Symmetrical Feeding Research Articles

The fluid dynamics of barnacle feeding.

Sessile barnacles feed by sweeping their basket-like cirral fan through the water, intercepting suspended prey. A primary component of the diet of adult barnacles is copepods that are sensitive to fluid disturbances and capable of escaping. How do barnacles manage to capture copepods despite the fluid disturbances they generate? We examined this question by describing the feeding current architecture of 1 cm sized Balanus crenatus using particle image velocimetry, and by studying the trajectories of captured copepods and the escapes of evading copepods. We found that barnacles produce a feeding current that arrives both from behind and the sides of the barnacle. The flow from the sides represents quiescent corridors of low fluid deformation and uninterrupted by the beating cirral fan. Potential prey arriving from behind are likely to encounter the cirral fan and, hence, capture here is highly unlikely. Accordingly, most captured copepods arrived through the quiet corridors, while most copepods arriving from behind managed to escape. Thus, it is the unique feeding flow architecture that allows feeding on evasive prey. We used the Landau-Squire jet as a simple model of the feeding current. For the Reynolds number of our experiments, the model reproduces the main features of the feeding current, including the lateral feeding corridors. Furthermore, the model suggests that smaller barnacle specimens, operating at lower Reynolds numbers, will produce a fore-aft symmetric feeding current without the lateral corridors. This suggests an ontogenetic diet shift from non-evasive prey to inclusion of evasive prey as the barnacle grows.

Study on the effects of manifold structure on the gas flow distribution uniformity of anode of PEMFC stack with 140-cell

The gas maldistribution of the large proton exchange membrane fuel cell (PEMFC) stack leads to the deterioration of power performance. This numerical investigation studies the gas flow rate distribution in anode of two U-type stacks (a 15-cell stack and a 140-cell stack) which are composed of the same type of unit fuel cells. The anode gas channels of the two stacks are regarded as porous medium whose characteristic parameters are determined from pressure drop test data. To consider the nitrogen permeation from cathode to anode gas channel during the purging process, an expression of an additional momentum source term is proposed which helps to better fit the simulation results with pressure drop test data. Results show that the anode of the 140-cell stack has a quite good flow distribution uniformity. However, its asymmetric feed header of the manifold structure still has some negative effect. The same 140-cell stack installed with a rotational symmetric feed header is investigated and the simulation result shows that it can reduce the original maximum non-uniformity by about 50%.

Metamaterial-Based Low-Profile Broadband In-Band Full-Duplex Antenna

A low-profile wideband antenna with extremely high isolation is proposed for in-band full-duplex applications. It is designed in a coplanar structure with a periodic array of non-uniform metamaterial cells, a hook-like feeding probe, and four mushroom-like structures. The non-uniform metamaterial cells are excited by a hook-like feeding probe to achieve horizontal polarization. Meanwhile, two slots at the end of the ground are coupled with microstrip feed lines for vertical polarization. As a result, leakage currents between two symmetrical feed structures are suppressed to realize high isolation in wide operation bandwidth. Furthermore, four mushroom-like structures are embedded in the corners of the metamaterial cells to improve bandwidth and isolation. Measured results demonstrate that the proposed antenna with a low profile of 0.06 λ <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">0</sub> (λ <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">0</sub> is the wavelength at the center frequency of the operating band) achieves a -10 dB impedance bandwidth of 24.5% from 3.20 GHz to 4.09 GHz and a high Rx/Tx isolation of more than 50 dB. The proposed design has the merits of low profile, wideband, high isolation, and simple feeding structure, which makes it a competitive candidate for in-band full-duplex applications.

