Illumination Intensity Research Articles

Photoelectricity Theory-Based Concrete Crack Image Segmentation and Optimal Exposure Interval Research

To solve the problem of low accuracy in automatic concrete crack image segmentation and the non-standardization of concrete crack image datasets, an exposure-based concrete crack image capture scene characterization method was proposed, and the optimal exposure interval for crack segmentation was presented by multiple scene image capture experiments. First, current public crack datasets were collected and analyzed, and it was shown that improper spatial resolution, mislabeling, overexposure, and defocus are frequent non-standardization problems in crack dataset production. Through the analysis of the photoelectric principle in concrete crack imaging, an equivalent exposure was set as a core indicator for scene characterization. Twenty-one indoor scenes were designed by varying the illumination intensity and exposure time, and the experimental results showed that an equivalent exposure can be a core control index for scene characterization. The grayscale distribution law of concrete crack images was analyzed with four specimens’ images captured indoors in 50 exposure scenes, and the segmentation accuracy of an image from each scene was calculated through comparison with corresponding manually labeled binary files. The experiment’s results revealed that 5~50 lx·s was the optimal equivalent exposure interval for concrete crack image segmentation, in which better segmentation accuracy was achieved with an F1 score of up to 96.3%.

Использование многофакторного анализа данных в оценке состояния предварительного и последующего возобновления сосняков после выборочных рубок

A research of qualitative and quantitative characteristics of regeneration after the first selective felling with an intensity of 20 to 50 % in pine forests of the northern part of the Krasnoyarsk forest-steppe has been carried out. Some of the plantations were covered by a ground fire 5 to 10 years before the felling. The aim of this research is a generalized analysis of the regeneration state in view of the forest type, the density of forest stand and exposure to fire before felling, as well as the disturbance of soil cover, the state of forest live cover and the microclimatic conditions in the felling areas. The methods of principal component analysis as well as correlation analysis and variance analysis for individual characteristics have been used. The advantages of multivariate data analysis using the method of principal component analysis for obtaining more information on the contribution and combined effects of various environmental factors on pine regeneration in felling areas are shown. The share of explained variance of the considered factors has equaled 87 %. The most significant factors for pine regeneration have turned out to be the type of forest (felling area) and exposure to fire. The second place in terms of importance has been taken by the density of forest stand before felling and the intensity of felling. Of the factors mediated by them, illumination intensity and soil moisture have turned out to be important. Based on the characteristics of the 4 main components, 2 options for combining the main factors for better regeneration of plantations have been established: 1) the large initial density of mature forest stands, as well as the moderate development of mosses and grasses in forest live cover make it possible to choose any felling intensity (within the studied limits), preferably in combination with preliminary burning of a part of the litter (or partial soil mineralization) 5 years before moderately-high or high intensity felling, 2) in case of lower initial density of the forest stand in forest types with significant development of forest live cover, preliminary burning of part of the litter or mineralization of the soil and the choice of a lower intensity of the the first felling (up to 20 %) are required. Analysis of the variability of linear increases in height-and-age groups of undergrowth confirmed the conclusions drawn from the analysis of the quantity and quality of regeneration, showed differences in the response of different groups of undergrowth to changes in microclimatic conditions in felling areas. The similarity of the northern forest-steppe with the southern taiga in terms of pine regeneration conditions has been noted. The results of the study can be used to clarify the requirements for felling and achieve better regeneration of pine forests.

Model-Based 3D Gaze Estimation Using a TOF Camera.

