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Wide color gamut display has become a new generation of display technology because of its good color saturation. However, the low quantum efficiency and wide half peak width of narrow‐band green phosphors are still the main barriers in their development and application. This work addresses these challenges by using Mn2+ as the luminescent center and constructing efficient Eu2+ → Mn2+ energy transfer in Na2MgAl10O17 (NMAO) matrix. The NMAO:0.15Eu2+, 0.30Mn2+ phosphor presents a single‐band emission peaking at 513 nm with a full width at half maximum (FWHM) of only 33 nm under the excitation of 365 nm LED chip. In addition, under the excitation wavelength of 365 nm, the energy transfer efficiency reaches 74%. Compared with the NMAO:0.30Mn2+, the intensity of the NMAO:0.15Eu2+, 0.30Mn2+ increases by 5.5 times and the internal quantum efficiency is up to 61.82%. A white LED device with the CIE coordinates of (0.2871, 0.3472) and a color gamut area of 94% NTSC has been assembled successfully by combining 365 nm LED chips with NMAO:0.15Eu2+, 0.30Mn2+, BaMgAl10O17:Eu2+, and K2SiF6:Mn4+ as green, blue, and red component. This work enriches the relevant content of Mn2+‐doped phosphors and provides a constructive insight into improving luminescent performance through energy transfer. [ABSTRACT FROM AUTHOR]

Electrofluorochromic (EFC) materials and devices with controllable fluorescence properties show great application potential in advanced anticounterfeiting, information storage and display. However, the low color purity caused by the broad emission spectra and underperforming switching time of the existing EFC materials limit their application. Through biomimetic exploration and the study of reversible electrochemical responsive coordination reactions, boron–nitrogen embedded polyaromatics (B,N‐PAHs) with narrow‐band emission and high color purity have been successfully integrated into EFC systems, which also help to better understand the role of boron in biological activity. The EFC device achieve good performance containing quenching efficiency greater than 90% within short switching time (ton: 0.6 s, toff: 2.4 s), and nearly no performance change after 200 cycles test. Three primary color (red, green, and blue) EFC devices are successfully prepared. In addition, new phenomena are obtained and discussed in this biomimetic exploration of related boron reactions. The success and harvest of this exploration are expected to provide new ideas for optimizing properties and broadening applications of EFC materials. Moreover, it may provide ideas and reference significance for further exploring and understanding the function of boron compounds in biological systems. [ABSTRACT FROM AUTHOR]

Summary: The proposed antenna is a small wideband monopole with wideband circular polarization using heterogeneous bidirectional recurrent neural network for both narrow and wide band applications (NWB‐MAD‐HBRNN). The electromagnetic structure is designed, fabricated, and simulated with 1 mm thickness on FR4 substrate material along dielectric constant 4.3. The proposed antenna includes 4.3–8.85 GHz for ultrawideband applications; it contains reconfigurable narrow band for L‐band 1.27 GHz, LTE, and ultrawideband applications. To enhance the antenna impedance bandwidth (BW) along axial ratio bandwidth (ARBW), a slit is etched at the antenna patch, a rectangular stub is inserted into the ground plane, and semicircular stub is added to the top of antenna feed line. The better agreement is observed in the measured and simulated gain performance of 4.8 dB for LTE band applications. The proposed NWB‐MAD‐HBRNN design provides 13.50%, 18.91%, and 22.58% higher bandwidth and 18.36%, 20.38%, and 27.58% lower return loss than the existing designs, such as bio‐inspired wideband antenna for wireless applications based on perturbation technique (BWA‐WA‐PA), a compact circularly polarized modified printed monopole antenna for wireless applications (CCP‐MPMA‐WA), and new multiband monopole antenna for certain broadband wireless applications along wireless personal communications (PA‐MMA‐BWA), respectively. [ABSTRACT FROM AUTHOR]

Abstract Electrofluorochromic (EFC) materials and devices with controllable fluorescence properties show great application potential in advanced anticounterfeiting, information storage and display. However, the low color purity caused by the broad emission spectra and underperforming switching time of the existing EFC materials limit their application. Through biomimetic exploration and the study of reversible electrochemical responsive coordination reactions, boron–nitrogen embedded polyaromatics (B,N‐PAHs) with narrow‐band emission and high color purity have been successfully integrated into EFC systems, which also help to better understand the role of boron in biological activity. The EFC device achieve good performance containing quenching efficiency greater than 90% within short switching time (ton: 0.6 s, toff: 2.4 s), and nearly no performance change after 200 cycles test. Three primary color (red, green, and blue) EFC devices are successfully prepared. In addition, new phenomena are obtained and discussed in this biomimetic exploration of related boron reactions. The success and harvest of this exploration are expected to provide new ideas for optimizing properties and broadening applications of EFC materials. Moreover, it may provide ideas and reference significance for further exploring and understanding the function of boron compounds in biological systems.