A Semi-Elliptical UWB Folded Dipole Antenna

In this paper, a novel structure of a semi-elliptical folded dipole for ultra-wideband (UWB) receiving applications is discussed. This proposed antenna has a directive radiation pattern resulting in a high gain over the bandwidth. The design uses a planar technology including a microstrip line to slot line transition and optimized curves to obtain a measured impedance bandwidth of 2.3–26 GHz with the condition of S11 &lt; −6 dB (level accepted for receiving antenna) and meets S11 &lt; −10 dB in several bands. Additionally, the simulated gain ranges from 5 dBi to 9.5 dBi across the entire bandwidth with an efficiency of at least 75%. This antenna model offers a reconfiguration capability. The symmetrical feeding used in this antenna creates the directive behavior. Characteristics of this semi-elliptical folded dipole antenna make it suitable for modern wireless communications, such as 5 G around 3.5 GHz, and easy to integrate in antenna arrays (MIMO systems). The four ports of the antenna also make it a candidate for radiation pattern reconfigurability applications reducing in this way the number of elements in network antennas.

Metamaterial-Based Pattern-Switchable Linear Array for 2-D Discrete Beam-Scanning Using Hybrid Digital Coding Method

A new low-cost, pattern-switchable, metamaterial-inspired, dielectric resonator (DR) 1-D linear array for 2-D beam-steering is presented by using a hybrid digital coding method. By loading the metasurface on the DR, a low-profile DR radiator is developed. To realize both phase and pattern digital coding, a beam-switching metasurface-loaded 1 bit DR antenna is explored by using a symmetrical feeding scheme and a Yagi-like endfire radiation mechanism. The novel hybrid digital coding method is realized by using p-i-n diodes to co-control the phase (1 bit, 0°/180°) and radiation states (three-beam). Based on the hybrid digital coding method, the developed 1-D linear array creatively achieves low-cost quasi-2-D discrete beam scanning. The pattern reconfiguration technique contributes to the E-plane beam scanning, while the H-plane beam steering is attributed to the phase digital coding sequence. To validate this working mechanism, a four-element linear array is implemented and tested. The realized overlapped −10 dB impedance bandwidth is about 17.6% (covering LTE B42/43 bands), and the realized peak gain is 9.05 dBi. By controlling the switch states of 16 p-i-n diodes, the proposed four-element linear array achieves digital 2-D beam steering (12 beams). The presented antenna features a miniaturized size, wideband, low cost, and good 2-D beam-steering capacity. It provides a new and feasible solution for low-cost 2-D beam scanning, demonstrating a good application potential for intelligent communication systems and low-cost arrays.

METHOD OF DESIGNING ANTENNAS BY SYNTHESIS OF A BAND FILTER

A novel antenna design technique is proposed, which offers bandwidth enhancement up to the limits defined by element radiation efficiency. The employed technique is referred as frequency pulling (FP) as it mimics the insertion loss design methodology of bandpass filters. This is essentially a wideband matching approach pushing the antenna efficiency to the limits set up by radiation efficiency. There are three options towards this trend: (1) first to enhance a single element bandwidth (compact element) exploiting its possibly multiple symmetrical feeding points as distinct resonator ports, (2) frequency pulled array as to design a small antenna array (less than about 10 elements) where eachelement acts as a resonator and (3) second order frequency-pulled array as to build a small array using compact elements of category (1). Similar to the band-pass filter design, all antennas or distinct-port circuits resonate at the same resonant frequency when isolated, cascading two or more of them; FP yields to multiple-overlapping successive resonances in their overall response. Although the proposed technique is general within this first effort, it is applied to simple patch antenna elements exhibiting multiple symmetrical feeding points, namely two-for rectangular, four-for square and five-for pentagonal. The third option is applied to an array of three compact 4-feeding point square elements offering triple bandwidth with respect to the already wideband single element. However, this is achieved at the expense of a significant beam squint. Thus, in general, these wideband compact elements should be used within a classical array design. Further bandwidth enhancement using FP to antenna elements with inherent multiple resonances as patches with slots or truncated edges constitutes our next task. Their inherent wider bandwidth in radiation efficiency is expected to allow multiply higher bandwidths when exploited with our FP technique.

