Cylinder Spacing Research Articles

Спектри власних хвиль плазмового твердотільного циліндра в сильному поздовжньому магнітному полі

Subject and Purpose. Eigenwave studies of various bounded structures make a prolific line of investigation in both modern radiophysics and solid-state and functional electronics. Conducting solids demonstrating plasma (semiconductor) properties attract particular attention. Owing to the high conductivity of semiconductors (as it is inversely proportional to the charge carrier effective mass that is smaller than the free electron mass), interest exists in propagation features of slow elliptical-polarization electromagnetic waves – helicons – in magnetized semiconductor waveguides. The present work aims to determine eigenwave spectra of a solid-state plasma cylinder in a strong constant concentric magnetic field. Methods and Methodology. The eigenwave theoretical study of a magnetoplasma cylinder in the free space is conducted in terms of Maxwell's equations. The motion equation of conduction electrons of a solid-state plasma is adopted with quasi-stationarity electromagnetic field conditions satisfied. The collision frequency of majority charge carriers is assumed substantially less than their cyclotron frequency. Results. The dispersion equation of a cylindrical solid-state plasma (semiconductor) waveguide has been obtained. It has been shown that a collisionless magnetoplasma waveguide supports propagation of bulk and surface helicons. The propagation is accompanied by the surface current flowing lengthways cylinder components. Charged particle collisions destroy the surface current and initiate additional (to helicons) H-type hybrid waves such that their phase velocities coincide with phase velocities of the helicons. It has been found that the nonreciprocity effect holds for the waveguide eigenwaves having identical field distribution structures but different azimuthal propagation directions, and it also does as soon as the external magnetic field changes its sense. Conclusion. The research results have deepened our understanding of physical properties of bounded structures with plasma-like filling media. More systematization has been added to the knowledge of eigenwave behavior of these structures in a quasi-stationarity electromagnetic field.

Image guidance based 3D vehicle detection in traffic scene

3D vehicle detection is a significant step for traffic scene understanding. Several recent works have achieved state-of-the-art performance with only LiDAR point clouds. However, there are still existing challenges due to the intrinsic limitations of lidar data. In this paper, we propose a novel 3D vehicle detection method, in which visual information is introduced to remedy the deficiency of sparse point clouds. Our method is composed of two stages. In first stage, a novel proposal generator with the guidance of visual information is proposed. In the proposal generator, 2D detected bounding boxes are registered with 3D candidates from LiDAR by calibrating and then weighted non-maximum suppression (WNMS) is applied to increase the confidence of proposals to remove redundant proposals. In second stage, to construct a box predictor, instead of sampling in a sphere space, a novel sampling with cylinder space for pointnet++ is leveraged to learn local features of the point clouds. Furthermore, to achieve a better balance between confidence and localization accuracy of boxes, an Intersection-over-Union (IoU) prediction branch is modified and attached to the network. We conduct multiple experiments on the KITTI 3D object detection dataset and compare our method with state-of-the-art methods. The comparison results show that our algorithm is effective and can improve the performance of 3D vehicle detection.

Fractional characterization of fluid and synergistic effects of free convective flow in circular pipe through Hankel transform

Although heat transfer by transient free convection has been investigated with different cross sections such as elliptical cones, rectangular or square ducts, and triangular plates, none of the analytical study of a circular cylinder in free space via fractional calculus approaches with sinusoidal conditions is explored. This manuscript presents fractional modeling of a circular cylinder to observe the heat transfer by transient free convection flow subject to the sinusoidal boundary conditions. The fractionalized mathematical model is solved via Hankel and Laplace transforms through two types of fractional calculus approaches called Atangana–Baleanu and Caputo–Fabrizio differential operators. The governing equations of the circular cylinder have been coupled for the sake of thermally interacting effects for knowing the hidden role of a particular geometry, viz., circular cylinder. In the literature, the analytic solutions for concentration, temperature, and velocity have been explored by means of Mittage–Leffler functions. The comparative investigation of heat transfer based on embedded rheological parameters such as the Prandtl number (Pr), Schmidt number (Sc), thermal Grashof number (Gr), and mass Grashof number (Gc) has been depicted as graphs via Atangana–Baleanu and Caputo–Fabrizio differential operators.

