Skylight Research Articles

Performance Comparison of Various Tunnel Lighting Scenarios on Driver Lane-Changing Behaviours in a Driving Simulator

Recent advances in tunnel infrastructure have emphasized safety, operational efficiency and low operating costs. Modern tunnels are equipped with systems to improve both safety and operational performance. This study investigates the effect of tunnel lighting and vehicle breakdown scenarios on driver lane changing behaviour (LCB) using a driving simulator modelled on the third longest twin-tube tunnel. Data were collected from 125 drivers considering various driver characteristics with different lighting conditions and the presence of a stopped vehicle in a lane. The results show that drivers tend to slow down and change lanes more safely in response to red and flashing lights. In contrast, blue sky lights, which are designed to reduce stress and compare with other dangerous scenarios, had no significant effect on LCB. In addition, demographic factors such as gender and previous simulator experience played a role in influencing LCB tendencies. Female drivers and those familiar with simulators showed more cautious behaviour. The findings showed valuable insights into how tunnel lighting systems can improve safety. Results highlighted the potential for dynamic lighting and targeted driver training programs to improve tunnel safety. All these findings may contribute to ongoing efforts to improve traffic management and reduce accidents in tunnel environments.

A multi-timescale image space model for dynamic cloud illumination

Sky illumination is a core source of lighting in rendering, and a substantial amount of work has been developed to simulate lighting from clear skies. However, in reality, clouds substantially alter the appearance of the sky and subsequently change the scene illumination. While there have been recent advances in developing sky models which include clouds, these all neglect cloud movement which is a crucial component of cloudy sky appearance. In any sort of video or interactive environment, it can be expected that clouds will move, sometimes quite substantially in a short period of time. Our work proposes a solution to this which enables whole-sky dynamic cloud synthesis for the first time. We achieve this by proposing a multi-timescale sky appearance model which learns to predict the sky illumination over various timescales, and can be used to add dynamism to previous static, cloudy sky lighting approaches.

Effects of gymnasium envelope and daylight pattern on exercisers’ feedback in a virtual reality

The daylight environment determined by the building envelope significantly influences the exercisers' well-being and perception. However, assessment methods that focus on exercisers' feedback for gymnasium envelope and associated daylight pattern have rarely been explored. Additionally, changing the detailed envelope form is time-consuming and costly in physical environment. The Cave Automated Virtual Environment (CAVE) was employed to investigate exercisers' feedback under a virtual matrix of four ratio of covered shadings on the facade (SFCR) conditions and four skylight (SL) conditions. Feedback from exercisers consisted of subjective and attention quality evaluation. The subjective evaluation was employed to measure psychosocial perception of exercisers and validity of virtual environment, including comprehensive assessment, psychological perception, the Igroup presence questionnaire (IPQ), and the Virtual Reality Sickness Questionnaire (VRSQ). Furthermore, exercisers' attention quality was also evaluated by task efficiency of the attention task and physiological responses including electrodermal activity (EDA) and heart rate variability (HRV). The results indicated that envelope form have significant impact on exercisers' feedback, suggesting that existing gymnasium envelope and irregular daylight pattern were inefficient for improving exercisers' perception. Specifically, better feedback was reported in conditions with SFCR3 (SFCR = 0.7) and SL3 (strip skylight) or SL4 (ring skylight), while the worst feedback was reported in conditions with SL2 (spot skylight), followed by conditions with SFCR1 (SFCR = 0) and SL1 (no-skylight), which were designed to replicate a real gymnasium. The novel assessment method for measuring exercisers' feedback in virtual environment has demonstrated its potential to enhance exercisers’ perception, health, and efficiency.

Night sky polarization model for a cloud-free atmosphere illuminated by ground-based light sources

ABSTRACT Skyglow from sources of artificial light at night poses a significant challenge to ground-based astronomical research and discovery. Although astronomers, conservationists, and light-pollution researchers have measured skyglow for decades, their data on diffuse night-time light fields are incomplete as they lacks information about the polarization state of the light. Here, we present the first successful theoretical model that predicts the degree and angle of linear polarization of scattered night sky light and accounts for complex, real-world distributions of ground light sources. The model proceeds from an analytical solution to the polarized radiative transfer equation that is validated by field experiments. We discuss several use cases of the model and demonstrate its practical consequences, such as the ability to more reliably determine which ground sources in the area around an observer contribute the most scattered light in a given sky element.

