Calorimetric efficiency determination of power electronic variable speed drives

A calorimeter test bench for the efficiency and power loss determination of power electronic variable speed drives is presented. The balanced calorimetric setup with air as the cooling medium is proposed to test small electronic drives for AC motors in a power range from 1 kW up to 7,5 kW. The construction, the required measurement equipment, the measurement procedure and especially the measurement results and uncertainty are important aspects of this test bench and are discussed in this paper. The device under test is a 2,2kW drive which is measured using both the input-output method and the calorimetric method. The test results are compared and conclusions are made concerning usability, repeatability and accuracy of the test bench. The overall goal is to further examine and optimize the calorimetric approach and to be able to obtain more accurate and comparable test results of very high efficient frequency converters. This setup reaches an uncertainty of ±2,39% or ±1,48W on the power loss at full load and speed using the calorimetric method

CT perfusion as a selection tool for mechanical thrombectomy, a single-centre study

Background: Recently, CT perfusion (CTP) has been proposed as a selection tool for stroke patients to be treated with endovascular thrombectomy. We investigated whether functional outcome following endo-vascular treatment was improved after the introduction of CTP. Methods: This retrospective single-centre study includes all patients with a major vessel occlusion in the anterior circulation that received a CTP and underwent a mechanical thrombectomy from 2014 up to 2015. CTP were visually evaluated. Demographics, stroke and time data, procedural data, functional outcomes as measured by the modified Rankin Scale (mRS) and the association between these variables were studied. A comparison was made with the results of a similar local retrospective study from before the CTP "era". Results: Eighty-nine patients were included in this study. Median National Institutes of Health Stroke Scale (NIHSS) was 16 (Interquartile range 6). At three months, good functional outcome (GFO; mRS 0-2) was achieved in 48.4% and excellent functional outcome (EFO; mRS 0-1) in 34.4% of patients. The mortality rate at three months was 14.5%. GFO at one year was 44.8%, EFO was 31.3% and mortality 21.1%. The duration of the thrombectomy procedure and the EFO were associated (p = 0.032). The outcome improvement achieved with CTP was higher compared to the reference study (GFO 48.4% versus 44%; EFO 34.4% versus 29%) but remained below the statistical significance. Conclusions: Mechanical thrombectomy for anterior circulation strokes based on CTP did not result in a significant functional outcome improvement. The duration of the thrombectomy procedure was the sole time-interval related to improved functional outcome

Energy efficiency measurement procedure for gearboxes in their entire operating range

Over the last decade, forced regulations and a growing social awareness with respect to energy efficiency have resulted in a renewed interest in the research for high efficient electrical machines. When an electrical motor is coupled to a machine, in many cases a gearbox or belt transmission is used. Research shows a lack of information on energy efficiency of these components. In comparison to electrical motors and drives, there is very few regulation and if efficiency values can be found in catalogues, there is no regulated test procedure available to validate the data. As a result, the reliability of these efficiency values is unknown and comparison between manufacturers and technologies is impossible. In this paper a test bench is proposed to measure the energy efficiency of a gearbox with an accuracy up to 0.4%. The test bench is used to measure the efficiency of gearboxes in their entire speed and torque range. Contour maps are used to visualize these measurement results. Moreover, a measurement campaign using different gearboxes is carried out to compare the energy efficiency in the manufacturers catalogue and the measured efficiency

Intracranial dural arteriovenous fistula successfully treated by combined open-endovascular procedure

Intracranial dural arteriovenous fistulas constitute a rare though potentially devastating disease. Because the arterial (high-pressure) blood flow drains directly into the low-pressure venous system, there is a high risk of bleeding and associated neurological deficit. The classifications by Borden and Cognard underline the correlation between bleeding risk and venous drainage pattern of the fistula. There are different treatment options for this vascular pathology, which always poses a challenge for the physicians involved to offer the optimal treatment for an individual patient. This case report illustrates how combining forces between the neurosurgical and endovascular team benefits outcome. Simultaneously, this contributes to the growing amount of evidence that a new endovascular technique with transarterial ONYX embolisation enables complete obliteration of the vascular malformation