Light Distribution Research Articles

Method for 3D light-field reconstruction based on a spatially free camera

This study introduces an advanced algorithm for 3D light-field displays, utilizing disparity images from non-fixed cameras to achieve precise 3D reconstructions, moving beyond the complexities of traditional methods. Unlike standard approaches that depend on complex 3D reconstruction or specific camera arrangements, this algorithm uses pixel similarity across different viewpoints to determine depth accurately. It integrates camera parameters and light paths to restore light-field information meticulously, ensuring an optimal light distribution. By comparing with the projector image array (PIA) and display effects generated by traditional light-field encoding algorithms, we proved the effectiveness of our algorithm.

Feelings of safety for visitors recreating outdoors at night in different artificial lighting conditions

Artificial light can impact the actual and perceived safety of visitors recreating outdoors at night. Actual safety refers to how visitors identify aspects of their environment such as pathways and obstacles, while perceptions of safety refer to how safe they feel based on perceptions of the environment. Both influence the acceptability of different light conditions. The objective of this study is to better understand how light conditions influence visitors' perceptions of safety and their potential for pleasant experiences while recreating at night in a park-like setting. This paper explores study participants' self-reported feelings of safety across eight different light conditions using two different colors, 3000 K Correlated Color Temperature (warm white) and monochromatic amber, and 4 four different intensities (0.5, 1.0, 5.0, or 10.0 lux) during a nighttime recreation-focused experiment in a university's arboretum. Prior experience with nighttime outdoor recreation and community type (urban, suburban, rural) during adolescence were evaluated alongside light conditions as predictors of feelings of safety using ordered logistic regression. Participants of this study were 31.6% more likely to report higher feelings of safety in warm white light than amber light and 81.7% more likely to report higher feelings of safety at 5.0 lux than 0.5 lux. Further, individuals who felt safer in any lighting condition were 19.6 times more likely to feel greater potential for a pleasant experience while recreating than someone who did not report feeling safe or felt unsafe. Understanding the connection between light and perceived safety in park settings can help managers tailor lighting conditions to the needs of visitors while reducing ecological impacts - brighter and cooler temperature lighting have greater negative impacts on wildlife. Adjusting the distribution and intensity of light can increase the accessibility of nighttime recreation opportunities and the potential for comfortable and pleasant experiences for visitors.

Ultrasonic liquid crystal tunable light diffuser

Conventional light diffusers have periodic surface profiles, periodic refractive index distributions, or light scattering layers containing colloids. In all such structures the optical directivity of the light diffuser is cannot typically be controlled. Here we propose an electrically tunable light diffuser based on the application of ultrasound to a nematic liquid crystal (LC) material. The ultrasonic LC diffuser consists of an LC layer sandwiched by two glass discs and an ultrasonic transducer. The electrodes of the transducer are divided in a circumferential direction so that a resonant non-coaxial flexural vibration mode can be generated on the diffuser by controlling the electrical input signals. A continuous reversed-phase sinusoidal electric signal to the transducer generates the non-coaxial resonant flexural vibration mode on the glass disc, inducing an acoustic radiation force acting on the boundary between the LC layer and glass discs. This effect changes the molecular orientation of the LC and the transmitted light distribution. The diffusion angle of the transmitted light depends on the input voltage amplitude, and the diffusion angle was maximized at 16.0 V. The vibrational distribution and the diffusion directivity could be rotated by adjusting the input voltages to different electrodes, meaning that an ultrasonic LC diffuser with a thin structure and no moving mechanical parts provided a tunable light-diffusing functionality with rotatable directivity.

Manipulation of Bloch surface beams based on perfectly matched Bragg diffraction.

A generalized method is proposed for the manipulation of Bloch surface waves (BSWs) with multiple designed phases. This method is based on perfectly matched Bragg diffraction with a wide range of available diffraction angles and can be used beyond the paraxial limit to realize nonparaxial accelerating BSW beams. When combined with the caustic method, multiple accelerating beams with pre-engineered trajectories have been successfully generated, including power-law, circular, elliptic, and bottle beams. Furthermore, the transverse light field distribution of these accelerating beams is consistent with the theoretical prediction, indicating that the beam width can be manipulated by controlling the trajectory of the beam. The results of this work will facilitate the development of novel applications where controlling the trajectory and width of the two-dimensional beams is crucial, such as surface tweezers, and lab-on-chip photonic integrations.

