Model-based control of a simulated moving bed chromatographic process for the separation of fructose and glucose

Chromatographic separations are an expanding technology for the separation of high value products, particularly in the area of pharmaceutics, food, and fine chemicals. The simulated moving bed (SMB) process as a continuous chromatographic separation process is an interesting alternative to conventional batch chromatography, and gained more and more impact recently. The SMB process is realized by connecting several single chromatographic columns in series. A countercurrent movement of the bed is approximated by a cyclic switching of the inlet and outlet ports in the direction of the fluid stream. Because of its complex dynamics, the optimal operation and automatic control of SMB processes is a challenging task. This paper presents the design of a model-based optimization and control scheme for SMB chromatographic separation processes and its application to the separation of fructose and glucose. We propose a two-layer control architecture where the optimal operating trajectory is calculated off-line by dynamic optimization based on a rigorous process model. The parameters of the model are adapted based on online measurements. The low-level control task is to keep the process on the optimal trajectory despite disturbances and plant/model mismatch. Here identification models based on simulation data of the rigorous process model along the optimal trajectory are combined with a suitable local controller. The efficiency of the trajectory control algorithm is shown in a simulation study for the separation of fructose and glucose on an 8-column SMB plant.     

An Architecture for Supporting Multi-Device, Client-Adaptive Services

The original idea of the World Wide Web was to create a universe of network-accessible information. Since its inception, the World Wide Web has evolved from a means to help people access and use information into an interactive medium. This has caused a dramatic increase in the development effort for interactive services, which now have to support multiple clients with widely varying computing and user interface capabilities. Personalization features tend to render this task even more complex. The paper presents the MUSA (Multiple User Interfaces, Single Application) system, which addresses both issues with the introduction of an event graph that abstracts user interface and personalization issues from the implementation of the service on different client-devices.     

An on-line respirographic biosensor for the characterization of load and toxicity of wastewaters

A respirographic biosensor is presented that is capable of monitoring the waste load and potential toxicity of wastewaters, both off-line in a laboratory or on-line at the wastewater treatment plant. The principles of the sensors' operation have been developed and implications of the design choices evaluated. Short term BOD values were obtained every 30 min. The linear dynamic range spanned concentrations differing by a factor of 5000. This range could be expanded by a factor of 10 by adjusting the aeration rate of the bioreactor in the sensor. The response time for toxicity detection was approximately 1 h. The use in the sensor of activated sludge from the plant concerned ensured relevant toxicity information was obtained. To check the condition of the sludge, an independent respiration measurement is proposed. When a siginificant activity change is observed, the sludge in the sensor must be replaced. The presence of oxidoreduction chemicals can cause interferences that may lead to measurement errors. Based on a difference in reaction kinetics, their presence can be assessed and the effect eliminated. Both on-line and laboratory applications in the chemical industry are presented. Special emphasis is given to the usefulness of the sensor data for waste management of production divisions. On-line assessment of load variations and hydrogen peroxide spills are given as illustrations of the implementation of the sensor on the treatment plant. Attention is drawn to the potential application of the data for process control and improved performance of the treatment plant.     

The Affinity of Basic Dyes for Leacril 16 Acrylic Fibre

The dyeing affinity of some thiazole and benzothiazole basic azo dyes for Leacril 16 acrylic fibre was measured using Langmuir isotherms. Results show a close dependence of dye structure on affinity.     

On the Ontological Status of Plans and Norms

This article describes an ontological model of norms. The basic assumption is that a substantial part of a legal system is grounded on the concept of agency. Since a legal system aims at regulating a society, then its goal can be achieved only by affecting the behaviour of the members of the society. We assume that a society is made up of agents (which can be individuals, institutions, software programs, etc.), that agents have beliefs, goals and preferences, and that they commit to intentions in order to choose a line of behaviour. The role of norms, within a legal system, is to specify how and when the chosen behaviour agrees with the basic principles of the legal system. In this article, we show how a model based on plans can be the basis for the ontological representation of norms, which are expressed as constraints on the possible plans an agent may choose to guide its behaviour. Moreover, the paper describes how the proposed model can be linked to the upper level of a philosophically well-founded ontology (DOLCE); in this way, the model is set in a wider perspective, which opens the way to further developments.     

Design and characterization of the balloon-borne Michelson Interferometer for Passive Atmospheric Sounding (MIPAS-B2)

MIPAS-B2 is a balloon-borne limb-emission sounder for atmospheric research. The heart of the instrument is a Fourier spectrometer that covers the mid-infrared spectral range (4-14 microns) and operates at cryogenic temperatures. Essential for this application is the sophisticated line-of-sight stabilization system, which is based on an inertial navigation system and is supplemented with an additional star reference system. The major scientific benefit of the instrument is the simultaneous detection of complete trace gas families in the stratosphere without restrictions concerning the time of day and viewing directions. The specifications, the design considerations, the actual realization of the instrument, and the results of characterization measurements that have been performed are described.     

An Integrated CMOS Front-End for Optical Absolute Rotary Encoders

This paper presents a front-end circuit for optical rotary encoders. The light pulses modulated by the encoder disc are transduced into current signals, which are pre-processed and converted into digital waveforms related to the disc angular position information. The proposed front-end circuit is compensated against temperature drifts. Digitally programmable calibration is provided to account for spreads in impinging light pulse power. Measurement results on integrated prototypes are shown, demonstrating correct operation of the front-end with an optical input power from 0.5 W to 3 W up to a signal frequency of 500 kHz in a temperature range from 0 °C to 80 °C.     

An O(nlog n)-SPACE Decision Procedure for the Propositional Dummett Logic

We present a tableau calculus for propositional Dummett logic, also known as LC (Linear Chain), where the depth of the deductions is linearly bounded by the length of the formulas to be proved. We then show that it is possible to decide propositional Dummett logic in O(nlogn)-SPACE.     

Anti-spam legislation: An analysis of laws and their effectiveness

More than half of worldwide e-mail traffic (an estimated total of several billion e-mails per day) consists of spam. This is becoming a considerable disturbance to telecommunications. Spam is also closely related to other kinds of cybercrime as it possibly contains malicious software or is pursuing some kind of fraudulent aim such as phishing. As well as technical and organizational measures, many countries have introduced anti-spam legislation. However, today's worldwide legislative coverage of spam is heterogeneous, and its effectiveness is discussed controversially. This article describes important parameters by which anti-spam legislation can vary and gives an overview and analysis of worldwide anti-spam legislation, including the European Directive 2002/58/EC and the United States CANSPAM Act 2003, and international cooperation, such as the London Action Plan. The article then proceeds to discuss the effectiveness of current laws and identifies problems resulting from the fact that an international phenomenon is being addressed by national legislation. Finally, the article presents suggestions for overcoming some of these problems.