Search

Several algorithms are presented for the J-spectral factorization of a para-Hermitian polynomial matrix. The four algorithms that are discussed are based on diagonalization, successive factor extraction, interpolation, and the solution of an algebraic Riccati equation, respectively. The paper includes a special algorithm for the factorization of unimodular para-Hermitian polynomial matrices and deals with canonical, noncanonical, and nearly noncanonical factorizations. >

SETTING: Surveillance data from the National Tuberculosis Register for the period 1993-1997 complemented with DNA fingerprinting results of Mycobacterium tuberculosis isolates. OBJECTIVE: To estimate the proportion of disease attributable to recent re-infection among Dutch tuberculosis patients with reported tuberculosis infection or disease before 1981. DESIGN: Data from 1,547 Dutch patients diagnosed between 1994 and 1997 in the Netherlands were studied. Cases with reported tuberculosis infection or disease before 1981 were attributed to reactivation if their M. tuberculosis isolate was unclustered based on DNA fingerprinting or if they were the first case in a cluster, and to re-infection if they were clustered, but not as the first case. RESULTS: In total, 183 Dutch tuberculosis patients (12%) had reported tuberculosis infection or disease before 1981. Tuberculosis in 29 of these patients (16%) was attributed to recent re-infection. CONCLUSION: In this setting with a low tuberculosis incidence, approximately one in six new disease episodes among patients with previous tuberculosis infection or disease may be attributable to recent re-infection

The Netherlands, May 1994 to May 1996. 1) To estimate to what extent drug-resistant tuberculosis was acquired or recently transmitted in The Netherlands, 2) to assess the relevance of drug resistance data as routinely collected, and 3) to describe case management. Prospective descriptive study. Patients diagnosed with drug-resistant tuberculosis were interviewed. Information on patient management and contact tracing was collected. IS6110 restriction fragment length polymorphism (RFLP) patterns of all strains were compared with those of the National RFLP library and clusters were analyzed. In total 193 cases were included in the study. Acquired drug resistance (ADR) was rare. Dutch ADR patients reported receiving treatment a long time previously (mean age 58, mean treatment interval 23 years). Most foreign ADR patients had been treated recently in their country of origin. Of 151 primary drug-resistant (PDR) cases, 129 (85%) were foreign-born, of whom few (8%-19%) had been infected in The Netherlands. Few Dutch PDR cases had been infected recently (mean age 49 years). Rifampicin resistance was more frequently observed in foreign ADR cases than in foreign PDR cases (28% vs 5%; P < 0.001). One third of cases had not been treated according to treatment guidelines. Only a small proportion of drug-resistant cases resulted from recent infection or treatment in The Netherlands. General rates of ADR and PDR do not reflect current Dutch programme performance. For programme monitoring, ADR/PDR rates and their trends must be reported and evaluated in Dutch and foreign patients separately

The problem of J-spectral factorization of polynomial matrices is studied. Existence and uniqueness are discussed, and the differences from the standard case are pointed out. Two first algorithms are proposed for a numerical solution. The first algorithm, which is based on the generalized symmetric factor extraction, features simplicity and is easy to implement via MATLAB. The second algorithm, which is based on diagonalization, applies to a more general class of matrices (including those with zeros on the imaginary axis)

Lightweight structures are increasingly installed in aerospace and automotive industries, stimulated by economic constraints and stringent emission standards. These lightweight structures are usually lightly damped and therefore prone to vibrating. Structural vibrations are detrimental to the safety and life-cycle of the mechanical structures, calling for effective vibration reduction techniques. In parallel, rapid advances and integration of computing, communication and smart sensing technologies have motivated deployment of small-size, low-cost sensing devices equipped with embedded processors and communication capabilities. The emerging networked control systems (NCS) provide a promising design paradigm for vibration control algorithms. In this envisioned paradigm, decision making process is delegated to intelligent agents which are facilitated by an array of actuators and sensors deployed throughout the structures. This dissertation is dedicated to adapting the networked or distributedcontrol concept specifically for vibration reduction of spatially distributed damping systems, i.e. flexible structures. Four decentralized approaches for distributed/cooperative observers over directed graph topology are developed. The first approach assumes that the information of graph topology is perfectly known to each agent. The second approach works independent of any specific graph topology and is only for locally detectable systems. The third approach does not require the exact information of graph topology as well, and can work for both locally detectable and undetectable systems. In the fourth approach, an observability decomposition is firstly applied locally at each agent, and parameters of the cooperative observers are designed in observable and unobservable subspaces, respectively. This approach can also be developed without the exact information of the graph topology. In particular, compared with centralized approaches in the literature, the four decentralized approaches have a few appealing features. Firstly, it is robust, to a certain degree, against graph reconfigurations. Secondly, the decentralized approaches have flexibility in integrating redundant sensors into the network. Thirdly, the computational complexity in designing the variables is reduced. The performance of proposed cooperative observers and controllers is examined with numerical simulations, where a smart flexible beam is considered. An experimental case study with a piezoelectric actuated composite plate is presented to validate the developed algorithms in real-time. This dissertation also performs a preliminary research on distributed homogeneous sensor fusion over the network. Inspired by the Bayesian-based fusion, variances of measurement noises are incorporated into the edge weight design of the network. The fusion performance is examined with numerical experiments. The steady-state expected values and variances of the state estimates of all the nodes in the network agree well with the analytical results. status: published