Morphological and Pigment Responses to Far-Red and Photosynthetically Active Radiation in an Olive Cultivar Suitable for Super-High-Density Orchards.

Plant density is increasing in modern olive orchards to improve yields and facilitate mechanical harvesting. However, greater density can reduce light quantity and modify its quality. The objective was to evaluate plant morphology, biomass, and photosynthetic pigments under different red/far-red ratios and photosynthetically active radiation (PAR) combinations in an olive cultivar common to super-high-density orchards. In a greenhouse, young olive trees (cv. Arbequina) were exposed to low (L) or high (H) PAR with or without lateral FR supplementation (L+FR, L-FR, H+FR, H-FR) using neutral-density shade cloth and FR light-emitting diode (LED) modules. Total plant and individual organ biomass were much lower in plants under low PAR than under high PAR, with no response to +FR supplementation. In contrast, several plant morphological traits, such as main stem elongation, individual leaf area, and leaf angle, did respond to both low PAR and +FR. Total chlorophyll content decreased with +FR when PAR was low, but not when PAR was high (i.e., a significant FR*PAR interaction). When evaluating numerous plant traits together, a greater response to +FR under low PAR than under high PAR appeared to occur. These findings suggest that consideration of light quality in addition to quantity facilitates a fuller understanding of olive tree responses to a light environment. The +FR responses found here could lead to changes in hedgerow architecture and light distribution within the hedgerow.

The emission mechanism of gamma-ray bursts from supernovae

The connection between gamma ray bursts and supernovae is studied using a temperature-dependent vacuum model. A harmonically bound particle–antiparticle system is consistent with both Hawking radiation and Casimir effect, therefore, the Maxwell–Sellmeier model correlates the speed of light to temperature. According to quantum field theory, Lorentz invariance is violated only for temperatures larger than [Formula: see text][Formula: see text]K. Introducing in the temperature distribution of a 2D simulation for a type Ia supernova the speed of light temperature dependence proposed in this paper, results a speed of light distribution. A theoretical snapshot of this distribution at an arbitrary distance is consistent with photon photo finish resulted from experiments. Variable speed of light shows that supernova could be accompanied by gamma-ray bursts.

Inferring intrahalo light from stellar kinematics. A deep learning approach

In the context of structure formation, disentangling the central galaxy stellar population from the stellar intrahalo light can help us shed light on the formation history of the halo as a whole, as the properties of the stellar components are expected to retain traces of the formation history. Many approaches are adopted to assess the task, depending on different physical assumptions (e.g. the light profile, chemical composition, and kinematical differences) and depending on whether the full six-dimensional phase-space information is known (much like in simulations) or whether one analyses projected quantities (i.e. observations). This paper paves the way for a new approach to bridge the gap between observational and simulation methods. We propose the use of projected kinematical information from stars in simulations in combination with deep learning to create a robust method for identifying intrahalo light in observational data to enhance understanding and consistency in studying the process of galaxy formation. Using deep learning techniques, particularly a convolutional neural network called U-Net, we developed a methodology for predicting these contributions in simulated galaxy cluster images. We created a sample of mock images from hydrodynamical simulations (including masking of the interlopers) to train, validate and test the network. Reinforced training (Attention U-Net) was used to improve the first results, as the innermost central regions of the mock images consistently overestimate the stellar intrahalo contribution. Our work shows that adequate training over a representative sample of mock images can lead to good predictions of the intrahalo light distribution. The model is mildly dependent on the training size and its predictions are less accurate when applied to mock images from different simulations. However, the main features (spatial scales and gradients of the stellar fractions) are recovered for all tests. While the method presented here should be considered as a proof of concept, future work (e.g. generating more realistic mock observations) is required to enable the application of the proposed model to observational data.

Design of a bioreactor as a vital biological support for testing microalgae cultures in the stratosphere.

