基于太阳漫射板的星上定标方法研究

基于太阳漫射板的星上定标方法是一种具有高精度、高频次、高效率等优点的独立定标方法,是目前提高我国遥感定标精度的重要手段之一。文章阐述了基于太阳漫射板的星上定标原理、方法及实现过程,建立了空间辐射标准,同时给出了星上反射率定标物理模型。分析定标物理模型发现,影响星上定标不确定度最主要的因素是太阳漫射板BRDF实时量值的确定。为此,首先介绍了星上定标时机的选择,根据所确定定标时机的太阳照明角度对太阳漫射板在实验室相应入射角度下的BRDF进行了测量。通过对太阳漫射板从制作完成到星上使用寿命终结整个过程中各阶段的BRDF量值的监测及修正,确保太阳漫射板定标时刻可为遥感器提供精确已知的辐射输入,实现遥感器全寿命期的高精度星上定标。最后,结合国内对定标模型中相关参数项测量的不确定度水平,按照测量不确定度B类评定的方法对基于太阳漫射板星上定标不确定度进行了预估,可实现星上反射率定标不确定度优于2.03%,绝对辐射定标方法不确定度优于2.04%。     

Multivariate Calibration with the Delaunay Triangulation Method: Definition of the Calibration Domain

The Delaunay triangulation (DT) method for multivariate calibration is a topological multivariate calibration method. In this paper, we present methods for the definition of the calibration domain. Outliers in the calibration set must be found and deleted and clusters detected. When clusters are found, it may be advantageous to make separate local models. Two methods are proposed. The first, called the DT calibration domain algorithm, is based on finding a kernel of samples that is then extended according to local rules. An alternative is to first eliminate gross outliers and then divide the data set in clusters, if such clusters exist, with Dbscan, a density‐based clustering method. The cluster(s) is (are) then used as kernels(s) and extended with the same rules as the DT calibration domain algorithm to develop DT models for each cluster. The two methods and some of the difficulties that can be encountered with them are demonstrated with three simulated data sets and tested with three real NIR data sets (one agricultural, one food, and one industrial). It is shown that the methods perform well and are at least comparable in prediction performance to partial least squares (PLS).     

氢原子光谱实验中里德堡常数的估计方法探讨

考察了氢原子光谱实验中估计里德堡常数的三种可能方法。我们的分析表明：由于标准差较大,且标准差不会随测量的谱线数趋于无穷而趋于零,采用所谓的斜率估计法是不太妥当的。虽然采用所谓截距估计法会使标准差大大减少,而且,标准差会随所测量的谱线数趋于无穷而趋于零。但RH的最佳估计值应该以波数为纵坐标y,（1／2^2—1／m^2）为横坐标x,作y=kx形式的拟合得到。     

Smooth decomposition of random fields

The Smooth Decomposition (SD) method was introduced to analyze discrete-time signals and generalized to continuous-time vector-valued random processes. The SD is obtained solving a generalized eigenproblem defined from the covariance matrix of the random process and the covariance matrix of the associated time-derivative random process which defines the decomposition basis. This paper presents a new extension of the SD to continuous-time and continuous-space vector-valued random processes, classically named random fields. This generalization is a major step since one now deals with operators in infinite-dimensional spaces and not matrices. It is shown that in this new context the main properties of the SD are preserved. Applied to the responses of randomly excited continuous mechanical systems, the SD can be considered as an output-only analysis tool. Moreover, two natural orderings are defined to classify the decomposition terms which permit to interpret the SD in terms of modal analysis or in terms of Karhunen–Loève analysis.     

用CCSD(T)方法计算基态SH和SD的光谱常数(英文)

利用CCSD(T)方法和系列相关一致基cc-pVXZ及aug-cc-pVXZ(X=D,T,Q,5)对SH和SD分子的基态平衡几何,谐振频率和离解能进行了优化计算.利用优选出的CCSD(T)/aug-cc-pV5Z方法对SH和SD的基态进行单点能计算,并将计算结果拟合成了Murrell-Sorbie函数.利用得到的解析势能函数,计算了SH和SD的其余3个光谱常数(ω_ex_e,α_e和B_c),结果表明:除SD的ω_ex_e值外,其余结果均与实验值符合得相当好,但计算得出的ω_ex_e值与推导出的值25.134 cm~(-1)符合得很好.     

