Back Ratio Research Articles

A dual-polarized reflector antenna with λ/2 printed dipoles for femtocell applications

A printed dipole antenna with reflector features a high gain. Accordingly a dual-polarized reflector antenna with high gain for base transceiver stations (BTS) is proposed. Design of this antenna is based on λ/2 printed dipoles supplied through Γ-shaped microstrip feed lines. The basic structure of the antenna is composed of two orthogonal radiating elements which are separately printed on two substrates. Each element has a λ/2 printed dipole on one side of the substrate and a 50 Ω Γ-shaped microstrip feed line on the other side. The combination of these two orthogonal radiating elements provides proper ± 45̂ dual-polarized characteristics for BTS applications. The radiating elements are placed on an aluminum slot reflector with side walls in order to make the antenna directional, and to increase the gain and the fron to back ratio (FBR) as well. A prototype of this antenna is manufactured and it covers the frequency range of 1.4–2.6 GHz due to the measured results. The average measured gain and half-power beamwidth (HPBW) are obtained 8.35 ± 0.55 dBi and 165̂, respectively.

Polarization reconfigurable slot antenna for 5.8 GHz wireless applications

A CPW-fed circular polarization reconfigurable antenna is proposed in this paper. The antenna consists of two symmetrically placed inverted L-shaped slots. By using a T-type bias device to change the bias states of two PIN diodes which connect the two slots with the feed port respectively, right-hand circular polarization (RHCP) and left-hand circular polarization (LHCP) can be realized accordingly. For both states, the measured −10 dB impedance bandwidth is 5.78–5.96 GHz, while the measured 3 dB axial ratio bandwidth is 5.64–5.91 GHz (4.7%), both the bandwidths can cover the 5.8 GHz ISM band. By using floating ground and reflector board to enhance the front to back ratio of the antenna, 6.84 dBi measured gain can be realized at 5.8 GHz.

Effect of short microwave heating time on physicochemical and functional properties of Bambara groundnut starch

Bambara groundnuts (Vigna subterranea) are a good source of starch that may be potentially used for various industrial applications. The effect of microwave heating time (0, 10, 30 and 60 s) on the physicochemical and functional properties of Bambara groundnut starch was investigated. Native and microwaved Bambara groundnut showed the A-type crystallinity pattern. However, there was a decrease in the relative crystallinity of the starch after microwaving. Microscopically, the native starch granules were smooth but had pinholes after microwaving. Microwaving resulted in significant (p ≤ 0.05) reduction in peak viscosity, hot paste viscosity, cold paste viscosity, pasting temperature and set back ratio. The swelling power of Bambara groundnut starch similarly decreased with increasing microwaving time. Microwave heating led to a shift in the gelatinization range to higher temperatures. However, the enthalpy of gelatinization decreased after microwaving. Short microwaving times (≤60 s) were sufficient to cause significant improvement in the pasting and thermal properties of Bambara groundnut starch. Microwaved Bambara groundnut starch with reduced swelling can be potentially used in food products that do not require high swelling such as noodles.

Critical back pressure ratio of critical flow Venturi nozzle with step diffuser

Critical back pressure ratio of critical flow Venturi nozzle with step diffuser

DEFECTED GROUND APPROACH TO REDUCE BACK RADIATIONS IN MAGNETO-ELECTRIC DIPOLE ANTENNA

An improved design of magneto-electric dipole antenna with high front to back ratio (FBR) for mobile base station is proposed. To reduce the back radiations in the antenna, semi oval defects in the ground plane has been proposed. The prototype antenna has achieved high FBR without much affecting the gain and bandwidth. The proposed antenna has achieved impedance bandwidth of 71.4% for the frequency range 1.8 GHz–3.8 GHz. The measured FBR varies from 21 dB to 29 dB with stable gain of 7.1 dBi and unidirectional radiation pattern with symmetrical E-plane and H-plane has also been obtained.

Spawning Potential Ratio of Feather Back (Chitala Lopis) at Kampar River, Riau

The feather back, Chitala lopis is an important economic fish, inhabit Kampar River and its population tend to decrease so that management and conservation efforts should be conducted. Limited data of the feather back is one of the problems in formulating the management of the population. Spawning potential ratio (SPR) approach is an option being used in the management of the fish stock in the poor data. The study aimed to analysis spawning potential ratio of the feather back in Kampar River, Riau. The research has been conducted in May, August and October 2016. The total length at first capture (Lc) of feather back was less than the total length at first maturity (Lm) with the SPR value of 5 %. This condition could impact to decreasing the feather back stock. The SPR value should increased more than 20 % so the feather back population would been stable. Regulation of the fisheries was mainly limited mesh size of the gillnet operated should be applied.