An accurate and realistic polarization model for night-sky brightness

Abstract Most measurements of the diffuse light of the night sky to date consider only the intensity of the light field, and current models can successfully reproduce these measurements. However, this approach is incomplete as it overlooks the polarization state of the light. Few measurements (and no successful models) of night-sky polarimetry appear in the literature. We present a new model of night-sky polarization that successfully reproduces observations in a heterogeneous environment and for a real distribution of finite-sized light sources over the intermediate region surrounding the observer. The model compares favourably with field measurements made in Slovakia in May 2021. The results described herein help advance understanding the angular distributions of artificial light at night from ground sources and the relative contributions of sources to the overall brightness of the night sky.

Direct comparison of SiPM and PMT sensor performances in a large-size imaging air Cherenkov telescope

The peak photon detection efficiency (PDE) of silicon photomultipliers (SiPMs) can be as good or better than the PDE of photomultiplier tubes (PMTs). There are experiments where the signal is measured in the presence of a strong, steady background light emission. In these, one needs to accurately evaluate the signal-to-noise ratio. Imaging Atmospheric Cherenkov Telescopes (IACT) observe in the presence of strong noise induced by the light of the night sky. It is certainly interesting to investigate the SiPM performance under operational conditions of IACTs and to compare it with that of the PMTs.For that purpose, we built a SiPM-based detector module, which was installed in one of the imaging cameras of the two Major Atmospheric Gamma-ray Imaging Cherenkov (MAGIC) telescopes in 2015. The experience gained from that module was used to design the second generation of modules of improved performance. Two such modules were installed in 2017.MAGIC is a system of two IACTs located on the Canary Island of La Palma. The mechanical structure of the MAGIC imaging cameras offers the possibility to install up to 6 additional detector modules of 7 pixels each into the open vertices of the hexagonal-shaped camera. This allows us to directly, without making any assumption, compare the performance of the PMT-based modules with that of the SiPM-based prototype modules, where SiPMs from three different manufacturers are used.

Why flying insects gather at artificial light

Explanations of why nocturnal insects fly erratically around fires and lamps have included theories of “lunar navigation” and “escape to the light”. However, without three-dimensional flight data to test them rigorously, the cause for this odd behaviour has remained unsolved. We employed high-resolution motion capture in the laboratory and stereo-videography in the field to reconstruct the 3D kinematics of insect flights around artificial lights. Contrary to the expectation of attraction, insects do not steer directly toward the light. Instead, insects turn their dorsum toward the light, generating flight bouts perpendicular to the source. Under natural sky light, tilting the dorsum towards the brightest visual hemisphere helps maintain proper flight attitude and control. Near artificial sources, however, this highly conserved dorsal-light-response can produce continuous steering around the light and trap an insect. Our guidance model demonstrates that this dorsal tilting is sufficient to create the seemingly erratic flight paths of insects near lights and is the most plausible model for why flying insects gather at artificial lights.

Deep learning for intra-hour solar forecasting with fusion of features extracted from infrared sky images

The increasing penetration of solar energy leaves power grids vulnerable to fluctuations in the solar radiation that reaches the surface of the Earth due to the projection of cloud shadows. Therefore, an intra-hour solar forecasting algorithm is necessary to reduce power instabilities caused by the impact of moving clouds on energy generation. The most accurate intra-hour solar forecasting methods apply convolutional neural networks to a series of visible light sky images. Instead, this investigation uses data acquired by a novel infrared sky imager on a solar tracker, which is capable of maintaining the Sun in the center of the images throughout the day and, at the same time, reducing the scattering effect produced by the Sun’s direct radiation. In addition, infrared sky images allow the derivation and extraction of physical cloud features. The cloud dynamics are analyzed in sequences of images to compute the probability of the Sun intercepting air parcels in the sky images (i.e., voxels). The method introduced in this investigation fuses sky condition information from multiple sensors (i.e., pyranometer, sky imager, solar tracker, weather station) and feature sources using a multi-task deep learning architecture based on recurrent neural networks. The proposed deterministic and Bayesian architectures reduce computation time by avoiding convolutional filters. The proposed intra-hour solar forecasting algorithm reached a forecast skill of 18.6% with a forecasting horizon of 8 min. Consequently, the proposed intra-hour solar forecasting method can potentially reduce the operational costs of power grids with high participation of solar energy.

