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In this paper, we present the first study of plane-strain problems within the framework of complete thermo-flexoelectric theory, incorporating strain-gradient elasticity, direct and converse flexoelectricity, as well as thermoelasticity. We derive the exact solutions for three typical thermoelastic plane strain problems, which are the mechanical-electrical-thermal coupling problem for an infinite-length strip, the mechanical-electrical-thermal coupling problem for a hollow cylinder, and the thermal eigenstrain problem for a cylindrical inclusion. We develop the mixed finite element framework for the plane-strain thermo-flexoelectric problems, benchmarked against the three analytical solutions. This study reveals that the electric field induced by inhomogeneous heating in thermo-flexoelectric solids exhibits a pronounced size effect. Notably, an increase in the strain-gradient length scale parameter diminishes the thermo-flexoelectric effects. This study not only deepens the understanding of the mechanisms of multiphysical fields coupling in thermo-flexoelectric solids, but also provides insights for designing nano thermo-electric converters based on the principle of thermo-flexoelectricity. [ABSTRACT FROM AUTHOR]

An induced cylinder and spherical power after implantation with an extended depth of focus (EDOF) and enhanced monofocal intraocular lens (IOL) could improve distance, intermediate (60 cm) and near (40 cm) visual acuity (VA). In this prospective study, forty eyes with Eyhance EDOF IOL (Johnson and Johnson, USA) and 40 eyes with Vivity EDOF IOL (Alcon Laboratories Inc. USA) were included. Induced cylinder (applied to non-dominant eye) in steps of + 0.25D were used and then VA was measured monocularly (only non-dominant eye). Similarly, induced sphere (applied to non-dominant eye) in steps of + 0.25D were used and then VA was measured monocularly (only non-dominant eye). The above methods were repeated for the dominant eye as well. Then, binocular defocus curve for each patient was obtained by inducing optimal sphere and cylinder (one at a time in front of the non-dominant eye only). In both IOL groups, induced cylinder and sphere independently led to significant improvement in near and distance vision (p < 0.05). Induced sphere binocularly caused a greater decrease (~ 0.1 LogMAR) in distance VA compared to induced cylinder but this was not clinically significant. Most patients accepted an induced cylinder of +1.0 to +1.5D in both IOL groups. Induced cylinder and sphere caused a favourable improvement in near and intermediate VA after surgery in both IOL groups without a significant drop in distance VA. [ABSTRACT FROM AUTHOR]

In chemical graph theory, various topological indices of the hexagonal lattices such as the energy, the numbers of perfect matchings and spanning trees, and so on, have been studied extensively. In this paper, we enumerate spanning trees with a perfect matching of the hexagonal lattices on the cylinder and Möbius strip. [ABSTRACT FROM AUTHOR]

In order to promote power conversion efficiency and reduce energy loss, we propose a perovskite solar cell based on cylindrical MAPbI3 microstructure composed of a MAPbI3 perovskite layer and a hole transport layer (HTL) composed of PEDOT:PSS. According to the charge transport theory, which effectually increases the contact area of the HTL, promoting the electronic transmission capability, the local field enhancement and scattering effects of the surface plasmon polaritons help to couple the incident light to the solar cell, which can increase the absorption of light in the active layer of the solar cell and improve its light absorption efficiency (LAE). based on simulation results, a cylindrical microstructure of the perovskite layer increases the contact area of the hole transport layer, which could improve light absorption, quantum efficiency (QE), short-circuit current density (JSC), and electric power compared with the perovskite layer of other structures. In the AM 1.5 solar spectrum, the average light absorption efficiency is 93.86%, the QE is 80.7%, the JSC is 24.50 mA/cm2, and the power conversion efficiency (PCE) is 20.19%. By enhancing the efficiency and reducing material usage, this innovative design approach for perovskite solar cells is expected to play a significant role in advancing solar technology and positively impacting the development of renewable energy solutions. [ABSTRACT FROM AUTHOR]

