scholarly journals Performance Degradations of MISFET-Based Hydrogen Sensors with a Pd-Ta2O5-SiO2-Si Structure During Long-Term Operation

Sensors ◽  
2019 ◽  
Vol 19 (8) ◽  
pp. 1855 ◽  
Author(s):  
Boris Podlepetsky ◽  
Nikolay Samotaev ◽  
Marina Nikiforova ◽  
Andrew Kovalenko
Keyword(s):  
Feedback Loop ◽  
Gas Analysis ◽  
Operating Conditions ◽  
Hydrogen Sensors ◽  
Term Operation ◽  
Special Measuring ◽  
Conventional Technology ◽  
Effect Transistor ◽  
Two Stages

We present the generalized experimental results of performance degradation of hydrogen sensors based on metal-insulator-semiconductor field effect transistor (MISFET)with the structure Pd-Ta2O5-SiO2-Si. The n-channel MISFET elements were fabricated on silicon single chips together with temperature sensors and heater-resistors by means of conventional -technology. Two hundred cycles of responses to different hydrogen concentrations were measured during eight weeks using special measuring and temperature stabilization circuitries with a feedback loop based on the chip’s thermo-sensor and heater. We show how the response parameters change during long-term tests of sensors under repeated hydrogen impacts. There were two stages of time-dependent response instability, the degradation of which depends on operating conditions, hydrogen concentrations, and time. To interpret results, we proposed the models, parameters of which were calculated using experimental data. These models can be used to predict performances of MISFET-based gas analysis devices for long-term operation.

scholarly journals Performance Degradations of MISFET-Based Hydrogen Sensors with Pd-Ta2O5-SiO2-Si Structure at Long-Time Operation

Proceedings ◽  
2018 ◽  
Vol 2 (13) ◽  
pp. 777 ◽  
Author(s):  
Boris Podlepetsky ◽  
Marina Nikiforova ◽  
Andrew Kovalenko
Keyword(s):  
Experimental Data ◽  
Time Dependence ◽  
Performance Degradation ◽  
Operating Conditions ◽  
Hydrogen Sensors ◽  
Time Operation ◽  
Long Time ◽  
Degradation Degree ◽  
Two Stages

There are presented the generalized results of studies of performance degradation of hydrogen sensors based on MISFET with structure Pd-Ta2O5-SiO2-Si. It was shown how responses’ parameters change during long-term tests of sensors under repeated hydrogen impacts. There were found two stages of time-dependence response’ instability, the degradation degree of which depends on operating conditions, hydrogen concentrations and time. To interpret results there were proposed the models, parameters of which were calculated using experimental data. These models can be used to predict performances of MISFET-based devices for long-time operation.

Investigation of long-term operation and biomass activity in a membrane bioreactor system

2011 ◽  
Vol 63 (9) ◽  
pp. 1906-1912 ◽  
Author(s):  
Simos Malamis ◽  
Andreas Andreadakis ◽  
Daniel Mamais ◽  
Constantinos Noutsopoulos
Keyword(s):  
Membrane Fouling ◽  
Membrane Bioreactor ◽  
Extracellular Polymeric Substances ◽  
Operating Conditions ◽  
Term Operation ◽  
Solids Retention ◽  
Biomass Activity ◽  
Long Term Performance ◽  
Term Performance

The aim of this work was to evaluate the long-term performance of a Membrane Bioreactor (MBR) that operated continuously for 2.5 years and to assess membrane fouling and biomass activity under various operating conditions. Furthermore, a method for the characterisation of influent wastewater was developed based on its separation into various fractions. The MBR system operated at the solids retention times (SRT) of 10, 15, 20 and 33 days. The increase of SRT resulted in a decrease of the fouling rate associated with the reduction of extracellular polymeric substances. Moreover, the SRT increase resulted in a significant reduction of the Oxygen Uptake Rate (OUR) due to the lower availability of substrate and in a notable decrease of the maximum OUR since high SRT allowed the development of slower growing microorganisms. Biomass consisted of small flocs due to extensive deflocculation caused by intense aeration. Finally, the method developed for wastewater characterisation is straightforward and less time consuming than the usual method that is employed.

