Generation and verification of optimal dispatching policies for multi-product multi-tool semiconductor manufacturing processes

Semiconductor manufacturing is one of the fastest-growing industries today. As the recent requirements for feature sizes and wafer sizes change rapidly, it becomes imperative to configure increasingly intricate control schemes to maintain product quality and tool utilization rate. For this purpose, it is assumed in this study that a semiconductor production environment can be viewed as multiple queues operated in parallel and, also, the EWMA controllers can be implemented independently to adjust the process recipes of different products in each queuing system. Based on these assumptions, a MINLP model is formulated to determine the optimal dispatching policies. Systematic numerical simulation procedure is also devised to confirm the validity of the dispatching model. Since accurate estimates of the model parameters may not always be available, the effects of model mismatch have been analyzed and the proper range of controller tuning parameter is recommended to achieve an acceptable level of process capability.     

DENSITY ESTIMATION OF AMMONIUM-BASED IONIC LIQUIDS

Density is an important property of ionic liquids (ILs) that is required for process and product design. A recent article by Gardas and Coutinho (2008) reports the extended density correlation of ILs in wide ranges of temperature and pressure. However, they validated the density correlation only for ILs based on the following cations: imidazolium, pyridinium, pyrrolidinium, and phosphonium. The objective of this study is to validate the density correlation for ammonium-based ILs. The density model was tested against experimental densities available in the literature of ammonium-based ILs at a wide range of temperatures (273.15–393.15 K) and at 1 atm (0.1 MPa) of pressure. The results show that the predicted densities are in good agreement with available experimental literature values. The average absolute relative deviation (AARD) is 1.57%.     

Solvation, solute rotation and vibration relaxation, and electron-transfer reactions in room-temperature ionic liquids

A brief account of recent simulation and theoretical model studies of various solution-phase processes in room-temperature ionic liquids is given. These include structure and dynamics of equilibrium and nonequilibrium solvation, solute rotation and vibrational energy relaxation, and free energetics and dynamics of unimolecular electron-transfer reactions. Special attention is paid to both the aspects shared by and the contrasts with polar solvents under normal conditions. A brief comparison with available experiments is also made.     

Effect of Temperature on the Ultimate Strength and Modulus of Whisker-Reinforced Ceramics

Whiskers are a very attractive means of reinforcing a ceramic material. It has been shown that the whiskers dramatically improve the ultimate strength and modulus of the materials at room temperature. However, recent studies indicate that at high temperatures the improvement is less pronounced, or there is no improvement at all. In this paper a model is developed to explain why the properties are degraded at high temperature. The parameters which seem most important for high-temerature performance are the coefficients of thermal expansion and Poisson's ratios for the constituents, the heat treatment temperature, and the cofficeint of friction between the whisker and the matrix. The model compares favorably with the experimental data available, so a parametric study was done to show the effect of different parameters on the strength and modulus of the composite.     

Modeling of biocatalytic reactions: A workflow for model calibration,selection, and validation using Bayesian statistics

We present a workflow for kinetic modeling of biocatalytic reactions which combines methods from Bayesian learning and uncertainty quantification for model calibration, model selection, evaluation, and model reduction in a consistent statistical framework. Our workflow is particularly tailored to sparse data settings in which a considerable variability of the parameters remains after the models have been adapted to available data, a ubiquitous problem in many real-world applications. Our workflow is exemplified on an enzyme-catalyzed two-substrate reaction mechanism describing the symmetric carboligation of 3,5-dimethoxy-benzaldehyde to (R)-3,3′,5,5′-tetramethoxybenzoin catalyzed by benzaldehyde lyase from Pseudomonas fluorescens. Results indicate a substrate-dependent inactivation of enzyme, which is in accordance with other recent studies.     

Oxygenated transportation fuels. Evaluation of properties and emission performance in light-duty vehicles in Mexico

Recently a “Biofuels Promotion and Development Law” was approved in Mexico that requires increasing volumes of renewable to blend into the transportation fuel pool, much of which is likely to be ethanol. Emissions data under the three different driving conditions of the United States FTP-75 certification cycle were obtained for regulated, toxic and carbonyl compounds using recent model year vehicles representing 61% of the typical fleet available in Mexico. Ozone-forming potential and specific reactivity of tailpipe and evaporative emissions were also calculated. Comparison were performed using the traditional methyl-tertiary butyl ether employed in Mexico with an ethanol fuel at the same level of oxygen content, taking into account the current fuel specifications and the stream stocks available at the Mexican refineries. The results suggest that the contribution of cold start to regulated emissions range from 37% to 40% whiles those of toxic from 40% to 47% in both fuels. Results also indicate an increase in the rates of evaporative emissions of higher Specific Reactivy with the ethanol fuel. Estimation of the percent reduction of pollutants using the Complex Model of the USA Environmental Protection Agency suggests that volatile organic compounds will exceeds the limits imposed by the model if vapour pressure of the ethanol gasoline is not properly adjusted.     

