A review of solar methane reforming systems

Because of the increasing demand for energy and the associated rise in greenhouse gas emissions, there is much interest in the use of renewable sources such as solar energy in electricity and fuels generation. One problem with solar energy, however, is that it is difficult to economically convert the radiation into usable energy at the desired locations and times, both daily and seasonally. One method to overcome this space-time intermittency is through the production of chemical fuels. In particular, solar reforming is a promising method for producing chemical fuels by reforming and/or water/carbon dioxide splitting. In this paper, a review of solar reforming systems is presented, as well as a comparison between these systems and a discussion on areas for potential innovation including chemical looping and membrane reactors. Moreover, a brief overview of catalysis in the context of reforming is presented

Zoonotic Endocarditis: Is the feather mightier than the sword?

The common causes of infective endocarditis (IE) in South Africa are Staphylococcus aureus, the viridans streptococci and Bartonella species. Infection with Erysipelothrix rhusiopathiae is a rare cause of IE that is usually associated with occupational exposure and can be acquired from humans and animals. It was fi rst reported in 1912 by Gunthar, and thereafter fewer than 60 cases have been reported. We describe a case of Erysipelothrix rhusiopathiae induced endocarditis in Cape Town, South Africa. S SAHeart 2022;19:24-2

Transition From a Single to a Double Flame Structure in Swirling Reacting Flows: Mechanism, Dynamics, and Effect of Thermal Boundary Conditions

We examine experimentally the transition from a single flame stabilized along the inner shear layer (ISL) to a double flame stabilized along both the inner and the outer shear layers (OSL) and spreading over the outside recirculation zone (ORZ) in a fully premixed swirl-stabilized combustor. This work is mainly driven by previous studies demonstrating the link between this transition in the flame macrostructure and the onset of thermo-acoustic instabilities. Here, we examine the transition mechanism under thermo-acoustically stable conditions as well as the dominant flow and flame dynamics associated with it. In addition, we explore the role of changing the thermal boundary conditions around the ORZ and its effect on the presence or absence of the flame there. We start by analyzing the two flames bounding the transition, namely the single conical flame stabilized along the ISL (flame III) and the double conical flames with reactions taking place in the ORZ (flame IV). A dual chemiluminescence approach — using two cameras with a narrow field of view focused on the ORZ — is undertaken to track the progression of the flame as it reaches the ORZ. During the transition, the flame front, initially stabilized along the ISL, is entrained by OSL vortices close to where the turbulent jet impinges on the wall, leading to the ignition of the reactants in the ORZ and the ultimately the stabilization of the flame along the outer shear layer (OSL). This ORZ flame is also subject to extinction when the equivalence ratio (ϕ) is between values corresponding to flames III and IV. For ϕ lower than the critical transitional value, the flame kernel originating from the ISL-stabilized flame is shown to reach the ORZ but fails to grow and quickly disappears. For ϕ higher than the critical value, the flame kernel expands as it is advected by the ORZ flow and ultimately ignites the reactants recirculating in the ORZ. Sudden and extreme peak-to-peak values of the overall heat release rate are found to be concomitant with the ignition and extinction of the ORZ reactants. Finally, Different thermal boundary conditions are tested by modifying the heat flux through the combustion chamber boundary, particularly around the ORZ. We find that the transition is affected in different ways: while the transition from flame III to IV (i.e. as ϕ increases) is insensitive to these changes; flame IV persists at lower ϕ as its value is reduced when heat losses through the boundaries are diminished.Center for Clean Water and Clean Energy at MIT and KFUPM (Grant R12-CE-10

Dual Band to Wideband Pentagon-shaped Patch Antenna with Frequency Reconfigurability using EBGs

A dual band to wideband reconfigurable pentagon-shaped antenna with EBG unit cell is proposed. A minimal number of two EBG unit cell is deployed to realize frequency reconfigurable mechanism.  By varying the state of the EBG the antenna is capable to change its dual band operation to wideband alternately. There are three cases that have been analysed, first case is the EBG incorporated antenna with ideal and second is with the active EBG. Subsequently, the third cases is the fabricated ideal EBG incorporated antenna. The dual band operation is at 1.8 GHz and 5.2 GHz while the wide band from 1.6 GHz to 2.37 GHz (770 MHz). The proposed reconfigurable antenna is suitable to be implemented for LTE (1.6 GHz), Wi-Fi (5.2 GHz), WiMAX (2.3 GHz) and cognitive radio application

