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  • Articles  (174,504)
  • Articles: DFG German National Licenses  (174,504)
  • Articles and Proceedings (GFZpublic)
  • Process Engineering, Biotechnology, Nutrition Technology  (174,504)
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  • Articles  (174,504)
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  • 1
    Electronic Resource
    Electronic Resource
    Performance of Statistical Process Control Tools under Different Plant Operation Strategies (2008)
    Berkeley, Calif. : Berkeley Electronic Press (now: De Gruyter)
    Chemical product and process modeling 3 (2008), S. 4 
    Details
    ISSN: 1934-2659
    Source: Berkeley Electronic Press Academic Journals
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: The outputs of statistical process control (SPC) tools developed for fault detection are comparatively examined while applied to actual data collected in an industrial plant. The influence of added information gathered from the plant operation under different strategies is analyzed. Particularly, standard principal component analysis (PCA), kernel PCA and the Hotelling's T2 charts are inspected for a reported problem. The effect of training the tools either with an extended historic databank obtained under standard operation, or including also non-conventional conditions, is studied. The ability of the tools to provide a specific alarm and identify the responsible variable is examined by analyzing the contributions per variable to the SPE and the T2 statistics. In addition, the capacity of the tested tools to adapt to a new operation strategy is compared.
    Type of Medium: Electronic Resource
    URL: http://www.bepress.com/cppm/vol3/iss1/4
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  • 2
    Electronic Resource
    Electronic Resource
    Dynamic Model for Polyethylene Production in a Multizone Circulating Reactor (2008)
    Berkeley, Calif. : Berkeley Electronic Press (now: De Gruyter)
    Chemical product and process modeling 3 (2008), S. 1 
    Details
    ISSN: 1934-2659
    Source: Berkeley Electronic Press Academic Journals
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: The multizone circulating reactor (MZCR) technology is a newly announced reactor design for solid-catalyzed gas-phase polymerization. The process is characterized by two hydrodynamically distinct but interconnecting polymerization zones, thus forming a continuous loop of polymer flow between the said zones. In the present study, a dynamic model for the MZCR reactor is developed to illustrate the basic dynamic behavior of the new reactor design; the model is used to study the copolymerization of ethylene with butene. Several parameter sensitivity analyses are performed to show the computer-simulated time responses for reactor temperature, number-average molecular weight, weight-average molecular weight, catalyst feed rate and the monomer concentration along the reactor length.
    Type of Medium: Electronic Resource
    URL: http://www.bepress.com/cppm/vol3/iss1/1
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  • 3
    Electronic Resource
    Electronic Resource
    Investigation and Modeling of Splashing in the Peirce Smith Converter (2008)
    Berkeley, Calif. : Berkeley Electronic Press (now: De Gruyter)
    Chemical product and process modeling 3 (2008), S. 2 
    Details
    ISSN: 1934-2659
    Source: Berkeley Electronic Press Academic Journals
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: To investigate the factors affecting splashing in Peirce-Smith copper converters of Sarcheshmeh copper complex, South-East Iran, a laboratory scale model with dimensions one eighth of the actual converter was designed and assembled. The model was filled with water. Air was impinged onto the water. The sequence of events was subsequently recorded using high speed cameras. Factors affecting splashing such as blowing angle, volumetric flow rate of air, and the distance of the blowers from water surface were studied.Using a value of 2.65×10-11 for Morton dimensionless number, it was found that splashing may be reduced by 75% if the air speed in the tuyeres is reduced from 155 m/s to 30 m/s while the nozzle distance from the melt free surface is between 2 to 0.5 meters.
    Type of Medium: Electronic Resource
    URL: http://www.bepress.com/cppm/vol3/iss1/2
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  • 4
    Electronic Resource
    Electronic Resource
    A Modeling and Optimization Tool for the Expandable Polystyrene Batch Process (2008)
    Berkeley, Calif. : Berkeley Electronic Press (now: De Gruyter)
    Chemical product and process modeling 3 (2008), S. 3 
    Details
    ISSN: 1934-2659
    Source: Berkeley Electronic Press Academic Journals
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Expandable Polystyrene (EPS), a material of the insulation productions and packages, is commonly produced in a batch process. The control of the batch process is based on predefined process recipes and process parameters such as mixing properties. The EPS production has to be able to satisfy the aims and quality requirements of the markets, which causes additional demands on the process control. In this paper we demonstrate the optimization and modeling application for the EPS-batch process. The application consists of a production optimization tool and a simulation tool for the process parameters based on the Multi-Layer Perceptron network (MLP) with retrain properties. The software can be used at the operational level as well as at the process management level. The features are programmed into standalone software built up in the Matlab environment and it is tailored for the needs of the EPS production company StyroChem Ltd. The results show that the application can offer an efficient tool to economize production and storage costs.
    Type of Medium: Electronic Resource
    URL: http://www.bepress.com/cppm/vol3/iss1/3
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  • 5
    Electronic Resource
    Electronic Resource
    CFD Simulations for Continuous Flow of Bubbles through Gas-Liquid Columns: Application of VOF Method (2007)
    Berkeley, Calif. : Berkeley Electronic Press (now: De Gruyter)
    Chemical product and process modeling 2 (2007), S. 9 
    Details
    ISSN: 1934-2659
    Source: Berkeley Electronic Press Academic Journals
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Hydrodynamics study of a continuous bubble chain rising through liquid column has been performed for laboratory scale bubble column using the volume-of-fluid (VOF) approach. The effect of operating and design parameters on the bubble size distribution and rise trajectory has been investigated for air-water system. For the same distributor, simulation results have indicated the formation of small bubbles at low superficial gas velocity and relatively large bubbles at higher velocities. The increase in the hole-size of distributor has shown similar behaviour. Analysis of bubble trajectories for different superficial gas velocities and distributors has demonstrated an oscillatory behaviour exhibited by small bubbles formed at low superficial gas velocity. A reasonable agreement between the predicted values of gas hold-up with the experimental work has validated the present model.
    Type of Medium: Electronic Resource
    URL: http://www.bepress.com/cppm/vol2/iss1/9
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  • 6
    Electronic Resource
    Electronic Resource
    Performance Analysis of Three Controllers for the Polymerisation of Styrene in a Batch Reactor (2007)
    Berkeley, Calif. : Berkeley Electronic Press (now: De Gruyter)
    Chemical product and process modeling 2 (2007), S. 3 
    Details
    ISSN: 1934-2659
    Source: Berkeley Electronic Press Academic Journals
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: The performance analysis of three advanced non linear controllers is the main focus of this paper. All three controllers are applied for the control of a batch polymerisation reactor which is defined by a very simple kinetic model for the polymerisation of styrene. This simple set of equations describing the polymerisation process is first solved using the sequential strategy i.e. Control Vector Parameterisation (CVP) technique within gPROMS to find optimal initial initiator concentrations and the reactor temperature trajectory necessary to yield desired polymer molecular properties (defined here as fixed values of monomer conversion and number average chain length) in minimum time. The sequential solution strategy has had limited application in solving optimisation problems for polymerisation in batch reactors, most researchers instead employing the Pontryagin's Maximum Principle (PMP) to solve optimal control problems involving these systems.The temperature trajectory obtained from the dynamic optimisation is used as the setpoint to be tracked by the three controllers: Dual Mode control with PID, which is representative of industrial practice, Generic Model Control (GMC) with Neural Networks as online heat release estimator, and Direct Inverse Control (DIC). Published work on the last two controllers as applied to the control of a batch polymerisation reactor is absent from the literature. When the performances of the different controllers are evaluated, it is seen that the GMC-NN controller performs better than the other two for the system under consideration.
    Type of Medium: Electronic Resource
    URL: http://www.bepress.com/cppm/vol2/iss1/3
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  • 7
    Electronic Resource
    Electronic Resource
    A Multi-Level Methodology for Conceptual Reaction-Separation Process Design (2007)
    Berkeley, Calif. : Berkeley Electronic Press (now: De Gruyter)
    Chemical product and process modeling 2 (2007), S. 2 
    Details
    ISSN: 1934-2659
    Source: Berkeley Electronic Press Academic Journals
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Generic technology is presented for the optimal screening of reaction and separation process interactions. The proposed scheme enables the use of particularly rich superstructure formulations that are comprised of two types of generic synthesis units with flexible representation modes. A reaction unit enables a detailed representation of the reaction and a conceptual representation of separation systems is facilitated through separation task units. Possible process design interactions are embedded in the superstructure formulations as combinations of generic units. The design options are explored using stochastic optimisation techniques suitable for this class of problems. The synthesis scheme supports the decision making process in early process design stages and prepares problem definitions for later stages. Conceptual screening functionalities reveal design insights into the performance of complex reaction-separation systems based on the limited modelling information available early in design. This enables the identification and inclusion of the relevant design information into the superstructure formulations employed in the subsequent design stages.
    Type of Medium: Electronic Resource
    URL: http://www.bepress.com/cppm/vol2/iss3/2
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  • 8
    Electronic Resource
    Electronic Resource
    Analysis and Simulation of Cross-Flow Reactor for Ethylene Epoxidation (2007)
    Berkeley, Calif. : Berkeley Electronic Press (now: De Gruyter)
    Chemical product and process modeling 2 (2007), S. 6 
    Details
    ISSN: 1934-2659
    Source: Berkeley Electronic Press Academic Journals
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: A steady-state cross-flow reactor for ethylene epoxidation was simulated using industrial data (low oxygen/ethylene feed ratio) and pilot plant data (high oxygen/ethylene feed ratio). A comparison between the conventional fixed-bed reactor and the cross-flow reactor with two types of feeding modes was performed. The present study showed the possibility of enhancing the reactor yield by distributing the ethylene optimally at equal spaced along the reactor for both commercial and pilot plant cases. We have shown that the evenly distributed feeding mode does not increase the desired ethylene oxide yield. The model results confirmed that the cross-flow reactor with ethylene is the best configuration, followed by the conventional fixed-bed reactor and the cross-flow reactor with oxygen, respectively.
    Type of Medium: Electronic Resource
    URL: http://www.bepress.com/cppm/vol2/iss1/6
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  • 9
    Electronic Resource
    Electronic Resource
    Estimating Output Variance in Closed Loop Systems (2007)
    Berkeley, Calif. : Berkeley Electronic Press (now: De Gruyter)
    Chemical product and process modeling 2 (2007), S. 8 
    Details
    ISSN: 1934-2659
    Source: Berkeley Electronic Press Academic Journals
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: This paper attempts to address a common difficulty encountered when trying to justify a process control revamp or upgrading project -- the ability to quantify potential savings/profits. A relatively simple procedure that is applicable to both continuous and digital controllers is described. Given models of the process and the controller, knowledge of the disturbance frequencies and their variances, the method is able to predict accurately the variance of the controlled output of linear control systems.
    Type of Medium: Electronic Resource
    URL: http://www.bepress.com/cppm/vol2/iss1/8
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  • 10
    Electronic Resource
    Electronic Resource
    Learning to Control pH Processes at Multiple Time Scales: Performance Assessment in a Laboratory Plant (2007)
    Berkeley, Calif. : Berkeley Electronic Press (now: De Gruyter)
    Chemical product and process modeling 2 (2007), S. 7 
    Details
    ISSN: 1934-2659
    Source: Berkeley Electronic Press Academic Journals
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: This article presents a solution to pH control based on model-free learning control (MFLC). The MFLC technique is proposed because the algorithm gives a general solution for acid-base systems, yet is simple enough for implementation in existing control hardware. MFLC is based on reinforcement learning (RL), which is learning by direct interaction with the environment. The MFLC algorithm is model free and satisfying incremental control, input and output constraints. A novel solution of MFLC using multi-step actions (MSA) is presented: actions on multiple time scales consist of several identical primitive actions. This solves the problem of determining a suitable fixed time scale to select control actions so as to trade off accuracy in control against learning complexity. An application of MFLC to a pH process at laboratory scale is presented, showing that the proposed MFLC learns to control adequately the neutralization process, and maintain the process in the goal band. Also, the MFLC controller smoothly manipulates the control signal.
