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PURPOSE: To investigate the feasibility and application of a novel imaging technique, a three-dimensional dual adiabatic inversion recovery prepared ultrashort echo time (3D DIR-UTE) sequence, for high contrast assessment of cartilaginous endplate (CEP) imaging with head-to-head comparisons between other UTE imaging techniques. METHOD: The DIR-UTE sequence employs two narrow-band adiabatic full passage (AFP) pulses to suppress signals from long T2 water (e.g., nucleus pulposus (NP)) and bone marrow fat (BMF) independently, followed by multispoke UTE acquisition to detect signals from the CEP with short T2 relaxation times. The DIR-UTE sequence, in addition to three other UTE sequences namely, an IR-prepared and fat-saturated UTE (IR-FS-UTE), a T1-weighted and fat-saturated UTE sequence (T1w-FS-UTE), and a fat-saturated UTE (FS-UTE) was used for MR imaging on a 3 T scanner to image six asymptomatic volunteers, six patients with low back pain, as well as a human cadaveric specimen. The contrast-to-noise ratio of the CEP relative to the adjacent structures-specifically the NP and BMF-was then compared from the acquired images across the different UTE sequences. RESULTS: For asymptomatic volunteers, the DIR-UTE sequence showed significantly higher contrast-to-noise ratio values between the CEP and BMF (CNRCEP-BMF) (19.9 ± 3.0) and between the CEP and NP (CNRCEP-NP) (23.1 ± 1.7) compared to IR-FS-UTE (CNRCEP-BMF: 17.3 ± 1.2 and CNRCEP-NP: 19.1 ± 1.8), T1w-FS-UTE (CNRCEP-BMF: 9.0 ± 2.7 and CNRCEP-NP: 10.4 ± 3.5), and FS-UTE (CNRCEP-BMF: 7.7 ± 2.2 and CNRCEP-NP: 5.8 ± 2.4) for asymptomatic volunteers (all P-values

The paper aims at studying dispersion of elastic waves in a sandwich plate with the parameters, characteristic of aerogel core and hard skin layers, typical for aerospace applications including optimal design of fuselage structural components. The proposed approach relies on multiparametric analysis, taking into account the effect of strong transverse inhomogeneity. It is demonstrated that both an additional low-frequency propagating wave and a slowly decaying evanescent one appear due to a high contrast in geometric and mechanical parameters of the layers. The key findings include the derivation of two-mode asymptotic expansions of the full dispersion relation at the low-frequency limit, as well as elucidation of the non-trivial link between long-wave evanescent and propagating modes. A sophisticated composite nature of the obtained expansions involving various shortened forms is investigated. The range of validity for each of these forms over frequency and wave-number domains is evaluated. Comparison of asymptotic results with the numerical solution of the full dispersion relation is presented. [ABSTRACT FROM AUTHOR]

Latent fingerprint imaging is a crucial tool for national security and crime recognition, requiring environmentally sustainable, nontoxic materials. To address this need, we have developed a green fluorescence‐emitting material, THCHO, that binds effectively to latent fingerprints, enabling clear, high‐resolution visualization. The solution produces strong green fluorescence that highlights fingerprint imprints with exceptional detail and contrast. The material is applicable across various substrates, making it efficient for on‐site visualization. The synthesized organic conjugated material THCHO rapidly visualizes precise fingerprint substructures within 5 s using a simple spray method. It maintains high contrast and low interference across different substrates, such as glass, aluminum foil, plastic, and ironware, even in diverse backgrounds. Additionally, the THCHO material demonstrates high stability, retaining its fluorescence imaging capabilities for up to 35 days and after water washing. This is the first report of using a conjugated organic thiophene material for latent fingerprint fluorescence imaging, suggesting potential applications in other fields. [ABSTRACT FROM AUTHOR]

Purposes The development of information technology has significantly impacted economic, political, cultural, and military fields, and the information security is of great importance in modern society. Deep information-hiding, i．e. hiding the confidential information in an overt carrier, is one of the most important approach in improving information security and has been driving long research efforts in material science, communication technology and cryptology. Organic stimuli-responsive luminescent (SRL) materials that change their luminescence in response to mechanical force, thermal treatment, and light or pH value are considered as promising media candidates. Among them, the materials that exhibit SRL turn-on capabilities have shown advanced performances such as high contrast and signal to noise ratio, and aroused enormous interest. Methods The recent progress of SRL turn-on materials based on the MRL mechanisms and performances is reviewed following the sequence from changes in molecular structure to modifications in aggregate structure. A systematic summary of the material system is provided. Conclusions The existing challenges facing high-performance MRL turn-on materials, including the development of luminescence mechanisms, regulation of kinetic process and control of multi-phase state transitions are elaborated and rational solution are proposed. It will provide theoretical insights and practical experiences for the design, synthesis, and application of novel high-performance SRL materials.

Since the establishment of liquid crystal display industries, larger sizes, faster response, higher contrast ratio, higher resolution and lower power consumption have become a pursuing target of various panel suppliers. Considering the marvelous viewing angle of the fringe‐field switching (FFS) mode, FFS displays with a higher contrast ratio are able to show more details in the dark pictures, resulting in a much better viewing experience. Herein, to develop the next‐generation liquid crystal (LC) materials for high‐contrast FFS panels, various high‐contrast LC (HCLC) materials were designed. By minimizing Δn and maximizing Kave, HCLCs exhibited lower light leakage in dark states, leading to a higher contrast ratio compared to the reference. Two HCLCs for improving the operation voltage, transmittance, contrast ratio and response time were developed by optimizing the properties of HCLC materials. Furthermore, FFS monitors with a contrast ratio of 2820:1 and a color gamut of 96.4% NTSC were demonstrated. [ABSTRACT FROM AUTHOR]

