Radiation Modes Research Articles

A Study on Heat and Mass Transfer Analysis of Solar Still

To evaluate the performance of solar still, it is very important to know about the energy balance and heat transfer. Heat transfer phenomena occur inside the still through three variable modes convection, evaporation, and radiation. As the temperature of water increases, the evaporation rate also increases. Therefore, many modifications have been done to increase the evaporation rate of basin water by the researchers, such as using nanoparticles, photovoltaic module, flat plate collector, heat exchangers, and phase change materials etc. The heat and mass transfer study on different parts of SS along with energy balance is presented in the paper. The reader will get information about the quantity of heat absorbed and the heat released inside the basin. Modification made on SS to increase productivity in the last 4-5 years has also been presented. The study found that the productivity of modified solar still gives 53.95% higher than the conventional solar still after adding external devices and energy storage

OpenFOAM solver for thermal and chemical conversion in porous media

We present the porousGasificationFoam solver and libraries, developed in the open-source C++ code OpenFOAM, for the comprehensive simulation of the thermochemical conversion in porous media.The code porousGasificationFoam integrates gas flow through a porous media with the models of heterogeneous (drying, gasification, pyrolysis, solid combustion, precipitation) and homogeneous (gas combustion) chemical reactions. Inside porous media transport equations are formulated applying the spatial averaging methodology. The mass and enthalpy transfer between solid and gas phases is suitable for systems out of the thermal equilibrium. The convection and radiation modes of the heat transfer are included for gas and solid phases, and the immersed boundary technique is applied for the porous media inside the computational domain.We validate the elements of the model against a set of experimental and theoretical results. Amongst them, Thermogravimetric Analysis experiments of thermal conversions of two wooden particles: one of millimeter size the other of centimeter size. Simulations feature reaction schemes and physical parameters established in the literature. We show the influence of the porous media size on the gasification process. The millimeter particle remains uniform, while for the centimeter setup, the pyrolysis front is reproduced. The spatial patterns in physical conditions modify the course of chemical reactions and influence media composition and structure evolution. Another important example is a gasifier where we obtain a self-sustaining front propagation because of an exothermic heterogeneous reaction. Program summaryProgram Title: porousGasificationFoamCPC Library link to program files:https://doi.org/10.17632/s6sj9kgp69.1Developer's repository link:https://github.com/pjzuk/porousGasificationFoam (foam-extend-4.1); https://github.com/btuznik/porousGasificationFoam (OpenFOAM 8)Licensing provisions: GNU General Public Licence version 3Programming language: C++External routines/libraries: OpenFOAM 8, foam-extend-4.1Nature of problem: The developed software is a solver and a set of libraries for simulating the thermal conversion in porous media, including drying, pyrolysis, gasification, and combustion. The model includes the flow of the reactive gas mixture and the transfer of mass and enthalpy between the gas and solid phases. The porous medium can change during the process. The model is transient and enables three-dimensional simulations.Solution method:: The finite-volume method is used in the code for equation discretization. A set of governing equations is solved for the gas and solid phases, including mass conservation of gas species and solid components, momentum conservation in the gas phase, and equations of enthalpy conservation in both phases. The porous media region inside the whole computational domain is defined using the immersed boundary approach.

Design Approach for a Dual-Band Circularly Polarized Slot Antenna With Flexible Frequency Ratio and Similar In-Band Gain

This letter presents an effective approach to design a dual-band circularly polarized (CP) slot antenna with flexible frequency ratio (FFR) and similar in-band gain under the 0.5 <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$\lambda$</tex-math></inline-formula> - and <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$\it\lambda$</tex-math></inline-formula> -mode radiation. Initially, a CP slot antenna is realized in virtue of two orthogonal slot radiators. Then, by folding both slot radiators at a 1/4 length position from the short-circuited terminal, a CP slot antenna operating at two distinct bands is successfully realized based on the 0.5 <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$\it\lambda$</tex-math></inline-formula> - and <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$\it\lambda$</tex-math></inline-formula> -mode, where stable gain with similar level for the dual working bands is achieved. After that, two pairs of slot stubs are properly introduced to effectively reallocate the higher band based on the <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$\it\lambda$</tex-math></inline-formula> -mode, thus acquiring for a wide frequency ratio ranging from 1.85 to 1.26. Finally, for experimental validation purposes, two specific CP slot antennas with distinctive frequency ratios of 1.85 and 1.26 are implemented and tested. A similar-level gain within their dual operating bands can be achieved as another merit in addition to the FFR.

