Gome ozone profiles retrieved by neural network techniques: A global validation with lidar measurements

Ozone profiles retrieved from Global Ozone Monitoring Experiment (GOME, flying on ERS-2 satellite) spectra from July 1995 to June 2003 by means of 2 independent neural network (NN) schemes have been validated with ozone lidar measurements performed at different stations belonging to the network for the detection of atmospheric composition changes (NDACC). The retrieval and the whole validation have been carried out by using the performances and resources of the European project Enabling Grid for E-sciencE (EGEE) and of a local Grid at the European Space Research Institute of the European Space Agency (ESRIN/ESA). Roughly 1800 collocated profiles have been found, in tropical, mid-latitude and high-latitude regions; for each lidar station the differences between GOME and lidar profiles have been evaluated and the global performance of the proposed NN approaches has been critically discussed. The results indicate the potentialities for obtaining reliable ozone field analysis on global scale, including detailed altitude resolved trend analysis.     

Experimental determination of air-broadening parameters of pure rotational transitions of HNO3: intercomparison of measurements by using different techniques

We report on the air-broadening of the 44_d, 25 ← 44_d, 26, 43_d, 25 ← 43_d, 26, 25_d, 25 ← 24_d, 24, 27_d, 25 ← 27_d, 26, 26_1, 25 ← 26_0, 26, 15_13, 3 ← 14_13, 2, and 27_d, 27 ← 26_d, 26 transitions of HNO₃ at room temperature, which are useful for measurements of nitric acid in the Earth’s atmosphere by microwave limb sounders. In fact, the lines selection was essentially made on the basis of the spectral range requirements of MASTER, a limb sounding instrument managed by ESA. It is well established that the collisional-broadening parameters have a crucial influence on reduction of remote sensing data, but it is also well known that systematic errors make the evaluation of pressure-broadening parameters accuracy difficult. To this purpose, the investigation has been carried out in two different laboratories employing different techniques: the intercomparison allowed us to check the accuracy of the retrieved parameters as well as to estimate the extent of systematic errors affecting them.     

Long-term invariant parameters obtained from 24-h Holter recordings: a comparison between different analysis techniques

Over the last two decades, a large number of different methods had been used to study the fractal-like behavior of the heart rate variability (HRV). In this paper some of the most used techniques were reviewed. In particular, the focus is set on those methods which characterize the long memory behavior of time series (in particular, periodogram, detrended fluctuation analysis, rescale range analysis, scaled window variance, Higuchi dimension, wavelet-transform modulus maxima, and generalized structure functions). The performances of the different techniques were tested on simulated self-similar noises (fBm and fGn) for values of alpha, the slope of the spectral density for very small frequency, ranging from -1 to 3 with a 0.05 step. The check was performed using the scaling relationships between the various indices. DFA and periodogram showed the smallest mean square error from the expected values in the range of interest for HRV. Building on the results obtained from these tests, the effective ability of the different methods in discriminating different populations of patients from RR series derived from Holter recordings, was assessed. To this extent, the Noltisalis database was used. It consists of a set of 30, 24-h Holter recordings collected from healthy subjects, patients suffering from congestive heart failure, and heart transplanted patients. All the methods, with the exception at most of rescale range analysis, were almost equivalent in distinguish between the three groups of patients. Finally, the scaling relationships, valid for fBm and fGn, when empirically used on HRV series, also approximately held.     

4He-stopping power measurements by using ion implantation and backscattering techniques

Experimental results on changes in conductivity of N₂+ and Ar⁺ bombarded thin copper, aluminium and bismuth films are given along with the preliminary observations on photoconductivity of N₂+ bombarded Bi₂O₃ thin films. The performance of a low cost, medium resolution 200 keV ion implantation system, used in the above experiments is also discussed.     

Leaf cuticle topography retrieved by using fringe projection

The combination (often referred to as phase-stepping profilometry, PSP) of the fringe projection technique and the phase-stepping method allowed us to retrieve topographic maps of cuticles isolated from the abaxial surface of leaves; these were in turn sampled from an apple tree (Malus domestica) of the variety Golden Delicious. The topographic maps enabled us to assess the natural features on the illuminated surface and also to detect the whole-field spatial variations in the thickness of the cuticle. Most of our attention was paid to retrieve the highly-resolved elevation information from the cuticle surface, which included the trace (in the order of tens of micrometers) left by ribs and veins. We expect that the PSP application for retrieving the cuticle topography will facilitate further studies on the dispersion and coverage of state-of-the-art agrochemical compounds meant to improve the defending properties of the cuticle. Methodological details are provided below.     