Natural convection heat transfer from two horizontal cylinders using a large lateral shearing interferometer

AbstractNatural convection heat transfer from two horizontal cylinders in the air was investigated experimentally and numerically. Two cylinders were spaced at 1.3, 1.8, and 2.7 cylinder diameters horizontally. The experiments were carried out by large lateral shear interferometry (LSI) for various Rayleigh numbers in the range of 103 to 104. Large LSI is common path interferometry with the advantages of simple structure, strong antivibration, and fewer required optical components. It is not necessary for LSI to perform a complex algorithm to restore wavefront with a large shear amount. Simple and infinite fringe interferograms of the cylinders heated from ambient temperature 282.15 to 723.15 K were obtained. A numerical simulation was carried out with ANSYS‐Fluent 18.0. The influence of two factors, the distance between the cylinders, and the Rayleigh number, on the heat transfer of two horizontal cylinders was examined. The average Nusselt number and local Nusselt number were determined from the experimental results and numerical results, respectively, and the two results were in good agreement. The rising direction for the plume flow pattern of each horizontal cylinder was no longer simply vertically upward but was inclined toward the central symmetry axis of the two cylinders. In addition, the heat transfer from a cylinder increased with the cylinder spacing at any Rayleigh number.

Periodic water waves through suspended canopy

Small-amplitude water waves passing through a suspended canopy is studied. The area of suspended canopy is modeled by an array of vertical rigid cylinders with periodic spacing. Assuming that the diameter of cylinders and their spacing are much smaller than the typical incident wavelength, the homogenization theory (method of multiple-scale perturbation) is applied to create coupled micro-scale (cylinder spacing) and macro-scale (wavelength) problems. The micro-scale problem describes turbulent flows within a unit cell of the cylinder array, being driven by the macro-scale pressure gradients. Employing the concept of averaged energy balance over a wave period, the micro-scale flows determine the eddy viscosity, which damps the waves in the macro-scale flows. Eigenfunction expansions method is used to solve the macro-scale problem, in which a complex frequency dispersion relation is solved numerically by a multiple successive approximation technique. The potential decomposition method, which can avoid solving a complex frequency dispersion relation, is also employed to validate the accuracy of the eigenfunction expansions method. Both methods yield accurate solutions. However, the eigenfunction expansions method is relatively straightforward and can unify the solutions for suspended canopy and emergent vegetation. A new set of flume experiments of waves through suspended canopy is conducted and experimental data are used to check present solutions. Very good agreement has been observed. Finally, the effectiveness of suspended canopy, submerged and emergent vegetation on wave attenuation is discussed.

Growth of antimony selenide solar absorber on micro textured substrates for efficient light trapping and enhanced optical absorption

We propose a method for substrate surface texturing with shallow micro structures (such as cylinders) made up of cross-linked SU8 2005 photoresist on glass substrates for conformal growth of thin films of functional materials. In this work, the textured substrates were used for the growth of antimony selenide (Sb2Se3) solar absorber and its properties were studied in comparison with films on plain glass substrates. Cross-linked SU8 2005 structures, i.e., an array of equally spaced cylinders having the dimensions of 100 µm/70 µm/40 µm diameter and 5 µm height, were introduced over an area of 20 mm × 20 mm on glass substrates via optical lithography process. Thin films of Sb2Se3 were grown above the textured surface using e-beam evaporation covering the glass-like resist structures underneath. Optical microscopy, scanning electron microscope (SEM) and optical profiler analyses confirm the morphological integrity of the Sb2Se3 absorber layer grown on textured substrates. Raman spectra were collected on plain and textured samples to probe the structural uniformity. The optical absorbance data of Sb2Se3 thin films grown on plain and periodically textured glass substrates were investigated using UV–Vis-NIR spectroscopy to study the effects of substrate texturing.

