Rows Of Elements Research Articles

Assessment of a Clinical Test for Detection of Alteration in Visual Perception Due to Astigmatism.

Astigmatism blurs the retinal image of a circular spot along a particular orientation rendering it an elliptical shape. Astigmatic patients demonstrate adaptation to residual astigmatic blur that may affect their discrimination between oval and circular targets. The Wilkins Egg and Ball Test (WEBT) was created to detect altered visual perception due to residual astigmatic blur by discriminating a circle within a row of oval elements. This prospective, cross-sectional study examined the utility of WEBT in detecting uncorrected residual astigmatism on the perception of form symmetry in astigmatic and keratoconic participants as well as normal participants with induced astigmatism at four primary meridians. The mean search time (sT) and number of errors (noE) of 33 non-astigmatic controls (mean age: 24±5, range: 18-43, 6 males), 23 astigmatic participants (mean age: 36±12, range: 18-43, 6 males) and 13 keratoconic participants (N=22 eyes, mean age: 36±12, range: 18-58, 6 males) were measured under baseline, and 2.00 DC induced cylinder at four primary meridians, and for uncorrected, spherical-correction only, and fully corrected conditions, respectively. Mean sT and noE were converted to Z-scores, combined for each condition, and compared using repeated measures ANOVA with post-hoc analysis. Combined Z-scores for the controls were significantly worse (p<0.001) for all induced cylinder conditions. The induced 180° condition was significantly better than 45° and 90° conditions (p=0.04), but not the 135° condition. For both astigmatic and keratoconic cohorts, Z-scores of the uncorrected condition were significantly worse than the fully corrected condition (both p<0.01), but the fully corrected and spherical-only conditions did not differ significantly (p=0.06 and p=0.05, respectively). In accommodating young adults, WEBT detected altered visual perception due to overall blur, and moderate-high amounts of uncorrected induced astigmatism and keratoconus, but is not useful as a tool for detection of altered visual perception due to small residual astigmatic blur.

Gas Cleaning with Dust Collection Device with Arc-Shaped Elements

To solve the issue of gas purification, a new dust collecting device with arc-shaped elements has been proposed. A feature of the device is noted, which consists in the capability of changing the flow area at its inlet by varying the number of rows of arc-shaped elements and their height, which makes it possible to select the inlet gas velocity at which the separation efficiency is maximum. The results of numerical modeling of the process of capturing solid particles from gas for various design solutions and process parameters of the unit are presented. It has been found that the high efficiency of a device with arc-shaped elements at a low pressure drop (no more than 380 Pa) is achieved by creating an arranged wave-like structure of the gas and dust flow, on the basis of which the centrifugal forces of high values arise at relatively low gas velocities at the inlet (0.25–2 m/s). A conclusion was made on the optimal design of the device, which has a height of arc-shaped elements of 250 mm and the number of their rows is 12 pcs.

Influence of the cross-sectional geometry of the heat exchanger element on heat flow and pressure drop

This paper examines the influence of the geometry of the heat exchanger element on heat flow, pressure drop, outlet temperature and energy efficiency. By numerical modeling in a two-dimensional formulation, we solved the problem of convective heat transfer when air flows transversely around one and three rows of heated elements of different cross-sections. The following cross-sectional shapes of heated elements are: circle, trefoil, trefoil (mirrored), quatrefoil, cinquefoil and cinquefoil (mirrored). Calculations were carried out using ANSYS Fluent v. 19.2 at the following air flow velocities: 0.01; 0.05; 0.25 and 1.25 m/s. The research results showed that when flowing around one row of elements, the highest energy efficiency is provided by elements with a trefoil shape in cross-section. When flowing around three rows of elements at lower air flow velocities (0.01, 0.05, and 0.25 m/s), trefoil-shaped elements also have the best energy efficiency values, and only at an air flow velocity of 1.25 m/s elements with a trefoil cross-section inferior by 3.67% to elements with a cinquefoil (mirrored) cross-section.