Consumer experience with high performing mobile device displays sets high expectations for the automotive market in contrast, color performance and brightness. OLED based displays continue to experience difficulties in penetrating the automotive display market primarily due to image burn at high luminance operation and high costs. The microZone™ LCD is an alternative display configuration that can meet the desirable properties of OLED displays while providing high luminance at high temperature operation without image burn in. [ABSTRACT FROM AUTHOR]

We developed a novel method for achieving long‐term (>24 hours) true bi‐stability in helix‐free Ferroelectric Liquid Crystals (FLCs). Instead of employing asymmetric boundary conditions, traditionally used for achieving bi‐stability, we utilized symmetric boundary conditions and carefully optimized the anchoring conditions on both the top and bottom substrates using the photoalignment technology. The key to the newly observed long term bi‐stability is the twisted alignment structure. Surface roughness was found to play a crucial role in achieving sustained bi‐stability. This breakthrough holds promise for developing truly bi‐stable, fast modulators for photonic applications. [ABSTRACT FROM AUTHOR]

In the forefront of quantitative solar physics research using large-aperture ground-based solar optical telescopes, high-contrast observation along with high-accuracy polarimetric measurement in the solar active region are required. In this paper, we propose a novel high-contrast imaging telescope construction with a 60 cm medium aperture, namely, the PAthfinder in Solar Adaptive Telescope (PASAT), in which a deformable secondary mirror is used as the adaptive optical correction device and a symmetrical optical path design is employed, leading to the least Muller matrix polarization instruments. The telescope can provide a high-resolution magnetic field with high accuracy for the solar active regions, as well as high-contrast images with a superior signal-to-noise ratio and photometric accuracy of the solar photosphere and chromosphere. These data will be directly used for a better understanding of the evolution and release of magnetic energy, which will help in improving space weather forecasting. Meanwhile, PASAT will accumulate the relevant techniques for constructing similar, larger solar telescopes in the future. [ABSTRACT FROM AUTHOR]

A high-performance resonant metasurface is rather promising for diverse application areas such as optical sensing and filtering. Herein, a metal–insulator–metal (MIM) optical sensor with merits of a high quality-factor (Q-factor), multiple operating bands, and high spectrum contrast is proposed using plasmonic square bracket dimer metasurface. Due to the complex square bracket itself, a dimer structure of two oppositely placed square brackets, and metasurface array configuration, multiple kinds of mode coupling can be devised in the inner and outer elements within the metasurface, enabling four sensing channels with the sensitivities higher than 200 nm/RIU for refractive index sensing. Among them, the special sensing channel based on the reflection-type surface lattice resonance (SLR) mechanism has a full width at half maximum (FWHM) of only 2 nm, a high peak-to-dip signal contrast of 0.82, a high Q-factor of 548, and it can also behave as a good sensing channel for the thickness measurement of the deposition layer. The multi-band sensor can work normally in a large refractive index or thickness range, and the number of resonant channels can be further increased by simply breaking the structural symmetry or changing the polarization angle of incident light. Equipped with unique advantages, the suggested plasmonic metasurface has great potential in sensing, monitoring, filtering, and other applications. [ABSTRACT FROM AUTHOR]

In the forefront of quantitative solar physics research using large-aperture ground-based solar optical telescopes, high-contrast observation along with high-accuracy polarimetric measurement in the solar active region are required. In this paper, we propose a novel high-contrast imaging telescope construction with a 60 cm medium aperture, namely, the PAthfinder in Solar Adaptive Telescope (PASAT), in which a deformable secondary mirror is used as the adaptive optical correction device and a symmetrical optical path design is employed, leading to the least Muller matrix polarization instruments. The telescope can provide a high-resolution magnetic field with high accuracy for the solar active regions, as well as high-contrast images with a superior signal-to-noise ratio and photometric accuracy of the solar photosphere and chromosphere. These data will be directly used for a better understanding of the evolution and release of magnetic energy, which will help in improving space weather forecasting. Meanwhile, PASAT will accumulate the relevant techniques for constructing similar, larger solar telescopes in the future.

Video in an outdoor environment suffers from the haze problem due to smoke, dust, and other particles in the atmosphere. The quality of video under these atmospheric conditions is clearly/dramatically degraded, leading to poor contrast and information leakage. The proposed algorithm in this paper depends on pre-processing of video frames prior to the dehazing process. Different enhancement techniques are used to remove noise and control the dynamic range, because each frame has some noise due to sensor measurement errors. This noise might be magnified during the haze removal process, if totally neglected. Previous dehazing algorithms enhance the video contrast and reduce frame degradation. We use optimized dehazing algorithms, namely a dual-transmission-map dehazing algorithm, and a recursive Deep Residual Learning (DRL) network, as dehazing tools. We modify the previous dehazing algorithms to generate new algorithms to be suitable not only for visible frames but also for Near Infrared (NIR) frames. In the optimized dehazing algorithms, the haze effect is reduced, according to the hazing model. In the dual-transmission-map dehazing algorithm, the effect of attenuation parameter R and attenuation weight U on the dehazed frames is investigated. A dual-transmission-map algorithm, depending on the Dark Channel Prior (DCP) technique, is studied. We study the effect of a regularization parameter Ω on the visible and NIR dehazed frames without and with enhancement techniques. For the recursive deep residual learning algorithm, we increase the number of iterations in the DRL network from three iterations in the traditional DRL algorithm without denoising techniques to nine iterations, in order to explore the impact of increasing the number of iterations on the output dehazed frames. Since elapsed time grows with the number of iterations, we terminate the operation after the ninth iteration. A comparison between traditional algorithms and the proposed dehazing algorithms is introduced for different types of video considering five frames. In addition, a comparison between previous algorithms and the proposed dehazing algorithms is introduced on real-world hazy images. We use correlation, Peak Signal-to-Noise Ratio (PSNR) between input hazy frame and dehazed one, histogram, and spectral entropy of hazy and dehazed frames as metrics for the proposed algorithms. We conclude that the best dehazing algorithm for the visible videos is the dual-transmission-map dehazing algorithm with enhancement. On the other hand, the best one for NIR videos is the optimized dehazing algorithm with enhancement. For the visible (riverside.avi) video, the enhancement score of the proposed dual-transmission-map dehazing algorithm is 14.74%. It is increased by 9.65% compared to the original dual-transmission-map dehazing algorithm. In contrary, the DRL network achieves a 9% enhancement, which is the lowest one due to the need for a huge training dataset. For NIR video, the enhancement scores of the three different proposed dehazing algorithms, the optimized, the dual-transmission-map, and the DRL network, are 22.28%, 21.57%, and 4.6%, respectively. [ABSTRACT FROM AUTHOR]