Gaia DR2 giants in the Galactic dust – I. Reddening across the whole dust layer and some properties of the giant clump

ABSTRACT We consider a complete sample of 101 810 giants with Gaia Data Realease 2 (DR2) parallaxes ϖ within the red clump domain of the Hertzsprung–Russell diagram in the space cylinder with a radius of 700 pc around the Sun and a height of |Z| = 1800 pc. We use the Gaia DR2 GBP, GRP, and Wide-field Infrared Survey Explorer W3 photometry. We describe the spatial variations of the modes of the observables GBP − GRP, GRP − W3, $G_\mathrm{BP}+5+5\, \log _{10}\varpi$, $G_\mathrm{RP}+5+5\, \log _{10}\varpi$, and $W3+5+5\, \log _{10}\varpi$ by extinction and reddening in combination with linear vertical gradients of the intrinsic colours and absolute magnitudes of the red giant clump. The derived clump median absolute magnitude in W3 agrees with its recent literature estimates. The clump median intrinsic colours and absolute magnitudes in GBP and GRP are derived for the first time at a precision level of 0.01 mag. We confirm the reliability of the derived clump absolute magnitudes, intrinsic colours, and their vertical gradients by comparing them with the theoretical predictions from the PAdova and TRieste Stellar Evolution Code, MESA Isochrones and Stellar Tracks, and Bag of Stellar Tracks and Isochrones. This leads us to the median age and [Fe/H] of the clump within |Z| < 1.7 kpc from the Galactic mid-plane as $(2.3\pm 0.5)+(3.2\pm 1.6)\, |Z|$ Gyr and $(-0.08\pm 0.08)-(0.16\pm 0.07)\, |Z|$ dex, respectively, where Z is expressed in kpc. These results agree with recent empirical and theoretical estimates. Moreover, all the models give similar age–metallicity relations by use of our results in the optical range. The derived extinctions and reddenings across the whole dust half-layer below or above the Sun converge to the reddening E(B − V) = 0.06 mag by use of the most reliable extinction laws.

Gaia DR2 giants in the Galactic dust – II. Application of the reddening maps and models

ABSTRACT We exploit a complete sample of 101 810 Gaia DR2 giants, selected in Paper I in the space cylinder with a radius of 700 pc around the Sun and a height of |Z| = 1800 pc, using the Gaia DR2 parallaxes, GBP and GRP photometry, and WISE W3 photometry. We explain the spatial variations of the modes of the observables GBP − GRP and GRP − W3 by the spatial variations of the corresponding reddenings described in the GM20 3D dust distribution model. Presented in this paper, GM20 is an advanced version of the model introduced by Gontcharov in 2009. GM20 proposes two intersecting dust layers, along the Galactic mid-plane and in the Gould Belt, with exponential vertical and sinusoidal longitudinal variations of the dust spatial density in each layer. The Belt layer is an ellipse, oriented nearly between the centre and anticentre of the Galaxy, and with semi-major and semi-minor axes of 600 and 146 pc, respectively. GBP − GRP and GRP − W3 give similar solutions, but different equatorial layer scale heights of 150 ± 15 and 180 ± 15 pc, respectively, and $(G_\mathrm{BP}-G_\mathrm{RP})_0=(1.14\pm 0.01)-(0.022\pm 0.010)\, |Z|$, $(G_\mathrm{RP}-W3)_0=(1.44\pm 0.01)-(0.015\pm 0.010)\, |Z|$, where Z is in kpc. We compare GM20 with several 3D reddening models and maps in their ability to predict the observed colour modes. GM20 and the 3D map by Gontcharov appear to be the best among the models and maps, respectively. However, the most reliable models and maps mainly disagree only in their estimates of low reddening, including the reddening across the whole dust layer.

Energy harvesting from and vibration response of different diameter cylinders

Energy harvesting from flow-induced vibrations (FIV) of an elastically-supported cylinder (diameter D) immersed in the wake of another cylinder with diameter d is systematically investigated. The diameter ratio of the two cylinders is d/D = 0.4. The incoming flow velocity considered is U∞ = 1.54–9.0 m/s, corresponding to Reynolds number Re = 3.3 × 103 to 1.95 × 104. A controllable magnetic damping system that can add harnessing damping ratio ξ is used to convert wind to electrical energy. The ξ is varied from 0.00091 to 0.00249. The cylinder spacing ratio L/d is varied from 1.0 to 4.0, where L is the distance from the upstream cylinder center to the forward stagnation point of the downstream cylinder. The vibration responses comprise combined vortex-induced vibration (VIV) and galloping vibration for small ξ and separated VIV and galloping for high ξ. The galloping offers harnessed power P three times larger than the VIV. The maximum efficiency η is 11.2–14.6% in the VIV regime but is only 1–2% and almost independent of reduced velocity Ur and ξ in the galloping regime.

