Rapid process refinement for the development of complex solution copolymers

The industrial manufacture of specialty free radical solution copolymers (FRPs) requires use of a variety of solvents and co-monomers based on the desired properties and end-use. The polymer composition, polymerization solvent, and process parameters have a significant impact on polymer properties such as copolymer composition and polymer molecular weight distribution (MWD). The scale-up and trouble-shooting of copolymerization processes is a significant challenge for the specialty polymers industry due to short project time-scales, limited resources available for each project, and the use of newly developed proprietary monomers. We present approaches that combine process systems and experimental approaches to support data and knowledge-based decisions in the context of live projects under commercial time constraints with only limited data available. These approaches are used for the evaluation and improvement of a batch process operating under reflux conditions that exhibits a large change in solvent boiling point due to the use of high boiling monomers. The approaches allow rapid process refinement and include thermodynamics and heat transfer considerations decoupled from the complexity of reaction kinetics and chemistry with assumptions on heat release rates. Controllability analysis can be carried out at different stages of the batch, sensitivity to the selected solvent tested, and recommendations made on solvent use and process conditions. In addition, we also present an innovative, sparse matrix-based representation of chain length dependent rates that has potential to deliver rapid solutions without loss of detail of MWD.     

Finite–Element Mesh Generation Using Self–Organizing Neural Networks

Neural networks are applied to the problem of mesh placement for the finite–element method. When the finite–element method is used to numerically solve a partial differential equation with boundary conditions over a domain, the domain must be divided into "elements." The precise placement of the nodes of the elements has a major affect on the accuracy of the numeric method. In this paper the self–organizing algorithm of Kohonen is adapted to solve the problem of automatically assigning (in a near–optimal way) coordinates from a two–dimensional domain to a given topologic grid (or mesh) of nodes in order to apply the finite–element method effectively when solving a partial differential equation with boundary conditions over that domain.
One novelty of the method is the interweaving of versions of the Kohonen algorithm in different dimensions simultaneously in order to handle the boundary of the domain properly.
Our method allows for the use of arbitrary types of two–dimensional elements (in particular, quadrilaterals or mixed shapes as opposed to just triangles) and for varying desired densities over the domain. (Thus more elements can be placed automatically near "areas of interest.")
The methods and experiments developed here are for two–dimensional domains but seem naturally extendible to higher–dimensional problems. The method uses a mixture of both one– and two–dimensional versions of the Kohonen algorithm, with an improvement suggested by Tabakman and Exman, and further adapted to the particular problem here. Experimental results comparing this algorithm with a well–known two–dimensional grid–generating system (PLTMG) are presented.     

Estimation of atmospheric ozone for Association of South East Asian Nations (ASEAN) countries

An empirical mathematical model due to Heuklon was used to evaluate atmospheric content of ozone over Association of South East Asian Nations (ASEAN) countries. The model is dependent on latitude, longitude, and day of the year. A comparison of the computed data of ozone was made with the measured data. The measured data on ozone content was collected from the meteorological departments of the ASEAN countries. Our preliminary calculations indicate that the model can estimate the ozone content in the northern as well as the southern hemisphere with a maximum error of 10%.     

Dynamic effects of turbocharging on adaptive speed control ofdiesel driven power-plants

The adaptive control scheme introduced by S. Roy et al. (1991) for naturally aspirated diesel prime-movers has been applied to turbocharged generation plants. The performance has been studied in comparison to that of a fixed PI (proportional plus integral) controller. It is seen that since the nonlinear effect of air dynamics now affects the dynamic fuel consumption, the turbocharger is a major determinant of the adaptive controller performance. Furthermore, the performance is found to have a very significant effect due to the droop. It can in general be concluded that the turbocharger inertia should be low for high-droop operations. However, despite this predominant factor, the adaptive scheme can achieve good improvement over the conventional controller     

Optimization technique for the design of a linear optimal powersystem stabilizer

A systematic optimization method for choosing the weighting matrix in linear optimal control system design, under the conditions of prespecified closed-loop dominant eigenvalue locations and feedback gain limit constraints, is presented. With the proposed method the desired weighting matrix can be obtained very quickly and conveniently without the heavy burden of choosing a suitable weighting matrix by trial and error. The analysis shows that a reduced-order feedback controller can be designed with the elements of the weighting matrix chosen in an optimal and coordinated manner. Simulation results of the linear optimal power system stabilizer designed by the proposed optimization technique are also given. The results show the correctness and effectiveness of the proposed method     

Neuropsychological correlates of short-term memory distractor tasks among patients with surgical repair of anterior communicating artery aneurysms.

The relative utility of the visual consonant trigram (VCT) and release from proactive inhibition (PI) versions of the short-term memory (STM) distractor task in investigating the separate but related cognitive realms of memory and executive frontal lobe functioning were explored in patients with anterior communicating artery (ACoA) aneurysms n?=?24. Compared with normal controls n?=?19, ACoA patients were impaired on clinical measures of memory and on measures of executive functioning, including concept formation and fluent word generation. Furthermore, ACoA patients were impaired on the VCT task but not on the release-from PI task, indicating a differential sensitivity of these tasks to the impairment manifested by ACoA patients. Regression modeling indicated that the VCT and release-from-PI tasks were closely associated with clinical memory tests, although the release-from-PI-task was also associated with fluency, an executive functioning domain. In general, our results fail to support the broad generalization that impaired performance on STM distractor tasks is necessarily symptomatic of frontal lobe dysfunction. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Rule-based design of a material processing component

The main thrust of this research is in developing aknowledge-based system for the design of components for a material processing system. In particular, this paper concentrates on developing methodologies forinitial design andredesign in a quantitative and qualitative format. A die for plastic extrusion has been selected as the subject material processing component. A design algorithm using best first heuristic search and expert knowledge, both in procedural and declarative form, is the core of the scheme. Apart from this expert, the suggestedselection procedure for candidate design is also seen to accelerate the design scheme. The methodologies presented enableefficient design of the component. Some generality has been accomplished by the implementation of the techniques to dies of different cross-sectional shapes. The software is written inLisp within an object-oriented software package using analysis modules written in C.     

Feasibility and optimization of the hollow optical fiber drawing process

The drawing process for the fabrication of a hollow optical fiber involves the flow of glass, which is largely heated by thermal radiation, in an inert gas environment. It is critical to maintain the central core, which can collapse if the thermal conditions are not properly imposed and controlled. This paper presents the analysis and simulation of this complicated process. A numerical model is developed, validated, and applied to simulate the hollow optical fiber drawing process under a wide range of boundary conditions, particularly draw speed, tension, and temperature. A feasible domain of the drawing process is identified to give the range of the drawing parameters for which the geometry of the fiber is maintained and collapse of the core and viscous rupture of the fiber are avoided. The effects of drawing temperature and feeding speed, which are crucial factors in determining the geometry and quality of the fiber, are investigated in detail. A multi-variable unconstrained optimal design problem is posed and considered in terms of the feasible domain. An appropriate objective function, comprised of the maximum velocity lag, thermally induced defect concentration and draw tension, is proposed to quantify the quality of the hollow fiber. The univariate search method is then applied to obtain the optimal drawing temperature and feeding speed. This study provides a basis for the optimization of hollow fiber drawing process and indicates that a substantial improvement in fiber quality can be achieved.