The control of surface wettability is a technological key aspect and usually poses considerable challenges connected to high cost, nanostructure, and durability, especially when aiming at surface patterning with high and extreme wettability contrast. This work shows a simple and scalable approach by using laser-induced graphene (LIG) and a locally inert atmosphere to continuously tune the wettability of a polyimide/LIG surface from hydrophilic to superhydrophobic (Φ ∼ 160°). This is related to the reduced amount of oxygen on the LIG surface, influenced by the local atmosphere. Furthermore, the influence of the roughness pattern of LIG on the wettability is investigated. Both approaches are combined, and the influence of surface chemistry and roughness is discussed. Measurements of the roll-off angle show that LIG scribed in an inert atmosphere with a low roughness has the highest droplet mobility with a roll-off angle of ΦRO = (1.7 ± 0.3)°. The superhydrophobic properties of the samples were maintained for over a year and showed no degradation after multiple uses. Applications of surfaces with extreme wettability contrast in millifluidics and fog basking are demonstrated. Overall, the proposed processing allows for the continuous tuning and patterning of the surface properties of LIG in a very accessible fashion useful for "lab-on-chip" applications. [ABSTRACT FROM AUTHOR]

The effect of high contrast on the multiscale behaviour of elastic laminates is studied. Mathematical modelling in this area is of significant interest for a variety of modern applications, including but not limited to advanced sandwich structures and photovoltaic panels. As an example, the antiplane shear of a symmetric, three-layered plate is considered. The problem parameters expressing relative thickness, stiffness and density are assumed to be independent. The high contrast may generally support extra length and time scales corresponding to degenerated boundary layers and propagating long-wave low-frequency vibration modes. The main focus is on the relation between these two phenomena. The developed multiparametric approach demonstrates that those do not always appear simultaneously. The associated explicit estimates on contrast parameters are established. In addition, the recent asymptotic extension of the classical Saint-Venant's principle is adapted for calculating the contribution of the degenerate boundary layer or long-wave low-frequency propagation mode. The peculiarity of the limiting absorption principle in application to layered media is also addressed. [ABSTRACT FROM AUTHOR]

A new face‐centred finite volume method (FCFV) for Stokes problems involving sharp interfaces is proposed. Two formulations, based on two strong forms of the Stokes problem, and using different mixed variables, are presented. Particular attention is paid to the symmetry of the resulting system of global equations, and a simple rewriting of the interface boundary condition is proposed to ensure that one of the formulations preserves the symmetry of the linear system that is usually lost when considering material interfaces. Four numerical examples are considered to test the implementation numerically by performing mesh convergence studies, in two and three dimensions. The examples account for discontinuous viscosity as well as the effect of surface tension. The results show that one of the formulations is less sensitive to the numerical stabilisation used in FCFV methods but does not preserve the symmetry of the global system, whereas the other formulation is more sensitive to the stabilisation, but preserves the symmetry of the resulting system of equations. The FCFV method appears as a promising alternative for the simulation of viscous flow involving internal boundaries on conformal meshes. The potential application of the FCFV method for the purpose of geodynamic modelling is discussed. [ABSTRACT FROM AUTHOR]

In this paper, we present a multiscale framework for solving the Helmholtz equation in heterogeneous media without scale separation and in the high frequency regime where the wavenumber k can be large. The main innovation is that our methods achieve a nearly exponential rate of convergence with respect to the computational degrees of freedom, using a coarse grid of mesh size O(1/k) without suffering from the well-known pollution effect. The key idea is a nonoverlapped domain decomposition and its associated coarse-fine scale decomposition of the solution space that adapts to the media property and wavenumber; this decomposition is inspired by the multiscale finite element method. We show that the coarse part is of low complexity in the sense that it can be approximated with a nearly exponential rate of convergence via local basis functions, due to the compactness of a restriction operator that maps Helmholtz-harmonic functions to their interpolation residues on edges, while the fine part is local such that it can be computed efficiently using the local information of the right-hand side. The combination of the two parts yields the overall nearly exponential rate of convergence of our multiscale method. Our method draws many connections to multiscale methods in the literature, which we will comment in detail. We demonstrate the effectiveness of our methods theoretically and numerically; an exponential rate of convergence is consistently observed and confirmed. In addition, we observe the robustness of our methods regarding the high contrast in the media numerically. We specifically focus on 2D problems in our exposition since the geometry of nonoverlapped domain decomposition is simplest to explain in such cases. [ABSTRACT FROM AUTHOR]

