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  • 2010-2014  (444)
  • 2012  (444)
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  • 2010-2014  (444)
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  • 1
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    Numerical study of mixing and thermal conduction of granular particles in rotating tumblers (2012)
    Wiley-Blackwell
    Details
    Publication Date: 2012-12-22
    Description: A discrete element method (DEM) study is conducted to investigate the mixing and heat transfer characteristics of steel spherical particles under various rotation speeds and flow regimes of a rotating tumbler. The mixing degree, weighted temperature, temperature discrepancy at the mixing interface, temperature radial distribution, and information entropy are used to analyze the effect of mixing structure and evolution duration on the heat transfer characteristics. The results under the same revolution and the same evolution time are compared to show the effects of evolution time and mixing structure on thermal conduction. After a detailed analysis, the joint contribution of mixing degree and duration to granular heat transfer is explained, and the different approaches in static thermal conduction and dynamic mixing are shown. Moreover, a new method is proposed using the mean increase rate of temperature information entropy to determine the most effective operating condition for thermal conduction in granular particles. © 2012 American Institute of Chemical Engineers AIChE J, 2012
    Print ISSN: 0001-1541
    Electronic ISSN: 1547-5905
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Published by Wiley-Blackwell on behalf of The American Institute of Chemical Engineers (AIChE).
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  • 2
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    Active fault isolation of nonlinear process systems (2012)
    Wiley-Blackwell
    Details
    Publication Date: 2012-12-19
    Description: This work considers the problem of designing an active fault isolation scheme for nonlinear process systems subject to uncertainty. The faults under consideration include bounded actuator faults and process disturbances. The key idea of the proposed method is to exploit the nonlinear way that faults affect the process evolution through supervisory feedback control. To this end, a dedicated fault isolation residual and its time-varying threshold are generated for each fault by treating other faults as disturbances. A fault is isolated when the corresponding residual breaches its threshold. These residuals, however, may not be sensitive to faults in the operating region under nominal operation. To make these residuals sensitive to faults, a switching rule is designed to drive the process states, upon detection of a fault, to move towards an operating point that, for any given fault, results in the reduction of the effect of other faults on the evolution of the same process state. This idea is then generalized to sequentially operate the process at multiple operating points that facilitate isolation of different faults for the case where the residuals are not simultaneously sensitive to faults at a single operating point. The effectiveness of the proposed active fault isolation scheme is illustrated using a chemical reactor example and demonstrated through application to a solution copolymerization of methyl methacrylate and vinyl acetate. © 2012 American Institute of Chemical Engineers AIChE J, 2012
    Print ISSN: 0001-1541
    Electronic ISSN: 1547-5905
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Published by Wiley-Blackwell on behalf of The American Institute of Chemical Engineers (AIChE).
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  • 3
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    Novel natural gas to liquids (GTL) processes: Process synthesis and global optimization strategies (2012)
    Wiley-Blackwell
    Details
    Publication Date: 2012-12-13
    Description: An optimization-based process synthesis framework is proposed for the conversion of natural gas to liquid transportation fuels. Natural gas conversion technologies including steam reforming, auto-thermal reforming, partial oxidation to methanol, and oxidative coupling to olefins are compared to determine the most economic processing pathway. Hydrocarbons are produced from Fischer-Tropsch conversion of syngas, ZSM-5 catalytic conversion of methanol, or direct natural gas conversion. Multiple Fischer-Tropsch units with different temperatures, catalyst types, and hydrocarbon effluent compositions are investigated. Gasoline, diesel, and kerosene are generated through upgrading units involving carbon-number fractionation or ZSM-5 catalytic conversion. A powerful deterministic global optimization method is introduced to solve the mixed-integer nonlinear optimization model that includes simultaneous heat, power, and water integration. Twenty-four case studies are analyzed to determine the effect of refinery capacity, liquid fuel composition, and natural gas conversion technology on the overall system cost, the process material/energy balances, and the lifecycle greenhouse gas emissions. © 2012 American Institute of Chemical Engineers AIChE J, 2012
    Print ISSN: 0001-1541
    Electronic ISSN: 1547-5905
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Published by Wiley-Blackwell on behalf of The American Institute of Chemical Engineers (AIChE).
