Wavelength Distribution Research Articles

Conversion of the wavelength distribution to the energy spectrum of the wave

When designing a vessel, spectral calculating methods of wave induced oscillation are used, and during vessel operation, available technical means allow us to obtain only the pitch spectrum. For a complete solution of navigational tasks, it is necessary to have a wave disturbance spectrum and pitch amplitude-frequency characteristic as well. The latter function can be received in sailing, if obtaining the actual wave disturbance spectrum is possible. The lack of available and sufficiently accurate methods of actual wave disturbance assessment in modern navigation creates the need to use statistical mathematical models in addition to available information in order to connect various wave elements. Taking into account the possibility of obtaining the wavelength distribution from the wave field radar image, a hypothesis is formulated about the possibility of using a statistical mathematical connection between the wind wave lengths and heights. Within the proposed hypothesis, an algorithm is presented for converting the actual wavelength probability distribution obtained from wave field radar images into the disturbance frequency spectrum. The conclusion is made about possible application of the hypothesis in pitch transfer function assessment.

High‐Cadence Lidar Observations of Middle Atmospheric Temperature and Gravity Waves at the Southern Andes Hot Spot

AbstractThe Southern Andes are the strongest hot spot for atmospheric gravity waves (GWs) in the stratosphere. Yet, until recently, no high‐cadence measurements of GWs within the middle atmosphere were available in this region. Therefore, the COmpact Rayleigh Autonomous Lidar (CORAL) was deployed to the Estación Astrónomica Río Grande (53.7°S, 67.7°W), Argentina, to obtain temperature profiles up to 100 km altitude. CORAL operates autonomously and obtained measurements during roughly two thirds of all nights between November 2017 and October 2020. The excellent measurement coverage allows for the quantification of GW properties at the hot spot with great detail. The hot spot nature of this region is reflected in nightly mean temperature profiles showing deviations from the monthly mean in the order of 25–55 K in each winter month. This is connected to winter mean growth rates of GW potential energy (Ep), which are to our knowledge the largest ever reported in the stratosphere. The monthly mean Ep profiles show a mesospheric limit of ∼100 Jkg−1, indicating a saturated GW spectrum at altitudes above 60 km. The winter mean power spectral density also reaches the saturation limit here. Moreover, we investigated the distribution of vertical wavelengths using our novel diagnostic technique WAVELET‐SCAN. It reveals waves with vertical wavelengths that are mostly between 10 and 16 km but also can exceed 25 km in rare occasions.

Boosting Cyanobacteria Growth by Fivefold with Aggregation-Induced Emission Luminogens: Toward the Development of a Biofactory

Light utilization is the vital first step of photosynthesis for photoautotrophic organisms. Boosting the growth and yield of photosynthetic organisms is critical in sustainable food and biofuel production in a photobioreactor. In this contribution, we improved the light quality of cyanobacteria by the addition of aggregation-induced emission luminogens (AIEgens), which could absorb the ultraviolet/blue light and emit the green/yellow light into the culture medium, thus effectively converted the light to a more usable range. Our designed AIEgens formed highly bright luminogenic aggregates in the exposure medium and dispersed around the cells, which effectively modified the wavelength and spatial distribution of the light source. The photosynthesis parameters of AIEgen-treated cyanobacteria, including the maximum photosynthetic quantum yield, the effective photochemical quantum yield of photosystem II, and the relative electron transport rate, were significantly improved with the application of our AIEgens. Specifically, after 14 days of incubation, we demonstrated that the AIEgens boosted the cell density of cyanobacteria by 5-fold and the lipid contents by 5- to 6-fold. Furthermore, cyanobacteria continued to grow under UV light irradiation in the presence of AIEgens, highlighting the important role of AIEgens in light conversion to improve light quality. Our study demonstrated the potential application of AIEgens in a photosynthetic biofactory without genetic modification of photosynthetic organisms.

Three‐Dimensional Analysis of Global Gravity Waves Based on COSMIC Multi‐Satellite Observations

AbstractGravity waves (GWs) transport momentum and energy in the atmosphere, and it has become a difficult problem how to use satellites data to extract the horizontal parameters of GWs. We firstly applied the multi‐channel maximum entropy method to the temperature profile triples based on the favorable conditions of satellite flight between year 2006 and 2007 after COSMIC launch, and analyzed the three‐dimensional properties of GWs. The latitudinal and seasonal distribution of horizontal wavelengths of gravity waves were obtained. The momentum fluxes showed the maximum in the summertime subtropics and the wintertime high latitudes, which revealed possible convective sources in the summertime subtropics and mountain waves expected to occur in the winter jet region in the winter hemisphere high latitudes. The fluxes also showed the maximum at summer high latitudes, which were seldom reported.