A high-performance resonant metasurface is rather promising for diverse application areas such as optical sensing and filtering. Herein, a metal–insulator–metal (MIM) optical sensor with merits of a high quality-factor (Q-factor), multiple operating bands, and high spectrum contrast is proposed using plasmonic square bracket dimer metasurface. Due to the complex square bracket itself, a dimer structure of two oppositely placed square brackets, and metasurface array configuration, multiple kinds of mode coupling can be devised in the inner and outer elements within the metasurface, enabling four sensing channels with the sensitivities higher than 200 nm/RIU for refractive index sensing. Among them, the special sensing channel based on the reflection-type surface lattice resonance (SLR) mechanism has a full width at half maximum (FWHM) of only 2 nm, a high peak-to-dip signal contrast of 0.82, a high Q-factor of 548, and it can also behave as a good sensing channel for the thickness measurement of the deposition layer. The multi-band sensor can work normally in a large refractive index or thickness range, and the number of resonant channels can be further increased by simply breaking the structural symmetry or changing the polarization angle of incident light. Equipped with unique advantages, the suggested plasmonic metasurface has great potential in sensing, monitoring, filtering, and other applications.

Transparent organic light emitting diode (OLED) display is one of the most promising devices among next-generation information displays because of beneficial characteristics, such as self-emissive and optically clear properties. Nevertheless, in conventional transparent OLED display devices, there are serious intrinsic problems in terms of the transmittance in the dark state because of empty windows in the cell, so the contrast ratio of the transparent OLED display would be deteriorated even though it can exhibit excellent bright state. In general, the transparent mode using the OLED device applies an empty area in each pixel because an emitting device could never reveal the background image, so the transparent OLED should contain the empty area in the pixel for transparent images. This may cause the optical degradation in the dark state. To solve this problem, we propose hybrid-type transparent OLED display modes that apply a liquid crystal (LC) to the transparent window part of the empty space. In this paper, we applied two dichroic LC modes— which use an electrically controlled birefringence (ECB) mode (Heilmeier type) for the polarized mode and a cholesteric LC mode (Guest-Host mode) for the non-polarized mode—to the empty area. In each hybrid mode, we have observed optical performance, including the transmittance in the dark/bright state, contrast ratio and response time as a function of cell parameters. As a result, we confirmed that the dark state and the contrast ratio could be improved by applying the proposed modes without serious decay of the transmittance in the bright state. [ABSTRACT FROM AUTHOR]

To realize efficient three-dimensional (3-D) super-resolution whole brain microwave imaging, a new machine- learning-based inversion method with a resolution enhancement technique is proposed. It consists of three parts: a parallel semiconnected backpropagation neural network (SJ-BPNN) scheme, a U-Net scheme, and a modified Akima piecewise cubic Hermite interpolation (MAPCHI) scheme. The parallel SJ-BPNN scheme is first employed to map the measured scattered field data to the preliminary electrical properties’ distribution of human brain. Then, U-Net is used to improve the quality of these preliminary reconstruction results. Finally, the MAPCHI scheme is adopted to greatly improve the resolution of reconstruction results with a very low computational cost. Numerical examples of a normal human brain and a human brain with abnormal scatterers show that the proposed method can achieve accurate high-resolution human brain imaging with 1024 × 1024 × 1024 voxels with a very low computational cost. [ABSTRACT FROM AUTHOR]

Oblique illumination imaging can significantly improve the contrast of transparent thin samples. However, in traditional oblique illumination methods, either the condenser is offset or a block is added to the condenser, which makes it complicated and challenged to build a stable oblique illumination imaging. Herein, we present a method to measure the optimal shading ratio of oblique illumination in an inverted microscope, and develop an apparatus for stable high‐speed high‐contrast imaging with uniform brightness. At optimal shading ratio, the oblique illumination imaging has better imaging quality than differential interference contrast, which characteristic is independent on sample. In oblique illumination with low magnification objective, the images have uneven brightness. According to target brightness, we have developed a brightness unevenness correction algorithm to form uniform background brightness for oblique illumination. Integrating the algorithm with imaging acquisition, corrected oblique illumination microscopy is appropriate to observe living cells with high contrast. [ABSTRACT FROM AUTHOR]

We demonstrate fast response and high contrast vertical alignment (VA) liquid crystal devices (LCDs) with polymer sustained alignment (PSA). In general, the rise time of a liquid crystal (LC) is a trade-off relationship with the decay time. In the present study, an appropriate tilt angle of LCs was anchored by polymerisation using UV irradiation with the application of a threshold voltage and optimisation of the reactive mesogen (RM) concentration. The PSA VA-LCDs showed a fast optical response to the applied electric field because the backflow (optical bounce) was suppressed by anchoring with the polymer. In addition, the fast response was maintained until a high voltage was applied. The transmittance of these PSA VA-LCDs at 0 V was identical to that of VA-LCDs without a polymer and the opaque phenomena at the applied voltage were eliminated because alignment of LCs and RMs was improved. The findings of this work are expected to enable the development of displays and phase modulators with improved performance. [ABSTRACT FROM AUTHOR]

Latent fingerprint imaging is a crucial tool for national security and crime recognition, requiring environmentally sustainable, nontoxic materials. To address this need, we have developed a green fluorescence-emitting material, THCHO, that binds effectively to latent fingerprints, enabling clear, high-resolution visualization. The solution produces strong green fluorescence that highlights fingerprint imprints with exceptional detail and contrast. The material is applicable across various substrates, making it efficient for on-site visualization. The synthesized organic conjugated material THCHO rapidly visualizes precise fingerprint substructures within 5 s using a simple spray method. It maintains high contrast and low interference across different substrates, such as glass, aluminum foil, plastic, and ironware, even in diverse backgrounds. Additionally, the THCHO material demonstrates high stability, retaining its fluorescence imaging capabilities for up to 35 days and after water washing. This is the first report of using a conjugated organic thiophene material for latent fingerprint fluorescence imaging, suggesting potential applications in other fields., (© 2024 John Wiley & Sons Ltd.)

