Determination of temperature and emissivity of opaque heated bodies via thermal radiation spectrum: simulation of measurements in spectral window

Computer simulation of emitted radiation intensity spectrum of tantalum object was carried out. Simulation measurements occurred in a narrow spectral window, which moved along the spectrum with the given step. In this way, spectral ranges at which the dependence of the emissivity (or its logarithm) on the wavelength is the simplest and fairly accurate, in particular linear, were sought for. In the case of successful search for the specified spectral range, the required temperature was determined in the spectral window with the least squares technique. If the emissivity (or its logarithm) is linearly dependent on the wavelength then the alternative estimation of the true temperature is possible. In this case, the required temperature is determined via the change of the convexity of the spectral emissivity dependence at selection of its numerical value from the values lower than the true temperature value to the values higher than the true temperature value. This approach is simple, does not require solution of the system of equations and can significantly narrow temperature range to which the true temperature belongs.     

整个生育期玉米叶片SPAD高光谱预测模型研究

以两年完整生育期玉米田间试验为基础,利用便携式地物光谱仪和叶绿素仪(SPAD-502)分别测定了叶片高光谱数据和叶绿素含量(SPAD),在两者相关分析的基础上,选取多种光谱参数分别构建了每年的叶片SPAD预测模型,并对模型进行了详细的验证和评价。结果表明：两年间叶片光谱反射率及其一阶导数的平均值曲线差别很小;两年间叶片SPAD与光谱反射率及其一阶导数的相关系数曲线的敏感区域基本相同;以一阶导数为光谱参数构建的预测模型效果不稳定;以LCI和DSI(R_550附近,R_680附近)和DSI(R_680附近,R_710附近)构建的预测模型效果良好,能有效预测玉米叶片SPAD。     

Plasmonic rainbow rings induced by white radial polarization

This Letter presents a scheme to embed both angular/spectral surface plasmon resonance (SPR) in a unique far-field rainbow feature by tightly focusing (effective NA=1.45) a polychromatic radially polarized beam on an Au (20 nm)/SiO2 (500 nm)/Au (20 nm) sandwich structure. Without the need for angular or spectral scanning, the virtual spectral probe snapshots a wide operation range (n=1-1.42; λ=400-700 nm) of SPR excitation in a locally nanosized region. Combined with the high-speed spectral analysis, a proof-of-concept scenario was given by monitoring the NaCl liquid concentration change in real time. The proposed scheme will certainly has a promising impact on the development of objective-based SPR sensor and biometric studies due to its rapidity and versatility.     

Spectral analysis of a laser beam

The formulas of the dependence of the spectral laser power distribution and its spectral half-width on the physical parameters of its laser active medium are derived. In addition it is found that, if the gain line profile has a Lorentzian or Gaussian distribution, the spectral laser power distribution is of a Lorentzian profile. The spectral halfwidth of the laser beam in both cases are slightly different form each other. For a general gain line profile, the spectral laser power distribution behaves as a differential form like that of the gain line profile.The spectral halfwidth of He/Ne laser beam having powers (0·5 mW, 1·0 mW, 3·0 mW and 50 mW) and that of their longitudinal modes, the laser gain factor and the difference between the population atomic densities of the upper and lower energy levels for the laser line transition are experimentally determined.     

背景扣除和强度校正对激光诱导等离子体光谱参数的影响

激光诱导击穿光谱技术以其无需样品预处理、分析速度快、能实现多元素同时检测和远程分析等优点已经被广泛应用于诸多领域的物质成分定性或定量分析。该技术的理论基础是激光诱导等离子体。对等离子体光谱参数(如光谱谱线强度、等离子体温度等)的准确测量是利用该技术进行定性或定量分析的前提条件。实际的实验系统中,由于仪器本身固有的性能限制,会造成采集光谱信号的失真,从而限制等离子体光谱参数的精确测量或计算。为了克服仪器固有性能的影响,分析了实验系统所用中阶梯光栅光谱仪和传输光纤的固有性能缺点对光谱信号背景噪声和元素谱线绝对强度的影响,然后采用剥峰法对光谱信号中存在的锯齿状背景噪声进行扣除,利用辐射定标光源的标准光谱数据对谱线绝对强度进行校正,并对比了背景扣除和强度校正对等离子体谱线强度和等离子体温度的影响,实验表明谱线强度校正对合金钢等离子体380 nm以下的光谱信号具有较大影响,通过背景扣除和强度校正后,等离子体温度由13 401.75 K降低至8 980.72 K,玻尔兹曼平面法求解等离子体温度的拟合决定系数由0.60提高至0.91。因此在光谱数据处理之前对测量光谱进行背景扣除和强度校正是十分必要的,为提供可靠地光谱数据进行物质成分定性或定量分析奠定了基础。     