Formirovanie to readiness of future teachers of physical culture to professional activity

Lately in Ukraine there was an anxious and difficult situation with worsening of health of students and student young people. Such state can be explained influence of pandemic and active war of Russia against our country. These realities hurt children and students in teaching, force to evacuation and stay in shelters. Therefore an increase of physical preparedness and state of health of children and young people is one of main tasks of educational process. In such terms an important role is taken professional activity of teacher of physical culture. The purpose of the article: Description of structure of forming of readiness of future teachers of physical culture to professional activity. Result: The issue of the day of modern higher school is marked is providing every student possibility maximally to develop the capabilities and successfully to master a select profession. It is indicated on importance of job of teacher of physical culture, on which the state of health, level of capacity and even professional future of students, depends to a great extent, performances. The basic are exposed requirement to preparedness of future teacher of physical culture, which are based on the aggregate of associate athletic-educate and psychological and pedagogical knowledge’s and abilities. Maintenance, structure and basic stages of professional activity of future specialist, is designated in area of physical cultures and sport. Conclusions: A teacher of physical culture must be well-prepared to execution of the professional duties. His professional-pedagogical activity has a row of elements which co-operate between itself and have affecting humanizing.

Using FGM concept and combined of XFEM-CZM technics to predict the damage in carbon/carbon-epoxy graded composites

The study and the proposal of the concepts of reinforcement in the notched structures, present an objective for many researchers. Recently, the use of bi-materials and graduated materials limits the choice to have more graduation concepts, except that the UD (uni-directional) fiber composites limit the choice to have more grading concepts. Through the finite element method and using the ABAQUS computer code, the main objective of this work is to analyze the damage of the graded Carbon/Carbon-Epoxy composite, using the FGM concept. This composite IM7/8552 in two qualities of fibers housed in the same epoxy matrix named CFRP-1 and CFRP-2, is graduated by row of finite elements to the size of fiber diameters according to the thickness. This approximation of the real behavior with more precision in the graduation is carried out by a proposed meshing technique, which gives a combination between XFEM and CZM. The CZM layers are introduced according to the thickness between the rows of finite elements. The graduation is in the volume of fibers between these two qualities, remains constant in the composite at 60%. A volume fraction exponent named (n) gives it. The response and the damage under the effect of different CFRP graduation parameters have been highlighted in this work by force-displacement and crack propagation path curves.

Effects of stress ratio on plasticity-induced crack closure through three-dimensional advanced numerical finite element models

The plasticity induced crack closure (PICC) is a local phenomenon that substantially influences crack growth. PICC is most commonly determined by numerical models. Specifically, the vertical displacements of the nodes behind the crack front have been extensively used to obtain the PICC and the crack opening loads (Pop/Pmax). Although this procedure has been demonstrated to be adequate for positive stress ratios, this work evidences the uncertainty of such procedure to obtain PICC under negative stress ratios. For this reason, the main objective of this paper is to investigate the effect of stress ratio on PICC by 3D advanced numerical methodology. The purposed method consists of evaluating the contact pressures of all nodes behind the crack tip, from the first to the last released row of elements included on a crack propagation finite element model. Moreover, this method is tested at positive stress ratios and results show a good agreement with the CTOD method.

Damage analysis of hybrid carbon/Glass-Epoxy pipe elbows under bending and pressure loading

Given their many advantages, composite materials have always proven their effectiveness. As in aeronautical structures where reinforcement techniques are used, their application is widened in various fields. Analyzing these composite structures or proposing new concepts for reinforcements remains an interest of several researchers. This work opts for the use of a hybrid composite of a tubular structure of an elbow attached by straight parts. The structural composite is twill. The aim of the elbow damage study is to evaluate the proposed reinforcement concept. The stiffness and damage parameters of the plies are introduced at the size of the fiber and according to the thickness per row of finite elements, hence the use of an adequate meshing technique. The linear behavior follows the equivalent stress flow theory of Von Mises. The results presented as moment-rotation curves were evaluated under design effect and bending moment mode. Depending on the loading conditions, the proposed concept of the hybrid composite showed an overcapacity of resistance where the location of the fiber qualities played the optimization of this capacity. The structure has shown even more resistance for certain locations of the folds which are reinforced in thickness. Depending on the bending moment mode applied, the results show that the damage is caused at very low deformations by ovalization of the elbow and in fiber tension.

