High Illumination Research Articles

Solar light performances of n-ZnO nanorods/p-Si-based photodetectors under high illumination intensity

Solar light performances of n-ZnO nanorods/p-Si-based photodetectors under high illumination intensity

Accumulation of polyhydroxybutyrate in Synechocystis sp. isolated from wastewaters: Effect of salinity, light, and P content in the biomass

Cyanobacteria are of particular interest as they can produce Polyhydroxybutyrate (PHB), which is a promising alternative to oil-based plastics, using only inorganic carbon and solar light. However, new strategies should be found to further increase their PHB content. In this study, the effect of salinity, light intensity, and internal phosphorus content in the inoculated biomass, on the production of PHB with the cyanobacteria Synechocystis sp. were investigated. Results indicated that a sudden increase in salinity (together with nutrients starvation) stimulated the accumulation of PHB. In a first experiment where the cells were adapted to an electrical conductivity of 12 mS cm−1, a maximum content of PHB of a 7.5%VSS was achieved by adding NaCl and NaHCO3- (electrical conductivity of 28 mS cm−1). While in a second experiment, where cells were not adapted, similar PHB content (7.2%VSS) was achieved by adding only NaCl and C-HCO3-, providing only 11.4 mS cm−1. Furthermore, it was observed a reduced molecular weight of the polymer (38 kDa with respect to around 100 kDa), when really high salinities were used. Eventually, it was observed an increased production of glycogen (maximum of a 32%VSS) when high illumination (500 µmol m−2 s−1) was applied. Similar PHB content was obtained independently of the illumination. However, the PHB productivity (15.7 mgPHB L−1 d−1) was increased with light intensity. These results contribute to decipher the effect of important parameters in the PHB production and bring research a step forward towards the optimization of PHB production with Synechocystis sp.

A New Type of Architecture of Dye-Sensitized Solar Cells as an Alternative Pathway to Outdoor Photovoltaics

The current investigation shows a possible new pathway for more efficient and cost-effective energy-harvesting photovoltaic devices. Our approach could permit all emerging technologies that are currently used for indoors and smart buildings to go a step forward and could be used for outdoor applications. The investigated architecture is a very promising geometry especially for Dye-Sensitized Solar Cells (DSSCs). It turns their main drawback, the lowering of their efficiency and lifetime when operating at high solar irradiation density, into an asset by increasing the total active area per horizontal unit area for light harvesting, while preserving the active elements from degradation and extending durable lifetime. The investigated architecture is based on a symmetric “U” type geometry, which is constructed by a highly reflective material on the inner surface. Solar irradiation is reflected internally at the bottom of the construction and splits towards two opposite sided solar cells; the two cells form a cavity where the solar light multiplies and is successively absorbed. Consequently, the vertically incoming irradiation is reduced when reaching the vertical internal sides on which the DSSCs are mounted. Thus, the solar cells operate at low light intensities, which provide significant lifetime extension and efficiency enhancement. Interestingly, the electrical energy per effective surface unit, which is produced by the two vertical DSSCs, is at least equal to that of a standalone, vertically irradiated cell. The advantage of the new architecture is that protects DSSCs from their degradation and deterioration, although the entire system operates under high illumination. This makes the cells more efficient outdoors, with a comparable performance to indoor conditions.

Aydınlatma alternatiflerinin insan odaklı aydınlatma açısından değerlendirilmesi: Büro örneği

In addition to its visual effects, light also has non-visual biological and behavioural effects. Nowadays, human centric lighting that takes into account the visual and non-visual effects of light has gained in importance. However, in this context there is no consensus on the appropriate illuminance and colour temperature of light according to the function. In this study, four static and one dynamic lighting scenarios were designed in a mock-up room in order to investigate the lighting conditions applicable to offices. These scenarios with different illuminances and colour temperatures were compared through surveys and lighting calculations. The research was planned for two separate conditions; long-term and short-term study. Each lighting scenario was applied for two weeks in the long-term study and twenty minutes in the short-term study. In addition to the emotional states of the participants, the lighting conditions were also questioned from various aspects with the questionnaire. Statistical evaluation of the survey data was conducted for both studies and the results supported each other. Cool light colour and high illuminance ensured that the subjects felt more energetic, alert and rested. On the other hand, neutral coloured light was preferred the most in both studies. Among the illuminance alternatives, 500 lx was assessed as low and 1500 lx as high. The most preferred lighting scenario was the option where 1250 lx illumination is provided with neutral coloured light. With the results obtained in this research, data for determining the optimum conditions for integrative lighting are presented.