Reconfigurable Metamaterial Structure at Millimeter Wave Frequency Range

In this paper, reconfigurable metamaterial structure at millimeter wave frequency range was designed and simulated for a future fifth generation (5G) mobile-phone beam switching applications. The new proposed structure was composed of a bridge-shaped resonator (BSR) in the front face and strip line at the back face of the unit cell which operates at 28 GHz. First, non-reconfigurable low loss BSR unit cell was designed and subsequently, the reconfigurability was achieved using four switches formed in the gaps of the structure. The proposed structure achieves the lowest loss and almost full transmission among its counterparts by -0.06 dB (0.99 in linear scale). To demonstrate the reconfigurability of the metamaterial, the reflection and transmission coefficients and real parts of the effective refractive index at each reconfigured frequency were studied and investigated. Simulation results showed that a high transmission and reflection peaks occur at each resonance frequency according to change the state of the switches

Wideband millimeter-wave substrate integrated waveguide cavity-backed antenna for satellites communications

This paper presents a new type of wideband waveguide (SIW) cavity-backed patch antenna for millimeter wave (mmW). The antenna proposed applies to applications of 31-36 GHz Ka-band such as satellites communications. The SIW is intended with settings for particular slots. The antenna is constructed on Rogers RT5880 (lossy) with 2.2 dielectric constant, l.27 mm thickness, and 0.0009 loss tangent. It is simulated in the programming of computer simulation technology (CST) Microwave Studio. The simulated results show that the SIW antenna resonates across 31 to 36 GHz bands, which means that this new antenna covers all applications within this range. The reflection coefficients in targeting range are below 10 dB. The antenna achieves good efficiency and gain with 80% and 8.87 dBi respectively

Negative refraction metamaterial with low loss property at millimeter wave spectrum

The design of the millimetre-wave (MMW) metamaterials (MMs) unit cell operates at 28 GHz is presented and numerically investigated. The proposed structure composed of a modified split ring resonator (MSRR) printed on both sides of the substrate layer. Popular MM structures such as S-shape, G-shape, and Ω-shape are adjusted to operate at the 28 GHz for comparison purpose. MSRR achieves a wide bandwidth of 1.1 GHz in comparison with its counterparts at the resonance frequency. Moreover, the proposed structure presents very low losses by providing the highest transmission coefficient, S21, at the corresponding frequency region. The radiation loss is substantially suppressed and the negativity of the constitutive parameters of the proposed MM structure is maintained. By applying the principle of the electromagnetically induced transparency (EIT) phenomenon, the MSRR unit cell induces opposite currents on both sides of the substrate which leads to cancelling out the scattering fields and suppresses the radiation loss. The constitutive parameters of the MM structures are retrieved using well-known retrieval algorithm. The proposed structure can be used to enhance the performance of fifth-generation (5G) antenna such as the gain and bandwidth

Reconfigurable metamaterial structure for 5G beam tilting antenna applications

In this paper, we propose a metamaterial (MTM) structure with a reconfigurable property designed to operate at the millimetre-wave (mm-wave) spectrum. Four switches are used to achieve the reconfigurable property of the MTM with two configurations. These two configurations exhibit different refractive indices, which used to guide the radiation beam of the antenna to the desired direction. The proposed planar dipole antenna operates at the 5th generation (5G) band of 28 GHz. The electromagnetic (EM) rays of the proposed antenna pass through different MTM configurations with different phases, subsequently results in the tilting of the radiation beam toward MTM configuration of high refractive index. Simulated and measured results of the proposed antenna loaded by MTM demonstrate that the radiation beam is tilted by angles of +34° and −31° in the E-plane depending on the arrangement of two MTM configurations onto the antenna substrate. Furthermore, the gain is improved by 1.7 and 1.5 dB for positive and negative tilting angles, respectively. The reflection coefficients of the antenna with MTM are kept below −10 dB at 28 GHz

Substrate integrated waveguide cavity backed frequency reconfigurable antenna for cognitive radio applies to internet of things applications

In this article, a new multiband frequency reconfigurable substrate integrated waveguide cavity slot antenna was designed using Computer Simulation Technology software tool for addressing the specific design challenges posed by the internet of things (IoT) based cognitive radio networks. Reconfiguration of frequency bands is achieved using PIN diodes. The antenna resonated at 2.624, 2.664, 2.720, 2.752, 4.304, 4.532, 4.556, 5.236, 5.304, 5.368, 5.332, and 5.392 GHz. The resonant frequency capability and radiation performance are demonstrated by both simulations and measurements. The simulated and measured results were in agreement. The higher efficiency, gain and average bandwidth obtained are 90%, 8.2 dBi and 65 MHz, respectively. The compactness, integrity, reliability, and performance at various operating frequencies make the proposed antenna a good candidate for IoT applications