Fractional calculus plays a pivotal role in modern scientific and engineering disciplines, providing more accurate solutions for complex fluid dynamics phenomena due to its non-locality and inherent memory characteristics. In this study, Caputo's time fractional derivative operator approach is employed for heat and mass transfer modeling in unsteady Maxwell fluid within a cylinder. Governing equations within a cylinder involve a system of coupled, nonlinear fractional partial differential equations (PDEs). A machine learning technique based on the Levenberg–Marquardt scheme with a backpropagation neural network (LMS-BPNN) is employed to evaluate the predicted solution of governing flow equations up to the required level of accuracy. The numerical data sheet is obtained using series solution approach Homotopy perturbation methods. The data sheet is divided into three portions i.e., 80 % is used for training, 10 % for validation, and 10 % for testing. The mean-squared error (MSE), error histograms, correlation coefficient (R), and function fitting are computed to examine the effectiveness and consistency of the proposed machine learning technique i.e., LMS-BPNN. Moreover, additional error metrics, such as R-squared, residual plots, and confidence intervals, are incorporated to provide a more comprehensive evaluation of model accuracy. The comparison of predicted solutions with LMS-BPNN and an approximate series solution are compared and the goodness of fit is found. The momentum boundary layer became higher and higher as there was an enhancement in the value of Caputo, fractional order α = 0.5 to α = 0.9. Higher thermal boundary layer (TBL) profiles were observed with the rising value of the heat source. [ABSTRACT FROM AUTHOR]

Extensive research has been conducted on the flow control of bluff bodies to address negative impacts such as vibration, acoustic noise, and resonance caused by wake flow. The circular cylinder, due to its simple geometry, is frequently studied as a bluff body and is utilized in various engineering applications including cooling system pipes, electrical pylons, industrial flue systems, overpasses, satellite antennas, electrical cables, and marine drilling platforms. In this investigation, a perforated splitter plate was strategically positioned at different downstream locations to manage the wake flow of the cylinder. The experiments were conducted in a sophisticated, closed-loop water channel at the Fluid Mechanics Laboratory of Cukurova University, providing a controlled environment for precise flow analysis. To measure the instantaneous velocity vector field in the wake region of the cylinder at a Reynolds number (Re) of 5000 (based on the cylinder diameter, D), particle image velocimetry (PIV) was employed. Three different permeability values for the splitter plate (e=0.30, 0.50, 0.70) and three lengths (ls*=1, ls*=2, ls*=3) were tested, maintaining a constant gap (G/D=1) between the splitter plate's leading edge and the cylinder surface. The splitter plates were aligned with the flow direction (θ=0°). The permeable separator plates minimize the interaction of boundary layers formed around the cylinder, enhancing their effect in downstream regions where shear layer interaction is more pronounced. Consequently, this results in reduced fluctuations and a more stabilized wake flow downstream of the cylinder. [ABSTRACT FROM AUTHOR]

In this paper a porous fluid-saturated cylinder subjected to a finite twist deformation is analyzed. The material of the skeleton of the porous cylinder is hyperelastic of Ogden-type and assumed nearly incompressible. The twist is applied to the cylinder in a fast rate so that the fluid pressure develops in the pores of the cylinder. The main objective of this paper is to study the stresses and the fluid pressure in the cylinder over a short period of time after the twist has been applied, or to study the initial response. The analytical expressions for the stress components and the fluid pressure are derived for Ogden material with arbitrary material parameters. The quantitative picture for the stress state is given and the signs of the normal stresses are explained. The stress arising in some imaginary fibers that were initially parallel to the axis of the cylinder is obtained. The present problem is similar to the torsion problem of a totally incompressible and nonporous cylinder in a sense that the total stresses are identical in both problems. But decomposition of the total stresses into the fluid pressure and the effective stresses, which is specific for the fluid-saturated body, can be found only using the present analysis. [ABSTRACT FROM AUTHOR]

Hollow cylindrical components of longer length are a crucial necessity in industries catering to products like gun barrels, cylinder liners of ship and locomotive engines, pneumatic and hydraulic cylinders, etc. A highly finished inner surface improves resistance to corrosion, wear, and friction. Conventional magnetorheological (MR) finishing techniques typically use axis-based CNC setups, which are limited in their ability to finish longer components (>30 cm) due to the Z-axis tool restriction. In this work, a novel MR finishing method has been designed and developed that is based on the pneumatic cylinder and has extremely high reach for the length of the hollow cylindrical workpiece thereby successfully mitigating the limitation of conventional CNC-based MR finishing techniques. Using mild steel as the material, the new technique achieved a significant reduction in surface roughness, with a minimum average roughness of 0.059 µm after 150 minutes of finishing. [ABSTRACT FROM AUTHOR]

