hingga 10 μm. Membran mikrofiltrasi banyak digunakan baik dalam proses pra-pengolahan, pengolahan, maupun pasca-pengolahan air dan air limbah. Pada bioproses, mikrofitrasi juga digunakan pada proses hulu untuk sterilisasi substrat atau pada proses hilir untuk pemisahan suspensi mikrob. Masalah yang paling utama dalam proses filtrasi membran adalah fouling. Dalam artikel ini, mekanisme terjadinya fouling pada membran mikrofiltrasi dijelaskan dengan menggunakan model pemblokiran yang mengacu pada filtrasi deposit partikel (cake) untuk menguraikan kerumitan fenomena fouling dalam mikrofiltrasi. Pada tulisan ini dijelaskan lebih rinci mengenai mekanisme fouling baik pada mikrofiltrasi searah (dead-end) maupun aliran silang (cross-flow). Mekanisme fouling pada proses mikrofiltrasi bisa dimodelkan dengan empat model yaitu pemblokiran pori, penyempitan pori, pemblokiran pori bersamaan dengan endapan permukaan dan formasi endapan permukaan. Mekanisme tersebut berlaku pada kondisi operasional bertekanan tetap dan ukuran pori yang seragam, baik pada aliran searah ataupun silang. Hanya saja, model mekanisme pada aliran silang hanya berlaku pada kondisi awal filtrasi hingga tercapai kondisi fluks kritis.Kata kunci: air limbah; bioproses; filtrasi cake; fouling; mikrofiltrasi; model pemblokiran
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Pereira, Deyse Celestte S., Vanderlane C. Silva, Josenildo I. Santos Filho, et al. "Freeze-Casting of Mining Wastes for Developing Sustainable Self-Supporting Ceramic Membranes." Sustainability 16, no. 24 (2024): 11227. https://doi.org/10.3390/su162411227.
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In this work, kaolin processing waste (KW) and columbite–tantalite waste (CTW) from mining activities were used to manufacture sustainable self-supporting ceramic membranes using the freeze-casting technique. The wastes were characterized, and formulations using only wastes were developed. Gelatin was used in the freeze-casting as a processing aid to avoid dendritic or lamellar pores. The membranes were sintered at different temperatures (1100 °C, 1200 °C and 1300 °C) and analyzed by X-ray diffraction, scanning electron microscopy, flexural strength measurement, and mercury porosimetry. The flux through the membranes was measured using a gravity-driven dead-end filtration system. The membranes containing 80% KW and 20% CTW sintered at 1200 °C showed high porosity (59%), a water permeate flux of 126.5 L/hm2, and a mechanical strength of 1.5 MPa. Filtration tests demonstrated effective turbidity removal (>99%) for synthetic water consisting of tap water and bentonite, reaching 0.1 NTU. The use of mining waste has shown considerable promise for the development of sustainable and affordable membranes for water treatment applications.
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Tang, Yong, Peng Zheng, Zhitao Tang, Minmao Cheng, and Yong Wang. "Research on Multi-Cycle Injection–Production Displacement Characteristics and Factors Influencing Storage Capacity in Oil Reservoir-Based Underground Gas Storage." Energies 18, no. 13 (2025): 3330. https://doi.org/10.3390/en18133330.
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In order to clarify the feasibility of constructing a gas storage reservoir through synergistic injection and production in the target reservoir, micro-displacement experiments and multi-cycle injection–production experiments were conducted. These experiments investigated the displacement characteristics and the factors affecting storage capacity during the multi-cycle injection–production process for converting the target reservoir into a gas storage facility. Microscopic displacement experiments have shown that the remaining oil is primarily distributed in the dead pores and tiny pores of the core in the form of micro-bead chains and films. The oil displacement efficiency of water flooding followed by gas flooding is 18.61% higher than that of gas flooding alone, indicating that the transition from water flooding to gas flooding can further reduce the liquid saturation and increase the storage capacity space by 2.17%. Single-tube long-core displacement experiments indicate that, during the collaborative construction of a gas storage facility, the overall oil displacement efficiency without a depletion process is approximately 24% higher than that with a depletion process. This suggests that depletion production is detrimental to enhancing oil recovery and expanding the capacity of the gas storage facility. During the cyclic injection–production stage, the crude oil recovery rate increases by 1% to 4%. As the number of cycles increases, the incremental oil displacement efficiency in each stage gradually decreases, and so does the increase in cumulative oil displacement efficiency. Better capacity expansion effects are achieved when gas is produced simultaneously from both ends. Parallel double-tube long-core displacement experiments demonstrate that, when the permeability is the same, the oil displacement efficiencies during the gas flooding stage and the cyclic injection–production stage are essentially identical. When there is a permeability contrast, the oil displacement efficiency of the high-permeability core is 9.56% higher than that of the low-permeability core. The ratio of the oil displacement efficiency between the high-permeability end and the low-permeability end is positively correlated with the permeability contrast; the greater the permeability contrast, the larger the ratio. The research findings can provide a reference for enhancing oil recovery and expanding the capacity of the target reservoir when it is converted into a gas storage facility.
