Middle Band Research Articles

Diffusive–Reflective Metasurface With Dual Independent Reflection Bands for RCS Reduction

A diffusive–reflective metasurface with dual independent bands is designed in this letter, which can be utilized to achieve specular reflection in the middle band and radar cross-section (RCS) reduction in the sidebands. The metasurface is made up of two elements, one of which consists of two diagonally arranged arrows with two tails of different lengths, and another is its mirror structure. Two independent bands are realized based on the resonances of two different-length tails, and their current distributions and parameter analysis are given for the comprehensible theory. Then, a prototype of the designed metasurface with one wide specular reflection band is fabricated and measured, and the 10.3% middle reflection band as well as 29.5% and 35.8% side RCS reduction bands are achieved.

Miniaturization of Microstrip Antenna Using Spiral labyrinth Method at Frequency of Work 3.5 GHz

Along with the times, communication technology has developed so that it is currently included in the Fifth Generation (5G) Communication System. The 5G communication system is divided into three frequency categories, namely low band, middle band and high band. One of the important devices in the telecommunications sector is the antenna. Antenna serves to send and receive electromagnetic signals at a certain working frequency. Currently, antennas have been completely integrated into the needs of modern society. One type of antenna that can support the needs of today's technology is a microstrip antenna. This antenna has several advantages, especially in its antenna compact design, low profile configuration and affordable manufacturing costs. In this article, a microstrip antenna is designed with the spiral labyrinth method that works at a frequency of 3.5 GHz for 5G communication system. Propsosed antena designed using RT Duroid R5880 with dielectric constant ( ) 2.2, dielectric loss (loss tan) 0.0009 and thickness (h) 1.57 mm. The simulation results show the reflection coefficient -29.58 dB, VSWR 1.069, gain 6.432 dB at frequency of 3.5 GHz . Spiral labyrinth has been succesfully reduced patch antenna and enclosure until 22.5% and 24.8%, respectively.

Environmental Assessment of a Diesel Engine Fueled with Various Biodiesel Blends: Polynomial Regression and Grey Wolf Optimization

A series of tests were carried out to assess the environmental effects of biodiesel blends made of different vegetable oil, such as corn, sunflower, and palm, on exhaust and noise diesel engine emissions. Biodiesel blends with 20% vegetable oil biodiesel and 80% diesel fuel by volume were developed. The tests were conducted in a stationary diesel engine test bed consisting of a single-cylinder, four-stroke, and direct injection engine at variable engine speed. A prediction framework in terms of polynomial regression (PR) was first adopted to determine the correlation between the independent variables (engine speed, fuel type) and the dependent variables (exhaust emissions, noise level, and brake thermal efficiency). After that, a regression model was optimized by the grey wolf optimization (GWO) algorithm to update the current positions of the population in the discrete searching space, resulting in the optimal engine speed and fuel type for lower exhaust and noise emissions and maximizing engine performance. The following conclusions were drawn from the experimental and optimization results: in general, the emissions of unburned hydrocarbon (UHC), carbon dioxide (CO2), and carbon monoxide (CO) from all the different types of biodiesel blends were lower than those of diesel fuel. In contrast, the concentration of nitrogen oxides (NOx) emitted by all the types of biodiesel blends increased. The noise level produced by all the forms of biodiesel, especially palm biodiesel fuel, was lowered when compared to pure diesel. All the tested fuels had a high noise level in the middle frequency band, at 75% engine load, and high engine speeds. On average, the proposed PR-GWO model exhibited remarkable predictive reliability, with a high square of correlation coefficient (R2) of 0.9823 and a low root mean square error (RMSE) of 0.0177. Finally, the proposed model achieved superior outcomes, which may be utilized to predict and maximize engine performance and minimize exhaust and noise emissions.