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Using characteristic mode analysis (CMA), a pair of ultra-wideband (UWB) and narrow band antennas is made. The Multiple Input Multiple Output (MIMO) configuration incorporates a circular monopole to attain UWB functionality, while an umbrella-shaped element generates the narrowband operation. The two radiators are symmetrically positioned to accomplish space diversity. Distinct sizes of small electromagnetic band gap cells separate the two radiators. The MIMO structure has dimensions of 40×40×1.6 mm3 (0.32λo×0.32λo×0.12 λo) and improved isolation is accomplished by adding a T-shaped stub to the ground plane. The exceptional bandwidth of 11.6 GHz offered by the Circular-pot UWB antenna covers a frequency range from 2.4 GHz to 14 GHz. The antenna demonstrates favorable MIMO performance, featuring a gain of 4.9dBi, isolation exceeding 23 dB. The diversity characteristics encompass an enveloped correlation coefficient (ECC) of under 0.0012, a diversity gain (DG) approaching 10 dB, a channel capacity loss of 0.28 b/s/Hz, and a mean effective gain (MEG) measuring -3.3 dB. A favorable agreement between the tested and simulated results.

In order to improve the efficiency of particle-based fluid surface reconstruction, this paper proposed a perspective-grid-based adaptive narrow-band surface particle extraction method. Compared with the object-space-based method, this scheme adaptively extracted the surface particles closest to the viewpoint within the frustum according to the particle density, dispersion coefficient, so that the number of surface particles and memory consumption were related to the visible surface area, rather than the entire fluid surface or simulation domain. In addition, this paper presented an adaptive thickness estimation method based on particle density by taking advantage of the arrangement of perspective grids along the view. Experiments show that this scheme effectively reduces surface particles by 40% to 76% and memory overhead by 30% to 50%,solves the problems of surface particle redundancy and holes, and quickly obtains thickness information at a lower cost. This scheme brings significant performance improvement for surface reconstruction and rendering, and can better handle the surface reconstruction and rendering of large-scale particle sets. [ABSTRACT FROM AUTHOR]

Narrow-band deep-blue organic light-emitting diodes (OLEDs) have played a key role in the field of high-quality full-color displays. However, because of the considerable challenges of inherent band gaps, unbalanced carrier injection and the lack of molecular structures, narrow-band deep-blue emitters develop slowly compared with red- and green-emitting materials. Encouragingly, with the continuous efforts of scientists in recent years, great progress has been made in the molecule design and material synthesis of highly efficient narrow-band deep-blue emitters. The typical deep-blue emitters which exhibit narrow emission with a full width at half maximum of < 50 nm are summarized in this article. They are divided into the three categories: fluorescence, phosphorescence and thermally activated delayed fluorescence. The methods of molecular design for realizing narrow-band deep-blue emission are described in detail and future research directions are also discussed in this article. [ABSTRACT FROM AUTHOR]

There are very few results in the literature on spectral content of seismic ground displacement; nonetheless, these results are singular as most of the spectral content is limited to a very narrow low frequency band, contrary to ground acceleration. These few spectral characterizations have been obtained, expectedly, by means of power spectral or Fourier analyses of ground displacement records, only. As these records are not as reliable as ground acceleration records, the existence of a clear predominant frequency in ground displacement warrants confirmation through a different procedure. We propose a corroboration method of this highly narrow-band characteristic that is based on the more dependable acceleration signal, rather than on the same ground displacement record that is the subject of study. Specifically, displacement response spectra are analyzed (which rely on acceleration records) to verify previously observed neat predominant frequencies in ground displacement, which is a novelty. [ABSTRACT FROM AUTHOR]