    Type of Medium: Electronic Resource
    URL: http://www.bepress.com/cppm/vol2/iss1/7
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  • 11
    Electronic Resource
    Electronic Resource
    Applications of Computational Fluid Dynamics (CFD) Tools for Gravity Concentrators in Coal Preparation (2007)
    Berkeley, Calif. : Berkeley Electronic Press (now: De Gruyter)
    Chemical product and process modeling 2 (2007), S. 11 
    Details
    ISSN: 1934-2659
    Source: Berkeley Electronic Press Academic Journals
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Extensive progress has been made in using CFD tool in the simulation of multiphase flows in some gravity concentrators. Several case studies for calculation of multiphase flows by different numerical models in spiral, dense medium cyclone, water only cyclones, hindered-settling bed separator, heavy medium vessel and jig are reviewed. The Euler-Lagrange approach in calculation of the particle movement and particle-liquid coupling effect are also discussed. The limitation of Euler-Euler models in the treatment of the particles with a size distribution, and disadvantages of discrete element method (DEM) in description of the jigging processes will be presented. The successful two-dimensional simulation of the hindered-settling bed separator, heavy medium vessel and jig by Euler-Lagrange approach is also addressed.
    Type of Medium: Electronic Resource
    URL: http://www.bepress.com/cppm/vol2/iss1/11
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  • 12
    Electronic Resource
    Electronic Resource
    CFD Diagnosis of the Cyclotol Manufacturing Plant: Product Quality and Process Operation (2007)
    Berkeley, Calif. : Berkeley Electronic Press (now: De Gruyter)
    Chemical product and process modeling 2 (2007), S. 2 
    Details
    ISSN: 1934-2659
    Source: Berkeley Electronic Press Academic Journals
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: The production of cyclotol, a military high explosive used in manufacture of aerial bombs, involves the multiphase mixing of molten TNT, RDX solid particles and water. Textural homogeneity of the final cyclotol mixture and near-zero water composition are critical requirements to minimize bomb-rejection rate and hence improved plant profitability. Although current data reveal significant statistical variation in product quality, detailed investigation of the complex mixing operation does not lend itself to physical experimentation due to the explosive nature of the process. This forestalls opportunities for improved process operation or re-design. To circumvent this constraint, a computational fluid dynamics (CFD) simulation of the industrial-scale process was carried out to understand how current mixing protocols impact on key in-tank profiles such as water draw-down, RDX particles suspension, turbulence kinetic energy, velocity magnitude, vector direction and water-entrainment. The analysis revealed that while the maximum impeller speed allowable to avoid water draw-down is 20 rpm, the minimum speed necessary to suspend the RDX particles for homogeneous mixing is 40 rpm. These opposing requirements are neither accommodated by the present mixing protocols nor achievable with the existing tank design. Even so, the 'mystery' of irrational cyclotol quality has been uncovered by a judicious use of CFD modeling and opened up the possibility of a revised tank design and optimal process operation for superior plant economics.
    Type of Medium: Electronic Resource
    URL: http://www.bepress.com/cppm/vol2/iss1/2
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  • 13
    Electronic Resource
    Electronic Resource
    CFD Simulation of Fine Particle Gravity Separation in Hindered-settling Bed Separators (2007)
    Berkeley, Calif. : Berkeley Electronic Press (now: De Gruyter)
    Chemical product and process modeling 2 (2007), S. 11 
    Details
    ISSN: 1934-2659
    Source: Berkeley Electronic Press Academic Journals
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: In the modeling of hindered-settling bed separators, the published separation mechanisms are based on differences of particle density and size distributions, without the details of the complexity of particles-liquid interactions. A fluid dynamic model for the separator is developed using the Euler-Lagrangian approach of Computational Fluid Dynamics (CFD). Fluid motion is obtained from solving the movement of liquid governing equations. The damping effect on flow patterns caused by the movement of particles resulting in liquid-particle coupling is included in the models. Effects of particle size, particle density compositions, feed rate, feed water flow rate, and upward fluidizing water flow rate, etc., are simulated in the 2-D separation model. Flow pattern effects on the separation of fine particles in the separators with center downward-flow and side cross-flow feed systems are investigated.
    Type of Medium: Electronic Resource
    URL: http://www.bepress.com/cppm/vol2/iss3/11
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  • 14
    Electronic Resource
    Electronic Resource
    Enhanced Explicit Scheme to Solve Transient Heat Conduction Problem (2007)
    Berkeley, Calif. : Berkeley Electronic Press (now: De Gruyter)
    Chemical product and process modeling 2 (2007), S. 4 
    Details
    ISSN: 1934-2659
    Source: Berkeley Electronic Press Academic Journals
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Improvement in accuracy without sacrificing stability and convergence of the solution to unsteady diffusion heat transfer problems by computational method of enhanced explicit scheme (EES), has been achieved and demonstrated, through transient one dimensional and two dimensional heat conduction. The truncation error induced in the explicit scheme using finite difference technique is eliminated by optimization of partial derivatives in the Taylor series expansion, by application of interface theory developed by the authors. This theory, in its simple terms gives the optimum values to the decision vectors in a redundant linear equation. The time derivatives and the spatial partial derivatives in the transient heat conduction, take the values depending on the time step chosen and grid size assumed. The time correction factor and the space correction factor defined by step sizes govern the accuracy, stability and convergence of EES. The comparison of the results of EES with analytical results, show decreased error as compared to the result of explicit scheme. The paper has an objective of reducing error in the explicit scheme by elimination of truncation error introduced by neglecting the higher order terms in the expansion of the governing function. As the pilot examples of the exercise, the implementation is aimed at solving one-dimensional and two-dimensional problems of transient heat conduction and compared with the results cited in the referred literature.
    Type of Medium: Electronic Resource
    URL: http://www.bepress.com/cppm/vol2/iss1/4
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  • 15
    Electronic Resource
    Electronic Resource
    Inference of Chemical Reaction Networks Using Hybrid S-system Models (2007)
    Berkeley, Calif. : Berkeley Electronic Press (now: De Gruyter)
    Chemical product and process modeling 2 (2007), S. 10 
    Details
    ISSN: 1934-2659
    Source: Berkeley Electronic Press Academic Journals
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: This article demonstrates, using simulations, the potential of the S-system formalism for the inference of unknown chemical reaction networks from simple experimental data, such as that typically obtained from laboratory scale reaction vessels. Virtually no prior knowledge of the products and reactants is assumed. S-systems are a power law formalism for the canonical approximate representation of dynamic non-linear systems. This formalism has the useful property that the structure of a network is dictated only by the values of the power law parameters. This means that network inference problems (e.g. inference of the topology of a chemical reaction network) can be recast as parameter estimation problems. The use of S-systems for network inference from data has been reported in a number of biological fields, including metabolic pathway analysis and the inference of gene regulatory networks. Here, the methodology is adapted for use as a hybrid modelling tool to facilitate the reverse engineering of chemical reaction networks using time series concentration data from fed-batch reactor experiments. The principle of the approach is demonstrated with noisy simulated data from fed-batch reactor experiments using a hypothetical reaction network comprising 5 chemical species involved in 4 parallel reactions. A co-evolutionary algorithm is employed to evolve the structure and the parameter values of the S-system equations concurrently. The S-system equations are then interpreted in order to construct a network diagram that accurately reflects the underlying chemical reaction network.
    Type of Medium: Electronic Resource
    URL: http://www.bepress.com/cppm/vol2/iss1/10
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  • 16
    Electronic Resource
    Electronic Resource
    Instrumentation Network Design for Solids Processes (2007)
    Berkeley, Calif. : Berkeley Electronic Press (now: De Gruyter)
    Chemical product and process modeling 2 (2007), S. 9 
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    ISSN: 1934-2659
    Source: Berkeley Electronic Press Academic Journals
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Proper plant control and operation has to be based on measurements of process data at different locations within the process. The design of the instrumentation network is therefore an important step in the design phase of a given process. An advanced instrumentation network design should not only allow process control on a minimum data basis but should enable the plant operator to gain more insights into the functionality and capabilities of his process. For this purpose in-process balancing based on a suitably configured instrumentation network is necessary. To make full use of the measurements the data has to be processed by data reconciliation methods. In the present work an earlier approach by Chmielewski et al. (2002) has been applied to solids processes. This paper shows how the selected approach can be adopted to the measurement and processing of distributed variables, e.g. particle size and densities. An optimal instrumentation with regard to investment cost can be found that ensures that all necessary data for the reconciliation problem can be collected. The application to solids processes is illustrated with the examples of a simple screening-crushing process and a hydrocyclone cascade.
    Type of Medium: Electronic Resource
    URL: http://www.bepress.com/cppm/vol2/iss3/9
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  • 17
    Electronic Resource
    Electronic Resource
    Crisp and Fuzzy Optimisation Approaches for Water Network Retrofit (2007)
    Berkeley, Calif. : Berkeley Electronic Press (now: De Gruyter)
    Chemical product and process modeling 2 (2007), S. 6 
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    ISSN: 1934-2659
    Source: Berkeley Electronic Press Academic Journals
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Material reuse/recycle has gained much attention in recent years for both economic and environmental reasons. Process integration techniques for water network synthesis have evolved rapidly in the past decade. With in-plant water reuse/recycle, fresh water and wastewater flowrates are reduced simultaneously. In this work, linear programming and mixed integer linear programming models that include piping cost and process constraints are developed to retrofit an existing water network in a paper mill that was not originally designed with process integration techniques. Five scenarios are presented, each representing different aspects of decision-making in real process integration projects. The fifth scenario makes use of fuzzy optimisation to achieve a compromise solution that considers the inherent conflict between maximising water recovery and minimising capital cost for retrofit.
    Type of Medium: Electronic Resource
    URL: http://www.bepress.com/cppm/vol2/iss3/6
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  • 18
    Electronic Resource
    Electronic Resource
    A Generalized Kinetic Model for Hydrometallurgical Processes (2007)
    Berkeley, Calif. : Berkeley Electronic Press (now: De Gruyter)
    Chemical product and process modeling 2 (2007), S. 1 
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    ISSN: 1934-2659
    Source: Berkeley Electronic Press Academic Journals
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: In electrochemical leaching processes the solid must be an electric conductor, e.g., a metal, or a semiconductor, e.g., certain metal sulfides or oxides. Reaction takes place by the transfer of electrons at the solid surface and involves oxidation-reduction processes that take place simultaneously at two different locations not far from each other. At one location, electrons are picked up by a depolarizer, D, in solution, e.g., O2, H+, etc. (the cathodic zone) and at another location metal ions are released in solution (the anodic zone) where they react with reagent C. A single kinetic law derived theoretically is obeyed:Rate = k1k2A[D][C] / (k1[D] + k2[C]) where k1 and k2 are constants, and A is the total surface area of the dissolving solid.