Adaptive and Progressive Multispectral Image Demosaicking

Common consumer RGB cameras use a single image sensor to capture RGB color images with a color filter array (CFA) placed in front of the image sensor. This system captures particularly one color sample ( <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$R$</tex-math></inline-formula> , <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$G$</tex-math></inline-formula> , or <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$B$</tex-math></inline-formula> ) at each pixel location. This captured raw image is called a CFA image. The CFA demosaicking is used then to construct the complete color image. A similar approach of working with a single image sensor and extension of CFA to multispectral filter array (MSFA) enables us to develop a low-cost multispectral camera with the help of MSFA demosaicking. However, due to many spectral bands and their very sparse sampling, extending CFA demosaicking to MSFA demosaicking is not easy. This paper proposes an adaptive and progressive MSFA demosaicking method for various MSFA patterns for 5 to 15 bands multispectral images. Binary tree-based MSFA patterns are used to create MSFA images, and these MSFA patterns can be designed for any N-band MSFA image. The spectral bands are arranged specifically so that the middle band has the highest probability of appearance (PoA) in the MSFA pattern. The middle band is interpolated first using PoA based progressive adaptive interpolation, and the modified bilinear spectral difference method is used to estimate all other spectral bands with the interpolated middle band’s help. Experimental results and comparative analysis on two different datasets reveal that our proposed MSFA demosaicking method outperforms the existing generic MSFA demosaicking methods in terms of computational time and various image quality metrics considered.

A Reconfigurable Metal Rim Antenna With Smallest Clearance for Smartphone Applications

In this paper, a reconfigurable metal rim antenna with a small clearance and compact structure for 4G/5G smartphones is proposed. It consists of the system ground plane and a metal rim with two slits, in which a U-shaped slot of 1 mm (the smallest) clearance is realized between the system ground and metal rim. The theory of characteristic modes is applied to analyze the eigenmodes of the antenna so as to aid the optimum design. The characteristic modes (CMs) in the band of interest are studied, and an inductive coupling exciter is identified as the best since three CMs can therefore be generated in the lower frequency band (0.69-0.96 GHz), and an SP4T switch can be utilized to increase the bandwidth of the whole lower band. A prototype antenna of the optimized design was fabricated. A good agreement was obtained between the measured and simulated results. The 6-dB frequency bands are the lower band (0.69-0.96 GHz), the middle band (1.7- 2.7 GHz), and the higher 5G band (3.4- 3.6 GHz), respectively, and the total efficiencies are over 50% in all these frequency bands. They indicate that the antenna is a very good candidate for smartphone applications.

A study on underexpanded radial jet impinging on inner wall of cylinder

A jet radially spreading like a disc from a small gap between two circular tubes placed face to face with each other was experimentally analysed in this study. The jet is underexpanded and impinges on a cylindrical inner wall concentric with the circular tubes. Typical cellular structure appears in the jet and a detached shock wave forms near the wall. As this flow pattern is distributed over the circumferential direction, visualization by the shadowgraph method captured them as some ring-shaped shock waves. They indicate the nodes of cell sstructure and a detached shock. The diameter of the shock ring increased as the nozzle pressure ratio increased, and the ring of the node gradually approached that of the detached shock. At a certain nozzle pressure ratio, the detached shock ring jumped in the upstream cell. These shock rings oscillated and amplitude of the oscillation was varied with the pressure ratio. Strain of the wall surface was measured at nozzle pressure ratios ranging from 2.0 to 4.8. The wall surface is deformed by the pressure acting on the wall. The strain histories were analyzed using FFT, and multiple dominant frequencies were observed. These were classified by frequency as high, middle and low bands. The middle-band frequency increased gradually and dropped suddenly at certain nozzle pressure ratios, where the jump of the detached shock occurred. Furthermore, the middle-band frequency was in good agreement with the integer multiple of the dominant frequency in the low band. This means the low-band frequency is the fundamental frequency of the pressure acting on the wall. Therefore, the pressure oscillation on the wall has multiple modes and the mode change synchronizes with the flow pattern change such as the detached shock jump.