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  • 4
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    Hydrogenation of dimethyl oxalate to ethylene glycol over mesoporous Cu-MCM-41 catalysts (2012)
    Wiley-Blackwell
    Details
    Publication Date: 2012-12-13
    Description: This paper describes the synthesis and utilization of mesoporous Cu-MCM-41 catalysts for hydrogenation of dimethyl oxalate to ethylene glycol. Physicochemical properties of these Cu-MCM-41 catalysts have been investigated by N 2 -physisorption, X-ray diffraction, inductively coupled plasma, N 2 O titration, transmission electron microscopy, temperature programmed reduction, Fourier transform infrared spectroscopy, and X-ray photoelectron spectroscopy. It was found that the copper loading significantly influenced the pore structure and copper surface area of the catalyst. High catalytic performance is obtained over a 20Cu-MCM-41 catalyst with a full DMO conversion and EG yield of 92% at a LHSV of 3.0 h -1 . The catalytic performance of optimized 20Cu-MCM-41 catalyst could be attributed to the fine copper dispersion and large copper surface areas. © 2012 American Institute of Chemical Engineers AIChE J, 2012
    Print ISSN: 0001-1541
    Electronic ISSN: 1547-5905
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Published by Wiley-Blackwell on behalf of The American Institute of Chemical Engineers (AIChE).
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  • 5
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    Multi-fluid modelling of the desulphurisation process within a bubbling fluidised bed coal gasifier (2012)
    Wiley-Blackwell
    Details
    Publication Date: 2012-12-13
    Description: The present work introduces the desulphurisation process to a two- and three-dimensional Eulerian-Eulerian CFD model of a coal bubbling fluidised gasifier. The desulphurisation process is important for the reduction of harmful SO x emissions, therefore the development of a CFD model capable of predicting chemical reactions involving desulphurisation is key to the optimisation of reactor designs and operating conditions. To model the process, one gaseous phase and five particulate phases are included. Devolatilisation, heterogeneous and homogeneous chemical reactions as well as calcination and desulphurisation reactions are incorporated. A calcination-only model and a calcination plus desulphurisation model are simulated in two and three dimensions and the concentrations of SO 2 leaving the reactors are compared. The simulated results are assessed against available published experimental data. The influence of the fluidised bed on the desulphurisation is also considered. © 2012 American Institute of Chemical Engineers AIChE J, 2012
    Print ISSN: 0001-1541
    Electronic ISSN: 1547-5905
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Published by Wiley-Blackwell on behalf of The American Institute of Chemical Engineers (AIChE).
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  • 6
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    Directed evolution: Past, present and future (2012)
    Wiley-Blackwell
    Details
    Publication Date: 2012-12-13
    Description: Directed evolution, the laboratory process by which biological entities with desired traits are created through iterative rounds of genetic diversification and library screening or selection, has become one of the most useful and widespread tools in basic and applied biology. From its roots in classical strain engineering and adaptive evolution, modern directed evolution came of age twenty years ago with the demonstration of repeated rounds of PCR-driven random mutagenesis and activity screening to improve protein properties. Since then, numerous techniques have been developed that have enabled the evolution of virtually any protein, pathway, network or entire organism of interest. Here we recount some of the major milestones in the history of directed evolution, highlight the most promising recent developments in the field, and discuss the future challenges and opportunities that lie ahead. © 2012 American Institute of Chemical Engineers AIChE J, 2012
    Print ISSN: 0001-1541
    Electronic ISSN: 1547-5905
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Published by Wiley-Blackwell on behalf of The American Institute of Chemical Engineers (AIChE).
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  • 7
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    Quantitative analysis of gas hydrates using raman spectroscopy (2012)
    Wiley-Blackwell
    Details
    Publication Date: 2012-12-12
    Description: A calibration protocol to quantify the compositional information ofgas hydrates using Raman spectroscopy is proposed. Structure I pure CH 4 -, CO 2 - and C 2 H 6 -hydrates in their deuterated and hydrogenated forms with known cage occupancieswere investigatedby Raman spectroscopy.Raman scattering crosssections of CH 4 inthe large and small cages were found to be very similar, but not identical. SomeC 2 H 6 bands of C 2 H 6 -hydrate were tentatively reassigned or newly reported and assigned. Our results show that the relative crosssections of guest vibrational modes in the deuterated hydrate are in agreement with those in the hydrogenated hydrate, whereasthey are considerably different from those in fluid phase. Using our Raman quantification factors, the relative cage occupancies can now be determined more reliably in CH 4 -hydrates. Moreover,with additional assumptions, the absolute cage occupancies, the bulk guest composition and hydration number of pure or mixed gas hydrates become accessible by Raman spectroscopy. © 2012 American Institute of Chemical Engineers AIChE J, 2012
    Print ISSN: 0001-1541
    Electronic ISSN: 1547-5905
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Published by Wiley-Blackwell on behalf of The American Institute of Chemical Engineers (AIChE).
