Time domain analysis of ship motion and wave loads by boundary integral equations

In this presentation, we like to discuss some aspects of a more general computational algorithm for the prediction of ship motion and loads induced by the interaction with wave systems. In particular, unlikely the more conventional models in frequency domain, we attack the problem by a time domain formulation. The purpose is twofold. First, within the framework of a linear analysis, the ship response function to a general wave excitation can be numerically determined by a transient test (i.e. the interaction with a wave pulse compact in time). In this way, a substantial saving of computational time with respect to the existing algorithm is achieved. Second, a time domain modeling is intrinsically prone to deal with the fully nonlinear problem or, at least, to recover some nonlinear effects

Confronto di solutori FEM e solutori BEM per lo sloshing in contenitori

Ė stato studiato il fenomeno di sloshing attraverso due diversi algoritmi numerici: il primo consiste in una discretizzazione con elementi finiti dell’equazione di Navier Stokes in formulazione Arbitrary Lagrangian Eulerian, è indicato nel seguito come FEM ed è descritto in [3]; il secondo è basato sulla discretizzazione delle equazioni agli integrali di contorno e delle equazioni di evoluzione della superficie libera ed è indicato come BEM e descritto in [2]. Per verificare la validità dei due codici sono stati confrontati i loro risultati con quelli presenti in letteratura, sia derivanti da altri codici numerici, sia ottenuti come risultati sperimentali. Il confronto è stato effettuato per un’ampia gamma di situazioni, in modo da studiare il comportamento dei due codici al variare delle caratteristiche della sollecitazione e delle dimensioni del dominio

The relevance of recoil and free swimming in aquatic locomotion

The study of the free swimming of undulating bodies in an otherwise quiescent fluid has always encountered serious difficulties for several reasons. When considering the full system, given by the body and the unbounded surrounding fluid, the absence of external forces leads to a subtle interaction problem dominated, at least at steady state conditions, by the equilibrium of strictly related internal forces, e.g. thrust and drag, under the forcing of a prescribed deformation. A major complication has been dictated by the recoil motion induced by the non linear interactions, which may find a quite natural solution when considering as unknowns the velocity components of the body center of mass. A simplified two-dimensional model in terms of impulse equations has been used and a fruitful separation of the main contributions due to added mass and to vorticity release is easily obtained. As main results we obtain either the mean locomotion speed and the oscillating recoil velocity components which have a large effect on the overall performance of free swimming. Several constrained gaits are considered to highlight the relevance of recoil for realizing graceful and efficient trajectories and to analyze its potential means for active control

Wave-Impact in a sloshing tank: hydroelastic challenges

Wave-impact in sloshing flows is an important issue for the safety of the Liquefied Natural Gas (LNG) carriers. Although LNG tanks have filling restrictions, they must be able to operate at any filling depth. The full understanding of the physical phenomena and the accurate evaluation of the local loads in sloshing-induced slamming events occurring in completely, partially or barely filling conditions, is a challenge of the research field. Violent free-surface motions in a sloshing tank generally occur when the energy spectrum of the ship motion is focused in the frequency region close to the lowest sloshing mode of the tank. Slamming events may occur originating impulsive and large local loads that undermine the integrity of the structure. Depending on the local flow features before the impact, several and complex scenarios can characterize the physical evolutions of a wave impact in a sloshing flow. For example, when the impact angle between water and body is small, air entrapment may occur making important the compressibility of the air and its interaction with the free surface. In contrast, for an incipient breaking wave approaching a vertical wall, flip-through event may happen causing localized and large loads without any air-entrapment or flat-impact may occur. In all these cases, when the typical temporal duration of the local load is comparable with the lowest natural period of the structure, hydroelasticity matters affecting the integrity of the structure. Present research investigation pursues the experimental study about the kinematic and dynamic features of a wave impacting a rigid vertical wall of a 2D sloshing tank in shallow water conditions. Previous papers, have emphasized how the maximum pressure around the impact area is an unreliable indicator of the maximum load (with value of the standard deviation up to 50%), because of the stochastic behaviour of the impact phenomena. Here, the strain distribution along a deformable aluminum plate inserted in a rigid vertical wall of a sloshing tank has been measured to characterize the features of the local loads

Biweekly Hizentra® in Primary Immunodeficiency: a Multicenter, Observational Cohort Study (IBIS)

