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  • Other Sources  (7)
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  • 1
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    Far-Infrared Properties of Superconducting YBa2Cu3O7-S Films in High Magnetic Fields (1997)
    In:  Other Sources
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    Publication Date: 2018-06-08
    Description: We report the far-infrared reflectance and transmittance of superconducting ab-plane-oriented films in magnetic fields up to 30 Tesla.
    Type: Physical Review Letters
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  • 2
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    A linear quadratic regulator approach to the stabilization of uncertain linear systems (1990)
    In:  Other Sources
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    Publication Date: 2019-07-13
    Description: This paper presents a linear quadratic regulator approach to the stabilization of uncertain linear systems. The uncertain systems under consideration are described by state equations with the presence of time-varying unknown-but-bounded uncertainty matrices. The method is based on linear quadratic regulator (LQR) theory and Liapunov stability theory. The robust stabilizing control law for a given uncertain system can be easily constructed from the symmetric positive-definite solution of the associated augmented Riccati equation. The proposed approach can be applied to matched and/or mismatched systems with uncertainty matrices in which only their matrix norms are bounded by some prescribed values and/or their entries are bounded by some prescribed constraint sets. Several numerical examples are presented to illustrate the results.
    Keywords: CYBERNETICS
    Type: AIAA PAPER 90-3509 , AIAA Guidance, Navigation and Control Conference; Aug 20, 1990 - Aug 22, 1990; Portland, OR; United States
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  • 3
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    Performance and durability of HgI2 X-ray detectors for space missions (1989)
    In:  Other Sources
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    Publication Date: 2019-07-12
    Description: Considerable progress has been achieved recently in HgI2 detector fabrication technology and amplification electronics. An energy resolution of 198 eV (full width at half maximum) has been obtained for the Mn k-alpha line of 5.9 keV in a practical X-ray probe without the use of cryogenic cooling. Detectors prepared with Parylene-C encapsulation have demonstrated perfect reliability in two-year tests under high vacuum and temperature and bias cycling. Other HgI2 detectors have been used to demonstrate proton-radiation-damage resistance to levels of 10 to the 12 protons/sq cm at 10.7 MeV. It is concluded that HgI2 detectors are suitable for the ordinary requirements of energy dispersive detectors in X-ray spectroscopy systems.
    Keywords: INSTRUMENTATION AND PHOTOGRAPHY
    Type: IEEE Transactions on Nuclear Science (ISSN 0018-9499); 36; 841-845
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  • 4
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    Hybrid state-space self-tuning control of uncertain linear systems (1993)
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    Publication Date: 2019-07-13
    Description: The paper presents a hybrid state-space self-tuner using a new dual-rate sampling scheme for digital adaptive control of continuous-time uncertain linear systems. A state-space-based recursive least-squares algorithm, together with a variable forgetting factor, is used for direct estimations of both the equivalent discrete-time uncertain linear system parameters and the associated discrete-time state of a continuous-time uncertain linear system from the sampled input and output data. An analogue optimal regional pole-placement design method is used for designing an optimal observer-based analogue controller. A suboptimal observer-based digital controller is then designed from the designed analogue controller using digital redesign technique. To enhance the robustness of parameter identification and state estimation algorithms, a dynamic bound for a class of uncertain bilinear parameters and a fast-rate digital controller are developed at each fast-sampling period. Also, to accommodate computation loads and computation delay for developing the advanced hybrid self-tuner, the designed analogue controller and observer gains are both updated at each slow-sampling period. This control technique has been successfully applied to benchmark control problems.
    Keywords: CYBERNETICS
    Type: IEE Proceedings, Part D - Control Theory and Applications (ISSN 0143-7054); 140; 2; p. 99-110.
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  • 5
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    Linear quadratic regulator approach to the stabilization of matched uncertain linear systems (1991)
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    Publication Date: 2019-07-12
    Keywords: CYBERNETICS
    Type: Journal of Guidance, Control, and Dynamics (ISSN 0731-5090); 14; 1074-107
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  • 6
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    Advances in the development of encapsulants for mercuric iodide X-ray detectors (1990)
    In:  Other Sources
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    Publication Date: 2019-07-12
    Description: Advances in the development of protective impermeable encapsulants with high transparency to ultra-low-energy X-rays for use on HgI2 X-ray detectors are reported. Various X-ray fluorescence spectra from coated detectors are presented. The X-ray absorption in the encapsulants has been analyzed using characteristic radiation from various elements. Results suggest that low-energy cutoffs for the detectors are not determined solely by the encapsulating coatings presently employed but are also influenced by the front electrode and surface effects, which can affect the local electric field or the surface recombination velocity. An energy resolution of 182 eV (FWHM) has been achieved for Ni L lines at 850 eV. Improved detector sensitivity to X-ray energies under 700 eV is demonstrated.
    Keywords: INSTRUMENTATION AND PHOTOGRAPHY
    Type: IEEE Transactions on Nuclear Science (ISSN 0018-9499); 37; 2214-221
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  • 7
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    Use of mercuric iodide X-ray detectors with alpha backscattering spectrometers for space applications (1991)
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    Publication Date: 2019-07-12
    Description: The authors present X-ray fluorescence (XRF) spectra of different extraterrestrial samples taken with a mercuric iodide (HgI2) spectrometer inserted into an alpha backscattering instrument identical to that used in the Soviet Phobos mission. The results obtained with the HgI2 ambient temperature detector are compared with those obtained using an Si(Li) cryogenically cooled detector. Efforts to design an optimized instrument for space application are also described. The results presented indicate that the energy resolution and sensitivity of HgI2 detectors are adequate to meet the performance needs of a number of proposed space applications, particularly those in which cooled silicon X-ray detectors are impractical or even not usable, such as for the target science programs on geoscience opportunities for lunar surface, Mars surface, and other comet and planetary missions being planned by NASA and ESA.
    Keywords: SPACECRAFT INSTRUMENTATION
    Type: IEEE Transactions on Nuclear Science (ISSN 0018-9499); 38; 574-579
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