Color Reflectance Research Articles

Evaluation of the effects of partition design on circadian daylighting in open-plan offices

Due to the changes in the modern human lifestyle, the average time people spend in interior spaces has increased, which calls attention to providing appropriate indoor lighting. Many studies have shown the considerable influence of luminous conditions on human circadian rhythm, productivity, and well-being. While the influence of a building’s architectural characteristics on the visual aspects of daylight has been extensively examined in the literature, there has been comparatively less emphasis on assessing these affects within the context of circadian daylighting considerations. The current study has employed a simulation-based approach to investigate the influence of interior space configurations; in particular, office space’s partition layout, height, and optical properties on the circadian potential of the space. Specifically, the study aimed to examine the impact of two partition layouts – arranged perpendicular and parallel to the window – alongside nine different materials featuring various color hues and reflection levels, and three distinct partition heights. Results indicate that, generally, the circadian potential of the office space rises with the increase of the melanopic reflectance of the partition material and the decrease of partition height. With partitions higher than the eye level, arranging them in a parallel position to the window would result in a better non-visual environment, whereas with lower partition heights, the perpendicular arrangement of partitions to the window would be a more suitable choice in most of the investigated cases. This study suggests a decision-making model to assist designers in creating efficient office spaces, particularly in terms of circadian lighting conditions.

Reflective Full‐Color Structural Colors with High Brightness and High Purity Based on Ge2Sb2Se4Te1 Chalcogenide Film

AbstractThis study proposes a general strategy for constructing an asymmetric Fabry–Perot structure based on an ultra‐thin composite absorber, Ni/Ge2Sb2Se4Te1, to produce reflective full‐color structural colors with high brightness and purity. The composite absorber effectively enhances the strong interference effect of thin film, which can significantly reduce the reflection bandwidth of the target band and the reflectivity of the non‐target band. Under the premise of optimizing the five‐layer base structure, full‐color structural colors can be tuned by only changing the thickness of the LaTiO3 layer. Using the ion‐assisted electron beam evaporation technique, a simple and efficient film deposition process, six color devices (namely red, orange, yellow, green, blue, and purple) are successfully prepared with reflection peaks exceeding 90%. The chromaticity coordinates of the proposed high‐purity red, green, and blue (RGB) samples are (0.554, 0.339), (0.280, 0.600), and (0.164, 0.075), respectively. These coordinates are fairly close to the standard RGB color coordinates used in liquid crystal displays. This device has a simple structure with a novel material combination and a low production cost, which makes it feasible for mass production using just one coating run process. It has excellent application potential in various fields such as micro‐nano displays, anti‐counterfeiting measures, reflective color filters, and decorations.

Investigation of angle-insensitive grating color filters at periods much smaller than the wavelength of incidence.

We designed and simulated one-dimensional (1D) and two-dimensional (2D) reflective grating color filters inside the aluminized polyethylene (PE) film. The filters have several advantages: high angle insensitivity (up to 45° for the 1D filter, 40° for the 2D filter), high reflectance at non-resonant wavelengths, deep resonance dips, and a large color gamut. Both structures are characterized by with their grating periods being much smaller than the wavelength of incidence. A grating modal analysis was utilized to reveal the physical mechanism behind such structures that exhibit angle-insensitive spectral responses which are favored in the fields of color display and packaging.

All‐Optical Switching of Structural Color with a Fabry–Pérot Cavity

Fine tuning the optical responses of thin‐film devices is highly attractive for emerging applications, such as optical memories, solar cells, nanophotonics, and photodetectors. Even though thin‐film technology is well established, dynamically switching the optical responses of thin films after fabrication remains challenging because of passive materials and device structures. This work demonstrates an approach for all‐optical switching of structural colors excited by a Fabry–Pérot (FP) cavity inside a metal–dielectric–metal (MDM) thin‐film stack. A low‐loss phase‐change material (PCM), that is, antimony trisulfide (Sb2S3), which is embedded in the stack, enables efficient FP cavity resonance in the visible spectrum. 1) Color reflectivity of >60%; 2) multistructural colors using a single MDM cavity; 3) a wide dynamic range of colors of up to ≈220 nm; and 4) a gamut coverage of more than 80% of standard RGB (sRGB) are achieved. The all‐optical switching is realized via the crystallization and reamorphization of Sb2S3 using continuous‐wave and pulsed lasers, respectively. The findings provide a framework for the cost‐effective realization of dynamically responsive thin‐film‐based nanophotonic devices.

