基于反射率、吸光度和Kubelka-Munk光谱的贡梨不同损伤程度检测

贡梨在收获、运输和销售过程中容易发生机械损伤,加速果实腐烂,降低贡梨品质。快速判别贡梨的不同损伤程度,进而采取不同的处理措施,以降低经济损失。以往运用高光谱技术研究水果的损伤程度,通常仅用反射率光谱。该研究运用高光谱技术获取贡梨的反射率(R)、吸光度(A)、和Kubelka-Munk(K-M)变换光谱结合3种深度学习算法对健康和不同损伤程度的贡梨进行判别。首先,选取60个新鲜无损伤贡梨作为健康样品,再利用自由落体碰撞装置制备出Ⅰ级损伤、Ⅱ级损伤、Ⅲ级损伤贡梨样品各60个。通过高光谱成像系统采集这240个贡梨样品的光谱数据,对采集的光谱进行黑白校正,以获得贡梨的反射率(R)、吸光度(A)、和Kubelka-Munk(K-M)变换光谱,然后用基准线校准(Baseline)、去趋势(De-Trending)、移动平均(MA-S)、乘法散射校正(MSC)、卷积平滑(SG-S)、标准正态变量变换(SNV)共6种预处理方法对3种原始光谱数据进行预处理,并建立BP神经网络(BP)、极限梯度提升(XGBoost)和随机森林(RF)判别分析模型对贡梨不同损伤程度进行判别。根据模型对贡梨损伤程度的判别结果显示,基于反射率、吸光度、K-M变换光谱的BP模型判别准确率较好,整体准确率达到了85%及以上,且发现经过Baseline预处理后的反射率光谱建立的BP模型比未经预处理的反射率光谱谱建立的BP模型有较大的提升,判别准确率达到了93.33%。为了提升BP模型的精准度和运行效率,对3种原始光谱和Baseline预处理后的光谱利用竞争性自适应重加权(CARS)和无信息变量消除(UVE)方法筛选出特征波段光谱信息,用筛选后的特征光谱数据来建立BP模型,其判别结果显示A-RAW-CARS-BP模型具有最佳的判别准确率,整体准确率达到了96.66%。结果表明,采用3种原始光谱对贡梨的损伤程度进行判别具有可行性,为高光谱技术检测贡梨的不同损伤程度提供了理论依据。

面向全色域转杯纺纱的Kubelka-Munk双常数理论模型构建及颜色预测

为了能在色纺纱的纺纱阶段即时调控纱线颜色,减少混色成本,缩短工艺流程,结合三通道数控转杯纺纱的特点构建了全色域网格化混色模型,该模型可在纺纱过程中进行全色域范围内的色相调控、明度调控和彩度调控。为了解决色纺纱的测配色问题,得到与之相匹配的测配色系统,根据来样快速进行计算机测配色,节约成本,结合传统Kubelka-Munk双常数理论模型的特点,从构建的全色域网格化混色模型中选取混合样来进行颜色预测。从传统Kubelka-Munk双常数理论模型颜色预测的结果发现,部分混合样的预测反射率明显低于实际的反射率,针对这个问题,重新构建了新的Kubelka-Munk双常数理论模型来进行颜色预测得到新的预测反射率,并用插值替换的方法,把传统Kubelka-Munk双常数理论模型预测结果中明显低于实际反射率的部分用新的预测反射率替换,得到最终的混合样预测反射率。结果表明:与传统的Kubelka-Munk双常数理论模型预测混合样颜色结果相比,新的Kubelka-Munk双常数理论模型预测颜色并用插值替换法替换后得到的最终的混合样的颜色,色差平均值从1.48降低到1.04,且所有混合样的色差均能控制在2.0以内。该预测方法较传统Kubelka-Munk双常数理论模型具有更好的预测精度,所构建的全色域网格化混色模型和新的Kubelka-Munk双常数理论模型可应用于多基色纤维混色色彩和混合比的预测。

Laser spectroscopy imaging technique coupled withnanomaterials for cancer diagnosis: A review

