Inverse approach for load identification in structural dynamics

Goal of this thesis is the identification of the external force field in the frequency domain at low and high frequency range. At low frequency the solution of the investigated problem is carried out by modal analysis. Input-Output relationship between force and velocity is defined by using the Frequency Response Function (FRF) calculated both by modal expansion and measurements. The identification procedure is performed for deterministic and random loads. By considering deterministic loads, the solution of this problem is obtained by the inversion of the FRF, that implies to deal with an ill-conditioning problem. Since it can be shown that the ill-conditioning of FRF matrix is strictly related to the selection of the DoF considered on the structure, a procedure to investigate the best experimental setup that allows to identify the deterministic load is proposed, by using classical regularization techniques based on the Singular Values Decomposition (SVD). Then, with the same purpose the relationship between the modes contribute and the ill-conditioning of the problem is investigated. Different input-output relationships from that used in the case of deterministic loads are adopted when random loads are considered. In fact, they are deduced by a probabilistic approach also for the solution of the direct problem. The results obtained by numerical simulation suggest that the identification of not deterministic loads requires a different methodology. So, a procedure based on the reduction of ill-conditioning it is not considered the conclusive approach; hence the issue has been tackled by a different modal formulation. In a first step the analysis of the coherence function allows to select the number of applied forces, once the position and the amplitude are identified. The validation of this proposed technique is tested in different experimental cases: Single Input Multi Output (SIMO) and Multi Input-Multi Output (MIMO). The numerical identification of deterministic and random loads is conducted also in the instance in which the measurement set of points do not overlap the excitation points. Whilst the first part of the thesis is focused on the identification of deterministic and random loads at low frequencies, the second part is focused on the identification of random loads at high frequencies. Let us remind that a high frequency problem is one in which the wavelength of the waves propagating in the studied media is shorter than the characteristic dimension of the media itself. Therefore the solution of a high frequency problem by a classical technique implies the study of a very large number of degrees of freedom of the model. The consequence is a high computational cost and large uncertainty on the simulation results. Therefore the problem is tackled by using the Statistical Energy Analysis (SEA). The identification is performed in two steps. The first step considers the identification of a "energy based" model of the structure by using the Power Injection Method (this technique allows to carry out the SEA parameters of the structure by experimental tests). The second step is the identification of the power injected by using the identified model and solving an "inverse problem" of SEA

Vibroacoustic optimization using a statistical energy analysis model

In this paper, an optimization technique for medium-high frequency dynamic problems based on Statistical Energy Analysis (SEA) method is presented. Using a SEA model, the subsystem energies are controlled by internal loss factors (ILF) and coupling loss factors (CLF), which in turn depend on the physical parameters of the subsystems. A preliminary sensitivity analysis of subsystem energy to CLFs is performed to select CLFs that are most effective on subsystem energies. Since the injected power depends not only on the external loads but on the physical parameters of the subsystems as well, it must be taken into account under certain conditions. This is accomplished in the optimization procedure, where approximate relationships between CLFs, injected power and physical parameters are derived. The approach is applied on a typical aeronautical structure: the cabin of a helicopter

Processing of logical-physical rules in the control of the autonomous vehicle

Recent advances in intelligent vehicles imply more sophisticated control laws. The standard concept of objective function and models of vehicle and driver represented by differential equations, are not anymore sufficient tools in a future scenario. The capability of reasoning of the machines imposes the use of logic as a fundamental tool to describe requirements of the behavior of the vehicle, and to characterize their response. However, logical statements exhibit a difficulty of integration with the differential physic laws to which the vehicle obeys. There is a clear heterogeneity between mathematics and logic, especially when they must fuse into a single model. The paper proposes an integrated model in which the physics and the logic fuse into a common model, able to generate a meaningful objective function to optimize the behavior through a physical-logic model of the vehicle in the context of control of hybrid dynamical systems. Not negligibly, a logic-statement design helps the autonomous driving to be more acceptable and comprehensible in an insurance and court law context