Study of mechanical choked Venturi nozzles used for liquid flow controlling

Motivated by the principles of the cavitating Venturi nozzle (CVN) used for controlling fluid flow and addressing limitations of CVN, this paper proposes a mechanical choked Venturi nozzle (MCVN) which achieves choking flow via a mechanical action. The MCVN is constructed by inserting a floating springed blockage into a Venturi nozzle to imitate the bubble dynamics of CVN. First, an initial MCVN design was derived theoretically. Then, using numerical simulation and an iterative procedure, this original design was corrected to build an optimized design. Finally, the optimized design was investigated and tested both numerically and experimentally. The experimental results show that the MCVN can maintain constant flow with a flow control error of 3.8% and a maximum back pressure ratio of 0.97. Since MCVN can achieve constant flow without fluid vaporization, the pressure ratio range for applying a choking flow device is expanded and some limitations of CVN are overcome. The principles and experimental results obtained in this research can be used as a framework for the design of improved constant flow control devices for liquid flow.

Microstructures and mechanical properties of fiber textures forming mesoscale structure of drawn fine high carbon steel wire

The crystal orientation of a drawn high carbon steel wire was analyzed through electron backscatter diffraction analysis under the assumption that the wire consists of a mesoscale structure characterized by the fiber texture. The microstructure forming the mesoscale structure and the mechanical properties depending on the mesoscale structure were explained by the results of transmission electron microscopy observation, measurement of the electrical resistivity, differential scanning calorimetry thermal analysis, and tensile testing. In the beginning of the wire drawing, the wire has only {100}<110>−{111}<110> (the primary fiber texture). Then, the wire has this orientation at the outer side and {110}<110>−{111}<110> (the secondary fiber texture) at the inner side. At a drawing strain larger than approximately 2.7, the subprimary fiber texture ({100}<110>−{111}<110>) is formed at the outer side and will occupy the volume of the wire. The results indicate that with the increase of the drawing strain, the lamellar spacing decreased, and the amount of lattice defects increased. The tensile strength, uniform elongation, and reduction of area were typically uniform in the radial direction of the wire. On the other hand, the wire with only the primary fiber texture had lamellae whose angle with respect to the drawing direction decreased during wire drawing, as well as a surface layer with low longitudinal ductility. The wire with the subprimary fiber texture contained decomposed cementite. The wire also had a large variation of reduction of area. Increasing the back stress ratio shifts the transition of the mesoscale structure to a lower drawing strain.

Compact four-element MIMO SIW cavity backed slot antenna with high front-to-back ratio

In this article, a novel design of single layer, compact, multiple input multiple output (MIMO) half-mode substrate integrated waveguide (HMSIW) cavity backed quad element slot antenna with high front-to-back ratio (FTBR) is proposed. The proposed antenna consists of four rectangular SIW cavities with semi-taper radiating slots. The antenna elements are placed in a fashion to achieve high isolation. This antenna is designed for WLAN vehicular communication system to cover the frequency range of 5.84 GHz to 5.96 GHz. It has high front to back ratio (FTBR) of more than 25 dB without using any external metallic reflector. It has more than 37 dB isolation in between orthogonal elements and more than 24 dB in between parallel elements. The envelop correlation coefficient (ECC) and diversity gain are 0.003 and 9.99 dB respectively in between all the elements. Moreover, the antenna has high gain and efficiency of more than 8 dB and 94%, respectively, in 10 dB impedance bandwidth. It can be tuned in a wide range of frequency.

Compact wide band directional antenna using cross-slot artificial magnetic conductor (CSAMC)

In this article a novel wide-band artificial magnetic conductor (AMC) based wideband directional antenna is presented for ultra-wideband (UWB) applications. The proposed novel cross-slot AMC (CSAMC) achieves wide ±90° reflection phase bandwidth of 4.07 GHz (44.69%) and is used as a reflector. The overall antenna structure is designed with 4 × 4 CSAMC unit cell array and has very compact size of (0.584λ0 × 0.584λ0). The proposed structure improves the radiation properties and exhibits 91.5% (3.13-8.41 GHz) impedance bandwidth (VSWR ≤2). Additionally, it results in significant improvement in gain and front to back ratio. The proposed antenna is fabricated and its measured performance is in good agreement with simulation results.

