Reasonable Experimental Error Research Articles

Experimental Evaluation of Fluid Connectivity in Two‐Phase Flow in Porous Media During Drainage

AbstractThis study aims to experimentally investigate the possibility of combining two extended continuum theories for two‐phase flow. One of these theories considers interfacial area as a separate state variable, and the other explicitly discriminates between connected and disconnected phases. This combination enhances our potential to effectively model the apparent hysteresis, which generally dominates two‐phase flow. Using optical microscopy, we perform microfluidic experiments in quasi‐2D artificial porous media for various cyclic displacement processes and boundary conditions. Specifically for a number of sequential drainage processes, with detailed image (post‐)processing, pore‐scale parameters such as the interfacial area between the phases (wetting, non‐wetting, and solid), and local capillary pressure, as well as macroscopic parameters like saturation, are estimated. We show that discriminating between connected and disconnected clusters and the concept of the interfacial area as a separate state variable can be an appropriate way of modeling hysteresis in a two‐phase flow scheme. The drainage datasets of capillary pressure, saturation, and specific interfacial area, are plotted as a surface, given by f (Pc, sw, awn) = 0. These surfaces accommodate all data points within a reasonable experimental error, irrespective of the boundary conditions, as long as the corresponding liquid is connected to its inlet. However, this concept also shows signs of reduced efficiency as a modeling approach in datasets gathered through combining experiments with higher volumetric fluxes. We attribute this observation to the effect of the porous medium geometry on the phase distribution. This yields further elaboration, in which this speculation is thoroughly studied and analyzed.

Development of the Crank’s diffusion model for the case of material-gas feedback regime in gas flow reactors. Advanced methodology of oxygen partial pressure relaxation for the kinetics of oxygen exchange in nonstoichiometric oxides

• The Crank model may give incorrect k and D in case of vigorous reaction. • Extended samples require consideration of convective and diffusion gas transfer. • Models taking into account these factors are developed in this study. In order to determine the kinetic parameters of oxygen exchange between nonstoichiometric oxides and the gas phase, the rate constant of surface exchange k and the coefficient of bulk oxygen diffusion in the oxide D , one needs to model the kinetics of relaxation occurring under mixed diffusion-reaction control. It is shown that the widely used Crank model can misestimate the k and D values as it does not take into account such factors as (i) changes in oxygen partial pressure p O 2 in the reactor caused by vigorous reaction, (ii) the non-uniform distribution of p O 2 over the elongated oxide sample. Models taking into account these factors are discussed sequentially in this work: the ideal continuous stirred-tank reactor (CSTR) model where p O 2 varies over time as reaction proceeds; the tanks-in-series (TIS) model imitating the non-uniform distribution of p O 2 over the sample under approximation of convective gas transfer; and the model of tanks-in-series with diffusion-convective gas transfer (TSD). The TIS and TSD models (the latter one being used for low gas flow rates), which take into account all of the above factors, give the most reasonable results: the scatter of the values of the kinetic constants k and D determined at different rates of gas flow in the reactor does not exceed the reasonable experimental error. An expression is proposed for estimating k TIS , which corrects the k values obtained from the Crank model.

Model and Analysis of Flexural Properties of Al<sub>2</sub>O<sub>3</sub> Ceramic Prepared by Centrifugal Slip Casting Using BP Neural Network Model

BP neural network model was developed for prediction of the flexural properties of Al2O3 ceramic prepared by centrifugal slip casting. In this paper, the model can well reflect the relationship between the process parameters including solid content of Al2O3 ceramic slurries (w), centrifugal acceleration (v), sintering temperature (T) and flexural properties of sintered products including fracture strength ( ) and fracture toughness (KIC). According to the registered BP model, the effects of w, v and T on and KIC were analyzed. The predicted results agree with the actual data within reasonable experimental error, which shows that the BP model is a practically very useful tool in the flexural properties prediction of the Al2O3 ceramic prepared by centrifugal slip casting. The system reduces the time required for planning and optimizing of centrifugal process parameters.