Investigation of the effects of intermediate reservoirs and intermediate feedings applications on the performance of proton exchange membrane fuel cells

This study presents the design principles and details of a new flow field based on the shape and reflex similarity of the circulatory systems of living things. This design has intermediate reservoirs that collect and distribute the flow channels and also allow for intermediate feedings. This design is applied to a proton exchange membrane fuel cell, and its performance is tested and compared with a conventional serpentine type of flow channel. The novel fuel cell with intermediate reservoirs reaches a current density of 0.171 A/cm2 at 0.406 V and displays a power density 10 % higher than the serpentine flow field. Moreover, eleven cases involving symmetrical and asymmetrical feeding arrangements are also examined. The case of 70 %, 20 % and 10 % symmetrical feeding at the main and intermediate inlets shows the highest performance by providing a 38 % higher power density compared to the serpentine flow field.

A Planar 4-Bit Reconfigurable Antenna Array Based on the Design Philosophy of Information Metasurfaces

Inspired by the design philosophy of information metasurfaces based on the digital coding concept, a planar 4-bit reconfigurable antenna array with low profile of 0.15 λ 0 (where λ 0 is the wavelength) is presented. The array is based on a digital coding radiation element consisting of a 1-bit magnetoelectric (ME) dipole and a miniaturized reflection-type phase shifter (RTPS). The proposed 1-bit ME dipole can provide two digital states of “0” and “1” (with 0° and 180° phase responses) over a wide frequency band by individually exciting its two symmetrical feeding ports. The designed RTPS is able to realize a relative phase shift of 173°. By digitally quantizing its phase in the range of 157.5°, additional eight digital states at intervals of 22.5° are obtained. To achieve low sidelobe levels, a 1:16 power divider based on the Taylor line source method is employed to feed the array. A prototype of the proposed 4-bit antenna array has been fabricated and tested, and the experimental results are in good agreement with the simulations. Scanning beams within a ±45° range were measured with a maximum realized gain of 13.4 dBi at 12 GHz. The sidelobe and cross-polarization levels are below –14.3 and –23 dB, respectively. Furthermore, the beam pointing error is within 0.8°, and the 3-dB gain bandwidth of the broadside beam is 25%. Due to its outstanding performance, the array holds potential for significant applications in radar and wireless communication systems.

CFD-DEM Simulation of Particle Fluidization Behavior and Glycerol Gasification in a Supercritical Water Fluidized Bed

In this study, a mathematical model of hydrogen production from glycerol gasification in supercritical water was established based on the CFD-DEM method. The fluidization process of a supercritical water fluidized bed and the effects of bed height and feed structure on particle distribution and residence time of feedstock were analyzed. Additionally, the temperature field in the fluidized bed, the reaction rate distribution of each reaction and the influence of wall temperature on gas yields were also studied. The simulation results show that the bubble channel is easy to form along the wall at one side of the feed inlet. When the initial bed height is high, and the double symmetric feed inlet structure is used, the residence time of the feedstock is prolonged. The pyrolysis of glycerol mainly occurs in the middle and lower part of the fluidized bed reactor, and the reaction rate of the water gas shift reaction and methanation reaction are highest near the outlet, and a high wall temperature is conducive to the glycerol gasification.

COMPARATIVE ANALYSIS OF TECHNICAL AND ECONOMIC INDICATORS OF THE OPERATIONAL EFFICIENCY OF MACHINES FOR ANTI-ICE TREATMENT OF PAVEMENTS

The article touches upon one of the most important problems associated with the winter maintenance of road construction elements (sidewalks, footpaths), namely, winter street injuries of pedestrians. As one of the possible solutions to this problem, a disk distributor with a symmetrical method of supplying solid anti-icing material to the disk is proposed for operation, which provides a better distribution compared to the traditional asymmetric method of supply. It is assumed that this equipment will be installed on the base machine – a typical distributor of anti-icing materials along the carriageway. The article carried out a comparative technical and economic analysis and evaluation of the technical and economic indicators of the operation of machines in order to select the most effective combination of machines for de-icing the roadway and sidewalks. Six models of machines were selected for analysis, similar in their technical characteristics to real machines used for the distribution of solid anti-icing materials. As a criterion for the efficiency of operation, the cost of production of work, the annual volume of work and operational shift productivity were chosen. As a result of the analysis, it was found that the operation of combinations of machines, including a disk distributor with a symmetrical feed method, will allow achieving higher technical and economic indicators due to a slight increase in the cost of production of anti-icing coatings.