Performance evaluation of three silicon photomultiplier detector modules within the MAGIC telescopes PMT-based camera

MAGIC is a system of two imaging atmospheric Cherenkov telescopes (IACTs) located on the Canary island of La Palma. Each telescope’s imaging camera consists of 1039 photomultiplier tubes (PMTs). We developed three detector modules based on silicon photomultipliers (SiPMs) of seven pixels each that are mechanically and electronically compatible with those used in the MAGIC camera. These prototype modules are installed next to the PMTs in the imaging camera and are operated in parallel. To achieve a similar active area per pixel we used seven to nine SiPMs for producing a composite pixel. The SiPM signals within one such pixel are actively summed up for retaining the fast signal pulse shapes. Two different PCB designs are tested for thermal performance. We present our simulations of Cherenkov and light of the night sky (LoNS) responses. Based on those we calculate the signal-to-noise ratio (SNR) for this imaging application. We compare our expectations with the measurements of one of the SiPM-based detector modules.

The Data Processing of the LAMOST Medium-resolution Spectral Survey of Galactic Nebulae (LAMOST MRS-N Pipeline)

The Large sky Area Multi-Object Fiber Spectroscopic Telescope (LAMOST) medium-resolution spectral survey of Galactic Nebulae (MRS-N) has conducted for more than three years since 2018 September and observed more than 190 thousand nebular spectra and 20 thousand stellar spectra. However, there is not yet a data processing pipeline for nebular spectra. To significantly improve the accuracy of nebulae classification and their physical parameters, we developed the MRS-N Pipeline. This article presented in detail each data processing step of the MRS-N Pipeline, such as removing cosmic rays, merging single exposure, fitting sky light emission lines, wavelength recalibration, subtracting skylight, measuring nebular parameters, creating catalogs and packing spectra. Finally, a description of the data products, including nebular spectra files and parameter catalogs, is provided.

Determining the Primary Sources of Uncertainty in Retrieval of Marine Remote Sensing Reflectance From Satellite Ocean Color Sensors

Uncertainties in the retrieval of the remote sensing reflectance, Rrs, from Ocean Color (OC) satellite sensors have a strong impact on the performance of algorithms for the estimation of chlorophyll-a, mineral concentrations, and inherent optical properties (IOPs). The uncertainties are highest in the blue bands. The total radiance measured at the top of the atmosphere captures the instantaneous state of the atmosphere-ocean system: the in-water conditions, sky and Sun glint reflected from the wind-roughened ocean surface, as well as light scattered from molecules and aerosols in the atmosphere. Each of these components has associated uncertainties, and when combined with the additional uncertainties from the instrument noise and the atmospheric correction process, they contribute to the total uncertainty budget for the retrieved Rrs. We analyzed the contribution of each component uncertainties to the total Rrs uncertainties in SNPP-VIIRS level 2 products, taking advantage of the spectral differences between the components. We examined multiple scenes in the open ocean and coastal waters at spatial resolutions ranging from 2250 to 5250 m by comparing the retrieved Rrs to in situ measurements made at several AERONET-OC sites and at the MOBY site. It was shown that uncertainties associated with the molecular (Rayleigh) scattering play the most significant role, while the contributions of other components are usually smaller. Uncertainties in Rayleigh scattering are primarily attributed to the variability of Rayleigh optical thickness (ROT) with a standard deviation of approximately 1.5% of ROT, which can largely explain the frequency of negative Rrs retrievals as observed using the current standard atmospheric correction process employed by NASA. Variability of the sky light reflected from the ocean surface in some conditions also contributed to uncertainties in the blue; water variability proportional to Rrs had a very pronounced peak in the green at coastal sites.

Performance of polarization-sensitive neurons of the locust central complex at different degrees of polarization

The polarization pattern of the sky is exploited by many insects for spatial orientation and navigation. It derives from Rayleigh scattering in the atmosphere and depends directly on the position of the sun. In the insect brain, the central complex (CX) houses neurons tuned to the angle of polarization (AoP), that together constitute an internal compass for celestial navigation. Polarized light is not only characterized by the AoP, but also by the degree of polarization (DoP), which can be highly variable, depending on sky conditions. Under a clear sky, the DoP of polarized sky light may reach up to 0.75 but is usually much lower especially when light is scattered by clouds or haze. To investigate how the polarization-processing network of the CX copes with low DoPs, we recorded intracellularly from neurons of the locust CX at different stages of processing, while stimulating with light of different DoPs. Significant responses to polarized light occurred down to DoPs of 0.05 indicating reliable coding of the AoP even at unfavorable sky conditions. Moreover, we found that the activity of neurons at the CX input stage may be strongly influenced by nearly unpolarized light, while the activity of downstream neurons appears less affected.