Kilometer-scale autonomous navigation in subarctic forests: challenges and lessons learned

Challenges inherent to autonomous wintertime navigation in forests include lack of a reliable Global Navigation Satellite System (GNSS) signal, low feature contrast, high illumination variations, and changing environment. This type of off-road environment is an extreme case of situations autonomous cars could encounter in northern regions. Thus, it is important to understand the impact of this harsh environment on autonomous navigation systems. To this end, we present a field report analyzing teach-and-repeat navigation in a subarctic forest while subject to fluctuating weather, including light and heavy snow, rain, and drizzle. First, we describe the system, which relies on point cloud registration to localize a mobile robot through a boreal forest, while simultaneously building a map. We experimentally evaluate this system in over 18.8km of autonomous navigation in the teach-and-repeat mode. Over 14 repeat runs, only four manual interventions were required, three of which were due to localization failure and another one caused by battery power outage. We show that dense vegetation perturbs the GNSS signal, rendering it unsuitable for navigation in forest trails. Furthermore, we highlight the increased uncertainty related to localizing using point cloud registration in forest trails. We demonstrate that it is not snow precipitation, but snow accumulation, that affects our system’s ability to localize within the environment. Finally, we expose some challenges and lessons learned from our field campaign to support better experimental work in winter conditions. Our dataset is available online.

Design of a composite lighting system based on a freeform and a rod lens for machine vision.

Light-emitting diodes (LEDs) have been widely utilized in machine vision lighting systems such as the process monitoring system in the additive manufacturing field, owing to their long life, high illumination efficiency, and controllable dimming. The quality of the lighting system directly affects the efficiency and accuracy of the entire monitoring system. However, existing designs cannot meet the optical efficiency and uniformity requirements at short lighting distances and small inspection areas with mixed multi-spectrum channels. This paper thus proposes a novel, to the best of our knowledge, design method of integrating a freeform surface lens and a square-shaped rod lens. The optical characteristics under different working distances and targeting surface types have been optimized and evaluated. Meanwhile, tolerance analysis has been utilized to demonstrate the feasibility of installation. With the use of the software Tracepro, simulation results showed that the designed composite machine vision lighting system can obtain an optical efficiency of 81.704% and an illuminance uniformity of 95.804% within the inspection area at a distance of 250 mm. Furthermore, verification experiments with a prototype were performed, demonstrating the feasibility of the proposed machine vision lighting system.

Modeling photovoltaic-electrochemical water splitting devices for the production of hydrogen under real working conditions

Photoelectrochemical splitting of water is potentially a sustainable and affordable solution to produce hydrogen from sun light. Given the infancy stage of technology development, it is important to compare the different experimental concepts and identify the most promising routes. The performance of photoelectrochemical devices is typically measured and reported under ideal irradiation conditions, i.e. 1 sun. However, real-life operating conditions are very different, and are varying in time according to daily and seasonal cycles. In this work, we present an equivalent circuit model for computing the steady state performance of photoelectrochemical cells. The model allows for a computationally efficient, yet precise prediction of the system performance and a comparison of different devices working in real operating conditions. To this end, five different photoelectrochemical devices are modeled using experimental results from literature. The calculated performance shows good agreement with experimental data of the different devices. Furthermore, the model is extended to include the effect of illumination and tilt angle on the hydrogen production efficiency. The resulting model is used to compare the devices for different locations with high and low average illumination and different tilt angles. The results show that including real illumination data has a considerable impact on the efficiency of the PV-EC device. The yearly average solar-to-hydrogen efficiency is significantly lower than the ideal one. Moreover, it is dependent on the tilt angle, whose optimal value for European-like latitude is around 40°. Notably, we also show that the most performing device through the whole year might not necessarily be the one with highest sun-to-hydrogen efficiency for one-sun illumination.

