Plant photosynthesis and biomass production are associated with the amount of intercepted light, especially the light distribution inside the canopy. Three virtual canopies (n = 80, 3.25 plants/m2) were constructed based on average leaf size of the digitized plant structures: ‘small leaf’ (98.1 cm2), ‘medium leaf’ (163.0 cm2) and ‘big leaf’ (241.6 cm2). The ratios of diffuse light were set in three gradients (27.8%, 48.7%, 89.6%). The simulations of light interception were conducted under different ratios of diffuse light, before and after the normalization of incident radiation. With 226.1% more diffuse light, the result of light interception could increase by 34.4%. However, the 56.8% of reduced radiation caused by the increased proportion of diffuse light inhibited the advantage of diffuse light in terms of a 26.8% reduction in light interception. The big-leaf canopy had more mutual shading effects, but its larger leaf area intercepted 56.2% more light than the small-leaf canopy under the same light conditions. The small-leaf canopy showed higher efficiency in light penetration and higher light interception per unit of leaf area. The study implied the 3D structural model, an effective tool for quantitative analysis of the interaction between light and plant canopy structure.
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Research demonstrated a large variety regarding effects of light (e.g. health, performance, or comfort effects). Since human health is related to each individual separately, the lighting conditions around these individuals should be analysed individually as well. This paper provides, based on a literature study, an overview identifying the currently used methodologies for measuring lighting conditions in light effect studies. 22 eligible articles were analysed and this resulted in two overview tables regarding the light measurement methodologies. In 70% of the papers, no measurement details were reported. In addition, light measurements were often averaged over time (in 84% of the papers) or location level (in 32% of the papers) whereas it is recommended to use continuous personal lighting conditions when light effects are being investigated. Conclusions drawn in light effect studies based on personal lighting conditions may be more trusting and valuable to be used as input for an effect-driven lighting control system.
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Light pollution is one of the fastest growing and most pervasive of environmental pollution (Chepesiuk, 2009). In the last couple of years, a lot of research has been done about the effects of light pollution. The interest in light pollution has been growing in many fields of science, extending from the traditional field of astronomy to atmospheric physics, environmental sciences, natural sciences and human sciences. Better insight in light pollution is likely to contribute to design and operation of Facility Management (FM) based on evidence. According to Cinzano, Falchi, & Elvidge (2001), the Netherlands is one of the countries with the highest amount of light pollution, just as the United States. A sample of students in the Netherlands and the United States has been taken to explore differences and similarities between the two countries.
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Light therapy is applied as treatment for a variety of problems related to health and ageing, including dementia. Light therapy is administered via light boxes, light showers, and ambient bright light using ceiling-mounted luminaires. Long-term care facilities are currently installing dynamic lighting systems with the aim to improve the well-being of residents with dementia and to decrease behavioural symptoms. The aim of this chapter is to provide an overview of the application of ceiling-mounted dynamic lighting systems as a part of intelligent home automation systems found in healthcare facilities. Examples of such systems are provided and their implementation in practice is discussed. The available, though limited, knowledge has not yet been converted into widespread implementable lighting solutions, and the solutions available are often technologically unsophisticated and poorly evaluated from the perspective of end-users. New validated approaches to the design and application of ambient bright light are needed.
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Light therapy is applied to older people with dementia as a treatment to reset the biological clock, to improve the cognitive functioning, and to reduce behavioral symptoms. Although the methodological quality of light therapy studies is essential, many aspects concerning the description of the lighting applied are missing. This study reviewed light therapy studies concerning the effects on people with dementia as a way to check the methodological quality of the description of light from a light engineering perspective. Twelve studies meeting the inclusion criteria were chosen for further analysis. Each study was scored on a list of aspects relevant to a proper description of lighting aspects. The overview demonstrates that the overall quality of the methodologies is poor. The studies describe the lighting insufficiently and not in the correct metrics. The robustness of light therapy studies can be improved by involving a light engineer or specialist.
