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121.
We apply what we call sequential projection to reformulate certain linear programs as recursive optimization problems. We then apply the standard idea of approximating the return function at each stage of the recursion by using inner (or outer) linearization, and iteratively refining the approximation until the original linear program has been solved. The contribution of the paper lies in its unification of existing decomposition approaches and in showing that they can be generalized to apply to what we call arborescent linear programs. 相似文献
122.
Paul Hoyningen-Huene 《Journal of statistical physics》1976,15(6):517-518
It is pointed out that the following two procedures are identical: (i) applying Zwanzig's projection operator to the distribution function; (ii) coarsegraining the distribution function with cells which are defined by means of the macroscopic variables and their inaccuracies, and going to the limit of vanishing inaccuracies. 相似文献
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基于发光二极管(Light-emitting Diode,LED)的电脉冲响应过程,建立了一个简便计算LED电脉冲响应模型。在此模型基础上研究了采用脉宽调制(Pulse-width Modulation,PWM)控制LED亮度时,由于LED响应延迟所导致的发光强度随占空比的非线性误差的变化情况,并进行了实验测试。结果表明:在PWM频率为2.5MHz时,LED发光强度与占空比的平均非线性误差为10%左右。最后,针对LED电脉冲响应模型,提出了显示屏像素亮度校正方法。该方法有效减小了由LED响应过程所造成的显示屏亮度控制误差,使得LED实际发光强度与所给亮度值近似成线性关系,从而减小了LED显示屏的色彩偏离,增强了显示效果。 相似文献
125.
背投影拼接显示屏一直被显示图像上存在的图像拼缝所困扰,根据背投影显示原理,分析了图像拼缝产生的原因,提出扩大投影光范围,采用光楔导光的方法将边缘投影光线引入拼接缝,利用全反射临界角原理使进入拼接缝的光线可以近似垂直的方向投射到屏幕上,使图像可以连续跨越拼接缝显示,完全消除了所显示图像上的拼缝黑线,实现了背投影拼接显示屏真正的无缝显示。 相似文献
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128.
Du J Carl M Bydder M Takahashi A Chung CB Bydder GM 《Journal of magnetic resonance (San Diego, Calif. : 1997)》2010,207(2):304-311
We describe the use of two-dimensional ultrashort echo time (2D UTE) sequences with minimum TEs of 8 μs to image and quantify cortical bone on a clinical 3T scanner. An adiabatic inversion pulse was used for long T(2) water and fat signal suppression. Adiabatic inversion prepared UTE acquisitions with varying TEs were used for T(2) measurement. Saturation recovery UTE acquisitions were used for T(1) measurement. Bone water concentration was measured with the aid of an external reference phantom. UTE techniques were evaluated on cadaveric specimens and healthy volunteers. A signal-to-noise ratio of around 30, contrast-to-noise ratio of around 27/20 between bone and muscle/fat were achieved in tibia in vivo with a nominal voxel size of 0.23 × 0.23 × 6.0 mm(3) in a scan time of 5 min. A mean T(1) of 223 ± 11 ms and mean T(2) of 390 ± 19 μs were found. Mean bone water concentrations of 23.3 ± 1.6% with UTE and 21.7 ± 1.3% with adiabatic inversion prepared UTE sequences were found in tibia in five normal volunteers. The results show that in vivo qualitative and quantitative evaluation of cortical bone is feasible with 2D UTE sequences. 相似文献
129.
Cornel Pasnicu 《Journal of Mathematical Analysis and Applications》2006,323(2):1213-1224
Let A be the C∗-algebra associated to an arbitrary continuous field of C∗-algebras. We give a necessary and sufficient condition for A to have the ideal property and, if moreover A is separable, we give a necessary and sufficient condition for A to have the projection property. Some applications of these results are given. We also prove that “many” crossed products of commutative C∗-algebras by discrete, amenable groups have the projection property, generalizing some of our previous results. 相似文献
130.
In range-resolved reflective tomography laser radar imaging system, for accurate image reconstruction, all projections must be aligned to the center of target rotation. Due to the unknown location of the axis of rotation and random target translation, the center of target rotation in each projection cannot be measured accurately and images reconstructed based on range-resolved projections without registration would be dislocated. Here, we apply a feature tracking method to align projections data for tomographic reconstruction in laboratory-scale laser radar imaging. The target was placed on a spin table with an unknown and fixed axis, and the oscillatory motion of the target translation was simulated by a second order inertia filter to accord with the real satellites vibrations. The experimental simulation results demonstrate the effectiveness of this method to improve images reconstruction equality. The application of this method to actual radar imaging in remote distance was discussed and the differences were compared with the lab setups. 相似文献