Minimum DC link Voltages for the Generator Bridge Converter of a SCIG Based Variable Speed Wind Turbine with Fully Rated Converters

Squirrel Cage Induction Generator (SCIG) based variable speed wind turbine with Fully Rated Converters (FRC) is a popular choice in the industry for the modern multi mega-watt wind turbines. Typical FRC system uses a fixed DC link voltage that allows operation in all steady state and dynamic operating conditions while allowing the modulation index of the PWM scheme to vary. However, the analysis made in this paper shows that at steady state, in the maximum power point tracking region where the turbine is operated at variable speeds with generator controlled using Rotor Flux Oriented Control (R-FOC), it is possible to operate the Generator Bridge (GB) converter with significantly lower DC link voltages than the fixed value used, by maintaining maximum modulation index in the PWM scheme. This paper presents a methodology of determining the minimum DC link voltages for such a system supported by simulation results showing the successful operation of a GB converter with minimum DC link voltages in the maximum power point tracking region

Patient perspectives on cervical cancer screening interventions among underscreened women

Background Cervical cancer is highly preventable with regular screening, yet over 4,000 women die from it annually in the United States. Over half of new cervical cancer cases in the U.S. are attributable to insufficient screening. Methods Participants were 23 low-income, uninsured or Medicaid-insured women in North Carolina who were overdue for cervical cancer screening according to national guidelines. Semi-structured interviews examined perspectives on barriers to cervical cancer screening and on interventions to reduce these barriers. We also elicited feedback on three proposed evidence-based interventions: one-on-one education, coupons to reduce out-of-pocket costs, and self-collection of samples for detection of high-risk human papillomavirus (HPV) infection, the primary cause of cervical cancer. Results Reported barriers included high cost, inconvenient clinic hours, lack of provider recommendation, poor transportation, difficulty finding a provider, fear of pain, and low perceived need. Participants suggested interventions including reducing cost, improving convenience through community-based screening or extended clinic hours, strengthening provider recommendations, and providing one-on-one counseling and education outreach. HPV self-collection was most frequently selected as the “most helpful” of 3 proposed interventions (n = 11), followed by reducing out-of-pocket costs (n = 7) and one-on-one education (n = 5). Conclusion Cost was the most reported barrier to cervical cancer screening, although women experience multiple simultaneous barriers. Novel interventions such as HPV self-collection promise to reduce some, but not all, barriers to primary screening. Interventions that work on reducing multiple barriers, including obstacles to receiving follow-up care, may be most effective to prevent cervical cancer among these high-risk women

Surface Instability of Icicles

Quantitatively-unexplained stationary waves or ridges often encircle icicles. Such waves form when roughly 0.1 mm-thick layers of water flow down the icicle. These waves typically have a wavelength of 1cm approximately independent of external temperature, icicle thickness, and the volumetric rate of water flow. In this paper we show that these waves can not be obtained by naive Mullins-Sekerka instability, but are caused by a quite new surface instability related to the thermal diffusion and hydrodynamic effect of thin water flow.Comment: 11 pages, 5 figures, Late

Neutrophil Extracellular Traps in COVID-19

In severe cases of coronavirus disease 2019 (COVID-19), viral pneumonia progresses to respiratory failure. Neutrophil extracellular traps (NETs) are extracellular webs of chromatin, microbicidal proteins, and oxidant enzymes that are released by neutrophils to contain infections. However, when not properly regulated, NETs have potential to propagate inflammation and microvascular thrombosis - including in the lungs of patients with acute respiratory distress syndrome. While elevated levels of blood neutrophils predict worse outcomes in COVID-19, the role of NETs has not been investigated. We now report that sera from patients with COVID-19 (n = 50 patients, n = 84 samples) have elevated levels of cell-free DNA, myeloperoxidase(MPO)-DNA, and citrullinated histone H3 (Cit-H3); the latter two are highly specific markers of NETs. Highlighting the potential clinical relevance of these findings, cell-free DNA strongly correlated with acute phase reactants including C-reactive protein, D-dimer, and lactate dehydrogenase, as well as absolute neutrophil count. MPO-DNA associated with both cell-free DNA and absolute neutrophil count, while Cit-H3 correlated with platelet levels. Importantly, both cell-free DNA and MPO-DNA were higher in hospitalized patients receiving mechanical ventilation as compared with hospitalized patients breathing room air. Finally, sera from individuals with COVID-19 triggered NET release from control neutrophils in vitro. In summary, these data reveal high levels of NETs in many patients with COVID-19, where they may contribute to cytokine release and respiratory failure. Future studies should investigate the predictive power of circulating NETs in longitudinal cohorts, and determine the extent to which NETs may be novel therapeutic targets in severe COVID-19