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FU, JINGANG, YULIANG SU, LEI LI, YONGMAO HAO, and WENDONG WANG. "PREDICTED MODEL OF RELATIVE PERMEABILITY CONSIDERING WATER DISTRIBUTION CHARACTERISTICS IN TIGHT SANDSTONE GAS RESERVOIRS." Fractals 28, no. 01 (2020): 2050012. http://dx.doi.org/10.1142/s0218348x20500127.
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A novel predictive model for calculating relative permeability was derived based on a capillary tube model with fractal theory. Different forms of immovable water including water film (WF) and microcapillary water were incorporated in the new model. Special immovable water called lost dynamic water (LDW) was introduced in the proposed model. The results of verification show that there is agreement between the calculated results and the published experimental data and analytical model. The results indicated that the effect of LDW, WF, and stress dependence had a significant influence on the relative permeability, which cannot be neglected. A larger LDW coefficient, more dead-end pores, and corners in porous media yielded a more complex pore structure. Therefore, more water was trapped in the pore and became connate water, resulting in higher gas relative permeability and lower water relative permeability at a given water saturation. Due to the microcapillary effect, the relative permeability of the water/gas increased/decreased as the drawdown pressure increased at the same water saturation. Higher effective stress was more likely to cause rock deformation, resulting in higher gas relative permeability and lower water relative permeability at a given water saturation. This study provides a significant reference for reservoir engineers conducting water and gas two-phase flow analysis. The theoretical model is beneficial for research into the interpolation of relative permeability via numerical simulation.
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Patacchini, Leonardo, Sébastien Duchenne, Marcel Bourgeois, Arthur Moncorgé, and Quentin Pallotta. "Simulation of Residual Oil Saturation in Near-Miscible Gasflooding Through Saturation-Dependent Tuning of the Equilibrium Constants." SPE Reservoir Evaluation & Engineering 18, no. 03 (2015): 28–302. http://dx.doi.org/10.2118/171806-pa.
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Summary Conventional miscible or near-miscible gasflooding simulation often overestimates oil recovery, mostly because it does not capture a series of physical effects tending to limit interphase compositional exchanges. Those can include microscopic bypassing of oil situated in dead-end pores or blocked by water films, as well as macroscopic bypassing caused by subgrid-size heterogeneities or fingering. We here present a new engineering solution to this problem in the near-miscible case, relying on our in-house research reservoir simulator. The principle is, while using a black-oil or an equation-of-state description, to dynamically decrease the K-value of heavy components and possibly increase the K-value of light components as the oil saturation reaches the desired residual limit; this enables changing the phase boundaries when needed while preserving the original fluid behavior during the initial production stages. The benefits of the proposed solution are demonstrated on a reservoir-conditions tertiary-gas-injection experiment, performed in our laboratories, for which residual saturations as well as oil-phase and individual-component production rates have easily and successfully been history matched. Results are then compared with matches obtained by use of saturation exclusion and α-factors methods. As a proof of concept, the suitability of the new method to simulate incomplete revaporization of condensate during gas cycling is also illustrated, on the third SPE comparative-solution-project case.
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Ahmed, Imran, Ramesh Rudra, Kevin McKague, Bahram Gharabaghi, and John Ogilvie. "Evaluation of the Root Zone Water Quality Model (RZWQM) for Southern Ontario: Part I. Sensitivity Analysis, Calibration, and Validation." Water Quality Research Journal 42, no. 3 (2007): 202–18. http://dx.doi.org/10.2166/wqrj.2007.024.
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Abstract This study focuses on the performance of the Root Zone Water Quality Model (RZWQM) for corn production in southern Ontario. The model was used to simulate the amount of subsurface tile drainage, residual soil nitrate-nitrogen (NO3-N), NO3-N in subsurface drainage water, and crop yield. A precalibration sensitivity analysis of the model was conducted for several key parameters using field data collected at the study site. The RZWQM's hydrology component was most sensitive to the Brooks and Corey fitting parameters and saturated hydraulic conductivity (Ks), while the tile drain flow and the water table depth were sensitive to the Brooks and Corey fitting parameters of bubbling pressure (ψbp) and pore-size-distribution index (λ). The fraction of dead-end pores had relatively little effect on tile drain N loss. The crop yield is most affected by N uptake, age, and evapotranspiration rate. RZWQM simulated evapotranspiration was within the range (568 ± 55 mm) of the observed evapotranspiration. The model simulated corn yield very well (-0.1% difference) at the calibration site; however, it underestimated yield (-14.1%) at the validation site. Overall, the RZWQM simulated tile drain flow, NO3-N loss to tile drainage water, and crop yield with reasonable accuracy, but tended to underestimate the amount of soil NO3-N (mean deviation, -0.971). The inability of the model to handle the spatial and temporal variability of the soil may have affected its prediction accuracy. The model also needs improvement in simulating early spring snowmelt hydrology.
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Antolín-Cerón, Víctor-Hugo, Francisco-Jesús González-López, Pablo Daniel Astudillo-Sánchez, Karla-Alejandra Barrera-Rivera, and Antonio Martínez-Richa. "High-Performance Polyurethane Nanocomposite Membranes Containing Cellulose Nanocrystals for Protein Separation." Polymers 14, no. 4 (2022): 831. http://dx.doi.org/10.3390/polym14040831.
