Elliptical Opening Research Articles

Stress Concentration for In-Plane Stressed Orthotropic Plate with Elliptic Opening

The paper discusses the analytical calculation procedure of stress at points along the elliptic opening boundary in an in-plane stressed infinite orthotropic plate. The presented procedure is a first step in the strength analysis of such plates. The stress dependence on material elasticity characteristics and a multilayer plate stacking sequence as well as on a position of the ellipse semi-axes for prescribed stress conditions has been presented on numerical examples while the calculation results have been illustrated by diagrams and numeric data. The specific attention is paid on the case of equal or close values of complex parameters of the orthotropic plate. The derived conclusions, pointing out a danger of stress concentration and orthotropy effects, can be very useful in engineering practice.

The Diagnosis Method for High-Energy Ion Beams Using Backscattered Particles for Laser-Driven Ion Acceleration Experiments

A single CR-39 detector mounted on plastic plates is irradiated with a 100 MeV He ion beam. Although the beam energy is much greater than the detection threshold limit of the CR-39 detector, a large number of etch pits having elliptical openings are observed on the rear surface. Detailed investigations reveal that these etch pits are created by heavy ions inelastically backscattered from the plastic plates. This method allows a simple diagnosis of the ion beam profile and the presence of the high-energy component beyond the detection threshold limit of the CR-39 detector, especially in mixed-radiation fields such as laser-driven ion acceleration experiments.

A new genus and species of the Didymozoidae (Digenea) from the skipjack tuna Katsuwonus pelamis (L.) (Scombridae)

A new genus and species of didymozoid digenean is described from the skipjack tuna Katsuwonus pelamis (Linnaeus) in the Southwest Atlantic Ocean off Brazil. Pozdnyakovia gibsoni n. g., n. sp. is placed in the Gonapodasmiinae Ishii, 1935. The new genus differs from other genera in the morphology of the posterior regions of the fused pair; this consists of an unlobed, rounded mass fused only dorsally and with a large, elliptical ventral aperture opening into a longitudinal deep cavity from which emerge the two elongate anterior regions. It also differs in the form of the testes, which form two sets of three to four branches in each partner.

A study on external CFRP reinforcement of precast concrete slabs with various cutout shapes

In some cases, openings must be introduced after slab construction to accommodate ducts, pipes, utilities, and elevators. This study involves the development of three-dimensional, complex, nonlinear finite element analysis (FEA) models of precast concrete slabs with and without openings. One solid precast concrete slab and five slabs with various opening shapes but equal areas were considered. The openings in the slabs were retrofitted with carbon-fiber-reinforced polymer (CFRP) sheets around their perimeters to restore the original flexural strength and stiffness of the floors. Rectangular, circular, square, elliptical, diamond-shaped openings were investigated for the control specimens and the corresponding CFRP-strengthened slab models. An experimental study on a reinforced concrete solid slab and as-built and CFRP-strengthened slabs with rectangular openings reported in the literature was used to validate the accuracy of the proposed FEA models. The FEA results revealed that the slabs with rectangular and elliptical openings outperformed the slabs with other opening shapes in terms of stiffness and ultimate-flexural-strength capacity. CFRP strengthening enhanced the performance of all of the slabs with openings compared with their corresponding control models. Through CFRP reinforcement, the losses in stiffness and flexural strength caused by the cutouts were restored. In the case of the slab with rectangular openings, similar flexural strength and increased stiffness were attained compared with the slab without any opening.

A Theoretical Study of Acid-Fracture Conductivity Under Closure Stress

Summary The conductivity of acid-etched fractures depends on spaces along the fracture created by uneven etching of the fracture walls remaining open after fracture closure. In this study, we have modeled the deformation of the irregular fracture surfaces created by acid etching and the resulting fracture conductivity as closure stress is applied to the fracture. In our previous work, we modeled the dissolution of the fracture surfaces in a formation having small-scale heterogeneities in both permeability and mineralogy. This model yielded the geometry of the etched fracture at zero closure stress. Beginning with this profile of fracture width, we have modeled the deformation of the fracture surfaces as closure stress is applied to the fracture. At any cross section along the fracture, we approximate the fracture shape as being a series of elliptical openings. Assuming elastic behavior of the rock, we calculate how many elliptical gaps remain open and their sizes as a function of the applied stress. The sections of the fracture that are closed are assigned a conductivity because of small-scale roughness features using a correlation obtained from laboratory measurements of acid-fracture conductivity as a function of closure stress. The overall conductivity of the fracture is then obtained by numerically modeling the flow through this heterogeneous system. Our previous work shows that high fracture conductivity can be created in acid fracturing if heterogeneity of the rock leads to the formation of channels along the fracture surfaces. In this study, we have determined how the channels in acid fracturing remain open as closure stress is applied. This model predicts the rock characteristics that are necessary for acid-fracture conductivity to be sustainable under high closure stress.

