Modal analysis
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... INTRODUCTION I3 -- 1.1 Modality in language 14 -- 1.1.1 Modality in logic and formal semantics-14 -- ... ... 1.1.2 Modality in cognitive linguistics-15 -- 1.1.3 Modality from a cross-linguistic perspective and ... ... MODAL MEANING POTENTIAL -> MODAL MEANING EVALUATIVE -9I -- 3.1 Esperar 93 -- 3.1.1 Corpus analysis 94 ... ... Corpus analysis -120 -- 5.1.2 Corpus analysis n. 2 125 -- 5.2 Conclusion -128 -- 6. ... ... MODAL MEANING POTENTIAL -> MODAL MEANING VOLITIVE I39 -- 7.1 Spanish modal verbs -140 -- 7.2 Relationship ...
1. elektronické vydání 1 online zdroj (160 stran)
The purpose of the present study was to describe the structural density and geometry of the bone, as well as its sensitivity to the resolution of finite element discretisation. The study introduces a novel way to validate biomechanical model of the bone by experimental modal analysis. The structural density and geometry of the model was obtained from a composite bone. A detailed investigation of the weight dependence of the bone on the mesh resolution was performed to obtain the best match with the real weight of the tested bone. The computational model was compared with the experimental results obtained from the modal analysis. The overall changes of the modal properties and bone weight in the model caused by different mesh resolutions and order of approximation were below 10%, despite the bone was modelled with simple isotropic material properties. The experimental modal analysis shows a great potential to be a robust verification tool of computational biomechanical models because it provides boundary conditions-free results. The sensitivity analysis revealed that the linear approximation of the density field is not suitable for the modelling of the modal response of composite bone.
- MeSH
- analýza metodou konečných prvků MeSH
- biomechanika MeSH
- lidé MeSH
- lineární modely MeSH
- mechanický stres MeSH
- pánevní kosti anatomie a histologie diagnostické zobrazování MeSH
- počítačová rentgenová tomografie MeSH
- počítačová simulace * MeSH
- reprodukovatelnost výsledků MeSH
- velikost orgánu MeSH
- Check Tag
- lidé MeSH
- Publikační typ
- časopisecké články MeSH
- validační studie MeSH
Digital models based on finite element (FE) analysis are widely used in orthopaedics to predict the stress or strain in the bone due to bone-implant interaction. The usability of the model depends strongly on the bone material description. The material model that is most commonly used is based on a constant Young's modulus or on the apparent density of bone obtained from computer tomography (CT) data. The Young's modulus of bone is described in many experimental works with large variations in the results. The concept of measuring and validating the material model of the pelvic bone based on modal analysis is introduced in this pilot study. The modal frequencies, damping, and shapes of the composite bone were measured precisely by an impact hammer at 239 points. An FE model was built using the data pertaining to the geometry and apparent density obtained from the CT of the composite bone. The isotropic homogeneous Young's modulus and Poisson's ratio of the cortical and trabecular bone were estimated from the optimisation procedure including Gaussian statistical properties. The performance of the updated model was investigated through the sensitivity analysis of the natural frequencies with respect to the material parameters. The maximal error between the numerical and experimental natural frequencies of the bone reached 1.74 % in the first modal shape. Finally, the optimised parameters were matched with the data sheets of the composite bone. The maximal difference between the calibrated material properties and that obtained from the data sheet was 34 %. The optimisation scheme of the FE model based on the modal analysis data provides extremely useful calibration of the FE models with the uncertainty bounds and without the influence of the boundary conditions.
Modal parameters are often investigated in order to assess the initial fixation of an implant. Most of studies are focused on the natural frequencies and frequency response function. Usually the femoral stem is tested although the acetabular cup fixation is important as well. The results of implant stability assessment are inconsistent and seem to suggest that frequency as a stability indicator is not sufficiently sensitive. In this study the sensitivity of the modal properties to changes in the bone-implant interface was investigated with the help of the finite element method (FEM). A novel fixation index based on modal shape curvature was investigated as a potential measure of the implant fixation. Modal frequencies are sensitive to interface changes in some manner, but suffer from insensitivity to local changes at bone-implant interface. The sensitivity up to 44% of natural frequencies to stiffness change due insertion steps was observed. The tested damage indicators are able to detect localized small changes in peripheral stiffness (5% stiffness reduction) with 95% confidence under the noise up to 1%. The modal shapes and their curvatures have a great potential to be a robust fixation indicator.