The effect of high contrast on the multiscale behaviour of elastic laminates is studied. Mathematical modelling in this area is of significant interest for a variety of modern applications, including but not limited to advanced sandwich structures and photovoltaic panels. As an example, the antiplane shear of a symmetric, three-layered plate is considered. The problem parameters expressing relative thickness, stiffness and density are assumed to be independent. The high contrast may generally support extra length and time scales corresponding to degenerated boundary layers and propagating long-wave low-frequency vibration modes. The main focus is on the relation between these two phenomena. The developed multiparametric approach demonstrates that those do not always appear simultaneously. The associated explicit estimates on contrast parameters are established. In addition, the recent asymptotic extension of the classical Saint-Venant’s principle is adapted for calculating the contribution of the degenerate boundary layer or long-wave low-frequency propagation mode. The peculiarity of the limiting absorption principle in application to layered media is also addressed.

Analytic representation formulas and power series are developed to describe the band structure inside periodic elastic crystals made from high contrast inclusions. We use source free modes associated with structural spectra to represent the solution operator of the Lamé system inside phononic crystals. Convergent power series for the Bloch wave spectrum are obtained using the representation formulas. An explicit bound on the convergence radius is given through the structural spectra of the inclusion array and the Dirichlet spectra of the inclusions. Sufficient conditions for the separation of spectral branches of the dispersion relation for any fixed quasi-momentum are identified. A condition is found that is sufficient for the emergence of band gaps. [ABSTRACT FROM AUTHOR]

Analytic representation formulas and power series are developed describing the band structure inside non-magnetic periodic photonic three-dimensional crystals made from high dielectric contrast inclusions. Central to this approach is the identification and utilization of a resonance spectrum for quasiperiodic source-free modes. These modes are used to represent solution operators associated with electromagnetic and acoustic waves inside periodic high contrast media. A convergent power series for the Bloch wave spectrum is recovered from the representation formulas. Explicit conditions on the contrast are found that provide lower bounds on the convergence radius. These conditions are sufficient for the separation of spectral branches of the dispersion relation for any fixed quasi-momentum. [ABSTRACT FROM AUTHOR]

Super-resolution three-dimensional (3-D) electromagnetic (EM) inversion for microwave human brain imaging is a typical high contrast EM inverse problem and requires huge computational costs. This work proposes a hybrid neural network electromagnetic inversion scheme (HNNEMIS) which contains shallow and deep neural networks to alleviate the required huge computational costs and solve this high contrast inverse problem. In the proposed scheme, semi-join back propagation neural network (SJ-BPNN) is employed to nonlinearly map the measured scattered electric field to two output channels, namely the permittivity and conductivity of scatterers, respectively. Such a semi-join strategy decreases the computational burden in training and testing processes. Then, a deep learning technique, termed U-Net, is employed to further enhance the imaging quality of the output from SJ-BPNN. To decrease the training cost and make neural networks fast convergent for human brain inversion, a novel training dataset construction strategy which contains the characteristics of human brain is also proposed. Noise-free and noisy numerical examples demonstrate that HNNEMIS has superior super-resolution inversion capabilities for human brain imaging. [ABSTRACT FROM AUTHOR]

The antiplane shear of a semi-infinite multi-layered elastic strip with traction free faces and edges subject to prescribed stress is studied. A high contrast is assumed in the stiffnesses of two types of homogeneous isotropic layers. Explicit conditions on the edge load are derived, ensuring the decay of stress components at the distance of order strip thickness. One of these conditions corresponds to the canonical Saint-Venant's principle, manifesting the self-equilibrium of the load. The rest of the decay conditions consider the presence of high contrast and are of an asymptotic nature, in contrast to the exact former condition. The number of asymptotic conditions is the same as that of soft layers. An example of the implementation of the proposed decay conditions for calculating the solution for the interior (outside of a boundary layer zone) domain of a three-layered semi-strip, considering geometric asymmetry, is presented. [ABSTRACT FROM AUTHOR]

• A new dicyanoethylene derivatives modified by tetraphenylethylene were designed and synthesized. • They possessed a highly twisted conformation, well-defined ICT property and AIE characteristic. • They also exhibited high-contrast mechanofluorochromism. Based on a rational design strategy by combining an electron-withdrawing dicyanoethylene unit and electron-donating tetraphenylethylene moiety, we successfully synthesized two π-conjugated molecules Ph-TPE-MMN and NA-TPE-MMN. According to the optical research and theoretical calculation results, they had highly distorted conformations, D-A type molecular structure and definite intramolecular charge transfer (ICT) properties. Moreover, two molecules Ph-TPE-MMN and NA-TPE-MMN showed aggregation-induced emission (AIE) properties in the THF/water mixture at higher f w (water fraction). Ph-TPE-MMN and NA-TPE-MMN also exhibited fluorescence response to external force. The emitting color of both had changed greatly before and after grinding. The maximum emission wavelengths of Ph-TPE-MMN and NA-TPE-MMN were redshifted by 46 nm and 33 nm, respectively, implying high-contrast mechanofluorochromism. Notably, mechanofluorochromic process also showed a good reversible. XRD experiments indicated that mechanofluorochromic mechanism originated from changes in molecular stacking in solid state. [Display omitted] [ABSTRACT FROM AUTHOR]

The Contrast of 4K ADS products was improved from 1500:1 to 3000:1 by material and process optimization, which includes the application of Ultra‐low Scattering Negative Liquid Crystal, Higher polarization polarizer, Thicker polyimide film and appropriately widened Black Matrix. The realization of Contrast 3000 records the highest in ADS Mode, greatly shortens the gap with VA products and also shows good applicability in high end LCD products. [ABSTRACT FROM AUTHOR]