Low-Frequency Acoustic Absorption of 3D Printed Cylinders

Abstract Attenuating low-frequency sound is often problematic, due to the large space required for common absorptive materials to mitigate such noise. However, natural hollow reeds are known to effectively attenuate low frequencies while occupying relatively little space compared to traditional absorptive materials. The present study determines the effect of varied outer diameter and outer spacing on the 200–1600 Hz acoustic absorption of 3D printed arrays of hollow cylinders. Samples were tested in a 100-mm diameter normal incidence impedance tube such that cylinder length was oriented perpendicular to the incoming plane wave. By varying only one geometric element of each array, the absorption due to any parameter can be assessed individually. It was found that minimizing cylinder spacing and maximizing cylinder diameter resulted in increased overall absorption and produced more focused absorption peaks at specific low frequencies. Wider cylinder spacing produced a broader absorptive frequency range, despite shifting upward in frequency. Thus, manipulating these variables can specifically target absorption for low-frequency noise that would otherwise disturb listeners.

Hyperbolic flowers

ABSTRACT Crochet models of a hyperbolic plane are very popular as they help to visualize complicated objects in hyperbolic geometry. We present another way to make crochet models as a part of a triangulated plane and also provide an example of a cylinder in hyperbolic space. This approach assists in understanding of various properties of hyperbolic geometry such as the relation between edges and angles in a hyperbolic triangle, tiling of a hyperbolic plane or Nash–Kuiper embedding theorem.

Development and Validation of 4 Stroke Marine Diesel Engine Numerical Model

Increasing demands on energy efficiency and environmental acceptance are being imposed on marine propulsion plants. The fulfilment of the conditions set by the MARPOL Convention, Annex VI, regarding the emissions from exhaust gases of marine diesel engines is of particular interest. This paper presents the development and validation of a zero-dimensional, single-zone diesel engine numerical model. Presented numerical model is based on the law of conservation of energy and mass and solving the resulting differential equations. The single-zone model will serve as the basis for a model where the cylinder space is divided into two or three zones during combustion. In this way, the multi-zone model will allow the modelling of nitrogen oxide emissions with satisfactory accuracy. Validation of the diesel engine model was carried out for the Wärtsilä 12V50DF 11700 kW motor designed to drive a synchronous alternator. Obtained results and deviations of certain parameters in the operation of the engine with respect to the data obtained from the measurements on the test bed, are more than satisfactory regarding complexity of the numerical model. This confirmed the usability of the model for research purposes to optimize the marine diesel engine.

Natural convection heat transfer from a bundle of heated circular cylinders with staggered arrangement immersed in molten solar salt

A two-dimensional steady-state natural convection heat transfer from a bundle of closely spaced isothermally heated cylinders in a staggered arrangement immersed in molten solar salt was investigated in this study for a laminar flow regime using numerical analysis. The flow and temperature fields and heat transfer from the cylinder bundle were predicted as functions of tube spacing and flow conditions. It was determined that flow patterns and heat transfer are strongly affected by the transverse and longitudinal cylinder-to-cylinder spacing ST and SL, Rayleigh number and thermo-physical properties of the heat storage fluid. Performance maps in the form of contour diagrams for the average Nusselt number Nu and dimensionless heat transfer volumetric density are presented for a staggered bundle of circular horizontal cylinders immersed in a molten solar salt.The variation of the heat transfer enhancement for the staggered bundle of horizontal cylinders shows that there is an optimal transverse cylinder spacing resulting in the highest heat transfer enhancement. The heat exchanger geometry was optimized by determining the optimal set of the tube (cylinder) spacings SL/D and ST/D in the bundle resulting in the maximum volumetric heat transfer rate q ̃, and smallest size, and lowest cost of a heat exchanger. A set of correlations were developed for the maximum and optimum dimensionless heat transfer volumetric densities as functions of the Rayleigh number RaD. The analyzed geometries are important in the solar heating and storage technology, nuclear reactor safety, and waste heat recovery applications.

