scholarly journals Methane Combustion Using Pd Deposited on CeOx-MnOx/La-Al2O3 Pellistors

Materials ◽  
2020 ◽  
Vol 13 (21) ◽  
pp. 4888
Author(s):  
Ovidiu G. Florea ◽  
Adelina Stănoiu ◽  
Marin Gheorghe ◽  
Cornel Cobianu ◽  
Florentina Neaţu ◽  
...  
Keyword(s):  
Surface Reaction ◽  
Wheatstone Bridge ◽  
Methane Combustion ◽  
Sensitive Material ◽  
Voltage Signal ◽  
Coating Method ◽  
Diffusion Phenomena ◽  
Selective Sensitivity ◽  
And Diffusion ◽  
Operating Temperature Range

Pd deposited on CeOx-MnOx/La-Al2O3 has been prepared as a sensitive material for methane (CH4) detection. The effect of different amounts (1.25%, 2.5% and 5%) of Pd loading has been investigated. The as prepared materials were deposited on Pt microcoils using a drop-coating method, as a way of developing pellistors operated using a Wheatstone bridge configuration. By spanning the operating temperature range between 300 °C and 550 °C, we established the linearity region as well as the maximum sensitivity towards 4900 ppm of CH4. By making use of the sigmoid dependence of the output voltage signal from the Wheatstone bridge, the gas surface reaction and diffusion phenomena have been decoupled. The pellistor with 5% Pd deposited on CeOx-MnOx/La-Al2O3 exhibited the highest selective-sensitivity in the benefit of CH4 detection against threshold limits of carbon monoxide (CO), sulfur dioxide (SO2) and hydrogen sulfide (H2S). Accordingly, adjusting the percent of Pd makes the preparation strategies of pellistors good candidates towards CH4 detection.

A Dynamic Voltage Compensation Method for Improving Weighing Accuracy

2013 ◽  
Vol 333-335 ◽  
pp. 317-321
Author(s):  
Rong Sen Yin ◽  
Jia Qiang Yang
Keyword(s):  
Measurement Error ◽  
Digital Signal Processor ◽  
Digital Signal ◽  
Wheatstone Bridge ◽  
External Source ◽  
Compensation Method ◽  
Voltage Fluctuation ◽  
Voltage Compensation ◽  
Voltage Signal ◽  
Dynamic Voltage

In order to eliminate the measurement error caused by working voltage fluctuation of weighing sensor, a dynamic voltage compensation method for improving the weighing accuracy was proposed in the paper. The method takes strain gauge type pressure sensor as the weighing sensor and corrects Wheatstone bridge circuit. By synchronously detecting output voltage signal and working voltage of the weighing sensor, the method dynamically compensates the working voltage fluctuation of the weighing sensor, corrects the measurement error caused by the voltage fluctuation of external source and calculates the weight in real time. A weighing system based on the digital signal processor (DSP) was designed. Results of simulation experiment verify the feasibility of the proposed method.

The geometry and motion of sharp fronts within geochemical transport problems

1995 ◽  
Vol 449 (1935) ◽  
pp. 123-138
Keyword(s):  
Front Propagation ◽  
Singular Perturbation Theory ◽  
Advective Transport ◽  
Natural Systems ◽  
Diffusion Phenomena ◽  
Sharp Fronts ◽  
Geochemical Transport ◽  
Transport Problems ◽  
Groundwater Flow Field ◽  
And Diffusion

We consider some reactive geochemical transport problems in groundwater sys­tems. When incoming fluid is in disequilibrium with the mineralogy, sharp tran­sition fronts may develop. We show that this is a generic property for a class of systems where the time scales associated with reaction and diffusion phenomena are much shorter than those associated with advective transport. Such multi­ple timescale problems are relevant to a variety of processes in natural systems: mathematically, methods of singular perturbation theory reduce the dimension of the problems to be solved locally. Furthermore, we consider how spatial heteroge­neous mineralogy can make an impact upon the propagation of sharp geochemical fronts. We develop an asymptotic approach in which we solve equations for the evolv­ing geometry of the front and indicate how the non-smooth perturbations, due to natural heterogeneity of the mineralogy on underlying groundwater flow field, are balanced against the smoothing effect of diffusion-dispersive processes. Fronts are curvature damped, and the results here indicate the generic nature of sepa­rate front propagation within both model (idealized) and natural (heterogeneous) geochemical systems.

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