Using Functionally Graduated Materials Concept to Predict the Damage of Heat-Treated Elbows Under Bending and Pressure Loading

Abstract Elbows in pressurized tubular structures are increasingly stressed by loadings with radial and tangential stresses. These stresses are completely different from those of straight tubular structures. Through the finite element method and using the ABAQUS computer code, the damage of a tubular structure in X60 of an elbow attached by straight parts stressed in internal pressure and in the moment of bending in closing is analyzed in this work. As a proposal for reinforcement, this structure is previously heat-treated and partially at the level of the elbow. The formulation of the heat-treated X60 material is based on the concept of functional graded materials (FGM), where the graduation by volume fraction between the metal in its base and that previously heat-affected named heat affected zone (HAZ) is under a power function of a parameter named volume fraction index (n). The graded properties of HAZ in the base metal along the thickness of the tubular structure are introduced by a row of finite elements using a proposed meshing technique. The elastic–plastic behavior of the HAZ-base metal mixture under the Voce model follows the equivalent stress flow theory of Von Mises. The technique of extended finite element technique (XFEM) in the damage and the mesh proposed in the graduation, were used to evaluate the various parameters, such as: the internal pressure and the heat treatment (surface and index n). The latter condition the response of the structure and the level of its damage.

A Faulty Line Selection Method for Flexible Grounding System Based on Transient Fault Data

In view of the problem of high-impedance grounding faults (HIFs) in flexible grounding systems (FGS), a faulty line selection method based on transient waveform slope is proposed in this paper. The change of zero sequence (ZS) current of faulty line and non-faulty line (before and after the neutral point parallel small resistance are put in) are analyzed. After the parallel small resistance is put into operation, the waveform slope curve of the transient zero sequence current of each line is obtained, and the modified Hausdorff distance (MHD) algorithm is used to obtain the transient slope matrix. The faulty line is identified by comparing the sizes of each row of elements in the matrix. Simulation verifies the effectiveness of the proposed faulty line selection method.

On the exine ultrastructure of fossil ginkgoaleans: In situ pollen of Sorosaccus Harris

The morphology and exine ultrastructure have been studied of pollen grains from pollen cones of Sorosaccus sibiricus Prynada from the Ust’-Baley (Aalenian, Siberia), Sorosaccus sp. from the Vladimirovka (Aalenian-Bajocian, Siberia), and S. ex gr. sibiricus Prynada from the Tyrma (Tithonian–Berriasian, Russian Far East) localities. The pollen grains are boat-shaped and monosulcate. A finely granulate pattern is discernible under high magnification of light microscope in pollen grains from Vladimirovka and Tyrma; SEM shows that this pattern is formed by flat verrucae. TEM shows that sculptural elements are present on the surface of pollen grains from Ust’-Baley, although it is not evident in LM and SEM. By previous data on modern and fossil members, we believed that ginkgoalean pollen grains can be differentiated from similar boat-shaped monosulcate pollen of other affinities by a ratio of ectexinal sublayers (a thick homogeneous tectum, a thin infratectum of one row of structural elements, and a thin foot layer) in combination with an ectexine that is greatly reduced in the aperture region. Freshly obtained data have revealed another set of characters, with a less prominent tectum by comparison to underlying sublayers, an infratectum with small granules within the alveoli, and a prominent verrucate surface pattern that is distinguishable even in transmitted light. Ginkgoaleans are characterized by more than one set of ultrastructural characters of the exine.

