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Measurement and Explanation of DC/RF Power Loci of an Active Patch Antenna
Neil J. McEwan,Nazar T. Ali,Kahtan A. Mezher,Elmahdi A. El-Khazmi,Raed A. Abd-Alhameed 한국전자통신연구원 2011 ETRI Journal Vol.33 No.1
A case study of an active transmitting patch antenna revealed a characteristic loop locus of DC power versus RF output power as drive frequency was varied, with an operational bandwidth substantially smaller than the impedance bandwidth of the radiator. An approximate simulation technique, based on separation of the output capacitance of the power transistor, yielded easily visualized plots of power dependence on internal load impedance, and a simple interpretation of the experimental results in terms of a near-resonance condition between the output capacitance and output packaging inductance.
Fabrizi, L,McEwan, A,Oh, T,Woo, E J,Holder, D S IOP Pub 2009 PHYSIOLOGICAL MEASUREMENT Vol.30 No.6
<P>Electrical impedance tomography of brain function poses special problems because applied current is diverted by the resistive skull. In the past, image resolution was maximized with the use of an electrode addressing protocol with widely spaced drive electrode pairs and use of a multiplexer so that many electrode pairs could be flexibly addressed. The purpose of this study was to develop and test an electrode protocol for a 16-channel semi-parallel system which uses parallel recording channels with fixed wiring, the Kyung Hee University (KHU) Mk1. Ten protocols were tested, all addressing pairs of electrodes for recording or current drive, based on recording with a spiral, spiral with suboccipital electrodes (spiral s-o) and zig-zag configurations, and combinations of current injection from electrode pairs at 180°, 120° and 60°. These were compared by assessing the image reconstruction quality of five simulated perturbations in a homogenous model of the human head and of four epileptic foci in an anatomically realistic model in the presence of realistic noise, in terms of localization error, resolution, image distortion and sensitivity in the region of interest. The spiral s-o with current injection at 180°+ 120°+ 60° gave the best image quality and permitted reconstruction with a localization error of less than 10% of the head diameter. This encourages the view that it might be possible to obtain satisfactory images of focal abnormalities in the human brain with 16 scalp electrodes and improved instrumentation avoiding multiplexers on recording circuits.</P>
Ramachandran Anirudh,Montenegro Michelle,Singh Maninder,Dixon Trevor,Kayani Waqas,Liang Timothy,Yu Nick,Reddy Srinivas,Liveris Anna,Manyapu Mallika,McEwan Alyssia A.,Nguyen Vincent T.,Sonenthal Necham 대한응급의학회 2022 Clinical and Experimental Emergency Medicine Vol.9 No.3
Objective Hip fractures are associated with significant morbidity and mortality. Ultrasound-guided peripheral nerve blocks are a safe method to manage pain and decrease opioid usage. The pericapsular nerve group (PENG) block is a novel, potentially superior block because of its motor-sparing effects. Through training, simulation, and supervision, we aim to determine whether it is feasible to perform the PENG block in the emergency department. Methods Phase 1 consisted of emergency physicians attending a workshop to demonstrate ultrasound proficiency, anatomical understanding, and procedural competency using a low-fidelity model. Phase 2 consisted of a prospective, observational, feasibility study of 10 patients with hip fractures. Pain scores, side effects, and opioid usage data were collected. Results The median pain score at time 0 (time of block) was 9 (interquartile range [IQR], 6.5–9). The median pain score at 30 minutes was 4 (IQR, 2.0–6.8) and 3.5 (IQR, 1.0–4.8) at 4 hours. All 10 patients required narcotics prior to the initiation of the PENG block with a median dosage of 6.25 morphine milligram equivalents (MME; IQR, 4.25–7.38 MME). After the PENG block, only 30% of the patients required further narcotics with a median dosage of 0 MME (IQR, 0–0.6 MME) until operative fixation. Conclusion In this feasibility study, PENG blocks were safely administered by trained emergency physicians under supervision. We demonstrated data suggesting a trend of pain relief and decreased opiate requirements, and further investigation is necessary to measure efficacy.
A comparison of two EIT systems suitable for imaging impedance changes in epilepsy
Fabrizi, L,McEwan, A,Oh, T,Woo, E J,Holder, D S IOP Pub 2009 PHYSIOLOGICAL MEASUREMENT Vol.30 No.6
<P>Electrical impedance tomography (EIT) has the potential to produce functional images of the conductivity changes associated with epilepsy to help localization of epileptic foci. Scalp voltage changes associated with internal conductivity changes due to focal seizures have been shown at the limit of detectability for present EIT systems. The performances of two EIT systems, which may be employed in clinical recordings during presurgical assessment of intractable epilepsy, were compared. Those were the 32-channel serial UCH Mk2.5 and the 16-channel semi-parallel KHU Mk1. Images of three conductivity perturbations, simulating epileptic foci, in a head-shaped saline tank without and with a real human skull were recorded using 31-channel and 16-channel protocols with the UCH Mk2.5, while only 16-channel protocols with the KHU Mk1. The UCH Mk2.5 employing the 31-channel protocol had better overall performance with a localization error of 12.7% of the tank diameter, which would be sufficient for lateralization of the epileptic activity. More blurred images, but with similar localization, were obtained using 16 electrodes.</P>
Fabrizi, L,McEwan, A,Woo, E,Holder, D S IOP Pub 2007 PHYSIOLOGICAL MEASUREMENT Vol.28 No.7
<P>Electrical impedance tomography measurements in clinical applications are limited by an undesired noise component. We have investigated the noise in three systems suitable for imaging epileptic seizures, the UCH Mark1b, UCH Mark2.5 and KHU Mark1 16 channel, at applied frequencies in three steps from 1 to 100 kHz, by varying load impedance, single terminal or multiplexed measurements, and in test objects of increasing complexity from a resistor to a saline filled tank and human volunteer. The noise was white, and increased from about 0.03% rms on the resistor to 0.08% on the human; it increased with load but was independent of use of the multiplexer. The KHU Mark1 delivered the best performance with noise spectra of about 0.02%, which could be further reduced by averaging to a level where reliable imaging of changes of about 0.1% estimated during epileptic seizures appears plausible.</P>
Bioimpedance spectroscopy tensor probe for anisotropic measurements
Kwon, H.,Wi, H.,Karki, B.,Lee, E. J.,McEwan, A.,Woo, E. J.,Harrach, B.,Seo, J. K.,Oh, T. I. IET 2012 Electronics letters Vol.48 No.20
<P>The tetrapolar electrode configuration used in bioimpedance suffers from negative sensitivity and is confounded by anisotropic tissue such as blood vessels or muscle and nerve fibres. Proposed is a circular array of electrodes to focus current directly underneath the probe and provide anisotropy information. It is shown that an implementation using 16 miniature electrodes is able to outperform the tetrapolar method in sensitivity and impedance estimation. The proposed method can also recover anisotropic conductivity tensors from experiments for the first time.</P>