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With the aim of exploring new materials and properties, we report the synthesis of a thermoplastic chain extended polyurethane membrane, with superior strength and toughness, obtained by incorporating two different concentrations of reactive cellulose nanocrystals (CNC) for potential use in kidney dialysis. Membrane nanocomposites were prepared by the phase inversion method and their structure and properties were determined. These materials were prepared from a polyurethane (PU) yielded from poly(1,4 butylene adipate) as a soft segment diol, isophorone diisocyanate (IPDI) and hexamethylenediamine (HMDA) as isocyanate and chain extender, respectively (hard segment), filled with 1 or 2% w/w CNC. Membrane preparation was made by the phase inversion method using N,N-dimethylformamide as solvent and water as nonsolvent, and subjected to dead-end microfiltration. Membranes were evaluated by their pure water flux, water content, hydraulic resistance and protein rejection. Polymers and nanocomposites were characterized by scanning electronic and optical microscopy, differential scanning calorimetry, infrared spectroscopy, strain stress testing and 13C solid state nuclear magnetic resonance. The most remarkable effects observed by the addition of CNCs are (i) a substantial increment in Young’s modulus to twenty-two times compared with the neat PU and (ii) a marked increase in pure water flux up to sixty times, for sample containing 1% (w/w) of CNC. We found that nanofiller has a strong affinity to soft segment diol, which crystallizes in the presence of CNCs, developing both superior mechanical and pure water flow properties, compared to neat PU. The presence of nanofiller also modifies PU intermolecular interactions and consequently the nature of membrane pores.
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Rumaizah, Che Zulkifli, Azaman Fazureen, Razali Mohd Hasmizam, Ali Asmadi, and Muhamad Nor Mohd Al Amin. "Properties and Filtration Performance of Porous Clay Membrane Produced Using Sawdust as Pore Forming Agent." Key Engineering Materials 821 (September 2019): 337–42. http://dx.doi.org/10.4028/www.scientific.net/kem.821.337.
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This study investigated the effect of sawdust at 0, 10, 20, 30 and 40 wt% towards physical properties and filtration efficiency of porous clay membrane. Sawdust in various quantities was added into water containing clay, polyethylene glycol and sodium silicate and then stirred to form homogenized slurry. The slurry then was casted into Plaster of Paris (PoP) mould. The green body was cut into required sizes, dried and sintered in furnace at 1000 °C. The porosity and density of porous clay was determined by Archimedes principle, while morphology was observed by Hitachi Tabletop Scanning Electron Microscope (TTSEM). The filtration test was examined on a dead-end filtration setup in batch mode operation using nitrogen as carrier gas. Distilled water was filtered and used to determine membrane permeability, while aquaculture wastewater filtration was used to determine the turbidity removal. Turbidity of aquaculture wastewater and effluent (after filtration) were measured using turbidity meter. The results indicated that porosity increased from 38 % to 64 %, while density decreased from 1.5 g/cm3 to 0.8 g/cm3 with increasing amount of sawdust from 0 to 40 wt%. This data was supported by TTSEM which is indicate that the amount of pores increased with increasing amount of sawdust. Permeation of membrane increased from 45289 to 143999 L.h-1.m-2.bar-1 and efficiency of turbidity removal increased from 87 % to 89 % with increasing amount of sawdust from 0 to 40 wt%. As conclusion, 30 wt% was an optimum amount of sawdust which is produced ceramic membrane with good structure integrity, porosity, high permeability and high turbidity removal.
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Zhao, Yanjie, Fugang Wang, Cangsong Li, Yuqing Cao, and Hailong Tian. "Study of the Corrosion Characteristics of Tunnel Fissures in a Karst Area in Southwest China." Geofluids 2018 (July 24, 2018): 1–19. http://dx.doi.org/10.1155/2018/6234932.
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The development of the fissures in soluble rock of karst areas directly affects the construction and operation safety of tunnel engineering. It is thus of theoretical and practical significance to study the characteristics of its corrosion and its influencing factors. Taking the Wulong tunnel as the research object, the numerical model of the study area was established to quantitatively analyze the corrosion range, corrosion ratio, and changes in the permeability and porosity of the fissures in soluble rock of karst areas of the tunnel over the past 100 years, and the simulation results were verified by field experiments. The results show that the main controlling factor of the fissure corrosion of the tunnel in the karst area is the flow rate. The corrosion range and corrosion ratio of the fissures of the tunnels in the karst area increased with temperature because the reaction rate constant increased with temperature, causing the reactions’ equilibrium to move towards the direction of the solution. The larger the initial permeability and the larger the porosity of the fissures, the faster the fissures corrode. In the same time period, the fissures with high permeability and large porosity will lead to the permeability and porosity being more enhanced, thus causing the corrosion of the fissures to exhibit secondary enhancement effects. The opening of the dead-end pores greatly enhanced the permeability and slightly increased the porosity, which caused the differential corrosion of fissures in the karst area. The protection of the tunnel should be strengthened, mainly in strong hydrodynamic conditions and in the fracture development zone.
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Dalton, Laura E., Dustin Crandall, and Angela Goodman. "Characterizing the Evolution of Trapped scCO2 Curvature in Bentheimer and Nugget Sandstone Pore Geometry." Geofluids 2020 (March 6, 2020): 1–11. http://dx.doi.org/10.1155/2020/3016595.