Effect of arc element row arrangement on separator efficiency

Dust emission gas cleaning is a crucial factor for many industries. The paper proposes a separator with the arc-shaped elements to clean dusty gas from solid particles. The study aims to examine how the distance between rows of arc-shaped elements affects separator efficiency and pressure drop, using numerical methods. In simulations, the inlet velocity of the gas flow varied from 0.5 to 5 m/s and the particle size was 10 to 170 μm. It was found that the change in the distance between the rows of the arc elements in the device leads to the formation of different streams. The results show that increasing the distance between the rows of the arc results in a decrease in the separator efficiency, since the particles during separation from the dusty gas due to centrifugal forces fly into the space between the elements, where they are inversed by the flow again. In this case, the pressure drop decreases. The maximum efficiency of particle separation by the developed device (95.4%) is achieved at a distance between rows of arc elements of 0.75. Pressure loss in the separator ranges from 16 to 1862 Pa at an inlet gas velocity of 0.5 to 5 m/s.

Water-air aerosol cooling of rows of cylindrical elements under conditions of natural convection

Water-air aerosol cooling of rows of cylindrical elements under conditions of natural convection

Numerical study of particles removal from dusty gas in separation device with straight arc-shaped elements

The paper presents an original design of the separator with straight rows of arc-shaped elements, which allows efficient separation of solid particles without significant abrasive wear of the device’s surfaces. A three-dimensional model of the device is developed, and the principle of its operation is described. In this paper, a numerical study of the capture of solid particles from a gas flow in the separation device is performed. It is found that at a relatively low inlet gas velocity (1 m/s), the separation efficiency of particles with a diameter of 20 to 100 μm is on average 78.9%. An increase in the inlet velocity of the dusty gas flow results in a decrease in the efficiency of the device for particles ranging in size from 25 to 80 μm. The pressure drop of the separator at a velocity of 1 m/s ranges from 45.5 to 95.4 Pa, and at a gas velocity of 4 and 7 m/s – from 740.8 to 4652.1 Pa. An increase in the number of straight arc-shaped elements from 4 to 12 and an increase in particle density from 3400 to 10000 kg/m3 leads to improved separation efficiency.

Increase of dynamic stability of a basis at operation of the compressor equipment of the Abazіvka unit of complex gas preparation

The object of research is the basis of the compressor equipment of the complex gas treatment plant at the Abazivka field and the strengthening of the base soils with soil-cement elements, which are proposed to be arranged with the use of drilling technology. The research area is located on the territory of the current Abazivka Integrated Gas Preparation, near the village of Bugaivka, Poltava region, Ukraine. Abazivka Integrated Gas Preparation receives products from wells in Abazivka and Sementsivske deposits. It is proposed to carry out the reconstruction of Integrated Gas Preparation, which includes strengthening the foundation of the compressor model C1004-JGT/2-1 manufactured by «Propak» (Alberta, Canada). The amplitudes of oscillations of the compressor foundation were determined at a speed of 1400 rpm at the appropriate site with geological conditions. The magnitudes of oscillations and subsidence of the compressor foundation of the Abazivka complex of complex gas treatment were investigated experimentally. When determining the amplitudes of oscillations of the compressor foundations, only the amplitudes of oscillations in the direction parallel to the sliding of the pistons were calculated, and the influence of the vertical component of the perturbing forces was not taken into account. It is established that the amplitude of horizontal-rotational oscillations of the upper face of the compressor foundation relative to the horizontal axis exceeds the maximum allowable. It is substantiated that soil cement is a sufficiently strong and waterproof material that can be used to strengthen the base during the construction of equipment foundations. The possibility of application of the technology of application of soil-cement piles, made by brown-mixing technology for strengthening the base under the foundation of the compressor, is described and investigated. It is proposed to reinforce the base with rows of soil-cement elements, which will increase the modulus of deformation of the base, which is represented by loam, light to 14.3 MPa. In the case of strengthening the base, the amplitude of horizontal-rotational oscillations of the upper face of the compressor foundation is much less than the maximum allowable 0.1 mm. The subsidence of the foundation at reinforcement of the base, which does not exceed the maximum allowable value, is determined. Soil-cement elements are proposed to be arranged according to the drilling technology.