Low-Profile Multifunctional Pattern Reconfigurable Antenna Using Periodic Capacitor-Loaded Surface for 5G and Beyond

This article describes a novel low-profile multifunctional pattern reconfigurable antenna using the periodic capacitor-loaded surface for 5G and beyond applications. A miniaturized periodic surface structure is first proposed using the shunt-loaded capacitor, which is studied by equivalent circuit models. A quarter-wavelength T-shaped director slot is etched on the edge of the ground, which leads to a tilted radiation pattern. By switching the ON-/OFF-states of p-i-n diodes embedded in the director slots, the main direction of the beam of the proposed antenna can be tuned among +35°, 0°, and −35°. To verify the design concept, a multifunctional pattern reconfigurable metamaterial-inspired antenna with a low profile of <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$0.05~\lambda _{0}$ </tex-math></inline-formula> is fabricated and measured. The measured overlapping bandwidth for the eight radiation modes is 3.10–3.85 GHz (21.6%), well covering the 5G-N78 band. The port isolation between the two polarizations in eight modes is higher than 20 dB. The proposed reconfigurable metamaterial-inspired antenna shows the merits of low profile, wide bandwidth, high port isolation, low cost, multifunctional pattern reconfigurable capability, and easy fabrication for 5G and other sub-6 GHz applications.

Coherent and incoherent superposition of transition matrix elements of the squeezing operator

We discuss the general matrix elements of the squeezing operator between number eigenstates of a harmonic oscillator (which may also represent a quantized mode of the electromagnetic radiation). These matrix elements have first been used by Popov and Perelomov (1969 Zh. Eksp. Teor. Fiz. 56 1375–90) long ago, in their thorough analysis of the parametric excitation of harmonic oscillators. They expressed the matrix elements in terms of transcendental functions, the associated Legendre functions. In the present paper we will show that these matrix elements can also be derived in a different form, expressed by the classical Gegenbauer polynomials. This new expression makes it possible to determine coherent and incoherent superpositions of these matrix elements in closed analytic forms. As an application, we describe multiphoton transitions in the system ‘charged particle + electromagnetic radiation’, induced by a (strong) coherent field or by a black-body radiation component (with a Planck–Bose photon number distribution). The exact results are compared with the semi-classical ones. We will show that in case of interaction with a thermal field, the semi-classical result (with a Gaussian stochastic field amplitude) yields an acceptable approximation only in the Rayleigh–Jeans limit, however, in the Wien limit it completely fails.

A Back-Fire to Forward Wide-Angle Beam Steering Leaky-Wave Antenna Based on SSPPs

We demonstrate an efficient back-fire to forward wide-angle beam steering leaky-wave antenna (LWA) based on a large dispersion gradient planar spoof surface plasmon polariton (SSPP) transmission line (TL) with split-ring units. To convert the highly confined SSPP waveguiding mode to a radiation mode, two arrays of metallic patches are periodically arranged on both sides of the SSPP TL. The patches are designed as two combined half-elliptical shapes to mitigate the open stopband effect and enhance the radiation performance. We propose a theoretical method to interpret the mechanism and predict the directional pattern of the LWA. To verify the proposed method, the SSPP TL and LWA prototypes are fabricated and measured. The calculation, simulation, and experimental results match well and show that the main beam of the LWA can steer a wide range of 112&#x00B0; from back-fire (&#x2212;90&#x00B0;) to the forward quadrant of 22&#x00B0; passing through the broadside in 6.3&#x2013;11 GHz, demonstrating a large scanning rate of 2.07&#x00B0;/&#x0025;. Furthermore, the LWA also possesses the advantages of low profile, high average gain (12 dBi), high average efficiency (95&#x0025;), and low sidelobe level (&#x003C;&#x2212;13 dB). This work provides an alternative route to achieving wide-angle LWAs for promising microwave radar and wireless communication applications.