Energy flux lines in a deformable rock mass with elliptical openings

The stress-strain state of an elastic plane with elliptical cuts is studied under different loading conditions. The lines of an energy flux are constructed. It is shown that energy transmission into a deformable medium is induced exclusively by external forces applied. The effect of boundary conditions on the energy flux lines is demonstrated.

Transesophageal Echocardiography of a Unicuspid Aortic Valve

Transesophageal Echocardiography of a Unicuspid Aortic Valve

Use of the slit arteriotomy for end-to-side arterial anastomosis in free-tissue transfers to the extremities

The purpose of this study was to demonstrate the reliability and advantages of the slit arteriotomy for end-to-side arterial anastomosis. Sixty free flaps for reconstruction of the upper and lower extremities were re-vascularised using this technique. Flaps used were: gracilis (20), latissimus dorsi (18), rectus abdominis (6), lateral arm (6), fibula (3), radial forearm (4), scapular (1) and anterolateral thigh (2). A double microclamp is applied. Using a 30 degrees microknife, a longitudinal slit is made on the recipient vessel. The clamps are then approximated slightly. This slackens the segment bearing the slit and opens up the slit to facilitate placement of sutures. Beginning at the heel, interrupted sutures are placed in such a way as to feed the redundancy of the donor artery wall towards the toe of the anastomosis. A slightly oversized slit is used to stretch the donor vessel, which due to its inherent elastic recoil keeps the anastomosis patent. Once the tourniquet is released, blood flow resumes and the slit forms an elliptical opening. A video is available for viewing at our website: www.microflap.com. The arterial patency rate was 98%. The mechanical advantage of the slit arteriotomy construct was demonstrated through computer simulation on a finite-element analysis model. The slit arteriotomy is simple, reliable, and can be consistently used in the transfer of free flaps to the extremities. As no portion of the recipient vessel wall is excised, the anastomotic diameter is increased. This promotes blood flow through the anastomosis.

An atypical coordination in hexacyanometallates: Structure and properties of hexagonal zinc phases

In hexacyanometallates, the involved transition metals are usually found with octahedral coordination. The exception corresponds to the hexagonal zinc phases where this metal appears tetrahedrally coordinated to N ends from the CN ligands. Those zinc hexacyanometallates where such atypical coordination appears were identified and for four of them the crystal structure was refined from X-ray diffraction powder patterns using the Rietveld method. Zinc hexacyanoferrates (III), hexacyanocobaltate (III), hexacyanoiridate (III) and the mixed zinc–cesium hexacyanoferrate (II) were found to be dimorphic, cubic (Fm-3m) and hexagonal (R-3c), related to the zinc atom in octahedral or tetrahedral coordination, respectively. In the absence of an exchangeable cation, the hexagonal phases result anhydrous. This last feature was attributed to a low polar character for the pores surface. The Mössbauer spectrum of hexagonal zinc hexacyanoferrate (III) is an unresolved quadrupole splitting doublet ( Δ=0.18 mm/s). The iron nucleus is sensing a weak electric field gradient related to a relatively high symmetry for its ligands and charge environment. The IR spectrum appears to be an excellent sensor to identify the coordination for the zinc atom in a given sample. For the tetrahedral coordination, the CN stretching absorption was found at least 8 cm −1 above the frequency observed for this vibration in the octahedral one. For hydrated phases, the crystal water evolves on heating preserving the material porous framework. The temperature at which the material becomes anhydrous parallels the polarizing power of the charge balancing cation sited within the channels. Hexagonal Zn–Cs ferrocyanide becomes anhydrous at 100 °C, while for the Zn–Na analogue a heating close to 200 °C is required. The stability temperature range for the anhydrous phases depends on the nature of the engaged hexacyanometallate anion; the higher stability was observed for hexacyanoferrates (II). Zinc ferricyanide shows the weaker magnetic interaction for the hexagonal modification due to an unfavourable geometry for the overlapping path between the unpaired electrons on the iron(III) atoms. The open 3D porous network is formed by relatively large ellipsoidal cavities, three per cell, communicated through elliptical openings (windows), six per cavity. For dimorphic zinc hexacyanometallates (III), the most compact structure (higher density) corresponds to the hexagonal modification, however, it has the largest cavity windows and cavity (pore) size, and also the higher thermal stability.

