Effect of paragliding wing dome shape on its aerodynamic characteristics

Double-membrane gliding parachutes (DGP) obtain their wide variety of application, including the solution of cargo transportation problems. This parachute is a flexible canopy, which shape is maintained by ram air. In terms of the aerodynamic performance calculation and analysis when operating, DGP is the most complex aero elastic system. The computation of DPG aerodynamic performance is only possible, utilizing the methods of nonlinear aerodynamics and the nonlinear theory of elasticity methods.This paper investigates the aerodynamic characteristics of stable geometric shapes for various gliding parachutes, taking into account their dome shape both chord-wise and span-wise. Notably, the volumetric parachute profile is modeled by its median surface. The research, conducted by the authors, showed that such an aero elastic model of DGP allows you to obtain results that reflect correctly the qualitative effects of detached and free streamline flow. To solve the problem about the airflow over a gliding parachute, considering its canopy curvature, the method of discrete vortices with closed frames is employed, which allows you to calculate the paragliding wing aerodynamic performance within a wide range of angles of attack. There is also a possibility of flow separation simulation. The ideal incompressible liquid flow over the median surface of a stable shape for a double-membrane gliding parachute is regarded. The parachute fabric porosity is not analyzed, since the upper and lower DGP panels are made of either the low permeable or non-porous fabric. In the separated flow past, the aerodynamic coefficients are identified by time averaging to its large values after computing. The DGP aerodynamic performance computation results are given at a different value of its dome shape, as in the free streamline flow as in the flow separation. The computed coefficients, that allow us to consider the influence of canopy dome shape on its aerodynamic characteristics, are obtained. The proposed technique can be used for operational estimates of aerodynamic forces while designing and planning a pipe experiment.

Evaluating Polishability of Zirconia Impregnated PMMA Nanocomposite for Denture Base Application

Artificial biomaterials are being developed for use in denture base with symmetrical properties to restore the aesthetics and functionalities. The rough surface of denture base resin promotes the adhesion of microorganisms and plaque accumulation. This study aimed to explore the consequences of polishing times on the surface roughness of high-impact (HI) heat-polymerized PMMA denture base acrylic resin reinforced with zirconia nanoparticles (nanocomposite). Thirty specimens (25 ± 0.50 mm in diameter and 2 ± 0.10 mm thickness) were fabricated from HI PMMA by adding zirconia nanoparticles at different concentrations of (0 wt.%, 1.5 wt.%, 3 wt.%, 5 wt.%, 7 wt.%, and 10 wt.%). Specimens were divided into six groups (n = 5) and surface roughness (Ra) was measured before and after polishing with a standard protocol for one and two minutes. The addition of zirconia in PMMA at low concentrations (1.5 wt.%, 3 wt.%, and 5 wt.%) did not negatively affect the surface finish of the denture base composites following conventional polishing and remained below the clinically acceptable limit (0.2 µm). After one minute of polishing, only the 10 wt.% zirconia (0.17 ± 0.03 µm) demonstrated a substantial rise in median surface roughness, in comparison with the control group (0.11 ± 0.01 µm). It is concluded that the group containing 3 wt.% (0.10 ± 0.01 µm) of zirconia is the optimum concentration to obtain the best symmetrical surface finish after two minutes of polishing.

Effectiveness of surface mould brachytherapy in electron era.