Terahertz radiation generated by electron-beam-driven plasma waves in a transverse external magnetic field

It is found that the plasma waves driven by an electron beam rotating in a magnetized overdense plasma can be converted into terahertz electromagnetic radiation by new mechanisms. According to the particle-in-cell simulation results, the radiation modes include a dominant extraordinary (X) mode at twice the plasma frequency 2fp and a subordinate X mode at fp. The 2fp radiation can be generated by the coupling of a beam mode and a scattered upper-hybrid (UH) mode, or by the coupling of a beam mode and a right-handed X mode. Here, the beam mode can be a UH mode or a left-handed X mode driven by the beam under the Cherenkov condition, and the right-handed X mode can be induced by high-order electron cyclotron maser instability. The fp radiation is the right- or left-handed fundamental X mode escaping from the plasma boundary. This study also shows that the breakdown of beam modulation is responsible for the radiation attenuation. The scheme proposed in this paper can be applied in high-power THz radiation sources and diagnosis of magnetized plasmas.

Machine learning‐assisted direction‐of‐arrival accuracy enhancement technique using oversized lens‐loaded cavity

This paper presents a framework for achieving machine learning (ML)-assisted direction-of-arrival (DoA) accuracy enhancement using a millimetre-wave (mmWave) dynamic aperture. The technique used for the enhanced DoA estimation accuracy leverages an over-sized lens-loaded cavity antenna connected to a single RF chain in the physical layer and a computational method in the computational layer of the framework. It is shown for the first time that by introducing a reconfigurable mode-mixing mechanism inside the over-sized lens-loaded cavity hardware, a greater number of spatially orthogonal radiation modes can be achieved giving rise to many cavity states. If the best cavity state is determined and selected by means of design exploration using a contemporary ML-assisted antenna optimisation method, the computational DoA estimation accuracy can be improved. The mode-mixing mechanism in this work is a randomly oriented metallic scatterer located inside an over-sized constant−ϵr lens-loaded cavity, connected to a stepper motor that is electronically controlled by inputs from the computational layer of the presented framework. Measurement results in terms of near-field radiation mode scans are included in this study to verify and validate that the proposed ML-assisted framework enhances the DoA estimation accuracy. Moreover, this investigation simultaneously provides a simplification in the physical layer implementation of mmWave radio hardware, and DoA accuracy enhancement, which in turn lends itself favourably to the adoption of the proposed framework for channel sounding in mmWave communication systems.

Clustering assisted artificial neural network for handling noisy big data: An application for estimation of parameter in combined mode conduction and radiation heat transfer

AbstractA pattern net assisted mapping artificial neural network (PAMANN) model for estimation of parameters in problem with large data (1300 × 121 matrix size) is reported. A pattern net‐based multilayer perceptron neural network (MLPNN) model for clustering the data, followed by mapping MLPNN model for mapping the target with the input, is developed as PAMANN model. A heat transfer problem with combined mode conduction and radiation in porous medium is solved numerically, and is called direct model. In the inverse model, a PAMANN model is developed by using data generated through the direct model. The PAMANN model is able to estimate two parameters (extinction coefficient β and convective coupling P2) after taking temperature profile as input. The model is tested for different number of neurons in hidden layer, and different levels of noise in input data. Twelve different algorithms are explored in training of mapping MLPNN, and compared for performance. Levenberg–Marquardt algorithm is found to estimate the parameters with high accuracy, but took high CPU time. Bayesian regularization is found to consume very high CPU time with moderate accuracy in estimation of parameters. Variations in hidden layer neuron number and noise in input data, were done to analyze the performance of mapping MLPNN with different training algorithms. Algorithms O‐Step Secant, conjugate gradient with Polak‐Ribiére updates, and conjugate gradient with Fletcher‐Reeves updates are able to handle all variations of noise and number of neurons in hidden layer, with good accuracy of estimation and low CPU time consumption. Under high computational resource LM algorithm can be used for all cases. Up to 0.99132 value of regression coefficient is obtained in mapping MLPNN model with 15 hidden neurons, indicating the high accuracy of the model. With the help of PAMANN model, highly accurate (absolute error 1.78%) estimation of parameters is obtained. The model can handle upto 1% noise in input data, while giving accurate results.

