Diffuse Illumination Research Articles

Diffuse retro-reflective imaging for improved video tracking of mosquitoes at human baited bednets.

Robust imaging techniques for tracking insects have been essential tools in numerous laboratory and field studies on pests, beneficial insects and model systems. Recent innovations in optical imaging systems and associated signal processing have enabled detailed characterization of nocturnal mosquito behaviour around bednets and improvements in bednet design, a global essential for protecting populations against malaria. Nonetheless, there remain challenges around ease of use for large-scale in situ recordings and extracting data reliably in the critical areas of the bednet where the optical signal is attenuated. Here, we introduce a retro-reflective screen at the back of the measurement volume, which can simultaneously provide diffuse illumination, and remove optical alignment issues while requiring only one-sided access to the measurement space. The illumination becomes significantly more uniform, although noise removal algorithms are needed to reduce the effects of shot noise, particularly across low-intensity bednet regions. By systematically introducing mosquitoes in front of and behind the bednet in laboratory experiments, we are able to demonstrate robust tracking in these challenging areas. Overall, the retro-reflective imaging set-up delivers mosquito segmentation rates in excess of 90% compared to less than 70% with backlit systems.

Evaluation of the Vertical Sky Component without Obstructions for Daylighting in Burgos, Spain

Daylight availability knowledge is the first step for an energetic and visually efficient building and city design. It can be estimated with the Vertical Sky Component (VSC), which is defined as the ratio of the vertical diffuse illuminance over the unobstructed horizontal diffuse illuminance, simultaneously measured at the same point. These illuminance magnitudes are obtained from luxmeter measurements but these data are scarce. Alternatively, VSC can be obtained from prior knowledge of the sky illuminance distribution, which can be measured with a sky scanner device or by reference to the CIE (Commission Internationale de L’Éclairage) Standard classification for homogeneous skies. Both approaches are compared in this study. The coherence of the results obtained for the four cardinal orientations are analyzed by applying classical statistical parameters and luxmeter measurements as references for the results. The measurement campaign was completed between September 2016 and January 2019 in Burgos (Spain), as representative case study and specific contribution of this work. It was observed that the VSC values were higher than 100 in many cases: 21.94% for the south- and 33.6% for the east-facing vertical surfaces. The study highlights the good daylighting conditions in Burgos, mainly due to the predominance of clear skies over much of the year. This fact implies high daylight availability that, with efficient city planning and building design, could potentially lead reduction energy consumption of buildings, improvements in visual comfort, and the well-being of occupants.

Optimising subjective anterior eye grading precision

PurposeTo establish the optimum grading increment which ensured parity between practitioners while maximising clinical precision. MethodsSecond year optometry students (n = 127, 19.5 ± 1.4 years, 55 % female) and qualified eye care practitioners (n = 61, 40.2 ± 14.8 years, 52 % female) had 30 s to grade each of bulbar, limbal and palpebral hyperaemia of the upper lid of 4 patients imaged live with a digital slit lamp under 16× magnification, diffuse illumination, with the image projected on a screen. The patients were presented in a randomised sequence 3 times in succession, during which the graders used the Efron printed grading scale once to the nearest 0.1 increment, once to nearest 0.5 increment and once to the nearest integer grade in a randomised order. Graders were masked to their previous responses. ResultsFor most grading conditions less than 20 % of clinicians showed a ≤0.1 difference in grade from the mean. In contrast, more than 50 % of the student graders and 40 % of experienced graders showed a difference in grade from the mean within 0.5 for all conditions under measurement. Student precision in grading was better with both 0.1 and 0.5 grading increments than grading to the nearest unit, except for limbal hyperaemia where they performed more accurately with 0.5 unit increment grading. Limbal grading precision was not affected by grading step increment for experienced practitioners, but 0.1 and 0.5 grading increments were both better than the 1.0 grading increment for bulbar hyperaemia and the 0.1 grading increment was better than the 0.5 grading increment and both were better than the 1.0 grading increment for palpebral hyperaemia. ConclusionAlthough narrower interval scales maximise the ability to detect smaller clinical changes, the grading increment should not exceed one standard deviation of the discrepancy between measurements. Therefore, 0.5 grading increments are recommended for subjective anterior eye physiology grading (limbal, bulbar and palpebral redness).