Experimental modal analysis (EMA) of ultrasonic waveguides is important for many applications including design of ultrasonic surgical tools. However, most of the known sensors and instruments for measuring parameters of ultrasonic vibrations are limited to the measurements on the face surface of the ultrasonic waveguide and therefore unable to determine the spatial distribution of the parameters along its length, which in turn makes it difficult to identify natural modes and shapes. The article describes EMA of ultrasonic surgical waveguides based on the effect of inverse magnetostriction. During vibration of an ultrasonic waveguide the inverse magnetostriction generates alternating magnetic field which can be detected by means of an induction coil. Spatial resolution of the measurements can be achieved by application of the sensors with flat (spiral) induction coils. The sensors used in the study have simple design and low cost making them affordable for wide circle of scientists and engineers. The results of experimental studies implemented on exemplary waveguide for ultrasonic angioplasty made of AISI 321 steel are presented and discussed. The article also discusses the methods for theoretical and experimental determination of the sensitivity of the sensors used in the study. Experimental data are validated by comparing them to the results of computer-aided modal analysis using the finite element method (FEM) and found to be in good agreement with the results of FEM modeling (relative deviation of the vibratory displacements amplitude is about 4.7 %). As it follows from the experimental data and their comparison to the results of FEM modeling, the effect of inverse magnetostriction can be efficiently used for EMA of ultrasonic waveguides.
The balanced initial fixation of an implant makes up a crucial condition for its long-term survival. However, the quantification of initial fixation is no easy task and, to date, only qualitative assessments can be made. Although the concept of measuring fixation by means of vibration analysis is already widely used in dental implantology, the rigorous application of this method for the assessment of the fixation of femoral and acetabular components remains a challenge. Moreover, most studies on this subject have tended to focus solely on the femoral stem even though acetabular cup fixation is also important and even more difficult with respect to qualitative measurement. This study describes a comprehensive experiment aimed at assessing acetabular cup fixation. Fixation is expressed in terms of the impact force and polar gap variables, which are correlated with the modal properties of the acetabular implant during the various insertion stages. The predictive capabilities of modal frequencies and frequency functions were investigated by means of surrogate models based on the Gaussian process and functional principal component analysis. The prediction accuracy of the proposed models was in the range 82-94%. The results indicate that natural frequencies, reduced frequency, impact force and polar gap features provide great potential in terms of the prediction of implant fixation.
... Defining Content Analysis 1 -- Is Content Analysis “Easy”? Is It Something That Anyone Can Do? ... ... 2 -- Myth 1 : Content analysis is easy. 2 -- Myth 2: The term content analysis to ^//examinations of ... ... . 8 -- Myth 4: Content analysis is for academic use only. 9 -- A Six-Part Definition of Content Analysis ... ... Content Analysis as Quantitative 14 -- 4. Content Analysis as Summarizing 15 -- 5. ... ... Analysis 53 -- Inferential Content Analysis 54 -- Psychometric Content Analysis 54 -- Predictive Content ...
1st ed. 301 s.
The size distribution of vesicles exocytosed from secretory cells displays quantal nature, vesicle volume is periodic multi-modal, suggesting that these heterogeneous vesicles are aggregate sums of a variable number of homogeneous basic granules. Whether heterogeneity is a lumping-together artifact of the measurement or an inherent intra-cell feature of the vesicles is an unresolved question. Recent empirical evidence will be provided for the quantal nature of intra-cell vesicle volume, supporting the controversial paradigm of homotypic fusion: basic cytoplasmic granules fuse with each other to create heterogeneously sized vesicles. An EM-algorithm-based method is presented for the conversion of multi-modal to quantal data that provides as by-product estimates of means and variances of basic granule packaging.
- MeSH
- biologie buňky statistika a číselné údaje MeSH
- cytoplazmatická granula chemie metabolismus MeSH
- interpretace statistických dat MeSH
- lidé MeSH
- proteiny metabolismus MeSH
- sekreční vezikuly chemie metabolismus MeSH
- synaptické vezikuly chemie metabolismus MeSH
- velikost částic MeSH
- zvířata MeSH
- Check Tag
- lidé MeSH
- zvířata MeSH
- Publikační typ
- časopisecké články MeSH