Fatigue Cracking Processes of a Thick-Walled Component of a Chemical Pipeline

2013 ◽  
Vol 586 ◽  
pp. 104-107 ◽  
Author(s):  
Marek Cieśla ◽  
Kazimierz Mutwil
Keyword(s):  
Mechanical Properties ◽  
Degradation Mechanism ◽  
Fatigue Cracking ◽  
Operating Conditions ◽  
Material Structure ◽  
Mechanical Loads ◽  
Factors Affecting ◽  
Term Operation ◽  
Materials Used

At present, there are no generally accepted and widely recognized procedures to determine condition of material of devices subject to complex long-term thermo-mechanical loads. Condition of pipeline material usually changes when subjected to the conditions of long-term operation. Its structure changes and, consequently, so do its mechanical properties, including fatigue characteristics and crack resistance. Therefore, the durability of a component operating under thermal and mechanical loads cannot be discussed separately from its current material properties. This applies in particular to changes that take place in the material micro-structure and to their connection with mechanical properties. This paper covers analyses of stress in the material of a selected pipeline component – pipe tee that is used in chemical plants. Thermo-mechanical interactions determining stress distribution in the component have been taken into account in the calculations. Morphology and location of the cracks indicated that a fatigue-like nature of impacts was the cause of material destruction. Loads of this type occur mainly in conditions of start-up and shut-down. For these reasons, condition of the material in the above-mentioned unstable conditions was subjected to numerical stress analysis. Due to geometric complexity of the pipeline, the distribution of stress in the T-pipe was calculated in two stages: the object was modeled from a global and local perspective. The resulting stress distributions helped to determine factors affecting durability of the tested object. Metallurgy tests were also conducted in order to ascertain factors determining the degradation of material structure and processes of crack formation and development. As a result of research one ascertained that the process of T-pipe cracking under operating conditions was a combined effect of thermo-mechanical and chemical actions determined by the course of intercrystalline corrosion. Synergic interaction of corrosion processes and variable thermal and mechanical loads caused nucleation and propagation of cracks. The crack systems in T-pipe areas subject to the highest stress showed courses characteristic for thermal fatigue of material. The results obtained will identify degradation mechanism of materials used in chemical installations.

Effect of Time and Temperature on TBC Failure Mode Under Oxidizing Environment

2008 ◽  
Author(s):  
N. S. Cheruvu ◽  
K. S. Chan ◽  
D. W. Gandy
Keyword(s):  
Failure Mode ◽  
Bond Coat ◽  
Turbine Blades ◽  
Thermally Grown Oxide ◽  
Isothermal Exposure ◽  
Term Operation ◽  
Long Term Stability ◽  
Two Stages ◽  
Failure Location

Thermal barrier coatings (TBC) have been recently introduced on hot section components; such as transition pieces and first two stages of turbine blades and vanes of advanced F, G, and H class land-based turbine engines. The TBC coating is typically applied on metallic coated components. The metallic bond coat provides oxidation and/or corrosion protection. It is generally believed that the primary failure mode of TBCs is delamination and fracture of the top ceramic coating parallel to the bond coat in the proximity of the thermally grown oxide (TGO) between the coatings. One of the concerns associated with the use of a TBC as a prime reliant coating is its long-term stability. The effect of long-term operation at typical land based turbine operating temperatures below 1010°C (1850°F) on the failure mode of TBCs is unknown. Long-term isothermal tests were conducted on the TBC coated specimens at three temperatures, 1010°C (1850°F), 1038°C (1900°F), and 1066°C (1950°F) to determine the effects of long term exposure on the TBC failure location (mode). Following isothermal testing, the samples were destructively examined to characterize the degradation of TBC and determine the extent of TGO cracking, TGO growth, bond coat oxidation, and TBC failure location after long term exposure for up to 18000 hours. Optical microscopy and scanning electron microscope (SEM) attached with an energy dispersive spectroscopy (EDS) system were used to study the degradation of the TBC and bond coatings. The results showed that long term isothermal exposure leads to a change in the TBC failure mode from delamination of TBC at the TGO/TBC interface to internal oxidation of the bond coat and the bond coat delamination. In this paper, the effect of long-term exposure on delamination of TBC and bond coat failure mode is discussed.