Hash-Based Hierarchical Caching and Layered Filtering for Interactive Previews in Global Illumination Rendering

Modern Monte-Carlo-based rendering systems still suffer from the computational complexity involved in the generation of noise-free images, making it challenging to synthesize interactive previews. We present a framework suited for rendering such previews of static scenes using a caching technique that builds upon a linkless octree. Our approach allows for memory-efficient storage and constant-time lookup to cache diffuse illumination at multiple hitpoints along the traced paths. Non-diffuse surfaces are dealt with in a hybrid way in order to reconstruct view-dependent illumination while maintaining interactive frame rates. By evaluating the visual fidelity against ground truth sequences and by benchmarking, we show that our approach compares well to low-noise path-traced results, but with a greatly reduced computational complexity, allowing for interactive frame rates. This way, our caching technique provides a useful tool for global illumination previews and multi-view rendering.

Evanescent Field Absorption Based Fiber Optic Sensor Using Chalcogenide Glasses for Biological Tissues Detection

An evanescent field based fiber optic sensor is proposed using ternary chalcogenide glasses under diffuse source illumination for straight fiber for detection of biological tissues. The field distribution within the core region and evanescent field beyond it has been shown pictorially. The simulation is performed in near infrared region for three liver tissues, normal liver tissue (N), Non-cancerous metastatic tissue (NMET) and non-cancerous hepatocellular carcinoma tissue (NHCC). Interrogation of absorption coefficient and transmitted power has been performed. The effect of variation in core diameter and wavelength on sensitivity of the samples have been studied to have high sensitivity.

Lenticular burns following PASCAL photocoagulation.

Lenticular burns following PASCAL photocoagulation.

Coenoflora of Dactylorhiza incarnata (L.) Soo populations of the Kalba ridge

The article provides an ecological-coenotic analysis of the flora of the Dactylorhiza incarnata populations on the Kalba ridge. The ecological optimum of the species is established. On the basis of fieldsurveys, 4 main populations were identified, 13 localities were recorded. The coenoflora of D. incarnatapopulations on the Kalba ridge includes 117 species belonging to 30 families and 80 genera. The typicalmarker species are Thalictrum simplex L., Salix viminalis L., Filipendula ulmaria (L.) Maxim., Sanguisorbaofficinalis L., Geranium pratense L., Festuca pratensis Huds. The conoecotypes are occupied by mossyrocks, gravelly banks of streams and mountain rivers. The floral similarity of the studied populations varies within 9–27%. Ecologically, in all populations, the basis of phytocenoses is formed by mesophytes– 67–75%, in a smaller proportion are mesohygrophytes – 16–27% and xeromesophytes – 6–16%. Thepredominant life form is herbaceous vegetation – 81–95%, the share of shrubs and trees is insignificant– 5–19%. The ecological optimum of D. incarnata falls on the southeastern slopes with diffuse illumination and moderate wind impact. The Thalictrum-Sanguisorba-Filipendula and herbal-Carex phytocenoses have optimal conditions: overly humid meadows and forest edges with low density and competition.Self-maintenance and reproduction of the species is carried out mainly by seeds, less often by vegetativedivision of the finger root. When analyzing the age composition of populations, the dynamics and stability of coenopopulations, it was found that the recovery index is within the optimum. The dominantposition is occupied by individuals of the virginal and pregenerative stages of growth.Key words: Dactylorhiza incarnata (L.) Soo, floristic composition, Kalba ridge, ecological-coenoticanalysis, state of the species.

Inadvertent inversion of corneal flap following microkeratome-assisted laser-assisted in situ keratomileusis.