Extensive research has been conducted on the flow control of bluff bodies to address negative impacts such as vibration, acoustic noise, and resonance caused by wake flow. The circular cylinder, due to its simple geometry, is frequently studied as a bluff body and is utilized in various engineering applications including cooling system pipes, electrical pylons, industrial flue systems, overpasses, satellite antennas, electrical cables, and marine drilling platforms. In this investigation, a perforated splitter plate was strategically positioned at different downstream locations to manage the wake flow of the cylinder. The experiments were conducted in a sophisticated, closed-loop water channel at the Fluid Mechanics Laboratory of Cukurova University, providing a controlled environment for precise flow analysis. To measure the instantaneous velocity vector field in the wake region of the cylinder at a Reynolds number (Re) of 5000 (based on the cylinder diameter, D), particle image velocimetry (PIV) was employed. Three different permeability values for the splitter plate (e=0.30, 0.50, 0.70) and three lengths (ls*=1, ls*=2, ls*=3) were tested, maintaining a constant gap (G/D=1) between the splitter plate's leading edge and the cylinder surface. The splitter plates were aligned with the flow direction (ϴ=0°). The permeable separator plates minimize the interaction of boundary layers formed around the cylinder, enhancing their effect in downstream regions where shear layer interaction is more pronounced. Consequently, this results in reduced fluctuations and a more stabilized wake flow downstream of the cylinder.

Flows of an oil-glycerin system of immiscible Newtonian fluids, driven by the independent rotation of the boundaries of a vertical cylinder with axial rod are investigated numerically. Moderate lid rotation rates are shown to generate breakdown in the adjacent oil phase, associated to significant interface displacement and flow reversal. The vortex pattern and interface behavior are found to be very sensitive to the distinct and combined effects of fluids volume fraction and background rotation. In particular, a decrease of the oil phase volume causes bubble expansion and evolution into a ring type vortex prior to its suppression as it coalesces onto a convex shaped interface. In addition, the vortex structure may efficiently be prevented (enhanced) by means of low rates of sidewall counterrotation (co-rotation). Moreover, addition of swirl by means of the central rod rotation is found to have a considerable impact on the lid driven vortex flows characteristics in qualitative accord with prior experiments. [ABSTRACT FROM AUTHOR]

In order to obtain a high-precision pneumatic control system, it is necessary to study the friction force of the cylinder. However, few researchers have considered the cylinder's frictional characteristics at small-displacements. This study investigated the influence of different conditions on the cylinder friction characteristics during the process from static to small-displacement of the pneumatic double O-ring seal. A set of experimental apparatuses controlled by an electric actuator perform a seal ring small-displacement friction test to achieve the goals. The working principle of sealing rings in different deformation stages is expounded. According to experiments, the sealing ring's friction force in small-displacement movement can be separated into tilt, elastic deformation, pre-sliding, and sliding friction stages. Furthermore, the clearance characteristics between the sealing ring and the piston groove are verified, which decreases with the sealing ring thickness. Finally, the friction displacement characteristics of sealing rings under different pressures and materials during the elastic deformation stage were verified. It can be concluded that when the displacement is between 0.05 and 0.25 mm, the friction of the sealing ring is almost linear with the displacement; when the displacement reaches 0.25 mm, with the increase of the displacement, the friction force changes in a similar parabolic manner. This study provides a detailed analysis of the friction characteristics of the seal in different stages of small displacement, which plays an important reference role in overcoming cylinder friction and promotes the development of pneumatic systems in the field of accurate position and speed control. [ABSTRACT FROM AUTHOR]

