An Updating Method for Finite Element Models of Flexible-Link Mechanisms Based on an Equivalent Rigid-Link System

This paper proposes a comprehensive methodology to update dynamic models of flexible-link mechanisms (FLMs) modeled through ordinary differential equations. The aim is to correct mass, stiffness, and damping matrices of dynamic models, usually based on nominal and uncertain parameters, to accurately represent the main vibrational modes within the bandwidth of interest. Indeed, the availability of accurate models is a fundamental step for the synthesis of effective controllers, state observers, and optimized motion profiles, as those employed in modern control schemes. The method takes advantage of the system dynamic model formulated through finite elements and through the representation of the total motion as the sum of a large rigid-body motion and the elastic deformation. Model updating is not straightforward since the resulting model is nonlinear and its coordinates cannot be directly measured. Hence, the nonlinear model is linearized about an equilibrium point to compute the eigenstructure and to compare it with the results of experimental modal analysis. Once consistency between the model coordinates and the experimental data is obtained through a suitable transformation, model updating has been performed solving a constrained convex optimization problem. Constraints also include results from static tests. Some tools to improve the problem conditioning are also proposed in the formulation adopted, to handle large dimensional models and achieve reliable results. The method has been experimentally applied to a challenging system: a planar six-bar linkage manipulator. The results prove their capability to improve the model accuracy in terms of eigenfrequencies and mode shapes

Multi-domain optimization of the eigenstructure of controlled underactuated vibrating systems

The paper proposes a multi-domain approach to the optimization of the dynamic response of an underactuated vibrating linear system through eigenstructure assignment, by exploiting the concurrent design of the mechanical properties, the regulator and state observers. The approach relies on handling simultaneously mechanical design and controller synthesis in order to enlarge the set of the achievable performances. The underlying novel idea is that structural properties of controlled mechanical systems should be designed considering the presence of the controller through a concurrent approach: this can considerably improve the optimization possibilities. The method is, first, developed theoretically. Starting from the definition of the set of feasible system responses, defined through the feasible mode shapes, an original formulation of the optimality criterion is proposed to properly shape the allowable subspace through the optimal modification of the design variables. A proper choice of the modifications of the elastic and inertial parameters, indeed, changes the space of the allowable eigenvectors that can be achieved through active control and allows obtaining the desired performances. The problem is then solved through a rank-minimization with constraints on the design variables: a convex optimization problem is formulated through the \u201csemidefinite embedding lemma\u201d and the \u201ctrace heuristics\u201d. Finally, experimental validation is provided through the assignment of a mode shape and of the related eigenfrequency to a cantilever beam controlled by a piezoelectric actuator, in order to obtain a region of the beam with negligible oscillations and the other one with large oscillations. The results prove the effectiveness of the proposed approach that outperforms active control and mechanical design when used alone

Pole assignment for active vibration control of linear vibrating systems through Linear Matrix Inequalities

This paper proposes a novel method for pole placement in linear vibrating systems through state feedback and rank-one control. Rather than assigning all the poles to the desired locations of the complex plane, the proposed method exactly assigns just the dominant poles, while the remaining ones are free to assume arbitrary positions within a pre-specified region in the complex plane. Therefore, the method can be referred to as "regional pole placement". A two-stage approach is proposed to accomplish both the tasks. In the first stage, the subset of dominant poles is assigned to exact locations by exploiting the receptance method, formulated for either symmetric or asymmetric systems. Then, in the second stage, a first-order model formulated with a reduced state, together with the theory of Linear Matrix Inequalities, are exploited to cluster the subset of the unassigned poles into some stable regions of the complex plane while keeping unchanged the poles assigned in the first stage. The additional degrees of freedom in the choice of the gains, i.e., the non-uniqueness of the solution, is exploited through a semidefinite programming problem to reduce the control gains. The method is validated by means of four meaningful and challenging test-cases, also borrowed from the literature. The results are also compared with those of classic partial pole placement, to show the benefits and the effectiveness of the proposed approach

Cost-of-illness in systemic sclerosis: a retrospective study of an italian cohort of 106 patients