Modeling and Analysis of Compressive Properties of Porous NiTi Shape Memory Alloy Using Artificial Neural Network

Artificial neural network (ANN) is an intriguing data processing technique. Over the last decade, it was applied widely in the chemistry field, but there were few applications in the porous NiTi shape memory alloy (SMA). In this paper, 32 sets of samples from thermal explosion experiments were used to build a three-layer BP (back propagation) neural network model. According to the registered BP model, the effect of process parameters including heating rate ( ), green density ( ) and particle size of Ti ( d ) on compressive properties of reacted products including ultimate compressive strength ( v D σ ) and ultimate compressive strain (ε ) was analyzed. The predicted results agree with the actual data within reasonable experimental error, which shows that the BP model is a practically very useful tool in the properties analysis and process parameters design of the porous NiTi SMA prepared by thermal explosion method.

BP neural network prediction of the mechanical properties of porous NiTi shape memory alloy prepared by thermal explosion reaction

BP neural network model was developed for prediction of the mechanical properties of porous NiTi shape memory alloy (SMA) prepared by thermal explosion. In this paper, the model can well reflect the relationship between the process parameters including heating rate ( v ) , green density ( D) and particle size of Ti ( d) and product mechanical properties including the compressive yield strength ( σ 0.2) and Young's modulus ( E). The model can satisfactorily predict σ 0.2 and E in the ranges used to build the model. The predicted results agree with the actual data within reasonable experimental error. So the model is critical for the quality control of the porous NiTi SMA and will be widely used in thermal explosion process. At the same time, it also provides a novel method for the study of thermal explosion products.

Determination of Metal Dispersion of Pt/CeO<sub>2</sub> Catalyst by CO-pulse Method

In order to establish a CO adsorption method for rapid measurement of metal dispersion of catalysts containing CeO2 that disturbs the measurement due to the adsorption of H2 or CO, the effect of reduction conditions on CO adsorption over Pt/CeO2 catalyst was examined on the basis of the standardized manual of CO-pulse method established by the Committee on Reference Catalyst, the Catalysis Society of Japan. Reduction of the catalysts under the standardized condition (673 K, 15 min) showed that Pt catalysts supported on low surface area CeO2 (12.6 m2·g−1) gave reasonable ratios of adsorbed CO to total Pt. However, the CO/Pt ratio exceeded unity on high surface area CeO2 support (66.7 m2·g−1), suggesting adsorption of CO on the CeO2 surface. Reduction of the catalyst under milder conditions at 373 to 573 K for 15 min to 5 h gave constant CO/Pt ratio of 0.40 within a reasonable experimental error. The mean particle diameter estimated from this CO/Pt ratio on the assumption of spherical particles closely agreed with a volume-area mean diameter measured by TEM. It was concluded that the dispersion of Pt supported on CeO2 can be measured by lowering the reduction temperature to suppress the effect of the CeO2 support.

Experimental testing of a random medium optical model of porous silicon for photovoltaic applications

AbstractWe have developed a model for light propagation in porous silicon (PS) based on the theory of wave propagation in random media. The low porosity case is considered, with silicon being the host material assuming randomly distributed spherical voids as scattering particles. The specular and the diffuse part of the light could be determined and treated separately. The model is applied to the case in which porous silicon would be used as a diffuse back reflector in a thin‐film crystalline silicon solar cell realized in an ultrathin (1–3 μm) epitaxially grown Si layer on PS. Three layer structures (epi/PS/Si) have been fabricated by atmospheric pressure chemical vapor deposition (APCVD) of 150–1000 nm epitaxial silicon layers on silicon wafers of which 150–450 nm of the surface has been electrochemically etched. An excellent agreement is found between the experimentally measured reflection data in the 400–1000 nm wavelength range and those calculated using the proposed model. The values of the layer thickness agree, within a reasonable experimental error, with those obtained independently by cross sectional transmission electron microscopy (XTEM) analysis. This provides an experimental verification of the random medium approach to porous silicon in the low porosity case. The analysis shows that the epitaxial growth process has led to appreciable porosity decrease of an initially high porosity layer from about 60% to 20–30%. Copyright © 2001 John Wiley & Sons, Ltd.

