An Enhanced Adaptive Algorithm to Mitigate Mis-coordination Problem of the Third Zone of Distance Relays

ABSTRACT Cascaded tripping of power lines due to mal-operation of zone 3 distance relays is one of the main causes of many blackouts worldwide. The improved protection technique for zone 3 can help to prevent such mal-operation and, thus, more reliable power systems can be envisaged. This paper presents a novel zone-3 setting scheme based on impedance seen by distance relays in order to calculate zone-3 setting of the relays when faults are simulated on the reach of zone-2 of primary distance relays. The new technique is also enhanced to be used in an adaptive protection system. Since three phase fault rarely occurs in the system and in order to have better demonstration of effectiveness of the proposed scheme, it is tested for various type of faults such as, two phase (AB), single phase to ground (AG) and two phase to ground (ABG) as well as three-phase (ABC) using data simulated through DIgSILENT in the IEEE 30-bus test system during different topologies. The simulation results show that the novel zone 3 distance relay elements using the proposed method operate correctly for various events

Assessment of subclinical left ventricular dysfunction in patients with chronic mitral regurgitation using torsional parameters described by tissue doppler imaging

Background: Left ventricular (LV) twist is due to oppositely directed apical and basal rotation and has been proposed as a sensitive marker of LV function. We sought to assess the impact of chronic pure mitral regurgitation (MR) on the torsional mechanics of the left human ventricle using tissue Doppler imaging. Methods: Nineteen severe MR patients with a normal LV ejection fraction and 16 non-MR controls underwent conventional echocardiography and apical and basal short-axis color Doppler myocardial imaging (CDMI). LV rotation at the apical and basal short-axis levels was calculated from the averaged tangential velocities of the septal and lateral regions, corrected for the LV radius over time. LV twist was defined as the difference in LV rotation between the two levels, and the LV twist and twisting/untwisting rate profiles were analyzed throughout the cardiac cycle. Results: LV twist and LV torsion were significantly lower in the MR group than in the non-MR group (10.38 ° ± 4.04 ° vs. 13.95 ° ± 4.27 °; p value = 0.020; and 1.29 ± 0.54 °/cm vs. 1.76 ± 0.56 °/cm; p value = 0.021, respectively), both suggesting incipient LV dysfunction in the MR group. Similarly, the untwisting rate was lower in the MR group (-79.74 ± 35.97 °/s vs.-110.96 ± 34.65 °/s; p value = 0.020), but there was statistically no significant difference in the LV twist rate. Conclusion: The evaluation of LV torsional parameters in MR patients with a normal LV ejection fraction suggests the potential role of these sensitive variables in assessing the early signs of ventricular dysfunction in asymptomatic patients

Huge arteriovenous fistula between a giant aneurismal right coronary artery and coronary sinus

Coronary arteriovenous fistulas are rare and may be congenital, traumatic, or iatrogenic. We report one of these rare congenital anomalies with a giant aneurismal right coronary artery (RCA) in a middle-aged lady who was asymptomatic for a long time

Geographically distributed hybrid testing & collaboration between geotechnical centrifuge and structures laboratories

© 2018, Institute of Engineering Mechanics (IEM). All rights reserved. Distributed Hybrid Testing (DHT) is an experimental technique designed to capitalise on advances in modern networking infrastructure to overcome traditional laboratory capacity limitations. By coupling the heterogeneous test apparatus and computational resources of geographically distributed laboratories, DHT provides the means to take on complex, multi-disciplinary challenges with new forms of communication and collaboration. To introduce the opportunity and practicability afforded by DHT, here an exemplar multi-site test is addressed in which a dedicated fibre network and suite of custom software is used to connect the geotechnical centrifuge at the University of Cambridge with a variety of structural dynamics loading apparatus at the University of Oxford and the University of Bristol. While centrifuge time-scaling prevents real-time rates of loading in this test, such experiments may be used to gain valuable insights into physical phenomena, test procedure and accuracy. These and other related experiments have led to the development of the real-time DHT technique and the creation of a flexible framework that aims to facilitate future distributed tests within the UK and beyond. As a further example, a real-time DHT experiment between structural labs using this framework for testing across the Internet is also presented

Doppler echocardiographic indices in aortic coarctation: A comparison of profiles before and after stenting

Background: Diagnosis of aortic coarctation is important as it is a difficult condition to evaluate, especially in adults. A Doppler echocardiographic index could provide a simple tool to evaluate coarctation. This study was performed to compare Doppler echocardiographic profiles before and after stenting and to assess the diagnostic value of a complete list of echocardiographic indices for detecting aortic coarctation. Methods: This prospective study was conducted on 23 patients with a diagnosis of aortic coarctation based on angiography. Echocardiographic assessment was done twice for all patients before and after stenting. Each time, two-dimensional and Doppler echocardiographic imaging modalities were performed and complete lists of indices were recorded for each case. After comparing the values of indices before and after stenting, diagnostic values of each index were calculated in order to diagnose significant coarctation. Results: Twenty-three patients, including 16 males and seven females with a mean age of 26.14 ± 10.17 years, were enrolled in this study. Except for the mean velocity and mean pressure gradient of the abdominal aorta, the values of the other indices of the abdominal/descending aorta showed enough change after stenting to indicate significant diagnostic accuracy for detecting aortic coarctation. The velocity-time integral and the pressure half-time were among the indices with the highest accuracy rates for this purpose (all p < 0.001). Conclusion: Post-stenting echocardiographic profiles could provide a reliable reference value of the normal aortic haemodynamics as a unique identification of each patient and it is presumed that these indices could be used as reliable indicators of response to treatment