Simulation of daylight in buildings with curved facades for rational use of solar energy

Simulation of daylight conditions in buildings with curved facades was carried out to show the possibility of more efficient use of solar energy with a constant change in the azimuth of the windows orientation. To optimize daylighting, a smart window with optical filter is proposed having an angular selectivity of light transmission due to two surface gratings with alternating transmissive and chromogenic parallel strips. Unlike conventional smart windows, the entire area of which is covered with chromogenic layers, a grating filter weakens or completely blocks direct solar radiation by allowing diffused sky light and reflected light to pass through. Methods for calculating the geometric parameters of the gratings are presented and the optimal slope angles of the filter gratings for windows with different azimuths of a building with round facade and the temporal characteristics of the light transmission of these windows are calculated. The results substantiate the advisability of using smart windows with grating filters in buildings with curved facades to improve the comfort of daylighting and insolation, to protect against direct rays when passing diffuse sky light and albedo by adapting the light transmission of windows to a change in the position of the sun relative to them.

Research on Signal-to-noise Ratio of Low-light Level Image Intensifier Based on Night Sky Light Spectrum Matching

Research on Signal-to-noise Ratio of Low-light Level Image Intensifier Based on Night Sky Light Spectrum Matching

Analysis of the visibility and signal strength of the LoRaWAN network in an urbanized area – a case study of the Bielany campus at the Nicolaus Copernicus University in Toruń

Abstract In order to assess or determine the overall quality of the surrounding geographical environment, it is necessary to measure selected factors that directly or indirectly affect its condition. The aspects to be monitored include i.a. air pollution levels, surface water purity, soil erosion rates, as well as night sky light pollution, a phenomenon increasingly often observed with the unaided eye. To collect data on the night sky brightness on a regular basis, a remote measuring device was designed and constructed using specialised electronic components, wireless communication, programming code, a high-sensitivity digital light data logger and custom-made programme code. LPWAN networks, including LoRa technology, were developed to support a number of mobile devices where long wireless operation is a priority. To determine the potential use of LoRa technology, as well as to plan the target locations of network access gates (gateways) and the deployment of measuring devices for the collection of environmental data, tests of signal coverage and signal visibility, including measurements of its strength, were carried out in a selected, compact part of the city of Toruń. The paper presents the results of research on the visibility of the LoRa network in a built-up area, such as a university campus, using antennas of two different lengths. The obtained results can be used to design distributed measurement networks in areas with varying density of buildings.

Approach trajectory and solar position affect host plant attractiveness to the small white butterfly

While it is well documented that insects exploit polarized sky light for navigation, their use of reflected polarized light for object detection has been less well studied. Recently, we have shown that the small white butterfly, Pieris rapae, distinguishes between host and non-host plants based on the degree of linear polarization (DoLP) of light reflected from their leaves. To determine how polarized light cues affect host plant foraging by female P. rapae across their entire visual range including the ultraviolet (300–650 nm), we applied photo polarimetry demonstrating large differences in the DoLP of leaf-reflected light among plant species generally and between host and non-host plants specifically. As polarized light cues are directionally dependent, we also tested, and modelled, the effect of approach trajectory on the polarization of plant-reflected light and the resulting attractiveness to P. rapae. Using photo polarimetry measurements of plants under a range of light source and observer positions, we reveal several distinct effects when polarized reflections are examined on a whole-plant basis rather than at the scale of pixels or plant canopies. Most notably from our modeling, certain approach trajectories are optimal for foraging butterflies, or insects generally, to discriminate between plant species on the basis of the DoLP of leaf-reflected light.