A SEMI-DEFECTED GROUND PLANE AND A BINARY GENETIC ALGORITHM FOR DESIGNING A VERY COMPACT TRIPLE-BAND PIFA ANTENNA

we suggest in this study a very compact triple band PIFA antenna for mobile and wireless applications.by using the binary genetic algorithm and a semi-defected ground plane. This antenna with the dimension of 38×40×1.9 mm3 is dedicated to LTE Band 11 (1427.9-1495.9 MHz), HIPERLAN/2 (5.15-5.35 GHz), WLAN (5.15-5.35 GHz) and 5G Sub-6GHz applications. To accomplish triple-band operation with acceptable performance purpose of using the genetic algorithm is to dictate the form of the ground plane of the antenna. The simulation results showed that the developed PIFA antenna has optimal operation on three frequencies. The first resonance frequency is 1.32 GHz with a bandwidth (S11 &lt; -10 dB) from 1.28 GHz to 1.38 GHz. The middle and higher bands are centred respectively at 3.12 GHz and 5.2 GHz, with a bandwidth from 3.05 to 3.17 GHz and 4.93 to 5.44 GHz, respectively.

Thermal and acoustic performance of silencing heat exchanger for engine waste heat recovery

The integrated design of gas heat exchanger and after-treatment unit can reduce the size and weight of the engine waste heat recovery system, releasing the back pressure of exhaust gas and enhancing net benefit of the waste heat recovery system. In this study, we propose a silencing heat exchanger that integrates an exhaust heat exchanger with an impedance composite muffler in the post-treatment system, using metal foam material instead of the sound absorbing material in the impedance composite muffler. By adapting ANSYS Fluent and LMS Virtual.Lab, thermal simulation and acoustic simulation of the silencing heat exchanger were realized, and comparative analysis of the modified structure and the basic structure was carried out. The modified silencing heat exchanger was then designed and fabricated, and the thermal and acoustic performance were tested. The results show that the modified silencing heat exchanger can achieve improved heat transfer and flow performance, and more uniform temperature distribution at the hot side, simultaneously resulting in an 8.4% reduction in exhaust pressure drop. Even more, the improvement of silence effect in the middle and high frequency band is fairly obvious, and the overall transmission loss is 44.4% higher than that of the basic structure.

Design and Analysis of Single Layer Proximity Fed Sierpinski Fractal 2x1 Array Antenna Embedded on Hexagon Shaped Patch with Defected Ground Structure

A novel innovative technique for producing a single layer proximity fed triple band antenna based on second iteration level Sierpinski fractal geometry implanted on a hexagonal shaped array antenna is being presented for next-generation cellular networks. The steps of fractal array antenna growth are examined. The array antenna is supplied using a single layer proximity fed method. The suggested single layer proximity fed hexagonal shaped array antenna with defective ground structure is developed and simulated using CST Microwave Studio, and characteristics such as bandwidth, return loss, directivity, and radiation pattern are investigated. The second iteration level single layer proximity fed array antenna's simulated -10 dB impedance bandwidth for the lower band is 237 MHz (1.6480 – 1.8850 GHz) with peak resonance at 1.8010 GHz, the middle band bandwidth is 66 MHz (2.4280 – 2.4940 GHz) with peak resonance at 2.4640 GHz, and the upper band bandwidth is 69 MHz (2.9080 – 2.9778 GHz) with peak resonance at 2.9 This antenna may be used for a wide range of wireless communication applications.

Radiation Pattern, Surface Current Distribution, and Q-Factor Improvement Technique Using DMS CSPA: Part-II

In order to improve the efficiency, reliability, and accuracy during fabrication of antenna in 5G regime of frequencies, a Double-Material Substrate (DMS) Cylindrical Surrounding micro-strip fed Patch Antenna (CSPA) has been designed for use in 2.4/5.8 GHz WLAN, 2.5/5.15 GHz WiMAX wireless standards, 5.9 GHz Intelligent Transportation Society (ITS) band (5.85-5.925 GHz) and middle band of 5G technology (2.3 GHz ~ 2.4 GHz and 2.5 GHz ~ 2.69 GHz). The proposed antenna addresses the negative effect of dimension inaccuracy caused by the high permittivity substrate material used in CSPA. The antenna was designed, simulated, and thoroughly analyzed on the basis of the radiation pattern, surface current distribution, and Q factor. Findings reveal that the DMS CSPA showed a worthy radiation pattern and Q-factor of 3.62 and 2.31 at 2.68 GHz and 5.55 GHz bands, respectively. The radiation plots of simulation results present the angular width values between 450 ~ 1040, showing a wider coverage area with minimal sidelobe level between -4.4 dB ~ 11.9 dB for the E-planes and H-planes at both resonance frequencies.