Control of Cowl-Shock/Boundary-Layer Interactions by Deformable Shape-Memory Alloy Bump

A deformable shape-memory alloy (SMA) bump is introduced to control the succeeding cowl-shock/boundary-layer interactions in a supersonic inlet with an operating Mach range of 2.0–3.8. The deformation characteristics and the control effect of the SMA bump are investigated by both experimental and numerical methods. It is found that the well-trained SMA bump can achieve the desired bump shape automatically. The total root mean square error between the actual SMA plate profile and the designed one is 0.05 times of designed bump’s height without aerodynamic load, whereas the value increases to 0.09 times of designed bump’s height at the end of the wind tunnel test. When the inlet operates at Mach 3.8 the shock-induced large separation is reduced substantially and transformed into two small-scale separation bubbles under the control of the deformable bump. The total pressure recovery of the bump controlled inlet is always higher than the uncontrolled one in the same back pressure ratio during the throttling process. The critical back pressure ratio of the controlled inlet reaches to 28, whereas the corresponding value of the uncontrolled inlet is only 23.

A compact multilayer wide-band and high-gain circularly polarized antenna

In this paper, we present a high-gain wide-band circularly polarized antenna that uses double circular radiation patches and a double Y-shaped slot fed by microstrip line. The antenna consists of four layers stacked on top of each other and spaced by air gaps. In proposed antenna a copper layer is used as a reflector for directing radiation patterns, increasing front to back ratio (FBR) and gain. Three other layers include radiation patches with the same dimensions. Second layer includes a microstrip feed line on one side and a double Y-shaped slot on its other side. Third and fourth layer include circular radiation patches for controlling the polarization and bandwidth of the proposed antenna. Right-hand circular polarization {is obtained by optimizing} the dimensions of the circular patches. {Measured frequency bandwidth ranges from 3.35 GHz to 6.45 GHz, with} an S11 less than -10 dB. {Moreover, axial ratio and gain} are less than 3 dB and more than 7.5 dBi, respectively.

The Effect of Adding Different Proportions of Ginger Powder on Production in Performance and Carcass Characteristics and Egg of Quail Strains

This study aimed to investigate the effect of adding different levels of ginger powder to the lying Quail rations of three strains (white, gray, black). 297 Quail bird (Coturnix coturnix japonica) were randomly distributed into 3 treatments with 3 and 3 strains, replications of 11 birds/ replication The addition of G.P to the treatments T1 (control), T2 and T3was (0,0.5 and 1%) respectively. The results revealed a significant increase (P≥0.05) in feed consumption and body weight at age of 5 weeks, and relative weight of chest, back and thigh as well as body and carcass weight, and significant increase (P≥0.05) in egg yolk weight and shell thickness in favor to T2. As for strain both white and black strain showed a significant increase (P≥0.05) in carcass percentage fragments, gnat ratio, carcass weight and fragment weights of chest, back and thigh compared to gray line, a significant increase (P≥0.05) in egg length and width in favor to black strain. while there were no significant differences of the ginger in average daily gain, coefficient of food conversion, gnat ratio, egg, white and shell weight respectively and egg white and yolk height between addition levels. As for the interaction between ginger addition and strain, the results revealed a significant differences (P≥0.05) in body weight and feed consumptions in fevor to interaction between gray, white strain, and between T2 and white, black strain of feed conversion efficiency and significant differences (P≥0.05) in egg width in favor to the interaction between T3 and gray strain, and egg produced for favor to the interaction between white strain and T1,T2, egg yolk and white weight and yolk height for favor to the interaction between B.S and both T1and T2. For shell thickness the interaction between W.S. and T1 was significantly superior (P≥0.05) than other treatments.

AMC loaded folded dipole with heart‐shaped radiation pattern

This Letter presents a novel pseudo-omnidirectional antenna that is appropriate for wide beam applications, e.g. handheld devices, along with a reduced back radiation that suits wearable applications as well. The design consists of a horizontal omnidirectional antenna placed on a proposed artificial magnetic conductor (AMC) surface that enhances the gain in the broadside direction, reduces the back radiation, and enables good radiation in the side directions. A 5 GHz folded dipole on a 2 × 2 AMC array surface is designed and characterised. Simulations and measurements, which are in a very good agreement, show that the radiation has a heart-shaped pattern, with a front to back ratio of >13 dB, a front to side ratio of 230°.

Gain Enhancement of Horn Antenna Using Meta Surface Lens

Three dimensional meta surface lens is proposed to improve the gain and beam shaping of horn antenna. Hence an array of SRR as a meta surface lens has been designed, fabricated and investigated. This meta surface lens can be used to convert the spherical wave to plane wave for a wide range of frequency. It is proved by permeability and permittivity of meta surface. In this work the operating bandwidth of the proposed antenna is in the range of 9GHz to 11GHz for satellite application. The radiation pattern of E and H plane is sharpened in this work. The antenna 3dB beam width, and front to back ratio were 9.2, 28dB at 10GHz. The radiation characteristics of horn antenna with meta surface have been studied numerically and confirmed experimentally, showing an average gain improvement of ~3dB with respect to horn antenna without meta surface lens.