Quantitative Estimation of Phytoplankton Species in Freshwater by Two Step Linear Regression Analysis Using Spectral Absorption Method

We proposed a passive method to distinguish and to estimate density of the Cyanobacteria (Cyanophyceae) in a mixed population by measuring the spectral absorption of sample waters, based on two step linear regression analysis. Natural freshwater usually contains a few species of algae and dissolved organic carbon (DOC). In the experiment, we picked out four typical algal groups characterized by their own colors, Cyanophycaeae or blue-green alga, Chlorophyceae or green alga, and Bacillariophyceae and Dinophyceae or brown algae. In the first step, for each of the pure sample waters which contained only one of these elemental substances, dependence of spectral characteristic on its density was determined using simple linear regression analysis. Resultant spectral characteristics which we call gradient vectors were used to estimate spectral absorption of mixed sample waters containing the four elementary algae and DOC by multiple linear regression analysis. This method offers new perspectives for identification and estimation of density of blue-green algae and other unialgal species in a mixed population.     

Incipient nodal pairing in planar d-wave superconductors

The possibility of a second pairing transition d --> d + is ( d + id') in planar d-wave superconductors which occurs in the absence of external magnetic field, magnetic impurities, or boundaries is established in the framework of the nonperturbative phenomenon of dynamical chiral symmetry breaking in the system of (2+1)-dimensional Dirac-like nodal quasiparticles. We determine the critical exponents and quasiparticle spectral functions that characterize the corresponding quantum-critical behavior and discuss some of its potentially observable spectral and transport features.     

Indication of the Expression of Transgene in Rice Plant Based on Hyperspectral Remote Sensing Technique Ⅱ——Growth Monitoring of Samples in the Contrast Experiment

Since the complication of monitoring and evaluating the problems about the transgenic expression and its impacts on the receptor in the transgenic crop breeding and other relevant evaluated works, the authors in the present work tried to assess the differences of spectral parameters of the transgenic rice in contrast with its parent group quantitatively and qualitatively, fulfilling the growth monitoring of the transgenic samples. The spectral parameters (spectral morphological characteristics and indices) chosen are highly related to internal or external stresses to the receipts, and thus could be applied as indicators of biophysical or biochemical processes changes of plant. By ASD portable field spectroradiometer with high-density probe, fine foliar spectra of 8 groups were obtained. By analyzing spectral angle and continuum removal, the spectral morphological differences and their locations of sample spectra were found which could be as auxiliary priori knowledge for quantitative analysis. By investigating spectral indices of the samples, the quantitative differences of spectra were revealed about foliar chlorophyll a+b and carotenoid content. In this study both the spectral differences between transgenic and parent groups and among transgenic groups were investigated. The results show that hyperspectral technique is promising and a helpful auxiliary tool in the study of monitoring the transgenic crop and other relevant researches. By this technique, quantitative and qualitative results of sample spectra could be provided as prior knowledge, as certain orientation, for laboratory professional advanced transgenic breeding study.     

Noninvasive determination of spectral depth of light penetration into skin

A noninvasive method for determining the spectral depth of light penetration into the skin has been developed. It is based on measuring fluxes of radiation reflected from the skin in N _Λ ≥ 3 narrow or wide spectral parts and spectral analysis thereof using the regression approach to solving ill-posed inverse problems. The possibility of estimating the spectral depth of light penetration into skin by skin images in three wide spectral parts (red, green, and blue) is demonstrated. Errors of the method are estimated under conditions of general variability of structural-morphological skin parameters, and its resistance to errors of optical measurements is analyzed.     

Wavelength and time evolution of multiple stimulated Raman spectra in CCl4 excited by an intense picosecond laser pulse

By focussing a Nd³⁺ YAG laser beam or its second harmonic into liquid CCl₄, many rather narrow bands are generated, both on the Stokes and the anti-Stokes sides of the pump. The spectral interval between consecutive bands (or pump) ranges from 460 to 400 cm^-1. The time evolution of the bands shows that their life-times decrease steadily as their spectral distance to the pump increases.     