Plasmonic metal nanostructures have promising applications in biosensing due to their ability to facilitate light–matter interaction. However, the damping of noble metal leads to a wide full width at half maximum (FWHM) spectrum which restricts sensing capabilities. Herein, we present a novel non-full-metal nanostructure sensor, namely indium tin oxide (ITO)–Au nanodisk arrays consisting of periodic arrays of ITO nanodisk arrays and a continuous gold substrate. A narrow-band spectral feature under normal incidence emerges in the visible region, corresponding to the mode-coupling of surface plasmon modes, which are excited by lattice resonance at metal interfaces with magnetic resonance mode. The FWHM of our proposed nanostructure is barely 14 nm, which is one fifth of that of full-metal nanodisk arrays, and effectively improves the sensing performance. Furthermore, the thickness variation of nanodisks hardly affects the sensing performance of this ITO-based nanostructure, ensuring excellent tolerance during preparation. We fabricate the sensor ship using template transfer and vacuum deposition techniques to achieve large-area and low-cost nanostructure preparation. The sensing performance is used to detect immunoglobulin G (IgG) protein molecules, promoting the widespread application of plasmonic nanostructures in label-free biomedical studies and point-of-care diagnostics. The introduction of dielectric materials effectively reduces FWHM, but sacrifices sensitivity. Therefore, utilizing structural configurations or introducing other materials to generate mode-coupling and hybridization is an effective way to provide local field enhancement and effective regulation. [ABSTRACT FROM AUTHOR]

Accurate stratospheric temperature observations are crucial for weather forecasts and climate change studies. This paper discusses a precise measurement method for the stratospheric temperature profile using narrow bands with ultra-high spectral resolution from nadir-viewing satellites. First, the CO2 absorption band around 15 μm is selected as the major sounding source by the calculation and analysis of the temperature Jacobian and the atmospheric molecular spectra. Next, the influence of spectral resolution, spectral range and instrumental noise on the sounding capability is analyzed, and the sounding feasibility of the single spectral band and multiple spectral bands is discussed under the condition that the spaceborne long-wave infrared space heterodyne spectrometer (SHS) is selected as suggested sounder onboard the satellite. Finally, the optimal joint-sounding scheme of narrow bands is proposed. The temperature retrieval and validation show that the joint-sounding of two discontinuous narrow bands can realize the high precision measurement of the stratospheric temperature profile for the given spectral resolution, spectral range, and instrumental noise. When the sounder adopts two narrow bands (the regions of 666.87–676.44 cm−1 and 683.58–693.15 cm−1) and a spectral resolution of 0.03 cm−1, the retrieval accuracy (RMSE) is about 0.9 K over a pressure range of 200 to 0.7 hPa (11.5–50 km). This study will provide technical preparation for high-precision and low-cost satellite sounder design for stratospheric temperature observations. [ABSTRACT FROM AUTHOR]

This paper proposes a quad-band graphene-based terahertz (THz) metamaterial perfect absorber for refractive index sensing. This proposed absorber consists of concentric hexagon-shaped rings on top of a thin graphene sheet and is numerically simulated using the Finite Integration Technique (FIT) and achieves four absorption peaks, i.e., 94.86%, 99.13%, 98%, and 99.37% at 2.9626 THz, 3.1576 THz, 3.4891 THz, and 3.9259 THz, respectively, at Fermi energy of 0.2 eV. In addition to this, this absorber is insensitive to the polarization of the incident wave. This proposed absorber can be used as a refractive index sensor to detect several chemicals whose refractive index varies from n = 1.33 to 1.54 with a sensitivity of 1.42 THz/RIU, 1.54 THz/RIU, 1.68 THz/RIU, and 1.90 THz/RIU where RIU stands for refractive index unit. By varying an external DC-bias voltage which changes the Fermi energy of the graphene layer, the absorption spectra of the proposed absorber can be adjusted. So, the Fermi energy of thin graphene sheet has been varied, and it is observed that the resonance frequency varied linearly with the refractive index, particularly at Fermi energy of 0.4 eV. The FoM (figure of merit) and Q-factor of four absorption peaks of this proposed absorber can reach 110.95, 117.25, 85.96, and 97.2 and 231.45, 239.21, 178.015, and 200.30, respectively, at the Fermi level of 0.2 eV. The geometrical parametric analysis has been carried out at the Fermi energy level of 0.4 eV to justify the choice of the design parameters. This proposed absorber finds applications in terahertz sensing and imaging. [ABSTRACT FROM AUTHOR]