Evanescent-wave coupled right angled buried waveguide: Applications in carbon nanotube mode-locking

In this paper we present a simple but powerful subgraph sampling primitive that is applicable in a variety of computational models including dynamic graph streams (where the input graph is defined by a sequence of edge/hyperedge insertions and deletions) and distributed systems such as MapReduce. In the case of dynamic graph streams, we use this primitive to prove the following results: -- Matching: First, there exists an $\tilde{O}(k^2)$ space algorithm that returns an exact maximum matching on the assumption the cardinality is at most $k$. The best previous algorithm used $\tilde{O}(kn)$ space where $n$ is the number of vertices in the graph and we prove our result is optimal up to logarithmic factors. Our algorithm has $\tilde{O}(1)$ update time. Second, there exists an $\tilde{O}(n^2/\alpha^3)$ space algorithm that returns an $\alpha$-approximation for matchings of arbitrary size. (Assadi et al. (2015) showed that this was optimal and independently and concurrently established the same upper bound.) We generalize both results for weighted matching. Third, there exists an $\tilde{O}(n^{4/5})$ space algorithm that returns a constant approximation in graphs with bounded arboricity. -- Vertex Cover and Hitting Set: There exists an $\tilde{O}(k^d)$ space algorithm that solves the minimum hitting set problem where $d$ is the cardinality of the input sets and $k$ is an upper bound on the size of the minimum hitting set. We prove this is optimal up to logarithmic factors. Our algorithm has $\tilde{O}(1)$ update time. The case $d=2$ corresponds to minimum vertex cover. Finally, we consider a larger family of parameterized problems (including $b$-matching, disjoint paths, vertex coloring among others) for which our subgraph sampling primitive yields fast, small-space dynamic graph stream algorithms. We then show lower bounds for natural problems outside this family

Microzonazione sismica di un centro abitato di piccole dimensioni: il caso studio di Sant’Agata Fossili (AL)

In questo lavoro sono descritte le attività svolte nell’ambito del Progetto Europeo Strategico RISKNAT riguardanti l’analisi di microzonazione di Sant’Agata Fossili (AL). Sono in particolare descritte tutte le indagini ed analisi numeriche condotte al fine di ottenere una microzonazione sismica di livello 3 secondo quanto previsto nelle recenti linee guida nazionali degli. Al fine inoltre di valutare le ricadute di tipo applicativo di una corretta microzonazione sismica del territorio, sono state realizzate delle simulazioni di scenario adottando come riferimento gli spettri di risposta ottenuti dall’analisi di microzonazione. Le valutazioni di scenario ottenute sono state infine confrontate con le previsioni di scenario realizzabili a priori sulla base dell’adozione degli spettri di risposta definiti nelle Norme Tecniche per le Costruzioni

Real-world efficacy and safety of eribulin in advanced and pretreated HER2-negative breast cancer in a Spanish comprehensive cancer center

Background Eribulin improves survival in pre-treated HER2-negative advanced breast cancer (ABC). However, limited data exist on co-morbidities and central nervous system (CNS) efficacy. The purpose of this study was to review eribulin's efficacy and safety in everyday clinical practice with special focus on age, body mass index (BMI) and central nervous system (CNS) activity. Methods An observational study was conducted in a series of HER2-negative ABC patients treated from January'14-December'17 outside a clinical trial. Objective Response Rate (ORR), Progression Free Survival (PFS), Overall Survival (OS), and association of clinical and pathological variables with outcome were evaluated. Results Ninety-five women were treated with at least one cycle of eribulin. Median age was 57 (33-83), and 18% were obese. Median number of prior chemotherapies for ABC was 3 (2-5) and 76% of patients had visceral metastases, including 21% with CNS involvement. Most tumors were estrogen receptor-positive (79%). ORR and stable disease (SD) at 6 months were 26.2 and 37.5%, respectively. Remarkably, relevant CNS efficacy was observed with eribulin: 20% of patients obtained partial response and 25% SD. Treatment was generally well tolerated and manageable, with 29% grade 3 and 10.9% grade 4 toxicities. Median PFS and OS were 4.1 months (CI95% 3.2-4.9) and 11.1 months (CI95% 9.5-14.7), respectively. Triple-negative disease, > 2organs involved and being younger than 70 years old were independent prognosis factors for worse OS in multivariate analysis. Most patients (75%) progressed in pre-existing metastases sites. Conclusion In everyday clinical practice, eribulin's efficacy seems similar to pivotal trials. CNS-efficacy was observed. TNBC, > 2 organs involved and being younger than 70 years old were independent prognosis factors for worse OS. Remarkably, less incidence of grade 4-toxicity compared to previous studies was found