Laser spectroscopic imaging techniques have received tremendous attention in the-eld of cancer diagnosis due to their high sensitivity,high temporal resolution,and short acquisition time.However,the limited tissue penetration of the laser is still a challenge for the in vivo diagnosis of deep-seated lesions.Nanomaterials have been universally integrated with spectroscopic imaging techniques for deeper cancer diagnosis in vivo.The components,morphology,and sizes of nanomaterials are delicately designed,which could realize cancer diagnosis in vivo or in situ.Considering the enhanced signal emitting from the nanomaterials,we emphasized their combination with spectroscopic imaging techniques for cancer diagnosis,like the surface-enhanced Raman scattering(SERS),photoacoustic,fluorescence,and laser-induced breakdown spectroscopy(LIBS).Applications ofthe above spectroscopic techniques offer new prospectsfor cancer diagnosis.

Functional near-infrared spectroscopy in non-invasive neuromodulation

Non-invasive cerebral neuromodulation technologies are essential for the reorganization of cerebral neural networks,which have been widely applied in the field of central neurological diseases,such as stroke,Parkinson’s disease,and mental disorders.Although significant advances have been made in neuromodulation technologies,the identification of optimal neurostimulation paramete rs including the co rtical target,duration,and inhibition or excitation pattern is still limited due to the lack of guidance for neural circuits.Moreove r,the neural mechanism unde rlying neuromodulation for improved behavioral performance remains poorly understood.Recently,advancements in neuroimaging have provided insight into neuromodulation techniques.Functional near-infrared spectroscopy,as a novel non-invasive optical brain imaging method,can detect brain activity by measuring cerebral hemodynamics with the advantages of portability,high motion tole rance,and anti-electromagnetic interference.Coupling functional near-infra red spectroscopy with neuromodulation technologies offe rs an opportunity to monitor the cortical response,provide realtime feedbac k,and establish a closed-loop strategy integrating evaluation,feedbac k,and intervention for neurostimulation,which provides a theoretical basis for development of individualized precise neuro rehabilitation.We aimed to summarize the advantages of functional near-infra red spectroscopy and provide an ove rview of the current research on functional near-infrared spectroscopy in transcranial magnetic stimulation,transcranial electrical stimulation,neurofeedback,and braincomputer interfaces.Furthermore,the future perspectives and directions for the application of functional near-infrared spectroscopy in neuromodulation are summarized.In conclusion,functional near-infrared spectroscopy combined with neuromodulation may promote the optimization of central pellral reorganization to achieve better functional recovery form central nervous system diseases.

A rened analytical model for reconstruction problems in diuse reectance spectroscopy

A rened analytical model of spatially resolved diffuse reectance with small source-detector separations(SDSs)for the in vivo skin studies is proposed.Compared to the conventional model developed by Farrell et al.,it accounts for the limited acceptance angle of the detectorber.The rened model is validated in the wide range of optical parameters by Monte Carlo simulations of skin diffuse reectance at SDSs of units of mm.Cases of uniform dermis and two-layered epidermis-dermis structures are studied.Higher accuracy of the rened model compared to the conventional one is demonstrated in the separate,constraint-free reconstruction of absorption and reduced scattering spectra of uniform dermis from the Monte Carlo simulated data.In the case of epidermis-dermis geometry,the recovered values of reduced scattering in dermis are overestimated and the recovered values of absorption are underestimated for both analytical models.Presumably,in the presence of a thin mismatched topical layer,only the effective attenuation coe±cient of the bottom layer can be accurately recovered using a diffusion theorybased analytical model while separate reconstruction of absorption and reduced scattering fails due to the inapplicability of the method of images.These-ndings require implementation of more sophisticated models of light transfer in inhomogeneous media in the recovery algorithms.

In situ infrared, Raman and X-ray spectroscopy for the mechanistic understanding of hydrogen evolution reaction

Hydrogen production by water reduction reactions has received considerable attention because hydrogen is considered a clean-energy carrier,key for a sustainable energy future.Computational methods have been widely used to study the reaction mechanism of the hydrogen evolution reaction(HER),but the calculation results need to be supported by experimental results and direct evidence to confirm the mechanistic insights.In this review,we discuss the fundamental principles of the in situ spectroscopic strategy and a theoretical model for a mechanistic understanding of the HER.In addition,we investigate recent studies by in situ Fourier transform infrared(FTIR),Raman spectroscopy,and X-ray absorption spectroscopy(XAS) and cover new findings that occur at the catalyst-electrolyte interface during HER.These spectroscopic strategies provide practical ways to elucidate catalyst phase,reaction intermediate,catalyst-electrolyte interface,intermediate binding energy,metal valency state,and coordination environment during HER.