Polymer dispersed liquid crystal (PDLC) films were prepared using a nematic liquid crystal, photo-curable polymer and TiO2 nanoparticles by polymerisation-induced phase separation (PIPS) method. Electro-optical properties of doped and undoped samples including transmittance, driving voltage, contrast ratio and response time of the transmittance-voltage were measured, compared and analysed. The morphology of polymer network has been investigated by means of SEM. The phase separation of LC droplets was found to be dependent on the content of prepolymer, LC and nanoparticles used. The high dielectric properties and high refractive index of TiO2 nanoparticles make PDLC have low driving voltage and high contrast. In particular, the nanoparticles concentration can be optimised to obtain promising electronic materials with minimum threshold and high contrast for display applications. [ABSTRACT FROM AUTHOR]

This article proposes a semijoin extreme learning machine (SJ-ELM) for super-resolution 3-D microwave imaging of objects with high contrasts. The proposed scheme develops a shallow neural network structure with the semijoin strategy to convert the scattered field data into two output channels, namely, the permittivity and the conductivity of objects, respectively. The semijoin strategy can decrease the inner matrix dimensions to reduce the computational burden for 3-D super-resolution imaging, so it is employed to connect between the nodes of the hidden layer and the output layer. The imaging performance of the proposed SJ-ELM and the conventional variational Born iterative method (VBIM) is first compared for imaging objects with different electrical sizes and contrasts, and then, different targets of imaging resolution are designed to evaluate both solvers. The proposed SJ-ELM is also assessed for imaging objects with high contrasts and experimental data and is demonstrated to have superior super-resolution imaging capabilities for high-contrast 3-D objects. [ABSTRACT FROM AUTHOR]

This article presents a novel voltage-programmed pixel circuit using a-IGZO TFTs to effectively compensate threshold voltage (VTH) variations of driving TFT. The compensation is very important to maintain the pixel brightness of active-matrix organic light-emitting diodes (AMOLED) displays. The proposed pixel design uses four-phase clocking schemes: reset period, VTH detection period, data input period and emission period. To maintain uniformity in phases, the duration of all the phases is taken to be same which results in easier design of the multi-phase clock. Moreover, the switching speed of control signals is as high as 25 kHz, ensuring a high frame rate. The circuit has been simulated extensively, and the operation has been verified using SPICE models of a-IGZO TFT and OLED on Cadence Spectre. The circuit also achieves high contrast as OLED does not emit light in any periods except the emission period. The OLED current error in the proposed design for a VTH variation of 170% is below 0.1%. This circuit also provides a high aperture ratio of 51.6%, which ensures high resolution of AMOLED displays. [ABSTRACT FROM AUTHOR]

Three-dimensional (3-D) super-resolution microwave imaging of human brain is a typical electromagnetic (EM) inverse scattering problem with high contrast. It is a challenge for the traditional schemes based on deterministic or stochastic inversion methods to obtain high contrast and high resolution, and they require huge computational time. In this work, a dual-module 3-D EM inversion scheme based on deep neural network is proposed. The proposed scheme can solve the inverse scattering problems with high contrast and super-resolution in real time and reduce a huge computational cost. In the EM inversion module, a 3-D full convolution EM reconstruction neural network (3-D FCERNN) is proposed to nonlinearly map the measured scattered field to a preliminary image of 3-D electrical parameter distribution of the human brain. The proposed 3-D FCERNN is completely composed of convolution layers, which can greatly save training cost and improve model generalization compared with fully connected networks. Then, the image enhancement module employs a U-Net to further improve the imaging quality from the results of 3-D FCERNN. In addition, a dataset generation strategy based on the human brain features is proposed, which can solve the difficulty of human brain dataset collection and high training cost. The proposed scheme has been confirmed to be effective and accurate in reconstructing the distribution of 3-D super-resolution electrical parameters distribution of human brain through noise-free and noisy examples, while the traditional EM inversion method is difficult to converge in the case of high contrast and strong scatterers. Compared with our previous work, the training of FCERNN is faster and can significantly decrease computational resources.

With its recent debut in various fields, piezochromic fluorescent (PCF) materials have attracted considerable attention due to their unique photophysical features with dynamically reversible emission wavelength and intensity. Herein, a novel luminogen DBCT is developed, which is sensitive to external pressure and displays dual color reversibly switched PCF fluorescence. The solid state emission can switch from bright orange (O) (λem = 586 nm, Φsolid = 0.47) to deep red (R) emission (λem = 646 nm, Φsolid = 0.34) with high contrast through pressing (0.6 MPa), heating and fuming processes. Single crystal X‐ray analysis and theoretical calculations verify that the reversible luminescence switching characteristic is highly related to the different molecular packing mode within O and R crystals, which amplifies the exciton coupling (EC) effect and results in good PCF performances with high Φsolid as well as distinguishable red‐shifted emission. With such multiple advantages that writable fluorescent inks are successfully fabricated with high contrast for security anti‐counterfeiting applications based on DBCT molecules. This research may offer an important guideline for molecular design of PCF materials and enrich the underlying mechanism of mechanochromic luminescence, which also broadens the real‐life applications of smart materials. [ABSTRACT FROM AUTHOR]

This paper is about solutions to PDEs in which the ratio between the largest and smallest values of the coefficient is very large. Such problems are referred to as high-contrast ones. A full asymptotic expansion of solutions to such high-contrast PDEs in terms of the high-contrast parameter is obtained for both scalar and vectorial cases. For the scalar case, we choose a diffusion process in a heterogeneous domain of finite conductivity with highly conducting particles, while for the vectorial case, we deal with the Lamé system of linearized elasticity in the domain that contains almost rigid particles. Error estimates for asymptotic expansions are also derived. [ABSTRACT FROM AUTHOR]

The antiplane shear of a semi-infinite multi-layered elastic strip with traction free faces and edges subject to prescribed stress is studied. A high contrast is assumed in the stiffnesses of two types of homogeneous isotropic layers. Explicit conditions on the edge load are derived, ensuring the decay of stress components at the distance of order strip thickness. One of these conditions corresponds to the canonical Saint-Venant’s principle, manifesting the self-equilibrium of the load. The rest of the decay conditions consider the presence of high contrast and are of an asymptotic nature, in contrast to the exact former condition. The number of asymptotic conditions is the same as that of soft layers. An example of the implementation of the proposed decay conditions for calculating the solution for the interior (outside of a boundary layer zone) domain of a three-layered semi-strip, considering geometric asymmetry, is presented.