Abstract In the present, the proposal for the design of an autonomous, light and completely closed bioreactor that will orbit in the stratosphere is developed, capable of promoting the growth of microalgae, specifically of the species: Chlorella vulgaris. The document will address the development of the relevant background information related to this proposal, which will support the bases and certain decisions described in the work, as well as the concepts that will define the theoretical framework for the identification of primary and secondary sources that allow to know, design and develop the proposed. In order to achieve a system capable of performing mixing and recirculation operations, necessary to promote the transfer of mass and energy, as well as the adequate distribution of light, the different existing bioreactor models and their most significant differences will be analyzed. For this work, only five of the nine stages of the mechatronic design methodology are covered: identification of needs, analysis of the problem, preparation of specifications, generation of possible solutions, and selection of the appropriate solution. The missing stages; detailed design, production of working drawings, prototype construction, and testing are underway.

Designerly Approach to Design Responsive Façade for Occupant Visual Comfort in Different Latitudes

In recent years, attention has focused on improving the health and satisfaction of employees by enhancing visual comfort in workplaces. This involves providing adequate natural daylight, glare control, and outdoor views. Adaptive facades, leveraging technological advancements, have gained popularity for improving indoor conditions but still face issues like window-area glare and insufficient daylight in rear spaces. Previous research indicates that inclined walls can help control glare and allow larger windows with better light distribution. This study examines the integration of an adaptive facade with an inclined wall to improve efficiency. It analyzes visual comfort in three cities with different latitudes and solar radiation angles: Mogadishu, Tehran, and Moscow. Using Grasshopper in Rhino software, the study evaluates visual comfort indices (UDI, ASE, sDA, DGP) for six employees on December 21 and June 21 at 9:00, 12:00, and 15:00. The results show that the integrated system effectively distributes daylight and controls glare, reducing it to 34% in Mogadishu and 29% in Tehran. However, in Moscow, the system is less effective, requiring facade rotation towards the sky to reduce glare to 25%. The research highlights the need to consider more variables such as window-to-wall ratio, material, and employees’ position or other objectives like energy consumption and thermal comfort for further research to improve the system.

A CFD Study on Optimization of Mass Transfer and Light Distribution in a Photocatalytic Reactor with Immobilized Photocatalyst on Spheres

A CFD Study on Optimization of Mass Transfer and Light Distribution in a Photocatalytic Reactor with Immobilized Photocatalyst on Spheres

Experimental study of light transmitting concrete with ultra-high content of polymethyl methacrylate

Light Transmitting Concrete (LTC) is an innovative material for crafting unique and sustainable architectural and civil structures. Previous studies primarily utilized optical fibers with diameters below 1.5 mm, which did not exceed 10 % of the volumetric content in concrete. This study aims to develop LTC with ultra-high light transmission capabilities while preserving its mechanical strength. An important innovation is the use of polymethyl methacrylate (PMMA) with larger diameters than normal optical fibers. Specifically, PMMA fibers of 2.0 mm diameter and PMMA tubes of 10–20 mm diameter were employed to increase the spacing between these materials when arranged in an ultra-high volumetric content within the concrete, facilitating easier compaction of the fresh concrete. Experiments of the material's mechanical properties, microstructure, and optical performance were conducted. The findings suggest that although the increased PMMA content might reduce the concrete’s mechanical strength due to a smaller effective cross-sectional area, the LTC still achieves compressive strength exceeding 40 MPa. This underscores the viability of LTC with a substantially higher content of light transmitting functional materials compared to previous studies, while still maintaining a mechanical strength greater than normal concrete. The light transmission efficiency of LTC is nearly directly proportional to its PMMA content, and able to reach up to 30 % of the light source's intensity. Additionally, LTC with PMMA fibers provides uniform light distribution across its surface because of scattering, while LTC with larger-diameter PMMA tubes focuses light around the core areas due to direct lighting.