Source-rock evaluation of the Triassic – Jurassic interval of the Tanga Basin, coastal Tanzania

The Triassic-Jurassic interval is known to be the main source of oil and gas generation across the world. In the Tanga Basin of Tanzania, however, the potentiality of these strata for oil and gas generation has remained poorly understood. This study presents the organic geochemical analysis of the source rock within the Triassic-Jurassic interval of the Tanga Basin, integrating rock-eval pyrolysis, vitrinite reflectance and spore coloration analyses to assess the organic richness, quality and maturity for hydrocarbon generation. The results reveal that the Triassic and Jurassic shales are organically rich, with average total organic carbon (TOC) values of 1 wt % and 2 wt %, respectively. Triassic shales demonstrate the dominance of kerogen types II (oil), III (gas pone), II/III (gas with minor oil), and IV (inert) as indicated by hydrogen index values between 365 and 15 mg HC/g TOC. The hydrogen index (HI) values in the Jurassic interval range from 87 to 162 mg/HC/TOC, suggesting the dominance of kerogen type III (gas prone). Pyrolysis Tmax, vitrinite reflectance (Ro) and spore color index (SCI) indicate that the Triassic interval is thermally mature into a gas generation window, with average Tmax values of 450 °C, Ro ∼ 1.7% and SCI ∼8.5. The Jurassic interval is also revealed as thermally mature, with average values of Tmax ∼ 452 °C, Ro ∼ 0.7% and SCI ∼ 7.2, indicative of oil window. The positive findings of this study lay out an important foundation to follow up studies and extended exploration for hydrocarbon accumulations in the poorly explored Tanga Basin and across the coastal Tanzania in general.

An integrated, non-destructive method for evaluating core quality from R/V Legend’s giant piston coring system (LGD-GPC)

Despite technological advances, some core disturbances due to piston coring process still occur and can be extremely difficult to identify characteristics of sedimentary structures during qualitative visual core description and core lithologies. Few quantitative methods have offered plausible ways to define the exact magnitude of the distorted sedimentary structures in imperfect sedimentary records in the context of overly limited sedimentary records. In this study, an investigation was conducted on the Kaoping slope offshore southwestern Taiwan, a region known for its high sedimentation rate (> 0.9 g/cm2/year), using both the LGD-GPC (giant piston corer) and giant gravity corer techniques. To examine how GPC procedures have shaped the retrieval of sedimentary sequences and affected core quality, we apply well-developed, non-destructive analyses, including physical property measurements, visible color reflectance and digital core images with quantitative curvature index (CI), to recovered sediments. Cores at 22° 23′N, 120° 13′E were as the basis for non-destructive measurement comparison. Evidence from digital core imaging and the CI calculation further supports the mechanism of piston suction. We suggest that shear deformation of sediment against the core barrel would be the prominent factor that govern the observed core disturbances in LGD-GPC cores. Meanwhile, excessive pulling forcing from a modified TORI piston and a slowly lift speed during LGD-GPC coring process may further aggravate core disturbances at the revisited site. The sedimentary length of core LGD-T43-B-PC is overestimated by more than 200%. We further demonstrate that an integration of the CI and color reflectance is an effective way to evaluate the transformation and distorted sedimentary sequences.

