Effect of estimation under nonnormality on the phase II performance of linear profile monitoring approaches

The number of studies about control charts proposed to monitor profiles, where the quality of a process/product is expressed as function of response and explanatory variable(s), has been increasing in recent years. However, most authors assume that the in‐control parameter values are known in phase II analysis and the error terms are normally distributed. These assumptions are rarely satisfied in practice. In this study, the performance of EWMA‐R, EWMA‐3, and EWMA‐3(d²) methods for monitoring simple linear profiles is examined via simulation where the in‐control parameters are estimated and innovations have a Student's t distribution or gamma distribution. Instead of the average run length (ARL) and the standard deviation of run length, we used average and standard deviation of the ARL as performance measures in order to capture the sampling variation among different practitioners. It is seen that the estimation effect becomes more severe when the number of phase I profiles used in estimation decreases, as expected, and as the distribution deviates from normality to a greater extent. Besides, although the average ARL values get closer to the desired values as the amount of phase I data increases, their standard deviations remain far away from the acceptable level indicating a high practitioner‐to‐practitioner variability.     

Effect of extrusion conditions on the physical properties of desi chickpea-barley extrudates and quality attributes of their resulting flours

In this study, response surface methodology (RSM) was used to evaluate the effect of extrusion conditions on physical properties of chickpea:barley extrudates (60:40), and the resulting protein quality of their flours. Barrel temperature (150–170°C) and moisture content (16–20%) were chosen as independent variables to generate a central composite design. Hardness, expansion index, bulk density, and protein quality were analyzed as responses parameters. Expansion was found to be higher at lower temperatures and higher moisture for the 60:40 chickpea:barley blend; bulk density became reduced with increased moisture; and hardness was found to increase at higher temperatures and lower moistures. The protein quality of their resulting flours was found to be greater at moisture contents higher than 16%. The composition, protein quality, and functional attributes were also examined for raw and precooked flours of chickpea, barley, and their blend at the center point of the RSM design (18% moisture, 160°C). Extrusion also leads to improved water hydration capacities and reduced viscosities for precooked individual and blended flours relative to the raw. Moreover, extrusion also led to improved protein quality in the chickpea and chickpea-barley blend, but not the individual barley flour.     

Dynamic probability control limits for CUSUM charts for monitoring proportions with time-varying sample sizes

We consider the problem of monitoring a proportion with time-varying sample sizes. Control charts are generally designed by assuming a fixed sample size or a priori knowledge of a sample size probability distribution. Sometimes, it is not possible to know, or accurately estimate, a sample size distribution or the distribution may change over time. An improper assumption for the sample size distribution could lead to undesirable performance of the control chart. To handle this problem, we propose the use of dynamic probability control limits (DPCLs) which are determined successively as the sample sizes become known. The method is based on keeping the conditional probability of a false alarm at a predetermined level given that there has not been any earlier false alarm. The control limits dynamically change, and the in-control performance of the chart can be controlled at the desired level for any sequence of sample sizes. The simulation results support this result showing that there is no need for any assumption of a sample size distribution with the use of this proposed approach.     

Investigation of the Usage of Depolymerized Nylon 66 Intermediate in Phenolic Resin Modification

In this study, the potential usage of the Nylon 66 hydrolysis products (HP) for curing “high ortho” novolac resin (N) was investigated. According to FTIR, DSC and TGA results, it is concluded that HP can be as a curing agent for N without the need for another crosslinking agent and thermal degradation stability of cured N-HP blends increased significantly up to 15% HP content. Furthermore, according to performed surface coating tests, it is shown that all films prepared with HP up to 30-wt % have excellent water resistance, drying and adhesion properties as well as with high hardness values.     

Comparing of the Magnetic Force Parameters of Superconducting Maglev System Using Horizontal and Vertical PMG Geometry in Multi-Surface HTS-PMG Arrangement

Journal of Superconductivity and Novel Magnetism - In this study, a detailed static and dynamic experimental studies were carried out in different cooling heights (CH) by using two different...     

Room temperature deposition of XRD-amorphous TiO2 thin films: Investigation of device performance as a function of temperature

In this study, TiO₂ thin films were fabricated by radio frequency sputtering at room temperature in pure Ar atmosphere starting from a 6?in. TiO₂ target. The thickness of the films was controlled by deposition time and the effect of Ar sputtering pressure on the characteristics of TiO₂ thin films was evaluated. Surface morphology and optical properties of TiO₂ films were investigated using X-ray diffraction (XRD), Atomic Force Microscopy (AFM), Scanning Electron Microscopy (SEM) and UV–Vis spectrophotometry. Also, the refractive index and extinction coefficient of films were inferred by fitting spectrophotometric data. Schottky diode were fabricated by evaporation of Ni on TiO₂ films. Current-voltage (I-V) measurements of Ni/TiO₂ films showed that the rectifying properties of the device improves with the increasing of TiO₂ film density and thickness. Therefore, the best I-V characteristic of the device was investigated depending on the temperature. Also, Ni/n-TiO₂/p-Si/Al devices were fabricated to understand their transport mechanism.     

Explaining and Integrating Machine Learning Models with Rigorous Simulation

First-principle flowsheet simulation is a reliable data resource for training machine learning (ML) models for process industry, especially when plant data is not available. Process simulators play an even more important role for evaluation and validation of ML models. In this work, we present a workflow for building and evaluating ML models based on data generated by a commercial flowsheet simulator. The resulting hybrid models, combining data-driven predictions with mass and energy balances, have much lower calculation times than the rigorous models. The implementation of such models shows great potential for solving more complex process engineering problems on the high-dimensional space in the future, while saving the process engineer's time in the present.     

Methane OSR over Pt-Ni/δ-Al2O3: Performance and power law type kinetics

Methane oxidative steam reforming (OSR) performance of two bimetallic Pt-Ni/δ-Al₂O₃ catalysts, having Pt:Ni loadings, 0.2:10 and 0.3:10, were tested first. In the tests, residence time (W/F), carbon-to-oxygen (C/O₂) feed ratio, and temperature were used as the experimental parameters. Increase in temperature resulted in direct and indirect - through enhanced TOX yielding higher energy - increase in SR rate. As Pt:Ni metal loading ratio did not lead to significant changes in activity, the preliminary kinetic tests to determine merely kinetically controlled region were conducted over 0.2Pt-10Ni catalyst. Considering the outcomes of the preliminary tests, the kinetic experiments were performed for practical reaction conditions extending up to 20% methane conversion with feed ratio intervals of 4.0 < C/O₂ < 7.34 and 2.03 < S/C < 3.08 at two different residence time (W/F) values to obtain a power-law type rate equation. Reaction orders were estimated as 0.81, 1.60 and 0.44 for methane, oxygen and steam, respectively, by using multivariable non-linear optimization function of MATLAB?. The apparent activation energy of methane OSR was calculated as 24.61 kJ mol^?1 and pre-exponential factor as 0.110 μmol mgcat^?1 s^?1 kPa^?2.85 for the 375–450 °C temperature interval. The same analysis performed for a narrower temperature range, 375–425 °C, gave k₀ and E_A values as 0.251 μmol mgcat^?1 s^?1 kPa^?2.85 and 29.17 kJ mol^?1, respectively, confirming the high sensitivity of OSR pathway to temperature.