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861.
862.
To minimize instrumentally the induced systematic errors, cosmic microwave background (CMB) anisotropy experiments measure
temperature differences across the sky using pairs of horn antennas, temperature map is recovered from temperature difference
obtained in sky survey through a map-making procedure. To inspect and calibrate residual systematic errors in the recovered
temperature maps is important as most previous studies of cosmology are based on these maps. By analyzing pixel-ring coupling
and latitude dependence of CMB temperatures, we find notable systematic deviation from CMB Gaussianity in released Wilkinson
Microwave Anisotropy Probe (WMAP) maps. The detected deviation cannot be explained by the best-fit LCDM cosmological model
at a confidence level above 99% and cannot be ignored for a precision cosmology study.
Supported by the National Natural Science Foundation of China (Grant No. 10533020), the National Basic Research Program of
China (Grant No. 2009CB-824800), and the Directional Research Project of the Chinese Academy of Sciences (Grant No. KJCX2-YW-T03)
Contributed by LI TiPei 相似文献
863.
The interaction of the vortex and edge dislocation embedded in a cosh-Gaussion (ChG) beam is studied, where the both dislocations are on-axis, off-axis, or one is on-(off-) axis. It is shown that by varying a beam parameter of the ChG background beam or in the free-space propagation, the break-up of the edge dislocation and the motion, creation and annihilation of vortices may take place. In the vortex evolution process the topological charge is not conserved in general. The results are illustrated numerically and compared with the previous work. 相似文献
864.
865.
866.
针对长波焦平面探测器特点,文章从多个方面分析讨论长波读出电路需要用到的技术和方法,使其能够获得较好的性能。 相似文献
867.
This paper presents a 12-bit 100 MS/s CMOS pipelined analog-to-digital converter (ADC) with digital background calibration. A large magnitude calibration signal is injected into the multiplying digital-to-analog converter (MDAC) while the architecture of the MDAC remains unchanged. When sampled at 100 MS/s, it takes only 2.8 s to calibrate the 12-bit prototype ADC and achieves a peak spurious-free dynamic range of 85 dB and a peak signal-to-noise plus distortion ratio of 66 dB with 2 MHz input. Integral nonlinearity is improved from 1.9 to 0.6 least significant bits after calibration. The chip is fabricated in a 0.18μm CMOS process, occupies an active area of 2.3 × 1.6 mm^2, and consumes 205 mW at 1.8 V. 相似文献
868.
《Mathematical Methods in the Applied Sciences》2018,41(10):3750-3763
By comparing the class ratio deviation and restoring error of first‐order accumulation with that of fractional‐order accumulation, a gray model for monotonically increasing sequences can obtain optimal simulation accuracy via selecting a proper cumulative order. In this study, a gray model for increasing sequences with nonhomogeneous index trends based on fractional‐order accumulation is proposed. To reduce the modeling error caused by the background value and to improve the prediction accuracy of the model, an optimized model using the 3/8 Simpson formula is constructed. Finally, the 2 proposed models are used to predict the total energy consumption in China and the monthly sales of new products in an enterprise. Compared with the GM(1,1) model based on fractional‐order accumulation, the proposed model exhibits better simulation and prediction accuracy. 相似文献
869.
Jason D. McEwen Claudio Durastanti Yves Wiaux 《Applied and Computational Harmonic Analysis》2018,44(1):59-88
Scale-discretised wavelets yield a directional wavelet framework on the sphere where a signal can be probed not only in scale and position but also in orientation. Furthermore, a signal can be synthesised from its wavelet coefficients exactly, in theory and practice (to machine precision). Scale-discretised wavelets are closely related to spherical needlets (both were developed independently at about the same time) but relax the axisymmetric property of needlets so that directional signal content can be probed. Needlets have been shown to satisfy important quasi-exponential localisation and asymptotic uncorrelation properties. We show that these properties also hold for directional scale-discretised wavelets on the sphere and derive similar localisation and uncorrelation bounds in both the scalar and spin settings. Scale-discretised wavelets can thus be considered as directional needlets. 相似文献
870.
本文通过分析阴影的像素特征,建立了一个关于目标帧与背景帧的对比帧来实现阴影监测和消除.为了研究问题方便,本文只考虑视频系统中的摄像头是固定位置的,并且检测目标区域中的较大阴影.利用光流法技术和背景差方法,运动目标能被快速准确的提取出来.同时,背景帧、前景帧及它们的对比帧也被提取出来,而对比帧具有更好的阴影特征.在对比帧上,可以使用静态图像处理技术的一些高效算法,来实时检测阴影区域.本文提出一个对比帧的建立方法,并进一步利用水平集方法来定位阴影区域和消除阴影.通过实验,在选择合适的阈值下,该方法是有效而快速的. 相似文献