Extensive Dynamic Analyses to Achieve Stringent Noise and Vibration Levels for an Offshore Reciprocating Compressor System

2011 ◽  
Author(s):  
Andre´ Eijk ◽  
Hans Elferink
Keyword(s):  
Operating Conditions ◽  
Reciprocating Compressor ◽  
Gas Well ◽  
Noise And Vibration ◽  
Term Operation ◽  
The North ◽  
Final Design ◽  
The North Sea ◽  
System Requirements

During the lifetime of an existing gas well, located in the D15FA/FB field in the North Sea, the pressure has dropped and consequently production is reduced. A depletion compressor had to be added to this existing platform to increase the production. This sounds easy but has been very challenging due to physical, noise and vibration restrictions. For this platform it appeared that a reciprocating compressor was the best choice based on its flexibility with respect to the specified operating conditions, available power, and efficiency. However, despite of several advantages a disadvantage of a reciprocating compressor is that it generates additional vibrations and noise in the living quarters, which are located close to the compressor system. The specified requirements, not to exceed the allowable noise limits in the living quarters and the vibration limits of the complete compressor system, could in this specific case, not be met with straightforward solutions. This presentation will explain the dynamic analysis and the efforts taken in compressor, skid, motor, piping and deck design to meet the very stringent specified requirements and to ensure a safe and reliable system for the long term operation. Special attention will be given to the measures taken to reduce the excitations acting on the platform, and the mechanical and acoustical analysis that have led to the final design of this reciprocating compressor system. The solutions that have been developed can be regarded as non-standard and have resulted in new directions in solving very demanding system requirements.

scholarly journals Rail Track with Rail Compression

2021 ◽  
Vol 20 (3) ◽  
pp. 234-242
Author(s):  
V. N. Sukhodoev
Keyword(s):  
Effective Property ◽  
Operating Conditions ◽  
Design Parameters ◽  
Labor Costs ◽  
Term Operation ◽  
Rail Track ◽  
Loading And Unloading ◽  
The Stability ◽  
The Cost

The problem of damping the noise on the track, arising from the movement of the train, is solved sufficiently but it is simple, if the rail with spacers is laid inside the longitudinally located band sleeper-mechanism. The result is a layered rail thread, consisting of belts: a rail tape with elastic spacers on three sides, a tie-mechanism tape and a ballast layer. The unity of the layers is carried out due to their own mass. This is the static track without external load. Rail compression is an effective property of rail tracks. It is formed in the sleeper mechanism under the influence of vertical forces with displacements and their horizontal derivatives. When loading the track, the compression is carried out repeatedly with subsequent unloading.n this case, each previous changes in the conditions in work of the track are taken into account in the subsequent cycle of loading and unloading. A rail track with a rail compression is a kind of self-adapting linear system, which is necessary with frequent changes in load and operating conditions for silent performance of a functional purpose. The specificity of this path is that the movement of the wheel creates rail vibration and noise, which are immediately damped by compression with damping. The balance between the occurrence of noise and its suppression is achieved by the ratio of the lengths of half-sleeper shoulders as a lever. The condition for the appearance of a shift of the compression forces in the direction from vertical shoulder of the half-sleepers is the unequal settlements of the horizontal shoulder of the L-shaped half-sleepers and its eccentric loading. As a result of the research, the advantages of a rail track with rail compression have been revealed, which is a guarantor of the stability of the design parameters during long-term operation of the track. The cost of a rail track with rail reduction is halved as a result of steel savings, lower labor costs and operational needs.

