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991.
Christophe Meyer 《Discrete Applied Mathematics》2009,157(4):738-748
A Golomb Ruler is a ruler with integer marks where the distances between every two marks are distinct. Golomb Rulers find diverse applications in computer science and electrical engineering. According to our knowledge the computational complexity of problems related to the construction of Golomb Rulers is unknown. We provide natural definitions for problems related to the construction of such rulers. The main contribution of this work is -completeness results for two such decision problems. 相似文献
992.
993.
A simulation of bi-direction pedestrian flow based on cellular automata (CA) will be presented from two aspects: direction split and pedestrians’ walking habit in this paper. The simulation uses Dynamic Parameters Model (DPM) to simplify tactically the decision-making process of pedestrians in their movements. A new parameter right-hand parameter is introduced to describe the pedestrians’ walking preference. The relationships of velocity–density and flow–density will be studied and analyzed. It is found that there are phase transitions at the critical density point, and the pedestrian flow shows distinctive characteristics at different phases with different relationships of velocity–density and flow–density. It is also found that direction split and pedestrians’ walking habit affect the value of critical density point and the figures of velocity–density and volume–density curves. In conclusion, the simulation can reflect and describe some pedestrian flow self-organization phenomena and transition trend of empirical pedestrian flow curves. 相似文献
994.
By using the detrended fluctuation analysis and detrended moving average method, 823 time series of tree-ring widths in Austrocedrus Chilensis in Patagonia were analyzed. The tree-ring widths of A. Chilensis have been widely used for climatological studies. The results point out to the presence of significant scaling in the temporal fluctuations of tree-ring, which is not due to singular probability density function of the widths but due to the presence of long-range correlations. Such results are in good agreement with those concerning the evidence of long-range dependencies in weather time series. 相似文献
995.
采用积分变换的技巧,推导出了径向分布高斯列阵光束通过湍流大气传输的二阶矩束宽和远场发散角的解析公式,并详细研究了大气湍流对光束扩展和方向性的影响.研究表明,相干合成情况下,子光束数N越小、径向分布半径r0越大,列阵光束扩展受湍流影响越小.相干较非相干合成时列阵光束的扩展小,但非相干合成时列阵光束扩展受湍流的影响比相干合成时的小.特别地,N足够小或r0足够大时,相干与非相干合成列阵光束的远场束宽相等.另一方面,还给出了相干和非相干合成径向分布高斯列阵
关键词:
径向分布高斯列阵光束
大气湍流
相干和非相干合成
二阶矩束宽 相似文献
996.
利用脉宽调制技术,设计了一台为高功率微波源提供导引磁场的脉宽调制型励磁电源,它可在励磁线圈中产生一定持续时间的准稳态强磁场。励磁电源的储能部分采用容量15 F、最高充电电压800 V的储能密度较高的超级电容器,最大储能为4.8 MJ,内阻小于0.25Ω。在储能电容充电645 V的情况下,对电感约为60 mH、电阻约0.40Ω的励磁线圈进行了励磁实验,获得了持续时间为1.9 s、幅值为900 A准稳态电流,电流波动幅度为5%,对应线圈中的最大轴向磁场为2.2 T。实验结果与理论计算基本一致,表明所研制的励磁电源达到了设计要求。 相似文献
997.
998.
W.L. Smith 《Journal of Molecular Spectroscopy》2010,260(1):19-22
Watson’s theory of pure rotational spectra in nonpolar molecules is adapted to show that, if appropriate symmetry conditions are met, centrifugal distortion can lead to the appearance of the forbidden 0-0 origin band in an electronically forbidden spectrum. The intensity of such bands will be low; in the case of the benzene Ã1B2u-1A1g system the maximum intensity of the forbidden origin is estimated to be about 10−7 of that of the 610 band in the main vibronic spectrum. The prospects for the experimental detection of such weak bands are discussed. 相似文献
999.
We present the numerical investigation of the optical transmission through a periodic gold nano-slit structure composed with two non-identical layers, and compare it with that of double-layer structure with two identical layers. The optical enhancement is attributed to the surface Plasmon resonance collaborated with the localized waveguide resonance. It is shown that the transmission behaviors are strongly dependent on the layer separation and lateral displacement between the two single metallic gratings. Especially, it is found that extraordinary transmission exists even if the slit of one layer shifts laterally over that of the other one to the situation that no light can propagate directly when layer separation D = 0. When the slit widths of two layers are not equal, the surface plasmon resonance peak alternately decreases and increases twice, and the localized waveguide resonance peak appears at a longer wavelength as the lateral displacement varies for a non-zero layer separation, which differs from the situation with two identical layers. These transmission properties of the structures show promise for applications in optical devices. 相似文献
1000.
Khrapitchev AA Newling B Balcom BJ 《Journal of magnetic resonance (San Diego, Calif. : 1997)》2006,178(2):288-296
A new approach to the construction of k-space trajectories for centric-scan SPRITE in both 2D and 3D is presented. All benefits of previous SPRITE methods are retained, most importantly the ability to image objects with short T*(2). This new approach gives more flexibility in the choice of number of interleaves with points more evenly distributed across k-space. All these improvements positively contribute to image quality and resolution, which can be also traded off against experimental speed. Sectoral sampling will have significant benefits for magnetisation preparation contrast imaging. 相似文献