STUDY ON RELATIONSHIP BETWEEN FASTENER SYSTEM MODE AND RAIL CORRUGATION OF MODERN TRAM LINE

To prevent rail clip fracture damage in tram fastener system, the finite element model of modern tram rail fastener system was built, and pre-stress modal analysis on the fastener system with different rail pad stiffness under installation state was carried out, then the correlation among train speed, corrugation wavelength, rail clip mode and stiffness of rail pad was studied. The results show that: The fracture at the small arc of the rail clip is related to the high-order mode, while the fracture at the large arc is related to the low-order mode. The train passing frequencies of modern tram system are below 500 Hz; With the increase of the rail pad stiffness, the natural frequency of the rail clip mode increases. Its frequency band is 196.64 Hz~258.31 Hz and 630.16 Hz~673.51 Hz; Under the condition of equal probability distribution of train speed (30 km/h~70 km/h) and rail corrugation wave length (25 mm~80 mm), the probability of three typical rail clip fracture types is 3.5%, 36.3% and 25.9%, respectively. By changing the speed and wavelength range, the probability analysis of rail clip fracture mode of the designated line can be carried out, so as to make targeted maintenance and damage detection plan.

Economic design of artificial light plant factories based on the energy conversion efficiency of biomass

Since plants with a high biomass conversion efficiency of light energy consume less energy and require shorter cultivation periods, it is expected that plant factories can have more output with less energy. However, there have been few studies on the biomass conversion efficiency of light energy in various cultivated plants, and this agricultural engineering field is still unexplored. If the amount of energy consumed by a plant factory can be obtained from the biomass conversion efficiency of light energy, the plant types that can be grown in a plant factory and the economic efficiency of the plant factory can be clarified. In this study, we determined the amount of light energy required for plant cultivation by measuring the wavelength distribution of sunlight and plant-growing light-emitting diodes. Also, we investigated the light to biomass conversion efficiency from the amount of heat generated by the biomass of cultivated plants. The light to biomass conversion efficiency was also used to analyze the payback period of plant factories so as to estimate the profitability of various cultivated plants. The solar to biomass conversion efficiency of the tested leafy vegetables ranged from 0.03% to 0.62%, while the efficiency of the cultivation LEDs ranged from 1.21% to 20.1%. The conversion efficiency including the energy consumption of air conditioning ranged from 0.13 to 5.7%. By measuring the biomass conversion efficiency of plants, it is possible to analyze the profitability of plant factories with a high degree of accuracy.

Applications of Different Light Spectra in Growing Forest Tree Seedlings

Light intensity, duration and wavelength distribution are amongst the most important factors affecting the success of plant production in different cultivation systems [...]

Characterizing spatial uniformity of tensile deformation with an elastic polymer based holographic sensor.

Tensile deformation uniformity of material has been studied with a stretchable polymer based holographic sensor. The diffraction spectrum distribution of a holographic grating with a large area as a main response parameter is scanned. A linear spatial distribution of peak wavelength provides an important foundation for exploring the tensile uniformity. The same ratio of wavelength to position confirms that the tensile deformation of the material is uniform in a small spot size. Over the entire length of the materials, gradually increasing deformation accumulation is the main uniformity feature of tensile deformation. The uniformity response is expected to apply in sensing the deformation and stress fluctuation distribution in the middle of the thin surface. The non-uniform distribution of stress can be expressed by the nonlinear distribution of the grating diffraction spectrum. The optical measurement of tensile deformation uniformity further validates the applicability of a stretchable polymer based holographic sensor.

Scientific study on the celadon glaze from the Donggou kiln, China

The raw material characteristics, glaze color, mineral composition, and microstructure of green-glazed porcelain samples excavated from the Donggou kiln site in Henan Province, China were subjected to scientific investigations. The results show that the glaze formula of Donggou kiln celadon is relatively stable, and the plant ash with higher Na2O and K2O content may be used as a flux for the celadon glaze. The pan-blue celadon glaze has a wide range of dominant wavelength, concentrated and high distribution of luminosity values, low color saturation, and light degree of yellow. The high content of K2O and P2O5 is one of the main factors for the bluish glaze color. The celadon glaze of the Donggou kiln is a typical crystalline phase-separated glaze with a large number of needle-like and columnar anorthite crystals and a worm-like phase-separated structure.