Immunoglobulin G (IgG) replacement therapy is a standard treatment for patients with primary immunodeficiency diseases (PIDs). Hizentra®, a 20% human subcutaneous IgG (SCIG), is approved for biweekly administration for PIDs. The aim of the multicenter IBIS study was to prospectively investigate the efficacy of biweekly Hizentra® compared with previous IVIG or SCIG treatment regimens in patients with PIDs. The study consisted of a 12-month retrospective period followed by 12-month prospective observational period. The main endpoints included pre-infusion IgG concentrations, proportion of patients with serious bacterial infections (SBIs), other infections, hospitalizations due to PID-related illnesses, and days with antibiotics during the study periods. Of the 36 patients enrolled in the study, 35 patients continued the study (mean age 26.1 ± 14.4 years; 68.6% male). The mean pre-infusion IgG levels for prior immunoglobulin regimens during the retrospective period (7.84 ± 2.09 g/L) and the prospective period (8.55 ± 1.76 g/L) did not show any significant variations (p = 0.4964). The mean annual rate of SBIs/patient was 0.063 ± 0.246 for both prospective and retrospective periods. No hospitalizations related to PIDs were reported during the prospective period versus one in the retrospective period. All patients were either very (76.5%) or quite (23.5%) satisfied with biweekly Hizentra® at the end of the study. In conclusion, the IBIS study provided real-world evidence on the efficacy of biweekly Hizentra® in patients with PIDs, thus verifying the data generated by the pharmacometric modeling and simulation study in a normal clinical setting

Ionized jet deposition of silver nanostructured coatings: Assessment of chemico-physical and biological behavior for application in orthopedics

Infection is one of the main issues connected to implantation of biomedical devices and represents a very difficult issue to tackle, for clinicians and for patients. This study aimed at tackling infection through antibacterial nanostructured silver coatings manufactured by Ionized Jet Deposition (IJD) for application as new and advanced coating systems for medical devices. Films composition and morphology depending on deposition parameters were investigated and their performances evaluated by correlating these properties with the antibacterial and antibiofilm efficacy of the coatings, against Escherichia coli and Staphylococcus aureus strains and with their cytotoxicity towards human cell line fibroblasts. The biocompatibility of the coatings, the nanotoxicity, and the safety of the proposed approach were evaluated, for the first time, in vitro and in vivo by rat subcutaneous implant models. Different deposition times, corresponding to different thicknesses, were selected and compared. All silver coatings exhibited a highly homogeneous surface composed of nanosized spherical aggregates. All coatings having a thickness of 50 nm and above showed high antibacterial efficacy, while none of the tested options caused cytotoxicity when tested in vitro. Indeed, silver films impacted on bacterial strains viability and capability to adhere to the substrate, in a thickness-dependent manner. The nanostructure obtained by IJD permitted to mitigate the toxicity of silver, conferring strong antibacterial and anti-adhesive features, without affecting the coatings biocompatibility. At the explant, the coatings were still present although they showed signs of progressive dissolution, compatible with the release of silver, but no cracking, delamination or in vivo toxicity was observed

Patient and physician perspectives on biological treatment in severe asthma: a Severe Asthma Network Italy survey

: Patients with severe asthma perceive beneficial effects of biologics and good self-reported adherence to treatment, even when self-administered at home https://bit.ly/48vP70w

Measurements of the leptonic branching fractions of the τ\tau

Data collected with the DELPHI detector from 1993 to 1995 combined with previous DELPHI results for data from 1991 and 1992 yield the branching fractions B({\tau \rightarrow \mbox{\rm e} \nu \bar{\nu}}) = (17.877 \pm 0.109_{stat} \pm 0.110_{sys} )\% and $B({\tau \rightarrow \mu \nu \bar{\nu}}) = (17.325 \pm 0.095_{stat} \pm 0.077_{sys} )\%$

Measurement of inclusive π0\pi^{0} production in hadronic Z0Z^{0} decays

An analysis is presented of inclusive \pi^0 production in Z^0 decays measured with the DELPHI detector. At low energies, \pi^0 decays are reconstructed by \linebreak using pairs of converted photons and combinations of converted photons and photons reconstructed in the barrel electromagnetic calorimeter (HPC). At high energies (up to x_p = 2 \cdot p_{\pi}/\sqrt{s} = 0.75) the excellent granularity of the HPC is exploited to search for two-photon substructures in single showers. The inclusive differential cross section is measured as a function of energy for {q\overline q} and {b \bar b} events. The number of \pi^0's per hadronic Z^0 event is N(\pi^0)/ Z_{had}^0 = 9.2 \pm 0.2 \mbox{(stat)} \pm 1.0 \mbox{(syst)} and for {b \bar b}~events the number of \pi^0's is {\mathrm N(\pi^0)/ b \overline b} = 10.1 \pm 0.4 \mbox{(stat)} \pm 1.1 \mbox{(syst)} . The ratio of the number of \pi^0's in b \overline b events to hadronic Z^0 events is less affected by the systematic errors and is found to be 1.09 \pm 0.05 \pm 0.01. The measured \pi^0 cross sections are compared with the predictions of different parton shower models. For hadronic events, the peak position in the \mathrm \xi_p = \ln(1/x_p) distribution is \xi_p^{\star} = 3.90^{+0.24}_{-0.14}. The average number of \pi^0's from the decay of primary \mathrm B hadrons is found to be {\mathrm N} (B \rightarrow \pi^0 \, X)/\mbox{B hadron} = 2.78 \pm 0.15 \mbox{(stat)} \pm 0.60 \mbox{(syst)}