Double‐State Anticounterfeiting Labels Based on Light‐Emitting Polymer‐Stabilized Blue Phase

AbstractAnticounterfeit labels with multiple information‐carrying functions serve a critical role in boosting security and minimizing counterfeit‐related losses, whose development remains challenging. Here, a security label with the ability to encode information in reflective and fluorescent sates is fabricated from light‐emitting polymer‐stabilized blue phase (LE‐PSBP) liquid crystals (LCs). The LE‐PSBP with temperature‐dependent reflective color can be encoded with information by UV irradiation through photomasks. On the other hand, introduction of a fluorescent molecule, which can be easily photocyclized upon UV irradiation, enables the convenient encoding of fluorescent information without impacting the reflective information. As an illustration, a security label with distinct information in reflective and fluorescent states is demonstrated. Such innovative security labels have tremendous potential to provide a platform for multi‐information encoding to enhance the protection level in anticounterfeiting technology.

산불진화대원의 복제 디자인 개발에 관한 연구

This study aimed to develop a new forest firefighting suit design by surveying the current state of forest firefighting suits in Korea and deriving improvement directions. We collected data on foreign forest firefighting suit designs through literature research and conducted a survey and discussion with people who wear forest firefighting suits. Based on the survey results, the primary areas for improvement were mobility, functionality, safety, portability, and design. We deduced design improvement directions and created three types of forest firefighting uniforms: “Colorful”, “Solid”, and “Utility”. After conducting a final product evaluation meeting, we selected the “Solid” type. The “Solid” type forest firefighting uniform incorporates stretchable spandex fabric for improved flexibility and enhances storage capacity for personal belongings. In addition, points were given using reflective film and material colors to ensure visibility. This study is expected to provide a variety of possibilities for the overall review of the forest firefighting suit management system and the development of forest firefighting suits through the design development and improvement of forest firefighting suits.

Constraints on metallogenic temperature and mineralization style from reflection color of sphalerite

The relationship between the color of sphalerite and trace elements has aroused the interest of researchers since a long time, but most of the study is still in the qualitative stage. In this contribution, we made attempt to reveal the relationship between the reflection color and its trace element, in order to discuss the genetic significance of various reflection colors of sphalerite through the quantitative study of reflection color of sphalerite. Based on LA-ICP-MS analysis and microspectrophotometer analysis of sphalerite samples in different types of deposits, the elements with significant correlation with the reflection color index were found and analyzed by factor analysis. Different genetic types of sphalerites have different color index, The average reflection color indices of each type sample are as follows, sphalerite from Mengya’a deposit: λd = 477.3 nm, Pe = 0.046, Rvis = 17.23%; sphalerite from Zhaxikang deposit: λd = 477.2 nm, Pe = 0.043, Rvis = 16.70%; sphalerite from Nanmushu deposit: λd = 476.4 nm, Pe = 0.038, Rvis = 16.55%. The reflection color index of sphalerite is correlated with the content of Mn, Fe, Ga, Ge, Ag, Cd, In, Tl, Pb. The results of factor analysis indicate that sphalerite with high reflectivity is more abundant in Fe, Mn and In, while the sphalerite with low reflectivity is more abundant in Ge, Tl, Pb and Ag. Furthermore, the reflection color index of sphalerite can be used to distinguish the genetic type of deposits. Based on an obvious linear relationship between the reflection color index of sphalerite and its mineralization temperature, we propose a new empirical equation: T(°C) = 61.4*Rvis + 1.1*λd + 6000*Pe-1533 which can be used as a geological thermometer.

Reflective color filters based on SiO2/Cu multilayer stacks

Due to strong inter-band transitions, the optical response of copper exhibits a high light absorbance in the visible region of the spectrum, recovering blue wavelengths and reflecting a reddish color. In this contribution, copper is split into subwavelength thin films, which are separated by silicon dioxide dielectric layers to take advantage of photonic bandgaps, which subtract bands from the reflected light and, thus, give rise to a wide range of reflective colors, including blue. Using numerical simulations, we investigate the photonic bandgaps of SiO2/Cu stacks, enabled by Fabry–Pérot transmission resonances, which demonstrate the color tunability of these structures.