Generalized transfer function: A simple model applied to active single-mode microring resonators

The spectral properties of an active single-mode microring resonator are investigated in the frame of the generalized transfer function (GTF) approach, as derived from extended scattering and/or transfer matrix formalism. Spontaneous emission, looked upon as the driving source of the radiation, is described in a semi-classical way in the spectral domain. The internal and emitted fields are filtered into the resonance modes of the whole structure. The generalized transfer function expresses the spectral density of internal saturating intensity and includes all essential mechanisms at work in a laser oscillator: gain, losses and sources. The active zone is saturated through amplified spontaneous emission (ASE), integrated over its whole spectral range. Continuously valid across threshold, the method enables one to derive in a simple way the main steady-state properties of the laser oscillation, with the pumping rate as the only external parameter.     

集成光波导静态傅里叶变换微光谱仪分辨率倍增方法

研究了铌酸锂波导静态傅里叶变换微光谱仪分辨率的影响因素, 并在此基础上提出了一种采用端面反射铌酸锂波导结构提高微光谱仪光谱分辨率的方法. 该方法容许在减小铌酸锂波导静态傅里叶变换微光谱仪尺寸的同时, 使两干涉臂间最大光程差增大1倍, 从而使其光谱分辨率实现倍增. 采用商业化铌酸锂波导电光调制器构建了一个傅里叶变换光谱仪原理样机, 并对样机在不同波长下的光谱分辨率进行了测量, 结果指出对调制器加载端面反射结构后获得的光谱分辨率是加载端面反射结构前的2倍, 与理论分析结果完全一致. 这种光波导端面反射结构制作工艺简单, 易于实现, 是一种提高集成光波导静态傅里叶微光谱仪分辨率的有效手段.     

Spectral sharpness and vowel dissimilarity

The effect of sharpening or smoothing the spectral envelopes of synthetic vowel-like sounds on the dissimilarities perceived among these sounds was investigated by means of triadic comparisons. When a spectral envelope (dB on a log-frequency scale) is considered the sum of a series of sinusoidal spectral modulations (or ripples) of different densities (the ripple spectrum), spectral sharpening or smoothing can be described as an amplification or attenuation of a part of the original ripple spectrum. For a set of nine sounds comprising different degrees of spectral sharpening of a single vowel, the perceived dissimilarities were found to be dominated by a specific part of the ripple spectrum, i.e., by spectral modulations with a density of about 2 ripples/oct. The possible role of lateral suppression in relation to this dominant region is discussed. For a set of 18 sounds comprising six vowels, each in three different versions (sharpened, normal, or smoothed), the dissimilarities were found to be determined mainly by the global shape of the spectral envelopes, i.e., by spectral modulations up to about 1.5-2 ripples/oct. Details of the spectral envelope (including the region of 2 ripples/oct where lateral suppression is effective) appear to be of minor influence on vowel dissimilarities.     

Spectral densities and nuclear spin relaxation in solids

We investigate the properties of ten spectral densities relevant for nuclear spin relaxation studies in solids. This is preceded by a brief review of nuclear spin relaxation in solids which includes a discussion of the appropriate spin-dependent interactions and the various relaxation rates which can be measured. Also, the link between nuclear spin relaxation and dielectric relaxation is discussed. Where possible and/or appropriate each of the spectral densities is expressed as a continuous distribution of Bloembergen-Purcell-Pound (or Debye) spectral densities 2ξ /(1 + ξ² ω²) for nuclear Larmor angular frequency ω and correlation time ξ. The spectral densities are named after their originators or the shape of the distributions of correlation times or both and are (1) Bloembergen-Purcell-Pound or δ-function, (2) Havriliak-Negami, (3) Cole-Cole, (4) Davidson-Cole, (5) Fang, (6) Fuoss-Kirkwood, (7) Bryn Mawr, (8) Wagner or log-Gaussian, (9) log-Lorentzian, and (10) Fröhlich or energy box. The Havriliak-Negami spectral density is related to the Dissado-Hill theory for dielectric relaxation. The spectral densities are expressed in a way which makes them easy to compare with each other and with experimental data. Many plots of the distributions of correlation times and of the spectral densities vs. various correlation times characterizing the distributions are given.     