Lattice Boltzmann方法模拟多孔介质Klinkenberg效应

格子Boltzmann数值模拟方法是研究复杂的多孔介质结构特别是Klinkenberg效应的有效方法之一，对处理复杂边值问题尤其有效，用格子Boltzmann方法研究了气流穿越多孔介质问题，并将数值计算结果与实验结果进行了比较，结果表明格子Boltzmann方法是数值模拟气流穿越多孔介质问题的有效方法之一。     

New Method for Spin Assignment of Superdeformed Rotational Bands

A new method for spin assignment of superdeformed rotational bands is proposed and it turns out to be more efficient than other methods used before. The application is made to superdeformed bands in A～190 and A～150 mass regions. By analyzing the standard deviation of the fixed gamma-ray energies of an SD band in different methods, the advantage of the present method over the other methods is presented. This method brings then a comprehensive interpretation of the methods used in spin assignment.     

Direct measurement of subglottic pressure and laryngealresistance in normal subjects and in spasmodic dysphonia

This study tested the accuracy of indirect methods of measurementof laryngeal airway resistance in normal subjects and in spasmodic dysphonia (SD). The indirect method assumes that subglottic air pressure remains constant during the voiced segment of a syllable. In this study subglottic air pressure was directly measured via puncture of the cricothyroid membrane in seven normal subjects and seven subjects with SD. The true laryngeal airway resistance was calculated and compared with airway resistance measured using indirect techniques based on intraoral air pressure. In five of the seven normal subjects, subglottic air pressure did not remain constant during the voiced segment. As a result, the error produced using indirect method of calculating average laryngeal resistance for the normal subjects varied from −44% to +50%. For SD subjects the error ranged from −49% to +22%. In general, the indirect technique over-estimated laryngeal airway resistance in normal subjects and underestimated the resistance in subjects with SD.     

The decay-out of superdeformed bands in theA=190 region: What have we learned?

One-step decay transitions linking the superdeformed (SD) bands 1 and 3 in¹⁹⁴Hg to yrast levels are discussed. Inter-band transitions between bands 1 and 3 have also been identified. For the first time, the spin, parity and excitation energy have been determined for two SD bands in the same nucleus. The low excitation energy of the excited band supports the view that it is based on an octupole excitation. It is believed that Porter-Thomas fluctuations play a major role in determining the strength of the one-step transitions as suggested by the fact that only one other SD band has been linked in theA=190 mass region (¹⁹⁴Pb) at the present time. When Porter-Thomas fluctuations prevent the observation of one-step or two-step linking transitions, as e.g. in the case of¹⁹²Hg, the analysis of the quasi-continuous part of the decay-out spectrum provides an alternative method for the determination of the excitation energy and spin of an SD band. This method is discussed in detail.     

Gamma decay of the giant dipole resonance and feeding of superdeformed states in 143Eu

The γ decay of the giant dipole resonance (GDR) built on excited nuclear states has been measured in coincidence with the low-energy γ discrete transitions for the nucleus ¹⁴³Eu. The reaction used was ¹¹⁰Pd(³⁷Cl, 4n)¹⁴³Eu at a beam energy of 165 MeV. The EUROBALL spectrometer (for the measurement of discrete γ transitions) coupled with the HECTOR array (for high-energy γ-ray detection) has been used. The high-energy γ-ray spectrum in coincidence with superdeformed (SD) discrete transitions of ¹⁴³Eu shows an “excess” between 9–12 MeV if compared with the one associated to cascades which do not pass through the SD configurations. Such an “excess” is in the energy region where one expects the low-energy component of the GDR strength function built on a SD state. The measured intensity can be reproduced by the statistical model assuming that the superdeformation survives only few MeV above the yrast line. A similar and consistent scenario has also been obtained by comparing the high-energy γ-ray spectra of ¹⁴³Eu in coincidence with its spherical (which is fed by the SD configuration) and its triaxial configuration (which is bypassed by the decay of the SD states).     