Comparison of carotid vessel wall area measurements using three different contrast-weighted black blood MR imaging techniques

Measuring carotid artery plaque burden from MRI is a reliable method for monitoring regression and progression of atherosclerosis. However, to measure all available images would be very time consuming, and in practice the image quality (IQ) of these images may be inconsistent, which can directly impact the quality of measurement. It is hypothesized that if IQ is comparable among different contrast weighted images, then carotid artery area measurements obtained from different contrast images of the same location will produce identical results. To test this, T1, proton density and T2 weighted images were acquired from ten patients (51 +/- 7 years old). Carotid lumen and vessel wall area was measured using a custom designed software program. The results showed strong agreement evidenced with only small differences on both lumen (mean: 40.5 mm(2)) and wall (mean: 52.6 mm(2)) area measurement among different weighted images. The maximum absolute mean differences are less than 2.7 mm(2) and 4.4 mm(2), and 90(th) percentile of the absolute differences are 5.6 mm(2) and 8.2 mm(2) respectively. In conclusion, different contrast weighted images with high and comparable IQ will yield similar results in lumen and vessel wall area measurement. At each matched location, it is recommended that the image with the highest IQ be used for area measurement.     

Temperature measurements in plasmas generated by using lasers at different intensities

The temperature of laser-generated pulsed plasmas is an important property that depends on many parameters, such as the particle species and the time elapsed from the laser interaction with the matter and the surface characteristics.

Laser-generated plasmas with low intensity (<10¹⁰ W/cm²) at INFN-LNS of Catania and with high intensity (>10¹⁴ W/cm²) in PALS laboratory in Prague have been investigated in terms of temperatures relative to ions, electrons, and neutral species. Time-of-flight (ToF) measurements have been performed with an electrostatic ion energy analyzer (IEA) and with different Faraday cups, in order to measure the ion and electron average velocities. The IEA was also used to measure the ion energy, the ion charge state, and the ion energy distribution.

The Maxwell–Boltzmann function permitted to fit the experimental data and to extrapolate the ion temperature of the plasma core.

The velocity of the neutrals was measured with a special mass quadrupole spectrometer. The Nd:Yag laser operating at low intensity produced an ion temperature core of the order of 400 eV and a neutral temperature of the order of 100 eV for many ablated materials. The ToF of electrons indicates the presence of hot electron emission with an energy of ～1 keV.     

基于不同作用体制的激光引信探测技术

随着激光技术的飞速发展,半导体激光传感器已被广泛应用于近炸引信领域。对目前广泛使用的激光近炸引信体制中的几何截断定距、距离选通定距、脉冲鉴相定距以及伪随机编码定距的原理、特点进行了分析,指出了每种体制的局限性,为应用在具体背景下的激光近炸探测体制的选择提供了一定的参考价值。     

多轴差分吸收光谱仪反演大气NO2的比对试验

为了满足卫星遥感产品地基验证平台中不同仪器观测数据一致性的要求, 2011年9月, 将3台不同设计方案、不同操作方式的多轴差分吸收光谱仪(MAX-DOAS) 集中在中国科学院大气物理研究所香河大气探测综合试验站, 进行了近20天的同步观测测试. 并对所有仪器统一观测方位角, 分别采用相同的紫外、可见光波段的特征吸收带及吸收截面进行NO₂柱浓度的反演试验. 系统的比对分析表明: 3台MAX-DOAS的反演误差大都保持在6%以内, 说明仪器性能良好, 比较稳定; 紫外波段的反演结果略小于可见光波段, 尤其在阴天, 这是由于两波段对分子及气溶胶散射的敏感性不同造成的; 以可见光波段的反演结果为标准, 对紫外波段的反演结果进行系统订正, 订正后的各组数据一致性非常好, 满足卫星大气成分NO₂柱浓度遥感产品不同地基验证站点数据稳定、一致的要求. 关键词： MAX-DOAS 2')" href="#">NO₂ 斜柱浓度 比对试验     

Obtaining three surface-film parameters from two ellipsometric measurements

A powerful approximation method for obtaining the thickness, d, and optical constants, n₂ and k₂, of a thin absorbing film on a known opaque substrate is described. The advantages of the method for certain ellipsometer systems are discussed. Instead of requiring a third measurement, for example the reflectance, |r|, as is often done, the effective reflectance, |r_eff|, is calculated in the two-phase approximation from the measured ellipsometric parameters. This provides the third quantity needed to obtain n₂, k₂ and d. Examples worked out for the systems Ag₂S/Ag and CoO/Co illustrate the accuracy and utility of the method. The technique is shown to be applicable to a wide range of films, roughly $\text{n}{}_2\text{? 2.0}$, k₂ ? 1.0 and $\text{d ? 40}\text{A}\text{?}$ on semiconducting and highly reflecting metal substrates and 2.0 ? n₂ ? 2.7, k₂ ≈ 0.5, and $\text{d ? 10}\text{A}\text{?}$ on less highly reflecting metal substrates. The important systems GeO₂/Ge, SiO₂/Si and Al₂O₃/Al are well within these limits. When the method is used in these ranges, the errors resulting from the approximation are less than those that would be introduced by a measurement of reflectance change on most ellipsometer systems.     

