2,239 research outputs found
Beamlike models for the analyses of curved, twisted and tapered horizontal-axis wind turbine (HAWT) blades undergoing large displacements
Abstract. Continuous ongoing efforts to better predict the mechanical behaviour of complex beamlike structures, such as wind turbine blades, are motivated by the need to improve their performance and reduce the costs. However, new design approaches and the increasing flexibility of such structures make their aeroelastic modelling ever more challenging. For the structural part of this modelling, the best compromise between computational efficiency and accuracy can be obtained via schematizations based on suitable beamlike elements. This paper addresses the modelling of the mechanical behaviour of beamlike structures which are curved, twisted and tapered in their unstressed state and undergo large displacements, in- and out-of-plane cross-sectional warping, and small strains. A suitable model for the problem at hand is proposed. Analytical and numerical results obtained by its application are presented and compared with results from 3D FEM analyses
3-DIMENSIONAL GEOMETRIC SURVEY AND STRUCTURAL MODELLING OF THE DOME OF PISA CATHEDRAL
This paper aims to illustrate the preliminary results of a research project on the dome of Pisa Cathedral (Italy). The final objective of the present research is to achieve a deep understanding of the structural behaviour of the dome, through a detailed knowledge of its geometry and constituent materials, and by taking into account historical and architectural aspects as well. A reliable survey of the dome is the essential starting point for any further investigation and adequate structural modelling. Examination of the status quo on the surveys of the Cathedral dome shows that a detailed survey suitable for structural analysis is in fact lacking. For this reason, high-density and high-precision surveys have been planned, by considering that a different survey output is needed, according both to the type of structural model chosen and purposes to be achieved. Thus, both range-based (laser scanning) and image-based (3D Photogrammetry) survey methodologies have been used. This contribution introduces the first results concerning the shape of the dome derived from surveys. Furthermore, a comparison is made between such survey outputs and those available in the literature
Food intake and nutritional status in stable hemodialysis patients.
evaluate changes of actual dietary nutrient intake in 94 stable
hemodialysis patients in respect to 52 normal subjects and guideline
recommendations, and to assess the prevalence of signs of
malnutrition. Energy and nutrients intake assessment was
obtained by a three-day period food recall. Anthropometric and
biochemical parameters of nutrition, bioelectric impedance vector
analysis, and subjective global assessment (SGA) have been
performed to assess nutritional status. SGA-B was scored in 5% of
the patients. Body mass index < 20 Kg/m2, serum albumin <35 g/L,
nPNA < 1.0 g/Kg, and phase angle <4.0° were detected in 16.3%,
16%, 23%, and 8.0 % of patients, respectively. HD patients
showed a lower energy and protein intake in respect to controls,
but no difference occurred when normalized per ideal body weight
(29.3 ± 8.4 vs. 29.5 ± 8.4 Kcal/Kg i.b.w./d and 1.08 ± 0.35 vs. 1.12
± 0.32 Kcal/Kg i.b.w. /d, respectively). Age was the only parameter
that inversely correlates with energy (r = −0.35, p < 0.001) and
protein intake (r = −0.34, p < 0.001). This study shows that in
stable dialysis patients, abnormalities of nutritional parameters
are less prevalent than expected by analysis of dietary food
intake. Age is the best predictor of energy and protein intake in
the dialysis patients who ate less than normal people, but no
difference emerged when energy and protein intakes were normalized
for body weight. These results recall the attention for
individual dietetic counseling in HD patients, and also for a
critical re-evaluation of their dietary protein and energy
requirements
A randomized clinical control study on the efficacy of three-dimensional upper limb robotic exoskeleton training in chronic stroke
Background : Although robotics assisted rehabilitation has proven to be effective in stroke rehabilitation, a limited functional improvements in Activities of Daily Life has been also observed after the administration of robotic training. To this aim in this study we compare the efficacy in terms of both clinical and functional outcomes of a robotic training performed with a multi-joint functional exoskeleton in goal-oriented exercises compared to a conventional physical therapy program, equally matched in terms of intensity and time. As a secondary goal of the study, it was assessed the capability of kinesiologic measurements—extracted by the exoskeleton robotic system—of predicting the rehabilitation outcomes using a set of robotic biomarkers collected at the baseline. Methods : A parallel-group randomized clinical trial was conducted within a group of 26 chronic post-stroke patients. Patients were randomly assigned to two groups receiving robotic or manual therapy. The primary outcome was the change in score on the upper extremity section of the Fugl-Meyer Assessment (FMA) scale. As secondary outcome a specifically designed bimanual functional scale, Bimanual Activity Test (BAT), was used for upper limb functional evaluation. Two robotic performance indices were extracted with the purpose of monitoring the recovery process and investigating the interrelationship between pre-treatment robotic biomarkers and post-treatment clinical improvement in the robotic group. Results : A significant clinical and functional improvements in both groups (p < 0.01) was reported. More in detail a significantly higher improvement of the robotic group was observed in the proximal portion of the FMA (p < 0.05) and in the reduction of time needed for accomplishing the tasks of the BAT (p < 0.01). The multilinear-regression analysis pointed out a significant correlation between robotic biomarkers at the baseline and change in FMA score (R2 = 0.91, p < 0.05), suggesting their potential ability of predicting clinical outcomes. Conclusion : Exoskeleton-based robotic upper limb treatment might lead to better functional outcomes, if compared to manual physical therapy. The extracted robotic performance could represent predictive indices of the recovery of the upper limb. These results are promising for their potential exploitation in implementing personalized robotic therapy. Clinical Trial Registration clinicaltrials.gov, NCT03319992 Unique Protocol ID: RH-UL-LEXOS-10. Registered 20.10.2017, https://clinicaltrials.gov/ct2/show/NCT0331999
Density functional theory study of (OCS)2^-
The structural and electronic properties of the carbonyl sulfide dimer anion
are calculated using density functional theory within a pseudopotential method.
Three geometries are optimized and investigated: C2v and C2 symmetric, as well
as one asymmetric structure. A distribution of an excess charge in three
isomers are studied by the Hirshfeld method. In an asymmetric (OCS)2^- isomer
the charge is not equally divided between the two moieties, but it is
distributed as OCS^{-0.6} OCS^{-0.4}. Low-lying excitation levels of three
isomers are compared using the time-dependent density functional theory in the
Casida approach.Comment: pdf (included all figures):
http://www.phy.hr/~goranka/Research/ocs.pd
A sub-150-nanometre-thick and ultraconformable solution-processed all-organic transistor
Recent advancements in the field of electronics have paved the way to the development of new applications, such as tattoo electronics, where the employment of ultraconformable devices is required, typically achievable with a significant reduction in their total thickness. Organic materials can be considered enablers, owing to the possibility of depositing films with thicknesses at the nanometric scale, even from solution. However, available processes do not allow obtaining devices with thicknesses below hundreds of nanometres, thus setting a limit. Here, we show an all-organic field effect transistor that is less than 150 nm thick and that is fabricated through a fully solution-based approach. Such unprecedented thickness permits the device to conformally adhere onto nonplanar surfaces, such as human skin, and to be bent to a radius lower than 1 μm, thereby overcoming another limitation for field-effect transistors and representing a fundamental advancement in the field of ultrathin and tattoo electronics
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