Among the numerous gaze-estimation methods currently available, appearance-based methods predominantly use RGB images as input and employ convolutional neural networks (CNNs) to detect facial images to regressively obtain gaze angles or gaze points. Model-based methods require high-resolution images to obtain a clear eyeball geometric model. These methods face significant challenges in outdoor environments and practical application scenarios. This paper proposes a model-based gaze-estimation algorithm using a low-resolution 3D TOF camera. This study uses infrared images instead of RGB images as input to overcome the impact of varying illumination intensity in the environment on gaze estimation. We utilized a trained YOLOv8 neural network model to detect eye landmarks in captured facial images. Combined with the depth map from a time-of-flight (TOF) camera, we calculated the 3D coordinates of the canthus points of a single eye of the subject. Based on this, we fitted a 3D geometric model of the eyeball to determine the subject's gaze angle. Experimental validation showed that our method achieved a root mean square error of 6.03° and 4.83° in the horizontal and vertical directions, respectively, for the detection of the subject's gaze angle. We also tested the proposed method in a real car driving environment, achieving stable driver gaze detection at various locations inside the car, such as the dashboard, driver mirror, and the in-vehicle screen.

Photoresponse, thermal and electrical behaviors of MXene-based polysulfone nanocomposite

The Ti3C2Tx MXene nanosheet was prepared by 40% (v/v) hydrofluoric acid etching at 20 °C for 48 h and delamination of bulk MAX Ti3AlC2 precursor material. A 2D nanomaterial MXene Ti3C2Tx as a nanofiller was introduced to polysulfone (PSulfone) matrix. MXene and PSulfone/MXene nanocomposite systems were characterized by X-ray diffraction, scanning electron microscopy, transmission electron microscope, Fourier-transform infrared and thermogravimetric analysis instruments. Dielectric and electrical characterization of PSulfone/MXene nanocomposite was carried out. The electrical resistance of Ti3C2Tx MXene from measurement current (I)–voltage (V) was measured as 116 Ω. Pure PSulfone matrix exhibits typical insulator behavior, and MXene exhibits a good conductor behavior. But, when MXene was added to the pure PSulfone matrix, the resistance of the MXene/PSulfone nanocomposite increased moderately compared to that of pure MXene. In spite of the excess of surface functional groups, MXene showed surprisingly good electron transport across the surface, while in the case of PSulfone/MXene nanocomposite, the insulating behavior of PSulfone significantly reduced the electron transport of MXene. The semiconductor behavior of PSulfone/Ti3C2Tx MXene nanocomposite indicates that MXene provides efficient charge carrier transfer in the nanocomposite system. By comparing the TGA results between the PSulfone and different weight ratios of PSulfone/Ti3C2Tx MXene nanocomposites, it was determined that MXene nanosheets had a significant effect in slightly accelerating the thermal degradation of PSulfone. Optical conductivity was investigated by preparing a film of PSulfone/MXene nanocomposite on an interdigital contact. It was observed that the optical current values changed depending on the increasing illumination intensity. Considering current–voltage measurements, the photocurrent generation potential of PSulfone/MXene nanocomposite shows that it can be used in photodevice production.

Investigating the Photostability of Organic Photovoltaics for Indoor and Outdoor Applications

Organic photovoltaics (OPVs) show great promise for both outdoor and indoor applications. However, there remains a lack of understanding around the stability of OPVs, particularly for indoor applications. In this work, the photostability of the poly[(thiophene)‐alt‐(6,7‐difluoro‐2‐(2‐hexyldecyloxy)quinoxaline)]:2,2′‐((2Z,2′Z)‐((4,4,9,9‐tetrahexyl‐4,9‐dihydro‐s‐indaceno[1,2‐b:5,6‐b′]dithiophene‐2,7‐diyl)bis(methanylylidene))bis(3‐oxo‐2,3‐dihydro‐1H‐indene‐2,1‐diylidene))dimalononitrile blend is investigated for both outdoor and indoor applications. Photostability is found to vary drastically with illumination intensity. Devices under high‐intensity white light‐emitting diode (LED) illumination, with their short‐circuit current density (JSC) matching JSC–EQE for AM1.5 G illumination, lose 42% of their initial performance after 30 days of illumination. Contrastingly, after almost 47 days of illumination devices under 1000 lux white LED illumination show no loss in performance. The poor photostability under 1 sun illumination is linked to the poor photostability of IDIC. Through Raman spectroscopy and mass spectrometry, IDIC is found to suffer from photoisomerization, which detrimentally impacts light absorption and carrier extraction. In this work, it is highlighted that under low light levels, the requirement of intrinsic material photostability may be less stringent.