A magnetoelectroelastic medium with an elliptical cavity under combined mechanical–electric–magnetic loading

The solution for an elliptical cavity in an infinite two-dimensional magnetoelectroelastic medium subject to remotely uniformly applied combined mechanical–electric–magnetic loadings is obtained by using the Stroh formalism and the exact boundary conditions along the surface of the cavity. By letting the minor-axis of the cavity to zero the solution for a crack is deduced. A self-consistent method is proposed to calculate the real crack opening under the combined mechanical–electric–magnetic loadings. The method requires that the crack opening is the minor-axis of the elliptical opening profile. Beside the real crack solution, four different extreme models, i.e., the impermeable crack, permeable crack, electrically impermeable and magnetically permeable crack and electrically permeable and magnetically impermeable crack, are discussed. An expression of the strain energy density factor is derived. Numerical results of the strain energy density at the crack tip are given for a BaTiO 3–CoFe 2O 4 composite with the piezoelectric BaTiO 3 material being the inclusion and the magnetostrictive CoFe 2O 4 material being the matrix. The effects of the proportion of the two phases, permeability of the crack to electric and magnetic fields, the electric and magnetic loadings on the strain energy density factor are discussed.

Stress Concentration in an Axially Compressed Cylindrical Shell of Medium Thickness with an Elliptic Opening

Stress concentrations at the periphery of elliptic and circular openings are determined experimentally by the photoelastic method for three compressed cylindrical shells of medium thickness made of epoxy resin. The experimental values are compared with numerical values obtained by the theory of thin shells

Large interarcuate spaces in the cervical vertebral column of the tyrolean mountain sheep.

Large interarcual spaces have been described between the arcus vertebrae C5/C6 and C6/C7 in the cervical vertebral column of Nubian goats. This aperture enables direct access to spinal cord and rootlets without the need to perform a hemilaminectomy. The present study was performed in order to determine whether these large interarcual spaces can also be found in the vertebral column of the Tyrolean mountain sheep, as this small ruminant, which is anatomically very similar to the Nubian goat, is frequently used for experimental purposes at the Surgical University Clinic in Austria. The carcasses of 10 sheep (six females, four males; range of age: 2.5-6 years, range of weight: 52-89 kg) were dissected and the vertebral column was exposed. All 10 sheep showed elliptic openings between the fourth cervical and the first thoracal vertebrae. Three sheep had additional openings between the first and the second thoracal vertebrae. All openings were covered solitarily by the ligamentum flavum and under this ligamentum lay the spinal cord without any further osseous or ligamentous protection. These findings are not mentioned in the common textbooks of veterinary anatomy and deserve attention, as they can be a step forward towards non-traumatic experimental surgery on the spinal cord.

Transversely isotropic solid with elliptical inclusions or cracks

Consider the elastostatic problem of a transversely isotropic space embedded with an inclusion in the form of a thin rigid sheet with an elliptical opening. The sheet is given an infinitesimal tangential shift along an arbitrary direction in the plane. By means of Fourier transforms, the problem is reduced to a system of coupled two-dimensional integro-differential equations. Closed-form solutions are derived by using the Ferrers–Dyson and Galin theorems. Explicit expressions for the displacements and stresses are obtained.

A novel strain sensor based on the campaniform sensillum of insects

The functional design of the campaniform sensillum was modelled as a hole in a plate using two- and three-dimensional finite-element modelling. Different shapes of opening in a fibrous composite plate amplify differently the global strains imposed on the plate, and different configurations of reinforcement also have an effect. In this paper, the main objective is to study the strain and displacement fields associated with circular or elliptical openings in laminated plates in order to investigate their potential for integrated strain sensors. Since we are therefore primarily interested with the detection of displacement, the detailed stress concentration levels associated with these openings are not of primary concern. However, strain energy density levels associated with different hole and fibre configurations have been used to assess the relative likely strength reduction effect of the openings. To compare the relative strain amplification effect of drilled and formed holes of the same size in loaded plates, we have used the relative change in length of diameters (circular) or semi-axes (elliptical) in directions parallel and normal to the load. Various techniques which could sense this deformation were investigated, in particular, the coupling mechanism of a campaniform sensillum of Calliphora vicina. This mechanism was resolved into discrete components: a cap surrounded by a collar, a joint membrane and an annulus-shaped socket septum with a spongy compliant zone. The coupling mechanism is a mechanical linkage which transforms the stimulus into two deformations in different directions: monoaxial transverse compression of the dendritic tip and vertical displacement of the cap. The mechanism is insensitive to change of the material properties of the socket septum, the cuticular cap and the spongy cuticle. The joint membrane may serve as a gap filler. The material properties of the collar have a substantial influence on the coupling mechanism's output. A 30% change of stiffness of the collar causes 45% change in the output of the coupling mechanism. The collar may be able to tune the sensitivity of the sensillum by changing its elastic properties.