In ultrasonic flaw detection, lateral cylindrical drilling is traditionally used to adjust and check equipment parameters. Other volumetric reflectors such as vertical drilling or spherical pores are rarely used. In this article, it is noted that volumetric reflectors of various types are convenient for use as a model of internal and surface defects of welds. Moreover, drillings of various orientations are easy to manufacture. For a long time, the limitations on using drilling for modeling in ultrasonic nondestructive testing were related to the noise caused by diffraction effects as elastic waves bypass cylindrical cavities. It is noted that these effects are currently well studied. They can be used to identify the type of defects and measure their size. The present paper describes the results of experiments on the observation of scattering of longitudinal and transverse waves with various polarization by cylinders and spheres and provides typical examples of the manifestation and use of these diffraction effects. The expediency of using not only drilling but also spherical pores is also noted. Experiments with scattering of ultrasonic waves by pores were performed on transparent glass samples for clarity. Comparative data are presented showing how diffraction effects manifest themselves on various volumetric cavities. In particular, it is noted that a focusing of signals that envelope spherical pores is observed. Limitations on the pulse duration of ultrasonic waves are noted in which diffraction signals can be used to increase information content in the detection of defects. It is recommended to expand the use of lateral drilling with a diameter of 2 mm in samples to adjust sensitivity during ultrasonic monitoring with an echometer. [ABSTRACT FROM AUTHOR]

In order to improve the carding efficiency of the main carding area of the card, the inlluence of the needle toolh density on the carding effect was discussed. Aiming at the invisible working process of carding mechanism of carding machine, UG, HYPRE MESH and ABAQUS software were used to model the main parts of carding area, mesh division and display dynamics module simulation analysis. 12, 16 and 20 fibers were used to measure the load of the needle cloth. The motion process of the fiber under different carding conditions was simulated by changing the configuration changes of the pin density of the tin and the cover plate, and the changes of the fiber projection length before and after carding were obtained. The results show that under the four collocation methods of tin and cover cloth, namely dense collocation, thin collocation, thin collocation and thin collocation, the carding effect is the best when the load oí tin cloth is 16, and the average projection length increase rate is 6.66%. [ABSTRACT FROM AUTHOR]

Biomimetic design has recently received widespread attention. Inspired by the Terebridae structure, this paper provides a structural form for suppressing vortex-induced vibration (VIV) response. Four different structural forms are shown, including the traditional smooth cylinder (P0), and the Terebridae-inspired cylinder with the helical angle of 30° (P30), 60° (P60), and 90° (P90). Computational fluid dynamics (CFD) method is adopted to solve the flow pass the Terebridae-inspired structures, and the vibration equation is solved using the Newmark-β method. The results show that for P30, P60 and P90, the VIV responses are effectively suppressed in the lock-in region, and P60 showed the best VIV suppression performance. The transverse amplitude and the downstream amplitude can be reduced by 82.67% and 91.43% respectively for P60 compared with that for P0, and the peak of the mean-drag coefficient is suppressed by 53.33%. The Q-criterion vortices of P30, P60, and P90 are destroyed, with irregular vortices shedding. It is also found that the boundary layer separation is located on the Terebridae-inspired ribs. The twisted ribs cause the separation point to constantly change along the spanwise direction, resulting in the development of the boundary layer separation being completely destroyed. The strength of the wake flow is significantly weakened for the Terebridae-inspired cylinder. [ABSTRACT FROM AUTHOR]

The problem of a symmetric stationary cavitation flow around a cylinder by an infinite flow of ideal incompressible weightless fluid in the presence of a given intensity point effluent located at the front point of the cylinder is considered. The exact solution to the problem is constructed by mapping the areas of change in the complex potential and complex flow velocity onto the area of change in the auxiliary parametric variable. A parametric analysis of the problem is performed. For a wide range of values of the cavitation number, the dimensionless flow rate, the shape and dimensions of the cavitation cavity, and the values of the drag coefficient are found. [ABSTRACT FROM AUTHOR]

Within this work, we perform a sensitivity analysis to determine the influence of the material input parameters on the pressure in an isotropic porous solid cylinder. We provide a step-by-step guide to obtain the analytical solution for a porous isotropic elastic cylinder in terms of the pressure, stresses, and elastic displacement. We obtain the solution by performing a Laplace transform on the governing equations, which are those of Biot's poroelasticity in cylindrical polar coordinates. We enforce radial boundary conditions and obtain the solution in the Laplace transformed domain before reverting back to the time domain. The sensitivity analysis is then carried out, considering only the derived pressure solution. This analysis finds that the time t, Biot's modulus M, and Poisson's ratio v have the highest influence on the pressure whereas the initial value of pressure P0 plays a very little role. [ABSTRACT FROM AUTHOR]

