scholarly journals Исследование массотранспортных потерь структурно-модифицированных электродов воздушно-водородных топливных элементов методом вольт-амперной характеристики

2021 ◽  
Vol 91 (4) ◽  
pp. 627
Author(s):  
Н.В. Глебова ◽  
А.О. Краснова ◽  
А.А. Нечитайлов ◽  
А.А. Томасов ◽  
Н.К. Зеленина
Keyword(s):  
Current Density ◽  
Oxygen Transfer ◽  
Limiting Current ◽  
Limiting Factors ◽  
Membrane Electrode ◽  
Structural Elements ◽  
Mixed Conductivity ◽  
Transport Losses ◽  
Electrode Assemblies

The article discusses platinum-carbon electrodes with mixed conductivity as part of membrane-electrode assemblies of fuel cells containing structural-modifying additives with structural elements of various types: carbon nanotubes with elongated structural elements and graphene-like materials with almost two-dimensional planes. Based on the data on the limiting current density obtained in potentiodynamic and potentiostatic modes, the mass transport losses of molecular oxygen transfer in these electrodes are investigated. Using different measurement conditions, the baric dependences of the current density were constructed, the limiting factors and mechanisms of oxygen transfer in the studied structures and the role of the introduced modifiers were clarified.

Analytical electron microscopy of grain boundaries in Al-Cu metallizations

1992 ◽  
Vol 50 (2) ◽  
pp. 1684-1685
Author(s):  
J. R. Michael ◽  
A. D. Romig ◽  
D. R. Frear
Keyword(s):  
Electron Microscopy ◽  
Integrated Circuits ◽  
Failure Mode ◽  
Current Density ◽  
Thermal History ◽  
Analytical Electron Microscopy ◽  
Cu Metallization ◽  
Analytical Electron ◽  
Interconnect Lines

Al with additions of Cu is commonly used as the conductor metallizations for integrated circuits, the Cu being added since it improves resistance to electromigration failure. As linewidths decrease to submicrometer dimensions, the current density carried by the interconnect increases dramatically and the probability of electromigration failure increases. To increase the robustness of the interconnect lines to this failure mode, an understanding of the mechanism by which Cu improves resistance to electromigration is needed. A number of theories have been proposed to account for role of Cu on electromigration behavior and many of the theories are dependent of the elemental Cu distribution in the interconnect line. However, there is an incomplete understanding of the distribution of Cu within the Al interconnect as a function of thermal history. In order to understand the role of Cu in reducing electromigration failures better, it is important to characterize the Cu distribution within the microstructure of the Al-Cu metallization.

“Eternal Bodies”: images of archangels in the upper parts of Nubian buildings

2020 ◽  
pp. 713-736
Author(s):  
Magdalena Łaptaś
Keyword(s):  
Near East ◽  
Structural Elements ◽  
Christian Art ◽  
The Earth ◽  
Cosmic Space

Images of archangels and angels, which were painted on the walls, in the upper parts of the buildings and, on their structural elements, were very popular in Christian Nubian painting as attested by the discoveries from Church SWN.BV on the citadel in Old Dongola. These images, which derive from pre-Christian art, depict the eternal nature of the archangels and angels. Presenting this group of representations, the author traces the origins of these images to highlight the role of these spiritual beings as intermediaries between God and humankind. As such, they move freely between the Heavens and the Earth, so the air and cosmic space are their natural surroundings. Moreover, archangels govern the forces of nature, the planets, and the seven skies. Therefore, their sanctuaries were located on hill summits, in the upper chapels, on structural elements of ecclesiastical buildings, etc. The Nubian tradition is therefore part of a broader Mediterranean tradition, the roots of which should be sought in the Near East.

Agenda-Setting Dynamics during the Campaign Period

2017 ◽  
Author(s):  
Julia Partheymüller
Keyword(s):  
Political Parties ◽  
News Media ◽  
Agenda Setting ◽  
Information Environment ◽  
Limiting Factors ◽  
Media Content ◽  
Agenda Setter ◽  
Memory Decay ◽  
The Media

It is widely believed that the news media have a strong influence on defining what are the most important problems facing the country during election campaigns. Yet, recent research has pointed to several factors that may limit the mass media’s agenda-setting power. Linking news media content to rolling cross-section survey data, the chapter examines the role of three such limiting factors in the context of the 2009 and the 2013 German federal elections: (1) rapid memory decay on the part of voters, (2) advertising by the political parties, and (3) the fragmentation of the media landscape. The results show that the mass media may serve as a powerful agenda setter, but also demonstrate that the media’s influence is strictly limited by voters’ cognitive capacities and the structure of the campaign information environment.

scholarly journals Evaluation of Electrodialysis Desalination Performance of Novel Bioinspired and Conventional Ion Exchange Membranes with Sodium Chloride Feed Solutions