Investigating the degradation behaviours of n+-doped Poly-Si passivation layers: An outlook on long-term stability and accelerated recovery

In this article, we study the kinetics of firing-activated degradation and recovery of industrially processed n + -doped poly-Si on thin oxide passivation layers subjected to illuminated annealing at elevated temperatures. The impact of a comprehensive range of fast-firing conditions on the subsequent degradation and recovery were assessed. The results indicate that the recovery process is dependent on the peak firing temperature, where higher temperatures led to an improvement in effective lifetime of up to 20% compared to the pre-fired state, and a very low surface dark saturation current density of 2.9 fA/cm 2 . By cycling through light soaking and dark anneal conditions, we show that unlike the commonly studied boron-oxygen light-induced degradation (BO-LID) and light- and elevated temperature-induced degradation (LeTID), this newly observed instability in n + -doped poly-Si passivation layers is not reversible, that is, once a degradation/recovery cycle is completed, the lifetime remains very stable under subsequent light soaking. This indicates that the surface related instability may be able to be completely resolved following the completion of the first degradation/recovery cycle. With this in mind, we investigate the potential for high intensity laser illumination (up to 150 kW/m 2 ) to rapidly increase the recovery rates, however, this does not seem sufficient to cycle through degradation and recovery on a timescale that is amenable with mass production. The mitigation of any potential instabilities at the poly-Si interface has significant implications for the reliability of n-type tunneling oxide passivated contact (TOPCon) solar cells. • Firing conditions have a significant impact in stability of polysilicon passivation. • The firing-induced surface instability is different to previous degradation modes. • Cycling between degraded and recovered states does not occur.

Evaluation of the main sensitivity drivers in relation to indoor comfort for individuals with autism spectrum disorder. Part 2: Influence of age, co-morbidities, gender and type of respondent on the stress caused by specific environmental stimuli

Variations of environmental parameters, like thermo-hygrometric, acoustic, visual and indoor air quality can influence the sensitivities of individuals on the spectrum. This paper presents research on this issue, studied by means of questionnaires administered to parents and professional caregivers taking care of people with Autism Spectrum Disorder (ASD).The study highlights that there are clear differences if the indirect evaluations are performed by parents or professional caregivers, in relation to the specific identification of stress sources. Additionally, acoustic domain is identified as the one causing the major stress, especially caused by strong noises and particular sounds such as voices, animal sounds and impacts, and its dependence on the severity of autism is evidenced. Furthermore, a lower impact of thermal, visual and IAQ factors is determined, with the exception of some specific stimuli like light contrast (glare), high illumination, particular light sources or stale air. Finally, this paper provides evidence of the influence of age, severity of autism and co-morbidities on perceived stress.

Evaluating Street Lighting Quality in Residential Areas by Combining Remote Sensing Tools and a Survey on Pedestrians’ Perceptions of Safety and Visual Comfort

The perceived quality of street lighting influences pedestrians’ perceptions of safety and visual comfort, as well as outdoors activities at night. This study explores the association between street lighting attributes, such as illuminance and wavelength, and pedestrians’ feeling of safety (FoS) and perceived lighting quality (PLQ) in eight residential districts in Dalian, China. To achieve this goal, we combine remote sensing technology with ground investigation. The ground research includes physical measurements of lighting attributes, such as intensity, color temperature, and glare, as well as survey evaluations of pedestrians’ perceptions of safety and visual comfort. We also analyze the influence of several environmental factors, such as traffic volumes and vegetation, while accounting for personal characteristics of the observers, such as gender and age. Findings from the remote sensing reveal that Dalian’s residential districts differ substantially by their nighttime light emissions, with high concentration of strong red band (i.e., long wavelength) emissions occurring in Zhongshan and Jinzhou, and strong blue band (i.e., short wavelength) emissions found in central Zhongshan. Results from the ground surveys further indicate that a satisfactory level of FoS reaches at the illumination levels of 5–17 lx, and that people feel safer if nighttime light is warm and uniform. From a multiple regression analysis, it is also found that illuminance and uniformity are the main factors affecting PLQ under conditions of low or high illuminance, while glare and color temperature play a more significant role under high illuminance. In addition, a satisfactory level of PLQ is found at illuminance levels of 25–35 lx and light color temperature of 4000 K–5500 K.

