scholarly journals On the Role of Oxidation in Tribological Contacts under Environmental Conditions

2015 ◽  
Vol 2015 ◽  
pp. 1-11 ◽  
Author(s):  
Rolf Merz ◽  
Alexander Brodyanski ◽  
Michael Kopnarski
Keyword(s):  
Environmental Conditions ◽  
Coupled System ◽  
Native Oxide ◽  
Oxide Layers ◽  
Transmission Electron ◽  
Debris Particles ◽  
Metal Metal ◽  
Long Time ◽  
Special Challenge ◽  
Induced Changes

Oxidation processes in tribological steel contacts are investigated, which are treated in a dry sliding, linear reciprocating model tribometer, by EDX (energy dispersive X-ray spectroscopy), AES (Auger electron spectroscopy), and HREFTEM (high resolution energy filtered transmission electron microscopy). Typical for steel contacts under environmental conditions is the feature that the counterparts are separated by oxide layers, which influence the tribological properties. And vice versa the tribological load will influence and change the oxide layers. The interaction of this dynamically coupled system was resolved by focussing the postexperimental surface analysis to long time stable balance states. As special challenge for the analyst of the tribological experiment under environmental conditions a postexperimental grown oxide layer covers the tribological induced changes and has to be distinguished from the tribological induced changes. Thick oxide layers, formed during the tribological load, were observed, which start to grow in form of islands and at the end separate the metallic bulk materials of the counterparts completely and avoid direct metal-metal contact. Thicknesses up to some microns strength, exceeding native oxide layers by magnitudes, were reached. Ploughing under fresh surface oxide and compacting and embedding of fresh oxidized debris particles were identified as main mechanisms responsible for the growing of these thick oxide layers.

scholarly journals Quasi-stability and continuity of attractors for nonlinear system of wave equations

2021 ◽  
Vol 8 (1) ◽  
pp. 27-45
Author(s):  
M. M. Freitas ◽  
M. J. Dos Santos ◽  
A. J. A. Ramos ◽  
M. S. Vinhote ◽  
M. L. Santos
Keyword(s):  
Wave Equations ◽  
Coupled System ◽  
Global Attractors ◽  
Time Behavior ◽  
Exponential Attractors ◽  
Small Perturbations ◽  
Recent Approach ◽  
Nonlinear Coupled System ◽  
Long Time ◽  
External Forces

Abstract In this paper, we study the long-time behavior of a nonlinear coupled system of wave equations with damping terms and subjected to small perturbations of autonomous external forces. Using the recent approach by Chueshov and Lasiecka in [21], we prove that this dynamical system is quasi-stable by establishing a quasistability estimate, as consequence, the existence of global and exponential attractors is proved. Finally, we investigate the upper and lower semicontinuity of global attractors under autonomous perturbations.

scholarly journals Ecophysiological, morphological, and biochemical traits of free-living Diplosphaera chodatii (Trebouxiophyceae) reveal adaptation to harsh environmental conditions

PROTOPLASMA ◽  
2021 ◽  
Author(s):  
Cynthia Medwed ◽  
Andreas Holzinger ◽  
Stefanie Hofer ◽  
Anja Hartmann ◽  
Dirk Michalik ◽  
...  
Keyword(s):  
Environmental Conditions ◽  
Botanical Garden ◽  
Tree Bark ◽  
Photon Flux ◽  
Low Light ◽  
Transmission Electron ◽  
Light Requirements ◽  
Adaptive Mechanisms ◽  
Terrestrial Habitats ◽  
Excellent Preservation

AbstractSingle-celled green algae within the Trebouxiophyceae (Chlorophyta) are typical components of terrestrial habitats, which often exhibit harsh environmental conditions for these microorganisms. This study provides a detailed overview of the ecophysiological, biochemical, and ultrastructural traits of an alga living on tree bark. The alga was isolated from a cypress tree in the Botanical Garden of Innsbruck (Austria) and identified by morphology and molecular phylogeny as Diplosphaera chodatii. Transmission electron microscopy after high-pressure freezing (HPF) showed an excellent preservation of the ultrastructure. The cell wall was bilayered with a smooth inner layer and an outer layer of polysaccharides with a fuzzy hair-like appearance that could possibly act as cell-cell adhesion mechanism and hence as a structural precursor supporting biofilm formation together with the mucilage observed occasionally. The photosynthetic-irradiance curves of D. chodatii indicated low light requirements without photoinhibition at high photon flux densities (1580 μmol photons m−2 s−1) supported by growth rate measurements. D. chodatii showed a high desiccation tolerance, as 85% of its initial value was recovered after controlled desiccation at a relative humidity of ~10%. The alga contained the low molecular weight carbohydrates sucrose and sorbitol, which probably act as protective compounds against desiccation. In addition, a new but chemically not elucidated mycosporine-like amino acid was detected with a molecular mass of 332 g mol−1 and an absorption maximum of 324 nm. The presented data provide various traits which contribute to a better understanding of the adaptive mechanisms of D. chodatii to terrestrial habitats.

