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Assessment of thermal instabilities and oscillations in multifinger heterojunction bipolar transistors through a harmonic-balance-based CAD-oriented dynamic stability analysis technique
Full text linkWe present a novel analysis of thermal instabilities and oscillations in multifinger heterojunction bipolar transistors (HBTs), based on a harmonic-balance computer-aided-design (CAD)-oriented approach to the dynamic stability assessment. The stability analysis is carried out in time-periodic dynamic conditions by calculating the Floquet multipliers of the limit cycle representing the HBT working point. Such a computation is performed directly in the frequency domain, on the basis of the Jacobian of the harmonic-balance problem yielding the limit cycle. The corresponding stability assessment is rigorous, and the efficient calculation method makes it readily implementable in CAD tools, thus allowing for circuit and device optimization. Results on three- and four-finger layouts are presented, including closed-form oscillation criteria for two-finger device
Efficient spectral domain technique for the frequency locking analysis of nonlinear oscillators
Full text linkAfter discussing an implementation of the harmonic balance technique that enables the efficient determination of the limit cycles for a nonlinear autonomous dynamical system, we consider the frequency locking of a set of oscillators that is studied by means of a proper extension of the aforementioned approach. Harmonic balance is also used for the numerical computation of the Floquet exponents and eigenvectors of the frequency locked limit cycle, thus enabling the assessment of its stability properties. The proposed technique is applied to the study of the frequency locking properties of a set of coupled Chua’s oscillators as a function of several parameters
Two-point versus multipartite entanglement in quantum phase transitions
Full text linkWe analyze correlations between subsystems for an extended Hubbard model exactly solvable in one dimension, which exhibits a rich structure of quantum phase transitions (QPTs). The T=0 phase diagram is exactly reproduced by studying singularities of single-site entanglement. It is shown how comparison of the latter quantity and quantum mutual information allows one to recognize whether two-point or shared quantum correlations are responsible for each of the occurring QPTs. The method works in principle for any number D of degrees of freedom per site. As a by-product, we are providing a benchmark for direct measures of bipartite entanglement; in particular, here we discuss the role of negativity at the transition
Il tumore polmonare da amianto
No full textIl tumore polmonare è una malattia frequente. Il fattore causale principale è il fumo di tabacco, ma moltissimi agenti fisici e chimici sono in grado di indurre la malattia. L’esposizione ad amianto aumenta l’incidenza e la mortalità per tumore polmonare nei soggetti esposti; tutti i tipi di amianto sono cancerogeni, e possono causare tutti i principali tipi istologici di tumore polmonare. Molti sono i fattori di tossicità dell’amianto; in generale è possibile individuare una relazione dose-risposta tra esposizione e incidenza di malattia. La cessazione dell’esposizione determina una riduzione del rischio. L’iter diagnostico che porta all’attribuzione eziologica di un caso di tumore polmonare all’esposizione ad amianto è un procedimento complesso a carattere probabilistico, nel quale intervengono la stima dell’esposizione e la valutazione di dati biologici e clinico-diagnostici, ma anche aspetti sociali, assicurativi ed economici. L’interazione tra amianto e fumo di sigaretta determina un aumento del rischio più che additivo. Il tumore polmonare amianto-correlato è riconosciuto in Italia come malattia professionale, ma la sua frequenza è sottostimata. In tutto il mondo sono in discussione programmi di screening del tumore polmonare e di sorveglianza sanitaria dei lavoratori esposti ed ex-esposti ad amianto.Lung cancer is a frequent disease. The main causal factor is tobacco smoking, but many physical and chemical agents can cause the disease. Asbestos exposure increases incidence and mortality for lung cancer in subjects exposed; all types of asbestos are carcinogenic, and can cause all the major histological types of lung cancer. Many are the asbestos toxicity factors; in general, it is possible to detect a dose-response relationship between exposure and incidence of disease. The cessation of exposure results in a reduction in risk. The diagnostic procedure that leads to the etiologic attribution of a case of lung cancer to asbestos exposure is a complex probabilistic process, involving estimation of exposure and evaluation of biological and clinical-diagnostic data as well as social, insurance and economic aspects. The interaction between asbestos and cigarette smoking causes a more than additive increase in risk. Asbestos-related lung cancer is recognized in Italy as a professional disease, but its frequency is underestimated. Worldwide screening programs for lung cancer and health surveillance of workers exposed and ex-exposed to asbestos are discussed
Un metodo rigoroso per l'analisi dell'instabilità elettrotermica in dispositivi di potenza per applicazioni adalta frequenza
No full textOscillator noise: a nonlinear perturbative theory including orbital fluctuations and phase-orbital correlation
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Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
HB-based CAD-oriented dynamic stability analysis of circuits and devices: application to the assessment of thermal instabilities in multifinger HBTs
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