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During a Geologic Carbon Storage process, supercritical CO2 (scCO2) is subjected to a series of dynamic and static conditions where the relationship between pore geometry and the trapped scCO2 curvature remains to be established. To mimic the dynamic process, two sandstones, Bentheimer and Nugget, were subjected to two successive drainage and imbibition (D-I) cycles and X-ray computed tomography scanned at each residual state to capture the wettability evolution at static conditions in the same pore geometry. Both sandstones contain similar grain size distributions, pore size distributions, and pore interconnectivity but differ in that the Nugget formation contains approximately half the porosity of the Bentheimer sandstone, and the pore network contains dead-end pores. scCO2 size distributions, strain calculations, and geometric contact angle measurements were used to characterize the curvature of scCO2 in different pore types between cycles. An increase in geometric contact angle was the greatest when advancement along the pore network of the same ganglion occurred between cycles while strain increased the most with pore-filling trapping. Moreover, Nugget sandstone results in a greater aggregated residual saturation and shows a clear increase in scCO2 sizes with an additional D-I cycle while scCO2 in the Bentheimer core shows a more complex response with some ganglion increasing and some decreasing in size with an additional D-I cycle. From this work, we suspect the pore geometry is playing a role in scCO2 size distributions and use this information to suggest using water pulses to enhance trapping capacity in lower porosity sandstones.
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Rosa, Erlyta Septa, Natalita Maulani Nursam, Shobih Shobih, and Rizky Abdillah. "Improving the Efficiency of Perovskite Solar Cell through the Addition of Compact Layer under TiO2 Electron Transfer Material." Materials Science Forum 929 (August 2018): 218–24. http://dx.doi.org/10.4028/www.scientific.net/msf.929.218.
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In the fabrication of perovskite solar cells, the perovskite layer is typically deposited onto the TiO2 semiconductor layer. The TiO2 layer serves as an electron transport material (ETM). In order to form the perovskite layer firmly and evenly, a structured mesoporous (MS) TiO2 surface is required. A porous layer could also make the electrons move more quickly through the pores to reach the contact. However, the electron-hole recombination and electron trapping in the dead end pore are still occurred. One of the solutions to overcome this problem is to add a thin compact layer (CL)-TiO2 under MS-TiO2 layer. The CL-TiO2 is expected as to prevent recombination and attract electrons trapped in the MS-TiO2 layer. In this paper, we report the addition of a thin compact layer (CL)-TiO2 under MS-TiO2 layer in the fabrication of perovskite solar cells based on methyl ammonium lead iodide (CH3NH3PbI3). The compact layer TiO2 was grown under mesoporous TiO2 layer by dip-coating in TiCl4 solution. The time of the dip coating was varied to obtain an optimum efficiency improvement. The structure of the device is glass/FTO/CL-TiO2/MS-TiO2/ CH3NH3PbI3/Spiro-OMeTAD/Ag/FTO/glass. It was concluded that the addition of CL-TiO2 can improve the perovskite solar cells power conversion efficiencies. The best efficiency was obtained from the 15 minutes dip-coating, which corresponded to the thinnest CL-TiO2 out of all samples. The electrical characterization performed under irradiation with an intensity of 50 mW/cm2 at 25 °C generated an open circuit voltage of 0.28 V, a short circuit current density of 0.25 mA/cm2 and a power conversion efficiency of 0.60 %.
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Young, August H., and Zbigniew J. Kabala. "Hydrodynamic Porosity: A New Perspective on Flow through Porous Media, Part I." Water 16, no. 15 (2024): 2158. http://dx.doi.org/10.3390/w16152158.
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Pore-scale flow velocity is an essential parameter in determining transport through porous media, but it is often miscalculated. Researchers use a static porosity value to relate volumetric or superficial velocities to pore-scale flow velocities. We know this modeling assumption to be an oversimplification. The variable fraction of porosity conducive to flow, what we define as hydrodynamic porosity, θmobile, exhibits a quantifiable dependence on the Reynolds number (i.e., pore-scale flow velocity) in the Laminar flow regime. This fact remains largely unacknowledged in the literature. In this work, we quantify the dependence of θmobile on the Reynolds number via numerical flow simulation at the pore scale for rectangular pores of various aspect ratios, i.e., for highly idealized dead-end pore spaces. We demonstrate that, for the chosen cavity geometries, θmobile decreases by as much as 42% over the Laminar flow regime. Moreover, θmobile exhibits an exponential dependence on the Reynolds number, Re = R. The fit quality is effectively perfect, with a coefficient of determination (R2) of approximately 1 for each set of simulation data. Finally, we show that this exponential dependence can be easily fitted for pore-scale flow velocity through use of only a few Picard iterations, even with an initial guess that is 10 orders of magnitude off. Not only is this relationship a more accurate definition of pore-scale flow velocity, but it is also a necessary modeling improvement that can be easily implemented. In the companion paper (Part 2), we build upon the findings reported here and demonstrate their applicability to media with other pore geometries: rectangular and non-rectangular cavities (circular and triangular).
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Duque, Luis, Antonio Molinero, Juan Carlos Oller, José Miguel Barcala, M. Antonia Folgado, and Antonio M. Chaparro. "Analysis of Hydrogen Feeding to the Anode of a PEMFC By a Transport Impedance Technique." ECS Meeting Abstracts MA2022-02, no. 39 (2022): 1406. http://dx.doi.org/10.1149/ma2022-02391406mtgabs.