Refinement of arrangement of purifying elements of integrated air treatment device for gas transmission systems and power generation based on computational fluid dynamics

Gas pumping units with gas turbine units (GTU) are widely used in gas transmission systems. In recent decades, GTUs are increasingly used in power generation at thermal power plants. The efficiency and reliability of a gas turbine plant largely depend on the quality of air preparation. Integrated air cleaning devices (KVOU) as part of the air intake duct of the GTU have stages of coarse and fine air purification and rather large dimensions. The possibility of using a battery cyclonefilter with cleaning elements, in which both stages of cleaning are combined, in the design of the KVOU is considered. Numerical studies of the movement of a two-phase flow in a multicyclone, which is a model of the first 2 rows of a serial multicyclone, have been carried out. The first two rows of the serial multicyclone TsB-16 of the Biysk boiler plant, consisting of 16 cyclone elements 245 mm in diameter with a semi-coil gas supply, were taken as the initial geometric model. The geometric model was built using the Gambit preprocessor: a two-dimensional 2D model and a finite element mesh based on square elements were built. The finite element mesh of the numerical model generated in the Gambit program was exported to the solver of the ANSYS Fluent software package. Using the methods of computational hydrodynamics, the nature of the movement of a dusty flow in a battery cyclone with a corridor arrangement of cyclone elements has been investigated, their most effective placement has been determined, which provides the maximum inertial capture of suspended particles, in accordance with which a localization scheme for semi-coil entrances to treatment elements has been determined. In numerical studies, the aerodynamic characteristics of the dispersed flow in the multicyclone body are obtained. In accordance with the results of numerical studies, the efficiency of inertial sedimentation of suspended particles from the flow in the first row of elements was 36%, in the second row — 99%.

Trace element content in alluvial soils landscape of the flood plains of the Iput river

The results of research on the content and distribution of trace elements in alluvial soils of various elements of the floodplain landscape, and their relationship with fertility indicators are presented. It has been found that the maximum concentrations of most trace elements (Ni, Zn, Mn, Cr, Co, Mo, As) are characteristic of the alluvial overhanging-marsh heavy-coal pristine subsystem of the floodplain landscape. In the riverine and perish subsystems of the floodplain landscape in individual layers of the corresponding soils, an excess of clark was found: in the alluvial sour acid layered primitive shortened sandy loam Cu by 1.5; Zn in 1.1; Cd 9.2 times, in alluvial chilli-marsh heavy-coal Cu 1.05; Zn in 1.4; Mn in 1.01; Cr in 1,2; Cd 3.2 times. For the riverine and perch subsystems, the excess of Cu, Mn and Cr was observed in the soil layer 0-5 cm, the remaining exceedances are characteristic of deeper layers. Decreasing rows of trace elements in alluvial soils have a similar structure. The microelements in question, in the soils of the floodplain landscape of the Iput River, in terms of clark concentration, belong to the group of dispersing. There is no significant correlation between micronutrient content and fertility of the alluvial soils under consideration.

Panderodus from the Waukesha Lagerstätte of Wisconsin, USA: a primitive macrophagous vertebrate predator

AbstractConodonts are an extinct group of early vertebrates. Articulated fossils of their feeding apparatus (‘natural assemblages’) are rare, and preserved soft tissues vanishingly so. Here, a primitive conodont with preserved soft tissues is redescribed from the Waukesha Lagerstätte of Wisconsin, USA. Although the feeding apparatus of derived prioniodontid conodonts is well understood, together with the homologies between taxa, the same is not true of more primitive conodonts that have apparatuses composed entirely of coniform elements. The new data provide insights into the long‐term problem of determining homology across different types of conodont feeding apparatus. The Waukesha Panderodus preserves an almost complete apparatus, consisting of two parallel rows of elements that occluded across the sagittal plane. A pair of M elements lies at the rostral end of the apparatus, with four pairs of S elements located immediately caudal to them. Three pairs of P elements are identified at the caudal end of the apparatus, for the first time in a primitive conodont with coniform elements. A symmetrical S0 element is located on the midline between the M–S and P suites and provides the key for establishing homology with more derived ramiform–pectiniform apparatuses. The exceptional preservation reveals cartilaginous supports for the elements that inserted into their basal cavities. The trunk of the animal is poorly preserved but was dorsoventrally flattened in life with transverse myomeres containing muscle fibrils. Overall, the specimen shows that Panderodus was a macrophagous feeder and provides an insight into the functional anatomy of early vertebrate predation.