Envisioning an Endfire Circularly Polarized Antenna: Presenting a Planar Antenna with a Wide Beamwidth and Enhanced Front-to-Back Ratio

We present a design approach to a novel nonturnstile planar endfire circularly polarized (CP) antenna with a widened beamwidth and an enhanced front-to-back ratio. This approach combines a semicircular magnetic dipole and a V-shaped open loop to widen the azimuthal beamwidth at first. Then, to further enhance the front-to-back ratio, the V-shaped loop is appropriately rotated with respect to its feed apex. The tradeoff between the azimuthal beamwidth and the front-to-back ratio is theoretically revealed based on the approximate closed-form radiation pattern functions. Antenna prototypes are simulated accordingly, and they are then designed and measured to validate the design approach. The measured impedance bandwidth for |S11| l-10 dB covers a frequency range of 2.25-2.5 GHz (10.5% in fraction), and the axial ratio (AR) bandwidth of l3 dB is 2.3-2.57 GHz (11.1% in fraction). The measured 3-dB AR beamwidths of the proposed antenna are equal to 180d and 115d in the elevational and azimuthal plane, respectively, at 2.35 GHz. In addition, the measured in-band average frontto- back ratio reaches up to 13.7 dB.

Investigation the scattering properties of silver nanowires with different densities

In this paper, the effect of spin-coating cycles with different densities on the light scattering properties of Ag nanowires (Ag NWs) transparent conductive films was investigated. The Ag NWs were characterized by scanning electron microscopy (SEM), and UV-Vis spectrophotometry. The results indicate that haze factor and the scattering in reflection and transmission directions increased with an increase in Ag NWs density. The resulting Ag NWs show cross point dropped down from ∼800 nm to ∼600 nm for spin coating 4–7 cycles. The ratio of back and forward scattering for Ag NWs exhibited a cross point that shifted to lower wavelengths with the increase in density. The controlling scattering properties of Ag NWs films may open a new avenue for Ag NWs application.

Matching and operating characteristics of working fluid pumps with organic Rankine cycle system

The present paper focuses on the comparative experimental operating characteristics of working fluid pumps used in the organic Rankine cycle (ORC) system with R245fa, including multistage centrifugal pump, hydraulic diaphragm metering pump, and roto-jet pump. Effects of mass flow rate and outlet pressure are investigated systemically on the performance of the three pumps. Further theoretical studies are conducted on the effects of various types of working fluid pumps on the system overall performance, such as exergy destruction rate, back work ratio (BWR), heat absorption rate, thermal and exergy efficiency, and net power output. Results show that the maximum actual efficiency of the three pumps can reach 58.76%, 55.26%, and 30.51%, respectively, when outlet pressure ranges from 0.4 to 1.1 MPa. A significant difference was observed between actual and theoretical BWR, which illustrates that the pump power cannot be ignored and lower pump efficiency has a negative impact on the increase in the net power output of the ORC system. Additionally, the selection of working fluid pumps has significant effects on the heat absorption rate. Consequently, the paper provides detailed and valuable insights into the selection of working fluid pumps for the ORC system with different heat capacities.

Development of portable power unit with catalytic micro-combustor

A prototype of the portable power unit with coupling catalytic microcombustor, thermo-electric modules and air/fuel supply devices was developed. The developed power unit was completely self-standing; the air supply system was driven by a part of electricity generated at the generator unit. When the thermal input from the combustor was 12W, the total electricity is 330 mW and the net output electricity was 225 mW, which corresponded to the back work ratio of 32%. The final conversion efficiency of the total system reached 1.87%, which was order of world record.

A Half-Mode SIW Cavity-Backed Semi-Hexagonal Slot Antenna for WBAN Application

ABSTRACTA half-mode substrate integrated waveguide (HMSIW) antenna covering industrial, scientific, and medical radio band at 5.8 GHz is designed, fabricated, and tested. An HMSIW technique is used to reduce the size to almost 50% while maintaining the same performance of the antenna. Afterwards, a semi-hexagonal slot is etched on the patch, which excites and tunes the dominant-mode of the cavity in the band of interest. Inspite of a substantial miniaturization, the proposed antenna provides a gain of 6.1 with front to back ratio of more than 10 dB along with a fair radiation efficiency of 83% in free space. In order to examine the performance of the antenna in the presence of a body, the antenna is tested on pork tissues. The measured on-body peak gain and simulated radiation efficiency are obtained as 5.25 and 69%, respectively. The antenna shows robust performance in the presence of pork tissues and the specific absorption rate value is under the Federal Communications Commission (FCC) guidelines, which makes it a suitable choice for wireless body area network applications.