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131.
The mechanism of the graphics distrotion in a laser display system was studied. Based on the mathematical analysis, the pincushion and linear distortions were calculated. Theoretical results agree well with the experimental observation. By tracing laser beams from image plan back to scanners, a relation between the image points on the screen and the scan angles was built. Thus, it has been able to rectify the scanning distortions by computer software effectively. 相似文献
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133.
Jan Weis Anders Ericsson Hans C.:Son Silander Anders Hemmingsson 《Magnetic resonance imaging》1998,16(10):1265-1272
We present a method for the quantification and correction of geometrical/intensity distortions of magnetic resonance images predominantly caused by bulk magnetic susceptibility shifts due to susceptibility heterogeneities of measured biologic tissues and shape of the object under investigation. The method includes precise and fast measurements of the static magnetic-field distribution inside the measured object and automated data processing. Magnetic-field deviations in the range −2.4; 2.6 ppm were found in the human brain at B0 = 1.5 T. For routinely used imaging parameters, with a read gradient strength of about 1 mT/m, the magnetic-field perturbations in the human brain can cause geometrical distortions up to ±4 mm and intensity changes up to ±50%. MR images corrected by the described method are suitable for planning high precision applications in neurosurgery. 相似文献
134.
Single crystals of the quaternary crystalline solid solution system RbxK1‐xBryCl1‐y have been grown by melt technique for three different compositions y = 0.25, 0.50 and 0.75, keeping x = 0.5 and X‐ray diffraction studies have been carried out for each case independently, using spherically ground single crystals. The results indicate an enhancement of Debye‐Waller B(total) factors for the compositions y = 0.25 and 0.75 whereas for the intermediate composition, y = 0.5, the factor B(total) is close to the end member value. This experimental investigation show that for this composition, the crystalline solid solution behaves like an end member crystal. 相似文献
135.
基于运动约束解过约束并联机构变形协调方程 总被引:2,自引:0,他引:2
提出利用运动约束关系来间接求解过约束并联机构变形协调方程.首先介绍了该方法的原理,接着分别针对平面和空间过约束并联机构,详述该方法的解决步骤,结果验证了该方法的正确性,从中还可看出该方法在求解复杂过约束并联机构时非常简洁,最后介绍了采用该方法解决多度过约束问题. 相似文献
136.
137.
用于免提通信设备的语音增强算法一直是研究的热点问题,而算法处理结果的音质问题近年来也备受关注。针对基于双传声器降噪的蓝牙耳机系统,将常用多通道传声器降噪算法归纳为基于相干函数法和基于空间预分离法这两大类进行分析和比较。基于相干函数法利用两个通道间信号的相干函数对含噪信号滤波达到降噪目的,而基于空间预分离法利用空间特性从含噪信号中分离出噪声参考信号来消除噪声。分析基于降噪量、语音音质和综合性能三个指标,从约束语音损伤的角度分析最优解的形式,并对比两类算法的实际性能。结果表明选择合适的算法可权衡降噪量与语音损伤,达到较好的综合性能。 相似文献
138.
V. Kaiser A. Le Lirzin J. Darriet A. Tressaud H. Holler D. Babel 《无机化学与普通化学杂志》2002,628(12):2617-2624
Structural Studies with Usovites: Ba2CaMIIV2F14 (MIII = Mn, Fe), Ba2CaMnFe2F14 and Ba2CaCuM2IIIF14 (MIII = Mn, Fe, Ga). Single crystals of six compounds Ba2CaMIIM2IIIF14 were prepared to refine their usovite type structure (space group C2/c, Z = 4) using X‐ray diffractometer data. The cell parameters of the phases studied with MIIM2III= MnV2, FeV2, CuMn2, MnFe2, CuFe2 und CuGa2 are within the range 1374≤a/pm≤1384, 534≤b/pm≤542, 1474≤c/pm≤1510, 91, 3≤ß/°≤93, 2. The atoms Ca and MII are incompletely ordered on the 8‐ and 6‐coordinated positions, 4e and 4b, respectively. In the case of Ba2CaFeV2F14 and Ba2CaCuGa2F14 there is reciprocal substitution (x≈0, 1): (Ca1‐xMxII) (4e) and (M1‐xIICax) (4b). In the case of the other usovites Ca‐enriched phases Ba2Ca(M1‐yIICay)M2IIIF14 occured (up to y≈0, 35), exhibiting partial substitution at the octahedral position (4b) only, showing a corresponding increase in MII‐F distances. The distortion of [MIIF6] and [MIIIF6] octahedra within the structure is considerably enhanced on replacement by CuII and MnIII. The results of powder magnetic susceptibility measurements of Ba2CaMnV2F14 and Ba2CaFeV2F14 (TN≈7K) are reported. 相似文献
139.
Songting YIN 《Frontiers of Mathematics in China》2018,13(2):435-448
We obtain the Laplacian comparison theorem and the Bishop-Gromov comparison theorem on a Finsler manifold with the weighted Ricci curvature Ric∞ bounded below. As applications, we prove that if the weighted Ricci curvature Ric∞ is bounded below by a positive number, then the manifold must have finite fundamental group, and must be compact if the distortion is also bounded. Moreover, we give the Calabi-Yau linear volume growth theorem on a Finsler manifold with nonnegative weighted Ricci curvature. 相似文献
140.
异构网络引起的视频传输失真是影响视频终端感知质量的重要因素,通常只能在解码端进行评估和补偿。因此在编码端建立一个面向内容的立体视频传输失真模型,考虑错误隐藏和错误扩散两种失真,通过近似估计视频中各帧对终端质量的贡献度,从而实现每帧重要性的区分。新模型综合考虑了视频帧编码位置以及表征内容的编码模式、运动矢量、视差矢量等关键信息,可以作为视频在异构网络中传输策略的重要依据。 相似文献