A revolutionary new smart window technology based on electrophoretic effect demonstrates unprecedented optical contrast transitioning from 0.2% to more than 70% transmittance while exhibiting fast switching performance. Adapted to already existing manufacturing display facilities, ELM (Electrophoretic Light Modulator) technology developed by eLstar Dynamics is highly scalable and based on known robust electrophoretic operation. ELM technology is exceptionally versatile and can be adapted to many product specifications and applications. [ABSTRACT FROM AUTHOR]

We provide in this paper homogenization results for the L2-topology leading to complete strain-gradient models and generalized continua. Actually, we extend to the L2-topology the results obtained in (Abdoul-Anziz & Seppecher, 2018 Homogenization of periodic graph-based elastic structures. Journal de l'Ecole polytechnique–Mathématiques5, 259–288) using a topology adapted to minimization problems set in varying domains. Contrary to (Abdoul-Anziz & Seppecher, 2018 Homogenization of periodic graph-based elastic structures. Journal de l'Ecole polytechnique–Mathématiques5, 259–288) we consider elastic lattices embedded in a soft elastic matrix. Thus our study is placed in the usual framework of homogenization. The contrast between the elastic stiffnesses of the matrix and the reinforcement zone is assumed to be very large. We prove that a suitable choice of the stiffness on the weak part ensures the compactness of minimizing sequences while the energy contained in the matrix disappears at the limit: the Γ-limit energies we obtain are identical to those obtained in (Abdoul-Anziz & Seppecher, 2018 Homogenization of periodic graph-based elastic structures. Journal de l'Ecole polytechnique–Mathématiques5, 259–288). [ABSTRACT FROM AUTHOR]

Fingerprints are an important kind of material evidence with the key function in personal identification, which are unique and life-long to everyone. Latent (invisible) fingerprints are common at the crime scene, needing to be visualized with proper methods in order to identify sources of the fingerprints in routine forensic practice. Fluorescent imaging of latent fingerprints has the advantage of high contrast, sensitivity, selectivity, and less dependency on instruments. Taking the environment and users' safety into consideration, organic materials for fluorescent imaging of latent fingerprints are reviewed mainly in recent 5 years. New strategies of fingerprint reagents and improved performances established for fingerprint development based on fluorescent organic materials are discussed in the view of forensic practice. In addition, we briefly highlight current challenges of recent fluorescent imaging works based on organic materials for the latent fingerprints development in forensic practice.

This article considers the computational (acoustic) wave propagation in strongly heterogeneous structures beyond the assumption of periodicity. A high contrast between the constituents of microstructured multiphase materials can lead to unusual wave scattering and absorption, which are interesting and relevant from a physical viewpoint, for instance, in the case of crystals with defects. We present a computational multiscale method in the spirit of the Localized Orthogonal Decomposition and provide its rigorous a priori error analysis for two-phase diffusion coefficients that vary between 1 and very small values. Special attention is paid to the extreme regimes of high frequency, high contrast, and their previously unexplored coexistence. A series of numerical experiments confirms the theoretical results and demonstrates the ability of the multiscale approach to efficiently capture relevant physical phenomena. [ABSTRACT FROM AUTHOR]

The goal of this work is to design high-resolution, high-contrast and robust MV adaptive beamforming algorithms, which are also implemented in real-time frame rate. Multi-operator optimization is introduced into MV adaptive beamforming in this work to propose a multi-operator MV adaptive beamforming algorithmic optimization framework. Based on the proposed algorithmic optimization framework, the algorithm optimization can be either conducted by activating a single optimization operator, or conducted by activating multiple optimization operators. The multi-operator MV (MOMV) adaptive beamforming algorithms are then derived from this framework. Moreover, in order to promote the real-time imaging capability of MOMV beamforming, a GPU-based parallel acceleration framework is proposed along with the algorithmic optimization framework by exploring the image-level coarse-grained parallelization and pixel-level fine-grained parallelization. GPU computing resource allocation strategy and memory access strategy are both explored to better design the acceleration framework. Comprehensive quantitative simulation evaluations and qualitative in vivo experiments of imaging performance are studied, and the results demonstrate that the proposed MOMV adaptive beamforming algorithms significantly improve the imaging performance as compared with other MV beamforming algorithms, which have high resolution, high contrast, good robustness, and real-time imaging capability with thousands of acceleration speedup. Furthermore, the MOMV beamforming algorithm without eigen-decomposition and projection optimization operator achieves much higher beamforming frame rate with little downgrade of image quality as compared with the MOMV beamforming algorithm with all optimization operators. [ABSTRACT FROM AUTHOR]