Near Infrared Spectroscopy (NIRS) Model-Based Prediction for Protein Content in Cowpea

Cowpea (Vigna unguiculata L. Walp) is a multi-purpose legume with high quality protein for human consumption and livestock. The objective of this work was to develop near-infrared spectroscopy (NIRS) prediction models to estimate protein content in cowpea. A total of 116 cowpea breeding lines with a wide range of protein contents (19.28 % to 32.04%) were selected to build the model using whole seed and ground seed samples. Partial least-squares discriminant analysis (PLS-DA) regression technique with different pre-treatments (derivatives, standard normal variate, and multiplicative scatter correction) were carried out to develop the protein prediction model. Results showed: 1) spectral plots of both the whole seed and ground seed showed higher spectral scatter at higher wavelengths (>1450 nm), 2) data pre-processing affects prediction accuracy for bot whole seed and ground seed samples, 3) prediction using ground seed samples (0.64 R2 0.85) is better than the whole seed (0.33 R2 0.78), and 4) the data pre-processing second derivative with standard normal variate has the best prediction (R2_whole seed = 0.78, R2_ground seed = 0.85). The results will be of interest in cowpea breeding programs aimed at improving total seed protein content.

New insights on thermal ageing of electrical insulating oils as revealed from photoluminescence and absorption spectroscopy

Recently,significant efforts have been exerted to replace mineral oil with environmentally friendly oils due to safety and environmental issues.However,there is a need to clarify the physical mechanisms behind the ageing impact of these oils.The authors use advanced optical spectroscopy techniques in correlation with dielectric measurements to understand the ageing processes in environmentally friendly oils as well as mineral oil.Firstly,different samples of environmentally friendly oils and mineral oil were utilised to investigate the ageing mechanism.The samples were subjected to different ageing periods using a thermal accelerated ageing process.Secondly,the severity of the produced byproducts due to the oil degradation is examined based on several measured properties representing macroscopic and microscopic categories.The macroscopic category was evaluated through dielectric properties,including breakdown voltage,dielectric permittivity,and dissipation factor.The microscopic category,on the other hand,was assessed using techniques such as ultraviolet-visible absorption spectroscopy and photoluminescence spectroscopy.These techniques enabled a deep understanding of the molecular-level changes occurring in the oil under ageing conditions,thereby getting new insights into oil ageing mechanisms.It is worth mentioning that natural ester oil demonstrated the most favourable performance across various properties under ageing conditions.

Investigation on Binding between Cations and Amides using UV Raman Spectroscopy

The interaction of proteins with salt ions plays an important role in life activities.We used butyramide as a model molecule to investigate the interaction of protein backbones with cations.The experiment was performed in an aqueous solution of metal chloride using UV Raman spectroscopy.It was found that well-hydrated metal cations(Ca^(2+),Mg^(2+))tend to bind to C=O in the amide bond,resulting in redistribution of the amide I band peaks.Specifically,the peak intensity ratio of 1655 cm^(-1)to 1610 cm^(-1)increases significantly with increasing concentrations.However,this phenomenon is not obviously observed in NaCl solution.Furthermore,we studied the effect of salt ions on the water structures.The addition of Ca^(2+)and Mg^(2+)is beneficial to the enhancement of the water signal at the 3400 cm^(-1)position,while the Na^(+)at the same concentration is not obvious.The results have shown that the interaction between cations and amides satisfies the following order:Ca^(2+)>Mg^(2+)>Na^(+),which conforms to the Hofmeister series.