Membranes ◽  
2021 ◽  
Vol 11 (3) ◽  
pp. 217
Author(s):  
AHM Golam Hyder ◽  
Brian A. Morales ◽  
Malynda A. Cappelle ◽  
Stephen J. Percival ◽  
Leo J. Small ◽  
...  
Keyword(s):  
Ion Exchange ◽  
Cation Exchange ◽  
Current Density ◽  
Feed Solution ◽  
Laboratory Scale ◽  
Cation Exchange Membrane ◽  
Limiting Current ◽  
Ion Exchange Membranes ◽  
Experimental Apparatus ◽  
Exchange Membrane

Electrodialysis (ED) desalination performance of different conventional and laboratory-scale ion exchange membranes (IEMs) has been evaluated by many researchers, but most of these studies used their own sets of experimental parameters such as feed solution compositions and concentrations, superficial velocities of the process streams (diluate, concentrate, and electrode rinse), applied electrical voltages, and types of IEMs. Thus, direct comparison of ED desalination performance of different IEMs is virtually impossible. While the use of different conventional IEMs in ED has been reported, the use of bioinspired ion exchange membrane has not been reported yet. The goal of this study was to evaluate the ED desalination performance differences between novel laboratory‑scale bioinspired IEM and conventional IEMs by determining (i) limiting current density, (ii) current density, (iii) current efficiency, (iv) salinity reduction in diluate stream, (v) normalized specific energy consumption, and (vi) water flux by osmosis as a function of (a) initial concentration of NaCl feed solution (diluate and concentrate streams), (b) superficial velocity of feed solution, and (c) applied stack voltage per cell-pair of membranes. A laboratory‑scale single stage batch-recycle electrodialysis experimental apparatus was assembled with five cell‑pairs of IEMs with an active cross-sectional area of 7.84 cm2. In this study, seven combinations of IEMs (commercial and laboratory-made) were compared: (i) Neosepta AMX/CMX, (ii) PCA PCSA/PCSK, (iii) Fujifilm Type 1 AEM/CEM, (iv) SUEZ AR204SZRA/CR67HMR, (v) Ralex AMH-PES/CMH-PES, (vi) Neosepta AMX/Bare Polycarbonate membrane (Polycarb), and (vii) Neosepta AMX/Sandia novel bioinspired cation exchange membrane (SandiaCEM). ED desalination performance with the Sandia novel bioinspired cation exchange membrane (SandiaCEM) was found to be competitive with commercial Neosepta CMX cation exchange membrane.

scholarly journals Limiting Current Density of Oxygen Reduction under Ultrathin Electrolyte Layers: From the Micrometer Range to Monolayers

2021 ◽  
Vol 8 (4) ◽  
pp. 712-718
Author(s):  
Xiankang Zhong ◽  
Matthias Schulz (née Uebel) ◽  
Chun‐Hung Wu ◽  
Martin Rabe ◽  
Andreas Erbe ◽  
...  
Keyword(s):  
Oxygen Reduction ◽  
Current Density ◽  
Limiting Current ◽  
Limiting Current Density

Critique and Improvement of a One-Dimensional Semianalytical Model of a Direct Methanol Fuel Cell

2012 ◽  
Vol 9 (5) ◽  
Author(s):  
C. C. Kuo ◽  
W. E. Lear ◽  
J. H. Fletcher ◽  
O. D. Crisalle
Keyword(s):  
Fuel Cell ◽  
Polarization Curve ◽  
Current Density ◽  
Direct Methanol Fuel Cell ◽  
Membrane Electrode Assembly ◽  
Membrane Electrode ◽  
One Dimensional ◽  
Implicit Equation ◽  
Direct Methanol ◽  
Methanol Fuel Cell

A constructive critique and a suite of proposed improvements for a recent one-dimensional semianalytical model of a direct methanol fuel cell are presented for the purpose of improving the predictive ability of the modeling approach. The model produces a polarization curve for a fuel cell system comprised of a single membrane-electrode assembly, based on a semianalytical one-dimensional solution of the steady-state methanol concentration profile across relevant layers of the membrane electrode assembly. The first improvement proposed is a more precise numerical solution method for an implicit equation that describes the overall current density, leading to better convergence properties. A second improvement is a new technique for identifying the maximum achievable current density, an important piece of information necessary to avoid divergence of the implicit-equation solver. Third, a modeling improvement is introduced through the adoption of a linear ion-conductivity model that enhances the ability to better match experimental polarization-curve data at high current densities. Fourth, a systematic method is advanced for extracting anodic and cathodic transfer-coefficient parameters from experimental data via a least-squares regression procedure, eliminating a potentially significant parameter estimation error. Finally, this study determines that the methanol concentration boundary condition imposed on the membrane side of the membrane-cathode interface plays a critical role in the model’s ability to predict the limiting current density. Furthermore, the study argues for the need to carry out additional experimental work to identify more meaningful boundary concentration values realized by the cell.

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