Determination of instantaneous interventricular septum wall thickness by processing sequential 2D echocardiographic images

Non-invasive quantitative analysis of the heart walls thickness is a fundamental step in diagnosis and discrimination of heart disease. Thickness measurements in 2D echocardiographic images have many applications in research and clinic for assessing of wall stress, wall thickening and viability parameters. Regarding to interventricular septum wall thickness measurement by conventional manual method is more dependent on sonographer experiment; this encouraged these researchers to develop a semi-automatic computer algorithm in accessing to interventricular septum segments thickness. We proposed and carried out a computerized algorithm for wall thickness measurements in 2D echocardiographic image frames. In this program, wall thickness measurement is based of intensity profile function and adaptive bilateral thresholding operation. For validation, thicknesses of septum base and mid segments were estimated in constituent image frames with use of proposed method and then were compared with conventional manual results at same images of the cardiac cycle by statistical methods. In our sample image frames (240 corresponding segments; with different rang of image quality), a bias of 0.10 and 0.12 mm with SD differences of ±0.81 and ±0.72 mm and correlation coefficients of 0.87 and 0.89 were found in base and mid segments, respectively. Interobserver variability using the Computer-Assisted Method (CAM) and Conventional Manual Method (CMM) were 4.0 and 4.7 for the basal and 2.8 and 3.9 for the middle segments. The method introduced in the present study permits precise thickness assessment of base and mid segments of the interventricular septum wall and has high concordance with CMM. © 2007 Asian Network for Scientific Information

Global and regional left ventricular function improvement following successful percutaneous coronary intervention in patients with ischemic left ventricular dysfunction

This study assessed changes in global and regional systolic left ventricular function after successful percutaneous recanalization of coronary artery occlusions. A consecutive series of 110 patients with mean ± SD age of 53.6 ± 9.1 years, in whom a complete angiographic evaluation was available before angioplasty, underwent successful percutaneous recanalization of significant occlusions of coronary arteries. Left ventricular ejection fraction and wall motion score index were assessed by echocardiography at baseline, and 1, and 6 months after recanalization. Left ventricular ejection fraction increased from a mean ± SD of 40.7 ± 4.52 at baseline to 50 ± 8.3 after one month (P < 0.001) and to 50.9 ± 8.5 after 6 months. There was no significant difference between left ventricular ejection fraction at the end of the first and the sixth month of treatment (P = NS). The wall motion score index decreased from 1.3 ± 0.2 at baseline to 1.1 ± 0.2 after one month (P < 0.01). There was no significant difference between 1 and 6 months results. Six-month follow-up of all patients showed significant improvement in both angina severity and NYHA class. The restoration of coronary potency of occluded coronary arteries by successful percutaneous recanalization is associated with significant improvement in regional and global left ventricular function and clinical outcome

Assessment of left atrial reservoir function in mitral valve disease by tissue doppler, strain and strain rate imaging

Introduction: Mitral valve stenosis and mitral valve regurgitation still result in significant morbidity and mortality. It has been shown that atrial remodeling and atrial fibrillation may occur in these patients. We sought to investigate how pressure or volume overload in the left atrium could impact atrial deformation properties obtained via Doppler-derived velocity and strain/strain rate imaging. Methods: Thirty-six patients, comprising 17 patients with a diagnosis of moderate to severe mitral stenosis and 19 patients with a diagnosis of moderate to severe mitral regurgitation, were compared with 16 healthy subjects. Two-dimensional, pulse Doppler, and tissue Doppler transthoracic echocardiographic study was performed. Measurement of regional velocity, strain and SR profiles, peak systolic velocity, peak strain, and strain rate was performed in two segments of the four left atrial walls. Results: There was a significant decline in peak systolic velocity in the mitral stenosis patients in both annular and roof segments, but the difference was not statistically significant between the mitral regurgitation patients and the healthy subjects. Total velocity was significantly lower in the mitral stenosis patients than in the healthy subjects, but the difference was not statistically significant between the healthy subjects and the mitral regurgitation patients. Comparison of total strain showed significant differences between the three groups mainly due to a decline in strain in the mitral stenosis patients in comparison with the other two groups. Comparison of total peak systolic strain rate between the groups showed significant differences due to a significant decline in the mitral stenosis group and a non-significant decline in the mitral regurgitation group by comparison with the healthy group. Conclusion: This reduction, especially in strain and strain rate, shows that the reservoir function of the left atrium could be compromised more severely in asymptomatic mitral stenosis patients. © 2014 American Scientific Publishers All rights reserved

Echocardiographic characteristics including tissue Doppler imaging after enhanced external counterpulsation therapy.

This study assessed the effects of a course of enhanced external counterpulsation (EECP) therapy on systolic and diastolic cardiac function using echocardiography to measure left ventricular ejection fraction (LVEF), end-systolic volume (ESV), end-diastolic volume (EDV), systolic wave (Sm), early diastolic wave (Ea), Vp, E/Ea, E/Vp, and diastolic function grade in 25 patients before and after 35 hours of EECP. EECP reduced ESV and EDV and increased ejection fraction significantly in patients with baseline LVEF or = 14 (P=.032, .038, .007), baseline grade II or III diastolic dysfunction (decreased compliance) (P=.014, .032, .027), baseline Ea 50, baseline E/Ea or = 7 cm/s, and Sm > or = 7 cm/s. These results demonstrate improved systolic and diastolic function in selected patients and provide new insight into potential clinical applications of EECP