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Hydrogen feeding to the catalyst layer of the anode of a proton-exchange membrane fuel cell (PEMFC) must be fast enough to allow for high power response and avoid starvation events. However, there are limitations to the flow rate posed by the anode architecture (manifold, inlet port, flow field), and the gas diffusion layer (GDL). Within the GDL, hydrogen transport conditions may change in-operando as a result of water generation and saturation of pores. Delays in hydrogen feeding will give rise to a decrease in power response, and transitory sub-stoichiometric conditions, that may damage the electrode and decrease fuel cell durability. Therefore, it is of high interest to probe hydrogen feeding conditions when designing new anode architectures, and during operation of the fuel cell. Mass transport conditions in the fuel cell and electrochemical systems can be probed by techniques based on the impedance concept [1,2,3]. Among them, one recently applied in our group is the current modulated H2 flow-rate spectroscopy (CH2S), which provides the transfer function H [4,5]: H(j w) = nF QH2 / I (Eq. 1) Where QH2 is the modulated hydrogen inlet flow, I the modulated cell current, n(=2) the electron exchanges per H2 molecule, and F(=96485 C mol-1) the Faraday constant. A typical response in a PEMFC with dead-end anode is shown in Fig. 1. The H function normally presents two or more semicircles in Nyquist plots, extending in the real axis from H'=0 to H'=1 (stoichiometric modulation). The high frequency semicircle is normally ascribed to the set-up time response limitation, mostly the flow meter. At higher frequencies, the H function shows characteristics of the time response of hydrogen flow up to the anodic catalyst layer. In this communication, the CH2S technique is applied in conventional single cells and in passive portable feeding PEMFCs. Some properties of H2 transport path towards the anodic catalyst layer are analyzed, like conduits length, inlet port type, anode flow field, liquid water contents, hydrogen stoichiometry, and anode hydrophobicity. Acknowledgement: The work is partially financed by the ELHYPORT project (PID2019−110896RB-I00), Spanish Ministry of Science and Innovation. [1] C. Deslouis, I. Epelboin, C. Gabrielli, P.S.-R. Fanchine, B. Tribollet, Relationship between the electrochemical impedance and the electrohydrodynamical impedances measured using a rotating disc electrode, J. Electroanal. Chem. Interfacial Electrochem. 107 (1980) 193–195. [2] A. Sorrentino, T. Vidakovic-Koch, R. Hanke-Rauschenbach, K. Sundmacher, Concentration-alternating frequency response: A new method for studying polymer electrolyte membrane fuel cell dynamics, Electrochim. Acta. 243 (2017) 53–64. [3] D. Grübl, J. Janek, W.G. Bessler, Electrochemical Pressure Impedance Spectroscopy (EPIS) as Diagnostic Method for Electrochemical Cells with Gaseous Reactants: A Model-Based Analysis, J. Electrochem. Soc. 163 (2016) A599–A610. [4] M.A. Folgado, H. Moreno, A. Molinero, J.C. Oller, J.M. Barcala, A.M. Chaparro Hydrogen Transport Impedance for the Study of Anodes in PEMFCs, European Fuel Cell Forum 2021, A0704 (Extended Abstract). Lucerne (Switzerland). [5] A. Molinero, J.C. Oller, J.M. Barcala, H. Moreno, M.A. Folgado, A.M. Chaparro, Experimental Set-Up for Transport Studies of Anodes in PEMFCs. European Fuel Cell Forum 2021, B0207 (Extended Abstract). Lucerne (Switzerland). Fig. 1. Nyquist plot of the H function according to Eq. 1, for a PEMFC cell with commercial electrodes (Pt/C 0.3mg·cm-2) and Nafion 212NR membrane, working with hydrogen feeding in dead-end mode, and air feeding in cathode. a) Full signal; b) Low frequency detail. Numbers are modulation frequencies. Figure 1
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Ismail, Nurul Qistina, Abdul Hafidz Yusoff, Noor Fazliani Shoparwe, et al. "The effect of Sodium Dodecyl Sulfate on Polysulfone membrane for Pb (II) ions removal in an aqueous solution." Kompleksnoe Ispolzovanie Mineralnogo Syra = Complex Use of Mineral Resources 334, no. 3 (2024): 26–36. http://dx.doi.org/10.31643/2025/6445.25.