Color coded metadevices toward programmed terahertz switching

Terahertz modulators play a critical role in high-speed wireless communication, non-destructive imaging, and so on, which have attracted a large amount of research interest. Nevertheless, all-optical terahertz modulation, an ultrafast dynamical control approach, remains to be limited in terms of encoding and multifunction. Here we experimentally demonstrated an optical-programmed terahertz switching realized by combining optical metasurfaces with the terahertz metasurface, resulting in 2-bit dual-channel terahertz encoding. The terahertz metasurface, made up of semiconductor islands and artificial microstructures, enables effective all-optical programming by providing multiple frequency channels with ultrafast modulation at the nanosecond level. Meanwhile, optical metasurfaces covered in terahertz metasurface alter the spatial light field distribution to obtain color code. According to the time-domain coupled mode theory analysis, the energy dissipation modes in terahertz metasurface can be independently controlled by color excitation, which explains the principle of 2-bit encoding well. This work establishes a platform for all-optical programmed terahertz metadevices and may further advance the application of composite metasurface in terahertz manipulation.

Reactor and Plant Designs for the Solar Photosynthesis of Fuels

Solar-boosted photo-technology stands out as a powerful strategy for photosynthesis and photocatalytic processes due to its minimal energy requirements, cost-effectiveness and operation under milder, environmentally friendly conditions compared to conventional thermocatalytic options. The design and development of photocatalysts have received a great deal of attention, whereas photoreactor development must be studied deeper to enable the design of efficient devices for practical exploitation. Furthermore, scale-up issues are important for this application, since light distribution through the photoreactor is a concurrent factor. This review represents a comprehensive study on the development of photoreactors to be used mainly for the photoreduction of CO2 to fuels, but with concepts easily transferable to other photosynthetic applications such as ammonia synthesis and water splitting, or wastewater treatment, photovoltaics combined to photoreactors, etc. The primary categories of photoreactors are thoroughly examined. It is also explained which parameters influence the design of a photoreactor and next-generation high-pressure photoreactors are also discussed. Last but not least, current technologies for solar concentrators are recalled, considering their possible integration within the photoreactor. While many reviews deal with photocatalytic materials, in the authors’ view, photoreactors with significant scale and their merged devices with solar concentrators are still unexploited solutions. These are the key to boost the efficiency of these processes towards commercial viability; thus, the aim of this review is to summarise the main findings on solar photoreactors for the photoreduction of CO2 and for related applications.

Assessing the light scattering properties of c-Si PV module materials for agrivoltaics: Towards more homogeneous light distribution in crop canopies

Increasing the diffusivity of transmitted light at crop canopies in agrivoltaic (AV) systems remains a desired objective. This is because diffuse light increases the uniformity of light distribution and penetrates deeper into compact crop canopies thereby enhancing the photosynthesis rate and crop yields. Current approaches in greenhouses and open horticultural systems involve the use of diffusing films, diffuse glass, and light diffusing coatings. While these methods are effective, their combination with photovoltaic (PV) modules in AV greenhouses and other AV farming practices remain relatively unknown. However, little to no work has been done to assess the light scattering properties of the existing PV module structural materials such as the glass, encapsulants and the transparent backsheet. This work therefore investigates the light scattering behaviour of c-Si PV module materials through haze and Hortiscatter measurements. 18 samples with the structural layout of glass/encapsulant/encapsulant/back cover (glass or transparent polymer backsheet), applying different commercial encapsulants, were manufactured and tested experimentally. Light in the photosynthetic spectrum was used in the optical characterization of the samples. Furthermore, the impact of UV degradation on the haziness was also tested and the uniformity of the light distribution was further assessed to obtain the Hortiscatter. The findings indicated that (i) Transparent backsheets increased the light diffusivity. (ii) UV degradation reduced the light scattering of most of the PV materials. (iii) For the haziest transparent backsheet sample, the distribution of the transmitted light increased with the incidence light angle and reduced with increasing wavelength in the visible spectrum (iv) Highest haze and Hortiscatter values of up to 80% and 84% respectively were obtained for a sample with glass/TPO/TPO/transparent backsheet layout. (v) Haze and Hortiscatter values could help in optimising the PV module bill of materials for AV applications.

Measurement of anisotropy factor of nanoparticle embedded tumor phantoms for plasmonic photothermal therapeutics.

