scholarly journals Development and investigation of the applicability of computed tomography data-based modelling technique for polymeric high-density foams

2021 ◽  
pp. 026248932110616
Author(s):  
Anna Hössinger-Kalteis ◽  
Martin Reiter ◽  
Michael Jerabek ◽  
Zoltan Major
Keyword(s):  
Computed Tomography ◽  
Constitutive Models ◽  
Core Layer ◽  
Computational Effort ◽  
High Density ◽  
Bending Test ◽  
Cell Size Distribution ◽  
Compression Load ◽  
Tension And Compression ◽  
Ct Data

As foams have become very important in several areas and since characterizing their properties is a crucial task, a finite element simulation model for high-density closed cell foams based on computed tomography (CT) measurements is developed. The model includes realistic microstructural features like cell size distribution due to the utilization of CT data. Moreover, a ‘skin-core-skin’ microstructure resulting from the manufacturing process (injection moulding) of the foams is also considered in the model. The mechanical behaviour of the foam’s core layer under tension and compression load is characterized based on the microstructural model to develop constitutive material models of the foam. These constitutive models enable further mechanical characterization of the foam with less computational effort. Compression and bending test simulations of injection moulded foams with three different densities are validated with corresponding experimental results. Thus, conclusions can be drawn regarding the reliability, applicability and possible further extensions of the high-density foam model.

scholarly journals Application of computed tomography data–based modelling technique for polymeric low density foams, Part A: Model development

2021 ◽  
pp. 0021955X2110281
Author(s):  
Anna Hössinger-Kalteis ◽  
Martin Reiter ◽  
Michael Jerabek ◽  
Zoltán Major
Keyword(s):  
Computed Tomography ◽  
Mechanical Performance ◽  
Model Development ◽  
Simulation Models ◽  
Computational Effort ◽  
Analytical Models ◽  
Modelling Technique ◽  
Low Density ◽  
Closed Cell ◽  
Ct Data

In this research study, a methodology is introduced for generating finite element simulation models for low density closed cell foams based on computed tomography (CT) measurement results. Creating this kind of simulation models can be very expensive with regard to modelling and computational effort. Hence, a combined modelling technique based on CT data and Voronoi diagrams is developed that minimizes this effort, but nevertheless, generates simulation models with a realistic microstructure. In this article, the generation of simulation models using this modelling method and the necessary adaptation of the models concerning microstructural features to consider, for example, anisotropic properties of the foam, are described. Furthermore, simulations are performed to investigate the mechanical performance of the foam models and to compare the results with several analytical models and experimental data. Finally, conclusions regarding the applicability and possible further extensions of the model are provided.

The diagnosis of early pneumoconiosis in dust-exposed workers: comparison of chest radiography and computed tomography

2021 ◽  
pp. 028418512110225
Author(s):  
Hideyuki Hayashi ◽  
Kazuto Ashizawa ◽  
Masashi Takahashi ◽  
Katsuya Kato ◽  
Hiroaki Arakawa ◽  
...  
Keyword(s):  
Computed Tomography ◽  
Chest Radiography ◽  
Pulmonary Emphysema ◽  
Early Stage ◽  
Pathological Changes ◽  
Occupational History ◽  
Exposed Workers ◽  
History Of ◽  
Ct Data ◽  
Positive Results

Background Chest radiography (CR) is employed as the evaluation of pneumoconiosis; however, we sometimes encounter cases in which computed tomography (CT) is more effective in detecting subtle pathological changes or cases in which CR yields false-positive results. Purpose To compare CR to CT in the diagnosis of early-stage pneumoconiosis. Material and Methods CR and CT were performed for 132 workers with an occupational history of mining. We excluded 23 cases of arc-welder’s lung. Five readers who were experienced chest radiologists or pulmonologists independently graded the pulmonary small opacities on CR of the remaining 109 cases. We then excluded 37 cases in which the CT data were not sufficient for grading. CT images of the remaining 72 cases were graded by the five readers. We also assessed the degree of pulmonary emphysema in those cases. Results The grade of profusion on CR (CR score) of all five readers was identical in only 5 of 109 cases (4.6%). The CR score coincided with that on CT in 40 of 72 cases (56%). The CT score was higher than that on CR in 13 cases (18%). On the other hand, the CT score was lower than that on CR in 19 cases (26%). The incidence of pulmonary emphysema was significantly higher in patients whose CR score was higher than their CT score. Conclusion CT is more sensitive than CR in the evaluation of early-stage pneumoconiosis. In cases with emphysema, the CR score tends to be higher in comparison to that on CT.