A dual-module machine learning scheme is proposed to reconstruct inhomogeneous scatterers with high contrasts and large electrical dimensions. The first nonlinear mapping module (NMM) is an extreme learning machine (ELM), which is used to convert the measured scattered fields at the receiver arrays into the preliminary images of the scatterers. The second image-enhancing module (IEM) is a convolutional neural network (CNN), which is used to refine further the images from the NMM to obtain high-accuracy pixel-based model parameter distribution in the inversion domain. Compared with the traditional approximate methods such as backpropagation, the NMM-IEM machine learning can produce the preliminary image with a much higher accuracy but the unknown weight matrices of the ELM are only solved once during training. Hence, the IEM connected to the NMM has a simple architecture and can be trained at a rather low cost. The performance of the proposed dual-module NMM-IEM scheme and the conventional variational Born iterative method is compared in terms of inversion of scatterers with different electrical sizes and contrasts. Meanwhile, the NMM-IEM is also assessed for the inversion of scatterers with high contrasts and large electrical dimensions and experimental data. Finally, the NMM-IEM is compared with the CNNs used in the previous works. [ABSTRACT FROM AUTHOR]

The purpose of this work is to provide a rigorous mathematical analysis of the expected superresolution phenomenon in the time-reversal imaging of electromagnetic (EM) radiating sources embedded in a high contrast medium. It is known that the resolution limit is essentially determined by the sharpness of the imaginary part of the EM Green's tensor for the associated background. We first establish the close connection between the resolution and the material parameters and the resolvent of the electric integral operator, via the Lippmann--Schwinger representation formula. We then present an insightful characterization of the spectral structure of the integral operator for a general bounded domain and derive the pole-pencil decomposition of its resolvent in the high contrast regime. For the special case of a spherical domain, we provide some quantitative asymptotic behavior of the eigenvalues and eigenfunctions. These mathematical findings shall enable us to provide a concise and rigorous illustration of the superresolution in the EM source reconstruction in high contrast media. Some numerical examples are also presented to verify our main theoretical results. [ABSTRACT FROM AUTHOR]

Harmonic vibrations of a strongly inhomogeneous elastic beam with piecewise uniform stiffnesses and densities are considered. The focus is on the lowest eigenmodes, which are often most harmful and unwanted. They are evaluated by perturbing the limiting rigid body translations and rotations of stiff beam components. The developed methodology is adapted for two particular configurations of a three-span beam. The derived approximate formulae are tested by comparison with the exact solution of a symmetric beam with two stiff outer components and free ends. [ABSTRACT FROM AUTHOR]

The Boltzmann equation, as a model equation in statistical mechanics, is used to describe the statistical behavior of a large number of particles driven by the same physics laws. Depending on the media and the particles to be modeled, the equation has slightly different forms. In this article, we investigate a model Boltzmann equation with highly oscillatory media in the small Knudsen number regime and study the numerical behavior of the generalized multiscale finite element method (GMsFEM) in the uid regime when high oscillation in the media presents. The GMsFEM is a general approach [E. Chung, Y. Efendiev, and T. Y. Hou, J. Comput. Phys., 320 (2016), pp. 69{ 95] to numerically treat equations with multiscale structures. The method is divided into the online and online steps. In the online step, basis functions are prepared from a snapshot space via a well- designed generalized eigenvalue problem (GEP), and these basis functions are then utilized to patch up for a solution through DG formulation in the online step to incorporate specific boundary and source information. We prove the well-posedness of the method on the Boltzmann equation and show that the GEP formulation provides a set of optimal basis functions that achieve spectral convergence. Such convergence is independent of the oscillation in the media, or the smallness of the Knudsen number, making it one of the few methods that simultaneously achieve numerical homogenization and asymptotic preserving properties across all scales of oscillations and the Knudsen number. [ABSTRACT FROM AUTHOR]

Electrochromic materials and corresponding devices display reversible optical changes under applied voltage. While inorganic and organic electrochromic materials are extensively studied, enhancing their performance is crucial. This study presents a high-contrast energy-efficient flexible electrochromic device based on viologen derivatives and driven by film solar cell. The aims are to foster applications in smart windows, displays, and energy-efficient technologies. Two symmetric viologen derivatives of 1,1′-bis(4-(dimethylamino) phenyl)- [4,4′-bipyridine]dihexafluorophosphate (DNPV) and 1,1′-bis(4-acetamidophenyl)-[4,4′-bipyridine]dihexafluorophosphate (DAcPV) and two asymmetric viologen derivatives of 1-benzyl-1'-(4-(dimethylamino)phenyl)-[4,4′-bipyridine]dihexafluoro-phosphate (Bn-NPV) and 1-(4-acetamidophenyl)-1′-benzyl-[4,4′-bipyridine]dihexa-fluorophosphate (Bn-AcPV) were synthesized. These viologen derivatives as active materials were used to assemble both flexible and rigid electrochromic devices (ECDs). After applying voltage of 1.0 V, both of flexible and rigid ECDs based on DNPV and Bn-NPV exhibited reversible color change from purple to deep purple and red to deep viologen respectively, while ECDs based on DAcPV and Bn-AcPV exhibited a color change from yellow to black and pale yellow to green under applied voltage of 1.2 V, respectively. After 1000 cycles, flexible and rigid ECDs showed good stability. Especially, the flexible ECDs maintained good performance after 1000 bending cycles. In additional, the ECDs based on these viologen derivatives were prepared to displayer, which showed clear display function. And ECDs driven by solar cells demonstrated good stability after 100 cycles. Furthermore, it showed that the rigid ECD based on DAcPV with high solar irradiation modulation of 70.3 %, holds great potential in smart window applications. [Display omitted] • The electrochromic devices based on four viologen derivatives were assembled. • The flexible ECD based on DAcPV exhibited a color change from yellow to black. • The ECDs based on these viologen derivatives were prepared to displayer. • ECDs driven by solar cells demonstrated good stability after 100 cycles. • The rigid ECD based on DAvPV showed high solar irradiation modulation of 70.3 %. [ABSTRACT FROM AUTHOR]