scholarly journals Incident-angle dependent operando XAS cell design: investigation of the electrochemical cells under operating conditions at various incidence angles

RSC Advances ◽  
2021 ◽  
Vol 11 (12) ◽  
pp. 6456-6463
Author(s):  
Seval Gunduz ◽  
Dhruba J. Deka ◽  
Jaesung Kim ◽  
Michael Wilson ◽  
Mark Warren ◽  
...  
Keyword(s):  
Oxidation State ◽  
Incident Angle ◽  
Operating Conditions ◽  
Time Dependent ◽  
Electrochemical Cells ◽  
Cell Design ◽  
Working Electrode ◽  
Electrode Interface ◽  
Operando Xas

Bias and time-dependent changes in the oxidation state and the atomic environment of the atoms of a working electrode occur on the gas/electrode interface.

Simplified Method for Time-Dependent Reliability Analysis of Aging Bridges Subjected to Nonstationary Loads

2016 ◽  
Vol 23 (01) ◽  
pp. 1650003
Author(s):  
Cao Wang ◽  
Quanwang Li
Keyword(s):  
Structural Reliability ◽  
Operating Conditions ◽  
Time Dependent ◽  
Structural Resistance ◽  
Simplified Method ◽  
Increasing Trend ◽  
Live Loads ◽  
Load Intensity ◽  
Existing Bridges ◽  
Dimensional Integral

The performance of existing bridges may deteriorate in time due to aggressive environmental or operating conditions in service, which may eventually cause changes in structural resistance and reliability beyond the baseline assumed for new ones. In addition, the increasing trend of live loads applied to the bridges, which has been reported in many researches, also contributes to the reduction of structural reliability. In order to perform time-dependent reliability assessment for aging bridges subjected to nonstationary loading process with improved efficiency, a simplified method is proposed in this paper, where lower dimensional integral is involved in the calculation of reliability. With the proposed method, time-dependent reliability of a real aging RC bridge is conducted, and the effect of nonstationarity in load intensity on structural reliability is investigated. It is found that structural reliability is sensitive to the increase of load intensity, and is less sensitive to the varying mechanism of load intensity.

scholarly journals Flow Cell for Operando X-Ray Photon-in-Photon-out Studies on Photo-Electrochemical Thin Film Devices

2020 ◽  
Author(s):  
Philipp Jäker ◽  
Dino Aegerter ◽  
Till Kyburz ◽  
Roman Staedler ◽  
Rea Fonjallaz ◽  
...  
Keyword(s):  
Thin Film ◽  
Water Oxidation ◽  
High Energy ◽  
Operating Conditions ◽  
High Energy Resolution ◽  
X Ray ◽  
Long Term Stability ◽  
Operando Xas ◽  
Artificial Photosynthetic ◽  
Thin Film Devices

Photo-electro-chemical (PEC) water splitting represents a promising technology towards an artificial photosynthetic device but many fundamental electronic processes, which govern long-term stability and energetics are not well understood. X-ray absorption spectroscopy (XAS), particularly its high energy resolution fluorescence-detected (HERFD) mode, emerges as a powerful tool to study photo-excited charge carrier behavior under operating conditions. The established thin film device architecture of PEC cells provides a well-defined measurement geometry, but it puts many constraints on conducting operando XAS experiments. So far, operando cells have not been developed that enable to concurrently measure highly intense X-ray fluorescence and photo-electro-chemical current without experimental artifacts caused by O<sub>2</sub> and H<sub>2</sub> bubbles formation. Moreover, we are missing a standardized thin film exchange procedure. Here, we address and overcome the instrumental limitations for operando HERFD-XAS to investigate photo- and electrochemical thin film devices. Our cell establishes a measurement routine that will provide experimental access to a broader scientific community, particularly due to the ease of sample exchange. Our operando photo-electro-chemical cell is optimized for the HERFD-XAS geometry and we demonstrate its operation by collecting high-resolution Fe K-edge spectra of hematite (α-Fe<sub>2</sub>O<sub>3</sub>) and ferrite thin film (MFe<sub>2</sub>O<sub>4</sub>, M= Zn, Ni) photoelectrodes during water oxidation.<br>

scholarly journals A phase-space beam position monitor for synchrotron radiation

2015 ◽  
Vol 22 (4) ◽  
pp. 946-955 ◽  
Author(s):  
Nazanin Samadi ◽  
Bassey Bassey ◽  
Mercedes Martinson ◽  
George Belev ◽  
Les Dallin ◽  
...  
Keyword(s):  
Phase Space ◽  
Synchrotron Radiation ◽  
Incident Angle ◽  
Operating Conditions ◽  
Photon Beam ◽  
Profile Measurement ◽  
Beam Position Monitor ◽  
Position Measurement ◽  
Beam Position ◽  
X Ray