Comparative Analysis of Dual-Band Double-Material Substrate Based Cylindrical Surrounding Patch Antenna for 5G/WiMAX/WLAN Applications

A high-gain, dual-band Double-Material Substrate (DMS) Cylindrical Surrounding micro-strip fed Patch Antenna (CSPA) composed of FR-4 (lossy), polyimide (lossy), and a partial ground plane of copper (annealed) have been proposed. In addition, it has been presented for use in IEEE 802.11, Wireless Local Area Network (WLAN) standards of 2.4 GHz (2.4 GHz ~ 2.484 GHz), 5.2 GHz (5.15 GHz ~ 5.35 GHz), and 5.8 GHz (5.725 GHz ~ 5.825 GHz), IEEE 802.16 Worldwide Interoperability for Microwave Access (WiMAX) standards of 2.5 GHz (2.5 GHz ~ 2.69 GHz) and 5.2 GHz (5.2 GHz ~ 5.8 GHz) and middle band of 5 G technology (2.3 GHz ~ 2.4 GHz and 2.5 ~ 2.69 GHz). The proposed antenna is a solution to the negative effect of dimension inaccuracy resulting from high permittivity substrate material used for CSPA design at high frequency. The antenna has been designed, simulated, and extensively analyzed for operation at frequencies ranging from 2.28 GHz ~ 3 GHz and 4.9 GHz ~ 6.1 GHz, providing an impedance bandwidth of 0.7 GHz and 1.1 GHz at the resonance frequency of 2.68 GHz and 5.5 GHz, respectively. In addition, by varying specific antenna dimensions at 5.5 GHz, the DMS CSPA has been observed to produce a Voltage Standing Wave Ratio (VSWR), directivity, gain, and radiation efficiency of 1.13, 8.19 dBi, 6.573 dBi, and 81 %, respectively.

Linear and second‐order nonlinear optical properties of non‐fullerene acceptor derivatives with A–D–A structure

AbstractIn this paper, in order to study the relationship between structure and performance, four new non‐fullerene acceptor (NFA) derivatives were designed based on the two reported NFA molecules BO‐4Cl and BTP‐S2 by replacing the benzothiadiazole unit with a less‐electron deficient benzotriazole unit and inserting another ethylene double bond between the central core and the terminal groups. Density functional theory (DFT) and Time‐dependent DFT were applied to investigate linear and nonlinear optical (NLO) properties, such as electronic structure, electronic absorption, reorganization energy, and the second‐order NLO properties. The investigation demonstrates that they are all narrow bandgap derivatives, the absorption spectrum extends to the near‐infrared region and using two ethylene double bond is the most effective way to reduce the energy gap, redshift the maximum absorption peak and the middle absorption band, and enhance second‐order NLO response. Considering the smaller electron and hole reorganization energy and the larger static first hyperpolarizability value, the studied NFA derivatives have great potential to become ambipolar charge transport materials and large second‐order NLO materials.

Circuit theory model‐based analysis of triple‐band stub and notches loaded epoxy substrate patch antenna for wireless applications

SummaryThe research presented in this paper is intended to design and analyze of a triple‐band stub and notches loaded antenna for wireless applications. The optimized and proposed antenna (Antenna‐4: 0.235λ0 × 0.238λ0 × 0.013λ0 mm3) is decided after systematic investigation of Antennas‐1 to ‐4 at design frequency of 2.45 GHz. One orthogonal and two parallel notches and one stub are used on the radiating patch of the substrate to obtain the desired specifications. Theoretical analysis based on circuit theory model has been performed to obtain the equivalent circuit of the proposed antenna. Antenna parameters are analyzed by means of IE3D electromagnetic solver and circuit theory model, and results are validated with experimental results. The impedance bandwidths (S11 &lt; –10 dB) of the proposed antenna are 41.3% between 1.42 and 2.16 GHz (theoretical), 21.6% between 1.61 and 2 GHz (simulated), and 41.4% between 1.40 and 2.13 GHz (measured) at lower resonant frequency ( ); 4.1% between 2.61 and 2.72 GHz (theoretical), 17.4% between 2.36 and 2.81 GHz (simulated), and 8.8% between 2.50 and 2.73 GHz (measured) at middle resonant frequency ( ); and 42.3% between 3.32 and 5.10 GHz (theoretical), 49.9% between 3.04 and 5.06 GHz (simulated), and 44.4% between 2.98 and 4.68 GHz (measured) at higher resonant frequency ( ) observed, respectively. The measured stable peak gain of 2.6 dB at 1.9 GHz, 3.8 dB at 2.6 GHz, and 5.4 dB at 3.6GHz is observed in lower, middle, and higher bands, respectively.

