The Effect of Diffuse Light on Crops

Light is not evenly distributed in Dutch glass greenhouses, but this can be improved with diffuse light. Modern greenhouse coverings are able to transform most of the light entering the greenhouse into diffuse light. Wageningen UR Greenhouse Horticulture has studied the effect of diffuse light on crops for several years. Modelling and experimental studies showed that crops such as fruit vegetables with a high plant canopy as well as ornamentals with a small plant canopy can utilize diffuse light better than direct light. Diffuse light penetrates the middle layers of a high-grown crop and results in a better horizontal light distribution in the greenhouse. Diffuse light is absorbed to a better degree by the middle leaf layers of cucumber, resulting in a higher photosynthesis. The actual photosynthesis of four pot plant species was found to be increased and crop temperatures were lower during high irradiation. The yield of cucumbers was increased, and the growth rate of several potted plants was increased. These investigations have resulted in a quantitative foundation for the potentials of diffuse light in Dutch horticultural greenhouses and the selection and verification of technological methods to convert direct sunlight into diffuse light

Diffuus glasdek geeft fikse productietoename

De eenmalige aanschaf van diffuus glas met een even grote lichtdoorlatendheid als helder glas, heeft grote gevolgen. Diffuus licht dringt dieper door in het gewas. Bij de kop van de plant loopt de temperatuur minder hoog op, waardoor meer licht kan worden toegelaten in de teelt. Als gevolg daarvan verandert de plant- en bladvorm en is meer fotosynthese mogelijk middenin het gewas. In een proef gaf dit een 6,5 tot 9,2% hogere komkommerproductie: meer kilo's door meer vruchten en een hoger vruchtgewich

Diversified Late Acceptance Search

The well-known Late Acceptance Hill Climbing (LAHC) search aims to overcome the main downside of traditional Hill Climbing (HC) search, which is often quickly trapped in a local optimum due to strictly accepting only non-worsening moves within each iteration. In contrast, LAHC also accepts worsening moves, by keeping a circular array of fitness values of previously visited solutions and comparing the fitness values of candidate solutions against the least recent element in the array. While this straightforward strategy has proven effective, there are nevertheless situations where LAHC can unfortunately behave in a similar manner to HC. For example, when a new local optimum is found, often the same fitness value is stored many times in the array. To address this shortcoming, we propose new acceptance and replacement strategies to take into account worsening, improving, and sideways movement scenarios with the aim to improve the diversity of values in the array. Compared to LAHC, the proposed Diversified Late Acceptance Search approach is shown to lead to better quality solutions that are obtained with a lower number of iterations on benchmark Travelling Salesman Problems and Quadratic Assignment Problems

Vroege komkommerteelt onder diffuus glas

Abstract NL In een vroege teelt met komkommer is bij Wageningen UR Glastuinbouw in Bleiswijk nagegaan wat het effect is van diffuus glas met een haze van 71% op productie, kwaliteit en energiegebruik. Er is vergeleken met een kas gedekt met standaardglas en een gelijke lichttransmissie. De proef duurde van eind december tot en met eind april. De eerste stamvruchten onder diffuus glas bloeiden sneller en de uitgroeiduur was gemiddeld een halve dag korter. Al vanaf de eerste oogst was de productie onder diffuus glas hoger. Uiteindelijk gaf diffuus glas een 6% hogere kiloproductie door 4% meer en 2% zwaardere vruchten. Diffuus glas beïnvloedde de kwaliteit niet. De gemeten lichttransmissie in de diffuus glazen kas was gemiddeld 2.5% hoger dan bij de referentie. Tegen het diffuse kasdek was 30 tot ruim 350% meer condens aanwezig. Het energiegebruik steeg onder diffuus glas met 5%, maar door de hogere productie kwam de energie-efficiëntie gelijk uit met die van de referentiekas. Abstract UK In an early cucumber crop at Wageningen UR Greenhouse Horticulture in Bleiswijk, the effect of diffuse glass with a haze of 71% to production, quality and energy consumption was studied. The effects of diffuse glass were compared with those in a greenhouse covered with standard glass and the same light transmission. The trial lasted from the end of December to the end of April. The first stem fruits under diffuse glass flowered earlier and the growth duration was half a dayshorter on average. From the first harvest onwards, production was higher under diffuse glass. In the end, a production increase of 6% was realized, 4% more fruits and 2% heavier fruits. The fruit quality under diffuse glass was not affected. The measured light transmission in the diffuse glass greenhouse was on average 2.5% higher than in the reference. In the diffuse greenhouse 30 to over 350% more condensation was measured. The energy consumption increased by 5% under diffuse glass, but because of the higher production, the energy efficiency was the same as that of the reference greenhouse

On the mechanism of accelerated sedimentation of fine fractions in bidisperse suspension