e21562 Background: In India, skin cancers constitute about 1-2% of all diagnosed cancers.Surgery stays main modality of treatment with adequate surgical margin shown excellent local control rates - generally 95%.However, conditions where surgery is not feasible, brachytherapy is alternative approach.Advanced technology improved the ability to deliver safe and effective radiotherapy, resulting in renewed interest in this modality.Brachytherapy has many advantages: they can deposit a significantly higher dose within a tumor, with better sparing of adjacent normal structures over external beam radiotherapy or electron therapy, which sometimes require irradiating a large volume of tissue in order to provide adequately coverage, which in term increase toxicity. The purpose of our paper is to find out the clinical outcomes of skin tumors and superficial tumours of head and neck region treated with Surface mould brachytherapy (SMB), in terms of survival and toxicity.We report on our institution’s experience with using Co-60 based HDR SMB for the treatment of skin and head and neck superficial malignancies. Methods: A retrospective review of all patients treated with surface mould Co-60-based HDR brachytherapy at our center.A total of 23 patients, with 23 lesions, were treated during this period, and included in the analysis. A total of three of these lesions were treated with a palliative intent, and were included. The most common fractionation scheme was 35 Gy in 10 fractions given daily (52%, n = 12), though a range of doses were used, from 8/2 fractions to 36 Gy/12 fractions. Results: Median age at diagnosis was 52 (range = 28-91). The majority were Squamous cell (43%, n = 10) or Basal cell carcinomas (34%, n = 8). Most lesions were located in the head and neck region. The most commonly used RT dose was 3GyX10 fractions; all patients had individualized CT-based planning.The 5-year overall survival (OS) was 86 %( twenty patients). Three patients were died. Most deaths were from unrelated causes. Response was assessed in OPD 2-4 months post-treatment. Our complete response (CR) rate was 73.9% (seventeen patients), with partial response in three patients; two patients could not be assessed for response and one patient died due to other medical condition. We report a 2-year local control (LC) rate of 91.3%, and local recurrence was found in two patients. The procedure was well tolerated, with no grade 3 or more acute or late toxicities. There was one case of grade 3 ulcer (CTCAE). The 100% isodose line median depth was 0.5 cm, and median surface dose = 126.5%. The median V90 = 92.3%. Conclusions: Surface mould brachytherapy is a safe, effective modality for treatment of skin malignancies or tumors. Brachytherapy was overall well tolerated, with no grade 3-5 acute or late toxicities. This treatment is a good alternative option for those patients unwilling or unable to undergo surgery for their skin malignancies

Analytical Solution of the Problem of Symmetric Thermally Stressed State of Thick Plates Based on the 3D Elasticity Theory

An important place among thermoelasticity problems is occupied by the plane elasticity problem obtained from the general three-dimensional problem after using plane stress state hypotheses for thin plates. In the two-dimensional formulation, this problem has become widespread in the study of the effect of temperature loads on the stress state of thin thermosensitive plates. The article proposes a general three-dimensional solution of the static problem of thermoelasticity in a form convenient for practical application. To construct it, a particular solution of the inhomogeneous equation, the thermoelastic displacement potential, was added by us to the general solution of Lamé's equations, the latter solution having been previously found by us in terms of three harmonic functions. It is shown that the use of the proposed solution allows one to satisfy the relation between the static three-dimensional theory of thermoelasticity and boundary conditions, and also to construct a closed system of partial differential equations for the introduced two-dimensional functions without using hypotheses about the plane stress state of a plate. The thermoelastic stress state of a thick or thin plate is divided into two parts. The first part takes into account the thermal effects caused by external heating and internal heat sources, while the second one is determined by a symmetrical force load. The thermoelastic stresses are expressed in terms of deformations and known temperature. A three-dimensional thermoelastic stress-strain state representation is used and the zero boundary conditions on the outer flat surfaces of the plate are precisely satisfied. This allows us to show that the introduced two-dimensional functions will be harmonic. After integrating along the thickness of the plate along the normal to the median surface, normal and shear efforts are expressed in terms of three unknown two-dimensional functions. The three-dimensional stress state of a symmetrically loaded thermosensitive plate was simplified to the two-dimensional state. For this purpose, we used only the hypothesis that the normal stresses perpendicular to the median surface are insignificant in comparison with the longitudinal and transverse ones. Displacements and stresses in the plate are expressed in terms of two two-dimensional harmonic functions and a particular solution, which is determined by a given temperature on the surfaces of the plate. The introduced harmonic functions are determined from the boundary conditions on the side surface of the thick plate. The proposed technique allows the solution of three-dimensional boundary value problems for thick thermosensitive plates to be reduced to a two-dimensional case.