基于特征约束的谱线自动提取

已有的谱线自动提取方法均采用整体阈值约束或局部阈值约束进行谱线识别,因而谱线提取结果中普遍存在谱线遗失或伪谱线过多的缺点。文章在谱线识别时加入了2个特征约束,第1个特征约束是： 谱线线心的强度必须大于局部阈值和整体下阈值,并且如果某一点的强度大于整体上阈值,则可认为在该点存在谱线;第2个特征约束是： 谱线的起始波长和终止波长处的强度必须小于谱线线心的强度。这2个特征约束使得该文的谱线提取效果较之已有方法有显著的提高。通过实验对该文方法和已有的方法进行了比较,实验结果充分体现了该文方法的优势。     

Diagnostics of femtosecond laser pulses based on generation of nonlinear-dispersive similariton

We propose and test experimentally a method, alternative to the autocorrelation technique, for determination of the duration of femtosecond laser pulses. The method is based on generation of nonlinear-dispersive similariton in a passive optical fiber (without gain) and measuring its spectral width (or duration) determined by the power of the initial pulse.     

An Overview of the Use of Yttrium for Internal Standardization in Inductively Coupled Plasma–Atomic Emission Spectrometry

Abstract

Internal standardization is a widely used method for compensating nonspectral interference in inductively coupled plasma (ICP) spectrometry. Emphasis is given on the choice of the suitable element and its specific spectral line as an efficient internal standard. This choice is the result of multi-variable evaluations and analytical applications. In inductively coupled plasma–atomic emission spectrometry (ICP-AES) and other spectrometric techniques several spectral lines of the same or different elements have been evaluated as potential internal standards. Yttrium spectral lines fulfill certain prerequisites and they are favored by a large number of researchers. In our discussed review, we present several reports of ICP-AES techniques that employ yttrium as the internal standard. These reports are classified according to specific sample origin and aim of the research.     

Survival Probability¶in Rank-One Perturbation Problems

A finite complex Borel measure μ on the unit circle or on the real line is called Rajchman if its Fourier coefficients tend to 0 as n→∞. In quantum dynamics the self-adjoint operators (Hamiltonians) whose spectral measures are Rajchman correspond to the systems having certain scattering properties. In this paper we study how a small perturbation of the operator can affect the Rajchman property of its spectral measure. Our approach is based on the notion of the local symmetry of measures. Received: 17 April 2001 / Accepted: 18 June 2001     

可见光-近红外、中红外光谱的土壤有机质组分反演

土壤有机质是土壤肥力的物质基础,其含量的高低是评价土壤肥力的重要标志。土壤有机质组分根据其溶解性可分为胡敏素(HM)、胡敏酸(HA)、富里酸(FA),不同组分的肥力特性差异显著,因此,土壤有机质组分数据可更加全面、客观的反映土壤肥力状况。传统土壤土壤有机质及组分的测定工序繁杂,效率低下且时效性差,大量研究表明高光谱技术能有效提高土壤属性的检测效率并降低测试成本,但关于可见光-近红外、中红外光谱检测土壤有机质组分的报道鲜见。为了探索中红外光谱及可见光-近红外-中红外组合光谱对土壤有机质组分检测的可行性,并对比有机质单一光谱模型与有机质不同组分的组合光谱模型的预测精度,以南疆地区农田土壤为例,在阿克苏及和田地区共采集93个土样,进行有机质、胡敏素、胡敏酸、富里酸含量及光谱数据的测定。其次,利用可见-近红外(VNIR)、中红外(MIR)及其组合光谱(VNIR-MIR)三种光谱数据集,采用偏最小二乘(PLSR)、支持向量机(SVM)、随机森林(RF)三种建模方式对土壤有机质、胡敏素、胡敏酸、富里酸含量进行组合模型分析预测。结果表明：(1)土壤有机质及各组分均与光谱反射率有较好的相关性,土壤有机质及组分在MIR谱段的特征波段数量明显多于VNIR谱段。(2)有机质最优预测模型的模式为VNIR-MIR-RF,该模型的决定系数R2为0.90;胡敏素与胡敏酸最优预测模型的模式均为VNIR-RF模型,R2均为0.92;富里酸最优预测模型的模式为MIR-RF模型,R2为0.94。(3) 基于胡敏素、胡敏酸和富里酸的有机质组合光谱模型的预测精度明显高于有机质单一光谱模型,两种模型的R2分别为0.93和0.90。实现了土壤有机质组分的高效快速反演,且基于有机质组分的组合模型提高了土壤有机质预测精度,为南疆地区大尺度土壤肥力的鉴定与精准施肥提供重要的参考价值。