Software sensor for the bulk polymerization of systems exhibiting the trommsdorff effect using viscosity measurements

A model-predictive software sensor was developed for on-line estimation of monomer conversion and average molecular weight during bulk polymerization of systems exhibiting a gel effect. The viscosity and temperature of the reaction mass are the measured secondary variables, which when used with the model allow the state of the system to be estimated. The viscometer-reactor assembly was modified so as to measure the viscosity of the reaction mass during bulk polymerization of methyl methacrylate (MMA) at temperatures higher than those reported in our earlier work (Mankar, R. B.; Saraf, D. N.; Gupta, S. K. Ind Eng Chem Res 1998, 37, 2436).The viscosity data were curve-fitted using the modified Martin equation. Optimal temperature histories were then computed off-line, using a genetic algorithm, and implemented on the viscometer-reactor assembly in which the bulk MMA polymerization was carried out. The fact that the model tuned with the data obtained under the isothermal reactor operation can be used to predict the viscosity for nonisothermal (optimal or otherwise) reactor conditions without further tuning establishes the efficacy of the software sensor. This study can now be extended to investigate, experimentally, the on-line optimizing control of bulk MMA polymerizations. © 1999 John Wiley & Sons, Inc. J Appl Polym Sci 73: 2309–2326, 1999     

Studies on a fiber reinforced plastics honeycomb structure

Based on an adhesive and fabric screening program, a rubber-modified resole adhesive and a flexible grade plain weave glass fabric were found appropriate for the fabrication of a glass-reinforced plastics honeycomb core material. Sandwich structures of different densities were fabricated. A linear regression analysis was performed to correlate the mechanical properties (S) with the density (p) for a wide range of sandwich structures based on honeycomb and cellular plastic core materials. An analytical model of the form S = Kρⁿ was derived, with two empirical constants K and n. The density exponent n was between 1 ≤ n ≤ 2 in all cases. An equation was also derived to relate density with thermal conductivity. The dynamic mechanical analysis (DMA) results revealed that the glass transition temperature of the resin matrix associated with the sandwich structure was higher than that of the corresponding facing laminate or near resin casting.     

Development of electrical conductivity with minimum possible percolation threshold in multi-wall carbon nanotube/polystyrene composites

A method is reported that involves the bulk polymerization of styrene monomer in the presence of multi-wall carbon nanotubes (MWCNTs) and polystyrene (PS) beads, for the preparation of MWCNT/PS conducting composites with a significantly lower (0.08 wt.% MWCNT) percolation threshold than previously reported. Thus, the conductivities of 7.62 × 10⁻⁵ and 1.48 × 10⁻³ S cm⁻¹ were achieved in the MWCNT/PS composites through homogeneous dispersion of 0.08 and 0.26 wt.% CNTs, respectively in the in situ polymerized PS region by using 70 wt.% PS beads during the polymerization. The extent of dispersion and location of the MWCNTs in the PS matrix has been investigated with a scanning and transmission electron microscopy. The conductivity of the composites was increased with increasing wt.% of the PS beads at a constant CNT loading, indicating the formation of a more continuous network structure of the CNTs in PS matrix.     

In situ transmission electron microscopy observation of microstructure and phase evolution in a SnO₂ nanowire during lithium intercalation

Recently we have reported structural transformation features of SnO(2) upon initial charging using a configuration that leads to the sequential lithiation of SnO(2) nanowire from one end to the other (Huang et al. Science2010, 330, 1515). A key question to be addressed is the lithiation behavior of the nanowire when it is fully soaked into the electrolyte (Chiang Science2010, 330, 1485). This Letter documents the structural characteristics of SnO(2) upon initial charging based on a battery assembled with a single nanowire anode, which is fully soaked (immersed) into an ionic liquid based electrolyte using in situ transmission electron microscopy. It has been observed that following the initial charging the nanowire retained a wire shape, although highly distorted. The originally straight wire is characterized by a zigzag structure following the phase transformation, indicating that during the phase transformation of SnO(2) + Li ? Li(x)Sn + Li(y)O, the nanowire was subjected to severe deformation, as similarly observed for the case when the SnO(2) was charged sequentially from one end to the other. Transmission electron microscopy imaging revealed that the Li(x)Sn phase possesses a spherical morphology and is embedded into the amorphous Li(y)O matrix, indicating a simultaneous partitioning and coarsening of Li(x)Sn through Sn and Li diffusion in the amorphous matrix accompanied the phase transformation. The presently observed composite configuration gives detailed information on the structural change and how this change takes place on nanometer scale.     

