Methods for estimation of the vacuum status in vacuum circuit breakers

In this paper several methods are described for the estimation of the pressure inside vacuum interrupters which have been in operation for many years. The methods are applicable without demounting the interrupters and use only electrical measuring techniques. According to these methods the vacuum circuit breakers are subjected to synthetic circuits, switch-off limited currents, either 10 A dc or 300 A ac. With the 10 A dc method the height of arc voltage spikes are measured and represented in a histogram. The shape of the histogram is discriminative for pressures below or above 10-2 Pa. Switching tests with currents of 200 to 400 A ac in inductive and capacitive circuits also showed different behavior for internal pressures below or above 10-1 Pa. A three phase 200 A test device with a 10 kV recovery voltage, fed from a standard 380 V supply, showed similar result

Sub-chronic toxicity study in rats orally exposed to nanostructured silica

Synthetic Amorphous Silica (SAS) is commonly used in food and drugs. Recently, a consumer intake of silica from food was estimated at 9.4 mg/kg bw/day, of which 1.8 mg/kg bw/day was estimated to be in the nano-size range. Food products containing SAS have been shown to contain silica in the nanometer size range (i.e. 5 – 200 nm) up to 43% of the total silica content. Concerns have been raised about the possible adverse effects of chronic exposure to nanostructured silica

Windsnelheidsprofiel boven zee

De processen die de winden veroorzaken in de atmosfeer veranderen met de hoogte. Dit rapport handelt over de eerste tientallen meters boven het zee-oppervlak. De richtingsverandering van de wind, die door de aardrotatie ste veroorzaakt wordt, blijft dan beperkt. Voor de 50 breedtegraad heeft de richtingsverandering de orde van grootte van 0.5° per 10 meter. Het windsnelheidsprofiel hangt in sterke mate af van de turbulentie. De turbulentie kan op twee manieren ontstaan: a) door over elkaar schuivende luchtlagen wordt zgn. mechanische turbulentie opgewekt; b) door warmte-uitwisseling van een luchtdeeltje met zijn omringende omgeving wordt zgn. konvektieve turbulentie opgewekt. Voorlopig wordt uitgegaan van de toestand waarin alleen mechanische turbulentie optreedt. Er is dus geen warmte-uitwisseling in de atmosfeer. Hetgeen per definitie betekent dat de processen adiabatisch zijn en dat de atmosfeer in de neutrals toestand verkeert.Hydraulic EngineeringCivil Engineering and Geoscience

Microplastics in aquatic food chain : sources, measurement, occurrence and potential health risks

Pollution of the environment with plastics is a growing problem, and is expected to persist for hundreds to thousands of years. As a result microplastics, plastic particles with size smaller than 5 mm, are ubiquitously present in the aquatic food chain. The present literature review shows that the information needed for such an evaluation is not available ye

Methods for estimation of the vacuum status in vacuum circuit breakers

In this paper several methods are described for the estimation of the pressure inside vacuum interrupters which have been in operation for many years. The methods are applicable without demounting the interrupters and use only electrical measuring techniques. According to these methods the vacuum circuit breakers are subjected to synthetic circuits, switch-off limited currents, either 10 A dc or 300 A ac. With the 10 A dc method the height of arc voltage spikes are measured and represented in a histogram. The shape of the histogram is discriminative for pressures below or above 10-2 Pa. Switching tests with currents of 200 to 400 A ac in inductive and capacitive circuits also showed different behavior for internal pressures below or above 10-1 Pa. A three phase 200 A test device with a 10 kV recovery voltage, fed from a standard 380 V supply, showed similar result

A Review of Analytical Methods for the Identification and Characterization of Nano Delivery Systems in Food

Detection and characterization of nano delivery systems is an essential part of understanding the benefits as well as the potential toxicity of these systems in food. This review gives a detailed description of food nano delivery systems based on lipids, proteins, and/or polysaccharides and investigates the current analytical techniques that can be used for the identification and characterization of these delivery systems in food products. The analytical approaches have been subdivided into three groups; separation techniques, imaging techniques, and characterization techniques. The principles of the techniques together with their advantages and drawbacks, and reported applications concerning nano delivery systems, or otherwise related compounds are discussed. The review shows that for a sufficient characterization, the nano delivery systems need to be separated from the food matrix, for which high-performance liquid chromatography or field flow fractionation are the most promising techniques. Subsequently, online photon correlation spectroscopy and mass spectrometry seem to be a convenient combination of techniques to characterize a wide variety of nano delivery system