Numerical Nonlinear Elastic Analysis of Orthotropic Spherical Shells with an Elliptic Cutout

Study is made of how the nonlinear properties of orthotropic composites and the ellipticity of an opening affect the stress–strain state of thin spherical shells subjected to internal pressure. An analysis of numerical results reveals compression on the inside surface of the shell near the broad of the elliptical opening. It is pointed out that as the ellipticity increases, the deformation process near the opening transforms from uniform tension and bending, typical of a shell with a circular opening, to dominated tension near the narrow of the opening and to dominated bending near the broad.

Suppression of Inharmonic Modes Using Elliptical Periphery Electrodes in Very High Frequency Fundamental AT-Cut Resonators

This paper describes suppression of inharmonic modes in a trapped-energy AT-cut resonator operating in a very high frequency (VHF) fundamental mode. This resonator has an elliptical excitation electrode conforming to the anisotropy in the AT-cut quartz plate. Moreover, the new resonator has a mesa to control the plateback and a second electrode with an elliptical opening to decrease the plateback. Resonators operating at 155 MHz are manufactured. In these resonators, the length of the excitation electrode is 53 times the thickness of the crystal substrate. Nevertheless, all of the inharmonic modes can be suppressed by employing the above electrode structure. The ratio of the impedance at the most strongly excited inharmonic mode to the impedance at the main mode in the new resonator is four times that in a conventional resonator with a rectangular excitation electrode.

On the stress distribution near a stiffened elliptical opening in a cylindrical shell beyond the elastic limit

The basic nonlinear relations describing the stress-strain state of flexible thin-walled elements (rods, rings) that stiffen the contour of curvilinear openings in shells with allowance for the plastic deformation of their materials are presented. The Lagrange variation equation is used to obtain sets of nonlinear resolving equations for a shell with a stiffened elliptical opening. Successive-approximation and finite-element methods are used to solve the nonlinear problems. Numerical results are given for an elastoplastic cylindrical shell loaded by an internal pressure of given intensity. The distribution of maximum stresses in the area of an elliptical opening with and without a stiffening ring is analyzed. The data obtained in elastoplastic and linearly elastic formulations of the problem are compared.

Numerical investigation of the elastoplastic state around an elliptical opening in cylindrical shells

Numerical investigation of the elastoplastic state around an elliptical opening in cylindrical shells

Model for Calculating Photosynthetic Photon Flux Densities in Forest Openings on Slopes

A model has been developed to calculate the spatial distribution of the photosynthetic photon flux density (PPFD) in elliptical forest openings of given slopes and orientations. The PPFD is separated into direct and diffuse components. The direct component is calculated according to the opening and radiation geometries, and pathlength of the solar beam through the forest canopy. The diffuse component is obtained from the sky, tree, and landscape view factors. In this model, the distribution of foliage area with height and the effect of foliage clumping on both direct and diffuse radiation transmission are considered. The model has been verified using measurements for six quantum sensors (LI-COR Inc.) located at different positions in a small clear-cut (0.37 ha) in a 90-year-old western hemlock-Douglas fir forest.

Application of an Excimer Laser Machining Technique in the Construction of an Optical Fiber Bus

An excimer laser technique was developed to machine precision tap openings in a polymer‐clad silica optical fiber for use in the construction of an optical backplane. In this technique, a telescope was used to image the laser beam onto the surface of the fiber at the desired tap location. The cladding then was removed using a prescribed number of pulses from the excimer laser. Single optical fiber taps were constructed using an ultraviolet‐curable acralate to attach a tap fiber to a laser‐machined opening in a central fiber. Tap measurements were made on single taps constructed from 650 × 350 micron elliptical openings and 250 micron diameter circular openings. Tap measurements also were made on a triple tap assembly which was fabricated using elliptical tap openings. The elliptical openings, with the major axis oriented along the longitudinal axis of the fiber, were determined to be more suitable for tap construction. The results of this study indicate that excimer laser machining is a promising technique for construction of a linear tapped bus for optical backplanes.