Acoustic parameter measurements by acousto-optic diffraction techniques using a light-beam of one acoustic wavelength width

A method is presented for measuring the Raman-Nath parameter by an acoustically diffracted light-beam of one acoustic wavelength width. The diffraction spectrum obtained is not discrete but broadened continuously because of the width of the light-beam itself. The Raman-Nath parameter can be determined from the intensity measurement at the centre of the diffraction pattern. The acoustic wavelength can also be determined by measuring the light-beam width of one acoustic wavelength at which a beating photocurrent, produced by the positive and negative first-order diffraction components, dies out at the centre of the pattern.     

Band parameters of nickel deduced from optical measurements

The gap Δ between the top of the d↑ band and the Fermi level is deduced from optical measurements on a nickel single crystal and found to be ≈50 meV, in agreement with previous estimates. The interpretation of the optical spectrum also suggests that the spin-splitting ΔE_d ? 0.40 eV and that a spin- splitting still exists at temperatures higher than T_C.     

Spectral measurements of local parameters of plasmas using CCD matrices

The possibility of obtaining local contours of spectral lines of strongly inhomogeneous doubly ionized nitrogen plasma with the help of a system that involves a spectrograph and a megapixel CCD matrix is shown. An automated measuring system based on a CCD matrix is described, and a procedure for processing matrix spectra is presented. The results of the Abel transform of the chord distributions of spectral line intensities of ions with different degrees of ionization are presented. Determined local contours of spectral lines can be used for estimating local temperatures and electron concentrations in strongly ionized spatially inhomogeneous plasmas.     

Displacement measurements in structural elements by optical techniques

Speckle metrology and holographic interferometry (HI) have been used in several civil engineering applications. We present the results obtained by applying speckle photography (SP) to the study of two quadratic shearwalls with different boundary conditions, and the potential of the technique in the study of this kind of structures is described. The analysis of Young's fringes obtained with this technique at certain points on each shearwall provides the whole field of displacement measurements. HI has been used to measure the three components of absolute displacement, verifying that the bulging phenomenon does not affect the in-plane components when the applied load remains on the same plane as the shearwall. A qualitative analysis is carried out following an electronic speckle pattern interferometry (ESPI) technique. The results obtained by optical techniques are compared to the numerical results obtained by the finite element method (FEM), finding good correlation between them in all the cases.     

Measuring the similarity between trajectories using clustering techniques

A clustering method has been developed to group signals that display similar dynamic behavior. The procedure involves using the method of time delay embedding to construct a trajectory in state space from a time series. Certain features that characterize the geometry of the trajectory have been defined. These features were subjected to a series of statistical tests to determine their usefulness in a hierarchical clustering analysis. The latter is aimed at finding groups of similar trajectories. The trajectory-based clustering algorithm has been applied to simulated data, which included both stochastic data generated by a linear AR model, and nonlinear data generated by a Duffing oscillator. The results show that the algorithm works reliably in both cases.     

Characteristic of nanoparticles generated from different nano-powders by using different dispersion methods

A standard rotating drum with a modified sampling train (RD), a vortex shaker (VS), and a SSPD (small-scale powder disperser) were used to investigate the emission characteristics of nano-powders, including nano-titanium dioxide (nano-TiO₂, primary diameter: 21 nm), nano-zinc oxide (nano-ZnO, primary diameter: 30–50 nm), and nano-silicon dioxide (nano-SiO₂, primary diameter: 10–30 nm). A TSI SMPS (scanning mobility particle sizer), a TSI APS (aerodynamic particle sizer), and a MSP MOUDI (micro-orifice uniform deposit impactor) were used to measure the number and mass distributions of generated particles. Significant differences in specific number and mass concentration or distributions were found among different methods and nano-powders with the most specific number and mass concentration and the smallest particles being generated by the most energetic SSPD, followed by VS and RD. Near uni-modal number or mass distributions were observed for the SSPD while bi-modal number or mass distributions existed for nano-powders except nano-SiO₂ which also exhibited bimodal mass distributions. The 30-min average results showed that the mass median aerodynamic diameter (MMAD) and number median diameter (NMD) of the SSPD ranged 1.1–2.1 μm and 166–261 nm, respectively, for all three nano-powders, which were smaller than those of the VS (MMAD: 3.3–6.0 μm and NMD: 156–462 nm), and the RD (MMAD: 5.2–11.2 μm and NMD: 198–479 nm). For nano-particles (electric mobility diameter < 100 nm), specific mass concentrations were nearly negligible for all three nano-powders and test methods. Specific number concentrations of nano-particles were low for the RD tester but were elevated when more energetic VS and SSPD testers were used. The quantitative size and concentration data obtained in this study is useful to elucidate the field emission and personal exposure data in the future provided that particle loss in the generation system is carefully assessed.