Formation process of interface states at grain boundaries in sputtered polycrystalline Si films

1999 ◽  
Vol 14 (2) ◽  
pp. 371-376 ◽  
Author(s):  
Yoshitaka Nakano ◽  
Jiro Sakata ◽  
Yasunori Taga
Keyword(s):  
Energy Levels ◽  
Columnar Structure ◽  
Systematic Investigation ◽  
Defect States ◽  
Electron Microscopic ◽  
Thermally Induced ◽  
Transmission Electron ◽  
Transmission Electron Microscopic ◽  
Si Films ◽  
Induced Changes

A systematic investigation has been made on surface defect states of crystallites in the crystallization process of sputtered amorphous silicon films by isothermal annealing. Transmission electron microscopic observations indicate a pronounced vertical columnar structure in the upper part of the films, where the crystallization is delayed. Admittance spectroscopy reveals that two newly generated energy levels with the crystallization are attributed to the crystallites in the lower and upper parts of the films in view of the anisotropic crystallization. These thermally induced changes can be well explained by Si–Si shearing modes at the interfaces of crystallites through the process of crystallization.

Carbon Supported Pt+Os Catalysts for Methanol Oxidation

2002 ◽  
Vol 57 (2) ◽  
pp. 193-201 ◽  
Author(s):  
Gülsün Gökağaç ◽  
Brendan J. Kennedy
Keyword(s):  
Methanol Oxidation ◽  
Photoelectron Spectroscopy ◽  
Surface Composition ◽  
Carbon Support ◽  
Methanol Oxidation Reaction ◽  
X Ray Diffraction ◽  
X Ray ◽  
Transmission Electron ◽  
Metal Metal ◽  
Metal Support

11% Pt/C, 10% Pt + 1%Os/C, 9% Pt + 2%Os/C, 8% Pt + 3%Os/C, 7% Pt + 4%Os/C, 6% Pt + 5%Os/C and 5%Pt + 6% Os/C catalysts have been prepared for methanol oxidation reaction. Transmission electron microscopy, X-ray photoelectron spectroscopy, X-ray diffraction and cyclic voltammetry have been used to understand the nature of the species present in these catalysts. 7% Pt + 4% Os/C was the most active catalyst, while 8% Pt + 3% Os/C was the least active one. It is found that the metal particle size and distribution on the carbon support, the surface composition and the oxidation states of the metal particles, the metal-metal and metal support interactions are important parameters to define the activity of the catalyst.

scholarly journals Default Mode Network Maturation and Environmental Adversities During Childhood

2018 ◽  
Vol 2 ◽  
pp. 247054701880829 ◽  
Author(s):  
Keila Rebello ◽  
Luciana M. Moura ◽  
Walter H. L. Pinaya ◽  
Luis A. Rohde ◽  
João R. Sato
Keyword(s):  
Default Mode Network ◽  
Environmental Conditions ◽  
Development Patterns ◽  
Default Mode ◽  
Functional Studies ◽  
Open Questions ◽  
Special Challenge ◽  
Brain Changes ◽  
Adverse Environmental Conditions ◽  
Atypical Development

Default mode network (DMN) plays a central role in cognition and brain disorders. It has been shown that adverse environmental conditions impact neurodevelopment, but how these conditions impact in DMN maturation is still poorly understood. This article reviews representative neuroimaging functional studies addressing the interactions between DMN development and environmental factors, focusing on early life adversities, a critical period for brain changes. Studies focused on this period of life offer a special challenge: to disentangle the neurodevelopmental connectivity changes from those related to environmental conditions. We first summarized the literature on DMN maturation, providing an overview of both typical and atypical development patterns in childhood and early adolescence. Afterward, we focused on DMN changes associated with chronic exposure to environmental adversities during childhood. This summary suggests that changes in DMN development could be a potential allostatic neural feature associated with an embodiment of environmental circumstances. Finally, we discuss about some key methodological issues that should be considered in paradigms addressing environmental adversities and open questions for future investigations.

