Noise Weighting in the Design of {\Delta}{\Sigma} Modulators (with a Psychoacoustic Coder as an Example)

A design flow for {\Delta}{\Sigma} modulators is illustrated, allowing quantization noise to be shaped according to an arbitrary weighting profile. Being based on FIR NTFs, possibly with high order, the flow is best suited for digital architectures. The work builds on a recent proposal where the modulator is matched to the reconstruction filter, showing that this type of optimization can benefit a wide range of applications where noise (including in-band noise) is known to have a different impact at different frequencies. The design of a multiband modulator, a modulator avoiding DC noise, and an audio modulator capable of distributing quantization artifacts according to a psychoacoustic model are discussed as examples. A software toolbox is provided as a general design aid and to replicate the proposed results.Comment: 5 pages, 18 figures, journal. Code accompanying the paper is available at http://pydsm.googlecode.co

Output Filter Aware Optimization of the Noise Shaping Properties of {\Delta}{\Sigma} Modulators via Semi-Definite Programming

The Noise Transfer Function (NTF) of {\Delta}{\Sigma} modulators is typically designed after the features of the input signal. We suggest that in many applications, and notably those involving D/D and D/A conversion or actuation, the NTF should instead be shaped after the properties of the output/reconstruction filter. To this aim, we propose a framework for optimal design based on the Kalman-Yakubovich-Popov (KYP) lemma and semi-definite programming. Some examples illustrate how in practical cases the proposed strategy can outperform more standard approaches.Comment: 14 pages, 18 figures, journal. Code accompanying the paper is available at http://pydsm.googlecode.co

Should {\Delta}{\Sigma} Modulators Used in AC Motor Drives be Adapted to the Mechanical Load of the Motor?

We consider the use of {\Delta}{\Sigma} modulators in ac motor drives, focusing on the many additional degrees of freedom that this option offers over Pulse Width Modulation (PWM). Following some recent results, we show that it is possible to fully adapt the {\Delta}{\Sigma} modulator Noise Transfer Function (NTF) to the rest of the drive chain and that the approach can be pushed even to a fine adaptation of the NTF to the specific motor loading condition. We investigate whether and to what extent the adaptation should be pursued. Using a representative test case and extensive simulation, we conclude that a mild adaptation can be beneficial, leading to Signal to Noise Ratio (SNR) improvements in the order a few dB, while the advantage pushing the adaptation to the load tracking is likely to be minimal.Comment: Sample code available at http://pydsm.googlecode.co

Harmonic analysis of oscillators through standard numerical continuation tools

In this paper, we describe a numerical continuation method that enables harmonic analysis of nonlinear periodic oscillators. This method is formulated as a boundary value problem that can be readily implemented by resorting to a standard continuation package - without modification - such as AUTO, which we used. Our technique works for any kind of oscillator, including electronic, mechanical and biochemical systems. We provide two case studies. The first study concerns itself with the autonomous electronic oscillator known as the Colpitts oscillator, and the second one with a nonlinear damped oscillator, a non-autonomous mechanical oscillator. As shown in the case studies, the proposed technique can aid both the analysis and the design of the oscillators, by following curves for which a certain constraint, related to harmonic analysis, is fulfilled.Comment: 20 pages, 4 figure

A sudden onset of parossistic atrial fibrillation

A 67 years old woman with a medical history notable for arterial hypertension presented with sudden onset of parossistic atrial fibrillation and shortness of breath. On examination, she appeared in good health condition. The blood pressure was 155/85 mm Hg, the pulse 125 beats per minute and the axillary temperature 36.5°C; the respirations were 24 breaths per minute. There was a grade 3/6 holosystolic murmur above the cardiac apex radiating posteriorly. Electrocardiography confirmed the presence of parossistic atrial fibrillation (Figure 1); a transthoracic echocardiography revealed a mass (3.4 by 7.8 cm) (Figure 2) attached to the left atrial septum and protruding through the mitral valve into the left ventricle, suggestive of a myxoma. Given the risk of systemic embolization and sudden syncope, the patient underwent prompt surgical resection of the mass (Figure 3). Pathological evaluation revealed a benign myxoma (Figure 4). The patient had a postoperative good course and was discharged home on the seventh postoperative day

Different ways to repair the mitral valve with artificial chordae: a systematic review

Myxomatous mitral regurgitation (type II Carpentier's functional classification) affects about 1-2% of the population. This represents a very common indication for valve surgery resulting in a low percentage of repairs compared to replacement which is actually performed. In the last decades, several methods for mitral valve repair have been developed, to make the surgical feasibility easier, improve the long-term follow-up thus avoiding the need for reoperations. A very interesting method is represented by the combination of various valve repair techniques, depending on the involvement of the anterior, posterior, or both leaflets, and the use of PTFE artificial chordae tendineae when excessive chordal elongation or rupture due to myxomatous degeneration co-exists. The aim of this review is to summarize the evolution of these techniques from the beginning till now

Left ventricular outflow tract false aneurysm late after aortic valve replacement.

Heart Surg Forum 2005; 8(3): E136-9

Klippel-Feil syndrome. When using fiberoptic bronchoscopy guide, a case report

Klippel-Feil syndrome is a rare disease with congenital musculoskeletal condition characterized by faulty segmentation of cervical vertebrae and consists of cervical vertebra fusions with limitation of head movements, short neck and low posterior hairline. In several cases the syndrome is associated with cardiovascular malformations. Patients affected by Klippel-Feil syndrome could be an anesthetic challenge, not only during cardiac surgery. We are presenting a case of Klippel-Feil Syndrome in an adult patient, who was operated on for a pulmonary valve insufficiency in a previously corrected Tetralogy of Fallot Syndrome. We are going to discuss the features of this rare syndrome

Awareness: An empirical model

In this work, we face the time-honored problem of the contraposition/integration of analytical and intuitive knowledge, and the impact of such interconnection on the onset of awareness resulting from human decision-making processes. Borrowing the definitions of concepts like intuition, tacit knowledge, uncertainty, metacognition, and emotions from the philosophical, psychological, decision theory, and economic points of view, we propose a skeletonized mathematical model grounded on Markov Decision Processes of these multifaceted concepts. Behavioral patterns that emerged from the solutions of the model enabled us to understand some relevant properties of the interaction between explicit (mainly analytical) and implicit (mainly holistic) knowledge. The impact of the roles played by the same factors for both styles of reasoning and different stages of the decision process has been evaluated. We have found that awareness emerges as a dynamic process allowing the decision-maker to switch from habitual to optimal behavior, resulting from a feedback mechanism of self-observation. Furthermore, emotions are embedded in the model as inner factors, possibly fostering the onset of awareness