Introduction Inhaled nitric oxide (INO) is a selective pulmonary vasodilator delivered from compressed gas cylinders filled to 2,200 psig (137.8 bar) with 800 ppm of NO in a balance of nitrogen. NO is currently FDA-approved for use in term or near-term infants with hypoxemia and signs of pulmonary hypertension in the absence of cardiac disease. INO has also been shown to improve oxygenation in adults with refractory hypoxemia. Current doctrine precludes the use of NO during military aeromedical transport owing to the requirement for large compressed gas cylinders. We performed a bench evaluation of 2 delivery systems that create NO from room air without the need for pressurized cylinders, Materials and Methods We evaluated 2 portable nitric oxide INO generation systems (LungFit PH, Beyond Air Inc, Garden City, NJ and a prototype NO generator, Odic Inc, Littleton, MA) at ground level, 8,000, and 14,000 feet (2,437 and 4,267 meter) simulated altitude in an altitude chamber. The output from each device was injected into the inspiratory limb of the ventilator circuit that was attached to a test lung. A 731 ventilator (Zoll Medical, Chelmsford, MA) and T1 (Hamilton Medical, Reno, NV) were used employing 24 combinations of ventilator settings each repeated in duplicate. An INOmax DS IR was used to measure delivered INO and NO2 via a sampling line attached in the ventilator circuit inspiratory limb. A fast response oxygen analyzer (O2CAP, Oxigraf Inc, Sunnyvale, CA) was used to measure inspired FiO2. Target INO concentration was 20 ppm. Results Across all ventilator settings, the LungFit device delivered INO was 19.8 ± 1.6 ppm, 16.1 ± 1.9 ppm, and 11.6 ± 1.7 ppm at ground level, 8,000 ft (2,437 meter), and 14,000 ft (4,267 meter), respectively. The Odic device delivered INO dose was 20.6 ± 1.4 ppm, 21.3 ± 5.5 ppm, and 20.4 ± 9.1 ppm at ground level, 8,000 ft (2,437 meter), and 14,000 ft (4,267 meter), respectively. Conclusions Both devices delivered a reliable INO dose at ground level. Altitude significantly affected INO delivery accuracy at 14,000 ft (4,267 meter) (P  < 0.01) with both devices and at 8,000 ft (2,437 meter) (P  < 0.01) with LungFit. Differences in INO dosage were not statistically significant with the Odic device at 8,000 ft (2,437 meter)(P  > 0.05) although there were large variations with selected ventilator settings. With careful monitoring, devices creating INO from room air without cylinders could be used during aeromedical transport without the need for pressurized cylinders. [ABSTRACT FROM AUTHOR]

Abstract This study presents a computational analysis of fluid flow characteristics around two staggered arranged square cylinders using the Lattice Boltzmann Method (LBM). With Reynolds number (Re) fixed at 200, numerical simulations explore the influence of varying gap ratios (G) ranging from 0 to 10 times the cylinder size. Emphasis is placed on understanding the impact of cylinders spacing on flow structure mechanisms and induced forces. Investigation of fluid flow parameters includes vorticity behavior, pressure streamlines, and variations in drag and lift coefficients alongside the Strouhal number under different values of G. From the results, four distinct flow patterns emerge: single bluff body flow, flip flopping flow, modulated synchronized flow, and synchronized flow, each exhibiting unique characteristics. This study reveals the strong dependence of fluid forces on G, with low spacing values leading to complex vortex structures and fluctuating forces influenced by jet flow effects. At higher spacing values, proximity effects between cylinders diminish, resulting in a smoother periodic flow. The Strouhal number, average drag force and the rms values of drag and lift force coefficients vary abruptly at narrow gaps and become smooth at higher gap ratios. Unlike the tandem and side-by-side arrangements the staggered cylinders arrangement is found to have significant impact on the pressure variations around both cylinders. Overall, this research could contribute to a comprehensive understanding of staggered cylinder arrangements and their implications for engineering applications.

