Product property and production rate control of styrene polymerization

A multivariable multi-rate nonlinear model predictive control (NMPC) strategy is applied to styrene polymerization. The NMPC algorithm incorporates a multi-rate Extended Kalman Filter (EKF) to handle state variable and parameter estimation. A fundamental model is developed for the styrene polymerization CSTR, and control of polymer properties such as number average molecular weight (NAMW) and polydispersity is considered. These properties characterize the final polymer distribution and are strong indicators of the polymer qualities of interest. Production rate control is also demonstrated. Temperature measurements are available frequently while laboratory measurements of concentration and molecular weight distribution are available infrequently with substantial time delays between sampling and analysis. Observability analysis of the augmented system provides guidelines for the design of the augmented disturbance model for use in estimation using the multi-rate EKF. The observability analysis links measurement sets and corresponding observable disturbance models, and shows that measurements of moments of the polymer distribution are essential for good estimation and control. The CSTR is operated at an open-loop unstable steady state. Control simulations are performed under conditions of plant-model structural mismatch and in the presence of parameter uncertainty and disturbances, and the proposed multi-rate NMPC algorithm is shown to provide superior performance compared to linear multi-rate and nonlinear single-rate MPC algorithms. The major contributions of this work are the development of the multi-rate estimator and the measurement design study based on the observability analysis.     

An Introduction to Using XML for the Management of Laboratory Data

Extensible Markup Language (XML) and the XML Path Language (XPath) are introduced with software examples demonstrating how one can use them to write laboratory data management programs. Topics explored include XML document creation, manipulation, and searching. Programming examples make use of the Microsoft® XML Parser library and the Visual Basic programming language. The problem of managing microplate screening data is used as an illustration. Source code for all examples can be downloaded from http://www.labprogrammer.net.     

An operating system independent WORM archival system

We describe the organization of a general purpose data archival system for Write-Once, Read-Many (WORM) optical disks. The system has been designed for large-scale and long-term data storage and retrieval. The archival system is independent of the operating system, flat, self-consistent, does not use any write cache on magnetic disk, and allows the exploitation of auxiliary information on magnetic disk, which can be rebuilt immediately in case of a crash, to speed up file retrieval. A library in C language, called pODLIB, has been implemented as a portable interface to the archival system.     

GTV<Emphasis Type="SmallCaps">cut</Emphasis> for neuro-radiosurgery treatment planning: an MRI brain cancer seeded image segmentation method based on a cellular automata model

Despite of the development of advanced segmentation techniques, achieving accurate and reproducible gross tumor volume (GTV) segmentation results is still an important challenge in neuro-radiosurgery. Nowadays, magnetic resonance imaging (MRI) is the most prominent modality in radiation therapy for soft-tissue anatomical districts. Gamma Knife stereotactic neuro-radiosurgery is a minimally invasive technology for dealing with inaccessible or insufficiently treated tumors with traditional surgery or radiotherapy. During a treatment planning phase, the GTV is generally contoured by experienced neurosurgeons and radiation oncologists using fully manual segmentation procedures on MR images. Unfortunately, this operative methodology is definitely time-expensive and operator-dependent. Delineation result repeatability, in terms of both intra- and inter-operator reliability, can be achieved only by using computer-assisted approaches. In this paper a novel semi-automatic seeded image segmentation method, based on a cellular automata model, for MRI brain cancer detection and delineation is proposed. This approach, called GTVcut, employs an adaptive seed selection strategy and helps to segment the GTV, by identifying the target volume to be treated using the Gamma Knife device. The accuracy of GTVcut was evaluated on a dataset composed of 32 brain cancers, using both spatial overlap-based and distance-based metrics. The achieved experimental results are very reproducible, showing the effectiveness and the clinical feasibility of the proposed approach.     

Formal methods integration for the specification of dependable distributed systems

This paper describes a real-world case study in the specification and analysis of dependable distributed systems. The case study is an automated transport system with safety requirements. In order to manage the complexity of the problem of specifying the dynamic behavior of the whole system, a compositional approach is used, based on the integration of the trace logic of the Communicating Sequential Processes (CSP) theory, and stochastic Petri nets (SPNs). It is argued that the integration of different formal methods is a useful approach in the definition of practical engineering methodologies for the specification, design and analysis of complex dependable distributed systems.     

Policy conflict analysis for diffserv quality of service management

Policy-based management provides the ability to (re-)configure differentiated services networks so that desired Quality of Service (QoS) goals are achieved. This requires implementing network provisioning decisions, performing admission control, and adapting bandwidth allocation to emerging traffic demands. A policy-based approach facilitates flexibility and adaptability as policies can be dynamically changed without modifying the underlying implementation. However, inconsistencies may arise in the policy specification. In this paper we provide a comprehensive set of QoS policies for managing Differentiated Services (DiffServ) networks, and classify the possible conflicts that can arise between them. We demonstrate the use of Event Calculus and formal reasoning for the analysis of both static and dynamic conflicts in a semi-automated fashion. In addition, we present a conflict analysis tool that provides network administrators with a user-friendly environment for determining and resolving potential inconsistencies. The tool has been extensively tested with large numbers of policies over a range of conflict types.     

The Time of Flight electronics for the PAMELA experiment in space

PAMELA, a cosmic ray telescope, was launched into space on 15th June 2006 from the Baikonur cosmodrome aboard of a Soyuz-U and it is in continuous data tacking since 11 July 2006. The Time of Flight system of the PAMELA telescope allows both to distinguish electrons to antiprotons up to about 2 GeV and to measure the absolute charge of the particle. In order to perform these goals the requested time resolution for the whole ToF system is . To fulfill the detector requirements the read out electronics is been required to have a time resolution better than 60 ps with wide dynamic range for charge measurements. The peculiarity of the developed electronics arises from the need to obtain such a time resolution operating in a satellite environment, which implies low-power consumption, radiation hardness, redundancy and high reliability.