What is a Glacier? Assessing Ice Dynamic Thresholds

<p>The current global Randolph Glacier Inventory (RGI V6) minimum area cutoff is 0.01 km<sup>2</sup>. Including features this small empowers comprehensive assessments of global glacier water resources. It also enables high-resolution glacier hindcasts, ensuring that sites where modern glacier extent is now diminutive are charted and not overlooked. Yet the automated and manual mapping techniques used to generate RGI glacier outlines do not necessarily discriminate based on ice motion. There is currently no RGI mask that discerns between glaciers that likely still deform under their own weight (classic glacier) versus glaciers that are unlikely to satisfy this criterion (stagnant ice patch). Here is a highly simplified, data-driven attempt to develop a globally complete ice dynamic mask. Features are treated as simple slabs, with area given by the RGI database, order of magnitude thickness derived from volume-area power law scaling, and median surface slope derived from topography data (RGI-TOPO dataset, beta release). Driving stress is calculated using these inputs and assuming material density 900 kg m<sup>-3</sup>. This is repeated using varying elevation data sources, the globally complete consensus ice thickness estimate, and sparse direct ice thickness measurements (GlaThiDa), to explore driving stress sensitivity to different slab representations. Slabs with driving stress less than 10<sup>5</sup> Pa are interpreted as features where the ambient driving stress is insufficient to overcome the yield strength of ice. Uncertainty analysis and comparison against ice motion observations determines if these sub 10<sup>5</sup> Pa slab features reliably mask RGI glaciers that are no longer in motion. This approach serves as a first cut at developing a reproducible, systematic way of discerning between classic glaciers (bodies of ice that move) versus other cryosphere features. This may enhance consistency across technical analyses within the glaciological research community and science communication with policy makers.</p>

Experiments on the grain size gap across gravel-sand transitions

<p>An abrupt transition in river bed grain size occurs from gravel to sand over a short downstream distance, often only a few channel widths, and is termed the gravel-sand transition (GST). At this point, the bed structure also changes from framework- to matrix-supported. Whether the GST is externally imposed, a result of internal dynamics (sediment sorting, abrasion, suspension deposition) or due to some other emergent property is unclear. There is also a general absence of rivers beds with median surface grain sizes between ~1 and 5 mm, often referred to as the grain size gap. Here we present two sets of new laboratory experiments, examining changes in fluid and sediment dynamics across the GST. In the first set, we created stable GSTs with a 10 mm gravel and 0.5 mm sand that show GST formation is consistent with  previous theory suggesting that at shear velocities of ~0.1 m/s, sand particles rapidly fall out of suspension as a result of a particle Reynolds number dependency (i.e. a viscous effect). In a second set of experiments, we explored the fate of grain size gap material. We formed a gravel wedge composed of ~2 to 5 mm sediment, then fed 0.5 mm sand.  Our observations indicate that where sand rapidly starts to fall out of suspension, the gravel bed becomes inherently unstable. Gravel is transported downstream until the grain size gap material is largely exhausted from the system (e.g. buried under sand or rafted out of the flume). This occurs because sand sized particles fill or bridge interstitial pockets in the fine gravel bed surface, generating fluid acceleration in the near-bed region (i.e. a geometric effect specific to these grain sizes). As such, particles in the grain size gap do not form the dominant mode in river bed sediments. </p>

Non-invasive assessment of cardiac percutaneous occluders healing process using computed tomography imaging: a proof of concept study

Funding Acknowledgements Type of funding sources: Other. Main funding source(s): National Research Agency (ANR) French Federation of Cardiology : “Aide à la recherche par équipe 2018, Cardiopathies de l’enfant” Introduction After percutaneous implantation of an atrial septal defect (ASD) occluder device, a complex healing process leads to the device coverage within several months. However, an unexplained incomplete device coverage is at risk of complications such as thrombosis or infectious endocarditis. Purpose The aim of the study was to assess the device coverage process of ASD occluder devices in a chronic sheep model using micro-CT technology. Methods After percutaneous creation of an ASD by catheterization, 8 ewes (mean age 5.4 ± 0.7 yo and mean weight 55.6 ± 7.9 kg) were implanted with a 16-mm Nit-Occlud ASD-R occluder (PFM medical, Cologne, Germany) and were followed for 1 month (N = 3) and 3 months (N =5). After heart explantation, a iodine contrast agent was used to enhance the tissue signal. The device coverage was then assessed by micro-CT and the results were compared to histology, used as the gold standard for healing evaluation. The micro-CT image resolution was 41.7 µm. Reconstruction was performed in 2D and 3D with Amira® software, allowing to obtain images that were exploited by a code to measure the surface for each disk of the analyzed devices. Histological study was performed after resin embedding and Richardson blue staining was used. The pathologist was blinded to the duration of animals’ follow-up and micro-CT results. Results ASD creation and device closure was successful in 100% animals without complications. Following heart explantation, macroscopic assessment of devices showed that the coverage was complete for the left-side disk regardless of the duration of the follow-up and variable for the right-side disk, depending of the protrusion of this disk. 2D and 3D micro-CT analysis allowed an accurate evaluation of device coverage of each disk and was overall well correlated to histology slices (cf Figure). Surface calculation from micro-CT images showed that the median surface of coverage was 93 ± 8% for the left-side disk and 55 ± 31% for the right-side disk. Conclusion This preliminary study made the proof of concept that micro-CT is a reliable tool to assess the coverage of intra-cardiac occluders in vitro. The translation to clinical practice is challenging but would allow an individual follow-up, to avoid thrombotic or infective complications. Abstract Figure.