A 21-year-old male with stable myopic astigmatism in OD (-1.50DS/-0.75 DCX900) and OS (-1.50DS/-0.75DCX900) underwent microkeratome-assisted laser-assisted in situ keratomileusis (LASIK). According to the referring surgeon, preoperative topography and pachymetry were normal. On postoperative day 1, UCVA in OD was 6/18 and 6/9 in OS. Slit-lamp biomicroscopy revealed the inferior epithelial defect. The patient was put on moxifloxacin 0.5%, prednisolone acetate 1% suspension, and sodium-hyaluronate eye drop 3 times a day. Epithelial defect healed after 24 h but UCVA remained 6/18 in OD. The patient was then referred for further management. On presentation, the patient had BCVA 6/6 (+2.00DS/-4.75DC × 980) in OD and UCVA 6/6 in OS. Slit-lamp biomicroscopy revealed a hvorizontal line in OD [Fig. 1a and b]. Tomography on Pentacam (OCULUS Optikgeräte GmbH Postfach, 35549 Wetzlar, GERMANY) showed corneal astigmatism and inferior steepening [Fig. 1c and d]. Clinical diagnosis of inadvertent inversion (inferior folding on itself) of the LASIK flap was considered. Lifting and repositioning of the LASIK flap were planned. The corneal epithelium between the horizontal line and peripheral cornea was removed. LASIK flap was lifted and repositioned with LASIK spatula. Interface irrigation was done. The margin of the flap was dried and uniformity of gutter width was ensured. A bandage contact lens (BCL) was placed. The lid speculum was removed carefully. The topical medication was continued as before surgery. On day 1, the LASIK flap was well apposed. On day 7, the patient achieved BCVA of 6/9 in OD (+0.75DS/-0.50DC × 930). After 4 weeks of flap repositioning, the patient achieved UCVA of 6/6 (-2). The horizontal line had disappeared, corneal astigmatism decreased considerably, and the area of steepening disappeared [Fig. 2a-d].Figure 1: Slit-lamp biomicroscopy and Scheimpflug corneal tomography of the right cornea with LASIK flap inversion. Diffuse illumination photograph shows an inferior horizontal line and irregularity of LASIK flap (a), these findings on retro-illumination suggestive of inadvertent inversion (b). The axial curvature map on Scheimpflug corneal tomography shows against the rule corneal astigmatism (c) and the area of inferior corneal steepening corresponding to inverted flap on anterior elevation map (d)Figure 2: Slit-lamp biomicroscopy and Scheimpflug corneal tomography of the right eye 4 weeks after flap lifting and reposition. The disappearance of the horizontal line and absence of inferior corneal irregularity on diffuse illumination (a) and retro-illumination suggestive of well-apposed LASIK flap (b). The axial curvature map on Scheimpflug corneal tomography shows a decrease in corneal astigmatism (c) and the absence of inferior corneal steepening on the anterior elevation map confirms proper apposition of LASIK flap (d)Discussion Inadvertent flap inversion occurs rarely. Inspection of the flap integrity and ensuring uniformity of gutter may prevent this complication. Prednisolone acetate 1% suspension being white has been advocated to enhance the visibility of gutter width.[1] Inadvertent flap inversion may occur if the patient squeezes the eyelids while removing the drapes and speculum.[2] Mechanical trauma due to forceful blinking, eyelid squeezing, and eye rubbing has been implicated to cause flap shift within 24 h of surgery.[3] In our case, most probably, this complication happened either due to squeezing during speculum removal or due to eyelids impinging on the flap margin, postoperatively in a flap that was not well adhered. Inadvertent flap inversion should be considered an emergency. Early repositioning of the flap should be done to prevent the development of fixed folds and epithelial ingrowth. Eyelid speculum and drapes should be removed carefully to prevent dislodgment of the flap. Declaration of patient consent The authors certify that they have obtained all appropriate patient consent forms. In the form the patient(s) has/have given his/her/their consent for his/her/their images and other clinical information to be reported in the journal. The patients understand that their names and initials will not be published and due efforts will be made to conceal their identity, but anonymity cannot be guaranteed. Financial support and sponsorship Nil. Conflicts of interest There are no conflicts of interest.