Incomplete accumulation of perilesional reactive astrocytes exacerbates wound healing after closed-head injury by increasing inflammation and BBB disruption

Wound healing after closed-head injury is a significant medical issue. However, conventional models of focal traumatic brain injury, such as fluid percussion injury and controlled cortical impact, employ mechanical impacts on the exposed cerebral cortex after craniotomy. These animal models are inappropriate for studying gliosis, as craniotomy itself induces gliosis. To address this, we developed a closed-head injury model and named “photo injury”, which employs intense light illumination through a thinned-skull cranial window. Our prior work demonstrated that the gliosis of focal cerebral lesion after the photo injury does not encompass artificial gliosis and comprises two distinct reactive astrocyte subpopulations. The reactive astrocytes accumulated in the perilesional recovery area actively proliferate and express Nestin, a neural stem cell marker, while those in distal regions do not exhibit these traits. The present study investigated the role of perilesional reactive astrocytes (PRAs) in wound healing using the ablation of reactive astrocytes by the conditional knockout of Stat3. The extensive and non-selective ablation of reactive astrocytes in Nestin-Cre:Stat3f/f mice resulted in an exacerbation of injury, marked by increased inflammation and BBB disruption. On the other hand, GFAP-CreERT2:Stat3f/f mice exhibited the partial and selective ablation of the PRAs, while their exacerbation of injury was at the same extent as in Nestin-Cre:Stat3f/f mice. The comparison of these two mouse strains indicates that the PRAs are an essential astrocyte component for wound healing after closed-head injury, and their anti-inflammatory and regenerative functions are significantly affected even by incomplete accumulation. In addition, the reporter gene expression in the PRAs by GFAP-CreERT2 indicated a substantial elimination of these cells and an absence of differentiation into other cell types, despite Nestin expression, after wound healing. Thus, the accumulation and subsequent elimination of PRA are proposed as promising diagnostic and therapeutic avenues to bolster wound healing after closed-head injury.

Experimental investigation of Cu@C core-shell nanoparticle suspensions for highly efficient solar-thermal conversion

The choice of working medium plays a pivotal role in achieving efficient solar-thermal utilization. Nanoparticle suspensions, due to their superior optical and thermal properties, emerge as promising candidates. However, their widespread use is hindered by high costs and a limited absorption bandwidth. In this study, Cu@C core-shell nanoparticles (NPs) were prepared through an experimental process, employing a straightforward in situ polymerization method followed by high-temperature carbonization. Finite element calculations reveals that the solar absorption power of Cu@C NPs surpasses that of C NPs and Cu NPs by 57.2 % and 22.9 %, respectively. This enhancement is attributed to the synergistic coupling between the localized surface plasmon resonance (LSPR) of the Cu core and the robust intrinsic absorption of the C shell. Under 1-sun illumination intensity, experimental findings show that the solar-thermal conversion efficiency (η) of the Cu@C nanoparticle suspension, with a mass fraction of 100 ppm, attains approximately 93 %, tripling that of the water base-fluid (∼31 %). Moreover, both η and the temperature profile exhibit negligible variations under different solar intensities and after repeated heating and cooling cycles, indicating the exceptional stability of the suspensions. These results suggest that Cu@C nanoparticle suspensions present a dependable and efficient solution for solar-thermal applications.