Nano on reflection

A number of experts from different areas of nanotechnology describe how the field has evolved in the last ten years

On-Chip Integrated, Silicon-Graphene Plasmonic Schottky Photodetector with High Responsivity and Avalanche Photogain.

We report an on-chip integrated metal graphene-silicon plasmonic Schottky photodetector with 85 mA/W responsivity at 1.55 μm and 7% internal quantum efficiency. This is one order of magnitude higher than metal-silicon Schottky photodetectors operated in the same conditions. At a reverse bias of 3 V, we achieve avalanche multiplication, with 0.37A/W responsivity and avalanche photogain ∼2. This paves the way to graphene integrated silicon photonics.We acknowledge funding from EU Graphene Flagship (No. 604391), ERC Grant Hetero2D, and EPSRC Grant Nos. EP/ K01711X/1, EP/K017144/1, EP/N010345/1, EP/M507799/ 1, and EP/L016087/1.This is the final version of the article. It first appeared from the American Chemical Society via https://doi.org/10.1021/acs.nanolett.5b0521

Scientific Opinion on Flavouring Group Evaluation 49, Revision 1 (FGE.49Rev1): xanthine alkaloids from the priority list

Publisher PD

Genetic determinants in a critical domain of ns5a correlate with hepatocellular carcinoma in cirrhotic patients infected with hcv genotype 1b

HCV is an important cause of hepatocellular carcinoma (HCC). HCV NS5A domain‐1 interacts with cellular proteins inducing pro‐oncogenic pathways. Thus, we explore genetic variations in NS5A domain‐1 and their association with HCC, by analyzing 188 NS5A sequences from HCV genotype‐1b infected DAA‐naïve cirrhotic patients: 34 with HCC and 154 without HCC. Specific NS5A mutations significantly correlate with HCC: S3T (8.8% vs. 1.3%, p = 0.01), T122M (8.8% vs. 0.0%, p < 0.001), M133I (20.6% vs. 3.9%, p < 0.001), and Q181E (11.8% vs. 0.6%, p < 0.001). By multivariable analysis, the presence of >1 of them independently correlates with HCC (OR (95%CI): 21.8 (5.7–82.3); p < 0.001). Focusing on HCC‐group, the presence of these mutations correlates with higher viremia (median (IQR): 5.7 (5.4–6.2) log IU/mL vs. 5.3 (4.4–5.6) log IU/mL, p = 0.02) and lower ALT (35 (30–71) vs. 83 (48–108) U/L, p = 0.004), suggesting a role in enhancing viral fitness without affecting necroinflammation. Notably, these mutations reside in NS5A regions known to interact with cellular proteins crucial for cell‐cycle regulation (p53, p85‐PIK3, and β‐ catenin), and introduce additional phosphorylation sites, a phenomenon known to ameliorate NS5A interaction with cellular proteins. Overall, these results provide a focus for further investigations on molecular bases of HCV‐mediated oncogenesis. The role of these NS5A domain‐1 mutations in triggering pro‐oncogenic stimuli that can persist also despite achievement of sustained virological response deserves further investigation