Eye care in the intensive care unit for COVID-19 patients

Purpose: To assess eye manifestations and ensure the importance of eye care for COVID-19 patients in the intensive care unit, they need regular ophthalmological examination and follow-up. Patients and Methods: In this case series study, 43 patients' (86) eyes with COVID-19 were included in the study. The ocular history was taken from hospital-registered data. They were ophthalmologically examined using a portable slit lamp or by a by-side examination (diffuse illumination), and the anterior segment was evaluated. Schirmer's test was done for all patients to assess dryness. A Tono-Pen™ Tonometer was used in all cases to measure intraocular pressure with full infection control measures. Results: Sixteen (18.6) per cent of eyes were affected either by dryness due to exposure, infection (mucopurulent conjunctivitis), and subconjunctival hemorrhage with no apparent vision affection, and two were on antiglaucoma medications before the infection and advised to continue their medication. Conclusion: Eye care is mandatory for patients in ICU with COVID-19.

Retinitis pigmentosa with bilateral irido-fundal coloboma

A 40-year-old male, presented with gradual painless progressive loss of vision in both the eyes more in right since 1 year. Born out of consanguineous marriage, he gave a history of night blindness since childhood. The best-corrected visual acuity was 20/200 and 20/40 in right and left eye, respectively. Refraction showed an axial myopia of -9.00 DS/-1.50 DC at 100 degree in the right eye. The left eye showed refraction of +1.00 DC at 170 degree. Intraocular pressure with noncontact tonometer was 15 and 16 mm of Hg. Axial length was found to be 24.93 mm and 23.60 mm in right and left eye, respectively. Vertical and horizontal corneal diameters were 11 mm in both eyes. Keratometry values in the right eye were K vertical 43.55D, K horizontal 44.06D and in the left eye were K vertical 43.05D, K horizontal 43.49D. Slit-lamp examination revealed a clear cornea and normal anterior chamber depth. Inferonasal iris coloboma was noted in both eyes [Fig. 1]. The lens showed nuclear sclerosis grade 2 with posterior subcapsular opacification in right and nuclear sclerosis grade 2 in the left eye according to the Lens Opacities Classification System II (LOCS II) The posterior segment showed a normal-looking disc with minimal arteriolar attenuation, boney spicules distributed from the mid periphery throughout the retina in both eyes. Chorio-retinal coloboma was type 3 (separated from the optic disc by a clear area of the retina) in the right eye [Fig. 2] and type 7 (extreme peripheral coloboma) in the left eye [Fig. 3] according to Ida Manns classification. B scan ultrasonography showed an excavated lesion in the inferior aspect suggestive of fundus coloboma in the right eye. In the left eye the coloboma was not well demarcated on B scan ultrasonography.Figure 1: Anterior segment photographs with diffuse illumination (a) Right eye showing inferonasal iris coloboma with cataractous lens. (b) Left eye showing inferonasal iris colobomaFigure 2: (a) Fundus photograph of right eye showing coloboma in the inferior quadrant sparing disc and macula with bony spicules in the mid periphery. (b) Fundus photograph right eye, superonasal quadrant showing bony spicules in the mid peripheryFigure 3: (a) Fundus photograph of left eye depicting bony spicules in mid periphery and extreme peripheral coloboma inferiorly. (b) Peripheral coloboma with bony spicules in inferior quadrantPhacoemulsification with intraocular lens implantation under topical anesthesia was done in the right eye. Postoperatively at the end of 1 month best-corrected visual acuity was 20/30 in the right eye with a refraction of -0.75 DC at 80 degrees and near vision of N6 with + 3.00 DS. Discussion Retinitis pigmentosa is most commonly associated with posterior subcapsular cataract 53%[1] glaucoma 2.3%[2] myopia, keratoconus, vitreous detachment, and optic disc drusen. Association of macular colobomas with retinitis pigmentosa, especially autosomal dominant RP and Ushers syndrome has been extensively reported in the literature. In 2004, phenotypically different RP with macular coloboma was reported by Parmeggiani in 3 adult siblings[3], which was stated as an autosomal dominant feature. The association of iris and fundal coloboma with RP has been rarely reported in the literature. Kelly et al.[4] described the incidence, ocular findings, and systemic associations of coloboma in a population-based cohort study in the United States, reported one case with unilateral coloboma in association with RP. Population-based studies in India are scanty. Pallavi Agrawal et al.[5] reported a similar case of unilateral coloboma from a case in Mumbai, India in 2013. Bilateral Irido-fundal coloboma and RP can be separate entities occurring together in this case, or it could be a rare association. Similar cases/case series need to be reported to come to a conclusive result. Declaration of patient consent The authors certify that they have obtained all appropriate patient consent forms. In the form the patient(s) has/have given his/her/their consent for his/her/their images and other clinical information to be reported in the journal. The patients understand that their names and initials will not be published and due efforts will be made to conceal their identity, but anonymity cannot be guaranteed. Financial support and sponsorship Nil. Conflicts of interest There are no conflicts of interest.