Measurement of anisotropy factor (g) in the presence of nanoparticles (NPs) is important for understanding light distribution for plasmonic photothermal cancer therapeutics. Here, anisotropy factor is investigated through bilayer phantoms (epidermal and dermal) of various thicknesses incorporated with gold nanorods (GNRs) concentrations of 10-40 μg/mL by using in-house developed goniometric setup. Results show that 10 μg/mL GNRs in the phantom increase g by ~50% (g = 0.9471) w.r.t. phantom without NPs. Higher concentrations (40 μg/mL) of GNRs decrease g by ~43% (g = 0.5341) w.r.t. phantom with 10 μg/mL GNRs. For 40 μg/mL GNRs phantom, the anisotropy factor reduces by 47% for phantom thickness from 600 to 1800 μm. Anisotropy factor of GNR embedded phantom increased by 44% by using glycerol (10%-40%). Incorporation of NPs in a tumor significantly affects g, a major parameter for light distribution. These measurements provide insights for light scattering based on nanoparticle doses for plasmonic photothermal therapeutics.

From Dawn to Dusk: High-Resolution Tree Shading Model Based on Terrestrial LiDAR Data

Light availability and distribution play an important role in every ecosystem as these affect a variety of ecosystem processes and functions. To estimate light availability and distribution, light simulations can be used. Many previous models were based on highly simplified tree models and geometrical assumptions about tree form, or were sophisticated and computationally demanding models based on 3D data which had to be acquired in every season to be simulated. The aim of this study was to model the shadow cast by individual trees at high spatial and temporal resolution without the need for repeated data collection during multiple seasons. For our approach, we captured trees under leaf-off conditions using terrestrial laser scanning and simulated leaf-on conditions for individual trees over the remainder of the year. The model was validated against light measurements (n=20,436) collected using 60 quantum sensors underneath an apple tree (Malus domestica Borkh.) on a sunny and cloudless summer day. On this day, the leaves and the shadow were simulated with a high spatial (1 cm) and temporal resolution (1 min). The simulated values were highly correlated with the measured radiation at r=0.84. Additionally, we simulated the radiation for a whole year for the sample apple tree (tree height: 6.6 m, crown width: 7.6 m) with a resolution of 10 cm and a temporal resolution of 10 min. Below the tree, an area of 49.55 m² is exposed to a radiation reduction of at least 10%, 17.74 m² to at least 20% and only 0.12 m² to at least 30%. The model could be further improved by incorporating branch growth, curved leaf surfaces, and gravity to take the weight of the foliage into account. The presented approach offers a high potential for modelling the light availability in the surroundings of trees with an unprecedented spatial and temporal resolution.

A Review of Factors Affecting the Lighting Performance of Light Shelves and Controlling Solar Heat Gain

In areas with a deep floor plan, the distribution of natural light is not uniform. Consequently, relying solely on daylight may not suffice to meet the space’s lighting requirements, necessitating the use of artificial lighting in darker areas. Therefore, a lighting system is needed that not only controls the glare near the windows but also increases the light at the end of the room and provides uniform daylight. One of the widely used systems is the “light shelf”, which has three main functions: shading, increasing the depth of light penetration, and reducing glare. Review articles about light shelves were published in 2015 and 2017, while more than 80% of the studies have been carried out since 2016, and light shelves with more diverse forms and dynamic elements and many consolidations have been proposed. Therefore, there is a need for a more comprehensive review. The main question of this research is how different parameters (including climate, material, ceiling, and integrated systems) can help to increase the efficiency of light shelves. By using a systematic review, studies in the past three decades were classified in order to determine the effect of these parameters on improving lighting performance and controlling solar heat gain.

Dynamics of China’s natural cities and their living structures derived from nighttime lights and populated grids

