Narrow-band Spectrum Research Articles

An Approach for Designing Mixed Light-Emitting Diodes to Match Greenhouse Plant Absorption Spectra

We report a methodological approach for simulating luminary output radiation, which is achieved by mixing light-emitting diodes (LEDs) in order to match any plant absorption spectrum. Various recorded narrow-band LED spectra of different colors were first characterized and then fitted with a multi-Gaussian model. An optimizing procedure computed the optimal weighting of the relevant parameters so as to minimize the discrepancy between the combined spectrum and the reference target curve. The particle swarm optimization (PSO) method was applied because it is the most suitable technique for mono-objective situations. Within the useful spectral interval, the worst relative standard deviation between the optimized curve and recorded LED spectral power distribution (SPD) was 3.4%. When combining different LED types, the simulated light output showed that we could limit ourselves to selecting only five colored sources. This work will help us to design an optimized 200 W laboratory luminaire with a pulse-width switched-mode power supply.

Validation and analysis of a 1-D variational assimilation scheme for bathymetry inversion

Results are presented from a variational data assimilation and nearshore bathymetry inversion scheme based on depth and wave-phase averaged surfzone hydrodynamics for a narrow-banded wave spectrum. 1-D Cross shore bathymetry is inverted based on 17-min-averaged significant wave height and longshore current observations made during the Duck94 field experiment. An inversion scenario is considered in which inversion is carried out separately for each 17-min-averaged set of observations. Results are used to quantify the inversion scheme's accuracy depending on time dependent wave and bathymetry conditions. The model generally produced a root-mean-square error of 0.46 m between modelled and actual bathymetry when both wave height observations and alongshore current observations were assimilated. The RMS error reduced to 0.44 m when only wave height observations were assimilated and increased to 0.69 m when only alongshore current observations were assimilated, suggesting that wave height is a more informative variable for bathymetry inversion. The model performed consistently in inverting bathymetry and thereby tracking morphologic change in varied wave conditions, including during large storm events.

Structure of Multiple Fano Resonances in Double-baffle MDM Waveguide Coupled Cascaded Square Cavity for Application of High Throughput Detection

A structure of double-baffle metal-dielectric-metal (MDM) waveguide coupled cascaded square cavity is designed based on the transmission characteristics of the surface plasmon polaritons. Combined with coupled mode theory (CMT), the mechanism of multiple Fano resonances generated by this structure is analyzed qualitatively. The wide-band spectrum mode generated by the F-P resonant cavity and the four narrow-band spectrum modes produced by the cascaded square resonant cavities interfere with each other. Moreover, an new scheme of introducing a semiconductor material InGaAsP into this structure is designed for improving the transmittance of the Fano peaks. Analyze the influence of refractive indexes of the test objects on sensing performance by finite element method (FEM) quantitatively, which shows the improved structure can achieve the independent tuning of multiple Fano resonances. Combining with 96-well microplate technology, the structure can achieve the detection of multiple different samples with high-performance simultaneously. It is believed that the proposed structure has a strong reference significance for the design of optical micro-nanostructures for high throughput detection.

Wave energy resources assessment for the multi-modal sea state of Hawaii

This paper describes development and validation of a 32-year wave hindcast for Hawaii as part of the energy resources assessment for the US and affiliated territories. The nested model system comprises structured WAVEWATCH III for the globe and unstructured SWAN around the Hawaiian Islands with wind forcing from the Climate Forecast System Reanalysis and its regional downscaling. The development effort follows the International Electrotechnical Commission (IEC) standards. The hindcast is first validated with buoy measurements in terms of the six IEC wave energy resources parameters. The comparison shows good overall agreement but with greater uncertainties for some of the parameters intended for narrowband spectra. The sea state of Hawaii includes a mix of short-period wind seas, long-period north and south swells as well as waves with moderate periods from multiple sources. We partition the hindcast spectra based on the respective period ranges and directions and validate the partitioned spectral energy and parameters with measured values. The partitioned hindcast spectra allow separate seasonal descriptions of dominant components from wind seas to swells for in-depth understanding of the wave climate and proper categorization of wave energy resources in terms of the six IEC parameters for Hawaii.