Analysis and Discussion About How to Determine the Variatiotnal Parameters in the Variational-Cumulant Expansion

Four methods of determining the variational parameter in the varia tional-cumulant expansion (VCE) are studied on the 2-dimensional Ising model. A comparison with the exact result shows that the main-variation method is the best one at low temperature, the completevariational method is better than others at high temperature, the accumulation-point method is the best one to approximate the intermediate coupling region, and each of the methods is analyzed from the original formulas or conjectures. Some suggestions are given in order to get optimal results. The VCE is also analyzed Gom a point of view of symmetry breaking for the first time.     

Usefulness of MRI for the pre-operative evaluation of the pulmonary arteries in Tetralogy of Fallot

Adequate pre-operative evaluation of patients with Tetralogy of Fallot (TF) includes cine-angiography to delineate the pulmonary vasculature and the coronary artery anatomy and to demonstrate the presence of multiple ventricular septal defects (VSDs). All other information is obtained from color-Doppler-echocardiography. Magnetic resonance imaging (MRI), using the spin-echo sequence and cine-angiography was employed on 18 patients with TF, four of whom had aorto-pulmonary shunts. Mean age at MRI was 12.9 m (SD 2.3 m) and 14.3 m (SD 2.8 m) at cine-angiography. To compare MRI and cine-angiography we measured the ascending aorta, the main, the left and right pulmonary arteries and each structure at three levels. Diagnostic agreement between the two imaging methods was found if, for each modality, one of the three measurements in one structure differed by more than 40% from the other two measured in case of a local stenosis, and the diameter of the main pulmonary artery was less than 60% of the aorta to diagnose hypoplasia of the main pulmonary artery. There was close agreement between cine-angiography and MRI. With regard to the intracardiac anatomy, MRI was superior to color-Doppler-echocardiography in the depiction of aortic override and of right ventricular hypertrophy. In three cases local stenoses in the pulmonary arteries were detected by MRI and cine-angiography. Hypoplasia of the main pulmonary artery was detected by MRI in six patients and by cine-angiography in five patients. Cine-angiography missed one case of hypoplasia. In the remaining 11 patients normal findings were found by MRI and cine-angiography. For the demonstration of shunts, gradient-recalled-echo MRI is expected to give better results than the spin-echo sequence which depicted two out of four shunts in this series. Cine-angiography can be substituted by MRI in delineating the pulmonary arteries. New developments in MRI indicate the feasibility of delineating the coronary arteries.     

Comparison of the light scattering methods using the spherical basis

A comparative analysis of the widely known methods for solving the problem of light scattering by nonspherical particles—of the method of separation of variables (MSV), of the extended boundary condition method (EBCM), and the point-matching method (PMM), which use the spherical wave functions as a basis for the expansions of the fields—is carried out. In the scientific literature, these methods have been analyzed independently of one another in spite of their evident similarity: The same expansion coefficients are determined from similar set of equations and all optical characteristics are calculated with the same formulas. The ranges of applicability of the methods for dielectric spheroids and Chebyshev particles are studied in the same manner. It was found that, when considering the far-field zone, theoretical conditions of mathematical correctness of the EBCM and the MSV, apparently, differ fundamentally, although, as was shown, the methods themselves are extremely closely related. The performed numerical calculations suggest that the EBCM is preferable for spheroids, the MSV is preferable for Chebyshev particles, and the PMM, which is the most time-consuming method, gives satisfactory results in many cases when two other methods are inapplicable. Since the methods supplement one another well and their programs differ only in several tens of operators, we propose combining these methods within the framework of one universal program.     