Simulation and experimental investigation of nonlinear effects in 5G fronthaul transmission system based on WDM-PON architecture

Wavelength-division multiplexing passive optical network (WDM-PON) is considered as a mainstream solution for 5G fronthaul transmission system to cope with the rapidly increasing bandwidth demand. In such a multi-wavelength system, nonlinear effects limit the achievable transmission distance and channel capacity. Therefore, in this paper, the impact of nonlinear effects on a multi-wavelength transmission system with 25 Gb/s/λ non-return-to-zero (NRZ) and a 200-GHz channel spacing over 25 km standard single-mode fiber (SSMF) is investigated through experiment and simulation. The effects of four-wavelength mixing (FWM) in O-band as well as cross-phase modulation (XPM) in C-band are both studied and discussed. Experiments are performed for 3- and 4-channel transmission cases, while 12-channel transmission is performed by simulation. The results show that in the O-band scenario, the FWM effect severely affects the performance of the channels near the zero-dispersion wavelength. Besides, the XPM products overlap the signal in the C-band, which also degrades the sensitivity. Based on these analyses, the nonlinear effects should be fully considered when planning wavelengths for 5G fronthaul transmission, including wavelength distribution and channel spacing selection.

Calibration and optimization of Bragg edge analysis in energy-resolved neutron imaging experiments

The investigation of microstructure of crystalline materials is one of the possible and frequently used applications of energy-resolved neutron imaging. The position of Bragg edges is defined by sharp changes in neutron transmission and can thus be determined by the measurement of the transmission spectra as a function of neutron wavelength. The accuracy of this measurement depends on both the data analysis technique and the quality of the measured spectra. While the optimization of reconstruction methods was addressed in several previous studies, here we introduce an important prerequisite when aiming for high resolution Bragg edge strain imaging — a well calibrated flight path across the entire field of view (FOV). Compared to e.g. powder diffraction, imaging often uses slightly different geometries and hence requires a calibration for each particular setup. We herein show the importance of this calibration across the entire FOV in order to determine the instrumental error correction for pulsed neutron beamlines. In addition, we also consider the precision of Bragg edge reconstruction as a function of integration time and the minimal sample area. We demonstrate that, with a proper calibration procedure, the Bragg edge wavelength distribution across the entire sample can be reconstructed with an accuracy of Δλ∕λ=±∼0.01%. Our experiments indicate that the strain maps of Inconel 625 samples printed by a direct metal laser melting additive manufacturing technique can be reconstructed with the precision of ±∼100με. The full FOV calibration technique becomes even more important with the development of advanced neutron energy-resolved imaging beamlines and detectors with large FOVs.

Measurement of fiber parameters of pure silica core fibers based on the OTDR technique.

We propose a simple technique based on optical time domain reflectometry (OTDR) for measuring the cutoff wavelength and core radius distributions in a pure silica core fiber for the first time. The proposed technique can simultaneously measure several important fiber parameters such as the mode field diameter, relative-index difference, effective area, and chromatic dispersion, including the cutoff wavelength and core radius. We experimentally demonstrate that our proposed technique can successfully evaluate these fiber parameter distributions and can be applied for the measurements of few-mode and multi-core fibers with pure silica cores using multi-channel OTDR and mode couplers.

A Flash‐Induced Robust Cu Electrode on Glass Substrates and Its Application for Thin‐Film μLEDs

A robust Cu conductor on a glass substrate for thin-film μLEDs using the flash-induced chemical/physical interlocking between Cu and glass is reported. During millisecond light irradiation, CuO nanoparticles (NPs) on the display substrate are transformed into a conductive Cu film by reduction and sintering. At the same time, intensive heating at the boundary of CuO NPs and glass chemically induces the formation of an ultrathin Cu2 O interlayer within the Cu/glass interface for strong adhesion. Cu nanointerlocking occurs by transient glass softening and interface fluctuation to increase the contact area. Owing to these flash-induced interfacial interactions, the flash-activated Cu electrode exhibits an adhesion energy of 10Jm-2 , which is five times higher than that of vacuum-deposited Cu. An AlGaInP thin-film vertical μLED (VLED) forms an electrical interconnection with the flash-induced Cu electrode via an ACF bonding process, resulting in a high optical power density of 41mWmm-2 . The Cu conductor enables reliable VLED operation regardless of harsh thermal stress and moisture infiltration under a high-temperature storage test, temperature humidity test, and thermal shock test. 50 × 50 VLED arrays transferred onto the flash-induced robust Cu electrode show high illumination yield and uniform distribution of forward voltage, peak wavelength, and device temperature.