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An unsustainable level of contamination increase is driven by industrialization, population growth and growth in developing countries. Contamination of heavy metal ions in wastewater such as Pb (II) are non-biodegradable and poses a serious threat to human health and other living things. One of the major methods for treating heavy metals contamination is by chemical precipitation. However, it produced hazardous sludge that requires further treatment and used a significant quantity of chemicals during the heavy metals treatment process due to its low impact on the environment. As a result, a membrane filtration method as an alternative treatment for treating heavy metals in wastewater has been investigated. In this study, the membranes were fabricated using the wet phase inversion method approach by incorporating polysulfone (PSF) polymer with dimethylacetamide (solvent) and inclusion of different concentrations of sodium dodecyl sulfate (SDS) (M1= 0 wt%, M2= 0.5 wt%, M3= 1.0 wt%, M4= 1.5 wt%, M5= 2.0 wt%). The fabricated membranes were tested to remove 50 mg/L Pb (II) ions in aqueous solution. Scanning electron microscopy (SEM) was used to investigate the morphological structures of membranes. Moreover, the structural characteristics of fabricated membranes were evaluated according to these parameters; contact angle, porosity and mean pores radius. Furthermore, the performance of the membrane was also evaluated for permeation and rejection flux by using dead-end cell filtration. The results indicate that the M4 membrane with 1.5 wt% SDS had the highest rejection rate (90.52%) for Pb (II) ions. This is likely due to the presence of macrovoids and a porous structure, as shown by SEM analyses. Other supporting evidence includes a lower contact angle (63.91o), higher water uptake (43.58%), higher porosity (85.21%), and a lower mean pore radius (6 nm) for the M4 membrane. The fouling mechanism model suggests that the complete blocking observed in the experimental data indicates that porous blockage occurred on the membrane's surface during the absorption of Pb (II) ions. In conclusion, compared to the pure membrane, it becomes evident that the addition of SDS into the membrane solution enhanced the properties of the membranes. The M4 membrane with a composition of 1.5 wt% concentration SDS demonstrated optimal filtration for removing Pb (II) ions in a water treatment process due to excellent properties mentioned above.
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Campbell, Bruce T., and Franklin M. Orr. "Flow Visualization for CO2/Crude-Oil Displacements." Society of Petroleum Engineers Journal 25, no. 05 (1985): 665–78. http://dx.doi.org/10.2118/11958-pa.
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Abstract Results of visual observations of high-pressure CO2 floods are reported. The displacements were performed in two-dimensional (2D) pore networks etched in glass plates. Results of secondary and tertiary first-contact miscible displacements and secondary and tertiary multiple-contact miscible displacements are compared. Three displacements with no water present were performed in each of three pore networks:displacement of a refined oil by the same oil dyed a different color;displacement of a refined oil by CO2 (first-contact miscible); anddisplacement of a crude oil at a pressure above the minimum miscibility pressure. In addition, three tertiary displacements were performed in the same pore networks;displacement of the refined oil by water, followed by displacement by the same refined oil dyed to distinguish it from the original oil;tertiary displacement of the refined oil by CO2; andtertiary displacement of crude oil by CO2. In addition, recovery of oil from dead-end pores, with and without water barriers shielding the oil, was investigated. Visual observations of pore-level displacement events indicate that CO2 displaced oil much more efficiently in both first-contact and multiple-contact miscible displacements when water was absent. In tertiary displacements of a refined oil, CO2 effectively displaced the oil it contacted, but high water saturations restricted access of CO2 to the oil. The low viscosity of CO2 aggravated effects of high water saturations because the CO2 did not displace water efficiently. CO2 did, however, contact trapped oil by diffusing through water to reach, to swell, and to reconnect isolated droplets. Finally, CO2 displaced crude oil more efficiently than it did the refined oil in tertiary displacements. Differences in wetting behavior between the refined and crude oils appear to account for the different flow behavior. Introduction If high-pressure CO2 displaces oil in a one-dimensional (1D), uniform porous medium (in which the effects of viscous fingering are necessarily absent), the displacement efficiency is controlled by the phase behavior of the CO2/crude-oil mixtures. The conventional description of the effects of phase behavior was given by Hutchinson and Braun1 for vaporizing gas drives and was extended to CO2 systems by Rathmell et al.2 In a rigorous mathematical treatment of the flow of three-component mixtures. Helfferich3 proved that the displacement will develop miscibility if the oil composition lies outside the region of tie-line extensions on a ternary diagram. Helfferich's analysis was for 1D flows in which fluids are mixed well locally, and the effects of dispersion are absent. Sigmund et al.,4 Gardner et al.,5 and Orr et al.6 showed that results of slim-tube displacements, which are nearly 1D and come close to eliminating the effects of viscous instability, can be predicted quantitatively by 1D process simulations based on independent measurements of the phase behavior and fluid properties of the CO2/crude-oil mixtures. Thus there is good experimental confirmation that the simple theory of the effects of phase behavior on displacement performance describes accurately the behavior of flow in an ideal displacement, such as a slim tube. In a CO2 flood in reservoir rock, however, a variety of other factors will influence process performance. Because the viscosity CO2 is much lower than that of most oils, viscous instability will limit the sweep efficiency of the injected CO2. In addition, Gardner and Ypma7 predicted, based on 2D simulations of the growth of a viscous finger, that an interaction between viscous instability and phase behavior would lead to higher residual oil saturation in regions penetrated by a viscous finger. Pore-structure heterogeneity may also influence displacement efficiency. Spence and Watkins8 found that residual oil saturations after CO2 waterfloods increased as the heterogeneity of the core increased. Several investigators have reported that high water saturations can alter mixing between oil and injected solvent. Raimondi and Torcaso9 found, in displacements in Berea sandstone cores, that significant fractions of the oil phase could not be contacted by injected solvent when the water saturation was high. Thomas et al.10 reported that a portion of the nonwetting phase can exist in "dendritic" pores whose shapes were determined by the surrounding wetting phase. They argued that material in the dendritic pores mixed with fluid in the flowing fraction only by diffusion. Stalkup11 and Shelton and Schneider12 also investigated effects of mobile water saturations in miscible displacements. Stalkup found that the flowing fraction decreased as the water saturation increased. Shelton and Schneider reported that the presence of a second mobile phase slowed recovery of either phase, but the nonwetting phase was affected more strongly. In their tests, all of the wetting phase was recovered by a miscible displacement, but significant amounts of nonwetting phase remained unrecovered.