Recurrent late onset diffuse lamellar keratitis.

A 27-year-old female with history of bilateral LASIK procedure 8 years ago, was referred for decreased vision in her left eye following blunt trauma by her child's hand, sustained three days earlier. Her best corrected visual acuity (BCVA) was finger counting @ 50 cms in the left eye. A well apposed LASIK flap with conjunctival congestion and corneal epithelial defects was noted in the left eye. A focal aggregation of large, greyish white cells was noted at the level of the interface, involving the pupillary area [Fig. 1A and A']. A diagnosis of grade III late onset Diffuse Lamellar Keratitis (DLK) was made. She was started on topical prednisolone acetate (1%) eye drops every hourly along with topical antibiotics and lubricants. The following day [Fig. 1B], anterior segment OCT revealed linear hypointense area at the flap interface indicating separation of the flap from the underlying bed, thus signifying interface edema [Fig. 1B']. Resolution of infiltration was noted at one week [Fig. 1C and C'] and at 7 weeks, her BCVA was 6/9, N6 with a clear interface and a well apposed flap [Fig. 1D and D'].Figure 1: (A, A') – Day 0 - Slit lamp photograph showing corneal epithelial defects and focal aggregation of greyish-white cells within in the pupillary area. (B) – Day 1 - Minimal reduction in greyish-white cells. (B') – Anterior segment OCT (AS OCT 3D OCT-1 Maestro, Topcon, Japan) image showing separation of the LASIK flap from the stromal bed, thus signifying interface edema. (C) – 1 week - Minimal cellular aggregates. (C') – Reduced interface edema on AS OCT. (D) – 7 weeks - Complete resolution of cellular aggregates. (D') – Normal apposition of the flap on AS OCTShe presented 3 months later, following blunt trauma again due to her child's hand to her left eye with BCVA of 6/18, N36 with resolving epithelial defect and diffuse cellular aggregates in the interface suggestive of grade II DLK [Fig. 2]. At final follow-up at one week, her BCVA was 6/9 partial, N6 with minimal interface infiltrates following treatment with topical 1% prednisolone acetate eye drops.Figure 2: Slit lamp photograph of the left eye under diffuse illumination showing resolving epithelial defect with infiltration at the interface involving the pupillary area, three months following resolution of first episodeDiscussion Late onset DLK may occur weeks, months or years after LASIK due to various inciting factors.[12] Our patient complained of decreased vision and was diagnosed elsewhere as non-healing epithelial defect. However, her vision loss was severe and disproportionate to the epithelial defects which were located away from the pupillary area. The characteristic appearance of large, greyish white infiltrates at the interface similar to that of postoperative DLK led us to the diagnosis of late onset DLK. Also, the severe visual loss could be attributed to the presence of the infiltrates within the pupillary area. This case further highlights that DLK may be recurrent in the same eye, if the inciting event recurs. In conclusion, accurate and timely diagnosis can avoid vision threatening complications and lead to successful outcomes in recurrent post traumatic late onset DLK. Declaration of patient consent The authors certify that they have obtained all appropriate patient consent forms. In the form the patient has given her consent for her images and other clinical information to be reported in the journal. The patient understands that her name and initials will not be published and due efforts will be made to conceal their identity, but anonymity cannot be guaranteed. Financial support and sponsorship Nil. Conflicts of interest There are no conflicts of interest.