A dual-route optical emission spectroscopy diagnostic with wide spectral range and high wavelength resolution on HL-2A tokamak

A dual-route optical emission spectroscopy(D-OES)diagnostic is newly developed to monitor the optical emission from the X-point plasma region on the HL-2 A tokamak.This diagnostic is composed of an imaging system,a beam-splitting system for dual-route measurements,fiber bundles,a spectrometer system,and a control and acquisition system.One route is used to obtain wide-spectral-range spectra,and the other route is used to acquire high-wavelengthresolution line shapes.The spectral resolution of the wide-range spectrometers is 0.8 nm with a coverage of 800 nm(@200-1000 nm).The spectral resolution of the high-resolution spectrometer is 0.01 nm with a coverage of 6 nm(@200-660 nm).The spatial resolution of each route of D-OES is about 4 cm with 11 channels.The temporal resolution is 16 ms at maximum in the single-channel mode.Wide-range spectra(containing Balmer series and a Fulcher band)and highly resolved Ha line shapes are obtained by D-OES in the hydrogen glow discharge in the lab.D-OES measurements are carried out in the high-density deuterium experiments of HL-2A.The electron density n_(e)and deuterium temperature T_(D) in the X-point multifaceted asymmetric radiation from the edge(MARFE)region are derived simultaneously by fitting the measured D_(a) shape.The density n_(e)is observed to increase from~8.7×10^(18)m^(-3)to~7.8×10^(19)m^(-3),and the temperature T_(D)drops from~14.4 eV to~2.3 eV after the onset of MARFE in the discharge#38260.

Core-level spectroscopy of the photodissociation process of BrCN molecule

Fewest-switches surfacing hopping(FSSH) simulations have been performed with the high-level multi-reference electronic structure method to explore the coupled electronic and nuclear dynamics upon photoexcitation of cyanogen bromide(BrCN). The potential energy surfaces(PES) of BrCN are charted as functions of the Jacobi coordinates(R, θ). An indepth examination of the FSSH trajectories reveals the temporal dynamics of the molecule and the population changes of the lowest twelve states during BrCN's photodissociation process, which presents a rich tapestry of dynamical information.Furthermore, the carbon K-edge x-ray absorption spectroscopy(XAS) is calculated with multi-reference inner-shell spectral simulations. The rotation of the CN fragment and the elongation of the C–Br bond are found to be the reason for the peak shifting in the XAS. Our findings offer a nuanced interpretation for inner-shell probe investigations of BrCN, setting the stage for a deeper understanding of the photodissociation process of cyanogen halides molecules.

Negligible normal fluid in superconducting state of heavily overdoped Bi_(2)Sr_(2)CaCu_(2)O_(8+δ) detected by ultra-low temperature angle-resolved photoemission spectroscopy

In high temperature cuprate superconductors,it was found that the superfluid density decreases with the increase of hole doping.One natural question is whether there exists normal fluid in the superconducting state in the overdoped region.In this paper,we have carried out high-resolution ultra-low temperature laser-based angle-resolved photoemission measurements on a heavily overdoped Bi2212 sample with a T_(c) of 48 K.We find that this heavily overdoped Bi2212 remains in the strong coupling regime with 2Δ_(0)/(k_(B)T_(c))=5.8.The single-particle scattering rate is very small along the nodal direction(~5 meV) and increases as the momentum moves from the nodal to the antinodal regions.A hard superconducting gap opening is observed near the antinodal region with the spectral weight at the Fermi level fully suppressed to zero.The normal fluid is found to be negligibly small in the superconducting state of this heavily overdoped Bi2212.These results provide key information to understand the high T_(c) mechanism in the cuprate superconductors.

Estimating the yield stress of soft materials via laser-induced breakdown spectroscopy

Taking three typical soft samples prepared respectively by loose packings of 77-,95-,and 109-μm copper grains as examples,we perform an experiment to investigate the energy-dependent laser-induced breakdown spectroscopy(LIBS)of soft materials.We discovered a reversal phenomenon in the trend of energy dependence of plasma emission intensity:increasing initially and then decreasing separated by a well-defined critical energy.The trend reversal is attributed to the laser-induced recoil pressure at the critical energy just matching the sample's yield strength.As a result,a one-to-one correspondence can be well established between the samples'yield stress and the critical energy that is easily obtainable from LIBS measurements.This allows us to propose an innovative method for estimating the yield stress of soft materials via LIBS with attractive advantages including in-situ remote detection,real-time data collection,and minimal destructive to sample.