利用叶片正反面反射光谱估算叶绿素含量

叶片叶绿素含量的快速无损估算方法对研究植被生长和环境胁迫都具有重要意义。传统叶绿素光谱估测方法,主要是基于叶片正面光谱信息。而在实际遥感观测中,传感器不仅会接收植被叶片正面光谱信息,植被叶片反面光谱信息也会同时被接收。该研究主要目的是找到在同时考虑叶片正反面光谱信息时也能精确估算叶片叶绿素含量的分析方法。对比了简单差值植被指数(SD),简单比值植被指数(SR),归一化植被指数(ND)与偏最小二乘(PLS)建模方法,并对检验样本集进行了精度比较。结果发现用PLS方法估算两种植被正反面叶片的叶绿素含量与真实叶片叶绿素含量的拟合精度更高,R2为0.91,RMSE为5.21 μg·cm-2。因此可以认为PLS方法在同时考虑植被叶片的正反面光谱信息时对植被叶片叶绿素含量的估算更准确。     

近红外光谱法快速测定工作场所莠去津浓度的研究

莠去津是一种广泛使用的除草剂,我国是其原药的主要生产国家。为加强工作场所莠去津暴露浓度的检测力度,保障职业接触工人身体健康,研究开发工作场所莠去津浓度的现场快速检测方法具有重要现实意义。利用自行组装的便携式近红外光谱仪,采集了实验室配置的浓度为10～1 000 mg·L-1的莠去津溶液样本光谱,并比较了多元散射校正、变量标准化、一阶导数方法、二阶导数方法及其组合等光谱预处理方法,竞争自适应重加权采样变量选择法和遗传算法等变量选择方法,偏最小二乘算法和支持向量机等回归方法对近红外光谱模型分析精度的影响。研究发现一阶导数是最佳光谱预处理方法;遗传算法优选的光谱变量表现优于竞争自适应重加权采样变量选择法;支持向量机模型表现优于偏最小二乘模型。基于遗传算法选择的16个光谱变量建立的支持向量机模型分析精度最高,其定标决定系数、验证决定系数、定标均方差、预测均方差和相对分析误差(成分浓度的标准偏差与预测均方差的比值)分别为1,0.99,17.54 mg·L-1,25.42 mg·L-1和11.43,有望应用于工作场所莠去津浓度的实际检测中。该研究探讨了近红外光谱法检测工作场所莠去津浓度的可行性,相关结果对于未来类似工作的开展具有重要参考价值。     

An optimized spectral difference scheme for CAA problems

In the implementation of spectral difference (SD) method, the conserved variables at the flux points are calculated from the solution points using extrapolation or interpolation schemes. The errors incurred in using extrapolation and interpolation would result in instability. On the other hand, the difference between the left and right conserved variables at the edge interface will introduce dissipation to the SD method when applying a Riemann solver to compute the flux at the element interface. In this paper, an optimization of the extrapolation and interpolation schemes for the fourth order SD method on quadrilateral element is carried out in the wavenumber space through minimizing their dispersion error over a selected band of wavenumbers. The optimized coefficients of the extrapolation and interpolation are presented. And the dispersion error of the original and optimized schemes is plotted and compared. An improvement of the dispersion error over the resolvable wavenumber range of SD method is obtained. The stability of the optimized fourth order SD scheme is analyzed. It is found that the stability of the 4th order scheme with Chebyshev–Gauss–Lobatto flux points, which is originally weakly unstable, has been improved through the optimization. The weak instability is eliminated completely if an additional second order filter is applied on selected flux points. One and two dimensional linear wave propagation analyses are carried out for the optimized scheme. It is found that in the resolvable wavenumber range the new SD scheme is less dispersive and less dissipative than the original scheme, and the new scheme is less anisotropic for 2D wave propagation. The optimized SD solver is validated with four computational aeroacoustics (CAA) workshop benchmark problems. The numerical results with optimized schemes agree much better with the analytical data than those with the original schemes.     