Wide color gamut display has become a new generation of display technology because of its good color saturation. However, the low quantum efficiency and wide half peak width of narrow-band green phosphors are still the main barriers in their development and application. This work addresses these challenges by using Mn 2+ as the luminescent center and constructing efficient Eu 2+  → Mn 2+ energy transfer in Na 2 MgAl 10 O 17 (NMAO) matrix. The NMAO:0.15Eu 2+ , 0.30Mn 2+ phosphor presents a single-band emission peaking at 513 nm with a full width at half maximum (FWHM) of only 33 nm under the excitation of 365 nm LED chip. In addition, under the excitation wavelength of 365 nm, the energy transfer efficiency reaches 74%. Compared with the NMAO:0.30Mn 2+ , the intensity of the NMAO:0.15Eu 2+ , 0.30Mn 2+ increases by 5.5 times and the internal quantum efficiency is up to 61.82%. A white LED device with the CIE coordinates of (0.2871, 0.3472) and a color gamut area of 94% NTSC has been assembled successfully by combining 365 nm LED chips with NMAO:0.15Eu 2+ , 0.30Mn 2+ , BaMgAl 10 O 17 :Eu 2+ , and K 2 SiF 6 :Mn 4+ as green, blue, and red component. This work enriches the relevant content of Mn 2+ -doped phosphors and provides a constructive insight into improving luminescent performance through energy transfer., (© 2024 John Wiley & Sons Ltd.)

There are very few results in the literature on spectral content of seismic ground displacement; nonetheless, these results are singular as most of the spectral content is limited to a very narrow low frequency band, contrary to ground acceleration. These few spectral characterizations have been obtained, expectedly, by means of power spectral or Fourier analyses of ground displacement records, only. As these records are not as reliable as ground acceleration records, the existence of a clear predominant frequency in ground displacement warrants confirmation through a different procedure. We propose a corroboration method of this highly narrow-band characteristic that is based on the more dependable acceleration signal, rather than on the same ground displacement record that is the subject of study. Specifically, displacement response spectra are analyzed (which rely on acceleration records) to verify previously observed neat predominant frequencies in ground displacement, which is a novelty.

Plasmonic metal nanostructures have promising applications in biosensing due to their ability to facilitate light–matter interaction. However, the damping of noble metal leads to a wide full width at half maximum (FWHM) spectrum which restricts sensing capabilities. Herein, we present a novel non-full-metal nanostructure sensor, namely indium tin oxide (ITO)–Au nanodisk arrays consisting of periodic arrays of ITO nanodisk arrays and a continuous gold substrate. A narrow-band spectral feature under normal incidence emerges in the visible region, corresponding to the mode-coupling of surface plasmon modes, which are excited by lattice resonance at metal interfaces with magnetic resonance mode. The FWHM of our proposed nanostructure is barely 14 nm, which is one fifth of that of full-metal nanodisk arrays, and effectively improves the sensing performance. Furthermore, the thickness variation of nanodisks hardly affects the sensing performance of this ITO-based nanostructure, ensuring excellent tolerance during preparation. We fabricate the sensor ship using template transfer and vacuum deposition techniques to achieve large-area and low-cost nanostructure preparation. The sensing performance is used to detect immunoglobulin G (IgG) protein molecules, promoting the widespread application of plasmonic nanostructures in label-free biomedical studies and point-of-care diagnostics. The introduction of dielectric materials effectively reduces FWHM, but sacrifices sensitivity. Therefore, utilizing structural configurations or introducing other materials to generate mode-coupling and hybridization is an effective way to provide local field enhancement and effective regulation.

Advances in visualization technologies have made it possible to detect non-muscle-invasive bladder cancer (NMIBC), which is difficult to identify with conventional white-light imaging (WLI). Among these technologies, narrow-band imaging (NBI) emphasizes capillaries on the mucosal surface by narrowing WLI to two wavelengths. NBI is significantly more sensitive than WLI for detection of cancer lesions, and thus is useful for the diagnosis of NMIBC. Moreover, several meta-analyses have shown that transurethral resection of NMIBC under NBI (NBI-TUR) significantly reduces postoperative recurrence, compared to TUR under WLI (WLI-TUR). However, some cancer lesions remain difficult to detect with NBI, and there is a need for a flexible treatment strategy that includes the addition of other appropriate treatment methods after understanding the limitations of NBI. Despite these limitations, NBI is attractive in clinical practice because it does not require special pretreatment, there are no concerns about side effects from the administration of a photosensitizing agent, and there is no need for complicated perioperative management. This is ideal for obtaining optimal results in facilities in which time and resources are limited. Thus, NBI is a natural choice for NMIBC with regard to provision of care with maximum benefit in certain medical environments. [ABSTRACT FROM AUTHOR]