A Wearable Tri-Band Half-Mode Substrate Integrated Waveguide Antenna

A wearable tri-band half-mode substrate integrated waveguide (HMSIW) antenna is proposed for wireless body area network (WBAN) applications. The lower frequency band is generated by combining the TE <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">010</sub> and TE <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">110</sub> modes of the HMSIW cavity, whereas the middle and upper bands are achieved with the stubs and the slot. Simulated and measured results show that the antenna can cover the three frequency bands, i.e., 2.36–2.5, 3.32–3.54, and 5.61–6.12 GHz with broadside radiation patterns. The antenna performance is evaluated on the human tissue model. Owing to the isolation characteristic of the cavity structure, the performance of the antenna on the body will not degenerate significantly compared to the results in free space. Due to the advantages of tri-band operation, simple topology, low back radiation, and low specific absorption ratio values, the proposed antenna is a competitive candidate for WBAN applications.

Evaluation of Pelvic Floor Muscles in Pregnancy and Postpartum With Non-Invasive Magnetomyography.

Objective: To record and characterize features of levator ani muscles (LAM) activity in pregnancy and postpartum using non-invasive and novel Magnetomyography (MMG) technique with amplitude and spectral parameters. Methods: Nulliparous women with uncomplicated pregnancies participated in the MMG data collection during rest and voluntary LAM contractions (Kegels) with modulated intensity in third trimester and approximately 2 months postpartum (PP). Simultaneous surface electromyography was recorded to document the recruitment of accessory muscles. Moderate strength Kegel (MK) MMG trials were analyzed. Amplitude and spectral parameters including root-mean square (RMS) amplitude, power spectrum density (PSD) and normalized PSD (rPSD) in three frequency bands (low, middle, high) were computed on MK epochs. Statistical comparisons between pregnancy and postpartum were calculated. Results: MMG recordings were measured from 10 pregnant women. Results showed decreased RMS and power between third trimester and postpartum, trending towards significance. rPSD values in the low frequency band decreased significantly (p = 0.028) from third trimester to postpartum, while significant increase was observed in the middle frequency band (p = 0.018). Conclusions: This study shows that MMG as non-invasive tool has the ability to detect and characterize changes of LAM activity with amplitude and spectral parameters during pregnancy and postpartum.

Raman efficiency in the middle ultraviolet band for G‐series nerve agents and sulfur mustard

AbstractRaman spectroscopy has proven useful for chemical agent detection, but the wavelength‐dependent scattering cross section and absorption, as well as induced fluorescence, usually affects the sensitivity. Ultraviolet (UV) wavelength excitation is investigated as a method to increase the efficiency and possibly enhance the applicability for detection of contamination on surfaces from a distance, potentially including an imaging capability. With this aim, we have measured UV Raman spectra and their strength as a function of laser wavelength in a range from 210 to 330 nm using a tunable pulsed laser and a response calibrated spectroscopic system. Results from small droplets of the low volatile chemical warfare agents, GA (tabun), GF (cyclosarin), sulfur mustard (HD), and the agent simulant tributyl phosphate (TBP) applied to silicon wafer surfaces are reported. Particular emphasis is put on the radiative ratio of observed Raman scattering to laser excitation, quantified as the Raman target efficiency. Measured absorption cross sections were used to estimate the effective optical depth and molecular Raman cross sections as a function of wavelength. In addition, a secondary optical probe and spectrometer were used to monitor any induced fluorescence.