Optimization of endocrine pancreas fluorescence analysis using machine methods

The study aims to establish the appropriate parameters of UV excitation intensity and permanent excitation time on the pancreatic islets photobleaching, the ratio of the intensity of the useful signal in the region of interest to the intensity of nonspecific background fluorescence. Materials and methods. The pancreas of three adult Wistar rats was fixed in Bouin solution (20 hours) and poured into paraplast after standard histological processing. The study was carried out on paraffin sections of the pancreas. The islets’ insulin and glucagon were determined by immunofluorescence method using monoclonal antibodies (Santa Cruz Biotechnology). The immunofluorescence reaction was studied using an AxioImager-M2 fluorescent microscope. AxioVision digital image analysis system was used for fluorescence imaging, and ImageJ 64-bit image analysis system was used for image quantification. 30 pancreatic islets with an area from 3000 µm2 to 5000 µm2 (8–13 % of the frame area) were analyzed. Results. Measurements carried out at constant values of hormone concentration in endocrinocytes showed a different estimate of the average fluorescence intensity for insulin and glucagon, which depended on the intensity of UV radiation. As the intensity of UV radiation increased, the average fluorescence intensity in the region of interest for insulin and glucagon increased, but when the camera exposure was corrected, it became almost the same. Regardless of this, the intensity of nonspecific background fluorescence increased monotonically. The use of the ratio of the logarithms of the background fluorescence of the drug and the fluorescence of endocrinocytes in the calculations gives a stable estimate of the relative concentration of hormones, which does not depend on the intensity of the selected UV radiation regime, as well as on the duration of UV irradiation of the drug. This makes it possible to neutralize the effect of photodynamic discoloration of the preparation caused by continuous irradiation. Methods for machine selection of the region of interest by various algorithms of the ImageJ program lead to different estimates of its area, integral, and average fluorescence values. At the same time, the result closest to the “ideal” interactive method of highlighting the area of interest for insulin and glucagon was shown by Otsu’s algorithm. Conclusions. In immunofluorescent examination of the pancreas, a moderate UV radiation mode should be selected, exposure correction of the CCD camera before taking each frame, and the total time for examining the visual field of the sample should be limited to 1–2 minutes. To highlight the area of interest for insulin and glucagon in automatic analysis, it is recommended to use the Otsu algorithm. To obtain a quantitative estimate of the average fluorescence intensity in the region of interest, it is recommended to use the ratio of the logarithms of the background fluorescence of the drug and endocrinocytes in the calculations.

Improved FULMS Algorithm for Multi-Modal Active Control of Compressor Vibration and Noise Reduction

Active control is currently a hot-button issue in the research of reducing vibration and noise created by rolling piston compressors. Active control can effectively suppress the modal vibration of the structure and reduce the modal resonance acoustic radiation. This paper, which focuses on the active control of the compressor shell’s multiple modes with the control of acoustic radiation power being the research objective, studies the relationship between vibration modes and acoustic radiation modes of the compressor shell and the primary sources of noise. An improved Filtered-U least mean square (FULMS) algorithm for compressor vibration and noise control, which is based on the Nesterov accelerated adaptive moment estimation (NADAM) optimization algorithm, is proposed to determine the multi-order modes to be controlled from the perspective of sound energy, and a particle swarm algorithm is used to determine the location and number of secondary sources. The active control model of the compressor shell was established by using the joint simulation platform, and the performance of the improved algorithm was verified and analyzed by the simulation test process. The results show that compared with the traditional FULMS algorithm, the improved FULMS algorithm has better active vibration control effect, higher convergence speed and can effectively suppress structural mode vibration in a short period time.