Advances and selected recent developments in state and parameter estimation

This paper deals with two topics from state and parameter estimation. The first contribution of this work provides an overview of techniques used for determining which parameters of a model should be estimated. This is a question that commonly arises when fundamental models are used as these models often contain more parameters than can be reliably estimated from data. The decision of which parameters to estimate is independent of the observer/estimator design, however, it is directly affected by the structure of the model as well as the available data. The second contribution is an overview of recent developments regarding the design of nonlinear Luenberger observers, with special emphasis on exact error linearization techniques, but also discussing more general issues, including observer discretization, sampled data observers and the use of delayed measurements.     

Deformation kinetics of pH‐sensitive hydrogels

Polymeric gels can undergo large deformation when subjected to external solutions of varying pH. It is imperative to understand the deformation process of pH‐sensitive hydrogels for the effective application of these attractive materials in the biomedical and microfluidic fields. In the modeling of these multi‐phase materials, finite element (FE) modeling is a useful tool for the development of future applications, and it allows developers to test a wide variety of material responses in a cost‐effective and efficient manner, reducing the need to conduct extensive laboratory experiments. Although a FE user‐defined material model is available for the equilibrium state, the transient response of pH‐sensitive gels has not been effectively modeled. Based on our recent work using the heat transfer analogy to tap into the readily available coupled temperature–displacement elements available in the commercial FE software ABAQUS for simulation of the transient swelling process of neutral hydrogels, the transient swelling process of a pH‐sensitive hydrogel is studied and a FE model is further developed to simulate the transient phenomena. Some benchmark examples are investigated to demonstrate the model's capabilities in the simulation of nonlinear deformation kinetics relevant to several applications of pH‐sensitive hydrogels. © 2013 Society of Chemical Industry     

On Hypotheses Testing for the Selection of Spatio‐Temporal Models

Abstract. Several models have been proposed in recent years for analysing spatial data and also, to some extent, spatio‐temporal data. One of the important problems, namely the choice of an appropriate model for describing real data sets, remains unsolved. Here we consider the analysis of spatio‐temporal processes from which observations over space and time are available. We propose statistical tests for discriminating between space–time autoregressive processes and multivariate autoregressive processes. The sampling properties of the proposed tests are considered. We illustrate the methods with a real example. We use the above tests to find the best model to describe spatio‐temporal variations of hourly carbon monoxide measurements at four locations in London in January 2004.     

RECENT PROGRESS IN THE COMPUTATION OF EQUILIBRIUM RATIOS

The computation of equilibrium ratios plays an important role in any distillation design calculation. Three different types of models are used for generating equilibrium ratios in non-ideal mixtures:(1)Equations of state (2)Activity coefficient models (3)Group contribution methods Significant developments have taken place for all three types of models in recent years. New models have appeared, many model parameters have become available, and efficient and safe algorithms for implementing the models in distillation calculations have been proposed. The purpose of this contribution is to review these developments.     

RECENT PROGRESS IN THE COMPUTATION OF EQUILIBRIUM RATIOS

The computation of equilibrium ratios plays an important role in any distillation design calculation. Three different types of models are used for generating equilibrium ratios in non-ideal mixtures:(1)Equations of state (2)Activity coefficient models (3)Group contribution methods Significant developments have taken place for all three types of models in recent years. New models have appeared, many model parameters have become available, and efficient and safe algorithms for implementing the models in distillation calculations have been proposed. The purpose of this contribution is to review these developments.     

Advances and gaps in the knowledge of thermodynamics and crystallography of acid mine drainage sulfate minerals

Acidic and metal-rich waters produced by sulfide decomposition at mining sites are termed acid mine drainage (AMD). They precipitate a number of minerals, very often sulfates. The recent advances in thermodynamic properties and crystallography of these sulfates are reviewed here. There is a reasonable amount of data for the divalent (Mg, Ni, Co, Fe(2+), Cu, Zn) sulfates and these data may be combined with and optimized by temperature-relative humidity brackets available in the literature. For the sulfates with Fe(3+), most data exist for jarosite; for other minerals and phases in this system, a few calorimetric studies were reported. No data whatsoever are available for the Fe(2+)-Fe(3+) sulfates. A significant advance is the development of the Pitzer model for Fe(3+)sulfate solutions and its confrontation with the available thermodynamic and solubility data. In summary, our knowledge about the thermodynamic properties of the AMD sulfates is unsatisfactory and fragmented.     