    Type of Medium: Electronic Resource
    URL: http://www.bepress.com/cppm/vol2/iss1/1
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  • 19
    Electronic Resource
    Electronic Resource
    Advanced Modeling of Reactive Separation Units with Structured Packings (2007)
    Berkeley, Calif. : Berkeley Electronic Press (now: De Gruyter)
    Chemical product and process modeling 2 (2007), S. 5 
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    ISSN: 1934-2659
    Source: Berkeley Electronic Press Academic Journals
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Reactive separations combining mass transfer with simultaneous chemical reactions within a single column unit provide an important synergistic effect and bring about several advantages. The influence of column internals in reactive separations increases significantly, because these internals have to enhance both separation and reaction and maintain a sound balance between them. To solve this problem, a novel generation of column internals with enhanced mass transfer performance and low pressure drop has been created. Among them, corrugated packings of the regular type or structured packings have gained a wide acceptance.This paper gives a state-of-the-art review of the structured packings modeling methods, focusing on two innovative and particularly promising approaches. The first of them is based on the application of CFD, whereas the second one employs the idea of hydrodynamic analogy between complex and simple flow patterns. Both approaches are illustrated with several case studies.
    Type of Medium: Electronic Resource
    URL: http://www.bepress.com/cppm/vol2/iss1/5
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  • 20
    Electronic Resource
    Electronic Resource
    Spatial and Temporal Resolution in Data-Driven Process Modeling of an Integrated Newsprint Mill (2007)
    Berkeley, Calif. : Berkeley Electronic Press (now: De Gruyter)
    Chemical product and process modeling 2 (2007), S. 13 
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    ISSN: 1934-2659
    Source: Berkeley Electronic Press Academic Journals
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Like many globalized industries, the pulp and paper sector finds itself with an increasingly demanding clientele, who continually expect a better and cheaper product. An important design strategy being employed to address this objective is through an analysis of the vast quantity of process and product data accumulated in plant-wide data historians, in order to improve operations. Mill processes are multivariate, meaning that the interactions between the variables are as important as the variables themselves. Process relationships must therefore be modeled as a group, using an appropriate simulation technique like Multivariate Analysis (MVA), with suitable data pre-processing to account for process upsets and other disturbances. In a previous paper, using an Eastern Canadian newsprint mill as an industrial case study, we showed that it was possible to find statistically significant correlations between wood chip refiner operation, intermediate pulp quality, and final paper quality using data-driven models. This was true even though some important process parameters went unmeasured, process lags changed with time, and the operation of key equipment items changed gradually with use. The present study compares the use of different timescales and combinations of unit operations to determine which ones yield the best MVA simulations. Because plant operating data were used, and experimental design was not practical, it is possible that some of the correlations found could be attributable to coincidence. We therefore added and removed variables and time periods to explore the validity of the models. The best MVA models were obtained by using a shorter (1-hour) data timescale, although use of a weighted-average filter helped to bridge the gap between these faster readings and the slower paper quality trends.
    Type of Medium: Electronic Resource
    URL: http://www.bepress.com/cppm/vol2/iss1/13
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  • 21
    Electronic Resource
    Electronic Resource
    Optimization of the Variable Reflux Ratio in a Batch Distillation Column through a Heuristic Method (2007)
    Berkeley, Calif. : Berkeley Electronic Press (now: De Gruyter)
    Chemical product and process modeling 2 (2007), S. 12 
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    ISSN: 1934-2659
    Source: Berkeley Electronic Press Academic Journals
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: The manuscript is focused on the optimization of a batch distillation column that is actually formulated in terms of control problem. The final objective is finding the optimal time-dependent reflux profile. In order to fulfill the call for simplicity and functionality from the industries, the reflux profile was approximated by means of a piece-wise function with three time intervals. A first-principles model, derived from the literature, proved to be a good trade-off between computational effort and accuracy. The capacity factor (CAP), defined as the on-specification products produced per time unit, is the performance index that must be maximized. The optimization problem was solved by a specifically modified Simplex method that demonstrated a good behavior in case of discontinuous objective function. Finally, a graphical analysis of the capacity factor was performed to show the irregularities of such a function.
    Type of Medium: Electronic Resource
    URL: http://www.bepress.com/cppm/vol2/iss1/12
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    Electronic Resource
    Hedge's Ultimate Numerical Technique (HUNT) for Steady State Diffusion Problem (2007)
    Berkeley, Calif. : Berkeley Electronic Press (now: De Gruyter)
    Chemical product and process modeling 2 (2007), S. 5 
    Details
    ISSN: 1934-2659
    Source: Berkeley Electronic Press Academic Journals
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: A more realistic numerical technique hereafter known as Hegde's Ultimate Numerical Technique (HUNT) is developed and demonstrated on a one dimensional and a two dimensional steady state diffusion problem of heat transfer. The available numerical methods developed are based on finite difference technique neglecting the contribution of higher order terms in Taylor series expansion of the function leading to an approximation and the error in the solution. In the present effort of the HUNT, the optimization of the partial derivatives leads to the elimination of the error and justifies the stability and the convergence of the solution. The HUNT procedure based on the interface theory developed by the author, is capable of providing the ultimate optimum solution to all the partial derivatives considered as decision vectors. Even though the HUNT is demonstrated on one dimensional and two dimensional steady state diffusion equations, it does not require rigorous efforts to apply it to three dimensional problems of fluid flow and heat transfer. As pilot exercises the HUNT is demonstrated on a one dimensional circular fin and a two dimensional plate to obtain the temperature distribution. The result is compared with the analytical method and the finite volume method for which the results are available in the literature. To the knowledge of the authors, HUNT is both different and a unique example of its kind.
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  • 23
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    Parallel Dynamic Artificial Neural Network for Temperature and Moisture Content Predictions in Microwave-Vacuum Dried Tomato Slices (2007)
    Berkeley, Calif. : Berkeley Electronic Press (now: De Gruyter)
    Chemical product and process modeling 2 (2007), S. 23 
    Details
    ISSN: 1934-2659
    Source: Berkeley Electronic Press Academic Journals
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Temperature (T) and moisture content (MC) of non-homogenous food undergoing microwave-vacuum (MV) drying (MVD) are directly dependent on microwave power, vacuum pressure, and the product's physical properties. A two-hidden-layer Artificial Neural Network (ANN) model was developed in an earlier study to predict temperature and moisture content of the product at a given time based on the present state of product conditions and process control parameters. This approach either provided lowest error in temperature prediction or in moisture content prediction but not the lowest error in both the prediction parameters simultaneously. The main objective of this work was to improve the performance of the ANN model for temperature and moisture content predictions in MV dried samples. Experimental data obtained from MVD of tomato slices at different drying conditions was normalized and divided into two groups for training and validating. The parallel dynamic ANN model consisted of two double-hidden-layer feed-forward ANN models with varying node numbers (10, 20, and 30). These models were separately trained, simultaneously for moisture content as well as temperature, with the Levenberg-Marquardt algorithm. Inputs for the ANN models were magnetron on-off status, vacuum pressure, temperature, and moisture content at time `ti'. The previous temperature and moisture content data at time `ti-1, i-2, , i-n' where n = 0, 10, 20, and 30 were also added to the input layer. Outputs from the ANN models were temperature and moisture content at time `ti+1'. The results indicated that the dynamic ANN model working in parallel with the previous temperature and moisture content data provided results that are more accurate and required less training time than those of ordinary ANN models. Model simulation may supply essential information regarding temperature and moisture content of non-homogenous foods corresponding to microwave power and vacuum pressure levels to the predictive control system. Therefore, improved drying efficiencies and thermal damage prevention may be achieved.
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  • 24
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    Estimation of Moisture Ratio of a Mushroom Undergoing Microwave-vacuum Drying Using Artificial Neural Network and Regression Models (2007)
    Berkeley, Calif. : Berkeley Electronic Press (now: De Gruyter)
    Chemical product and process modeling 2 (2007), S. 25 
    Details
    ISSN: 1934-2659
    Source: Berkeley Electronic Press Academic Journals
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: The drying rate of a mushroom undergoing microwave-vacuum (MV) drying (MVD) was controlled by moisture dissipation and was dependent on vacuum pressure levels. The main objective of this work was to develop artificial neural network (ANN) model to predict moisture ratio of MV-dried mushrooms. One-hidden-layer feed-forward ANN models were trained and validated with experimental data. The Levenberg-Marquardt algorithm was utilized in regulating the ANN model weights and biases. Inputs for ANN models were vacuum pressure and drying time. Output from ANN models was moisture ratio at a given drying time. Reduced chi-square (X 2) and root mean square error (RMSE), and residual sum of squares (RSS) of the results from ANN models were calculated and compared with those of a modified Page's model (an experimental-based mathematical model), which is commonly used in the literature. The X 2, RMSE, and RSS of the ANN model (2.272 x 10 -5, 4.023 x 10 -3, and 3.204 x 10 -3, respectively) were found to be lower than those of the modified Page's model (6.692 x 10 -4, 2.561 x 10 -2, and 12.98 x 10 -2, respectively). These results indicate that the feed-forward ANN model represented the drying characteristics of mushrooms better than the modified Page's model. Therefore, the ANN model could be considered as a better tool for estimation of the moisture content of mushrooms than by the modified Page's model.
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    Mathematical Analysis of a Novel Formaldehyde Remediation Process (2007)
    Berkeley, Calif. : Berkeley Electronic Press (now: De Gruyter)
    Chemical product and process modeling 2 (2007), S. 1 
    Details
    ISSN: 1934-2659
    Source: Berkeley Electronic Press Academic Journals
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: The NASA low-temperature oxidation catalyst (Pt/SnO2), originally developed for space-based carbon dioxide laser applications has been recently adapted to address formaldehyde destruction in industrial smoke stack emission streams. A mathematical model is developed that can be used to correlate the observable chemistry occurring on the surfaces of a monolith with the volumetric flow rate of the gas and cross sectional area of catalyst surfaces as well as quantifying process design variables such as pressure or temperature of an exhaust gas stream.
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    Sliding-mode Observer for Uncertainty Estimation in a Class of Chemical Reactor: A Differential-Algebraic Approach (2007)
    Berkeley, Calif. : Berkeley Electronic Press (now: De Gruyter)
    Chemical product and process modeling 2 (2007), S. 10 
    Details
    ISSN: 1934-2659
    Source: Berkeley Electronic Press Academic Journals
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: The problem of the on-line estimation of the reaction heat in a continuous stirred tank reactor from temperature measurements is addressed in this paper. The proposed uncertainty observer is based on differential algebraic techniques, such that the algebraic observability condition of the uncertainty from noisy temperature measurements is easily verified and the observer structure is very simple, which lead to feasible implementation. The observer proposed is robust against noisy measurements and sustained disturbances. The good performance of the observer is shown by means of numerical simulations and is compared with a nonlinear Luenberger-type observer.
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  • 27
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    Forecasting Influent-Effluent Wastewater Treatment Plant Using Time Series Analysis and Artificial Neural Network Techniques (2007)
    Berkeley, Calif. : Berkeley Electronic Press (now: De Gruyter)
    Chemical product and process modeling 2 (2007), S. 3 
    Details
    ISSN: 1934-2659
    Source: Berkeley Electronic Press Academic Journals
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: We consider the problem of predicting the future behavior of wastewater treatment plant quality indicators by creating prediction models using historical plant data. One of the main aims of this work is to be able to predict plant operational situations in advance so that corrective actions can be taken in time. Sets of historical plant data, such as BOD, COD and TSS were collected for a local wastewater treatment plant in Doha, the capital of the State of Qatar. These variables characterize the performance of any wastewater treatment plant and can be considered as quality indicators of the plant performance. Data were collected over a period of 4 years for the influent and effluent streams of the station. The plant influent and effluent predictions were performed using different techniques. These include time-series analysis, where the ARIMA (Autoregressive Integrated Moving Average) model was implemented in this case, and two Artificial Neural Networks (ANN) algorithms, namely Adaptive Linear Neuron networks (ADALINE) and Multi-layer Feedforward (ML-FF) neural networks. The predictions from the three techniques were presented and compared. The ML-FF model predictions proved to be more reliable than that of the equivalent ARIMA predictions followed by the ADALINE predictions, particularly for the finial effluent stream variables.
