Green H2 Production by Water Electrolysis Using Cation Exchange Membrane: Insights on Activation and Ohmic Polarization Phenomena

Low-temperature electrolysis by using polymer electrolyte membranes (PEM) can play an important role in hydrogen energy transition. This work presents a study on the performance of a proton exchange membrane in the water electrolysis process at room temperature and atmospheric pressure. In the perspective of applications that need a device with small volume and low weight, a miniaturized electrolysis cell with a 36 cm2 active area of PEM over a total surface area of 76 cm2 of the device was used. H2 and O2 production rates, electrical power, energy efficiency, Faradaic efficiency and polarization curves were determined for all experiments. The effects of different parameters such as clamping pressure and materials of the electrodes on polarization phenomena were studied. The PEM used was a catalyst-coated membrane (Ir-Pt-Nafion™ 117 CCM). The maximum H2 production was about 0.02 g min−1 with a current density of 1.1 A cm−2 and a current power about 280 W. Clamping pressure and the type of electrode materials strongly influence the activation and ohmic polarization phenomena. High clamping pressure and electrodes in titanium compared to carbon electrodes improve the cell performance, and this results in lower ohmic and activation resistances.

Multiphysics Modeling and Analysis of a Solar Desalination Process Based on Vacuum Membrane Distillation

A hollow fiber vacuum membrane distillation (VMD) module was modeled using finite element analysis, and the results were used to conduct an exergy efficiency analysis for a solar-thermal desalination scheme. The performance of the VMD module was simulated under various operating conditions and membrane parameters. Membrane porosity, tortuosity, pore diameter, thickness, and fiber length were varied, along with feed temperature and feed configuration. In all cases, polarization phenomena were seen to inhibit the performance of the module. Under VMD operation, polarization of salt concentration was seen to be the main determining factor in the reduction of permeate flux. Within the boundary layer, salt concentration was seen to rapidly increase from the feed mass fraction of 0.035 to the saturation point. The increase in salt concentration led to a decrease in saturation pressure, the driving force for separation. Charging the feed into the shell instead of the lumen side of the membranes resulted in a further decrease in permeate flux. It is shown that adding a baffling scheme to the surface of the fibers can effectively reduce polarization phenomena and improve permeate flux. Increasing the overall recovery ratio was seen to increase the exergy efficiency of the system. Exergy efficiency was seen to have almost no dependency on membrane parameters due to the low recovery ratio in a single pass and the high heating duty required to reach the desired temperature for the feed stream.

Comparative Studies of Ionizing Radiation Detectors Made on the Basis of Various Types of Diamond Plates

The results of experiments on the study of polarization phenomena and the charge collection efficiency in test structures of diamond ionizing radiation detectors using diamond plates of various types, including single-crystal NRNT-type, single-crystal CVD-type, as well as polycrystalline type, when exposed to alpha-radiation with an energy of 5.5 MeV are presented. Studies have demonstrated the existence of a number of problems with the device quality of diamond plates that affect the performance of spec-trometric-type detectors.

Polarization in the contemporary political and media landscape

Political polarization is on the rise in America. Although social psychologists frequently study the intergroup underpinnings of polarization, they have traditionally had less to say about macro societal processes that contribute to its rise and fall. Recent cross-disciplinary work on the contemporary political and media landscape provides these complementary insights. In this paper, we consider the evidence for and implications of political polarization, distinguishing between ideological, affective, and false polarization. We review three key societal-level factors contributing to these polarization phenomena: the role of political elites, partisan media, and social media dynamics. We argue that institutional polarization processes (elites, media and social media) contribute to people’s misperceptions of division among the electorate, which in turn can contribute to a self-perpetuating cycle fueling animosity (affective polarization) and actual ideological polarization over time.

Polarization in the Contemporary Political and Media Landscape

Political polarization is on the rise in America. Although social psychologists frequently study the intergroup underpinnings of polarization, they have traditionally had less to say about macro societal processes that contribute to its rise and fall. Recent cross-disciplinary work on the contemporary political and media landscape provides these complementary insights. In this paper, we consider the evidence for and implications of political polarization, distinguishing between ideological, affective, and false polarization. We review three key societal-level factors contributing to these polarization phenomena: the role of political elites, partisan media, and social media dynamics. We argue that institutional polarization processes (elites, media and social media) contribute to people’s misperceptions of division among the electorate, which in turn can contribute to a self-perpetuating cycle fueling animosity (affective polarization) and actual ideological polarization over time.

The Young Interferometer as an Optical System for a Variable Depolarizer Characterization

This article proposes an interferometric method for a variable depolarizer characterization with features that distinguish it from the polarimetric system. Information about the behavior of a vertically aligned nematic cell as a variable depolarizer can be extracted from Young interferometer measurements in real time. These results could be significant for understanding the polarization phenomena in depolarizing media such as biological tissue.