Low-Lying Electronic States of the Nickel Dimer.

The generalized Van Vleck second order multireference perturbation theory (GVVPT2) method was used to investigate the low-lying electronic states of Ni2. Because the nickel atom has an excitation energy of only 0.025 eV to its first excited state (the least in the first row of transition elements), Ni2 has a particularly large number of low-lying states. Full potential energy curves (PECs) of more than a dozen low-lying electronic states of Ni2, resulting from the atomic combinations 3F4 + 3F4 and 3D3 + 3D3, were computed. In agreement with previous theoretical studies, we found the lowest lying states of Ni2 to correlate with the 3D3 + 3D3 dissociation limit, and the holes in the d-subshells were in the subspace of delta orbitals (i.e., the so-dubbed δδ-states). In particular, the ground state was determined as X 1Γg and had spectroscopic constants: bond length (R e) = 2.26 Å, harmonic frequency (ωe) = 276.0 cm−1, and binding energy (D e) = 1.75 eV; whereas the 1 1Σg + excited state (with spectroscopic constants: R e = 2.26 Å, ωe = 276.8 cm−1, and D e = 1.75) of the 3D3 + 3D3 dissociation channel lay at only 16.4 cm−1 (0.002 eV) above the ground state at the equilibrium geometry. Inclusion of scalar relativistic effects through the spin-free exact two component (sf-X2C) method reduced the bond lengths of both of these two states to 2.20 Å, and increased their binding energies to 1.95 eV and harmonic frequencies to 296.0 cm−1 for X 1Γg and 297.0 cm−1 for 1 1Σg +. These values are in good agreement with experimental values of R e = 2.1545 ± 0.0004 Å, ωe = 280 ± 20 cm−1, and D 0 = 2.042 ± 0.002 eV for the ground state. All states considered within the 3F4 + 3F4 dissociation channel proved to be energetically high-lying and van der Waals-like in nature. In contrast to most previous theoretical studies of Ni2, full PECs of all considered electronic states of the molecule were produced.

Generation of attached Langmuir circulations by a suspended macroalgal farm

Abstract

A non-local damage approach compatible with dynamic explicit simulations and parallel computing

In the automotive industry, crack prediction is an important step of the design: its accuracy is crucial to avoid additional development costs and delays. However, its simulation is not always reliable yet which could be explained by the use of too simple fracture criteria. A possible solution could be the improvement of the fracture behavior prediction through the use of coupled damage models. Unlike the fracture criteria, damage models consider the loss of resistance on the elements behavior, which gives a better definition of the strain localization and crack path. However, due to stress softening, the problem becomes ill posed, generating damage localization on a single row of elements. The results are then dependent on the mesh size and the mesh orientation. To obtain mesh independent results, a possible solution is to resort to regularization methods, but only a few of them are compatible with dynamic explicit simulations, especially for ductile failure. This paper proposes to extend the implicit second gradient non-local regularization approach to crash simulations. This is achieved by modifying the second gradient equation to ensure its robustness for dynamic explicit simulations. This extended second gradient approach is implemented by enriching under-integrated continuum elements so as to naturally preserve the parallel computing ability. A comparison between simulations and experimental results obtained with specimens machined in a dual-phase steel sheet is realized to validate the proposed approach. Numerical results obtained with different mesh sizes and mesh orientations illustrate the mesh independence and are in very good agreement with the experiments in terms of both load–displacement curves and crack path.