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    URL: http://www.bepress.com/cppm/vol2/iss3/3
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    Multirate Constrained Predictive Control: Algorithm and Experimental Results (2007)
    Berkeley, Calif. : Berkeley Electronic Press (now: De Gruyter)
    Chemical product and process modeling 2 (2007), S. 13 
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    ISSN: 1934-2659
    Source: Berkeley Electronic Press Academic Journals
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Control of multirate systems is a challenging problem due to several reasons such as increased complexity in the design with tighter performance specifications. In this work, an algorithm for multirate constrained predictive control (MCPC) is presented. The multirate predictive control system includes a multirate state estimator, which provides inter-sample estimates of state variables of the process from infrequent and slow measurements. Constraints are addressed rigorously in this framework. The proposed design method is verified via simulation as well as experimentation. The results of the multirate predictive control for temperature control of a stirred tank system are shown and compared with those of a proportional integral (PI) control system.
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  • 29
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    Passivity Based Dynamic Controllability Analysis for Multi-Unit Processes (2007)
    Berkeley, Calif. : Berkeley Electronic Press (now: De Gruyter)
    Chemical product and process modeling 2 (2007), S. 7 
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    ISSN: 1934-2659
    Source: Berkeley Electronic Press Academic Journals
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: In this paper, a simple dynamic controllability analysis is developed to analyze the achievable control performance of different control structures for multi-unit processes. Based on the concept of passive systems, this approach extends the concepts of Decentralized Integral Controllability (DIC) and Block-Decentralized Integral Controllability (BDIC) so that process dynamics are considered. By using particular multipliers that represent different control structures, the frequency ranges in which perfect control may be achieved by multi-loop, multi-unit (block diagonal) and multivariable controllers are estimated. This bandwidth indicates the swiftness of the feedback control systems (e.g., the time the control systems take to reject a disturbance).
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    Prediction of Biomedical Waste Load at Centralized Treatment Facility (2007)
    Berkeley, Calif. : Berkeley Electronic Press (now: De Gruyter)
    Chemical product and process modeling 2 (2007), S. 4 
    Details
    ISSN: 1934-2659
    Source: Berkeley Electronic Press Academic Journals
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: The Local Municipal Corporation operates a centralized treatment facility (CTF) to facilitate effective and safe disposal of hazardous biomedical waste generated from various health care facilities (HCFs) in a region. Managing these wastes is a challenging task due to unpredictable variation in amount of waste received at a CTF. In this paper a mathematical model is presented that predicts the load on CTF as a function of bed occupancy of some representative hospitals in the region. Models are available to predict waste generated from a particular hospital in terms of bed occupancy; however, it is difficult to predict total waste received at CTF that also includes wastes from HCFs other than hospitals. To develop the model, data for the waste generated at source and for waste incinerated at CTF were collected for two consecutive years on daily basis. It was observed that two hospitals are representative of the rate of biomedical waste generation in the region from all HCFs. In two consecutive years, there were significantly different trends in overall waste incinerated at CTF. The reason for variation in waste load at CTF was observed to be due to uneven load on the HCFs in two consecutive years.
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    Simulation of Free Chlorine Decay and Adaptive Chlorine Dosing by Discrete Time-Space Model for Drinking Water Distribution System (2007)
    Berkeley, Calif. : Berkeley Electronic Press (now: De Gruyter)
    Chemical product and process modeling 2 (2007), S. 3 
    Details
    ISSN: 1934-2659
    Source: Berkeley Electronic Press Academic Journals
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: An ideal drinking water distribution system (DWDS) must supply safe drinking water with free chlorine residual (FCR) in the form of HOCl and OCl- at a required concentration level. The FCR as a disinfectant decreases over time due to chemical reactions in the bulk phase and at the pipe wall in the DWDS. In order to supply drinking water with the FCR concentration within the safety range of 0.2-0.6 mg/l at the points of water consumption, it is important to develop a dynamic model of the FCR using a discrete time-space model (DTSM) that accounts for free chlorine transport in the axial direction by convection, diffusion and the decay kinetic. A DTSM has been developed using Finite Difference Method (FDM) to predict the FCR in single pipes in the DWDS. The DTSM has been computed using Matlab 7.0.1 and tested with step inputs and rectangular pulse inputs to estimate the FCR at any point in the pipes over time. Data found in the literature have been used to validate the DTSM. The modelling and simulation study shows that the water velocity significantly affects the FCR concentration distribution along the pipe. Due to the fluctuation of the drinking water demand, a model-based adaptive chlorine dosing scheme is proposed to control the proper injection of chlorine.
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  • 32
    Electronic Resource
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    Dynamic Simulation of Reactive Batch Distillation Column for Ethyl Acetate Synthesis (2007)
    Berkeley, Calif. : Berkeley Electronic Press (now: De Gruyter)
    Chemical product and process modeling 2 (2007), S. 5 
    Details
    ISSN: 1934-2659
    Source: Berkeley Electronic Press Academic Journals
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: A detailed mathematical dynamic model of reactive batch distillation column is formulated for ethyl acetate synthesis and presented in terms of differential and algebraic equations (DAEs). These DAEs are solved using fourth order Runge-Kutta method in MATLAB® to obtain the detailed column dynamics. The simulation results provide the dynamics of reboiler and distillate compositions, reboiler temperature, ethyl acetate purity in the accumulated distillate and conversion of the reactants. These results are analyzed to derive the optimum operating policy, i.e., reflux ratio and batch time.
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    Three-Dimensional Hydrodynamics and Reaction Kinetics Analysis in FCC Riser Reactors (2007)
    Berkeley, Calif. : Berkeley Electronic Press (now: De Gruyter)
    Chemical product and process modeling 2 (2007), S. 4 
    Details
    ISSN: 1934-2659
    Source: Berkeley Electronic Press Academic Journals
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Fluid catalytic cracking (FCC) is the refinery process for the conversion of high molecular-weight hydrocarbons to produce higher valuable products such as gasoline. The optimization of FCC process is challenging due to the complex interactions between a large number of dependent and independent parameters. One of the most uncertain aspects of a fluid catalytic cracking (FCC) unit is the description of fluid-solid mixing at the riser entrance. Most of the existing models assume an instant mixing of solids and gaseous reactants. However, a finite mixing length at the bottom of the riser may have a pronounced effect on the FCC operation, particularly, when very short residence times are allowed in the current commercial FCC risers. A good solid-fluid mixing is essential to ensure a complete feed vaporization which is important for several reasons including assuring a thorough catalyst to oil contact and minimizing coke deposition. In this study, the Eulerian-Eulerian multiphase flow and the 3-lump kinetic models were used to simulate the hydrodynamics and cracking reactions occurring in the FCC riser reactors. The model demonstrated the capability of commercial CFD code FLUENT 6.2 to describe the flow field in the riser reactor. The model also takes into account the temperature, the heat of reactions and gasoline distribution along the riser height.
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    Mathematical Modelling of the Self-Heating Process in Compost Piles (2007)
    Berkeley, Calif. : Berkeley Electronic Press (now: De Gruyter)
    Chemical product and process modeling 2 (2007), S. 8 
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    ISSN: 1934-2659
    Source: Berkeley Electronic Press Academic Journals
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: We model the increase in temperature in compost piles or landfill sites due to micro-organisms undergoing exothermic reactions. The model incorporates the heat release due to biological activity within the pile and the heat release due to the oxidation of cellulosic materials. The heat release rate due to biological activity is modelled by a function which is a monotonic increasing function of temperature over a particular range and followed by a monotone decreasing function of temperature. This functionality represents the fact that micro-organisms die or become dormant at high temperatures. The heat release due to the oxidation reaction is modelled by the usual manner using Arrhenius kinetics. The bifurcation behaviour is investigated for two-dimensional slab geometries to determine the critical sizes of the compost piles.
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    Nonlinear Process Operability Analysis Based on Steady-State Simulation: A Case Study (2007)
    Berkeley, Calif. : Berkeley Electronic Press (now: De Gruyter)
    Chemical product and process modeling 2 (2007), S. 6 
    Details
    ISSN: 1934-2659
    Source: Berkeley Electronic Press Academic Journals
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: In this paper, the operability of a high-purity distillation column is presented. This process is known to be difficult to control and operate due to the high degree of nonlinearity of the process. The analytical framework used to assess the process operability are the regions of steady-state attainability, recently developed by Rojas et al (2006). This framework is selected because it allows one to assess the viability of applying linear control to a nonlinear process solely based on the process nonlinear steady-state information. In this approach, two operating regions are defined in both input and output spaces, which provide an indication of the inherent difficulty of controlling the nonlinear process using linear output feedback. In order to integrate this operability analysis in process design practice, the analysis is based on a numerical steady-state simulation of the column using ASPEN PLUS®. By using ASPEN Sensitivity Analysis Tool that varies the column inputs across a pre-defined Available Input Space, the steady-state nonlinear map of the column outputs can be generated. Based on these simulation results, the regions of steady-state attainability can be obtained and used to provide insights to the operability properties of this highly non linear system.
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    On-Line Dynamic Data Reconciliation Incorporating Dynamic Simulation (2007)
    Berkeley, Calif. : Berkeley Electronic Press (now: De Gruyter)
    Chemical product and process modeling 2 (2007), S. 9 
    Details
    ISSN: 1934-2659
    Source: Berkeley Electronic Press Academic Journals
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: The formulations for dynamic data reconciliation found in the literature assume that the error minimization problem is solved as a non-linear optimization problem constrained by the material and energy balances in the form of time-dependant non-linear differential equations. In this paper we introduce a new approach or an unconstrained formulation of this problem using a dynamic process simulator or model calculator and its potential application to chemical process control.
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    Development of Heat Exchanger Fouling Model and Preventive Maintenance Diagnostic Tool (2007)
    Berkeley, Calif. : Berkeley Electronic Press (now: De Gruyter)
    Chemical product and process modeling 2 (2007), S. 10 
    Details
    ISSN: 1934-2659
    Source: Berkeley Electronic Press Academic Journals
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: The Crude Preheat Train (CPT) is a set of large heat exchangers which recover the waste heat from product streams back to preheat the crude oil. The overall heat transfer coefficient in these heat exchangers may be significantly reduced due to fouling. One of the major impacts of fouling in CPT operation is the reduced heat transfer efficiency. The objective of this paper is to develop a predictive model using statistical methods which can a priori predict the rate of the fouling and the decrease in heat transfer efficiency in a heat exchanger in a crude preheat train. This predictive model will then be integrated into a preventive maintenance diagnostic tool to plan the cleaning of the heat exchanger to remove the fouling and bring back the heat exchanger efficiency to their peak values. The fouling model was developed using historical plant operating data and is based on Neural Network. Results show that the predictive model is able to predict the shell and tube outlet temperatures with excellent accuracy, where the Root Mean Square Error (RMSE) obtained is less than 1%, correlation coefficient R2 of approximately 0.98 and Correct Directional Change (CDC) values of more than 90%. A preliminary case study shows promising indication that the predictive model may be integrated into a preventive maintenance scheduling for the heat exchanger cleaning.