Fusion of effective dimension reduction and discriminative dictionary learning for high-dimensional classification

High-dimensional classification is a hot topic of pattern recognition. However, its performance has much room for improvement due to environment uncertainties and other factors. For example, redundant information from high dimensional data, illumination, and occlusion may lead to the inferior classification performance. Additionally, some potentially useful features of high-dimensional data are not fully captured. To address these problems, we propose a fusion of effective dimension reduction and discriminative dictionary learning for high-dimensional classification. A novel dimension reduction approach is employed to map training samples into a low-dimensional space by using the distance and label information. Then in the low-dimensional subspace, we integrate atomic Fisher constraint and local constraint of coding coefficients into the dictionary learning. Thus the discriminative atoms are effectively extracted. Finally, experimental results prove the efficacy of the proposed model. Besides, the comparative experiments with AlexNet and VGG19 prove the superiority of our method over some deep learning approaches.

High performance and illumination stable In2O3 nanofibers-based field effect transistors by doping praseodymium

Although different kinds of one dimensional (1D) metal oxide nanofibers (MO-NFs) based field effect transistors (FETs) have been developed in recent years, their intrinsic deficiency in illumination instability are not addressed yet, which further prevented their application in practical life. In this work, due to the outstanding performance of suppressing oxygen vacancies and the blue light down-conversion with low charge transfer transition energy, praseodymium (Pr) is demonstrated an ideal candidate to dope into In2O3 NFs for both transferring the depletion mode to the enhancement mode and enhancing the illumination stability of the FETs. The optima In2O3 NFs-based FET was achieved by doping with 3 mol% Pr and exhibited an excellent electrical performance with a carrier mobility of 6.92 cm2V−1s−1, an on/off current ratio of ∼5.4 × 107, threshold voltage of 5.2 V, and subthreshold swing of 0.37 V/dec. Moreover, the FETs exhibited good illumination stability under 3600 s negative gate bias stress test with illumination (NBIS). Finally, the FET was also used as a switch to bright the LED in this work, demonstrating its great promise of Pr-doped In2O3 NFs in future one-dimensional electronic devices.

The Absence of the AtSYT1 Function Elevates the Adverse Effect of Salt Stress on Photosynthesis in Arabidopsis.

Arabidopsis thaliana SYNAPTOTAGMIN 1 (AtSYT1) was shown to be involved in responses to different environmental and biotic stresses. We investigated gas exchange and chlorophyll a fluorescence in Arabidopsis wild-type (WT, ecotype Col-0) and atsyt1 mutant plants irrigated for 48 h with 150 mM NaCl. We found that salt stress significantly decreases net photosynthetic assimilation, effective photochemical quantum yield of photosystem II (ΦPSII), stomatal conductance and transpiration rate in both genotypes. Salt stress has a more severe impact on atsyt1 plants with increasing effect at higher illumination. Dark respiration, photochemical quenching (qP), non-photochemical quenching and ΦPSII measured at 750 µmol m−2 s−1 photosynthetic photon flux density were significantly affected by salt in both genotypes. However, differences between mutant and WT plants were recorded only for qP and ΦPSII. Decreased photosynthetic efficiency in atsyt1 under salt stress was accompanied by reduced chlorophyll and carotenoid and increased flavonol content in atsyt1 leaves. No differences in the abundance of key proteins participating in photosynthesis (except PsaC and PsbQ) and chlorophyll biosynthesis were found regardless of genotype or salt treatment. Microscopic analysis showed that irrigating plants with salt caused a partial closure of the stomata, and this effect was more pronounced in the mutant than in WT plants. The localization pattern of AtSYT1 was also altered by salt stress.

The Oxygen Paradigm—Quantitative Impact of High Concentrations of Dissolved Oxygen on Kinetics and Large-Scale Production of Arthrospira platensis

The cultivation of Arthrospira platensis in tubular photobioreactors (tPBRs) presents a promising approach for the commercial production of nutraceuticals and food products as it can achieve high productivity and effective process control. In closed photobioreactors, however, high amounts of photosynthetically produced oxygen can accumulate. So far, there has been a wide range of discussion on how dissolved oxygen concentrations (DOCs) affect bioprocess kinetics, and the subject has mainly been assessed empirically. In this study, we used photorespirometry to quantify the impact of DOCs on the growth kinetics and phycocyanin content of the widely cultivated cyanobacterium A. platensis. The photorespirometric routine revealed that the illumination intensity and cell dry weight concentration are important interconnected process parameters behind the impact that DOCs have on the bioprocess kinetics. Unfavorable process conditions such as low biomass concentrations or high illumination intensities yielded significant growth inhibition and reduced the phycocyanin content of A. platensis by up to 35%. In order to predict the biomass productivity of the large-scale cultivation of A. platensis in tPBRs, a simple process model was extended to include photoautotrophic oxygen production and accumulation in the tPBR to evaluate the performance of two configurations of a 5000 L tPBR.

