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排序方式: 共有1262条查询结果,搜索用时 15 毫秒
91.
This paper focuses on a stochastic version of contraction theory to construct observer-controller structure for a flight dynamic system with noisy velocity measurement. A nonlinear stochastic observer is designed to estimate the pitch rate, the pitch angle, and the velocity of an aircraft example model using stochastic contraction theory. Estimated states are used to compute feedback control for solving a tracking problem. The structure and gain selection of the observer is carried out using Itô's stochastic differential equations and the contraction theory. The contraction property of integrated observer-controller structure is derived to ensure the exponential convergence of the trajectories of closed-loop nonlinear system. The upper bound of the state estimation error is explicitly derived and the efficacy of the proposed observer-controller structure has been shown through the numerical simulations. 相似文献
92.
Anjan Biswas Abhijit Bandyopadhyay Nikhil K. Singha Anil K. Bhowmick 《应用聚合物科学杂志》2007,105(6):3409-3417
In the present work, the metallocene‐based polyethylene–octene elastomer (POE) was chemically modified by solution grafting of acrylic acid in presence of benzoyl peroxide. The relative proportions of graft and gel formation were optimized through %weight gain, Fourier Transform infrared spectroscopy, elemental analysis and proton nuclear magnetic resonance spectroscopy. The gel formation in the POE matrix was found to be the prime competitor. The effect of grafting at its maximum level on various physicomechanical properties was thoroughly investigated, using X‐ray diffraction analysis, differential scanning calorimetry, mechanical, dynamic mechanical, and thermogravimetric analysis. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 2007 相似文献
93.
Content-based assembly search: A step towards assembly reuse 总被引:1,自引:0,他引:1
The increased use of CAD systems by product development organizations has resulted in the creation of large databases of assemblies. This explosion of assembly data is likely to continue in the future. In many situations, a text-based search alone may not be sufficient to search for assemblies and it may be desirable to search for assemblies based on the content of the assembly models. The ability to perform content-based searches on these databases is expected to help the designers in the following two ways. First, it can facilitate the reuse of existing assembly designs, thereby reducing the design time. Second, a lot of useful designs for manufacturing, and assembly knowledge are implicitly embedded in existing assemblies. Therefore a capability to locate existing assemblies and examine them can be used as a learning tool by designers to learn from the existing assembly designs. This paper describes a system for performing content-based searches on assembly databases. We identify templates for comprehensive search definitions and describe algorithms to perform content-based searches for mechanical assemblies. We also illustrate the capabilities of our system through several examples. 相似文献
94.
Piyush Kar 《Inorganic Materials》2010,46(4):377-382
Carbon doped titania nanotubes were prepared by anodization of titanium in a fluoride containing ethylene glycol based electrolyte.
Anatase crystallization temperature of the nanotubes varied with respect to anodization voltage. A detailed characterization
study and mechanistic analysis of formation and stability of anatase phase of the nanotubes is reported. The findings suggest
useful heat treatment parameters for obtaining pure anatase phases of the carbon doped titania nanotubes synthesized by anodization
at 40 and 60 V. 相似文献
95.
Corrosion properties of three different Sn‐Ag lead free solder alloys have been investigated in 0.3 wt% Na2SO4 solution as corrosive environment. As cast solder alloy was analyzed by X‐ray diffraction (XRD) and scanning electron microscopy (SEM). Volume fractions of the Ag3Sn in the solders were determined by image analysis technique. Pitting potential and corrosion potential for the alloys were determined by potentiodynamic tests. Electrochemical impedance spectroscopy (EIS) was carried out to measure the film and charge transfer resistance. Alloys with lower Ag content have been found as better corrosion resistance material. 相似文献
96.
Pranesh Chowdhury Abhijit Mukherjee B. Singha Palash Mondal Kousik Roy 《Journal of Polymer Research》2010,17(6):853-860
The effects of different parameters such as time, concentration, pH and temperature, on metal ion retention properties of
the polymer have been investigated. Metal ion adsorption kinetics, isotherms and thermodynamics have been studied. A plausible
mechanism for mercury ion retention has been suggested. Mercuric ion has been isolated quantitatively from various synthetic
mixture containing metal ions (Ni2+, Cd2+, Pb2+ and Zn2+). 相似文献
97.
Daniel Franta Lenka Zajíčková Monika Karásková Ondřej Jašek David Nečas Petr Klapetek Miroslav Valtr 《Diamond and Related Materials》2008,17(7-10):1278-1282
Optical properties of the ultrananocrystalline diamond films were studied by multi-sample method based on the combination of variable angle spectroscopic ellipsometry and spectroscopic reflectometry applied in the range 0.6–6.5 eV. The films were deposited by PECVD in a conventional bell jar (ASTeX type) reactor using dual frequency discharge, microwave cavity plasma and radio frequency plasma inducing dc self-bias at a substrate holder. The optical model of the samples included a surface roughness described by the Rayleigh–Rice theory and a refractive index profile in which Drude approximation was used. The results conformed with the present understanding of the polycrystalline diamond growth on the silicon substrate because the existence of silicon carbide and amorphous hydrogenated carbon film between the silicon substrate and nucleation layer was proved. 相似文献
98.
Chih‐Wei Hsu Abhijit Ganguly Chi‐Hui Liang Yu‐Ting Hung Chien‐Ting Wu Geng‐Ming Hsu Yang‐Fang Chen Chia‐Chun Chen Kuei‐Hsien Chen Li‐Chyong Chen 《Advanced functional materials》2008,18(6):938-942
We report the structure and emission properties of ternary (In,Ga)N nanowires (NWs) embedded with self‐assembled quantum dots (SAQDs). InGaN NWs are fabricated by the reaction of In, Ga and NH3 via a vapor–liquid–solid (VLS) mechanism, using Au as the catalyst. By simply varying the growth temperature, In‐rich or Ga‐rich ternary NWs have been produced. X‐ray diffraction, Raman studies and transmission electron microscopy reveal a phase‐separated microstructure wherein the isovalent heteroatoms are self‐aggregated, forming SAQDs embedded in NWs. The SAQDs are observed to dominate the emission behavior of both In‐rich and Ga‐rich NWs. Temperature‐dependent photoluminescence (PL) measurements indicate relaxation of excited electrons from the matrix of the Ga‐rich NWs to their embedded SAQDs. A multi‐level band schema is proposed for the case of In‐rich NWs, which showed an anomalous enhancement in the PL peak intensity with increasing temperature accompanies with red shift in its peak position. 相似文献
99.
Nagalingam Saravanan Geok Bee Teh Samuel Yong Peen Yap Kar Mun Cheong 《Journal of Materials Science: Materials in Electronics》2008,19(12):1206-1208
ZnS nanoparticles were successfully synthesized by reflux under an alkaline medium. The nanoparticles were characterized by
using X-Ray diffraction (XRD), scanning electron microscopy (SEM) and transmission electron microscopy (TEM). The optical
properties of ZnS nanoparticles were examined by photoluminescence (PL) spectrum. The result shows that the as-synthesized
ZnS nanoparticles had a cubic phase. SEM image shows that ZnS nanoparticles are basically in spherical shape and are homogeneous.
The particle size was found to be in the range of 18 nm. 相似文献
100.