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  • 8
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    Delay-range-dependent guaranteed cost control for batch processes with state delay (2012)
    Wiley-Blackwell
    Details
    Publication Date: 2012-12-08
    Description: A guaranteed cost control scheme is proposed for batch processes described by a two-dimensional (2D) system with uncertainties and interval time-varying delay. First, a 2D controller, which includes a robust feedback control to ensure performances over time and an iterative learning control (ILC) to improve the tracking performance from cycle to cycle, is formulated. The guaranteed cost law concept of the proposed 2D controller is then introduced. Subsequently, by introducing the Lyapunov–Krasovskii function and adding a differential inequality to the Lyapunov function for the 2D system, sufficient conditions for the existence of the robust guaranteed cost controller are derived in terms of matrix inequalities. A design procedure for the controller is also presented. Furthermore, a convex optimization problem with linear matrix inequality constraints is formulated to design the optimal guaranteed cost controller that minimizes the upper bound of the closed-loop system cost. The proposed control law can stabilize the closed-loop system as well as guarantee performance level and a cost function with upper bounds for all admissible uncertainties. The results can be easily extended to the constant delay case. Finally, an illustrative example is given to demonstrate the effectiveness and advantages of the proposed 2D design approach. © 2012 American Institute of Chemical Engineers AIChE J, 2012.
    Print ISSN: 0001-1541
    Electronic ISSN: 1547-5905
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Published by Wiley-Blackwell on behalf of The American Institute of Chemical Engineers (AIChE).
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  • 9
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    Biomimetic multi-enzyme complexes based on nanoscale platforms (2012)
    Wiley-Blackwell
    Details
    Publication Date: 2012-12-08
    Description: Significance Inspired by the widely present multi-enzyme complexes in Nature that enable highly cooperative catalytic mechanisms, we designed a biomimetic dual-functionalized nanoparticle-based platform for co-localizing multiple enzymes. The use of nanoscale materials together with a novel sequential co-localization approach with two model enzymes (glucose oxidase and horseradish peroxidase) resulted in a 100% increase in the overall conversion rate compared to the equivalent amount of free enzymes in solution and a physical mixture of individual immobilized enzymes on nanoparticles. Glucose oxidase is an important enzyme used in glucose biosensors for diagnostics. Co-localizing glucose oxidase with peroxidase allows for colorimetric visualization of the peroxide formed that enables monitoring glucose levels in solution. This platform can be readily applicable to other multi-enzyme systems as well. © 2012 American Institute of Chemical Engineers AIChE J, 2012.
    Print ISSN: 0001-1541
    Electronic ISSN: 1547-5905
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Published by Wiley-Blackwell on behalf of The American Institute of Chemical Engineers (AIChE).
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  • 10
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    A thermal-flywheel approach to distributed temperature control in microchannel reactors (2012)
    Wiley-Blackwell
    Details
    Publication Date: 2012-12-08
    Description: Microchannel reactors are a promising route for monetizing distributed natural gas resources. However, intensification and miniaturization represent a significant challenge for reactor control. Focusing on autothermal methane-steam reforming reactors, we introduce a novel microchannel reactor temperature control strategy based on confining a layer of phase-change material (PCM) between the reactor plates. Melting-solidification cycles, which occur with latent heat exchange at constant temperature, allow the PCM layer to act as an energy storage buffer –a “therma flywheel”– constituting a distributed controller that mitigates temperature excursions caused by fluctuations in feedstock quality. We introduce a novel stochastic optimization algorithm for selecting the PCM layer thickness (i.e., distributed controller “tuning”). Furthermore, we propose a hierarchical control structure, whereby the PCM layer is complemented by a supervisory controller that addresses persistent disturbances. The proposed concepts are illustrated in a comprehensive case study using a detailed 2D reactor model. © 2012 American Institute of Chemical Engineers AIChE J, 2012.
    Print ISSN: 0001-1541
    Electronic ISSN: 1547-5905
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Published by Wiley-Blackwell on behalf of The American Institute of Chemical Engineers (AIChE).
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