Research on batch multielement rapid quantitative analysis based on the standard curve-assisted calibration-free laserinduced breakdown spectroscopy method

This study proposes a batch rapid quantitative analysis method for multiple elements by combining the advantages of standard curve(SC)and calibration-free laser-induced breakdown spectroscopy(CF-LIBS)technology to achieve synchronous,rapid,and accurate measurement of elements in a large number of samples,namely,SC-assisted CF-LIBS.Al alloy standard samples,divided into calibration and test samples,were applied to validate the proposed method.SC was built based on the characteristic line of Pb and Cr in the calibration sample,and the contents of Pb and Cr in the test sample were calculated with relative errors of 6%and 4%,respectively.SC built using Cr with multiple characteristic lines yielded better calculation results.The relative contents of ten elements in the test sample were calculated using CF-LIBS.Subsequently,the SC-assisted CF-LIBS was executed,with the majority of the calculation relative errors falling within the range of 2%-5%.Finally,the Al and Na contents of the Al alloy were predicted.The results demonstrate that it effectively enables the rapid and accurate quantitative analysis of multiple elements after a single-element SC analysis of the tested samples.Furthermore,this quantitative analysis method was successfully applied to soil and Astragalus samples,realizing an accurate calculation of the contents of multiple elements.Thus,it is important to advance the LIBS quantitative analysis and its related applications.

Wavelength calibration and spectral analysis of vacuum ultraviolet spectroscopy in EAST

A vacuum ultraviolet(VUV)spectroscopy with a focal length of 1 m has been engineered specifically for observing edge impurity emissions in Experimental Advanced Superconducting Tokamak(EAST).In this study,wavelength calibration for the VUV spectroscopy is achieved utilizing a zinc lamp.The grating angle and charge-coupled device(CCD)position are carefully calibrated for different wavelength positions.The wavelength calibration of the VUV spectroscopy is crucial for improving the accuracy of impurity spectral data,and is required to identify more impurity spectral lines for impurity transport research.Impurity spectra of EAST plasmas have also been obtained in the wavelength range of 50–300 nm with relatively high spectral resolution.It is found that the impurity emissions in the edge region are still dominated by low-Z impurities,such as carbon,oxygen,and nitrogen,albeit with the application of fulltungsten divertors on the EAST tokamak.

Laser-induced breakdown spectroscopy as a method for millimeter-scale inspection of surface flatness

A non-contact method for millimeter-scale inspection of material surface flatness via Laser-Induced Breakdown Spectroscopy(LIBS)is investigated experimentally.The experiment is performed using a planished surface of an alloy steel sample to simulate its various flatness,ranging from 0 to 4.4 mm,by adjusting the laser focal plane to the surface distance with a step length of 0.2 mm.It is found that LIBS measurements are successful in inspecting the flatness differences among these simulated cases,implying that the method investigated here is feasible.It is also found that,for achieving the inspection of surface flatness within such a wide range,when univariate analysis is applied,a piecewise calibration model must be constructed.This is due to the complex dependence of plasma formation conditions on the surface flatness,which inevitably complicates the inspection procedure.To solve the problem,a multivariate analysis with the help of Back-Propagation Neural Network(BPNN)algorithms is applied to further construct the calibration model.By detailed analysis of the model performance,we demonstrate that a unified calibration model can be well established based on BPNN algorithms for unambiguous millimeter-scale range inspection of surface flatness with a resolution of about 0.2 mm.

基于Kubelka-Munk双常数理论的涤/黏双组分三色混色纤维配方预测

为了提高原液着色涤/黏双组分混配色打样效率,基于Kubelka-Munk双常数理论模型,选用3种单色(大红、宝兰G、金黄)涤纶短纤维和3种单色(大红、蓝色、黄色)黏胶短纤维为研究对象,以6种单色纤维进行双组分混色,按9种不同混合比例共得到54种三色混色双组分纤维样品。利用测色仪测定混色样的颜色特征参数:反射率(R)、颜色深度(K/S)、明亮度(L)、红绿色度(a)及黄蓝色度(b),利用最小二乘法对数据进行处理;最后对计算混色比例与实际混色比例之间的误差进行评价,以验证Kubelka-Munk双常数理论模型在双组分混配色中的适用性。结果表明,54种样品的色差均在1.0以下,均值为0.2775,标准差为0.2177,预测比例与实际比例差距较小,红色涤纶与蓝色、黄色黏胶组合的平均比例误差最小,为1.109%,说明其比例预测效果较好,而黄色涤纶与红色、蓝色黏胶组合的平均色差最小,为0.1721,说明其颜色预测较好。