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Kim, Jae-Hyun, Kyoung-Soo Cha, Sung-Woo Hwang, et al. "Analysis of Effect of the Magnetization Distribution of Multi-Pole PM on SPMSM Performance Using Equivalent Magnetic Circuit Considering Dead Zone." Energies 14, no. 11 (2021): 3279. http://dx.doi.org/10.3390/en14113279.
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In multi-pole permanent magnets (PMs) such a ring-type PMs, as multi-poles are magnetized in one segment, the ends of each pole are weakly magnetized, which is known as the dead zone. Thus, when analyzing characteristics of the motor with multi-pole PMs, accurate results can be obtained by considering the magnetization distribution. For this reason, this paper proposed an equivalent magnetic circuit (EMC) for external-rotor surface-mounted permanent magnet synchronous motors (SPMSMs) considering the dead zone to analyze the effects of the dead zone on the characteristics of the motor. As the magnetization in the dead zone gradually decreases toward the end of the pole, the magnetization distribution is assumed to have a trapezoidal shape. To describe the magnetization distribution, each pole was divided into several elements, and the equivalent residual magnetic flux density was applied to the elements of the dead zone. Finally, the validity of the proposed EMC was verified by comparing the back electro-motive force and air-gap magnetic flux density obtained by the EMC, finite-element analysis, and test.
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Pidaparti, Ramana, and Sriram Kalaga. "A Comparative Study of Distribution Structure Cross Arms." Open Civil Engineering Journal 11, no. 1 (2017): 757–67. http://dx.doi.org/10.2174/1874149501711010757.
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Background: The structural performance of cross arms used on distribution poles is studied in this paper. Tangent and Dead End configurations involving conventional (wood) and composite (fiber glass) cross arms are analyzed. Strength-to-Stiffness and Weight-to-Stiffness ratios associated with study cases are determined and evaluated. Results and Conclusion: It is observed that although initial costs are higher, composite cross arms offer long-term advantages in terms of strength, stiffness, performance and durability.
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Yokoyama, Hideki, Oliver J. Gruss, Sofia Rybina, et al. "Cdk11 is a RanGTP-dependent microtubule stabilization factor that regulates spindle assembly rate." Journal of Cell Biology 180, no. 5 (2008): 867–75. http://dx.doi.org/10.1083/jcb.200706189.
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Production of Ran–guanosine triphosphate (GTP) around chromosomes induces local nucleation and plus end stabilization of microtubules (MTs). The nuclear protein TPX2 is required for RanGTP-dependent MT nucleation. To find the MT stabilizer, we affinity purify nuclear localization signal (NLS)–containing proteins from Xenopus laevis egg extracts. This NLS protein fraction contains the MT stabilization activity. After further purification, we used mass spectrometry to identify proteins in active fractions, including cyclin-dependent kinase 11 (Cdk11). Cdk11 localizes on spindle poles and MTs in Xenopus culture cells and egg extracts. Recombinant Cdk11 demonstrates RanGTP-dependent MT stabilization activity, whereas a kinase-dead mutant does not. Inactivation of Cdk11 in egg extracts blocks RanGTP-dependent MT stabilization and dramatically decreases the spindle assembly rate. Simultaneous depletion of TPX2 completely inhibits centrosome-dependent spindle assembly. Our results indicate that Cdk11 is responsible for RanGTP-dependent MT stabilization around chromosomes and that this local stabilization is essential for normal rates of spindle assembly and spindle function.
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Szymoniczek, Joanna. "Niemieckie groby wojenne z okresu II wojny światowej w Polsce. Zagadnienia wstępne." Rocznik Polsko-Niemiecki, no. 17 (April 28, 2009): 87–100. http://dx.doi.org/10.35757/rpn.2009.17.04.
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446 thousand German soldiers died in Poland in World War II. Until the end of the 1980s, the Poles were unwilling to remember most of the German graves situated in their country. The breakthrough of 1989, together with a series of bilateral agreements, on the basis of which the graves of the German war victims were to be legally protected, respected and appropriately maintained, changed this. As a result, the remains of over 100 thousand German soldiers have been disinterred, the graves of German soldiers at the cemeteries in Joachimów-Mogiły, Kraków, Warsaw (The Northern Cemetery) and Poznań have been commemorated, and new, mass cemeteries have been built in Przemyśl, Mławka, Modlin, Siemianowice Śląskie, Nadolice Wielkie, Gdańsk, Puławy, Bartosze, near Ełk, and Stary Czarnów (Glinna) near Szczecin. These cemeteries are to provide for reconciliation and a genuine normalisation in relations between Poles and Germans. Since the late 1990s, youth camps as well as the Bundeswehr and Polish army camps have been organised in localities where German war cemeteries are situated, during which the participants carry out building work and repair the architectural artefacts in German cemeteries from both World War I and the World War II. The camp organisers’ aim is for these events to help the youth of both countries to become acquainted with each other, to learn history and tolerance, to disperse prejudices, and so forth. While to most of the Poles such actions are a form of expressing a humanitarian attitude, some of them find it unacceptable to commemorate the aggressor’s dead, while others perceive these efforts as a business opportunity.
