Right heart failure (RHF) is a serious health issue with increasing incidence and high mortality. Right ventricular assist devices (RVADs) have been used to support the end-stage failing right ventricle (RV). Current RVADs operate in parallel with native RV, which alter blood flow pattern and increase RV afterload, associated with high tension in cardiac muscles and long-term valve complications. We are developing an in-series RVAD for better RV unloading. This article presents a mathematical model to compare the effects of RV unloading and hemodynamic restoration on an overloaded or failing RV. The model was used to simulate both in-series (sRVAD) and in-parallel (pRVAD) (right atrium-pulmonary artery cannulation) support for severe RHF. The results demonstrated that sRVAD more effectively unloads the RV and restores the balance between RV oxygen supply and demand in RHF patients. In comparison to simulated pRVAD and published clinical and in silico studies, the sRVAD was able to provide comparable restoration of key hemodynamic parameters and demonstrated superior afterload and volume reduction. This study concluded that in-series support was able to produce effective afterload reduction and preserve the valve functionality and native blood flow pattern, eliminating complications associated with in-parallel support.
A double-Orbital-Angular-Momentum (OAM)-mode microstrip antenna is designed, simulated, fabricated and measured, which generates OAM with mode number l = 2 and 3 on 5 GHz by two resistor loaded microstrip rings respectively. For existing OAM antennas, structures like circular array, parabolic reflector and electromagnetic meta-surface are widely adopted, which are electrically large and hard to be integrated. However, the proposed antenna has a compact size and a low profile, which can be integrated in RF circuit as a component. To solve the problem of low gain in microstrip OAM antenna, parameters are optimised and a top dielectric layer is adopted, and its measured peak gain reaches 1.5 dB for l = 2 and 1.8 dB for l = 3. The measured frequency band, on which a near field vortex phase is observed and orbital angular momentum is generated, is 4.65-5.25 GHz for l = 2, and 4.5-5.2 GHz for l = 3. Besides, this antenna can multiplex more OAM modes by adopting more microstrip rings.
Abstract-This letter presents an omnidirectional printed dipole antenna array with a wide bandwidth. The array is composed of four dipole units etched on a thin substrate, which is simple in structure and easy to be processed. By modifying the triangle-shaped radiation dipole units and gradually increasing the width of microstrip feeding transmission line, the performance of the dipole antenna array is greatly improved. Simulation results show that this omnidirectional antenna has a peak gain greater than 7.39 dBi, and the impedance bandwidth is 16% (VSWR < 1.6), ranging from 2.3 to 2.7 GHz.
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