192 Engineering Strategies and Solutions to Improve Swine Resilience and Alleviate Physiological Stress in a Changing Climate

Abstract Heat stress negatively affects a variety of production parameters in the swine industry including growth, carcass composition, and reproduction. The combination of climate forecasts and improved genetic performance, indicate increasingly negative impacts of heat stress for the future. Therefore, future heat stress mitigation approaches will need engineered solutions that also consider expected economic risk and corresponding uncertainty. Physically modifying the environment is currently the best approach by utilizing the heat dissipation (albeit, poor) mechanisms of the pig, that is, via the 4 modes of heat transfer, conduction, convection, radiation, and evaporation. A temperature gradient for sensible or vapor pressure gradient for latent heat loss are needed to drive heat exchange. Strategies can then be grouped into (a) modifying the thermodynamic properties of the incoming air via the ventilation system; (b) building characteristics or features; (c) animal zone environment modification; and (d) changes in management. Examples of each strategy include (a) evaporative cooling pads, earth-air-heat exchanger; (b) insulation, spatial orientation; (c) fogging, cooling the drinking water, increasing air velocity; and (d) stocking density. Engineering of future controlled swine environments will need enhanced modeling of heat transfer between pigs and their environment, advanced design/analysis methods of environmental control, and creation of innovative technology that improves sensing, controlling, and modifying the environment. Much of the engineering process starts with and relies on established standards that describe key analytical methods for design, data to enable design computations, and criteria/goals for different environments. There is and will continue to be a need for consistent updates to these data to ensure modern intensive housing is able to provide the proper thermoneutral zone, ventilation rates, etc. for prolific pigs in a changing climate.

Multi-order resonators for acoustic multiband asymmetric absorption and reflection

We propose a multiband asymmetric acoustic absorption and reflection system constructed from a waveguide and multi-order resonators with different radiant modes. Theoretical and experimental results confirm that the coupling of the dark and bright modes at each resonant frequency enables multiband high-efficiency absorption requiring only two functional units. More interestingly, we demonstrate a hybrid multiband asymmetric system based on customized multi-mode pairs. One side of the hybrid multiband system almost completely absorbs the lower frequency incident sound waves while reflecting the higher frequency ones; conversely, the other side effectively reflects the lower frequency ones and absorbs the higher frequency ones. Our design showcases the flexibility of customized multiband asymmetric absorption and also provides an approach for the design of bidirectional wave-manipulation devices.

A Planar Pattern-Reconfigurable Antenna With Stable Radiation Performance

In this letter, a planar antenna withreconfigurable radiation pattern is investigated for smart Wi-Fi systems. The design incorporates one pair of folded dipoles, a microstrip-to-via feeding balun and two reconfigurable parasitic strips which are near-field excited by the dipole pair. By controlling the states of two Pin diodes embedded in two reconfigurable printed lines, the proposed antenna can switch between one omnidirectional mode and two unidirectional endfire radiation modes. This optimized antenna exhibits a decent size of 0.5 λ <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">0</sub> × 0.38 λ <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">0</sub> ×0.004 λ <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">0</sub> (where λ <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">0</sub> is free space wavelength at 2.45 GHz). Good agreement is observed between the simulated and measured results. The overlapped impedance bandwidth with | <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">S</i> <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">11</sub> | < −10 dB for the three pattern modes is from 2.34 to 2.6 GHz in the measurement. Throughout the overlapping bandwidth, the front-to-back ratios are higher than 15 dB for the two unidirectional radiation modes and out-of-roundness is less than 1.2 dB for omnidirectional radiation mode. The measured peak realized gain of the proposed pattern-reconfigurable antenna is 6 dBi. This proposed Wi-Fi antenna is well poised for intelligent Wi-Fi communication systems.