A study on the dark and illuminated operation of Al/Si3N4/p-Si Schottky photodiodes: optoelectronic insights

This work extensively investigates the operation of an Al/ Si3N4/p-Si Schottky-type photodiode under dark and varying illumination intensities. The photodiode is fabricated by employing the metal–organic chemical vapor deposition (MOCVD) method. A thorough electrical characterization is performed at room temperature, encompassing measurements of current–voltage (I–V), current–time (I–t), capacitance–time (C–t), and conductance time (G–t). The photodiode’s rectification factor and reverse bias area increased under illumination. The relationship between light power density, barrier height, and diode ideality factor is found. The study also found a strong correlation between light intensity and applied voltage on series resistance (Rs) and shunt resistance (Rsh). Rs values are calculated using Cheung’s functions, revealing the diode’s resistance behavior. The study also examines the photodiode’s photoconductivity and photoconductance, finding a non-linear relationship between photocurrent and illumination intensity, suggesting bimolecular recombination. Calculated photosensitivity (K), responsivity (R), and detectivity (D*) values show the device’s light response effectiveness, but efficiency decreases at higher illumination intensities. Transient experiments indicate stable and reproducible photocurrent characteristics, revealing photogenerated charge temporal evolution. This study provides a complete understanding of the Al/Si3N4/p-Si Schottky photodiode’s behavior under different illumination intensities. The findings advance optoelectronic device knowledge and enable their use in advanced technologies.

Time-resolved study of laser-induced phase separation in CsPb(IxBr1−x)3 perovskite under high pressure

Mixed-halide perovskites have attracted extensive interest with their broadly tunable bandgap and optoelectronic properties, which makes them ideal candidates for various solar cells and light-emitting diodes. However, the mixed-halide perovskites often encounter phase separation and degradation under light illumination, which prevents them from many optoelectronic applications. The study on the underlying mechanism and the controlling of the phase separation is crucial to improve the tailored properties for practical applications. Here, we report our systematical investigations of the time-resolved photoluminescence shift and crystal structure evolution on the nanocrystalline CsPb(IxBr1−x)3 perovskite under intense laser illumination and found the increasing contribution of bromine-rich phase over time. Furthermore, we subject the nanocrystalline CsPb(IxBr1−x)3 perovskite to a quasi-hydrostatic pressure environment and observed that the phase separation slows down quickly with increasing pressure and can be totally suppressed at a rather mild pressure below 0.2 GPa. These findings suggest the light-induced separation of the crystalline structure, and their optoelectronic properties can be largely suppressed, which provides a useful approach to overcome the problem caused by the intense light applications.

New horizons in light control of plant photomorphogenesis and development

Light from Sun has tremendously shaped the evolution of plants and represents one of their key triggers for proper morphogenesis and development. Energy from Sun light is converted by photosynthesis into chemical energy that ultimately drives all energy consuming processes in plants. Besides, Sun light provides information about environmental conditions or constraints and signals important parameters such as day length, time point of season, direction and intensity of illumination or spatial competition with neighbouring plants. Plants possess a sophisticated array of photoreceptors that perceive this information (photoperception) and initiate signalling pathways that control appropriate responses at developmental or physiological level. While the primary processes of photoperception are largely understood, many aspects of the subsequent signalling networks are still elusive and especially the interaction with other signalling networks is far from understood. Light represents also a highly versatile tool for scientists to study morphogenesis and development of plants by a steadily increasing number of remote sensing technologies that allow to observe plants in real time and high resolution (photodetection). Further, scientists now can even use the knowledge about photobiology and photoreceptors to construct synthetic tools that can be genetically introduced into plants to monitor internal processes (so-called biosensors). Recent technological developments in optogenetics even allow to generate tools that actively regulate gene expression or metabolism by selective illumination (photocontrol). In this perspective article we highlight progress in our understanding of light signalling and a number of selected technological improvements in photocontrol with a special focus on the areas of phytochrome signalling and plant optogenetics.