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    Suppression and Reversal of Drop Formation in a Model Paint Film (2007)
    Berkeley, Calif. : Berkeley Electronic Press (now: De Gruyter)
    Chemical product and process modeling 2 (2007), S. 19 
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    ISSN: 1934-2659
    Source: Berkeley Electronic Press Academic Journals
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: When a paint film is applied to the underside of a horizontal substrate, instabilities will lead to the formation of pendant drops. For sufficiently thick coatings, the drops may even detach from the coating before the coating dries. But even for thin paint films, with sufficiently high evaporation rates and viscosity, drop formation will lead to coating irregularities with thick regions (corresponding to the center of the drop) adjacent to much thinner regions (corresponding to troughs between drops.) In this paper we present a mathematical and numerical model based on the lubrication approximations for the drying of paint films on the underside of horizontal substrates. The paint is modeled as a multicomponent liquid with one non-volatile and one volatile component, termed the ``resin'' and ``solvent'' respectively. Our model includes the effects of surface tension and gravitational forces, and we show that surface tension gradient effects due to solvent evaporation must be considered to correctly model the post-application flow of certain paints. Simulations are given for an array of parameters, and they show that surface tension gradients can dramatically affect the post-application behavior of a model paint film, generally causing the suppression and reversal in drop growth, consequently leading to a more even final coating layer.
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  • 39
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    Modelling of the Development of the Vertical Density Profile of MDF during Hot Pressing (2007)
    Berkeley, Calif. : Berkeley Electronic Press (now: De Gruyter)
    Chemical product and process modeling 2 (2007), S. 2 
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    ISSN: 1934-2659
    Source: Berkeley Electronic Press Academic Journals
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: The hot pressing operation is one of the most important operations in medium density fibreboard (MDF) manufacture. Complicated dynamic interactions occur during pressing, including heat transfer, moisture movement, development of gas pressure, internal stress development and relaxation, wood consolidation, resin curing, bonding between particles and eventual development of a non-uniform density distribution through the panel thickness. Consequently the mat experiences continuously changing internal conditions (temperature and moisture content) as the pressing operation proceeds. The vertical density profile (VDP) has a major influence on the MDF strength and physical properties. This influence of the VDP on the board properties is generally recognised, but the formation of the density profile and their specific effects on the board performance have proved difficult to quantify. A mathematical model based on theoretical analysis and experimental information is being developed. In the model, the mat is divided into a number of thin parallel layers. The deformation of each layer is a function of stress, temperature and moisture content of the layer. The model incorporates the variation of the mat mechanical and rheological properties with moisture content and temperature. The changes in temperature and moisture content are provided by a separate heat and mass transfer model. The present model can predict stress, strain, layer deformation and density across the thickness during pressing. The performance of the model was validated by experiments conducted in a pilot-scale press. Twelve MDF boards were made with different pressing parameters, and the VDP were measured and compared with the simulation results from the model. The model could predict the density profile with an acceptable accuracy for the main variables that control the manufacturing of MDF boards.
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    Numerical Simulation of Electrolyte Two-Phase Flow Induced by Anode Bubbles in an Aluminum Reduction Cell (2007)
    Berkeley, Calif. : Berkeley Electronic Press (now: De Gruyter)
    Chemical product and process modeling 2 (2007), S. 11 
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    ISSN: 1934-2659
    Source: Berkeley Electronic Press Academic Journals
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: In the production process of aluminium reduction cells, the anode bubble laden layer has several important influences on the performance of the aluminium reduction cells. Especially for a "drained cathode cell", without the agitating of movement of the melted metal, the bath flow field could be more important. In this paper, the electrolyte two-phase flow fields were studied by using numerically simulation method based on a two-phase turbulence model combining the k - ? model and the Discrete Random Walk model. The results show that: the motion of the bubbles mostly exists within a thin layer under the anode, which results in inducing local electrolyte to flow around the anode in various circulation flows; the flow field in the anode-cathode space can be divided into three regions with different characters; the results also show the Driving action of bubbles is closely related to the current density, inclination of anode and the anode-cathode distance. In general, the increasing in the current density increases the electrolyte velocity and the turbulent kinetic energy. The decrease in ACD significantly enhances the uniformity of the electrolyte flow field in the anode-cathode space. The increase in anode inclination angle increases the velocity of the electrolyte in the anode-cathode space, which would be beneficial to improving the diffusion and dissolution of the alumina and reducing the resistance between the anode and cathode.
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    A Model to Predict Radial Solids Holdup and Liquid Velocity Distributions in Liquid-Solid Circulating Fluidized Bed (2007)
    Berkeley, Calif. : Berkeley Electronic Press (now: De Gruyter)
    Chemical product and process modeling 2 (2007), S. 28 
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    ISSN: 1934-2659
    Source: Berkeley Electronic Press Academic Journals
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: A general expression which is useful for predicting the radial distributions or for analyzing and interpreting experimental data is derived for a liquid-solid circulating fluidized bed. The effect of both the radial liquid velocity and solids holdup distributions are taken into account in the analysis. Both effects are analyzed and are related to the operating variables of superficial liquid velocity, jl, superficial solids velocity, js, and cross-sectional average solids holdup. The results predicted by the analysis are compared with the experimental data obtained for various two-phase flow regimes, when different solids and bed dimensions are applied. The model predictions show good agreements with the experimental data and reasonable trends when different solids and bed dimensions are applied. Stronger non-uniformities in flow structures are found in larger size particles systems, with larger solids density and/or larger diameter columns. Radial solids holdup distribution is related with the cross-sectional average solids holdup. Good agreement with data and reasonable trends are observed.
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    Editorial: Special Issue Contributed from CHEMECA 2006-Australasian Process Modelling and Control Selected Papers (2007)
    Berkeley, Calif. : Berkeley Electronic Press (now: De Gruyter)
    Chemical product and process modeling 2 (2007), S. 1 
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    ISSN: 1934-2659
    Source: Berkeley Electronic Press Academic Journals
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: The papers in this issue of Chemical Product and Process Modelling are substantially those that arose from special sessions on ``process simulation and control" (organised by Brent R. Young) and ``mathematical modeling" (organised by Mark I. Nelson) at the 34th Australasian Chemical Engineering Conference (held between 17-20th September 2006, in Auckland, New Zealand). The papers in this special issue are available at: http://www.bepress.com/cppm/vol2/iss2. The papers featured in this issue have been revised and extended from CHEMECA and re-reviewed before publication here.All the papers in this issue use mathematics. However, this special issue only features a small number of the presentations at CHEMECA that use mathematics. Mathematics finds many practical applications within chemical engineering and consequently presentations involving mathematics were featured in many special sessions throughout CHEMECA. Some of these presentations will appear in special issues elsewhere. In particular, the papers from every session that were nominated for the John Brodie award are appearing in a special issue of the Asian-Pacific Journal of Chemical Engineering.
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    Assessing the Deposition of a Water Spray on a Plate in a Simple Box Configuration Using Computational Fluid Dynamics (CFD) (2007)
    Berkeley, Calif. : Berkeley Electronic Press (now: De Gruyter)
    Chemical product and process modeling 2 (2007), S. 16 
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    ISSN: 1934-2659
    Source: Berkeley Electronic Press Academic Journals
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: The deposition rates for a water spray on a plate have been studied in a rectangular box configuration to determine the effects of turbulence and droplet size in a relatively simple geometrical configuration, with the aim being to assess the ability of a CFD simulation to predict the actual wall deposition fluxes and the trends in these fluxes in such a geometry. The main air velocities that were used in this study were 1 m/s and 2 m/s inside the box. The results from the Computational Fluid Dynamics (CFD) simulations underpredicted the percentage deposition on the plate significantly (by about 75% and lower) compared with the experiments. The droplet size effects on the deposition rates were studied by varying the atomizer air pressure (air flow rate). The inlet turbulence level was changed by placing a mesh at the box inlet. The results of experiments and simulations showed similar trends when decreasing the droplet size. Increasing the turbulence intensity at the box inlet seems to result in underpredicting the actual amounts of deposition, since the movements of the fine droplets are not well predicted by RANS approaches, because the RANS approaches do not predict the gas-phase turbulence levels near the walls well. The other reasons for the underprediction in the simulations could be coalescence of droplets in the spray, dispersion of droplets due to turbulence and radial variations in droplet velocities and sizes in the spray.
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    Nonlinear Modelling Application in Distillation Column (2007)
    Berkeley, Calif. : Berkeley Electronic Press (now: De Gruyter)
    Chemical product and process modeling 2 (2007), S. 12 
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    ISSN: 1934-2659
    Source: Berkeley Electronic Press Academic Journals
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Distillation columns are widely used in chemical processes and exhibit nonlinear dynamic behavior. In order to gain optimum performance of the distillation column, an effective control strategy is needed. In recent years, model based control strategies such as internal model control (IMC) and model predictive control (MPC) have been revealed as better control systems compared to the conventional method. But one of the major challenges in developing this effective control strategy is to construct a model which is utilized to describe the process under consideration. The purpose of this paper is to provide a review of the models that have been implemented in continuous distillation columns. These models are categorized under three major groups: fundamental models, which are derived from mass, energy and momentum balances of the process, empirical models, which are derived from input-output data of the process, and hybrid models which combine both the fundamental and the empirical model. The advantages and limitations of each group are discussed and compared. The review reveals a remarkable prospect of developing a nonlinear model in this research area. It also shows the discovery of new advance methods in an attempt to gain a nonlinear model that is able to be used in industries. Neural network models have become the most popular framework in nonlinear model development over the last decade even though hybrid models are the most promising method to be applied for future nonlinear model development.
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    Simulation and Analysis of Fluid Dynamic Behaviour of Foods during Filling Processes (2007)
    Berkeley, Calif. : Berkeley Electronic Press (now: De Gruyter)
    Chemical product and process modeling 2 (2007), S. 18 
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    ISSN: 1934-2659
    Source: Berkeley Electronic Press Academic Journals
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: This research presents a model describing the behaviour of a non-Newtonian shear-thinning fluid during aseptic filling processes, in order to determine the influence of the behaviour of fluids on the performance of filling valves in aseptic beverage plants, mainly in terms of the time required to perform the filling process. The ultimate aim of the study is to explore the possibility of improving the accuracy of industrial filling processes, so as to be able to utilise them with high viscosity fluids.The numerical model, exploiting the Finite Elements Method (FEM), was designed using the commercial software Comsol Multiphysics, and validated by comparing the steady state predictions with outcomes of filling experiments performed in industrial laboratories. Hence, subsequent numerical simulations were performed to investigate the transition from laminar to turbulent flow for shear-thinning fluids under different pressure conditions, in 3D time-dependent configurations. Results of the simulations, performed on a low fat yoghurt, show that laminar flow subsists within the whole filling system when the Metzner-Reed Reynolds number at the inlet section of the valve is lower than approx 444.
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    Parameter Estimation Using Sliding Mode Observers: Application to the Monod Kinetic Model (2007)
    Berkeley, Calif. : Berkeley Electronic Press (now: De Gruyter)
    Chemical product and process modeling 2 (2007), S. 21 
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    ISSN: 1934-2659
    Source: Berkeley Electronic Press Academic Journals
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: In this paper a technique borrowed from modern control theory, called sliding mode observers, is used as the vehicle for nonlinear parameter estimation. The observer is a dynamic system derived from the original state equations that guides, in real time, parameter values from initial estimates to optimal ones. This is done by driving errors between the estimated and "data" states to zero. Observers are developed and demonstrated for the Monod model for biokinetics, which has been used widely in bioprocess design for both aerobic and anaerobic bio-processes under both toxic and non-toxic conditions. The Monod model has four parameters; often, two of the parameters (y, yield and b, decay coefficient) are assumed or calculated from other sources such as from thermodynamic considerations. The other two parameters (k, maximum specific uptake rate of the substrate and ks, the half saturation constant for growth) are determined from experimental data. The determination of these parameters is often performed using nonlinear regression or related methods and it has been demonstrated that these are particularly difficult parameter estimation problems. Examples are presented where only k is unknown and when both k and ks are to be determined. One case where the data are corrupted with noise is considered. The primary objective of the paper is to introduce the methodology of sliding mode observers for nonlinear parameter estimation to the chemical and process engineering communities.