An approach to dose measurement for total body irradiation

An approach is proposed to allow the interpretation of diode measurements on patients receiving total body irradiation (TBI) in opposed lateral fields as midplane dose measurements. This technique consists of making measurements on both entrance and exit sides of any ray path along which the midplane dose is desired. The diode on the entrance side is calibrated so that its output is indicative of the dose delivered at the depth of maximum dose along the ray. The diode on the exit side is calibrated so that its output represents the dose that would have been delivered to that depth had the medium (the patient) been semi-infinite. Because these two measurements lie along the same ray, they are related by a simple depth-dose equation from which the effective absorption coefficient (mueff) can be determined. The dose at the midplane is calculated using this mueff in a similar equation. The validity of this approach was checked with measurements at isocenter and at the TBI distance using a polystyrene phantom. In both cases, the calculated midplane dose was within reasonable experimental error (range approximately +/- 2% on average) of the measured dose. Measurements on eight patients showed the excellent reproducibility of entrance surface measurements (standard deviation [SD] approximately +/- 1%), compared to that of midplane measurements (SD approximately +/- 4%) and exit surface measurements (SD approximately < or = 8%). Midplane doses determined from these equations confirmed that dose inhomogeneity using this opposed lateral technique is on the order of +/- 10% with highest doses delivered to the calves and lowest to the lungs. Recent measurements made on TBI patients have shown that a commercial eight-diode system can be used successfully to measure the dose delivered to the midplane within an accuracy of approximately +/- 4%. The reproducibility of entrance surface measurements (approximately +/- 1%) shows that such measurements provide the accuracy required for quality assurance purposes.

Use of a Cu/Ag/Au alloy as a reference material for the calibration of x-ray photoelectron spectrometers

The use of a sputter-cleaned copper/silver/gold (Cu/Ag/Au) alloy for calibrating the energy scale and instrument resolution as full width at half-maximum (FWHM) of x-ray photoelectron spectrometers is described. The Cu 3p3/2, Cu 2p3/2, Cu L3M4,5M4,5, Ag 3d5/2, Ag M4NN, and Au 4f7/2 lines have been recommended in the literature for calibrating x-ray photoelectron spectroscopy (XPS) instruments. The three-component alloy material is a convenient alternative to the common practice of using three separate sputter-cleaned reference materials (i.e., Cu, Ag, and Au foils) to obtain these measurements. Results indicate that the Cu/Ag/Au alloy yields XPS binding energies within reasonable experimental error (i.e., ±0.2 eV or less) of the values obtained for pure Cu, Ag, and Au materials. In addition, the FWHM values obtained for the major XPS peaks of the Cu/Ag/Au alloy were essentially equivalent (i.e., within ±0.03 eV or less) to the values obtained for pure Cu, Ag, and Au metal foils. This material, however, is not suitable as a standard reference material for calibrating the intensity scale of XPS instruments because of localized variations in composition across the alloy surface.

Neural network as a tool for catalyst development

This article introduces a novel information science technique, an artificial neural network, which will possibly be a powerful tool for catalyst development. As an example of synergistically generated catalytic functions, the neural network has been applied to the estimation of acid strengths of mixed oxides, and it has been shown that not only the interpolation but also the extrapolation of given acid strength data is possible within reasonable experimental error. The neural network also has been successfully applied to the estimation of catalytic performance, such as the catalytic activity of a series of lanthanide oxides in the oxidation of butane and the selectivities to various products in the oxidative dehydrogenation of ethylbenzene on a series of promoted SnO 2 catalysts. On the basis of these results, some remarks are given on its application to catalyst development.