Optoelectric response of Schottky photodiode with a PVP: ZnTiO3 nanocomposite as an interfacial layer

This work aims to study the photo-response of the fabricated silicon-based Al/PVP:ZnTiO3/p-Si photodiode (PD) in a wide range of illumination intensities. To make a metal-polymer/nanocomposite-semiconductor (MPS) PD, a thin film of PVP:ZnTiO3 nanocomposite is deposited at the interface of the metal-semiconductor (MS) structure. Information regarding the preparation and manufacturing procedures is provided. Through the examination of the current-voltage (I–V) behavior, essential electrical properties such as leakage current (I0), barrier height (ΦB0), ideality factor (n), series and shunt resistances (Rs, Rsh), energy-dependent interface states density (Nss), photocurrent (Iph), and photosensitivity (S) are acquired. The thermionic emission (TE) theory, along with the Norde and Cheung methods, is employed to calculate the parameters ΦB0, n, and Rs. The values of ΦB0 and Rs are decreased by raising the illumination intensity while the n value is increased. In addition, the illumination coefficient (α) and the value of ΦB0 in the ideal case are determined from the ΦB0-P and ΦB0-n plots. The efficiency (η) of the sample is calculated at each illumination intensity whose maximum value is 2.30 % at the intensity of 450 mW/cm2. The illumination-dependent photocurrent is investigated at the negative bias region that shows a good linear behavior in the ln(Iph)-ln(P) profile. The photosensitivity (S) of the fabricated PD is obtained as ⁓500 which is, compared with previous PDs. These findings demonstrate that the developed silicon-based MPS-type PD with a structure of Al/PVP:ZnTiO3/p-Si exhibits a good photo-response and can successfully replace traditional MS PDs in optoelectronic and photovoltaic applications.

Illumination homogenization of highly coherent light source based on phase modulation

When using a fly’s eye lens system to homogenize highly coherent light sources, the interference effect between the sub-beams can cause a periodic speckle distribution of illumination intensity, thereby disrupting illumination uniformity. It has been shown that using a rotating optical phase-shift plate behind the fly’s eye lens can eliminate interference patterns, but it only demonstrates engineering realizations. And the theoretical analysis and technical guidance on the phase modulation method and statistical averaging method for fly’s eye lens homogenization systems are still lacking. In this work, a simulation model of fly’s eye random phase modulation homogenization system is developed and studied in detail. Each sub-beam of the fly’s eye lens is randomly phase-modulated to break the coherence condition, and the illumination intensity of multiple independent modulations is accumulated to eliminate the interference pattern. The more times the intensity is accumulated, the better the homogenization is. Meanwhile, studied in this paper are the influence of the diffraction effect on homogenization, and the influence of the sub-lens size and focal length on the homogenization, which result in the diffracting-type system and the imaging-type system respectively. For an imaging type system, it is necessary to ensure that the first fly’s eye lens is in the front focal plane of the second fly’s eye lens. By optimizing the parameters of the fly’s eye lens and using an imaging-type system with <i>p</i> = 1.8 mm and <i>f</i><sub>A</sub> = 9 mm, a Gaussian beam with the non-uniformity of 117% is homogenized into a flat-topped beam with the non-uniformity of 1.2% in a square illumination area of 100 mm<sup>2</sup>. This fly’s eye lens random phase modulation homogenization system has a simple structure, low energy loss, and good illumination uniformity, and can be used in systems that require high coherent laser input and high resolution. This technology can be used in the field of deep-ultraviolet mask defect detection.

Assessing illumination fatigue in tunnel workers through eye-tracking technology: A laboratory study

Considering the vigorous development of the tunnel transportation industry, research on improving the health and comfort of tunnel workers has become important. Requirements for tunnel construction illumination vary worldwide, and the use of inappropriate illumination can lead to increased worker fatigue. This study used virtual-reality simulation of tunnel construction environments, with illumination intensity as the sole variable, combined with eye-tracking technology to record and analyze the performance of eight indicators across four categories under nine illumination conditions. The optimal illumination range was found to be 100–150 lx. The potential significance of each indicator was explored based on the varying interpretative capacities. A random forest algorithm was employed to construct a classification prediction model for illumination fatigue, achieving an accuracy rate of 75.5%. Noticeable fatigue was predicted with an accuracy of 85%, and that of mild fatigue was 80%. The significance of this study lies in the successful application of eye-tracking technology to detect and classify illumination fatigue in tunnel construction environments. However, illumination fatigue is not confined to underground environments. The experimental methods and results presented in this paper can aid in conducting research in various construction environments with limited natural light.