scholarly journals Programming Effect of the Parental Obesity on the Skeletal System of Offspring at Weaning Day

Animals ◽  
2021 ◽  
Vol 11 (2) ◽  
pp. 424
Author(s):  
Radoslaw Piotr Radzki ◽  
Marek Bienko ◽  
Dariusz Wolski ◽  
Monika Ostapiuk ◽  
Pawel Polak ◽  
...  
Keyword(s):  
Computed Tomography ◽  
Bone Mineral ◽  
High Energy ◽  
Diet Group ◽  
Male Rats ◽  
Bending Test ◽  
Male Rat ◽  
Skeletal System ◽  
Mineral Density ◽  
Trabecular Thickness

Our study aimed to verify the hypothesis of the existence of a programming effect of parental obesity on the growth, development and mineralization of the skeletal system in female and male rat offspring on the day of weaning. The study began with the induction of obesity in female and male rats of the parental generation, using a high-energy diet (group F). Females and males of the control group received the standard diet (group S). After 90 days of dietary-induced obesity, the diet in group F was changed into the standard. Rats from groups F and S were mated to obtain offspring which stayed with their mothers until 21 days of age. Tibia was tested using dual-energy X-ray absorptiometry (DXA), peripheral quantitative computed tomography (pQCT), micro-computed tomography (µCT) and mechanical strength using the three-point bending test. Biochemical analysis of blood serum bone metabolism markers was performed. DXA analysis showed higher tibia bone mineral content (BMC) and area. pQCT measurements of cortical and trabecular tissue documented the increase of the volumetric bone mineral density and BMC of both bone compartments in offspring from the F group, while µCT of the trabecular tissue showed an increase in trabecular thickness and a decrease of its separation. Parental obesity, hence, exerts a programming influence on the development of the skeletal system of the offspring on the day of the weaning, which was reflected in the intensification of mineralization and increased bone strength.

4D Computed Tomography for Dynamic Upper Airway Evaluation in Robin Sequence

2021 ◽  
pp. 019459982110021
Author(s):  
Austin S. Lam ◽  
Michael D. Bindschadler ◽  
Kelly N. Evans ◽  
Seth D. Friedman ◽  
Jeffrey P. Otjen ◽  
...  
Keyword(s):  
Computed Tomography ◽  
Upper Airway ◽  
Quantitative Information ◽  
4D Ct ◽  
Robin Sequence ◽  
Analysis Tools ◽  
Airway Caliber ◽  
4D Computed Tomography ◽  
Ct Data ◽  
Sample Case

Thorough assessment of dynamic upper airway obstruction (UAO) in Robin sequence (RS) is critical, but traditional evaluation modalities have significant limitations. Four-dimensional computed tomography (4D-CT) is promising in that it enables objective and quantitative evaluation throughout all phases of respiration. However, there exist few protocols or analysis tools to assist in obtaining and interpreting the vast amounts of obtained data. A protocol and set of data analysis tools were developed to enable quantification and visualization of dynamic 4D-CT data. This methodology was applied to a sample case at 2 time points. In the patient with RS, overall increases in normalized airway caliber were observed from 5 weeks to 1 year. There was, however, continued dynamic obstruction at all airway levels, though objective measures of UAO did improve at the nasopharynx and oropharynx. Use of 4D-CT and novel analyses provide additional quantitative information to evaluate UAO in patients with RS.

A case of fatal drug intoxication showing a high-density duodenal content by postmortem computed tomography

2011 ◽  
Vol 13 (1) ◽  
pp. 39-40 ◽  
Author(s):  
Rie Sano ◽  
Keiko Takahashi ◽  
Yoshihiko Kominato ◽  
Takuya Araki ◽  
Koujiro Yamamoto ◽  
...  
Keyword(s):  
Computed Tomography ◽  
Duodenal Content ◽  
High Density ◽  
Postmortem Computed Tomography ◽  
Drug Intoxication

Characterization of Flow Stress for Commercially Pure Titanium Subjected to Electrically-Assisted Deformation

2013 ◽  
Author(s):  
James Magargee ◽  
Fabrice Morestin ◽  
Jian Cao
Keyword(s):  
Flow Stress ◽  
Heating Temperature ◽  
Pure Titanium ◽  
Constitutive Models ◽  
Plastic Behavior ◽  
Commercially Pure Titanium ◽  
Coupled Models ◽  
Commercially Pure ◽  
Electrically Assisted ◽  
Tension And Compression

Uniaxial tension tests were conducted on thin commercially pure titanium sheets subjected to electrically-assisted deformation using a new experimental setup to decouple thermal-mechanical and possible electroplastic behavior. The observed absence of stress reductions for specimens air-cooled to near room temperature motivated the need to reevaluate the role of temperature on modeling the plastic behavior of metals subjected to electrically-assisted deformation, an item that is often overlooked when invoking electroplasticity theory. As a result, two empirical constitutive models, a modified-Hollomon and the Johnson-Cook models of plastic flow stress, were used to predict the magnitude of stress reductions caused by the application of constant DC current and the associated Joule heating temperature increase during electrically-assisted tension experiments. Results show that the thermal-mechanical coupled models can effectively predict the mechanical behavior of commercially pure titanium in electrically-assisted tension and compression experiments.