Simulations of a Wide-Gamut and Angle-Dependent Color Reflector by Addition of a Nanometer-Thick Interference Medium in a Fabry–Perot Structure

Simulations of a Wide-Gamut and Angle-Dependent Color Reflector by Addition of a Nanometer-Thick Interference Medium in a Fabry–Perot Structure

Planar Coupled Nanocavities for Efficient Solar Spectrum Engineering

AbstractTailoring the solar spectrum is critical for energy devices including solar cells and colorful radiative coolers, requiring additional photonic structures with manipulation capabilities adaptable to different application circumstances. However, existing photonic structures cannot effectively balance the trade‐offs between these energy devices' primary functionality, coloration, and visible transparency. Here, a series of planar coupled nanocavities (PCNs) are designed and fabricated, which can manipulate the solar spectrum of energy devices more versatilely than conventional planar multilayers. By judiciously designing and tailoring the coupling effect in the PCNs, the transmissive colors of the PCNs can occupy 99.9% of the sRGB area provided the benchmark for window applications is achieved (average visible transmittance, AVT > 25%), while 25.4% of the sRGB area can be covered by the reflective colors of sub‐ambient radiative coolers with PCNs. Moreover, when serving as the semitransparent electrodes of colorful organic solar cells (OSCs), the PCNs can provide a significantly larger color gamut than commonly used multilayered electrodes under different performance benchmarks. Remarkably, the PCNs can even locally break the trade‐offs between the power conversion efficiency (PCE) and AVT and electrode conductivity of the OSCs. The proposed PCNs provide a promising route for delicately tailoring the solar spectrum with simple multilayered structures.

Optimized principal component analysis for camera spectral sensitivity estimation.

This paper describes the use of a weighted principal component analysis (PCA) method for camera spectral sensitivity estimation. A comprehensive set of spectral sensitivities of 111 cameras was collected from four publicly available databases. It was proposed to weight the spectral sensitivities in the database according to the similarities with those of the test camera. The similarity was evaluated by the reciprocal predicted errors of camera responses. Thus, a set of dynamic principal components was generated from the weighted spectral sensitivity database and served as the basis functions to estimate spectral sensitivities. The test stimuli included self-luminous colors from a multi-channel LED system and reflective colors from a color chart. The proposed method was tested in both the simulated and practical experiments, and the results were compared with the classical PCA method, three commonly used basis function methods (Fourier, polynomial, and radial bases), and a regularization method. It was demonstrated that the proposed method significantly improved the accuracy of spectral sensitivity estimation.

High‐Performance Colorful Organic Photovoltaics with Microcavity Resonance Color Filter

AbstractMicrocavity resonance is an effective technique for making promising semitransparent organic photovoltaics (ST‐OPVs) even more aesthetically attractive with high color saturation, by tailoring the visible transmittance spectrum to narrow the transmission peak. In this study, a distinctive microcavity resonance color filter (CF) structure of silver/ bismuth(III) fluoride /silver (Ag/BiF3/Ag) is integrated upon the rear transparent electrode, which simultaneously achieves high color purity and high power conversion efficiency (PCE) for colorful OPVs. By precisely regulating the thickness of the BiF3 layer, colorful OPVs with a wide color gamut and high color purity are achieved, including the colors of indigo, blue, bluish‐green, green, orange, and red, as well as compound color devices with dual or multiple transmission peaks in the visible region. A recorded PCE of 16.27% is obtained for the indigo OPV, with the Commission Internationale de l´Eclairage 1931 coordinates of (0.164 and 0.087) and a maximum transmittance of 18.7% at the transmission peak wavelength of 393 nm. Furthermore, colorful OPVs as color reflectors are systematically investigated under different light incident surfaces. The improved stability of colorful OPVs is attributed to the excellent moisture resistance of BiF3. The colorful OPVs with desired transmitted/reflected colors, and wide color gamut show great potential for future energy harvesting solutions.

Video-Rate Switching of High-Reflectivity Hybrid Cavities Spanning All Primary Colors.

