Assessing the quality of angiographic display of brain blood vessels aneurysms compared to intraoperative state

Background/Aim. Aneurysms in brain blood vessels are expanding bags composed of a neck, body and fundus. Clear visibility of the neck, the position of the aneurysm and surrounding structures are necessary for a proper choice of methods for excluding the aneurysm from the circulation. The aim of this study was to evaluate the reliability of spatial reconstruction of blood vessels of the brain based on the original software for 3D reconstruction of the equipment manufacturer and a personal computer model developed earlier in the Clinic for Neurosurgery, Clinical Center of Serbia, Belgrade, compared to intraoperative identification of these aneurysms. Methods. This study included 137 patients of both sexes. The presence of an aneurysm was verified by angiographic methods [computed tomographic angiography (CTA), multislice computed tomography angiography (MSCTA), magnetic resonance imaging angiography (MRA), or digital subtraction angiography (DSA)]. Results. The quality score (0 to 5) for CTA was 3.180 ± 0.961, MSCTA 4.062 ± 0.928, and for DSA 4.588 ± 0.758 (p < 0.01). The results of this study favorite conventional angiography as the gold standard for diagnostic of intracranial aneurysms. Conclusion. The results of this study are consistent with current publications review and clearly recognize the advantages and disadvantages of diagnostic neuroradiological procedures, with DSA of brain blood vessels as a binding preoperative diagnostic procedure in cases in who it is not possible to clearly visualize the supporting blood vessel and neck of the aneurysm by using the findings of CTA, MRA and MSCTA

Identification of parameters in nonlinear geotechnical models using extenden Kalman filter

Direct measurement of relevant system parameters often represents a problem due to different limitations. In geomechanics, measurement of geotechnical material constants which constitute a material model is usually a very diffcult task even with modern test equipment. Back-analysis has proved to be a more effcient and more economic method for identifying material constants because it needs measurement data such as settlements, pore pressures, etc., which are directly measurable, as inputs. Among many model parameter identification methods, the Kalman filter method has been applied very effectively in recent years. In this paper, the extended Kalman filter – local iteration procedure incorporated with finite element analysis (FEA) software has been implemented. In order to prove the effciency of the method, parameter identification has been performed for a nonlinear geotechnical model

Projektowanie i implementacja sterownika do aktywnej redukcji drgań powłokowej struktury "inteligentnej" z elementami piezoelektrycznymi

The paper is dealing with the model based controller design for a shell structure attached with piezoelectric patches as actuators and sensors. The state-space model used for the controller design was obtained using the finite element (FE) approach, modal analysis and modal reduction resulting in a form convenient for the controller development. The optimal LQ controller was designed for the vibration suppression purposes of a funnel shaped shell structure. The design model for the controller development was augmented with additional dynamics which takes into account excitations/disturbances, contributing thus to a better vibration suppression. The controller was implemented on a funnel-shaped piezoelectric structure. The structure was intensively investigated experimentally, and the achieved results of the controlled behaviour with respect to vibration suppression are presented and discussed.Praca dotyczy problemu modelowego projektowania struktury powłokowej z naklejonymi do niej elementami piezoelektrycznymi. Zastosowany w procesie projektowania model, który opisano w przestrzeni stanu, został sformułowany za pomocą metody elementów skończonych, analizy modalnej i modalnej redukcji, co dało wygodny do implementacji rezultat. Optymalny sterownik LQ zaprojektowano w celu ograniczenia amplitudy drgań struktury powłokowej o lejkowatym kształcie. Użyty model został uzupełniony o zjawiska dynamiczne uwzględniające zewnętrzne wymuszenia i zakłócenia oddziaływujące na powłokę, co poprawiło docelową efektywność aktywnego tłumienia drgań. Ostatecznie, dokonano praktycznego wdrożenia sterownika, który współpracował z lejkowato-kształtną powłoką wyposażoną w piezoelektryczne czujniki i elementy wykonawcze. Powłokowa struktura została następnie poddana badaniom eksperymentalnym, a rezultaty pomiarów w kontekście skuteczności redukcji drgań uzyskanej wskutek implementacji analizowanego sterownika zaprezentowano i omówiono w pracy