An experimental study on the evaluation of temperature uniformity on the surface of a blackbody using infrared cameras

ABSTRACT Blackbody radiation is standardised electromagnetic energy emitted into space at a given temperature and wavelength distribution. It is used as a reference model to compare radiation emitted from various objects. This reference performance of blackbody systems should be maintained through periodic inspection and calibration. In this study, temperature uniformity on the surface of the blackbody was evaluated using infrared cameras. To this end, we divided the blackbody system measurements into ‘before’ and ‘after’ calibration sets and examined the blackbody surface in different bands, using two infrared cameras with different measurement principles. To evaluate surface temperature uniformity, we calculated the signal transfer function, equivalent noise temperature difference, and 3D noise of the infrared detector, and then comparatively analysed them.

LaUV: A Physics-Based UV Light Simulator for Disinfection and Communication Applications

The sterilization properties of the C-band of the ultraviolet (UV) light have been well-known for many years; however, their application has become more vital and widespread today due to the Covid-19 pandemic. Nevertheless, minimal work has been devoted to simulating UV-C propagation for surface disinfection in indoor environments. UV light has also been proposed for non-line-of-sight (NLOS) outdoor communication applications, where a number of simulators have been developed, but with several simplifications. The current work presents a fully-featured simulator for UV light propagation, called LaUV, designed mainly for indoor settings, capable of calculating measurable parameters that can be used for indoor surface disinfection and communication applications. LaUV considers atmospheric absorption and scattering according to Rayleigh and Mie theory, and reflections from rough surfaces. The scattering cross-section and probability density function of the scattering angles (phase function) are calculated accurately for any wavelength, concentration, and diameter distribution of spherical scattering particles (aerosols and droplets). Examples are presented for indoor environments, including empty rooms and rooms with furniture, for different environmental conditions and surface albedos. Interesting initial conclusions can be drawn, considering the spatial distribution of UV exposure for surface disinfection applications and channel modeling for line-of-sight (LOS) and NLOS communication, demonstrating the versatility and the potential applications of the proposed simulator.

ОСОБЛИВОСТІ МОДЕЛЮВАННЯ ВКР ПІДСИЛЮВАЧА НА ОСНОВІ ВОЛОКНА З КОМПЕНСОВАНОЮ ДИСПЕРСІЄЮ З РІВНОМІРНОЮ СМУГОЮ ПІДСИЛЕННЯ У C+L ТЕЛЕКОМУНІКАЦІЙНИХ ВІКНАХ

The results of the modeling of a broadband optical fiber Raman amplifier (FRA) with a multi-wavelength pumping and a uniform gain band covering C+L telecommunication windows in an active fiber with compensation of dispersion type DCF are presented. It has been demonstrated that the SRS gain profile, that is, the distribution of the optical radiation gain over the frequency range of the Stokes shift in Raman scattering, is the main characteristic of the FRA. Optimum values of the parameters of the pump sources are presented, namely spectral distribution of wavelengths and relative power of all pump sources, at which it is possible to obtain a minimum non-uniformity of the gain band. Based on the results of the calculations, a minimum non-uniformity of the SRS gain profile on almost the whole operating range was obtained for 6 pumping sources. It is shown that the analytical form of the gain profile greatly simplifies the procedure of modeling of the main gain parameters for FRA with multi-wavelength pumping for 3-6 wavelengths of pump sources. Furthermore, the proposed simplified analytical model makes it possible to quickly obtain theoretical estimates of the main parameters of the operating wavelength band of FRA with an arbitrary number of pumping lasers in the multiwave pump source.