The analysis of facial beauty: an emerging area of research in pattern analysis

Much research presented recently supports the idea that the human perception of attractiveness is data-driven and largely irrespective of the perceiver. This suggests using pattern analysis techniques for beauty analysis. Several scientific papers on this subject are appearing in image processing, computer vision and pattern analysis contexts, or use techniques of these areas. In this paper, we will survey the recent studies on automatic analysis of facial beauty, and discuss research lines and practical application

NMR Experiments on a Three-Dimensional Vibrofluidized Granular Medium

A three-dimensional granular system fluidized by vertical container vibrations was studied using pulsed field gradient (PFG) NMR coupled with one-dimensional magnetic resonance imaging (MRI). The system consisted of mustard seeds vibrated vertically at 50 Hz, and the number of layers N_ell <= 4 was sufficiently low to achieve a nearly time-independent granular fluid. Using NMR, the vertical profiles of density and granular temperature were directly measured, along with the distributions of vertical and horizontal grain velocities. The velocity distributions showed modest deviations from Maxwell-Boltzmann statistics, except for the vertical velocity distribution near the sample bottom which was highly skewed and non-Gaussian. Data taken for three values of N_ell and two dimensionless accelerations Gamma=15,18 were fit to a hydrodynamic theory, which successfully models the density and temperature profiles including a temperature inversion near the free upper surface.Comment: 14 pages, 15 figure

Bifurcations of a driven granular system under gravity

Molecular dynamics study on the granular bifurcation in a simple model is presented. The model consists of hard disks, which undergo inelastic collisions; the system is under the uniform external gravity and is driven by the heat bath. The competition between the two effects, namely, the gravitational force and the heat bath, is carefully studied. We found that the system shows three phases, namely, the condensed phase, locally fluidized phase, and granular turbulent phase, upon increasing the external control parameter. We conclude that the transition from the condensed phase to the locally fluidized phase is distinguished by the existence of fluidized holes, and the transition from the locally fluidized phase to the granular turbulent phase is understood by the destabilization transition of the fluidized holes due to mutual interference.Comment: 35 pages, 17 figures, to be published in PR

A nonlinear hydrodynamical approach to granular materials

We propose a nonlinear hydrodynamical model of granular materials. We show how this model describes the formation of a sand pile from a homogeneous distribution of material under gravity, and then discuss a simulation of a rotating sandpile which shows, in qualitative agreement with experiment, a static and dynamic angle of repose.Comment: 17 pages, 14 figures, RevTeX4; minor changes to wording and some additional discussion. Accepted by Phys. Rev.

Targeting Potential Drivers of COVID-19: Neutrophil Extracellular Traps

Coronavirus disease 2019 (COVID-19) is a novel, viral-induced respiratory disease that in ∼10-15% of patients progresses to acute respiratory distress syndrome (ARDS) triggered by a cytokine storm. In this Perspective, autopsy results and literature are presented supporting the hypothesis that a little known yet powerful function of neutrophils-the ability to form neutrophil extracellular traps (NETs)-may contribute to organ damage and mortality in COVID-19. We show lung infiltration of neutrophils in an autopsy specimen from a patient who succumbed to COVID-19. We discuss prior reports linking aberrant NET formation to pulmonary diseases, thrombosis, mucous secretions in the airways, and cytokine production. If our hypothesis is correct, targeting NETs directly and/or indirectly with existing drugs may reduce the clinical severity of COVID-19