Investigations of PMN-PT Single Crystal Performance

2010 ◽  
Author(s):  
Virginia G. DeGiorgi ◽  
E. P. Gorzkowski ◽  
M.-J. Pan ◽  
M. A. Qidwai ◽  
Stephanie A. Wimmer
Keyword(s):  
Finite Element ◽  
Electric Field ◽  
Single Crystals ◽  
Domain Switching ◽  
Fatigue Behavior ◽  
Constitutive Models ◽  
Nonlinear Behavior ◽  
Computational Effort ◽  
Basic Material ◽  
Poling Direction

Application of new materials, such as PMN-PT single crystals, requires a good understanding of basic material performance under both electrical and mechanical loading. Over the past 5 years the authors have used both computational and experimental techniques to examine the relationships between poling direction, crystal orientation, and electric field actuation. Experiments show mixed results indicating that the relationship between material orientation and loading is more complex than originally imagined. In some cases crack initiation and propagation perpendicular to the applied field was observed within a few thousand cycles but in other cases no failure was observed even after a few hundred thousand cycles despite crack growth in the presence of introduced defects. Computational effort quickly identified a gap between development of theoretical constitutive models that addressed domain switching based nonlinear behavior and what was available in workable form as part of commercial finite element codes. This led to the implementation of a macro-mechanical constitutive model which addresses domain switching, into a commercially available finite element code. The rate independent version has been used to investigate issues of electric field actuation and poling direction. Presented here are insights into the fracture and fatigue behavior of piezoelectric single crystals from both experimental and computational studies.

Computed Tomography in the Elderly 3. Affective Disorder

1980 ◽  
Vol 136 (3) ◽  
pp. 270-275 ◽  
Author(s):  
Robin J. Jacoby ◽  
Raymond Levy
Keyword(s):  
Computed Tomography ◽  
Elderly Patients ◽  
Affective Disorders ◽  
The Elderly ◽  
Consecutive Series ◽  
Healthy Controls ◽  
Ventricular Size ◽  
Radiological Criteria ◽  
Computed Tomographic ◽  
Ct Data

SummaryClinical and computed tomographic (CT) data on a consecutive series of 41 elderly patients with affective disorders are presented, and comparisons made with a group of 50 healthy controls. In both groups ventricular size increased with age, but only in the controls was there an age correlation with sulcal widening. Using clinical and radiological criteria, the prevalence of cerebrovascular disease in the patient group was 12 per cent. A sub-group of patients with enlarged ventricles emerged, whose first depression began later in life, and who at the time of this study were older and showed more ‘endogenous’ features than the remainder. It is suggested that this provides further evidence that organic cerebral factors may have aetiological significance in some depressions of old age.

scholarly journals Comparative Analysis of Capabilities of Different Types of Cone-Beam Tomography in an Experimental Study of Root Canals of Teeth Filled with High-Density Materials (part 2)

2021 ◽  
pp. 51-61
Author(s):  
A. Yu. Vasil'ev ◽  
V. V. Petrovskaya ◽  
E. A. Nichipor ◽  
V. G. Alpatova ◽  
N. N. Potrakhov ◽  
...  
Keyword(s):  
Computed Tomography ◽  
Experimental Study ◽  
Cone Beam Computed Tomography ◽  
Comparative Assessment ◽  
High Density ◽  
Cone Beam ◽  
Root Canals ◽  
Different Types ◽  
Before And After ◽  
Cone Beam Tomography

During the course of this experimental study tomograms of extracted teeth were analyzed before and after filling the root canals with an endodontic material and fragments of broken metal instruments for root canal treatment. During the first stage of the experiment, untreated extracted teeth were scanned using conebeam computed tomography and microfocus cone-beam computed tomography. A comparative assessment of capabilities of the two methods of cone-beam computed tomography based on examination of untreated root canals was carried out. The second part of the study is dedicated to visualization of root canals that contain foreign high-density materials.

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