Measuring the Performance of Underplatform Dampers for Turbine Blades by Rotating Laser Doppler Vibrometer

Underplatform friction dampers are commonly used to control the vibration level of turbine blades in order to prevent high-cycle fatigue failures. Experimental validation of highly non-linear response predictions obtained from FEM bladed disk models incorporating underplatform dampers models, has proved to be very difficult so as the assessment of the performance of a chosen design. In this paper, the effect of wedgeshaped underplatform dampers on the dynamics of a simple bladed disk under rotating conditions is measured and the effect of the excitation level on the UPDs performances is investigated at different number of the engine order excitation nearby resonance frequencies of the 1st blade bending modes of the system. The measurements are performed with an improved configuration of a rotating test rig, designed with a noncontact magnetic excitation and a non-contact rotating SLDV measurement syste

A Method to Discriminate Between the Candida stellata and Saccharomyces cerevisiae in Mixed Fermentation on WLD and Lysine Agar Media

This paper presents a simple method to distinguish between Candida stellata and Saccharomyces cerevisiaeyeasts during microbiological analyses. The method is based on differential yeast growth on a mediumcontaining cycloheximide and a medium containing lysine as only nitrogen source (lysine agar). Thecycloheximide resistance of 45 yeast strains belonging to Candida stellata, Hanseniaspora uvarum, Hanseniasporaguilliermondii, Metschnikowia pulcherrima, Torulaspora delbrueckii, Zygosaccharomyces bailii, Kluyveromycesthermotolerans and Zygoascus hellenicus, and 14 strains of Saccharomyces cerevisiae and Saccharomycesbayanus on WL nutrient agar, was assayed. Cycloheximide resistance is characteristic of the species H. uvarum,H. guilliermondii and Z. hellenicus, while for the other yeasts it depends on the strain and the concentrationof cycloheximide used. Two mg/L of cycloheximide allows selective counting of a strain of C. stellata (Cs3)compared to one of the sensitive S. cerevisiae strain (NDA21). Similar results can be obtained on lysine agar,but counts are reliable only with the additional spreading of a monolayer of Saccharomyces cells. The differentcycloheximide resistance of C. stellata and S. cerevisiae can be used in the microbiological analysis of mixedcultures to monitor the individual growth of the two yeast species. This method can be applied to the studyof mixed fermentations with other non-Saccharomyces species. The modified use of lysine agar is useful to acertain extent in the distinction of multistarter yeasts from the indigenous yeasts

Dental pulp stem cells bioadhesivity: evaluation on mineral-trioxide-aggregate.

Stem cells are undifferentiated cells that have the capacity to self-renew. They have been discovered in many adult tissues, including teeth. Dental Pulp Mesenchymal Stem Cells (DP-MSCs) are involved in dental repair by activation of growth factors, released after caries and have the ability to regenerate a dentin-pulp-like complex. The molecular/cellular research gives the possibility to grow new tissues and biological structures for clinical applications, providing cells for therapies including cell transplantation and tissue engineering. In this study DP-MSCs were derived from dental pulp of 10 donors. To evaluate material toxicity, after in vitro isolation, the cells were seeded on mineral trioxide aggregate (MTA). Initial light microscopy investigation of cells revealed no signs of cell death due to toxicity or infection, on the contrary the scaffolds supplied an excellent support for cell structures, the cells proliferated and adhered to substrate. Similar observation was seen in scanning electron microscopy, in particular the cells had proliferated and spread, covering a considerable part of the surface of the biomaterials investigated, with an elaborate form of attachment, in fact, the cells formed a continuous layer on the upper surface of the MTA. In conclusion, the aim of this study is to demonstrate that DP-MSCs combined with MTA could be a potential source for regenerative medicine, encouraging further study to evaluate the new-dentin formation

Are Bankers “Crying Wolf”? Type I, Type II Errors and Deterrence in Anti-Money Laundering: The Italian Case

Excessive and useless reporting, called the "crying wolf effect," is a crucial shortcoming that any anti-money laundering (AML) design aims to address. For this reason, in recent years, AML policies in both the US and Europe have switched from a rule-based to a risk-based approach. This study theoretically and empirically investigates whether the risk-based approach delivers the expected results. The theoretical model shows that a trade-off can emerge between accuracy (fewer type-I and type-II errors) and deterrence. The empirical analysis, conducted after the risk-based approach was introduced in Italy, confirms this trade-off. More specifically, deterrence seems a priority, whereas accuracy is sacrificed. In this respect, the data suggest that Italian bankers are likely to "cry wolf.

An Investigation of Complex Mode Shapes

This paper presents an investigation of complex mode shape analysis caused by non-linear damping. Nowadays, most academics are accustomed to complex mode shapes, which are a characteristic of most axisymmetric structures. The topic was deeply investigated during the 1980s, sparking the sharpest debates about their physical existence or not. However, after nearly three decades, one question still stands, do we know all about complex mode shapes? This paper takes the dust off this topic again and explores how complex eigenvectors arise when the percentage frequency separation between two mode shapes is the same order of magnitude as the percentage damping. The difference between the past and present investigations relates to the non-linear damping that might arise from joint dynamics under various vibration amplitudes. Hence, the new research question is about the investigation of amplitude-dependent damping on the modal complexity. Why bother? There are several engineering applications in both space and aerospace where axisymmetric structures and joint dynamics can impair the numerical analysis that is currently performed. This paper does not offer any solutions but does expand the research on an unsolved challenge by identifying the questions posed.</p

Modeling and simulation of viscoelastic film retraction

In this paper, we investigate the retraction of a circular viscoelastic liquid film with a hole initially present in its center by means of finite element numerical simulations. We study the whole retraction process, aiming at understanding the hole opening dynamics both when the hole does not feel any confinement and when it interacts with the solid wall bounding the film. The retraction behavior is also interpreted through a simple toy model, that highlights the physical mechanism underlying the process.We consider three different viscoelastic constitutive equations, namely, Oldroyd-B, Giesekus (Gsk), and Phan Thien-Tanner (PTT) models, and several system geometries, in terms of the film initial radius and thickness. For each given geometry, we investigate the effects of liquid inertia, elasticity, and flow-dependent viscosity on the dynamics of the hole opening. Depending on the relative strength of such parameters, qualitatively different features can appear in the retracting film shape and dynamics.When inertia is relevant, as far as the opening hole does not interact withthe wall bounding the film, the influence of liquid elasticity is very moderate,and the retraction dynamics tends to the one of Newtonian sheets; whenthe hole starts to interact with the solid wall, hole radius/opening velocityoscillations are detected. Such oscillations enhance at increasing elasticity.From the morphological point of view, the formation of a rim at the edge ofthe retracting film is observed. If inertial forces become less relevant withrespect to viscous forces, R-oscillations disappear, the hole opening velocitygoes through a maximum and then monotonically decays to zero, and norim forms during the film retraction. Geometrical changes have the effect ofenlarging or reducing the portion of the retraction dynamics not influencedby the presence of the solid wall with respect to the one governed by thehole-wall interactions