Switching Arc Energy Limitation Approach for LV Circuit Breakers

This paper presents an experimentally verified approach to deriving switching arc energy limitations for low-voltage (LV) circuit breakers (CBs). Air-insulated contactors equipped with additional vacuum-insulated (VI) arcing contacts were tested for AC and DC current interruption efficiency, respectively. In the study, the contact arrangements of reed relay VI contact switches of low current breaking capacity combined with air-insulated contactors were examined. Tests were performed on selected LV CBs inductively loaded for LV power network rated voltages. A comparative analysis of the arc energy resulting from various arc time durations recorded during the switching-off operation was performed. Using a variety of either basic CB air-insulated contact systems or combined contact systems, a practical assessment of the proposed idea for enhancing the arc quenching efficiency was undertaken. As a result of the implementation of the proposed idea, the arc burning duration time was indicated as being hundreds of times shorter. In most cases, a complete arc reduction was achieved. Moreover, the resulting arc energy dissipation during the breaking operation was substantially minimized. Consequently, a significant increase in the total current breaking capacity of the tested CBs was achieved.

MRI only in a patient with prostate cancer with bilateral metal hip prostheses: case study

Objective: To outline a practical method of performing prostate cancer radiotherapy in patients with bilateral metal hip prostheses with the standard resources available in a modern general hospital. The proposed workflow is based exclusively on magnetic resonance imaging (MRI) to avoid computed tomography (CT) artifacts. Case description: This study concerns a 73-year-old man with bilateral hip prostheses with an elevated risk prostate cancer. Magnetic resonance images with assigned electron densities were used for planning purposes, generating a synthetic CT (sCT). Imaging acquisition was performed with an optimized Dixon sequence on a 1.5T MRI scanner. The images were contoured by autosegmentation software, based on an MRI database of 20 patients. The sCT was generated assigning averaged electron densities to each contour. Two volumetric modulated arc therapy plans, a complete arc and a partial one, where the beam entrances through the prostheses were avoided for about 50° on both sides, were compared. The feasibility of matching daily cone beam CT (CBCT) with MRI reference images was also tested by visual evaluations of different radiation oncologists. Conclusions: The use of magnetic resonance images improved accuracy in targets and organs at risk (OARs) contouring. The complete arc plan was chosen because of 10% lower mean and maximum doses to prostheses with the same planning target volume coverage and OAR sparing. The image quality of the match between performed CBCTs and MRI was considered acceptable. The proposed method seems promising to improve radiotherapy treatments for this complex category of patients.

Validation of high bleeding risk criteria and definition as proposed by the academic research consortium for high bleeding risk

Aims To validate the set of clinical and biochemical criteria proposed by consensus by the Academic Research Consortium (ARC) for High Bleeding Risk (HBR) for the identification of HBR patients. These criteria were categorized into major and minor, if expected to carry in isolation, respectively, ≥4% and <4% Bleeding Academic Research Consortium (BARC) 3 or 5 bleeding risk within 1-year after percutaneous coronary intervention (PCI). High bleeding risk patients are those meeting at least 1 major or 2 minor criteria. Methods and results All patients undergoing PCI at Bern University Hospital, between February 2009 and September 2018 were prospectively entered into the Bern PCI Registry (NCT02241291). Age, haemoglobin, platelet count, creatinine, and use of oral anticoagulation were prospectively collected, while the remaining HBR criteria except for planned surgery were retrospectively adjudicated. A total of 16 580 participants with complete ARC-HBR criteria were included. After assigning 1 point to each major and 0.5 point to each minor criterion, we observed for every 0.5 score increase a step-wise augmentation of BARC 3 or 5 bleeding rates at 1 year ranging from 1.90% among patients fulfilling no criterion, through 4.01%, 5.98%, 7.42%, 8.60%, 12.21%, 12.29%, and 17.64%. All major and five out of six minor criteria, conferred in isolation a risk for BARC 3 or 5 bleeding at 1 year exceeding 4% at the upper limit of the 95% confidence intervals. Conclusion All major and the majority of minor ARC-HBR criteria identify in isolation patients at HBR.

On Almost Complete Caps in PG(N, q)

We propose the concepts of almost complete subset of an elliptic quadric in the projective space PG(3, q) and of almost complete cap in the space PG(N, q), N ≥ 3, as generalizations of the concepts of almost complete subset of a conic and of almost complete arc in PG(2, q). Upper bounds of the smallest size of the introduced geometrical objects are obtained by probabilistic and algorithmic methods.

Oil Aging due to Partial Discharge Activity

<p>Oil is the main insulation in power transformers and over long time of ageing its insulation properties can change. In this paper ageing of oil due to the exposure to electric discharges was investigated. The effect of high energy discharges (complete arc) and low energy discharges (partial discharges) on oil properties such as breakdown strength and oil conductivity was investigated.<br />An experimental setup consisting of two spherical electrodes was designed. The adjustable distance between the two electrodes made it possible to have PD with different magnitude.<br />The oil conductivity and breakdown strength was measured for three sets of experiments. The first group of experiments was performed on new oil in order to have a reference for comparison. In the second group of experiments the new oil samples was exposed to 1000 and 3000 lightning impulses. In the third group of experiments new oil samples was exposed to partial discharge for different duration of time. Oil conductivity and breakdown strength of these aged samples were compared with new oil. The results show that after exposure to lightning impulse oil conductivity increases and breakdown strength decreases, However PD activity for short time does not change the oil conductivity but it reduces the breakdown strength.</p>

The proximal and distal position of the radius relative to the ulna through a full range of elbow flexion and forearm rotation

The purpose of this study was to measure the position of the radius relative to the ulna through a complete range of elbow flexion and forearm rotation. Twenty cadaveric upper extremities were mounted on a testing jig that allowed simultaneous control of elbow flexion and forearm rotation. The longitudinal position of the radius relative to the ulna was measured using a three-dimensional digitizer at full pronation, mid-pronation (45°), neutral (0°), mid-supination (45°) and full supination at 10°, 30°, 60°, 90° and 120° of elbow flexion. Our results showed that the radius is located distally when in supination and is located more proximally as it is rotated into pronation. The longitudinal position of the radius changes over 9 mm when moving through a complete arc of forearm rotation. The angle of elbow flexion had a secondary effect on the longitudinal position of the radius, causing changes of less than 0.8 mm.