Wheat head counting in the wild by an augmented feature pyramid networks-based convolutional neural network

• Multi-scale and dense wheat heads in a wild environment were counted in this study. • Contrast adjustment and Gaussian blur were used to increase image features. • AugFPN and cascaded IoU threshold were used to extract multi-dimensional features. • These features could be used to detect wheat heads with a precision of 95.17%. • The error rate was 3.7% so it could provide reliable data for yield estimation. Wheat head counting plays an important role in crop yield estimation, which also meets great challenges of high density, scale variation, and illumination difference. In this paper, an improved wheat head counting network (WHCnet) was proposed to count wheat heads from the top view in the wild, with a novel object counting by detection pipeline. Firstly, data enhancement such as contrast adjustment and Gaussian blur were conducted to improve the generalization ability. Secondly, the Augmented Feature Pyramid Networks (AugFPN) was used to pool the original information adaptively, which made full use of the underlying information and solved the problem of poor detection of small wheat heads. Finally, cascaded Intersection over Union (IoU) threshold was used to make the IoU of the training model as close as possible to the input target, which could effectively remove negative samples in the complex background, reduce the noise bounding box and improve the target positioning accuracy of occluded wheat heads. Experiments on the test set image showed that the proposed method had an average error rate of 3.7% and an AP of 95.17%, which was significantly better than other state-of-the-art methods. Besides, the average counting time for a single wheat field image (3968 × 2976) obtained by an unmanned aerial vehicle was 87 ms, and the counting accuracy was 95.8%, which effectively verified the generalization ability of the model. These results indicate that the proposed method can meet the requirements of wheat head counting in the field environment and provide reliable reference data for wheat yield estimation.

Effect of Classroom Illuminance on the Development and Progression of Myopia in School Children

PurposeTo evaluate the effect of classroom illuminance on the development and progression of myopia in elementary school children.MethodsThe daylight factor, a ratio of inside and outside illuminance, was obtained in 50 elementary schools. The first-grade students in the school with the lowest daylight (LD) factor (LD school, 145 subjects; 0.51%) and with the highest daylight (HD) factor (HD school, 147 subjects; 13.35%) were selected. A survey was conducted to evaluate parental myopia, the amount of near-work and outdoor activities. The refractive error and axial length (AL) were measured at initial and after 6 months. The spherical equivalent, AL, and the survey results were compared between the two schools. The mean AL of the emmetropic children was obtained, and all subjects were divided into two groups, more and less than mean AL. Changes in refractive errors and AL were also compared according to AL.ResultsThe amount of change in spherical equivalent and AL after 6 months were not different between the two schools. Initial prevalence of myopia was high in the HD school. However, it became similar between the two schools after 6 months. The mean AL of 155 emmetropic children was 22.7 ± 0.63 mm. In the 185 children with AL ≥22.7 mm, there was no difference in the AL change between the two schools. However, the change in AL in 107 children with AL <22.7 mm was significantly larger in the LD school (0.19 mm) than that in the HD school (0.15 mm, p = 0.049). Parental myopia, near-work and outdoor activities were not different between the two schools.ConclusionsHigh classroom illuminance during the day reduced axial elongation in eyes of children with a shorter AL. Increase in classroom light level by permitting more sunlight can be a protective measure against the development of myopia.