Multiplasmons-Pumped Excited-State Absorption and Energy Transfer Upconversion of Rare-Earth-Doped Luminescence beyond the Diffraction Limit

Rare-earth-doped upconversion luminescence has attracted extensive attention due to its narrow-band and wide-range emission spectra, which cover biological and optical communication windows. For di...

Analyzing the bearing wear using direct spectrum method when transferring the torque motion from the machine

The present article examines rolling bearings with varying degrees of wear using direct spectrum method when operating from a machine drive. To achieve this purpose, a narrow-band spectrum analyzer was used. Also, several experiments were carried out to determine the effects of different types of bearing wear on the frequency characteristics of the vibroacoustic signal, which allows to predict the occurrence of defects in the bearing structure. Eventually, data were gathered on the increase in vibroacoustic noise in different types of wear and conclusions were drawn about the possibility of using the spectral method to predict failures during the operation of bearings. The results showed the lack of lubrication in the bearing and the presence of corrosion leads to an increase in amplitude frequencies in the high frequency range of 4000 - 10000 Hz. Moreover, the amplitude of the bearing without lubrication is about 35% higher than the amplitude of the worn bearing. Finally, due to the research carried out, it becomes possible to create a method for determining the type and nature of wear of rolling bearings of metal-cutting and other equipment. This will allow in the future to create a system for monitoring malfunctions directly during the operation of technological equipment without disassembling its units, reduce the cost of repair work and prevent emergency failures.

EXPERIENCE OF HANDLING ON THE ISS TECHNICAL COMPONENTS OF RESEARCH EQUIPMENT «BAR». CHAPTER 1. ACOUSTIC COMPONENTS

The paper presents the results of operational testing of two acoustic components of research equipment «Bar» (a leak detector and ultrasound analyzer) onboard the ISS Russian segment. It was found that the ultrasonic (US) background noise interferes in leak search; besides, it exceeds dramatically the adopted noise level constraint thus impacting crew health and efficiency, and oral communication. The narrow-band noise spectra were measured and the expressed tone property of the US noise was demonstrated. The authors make the point that the present noise level constraints for space habitats do not take into account all realities of the life of cosmonauts and lack a solid medical and acoustic background.

Narrowband nonlinear optical spectroscopy with spatially chirped broadband pulses.

Nonlinear optical vibrational spectroscopies are powerful experimental tools for inspecting material properties that are difficult to acquire otherwise. As ultrafast lasers used in such experiments are typically of much broader bandwidth than vibrational modes, narrowband filtering is usually essential, and the utility of laser energy is often highly inefficient. Here we introduce an experimental scheme to break this trade-off. A broadband beam is spatially chirped as it reaches the sample, and generates sum-frequency signals upon overlapping with another broadband, unchirped beam. A narrowband spectrum can then be retrieved from the spatially dispersed image of signals, with both broadband pulses fully utilized. The scheme is also readily employed as a spatially resolved spectroscopy technique without scanning, and can be easily extended to other wave-mixing experiments.

Thermally Stable Quantum Rods, Covering Full Visible Range for Display and Lighting Application.

Recently, quantum rods (QRs) have been studied heavily for display and lighting applications. QRs offer serious advantages over the quantum dots such as higher light out-coupling coefficient, and polarized emission. The QR enhancement films double liquid crystal display efficiency. However, it is still a challenge to synthesize good quality green (λem ≈ 520nm) and blue (λem ≈ 465nm) emitting QRs, due to very large bathochromic shift during the shell growth. Furthermore, until now, the presence of cadmium in high-quality QRs is inevitable, but due to its toxicity, RoHS has restricted the amount of cadmium in consumer products. In this article, low Cd core-shell QRs, with a narrow-band luminescence spectrum tuned in the whole visible range, are prepared by replacing Cd with Zn in a one-pot post-synthetic development. These QRs possess the good thermal stability of photoluminescence properties, and therefore, show high performance for the on-chip LED configuration. The designed white LEDs (WLEDs) are characterized by a high brightness of 120000 nits, and color gamut covering 122% NTSC (90% of BT2020), in the 1931CIE color space. Additionally, these LEDs show a high luminous efficiency of 115lmW-1 . Thus, these quantum rod LED are perfectly viable for display backlighting and lighting applications.