Modernizing A Methodology for Designing and Assembling Four-Faceted Metallic Systems Utilizing Parametric Design Principles (An Empirical Study)

AIMS AND OBJECTIVES: Adapting prefabricated aluminum profiles to design and produce atypical forms using parametric computer software & Increase the competitiveness of prefabricated metal systems through the development of atypical production and assembly methods. HYPOTHESIS: By studying and analyzing some metal systems in traditional four-sided shapes through a parametric design perspective, a system can be created, produced and adapted to design and produce atypical forms. CONCLUSIONS: 1. The proposed parametric system offers the possibility of adjustments in the values of the parameters involved in the design of the four-sided metal systems and to reach a new design for them according to the modifications without the need to re-steps as well as provide feedback to the designer explaining any problems that may arise at the stage Design or in the manufacturing phase to be corrected. 2. The research found the effectiveness of the proposed system in developing innovative formal patterns of four-sided metal systems that allow for ease and quality of manufacturing and installation through the application of pyramid Sky Light. 3. Digital technologies have provided enormous potential that has helped to uniquely the results of metal systems with the use of parametric software. 4. The system has reduced the incidence of any errors during the design and manufacturing process, ensuring a final, flawless product. 5. The process of designing and issuing the order for the implementation of four-sided metal systems is so fast, as well as the lack of need for an experienced person in those processes.

The Stereoscopic Analog Trigger of the MAGIC Telescopes

The current generation of ground-based imaging atmospheric Cherenkov telescopes (IACTs) operate in the very-high-energy (VHE) domain from ~100 GeV to ~100 TeV. They use electronic digital trigger systems to discern the Cherenkov light flashes emitted by extensive air showers (EASs), from the overwhelming light of the night sky (LoNS) background. Near the telescope energy threshold, the number of emitted Cherenkov photons by gamma-ray-induced EASs is comparable to the fluctuations of the LoNS and the photon distribution at the Cherenkov-imaging camera plane becomes patchy. This results in a severe loss of effectiveness of the digital triggers based on combinatorial logic of thresholded signals. A stereoscopic analog trigger system has been developed for improving the detection capabilities of the Major Atmospheric Gamma-ray Imaging Cherenkov (MAGIC) telescopes at the lowest energies. It is based on the analog sum of the photosensor electrical signals. In this article, the architectural design, technical performances, and configuration of this stereoscopic analog trigger, dubbed “Sum-Trigger-II,” are described.

Uncertainty assessment of unattended above-water radiometric data collection from research vessels with the Dynamic Above-water Radiance (L) and Irradiance (E) Collector (DALEC).

We used above- and below-water radiometry measurements collected during a research voyage in the eastern Indian Ocean to assess uncertainties in deriving the remote sensing reflectance, Rrs, from unattended above-water radiometric data collection with the In-Situ Marine Optics Pty. Ltd. (IMO) Dynamic Above-water Radiance (L) and Irradiance (E) Collector (DALEC). To achieve this, the Rrs values derived from using the latest version of this hyperspectral radiometer were compared to values obtained from two in-water profiling radiometer systems of rather general use in the ocean optics research community, i.e., the Biospherical Instruments Inc. Compact Optical Profiling System (C-OPS) and the Seabird HyperPro II. Our results show that unattended, carefully quality-controlled, DALEC measurements provide Rrs for wavelengths < 600 nm that match those derived from the in-water systems with no bias and a dispersion of about 8%, provided that the appropriate technique is used to quantify the contribution of sky light reflection to the measured signal. The dispersion is larger (25-50%) for red bands, which is expected for clear oligotrophic waters as encountered during the voyage, where ∼2 10-5 < Rrs < ∼2 10-4 sr-1. For comparison, the two in-water systems provided Rrs in agreement within 4% for wavelengths < 600 nm.

Accurate and fast simulation of remote sensing images at top of atmosphere with DART-Lux

DART model is one of the most comprehensive and accurate radiative transfer (RT) models to simulate remotely sensed signals in the Earth-atmosphere system. Its standard RT modelling mode, called DART-FT, relies on the discrete ordinates method. Its recently developed Monte Carlo mode using an unbiased bidirectional path tracing method, called DART-Lux, increases hundredfold DART efficiency to simulate images. Since DART-Lux does not simulate yet atmospheric RT, a hybrid method has been designed to accurately and fast simulate remote sensing images at top of atmosphere (TOA). It couples the atmospheric RT modelling of DART-FT with the very efficient Earth surface RT modelling of DART-Lux. For that, a new sky light modelling, an innovative BRF camera modelling and an adapted radiative coupling framework have been designed. The efficiency and accuracy of this hybrid method have been validated using DART-FT as a reference. Here, we present this validation for a realistic forest stand. Simulation time is reduced by a factor of 750 with a relative difference of solar plane reflectance factor smaller than 1%. This hybrid method opens new perspectives for the use of 3D modelling in remote sensing applications. It is already part of the DART version freely available for scientists (https://dart.omp.eu).