Quantifying the chemical composition of weathering products of Hainan basalts with reflectance spectroscopy and its implications for Mars

With the development of the hyperspectral remote sensing technique,extensive chemical weathering profiles have been identified on Mars.These weathering sequences,formed through precipitation-driven leaching processes,can reflect the paleoenvironments and paleoclimates during pedogenic processes.The specific composition and stratigraphic profiles mirror the mineralogical and chemical trends observed in weathered basalts on Hainan Island in south China.In this study,we investigated the laboratory reflectance spectra of a 53-m-long drilling core of a thick basaltic weathering profile collected from Hainan Island.We established a quantitative spectral model by combining the genetic algorithm and partial least squares regression(GA-PLSR)to predict the chemical properties(SiO2,Al2O3,Fe2O3)and index of laterization(IOL).The entire sample set was divided into a calibration set of 25 samples and a validation set of 12 samples.Specifically,the GA was used to select the spectral subsets for each composition,which were then input into the PLSR model to derive the chemical concentration.The coefficient of determination(R2)values on the validation set for SiO2,Al2O3,Fe2O3,and the IOL were greater than 0.9.In addition,the effects of various spectral preprocessing techniques on the model accuracy were evaluated.We found that the spectral derivative treatment boosted the prediction accuracy of the GA-PLSR model.The improvement achieved with the second derivative was more pronounced than when using the first derivative.The quantitative model developed in this work has the potential to estimate the contents of similar weathering basalt products,and thus infer the degree of alteration and provide insights into paleoclimatic conditions.Moreover,the informative bands selected by the GA can serve as a guideline for designing spectral channels for the next generation of spectrometers.

Initial measurement of ultrafast charge exchange recombination spectroscopy on the EAST tokamak

Ultrafast charge exchange recombination spectroscopy(UF-CXRS)has been developed on the EAST tokamak(Yingying Li et al 2019 Fusion Eng.Des.146522)to measure fast evolutions of ion temperature and toroidal velocity.Here,we report the preliminary diagnostic measurements after relative sensitivity calibration.The measurement results show a much higher temporal resolution compared with conventional CXRS,benefiting from the usage of a prismcoupled,high-dispersion volume-phase holographic transmission grating and a high quantum efficiency,high-gain detector array.Utilizing the UF-CXRS diagnostic,the fast evolutions of the ion temperature and rotation velocity during a set of high-frequency small-amplitude edgelocalized modes(ELMs)are obtained on the EAST tokamak,which are then compared with the case of large-amplitude ELMs.

Rapid and real-time analysis of multi-component dissolved gas in seawater by Raman spectroscopy combined with continuous gas-liquid separator

Rapid and sensitive detection of dissolved gases in seawater is quite essential for the investigation of the global carbon cycle.Large quantities of in situ optical detection techniques showed restricted measurement efficiency,owing to the single gas sensor without the identification ability of multiple gases.In this work,a novel gas-liquid Raman detection method of monitoring the multi-component dissolved gases was proposed based on a continuous gas-liquid separator under a large difference of partial pressure.The limit of detection(LOD)of the gas Raman spectrometer could arrive at about 14 ml·L^(-1)for N_(2)gas.Moreover,based on the continuous gas-liquid separation process,the detection time of the dissolved gases could be largely decreased to about 200 s compared with that of the traditional detection method(30 min).Effect of equilibrium time on gas-liquid separation process indicated that the extracted efficiency and decay time of these dissolved gases was CO_(2)>O_(2)>N_(2).In addition,the analysis of the relationship between equilibrium time and flow speed indicated that the decay time decreased with the increase of the flow speed.The validation and application of the developed system presented its great potential for studying the components and spatiotemporal distribution of dissolved gases in seawater.