Ecopoiesis and Liquid Water Transportation on Mars

Mars ◽  
2009 ◽  
pp. 661-682
Author(s):  
Viorel Badescu ◽  
Dragos Isvoranu ◽  
Richard B. Cathcart
Keyword(s):  
Liquid Water ◽  
Water Transportation

Effect of Hydrophobicity in Cathode Porous Media on PEM Fuel Cell Performance

2009 ◽  
Author(s):  
Lijun Yang ◽  
Wenan Li ◽  
Xiaoze Du ◽  
Yongping Yang
Keyword(s):  
Fuel Cell ◽  
Flow Field ◽  
Water Content ◽  
Liquid Water ◽  
Pem Fuel Cell ◽  
Liquid Water Content ◽  
Contact Angles ◽  
Water Flooding ◽  
Water Transportation ◽  
Overall Performance

The water management is a key issue for the performance of a polymer electrolyte membrane (PEM) fuel cell. Materials of the fuel cell would affect the water transportation in the flow field thus influence the overall performance of a fuel cell. Three dimensional single-channel, counter-flow model was built to analyze the performance of PEM fuel cell. Different surface contact angles were set to the liquid water droplets in the catalyst layers (CL) and gas diffusion layers (GDL) to present the different wetting property characterizations of the materials. Assuming that the contact angles range from 75° to 150°, the liquid water content and distribution in the cathode GDL were investigated in details. Numerical analysis showed that the hydrophobicity of the structure affects water transportation in the fuel cell significantly. Hydrophobic materials could lower the rate of water saturation in the flow field thus prevent the water flooding in the cathode side. When the surface contact angel of cathode CL and GDL was set to 135°, the liquid water content is least in the GDL. I-V polarization curves of the fuel cell with different materials were also developed to analyze the overall performance. As a result, proper hydrophobic material would lower the rate of cathode water flooding in PEM and benefit the performance of PEM fuel cell.

Effect of Hydrophobicity in Cathode Porous Media on PEM Fuel Cell Performance

2010 ◽  
Vol 7 (6) ◽  
Author(s):  
Lijun Yang ◽  
Wenan Li ◽  
Xiaoze Du ◽  
Yongping Yang
Keyword(s):  
Fuel Cell ◽  
Flow Field ◽  
Water Content ◽  
Liquid Water ◽  
Pem Fuel Cell ◽  
Liquid Water Content ◽  
Contact Angles ◽  
Water Flooding ◽  
Water Transportation ◽  
Overall Performance

Water management is a key issue for the performance of a polymer electrolyte membrane (PEM) fuel cell. Materials of the fuel cell would affect the water transportation in the flow field, thus influence, the overall performance of the fuel cell. A three dimensional, single-channel, counterflow model was built to analyze the performance of the PEM fuel cell. Different surface contact angles were set to the liquid water droplets in the catalyst layers (CLs) and gas diffusion layers (GDLs) to present the different wetting property characterizations of the materials. Assuming that the contact angle ranges from 75 deg to 150 deg, the liquid water content and distribution in the cathode GDL were investigated in details. Numerical analysis showed that the hydrophobicity of the structure affects the water transportation in the fuel cell significantly. Hydrophobic materials could lower the rate of water saturation in the flow field, thus preventing the water flooding in the cathode side. When the surface contact angles of the cathode CL and GDL were set to 135 deg, the liquid water content is least in the GDL. I-V polarization curves of the fuel cell with different materials were also developed to analyze the overall performance. As a result, proper hydrophobic material would lower the rate of cathode water flooding in PEM and benefit the performance of PEM fuel cell.

Ancient Mars probably too cold for liquid water

Nature ◽  
2014 ◽  
Author(s):  
Sid Perkins
Keyword(s):  
Liquid Water

The Evolution of a Nation

2011 ◽  
Author(s):  
Daniel Berkowitz ◽  
Karen B. Clay
Keyword(s):  
Political Competition ◽  
Common Law ◽  
Civil Law ◽  
Legal Institutions ◽  
Colonial History ◽  
Legal Systems ◽  
Water Transportation ◽  
Long Run ◽  
Access To Water ◽  
Late Twentieth

Although political and legal institutions are essential to any nation's economic development, the forces that have shaped these institutions are poorly understood. Drawing on rich evidence about the development of the American states from the mid-nineteenth to the late twentieth century, this book documents the mechanisms through which geographical and historical conditions—such as climate, access to water transportation, and early legal systems—impacted political and judicial institutions and economic growth. The book shows how a state's geography and climate influenced whether elites based their wealth in agriculture or trade. States with more occupationally diverse elites in 1860 had greater levels of political competition in their legislature from 1866 to 2000. The book also examines the effects of early legal systems. Because of their colonial history, thirteen states had an operational civil-law legal system prior to statehood. All of these states except Louisiana would later adopt common law. By the late eighteenth century, the two legal systems differed in their balances of power. In civil-law systems, judiciaries were subordinate to legislatures, whereas in common-law systems, the two were more equal. Former civil-law states and common-law states exhibit persistent differences in the structure of their courts, the retention of judges, and judicial budgets. Moreover, changes in court structures, retention procedures, and budgets occur under very different conditions in civil-law and common-law states. This book illustrates how initial geographical and historical conditions can determine the evolution of political and legal institutions and long-run growth.

Reciprocal Polarizable Embedding with a Transferable H2O Potential Function II: Application to (H2O)n Clusters & Liquid Water

2019 ◽  
Author(s):  
Asmus Ougaard Dohn ◽  
Elvar Jónsson ◽  
Hannes Jonsson
Keyword(s):  
Density Functional Theory ◽  
Liquid Water ◽  
Density Functional ◽  
Water Clusters ◽  
Theory Model ◽  
Coupling Scheme ◽  
Functional Theory ◽  
Total Polarization ◽  
Electrostatic Embedding ◽  
Polarizable Embedding

The manuscript analyzes the accuracy of our recently developed reciprocal polarizable embedding scheme, where a density functional theory model of the QM region is coupled to a dipole- and quadrupole polarizable water potential of the MM region. We present calculations of water clusters and liquid water where we analyze the energy, atomic forces and total polarization to demonstrate that artifacts in energy and polarization introduced by the QM/MM coupling are small and well-behaved. Furthermore, our methodology improves the consistency of the structure of optimized water hexamer geometries when compared to results obtained with models that neglect polarization. Additionally, the manuscript provides evidence that our coupling scheme eliminates artifacts in the structure of liquid water obtained with simpler electrostatic embedding models.

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