Electrochemical Impedance Spectroscopic Investigation of Vanadium Redox Flow Battery

The kinetics of redox reactions relevant to vanadium redox flow battery (VRFB) is investigated using voltammetry (CV) and electrochemical impedance spectroscopy (EIS) in a three-electrode configuration and in a VRFB setup (two-electrode configuration). Impedance spectra are recorded in the VRFB setup with equimolar concentration of V5+/V4+ and V3+/V2+ solutions as positive and negative electrolytes, respectively (full-cell; asymmetric feed system); with an equimolar V5+/V4+ electrolyte on both sides (symmetric feed system 1); and also with V3+/V2+ electrolyte on both sides (symmetric feed system 2). Impedance of the full-cell VRFB (recorded with asymmetric feed system) is comparable to the sum of the half of the impedance of symmetric feed systems (of V5+/V4+ and V3+/V2+ electrolytes) at open circuit potential (OCP). Impedance and voltammograms recorded in the three-electrode configuration using Vulcan XC-72 modified rotating disk electrode, and the impedance recorded in the two-electrode full-cell configuration unequivocally confirms that the V5+/V4+ redox reaction limits the VRFB performance. The optimal performance of the VRFB with the in situ treated carbon felt compressed to 47% is ∼389 and ∼336 mW cm−2 with 5 and 25 cm2 cell area, respectively.

Design and Analysis of Metamaterial-Based SWB-MIMO Antenna

The design and analysis of a four-port multi-input multi-output (MIMO) super wideband antenna (SWB) with a metamaterial superstrate are proposed. Initially, a single antenna is constructed with a hexagonal radiator loaded with dodecagon slots along with a slotted partial ground. An impedance bandwidth of 4.1–14.7 GHz is achieved by using symmetric coplanar waveguide feeding technique and three iterations of dodecagon slot-loaded radiating element. The design is extended to a 2 × 2 MIMO antenna with dimensions 50 × 50 × 1.6 mm3. The four symmetrical SWB antennas are placed orthogonally to each other at four corners of a square-shaped FR4 substrate. A metamaterial superstrate is used above the four-port antenna to increase the antenna’s performance characteristics. A 7 × 7 array of rectangular metamaterial unit cells acts as a building block for the metamaterial superstrate to improve impedance matching, enhance isolation between the elements, and boost the antenna’s gain. The metamaterial unit cells are made up of three rectangular rings that are put on top of a 1.6 mm thick FR4 substrate. With a mutual coupling of (>15 dB), the antenna achieved S11 < −10 dB for an impedance bandwidth of 11 GHz. The gain enhancement of up to 1.73 dB is obtained in C and X bands using metamaterial superstrate. The antenna characteristics mainly peak gain, return loss, bandwidth, and isolation are examined. The simulated results affirm a decent deal with experimental results.

Bandwidth enhancement of antennas designed by band‐pass filter synthesis due to frequency pulling techniques