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    A Unified Approach for Modeling Three-Way Catalytic Converters and NOx Traps with a Minimum Set of Tunable Parameters (2007)
    Berkeley, Calif. : Berkeley Electronic Press (now: De Gruyter)
    Chemical product and process modeling 2 (2007), S. 15 
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    ISSN: 1934-2659
    Source: Berkeley Electronic Press Academic Journals
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: The demanding legislation for vehicle emissions pushes the automotive industry to the commercialization of advanced exhaust systems. The careful design of each aftertreatment device fitted in exhaust line and the interactions with the engine management, makes modelling an important part of systems engineering for these applications. Almost all catalytic converter models that are found in the literature use tunable parameters which typically address the kinetic terms of chemical reactions. A great effort has been given to the definition of complex reaction schemes and mechanistic description of them in-vitro, in order to assist the advanced design of catalytic washcoats and explain their complex chemistry. This paper presents a systematic effort towards the modelling of advanced commercial exhaust treatment systems, using a unified approach for the different devices. The model used in this work describes the catalytic processes with global reactions, using apparent Arrhenius type rate expressions with L-H kinetics. The model is used to predict transient performance of commercial catalytic converters under legislated test conditions. During these tests the existing uncertainties and intrinsic variations of engine and catalyst operation make the robustness and flexibility of the model prominent targets. Comparison of computed and measured second-by-second emissions demonstrate a high level of modelling accuracy, adequate to fit the behavior of advanced commercial applications of three-way catalytic converters and NOx traps, using a minimum set of 3 tunable parameters for each device.
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    On-line Fault Detection and Isolation for State Space Models Using a Combination of Extended Kalman Filters and the Standardized Innovation Approach (2007)
    Berkeley, Calif. : Berkeley Electronic Press (now: De Gruyter)
    Chemical product and process modeling 2 (2007), S. 27 
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    ISSN: 1934-2659
    Source: Berkeley Electronic Press Academic Journals
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: This paper presents a Fault Detection and Isolation (FDI) method for stochastic nonlinear dynamic systems. Our contribution consists of showing another method of tackling the problem of the physical origin diagnosis of faults by combining the technique based on the innovations and the technique using the multiple Kalman filters for a nonlinear dynamic system strongly non-stationary. The usefulness of this combination is the implementation of all the faults dynamics if the decision threshold on the standardized innovation exceeds a fixed value. In the other case, one filter is enough to estimate the process state. An algorithm is described and applied to a perfectly stirred chemical reactor functioning in a semi-batch mode. In this paper, the chemical reaction used is an oxido reduction one, the oxidation of sodium thiosulfate by hydrogen peroxide.
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    Development of Web Based Computer Package for the Simulation of Thermal Desalination Processes (2007)
    Berkeley, Calif. : Berkeley Electronic Press (now: De Gruyter)
    Chemical product and process modeling 2 (2007), S. 14 
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    ISSN: 1934-2659
    Source: Berkeley Electronic Press Academic Journals
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: A computer package based on visual basic code is developed for single and multiple effect evaporation desalination systems (SEE and MEE). The package features design calculations of heat transfer area, power consumption, and costing. The package is user-friendly and is equipped with interactive menus for report and form printing, file saving and retrieving, help files, and tutorial. The computer code is designed to run a default design case and also allows the user to change variables within pre-specified practical ranges. A rigorous process model is used in the package, which is based on detailed fundamental material and energy balance equations, well-proven correlations for the heat transfer coefficients, physical properties, and thermodynamic losses. Illustrations of the package displays are presented together with a number of case studies. Model predictions generated from the code are validated against actual field data and they showed a very good agreement. Future plans involve development of design simulator for the multistage flash desalination (MSF) and reverse osmosis (RO).
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    Mathematical Modeling of Supercritical Fluid Extraction of Fatty Acids from Trout Powder: Correlation of Mass Transfer Parameters (2007)
    Berkeley, Calif. : Berkeley Electronic Press (now: De Gruyter)
    Chemical product and process modeling 2 (2007), S. 17 
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    ISSN: 1934-2659
    Source: Berkeley Electronic Press Academic Journals
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Supercritical fluid extraction (SCFE) has been introduced as an excellent method especially for food and pharmaceutical industries. Trout powder was selected as a source of high amount of valuable materials such as essential fatty acids (FAs). In this work, a mathematical model is introduced to simulate the transitional behavior of the extraction process. This model is able to explain the variation of FAs concentration profile in the bulk and solid phases versus the time of extraction. Effects of main operational parameters such as pressure (280 to 340 bar) and temperature (310 to 326 K) on the extraction yields were investigated in the supercritical fluid extraction system of laboratory scale and the results were compared with that information obtained from the solution of the model. In order to describe solid-solvent interactions, a linear equilibrium relationship was used in the model. Partial differential mass balance equations for the solid and fluid phases were solved numerically using an implicit method. The effective diffusivity into the particle pores and mass transfer coefficient to the bulk phase were the model parameters and they were correlated at different temperatures and pressures by fitting the results of the model to the experiments. The axial diffusivity and equilibrium coefficient of solid-solvent were kept constant in whole range of the operational conditions and they were estimated as the model constants.
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    Extended Modeling Framework for Heat and Power Integration in Batch and Semi-continuous Processes (2007)
    Berkeley, Calif. : Berkeley Electronic Press (now: De Gruyter)
    Chemical product and process modeling 2 (2007), S. 24 
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    ISSN: 1934-2659
    Source: Berkeley Electronic Press Academic Journals
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Flexible manufacturing and processing, which are becoming crucial for companies that wish to remain competitive in today's changing market environment, require the detailed modeling of process operations, as well as the incorporation of utility consumption modeling and energy integration strategies. In this paper, a comprehensive modeling environment for heat and power integration in batch and semi-continuous processes is presented. Moreover, a general procedure concerning utility generation and utility system design optimization is described. This framework has been tested and evaluated as part of an industrial case study. The results obtained indicate that the general design methodology developed is effective for process integration of time-dependent processes with combined heat and power.
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    Molecular Simulation Study of Vapor-Liquid Equilibrium of Morse Fluids (2007)
    Berkeley, Calif. : Berkeley Electronic Press (now: De Gruyter)
    Chemical product and process modeling 2 (2007), S. 8 
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    ISSN: 1934-2659
    Source: Berkeley Electronic Press Academic Journals
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: The Morse potential energy function (PEF) is considered regarding the characterization of interaction forces of particles with tuning parameters. Phase coexistence of Morse fluids is predicted for different steepness and range of the PEF parameters using the grand-canonical transition matrix Monte Carlo (GC-TMMC) method, with quantification of the parameter S, which is the product of a constant with a unit of reciprocal length and the equilibrium distance between two molecules. We found that a lower limit of S exists bounded by infinite critical temperature. The critical properties of the vapor-liquid equilibrium curves are estimated using a rectilinear diameter method and a scaling law approach. A Clausius-Clayperon type relation of S and critical temperature is derived in this work. Vapor-liquid surface tension of Morse fluids by finite size scaling and GC-TMMC is also reported. Surface tensions are found to be higher at lower S.
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    A MINLP Solution for Pellet Reactor Modeling (2007)
    Berkeley, Calif. : Berkeley Electronic Press (now: De Gruyter)
    Chemical product and process modeling 2 (2007), S. 7 
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    ISSN: 1934-2659
    Source: Berkeley Electronic Press Academic Journals
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: A fluidized bed reactor for phosphate precipitation and removal from wastewater is modeled according to a two-step procedure. The first modeling phase, based on the development of a thermodynamic model for the computation of phosphate conversion, previously presented elsewhere is not reported here. The second step is related to the reactor modeling in the core of this paper. The pellet reactor is modeled as a reactor network involving a set of elementary cells representing ideal flow patterns. All the potential solutions are imbedded into a superstructure and the modeling problem is expressed as a MINLP problem. The MINLP problem is solved by means of the GAMS package, first for two flow rate values corresponding to two experimental fluidized bed behaviours, and then for the two flow rates considered simultaneously. In each case, the problem consists in finding an output concentration as close as possible to the experimental output concentration. Three objective functions are studied. The results are compared with those of Montastruc et al. (2004) who used a different numerical procedure. Whatever the considered case, the solutions found are structurally simpler than the ones of Montastruc et al. (2004). A major assessment of this study is that the reactor efficiency can easily be deduced, without any precise knowledge of some key parameters such as the density and thickness of the calcium phosphate layer. Finally a last numerical study concerning the superstructure definition shows that too complex a superstructure does not provide significant refinements on the solution.
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    Determining the Optimized Controller Parameters Using a Hybrid GA-SQP Technique (2007)
    Berkeley, Calif. : Berkeley Electronic Press (now: De Gruyter)
    Chemical product and process modeling 2 (2007), S. 30 
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    ISSN: 1934-2659
    Source: Berkeley Electronic Press Academic Journals
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Dynamic simulation and optimization of a hydrogenation reactor system were developed and investigated in the present work. The process mainly consists of three adiabatic fixed bed hydrogenation reactors in series in addition to one heater before the first reactor and three coolers after each reactor for interstage cooling. The feed flow rate to the unit, the feed temperature or the carbon monoxide content of the feed may change and cause variations of the outlet temperature of reactors. Therefore, it is essential to control the inlet temperature of each reactor. There is a temperature controller before each reactor and also one after the third reactor. The tuning parameters of the controllers were optimized in three different cases, taking into account the process constraints. In each case, a special disturbance was forced to the process. Because of catalyst deactivation, the inlet temperature of reactors must be increased during the running period in order to have the desired conversion. Therefore, the optimal inlet temperature profile was determined based on SOR, MOR and EOR data. Optimization of the process was done by the use of a hybrid GA-SQP method. The new hybrid method was developed to overcome the difficulties of both methods. The genetic algorithm (GA) which is a stochastic method, is relatively slow, but is not sensitive to the initial point. In contrast, sequential quadratic programming (SQP) method is a deterministic method which is fast, but very sensitive to the initial point and gets trapped in local optima. In the newly developed hybrid method, the SQP method speeds the solving procedure, while the GA enables the algorithm to escape from local optima. An industrial acetylene hydrogenation system was used to provide the necessary data to adjust kinetics and to validate the approach.
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    Simulation of the Coke Calcining Processes in Rotary Kilns (2007)
    Berkeley, Calif. : Berkeley Electronic Press (now: De Gruyter)
    Chemical product and process modeling 2 (2007), S. 20 
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    ISSN: 1934-2659
    Source: Berkeley Electronic Press Academic Journals
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: The objective of this study is to simulate the green petroleum coke calcining processes using the simulation program HYSYS and using actual industrial data. Because counter-current mass flow is not allowed in the HYSYS program, the kiln was described by using fictive streams and unit operations. By the simulation, it is possible to predict the operating conditions that control the contents of undesirable impurities in the calcined petroleum coke, namely, sulfur, volatile matter and moisture contents. It also gives the desirable calcined petroleum coke properties such as density. Apart from the metal contents, the simulation allows the coke calciner to utilize any type of green coke regardless of the undesirable impurities. This is done without resorting to the costly blend from different types of green cokes. Simulation is also effective in controlling and optimizing calcination processes' variables. From the simulation it was found that it is possible to process any type of green coke for varying sulfur, volatile matter and water content by adjusting the amount of tertiary air and/or fuel. Two simulation cases were studied for low and high volatile matter contents of 8.5 and 14.7 wt% in the feed. Mass flow rates of fuel and tertiary air were both increased in the first case, while no fuel was required in the second case. The benefit from this is to reduce the operating costs.