Coherent vibrational dynamics of [Au25(SR)18]- nanoclusters

Coherent vibrational dynamics can be observed in atomically precise gold nanoclusters using femtosecond time-resolved pump-probe spectroscopy. It can not only reveal the coupling between electrons and vibrations, but also reflect the mechanical and electronic properties of metal nanoclusters, which holds potential applications in biological sensing and mass detection. Here, we investigated the coherent vibrational dynamics of [Au25(SR)18]− nanoclusters by ultrafast spectroscopy and revealed the origins of these coherent vibrations by analyzing their frequency, phase and probe wavelength distributions. Strong coherent oscillations with frequency of 40 cm−1 and 80 cm−1 can be reproduced in the excited state dynamics of [Au25(SR)18]−, which should originate from acoustic vibrations of the Au13 metal core. Phase analysis on the oscillations indicates that the 80 cm−1 mode should arise from the frequency modulation of the electronic states while the 40 cm−1 mode should originate from the amplitude modulation of the dynamic spectrum. Moreover, it is found that the vibration frequencies of [Au25(SR)18]− obtained in pump-probe measurements are independent of the surface ligands so that they are intrinsic properties of the metal core. These results are of great value to understand the electron-vibration coupling of metal nanoclusters.

Design and Numerical Simulation of a Bandpass Filter Nano-film

A bandpass filtering nano-film based on high refractive index materials is designed in this paper, it shows high transmittance for red light and high reflectance for visible light. The structure of the nano-filtration membrane is simple, which is composed of three nano-films with the overall thickness no more than 100 nm. At normal incidence, the red light (620-760nm) transmittance of the filter film is above 0.6, and the reflectance is below 0.05. At oblique incidence from 0 to 45 degree, the red light transmittance of the filter film under both TM and TE wave mode are all above 0.5, which achieve the transmission of red light in a wide range of incident angles. The light transmittance of the nano-filtration membrane was calculated by transfer matrix method (TMM), it is verified by finite-difference frequency-domain (FDFD) method, and the field distribution of the typical wavelength in the film was calculated. The thickness variation of each layer effects the transmittance of light wave in nano-film was studied. The passband of this filter is easy to be modulated, the bandwidth and waveband of the transmitted light can be modulated as long as changing the thickness of the film, which can be applied to medical or scientific research fields that requires specific light waveband.

Image-Based Measurement of Structural Color using Spectral Camera

We perceive structural colors by optical phenomena such as light interference and diffraction caused by a fine structure of the object surface. One of the characteristics of structural colors is that a wavelength distribution of light changes depending on an incident angle of a light source and a viewing angle. Generally, for color evaluation and reproduction, it is required to acquire reflection characteristics of objects. Therefore, BRDF (Bidirectional Reflectance Distribution Function) is often used as a function that represents reflection characteristics depending on incident and viewing angles. In this study, we measured BRDF of structural colors based on a method to acquire image-based material reflection characteristics using a spectral camera. The measurement was performed by aligning an optical axis of a spectral camera with a structural color sample and changing an irradiation angle of a light source. Reflection characteristics were represented by using a radiance factor, which was a ratio between a spectral radiance of white material and that of structural color. From measurement results, we confirmed an angle-dependent radiance factor. Finally, based on a measured spectral radiance of a structural color sample, we spectrally reproduced the structural color using a spectral projector based on model fitting of spectral data.

The Magellan M2FS Spectroscopic Survey of High-redshift Galaxies: A Sample of 260 Lyα Emitters at Redshift z ≈ 5.7

Abstract We present a spectroscopic survey of Lyα emitters (LAEs) at z ≈ 5.7 using the multiobject spectrograph M2FS on the Magellan Clay telescope. This is part of a high-redshift galaxy survey carried out in several well-studied deep fields. These fields have deep images in multiple UV/optical bands, including a narrow NB816 band that has allowed an efficient selection of LAE candidates at z ≈ 5.7. Our sample consists of 260 LAEs and covers a total effective area of more than 2 deg2 on the sky. This is so far the largest (spectroscopically confirmed) sample of LAEs at this redshift. We use the secure redshifts and narrowband photometry to measure Lyα luminosities. We find that these LAEs span a Lyα luminosity range of erg s−1 and include some of the most luminous galaxies known at in terms of Lyα luminosity. Most of them have rest-frame equivalent widths between 20 and 300 Å, and more luminous Lyα emission lines tend to have broader line widths. We detect a clear offset of ∼20 Å between the observed Lyα wavelength distribution and the NB816 filter transmission curve, which can be explained by the intergalactic medium absorption of continua blueward of Lyα in the high-redshift spectra. This sample is being used to study the Lyα luminosity function and galaxy properties at z ≈ 5.7.