Within the framework of the linear theory of elasticity, using the model of an isotropic body, the problem of steady-state vibrations of an inhomogeneous hollow cylinder is formulated. The vibrations of the cylinder are caused by a load applied to the side surface, and the conditions of sliding embedding are implemented at the ends. The variable material properties are described by the Lamé parameters and density, which change along the radial and longitudinal coordinates. The direct problem solution of the cylinder vibrations is constructed using the finite element method implemented in the FlexPDE package, its main advantages are noted. To study the influence of variable properties on the values of resonant frequencies and components of the displacement field, the laws of these properties are considered in the general form used in modern works for modeling functionally graded materials. On the basis of the performed numerical calculations, the degree of influence of the amplitude values of each of the Lamé parameters and density on the first resonant frequency and the displacement field are studied. Graphs are also presented that demonstrate the influence of the type of the law of density change on the values of the displacement field components. A new inverse coefficient problem is formulated to determine the density distribution function in the cylinder wall from the displacement field data measured at a finite set of points inside the considered area for a fixed frequency. The main difficulties in the implementation of the reconstruction procedure in practice are noted. To increase the accuracy of calculating the first and second derivatives of the two-dimensional functions calculated in the finite element package, which are used in solving the inverse problem, an approach based on the locally weighted regression algorithm is proposed. The results of computational experiments on solving the inverse problem are presented, which demonstrate the possibility of using the proposed method to restore various types of two-dimensional laws of density. Practical recommendations are given for the implementation of the most accurate reconstruction procedure.

The investigation of aerodynamics and the establishment of flow patterns around finite-length cylinders with various end shapes in a free, boundless air flow with longitudinal and transverse flow over a wide range of geometric and regime parameters is sketchy and does not have a wide range of geometric and regime parameters. This, in turn, affects the entire aerodynamics of the streamlined body. This paper considers the numerical simulation of a wind turbine made of combined blades. CFD (computational fluid dynamics) methods based on the realisable k-ε turbulence model were used in the study. The results on the influence of the position of the fixed blade on the angle of inclination are obtained (0°, 15°, 30°, 45°, and 60°). The authors found that the pressure of a fixed blade at an optimal angle increases the power coefficient Cp by 35–40%. The dependence of the Cp power coefficient on the rotational speed (speed coefficient) for a three-bladed wind turbine was also established, and it was determined that the maximum value of Cp = 0.28 at Z = 4.9. Based on the results obtained, it was determined that the wind turbine has a maximum power coefficient at an angle of inclination of 0 degrees. [ABSTRACT FROM AUTHOR]

Background: Existing research on the relationship between body mass index (BMI) and astigmatism yields inconsistent results. This study analyses this association in a nationally representative sample of adolescents. Methods: This retrospective, cross‐sectional study included Israeli adolescents who underwent medical assessments before mandatory military service between 2011 and 2022. BMI was categorised based on the US age‐ and sex‐matched percentiles. Astigmatism was categorised by magnitude [low‐moderate: 0.75 to <3.00 diopters (D), high: ≥3.00 D], and axis orientation [with‐the‐rule (WTR), against‐the‐rule (ATR), or oblique (OBL)]. Sex‐stratified regression models adjusted for sociodemographic variables were used. Results: Of 935 989 adolescents evaluated, 887 325 were included [511 465 (57.6%) males, mean age 17.2 years]. Astigmatism was diagnosed in 123 675 (13.9%) adolescents, of whom 117 081 (13.2%) had low‐moderate and 6594 (0.7%) had high astigmatism. WTR astigmatism was the most prevalent (8.2%), followed by ATR (4.1%) and OBL (1.6%) types. Compared with low‐normal BMI (5th to 50th percentile), the adjusted ORs for total astigmatism increased with increasing BMI, peaking at 1.65 (1.57–1.74) in males and 1.74 (1.64–1.86) in females with severe obesity. ORs were accentuated for high astigmatism, reaching 3.51 (3.01–4.09) in males, and 3.45 (2.83–4.22) in females with severe obesity. WTR astigmatism demonstrated the strongest association with BMI, with ORs reaching 2.26 (2.13–2.40) in males and 2.04 (1.90–2.20) in females with severe obesity. The results persisted in a series of subgroup analyses. Conclusions: Obesity is associated with higher odds of astigmatism in adolescence. Further investigation into the role of weight management in astigmatism development is warranted. [ABSTRACT FROM AUTHOR]