Synthesis of quantitative and qualitative evidence for accident analysis in risk-based highway planning

Accident analysis involves the use of both quantitative and qualitative data in decision-making. The aim of this paper is to demonstrate the synthesis of relevant quantitative and qualitative evidence for accident analysis and for planning a large and diverse portfolio of highway investment projects. The proposed analysis and visualization techniques along with traditional mathematical modeling serve as an aid to planners, engineers, and the public in comparing the benefits of current and proposed improvement projects. The analysis uses data on crash rates, average daily traffic, cost estimates from highway agency databases, and project portfolios for regions and localities. It also utilizes up to two motivations out of seven that are outlined in the Transportation Equity Act for the 21st Century (TEA-21). Three case studies demonstrate the risk-based approach to accident analysis for short- and long-range transportation plans. The approach is adaptable to other topics in accident analysis and prevention that involve the use of quantitative and qualitative evidence, risk analysis, and multi-criteria decision-making for project portfolio selection.     

A Landsat TM based comparative study of surface and subsurface fires in the Jharia coalfield,India

Landsat TM data were used to detect surface and subsurface fires in the Jharia coalfield (JCF). TM-6 was useful for mapping subsurface fires and TM-5 and TM-7 were useful for mapping surface fires. The distribution pattern of fires was studied and their temperature and areal extents were estimated. A comparison of the distribution of surface and subsurface coal fires indicated that at some sites fires occur only on the surface or only in the subsurface, while at other sites both surface and subsurface fires occur.     

Adaptive dynamic matrix control of a distillation column with closed-loop online identification

This paper presents an online identification technique where a process is identified in terms of pseudo impulse response coefficients and subsequently used to update convolution type models to accommodate process-model mismatch. As an example, dynamic matrix control has been applied adaptively to control the top product composition of a distillation column for both servo and regulatory problems. The algorithm automatically detects a large step-like disturbance requiring fresh identification of the process and subsequently adapts the controller to the new model. Simulation studies using an analytical dynamic full order model of a distillation column demonstrated the usefulness of the adaptation scheme. Experimentation on a pilot scale distillation unit vindicated the simulation results.     

IS integration and knowledge sharing in multi-unit firms: the winner's curse

Knowledge sharing across business units (BUs) is paramount for enterprises that aim to exploit latent cross-BU synergies. This paper examines how information systems (ISs) integration and two forms of cross-BU knowledge complementarities (workflow interdependence and BU relatedness) affect an important dimension of a firm's absorptive capacity – cross-BU knowledge sharing. The analysis, performed on survey data from 75 enterprises, supports all of our hypotheses. First, we hypothesized that cross-BU workflow serves as a conduit for knowledge transfer as participants continually engage in spontaneous adaptations. Second, IS application integration and cross-BU relatedness should both directly contribute to knowledge sharing. Third, IS application integration should positively moderate the impacts of cross-BU relatedness. Finally, and most interestingly, we hypothesized a redistribution of the effects of IS integration by which it becomes a key contributor to knowledge sharing, but also causes a reduction in the impact of workflow interdependence. Thus, while the seamlessness of high IS application integration has obvious benefits, it paradoxically also reduces the occasions for cross-BU workflow adaptations, which is a key mechanism for knowledge transfer. That is the phenomenon we call the ‘winner's curse’.