Emission spectra of light-pollution sources determined from the light-scattering spectrometry of the night sky

ABSTRACT The emission spectrum of a light-pollution source is a determining factor for modelling artificial light at night. The spectral composition of skyglow is normally derived from the initial spectra of all artificial light sources contributing to the diffuse illumination of an observation point. However, light scattering in the ambient atmosphere imposes a wavelength-specific distortion on the optical signals captured by the measuring device. The nature of the emission, the spectra and the light-scattering phenomena not only control the spectral properties of the ground-reaching radiation, but also provide a unique tool for remote diagnosis and even identification of the emission spectra of the light-polluting sources. This is because the information contained in the night-sky brightness is preferably measured in directions towards a glowing dome of light over the artificial source of light. We have developed a new method for obtaining the emission spectra using remote terrestrial sensing of the bright patches of sky associated with a source. Field experiments conducted in Vienna and Bratislava have been used to validate the theoretical model and the retrieval method. These experiments demonstrate that the numerical inversion is successful even if the signal-to-noise ratio is small. The method for decoding the emission spectra by the light-scattering spectrometry of a night sky is a unique approach that enables for (i) a systematic characterization of the light-pollution sources over a specific territory, and (ii) a significant improvement in the numerical prediction of skyglow changes that we can expect at observatories.

The sky characterization according to the CIE Standard General Sky: Comparative analysis of three classification methods

Since the publication of the standard sky luminance distributions (SSLD) that was consolidated in the ISO 15469:2004(E)/CIE S 011/E:2003, numerous procedures have emerged for the characterization of the sky condition according to that standard. Precisely, the use of different procedures for the classification of the skies of a certain place according to the ISO/CIE standard can lead to obtain different frequencies of sky types. The existing uncertainties in the characterization of the sky condition according to the CIE Standard General Sky as a consequence of the classification procedure used are analyzed in this study. For this, three different classification procedures are used to characterize the sky radiance and luminance distribution measurements made by means of a sky-scanner in Pamplona (Spain) from 2007 to 2013. That is, (1) a method focused on determining the relative gradation and indicatrix functions, (2) a method based on the comparison of measured and standard luminances normalized against the horizontal diffuse illuminance, and (3) a new high-spatial-resolution approach that compares measured and standard luminances relative to zenith. In general terms, it is concluded that there is some uncertainty in the classification depending on the procedure used to characterize the sky.

Correction of the Uneven Brightness Coefficient for the Tropical Sky Conditions

In the design of buildings and structures, the calculation of natural lighting plays an important role in providing visual comfort, rational use of the daylight resource and achieving energy efficiency. Calculation methods and parameters are improved in the research process to imitate/simulate as much reality as possible. Until now, the overcast sky CIE is mainly used in the daylight calculations as the most unfavourable condition. This sky condition is characteristic of a long winter period of temperate climate and is not typical of the tropical sky, where diffuse horizontal illuminance values are very high. For these reasons, an update of theoretical studies in the daylighting calculations and design the daylighting systems must be completed. Accordingly, this study proposes modern methods of analysing the firmament luminance distributions to determine the coefficient of uneven brightness when calculating the Daylight Factor for more realistic sky conditions in the tropical climate of Vietnam. For this, the sky types have to be defined according to the locations. Fifteen international standard types of the firmament with their descriptors are provided by Kittler et al. and a technique using a relation of diffuse and total solar illuminance levels named the cloudiness coefficient Ko are considered to confirm the sky type for Hanoi and Ho Chi Minh City. Parameters were found to computing the sky luminance distributions and the coefficient of uneven brightness for Hanoi and Hochiminh City. A comparison of the results shows the differences of using classical Overcast sky condition and the proposed sky conditions. The method offered and verified in this study showed that, it has potential to be used for difference climate area.