Aims: It is increasingly important to determine the economic consequences of diseases considering the policy of limited health–care budgets. In this study we evaluated the annual direct and indirect costs of Systemic Sclerosis (SSc) and we tried also to identify any cost predictors. Methods: We studied 106 patients (103 female, 3 male), 57 affected by Limited Systemic Sclerosis (LSSc) and 49 affected by Diffuse Systemic Sclerosis (DSSc). Mean age was 57 years (SD±13,8) and mean disease duration was 8,9 years (SD±7,2). Direct costs: data were calculated referring to DRG (Disease Related Group) expenses for the in-patients. We referred to national pharmacopoeia to calculate the pharmaceutical cost for the out-patients. Indirect costs: we estimated the expense comparing our cases to literature data. Intangible costs: these are attributable to pain and psychological suffering. It is very difficult to express the intangible costs in monetary terms and they are often conveyed as disability and poorer quality-of-life. We used the Health Assessment Questionnaire "HAQ" and the Short Form-36 "SF-36" to evaluate this issues. Results: Our study confirms, the extremely high costs caused by Systemic Sclerosis (total cost's 2001 year is € 1.173.842,93, and average yearly patient cost is € 11.073,99). Considering an estimated prevalence of 375 cases/106, the total yearly economic impact of SSc in Italy should be € 249.000.000,00. Intangible costs were calculated as modifications of the health status. Average value of the HAQ was significantly higher than the control population (0,94±0,72), average values in the SF-36 were significantly lower than the control population (49,99±19,16 for physical dimension and 58,42±27,71 for mental dimension). The diffuse form of SSc, positivity for anti-Scl 70 antibodies, high skin score and a poor health status (HAQ and SF-36) were found to be cost predictors. Conclusions: As reported in the literature, our study confirms, the extremely high costs for total and single patients caused by Systemic Sclerosis. The DSSc are more expensive than the LSSc approximately 11% (p=0,0067). The direct costs are 30% higher in the DSSc than the LSSc (p<0.001). The indirect and intangible costs are not significantly different. Moreover, our study shows also the possibility of identifying different cost predictors

Probing the Evaporation Dynamics of Ethanol/Gasoline Biofuel Blends Using Single Droplet Manipulation Techniques

Peer reviewedPublisher PD

The use of cosmic muons in detecting heterogeneities in large volumes

The muon intensity attenuation method to detect heterogeneities in large matter volumes is analyzed. Approximate analytical expressions to estimate the collection time and the signal to noise ratio, are proposed and validated by Monte Carlo simulations. Important parameters, including point spread function and coordinate reconstruction uncertainty are also estimated using Monte Carlo simulations.Comment: 8 pages, 11 figures, submetted to NIM

A Lithium Experiment in the Program of Solar Neutrino Research

The experiments sensitive to pp-neutrinos from the Sun are very perspective for the precise measurement of a mixing angle $\theta_{12}$. A $\nu$e$^{-}$ scattering experiment (Xmass) and/or a charged-current experiment (the indium detector) can measure the flux of electron pp-neutrinos. One can find the total flux of pp-neutrinos from a luminosity constraint after the contribution of $^7$Be and CNO neutrinos to the total luminosity of the Sun are measured. The radiochemical experiment utilizing a lithium target has the high sensitivity to the CNO neutrinos, thus, it has a good promise for the precise measurement of a mixing angle and for the test of a current theory of the evolution of the stars.Comment: 6 pages, 2 figures, 1 table, A report made by A.Kopylov at International Conference NANP-2005, June 2005, Dubna, Russi

Not All Children with Under-Control Asthma are Controlled

Subclinical lung function alterations can sometimes be discovered in asthmatic patients under clinical control. This study aimed to identify the burden of asthmatic children with subclinical airways abnormalities who may benefit from an adjustment in asthma therapy. 134 6-to-17-year-old asthmatic children were enrolled. Of them, 98 presented apparently under clinical control disease and all performed spirometry before and after bronchodilation: 17 (17.3%) had a positive bronchodilation test, in addition to significantly lower lung function indexes as compared to those with under-control asthma who had a negative bronchodilation test. These patients were randomized and re-evaluated: patients (n=8) receiving an adjustment in their therapy showed an improvement in lung function tests and quality of life indexes as compared to 7 without therapy adjustment. In conclusion, a substantial number of apparently-under-control asthmatic children show airways alterations that can be improved by adjusting their therapy, which also seems to enhance their quality of life

OSPF routing with optimal oblivious performance ratio under polyhedral demand uncertainty

We study the best OSPF style routing problem in telecommunication networks, where weight management is employed to get a routing configuration with the minimum oblivious ratio. We consider polyhedral demand uncertainty: the set of traffic matrices is a polyhedron defined by a set of linear constraints, and a routing is sought with a fair performance for any feasible traffic matrix in the polyhedron. The problem accurately reflects real world networks, where demands can only be estimated, and models one of the main traffic forwarding technologies, Open Shortest Path First (OSPF) routing with equal load sharing. This is an NP-hard problem as it generalizes the problem with a fixed demand matrix, which is also NP-hard. We prove that the optimal oblivious routing under polyhedral traffic uncertainty on a non-OSPF network can be obtained in polynomial time through Linear Programming. Then we consider the OSPF routing with equal load sharing under polyhedral traffic uncertainty, and present a compact mixed-integer linear programming formulation with flow variables. We propose an alternative formulation and a branch-and-price algorithm. Finally, we report and discuss test results for several network instances. © 2009 Springer Science+Business Media, LLC

Features, risk factors and clinical outcome of {"}very late{"} recurrences after surgery for localized renal carcinoma: A retrospective evaluation of a cohort with a minimum of 10 years of follow up

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