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Unstructured uncertainty models are commonly used within robust control framework to cover unmodeled dynamics, particularly at high frequency. The resulting uncertain linear time invariant (LTI) models (i.e. models comprised of a LTI nominal model and an uncertainty model) are then used in robust controller synthesis procedure, and have significant influence on the controller performance. This paper proposes a novel procedure for constructing unstructured uncertainty models for a class of mechanical vibration systems comprised of a number of interconnected (coupled) vibration subsystems. For each subsystem, a finite element mesh refinement technique is used to construct a series of successively finer spatial discretizations. After constructing a low-order nominal model of the subsystem via appropriate model order reduction technique, a weighted unstructured uncertainty model is constructed for each level of discretization. The resulting uncertainty models primarily cover discretization errors and resulting higher order dynamics. Furthermore, by taking into the account that the individual subsystem is coupled with neighbouring subsystems, which we assumed to be dissipative, we are able to improve the uncertainty models. To be more specific, we discard frequency content which is effectively damped by the neighbouring subsystems and have no significant influence on the response of the entire vibration system. When performing the uncertainty improvement, we also investigate the use of a reduced order model which approximates a set of neighbouring subsystems. As the result of the proposed procedure, we are able to significantly reduce conservatism in the resulting uncertain LTI models of the individual subsystems, thus improving the performance of subsequent robust control strategies. We illustrate the results on a numerical example comprised of a series of simply-supported beams coupled with a set of springs and viscous dampers.

Accurate predictions of vibration transmission of rib-stiffened plates can be quite problematic in that both long- and short-wavelength deformations are commonly generated within the same system model. In this case, it is widely acknowledged that hybrid methods which can combine both the deterministic and statistical modelling techniques are more appropriate than single deterministic or statistical methods. In this paper, a simple hybrid technique, i.e., the so-called “mode-based approach”, is applied to predict the vibration transmission of a rib-stiffened plate model. The results are then compared with those of the well-established hybrid FE/SEA method and the exact modal analysis. It is found that the mode-based approach has a better performance than the hybrid FE/SEA method regarding both accuracy and efficiency, although the former is far less generic than the latter at the current stage.

Acquire knowledge concerning the diagnosis and treatment of otogenic cavernous sinus thrombophlebitis.We report a case of otogenic cavernous sinus thrombophlebitis (CST) in a 6-year-old boy.CST diagnosis was based on clinical signs (septic illness, ocular nerve palsy and chemosis), and neuro-imaging confirmed the diagnosis. Contrast-enhanced CT scan demonstrates different signs: (i) filling defect or heterogeneous enhancement of cavernous sinus, (ii) cavernous sinus enlargement with bulging of the lateral wall, (iii) intensive enhancement of lateral wall corresponding to enhancement of a collateral network replacing the thrombosed cavernous veins, (iiii) and sometimes indirect orbital signs (exophthalmus, densification of the retro-orbital fat, superior ophthalmic dilatation with partial or no enhancement in case of thrombosis extension). The bacteria most frequently found are Streptococci, Streptococcus pneumoniae, Staphylococcus aureus, Gram-negative rods and anaerobes combined. The therapeutic management of CST consists of intravenous administration of appropriate antibiotics combined radical mastoidectomy if medical therapy has failed. Anticoagulant therapy is controversial.Knowledge of early diagnosis of otogenic cavernous sinus is important because prior to the antibiotic era, CST was almost always fatal. Currently, therapeutic outcome is not always favorable due to high morbidity after aggressive treatment.