Convective transport around two rotating tandem circular cylinders at low Reynolds numbers

The convective transport around two rotating circular cylinders kept in a tandem configuration to an unconfined flow of an incompressible fluid (Prandtl number, Pr = 0.717) is investigated through two-dimensional numerical simulation. The flow Reynolds number is considered constant at Re = 100. Four different gap spacings between the tandem cylinders such as 0.2, 0.7, 1.5 and 3.0 are chosen for simulation. The cylinders are rotating about their centroidal axes for a range of dimensionless speed $$ \left( {0 \le \Omega \le 2.75} \right) $$ . The rotation to the objects causes the unsteady periodic flow around them to become stabilized and at some critical rotational speed, the vortex shedding stops completely resulting in a steady flow pattern. The critical speed of rotation at which the vortex shedding completely stops is a function of the cylinder spacing. Overall, it is observed that increasing the gap increases the critical rotation rate. The thermal fields are also strongly stabilized as a result of the cylinder rotation. The rotating cylinders actually create a zone in their proximity which acts like a buffer to the convective transport. The conduction mode of heat transfer predominates in these regions causing the heat transfer rate to assume a decaying pattern with increasing the rotational speed at all cylinder spacings.

Inflatable penile prosthesis cylinders out of place during implantation.

It is safe to say that the overwhelming majority of cylinders out of place result from surgeon error at the time of implantation. There are some instances where patient comorbidities could increase the difficulty of accurate development of cylinder insertion or space. Most of the time the operator recognizes his instrument out of place and corrects it intraoperatively. Other times the surgeon makes a flawed movement with a sharp instrument piercing some tissue. When the cylinder is placed initially and inflated the wayward position is usually not evident. However, in the postoperative period, the inaccurate position of the cylinder(s) can become readily apparent. The reader will notice this repeatedly stressed in Wilson's Workshop-over 90% of cylinders that are out of position can be diagnosed or prevented if one utilizes the two safety checks outlined below.

Numerical Investigation of Flow around Two Tandem Identical Trapezoidal Cylinders

The trapezoidal beam structure is ubiquitous in giant engineering equipment, while their aerodynamic characteristics have not been clearly understood. Numerical simulation method was adopted to investigate the flow around two tandem identical trapezoidal cylinders. The study was conducted using a Reynolds number of 2.2 × 104, and with a spacing ratio varying from 0.5 to 10. The incompressible two-dimensional finite volume method was used for solving Reynolds-Averaged Navier–Stokes (RANS) equations with realizablek−εmodel. The effects of cylinder geometry and spacing between the cylinders on aerodynamic characteristics, unsteady flow patterns, time-averaged flow characteristics, and flow instability was studied. The results show that the flow around the two tandem trapezoidal cylinders is highly dependent on the spacing ratio. The flow modes can be classified into: extended-body regime (Mode I,S∗ ≤ 1), reattachment regime (Mode II, 2 ≤ S∗ ≤ 3), and binary regime (Mode III,S∗ ≥ 4). We explored their respective flow characteristics and distinctions through the force/pressure coefficients, time-average streamwise velocity, and the flow field evolution.

Abrupt Change Effect of Bandgap Energy on Quantum System of Silicon Nanowire

In the quantum system of Si nanowire (NW), the energy bandgap obviously increases with decreasing radius size of NW, in which the quantum confinement (QC) effect plays a main role. Furthermore, the simulation result demonstrated that the direct bandgap can be obtained as the NW diameter is smaller than 3 nm in Si NW with (001) direction. However, it is discovered in the simulating calculation that the QC effect disappears as the NW diameter arrives at size of monoatomic line, in which its bandgap sharply deceases where the abrupt change effect in bandgap energy occurs near the idea quantum wire. In the experiment, we fabricated the Si NW structure by using annealing and pulsed laser deposition methods, in which a novel way was used to control the radius size of Si NW by confining cylinder space of NW in nanolayer. It should have a good application on optic-electronic waveguide of silicon chip.