The impact of illuminance level, correlated colour temperature and viewing background on the purchase intention for bread and cakes

This study aimed to investigate whether the illuminance level and correlated colour temperature of light sources, as well as the viewing background, influenced the human visual assessment and purchase intention for bread and cakes. The impact of gender difference, hunger status and many other personal factors on consumption behaviour was also explored. Eighty participants, 40 males and 40 females, were asked to evaluate the appearance of bread and cakes against two different backgrounds under 15 light sources with different illuminance levels and correlated colour temperatures. The experimental results showed that illuminance level and correlated colour temperature had a significant effect on the colour appearance evaluation of bread and cakes. Bread was more suitable to be displayed under light sources with high illuminance levels and low correlated colour temperatures while cakes turned out to be more appealing under light sources with high illuminance and relatively higher correlated colour temperatures. In most cases, the impact of other potential factors, for example, the view background, hunger status and gender difference, turned out to be insignificant. Compared with a white background, a wood-like background significantly promoted the visual assessment of bread for male participants or assessed under light sources of 3300 K, but this impact was practically less meaningful than that of the lighting. The findings highlight the prominent influence of lighting for the display of baked products and provide empirical reference for people who expect attractive presentation of bread and cakes.

Laser Light Durability and Nonlinear Optical Properties of Acrylate Polymer−Chalcogenide Glass−Gold Nanocomposites

Synthesis of acrylate‐based nanocomposites (NCs) for photonic applications is performed, and the influence of gold and chalcogenide glass nanoparticles (NPs) on optical parameters of NC layers at high laser intensities is investigated, whereas the polymerization, recording of optical gratings or other elements, and variations of their functional parameters in As2S3 and Au‐containing NC layers are possible at low, 532 nm laser light intensities in the absorption edge range; optical stability under high intensity illumination and threshold laser damage intensities in NIR optical transmission range are important for nonlinear optical experiments, measurements of n2. Hence, these parameters are determined and show the increase in NCs’ stability due to the addition of Au NPs, as well as increase in n2 in gold‐ and chalcogenide‐containing NCs. Thus, the functionality of such NCs and optical elements on their basis can be extended to high‐intensity applications and nonlinear optics.

A Systematic Review for Establishing Relevant Environmental Parameters for Urban Lighting: Translating Research into Practice

The application of lighting technologies developed in the 20th century has increased the brightness and changed the spectral composition of nocturnal night-time habitats and night skies across urban, peri-urban, rural, and pristine landscapes, and subsequently, researchers have observed the disturbance of biological rhythms of flora and fauna. To reduce these impacts, it is essential to translate relevant knowledge about the potential adverse effects of artificial light at night (ALAN) from research into applicable urban lighting practice. Therefore, the aim of this paper is to identify and report, via a systematic review, the effects of exposure to different physical properties of artificial light sources on various organism groups, including plants, arthropods, insects, spiders, fish, amphibians, reptiles, birds, and non-human mammals (including bats, rodents, and primates). PRISMA 2020 guidelines were used to identify a total of 1417 studies from Web of Science and PubMed. In 216 studies, diverse behavioral and physiological responses were observed across taxa when organisms were exposed to ALAN. The studies showed that the responses were dependent on high illuminance levels, duration of light exposure, and unnatural color spectra at night and also highlighted where research gaps remain in the domains of ALAN research and urban lighting practice. To avoid misinterpretation, and to define a common language, key terminologies and definitions connected to natural and artificial light have been provided. Furthermore, the adverse impacts of ALAN urgently need to be better researched, understood, and managed for the development of future lighting guidelines and standards to optimize sustainable design applications that preserve night-time environment(s) and their inhabiting flora and fauna.

Assessing the influence of environmental conditions on secondary organic aerosol formation from a typical biomass burning compound

The atmospheric chemistry in complex air pollution remains poorly understood. In order to probe how environmental conditions can impact the secondary organic aerosol (SOA) formation from biomass burning emissions, we investigated the photooxidation of 2,5-dimethylfuran (DMF) under different environmental conditions in a smog chamber. It was found that SO2 could promote the formation of SOA and increase the amounts of inorganic salts produced during the photooxidation. The formation rate of SOA and the corresponding SOA mass concentration increased gradually with the increasing DMF/OH ratio. The addition of (NH4)2SO4 seed aerosol accelerated the SOA formation rate and significantly shortened the time for the reaction to reach equilibrium. Additionally, a relatively high illumination intensity promoted the formation of OH radicals and, correspondingly, enhanced the photooxidation of DMF. However, the enhancement of light intensity accelerated the aging of SOA, which led to a gradual decrease of the SOA mass concentration. This work shows that by having varying influence on atmospheric chemical reactions, the same environmental factor can affect SOA formation in different ways. The present study is helpful for us to better understand atmospheric complex pollution.