Spectral difference method for compressible flow on unstructured grids with mixed elements

This paper presents the development of a 2D solver for inviscid and viscous compressible flows using the spectral difference (SD) method for unstructured grids with mixed elements. A mixed quadrilateral and triangular grid is first refined using one-level h-refinement to generate a quadrilateral grid while keeping the curvature of boundary edges. The SD method designed for quadrilateral meshes can subsequently be applied for the refined unstructured grid. Results obtained with the SD method for both inviscid and viscous compressible flows compare well with analytical solutions and other published results.     

Multiple spin-echo MR imaging of the body: image contrast and motion-induced artifact

For a given TR and TE, image quality changes when the number of spin echoes obtained is varied. To investigate the importance of this in clinical imaging, a total of 4 patients and 9 volunteers had MRI examinations of the abdomen (n = 7) and/or pelvis (n = 8) which included at least 2 sequences with identical TR (2000 or 2500 ms), TE (80 ms) and other parameters, but with a different series of refocusing pulses. Sequences included single-echo (S), asymmetric and symmetric double-echo (AD and SD) and quadruple-echo (Q) techniques. Image contrast and severity of motion-induced artifact was measured via blind examination by 3 independent MRI radiologists and calculation of signal-difference, signal-difference-to-noise ratios and intensity of motion-induced "ghost artifact." The order of decreasing signal differences was S, SD, AD and Q, and all of three liver lesions were better seen with S than with SD techniques. These observations are consistent with signal loss from cumulative inaccuracies from multiple 180 degrees RF pulses. The order of increasing intensity of ghost artifact was Q, SD, AD and S, consistent with the beneficial motion artifact-reducing effects of even-echo rephasing. Knowledge of these effects of multi-echo imaging allows one to make informed decisions about imaging protocols rather than to simply obtain multiple echoes "because they are free."     

New excited superdeformed bands in heavy Pb nuclei: Clue for an octupole softness near the N = 118 gap at large deformation

We report the identification of six new superdeformed (SD) bands in ^197,198Pb observed with the EUROBALL IV spectrometer. The results are interpreted in the framework of cranked Hartree-Fock calculations with approximate projection on the particle number by means of the Lipkin-Nogami method. A mixing between quasi-particle excitations and an octupole vibration is suggested in the two SD isotopes. We have estimated the ordering of the neutron valence orbitals and confirm indirectly a N = 118 SD gap. Received: 20 December 2000 / Accepted: 24 January 2001     

Psychogenic spasmodic dysphonia: A case study with expert opinions

Spasmodic (spastic) dysphonia (SD) is considered by some to be a neurologic syndrome and by others a symptom complex of multiple etiologies, neurologic and psychogenic. A case of a 26-year-old female psychiatric nurse with psychogenic SD (PSD) is presented. The dysphonia was alleviated within one session of voice therapy. Psychogenic etiology was established by the author, based on three diagnostic criteria—symptom incongruity, symptom reversibility, and symptom psychogenicity. Seven nationally recognized voice experts listened to audio-recorded samples of the patient's pre- and posttherapy voice during conversational speech. The experts agreed that the dysphonia was psychogenic and characterized it as staccato-like speech, effortful phonation, and interrupted flow of speech; six characterized it with intermittent voice arrests (voice stoppages); five with hoarse-harsh voice; and four with waxing and waning, strained-strangled phonation. These are often described as salient features of SD. Nevertheless, the experts disagreed among themselves as to whether the dysphonia was characteristic of SD and should be labeled as such. The author argues that as long as the voice characteristics and pathophysiologic findings that constitute SD are not well delineated, and as long as the diagnosis of SD is based on symptoms alone, patients with psychogenic or poorly understood voice disorders are likely to be misdiagnosed with organic (neurologic) SD and thus subjected to undue medical treatment. The author also argues that the debate over the etiology of SD can be resolved if SD is considered a neurologic syndrome, PSD a nonorganic phonatory disorder that mimics the syndrome, and if the voice symptoms and pathophysiologic characteristics of SD are well defined and agreed on.