Investigation on the removal of suspended particles during internal rotating plasma spraying using numerical and experimental methods

Internal rotating plasma spraying (IRPS) plays an important role in improving the properties and prolonging the service life of internal parts and components of mechanical systems. IRPS is conducted in the confined and semi-enclosed spaces at a spraying distance of 30–70 mm to coat the engine cylinders of automobiles or heavy equipment. Occasionally, particles cannot be appropriately treated in the plasma flow, and owing to several factors, the particles remain suspended in the air rather than being deposited onto the substrate. Consequently, the suspended particles are difficult to remove efficiently within the confined space, and can thus have severe effects on the properties of coatings, including porosities and inclusions. It is therefore essential to develop appropriate methods to avoid defects in the coating by removing suspended particles inside the cylinder. In this study, numerical simulations were conducted to investigate the flow-velocity field and particle-mass-concentration distribution within the cylinder. The flow-velocity and particle mass concentration in the cylinder space were analyzed under different working conditions that can induce different suction pressures driven by a three-phase asynchronous motor connected to the bottom of the cylinder by a suction tube. The results showed that the flow-velocity field is symmetrical along the axis of the cylinder and the mass concentration of particle is concentrated on the region from middle to bottom of the cylinder, under the effect of the suction pressure. In addition, the low-velocity and high-particle-mass-concentration regions are mainly located in the vicinity of the internal wall. Furthermore, the flow velocity was measured using a hot-wire-anemometer and the coating microstructure was observed using scanning electron microscope (SEM). We compared numerical simulation results and experimental measurements, which validated the flow-velocity field directly and the distribution of particle mass concentration indirectly. Based on the numerical results that consider the removal degree of suspending particles and the stability of the plasma jet, it can be determined that the optimal suction pressure is −100 Pa for decreasing dust pollution during the spraying process.

Simulation Study on the Impact of Uneven Fuel Injection of Each Hole of the Diesel Engine Injector on the Combustion Process

The spray impulse and injection pressure of each hole of the 4-hole injector of F186 engine were tested by using the transient test system for flow coefficient and injection rate of each hole of the injector, and the injection rate, fuel injection quantity and flow coefficient of each hole were obtained. According to the measured injection rate of each hole and cycle fuel injection quantity, a 3D model of the diesel engine was established with the FIRE software, and the uniform injection rate and uneven injection rate of each hole were made as the injection setting for the combustion simulation to comparatively analyze the influence of the uneven injection rate of each hole on the combustion process of diesel engine. As the injection of each hole is uneven, some holes with high injection rate have long fuel spray penetration distance and the fuel spray is fully mixed with the air, and the ignition starting point is moved ahead. When compared with the case of uniform injection rate, the phase corresponding to the heat release rate in the case of uneven injection rate is moved forwards, the maximum cylinder pressure and temperature rise fast, the maximum cylinder pressure and maximum average temperature in cylinder are higher, the NO generation is larger, and the Soot generation is slightly larger. In the case of uneven injection rate from four holes, as the utilization of air in the hole-located cylinder space by the fuel spray is uneven, the hole with a large quantity of injection makes the oxygen in the hole-located cylinder space relatively low, the wall collision of the hole with high injection rate is more, and the diffusion combustion is incomplete and insufficient.

AN ANALYTICAL APPROXIMATION FOR THE LOCAL FLOW BETWEEN COUNTER-ROTATING CYLINDER PAIR

Flow around a pair of cylinders is of interest for various applications. Especially with the development of self-propelled, autonomous vehicles, this topic has gained further importance. There have been experimental, numerical and, to a much less extent, theoretical studies of this flow and its implications on the cylinders. However, the complexity of the problem does not allow a general solution, and case-by-case solutions have been produced. In this study, a theoretical approach was embraced, in which differential geometry is employed to model the local flow between a pair of counter-rotating cylinders. In order to obtain practical formulae for a steady, laminar, incompressible flow, Navier-Stokes equations were simplified and expressed in a new, parabolic coordinate system. Then, further simplifications due to the symmetrical nature of the problem were applied. Finally, boundary conditions were imposed while performing the integrals, and the desired equations for velocity and pressure were reached. Unlike the previous studies that are limited to very slow flows, the equations obtained in this study are applicable in the entire incompressible, laminar regime, albeit only between the cylinders. Using these equations, the effects of the rotation speed, cylinder spacing and cylinder radius were studied and presented graphically.