Optical analysis of the dual-microcavity effect in a red light-emitting organic device

ABSTRACT In this study, the effect of a dual microcavity on the luminescent characteristics and light extraction efficiency of organic red light-emitting devices with a multi-cathode structure was investigated. It was clarified that surface plasmon loss on a metal cathode was reduced to about one-fifth and can be efficiently extracted from the outside with the help of the dual-microcavity effect. About half of the radiant energy in dipole emission was successfully utilized as external and substrate modes. The luminous efficiency increased by about 1.52 times, and a narrow-band emission spectrum was observed with a forward directional red emission. The relationship between the luminescence characteristics and the dual-microcavity effect will be discussed from the viewpoint of the optical design of multi-stacked thin film devices.

Spatial Variation in Coastal Dune Evolution in a High Tidal Range Environment

Coastal dunes have global importance as ecological habitats, recreational areas, and vital natural coastal protection. Dunes evolve due to variations in the supply and removal of sediment via both wind and waves, and on stabilization through vegetation colonization and growth. One aspect of dune evolution that is poorly understood is the longshore variation in dune response to morphodynamic forcing, which can occur over small spatial scales. In this paper, a fixed wing unmanned aerial vehicle (UAV), is used to measure the longshore variation in evolution of a dune system in a megatidal environment. Dune sections to the east and west of the study site are prograding whereas the central portion is static or eroding. The measured variation in dune response is compared to mesoscale intertidal bar migration and short-term measurements of longshore variation in wave characteristics during two storms. Intertidal sand bar migration is measured using satellite imagery: crescentic intertidal bars are present in front of the accreting portion of the beach to the west and migrate onshore at a rate of 0.1–0.2 m/day; episodically the eastern end of the bar detaches from the main bar and migrates eastward to attach near the eastern end of the study area; bypassing the central eroding section. Statistically significant longshore variation in intertidal wave heights were measured using beachface mounted pressure transducers: the largest significant wave heights are found in front of the dune section suffering erosion. Spectral differences were noted with more narrow-banded spectra in this area but differences are not statistically significant. These observations demonstrate the importance of three-dimensionality in intertidal beach morphology on longshore variation in dune evolution; both through longshore variation in onshore sediment supply and through causing longshore variation in near-dune significant wave heights.

Third-order generation of narrow-banded wave trains by a wavemaker

Analytic method for nonlinear wave generation by a wavemaker that is free of 2nd order limitation inherent to existing wavemaker theories is proposed. The method is based on the Nonlinear Schrödinger (NLS) equation and the nonlinear boundary condition at the wavemaker. Advantages offered by the NLS model allowed simplification of the expressions for determination of the wavemaker driving signal and thus made them easily applicable in practice. The 2nd and the 3rd-order corrections to the wavemaker driving signal are calculated from the complex surface elevation envelope obtained as a solution of the NLS equation at the prescribed location in the wave flume. The domain of applicability of the generation method was determined on the basis of numerous experiments in the wave flume as well as numerical simulations using a fully-nonlinear Numerical Wave Tank (NWT). A very good generation of the required wave train shape was obtained for sufficiently narrow-banded spectra in both deep-water and intermediate depth conditions. The generation of the sheared current due to oscillatory wavemaker motion has been discussed.

Narrowband and ultra-wideband modulation instability in nonlinear metamaterial waveguides

Waveguides based on metamaterials may exhibit strongly frequency-dependent nonlinearities. In this work, we focus on the phenomenon of modulation instability in this type of waveguide, departing from a new modeling equation that ensures strict conservation of both the energy and photon number of the parametric process. In particular, we analyse the case of a waveguide with a linearly frequency-dependent nonlinear coefficient, revealing unique features such as narrowband and ultra-wideband gain spectra and the suppression of the power cutoff giving rise to an ever-growing MI gain. These markedly distinct regimes are enabled by self-steepening (SS) and manifest themselves depending upon the magnitude and sign of the SS parameter. We believe these findings to be most relevant in the context of mid-IR supercontinuum sources.