A novel antenna design technique is proposed, which offers bandwidth enhancement up to the limits defined by element radiation efficiency. The employed technique is referred as frequency pulling (FP) as it mimics the ‘insertion loss design methodology of band-pass filters’. This is essentially a wideband matching approach pushing the antenna efficiency to the limits set up by radiation efficiency. There are three options towards this trend: (i) first to enhance a single element bandwidth (compact element) exploiting its possibly multiple symmetrical feeding points as distinct resonator ports, (ii) frequency pulled array as to design a small antenna array (less than about 10 elements) where each element acts as a resonator and (iii) second order frequency-pulled array as to build a small array using compact elements of category (i). Similar to the band-pass filter design, all antennas or distinct-port circuits resonate at the same resonant frequency when isolated, cascading two or more of them; FP yields to multiple-overlapping successive resonances in their overall response. Although the proposed technique is general within this first effort, it is applied to simple patch antenna elements exhibiting multiple symmetrical feeding points, namely two—for rectangular, four—for square and five—for pentagonal. The third option is applied to an array of three compact 4-feeding point square elements offering triple bandwidth with respect to the already wideband single element. However, this is achieved at the expense of a significant beam squint. Thus, in general, these wideband compact elements should be used within a classical array design. Further bandwidth enhancement using FP to antenna elements with inherent multiple resonances as patches with slots or truncated edges constitutes our next task. Their inherent wider bandwidth in radiation efficiency is expected to allow multiply higher bandwidths when exploited with our FP technique.

Design of miniaturized dual-polarized dipole antenna for 4G &amp; sub-6 GHz 5G applications

Abstract Dual-polarization, enhanced gain and compact size is the basic need of the base station antennas whereas a modern communication system needs a wideband antenna which can cover both the LTE &amp; 5G applications. In the present work, a cross dipole antenna is proposed for LTE &amp; sub 6 GHz 5G frequency band for Base Station Antenna Applications. By introducing asymmetrically shaped pentagon slots in the dipole and open-loop dipole patches, wide impedance bandwidth of 1.65–4.05 GHz at a return loss of −14 dB are achieved for 4G &amp; 5G applications. Two symmetric feeding lines orthogonal to each other have been used to obtain the dual-polarization. Also, a high stable gain of 7 ± 1 dBi &amp; HPBW of 80 ± 5° was achieved over the entire operating band at both the ports due to the symmetric structure. The proposed antenna is compared for size and bandwidth with the structures already proposed in the literature and significant enhancement is observed to be used for Base station antennas.

Design of Broadband Dual-Polarized Rectenna Array for WPT Applications

A broadband dual-polarized microstrip array antenna designed is proposed. To achieve wide 10 dB bandwidth for broadband operation, the technique of applying a ladder-shaped monopole antenna type with a rectangular slot insertion in the ground plane is implemented. The proposed design showed wide impedance bandwidth of the 1702-2755 MHz (47.2%). In addition, adding an open slot into the rectangular radiating element with an asymmetric ground plane was used and resulted in a slightly displacement of the radiation pattern. The 1 × 2 array type for two ladder-shaped patch array elements are arranged in symmetric feed network. By meticulously arrangement the two array antennas’ positions to achieved good ports isolation, with 10 dB bandwidth for the operating bands in free-space can be achieved. This antenna is used as a rectenna (rectifying antenna), which receives the RF energy of vertical and horizontal polarization wave in free space for 2.4 GHz wireless power transmission. The rectifier circuit setup using two zero biased rectifier and voltage doubler circuit. A matching network designed with small size chip components have a significant improvement in impedance matching and eliminate high order harmonics between the antenna and rectifying circuit. The proposed dual-polarized rectenna provided the RF-to-DC conversion efficiency as high as 78.8% when 14 dBm microwave power was received at 2.4 GHz with a 1 KΩ load.

A Reconfigurable Polarization—Frequency Supershape Patch Antenna with Enhanced Bandwidth

In this article a reconfigurable antenna for WLAN/WiMAX applications is presented. A super-shape radiator of an ellipsis shape is used to achieve wider intrinsic bandwidth compared to the classical rectangular patch antenna, while the dimensions remain comparable. The proposed antenna is fed at two points exciting both horizontal and vertical polarization but in different operating frequencies. To achieve wider bandwidth, as a whole but also for each polarization, the symmetrical feeding points for each excitation are also employed with a proper feeding network. PIN diodes are also used in the feeding network to provide the option of narrower bandwidth. The antenna substrate is Rogers RO4003C with dielectric constant εr = 3.55 and dissipation losses tanδ = 0.0027 with height h = 1.524 mm. The antenna operates in the range of 2.3 GHz to 2.55 GHz but, using the proposed procedure, it can be designed for different frequency ranges.