Coherent and incoherent superposition of transition matrix elements of the squeezing operator

Abstract We discuss the general matrix elements of the squeezing operator between number eigenstates of a harmonic oscillator (which may also represent a quantized mode of the electromagnetic radiation). These matrix elements have first been used by Popov and Perelomov (1969) long ago, in their thorough analysis of the parametric excitation of harmonic oscillators. They expressed the matrix elements in terms of transcendental functions, the associated Legendre functions. In the present paper we will show that these matrix elements can also be derived in an different form, expressed by the classical Gegenbauer polynomials. This new expression makes it possible to determine coherent and incoherent superpositions of these matrix elements in closed analytic forms. As an application, we describe multiphoton transitions in the system “charged particle + electromagnetic radiation”, induced by a (strong) coherent field or by a black-body radiation component (with a Planck-Bose photon number distribution). The exact results are compared with the semi-classical ones. We will show that in case of interaction with a thermal field, the semi-classical result (with a Gaussian stochastic field amplitude) yields an acceptable approximation only in the Rayleigh-Jeans limit, however, in the Wien limit it completely fails.

One-Dimensional Modeling and Experimental Analysis of Nail Penetration Thermal Runaway for Large Capacity Li-Ion Power Battery

This paper takes a certain type of large-capacity pure electric vehicle NCM li-ion power battery as the object, and analyzes and studies the process of nail penetration thermal runaway(TR). With the aid of AMEsim one-dimensional simulation software, considering the structure composition of the cell, the heat generation mechanism of each side reaction and the three heat transfer modes of thermal radiation, heat conduction and convective heat transfer between the cells, box and the environment, the thermoelectric characteristics of the battery module (six cells) are modeled. The TR behavior of the battery module during nail penetration is simulated and analyzed, and the experiment of the battery module is carried out according to Chinese new regulation GB 38031−2020. The experimental results verify the accuracy of the established model and the reliability of the simulation results, and provide technical reference for the design and development of battery thermal management such as the prediction of TR temperature and the safety of preventing TRP of battery pack.

Multiband Monopole Smartphone Antenna With Bandwidth Enhancement Under Radiation of Multiple Same-Order Modes

A novel design approach to excite multiple applicable modes under an inverted-L antenna (ILA) for bandwidth enhancement is proposed. First, the working principle about how to excite multiple modes with the same order/electrical-length is theoretically investigated based on an equivalent transmission line model. Under this method, the antenna, in theory, breaks down the limitations in the number of applicable resonances and the number of available operating bands. Second, how to load parallel capacitor to shift resonant modes to the desired band is investigated, so as to achieve the enhanced-bandwidth in multiple working bands. With these arrangements, a simple dual-band ILA is proposed as an application example to highlight the merits of above approach. Herein, the same 0.25 and 0.75 wavelength modes are generated at different operating bands so that the balanced radiation performance can be well maintained at dual bands. This ILA has gained both the lower 4G band (1.71–2.69 GHz) and upper 5G band (3.3–4.2 GHz) as desired. As a result, it not only achieves two wide bandwidths of around 44.5% and 24%, but also keeps the electrically short length of around <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$0.15\lambda _{0}$ </tex-math></inline-formula> and a small clearance of 3 mm. The total efficiencies, ECC, and isolations are satisfactorily acquired for the MIMO system. All in all, it is believed that the approach proposed herein for realizing multiple resonances is a powerful alternative for multiband antennas.

