Dynamic stabilization of large flexible space structures

In dit proefschrift wordt als voorbeeld van een grote constructie een communicatiesatelliet beschouwd. Deze communicatiesatelliet bestaat in dit geval uit een centraal satellietlichaam met lange armen waarop zonnepanelen zijn bevestigd. ... Zie: Samenvatting

Plantmonitoring op basis van fotosynthese sensoren : ontwikkelen en testen van sensoren

The basic process for crop growth and production is photosynthesis. Measuring crop photosynthesis is therefore important to monitor the status of the crop and whether the greenhouse climate is set to the needs of the crop. In this project, two monitoring systems for crop photosynthesis were developed and tested. (1) The crop photosynthesis monitor is a soft sensor that can calculate the CO2 uptake of an entire crop. The basis for these calculations are the balance between CO2 supply and CO2 loss via ventilation and crop photosynthesis. By measuring the CO2 concentration and humidity inside and outside the greenhouse, the crop photosynthesis can be calculated. (2) The CropObserver is a fluorescence sensor that measures the light use efficiency of photosynthesis of a large crop area (3 x 3 m2). The crop receives light pulses from a laser in the top of the greenhouse, the sensor measures the fluorescence signal of the crop. Both sensors were tested in a tomato crop in 2014 with promising results. The sensors functioned without problems and delivered patterns of daily photosynthesis which matched the reference measurements reasonably well up to well

Development and validation of two crop photosynthesis monitoring systems to support greenhouse climate control

Over the last years, energy consumption in greenhouse horticulture has been reduced considerably by using (multiple) screens, controlled dehumidification and more efficient use of assimilation light. All these actions affect greenhouse climate and thereby plant processes. Measuring crop photosynthesis, a process that responds very rapidly to changes in climate, would be suited to monitor whether the climate is set according to the needs of the plant. Two monitoring systems have been developed, the crop photosynthesis monitor and the CropObserver. The crop photosynthesis monitor is a soft sensor that calculates the CO2 uptake of the entire greenhouse, based on the mass balance of a greenhouse for CO2. At known CO2 supply rates, measuring the CO2 concentrations inside and outside the greenhouse, and determining the ventilation loss allows the calculation of the crop photosynthesis. The CropObserver is a fluorescence sensor that provides laser light pulses from above in a surface of 3×3 m. Since the measurements are fast, the sensor provides a good image of the electron transport rate (ETR) of a large crop area in a short period of time. Evaluation of the sensors in a tomato cultivation showed that the data of the crop photosynthesis monitor matched the daily pattern of manual photosynthesis data up-scaled to crop photosynthesis by a crop growth model reasonably well. The CropObserver data were very comparable to local reference fluorescence measurements, and closely followed irradiance patterns over the day. Both systems have attracted the attention of Dutch growers, and will be further evaluated in commercial greenhouses

Kroon de boom tot airco van de stad : Verkoeling door groen en beplanting gemodelleerd

Dit artikel sluit aan op de publicatie over droogteschade bij stadsbomen in het vorige nummer van het vakblad (Bomen 53). Vijf studenten aan Hogeschool Van Hall Larenstein (VHL) hebben in 2019/2020 als onderdeel van de minor ‘Bomen en Stedelijke Omgeving’ onderzoek uitgevoerd naar het effect van groen/beplanting op de gevoelstemperatuur in ‘bloemkoolwijken’. De opdrachtgever voor dit onderzoek was dr. ir. Jelle Hiemstra van Wageningen University & Research. Op het gebied van ENVI-met kregen zij begeleiding van dr. ir. Cor Jacobs van Wageningen University & Research, die hen hielp met het bouwen van het model en het berekenen van de temperatuur, luchtvochtigheid, windstromen en gevoelstemperatuur. De studenten werden begeleid door docent dr. Mart Vlam. Onderstaand verslag van dit onderzoek is geschreven op basis van vragen die ex-redactielid Jozé ’t Hoen en redactielid Jaco Houweling de studenten hebben voorgelegd