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991.
992.
Let G be a finite group. We say that a subgroup H of G is weakly SΦ-supplemented in G if G has a subgroup T such that G = HT and H∩T ≤ Φ(H)HsG, where HsG is the subgroup of H generated by all those subgroups of H that are s-permutable in G. In this paper, we investigate the influence of weakly SΦ-supplemented subgroups on the structure of finite groups. Some new characterizations of p-nilpotency and supersolubility of finite groups are obtained. 相似文献
993.
WU Chong TANG Bin SUN ZhiJia ZHANG Qiang YANG Zhen LUO Wei WANG Tuo 《中国科学:物理学 力学 天文学(英文版)》2013,56(10):1892-1896
A simulation of the properties of the shifting scintillator neutron detector using 6LiF/ZnS(Ag) scintillation screens is performed.The simulation results show that the light attenuation length of standard BC704 scintillator is about 0.65 mm.Its thermal neutron detection efficiency,gamma sensitivity and intrinsic spatial resolution can achieve around 50.0%,10 5and 0.18 mm(along X-axis) respectively.For the detector,air coupling position resolution is better than the silicone oil coupling.Some of the simulation results are compared with experimental results.They are in agreement.This work will be helpful for constructing neutron detector for high intensity powder diffractometer at Chinese spallation neutron source. 相似文献
994.
995.
利用无线电全息方法, 如正则变换方法或全谱反演方法, 可以有效地解决大气多路径条件下GPS掩星信号的反演问题. 本文采用正则变换方法反演掩星资料, 模拟仿真反演结果显示正则变换方法可以准确地反演包含大气多路径效应的信号. 在模拟信号的相位中加入不同程度的高斯相位噪声后, 正则变换方法的反演结果会受到不同程度的影响. 用正则变换方法对2007年第71天至73天共约4500个COSMIC数据进行处理. 将其折射率反演结果和atmPrf资料 (利用全谱反演方法计算得到) 一起, 与对应的ECMWF 分析场资料进行统计比较, 结果表明: 在5 km以下, 正则变换方法计算的折射率的相对误差的平均值普遍大于atmPrf资料. 其原因可能为: 正则变换方法将信号从LEO轨迹后传播至辅助屏, 造成孔径缩小, 精度下降. 同时也讨论了信号截断对低对流层中反演精度和掩星个数的影响.
关键词:
无线电掩星
大气多路径
多相位屏技术
正则变换方法 相似文献
996.
997.
The application of Data Envelopment Analysis (DEA) as an alternative multiple criteria decision making (MCDM) tool has been gaining more attentions in the literatures. Doyle (Organ. Behav. Hum. Decis. Process. 62(1):87?C100, 1995) presents a method of multi-attribute choice based on an application of DEA. In the first part of his method, the straightforward DEA is considered as an idealized process of self-evaluation in which each alternative weighs the attributes in order to maximize its own score (or desirability) relative to the other alternatives. Then, in the second step, each alternative applies its own DEA-derived best weights to each of the other alternatives (i.e., cross-evaluation), then the average of the cross-evaluations that get placed on an alternative is taken as an index of its overall score. In some cases of multiple criteria decision making, direct or indirect competitions exist among the alternatives, while the factor of competition is usually ignored in most of MCDM settings. This paper proposes an approach to evaluate and rank alternatives in MCDM via an extension of DEA method, namely DEA game cross-efficiency model in Liang, Wu, Cook and Zhu (Oper. Res. 56(5):1278?C1288, 2008b), in which each alternative is viewed as a player who seeks to maximize its own score (or desirability), under the condition that the cross-evaluation scores of each of other alternatives does not deteriorate. The game cross-evaluation score is obtained when the alternative??s own maximized scores are averaged. The obtained game cross-evaluation scores are unique and constitute a Nash equilibrium point. Therefore, the results and rankings based upon game cross-evaluation score analysis are more reliable and will benefit the decision makers. 相似文献
998.
Xiangdong Zhang Peiyi Shen Chengke Wu Zhensen Wu 《International Journal of Infrared and Millimeter Waves》1998,19(12):1735-1743
Sea surfaces should be considered as randomly rough surfaces at the infrared(IR) and optical bands. The geometric model of sea surfaces has been obtained by using image processing. Based on the electromagnetic scattering theory, the Laser Radar Cross Section(LRCS) for the sea surfaces is analyzed at IR band and the scattering properties of the sea surfaces have been gotten. 相似文献
999.
在采用冻结湍流假设和几何光学近似的条件下,得到了经自适应光学系统校正后的剩余波前相位扰动的结构函数,进而根据剩余相位结构函数与系统Strehl比的关系,求出自适应光学系统的补偿效果受系统的时空传递函数,大气湍流,光波传播路径上的横向风,观察目标的旋转角速度以及系统时间延迟影响情况的解析表达式。 相似文献
1000.
Targeted damage effects of high intensity focused ultrasound (HIFU) on liver tissues of Guizhou Province miniswine 总被引:12,自引:0,他引:12
Wang ZB Wu F Wang ZL Zhang Z Zou JZ Liu C Liu YG Cheng G Du YH He ZC Gu ML Wang ZG Feng R 《Ultrasonics sonochemistry》1997,4(2):181-182
HIFU can pass through tissues and accurately damage target tissues inside organisms. This article reports on the oriented damage effects of HIFU upon miniswine internal and external liver tissues, and suggests a new conception of the 'biological focal field'. The results revealed that: (1) HIFU can be used to damage accurately liver tissues under the guide of a B-modal ultrasound device; (2) the scope of the injury is connected with sound intensity and irradiation time; and (3) the different layers of tissue through which the ultrasound has passed remain undamaged. 相似文献