Long-Term Degradation-Based Modeling and Optimization Framework

2018 ◽  
pp. 192-220
Author(s):  
Tarannom Parhizkar
Keyword(s):  
Energy Systems ◽  
Optimization Procedure ◽  
Energy System ◽  
Operating Conditions ◽  
Energy Prices ◽  
Ambient Conditions ◽  
Term Operation ◽  
Optimization Framework ◽  
Degradation Models

Energy systems degrade during long-term operation. Thus, performance profile of the system deteriorates over time. To optimize energy system parameters more reliably and accurately, it is necessary to consider degradation models of the system in the optimization procedure. In this chapter, a novel degradation-based optimization framework is proposed. This framework optimizes design and operation parameters of energy systems while accounting for the degradation effects on system performance. Therefore, this framework is beneficial for long-term analysis and optimization of energy systems. Validity and usefulness of the proposed methodology are demonstrated by optimizing the operating conditions and maintenance intervals of a gas turbine power plant, under different seasonal ambient conditions and energy prices. The case study results effectively meet all the positive expectations that are placed on the proposed degradation-based optimization framework.

Management of PWR Steam Generator Tube Plugging and Primary Flow-Rate Predictions

2011 ◽  
Author(s):  
Olivier Brunin
Keyword(s):  
Steam Generator ◽  
Flow Rate ◽  
Exchange Capacity ◽  
Operating Conditions ◽  
Steam Generators ◽  
Primary Flow ◽  
The Real ◽  
Term Operation ◽  
Tube Plugging

The tubes of PWR steam generators are part of the second barrier between the nuclear fuel and the environment. The integrity in operation of the tubes is addressed with Non Destructive Examinations (NDE) and flaw allowances criteria. If a tube does not match the criteria, it is plugged. As a consequence, the steam generators tube plugging (SGTP) may increase during the maintenance outages. This increase has to be managed properly because it basically affects the heat exchange capacity of the Nuclear Steam Supply System (NSSS). This can be managed by performing long-term predictions in order to prepare in advance the possibility of steam generator replacements. But this “long-term operation” management is to be completed with an intermediate term management considering the real operating conditions of the NSSS. Intermediate term predictions, based on a simulation of the mechanisms leading to the degradation of the tubes, are annually compared with the evolution of real NDE and real SGTP. These predictions are completed with the set-up of a model, for each Reactor Coolant System (RCS), considering the relation between the average SGTP and the primary flow-rate. The predictions are used to check that the real operating conditions of each NSSS can be matched with an existing safety file.

scholarly journals Effect of Additives Ag and Rare‐Earth Elements Y and Sc on the Properties of Hydrogen Sensors Based on Thin SnO2 Films during Long‐Term Testing

Coatings ◽  
2019 ◽  
Vol 9 (7) ◽  
pp. 423 ◽  
Author(s):  
Maksimova ◽  
Almaev ◽  
Sevastyanov ◽  
Potekaev ◽  
Chernikov ◽  
...  
Keyword(s):  
Tin Dioxide ◽  
Oxygen Adsorption ◽  
Hydrogen Sensors ◽  
Band Bending ◽  
Term Operation ◽  
Adsorption Sites ◽  
Effect Of Additives ◽  
Clean Air ◽  
The Stability

The paper presents the results of an investigation of the nanostructure, elements, and phase composition of thin (100–140 nm) tin dioxide films obtained via magnetron sputtering and containing Ag, Y, Sc, Ag + Y, and Ag + Sc additives in the volume. Electrical and gas‐sensitive characteristics of hydrogen sensors based on these films with dispersed Pt/Pd layers deposited on the surface were studied. The additives had a significant effect on the nanostructure of the films, the density of oxygen adsorption sites on the surface of tin dioxide, the band bending at the grain boundaries of tin dioxide, the resistance values in pure air, and the responses to hydrogen in the concentration range of 50–2000 ppm. During the long‐term tests of most of the samples studied, there was an increase in the resistance of the sensors in clean air and in the response to hydrogen. It has been established that the joint introduction of Ag + Y into the volume of films prevents the increase in the resistance and response. For these sensors based on thin films of Pt/Pd/SnO2:Sb, Ag, Y the responses to 100 and 1000 ppm of H2 are 25 and 575, correspondingly, the response time at exposure to 100 and 1000 ppm of H2 are 10 and 90 s, the recovery time at exposure to 100 and 1000 ppm of H2 17 and 125 s. Possible mechanisms of the effect of additives on the properties of sensors and the stability of their parameters during long‐term operation were considered.

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