Numerical and Experimental Tools for Offshore DP Operations

2011 ◽  
Author(s):  
Fabiano P. Rampazzo ◽  
Joa˜o Luis B. Silva ◽  
Daniel P. Vieira ◽  
Antonio L. Pacifico ◽  
Lazaro Moratelli Junior ◽  
...  
Keyword(s):  
Environmental Conditions ◽  
Experimental Tests ◽  
Coupled System ◽  
Coupled Analysis ◽  
Cfd Analysis ◽  
Maximum Condition ◽  
Commercial Code ◽  
Close Proximity ◽  
Fully Coupled ◽  
Two Bodies

DP crane vessel operation can be analyzed based on the uncoupled system or considering the fully coupled system. Parameters such as top-crane acceleration, thruster capability and vessel motions are evaluated for several environmental conditions. Numerical and experimental tools are used and the important result of this analysis is the maximum condition in such that the operation can be safely executed. Those operations are critical, since the vessel is kept in close proximity with other unit and large loads are transported in a pendulum configuration. A precise positioning of the crane-vessel is required, in order to avoid unsafe relative motions, as well as keep the load being transported on a stable position. The uncoupled analysis approach does not consider the influence of the other unit in the crane vessel. This paper presents a methodology for evaluating a DP crane vessel in the offshore operations (DP crane vessel, load being transported, mooring and assistance lines, platform) considering the fully coupled method based on integration of the in house codes with the commercial code WAMIT® system. The methodology is based on the integration of numerical and experimental tools. The dimensions of the transported modules and the proximity of the vessels change the behavior of the vessel motions and line tensions. So, a full nonlinear time domain simulator (TPN – Numerical Offshore Tank) is used to perform the coupled analysis of the system subjected to several environmental conditions, considering also the dynamics of the suspended load and the hydrodynamic interference between the bodies. In order to calibrate the numerical model, several experimental tests are performed such as wind tests with some positions of the crane, tests in towing tanks to evaluated the current effects, thrusters tests to calibrate DP algorithm and wave test with the two bodies. In some cases a complementary CFD analysis is requested in order to evaluate the current and wind shadow effect. Several alternative relative positions between the vessels can be evaluated. This methodology results a more accurate estimative of the system performance.

Single-mode AlGaAs-GaAs lasers using lateral confinement by native-oxide layers

1998 ◽  
Vol 10 (4) ◽  
pp. 498-500 ◽  
Author(s):  
J. Heerlein ◽  
M. Grabherr ◽  
R. Jager ◽  
P. Unger
Keyword(s):  
Single Mode ◽  
Native Oxide ◽  
Oxide Layers ◽  
Lateral Confinement

A Thermodynamic Model for Nearest-Neighbor Distributions in Annealed Quaternary Alloys

2011 ◽  
Vol 383-390 ◽  
pp. 768-773
Author(s):  
Li Li Tang ◽  
Chun Bo Wang
Keyword(s):  
Nearest Neighbor ◽  
Blue Shift ◽  
Type Conversion ◽  
Quaternary Alloys ◽  
Separation Result ◽  
Atomic Relaxation ◽  
Long Time ◽  
Higher Temperature ◽  
Induced Changes ◽  
Short Time

We focus on the annealing-induced changes of N-centered nearest-neighbor (NN) entironment in Ga1-xlnxNyAs1-y quaternary alloys and present a statistical distributing model of the binary bonds under thermodynamics equilibrium state. The core of this model is the assumption that the phase separation result of equimolar system at T=0 K is “ + ”, in which the effect of strain has been ignored. We propose two mechanisms for annealing: (i) Atomic relaxation lead to a total energy minimum. (ii) The type conversion of bond configuration is the main reason for the remarkable blue shift. Then parameter r, the number of NN In atoms per N atom, is calculated. We find that the theoretical NN distributions strain is in good agreement with former studies. It can be concluded that the blue shift induced by long-time annealing at low temperature is able to be equal with that induced by short-time annealing at higher temperature. The results are close to recent investigations. But an allegorical linear relation between band gap and composition (x, y) is still in question.

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