Angular reflectance model for ridged specular surfaces, with comprehensive calculation of inter-reflections and polarization.

The color of a surface structured at the mesoscopic scale differs from the one of a flat surface of the same material because of the light inter-reflections taking place in the concavities of the surface, as well as shadowing effects. The color variation arises not only in scattering materials, but also in the absence of scattering, e.g., in metals and clear dielectrics, just as a consequence of multiple specular reflections between neighboring flat facets of the surface. In this paper, we investigate such color variation in the case of an infinitely long V-shaped groove, having in mind the visual appearance of a surface composed of many structures of that sort, all parallel and identical. We develop a full model of multiple specular reflections, accounting for the ray position and orientation and the polarization effects occurring at each reflection. We compare that situation with two approximate models, more usual and easier to compute, where light is assumed to remain unpolarized all along, or where the $p$p- and $s$s-polarized components are treated separately. Spectral reflectances were predicted for various materials and angles of cavities, under diffuse illumination. In most cases, the three models predict very similar bi-hemispherical reflectances, but the hemispherical-directional reflectances can vary noticeably in certain observation directions. This study might help achieve a more physically realistic rendering of dielectric or metallic ridged surfaces in computer graphics.

Improving the efficiency of thin-film fiber-shaped dye-sensitized solar cells by using organic sensitizers

Fiber-shaped Dye-Sensitized Solar Cells (DSSFs) represent one of the most interesting technologies aimed at the light harvesting and the production of electricity for wearable applications. In order to boost DSSFs commercialization, their production costs and environmental impact must be reduced. To this end, a suitable strategy could be to build thin film-based devices endowed with metal-free organic sensitizers, exploiting their higher molar extinction coefficients compared to typical ruthenium-containing organometallic dyes. In this work, three thiazolo[5,4-d]thiazole-based organic dyes, TTZ3, TTZ5 and TTZ7, capable of strongly absorb visible light, were used for the first time to manufacture titanium wire-based DSSFs. DSSFs based on a thin TiO2 layer (5 μm) sensitized with the three organic dyes were prepared and tested and the obtained results show that power conversion efficiencies for the organic dyes (0.80%) are higher than that obtained with the reference N719 dye (0.45%). An efficiency of 0.99% with short circuit current density equal to 3 mA/cm2 was achieved when the TTZ7-based DSSFs were tested in diffuse illumination condition, highlighting the supremacy of these dyes compared to the metal-organic reference. The excellent photovoltaic performances of TTZ dyes were attributed to their better light harvesting properties, resulting in the production of higher photocurrent densities, which was confirmed by the electrochemical impedance spectroscopy (EIS) analysis. The superiority of organic dyes on DSSFs performances compared to N719, shown for the first time in this work, support the real possibility to apply these molecules for the preparation of efficient light-harvesting devices based on thin film photoanodes.

The Calculation Method for Light Climate Parameters Based on Sun-Lighting Efficiency and the Comparative Analysis of Light Climate in Hanoi and Moscow

The main source of daylight is the Sun. The EarthТs atmosphere scatters its light due to the air, water vapour, ice particles (at high altitudes), dust, various gases, and other contaminants that appear in the air as a result of human activities. This forms a daylight diffuse (scattered) component, which is a data basis for calculation of daylight in buildings. This basis has its own features for a given region. This article shows a calculation of sun-lighting efficiency in Vietnam. We obtained a variation of horizontal daylight illuminance in Hanoi (21.03∞N). Comparing it with the variation of horizontal daylight illuminance in Moscow (55.70∞N), we can see a high level and a distribution uniformity of outdoor illuminance in Vietnam. The maximum levels of diffuse illuminance and total illuminance in Hanoi are 45.2 and 58.52 klx; the maximum levels of diffuse illuminance and total illuminance in Moscow are 28.3 and 53.1 klx. Besides, illuminance levels in winter months are much higher for Hanoi than for Moscow. This can be explained by different latitudes of these cities and by the Sun motion.