The stability of the photon beam position on synchrotron beamlines is critical for most if not all synchrotron radiation experiments. The position of the beam at the experiment or optical element location is set by the position and angle of the electron beam source as it traverses the magnetic field of the bend-magnet or insertion device. Thus an ideal photon beam monitor would be able to simultaneously measure the photon beam's position and angle, and thus infer the electron beam's position in phase space. X-ray diffraction is commonly used to prepare monochromatic beams on X-ray beamlines usually in the form of a double-crystal monochromator. Diffraction couples the photon wavelength or energy to the incident angle on the lattice planes within the crystal. The beam from such a monochromator will contain a spread of energies due to the vertical divergence of the photon beam from the source. This range of energies can easily cover the absorption edge of a filter element such as iodine at 33.17 keV. A vertical profile measurement of the photon beam footprint with and without the filter can be used to determine the vertical centroid position and angle of the photon beam. In the measurements described here an imaging detector is used to measure these vertical profiles with an iodine filter that horizontally covers part of the monochromatic beam. The goal was to investigate the use of a combined monochromator, filter and detector as a phase-space beam position monitor. The system was tested for sensitivity to position and angle under a number of synchrotron operating conditions, such as normal operations and special operating modes where the photon beam is intentionally altered in position and angle at the source point. The results are comparable with other methods of beam position measurement and indicate that such a system is feasible in situations where part of the synchrotron beam can be used for the phase-space measurement.

Numerical Calculation of Pressure Fluctuations in the Volute of a Centrifugal Fan

2005 ◽  
Vol 128 (2) ◽  
pp. 359-369 ◽  
Author(s):  
Rafael Ballesteros-Tajadura ◽  
Sandra Velarde-Suárez ◽  
Juan Pablo Hurtado-Cruz ◽  
Carlos Santolaria-Morros
Keyword(s):  
Fluid Dynamics ◽  
Pressure Fluctuations ◽  
Three Dimensional ◽  
Power Spectra ◽  
Operating Conditions ◽  
Experimental Results ◽  
Time Dependent ◽  
Centrifugal Fan ◽  
Wall Pressure Fluctuations ◽  
Good Agreement

In this work, a numerical model has been applied in order to obtain the wall pressure fluctuations at the volute of an industrial centrifugal fan. The numerical results have been compared to experimental results obtained in the same machine. A three-dimensional numerical simulation of the complete unsteady flow on the whole impeller-volute configuration has been carried out using the computational fluid dynamics code FLUENT®. This code has been employed to calculate the time-dependent pressure both in the impeller and in the volute. In this way, the pressure fluctuations in some locations over the volute wall have been obtained. The power spectra of these fluctuations have been obtained, showing an important peak at the blade passing frequency. The amplitude of this peak presents the highest values near the volute tongue, but the spatial pattern over the volute extension is different depending on the operating conditions. A good agreement has been found between the numerical and the experimental results.

Preliminary Analysis of Compressor System Designed for Cyclical Operation

2015 ◽  
Author(s):  
Viktor Kilchyk ◽  
Ozhan H. Turgut ◽  
Ahmed Abdelwahab
Keyword(s):  
Boundary Conditions ◽  
Preliminary Analysis ◽  
Operating Conditions ◽  
Time Dependent ◽  
System Model ◽  
Lumped Parameter ◽  
Compressor Performance ◽  
Specific Speed ◽  
Cycle Efficiency ◽  
Effective Design

Conventional methods of the compressor performance analysis do not allow effective design matching to the specific operating conditions of cyclical or unsteady operated machines. Under dynamic loading the actual compressor performance often departs from the best efficiency region reducing its cycle efficiency. This departure may be caused by a number of reasons such as non-controlled deceleration, speed or torque constraints, and rapid boundary conditions variation caused by the cycle operation. In order to analyze this influence of cycle dynamics on compressor performance a modified lumped-parameter compressor-system model was applied. The model included time-dependent boundary conditions, effects of flow compressibility, motor and compressor inertia, and was combined with compressor speed control. The study was performed within the system constrains, e.g. surge avoidance, maximum motor torque and impeller speed. Results of the developed analysis showed that in the presence of rapidly changing boundary conditions the average cycle efficiency is strongly affected by the design specific speed of the compressor.

Load Control–Strain Control Isochronous Stress–Strain Curves for High Temperature Nonlinear Analysis

1995 ◽  
Vol 117 (2) ◽  
pp. 364-370 ◽  
Author(s):  
G. S. Bechtel ◽  
T. S. Cook
Keyword(s):  
Rupture Life ◽  
Nonlinear Behavior ◽  
General Purpose ◽  
Operating Conditions ◽  
Time Dependent ◽  
Load Control ◽  
New Techniques ◽  
Time Stepping ◽  
The Past ◽  
Computer Resources

Aircraft gas turbine components are subjected to severe operating conditions. High temperatures, large thermal strains, and mechanical loads combine to cause the material to undergo significant nonlinear behavior. In order to assure safe, durable components, it is necessary that analysis methods be available to predict the nonlinear deformation. General purpose finite element codes are available to perform elastic and viscoplastic analyses, but the analyses are expensive. Both large plastic and creep strain analyses can require significant computer resources, but typically a plastic solution is more economical to run than a time-stepping creep or viscoplastic model solution. For those applications where the deformation is principally time dependent, it is advantageous to include time-dependent creep effects in a “constant time” or “isochronous” analysis. Although this approach has been used in the past to estimate rupture life, this paper will present several significant new techniques for doing an isochronous analysis to analyze time-dependent deformation.