Investigating the Impact of Base Heating and External Electric Field on PV Cell Performance under Intense Illumination

Investigating the Impact of Base Heating and External Electric Field on PV Cell Performance under Intense Illumination

The heterogeneous reactions of toluene/O3/NH3 on hematite nanoparticles: the impact of light illumination on organic ammonium salt formation

The intensity of light illumination played an important role in the formation of organic ammonium salts on nano-hematite.

Voltage controlled polarity switching of photoresponse in graphene oxide-based memristor

Graphene oxide-based metal/insulator/metal device: a memristor exhibiting voltage-dependent polarity switching of photoresponse by precisely controlling the intensity of illumination.

The effect of soil liming, nitrogen and potassium application on the growth, development and physiological parameters of Calendula officinalis L.

The effect of soil liming and the addition of different doses of nitrogen and potassium on the growth, development and operation of FAS pot marigold plants (Calendula officinalis L. abrikosovy jam variety was studied. Experimental options: option 1 (control); option 2 (lime 4.6 t/ha); option 3 (lime 4.6 t/ha, N70K140); option 4 (lime 4.6 t/ha, N100K200). The plants were grown at an illumination intensity of PAR 200 mmol/m2, with a photoperiod of 12 hours before the flowering stage. The results of the study showed that the application of lime and mineral fertilizers significantly increased the biomass, height, leaf area of plants and the intensity of photosynthesis, accelerated the development of plants compared with the control. At the same time, the greatest influence on plant productivity was exerted by the introduction of lime into the soil, which caused a maximum increase in the intensity of photosynthesis and the water use efficiency (WUE), an increase in the number of inflorescences and their mass. The addition of urea and potassium sulfate caused an additional increase in plant weight and leaf area. There was no significant effect of nitrogen and potassium addition on the chlorophyll content, stomatal conductance, transpiration intensity and WUE.

Intrinsic Omnidirectional Image Decomposition With Illumination Pre-Extraction.

Capturing an omnidirectional image with a 360-degree field of view entails capturing intricate spatial and lighting details of the scene. Consequently, existing intrinsic image decomposition methods face significant challenges when attempting to separate reflectance and shading components from a low dynamic range (LDR) omnidirectional images. To address this, our article introduces a novel method specifically designed for the intrinsic decomposition of omnidirectional images. Leveraging the unique characteristics of the 360-degree scene representation, we employ a pre-extraction technique to isolate specific illumination information. Subsequently, we establish new constraints based on these extracted details and the inherent characteristics of omnidirectional images. These constraints limit the illumination intensity range and incorporate spherical-based illumination variation. By formulating and solving an objective function that accounts for these constraints, our method achieves a more accurate separation of reflectance and shading components. Comprehensive qualitative and quantitative evaluations demonstrate the superiority of our proposed method over state-of-the-art intrinsic decomposition methods.

Improved Generalization of White Blood Cell Classification by Learnable Illumination Intensity Invariant Layer

Improved Generalization of White Blood Cell Classification by Learnable Illumination Intensity Invariant Layer

Increasing the two-photon photocurrent saturation limit in a quantum ratchet intermediate band solar cell

A quantum ratchet intermediate band solar cell based on a quantum well superlattice is investigated. The design is similar to that of a previously reported device, but it employs a stronger built-in electric field across the heterojunction; therefore, it works at higher illumination intensities before the photocurrent saturates due to photocarrier accumulation screening out the field and causing leveling of the bands. In this present device, saturation of the two-photon photocurrent occurred at a valence-to-intermediate band pulse energy of ∼4 nJ, approximately ten times greater than the previously reported device, making it more suitable for concentrator applications.