Tribological Behaviour of Additively Manufactured Fiber-Reinforced Thermoplastic Composites in Various Environments.

Polymer composites with increased utility properties are becoming competition for conventional materials, in conjunction with additive manufacturing techniques. The aim of this study was to evaluate tribological characteristics of fibrous composites produced in fused deposition modeling (FDM) with the use of an innovative head with symmetrical feeding of the matrix material. Analysis of the influence of composite-forming temperature on their tribological properties allowed the determining of the optimal printing process parameters for this group of composites. Significant differences in the friction process of the same reinforced materials were observed in dry and wet environments. Fibrous composites showed 10 times lower wear intensity as well as two times lower friction value in water than in air. Research shows friction in the water environment ensures more even wear of the surface of the composites involved in the work. The article contains 3D microscopic imaging of the friction plane of the tested composites and a description of a typical course of material wear is described.

DESIGN OF DUAL BAND PATCH ANTENNA AT KU-BAND FOR WIRELESS APPLICATIONS

In this paper, U-shaped patch antenna with triangular stub antenna is proposed for satellite and radar applications. The U-shaped with triangular stub structure is considered on the patch antenna with symmetric feed is presented on the substrate. The antenna design is impressed on FR4_Epoxy substrate material whose dielectric constant is 4.4. The adopted antenna resonates dual band frequencies at 14.1049GHz and 15.1610GHz which are used for satellite communications and 16.9363GHz and 17.7903 GHz which are used for radar communications. The parameters of antenna like gain, reflection coefficient, radiation pattern and bandwidth are analyzed and presented in the results. The adopted design achieves gain of 5.18dB and reflection coefficient of -28.75dB at 14.1049GHz, gain of 3.79dB and reflection coefficient of -16.31dB at 15.1610GHz, gain of 3.40dB and reflection coefficient of -16.45dB at 16.9363GHz and gain of 4.17dB and reflection coefficient of -15.93dB at 17.7903GHz.

A surface wave exciter adapting to different‐diameter lines and its application to single power line communications

A surface wave exciter adapting to different-diameter lines for single power line communications is proposed in this article. A side-feeding structure is designed which enables surface wave communication on existing power lines without any damage. The proposed surface wave exciter is mainly composed of a horn, two symmetrical feeding structures, a separable feeding ring, and a separable short-circuit metal ring. In order to avoid high order modes caused by insufficient excitation of side-feeding structure, two-port feeding structure is proposed. Meanwhile, the impedance matching of the exciter is improved. The exciter is designed to adapt to several lines with different diameters by using the separable feeding ring and short-circuit metal ring. Two prototypes for the proposed design are fabricated and tested. The measured results indicated that the input reflection coefficients ( S11) are less than −10 dB and the efficiencies are better than 30% in the Sub-6 GHz wireless communications. Moreover, a single power line communication system, which uses surface wave to transmit signal, is set up and tested. The transmission loss and the throughput are investigated to further prove the reliability of single power line surface wave communications.

Physical modelling of fluids’ interaction during liquid steel alloying by pulse-step method in the continuous casting slab tundish

ABSTRACT The continuous steel casting process is characterised by physico-chemical phenomena that are considered in the macro- and microscale. This paper attempts to assess the impact of local changes in the hydrodynamics of liquid steel flow in a one-strand slab tundish on the behaviour of the alloy addition, and consequently, the chemical homogenisation of the liquid steel entering the mould. Four variants of feeding the alloy addition to the liquid steel were considered. Water glass model was used for laboratory experiments. A tracer was fed into the water using the pulse-step method. Based on the mixing curves, the mixing time was calculated. Based on the laboratory experiments carried out, it has been found that, the alloy addition feeding site affects the mixing time, both for symmetric and asymmetric feeding relative to the longitudinal axis of the tundish.