Dynamically tunable reflective structural colors are attractive for reflective displays (electronic paper). However, it is challenging to tune a thin layer of structural color across the full red-green-blue (RGB) basis set of colors at video rates and with long-term stability. In this work, this is achieved through a hybrid cavity built from metal-insulator-metal (MIM) "nanocaves" and an electrochromic polymer (PProDOTMe2 ). The reflective colors are modulated by electrochemically doping/dedoping the polymer. Compared with traditional subpixel-based systems, this hybrid structure provides high reflectivity (>40%) due to its "monopixel" nature and switches at video rates. The polymer bistability helps deliver ultralow power consumption (≈2.5mWcm-2 ) for video display applications and negligible consumption (≈3µWcm-2 ) for static images, compatible with fully photovoltaic powering. In addition, the color uniformity of the hybrid material is excellent (over cm-2 ) and the scalable fabrication enables large-area production.

Climate transition over the past two centuries revealed by lake Ebinur in Xinjiang, northwest China

Global climate has undergone dramatic changes over the past 200 years, accurately identifying the climate transition (from LIA to 20th century warming) and its controlling factors will help to address the risks posed by global warming. Detailed analyses of chronology, grain size, color reflectance (L*, a*) and carbon content (TOC, TIC) were conducted on a 200-year sedimentary record from lake Ebinur in Xinjiang, northwest China. The results show that lake sediments are mainly transported by wind, and there are two kinds of different sources and transport processes. Comparative analysis of multi-proxies reveals that the climate transition took place in 1920 AD. In the early period (1816–1920 AD), the high C values indicate strong transport dynamics; the high proportion of ultrafine component indicates strong pedogenesis, combined with high TOC and a* values, it is inferred that the climate is cold and wet. In the later period (1920–2019 AD), the proxies show opposite changes, which may reveal a warm and dry climate. Based on a comprehensive analysis of multi-drivers, we propose that the increase of solar irradiance played a dominant role in 1920 AD climate transition, and the gradual rise in the concentrations of greenhouse gases may have a positive feedback effect.

Encoding Mie, plasmonic, and diffractive structural colors in the same pixel

Abstract We present a 1D reflective multi-level structural color design that incorporates Mie, plasmonic, and diffractive mechanisms in the same pixel. Comprised of a metallodielectric grating made of TiOx nanowires sandwiched between Ag thin film and Ag substrate, the design can exhibit either a Mie resonance or a localized plasmonic resonance depending on the polarization of incident light, resulting in dramatically different color states. Due to the periodicity, the grating also diffracts light, providing an additional color state. Since diffraction can be turned on or off by the degree of coherence of the incoming light, both Mie and plasmonic colors can be modulated using objective lenses with different numerical apertures. Exploiting the different color generating modes, we encode four layers of information in a pixel array, where each layer is unveiled using a different combination of excitation and imaging settings. These results introduce new possibilities for data encryption, anticounterfeiting, and data storage.

Relationship between cooling and optical properties of polyester fabric treated with TiO2 nanopigments

The absorption of solar radiations (especially near infrared region) is the reason for solar heating the surface of object and increasing its temperature. To avoid this undesirable heating, it is possible to use some special nanopigments that can reflect the solar radiation in the near-infrared spectrum. Consequently, the thermal regulation and cooling property of fabric as a result of the surface coating is really important. This work studies the possibility of using Visible, NIR and SWIR reflective coatings on polyester fabric to reduce surface temperature when irradiated with solar radiations. Polyester fabrics were dyed with disperse dye and coated with TiO2 nanopigment with different diameters and concentrations. Field Emission Scanning Electron Microscopy (FESEM), Energy-dispersive X-ray spectroscopy (EDS), and heat box were used to characterize the coating process. Obtained results indicate that, the lower surface temperature was recorded by applying the TiO2 nanopigment on polyester fabric and selected materials can considerably increase the thermal regulation and cooling property of the polyester fabric. The pristine (white) and colored polyester fabric coated with TiO2 (500 nm diameter, 3 gr/L) has the highest reflectance throughout the NIR and SWIR regions of solar radiation. The treated polyester fabric respect to pristine polyester fabric exhibits reasonable cooling power and about 4 °C thermal regulation and cooling. Based on the obtained results by heat box system, the thermal regulation and cooling property as the temperature difference between pristine and coated fabric were increased with increasing the diameter and concentration of TiO2 nanopigments. The statistical analysis of variance (ANOVA) was used to study the effect of physical characteristics of TiO2 nanopigments (size and concentration) on the optical parameters as color difference (ΔE), reflectance factor (R) and reflectance function (K/S) and thermal regulation and cooling property as the temperature difference (ΔT). The obtained results indicate that there are good relationship and correlation between the NIR and SWIR reflectance and cooling properties.