Vibration Analysis of Driving-Point System with Uncertainties Using Polynomial Chaos Expansion

A vibration transfer analysis method based on polynomial chaos expansion (PCE) is proposed in this study and is used to analyze the stochastic dynamic compliance of uncertain systems with the Gaussian distribution. The random dynamic compliance is established by utilizing mode superposition on the system as the parameters of system uncertainties are regarded as input variables. Considering the asymptotic probability density function of mode shape, the dynamic compliance is decomposed into the mean of mode shape and the subsystem represented as an orthogonal polynomial expansion. Following this, the vibration transmission analysis approach is proposed for the random vibration. Results of a numerical simulation carried out employing the PCE approach show that broad-band spectrum analysis is more effective than narrow-band spectrum analysis because the former jump of the dynamic compliance amplitude is weakened. This proposed approach is valid and feasible, but since broad-band spectrum analysis loses some important information about the random vibration, both the aforementioned processes need to simultaneously be applied to analyze the random vibration transmission of low-medium frequency systems.

Correlated colour temperature index of lighting source for polychrome artworks in museums

In museums, polychrome artworks are highly sensitive to light. They are incredibly vulnerable to irreversible permanent photochemical damage, such as fading and discolouration caused by radiation from light sources. At the same time, such artworks need light sources with excellent colour rendering ability. Therefore, museum lighting sources have dual needs for protection and viewing. For light sources, correlated colour temperature (CCT) is a crucial index, and there are problems such as inconsistency of standards and lack of accuracy. In this work, ten kinds of narrow-band light sources were used to irradiate 17 kinds of pigment samples of polychrome artworks for 1440 h. The colour parameters were measured every 240 h to calculate the colour difference. Based on the data analysis, the law of colour damage of pigments under different narrow-band light sources was obtained, and the damage response function of pigments to different wavelengths of the spectrum was established. By screening the 610 spectra obtained by exhaustively fitting ten kinds of narrow-band spectra, 9477 spectra which meet the visual requirements were left. Combining the response function and spectral distribution, the relative damage values of the 9477 spectra to pigments were calculated, and the relationship between the relative damage value of pigments and the spectral CCT was obtained. It is proposed that 3100 ± 50 K is the CCT range with the lowest average damage to polychrome artworks. Moreover, a method for calculating the recommended CCT of precious polychrome artworks was given.

Constructing Charge‐Transfer Excited States Based on Frontier Molecular Orbital Engineering: Narrowband Green Electroluminescence with High Color Purity and Efficiency

AbstractThe design and synthesis of organic materials with a narrow emission band in the longer wavelength region beyond 510 nm remain a great challenge. For constructing narrowband green emitters, we propose a unique molecular design strategy based on frontier molecular orbital engineering (FMOE), which can integrate the advantages of a twisted donor–acceptor (D‐A) structure and a multiple resonance (MR) delayed fluorescence skeleton. Attaching an auxiliary donor to a MR skeleton leads to a novel molecule with twisted D‐A and MR structure characteristics. Importantly, a remarkable red‐shift of the emission maximum and a narrowband spectrum are achieved simultaneously. The target molecule has been employed as an emitter to fabricate green organic light‐emitting diodes (OLEDs) with Commission Internationale de L'Eclairage (CIE) coordinates of (0.23, 0.69) and a maximum external quantum efficiency (EQE) of 27.0 %.

Constructing Charge-Transfer Excited States Based on Frontier Molecular Orbital Engineering: Narrowband Green Electroluminescence with High Color Purity and Efficiency.

The design and synthesis of organic materials with a narrow emission band in the longer wavelength region beyond 510 nm remain a great challenge. For constructing narrowband green emitters, we propose a unique molecular design strategy based on frontier molecular orbital engineering (FMOE), which can integrate the advantages of a twisted donor-acceptor (D-A) structure and a multiple resonance (MR) delayed fluorescence skeleton. Attaching an auxiliary donor to a MR skeleton leads to a novel molecule with twisted D-A and MR structure characteristics. Importantly, a remarkable red-shift of the emission maximum and a narrowband spectrum are achieved simultaneously. The target molecule has been employed as an emitter to fabricate green organic light-emitting diodes (OLEDs) with Commission Internationale de L'Eclairage (CIE) coordinates of (0.23, 0.69) and a maximum external quantum efficiency (EQE) of 27.0 %.