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Light profoundly impacts many aspects of human physiology and behaviour, including the synchronization of the circadian clock, the production of melatonin, and cognition. These effects of light, termed the non-visual effects of light, have been primarily investigated in laboratory settings, where light intensity, spectrum and timing can be carefully controlled to draw associations with physiological outcomes of interest. Recently, the increasing availability of wearable light loggers has opened the possibility of studying personal light exposure in free-living conditions where people engage in activities of daily living, yielding findings associating aspects of light exposure and health outcomes, supporting the importance of adequate light exposure at appropriate times for human health. However, comprehensive protocols capturing environmental (e.g., geographical location, season, climate, photoperiod) and individual factors (e.g., culture, personal habits, behaviour, commute type, profession) contributing to the measured light exposure are currently lacking. Here, we present a protocol that combines smartphone-based experience sampling (experience sampling implementing Karolinska Sleepiness Scale, KSS ratings) and high-quality light exposure data collection at three body sites (near-corneal plane between the two eyes mounted on spectacle, neck-worn pendant/badge, and wrist-worn watch-like design) to capture daily factors related to individuals’ light exposure. We will implement the protocol in an international multi-centre study to investigate the environmental and socio-cultural factors influencing light exposure patterns in Germany, Ghana, Netherlands, Spain, Sweden, and Turkey (minimum n = 15, target n = 30 per site, minimum n = 90, target n = 180 across all sites). With the resulting dataset, lifestyle and context-specific factors that contribute to healthy light exposure will be identified. This information is essential in designing effective public health interventions.
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Nightshift workers go against the natural sleep–wake rhythm. Light can shift the circadian clock but can also induce acute alertness. This placebo-controlled exploratory field study examined the effectiveness of light glasses to improve alertness while reducing the sleep complaints of hospital nurses working nightshifts. In a crossover within-subjects design, 23 nurses participated, using treatment glasses and placebo glasses. Sleepiness and sleep parameters were measured. A linear mixed model analysis on sleepiness revealed no significant main effect of the light intervention. An interaction e ect was found indicating that under the placebo condition, sleepiness was significantly higher on the first nightshift than on the last night, while under the treatment condition, sleepiness remainedstable across nightshift sessions. Sleepiness during the commute home also showed a significant interaction effect, demonstrating that after the first nightshift, driver sleepiness was higher for placebo than for treatment. Subjective sleep quality showed a negative main effect of treatment vs. placebo, particularly after the first nightshift. In retrospect, both types of light glasses were self-rated as effective. The use of light glasses during the nightshift may help to reduce driver sleepiness during the commute home, which is relevant, as all participants drove home by car or (motor) bike.
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A modified genetic algorithm (MGA) optimization procedure, alongside time series machine learning (ML) classifiers, is proposed to minimize handovers in a digital twin-based visible light communication (VLC) system. Frequent handovers have a direct impact on the overall performance of the VLC system due to the inherent connection downtime of a handover process. The handover scheme proposed in this article considers the receiver trajectory information to minimize handovers, maintaining the system performance below the forward error correction limit. Simulation results indicate that the proposed scheme outperforms a power-based handover scheme, achieving handover reductions of 42.47%. Therefore, the MGA combined to the ML models approach is an effective means of minimizing handovers, as well as improving overall VLC system performance.
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Purpose In the Netherlands, the prevalence of visual impairments is the highest among the subgroup of nursing home residents. Over 40 percent are estimated to have visual impairments1. Older adults experience visual problems due to biological aging or eye disease2. These problems can affect several visual functions as well as daily functions in general3,4. Providing appropriate lighting of sufficient intensity and color temperature (CT), and making use of capabilities of the visual environment in the nursing home4 is one of the tasks for professional carers.Light conditions were measured in order to find out to what extent older adults live with the proper lighting conditions. With these data, we wanted to enhance the awareness among care professionals of how light conditions affect the daily lives of the nursing home residents. Moreover, care professionals and technical staff could make the right improvements to the nursing home environment based on the outcomes. Method We assessed light conditions (Konica Minolta chromameter CL-200) in seven nursing homes in the Netherlands. Light conditions were measured in places where residents spend most of their time during the day. In total, 59 living rooms and corridors were assessed in this study. Horizontal and vertical illuminances as well as CT were measured and compared to the values given in a guideline by the Dutch Society for Illumination5. The study was performed between October 2009 and the end of March 2010 at daytime between 10:00 and 15:00 hours. By measuring in autumn, winter and early spring, the contribution of daylight to the indoor illuminance levels was kept at a minimum. Results & Discussion In general lighting conditions encountered in the nursing homes were poor. Four-fifths of the measured illuminances in the common rooms were below the 1,000 lx threshold. Illuminances in the corridors fell below the 200 lx threshold in at least three quarters of the measurements. This means that nursing home residents may have difficulty carrying out tasks and could fall during transfers. The CT of light to which nursing home residents were exposed, fell below the reference value for daylight of 5,000 K with median scores of 3,400 to 4,500 K. High CT of light, in combination with higher illuminances, may positively affect the biological clock, resulting in better sleep quantity and quality.Nursing home staff should be aware of these data in order to arrange better light conditions. Technical staff should be aware that lighting guidelines are not specifically developed for older adults. Special attention should be paid to the fact that older adults need more light than younger persons to perform Activities of Daily Living (ADL).
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