Copper/Silver/Gold Alloy by XPS

The use of a sputter-cleaned copper/silver/gold (Cu/Ag/Au) alloy for calibrating the energy scale and instrument resolution (as full width at half-maximum or FWHM) of x-ray photoelectron spectrometers (XPS) was evaluated. The three component alloy material is a convenient alternative to the common practice of using three separate sputter-cleaned reference materials (i.e., Cu, Ag, and Au foils) for the calibration of XPS. The Cu 3p3/2, Cu 2p3/2, Cu L3M4,5M4,5, Ag 3d5/2, Ag M4NN, and Au 4f7/2 peaks have been recommended in the literature for calibrating XPS spectrometers. Results indicate that the Cu/Ag/Au alloy yields XPS binding energies for these peaks within reasonable experimental error (i.e., ± 0.1–0.2 eV or less) of the values obtained for pure Cu, Ag, and Au materials. In addition, the FWHM values obtained for these peaks with the Cu/Ag/Au alloy were essentially equivalent (within 0–0.03 eV) with the values obtained for pure Cu, Ag, and Au foils.

On the hygrothermomechanical characterization of polyvinyl acetate

As a part of a program to understand the mechanisms of failure in time-dependent adhesion and film bonding, the creep compliance of polyvinyl acetate (PVAc) in shear has been determined both as a function of temperature and absorbed moisture. Volumetric expansion as a function of temperature or moisture takeup was also measured. We find that practically realizable changes in moisture content affect both the creep compliance and the swelling of PVAc to a degree comparable to that resulting from realistic changes in temperature. For example, the creep rates (histories) at corresponding times for PVAc subjected to 92% relative humidity storage are accelerated by approximately four orders of magnitude over those found for the dry material. Moreover, we find within reasonable experimental error that water concentration affects the time scale of creep like temperature through a concentration-dependent shift factor. An attempt is made at discussing the interrelation of temperature- and moisture-induced volume changes.

THE EXTRACTION OF EXCHANGEABLE CATIONS FROM SOILS

A study was made of techniques for the measurement of soil pH and corrected lime potential and for the extraction of exchangeable cations from soils. The experiments showed that in order to obtain stable and reliable pH values and ion concentrations it was necessary to equilibrate the soil samples in CaCl2 (0.005 to 0.02 M) for 4 to 5 days. After the soil was washed twice with water, the exchangeable cations were extracted from the equilibrated samples by shaking for 16 to 24 hours with 100 ml 2 N NaCl for 0.5 to 2.5 meq of exchangeable cations. In order to obtain reliable values for exchangeable Al with the soils studied, it was necessary to use a colorimetric method instead of titration with NaOH. When these precautions were observed the relation between corrected lime potential and percent base saturation for a number of soils agreed within reasonable experimental error with the theoretical one obtained for Wyoming bentonite.

Comparison of Tests for Activated Carbons

The task of preparing specifications for activated carbon suitable for the removal of tastes and odors from water is a formidable one, because it is a material with properties entirely different from those of other treatment chemicals with which the water-works industryis familiar. To prepare such specifications in a manner satisfactory to both the user and the manufacturer, has required an enormous amount of careful work by the Sub-Committee on Activated Carbons. Of the two methods which are now available for measuring the primary property of activated carbons, viz., their capacity for removing tastes and odors from water, one, the phenol test, is an indirect method, and the other, the threshold odor test, is a direct one. Extensive work has been done on the phenol test, to ascertain and correct sources of error, and to establish the magnitude of reasonable experimental error, now accepted as ±10 per cent. Work on the threshold odor test has now reached a point at which similar reliance is possible on that procedure as a method of evaluating adsorptive capacities of carbons. Demonstration of this reliability is based upon demonstration that in adsorbing odors from water, carbons follow the fundamental adsorption equation of Freundlich,

Speed of ‘Uniform Movement’ of Flame in Mixtures of Carbon Monoxide and Oxygen

IN the year 19311 Prof. W. A. Bone and Mr. R. P. Fraser published figures for the speed of the uniform movement of flame in moist (stated to be saturated at 12°–13°) mixtures of carbon monoxide and oxygen. Their values are represented by the crosses in the accompanying diagram (Fig. 1). In a paper published in 19322, we challenged both the absolute and the relative correctness of those values. Our results, for mixtures saturated at 13.1°, are indicated by circles in the diagram. Prof. Bone and Mr. J. Bell have repeated the experiments3 and, whilst unable to confirm the earlier determinations, have obtained some (for mixtures saturated at 15°) that correspond with ours, within the limits of reasonable experimental error, as is shown by their curve reproduced in the diagram.