Structure-preserving tangential interpolation for model reduction of port-Hamiltonian Systems

Port-Hamiltonian systems result from port-based network modeling of physical systems and are an important example of passive state-space systems. In this paper, we develop the framework for model reduction of large-scale multi-input/multi-output port-Hamiltonian systems via tangential rational interpolation. The resulting reduced-order model not only is a rational tangential interpolant but also retains the port-Hamiltonian structure; hence is passive. This reduction methodology is described in both energy and co-energy system coordinates. We also introduce an $\mathcal{H}_2$-inspired algorithm for effectively choosing the interpolation points and tangential directions. The algorithm leads a reduced port-Hamiltonian model that satisfies a subset of $\mathcal{H}_2$-optimality conditions. We present several numerical examples that illustrate the effectiveness of the proposed method showing that it outperforms other existing techniques in both quality and numerical efficiency

Oral bisphosphonate-related osteonecrosis of the jaws in rheumatoid arthritis patients: a critical discussion and two case reports

<p>Abstract</p> <p>Background</p> <p>Bisphosphonate-related osteonecrosis of the jaw (BRONJ) is a clinical condition characterized by the presence of exposed bone in the maxillofacial region. Its pathogenesis is still undetermined, but may be associated with risk factors such as rheumatoid arthritis (RA). The aim of this paper is to report two unpublished cases of BRONJ in patients with RA and to conduct a literature review of similar clinical cases with a view to describe the main issues concerning these patients, including demographic characteristics and therapeutic approaches applied.</p> <p>Methods</p> <p>Two case reports of BRONJ involving RA patients were discussed</p> <p>Results</p> <p>Both patients were aging female taking alendronate for more than 3 years. Lesions were detected in stage II in posterior mandible with no clear trigger agent. The treatment applied consisted of antibiotics, oral rinses with chlorhexidine, drug discontinuation and surgical procedures. Complete healing of the lesions was achieved.</p> <p>Conclusions</p> <p>This paper brings to light the necessity for rheumatologists to be aware of the potential risk to their patients of developing BRONJ and to work together with dentists for the prevention and early detection of the lesions. Although some features seem to link RA with oral BRONJ and act as synergistic effects, more studies should be developed to support the scientific bases for this hypothesis.</p

Count rate meter with a time constant using adaptive digital signal processing

Two methods developed to improve the classical time constant count rate meters by using the adaptive signal-processing tools are presented. An optimized detection algorithm that senses the change of the mean count rate was implemented in both methods. Three different types of low-pass filters of various structures with adaptive parameters to implement the control of the mean count rate error by suppressing the fluctuations in a controllable way were considered, and one of them was implemented in both methods. An adaptation algorithm for time constant interval calculation was executed after the low-pass filter was devised and implemented in the first method. This adaptation algorithm makes it possible to obtain shorter time constant intervals for higher stationary mean count rates. The adaptation algorithm for time constant interval calculation executed before the low-pass filter was devised and implemented in the second method. This adaptation algorithm enables sensing of the rapid change of the mean count rate before the fluctuations suppression is carried out. Some parameters were fixed to their optimum values after appropriate optimization procedures had been performed. The implemented low-pass filter has variable number of stationary coefficients depending on the specified error and the mean count rate. It implements the control of the mean count rate error by suppressing the fluctuations in a controllable way. The simulated and realized methods, using the developed algorithms, guarantee: a response time not in excess of 2 s for a mean count rate higher than 2 counts/s and a controllable mean count rate error in the range of 4-10%. (c) 2005 Elsevier Ltd. All rights reserved