This study presents a computational analysis of fluid flow characteristics around two staggered arranged square cylinders using the Lattice Boltzmann Method (LBM). With Reynolds number (Re) fixed at 200, numerical simulations explore the influence of varying gap ratios (G) ranging from 0 to 10 times the cylinder size. Emphasis is placed on understanding the impact of cylinders spacing on flow structure mechanisms and induced forces. Investigation of fluid flow parameters includes vorticity behavior, pressure streamlines, and variations in drag and lift coefficients alongside the Strouhal number under different values of G. From the results, four distinct flow patterns emerge: single bluff body flow, flip flopping flow, modulated synchronized flow, and synchronized flow, each exhibiting unique characteristics. This study reveals the strong dependence of fluid forces on G, with low spacing values leading to complex vortex structures and fluctuating forces influenced by jet flow effects. At higher spacing values, proximity effects between cylinders diminish, resulting in a smoother periodic flow. The Strouhal number, average drag force and the rms values of drag and lift force coefficients vary abruptly at narrow gaps and become smooth at higher gap ratios. Unlike the tandem and side-by-side arrangements the staggered cylinders arrangement is found to have significant impact on the pressure variations around both cylinders. Overall, this research could contribute to a comprehensive understanding of staggered cylinder arrangements and their implications for engineering applications. [ABSTRACT FROM AUTHOR]

The single spiral profile and the single spiral-double roundness profiles extraction strategies of cylindrical feature were promoted. According to the definitions of cylinder's global sizes, their evaluation models were established based on two extraction strategies. The axis parameters of the reference cylindrical surface for two extraction strategies were determined by using the artificial ecosystem-based optimization algorithm, the program flowchart of which was given. Through the profiles' extraction of one sample and evaluation of global sizes, the correctness of the established evaluation models and the availability of the developed program were verified. The optimal eigenvalues of nine optimization algorithms showed that the artificial ecosystem-based optimization algorithm is one of the optimization algorithms suitable for evaluating cylinder's global sizes. [ABSTRACT FROM AUTHOR]

The study of the flow around the cylinder is still a focus of research in various aspects. In this case, the flow around an electrically heated cylinder with a diameter Ød=10 mm is investigated at low velocities (mainly in the laminar range). In the literature, the wall temperature Tw is used in many places to characterize such flows. This is usually considered constant, because experimental tests are mainly performed with electrically heated rods of small diameter (max ~2 mm). Since in our case the rod diameter is a multiple of this, the question arises whether the two-dimensional nature of the flow behind the cylinder is preserved. The spanwise effect behind a transversely placed heated cylinder was investigated. The results obtained provide a good basis for designing further measurement options. [ABSTRACT FROM AUTHOR]

The article presents the results of experiments performed in order to investigate the relevant, though understudied, issues concerning the contribution of various sources of oil supply to the friction of the cylinder piston group (CPG) of a piston engine with a conventional crank mechanism (CM); the relationship between the oil amount supplied to the area of movable contact of parts and their frictional losses. The methodology and equipment used in the experiments are described, and the measurement errors of the control values are estimated. The experimental results enabled identifying the dominant source of oil supply to the CPG parts, as well as verified the reliability of previously obtained calculation data on the uneven distribution of the oil quantity on the loaded and unloaded sides of the cylinder wall. Furthermore, the hypothesis was confirmed that matching the oil quantity supplied to the friction area of the parts with the level of their dynamic loading contributes to minimizing the friction of these parts. Experimental methods and their results are proposed for use in the design and operation of lubrication systems, as well as for improving the efficiency and reliability of modern piston engines, including those operating as power units of electric generating sets. [ABSTRACT FROM AUTHOR]

Ultrasounds and their applications constitute fields of theoretical and practical research with applicability starting with the military, medicine, automotive industry, and ending with household appliances. The use of ultrasonic field in the cross‐linking of epoxy resins reduces the time required to produce composite structures, independent of the type of reinforcing components used. Brake cylinders, made by successive deposition of two layers of epoxy resin and quartz sand used in applications where frictional forces are very high, constitute a challenge for composite structures. The article presents the analytical calculation and the design of the ultrasonic system used in making a sample made of metallic base material and two layers of epoxy resin reinforced with quartz sand. Using this new proposed technology, there is a substantial reduction in the time required to solidify the structure and the elimination of the need for a high temperature necessary to carry out the traditional technological process. [ABSTRACT FROM AUTHOR]