Фототерапія в лікуванні псоріазу

SummaryObjective – to determine and evaluate the results of narrow-band phototherapy inthe treatment of psoriasis using a dermatological ultraviolet apparatus.Materials and methods. Irradiation of psoriatic rashes was carried out using aUVB-311 dermatological ultraviolet apparatus (Psorolight 100-3). Under oursupervision there were 36 patients. The treatment was carried out in the form ofmonotherapy according to the method of triple exposure per week.Results and its discussion. As a result of the treatment, 7 patients (64%) withpalmar-plantar psoriasis showed a marked improvement (Psoriasis Area and SeverityIndex (PASI) >75%), 4 patients (36%) achieved satisfactory improvement, PASI >50%.Clinical cure was observed in the majority of patients (19 people – 76%) with vulgarand exudative psoriasis (PASI reduction – 90–95%), others had significant improvement(PASI reduction from 75 to 80%).Conclusions: The treatment of psoriasis is often problematic due to its highresistance to existing drugs and treatment methods. An original method for treatingpatients with psoriasis is proposed. Apparatus for irradiation based on fluorescentlamps of a narrow-band spectrum of 311 nm was used as a physiotherapeutic treatment.The proposed method of treatment is effective, has good tolerance and minorcomplications. It can be recommended for widespread use in healthcare facilities.

The effect of artificial solar spectrum on growth of cucumber and lettuce under controlled environment

Light-emitting diodes (LEDs) have been widely applied in the controlled environment agriculture, which are characterized by relatively narrow-band spectra and energetical efficiency. Most recently, the spectrum of Sunlike LEDs has been engineered and it closely resembles solar spectrum in the range of photosynthetic active radiation (PAR, 400–700 nm). To investigate how plant growth responses to the spectrum of Sunlike LEDs, cucumber and lettuce plants were cultivated and their responses were compared with the conventional white LEDs as well as composite of red and blue LEDs (RB, R/B ratio was 9:1). We observed that although Sunlike LEDs resulted in a longer stem in cucumber, dry weight and leaf area were similar as those under RB LEDs, and significantly higher than those under white LEDs. Moreover, cucumber leaves grown under Sunlike and white LEDs showed higher photosynthetic capacity than those grown under RB LEDs. For lettuce, plants grown under Sunlike LEDs showed larger leaf area and higher dry weight than the other two treatments. However, the leaf photosynthetic capacity of lettuce grown under Sunlike LEDs was the lowest. In this context, the spectrum induced plant functions are species-dependent. Furthermore, the three types of LEDs show distinct light spectra and they are different in many aspects. Therefore, it is difficult to attribute the different plant responses to certain specific light spectra. We conclude that plants grown under Sunlike LEDs exhibit larger leaf area, which may be due to some specific spectrum distributions (such as more far-red radiation), and consequently are favorable for light interception and therefore result in greater production.

Aflatoxin contaminated degree detection by hyperspectral data using band index

Aflatoxin is a highly toxic and carcinogenic substance with fluorescence characteristic. To explore the feasibility of detection the degree of aflatoxin contamination using hyperspectral imaging technology, we proposed a machine learning detection method based on support vector machine (SVM) combining band index and narrow band. First, five concentrations of aflatoxin solutions (10ug/L, 20ug/L, 50ug/L, 100ug/L and 10 mg/L) were prepared and dripped onto the surface of different peanut kernels. Next, hyperspectral images with 33 bands (400–720 nm) were acquired for each sample using a hyperspectral imaging system under 365 nm ultraviolet (UV) light. Then four fluorescence indexes including Radiation Index (RI), Difference Radiation Indexes (DRI), Ratio Radiation Index (RRI) and Normalized Difference Radiation Index (NDRI) were proposed. Finally, Fisher method was used to optimize and obtain a narrowband spectrum, and RBF-SVM model was used to recognize aflatoxin and make regression analysis on the degree of aflatoxin contamination. Experimental results showed that DRI index had the optimal performance, and the accuracy rate of 5-fold cross validation of SVM were 95.5% and the mean square error (MSE) and correlation coefficient R were respectively 0.0223 and 0.9785. Results of this paper are of positive significance for the online aflatoxin detection and grading of agricultural products.