The term “natural cities” refers to human settlements or human activities in general that are naturally or objectively defined. In this study, we utilized the head/tail breaks method to identify natural cities and characterize their living structures in mainland China from 2000 to 2020. This identification was based on nighttime light (NTL) and gridded population distribution (GPD) data, which, respectively, indicate urban areas and residential settlements. Furthermore, we explicitly identified the evolutions of two distinct categories of natural cities and the dynamics of their inherent living structures. Our objective was to verify that the head/tail breaks method is a powerful approach to deriving natural cities that signify various types of human settlements from diverse data sources, while also effectively characterizing their living structures. Also, this article contributes a novel perspective to examine the inequality between the urban-area expansion and the evolution of residential settlements in urban areas (or urban settlements). Our findings reveal a substantial increase in both the number and sizes of urban areas over time. However, there was an intriguing trend observed in urban settlements, where an increasing number corresponded to a gradual decrease in size. Additionally, the inequality exhibited regional disparities and rapidly developing regions showed a higher potential to enter a turning year of urban areas surpassing urban settlements. The dynamics of living structures show that urban settlements always had more hierarchical levels, more substructures, a much higher degree of order, and a much more living (orderly or beautiful) structure than urban areas. The urban-area expansion in mainland China was extremely rapid over the past decades, but the evolution of urban settlements was more “natural” than that (i.e., it consistently generated a living structure characterized by a higher degree of order).

Advancing sustainable construction through innovative transparent wood composite structures with enhanced functionalities

Advancements in transparent wood materials hold immense promise for eco-friendly construction, combating resource depletion, and enhancing energy efficiency. Yet, the quest for versatility and global uniformity poses challenges. Enter our breakthrough: a three-layer transparent wood that integrates thermal energy storage. We achieved this by compressing three partially impregnated wood substrates, featuring a silica-stabilized polyethylene glycol (PEG) core flanked by two polymethyl methacrylate (PMMA) layers. In pursuit of optical and mechanical perfection, we employed a multi-layer approach to ensure global isotropy. Morphological analysis unveiled compact, hierarchical structures in the core, PEG encapsulation, and an innovative solution for preventing leaks, culminating in a remarkable latent heat of 15.0 J/g and superior thermal stability. Optical testing reported outstanding properties, with an optical transmittance of 45 % and a haze of 76 % at 800 nm. Our design featuring crossed-lamination not only achieved isotropic light distribution but also improved mechanical consistency and water resistance. Notably, our environmentally-simulated tests showcased remarkable thermal insulation properties, credited to a low thermal conductivity (0.34 W/mK) surpassing traditional glass, as well as phase-change functionality. Our pioneering multilayer transparent wood stands to revolutionize energy-efficient construction and elevate indoor thermal comfort.

Optimizing canopy spacing configuration enhances foxtail millet grain yield and water productivity by improving stalk lodging resistance in the North China Plain

Optimizing canopy spacing configuration can enhance resources utilization, supporting robust growth and dry matter production, while mitigating the risk of lodging and improving crop yield and quality. However, research specifically addressing optimal canopy spacing configurations for foxtail millet remains limited. Over a two-year period, a field experiment in the North China Plain assessed the impacts of four-row spacing configurations (T0: 40 + 40 cm; T1: 30 + 50 cm; T2: 20 + 60 cm; T3: 10 + 70 cm), to investigate the effects of row spacing configuration on lodging resistance, canopy spatial configuration, stem characteristics, yield, and water productivity (WP) of foxtail millet, aiming to elucidate the underlying regulatory mechanisms. Row spacing configurations significantly influenced lodging resistance, yield, and WP. Under T1, improvements were observed in stem morphology and mechanical properties, particularly in the 2nd-6th basal internodes (I2-I6). The light interception rate in T1 at wide rows in the middle canopy (30–90 cm aboveground) increased by 97.89 %, compared to T0. Partial least squares-structural equation modeling revealed that improved light interception in wide rows in the middle canopy contributed to a rise in diameter and dry plumpness of I2. This, in turn, promoted greater breaking resistance of I2 and tensile resistance, ultimately reducing the lodging likelihood. Simultaneously, the decrease in lodging resulted in higher yield and WP at yield level of foxtail millet. Therefore, T1 demonstrated the lowest lodging rate (67.34 %–91.92 % lower than T0), and the highest yield and WP at yield level (4.10 %–8.03 % and 20.79 %–22.46 % higher than T0). Optimizing canopy spacing configuration is essential for cultivating high-yielding and water-efficient foxtail millet populations. The results indicated that the 30 + 50 cm row spacing configuration improves light distribution in the middle canopy, enhancing lodging resistance and consequently increasing both yield and WP. This research offers a theoretical foundation for foxtail millet breeding and agronomic practices to achieve lower lodging rate, higher yields, and enhanced WP in the North China Plain.