Active damping control of vibrational systems

The problem of vibration suppression in large flexible space structure (LFSS) is investigated. Based on the structure property of LFSS, an active damping strategy is proposed to effectively attenuate the critical vibrations of the structure subject to modeling uncertainty and external disturbance. Control algorithms are derived with the aim of suppressing both the vibrating magnitude and vibrating rate to an acceptable level. It is shown that the strategy exhibits robust and adaptive properties and is truly model-independent. The novelty of the proposed approach lies in the fact that it is fairly easy to set up the strategy and the overall computation involved is much less than any other strategies available to date. A two-bay truss is used to verify the validity of the proposed approach     

Radar target classification of commercial aircraft

With the increased availability of coherent wideband radars there has been a renewed interest in radar target recognition. A large bandwidth gives high resolution in range which means target discrimination may be possible. Coherence makes cross-range resolution and radar images possible. Some of the problems of classifying high resolution range profiles (HRRPs) are examined and simple preprocessing techniques which may aid subsequent target classification are investigated. These techniques are applied to HRRP data acquired at a local airport using the Microwave Radar Division (MRD) mobile radar facility It is found that Boeing 727 and Boeing 737 aircraft can be reliably distinguished over a range of aspect angles. This augers well for future target classification studies using HRRPs     

On adaptive multiband signal detection with the SMI algorithm

In a nonstationary and/or nonhomogeneous interference environment, an adaptive system for target detection may suffer a severe performance degradation due to the lack of a sufficient amount of data from which the system can learn (estimate) the statistics of the environment. The detection performance of an adaptive system, which employs a frequency diversity (multiband) signaling waveform and a multiband sample matrix inversion algorithm (SMI), is analyzed. By comparison with the corresponding single-band system under the chosen system constraint, it is shown that the multiband system can significantly outperform the single band when the amount of data available from a single frequency band is severely limited by the environment     

Ground Radiation Pattern Generated by High-Altitude Reflectors

A method is given to calculate the shape a high-altitude reflector must have to produce any intensity distribution inside the illuminated ground area. The method consists of setting up and solving a differential equation appropriate to the required ground intensity distribution. Cylindrical and spherical mirrors are discussed in detail, and mirror shapes for producing a particular type of uniform ground illumination are derived. These shapes approach paraboloids in the limit when the mirror altitude is much greater than the diameter of the illuminated area.     

Late Stages of Stellar Evolution

A large fraction of ISO observing time was used to study the late stages of stellar evolution. Many molecular and solid state features, including crystalline silicates and the rotational lines of water vapour, were detected for the first time in the spectra of (post-)Asymptotic Giant Branch (AGB) stars. Their analysis has greatly improved our knowledge of stellar atmospheres and circumstellar environments. A surprising number of objects, particularly young planetary nebulae with Wolf-Rayet (WR) central stars, were found to exhibit emission features in their ISO spectra that are characteristic of both oxygen-rich and carbon-rich dust species, while far-IR observations of the PDR around NGC 7027 led to the first detections of the rotational line spectra of CH and CH⁺. Based on observations with ISO, an ESA project with instruments funded by ESA Member States (especially the PI countries: France, Germany, The Netherlands, and the United Kingdom), and with the participation of ISAS and NASA.     

Detection of microlesions induced by heavy ions using liposomes filled with fluorescent dye.

In cells irradiation by heavy ions has been hypothesized to produce microlesions, regions of local damage. In cell membranes this damage is thought to manifest itself in the form of holes. The primary evidence for microlesions comes from morphological studies of cell membranes, but this evidence is still controversial, especially since holes also have been observed in membranes of normal, nonirradiated, cells. However, it is possible that damage not associated with histologically discernable disruptions may still occur. In order to resolve this issue, we developed a system for detecting microlesions based on liposomes filled with fluorescent dye. We hypothesized that if microlesions form in these liposomes as the result of irradiation, then the entrapped dye will leak out into the surrounding medium in a measurable way. Polypropylene vials containing suspensions of vesicles composed of either dipalmitoyl phosphatidylcholine, or a combination of egg phosphatidylcholine and cholesterol were irradiated at the Brookhaven National Laboratory using 56Fe ions at 1 GeV/amu. In several cases we obtained a significant loss of the entrapped dye above the background level. Our results suggest that holes may form in liposomes as the result of heavy ion irradiation, and that these holes are large enough to allow leakage of cell internal contents that are at least as large as a 1 nm diameter calcein molecule.     

称重传感器的一种新的滞后补偿方法(英文)

通过对电阻应变式称重传感器在各种加载卸载情况下的滞后特性的分析 ,建立了其相应的数学模型 ,并初步探讨了一种可以通过程序在仪表中对传感器的重要指标—滞后进行补偿从而提高整个传感器的精度的方法。最后 ,对以上方法进行了验证性试验 ,证明了补偿方法的可行性。     

Analyses of exobiological and potential resource materials in the Martian soil.

Potential Martian soil components relevant to exobiology include water, organic matter, evaporites, clays, and oxides. These materials are also resources for human expeditions to Mars. When found in particular combinations, some of these materials constitute diagnostic paleobiomarker suites, allowing insight to be gained into the probability of life originating on Mars. Critically important to exobiology is the method of data analysis and data interpretation. To that end we are investigating methods of analysis of potential biomarker and paleobiomarker compounds and resource materials in soils and rocks pertinent to Martian geology. Differential thermal analysis coupled with gas chromatography is shown to be a highly useful analytical technique for detecting this wide and complex variety of materials.