A MODEL FOR THE DISTRIBUTION OF ACID GASES BETWEEN AN AQUEOUS ALKANOLAMINE SOLUTION AND LPG

The model of Deshmukh and Mather (1981) is a popular method for correlating and predicting the vapor-liquid equilibria in systems containing acid gases (hydrogen sulfide and carbon dioxide) and aqueous solutions of alkanolamines. The model includes phase equilibrium between an aqueous liquid and a gas as well as chemical equilibrium in the aqueous phase. A recent review by Weiland et al. (1993) demonstrated the accuracy of the correlation. Presented here is a model based on that of Deshmukh and Mather (1981) for calculating the distribution of acid gases between two liquid phases - an aqueous phase and a non-aqueous liquid (typically a propane- or butane-rich liquid)

In the new model the phase equilibrium is modeled using a modified Henry's law approach. Fugacities of the components in the non-aqueous phase are calculated using the Peng and Robinson (1976a) equation of state. All of the parameters in the model are taken from the literature. Thus the model represents a prediction of the behavior. It is demonstrated that the predictions are in good agreement with the available experimental data     

Linear viscoelasticity of polymer blends with co-continuous morphology

The co-continuous morphology of polymer blends has received much attention not only because of its potential promotion of mechanical or electrical properties of polymer blends, but also due to its importance in phase separation by spinodal decomposition. Compared to the recent advances in the characterization of co-continuous structure, the rheology of co-continuous blends has not been understood clearly. In this work, a rheological model is suggested to correlate the linear viscoelasticity and the structural information of co-continuous blends. The dynamic modulus of co-continuous blends is composed of the contribution from components and the interface. The interfacial contribution, which is most important in the rheology of blends, is calculated from a simplified co-continuous structure. This model has been compared satisfactorily with available experimental results, which proves a reasonable connection between the co-continuous structure and linear viscoelasticity of blends.     

Identifying a putative common binding site shared by substance P receptor and an anti-substance P monoclonal antibody

Substance P G-protein coupled receptor and the antigen recognitionsite of a monoclonal antibody raised against substance P sharea stretch of five contiguous identical amino acids. This observationprompted us to build an atomic model of both the receptor andthe antibody and to analyse their common features. In particular,we report here that a pocket of similar size and compositionis present in both proteins, strongly suggesting a similarityin the mode of binding of both macromolecules to substance P.From the analysis of our models, the available data on the modeof binding of the antibody to substance P and recent data onsubstance P receptor mutants, we concluded that the pocket isvery likely to be involved in binding of the C-terminal 'messagesequence' of the tachykinin. This allowed us to suggest specificsite-directed mutants of the receptor which should shed somelight on the mechanism of peptide recognition by G-protein coupledreceptors.     

A new model of resorbable device degradation and drug release ‐ part I: zero order model

BACKGROUND: Within the field of resorbable devices, recent years have seen an increased demand for better reliability from drug delivery systems and resorbable polymer degradation control, causing researchers to abandon trial‐and‐error approaches towards model‐based methods. In this context, we developed a lumped‐parameters zero‐order model for the degradation of resorbable polymeric drug release systems. Such a model is thought to be applicable in the design of specific devices based on the expected degradation time and drug delivery rates, as it is based on a ‘shrinking core’ approach and takes into account the main physicochemical parameters involved in polymer degradation, in drug release and in mechanical strength prediction, all independently estimated. RESULTS: The model, based on conservation equations, leads to numerically solved ordinary differential equations, the predictions of which were verified through literature data. Data of different authors and various systems were satisfactorily matched by model predictions, thus confirming the reliability of parameter estimation procedures. CONCLUSION: The present model is among the very few that completely address all aspects involved in device degradation and drug delivery altogether, and thus represents a step ahead with respect to current available solutions, firmly enforcing itself into the ongoing debate on the modelling of degradation and release behaviour. Copyright © 2008 Society of Chemical Industry     

Modeling of the bulk free radical polymerization up to high conversion—three stage polymerization model I. Model examination and apparent reaction rate constants

In this paper, a simple and useful model, the three stage polymerization model (TSPM) is proposed on the basis of recent experimental evidence and our preliminary treatment of the experimental kinetic results found in the literature. The model accounts for gel effect and glass effect in bulk free-radical polymerization. Equations for calculating the conversion of the polymerization reaction are derived based on TSPM. Using experimental kinetic data available in the literature, general expressions for apparent reaction rate constants in three stages for methylmethacrylate (MMA) and styrene (St) are obtained. In general, the experimental kinetic data can be treated very well with the TSPM from the low conversion stage to high conversion, except for some experimental data near the transition points. However, the deviation for this data may be reasonably explained by the non-isothermal effects that occur in this regime of experiments. This deviation is smaller for a smaller ampoule reactor used in polymerization experiments because of its better heat transfer ability. In order to establish that there is no glass effect stage when the reaction temperature is greater than the glass transition temperature for a polymerization process, some experimental data for ethylmethacrylate (EMA) bulk polymerization at a reaction temperature higher than its glass transition temperature were checked with TSPM. The plots show that the model is also suitable for EMA bulk polymerization.     

From monomers to polymers from renewable resources: Recent advances

Considering the state of affairs related to polymers and their applications, the plastic-dependence of the modern society is evident and becomes now needless to mention. Together with that, the exhaustive discussion about the quick depletion of petroleum resources and the obvious alternative that lies on the great versatility of renewable feedstocks, it is clear that the most recent efforts should be – and are – directed to design more sustainable polymers to replace the classic ones. This review aims to offer a panoramic overview of the recent progress, but mainly of the broad possibilities that are still available in the hands of researchers working on this topic.