A Hybrid Robust Image Watermarking Method Based on DWT-DCT and SIFT for Copyright Protection.

In this paper, a robust hybrid watermarking method based on discrete wavelet transform (DWT), discrete cosine transform (DCT), and scale-invariant feature transformation (SIFT) is proposed. Indeed, it is of prime interest to develop robust feature-based image watermarking schemes to withstand both image processing attacks and geometric distortions while preserving good imperceptibility. To this end, a robust watermark is embedded in the DWT-DCT domain to withstand image processing manipulations, while SIFT is used to protect the watermark from geometric attacks. First, the watermark is embedded in the middle band of the discrete cosine transform (DCT) coefficients of the HL1 band of the discrete wavelet transform (DWT). Then, the SIFT feature points are registered to be used in the extraction process to correct the geometric transformations. Extensive experiments have been conducted to assess the effectiveness of the proposed scheme. The results demonstrate its high robustness against standard image processing attacks and geometric manipulations while preserving a high imperceptibility. Furthermore, it compares favorably with alternative methods.

Diversity and Inclusion in Drug Development: Rethinking Intrinsic and Extrinsic Factors with Patient Centricity.

Diversity and Inclusion in Drug Development: Rethinking Intrinsic and Extrinsic Factors with Patient Centricity.

HYDRODYNAMICS OF A DUAL-CHAMBER OWC WAVE ENERGY CONVERTER IN HEAVING MOTION

The oscillating water column (OWC) wave energy conversion device have been recognized as the most promising wave energy conversion technology due to the advantages of its simple structure, convenient assembly and easy maintenance. A heave-only dual-chamber OWC device was numerically investigated by a well-developed open source software OpenFOAM coupled with a wave generation and absorption toolbox Waves2Foam. The volume of fluid (VOF) method tracking the water-air interface and the six-degree-freedom (6DOF) Dynamic Mesh solver duplicating the heave motion of the OWC device were employed to examine the influences of the relative width of the front and rear chambers and the spring elastic coefficient on the energy capture width ratio and hydrodynamic characteristics of the device under the actions of different incident regular waves. Through comparing the present results with the existing ones of a fixed dual-chamber OWC wave energy converter, and examining the free-decay motion of a cylinder, the rationality and effectiveness of the present numerical model has been revealed. The results show that the wider rear chamber can make for the extraction of wave energy of the dual-chamber OWC in heave motion. The heave-only dual-chamber OWC device can improve the device performance as the relative width ratio of the front and rear chambers is 1/2, and the rear chamber has larger capture width ratio in the middle and high frequency wave bands, compared with that of the fixed one. Multiple-peak values of the relative water surface elevation and the relative pressure occur in the whole test wave frequency bands due to the phase gap between the dual-chamber OWC device and the water columns in the front and rear chambers. In addition, it is found that by adjusting the spring stiffness coefficient, the wave-frequency bandwidth of high-efficiency can be significantly broadened and larger energy capture width ratio can be achieved.

Concurrently Improved Jsc, Fill Factor, and Stability in a Ternary Organic Solar Cell Enabled by a C-Shaped Non-fullerene Acceptor and Its Structurally Similar Third Component

A ternary strategy is recognized as a promising approach that enjoys both the simplicity of fabrication conditions and potential to improve performance in organic solar cells. Herein, a C-shaped narrow band gap non-fullerene acceptor GL1 with a C2v symmetry based on a new core was designed and synthesized. A power conversion efficiency (PCE) of 11.43% was achieved by employing PBDB-T:GL1 as an active layer to fabricate photovoltaic devices. To further promote photovoltaic performance, following a similar-structure prescreen principle, a middle band gap acceptor F-2Cl with the same backbone shape, side-chain distribution, and dipole moment orientation as GL1 was introduced as the guest acceptor into the active layer. Thus, benefiting from the collaboration of complementary absorption, cascade energy levels, and well-modified microstructure of the active layer, a 13.17% PCE was obtained with concurrently elevated Jsc, fill factor, and stability for the optimized ternary device. This work presents a successful example of prescreening the third component to simplify the workload for a high-performance ternary device.