Identification of modal parameters for complex structures by experimental modal analysis approach

In this research, we have proposed a methodology for experimental identification of modal parameters based on measurement of the frequency responses of structures with complex geometries and performed an overall investigation of structural behavior on a funnel-shaped inlet of magnetic resonance tomograph. Several identification methods are implemented and compared: complex exponential, least-squares complex exponential, and polyreference least-squares complex exponential. We have implemented the modal parameter identification methodology within our own graphical user interface supported by MATLAB to create an independent tool for modal analysis. The estimation methods are compared and the comparison results are summarized showing based on tabular representation and stabilization diagrams significant advantage of the proposed methodology for determining eigenfrequencies, damping coefficients, mode shapes, and residues for complex structures investigated in broad band of frequencies. Runtime for the execution of algorithms vary depending on the applied method, assumed order of the model used for estimation, and the number of measurements, that is, inputs and outputs

Imaging disturbance zones ahead of a tunnel by elastic full-waveform inversion: Adjoint gradient based inversion vs. parameter space reduction using a level-set method

We present and compare two flexible and effective methodologies to predict disturbance zones ahead of underground tunnels by using elastic full-waveform inversion. One methodology uses a linearized, iterative approach based on misfit gradients computed with the adjoint method while the other uses iterative, gradient-free unscented Kalman filtering in conjunction with a level-set representation. Whereas the former does not involve a priori assumptions on the distribution of elastic properties ahead of the tunnel, the latter introduces a massive reduction in the number of explicit model parameters to be inverted for by focusing on the geometric form of potential disturbances and their average elastic properties. Both imaging methodologies are validated through successful reconstructions of simple disturbances. As an application, we consider an elastic multiple disturbance scenario. By using identical synthetic time-domain seismograms as test data, we obtain satisfactory, albeit different, reconstruction results from the two inversion methodologies. The computational costs of both approaches are of the same order of magnitude, with the gradient-based approach showing a slight advantage. The model parameter space reduction approach compensates for this by additionally providing a posteriori estimates of model parameter uncertainty. Keywords: Tunnel seismics, Full waveform inversion, Seismic waves, Level-set method, Adjoint method, Kalman filte

Electro-mechanical analysis of composite and sandwich multilayered structures by shell elements with node-dependent kinematics

In this work, a new class of finite elements for the analysis of composite and sandwich shells embedding piezoelectric skins and patches is proposed. The main idea of models coupling is developed by presenting the concept of nodal dependent kinematics where the same finite element can present at each node a different approximation of the main unknowns by setting a node-wise through-the-thickness approximation base. In a global/local approach scenario, the computational costs can be reduced drastically by assuming refined theories only in those zones/nodes of the structural domain where the resulting strain and stress states, and their electro-mechanical coupling present a complex distribution. Several numerical investigations are carried out to validate the accuracy and efficiency of the present shell element. An accurate representation of mechanical stresses and electric displacements in localized zones is possible with reduction of the computational costs if an accurate distribution of the higher-order kinematic capabilities is performed. On the contrary, the accuracy of the solution in terms of mechanical displacements and electric potential values depends on the global approximation over the whole structure. The efficacy of the present node-dependent variable kinematic models, thus, depends on the characteristics of the problem under consideration as well as on the required analysis type

Poor life habits: Risk factors for formation osteoporosis

The use of bone density measurements is of central importance for diagnosis, prognosis end the assessment of treatment of patients with osteoorosis. Risk factors are variables which significantly change expected absolute risk, that is, the probability of variable disease in a certain population. Aging and smoking are the most common listed risk factors for the development of osteoporosis. The aim of our work was to confirm the most common risk factors for osteoporosis. In our research work has processed a total of 88 smokers were divided into groups according to the number of cigarettes smoked and the length of smokers. Results showed that risk factors: poor life habits (smoking and use of coffee), are significantly represented on patients with osteoporosis. In order to timely implement treatment, we concluded based on the results, that there is a need actively look for presence of risk factors responsible for osteoporosis in our patients