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121.
教科书的编排有其内在的逻辑结构,视觉表征是教科书的重要组成部分,因此视觉表征的选用也应遵循一定的原则。研究借鉴Gkitzia等人的分析框架对人教版初、高中化学教科书中“物质结构”相关内容的视觉表征进行编码分析。在对表征类型及功能分布分析的基础上,结合教科书中物质结构相关知识内容的编排及学生认知、心理发展规律展开讨论。研究发现,人教版教科书中视觉表征的分布与教科书编排的“三序”原则较为契合,能够针对不同学段、学生特点选用视觉表征。最后,依据研究结论,针对教科书中视觉表征的编选和使用提出建议。 相似文献
122.
视距是评估微光夜视成像系统性能的一个重要参数。随着微光夜视探测技术的发展,经典视距模型的视距仿真结果与实测结果出现了一些偏差,特别是在10-3 lx低照度条件下视距仿真结果不甚理想,这对微光夜视仪在实际应用中造成了很大的阻碍。针对这一问题,从微光成像系统成像链路的三个环节对经典视距模型进行修正:考虑大气透过率对微光夜视系统视距的影响并对经典视距模型中的大气透过率因子进行修正;基于像增强器噪声因子对视距模型进行修正;考虑人眼视觉传递特性对微光夜视系统视距的影响,在系统的传递函数模型中加入了简化的人眼视觉模型。进而推导出改进的视距模型。结合野外试验数据,验证了改进视距模型的有效性和实用性,这对于微光夜视系统的设计、评估和应用具有一定的指导性意义。 相似文献
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Christian E. Willert 《Experiments in fluids》2006,41(1):135-143
The performance of three implementations of pinhole-based camera models for use in common light-sheet imaging arrangements is investigated on the background of application to particle image velocimetry (PIV) and Doppler global velocimetry (DGV). Calibration data obtained from translated planar calibration targets was found to yield camera attitude within 0.1° on four different test cases with object distance varying as little as 2% depending on the choice of camera model. Camera calibration using data from a single image of coplanar points is considered a viable alternative to manual triangulation of camera positions but is restricted to off-normal viewing directions.
相似文献
Christian E. WillertEmail: |
127.
Ha Youn Lee 《Physica A》2010,389(15):2975-2980
As borders between different regions, lines are an important element of natural images. Already at the level of the mammalian primary visual cortex (V1), neurons respond best to oriented bars. We reduce a set of images to linear segments and analyze their statistical properties. In particular, appropriately defined Fourier spectra show more power in their transverse component than in the longitudinal one. We then characterize filters that are best suited for extracting information from such images, and find some qualitative consistency with neural connections in V1. We also demonstrate that such filters are efficient in reconstructing missing lines in an image. 相似文献
128.
一种基于HVS的码率控制方法 总被引:1,自引:0,他引:1
本文在小波分解图像的不同级上采用不同长度的滤波器以消减“振铃”效应,然后重新组织小波系数成小波块,根据每个小波块所含能量的多少给其分配不同的码率,最后根据人体视觉系统(HVS)的特点,提出了一种码率控制方法。 相似文献
129.
When confronted with a reversible figure, such as the Necker Cube, viewers experience a spontaneously changing percept. We assess the dynamic of how the human visual system resolves perceptual ambiguity in stimuli that offer multiple interpretations. Subjects observed the Necker cube for one of three viewing durations during which they pressed a key each time they perceived a change in the orientation of the cube. Manipulations of binocular disparity served as a parameter to control perceptual stability. Low-depth conditions yielded more perceptual reversals than high-depth conditions. A Fourier analysis performed on the time series of reversals show 1/f (pink) noise was evident in their power spectra. These results together with theoretical models of complex systems (e.g., Bak, Tang, & Wiesenfeld, 1987) suggest that depth information may guide our perceptual system into a self-organized state to assist us in resolving ambiguous information. Moreover, slopes of the spectra were steeper in high-depth and brief viewing conditions, suggesting that the visual system relies more on previous perceptual states and filters more white noise in these conditions. 相似文献
130.
A New Approach for Visual Cryptography 总被引:1,自引:0,他引:1
Visual cryptography is to encrypt a secret image into some shares (transparencies) such that any qualified subset of the shares can recover the secret visually. The conventional definition requires that the revealed secret images are always darker than the backgrounds. We observed that this is not necessary, in particular, for the textual images.In this paper, we proposed an improved definition for visual cryptography based on our observation, in which the revealed images may be darker or lighter than the backgrounds. We studied properties and obtained bounds for visual cryptography schemes based on the new definition. We proposed methods to construct visual cryptography schemes based on the new definition. The experiments showed that visual cryptography schemes based on our definition indeed have better pixel expansion in average. 相似文献