A Simulation-Based Random Process Method for Time-Dependent Reliability of Dynamic Systems

2010 ◽  
Author(s):  
Amandeep Singh ◽  
Zissimos P. Mourelatos ◽  
Efstratios Nikolaidis
Keyword(s):  
Random Process ◽  
Operating Conditions ◽  
Time Dependent ◽  
Process Time ◽  
Cumulative Probability ◽  
Repairable Systems ◽  
First Passage ◽  
True Value ◽  
Warranty Costs ◽  
Short Time

Reliability is an important engineering requirement for consistently delivering acceptable product performance through time. As time progresses, a product may fail due to time-dependent operating conditions and material properties, and component degradation. The reliability degradation with time may significantly increase the lifecycle cost due to potential warranty costs, repairs and loss of market share. In this work, we consider the first-passage reliability, which accounts for the first time failure of non-repairable systems. Methods are available that provide an upper bound to the true reliability, but they may overestimate the true value considerably. This paper proposes a methodology to calculate the cumulative probability of failure (probability of first passage or upcrossing) of a dynamic system with random properties, driven by an ergodic input random process. Time series modeling is used to characterize the input random process based on data from a “short” time period (e.g. seconds) from only one sample function of the random process. Sample functions of the output random process are calculated for the same “short” time because it is usually impractical to perform the calculation for a “long” duration (e.g. hours). The proposed methodology calculates the time-dependent reliability, at a “long” time using an accurate “extrapolation” procedure of the failure rate. A representative example of a quarter car model subjected to a stochastic road excitation demonstrates the improved accuracy of the proposed method compared with available methods.

scholarly journals Flow Cell for Operando X-Ray Photon-in-Photon-out Studies on Photo-Electrochemical Thin Film Devices

2020 ◽  
Author(s):  
Philipp Jäker ◽  
Dino Aegerter ◽  
Till Kyburz ◽  
Roman Staedler ◽  
Rea Fonjallaz ◽  
...  
Keyword(s):  
Thin Film ◽  
Water Oxidation ◽  
High Energy ◽  
Operating Conditions ◽  
High Energy Resolution ◽  
X Ray ◽  
Long Term Stability ◽  
Operando Xas ◽  
Artificial Photosynthetic ◽  
Thin Film Devices

Photo-electro-chemical (PEC) water splitting represents a promising technology towards an artificial photosynthetic device but many fundamental electronic processes, which govern long-term stability and energetics are not well understood. X-ray absorption spectroscopy (XAS), particularly its high energy resolution fluorescence-detected (HERFD) mode, emerges as a powerful tool to study photo-excited charge carrier behavior under operating conditions. The established thin film device architecture of PEC cells provides a well-defined measurement geometry, but it puts many constraints on conducting operando XAS experiments. So far, operando cells have not been developed that enable to concurrently measure highly intense X-ray fluorescence and photo-electro-chemical current without experimental artifacts caused by O<sub>2</sub> and H<sub>2</sub> bubbles formation. Moreover, we are missing a standardized thin film exchange procedure. Here, we address and overcome the instrumental limitations for operando HERFD-XAS to investigate photo- and electrochemical thin film devices. Our cell establishes a measurement routine that will provide experimental access to a broader scientific community, particularly due to the ease of sample exchange. Our operando photo-electro-chemical cell is optimized for the HERFD-XAS geometry and we demonstrate its operation by collecting high-resolution Fe K-edge spectra of hematite (α-Fe<sub>2</sub>O<sub>3</sub>) and ferrite thin film (MFe<sub>2</sub>O<sub>4</sub>, M= Zn, Ni) photoelectrodes during water oxidation.<br>

scholarly journals Operando XAS of a Bifunctional Gas Diffusion Electrode for Zn-Air Batteries under Realistic Application Conditions

2021 ◽  
Vol 11 (24) ◽  
pp. 11672
Author(s):  
Emanuele Marini ◽  
Danilo Oliveira De Souza ◽  
Giuliana Aquilanti ◽  
Michael Liebert ◽  
Francesca Rossi ◽  
...  
Keyword(s):  
Signal To Noise Ratio ◽  
Gas Diffusion ◽  
Gas Diffusion Electrode ◽  
Operating Conditions ◽  
Critical Conditions ◽  
Oxygen Starvation ◽  
Current Densities ◽  
Operando Xas ◽  
Battery Discharge ◽  
X Ray Absorption

In this study, operando X-ray absorption spectroscopy (XAS) measurements were carried out on a newly developed O2 bi-functional gas diffusion electrode (GDE) for rechargeable Zn-air batteries, consisting of a mixture of α-MnO2 and carbon black. The architecture and composition of the GDE, as well as the electrochemical cell, were designed to achieve optimum edge-jumps and signal-to-noise ratio in the absorption spectra for the Mn K-edge at current densities that are relevant for practical conditions. Herein, we reported the chemical changes that occur on the MnO2 component when the GDE is tested under normal operating conditions, during both battery discharge (ORR) and charge (OER), on the background of more critical conditions that simulate oxygen starvation in a flooded electrode.

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