Silicon carbide (SiC) is a promising candidate for large-scale mirrors due to its high stiffness and thermal stability. However, it is very challenging to obtain a super smooth surface for high precision optical teles...
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Silicon carbide (SiC) is a promising candidate for large-scale mirrors due to its high stiffness and thermal stability. However, it is very challenging to obtain a super smooth surface for high precision optical telescopes due to the intrinsic defects of SiC. In this letter, a super smooth surface with a roughness lower than 1 nm and a surface profile of \lambda/50 is achieved by depositing a uniform and dense silicon surface modification cladding by plasma ion assisted deposition (PIAD) on a lightweight concave reaction bonded (RB) SiC mirror, followed by a polishing procedure. Characterization data from the high resolution optical microscope, WYKO profilometer, Zygo interferometer, and nanoindentation are further discussed. The thermal shock resistance test indicates that the surface modification cladding is very stable and shows firm adherence. A reflectance of over 98% in the visible light region is obtained on the spectrometer after being coated with the silver-enhanced coatings.
Self-similar fractal elements that has multiband properties can be advantageously exploited to design simple, multiband FSS on single screen. In this paper, fractal Y aperture FSS has been designed using recursive tec...
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Self-similar fractal elements that has multiband properties can be advantageously exploited to design simple, multiband FSS on single screen. In this paper, fractal Y aperture FSS has been designed using recursive technology and the periodic method of moments (PMoM) is employed to characterize the transmission properties of FSS as band-pass filters. The frequency response to the structure parameters when electromagnetic wave incident with different angles and polarizations is discussed and the numerical analysis show good correlation to the measured results.
This paper puts forward the initial dimensions and items' formation the indexe system for logistics service quality based on the perceived value of customers that logistics suppliers provide service quality, inter...
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ISBN:
(纸本)9780784410394
This paper puts forward the initial dimensions and items' formation the indexe system for logistics service quality based on the perceived value of customers that logistics suppliers provide service quality, interview information from logistics enterprise and expert opinion. Then the index system is simplified according to correlation value and four quadrants. The evaluation model and the quality house basde on relationship between these factors. Finally, the pertinence measure is put forward in order to improve logistics service quality and the whole benefit of the logistics suppliers. Copyright ASCE 2009.
A new method combined subaperture stitching with interferometry(SSI) is introduced. It can test large and off-axis aspheric surfaces without the aid of other null optics. In this paper the basic principle and theory o...
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The effect of parametric instability in advanced interferometric gravitational wave detectors is a potential problem for their proper operation. Great efforts have been made to study the onset of parametric instabilit...
The effect of parametric instability in advanced interferometric gravitational wave detectors is a potential problem for their proper operation. Great efforts have been made to study the onset of parametric instabilities and to find ways to control them. Here we present an experimental design for studying parametric instability in a 72 m cavity with suspended high quality fused silica mirrors. With 5 W input power and 20 kW circulation power inside the cavity, it is predicted that parametric instability will occur. The resonant condition of parametric instability can be met by thermally tuning the radius of curvature of a test mass. We will present simulation results of parametric gains for different radii of curvature of a test mass. The simulation results will provide the basis for designing the thermal tuning and observation parametric instability experiments. This will provide a test bed for studying parametric instability and its control for next generation detectors.
The photoresist coating is an important micromachining process widely applied in engineering. The formed film should be uniform and enough thin to assure the quality of final pattern whose line width is micrometer or ...
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The photoresist coating is an important micromachining process widely applied in engineering. The formed film should be uniform and enough thin to assure the quality of final pattern whose line width is micrometer or nanometer. It is more difficult to process it on the spherical surface than on the flat. In this work, mathematic model of film thickness on the spherical surface is proposed by using hydromechanics. The key factors that influence the film thickness are obtained from the analysis of coating process. Then, the rational parameters which be controlled by the automatic photoresist coating machine can be final set up according to the result of the coating experiments. And the accuracy analysis of the key part which is used for the main process is performed by the error analytics. This machine not only makes the whole coating process automation, but also monitors the film quality in real time. It is adequate for aspheric surface also.
In this paper, a hybrid method is developed to real-timely solve dynamic problems governed by second partial differential equation (PDE). The present method involves the combination of reduced-basis method (RBM) and i...
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In this paper, a hybrid method is developed to real-timely solve dynamic problems governed by second partial differential equation (PDE). The present method involves the combination of reduced-basis method (RBM) and implicit Newmark's method. In this method, it needs a training space, which contains the solutions corresponding to some carefully selected sample parameters and all time steps. A greedy algorithm is adopted to adaptively select basis vectors from the training space for constructing reduced basis space. It results in a reduced system by the standard Galerkin projection the matrices and loading vector. The solutions in arbitrary new parameters are approximately regenerated by solving the reduced Newmark's formulas. To further enhance the efficiency, an off-line/on-line decomposition is suggested for the computational implementation of the method. The present method is applied to analysis the transient response in an actual functionally graded material (FGM) plate. In comparison, the computational cost of transient displacement analysis in FGM plate is reduced significantly. The numerical example demonstrates the efficiency and accuracy of our algorithm.
The roundness error and rotation motion error of the least square center of measured section are separated by applying the roundness error separation principle based on the three-point method. Furthermore, the relatio...
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The roundness error and rotation motion error of the least square center of measured section are separated by applying the roundness error separation principle based on the three-point method. Furthermore, the relationship between the pure rotation motion error and the initial position(linear eccentricity) of the least square center of measured section is described. The mathematical expression for separating the pure rotation motion error is put forward, in which the orthogonality of the trigonometric function and the above-obtained relationship is used. The experimental result indicates that the precision measurement of the radial rotation motion error of the gyro-axle can be achieved by three-point method.
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