Paper presented to the 10th International Conference on Heat Transfer, Fluid Mechanics and Thermodynamics, Florida, 14-16 July 2014.An estimation of increasing the average volume of sedimentation velocity of fine particles in bidisperse suspension due to their capturing in the circulation zone formed in the laminar flow of incompressible viscous fluid around the spherical coarse particle is proposed. The estimation is important for an explanation of the non-monotonic shape of the separation curve observed for hydrocyclones. The average volume sedimentation velocity is evaluated on the basis of a cellular model. The characteristic dimensions of the circulation zone are obtained on the basis of a numerical solution of Navier-Stokes equations. Furthermore, these calculations are used for modelling the fast sedimentation of fine particles during their co-sedimentation in bidisperse suspension. It was found that the acceleration of sedimentation of fine particles is determined by the concentration of coarse particles in bidisperse suspension, and the sedimentation velocity of fine fraction is proportional to the square of the coarse and fine particle diameter ratio. The limitations of the proposed model are ascertained.dc201

Effects of Carpal Tunnel Syndrome on adaptation of multi-digit forces to object mass distribution for whole-hand manipulation

Background Carpal tunnel syndrome (CTS) is a compression neuropathy of the median nerve that results in sensorimotor deficits in the hand. Until recently, the effects of CTS on hand function have been studied using mostly two-digit grip tasks. The purpose of this study was to investigate the coordination of multi-digit forces as a function of object center of mass (CM) during whole-hand grasping. Methods Fourteen CTS patients and age- and gender-matched controls were instructed to grasp, lift, hold, and release a grip device with five digits for seven consecutive lifts while maintaining its vertical orientation. The object CM was changed by adding a mass at different locations at the base of the object. We measured forces and torques exerted by each digit and object kinematics and analyzed modulation of these variables to object CM at object lift onset and during object hold. Our task requires a modulation of digit forces at and after object lift onset to generate a compensatory moment to counteract the external moment caused by the added mass and to minimize object tilt. Results We found that CTS patients learned to generate a compensatory moment and minimized object roll to the same extent as controls. However, controls fully exploited the available degrees of freedom (DoF) in coordinating their multi-digit forces to generate a compensatory moment, i.e., digit normal forces, tangential forces, and the net center of pressure on the finger side of the device at object lift onset and during object hold. In contrast, patients modulated only one of these DoFs (the net center of pressure) to object CM by modulating individual normal forces at object lift onset. During object hold, however, CTS patients were able to modulate digit tangential force distribution to object CM. Conclusions Our findings suggest that, although CTS did not affect patients’ ability to perform our manipulation task, it interfered with the modulation of specific grasp control variables. This phenomenon might be indicative of a lower degree of flexibility of the sensorimotor system in CTS to adapt to grasp task conditions

Combining Survival and Toxicity Effect Sizes from Clinical Trials: NCCTG 89-20-52 (Alliance)

Background: How can a clinician and patient incorporate survival and toxicity information into a single expression of comparative treatment benefit? Sloan et al. recently extended the ½ standard deviation concept for judging the clinical importance of findings from clinical trials to survival and tumor response endpoints. A new method using this approach to combine survival and toxicity effect sizes from clinical trials into a quality-adjusted effect size is presented.Methods: The quality-adjusted survival effect size (QASES) is calculated as survival effect size (ESS) minus the calibrated toxicity effect sizes (EST) (QASES=ESS-EST). This combined effect size can be weighted to adjust for the relative emphasis placed by the patient on survival and toxicity effects.Results: As an example, consider clinical trial NCCTG 89-20-52 which randomized patients to once-daily thoracic radiotherapy (ODTRT) versus twice-daily treatment of thoracic radiotherapy (TDRT) for the treatment of lung cancer. The ODTRT vs. TDRT arms had median survival time of 22 vs. 20 months (p=0.49) and toxicity rate of 39% vs. 54%, (p<0.05). The QASES of 0.18 standard deviations translates to a quality-adjusted survival difference of 5.7 months advantage for the ODRT arm over the TDRT treatment arm (22(16.3) months), p<0.05). Similar results are presented for the four possible case combinations of significant/non-significant survival and toxicity benefits using completed clinical trials.Conclusions: We used a novel approach to re-analyze clinical trial data to produce a single estimate for each treatment that combines survival and toxicity data. The QASES approach is an intuitive and mathematically simple yet robust approach

Invloed van een landschapselement (windsingel) op de verspreiding van ammoniak uit een varkenshouderij: eindrapport

Aanleiding van het in dit rapport gepresenteerde onderzoek was het vermoeden dat landschapselementen zoals windsingels, naast de ecologische- en landschappelijke waarde ook een rol zouden kunnen spelen bij het terugdringen van de verspreiding van emissies uit de veehouderij zoals ammoniak, fijn stof en geur. Dit vermoeden was gebaseerd op modelvoorspellingen en aanwijzingen uit de literatuur, waaruit bleek dat landschapselementen in staat zijn de verspreiding van agrarische emissies aanzienlijk te beïnvloeden. Door de fysieke aanwezigheid en het deels afvangen van de emissie door de beplanting zou de ongewenste verspreiding van luchtverontreinigingscomponenten worden tegengegaan. Aanleg van landschapselementen rond veehouderijen zou daarom, in aanvulling op andere emissie reducerende maatregelen (in de stal, management, etc.), een bijdrage kunnen leveren aan het terugdringen en vastleggen van agrarische emissies. Het in dit rapport gepresenteerde onderzoek richt zich met name op de effectiviteit van landschapselementen op het terugdringen van de verspreiding van ammoniak. Ook wordt enige informatie gegeven met betrekking tot andere agrarische emissies dan ammoniak zoals geur, fijnstof en de verspreiding van dierziekte