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Ioselli, Giulia, Philipp Seidel, Sooyoung Yoon, Sonja Blaseio, Frédéric Hasché, and Mehtap Oezaslan. "Bifunctionality and Reversibility of Colloidal Pt-Ir Anode Catalyst Material for Hydrogen Starvation." ECS Meeting Abstracts MA2024-02, no. 41 (2024): 2736. https://doi.org/10.1149/ma2024-02412736mtgabs.
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Cell reversal events are based on the hydrogen starvation, that takes place during to fast load changes, blockage of flow field channels or catalyst layer pores by liquid water. During the hydrogen starvation, protons and electrons continue to be supplied to the cathode, which is why carbon oxidation reaction (COR) sets in at the anode.[1] To mitigate the carbon oxidation reaction (COR), various catalyst strategies have been reported in the literature. For instance, the addition of iridium-based co-catalysts such as IrOx promote the oxygen evolution reaction (OER) instead of the carbon oxidation reaction (COR). [1-5] Although iridium is very costly and scarce, its use can be further increased by atomically mixing it with platinum to form a Pt-Ir alloy.In this work, we have prepared atomically mixed Pt-Ir alloy catalysts that combine both functionalities (hydrogen oxidation reaction and OER) in one nanoparticle (NP) in a unique matter. A colloidal route was chosen to control the particle size and composition of Pt-Ir NPs. The adopted synthesis method is based on the “Co4Cat” concept in methanol. [6] Afterwards, the colloidal NPs with controlled size of 1 – 2 nm and atomic Pt:Ir ratio of 1:1 and 3:1 were deposited on Vulcan XC72 Carbon and characterized by TEM, XPS and XRF techniques.The electrochemical experiments were performed in a three-electrode arrangement using a thin film rotating disc electrode (TF-RDE) technique. 0.1 M HClO4 was used as electrolyte solution. The ECSA was determined by underpotential deposited hydrogen (Hupd). Linear sweep voltammetry (LSV) measurements were performed to establish the HOR and OER activity. Thereby, the electrolyte was saturated with H2 and Ar for HOR and OER measurements, respectively.The PtIr/V and Pt3Ir/V catalysts with 1 – 2 nm show values of electrochemically active surface area (ECSA) of 70 ± 2 m2 g-1 PtIr and 73 ± 3 m2 g-1 PtIr. The HOR kinetics on platinum – iridium surfaces is very fast in acidic media. Therefore, we could only compare the measured HOR polarization curves with the theoretical diffusion limiting current. Since these are always on top of each other, we can conclude that the Pt-Ir catalysts are very active for HOR. In addition, the OER polarization curves were analyzed and showed an Ir-based mass activity of 70 ± 6 A g-1 Ir for PtIr/V and 104 ± 6 A g-1 Ir for Pt3Ir/V at iR-corrected potential of 1.50 VRHE. As a comparison, commercial IrOx shows a mass activity of 47 ± 6 A g-1 Ir at 1.50 VRHE.To investigate the electrochemical reversibility of Pt-Ir alloy catalysts, we alternated between the LSV measurements in the region of HOR and OER at least five times. One cycle includes three LSV measurements under each HOR and OER conditions. The HOR and OER activities for PtIr/V and Pt3Ir/V continuously decrease within the 5 cycles between HOR and OER. In other words, after the 5th cycle the OER mass activity dropped to 28 ± 3 A g-1 Ir and 32 ± 4 A g-1 Ir for PtIr/V and Pt3Ir/V catalysts, respectively. However, the ECSA values mainly retain and are 68 ± 2 m2 g-1 PtIr for PtIr/V and 70 ± 2 m2 g-1 PtIr for Pt3Ir/V.We can sum up that the colloidal Pt-Ir catalysts show bifunctional properties towards HOR and OER and reversible behaviour, which can be helpful to improve the cell reversal tolerance during the H2 starvation. Literature: [1] R. Marić et al., Towards a Harmonized Accelerated Stress Test Protocol for Fuel Starvation Induced Cell Reversal Events in PEM Fuel Cells, Journal of Electrochemical Society (2020)167, 124520 DOI:10.1149/1945-7111/abad68, [2] E. Alizadeh et al., The experimental analysis of a dead-end H2 /O2 PEM fuel cell stack with cascade type design, International Journal of Hydrogen Energy 42 (2017)11662 -11672DOI: https./7doi.org/10.1016/j.ijhydene.2017.03.094[3]Wang et al., Ir-Pt/C composite with high metal loading as a high-performance anti-reversal anode catalyst for proton exchange membrane fuel cells, International journal of hydrogen energy 47 (2022) DOI:10.1016/j.ijhydene.2022.02.065 [4] Kim et al., Pt-IrO x catalysts immobilized on defective carbon for efficient reversal tolerant anode in proton exchange membrane fuel cell, Journal of Catalysis (2021)DOI:https://doi.org/10.1016/j.jcat.2021.01.028[5]Fang et al, Facile synthesis of Pt-decorated Ir black as bifunctional oxygen catalyst Nanoscale(2019)11,9091DOI:10.1039/c9nr00279k[6]Quinson et al., Surfactant-free synthesis of size controlled platinum nanoparticles: Insights from in situ studies;Applied Surface Science (2021)549,149263 DOI: 10.1016/j.apsusc.2021.149263