The Common Spatial Pattern (CSP) algorithm is the most widely used method for decoding Electroencephalography (EEG) signals from motor imagery (MI) paradigm. However, due to the inter-subject variability, the CSP algorithm heavily relies on the selection of filter bands and extensive analytical processing time required to build an effective model, which has been a challenge in current research. In this paper, we propose a narrow filter bank CSP (NFBCSP) algorithm, which automatically determines the optimal narrow band for two-class motor imagery by band search tree, and a high-performance classification model dedicated to each subject can be obtained in a short time for online processing or further offline analysis. The optimal narrow band is combined with the CSP algorithm to extract the dynamic features in the EEG signals. For the multi-class motor imagery task, it is first transformed into multiple One-Versus-Rest (OVR) tasks and determines the corresponding optimal narrow bands. After extracting the features of each optimal narrow band separately, the Deep Convolutional Neural Network (DCNN) is used for the fusion of band features and classification of multi-class motor imagery. Finally, we verified our method using two different motor imagery datasets, the BCI-VR dataset with two classes of motor imagery and the BCI Competition IV dataset 2a with four classes of motor imagery. The experimental results show that the proposed method achieves an average classification accuracy of 86.43% for the two-class motor imagery task, and 76.87% for the four-class motor imagery task, which outperforms other recent methods. [ABSTRACT FROM AUTHOR]

This paper presents a novel pipeline that improves the efficiency of narrowband surface reconstruction for particle-based fluids. Different from previous narrow band methods, we only construct the scalar field in the outer surface region. A method with robust criteria for detecting the outer surface vertices of the scalar field is then proposed to eliminate the redundant inner vertices, leading to a significant reduction in the computational complexity and memory consumption. The presented pipeline is fully parallel with a parallel compact memory scheme to avoid race conditions. Several experiments are conducted to compare our present method with the state-of-the-art approach, and the results indicate that our method saves nearly half of the computing time and ten percent of the memory consumption. [Display omitted] [ABSTRACT FROM AUTHOR]

Accurate stratospheric temperature observations are crucial for weather forecasts and climate change studies. This paper discusses a precise measurement method for the stratospheric temperature profile using narrow bands with ultra-high spectral resolution from nadir-viewing satellites. First, the CO2 absorption band around 15 μm is selected as the major sounding source by the calculation and analysis of the temperature Jacobian and the atmospheric molecular spectra. Next, the influence of spectral resolution, spectral range and instrumental noise on the sounding capability is analyzed, and the sounding feasibility of the single spectral band and multiple spectral bands is discussed under the condition that the spaceborne long-wave infrared space heterodyne spectrometer (SHS) is selected as suggested sounder onboard the satellite. Finally, the optimal joint-sounding scheme of narrow bands is proposed. The temperature retrieval and validation show that the joint-sounding of two discontinuous narrow bands can realize the high precision measurement of the stratospheric temperature profile for the given spectral resolution, spectral range, and instrumental noise. When the sounder adopts two narrow bands (the regions of 666.87–676.44 cm−1 and 683.58–693.15 cm−1) and a spectral resolution of 0.03 cm−1, the retrieval accuracy (RMSE) is about 0.9 K over a pressure range of 200 to 0.7 hPa (11.5–50 km). This study will provide technical preparation for high-precision and low-cost satellite sounder design for stratospheric temperature observations.

An activator's selective occupation of a host is of great significance for designing high-quality white light-emitting diodes (w-LEDs) phosphors, while achieving a full-spectrum single-phase white light emission phosphor is challenging. For developing high-performance and green-emitting phosphors with narrow bands used for backlight display, a series of Na 2 Mg 1-x Al 10 O 17 :xMn2+ (NMAO:xMn2+) phosphors with high Mn2+ concentration were synthesized. The NMAO:0.65Mn2+ green phosphor exhibits an ultra-narrow band green emission with full width at half maximum (FWHM) about 27 nm and peak position at 513 nm when excited by the blue light with wavelength of 450 nm. The NMAO:0.65Mn2+ not only has a super narrow band which is narrower than β -SiAlON:Eu2+ (FWHM ∼ 55 nm) but also shows an exceptional thermal stability performance (77% peak intensity @423 K). A w-LED device was assembled with NMAO:0.65Mn2+, a blue GaInN chip and K 2 SiF 6 :Mn4+ phosphors, which represents a wide color-gamut of 112% National Television System Committee (NTSC) standard under the current of 50 mA. These results demonstrate the NMAO:0.65Mn2+ has potential superiority in application of backlight display. • A narrow-band green Na 2 MgAl 10 O 17 :Mn2+ phosphor was prepared by solid state method. • Na 2 Mg 0.35 Al 10 O 17 :0.65Mn2+ shows emission peaked at 513 nm and the FWHM of 27 nm. • Na 2 Mg 0.35 Al 10 O 17 :0.65Mn2+ shows good thermal stability with 77%@423 K. • A w-LED device with wide color-gamut of 112% NTSC was fabricated. [ABSTRACT FROM AUTHOR]