The hypothesis of curved models is used to calculate the flow around a cylinder performing damped rotational oscillations in the air flow. The influence of a disk coaxially fixed in the head of the cylinder on the oscillations is studied. The elongation of the cylinder (the ratio of the length of the cylinder to its diameter) is nine. The diameter of the disk is equal to 0.6 of the diameter of the cylinder. It is assumed that the only reason for the damping of on the oscillations is aerodynamic force. The parameters characterizing the attenuation of rotational on the oscillations of the cylinder occurring in the air flow at the Reynolds number Re = 750 are determined. It turned out that the presence of a coaxial disk in the head leads to a faster attenuation of on the oscillations. This fact is in qualitative agreement with the results of an experiment to determine rotational derivatives in a wind tunnel at large Reynolds numbers. The hypothesis of quasi-stationary is applied in the calculation of translation vibrations of the cylinder. The parameter characterizing the damping of vibrations of a cylinder with a disk in absolute magnitude slightly exceeds the same parameter for a cylinder without a disk, which corresponds to the results of the experiment. [ABSTRACT FROM AUTHOR]

In this paper, we give multiple situations when having one or two geometrically distinct closed geodesics on a complete Riemannian cylinder, a complete Möbius band or a complete Riemannian plane leads to having infinitely many geometrically distinct closed geodesics. In particular, we prove that any complete cylinder with isolated closed geodesics has zero, one or infinitely many homologically visible closed geodesics; this answers a question of Alberto Abbondandolo. [ABSTRACT FROM AUTHOR]

It is shown that the front of the flame of a thoroughly mixed diluted methane-oxygen mixture at 298 K and 100–300 Torr propagating to the ends of hollow cylindrical and conical obstacles does not form a von Kármán path (vortex shedding) behind them; however, this instability occurs under the same conditions in the flow of hot products after obstacles. The reason that vortex shedding is not observed behind an obstacle during flame propagation but appears in the course of propagation of a reflected stream of hot products is that thermal conductivity reduces the curvature of the flame and leads to its stabilization. Indeed, the convex areas of the chemical reaction zone in a combustible mixture give off more heat in relation to cold ones than in a flat flame: the heat from them is not only transmitted forward in the direction of flame propagation but also in the lateral directions. The resulting cooling of the reaction zone causes the flame regions that burst forward to lag behind. The opposite situation is observed in concave areas, where the temperature rises for the same reasons. The rate of reactions increases and they spread forward faster as the flame spreads. Thus, the surface of the curved front of the flame is evened out. In other words, thermal conductivity has a stabilizing effect on a curved flame. This effect is missing in non-reactive gas. This effect is absent in a nonreacting gas. Calculations based on the acoustic approximation of the Navier–Stokes equations for a compressible reacting medium make it possible to take into account the main observed feature of the flame front approaching an obstacle in the form of a cylinder: vortex shedding is not observed behind the obstacle during flame propagation. Thus, a qualitative model allows obtaining both the mode of the emergence of a von Kármán instability in a chemically inert gas and its absence during flame propagation. [ABSTRACT FROM AUTHOR]

The density of the ocean is unevenly distributed along the depth direction, showing a stratified structure. When there is an external disturbance, large-scale internal solitary waves are easily generated. The internal solitary waves are bounded by the intermediate pycnocline, and the currents in the upper and lower layers will flow in opposite directions. This generates strong shear forces that threaten the safety of marine structures. In this paper, the flow field distribution characteristics of a cylinder under the action of internal solitary waves at different scales are analyzed as a research object. The whole cylinder is discretized into 40 regions, and the horizontal force applied to each section of the cylinder is extracted. The force characteristics of the cylinder are analyzed. It is concluded that the pressure is the main factor determining the magnitude of the total combined force. In addition, the paper extracts the main flow structures from the modal decomposition point of view and explains the reasons affecting the force behavior of the cylinder. [ABSTRACT FROM AUTHOR]