Determination of luminance distribution under tropical sky conditions

Introduction. Natural illumination calculations depend on the sky luminance distribution. The most often used diagram of sky luminance in handbooks and guidelines is the luminance distribution in the cloudy sky proposed by Moon and Spencer. This concept actually includes the tropical areas of Vietnam, where the overcast sky and clear sky does not typically occur. To improve the calculation of natural illumination, it is necessary to determine the luminance distribution in the real sky.
 Materials and methods. In solving the research problem, the real sky types for Hanoi were identified using the 15 international standard sky types with their descriptions by lighting climate, which is provided using the method by R. Kittler. The descriptions are derived from the data on diffuse horizontal illumination Dv, extraterrestrial horizontal illumination Ev and light turbidity coefficient Tv. For a specific sky type, the standard parameters were selected for calculating the luminance distribution of the real sky.
 Results. The obtained results show that the typical sky type of Hanoi is the partly cloudy sky, no gradation towards zenith, with slight bleaching towards the Sun (type VI). The sky types from October to December are partly cloudy with the obscured Sun (type IX) and partly cloudy with the more luminant circumsolar area (type X). The study shows that the state of cloud coverage has a great influence on the level of diffuse horizontal illumination and luminance distribution under tropical sky conditions.
 Conclusions. It is revealed that the typical sky type for Hanoi is neither overcast nor clear sky. A typical sky with statistic dominance of cirrus and stratus clouds under effect of high solar radiation of Vietnamese tropical climate gives a high level of diffuse horizontal illuminance. The results show that the difference in luminance distribution between the CIE standard overcast sky and Kittler’s intermediate sky can be resolved at the angles of sky point elevation above horizon γ is higher than 50° with the relative errors below 10 %. In other words, the luminance distribution β of the considered sky type is significant for a system of side natural illumination.

A new diffuse luminous efficacy model for daylight availability in Burgos, Spain

The determination of optimal illumination conditions in buildings is of great interest both for reducing energy consumption and for exploiting solar resources with greater efficiency and sustainability. The most commonplace method of estimating daylight is the luminous efficacy approach, using the more widely measured solar irradiance. In this present study, a new model of diffuse luminous efficacy over a horizontal surface is proposed. A comparative study of twenty-two classic models is presented, to obtain diffuse illuminance, using both, the original mathematical models and the adapted models with local coefficients, in order to determine the most suitable models for Burgos, a city located in north-western Spain. With this purpose in mind, twelve models are selected for all sky conditions, five models for modelling clear sky, two for partly cloudy sky, and three for overcast sky. These twenty-two models are then compared with the new model both for all sky conditions and for particular sky conditions (clear, partly cloudy, and overcast). The behaviour of the new model showed greater accuracy than most of the classic models under analysis. Hence, the advantage of the diffuse luminous efficacy model that can be applied both to all sky and to particular sky conditions.

Image Classification for Automated Image Cross-Correlation Applications in the Geosciences

In Earth Science, image cross-correlation (ICC) can be used to identify the evolution of active processes. However, this technology can be ineffective, because it is sometimes difficult to visualize certain phenomena, and surface roughness can cause shadows. In such instances, manual image selection is required to select images that are suitably illuminated, and in which visibility is adequate. This impedes the development of an autonomous system applied to ICC in monitoring applications. In this paper, the uncertainty introduced by the presence of shadows is quantitatively analysed, and a method suitable for ICC applications is proposed: The method automatically selects images, and is based on a supervised classification of images using the support vector machine. According to visual and illumination conditions, the images are divided into three classes: (i) No visibility, (ii) direct illumination and (iii) diffuse illumination. Images belonging to the diffuse illumination class are used in cross-correlation processing. Finally, an operative procedure is presented for applying the automated ICC processing chain in geoscience monitoring applications.