Cenozoic morphotectonic evolution of the northeasternmost Tibetan Plateau: Evidence from detrital thermochronology

Despite much research we still lack a comprehensive understanding of the formation and evolution of the northeastern (NE) Tibetan Plateau. The West Qinling is regarded as the northeastward front of the transmission of the compression induced by the India-Asia collision and convergence, and thus its Cenozoic morphotectonic evolution can be used to elucidate the growth history of the northeastern plateau. The Cenozoic deposits of the intermontane Wushan basin of the West Qinling provide a long-term and continuous archive of information about the morphotectonic evolution of the plateau on its northeastern margin. Based on magnetostratigraphy and mammalian biostratigraphy, these deposits are well dated to ∼34–6 Ma, and here we present the results of apatite fission-track thermochronology (AFT), sedimentation rates and facies, color reflectance and magnetic susceptibility, and structural and provenance analyses. Our results indicate a series of exhumation events, likely related to tectonics, with ages ranging from Paleocene through Late Miocene. Morphologic analyses indicate two levels of relict low-relief surfaces at high elevations in the source regions of the Wushan basin sediments. Based mainly on analyses of bedrock AFT and regional deformation signals, we speculate that these landscape remnants developed at low elevations during quiescent phases of orogenic construction, with the age ranges of Middle Eocene and Early–Middle Miocene, respectively. We use a synthesis of our data with existing records of deformation and paleo-altimetry to produce a morphotectonic scenario for West Qinling during the Cenozoic. This suggests that far-field stress due to the India-Asia collision was propagated to the modern northeasternmost boundary as early as the Paleocene. Subsequently, the topography of the West Qinling developed via discrete episodes of tectonic uplift activity/quiescence, or by enhanced denudation, until the Late Miocene, when the modern morphology of the northeasternmost plateau finally developed. Our accurate chronology of surface processes related to tectonic uplift-exhumation-denudation-sedimentation for the West Qinling provides key morphotectonic criteria for a comprehensive understanding of the pulsed growth history of the NE Tibetan Plateau.

Input data requirements for daylight simulations in urban densifications

One of the biggest challenges in urban densifications is securing adequate daylight access. This study examines the potential of using semantic 3D city models as input to daylight simulations. It is focusing on investigating input data requirements to these simulations from a geodata, 3D city model specification and measuring guideline perspective. To achieve this, geodata simulation input requirements for the most common daylight metrics are documented. Next, 3D city model data from two Swedish municipalities along with 3D data constructed by ourselves in CAD- and GIS-environments are utilized to explore the impact of using 3D city models of different levels of detail (LOD) and positional accuracy in daylight simulations linked to Swedish and European laws and recommendations. Similarly, the measuring guidelines and 3D city model specification requirements related to balconies and other façade accessories are also evaluated along with the utilization of façade reflectance properties and colour. It is found that LOD1 is sufficient for the obstruction angle metric for most roof types but for e.g., gabled roofs LOD2 should be used. A positional accuracy on a decimetre-level is accurate enough for the aforementioned metric. Daylight factor simulations require that balconies and façade accessories protruding more than a couple of decimetres must be represented in the 3D city model along with information on façade material and colour. The outcome of the study is expressed in the form of a list of recommendations for the creation of national profiles of 3D city models supporting daylight simulations.