Adaptive optics for airborne platforms—Part 1: modeling

Adaptive optics systems mitigate the atmospheric turbulence-induced distortion of a propagating light wavefront. The use of adaptive optics entails the design of a feedback controller, which requires the development of a model of the plant to be controlled. In adaptive optics, the plant consists of the atmosphere through which light is traveling. Moreover, a distinct feature of the adaptive optics control application is the presence of random signals in the plant. In optics, Zernike orthonormal polynomials are commonly used as a basis set for the expansion of wavefront phase distortions. Due to the atmospheric turbulence-induced random nature of the underlying physical process, the spatial-temporal correlation functions of the Zernike polynomial phase distortion expansion coefficients must be evaluated if a proper stochastic model of the plant is to be developed and adaptive optics is to be employed. In Part 1 of this paper, these correlation functions are developed using a layered atmospheric model and calculations for the first few low-order Zernike modes are performed. Using these correlation functions, an underlying stochastic linear dynamical system, which is adequate for control design, is synthesized. This system models the plant and, in turn, provides the basis for the employment of advanced model-based control and estimation concepts in an adaptive optics system for an airborne platform application.     

An airborne diode laser spectrometer for the simultaneous measurement of H2O and HNO3 content of stratospheric cirrus clouds

We describe a tunable diode laser spectrometer for the in situ simultaneous detection of the nitric acid and the water vapour by means of high resolution absorption spectroscopy on rovibronic lines, using a single laser emitting in the mid-infrared (5.8 μm) and a multipass cell. The instrument was designed to be installed on a high altitude aircraft, as a part of a composite payload for atmospheric aerosol studies. The instrument design criteria are discussed and the expected performances are compared with results of laboratory and field operation. Due to the high chemical activity of HNO₃, that makes difficult to use a reference cell, a fast sweep detection of direct absorption was used for the measurement. An absorption sensitivity of about 2×10⁻⁴ was achieved with an integration time of 2.5 s, corresponding to a concentration of about 4 ppb of HNO₃ in the cell and 0.1 ppb in the external aerosol. The data acquisition and processing techniques, based on the full molecular lineshape fitting are also shown and discussed, including some examples of the data acquired during the scientific flights.     

一维大气边界层光学折射率结构常数数值模式的敏感性分析

 提出了一种大气光学折射率结构常数的数值模式。通过敏感性分析发现，对折射率结构常数有显著影响的参数是：一年中的不同日期、土壤的热容量和含水量、雪地和水面上、云量等，风速大小几乎对折射率结构常数没有什么影响。     

Composition of extraction products from alkylated high-sulphur coals

Products of reductive and non-reductive methylation of two high-sulphur coals (Mequinenza and Illinois No. 6) have been extracted by dichloromethane. It has been established that the efficiency of the transformation of coal to the products soluble in CH₂Cl₂ is higher for coals subjected to non-reductive methylation by the Liotta method than for those after reduction in the potassium/liquid ammonia system. The extracts and the extraction residues were subjected to elemental analysis, IR spectroscopy, and AP-TPR (Atmospheric Pressure-Temperature Programmed Reduction) measurements. It has been shown that the main species undergoing extraction by CH₂Cl₂ are aliphatic compounds or aromatic structures of low degree of condensation. The effect of the extraction on the sulphur groups in coal has been discussed.     

萃取色谱在线预浓集流动注射原子吸收光谱测定地质样品中痕量银

选用三苯膦萃取色谱柱，在线预浓集与分离地质样品中痕量银、建立了流动注射火焰原子吸收光谱测定的方法。     

热水解离子色谱法测定岩石样品中的氯和硫

研究开发了一种热水解离子色谱法测定岩石样品中的氯和硫的方法技术。所研究开发的方法具有灵敏、高效、无干扰和准确的特点。实验研究和选择了热水解离子色谱测定的最佳工作条件。用测定的方法对6个国家一级岩石地球化学标准物质GSR1－6进行了分析测定，并在研究我国东部上地壳区域元素丰度实践中测定了2000件岩石样品。测定结果表明，测定值与标准物质的标准值一致。该方法的检出限分别国；氯31×10^-6。方法的精密度（RSD，％）对氯含量水平为40×10^-6，硫酸根含量水平180×10^-6时分别为6.1%和3.0%。