A Novel Double U-Slot Microstrip Patch Antenna Design for Low-Profile and Broad Bandwidth Applications

A low-profile double U-slot microstrip patch antenna with a wide operating bandwidth has been developed in this article. This design produces the dual radiative resonant modes adjacent to each even at the thickness of the antenna of <inline-formula> <tex-math notation="LaTeX">$0.02 {\lambda _{0}}$ </tex-math></inline-formula>. An extremely stable radiation gain that varied from 6.2 to 6.8 dBi is achieved within the whole operating band. In addition, detailed parametric studies in this article provide antenna engineers with simple approximate rules that result in an excellent first-pass design with prescribed characteristics requiring only minimal tuning. Finally, the proposed antenna with the thickness of <inline-formula> <tex-math notation="LaTeX">$0.04 {\lambda _{0}}$ </tex-math></inline-formula> is fabricated and measured. Simulated and measured results are found in good agreement with each other. They have evidently illustrated that the bandwidth is increased by 50&#x0025; compared to the traditional U-slot antenna. With the help of these simple design procedures and examples in this article, antenna designers could easily develop a low-profile broadband antenna.

Vibration reconstruction for a point-excited plate based on acoustic radiation modes and sound pressure measurement

The inverse problem of sound radiation from a vibrating structure is one of the key problems in vibro-acoustics; however, sound source reconstruction with sound pressure measurement still has challenges from sound field assumptions and measurement noise. Due to orthogonality and unrestricted source, Acoustic Radiation Modes (ARMs) are seen as promising basis vectors to realize sound source reconstruction. Here, near-field ARMs obtained by the pressure-velocity method were proposed to construct a series of orthogonal basis vectors for the vibration velocity of a point-excited rectangular plate, and a new procedure of rearrangement and truncation of basis vectors is proposed to obtain the top-ranking vectors with their contribution. Finally, vibration reconstruction is realized with least finite vectors to reach a certain accuracy. Numerical simulations show that vibration reconstruction errors are below 10% with less than 20 orders of basis vectors at frequency range kL ≤ 2π and white noise SNR = 30 dB. The smaller distance of the measuring surface and lower frequency of sound lead to higher reconstruction accuracy and less necessary basis vectors. The factors affecting reconstruction accuracy were also studied by white noise level, amount of basis vectors, and number of measuring points.

Design Approach for Low-Profile Tri-Polarization Patch Antenna With Simultaneous Harmonic Suppression

A novel design approach to achieve harmonic suppression of a low-profile microstrip patch antenna (MPA) under tri-polarization is proposed. Herein, the tri-polarization consists of the left-handed circular polarization (LHCP), right-handed circular polarization (RHCP), and linear-polarization (LP). First, the resonant frequencies of the traditional MPA are deeply studied. It is demonstrated that a set of radiative modes are excited in a single patch resonator. In order to suppress a few undesired modes, an array of shorting vias is loaded around two edges of the quarter patch1. Then, a linear slot is introduced to move dual orthogonal modes closely to each other, resulting in achieving LHCP patterns with harmonic suppression. Similarly, both of RHCP patterns and harmonic suppression are acquired for the quarter patch2 via this method. After that, the shorting vias and slots are adopted on the half patch3, aiming to suppress or push up higher modes for LP generation and harmonic suppression. Lastly, all these three patches are integrated with each other for size reduction. Finally, the proposed MPA is fabricated and measured. The results illustrate that the antenna has satisfactorily gained LHCP, RHCP, and LP radiation patterns of around 2.65 GHz. Besides, the volume of the radiator ( <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$0.0058\lambda _{0}^{3}$ </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">$\lambda _{0}$ </tex-math></inline-formula> is the free-space wavelength) is only half of the traditional counterpart ( <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$0.01\lambda _{0}^{3}$ </tex-math></inline-formula> ). Additionally, the port isolation is kept as large as about 22 dB in the operating band. Most importantly, the harmonic suppression of around <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$2.7~f_{0}$ </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">$f_{0}$ </tex-math></inline-formula> is the operating frequency) is successfully acquired without extra feeding circuits.