Non-stationary dynamics of anisotropic Kirchhoff-Love type shel

Строится нестационарная функция прогиба для тонкой бесконечной цилиндрической оболочки постоянной толщины при воздействии на ее боковую поверхность вынужденной нестационарной движущейся нагрузки, распределенной по прямоугольной области. Материал рассматриваемой цилиндрической оболочки принят упругим и анизотропным, обладающим симметрией относительно ее срединной плоскости. Теория тонких упругих оболочек строится на гипотезах Кирхгофа-Лява. Для математического описания мгновенно приложенной нагрузки используются дельта-функции Дирака. A non-stationary deflection function is determined for a thin infinite cylindrical shell of constant thickness under the influence of non-stationary moving pressure. The pressure is distributed over a rectangular region, which belongs to the side surface of the shell. The shell material is elastic, anisotropic, and has symmetry to the median surface. The theory of thin elastic shells is based on the Kirchhoff-Love’s hypotheses. The Dirac delta-functions are used to describe an instantaneously applied pressure.

Study of modern software capabilities for complex shell analysis

Relevance. In design and calculation of civil engineering structures, several standard commercial software packages, which are successfully applied to solve everyday engineering problems, are traditionally used. However, when it is necessary to design the models of complex shape shell structures with defining surfaces based on parametric equations, such programs often have certain drawbacks. The aim of the work - analysis of existing types of commercial computational software packages in order to check which allow to design finite element models for shell structures with median surfaces of complex geometry given by parametric equations. Methods. The analysis of commercial computational software packages is carried out by studying the software manuals, and by building and calculating a model in the shape of a right helicoid as a test example. To evaluate the results of the stress-strain state of a shell with a middle surface in the form of a right helicoid, an analytical calculation method based on the Reissner’s equations and Fourier series expansion is used. Results. A review of modern commercial computational software packages as applied to models defined by parametric equations is carried out. A model for a shell structure with a median surface in the form of right helicoid is built. The numerical results of stress-strain behavior of the right helicoid are obtained and analyzed in comparison with the analytical solutions obtained using the Reissner’s equations with Fourier series expansion. The pros and cons of several popular means of software are presented.

The Scale of Submesoscale Baroclinic Instability Globally

The spatial scale of submesoscales is an important parameter for studies of submesoscale dynamics and multiscale interactions. The horizontal spatial scales of baroclinic, geostrophic-branch mixed layer instabilities (MLI) are investigated globally (without the equatorial or Arctic oceans) based on observations and simulations in the surface and bottom mixed layers away from significant topography. Three high-vertical-resolution boundary layer schemes driven with profiles from a MITgcm global submesoscale-permitting model improve robustness. The fastest-growing MLI wavelength decreases toward the poles. The zonal median surface MLI wavelength is 51–2.9 km when estimated from the observations and from 32, 25, and 27 km to 2.5, 1.2, and 1.1 km under the K-profile parameterization (KPP), Mellor–Yamada (MY), and κ–ε schemes, respectively. The surface MLI wavelength has a strong seasonality with a median value 1.6 times smaller in summer (10 km) than winter (16 km) globally from the observations. The median bottom MLI wavelengths estimated from simulations are 2.1, 1.4, and 0.41 km globally under the KPP, MY, and κ–ε schemes, respectively, with little seasonality. The estimated required ocean model grid spacings to resolve wintertime surface mixed layer eddies are 1.9 km (50% of regions resolved) and 0.92 km (90%) globally. To resolve summertime eddies or MLI seasonality requires grids finer than 1.3 km (50%) and 0.55 km (90%). To resolve bottom mixed layer eddies, grids finer than 257, 178, and 51 m (50%) and 107, 87, and 17 m (90%) are estimated under the KPP, MY, and κ–ε schemes.