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    Advanced Computational Techniques for Solving Desalination Plant Models Using Neural and Genetic Based Methods (2007)
    Berkeley, Calif. : Berkeley Electronic Press (now: De Gruyter)
    Chemical product and process modeling 2 (2007), S. 29 
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    ISSN: 1934-2659
    Source: Berkeley Electronic Press Academic Journals
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Simulation of multi-stage flash (MSF) desalination processes that have a production capacity range between 50,000 to 75,000 m3/d is an intensive computational problem that requires high computer processing speed despite the availability of advanced processing computer power in hand nowadays. In this work, a comparative study is conducted to explore the performance of different numerical techniques to solve large set of nonlinear equations generated by large scale MSF models. These algorithms can be categorized into three groups, namely: conventional numerical approximation methods, multi-objective optimization based methods, and the last group comprises artificial neural networks (ANN) based models and genetic algorithms (GA) based methods. The problem of solving large sets of nonlinear equations with upper and lower constraints is accomplished successfully using all algorithms with different prediction efficiency and speed. The idea of using GA and ANN based algorithms in simulating the MSF model is basically used to generate feasible initial solution estimates that were used as starting guesses for other numerical methods in the former case and to eliminate the step of providing these initial guesses in the later case. Significant reduction of computation effort was attained using ANN-based techniques. The outcome of this work can be utilized to develop new generations of process simulators that are based on well-trained ANNs in order to achieve speedup of computations and to generate more reliable predictions without detracting from accuracy.
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    The Equilibrium Network: A New Approach for Simulation and Visualization of Aqueous Electrolyte Systems (2007)
    Berkeley, Calif. : Berkeley Electronic Press (now: De Gruyter)
    Chemical product and process modeling 2 (2007), S. 22 
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    ISSN: 1934-2659
    Source: Berkeley Electronic Press Academic Journals
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: A new simulation method for investigating mixed aqueous electrolyte systems at thermodynamic equilibrium is presented. Based on the commercial simulation package IPSEpro, a graphical procedure for assembling equilibrium systems followed by simultaneous solution of the underlying equation system was developed. At graphical setup, species and reactions objects are connected by the information of activity and stoichiometry in a network-like manner. Consequently, the resulting equations of mass action, the electro-neutrality and balance conditions are solved incorporating the Pitzer activity coefficient model and equilibrium constants from thermodynamic standard data. The method developed allows fast and flexible application of the complex thermodynamic principles to engineering tasks. The modeling approach and all basic models for graphical input and simultaneous solution of coupled equilibrium conditions are explained. For demonstration of the simulation method, example simulations for the systems of H2SO4-H2O, CaSO4-H2SO4-H2O and NaCl-CaSO4-CO2-H2O are described and evaluated successfully.
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    Prediction of Deposition Patterns in a Pilot-Scale Spray Dryer Using Computational Fluid Dynamics (CFD) Simulations (2007)
    Berkeley, Calif. : Berkeley Electronic Press (now: De Gruyter)
    Chemical product and process modeling 2 (2007), S. 26 
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    ISSN: 1934-2659
    Source: Berkeley Electronic Press Academic Journals
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: This paper presents the predictions of deposition patterns using CFD simulations based on transient-flow behaviour of a 1.6 m high, 0.8 m diameter, pilot-scale spray dryer, following from previous studies assessing the use of Computational Fluid Dynamics (CFD) simulations to predict the deposition on a plate in a simple box configuration. The predicted deposition fluxes here have been compared with experimental data for the deposition fluxes of skim milk, maltodextrin and water. The CFD simulation results suggested that the effect of transient air flows on the vertical patterns of deposition fluxes with distance up the dryer wall for no inlet air swirl is small. The CFD simulations underpredicted the experimental values of the deposition fluxes by approximately 50%, but the simulations predicted the same experimental trends when changing the main air flow rate through the dryer. The experimentally-measured deposition fluxes were 38%, on average, higher at a main air flow rate of 113 kg/h compared with those at a flow rate of 88 kg/h. The CFD simulations predicted an average increase in deposition flux of 26% at 113 kg/h compared with 88 kg/h, so the trends with this change in operating conditions have been predicted well by the CFD simulations. One-way particle coupling has therefore shown correct trends in the deposition fluxes with respect to both positions in the dryer and different operating conditions, and such one-way coupling is several orders of magnitude faster than the more rigorous two-way coupling.
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    Erratum: Tech transfer fails to translate into startups (2007)
    [s.l.] : Nature Publishing Group
    Nature biotechnology 25 (2007), S. 1057-1057 
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    ISSN: 1546-1696
    Source: Nature Archives 1869 - 2009
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: [Auszug] Nature Biotechnology 25, 616 (2007); published online 30 April 2007 In the version of this article originally published, the second sentence incorrectly stated “In its annual survey, the Association of University Technology Managers (AUTM) estimates tech transfer resulted in 527 new products ...
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    Profile: Villoo Morawala Patell (2007)
    [s.l.] : Nature Publishing Group
    Nature biotechnology 25 (2007), S. 705-705 
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    ISSN: 1546-1696
    Source: Nature Archives 1869 - 2009
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: [Auszug] Seven months ago, global investors pumped $32 million into Avesthagen, a multidisciplinary biotech firm in Bangalore, India. Participants included Limagrain, of Chappes, France, the world's fourth-largest seeds company, and food giant Danone, of Paris. In April, another $5 million ...
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    Access all areas (2007)
    [s.l.] : Nature Publishing Group
    Nature biotechnology 25 (2007), S. 950-950 
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    Source: Nature Archives 1869 - 2009
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: [Auszug] Improving access to lifesaving biotech products and encouraging homegrown innovation in poorer nations are long-standing problems. Key challenges are how to galvanize investment by firms in the industrialized world in startups and companies in emerging economies (North-South partnerships), but also ...
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    BioPolis report paints fractured picture of EU biotech (2007)
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    Nature biotechnology 25 (2007), S. 956-957 
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    Source: Nature Archives 1869 - 2009
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: [Auszug] A survey published this summer by the BioPolis Initiative was designed to shed some light on how best to grow a national biotech sector. Among its findings, the report puts in perspective the gap between areas of established biotech development and nascent regions. One study author suggests that ...
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    The other side of staying out of a BIND (2007)
    [s.l.] : Nature Publishing Group
    Nature biotechnology 25 (2007), S. 971-971 
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    Source: Nature Archives 1869 - 2009
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: [Auszug] To the editor: Last September, Nature Biotechnology published a letter by William Busa critical of an editorial in a previous issue bemoaning the lack of public funding available for the Biomolecular Interaction Network Database (BIND). On March 20 this year, Thomson Scientific (Philadelphia) ...
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    Ethical framework for previously collected biobank samples (2007)
    [s.l.] : Nature Publishing Group
    Nature biotechnology 25 (2007), S. 973-976 
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    Source: Nature Archives 1869 - 2009
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: [Auszug] To the editor: An increasing trend in biobank research is to pool collections of biological samples in international scientific studies, thereby amplifying their potential scientific value. The pooling of samples, however, poses several challenges to national/international legislation and ethical ...
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    Fatal flaws in agbiotech regulatory policies (2007)
    [s.l.] : Nature Publishing Group
    Nature biotechnology 25 (2007), S. 725-727 
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    Source: Nature Archives 1869 - 2009
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: [Auszug] Every nation claims its agbiotech regulatory policies governing genetically modified organisms (GMOs; products of recombinant DNA technologies) are 'scientifically sound'. But a simple declaration of scientific validity by politicians or regulators does not make it so; that judgment can be bestowed ...
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    Patents and translational research in genomics (2007)
    [s.l.] : Nature Publishing Group
    Nature biotechnology 25 (2007), S. 739-741 
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    Source: Nature Archives 1869 - 2009
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: [Auszug] The aim of translational research is to take the outcomes and innovations developed within the research context into clinical practice. In the United Kingdom, the importance of this process has been recognized in a recent review of health research funding, undertaken by Sir David Cooksey, which ...
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    Human embryonic stem cells flock together (2007)
    [s.l.] : Nature Publishing Group
    Nature biotechnology 25 (2007), S. 748-750 
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    Source: Nature Archives 1869 - 2009
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: [Auszug] How similar are the many human embryonic stem (hES) cell lines being studied in laboratories around the world? In the absence of standardized methods for deriving, culturing and characterizing hES cells, the International Stem Cell Initiative (ISCI) has sought to answer this question with an ...
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    People (2007)
    [s.l.] : Nature Publishing Group
    Nature biotechnology 25 (2007), S. 820-820 
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    Source: Nature Archives 1869 - 2009
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: [Auszug] Helicos BioSciences (Cambridge, MA, USA) has announced the appointments of Chip Leveille and Mark Solakian to its executive management team. Mr. Leveille has been appointed vice president of sales and marketing and Mr. Solakian has been named vice president and general counsel. “Chip and ...
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    Complete genome sequence of the fish pathogen Flavobacterium psychrophilum (2007)
    [s.l.] : Nature Publishing Group
    Nature biotechnology 25 (2007), S. 763-769 
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    Source: Nature Archives 1869 - 2009
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: [Auszug] We report here the complete genome sequence of the virulent strain JIP02/86 (ATCC 49511) of Flavobacterium psychrophilum, a widely distributed pathogen of wild and cultured salmonid fish. The genome consists of a 2,861,988–base pair (bp) circular chromosome with 2,432 predicted protein-coding ...
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    An improved zinc-finger nuclease architecture for highly specific genome editing (2007)
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    Nature biotechnology 25 (2007), S. 778-785 
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    Source: Nature Archives 1869 - 2009
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: [Auszug] Genome editing driven by zinc-finger nucleases (ZFNs) yields high gene-modification efficiencies (〉10%) by introducing a recombinogenic double-strand break into the targeted gene. The cleavage event is induced using two custom-designed ZFNs that heterodimerize upon binding DNA to form a ...
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    News in brief (2007)
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    Nature biotechnology 25 (2007), S. 613-614 
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    Source: Nature Archives 1869 - 2009
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: [Auszug] Big Pharma vies for mice Tarrytown, New York–based Regeneron has inked two lucrative, nonexclusive licensing deals recently for its VelocImmune humanized mouse antibody system designed to accelerate the discovery and development of fully human antibodies. In March, Astellas Pharma of Tokyo ...
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    Trends in GM crop, food and feed safety literature (2007)
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    Nature biotechnology 25 (2007), S. 624-626 
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    Source: Nature Archives 1869 - 2009
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: [Auszug] To the editor: A letter by David Pelletier published last year (Nat. Biotechnol. 24, 498, 2006) highlights the paucity of primary research articles focusing on genetically modified (GM) crop and food safety. This observation, also voiced by others, contrasts with trends that I have identified in ...
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    Profile: Susan Wood (2007)
    [s.l.] : Nature Publishing Group
    Nature biotechnology 25 (2007), S. 495-495 
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    Source: Nature Archives 1869 - 2009
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    Notes: [Auszug] When this FDA official resigned over foot-dragging on Plan B, she was placed at the center of a maelstrom concerning political interference in agency ...
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    Why the omega-3 piggy should go to market (2007)
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    Nature biotechnology 25 (2007), S. 506-506 
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    Source: Nature Archives 1869 - 2009
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    Notes: [Auszug] Autumn Fiester responds: Kang and Leaf charge that I misunderstood their science, ignored evidence and made erroneous statements, implying that if I were better informed, I would support their omega-3 transgenic pig project. I disagree on all points. The most serious charge of their letter is ...
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    Toppling the organic house of cards (2007)
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    Nature biotechnology 25 (2007), S. 522-523 
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    Source: Nature Archives 1869 - 2009
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: [Auszug] Alex Avery's controversial The Truth About Organic Foods begins by reminding us that the roots of organic agriculture are deeply embedded in occult and Romantic mysticism. Rudolf Steiner (“When I eat roots, their minerals go up into my head. When I eat salad greens, their forces go to my ...
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    Functional foods from biotech—an unappetizing prospect? (2007)
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    Nature biotechnology 25 (2007), S. 525-531 
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    Source: Nature Archives 1869 - 2009
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: [Auszug] Functional foods were once touted as the next wave in the food and beverage industries. Yet as these products—defined as “any modified food or food ingredient that may provide a healthful benefit beyond that of the traditional nutrients it contains”—have begun to make their ...
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    Found in translation (2007)
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    Nature biotechnology 25 (2007), S. 601-601 
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    Source: Nature Archives 1869 - 2009
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: [Auszug] The appeal of the career path as a physician-scientist is perhaps matched only by the challenge of the career itself. Many trainees ultimately discover that the elegant concept of uniting the rigor of basic science with the compassion of patient care can be remarkably unwieldy in practice.... The ...
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    Chloroplastic photorespiratory bypass increases photosynthesis and biomass production in Arabidopsis thaliana (2007)
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    Nature biotechnology 25 (2007), S. 593-599 
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    Source: Nature Archives 1869 - 2009
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: [Auszug] We introduced the Escherichia coli glycolate catabolic pathway into Arabidopsis thaliana chloroplasts to reduce the loss of fixed carbon and nitrogen that occurs in C3 plants when phosphoglycolate, an inevitable by-product of photosynthesis, is recycled by photorespiration. Using step-wise nuclear ...
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    Nanobiotech versus synthetic nanotech? (2007)
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    Nature biotechnology 25 (2007), S. 389-390 
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    Source: Nature Archives 1869 - 2009
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: [Auszug] To the editor: With over 350 nanotechnology products on the market, concerns have been raised that the intrinsic near-atomic size, surface area and surface chemistry of nanomaterials could be associated with unforeseen human health or environmental risks. As more data needs to be gathered to ...
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    Gene patents—more evidence needed, but policymakers must act (2007)
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    Nature biotechnology 25 (2007), S. 388-389 
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    Source: Nature Archives 1869 - 2009
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: [Auszug] To the editor: We congratulate Timothy Caulfield et al. for their analysis of major policy documents on gene patents in the September issue (Nat. Biotechnol. 24, 1091–1095, 2006) for prompting a timely and interdisciplinary dialog on the policy debate about the appropriate role of gene ...
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    Research sharing, ethics and public benefit (2007)
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    Nature biotechnology 25 (2007), S. 398-401 
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    Source: Nature Archives 1869 - 2009
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: [Auszug] New ethical guidelines of the International Society for Stem Cell Research (ISSCR; Northbrook, IL) for work on human embryonic stem (ES) cells direct researchers, companies and academic institutions to share research materials, data and intellectual property (IP) rights necessary for published ...
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    Antibiotic production from the ground up (2007)
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    Nature biotechnology 25 (2007), S. 428-429 
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    Source: Nature Archives 1869 - 2009
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: [Auszug] Life in the soil is a difficult proposition for a bacterium: nutrient supply is limited, predators with a vast arsenal of molecular weapons occupy the neighborhood and other stresses such as temperature changes abound. To defend themselves against prokaryotic enemies, many bacteria produce ...
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    Commercializing cognitive neurotechnology—the ethical terrain (2007)
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    Nature biotechnology 25 (2007), S. 393-397 
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    Source: Nature Archives 1869 - 2009
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: [Auszug] Mental illness is one of the leading causes of disability worldwide, afflicting one in five Americans and over one in four Europeans. Cognitive neurotechnologies—technologies that enable the monitoring and/or modulation of the function of the brain—promise to improve the treatment of ...
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    The global stem cell patent landscape: implications for efficient technology transfer and commercial development (2007)
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    Nature biotechnology 25 (2007), S. 419-424 
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    Source: Nature Archives 1869 - 2009
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: [Auszug] The debate over access to research tools essential for stem cell research and development has been waged most strongly over patents granted in the United States to the Wisconsin Alumni Research Foundation (WARF) for work done at the University of Wisconsin on embryonic stem cells. Although those ...
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    An expression atlas of rice mRNAs and small RNAs (2007)
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    Nature biotechnology 25 (2007), S. 473-477 
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    Source: Nature Archives 1869 - 2009
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: [Auszug] Identification of all expressed transcripts in a sequenced genome is essential both for genome analysis and for realization of the goals of systems biology. We used the transcriptional profiling technology called 'massively parallel signature sequencing' to develop a comprehensive expression atlas ...
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    Flogging Gardasil (2007)
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    Nature biotechnology 25 (2007), S. 261-261 
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    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: [Auszug] In its rush to market its human papillomavirus vaccine, Merck forgot to make a strong and compelling case for compulsory ...
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    Managing change in biotech: startup and growth (2007)
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    Nature biotechnology 25 (2007), S. 479-480 
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    Source: Nature Archives 1869 - 2009
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: [Auszug] Like all businesses, life science companies face the trying challenges of accessing sufficient capital, wisely allocating constrained resources, developing and executing beneficially designed collaborations and partnerships, demonstrating the courage to make difficult, sometimes complex, go/no-go ...
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    Incretin mimetics vie for slice of type 2 diabetes market (2007)
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    Nature biotechnology 25 (2007), S. 263-263 
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    Source: Nature Archives 1869 - 2009
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: [Auszug] This February, New York–based Pfizer announced the acquisition of BioRexis Pharmaceutical, a biotech company in King of Prussia, Pennsylvania, with a strong product pipeline in type 2 diabetes, including long-acting agonists of glucagon-like peptide 1 (GLP-1) receptor, a key target in ...
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    The threat from within: trade secret theft by employees (2007)
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    Nature biotechnology 25 (2007), S. 293-295 
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    Source: Nature Archives 1869 - 2009
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: [Auszug] Biotechnology companies are no strangers to economic and industrial espionage. The high cost of developing new technologies or products, combined with the enormous potential value of viable innovations, make biotech companies prime targets for trade secret theft. Recent cases include theft or ...
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    Promoting angiogenesis to a fault (2007)
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    Nature biotechnology 25 (2007), S. 300-302 
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    Source: Nature Archives 1869 - 2009
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: [Auszug] Antiangiogenesis agents, such as antibodies against vascular endothelial growth factor (VEGF), are now part of the standard repertoire of cancer therapies, but responses are short lived, and resistance occurs in the majority of patients. Seeking to identify additional angiogenic pathways that could ...
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    Research training and academic disciplines at the convergence of nanotechnology and biomedicine in the United States (2007)
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    Nature biotechnology 25 (2007), S. 359-361 
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    Notes: [Auszug] Nanotechnology is multidisciplinary and encompasses knowledge from many different fields of study, including physics, engineering and materials science. Although nanotechnology's impact in various industrial sectors began in the 1980s, its application to biomedicine is a relatively recent ...
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    A human phenome-interactome network of protein complexes implicated in genetic disorders (2007)
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    Nature biotechnology 25 (2007), S. 309-316 
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    Notes: [Auszug] We performed a systematic, large-scale analysis of human protein complexes comprising gene products implicated in many different categories of human disease to create a phenome-interactome network. This was done by integrating quality-controlled interactions of human proteins with a validated, ...
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    Next-generation sequencing outpaces expectations (2007)
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    Nature biotechnology 25 (2007), S. 149-149 
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    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: [Auszug] On January 8, Solexa, of Hayward, California, announced the completion of an early-access program evaluating its next-generation Genome Analysis system with customers and reiterated its intention to begin full commercial sales this quarter. Two months earlier, in anticipation of the entry of ...
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    A stellar year for financing (2007)
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    Nature biotechnology 25 (2007), S. 156-156 
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    Source: Nature Archives 1869 - 2009
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: [Auszug] Last year, biotech excelled in terms of financing, but failed to set the stock markets alight. Total biotech financing surpassed 2000 levels to reach $46 billion, although much of this came from partnership deals where payments may (or may not) extend into the future. Debt deals led all ...
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    Research Highlights (2007)
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    Nature biotechnology 25 (2007), S. 195-195 
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    Source: Nature Archives 1869 - 2009
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: [Auszug] Golden cauliflower First Golden Rice, now Golden Cauliflower, albeit via a completely different approach. Lu et al. have characterized in cauliflower a spontaneous mutant of a highly conserved gene, Or, that boosts accumulation of β-carotene and is semi-dominant across plant species when ...
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1038/nbt0207-195
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    Targeting brain-tumor stem cells (2007)
    [s.l.] : Nature Publishing Group
    Nature biotechnology 25 (2007), S. 193-194 
    Details
    ISSN: 1546-1696
    Source: Nature Archives 1869 - 2009
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: [Auszug] The cancer stem-cell hypothesis proposes that a minority of transformed stem cells, or progenitors with acquired self-renewal properties, are the source of tumor-cell renewal and thereby determine a tumor's behavior, including proliferation, progression and response to therapy. Evidence for the ...
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1038/nbt0207-193
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  • 97
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    Proposed changes to patent code loom over biotech industry (2007)
    [s.l.] : Nature Publishing Group
    Nature biotechnology 25 (2007), S. 1333-1334 
    Details
    ISSN: 1546-1696
    Source: Nature Archives 1869 - 2009
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: [Auszug] In response to a suit filed by London-based GlaxoSmithKline (GSK), the US District Court for the Eastern District of Virginia issued an injunction on 31 October against proposed changes to the US patent code. The order came just one day before the changes were to take effect, leaving the fate of ...
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1038/nbt1207-1333
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  • 98
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    Adaptation to culture of human embryonic stem cells and oncogenesis in vivo (2007)
    [s.l.] : Nature Publishing Group
    Nature biotechnology 25 (2007), S. 207-215 
    Details
    ISSN: 1546-1696
    Source: Nature Archives 1869 - 2009
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: [Auszug] The application of human embryonic stem cells (HESCs) to provide differentiated cells for regenerative medicine will require the continuous maintenance of the undifferentiated stem cells for long periods in culture. However, chromosomal stability during extended passaging cannot be guaranteed, as ...
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1038/nbt1285
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  • 99
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    Stop the cull (2007)
    [s.l.] : Nature Publishing Group
    Nature biotechnology 25 (2007), S. 1329-1329 
    Details
    ISSN: 1546-1696
    Source: Nature Archives 1869 - 2009
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: [Auszug] Conventional 'slaughtering-out' measures for containing outbreaks of animal diseases are draconian and medieval. They basically boil down to death and imprisonment. Livestock movement is banned, all exposed animals are slaughtered, buried or burned, and exports abroad stop immediately. Each disease ...
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1038/nbt1207-1329
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    Another inconvenient truth (2007)
    [s.l.] : Nature Publishing Group
    Nature biotechnology 25 (2007), S. 1330-1330 
    Details
    ISSN: 1546-1696
    Source: Nature Archives 1869 - 2009
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: [Auszug] There have been two distinct calls for complete bans on the release of GMOs in France and Italy in recent weeks. Predictably, both are motivated strictly by political ambitions. Less predictably and of much greater concern, both have complete disregard for any of the data that surround the GMO ...
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1038/nbt1207-1330
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